for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (42 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (598 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: 32)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 224)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 1)
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: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 49)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
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: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 18)
Advances in Nanoparticles     Open Access   (Followers: 13)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
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)
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: 66)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Full-text available via subscription   (Followers: 12)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 158)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 213)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
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: 14)
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: 22)
Applied Surface Science     Hybrid Journal   (Followers: 26)
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: 3)
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: 9)
Biochemistry     Full-text available via subscription   (Followers: 284)
Biochemistry Insights     Open Access   (Followers: 5)
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: 18)
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: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 112)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 96)
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: 2)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
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: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 172)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 15)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
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: 141)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 17)
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: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 194)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 8)
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: 23)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
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: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
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: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 11)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 53)
Dalton Transactions     Full-text available via subscription   (Followers: 19)
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: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
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  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [158 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  [1583 journals]
  • A Switchable Open/closed Polyaromatic Macrocycle and its Reversible
           Binding of Long Hydrophilic Molecules
    • Authors: Kohei Kurihara; Kohei Yazaki, Munetaka Akita, Michito Yoshizawa
      Abstract: In spite of wide-ranging previous studies on synthetic macrocycles, installation of open-close functions into the frameworks remains a knotty challenge. Here we present a new polyaromatic macrocycle capable of switching between open and closed forms in response to external stimuli, base and acid. The macrocycle, prepared in three steps, has a well-defined hydrophobic cavity with dimensions of ~1 nm, surrounded by four pH-responsive acridinium panels. The open and closed structures are definitely confirmed by X-ray single-crystal analysis. The cylindrical cavity can bind long hydrophilic molecules up to 2.7 nm in neutral water as well as release the bound guests through the open-to-closed structural change by simple addition of base, in a reversible fashion.
      PubDate: 2017-06-26T03:17:56.246361-05:
      DOI: 10.1002/ange.201703357
       
  • Geometry-retentive C-alkenylation of lithiated α-aminonitriles:
           quaternary α-alkenyl amino acids and hydantoins
    • Authors: Josep Mas-Roselló; Shuji Hachisu, Jonathan Clayden
      Abstract: α-Amino nitriles tethered to alkenes through a urea linkage undergo intramolecular C-alkenylation on treatment with base by attack of the lithionitrile derivatives on the N'-alkenyl group. The geometry-retentive alkene shift affords stereospecifically the E or Z isomer of the 5-alkenyl-4-iminohydantoin products from the corresponding starting E- or Z-N'-alkenyl urea, each of which may be formed from the same N-allyl precursor by stereodivergent alkene isomerisation. The reaction, formally a nucleophilic substitution at an sp2 carbon atom, allows the direct regioselective incorporation of mono-, di-, tri- and tetrasubstituted olefins at the α-carbon of amino acid derivatives. The initially formed 5-alkenyl iminohydantoins may be hydrolysed and oxidatively deprotected to yield hydantoins and unsaturated α-quaternary amino acids.
      PubDate: 2017-06-26T03:17:41.687841-05:
      DOI: 10.1002/ange.201704908
       
  • Unified Asymmetric Total Syntheses of (−)-Alotaketals A–D and
           (−)-Phorbaketal A
    • Authors: Hang Cheng; Zhihong Zhang, Hongliang Yao, Wei Zhang, Jingxun Yu, Rongbiao Tong
      Abstract: The novel tricyclic spiroketal alotane-type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the tricyclic sesterterpenoids (−)-alotaketals A–D and (−)-phorbaketal A were accomplished [29–31 steps from (−)-malic acid] in a collective way for the first time. The key features of the strategy included 1) a new cascade cyclization of vinyl epoxy δ-keto-alcohols to forge the common tricyclic spiroketal intermediate, 2) a late-stage allylic C−H oxidation, and 3) olefin cross-metathesis to install the different side chains.Alleskönner: Ein gemeinsamer Ansatz für die Totalsynthesen der tricyclischen Sesterterpenoide (−)-Alotaketal A–D und (−)-Phorbaketal A liefert die Produkte in 29–31 Stufen ausgehend von (−)-Äpfelsäure. Dabei stehen eine neue Cyclisierungskaskade von Vinylepoxy-δ-ketoalkoholen, eine späte C-H-Oxidation und eine Olefin-Kreuzmetathese im Vordergrund.
      PubDate: 2017-06-26T02:39:38.895299-05:
      DOI: 10.1002/ange.201704628
       
