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  Subjects -> CHEMISTRY (Total: 844 journals)
    - ANALYTICAL CHEMISTRY (51 journals)
    - CHEMISTRY (594 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
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    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (594 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 245)
ACS Photonics     Full-text available via subscription   (Followers: 12)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 23)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chimica Slovenica     Open Access  
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 51)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 56)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 21)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 15)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 225)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 222)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 16)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 313)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 122)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 89)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 15)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 72)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 25)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 20)
Chemical Reviews     Full-text available via subscription   (Followers: 179)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 151)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 20)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 227)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 17)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 62)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [225 followers]  Follow
    
   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  [1589 journals]
  • ortho-Directing Chromium Arene Complexes as Efficient Mediators for
           Enantiospecific sp2-sp3 Cross-Coupling Reactions
    • Authors: Raphael Bigler; Varinder Kumar Aggarwal
      Abstract: A new strategy for the coupling of a broad scope of electronically diverse aromatics to boronic esters is reported. The coupling sequence, which relies on the directed ortho-lithiation of chromium arene complexes followed by boronate formation and oxidation, occurs with complete ortho-selectivity and enantiospecificity to give the coupling products in excellent yields and with high functional group tolerance. An intermediate chromium arene boronate complex was characterized by X-ray, NMR and IR to elucidate the reaction mechanism.
      PubDate: 2017-12-11T05:27:09.901896-05:
      DOI: 10.1002/ange.201711816
       
  • Magnetic Actuation of Drops and Liquid Marbles Using a Deformable
           Paramagnetic Liquid Substrate
    • Authors: Jacopo Vialetto; Masayuki Hayakawa, Nikita Kavokine, Masahiro Takinoue, Subramanyan Namboodiri Varanakkottu, Sergii Rudiuk, Manos Anyfantakis, Mathieu Morel, Damien Baigl
      Abstract: Wie ein Brunnen, aus dem Wasser abfließt, so ermöglicht auch die lokale Deformation eines paramagnetischen Substrats mit einem Magneten einen gravitationsgetriebenen Flüssigkeitstransport. Dieses Phänomen beschreiben D. Baigl et al. in ihrer Zuschrift (
      DOI : 10.1002/ange.201710668) und auf dem Titelbild schematisch anhand der Deformation des Texts, wobei die „i”-Punkte für manipulierte Tröpfchen und Flüssigkeitsmurmeln stehen. Die Methode erfordert keinerlei magnetisch responsiven Partikeln und ist für die meisten Flüssigkeiten geeignet, etwa für Wasser und Öl.
      PubDate: 2017-12-11T05:02:48.05414-05:0
       
  • CO oxidation on metal-supported monolayer oxide films: Do we know which
           phase (interface) is active'
    • Authors: Ke Zhang; Linfei Li, Shamil Shaikhutdinov, Hans-Joachim Freund
      Abstract: Ultrathin ("monolayer") films of transition metal oxides grown on metal substrates have recently received considerable attention as promising catalytic materials, in particular for low-temperature CO oxidation. The reaction rate on such systems often increases when the film only partially covers the support, and the effect is commonly attributed to the formation of active sites at the metal/oxide boundary. By studying the structure and reactivity of FeO(111) films on Pt(111), here we show that, independently of the film coverage, CO oxidation takes place at the interface between reduced and oxidized phases in the oxide film formed under reaction conditions. The promotional role of a metal support is to ease formation of the reduced phase via reaction between CO adsorbed on metal and oxygen at the oxide island edge.
      PubDate: 2017-12-11T04:57:26.577795-05:
      DOI: 10.1002/ange.201710934
       
  • Enantio- and Diastereoselective Cyclopropanation of 1-Alkenylboronates:
           Synthesis of 1-boryl-2,3-disubstituted Cyclopropanes
    • Authors: Pedro J. Pérez; Javier Carreras, Ana Caballero
      Abstract: A novel, highly enantio- and diastereoselective synthesis of 1-boryl-2,3-disubstituted cyclopropanes has been developed by means of the cyclopropanation of alkenylboronates with ethyl diazoacetate in the presence of catalytic amounts of a chiral copper-(I) complex. The products can also be directly accessed from alkynes through an operationally simple sequential hydroboration-cyclopropanation protocol. The resulting enantioenriched 1-boryl-2,3-disubstituted-cyclopropanes are versatile synthetic intermediates through further transformations at the carbon-boron bonds
      PubDate: 2017-12-11T03:51:15.2264-05:00
      DOI: 10.1002/ange.201710415
       
  • Thioketone Directed Palladium(II)-Catalyzed C-H Arylation of Ferrocenes
           with Aryl Boronic Acids
    • Authors: Shuli You; Zhong-Jian Cai, Chen-Xu Liu, Qing Gu
      Abstract: A palladium(II)-catalyzed thioketone-chelation-assisted C-H direct arylation of ferrocenes is described. With thioketone as an efficient directing group, various mono- and di-aryl-substituted thiocarbonylferrocenes were obtained via Pd-catalyzed C-H direct functionalization reaction in high yields under mild and base-free conditions. Furthermore, the arylated thiocarbonylferrocene could undergo diverse transformations.
      PubDate: 2017-12-11T03:21:39.809759-05:
      DOI: 10.1002/ange.201711451
       
  • Dicarboxylic Acid Separation by Dynamic and Size-Matched Recognition in
           Solution and in the Solid State
    • Authors: Pierangelo Metrangolo; giancarlo terraneo, giuseppe resnati, tullio pilati, vijith kumar, alceo macchioni, gianluca ciancaleoni
      Abstract: Bis(trimethylammonium) alkane diiodides dynamically encapsulate dicarboxylic acids through intermolecular hydrogen bonds between the hosts' I- anions and the guests' carboxylic OH groups. A selective recognition is realized when the size of the I-∙∙∙HOOC-(CH2/CF2)n-COOH∙∙∙I- superanion matches the dication alkyl chain length. Dynamic recognition is demonstrated also in solution, where the presence of the size-matching organic salt boosts acid solubility profile thus allowing efficient mixture separation.
      PubDate: 2017-12-10T21:51:54.26273-05:0
      DOI: 10.1002/ange.201711822
       
  • Photocatalytic Aerobic Phosphatation of Alkenes
    • Authors: Alexander Breder; Christian Depken, Felix Krätzschmar, Rene Rieger, Katharina Rode
      Abstract: A catalytic regime for the direct phosphatation of simple, non-polarized alkenes, using ordinary, non-activated phosphoric acid diesters as the phosphate source and O2 as the terminal oxidant, has been devised. The title method allows for the direct and highly econo-mic construction of a diverse range of allylic phosphate esters. From a conceptual viewpoint, the aerobic phosphatation is entirely complementary to traditional protocols for phosphate ester formation, which predominantly rely on the use of pre-functionalized or pre-activated reactants, such as alcohols and phosphoryl halides. The title transformation is enabled by the dual interplay of a photoredox- and a selenium-π-acid catalyst involving a sequence of single-electron-transfer processes.
      PubDate: 2017-12-08T08:55:59.737351-05:
      DOI: 10.1002/ange.201711599
       
  • Nanosheet Catalysis of Carbon Dioxide Photoreduction: Fundamentals and
           Challenges
    • Authors: Zhenyu Sun; Neetu Talreja, Hengcong Tao, John Texter, Jennifer Strunk, Martin Muhler, Jianfeng Chen
      Abstract: Transformation of CO2 into fuels and chemicals by using photocatalysis is a promising strategy to provide a long-term solution to mitigating global warming and energy supply problems. Achievements in photocatalysis during the last decade have sparked increased interest in using sunlight to reduce CO2. Traditional semiconductors used in photocatalysis (e.g. TiO2), are not suitable for the use in natural sunlight, and even under UV irradiation their performance is not sufficient. Some two-dimensional (2D) materials have recently been designed for catalytic reduction of CO2. These materials still require significant modification, which remains a challenge for photocatalytic process design. An overarching aim of this article is to summarize the literature reported on photocatalytic conversion of CO2 by various 2D materials in the liquid phase, with special attention given to development of novel 2D photocatalyst materials, to provide a basis to suggest improved materials.
      PubDate: 2017-12-08T07:26:19.537577-05:
      DOI: 10.1002/ange.201710509
       
  • The common Intermediates of Oxygen Evolution and Dissolution Reactions
           during Water Electrolysis on Iridium
    • Authors: Olga Kasian; Jan-Philipp Grote, Simon Geiger, Serhiy Cherevko, Karl J.J. Mayrhofer
      Abstract: Understanding the pathways of catalyst degradation during the oxygen evolution reaction is a cornerstone in development of efficient and stable electrolyzers, since even for most promising Ir based anodes the destined harsh conditions are detrimental. The dissolution mechanism has a complex nature and the correlation to the oxygen evolution reaction itself is still poorly understood. Here, hyphening a scanning flow cell with inductively coupled plasma and online electrochemical mass spectrometers, we in-situ monitor the oxygen evolution and degradation products of Ir and Ir-oxides. We show that at high anodic potentials several dissolution routes become possible, including formation of gaseous IrO3. On the basis of our experimental data possible pathways of oxygen evolution triggered dissolution of Ir are proposed, and the role of common intermediates for these reactions is discussed.
      PubDate: 2017-12-08T07:26:03.983751-05:
      DOI: 10.1002/ange.201709652
       
  • Hochselektive Mangan(I)/Lewis-Säure-cokatalysierte direkte
           C-H-Propargylierung unter Verwendung von Bromallenen
    • Authors: Can Zhu; Jonas Luca Schwarz, Sara Cembellín, Steffen Greßies, Frank Glorius
      Abstract: Eine Mangan(I)/Lewis-Säure-cokatalysierte direkte hochselektive C-H-Propargylierung wurde entwickelt. BPh3 erhöht bei dieser Propargylierung nicht nur die Reaktivität, sondern auch die Selektivität. Sekundäre, tertiäre und sogar quartäre Kohlenstoffzentren konnten in der propargylischen Position direkt aufgebaut werden. Sowohl interne als auch terminale Alkine können leicht gebildet werden. Die Chiralität konnte erfolgreich von einem axial-chiralen Allen zu einem Chiralitätszentrum transferiert werden. Die Reaktivität des Mangan-Katalysators in dieser Umsetzung ist im Vergleich zu anderen Übergangsmetallkatalysatoren einzigartig.Robuste Propargylierung: Bei einer hoch selektiven Mangan(I)/Lewis-Säure-cokatalysierten direkten C-H-Propargylierung erhöht BPh3 nicht nur die Reaktivität, sondern auch die Selektivität. Sekundäre, tertiäre und sogar quartäre Kohlenstoffzentren konnten in der propargylischen Position direkt aufgebaut werden. Die Reaktivität des Mangan-Katalysators in dieser Umsetzung ist im Vergleich zu anderen Übergangsmetallkatalysatoren einzigartig.
      PubDate: 2017-12-08T07:07:58.138791-05:
      DOI: 10.1002/ange.201710835
       
  • Benjamin List
    • PubDate: 2017-12-08T07:07:07.528011-05:
      DOI: 10.1002/ange.201711047
       
  • Stability of Residual Oxides in Oxide-Derived Copper Catalysts for
           Electrochemical CO2 Reduction Investigated with 18O Labeling
    • Authors: Yanwei Lum; Joel W. Ager
      Abstract: Oxide-derived (OD) Cu catalysts have high selectivity towards the formation of multi-carbon products (C2/C3) for aqueous electrochemical CO2 reduction (CO2R). It has been proposed that a large fraction of the initial oxide can be surprisingly resistant to reduction, and these residual oxides play a crucial catalytic role. The stability of residual oxides was investigated by synthesizing 18O-enriched OD Cu catalysts and testing them for CO2R. These catalysts maintain a high selectivity towards C2/C3 products (ca. 60 %) for up to 5 h in 0.1 m KHCO3 at −1.0 V vs. RHE. However, secondary-ion mass spectrometry measurements show that only a small fraction (
      PubDate: 2017-12-08T07:07:05.646802-05:
      DOI: 10.1002/ange.201710590
       
  • Conformational Selection of Dimethylarginine Recognition by the Survival
           Motor Neuron Tudor Domain
    • Authors: Shreyas Supekar; Anna C. Papageorgiou, Gerd Gemmecker, Raphael Peltzer, Mikael P. Johansson, Konstantinos Tripsianes, Michael Sattler, Ville R. I. Kaila
      Abstract: Tudor domains bind to dimethylarginine (DMA) residues, which are post-translational modifications that play a central role in gene regulation in eukaryotic cells. NMR spectroscopy and quantum calculations are combined to demonstrate that DMA recognition by Tudor domains involves conformational selection. The binding mechanism is confirmed by a mutation in the aromatic cage that perturbs the native recognition mode of the ligand. General mechanistic principles are delineated from the combined results, indicating that Tudor domains utilize cation–π interactions to achieve ligand recognition.Die Tudor-Domäne des humanen SMN-Proteins („survival motor neuron”) erkennt über Kation-π-Wechselwirkungen die Stereoisomere von Dimethylarginin-Resten innerhalb des aromatischen Ligandenbindekäfigs. Die Stereoselektivität lässt sich durch eine Einzelpunktmutation modulieren.
      PubDate: 2017-12-08T07:06:59.252031-05:
      DOI: 10.1002/ange.201708233
       
  • A Chiral Halogen-Bonding [3]Rotaxane for the Recognition and Sensing of
           Biologically Relevant Dicarboxylate Anions
    • Authors: Jason Y. C. Lim; Igor Marques, Vítor Félix, Paul D. Beer
      Abstract: The unprecedented application of a chiral halogen-bonding [3]rotaxane host system for the discrimination of stereo- and E/Z geometric isomers of a dicarboxylate anion guest is described. Synthesised by a chloride anion templation strategy, the [3]rotaxane host recognises dicarboxylates through the formation of 1:1 stoichiometric sandwich complexes. This process was analysed by molecular dynamics simulations, which revealed the critical synergy of halogen and hydrogen bonding interactions in anion discrimination. In addition, the centrally located chiral (S)-BINOL motif of the [3]rotaxane axle component facilitates the complexed dicarboxylate species to be sensed via a fluorescence response.Die Diskriminierung zwischen Stereoisomeren und geometrischen Isomeren von Dicarboxylat-Verbindungen durch ein chirales halogenverbrückendes [3]Rotaxan kann durch Fluoreszenzmessungen beobachtet werden. Rechnergestützte Modellierungen lassen vermuten, dass die Synergie zwischen der Achse des Rotaxan-Wirts und den Komponenten des Makrocyclus für die Gast-Selektivität entscheidend ist.
      PubDate: 2017-12-08T05:24:10.17079-05:0
      DOI: 10.1002/ange.201711176
       
  • Intramolecular Acetyl Transfer to Olefins by Catalytic C−C Bond
           Activation of Unstrained Ketones
    • Authors: Zi-Qiang Rong; Hee Nam Lim, Guangbin Dong
      Abstract: A rhodium-catalyzed intramolecular acetyl-group transfer has been achieved through a “cut and sew” process. The challenge arises from the existence of different competitive pathways. Preliminary success has been achieved with unstrained enones that contain a biaryl linker. The use of an electron-rich N-heterocycilc carbene (NHC) ligand is effective to inhibit undesired β-hydrogen elimination. Various 9,10-dihydrophenanthrene derivatives can be prepared with excellent functional-group compatibility. The 13C-labelling study suggests that the reaction begins with cleavage of the unstrained C−C bond, followed by migratory insertion and reductive elimination.Kreuzstich: Ein Rhodium-katalysierter intramolekularer Acetylgruppentransfer wird durch „Schneiden und Nähen” des Moleküls erreicht. Ungespannte Enone, die ein Biaryl-Zwischenstück enthalten, unterliegen einer C-C-Aktivierung unter der Wirkung einer temporären dirigierenden Gruppe. Verschiedene 9,10-Dihydrophenanthren-Derivate können mit zahlreichen funktionellen Gruppen hergestellt werden.
      PubDate: 2017-12-08T05:16:01.262165-05:
      DOI: 10.1002/ange.201711394
       
  • Palladium-Catalyzed Intramolecular Trost-Oppolzer-Type Alder-Ene Reaction
           of Dienyl Acetates to Cyclopentadienes
    • Authors: Siddheshwar K. Bankar; Bara Singh, Pinku Tung, S. S. V. Ramasastry
      Abstract: A new approach for the synthesis of highly substituted cyclopentadienes, indenes and cyclopentene-fused heteroarenes via the Pd-catalyzed Trost-Oppolzer-type intramolecular Alder-ene reaction of 2,4-pentadienyl acetates is described. This unprecedented transformation combines the electrophilic features of the Tsuji-Trost reaction with the nucleophilic features of the Alder-ene reaction. The overall outcome can be perceived as a hitherto unknown 'acid-free' iso-Nazarov-type cyclization. The versatility of this strategy was further demonstrated via the formal synthesis of paucifloral F, a resveratrol-based natural product.
      PubDate: 2017-12-08T05:12:41.431239-05:
      DOI: 10.1002/ange.201711797
       
  • Temperature-Directed Biocatalysis for the Sustainable Production of
           Aromatic Aldehydes or Alcohols
    • Authors: Jun Ni; Yan-Yan Gao, Fei Tao, Hong-Yu Liu, Ping Xu
      Abstract: The biosynthesis of aromatic aldehydes and alcohols from renewable resources is currently receiving considerable attention because of an increase in demand, finite fossil resources, and growing environmental concerns. Here, a temperature-directed whole-cell catalyst was developed by using two novel enzymes from a thermophilic actinomycete. Ferulic acid, a model lignin derivative, was efficiently converted into vanillyl alcohol at a reaction temperature at 30 °C. However, when the temperature was increased to 50 °C, ferulic acid was mainly converted into vanillin with a productivity of 1.1 g L−1 h−1. This is due to the fact that the redundant endogenous alcohol dehydrogenases (ADHs) are not active at this temperature while the functional enzymes from the thermophilic strain remain active. As the biocatalyst could convert many other renewable cinnamic acid derivatives into their corresponding aromatic aldehydes/alcohols, this novel strategy may be extended to generate a vast array of valuable aldehydes or alcohols.Mit zwei neuen Enzymen aus einem thermophilen Actinomyceten wurde ein Ganzzellkatalysator für die nachhaltige Erzeugung aromatischer Aldehyde oder Alkohole aus erneuerbaren Zimtsäurederivaten entwickelt. Ferulasäure wurde bei 30 °C in Vanillylalkohol überführt, während die gleiche Reaktion bei 50 °C hauptsächlich Vanillin lieferte, da bei dieser Temperatur die endogenen Alkoholdehydrogenasen nicht mehr aktiv sind.
      PubDate: 2017-12-08T05:08:01.517826-05:
      DOI: 10.1002/ange.201710793
       
  • Crochelins: Siderophores with an Iron-Chelating Moiety from the
           Nitrogen-Fixing Bacterium Azotobacter chroococcum
    • Authors: Oliver Baars; Xinning Zhang, Marcus I. Gibson, Alan T. Stone, François M. M. Morel, Mohammad R. Seyedsayamdost
      Abstract: Microbes use siderophores to access essential iron resources in the environment. Over 500 siderophores are known, but they utilize a small set of common moieties to bind iron. Azotobacter chroococcum expresses iron-rich nitrogenases, with which it reduces N2. Though an important agricultural inoculant, the structures of its iron-binding molecules remain unknown. Here, the “chelome” of A. chroococcum is examined using small molecule discovery and bioinformatics. The bacterium produces vibrioferrin and amphibactins as well as a novel family of siderophores, the crochelins. Detailed characterization shows that the most abundant member, crochelin A, binds iron in a hexadentate fashion using a new iron-chelating γ-amino acid. Insights into the biosynthesis of crochelins and the mechanism by which iron may be removed upon import of the holo-siderophore are presented. This work expands the repertoire of iron-chelating moieties in microbial siderophores.Neue Siderophore: Crochelin A, erstes Mitglied einer neuen Siderophor-Familie, wurde in dem landwirtschaftlichen Nutzorganismus Azotobacter chroococcum entdeckt. Der Siderophor bindet Eisen in beispielloser Weise über eine γ-Aminosäure-Einheit (rot). Experimente und bioinformatische Studien geben Einblick in die Eisenbindefähigkeit und die Biosynthese des Mikroorganismus.
      PubDate: 2017-12-08T05:07:46.452305-05:
      DOI: 10.1002/ange.201709720
       
  • Controlled Sol–Gel Transitions of a Thermoresponsive Polymer in a
           Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger
    • Authors: Caihong Wang; Kei Hashimoto, Ryota Tamate, Hisashi Kokubo, Masayoshi Watanabe
      Abstract: Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light-controlled mechanical sol–gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light-controlled sol–gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol–gel transitions.Ein ABA-Triblockcopolymer mit thermoresponsiven A-Blöcken wurde in einer gemischten konventionell-photoresponsiven ionischen Flüssigkeit (IL) gelöst. Über das Azobenzol-Mesogen lässt sich die Affinität zwischen den A-Blöcken und dem Lösungsmittel einstellen: In der trans-IL ist das Polymer löslich, in der cis-IL unlöslich. Ein molekularer Schaltprozess führt so zu einem reversiblen makroskopischen Sol-Gel-Übergang.
      PubDate: 2017-12-08T05:02:55.626707-05:
      DOI: 10.1002/ange.201710288
       
  • Thermally Activated Delayed Fluorescence in a Y3N@C80 Endohedral
           Fullerene: Time-Resolved Luminescence and EPR Studies
    • Authors: Michal Zalibera; Denis S. Krylov, Dimitrios Karagiannis, Paul-Anton Will, Frank Ziegs, Sandra Schiemenz, Wolfgang Lubitz, Sebastian Reineke, Anton Savitsky, Alexey A. Popov
      Abstract: The endohedral fullerene Y3N@C80 exhibits luminescence with reasonable quantum yield and extraordinary long lifetime. By variable-temperature steady-state and time-resolved luminescence spectroscopy, it is demonstrated that above 60 K the Y3N@C80 exhibits thermally activated delayed fluorescence with maximum emission at 120 K and a negligible prompt fluorescence. Below 60 K, a phosphorescence with a lifetime of 192±1 ms is observed. Spin distribution and dynamics in the triplet excited state is investigated with X- and W-band EPR and ENDOR spectroscopies and DFT computations. Finally, electroluminescence of the Y3N@C80/PFO film is demonstrated opening the possibility for red-emitting fullerene-based organic light-emitting diodes (OLEDs).Verzögerung durch den Käfig: Eine effiziente thermisch aktivierte verzögerte Fluoreszenz wird für das endohedrale Fulleren Y3N@C80 beobachtet. Wie ENDOR-Spektroskopie bestätigt, ist das Exziton dabei vorrangig auf dem Kohlenstoffkäfig lokalisiert.
      PubDate: 2017-12-08T04:56:01.958843-05:
      DOI: 10.1002/ange.201710637
       
  • Purely Physisorption-Based CO-Selective Gate-Opening in Microporous
           Organically Pillared Layered Silicates
    • Authors: Markus M. Herling; Martin Rieß, Hiroshi Sato, Liangchun Li, Thomas Martin, Hussein Kalo, Ryotaro Matsuda, Susumu Kitagawa, Josef Breu
      Abstract: Separation of gas molecules with similar physical and chemical properties is challenging but nevertheless highly relevant for chemical processing. By introducing the elliptically shaped molecule, 1,4-dimethyl-1,4-diazabicyclo[2.2.2]octane, into the interlayer space of a layered silicate, a two-dimensional microporous network with narrow pore size distribution is generated (MOPS-5). The regular arrangement of the pillar molecules in MOPS-5 was confirmed by the occurrence of a 10 band related to a long-range pseudo-hexagonal superstructure of pillar molecules in the interlayer space. Whereas with MOPS-5 for CO2 adsorption, gate-opening occurs at constant volume by freezing pillar rotation, for CO the interlayer space is expanded at gate-opening and a classical interdigitated layer type of gate-opening is observed. The selective nature of the gate-opening might be used for separation of CO and N2 by pressure swing adsorption.MOPS (kurz für „microporous organically pillared layered silicates”) sind in der Lage, zwei physikalisch sehr ähnliche Gase, CO und N2, durch eine selektive Porenöffnung zu unterscheiden. Gate-Opening scheint ein allgemeines Merkmal von MOPS zu sein, wobei die Selektivität einfach über das hochmodulare Design der MOPS eingestellt werden kann.
      PubDate: 2017-12-08T04:46:00.804404-05:
      DOI: 10.1002/ange.201710717
       
  • Rhodium-Catalyzed Cyclization of O,ω-Unsaturated Alkoxyamines: Formation
           of Oxygen-Containing Heterocycles
    • Authors: Julien Escudero; Véronique Bellosta, Janine Cossy
      Abstract: O,ω-Unsaturated N-tosyl alkoxyamines undergo unexpected RhIII-catalyzed intramolecular cyclization by oxyamination to produce oxygen-containing heterocycles. Mechanistic studies show that an aziridine intermediate seems to be responsible for the formation of the heterocycles, possibly via a RhV species.In unerwarteter Weise werden funktionalisierte Tetrahydrofurane anstelle von Isoxazolidinen erhalten, wenn N-Tosyl-O,ω-ungesättigte Alkoxyamine einer bekannten Rhodium(III)-katalysierten allylischen C-H-Aktivierung unterworfen werden. Der Anwendungsbereich der überraschenden Reaktion wird ausgelotet, und ein Mechanismus wird diskutiert, der ein Rhodium(V)-Nitrenoid und einen Aziridinierungsschritt umfasst.
      PubDate: 2017-12-08T04:42:25.932039-05:
      DOI: 10.1002/ange.201710895
       
  • Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with
           Organoboron Compounds
    • Authors: Li-Jun Xiao; Lei Cheng, Wei-Min Feng, Mao-Lin Li, Jian-Hua Xie, Qi-Lin Zhou
      Abstract: A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni−H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C−H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.Neutral bleiben: Eine Nickel(0)-katalysierte Hydroarylierung von Alkenen mit Organobor-Reagentien nutzt die OH-Gruppe eines Alkohols als Quelle für das H-Atom. Die Reaktion bietet einen hoch selektiven Zugang zu Diarylalkanen und Allylarenen unter redoxneutralen Bedingungen.
      PubDate: 2017-12-08T04:41:42.961688-05:
      DOI: 10.1002/ange.201710735
       
  • Mangankomplexe in der (De)Hydrier-Katalyse – ein Vergleich mit
           Cobalt- und Eisenkatalysatoren
    • Authors: Fabian Kallmeier; Rhett Kempe
      Abstract: Der nachhaltige Umgang mit den Ressourcen unseres Planeten ist essenziell. Edelmetalle sind sehr selten und werden vielfältig in Schlüsseltechnologien wie der Katalyse genutzt. Mangan ist das dritthäufigste Übergangsmetall der Erdkruste und aufgrund seiner kürzlich entdeckten beeindruckenden Reaktivität für Hydrierungen und Dehydrierungen ein potenzieller Edelmetall-“Ersatz”. An einen derartigen “Ersatz” sind auch Hoffnungen auf neuartige Selektivitätsprofile geknüpft, die mit Edelmetallen nicht erzielt werden können. Dass Mangankomplexe eine solche Reaktivität für (De)Hydrierungen aufweisen, wurde erstmals 2016 gezeigt. Hier fassen wir die seitdem publizierten Arbeiten auf diesem Gebiet zusammen und diskutieren im Besonderen die Bedeutung der Mangankatalysatoren im Vergleich zu Cobalt- und Eisenkatalysatoren.Vielversprechender Nachzügler: Mangankomplexe wurden in den vergangenen beiden Jahren als hochaktive Katalysatoren für diverse Hydrierungen und Dehydrierungen identifiziert. Hier werden bisherige Ergebnisse auf dem Gebiet zusammengefasst und mit Eisen- und Cobaltkatalysen verglichen.
      PubDate: 2017-12-08T04:35:50.813667-05:
      DOI: 10.1002/ange.201709010
       
  • Quantum Refinement Does Not Support Dinuclear Copper Sites in Crystal
           Structures of Particulate Methane Monooxygenase
    • Authors: Lili Cao; Octav Caldararu, Amy C. Rosenzweig, Ulf Ryde
      Abstract: Particulate methane monooxygenase (pMMO) is one of the few enzymes that can activate methane. The metal content of this enzyme has been highly controversial, with suggestions of a dinuclear Fe site or mono-, di-, or trinuclear Cu sites. Crystal structures have shown a mono- or dinuclear Cu site, but the resolution was low and the geometry of the dinuclear site unusual. We have employed quantum refinement (crystallographic refinement enhanced with quantum-mechanical calculations) to improve the structure of the active site. We compared a number of different mono- and dinuclear geometries, in some cases enhanced with more protein ligands or one or two water molecules, to determine which structure fits two sets of crystallographic raw data best. In all cases, the best results were obtained with mononuclear Cu sites, occasionally with an extra water molecule. Thus, we conclude that there is no crystallographic support for a dinuclear Cu site in pMMO.Zwei Kristallstrukturen der partikulären Methan-Monooxygenase (pMMO) wurden durch Quantenverfeinerung untersucht. Für das vermutete aktive Zentrum wurden verschiedene ein- und zweikernige Anordnungen mit unterschiedlichen Proteinliganden und ein oder zwei Wassermolekülen verglichen, um diejenige zu identifizieren, die mit den kristallographischen Daten am besten übereinstimmt. Ein zweikerniges Kupfer-Zentrum in pMMO wird von den Ergebnissen nicht unterstützt.
      PubDate: 2017-12-08T04:31:04.496668-05:
      DOI: 10.1002/ange.201708977
       
