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Journal Cover Angewandte Chemie
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0044-8249 - ISSN (Online) 1521-3757
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Breaking bonds, Forming Nanographene Diradicals with Pressure
    • Authors: Juan Casado; Maude Desroches, Paula Mayorga Burrezo, Joel Boismenu-lavoie, Miriam Peña Alvarez, Carlos Gómez Garcia, Jon Mattin Matxain, David Casanova, Jean Francois Morin
      Abstract: New anthanthrone-based polycyclic scaffolds possessing peripheral crowed quinodimethanes have been prepared. While the compounds adopt a closed-shell butterfly shaped structure in the ground state, a curved-to-planar fluxional dynamic inversion is accessible with a low energy barrier through a diradical transition-state. Mainly driven by the release of strain attributed to the steric hindrance at the peri position of the anthanthrone core, a low-lying diradical state is accessible through planarization of the core. The most significant aspect is that planarization is also achieved by application of mild pressure in the solid state, wherein the diradical remains kinetically trapped. Cross-information from quantum chemistry, 1H NMR and Raman spectroscopies together with magnetic experiments allow us to propose the formation of a nanographene-like structure which possesses unpaired electrons radical centers mainly localized at the exo-anthanthrone carbons bearing phenyl substituents.
      PubDate: 2017-10-18T04:15:34.861898-05:
      DOI: 10.1002/ange.201708740
       
  • C3-Symmetric Tricyclo[2.2.1.02,6]heptane-3,5,7-triol
    • Authors: Volodymyr Kozel; Constantin-Gabriel Daniliuc, Peer Kirsch, Günter Haufe
      Abstract: A straightforward access to a hitherto unknown C3-symmetric tricyclic triol both in racemic and enantiopure forms has been elaborated. Treatment of 7-tert-butoxynorbornadiene with peroxycarboxylic acids provided mixtures of C1- and C3-symmetric 3,5,7-triacyloxy-nortricyclenes via transannular π-cyclization and substitution of the tert-butoxy group. Refluxing in formic acid, the C1-symmetric esters were converted to the C3-symmetric formate. Hydrolysis gave diastereoisomeric triols, which were separated by recrystallization. Enantiomer resolution via diastereoisomeric tri(O-methylmandelates) delivered the target triols in gram scale. The pure enantiomers are useful as core units of dopants for liquid crystals.
      PubDate: 2017-10-18T03:45:23.459598-05:
      DOI: 10.1002/ange.201709279
       
  • Induction of Single-Handed Helicity of Polyacetylenes Using Mechanically
           Chiral Rotaxanes as Chiral Sources
    • Authors: Fumitaka Ishiwari; Kazuko Nakazono, Yasuhito Koyama, Toshikazu Takata
      Abstract: Effective induction of preferred-handed helicity of polyacetylenes by pendant mechanically chiral rotaxanes is discussed. Polyacetylenes possessing optically active mechanically chiral rotaxanes in the side chains were synthesized by the polymerization of the corresponding enantiopure [2]rotaxane-type ethynyl monomers prepared by the chiral-phase HPLC separations. The CD Cotton effects revealed that the polyacetylenes took preferred-handed helical conformations depending on the rotaxane chirality. The preferred-handed helix was not disturbed by an additional chiral substituent on the rotaxane side chain. These results demonstrate the significance and utility of mechanically chiral rotaxanes for the effective construction of asymmetric fields.Mechanisch chirale Verbindungen dienen als Quelle für Chiralität. Polyacetylene mit optisch aktiven, mechanisch chiralen Rotaxanen als Seitenketten ergeben einen starken Zirkulardichroismus in den Absorptionsbereichen der Hauptketten, woraus sich eine effiziente Helizitätsinduktion durch die Rotaxane ableiten lässt. Die Ergebnisse belegen die Erzeugung asymmetrischer Felder durch mechanisch chirale Rotaxane.
      PubDate: 2017-10-18T03:35:25.696285-05:
      DOI: 10.1002/ange.201707926
       
  • P−B Desulfurization: An Enabling Method for Protein Chemical Synthesis
           and Site-Specific Deuteration
    • Authors: Kang Jin; Tianlu Li, Hoi Yee Chow, Han Liu, Xuechen Li
      Abstract: Cysteine-mediated native chemical ligation is a powerful method for protein chemical synthesis. Herein, we report an unprecedentedly mild system (TCEP/NaBH4 or TCEP/LiBEt3H; TCEP=tris(2-carboxyethyl)phosphine) for chemoselective peptide desulfurization to achieve effective protein synthesis via the native chemical ligation–desulfurization approach. This method, termed P−B desulfurization, features usage of common reagents, simplicity of operation, robustness, high yields, clean conversion, and versatile functionality compatibility with complex peptides/proteins. In addition, this method can be used for incorporating deuterium into the peptides after cysteine desulfurization by running the reaction in D2O buffer. Moreover, this method enables the clean desulfurization of peptides carrying post-translational modifications, such as phosphorylation and crotonylation. The effectiveness of this method has been demonstrated by the synthesis of the cyclic peptides dichotomin C and E and synthetic proteins, including ubiquitin, γ-synuclein, and histone H2A.Außergewöhnlich milde Reaktionsbedingungen (TCEP/NaBH4 oder TCEP/LiBEt3H; TCEP=Tris(2-carboxyethyl)phosphin) wurden für die chemoselektive Peptid-Desulfurierung entwickelt und können für die Proteinsynthese durch native chemische Ligation und Desulfurierung eingesetzt werden. Diese Methode ermöglicht zudem die selektive Deuterierung der Peptide, wenn die Reaktion in D2O-Puffer durchgeführt wird.
      PubDate: 2017-10-18T03:21:26.851379-05:
      DOI: 10.1002/ange.201709097
       
  • Polyion Covalency: Exotic Species from the Unexplored World of
           Electrostatically Shielded Molecular Ion Chemistry
    • Authors: Frank Weinhold
      Abstract: Standard quantum chemical methods have been employed to describe a variety of kinetically stable polyionic molecular species that are trapped in appreciable potential wells by chemical bonding forces, despite powerful electrostatic opposition that challenges conventional chemical detection and characterization. The studied species are covalent or dative analogs of “anti-electrostatic” hydrogen-bonded (AEHB) species, all illustrating how short-range quantum covalency can overcome the powerful “shielding” opposition of long-range electrostatic forces to form highly charged molecular species, analogous to known neutral or singly ionic counterparts. Computational predictions of representative structural, spectroscopic, and NBO-based electronic signatures of multiply charged analogs of common neutral species (CH3CH3, CO2, FeCO) are provided to suggest the unique material properties characteristic of this shielded domain of polyionic chemical phenomena.Antielektrostatische Wasserstoffbrücken: Kinetisch stabile, polyionische Spezies wurden mit quantenchemischen Methoden untersucht. Die polyionischen Spezies sind in Potentialtöpfen durch chemische Bindungskräfte gefangen, trotz einer großen elektrostatischen Gegenkraft, die für die konventionelle Detektion und Charakterisierung eine Herausforderung darstellt.
      PubDate: 2017-10-18T03:21:18.287981-05:
      DOI: 10.1002/ange.201708691
       
  • Biosynthese des enterotoxischen Pyrrolobenzodiazepin-Naturstoffs
           Tilivallin
    • Authors: Elisabeth Dornisch; Jakob Pletz, Ronald A. Glabonjat, Florian Martin, Christian Lembacher-Fadum, Margit Neger, Christoph Högenauer, Kevin Francesconi, Wolfgang Kroutil, Klaus Zangger, Rolf Breinbauer, Ellen L. Zechner
      Abstract: Das nichtribosomale Enterotoxin Tilivallin war das erste natürliche Pyrrolobenzodiazepin, das als Ursache von Erkrankungen des menschlichen Darm erkannt worden ist. Der produzierende Organismus Klebsiella oxytoca ist Bestandteil des Darmmikrobioms. Da die Pathogenese der Darmcolitis durch das Pyrrolobenzodiazepin verursacht wird, ist es wichtig, die Biosynthese und Regulierung der Aktivität von Tilivallin zu verstehen. Wir berichten über die Biosynthese von Tilivallin und zeigen, dass in einem nichtribosomalem Peptidaufbauweg zunächst Tilimycin, ein einfaches Pyrrolobenzodiazepin mit zytotoxischen Eigenschaften, gebildet wird. Tilivallin entsteht durch eine nichtenzymatische spontane Reaktion von Tilimycin mit biogenetisch erzeugtem Indol. Durch chemische Totalsynthese von Tilimycin konnten wir die über die Biosynthese gemachten Vorhersagen belegen. Die Produktion von zwei zytotoxischen Pyrrolobenzodiazepinen mit unterschiedlichen Funktionen durch Klebsiella oxytoca hat Implikationen für das Verständnis von Darmkrankheiten.Das Klebsiella-oxytoca-Enterotoxin Tilivallin war das erste natürliche Pyrrolobenzodiazepin, das mit Krankheiten des menschlichen Darms in Verbindung gebracht wurde. Eine Biosynthese von Tilivallin wird vorgestellt, und es wird gezeigt, dass ein nichtribosomaler Peptidaufbauweg zunächst das zytotoxische Pyrrolobenzodiazepin Tilimycin liefert. Tilivallin entsteht aus der nichtenzymatischen Reaktion von Tilimycin mit biogenetisch erzeugtem Indol.
      PubDate: 2017-10-18T03:21:12.195531-05:
      DOI: 10.1002/ange.201707737
       
  • Programmable Supra-Assembly of a DNA Surface Adapter for Tunable Chiral
           Directional Self-Assembly of Gold Nanorods
    • Authors: Xiang Lan; Zhaoming Su, Yadong Zhou, Travis Meyer, Yonggang Ke, Qiangbin Wang, Wah Chiu, Na Liu, Shengli Zou, Hao Yan, Yan Liu
      Abstract: An important challenge in molecular assembly and hierarchical molecular engineering is to control and program the directional self-assembly into chiral structures. Here, we present a versatile DNA surface adapter that can programmably self-assemble into various chiral supramolecular architectures, thereby regulating the chiral directional “bonding” of gold nanorods decorated by the surface adapter. Distinct optical chirality relevant to the ensemble conformation is demonstrated from the assembled novel stair-like and coil-like gold nanorod chiral metastructures, which is strongly affected by the spatial arrangement of neighboring nanorod pair. Our strategy provides new avenues for fabrication of tunable optical metamaterials by manipulating the directional self-assembly of nanoparticles using programmable surface adapters.Programmieren mit DNA: DNA-Adapter können über die selektiven Wechselwirkungen zwischen spezifischen Bindedomänen auf programmierte Weise zu chiralen supramolekularen Architekturen angeordnet werden. Gold-Nanostäbe, die ortsspezifisch an den DNA-Adaptern angebracht sind, selbstorganisieren innerhalb der chiralen DNA-Matrix zu neuen plasmonischen chiralen Metastrukturen mit einstellbaren Konfigurationen und Händigkeiten.
      PubDate: 2017-10-18T03:20:54.231916-05:
      DOI: 10.1002/ange.201709775
       
  • Magnetless Device for Conducting Three-Dimensional Spin-Specific
           Electrochemistry
    • Authors: Anup Kumar; Eyal Capua, Kiran Vankayala, Claudio Fontanesi, Ron Naaman
      Abstract: Electron spin states play an important role in many chemical processes. Most spin-state studies require the application of a magnetic field. Recently it was found that the transport of electrons through chiral molecules also depends on their spin states and may also play a role in enantiorecognition. Electrochemistry is an important tool for studying spin-specific processes and enantioseparation of chiral molecules. A new device is presented, which serves as the working electrode in electrochemical cells and is capable of providing information on the correlation of spin selectivity and the electrochemical process. The device is based on the Hall effect and it eliminates the need to apply an external magnetic field. Spin-selective electron transfer through chiral molecules can be monitored and the relationship between the enantiorecognition process and the spin of electrons elucidated.Spin-Meister: Mithilfe eines dreidimensionalen elektrochemischen Verfahrens lässt sich der Spin-selektive Elektronentransfer über chirale Moleküle verfolgen. Eine Hall-Einheit als Teil des elektrochemischen Systems ermöglicht direkte Messungen der Spinpolarisation im Zuge des elektrochemischen Prozesses. Ein Magnetfeld ist hierfür nicht erforderlich.
      PubDate: 2017-10-18T03:20:24.452056-05:
      DOI: 10.1002/ange.201708829
       
  • Fast, Efficient and Low E-Factor One-Pot Palladium-Catalyzed
           Cross-Coupling of (Hetero)Arenes
    • Authors: Erik B. Pinxterhuis; Paco Visser, Iwan Esser, Jean-Baptiste Gualtierotti, Ben L. Feringa
      Abstract: The homocoupling of aryl halides and the heterocoupling of aryl halides with either aryl bromides or arenes bearing an ortho-lithiation directing group are presented. The use of a Pd catalyst, in combination with t-BuLi, allows for the rapid and efficient formation of a wide range of polyaromatic compounds in a one pot procedure bypassing the need for the separate preformation of an organometallic coupling partner. These polyaromatic structures are obtained in high yields, in 10 min at room temperature, with minimal waste generation (E-factors as low as 1.5) and without the need for strict inert conditions, making this process highly efficient and practical in comparison to classical methods. As illustration, several key intermediates of widely used BINOL-derived structures are readily prepared including the highly desired precursor to the chiral TRIP phosphoric acid.Schnell und sauber: Die Kreuzkupplung von (Hetero)arenen gelingt mithilfe eines Pd-Katalysators und t-BuLi unter Umgebungsbedingungen ohne nennenswerten Abfall. Eine Vielzahl von Polyarenen wird erhalten, darunter auch sterisch stark gehinderte Produkte und fortgeschrittene Zwischenstufen für chirale Brønsted-Säure-Katalysatoren, die normalweise nur mühsam zugänglich sind.
      PubDate: 2017-10-18T03:15:29.154841-05:
      DOI: 10.1002/ange.201707760
       
  • Frontispiz: Because the Light is Better Here: Correlation-Time Analysis by
           NMR Spectroscopy
    • Authors: Albert A. Smith; Matthias Ernst, Beat H. Meier
      Abstract: NMR-Spektroskopie In der Zuschrift auf S. 13778 untersuchen M. Ernst, B. H. Meier und A. A. Smith Fehlerquellen bei der NMR-spektroskopischen Analyse von Proteindynamiken und schlagen die Verwendung von Dynamikdetektoren vor, die unterschiedliche Korrelationszeitbereiche charakterisieren.
      PubDate: 2017-10-18T02:09:35.546693-05:
      DOI: 10.1002/ange.201784461
       
  • Low-Temperature Molten-Salt Production of Silicon Nanowires by the
           Electrochemical Reduction of CaSiO3
    • Authors: Yifan Dong; Tyler Slade, Matthew J. Stolt, Linsen Li, Steven N. Girard, Liqiang Mai, Song Jin
      Abstract: Silicon is an extremely important technological material, but its current industrial production by the carbothermic reduction of SiO2 is energy intensive and generates CO2 emissions. Herein, we developed a more sustainable method to produce silicon nanowires (Si NWs) in bulk quantities through the direct electrochemical reduction of CaSiO3, an abundant and inexpensive Si source soluble in molten salts, at a low temperature of 650 °C by using low-melting-point ternary molten salts CaCl2–MgCl2–NaCl, which still retains high CaSiO3 solubility, and a supporting electrolyte of CaO, which facilitates the transport of O2− anions, drastically improves the reaction kinetics, and enables the electrolysis at low temperatures. The Si nanowire product can be used as high-capacity Li-ion battery anode materials with excellent cycling performance. This environmentally friendly strategy for the practical production of Si at lower temperatures can be applied to other molten salt systems and is also promising for waste glass and coal ash recycling.Altglas zu Batterien: Eine neue Methode zur Produktion von Silicium-Nanodrähten basiert auf der direkten elektrochemischen Reduktion von CaSiO3 bei 650 °C. Die Methode verwendet niedrig schmelzende ternäre Salze CaCl2-MgCl2-NaCl, die eine hohe Löslichkeit für CaSiO3 aufweisen, sowie einen Hilfselektrolyten, CaO, der die Reaktionskinetik verbessert und die Elektrolyse bei vergleichsweise niedrigen Temperaturen ermöglicht.
      PubDate: 2017-10-18T01:45:32.26343-05:0
      DOI: 10.1002/ange.201707064
       
  • Side Group-Mediated Mechanical Conductance Switching in Molecular
           Junctions
    • Authors: Simon J. Higgins; Ali Khalid Ismael, Kun Wang, Andrea Vezzoli, Mohsin K. Al-Khaykanee, Harry E. Gallagher, Iain M. Grace, Colin J. Lambert, Bingqian Xu, Richard J. Nichols
      Abstract: A key target in molecular electronics has been molecules having switchable electrical properties. Switching between two electrical states has been demonstrated using such stimuli as light, electrochemical voltage, complexation and mechanical modulation. A classic example of the latter is the switching of 4,4'-bipyridine, leading to conductance modulation of ~1 order of magnitude. Here, we describe the use of side-group chemistry to control the properties of a single-molecule electromechanical switch, which can be cycled between two conductance states by repeated compression and elongation. While bulky alkyl substituents inhibit the switching behaviour, -conjugated side-groups reinstate it. DFT calculations show that weak interactions between aryl moieties and the metallic electrodes are responsible for the observed phenomenon. This represents a significant expansion of the single-molecule electronics "tool-box" for the design of junctions with electromechanical properties.
      PubDate: 2017-10-17T11:40:54.795887-05:
      DOI: 10.1002/ange.201709419
       
  • Surface-assisted self-assembly strategies leading to supramolecular
           hydrogels
    • Authors: Pierre Schaaf; Cécile Vigier-Carrière, Fouzia Boulmedais, Loïc Jierry
      Abstract: Localized molecular self-assembly processes leading to the growth of nanostructures exclusively from the surface of a material is one of the great challenges in surface chemistry. In the last decade, several works have been reported about the ability of modified or unmodified surfaces to manage the self-assembly of low molecular weight hydrogelators (LMWH) resulting in localized supramolecular hydrogel coatings mainly based on nanofiber architectures. This minireview highlights all strategies that emerged recently to initiate and localize LMWH supramolecular hydrogel formation, their related fundamental issues and applications.
      PubDate: 2017-10-17T09:45:25.585344-05:
      DOI: 10.1002/ange.201708629
       
  • Semiconductive Copper(I)–Organic Frameworks for Efficient Light-Driven
           Hydrogen Generation Without Additional Photosensitizers and Cocatalysts
    • Authors: Dongying Shi; Rui Zheng, Ming-Jun Sun, Xinrui Cao, Chun-Xiao Sun, Chao-Jie Cui, Chun-Sen Liu, Junwei Zhao, Miao Du
      Abstract: As the first example of a photocatalytic system for splitting water without additional cocatalysts and photosensitizers, the comparatively cost-effective Cu2I2-based MOF, Cu-I-bpy (bpy=4,4′-bipyridine) exhibited highly efficient photocatalytic hydrogen production (7.09 mmol g−1 h−1). Density functional theory (DFT) calculations established the electronic structures of Cu-I-bpy with a narrow band gap of 2.05 eV, indicating its semiconductive behavior, which is consistent with the experimental value of 2.00 eV. The proposed mechanism demonstrates that Cu2I2 clusters of Cu-I-bpy serve as photoelectron generators to accelerate the copper(I) hydride interaction, providing redox reaction sites for hydrogen evolution. The highly stable cocatalyst-free and self-sensitized Cu-I-bpy provides new insights into the future design of cost-effective d10-based MOFs for highly efficient and long-term solar fuels production.Ein Cu2I2-organisches Gerüst vermittelt die effiziente photokatalytische H2-Entwicklung ohne weitere Photosensibilisatoren oder Kokatalysatoren. DFT-Rechnungen zeigen eine gute Übereinstimmung der Bandenergien mit den Redox-Energieniveaus des Wassers. Im vorgeschlagenen Mechanismus erzeugen Cu2I2-Cluster in Cu-I-bpy die Photoelektronen für eine beschleunigte Kupfer(I)-Hydrid-Wechselwirkung bei der H2-Entwicklung.
      PubDate: 2017-10-17T07:51:39.287396-05:
      DOI: 10.1002/ange.201709869
       
  • Stereoselective Direct Chlorination of Alkenyl MIDA Boronates: Divergent
           Synthesis of E and Z α-Chloroalkenyl Boronates
    • Authors: Yao-Fu Zeng; Wei-Wei Ji, Wen-Xin Lv, Yunyun Chen, Dong-Hang Tan, Qingjiang Li, Honggen Wang
      Abstract: The individual molecules of α-chloroalkenyl boronates include both an electrophilic C−Cl bond and a nucleophilic C−B bond, which makes them intriguing organic synthons. Reported herein is a stereodivergent synthesis of both E and Z α-chloroalkenyl N-methyliminodiacetyl (MIDA) boronates through the direct chlorination of alkenyl MIDA boronates using tBuOCl and PhSeCl reagents, respectively. Both reaction processes are stereospecific and the use of sp3-B MIDA boronate is the key contributor to the reactivity. The synthetic value of the boronate products was also demonstrated.Stereodivergente Synthesen von E- oder Z-α-Chloralkenyl-N-methyliminodiacetyl(MIDA)-Boronsäureestern gelingen durch direkte Chlorinerung von E-Alkenyl-MIDA-Boronsäureestern mit tBuOCl bzw. PhSeCl. Beide Reaktionen verlaufen stereospezifisch, und der sp3-B-MIDA-Boronsäureester entscheidet über die Reaktivität. Vielfältige Substrate wurden umgesetzt, und der Wert der Produkte für Synthesen wurde aufgezeigt.
      PubDate: 2017-10-17T07:46:36.319655-05:
      DOI: 10.1002/ange.201709070
       
  • Influence of Polyethylene Glycol Unit on Palladium- and Nickel-Catalyzed
           Ethylene Polymerization and Copolymerization
    • Authors: Dan Zhang; Changle Chen
      Abstract: The transition-metal-catalyzed copolymerization of olefins with polar functionalized co-monomers represents a major challenge in the field of olefin polymerization. It is extremely difficult to simultaneously achieve improvements in catalytic activity, polar monomer incorporation, and copolymer molecular weight through ligand modifications. Herein we introduce a polyethylene glycol unit to some phosphine-sulfonate palladium and nickel catalysts, and its influence on ethylene polymerization and copolymerization is investigated. In ethylene polymerization, this strategy leads to enhanced activity, catalyst stability, and increased polyethylene molecular weight. In ethylene copolymerization with polar monomers, improvements in all copolymerization parameters are realized. This effect is most significant for polar monomers with hydrogen-bond-donating abilities.PEG für Polymerisationen: Polyethylenglykol(PEG)-Substituenten an Phosphansulfonat-Liganden von Palladium- und Nickel-Katalysatoren wirken sich günstig auf Ethylen- und Copolymerisationen aus.
      PubDate: 2017-10-17T07:46:29.52667-05:0
      DOI: 10.1002/ange.201708212
       
  • Flexible Zirconium MOFs as Bromine-Nanocontainers for Bromination
           Reactions under Ambient Conditions
    • Authors: Jiandong Pang; Shuai Yuan, Dongying Du, Christina Lollar, Liangliang Zhang, Mingyan Wu, Daqiang Yuan, Hong-Cai Zhou, Maochun Hong
      Abstract: A series of flexible MOFs (PCN-605, PCN-606, and PCN-700) are synthesized and applied to reversible bromine encapsulation and release. The chemical stability of these Zr-MOFs ensures the framework's integrity during the bromine adsorption, while the framework's flexibility allows for structural adaptation upon bromine uptake to afford stronger host–guest interactions and therefore higher bromine adsorption capacities. The flexible MOFs act as bromine-nanocontainers which elongate the storage time of volatile halides under ambient conditions. Furthermore, the bromine pre-adsorbed flexible MOFs can be used as generic bromine sources for bromination reactions giving improved yields and selectivities under ambient conditions when compared with liquid bromine.Brom-Lieferant: Nach einer topologiegestützten Strategie wurden elastische Zirconium-organische Gerüste aufgebaut, die ihre Struktur im Zuge von Desolvatisierung und Bromadsorption deutlich ändern. Die Spezies mit adsorbiertem Brom können dieses für Bromierungen freisetzen und so die Ausbeuten und Selektivitäten gegenüber dem Einsatz von flüssigem Brom verbessern.
      PubDate: 2017-10-17T07:46:14.370307-05:
      DOI: 10.1002/ange.201709186
       
  • A Highly Reactive Oxoiron(IV) Complex Supported by a Bioinspired N3O
           Macrocyclic Ligand
    • Authors: Inés Monte Pérez; Xenia Engelmann, Yong-Min Lee, Mi Yoo, Elumalai Kumaran, Erik R. Farquhar, Eckhard Bill, Jason England, Wonwoo Nam, Marcel Swart, Kallol Ray
      Abstract: The sluggish oxidants [FeIV(O)(TMC)(CH3CN)]2+ (TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and [FeIV(O)(TMCN-d12)(OTf)]+ (TMCN-d12=1,4,7,11-tetra(methyl-d3)-1,4,7,11-tetraazacyclotetradecane) are transformed into the highly reactive oxidant [FeIV(O)(TMCO)(OTf)]+ (1; TMCO=4,8,12-trimethyl-1-oxa-4,8,12-triazacyclotetradecane) upon replacement of an NMe donor in the TMC and TMCN ligands by an O atom. A rate enhancement of five to six orders of magnitude in both H atom and O atom transfer reactions was observed upon oxygen incorporation into the macrocyclic ligand. This finding was explained in terms of the higher electrophilicity of the iron center and the higher availability of the more reactive S=2 state in 1. This rationalizes nature's preference for using O-rich ligand environments for the hydroxylation of strong C−H bonds in enzymatic reactions.Das Oxoeisen(IV)-Zentrum in [FeIV(O)(TMCO)(OTf)]+ (TMCO=4,8,12-Trimethyl-1-oxa-4,8,12-triazacyclotetradecan) in einer N3O-Umgebung zeigt deutlich höhere Reaktivität als der [FeIV(O)(TMC)(CH3CN)]2+-Komplex (TMC=1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradecan) in einer N4-Umgebung. Dies erklärt, warum in der Natur sauerstoffreiche Ligandenumgebungen für die Hydroxylierung starker C-H-Bindungen bevorzugt werden.
      PubDate: 2017-10-17T07:46:04.017589-05:
      DOI: 10.1002/ange.201707872
       
  • Construction of π-Surface-Metalated Pillar[5]arenes which Bind Anions via
           Anion–π Interactions
    • Authors: Bo Jiang; Wei Wang, Ying Zhang, Ye Lu, Chang-Wei Zhang, Guang-Qiang Yin, Xiao-Li Zhao, Lin Xu, Hongwei Tan, Xiaopeng Li, Guo-Xin Jin, Hai-Bo Yang
      Abstract: By simple ligand exchange of the cationic transition-metal complexes [(Cp*)M(acetone)3](OTf)2 (Cp*=pentamethylcyclopentadienyl and M=Ir or Rh) with pillar[5]arene, mono- and polynuclear pillar[5]arenes, a new class of metalated host molecules, is prepared. Single-crystal X-ray analysis shows that the charged transition-metal cations are directly bound to the outer π-surface of aromatic rings of pillar[5]arene. One of the triflate anions is deeply embedded within the cavity of the trinuclear pillar[5]arenes, which is different to the host–guest behavior of most pillar[5]arenes. DFT calculation of the electrostatic potential revealed that the metalated pillar[5]arenes featured an electron-deficient cavity due to the presence of the electron-withdrawing transition metals, thus allowing encapsulation of electron-rich guests mainly driven by anion–π interactions.Auf einfache Weise können die π-Oberflächen von Pillar[5]arenen hoch effizient metalliert werden. Da die eingefügten Übergangsmetallfragmente elektronenziehend wirken, enthalten die resultierenden Pillar[5]aren-Wirte einen elektronenarmen Hohlraum, in dem sie negativ geladene Gastspezies über Anion-π-Wechselwirkungen einlagern können.
      PubDate: 2017-10-17T07:40:36.641517-05:
      DOI: 10.1002/ange.201707209
       
  • Tri(pyrazolyl)phosphane als Vorstufen für die Synthese von stark
           emittierenden InP/ZnS-Quantenpunkten
    • Authors: René Panzer; Chris Guhrenz, Danny Haubold, René Hübner, Nikolai Gaponik, Alexander Eychmüller, Jan J. Weigand
      Abstract: Tri(pyrazolyl)phosphane werden als alternative kostengünstige und weniger toxische Phosphorquelle in der Synthese von InP/ZnS-Quantenpunkten (QDs) eingesetzt. Ausgehend von ihnen können langzeitstabile (>6 Monate) P(OLA)3-Stammlösungen (OLAH=Oleylamin) synthetisiert werden, aus denen sich die entsprechenden Pyrazole einfach zurückgewinnen lassen. P(OLA)3 fungiert in der Synthese von stark emittierenden InP/ZnS-QDs sowohl als Phosphorquelle als auch als Reduktionsmittel. Die erhaltenen Kern/Schale-Partikel zeichnen sich durch hohe Photolumineszenz-Quantenausbeuten von 51–62 % in einem Spektralbereich von 530–620 nm aus. Die Verarbeitung und Anwendung dieser InP/ZnS-QDs als Farbkonversionsschicht wurde anhand des Einsatzes in einer weißen Leuchtdiode demonstriert.Weniger giftig und ökonomischer, das sind die Vorteile der hier beschriebenen Synthese einer langzeitstabilen P(OLA)3-Stammlösung (OLAH=Oleylamin) aus Tri(pyrazolyl)phosphanen und ihrer Verwendung in der Synthese von stark emittierenden InP/ZnS-Quantenpunkten im Spektralbereich von 530–620 nm mit Photolumineszenz-Quantenausbeuten von 51–62 %. Die freigesetzten Pyrazole können leicht zurückgewonnen und wiederverwendet werden.
      PubDate: 2017-10-17T07:37:56.281161-05:
      DOI: 10.1002/ange.201705650
       
  • Direct Synthesis of Polymer Nanotubes via Aqueous Dispersion
           Polymerization of Cyclodextrin/Styrene Complex
    • Authors: Xi Chen; Lei Liu, Meng Huo, Min Zeng, Liao Peng, Anchao Feng, Xiaosong Wang, Jinying Yuan
      Abstract: We report a one-step synthesis of nanotubes by RAFT dispersion polymerization of cyclodextrin/styrene (CD/St) complexes directly in water. The resulted amphiphilic PEG-b-PS diblock copolymers self-assemble in situ into nanoparticles with various morphologies. Spheres, worms, lamellae, and nanotubes were controllably obtained. Because of the complexation, the swelling degree of polystyrene (PS) blocks by free St is limited, resulting limited mobility of PS chains. Consequently, kinetically trapped lamellae and nanotubes were obtained instead of spherical vesicles. During the formation of nanotubes, small vesicles firstly formed at the ends of the tape-like lamellae, then grew and fused into nanotubes with limited chain rearrangement. The introduction of host-guest interaction based on CDs enables the aqueous dispersion polymerization of water-immiscible monomers, and produces kinetically trapped nanostructures, which could be a powerful technique for nanomaterials synthesis.
      PubDate: 2017-10-17T06:47:03.043554-05:
      DOI: 10.1002/ange.201709129
       