  • Living and Conducting: Coating Individual Bacterial Cells with
           In Situ Formed Polypyrrole
    • Authors: Rong-Bin Song; YiChao Wu, Zong-Qiong Lin, Jian Xie, Chuan Hao Tan, Joachim Say Chye Loo, Bin Cao, Jian-Rong Zhang, Jun-Jie Zhu, Qichun Zhang
      Abstract: Coating individual bacterial cells with conjugated polymers to endow them with more functionalities is highly desirable. Here, we developed an in situ polymerization method to coat polypyrrole on the surface of individual Shewanella oneidensis MR-1, Escherichia coli, Ochrobacterium anthropic or Streptococcus thermophilus. All of these as-coated cells from different bacterial species displayed enhanced conductivities without affecting viability, suggesting the generality of our coating method. Because of their excellent conductivity, we employed polypyrrole-coated Shewanella oneidensis MR-1 as an anode in microbial fuel cells (MFCs) and found that not only direct contact-based extracellular electron transfer is dramatically enhanced, but also the viability of bacterial cells in MFCs is improved. Our results indicate that coating individual bacteria with conjugated polymers could be a promising strategy to enhance their performance or enrich them with more functionalities.Oberflächenmodifizierung von Bakterien: Einzelne Bakterienzellen wurde in situ mit Polypyrrol (PPy) als leitfähiger Schicht überzogen, um den Bakterien eine verbesserte elektrische Leitfähigkeit zu verleihen. Die PPy-Beschichtungen fördern den kontaktbasierten Elektronentransfer zwischen S. oneidensis MR-1 und der Elektrode, wodurch die Erzeugung von Bioelektrizität in mikrobiellen Brennstoffzellen (MFCs) verbessert wird.
      PubDate: 2017-06-26T02:37:54.404636-05:
      DOI: 10.1002/ange.201704729
       
  • Electrochemical Exfoliation of Layered Black Phosphorous to Phosphorene
    • Authors: Martin Pumera
      Abstract: Among 2D materials that recently have attracted enormous interest, black phosphorous (BP) is gaining a rising popularity due to its tunable band gap structure strongly correlated to the thickness and which can enable its use in optoelectronic and electronic applications. It is therefore important to provide a facile and scalable methodology to prepare single or few-layer BP nanosheets. We propose here a simple and fast top-down method to exfoliate a BP crystal into nanosheets of reduced thickness using electrochemistry. The application of an anodic potential to the crystal in acidic aqueous solution allows a control over the exfoliation efficiency and quality of the nanosheets produced. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning transmission electron microscopy (STEM) have been applied to fully characterize the exfoliated material which presented significantly reduced layer thickness compared to the starting bulk material.
      PubDate: 2017-06-26T02:19:06.457081-05:
      DOI: 10.1002/ange.201705071
       
  • Bioorthogonal Labeling of Human Prostate Cancer Tissue Slice Cultures for
           Glycoproteomics
    • Authors: David R. Spiciarich; Rosalie Nolley, Sophia L. Maund, Sean C. Purcell, Jason Herschel, Anthony T. Iavarone, Donna M. Peehl, Carolyn R. Bertozzi
      Abstract: Sialylated glycans are found at elevated levels in many types of cancer and have been implicated in disease progression. However, the specific glycoproteins that contribute to the cancer cell-surface sialylation are not well characterized, specifically in bona fide human disease tissue. Metabolic and bioorthogonal labeling methods have previously enabled the enrichment and identification of sialoglycoproteins from cultured cells and model organisms. Herein, we report the first application of this glycoproteomic platform to human tissues cultured ex vivo. Both normal and cancerous prostate tissues were sliced and cultured in the presence of the azide-functionalized sialic acid biosynthetic precursor Ac4ManNAz. The compound was metabolized to the azidosialic acid and incorporated into cell surface and secreted sialoglycoproteins. Chemical biotinylation followed by enrichment and mass spectrometry led to the identification of glycoproteins that were found at elevated levels or uniquely in cancerous prostate tissue. This work therefore extends the use of bioorthogonal labeling strategies to problems of clinical relevance.Durch metabolische Markierung von humanen Prostatakrebs-Gewebeschnitten in Kultur wurde azidfunktionalisierte Sialinsäure in Zelloberflächen- und Sekret-Glykoproteine eingeführt. Eine chemische Biotinylierung mit anschließender Anreicherung und massenspektrometrischer Analyse führte zur Identifizierung von Glykoproteinen, die ausschließlich oder in erhöhter Konzentration in Prostatakrebsgewebe vorkommen.
      PubDate: 2017-06-26T02:03:54.573994-05:
      DOI: 10.1002/ange.201701424
       
