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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  [1597 journals]
  • Scrutinizing Defects and Defect Density of Selenium-Doped Graphene for
           High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells
    • Authors: Xiangtong Meng; Chang Yu, Xuedan Song, James Iocozzia, Jiafu Hong, Matthew Rager, Huile Jin, Shun Wang, Longlong Huang, Jieshan Qiu, Zhiqun Lin
      Abstract: Understanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I3−) reduction reaction of dye-sensitized solar cells (DSSCs) is indispensable for the design and construction of high-efficiency counter electrodes (CEs). Active-site-enriched selenium-doped graphene (SeG) was crafted by ball-milling followed by high-temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I3− reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode–electrolyte interface.Ab in die Sonne! Selen-dotiertes Graphen (SeG) mit angereicherten aktiven Zentren wurde durch Kugelmahlen und nachfolgendes Erhitzen auf hohe Temperaturen erhalten. Bei 900 °C gebildetes SeG (SeG-900) lieferte als Elektrokatalysator für DSSCs eine hohe Effizienz von 8.42 %, mehr als die Pt-Referenz (7.88 %). Dies lässt sich auf die verringerte Ionisierungsenergie infolge des Einbaus von Se-Spezies und eine verbesserte Fähigkeit zum Ladungstransfer zurückführen.
      PubDate: 2018-03-15T10:57:33.424011-05:
      DOI: 10.1002/ange.201801337
  • Crystalline Radicals Derived from Classical N-Heterocyclic Carbenes
    • Authors: Dennis Rottschäfer; Beate Neumann, Hans-Georg Stammler, Maurice van Gastel, Diego M. Andrada, Rajendra S. Ghadwal
      Abstract: One-electron reduction of C2-arylated 1,3-imidazoli(ni)um salts (IPrAr)Br (Ar=Ph, 3 a; 4-DMP, 3 b; 4-DMP=4-Me2NC6H4) and (SIPrAr)I (Ar=Ph, 4 a; 4-Tol, 4 b) derived from classical NHCs (IPr=:C{N(2,6-iPr2C6H3)}2CHCH, 1; SIPr=:C{N(2,6-iPr2C6H3)}2CH2CH2, 2) gave radicals [(IPrAr)]. (Ar=Ph, 5 a; 4-DMP, 5 b) and [(SIPrAr)]. (Ar=Ph, 6 a; 4-Tol, 6 b). Each of 5 a,b and 6 a,b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid-state characterization of NHC-derived carbon-centered radicals 6 a,b by single-crystal X-ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group.Kristalline Radikale (IPrAr). und (SIPrAr)., die von klassischen N-heterocyclischen Carbenen (NHCs; IPr=:C{N(2,6-iPr2C6H3)}2CHCH, SIPr=:C{N(2,6-iPr2C6H3)}2CH2CH2) abstammen, wurden durch Ein-Elektronen-Reduktion der entsprechenden C2-arylierten 1,3-Imidazoli(ni)um-Kationen synthetisiert. Zyklovoltammetrie, EPR- und Röntgenbeugungsstudien sowie DFT-Rechnungen decken die Schlüsselrolle des C2-Substituenten für die Stabilität der NHC-abgeleiteten Radikale auf.
      PubDate: 2018-03-15T10:57:23.683477-05:
      DOI: 10.1002/ange.201801596
  • Assessing human exposure to organic pollutants in the indoor environment
    • Authors: Tunga Salthammer; Yinping Zhang, Jinhan Mo, Holger M. Koch, Charles J. Weschler
      Abstract: There is an ongoing probing of the role of chemicals in the indoor environment. The majority of potential target substances are so-called very volatile, volatile and semi volatile organic compounds (VVOCs, VOCs and SVOCs). Depending on their physical properties and mass transfer conditions, they distribute in or between the gas phase, particle phase, settled house dust, surface films, clothing and other fabrics as well as the exposed skin and hair of the occupants themselves. Therefore, inhalation, ingestion and dermal uptake all must be considered as relevant pathways for the exposure assessment in human habitats. Exposure to VVOCs, VOCs and SVOCs can be estimated by measuring their concentrations in the relevant indoor compartments or by measuring the target compounds and/or their metabolites in urine and blood. Assessing the various routes of exposure often requires the combination of sophisticated and interdisciplinary theoretical background and experimental techniques. Consequently, close communication and collaboration between chemical and exposure scientists are needed to achieve a better understanding of human exposure to chemical substances in various indoor environments. Embedded in the toxicological context, this is the basis for assessing the corresponding health risks and for determining the control strategies or approaches to limit such risks.
      PubDate: 2018-03-15T10:06:16.081138-05:
      DOI: 10.1002/ange.201711023
  • Tailored Microstructured Hyperpolarizing Matrices for Optimal Magnetic
           Resonance Imaging
    • Authors: Matthieu Cavaillès; Aurélien Bornet, Xavier Jaurand, Basile Vuichoud, David Baudouin, Mathieu Baudin, Laurent Veyre, Geoffrey Bodenhausen, Jean-Nicolas Dumez, Sami Jannin, Christophe Copéret, Chloé Thieuleux
      Abstract: Tailoring the physical features and the porous network architecture of silica-based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (hybrid polarizing solids), enabled unprecedented performance of dissolution dynamic nuclear polarization (d-DNP). High polarization values up to P(1H)=99 % were reached for samples impregnated with a mixture of H2O/D2O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices, which provide hyperpolarized solutions free of any—potentially toxic—additives (radicals and glass-forming agents). The hyperpolarized solutions can be expelled from the porous solids, filtered, and rapidly transferred either to a nuclear magnetic resonance (NMR) spectrometer or to a magnetic resonance imaging (MRI) system.Eine Frage der Polarisation: Die Oberflächen von porösen Kieselgel-basierten Feststoffen wurden mit TEMPO-Einheiten funktionalisiert, und mit den resultierenden Systemen wurden durch dynamische Kernpolarisation hohe Protonen- und Kohlenstoffpolarisationen erzielt. Zudem wurden sie als polarisierende Matrizen in der 13C-Kernspintomographie eingesetzt.
      PubDate: 2018-03-15T10:00:26.109642-05:
      DOI: 10.1002/ange.201801009
  • A Porous Network of Bismuth Used as the Anode Material for
           High-Energy-Density Potassium-Ion Batteries
    • Authors: Kaixiang Lei; Chenchen Wang, Luojia Liu, Yuwen Luo, Chaonan Mu, Fujun Li, Jun Chen
      Abstract: Potassium-ion batteries (KIBs) are plagued by a lack of materials for reversible accommodation of the large-sized K+ ion. Herein we present, the Bi anode in combination with the dimethoxyethane-(DME) based electrolyte to deliver a remarkable capacity of ca. 400 mAh g−1 and long cycle stability with three distinct two-phase reactions of Bi KBi2K3Bi2K3Bi. These are ascribed to the gradually developed three-dimensional (3D) porous networks of Bi, which realizes fast kinetics and tolerance of its volume change during potassiation and depotassiation. The porosity is linked to the unprecedented movement of the surface Bi atoms interacting with DME molecules, as suggested by DFT calculations. A full KIB of Bi//DME-based electrolyte//Prussian blue of K0.72Fe[Fe(CN)6] is demonstrated to present large energy density of 108.1 Wh kg−1 with average discharge voltage of 2.8 V and capacity retention of 86.5 % after 350 cycles.Bi-Anoden: In einer Kaliumionenbatterie ergibt Bismut eine bemerkenswerte Kapazität von ca. 400 mAh g−1 und Zyklenstabilität. Die Elektrodenreaktionen in einem Dimethoxyethan-basierten Elektrolyt bestehen dabei aus den drei Zwei-Phasen-Reaktionen Bi ⇌ KBi2 ⇌ K3Bi2 ⇌ K3Bi. Die Eigenschaften dieses Systems werden auf die Fähigkeit von Bismut zur Bildung poröser 3D-Gerüste zurückgeführt.
      PubDate: 2018-03-15T10:00:00.43454-05:0
      DOI: 10.1002/ange.201801389
  • Mit N-heterocyclischen Carbenen behandelte Goldoberflächen in
           Pentacen-Transistoren: Verbesserte Stabilität und Kontakt an der
    • Authors: Aifeng Lv; Matthias Freitag, Kathryn M. Chepiga, Andreas H. Schäfer, Frank Glorius, Lifeng Chi
      Abstract: N-Heterocyclische Carbene (NHCs), die mit der Oberfläche von Au-Elektroden reagieren, wurden erfolgreich in Pentacen-Transistoren eingesetzt. Mit der Anwendung von NHCs stieg die Ladungsträgermobilität von Pentacen-Transistoren um das Fünffache, während der Kontaktwiderstand an der Pentacen-Au-Grenzfläche um 85 % reduziert wurde. Selbst nach zweistündigem Tempern der NHC-Au-Elektroden bei 200 °C vor der Pentacen-Abscheidung nahm die Ladungsträgermobilität der Pentacen-Transistoren nicht ab. Die hervorragenden Eigenschaften machen NHCs zu ausgezeichneten Alternativen zu Thiolen als Metallmodifikatoren für die Anwendung in organischen Feldeffekttransistoren (OFETs).Gold veredelt! Die Oberfläche von Au-Elektroden in organischen Feldeffekttransistoren (OFETs) wurde mit N-heterocyclischen Carbenen (NHCs) modifiziert. Die stark verbesserte Transistorleistung und die ausgezeichnete thermische Stabilität an Luft zeigen, dass NHCs ausgezeichnete Alternativen zu Thiolen als Metallmodifikatoren für die Anwendung in OFETs darstellen.
      PubDate: 2018-03-15T09:59:43.505206-05:
      DOI: 10.1002/ange.201713415
  • A Delamination Strategy for Thinly Layered Defect-Free High-Mobility Black
           Phosphorus Flakes
    • Authors: Sheng Yang; Ke Zhang, Antonio Gaetano Ricciardulli, Panpan Zhang, Zhongquan Liao, Martin R. Lohe, Ehrenfried Zschech, Paul W. M. Blom, Wojciech Pisula, Klaus Müllen, Xinliang Feng
      Abstract: Extraordinary electronic and photonic features render black phosphorus (BP) an important material for the development of novel electronics and optoelectronics. Despite recent progress in the preparation of thinly layered BP flakes, scalable synthesis of large-size, pristine BP flakes remains a major challenge. An electrochemical delamination strategy is demonstrated that involves intercalation of diverse cations in non-aqueous electrolytes, thereby peeling off bulk BP crystals into defect-free flakes comprising only a few layers. The interplay between tetra-n-butylammonium cations and bisulfate anions promotes a high exfoliation yield up to 78 % and large BP flakes up to 20.6 μm. Bottom-gate and bottom-contact field-effect transistors, comprising single BP flakes only a few layers thick, exhibit a high hole mobility of 252±18 cm2 V−1 s−1 and a remarkable on/off ratio of (1.2±0.15)×105 at 143 K under vacuum. This efficient and scalable delamination method holds great promise for development of BP-based composites and optoelectronic devices.Defekt-freier schwarzer Phosphor (BP) in Flockenform wurde mithilfe einer einfachen und skalierbaren Exfolierungsmethode erhalten. Delaminierte und mechanisch exfolierte BP-Flocken haben vergleichbare elektronische Eigenschaften. Diese effiziente Methode ist vielversprechend für die Entwicklung BP-basierter Komposite und optoelektronischer Baueinheiten.
      PubDate: 2018-03-15T09:59:35.647998-05:
      DOI: 10.1002/ange.201801265
  • Highly Stable Aqueous Zinc-Ion Storage Using Layered Calcium Vanadium
           Oxide Bronze Cathode
    • Authors: Chuan Xia; Jing Guo, Peng Li, Xixiang Zhang, Husam N. Alshareef
      Abstract: Eine Calciumvanadiumoxid-Bronze (Ca0.25V2O5⋅nH2O, CVO) mit Schichtstruktur wurde synthetisiert und als Kathode für wässrige Zinkionenbatterien verwendet. H. N. Alshareef und Mitarbeiter beschreiben in ihrer Zuschrift (
      DOI : 10.1002/ange.201713291), wie Zn-Atome (silberne Kugeln) bei der Entladung von der Anode zur CVO-Kathode wandern und dabei die Energie liefern, welche die Lampe zum Leuchten bringt. Die Darstellung von Zn als fliegendes „Super”-Element bringt die hohe Effizienz des Systems zum Ausdruck.
      PubDate: 2018-03-15T09:59:27.250416-05:
  • Low-Coordinate Single-Ion Magnets by Intercalation of Lanthanides into a
           Phenol Matrix
    • Authors: Yin-Shan Meng; Ling Xu, Jin Xiong, Qiong Yuan, Tao Liu, Bing-Wu Wang, Song Gao
      Abstract: It is very challenging to synthesize stable trivalent rare-earth complexes in which the coordination number is lower than 3 for the high oxidation state, there is a large ion radius and nearly non-bonding character of trivalent lanthanide ions. The bulky phenol ligand ArOH (Ar=2,6-Dipp2C6H3, Dipp=2,6-diisopropylphenyl) was utilized to construct low-coordinate lanthanide compound [(ArO)Ln(OAr′)] (Ar′=6-Dipp-2-(2′-iPr-6′-CHMe(CH2−)C6H3)C6H3O−; Ln=Tb, Dy, Ho, Er, Tm). These complexes and the free ligand ArOH were isostructural. Magnetic measurements and theoretical studies demonstrated that both the oblate-type dysprosium and prolate-type erbium analogues exhibited single-ion magnet (SIM) behavior. The bulky phenol ligands provided strong uniaxial ligand field, making the dysprosium SIM possessing blocking barrier up to 961 K.SIM-City: Niedrig koordinierte Einzelionenmagnete (SIM) wurden erhalten, indem Dysprosium und Erbium durch ein sperriges Phenol umschlossen wurden. Sowohl das Dysprosium- als auch das Erbiumanalogon vom oblaten bzw. prolaten Typ zeigten SIM-Verhalten. Der Dysprosium-SIM zeigte außerdem eine Sperrbarriere bis 961 K.
      PubDate: 2018-03-15T09:59:06.059195-05:
      DOI: 10.1002/ange.201801223
  • Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen
    • Authors: Nika Mahne; Sara E. Renfrew, Bryan D. McCloskey, Stefan A. Freunberger
      Abstract: Solid alkaline carbonates are universal passivation layer components of intercalation battery materials, common side products in metal-O₂ batteries, and are believed to form and decompose reversibly in metal-O₂/CO₂ cells. In all of these cathode chemistries, Li₂CO₃ decomposes to CO₂ when exposed to potentials>3.8 V vs. Li/Li+. Notably, though, O₂ evolution is not detected, as is expected according to the decomposition reaction 2 Li₂CO₃ 4 Li+ + 4 e- + 2 CO₂ + O₂. O-moieties were therefore previously considered unaccounted for in unidentified parasitic reactions. Here we show that highly reactive singlet oxygen (¹O₂) forms upon oxidizing Li₂CO₃ in an aprotic electrolyte and therefore does not evolve as O₂. These results have substantial implications for long-term cyclability of battery chemistries: they underpin the importance of avoiding ¹O₂ in metal-O₂ batteries, question the possibility of a reversible metal-O₂/CO₂ battery based on a carbonate discharge product, and help explain interfacial reactivity of transition metal cathodes with residual Li₂CO₃.
      PubDate: 2018-03-15T09:58:22.37206-05:0
      DOI: 10.1002/ange.201802277
  • Asymmetric [3+2] Photocycloadditions of Cyclopropanes with Alkenes or
           Alkynes via Visible Light Excitation of Catalyst-Bound Substrates
    • Authors: Xiaoqiang Huang; Jiahui Lin, Tianqi Shen, Klaus Harms, Marianna Marchini, Paola Ceroni, Eric Meggers
      Abstract: Here reported visible-light-activated catalytic asymmetric [3+2] photocycloadditions between cyclopropanes and alkenes or alkynes provide access to chiral cyclopentanes and cyclopentenes, respectively, in 63-99% yields and with excellent enantioselectivities of up to>99% ee. The reactions are catalyzed by a single bis-cyclometalated chiral-at-rhodium complex (2-8 mol%) which after coordination to the cyclopropane generates the visible-light-absorbing complex, lowers the reduction potential of the cyclopropane, and provides the asymmetric induction and overall stereocontrol. Enabled by a mild single electron transfer (SET) reduction of directly photoexcited catalyst/substrate complexes, the present transformations expand the scope of rhodium-catalyzed asymmetric photocycloadditions to simple mono-acceptor-substituted cyclopropanes affording previously inaccessible chiral cyclopentane and cyclopentene derivatives.
      PubDate: 2018-03-15T09:31:09.854746-05:
      DOI: 10.1002/ange.201802316
  • One-Pot Sequence-Controlled Synthesis of Oligosiloxanes
    • Authors: Kazuhiro Matsumoto; Yuki Oba, Yumiko Nakajima, Shigeru Shimada, Kazuhiko Sato
      Abstract: Silicones (organopolysiloxanes) have found applications in a wide range of research areas, and their unique and valuable properties have rendered these materials virtually irreplaceable. Despite the fact that silicones have been employed industrially for more than 70 years, synthetic routes to generate silicones remain limited, and the sequence-controlled synthesis of oligo- and polysiloxanes still represents a major challenge in silicone chemistry. Described here is a highly selective sequence-controlled synthesis of linear, branched, and cyclic oligosiloxanes by simple iteration of two reactions, specifically, a B(C6F5)3-catalyzed dehydrocarbonative cross-coupling of alkoxysilanes with hydrosilanes and a B(C6F5)3-catalyzed hydrosilylation of carbonyl compounds, in a single flask. The sequence of the resulting oligosiloxanes can be controlled precisely by the order of addition of the hydrosilane monomers.Geordnetes Vorgehen: Ein iterativer Eintopfprozess aus B(C6F5)3-katalysierter dehydrocarbonierender Kreuzkupplung von Alkoxysilanen mit Hydrosilanen und B(C6F5)3-katalysierter Hydrosilylierung von Carbonylverbindungen ergibt lineare, verzweigte und cyclische Oligosiloxane in selektiver Weise. Die Sequenz der Oligosiloxan-Produkte lässt sich über die Reihenfolge der Zugabe der Hydrosilan-Monomere genau steuern.
      PubDate: 2018-03-15T08:58:24.972672-05:
      DOI: 10.1002/ange.201801031
  • Access to Enantioenriched Organosilanes from Enals and β-Silyl
           Enones: Carbene Organocatalysis
    • Authors: Yuxia Zhang; Jie Huang, Yingying Guo, Lin Li, Zhenqian Fu, Wei Huang
      Abstract: Herein, an efficient route to enantioenriched organosilanes, containing two consecutive stereogenic centers, from enals and β-silyl enones under carbene organocatalysis is described. Under mild reaction conditions, this transition-metal-free strategy exhibits a broad substrate scope, and excellent diastereo- and enantioselectivity.Eine Carben-katalysierte formale [4+2]-Anellierung von Enalen mit β-Silylenonen unter milden Reaktionsbedingungen führt zu einem diversen Satz an enantiomerenangereicherten Organosilanen mit zwei aufeinanderfolgenden Stereozentren. Die übergangsmetallfreie Strategie liefert die Produkte in guten Ausbeuten mit exzellenten Diastereo- und Enantioselektivitäten.
      PubDate: 2018-03-15T08:57:58.006084-05:
      DOI: 10.1002/ange.201800483
  • Genexpression auf DNA-Biochips: Strukturierung durch
    • Authors: Günther Pardatscher; Matthaeus Schwarz-Schilling, Shirley S. Daube, Roy H. Bar-Ziv, Friedrich C. Simmel
      Abstract: Die lithographische Strukturierung von DNA-Molekülen ermöglicht die räumliche Organisation von zellfreien, genetischen Schaltkreisen unter streng kontrollierten Bedingungen. Im Folgenden beschreiben wir einen biokompatiblen, DNA-basierten Chip-Photolack namens “Bephore”, der mittels Photo- und Elektronenstrahllithographie strukturiert werden kann. Das Verfahren basiert auf der Spaltung eines chemisch modifizierten, haarnadelförmigen DNA-Moleküls durch ultraviolettes Licht oder Elektronen, und auf einer nachfolgenden DNA-Strangverdrängungsreaktion. Hierbei werden alle Schritte in wässriger Lösung und ohne eine chemische Entwicklung des Photolacks durchgeführt, wodurch sich der lithographische Prozess als besonders robust und biokompatibel auszeichnet. Bephore eignet sich auch für ein mehrstufiges lithographisches Verfahren und erlaubt dadurch die Immobilisierung verschiedener DNA-Moleküle mit Mikrometer-Präzision. Als Anwendung für das Verfahren zeigen wir die Expression dreier Gene, die in Kompartimenten auf einem Chip immobilisiert wurden, und die Entstehung der daraus resultierenden, räumlichen Proteinexpressions-Gradienten.Tiger auf einem Chip: Ein mehrstufiges Lithographieverfahren zur Immobilisierung verschiedener DNA-Stränge auf einem Biochip wurde entwickelt. In Hinblick auf die Anwendung dieser Technik in der Entwicklung chipbasierter, synthetischer biologischer Systeme wird die Expression unterschiedlicher Proteine in Kompartimenten auf einem Chip demonstriert.
      PubDate: 2018-03-15T08:57:36.771915-05:
      DOI: 10.1002/ange.201800281
  • Towards Sequence-Controlled Antimicrobial Polymers: Effect of Polymer
           Block Order on Antimicrobial Activity
    • Authors: Peter R. Judzewitsch; Thuy-Khanh Nguyen, Sivaprakash Shanmugam, Edgar H. H. Wong, Cyrille Boyer
      Abstract: Synthetic polymers have shown promise in combating multidrug-resistant bacteria. However, the biological effects of sequence control in synthetic antimicrobial polymers are currently not well understood. As such, we investigate the antimicrobial effects of monomer distribution within linear high-order quasi-block copolymers consisting of aminoethyl, phenylethyl, and hydroxyethyl acrylamides made in a one-pot synthesis approach via photoinduced electron transfer–reversible addition–fragmentation chain transfer polymerisation (PET-RAFT). Through different combinations of monomer/polymer block order, antimicrobial and haemolytic activities are tuneable in a manner comparable to antimicrobial peptides.Die antimikrobiellen Effekte der Monomerverteilung in linearen hochgeordneten Quasi-Blockcopolymeren aus Aminoethyl-, Phenylethyl- und Hydroxyethylacrylamiden wurden untersucht. Eine gezielte Sequenzkontrolle führt zur spezifischen Abtötung von Bakterienspezies.
      PubDate: 2018-03-15T08:57:27.191994-05:
      DOI: 10.1002/ange.201713036
  • Das Rezept für die Langlebigkeit von Unternehmen – aus Sicht des
    • Authors: Klaus Griesar; John Bessant, Sabine Bernschneider-Reif
      Abstract: Ein Wort der Warnung gleich zu Beginn: Dieses stellt keine Zusammenfassung bahnbrechender Erkenntnisse oder Schlussfolgerungen dar. Ganz im Gegenteil. Es möchte lediglich die Neugier dafür wecken, was unternehmerisches Überleben eigentlich bedeutet. Gibt es ein Geheimrezept, das Unternehmen befolgen könnten, um zu überleben' Die Antworten kommen weder aus den bescheidenen und traditionellen Studierstuben von Philosophen noch aus der Durchsicht moderner, faktenbasierter Studien aus den Büroräumen (und den hochbezahlten Meinungen) von Unternehmensberatern. Den archimedischen Punkt, von dem aus wir objektiv der Frage nach dem unternehmerischen Überleben nachgehen könnten, gibt es schlichtweg nicht. Aber wir können 7 Analogien (oder Metaphern) als intellektuelle Sprungbretter bemühen, welche Raum für neue Sichtweisen schaffen könnten. Innovation spielt für das unternehmerische Überleben ganz offensichtlich eine wichtige Rolle; dennoch ist diese naturgemäß eine recht chaotische Angelegenheit. Um dem Chaos Form zu verleihen, stellen wir in diesem einige Schlüsselbegriffe in alphabetischer Reihenfolge vor. Wir beginnen mit A, das für Ambidextrie, Architektur und Ameisenkolonien steht. Dann folgt B für Begriffe wie (mentale) Boxen und Biodiversität. Natürlich spielt auch C eine große Rolle – wir haben bereits verraten, dass Neugier (Curiosity) Teil der Antwort ist. Weiter geht es mit D (Darwin, DNS und Diskontinuität) und E (Erdbeben und Evolution). Eine weitere Warnung zum Abschluss: Dieser Beitrag hat nicht die Absicht, die reichhaltige und komplexe Geschichte des Unternehmens Merck KGaA Darmstadt, Germany, zu beschreiben. Zum Abschluss dieses Essays folgt lediglich – in Würdigung dieser Geschichte – ein Epilog, in dem einer der Protagonisten der 350 Jahre währenden Reise des Unternehmens – Emanuel Merck – auf die Bühne treten und “die Geschichte für sich selbst sprechen lassen soll.” Immer noch neugierig'Erfolgsrezept: Gibt es ein Geheimrezept, das Unternehmen befolgen könnten, um zu überleben' Die Antworten kommen weder von Philosophen noch von Unternehmensberatern. In diesem Essay werden 7 Analogien (oder Metaphern) als intellektuelle Sprungbretter bemüht, welche Raum für neue Sichtweisen zur Langlebigkeit von Unternehmen schaffen könnten. Was können wir von Ameisenkolonien, der Eisindustrie und der DNA einer Organisation lernen'
      PubDate: 2018-03-15T08:57:11.986215-05:
      DOI: 10.1002/ange.201712514
  • Grundlegende Bemerkungen zur Azidität
    • Authors: Daniel Himmel; Valentin Radtke, Burkhard Butschke, Ingo Krossing
      Abstract: Dieser Aufsatz beschreibt eine vereinheitlichte Sichtweise auf Brønsted-Azidität. Zunächst wird ein Überblick über die Konzepte Azidität, Säurestärke und pH-Wert gegeben. Anschließend wird die in der Arbeitsgruppe Krossing entwickelte pHabs- oder pHabsH2O-Skala als vereinheitlichendes Konzept mit einigen Beispielen für ihre Anwendbarkeit vorgestellt. Abgerundet wird der Aufsatz durch die Analogie zwischen Säure-Base- und Redoxchemie mit der Einführung der vereinheitlichten Redoxpotentialskala peabs. Die Kombination von pHabs- und peabs-Werten resultiert in der protoelektrischen Potentialkarte (Protoelectric Potential Map, PPM) als Ergebnis aktueller Forschung zur Thermochemie einzelner Ionen. Die PPM ist also ein Instrument zum Vergleich aller möglichen Säure-Base- und/oder Redoxreaktionen in allen denkbaren Reaktionsmedien.Vereinheitlichte Azidität: eine Skala für alle! Wie lässt sich Brønsted-Azidität in verschiedenen Medien miteinander vergleichen' Wie die Säurestärken flüssiger oder gasförmiger Säuren' Wie können ihre Eigenschaften für Anwendungen wie Flüssigchromatographie, Polymerisationen oder Katalyse thermodynamisch korrekt abgeleitet werden' Die vereinheitlichte Azidität, die auf dem chemischen Potential des Protons basiert, ermöglicht all dies und vieles mehr.