  • Aqueous Gold Overgrowth of Silver Nanoparticles: Merging the Plasmonic
           Properties of Silver with the Functionality of Gold
    • Authors: Martin Mayer; Anja Maria Steiner, Falk Röder, Petr Formanek, Tobias König, Andreas Fery
      Abstract: To date, it has not been possible to combine the high optical quality of silver particles with good chemical stability and synthetic convenience in a fully aqueous system, while simultaneously allowing chemical surface functionalization. We present a synthetic pathway for future developments in information, energy and medical technology where strong optical/electronic properties are crucial. Therefore, the advantages inherent to gold are fused with the plasmonic properties of silver in a fully aqueous Au/Ag/Au core-shell-shell system. These nanoparticles inherit low dispersity from their masked gold cores, yet simultaneously exhibit the strong plasmonic properties of silver. Protecting the silver surface with a sub-skin depth gold layer enables oxidant stability and functionality without altering the Ag-controlled optical properties. This combines both worlds - optical quality and chemical stability - and furthermore it is not limited to a specific particle shape.
      PubDate: 2017-10-17T06:46:55.54093-05:0
      DOI: 10.1002/ange.201708398
       
  • Supramolecular recognition allows remote, site-selective C-H oxidation of
           methylenic sites in linear amines
    • Authors: Giorgio Olivo; Giulio Farinelli, Alessia Barbieri, Osvaldo Lanzalunga, Stefano Di Stefano, Miquel Costas
      Abstract: Site-selective C-H functionalization of aliphatic alkyl chains stands as a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. Herein, we describe a supramolecular, bioinspired approach to address this challenge. We decorated a manganese complex, able to catalyze C(sp3)-H hydroxylation with H2O2, with a supramolecular receptor (an 18-benzocrown-6 ether) that binds ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether thus selectively exposes only remote positions (C8 and C9) to the oxidizing unit, yielding the site-selective oxidation and overriding the intrinsic reactivity of C-H bonds. Remarkably, the supramolecular control of the selectivity holds true for a whole series of linear amines, no matter the chain length and the presence of more (sterically) activated sites.
      PubDate: 2017-10-17T06:46:31.397423-05:
      DOI: 10.1002/ange.201709280
       
  • Edith-Flanigen-Preis für Jovana Zečević / Hamburger Wissenschaftspreis
           für Xinliang Feng und Klaus Müllen / Kurz gemeldet
    • PubDate: 2017-10-17T06:21:12.351244-05:
      DOI: 10.1002/ange.201709758
       
  • Unlocking the Electrocatalytic Activity of Antimony for CO2 Reduction by
           Two-Dimensional Engineering of the Bulk Material
    • Authors: Fengwang Li; Mianqi Xue, Jiezhen Li, Xinlei Ma, Lu Chen, Xueji Zhang, Douglas R. MacFarlane, Jie Zhang
      Abstract: Two-dimensional (2D) materials are known to be useful in catalysis. Engineering 3D bulk materials into the 2D form can enhance the exposure of the active edge sites, which are believed to be the origin of the high catalytic activity. Reported herein is the production of 2D “few-layer” antimony (Sb) nanosheets by cathodic exfoliation. Application of this 2D engineering method turns Sb, an inactive material for CO2 reduction in its bulk form, into an active 2D electrocatalyst for reduction of CO2 to formate with high efficiency. The high activity is attributed to the exposure of a large number of catalytically active edge sites. Moreover, this cathodic exfoliation process can be coupled with the anodic exfoliation of graphite in a single-compartment cell for in situ production of a few-layer Sb nanosheets and graphene composite. The observed increased activity of this composite is attributed to the strong electronic interaction between graphene and Sb.Weniger bringt mehr: Durch elektrochemische Exfoliierung von festem Antimon wurden zweidimensionale Antimon-Nanoschichten sowie Komposite mit Graphen gebildet. Die Aktivität beider Materialien in der elektrokatalytischen CO2-Reduktion übertrifft die von festem Antimon.
      PubDate: 2017-10-17T06:21:09.075748-05:
      DOI: 10.1002/ange.201710038
       
  • Pnictogen (As, Sb, Bi) Nanosheets for Electrochemical Applications Are
           Produced by Shear Exfoliation Using Kitchen Blenders
    • Authors: Rui Gusmão; Zdeněk Sofer, Daniel Bouša, Martin Pumera
      Abstract: Gruppe-5-Elemente (Pniktogene) bilden viel beachtete Ein-Element-2D-Materialien mit Halbleitereigenschaften. In ihrer Zuschrift (
      DOI : 10.1002/ange.201706389) stellen M. Pumera et al. eine umweltverträgliche und skalierbare Herstellungsmethode für solche Pniktogen-Formen durch scherkraftvermitteltes Abblättern in wässriger Lösung mithilfe eines Küchenmixers vor. Bei einem Test der erhaltenen Nanoplättchen in Wasserspaltungsreaktionen ergab Sb die besten Resultate. Die Ergebnisse bilden die Grundlage für künftige elektrochemische Anwendungen der Pniktogene.
      PubDate: 2017-10-17T06:21:04.478452-05:
       
  • Authors Profile
    • PubDate: 2017-10-17T06:20:58.13143-05:0
      DOI: 10.1002/ange.201710183
       
  • Meso-aryl [20]π Homoporphyrin: The simplest expanded porphyrin with
           smallest Möbius Topology
    • Authors: Alagar Srinivasan
      Abstract: The unstable conjugated homoporphyrin is successfully stabilized by introducing the meso-aryl substitutents. It was evident from the moderate diatropic ring current in NMR analysis that the newly formed 20π conjugated freebase and its protonated form exhibit the Möbius aromatic character. Further, the complexation of ligand with Rh(I) salt afforded a unique binding mode and retaining Möbius aromaticity. Overall, these are the smallest Möbius aromatic molecules, which are unambiguously confirmed by spectral, crystal analyses and supported by theoretical studies.
      PubDate: 2017-10-17T06:10:32.618388-05:
      DOI: 10.1002/ange.201709859
       
  • Identification of Ubiquitin Chain Interacting Proteins
    • Authors: Andreas Marx; Xiaohui Zhao, Joachim Lutz, Eva Höllmüller, Martin Scheffner, Florian Stengel
      Abstract: Ubiquitylation, the modification of proteins by ubiquitin (Ub), is one of the most prevalent and versatile post-translational modifications in eukaryotic cells. As Ub also serves as its own substrate, proteins can be modified by numerous different Ub chains, in which the individual moieties are linked via one or several of the seven lysines of Ub. Homogeneous Ub chains, in which the moieties are sequentially linked via the same residue, have been most extensively studied. Yet, due to their restricted availability, the functions of Ub chains linked via K27, K29 or K33 are poorly understood. We have developed an approach that, for the first time, allows the generation of all seven homogeneous Ub chains in large quantities. We show that the chains enable the identification of Ub chain binding proteins by affinity-based proteomics. The potential of our approach is demonstrated by the identification of previously unknown interaction partners of K27-, K29-, and K33-linked Ub chains.
      PubDate: 2017-10-17T06:10:23.909979-05:
      DOI: 10.1002/ange.201705898
       
  • Single-Molecule Observation of The Photoregulated Conformational Dynamics
           of DNA Origami Nanoscissors
    • Authors: Masayuki Endo; Elena M Willner, Yuu Kamada, Yuki Suzuki, Tomoko Emura, Kumi Hidaka, Hendrik Dietz, Hiroshi Sugiyama
      Abstract: We demonstrate direct observation of the dynamic opening and closing behavior of photo-controllable DNA origami nanoscissors (NS) using high-speed AFM. First the conformational change between the open and closed state controlled by adjustment of salt concentration could be directly observed during AFM scanning. Then light-responsive moieties were incorporated into the NS to control the structural changes by irradiation. Using photo-switchable DNA strands, we created a photoresponsive NS variant and were able to distinguish between the open and closed conformations after respective irradiation with UV and visible (Vis) light via gel electrophoresis and AFM imaging. Additionally, these reversible changes in shape during photoirradiation were directly visualized using HS-AFM. Moreover, four photo-switchable NS were assembled into a scissor-actuator-like higher-order object whose configuration could be controlled by the open and close switching as induced by UV and Vis light irradiation.
      PubDate: 2017-10-17T05:40:47.27961-05:0
      DOI: 10.1002/ange.201708722
       
  • Noncovalent Functionalization and Charge Transfer in Antimonene
    • Authors: Gonzalo Abellán; Pablo Ares, Stefan Wild, Edurne Nuin, Christian Neiss, David Rodriguez-San Miguel, Pilar Segovia, Carlos Gibaja, Enrique G. Michel, Andreas Görling, Frank Hauke, Julio Gómez-Herrero, Andreas Hirsch, Félix Zamora
      Abstract: Antimonene, a novel group 15 two-dimensional material, is functionalized with a tailormade perylene bisimide through strong van der Waals interactions. The functionalization process leads to a significant quenching of the perylene fluorescence, and surpasses that observed for either graphene or black phosphorus, thus allowing straightforward characterization of the flakes by scanning Raman microscopy. Furthermore, scanning photoelectron microscopy studies and theoretical calculations reveal a remarkable charge-transfer behavior, being twice that of black phosphorus. Moreover, the excellent stability under environmental conditions of pristine antimonene has been tackled, thus pointing towards the spontaneous formation of a sub-nanometric oxide passivation layer. DFT calculations revealed that the noncovalent functionalization of antimonene results in a charge-transfer band gap of 1.1 eV.Maßgeschneiderte Flocken: Die nichtkovalente Funktionalisierung von Antimonen mit Perylenbisimid (PDI) wird beschrieben. Die starke Fluoreszenzlöschung von PDI ermöglicht die direkte Charakterisierung der auf Si/SiO2-Substraten abgeschiedenen Antimonenflocken. Die Ergebnisse bereiten den Weg für neuartige Anwendungen auf Antimonenbasis durch die gezielte Justierung der elektronischen Eigenschaften.
      PubDate: 2017-10-17T05:30:11.401061-05:
      DOI: 10.1002/ange.201702983
       
  • Analytical Description of NMR Relaxation Highlights Correlated Dynamics in
           Intrinsically Disordered Proteins
    • Authors: Nicola Salvi; Anton Abyzov, Martin Blackledge
      Abstract: Die Potentialenergiediagramme von intrinsisch fehlgeordneten Proteinen sind bemerkenswert flach im Vergleich zu ihren gefalteten Gegenstücken, was die Untersuchung ihrer Funktionsweisen schwierig macht. M. Blackledge et al. beschreiben in ihrer Zuschrift (
      DOI : 10.1002/ange.201706740) eine Kombination aus hochauflösender NMR-Spektroskopie und Moleküldynamiksimulationen, um korrelierte funktionelle Bewegungen in dieser wichtigen Klassen von Proteinen zu erforschen.
      PubDate: 2017-10-17T05:24:16.946811-05:
       
  • Asymmetric Squaramide Catalyzed Domino aza-Friedel-Crafts/N,O
           Acetalization Reactions Between 2-Naphthols and Pyrazolinone Ketimines
    • Authors: Dieter Enders; Ugur Kaya, Pankaj Chauhan, Suruchi Mahajan, Kristina Deckers, Arto Valkonen, Kari Rissanen
      Abstract: Pyrazolin-5-one derived N-Boc ketimines have been explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel protocol requires only a catalyst loading of 0.5 mol% of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98%) and stereoselectivities (>99:1 dr and 97-98% ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98% yield and 47-98% ee.
      PubDate: 2017-10-17T04:49:04.23508-05:0
      DOI: 10.1002/ange.201709224
       
  • Mechanism-based Inhibitors of the Human Sirtuin 5 Deacylase:
           Structure-Activity Relationship, Biostructural, and Kinetic Insight
    • Authors: Nima Rajabi; Marina Auth, Kathrin R. Troelsen, Martin Pannek, Dhaval Bhatt, Martin Fontenas, Matthew D Hirshey, Clemens Steegborn, Andreas S. Madsen, Christian Adam Olsen
      Abstract: The sirtuin enzymes are important regulatory deacylases in a variety of biochemical contexts and may therefore be potential therapeutic targets through either activation or inhibition by small molecules. Here, we describe the discovery of the most potent inhibitor of sirtuin 5 (SIRT5) reported to date. We provide rationalization of the mode of binding by solving co-crystal structures of selected inhibitors in complex with both human and zebrafish SIRT5, which provide insight for future optimization of inhibitors with more "drug-like" properties. Importantly, enzyme kinetic evaluation revealed a slow, tight-binding mechanism of inhibition, which is unprecedented for sirtuins. This is important information when applying inhibitors to probe mechanisms in biology.
      PubDate: 2017-10-17T04:12:22.662354-05:
      DOI: 10.1002/ange.201709050
       
  • An easy-to-machine electrochemical flow microreactor: Efficient
           isoindolinone synthesis and flow functionalization
    • Authors: Ana A Folgueiras-Amador; Kai Philipps, Sebastien Guilbaud, Jarno Poelakker, Thomas Wirth
      Abstract: Flow electrochemistry is an efficient methodology to generate radical intermediates. An electrochemical flow microreactor has been designed and manufactured to improve the efficiency of electrochemical flow reactions. With this device only little or no supporting electrolytes are needed, making processes less costly and enabling easier purification. This is demonstrated by the facile synthesis of amidyl radicals used in intramolecular hydroaminations to isoindolinones. The combination with inline mass spectrometry facilitates a much easier telescoping of chemical steps in a single flow process.
      PubDate: 2017-10-17T03:11:44.915397-05:
      DOI: 10.1002/ange.201709717
       
  • Discovery of New Click and Release Reactions by Screening of Mesoionics
           and Cycloalkynes Combinations
    • Authors: Frédéric Taran; Sabrina Bernard, Davide Audisio, Riomet margaux, Sarah Bregant, Antoine Sallustrau, lucie plougastel, Elodie Decuypere, Sandra Gabillet, Ramar Arun Kumar, Jijy Elyian, Minh Nguyet Trinh, Oleksandr Koniev, Alain Wagner, Sergii Kolodych
      Abstract: We report the discovery of a new bioorthogonal click and release reaction involving imino-sydnones and strained alkynes. This transformation leads to two products resulting from both ligation and fragmentation of imino-sydnones under physiological conditions. Optimized imino-sydnones were successfully used to design innovative cleavable linkers for protein modifications opening new areas in the fields of drug release and target fishing applications. This click and release technology offers for the first time the possibility to exchange tags on proteins with functionalized cyclooctynes under mild and bioorthogonal conditions.
      PubDate: 2017-10-17T02:10:33.995814-05:
      DOI: 10.1002/ange.201708790
       
  • Docking of Antibodies into the Cavities of DNA Origami Structures
    • Authors: Xiangyuan Ouyang; Mattia De Stefano, Abhichart Krissanaprasit, Anne Louise Bank Kodal, Christian Bech Rosen, Tianqiang Liu, Sarah Helmig, Chunhai Fan, Kurt V. Gothelf
      Abstract: Immobilized antibodies are extensively employed for medical diagnostics, such as in enzyme-linked immunosorbent assays. Despite their widespread use, the ability to control the orientation of immobilized antibodies on surfaces is very limited. Herein, we report a method for the covalent and orientation-selective immobilization of antibodies in designed cavities in 2D and 3D DNA origami structures. Two tris(NTA)-modified strands are inserted into the cavity to form NTA–metal complexes with histidine clusters on the Fc domain. Subsequent covalent linkage to the antibody was achieved by coupling to lysine residues. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) confirmed the efficient immobilization of the antibodies in the origami structures. This increased control over the orientation of antibodies in nanostructures and on surfaces has the potential to direct the interactions between antibodies and targets and to provide more regular surface assemblies of antibodies.Genau eingepasst: Antikörper wurden in Hohlräumen einer DNA-Origami-Struktur durch Metallchelatisierung an jeder Hohlraumwand immobilisiert und dort mit aktivierten Estern kovalent gekuppelt.
      PubDate: 2017-10-17T02:03:12.629723-05:
      DOI: 10.1002/ange.201706765
       
  • Intrinsic Broadband White-Light Emission from Ultrastable, Cationic Lead
           Halide Layered Materials
    • Authors: Zewen Zhuang; Chengdong Peng, Guiyang Zhang, Huimin Yang, Jinlin Yin, Honghan Fei
      Abstract: We report a family of cationic lead halide layered materials, formulated as [Pb2X2]2+[−O2C(CH)2CO2−] (X=F, Cl, Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8 %, which is comparable to the highest reported value (ca.9 %) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (ca.60 % relative humidity). Our mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.Strahlend weiß: Die Schichtmaterialien [Pb2X2]2+[−O2C(CH)2CO2−] (X=F, Cl, Br) mit kationischen Bleihalogenid-Schichten geben ein stabiles weißes Leuchten mit großer Bandbreite und externen Quantenausbeuten bis 11.8 % ab. Unter normaler Atmosphäre sind sie lichtbeständig und dadurch nicht durch die Luft- und Feuchtigkeitsempfindlichkeit von Blei-Perowskiten beeinträchtigt.
      PubDate: 2017-10-17T02:02:24.352246-05:
      DOI: 10.1002/ange.201706660
       
  • Cove-Edge Nanoribbon Materials for Efficient Inverted Halide Perovskite
           Solar Cells
    • Authors: Edison Castro; Thomas J. Sisto, Elkin L. Romero, Fang Liu, Samuel R. Peurifoy, Jue Wang, Xiaoyang Zhu, Colin Nuckolls, Luis Echegoyen
      Abstract: Two cove-edge graphene nanoribbons hPDI2-Pyr-hPDI2 (1) and hPDI3-Pyr-hPDI3 (2) are used as efficient electron-transporting materials (ETMs) in inverted planar perovskite solar cells (PSCs). Devices based on the new graphene nanoribbons exhibit maximum power-conversion efficiencies (PCEs) of 15.6 % and 16.5 % for 1 and 2, respectively, while a maximum PCE of 14.9 % is achieved with devices based on [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). The interfacial effects induced by these new materials are studied using photoluminescence (PL), and we find that 1 and 2 act as efficient electron-extraction materials. Additionally, compared with PC61BM, these new materials are more hydrophobic and have slightly higher LUMO energy levels, thus providing better device performance and higher device stability.Blaue Nanobänder-Solarzellen: Zwei elektronenarme Graphen-Nanobänder werden als Elektronentransportmaterialien (ETMs) in invertierten Perowskit-Solarzellen (PSCs) genutzt und zeigen höhere Leistungen als das übliche PC61BM. Die wichtigsten Vorteile sind der höhere Wirkungsgrad (>10 % als PC61BM) und die längere Lebensdauer der Zelle, die den hydrophoben Alkylketten in den Bändern zu verdanken ist.
      PubDate: 2017-10-17T02:02:07.47122-05:0
      DOI: 10.1002/ange.201706895
       
  • Morphology-Dependent Cell Imaging by Using a Self-Assembled Diacetylene
           Peptide Amphiphile
    • Authors: Hao Jiang; Xiao-Yu Hu, Stefanie Schlesiger, Mao Li, Eilo Zellermann, Shirley K. Knauer, Carsten Schmuck
      Abstract: Herein, a novel cationic peptide gemini amphiphile containing diacetylene motifs (DA2P) is presented, which self-assembles into novel tadpole- and bola-shaped nanostructures at low concentrations and nanofibers at higher concentrations. Interestingly, the DA2P assemblies can be polymerized into a fluorescent red phase but only during incubation with HeLa cells, most likely owing to the reorganization of the diacetylene chains of DA2P upon interaction with the cell membrane. The red-fluorescent polymerized DA2P assemblies can serve as a novel cell imaging probe. However, only vesicles, tadpole- and bola-shaped DA2P assemblies can be translocated into HeLa cells, whereas the nanofiber-like DA2P assemblies are trapped by the cell membranes and do not enter the cells. Hence, morphology-dependent cell imaging is observed.Ein peptidisches Zwillingsamphiphil mit Diacetylen-Motiven bildet selbstorganisiert Kaulquappen- und Bola-förmige Nanostrukturen (bei niedrigen Konzentrationen) sowie Nanofasern (bei höheren Konzentrationen). Als Folge von Diacetylen-Polymerisation bei der Wechselwirkung mit der Zellmembran gelingt eine interessante, morphologieabhängige Zellbildgebung.
      PubDate: 2017-10-17T02:01:36.117165-05:
      DOI: 10.1002/ange.201708168
       
  • Oxyfunctionalization of the remote C-H bonds of aliphatic amines via
           decatungstate photocatalysis
    • Authors: Danielle Schultz; François Lévesque, Daniel A. DiRocco, Mikhail Reibarkh, Yining Ji, Leo A. Joyce, James F. Dropinski, Huaming Sheng, Benjamin D. Sherry, Ian W. Davies
      Abstract: Remotely oxygenated aliphatic amines represent an important class of synthetic building blocks to which there are currently no direct means of access. Reported here is an efficient and scalable solution that relies upon decatungstate photocatalysis under acidic conditions using either H2O2 or O2 as the terminal oxidant. Using these conditions a series of simple and unbiased aliphatic amine starting materials can be oxidized to value added ketone products. Lastly, in situ LED-irradiated NMR spectroscopy was utilized to monitor the kinetics of the reaction, enabling direct translation of the reaction in flow.
      PubDate: 2017-10-16T13:55:30.420419-05:
      DOI: 10.1002/ange.201707537
       
  • Experimental proof of the bifunctional mechanism for the hydrogen
           oxidation in alkaline media
    • Authors: Jingkun Li; Shraboni Ghoshal, Michael K. Bates, Todd E Miller, Veronica Davies, Eli Stavitski, Klaus Attenkofer, Sanjeev Mukerjee, Zi-Feng Ma, Qingying Jia
      Abstract: Realization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt-Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data, which provide convincing evidence for the presence of hydroxyl on surface Ru sites in the HOR potential region and its key role in promoting the rate-determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.
      PubDate: 2017-10-16T10:56:25.746368-05:
      DOI: 10.1002/ange.201708484
       
  • Enantioselective Copper-Catalyzed Alkylation of Quinoline N-Oxides with
           Vinylarenes
    • Authors: Songjie Yu; Hui Leng Sang, Shaozhong Ge
      Abstract: We report an asymmetric copper-catalyzed alkylation of quinoline N-oxides with chiral Cu-alkyl species generated by migratory insertion of vinylarene into a chiral Cu-H complex. A variety of quinoline N-oxides and vinylarenes underwent this Cu-catalyzed enantioselective alkylation reaction, yielding the corresponding chiral alkylated N-heteroarenes in high isolated yields with high to excellent enantioselectivities. This enantioselective protocol represents the first general and practical approach to access a wide range of chiral alkylated quinolines.
      PubDate: 2017-10-16T10:55:58.934352-05:
      DOI: 10.1002/ange.201709411
       
  • Asymmetric Cycloisomerization of o-Alkenyl-N-Methylanilines to Indolines
           by Iridium-Catalyzed C(sp3)−H Addition to Carbon–Carbon Double Bonds
    • Authors: Takeru Torigoe; Toshimichi Ohmura, Michinori Suginome
      Abstract: Highly enantioselective cycloisomerization of N-methylanilines, bearing o-alkenyl groups, into indolines is established. An iridium catalyst bearing a bidentate chiral diphosphine effectively promotes the intramolecular addition of the C(sp3)−H bond across a carbon–carbon double bond in a highly enantioselective fashion. The reaction gives indolines bearing a quaternary stereogenic carbon center at the 3-position. The reaction mechanism involves rate-determining oxidative addition of the N-methyl C−H bond, followed by intramolecular carboiridation and subsequent reductive elimination.Von der Methylgruppe zur Methylenbrücke: Bei der hoch enantioselektiven Cycloisomerisierung von N-Methylanilinen mit o-Alkenylgruppen vermittelt ein Iridiumkatalysator mit zweizähnigem chiralen Diphosphanligand effektiv die intramolekulare Addition einer C(sp3)-H-Bindung an die C=C-Bindung. Als Produkte werden Indoline mit quartärem C3-Stereozentrum erhalten.
      PubDate: 2017-10-16T08:01:15.809938-05:
      DOI: 10.1002/ange.201708578
       
  • An Eighteen-Membered Macrocyclic Ligand for Actinium-225 Targeted Alpha
           Therapy
    • Authors: Nikki A. Thiele; Victoria Brown, James M. Kelly, Alejandro Amor-Coarasa, Una Jermilova, Samantha N. MacMillan, Anastasia Nikolopoulou, Shashikanth Ponnala, Caterina F. Ramogida, Andrew K. H. Robertson, Cristina Rodríguez-Rodríguez, Paul Schaffer, Clarence Williams, John W. Babich, Valery Radchenko, Justin J. Wilson
      Abstract: The 18-membered macrocycle H2macropa was investigated for 225Ac chelation in targeted alpha therapy (TAT). Radiolabeling studies showed that macropa, at submicromolar concentration, complexed all 225Ac (26 kBq) in 5 min at RT. [225Ac(macropa)]+ remained intact over 7 to 8 days when challenged with either excess La3+ ions or human serum, and did not accumulate in any organ after 5 h in healthy mice. A bifunctional analogue, macropa-NCS, was conjugated to trastuzumab as well as to the prostate-specific membrane antigen-targeting compound RPS-070. Both constructs rapidly radiolabeled 225Ac in just minutes at RT, and macropa-Tmab retained >99 % of its 225Ac in human serum after 7 days. In LNCaP xenograft mice, 225Ac-macropa-RPS-070 was selectively targeted to tumors and did not release free 225Ac over 96 h. These findings establish macropa to be a highly promising ligand for 225Ac chelation that will facilitate the clinical development of 225Ac TAT for the treatment of soft-tissue metastases.Actinium in Aktion: Ein makrocyclischer Ligand, der für eine effiziente Radiomarkierung mit dem schweren Radionuklid 225Ac3+ sorgt, könnte der Einführung dieses α-Strahlers in die gezielte Krebstherapie den Weg ebnen. RCY=radiochemische Ausbeute.
      PubDate: 2017-10-16T07:56:04.780755-05:
      DOI: 10.1002/ange.201709532
       
  • Chemie / Physiologie oder Medizin und Physik
    • PubDate: 2017-10-16T07:55:36.629103-05:
      DOI: 10.1002/ange.201710180
       
  • Medium-Sized-Ring Analogues of Dibenzodiazepines by a Conformationally
           Induced Smiles Ring Expansion
    • Authors: Romain Costil; Quentin Lefebvre, Jonathan Clayden
      Abstract: Analogues of dibenzodiazepines, in which the seven-membered nitrogen heterocycle is replaced by a 9–12-membered ring, were made by an unactivated Smiles rearrangement of five- to eight-membered heterocyclic anthranilamides. The conformational preference of the tertiary amide in the starting material leads to intramolecular migration of a range of aryl rings, even those lacking electron-withdrawing activating groups, and provides a method for nn+4 ring expansion. The medium-ring products adopt a chiral ground state with an intramolecular, transannular hydrogen bond. The rate of interconversion of their enantiomeric conformers depends on solvent polarity. Ring size and adjacent steric hindrance modulate this hidden hydrophilicity, thus making this scaffold a good candidate for drug development.Die Smiles-Umlagerung leicht herstellbarer Amid-Derivate von benzanellierten Stickstoffheterocyclen führt zu Analoga der tricyclischen Dibenzodiazepin-Antidepressiva mit mittelgroßen Ringen. Elektronenreiche und elektronenarme Ringe sind geeignet, um die 9- bis 12-gliedrigen, konformativ festgelegten Produkte aufzubauen.
      PubDate: 2017-10-16T07:55:33.863756-05:
      DOI: 10.1002/ange.201708991
       
  • Tuneable Transient Thermogels Mediated by a pH- and Redox-Regulated
           Supramolecular Polymerization
    • Authors: Daniel Spitzer; Leona Lucas Rodrigues, David Straßburger, Markus Mezger, Pol Besenius
      Abstract: We present a multi-stimuli responsive transient supramolecular polymerization of ß-sheet encoded dendritic peptide monomers in water. The glutamic acid and methionine containing amphiphiles undergo a glucose oxidase-catalyzed, glucose-fueled transient hydrogelation in response to an interplay of pH- and oxidation-stimuli, promoted by the production of reactive oxygen species (ROS). By adjusting the enzyme and glucose concentration we tune the assembly and the disassembly rates of the supramolecular polymers, which dictate the stiffness and transient stability of the hydrogels. The incorporation of triethylene glycol chains introduces thermoresponsive properties to the materials. We further show that repair enzymes are able to reverse the oxidative damage in the methionine-based thioether side chains. Since ROS play an important role in signal transduction cascades, our strategy offers great potential for applications of these dynamic biomaterials in redox microenvironments.
      PubDate: 2017-10-16T07:26:47.473865-05:
      DOI: 10.1002/ange.201708857
       
  • High-Temperature Formation of a Functional Film at the Cathode/Electrolyte
           Interface in Lithium–Sulfur Batteries: An In Situ AFM Study
    • Authors: Shuang-Yan Lang; Yang Shi, Yu-Guo Guo, Rui Wen, Li-Jun Wan
      Abstract: Lithium–sulfur (Li–S) batteries have been attracting wide attention for their promising high specific capacity. A deep understanding of Li–S interfacial mechanism including the temperature (T) effect is required to meet the demands for battery modification and systematic study. Herein, the interfacial behavior during discharge/charge is investigated at high temperature (HT) of 60 °C in an electrolyte based on lithium bis(fluorosulfonyl) imide (LiFSI). By in situ atomic force microscopy (AFM), dynamic evolution of insoluble Li2S2 and Li2S is studied at the nanoscale. An in situ formed functional film can be directly monitored at 60 °C after Li2S nucleation. It retards side reactions and facilitates interfacial redox. The insight into the interfacial processes at HT provides direct evidence of the existence of the film and reveals its dynamic behavior, providing a new avenue for electrolyte design and performance enhancement.Filmanalyse: Durch elektrochemische AFM-Studien bei 60 °C lässt sich in Li-S-Batterien die In-situ-Bildung eines funktionellen Films an der Grenzfläche zwischen der HOPG-Kathode und dem Polysulfid-Elektrolyt direkt verfolgen (HOPG=hoch orientierter pyrolytischer Graphit). Der Film bildet sich ausgehend von einem LiF-Netz, das Polysulfid(PS)-Intermediate durch physikalische Einschränkung sowie durch chemische Verankerung abfängt.
      PubDate: 2017-10-16T07:00:51.886942-05:
      DOI: 10.1002/ange.201706979
       
  • Synthesis of Biphenylenes and Their Higher Homologues by Cyclization of
           Aryne Derivatives
    • Authors: Sheng-Li Wang; Ming-Lun Pan, Wei-Siang Su, Yao-Ting Wu
      Abstract: This investigation demonstrates that a series of biphenylenes can be easily prepared from their corresponding halobiphenyls by the cyclization of in situ generated 2′,3′-didehydro-2-lithiobiphenyls at low temperature. Two remarkable advantages of this synthetic method include 1) the lack of any need for transition-metal catalysts or reagents in the cyclization, and 2) the ability to obtain C1-functionalized products by treating the reaction intermediate 1-lithiobiphenylene with an electrophilic reagent. π-Extended derivatives, such as benzobiphenylenes, dibenzobiphenylene, linear/angular [3]phenylenes, and biphenyleno[2,3-b]biphenylenes, were synthesized similarly using suitable biaryls or teraryls.Biphenylene können durch die Organolithium-vermittelte Cyclisierung von Halogenbiphenylen über ein Arin-Intermediat leicht und effizient bei niedriger Temperatur erhalten werden. Diese Methode bietet Vorteile für die direkte und gezielte Funktionalisierung an der C1-Position.
      PubDate: 2017-10-16T06:30:56.089706-05:
      DOI: 10.1002/ange.201708892
       