  • Solar hydrogen generation from lignocellulose
    • Authors: Moritz Kuehnel; Erwin Reisner
      Abstract: Photocatalytic reforming of lignocellulosic biomass is an emerging approach to produce renewable H2. This process combines photo-oxidation of aqueous biomass with photocatalytic hydrogen evolution at ambient temperature and pressure. Biomass conversion is less energy demanding than water splitting and generates high-purity H2 without O2 production. Direct photoreforming of raw, unprocessed biomass has the potential to provide affordable, clean energy across the globe from locally sourced materials.
      PubDate: 2017-12-08T02:42:00.79568-05:0
      DOI: 10.1002/ange.201710133
       
  • Reversing Conventional Reactivity of Mixed Oxo/Alkyl Rare Earth Complexes:
           Non-Redox Oxygen Atom Transfer
    • Authors: Xigeng Zhou; Jianquan Hong, Haiwen Tian, Lixin Zhang, Linhong Weng, Iker del Rosal, Laurent Maron
      Abstract: The preferential substitution of oxo ligands over alkyl ones of rare earth complexes is commonly considered as "impossible" due to the high oxophilicity of metal centers. Now, it has been shown that simply assembling mixed methyl/oxo rare earth complexes to a rigid trinuclear cluster framework can not only enhance the activity of the Ln-oxo bond, but also protect the highly reactive Ln-alkyl bond, thus providing a previously unrecognized opportunity to selectively manipulate the oxo ligand in the presence of numerous reactive functionalities. Such trimetallic cluster has proved to be a suitable platform for developing the unprecedented non-redox rare earth-mediated oxygen atom transfer from ketones to CS2 and PhNCS. Controlled experiments and computational studies shed light on the driving force for these reactions, emphasizing the importance of the sterical accessibility and multimetallic effect of the cluster framework in promoting reversal of reactivity of rare earth oxo complexes.
      PubDate: 2017-12-08T02:41:13.005555-05:
      DOI: 10.1002/ange.201711305
       
  • Single-cell Mass Spectrometry Approaches to Explore Cellular Heterogeneity
    • Authors: Linwen Zhang; Akos Vertes
      Abstract: Compositional diversity is a fundamental property in cell populations that is responsible for evolutionary adaptation and resilience. Single-cell analysis promises new insights into this cellular heterogeneity and the corresponding subpopulations on the genomic, transcriptomic, proteomic, and metabolomic levels. Mass spectrometry (MS) is a label-free technique that enables the multiplexed analysis of proteins, peptides, lipids, and metabolites in individual cells. The abundances of these molecular classes are correlated with the physiological states and environmental responses of the cells. In this Minireview, we discuss recent advances in single-cell MS techniques with an emphasis on sampling and ionization methods developed for volume-limited samples. Strategies for sample treatment, separation methods, and data analysis require special considerations for single cells. Ongoing analytical challenges include the need for high-throughput, high molecular coverage, minimal perturbation, subcellular heterogeneity, and non-normal statistical distributions of cellular properties. The insights obtained by single-cell MS techniques inform fundamental cell biology, immunology, and individualized medicine.
      PubDate: 2017-12-07T23:06:06.937436-05:
      DOI: 10.1002/ange.201709719
       
  • A Cesium Rare-Earth Silicate Cs3RESi6O15 (RE = Dy-Lu, Y, In): The "Parent"
           of an Unusual Structural Class Featuring a Remarkable 57 Å Unit Cell Axis
           
    • Authors: Rylan Terry; Daniel Vinton, Colin McMillen, Joseph Kolis
      Abstract: A new structural member of the broad class of A3RESi6O15 compounds has been discovered for the formula Cs3RESi6O15, where RE = Dy-Lu,Y,In. The structure is unusual in that it contains octahedrally coordinated rare earth ions whose relative orientation dictates the structure as they rotate about the c-axis supported by the cyclic Si6O15 framework. The repeat unit of the rotation is eight units generating a very long, ~57 Å, unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. The products described here are prepared as large, high quality single crystals using a high temperature (650˚C) hydrothermal method with CsOH and F- mineralizers. The presence of fluoride is essential to the formation of the product, as reactions without fluoride do not form these products.
      PubDate: 2017-12-07T14:05:54.587074-05:
      DOI: 10.1002/ange.201708798
       
  • Quantum machine learning in chemical compound space
    • Authors: Anatole von Lilienfeld
      Abstract: Rather than numerically solving the computationally demanding equationsof quantum or statistical mechanics, machine learning methods caninfer approximate solutions, interpolating previously acquired propertydata sets of molecules and materials. The case is made for quantum machine learning: An inductive molecular modeling approach which can beapplied to quantum chemistry problems.
      PubDate: 2017-12-07T14:05:52.534421-05:
      DOI: 10.1002/ange.201709686
       
  • A Zero-Dimensional Organic Seesaw-Shaped Tin Bromide with Highly Efficient
           Strongly Stokes-Shifted Deep-Red Emission
    • Authors: Chenkun Zhou; Haoran Lin, Hongliang Shi, Yu Tian, Chongin Pak, Michael Shatruk, Yan Zhou, Peter Djurovich, Maohua Du, Biwu Ma
      Abstract: We report the synthesis and characterization of (C9NH20)2SnBr4, a novel organic metal halide hybrid with a zero-dimensional (0D) structure, in which individual seesaw-shaped tin (II) bromide anions (SnBr42-) are co-crystallized with 1-butyl-1-methylpyrrolidinium cations (C9NH20+). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep-red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46%. The unique photophysical properties of this hybrid material are attributed to two major factors, (i) the 0D structure allowing the bulk crystals to exhibit the intrinsic properties of individual SnBr42- species, and (ii) the seesaw structure enabling a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.
      PubDate: 2017-12-07T11:46:04.062199-05:
      DOI: 10.1002/ange.201710383
       
  • New views of head-to-middle and cis- head-to-tail prenyltransferases:
           Structure of isosesquilavandulyl diphosphate synthase
    • Authors: Jian Gao; Tzu-Ping Ko, Lu Chen, Satish R. Malwal, Jianan Zhang, Xiangying Hu, Fiona Qu, Weidong Liu, Jian-Wen Huang, Ya-Shan Cheng, Chun-Chi Chen, Yunyun Yang, Yonghui Zhang, Eric Oldfield, Rey-Ting Guo
      Abstract: We report the first X-ray crystallographic structure of the "head-to-middle" prenyltransferase, isosesquilavandulyl diphosphate synthase, involved in biosynthesis of the merochlorin class of antibiotics. The protein adopts the ζ or cis-prenyl transferase fold but remarkably, unlike tuberculosinol adenosine synthase and other cis-prenyl transferases (e.g. cis-farnesyl, decaprenyl, undecaprenyl diphosphate synthases), the large, hydrophobic side-chain does not occupy a central hydrophobic tunnel. Instead, it occupies a surface pocket oriented at ~90º to the hydrophobic tunnel. Product chain-length control is achieved by squeezing out the ligand from the conventional allylic S1 binding site, with proton abstraction being achieved via a diphosphate-Asn-Ser relay. The structures revise and unify our thinking as to the mechanism of action of many other prenyl transferases and may also be of use in engineering new merochlorin-class antibiotics.
      PubDate: 2017-12-07T11:40:45.758862-05:
      DOI: 10.1002/ange.201710185
       
  • Deuterated Molecular Ruby with Record Luminescence Quantum Yield
    • Authors: Cui Wang; Sven Otto, Matthhias Dorn, Elisabeth Kreidt, Jakob Lebon, Laura Sran, Patrick Di Martino-Fumo, Markus Gerhards, Ute Resch-Genger, Michael Seitz, Katja Heinze
      Abstract: The recently reported luminescent chromium(III) complex [Cr(ddpd)2]3+ shows exceptionally strong near-IR emission in water under ambient conditions (QY 11 %) with a microsecond lifetime. In the absence of energy acceptors such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and theddpd ligands probes the efficiency of these oscillators in the excitedstate deactivation. Addressing these energy transfer pathways in thefirst and second coordination sphere furnishes a record 30 % quantumyield and a 2.3 millisecond lifetime for a metal complex with an earth abundant metal ion in solution at room temperature. The combinedfundamental insights will pave the way for selective design strategiesin the field of luminescent complexes with earth-abundant metal ions.
      PubDate: 2017-12-07T11:06:06.671974-05:
      DOI: 10.1002/ange.201711350
       
  • Polymer film dewetting by water/surfactant/good solvent mixtures: a
           mechanistic insight and its implications for the conservation of Cultural
           Heritage
    • Authors: Michele Baglioni; Costanza Montis, David Chelazzi, Rodorico Giorgi, Debora Berti, Piero Baglioni
      Abstract: Aqueous nanostructured fluids (NSFs) have been proposed in the recent past to remove polymer coatings from the surfaces of works of art; this process usually involves film dewetting. Here we report on a major advancement in the study of NSFs cleaning mechanisms using several complementary techniques that are employed to get a mechanistic insight on the interaction of a methacrylic/acrylic copolymer (Paraloid B72®) film laid on glass surfaces and several NSFs, based on two different solvents, i.e. propylene carbonate (PC) and 2-butanone (MEK), and two different surfactants, i.e. a nonionic alcohol ethoxylate (C9-11E6) and sodium dodecylsulfate (SDS). The experimental results provide a detailed picture of the dewetting process, where the role of each component is elucidated. These findings open new perspectives in the formulation of cleaning systems in the field of cultural heritage conservation, as well as coatings and detergency.
      PubDate: 2017-12-07T10:15:31.052555-05:
      DOI: 10.1002/ange.201710930
       
  • Triplet Tellurophene-based Acceptors for Organic Solar Cells
    • Authors: Lei Yang; Wenxing Gu, Lei Lv, Yusheng Chen, Yufei Yang, Pan Ye, Jianfei Wu, Ling Hong, Aidong Peng, Hui Huang
      Abstract: Triplet materials have been employed to achieve high performing OSCs, while the triplet nonfullerene acceptor materials have never been reported for bulk heterojunction OSCs. Herein, for the first time, three triplet molecular acceptors based on tellurophene with different extent of ring fusing were designed and synthesized for OSCs. Significantly, these molecules possess long exciton lifetime and diffusion length, leading to efficient power conversion efficiency (7.52%), which is the highest values for tellurophene based OSCs. Moreover, the influence of the extent of ring fusing on molecular geometry and OSCs performance was investigated to show the PCEs continuously increased along with increasing the extent of ring fusing. This contribution demonstrated a novel method to design high performing nonfullerene acceptors for OSCs and provided new insights for understanding the relationship between molecular geometry and OSCs performances.
      PubDate: 2017-12-07T10:10:35.164649-05:
      DOI: 10.1002/ange.201712011
       
  • Photochemical Creation of Fluorescent Quantum Defects in Semiconducting
           Carbon Nanotube Hosts
    • Authors: Xiaojian Wu; Mijin Kim, Hyejin Kwon, YuHuang Wang
      Abstract: Quantum defects are an emerging class of synthetic single photon emitters that hold potential for near-infrared imaging, chemical sensing, materials engineering, and quantum information processing. Herein, we show it is possible to optically direct the synthetic creation of molecularly tunable fluorescent quantum defects in semiconducting single-walled carbon nanotube hosts through photochemical reactions. By exciting the host semiconductor with light that resonates with its electronic transition, we find that halide-containing aryl groups can covalently bond to the sp2 carbon lattice. The reaction is independent of temperature but correlates strongly with the photon energy used to drive the reaction, suggesting a photochemical mechanism rather than photothermal effects. This type of photochemical reactions opens the possibility to control the synthesis of quantum defects using light and may enable lithographic patterning of quantum emitters with electronic and molecular precision.
      PubDate: 2017-12-07T09:35:55.035708-05:
      DOI: 10.1002/ange.201709626
       
  • Restoration of Ribozyme Tertiary Contact and Function by Using a Molecular
           Glue for RNA
    • Authors: Chikara Dohno; Maki Kimura, Kazuhiko Nakatani
      Abstract: Some RNA classes require folding into the proper higher-order structures to exert their functions. Hammerhead ribozyme (HHR) requires a folding conformation stabilized by tertiary interaction for full activity. A rationally engineered HHR was developed that was inactive, but could be activated by a synthetic RNA-binding ligand, naphthyridine carbamate tetramer with Z-stilbene linker (Z-NCTS). Binding of Z-NCTS could induce the formation of an active folding structure and thereby restore ribozyme activity, where Z-NCTS acts as a molecular glue to bring two isolated RNA loops into contact with each other. Next, we designed a Z-NCTS-responsive genetic switch using the HHR sequence inserted into the 3′ untranslated region as a cis-acting element. We demonstrated that the rationally designed ribozyme switch enabled regulation of gene expression by Z-NCTS and was functional in mammalian cells.Ein inaktives Hammerhead-Ribozym kann mithilfe eines synthetischen Liganden als RNA-Klebstoff aktiviert werden. Dabei werden zwei RNA-Schleifen in Kontakt gebracht, und die aktive Tertiärstruktur wird wiederhergestellt. Das für diesen Zweck entworfene Ribozym wirkt als Schalter und ermöglicht die Genexpression durch Z-NCTS in Säugerzellen.
      PubDate: 2017-12-07T08:57:20.860781-05:
      DOI: 10.1002/ange.201709041
       
  • Elektrochemische Synthese von Aryliodiden durch anodische
           Iododesilylierung
    • Authors: Robert Möckel; Jessica Hille, Erik Winterling, Stephan Weidemüller, Tabea Melanie Faber, Gerhard Hilt
      Abstract: Ein neuer elektrochemischer Zugang zu Iodaromaten ausgehend von Trimethylsilyl-substituierten Aromaten wird präsentiert. Durch statistische Versuchsplanung konnten sehr effiziente und milde Reaktionsbedingungen gefunden und auf eine Vielzahl von Substraten angewendet werden. Ein Kompatibilitätstest und die Verwendung der Methode zur Synthese eines 3-Iodbenzylguanidin-Derivats (Radiomarker) illustrieren die Anwendungsbreite.Holt mich hier raus: Ein neuer elektrochemischer Zugang zu Iodaromaten ausgehend von Trimethylsilyl-substituierten Aromaten wird präsentiert. Durch statistische Versuchsplanung konnten sehr effiziente und milde Reaktionsbedingungen gefunden und auf eine Vielzahl von Substraten angewendet werden. Ein Kompatibilitätstest und die Verwendung der Methode zur Synthese eines 3-Iodbenzylguanidin-Derivats (Radiomarker) illustrieren die Anwendungsbreite.
      PubDate: 2017-12-07T08:54:40.110054-05:
      DOI: 10.1002/ange.201711293
       
  • A Bottom-Up Proteomic Approach to Identify Substrate Specificity of
           Outer-Membrane Protease OmpT
    • Authors: Sarah E. Wood; Gaurav Sinsinbar, Sushanth Gudlur, Madhavan Nallani, Che-Fan Huang, Bo Liedberg, Milan Mrksich
      Abstract: Peptidanordnungen ermöglichen die Identifizierung hoch aktiver Substrate für die OmpT-Protease. M. Mrksich, B. Liedberg et al. beschreiben in ihrer Zuschrift (
      DOI : 10.1002/ange.201707535) die Herstellung der Peptidanordnungen auf selbstorganisierten Monoschichten und die massenspektrometrische Charakterisierung des Ausmaßes an Spaltung für jedes Peptid mithilfe der SAMDI-Methode. Eine häufig eingesetzte Protease-Mutante, der man eine identische Aktivität zuschreibt, zeigte eine abweichende Substratspezifität.
      PubDate: 2017-12-07T08:54:36.6791-05:00
       
  • Maximizing the Catalytic Activity of Nanoparticles through Monolayer
           Assembly on Nitrogen-Doped Graphene
    • Authors: Chao Yu; Xuefeng Guo, Mengqi Shen, Bo Shen, Michelle Muzzio, Zhouyang Yin, Qing Li, Zheng Xi, Junrui Li, Christopher T. Seto, Shouheng Sun
      Abstract: We report a facile method for assembly of a monolayer array of nitrogen-doped graphene (NG) and nanoparticles (NPs) and the subsequent transfer of two layers onto a solid substrate (S). Using 3 nm NiPd NPs as an example, we demonstrate that NiPd-NG-Si (Si=silicon wafer) can function as a catalyst and show maximum NiPd catalysis for the hydrolysis of ammonia borane (H3NBH3, AB) with a turnover frequency (TOF) of 4896.8 h−1 and an activation energy (Ea) of 18.8 kJ mol−1. The NiPd-NG-S catalyst is also highly active for catalyzing the transfer hydrogenation from AB to nitro compounds, leading to the green synthesis of quinazolines in water. Our assembly method can be extended to other graphene and NP catalyst materials, providing a new 2D NP catalyst platform for catalyzing multiple reactions in one pot with maximum efficiency.Ein vielseitiger Katalysator: Eine einfache Methode zur Anordnung von Nanopartikeln und Monoschichten von Stickstoff-dotiertem Graphen auf einem festen Träger wurde entwickelt. Das NiPd-NG-Si-Material (Si=Silicium-Wafer) ist ein hocheffizienter Katalysator für die Hydrolyse von Ammoniak-Boran und anschließende Tandemreaktionen, die mit hoher Ausbeute Chinazoline in Wasser liefern.
      PubDate: 2017-12-07T08:23:31.898133-05:
      DOI: 10.1002/ange.201709815
       
  • Photoinduced Pedalo-Type Motion in an Azodicarboxamide-Based Molecular
           Switch
    • Authors: Saeed Amirjalayer; Alberto Martinez-Cuezva, Jose Berna, Sander Woutersen, Wybren Jan Buma
      Abstract: Well-defined structural changes of molecular units that can be triggered by light are crucial for the development of photoactive functional materials. Herein, we report on a novel switch that has azodicarboxamide as its photo-triggerable element. Time-resolved UV-pump/IR probe spectroscopy in combination with quantum-chemical calculations shows that the azodicarboxamide functionality, in contrast to other azo-based chromophores, does not undergo trans–cis photoisomerization. Instead, a photoinduced pedalo-type motion occurs, which because of its volume-conserving properties enables the design of functional molecular systems with controllable motion in a confined space.Bewegung auf der Stelle: Die volumenneutrale Pedalobewegung eines molekularen Schalters wurde durch die Kombination von zeitaufgelöster Infrarotspektroskopie und quantenmechanischen Rechnungen untersucht. Diese Azodicarboamid-Systeme sind vielversprechende Kandidaten für die Implementierung von Bewegung in begrenzten Umgebungen.
      PubDate: 2017-12-07T08:23:14.938835-05:
      DOI: 10.1002/ange.201709666
       
  • MoB/g-C3N4 Interface Materials as a Schottky Catalyst to Boost Hydrogen
           Evolution
    • Authors: Zechao Zhuang; Yong Li, Zilan Li, Fan Lv, Zhiquan Lang, Kangning Zhao, Liang Zhou, Lyudmila Moskaleva, Shaojun Guo, Liqiang Mai
      Abstract: Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal–semiconductor junction principles is presented. With metallic MoB, the introduction of n-type semiconductive g-C3N4 induces a vigorous charge transfer across the MoB/g-C3N4 Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec−1 and a high exchange current density of 17 μA cm−2, which is far better than that of pristine MoB. First-principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation.Schottky-Katalysator: Die Aktivität eines metallischen MoB-Katalysators in der Wasserstoffentwicklung kann deutlich erhöht werden, indem die Oberflächenladungsdichte an einem Schottky-Kontakt mit einem n-Halbleiter vergrößert wird.
      PubDate: 2017-12-07T08:22:58.559898-05:
      DOI: 10.1002/ange.201708748
       
  • Übergangsmetall-π-Komplexierung eines Tetrahalogendiborans
    • Authors: Holger Braunschweig; Rian D. Dewhurst, J. Oscar C. Jiménez-Halla, Eduard Matito, Jonas H. Muessig
      Abstract: Die Reaktion von Tetraioddiboran (B2I4) mit trans-[Pt(BI2)I(PCy3)2] führte zur Isolierung des Diplatin(II)-Komplexes [{(Cy3P)(I2B)Pt}2(μ2:η3:η3-B2I4)], der durch den verbrückenden dianionischen Diboranyl-Liganden [B2I4]2− stabilisiert wird. Der Komplex ist der erste Übergangsmetallkomplex mit einem dianionischen Diboranyl-Liganden und ist ebenso das erste Beispiel einer intakten Koordination einer B2X4-Einheit (X=Halogen) an ein Metallzentrum.Intakt, aber reaktiv: Die Reaktion von Tetrahalogendiboranen mit trans-[Pt(BI2)I(PCy3)2] führt zu einem Diplatin(II)-Komplex mit verbrückender [B2I4]-Einheit (siehe Schema). Der Komplex ist der erste Übergangsmetallkomplex mit einem dianionischen Diboranyl-Liganden und ist ebenso das erste Beispiel einer intakten Koordination einer B2X4-Einheit (X=Halogen) an ein Metallzentrum.
      PubDate: 2017-12-07T08:22:49.256162-05:
      DOI: 10.1002/ange.201709515
       
  • Entwicklung einer DNA-Polymerase für die direkte m6A-Sequenzierung
    • Authors: Joos Aschenbrenner; Stephan Werner, Virginie Marchand, Martina Adam, Yuri Motorin, Mark Helm, Andreas Marx
      Abstract: Methoden zur Analyse von RNA-Modifikationen sind essenziell für das Forschungsfeld der Epitranskriptomik. N6-Methyladenosin (m6A) ist die häufigste Modifikation in der mRNA von Säugetieren und erfüllt Funktionen in der Regulation der Genexpression. Techniken zur Detektion dieser Modifikation basieren derzeit auf der Anreicherung von m6A-haltigen RNA-Fragmenten durch Antikörper. Dieser m6A-spezifische Schritt vor der Sequenzierung ist nötig, da die Information über die Modifikation während der reversen Transkription (RT) gelöscht wird. Um die Nachteile einer solchen indirekten Detektion zu überwinden, haben wir uns zum Ziel gesetzt, neue DNA-Polymerasen zu entwickeln, die eine direkte m6A-Sequenzierung ermöglichen. Zu diesem Zweck wurde ein Verfahren etabliert, das die Identifizierung von RT-aktiven KlenTaq-DNA-Polymerase-Varianten mit einer erhöhten Fehleinbaurate gegenüber m6A ermöglicht. So konnten m6A-haltige Stellen direkt aus RNA-Sequenzierungsdaten identifiziert werden.Vorsätzlicher Fehler: Durch ein auf Primerverlängerung basierendes Verfahren konnte eine Variante der KlenTaq-DNA-Polymerase mit erhöhter Fehleinbaurate gegenüber m6A und nicht unmodifiziertem A evolviert werden. Das Enzym wurde im RT-Schritt eines Protokolls zur Erstellung von NGS-Bibliotheken eingesetzt, und m6A-Stellen konnten direkt aus den Sequenzierungsdaten identifiziert werden.
      PubDate: 2017-12-07T08:18:12.337577-05:
      DOI: 10.1002/ange.201710209
       
  • A Vinyl Sulfone-Based Fluorogenic Probe Capable of Selective Labeling of
           PHGDH in Live Mammalian Cells
    • Authors: Sijun Pan; Se-Young Jang, Si Si Liew, Jiaqi Fu, Danyang Wang, Jun-Seok Lee, Shao Q. Yao
      Abstract: Chemical probes are powerful tools for interrogating small molecule-target interactions. With additional fluorescence Turn-ON functionality, such probes might enable direct measurements of target engagement in live mammalian cells. DNS-pE (and its terminal alkyne-containing version DNS-pE2) is the first small molecule that can selectively label endogenous 3-phosphoglycerate dehydrogenase (PHGDH) from various mammalian cells. Endowed with an electrophilic vinyl sulfone moiety that possesses fluorescence-quenching properties, DNS-pE/DNS-pE2 became highly fluorescent only upon irreversible covalent modification of PHGDH. With an inhibitory property (in vitro Ki=7.4 μm) comparable to that of known PHGDH inhibitors, our probes thus offer a promising approach to simultaneously image endogenous PHGDH activities and study its target engagement in live-cell settings.Eine fluorogene Sonde, die an endogene PHGDH aus verschiedenen Säugerzellen selektiv kovalent bindet, wurde auf Basis eines Vinylsulfon-Dansyl-Fluorophors entwickelt. Die Sonde ebnet den Weg für die Bildgebung der PHGDH-Aktivität in lebenden Zellen und die simultane Untersuchung ihres aktiven Zentrums.
      PubDate: 2017-12-07T08:18:05.803324-05:
      DOI: 10.1002/ange.201710856
       
  • Ruthenium(II)-catalyzed C-H Difluoromethylation of Ketoxime: Tuning the
           Regioselectivity from meta to para Position
    • Authors: Chunchen Yuan; Lei Zhu, Runsheng Zeng, Yu Lan, Yingsheng Zhao
      Abstract: A highly para-selective CAr-H difluoromethylation of ketoxime ether using a ruthenium catalyst has been developed. A wide variety of ketoxime ethers are compatible in the reaction, leading to the corresponding para-selective difluorometylated products in moderate to good yield. A mechanistic study clearly shows that chelation-assisted cycloruthenation is the key factor in achieving the para-selective difluoromethylation of ketoxime ethers. The density functional theory (DFT) method was used to gain a theoretical understanding of the para-selectivity.
      PubDate: 2017-12-07T08:14:22.293978-05:
      DOI: 10.1002/ange.201711221
       
  • Integration of Plasmonic Effect and Schottky Junction into Metal-Organic
           Framework Composites: Steering Charge Flow for Enhanced Visible-Light
           Photocatalysis
    • Authors: Hai-Long Jiang; Juan-Ding Xiao, Lili Han, Jun Luo, Shu-Hong Yu
      Abstract: A wide range of light absorption and rapid electron-hole separation are desired for efficient photocatalysis. Herein, on the basis of a semiconductor-like metal-organic framework (MOF), the rationally designed Pt@MOF/Au catalyst with two types of metal-MOF interfaces integrates the surface plasmon resonance excitation of Au nanorods with Pt-MOF Schottky junction, which not only extends the light absorption of the MOF from UV to visible region but also greatly accelerates charge transfer. The spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites the charge migration. As a result, the Pt@MOF/Au presents an exceptionally high photocatalytic H2 production rate by water splitting under visible light irradiation, far superior to Pt/MOF/Au, MOF/Au and other counterparts with similar Pt or Au contents, highlighting the important role of each component and the Pt location in the catalyst.
      PubDate: 2017-12-07T08:12:59.161616-05:
      DOI: 10.1002/ange.201711725
       
  • A General Approach Towards Triazole-linked Adenosine Diphosphate
           Ribosylated Peptides and Proteins
    • Authors: Qiang Liu; Hans A. V. Kistemaker, Sagar Bhogaraju, Ivan Dikic, Herman S. Overkleeft, Gijsbert A. van der Marel, Huib Ovaa, Gerbrand van der Heden van Noort, Dmitri V. Filippov
      Abstract: Current chemistries to prepare Adenosine Diphosphate ribosylated (ADPr) peptides are not generally applicable due to the labile nature of this post-translational modification and its incompatibility with strong acidic conditions used in standard solid phase peptide synthesis protocols. We present a general strategy to prepare ADPr peptide analogues based on a copper catalysed click reaction between an azide modified peptide and an alkyne modified ADPr counterpart. We expand the scope of this approach to proteins by preparing two ADPr Ubiquitin analogues carrying the biological relevant α-glycosidic linkage. Biochemical validation using Legionella effector enzyme SdeA shows that clicked Ub-ADPr is well tolerated and highlights the potential of this strategy to prepare ADPr proteins.
      PubDate: 2017-12-07T05:35:59.956573-05:
      DOI: 10.1002/ange.201710527
       
  • Sulfamate Esters Guide Selective Radical-Mediated Chlorination of
           Aliphatic C−H Bonds
    • Authors: Melanie A. Short; J. Miles Blackburn, Jennifer L. Roizen
      Abstract: Masked alcohols are particularly appealing as directing groups because of the ubiquity of hydroxy groups in organic small molecules. Herein, we disclose a general strategy for aliphatic γ-C(sp3)−H functionalization guided by a masked alcohol. Specifically, we determine that sulfamate ester derived nitrogen-centered radicals mediate 1,6-hydrogen-atom transfer (HAT) processes to guide γ-C(sp3)−H chlorination. This reaction proceeds through a light-initiated radical chain-propagation process and is capable of installing chlorine atoms at primary, secondary, and tertiary centers.Am Anfang war das Licht: Die Chlorierung aliphatischer γ-C(sp3)-H-Bindungen des Alkoholmotivs von Sulfamatestern wird ausgelöst durch N-Cl-Photolyse, gefolgt von einer ungewöhnlichen radikalvermittelten 1,6-Wasserstoffatomabstraktion und Chlorierung in einer Kettenreaktion. Die Methode führt Chloratome gezielt und selektiv an primären, sekundären und tertiären Reaktionszentren ein.
      PubDate: 2017-12-07T05:15:22.439012-05:
      DOI: 10.1002/ange.201710322
       