      PubDate: 2018-03-15T08:57:01.781404-05:
      DOI: 10.1002/ange.201709057
  • Synthesis of branched-chain sugars with a DHAP-aldolase: ketones are
           electrophile substrates of rhamnulose-1-phosphate aldolases
    • Authors: Victor Laurent; Ekaterina Darii, Angelina Aujon, Marine Debacker, Jean-Louis Petit, Virgil Hélaine, Tibor Liptaj, Martin Breza, Aline Mariage, Lionel Nauton, Mounir Traikia, Marielle Lemaire, Marcel Salanoubat, Christine Guérard-Hélaine, Véronique De Berardinis
      Abstract: Dihydroxyacetone phosphate (DHAP)-dependent rhamnulose aldolases display an unprecedented versatility for ketones as electrophile substrates. We selected and characterized a rhamnulose aldolase from Bacteroides thetaiotaomicron (RhuABthet) to provide a proof of concept. DHAP was added as a nucleophile to several alpha-hydroxylated ketones used as electrophiles. This aldol addition was stereoselective and produced branched-chain monosaccharide adducts with a tertiary alcohol moiety. Several aldols were thus readily obtained in good to excellent yields (from 76 to 95%). These results contradict the general view that aldehydes are the only electrophile substrates for DHAP-aldolases and extend the chemists' toolbox to a new C−C bond-forming enzyme for stereoselective synthesis of tertiary alcohols.
      PubDate: 2018-03-15T06:53:49.508671-05:
      DOI: 10.1002/ange.201712851
  • Strain-promoted cycloaddition of cyclopropenes with o-quinones: a rapid
           click reaction.
    • Authors: Han Zuilhof; Digvijay Gahtory, rickdeb Sen, Andriy R Kuzmyn, Jorge Escorihuela
      Abstract: Novel click reactions are of continued interest in fields as diverse as bio-conjugation, polymer science and surface chemistry. Qualification as a proper 'click' reaction requires stringent criteria, including fast kinetics and high conversion, to be met. Herein, we report a novel strain-promoted cycloaddition between cyclopropenes and o-quinones in solution and on a surface. We demonstrate the 'click character' of the reaction in solution and on surfaces for both monolayer and polymer brush functionalization.
      PubDate: 2018-03-15T04:30:36.147328-05:
      DOI: 10.1002/ange.201800937
  • A Stable Metal–Organic Framework Featuring a Local Buffer Environment
           for Carbon Dioxide Fixation
    • Authors: Hongming He; Qi Sun, Wenyang Gao, Jason A. Perman, Fuxing Sun, Guangshan Zhu, Briana Aguila, Katherine Forrest, Brian Space, Shengqian Ma
      Abstract: A majority of metal–organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid–base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.Eine Pufferstrategie erhöht die Stabilität eines MOF in Wasser über einen breiten pH-Bereich. Die lokale Pufferumgebung, die aus den schwachen Säure-Base-Paaren (grünblaue Stäbe rechts im Bild) des maßgeschneidert entwickelten organischen Liganden resultiert, verbessert außerdem erheblich die Eigenschaften des MOF in der chemischen Fixierung von Kohlendioxid unter Umgebungsbedingungen.
      PubDate: 2018-03-15T04:22:53.723355-05:
      DOI: 10.1002/ange.201801122
  • Alkenylation of C(sp3)−H Bonds by Zincation/Copper-Catalyzed
           Cross-Coupling with Iodonium Salts
    • Authors: Chuan Liu; Qiu Wang
      Abstract: α-Vinylation of phosphonates, phosphine oxides, sulfones, sulfonamides, and sulfoxides has been achieved by selective C−H zincation and copper-catalyzed C(sp3)−C(sp2) cross-coupling reaction using vinylphenyliodonium salts. The vinylation transformation proceeds in high efficiency and stereospecificity under mild reaction conditions. This zincative cross-coupling reaction represents a general alkenylation strategy, which is also applicable for α-alkenylation of esters, amides, and nitriles in the synthesis of β,γ-unsaturated carbonyl compounds.Universelle Vinylierungsstrategie: Die α-Vinylierung von Phosphonaten, Phosphinoxiden, Sulfonen, Sulfonamiden, Sulfoxiden und Carbonylderivaten gelingt durch eine Ein-Topf-Reaktion aus C-H-Zinkierung und Kupfer-katalysierter C(sp3)-C(sp2)-Kreuzkupplung unter Verwendung von Vinylphenyliodoniumsalzen unter milden Bedingungen.
      PubDate: 2018-03-15T04:22:44.929293-05:
      DOI: 10.1002/ange.201713278
  • A Paper Sensor Printed with Multifunctional Bio/Nano Materials
    • Authors: Christy Y. Hui; Meng Liu, Yingfu Li, John D. Brennan
      Abstract: We report a paper-based aptasensor platform that uses two reaction zones and a connecting bridge along with printed multifunctional bio/nano materials to achieve molecular recognition and signal amplification. Upon addition of analyte to the first zone, a fluorescently labelled DNA or RNA aptamer is desorbed from printed graphene oxide, rapidly producing an initial fluorescence signal. The released aptamer then flows to the second zone where it reacts with printed reagents to initiate rolling circle amplification, generating DNA amplicons containing a peroxidase-mimicking DNAzyme, which produces a colorimetric readout that can be read in an equipment-free manner or with a smartphone. The sensor was demonstrated using an RNA aptamer for adenosine triphosphate (a bacterial marker) and a DNA aptamer for glutamate dehydrogenase (Clostridium difficile marker) with excellent sensitivity and specificity. These targets could be detected in spiked serum or feacal samples, demonstrating the potential for testing clinical samples.Ein Papiersensor wurde so entworfen, dass er zwei Reaktionszonen und eine Verbindungsbrücke aufweist und zwei Signalausgaben ermöglicht: ein Fluoreszenzsignal in Zone 1 bei der zielinduzierten Desorption fluoreszierender Aptamere von einer Graphenoberfläche sowie ein kolorimetrisches Signal als Resultat einer DNA-Amplifizierung nach Probentransfer über die Brücke.
      PubDate: 2018-03-15T04:22:36.99265-05:0
      DOI: 10.1002/ange.201712903
  • Solvent-Induced Crystal Polymorphism as Studied by Pyroelectric
           Measurements and Impedance Spectroscopy: Alcohols as Tailor-Made
           Inhibitors of α-Glycine
    • Authors: Elena Meirzadeh; Shiri Dishon, Isabelle Weissbuch, David Ehre, Meir Lahav, Igor Lubomirsky
      Abstract: Metastable polymorphs commonly emerge when the formation of the stable analogues is inhibited by using different solvents or auxiliaries. Herein, we report that when glycine is grown in aqueous solutions in the presence of low concentrations of different co-solvents, only alcohols and acetone, unlike water and acetic acid, are selectively incorporated in minute amounts within the bulk of the α-polymorph. These findings demonstrate that although water binds more strongly to the growing face of the crystal, alcohols and acetone are exclusively incorporated, and thus serve as efficient inhibitors of this polymorph, leading to the precipitation of the β-form. These solvents then create polar domains detectable by pyroelectric measurements and impedance spectroscopy. These results suggest that in the control of crystal polymorphism with co-solvents, one should consider also the different desolvation rates in addition to the energy of binding to the growing faces of the crystal.Der selektive Einschluss kleinster Mengen an Alkohol in α-Glycin-Kristallen wurde durch pyroelektrische Messungen und Impedanzspektroskopie untersucht. Die dielektrischen Eigenschaften von α-Glycin-Kristallen unterscheiden sich deutlich, je nachdem ob sie in wässriger Lösung oder Alkohol/Wasser-Mischungen gezüchtet wurden. Der Unterschied erklärt, warum Alkohole die Bildung des metastabilen β-Polymorphs induzieren.
      PubDate: 2018-03-15T04:21:51.258272-05:
      DOI: 10.1002/ange.201800741
  • Ring expansion and re-contraction for the synthesis of 1-aryl
           tetrahydroisoquinolines and tetrahydrobenzazepines from readily available
           heterocyclic precursors
    • Authors: Jessica Hill; Johnathan Matlock, Quentin Lefebvre, Katie Cooper, Jonathan Clayden
      Abstract: Tetrahydroisoquinolines and tetrahydrobenzazepines are prepared by acid-promoted ring contraction of cyclic ureas, themselves formed by ring expansion of indolines and tetrahydroquinolines. The consequent overall one-carbon insertion reaction gives these 6- and 7-membered heterocyclic scaffolds in three steps from readily available precursors. Other ring sizes may be formed by an alternative elimination reaction of bicyclic structures. Scalability of the method was demonstrated by operating it in a flow system.
      PubDate: 2018-03-14T12:30:26.384516-05:
      DOI: 10.1002/ange.201802188
  • Engineering Fast Ion Conduction and Selective Cation Channels for
           High-Rate and High-Voltage Hybrid Aqueous Battery
    • Authors: Chunyi Liu; Xusheng Wang, Wenjun Deng, Chang Li, Jitao Chen, Mianqi Xue, Rui Li, Feng Pan
      Abstract: Rechargeable aqueous metal-ion battery (RAMB) has attracted considerable attention due to its safety, low cost, and environmental friendliness. Yet the poor-performance electrode materials lead to a low feasibility of practical application. Hybrid aqueous battery (HAB) built by electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. In this work, we construct a high-voltage K-Na HAB based on K2FeFe(CN)6 cathode and carbon-coated NaTi2(PO4)3 (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g-1 at 0.5C rate. Considerable capacity retention of 94.3% is also obtained after 1000 cycles at even 60C rate. Meanwhile, high energy density of 69.6 Wh kg-1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.
      PubDate: 2018-03-14T11:01:12.476546-05:
      DOI: 10.1002/ange.201800479
  • Quantum Machine Learning im chemischen Raum
    • Authors: O. Anatole von Lilienfeld
      Abstract: Lerneifrige Algorithmen: Anstatt die rechnerisch anspruchsvollen Gleichungen der Quantenmechanik (QM) und statistischen Mechanik numerisch zu lösen, kann man mithilfe maschinellen Lernens Lösungen inferieren, indem zuvor erfasste Eigenschaften von Molekülen und Materialien interpoliert werden. Quantum Machine Learning (QML) ist ein induktives, molekulares Modellierungsverfahren, das auf quantenchemische Probleme anwendbar ist.
      PubDate: 2018-03-14T10:00:48.645208-05:
      DOI: 10.1002/ange.201709686
  • Chelating Rotaxane Ligands as Fluorescent Metal Ion Sensors
    • Authors: Mathieu Denis; Jessica Pancholi, Kajally Jobe, Michael Watkinson, Stephen Michael Goldup
      Abstract: Although metal ion-binding interlocked molecules have been under intense investigation for over three decades, their application as scaffolds for the development of sensors for metal ions remains under-explored. Here we demonstrate the potential of simple rotaxane scaffolds as metal ion-responsive ligand scaffolds through the development of a proof-of-concept selective sensor for Zn2+.
      PubDate: 2018-03-14T09:08:20.859196-05:
      DOI: 10.1002/ange.201712931
  • A Cell-Targeted Non-Cytotoxic Fluorescent Nanogel Thermometer Created with
           an Imidazolium-Containing Cationic Radical Initiator
    • Authors: Seiichi Uchiyama; Toshikazu Tsuji, Kyoko Kawamoto, Kentaro Okano, Eiko Fukatsu, Takahiro Noro, Kumiko Ikado, Sayuri Yamada, Yuka Shibata, Teruyuki Hayashi, Noriko Inada, Masaru Kato, Hideki Koizumi, Hidetoshi Tokuyama
      Abstract: A cationic fluorescent nanogel thermometer based on thermo-responsive N-isopropylacrylamide and environment-sensitive benzothiadiazole was developed with a new azo compound bearing imidazolium rings as the first cationic radical initiator. This cationic fluorescent nanogel thermometer showed an excellent ability to enter live mammalian cells in a short incubation period (10 min), a high sensitivity to temperature variations in live cells (temperature resolution of 0.02-0.84 °C in the range 2040 °C), and remarkable non-cytotoxicity, which permitted ordinary cell proliferation and even differentiation of primary cultured cells.
      PubDate: 2018-03-14T08:55:52.559728-05:
      DOI: 10.1002/ange.201801495
  • Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin
           Polyoxometalate with a Co(IV) Heteroatom
    • Authors: Ronny Neumann; Alexander M Khenkin, Miriam Somekh, Raanan Carmieli
      Abstract: The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol is an important research challenge. Mostly thermochemical approaches have been studied, but these still have various drawbacks. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates that are easily hydrolyzed by water yielding the corresponding phenols is presented. The formylation reaction occurs on a Pt anode in the presence of [Co(III)W12O40]5- as catalyst and Li formate as electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH + H2O ArOH + H2. Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid to CO2 and H2 is the side-reaction. This electrocatalytic reaction may lead to new processes for arene hydroxylation.
      PubDate: 2018-03-14T06:07:48.985776-05:
      DOI: 10.1002/ange.201801372
  • Bottleable Neutral Analogues of [B2H5]- as Versatile and Strongly Binding
           eta2 Donor Ligands
    • Authors: Sunewang Wang; Dominic Prieschl, James Mattock, Merle Arrowsmith, Conor Pranckevicius, Tom Stennett, Rian Dewhurst, Alfredo Vargas, Holger Braunschweig
      Abstract: Herein we report the discovery that two bottleable, neutral, base-stabilized diborane(5) compounds are able to bind strongly to a number of copper(I) complexes exclusively through their B-B bond. The resulting complexes represent the first known complexes containing unsupported, neutral σB-B diborane ligands. Single-crystal X-ray analyses of these complexes show that the X-Cu moiety (X = Cl, OTf, C6F5) lies opposite the bridging hydrogen of the diborane and is near perpendicular to the B-B bond, interacting almost equally with both boron atoms and causing a B-B bond elongation. DFT studies show that σ donation from and π backdonation to the pseudo-π-like B-B bond account for their formation. Astoundingly, these copper σB-B-complexes are inert to ligand exchange with pyridine under either heating or photoirradiation.
      PubDate: 2018-03-14T05:01:06.669462-05:
      DOI: 10.1002/ange.201801722
  • Pathway Complexity Versus Hierarchical Self-Assembly in N-Annulated
           Perylenes: Structural Effects in Seeded Supramolecular Polymerization
    • Authors: Elisa E. Greciano; Beatriz Matarranz, Luis Sánchez
      Abstract: Studies were carried out on the hierarchical self-assembly versus pathway complexity of N-annulated perylenes 1–3, which differ only in the nature of the linking groups connecting the perylene core and the side alkoxy chains. Despite the structural similarity, compounds 1 and 2 exhibit noticeable differences in their self-assembly. Whereas 1 forms an off-pathway aggregate I that converts over time (or by addition of seeds) into the thermodynamic, on-pathway product, 2 undergoes a hierarchical process in which the kinetically trapped monomer species does not lead to a kinetically controlled supramolecular growth. Finally, compound 3, which lacks the amide groups, is unable to self-assemble under identical experimental conditions and highlights the key relevance of the amide groups and their position to govern the self-assembly pathways.Die Zahl und Position der Amidgruppen bestimmen das Ergebnis der Selbstorganisation von N-anellierten Perylenen. Die inneren Amide (siehe Bild, links) bevorzugen ein Nichtgleichgewichtssystem, dessen Bildung durch Impfung beschleunigt werden kann. Die äußeren Amide (rechts) erzeugen mehr planare molekulare Systeme, die eine rasche hierarchische Selbstorganisation zu superhelikalen Strukturen erfahren.
      PubDate: 2018-03-14T03:26:17.466362-05:
      DOI: 10.1002/ange.201801575
  • A Highly Active N-Heterocyclic Carbene Manganese(I) Complex for Selective
           Electrocatalytic CO2 Reduction to CO
    • Authors: Federico Franco; Mara F. Pinto, Beatriz Royo, Julio Lloret-Fillol
      Abstract: We report here the first purely organometallic fac-[MnI(CO)3(bis-MeNHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO2 to CO, exceeding 100 turnovers with excellent faradaic yields (ηCO≈95 %) in anhydrous CH3CN. Under the same conditions, a maximum turnover frequency (TOFmax) of 2100 s−1 was measured by cyclic voltammetry, which clearly exceeds the values reported for other manganese-based catalysts. Moreover, the addition of water leads to the highest TOFmax value (ca. 320 000 s−1) ever reported for a manganese-based catalyst. A MnI tetracarbonyl intermediate was detected under catalytic conditions for the first time.Der metallorganische Komplex fac-[MnI(CO)3(bis-MeNHC)Br] ist ein hoch aktiver Katalysator der selektiven elektrokatalytischen Reduktion von CO2 zu CO, mit Wechselzahlen über 100 und exzellenten faradayschen Ausbeuten (ηCO≈95 %) in wasserfreiem CH3CN. Die Hinzugabe von Wasser führt zur höchsten maximalen Wechselfrequenz (TOFmax≈320 000 s−1), die je für einen Mn-Katalysator gemessen wurde.
      PubDate: 2018-03-14T03:25:56.114758-05:
      DOI: 10.1002/ange.201800705
  • Perfluoroaryl Bicyclic Cell-Penetrating Peptides for Delivery of Antisense
    • Authors: Justin M. Wolfe; Colin M. Fadzen, Rebecca L. Holden, Monica Yao, Gunnar J. Hanson, Bradley L. Pentelute
      Abstract: Exon-skipping antisense oligonucleotides are effective treatments for genetic diseases, yet exon-skipping activity requires that these macromolecules reach the nucleus. While cell-penetrating peptides can improve delivery, proteolytic instability often limits efficacy. It is hypothesized that the bicyclization of arginine-rich peptides would improve their stability and their ability to deliver oligonucleotides into the nucleus. Two methods were introduced for the synthesis of arginine-rich bicyclic peptides using cysteine perfluoroarylation chemistry. Then, the bicyclic peptides were covalently linked to a phosphorodiamidate morpholino oligonucleotide (PMO) and assayed for exon skipping activity. The perfluoroaryl cyclic and bicyclic peptides improved PMO activity roughly 14-fold over the unconjugated PMO. The bicyclic peptides exhibited increased proteolytic stability relative to the monocycle, demonstrating that perfluoroaryl bicyclic peptides are potent and stable delivery agents.Peptid-Bicyclen wurden mithilfe von Cysteinperfluorarylierungschemie synthetisiert. Die bicyclischen Peptide haben eine höhere Proteolysestabilität als das monocyclische Peptid, und nach Konjugation an Antisense-Oligonukleotide zeigen die bicyclischen Konjugate einen 14-fachen Anstieg der zellulären Aktivität im Vergleich zum unkonjugierten Oligonukleotid.
      PubDate: 2018-03-14T01:46:27.238244-05:
      DOI: 10.1002/ange.201801167
  • Mitigation of Inflammatory Immune Responses with Hydrophilic Nanoparticles
    • Authors: Bowen Li; Jingyi Xie, Zhefan Yuan, Priyesh Jain, Xiaojie Lin, Kan Wu, Shaoyi Jiang
      Abstract: While hydrophobic nanoparticles (NPs) have been long recognized to boost the immune activation, whether hydrophilic NPs modulate an immune system challenged by immune stimulators and how their hydrophilic properties may affect the immune response is still unclear. To answer this question, three polymers, poly(ethylene glycol) (PEG), poly(sulfobetaine) (PSB) and poly(carboxybetaine) (PCB), which are commonly considered hydrophilic, are studied in this work. For comparison, nanogels with uniform size and homogeneous surface functionalities were made from these polymers. Peripheral blood mononuclear cells (PBMCs) stimulated by lipopolysaccharide (LPS) and an LPS-induced lung inflammation murine model were used to investigate the influence of nanogels on the immune system. Results show that the treatment of hydrophilic nanogels attenuated the immune responses elicited by LPS both in vitro and in vivo. Moreover, we found that PCB nanogels, which have the strongest hydration and the lowest non-specific protein binding, manifested the best performance in alleviating the immune activation, followed by PSB and PEG nanogels. This reveals that the immunomodulatory effect of hydrophilic materials is closely related to their hydration characteristics and their ability to resist non-specific binding in complex media.Zahme Antwort: Die Behandlung von peripheren einkernigen Blutzellen mit hydrophilen Nanogelen führte zu einer abgeschwächten Immunantwort auf Stimulation durch Lipopolysaccharide in vitro und in vivo. Der immunmodulatorische Effekt der hydrophilen Materialien hängt eng mit ihren Hydratationseigenschaften sowie ihrer Fähigkeit zusammen, sich der nichtspezifischen Bindung in komplexen Medien zu widersetzen.
      PubDate: 2018-03-14T01:40:41.882429-05:
      DOI: 10.1002/ange.201710068
  • Universal Scaling of Intrinsic Resistivity in Two-Dimensional Metallic
    • Authors: Jin Zhang; Jia Zhang, Liujiang Zhou, Cai Cheng, Chao Lian, Jian Liu, Sergei Tretiak, Johannes Lischner, Feliciano Giustino, Sheng Meng
      Abstract: Two-dimensional boron sheets (borophenes) have been successfully synthesized in experiments and are expected to exhibit intriguing transport properties. A comprehensive first-principles study is reported of the intrinsic electrical resistivity of emerging borophene structures. The resistivity is highly dependent on different polymorphs and electron densities of borophene. Interestingly, a universal behavior of the intrinsic resistivity is well-described using the Bloch–Grüneisen model. In contrast to graphene and conventional metals, the intrinsic resistivity of borophenes can be easily tuned by adjusting carrier densities, while the Bloch–Grüneisen temperature is nearly fixed at 100 K. This work suggests that monolayer boron can serve as intriguing platform for realizing tunable two-dimensional electronic devices.Der intrinsische Widerstand von Borophen ist stark abhängig vom Polymorphietyp und der Ladungsträgerdichte. Der Widerstand lässt sich mit dem Bloch-Grüneisen-Modell gut beschreiben und skaliert universell.
      PubDate: 2018-03-14T01:40:35.950096-05:
      DOI: 10.1002/ange.201800087
  • Spectroscopic and Computational Characterization of
           Diethylenetriaminepentaacetic Acid/Transplutonium Chelates: Evidencing
           Heterogeneity in the Heavy Actinide(III) Series
    • Authors: Gauthier J.-P. Deblonde; Morgan P. Kelley, Jing Su, Enrique R. Batista, Ping Yang, Corwin H. Booth, Rebecca J. Abergel
      Abstract: The chemistry of trivalent transplutonium ions (Am3+, Cm3+, Bk3+, Cf3+, Es3+…) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. Herein, we present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal–oxygen nearest-neighbor bond lengths in the case of Cf3+. Corroborating those results, density functional theory calculations, extended to Es3+, suggest that the shorter Cf−O and Es−O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [MIIIDTPA(H2O)]2− (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.Die Koordinationseigenschaften von Transplutonium-Elementen wurden durch EXAFS-Spektroskopie und Dichtefunktionalrechnungen untersucht. Bei den Diethylentriaminpentaessigsäure-Chelaten von Am3+, Cm3+, Bk3+, Cf3+ und Es3+ sind die M-O-Bindungen für Cf und Es deutlich kürzer, was ein klare Trendwende bei den schweren Actiniden darstellt.
      PubDate: 2018-03-14T01:40:23.451294-05:
      DOI: 10.1002/ange.201709183
  • Structural Basis of a Broadly Selective Acyltransferase from the
           Polyketide Synthase of Splenocin
    • Authors: Yuan Li; Wan Zhang, Hui Zhang, Wenya Tian, Lian Wu, Shuwen Wang, Mengmeng Zheng, Jinru Zhang, Chenghai Sun, Zixin Deng, Yuhui Sun, Xudong Qu, Jiahai Zhou
      Abstract: Polyketides are a large family of pharmaceutically important natural products, and the structural modification of their scaffolds is significant for drug development. Herein, we report one apo- and two complex structures (with a pentynylmalonyl and benzylmalonyl, respectively) of the broadly selective acyltransferase (AT) from the splenocin polyketide synthase. These structures revealed the molecular basis of the stereo-selectivity and substrate specificity of SpnD-AT and enabled engineering the industrially important Ery-AT6 to broaden its substrate scope to include three new types of extender units.
      PubDate: 2018-03-14T01:00:31.936235-05:
      DOI: 10.1002/ange.201802805
  • [1+1+3] Annulation of Diazoenals and Vinyl Azides: Direct Synthesis of
           Functionalized 1-Pyrrolines via a New Olefination
    • Authors: Sreenivas Katukojvala; Vinaykumar Kanchupalli
      Abstract: Described herein is a dirhodium carboxylate catalyzed [1+1+3] annulation reaction of diazoenals and vinyl azides which gives synthetically important enal-functionalized 1-pyrroline derivatives. The reaction involves a novel rhodium-catalyzed olefination of diazoenals with vinyl azides via electrophilic enalcarbenoid, resulting in the new class of enal-acrylates. The annulation reaction was used for the direct synthesis of valuable deuterated 1-pyrrolines. Structural diversification of the enal-functionalized 1-pyrrolines resulted in the biologically important pyrrolidine fused oxaziridine, amino acid derivatives, and a 6-azabicyclo[3.2.1]octane motif present in polycyclic alkaloids.
      PubDate: 2018-03-14T00:00:51.267334-05:
      DOI: 10.1002/ange.201801976
  • Enantioselective Denitrogenative Annulation of 1H-Tetrazoles with Styrenes
           Catalyzed by Rhodium
    • Authors: Takayuki Nakamuro; Kohei Hagiwara, Tomoya Miura, Masahiro Murakami
      Abstract: Sulfonylation of 1H-tetrazoles with triflic anhydride in the presence of chiral rhodium(II) carboxylate dimers causes denitrogenation to generate alpha-azo rhodium(II) carbenoid species as new types of donor/acceptor carbenoids, which then readily react with styrenes to afford 3,5-diaryl-2-pyrazolines with induction of high levels of enantioselectivities.
      PubDate: 2018-03-13T23:00:32.24219-05:0
      DOI: 10.1002/ange.201801283
  • Long-Persistent Enzyme-MOF Nanoreactor Activates Non-toxic Paracetamol for
           Cancer Therapy
    • Authors: Xizhen Lian; Yanyan Huang, Yuanyuan Zhu, Yu Fang, Rui Zhao, Elizabeth Joseph, Jialuo Li, Jean-Phillipe Pellois, Hongcai Zhou
      Abstract: Prodrug activation by exogenously administered enzymes for cancer therapy is an approach to achieve better selectivity and less systemic toxicity than conventional chemotherapy. However, the short half-lives of the activating enzymes in bloodstream has limited its success. Here, we demonstrate that a tyrosinase-MOF nanoreactor activates the prodrug paracetamol in cancer cells in a long-lasting manner. By generating reactive oxygen species (ROS) and depleting glutathione (GSH), the product of enzymatic conversion of paracetamol is toxic to drug-resistant cancer cells. Tyrosinase-MOF nanoreactors cause significant cell death in the presence of paracetamol for up to three days after being internalized by cells, while free enzymes totally lose activity in a few hours. Thus, we envision enzyme-MOF nanocomposites to be novel long-persistent platforms for various biomedical applications.