  • On the Thermodynamics and Experimental Control of Twinning in Metal
           Nanocrystals
    • Authors: Kyle D. Gilroy; Joël Puibasset, Madeline Vara, Younan Xia
      Abstract: This work demonstrates a new strategy for controlling the evolution of twin defects in metal nanocrystals by simply following thermodynamic principles. With Ag nanocrystals supported on amorphous SiO2 as a typical example, we establish that twin defects can be rationally generated by equilibrating nanoparticles of different sizes through heating and then cooling. We validate that Ag nanocrystals with icosahedral, decahedral, and single-crystal structures are favored at sizes below 7 nm, between 7 and 11 nm, and greater than 11 nm, respectively. This trend is then rationalized by computational studies based on density functional theory and molecular dynamics, which show that the excess free energy for the three equilibrium structures correlate strongly with particle size. This work not only highlights the importance of thermodynamic control but also adds another synthetic method to the ever-expanding toolbox used for generating metal nanocrystals with desired properties.Kristalle à la carte: Eine neue Strategie für die kontrollierte Bildung von Zwillingsdefekten in Metallnanokristallen folgt einfachen thermodynamischen Prinzipien. Am Beispiel von Ag-Nanokristallen auf amorphem SiO2 wird gezeigt, wie Zwillingsdefekte durch Erhitzen und Abkühlen in äquilibrierenden Nanopartikeln unterschiedlicher Größen rational erzeugt werden können.
      PubDate: 2017-06-26T01:52:53.581908-05:
      DOI: 10.1002/ange.201705443
       
  • Reversible Photothermal Isomerization of Carborane-Fused Azaborole to
           Borirane: Synthesis and Reactivity of Carbene-Stabilized Carborane-Fused
           Borirane
    • Authors: Hao Wang; Jiji Zhang, Zuowei Xie
      Abstract: A fully reversible photothermal isomerization between carborane-fused trigonal-planar azaborole (dark-purple) and tetrahedral borirane (pale-yellow) has been observed, leading to the isolation and structural characterization of the first example of carborane-fused borirane. DFT calculations indicate that the azaborole is thermodynamically more stable than the borirane by 11.2 kcal mol−1, and the energy barrier for the thermal conversion from azaborole to borirane is 35.5 kcal mol−1. The reactivity studies show that the B−C(cage) bond in borirane can be broken in the reaction with CuCl, HCl, or elemental sulfur.Ein Kind des Lichts: Eine vollständig reversible photochemisch-thermische Isomerisierung zwischen einem Carboran-kondensierten trigonal-planaren Azaborol (violett) und Boriran (hellgelb) wurde beobachtet. Das Carboran-kondensierte Boriran wurde isoliert und strukturanalytisch charakterisiert. Es reagiert mit CuCl, HCl und elementarem Schwefel unter Spaltung der C(Käfig)-B-Bindung.
      PubDate: 2017-06-26T01:52:39.790292-05:
      DOI: 10.1002/ange.201704642
       
  • Unique spectral overlap and resonant energy transfer between Eu2+ and Yb3+
           : no quantum cutting
    • Authors: Lei Zhou; Peter Anthony Tanner, Weijie Zhou, Yeye Ai, Lixin Ning, Mingmei Wu, Hongbin Liang
      Abstract: Samples of the Ca3Sc2Si3O12 (CSS) host singly-doped with Eu2+ or Yb3+, doubly-doped with Eu2+ and Yb3+, and triply-doped with Ce3+, Eu2+ and Yb3+ were synthesized by a sol-gel combustion process under reducing conditions. Unlike previous reports of Eu2+ Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100% for lightly-doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co-doping with Ce3+ in addition to Eu2+. The quantum efficiencies of the doped materials range between 9% and 93%.
      PubDate: 2017-06-25T22:17:32.033823-05:
      DOI: 10.1002/ange.201703331
       
  • Structure of Amorphous Selenium by 2D 77Se NMR Spectroscopy: An End to The
           Dilemma of Chain vs. Ring
    • Authors: Maxwell Marple; Jackson Badger, Ivan Hung, Zhehong Gan, Kirill Kovnir, Sabyasachi Sen
      Abstract: Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking in the literature to date. The primary controversy regarding the structure of a-Se relates to the relative fraction of Se atoms residing in infinite (Se) chains vs. in Se8 rings. Here we present the results of a two-dimensional solid-state 77Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that (i) the Se8 rings and the infinite (Se) chains are characterized by their unique 77Se NMR signatures and (ii) the structure of amorphous Se consists exclusively of infinite (Se) chains.
      PubDate: 2017-06-25T21:18:51.960364-05:
      DOI: 10.1002/ange.201704323
       