  • Gram-Scale Synthesis of the (−)-Sparteine Surrogate and
           (−)-Sparteine
    • Authors: James D. Firth; Steven J. Canipa, Leigh Ferris, Peter O'Brien
      Abstract: An 8-step, gram-scale synthesis of the (−)-sparteine surrogate (22 % yield, with just 3 chromatographic purifications) and a 10-step, gram-scale synthesis of (−)-sparteine (31 % yield) are reported. Both syntheses proceed with complete diastereocontrol and allow access to either antipode. Since the syntheses do not rely on natural product extraction, our work addresses long-term supply issues relating to these widely used chiral ligands.Im Gramm-Maßstab wurden (−)-Spartein und eines seiner Surrogate synthetisiert. Die konvergente Route zu den beiden Diaminen liefert (−)-Spartein über eine Racematspaltung und Rekombination. Auf dem beschriebenen Weg können die häufig genutzten chiralen Liganden zuverlässig bereitgestellt werden.
      PubDate: 2017-12-07T05:08:27.810711-05:
      DOI: 10.1002/ange.201710261
       
  • Bio- und Chemilumineszenz in der biologischen Bildgebung: von
           Luciferin-basierten Sonden zu aktivierbaren Dioxetanen
    • Authors: Nir Hananya; Doron Shabat
      Abstract: Bio- und chemilumineszierende Sonden finden weit verbreitete Anwendung für die nichtinvasive Bildgebung. Sie sind hoch empfindlich, und es genügt eine relativ einfache instrumentelle Ausrüstung, um die Messung durchzuführen. Verfügbar sind heute synthetische Luciferin-analoge Sonden, die in der In-vivo-Bildgebung bessere Eigenschaften als Luciferin zeigen. Auch photoaktivierbare Luciferin-basierte bioluminogene Sonden wurden als sehr universell verwendbare Systeme für die In-vivo-Visualisierung von Enzymen und Analyten entwickelt. Jüngste Forschungen haben ferner hoch effiziente Sonden hervorgebracht, die unter physiologischen Bedingungen eine extrem helle Chemilumineszenz zeigen. Dieser Kurzaufsatz soll demonstrieren, dass chemilumineszierende Sonden weit genug entwickelt sind, um schon bald für die Bildgebung lebender Systeme eingesetzt werden zu können.Zahlreiche Kontrastmittel in Form bio- und chemilumineszierender Verbindungen sind in den letzten zehn Jahren entwickelt worden. Dazu gehören synthetische Analoga von Luciferin, photoaktivierbare Luciferin-basierte bioluminogene Sonden und die erst kürzlich beschriebenen chemilumineszierenden Dioxetansonden mit hoher Helligkeit.
      PubDate: 2017-12-07T05:03:08.09786-05:0
      DOI: 10.1002/ange.201706969
       
  • Microemulsions, Micelles and Functional Gels. How Colloid and Soft Matter
           Preserve Works of Art
    • Authors: David Chelazzi; Rodorico Giorgi, Piero Baglioni
      Abstract: Colloid Science provides fundamental knowledge to fields such as pharmaceutical, detergency, paint and food industry. An exciting application is art conservation, which poses a challenge owing to the complex range of interfacial interactions involved in restoring artefacts. Currently, the majority of the most performing and environmentally safe cleaning and consolidation agents for artworks belong to soft matter and colloids. We report here on the development and application of increasingly complex systems, from microemulsions to semi-interpenetrating hydrogels containing such fluids. These systems have been used on diverse artefacts, from Renaissance frescos to works by Picasso and Pollock. Chemical design can be implemented to meet the requirements of curators, and knowledge of the colloids structure and dynamics can overcome serendipitous approaches of traditional conservation practice. Finally, we summarize future perspectives that soft matter and colloid science can disclose in the field of cultural heritage preservation.
      PubDate: 2017-12-07T04:37:22.310337-05:
      DOI: 10.1002/ange.201710711
       
  • Visible Light-Driven Iminyl Radical-Mediated C-C Single Bond
           Cleavage/Radical Addition Cascade of Oxime Esters
    • Authors: Wen-Jing Xiao; Xiao-Ye Yu, Jia-Rong Chen, Peng-Zi Wang, Meng-Nan Yang, Dong Liang
      Abstract: A room temperature, visible light-driven N-centered iminyl radical-mediated and redox-neutral C-C single bond cleavage/radical addition cascade reaction of oxime esters and unsaturated systems has been accomplished. The strategy tolerates a wide range of O-acyl oximes and unsaturated systems such as alkenes, silyl enol ethers, alkynes, and isonitrile, enabling highly selective formation of various chemical bonds. This protocol thus provides an efficient approach to various diversely substituted cyano-containing alkenes, ketones, carbocycles and heterocycles.
      PubDate: 2017-12-07T03:36:40.922136-05:
      DOI: 10.1002/ange.201710618
       
  • Incorporation of 2,6-Connected Azulene Units into the Backbone of
           Conjugated Polymers towards High-Performance Organic Optoelectronic
           Materials
    • Authors: Xike Gao; Hanshen Xin, Congwu Ge, Xuechen Jiao, Xiaodi Yang, Kira Rundel, Chris McNeill
      Abstract: Azulene is considered to be a promising candidate for constructing optoelectronic materials. We present herein an effective strategy to obtain high performance conjugated polymers by incorporating 2,6-connected azulene units into the polymeric backbone, and two conjugated copolymers P(TBAzDI-TPD) and P(TBAzDI-TFB) are designed and synthesized based on this strategy. They are the first two examples for 2,6-connected azulene-based conjugated polymers and exhibit unipolar n-type transistor performance with an electron mobility of up to 0.42 cm2 V-1 s-1, which is among the highest values for n-type polymeric semiconductors in bottom-gate top-contact organic field effect transistors. Besides, preliminary all-polymer solar cell devices with P(TBAzDI-TPD) as the electron acceptor and PTB7-Th as the electron donor display a power conversion efficiency of 1.82%.
      PubDate: 2017-12-07T03:36:10.776836-05:
      DOI: 10.1002/ange.201711802
       
  • Katalytische Drei-Komponenten-Maschinen: Steuerung der katalytischen
           Aktivität mittels Maschinengeschwindigkeit
    • Authors: Indrajit Paul; Abir Goswami, Nikita Mittal, Michael Schmittel
      Abstract: Drei supramolekulare Gleitsysteme DS1–DS3 wurden als Zwei-Komponenten-Aggregate aus den Gleitern S1–S3 und der Plattform D mit ihren drei Zinkporphyrin(ZnPor)-Bindungsstellen erzeugt. Die Anbindung des zweifüßigen Gleiters an die Plattform variiert mit der Donorqualität und sterischen Hinderung an den Pyridin/Pyrimidin(pyr)-Gleitfüßen und wird durch zwei NpyrZnPor-Wechselwirkungen bewirkt. Entsprechend bewegen sich die Gleiter mit unterschiedlichen Geschwindigkeiten über die drei Zinkporphyrine der Plattform: bei Raumtemperatur mit 32.2, 220 und 440 kHz. Die Zugabe von N-Methylpyrrolidin als Organokatalysator zu DS1–DS3 erzeugt katalytische Drei-Komponenten-Maschinen. Für eine konjugierte Addition als Testreaktion kann man eine Korrelation zwischen der Maschinengeschwindigkeit des Gleitsystems und den Ausbeuten der katalytischen Reaktion feststellen. Mit abnehmender thermodynamischer Bindung des Gleiters nimmt sowohl die Frequenz der Gleitbewegung als auch die Ausbeute der katalytischen Reaktion zu.Die Drehzahl macht's! Die Verknüpfung eines Ausgabesignals (hier Katalyse) mit der Geschwindigkeit einer mechanischen Bewegung ist ein Charakteristikum einer Maschine. Mit zunehmender Gleitgeschwindigkeit der Drei-Komponenten-Maschine wird die Katalyse einer organischen Transformation gesteigert. Erklärt werden kann dieser Effekt durch eine dynamische Nachbargruppen-Beteiligung.
      PubDate: 2017-12-07T02:36:20.451647-05:
      DOI: 10.1002/ange.201709644
       
  • A Gold-Catalyzed Domino Cyclization Enabling Rapid Construction of Diverse
           Polyheterocyclic Frameworks
    • Authors: Yi He; Zhenghua Li, Koen Robeyns, Luc Van Meervelt, Erik V. Van der Eycken
      Abstract: We report herein an efficient gold(I)-catalyzed post-Ugi domino dearomatization/ipso-cyclization/Michael sequence that enables access to libraries of diverse (hetero)arene-annulated tricyclic heterocycles. This process affords novel complex polycyclic scaffolds in moderate to good yields from readily available acyclic precursors with excellent chemo-, regio-, and diastereoselectivity. The power of this strategy has been demonstrated by the rapid synthesis of 40 highly functionalized polyheterocycles bearing indole, pyrrole, (benzo)furan, (benzo)thiophene, pyrazole, and electron-rich arene groups in two operational steps.Vielseitigkeitsprüfung: Eine Gold(I)-katalysierte Dominosequenz aus Dearomatisierung, ipso-Cyclisierung und Michael-Reaktion ermöglicht den Zugang zu diversen (Hetero)Aren-anellierten tricyclischen Heterocyclen aus leicht verfügbaren Vorstufen. Die Leistungsfähigkeit dieser Strategie wurde anhand der schnellen Synthese von 40 hochfunktionalisierten Polyheterocyclen demonstriert.
      PubDate: 2017-12-07T02:32:47.173209-05:
      DOI: 10.1002/ange.201710592
       
  • Kryo-Elektronenmikroskopie revolutioniert die Strukturbestimmung von
           Biomolekülen
    • Authors: Stefan Raunser
      Abstract: Kalt erwischt: Der Nobelpreis für Chemie 2017 geht an Jacques Dubochet, Joachim Frank und Richard Henderson für die Entwicklung der Kryo-Elektronenmikroskopie (Kryo-EM) zur hochauflösenden Strukturbestimmung von Biomolekülen in Lösung. Dieses Highlight beschreibt, wie sich die Methode der Kryo-EM vom Bau des ersten Transmissionselektronenmikroskops im Jahr 1931 bis zur heutigen, ausgereiften Technik entwickelt hat (Beispiel: Struktur eines F-Aktins).
      PubDate: 2017-12-07T02:31:34.150461-05:
      DOI: 10.1002/ange.201710679
       
  • Initial Steps of Amyloidogenic Peptide Assembly Revealed by Cold-Ion
           Spectroscopy
    • Authors: Jakub Ujma; Vladimir Kopysov, Natalia S. Nagornova, Lukasz G. Migas, Maria Giovanna Lizio, Ewan W. Blanch, Cait MacPhee, Oleg V. Boyarkin, Perdita E. Barran
      Abstract: The early stages of fibril formation are difficult to capture in solution. We use cold-ion spectroscopy to examine an 11-residue peptide derived from the protein transthyretin and clusters of this fibre-forming peptide containing up to five units in the gas phase. For each oligomer, the UV spectra exhibit distinct changes in the electronic environment of aromatic residues in this peptide compared to that of the monomer and in the bulk solution. The UV spectra of the tetra- and pentamer are superimposable but differ significantly from the spectra of the monomer and trimer. Such a spectral evolution suggests that a common structural motif is formed as early as the tetramer. The presence of this stable motif is further supported by the low conformational heterogeneity of the tetra- and pentamer, revealed from their IR spectra. From comparison of the IR-spectra in the gas and condensed phases, we propose putative assignments for the dominant motif in the oligomers.Das Frühstadium der Amyloidbildung eines von dem Protein Transthyretin abgeleiteten Peptids mit 11 Resten wurde in der Gasphase mit UV- und IR-Spektroskopie kalter Ionen studiert. Veränderungen der Spektren sprechen dafür, dass schon ab der Peptidtrimerisierung ein allgemeines Strukturmotiv auftritt.
      PubDate: 2017-12-07T02:31:02.106209-05:
      DOI: 10.1002/ange.201710188
       
  • A Redox-Activated G-Quadruplex DNA Binder Based on a
           Platinum(IV)–Salphen Complex
    • Authors: Stephane Bandeira; Jorge Gonzalez-Garcia, Evangelina Pensa, Tim Albrecht, Ramon Vilar
      Abstract: There has been increasing interest in the development of small molecules that can selectively bind to G-quadruplex DNA structures. The latter have been associated with a number of key biological processes and therefore are proposed to be potential targets for drug development. Herein, we report the first example of a reduction-activated G-quadruplex DNA binder. We show that a new octahedral platinum(IV)–salphen complex does not interact with DNA in aqueous media at pH 7.4; however, upon addition of bioreductants such as ascorbic acid or glutathione, the compound is readily reduced to the corresponding square planar platinum(II) complex. In contrast to the parent platinum(IV) complex, the in situ generated platinum(II) complex has good affinity for G-quadruplex DNA.Reduktion aktiviert einen oktaedrisch koordinierten Platin(IV)-Salphen-Komplex, der in wässrigem Milieu bei pH 7.4 nicht mit DNA wechselwirkt, zur Bindung an G-Quadruplexe. Biologische Reduktionsmittel wie Ascorbinsäue oder Glutathion überführen den Platin(IV)-Komplex in einen quadratisch-planar koordinierten Platin(II)-Komplex mit hoher Affinität für G-Quadruplex-DNA.
      PubDate: 2017-12-07T02:30:45.384426-05:
      DOI: 10.1002/ange.201709968
       
  • Direct Dehydroxytrifluoromethoxylation of Alcohols
    • Authors: Xiaohuan Jiang; Zhijie Deng, Pingping Tang
      Abstract: The first example of a direct dehydroxytrifluoromethoxylation of alcohols has been developed. This method generated an alkyl fluoroformate in situ from alcohols, followed by nucleophilic trifluoromethoxylation with trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxylation reagent. The reaction is operationally simple and scalable, and it proceeds under mild reaction conditions to provide access to a wide range of trifluoromethyl ethers from alcohols. In addition, this method is suitable for the late-stage trifluoromethoxylation of complex small molecules.Kurz und einfach: Die direkte Dehydroxytrifluormethoxylierung von Alkoholen mit Trifluormethylarylsulfonat (TFMS) ist einfach durchzuführen und ermöglicht die Synthese von Gramm-Mengen. Erste mechanistische Studien lassen eine Alkylfluorformiat-Zwischenstufe vermuten, die über eine nukleophile Trifluormethoxylierung weiterreagiert.
      PubDate: 2017-12-07T02:26:11.313563-05:
      DOI: 10.1002/ange.201711050
       
  • Boosting Electrochemical Water Oxidation with Metal Hydroxide Carbonate
           Templated Prussian Blue Analogues
    • Authors: Arindam Indra; Ungyu Paik, Taeseup Song
      Abstract: Development of efficient and stable catalyst systems with low cost, abundant and non-toxic materials is the primary demand for the electrochemical water oxidation. Here, we report a unique method for the syntheses of metal hydroxide carbonate templated Prussian blue analogues (PBAs) on carbon cloth and their outstanding water oxidation activities in alkaline medium. The best water oxidation activity is obtained with cobalt hydroxide carbonate templated t-CoII-CoIII with overpotential as low as 240 mV to reach the current density 10 mA cm-2 and produces constant current over 48 h in chronoamperometric measurements. Moreover, the catalysts outperform the activities of the PBAs prepared without any template and even the noble metal catalyst RuO2. Spectroscopic and microscopic studies clearly prove that the PBAs are transformed into layered hydroxide-oxyhydroxide structures during electrochemical process and provide the active sites for the water oxidation.
      PubDate: 2017-12-07T01:36:31.187046-05:
      DOI: 10.1002/ange.201710809
       
  • Chemicals on demand: Photo-induced release from nano- and microparticle
           containers
    • Authors: Ulrich S. Schubert; Christoph Englert, Ivo Nischang, Cornelia Bader, Philipp Borchers, Julien Alex, Michael Proehl, Martin Hentschel, Matthias Hartlieb, Anja Traeger, Georg Pohnert, Stephanie Schubert, Michael Gottschaldt
      Abstract: A benzoin-derived diol linker was synthesized and used to create biocompatible polyesters, which can be fully decomposed on demand triggered by UV light. Extensive structural optimization of the linker unit was performed to enable a defined encapsulation of structurally diverse organic compounds in polymeric structures and a well-controllable polymer cleavage process. Selective tracking of release kinetics of encapsulated model compounds from the polymeric nano- and microparticle containers was enabled by confocal laser scanning microscopy as a proof-of-principle for desired applications. The model compounds comprised physico-chemical properties from fully hydrophilic to fully hydrophobic. Demonstrated biocompatibility of the utilized polyesters and degradation products enables advanced applications, e.g. for smart packaging of UV sensitive pharmaceuticals or nutrition components, or even in the area of spatially-selective self-healing processes.
      PubDate: 2017-12-06T22:07:00.362828-05:
      DOI: 10.1002/ange.201710756
       
  • Breaking Unstrained C-C Bond in Acenes by Boron and Light: Transformation
           of Naphthalene to Benzoborepin
    • Authors: Suning Wang; Kang Yuan, Ming-feng Hu, Xiang Wang, Tai Peng, nan wang, Quansong Li
      Abstract: Naphthalene and acenaphthene with peri 2-py and BMes2 (Mes = mesityl) substituents have been found to undergo facile phototransformation, cleaving a C-C bond of naphthalene and forming 2-py-bound benzoborepins as the major products. Mechanistic pathways of this new photoreaction are established by examining both excited and ground states using CASSCF and CASPT2 methods with DFT and TD-DFT. The Mes to py-naphthyl charge transfer transition and the Mes migration from boron to naphthyl drive this unprecedented C-C bond cleavage and boron insertion reaction.
      PubDate: 2017-12-06T15:05:37.122035-05:
      DOI: 10.1002/ange.201711658
       
  • Heterotelechelic polymers via ring opening metathesis and regioselective
           chain transfer
    • Authors: Andreas F.M. Kilbinger; Peng Liu, Mohammad Yasir, Albert Ruggi
      Abstract: Heterotelechelic polymers were synthesized via a kinetic telechelic ring opening metathesis polymerization method relying on the regioselective cross metathesis of the propagating Grubbs' first generation catalyst with cinnamyl alcohol derivatives. This procedure allowed the synthesis of hetero-bis-end-functional polymers in a one-pot setup. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer. The end functional groups can be changed using different aromatically substituted cinnamyl alcohol derivatives. Different monomers were investigated and the presence of the functional groups was shown by NMR spectroscopy and MALDI-ToF mass spectrometry. Labeling experiments with dyes were conducted to demonstrate the orthogonal addressability of both chain ends of the heterotelechelic polymers obtained.
      PubDate: 2017-12-06T13:06:39.727039-05:
      DOI: 10.1002/ange.201708733
       
  • Fabrication of defined polydopamine nanostructures by DNA
           origami-templated polymerization
    • Authors: Yu Tokura; Sean Harvey, Chaojian Chen, Yuzhou Wu, David Yuen Wah Ng, Tanja Weil
      Abstract: A versatile, bottom-up approach allows the controlled fabrication of polydopamine (PD) nanostructures on DNA origami. PD is a biosynthetic polymer that has been investigated as an adhesive and promising surface coating material. However, the control of dopamine polymerization is challenged by the multistage-mediated reaction mechanism and diverse chemical structures in PD. DNA origami decorated with multiple horseradish peroxidase-mimicking DNAzyme motifs was used to control the shape and size of PD formation with nanometer resolution. These fabricated PD nanostructures can serve as "supramolecular glue" for controlling DNA origami conformations. Facile liberation of the PD nanostructures from the DNA origami templates has been achieved in acidic medium. This presented DNA origami-controlled polymerization of a highly crosslinked polymer provides a unique access towards anisotropic PD architectures with distinct shapes that were retained even in the absence of the DNA origami template
      PubDate: 2017-12-06T11:05:56.485105-05:
      DOI: 10.1002/ange.201711560
       
  • Cross-Coupling of Sodium Sulfinates with Aryl, Heteroaryl and Vinyl
           Halides by Nickel/photoredox dual catalysis
    • Authors: Huifeng Yue; Chen Zhu, Magnus Rueping
      Abstract: An efficient photoredox/nickel dual catalyzed sulfonylation reaction of aryl, heteroaryl, and vinyl halides has been achieved for the first time. This newly developed sulfonylation protocol provides a versatile method for the synthesis of diverse aromatic sulfones at room temperature and shows excellent functional group tolerance. The electrophilic coupling partners are not limited to aryl, heteroaryl and vinyl bromides but also less reactive aryl chlorides are suitable substrates for this transformation.
      PubDate: 2017-12-06T11:05:40.434788-05:
      DOI: 10.1002/ange.201711104
       
  • Visible-light Emulsion Photopolymerization of Styrene
    • Authors: Frédéric Le Quéméner; Daniel Subervie, Fabrice Morlet-Savary, Jacques Lalevée, Muriel Lansalot, Elodie Bourgeat-Lami, Emmanuel Lacote
      Abstract: The photopolymerization of styrene in emulsion is achieved in a conventional double wall reactor equipped with a LED ribbon coiled around the external glass wall. Styrene mixed to acridine orange is added to the water phase containing sodium dodecyl sulfate, a water-soluble N-heterocyclic carbene-borane and disulfide, and irradiated. Highly stable latexes are obtained, with particles up to a diameter of 300 nm. The ability to reach such large particles sizes via a photochemical process in a dispersed medium is due to the use of visible light: the photons in the visible range are less scattered by larger objects and thus penetrate and initiate better the polymerizations. They are also greener and cheaper to produce via LEDs, and much safer than UVs. The method presented does not require any specific glassware; it works at lower temperature and delivers larger particles compared to thermal processes at similar solids contents and surfactant concentrations.
      PubDate: 2017-12-06T10:05:38.39993-05:0
      DOI: 10.1002/ange.201710488
       
  • Synthese und Reaktivität von Nickel-stabilisierten μ2:η2,η2-P2-, As2-
           und PAs-Einheiten
    • Authors: Gabriele Hierlmeier; Alexander Hinz, Robert Wolf, Jose M. Goicoechea
      Abstract: Reaktionen der paramagnetischen Nickel(I)-Verbindungen CpNi(NHC) (Cp=Cyclopentadienyl; NHC=1,3-Bis(2,4,6-trimethylphenyl)imidazol-2-yliden (IMes) bzw. 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-yliden (IPr)) mit [Na(Dioxan)x][PnCO] (Pn=P, As) ergeben symmetrische bimetallische Verbindungen (μ2:η2,η2-E2){Ni(NHC)(CO)}2. Mehrere Intermediate wurden identifiziert und charakterisiert, unter anderem eine Verbindung mit dem für das PCO−-Anion zuvor unbekannten μ2:η2,η2-Koordinationsmodus. Untersuchungen der Folgechemie zeigten, dass bei der Reaktion von (μ2:η2,η2-Pn2){Ni(IMes)(CO)}2 mit Kohlenstoffmonoxid die Pn2-Einheit freigesetzt wird. Im Fall der phosphorhaltigen Spezies führt dies zur Bildung von P4 und im Fall von (μ2:η2,η2-As2){Ni(IMes)(CO)}2 zur Bildung von elementarem Arsen.Butterfly-Effekt: Das Reaktionsverhalten zweier paramagnetischer Nickel(I)-Verbindungen CpNi(NHC) (Cp=Cyclopentadienyl; NHC=N-heterocyclisches Carben) mit [Na(Dioxan)x][PnCO] (Pn=P, As) wird beschrieben.
      PubDate: 2017-12-06T09:06:45.530327-05:
      DOI: 10.1002/ange.201710582
       
  • Ruthenium(II)-Catalyzed Synthesis of Spirobenzofuranones by a
           Decarbonylative Annulation Reaction
    • Authors: Partha P. Kaishap; Gauri Duarah, Bipul Sarma, Dipak Chetia, Sanjib Gogoi
      Abstract: The first decarbonylative insertion of an alkyne through C−H/C−C activation of six-membered compounds is reported. The Ru-catalyzed reaction of 3-hydroxy-2-phenyl-chromones with alkynes works most efficiently in the presence of the ligand PPh3 to provide spiro-indenebenzofuranones. Unlike previously reported metal-catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide.Sequenzen aus Ruthenium(II)-katalysierter C-H-/C-C-Aktivierung, Alkininsertion und Decarbonylierung in Umsetzungen von 3-Hydroxy-2-phenylchromonen mit disubstituierten Alkinen liefern Spiroindenbenzofuranone in guten Ausbeuten.
      PubDate: 2017-12-06T09:06:32.839188-05:
      DOI: 10.1002/ange.201710049
       
  • Isoindigo-3,4-Difluorothiophene Polymer Acceptors Yield “All-Polymer”
           Bulk-Heterojunction Solar Cells with over 7 % Efficiency
    • Authors: Shengjian Liu; Yuliar Firdaus, Simil Thomas, Zhipeng Kan, Federico Cruciani, Sergei Lopatin, Jean-Luc Bredas, Pierre M. Beaujuge
      Abstract: Poly(isoindigo-alt-3,4-difluorothiophene) (PIID[2F]T) analogues used as “polymer acceptors” in bulk-heterojunction (BHJ) solar cells achieve>7 % efficiency when used in conjunction with the polymer donor PBFTAZ (model system; copolymer of benzo[1,2-b:4,5-b′]dithiophene and 5,6-difluorobenzotriazole). Considering that most efficient polymer-acceptor alternatives to fullerenes (e.g. PC61BM or its C71 derivative) are based on perylenediimide or naphthalenediimide motifs thus far, branched alkyl-substituted PIID[2F]T polymers are particularly promising non-fullerene candidates for “all-polymer” BHJ solar cells.Polymere als Sonnenanbeter: Analoga von Poly(isoindigo-alt-3,4-difluorthiophen) (PIID[2F]T) bieten eine Alternative zu Fullerenen in ausschließlich aus Polymeren aufgebauten Bulk-Heterokontakt(BHJ)-Solarzellen. Die Verwendung von PIID[2F]T mit einem Polymerdonor mit großer Bandlücke ergibt Effizienzen von bis zu 7.3 % und für BHJ-Solarzellen sehr gute Leerlaufspannungen von ca. 1.0 V.
      PubDate: 2017-12-06T09:06:14.232937-05:
      DOI: 10.1002/ange.201709509
       
  • Eine biokatalytische oxidative Kaskade für die Umsetzung von Fettsäuren
           zu α-Ketosäuren mit interner H2O2-Regeneration
    • Authors: Somayyeh Gandomkar; Alexander Dennig, Andela Dordic, Lucas Hammerer, Mathias Pickl, Thomas Haas, Mélanie Hall, Kurt Faber
      Abstract: Eine Wertschöpfung aus natürlichen Kohlenstoffquellen erfordert die Funktionalisierung von biobasierten Chemikalien. Eine atomeffiziente biokatalytische oxidative Kaskade wurde entwickelt, um aus gesättigten Fettsäuren α-Ketosäuren herzustellen. Dafür wurde ein Cytochrom P450 im Peroxygenase-Modus für die regioselektive α-Hydroxylierung der Fettsäuren gemeinsam mit α-Hydroxysäure-Oxidase(n) für die nachfolgende enantioselektive Oxidation eingesetzt, was zu einer internen Regeneration des Oxidationsmittels H2O2 führte. Dadurch konnte die Zersetzung der Ketosäure unterdrückt werden, und die Lebensdauer des Biokatalysators wurde wenig beeinflusst. Die O2-abhängige Kaskade beruht auf katalytischen Mengen an H2O2 und bildet Wasser als einziges Nebenprodukt. Aus Octansäure konnte unter milden Bedingungen 2-Oxooctansäure in einer simultanen zweistufigen Eintopf-Kaskade in wässrigem Puffer mit bis zu>99 % Umsatz ohne Anreicherung der Hydroxysäure hergestellt werden. Das Produkt wurde in präparativem Maßstab mit 91 % Ausbeute isoliert, und die Kaskade wurde für Fettsäuren mit verschiedenen Kettenlängen angewendet (C6:0 bis C10:0).Eine atomeffiziente biokatalytische oxidative Kaskade mit einer P450-Monooxygenase im Peroxygenase-Modus und α-Hydroxysäure Oxidase(n) ermöglicht die Umsetzung von gesättigten Fettsäuren zu α-Ketosäuren mit interner Regeneration des Oxidationsmittels H2O2. Insgesamt benötigt die O2-abhängige Kaskade nur katalytische Mengen an H2O2 und bildet Wasser als einziges Nebenprodukt.
      PubDate: 2017-12-06T09:06:00.272168-05:
      DOI: 10.1002/ange.201710227
       