      PubDate: 2018-03-13T22:30:45.193558-05:
      DOI: 10.1002/ange.201801378
  • Silyl-Phosphino-Carbene Complexes of Uranium(IV)
    • Authors: Stephen Liddle; Erli lu, Josef Boronski, Matthew Gregson, Ashley Wooles
      Abstract: We report unprecedented silyl-phosphino-carbene complexes of uranium(IV), where before all covalent actinide-carbon double bonds were stabilised by phosphorus(V) substituents or restricted to matrix isolation experiments. Conversion of [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (1, BIPMTMS = C(PPh2NSiMe3)2) to [U(BIPMTMS)(Cl){CH(Ph)(SiMe3)}] (2), and addition of [Li{CH(SiMe3)(PPh2)}(THF)] and Me2NCH2CH2NMe2 (TMEDA) gave [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (3) by α-hydrogen abstraction. Addition of 2,2,2-cryptand or two equivalents of 4-N,N-dimethylaminopyridine (DMAP) to 3 gave [U{C(SiMe3)(PPh2)}(BIPMTMS)(Cl)][Li(2,2,2-cryptand)] (4) or [U{C(SiMe3)(PPh2)}(BIPMTMS)(DMAP)2] (5). The characterisation data for 3-5 suggest that whilst there is evidence for 3-centre P-C-U π-bonding character, the U=C double bond component is dominant in each case. These U=C bonds are the closest to a 'true' uranium-alkylidene, yet outside of matrix isolation experiments.
      PubDate: 2018-03-13T13:30:41.929238-05:
      DOI: 10.1002/ange.201802080
  • A High-Energy-Density Potassium Battery with a Polymer-Gel Electrolyte and
           a Polyaniline Cathode
    • Authors: Hongcai Gao; Leigang Xue, Sen Xin, John B. Goodenough
      Abstract: A safe potassium rechargeable battery of high energy density and excellent cycling stability is demonstrated. The cell contained a polyaniline cathode into which the anion component of the electrolyte salt is inserted on charge, extracted on discharge; but the K+ ion of a KPF6 salt is plated/stripped on the potassium-metal anode. The use of a p-type polymer cathode increases the cell voltage. By replacing the organic-liquid electrolyte in a glass-fiber separator by a polymer-gel electrolyte of cross-linked poly(methyl methacrylate), a dendrite-free potassium anode can be plated/stripped and the electrode/electrolyte interface stabilized. The potassium anode wets the polymer, and the cross-linked architecture provides small pores of adjusted sizes to stabilize a solid-electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to a low-cost potassium battery for stationary storage of electric power.
      PubDate: 2018-03-13T12:30:56.557583-05:
      DOI: 10.1002/ange.201802248
  • Metal-Organic Framework (MOF) Nanorods, Nanotubes, and Nanowires
    • Authors: Roberto Christian Arbulu; Ying-Bing Jiang, Eric John Peterson, Yang Qin
      Abstract: New mechanisms of controlled growth of one-dimensional (1D) metal-organic framework (MOF) nano- and super-structures under size-confinement and surface directing effects have been discovered. Through applying interfacial synthesis templated by track-etched polycarbonate (PCTE) membranes, congruent polycrystalline zeolitic imidazolate framework-8 (ZIF-8) solid nanorods and hollow nanotubes were found to form within 100 nm membrane pores, while single crystalline ZIF-8 nanowires grew inside 30 nm pores, all of which possess large aspect ratios up to 60 and show preferential crystal orientation with the {100} planes aligned parallel to the pore's long axis. Our findings provide a generalizable methodology for controlling size, morphology, and lattice orientation of MOF nanomaterials.
      PubDate: 2018-03-13T12:30:49.998048-05:
      DOI: 10.1002/ange.201802694
  • Conjugated Dienyne-Imides as Robust Precursors of 1-Azatrienes for 6π
           Electrocyclizations to Furo[2,3-b]dihydropyridine Cores
    • Authors: Yanjun Wan; Xuchun Zheng, Cheng Ma
      Abstract: A novel strategy to generate functionalized 1-azatriene intermediates for 6π electrocyclizations was developed by using readily accessible dienyne-imides and various terminal olefins under Pd(II) catalysis. Taking advantage of the sequential cooperation between preloaded and incorporated functional handles at 1,3-dien-5-yne skeletons, this protocol not only enables the selective generation of putative 1-azatrienes but significantly accelerates their thermal 6π-electrocyclic ring closure processes to a series of highly substituted furo[2,3-b]dihydropyridine derivatives in good yields.
      PubDate: 2018-03-13T12:05:23.849616-05:
      DOI: 10.1002/ange.201800303
  • Einzelzell-Massenspektrometrie zur Untersuchung zellulärer
    • Authors: Linwen Zhang; Akos Vertes
      Abstract: Die Diversität der Zusammensetzung ist eine fundamentale Eigenschaft von Zellpopulationen. Neue Einblicke in diese zelluläre Heterogenität auf Genom-, Transkriptom-, Proteom- und Metabolomniveau verspricht die Einzelzellanalyse. Die Massenspektrometrie (MS) ist ein markierungsfreies Verfahren, das die Multiplex-Analyse von Proteinen, Peptiden, Lipiden und Metaboliten in Einzelzellen ermöglicht. Die Häufigkeiten dieser Verbindungsklassen werden mit den physiologischen Zuständen und den Reaktionen der Zellen auf Umgebungsänderungen korreliert. Dieser Kurzaufsatz beschreibt neue Fortschritte bei den Einzelzell-MS-Techniken mit dem Schwerpunkt auf Entnahme- und Ionisationsmethoden, die für volumenbegrenzte Proben entwickelt wurden. Bei Einzelzellen erfordern die Strategien zur Probenbehandlung, die Trennmethoden und die Datenanalyse besondere Überlegungen. Aktuelle analytische Herausforderungen betreffen unter anderem die subzelluläre Heterogenität, nicht normale statistische Verteilungen von Zelleigenschaften sowie die Notwendigkeit von Hochdurchsatzanwendungen, einem breiten Molekülspektrum und minimaler Störung.Einzeluntersuchung: Die Massenspektrometrie (MS) hat sich zu einer wichtigen Methode für die Untersuchung der zellulären Heterogenität bezüglich ihrer Metabolomik und Proteomik entwickelt. Der Kurzaufsatz gibt einen Überblick über neue Fortschritte in der Einzelzell-MS mit einem Schwerpunkt auf Mikromanipulation, Nanofabrikation und schnellen Gasphasen-Trenntechniken.
      PubDate: 2018-03-13T12:00:46.021637-05:
      DOI: 10.1002/ange.201709719
  • Von funktionellen Flüssigkristallen zur nächsten Generation von
    • Authors: Takashi Kato; Junya Uchida, Takahiro Ichikawa, Takeshi Sakamoto
      Abstract: Seit der Entdeckung des flüssigkristallinen Zustandes im Jahr 1888 wurden Flüssigkristalle unter Einsatz verschiedener Technologien in unterschiedlichen Disziplinen eingehend erforscht. In letzter Zeit wurden dank der Fortschritte bei Synthese- und Charakterisierungsmethoden ein neuartiges Moleküldesign und neue selbstorganisierte Strukturen entwickelt. Für diese Flüssigkristalle, deren neuartige Funktionen und Eigenschaften sich von ihren Nanostrukturen und ihrer Ausrichtung ableiten, wurde eine Vielzahl möglicher Anwendungen vorgeschlagen, etwa im Energietransport, in Trennverfahren für die Umwelttechnik, als Sensoren, Aktuatoren oder Template sowie auf der Grundlage von Farbänderungen oder elektrooptischen Effekten. Dieser Aufsatz präsentiert die neuesten Fortschritte bei Flüssigkristallen, die zu einer neuen Generation von Materialien führen könnten.Neuartige Moleküle und selbstorganisierte Strukturen sind in jüngster Zeit für Flüssigkristalle entwickelt worden. Außerdem wurde eine Vielzahl neuer Funktionen für Flüssigkristalle beschrieben, von Farbänderungen über elektrooptische Effekte bis hin zu Anwendungen als Sensoren, Aktuatoren oder Template, zum Energietransport und in Trennverfahren für die Umwelttechnik.
      PubDate: 2018-03-13T12:00:14.188196-05:
      DOI: 10.1002/ange.201711163
  • Kontinuierliche heterogene Photokatalyse in seriellen
    • Authors: Bartholomäus Pieber; Menny Shalom, Markus Antonietti, Peter H. Seeberger, Kerry Gilmore
      Abstract: Während unlösliche Reagenzien, auslaugende Katalysatoren und heterogene Photokatalysatoren problemlos in Batch-Verfahren verwendet werden können, ist deren Einsatz in der Durchflusschemie problematisch. Festbettreaktoren werden typischerweise für thermische Reaktionen mit heterogenen Katalysatoren verwendet, sind aber aufgrund schlechter Lichtdurchdringung für die Photochemie ungeeignet. Wir zeigen, dass serielle Mikro-Batch-Reaktoren (SMBRs) die kontinuierliche Verwendung von Feststoffen in Kombination mit Flüssigkeiten und Gasen ermöglichen. Das Potenzial dieser Technologie wurde anhand photokatalytischer Fluorierungen mit graphitischem Kohlenstoffnitrid anstatt teurer, homogener Metallkomplexe demonstriert. Die Kombination dieser billigen, wiederverwendbaren Materialien mit der SMBR-Technologie ermöglicht nachhaltige, skalierbare Photokatalyse.Ein Durchflussreaktorsystem für die Verwendung von Feststoffen ermöglicht effiziente und skalierbare heterogene Photokatalyse für selektive Fluorierungen.
      PubDate: 2018-03-13T11:34:37.612497-05:
      DOI: 10.1002/ange.201712568
  • NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for the Remote
           C(sp3)−H Alkylation of Alkenes
    • Authors: Fang Zhou; Jin Zhu, Yao Zhang, Shaolin Zhu
      Abstract: The terminal-selective, remote C(sp3)−H alkylation of alkenes was achieved by a relay process combining NiH-catalyzed hydrometalation, chain walking, and alkylation. This method enables the construction of unfunctionalized C(sp3)−C(sp3) bonds under mild conditions from two simple feedstock chemicals, namely olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins at low catalyst loadings.Die erfolgreiche Kombination von Kettenwanderung – ein Prozess aus wiederholten migratorischen Insertionen und β-H-Eliminierungen, und Kreuzkupplungschemie führte zur Entwicklung einer milden und effizienten NiH-katalysierten Reaktion für die Hydroalkylierung von Alkenen. Nicht funktionalisierte C(sp3)- C(sp3)-Bindungen wurden so ausgehend von zwei einfachen Grundchemikalien – Olefine und Alkylhalogenide – gebildet.
      PubDate: 2018-03-13T11:33:59.76021-05:0
      DOI: 10.1002/ange.201712731
  • An Organic Mixed-Valence Ligand for Multistate Redox-Active Coordination
    • Authors: Joo Yeon Ha; Jin Young Koo, Hiroyoshi Ohtsu, Yumi Yakiyama, Kimoon Kim, Daisuke Hashizume, Masaki Kawano
      Abstract: The multistate redox-active/multi-interactive ligand 5,5′,8,8′-tetra(4-pyridyl)-2,2′-(1,4-phenylene)bis-1H-perimidine (H2TPP) was designed and synthesized. H2TPP undergoes four one-electron oxidation steps, and was used for the preparation of a multistate redox-active coordination network in a solid–liquid interface reaction using molten Cd2+ salts. The multiple redox states of H2TPP were confirmed spectroscopically by stepwise four-electron oxidation. Spectroscopic analysis indicated that the mixed-valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale.Ein redoxaktives Koordinationsnetzwerk wurde in einer lösungsmittelfreien Reaktion aus einer Metallschmelze und dem redoxaktiven Liganden H2TPP gewonnen. Aufgrund der zwei redoxaktiven Zentren im H2TPP-Liganden können Ligand und Netzwerk unterschiedliche Redoxzustände annehmen.
      PubDate: 2018-03-13T11:33:39.223029-05:
      DOI: 10.1002/ange.201713035
  • Confinement Effects on the Benzene Orientational Structure
    • Authors: Marta Falkowska; Daniel T. Bowron, Haresh Manyar, Tristan G. A. Youngs, Christopher Hardacre
      Abstract: Liquids under confinement exhibit different properties compared with their corresponding bulk phases, for example, miscibility, phase transitions, and diffusion. The underlying cause is the local ordering of molecules, which is usually only studied using pure simulation methods. Herein, we derive experimentally the structure of benzene confined in MCM-41 using total neutron scattering measurements. The study reveals a layering of molecules across a pore, and four concentric cylindrical shells can be distinguished for a pore with the radius of 18 Å. The nanoscale confinement of the liquid has a major effect on the spatial and orientational correlations observed between the molecules, when compared with the structure of the bulk liquid. These differences are most marked for molecules in parallel configurations, and this suggests differences in chemical reactivity between the confined and bulk liquids.Beschränkung auf kleinstem Raum: In Poren beschränkte Benzolmoleküle haben eine andere Struktur als in der flüssigen Phase. Die begrenzten Benzolmoleküle wurden experimentell mit totaler Neutronenstreuung untersucht. Unterschiede sind in den Abständen zwischen den Molekülen und der Orientierung der Moleküle untereinander ausgeprägt.
      PubDate: 2018-03-13T11:33:33.716695-05:
      DOI: 10.1002/ange.201713115
  • Site-Specific Studies of Nucleosome Interactions by Solid-State NMR
    • Authors: ShengQi Xiang; Ulric B. le Paige, Velten Horn, Klaartje Houben, Marc Baldus, Hugo van Ingen
      Abstract: Chromatin function depends on a dense network of interactions between nucleosomes and a wide range of proteins. A detailed description of these protein–nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Herein, we show that the structure, dynamics, and interactions of nucleosomes can be interrogated in a residue-specific manner by using state-of-the-art solid-state NMR spectroscopy. Using sedimented nucleosomes, high-resolution spectra were obtained for both flexible histone tails and the non-mobile histone core. Through co-sedimentation of a nucleosome-binding peptide, we demonstrate that protein-binding sites on the nucleosome surface can be determined. We believe that this approach holds great promise as it is generally applicable, extendable to include the structure and dynamics of the bound proteins, and scalable to interactions of proteins with higher-order chromatin structures, including isolated and cellular chromatin.Nucleosome mit oder ohne Bindungspartner wurden durch Ultrazentrifugation sedimentiert und durch Festkörper-NMR-Spektroskopie untersucht. Hochaufgelöste Spektren ermöglichten die genaue Charakterisierung der Histonkerne und -enden. Die Proteinbindungsstelle wurde anhand spezifischer spektraler Veränderungen bestimmt, was das Potential dieser Methode in der Untersuchung von Nucleosom-Protein-Wechselwirkungen verdeutlicht.
      PubDate: 2018-03-13T11:33:28.028352-05:
      DOI: 10.1002/ange.201713158
  • Peptide-Guided Assembly of Repeat Protein Fragments
    • Authors: Erich Michel; Andreas Plückthun, Oliver Zerbe
      Abstract: Herein, we present the peptide-guided assembly of complementary fragments of designed armadillo repeat proteins (dArmRPs) to create proteins that bind peptides not only with high affinity but also with good selectivity. We recently demonstrated that complementary N- and C-terminal fragments of dArmRPs form high-affinity complexes that resemble the structure of the full-length protein, and that these complexes bind their target peptides. We now demonstrate that dArmRPs can be split such that the fragments assemble only in the presence of a templating peptide, and that fragment mixtures enrich the combination with the highest affinity for this peptide. The enriched fragment combination discriminates single amino acid variations in the target peptide with high specificity. Our results suggest novel opportunities for the generation of new peptide binders by selection from dArmRP fragment mixtures.Optimierung der Selektivität von Proteinen, die bereits mit sehr guten Affinitäten an Peptide binden, ist oftmals schwierig, da der Selektionsdruck vergleichsweise gering ist. Ein neuer Ansatz wird vorgestellt, der komplementäre Fragmente von Armadillo-Repeat-Proteinen nutzt und eine hohe Trennschärfe ermöglicht.
      PubDate: 2018-03-13T11:33:16.234215-05:
      DOI: 10.1002/ange.201713377
  • Dye-Incorporated Polynaphthalenediimide Acceptor for Additive-Free
           High-Performance All-Polymer Solar Cells
    • Authors: Dong Chen; Jia Yao, Lie Chen, Jingping Yin, Ruizhi Lv, Bin Huang, Siqi Liu, Zhi-Guo Zhang, Chunhe Yang, Yiwang Chen, Yongfang Li
      Abstract: All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. Herein, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor by simple random copolymerization and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Consequently, additive-free all-PSCs demonstrated a high PCE of 8.13 %, which is one of the highest performance characteristics reported for all-PSCs to date. These results indicate that incorporating a dye into the n-type polymer gives insight into the precise design of high-performance polymer acceptors for all-PSCs.Ein Rhodamin-Farbstoff wurde in einen Naphthalendiimid-haltigen Polymerakzeptor mittels statistischer Copolymerisation integriert, wodurch der Lichtabsorptionskoeffizent gesteigert, das LUMO angehoben und die Kristallisation reduziert wurde. Polymersolarzellen mit diesem Akzeptor erreichen einen Wirkungsgrad (PCE) von 8.13 %.
      PubDate: 2018-03-13T11:33:02.57875-05:0
      DOI: 10.1002/ange.201800035
  • Catalytic C−H Trifluoromethoxylation of Arenes and Heteroarenes
    • Authors: Weijia Zheng; Cristian A. Morales-Rivera, Johnny W. Lee, Peng Liu, Ming-Yu Ngai
      Abstract: The intermolecular C−H trifluoromethoxylation of arenes remains a long-standing and unsolved problem in organic synthesis. Herein, we report the first catalytic protocol employing a novel trifluoromethoxylating reagent and redox-active catalysts for the direct (hetero)aryl C−H trifluoromethoxylation. Our approach is operationally simple, proceeds at room temperature, uses easy-to-handle reagents, requires only 0.03 mol % of redox-active catalysts, does not need specialized reaction apparatus, and tolerates a wide variety of functional groups and complex structures such as sugars and natural product derivatives. Importantly, both ground-state and photoexcited redox-active catalysts are effective. Detailed computational and experimental studies suggest a unique reaction pathway where photoexcitation of the trifluoromethoxylating reagent releases the OCF3 radical that is trapped by (hetero)arenes. The resulting cyclohexadienyl radicals are oxidized by redox-active catalysts and deprotonated to form the desired products of trifluoromethoxylation.Radikaler Ansatz: Photoanregung eines neuartigen Ttrifluormethoxylierungsreagens mit einer N-OCF3-Einheit führt zur homolytischen Spaltung der N-OCF3-Bindung und Freisetzung des OCF3-Radikals bei Raumtemperatur. Abfang des OCF3-Radikals durch Hetero(Arene) in Gegenwart von redoxaktiven Katalysatoren führt zu dem ersten Beispiel einer intermolekularen, katalytischen (Hetero)Aryl-C-H-Trifluormethoxylierung.
      PubDate: 2018-03-13T11:32:56.445694-05:
      DOI: 10.1002/ange.201800598
  • Palladium-Catalyzed Decarbonylative Trifluoromethylation of Acid Fluorides
    • Authors: Sinead T. Keaveney; Franziska Schoenebeck
      Abstract: While acid fluorides can readily be made from widely available or biomass-feedstock-derived carboxylic acids, their use as functional groups in metal-catalyzed cross-coupling reactions is rare. This report presents the first demonstration of Pd-catalyzed decarbonylative functionalization of acid fluorides to yield trifluoromethyl arenes (ArCF3). The strategy relies on a Pd/Xantphos catalytic system and the supply of fluoride for transmetalation through intramolecular redistribution to the the Pd center. This strategy eliminated the need for exogenous and detrimental fluoride additives and allows Xantphos to be used in catalytic trifluoromethylations for the first time. Our experimental and computational mechanistic data support a sequence in which transmetalation by R3SiCF3 occurs prior to decarbonylation.Homogene Katalyse: Trifluormethylarene wurden durch Pd-katalysierte decarbonylierende Funktionalisierung von Säurefluoriden erhalten. Rechnergestützte und experimentelle mechanistische Untersuchungen zeigen, dass der Schlüssel zur erfolgreichen Trifluormethylierung in der intramolekularen Umlagerung des Fluorids zum Pd-Zentrum liegt, wodurch die Transmetallierung direkt stattfinden kann.
      PubDate: 2018-03-13T11:32:43.497788-05:
      DOI: 10.1002/ange.201800644
  • Solid-Solution Alloy Nanoparticles of the Immiscible Iridium–Copper
           System with a Wide Composition Range for Enhanced Electrocatalytic
    • Authors: Fenglong Wang; Kohei Kusada, Dongshuang Wu, Tomokazu Yamamoto, Takaaki Toriyama, Syo Matsumura, Yusuke Nanba, Michihisa Koyama, Hiroshi Kitagawa
      Abstract: For the first time, we synthesize solid-solution alloy nanoparticles of Ir and Cu with a size of ca. 2 nm, despite Ir and Cu being immiscible in the bulk up to their melting over the whole composition range. We performed a systematic characterization on the nature of the IrxCu1−x solid-solution alloys using powder X-ray diffraction, scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the IrxCu1−x alloys had a face-centered-cubic structure; charge transfer from Cu to Ir occurred in the alloy nanoparticles, as the core-level Ir 4f peaks shifted to lower energy region with the increase in Cu content. Furthermore, we observed that the alloying of Ir with Cu enhanced both the electrocatalytic oxygen evolution and oxygen reduction reactions. The enhanced activities could be attributed to the electronic interaction between Ir and Cu arising from the alloying effect at atomic-level.Gute Mischung: Eine chemische Methode wurde eingesetzt, um Ir-Cu-Nanopartikel als feste Lösungen mit variabler Zusammensetzung herzustellen; im Festkörper sind Ir und Cu dagegen nicht gegenseitig löslich. Die Ir-Cu-Nanopartikel können als preiswerte Katalysatoren in der Sauerstoffentwicklung (OER) und Sauerstoffreduktion (ORR) genutzt werden.
      PubDate: 2018-03-13T11:32:34.934681-05:
      DOI: 10.1002/ange.201800650
  • Unsymmetrische, cyclische Diborene und thermische Umlagerung zu einem
    • Authors: Tom E. Stennett; James D. Mattock, Ivonne Vollert, Alfredo Vargas, Holger Braunschweig
      Abstract: Cyclische Diborane(4), die auf einer chelatisierenden, monoanionischen Benzylphosphan-Brücke basieren, wurden mittels Bor-Silicium-Austausch aus Arylsilanen und B2Br4 hergestellt. Koordination von Lewis-Basen an das verbleibende sp2-Boratom ergab unsymmetrische sp3-sp3-Diborane, die mit KC8 zu ihren entsprechenden trans-Diborenen reduziert wurden. Diese Verbindungen wurden mit einer Kombination aus spektroskopischen Methoden, Röntgenstrukturanalyse und DFT-Rechnungen untersucht. Beim PMe3-stabilisierten Diboren 6 wurde eine thermische Umlagerung zum gem-Diboren 8 beobachtet. DFT-Rechnungen an 8 lassen auf eine Borylborylen-Struktur mit einer polaren Bor-Bor-Bindung schließen.Bor geht vor! Unsymmetrische Diborene wurden durch Reduktion von cyclischen Diboranen(4) mit einer Benzylphosphan-Brücke hergestellt. Durch eine neuartige, thermische Umlagerung eines zweifach basenstabilisierten Diborens bildete sich ein Borylborylen.
      PubDate: 2018-03-13T11:32:27.025024-05:
      DOI: 10.1002/ange.201800671
  • Synthesis of a Helical Bilayer Nanographene
    • Authors: Paul J. Evans; Jiangkun Ouyang, Ludovic Favereau, Jeanne Crassous, Israel Fernández, Josefina Perles, Nazario Martín
      Abstract: A rigid, inherently chiral bilayer nanographene has been synthesized as both the racemate and enantioenriched M isomer (with 93 % ee) in three steps from established helicenes. This folded nanographene is composed of two hexa-peri-hexabenzocoronene layers fused to a [10]helicene, with an interlayer distance of 3.6 Å as determined by X-ray crystallography. The rigidity of the helicene linker forces the layers to adopt a nearly aligned AA-stacked conformation, rarely observed in few-layer graphene. By combining the advantages of nanographenes and helicenes, we have constructed a bilayer system of 30 fused benzene rings that is also chiral, rigid, and remains soluble in common organic solvents. We present this as a molecular model system of bilayer graphene, with properties of interest in a variety of potential applications.Ein inhärent chirales, doppellagiges Nanographen mit Helicen-Linker wurde einmal als Racemat und als M-Isomer mit 93 % ee synthetisiert. Das Material stellt das erste Beispiel einer neuen Klasse von verdrillten, doppellagigen, polyaromatischen Kohlenwasserstoffen dar. Die elektrochemischen und photophysikalischen Eigenschaften wurden untersucht.
      PubDate: 2018-03-13T11:32:20.083059-05:
      DOI: 10.1002/ange.201800798
  • Lithium-Ion Endohedral Fullerene (Li+@C60) Dopants in Stable Perovskite
           Solar Cells Induce Instant Doping and Anti-Oxidation
    • Authors: Il Jeon; Hiroshi Ueno, Seungju Seo, Kerttu Aitola, Ryosuke Nishikubo, Akinori Saeki, Hiroshi Okada, Gerrit Boschloo, Shigeo Maruyama, Yutaka Matsuo
      Abstract: Herein, we report use of [Li+@C60]TFSI− as a dopant for spiro-MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10-fold that of conventional devices using Li+TFSI−. Such high stability is attributed to the hydrophobic nature of [Li+@C60]TFSI− repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li+@C60]TFSI− could oxidize spiro-MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions.Luftbeständigkeit ist die größte aktuelle Herausforderung bei der Kommerzialisierung von Perowskit-Solarzellen. Konventionelle Li+TFSI−-Dotierung führt zu Problemen durch Hygroskopie. Fulleren-verkapseltes Li+@C60 TFSI− ergibt 10-mal luftstabilere Perowskit-Solarzellen, da der Dotierstoff hydrophob ist, Spiro-MeOTAD sofort oxidiert und antioxidativ wirkt.
      PubDate: 2018-03-13T11:32:03.69375-05:0
      DOI: 10.1002/ange.201800816
  • One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single
           Palladium Carbodicarbene Complex
    • Authors: Yu-Cheng Hsu; Vincent C.-C. Wang, Ka-Chun Au-Yeung, Chung-Yu Tsai, Chun-Chi Chang, Bo-Chao Lin, Yi-Tsu Chan, Chao-Ping Hsu, Glenn P. A. Yap, Titel Jurca, Tiow-Gan Ong
      Abstract: The combination of conventional transition-metal-catalyzed coupling (2 e− process) and photoredox catalysis (1 e− process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki–Miyaura coupling and photoredox catalysis for C−N bond formation upon visible-light irradiation. These two catalytic pathways can be combined to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C−H arylation under ambient conditions with a single catalyst in an efficient one-pot process.Und eins, und zwei: Die Kombination von herkömmlicher übergangsmetallkatalysierter Kupplung (2e−-Prozess) und Photoredoxkatalyse (1e−-Prozess) ermöglicht schwierige Kreuzkupplungen unter milden Reaktionsbedingungen. Ein einzelner Palladium-Carbodicarben(CDC)-Komplex vermittelt sowohl eine Suzuki-Miyaura-Kupplung als auch eine photoredoxkatalysierte C-N-Kupplung mit sichtbarem Licht.