  • Mild Hydrogenation of Amides to Amines over Platinum-Vanadium Bimetallic
           Catalyst
    • Authors: Takato Mitsudome; Kazuya Miyagawa, Zen Maeno, Tomoo Mizugaki, Koichiro Jitsukawa, Jun Yamasaki, Yasutaka Kitagawa, Kiyotomi Kaneda
      Abstract: Hydrogenation of amides to amines is an important reaction, but the need for high temperatures and H₂ pressures is a problem. No catalysts that are effective under mild conditions, i.e., lower than 30 bar H₂/70 °C, have yet been reported. Here, the mild hydrogenation of amides was achieved for the first time, using a Pt-V bimetallic catalyst. Amide hydrogenation under just 1 bar H₂ at 70 °C or 5 bar H₂ at room temperature was achieved using the bimetallic catalyst. The mild reaction conditions enabled highly selective hydrogenation of various amides to the corresponding amines, while inhibiting arene-hydrogenation. Catalyst characterization showed that the origin of the bimetallic catalyst's activity is oxophilic V-decorated Pt nanoparticles of diameter 2 nm.
      PubDate: 2017-06-25T21:18:49.81706-05:0
      DOI: 10.1002/ange.201704199
       
  • Powder Catalyst Fixation for Post-Electrolysis Structural Characterisation
           of NiFe Layered Double Hydroxide Based Oxygen Evolution Reaction
           Electrocatalysts
    • Authors: Corina Andronescu; Stefan Barwe, Edgar Ventosa, Justus Masa, Eugeniu Vasile, Bharathi Konkena, Sandra Möller, Wolfgang Schuhmann
      Abstract: Highly active electrocatalysts for the oxygen evolution reaction are in most cases powder nanomaterials which undergo substantial changes upon applying the high potentials required for high current density oxygen evolution. Due to the vigorous gas evolution the durability under OER conditions is disappointingly low for most powder electrocatalysts due to missing strategies to securely fix powder catalysts to electrode surfaces. Thus, reliable studies of catalysts during or after OER are often impaired. We propose composites of precursors of polybenzoxazines and organophilic modified NiFe layered double hydroxides (LDHs) to form a stable and highly conducting catalyst layer, which allows the study of the catalyst before and after electrocatalysis. Characterisation of the material by XRD, SEM and TEM before and after 100 h electrolysis in 5 M KOH and 60 °C at a current density of 200 mA cm-2 is presented and reveals previously not observed structural changes.
      PubDate: 2017-06-25T21:18:40.22112-05:0
      DOI: 10.1002/ange.201705385
       
  • Human vs Robots in the Discovery and Crystallization of Gigantic
           Polyoxometalates
    • Authors: Lee Cronin; Vasilios Duros, Jonathan Grizou, Weimin Xuan, Zied Hosni, De-Liang Long, Haralampos Miras
      Abstract: The discovery of new gigantic molecules formed by self-assembly using single crystal X-ray crystallography is a challenging endeavor as it combines two contingent events; first is the formation of a new molecule, and second its crystallization. Herein, we constructed a workflow that can be followed manually or by a robot to probe the envelope of both events and employed it in the chemical space of a new polyoxometalate cluster, namely Na6[Mo120Ce6O366H12(H2O)78]·200H2O (1) which has a trigonal-ring type architecture (yield 4.3% based on Mo). This compound features a dodecameric ring with an inner diameter of 17 Å and an outer of 31 Å and the synthesis and crystallization was probed using an active machine-learning algorithm developed by us to explore the crystallization space and compare it to human experimenters. The algorithm covers ca. 9 times more space versus random and ca. 6 times more than humans and increases prediction accuracy to 82.4±0.7% over 77.1±0.9% from humans.
      PubDate: 2017-06-25T21:18:27.638551-05:
      DOI: 10.1002/ange.201705721
       
  • Reconstitution of Low-Density Lipoproteins with Fatty Acids for the
           Targeted Delivery of Drugs into Cancer Cells
    • Authors: Chunlei Zhu; Pallab Pradhan, Da Huo, Jiajia Xue, Song Shen, Krishnendu Roy, Younan Xia
      Abstract: Low-density lipoproteins (LDLs) represent a novel class of nanocarriers for the targeted delivery of therapeutics into aberrant cells that overexpress the LDL receptor. Here we report a facile procedure for reconstituting the hydrophobic core of LDLs with a binary fatty acid mixture. Facilitated by the tumor targeting capability of the apolipoprotein, the reconstituted, drug-loaded LDLs can effectively target cancer cells that overexpress the LDL receptor while showing minor adverse impact on normal fibroblasts. According to a hypothesized mechanism, the reconstituted LDLs can also enable metabolism-triggered drug release while preventing the payloads from lysosomal degradation. This study demonstrates that LDLs reconstructed with fatty acids hold great promise to serve as effective and versatile nanocarriers for targeted cancer therapy.
      PubDate: 2017-06-24T01:47:37.259978-05:
      DOI: 10.1002/ange.201704674
       