  • Living Supramolecular Polymerization of a Perylene Bisimide Dye into
           Fluorescent J-Aggregates
    • Authors: Wolfgang Wagner; Marius Wehner, Vladimir Stepanenko, Soichiro Ogi, Frank Würthner
      Abstract: Self-assembly of a new, in bay-position 1,7- dimethoxy-substituted perylene bisimide (PBI) organogelator affords non-fluorescent H-aggregates at fast cooling rates and fluorescent J-aggregates at slow cooling rates. Under properly adjusted conditions the kinetically trapped "off-pathway" H-aggregates transform into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of pi-pi interactions and intra- and intermolecular hydrogen bonding for monomeric, H- and J-aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain-growth supramolecular polymerization process.
      PubDate: 2017-10-16T06:26:04.631716-05:
      DOI: 10.1002/ange.201709307
       
  • Two-Dimensional Calix[4]arene-based Metal–Organic Coordination Networks
           of Tunable Crystallinity
    • Authors: Mina Moradi; Ludovico G. Tulli, Jan Nowakowski, Milos Baljozovic, Thomas A. Jung, Patrick Shahgaldian
      Abstract: A flexible and versatile method to fabricate two-dimensional metal–organic coordination networks (MOCNs) by bottom-up self-assembly is described. 2D crystalline layers were formed at the air–water interface, coordinated by ions from the liquid phase, and transferred onto a solid substrate with their crystallinity preserved. By using an inherently three-dimensional amphiphile, namely 25,26,27,28-tetrapropoxycalix[4]arene-5,11,17,23-tetracarboxylic acid, and a copper metal node, large and monocrystalline dendritic MOCN domains were formed. The method described allows for the fabrication of monolayers of tunable crystallinity on liquid and solid substrates. It can be applied to a large range of differently functionalized organic building blocks, also beyond macrocycles, which can be interconnected by diverse metal nodes.Übertragbare Monoschicht: Ein Metall-organisches Koordinationsnetzwerk, das aus einem Calix[4]aren-Derivat als erstem Beispiel für einen 3D-Baustein und Kupferknoten besteht, entsteht als Monoschicht an der Luft-Wasser-Grenzfläche. Die Monoschicht lässt sich erfolgreich auf eine feste Oberfläche übertragen.
      PubDate: 2017-10-16T04:41:20.812393-05:
      DOI: 10.1002/ange.201703825
       
  • Main Group Metal Coordination Polymers. Structures and Nanostructures Von
           Ali Morsali und Lida Hashemi.
    • Authors: Lars Öhrström
      Abstract: John Wiley and Sons, Hoboken 2017. 272 S., geb., 195.00 €.—ISBN 978-1119370239
      PubDate: 2017-10-16T04:40:55.710379-05:
      DOI: 10.1002/ange.201710246
       
  • (4+3) Cycloaddition Reactions of N-Alkyl Oxidopyridinium Ions
    • Authors: Chencheng Fu; Nestor Lora, Patrick L. Kirchhoefer, Dong Reyoul Lee, Erich Altenhofer, Charles L. Barnes, Natasha L. Hungerford, Elizabeth H. Krenske, Michael Harmata
      Abstract: N-Methylation of methyl 5-hydroxynicotinate followed by reaction with a diene in the presence of triethylamine afforded (4+3) cycloadducts in good to excellent yields. High regioselectivity was observed with 1-substituted and 1,2-disubstituted butadienes. Density functional theory calculations indicate that the cycloaddition involves concerted addition of the diene onto the oxidopyridinium ion. The process provides rapid access to bicyclic nitrogenous structures resembling natural alkaloids.Größer als die Summe der Teile: N-methyliertes Methyl-5-hydroxynicotinat reagiert durch (4+3)-Cycloaddition mit Dienen in Gegenwart von Triethylamin zu bicyclischen stickstoffhaltigen Strukturen mit Ähnlichkeit zu natürlichen Alkaloiden (siehe Schema). Hohe Regioselektivitäten wurden mit 1-substituierten und 1,2-disubstituierten Butadienen beobachtet. Dichtefunktionalrechnungen belegen eine konzertierte Addition des Diens an das Oxidopyridinium-Ion.
      PubDate: 2017-10-16T04:40:43.441322-05:
      DOI: 10.1002/ange.201708320
       
  • New Insights into the Activation and Deactivation of Au/CeZrO4 in the
           Low-Temperature Water-Gas Shift Reaction
    • Authors: Graham John Hutchings; James Carter, Xi Liu, Qian He, Sultan Althahban, Ewa Nowicka, Simon Freakley, Liwei Niu, David Morgan, Yongwang Li, Hans Niemantsverdriet, Stanislaw Golunski, Christopher Kiely
      Abstract: Gold on ceria-zirconia is an active catalyst for the low-temperature water-gas shift reaction (LTS), a key stage of upgrading H2 reformate streams for fuel cells. However, this catalyst rapidly deactivates and the mechanism remains unclear. Using stop-start scanning transmission electron microscopy (STEM) to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X-ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (1-2 nm) from sub-nm Au species. These nanoparticles then agglomerated further over 48 h on-stream, most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au nanoparticles.
      PubDate: 2017-10-16T03:50:24.24808-05:0
      DOI: 10.1002/ange.201709708
       
  • Silicon Wafers Revealing Facet-Dependent Electrical Conductivity
           Properties
    • Authors: Chih-Shan Tan; Pei-Lun Hsieh, Lih-Juann Chen, Michael Hsuan-Yi Huang
      Abstract: By breaking intrinsic Si (100) and (111) wafers to expose sharp {111} and {112} facets, electrical conductivity measurements on single and different silicon crystal faces have been performed through contacts with two tungsten probes. While Si {100} and {110} faces are barely conductive at low applied voltages as expected, Si {112} surface is highly conductive and Si {111} surface also shows good conductivity. Asymmetrical I-V curves have been recorded for the {111}/{112}, {111}/{110}, and {112}/{110} facet combinations because of different degrees of conduction band bending at these crystal surfaces presenting different barrier heights to current flow. In particular, the {111}/{110}, and {112}/{110} facet combinations give I-V curves resembling those of p-n junctions, suggesting a novel field effect transistor design is possible capitalizing on the pronounced facet-dependent electrical conductivity properties of silicon.
      PubDate: 2017-10-16T03:16:42.820691-05:
      DOI: 10.1002/ange.201709020
       
  • Near-Infrared-Light-Driven Hydrogen Evolution from Water using a
           Polypyridyl Triruthenium Photosensitizer
    • Authors: Yutaro Tsuji; Keiya Yamamoto, Kosei Yamauchi, Ken Sakai
      Abstract: In order to realize the artificial photosynthetic devices splitting water to H2 and O2 (2H2O + hν 2H2 + O2), it is desirable to utilize a wider wavelength range of light that extends to a lower energy region of solar spectrum. Here we report a triruthenium photosensitizer [Ru3(dmbpy)6(μ-HAT)]6+ (dmbpy = 4,4'-dimethyl-2,2'-bipyridine, HAT = 1,4,5,8,9,12-hexaazatriphenylene), which absorbs near-infrared light up to 800 nm based on its 1MLCT transition. Importantly, [Ru3(dmbpy)6(μ-HAT)]6+ is found to be the first example of a photosensitizer which can drive H2 evolution under the illumination of near-infrared light above 700 nm. The electrochemical and photochemical studies reveal that the reductive quenching within the ion-pair adducts of [Ru3(dmbpy)6(μ-HAT)]6+ and ascorbate anions affords a singly reduced form of [Ru3(dmbpy)6(μ-HAT)]6+, which is used as a reducing equivalent in the subsequent water reduction process.
      PubDate: 2017-10-16T02:21:23.460029-05:
      DOI: 10.1002/ange.201708996
       
  • Reduction of a CeIII Siloxide Complex Affords a Tetradecker Arene-bridged
           CeII Sandwich
    • Authors: Marinella Mazzanti; Rory Kelly, Laurent Maron, Rosario Scopelliti
      Abstract: Organometallic multiple-decker sandwich complexes containing f-elements remain rare in spite of their attractive magnetic and electronic properties. The reduction of the CeIII siloxide complex, [KCeL4] (1; L = OSi(OtBu)3) with excess potassium in a THF/toluene mixture affords a rare tetradecker arene-bridged complex [K(2.2.2-crypt)]2[{(KL3Ce)(µ-η6:η6-C7H8)}2Ce] (3). The structure of 3 features a [Ce(C7H8)2] sandwich capped by [KL3Ce] moieties with a linear arrangement of the Ce ions. Structural parameters, UV-Vis data and DFT studies indicate the presence of CeII ions involved in δ bonding between the Ce cations and toluene dianions. Complex 3 is a rare lanthanide multidecker complex and the first containing non-classical divalent lanthanide ions. Moreover, oxidation of 1 by AgOTf (OTf = O3SCF3) yielded the CeIV complex, [CeL4] (2), showing that siloxide ligands can stabilize Ce in three oxidation states.
      PubDate: 2017-10-16T01:55:45.785296-05:
      DOI: 10.1002/ange.201709769
       
  • Controlling Lanthanide Exchange in Triple-Stranded Helicates: A Way to
           Optimize Molecular Light-Upconversion
    • Authors: Davood Zare; Yan Suffren, Homayoun Nozary, Andreas Hauser, Claude Piguet
      Abstract: The kinetic lability of hexadentate gallium-based tripods is sufficient to ensure thermodynamic self-assembly of luminescent heterodimetallic [GaLn(L3)3]6+ helicates on the hour time scale, where Ln is a trivalent 4f-block cation. The inertness is, however, large enough for preserving the triple-helical structure when [GaLn(L3)3]6+ is exposed to lanthanide exchange. The connection of a second gallium-based tripod further slows down the exchange processes to such an extent that spectroscopically active [CrErCr(L4)3]9+ can be diluted into closed-shell [GaYGa(L4)3]9+ matrices without metal scrambling. This feature is exploited for pushing molecular-based energy-transfer upconversion (ETU) at room temperature.Inerte nichtkovalent gebundene [GaL3]3+-Ionen vermitteln das Einfangen/Freisetzen labiler trivalenter Lanthanoide auf der Stundenzeitskala. Die Kooperation zweier tripodaler [GaL3]3+-Einheiten sorgt für monatelange Inertheit, sodass sich die neuen Materialien für die Herstellung fester Lösungen mit molekülbasierter Energietransfer-Aufwärtskonversion bei Raumtemperatur eignen.
      PubDate: 2017-10-16T01:21:12.712224-05:
      DOI: 10.1002/ange.201709156
       
  • An Epitope-Imprinted Biointerface with Dynamic Bioactivity for Modulating
           Cell–Biomaterial Interactions
    • Authors: Guoqing Pan; Sudhirkumar Shinde, Sing Yee Yeung, Miglė Jakštaitė, Qianjin Li, Anette Gjörloff Wingren, Börje Sellergren
      Abstract: In this study, an epitope-imprinting strategy was employed for the dynamic display of bioactive ligands on a material interface. An imprinted surface was initially designed to exhibit specific affinity towards a short peptide (i.e., the epitope). This surface was subsequently used to anchor an epitope-tagged cell-adhesive peptide ligand (RGD: Arg-Gly-Asp). Owing to reversible epitope-binding affinity, ligand presentation and thereby cell adhesion could be controlled. As compared to current strategies for the fabrication of dynamic biointerfaces, for example, through reversible covalent or host–guest interactions, such a molecularly tunable dynamic system based on a surface-imprinting process may unlock new applications in in situ cell biology, diagnostics, and regenerative medicine.Ein Epitop-geprägter Polymerfilm wurde zur reversiblen Verankerung des zelladhäsiven Peptids RGD genutzt. Funktionalität wurde anhand eines kontrollierbaren Zelladhäsionsverhaltens demonstriert (siehe Bild).
      PubDate: 2017-10-16T01:21:05.623585-05:
      DOI: 10.1002/ange.201708635
       
  • Enantioselective Synthesis of Tetrahydropyrano[3,4-b]indoles:
           Palladium(II)-Catalyzed Aminopalladation/1,4-Addition Sequence
    • Authors: Junjie Chen; Xiuling Han, Xiyan Lu
      Abstract: A novel palladium(II)-catalyzed cyclization of aniline-tethered alkynyl cyclohexadienones is reported. This reaction offers an atom-economical and redox-neutral access to various cyclohexenone-fused tetrahydropyrano[3,4-b]indoles with high yield and excellent enantioselectivity. Remarkably, this work represents the first example on a transition-metal-catalyzed asymmetric intramolecular aminopalladation/1,4 addition sequence.Aus Ketten werden Ringe: Die Palladium(II)-katalysierte asymmetrische Cyclisierung von Anilinen mit über eine Alkinbrücke angebundenen Cyclohexadienon-Ringen ergibt funktionalisierte Tetrahydropyrano[3,4-b]indole in guten Ausbeuten und hervorragenden Enantioselektivitäten. Der Prozess verläuft als Sequenz aus intramolekularer Aminopalladierung und 1,4-Addition.
      PubDate: 2017-10-16T01:20:51.319373-05:
      DOI: 10.1002/ange.201708900
       
  • Asymmetric Intermolecular Heck Reaction of Propargylic Acetates and
           Cycloalkenes to Access Fused Cyclobutenes
    • Authors: Zhiwei Jiao; Qi Shi, Jianrong Steve Zhou
      Abstract: An asymmetric Heck annulation of propargylic acetates with several types of cyclic olefins affords highly strained cyclobutenes in high enantioselectivity.Eine intermolekulare Heck-Reaktion zwischen Propargylacetaten und cyclischen Olefinen ermöglicht die enantioselektive Synthese hoch gespannter Cyclobutene.
      PubDate: 2017-10-16T01:20:41.014574-05:
      DOI: 10.1002/ange.201708435
       
  • Synthesis of Anisotropic Hydrogels and Their Applications
    • Authors: Koki Sano; Yasuhiro Ishida, Takuzo Aida
      Abstract: Owing to their water-rich structures similar to biological tissues, hydrogels have long been regarded as promising scaffolds for artificial tissues and organs. However, in terms of structural anisotropy, most synthetic hydrogels are substantially different from biological systems. Synthetic hydrogels are usually composed of randomly oriented three-dimensional polymer networks, whereas biological systems adopt anisotropic structures with hierarchically integrated building units. Such anisotropic structures often play an essential role in biological systems to exhibit their particular functions, as represented by muscular textures comprising unidirectionally oriented actin-myosin units. In this context, anisotropic hydrogels provide an entry point for exploring the biomimetic applications of hydrogels. Reflecting these aspects, an increasing number of studies on anisotropic hydrogels have been reported recently. This Minireview highlights the outline and perspective of these anisotropic hydrogels, particularly focusing on their preparation, structures, and applications.
      PubDate: 2017-10-16T00:50:34.123189-05:
      DOI: 10.1002/ange.201708196
       
  • Ynamide Preactivation Allows a Regio- and Stereoselective Synthesis of
           α,β-disubstituted Enamides
    • Authors: Lucas Loss Baldassari; Aurelien de la Torre, Jing Li, Diogo Seibert Lüdtke, Nuno Maulide
      Abstract: A novel ynamide preactivation strategy enables the use of otherwise incompatible reagents and allows preparation of α,β-disubstituted enamides with high regio- and stereoselectivity. Mechanistic analysis reveals the intermediacy of a triflate-bound intermediate as a solution-stable, effective keteniminium reservoir, whilst still allowing subsequent addition of organometallic reagents.
      PubDate: 2017-10-15T20:55:50.10522-05:0
      DOI: 10.1002/ange.201709128
       
  • Total Syntheses of the Isomeric Aglain Natural Products Foveoglin A and
           Perviridisin B: Selective Excited-State Intramolecular Proton-Transfer
           Photocycloaddition
    • Authors: Wenyu Wang; Anthony Clay, Retheesh Krishnan, Neil J. Lajkiewicz, Lauren E. Brown, Jayaraman Sivaguru, John A. Porco
      Abstract: Selective excited-state intramolecular proton-transfer (ESIPT) photocycloaddition of 3-hydroxyflavones with trans, trans-1,4-diphenyl-1,3-butadiene is described. Using this methodology, total syntheses of the natural products (±)-foveoglin A and (±)-perviridisin B were accomplished. Enantioselective ESIPT photocycloaddition using TADDOLs as chiral hydrogen-bonding additives provided access to (+)-foveoglin A. Mechanistic studies have revealed the possibility for a photoinduced electron-transfer (PET) pathway.Erhellend: Eine selektive ESIPT-Photocycloaddition (ESIPT=intramolekularer Protonentransfer aus einem angeregten Zustand) von 3-Hydroxyflavonen mit trans,trans-1,4-Diphenyl-1,3-butadien ermöglichte die Totalsynthese der isomeren Aglain-Naturstoffe Foveoglin A und Perviridisin B. Mechanistische Studien sprechen für einen Reaktionsweg unter Beteiligung eines photoinduzierten Elektronentransfers.
      PubDate: 2017-10-13T06:21:18.777243-05:
      DOI: 10.1002/ange.201707539
       
  • Copper-Catalyzed Synthesis and Applications of Yndiamides
    • Authors: Steven J. Mansfield; Kirsten E. Christensen, Amber L. Thompson, Kai Ma, Michael W. Jones, Aroonroj Mekareeya, Edward A. Anderson
      Abstract: The first synthetic route to yndiamides, a novel class of double aza-substituted alkyne, has been established by the copper(I)-catalyzed cross-coupling of 1,1-dibromoenamides with nitrogen nucleophiles. The utility of these compounds is demonstrated in a range of transition-metal-catalyzed and acid-catalyzed transformations to afford a wide variety of 1,2-diamide functionalized products.Die erste Syntheseroute zu Indiamiden, einer neuartigen Klasse doppelt Aza-substituierter Alkine, beruht auf der CuI-katalysierten Kreuzkupplung von 1,1-Dibromenamiden mit N-Nucleophilen. Die Nützlichkeit dieser Verbindungen wurde anhand einer Reihe übergangsmetall- und säurekatalysierter Umwandlungen demonstriert, die eine Vielfalt 1,2-Diamid-funktionalisierter Produkte ergeben.
      PubDate: 2017-10-13T06:20:47.754569-05:
      DOI: 10.1002/ange.201706915
       
  • Nickel-Catalyzed N-Alkylation of Acylhydrazines and Arylamines Using
           Alcohols and Enantioselective Examples
    • Authors: Peng Yang; Caili Zhang, Yu Ma, Caiyun Zhang, Aijie Li, Bo Tang, Jianrong Steve Zhou
      Abstract: A borrowing-hydrogen reaction between amines and alcohols is an atom-economic way to prepare alkylamines, ideally with water as the sole byproduct. Herein, nickel catalysts are used for direct N-alkylation of hydrazides and arylamines using racemic alcohols. Moreover, a nickel catalyst of (S)-binapine was used for an asymmetric N-alkylation of benzohydrazide with racemic benzylic alcohols.Wasserstoff-Autotransfer: Nickel-Katalysatoren bewirken die direkte N-Alkylierung von Hydraziden und Arylaminen mit racemischen Alkoholen über einen Wasserstofftransfer-Mechanismus. Zu dieser Reaktion wurde auch eine asymmetrische Variante der Reaktion von N-Acylhydrazinen entwickelt.
      PubDate: 2017-10-13T06:17:05.560783-05:
      DOI: 10.1002/ange.201708949
       
  • Photoluminescence Lifetime Imaging of Synthesized Proteins in Living Cells
           Using an Iridium–Alkyne Probe
    • Authors: Jinyu Wang; Jie Xue, Zihe Yan, Sichun Zhang, Juan Qiao, Xinrong Zhang
      Abstract: Designing probes for real-time imaging of dynamic processes in living cells is a continuous challenge. Herein, a novel near-infrared (NIR) photoluminescence probe having a long lifetime was exploited for photoluminescence lifetime imaging (PLIM) using an iridium-alkyne complex. This probe offers the benefits of deep-red to NIR emission, a long Stokes shift, excellent cell penetration, low cytotoxicity, and good resistance to photobleaching. This example is the first PLIM probe applicable to the click reaction of copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) with remarkable lifetime shifts of 414 ns, before and after click reaction. The approach fully eliminates the background interference and distinguishes the reacted probes from the unreacted probes, thus enabling the wash-free imaging of the newly synthesized proteins within single living cells. Based on the unique properties of the iridium complexes, it is anticipated to have applications for imaging other processes within living cells.Pflegeleichte Bildgebung: Eine neuartige bioorthogonale Sonde, ein Ir-Alkin-Komplex, zeigt eine Emission vom tiefroten bis in den Nah-IR-Bereich und eine unerwartet große Lebensdauerdifferenz von 414 ns vor und nach der Klick-Reaktion. Die Sonde ermöglichte die aufreinigungsfreie Bildgebung neu synthetisierter Proteine in lebenden Zellen. NP=Nanopartikel.
      PubDate: 2017-10-13T06:16:29.144874-05:
      DOI: 10.1002/ange.201708566
       
  • Radical Heterocyclization and Heterocyclization Cascades Triggered by
           Electron Transfer to Amide-Type Carbonyl Compounds
    • Authors: Huan-Ming Huang; David J. Procter
      Abstract: Radical heterocyclizations triggered by electron transfer to amide-type carbonyls, using SmI2-H2O, provide straightforward access to bicyclic heterocyclic scaffolds containing bridgehead nitrogen centers. Furthermore, the first radical heterocyclization cascade triggered by reduction of amide-type carbonyls delivers novel, complex tetracyclic architectures containing five contiguous stereocenters with excellent diastereocontrol.Brückenkopf-Kommando: Radikalische Heterocyclisierungen und Heterocyclisierungskaskaden als Folge eines Elektronentransfers auf Amid-artige Carbonylverbindungen bieten direkten Zugang zu Molekülgerüsten mit Brückenkopf-Stickstoffatomen. Die radikalischen Cyclisierungskaskaden ergeben hoch diastereokontrolliert neuartige tetracyclische Architekturen mit fünf benachbarten Stereozentren.
      PubDate: 2017-10-13T06:16:00.302735-05:
      DOI: 10.1002/ange.201708354
       
  • Low-Temperature Reductive Aminolysis of Carbohydrates to Diamines and
           Aminoalcohols by Heterogeneous Catalysis
    • Authors: Michiel Pelckmans; Walter Vermandel, Frederik Van Waes, Kristof Moonen, Bert F. Sels
      Abstract: Short amines, such as ethanolamines and ethylenediamines, are important compounds in today's bulk and fine chemicals industry. Unfortunately, current industrial manufacture of these chemicals relies on fossil resources and requires rigorous safety measures when handling explosive or toxic intermediates. Inspired by the elegant working mechanism of aldolase enzymes, a novel heterogeneously catalyzed process—reductive aminolysis—was developed for the efficient production of short amines from carbohydrates at low temperature. High-value bio-based amines containing a bio-derived C2 carbon backbone were synthesized in one step with yields up to 87 C%, in the absence of a solvent and at a temperature below 405 K. A wide variety of available primary and secondary alkyl- and alkanolamines can be reacted with the carbohydrate to form the corresponding C2-diamine. The presented reductive aminolysis is therefore a promising strategy for sustainable synthesis of short, acyclic, bio-based amines.Aminreagentien befördern die Spaltung von C-C-Bindungen in der reduktiven Aminolyse von Kohlenhydraten. Kurze Diamine und Aminoalkohole werden bei tiefen Temperature in der Gegenwart von heterogenen Metallkatalysatoren gebildet.
      PubDate: 2017-10-13T06:15:44.228284-05:
      DOI: 10.1002/ange.201708216
       
  • Decatwistacene with a 170 Torsion
    • Authors: Wei Fan; Thorsten Winands, Nikos L. Doltsinis, Yan Li, Zhaohui Wang
      Abstract: Two different lengths of twistacenes, namely hexatwistacene and decatwistacene induced by the steric-hindrance effect between imide groups and neighbouring annulated benzene rings, were synthesized via bottom-up synthesis of palladium-catalyzed Suzuki cross-coupling and C-H activation reaction. Single-crystal X-ray analyses revealed that decatwistacene, which is the longest twistacene reported until now, exhibits an astonishing overall end-to-end torsion angle of about 170, the largest torsion angle reported so far. Both twistacenes have an enhanced solubility and stability with respect to light and oxygen due to their large twisting deformations together with much lower LUMO levels caused by the introduction of imide groups, opening a window to the narrowest chiral graphene nanoribbons with good stability and processability.
      PubDate: 2017-10-13T05:25:46.788698-05:
      DOI: 10.1002/ange.201709342
       
  • Theoretische Abhandlung über CH3NH3PbI3-Perowskit-Solarzellen
    • Authors: Sining Yun; Xiao Zhou, Jacky Even, Anders Hagfeldt
      Abstract: Hybrid-Halogenid-Perowskit-Solarzellen (PSCs) mit Wirkungsgraden über 22 % haben große Aufmerksamkeit auf sich gezogen. Trotz verstärkter Forschungen konnten die mit Perowskiten in PSCs zusammenhängenden grundlegenden Theorien aber noch nicht geklärt werden. In diesem Kurzaufsatz beurteilen wir die derzeitigen Erkenntnisse basierend auf “First-Principles”-Berechnungen zu Struktur, elektronischen Eigenschaften, Defekten, Ionendiffusion und Verschiebestrom von CH3NH3PbI3-Perowskit sowie auf dem Einfluss des Ionentransports auf die Hysterese der Strom-Spannungs-Kennlinie in PSCs. Der mit einer möglicherweise vorhandenen Ferroelektrizität verbundene Verschiebestrom wird ebenfalls diskutiert. Außerdem werden der derzeitige Wissensstand und einige offene Fragen hinsichtlich PSCs hervorgehoben, und die Vorteile, Herausforderungen und das Potenzial der Perowskit-Materialien werden betont.„First-Principles”-Berechnungen zu CH3NH3PbI3, die dessen Struktur, elektronische Eigenschaften, Defekte, Ionendiffusion und Verschiebestrom analysieren, können eine wertvolle Hilfe bei der Weiterentwicklung von Perowskit-Solarzellen (PSCs) sein.
      PubDate: 2017-10-13T04:31:11.000482-05:
      DOI: 10.1002/ange.201702660
       
  • Eine NMR-Methode zur Bestimmung der Bindungsreihenfolge supramolekularer
           Liganden an basische Reste in Proteinen
    • Authors: Anna Hogeweg; Andrea Sowislok, Thomas Schrader, Christine Beuck
      Abstract: Die Erkennung von Proteinoberflächen, die in Protein-Protein-Wechselwirkungen eine Rolle spielen, entwickelt sich zu einem Fokus der supramolekularen Chemie. NMR-Spektroskopie ist die Methode der Wahl, um Bindungsstellen von Liganden mittels Signalverschiebung und Linienverbreiterung zu identifizieren. Für große aromatische Liganden ist dies anhand klassischer NMR-Spektren oft jedoch nicht eindeutig möglich. Wir verwenden Lys- und Arg-spezifische H2(C)N-NMR-Experimente, um die Seitenkettenatome, die in engem Kontakt mit den Liganden stehen und für die die größten Änderungen in den NMR-Signalen zu erwarten sind, direkt zu beobachten. Dazu wurde die Bindung von Lys- und Arg-spezifischen supramolekularen Pinzetten und einem Calixaren an zwei Modellproteine untersucht. In den H2(C)N-Spektren sind Signale für die terminalen CH2-Gruppen aller Lys- und Arg-Reste sichtbar und anhand signifikanter Unterschiede in ihren Intensitäten oder Verschiebungen kann die Bindungsreihenfolge eines Liganden eindeutig identifiziert werden.Lysin- und Arginin-spezifische NMR-Experimente ermöglichen es, selektiv die Seitenkettenatome zu beobachten, die an der Bindung supramolekularer Liganden beteiligt sind, und offenbaren eine eindeutige Bindungsreihenfolge für mehrere Bindungsstellen auf einer Proteinoberfläche.
      PubDate: 2017-10-13T03:55:24.989516-05:
      DOI: 10.1002/ange.201707950
       
  • Flexible Viologen-Based Porous Framework Showing X-ray Induced
           Photochromism with Single-Crystal-to-Single-Crystal Transformation
    • Authors: Cheng Chen; Jian-Ke Sun, Ya-Jun Zhang, Xiao-Dong Yang, Jie Zhang
      Abstract: A viologen-based Borromean entangled porous framework was found to be sensitive to both CuKα and MoKα X-ray sources, showing rapid photochromic response and recovery within one minute. The X-ray-induced photochromic process is accompanied by a reversible single-crystal-to-single-crystal (SC-SC) structural transformation, an unprecedented phenomenon for X-ray sensitive materials. The complex can be further processed into portable thin films for detecting the dose of the X-ray exposure. Moreover, the photochromism can occur over a broad temperature range of 100–333 K, both in the form of single crystals and thin films, making it a potential candidate for practical indoor and outdoor applications.Ein verzahntes poröses Gerüst auf Viologen-Basis zeigt unter Röntgen-Bestrahlung eine schnelle photochrome Reaktion und Erholung. Dieser Prozess geht mit einer reversiblen Einkristall-Einkristall-Umwandlung einher. Das Material lässt sich zu dünnen Filmen für die Messung von Röntgen-Strahlungsdosen verarbeiten.
      PubDate: 2017-10-13T01:15:46.91947-05:0
      DOI: 10.1002/ange.201707290
       
  • Improved Biocompatibility of Black Phosphorus Nanosheets by Chemical
           Modification
    • Authors: Guangbo Qu; Wei Liu, Yuetao Zhao, Jie Gao, Tian Xia, Jianbo Shi, Ligang Hu, Wenhua Zhou, Jiejun Gao, Huaiyu Wang, Qian Luo, Qunfang Zhou, Sijin Liu, Xue-Feng Yu, Guibin Jiang
      Abstract: Nanoschichten aus schwarzem Phosphor (BPs) können Entzündungen auslösen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201706228) berichten X.-F. Yu, G. Jiang et al. über die Reduzierung dieses Effekts durch Titansulfat-Modifizierung der BPs (TiL4@BPs). Am Beispiel des Mädchens sind verschiedene abträgliche Effekte bei einer breiten Anwendung von reinen BPs in roter Schattierung dargestellt. Durch Umwandlung in TiL4@BPs werden die BPs weniger schädlich.
      PubDate: 2017-10-13T01:15:22.597648-05:
       
  • Charakterisierung von Wasserstoffbrücken zwischen Ionen in protischen
           ionischen Flüssigkeiten mittels
           NMR-Deuteron-Quadrupol-Kopplungskonstanten – Unterschiede zu H-Brücken
           in Amiden, Peptiden und Proteinen
    • Authors: Alexander E. Khudozhitkov; Peter Stange, Benjamin Golub, Dietmar Paschek, Alexander G. Stepanov, Daniil I. Kolokolov, Ralf Ludwig
      Abstract: Wasserstoffbrücken zwischen Ionen wurden anhand der Messung von Deuteron-Quadrupol-Kopplungskonstanten (DQCCs) für protische ionische Flüssigkeiten (PILs) mit Festkörper-NMR-Spektroskopie charakterisiert. In ihrer Zuschrift (
      DOI : 10.1002/ange.201708340) identifizieren D. I. Kolokolov, R. Ludwig et al. diesen NMR-Parameter als einen empfindlichen Indikator für die doppelt ionischen Wasserstoffbrücken in PILs. Die Illustration zeigt die NMR-Spektren als Brücken zwischen den entgegengesetzt geladenen Ionen und als Übergang zur skizzierten Gebirgslandschaft im Bildhintergrund.
      PubDate: 2017-10-13T01:15:20.051139-05:
       