      PubDate: 2018-03-13T11:31:55.254275-05:
      DOI: 10.1002/ange.201800951
  • Electrochemical Exfoliation of Pillared-Layer Metal–Organic Framework to
           Boost the Oxygen Evolution Reaction
    • Authors: Jin Huang; Yun Li, Rui-Kang Huang, Chun-Ting He, Li Gong, Qiong Hu, Lishi Wang, Yan-Tong Xu, Xiao-Yun Tian, Si-Yang Liu, Zi-Ming Ye, Fuxin Wang, Dong-Dong Zhou, Wei-Xiong Zhang, Jie-Peng Zhang
      Abstract: Two-dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism of heterogeneous catalysts, but they are mostly restricted to inorganic or organic materials based on covalent bonds. We report an electrochemical/chemical exfoliation strategy for synthesizing metal–organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared-layer framework. When the 3D pillared-layer MOF serves as an electrocatalyst for water oxidation (pH 13), the pillar ligands can be oxidized in situ and removed. The remaining ultrathin (2 nm) nanosheets of the metal–organic layers are an efficient catalyst with overpotentials as low as 211 mV at 10 mA cm−2 and a turnover frequency as high as 30 s−1 at an overpotential of 300 mV.Extra dünn geschnitten: Ein Metall-organisches Gerüst (MOF) mit säulenverknüpfter Schichtstruktur, liefert nach elektrochemischer Oxidation und Entfernung der Catechol-funktionalisierten Säulen nur 2 nm dünne Nanoblätter. Diese Nanoblätter sind effiziente Elektrokatalysatoren der Wasseroxidation bei pH 13 mit niedrigem Überpotential und hoher Umsatzfrequenz (TOF).
      PubDate: 2018-03-13T11:31:37.997556-05:
      DOI: 10.1002/ange.201801029
  • A Ligand System for the Flexible Functionalization of Quantum Dots via
           Click Chemistry
    • Authors: Yue Chen; Jose M. Cordero, Hua Wang, Daniel Franke, Odin B. Achorn, Francesca S. Freyria, Igor Coropceanu, He Wei, Ou Chen, David J. Mooney, Moungi G. Bawendi
      Abstract: We present a novel ligand, 5-norbornene-2-nonanoic acid, which can be directly added during established quantum dot (QD) syntheses in organic solvents to generate “clickable” QDs at a few hundred nmol scale. This ligand has a carboxyl group at one terminus to bind to the surface of QDs and a norbornene group at the opposite end that enables straightforward phase transfer of QDs into aqueous solutions via efficient norbornene/tetrazine click chemistry. Our ligand system removes the traditional ligand-exchange step and can produce water-soluble QDs with a high quantum yield and a small hydrodynamic diameter of approximately 12 nm at an order of magnitude higher scale than previous methods. We demonstrate the effectiveness of our approach by incubating azido-functionalized CdSe/CdS QDs with 4T1 cancer cells that are metabolically labeled with a dibenzocyclooctyne-bearing unnatural sugar. The QDs exhibit high targeting efficiency and minimal nonspecific binding.Klickfähige Quantenpunkte: Der Zusatz eines Carbonsäureliganden mit Norbornen-Motiv bei der Synthese von Quantenpunkten (QD) liefert durch Klick-Reaktionen funktionalisierbare QDs. Eine entsprechende Funktionalisierung mit hydrophilen Molekülen führt zu wasserlöslichen QDs mit Anwendungsmöglichkeiten in der Zellmarkierung.
      PubDate: 2018-03-13T11:31:26.643081-05:
      DOI: 10.1002/ange.201801113
  • Tracking the Dynamic Folding and Unfolding of RNA G-Quadruplexes in Live
    • Authors: Xiu-Cai Chen; Shuo-Bin Chen, Jing Dai, Jia-Hao Yuan, Tian-Miao Ou, Zhi-Shu Huang, Jia-Heng Tan
      Abstract: Because of the absence of methods for tracking RNA G-quadruplex dynamics, especially the folding and unfolding of this attractive structure in live cells, understanding of the biological roles of RNA G-quadruplexes is so far limited. Herein, we report a new red-emitting fluorescent probe, QUMA-1, for the selective, continuous, and real-time visualization of RNA G-quadruplexes in live cells. The applications of QUMA-1 in several previously intractable applications, including live-cell imaging of the dynamic folding, unfolding, and movement of RNA G-quadruplexes and the visualization of the unwinding of RNA G-quadruplexes by RNA helicase have been demonstrated. Notably, our real-time results revealed the complexity of the dynamics of RNA G-quadruplexes in live cells. We anticipate that the further application of QUMA-1 in combination with appropriate biological and imaging methods to explore the dynamics of RNA G-quadruplexes will uncover more information about the biological roles of RNA G-quadruplexes.Die geheime Dynamik der RNA: Die Fluoreszenzsonde QUMA-1 für die selektive und kontinuierliche Echtzeit-Bildgebung von RNA-G-Quadruplexen in lebenden Zellen wird vorgestellt. Mithilfe von QUMA-1 kann die RNA-G-Quadruplex-Dynamik untersucht und die Entfaltung von RNA-G-Quadruplexen durch RNA-Helikase visualisiert werden.
      PubDate: 2018-03-13T11:31:05.809546-05:
      DOI: 10.1002/ange.201801999
  • Two Stereoinduction Events in One C−H Activation Step: A Route towards
           Terphenyl Ligands with Two Atropisomeric Axes
    • Authors: Quentin Dherbassy; Jean-Pierre Djukic, Joanna Wencel-Delord, Françoise Colobert
      Abstract: Herein we disclose the synthesis of original chiral scaffolds—ortho-orientated terphenyls presenting two atropisomeric Ar–Ar axes. These unusual structures were built up by using the C−H activation approach, and remarkably, both chiral axes were controlled with excellent stereoselectivity in a single transformation. During the reaction, not only does atroposelective functionalization of a biaryl precursor occur to establish one stereogenic axis, but an unprecedented atropo-stereoselective C−H arylation also takes place to generate the second stereogenic element. These enantiomerically pure ortho-terphenyls show an original tridimensional structure and thus constitute a unique foundation for building up a library of enantiomerically pure bidentate ligands, such as the new ligands S/N-Biax and diphosphine BiaxPhos.Muschel-Ligand: Ungewöhnliche chirale Strukturen – ortho-orientierte Terphenyle mit zwei atropisomeren Ar-Ar-Achsen – wurden durch C-H-Aktivierung hergestellt. Beide stereogenen Achsen wurden mit exzellenter Stereokontrolle in einer einzigen Umwandlung erzeugt (siehe Schema). Die chiralen ortho-Terphenyl-Produkte bilden eine neuartige dreidimensionale Architektur für zweizähnige Liganden.
      PubDate: 2018-03-13T11:30:54.396063-05:
      DOI: 10.1002/ange.201801130
  • Sigmatropic Rearrangements of Hypervalent-Iodine-Tethered Intermediates
           for the Synthesis of Biaryls
    • Authors: Mitsuki Hori; Jing-Dong Guo, Tomoyuki Yanagi, Keisuke Nogi, Takahiro Sasamori, Hideki Yorimitsu
      Abstract: Metal-free dehydrogenative couplings of aryliodanes with phenols to afford 2-hydroxy-2′-iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π-extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C−C bond formation and I−O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement.Metallfreie dehydrierende Kupplungen von Aryliodanen mit Phenolen führen über Ligandenaustausch am hypervalenten Iod-Atom und eine [3,3]-sigmatrope Umlagerung zu 2-Hydroxy-2′-iodbiarylen. DFT-Rechnungen beweisen, dass die Umlagerung sigmatrop ist, d. h. die C-C-Bindungsknüpfung und die I-O-Bindungspaltung laufen konzertiert ab.
      PubDate: 2018-03-13T11:30:31.061162-05:
      DOI: 10.1002/ange.201801132
  • Me3Si−SiMe2[oCON(iPr)2−C6H4]: An Unsymmetrical Disilane Reagent for
           Regio- and Stereoselective Bis-Silylation of Alkynes
    • Authors: Peihong Xiao; Yanjun Cao, Yingying Gui, Lu Gao, Zhenlei Song
      Abstract: Das unsymmetrische, luftstabile Disilan Me3Si-SiMe2[oCON(iPr)2C6H4] bis-silyliert terminale Alkine hoch regioselektiv und gut verträglich mit funktionellen Gruppen zu Z-Vinyldisilanen. Z. L. Song et al. beschreiben in ihrer Zuschrift (
      DOI : 10.1002/ange.201800513) eine Umwandlung, die mit herkömmlichen Halogenid- oder Methoxy-substituierten, unsymmetrischen Disilanen schwer zu erreichen ist – die Metamorphose Kokon-ähnlicher Alkine zu Schmetterlings-ähnlichen Z-Vinylsilanen.
      PubDate: 2018-03-13T11:30:21.10539-05:0
  • Prebiotic methylations and carbamoylations generate non-canonical RNA
           nucleosides as molecular fossils of an early Earth
    • Authors: Christina Schneider; Sidney Becker, Hidenori Okamura, Antony Crisp, Tynchtyk Amatov, Michael Stadlmeier, Thomas Carell
      Abstract: The RNA world hypothesis assumes that life on earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G and U), but it contains in addition many chemically modified (non-canonical) bases. A yet open question is if these non-canonical bases were formed in parallel to the canonical bases (chemical origin), or whether they were created later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. This chemistry leads to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain non-canonical bases, which suggests that they are fossils of an early Earth.
      PubDate: 2018-03-13T10:27:48.677129-05:
      DOI: 10.1002/ange.201801919
  • Photo-biocatalytic one-pot cascades for the enantioselective synthesis of
           1,3-mercaptoalkanol volatile sulfur compounds
    • Authors: Daniele Castagnolo; Kate Lauder, Anita Toscani, Yuyin Qi, Jesmine Lim, Simon Charnock, Krupa Korah
      Abstract: 1,3-Mercaptoalkanols constitute an important class of volatile sulfur compounds and contribute to both agreeable and disagreeable flavours and fragrances of many foods and beverages. Most mercaptoalkanols exist as chiral isomers and their olfactory perception may depend on their diastereomeric and enantiomeric configuration. A number of mercaptoalkanols bear a chiral hydroxyl group whose configuration is strictly related to their olfactory properties. To date, few synthetic methods have been described for the synthesis of enantiomerically pure mercaptoalkanols bearing a chiral hydroxyl-moiety. These methods rely on the use of chiral auxiliaries and metal catalysts. The few biocatalytic methods reported in the literature suffer from poor yields and enantiomeric excess.This manuscript describes the discovery of two novel ketoreductase (KRED) enzymes able to catalyse the reduction of carbonyl precursors into enantiomerically pure mercaptoalkanols with opposite enantioselectivity under mild conditions. In addition, in order to develop a more efficient and sustainable methodology, a photocatalytic synthesis of the carbonyl precursors from appropriate thiols and mercaptanes has been developed. Finally, the photocatalytic and biocatalytic steps have been combined in a one-pot cascade reaction leading to chiral mercaptoalkanols with excellent yields and ee.
      PubDate: 2018-03-13T09:14:16.659768-05:
      DOI: 10.1002/ange.201802135
  • Supramolecularly-Driven Mild Friedel-Crafts Reaction Inside the Hexameric
           Resorcinarene Capsule: C-Cl Bond Activation by H-Bonding with the Bridged
           Water Molecules
    • Authors: Carmine Gaeta; Pellegrino La Manna, Carmen Talotta, Giuseppe Floresta, Margherita De Rosa, Annunziata Soriente, Antonio Rescifina, Placido Neri
      Abstract: A novel catalytical feature of the hexameric resorcinarene capsule (C) is here highlighted. The self-assembled cage C has been exploited to promote a mild Friedel-Crafts benzylation of several arenes and heteroarenes. In silico studies show the existence of a catalytically relevant H-bonding interaction between the bridged water molecules of the capsule and benzyl chloride, which is fundamental for the activation of the C-Cl bond. A supramolecular control of the capsule on the reaction outcome is evidenced. Inside the inner space of the capsule, N-methylpyrrole is preferentially benzylated in the unusual -position, while mesitylene reacts faster than 1,3-dimethoxybenzene, despite the greater -nucleophilicity of this latter.
      PubDate: 2018-03-13T09:13:23.12051-05:0
      DOI: 10.1002/ange.201801642
  • Dual Functionalization of α-Monoboryl Carbanion via A Deoxygenative
           Enolization with Carboxylic Acids
    • Authors: Wei Sun; Lu Wang, Chungu Xia, Chao Liu
      Abstract: Dual functionalization of 1,1-diborylalkanes via a deoxygenative enolization with carboxylic acids strategy has been developed for the first time. 1,1-Diborylalkanes were activated by MeLi to generate α-monoboryl carbanion. In-situ IR spectroscopy exhibited the interaction between carboxylic acid and 1,1-diborylalkane before adding activation reagent. The release of active α-monoboryl carbanion from its masked form was necessary for its reaction with carboxylate to afford enolate species. Electrophilic trapping of enolate species with various electrophiles achieved dual functionalization of 1,1-diborylalkanes to afford a variety of α-mono, di- and tri-substituted ketones.
      PubDate: 2018-03-13T08:25:31.448371-05:
      DOI: 10.1002/ange.201801679
  • Temperature-dependent atomic models of detergent micelles refined against
           small-angle X-ray scattering data
    • Authors: Milos T Ivanovic; Linda K Bruetzel, Jan Lipfert, Jochen S Hub
      Abstract: Surfactants have found a wide range of industrial and scientific applications. In particular, detergent micelles are used as lipid membrane mimics to solubilize membrane proteins for functional and structural characterisation. However, an atomic-level understanding of surfactants remains limited because many experiments provide only low-resolution structural information on surfactant aggregates. Here, we combine small-angle X-ray scattering with molecular dynamics simulations to derive fully atomic models of two maltoside micelles, at temperatures between 10°C and 70°C. We find that the micelles take the shape of general tri-axial ellipsoids and decrease in size and aggregation number with increasing temperature. Density profiles of hydrophobic groups and water along the three principal axes reveal that the minor micelle axis closely mimics lipid membranes. Our results suggest that coupling atomic simulations with low-resolution data allows for a structural characterisation of surfactant aggregates.
      PubDate: 2018-03-13T06:30:37.463675-05:
      DOI: 10.1002/ange.201713303
  • On the interaction of guest molecules with Co-MOF-74: A Vis/NIR and Raman
    • Authors: Ina Strauss; Alexander Mundstock, Dominik Hinrichs, Rasmus Himstedt, Alexander Knebel, Carsten Reinhardt, Dirk Dorfs, Jürgen Caro
      Abstract: Co-MOF-74 rod like crystals with a length of several hundred micrometers have been synthesized via a solvothermal procedure and their interaction with different gases has been evaluated in view of selective gas sensing. We show strongly anisotropic absorption behaviour of the Co-MOF-74 crystals when illuminated with polarized light. This study then addresses the interactions of guests (CO2, propane, propene, Ar, MeOH, H2O) with Co-MOF-74, studied by various spectroscopic techniques. Via Vis/NIR measurements, peak shifts of Co-MOF-74 depending on the interaction with the guest molecules were observed and distinguished. In the visible as well as in the near infrared region, the maximum absorbance is shifted selectively corresponding to the intensity of the CoII-guest interaction. Even propene and propane could be distinguished at room temperature according to their different interactions with Co-MOF-74. Furthermore, we used Raman spectroscopy to detect a modified vibrational behaviour of Co-MOF-74 upon gas adsorption. We show that the adsorption of H2O leads to a characteristic shift of the peak maxima in the Raman spectra.
      PubDate: 2018-03-13T05:25:27.714835-05:
      DOI: 10.1002/ange.201801966
  • Transient and Persistent Room-Temperature Mechanoluminescence from a
           White-Light Emitting AIEgen with Tricolor Emission Switching Triggered by
    • Authors: Jian-An Li; Jinghong Zhou, Zhu Mao, Zongliang Xie, Zhan Yang, Bingjia Xu, Cong Liu, Xin Chen, Dingyang Ren, Hui Pan, Guang Shi, Yi Zhang, Zhenguo Chi
      Abstract: Persistent luminescence from purely organic materials is basically triggered by light and electricity, which largely confines its practical applications. Herein, we present a purely organic AIEgen that exhibited not only persistent photoluminescence, but also transient and persistent room-temperature mechanoluminescence. By simply turning on and off the UV lamp, tricolor emission switching between blue, white and yellow was also achieved. The data from single-crystal structure analysis and theoretical calculation suggest that mechanism of the observed persistent mechanoluminescence (pML) is correlated with the strong spin-orbit coupling of bromine atom, as well as the formation of H-aggregates and restriction of intramolecular motions in noncentrosymmetric crystal structure. These results outline a fundamental principle for the development of new pML materials, providing an important step forward in expanding the application scope of persistent luminescence.
      PubDate: 2018-03-13T03:55:32.082757-05:
      DOI: 10.1002/ange.201800762
  • Frontispiz: Nitrogen-Based Lewis Acids: Synthesis and Reactivity of a
           Cyclic (Alkyl)(Amino)Nitrenium Cation
    • Authors: Jiliang Zhou; Liu Leo Liu, Levy L. Cao, Douglas W. Stephan
      Abstract: Stickstoff-basierte Lewis-Säuren D. W. Stephan et al. zeigen in ihrer Zuschrift auf S. 3380 ff., dass ein cyclisches (Alkyl)(amino)nitrenium mit kationischem Stickstoffatom eine verbesserte Elektrophilie aufweist.
      PubDate: 2018-03-13T03:02:00.667097-05:
      DOI: 10.1002/ange.201881361
  • A novel approach to synthesize crystalline porous organic salts with high
           proton conductivity
    • Authors: Guolong Xing; Tingting Yan, Saikat Das, Teng Ben, Shilun Qiu
      Abstract: Self-assembled crystalline porous organic salts (CPOSs) formed by the acid-base combination and with one-dimensional polar channels containing water molecules inside the channels have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2 x10-2 S cm-1 at 333 K and high humid conditions, which is among the best conductivity values reported yet for other porous materials e.g. Metal Organic Frameworks, Hydrogen-bonded Organic Frameworks etc. These materials exhibiting permanent porosity represent a novel group of porous materials and can find interesting applications as proton exchange membrane fuel cells.
      PubDate: 2018-03-13T02:00:59.028297-05:
      DOI: 10.1002/ange.201800423
  • Synthesis of bis-Silicon Complexes of [38]-. [37]-, and [36] Octaphyrins:
           Aromaticity Switch and Stable Radical Cation
    • Authors: Atsuhiro Osuka; Shin-ichiro Ishida, Jinseok Kim, Daiki Shimizu, Dongho Kim
      Abstract: Silicon complexation of [38]octaphyrin 1 was accomplished by reaction with an excess amount of MeSiCl3 in the presence of N,N-diisopropylethylamine, giving aromatic [38]octaphyrin bis-silicon complex 2. This complex was interconvertible with antiaromatic [36]octaphyrin congener 3 via oxidation with MnO2 and reduction with NaBH4. Curiously, mild oxidation of 2 with ferrocenium hexafluorophosphate afforded [37]octaphyrin bis-silicon complex 4 as an stable radical cation that can be stored under ambient conditions in the solid state. Owing to the two NNNCC-five-coordinated Si atoms bearing trigonal bipyramidal geometry, these octaphyrin bis-Si complexes take on similar and rigid figure-of-eight structures with different consecutive number of conjugated π-electrons (38, 37, and 36) that are all stable as a rare example.
      PubDate: 2018-03-13T00:01:11.024702-05:
      DOI: 10.1002/ange.201801986
  • An Extra-Large Pore Zeolite with 24 × 8 × 8-Ring Channels Using a
           Structure Directing Agent Derived from Traditional Chinese Medicine
    • Authors: Chuanqi Zhang; Elina Kapaca, Jiyang Li, Yunling Liu, Xianfeng Yi, Anmin Zheng, Xiaodong Zou, Jiuxing Jiang, Jihong Yu
      Abstract: Extra-large pore zeolites have aroused increasing interests because of their important applications for possessing of large molecules. Although great progress has been made by academy and industry, it is challenging to synthesize these materials. A new extra-large pore zeolite SYSU-3 (Sun Yat-sen University no. 3) has been synthesized by using a novel sophoridine derivative as an organic structure directing agent (OSDA). The framework structure was solved and refined using continuous rotation electron diffraction (cRED) data from nanosized crystals. SYSU-3 exhibits a new zeolite framework topology, which has the first 24 × 8 × 8 -ring extra-large pore system and a framework density (FD) as low as 11.4 T/1000 Å3. The unique skeleton of the OSDA plays an essential role in the formation of the distinctive zeolite structure. This work provides new perspective for developing new zeolitic materials by using alkaloids as cost-effective OSDAs.
      PubDate: 2018-03-12T22:02:35.839597-05:
      DOI: 10.1002/ange.201801386
  • A High Voltage Molecular Engineered Organic Sensitizer-Iron Redox Shuttle
           Pair: 1.4 V DSC and 3.3 V SSM-DSC Devices
    • Authors: Roberta R. Rodrigues; Jared Heath Delcamp, Hammad Cheema
      Abstract: The development of high voltage solar cells is an attractive way to use sunlight for solar-to-fuel devices, multijunction solar-to-electric systems, and to power limited area consumer electronics. By designing a low oxidation potential organic dye (RR9)/redox shuttle (Fe(bpy)33+/2+) pair for dye-sensitized solar cell (DSC) devices, the highest single device photovoltage (1.42 V) has been realized for a DSC not relying on doped TiO2. Additionally, Fe(bpy)33+/2+ offers a robust, readily tunable ligand platform for redox potential tuning. RR9 was found to be regenerated with a low driving force (150 mV), and by utilizing the RR9/Fe(bpy)33+/2+ redox shuttle pair in a subcell for a sequential series multijunction (SSM)-DSC system, the highest known three subcell photovoltage was reported for any solar cell technology (3.34 V,>1.0 V per subcell).
      PubDate: 2018-03-12T22:02:07.809961-05:
      DOI: 10.1002/ange.201712894
  • Tuning the Size of Nanoassembles: A Hierarchical Transfer of Information
           from Dendrimers to Polyion Complexes
    • Authors: Sandra P. Amaral; Maun H. Tawara, Marcos Fernandez-Villamarin, Erea Borrajo, José Martínez-Costas, Anxo Vidal, Ricardo Riguera, Eduardo Fernandez-Megia
      Abstract: Herein we describe that the generation of dendrimers represents a powerful tool in the control of the size and biodistribution of polyion complexes (PIC). Using a combinatorial screening of six dendrimers (18-243 terminal groups) and five oppositely charged PEGylated copolymers, a dendrimer to PIC hierarchical transfer of structural information was revealed with PIC diameters that increased from 80 to 500 nm on decreasing the dendrimer generation. This rise in size, also accompanied by a micelle to vesicle transition, is interpreted according to a cone- to rod-shaped progression in the architecture of the unit PIC (uPIC). This precise size tuning entitled dendritic PIC as nanorulers for controlled biodistribution. Overall, a domino-like control of the size and biological properties of PIC -not attainable with linear polymers- is feasible through dendrimer generation.
      PubDate: 2018-03-12T14:55:34.585576-05:
      DOI: 10.1002/ange.201712244
  • Charge neutralization-driven shape reconfiguration of DNA nanotubes
    • Authors: Pi Liu; Yan Zhao, Xiaoguo Liu, Jixue Sun, Dede Xu, Yang Li, Qian Li, Lihua Wang, Sichun Yang, Chunhai Fan, Jianping Lin
      Abstract: Shape reconfiguration of membrane protein channels is highly regulated under physiological conditions for gated transportation. Nevertheless, mechanistic understanding of molecular channels remains challenging due to the difficulty in probing gating-associated subtle structural changes. Here we show that charge neutralization can drive shape reconfiguration of a biomimetic 6-helix bundle DNA nanotube (6HB). Specifically, 6HB adopts a compact state when being neutralized by Mg2+; and monovalent ions (Na+) switch it to the expansion state, as revealed by molecular dynamics (MD) simulation, small angle X-ray scattering (SAXS) and Förster resonance energy transfer (FRET) characterization. Furthermore, partially neutralizing of the DNA backbone with ethyl-phosphorothioate substitution renders 6HB constantly compact and insensitive to ions, suggesting the interplay between electrostatic and hydrophobic forces in channels. This biomimetic DNA nanotube system provides not only a platform for understanding structure-function relationship of biological channels but also designing rules for shape control of DNA nanostructures in biomedical applications.
      PubDate: 2018-03-12T09:25:42.931844-05:
      DOI: 10.1002/ange.201801498
  • Samarium Polystibides Derived from Highly Activated Nanoscale Antimony
    • Authors: Peter Werner Roesky; Christoph Schoo, Sebastian Bestgen, Alexander Egeberg, Svetlana Klementieva, Claus Feldmann, Sergey N Konchenko
      Abstract: Zintl-ions in molecular compounds are of fundamental interest for basic research and application. However, in contrast to the lighter group 15 elements, elemental antimony has never been applied as reagent for the preparation of molecular polystibides. Herein, we report for the first time two reactive antimony sources, which allow the direct access to molecular polystibide compounds. These are Sb amalgam (Sb/Hg) and ultrasmall Sb0 nanoparticles (d = 6.6±0.8 nm), which were used independently as precursors for the synthe-sis of the largest f-element polystibide, [(Cp*2Sm)4Sb8]. Whereas the reaction of the nanoparticles with [Cp*2Sm] directly led to [(Cp*2Sm)4Sb8], Sm/Sb/Hg intermediates were isolated when using Sb/Hg as precursor. These Sm/Sb/Hg intermediates [{(Cp*2Sm)2Sb}2(μ-Hg)] and [{(Cp*2Sm)3(μ4,η1:2:2:2-Sb4)}2Hg] were synthetically trapped and structurally characterized giving insight in the formation mechanism of polystibide compounds.
      PubDate: 2018-03-12T08:25:28.416552-05:
      DOI: 10.1002/ange.201802250
  • Synthesis of C2 Substituted Benzothiophenes via an Interrupted
           Pummerer/[3,3]-Sigmatropic/1,2-Migration Cascade of Benzothiophene
    • Authors: Zhen He; Harry Shrives, José A Fernández-Salas, Alberto Abengózar, Jessica Neufeld, Kevin Yang, Alex P Pulis, David John Procter
      Abstract: Functionalized benzothiophenes are important scaffolds found in molecules with wide ranging biological activity and in organic materials. We describe an efficient, metal-free synthesis of C2 arylated, allylated and propargylated benzothiophenes. The reaction utilizes synthetically unexplored yet readily accessible benzothiophene S-oxides and phenols, allyl- or propargyl silanes in a unique cascade sequence. An interrupted Pummerer reaction between benzothiophene S-oxides and the coupling partners yields sulfonium salts that lack aromaticity and therefore allow facile [3,3]-sigmatropic rearrangement. The subsequently generated benzothiophenium salts undergo a previously unexplored 1,2-migration to access C2 functionalized benzothiophenes.