  • Exploiting the Strong Hydrogen Bond Donor Properties of a Borinic Acid
           Functionality for Fluoride Anion Recognition
    • Authors: Chang-Hong Chen; François P. Gabbaï
      Abstract: Borinic acids have typically not been considered as hydrogen bond donor groups in molecular recognition. Described herein is a bifunctional borane/borinic acid derivative (2) in which the two functionalities are connected by a 1,8-biphenylenediyl backbone. Anion binding studies reveal that 2 readily binds a fluoride anion by formation of a unique B−F⋅⋅⋅H−O−B hydrogen bond. This hydrogen bond is characterized by a short H-F distance of 1.79(3) Å and a large coupling constant (1JHF) of 57.2 Hz. The magnitude of this interaction, which has also been investigated computationally, augments the fluoride anion binding properties of 2, thus making it compatible with aqueous environments.Ringübergreifende Kooperation: Die Borinsäurefunktion überbrückt die Bindetasche einer diborierten elektrophilen Wirtspezies, um mit einem Boran-gebundenen Fluorid-Anion eine starke Wasserstoffbrücke einzugehen. Die B-F⋅⋅⋅H-O-B-Wechselwirkung stabilisiert den Komplex in wässrigen Lösungen, was das Potenzial von Borinsäuren als Wasserstoffbrückendonoren belegt.
      PubDate: 2017-12-06T09:05:55.309784-05:
      DOI: 10.1002/ange.201709494
       
  • Dynamic Cross-Exchange in Halophosphonium Species: Direct Observation of
           Stereochemical Inversion in the Course of an SN2 Process
    • Authors: Kirill Nikitin; Elizabeth V. Jennings, Sulaiman Al Sulaimi, Yannick Ortin, Declan G. Gilheany
      Abstract: The complex fluxional interconversions between otherwise very similar phosphonium bromides and chlorides R3PX+X− (R=Alk, Ar, X=Cl or Br) were studied by NMR techniques. Their energy barriers are typically ca. 11 kcal mol−1, but rise rapidly as bulky groups are attached to phosphorus, revealing the importance of steric factors. In contrast, electronic effects, as measured by Hammett analysis, are modest (ρ 1.46) but still clearly indicate negative charge flow towards phosphorus in the transition state. Most significantly, detailed analysis of the exchange pathways unequivocally, and for the first time in any such process, shows that nucleophilic attack of the nucleophilic anion on the tetrahedral centre results in inversion of configuration.Die Energiebarriere des Halogenaustauschs in halogenierten Phosphorspezies steigt schnell mit der Einführung von entweder sperrigen Substituenten oder Elektronendonorgruppen. Bei doppelter Aufhebung der Entartung (siehe Schema) gibt eine Messung des Diastereomerenprofils direkte Rückschlüsse über die stereochemische Inversion im Zuge eines SN2-Prozesses.
      PubDate: 2017-12-06T09:05:49.333984-05:
      DOI: 10.1002/ange.201708649
       
  • Structure Re-Determination and Superconductivity Observation of Bulk 1T
           MoS2
    • Authors: Yuqiang Fang; Jie Pan, Jianqiao He, Ruichun Luo, Dong Wang, Xiangli Che, Kejun Bu, Wei Zhao, Pan Liu, Gang Mu, Hui Zhang, Tianquan Lin, Fu-Qiang Huang
      Abstract: 2H MoS2 has been intensively studied because of layer-dependent electronic structures and novel physical properties. Though the metastable 1T MoS2 with the [MoS6] octahedron was observed from the microscopic area, the true crystal structure of 1T phase has not been determined strictly. Moreover, the true physical properties have not been demonstrated from experiments due to the challenge for the preparation of pure 1T MoS2 crystals. Here, we successfully synthesized the 1T MoS2 single crystals and re-determined the crystal structure of 1T MoS2 from single-crystal X-ray diffraction. 1T MoS2 crystalizes in space group P-3m1 with a cell of a = b = 3.190(3) Å and c = 5.945(6) Å. The individual MoS2 layer consists of MoS6 octahedron sharing edge with each other. More surprisingly, the bulk 1T MoS2 crystals undergo a superconducting transition of Tc = 4 K, which is the first observation of superconductivity in pure 1T MoS2 phase.
      PubDate: 2017-12-06T08:07:00.074148-05:
      DOI: 10.1002/ange.201710512
       
  • Total Synthesis of Bryostatin 8 via an Organosilane-Based Strategy
    • Authors: Zhen Lei Song; Yuebao Zhang, Qianyou Guo, Ji Lu, Xianwei Sun, Qiang Pu, Yanjun Cao, Zhiwen Chu, Lu Gao
      Abstract: Convergent total synthesis of bryostatin 8 has been accomplished via an organosilane-based strategy. The C ring is constructed stereoselectively through geminal bis(silane)-based [1,5]-Brook rearrangement, and the B ring through geminal bis(silane)-based Prins cyclization, efficiently joining the northern and southern parts of the molecule.
      PubDate: 2017-12-06T08:06:50.513172-05:
      DOI: 10.1002/ange.201711452
       
  • Highly Crystalline Mesoporous C60 with Ordered Pores: A Class of
           Nanomaterials for Energy Applications
    • Authors: Mercy R. Benzigar; Stalin Joseph, Hamid Ilbeygi, Dae-Hwan Park, Sujoy Sarkar, Goutam Chandra, Siva Umapathy, Sampath Srinivasan, Siddulu Naidu Talapaneni, Ajayan Vinu
      Abstract: Highly ordered mesoporous C60 with a well-ordered porous structure and a high crystallinity is prepared through the nanohard templating method using a saturated solution of C60 in 1-chloronaphthalene (51 mg mL−1) as a C60 precursor and SBA-15 as a hard template. The high solubility of C60 in 1-chloronaphthalene helps not only to encapsulate a huge amount of the C60 into the mesopores of the template but also supports the oligomerization of C60 and the formation of crystalline walls made of C60. The obtained mesoporous C60 exhibits a rod-shaped morphology, a high specific surface area (680 m2 g−1), tuneable pores, and a highly crystalline wall structure. This exciting ordered mesoporous C60 offers high supercapacitive performance and a high selectivity to H2O2 production and methanol tolerance for ORR. This simple strategy could be adopted to make a series of mesoporous fullerenes with different structures and carbon atoms as a new class of energy materials.Gut geordnete mesoporöse Fullerenstrukturen mit hochkristallinen C60-Wänden wurden mithilfe von mesoporösen Siliciumoxid-Nanotemplaten (SBA-15) und eines Polymerisationsschritts hergestellt. Das Resultat ist ein hoch leistungsfähiges Material für die Energiespeicherung und -umwandlung.
      PubDate: 2017-12-06T07:41:32.475058-05:
      DOI: 10.1002/ange.201710888
       
  • Einblicke in die duale Aktivität einer bifunktionalen
           Dehydratase-Cyclase-Domäne
    • Authors: Kwang Hoon Sung; Gesche Berkhan, Tim Hollmann, Lisa Wagner, Wulf Blankenfeldt, Frank Hahn
      Abstract: Sauerstoffheterocyclen sind verbreitete Strukturmotive in Polyketid-Naturstoffen. Wir berichten über strukturelle und mechanistische Untersuchungen zu AmbDH3, einer Polyketidsynthase-Domäne mit dualer Aktivität als Dehydratase (DH) und pyranbildende Cyclase in der Ambruticin-Biosynthese. AmbDH3 ähnelt monofunktionalen DH-Domänen und verwendet H51 und D215 zur Dehydratisierung. Durch Mutationsstudien und In-vitro-Experimente konnte V173 als entscheidende Aminosäure für die Cyclisierungsaktivität identifiziert werden. Vergleichbare Motive wurden zudem in der scheinbar monofunktionalen Domäne AmDH2 gefunden, welche zusätzlich eine unerwartete Cyclisierungsaktivität zeigte. Unsere Ergebnisse ebnen den Weg zur möglichen Entdeckung bisher verborgener Cyclasen in Biosynthesewegen. Sie ermöglichen zudem interessante Aussichten für die Entwicklung neuer Biokatalysatoren für die chemoenzymatische Synthese und die Herstellung pyranhaltiger Polyketide durch kombinatorische Biosynthese.Die Kristallstruktur der bifunktionalen Dehydratase-Cyclase AmbDH3 aus der Ambruticin-Biosynthese wurde mit einer Auflösung von 1.17 Å gelöst. Bioinformatische Analyse und Molekulare Modellierungen identifizierten eine für die Cyclisierungsaktivität essenzielle Y-V-Mutation im aktiven Zentrum. Eine mit In-vitro-Experimenten kombinierte Mutationsstudie bestätigte die zentrale Rolle von V173.
      PubDate: 2017-12-06T07:40:54.592505-05:
      DOI: 10.1002/ange.201707774
       
  • Catalytic Dibenzocyclooctene Synthesis via Cobalt(III)–Carbene Radical
           and ortho-Quinodimethane Intermediates
    • Authors: Colet te Grotenhuis; Naudin van den Heuvel, Jarl Ivar van der Vlugt, Bas de Bruin
      Abstract: The metalloradical activation of ortho-benzallylaryl N-tosyl hydrazones with [Co(TPP)] (TPP=tetraphenylporphyrin) as the catalyst enabled the controlled exploitation of the single-electron reactivity of the redox non-innocent carbene intermediate. This method offers a novel route to prepare eight-membered rings, using base metal catalysis to construct a series of unique dibenzocyclooctenes through selective Ccarbene−Caryl cyclization. The desired eight-membered-ring products were obtained in good to excellent yields. A large variety of aromatic substituents are tolerated. The proposed reaction mechanism involves intramolecular hydrogen atom transfer (HAT) to CoIII–carbene radical intermediates followed by dissociation of an ortho-quinodimethane that undergoes 8π cyclization. The mechanism is supported by DFT calculations, and the presence of radical-type intermediates was confirmed by trapping experiments.Metalloradikal-Aktivierung der gezeigten N-Tosylhydrazone mit [Co(TPP)] ermöglicht die effiziente Synthese einer Reihe von Dibenzocyclooctenen in guten bis hervorragenden Ausbeuten. Der postulierte Reaktionsmechanismus umfasst einen intramolekularen Wasserstoffatomtransfer zu einem CoIII-Carben-Radikal gefolgt von der Dissoziation eines ortho-Chinodimethans, das in einer 8π-Cyclisierung weiterreagiert.
      PubDate: 2017-12-06T07:40:46.588231-05:
      DOI: 10.1002/ange.201711028
       
  • Photocatalytic Oxygen Evolution from Functional Triazine-Based Polymers
           with Tunable Band Structures
    • Authors: Zhi-An Lan; Yuanxing Fang, Yongfan Zhang, Xinchen Wang
      Abstract: Conjugated polymers (CPs) are emerging and appealing light harvesters for photocatalytic water splitting owing to their adjustable band gap and facile processing. Herein, we report an advanced mild synthesis of three conjugated triazine-based polymers (CTPs) with different chain lengths by increasing the quantity of electron-donating benzyl units in the backbone. Varying the chain length of the CTPs modulates their electronic, optical, and redox properties, resulting in an enhanced performance for photocatalytic oxygen evolution, which is the more challenging half-reaction of water splitting owing to the sluggish reaction kinetics. Our results could stimulate interest in these functional polymers where a molecular engineering strategy enables the production of suitable semiconductor redox energetics for oxygenic photosynthesis.Optimierte Kettenlängen: Konjugierte Triazin-basierte Polymere mit justierbaren Bandstrukturen und optischen Eigenschaften wurden als organische Halbleiter in der photokatalytischen Sauerstoffentwicklung eingesetzt. Die Leistung der Polymere kann durch Veränderungen der Kettenstruktur optimiert werden, was die Vorteil von Polymeren für Anwendungen in der oxygenen Photosynthese verdeutlicht.
      PubDate: 2017-12-06T07:36:12.967741-05:
      DOI: 10.1002/ange.201711155
       
  • Atropoenantioselective Redox-Neutral Amination of Biaryl Compounds through
           Borrowing Hydrogen and Dynamic Kinetic Resolution
    • Authors: Jianwei Zhang; Jian Wang
      Abstract: We report herein a novel atropoenantioselective redox-neutral amination of biaryl compounds triggered by a cascade of borrowing hydrogen and dynamic kinetic resolution under the cooperative catalysis of a chiral iridium complex and an achiral Brønsted acid. This protocol features broad substrate scope and good functional-group tolerance, and allows the rapid assembly of axially chiral biaryl compounds in good to high yields and with high to excellent enantioselectivity.Clever kombiniert: Biarylverbindungen mit o-Hydroxy- und o-Hydroxymethylgruppe unterliegen einer redoxneutralen Aminierung über eine Kaskade aus Wasserstoff-Ausleihe und dynamischer kinetischer Racematspaltung unter der kooperativen Katalyse eines chiralen Iridiumkomplexes und einer achiralen Brønsted-Säure (siehe Schema). Diese Methode ermöglichte die zügige Synthese einer Reihe von axial-chiralen Biarylverbindungen in guten Ausbeuten und mit hoher Enantioselektivität.
      PubDate: 2017-12-06T07:36:08.009821-05:
      DOI: 10.1002/ange.201711126
       
  • Das schwach koordinierende Tris(trichlorsilyl)silyl-Anion
    • Authors: Marian Olaru; Maxie F. Hesse, Elena Rychagova, Sergey Ketkov, Stefan Mebs, Jens Beckmann
      Abstract: HSi(SiCl3)3 ist eine starke Brønsted-Säure, mehr als 43mal stärker als HSiMe3 und sogar leicht stärker als HCl in Acetonitril. In ihrer Zuschrift (
      DOI : 10.1002/ange.201710416) zeigen S. Ketkov, S. Mebs, J. Beckmann und Mitarbeiter, dass die Deprotonierung von HSi(SiCl3)3 mit einem N-heterocyclischen Carben zur Bildung von Si(SiCl3)3−, einem schwach koordinierenden Anion, führt.
      PubDate: 2017-12-06T07:35:23.529786-05:
       
  • Molecular pillar approach to grow vertical covalent organic framework
           nanosheets on graphene: new hybrid materials for energy storage
    • Authors: Jinhua Sun; Alexey Klechikov, Calin Moise, Mariana Prodana, Marius Enachescu, Alexandr V. Talyzin
      Abstract: Hybrid 2D-2D materials composed by perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material shows forest of COF-1 nanosheets with thickness of ~3 to 15 nm in edge-on orientation relative to GO. The same reaction performed in absence of molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.
      PubDate: 2017-12-06T07:06:06.030606-05:
      DOI: 10.1002/ange.201710502
       
  • Protection Group Effects during α,γ-Diol Lignin Stabilization Promote
           High-Selectivity Monomer Production
    • Authors: Wu Lan; Masoud Talebi Amiri, Christopher M. Hunston, Jeremy Luterbacher
      Abstract: Protection groups were introduced during biomass pretreatment to stabilize lignin's α,γ-diol group during its extraction and prevent its condensation. Acetaldehyde and propionaldehyde stabilized the α,γ-diol without any aromatic ring alkylation, which significantly increased final product selectivity. The subsequent hydrogenolysis catalyzed by Pd/C, generated lignin monomers at near-theoretical yields based on Klason lignin (48% from birch, 20% from spruce, 70% from high-syringyl transgenic poplar) with - in the case of the poplar - high selectivity to a single 4-n-propanolsyringol product (80%). Unlike direct hydrogenation of native wood, hydrogenolysis of protected lignin with Ni/C also led to high selectivity to this single product (78%), paving the way to high-selectivity lignin upgrading with base metal catalysts. The use of extracted lignin facilitated valorization of biomass's polysaccharides, leading to high yields of all three major biomass polymers to a single product.
      PubDate: 2017-12-06T06:36:38.636723-05:
      DOI: 10.1002/ange.201710838
       
  • "Dumbbell"- and "Clackers"-Shaped Dimeric Derivatives of
           Monocarba-closo-dodecaborate
    • Authors: Yu Kitazawa; Mamoru Watanabe, Yui Masumoto, Mai Otsuka, Kazunori Miyamoto, Atsuya Muranaka, Daisuke Hashizume, Ryo Takita, Masanobu Uchiyama
      Abstract: We designed, synthesized and characterized two types of dimeric forms of monocarba-closo-dodecaborate, namely, a "dumbbell"-shaped dianion having a C-C bond and a "clackers"-shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X-ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions.
      PubDate: 2017-12-06T04:35:42.459163-05:
      DOI: 10.1002/ange.201710122
       
  • Frontispiz: Adsorption von hydrierten Protonen an der
           Luft-Wasser-Grenzfläche durch Orientierung
    • Authors: Shavkat I. Mamatkulov; Christoph Allolio, Roland R. Netz, Douwe Jan Bonthuis
      Abstract: Luft-Wasser-Grenzfläche D. J. Bonthuis et al. berechnen in der Zuschrift auf S. 16058 Oberflächenspannungen und Ionenaffinitäten zur Luft-Wasser-Oberfläche durch Moleküldynamiksimulationen.
      PubDate: 2017-12-06T03:00:49.269565-05:
      DOI: 10.1002/ange.201785061
       
  • A 30 nm Nanopore Electrode: Facile Fabrication and Direct Revealing of the
           Intrinsic Feature in Single Nanoparticle Collision
    • Authors: Rui Gao; Yi-Lun Ying, Yuan-Jie Li, Yong-Xu Hu, Ru-Jia Yu, Yao Lin, Yi-Tao Long
      Abstract: Clarifying the hidden but intrinsic feature of single nanoparticles by nanoelectrochemistry could help understand its potential for diverse applications. The uncontrolled interface and bandwidth limitation in the electrochemical measurement put the obstacle in single particle collision. Here, we demonstrate a well-defined 30 nm nanopore electrode with a rapid chemical-electrochemical fabrication method which provides a high reproducibility in both size and nanoelectrode performance. A capacitance-based detection mechanism is demonstrated to achieve a high current resolution of 0.6 pA ± 0.1 pA (RMS) and a high the temporal resolution of 0.01 ms. By utilizing this electrode, the dynamic interactions of every single particle in the mixture could be directly read during the collision process. The collision frequency is two orders of magnitude higher than previous reports, which helps reveal the hidden features of nanoparticles during the complex and multidimensional interaction processes.
      PubDate: 2017-12-06T02:35:22.858141-05:
      DOI: 10.1002/ange.201710201
       
  • Environmental-Friendly Solid Synthesis of Fe-N-C Electrocatalyst with Fe
           Exclusively in Atomically Dispersed Fe-N4 Moieties for High-Power Proton
           Exchange Membrane Fuel Cells
    • Authors: Qingtao Liu; Xiaofang Liu, Lirong Zheng, Jianglan Shui
      Abstract: Environmental-friendly synthesis of highly active Fe-N-C electrocatalyst for proton exchange membrane fuel cells (PEMFCs) is desirable but remains challenging. Herein, we report a green, simple and scalable method to fabricate Fe(II)-doped ZIF-8, which can be further pyrolyzed into Fe-N-C with 3 wt.% of Fe exclusively in Fe-N4 active moieties. Significantly, this Fe-N-C derived acidic PEMFC exhibits an unprecedented current density of 1.65 A cm-2 at 0.6 V and the highest power density of 1.14 W cm-2 compared with previously reported NPMCs. The excellent PEMFC performance can be attributed to the densely and atomically dispersed Fe-N4 active moieties on the small and uniform catalyst nanoparticles.
      PubDate: 2017-12-05T23:35:33.23238-05:0
      DOI: 10.1002/ange.201709597
       
  • Selective Nascent Polymer Catch and Release Enables Scalable Isolation of
           Multi-Kilobase Single-Stranded DNA
    • Authors: Elisha Krieg; William M. Shih
      Abstract: Scalable methods currently are lacking for isolation of long ssDNA, an important material for numerous biotechnological applications. Conventional biomolecule purification strategies achieve target capture using solid supports, which are limited in scale and susceptible to contamination due to nonspecific adsorption and desorption on the substrate surface. We herein disclose Selective Nascent Polymer Catch and Release (SNAPCAR), a method that utilizes the reactivity of growing poly(acrylamide-co-acrylate) chains to capture acrylamide-labeled molecules in free solution. The copolymer acts as a stimuli-responsive anchor that can be precipitated on demand to pull down the target from solution. SNAPCAR enabled scalable isolation of multi-kilobase ssDNA with high purity and 50-70% yield. The ssDNA products were used to fold various DNA origami. SNAPCAR-produced ssDNA will expand the scope of applications in nanotechnology, gene editing, and DNA library construction.
      PubDate: 2017-12-05T22:05:57.772658-05:
      DOI: 10.1002/ange.201710469
       
  • Hydrophilicity and microsolvation of an organic molecule resolved on the
           sub-molecular level by scanning tunneling microscopy
    • Authors: Karsten Lucht; Dirk Loose, Maximilian Ruschmeier, Valerie Strotkötter, Gerald Dyker, Karina Morgenstern
      Abstract: We used low-temperature scanning tunneling microscopy to follow the formation of a solvation shell around an adsorbed functionalized azo dye from the attachment of the first water molecule to a fully solvated molecule. Specific functional groups bind initially one water molecule each, which act as anchor points for additional water molecules. Further water attachment occurs in areas close to these functional groups even when the functional groups themselves are already saturated. In contrast, water molecules surround the hydrophobic parts of the molecule only, when the two-dimensional solvation shell closes around them. Our study thus traces hydrophilic and hydrophobic properties of an organic molecule down to a sub molecular length scale.
      PubDate: 2017-12-05T12:00:33.955858-05:
      DOI: 10.1002/ange.201711062
       
  • Solventless and Metal-Free Synthesis of High Molecular Mass
           Polyaminoboranes from Diisopropylaminoborane and Primary Amines
    • Authors: Carlos Antonio De Albuquerque Pinheiro; Claire Roiland, Philippe Jéhan, Gilles Alcaraz
      Abstract: The solventless reaction of diisopropylaminoborane with n-butylamine, at room temperature, leads to a mixture of well identified B(sp2)H, B(sp3)H2 and B(sp3)H3 boron containing species. At low temperature, the reaction outcome is completely modified leading selectively to the formation of high mass polybutylaminoborane. Extended to a variety of primary amines under solventless conditions and at low temperature, this reaction provides a new, efficient and direct metal-free access to high molecular mass polyaminoboranes in good to high yield, in very mild conditions.
      PubDate: 2017-12-05T11:05:43.139897-05:
      DOI: 10.1002/ange.201710293
       
  • A Permselective CeOx Coating Improves the Stability of Oxygen Evolution
           Electrocatalysts
    • Authors: Keisuke Obata; Kazuhiro Takanabe
      Abstract: Highly active NiFeOx electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time due to the loss of Fe species from the active sites into solution during catalysis. Here, we describe the anodic deposition of a CeOx layer that prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeOx layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH− and O2 through while preventing the diffusion of redox ions through the layer to function as a selective O2-evolving electrode. The use of such permselective protective layer provides a new strategy for improving the durability of electrocatalysts.
      PubDate: 2017-12-05T11:05:25.809845-05:
      DOI: 10.1002/ange.201712121
       
  • Diversity-Oriented Synthesis of Furo[3,2-c]coumarins and Benzofuranyl
           Chromenones via Chemoselective Acylation/Wittig Reaction
    • Authors: Shu-Mei Yang; Chein-Yi Wang, Chun-Kai Lin, Praneeth Karanam, Ganapuram Madhusudhan Reddy, Yi-Ling Tsai, Wenwei Lin
      Abstract: A highly efficient and chemoselective one-pot protocol for the diversity-oriented synthesis of two coumarin-based formal cross-coupling adducts, viz. furo[3,2-c]coumarins and 3-benzofuranyl chromenones is described. Key attributes of the methodology comprise an initial chemoselective acylation of functionalized phosphorus zwitterions followed by chemoselective intramolecular Wittig reaction that preferentially resulted in one of the two coumarin derivatives in high yields, depending on relative reactivities and addition sequence of acylating agents.
      PubDate: 2017-12-05T10:36:14.047107-05:
      DOI: 10.1002/ange.201711524
       
  • Conversion of Olefins to Ketones by an Iron-Catalyzed Wacker-type
           Oxidation Using Oxygen as Sole Oxidant
    • Authors: Florian Puls; Hans-Joachim Knölker
      Abstract: We describe a mild and operationally simple protocol for the oxidation of olefins to ketones. The reaction is catalyzed by the hexadecafluorinated iron-phthalocyanine complex FePcF16 using stoichiometric amounts of triethylsilane as additive under oxygen to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Up to 95 % yield and 100 % regioselectivity for ketone formation are obtained, while the corresponding alcohol was observed as a by-product.
      PubDate: 2017-12-05T10:36:06.05325-05:0
      DOI: 10.1002/ange.201710370
       
  • Organocatalytic Enantioselective Higher-Order Cycloadditions of in situ
           Generated Amino Isobenzofulvenes
    • Authors: Karl Anker Jørgensen; Bjarke Skyum Donslund, Alicia Monleón, Teresa Palazzo, Mette Louise Christensen, Anne Dahlgaard, Jeremy Erickson
      Abstract: The [8+2]-cycloaddition of indene-2-carbaldehydes and nitro olefins is described to provide benzonorbornene scaffolds in a highly peri-, diastereo- and enantioselective fashion in the presence of a C2-symmetric aminocatalyst. This reaction, which proceeds through a transient semi-aromatic amino isobenzofulvene, represents the first example of catalytic formation and transformation of these species. Quantum chemical calculations suggest a kinetically controlled stepwise mechanism where the stereochemistry is determined in the first bond-forming event. Beyond the fruitful [8+2]-cycloadducts, [10+4]-cycloadducts have been identified in silico as potential off-pathway intermediates.
      PubDate: 2017-12-05T10:07:23.657847-05:
      DOI: 10.1002/ange.201710694
       
  • Photo-Oxidation Induced Selective Oxidative [4+2] Imine/Alkene Annulation
           with H2 Liberation
    • Authors: Xia Hu; Guoting Zhang, Faxiang Bu, Aiwen Lei
      Abstract: The oxidative [4+2] annulation reaction represents an elegant and versatile synthetic protocol for the construction of six-membered heterocyclic compounds. Herein, a photo-induced oxidative [4+2] annulation of N-H imines and alkenes was developed by utilizing a dual photoredox/cobaloxime catalytic system. Various multi-substituted 3,4-dihydroisoquinolines can be obtained in good yields. This method not only obviated the need of stiochiometric oxidants but also exhibited excellent atom economy by generating H2 as the only byproduct. Remarkably, high regioselectivity and trans-diastereoselectivity can be achieved in this transformation even if the Z/E mixture of alkenes were employed
      PubDate: 2017-12-05T10:06:46.308515-05:
      DOI: 10.1002/ange.201711359
       
  • Komplementäre Strategien für die dirigierte C(sp3)-H-Funktionalisierung:
           ein Vergleich von übergangsmetallkatalysierter Aktivierung,
           Wasserstoffatomtransfer und Carben- oder Nitrentransfer
    • Authors: John C. K. Chu; Tomislav Rovis
      Abstract: Funktionalisierungen von C(sp3)-H-Bindungen verkürzen und vereinfachen chemische Synthesen, indem sie die Verwendung einfacher Moleküle ermöglichen und neuartige Retrosynthesen bereitstellen. Intensive Forschungen, die auf die Entwicklung neuer Reaktionen basierend auf dem Ansatz der C-H-Funktionalisierung abzielten, haben zur weiten Verbreitung dieser Methoden in einer Vielzahl von Bereichen geführt. Dieser Aufsatz erörtert die Stärken und Schwächen der drei Hauptstrategien – übergangsmetallkatalysierte C-H-Aktivierung, 1,n-Wasserstoffatomtransfer und übergangsmetallkatalysierter Carben- oder Nitrentransfer – in der gezielten Funktionalisierung nichtaktivierter C(sp3)-H-Bindungen. Für jede Strategie werden der Anwendungsbereich, die Reaktivität verschiedener C-H-Bindungen, die Position der reagierenden C-H-Bindungen bezüglich der dirigierenden Gruppe und die stereochemischen Auswirkungen mit Beispielen aus der Literatur veranschaulicht. Das Ziel dieses Aufsatzes ist es, dem Anwender von C-H-Funktionalisierungsreaktionen eine Orientierungshilfe zu geben und künftige Forschungen auf diesem Gebiet anzuregen.Die gezielte Funktionalisierung von C(sp3)-H-Bindungen ermöglicht kurze chemische Synthesen und die Verwendung einfacher Ausgangsverbindungen. Dieser Aufsatz erörtert die Stärken und Schwächen der drei Hauptstrategien: übergangsmetallkatalysierte C-H-Aktivierung, 1,n-Wasserstoffatomtransfer und übergangsmetallkatalysierter Carben- oder Nitrentransfer.
      PubDate: 2017-12-05T09:51:15.584456-05:
      DOI: 10.1002/ange.201703743
       