  • Das Aufrollen von Oligophenylenen zu Nanographenen durch einen
           HF-Reißverschluss
    • Authors: Ann-Kristin Steiner; Konstantin Y. Amsharov
      Abstract: Die intramolekulare Aryl-Aryl-Kupplung ist die Schlüsselumwandlung in der rationalen Synthese von Nanographenen und Nanobändern. In dieser Hinsicht erwies sich die C-F-Bindungsaktivierung als eine vielseitige Alternative, die die Synthese mehrerer einzigartiger Kohlenstoff-basierter Nanostrukturen ermöglicht. Hier beschreiben wir eine beispiellos anspruchsvolle Transformation, die zeigt, dass die C-F-Bindungsaktivierung durch Aluminiumoxid eine hochwirksame Domino-C-C-Bindungsbildung ermöglicht. Trotz der flexiblen Struktur der Oligophenylen-basierten Vorstufen gelingt ein effizienter regioselektiver Aufbau der Zielstrukturen. Die Fluorpositionen in der Vorstufe geben eindeutig das “Reißverschluss-Programm” vor, welches zu einem Aufrollen von linearen Oligophenylenketten um einen Phenylrest führt und die gewünschten Nanographene ergibt. Das hoch effiziente Verfahren ist attraktiv für die Synthese nichtsubstituierter Nanographenen, die durch alternative Methoden in reiner Form schwer zugänglich sind.Eine anspruchsvolle Transformation besteht in der programmierten Umwandlung von nahezu linearen fluorierten Oligophenylenen zu Nanographenen durch effektive Domino-Aryl-Aryl-Kupplung. Fluorsubstituenten in der Vorstufe geben die Bahn des „H-F-Reißverschlusses” eindeutig vor, der zur Bildung einer Nanographen-Zielstruktur führt.
      PubDate: 2017-10-13T01:10:38.24962-05:0
      DOI: 10.1002/ange.201707272
       
  • Adenylation Activity of Carboxylic Acid Reductases Enables the Synthesis
           of Amides
    • Authors: Alexander J. L. Wood; Nicholas J. Weise, Joseph D. Frampton, Mark S. Dunstan, Michael A. Hollas, Sasha R. Derrington, Richard C. Lloyd, Daniela Quaglia, Fabio Parmeggiani, David Leys, Nicholas J. Turner, Sabine L. Flitsch
      Abstract: Carboxylic acid reductases (CARs) catalyze the reduction of a broad range of carboxylic acids to aldehydes using the cofactors adenosine triphosphate and nicotinamide adenine dinucleotide phosphate, and have become attractive biocatalysts for organic synthesis. Mechanistic understanding of CARs was used to expand reaction scope, generating biocatalysts for amide bond formation from carboxylic acid and amine. CARs demonstrated amidation activity for various acids and amines. Optimization of reaction conditions, with respect to pH and temperature, allowed for the synthesis of the anticonvulsant ilepcimide with up to 96 % conversion. Mechanistic studies using site-directed mutagenesis suggest that, following initial enzymatic adenylation of substrates, amidation of the carboxylic acid proceeds by direct reaction of the acyl adenylate with amine nucleophiles.CARpe diem: Carbonsäure-Reduktasen können als Biokatalysatoren für die Aktivierung und nachfolgende Amidierung einer Reihe von Carbonsäuren mit primären und sekundären Aminen sowie Ammoniak verwendet werden. Die Enzyme fanden Anwendung für die Herstellung von Ilepcimid, einem krampflösenden Mittel. ATP=Adenosintriphosphat, NADPH=Nicotinamid-Adenin-Dinucleotid-Phosphat.
      PubDate: 2017-10-13T00:15:50.577269-05:
      DOI: 10.1002/ange.201707918
       
  • A Strategy for Specific Fluorescence Imaging of Monoamine Oxidase A in
           Living Cells
    • Authors: Huimin Ma; Xiaofeng Wu, Wen Shi, Xiaohua Li
      Abstract: Monoamine oxidase (MAO) has two isoforms, MAO-A and MAO-B, which show different functions and thus selective fluorescence imaging of which is important for biological studies. Currently, however, specific detection of MAO-A remains a great challenge. Herein, we report a new strategy for specific imaging of MAO-A via designing fluorescent probes by combining the characteristic structure of the enzymatic inhibitor with propylamine as a recognition moiety. The high specificity of our representative probe is demonstrated by imaging MAO-A in different live cells such as SH-SY5Y (high level of MAO-A) and HepG2 (high level of MAO-B), as further validated by both control probe and western blot analyses. The superior specificity of the probe may benefit the accurate detection of MAO-A in complex biosystems. Importantly, in this work the use of the characteristic structure of an inhibitor may serve as a general strategy to design a specific recognition moiety of fluorescent probes for an enzyme.
      PubDate: 2017-10-12T21:30:31.09911-05:0
      DOI: 10.1002/ange.201708428
       
  • Feedback kinetics in mechanochemistry; the importance of cohesive states
    • Authors: Stuart Lloyd James; Ben Hutchings, Peijun Hu, Lei Gao, Deborah Elizabeth Crawford
      Abstract: Abstract: Although mechanochemical synthesis is becoming more widely applied and even commercialised, greater basic understanding is needed if the field is to progress on less of a trial-and-error basis. We report that a mechanochemical reaction in a ball mill exhibits unusual sigmoidal feedback kinetics that differ dramatically from the simple first-order kinetics for the same reaction in solution. An induction period followed by a rapid increase in reaction rate before the rate decreases again as the reaction goes to completion. The origin of these unusual kinetics is found to be a feedback cycle involving both chemical and mechanical factors. During the reaction the physical form of the reaction mixture changes from a powder to a cohesive rubber-like state, and this results in the observed reaction rate increase. The study reveals that non-obvious and dynamic rheological changes in the reaction mixture must be appreciated to understand how mechanochemical reactions progress.
      PubDate: 2017-10-12T14:32:01.124703-05:
      DOI: 10.1002/ange.201706723
       
  • Diastereoselective C-H bond amination for disubstituted pyrrolidines
    • Authors: Theodore Alexander Betley; Diana A Iovan, Matthew J. T. Wilding, Elisabeth T. Hennessy, Yunjung Baek
      Abstract: We report herein on the improved diastereoselective synthesis of 2,5-disubstituted pyrrolidines from aliphatic azides. Experimental and theoretical studies of the C-H amination reaction mediated by the iron dipyrrinato complex (AdL)FeCl(OEt2) provided a model for diastereoinduction and allowed for systematic variation of the catalyst to enhance selectivity. Among the iron alkoxide and aryloxide catalysts evaluated, the iron-phenoxide complex exhibited superior performance towards the generation of syn 2,5-disubstituted pyrrolidines with high diastereoselectivity.
      PubDate: 2017-10-12T13:25:32.928158-05:
      DOI: 10.1002/ange.201708519
       
  • Biocatalytic Routes to Enantiomerically Enriched Dibenz[c,e]azepines
    • Authors: Scott P France; Godwin A Aleku, Mahima Sharma, Juan Mangas-Sanchez, Roger M Howard, Jeremy Steflik, Rajesh Kumar, Ralph W Adams, Iustina Slabu, Robert Crook, Gideon Grogan, Timothy W Wallace, Nicholas John Turner
      Abstract: Biocatalytic retrosynthetic analysis of dibenz[c,e]azepines has highlighted the use of imine reductase (IRED) and w-transaminase (w-TA) biocatalysts to establish the key stereocentres of these molecules. Several enantiocomplementary IREDs were identified for the synthesis of (R)- and (S)-5-methyl-6,7-dihydro-5H-dibenz[c,e]azepine with excellent enantioselectivity by reduction of the parent imines. Crystallographic evidence suggests that IREDs may be able to bind one conformer of the imine substrate such that, upon reduction, the major product conformer is generated directly. ω-TA biocatalysts were also successfully employed for the production of enantiopure 1-(2-bromophenyl)ethan-1-amine enabling an orthogonal route for the installation of chirality into dibenz[c,e]azepine frameworks.
      PubDate: 2017-10-12T08:25:44.850462-05:
      DOI: 10.1002/ange.201708453
       
  • Enzyme Encapsulation by a Ferritin Cage
    • Authors: Stephan Tetter; Donald Hilvert
      Abstract: Ferritins, conserved across all kingdoms of life, are protein nanocages that evolved to mineralize iron. The last several decades have shown that these cages have considerable technological and medical potential owing to their stability and tolerance to modification, as well as their ability to template nanoparticle synthesis and incorporate small molecules. Here we show that it is possible to encapsulate proteins in a ferritin cage by exploiting electrostatic interactions with its negatively charged interior. Positively supercharged green fluorescent protein is efficiently taken up by Archaeoglobus fulgidus ferritin in a tunable fashion. Moreover, several enzymes were readily incorporated when genetically tethered to this fluorescent protein. These fusion proteins retained high catalytic activity and showed increased tolerance to proteolysis and heat. Equipping ferritins with enzymatic activity paves the way for many new nanotechnological and pharmacological applications.Aktives Innenleben: Der natürliche Nanokäfig Ferritin aus Archaeoglobus fulgidus verkapselt positiv geladene Proteine (grün) mithilfe elektrostatischer Wechselwirkungen. Enzyme (grau), die an solche geladenen Gastspezies gebunden sind, behalten ihre Aktivität bei [Substrat (S)Produkt (P)] und verleihen dem Ferritin dadurch neue katalytische Funktionen, die nanotechnologisch oder pharmakologisch nutzbar sein könnten.
      PubDate: 2017-10-12T08:15:38.305466-05:
      DOI: 10.1002/ange.201708530
       
  • C-H Functionalization for Hydrogen Isotope Exchange
    • Authors: Jens Atzrodt; Volker Derdau, William John Kerr, Marc Reid
      Abstract: The varied applications of hydrogen isotopes (deuterium, D, and tritium, T) in the physical and life sciences demands a range of methods for their installation in an array of molecular architectures. In this review, we describe recent advances in synthetic C-H functionalization for hydrogen isotope exchange.
      PubDate: 2017-10-12T06:55:26.496127-05:
      DOI: 10.1002/ange.201708903
       
  • Gold-Katalyse für die Heterocyclenchemie: eine repräsentative Fallstudie
           zu Naturstoffen der Pyron-Reihe
    • Authors: Alois Fürstner
      Abstract: 2-Pyrone und 4-Pyrone finden sich als Strukturmotiv in vielen biologisch aktiven Naturstoffen. Allerdings erweisen sich traditionelle Synthesemethoden für dieses heterocyclische Ringsystem, die den biosynthetischen Weg der Cyclisierung von 1,3,5-Tricarbonyl-Vorstufen nachstellen, häufig als zu harsch und daher wenig geeignet für die Herstellung hoch funktionalisierter und/oder empfindlicher Zielmoleküle dieses Typs. Dagegen eignet sich die π-Säure-Katalyse hervorragend zur systematischen Erkundung des von Pyronen definierten Strukturraums. Dazu macht man sich die synthetische Äquivalenz von Carbonylverbindungen und Alkinen zunutze, die auf Grund der hohen Carbophilie von [LAu]+-Fragmenten unter außerordentlich milden Bedingungen aktiviert werden können; Angriff einer geeignet positionierten Estergruppe auf den primär gebildeten Alkin-Gold-Komplex führt zur Pyronbildung, wobei der regioselektive Verlauf verlässlich vorprogrammiert werden kann.Pars pro toto: Eine auf konsequentem Einsatz von π-Säuren als Katalysatoren beruhende moderne Heterocyclenchemie weist viele Vorzüge auf, die exemplarisch anhand der Totalsynthese von Pyron-Naturstoffen vorgestellt werden. In konzeptueller Hinsicht ist diese Methodik vielfach komplementär zu traditionellen Vorgehensweisen und überzeugt durch ihre Leistungsfähigkeit sowie Toleranz gegenüber funktionellen Gruppen.
      PubDate: 2017-10-12T06:21:26.121632-05:
      DOI: 10.1002/ange.201707260
       
  • Direct Observation of Hemithioindigo-Motor Unidirectionality
    • Authors: Ludwig Alexander Huber; Kerstin Hoffmann, Stefan Thumser, Niklas Böcher, Peter Mayer, Henry Dube
      Abstract: Hemithioindigo molecular motors undergo very fast unidirectional rotation upon irradiation with visible light, which has prevented a complete analysis of their working mechanism. In this work, we have considerably slowed down their motion by using a new synthesis for sterically hindered motor derivatives. This method allowed the first observation of all four intermediate states populated during rotation. The exact order in which each isomeric state is formed under irradiation conditions was elucidated using low temperature 1H NMR spectroscopy in conjunction with other analytical methods. At the same time, complete unidirectionality could also be directly shown. Access to slowly rotating hemithioindigo motors opens up a plethora of new applications for visible-light-induced unidirectional motions, especially in areas such as catalysis, smart materials, and supramolecular chemistry.Rotation ist eine Einbahnstraße: Mithilfe einer neuen Methode zur Synthese sterisch gehinderter, Hemithioindigo-basierter molekularer Motoren wurden erstmals der vollständige Rotationszyklus und seine völlige Unidirektionalität experimentell aufgezeigt. Das Verfahren ermöglicht die zuverlässige Synthese substituierter Hemithioindigo-Motoren für fortgeschrittene molekulare Maschinen.
      PubDate: 2017-10-12T06:20:57.692529-05:
      DOI: 10.1002/ange.201708178
       
  • Lanthanide-Coordinated Semiconducting Polymer Dots Used for Flow Cytometry
           and Mass Cytometry
    • Authors: Xu Wu; Quinn DeGottardi, I-Che Wu, Jiangbo Yu, Li Wu, Fangmao Ye, Chun-Ting Kuo, William W. Kwok, Daniel T. Chiu
      Abstract: Simultaneous monitoring of biomarkers as well as single-cell analyses based on flow cytometry and mass cytometry are important for investigations of disease mechanisms, drug discovery, and signaling-network studies. Flow cytometry and mass cytometry are complementary to each other; however, probes that can satisfy all the requirements for these two advanced technologies are limited. In this study, we report a probe of lanthanide-coordinated semiconducting polymer dots (Pdots), which possess fluorescence and mass signals. We demonstrated the usage of this dual-functionality probe for both flow cytometry and mass cytometry in a mimetic cell mixture and human peripheral blood mononuclear cells as model systems. The probes not only offer high fluorescence signal for use in flow cytometry, but also show better performance in mass cytometry than the commercially available counterparts.Lanthanoid-koordinierte, halbleitende Polymernanopartikel mit starker Fluoreszenz zeigen hervorragende Leistungen in der Durchfluss- und Massenzytometrie bei Zellanalysen.
      PubDate: 2017-10-12T06:20:35.314438-05:
      DOI: 10.1002/ange.201708463
       
  • Far-UV-Excited Luminescence of Nitrogen-Vacancy Centers: Evidence for
           Diamonds in Space
    • Authors: Hsiao-Chi Lu; Yu-Chain Peng, Sheng-Lung Chou, Jen-Iu Lo, Bing-Ming Cheng, Huan-Cheng Chang
      Abstract: The nitrogen-vacancy (NV) centers in diamond are among the most thoroughly investigated defects in solid-state matter; however, our understanding of their properties upon far-UV excitation of the host matrix is limited. This knowledge is crucial for the identification of NV as the carrier of extended red emission (ERE) bands detected in a wide range of astrophysical environments. Herein, we report a study on the photoluminescence spectra of NV-containing nanodiamonds excited with synchrotron radiation over the wavelength range of 125–350 nm. We observed, for the first time, an emission at 520–850 nm with a quantum yield greater than 20 %. Our results share multiple similarities with the ERE phenomena, suggesting that nanodiamonds are a common component of dust in space.Nach Anregung mit Fern-UV-Licht können Stickstoff-Fehlstellenzentren in Diamanten bei Wellenlängen von 520 bis 850 nm mit Quantenausbeuten über 20 % fluoreszieren. Ähnlichkeiten mit der erweiterten roten Emission des interstellaren Mediums deuten darauf hin, dass Nanodiamanten eine wichtige Komponente des kosmischen Staubs sind.
      PubDate: 2017-10-12T06:15:27.315807-05:
      DOI: 10.1002/ange.201707389
       
  • Visible light-driven and Iron-promoted Thiocarboxylation of Styrenes and
           Acrylates with CO2
    • Authors: Jian-Heng Ye; Meng Miao, He Huang, Si-Shun Yan, Zhu-Bao Yin, Wen-Jun Zhou, Da-Gang Yu
      Abstract: The first thiocarboxylation of styrenes and acrylates with CO2 is realized by using visible light as a driving force and catalytic iron salts as promoters. A variety of important β-thioacids are obtained in high yields. This multicomponent reaction proceeds in an atom- and redox-economical way with broad substrate scope under mild reaction conditions. Notably, high regio-, chemo- and diastero-selectivity are observed. Mechanistic studies indicate that a radical pathway can account for the unusual regioselectivity.
      PubDate: 2017-10-12T05:30:41.342254-05:
      DOI: 10.1002/ange.201707862
       
  • Verringerung der Virulenz von multiresistentem Staphylococcus aureus
           mithilfe eines chemischen Disruptors des ClpX-Chaperon-Komplexes
    • Authors: Christian Fetzer; Vadim S. Korotkov, Robert Thänert, Kyu Myung Lee, Martin Neuenschwander, Jens Peter von Kries, Eva Medina, Stephan A. Sieber
      Abstract: Die ClpXP-Protease von Staphylococcus aureus ist ein wichtiger Regulator der Zellhomöostase und Virulenz. Mithilfe eines Hochdurchsatz-Screenings gegen den ClpXP-Komplex wurde ein spezifischer Inhibitor des ClpX-Chaperons identifiziert, der den oligomeren Zustand zerstört. Die Synthese von 34 Derivaten offenbarte, dass das molekulare Grundgerüst nur eingeschränkte Veränderungen ermöglicht und nur geringe Änderungen toleriert werden. Eine Analyse der aktivsten Verbindungen zeigte eine starke Verringerung der Toxinproduktion von S. aureus, die durch eine maßgeschneiderte, MS-basierte Assayplattform quantifiziert wurde. Transkriptom- und Gesamtproteomstudien bestätigten die globale Virulenzreduktion und enthüllten eine charakteristische Signatur der Proteinexpression in mit Substanz behandelten Zellen. Obwohl diese Signatur teilweise mit dem Muster der ClpX-Deletionszellen übereinstimmte, wurde eine weitere Verringerung der Toxine beobachtet, was zu der vielversprechenden Möglichkeit führt, dass weitere Virulenzpfade direkt oder indirekt von der niedermolekularen Verbindung adressiert werden könnten.Ein Hochdurchsatz-Screening gegen die ClpXP-Protease enthüllte die ersten nicht-kovalenten Inhibitoren des ClpX-Chaperons. Bindung des Inhibitors induziert die Zerstörung des ClpX-Hexamers und sogar des kompletten proteolytischen ClpXP-Komplexes. Behandlung von Staphylococcus aureus mit den Verbindungen führt zu einer globalen Herunterregulation einer Vielzahl sekretierter Virulenzfaktoren.
      PubDate: 2017-10-12T04:26:42.81099-05:0
      DOI: 10.1002/ange.201708454
       
  • A Space-Charge Treatment of the Increased Concentration of Reactive
           Species at the Surface of a Ceria Solid Solution
    • Authors: Alexander F. Zurhelle; Xiaorui Tong, Andreas Klein, David S. Mebane, Roger A. De Souza
      Abstract: A space-charge theory applicable to concentrated solid solutions (Poisson–Cahn theory) was applied to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce3+ (the reactive species) at the surface of the oxide catalyst Ce0.8Sm0.2O1.9. In contrast to previous theoretical treatments, these calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone. The high space-charge potential that develops at the surface (>0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space-charge layer. This approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts.Eine Poisson-Cahn-Analyse erklärt das experimentell beobachtete komplexe Verhalten von [Ce3+] auf der Oberfläche des Ceroxid-basierten Katalysators Ce0.8Sm0.2O1.9. Sogar auf der Oberfläche einer derart hoch konzentrierten festen Lösung wird das Prinzip der lokalen Ladungsneutralität verletzt, mit Bildung einer positiv geladenen Oberfläche und einer ausgedehnten negativen Raumladungszone.
      PubDate: 2017-10-12T04:26:11.20704-05:0
      DOI: 10.1002/ange.201708118
       
  • Ligand and Solvent Controlled Regio- and Chemo-divergent Carbonylative
           Reactions
    • Authors: Xiao-Feng Wu; Jin-Bao Peng
      Abstract: The development of high selective procedures is one of the core goals in organic chemistry, and the target which generations of chemists are pursuing. Among the known organic transformations, carbonylation reactions present an ideal choice for carbonyl-containing compounds preparation. In this review, the recent achievements on selectivity controlled carbonylation reactions have been summarized. The effects of ligands, solvents and bases on the selectivity have been discussed.
      PubDate: 2017-10-12T04:25:20.687871-05:
      DOI: 10.1002/ange.201709807
       
  • A Zwitterionic, 10 π Aromatic Hemisphere
    • Authors: Nema Hafezi; Wondimagegn T. Shewa, James C. Fettinger, Mark Mascal
      Abstract: A new concept in anionic 10 π aromaticity is described by the embedding of a compensating charge within an aromatic cyclononatetraenide ring by the symmetric superposition of an alkyl ammonium bridge. This is accomplished by the methylation of azatriquinacene to give a quaternary ammonium salt, followed by oxidation to the tetraene and final deprotonation. The resulting zwitterion is a stable [9]annulene with strong aromaticity as shown by its degree of C−C bond equalization and a nucleus-independent chemical shift value lower than that of benzene. The solid-state structure shows an eclipsed stacking motif with the electron-poor ammonium methyl groups occupying the electron-rich cavity of the aromatic bowl.Gegensätze ziehen sich mehr als nur an: Ein Ammoniumzentrum wird über einem anionischen 10π-Kohlenstoff-Toroid platziert, wodurch ein neuartiges, symmetrisches, schalenförmiges, stark aromatisches System entsteht, das, obwohl es zwitterionisch ist, in Kohlenwasserstoffen löslich ist. Interner Ladungsausgleich resultiert in einer ungewöhnlichen Stabilität für ein anionisches Annulen.
      PubDate: 2017-10-12T04:20:43.012718-05:
      DOI: 10.1002/ange.201708521
       
  • Unprecedented Sensitivity in a Probe for Detection and Imaging of
           Cathepsin B: Chemiluminescence Microscopy Cell Images of
           Natively-Expressed Enzyme
    • Authors: Doron Shabat; Michal Roth-Konforti, Christoph Bauer
      Abstract: Until recently, chemiluminescence cell images could be obtained only using luciferase-activated probes. Moreover, chemiluminescence microscopy cell-imaging was never demonstrated for natively expressed enzymes like cathepsin B. Here we describe the design synthesis and evaluation of the first chemiluminescence probe for detection and imaging of cathepsin B. The probe activation mechanism relies on the release of a dioxetane intermediate, which undergoes chemiexcitation to emit green light with high efficiency under physiological conditions. Using the probe, we obtained clear images of cancerous leukemia and colon cells. This is the first demonstration of chemiluminescence cell images obtained by a probe for a natively-expressed endogenous enzyme. We anticipate that the concept presented in this study will be broadly used to develop analogous probes for other important proteases relevant to biomolecular processes.
      PubDate: 2017-10-11T20:55:58.39393-05:0
      DOI: 10.1002/ange.201709347
       
  • Lanthanide-based T2ex and CEST complexes provide new insights into the
           design of pH sensitive MRI agents
    • Authors: Lei Zhang; Andre F. Martins, Piyu Zhao, Yunkou Wu, Gyula Tircso, Dean Sherry
      Abstract: A series of Eu3+ and Dy3+ DOTA-tetraamide complexes with four appended primary amine groups were prepared and their CEST and T1/T2 relaxation properties measured as a function of pH. The CEST signals in the Eu3+ complexes show a surprisingly strong CEST signal after the pH was reduced from 8 to 5. The opposite trend was observed for the Dy3+ complexes where the r2ex of bulk water protons increased dramatically from ~1.5 mM-1s-1 to ~13 mM-1s-1, while r1 remained unchanged. A fit of the CEST data (Eu3+ complexes) to Bloch theory and the T2 data (Dy3+ complexes) to Swift-Connick theory provided the proton exchange rates as a function of pH. These data showed that the four amine groups contribute significantly to proton catalyzed exchange of the Ln3+-bound water protons even though their pka's are much higher than the observed CEST or T2ex effects. This demonstrated the utility of using appended acidic/basic groups to catalyze prototropic exchange for imaging tissue pH by MRI.
      PubDate: 2017-10-11T14:25:26.073376-05:
      DOI: 10.1002/ange.201707959
       
  • Sequence Mandated, Distinct Assembly of Giant Molecules
    • Authors: Wei Zhang; Xinlin Lu, Jialin Mao, Chih-Hao Hsu, Gaoyan Mu, Mingjun Huang, Qingyun Guo, Hao Liu, Chrys Wesdemiotis, Tao Li, Wen-Bin Zhang, Yiwen Li, Stephen Z. D. Cheng
      Abstract: Although controlling primary structures is by itself an enormous challenge for synthetic polymers, the potential of sequence control for tailoring hierarchical structures remains to be exploited, especially in the creation of new and unconventional phases. Herein, we design a series of model amphiphilic chain-like giant molecules by connecting both hydrophobic and hydrophilic molecular nanoparticles in precisely defined sequence and composition to investigate their intriguing sequence-dependent phase structures. Not only has composition changed the self-assembled phases, but also specific sequences are found to induce unconventional phase formation, including Frank-Kasper phases. The formation mechanism has been attributed to the conformational change driven by the collective hydrogen bonding and the sequence-mandated topology of the molecules. These results support that sequence-control in synthetic polymers can have dramatic impacts on the polymer properties and self-assembly.
      PubDate: 2017-10-11T13:55:24.579303-05:
      DOI: 10.1002/ange.201709354
       
  • Double Catalytic Kinetic Resolution (DoCKR) of Acyclic anti-1,3-Diols
           using Additive Horeau Amplification
    • Authors: Cyril Bressy; Jérémy Merad, Prashant Borkar, Frédéric Caijo, Jean-Marc Pons, Jean-Luc Parrain, Olivier Chuzel
      Abstract: The concept of synergistic double catalytic kinetic resolution (DoCKR) described in this article, was successfully applied to racemic acyclic anti-1,3-diols, a common motif in natural products. This process takes advantage of an additive Horeau amplification involving two successive enantioselective organocatalytic acylations reactions, and leading to diesters and recovered diols with high enantiopurities. It was first developed with C2-symmetrical diols and then further extended to non-C2-symmetrical anti diols to prepare useful chiral building blocks. The protocol is highly practical as it only requires 1 mol% of a commercially available organocatalyst and leads to easily separable products. This procedure was applied to the shortest reported total synthesis of (+)-cryptocaryalactone, a natural product with anti-germinative activity.
      PubDate: 2017-10-11T10:55:55.667053-05:
      DOI: 10.1002/ange.201709844
       
  • Detailed Evidence for an Unparalleled Interaction Mode between Calmodulin
           and Orai Proteins
    • Authors: Lukas Traxler; Petr Rathner, Marc Fahrner, Michael Stadlbauer, Felix Faschinger, Tatsiana Charnavets, Norbert Müller, Christoph Romanin, Peter Hinterdorfer, Hermann J. Gruber
      Abstract: Calmodulin (CaM) binds most of its targets by wrappingaround an amphipathic α-helix. The N-terminus of Orai proteins contains a conserved CaM-binding segment but the binding mechanism is only partially characterized. Here, microscale thermophoresis (MST), surface plasmon resonance (SPR), andatomic force microscopy (AFM) were employed to study the binding equilibria, the kinetics, and the single-molecular interaction forces involved in the binding of CaM to the conserved helical segments of Orai1 and Orai3. The results consistently indicated step-wise binding of two separate target peptides to the two lobes of CaM. An unparalleled high affinity was found when two Orai peptides were dimerized or immobilized at high lateral density, thereby mimicking the close proximity of the N-termini in native Orai oligomers. The analogous experiments with smooth muscle myosin light chain kinase (smMLCK) showed only the expected 1:1 binding, confirming the validity of our methods.
      PubDate: 2017-10-11T09:56:24.182504-05:
      DOI: 10.1002/ange.201708667
       
  • Total Synthesis of Lycoricidine and Narciclasine via Chemical
           Dearomatization of Bromobenzene
    • Authors: Emma Southgate; Daniel Holycross, David Sarlah
      Abstract: The total synthesis of lycoricidine and narciclasine is enabled by the use of arenophile-mediated dearomative dihydroxylation of bromobenzene. Subsequent transpositive Suzuki coupling and cycloreversion deliver a key biaryl dihydrodiol intermediate, which is rapidly converted to lycoricidine through site-selective syn-1,4-hydroxyamination and deprotection. The total synthesis of narciclasine is accomplished via a late stage, amide-directed C-H hydroxylation of a lycoricidine intermediate. Moreover, the general applicability of this strategy to access dihydroxylated biphenyls has been demonstrated with several examples.
      PubDate: 2017-10-11T09:55:41.944454-05:
      DOI: 10.1002/ange.201709712
       
  • Mass-production of Mesoporous MnCo2O4 Spinel with MnIV- and CoII-rich
           Surface for Superior Bifunctional Oxygen Electrocatalysis
    • Authors: Wenhai Wang; Long Kuai, Wei Cao, Marko Huttula, Sami Ollikkala, Taru Ahopelto, Ari-Pekka Honkanen, Simo Huotari, Mengkang Yu, Baoyou Geng
      Abstract: A mesoporous MnCo2O4 electrode materials is successfully fabricated for bifunctional oxygen electrocatalysis. The MnCo2O4 exhibits both Co3O4-like activity for oxygen evolution reaction (OER) and Mn2O3-approaching performance for oxygen reduction reaction (ORR). The potential difference between ORR metric and OER metric of MnCo2O4 is as low as 0.84 V. By XANES and XPS investigation, the notable activity is resulted from the preferred MnIV- and CoII-rich surface. Valuably, the products can be obtained in large-scale with the precise chemical components at relatively low temperature. The surface state engineering maybe open a new avenue to optimize electrocatalysis performance of electrode materials. The prominent bifunctional activity shows that MnCo2O4 has the possibility of being used in metal-air batteries and/or other energy devices.
      PubDate: 2017-10-11T08:57:37.120028-05:
      DOI: 10.1002/ange.201708765
       
  • CODH-IV: A novel high efficiency CO-scavenging CO dehydrogenase with
           increased resistance to O2
    • Authors: Lilith Domnik; Meriem Merrouch, Sebastian Goetzl, Jae-Hun Jeoung, Christophe Leger, Sebastien Dementin, Vincent Fourmond, Holger Dobbek
      Abstract: CO dehydrogenases (CODHs) catalyse the reversible conversion between CO and CO2. Genomic analysis indicated that the metabolic functions of CODHs vary. The genome of Carboxydothermus hydrogenoformans encodes five CODHs (CODH-I - V), of which CODH-IV is found in a gene cluster near a peroxide reducing enzyme. Our kinetic and crystallographic experiments reveal that CODH-IV differs from other CODHs by characteristic properties: it has a very high affinity for CO, oxidizes CO at diffusion-limited rate over a wide range of temperatures, and is more tolerant to oxygen than CODH-II. Thus, our observations support the idea that CODH-IV is a CO scavenger in defence against oxidative stress and highlight that CODHs are more diverse in terms of reactivity than expected.
      PubDate: 2017-10-11T08:57:25.415899-05:
      DOI: 10.1002/ange.201709261
       