      PubDate: 2018-03-12T07:25:53.229196-05:
      DOI: 10.1002/ange.201801982
  • Oxidative Coupling of Anionic Abnormal N-Heterocyclic Carbenes: an
           Efficient Access to Janus-Type 4,4'-Bis(2H-Imidazol-2-Ylidenes)
    • Authors: Noel Lugan; Dmitry A. Valyaev, Alina A. Grineva, Vincent César, Oleg A. Filippov, Victor N. Khrustalev, Sergei N. Nefedov
      Abstract: The oxidative coupling of anionic imidazol-4-ylidenes protected at the C2 position with [MnCp(CO)2] or BH3 leads to the corresponding 4,4'-bis(2H-imidazol-2-ylidenes) complexes or adducts, in which the two carbenic moieties are connected through a single C-C bond. Subsequent acidic treatment of the later species leads to the corresponding 4,4'-bis(imidazolium) salts in good yields, the overall procedure offering a practical access to a novel class of Janus-type bis(NHC)s. Strikingly, the coplanarity of the two NHC rings within the mesityl derivative 4,4'-bis(IMes), favored by steric hindrance along with stabilizing intramolecular C-H... aryl interactions, allows the alignment of the π-systems and, as a direct consequence, a significant electron communication through the bis-carbenic scaffold.
      PubDate: 2018-03-12T05:57:07.330249-05:
      DOI: 10.1002/ange.201801530
  • A Readily Accessible Class of Chiral Cp Ligands and their Application in
           Ru(II)-Catalyzed Enantioselective Syntheses of Dihydrobenzoindoles
    • Authors: Nicolai Cramer; Shuo-Guo Wang, Sung-Hwan Park
      Abstract: Chiral Cpx ligands have a large application potential in enantioselective transition-metal catalysis. However the development of concise and practical routes to such ligands remains in its infancy stage. We present a convenient and efficient two step synthesis of a novel class of chiral Cpx ligands with tunable sterics that can be readily used for complexation giving CpxRh(I), CpxIr(I) and CpxRu(II) complexes. The potential of this ligand class is demonstrated with the latter in the enantioselective cyclization of azabenzonorbornadienes with alkynes, affording dihydrobenzo¬indoles in up to 98:2 er, significantly outperforming existing binaphthyl-derived Cpx ligands.
      PubDate: 2018-03-12T05:56:13.994788-05:
      DOI: 10.1002/ange.201802244
  • Solvent-Induced Crystal Polymorphism as Studied by Pyroelectric
           Measurements and Impedance Spectroscopy: Alcohols as Tailor-Made
           Inhibitors of α-Glycine
    • Authors: Elena Meirzadeh; Shiri Dishon, Isabelle Weissbuch, David Ehre, Meir Lahav, Igor Lubomirsky
      Abstract: Kleinste Mengen an Methanol werden selektiv in α-Glycin-Kristallen eingeschlossen, was durch pyroelektrische Messungen und Impedanzspektroskopie belegt wurde. In ihrer Zuschrift (
      DOI : 10.1002/ange.201800741) zeigen E. Meirzadeh, M. Lahav, I. Lubomirsky et al., dass sich die dielektrischen Eigenschaften von α-Glycin-Kristallen deutlich unterscheiden, je nachdem ob sie in wässriger Lösung oder Alkohol/Wasser-Mischungen gezüchtet wurden. Der Unterschied erklärt, warum Alkohole die Bildung des metastabilen β-Polymorphs induzieren.
      PubDate: 2018-03-12T05:06:01.548518-05:
  • The Large Second-Harmonic Generation of LiCs2PO4 is caused by the
           Metal-Cation-Centered Groups
    • Authors: Xiyue Cheng; Myung-Hwan Whangbo, Guo-Cong Guo, Maochun Hong, Shuiquan Deng
      Abstract: We evaluated the individual atom contributions to the second harmonic generation (SHG) coefficients of LiCs2PO4 (LCPO) by introducing the partial response functionals on the basis of first principles calculations. The SHG response of LCPO is dominated by the metal-cation-centered groups CsO6 and LiO4, not by the nonmetal-cation-centered groups PO4 expected from the existing models and theories. The SHG coefficients of LCPO are determined mainly by the occupied orbitals O 2p and Cs 5p as well as by the unoccupied orbitals Cs 5d and Li 2p. For the SHG response of a material, the polarizable atomic orbitals of the occupied and the unoccupied states are both important.Metall-zentriert: Die Ursache für die ausgeprägte Frequenzverdopplung (second-harmonic generation, SHG) von LiCs2PO4 sind die Metallkation-zentrierten CsO6- und LiO4-Gruppen. Dagegen sind die Nichtmetallkation-zentrierten PO4-Gruppen an dem Effekt unbeteiligt.
      PubDate: 2018-03-12T04:28:36.55912-05:0
      DOI: 10.1002/ange.201711465
  • One-Step Synthesis of Hybrid Core–Shell Metal–Organic
    • Authors: Xinyu Yang; Shuai Yuan, Lanfang Zou, Hannah Drake, Yingmu Zhang, Junsheng Qin, Ali Alsalme, Hong-Cai Zhou
      Abstract: Epitaxial growth of MOF-on-MOF composite is an evolving research topic in the quest for multifunctional materials. In previously reported methods, the core–shell MOFs were synthesized via a stepwise strategy that involved growing the shell-MOFs on top of the preformed core-MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice-matching requirement have limited the preparation of core–shell MOFs. Herein, we demonstrate that hybrid core–shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetic analysis. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X-ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.MOF auf MOF: Eine Serie von Kern-Schale-MOFs mit fehlgepassten Gittern wurde mithilfe von Nukleationskinetikanalysen synthetisiert. Die isoretikuläre Erweiterung der mikroporösen Schalen und orthogonale Modifizierung des Kerns führten zu multifunktionellen MOF-Kompositen, die als größenselektive Katalysatoren in der Olefin-Epoxidation wirken.
      PubDate: 2018-03-12T04:28:28.181687-05:
      DOI: 10.1002/ange.201710019
  • Activity-Based Probes Developed by Applying Sequential Dehydroalanine
           Strategy on Expressed Proteins Reveal a Potential α-globin Modulating
    • Authors: Ashraf Brik; Roman Meledin, Sachitanand Mali, Oded Kleifeld
      Abstract: We report a general and novel semisynthetic strategy for the preparation of ubiquitinated protein activity based probes applying sequential dehydroalanine formation on expressed proteins. We applied this approach to construct physiologically and therapeutically relevant ubiquitinated α-globin probe, which was used for the enrichment and proteomic identification of α-globin modulating deubiquitinases. We found USP15 as a potential deubiquitinase, modulating α-globin, which excess aggravates beta-thalassemia symptoms. This development opens new opportunities for the activity based probe design to shed light on the important aspects underlining ubiquitination and deubiquitination in health and disease.
      PubDate: 2018-03-12T03:26:52.453263-05:
      DOI: 10.1002/ange.201800032
  • Helicenophyrins: Expanded Carbaporphyrins Incorporating Aza[5]helicene and
           Heptacyclic S-Shaped Aza[5]helicene Motifs
    • Authors: Bartosz Szyszko; Monika Przewoźnik, Michał J. Białek, Agata Białońska, Piotr J. Chmielewski, Jakub Cichos, Lechosław Latos-Grażyński
      Abstract: Incorporation of phenanthrene into a hexaphyrin( frame resulted in intramolecular ring fusion, thus giving rise to chiral helicenophyrins. These molecules contain helicene and porphyrin features by incorporating either an aza[5]helicene or heptacyclic S-shaped aza[5]helicene.Kreuzweise Einführung einer Phenanthreneinheit in einen Hexaphyrin( führte zu einer intramolekularen Ringfusion unter Bildung chiraler Helicenophyrine. Diese Moleküle enthalten Helicen- und Porphyrineinheiten.
      PubDate: 2018-03-12T03:16:50.960484-05:
      DOI: 10.1002/ange.201800879
  • Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High
           Thermoelectric Performance in AgCuTe
    • Authors: Subhajit Roychowdhury; Manoj K. Jana, Jaysree Pan, Satya N. Guin, Dirtha Sanyal, Umesh V. Waghmare, Kanishka Biswas
      Abstract: Crystalline solids with intrinsically low lattice thermal conductivity (κL) are crucial to realizing high-performance thermoelectric (TE) materials. Herein, we show an ultralow κL of 0.35 Wm−1 K−1 in AgCuTe, which has a remarkable TE figure-of-merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First-principles DFT calculation reveals several soft phonon modes in its room-temperature hexagonal phase, which are also evident from low-temperature heat-capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κL in the room-temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high-temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor.Niedrige Wärmeleitung: Weiche Phononenmoden und optisch-akustische Phononenkopplung führen zu einer sehr niedrigen Wärmeleitfähigkeit in der hexagonalen Phase von AgCuTe bei Raumtemperatur. Eine dynamische Fehlordnung der Ag/Cu-Kationen reduziert die Phononenfrequenzen und die mittlere freie Weglänge in der Steinsalz-Phase bei hohen Temperaturen. p-AgCuTe erreicht bei ca. 670 K eine hohe thermoelektrische Gütezahl (zT) von 1.6.
      PubDate: 2018-03-12T03:12:21.368383-05:
      DOI: 10.1002/ange.201801491
  • Ion-Selective Electrodes Based on Hydrophilic Ionophore-Modified Nanopores
    • Authors: Soma Papp; Gyula Jágerszki, Róbert E. Gyurcsányi
      Abstract: We report the synthesis and analytical application of the first Cu2+-selective synthetic ion channel based on peptide-modified gold nanopores. A Cu2+-binding peptide motif (Gly-Gly-His) along with two additional functional thiol derivatives inferring cation-permselectivity and hydrophobicity was self-assembled on the surface of gold nanoporous membranes comprising of about 5 nm diameter pores. These membranes were used to construct ion-selective electrodes (ISEs) with extraordinary Cu2+ selectivities, approaching six orders of magnitude over certain ions. Since all constituents are immobilized to a supporting nanoporous membrane, their leaching, that is a ubiquitous problem of conventional ionophore-based ISEs was effectively suppressed.Ionenselektivität wurde durch die chemische Modifikation von Nanoporen in einer Goldmembran etabliert. Drei SH-terminierte funktionelle Komponenten, einschließlich eines Kupfer-bindenden Peptids, wurden durch Selbstorganisation an eine Goldoberfläche gebunden. Dieses Konzept ermöglicht die Verwendung von hydrophilen Ionophoren zum Aufbau von ionenselektiven Elektroden, und ihre Immobilisierung verhindert das Auswaschen der aktiven Komponenten.
      PubDate: 2018-03-12T03:11:56.490381-05:
      DOI: 10.1002/ange.201800954
  • Reversible Wasserstoffaktivierung durch einen Pyridonat-Boran-Komplex: Ein
           Zusammenspiel von frustrierter Lewis-Paar-Reaktivität und
    • Authors: Urs Gellrich
      Abstract: Ein Pyridon-Boran-Komplex, der unter milden Bedingungen Wasserstoff abspaltet, wird beschrieben. Die umgekehrte Reaktion, Wasserstoffaktivierung durch den gebildeten Pyridonat-Boran-Komplex, wird unter moderatem H2-Druck (2 bar) und bei Raumtemperatur beobachtet. DFT- und DLPNO-CCSD(T)-Rechnungen zeigen, dass es sich bei der aktiven Form des Pyridonat-Boran-Komplexes um ein Boroxypyridin handelt, das als frustriertes Lewis-Paar betrachtet werden kann. Bemerkenswert ist die Umwandlung des Boroxypyridins zu einem neutralen Pyridonliganden im Zuge der H2-Aktivierung. In Analogie zum Konzept der Metall-Liganden-Kooperation kann diese neuartige Funktionsweise als Bor-Liganden-Kooperation beschrieben werden.Reversible Wasserstoffaktivierung unter milden Bedingungen durch einen Pyridonat-Boran-Komplex wird beschrieben. Während der Bindungsaktivierung wandelt sich der Pyridonat-Substituent in einen neutralen Pyridon-Liganden um. Diese bislang nicht beschriebene Funktionsweise kann, in Analogie zum Konzept der Metall-Liganden-Kooperation, als Bor-Liganden-Kooperation beschrieben werden.
      PubDate: 2018-03-12T02:17:25.127706-05:
      DOI: 10.1002/ange.201713119
  • Temperature-Correlated Afterglow of a Semiconducting Polymer Nanococktail
           for Imaging-Guided Photothermal Therapy
    • Authors: Xu Zhen; Chen Xie, Kanyi Pu
      Abstract: Nanoparticles for photothermal therapy: Real-time temperature monitoring is critical to reduce the nonspecific damage during photothermal therapy (PTT); however, PTT agents that can emit temperature-related signals are rare and limited to few inorganic nanoparticles. We herein synthesize a semiconducting polymer nanococktail (SPNCT) that can not only convert photo-energy to heat but also emit temperature-correlated luminescence after cessation of light excitation. Such an afterglow luminescence of the SPNCT detects tumors more sensitively than fluorescence as a result of the elimination of tissue autofluorescence, while its temperature-dependent nature allows tumor temperature to be optically monitored under near-infrared (NIR) laser irradiation. Thus, SPNCT represents the first organic optical nanosystem that enables optical-imaging guided PTT without real-time light excitation.Zum Ausklang, ein Cocktail: Ein Nanococktail aus Halbleiterpolymeren (SPNCT) mit temperaturkorrelierter Nachleuchtlumineszenz wurde für die bildgebungbasierte photothermische Therapie entwickelt. Die Nachleuchtintensität des SPNCT zeigt eine gute lineare Korrelation mit der Temperatur, was die Aufzeichnung der photothermischen Temperatur des Tumors unter Bestrahlung mit einem NIR-Laser ermöglicht.
      PubDate: 2018-03-12T02:17:00.044756-05:
      DOI: 10.1002/ange.201712550
  • Fire-Retardant and Thermally Insulating Phenolic-Silica Aerogels
    • Authors: Zhi-Long Yu; Ning Yang, Varvara Apostolopoulou-Kalkavoura, Bing Qin, Zhi-Yuan Ma, Wei-Yi Xing, Chan Qiao, Lennart Bergström, Markus Antonietti, Shu-Hong Yu
      Abstract: Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co-polymerization and nanoscale phase separation of the phenol-formaldehyde-resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO2 aerogel can resist a high-temperature flame without disintegration and prevents the temperature on the non-exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.Feuer einstellen: Mithilfe einer Copolymerisationsstrategie kann ein binäres organisch-anorganisches Hybridaerogel mit Homogenität auf der Nanoskala hergestellt werden. Das Phenol-Formaldehyd-Harz/SiO2-Aerogel ist mechanisch widerstandsfähig und leitet Wärme deutlich schlechter als expandiertes Polystyrol, sodass es sich hervorragend für den Brandschutz eignet.
      PubDate: 2018-03-12T02:16:21.754876-05:
      DOI: 10.1002/ange.201711717
  • Synergistic Photoredox Catalysis and Organocatalysis for Inverse
           Hydroboration of Imines
    • Authors: Nengneng Zhou; Xiang-Ai Yuan, Yue Zhao, Jin Xie, Chengjian Zhu
      Abstract: The first catalytic inverse hydroboration of imines with N-heterocyclic carbene (NHC) boranes has been realized by means of cooperative organocatalysis and photocatalysis. This catalytic combination provides a promising platform for promoting NHC-boryl radical chemistry under sustainable and radical-initiator-free conditions. The highly important functional-group compatibility and possible application in late-stage hydroborations represent an important step forward to an enhanced α-amino organoboron library.Präzedenzlose Inversion: Die erste katalytische inverse Hydroborierung von Iminen mit NHC-Boranen (NHC=N-heterocyclisches Carben) gelang mithilfe einer kooperativen Organo- und Photokatalyse. Die Art des Thiols ist entscheidend für die inverse Hydroborierung. Dieses Verfahren ist wichtiger Schritt hin zur Verbesserung von α-Aminoorganobor-Bibliotheken.
      PubDate: 2018-03-12T02:11:48.150783-05:
      DOI: 10.1002/ange.201800421
  • Chemoselective Synthesis of Z-Olefins through Rh-Catalyzed
           Formate-Mediated 1,6-Reduction
    • Authors: Raphael Dada; Zhongyu Wei, Ruohua Gui, Rylan J. Lundgren
      Abstract: Z-olefins are important functional units in synthetic chemistry; their preparation has thus received considerable attention. Many prevailing methods for cis-olefination are complicated by the presence of multiple unsaturated units or electrophilic functional groups. In this study, Z-olefins are delivered through selective reduction of activated dienes using formic acid. The reaction proceeds with high regio- and stereoselectivity (typically>90:10 and>95:5, respectively) and preserves other alkenyl, alkynyl, protic, and electrophilic groups.Selektive Reduktion: Bei vielen Methoden zur cis-Olefinierung stört die Gegenwart weiterer ungesättigter Einheiten oder elektrophiler Gruppen. Hier wird ein Verfahren vorgestellt, das Z-Olefine durch selektive Reduktion aktivierter Diene mit Ameisensäure liefert. Die Reaktion ist hoch regio- und stereoselektiv (in der Regel>90:10 bzw.>95:5) und kompatibel mit anderen Alkenyl-, Alkinyl-, protischen und elektrophilen Gruppen.
      PubDate: 2018-03-12T02:10:57.753105-05:
      DOI: 10.1002/ange.201800361
  • Eva Hevia
    • Abstract: „Das Geheimnis, ein erfolgreicher Wissenschaftler zu sein, ist Zielstrebigkeit und Begeisterung. Mein Rat an Studenten: Folgt euren Träumen und habt Spaß dabei. …” Dies und mehr von und über Eva Hevia finden Sie in ihrem Autoren-Profil.
      PubDate: 2018-03-12T01:51:59.145849-05:
      DOI: 10.1002/ange.201801407
  • Selective C(sp3)−H Aerobic Oxidation Enabled by Decatungstate
           Photocatalysis in Flow
    • Authors: Gabriele Laudadio; Sebastian Govaerts, Ying Wang, Davide Ravelli, Hannes F. Koolman, Maurizio Fagnoni, Stevan W. Djuric, Timothy Noël
      Abstract: A mild and selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C−H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (−)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.In einem Mikroströmungsreaktor, der die sichere Verwendung von Sauerstoff und eine effektivere Bestrahlung des Reaktionsgemischs ermöglichte, konnte eine selektive C(sp3)-H-Oxidation mit einem preiswerten Decawolframat-Photokatalysator deutlich effizienter durchgeführt werden. Sowohl aktivierte als auch nichtaktivierte C-H-Bindungen ließen sich oxidieren, einschließlich solcher in Naturstoffen wie (−)-Ambroxid und Artemisinin.
      PubDate: 2018-03-12T01:51:40.340894-05:
      DOI: 10.1002/ange.201800818
  • Avoiding Thiol Compound Interference: A High-Fidelity Au-Se Bonding
           Nanoplatform and Its Biological Applications
    • Authors: Bo Hu; Fanpeng Kong, Xiaonan Gao, Lulu Jiang, Xiaofeng Li, Wen Gao, Kehua Xu, Bo Tang
      Abstract: Gold nanoparticles (Au NPs) assembled through Au-S covalent bond have been widely used for biomolecules sensing technologies. However, during the process, detecting distortions caused by high level of thiol compounds can still significant influence the result and it has been barely solved. Herein, based on the higher stability of Au-Se bonds towards Au-S bonds, we prepared selenol-modified Au NPs as Au-Se nanoplatform (NPF). Compared with Au-S NPF, the Au-Se NPF exhibits an excellent anti-interference ability in the presence of millimolar levels of glutathione (GSH). Thus, such Au-Se NPF that can effectively avoid detection distortions caused by high levels of thiols offers a new perspective in future nanomaterial designing, as well as a novel platform with higher stability and selectivity for the in vivo application of chemical sensing and clinical therapies.
      PubDate: 2018-03-11T21:55:55.914663-05:
      DOI: 10.1002/ange.201712921
  • Monoaryllead Trichloride Defying Reductive Elimination
    • Authors: Marian Olaru; Ralf Kather, Emanuel Hupf, Enno Lork, Stefan Mebs, Jens Beckmann
      Abstract: Transmetallation of Pb(OAc)4 with R2Hg (1), followed by treatment with HCl in Et2O, provided RPbCl3 (2), the first kinetically-stabilized monoorganolead trihalide that defies reductive elimination under ambient conditions. The kinetic stabilisation relies on an intramolecularly coordinating O-donor substituent (R = 6-Ph2P(O)-Ace-5-). The gram scale preparation of 2 was the key for the synthesis of unsymmetrically substituted diaryllead dichlorides RR'PbCl2 (3a, R' = Ph; 3b, R' = 4-MeOC6H4; 3c, R' = 4-Me2NC6H4).
      PubDate: 2018-03-11T21:55:39.382435-05:
      DOI: 10.1002/ange.201712944
  • Cytotoxic oligomers and fibrils trapped in a gel-like state of
           α-synuclein assemblies
    • Authors: Rakesh Kumar; Subhadeep Das, Ganesh M Mohite, Saroj K Rout, Saayak Halder, Narendra Nath Jha, Soumik Ray, Surabhi Mehra, Vipin Agarwal, Samir K. Maji
      Abstract: α-synuclein (α-Syn) aggregation is associated with Parkinson's disease (PD) pathogenesis. In PD, the role of oligomer versus fibrils in neuronal cell death is debatable but recent studies suggest oligomers are a proximate neurotoxin. Here, we show that soluble α-Syn monomers convert from solution to gel state on incubation at high concentration that might be relevant to PD-associated local increase in α-Syn concentration. A detailed characterization of the gel showed co-existence of monomers, oligomers and short fibrils. In vitro, the gel is highly cytotoxic to human neuroblastoma cells. The individual constituents of gels are short-lived species but toxic to the cells, comprise of a structurally heterogeneous population of α-helical and β-sheet rich oligomers and short-fibrils with the cross-β motif. Given, the recent evidences of the gel-like state of the protein associated with neurodegenerative diseases, the gel-state of α-Syn in this study represents a mechanistic and structural model for in vivo toxicity of α-Syn in PD.
      PubDate: 2018-03-10T05:21:05.7102-05:00
      DOI: 10.1002/ange.201711854
  • Combined non-invasive PIXE/PIGE analyses of mammoth ivory from Aurignacian
           archaeological sites
    • Authors: Ina REICHE; Claire Heckel, Katharina Müller, Olaf Jöris, Tim Matthies, Nicholas Conard, Harald Floss, Randall White
      Abstract: Among the earliest Homo sapiens societies in Eurasia, the Aurignacian phase of the Early Upper Palaeolithic, approximately 40,000-30,000 uncal. BP, mammoth ivory assumed great social and economic significance, and was used to create hundreds of personal ornaments as well as the earliest known works of three-dimensional figurative art in the world. This paper reports on the results of micro-PIXE/PIGE analyses of mammoth-ivory artefacts and debris from five major sites of Aurignacian ivory use. Patterns of variable F-content indicate regionally-distinct strategies of ivory procurement that correspond to apparent differences in human-mammoth interactions. Preserved trace elements (Br, Sr, Zn) indicate that differences at the regional level are applicable to sourcing Palaeolithic ivory at the regional scale.
      PubDate: 2018-03-09T13:51:15.317625-05:
      DOI: 10.1002/ange.201712911
  • Functionalized Proline-Rich Peptides Bind the Bacterial Second Messenger
    • Authors: Helma Wennemers; Carlotta Foletti, Rolf Kramer, Harald Mauser, Urs Jenal, Konrad Bleicher
      Abstract: c di GMP is an attractive target in the fight against bacterial infections as it is a near ubiquitous second messenger that regulates important cellular processes, including biofilm formation and virulence of pathogens. The screening of a combinatorial peptide library enabled the identification of the proline-rich tetrapeptide Gup-Gup-Nap-Arg that binds c di GMP in water with selectivity over other nucleotides. Computational and CD spectroscopic studies provided a binding mode of the complex and enabled the design of a pentapeptide with even higher binding strength towards c di GMP. Biological studies showed that the tetrapeptide inhibits biofilm growth of the opportunistic pathogen P. aeruginosa.
      PubDate: 2018-03-09T06:51:07.016596-05:
      DOI: 10.1002/ange.201801845
  • Recent advances in analytical pyrolysis to investigate organic materials
           in heritage science
    • Authors: Ilaria Degano; Francesca Modugno, Ilaria Bonaduce, Erika Ribechini, Maria Perla Colombini
      Abstract: The molecular characterization of organic materials in samples from artworks and historical objects traditionally entailed qualitative and quantitative analyses by HPLC and GC. Today innovative approaches based on analytical pyrolysis enable samples to be analysed without any chemical pre-treatment. Pyrolysis, which is often considered as a screening technique, shows previously unexplored potential thanks to recent instrumental developments. Organic materials that are macromolecular in nature, or undergo polymerization upon curing and ageing can now be better investigated. Most constituents of paint layers and archaeological organic substances contain major insoluble and chemically non-hydrolysable fractions that are inaccessible to GC or HPLC. To date, molecular scientific investigations of the organic constituents of artworks and historical objects have mostly focused on the minor constituents of the sample. This review presents recent advances in the qualitative and semi-quantitative analyses of organic materials in heritage objects based on analytical pyrolysis coupled with mass spectrometry.
      PubDate: 2018-03-09T06:21:16.390933-05:
      DOI: 10.1002/ange.201713404
  • LaSr3NiRuO4H4: a 4d transition-metal oxide-hydride containing metal
           hydride sheets.
    • Authors: Lun Jin; Michael Lane, Dihao Zeng, Franziska Kirschner, Franz Lang, Pascal Manuel, Stephen Blundell, John McGrady, Michael A. Hayward
      Abstract: We report the synthesis of the first 4d transition metal oxide-hydride, LaSr3NiRuO4H4, prepared via topochemical anion exchange. Neutron diffraction data show that the hydride ions occupy the equatorial anion sites in the host lattice and as a result the Ru and Ni cations are located in a plane containing only hydride ligands - a unique structural feature with obvious parallels to the CuO2 sheets present in the superconducting cuprates. DFT calculations confirm the presence of S = ½ Ni1+ and S = 0, Ru2+ centres, but neutron diffraction and μSR data show no evidence for long-range magnetic order between the Ni centres down to 1.8 K. The observed weak inter-cation magnetic coupling can be attributed to poor overlap between Ni 3d_(z^2 ) and H 1s in the super-exchange pathways.
      PubDate: 2018-03-09T04:51:01.718156-05:
      DOI: 10.1002/ange.201800989
  • Water does not always hurt: synthesis of an iron(IV)aqua-oxido complex
           using ozone as an oxidant
    • Authors: Stefan Schaub; Andreas Miska, Jonathan Becker, Stefan Zahn, Doreen Mollenhauer, Sakshath Sadashivaiah, Volker Schünemann, Siegfried Schindler
      Abstract: The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclo-tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of Fe(IV) oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of = 0.19 mms-1 and a quadrupole splitting EQ = 1.38 mms-1 confirming the high valent Fe(IV) state. DFT calculations furthermore were performed and assigned a triplet spin multiplicity. Crystallographic characterization of [(H2O)(tmc)Fe=O)](OTf)2 as well as of starting materials [(tmc)Fe(CH3CN)](OTf)2 and [(tmc)Fe(OTf)]OTf together with previous results from the literature strongly suggest that [(H2O)(tmc)Fe=O)](OTf)2 was formed similar to the oxido-hydroxido tautomerism analogous to heme systems.