  • Formation and Isolation of a Four-Electron Reduced Porphyrin Derivative
           via Further Reduction of a Stable 20π Isophlorin
    • Authors: Takahiko Kojima; Wataru Suzuki, Hiroaki Kotani, Tomoya Ishizuka, Yoshihito Shiota, Kazunari Yoshizawa
      Abstract: The two-electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na2S2O4 gave a corresponding isophlorin (Iph) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetra-methylated Iph. Further reduction of Iph proceeded to form an unprecedented four-electron reduced porphyrin (IphH2), which is fully characterized by spectroscopic and X-ray crystallographic analysis. IphH2 with a unique conformation is capable of performing a reversibility to reproduce the starting porphyrin by the chemical oxidation, which acts as a proton-coupled four-electron reversible redox system.
      PubDate: 2017-12-05T09:30:33.152799-05:
      DOI: 10.1002/ange.201711058
       
  • Superconductivity in a Copper(II)-Based Coordination Polymer with Perfect
           Kagome Structure
    • Authors: Xing Huang; Shuai Zhang, Liyao Liu, Lei Yu, Genfu Chen, Wei Xu, Daoben Zhu
      Abstract: A highly crystalline copper(II) benzenehexathiolate coordination polymer (Cu-BHT) has been prepared. The two-dimensional kagome structure has been confirmed by powder X-ray diffraction, high-resolution transmission electron microscopy, and high-resolution scanning transmission electron microscopy. The as-prepared sample exhibits bulk superconductivity at about 0.25 K, which is confirmed by the zero resistivity, AC magnetic susceptibility, and specific heat measurements. Another diamagnetic transition at about 3 K suggests that there is a second superconducting phase that may be associated with a single layer or few layers of Cu-BHT. It is the first time that superconductivity has been observed in a coordination polymer.Super Kagome-Gitter: Supraleitfähigkeit wurde für ein Kupfer(II)-Benzolhexathiolat-Koordinationspolymer (Cu-BHT) beobachtet.
      PubDate: 2017-12-05T09:22:41.676694-05:
      DOI: 10.1002/ange.201707568
       
  • A Copper(II) Phenanthroline Metallopeptide That Targets and Disrupts
           Mitochondrial Function in Breast Cancer Stem Cells
    • Authors: Kristine Laws; Ganka Bineva-Todd, Arvin Eskandari, Chunxin Lu, Nicola O'Reilly, Kogularamanan Suntharalingam
      Abstract: The breast cancer stem cell (CSC) and bulk breast cancer cell potency of a series of metallopeptides containing dichloro(1,10-phenanthroline)copper(II) and various organelle-targeting peptide sequences is reported. The mitochondria-targeting metallopeptide 1 exploits the higher mitochondrial load in breast CSCs over the corresponding non-CSCs and the vulnerability of breast CSCs to mitochondrial damage to potently and selectively kill breast CSCs. Strikingly, 1 reduces the formation and size of mammospheres to a greater extent than salinomycin, an established CSC-potent agent. Mechanistic studies show that 1 enters CSC mitochondria, induces mitochondrial dysfunction, generates reactive oxygen species (ROS), activates JNK and p38 pathways, and prompts apoptosis. To the best of our knowledge, 1 is the first metallopeptide to selectivity kill breast CSCs in vitro.Ein Metallopeptid mit einer Dichlor(1,10-phenanthrolin)kupfer(II)-Einheit, die reaktive Sauerstoffspezies generiert, und einem Mitochondrien-penetrierenden Peptid (MPP) wurde entwickelt. Es nutzt die höhere Mitochondriendichte in Brustkrebs-Stammzellen (CSCs) und ihre Anfälligkeit für Mitochondrienschädigung aus, um diese wirksam und selektiv abzutöten.
      PubDate: 2017-12-05T09:22:32.840954-05:
      DOI: 10.1002/ange.201710910
       
  • Ein Strontium- und Chlor-freies rotes pyrotechnisches Leuchtsignal mit
           hoher spektraler Reinheit
    • Authors: Johann Glück; Thomas M. Klapötke, Magdalena Rusan, Jesse J. Sabatini, Jörg Stierstorfer
      Abstract: Durch die drohende Reglementierung der in roten pyrotechnischen Leuchtsätzen enthaltenen Strontium- und Organochlorverbindungen durch die US-Umweltschutzbehörde richtet sich der Fokus zunehmend auf die Entwicklung alternativer chlorfreier Leuchtsätze. Aus diesem Grund berichten wir über die Entwicklung Lithium-basierter roter Leuchtsätze mit hoher Farbqualität und Lichtreinheit. Diese Formulierungen verzichten vollkommen auf Strontium und Organochlorverbindungen. Stattdessen fungiert ein neu synthetisiertes, nicht hygroskopisches, stickstoffreiches Dilithiumsalz gleichzeitig als Oxidationsmittel und Farbgeber. Die Lithium-basierten Mischungen können sowohl im militärischen als auch im zivilen Bereich als Ausgangspunkt für die Entwicklung von umwelt- und gesundheitsverträglicheren Leuchtsätzen dienen.Im roten Bereich: Ein rotes pyrotechnisches Signal mit hoher Farbreinheit, das frei von Strontium und Halogenen ist, beruht auf einem stickstoffreichen Lithiummaterial, das als Oxidationsmittel und Farbgeber fungiert. Die Formulierung könnte für militärische und zivile Anwendungen von Interesse sein.
      PubDate: 2017-12-05T09:22:16.57565-05:0
      DOI: 10.1002/ange.201710746
       
  • A Versatile Route to Unstable Diazo Compounds via Oxadiazolines and their
           Use in Aryl–Alkyl Cross-Coupling Reactions
    • Authors: Andreas Greb; Jian-Siang Poh, Stephanie Greed, Claudio Battilocchio, Patrick Pasau, David C. Blakemore, Steven V. Ley
      Abstract: Coupling of readily available boronic acids and diazo compounds has emerged recently as a powerful metal-free carbon–carbon bond forming method. However, the difficulty in forming the unstable diazo compound partner in a mild fashion has hitherto limited their general use and the scope of the transformation. Here, we report the application of oxadiazolines as precursors for the generation of an unstable family of diazo compounds using flow UV photolysis and their first use in divergent protodeboronative and oxidative C(sp2)−C(sp3) cross-coupling processes, with excellent functional-group tolerance.Die Photolyse von Oxadiazolinen stellt unter milden Bedingungen unbeständige Diazoverbindungen für Kupplungen mit Boronsäuren bereit. Variationen des Aufarbeitungsprozesses führen in divergenter Weise zu protodeborierten oder oxidierten Produkten sowie zu Boronsäurepinakolaten. Funktionelle Gruppen werden bei diesem vielseitigen Ansatz hervorragend toleriert.
      PubDate: 2017-12-05T09:22:07.501541-05:
      DOI: 10.1002/ange.201710445
       
  • Das schwach koordinierende Tris(trichlorsilyl)silyl-Anion
    • Authors: Marian Olaru; Maxie F. Hesse, Elena Rychagova, Sergey Ketkov, Stefan Mebs, Jens Beckmann
      Abstract: In Anlehnung an die Vorschrift von Roesky und Stalke et al. (Angew. Chem. 2009, 121, 5793–5796) zur Herstellung des basenstabilisierten Dichlorsilylen-Komplexes NHCDipp⋅SiCl2 wurden neben dem beschriebenen Nebenprodukt [NHCDipp-H+⋅⋅⋅Cl-] wenige Kristalle des Salzes [NHCDipp-H⋅⋅⋅Cl⋅⋅⋅H-NHCDipp]Si(SiCl3)3 isoliert und kristallographisch charakterisiert (NHCDipp=N,N-Bis(2,6-diisopropylphenyl)imidazo-2-yliden). Sie enthalten das schwach koordinierende Si(SiCl3)3−-Anion, das systematisch in hohen Ausbeuten durch die Deprotonierung der konjugierten Brønsted-Säure HSi(SiCl3)3 mit NHCDipp oder 1,2,2,6,6-Pentamethylpiperidin erhalten wurde. Die durch DFT-Rechnungen abgeschätzte Acidität von HSi(SiCl3)3 ist bedeutend höher als die anderer H-Silane. DFT-Rechnungen zur elektronischen Struktur von Si(SiCl3)3−, einschließlich des elektrostatischen Potentials und der Elektronenlokalisierbarkeit, bestätigen die geringe Basizität und Nukleophilie im Vergleich zu anderen Silylanionen.Das H-Silan HSi(SiCl3)3 zeigt eine extrem hohe Brønsted-Acidität – mehr als 43 Größenordnungen höher als HSiMe3 und sogar leicht höher als HCl in MeCN. Seine Deprotonierung durch ein N-heterocyclisches Carben lieferte die konjugierte Base, Si(SiCl3)3−, ein schwach koordinierendes Anion.
      PubDate: 2017-12-05T09:21:51.41215-05:0
      DOI: 10.1002/ange.201710416
       
  • Site-Selective O-Arylation of Glycosides
    • Authors: Weidong Shang; Ze-Dong Mou, Hua Tang, Xia Zhang, Jie Liu, Zhengyan Fu, Dawen Niu
      Abstract: Direct and site-selective O-arylation of carbohydrates has been a challenge in synthesis. Herein we report a method based on copper-catalyzed O-arylation to address this challenge. Proper choice of the ancillary ligand on copper is critical for the efficiency and site selectivity of this transformation. This method features mild conditions, tolerates various functional groups, and demonstrates broad substrate scope.Eine Kupfer-katalysierte Reaktion für die regioselektive O-Arylierung von Glykosiden unter milden Bedingungen wurde entwickelt (siehe Schema). Die Verwendung eines geeigneten Liganden war entscheidend für die Effizienz und Selektivität der Reaktion, die mit einer sehr breiten Auswahl an Kohlenhydraten und Arylierungsreagentien gelingt.
      PubDate: 2017-12-05T09:21:42.992739-05:
      DOI: 10.1002/ange.201710310
       
  • 1,1-Hydroboration and a Borane Adduct of Diphenyldiazomethane: A Potential
           Prelude to FLP-N2 Chemistry
    • Authors: Connie Tang; Quiming Liang, Andrew R. Jupp, Timothy C. Johnstone, Rebecca C. Neu, Datong Song, Stefan Grimme, Douglas W. Stephan
      Abstract: Diphenyldiazomethane reacts with HB(C6F5)2 and B(C6F5)3, resulting in 1,1-hydroboration and adduct formation, respectively. The hydroboration proceeds via a concerted reaction involving initial formation of the Lewis adduct Ph2CN2BH(C6F5)2. The highly sensitive adduct Ph2CN2(B(C6F5)3) liberates N2 and generates Ph2CB(C6F5)3. DFT computations reveal that formation of Ph2CN2B(C6F5)3 from carbene, N2, and borane is thermodynamically favourable, suggesting steric frustration could preclude carbene–borane adduct formation and affect FLP-N2 capture.N-N verbrückt: Diphenyldiazomethan reagiert mit HB(C6F5)2 und B(C6F5)3 unter 1,1-Hydroborierung bzw. Adduktbildung. N2-Freisetzung aus dem Addukt Ph2CN2B(C6F5)3 liefert das Diphenylcarben-Boran-Addukt. Rechnungen zufolge ist die N2-Aufnahme thermodynamisch günstig, obwohl die Bildung des Carben-Boran-Addukts exotherm ist.
      PubDate: 2017-12-05T09:21:24.270472-05:
      DOI: 10.1002/ange.201710337
       
  • Evolving Accelerated Amidation by SpyTag/SpyCatcher to Analyze Membrane
           Dynamics
    • Authors: Anthony H. Keeble; Anusuya Banerjee, Matteo P. Ferla, Samuel C. Reddington, Irsyad N. A. Khairil Anuar, Mark Howarth
      Abstract: SpyTag is a peptide that forms a spontaneous amide bond with its protein partner SpyCatcher. This protein superglue is a broadly useful tool for molecular assembly, locking together biological building blocks efficiently and irreversibly in diverse architectures. We initially developed SpyTag and SpyCatcher by rational design, through splitting a domain from a Gram-positive bacterial adhesin. In this work, we established a phage-display platform to select for specific amidation, leading to an order of magnitude acceleration for interaction of the SpyTag002 variant with the SpyCatcher002 variant. We show that the 002 pair bonds rapidly under a wide range of conditions and at either protein terminus. SpyCatcher002 was fused to an intimin derived from enterohemorrhagic Escherichia coli. SpyTag002 reaction enabled specific and covalent decoration of intimin for live cell fluorescent imaging of the dynamics of the bacterial outer membrane as cells divide.Nichtnatürlich selektiert: Das spontan reagierende SpyTag/SpyCatcher-Paar wurde durch Modifizierung des Adhäsin-Proteins aus S. pyogenes entwickelt. Selektion mit einer Phagenbibliothek ergab Peptid- und Protein-Partner für eine hoch spezifische und beschleunigte Isopeptidverknüpfung. SpyCatcher002 auf der äußeren Bakterienmembran ermöglicht die Fluoreszenzbildgebung der Zellteilungsdynamik.
      PubDate: 2017-12-05T08:00:46.913898-05:
      DOI: 10.1002/ange.201707623
       
  • A Supramolecular Capsule for Reversible Polysulfide Storage/Delivery in
           Lithium-Sulfur Batteries
    • Authors: Jin Xie; Hong-Jie Peng, Jia-Qi Huang, Wen-Tao Xu, Xiang Chen, Qiang Zhang
      Abstract: Eine supramolekulare Kapsel, die einer Krake ähnelt, ermöglicht die reversible Speicherung von Polysulfiden in einer funktionsfähigen Batterie. In ihrer Zuschrift (
      DOI : 10.1002/ange.201710025) berichten Q. Zhang et al. über den Einsatz von Cucurbit[6]uril-Kapseln, die Lithium-Schwefel-Batterien eine hohe Stabilität und einen hohen Wirkungsgrad verleihen und eine hohe Schwefelbeladung möglich machen.
      PubDate: 2017-12-05T08:00:33.979615-05:
       
  • The MOF+ Technique: A Significant Synergic Effect Enables High Performance
           Chromate Removal
    • Authors: Ming Biao Luo; Yang Yang Xiong, Hui Qiong Wu, Xue Feng Feng, Jian Qiang Li, Feng Luo
      Abstract: Metall-organische Gerüste (MOFs) sind bei der Absorption von Chrom(VI) vor allem durch ihre geringe Kapazität beschränkt. F. Luo et al. setzen in ihrer Zuschrift (
      DOI : 10.1002/ange.201709197) auf die so genannte MOF+-Methode, bei der nicht die Poren, sondern die Oberfläche des MOF genutzt werden, um bis zu 796 Cr mg g−1 an Chrom (VI) zu binden. Der Schlüssel ist ein synergistischer Effekt des MOF mit FeSO4.
      PubDate: 2017-12-05T08:00:30.973744-05:
       
  • Layer-by-Layer Assembled Conductive Metal–Organic Framework Nanofilms
           for Room-Temperature Chemiresistive Sensing
    • Authors: Ming-Shui Yao; Xiao-Jing Lv, Zhi-Hua Fu, Wen-Hua Li, Wei-Hua Deng, Guo-Dong Wu, Gang Xu
      Abstract: Elektrisch leitfähige Metall-organische Gerüste (EC-MOF) wurden in Form dünner Filme nach einem Lösungssprühverfahren schichtweise abgeschieden. In ihrer Zuschrift (
      DOI : 10.1002/ange.201709558) richten G. Xu und Mitarbeiter das Filmwachstum an OH-funktionalisierten Substraten aus. Ein auf diese Weise erhaltener chemoresistiver Gassensor kann bei Raumtemperatur NH3 nachweisen – einen für Nieren- und Lebererkrankungen charakteristischen Biomarker in Atemluft.
      PubDate: 2017-12-05T08:00:28.384126-05:
       
  • Ein antibakterielles β-Lacton bekämpft Mycobacterium tuberculosis durch
           Infiltration der Mykolsäurebiosynthese
    • Authors: Johannes Lehmann; Tan-Yun Cheng, Anup Aggarwal, Annie S. Park, Evelyn Zeiler, Ravikiran M. Raju, Tatos Akopian, Olga Kandror, James C. Sacchettini, D. Branch Moody, Eric J. Rubin, Stephan A. Sieber
      Abstract: Eine der größten Herausforderungen für die Behandlung von Infektionen mit Mykobakterium tuberculosis ist Resistenzverbreitung. Des Weiteren ist die Aktivität vieler Wirkstoffe durch die limitierte Durchlässigkeit der Mykomembran eingeschränkt. Etablierte Antibiotika setzen daher auf die Lahmlegung der Mykomembranbiosynthese und führen zu einem schnellen Sterben der Zellen. Dieser Wirkmechanismus lieferte die Motivation, β-Lactone als mögliche Mykolsäuremimetika einzusetzen und so Serinhydrolasen, die in den Biosyntheseweg involviert sind, zu inhibieren. Tests an einer Sammlung von β-Lactonen brachten eine Verbindung hervor, die vielversprechende mykobakterielle und bakteriolytische Wirkung zeigte. Chemische Proteomanalysen mithilfe einer alkinhaltigen Sonde ließen auf die Serinhydrolasen Pks13 und Ag85 als Hauptziele schließen. Durch Enzymstudien und eine neuartige Methode zur 13C-Markierung von Metaboliten wurde gezeigt, dass beide Enzyme durch das β-Lacton funktionell inhibiert wurden. In Kombination mit Antibiotika konnte zudem eine mehr als 100-fach gesteigerte antibakterielle Aktivität gezeigt werden, was ein therapeutisches Potenzial für die Inhibition der Mykomembranbiosynthese birgt.Süßes oder Saures: Ein β-Lacton, das elektrophile Mykolsäuren imitiert, bindet an essenzielle Serinhydrolasen für die Mykomembranbiosynthese. Ein aktivitätsbasiertes Proteinprofil in Kombination mit Metabolitmarkierung bestätigte diese Art der Inhibition, die für eine potente antibiotische Aktivität gegen M. tuberculosis verantwortlich ist.
      PubDate: 2017-12-05T07:56:04.967905-05:
      DOI: 10.1002/ange.201709365
       
  • Covalent Organic Frameworks and Cage Compounds: Design and Applications of
           Polymeric and Discrete Organic Scaffolds
    • Authors: Florian Beuerle; Bappaditya Gole
      Abstract: Porous organic materials are an emerging class of functional nanostructures with unprecedented properties. Dynamic covalent assembly of small organic building blocks under thermodynamic control is utilized for the intriguingly simple formation of complex molecular architectures in one-pot procedures. In this review, we aim to analyze the basic design principles that govern the formation of either covalent organic frameworks as crystalline porous polymers or covalent organic cage compounds as shape-persistent molecular objects. Common synthetic protocols and characterization techniques will be discussed besides more advanced strategies such as postsynthetic modification or self-sorting. When appropriate, healthy comparisons are drawn between polymeric frameworks and discrete organic cages considering their underlying properties. Furthermore, we highlight the potential of these materials for applications ranging from gas storage to catalysis or organic electronics.
      PubDate: 2017-12-05T07:36:55.633164-05:
      DOI: 10.1002/ange.201710190
       
  • Triangles and square for unique molecular and crystal structures:
           unsupported two-coordinate lithium cations and CC agostic interactions in
           cyclopropyllithium derivatives
    • Authors: Quentin Dufrois; Jean-Claude Daran, Laure Vendier, Chiara Dinoi, Michel Etienne
      Abstract: Understanding and controlling the aggregation state is germane to alkyllithium chemistry. Lewis base-free alkyllithiums normally form tetrahedral tetramers or octahedral hexamers in the solid state with the lithium cations being three-coordinate. We report that the unsupported cyclopropyl derivative 1-(trimethylsilyl)cyclopropyllithium [{μ-c-C(SiMe3)C2H4}Li]4 (1), synthesized by the reduction of 1-(phenylthio)-1-(trimethylsilyl)cyclopropane, crystallizes as a tetramer in the space group I-4 with the two-coordinate lithiums forming a square. CC agostic interactions complete the coordination sphere around each lithium. The aggregate is preserved in hydrocarbon solution. Furthermore, CC agostic interactions compete intra- and intermolecularly with Lewis base donation as in the unsaturated dimer of 1-(phenylthio)cyclopropyllithium [Li(thf)2{μ-c-C(SPh)C2H4}2Li(thf)] (3) which is also fully characterized.
      PubDate: 2017-12-05T05:32:13.405821-05:
      DOI: 10.1002/ange.201711426
       
  • Enantioselective Photochemical Organo-Cascade Catalysis
    • Authors: Łukasz Woźniak; Giandomenico Magagnano, Paolo Melchiorre
      Abstract: Reported herein is a photochemical cascade process that combines the excited-state and ground-state reactivity of chiral organocatalytic intermediates. This strategy directly converts racemic cyclopropanols and α,β-unsaturated aldehydes into stereochemically dense cyclopentanols with exquisite stereoselectivity. Mechanistic investigations have elucidated the origin of the stereoconvergence, which is governed by a kinetic resolution process.
      PubDate: 2017-12-05T05:00:28.192843-05:
      DOI: 10.1002/ange.201711397
       
  • Generating hydrated electrons for chemical syntheses with a green LED
    • Authors: Robert Naumann; Florian Lehmann, Martin Goez
      Abstract: We present the first working system for accessing and utilizing laboratory-scale concentrations of hydrated electrons by photoredox catalysis with a green light-emitting diode (LED). Decisive are micellar compartmentalization and photon pooling in an intermediate that decays with second-order kinetics. The only consumable is the nontoxic and bioavailable vitamin C. A turnover number of 1380 shows the LED method to be on par with electron generation by high-power pulsed lasers, but at a fraction of the cost. The extreme reducing power of the electron and its long unquenched life as a ground-state species are synergistic. We demonstrate the applicability to the dechlorination, defluorination, and hydrogenation of compounds that are inert towards all other visible-light photoredox catalysts known to date. A comprehensive mechanistic investigation from microseconds to hours yields results of general validity for photoredox catalysis with photon pooling, allowing optimization and upscaling.
      PubDate: 2017-12-05T04:30:24.774965-05:
      DOI: 10.1002/ange.201711692
       
  • Increasing Catalyst Efficiency in C−H Activation Catalysis
    • Authors: Tobias Gensch; Michael James, Toryn Dalton, Frank Glorius
      Abstract: C−H activation reactions with high catalyst turnover numbers are still very rare in the reported literature and 10 mol% is a common catalyst loading in this field. We offer a representative overview of efficient C−H activation catalysis to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation. Examples ranging from palladium catalysis, Cp*Rh(III)- and Cp*Co(III)-catalysis, the C−H borylation and silylation to methane C−H activation are presented. In these reactions, up to ten thousands of catalyst turnovers have been observed.
      PubDate: 2017-12-05T03:30:55.466523-05:
      DOI: 10.1002/ange.201710377
       
  • Chemoselectivity Control in the Asymmetric Hydrogenation of γ- and
           δ-Keto Esters into the Hydroxy Esters or the Diols
    • Authors: Noriyoshi Arai; Takanori Namba, Kei Kawaguchi, Yuki Matsumoto, Takeshi Ohkuma
      Abstract: Asymmetric hydrogenation of aromatic γ- and δ-keto esters into the optically active hydroxy esters or the diols catalyzed by a novel DIPSkewphos/3-AMIQ-Ru(II) complex was studied. Under the optimized conditions (8 atm H2, Ru complex/t-C4H9OK = 1:3.5, 25°C) the γ- and δ-hydroxy esters (including γ-lactones) were obtained in 97%-99% ee quantitatively. When the reaction was conducted under slightly harsh conditions (20 atm H2, [t-C4H9OK] = 50 mM, 40°C), the 1,4- and 1,5-diols were predominantly obtained in 95%-99% ee. The reactivity of the ester group was notably dependent on the length of the carbon-spacer between the two carbonyl moieties of the substrate. The reaction of β- and ε-keto esters selectively afforded the hydroxy esters regardless of the reaction conditions. This catalyst system was applied to the enantioselective and ester regio (position)-selective hydrogenation of a γ-ε-diketo diester into the tri-hydroxy ester.
      PubDate: 2017-12-05T03:30:52.467254-05:
      DOI: 10.1002/ange.201711363
       
  • Borazine-CF3- Adducts for Rapid, Room Temperature, and Broad Scope
           Trifluoromethylation
    • Authors: Jacob Benjamin Geri; Michael McCreery Wade Wolfe, Nathaniel Kolnik Szymczak
      Abstract: We present a strategy to use a fluoroform-derived borazine CF3- transfer reagent to effect rapid nucleophilic reactions in the absence of exogenous activator additives within minutes at room temperature. Inorganic electrophiles spanning 7 groups of the periodic table can be trifluoromethylated in high yield, including transition metals used for catalytic trifluoromethylation. Organic electrophiles included arenes and heteroarenes, enabling C-H, C-X (F, Cl), and C-NO2 trifluoromethylation reactions. Mechanistic analysis supports a dissociative mechanism for CF3- transfer, and cation modification afforded a reagent with enhanced stability.
      PubDate: 2017-12-04T22:00:57.489529-05:
      DOI: 10.1002/ange.201711316
       
  • Standoff Mid-Infrared Emissive Imaging Spectroscopy To Identify and Map
           Materials in Polychrome Objects
    • Authors: Francesca Gabrieli; Kathryn A Dooley, Jason G Zeibel, James D Howe, John Delaney
      Abstract: Microscale mid-infrared (mid-IR) imaging spectroscopy is used for mapping chemical functional groups. The extension to macroscale imaging requires either the mid-IR radiation reflected off or emitted by the object be greater than the radiation from the thermal background. Reflectance spectra can be obtained using an active IR source to increase the amount of radiation reflected off the object, but rapid heating>4 C can occur, a problem for paintings. Rather than using an active source, by placing a highly reflective tube between the painting and camera and introducing a low temperature source, thermal radiation from the room can be reduced, allowing the IR radiation emitted by the painting to dominate. Thus, emissivity spectra of the object can be recovered. Using this technique, mid-IR emissivity image cubes of paintings were collected at high collection rates with a low noise, line-scanning imaging spectrometer which allowed pigments and paint binders to be identified and mapped.
      PubDate: 2017-12-04T12:31:13.469981-05:
      DOI: 10.1002/ange.201710192
       
  • Sinter-Resistant Platinum Catalyst Supported by Metal-Organic Framework
    • Authors: In Soo Kim; Zhanyong Li, Jian Zheng, Ana E Platero-Prats, Andreas Mavrandonakis, Steven Pellizzeri, Magali Ferrandon, Aleksei Vjunov, Leighanne C Gallington, Thomas Webber, Nicolaas A Vermeulen, R Lee Penn, Rachel B Getman, Christopher J Cramer, Karena W Chapman, Donald M Camaioni, John L Fulton, Johannes A Lercher, Omar K Farha, Joseph T Hupp, Alex Martinson
      Abstract: Single atoms and few-atom clusters of platinum are uniformly installed on the zirconia nodes of a metal-organic framework (MOF) NU-1000 via targeted vapour-phase synthesis. The catalytic Pt clusters, site-isolated by organic linkers, are shown to exhibit high catalytic activity for ethylene hydrogenation while exhibiting resistance to sintering up to 200 °C. In situ IR spectroscopy reveals the presence of both single atoms and few-atom clusters that depend upon synthesis conditions. Operando X-ray absorption spectroscopy and X-ray pair distribution analyses reveal unique changes in chemical bonding environment and cluster size stability while on stream. Density functional theory calculations elucidate a favourable reaction pathway for ethylene hydrogenation with the novel catalyst. These results provide evidence that atomic layer deposition (ALD) in MOFs is a versatile approach to the rational synthesis of size-selected clusters, including noble metals, on a high surface area support.
      PubDate: 2017-12-04T12:31:08.757042-05:
      DOI: 10.1002/ange.201708092
       
  • A Molecular Approach to Manganese Nitride Acting as a High Performance
           Electrocatalyst in the Oxygen Evolution Reaction
    • Authors: Matthias Driess; Carsten Walter, Prashanth W Menezes, Martin Lerch, Steven Orthmann, Bernard Kaiser, Jona Schuch, Paula Connor
      Abstract: The first scalable synthesis of phase-pure crystalline and air-stable manganese nitride (Mn3N2) from a molecular precursor is reported; it acts as a superiorly active and durable electrocatalyst in the oxygen evolution reaction (OER) from water under alkaline conditions. While electrophoretically deposited Mn3N2 on fluorine tin oxide (FTO) requires an overpotential of 390 mV, the latter is substantially decreased to merely 270 mV on nickel foam at a current density of 10 mAcm-2 with a durability of weeks. The high performance of this material is due to the rapid transformation of manganese sites at the surface of Mn3N2 into an amorphous active MnOx overlayer under operation conditions intimately connected with metallic Mn3N2 which increases the charge transfer from the active catalyst surface to the electrode substrates and thus outperforms the electrocatalytic activity in comparison to solely MnOx-based OER catalysts.
      PubDate: 2017-12-04T12:30:37.639154-05:
      DOI: 10.1002/ange.201710460
       