  • Manganese catalyzed C-H functionalizations involving an unexpected
           heteroaryl-shift
    • Authors: Magnus Rueping
      Abstract: A manganese catalyzed regio- and stereoselective hydroarylation of allenes is reported. The C-H functionalization protocol offers access to various alkenylated indoles with excellent yields. Moreover, a hydroarylation/cyclization cascade involving an unexpected C-N bond cleavage and aryl shift has been developed which provides a new synthetic approach to substituted pyrroloindolones.
      PubDate: 2017-06-24T01:23:44.903441-05:
      DOI: 10.1002/ange.201704682
       
  • Palladium-Catalyzed Fluoroarylation of gem-Difluoroalkenes
    • Authors: Hai-Jun Tang; Ling-Zhi Lin, chao feng, Teck-Peng Loh
      Abstract: Pd-catalyzed fluoroarylation of gem-difluoroalkenes with aryl halides is disclosed. By taking advantage of the in situ generated α-CF3-benzylsilver intermediates derived from the nucleophilic addition of silver fluoride onto gem-difluoroalkenens, the present strategy bypasses the employment of strong base, thus enabling a mild and general synthetic protocol for the ready access of non-symmetric α,α-disubstituted trifluoroethane derivatives.
      PubDate: 2017-06-24T01:23:28.779033-05:
      DOI: 10.1002/ange.201705321
       
  • A Highly Efficient Synthesis of Z-Macrocycles using Stereoretentive,
           Ruthenium-Based Metathesis Catalysts
    • Authors: Tonia Sarah Ahmed; Robert H. Grubbs
      Abstract: A highly efficient, Z-selective ring-closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium-based catalyst supported by a dithiolate ligand is reported. This catalyst is demonstrated to be remarkably active as observed in initiation experiments showing complete catalyst initiation at -20 °C within 10 min. Macrocyclization reactions generated Z-products from easily accessible diene starting materials bearing a Z-olefin moiety. This stereoretentive approach provides a more efficient and selective route to Z-macrocyles than in previously reported systems. Reactions were completed in appreciably shorter reaction times, and turnover numbers of up to 100 could be achieved. Macrocyclic lactones ranging in size from twelve-membered to seventeen-membered rings are synthesized in moderate to high yields (68 - 79% yield) with excellent Z-selectivity (95% - 99% Z).
      PubDate: 2017-06-23T13:50:22.775558-05:
      DOI: 10.1002/ange.201704670
       
  • Heterogeneous Microtesla SABRE Enhancement of 15N NMR Signals
    • Authors: Kirill V. Kovtunov; Larisa M. Kovtunova, Max E. Gemeinhardt, Andrey V. Bukhtiyarov, Jonathan Gesiorski, Valerii I. Bukhtiyarov, Eduard Y. Chekmenev, Igor V. Koptyug, Boyd Goodson
      Abstract: The hyperpolarization of heteronuclei via Signal Amplification by Reversible Exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes = 1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD = cyclooctadiene] catalyst onto silica particles modified with NH2(CH2)3- linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate ~102-fold enhancement of 15N NMR signals in pyridine at 9.4 T following parahydrogen bubbling within a magnetic shield. No 15N NMR enhancement was observed from the supernatant liquid following catalyst separation, which along with XRD characterization, supports that the effects result from SABRE under heterogeneous catalytic conditions. The technique can be developed further for producing catalyst-free agents via SABRE with hyperpolarized heteronuclear spins, and thus is promising for biomedical NMR and MRI applications.
      PubDate: 2017-06-23T11:45:21.748501-05:
      DOI: 10.1002/ange.201705014
       