      PubDate: 2018-03-09T04:15:37.000792-05:
      DOI: 10.1002/ange.201800475
  • Bimetallic Chromium Catalysts with Chain Transfer Agents: A New Route to
           Isotactic Poly(propylene oxide)s with Narrow Dispersities
    • Authors: Lilliana S. Morris; Matthew Ian Childers, Geoffrey William Coates
      Abstract: Bimetallic chromium catalysts are investigated for the enantioselective polymerization of propylene oxide. The catalyst is composed of two salen chromium species linked by an alkyl chain, the length of which significantly impacts the rate of polymerization. While the use of a chloride initiator on the catalyst resulted in bimodal molecular weight distributions, switching to a trifluoroacetate initiating group and adding a diol chain transfer agent afforded polymers of controllable molecular weight with low, unimodal dispersities.
      PubDate: 2018-03-09T00:45:39.351252-05:
      DOI: 10.1002/ange.201801380
  • Silica Protection-Assisted Encapsulation of Cu₂O Nanocubes into
           Metal-Organic Framework (ZIF-8) as Composite Catalyst
    • Authors: Bo Li; Jian-Gong Ma, Peng Cheng
      Abstract: The integration of metal/metal oxide nanoparticles (NPs) into metal-organic frameworks (MOFs) to form composite materials has attracted great interest in recent years, due to the broad applications. However, it is still vacant to encapsulate NPs with high catalytic activity yet low stability into MOFs, due to their instability during the preparation process. For the first time, we successfully developed a template protection-sacrifice (TPS) method to encapsulating meta-stable metal/metal oxide NPs such as Cu₂O into MOFs. SiO₂ was used as both a protective shell for Cu₂O nanocubes and a sacrificial template for forming a yolk-shell structure. The obtained Cu₂O@ZIF-8 composite exhibit an excellent cycle stability in catalytic hydrogenation of 4-nitrophenol with high activity. This is the first report of a Cu₂O@MOFs type composite material. The TPS method provides an efficient strategy for encapsulating unstable active metal/metal oxide NPs into MOFs or maybe other porous materials.
      PubDate: 2018-03-08T22:29:51.82381-05:0
      DOI: 10.1002/ange.201801588
  • Selective Etching of Silicon from Ti3SiC2 (MAX) Produces 2D Titanium
           Carbide (MXene)
    • Authors: Mohamed Alhabeb; Kathleen Maleski, Tyler S. Mathis, Asia Sarycheva, Christine B. Hatter, Simge Uzun, Ariana Levitt, Yury Gogotsi
      Abstract: Until now, MXenes could only be produced from MAX phases containing aluminum, such as Ti3AlC2. Here, we report on the synthesis of Ti3C2 (MXene) through selective etching of silicon from titanium silicon carbide - the most common MAX phase. Liters of colloidal solutions of delaminated Ti3SiC2-derived MXene (0.5-1.3 mg/mL) were produced and processed into flexible and electrically conductive films, which show higher oxidation resistance than MXene synthesized from Ti3AlC2. This new synthesis method greatly widens the range of precursors for MXene synthesis.
      PubDate: 2018-03-08T15:48:23.521563-05:
      DOI: 10.1002/ange.201802232
  • Selective Polymerization Catalysis From Monomer Mixtures: Using A
           Commercial Cr-Salen Catalyst to Access ABA Block Polyesters
    • Authors: Charlotte Katherine Williams; Tim Stoesser
      Abstract: ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring-opening copolymerization and subsequently by lactone ring-opening polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post-functionalization and chain extension reactions. The ability to use a commercial catalyst and switchable catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers.
      PubDate: 2018-03-08T12:50:37.531694-05:
      DOI: 10.1002/ange.201801400
  • Nanofluorides as nano-sized tracers for in vivo 19F-magnetic resonance
    • Authors: Idan Ashur; Hyla Allouche-Arnon, Amnon Bar-Shir
      Abstract: Inorganic nanocrystals (NCs) have been extensively developed for a variety of uses. The ability to obtain high-resolution NMR signals from the core nuclei of NCs in solution could offer new opportunities in materials sciences and MR imaging. Here, we demonstrate that small, water-soluble 19F-ionic NCs can average out homonuclear dipolar interactions, enabling one to obtain high-resolution 19F-NMR signals in solution that reflect the MR properties of F- in the crystal core. Decorating 19F-NC surfaces with a biocompatible polyethylene-glycol coating maintains colloidal stability in water while preserving the NC high-resolution 19F-NMR properties, even after further functionalization. The high content and magnetic equivalence of the fluorides within the NCs enable their use as imaging tracers for in vivo 19F-MRI by facilitating a "hot-spot" display of their distribution.
      PubDate: 2018-03-08T12:47:26.196488-05:
      DOI: 10.1002/ange.201800838
  • Stimuli-Responsive NO Release for On-Demand Gas-Sensitized Synergistic
           Cancer Therapy
    • Authors: Wenpei Fan; Bryant C. Yung, Xiaoyuan Chen
      Abstract: Featuring high biocompatibility, the emerging field of gas therapy has attracted extensive attention in the medical and scientific communities. Currently, considerable research has focused on nitric oxide (NO) gasotransmitter due to its unparalleled dual roles in directly killing cancer cells at high concentrations and cooperatively sensitizing cancer cells to other treatments for synergistic therapy. Of particular note, recent state-of-the-art studies have turned our attention to the chemical design of various endogenous/exogenous stimuli-responsive NO releasing nanomedicines and their biomedical applications for on-demand NO-sensitized synergistic cancer therapy, which have been systemically discussed in this minireview. Moreover, the potential challenges regarding NO gas therapy are also prescribed, aiming to advance the development of NO nanomedicines as well as usher in new frontiers in this fertile research area.
      PubDate: 2018-03-08T10:47:33.912408-05:
      DOI: 10.1002/ange.201800594
  • Traveling two diverging roads, cytochrome-P450 catalyzed demethylation and
           γ-lactone formation in bacterial gibberellin biosynthesis
    • Authors: Raimund Nagel; Reuben J. Peters
      Abstract: Biosynthesis of the gibberellin plant hormones evolved independently in plants and microbes, but the pathways proceed via similar transformations. The combined demethylation and -lactone ring forming transformation is of significant mechanistic interest, yet remains opaque. The relevant CYP112 from bacteria was probed via activity assays and 18O2 labeling experiments. Notably, the ability of tert-butyl hydroperoxide to drive this transformation indicates use of the ferryl-oxo (Compound I) from the CYP catalytic cycle for this reaction. Together with the confirmed loss of C-20 as CO2, this necessitates two catalytic cycles for carbon-carbon bond scission and -lactone formation. The ability of CYP112 to hydroxylate the -lactone form of GA15 shown by the labeling studies is consistent with the implied use of a further oxygenated heterocycle in the final conversion of GA24 to GA9, with the partial labeling of GA9 demonstrating that CYP112 partitions its reactants between two diverging mechanisms.
      PubDate: 2018-03-08T10:15:29.05442-05:0
      DOI: 10.1002/ange.201713403
  • Hydroxyl-mediated Non-oxidative Propane Dehydrogenation over VOx/Al2O3
           Catalysts with Promoted Stability
    • Authors: Jinlong Gong; Zhijian Zhao, Tengfang Wu, Chuanye Xiong, Guodong Sun, Rentao Mu, Liang Zeng
      Abstract: Supported vanadium oxides are one of the most promising alternative catalysts for propane dehydrogenation (PDH) and massive efforts have been made to improve its catalytic performance. However, unlike Pt-based catalysts, the nature of the active site and surface structure of supported vanadium catalysts under reductive reaction condition still remain elusive. This paper describes the surface structure and the important role of surface-bound hydroxyls of VOx/Al2O3 catalysts under reaction conditions employing in situ DRIFTS experiments and DFT calculations. We show that hydroxyl groups on the VOx/Al2O3 catalyst (V-OH) are produced under H2 pre-reduction, and the catalytic performance for PDH are closely connected to the concentration of superficial V-OH species on the catalyst. The hydroxyl groups are found to promote the catalyst, which leads to better stability by suppressing the coke deposition.
      PubDate: 2018-03-08T09:45:43.493321-05:
      DOI: 10.1002/ange.201800123
  • Cobalt-Catalyzed Tandem C-H Activation/C-C Cleavage/C-H Cyclization of
           Aromatic Amides with Alkylidenecyclopropanes
    • Authors: Mingliang Li; Fuk Yee Kwong
      Abstract: A cobalt-catalyzed chelation-assisted tandem C-H activation/C-C cleavage/C-H cyclization of aromatic amides with alkylidenecyclopropanes (ACPs) is reported. This process allows the sequential formation of two C-C bonds, in which it is in sharp contrast to previous report of using Rh catalyst for the formation of C-N bond. Here the inexpensive catalyst system exhibits good functional group compatibility and relatively broad substrate scope. The desired products can be easily transformed into polycyclic lactones with m-CPBA. Mechanistic studies revealed that the tandem reaction proceeds through a sequential C−H cobaltation, β-carbon elimination and intramolecular C−H cobaltation pathway.
      PubDate: 2018-03-08T05:15:51.694965-05:
      DOI: 10.1002/ange.201801706
  • On the Origin of the Distinctly Different Reactivity Behavior of Ruthenium
           in [MO]+/CH₄ Systems (M = Fe, Ru, Os)
    • Authors: Xiaoyan Sun; Shaodong Zhou, Lei Yue, Maria Schlangen, Helmut Schwarz
      Abstract: The thermal gas-phase reactions of [RuO]+ with methane have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied [FeO]+/CH₄ and [OsO]+/CH₄ couples which bring about oxygen/hydrogen atom transfers and dehydrogenation, respectively, [RuO]+/CH₄ produces selectively [Ru(CH)₂]+ and H₂O but with much lower efficiency. Various mechanistic scenarios were uncovered, and the associated electronic origins were revealed by high-level quantum chemical calculations. It is the subtle interplay of spin-orbit coupling efficiency, orbital overlap, and relativistic effects that causes the reactivity differences observed for the [MO]+/CH₄ couples (M = Fe, Ru, Os).
      PubDate: 2018-03-08T04:46:14.803146-05:
      DOI: 10.1002/ange.201800173
  • Conformational Planarization vs Singlet Fission: Distinct Excited-State
           Dynamics of Cyclooctatetraene-Fused Acene Dimers
    • Authors: Takuya Yamakado; Shota Takahashi, Kazuya Watanabe, Yoshiyasu Matsumoto, Atsuhiro Osuka, Shohei Saito
      Abstract: A set of flapping acene dimers fused with an 8pi cyclooctatetraene (COT) ring showed distinct excited-state dynamics in solution. While the anthracene dimer showed a fast V-shaped-to-planar conformational change within 10 ps in the lowest excited singlet state, reminding us of extended Baird aromaticity, the tetracene dimer and the pentacene dimer underwent intramolecular singlet fission (SF) in different manners: A fast and reversible SF with a characteristic delayed fluorescence (FL), and a fast and quantitative SF, respectively. Conformational flexibility of the fused COT linkage plays an important role in these ultrafast dynamics, demonstrating the utility of the flapping molecular series as a versatile platform for designing photofunctional systems.
      PubDate: 2018-03-08T03:16:00.888393-05:
      DOI: 10.1002/ange.201802185
  • Experimental Identification of Ultrafast Reverse Hole Transfer at the
           Interface of Photoexcited Methanol/Graphitic Carbon Nitride System
    • Authors: Zongwei Chen; Qun Zhang, Yi Luo
      Abstract: We report on an experimental scrutiny of the photoexcited hole dynamics in a prototypical system in which the hole-scavenging methanol molecules are chemisorbed on the graphitic carbon nitride (g-C3N4) substrate. A set of comparison and control experiments by means of femtosecond time-resolved transient absorption (fs-TA) spectroscopy were conducted. We identified the elusive reverse hole transfer (RHT) process, which occurs on a timescale of a few hundred picoseconds. The critical role of interfacially chemisorbed methoxy (instead of methanol) as the dominant species responsible for hole scavenging was confirmed by a control experiment using protonated g-C3N4 as the substrate. A hot-hole transfer effect was revealed by implementing different interband photoexcitation scenarios. More importantly, we revealed that the RHT rate is the key factor governing the hole-scavenging ability of different hole scavengers, thereby deciphering the fundamental mechanism behind the well-known empirical practice that methanol is routinely adopted as one of the most popular hole-scavenging reagents in realistic semiconductor-based photoelectrochemical applications.
      PubDate: 2018-03-08T02:45:27.266904-05:
      DOI: 10.1002/ange.201713102
  • Lead-Free Silver-Bismuth Halide Double Perovskite Nanocrystals
    • Authors: Keli Han; Bin Yang, Junsheng Chen, Songqiu Yang, Feng Hong, Lei Sun, Peigeng Han, Tõnu Pullerits, Weiqiao Deng
      Abstract: Lead-free perovskite nanocrystals (NCs) were obtained mainly by substituting a Pb2+ cation with a divalent cation or substituting three Pb2+cations with two trivalent cations. Herein we report the substitution of two Pb2+cations with one monovalent Ag+ and one trivalent Bi3+ cations to synthesize Cs2AgBiX6 (X= Cl, Br, I) double perovskite NCs. Using femtosecond transient absorption spectroscopy, we have elucidated the charge carrier relaxation mechanism in the double perovskite NCs. The Cs2AgBiBr6 NCs exhibit ultrafast hot-carrier cooling (
      PubDate: 2018-03-07T23:16:05.027434-05:
      DOI: 10.1002/ange.201800660
  • Enhancing Capacity Performance by Utilizing the Redox Chemistry of the
           Electrolyte in a Dual-Electrolyte Sodium Ion Battery
    • Authors: Youngsik Kim; Senthilkumar ST, Hyuntae Bae, Jinhyup Han
      Abstract: We describe a new strategy to increase charge storage in a dual electrolyte Na-ion battery (DESIB) by combining the redox chemistry of the electrolyte with a Na+ ion de-insertion/insertion cathode. Conventional electrolytes do not contribute to charge storage in battery systems, but redox-active electrolytes augment this property via charge transfer reactions at the electrode-electrolyte interface. Hence, the capacity of the cathode combined with that provided by the electrolyte redox reaction increases overall charge storage. We employ an aqueous sodium hexacyanoferrate (Na4Fe(CN)6) solution as the redox-active electrolyte (Na-FC) and sodium nickel Prussian blue (Nax-NiBP) as the Na+ ion insertion/de-insertion cathode. The capacity of DESIB with Na-FC electrolyte is twice that of a battery using conventional (Na2SO4) electrolyte. The use of redox-active electrolytes in batteries of any kind is an efficient and scalable approach to develop advanced high-energy-density storage systems.
      PubDate: 2018-03-07T21:46:10.779743-05:
      DOI: 10.1002/ange.201800181
  • Efficient Light-Induced pKa-Modulation coupled to Base-Catalyzed
    • Authors: Johannes Gurke; Simon Budzak, Bernd Schmidt, Denis Jacquemin, Stefan Hecht
      Abstract: Photoswitchable acid-base pairs, allowing for a reversible alteration of their pKa values, are attractive molecular tools to control chemical and biological processes by light. A significant, light-induced pKa change of three units in aqueous medium has been realized involving two thermally stable states, which can be interconverted using UV and green light. The light-induced pKa modulation is based on incorporating a 3-H-thiazol-2-one moiety into the framework of a diarylethene photoswitch, which upon photochemical ring-closure loses the heteroaromatic stabilization of the corresponding, negatively charged base and hence, becomes significantly less acidic. In addition, the efficiency of the photoreactions in the deprotonated state is drastically increased, thereby giving rise to catalytically enhanced photochromism. It appears that protonation has a significant influence on the shape of ground and excited state potential energy surface as indicated by quantum chemical calculations. Using this concept of interconnected photoisomerization and acid-base equilibria allows to adjust the degree of photoconversion by the pH of the solution and constitutes a powerful tool to precisely and remotely control the charge state by light.
      PubDate: 2018-03-07T21:46:04.433635-05:
      DOI: 10.1002/ange.201801270
  • Competitive Affinity Release for Long-Term Delivery of Antibodies from
    • Authors: Vincent Huynh; Ryan G. Wylie
      Abstract: With increased clinical use of antibodies, long-term delivery strategies are needed to decrease injection frequency and improve health outcomes. A three-component drug-delivery system was developed for competitive affinity release of a streptavidin–antibody conjugate from agarose–desthiobiotin hydrogels via controlled dissolution of sparingly soluble biotin derivatives. The antibody conjugate was localized in the hydrogel through streptavidin–desthiobiotin complexation. Dissolution of sparingly soluble biotin derivatives disrupts streptavidin–desthiobiotin complexation for controlled release of the antibody conjugate. Release was tuned by altering the total biotin derivative concentration without further hydrogel or antibody modification. First-order tunable release of bioactive Avastin, a therapeutic anti-VEGF antibody, was demonstrated from a non-cytotoxic system for over 100 days.Langzeitversorgungsstrategien für therapeutische Antikörper werden benötigt. Daher wurde ein System entwickelt, das Streptavidin-Antikörper-Konjugate aus Desthiobiotin-Agarose-Hydrogelen freisetzt, indem schlecht lösliche Biotinderivate kontrolliert abgegeben werden. Die Geschwindigkeit des Freisetzungsprozesses lässt sich über die Konzentration des Biotinderivats einstellen. Der Anti-VEGF-Antikörper Avastin wurde so über mehr als 100 Tage bereitgestellt.
      PubDate: 2018-03-07T08:30:29.87183-05:0
      DOI: 10.1002/ange.201713428
  • Evaluation of the Catalytic Relevance of the CO-Bound States of
    • Authors: Chi Chung Lee; Jarett Wilcoxen, Caleb J. Hiller, R. David Britt, Yilin Hu
      Abstract: Binding and activation of CO by nitrogenase is a topic of interest because CO is isoelectronic to N2, the physiological substrate of this enzyme. The catalytic relevance of one- and multi-CO-bound states (the lo-CO and hi-CO states) of V-nitrogenase to C−C coupling and N2 reduction was examined. Enzymatic and spectroscopic studies demonstrate that the multiple CO moieties in the hi-CO state cannot be coupled as they are, suggesting that C−C coupling requires further activation and/or reduction of the bound CO entity. Moreover, these studies reveal an interesting correlation between decreased activity of N2 reduction and increased population of the lo-CO state, pointing to the catalytic relevance of the belt Fe atoms that are bridged by the single CO moiety in the lo-CO state. Together, these results provide a useful framework for gaining insights into the nitrogenase-catalyzed reaction via further exploration of the utility of the lo-CO conformation of V-nitrogenase.Mehrere CO-Einheiten, die im hi-CO-Zustand von V-Nitrogenase gebunden sind, können nicht direkt gekuppelt werden, wohingegen die einzelne CO-Einheit im lo-CO-Zustand ohne Zufuhr externer CO Moleküle C-C-Kupplungen eingeht. Eine stärkere Besetzung des lo-CO-Zustands korreliert überdies mit einer Aktivitätsabnahme bezüglich der N2-Reduktion. Dies spricht dafür, dass die Fe-Atome, die im lo-CO-Zustand durch CO verbrückt werden, an der Katalyse beteiligt sind.
      PubDate: 2018-03-07T08:25:27.491412-05:
      DOI: 10.1002/ange.201800189
  • Titelbild: Epoxides as Alkylating Reagents for the Catellani Reaction
           (Angew. Chem. 13/2018)
    • Authors: Hong-Gang Cheng; Chenggui Wu, Han Chen, Ruiming Chen, Guangyin Qian, Zhi Geng, Qiang Wei, Yuanyuan Xia, Jingyang Zhang, Yuming Zhang, Qianghui Zhou
      Pages: 3321 - 3321
      Abstract: Epoxide sind anspruchsvolle Alkylierungsreagentien in der Catellani-Reaktion. Q. Zhou und Mitarbeiter berichten in ihrer Zuschrift auf S. 3502 über ein kooperatives Katalysatorsystem aus einem PdII/XPhos-Komplex und dem Kaliumsalz von 5-Norbornen-2-carbonsäure, das die Verwendung von Epoxiden als Alkylierungsreagentien in Catellani-Reaktionen ermöglicht. Das Titelbild zeigt die Schlüsselkomponenten dieser neuartigen Transformation, mit repräsentativen Gebäuden der Universität Wuhan im Hintergrund. Bildentwurf: Jun Deng, Wuhan University.
      PubDate: 2018-02-23T10:18:55.875289-05:
      DOI: 10.1002/ange.201801898
  • Innentitelbild: Solvation-Induced Changes in the Mechanism of Alcohol
           Oxidation at Gold/Titania Nanocatalysts in the Aqueous Phase versus Gas
           Phase (Angew. Chem. 13/2018)
    • Authors: Daniel Muñoz-Santiburcio; Matteo Farnesi Camellone, Dominik Marx
      Pages: 3322 - 3322
      Abstract: Lösungsmittel können heterogenkatalysierte Prozesse stark beeinflussen. In ihrer Zuschrift auf S. 3385 studieren D. Muñoz-Santiburcio et al. mithilfe von Ab-initio-Simulationen die Auswirkungen von Wasser auf die Methanol-Oxidation an Gold-Nanopartikeln auf einem Titandioxid-Träger. Die Mechanismen der Reaktionen in Gas- und Flüssigphase unterscheiden sich deutlich, da Wassermoleküle aktiv an der Oxidation teilnehmen und die Ladungstransferschritte ändern.
      PubDate: 2018-02-23T05:21:47.031381-05:
      DOI: 10.1002/ange.201801947
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 13/2018
    • Pages: 3325 - 3337
      PubDate: 2018-03-13T03:01:57.955138-05:
      DOI: 10.1002/ange.201881311
  • Berichtigung: Asymmetric [4+2] Annulation of C1 Ammonium Enolates with
    • Authors: Jin Song; Zi-Jing Zhang, Liu-Zhu Gong
      Pages: 3337 - 3337
      PubDate: 2018-03-13T03:02:05.414937-05:
      DOI: 10.1002/ange.201801392
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 13/2018
    • Pages: 3338 - 3341
      PubDate: 2018-03-13T03:01:55.529011-05:
      DOI: 10.1002/ange.201881313
  • Wolf Prize in Chemistry: M. Fujita und O. M. Yaghi /
           Albrecht-Kossel-Preis: A. Beck-Sickinger
    • Pages: 3343 - 3343
      PubDate: 2018-03-05T07:26:07.262624-05:
      DOI: 10.1002/ange.201802237
  • Sonnengetriebene Wasserstofferzeugung aus Lignocellulose
    • Authors: Moritz F. Kuehnel; Erwin Reisner
      Pages: 3346 - 3353
      Abstract: Die photokatalytische Reformierung Lignocellulose-haltiger Biomasse ist eine aufstrebende Methode zur Produktion von erneuerbarem H2. Dieser Prozess verbindet Photooxidation von Biomasse mit photokatalytischer Wasserstoffentwicklung bei Raumtemperatur und Atmosphärendruck. Die Umsetzung von Biomasse ist weniger energieaufwändig als Wasserspaltung und liefert dabei hochreinen H2, ohne dass sich O2 bildet. Die direkte Reformierung von unbehandelter Rohbiomasse birgt das Potenzial, weltweit lokal verfügbares Material als kostengünstige Energiequelle zu nutzen.Die photokatalytische Reformierung Lignocellulose-haltiger Biomasse ist eine aufstrebende Methode zur Produktion von erneuerbarem H2 bei Umgebungstemperatur und -druck. Die direkte Reformierung von unbehandelter Rohbiomasse birgt das Potenzial, weltweit kostengünstig saubere Energie zu liefern.
      PubDate: 2018-02-05T10:19:23.727368-05:
      DOI: 10.1002/ange.201710133
  • Ein Instrumentarium von αv-RGD-Integrin-Inhibitoren: Wirkstoffsuche,
           Herausforderungen und Möglichkeiten
    • Authors: Richard J. D. Hatley; Simon J. F. Macdonald, Robert J. Slack, Joelle Le, Steven B. Ludbrook, Pauline T. Lukey
      Pages: 3354 - 3379
      Abstract: Es gibt einen Bedarf an wirksamen und sicheren Pharmazeutika für die Behandlung vernachlässigter Krankheiten, und aktuelle Bestrebungen bei der Suche von Inhibitoren des αv-RGD-Integrins zielen in diese Richtung. Allerdings erweist sich die Entwicklung von Wirkstoffen im Bereich der αv-Integrine aufgrund der sehr ähnlichen Strukturen dieser Rezeptoren und der polaren, zwitterionischen Natur des Pharmakophors als notorisch schwierig. Ziel dieses Aufsatzes ist es, einen Leitfaden für die Wirkstoffsuche in diesem Gebiet anzubieten. Wir tun dies, indem wir hier ein Instrumentarium von αv-Inhibitoren bestehend aus niedermolekularen Verbindungen (“kleinen Molekülen”) und Antikörpern vorstellen. Niedermolekulare αv-Verbindungen mit erweiterten Profilen in αvβ1-, αvβ3-, αvβ5-, αvβ6- und αvβ8-Zelladhäsionsassays wurden zusammengetragen, um die Auswahl der richtigen Verbindung für das richtige Experiment zu unterstützen. Dies sollte außerdem helfen, die partiellen Selektivitätsprofile von Verbindungen besser zu verstehen, die in unterschiedlichen Assays unterschiedlicher Forschungsinstitute generiert wurden. Die Perspektiven der zukünftigen Forschung an αv-Integrinen und die zentral wichtige Targetvalidierung werden diskutiert; fundierte Kenntnisse der Selektivität individueller RGD-αv-Integrine sind hier ganz entscheidend. Einblicke in das Design niedermolekularer RGD-Chemotypen für die topische oder orale Verabreichung werden vorgestellt und klinische Befunde zu fortgeschrittenen Molekülen betrachtet.Integrine sind Transmembranproteine, die die extrazelluläre Matrix mit dem Cytoskelett von Zellen verknüpfen und als Rezeptoren für die Signaltransduktion wirken. Dieser Aufsatz stellt ein Instrumentarium von αv-Inhibitoren bestehend aus kleinen Molekülen und Antikörpern vor und soll als Leitfaden für die Wirkstoffentwicklung im Bereich der αv-Integrine dienen.
      PubDate: 2018-02-21T05:15:38.667776-05:
      DOI: 10.1002/ange.201707948
  • Nitrogen-Based Lewis Acids: Synthesis and Reactivity of a Cyclic
           (Alkyl)(Amino)Nitrenium Cation
    • Authors: Jiliang Zhou; Liu Leo Liu, Levy L. Cao, Douglas W. Stephan
      Pages: 3380 - 3384
      Abstract: A room-temperature-stable crystalline cyclic (alkyl)(amino)nitrenium cation 2 features cationic nitrogen atom with a smaller HOMO–LUMO gap compared to that of a 1,2,3-triazolium 5 (an N-heterocyclic nitrenium cation). The low-lying LUMO of 2 results in an enhanced electrophilicity, which allowed for the formation of Lewis adducts with neutral Lewis bases, such as Me3P, nBu3P, and IiPr. The N-based Lewis acid 2 also forms an FLP with tBu3P but subsequently reacts with (PrS)2 to cleave the S−S bond. Both experimental and theoretical results suggest that the Lewis acidity of 2 is stronger than its N3 analogues.Das bei Raumtemperatur stabile kristalline, cyclische Alkylaminonitrenium weist ein kationisches Stickstoffatom auf und zeigt erhöhte Elektrophilie, wobei Lewis-Addukte mit Me3P, nBu3P und IiPr und ein frustriertes Lewis-Paar mit tBu3P erhalten werden.