  • Stereoselective Total Synthesis of Hetisine-Type C20-Diterpenoid
           Alkaloids: Spirasine IV and XI
    • Authors: Min Zhang; Quanzheng Zhang, Zhongshan Zhang, Zhong Huang, Changhui Zhang, Song Xi
      Abstract: The first total synthesis of the architecturally complex hetisine-type heptacyclic C20-diterpenoid alkaloids (±)-spirasine IV and XI is reported. The A/F/G/C tetracyclic skeleton with the challenging N-C6 and C14-C20 linkages was efficiently constructed by an intramolecular azomethine ylide-based 1,3-dipolar cycloaddition, wherein an unusual regioselectivity was obtained. A SmI2-mediated, free radical addition to the arene moiety without prior dearomatization and a stereoselective intramolecular aldol reaction were further employed to enable rapid access to the hetisine core, providing a bicyclo[2.2.2]octane ring with a new oxygen substitution pattern.
      PubDate: 2017-12-04T11:30:47.412244-05:
      DOI: 10.1002/ange.201711414
       
  • Three-Dimensional Printing with Biomass-Derived PEF for Carbon-Neutral
           Manufacturing
    • Authors: Fedor A. Kucherov; Evgeny G. Gordeev, Alexey S. Kashin, Valentine P. Ananikov
      Abstract: Die Synthese von Bioplastik aus Pflanzen und dessen Verwendung in einem 3D-Druckprozess wird von V. P. Ananikov et al. in ihrer Zuschrift (
      DOI : 10.1002/ange.201708528) vorgestellt. Aus Biomasse gewonnenes, leicht zugängliches Poly(ethylen-2,5-furandicarboxylat) wurde zum 3D-Schmelzschichtdrucken verwendet. Der vorgeschlagene Ansatz erweitert additive Herstellungsprozesse auf Kohlenstoff-neutrale Materialien und eröffnet neue Wege für nachhaltige Entwicklungen.
      PubDate: 2017-11-30T04:42:31.49381-05:0
       
  • Titelbild: Mild Reduction of Phosphine Oxides with Phosphites To Access
           Phosphines (Angew. Chem. 50/2017)
    • Authors: Peng Li; Raphael Wischert, Pascal Métivier
      Pages: 15979 - 15979
      Abstract: Im Jahr 1669 entdeckte Henning Brand das Element Phosphor, indem er in Urin enthaltenes Phosphat unter harschen Reaktionsbedingungen reduzierte. Das Experiment markiert den Beginn der Phosphorchemie, wobei Brand nicht wusste, dass er P=O-Bindungen reduziert hatte. P. Li, P. Métivier und R. Wischert beschreiben in der Zuschrift auf S. 16205 eine effiziente, milde und kostengünstige Methode für die Reduktion von P=O-Bindungen in Phosphinoxiden durch Sauerstofftransfer und Transmutation mit weiteren Phosphorverbindungen.
      PubDate: 2017-11-06T08:05:57.136401-05:
      DOI: 10.1002/ange.201710929
       
  • Innentitelbild: Ferroelasticity in an Organic Crystal: A Macroscopic and
           Molecular Level Study (Angew. Chem. 50/2017)
    • Authors: Sajjad Husain Mir; Yuichi Takasaki, Emile Richard Engel, Satoshi Takamizawa
      Pages: 15980 - 15980
      Abstract: Eine ferroelastische Verformung von Kristallen wird beobachtet, wenn durch Richtungswechsel einer mechanischen Kraft eine reversible Änderung der makroskopischen Zugspannung an der Grenzfläche zwischen zwei Kristalldomänen induziert wird. In ihrer Zuschrift auf S. 16098 beschreiben S. Takamizawa et al. das makroskopische Verhalten, die mikroskopischen Mechanismen und die mechanischen Eigenschaften der organischen Ferroelastizität in Kristallen von 5-Chlor-2-nitroanilin.
      PubDate: 2017-11-06T08:05:47.101644-05:
      DOI: 10.1002/ange.201710878
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 50/2017
    • Pages: 15983 - 15997
      PubDate: 2017-12-06T03:00:53.617088-05:
      DOI: 10.1002/ange.201785011
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 50/2017
    • Pages: 16000 - 16003
      PubDate: 2017-12-06T03:01:01.530438-05:
      DOI: 10.1002/ange.201785013
       
  • Jan-E. Bäckvall
    • Pages: 16004 - 16006
      Abstract: „Ich begutachte wissenschaftliche Arbeiten gerne, weil ich so auf dem Laufenden bleibe und gezwungen bin, interessante Arbeiten kritisch zu lesen. Nach was ich in einer Publikation als Erstes schaue, sind der und die Zusammenfassung. ...“ Dies und mehr von und über Jan-E. Bäckvall finden Sie auf Seite 16004.
      PubDate: 2017-11-22T04:06:32.258584-05:
      DOI: 10.1002/ange.201711014
       
  • Bilaterale Preise europäischer chemischer Gesellschaften
    • Pages: 16007 - 16007
      PubDate: 2017-11-23T04:50:28.902132-05:
      DOI: 10.1002/ange.201711378
       
  • Palladium-katalysierte Kreuzkupplung von Nitroarenen
    • Authors: Yang Yang
      Pages: 16010 - 16012
      Abstract: Über Kreuz: Die Pd-katalysierte Kreuzkupplung von Nitroarenen blieb für Chemiker über Jahrzehnte hinweg unzugänglich. Kürzlich wurden die ersten Pd-katalysierten Suzuki-Miyaura- und Buchwald-Hartwig-Kreuzkupplungen von Nitroarenen vorgestellt. Mechanistisch verläuft dieser Prozess über eine anspruchsvolle oxidative Addition von LPd0 in die Ar-NO2-Bindung. Die Substratbandbreite bezüglich des Nitroarens wie auch der nucleophilen Kupplungspartner ist groß.
      PubDate: 2017-10-19T01:45:22.299759-05:
      DOI: 10.1002/ange.201708940
       
  • Theoretische Abhandlung über CH3NH3PbI3-Perowskit-Solarzellen
    • Authors: Sining Yun; Xiao Zhou, Jacky Even, Anders Hagfeldt
      Pages: 16014 - 16026
      Abstract: Hybrid-Halogenid-Perowskit-Solarzellen (PSCs) mit Wirkungsgraden über 22 % haben große Aufmerksamkeit auf sich gezogen. Trotz verstärkter Forschungen konnten die mit Perowskiten in PSCs zusammenhängenden grundlegenden Theorien aber noch nicht geklärt werden. In diesem Kurzaufsatz beurteilen wir die derzeitigen Erkenntnisse basierend auf “First-Principles”-Berechnungen zu Struktur, elektronischen Eigenschaften, Defekten, Ionendiffusion und Verschiebestrom von CH3NH3PbI3-Perowskit sowie auf dem Einfluss des Ionentransports auf die Hysterese der Strom-Spannungs-Kennlinie in PSCs. Der mit einer möglicherweise vorhandenen Ferroelektrizität verbundene Verschiebestrom wird ebenfalls diskutiert. Außerdem werden der derzeitige Wissensstand und einige offene Fragen hinsichtlich PSCs hervorgehoben, und die Vorteile, Herausforderungen und das Potenzial der Perowskit-Materialien werden betont.„First-Principles”-Berechnungen zu CH3NH3PbI3, die dessen Struktur, elektronische Eigenschaften, Defekte, Ionendiffusion und Verschiebestrom analysieren, können eine wertvolle Hilfe bei der Weiterentwicklung von Perowskit-Solarzellen (PSCs) sein.
      PubDate: 2017-10-13T04:31:11.000482-05:
      DOI: 10.1002/ange.201702660
       
  • Selen und Selenocystein in der Proteinchemie
    • Authors: Reem Mousa; Rebecca Notis Dardashti, Norman Metanis
      Pages: 16027 - 16037
      Abstract: Selenocystein, das selenhaltige Analogon des Cysteins, ist die 21. proteinogene Aminosäure. Seit ihrer Entdeckung vor beinahe fünfzig Jahren ist ihre Rolle biologischen Systemen intensiv untersucht worden, in nichtnatürlichen noch häufiger als in natürlichen. Die Chemie des Selenocysteins hat aufgrund der hohen Reaktivität der Verbindung und des daraus resultierenden Potentials für diverse Anwendungen, z. B. in der chemischen Modifizierung, der chemische Protein(semi)synthese oder der Proteinfaltung, viel Aufmerksamkeit auf dem Gebiet der chemischen Biologie auf sich gezogen. In diesem Kurzaufsatz richten wir den Fokus auf die Chemie des Selens und des Selenocysteins sowie deren Nutzen in der Proteinchemie.Seit der Entdeckung von Selen in Proteinen vor über 40 Jahren haben Proteinchemiker die einzigartigen Eigenschaften dieses Elements für eine Vielzahl von Zwecken genutzt. Dieser Kurzaufsatz fasst die Verwendung von Selen und Selenocystein für die chemische Modifizierung, in der Proteinsynthese und der Proteinfaltung zusammen.
      PubDate: 2017-11-08T09:09:16.230488-05:
      DOI: 10.1002/ange.201706876
       
  • 3D-Laser-Mikro-Nanodruck: Herausforderungen für die Chemie
    • Authors: Christopher Barner-Kowollik; Martin Bastmeyer, Eva Blasco, Guillaume Delaittre, Patrick Müller, Benjamin Richter, Martin Wegener
      Pages: 16038 - 16056
      Abstract: 3D-Druck ist eine leistungsfähige Technik für die maßgeschneiderte Herstellung funktionaler Materialien. Dieser Aufsatz fasst den Stand der Technik im Hinblick auf 3D-Laser-Mikro- und -Nanodruck zusammen und erkundet die chemischen Herausforderungen, die derzeit die volle Etablierung dieser Technologie limitieren: von der Entwicklung fortgeschrittener Materialien für Anwendungen in der Zellbiologie und der Elektronik bis hin zu den bestehenden chemischen Grenzen des schnellen Schreibens mit Auflösungen unterhalb der Beugungsgrenze. Des Weiteren untersuchen wir Möglichkeiten zur Realisierung des direkten Laserschreibens mehrerer Materialien aus einem Photolack heraus, basierend auf wellenlängenselektiven photochemischen Prozessen (λ-Orthogonalität). Schließlich betrachten wir chemische Prozesse, mit deren Hilfe adaptive 3D-Strukturen geschrieben werden können, die auf externe Stimuli wie Licht, Wärme, pH-Wert oder spezifische Moleküle reagieren, sowie fortgeschrittene Konzepte für abbaubare Stützstrukturen.Alles ist gedruckt: Fortschritte im Mikro- und Nanodruck durch 3D-Laserlithographie werden vorgestellt, und verbleibende chemischen Herausforderungen der Technologie werden identifiziert – z. B. das Design funktionaler Photolacke für die Erzeugung multifunktionaler Nanostrukturen sowie die Fähigkeit, unterschiedliche Materialeigenschaften aus einem Lack heraus mit unterschiedlichen Lichtfarben zu schreiben, und die Fähigkeit, 3D-Lithographie unterhalb der Beugungsgrenze zu betreiben.
      PubDate: 2017-11-14T12:50:32.003217-05:
      DOI: 10.1002/ange.201704695
       
  • Adsorption von hydrierten Protonen an der Luft-Wasser-Grenzfläche
           durch Orientierung
    • Authors: Shavkat I. Mamatkulov; Christoph Allolio, Roland R. Netz, Douwe Jan Bonthuis
      Pages: 16058 - 16064
      Abstract: Die Oberflächenspannung der Wasser-Luft-Grenzfläche steigt bei Zugabe von anorganischen Salzen, entsprechend einer Verarmung von Ionen. Hingegen verursachen die meisten Säuren eine Verringerung der Oberflächenspannung, was einen Überschuss von hydrierten Protonen an der Oberfläche anzeigt. Zusammen mit der scheinbar negativen Ladung der Grenzfläche zwischen Luft und reinem Wasser, die aus elektrokinetischen Experimenten folgt, führte diese experimentelle Beobachtung zu heftigen Diskussionen seit der Mitte des 19. Jahrhunderts. Hier bestimmen wir die Oberflächenspannung und Affinität der Ionen zur Oberfläche aus klassischen, thermodynamisch konsistenten Molekulardynamiksimulationen. Die Oberflächenspannungen der Lösungen mit NaOH, HCl und NaCl stimmen quantitativ bemerkenswert gut mit experimentell gemessenen Werten überein. Von den untersuchten Ionen wird nur H3O+ an der Luft-Wasser-Grenzfläche adsorbiert. Die Adsorption lässt sich durch den tiefen Potentialtopf erklären, der durch die Ausrichtung des H3O+-Dipols im elektrischen Feld der Grenzfläche entsteht, was wir mit Ab-initio-Simulationen bestätigen.Oberflächenspannungen und Ionenaffinitäten zur Luft-Wasser-Oberfläche wurden mithilfe von Molekulardynamiksimulationen bestimmt. Die Oberflächenspannungen von NaOH-, HCl- und NaCl-Lösungen stimmen bemerkenswert gut mit Experimenten überein, und von den untersuchten Ionen wird nur H3O+ an der Luft-Wasser-Grenzfläche adsorbiert. Die Adsorption lässt sich durch den tiefen Potentialtopf erklären, der durch die Ausrichtung des H3O+-Dipols im elektrischen Feld der Grenzfläche entsteht.
      PubDate: 2017-11-13T06:30:37.759822-05:
      DOI: 10.1002/ange.201707391
       
  • Polycyclische, polyprenylierte Acylphloroglucinole – eine Klasse
           nicht-peptidbasierter MRSA- und VRE-aktiver Antibiotika
    • Authors: Claudia Guttroff; Aslihan Baykal, Huanhuan Wang, Peter Popella, Frank Kraus, Nicole Biber, Sophia Krauss, Friedrich Götz, Bernd Plietker
      Pages: 16065 - 16070
      Abstract: In den vergangenen 20 Jahren wurden peptidbasierte Antibiotika wie Vancomycin, Teicoplanin oder Daptomycin als Reserveantibiotika betrachtet. In den letzten Jahren erschienen jedoch vermehrt Berichte über Vancomycin-resistente Krankheitserreger, was die Entwicklung neuartiger Leitstrukturen für neue wirksame Antibiotika motivierte. Hier wird über die Totalsynthese einer definierten endo-Typ-B-PPAP-Bibliothek und deren antibiotische Aktivität gegen multiresistente Staphylococcus-aureus- und diverse Vancomycin-resistente Enterococcus-Stämme berichtet. Es wurden vier neue Strukturen identifiziert, die zeigen, dass das PPAP-Grundgerüst eine neue nicht-peptidbasierte Leitstruktur in der Antibiotika-Forschung werden könnte, die sich durch die Kombination von hoher Aktivität und geringer Zytotoxizität auszeichnet.Eine definierte endo-Typ-B-PPAP-Bibliothek wurde synthetisiert und auf ihre antibiotische Aktivität gegen multiresistente Staphylococcus-aureus- und Vancomycin-resistente Enterococci-Stämme untersucht. Vier neue Strukturen wurden identifiziert (Beispiel siehe Bild), die zeigen, dass PPAPs in der Antibiotikaforschung eine neue Leitstruktur mit hoher Aktivität und geringer Zytotoxizität werden könnten. PPAP=polycyclisches, polyprenyliertes Acylphloroglucinol.
      PubDate: 2017-11-17T04:31:14.945732-05:
      DOI: 10.1002/ange.201707069
       
  • Durch sichtbares Licht und Nahinfrarotstrahlung abbaubare supramolekulare
           Metallo-Gele
    • Authors: Sabrina Theis; Aitziber Iturmendi, Christian Gorsche, Marco Orthofer, Markus Lunzer, Stefan Baudis, Aleksandr Ovsianikov, Robert Liska, Uwe Monkowius, Ian Teasdale
      Pages: 16071 - 16075
      Abstract: Der lichtempfindliche Rutheniumkomplex [Ru(bpy)2(4AMP)2](PF6)2 (4AMP=4-(Aminomethyl)pyridin) wurde über die reaktiven Aminogruppen der durch Licht abspaltbaren 4AMP-Liganden in Polyharnstoff-Organo- oder -Hydrogele eingebaut. Im Dunkeln sind diese Gele sehr stabil. Durch Bestrahlen mit sichtbarem Licht oder NIR-Strahlung (letzteres mittels Zweiphotonenabsorption) werden die Ruthenium-Pyridin-Bindungen gespalten, was zum Abbau des supramolekularen Gels führt. Dies ermöglicht eine räumlich und zeitlich aufgelöste Mikrostrukturierung des Gels mithilfe einer Photomaske oder eines gepulsten NIR-Lasers.Ein Hydrogel auf Basis eines supramolekularen, Ruthenium-haltigen Metallopolymers ist im Dunkeln oder bei Abwesenheit von Lösungsmitteln stabil, zeigt aber bei Belichtung mit sichtbarem Licht oder NIR-Strahlung Abbau und schnelle Degelierung.
      PubDate: 2017-11-15T05:32:57.857035-05:
      DOI: 10.1002/ange.201707321
       
  • Enantioselektive Totalsynthese von 3β-Hydroxy-7β-kemp-8(9)-en-6-on, ein
           aus höheren Termiten isoliertes Diterpen
    • Authors: Yuzhou Wang; Anne Jäger, Margit Gruner, Tilo Lübken, Peter Metz
      Pages: 16076 - 16081
      Abstract: Die erste Totalsynthese des Titelditerpens wurde ausgehend vom Wieland-Miescher-Keton erreicht. Eine diastereoselektive Sulfa-Michael-Addition ermöglichte die Erzeugung der empfindlichen β,γ-ungesättigten Ketoneinheit, während das tetracyclische Kempan-Gerüst problemlos durch Dominometathese aufgebaut wurde.Schwefel hilft! Die erste Totalsynthese des Titelditerpens wurde ausgehend vom Wieland-Miescher-Keton erreicht. Eine diastereoselektive Sulfa-Michael-Addition ermöglichte die Erzeugung der empfindlichen β,γ-ungesättigten Ketoneinheit, während das tetracyclische Kempan-Gerüst problemlos durch Dominometathese aufgebaut wurde.
      PubDate: 2017-11-15T05:32:03.778848-05:
      DOI: 10.1002/ange.201708561
       
  • Wässrige Goldüberwachsung von Silbernanopartikeln: Vereinigung der
           plasmonischen Eigenschaften von Silber mit der Funktionalität von Gold
    • Authors: Martin Mayer; Anja Maria Steiner, Falk Röder, Petr Formanek, Tobias A. F. König, Andreas Fery
      Pages: 16082 - 16086
      Abstract: Bis heute war es nicht möglich, die optische Güte von Silbernanopartikeln mit Eigenschaften wie chemischer Stabilität, Oberflächenmodifizierbarkeit und kontrollierter Synthese in Verbindung zu bringen. Wir präsentieren eine Synthesemethode, die zukünftige Entwicklungen in Informations-, Energie- und Medizintechnologie ermöglicht, in denen optische oder elektronische Eigenschaften eine zentrale Rolle spielen. Dafür kombinieren wir die goldtypischen Eigenschaften mit der Plasmonik von Silber in einem rein wasserbasierten Au/Ag/Au-Kern-Schale-Schale-System. Die Dispersität der Nanopartikel wird durch maskierte Goldkerne vorgegeben, wobei die Optik von Silber bestimmt wird. Die Überwachsung mit einer sehr dünnen, schützenden Goldschicht verleiht Oxidationsstabilität und Oberflächenfunktionalität, ohne die optischen Eigenschaften des Silbers zu beeinträchtigen. Damit werden die optische Güte von Silber und die chemische Stabilität von Gold vereint – ohne Limitierung auf eine Morphologie.Optische Güte und chemische Stabilität: In einem allgemeinen Syntheseansatz wird die Dispersität durch die maskierten Goldkerne vorgegeben, während die Optik von Silber bestimmt wird. Die erneute Überwachsung mit einer sehr dünnen, schützenden Goldschicht ermöglicht Oxidationsstabilität und Oberflächenfunktionalität, ohne die durch Silber gewonnenen optischen Eigenschaften zu beeinträchtigen.
      PubDate: 2017-11-21T03:31:43.187136-05:
      DOI: 10.1002/ange.201708398
       
  • Oxidative P-P-Bindungsaddition an Cobalt(−I): Bildung eines
           Low-spin-Cobalt(III)-Phosphanidokomplexes
    • Authors: Peter Coburger; Serhiy Demeshko, Christian Rödl, Evamarie Hey-Hawkins, Robert Wolf
      Pages: 16087 - 16091
      Abstract: Die oxidative P-P-Bindungsaddition eines ortho-Carboran-substituierten 1,2-Diphosphetans an Cobalt(−I) in [K(thf)0.2][Co(η4-cod)2)] (cod=1,5-Cycloctadien) ermöglichte die Darstellung des ersten homoleptischen Cobalt(III)-Phosphanidokomplexes [K(thf)4][Co{1,2-(PtBu)2C2B10H12}2] (1). Diese Verbindung ist ein seltenes Beispiel eines verzerrt tetraedrisch koordinierten 3d6-Komplexes mit einem Low-spin-Grundzustand. Magnetische Messungen ergaben, dass 1 zwischen 2 und 270 K im Festkörper und bei 298 K in einer [D8]THF-Lösung diamagnetisch ist. Dichtefunktionalrechnungen zeigten, dass der diamagnetische Grundzustand durch die starken σ-Donor- und die moderaten π-Donoreigenschaften der Bisphosphanidoliganden verursacht wird.Ein homoleptischer Cobaltphosphanidokomplex wird durch die Reaktion eines Carboran-1,2-diphosphetans mit einer Cobalt(−I)-Quelle gebildet. Die resultierende Cobalt(III)-Verbindung ist der erste Vertreter einer neuen Klasse tetraedrischer Low-spin-Phosphanidokomplexe.
      PubDate: 2017-11-15T05:31:37.643735-05:
      DOI: 10.1002/ange.201709140
       
  • Kationische stickstoffdotierte helikale Nanographene
    • Authors: Kun Xu; Yubin Fu, Youjia Zhou, Felix Hennersdorf, Peter Machata, Ilka Vincon, Jan J. Weigand, Alexey A. Popov, Reinhard Berger, Xinliang Feng
      Pages: 16092 - 16097
      Abstract: Wir berichten über Design und Synthese einer Serie von neuen kationischen stickstoffdotierten Nanographenen (CNDN) mit einer nichtplanaren Geometrie und axialer Chiralität. Einkristall-Röntgendiffraktometrie beweist deren helikale und teils “Cove”-terminierte Struktur. Verglichen mit den reinen Kohlenstoffanalogen liegen die Grenzorbitale der CNDN energetisch tiefer, was zu einer verringerten optischen Energielücke und einer erhöhten Elektronenaffinität führt. Alle Derivate zeigen in cyclovoltammetrischen Untersuchungen quasireversibles Reduktionsverhalten. Abhängig von der Zahl an Stickstoffdotanden ist es möglich, neutrale Radikale (bei einem Stickstoffdotanden) oder Radikalkationen (bei zwei Stickstoffdotanden) während des Reduktionsprozesses über In-situ-Spektroelektrochemie zu analysieren. Kationische Stickstoffdotierung kombiniert mit Helizität erschließt neue Wege für das Design und die Synthese von ausgedehnten Nanographenen und Nanographenstreifen.Stickstoff Plus: Ein „Bottom-up”-Ansatz ermöglicht einen einfachen Zugang zu kationischen stickstoffdotierten helikalen Nanographenen. Die neuen Nanographene haben vielversprechende Eigenschaften für optische und elektronische Anwendungen.
      PubDate: 2017-11-14T12:50:54.490552-05:
      DOI: 10.1002/ange.201707714
       
  • Ferroelasticity in an Organic Crystal: A Macroscopic and Molecular Level
           Study
    • Authors: Sajjad Husain Mir; Yuichi Takasaki, Emile Richard Engel, Satoshi Takamizawa
      Pages: 16098 - 16101
      Abstract: Ferroelasticity has been relatively well-studied in mechanically robust inorganic atomic solids but poorly investigated in organic crystals, which are typically inherently fragile. The absence of precise methods for the mechanical analysis of small crystals has, no doubt, impeded research on organic ferroelasticity. The first example of ferroelasticity in an organic molecular crystal of 5-chloro-2-nitroaniline is presented, with thorough characterization by macro- and microscopic methods. The observed cyclic stress–strain curve satisfies the requirements of ferroelasticity. Single-crystal X-ray structure analysis provides insight into lattice correspondence at the twining interface, which enables substantial crystal bending by a large molecular orientational shift. This deformation represents the highest maximum strain (115.9 %) among reported twinning materials, and the associated dissipated energy density of 216 kJ m−3 is relatively large, which suggests that this material is potentially useful as a mechanical damping agent.Zwei aus einem: Ein organischer 5-Chlor-2-nitroanilin-Einkristall zeigt Ferroelastizität bei mechanischer Verzwillingung. Strukturanalysen der Grenzfläche zeigen eine große Molekülverschiebung mit begleitender Kristallverbiegung. Die Deformation erzeugt eine maximale Scherspannung von 115.9 % und eine hohe Dichte an dissipierter Zugenergie (Ed: 216 kJ m−3), die für Anwendungen, etwa als Stoßdämpfer, interessant sind.
      PubDate: 2017-11-02T08:16:07.101212-05:
      DOI: 10.1002/ange.201707749
       
  • Dual Functionalization of White Phosphorus: Formation, Characterization,
           and Reactivity of Rare-Earth-Metal Cyclo-P3 Complexes
    • Authors: Shanshan Du; Jianhao Yin, Yue Chi, Ling Xu, Wen-Xiong Zhang
      Pages: 16102 - 16106
      Abstract: The [3+1] fragmentation reaction of rare-earth metallacyclopentadienes 1 a–c with 0.5 equivalents of P4 affords a series of rare-earth metal cyclo-P3 complexes 2 a–c and a phospholyl anion 3. 2 a–c demonstrate an unusual η3 coordination mode with one P−P bond featuring partial π-bonding character. 2 a–c are the first cyclo-P3 complexes of rare-earth metals, and also the first organo-substituted polyphosphides in the category of Group 3 and f-block elements. Rare-earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels–Alder reaction. Compounds 2 a–c can coordinate to one or two [W(CO)5] units, yielding 4 a–c or 5 c, respectively. Furthermore, oxidation of 2 a with p-benzoquinone produces its corresponding phospholyllithium and regenerated P4.Die Fragmentierung von P4 liefert cyclo-P3-Seltenerdmetallkomplexen mit ungewöhnlicher η3-Koordination, wobei eine P-P-Bindung π-Anteile aufweist. Durch Oxidation des cyclo-P3-Komplexes mit p-Benzochinon sind Phospholylanionen zugänglich; bei diesem Prozess wird zusätzlich P4 regeneriert.
      PubDate: 2017-11-17T05:36:32.397334-05:
      DOI: 10.1002/ange.201708897
       
  • Bifurcated Nickel-Catalyzed Functionalizations: Heteroarene C−H
           Activation with Allenes
    • Authors: Sachiyo Nakanowatari; Thomas Müller, João C. A. Oliveira, Lutz Ackermann
      Pages: 16107 - 16111
      Abstract: A unified strategy for nickel(0)-catalyzed C−H allylations, alkenylations, and dienylations has been realized through versatile hydroarylations of allenes with ample scope. Thus, an inexpensive nickel catalyst modified with a N-heterocyclic carbene ligand enabled the direct transformation of C−H bonds of biologically relevant imidazole and purine derivatives with full control of regio- and chemoselectivity.Einfache C-H-Aktivierung: Gegabelte Nickel(0)-katalysierte C-H-Allylierungen, Alkenylierungen und Dienylierungen wurden durch Hydroarylierung von Allenen unter vollständiger Kontrolle der Regio- und Chemoselektivität durchgeführt. Das Substratspektrum umfasst eine Vielzahl von Imidazol- und Purinderivaten.
      PubDate: 2017-11-22T03:11:41.908751-05:
      DOI: 10.1002/ange.201709087
       
  • Enantioselective Copper-Catalyzed Alkylation of Quinoline N-Oxides with
           Vinylarenes
    • Authors: Songjie Yu; Hui Leng Sang, Shaozhong Ge
      Pages: 16112 - 16116
      Abstract: An asymmetric copper-catalyzed alkylation of quinoline N-oxides with chiral Cu–alkyl species, generated by migratory insertion of a vinylarene into a chiral Cu−H complex, is reported. A variety of quinoline N-oxides and vinylarenes underwent this Cu-catalyzed enantioselective alkylation reaction, affording the corresponding chiral alkylated N-heteroarenes in high yield with high-to-excellent enantioselectivity. This enantioselective protocol represents the first general and practical approach to access a wide range of chiral alkylated quinolines.Ein breites Spektrum an Chinolin-N-oxiden und Vinylarenen kann in der Titelreaktion zu den entsprechenden chiralen alkylierten Chinolinen umgesetzt werden. Die Produkte werden hoch enantioselektiv und in hohen Ausbeuten erhalten.
      PubDate: 2017-11-14T12:51:08.61571-05:0
      DOI: 10.1002/ange.201709411
       