  • Bacteriophage Tail Tube Assembly Studied by Proton-Detected 4D Solid-State
           NMR
    • Authors: Maximilian Zinke; Pascal Fricke, Camille Samson, Songhwan Hwang, Joseph Wall, Sascha Lange, Sophie Zinn-Justin, Adam Lange
      Abstract: Obtaining unambiguous resonance assignments remains a major bottleneck in solid-state NMR studies of protein structure and dynamics. Particularly for supramolecular assemblies with large subunits (>150 residues), the analysis of crowded spectral data presents a challenge, even if three-dimensional (3D) spectra are used. Here, we present a proton-detected 4D solid-state NMR assignment procedure that is tailored for large assemblies. The key to recording 4D spectra with three indirect carbon or nitrogen dimensions with their inherently large chemical shift dispersion lies in the use of sparse non-uniform sampling (as low as 2%). As a proof-of-principle we acquired 4D (H)COCANH, (H)CACONH and (H)CBCANH spectra of the 20 kDa bacteriophage tail tube protein gp17.1 in a total time of two and a half weeks. These spectra were sufficient to obtain complete resonance assignments in a straightforward manner without use of previous solution NMR data.
      PubDate: 2017-06-23T09:57:14.005498-05:
      DOI: 10.1002/ange.201706060
       
  • The Cope Rearrangement of 1,5 Dimethylsemibullvalene-2(4)-d1: Experimental
           Evidence for Heavy Atom Tunneling
    • Authors: Tim Schleif; Joel Mierez-Perez, Stefan Henkel, Melanie Ertelt, Weston Thatcher Borden, Wolfram Sander
      Abstract: As an experimental test of the theoretical prediction that heavy-atom tunneling is involved in the degenerate Cope rearrangement of semibullvalenes at cryogenic temperatures, mono-deuterated 1,5-dimethyl¬semibullvalene isotopomers were prepared and investigated by IR spectroscopy, using the matrix isolation technique. As predicted, the less thermodynamically stable isotopomer rearranges at cryogenic temperatures in the dark to the more stable one, while broadband IR irradiation above 2000 cm-1 results in an equilibration of the isotopomeric ratio. Since this reaction proceeds with a rate constant in the order of 10-4 s-1 despite an experimental barrier of Ea = 4.8 kcal mol-1 and with only a shallow temperature-dependence, the results are interpreted in terms of heavy-atom tunneling.
      PubDate: 2017-06-23T05:50:35.794138-05:
      DOI: 10.1002/ange.201704787
       
  • Ceria-Zirconia Nanoparticles as Enhanced Multi-Antioxidant for Sepsis
           Treatment
    • Authors: Min Soh; Dong-Wan Kang, Han-Gil Jeong, Dokyoon Kim, Do Yeon Kim, Wookjin Yang, Changyeong Song, Seungmin Baik, In-Young Choi, Seul-Ki Ki, Hyek Jin Kwon, Taeho Kim, Chi Kyung Kim, Seung-Hoon Lee, Taeghwan Hyeon
      Abstract: The two oxidation states of ceria nanoparticles, Ce3+ and Ce4+, play a pivotal role in scavenging reactive oxygen species (ROS). In particular, Ce3+ is largely responsible for removing O2- and *OH that are associated with inflammatory response and cell death. Here, we report the synthesis of 2 nm ceria-zirconia nanoparticles (CZ NPs) that possess a higher Ce3+/Ce4+ ratio and faster conversion from Ce4+ to Ce3+ than those exhibited by ceria nanoparticles. The obtained Ce0.7Zr0.3O2 (7CZ) NPs greatly improve ROS scavenging performance, thus regulating inflammatory cells in a very low dose. Moreover, 7CZ NPs are demonstrated to be effective in reducing mortality and systemic inflammation in two representative sepsis models. These findings suggest that 7CZ NPs have the potential as a therapeutic nanomedicine for treating ROS-related inflammatory diseases.
      PubDate: 2017-06-23T05:50:25.590348-05:
      DOI: 10.1002/ange.201704904
       
  • A Critical Assessment of the Direct Catalytic Oxidation of Methane to
           Methanol
    • Authors: Manoj Ravi; Marco Ranocchiari, Jeroen A. van Bokhoven
      Abstract: Despite the emerging number of disparate approaches for the direct selective partial oxidation of methane, none of them has translated into an industrial process. The oxidation of methane to methanol is a difficult yet intriguing and rewarding task as it has the potential to eliminate the prevalent natural gas flaring by providing novel routes to its valorisation. This review considers the synthesis of methanol and methanol derivatives from methane by homogeneous and heterogeneous pathways. In establishing the severe limitations related to the direct catalytic synthesis of methanol from methane, we highlight the vastly superior performance of systems, which produce methanol derivatives or incorporate specific measures such as the use of multi-component catalysts to stabilise methanol. We thereby identify methanol protection as being indispensable in homogeneous and heterogeneous catalysis with regard to future research on this topic.
      PubDate: 2017-06-23T04:05:42.338908-05:
      DOI: 10.1002/ange.201702550
       