      PubDate: 2018-02-21T06:07:23.754708-05:
      DOI: 10.1002/ange.201713118
  • Solvation-Induced Changes in the Mechanism of Alcohol Oxidation at
           Gold/Titania Nanocatalysts in the Aqueous Phase versus Gas Phase
    • Authors: Daniel Muñoz-Santiburcio; Matteo Farnesi Camellone, Dominik Marx
      Pages: 3385 - 3389
      Abstract: Gold/titania catalysts are widely used for key reactions, notably including the selective oxidation of alcohols in the liquid phase. Our large-scale ab initio simulations disclose that the liquid-phase reaction mechanism is distinctly different from that in the gas phase because of active participation of water molecules. While concerted charge transfers related to O2 splitting and abstraction of both protonic and hydridic hydrogens are enforced under dry conditions, stepwise charge transfer is preferred in the condensed phase. Dissociation of reactive water molecules and subsequent Grotthuss migration of protonic defects, H+(aq), allows for such a decoupling of the oxidation process, both in time and space. It is expected that these observations are paradigmatic for heterogeneous catalysis in aqueous phases.Die Wirkung von Wasser: Lösungsmittel können heterogenkatalysierte Prozesse stark beeinflussen. Ab-initio-Simulationen enthüllen dies für den Effekt von Wasser auf die Methanol-Oxidation über Gold-Nanopartikeln auf einem TiO2-Träger. Der Reaktionsmechanismus in der Flüssigphase und in der Gasphase unterscheidet sich deutlich, da Wassermoleküle aktiv am Oxidationsprozess teilnehmen und alle Ladungsübertragungsschritte verändern.
      PubDate: 2018-02-05T10:15:39.95456-05:0
      DOI: 10.1002/ange.201710791
  • Efficient CO2 Removal for Ultra-Pure CO Production by Two Hybrid
           Ultramicroporous Materials
    • Authors: Kai-Jie Chen; Qing-Yuan Yang, Susan Sen, David G. Madden, Amrit Kumar, Tony Pham, Katherine A. Forrest, Nobuhiko Hosono, Brian Space, Susumu Kitagawa, Michael J. Zaworotko
      Pages: 3390 - 3394
      Abstract: Removal of CO2 from CO gas mixtures is a necessary but challenging step during production of ultra-pure CO as processed from either steam reforming of hydrocarbons or CO2 reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX-3-Ni and TIFSIX-2-Cu-i, which are known to exhibit strong affinity for CO2, were examined with respect to their performance for this separation. The single-gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO2/CO selectivity (>4000 for SIFSIX-3-Ni). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra-pure CO (99.99 %) was thereby obtained from CO gas mixtures containing both trace (1 %) and bulk (50 %) levels of CO2 in a one-step physisorption-based separation process.Ein Referenzwert für die CO2/CO-Selektivität unter Umgebungsbedingungen zeichnet zwei mikroporöse Hybridmaterialien aus, die deutlich schwächer mit CO wechselwirken als mit CO2. Ausgehend von CO2-haltigen Gasmischungen (1 % und 50 % CO2) wird hoch reines CO (>99.99 %) effizient in einer einstufigen Trennung an einer Festbettsäule des Adsorptionsmittels erzeugt.
      PubDate: 2018-02-22T04:45:43.277465-05:
      DOI: 10.1002/ange.201706090
  • Water-Assisted Size and Shape Control of CsPbBr3 Perovskite Nanocrystals
    • Authors: Xiaoyu Zhang; Xue Bai, Hua Wu, Xiangtong Zhang, Chun Sun, Yu Zhang, Wei Zhang, Weitao Zheng, William W. Yu, Andrey L. Rogach
      Pages: 3395 - 3400
      Abstract: Lead-halide perovskites are well known to decompose rapidly when exposed to polar solvents, such as water. Contrary to this common-place observation, we have found that through introducing a suitable minor amount of water into the reaction mixture, we can synthesize stable CsPbBr3 nanocrystals. The size and the crystallinity, and as a result the band gap tunability of the strongly emitting CsPbBr3 nanocrystals correlate with the water content. Suitable amounts of water change the crystallization environment, inducing the formation of differently shaped perovskites, namely spherical NCs, rectangular nanoplatelets, or nanowires. Bright CsPbBr3 nanocrystals with the photoluminescence quantum yield reaching 90 % were employed for fabrication of inverted hybrid inorganic/organic light-emitting devices, with the peak luminance of 4428 cd m−2 and external quantum yield of 1.7 %.Bleihalogenid-Perowskite sind normalerweise zersetzlich in polaren Lösungsmitteln. Dagegen konnten stabile CsPbBr3-Nanokristalle durch die Einbringung einer geringen Menge Wasser in die Reaktionsmischung synthetisiert werden. Die Größe, Kristallinität und Bandlücke der stark emittierenden CsPbBr3-Nanokristalle können über den Wassergehalt eingestellt werden.
      PubDate: 2018-02-23T05:05:59.53271-05:0
      DOI: 10.1002/ange.201710869
  • Monitoring Dissociation Kinetics during Electrophoretic Focusing to Enable
           High-Specificity Nucleic Acid Detection
    • Authors: Tal Zeidman Kalman; Rebecca Khalandovsky, Elena Tenenbaum Gonikman, Moran Bercovici
      Pages: 3401 - 3406
      Abstract: A wide range of medical conditions can be diagnosed through sequence-specific analysis of nucleic acids. However, a major challenge remains in detecting a specific target in samples containing a high concentration of mismatching sequences. A single-step kinetic homogenous (free solution) assay is presented in which free sequence-specific probes are continuously separated from probe–target hybrids during electrophoretic sample focusing, allowing monitoring of dissociation kinetics. Under these conditions, the different kinetics of targets versus mismatches result in distinct patterns of the signal (for example, linear increase for target versus exponential decay for mismatch), allowing the detection of desired sequences even in the presence of high background nucleic acid content. Additionally, an analytical model provides insight into the underlying dynamics, and allows design of assays based on this mechanism.In einem Schritt und in homogener Lösung arbeitet ein Assay, das im Zuge einer elektrophoretischen Probenfokussierung freie sequenzspezifische Sonden kontinuierlich von Sonde-Analyt-Hybriden trennt. Die Methode kann gewünschte Sequenzen auch in Proben mit einem hohen Gehalt an anderen Nukleinsäuren nachweisen.
      PubDate: 2018-02-14T05:36:20.856479-05:
      DOI: 10.1002/ange.201711673
  • Catalytic CO Oxidation by O2 Mediated by Noble-Metal-Free Cluster Anions
    • Authors: Li-Na Wang; Xiao-Na Li, Li-Xue Jiang, Bin Yang, Qing-Yu Liu, Hong-Guang Xu, Wei-Jun Zheng, Sheng-Gui He
      Pages: 3407 - 3411
      Abstract: Catalytic CO oxidation by molecular O2 is an important model reaction in both the condensed phase and gas-phase studies. Available gas-phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O2 under thermal collision conditions. Herein, we identified the first example of noble-metal-free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu2VO3–5− for CO oxidation by O2. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu−Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O2 activation during the catalysis.Edelmetallfreie Mischoxidcluster-Katalysatoren der Zusammensetzung Cu2VO3–5− für die CO-Oxidation durch O2 wurden experimentell identifiziert. Die Katalyse wird durch den Redoxzyklus innerhalb der Cu-Cu-Einheit der Cu2VO3–5−-Cluster angetrieben.
      PubDate: 2018-02-21T06:06:46.930565-05:
      DOI: 10.1002/ange.201712129
  • Ice Melting to Release Reactants in Solution Syntheses
    • Authors: Hehe Wei; Kai Huang, Le Zhang, Binghui Ge, Dong Wang, Jialiang Lang, Jingyuan Ma, Da Wang, Shuai Zhang, Qunyang Li, Ruoyu Zhang, Naveed Hussain, Ming Lei, Li-Min Liu, Hui Wu
      Pages: 3412 - 3417
      Abstract: Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 °C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.Eine Lösung einfrieren und in einer anderen wieder auftauen bildet eine Strategie zur Mischung von Chemikalien, wodurch kinetische und thermodynamische Reaktionseigenschaften modifiziert werden können. Einfrieren einer AgNO3-Lösung und Zugabe zu einer NaBH4-Lösung bei ungefähr 0 °C lieferte beispielsweise dispergierte Metallatome. Die Methode kann aber auch auf Fällungsvorgänge, Hydrolysen und Austauschreaktionen angewendet werden.
      PubDate: 2018-02-14T05:21:01.939182-05:
      DOI: 10.1002/ange.201711128
  • Size-Selective Exclusion Effects of Liquid Crystalline Tactoids on
           Nanoparticles: A Separation Method
    • Authors: Pei-Xi Wang; Wadood Y. Hamad, Mark J. MacLachlan
      Pages: 3418 - 3423
      Abstract: Liquid crystalline tactoids are anisotropic microdroplets existing in isotropic phases. We studied the structure and evolution of tactoids in the presence of doping nanoparticles by electron microscopy at the resolution of individual mesogens and observed size-selective exclusion effects of liquid crystalline tactoids on foreign nanoparticles. We applied this principle to the separation of polymer nanospheres, gold nanoparticles, and magnetic nanoparticles by size. These results indicate a new way to size-selectively separate nanoparticles using lyotropic liquid crystals, in which nanoparticles smaller than a threshold size will be selectively transferred from the disordered phase into the ordered phase by tactoids during the phase separation process.Tic-Tac-Toide: Flüssigkristalline Tactoide haben einen größenselektiven Ausschluss-Effekt auf dotierende Nanopartikel, der bewirkt, dass Partikel unterhalb einer bestimmten Größe durch Tactoide selektiv gesammelt und in die flüssigkristalline Phase transferiert werden. Dieses Prinzip wurde auf die größenbasierte Trennung von Polymer-, Gold- und magnetischen Nanopartikeln angewendet.
      PubDate: 2018-02-23T05:08:34.777273-05:
      DOI: 10.1002/ange.201712158
  • Supramolecular Nanostructures of Structurally Defined Graphene Nanoribbons
           in the Aqueous Phase
    • Authors: Yinjuan Huang; Wei-Tao Dou, Fugui Xu, Hong-Bo Ru, Qiuyu Gong, Dongqing Wu, Deyue Yan, He Tian, Xiao-Peng He, Yiyong Mai, Xinliang Feng
      Pages: 3424 - 3429
      Abstract: Structurally well-defined graphene nanoribbons (GNRs) have attracted great interest because of their unique optical, electronic, and magnetic properties. However, strong π–π interactions within GNRs result in poor liquid-phase dispersibility, which impedes further investigation of these materials in numerous research areas, including supramolecular self-assembly. Structurally defined GNRs were synthesized by a bottom-up strategy, involving grafting of hydrophilic poly(ethylene oxide) (PEO) chains of different lengths (GNR-PEO). PEO grafting of 42–51 % percent produces GNR-PEO materials with excellent dispersibility in water with high GNR concentrations of up to 0.5 mg mL−1. The “rod–coil” brush-like architecture of GNR-PEO resulted in 1D hierarchical self-assembly behavior in the aqueous phase, leading to the formation of ultralong nanobelts, or spring-like helices, with tunable mean diameters and pitches. In aqueous dispersions the superstructures absorbed in the near-infrared range, which enabled highly efficient conversion of photon energy into thermal energy.Supramolekulare Nanostrukturen aus wohldefinierten Graphen-Nanobändern mit aufgepfropften hydrophilen Poly(ethylenoxid)-Ketten sind hervorragend in wässrigen Phasen dispergierbar. Solche Dispersionen absorbieren Nahinfrarotstrahlung und wandeln die Energie der Photonen in thermische Energie um.
      PubDate: 2018-02-22T04:35:36.029517-05:
      DOI: 10.1002/ange.201712637
  • Interrupted Baeyer–Villiger Rearrangement: Building A Stereoelectronic
           Trap for the Criegee Intermediate
    • Authors: Vera A. Vil'; Gabriel dos Passos Gomes, Oleg V. Bityukov, Konstantin A. Lyssenko, Gennady I. Nikishin, Igor V. Alabugin, Alexander O. Terent'ev
      Pages: 3430 - 3434
      Abstract: The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer–Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2-alkyl shift. Stable cyclic Criegee intermediates constrained within a five-membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β-hydroperoxy-β-peroxylactones) which were formed in high yields in reaction of β-ketoesters with BF3⋅Et2O/H2O2.Abhilfe gegen die Unbeständigkeit von Hydroxyperoxyestern, den Criegee-Intermediaten der Baeyer-Villiger-Umlagerung, kann durch selektive Deaktivierung primärer und sekundärer stereoelektronischer Effekte geschaffen werden, die 1,2-Alkyl-Verschiebungen begünstigen. Stabile cyclische Criegee-Intermediate mit Fünfringstruktur sind durch milde Reduktion der entsprechenden Hydroperoxy-Peroxyester zugänglich.
      PubDate: 2018-02-23T05:06:56.704321-05:
      DOI: 10.1002/ange.201712651
  • Utilization of a Fluorescent Dye Molecule as a Proton and Electron
    • Authors: Ian A. Kieffer; Robert J. Allen, Jordan L. Fernandez, Jackson L. Deobald, Brena L. Thompson, Jacob D. Wimpenny, Zachariah M. Heiden
      Pages: 3435 - 3438
      Abstract: Fluorescent dyes have been widely utilized as chemical sensors and in photodynamic therapy, but exploitation of their redox-active nature in chemical reactions has remained mostly unexplored. This report describes the isolation of a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based radical. The redox-active nature of the BODIPY compound can be utilized in combination with a guanidine center, the basicity of which can be manipulated by greater than 14 pKa units, to promote the conversion of protons and electrons into H-atoms for transfer to substrate molecules.Fluoreszenzfarbstoffe werden weithin als chemische Sensoren eingesetzt, ihre Redoxaktivität wird aber nur selten untersucht. Ein 4,4-Difluor-4-bora-3a,4a-diaza-s-indacen(BODIPY)-basiertes Radikal wurde isoliert, dessen Redoxaktivität in Kombination mit einem Guanidin-Motiv genutzt werden kann, um Protonen und Elektronen im Sinne eines H-Atomtransfers auf Substratmoleküle zu übertragen.
      PubDate: 2018-02-23T10:20:26.98756-05:0
      DOI: 10.1002/ange.201713174
  • Palladium-Catalyzed Regioselective Aromatic Extension of Internal Alkynes
           through a Norbornene-Controlled Reaction Sequence
    • Authors: Qingyang Zhao; Wai Chung Fu, Fuk Yee Kwong
      Pages: 3439 - 3443
      Abstract: A regioselective aromatic π-extension reaction of internal alkynes is reported. The proposed method employs three easily available components, namely aryl halides, 2-haloarylcarboxylic acids, and disubstituted acetylenes. The transformation is driven by a controlled reaction sequence of C−H activation, decarboxylation, and annulation to give poly(hetero)aromatic compounds in a site-selective fashion. Unlike in previously reported palladium-catalyzed three-component annulations, alkyne carbopalladation is the last step of this tandem reaction.In eine Richtung: Eine regioselektive Mehrkomponentenreaktion von Arylhalogeniden, 2-Halogenarylcarbonsäuren und disubstituierten Alkinen liefert nach C-H-Aktivierung, Decarboxylierung und Anellierung durch aromatische Erweiterung poly(hetero)aromatische Verbindungen. Alkin-Carbopalladierung ist der letzte Schritt dieser Tandemreaktion.
      PubDate: 2018-02-22T04:36:38.808455-05:
      DOI: 10.1002/ange.201713207
  • Total Synthesis of Astellatol
    • Authors: Nan Zhao; Shuqiang Yin, Shengling Xie, Hao Yan, Pan Ren, Gui Chen, Fang Chen, Jing Xu
      Pages: 3444 - 3448
      Abstract: A nearly-30-year-old unanswered synthetic puzzle, astellatol, has been solved in an enantiospecific manner. The highly congested pentacyclic skeleton of this rare sesterterpenoid, which possesses a unique bicyclo[4.1.1]octane motif, ten stereocenters, a cyclobutane that contains two quaternary centers, an exo-methylene group, and a sterically encumbered isopropyl trans-hydrindane motif, makes astellatol arguably one of the most challenging targets for sesterterpenoid synthesis. An intramolecular Pauson–Khand reaction was exploited to construct the right-hand side scaffold of this sesterterpenoid. An unprecedented reductive radical 1,6-addition, mediated by SmI2, forged the cyclobutane motif. Last, a strategic oxidation/reduction step provided not only the decisive solution for the remarkably challenging late-stage transformations, but also a highly valuable unravelling of the notorious issue of trans-hydrindane synthesis. Importantly, the synthesis of astellatol showcases a rapid, scalable strategy to access diverse complex isopropyl trans-hydrindane sesterterpenoids.Ein pentacyclisches Sesterterpenoid – Astellatol – wurde enantiospezifisch synthetisiert. Eine Pauson-Khand-Reaktion erzeugte die rechte Seite des Produkts, und eine reduktive radikalische 1,6-Addition unter Verwendung von SmI2 lieferte die Bicyclo[4.1.1]octan-Einheit. Durch strategische Oxidation/Reduktion gegen Ende der Syntheseroute wurde das hoch substituierte trans-Hydrindan fertiggestellt.
      PubDate: 2018-02-15T09:01:04.368077-05:
      DOI: 10.1002/ange.201800167
  • Cytochrome-P450-Induced Ordering of Microsomal Membranes Modulates
           Affinity for Drugs
    • Authors: Carlo Barnaba; Bikash Ranjan Sahoo, Thirupathi Ravula, Ilce G. Medina-Meza, Sang-Choul Im, G. M. Anantharamaiah, Lucy Waskell, Ayyalusamy Ramamoorthy
      Pages: 3449 - 3453
      Abstract: Although membrane environment is known to boost drug metabolism by mammalian cytochrome P450s, the factors that stabilize the structural folding and enhance protein function are unclear. In this study, we use peptide-based lipid nanodiscs to “trap” the lipid boundaries of microsomal cytochrome P450 2B4. We report the first evidence that CYP2B4 is able to induce the formation of raft domains in a biomimetic compound of the endoplasmic reticulum. NMR experiments were used to identify and quantitatively determine the lipids present in nanodiscs. A combination of biophysical experiments and molecular dynamics simulations revealed a sphingomyelin binding region in CYP2B4. The protein-induced lipid raft formation increased the thermal stability of P450 and dramatically altered ligand binding kinetics of the hydrophilic ligand BHT. These results unveil membrane/protein dynamics that contribute to the delicate mechanism of redox catalysis in lipid membrane.Redoxkatalyse in der Lipidmembran: Eine neue Anwendung von Peptidnanoscheiben zeigt, dass Cytochrom P450 2B4 die Bildung von Lipid-Raft-Domänen in einer biomimetischen Verbindung des endoplasmatischen Retikulums (ER) induzieren kann. Die proteininduzierten Lipidflöße steigern die thermische Stabilität von Cytochrom P450 und modulieren die Ligandenbindungskinetik des hydrophilen BHT-Liganden.
      PubDate: 2018-02-22T04:36:08.329267-05:
      DOI: 10.1002/ange.201713167
  • Nickel(0)-Catalyzed Hydroalkenylation of Imines with Styrene and Its
    • Authors: Li-Jun Xiao; Chao-Yue Zhao, Lei Cheng, Bo-Ya Feng, Wei-Min Feng, Jian-Hua Xie, Xiu-Fang Xu, Qi-Lin Zhou
      Pages: 3454 - 3458
      Abstract: A nickel(0)-catalyzed hydroalkenylation of imines with styrene and its derivatives is described. A wide range of aromatic and aliphatic imines directly coupled with styrene and its derivatives, thus providing various synthetically useful allylic amines with up to 95 % yield. The reaction offers a new atom- and step-economical approach to allylic amines by using alkenes instead of alkenyl-metallic reagents. Experiments and DFT calculations showed that TsNH2 promotes the proton transfer from the coordinated olefin to the imine, accompanied by a new C−C bond formation.Ohne Metallreagentien: Die Nickel(0)-katalysierte Hydroalkenylierung von Iminen mit Styrol und Styrolderivaten bietet einen neuen atomökonomischen und direkten Ansatz für die Synthese von Allylaminen ausgehend von Alkenen anstelle von Alkenylmetallreagentien. PG=Schutzgruppe, Ts=4-Toluolsulfonyl.
      PubDate: 2018-02-23T10:20:58.338547-05:
      DOI: 10.1002/ange.201713333
  • Transient-Ligand-Enabled ortho-Arylation of Five-Membered Heterocycles:
           Facile Access to Mechanochromic Materials
    • Authors: Bijin Li; Kapileswar Seth, Ben Niu, Lei Pan, Huiwen Yang, Haibo Ge
      Pages: 3459 - 3463
      Abstract: Reported herein is the first example of a direct arylation of heteroarenes by a transient-ligand-directed strategy without the need to construct and deconstruct the directing group. A wide range of heteroarenes undergoes the coupling with diverse aryl iodides to assemble a large library of highly selective and functionalized 3-arylthiophene-2-carbaldehydes. This route provides an opportunity to rapidly access new mechanofluorochromic materials. Moreover, a novel strategy for mechanochromic luminogens with chromism trends of red- and blue-shifts has been disclosed for the first time by facile functional-group modifications to a common structural core.Farbwandler: Die direkte Arylierung von Heteroarenen mithilfe transienter Liganden umgeht die Einführung und Abspaltung einer dirigierenden Gruppe. Der Ansatz öffnet einen schnellen Zugang zu neuartigen mechanofluorochromen Materialien.
      PubDate: 2018-02-23T05:16:03.772695-05:
      DOI: 10.1002/ange.201713357
  • A Robust 3D Cage-like Ultramicroporous Network Structure with High
           Gas-Uptake Capacity
    • Authors: Javeed Mahmood; Seok-Jin Kim, Hyuk-Jun Noh, Sun-Min Jung, Ishfaq Ahmad, Feng Li, Jeong-Min Seo, Jong-Beom Baek
      Pages: 3473 - 3478
      Abstract: A three-dimensional (3D) cage-like organic network (3D-CON) structure synthesized by the straightforward condensation of building blocks designed with gas adsorption properties is presented. The 3D-CON can be prepared using an easy but powerful route, which is essential for commercial scale-up. The resulting fused aromatic 3D-CON exhibited a high Brunauer–Emmett–Teller (BET) specific surface area of up to 2247 m2 g−1. More importantly, the 3D-CON displayed outstanding low pressure hydrogen (H2, 2.64 wt %, 1.0 bar and 77 K), methane (CH4, 2.4 wt %, 1.0 bar and 273 K), and carbon dioxide (CO2, 26.7 wt %, 1.0 bar and 273 K) uptake with a high isosteric heat of adsorption (H2, 8.10 kJ mol−1; CH4, 18.72 kJ mol−1; CO2, 31.87 kJ mol−1). These values are among the best reported for organic networks with high thermal stability (ca. 600 °C).Formbeständige Käfige in einer organischen Gerüststruktur wurden mithilfe eines starren Triptycenhexamin-Bausteins konstruiert. Die Struktur ist ultramikroporös und temperaturbeständig, sie hat eine BET-Oberfläche bis 2247 m2 g−1 und eine hohe Gasadsorptionskapazität.
      PubDate: 2018-02-27T03:31:42.161467-05:
      DOI: 10.1002/ange.201800218
  • From Symmetry Breaking to Unraveling the Origin of the Chirality of
           Ligated Au13Cu2 Nanoclusters
    • Authors: Guocheng Deng; Sami Malola, Juanzhu Yan, Yingzi Han, Peng Yuan, Chaowei Zhao, Xiting Yuan, Shuichao Lin, Zichao Tang, Boon K. Teo, Hannu Häkkinen, Nanfeng Zheng
      Pages: 3479 - 3483
      Abstract: A general method, using mixed ligands (here diphosphines and thiolates) is devised to turn an achiral metal cluster, Au13Cu2, into an enantiomeric pair by breaking (lowering) the overall molecular symmetry with the ligands. Using an achiral diphosphine, a racemic [Au13Cu2(DPPP)3(SPy)6]+ was prepared which crystallizes in centrosymmetric space groups. Using chiral diphosphines, enantioselective synthesis of an optically pure, enantiomeric pair of [Au13Cu2((2r,4r)/(2s,4s)-BDPP)3(SPy)6]+ was achieved in one pot. Their circular dichroism (CD) spectra give perfect mirror images in the range of 250–500 nm with maximum anisotropy factors of 1.2×10−3. DFT calculations provided good correlations with the observed CD spectra of the enantiomers and, more importantly, revealed the origin of the chirality. Racemization studies show high stability (no racemization at 70 °C) of these chiral nanoclusters, which hold great promise in applications such as asymmetry catalysis.Eines oder das Andere: Eine Mischung aus Diphosphan- und Pyridinthiol-Liganden kann einen achiralen Au13Cu2-Cluster durch Bruch von Spiegel- und Punktsymmetrie in ein Enantiomerenpaar umwandeln. Chirale Diphosphane liefern optisch reine Enantiomere in einem Eintopfverfahren. In Racemisierungsstudien durch Erhitzen war die Chiralität bis 70 °C stabil. Dichtefunktionalrechnungen erklären, wie die Chiralität entsteht.
      PubDate: 2018-02-23T05:16:33.197337-05:
      DOI: 10.1002/ange.201800327
  • A Cisplatin-Loaded Immunochemotherapeutic Nanohybrid Bearing Immune
           Checkpoint Inhibitors for Enhanced Cervical Cancer Therapy
    • Authors: Na Wang; Zhigang Wang, Zoufeng Xu, Xianfeng Chen, Guangyu Zhu
      Pages: 3484 - 3488
      Abstract: The efficacy of conventional chemotherapy is hindered by cancer cell escape from the immune system. A multifunctional nanohybrid system is reported for effective immunochemotherapy against cervical cancer. This nanohybrid contains both immune checkpoint inhibitor and cisplatin anticancer prodrug, showing improved cellular accumulation and increased binding of Pt to DNA and resulting in elevated apoptosis than using cisplatin alone when tested in cervical cancer cells. The immune checkpoint inhibitor enables the inhibition of indoleamine-2,3-dioxygenase and reverses immunosuppressive T cells to recognize cancer cells, leading to T cell proliferation and activation, cancer cell cycle arrest, and ultimately increased cancer cell death. The nanohybrid is also active in vivo against the growth of human cervical tumors. Overall, a strategy is provided using a multifunctional nanohybrid system to boost the antitumor activity of cisplatin.Eine Waffe für die Immunchemotherapie: Ein mit Cisplatin beladenes Nanohybrid, das Inhibitoren der Indolamin-2,3-Dioxygenase trägt, aktiviert signifikant T-Zellen und bewirkt auf diese Weise den Zellzyklusarrest von Gebärmutterhalskrebszellen und erhöhten Krebszelltod.