  • A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic
           Acids and Esters
    • Authors: Fabio Lima; Upendra K Sharma, Lars Grunenberg, Debasmita Saha, Sandra Johannsen, Joerg Sedelmeier, Erik V Van der Eycken, Steven Victor Ley
      Abstract: We report herein the use of a dual catalytic system comprising of a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine combined with a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react via radical addition with electron-deficient olefins to efficiently form C-C coupled products in a redox neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either boronic esters or the trimeric form of the boronic acids (boroxines) in solution.
      PubDate: 2017-10-11T08:56:12.135719-05:
      DOI: 10.1002/ange.201709690
       
  • Selective Radical Fluorination of Tertiary Alkyl Halides at Room
           Temperature
    • Authors: He Chen; Zhonglin Liu, Ying Lv, Xinqiang Tan, Haigen Shen, Hai-Zhu Yu, Chaozhong Li
      Abstract: Direct fluorination of tertiary alkyl bromides and iodides with Selectfluor reagent is described. The halogen-exchange fluorination proceeds efficiently in acetonitrile at room temperature under metal-free conditions and exhibits a wide range of functional group compatibility. Furthermore, the reactions are highly selective in that alkyl chlorides and primary and secondary alkyl bromides remain intact. A radical mechanism is proposed for this selective fluorination.
      PubDate: 2017-10-11T08:25:58.719368-05:
      DOI: 10.1002/ange.201708197
       
  • Non-Uniform Optical Inscription of Actuation Domains in a Liquid Crystal
           Polymer of Uniaxial Orientation: An Approach to Complex and Programmable
           Shape Changes
    • Authors: Rong Yang; Yue Zhao
      Abstract: Achieving complex shape change of liquid-crystal polymer networks (LCNs) under stimulation generally requires spatial configuration of the orientation direction, that is, patterned directors, of liquid crystal monomers prior to polymerization by means of treated surfaces. A strategy is demonstrated that needs only the simple uniaxial orientation of mesogens (monodomain) induced by mechanical stretching of LCNs. Using a rationally designed liquid crystal polymer, photocrosslinking is utilized to pattern or spatially organize the actuating monodomains in order to generate a differential contractile and/or extensional force field required for targeted shape change. Moreover, the approach enables versatile actuation modes and allows multiple shape changes to be programmed on a single piece of the polymer. This important feature is demonstrated with a specimen cut to have eight strips that, upon thermal stimulation, simultaneously display eight types of shape morphing.Variable Form: Leicht zu bearbeitende Polymer-Flüssigkristalle mit uniaxialer Mesogen-Orientierung lassen sich so programmieren, dass ein Materialstück mehrere komplexe Formen einnehmen kann. (Das Bild zeigt acht Formwechsel.) Der Ansatz nutzt Photovernetzung zur räumlichen Konfiguration und Organisation der Aktuatordomänen im mechanisch gestreckten Zustand.
      PubDate: 2017-10-11T08:05:38.065373-05:
      DOI: 10.1002/ange.201709528
       
  • Singlet Oxygen during Cycling of the Aprotic Na-O2 Battery
    • Authors: Lukas Schafzahl; Nika Mahne, Bettina Schafzahl, Martin Wilkening, Christian Slugovc, Sergey M Borisov, Stefan A. Freunberger
      Abstract: Aprotic sodium-O2 batteries require the reversible formation/dissolution of sodium superoxide (NaO2) on cycling. Poor cycle life has been associated with parasitic chemistry caused by the reactivity of electrolyte and electrode with NaO2, a strong nucleophile and base. Its reactivity can, however, not consistently explain the side reactions and irreversibility. Here we show that singlet oxygen (1O2) forms at all stages of cycling and that it is a main driver for parasitic chemistry. It was detected in- and ex-situ via a 1O2 trap that selectively and rapidly forms a stable adduct with 1O2. The 1O2 formation mechanism involves proton mediated superoxide disproportionation on discharge, rest, and charge below ~3.3 V, and direct electrochemical 1O2 evolution above ~3.3 V. Trace water, which is needed for high capacities drives at the same time parasitic chemistry. Controlling the highly reactive singlet oxygen is thus crucial for achieving highly reversible cell operation.
      PubDate: 2017-10-11T07:55:31.328649-05:
      DOI: 10.1002/ange.201709351
       
  • Hydrogen-bonded Hexagonal Buckybowl Framework
    • Authors: Ichiro Hisaki; Hideaki Toda, Hiroyasu Sato, Norimitsu Tohnai, Hidehiro Sakurai
      Abstract: We report a hydrogen-bonded two-dimensionally networked buckybowl architecture for the first time. Two types of hexagonal network (HexNet) structures (CPSM-1 and -2) have been achieved based on a sumanene derivative (CPSM) possessing 4,4'-dicarboxy-o-terphenyl groups in the periphery. CPSM-1 has a waved HexNet structure with an alternate alignment of upward and downward bowls. CPSM-2 has a bilayered HexNet structure composed of hamburger-shaped dimers of the bowls. This demonstrates that non-planar π-systems can be networked two-dimensionally by an appropriate supramolecular synthon to achieve structurally well-defined unique bumpy π-sheets. Furthermore, we revealed that CPSM-2 undergoes anisotropic shrinking along the c axis by 11% under high pressure conditions (970 MPa). The shrinkage is brought about by offset sliding between bumpy π-surfaces of the bilayered HexNet sheets.
      PubDate: 2017-10-11T07:25:27.990044-05:
      DOI: 10.1002/ange.201708115
       
  • Non-enzymatic Oxidation of a Pentagalloylglucose Analog to Ellagitannins
    • Authors: Seiya Ashibe; Kazutada Ikeuchi, Yuji Kume, Shinnosuke Wakamori, Yuri Ueno, Takashi Iwashita, Hidetoshi Yamada
      Abstract: The occurrence of more than 1,000 structural diversity in ellagitannins has been hypothesized to begin with oxidation of penta-O-galloyl--D-glucose (-PGG) to couple the galloyl groups. However, the non-enzymatic behavior of -PGG in the oxidation is unknown. Here, we disclose which galloyl groups on glucose tended to couple and which axial chirality was predominant in the derived hexahydroxydiphenoyl groups, when an analog of -PGG was subjected to oxidation. The study revealed that the galloyl groups coupled, in the following order of production ratio: at the 4,6-, 1,6-, 1,2-, 2,3-, and 3,6-positions with respective S, S, R, S, and R-axial chirality. Among them, the most preferred 4,6-coupling reflected the tendency observed in natural ellagitannins. An astonishing fact was that the second best was the 1,6-coupling. With the detection of a 3,6-coupled product, this work demonstrated that even ellagitannin skeletons with an axial-rich glucose core may generate non-enzymatically.
      PubDate: 2017-10-11T05:56:57.977785-05:
      DOI: 10.1002/ange.201708703
       
  • Precise Assembly of Particles for Zigzag or Linear Patterns
    • Authors: Dan Guo; Chang Li, Yang Wang, Yanan Li, Yanlin Song
      Abstract: Precise control of particles assembly has tremendous potential for fabricating intricate structures and functional materials. However, it is still a challenge to achieve one-dimensional assembly with precisely controlled morphology. In this work, we report an effective strategy to precisely assemble particles into well-defined patterns by liquid confinement through controlling the viscosity of the assembly system. It is found that high viscosity of the system impedes particles rearrangement, and facilitates the generation of zigzag or twined zigzag assembly structures; while low viscosity of the system allows particles to rearrange into linear or zipper structures driven by lowering the surface deformation of the liquid. As a result, precise control of different assembly patterns can be achieved through tuning the viscosity of solvent and size confinement ratios. This facile approach shows generality for particles assembly of different sizes and materials.
      PubDate: 2017-10-11T05:56:44.913181-05:
      DOI: 10.1002/ange.201709115
       
  • O2 Activation on Ceria Catalysts - The Importance of Substrate
           Crystallographic Orientation
    • Authors: Chengwu Yang; Xiaojuan Yu, Stefan Heissler, Peter Weidler, Alexei Nefedov, Yuemin Wang, Christof Wöll, Thomas Kropp, Joachim Paier, Joachim Sauer
      Abstract: An atomic-level understanding of dioxygen activation on metal oxides remains one of the major challenges in heterogeneous catalysis. By performing a thorough surface-science study of all three low-index single-crystal surfaces of ceria, probably the most important redox catalysts, we provide a direct spectroscopic characterization of reactive dioxygen species at defect sites on the reduced ceria (110) and (100) surfaces. Surprisingly, neither of these superoxo and peroxo species was found on ceria (111), the thermodynamically most stable surface of this oxide. Applying density functional theory, we could relate these apparently inconsistent findings to a sub-surface diffusion of O-vacancies on (111) substrates, but not on the less closely packed surfaces. These observations resolve a long standing debate concerning the location of O-vacancies on ceria surfaces and the activation of O2 on ceria powders.
      PubDate: 2017-10-11T05:25:43.554537-05:
      DOI: 10.1002/ange.201709199
       
  • Phosphorylation-Responsive Membrane Transport of Peptides
    • Authors: Shu Peng; Andrea Barba-Bon, Yu-Chen Pan, Werner M. Nau, Dong-Sheng Guo, Andreas Hennig
      Abstract: Phosphorylation and dephosphorylation of peptides by kinases and phosphatases is essential for signal transduction in biological systems and many diseases involve abnormal activities of these enzymes. Herein, we introduce amphiphilic calixarenes as key components for supramolecular, phosphorylation-responsive membrane transport systems. Dye efflux experiments with liposomes demonstrated that calixarenes are highly active counterion activators for established cell-penetrating peptides with EC50 values in the low nanomolar range. We have now found that they can even activate membrane transport of short peptide substrates for kinases involved in signal transduction, whereas the respective phosphorylated products are much less efficiently transported. This allows regulation of membrane transport activity by protein kinase A (PKA) and protein kinase C (PKC) as well as monitoring their activity in a label-free kinase assay.
      PubDate: 2017-10-11T05:25:30.609237-05:
      DOI: 10.1002/ange.201707979
       
  • Blockable Zn10L15 ion channels via subcomponent self-assembly
    • Authors: Cally Jo Elizabeth Haynes; Jinbo Zhu, Imogen Riddell, Catalin Chimerel, Silvia Hernández-Ainsa, Tanya Ronson, Ulrich Keyser, Jonathan Nitschke
      Abstract: Metal-organic ion channels based on Zn10L15 pentagonal prisms have been prepared by subcomponent self-assembly. The insertion of these prisms into lipid membranes was investigated by ion-current and fluorescence measurements. The channels were found to mediate the transport of Cl- anions through planar lipid bilayers and into vesicles. Toluenesulfonate anions were observed to bind and plug the central channels of the prisms in the solid state and in solution. In membranes, adding dodecylsulfate impeded ion transport by channel blocking. Our Zn10L15 prism thus inserts into lipid bilayers to turn on ion transport, which can then be turned off through addition of the blocker dodecylsulfate.
      PubDate: 2017-10-11T01:55:31.451041-05:
      DOI: 10.1002/ange.201709544
       
  • Facile Supramolecular Processing of Carbon Nanotubes and Polymers Enabling
           Electromechanical Sensors
    • Authors: Chae Bin Kim; Ki-Beom Jeong, Beom Joo Yang, Jong-Won Song, Bon Cheol Ku, Seunghyun Lee, Seung Ki Lee, Chiyoung Park
      Abstract: We herein report a facile, cost-competitive, and scalable method for producing viscoelastic conductors via one-pot melt-blending using polymers and supramolecular gels composed of carbon nanotubes (CNTs), diphenylamine (DP), and benzophenone (BP). When mixed, a non-volatile eutectic liquid (EL) produced by simply blending DP with BP (1:1 molar ratio) enabled not only the gelation of CNTs (EL-CNTs) but also the dissolution of a number of commodity polymers. In order to take these advantages, viscoelastic conductors were produced via one-pot melt-blending the EL and CNTs with a model thermoplastic elastomer, poly(styrene-b-butadiene-b-styrene) (SBS, styrene 30 wt%). The resulting composites displayed an excellent electromechanical sensory along with re-mendable properties. This simple method using cost-competitive EL components is expected to provide an alternative to the use of expensive ionic liquids as well as to facilitate the fabrication of novel composites for various purposes.
      PubDate: 2017-10-10T23:50:22.432345-05:
      DOI: 10.1002/ange.201708111
       
  • Evolving accelerated amidation by SpyTag/SpyCatcher to analyze membrane
           dynamics
    • Authors: Anthony Howard Keeble; Anusuya Banerjee, Samuel C Reddington, Matteo Paolo Ferla, Mark Howarth, Irsyad Noor Abadi Khairil Anuar
      Abstract: SpyTag is a peptide that forms a spontaneous amide bond with its protein partner SpyCatcher. This protein superglue is a broadly useful tool for molecular assembly, locking together biological building blocks efficiently and irreversibly in diverse architectures. We initially developed SpyTag and SpyCatcher by rational design, through splitting a domain from a Gram-positive bacterial adhesin. Here we establish a phage display platform able to select for specific amidation, achieving an order of magnitude acceleration for interaction of the SpyTag002 variant with the SpyCatcher002 variant. We show that the 002 pair bonds rapidly under a wide range of conditions and at either protein terminus. SpyCatcher002 was fused to an intimin derived from enterohemorrhagic Escherichia coli. SpyTag002 reaction enabled specific and covalent decoration of intimin, for live cell fluorescent imaging of the dynamics of the bacterial outer membrane as cells divide.
      PubDate: 2017-10-10T20:55:53.612525-05:
      DOI: 10.1002/ange.201707623
       
  • Size and Interface Modulated Metal-Insulator Transition in
           Solution-Synthesized Nanoscale VO2-TiO2-VO2 Heterostructures
    • Authors: Raymond E Schaak; Xuefei Li
      Abstract: The M1 form of vanadium dioxide, which exhibits a reversible insulator-metal transition above room temperature, has been incorporated into nanoscale heterostructures through solution-phase epitaxial growth on the tips of rutile TiO2 nanorods. Four distinct classes of VO2-TiO2-VO2 nanorod heterostructures are accessible by modulating the growth conditions. Each type of VO2-TiO2-VO2 nanostructure has a different insulator-metal transition temperature that depends on the VO2 domains sizes and the TiO2-VO2 interfacial strain characteristics.
      PubDate: 2017-10-10T20:55:44.573769-05:
      DOI: 10.1002/ange.201706599
       
  • Post Graphene 2D Chemistry: The Emerging Field of Molybdenum Disulfide and
           Black Phosphorus Functionalization
    • Authors: Andreas Hirsch; Frank Hauke
      Abstract: The current state of the chemical functionalization of three types of single sheet 2D materials, namely, graphene, molybdenum disulfide (MoS2), and black phosphorus (BP) is summarized. Such 2D sheet polymers represent currently an emerging field at the interface of synthetic chemistry, physics, and materials science. Both covalent and non-covalent functionalization of sheet architectures allows for a systematic modification of their properties, i.e. an improvement of solubility and processability, the prevention of re-aggregation or a band gap tuning. Next to successful functionalization concepts also fundamental challenges are addressed. These include the insolubility and polydispersity of most 2D sheet polymers, the development of suitable characterization tools, the identification of effective binding strategies, the chemical activation of the usually rather unreactive basal planes for covalent addend binding, and the regioselectivity of plane addition reactions. Although a number of these questions remain elusive in this review, the first promising concepts to overcome such hurdles have been listed.
      PubDate: 2017-10-10T07:50:32.993066-05:
      DOI: 10.1002/ange.201708211
       
  • Characterization of conjugation pattern in large polysaccharide-protein
           conjugates by NMR
    • Authors: Stefano Giuntini; Evita Balducci, Linda Cerofolini, Enrico Ravera, Marco Fragai, Francesco Berti, Claudio Luchinat
      Abstract: Carbohydrate-based vaccines are among the safest and most effective vaccines and represent potent tools for prevention of life-threatening bacterial infectious diseases, like meningitis and pneumonia. The chemical conjugation of a weak antigen to protein as a source of T-cell epitopes generates a glycoconjugate vaccine, that results more immunogenic. Several methods have been used so far to characterize the resulting polysaccharide-protein conjugates. However, a reduced number of methodologies has been proposed for measuring the degree of saccharide conjugation at the possible protein sites. Here we show that detailed information on large proteins conjugated with large polysaccharides can be achieved by a combination of solution and solid state NMR. As a test case, a large protein assembly, L-asparaginase II, has been conjugated with Neisseria meningitidis serogroup C capsular polysaccharide and the pattern and degree of conjugation were determined.
      PubDate: 2017-10-10T06:20:36.31096-05:0
      DOI: 10.1002/ange.201709274
       
  • Catalytic Enantioselective Synthesis of Mariline A and Related
           Isoindolinones via a Biomimetic Approach
    • Authors: Chang Min; Yingfu Lin, Daniel Seidel
      Abstract: The catalytic enantioselective synthesis of isoindolinones was achieved via the condensation of ortho-formyl-arylketones and anilines. In the presence of 1 mol% of a chiral phosphoric acid catalyst, reactions reach completion within 10 minutes and provide products with up to 98% ee. Anilines with an ortho t-butyl group form atropisomeric products, enabling the simultaneous generation of axial and point chirality from two achiral substrates. This method was applied to the first synthesis of mariline A.
      PubDate: 2017-10-10T05:51:01.201066-05:
      DOI: 10.1002/ange.201709182
       
  • Three-dimensionally π-Conjugated Diradical Molecular Cage
    • Authors: Jishan Wu; Xiao Gu, Tullimilli Y. Gopalakrishna, Hoa Phan, Yong Ni, Tun Seng Herng, Jun Ding
      Abstract: π-Conjugated molecular cages are very challenging targets in structural organic chemistry, supramolecular chemistry and materials science. Herein, we report the synthesis and physical characterizations of the first three-dimensionally π-conjugated diradical molecular cage PTM-C, in which two polychlorotriphenylmethyl (PTM) radicals are linked by three bis(3,6-carbazolyl) bridges. This cage compound was synthesized mainly by intermolecular Yamamoto coupling followed by deprotonation and oxidation. It is stable and its structure was confirmed by X-ray crystallographic analysis. The two carbon-centered PTM radicals are weakly coupled through electronic interactions with the carbazole spacers, as revealed by optical, electronic and magnetic measurements as well as theoretical calculations.
      PubDate: 2017-10-10T05:20:47.277365-05:
      DOI: 10.1002/ange.201709537
       
  • Decoupled Thermo- and pH-responsive Hydrogel Microspheres Cross-linked by
           Rotaxane Networks
    • Authors: Takuma Kureha; Daichi Aoki, Seina Hiroshige, Keisuke Iijima, Daisuke Aoki, Toshikazu Takata, Daisuke Suzuki
      Abstract: Rotaxane cross-linked (RC) microgels that exhibit a decoupled thermo- and pH-responsive volume transition were developed. The pH-induced changes of the aggregation/disaggregation states of cyclodextrin in the RC networks were used to control the swelling capacity of the entire microgels. Different from conventional thermo- and pH-responsive microgels, which are usually obtained from copolymerizations involving charged monomers, the RC microgels respond to temperature as intended, even in the presence of charged functional molecules such as dyes in the microgel dispersion. The results of this study should lead to new applications, including drug delivery systems, that require a retention of their "smart" functions even in environments that may contain foreign ions, e.g. in in vivo experiments.
      PubDate: 2017-10-10T05:20:28.874208-05:
      DOI: 10.1002/ange.201709633
       
  • Selective activation of C-H bonds by cascading photochemistry with
           biocatalysis
    • Authors: Wuyuan Zhang; Bastien O. Burek, Elena Fernández-Fueyo, Miguel Alcalde, Jonathan Z. Bloh, Frank Hollmann
      Abstract: Selective oxyfunctionalisation of inert C-H bonds under mild conditions can be achieved using peroxygenases. This approach, however, is impaired by the poor robustness of these enzymes in the presence of hydrogen peroxide as the stoichiometric oxidant. Here, we demonstrate that inorganic photocatalysts such as gold-titanium dioxide efficiently provide H2O2 from methanol-driven reductive activation of ambient oxygen in suitable amounts to ensure high reactivity and robustness of the enzyme. Using this approach stereoselective hydroxylation of ethyl benzene to (R)-1-phenyl ethanol in high enantioselectivity (>98% ee) and excellent turnover numbers of the biocatalyst (>71.000) was achieved.
      PubDate: 2017-10-10T04:27:57.200373-05:
      DOI: 10.1002/ange.201708668
       
  • Targeting the Protein Kinases Cysteinome
    • Authors: Apirat Chaikuad; Pierre Koch, Stefan Laufer, Stefan Knapp
      Abstract: Drugs that function by covalent bond formation represent a considerable fraction of our repository of effective medicines but safety concerns and the complexity of developing covalent inhibitors has rendered covalent targeting a less attractive strategy for rational drug design. The recent approval of four covalent kinase inhibitors and the development of highly potent covalent kinase probes with exceptional selectivity has raised significant interest in industry and academic research and validated the concept of covalent kinase targeting for clinical applications. The abundance of cysteines at diverse positions in and around the kinase active site suggests that a large fraction of kinases can be targeted by covalent inhibitors. Here we review recent developments of this rapidly growing area in kinase drug development and highlight the unique opportunities and challenges of this strategy.
      PubDate: 2017-10-10T04:27:46.212427-05:
      DOI: 10.1002/ange.201707875
       
  • Titelbild: A Pyrene-Linked Cavity within a β-Barrel Protein Promotes an
           Asymmetric Diels–Alder Reaction (Angew. Chem. 44/2017)
    • Authors: Tomoki Himiyama; Naomasa Taniguchi, Shunsuke Kato, Akira Onoda, Takashi Hayashi
      Pages: 13719 - 13719
      Abstract: Ein Pyren-verknüpfter Proteinhohlraum zieht zwei Substratmoleküle an – ungefähr so wie der Duft einer Blume Schmetterlinge anlockt. A. Onoda, T. Hayashi und Mitarbeiter demonstrieren in ihrer Zuschrift auf S. 13806, dass eine polycyclische Pyrengruppe, die an das starre Proteingerüst der β-Fass-Struktur von Nitrobindin geknüpft ist, aromatische Wechselwirkungen mit einem Substrat bereitstellt. Eine asymmetrische Diels-Alder-Reaktion zwischen Azachalkon und Cyclopentadien verläuft glatt mit hoher Stereoselektivität innerhalb des Reaktionsgerüsts.
      PubDate: 2017-10-05T03:41:51.723043-05:
      DOI: 10.1002/ange.201710001
       
  • Innentitelbild: Precisely Assembled Cyclic Gold Nanoparticle Frames by 2D
           Polymer Single-Crystal Templating (Angew. Chem. 44/2017)
    • Authors: Shan Mei; Hao Qi, Tian Zhou, Christopher Y. Li
      Pages: 13720 - 13720
      Abstract: Freistehende molekulare Rahmen wurden durch eine gerichtete Assemblierungsmethode hergestellt, bei der Nanopartikel mithilfe von Polymerkristallen (PSCs) als Templat präzise verknüpft werden. C. Y. Li und Mitarbeiter beschreiben in ihrer Zuschrift auf S. 13833, wie PSCs die Kristallisation von Blockcopolymeren vermitteln, die wiederum Gold-NPs (AuNPs) auf präzise Weise zu AuNP-Rahmen anordnen. Die AuNP-Rahmen ähneln in ihrer Topologie Nanopartikelringen und cyclischen Polymerketten und zeigen ein charakteristisches Oberflächenplasmonenresonanzverhalten.
      PubDate: 2017-10-05T03:41:56.732027-05:
      DOI: 10.1002/ange.201709998
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 44/2017
    • Pages: 13723 - 13740
      PubDate: 2017-10-18T02:09:27.215534-05:
      DOI: 10.1002/ange.201784411
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 44/2017
    • Pages: 13744 - 13747
      PubDate: 2017-07-19T06:05:25.165425-05:
      DOI: 10.1002/ange.201707079
       
  • Yasujiro Murata
    • Pages: 13748 - 13748
      Abstract: „Wenn ich ein Auto wäre, wäre ich ein roter Porsche 911. Wenn ich für einen Tag jemand anders sein könnte, wäre ich Dirigent eines Orchesters ...“ Dies und mehr von und über Yasujiro Murata finden Sie auf Seite 13748.
      PubDate: 2017-07-12T05:00:55.818234-05:
      DOI: 10.1002/ange.201706519
       
  • Medaillen der Società Chimica Italiana für 2017
    • Pages: 13749 - 13750
      PubDate: 2017-10-05T08:32:57.25241-05:0
      DOI: 10.1002/ange.201709467
       
  • Enantioselektive [2,3]-sigmatrope Umlagerungen – metallgebundene oder
           freie Ylide als Zwischenstufen'
    • Authors: Katharina J. Hock; Rene M. Koenigs
      Pages: 13752 - 13754
      Abstract: Ein wichtiges Forschungsgebiet in der organischen Synthese sind enantioselektive Umlagerungen. Dieses Highlight zeigt jüngste Fortschritte, die zur Entwicklung der ersten enantioselektiven Doyle-Kirmse-Reaktion und der enantioselektiven Umlagerung von Iodonium-Yliden führten.
      PubDate: 2017-09-18T08:56:12.324822-05:
      DOI: 10.1002/ange.201707092
       
  • Erweiterung des Strukturraums ribosomaler Peptide: autokatalytische
           N-Methylierung in der Omphalotin-Biosynthese
    • Authors: Hülya Aldemir; Tobias A. M. Gulder
      Pages: 13756 - 13758
      Abstract: Tail-Me: Die N-Methylierung von Amidbindungen im Rückgrat von Peptidnaturstoffen war nur für nicht-ribosomale Peptide bekannt. Ein neuartiger Methylierungsmechanismus überträgt dieses Strukturmerkmal nun in die Welt der ribosomalen Peptide und erweitert so die Strukturvielfalt ribosomal synthetisierter, posttranslational modifizierter Peptide (RiPPs) signifikant.
      PubDate: 2017-09-26T09:27:25.828245-05:
      DOI: 10.1002/ange.201708456
       
  • Kaskaden in Kompartimenten: auf dem Weg zu maschinengestützter
           Biotechnologie
    • Authors: Kersten S. Rabe; Joachim Müller, Marc Skoupi, Christof M. Niemeyer
      Pages: 13760 - 13777
      Abstract: Biologische Kompartimentierung ist ein fundamentales Prinzip des Lebens, das Zellen den Stoffwechsel, die Vermehrung und die Kommunikation mit ihrer Umgebung ermöglicht. Es wird viel am Verständnis dieses grundsätzlichen Prinzips geforscht, um biomimetische Kompartimente und katalytische Kaskaden als Hilfsmittel für den technologischen Fortschritt zu nutzen. Dieser Aufsatz fasst den aktuellen Stand der Entwicklung zusammen und legt besondere Schwerpunkte auf die Größenordnung der Systeme, den Stofftransport und die Anordnung katalytischer Einheiten mithilfe von molekularen Gerüsten. Dabei reicht das Spektrum von kleinen Vernetzern über Proteine und Nucleinsäuren bis zu Kolloiden und strukturierten Oberflächen. Die Schlussfolgerung lautet, dass die zukünftige Erforschung und Anwendung dieser komplexen Systeme stark von technischen Lösungen profitieren wird, die eine integrierte, maschinengestützte Entwicklung und Durchführung einer nächsten Generation biotechnologischer Prozesse ermöglichen. Dieses Ziel sollte durch Implementierung von Mikrofluidik, Robotik und ergänzenden Fertigungsverfahren erreichbar sein und maßgeblich durch Simulationen und computergestützte Prozessmodellierung auf Basis von “Big Data” aus multiskalaren experimentellen Analysen ergänzt werden.Maschinell erstellte Multienzymkaskaden: Die maschinengestützte Entwicklung biomimetischer Kompartimente und katalytischer Kaskaden wird den Weg zu einer neuen Generation biotechnologischer Prozesse ebnen. Für die Anordnung der katalytischen Einheiten kommen dabei molekulare Gerüste von kleinen Vernetzern über Proteine und Nucleinsäuren bis zu Kolloiden und strukturierten Oberflächen zum Einsatz. S: Substrat, P: Produkt.
      PubDate: 2017-09-14T02:54:46.943432-05:
      DOI: 10.1002/ange.201703806
       
  • Because the Light is Better Here: Correlation-Time Analysis by NMR
           Spectroscopy
    • Authors: Albert A. Smith; Matthias Ernst, Beat H. Meier
      Pages: 13778 - 13783
      Abstract: Relaxation data in NMR spectra are often used for dynamics analysis, by modeling motion in the sample with a correlation function consisting of one or more decaying exponential terms, each described by an order parameter, and a correlation time. This method has its origins in the Lipari–Szabo model-free approach, which originally considered overall tumbling plus one internal motion and was later expanded to several internal motions. Considering several of these cases in the solid state it is found that if the real motion is more complex than the assumed model, model fitting is biased towards correlation times where the relaxation data are most sensitive. This leads to unexpected distortions in the resulting dynamics description. Therefore dynamics detectors should be used, which characterize different ranges of correlation times and can help in the analysis of protein motion without assuming a specific model of the correlation function.Verzerrung verhindern: NMR-Dynamikdaten reagieren auf manche Korrelationszeiten empfindlicher als auf andere. Korrelationsfunktionsmodelle zeigen häufig eine Verzerrung dorthin, wo das Licht besser, sprich das Experiment empfindlicher ist, was zu einer nichtverlässlichen Charakterisierung der Bewegung führt. Statt der Modellierung Detektoren zu nutzen, die auf unterschiedliche Korrelationszeitbereiche ansprechen, könnte hier Abhilfe bringen.
      PubDate: 2017-09-14T06:26:31.278186-05:
      DOI: 10.1002/ange.201707316
       
  • Enzyme Activity by Design: An Artificial Rhodium Hydroformylase for Linear
           Aldehydes
    • Authors: Amanda G. Jarvis; Lorenz Obrecht, Peter J. Deuss, Wouter Laan, Emma K. Gibson, Peter P. Wells, Paul C. J. Kamer
      Pages: 13784 - 13788
      Abstract: Artificial metalloenzymes (ArMs) are hybrid catalysts that offer a unique opportunity to combine the superior performance of natural protein structures with the unnatural reactivity of transition-metal catalytic centers. Therefore, they provide the prospect of highly selective and active catalytic chemical conversions for which natural enzymes are unavailable. Herein, we show how by rationally combining robust site-specific phosphine bioconjugation methods and a lipid-binding protein (SCP-2L), an artificial rhodium hydroformylase was developed that displays remarkable activities and selectivities for the biphasic production of long-chain linear aldehydes under benign aqueous conditions. Overall, this study demonstrates that judiciously chosen protein-binding scaffolds can be adapted to obtain metalloenzymes that provide the reactivity of the introduced metal center combined with specifically intended product selectivity.Künstliche Metalloenzyme sind Hybridkatalysatoren, die von der Leistungsfähigkeit natürlicher Proteinstrukturen und der nichtnatürlichen Reaktivität katalytisch aktiver Übergangsmetallzentren profitieren. Eine künstliche Rhodiumhydroformylase wurde entwickelt, die sich durch hohe Aktivität und Selektivität in der zweiphasigen Herstellung von langkettigen linearen Aldehyden auszeichnet.
      PubDate: 2017-09-13T13:07:51.608187-05:
      DOI: 10.1002/ange.201705753
       