  • A Manganese Pre-Catalyst: Mild Reduction of Amides, Ketones, Aldehydes,
           and Esters
    • Authors: Colin M. Kelly; Robert McDonald, Orson L. Sydora, Mark Stradiotto, Laura Turculet
      Pages: 16117 - 16120
      Abstract: A new (N-phosphinoamidinate)manganese complex is shown to be a useful pre-catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn-catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.Man(gan) kann: Ein neuer (N-Phosphinoamidinat)mangan-Präkatalysator vermittelt die Reduktion verschiedener Carbonylverbindungen durch Hydrosilylierung unter vergleichbaren Reaktionsbedingungen wie bekannte effektive Übergangsmetallkatalysatoren. Das Ergebnis ist eine Klasse präparativ nützlicher Mn-katalysierter Umsetzungen.
      PubDate: 2017-11-14T12:51:12.123332-05:
      DOI: 10.1002/ange.201709441
       
  • Gold-Catalyzed Asymmetric Intramolecular Cyclization of N-Allenamides for
           the Synthesis of Chiral Tetrahydrocarbolines
    • Authors: Yidong Wang; Peichao Zhang, Xiaoyu Di, Qiang Dai, Zhan-Ming Zhang, Junliang Zhang
      Pages: 16121 - 16125
      Abstract: Highly enantioselective gold-catalyzed intramolecular cyclization of N-allenamides was implemented by utilizing a designed chiral sulfinamide phosphine ligand (PC-Phos). This represents the first example of highly enantioselective intramolecular cyclization of N-allenamides. The practicality of this reaction was validated in the total synthesis of (R)-desbromoarborescidine A and formal synthesis of (R)-desbromoarborescidine C and (R)-deplancheine. Moreover, the catalyst system PC-Phos/AuNTf2 proved to be specifically efficient to promote the desymmetrization of N-allenamides in excellent yields with satisfactory ee values.Dritter Ring: Eine hoch enantioselektive goldkatalysierte intramolekulare Cyclisierung von N-Allenamiden unter Verwendung von PC-Phos-Liganden wurde entwickelt und in der Totalsynthese von (R)-Debromarborescidin A verwendet.
      PubDate: 2017-11-20T05:36:01.319272-05:
      DOI: 10.1002/ange.201709595
       
  • Efficient Water Reduction with sp3-sp3 Diboron(4) Compounds: Application
           to Hydrogenations, H–D Exchange Reactions, and Carbonyl Reductions
    • Authors: Mathias Flinker; Hongfei Yin, René W. Juhl, Espen Z. Eikeland, Jacob Overgaard, Dennis U. Nielsen, Troels Skrydstrup
      Pages: 16126 - 16131
      Abstract: A series of crystalline sp3-sp3 diboron(4) compounds were synthesized and shown to promote the facile reduction of water with dihydrogen formation. The application of these diborons as simple and effective dihydrogen and dideuterium sources was demonstrated by conducting a series of selective reductions of alkynes and alkenes, and hydrogen–deuterium exchange reactions using two-chamber reactors. Finally, as the water reduction reaction generates an intermediate borohydride species, a range of aldehydes and ketones were reduced by using water as the hydride source.BH-Chemie: sp3-sp3-Diborane(4) können Wasser reduzieren und dadurch Wasserstoff für eine Reihe von Umsetzungen zur Verfügung stellen. Ausgewählte Aldehyde und Ketone wurden in Gegenwart dieser Diborane in Wasser durch intermediäre Borhydridspezies reduziert.
      PubDate: 2017-11-17T05:10:43.29944-05:0
      DOI: 10.1002/ange.201709685
       
  • Cyclic (Amino)(Phosphonium Bora-Ylide)Silanone: A Remarkable
           Room-Temperature-Persistent Silanone
    • Authors: Alfredo Rosas-Sánchez; Isabel Alvarado-Beltran, Antoine Baceiredo, Nathalie Saffon-Merceron, Stéphane Massou, Daisuke Hashizume, Vicenç Branchadell, Tsuyoshi Kato
      Pages: 16132 - 16136
      Abstract: A silanone substituted by bulky amino and phosphonium bora-ylide substituents has been isolated in crystalline form. Thanks to the exceptionally strong electron-donating phosphonium bora-ylide substituent, the lifetime at room temperature of the silanone is dramatically extended (t1/2=4 days) compared to the related (amino)(phosphonium ylide)silanone VI (t1/2=5 h), allowing easier manipulation and its use as precursor of new valuable silicon compounds. The interaction of silanone with a weak Lewis acid such as MgBr2 increases further its stability (no degradation after 3 weeks at room temperature).Ein Silanon mit sperrigen Amino- und Phosphoniumbor-Ylid-Substituenten wurde synthetisiert und in kristalliner Form isoliert. Der stark elektronenschiebende Ylid-Substituent verleiht der Verbindung eine lange Lebensdauer (t1/2=4 Tage). Die Wechselwirkung mit einer schwachen Lewis-Säure wie MgBr2 wirkt weiter stabilisierend, sodass nach 3 Wochen bei Raumtemperatur keine Zersetzung des Silanons beobachtet wurde.
      PubDate: 2017-11-22T03:12:51.305312-05:
      DOI: 10.1002/ange.201710358
       
  • Microwave-Assisted Synthesis of Heterocycles by Rhodium(III)-Catalyzed
           Annulation of N-Methoxyamides with α-Chloroaldehydes
    • Authors: Ji-Rong Huang; Carsten Bolm
      Pages: 16137 - 16141
      Abstract: α-Chloroaldehydes have been used as alkyne equivalents in rhodium-catalyzed syntheses of isoquinolones and 3,4-dihydroisoquinolins starting from N-methoxyamides. Compared to the existing technology, a complementary regioselectivity is achieved. Mechanistic investigations have been performed, and it was found that steric effects of both substrate and additive determine the product selectivity. Various other heterocycles, such as isoquinolines and lactones, can be prepared by transformation of the obtained products.Salzeffekt: α-Chloraldehyde dienen als Äquivalente für endständige Alkine in einer Synthese von Isochinolonen, 2-Pyridonen und 3,4-Dihydroisochinolinen, welche die Regioselektivität bekannter Prozesse umkehrt. Die Produkte sind nützlich für die Herstellung weiterer Heterocyclen. Das Anion eines zugesetzten Natriumsalzes scheint die Esterenolat-Bildung zu unterstützen oder durch Wasserstoffbrücken gebildete Aggregate zu stabilisieren.
      PubDate: 2017-11-22T03:13:00.924442-05:
      DOI: 10.1002/ange.201710776
       
  • Access to α-Amino Acid Esters through Palladium-Catalyzed Oxidative
           Amination of Vinyl Ethers with Hydrogen Peroxide as the Oxidant and Oxygen
           Source
    • Authors: Lu Ouyang; Jianxiao Li, Jia Zheng, Jiuzhong Huang, Chaorong Qi, Wanqing Wu, Huanfeng Jiang
      Pages: 16142 - 16146
      Abstract: A novel and convenient palladium catalytic system for the synthesis of α-amino acid esters from simple starting materials is reported. Hydrogen peroxide not only acts as the green oxidant, but also as the oxygen source. This strategy for the conversion of amines and vinyl ethers into highly functionalized and structurally diverse α-amino acid esters is characterized by the simplicity of the experimental procedure, mild reaction conditions, high atom economy, scalability, and practicability.Beginnen wir mit etwas Einfachem: Ein praktisches Palladiumkatalysesystem, in dem Wasserstoffperoxid zugleich als Oxidationsmittel und Sauerstoffatomquelle fungiert, überführt leicht verfügbare Amine und Vinylether in hoch funktionalisierte α-Aminosäureester (siehe Schema). Die vielseitige Strategie zeichnet sich durch ein einfaches Syntheseprotokoll, milde Reaktionsbedingungen und hohe Atomökonomie aus.
      PubDate: 2017-11-17T05:15:41.492383-05:
      DOI: 10.1002/ange.201709285
       
  • Three-Dimensional Printing with Biomass-Derived PEF for Carbon-Neutral
           Manufacturing
    • Authors: Fedor A. Kucherov; Evgeny G. Gordeev, Alexey S. Kashin, Valentine P. Ananikov
      Pages: 16147 - 16151
      Abstract: Biomass-derived poly(ethylene-2,5-furandicarboxylate) (PEF) has been used for fused deposition modeling (FDM) 3D printing. A complete cycle from cellulose to the printed object has been performed. The printed PEF objects created in the present study show higher chemical resistance than objects printed with commonly available materials (acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), glycol-modified poly(ethylene terephthalate) (PETG)). The studied PEF polymer has shown key advantages for 3D printing: optimal adhesion, thermoplasticity, lack of delamination and low heat shrinkage. The high thermal stability of PEF and relatively low temperature that is necessary for extrusion are optimal for recycling printed objects and minimizing waste. Several successive cycles of 3D printing and recycling were successfully shown. The suggested approach for extending additive manufacturing to carbon-neutral materials opens a new direction in the field of sustainable development.Von der Cellulose zum Druck: Aus Biomasse gewonnenes Poly(ethylen-2,5-furandicarboxylat) (PEF) wurde für 3D-Schmelzschichtdruck verwendet. Ein vollständiger Zyklus von der Cellulose zum gedruckten Objekt wurde realisiert, und die gedruckten PEF-Objekte zeigen eine bessere chemische Beständigkeit als Objekte, die mit handelsüblichen Materialien gedruckt wurden.
      PubDate: 2017-10-19T07:22:18.635177-05:
      DOI: 10.1002/ange.201708528
       
  • Time-Resolved Interception of Multiple-Charge Accumulation in a
           Sensitizer–Acceptor Dyad
    • Authors: Stéphanie Mendes Marinho; Minh-Huong Ha-Thi, Van-Thai Pham, Annamaria Quaranta, Thomas Pino, Christophe Lefumeux, Thierry Chamaillé, Winfried Leibl, Ally Aukauloo
      Pages: 16152 - 16156
      Abstract: Biomimetic models that contain elements of photosynthesis are fundamental in the development of synthetic systems that can use sunlight to produce fuel. The critical task consists of running several rounds of light-induced charge separation, which is required to accumulate enough redox equivalents at the catalytic sites for the target chemistry to occur. Long-lived first charge-separated state and distinct electronic signatures for the sequential charge accumulated species are essential features to be able to track these events on a spectroscopic ground. Herein, we use a double-excitation nanosecond pump–pump–probe experiment to interrogate two successive rounds of photo-induced electron transfer on a molecular dyad containing a naphthalene diimide (NDI) linked to a [Ru(bpy)3]2+ (bpy=bipyridine) chromophore by using a reversible electron donor. We report an unprecedented long-lived two-electron charge accumulation (t=200 μs).Eine molekulare Dyade aus einer Naphthalindiimid(NDI)-Einheit und einem [Ru(bpy)3]2+-Chromophor (bpy=Bipyridin) wurde in einem Nanosekunden-Pump-Probe-Experiment mit Doppelblitzanregung hinsichtlich zweier aufeinanderfolgender lichtinduzierter Elektronentransfers untersucht. Dabei tritt eine beispiellos langlebige Zwei-Elektronen-Ladungsakkumulation auf. CSS=ladungsgetrennter Zustand.
      PubDate: 2017-11-14T12:50:36.970807-05:
      DOI: 10.1002/ange.201706564
       
  • Polyproline as a Minimal Antifreeze Protein Mimic That Enhances the
           Cryopreservation of Cell Monolayers
    • Authors: Ben Graham; Trisha L. Bailey, Joseph R. J. Healey, Moreno Marcellini, Sylvain Deville, Matthew I. Gibson
      Pages: 16157 - 16160
      Abstract: Tissue engineering, gene therapy, drug screening, and emerging regenerative medicine therapies are fundamentally reliant on high-quality adherent cell culture, but current methods to cryopreserve cells in this format can give low cell yields and require large volumes of solvent “antifreezes”. Herein, we report polyproline as a minimum (bio)synthetic mimic of antifreeze proteins that is accessible by solution, solid-phase, and recombinant methods. We demonstrate that polyproline has ice recrystallisation inhibition activity linked to its amphipathic helix and that it enhances the DMSO cryopreservation of adherent cell lines. Polyproline may be a versatile additive in the emerging field of macromolecular cryoprotectants.Kein Kulturschock: Polyprolin imitiert Frostschutzproteine und inhibiert aufgrund seiner amphipathischen Helix die Eisrekristallisation, was zur besseren Kryokonservierung von Zellmonoschichten genutzt werdenkann. Polyprolin kann synthetisch und biosynthetisch hergestellt werden und bietet sich als ein makromolekulares Kryokonservierungsmittel für die Lagerung von Zellen und Geweben an.
      PubDate: 2017-11-22T03:10:50.730814-05:
      DOI: 10.1002/ange.201706703
       
  • A Tunable and Enantioselective Hetero-Diels–Alder Reaction Provides
           Access to Distinct Piperidinoyl Spirooxindoles
    • Authors: Samydurai Jayakumar; Kathrin Louven, Carsten Strohmann, Kamal Kumar
      Pages: 16161 - 16165
      Abstract: The active complexes of chiral N,N′-dioxide ligands with dysprosium and magnesium salts catalyze the hetero-Diels–Alder reaction between 2-aza-3-silyloxy-butadienes and alkylidene oxindoles to selectively form 3,3′- and 3,4′-piperidinoyl spirooxindoles, respectively, in very high yields and with excellent enantioselectivities. The exo-selective asymmetric cycloaddition successfully regaled the construction of sp3-rich and highly substituted natural-product-based spirooxindoles supporting many chiral centers, including contiguous all-carbon quaternary centers.Spirocyclisierung: DyIII- und MgII-Salze katalysieren in Kombination mit einem N,N′-Dioxid-Liganden hoch enantioselektive Hetero-Diels-Alder-Reaktionen von Silyloxy-2-azadienen mit Alkylidenoxindolen zu 3,3′- bzw. 3,4′-Piperidinoyl-Spirooxindolen in ausgezeichneten Ausbeuten. Boc=tert-Butoxycarbonyl, TBS=tert-Butyldimethylsilyl, Tf=Trifluormethansulfonyl.
      PubDate: 2017-11-22T03:11:16.392217-05:
      DOI: 10.1002/ange.201708355
       
  • Crossover between Tilt Families and Zero Area Thermal Expansion in Hybrid
           Prussian Blue Analogues
    • Authors: Anthony E. Phillips; A. Dominic Fortes
      Pages: 16166 - 16169
      Abstract: Materials in the family of Prussian blue analogues (C3H5N2)2K[M(CN)6], where C3H5N2 is the imidazolium ion and M=Fe, Co, undergo two phase transitions with temperature; at low temperatures the imidazolium cations have an ordered configuration (C2/c), while in the intermediate- and high-temperature phases (both previously reported as R3‾m) they are dynamically disordered. We show from high-resolution powder neutron diffraction data that the high-temperature phase has zero area thermal expansion in the ab-plane. Supported by Landau theory and single-crystal X-ray diffraction data, we re-evaluate the space group symmetry of the intermediate-temperature phase to R3‾. This reveals that the low-to-intermediate temperature transition is due to competition between two different tilt patterns of the [M(CN)6]3− ions. Controlling the relative stabilities of these tilt patterns offers a potential means to tune the exploitable electric behaviour that arises from motion of the imidazolium guest.Zerrbilder und Kippschalter: Eine erneute Untersuchung der Symmetrie zweier cyanidverbrückter Perowskit-Analoga zeigt, dass die Phasenübergänge in diesen Materialien auf zwei konkurrierende Verkippungsmuster zurückzuführen sind. Eine Beeinflussung der Verkippung dieser Hybridmaterialien führt zu Kombinationen von Verzerrungen, die für anorganische Perowskite selten, wenn nicht unmöglich sind.
      PubDate: 2017-11-15T05:32:09.404786-05:
      DOI: 10.1002/ange.201708514
       
  • Atom-Specific Mutagenesis Reveals Structural and Catalytic Roles for an
           Active-Site Adenosine and Hydrated Mg2+ in Pistol Ribozymes
    • Authors: Sandro Neuner; Christoph Falschlunger, Elisabeth Fuchs, Maximilian Himmelstoss, Aiming Ren, Dinshaw J. Patel, Ronald Micura
      Pages: 16170 - 16174
      Abstract: The pistol RNA motif represents a new class of self-cleaving ribozymes of yet unknown biological function. Our recent crystal structure of a pre-catalytic state of this RNA shows guanosine G40 and adenosine A32 close to the G53–U54 cleavage site. While the N1 of G40 is within 3.4 Å of the modeled G53 2′-OH group that attacks the scissile phosphate, thus suggesting a direct role in general acid–base catalysis, the function of A32 is less clear. We present evidence from atom-specific mutagenesis that neither the N1 nor N3 base positions of A32 are involved in catalysis. By contrast, the ribose 2′-OH of A32 seems crucial for the proper positioning of G40 through a H-bond network that involves G42 as a bridging unit between A32 and G40. We also found that disruption of the inner-sphere coordination of the active-site Mg2+ cation to N7 of G33 makes the ribozyme drastically slower. A mechanistic proposal is suggested, with A32 playing a structural role and hydrated Mg2+ playing a catalytic role in cleavage.Feuer frei: Atomspezifische Mutagenese zeigt, dass die Ribose-Einheit des konservierten Adenosins A32 und ein hydratisiertes Mg2+-Ion im aktiven Zentrum des Pistolen-Ribozyms zur Spaltungsaktivität beitragen. Im vorgeschlagenen Mechanismus nimmt A32 einen strukturellen Einfluss, und das hydratisierte Mg2+ katalysiert den Spaltungsprozess.
      PubDate: 2017-11-15T12:08:21.27875-05:0
      DOI: 10.1002/ange.201708679
       
  • An Epitope-Imprinted Biointerface with Dynamic Bioactivity for Modulating
           Cell–Biomaterial Interactions
    • Authors: Guoqing Pan; Sudhirkumar Shinde, Sing Yee Yeung, Miglė Jakštaitė, Qianjin Li, Anette Gjörloff Wingren, Börje Sellergren
      Pages: 16175 - 16179
      Abstract: In this study, an epitope-imprinting strategy was employed for the dynamic display of bioactive ligands on a material interface. An imprinted surface was initially designed to exhibit specific affinity towards a short peptide (i.e., the epitope). This surface was subsequently used to anchor an epitope-tagged cell-adhesive peptide ligand (RGD: Arg-Gly-Asp). Owing to reversible epitope-binding affinity, ligand presentation and thereby cell adhesion could be controlled. As compared to current strategies for the fabrication of dynamic biointerfaces, for example, through reversible covalent or host–guest interactions, such a molecularly tunable dynamic system based on a surface-imprinting process may unlock new applications in in situ cell biology, diagnostics, and regenerative medicine.Ein Epitop-geprägter Polymerfilm wurde zur reversiblen Verankerung des zelladhäsiven Peptids RGD genutzt. Funktionalität wurde anhand eines kontrollierbaren Zelladhäsionsverhaltens demonstriert (siehe Bild).
      PubDate: 2017-10-16T01:21:05.623585-05:
      DOI: 10.1002/ange.201708635
       
  • Scandium-Catalyzed Self-Assisted Polar Co-monomer Enchainment in Ethylene
           Polymerization
    • Authors: Jiazhen Chen; Yanshan Gao, Binghao Wang, Tracy L. Lohr, Tobin J. Marks
      Pages: 16180 - 16184
      Abstract: Direct coordinative copolymerization of ethylene with functionalized co-monomers is a long-sought-after approach to introducing polyolefin functionality. However, functional-group Lewis basicity typically depresses catalytic activity and co-monomer incorporation. Finding alternatives to intensively studied group 4 d0 and late-transition-metal catalysts is crucial to addressing this long-standing challenge. Shown herein is that mono- and binuclear organoscandium complexes with a borate cocatalyst are active for ethylene + amino olefin [AO; H2C=CH(CH2)nNR2] copolymerizations in the absence of a Lewis-acidic masking reagent. Both activity (up to 4.2×102 kg mol−1⋅h−1> atm−1>) and AO incorporation (up to 12 % at 0.2 m [AO]) are appreciable. Linker-length-dependent (n) AO incorporation and mechanistic probes support an unusual functional-group-assisted enchainment mechanism. Furthermore, the binuclear catalysts exhibit enhanced AO tolerance and enhanced long chain AO incorporation.Selbstunterstützt: Scandium-katalysierte Copolymerisationen von Ethylen mit Aminoolefin (AO) gelingen ohne Zugabe von Lewis-sauren Maskierungsreagentien. Von der Linkerlänge abhängige AO-Verkettungsmuster verweisen auf einen ungewöhnlichen Aminogruppen-unterstützten Verkettungsmechanismus. Die Polymerisationsraten mit zweikernigen Katalysatoren hängen weniger von der AO-Konzentration ab, und die Einbaumuster bei größeren Linkerlängen sprechen für eine bimetallische kooperative Verkettung.
      PubDate: 2017-11-15T05:31:51.361308-05:
      DOI: 10.1002/ange.201708797
       
  • High-Pressure Band-Gap Engineering in Lead-Free Cs2AgBiBr6 Double
           Perovskite
    • Authors: Qian Li; Yonggang Wang, Weicheng Pan, Wenge Yang, Bo Zou, Jiang Tang, Zewei Quan
      Pages: 16185 - 16189
      Abstract: Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices.Hochdruck wurde verwendet, um die Kristallstruktur des Cs2AgBiBr6-Doppelperowskits zu modulieren und seine Bandlücke zu manipulieren. Eine um 22.3 % verengte Bandlücke wurde für den anorganischen photovoltaischen Doppelperowskit erzielt. Die verengte Bandlücke bleibt nach Druckentlastung teilweise bestehen, was Anwendungsmöglichkeiten des Perowskits in der Optoelektronik eröffnet.
      PubDate: 2017-11-15T05:31:58.706988-05:
      DOI: 10.1002/ange.201708684
       
  • Site-Specific Pre-Swelling-Directed Morphing Structures of Patterned
           Hydrogels
    • Authors: Zhi Jian Wang; Wei Hong, Zi Liang Wu, Qiang Zheng
      Pages: 16190 - 16194
      Abstract: Morphing materials have promising applications in various fields, yet how to program the self-shaping process for specific configurations remains a challenge. Herein we show a versatile approach to control the buckling of individual domains and thus the outcome configurations of planar-patterned hydrogels. By photolithography, high-swelling disc gels were positioned in a non-swelling gel sheet; the swelling mismatch resulted in out-of-plain buckling of the disc gels. To locally control the buckling direction, masks with holes were used to guide site-specific swelling of the high-swelling gel under the holes, which built a transient through-thickness gradient and thus directed the buckling during the subsequent unmasked swelling process. Therefore, various configurations of an identical patterned hydrogel can be programmed by the pre-swelling step with different masks to encode the buckling directions of separate domains.Unterschiedliche Strukturänderungen in photolithographisch gemusterten Hydrogelen wurden durch selektives Vorquellen von stark quellfähigen Bereichen vorprogrammiert. Dieser Schritt erzeugt einen vorübergehenden Dickegradienten und gibt die Wölbungsrichtung vor. Verschiedene Kombinationen lokalisierter Wölbungen in identisch gemusterten Hydrogelen ergaben verschiedene Strukturen.
      PubDate: 2017-11-22T03:11:31.527489-05:
      DOI: 10.1002/ange.201708926
       
  • Ring-Size-Modulated Reactivity of Putative Dicobalt-Bridging Nitrides:
           C−H Activation versus Phosphinimide Formation
    • Authors: Peng Cui; Qiuran Wang, Samuel P. McCollom, Brian C. Manor, Patrick J. Carroll, Neil C. Tomson
      Pages: 16195 - 16199
      Abstract: Dicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [(nPDI2)Co2(μ-N)(PMe3)2]3+ (PDI=2,6-pyridyldiimine; n=2, 3, corresponding to the number of catenated methylene units between imino nitrogen atoms). Depending on the size of the macrocycle and the reaction conditions (solution versus solid-state), the thermolysis of azide precursors yielded bridging phosphinimido [(2PDI2)Co2(μ-NPMe3)(PMe3)2]3+, amido [(nPDI2)Co2(μ-NH2)(PMe3)2]3+ (n=2, 3), and C−H amination [(3PDI2*-μ-NH)Co2(PMe3)2]3+ products. All results are consistent with the initial formation of [(nPDI2)Co2(μ-N)(PMe3)2]3+, followed by 1) PMe3 attack on the nitride, 2) net hydrogen-atom transfer to form N−H bonds, or 3) C−H amination of the alkyl linker of the nPDI2 ligand.Produkte von C-H-Aminierung, Wasserstoffatomtransfer und Phosphinimid-Bildung wurden nach thermischer Aktivierung von azidverbrückten Dicobaltkomplexen mit flexiblen makrocyclischen Liganden erhalten. Die Größe des Makrocyclus beeinflusst dabei die Produktverteilung.
      PubDate: 2017-11-17T05:05:40.427537-05:
      DOI: 10.1002/ange.201708966
       
  • Localized Supramolecular Peptide Self-Assembly Directed by Enzyme-Induced
           Proton Gradients
    • Authors: Jennifer Rodon Fores; Miguel Leonardo Martinez Mendez, Xiyu Mao, Déborah Wagner, Marc Schmutz, Morgane Rabineau, Philippe Lavalle, Pierre Schaaf, Fouzia Boulmedais, Loïc Jierry
      Pages: 16200 - 16204
      Abstract: Electrodes are ideal substrates for surface localized self-assembly processes. Spatiotemporal control over such processes is generally directed through the release of ions generated by redox reactions occurring specifically at the electrode. The so-used gradients of ions proved their effectiveness over the last decade but are in essence limited to material-based electrodes, considerably reducing the scope of applications. Herein is described a strategy to enzymatically generate proton gradients from non-conductive surfaces. In the presence of oxygen, immobilization of glucose oxidase (GOx) on a multilayer film provides a flow of protons through enzymatic oxidation of glucose by GOx. The confined acidic environment located at the solid–liquid interface allows the self-assembly of Fmoc-AA-OH (Fmoc=fluorenylmethyloxycarbonyl and A=alanine) dipeptides into β-sheet nanofibers exclusively from and near the surface. In the absence of oxygen, a multilayer nanoreactor containing GOx and horseradish peroxidase (HRP) similarly induces Fmoc-AA-OH self-assembly.Die Kraft der Enzyme: In einem mehrschichtigen Film mit Protonengradient und einem Reaktionssystem aus zwei Enzymen wird lokalisiert ein supramolekulares Hydrogel gebildet. Dieser Ansatz bildet eine Alternative zur pH-responsiven Selbstorganisation an Elektrodenoberflächen.
      PubDate: 2017-11-15T05:31:44.58671-05:0
      DOI: 10.1002/ange.201709029
       
  • Mild Reduction of Phosphine Oxides with Phosphites To Access Phosphines
    • Authors: Peng Li; Raphael Wischert, Pascal Métivier
      Pages: 16205 - 16208
      Abstract: A new method for the iodine-catalyzed reduction of phosphine oxides with phosphites at room temperature is reported. The mild reaction conditions, scalability, and simple purification requirements render it a method of choice for the large-scale production and facile regeneration of a variety of phosphines. Mechanistic studies, supported by DFT calculations of the oxygen transfer between the starting phosphine oxide and the phosphite reagent, are also presented. Such transmutations of phosphorus species were previously unknown.Die Reduktion von Phosphinoxiden zu Phosphinen gelingt mit günstigen Phosphiten bei Raumtemperatur. Aufgrund der milden Reaktionsbedingungen, der Skalierbarkeit und der einfachen Aufreinigung bietet sich diese Methode für die Massenproduktion und Regenerierung unterschiedlicher Phosphine an.
      PubDate: 2017-10-26T08:27:45.314021-05:
      DOI: 10.1002/ange.201709519
       
  • The Metal–Support Interaction Concerning the Particle Size Effect of
           Pd/Al2O3 on Methane Combustion
    • Authors: Kazumasa Murata; Yuji Mahara, Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Atsushi Satsuma
      Pages: 16209 - 16213
      Abstract: The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/θ, α-Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/γ-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal–support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.Größe und Phase: Pd/θ-Al2O3 und Pd/ α-Al2O3 zeigen einen anderen Größeneffekt als Pd/γ-Al2O3. Einer spektroskopischen und mikroskopischen Strukturanalyse zufolge beruht die Größen- und Phasenabhängigkeit der katalytischen Aktivität auf dem Anteil an Stufenpositionen im Pd-Partikel. Unterschiedliche Anteile ergeben sich aus der Partikelform, die von der Größe der Pd-Partikel und der Stärke der Metall-Träger-Wechselwirkungen bestimmt wird.
      PubDate: 2017-11-15T12:26:33.419572-05:
      DOI: 10.1002/ange.201709124
       