      PubDate: 2018-02-27T03:31:49.161967-05:
      DOI: 10.1002/ange.201800422
  • Ultrathin Palladium Nanomesh for Electrocatalysis
    • Authors: Jingjie Ge; Pei Wei, Geng Wu, Yudan Liu, Tongwei Yuan, Zhijun Li, Yunteng Qu, Yuen Wu, Hai Li, Zhongbin Zhuang, Xun Hong, Yadong Li
      Pages: 3493 - 3496
      Abstract: An ordered mesh of palladium with a thickness of about 3 nm was synthesized by a solution-based oxidative etching. The ultrathin palladium nanomeshes have an interconnected two-dimensional network of densely arrayed, ultrathin quasi-nanoribbons that form ordered open holes. The unique mesoporous structure and high specific surface area make these ultrathin Pd nanomeshes display superior catalytic performance for ethanol electrooxidation (mass activity of 5.40 Am g−1 and specific activity of 7.09 mA cm−2 at 0.8 V vs. RHE). Furthermore, the regular mesh structure can be applied to support other noble metals, such as platinum, which exhibits extremely high hydrogen evolution reaction (HER) activity and durability.Gitter „top-down”: Ein ultradünnes Pd-Nanogitter mit dicht angeordneten Quasi-Nanobändern und regelmäßigen Löchern wurde durch lösungsmittelbasierte freie Korrosion aus einer Pd-Nanoschicht erhalten. Das Nanogitter zeigt eine außergewöhnliche elektrokatalytische Leistung.
      PubDate: 2018-02-21T06:08:40.925278-05:
      DOI: 10.1002/ange.201800552
  • Aqueous-Phase Synthesis of Mesoporous Zr-Based MOFs Templated by
           Amphoteric Surfactants
    • Authors: Ke Li; Shaoliang Lin, Yongsheng Li, Qixin Zhuang, Jinlou Gu
      Pages: 3497 - 3501
      Abstract: Zr-based mesoporous metal–organic frameworks (mesoMOFs) with uniform mesochannels and crystallized microporous framework were constructed in a water-based system using amphoteric surfactants as templates. Aqueous-phase synthesis guaranteed the formation of rod-shaped surfactant micelles. Meanwhile, the carboxylate groups of amphoteric surfactants provided the anchoring to bridge Zr-oxo clusters and surfactant assemblies. As a result, the directed crystallization of MOFs proceeded around cylindrical micelles and the hierarchical micro- and mesostructure was produced. The dimensions of mesopores were easily tailored by changing the alkyl chain length of the applied surfactants. The included surfactant was effectively extracted thanks to the exceptional stability of the obtained Zr-based mesoMOFs. The almost complete occupation of the mesopore by cytochrome c exemplifies the accessibility of the mesochannels, suggesting the potential applications of the obtained mesoMOFs with bulky molecules.Zirconium-organische Gerüste mit einheitlichen Mesokanälen und kristallinem mikroporösem Gerüst wurden in einem wasserbasierten System mit amphoteren Tensiden als Templat erhalten. Die Tenside bauen dabei eine hexagonale zylindrische Mesophase auf und richten die Metallvorstufe durch Koordination für den Aufbau des Metall-organischen Gerüsts aus.
      PubDate: 2018-02-26T05:50:45.005842-05:
      DOI: 10.1002/ange.201800619
  • Epoxides as Alkylating Reagents for the Catellani Reaction
    • Authors: Hong-Gang Cheng; Chenggui Wu, Han Chen, Ruiming Chen, Guangyin Qian, Zhi Geng, Qiang Wei, Yuanyuan Xia, Jingyang Zhang, Yuming Zhang, Qianghui Zhou
      Pages: 3502 - 3506
      Abstract: We report a cooperative catalytic system comprising a PdII complex, XPhos, and the potassium salt of 5-norbornene-2-carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5-norbornene-2-carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom-economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa-Michael addition to furnish ubiquitous isochroman scaffolds.Ein kooperatives katalytisches System aus einem PdII/XPhos-Komplex und dem Kaliumsalz von 5-Norbornen-2-carbonsäure, das als Reaktionsvermittler und Base zugleich fungiert, ermöglichte die Verwendung von Epoxiden als Alkylierungsreagentien in der Catellani-Reaktion (siehe Schema). Die Produkte können durch Oxa-Michael-Addition in Isochroman-Gerüste umgewandelt werden.
      PubDate: 2018-02-15T09:15:33.519167-05:
      DOI: 10.1002/ange.201800573
  • Light-Driven Water Splitting Mediated by Photogenerated Bromine
    • Authors: Matthew V. Sheridan; Ying Wang, Degao Wang, Ludovic Troian-Gautier, Christopher J. Dares, Benjamin D. Sherman, Thomas J. Meyer
      Pages: 3507 - 3511
      Abstract: Light-driven water splitting was achieved using a dye-sensitized mesoporous oxide film and the oxidation of bromide (Br−) to bromine (Br2) or tribromide (Br3−). The chemical oxidant (Br2 or Br3−) is formed during illumination at the photoanode and used as a sacrificial oxidant to drive a water oxidation catalyst (WOC), here demonstrated using [Ru(bda)(pic)2], (1; pic=picoline, bda=2,2′-bipyridine-6,6′-dicarboxylate). The photochemical oxidation of bromide produces a chemical oxidant with a potential of 1.09 V vs. NHE for the Br2/Br− couple or 1.05 V vs. NHE for the Br3−/Br− couple, which is sufficient to drive water oxidation at 1 (RuV/IV≈1.0 V vs. NHE at pH 5.6). At pH 5.6, using a 0.2 m acetate buffer containing 40 mm LiBr and the [Ru(4,4′-PO3H2-bpy)(bpy)2]2+ (RuP2+, bpy=2,2′-bipyridine) chromophore dye on a SnO2/TiO2 core–shell electrode resulted in a photocurrent density of around 1.2 mA cm−2 under approximately 1 Sun illumination and a Faradaic efficiency upon addition of 1 of 77 % for oxygen evolution.Wasserspaltung durch Licht mithilfe molekularer Katalysatoren ist anspruchsvoll wegen des Mehrelektronenprozesses 2 H2OO2+4 H++4 e− bei der Wasseroxidation. Dies verringert die Lebensdauern der Ladungstrennung an der Photoanode und damit die Effizienz. Dieses Problem wurde mithilfe eines Einelektronenüberträgers zur Erzeugung eines Oxidationsmittel-Pools gelöst (1). Katalysatorzugabe nach der Photolyse ermöglichte die O2-Bildung mit hohem Faraday-Wirkungsgrad (2).
      PubDate: 2018-03-01T06:00:44.923094-05:
      DOI: 10.1002/ange.201708879
  • Van der Waals Heterostructures Comprised of Ultrathin Polymer Nanosheets
           for Efficient Z-Scheme Overall Water Splitting
    • Authors: Lei Wang; Xusheng Zheng, Liang Chen, Yujie Xiong, Hangxun Xu
      Pages: 3512 - 3516
      Abstract: Inspired by natural photosynthesis, Z-scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal-free Z-scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer-based van der Waals heterostructures as metal-free Z-scheme photocatalytic systems for overall water splitting is described using aza-fused microporous polymers (CMP) and C2N ultrathin nanosheets as O2- and H2-evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H2 and O2 was observed when aza-CMP/C2N heterostructures were used. A solar-to-hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge-transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting.Ein photokatalytisches System, das auf dem Z-Schema beruht und auf Metalle verzichtet, vermittelt effizient die gesamte Wasserspaltung. 2D-van-der-Waals-Heterostrukturen aus Polymernanoschichten erleichtern die Ladungstrennung mit der Folge verlängerter Lebensdauern und einer erhöhten Dichte an photogenerierten Exzitonen.
      PubDate: 2018-02-22T04:41:15.605308-05:
      DOI: 10.1002/ange.201710557
  • Direct Synthesis of Nano-Ferrierite along the 10-Ring-Channel Direction
           Boosts Their Catalytic Behavior
    • Authors: Vicente J. Margarit; M. Rocío Díaz-Rey, M. Teresa Navarro, Cristina Martínez, Avelino Corma
      Pages: 3517 - 3521
      Abstract: Ferrierite zeolites with nanosized crystals and external surface areas higher than 250 m2 g−1 have been prepared at relatively low synthesis temperature (120 °C) by means of the collaborative effect of two organic structure directing agents (OSDA). In this way, hierarchical porosity is achieved without the use of post-synthesis treatments that usually involve leaching of T atoms and solid loss. Adjusting the synthesis conditions it is possible to decrease the crystallite size in the directions of the 8- and 10-ring channels, [010] and [001] respectively, reducing their average pore length to 10–30 nm and increasing the number of pores accessible. The small crystal size of the nano-ferrierites results in an improved accessibility of reactants to the catalytic active centers and enhanced product diffusion, leading to higher conversion and selectivity with lower deactivation rates for the oligomerization of 1-pentene into longer-chain olefins.Kurze Kanäle: Nanokristalline Ferrierite mit reduzierten Kristallabmessungen entlang der 10-Ring-Kanäle sind effiziente und stabile Katalysatoren für die Oligomerisierung von 1-Penten zu Diesel-Kraftstoff. Dieses Resultat ist eine Folge verkürzter Diffusionswege.
      PubDate: 2018-02-27T08:15:38.495888-05:
      DOI: 10.1002/ange.201711418
  • Electrochemical Dynamics of a Single Platinum Nanoparticle Collision Event
           for the Hydrogen Evolution Reaction
    • Authors: Zhi-peng Xiang; Hai-qiang Deng, Pekka Peljo, Zhi-yong Fu, Su-li Wang, Daniel Mandler, Gong-quan Sun, Zhen-xing Liang
      Pages: 3522 - 3526
      Abstract: Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0 mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen-containing atmospheres. The particle size distribution estimated from the diffusion-controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry.Das Stromprofil der elektrokatalytischen Wasserstoffentwicklung an einem einzelnen Platinnanopartikel (Pt NP) unter einer Heliumatmosphäre verändert sich von Spitzenform zu Stufenform, wenn das Potential der als Substrat dienenden inerten Ultramikroelektrode (UME) gesenkt wird. Unter Wasserstoffatmosphäre stabilisiert sich die Stufenform des Stromprofils bei allen Polarisierungspotentialen, und es ist mindestens 5-mal kleiner als unter Helium.
      PubDate: 2018-02-22T07:16:16.667275-05:
      DOI: 10.1002/ange.201712454
  • Catalytic and Atom-Economic Csp3 −Csp3 Bond Formation: Alkyl Tantalum
           Ureates for Hydroaminoalkylation
    • Authors: Rebecca C. DiPucchio; Sorin-Claudiu Roşca, Laurel L. Schafer
      Pages: 3527 - 3530
      Abstract: Atom-economic and regioselective Csp3−Csp3 bond formation has been achieved by rapid C−H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2, and a ureate N,O-chelating-ligand salt gives catalytic systems prepared in situ that can realize high yields of β-alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C−H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.Auf Geschwindigkeit ausgelegt: Die Titelreaktion beruht auf der schnellen C-H-Alkylierung ungeschützter sekundärer Arylamine mit nichtaktivierten Alkenen. Die Kombination von Ta(CH2SiMe3)3Cl2 mit einem N,O-chelatisierenden Harnstoffanion sorgt dabei für hohe Ausbeuten an β-alkylierten Anilinderivaten.
      PubDate: 2018-02-22T07:16:44.502023-05:
      DOI: 10.1002/ange.201712668
  • Achieving Simultaneous CO2 and H2S Conversion via a Coupled Solar-Driven
           Electrochemical Approach on Non-Precious-Metal Catalysts
    • Authors: Weiguang Ma; Hong Wang, Wei Yu, Xiaomei Wang, Zhiqiang Xu, Xu Zong, Can Li
      Pages: 3531 - 3535
      Abstract: Carbon dioxide (CO2) and hydrogen sulfide (H2S) are generally concomitant with methane (CH4) in natural gas and traditionally deemed useless or even harmful. Developing strategies that can simultaneously convert both CO2 and H2S into value-added products is attractive; however it has not received enough attention. A solar-driven electrochemical process is demonstrated using graphene-encapsulated zinc oxide catalyst for CO2 reduction and graphene catalyst for H2S oxidation mediated by EDTA-Fe2+/EDTA-Fe3+ redox couples. The as-prepared solar-driven electrochemical system can realize the simultaneous conversion of CO2 and H2S into carbon monoxide and elemental sulfur at near neutral conditions with high stability and selectivity. This conceptually provides an alternative avenue for the purification of natural gas with added economic and environmental benefits.CO2 und H2S werden generell als schädliche Anteile von Erdgas angesehen. Ein solares elektrochemisches Verfahren, das die gekoppelte Umsetzung von CO2 und H2S zu CO und S unter nahezu neutralen Bedingungen mit hoher Aktivität und Stabilität erzielt, bietet eine wirtschaftliche und umweltfreundliche Alternative für die Erdgasaufreinigung.
      PubDate: 2018-02-27T03:53:06.83251-05:0
      DOI: 10.1002/ange.201713029
  • Small Molecules Targeting Mycobacterium tuberculosis Type II NADH
           Dehydrogenase Exhibit Antimycobacterial Activity
    • Authors: Michael B. Harbut; Baiyuan Yang, Renhe Liu, Takahiro Yano, Catherine Vilchèze, Bo Cheng, Jonathan Lockner, Hui Guo, Chenguang Yu, Scott G Franzblau, H. Mike Petrassi, William R. Jacobs, Harvey Rubin, Arnab K. Chatterjee, Feng Wang
      Pages: 3536 - 3540
      Abstract: The generation of ATP through oxidative phosphorylation is an essential metabolic function for Mycobaterium tuberculosis (Mtb), regardless of the growth environment. The type II NADH dehydrogenase (Ndh-2) is the conduit for electrons into the pathway, and is absent in the mammalian genome, thus making it a potential drug target. Herein, we report the identification of two types of small molecules as selective inhibitors for Ndh-2 through a multicomponent high-throughput screen. Both compounds block ATP synthesis, lead to effects consistent with loss of NADH turnover, and importantly, exert bactericidal activity against Mtb. Extensive medicinal chemistry optimization afforded the best analogue with an MIC of 90 nm against Mtb. Moreover, the two scaffolds have differential inhibitory activities against the two homologous Ndh-2 enzymes in Mtb, which will allow precise control over Ndh-2 function in Mtb to facilitate the assessment of this anti-TB drug target.Einfach mal abschalten: Ein Hochdurchsatz-Screening gegen den oxidativen Phosphorylierungsweg von M. tuberculosis führte zur Identifizierung zweier Inhibitoren der Typ-II-Dehydrogenase Ndh-2. Sie zeigen unterschiedliche Hemmaktivitäten gegen eines oder beide Ndh-2-Isozyme. Durch die Behandlung von Mtb mit diesen Verbindungen wird die ATP-Synthese abgeschaltet und das Bakterium getötet.
      PubDate: 2018-02-22T07:36:22.675296-05:
      DOI: 10.1002/ange.201800260
  • Halogen Bond Catalyzed Bromocarbocyclization
    • Authors: Yuk-Cheung Chan; Ying-Yeung Yeung
      Pages: 3541 - 3545
      Abstract: A halogen bond catalyzed bromo-carbocyclization of N-cinnamyl sulfonamides and O-cinnamyl phenyl ethers has been developed. N-methyl 4-iodopyridinium triflate is used as the halogen-bonding organocatalyst and the reaction is highly chemoselective. This report represents the first proof-of-concept for halogen-bonding organocatalyst-promoted electrophilic halogenation. Mechanistic study suggests the autocatalytic nature of this reaction.Eine bromierende Carbocyclisierung von N-Cinnamylsulfonamiden oder O-Cinnamylphenylethern unter Halogenbrücken-Katalyse liefert gute Ausbeuten bei hoher Chemoselektivität. Unter milden Bedingungen wird ein breites Spektrum an Substraten umgesetzt, und der Katalysator N-Methyl-4-iodpyridinium-Triflat ist luft- und feuchtigkeitsbeständig.
      PubDate: 2018-02-23T05:16:26.987964-05:
      DOI: 10.1002/ange.201800261
  • Sulfonamidation of Aryl and Heteroaryl Halides through Photosensitized
           Nickel Catalysis
    • Authors: Taehoon Kim; Stefan J. McCarver, Chulbom Lee, David W. C. MacMillan
      Pages: 3546 - 3550
      Abstract: Herein we report a highly efficient method for nickel-catalyzed C−N bond formation between sulfonamides and aryl electrophiles. This technology provides generic access to a broad range of N-aryl and N-heteroaryl sulfonamide motifs, which are widely represented in drug discovery. Initial mechanistic studies suggest an energy-transfer mechanism wherein C−N bond reductive elimination occurs from a triplet excited NiII complex. Late-stage sulfonamidation in the synthesis of a pharmacologically relevant structure is also demonstrated.Die C-N-Kupplung von Sulfonamiden mit Arylelektrophilen nach einem allgemeinen Verfahren ebnet den Weg zu vielfältigen N-Aryl- und N-Heteroaryl-Sulfonamid-Motiven, die in der Wirkstoffentwicklung weit verbreitet sind. Mechanistische Studien sprechen für einen Energietransfermechanismus und die Bildung der C-N-Bindung durch reduktive Eliminierung aus einem angeregten NiII-Komplex im Triplettzustand.
      PubDate: 2018-02-27T08:48:11.281489-05:
      DOI: 10.1002/ange.201800699
  • Zirconium–Porphyrin-Based Metal–Organic Framework Hollow Nanotubes for
           Immobilization of Noble-Metal Single Atoms
    • Authors: Ting He; Shuangming Chen, Bing Ni, Yue Gong, Zhao Wu, Li Song, Lin Gu, Wenping Hu, Xun Wang
      Pages: 3551 - 3556
      Abstract: Single atoms immobilized on metal–organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single noble-metal atoms have now been successfully anchored on the well-defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration-corrected scanning transmission electron microscopy and synchrotron-radiation-based X-ray absorption fine-structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM-Ir/Pt exhibits outstanding catalytic activity in the visible-light photocatalytic H2 evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.Einzelne Edelmetallatome können an den wohldefinierten Ankerzentren von hohlen Zirconiumporphyrin-MOF-Nanoröhren immobilisiert werden. Dank der hohlen Struktur und exzellenten photoelektrochemischen Eigenschaften zeigt HNTM-Ir/Pt eine herausragende Aktivität in der photokatalytischen Wasserspaltung und H2-Entwicklung unter sichtbarem Licht.
      PubDate: 2018-02-22T07:37:20.43514-05:0
      DOI: 10.1002/ange.201800817
  • Regioselective Cyclotrimerization of Terminal Alkynes Using a Digermyne
    • Authors: Tomohiro Sugahara; Jing-Dong Guo, Takahiro Sasamori, Shigeru Nagase, Norihiro Tokitoh
      Pages: 3557 - 3561
      Abstract: The catalytic activation of small neutral molecules followed by the formation of C−C bonds is a highly important method to increase the complexity and/or value of simple starting materials. Reported is an isolable digermyne, a compound with a Ge≡Ge bond, which acts as a precatalyst for the cyclotrimerization of terminal arylacetylenes to afford the corresponding 1,2,4-triarylbenzenes with absolute regioselectivity. The results demonstrate that bespoke main-group-element compounds can catalytically activate and transform small neutral organic molecules and induce the formation of C−C bonds.Ring Ge-schlossen: Ein isolierbares Digermin mit Ge≡Ge-Bindung wirkt als Präkatalysator der vollständig regioselektiven Cyclotrimerisierung terminaler Arylacetylene zu 1,2,4-Triarylbenzolen. Die Resultate zeigen, dass derartige Hauptgruppenelementverbindungen kleine neutrale organische Moleküle katalytisch aktivieren und die Bildung von C-C-Bindungen bewirken können.
      PubDate: 2018-02-27T08:40:52.826104-05:
      DOI: 10.1002/ange.201801222
  • A Chiral Ligand Assembly That Confers One-Electron O2 Reduction Activity
           for a Cu2+-Selective Metallohydrogel
    • Authors: Xiaojuan Wang; Chuanwan Wei, Ji-Hu Su, Bo He, Ge-Bo Wen, Ying-Wu Lin, Yi Zhang
      Pages: 3562 - 3566
      Abstract: The design of functional metallohydrogels is attractive but challenging. A rational approach is introduced for designing functional metallohydrogels using chiral ligands, a phenylalanine derivative with a pyridyl group (l/d-PF). Intriguingly, the as-prepared metallohydrogel exhibits excellent O2 binding and activating properties. Insights into the O2 binding pathway reveals the presence of a novel [(l+d)-PF-Cu3+-O2−] species, which can efficiently reduce ferric cytochrome c with the reactive O2− by receiving an electron from reductant ascorbic acid. This study provides helpful instructions for developing new artificial systems with specific functions through the effective combination of chiral ligands with metal ions.Mit beiden Händen: Die Kombination chiraler Liganden – wie am Beispiel eines Phenylalaninderivats mit einer Pyridylgruppe (l/d-PF) vorgeführt – ergibt ein Cu2+-selektives Metallohydrogel mit Ein-Elektronen-Reaktivität in der O2-Reduktion.
      PubDate: 2018-02-23T05:21:25.188363-05:
      DOI: 10.1002/ange.201801290
  • Kinetische Analyse und strukturelle Interpretation der kompetitiven
           Ligandenbindung für Denitrifikation in gekürztem Hämoglobin N
    • Authors: Akshaya Kumar Das; Markus Meuwly
      Pages: 3567 - 3572
      Abstract: Die Umwandlung von Stickstoffmonoxid (NO) zu Nitrat (NO3−) durch Dioxygenierung schützt Zellen vor tödlichem NO. Ausgehend von NO-gebundendem Häm ist der erste Schritt in der Umwandlung von NO zu harmlosem NO3− die Ligandenaustauschreaktion FeNO+O2FeO2+NO, die auf molekularer Ebene nach wie vor schlecht verstanden ist. Die berechnete Barriere für die Austauschreaktion zwischen dem Wildtyp (WT) und der Y33A-Mutante unterscheidet sich um 1.5 kcal mol−1, verglichen mit experimentell gemessenen 1.7 kcal mol−1. Es wird direkt bestätigt, dass die Ligandenaustauschreaktion in trHbN geschwindigkeitsbestimmend ist und dass entropische Beiträge 75 % des Unterschieds zwischen WT und der Y33A-Mutanten ausmachen. Die Reste Tyr 33, Phe 46, Val 80, His 81 und Gln 82, welche das aktive Zentrum umgeben, nehmen im Ligand-gebundenen Zustand sowie im Übergangszustand jeweils unterschiedliche Konfigurationen ein und kontrollieren deshalb vermutlich den Reaktionspfad. Durch den Vergleich mit Berechnungen der elektronischen Struktur des Übergangszustandes zwischen den zwei Ligand-gebundenen Zuständen kann dieser dem 2A-Zustand zugeordnet werden.Kompetitive O2- und NO-Bindung: Ausgehend von einem NO-gebundenen Zustand wird der Ligand am Häm in trHbN durch O2 ersetzt. Dieser Schritt ist geschwindigkeitsbestimmend für die Dioxygenierungsreaktion. Die berechneten Energiebarrieren für den Wildtyp und die Y33A-Mutante stimmen quantitativ mit Experimenten überein und ermöglichen es, die Unterschiede zwischen den beiden Proteinen strukturell zu erklären.
      PubDate: 2018-02-23T10:20:40.136759-05:
      DOI: 10.1002/ange.201711445
  • Ein aktiver und stabiler Cobaltkatalysator für die
           Sauerstoffentwicklungsreaktion: Polymerisation einer ionischen
    • Authors: Yuxiao Ding; Alexander Klyushin, Xing Huang, Travis Jones, Detre Teschner, Frank Girgsdies, Tania Rodenas, Robert Schlögl, Saskia Heumann
      Pages: 3573 - 3577
      Abstract: Inspiriert durch die katalytischen Eigenschaften von Single-site-Katalysatoren und der erhöhten Leistungsfähigkeit von Metallkatalysatoren durch ionische Flüssigkeiten wurde eine Methode zur gezielten und skalierbaren Platzierung von einzelnen Cobaltatomen auf Kohlenstoffnanoröhrenoberflächen mithilfe einer polymerisierten ionischen Flüssigkeit entwickelt. Durch eine ionische Flüssigkeit wurden einzelne, fein verteilte Cobaltionen koordiniert und als heterogener Katalysator für die Sauerstoffententwicklungsreaktion (OER) genutzt. Die erhaltenen Daten zeigen eine hohe Aktivität bei gleichzeitig vorhandener Stabilität.Eine skalierbare Methode wurde entwickelt, um Single-Site-Cobalt-Ionen auf CNT-Oberflächen abzuscheiden. Hierzu wurden ionische Flüssigkeiten polymerisiert, und die elektronische Struktur des atomar verteilten Co wird durch die polymerisierte Flüssigkeit justiert, mit positiven Auswirkungen auf die Sauerstoffentwicklungsreaktion. Die komplexe Struktur fungiert als Gegenion zum Co und erhöht dadurch die Gesamtstabilität.
      PubDate: 2018-02-21T03:20:44.134333-05:
      DOI: 10.1002/ange.201711688
  • Innenrücktitelbild: Ice Melting to Release Reactants in Solution
           Syntheses (Angew. Chem. 13/2018)
    • Authors: Hehe Wei; Kai Huang, Le Zhang, Binghui Ge, Dong Wang, Jialiang Lang, Jingyuan Ma, Da Wang, Shuai Zhang, Qunyang Li, Ruoyu Zhang, Naveed Hussain, Ming Lei, Li-Min Liu, Hui Wu
      Pages: 3579 - 3579
      Abstract: Wie ein Eisberg langsam im Ozean schmilzt, so können Eisstücke eingeschlossene Chemikalien beim Schmelzen in eine Reaktionslösung freisetzen. B. Ge, L.-M. Liu, H. Wu et al. beschreiben diesen Ansatz in ihrer Zuschrift auf S. 3412. Durch dieses einfache Verfahren lassen sich Keimbildungs- und Wachstumsprozesse unterdrücken.
      PubDate: 2018-02-27T08:15:25.388729-05:
      DOI: 10.1002/ange.201802191
  • Rücktitelbild: Total Synthesis of Astellatol (Angew. Chem. 13/2018)
    • Authors: Nan Zhao; Shuqiang Yin, Shengling Xie, Hao Yan, Pan Ren, Gui Chen, Fang Chen, Jing Xu
      Pages: 3580 - 3580
      Abstract: Der Chinesische Scherenschnitt …… hat eine lange Tradition, auch als Dekoration von Türen und Fenstern beim Neujahrsfest. Das chinesische Schriftzeichen steht für Glück, für Frühling. Vor diesem Hintergrund präsentieren J. Xu et al. in ihrer Zuschrift auf S. 3444 die erste enantiospezifische Synthese für Astellatol, das drei Jahrzehnte lang eine Herausforderung darstellte.
      PubDate: 2018-02-19T08:10:24.460137-05:
      DOI: 10.1002/ange.201801794
  • Yanlin Song
    • Pages: 3342 - 3342
      Abstract: „Mein Lieblingsautor ist Mark Twain. Meine drei Lieblingsfilme sind Vom Winde verweht, Ein Herz und eine Krone, The King's Speech ...“ Dies und mehr von und über Yanlin Song finden Sie auf Seite 3342.
      PubDate: 2017-11-29T02:26:01.833166-05:
      DOI: 10.1002/ange.201710897
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