  • Regioselective Transformation of Long π-Conjugated Backbones: From
           Oligofurans to Oligoarenes
    • Authors: Sunita Gadakh; Linda J. W. Shimon, Ori Gidron
      Pages: 13789 - 13793
      Abstract: We demonstrate the transformation of oligofurans through sequential Diels–Alder cycloaddition reactions to provide oligoarenes in two chemical steps, regardless of the oligomer length. By this method, oligonaphthalenes containing up to six units were obtained in high yield through the formation of up to 12 new C−C bonds. The versatility of this method was demonstrated for various polyaromatic hydrocarbons. The regioselectivity of this process enabled the synthesis of a library of substituted triarylenes from a single terfuran precursor by modification of the dienophile strength and the order of addition. Overall, this study demonstrates that long oligofurans are interesting not only as organic electronic materials, but also as starting materials for the formation of various conjugated systems.Um es kurz zu machen: Oligofurane gehen sequenzielle Diels-Alder-Reaktionen ein, die unabhängig von der Oligomerlänge in zwei chemischen Schritten zu Oligoarenen führen (siehe Bild). Verschiedene Maleimid- und Benzin-Dienophile wurden ebenfalls verwendet, um eine Reihe von substituierten Oligoarenen aus einer einzigen Oligofuran-Vorstufe in hoch regioselektiver Weise zu synthetisieren.
      PubDate: 2017-10-02T04:35:52.658333-05:
      DOI: 10.1002/ange.201705914
       
  • Manipulation of Biomolecule-Modified Liquid-Metal Blobs
    • Authors: Yue Yu; Eijiro Miyako
      Pages: 13794 - 13799
      Abstract: Soft and deformable liquid metals (LMs) are building components in various systems related to uncertain and dynamic task environments. Herein we describe the development of a biomolecule-triggered external-manipulation method involving LM conjugates for the construction of future innovative soft robotics operating in physiological environments. Functional soft hybrids composed of a liquid-metal droplet, a thiolated ligand, and proteins were synthesized for the expression of diverse macroscopic commands, such as attachment to cells, binary fusion, and self-propelled movement through molecular recognition and enzymatic reactions. Our technology could be used to create new state-of-the-art soft robots for chemical and biomedical engineering applications.Tropfenroboter: Mit Biomolekülen funktionalisierte Flüssigmetall(LM)-Tropfen (siehe Bild) führen makroskopische Operationen auf der Basis molekularer Erkennung aus, z. B. durch die Bildung des Biotin-Avidin-Komplexes. Blasenbildung auf der Oberfläche enzymmodifizierter LM-Konjugate ermöglicht außerdem selbstangetriebene dynamische Bewegungen, was zu effizienten weichen LM-Robotern für den Betrieb unter physiologischen Bedingungen führen könnte.
      PubDate: 2017-10-02T04:36:13.811063-05:
      DOI: 10.1002/ange.201705996
       
  • Combining Orthogonal Chain-End Deprotections and Thiol–Maleimide Michael
           Coupling: Engineering Discrete Oligomers by an Iterative Growth Strategy
    • Authors: Zhihao Huang; Junfei Zhao, Zimu Wang, Fanying Meng, Kunshan Ding, Xiangqiang Pan, Nianchen Zhou, Xiaopeng Li, Zhengbiao Zhang, Xiulin Zhu
      Pages: 13800 - 13805
      Abstract: Orthogonal maleimide and thiol deprotections were combined with thiol–maleimide coupling to synthesize discrete oligomers/macromolecules on a gram scale with molecular weights up to 27.4 kDa (128mer, 7.9 g) using an iterative exponential growth strategy with a degree of polymerization (DP) of 2n−1. Using the same chemistry, a “readable” sequence-defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated using sequential growth (DP=2n−1) or double exponential dendrimer growth approaches (DP=22n−1) with significantly accelerated growth rates. A versatile, efficient, and metal-free method for construction of discrete oligomers with tailored structures and a high growth rate would greatly facilitate research into the structure–property relationships of sophisticated polymeric materials.Diskrete Oligomere wurden in einem effizienten metallfreien Prozess synthetisiert, der die orthogonale Entschützung von Maleimid- und Thiolgruppen mit einer Thiol-Maleimid-Michael-Kupplung verbindet. IEG: iteratives exponentielles Wachstum, DEDG: doppelt exponentielles Dendrimerwachstum, DP: Polymerisationsgrad.
      PubDate: 2017-09-27T01:16:05.990542-05:
      DOI: 10.1002/ange.201706522
       
  • A Pyrene-Linked Cavity within a β-Barrel Protein Promotes an Asymmetric
           Diels–Alder Reaction
    • Authors: Tomoki Himiyama; Naomasa Taniguchi, Shunsuke Kato, Akira Onoda, Takashi Hayashi
      Pages: 13806 - 13810
      Abstract: A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide (Pyr) to prepare a series of NB-Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB-Pyr indicates that azachalcone (aza), which is a dienophile for a Diels–Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB-Pyr in the presence of CuII ion in high yield and high enantio- and regioselectivity.Eine Reaktionshöhle mit einer hineinragenden polycyclischen Pyrengruppe, die als Plattform für aromatische Wechselwirkungen dient, wurde innerhalb des starren Gerüsts des β-Fass-Proteins Nitrobindin erzeugt. Die asymmetrische Diels-Alder-Reaktion zwischen Azachalcon und Cyclopentadien läuft mit hoher Stereoselektivität in der Reaktionshöhle ab.
      PubDate: 2017-08-31T11:01:14.875698-05:
      DOI: 10.1002/ange.201704524
       
  • Peristome-Mimetic Curved Surface for Spontaneous and Directional
           Separation of Micro Water-in-Oil Drops
    • Authors: Chuxin Li; Lei Wu, Cunlong Yu, Zhichao Dong, Lei Jiang
      Pages: 13811 - 13816
      Abstract: Separation of micro-scaled water-in-oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil–water separation has been achieved by membrane separation and sponge absorption, but micro-drop separation still remains a challenge. Herein we report that instead of the “plug-and-go” separation model, tiny water-in-oil droplets can be separated into pure water and oil droplets through “go-in-opposite ways” on curved peristome-mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil-in-oil droplets with surface tension differences as low as 14.7 mN m−1 and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro-scaled separation. Furthermore, the curved peristome-mimetic surface guides the separated drops in different directions with high efficiency.Wasser links, Öl rechts: Eine künstliche gekrümmte Oberfläche ähnlich dem Peristom (der Saum um die Öffnung der Fallen tropischer Kannenpflanzen) scheidet ohne Energiezufuhr Wasser und Öl aus Wasser-in-Öl-Mikrotropfen. Der Vorgang dauert nur Millisekunden, und die getrennten Flüssigkeiten werden spontan in verschiedene Richtungen abgeführt.
      PubDate: 2017-09-22T06:10:58.687406-05:
      DOI: 10.1002/ange.201706665
       
  • An Extensive Family of Heterometallic Titanium(IV)–Metal(III) Rings with
           Structure Control through Templates
    • Authors: Grigore A. Timco; Antonio Fernandez, Andreas K. Kostopoulos, Christopher A. Muryn, Robin G. Pritchard, Ilya Strashnov, Inigo J. Vitorica-Yrezebal, George F. S. Whitehead, Richard E. P. Winpenny
      Pages: 13817 - 13820
      Abstract: A family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1].Größenkontrolle: Eine Familie von [Kat][TixMO(x+1)(O2CtBu)2x+2]-Heterometallringen wird vorgestellt (Kat=ein sekundäres oder tertiäres Alkylammoniumion; x=7, 8 oder 9; M=Fe, Ga, Cr, In, Al). Die Strukturen sind regelmäßige Acht-, Neun- oder Zehnecke, in denen jede Kante von einem Oxid und zwei Pivalaten überbrückt wird. Die Ringgröße hängt vom vorliegenden Alkylammoniumkation ab.
      PubDate: 2017-09-22T06:10:37.88494-05:0
      DOI: 10.1002/ange.201706679
       
  • AFM Imaging of Hybridization Chain Reaction Mediated Signal Transmission
           between Two DNA Origami Structures
    • Authors: Sarah Helmig; Kurt Vesterager Gothelf
      Pages: 13821 - 13824
      Abstract: Signal transfer is central to the controlled exchange of information in biology and advanced technologies. Therefore, the development of reliable, long-range signal transfer systems for artificial nanoscale assemblies is of great scientific interest. We have designed such a system for the signal transfer between two connected DNA nanostructures, using the hybridization chain reaction (HCR). Two sets of metastable DNA hairpins, one of which is immobilized at specific points along tracks on DNA origami structures, are polymerized to form a continuous DNA duplex, which is visible using atomic force microscopy (AFM). Upon addition of a designed initiator, the initiation signal is efficiently transferred more than 200 nm from a specific location on one origami structure to an end point on another origami structure. The system shows no significant loss of signal when crossing from one nanostructure to another and, therefore, has the potential to be applied to larger multi-component DNA assemblies.Domino-Kettenreaktion: Die Hybridisierungs-Kettenreaktion (HCR) zwischen metastabilen DNA-Haarnadeln wurde immobilisiert auf einer DNA-Origamistruktur ausgeführt und für den Signaltransfer über zwei DNA-Origamistrukturen hinweg verwendet.
      PubDate: 2017-09-27T09:46:57.784178-05:
      DOI: 10.1002/ange.201706680
       
  • Engineered Fluorine Metabolism and Fluoropolymer Production in Living
           Cells
    • Authors: Benjamin W. Thuronyi; Thomas M. Privalsky, Michelle C. Y. Chang
      Pages: 13825 - 13828
      Abstract: Fluorine has become an important element for the design of synthetic molecules for use in medicine, agriculture, and materials. Despite the many advantages provided by fluorine for tuning key molecular properties, it is rarely found in natural metabolism. We seek to expand the molecular space available for discovery through the development of new biosynthetic strategies that cross synthetic with natural compounds. Towards this goal, we engineered a microbial host for organofluorine metabolism and show that we can achieve the production of the fluorinated diketide 2-fluoro-3-hydroxybutyrate at approximately 50 % yield. This fluorinated diketide can be used as a monomer in vivo to produce fluorinated poly(hydroxyalkanoate) (PHA) bioplastics with fluorine substitutions ranging from around 5–15 %. This system provides a platform to produce mm flux through the key fluoromalonyl coenzyme A (CoA) building block, thereby offering the potential to generate a broad range of fluorinated small-molecule targets in living cells.Fluor-biologisch: Ein auf den Organofluorstoffwechsel abgestimmter mikrobieller Wirt produziert ein fluoriertes Diketid mit rund 50 % Ausbeute. Das Diketid kann in vivo als Monomer für fluorierte Poly(hydroxyalkanoat)-Biopolymere mit bis zu 15 % Fluorsubstitution dienen. Auf der Grundlage dieses Systems ist eine Reihe fluorierter niedermolekularer Zielstrukturen in lebenden Zellen herstellbar.
      PubDate: 2017-09-26T09:37:25.098566-05:
      DOI: 10.1002/ange.201706696
       
  • Phosphate Transfer in Activated Protein Complexes Reveals Interaction
           Sites
    • Authors: Sem Tamara; Richard A. Scheltema, Albert J. R. Heck, Aneika C. Leney
      Pages: 13829 - 13832
      Abstract: For many proteins, phosphorylation regulates their interaction with other biomolecules. Herein, we describe an unexpected phenomenon whereby phosphate groups are transferred non-enzymatically from one interaction partner to the other within a binding interface upon activation in the gas phase. Providing that a high affinity exists between the donor and acceptor sites, this phosphate transfer is very efficient and the phosphate groups only ligate to sites in proximity to the binding region. Consequently, such phosphate-transfer reactions may define with high precision the binding site between a phosphoprotein and its binding partner, as well as reveal that the binding site in this system is retained in the phase transfer from solution to the gas phase.Partnerwechsel: Im Zuge der Gasphasenaktivierung können Phosphatgruppen nichtenzymatisch von einem Wechselwirkungspartner auf den anderen übertragen werden. Da dieser Phosphattransfer in hochaffinen Komplexen an der Bindestelle auftritt, können auf diese Weise Informationen über die Wechselwirkungsfläche in Protein-Phosphopeptid-Komplexen erhalten werden.
      PubDate: 2017-09-27T03:45:27.144267-05:
      DOI: 10.1002/ange.201706749
       
  • Precisely Assembled Cyclic Gold Nanoparticle Frames by 2D Polymer
           Single-Crystal Templating
    • Authors: Shan Mei; Hao Qi, Tian Zhou, Christopher Y. Li
      Pages: 13833 - 13837
      Abstract: In recent decades, extensive studies have been devoted to assembling nanoparticles (NPs) into various ordered structures to achieve novel optical properties. However, it still remains a challenging task to assemble NPs into cyclic one-dimensional (1D) shapes, such as rings and frames. Herein, we report a directed assembly method to precisely assemble NPs into well-defined, free-standing frames using polymer single crystals (PSCs) as the template. Preformed poly(ethylene oxide) (PEO) single crystals were used as the template to direct the crystallization of block copolymer (BCP) poly(ethylene oxide)-b-poly(4-vinylpyridine) (PEO-b-P4VP), which directs the gold NPs (AuNPs) to form AuNP frames. By controlling the PSC growth, we were able to, for the first time, precisely tune both the size and width of the AuNP frame. These novel AuNP frames topologically resemble NP nanorings and cyclic polymer chains, and show unique surface plasmon resonance (SPR) behaviors.Noch im Rahmen: Freie Goldnanopartikel(AuNP)-Rahmenstrukturen entstehen direkt durch Anlagerung von AuNPs an Polymer-Einkristall-Template. Größe und Dicke der Strukturen lassen sich präzise vorgeben. Diese Rahmen entsprechen NP-Nanoringen und cyclischen 1D-Polymer-Ketten; bezüglich ihrer optischen Eigenschaften erinnern sie an Au-Nanostäbe.
      PubDate: 2017-08-18T04:10:57.475304-05:
      DOI: 10.1002/ange.201706180
       
  • High-Performance CsPb1−xSnxBr3 Perovskite Quantum Dots for
           Light-Emitting Diodes
    • Authors: Hung-Chia Wang; Weigao Wang, An-Cih Tang, Hsin-Yu Tsai, Zhen Bao, Toshiyuki Ihara, Naoki Yarita, Hirokazu Tahara, Yoshihiko Kanemitsu, Shuming Chen, Ru-Shi Liu
      Pages: 13838 - 13842
      Abstract: All inorganic CsPbBr3 perovskite quantum dots (QDs) are potential emitters for electroluminescent displays. We have developed a facile hot-injection method to partially replace the toxic Pb2+ with highly stable Sn4+. Meanwhile, the absolute photoluminescence quantum yield of CsPb1−xSnxBr3 increased from 45 % to 83 % with SnIV substitution. The transient absorption (TA) exciton dynamics in undoped CsPbBr3 and CsPb0.67Sn0.33Br3 QDs at various excitation fluences were determined by femtosecond transient absorption, time-resolved photoluminescence, and single-dot spectroscopy, providing clear evidence for the suppression of trion generation by Sn doping. These highly luminescent CsPb0.67Sn0.33Br3 QDs emit at 517 nm. A device based on these QDs exhibited a luminance of 12 500 cd m−2, a current efficiency of 11.63 cd A−1, an external quantum efficiency of 4.13 %, a power efficiency of 6.76 lm w−1, and a low turn-on voltage of 3.6 V, which are the best values among reported tin-based perovskite quantum-dot LEDs.Unterdrückte Trionenbildung: CsPb1−xSnxBr3-Quantenpunkte (QDs) wurden durch Heißinjektion synthetisiert. Da die Trionenbildung durch die SnIV-Substitution unterdrückt wird, haben Leuchtdioden (LEDs) auf Basis dieser lumineszierenden QDs die höchsten Stromausbeuten und externen Quanteneffizienzen, die je für solche Sn-basierten Systeme beschrieben wurden.
      PubDate: 2017-09-26T03:10:35.395523-05:
      DOI: 10.1002/ange.201706860
       
  • Gas-Phase Synthesis of the Elusive Cyclooctatetraenyl Radical (C8H7) via
           Triplet Aromatic Cyclooctatetraene (C8H8) and Non-Aromatic Cyclooctatriene
           (C8H8) Intermediates
    • Authors: Michael Lucas; Aaron M. Thomas, Long Zhao, Ralf I. Kaiser, Gap-Sue Kim, Alexander M. Mebel
      Pages: 13843 - 13848
      Abstract: The 1,2,4,7-cyclooctatetraenyl radical (C8H7) has been synthesized for the very first time via the bimolecular gas-phase reaction of ground-state carbon atoms with 1,3,5-cycloheptatriene (C7H8) on the triplet surface under single-collision conditions. The barrier-less route to the cyclic 1,2,4,7-cyclooctatetraenyl radical accesses exotic reaction intermediates on the triplet surface, which cannot be synthesized via classical organic chemistry methods: the triplet non-aromatic 2,4,6-cyclooctatriene (C8H8) and the triplet aromatic 1,3,5,7-cyclooctatetraene (C8H8). Our approach provides a clean gas-phase synthesis of this hitherto elusive cyclic radical species 1,2,4,7-cyclooctatetraenyl via a single-collision event and opens up a versatile, unconventional path to access this previously largely obscure class of cyclooctatetraenyl radicals, which have been impossible to access through classical synthetic methods.Kohlenstoffatome im Grundzustand reagieren mit Cycloheptatrien (C7H8) unter Einzelstoßbedingungen in der Gasphase zum 1,2,4,7-Cyclooctatetraenyl-Radikal (C8H7). Ab-initio-Berechnungen der elektronischen Struktur zufolge verläuft die Reaktion über ungewöhnliche Triplett-C8H8-Zwischenstufen: nichtaromatisches 2,4,6-Cyclooctatrien und aromatisches 1,3,5,7-Cyclooctatetraen. Abgebildet ist die Flusskonturkarte der Reaktion.
      PubDate: 2017-09-22T06:11:04.671525-05:
      DOI: 10.1002/ange.201706861
       
  • Manganese Dioxide Nanozymes as Responsive Cytoprotective Shells for
           Individual Living Cell Encapsulation
    • Authors: Wei Li; Zhen Liu, Chaoqun Liu, Yijia Guan, Jinsong Ren, Xiaogang Qu
      Pages: 13849 - 13853
      Abstract: A powerful individual living cell encapsulation strategy for long-term cytoprotection and manipulation is reported. It uses manganese dioxide (MnO2) nanozymes as intelligent shells. As expected, yeast cells can be directly coated with continuous MnO2 shells via bio-friendly Mn-based mineralization. Significantly, the durable nanozyme shells not only can enhance the cellular tolerance against severe physical stressors including dehydration and lytic enzyme, but also enable the survival of cells upon contact with high levels of toxic chemicals for prolonged periods. More importantly, these encased cells after shell removal via a facile biomolecule stimulus can fully resume growth and functions. This strategy is applicable to a broad range of living cellsHarte Schale: Einzelne lebende Zellen wurden mit einem biologisch abbaubaren MnO2-Nanozym-Überzug versehen. Diese Schale stärkt nicht nur die Widerstandskraft der Zelle gegen physikalische Stressfaktoren, sondern sichert auch ihr Überleben bei längerem Kontakt mit hochkonzentrierten toxischen Chemikalien.
      PubDate: 2017-10-02T04:36:19.727823-05:
      DOI: 10.1002/ange.201706910
       
  • Regioselective Intermolecular Allylic C−H Amination of Disubstituted
           Olefins via Rhodium/π-Allyl Intermediates
    • Authors: Jacob S. Burman; Simon B. Blakey
      Pages: 13854 - 13857
      Abstract: A method for catalytic intermolecular allylic C−H amination of trans-disubstituted olefins is reported. The reaction is efficient for a range of common nitrogen nucleophiles bearing one electron-withdrawing group, and proceeds under mild reaction conditions. Good levels of regioselectivity are observed for a wide range of electronically diverse trans-β-alkyl styrene substrates.Ein katalytischer Ansatz für die intermolekulare allylische C-H-Aminierung trans-disubstituierter Olefine eignet sich für ein breites Spektrum gängiger Stickstoffnukleophile mit elektronenziehender Gruppe (EWG). Unter milden Bedingungen reagieren trans-β-Alkylstyrol-Substrate mit unterschiedlichen elektronischen Merkmalen hoch regioselektiv.
      PubDate: 2017-10-04T12:20:33.596446-05:
      DOI: 10.1002/ange.201707021
       
  • Olefins from Natural Gas by Oxychlorination
    • Authors: Guido Zichittella; Nicolas Aellen, Vladimir Paunović, Amol P. Amrute, Javier Pérez-Ramírez
      Pages: 13858 - 13862
      Abstract: Ethylene and propylene are the key building blocks of the chemical industry, but current processes are unable to close the growing gap between demand and manufacture. Reported herein is an exceptional europium oxychloride (EuOCl) catalyst for the selective (≥95 %) production of light olefins from ethane and propane by oxychlorination chemistry, thus achieving yields of ethylene (90 %) and propylene (40 %) unparalleled by any existing olefin production technology. Moreover, EuOCl is able to process mixtures of methane, ethane, and propane to produce the olefins, thereby reducing separation costs of the alkanes in natural gas. Finally, the EuOCl catalyst was supported on suitable carriers and evaluated in extrudate form, and preserves performance for >150 h under realistic process conditions.Ethen und Propen werden aus Ethan bzw. Propan oder aus Methan/Ethan/Propan-Gemischen über einem Europiumoxychlorid-Katalysator gebildet. Die oxychlorierungsbasierte Reaktion liefert höhere Ausbeuten als etablierte Herstellungsverfahren für Alkene. Eine erfolgreiche Übertragung in den technischen Maßstab belegt die praktische Bedeutung dieser Technik für die Olefinproduktion.
      PubDate: 2017-08-23T12:11:51.204893-05:
      DOI: 10.1002/ange.201706624
       
  • Molecular Dynamics of Hexamethylbenzene at Low Temperatures: Evidence of
           Unconventional Magnetism Based on Rotational Motion of Protons
    • Authors: Fei Yen; Zhenzheng Zhao, Sixia Hu, Lang Chen
      Pages: 13863 - 13866
      Abstract: The types of magnetism known to date are all mainly based on contributions from electron motion. We show how rotational motion of protons (H+) within the methyl groups in hexamethylbenzene (C6(CH3)6) also contribute significantly to the magnetic susceptibility. Starting from below 118 K, as the rotational motion of the methyl groups set in, an associated magnetic moment positive in nature due to charge of the protons renders the susceptibility to become anomalously dependent on temperature. Starting from 20 K, the susceptibility diverges with decreasing temperature indicative of spin–spin interactions between methyl groups aligned in a previously unclassified type of anti-ferromagnetic configuration. Complementary dielectric constant measurements also show the existence of magneto-dielectric coupling. Our findings allow for the study of strongly correlated systems that are based on a species that possesses much slower dynamics.Ein stark korreliertes System: In Hexamethylbenzol tritt eine bisher nicht identifizierte Art von Magnetismus auf, die auf der Rotationsbewegung von Protonen in Methylgruppen basiert. Bei tiefen Temperaturen existieren Spin-Spin-Wechselwirkungen zwischen den in einer neuartigen antiferromagnetischen Konfiguration ausgerichteten Methylgruppen.
      PubDate: 2017-09-07T07:00:27.38071-05:0
      DOI: 10.1002/ange.201707024
       
  • One-Step Reforming of CO2 and CH4 into High-Value Liquid Chemicals and
           Fuels at Room Temperature by Plasma-Driven Catalysis
    • Authors: Li Wang; Yanhui Yi, Chunfei Wu, Hongchen Guo, Xin Tu
      Pages: 13867 - 13871
      Abstract: The conversion of CO2 with CH4 into liquid fuels and chemicals in a single-step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH4 and CO2 is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.Elegante Abkürzung: Die Synthese von flüssigen Brennstoffen und Chemikalien (z. B. Essigsäure, Methanol, Ethanol und Formaldehyd) aus CO2 und CH4 gelang durch die Verwendung eines neuen Plasmareaktors mit einer Wasserelektrode erstmals in einem einstufigen Prozess bei Raumtemperatur (30 °C) und Atmosphärendruck. Die Selektivität für sauerstoffhaltige Verbindungen beträgt 50–60 %, mit Essigsäure als Hauptkomponente.
      PubDate: 2017-09-19T08:06:10.578202-05:
      DOI: 10.1002/ange.201707131
       
  • Black Pigment Gallstone Inspired Platinum-Chelated Bilirubin Nanoparticles
           for Combined Photoacoustic Imaging and Photothermal Therapy of Cancers
    • Authors: Dong Yun Lee; Jin Yong Kim, Yonghyun Lee, Soyoung Lee, Wenjun Miao, Hyeon Sik Kim, Jung-Joon Min, Sangyong Jon
      Pages: 13872 - 13876
      Abstract: Bilirubin (BR), a bile pigment that exerts potent antioxidant and anti-inflammatory effects, is also a major constituent of black pigment gallstones found in bile ducts under certain pathological conditions. Inspired by the intrinsic metal-chelating power of BR found in gallstones, herein we report a cisplatin-chelated BR-based nanoparticle (cisPt@BRNP) for use as a new photonic nanomedicine for combined photoacoustic imaging and photothermal therapy of cancers. The cisPt@BRNPs were prepared by simply mixing cisplatin with BRNPs, yielding ca. 150-nm-size NPs. Upon near-IR laser irradiation at 808 nm, cisPt@BRNPs generated considerable heat and induced clear death of cancer cells in vitro. Following intravenous injection into human colon cancer-bearing mice, cisPt@BRNPs allowed effective tumor visualization by photoacoustic imaging and remarkable antitumor efficacy by photothermal therapy, suggesting their potential for use as a new photonic nanomedicine for cancer therapy.Gallig gegen Krebs: Biologisch verträgliche und abbaubare, auf Nahinfrarotlicht reagierende photonische Nanomaterialien auf Basis des metallchelatisierenden Gallenfarbstoffs Bilirubin wurden entwickelt. Bilirubin-Nanopartikel mit chelatisiertem Cisplatin (cisPt@BRNPs) sind vielversprechend für eine kombinierte Krebsbehandlungen mit photoakustischer Bildgebung (PAI) und Photothermaltherapie (PTT).
      PubDate: 2017-09-22T06:05:32.000786-05:
      DOI: 10.1002/ange.201707137
       
  • Catanionic Coacervate Droplets as a Surfactant-Based Membrane-Free
           Protocell Model
    • Authors: Jean-Paul Douliez; Nicolas Martin, Cédric Gaillard, Thomas Beneyton, Jean-Christophe Baret, Stephen Mann, Laure Beven
      Pages: 13877 - 13881
      Abstract: We report on the formation of surfactant-based complex catanionic coacervate droplets in mixtures of decanoic acid and cetylpyridinium chloride or cetyltrimethylammonium bromide. We show that coacervation occurs over a broad range of composition, pH, and ionic strength. The catanionic coacervates consist of elongated micelles, sequester a wide range of solutes including water-soluble organic dyes, polysaccharides, proteins, enzymes, and DNA, and can be structurally stabilized by sodium alginate or gelatin-based hydrogelation. These results suggest that catanionic coacervates could be exploited as a novel surfactant-based membrane-free protocell model.Katanionische Koazervate als Protozellen: Proteine, Enzyme und DNA finden spontan im Inneren von katanionischen Tensidkoazervaten zueinander. Das Resultat ist ein neuartiges Protozellmodell.
      PubDate: 2017-10-02T04:36:30.096588-05:
      DOI: 10.1002/ange.201707139
       
  • Potential-Cycling Synthesis of Single Platinum Atoms for Efficient
           Hydrogen Evolution in Neutral Media
    • Authors: Lihan Zhang; Lili Han, Haoxuan Liu, Xijun Liu, Jun Luo
      Pages: 13882 - 13886
      Abstract: Single-atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential-cycling method to synthesize a catalyst comprising single Pt atoms on CoP-based nanotube arrays supported by a Ni foam, termed PtSA-NT-NF. This binder-free catalyst is centimeter-scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA-NT-NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large-scale production strategy for binder-free Pt SAC electrodes for efficient HER in neutral media.Einzelkämpfer: An CoP-Nanoröhren-Anordnungen auf einem Ni-Schaum-Substrat wurden in Potentialzyklen einzelne Pt-Atome abgeschieden. Die resultierenden bindemittelfreien Elektrokatalysatoren wurden im Zentimetermaßstab hergestellt und können noch vergrößert werden. Bei der katalytischen Wassserstoffentwicklung in neutralen Medien sind sie außergewöhnlich leistungsfähig.
      PubDate: 2017-08-23T12:12:27.299194-05:
      DOI: 10.1002/ange.201706921
       
  • Rotational Spectroscopy Probes Water Flipping by Full Fluorination of
           Benzene
    • Authors: Luca Evangelisti; Kai Brendel, Heinrich Mäder, Walther Caminati, Sonia Melandri
      Pages: 13887 - 13891
      Abstract: The topology of the interaction of water with benzene changes drastically upon full HF substitution on the aromatic ring: the weak O−H⋅⋅⋅π hydrogen bond is replaced by a O⋅⋅⋅π linkage, of about the same strength. Hexafluorobenzene–water appears to be the prototype system to investigate this kind of weak bond. The pulsed Fourier transform microwave technique has been used for the detection of the rotational spectra of the normal species and five isotopologues which unambiguously led to the identification of the geometry. Quantum mechanical calculations have been performed to interpret the experimental evidence.H2O/OH2: Eine rotationsspektroskopische Studie von Hexafluorbenzol-Wasser, einem prototypischen System für Elektronenpaar⋅⋅⋅π-Loch-Wechselwirkungen, deckt interessante chemische und dynamische Eigenschaften auf: a) Die Fluorsubstitution kehrt die Bindungsorientierung von Wasser an Benzol von O-H⋅⋅⋅π zu O⋅⋅⋅π-Loch um; b) das Wassermolekül kann fast frei über dem Ring rotieren, sodass das Spektrum eines symmetrischen Kreisels resultiert.
      PubDate: 2017-10-02T04:36:23.850375-05:
      DOI: 10.1002/ange.201707155
       
  • Specific and Direct Amplified Detection of MicroRNA with
           MicroRNA:Argonaute-2 Cleavage (miRACle) Beacons
    • Authors: Benjamin M. Luby; Gang Zheng
      Pages: 13892 - 13896
      Abstract: MicroRNA detection is a valuable method for determining cell identity. Molecular beacons are elegant sensors that can transform intracellular microRNA concentration into a fluorescence intensity. While target binding enhances beacon fluorescence, the degree of enhancement is insufficient for demanding applications. The addition of specialty nucleases can enable target recycling and signal amplification, but this process complicates the assay. We have developed and characterized a class of beacons that are susceptible to the endogenous nuclease Argonaute-2 (Ago2). After purification of the complex by co-immunoprecipitation, microRNA:Ago2 cleavage (miRACle) beacons undergo site- and sequence-specific cleavage, and show a 13-fold fluorescence enhancement over traditional beacons. The system can be adapted to any microRNA sequence, and can cleave nuclease-resistant, non-RNA bases, potentially allowing miRACle beacons to be designed for cells without interference from non-specific nucleases.Die Erkennung von MikroRNA mit Molecular Beacons ermöglicht die Erstellung von genetischen Profilen. Hier wurden Beacons für die endogene Nuclease Argonaute-2 (Ago2) entwickelt. Nach der Aufreinigung des Komplexes durch Coimmunpräzipitation werden die „miRACle-Beacons” (microRNA:Ago2 cleavage) positions- und sequenzspezifisch gespalten und zeigen einen 13-mal höheren Fluoreszenzanstieg als gewöhnliche Beacons.
      PubDate: 2017-09-27T09:46:47.391704-05:
      DOI: 10.1002/ange.201707366
       