  • Heterocorrole Conformations: Little Saddling, Much Ruffling
    • Authors: Jörn Rösner; Birte Cordes, Stefanie Bahnmüller, Gabor Homolya, Dimitri Sakow, Peter Schweyen, Richard Wicht, Martin Bröring
      Abstract: 10-Heterocorrole complexes with oxygen, sulfur, and selenium at position 10 of the macrocycle, and with the divalent ions of nickel, copper, and palladium were prepared and investigated. The focus was set onto the size adaptation and matching mechanisms of cavity sizes vs. ionic radii in corrole-type macrocycles. A full set of single crystal X-ray analyses was obtained and revealed that in all but one case the N4 binding site of the ring-contracted tetrapyrrole is larger than necessary to bind the metal ion without deformation. In plane size adaptation through M-N bond length elongation of 2.5%-3.2% is effective, in addition to pronounced out-of-plane ruffling of the macrocycle for those compounds with a more severe size mismatch. Such ruffling had been excluded for corroles before but is apparently the most efficient mechanism to adapt to small central ions.
      PubDate: 2017-06-23T03:52:46.512509-05:
      DOI: 10.1002/ange.201705551
       
  • Phosphaborenes: accessible reagents for C-C/P-B isosteres
    • Authors: Michael J Cowley; Amy N Price, Gary S Nichol
      Abstract: Formal exchange of C=C units with isoelectronic B=N or B=P units can provide access to molecules with unique electronic or chemical properties. Here, we report the simple solution-phase generation of highly reactive phosphaborenes, RP=BR, and demonstrate their use for the introduction of P=B units into organic systems. A P-B containing cyclobutene isostere can be ring opened to access unique 1,4-bora-phospha-butadiene systems with conjugated main-group multiple bonds.
      PubDate: 2017-06-23T03:52:39.316495-05:
      DOI: 10.1002/ange.201705050
       
  • Selenium-Doped Carbon Quantum Dots (Se-CQDs) for Free Radical Scavenging
    • Authors: Feng Li; Tianyu Li, Chenxing Sun, Jiahao Xia, Yang Jiao, Huaping Xu
      Abstract: Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium-doped carbon dots have rarely been reported even though selenium has unique chemical properties like redox-responsive properties owing to its special electronegativity. Herein, a facile and high-output strategy to fabricate selenium-doped carbon quantum dots (Se-CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se-CQDs with redox-dependent reversible fluorescence. In addition, free radicals such as *OH can be effectively scavenged by the Se-CQDs. Once Se-CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are reduced. This property makes the Se-CQDs capable of protecting the biosystems from oxidative stress.
      PubDate: 2017-06-23T03:52:23.111144-05:
      DOI: 10.1002/ange.201705989
       
  • Enantioselektive Chemo- und Biokatalyse: Partner in der Retrosynthese
    • Authors: Moritz Hönig; Philipp Sondermann, Nicholas J. Turner, Erick M. Carreira
      Abstract: In diesem Aufsatz werden neue Entwicklungen auf den Gebieten der biokatalytischen und chemokatalytischen Synthese diskutiert. Der Beitrag soll als Anleitung für die Verwendung biokatalytischer Methoden in der chemischen Synthese dienen, insbesondere bei retrosynthetischen Überlegungen und Analysen. Die Gliederung dieses Aufsatzes ist nach den Bindungsknüpfungen und ihren jeweiligen synthetischen Methoden strukturiert.Partner in der Synthese: Die Verwendung biokatalytischer Methoden in der chemischen Synthese gewinnt immer mehr an Bedeutung, insbesondere bei retrosynthetischen Überlegungen und Analysen. Dieser Aufsatz soll als Leitfaden für die Anwendung dieser Methoden dienen und ein besseres Verständnis der Merkmale und Unterschiede dieser beiden komplementären Ansätze ermöglichen.
      PubDate: 2017-06-23T03:35:57.164333-05:
      DOI: 10.1002/ange.201612462
       
  • Switching Between Giant Positive and Negative Thermal Expansions of a
           YFe(CN)6-based Prussian Blue Analogue Induced by Guest Species
    • Authors: Qilong Gao; Jun Chen, Qiang Sun, Dahu Chang, Qingzhen Huang, Hui Wu, Andrea Sanson, Ruggero Milazzo, He Zhu, Qiang Li, Zhanning Liu, Jinxia Deng, Xianran Xing
      Abstract: The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K+) and molecules (H2O) can substantially switch thermal expansion of YFe(CN)6 from negative (αv=−33.67×10−6 K−1) to positive (αv=+42.72×10−6 K−1)—a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests.Ehrengast: Das thermische Ausdehnungsverhalten eines offenen YFe(CN)6-Gerüsts kann durch Einlagerung von Kaliumionen oder H2O-Molekülen von stark negativ auf positiv umgeschaltet werden. Die Gastspezies dämpfen Transversalschwingungen der Stickstoff- und Kohlenstoffatome und wirken so der negativen thermischen Ausdehnung entgegen.
      PubDate: 2017-06-23T03:35:27.84798-05:0
      DOI: 10.1002/ange.201702955
       