  • A Multivalent Structure-Specific RNA Binder with Extremely Stable Target
           Binding but Reduced Interaction with Nonspecific RNAs
    • Authors: Jeong Min Lee; Ahreum Hwang, Hyeongjoo Choi, Yongsang Jo, Bongsoo Kim, Taejoon Kang, Yongwon Jung
      Pages: 16214 - 16218
      Abstract: By greatly enhancing binding affinities against target biomolecules, multivalent interactions provide an attractive strategy for biosensing. However, there is also a major concern for increased binding to nonspecific targets by multivalent binding. A range of charge-engineered probes of a structure-specific RNA binding protein PAZ as well as multivalent forms of these PAZ probes were constructed by using diverse multivalent avidin proteins (2-mer, 4-mer, and 24-mer). Increased valency vastly enhanced the binding stability of PAZ to structured target RNA. Surprisingly, nonspecific RNA binding of multivalent PAZ can be reduced even below that of the PAZ monomer by controlling negative charges on both PAZ and multivalent avidin scaffolds. The optimized 24-meric PAZ showed nearly irreversible binding to target RNA with negligible binding to nonspecific RNA, and this ultra-specific 24-meric PAZ probe allowed SERS detection of intact microRNAs at an attomolar level.Ein RNA-bindendes Monomer und multivalente Gerüstproteine wurden optimiert, um eine multivalente Sonde zu erzeugen, die praktisch irreversibel an die Ziel-RNA und vernachlässigbar an nichtspezifische RNA bindet. Der resultierende hochspezifische 24-mere RNA-Binder ermöglicht den SERS-Nachweis von intakten miRNAs auf attomolarem Niveau.
      PubDate: 2017-11-13T04:47:22.043943-05:
      DOI: 10.1002/ange.201709153
       
  • Mesoporous Carbon@Titanium Nitride Hollow Spheres as an Efficient SeS2
           Host for Advanced Li–SeS2 Batteries
    • Authors: Zhen Li; Jintao Zhang, Bu Yuan Guan, Xiong Wen (David) Lou
      Pages: 16219 - 16223
      Abstract: The introduction of a certain proportion of selenium into sulfur-based cathodes is an effective strategy for enhancing the integrated battery performance. However, similar to sulfur, selenium sulfide cathodes suffer from poor cycling stability owing to the dissolution of reaction intermediate products. In this study, to exploit the advantages of SeS2 to the full and avoid its shortcomings, we designed and synthesized a hollow mesoporous carbon@titanium nitride (HMC@TiN) host for loading 70 wt % of SeS2 as a cathode material for Li–SeS2 batteries. Benefiting from both physical and chemical entrapment by hollow mesoporous carbon and TiN, the HMC@TiN/SeS2 cathode manifests high utilization of the active material and excellent cycling stability. Moreover, it exhibits promising areal capacity (up to 4 mAh cm−2) with stable cell performance in the high-mass-loading electrode.Eine Doppelfalle: Hohles mesoporöses Kohlenstoff@Titannitrid (HMC@TiN) mit 70 Gew.-% SeS2 wurde als Kathodenmaterial für Li-SeS2-Batterien entwickelt (siehe Bild). Resultierend aus dem physikalischen und chemischen Einschluss in dem hohlen mesoporösen Kohlenstoff und TiN zeigt die HMC@TiN/SeS2-Kathode einen hohen Nutzungsgrad des aktiven Materials und exzellente Zyklenstabilität.
      PubDate: 2017-11-13T04:47:56.545167-05:
      DOI: 10.1002/ange.201709176
       
  • Living Supramolecular Polymerization of a Perylene Bisimide Dye into
           Fluorescent J-Aggregates
    • Authors: Wolfgang Wagner; Marius Wehner, Vladimir Stepanenko, Soichiro Ogi, Frank Würthner
      Pages: 16224 - 16228
      Abstract: The self-assembly of a new perylene bisimide (PBI) organogelator with 1,7-dimethoxy substituents in the bay position affords non-fluorescent H-aggregates at high cooling rates and fluorescent J-aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped “off-pathway” H-aggregates are transformed into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of π–π interactions and intra- and intermolecular hydrogen bonding for monomeric, H-, and J-aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain-growth supramolecular polymerization process.Lebende supramolekulare Polymerisation: Erstmals konnte ein Perylenbisimid (PBI) durch lebende Keimpolymerisation in mehreren Wachstumszyklen verlängert werden. Der PBI-Organogelator bildet „off-pathway”-H-Aggregate, die in die thermodynamisch begünstigten fluoreszierenden J-Aggregate überführt werden.
      PubDate: 2017-11-15T12:08:02.314245-05:
      DOI: 10.1002/ange.201709307
       
  • Rhodium(II)- or Copper(I)-Catalyzed Formal Intramolecular Carbene
           
    • Authors: Qi Zhou; Shichao Li, Yan Zhang, Jianbo Wang
      Pages: 16229 - 16233
      Abstract: A rhodium(II)- or copper(I)-catalyzed formal intramolecular carbene insertion into vinylic C(sp2)−H bonds is reported herein. This method provides straightforward access to 1H-indenes with high efficiency and excellent functional-group compatibility. Mechanistically, the reaction is proposed to involve the following sequence: metal carbene formation, intramolecular nucleophilic addition of the double bond to the electron-deficient carbene carbon atom, dearomatization, and finally a 1,5-H shift.Kurz und bündig: Eine Rhodium(II)- oder Kupfer(I)-katalysierte formale Carben-Insertion in vinylische C-H-Bindungen wurde entwickelt und für die kurze Synthese von 1H-Indenen genutzt (siehe Schema). Die Reaktion ist gut verträglich mit funktionellen Gruppen und folgt vermutlich einem stufenweisen Mechanismus aus nukleophiler Addition der Doppelbindung an das Metallcarben und Dearomatisierungs/Aromatisierungs-Prozessen.
      PubDate: 2017-11-22T03:11:51.333701-05:
      DOI: 10.1002/ange.201709375
       
  • Creation of “Rose Petal” and “Lotus Leaf” Effects on Alumina by
           Surface Functionalization and Metal-Ion Coordination
    • Authors: Rahul Dev Mukhopadhyay; Balaraman Vedhanarayanan, Ayyappanpillai Ajayaghosh
      Pages: 16234 - 16238
      Abstract: Functional differences between superhydrophobic surfaces, such as lotus leaf and rose petals, are due to the subtle architectural features created by nature. Mimicry of these surfaces with synthetic molecules continues to be fascinating as well as challenging. Herein, we demonstrate how inherently hydrophilic alumina surface can be modified to give two distinct superhydrophobic behaviors. Functionalization of alumina with an organic ligand resulted in a rose-petal-like surface (water pinning) with a contact angle of 145° and a high contact angle hysteresis (±69°). Subsequent interaction of the ligand with Zn2+ resulted in a lotus-leaf-like surface with water rolling behavior owing to high contact angle (165°) and low-contact-angle-hysteresis (±2°). In both cases, coating of an aromatic bis-aldehyde with alkoxy chain substituents was necessary to emulate the nanowaxy cuticular feature of natural superhydrophobic materials.Ein neues Blatt: Oberflächenfunktionalisierung und Koordinationspolymerchemie werden genutzt, um MOF-basierte Nanoarchitekturen auf einer Aluminiumoxidoberfläche zu erzeugen. Die inhärente Superhydrophilie der Oberfläche wird derart modifiziert, dass sie das superhydrophobe Verhalten von Rosenblüten und Lotusblättern annimmt.
      PubDate: 2017-11-15T12:08:53.0811-05:00
      DOI: 10.1002/ange.201709463
       
  • Systemic Delivery of Bc12-Targeting siRNA by DNA Nanoparticles Suppresses
           Cancer Cell Growth
    • Authors: Mohammad Aminur Rahman; Pengfei Wang, Zhixiang Zhao, Dongsheng Wang, Sreenivas Nannapaneni, Chao Zhang, Zhengjia Chen, Christopher C. Griffith, Selwyn J. Hurwitz, Zhuo G. Chen, Yonggang Ke, Dong M. Shin
      Pages: 16239 - 16243
      Abstract: Short interfering RNA (siRNA) is a promising molecular tool for cancer therapy, but its clinical success is limited by the lack of robust in vivo delivery systems. Rationally designed DNA nanoparticles (DNPs) have emerged as facile delivery vehicles because their physicochemical properties can be precisely controlled. Nonetheless, few studies have used DNPs to deliver siRNAs in vivo, and none has demonstrated therapeutic efficacy. Herein, we constructed a number of DNPs of rectangular and tubular shapes with varied dimensions using the modular DNA brick method for the systemic delivery of siRNA that targets anti-apoptotic protein Bcl2. The siRNA delivered by the DNPs inhibited cell growth both in vitro and in vivo, which suppressed tumor growth in a xenograft model that specifically correlated with Bcl2 depletion. This study suggests that DNPs are effective tools for the systemic delivery of therapeutic siRNA and have great potential for further clinical translation.DNA-Nanopartikel unterdrücken als systemische Transporter von siRNA das Tumorwachstum, indem sie ein antiapoptotisches Protein Bcl2 spezifisch inaktivieren.
      PubDate: 2017-11-16T04:50:59.566117-05:
      DOI: 10.1002/ange.201709485
       
  • Multi-Step Crystallization of Barium Carbonate: Rapid Interconversion of
           Amorphous and Crystalline Precursors
    • Authors: Michael L. Whittaker; Paul J. M. Smeets, Hasti Asayesh-Ardakani, Reza Shahbazian-Yassar, Derk Joester
      Pages: 16244 - 16247
      Abstract: The direct observation of amorphous barium carbonate (ABC), which transforms into a previously unknown barium carbonate hydrate (herewith named gortatowskite) within a few hundred milliseconds of formation, is described. In situ X-ray scattering, cryo-, and low-dose electron microscopy were used to capture the transformation of nanoparticulate ABC into gortatowskite crystals, highly anisotropic sheets that are up to 1 μm in width, yet only about 10 nm in thickness. Recrystallization of gortatowskite to witherite starts within 30 seconds. We describe a bulk synthesis and report a first assessment of the composition, vibrational spectra, and structure of gortatowskite. Our findings indicate that transient amorphous and crystalline precursors can play a role in aqueous precipitation pathways that may often be overlooked owing to their extremely short lifetimes and small dimensions. However, such transient precursors may be integral to the formation of more stable phases.Die Präzipitation von Witherit (BaCO3) aus wässriger Lösung erfolgt unter Beteiligung von nicht nur einer, sondern zwei Vorstufen: amorphem Bariumcarbonat (ABC) und kristallinem Bariumcarbonat-Monohydrat (Gortatowskit), das mit quasi-zweidimensionalem Habitus kristallisiert. Beide Intermediate sind sehr kurzlebig, und ihre Charakterisierung erfordert In-situ-Techniken mit hoher Zeitauflösung, niedriger Strahlendosis und/oder Kryo-Elektronenmikroskopie.
      PubDate: 2017-11-15T12:27:21.256841-05:
      DOI: 10.1002/ange.201709526
       
  • Access to Chiral Hydropyrimidines through Palladium-Catalyzed Asymmetric
           Allylic C−H Amination
    • Authors: Pu-Sheng Wang; Meng-Lan Shen, Tian-Ci Wang, Hua-Chen Lin, Liu-Zhu Gong
      Pages: 16248 - 16252
      Abstract: A palladium-catalyzed asymmetric intramolecular allylic C−H amination controlled by a chiral phosphoramidite ligand was established for the preparation of various substituted chiral hydropyrimidinones, the precursors of hydropyrimidines, in high yields with high enantioselectivities. In particular, dienyl sodium N-sulfonyl amides bearing an arylethene-1-sulfonyl group underwent a sequential allylic C−H amination and intramolecular Diels–Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidinone frameworks in high yields and with high levels of stereoselectivity. Significantly, this method was used as the key step in an asymmetric synthesis of letermovir.Der Kern der Sache: Eine asymmetrische Palladium-katalysierte intramolekulare allylische C-H-Aminierung, die von einem chiralen Phosphoramiditliganden dirigiert wird, wurde zur effizienten Synthese unterschiedlich substituierter chiraler Hydropyrimidine genutzt. Diese Methode wurde zur asymmetrischen Synthese von Letermovir verwendet (siehe Schema; IMDA=intramolekulare Diels-Alder-Reaktion).
      PubDate: 2017-11-15T12:08:12.832036-05:
      DOI: 10.1002/ange.201709681
       
  • Activation and Deactivation of Gold/Ceria–Zirconia in the
           Low-Temperature Water–Gas Shift Reaction
    • Authors: James H. Carter; Xi Liu, Qian He, Sultan Althahban, Ewa Nowicka, Simon J. Freakley, Liwei Niu, David J. Morgan, Yongwang Li, J. W. (Hans) Niemantsverdriet, Stanislaw Golunski, Christopher J. Kiely, Graham J. Hutchings
      Pages: 16253 - 16257
      Abstract: Gold (Au) on ceria–zirconia is one of the most active catalysts for the low-temperature water–gas shift reaction (LTS), a key stage of upgrading H2 reformate streams for fuel cells. However, this catalyst rapidly deactivates on-stream and the deactivation mechanism remains unclear. Using stop–start scanning transmission electron microscopy to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X-ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (NPs; 1–2 nm) from subnanometer Au species. These NPs were then seen to agglomerate further over 48 h on-stream, and most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au NPs.Nach dem Goldrausch: Stopp-Start-Raster-TEM wurde genutzt, um während der Niedertemperatur-Wassergasreaktion über Au/CeZrO4 gebildete Au-Spezies zu detektieren. Au-Nanopartikel, die beim Aufheizen des Katalysators auf Reaktionstemperatur gebildet werden, agglomerieren unter den Reaktionsbedingungen. Röntgen-PES offenbart, dass die Katalysatordeaktivierung aus der Partikelagglomeration resultiert.
      PubDate: 2017-11-15T12:09:41.483644-05:
      DOI: 10.1002/ange.201709708
       
  • Intermolecular Pummerer Coupling with Carbon Nucleophiles in
           Non-Electrophilic Media
    • Authors: Kilian Colas; Raúl Martín-Montero, Abraham Mendoza
      Pages: 16258 - 16262
      Abstract: A new Pummerer-type C−C coupling protocol is introduced based on turbo-organomagnesium amides, which unlike traditional Pummerer reactions, does not require strong electrophilic activators, engages a broad range of C(sp3)-, C(sp2)-, and C(sp)-nucleophiles, and seamlessly integrates with C−H and C−X magnesiation. Given the central character of sulfur compounds in organic chemistry, this protocol allows access to unrelated carbonyls, olefins, organometallics, halides, and boronic esters through a single strategy.C-C-Verknüpfungen durch Pummerer-Kupplung gelingen in einem einzigen Arbeitsschritt, zur Aktivierung werden jedoch Elektrophile benötigt. Eine effiziente orthogonale Vorgehensweise für elektrophilfreie Pummerer-C-C-Kupplungen unter Verwendung von DIPAMgCl⋅ LiCl wird vorgestellt, die Einschränkungen des etablierten Protokolls überwindet.
      PubDate: 2017-11-15T12:09:27.708147-05:
      DOI: 10.1002/ange.201709715
       
  • Atomically Dispersed Copper–Platinum Dual Sites Alloyed with Palladium
           Nanorings Catalyze the Hydrogen Evolution Reaction
    • Authors: Tingting Chao; Xuan Luo, Wenxing Chen, Bin Jiang, Jingjie Ge, Yue Lin, Geng Wu, Xiaoqian Wang, Yanmin Hu, Zhongbin Zhuang, Yuen Wu, Xun Hong, Yadong Li
      Pages: 16263 - 16267
      Abstract: Designing highly active catalysts at an atomic scale is required to drive the hydrogen evolution reaction (HER). Copper–platinum (Cu-Pt) dual sites were alloyed with palladium nanorings (Pd NRs) containing 1.5 atom % Pt, using atomically dispersed Cu on ultrathin Pd NRs as seeds. The ultrafine structure of atomically dispersed Cu-Pt dual sites was confirmed with X-ray absorption fine structure (XAFS) measurements. The Pd/Cu-Pt NRs exhibit excellent HER properties in acidic solution with an overpotential of only 22.8 mV at a current density of 10 mA cm−2 and a high mass current density of 3002 A g−1(Pd+Pt) at a −0.05 V potential.Atomar dispergierte duale Kupfer-Platin(Cu-Pt)-Zentren legiert mit Palladium(Pd)-Nanoringen zeigen exzellente Eigenschaften in der Wasserstoffentwicklung. Die elektrokatalytische Aktivität übertrifft diejenige kommerzieller Platin-Kohlenstoff(Pt/C)-Katalysatoren.
      PubDate: 2017-11-15T12:08:28.623015-05:
      DOI: 10.1002/ange.201709803
       
  • Double Catalytic Kinetic Resolution (DoCKR) of Acyclic anti-1,3-Diols: The
           Additive Horeau Amplification
    • Authors: Jérémy Merad; Prashant Borkar, Frédéric Caijo, Jean-Marc Pons, Jean-Luc Parrain, Olivier Chuzel, Cyril Bressy
      Pages: 16268 - 16272
      Abstract: The concept of a synergistic double catalytic kinetic resolution (DoCKR) as described in this article was successfully applied to racemic acyclic anti-1,3-diols, a common motif in natural products. This process takes advantage of an additive Horeau amplification involving two successive enantioselective organocatalytic acylation reactions, and leads to diesters and recovered diols with high enantiopurities. It was first developed with C2-symmetrical diols and then further extended to non-C2-symmetrical anti diols to prepare useful chiral building blocks. The protocol is highly practical as it only requires 1 mol % of a commercially available organocatalyst and leads to easily separable products. This procedure was applied to the shortest reported total synthesis of (+)-cryptocaryalactone, a natural product with anti-germinative activity.Dem Katalysator eine zweite Chance: Eine synergistische doppelte katalytische kinetische Racematspaltung (DoCKR) wurde auf racemische acyclische anti-1,3-Diole, ein häufiges Strukturmotiv von Naturstoffen, angewendet. Die organokatalytische doppelte Acylierung liefert Diester und nichtumgesetzte Diole in hohen Enantiomerenreinheiten. Nach C2-symmetrischen Diolen bewährten sich auch nicht-C2-symmetrische anti-Diole beim Aufbau chiraler Synthesebausteine.
      PubDate: 2017-11-15T12:07:32.1201-05:00
      DOI: 10.1002/ange.201709844
       
  • Understanding LiOH Chemistry in a Ruthenium-Catalyzed Li–O2 Battery
    • Authors: Tao Liu; Zigeng Liu, Gunwoo Kim, James T. Frith, Nuria Garcia-Araez, Clare P. Grey
      Pages: 16273 - 16278
      Abstract: Non-aqueous Li–O2 batteries are promising for next-generation energy storage. New battery chemistries based on LiOH, rather than Li2O2, have been recently reported in systems with added water, one using a soluble additive LiI and the other using solid Ru catalysts. Here, the focus is on the mechanism of Ru-catalyzed LiOH chemistry. Using nuclear magnetic resonance, operando electrochemical pressure measurements, and mass spectrometry, it is shown that on discharging LiOH forms via a 4 e− oxygen reduction reaction, the H in LiOH coming solely from added H2O and the O from both O2 and H2O. On charging, quantitative LiOH oxidation occurs at 3.1 V, with O being trapped in a form of dimethyl sulfone in the electrolyte. Compared to Li2O2, LiOH formation over Ru incurs few side reactions, a critical advantage for developing a long-lived battery. An optimized metal-catalyst–electrolyte couple needs to be sought that aids LiOH oxidation and is stable towards attack by hydroxyl radicals.Energiespeicher der nächsten Generation: Die Ru-katalysierte Bildung von LiOH und dessen Zersetzungsreaktionen werden in einer Li-O2-Batterie mit zugesetztem Wasser demonstriert. Der Batteriemechanismus wurde durch Isotopenmarkierung aufgeklärt.
      PubDate: 2017-11-21T03:31:25.21615-05:0
      DOI: 10.1002/ange.201709886
       
  • Antibacterial Narrow-Band-Gap Conjugated Oligoelectrolytes with High
           Photothermal Conversion Efficiency
    • Authors: Bing Wang; Guangxue Feng, Martin Seifrid, Ming Wang, Bin Liu, Guillermo C. Bazan
      Pages: 16279 - 16282
      Abstract: Two conjugated oligoelectrolytes (COEs), WMG1 and WMG2, were designed with the goal of achieving near infrared absorption and high photothermal conversion efficiency. Specifically, electron-rich thiophene and electron-poor benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole subunits were introduced into the conjugated core to modulate the optical gap and to reduce the fluorescence emission efficiency. WMG1 and WMG2 show absorption maxima at around 800 nm, which favors tissue penetration. Although relatively small in size, WMG1 and WMG2 exhibit photothermal conversion efficiencies of circa 60 % and 54 %, respectively. WMG1 shows dark toxicity to the Gram positive bacterium B. subtilis and good photothermal killing efficiency toward both B. subtilis and Gram negative E. coli, features that demonstrate the promising potential of the COE molecular design for photothermal applications.Zwei konjugierte Oligoelektrolyte (COEs), WMG1 und MWG2, zeigen NIR-Absorption und hohe photothermische Wirkungsgrade. WMG1 zeichnet sich durch eine effiziente photothermische Abtötung von Pathogenen aus und wirkt im Dunkeln toxisch gegen Gram-positive Bakterien.
      PubDate: 2017-11-15T05:31:17.784482-05:
      DOI: 10.1002/ange.201709887
       
  • Lead- and Iodide-Deficient (CH3NH3)PbI3 (d-MAPI): The Bridge between 2D
           and 3D Hybrid Perovskites
    • Authors: Antonin Leblanc; Nicolas Mercier, Magali Allain, Jens Dittmer, Vincent Fernandez, Thierry Pauporté
      Pages: 16283 - 16288
      Abstract: 3D and 2D hybrid perovskites, which have been known for more than 20 years, have emerged recently as promising materials for optoelectronic applications, particularly the 3D compound (CH3NH3)PbI3 (MAPI). The discovery of a new family of hybrid perovskites called d-MAPI is reported: the association of PbI2 with both methyl ammonium (MA+) and hydroxyethyl ammonium (HEA+) cations leads to a series of five compounds with general formulation (MA)1−2.48x(HEA)3.48x[Pb1−xI3−x]. These materials, which are lead- and iodide-deficient compared to MAPI while retaining 3D architecture, can be considered as a bridge between the 2D and 3D materials. Moreover, they can be prepared as crystallized thin films by spin-coating. These new 3D materials appear very promising for optoelectronic applications, not only because of their reduced lead content, but also in account of the large flexibility of their chemical composition through potential substitutions of MA+, HEA+, Pb2+ and I− ions.Die Assoziation von PbI2 mit Methylammonium (MA+) und Hydroxyethylammonium (HEA+) führt zu fünf Verbindungen der allgemeinen Summenformel (MA)1−2.48x(HEA)3.48x[Pb1−xI3−x]. Diese d-MAPI-Materialien, die gegenüber der Stammverbindung (CH3NH3)PbI3 (MAPI) einen Blei- und Iodidunterschuss aufweisen, können in Form dünner Filme hergestellt werden. Durch Beibehaltung ihrer 3D-Architektur bilden sie eine Brücke zwischen 2D-Hybridperowskiten und MAPI.
      PubDate: 2017-11-15T12:09:08.625175-05:
      DOI: 10.1002/ange.201710021
       
  • The Effect of Methylammonium Iodide on the Supersaturation and Interfacial
           Energy of the Crystallization of Methylammonium Lead Triiodide Single
           Crystals
    • Authors: Bichen Li; Furkan H. Isikgor, Hikmet Coskun, Jianyong Ouyang
      Pages: 16289 - 16292
      Abstract: It is very important to study the crystallization of hybrid organic–inorganic perovskites because their thin films are usually prepared from solution. The investigation on the growth of perovskite films is however limited by their polycrystallinity. In this work, methylammonium lead triiodide single crystals grown from solutions with different methylammonium iodide (MAI):lead iodide (PbI2) ratios were investigated. We observed a V-shaped dependence of the crystallization onset temperature on the MAI:PbI2 ratio. This is attributed to the MAI effects on the supersaturation of precursors and the interfacial energy of the crystal growth. At low MAI:PbI2 ratio (
      PubDate: 2017-11-23T04:56:43.805384-05:
      DOI: 10.1002/ange.201710234
       
  • Valence-Engineering of Quantum Dots Using Programmable DNA Scaffolds
    • Authors: Jianlei Shen; Qian Tang, Li Li, Jiang Li, Xiaolei Zuo, Xiangmeng Qu, Hao Pei, Lihua Wang, Chunhai Fan
      Pages: 16293 - 16297
      Abstract: Precise control over the valency of quantum dots (QDs) is critical and fundamental for quantitative imaging in living cells. However, prior approaches on valence control of QDs remain restricted to single types of valences. A DNA-programmed general strategy is presented for valence engineering of QDs with high modularity and high yield. By employing a series of programmable DNA scaffolds, QDs were generated with tunable valences in a single step with near-quantitative yield (>95 %). The use of these valence-engineered QDs was further demonstrated to develop 12 types of topologically organized QDs-QDs and QDs-AuNPs and 4 types of fluorescent resonance energy transfer (FRET) nanostructures. Quantitative analysis of the FRET nanostructures and live-cell imaging reveal the high potential of these nanoprobes in bioimaging and nanophotonic applications.Eine DNA-programmierte, allgemeingültige Strategie ermöglicht die gezielte Einstellung der Valenz von Quantenpunkten (QDs). Unter Verwendung einer Reihe von programmierbaren DNA-Gerüsten wurden QDs mit einstellbaren Valenzen in einem einzigen Schritt fast quantitativ (>95 %) erhalten. Die QDs wurden verwendet, um zwölf Typen topologisch organisierter QDs-QDs und QDs-AuNPs sowie vier Typen von FRET-Nanostrukturen zu entwickeln.
      PubDate: 2017-11-13T04:46:58.569341-05:
      DOI: 10.1002/ange.201710309
       
  • GOx@ZIF-8(NiPd) Nanoflower: An Artificial Enzyme System for Tandem
           Catalysis
    • Authors: Qingqing Wang; Xueping Zhang, Liang Huang, Zhiquan Zhang, Shaojun Dong
      Pages: 16298 - 16301
      Abstract: We report a facile approach to prepare an artificial enzyme system for tandem catalysis. NiPd hollow nanoparticles and glucose oxidase (GOx) were simultaneously immobilized on the zeolitic imidazolate framework 8 (ZIF-8) via a co-precipitation method. The as-prepared GOx@ZIF-8(NiPd) nanoflower not only exhibited the peroxidase-like activity of NiPd hollow nanoparticles but also maintained the enzymatic activity of GOx. A colorimetric sensor for rapid detection of glucose was realized through the GOx@ZIF-8(NiPd) based multi-enzyme system. Moreover, the GOx@ZIF-8(NiPd) modified electrode showed good bioactivity of GOx and high electrocatalytic activity for the oxygen reduction reaction (ORR), which could also be used for electrochemical detection of glucose.Flower Power: Hohle NiPd-Nanopartikel und Glucose-Oxidase (GOx) wurden durch gemeinsame Fällung in einem Metall-organischen Gerüst (ZIF-8) immobilisiert. Das resultierende System verbindet GOx-Aktivität mit Sauerstoffreduktionsfähigkeit und schlägt somit eine Brücke zwischen natürlichen Enzymen und Nanozymen.
      PubDate: 2017-11-20T05:45:24.387412-05:
      DOI: 10.1002/ange.201710418
       
  • Rational Design of Single Molybdenum Atoms Anchored on N-Doped Carbon for
           Effective Hydrogen Evolution Reaction
    • Authors: Wenxing Chen; Jiajing Pei, Chun-Ting He, Jiawei Wan, Hanlin Ren, Youqi Zhu, Yu Wang, Juncai Dong, Shubo Tian, Weng-Chon Cheong, Siqi Lu, Lirong Zheng, Xusheng Zheng, Wensheng Yan, Zhongbin Zhuang, Chen Chen, Qing Peng, Dingsheng Wang, Yadong Li
      Pages: 16302 - 16306
      Abstract: The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo1N1C2). Importantly, the Mo1N1C2 catalyst displayed much more excellent activity compared with Mo2C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo1N1C2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts.Einzelne Mo-Atome dispergiert auf N-dotiertem Kohlenstoff zeigen hohe katalytische Aktivität und Stabilität in der Wasserstoffentwicklung (HER). Die Katalysatorstruktur wurde durch Elektronenmikroskopie und XAFS charakterisiert, und die einzigartigen katalytischen Eigenschaften wurden in DFT-Rechnungen untersucht.
      PubDate: 2017-11-15T05:31:08.15851-05:0
      DOI: 10.1002/ange.201710599
       
  • Innenrücktitelbild: An Epitope-Imprinted Biointerface with Dynamic
           Bioactivity for Modulating Cell–Biomaterial Interactions (Angew. Chem.
           50/2017)
    • Authors: Guoqing Pan; Sudhirkumar Shinde, Sing Yee Yeung, Miglė Jakštaitė, Qianjin Li, Anette Gjörloff Wingren, Börje Sellergren
      Pages: 16307 - 16307
      Abstract: Molekular geprägte synthetische Rezeptoren erreichen die Perfektion natürlicher Rezeptoren! In ihrer Zuschrift auf S. 16175 berichten G. Pan, B. Sellergren und Mitarbeiter über eine Methode der Epitop-Prägung zur reversiblen Verankerung des Zelladhäsionspeptids RGD und demonstrieren damit ein steuerbares Zelladhäsionsverhalten.
      PubDate: 2017-11-07T06:05:51.971504-05:
      DOI: 10.1002/ange.201710972
       
 
 
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