  • Polyamine-Mediated Stoichiometric Assembly of Ribonucleoproteins for
           Enhanced mRNA Delivery
    • Authors: Jiahe Li; Yanpu He, Wade Wang, Connie Wu, Celestine Hong, Paula T. Hammond
      Pages: 13897 - 13900
      Abstract: Messenger RNA (mRNA) represents a promising class of nucleic acid drugs. Although numerous carriers have been developed for mRNA delivery, the inefficient mRNA expression inside cells remains a major challenge. Inspired by the dependence of mRNA on 3′-terminal polyadenosine nucleotides (poly A) and poly A binding proteins (PABPs) for optimal expression, we complexed synthetic mRNA containing a poly A tail with PABPs in a stoichiometric manner and stabilized the ribonucleoproteins (RNPs) with a family of polypeptides bearing different arrangements of cationic side groups. We found that the molecular structure of these polypeptides modulates the degree of PABP-mediated enhancement of mRNA expression. This strategy elicits an up to 20-fold increase in mRNA expression in vitro and an approximately fourfold increase in mice. These findings suggest a set of new design principles for gene delivery by the synergistic co-assembly of mRNA with helper proteins.Obwohl bereits mehrere Träger für den mRNA-Transport entwickelt worden sind, stellt die ineffiziente mRNA-Expression in Zellen weiterhin ein großes Hindernis dar. Weil zur optimalen Expression von mRNA 3′-terminale Polyadenosin-Nucleotide (poly A) und poly-A-bindende Proteine (PABPs) notwendig sind, wurde synthetische mRNA mit einem poly-A-Rest stöchiometrisch mit PABPs komplexiert.
      PubDate: 2017-09-19T00:30:52.144065-05:
      DOI: 10.1002/ange.201707466
       
  • Spin Changes Accompany Ultrafast Structural Interconversion in the Ground
           State of a Cobalt Nitrosyl Complex
    • Authors: Hugo J. B. Marroux; Basile F. E. Curchod, Charly A. Faradji, Timothy A. Shuttleworth, Hazel A. Sparkes, Paul G. Pringle, Andrew J. Orr-Ewing
      Pages: 13901 - 13904
      Abstract: Ultrafast, reversible intersystem crossing (ISC) is reported under ambient conditions for the electronic ground state of the pentacoordinate cobalt nitrosyl complexes, [CoX2(NO)(PMePh2)2] (X=Cl, Br), in solution. ISCs on such short timescales are more typically observed in electronically excited states reached by absorption of ultraviolet or visible light. Singlet and triplet electron spin states of the complex, corresponding to two different isomers, are populated at room temperature, and the two isomers exchange on a timescale of a few picoseconds. Ultrafast two-dimensional infrared spectroscopy observes the change in wavenumber of the NO ligand band accompanying the isomerization and associated ISC on the (spin) adiabatic ground potential energy surface. Comparison of the dynamics of the chloro- and bromo-complexes shows that inertial effects of the ligand motion have a greater effect than spin–orbit coupling on determining the forward and reverse isomerization and ISC rates.Intersystem-Crossing im Grundzustand wird für einen Cobalt-Nitrosylkomplex auf ultraschneller Zeitskala nachgewiesen. Die Dynamik des Elektronenspinübergangs wird mit 2DIR-Spektroskopie der mit den Elektronenzuständen assoziierten Kernschwingungsfrequenzen verfolgt. Vergleiche der Spinaustauschraten in zwei Halido-substituierten Komplexen belegen, dass Trägheitseffekte Spin-Bahn-Kopplungseffekte des Liganden überwiegen.
      PubDate: 2017-09-22T06:31:02.644499-05:
      DOI: 10.1002/ange.201707508
       
  • Black Phosphorus Quantum Dots Used for Boosting Light Harvesting in
           Organic Photovoltaics
    • Authors: Shenghua Liu; Shenghuang Lin, Peng You, Charles Surya, Shu Ping Lau, Feng Yan
      Pages: 13905 - 13909
      Abstract: Although organic photovoltaic devices (OPVs) have been investigated for more than two decades, the power conversion efficiencies of OPVs are much lower than those of inorganic or perovskite solar cells. One effective approach to improve the efficiency of OPVs is to introduce additives to enhance light harvesting as well as charge transportation in the devices. Here, black phosphorus quantum dots (BPQDs) are introduced in OPVs as an additive. By adding 0.055 wt % BPQDs relative to the polymer donors in the OPVs, the device efficiencies can be dramatically improved for more than 10 %. The weight percentage is much lower than that of any other additive used in OPVs before, which is mainly due to the two-dimentional structure as well as the strong broadband light absorption and scattering of the BPQDs. This work paves a way for using two-dimentional quantum dots in OPVs as a cost-effective approach to enhance device efficiencies.Starke Lichtabsorption: Die Wirkungsgrade organischer Photovoltaikeinheiten wurden durch Einführung von Quantenpunkten aus schwarzem Phosphor (BPQDs; 0.055 Gew.-% relativ zu den Donorpolymeren) verbessert. Der Effekt wird der starken Lichtabsorption und der zweidimensionalen Struktur der BPQDs zugeschrieben. Ein ausgeprägter Größeneffekt der BPQDs auf die Leistungssteigerung wird beobachtet.
      PubDate: 2017-09-25T01:51:02.27211-05:0
      DOI: 10.1002/ange.201707510
       
  • Organocatalytic Intramolecular [4+2] Cycloaddition between In Situ
           Generated Vinylidene ortho-Quinone Methides and Benzofurans
    • Authors: Xiaoyan Wu; Lu Xue, Dongmei Li, Shiqi Jia, Jun Ao, Jun Deng, Hailong Yan
      Pages: 13910 - 13914
      Abstract: Described herein is the enantioselective construction of oxygen-containing [5-6-5] tricyclic heterocycles by an organocatalyzed asymmetric [4+2] cycloaddition of vinylidene ortho-quinone methides and benzofurans. According to this methodology, a series of oxygen-containing [5-6-5] tricyclic heterocycles with various functional groups were synthesized in excellent enantio- and diastereoselectivities (>99 % ee, >20:1 d.r.). Furthermore, the deuterium-labeling experiments and high-resolution mass spectroscopy demonstrated that a vinylidene ortho-quinone methide intermediate was involved and possibly resulted from a prototropic rearrangement of 2-ethynylphenol. Remarkably, a catalyst loading as low as 0.1 mol %, and a gram-scale synthesis were achieved for this transformation.Drei Gruppen am Werk: Sauerstoff enthaltende [5-6-5]-Tricyclen werden durch Thioharnstoff-katalysierte asymmetrische [4+2]-Cycloadditionen zwischen Vinyliden-ortho-chinonmethiden (VQMs) und Benzofuranen aufgebaut. Auf diesem Weg sind Produkte mit verschiedenen funktionellen Gruppen hoch enantio- und diastereoselektiv zugänglich.
      PubDate: 2017-09-27T09:46:33.768284-05:
      DOI: 10.1002/ange.201707523
       
  • Extended Ladder-Type Benzo[k]tetraphene-Derived Oligomers
    • Authors: Jongbok Lee; Huanbin Li, Alexander J. Kalin, Tianyu Yuan, Chenxu Wang, Troy Olson, Hanying Li, Lei Fang
      Pages: 13915 - 13919
      Abstract: Well-defined, fused-ring aromatic oligomers represent promising candidates for the fundamental understanding and application of advanced carbon-rich materials, though bottom-up synthesis and structure–property correlation of these compounds remain challenging. In this work, an efficient synthetic route was employed to construct extended benzo[k]tetraphene-derived oligomers with up to 13 fused rings. The molecular and electronic structures of these compounds were clearly elucidated. Precise correlation of molecular sizes and crystallization dynamics was established, thus demonstrating the pivotal balance between intermolecular interaction and molecular mobility for optimized processing of highly ordered solids of these extended conjugated molecules.Aromatische Sprossenleitern: Eine hoch effiziente thermodynamische Anellierung liegt der „Bottom-up”-Synthese definierter kondensierter Oligomere zugrunde, die Graphen-Nanostreifen ähneln. Die elektronischen Strukturen dieser Oligomere und ihre Kristallisationsdynamik hängen stark von der Molekülgröße ab.
      PubDate: 2017-10-02T08:57:33.024366-05:
      DOI: 10.1002/ange.201707595
       
  • Bioactive Macrocyclic Inhibitors of the PD-1/PD-L1 Immune Checkpoint
    • Authors: Katarzyna Magiera-Mularz; Lukasz Skalniak, Krzysztof M. Zak, Bogdan Musielak, Ewa Rudzinska-Szostak, Łukasz Berlicki, Justyna Kocik, Przemyslaw Grudnik, Dominik Sala, Tryfon Zarganes-Tzitzikas, Shabnam Shaabani, Alexander Dömling, Grzegorz Dubin, Tad A. Holak
      Pages: 13920 - 13923
      Abstract: Blockade of the immunoinhibitory PD-1/PD-L1 pathway using monoclonal antibodies has shown impressive results with durable clinical antitumor responses. Anti-PD-1 and anti-PD-L1 antibodies have now been approved for the treatment of a number of tumor types, whereas the development of small molecules targeting immune checkpoints lags far behind. We characterized two classes of macrocyclic-peptide inhibitors directed at the PD-1/PD-L1 pathway. We show that these macrocyclic compounds act by directly binding to PD-L1 and that they are capable of antagonizing PD-L1 signaling and, similarly to antibodies, can restore the function of T-cells. We also provide the crystal structures of two of these small-molecule inhibitors bound to PD-L1. The structures provide a rationale for the checkpoint inhibition by these small molecules, and a description of their small molecule/PD-L1 interfaces provides a blueprint for the design of small-molecule inhibitors of the PD-1/PD-L1 pathway.Trennender Ring: Makrocyclische Peptid-Inhibitoren können den PD-1/PD-L1-Pfad blockieren, indem sie direkt an PD-L1 binden und, ähnlich wie Anti-PD-L1-Antikörper, die Funktion von T-Zellen wiederherstellen. Strukturen der Grenzfläche zwischen Makrocyclus und PD-L1 bilden die Grundlage für den Entwurf von niedermolekularen Inhibitoren mit Antitumoreigenschaften.
      PubDate: 2017-09-26T09:27:51.490438-05:
      DOI: 10.1002/ange.201707707
       
  • A Biomimetic Escape Strategy for Cytoplasm Invasion by Synthetic Particles
    • Authors: Nerea Iturrioz-Rodríguez; Elena González-Domínguez, Eloisa González-Lavado, Laura Marín-Caba, Belén Vaz, Moisés Pérez-Lorenzo, Miguel A. Correa-Duarte, Monica L. Fanarraga
      Pages: 13924 - 13928
      Abstract: The translocation of nanomaterials or complex delivery systems into the cytosol is a major challenge in nanobiotechnology. After receptor-mediated endocytosis, most nanomaterials are sequestered and undergo degradation, therapy inactivation, or exocytosis. Herein we explore a novel surface particle coating made of adsorbed carbon nanotubes that provides coated materials with new properties that reproduce the viral cell-invasive mechanisms, namely, receptor-mediated endocytosis, endolysosomal escape, and cytosolic particle release preserving cell viability. This novel biomimetic coating design will enable the intracytoplasmic delivery of many different functional materials endowed with therapeutic, magnetic, optical, or catalytic functionalities, thus opening the door to a wide array of chemical and physical processes within the cytosolic or nuclear domains, and supporting new developments in the biotechnological, pharmaceutical, and biomedical industries.Eine Nanobeschichtung aus Kohlenstoffnanoröhren (CNTs) ermöglicht es nm/μm-großen Partikeln, lysosomale Membranen zu durchbrechen und in den intrazellulären Raum einzudringen (siehe Bild). Die beschichteten Materialien ähneln in ihrer Struktur Viren und reproduzieren die viralen Zellinvasionsmechanismen der rezeptorvermittelten Endocytose, des endolysosomalen Austritts und der cytosolischen Partikelfreisetzung unter Beibehaltung der Zellviabilität.
      PubDate: 2017-10-02T04:37:06.339938-05:
      DOI: 10.1002/ange.201707769
       
  • An Ultraflexible Silicon–Oxygen Battery Fiber with High Energy
           Density
    • Authors: Ye Zhang; Yiding Jiao, Lijun Lu, Lie Wang, Taiqiang Chen, Huisheng Peng
      Pages: 13929 - 13934
      Abstract: To satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progress has been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon–oxygen battery fiber with high energy density and ultra-high flexibility by designing a coaxial architecture with a lithiated silicon/carbon nanotube hybrid fiber as inner anode, a polymer gel as middle electrolyte and a bare carbon nanotube sheet as outer cathode. The fiber showed a high energy density of 512 Wh kg−1 and could effectively work after bending for 20 000 cycles. These battery fibers have been further woven into flexible textiles for a large-scale application.Eine Silicium-Sauerstoff-Batteriefaser mit hoher Energiedichte und ultrahoher Flexibilität wurde entwickelt. Die koaxiale Architektur der Faser wurde mittels einer lithiierten Silicium-Kohlenstoff-Hybridnanoröhrenfaser als innere Anode, einem Polymergel als Zwischenelektrolyt und einer Schicht aus Kohlenstoffnanoröhren als äußere Kathode erhalten.
      PubDate: 2017-10-02T04:37:35.018281-05:
      DOI: 10.1002/ange.201707840
       
  • Electron-Transfer and Hydride-Transfer Pathways in the Stoltz–Grubbs
           Reducing System (KOtBu/Et3SiH)
    • Authors: Andrew J. Smith; Allan Young, Simon Rohrbach, Erin F. O'Connor, Mark Allison, Hong-Shuang Wang, Darren L. Poole, Tell Tuttle, John A. Murphy
      Pages: 13935 - 13939
      Abstract: Recent studies by Stoltz, Grubbs et al. have shown that triethylsilane and potassium tert-butoxide react to form a highly attractive and versatile system that shows (reversible) silylation of arenes and heteroarenes as well as reductive cleavage of C−O bonds in aryl ethers and C−S bonds in aryl thioethers. Their extensive mechanistic studies indicate a complex network of reactions with a number of possible intermediates and mechanisms, but their reactions likely feature silyl radicals undergoing addition reactions and SH2 reactions. This paper focuses on the same system, but through computational and experimental studies, reports complementary facets of its chemistry based on a) single-electron transfer (SET), and b) hydride delivery reactions to arenes.Das vielseitige System Triethylsilan/Kalium-tert-butoxid wurde für die C-N-Bindungsspaltung in N-Benzyl- (siehe Schema) und N-Allylindolen sowie für die Reduktion polycyclischer Arene zu ihren Dihydroderivaten genutzt.
      PubDate: 2017-10-02T04:37:47.930844-05:
      DOI: 10.1002/ange.201707914
       
  • H2S-Activable MOF Nanoparticle Photosensitizer for Effective Photodynamic
           Therapy against Cancer with Controllable Singlet-Oxygen Release
    • Authors: Yu Ma; Xiangyuan Li, Aijie Li, Peng Yang, Caiyun Zhang, Bo Tang
      Pages: 13940 - 13944
      Abstract: Photodynamic therapy (PDT) has emerged as an important minimally invasive tumor treatment technology. The search for an effective photosensitizer to realize selective cancer treatment has become one of the major foci in recent developments of PDT technology. Controllable singlet-oxygen release based on specific cancer-associated events, as another major layer of selectivity mode, has attracted great attention in recent years. Here, for the first time, we demonstrated that a novel mixed-metal metal–organic framework nanoparticle (MOF NP) photosensitizer can be activated by a hydrogen sulfide (H2S) signaling molecule in a specific tumor microenvironment for PDT against cancer with controllable singlet-oxygen release in living cells. The effective removal of tumors in vivo further confirmed the satisfactory treatment effect of the MOF NP photosensitizer.Selektive Krebsbehandlung: Ein gemischtmetallischer MOF-Nanopartikelphotosensibilisator wird durch ein H2S-Signalmolekül in einer spezifischen Tumormikroumgebung durch steuerbare Freisetzung von Singulett-Sauerstoff für die photodynamische Therapie aktiviert. Die effektive Tumorbeseitigung in vivo bestätigt den zufriedenstellenden Behandlungseffekt des Photosensibilisators.
      PubDate: 2017-09-22T06:26:02.002853-05:
      DOI: 10.1002/ange.201708005
       
  • Selective C−O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by
           Piers’ Borane Generated In Situ
    • Authors: Jianbo Zhang; Sehoon Park, Sukbok Chang
      Pages: 13945 - 13949
      Abstract: Described herein is the selective reduction of sugars with hydrosilanes catalyzed by using Piers’ borane [(C6F5)2BH] generated in situ. The hydrosilylative C−O bond cleavage of silyl-protected mono- and disaccharides in the presence of a (C6F5)2BH catalyst, generated in situ from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. A study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.Piers-Boran, [(C6F5)2BH], kann in situ für die Reduktion von Zuckern über Hydrosilylierung erzeugt werden. Die hoch chemo- und regioselektive Reaktion liefert eine Reihe linearer oder cyclischer Polyole unter milden Bedingungen. Studien zur Reaktivität und zur Regioselektivität der C-O-Bindungsspaltung mit Hydrosilanen deuten auf einen Einfluss der sterischen Verhältnisse am anomeren Kohlenstoffzentrum des Zuckers hin.
      PubDate: 2017-10-02T04:45:38.445003-05:
      DOI: 10.1002/ange.201708109
       
  • Valence Interconversion of Octahedral Nickel(II/III/IV) Centers
    • Authors: Masahiro Kouno; Nobuto Yoshinari, Naoto Kuwamura, Kohei Yamagami, Akira Sekiyama, Mitsutaka Okumura, Takumi Konno
      Pages: 13950 - 13954
      Abstract: Three oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuclear complex, [Ni{Rh(apt)3}2]n+ (apt=3- aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox-inert fac-[RhIII(apt)3] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single-crystal X-ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn–Teller distortion.Farbige Nickelchemie: Eine Reihe S-verbrückter RhNiRh-Dreikernkomplexe mit oktaedrisch umgebenem Nickelzentrum in drei verschiedenen Oxidationsstufen (+2, +3, +4) wurde isoliert. Wechsel der Oxidationsstufe gehen mit Änderungen von Farbe, magnetischen Eigenschaften und geometrischen Jahn-Teller-Verzerrungen einher, die dreikernige Gesamtstruktur bleibt aber erhalten.
      PubDate: 2017-09-22T06:25:32.259731-05:
      DOI: 10.1002/ange.201708169
       
  • Visualization of Stereoselective Supramolecular Polymers by
           Chirality-Controlled Energy Transfer
    • Authors: Aritra Sarkar; Shikha Dhiman, Aditya Chalishazar, Subi J. George
      Pages: 13955 - 13959
      Abstract: Chirality-driven self-sorting is envisaged to efficiently control functional properties in supramolecular materials. However, the challenge arises because of a lack of analytical methods to directly monitor the enantioselectivity of the resulting supramolecular assemblies. Presented herein are two fluorescent core-substituted naphthalene-diimide-based donor and acceptor molecules with minimal structural mismatch and they comprise strong self-recognizing chiral motifs to determine the self-sorting process. As a consequence, stereoselective supramolecular polymerization with an unprecedented chirality control over energy transfer has been achieved. This chirality-controlled energy transfer has been further exploited as an efficient probe to visualize microscopically the chirality driven self-sorting.Nicht gleich, aber im Kern ähnlich: Zwei strukturell sehr ähnliche Moleküle mit Donor- oder Akzeptor-substituierten fluoreszierenden Naphthalindiimid-Gruppen und chiralen Erkennungsmotiven für die leichtere Selbstsortierung werden vorgestellt. Auf der Grundlage eines chiralitätsgesteuerten Energietransfers können stereoselektiv selbstsortierte und gemischte supramolekulare Polymere unterschieden werden.
      PubDate: 2017-10-02T04:45:50.180838-05:
      DOI: 10.1002/ange.201708267
       
  • Single Turnover at Molecular Polymerization Catalysts Reveals
           Spatiotemporally Resolved Reactions
    • Authors: Quinn T. Easter; Suzanne A. Blum
      Pages: 13960 - 13963
      Abstract: Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components.Lichtzeichen: Einzelne katalytische Umsätze in wachsenden Polymeren können räumlich und zeitlich aufgelöst nachgewiesen werden. Durch Anbringen eines Fluorophors sind die Reaktionen der Norbornen-Monomere an einem industriell bedeutsamen molekularen Rutheniumkatalysator der Ringöffnungsmetathesepolymerisation als hellgrüne Lichtblitze fluoreszenzmikroskopisch detektierbar.
      PubDate: 2017-09-25T05:24:25.072994-05:
      DOI: 10.1002/ange.201708284
       
  • One-Step Multigram-Scale Biomimetic Synthesis of Psiguadial B
    • Authors: Christopher G. Newton; Duc N. Tran, Matthew D. Wodrich, Nicolai Cramer
      Pages: 13964 - 13968
      Abstract: A gram-scale synthesis of psiguadial B, a purported inhibitor of human hepatoma cell growth, has been achieved in one step by a biomimetic three-component coupling of caryophyllene, benzaldehyde, and diformylphloroglucinol. This cascade reaction is catalyzed by N,N′-dimethylethylenediamine, and proceeds at ambient temperature to generate four stereocenters, two rings, one C−O bond, and three C−C bonds. Combined computational and experimental investigations suggest the biosynthesis of the natural product is non-enzyme mediated, and is the result of a Michael addition between caryophyllene and a reactive ortho-quinone methide, followed by two sequential intramolecular cationic cyclization events.Eine biomimetische Dreikomponentenkupplung unter Bildung von drei C-C-Bindungen, einer C-O-Bindung, zwei Ringen und vier Stereozentren ist die Basis einer einstufigen Synthese von Psiguadial B. Synthese- und Computerstudien zufolge verläuft die Reaktion über eine Michael-Addition von Caryophyllen an ein in situ generiertes ortho-Chinonmethid und zwei nachfolgende sequenzielle kationische Cyclisierungen.
      PubDate: 2017-09-26T09:27:45.000926-05:
      DOI: 10.1002/ange.201708333
       
  • Three-Dimensional Hierarchical Architectures Derived from Surface-Mounted
           Metal–Organic Framework Membranes for Enhanced Electrocatalysis
    • Authors: Gan Jia; Wen Zhang, Guozheng Fan, Zhaosheng Li, Degang Fu, Weichang Hao, Chunwei Yuan, Zhigang Zou
      Pages: 13969 - 13973
      Abstract: Inspired by the rapid development of metal–organic-framework-derived materials in various applications, a facile synthetic strategy was developed for fabrication of 3D hierarchical nanoarchitectures. A surface-mounted metal–organic framework membrane was pyrolyzed at a range of temperatures to produce catalysts with excellent trifunctional electrocatalytic efficiencies for the oxygen reduction, hydrogen evolution, and oxygen evolution reactions.Heißer als MOFs: Auf Oberflächen verankerte Membranen aus Metall-organischen Gerüsten (MOFs) wurden pyrolysiert, um elektrokatalytische Materialien mit 3D-Nanoarchitekturen und zahlreichen katalytischen Zentren zu erhalten. Cobalt aus dem dünnen MOF-Film hat eine doppelte Funktion: Es erleichtert das Wachstum stickstoffdotierter Kohlenstoff-Nanoröhren, und es vermittelt Sauerstoff-Reduktion sowie Wasserstoff- und Sauerstoff-Entwicklung.
      PubDate: 2017-09-25T05:24:57.858845-05:
      DOI: 10.1002/ange.201708385
       
  • Integration of Bromine and Cyanogen Bromide Generators for the
           Continuous-Flow Synthesis of Cyclic Guanidines
    • Authors: Gabriel Glotz; René Lebl, Doris Dallinger, C. Oliver Kappe
      Pages: 13974 - 13977
      Abstract: A continuous-flow process for the in situ on-demand generation of cyanogen bromide (BrCN) from bromine and potassium cyanide that makes use of membrane-separation technology is described. In order to circumvent the handling, storage, and transportation of elemental bromine, a continuous bromine generator using bromate–bromide synproportionation can optionally be attached upstream. Monitoring and quantification of BrCN generation was enabled through the implementation of in-line FTIR technology. With the Br2 and BrCN generators connected in series, 0.2 mmol BrCN per minute was produced, which corresponds to a 0.8 m solution of BrCN in dichloromethane. The modular Br2/BrCN generator was employed for the synthesis of a diverse set of biologically relevant five- and six-membered cyclic amidines and guanidines. The set-up can either be operated in a fully integrated continuous format or, where reactive crystallization is beneficial, in semi-batch mode.Bromcyan auf Abruf: Das hoch giftige, aber sehr nützliche Reagens Bromcyan (BrCN) kann komplett kontinuierlich aus leichter zu handhabenden Vorstufen erzeugt und direkt in der Synthese medizinisch relevanter Stickstoffheterocyclen eingesetzt werden.
      PubDate: 2017-10-02T08:56:39.680563-05:
      DOI: 10.1002/ange.201708533
       
  • Mass Production and Pore Size Control of Holey Carbon Microcages
    • Authors: Lei Zhang; Xiaoxiao Liu, Yuhai Dou, Binwei Zhang, Huiling Yang, Shixue Dou, Huakun Liu, Yunhui Huang, Xianluo Hu
      Pages: 13978 - 13982
      Abstract: Architectural control of porous solids, such as porous carbon cages, has received considerable attention for versatile applications because of their ability to interact with liquids and gases not only at the surface, but throughout the bulk. Herein we report a scalable, facile spray-pyrolysis route to synthesize holey carbon microcages with mosquito-net-like shells. Using the surfaces of water droplets as the growth templates, styrene–butadiene rubber macromolecules are controllably cross-linked, and size-controllable holes on the carbon shells are generated. The as-formed carbon microcages encapsulating Si nanoparticles exhibit enhanced lithium-storage performances for lithium-ion batteries. The scalable, inexpensive synthesis of porous carbon microcages with controlled porosity and the demonstration of outstanding electrochemical properties are expected to extend their uses in energy storage, molecular sieves, catalysis, adsorbents, water/air filters, and biomedical engineering.Löchrige hohle Kohlenstoffmikrokugeln mit einstellbarer Porengröße sind mittels einer Sprühpyrolysetechnik leicht zugänglich. Diese Strukturen sind für Energiespeicheranwendungen von Interesse, wie der Einsatz als Lithiumionenspeicher in Batterien zeigt, sie können aber auch zu Mikrobehältern für andere funktionelle Materialien weiterentwickelt werden.
      PubDate: 2017-10-04T12:00:23.121189-05:
      DOI: 10.1002/ange.201708732
       
  • Repairing Nanoparticle Surface Defects
    • Authors: Emanuele Marino; Thomas E. Kodger, Ryan W. Crisp, Dolf Timmerman, Katherine E. MacArthur, Marc Heggen, Peter Schall
      Pages: 13983 - 13987
      Abstract: Solar devices based on semiconductor nanoparticles require the use of conductive ligands; however, replacing the native, insulating ligands with conductive metal chalcogenide complexes introduces structural defects within the crystalline nanostructure that act as traps for charge carriers. We utilized atomically thin semiconductor nanoplatelets as a convenient platform for studying, both microscopically and spectroscopically, the development of defects during ligand exchange with the conductive ligands Na4SnS4 and (NH4)4Sn2S6. These defects can be repaired via mild chemical or thermal routes, through the addition of L-type ligands or wet annealing, respectively. This results in a higher-quality, conductive, colloidally stable nanomaterial that may be used as the active film in optoelectronic devices.Für Solarzellen basierend auf Halbleiternanopartikeln müssen leitfähige Liganden verwendet werden – allerdings führt der Austausch isolierender Liganden durch leitfähige Metallchalkogenid-Komplexe zu Strukturdefekten, die Ladungsträger abfangen. Mit CdSe-Nanoplättchen als Modellsystem wird gezeigt, dass die Bildung von Defekten durch sorgfältige Wahl milder Behandlungsbedingungen minimiert werden kann.
      PubDate: 2017-09-26T09:37:42.54331-05:0
      DOI: 10.1002/ange.201705685
       
  • Synergistic Effects between Atomically Dispersed Fe−N−C and C−S−C
           for the Oxygen Reduction Reaction in Acidic Media
    • Authors: Hangjia Shen; Eduardo Gracia-Espino, Jingyuan Ma, Ketao Zang, Jun Luo, Le Wang, Sanshuang Gao, Xamxikamar Mamat, Guangzhi Hu, Thomas Wagberg, Shaojun Guo
      Pages: 13988 - 13992
      Abstract: Various advanced catalysts based on sulfur-doped Fe/N/C materials have recently been designed for the oxygen reduction reaction (ORR); however, the enhanced activity is still controversial and usually attributed to differences in the surface area, improved conductivity, or uncertain synergistic effects. Herein, a sulfur-doped Fe/N/C catalyst (denoted as Fe/SNC) was obtained by a template-sacrificing method. The incorporated sulfur gives a thiophene-like structure (C−S−C), reduces the electron localization around the Fe centers, improves the interaction with oxygenated species, and therefore facilitates the complete 4 e− ORR in acidic solution. Owing to these synergistic effects, the Fe/SNC catalyst exhibits much better ORR activity than the sulfur-free variant (Fe/NC) in 0.5 m H2SO4.Ein Schwefel-dotierter Fe/N/C-Katalysator mit deutlich besserer Aktivität in der Sauerstoffreduktion (ORR) in H2SO4-Lösung (0.5 m) als die schwefelfreie Variante wurde entwickelt. Die Schwefelatome reduzieren die Elektronenlokalisation um die Eisenzentren, verbessern die Wechselwirkung mit den Sauerstoffspezies und erleichtern daher die vollständige 4 e−-ORR in saurer Lösung.
      PubDate: 2017-09-27T09:47:07.242292-05:
      DOI: 10.1002/ange.201706602
       
  • Silver-Catalyzed Stereoselective Aminosulfonylation of Alkynes
    • Authors: Yongquan Ning; Qinghe Ji, Peiqiu Liao, Edward A. Anderson, Xihe Bi
      Pages: 13993 - 13996
      Abstract: A silver-catalyzed intermolecular aminosulfonylation of terminal alkynes with sodium sulfinates and TMSN3 is reported. This three-component reaction proceeds through sequential hydroazidation of the terminal alkyne and addition of a sulfonyl radical to the resultant vinyl azide. The method enables the stereoselective synthesis of a wide range of β-sulfonyl enamines without electron-withdrawing groups on the nitrogen atom. These enamines are found to be suitable for a variety of further transformations.Dreikomponentenkupplung: Die erste intermolekulare Aminosulfonylierung terminaler Alkine mit Natriumsulfinaten und TMSN3 ist gut verträglich mit funktionellen Gruppen und verläuft über eine sequenzielle Hydroazidierung des terminalen Alkins und Addition eines Sulfonylradikals an das resultierende Vinylazid. Die Reaktion ermöglicht die stereoselektive Synthese vielfältiger N-ungeschützter β-Sulfonylenamine.
      PubDate: 2017-07-07T02:16:42.205476-05:
      DOI: 10.1002/ange.201705122
       
  • Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To
           Form an Ester by Visible-Light Photoredox Catalysis
    • Authors: Shao-Feng Wang; Xiao-Ping Cao, Yang Li
      Pages: 13997 - 14001
      Abstract: We have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro-Smiles rearrangement by visible-light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C−O bond cleavage, we developed a novel approach to the C−O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one-pot, two-step gram-scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway.In einer Retro-Smiles-Umlagerung unter Photoredoxkatalyse mit sichtbarem Licht bei Umgebungstemperatur wandert eine der Arylgruppen eines Diarylethers zur Carboxygruppe, um einen Ester zu bilden (siehe Schema). Die Reaktion erfordert keine Übergangsmetalle, stöchiometrische Oxidationsmittel oder Basen. Anschließende Verseifung führt insgesamt zur C-O-Spaltung des Arylethers.
      PubDate: 2017-09-26T09:37:35.854796-05:
      DOI: 10.1002/ange.201706597
       
  • Catalytic Asymmetric Mannich Reaction with N-Carbamoyl Imine Surrogates of
           Formaldehyde and Glyoxylate
    • Authors: Yang'en You; Long Zhang, Linfeng Cui, Xueling Mi, Sanzhong Luo
      Pages: 14002 - 14006
      Abstract: N,O-acetals (NOAcs) were developed as bench stable surrogates for N-carbamoyl, (Boc, Cbz and Fmoc) formaldehyde and glyoxylate imines in asymmetric Mannich reactions. The NOAcs can be directly utilized in the chiral primary amine catalyzed Mannich reactions of both acyclic and cyclic β-ketocarbonyls with high yields and excellent stereoselectivity. The current reaction offers a straightforward approach in the asymmetric synthesis of α- or β-amino carbonyls bearing chiral quaternary centers in a practical and highly stereocontrolled manner.Hart genug für die Laborbank: N,O-Acetale (NOAcs) sind luftstabile Surrogate für N-Carbamoyl(Boc, Cbz, Fmoc)-Formaldehyde und Glyoxylat-Imine in asymmetrischen Mannich-Reaktionen. Mit ihrer Hilfe gelingen praktische direkte und hoch stereokontrollierte Synthesen von α- oder β-Aminocarbonylverbindungen mit quartären Chiralitätszentren. EWG=elektronenziehende Gruppe, PG=Schutzgruppe.
      PubDate: 2017-10-02T08:57:42.939218-05:
      DOI: 10.1002/ange.201707005
       
  • Formation of Stable Tin Perovskites Co-crystallized with Three Halides for
           Carbon-Based Mesoscopic Lead-Free Perovskite Solar Cells
    • Authors: Cheng-Min Tsai; Nayantara Mohanta, Chi-Yung Wang, Yu-Pei Lin, Yaw-Wen Yang, Chien-Lung Wang, Chen-Hsiung Hung, Eric Wei-Guang Diau
      Pages: 14007 - 14011
      Abstract: We synthesized and characterized methylammonium (MA) mixed tri-halide tin perovskites (MASnIBr2−xClx) for carbon-based mesoscopic solar cells free of lead and hole-transporting layers. Varied SnCl2/SnBr2 ratios yielded tin perovskites with three halides (I, Br, and Cl) co-crystallized inside the tin-perovskite. When the SnCl2 proportion was ≥50 % (x≥1), phase separation occurred to give MASnI3−yBry and MASnCl3−zBrz in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr1.8Cl0.2 (SnCl2=10 %) showed the best photovoltaic performance: JSC=14.0 mA cm−2, VOC=380 mV, FF=0.573, and PCE=3.1 %, and long-term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr1.8Cl0.2 cell. Transient PL decays showed the intrinsic problem of tin-based perovskites with average lifetimes less than 100 ps.Da ist Zinn drin: Stabile Zinn-Perowskite, die drei verschiedene Halogenide enthalten (I, Br und Cl), wurden durch Umsetzung von Methylammonium(MA)-Iodid mit SnCl2/SnBr2-Mischungen in Verhältnissen ≤25:75 synthetisiert. Die beste Solarzelle mit kohlenstoffbasierter mesoskopischer Elektrode und MASnIBr1.8Cl0.2 erzielte eine Wirkungsgrad von 3.1 %.
      PubDate: 2017-09-22T06:11:18.782606-05:
      DOI: 10.1002/ange.201707037
       
  • Reductive Coupling of Acrylates with Ketones and Ketimines by a
           Nickel-Catalyzed Transfer-Hydrogenative Strategy
    • Authors: Craig S. Buxton; David C. Blakemore, John F. Bower
      Pages: 14012 - 14016
      Abstract: Nickel-catalyzed coupling of benzyl acrylates with activated ketones and imines provides γ-butyrolactones and lactams, respectively. The benzyl alcohol byproduct released during the lactonization/lactamization event is relayed to the next cycle where it serves as the reductant for C−C bond formation. This strategy represents a conceptually unique approach to transfer-hydrogenative C−C bond formation, thus providing examples of reductive heterocyclizations where hydrogen embedded within an alcohol leaving group facilitates turnover.Ein direkter Zugang zu γ-Butyrolactonen und Lactamen wird durch die Ni-katalysierte Kupplung von Benzylacrylaten mit aktivierten Ketonen bzw. Iminen ermöglicht. Als Nebenprodukt der Lactonisierung oder Lactamisierung wird ein Benzylalkohol freigesetzt, der in einem Relaisprozess in den nächsten Zyklus überführt wird, wo er als Reduktionsmittel zur C-C-Bindungsbildung fungiert.
      PubDate: 2017-10-04T12:17:34.190831-05:
      DOI: 10.1002/ange.201707531
       
  • Benzodisilacyclobutadienes: 8π-Electron Systems with an Antiaromatic
           Silicon Ring
    • Authors: Shintaro Ishida; Yoshifumi Misawa, Shohei Sugawara, Takeaki Iwamoto
      Pages: 14017 - 14020
      Abstract: Benzodisilacyclobutadienes 2 a–c were isolated as blue to green crystalline solids from the reaction of stable disilyne 1 and 1,2-dibromobenzenes in the presence of potassium graphite. In the solid state, substantial bond alternation was observed within the benzene rings of 2 a–c. In hexane, 2 a–c showed remarkable bathochromic shifts of the ππ* (HOMOLUMO) absorption bands at 625–670 nm. NMR spectra and theoretical calculations indicated that the diamagnetic ring currents of the benzene rings of 2 a–c are considerably reduced by contributions from the antiaromatic 1,2-disilacyclobutadienes. In their entirety, the obtained results indicate that 2 a–c represent 8π-electron systems that contain an antiaromatic 1,2-disilacyclobutadiene.Schwierige Nachbarn: Benzodisilacyclobutadiene (siehe Struktur) wurden synthetisiert und als blaue und grüne kristalline Festkörper isoliert. UV/Vis- und NMR-Spektren sowie theoretische Rechnungen bestätigen, dass die Moleküle im Festkörper als 8π-Elektronensysteme mit einer antiaromatischen 1,2-Disilacyclobutadien-Einheit vorliegen.
      PubDate: 2017-10-02T08:57:19.510874-05:
      DOI: 10.1002/ange.201707553
       
  • Bioinspired Total Synthesis of (−)-Vescalin: A Nonahydroxytriphenoylated
           C-Glucosidic Ellagitannin
    • Authors: Antoine Richieu; Philippe A. Peixoto, Laurent Pouységu, Denis Deffieux, Stéphane Quideau
      Pages: 14021 - 14025
      Abstract: The first total synthesis of the 2,3,5-O-(S,R)-nonahydroxytriphenoylated (NHTP) C-glucosidic ellagitannin (−)-vescalin was accomplished through a series of transformations mimicking the sequence of events leading to its biogenesis. The key steps of this synthesis encompass a Wittig-mediated ring opening of a glucopyranosic hemiacetal, a C-glucosidation event through a phenolic aldol-type reaction, and a Wynberg–Feringa–Yamada-type oxidative phenolic coupling, which forged the NHTP unit of (−)-vescalin.Nah an der Biosynthese: Eine Totalsynthese für das nonahydroxytriphenoylierte (NHTP) C-glucosidische Ellagitannin (−)-Vescalin lehnt sich eng an die allgemein angenommene Biogenesesequenz an. Die charakteristische 2,3,5-(S,R)-NHTP-Einheit wird durch eine Kupfer(II)-vermittelte Wynberg-Feringa-Yamada-Phenolkupplung unter Verwendung des achiralen bicyclischen Diamins N,N′-Dimethylbispidin aufgebaut.
      PubDate: 2017-09-27T09:46:18.177874-05:
      DOI: 10.1002/ange.201707613
       
  • Correct Modeling of Cisplatin: a Paradigmatic Case
    • Authors: Nicola Tasinato; Cristina Puzzarini, Vincenzo Barone
      Pages: 14026 - 14029
      Abstract: Quantum chemistry is a useful tool in modern approaches to drug and material design, but only when the adopted model reflects a correct physical picture. Paradigmatic is the case of cis-diaminodichloroplatinum(II), cis-[Pt(NH3)2Cl2], for which the correct simulation of the structural and vibrational properties measured experimentally still remains an open question. By using this molecule as a proof of concept, it is shown that state-of-the-art quantum chemical calculations and a simple model, capturing the basic physical flavors, a cis-[Pt(NH3)2Cl2] dimer, can provide the accuracy required for interpretative purposes. The present outcomes have fundamental implications for benchmark studies aiming at assessing the accuracy of a given computational protocol.Es braucht zwei für eine treffende Vorhersage: Ein cis-[Pt(NH3)2Cl2]-Dimer als quantenchemisches Modell für Cisplatin liefert die erste quantitative Übereinstimmung mit experimentellen Struktur- und Schwingungseigenschaften. Dies belegt, dass für ein verlässliches In-silico-Wirkstoffdesign ein Modell, das das wesentliche physikalische Bild des Systems erfasst, und ein geeignetes theoretisches Verfahren nowendig sind.
      PubDate: 2017-09-14T03:57:02.834062-05:
      DOI: 10.1002/ange.201707683
       
  • Organocatalytic Enantioselective Protonation for Photoreduction of
           Activated Ketones and Ketimines Induced by Visible Light
    • Authors: Lu Lin; Xiangbin Bai, Xinyi Ye, Xiaowei Zhao, Choon-Hong Tan, Zhiyong Jiang
      Pages: 14030 - 14034
      Abstract: The first catalytic asymmetric photoreduction of 1,2-diketones and α-keto ketimines under visible light irradiation is reported. A transition-metal-free synergistic catalysis platform harnessing dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst and a non-covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Brønsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α-hydroxy ketones and α-amino ketones were obtained with high yields and enantioselectivities.Enantioselektive Protonierung: Die erste katalytische asymmetrische Photoreduktion von 1,2-Diketonen und α-Ketoketiminen mit sichtbarem Licht beruht auf einem übergangsmetallfreien kooperativen Katalysesystem mit dem Dicyanpyrazin-abgeleiteten Chromophor (DPZ) als Photoredoxkatalysator und einem nichtkovalenten chiralen Organokatalysator. Zahlreiche chirale α-Hydroxy- und α-Aminoketone wurden mit hohen Ausbeuten und Enantioselektivitäten erhalten.
      PubDate: 2017-10-04T12:16:50.166096-05:
      DOI: 10.1002/ange.201707899
       
  • Synthesis of Acylborons by Ozonolysis of Alkenylboronates: Preparation of
           an Enantioenriched Amino Acid Acylboronate
    • Authors: Jumpei Taguchi; Toshiki Ikeda, Rina Takahashi, Ikuo Sasaki, Yasushi Ogasawara, Tohru Dairi, Naoya Kato, Yasunori Yamamoto, Jeffrey W. Bode, Hajime Ito
      Pages: 14035 - 14039
      Abstract: A concise synthesis of acylborons was achieved by ozonolysis of alkenyl MIDA (N-methyliminodiacetic acid) boronates. This reaction exhibits excellent functional-group tolerance and is applicable to various acyl MIDA boronates and potassium acyltrifluroborates (KATs) which could not be synthesized by previous methods. In addition, α-amino acylborons, which would be essential for peptide ligations, were prepared for the first time. The acylboron of l-alanine was obtained in high enantiopurity and found to be configurationally stable. Oligopeptide synthesis between the α-amino KATs and amino acid in dilute aqueous media was studied.Mit Ozon gemacht: Hoch funktionalisierte Acylborverbindungen wurden durch Ozonolyse von Alkenyl-MIDA-Boronaten erhalten. α-Aminoacylborverbindungen, einschließlich enantiomerenreiner Alanin-Derivate, wurden synthetisiert. Die Produkte sind wichtig für die Proteinkonjugation über Kaliumacyltrifluorborat-Ligation. Unter den Bedingungen der Oligopeptidsynthese in wässrigem Medium erwiesen sich die Reagentien vom Alanin-Typ als konfigurationsstabil.
      PubDate: 2017-09-29T12:08:42.133597-05:
      DOI: 10.1002/ange.201707933
       
  • Enzymatic Cascade Catalysis for the Synthesis of Multiblock and
           Ultrahigh-Molecular-Weight Polymers with Oxygen Tolerance
    • Authors: Zhifen Liu; Yue Lv, Zesheng An
      Pages: 14040 - 14044
      Abstract: Synthesis of well-defined multiblock and ultrahigh-molecular-weight (UHMW) polymers has been a perceived challenge for reversible-deactivation radical polymerization (RDRP). An even more formidable task is to synthesize these extreme polymers in the presence of oxygen. A novel methodology involving enzymatic cascade catalysis is developed for the unprecedented synthesis of multiblock polymers in open vessels with direct exposure to air and UHMW polymers in closed vessels without prior degassing. The success of this methodology relies on the extraordinary deoxygenation capability of pyranose oxidase (P2Ox) and the mild yet efficient radical generation by horseradish peroxidase (HRP). The facile and green synthesis of multiblock and UHMW polymers using biorenewable enzymes under environmentally benign and scalable conditions provides a new pathway for developing advanced polymer materials.Eine enzymatische Katalysekaskade liefert Multiblockcopolymere (bis 10 Blöcke) und Polymere mit sehr hohem Molekulargewicht (UHMW; bis 2.3×106 g mol−1). Die Reaktion nutzt ein P2Ox-HRP-System, und da sie sauerstoffverträglich ist, kann sie in einem offenen Gefäß ausgeführt werden. P2Ox=Pyranoseoxidase, HRP=Meerrettichperoxidase, ACAC=Acetylaceton.
      PubDate: 2017-10-02T08:56:55.490446-05:
      DOI: 10.1002/ange.201707993
       
  • Enantioselective Total Synthesis of (−)-Deoxoapodine
    • Authors: Taek Kang; Kolby L. White, Tyler J. Mann, Amir H. Hoveyda, Mohammad Movassaghi
      Pages: 14045 - 14048
      Abstract: The first enantioselective total synthesis of (−)-deoxoapodine is described. Our synthesis of this hexacyclic aspidosperma alkaloid includes an efficient molybdenum-catalyzed enantioselective ring-closing metathesis reaction for the desymmetrization of an advanced intermediate that introduces the C5-quaternary stereocenter. After C21-oxygenation, the pentacyclic core was accessed by electrophilic C19-amide activation and transannular spirocyclization. A biogenetically inspired dehydrative C6-etherification reaction proved highly effective to secure the F-ring and the fourth contiguous stereocenter of (−)-deoxoapodine with complete stereochemical control.Ein Schlüsselschritt der Totalsynthese von (−)-Deoxoapodin ist eine Molybdän-katalysierte desymmetrisierende Ringschlussmetathese. Nach C21-Oxygenierung wurde das pentacyclische Gerüst durch Amidaktivierung und transannulare Spirocyclisierung erhalten. Eine dehydratisierende C6-Veretherung ergibt schließlich den F-Ring und das vierte aufeinanderfolgende Stereozentrum.
      PubDate: 2017-09-27T09:45:59.711561-05:
      DOI: 10.1002/ange.201708088
       
  • Gold(III) Alkyne Complexes: Bonding and Reaction Pathways
    • Authors: Luca Rocchigiani; Julio Fernandez-Cestau, Gabriele Agonigi, Isabelle Chambrier, Peter H. M. Budzelaar, Manfred Bochmann
      Pages: 14049 - 14053
      Abstract: The synthesis and characterization of hitherto hypothetical AuIII π-alkyne complexes is reported. Bonding and stability depend strongly on the trans effect and steric factors. Bonding characteristics shed light on the reasons for the very different stabilities between the classical alkyne complexes of PtII and their drastically more reactive AuIII congeners. Lack of back-bonding facilitates alkyne slippage, which is energetically less costly for gold than for platinum and explains the propensity of gold to facilitate C−C bond formation. Cycloaddition followed by aryl migration and reductive deprotonation is presented as a new reaction sequence in gold chemistry.Gold hat seine eigenen Gesetze: Die Synthese bisher nur vermuteter Gold(III)-π-Alkin-Komplexe bestätigt, dass diese deutlich reaktiver sind als die entsprechenden klassischen Platin-Alkinkomplexe. Die Alkinbindung in den Goldkomplexen unterliegt einem starken trans-Einfluss: Die Liganden sind in trans-Stellung zu einem Pyridin-N-Atom signifikant fester gebunden als trans zu einem negativ geladenen C-Donor.
      PubDate: 2017-10-02T04:45:27.24127-05:0
      DOI: 10.1002/ange.201708640
       
  • Diradikaloid oder zwitterionischer Charakter: die ungesättigte Verbindung
           [Si4{N(SiMe3)Dipp}4] mit gefaltetem Si4-Strukturmotiv
    • Authors: Jan Keuter; Kevin Schwedtmann, Alexander Hepp, Klaus Bergander, Oliver Janka, Carsten Doerenkamp, Hellmut Eckert, Christian Mück-Lichtenfeld, Felicitas Lips
      Pages: 14054 - 14059
      Abstract: Reduktion des Tribromoamidosilans {N(SiMe3)Dipp}SiBr3 mit Kaliumgraphit oder Magnesium führte zur Bildung eines Bicyclo[1.1.0]tetrasilatetraamids [Si4{N(SiMe3)Dipp}4] (1). Das Si4-Motiv in 1 weist keine tetraedrische Struktur auf und hat zwei dreifach- und zwei vierfach-koordinierte Siliciumatome. Die dreifach-koordinierten Siliciumatome sind positiv und negativ polarisiert, was durch Messungen der magnetischen Suszeptibilität, EPR-Messungen, DFT-Rechnungen, 29Si-CP-MAS-NMR- und multinukleare NMR-Spektroskopie in Lösung herausgefunden wurde. Untersuchungen der Reaktivität von 1 mit Radikalfängern waren nicht erfolgreich und bestätigen somit die partiellen Polarisierungen der Verbindung. 1 reagiert mit Schwefel zu einer neuartigen Si-S-Käfigverbindung [Si4S3{N(SiMe3)Dipp}4] (2), die von Amidosubstituenten stabilisiert wird.Schmetterling und Käfig: Die ungesättigte schmetterlingsförmige Si4-Ringverbindung [Si4{N(SiMe3)Dipp}4] (1; Dipp=2,6-iPr2C6H3) entstand durch Reduktion von {N(SiMe3)Dipp}SiBr3. 1 weist positiv und negativ polarisierte dreifach-koordinierte Si-Atome mit flexibler Geometrie auf, wie experimentelle und theoretische Studien ergaben. Reaktionen von 1 mit 5 und 8 Äquiv. Schwefel führten zu 2, einer neuartigen Amido-substituierten Si4S3-Käfigverbindung.
      PubDate: 2017-09-27T09:47:41.002952-05:
      DOI: 10.1002/ange.201705787
       
  • Übergangsmetallfreie ringöffnende Silylierung von Indolen und
           Benzofuranen mit (Diphenyl-tert-butylsilyl)lithium
    • Authors: Pan Xu; Ernst-Ulrich Würthwein, Constantin G. Daniliuc, Armido Studer
      Pages: 14060 - 14063
      Abstract: Eine praktische Methode zur Ringöffnung verschiedener Indole und Benzofurane mit einhergehender stereoselektiver Silylierung unter Nutzung von leicht erzeugtem (Diphenyl-tert-butylsilyl)lithium führt zu ortho-β-Silylvinylanilinen bzw. -phenolen. Die Desaromatisierung der Heteroarene erfolgt in Abwesenheit von Übergangsmetallkatalysatoren durch Addition des Silylanions und nachfolgende stereoselektive β-Eliminierung. Einblicke in den Reaktionsmechanismus werden durch DFT-Rechnungen erhalten. Funktionalisierende C-X-Bindungsbrüche in Heteroarenen sind ungewöhnlich und erfordern im Allgemeinen Übergangsmetallkatalysatoren.Offen für Neues: Ringöffnende Silylierung verschiedener Indole und Benzofurane mittels Diphenyl-tert-butylsilyllithium liefert ortho-β-Silylvinylaniline bzw. -phenole. Die Desaromatisierung des Heteroarengerüsts erfolgt in Abwesenheit jeglicher Übergangsmetalle über eine Addition des Silylanions und anschließende stereoselektive β-Eliminierung.
      PubDate: 2017-09-29T12:09:08.727286-05:
      DOI: 10.1002/ange.201707309
       
  • Produktion von Methanol und Ethanol aus Methan in einem einzigen Reaktor
           mit einem Nickeloxid auf Ceroxid-Zirconiumoxid-Katalysator
    • Authors: Chukwuemeka Okolie; Yasmeen F. Belhseine, Yimeng Lyu, Matthew M. Yung, Mark H. Engelhard, Libor Kovarik, Eli Stavitski, Carsten Sievers
      Pages: 14064 - 14069
      Abstract: Die Umwandlung von Methan in Alkohole unter milden Reaktionsbedingungen ist eine vielversprechende Technologie für die Nutzung abgelegener Methanvorkommen. Die flüssigen Alkohole können in Pipelines transportiert und zu wertvolleren Chemikalien weiterverarbeitet werden. Hier wird gezeigt, dass ein Katalysator aus Nickeloxidpartikeln auf einen Ceroxid-Zirconiumoxid-Träger (NiO/CZ) Methan in einem einzigen, kontinuierlich betriebenen Reaktor zu Methanol und Ethanol umwandeln kann. Die Reaktion geschieht bei milden Temperaturen (723 K) mit O2 als Oxidationsmittel. Die Produktion von Alkoholen erfordert die Gegenwart von Wasserdampf, um die vollständige Oxidation zu CO2 zu unterdrücken. Die Synergie zwischen Lewis-aciden NiO-Partikeln und dem redoxaktiven Ceroxid-Zirconiumoxid-Träger ermöglicht die ungewöhnliche Reaktivität dieses Katalysators.Schnapszahlen: Mit einer Turnover-Frequenz von mindestens 50 h−1 werden Methanol und Ethanol über NiO-Clustern auf Ceroxid-Zirconiumoxid in einem kontinuierlich betriebenen Reaktor aus Methan gebildet. Sauerstoff findet dabei als kostengünstiges Oxidationsmittel Verwendung, und die Gegenwart von Wasserdampf ermöglicht die Bildung von Alkoholen statt Verbrennungsprodukten.
      PubDate: 2017-09-26T09:37:50.719405-05:
      DOI: 10.1002/ange.201704704
       
  • Hoch fluoreszierende Pyridiniumbetaine für die Lichtsammlung
    • Authors: Jingjing Xu; Bolong Zhang, Marina Jansen, Lars Goerigk, Wallace W. H. Wong, Chris Ritchie
      Pages: 14070 - 14074
      Abstract: Die Ergebnisse experimenteller und theoretischer Untersuchungen der Eigenschaften von Pyridiniumenolaten werden vorgestellt, und ihre potenzielle Nutzbarkeit in Lichtsammelanwendungen, insbesondere lumineszierenden Solarkonzentratoren (LSCs), wird demonstriert. Synthesen, Strukturen, photophysikalische Charakterisierung und wellenfunktionsbasierte quantenchemische Studien für fünf Cyclobetaine werden präsentiert und die Leistungsfähigkeit einer LSC-Apparatur, die eines dieser Cyclobetaine enthält, wird mit dem aktuellen Stand der Technik verglichen.Experiment und Theorie: Pyridiniumenolate und ihre mögliche Anwendung in Lichtsammelsystemen, z. B. in lumineszierenden Solarkonzentratoren, wurden experimentell und theoretisch untersucht. Die Synthesen, Strukturen, photophysikalischen Eigenschaften und wellenfunktionsbasierte quantenchemische Studien von fünf Cyclobetainen werden beschrieben.
      PubDate: 2017-08-21T02:50:46.517998-05:
      DOI: 10.1002/ange.201704832
       
  • Von Vorläuferpulvern zu CsPbX3-Perowskit-Nanodrähten: Eintopfreaktion,
           Wachstumsmechanismus und gerichtete Selbstassemblierung
    • Authors: Yu Tong; Bernhard J. Bohn, Eva Bladt, Kun Wang, Peter Müller-Buschbaum, Sara Bals, Alexander S. Urban, Lakshminarayana Polavarapu, Jochen Feldmann
      Pages: 14075 - 14080
      Abstract: Die Synthese kolloidaler Nanokristalle sowie die Herstellung von Halbleiter-Nanodrähten (NWs) sind ein wichtiger Aspekt der aktuellen Forschung. Wir berichten über eine einstufige, Liganden-kontrollierte Synthese von kristallinen CsPbBr3-Perowskit-NWs direkt aus den Vorläuferpulvern. Untersuchungen des Reaktionsprozesses sowie der Entstehung der Kristallmorphologie zeigen, dass sich die eingangs hergestellten CsPbBr3-Nanowürfel in einem gerichteten Mechanismus aneinandergereiht zusammenfügen und NWs bilden. Die optischen Eigenschaften der NWs können über die gesamte Breite des sichtbaren Spektrums kontrolliert werden, indem die Halogenzusammensetzung aus Cl, Br und I durch nachträglichen Halogenaustausch verändert wird. Die Beobachtung einzelner Partikel ergab, dass diese NWs stark polarisiertes Licht mit einer Polarisationsanisotropie von 0.36 emittieren. Zudem können wir zeigen, dass die NWs sich selbstständig in einer quasi-geordneten Art an Luft/Flüssigkeit-Grenzflächen ansammeln können. Dieser Prozess sollte einfach auf andere Perowskit-Nanokristalle angewendet werden können, um deren Morphologie in Hinblick auf ihre Verwendung in zukünftigen optoelektronischen Vorrichtungen im Nanobereich zu beeinflussen.Würfel, Drähte, Assemblate: Kristalline Perowskit-Nanodrähte wurden in einem einstufigen, Liganden-kontrollierten Verfahren mittels Ultraschalldispersion direkt aus Vorläuferpulvern synthetisiert. Es wird vermutet, dass die Nanodrähte durch die gerichtete Aneinanderfügung einzelner Nanowürfel enstehen. Quasi-geordnete, selbstassemblierte Perowskit-Nanodrähte können an Luft/Flüssigkeit-Grenzflächen prozessiert werden.
      PubDate: 2017-09-26T09:37:20.989173-05:
      DOI: 10.1002/ange.201707224
       
  • Regioselektive para-Carboxylierung von Catecholen mit einer
           Prenylflavin-abhängigen Decarboxylase
    • Authors: Stefan E. Payer; Stephen A. Marshall, Natalie Bärland, Xiang Sheng, Tamara Reiter, Andela Dordic, Georg Steinkellner, Christiane Wuensch, Susann Kaltwasser, Karl Fisher, Stephen E. J. Rigby, Peter Macheroux, Janet Vonck, Karl Gruber, Kurt Faber, Fahmi Himo, David Leys, Tea Pavkov-Keller, Silvia M. Glueck
      Pages: 14081 - 14085
      Abstract: Die Verwendung von CO2 als Kohlenstoffquelle in der Synthese organischer Verbindungen entspricht den aktuellen Bemühungen für eine nachhaltigere Produktion von Chemikalien. Wir beschreiben hier die enzymkatalysierte para-Carboxylierung von Catecholen durch eine 3,4-Dihydroxybenzoesäure-Decarboxylase (AroY) aus der UbiD-Enzymfamilie. Die Kristallstrukturen und experimentelle Daten zeigen, dass dieses Enzym ein erst kürzlich entdecktes prenyliertes Flavin als Cofaktor benötigt (prFMN) und oxidative Prozesse zur Bildung der katalytisch aktiven prFMNiminium-Spezies führen. Diese Studie beschreibt die In-vitro-Rekonstitution und Aktivierung dieser prFMN-abhängigen Enzyme, welche die direkte Carboxylierung von aromatischen Catecholen unter milden Bedingungen katalysieren. Ein Reaktionsmechanismus für den reversiblen Carboxylierungsprozess über ein Intermediat mit einfach kovalent gebundener Chinoidform des Substrats wird vorgeschlagen, der sich von dem 1,3-Cycloadditionsmechanismus in verwandten Enzymen unterscheidet.Biokatalytische CO2-Fixierung: Die regioselektive para-Carboxylierung am aromatischen Ring von Catecholen wird von 3,4-Dihydroxybenzoesäure-Decarboxylasen unter milden Bedingungen katalysiert. Die Enzyme benötigen dazu ein kürzlich entdecktes prenyliertes FMN als Cofaktor, das im vorgeschlagenen Mechanismus über ein Intermediat mit einfach kovalent gebundener Chinoidform des Substrats reagiert.
      PubDate: 2017-10-02T04:35:34.088095-05:
      DOI: 10.1002/ange.201708091
       
  • Innenrücktitelbild: Olefins from Natural Gas by Oxychlorination
           (Angew. Chem. 44/2017)
    • Authors: Guido Zichittella; Nicolas Aellen, Vladimir Paunović, Amol P. Amrute, Javier Pérez-Ramírez
      Pages: 14087 - 14087
      Abstract: Die Produktion leichter Olefine aus Ethan und Propan durch Oxychlorierung mit EuOCl ist das Thema der Zuschrift auf S. 13858 von J. Pérez-Ramírez et al. Das beschriebene System verfügt über hohe Aktivität, Selektivität und Stabilität. Die mythologische Prinzessin Europa, die Zeus in seiner Verkörperung als weißer Stier aus Asien in die hellenische Welt entführte, ist namensgebend für den Erdteil wie für das zentrale Element dieser Studie.
      PubDate: 2017-10-05T03:45:25.810312-05:
      DOI: 10.1002/ange.201709951
       
  • Rücktitelbild: Potential-Cycling Synthesis of Single Platinum Atoms for
           Efficient Hydrogen Evolution in Neutral Media (Angew. Chem. 44/2017)
    • Authors: Lihan Zhang; Lili Han, Haoxuan Liu, Xijun Liu, Jun Luo
      Pages: 14088 - 14088
      Abstract: Einzelne Pt-Atome …… auf CoP-basierten Nanoröhren, die wiederum Anordnungen auf Ni-Schäumen bilden, wurden durch Anwendung von Potentialzyklen synthetisiert. In ihrer Zuschrift auf S. 13882 übertragen J. Luo, X. J. Liu und Mitarbeiter im Zuge dieser Strategie einzelne Pt-Atome von einer Pt-Quelle in neutralem Phosphat-Puffer (PBS) auf die Nanoröhren. Als Elektrokatalysator der Wasserstoffentwicklung in PBS übertreffen diese Einzelatomstrukturen kommerzielles Pt/CIn in Bezug auf Pt-Masseaktivität und Beständigkeit.
      PubDate: 2017-10-05T03:41:13.285691-05:
      DOI: 10.1002/ange.201709950
       
 
 
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