  • Imaging Endogenous Metal Ions in Living Cells Using a
           DNAzyme–Catalytic Hairpin Assembly Probe
    • Authors: Zhenkun Wu; Huanhuan Fan, Nitya Sai Reddy Satyavolu, WenJing Wang, Ryan Lake, Jian-Hui Jiang, Yi Lu
      Abstract: DNAzymes are a promising platform for metal ion detection, and a few DNAzyme-based sensors have been reported to detect metal ions inside cells. However, these methods required an influx of metal ions to increase their concentrations for detection. To address this major issue, the design of a catalytic hairpin assembly (CHA) reaction to amplify the signal from photocaged Na+-specific DNAzyme to detect endogenous Na+ inside cells is reported. Upon light activation and in the presence of Na+, the NaA43 DNAzyme cleaves its substrate strand and releases a product strand, which becomes an initiator that trigger the subsequent CHA amplification reaction. This strategy allows detection of endogenous Na+ inside cells, which has been demonstrated by both fluorescent imaging of individual cells and flow cytometry of the whole cell population. This method can be generally applied to detect other endogenous metal ions and thus contribute to deeper understanding of the role of metal ions in biological systems.Cha-Cha-Cha: Eine katalytische Haarnadelbildung („catalytic hairpin assembly”, CHA) wurde entworfen, um das Signal der lichtaktivierten Na+-spezifischen DNAzym-Spaltung zu verstärken und endogenes Na+ in Zellen nachzuweisen. In Gegenwart von Na+ spaltet das NaA43-DNAzym nach Bestrahlung seinen Substratstrang und setzt einen Produktstrang frei, der zu einem Initiator für die nachfolgende CHA-Signalverstärkung wird.
      PubDate: 2017-06-23T03:31:19.835017-05:
      DOI: 10.1002/ange.201703540
       
  • Electrically Activated Conductivity and White Light Emission of a
           Hydrocarbon Nanoring–Iodine Assembly
    • Authors: Noriaki Ozaki; Hirotoshi Sakamoto, Taishi Nishihara, Toshihiko Fujimori, Yuh Hijikata, Ryuto Kimura, Stephan Irle, Kenichiro Itami
      Abstract: Numerous otherwise difficult applications have been realized with materials, the chemical/physical properties of which can be controlled by external stimuli such as heat, pressure, photo-irradiation, and voltage bias. However, the complexity of design and the lack of easy-to-conduct synthetic methods make the creation of on-demand stimuli responsive materials a formidable task. Here we report an electric-stimuli-responsive multifunctional material, [10]CPP-I: crystalline assembly of a hydrocarbon nanoring ([10]cycloparaphenylene: [10]CPP) as an “electro-responsive porous host” and iodine as a “potentially functional molecule”. Through applying electric stimulus, [10]CPP-I turned to exhibit two attractive properties: electronic conductivity and white light emission. We revealed that electric stimuli trigger the cascade formation of polyiodide chains inside the [10]CPP assembly through charge transfer, leading to the emergence of these properties. This “responsive porous host” approach is expected to be applicable for different stimuli, and opens the path for devising a generic strategy to the development of stimuli-responsive materials.Wirt-Gast-Systeme: Ein auf elektrische Reize reagierendes, multifunktionelles Material kann einfach durch Mischen eines Kohlenwasserstoffrings ([10]Cycloparaphenylen: [10]CPP) mit Iod ([10]CPP-I) hergestellt werden. Ein elektrischer Reiz verleiht dem Material [10]CPP-I zwei attraktive Eigenschaften: elektronische Einschaltleitfähigkeit und weiße Lichtemission.
      PubDate: 2017-06-23T03:22:35.999276-05:
      DOI: 10.1002/ange.201703648
       
  • Single-enzyme biofuel cells
    • Authors: Chao Ji; Jingwei Hou, Kai Wang, Yun Hau Ng, Vicki Chen
      Abstract: Here, we firstly demonstrate that the intramolecular electron transfer within signle enzyme molecule is an important alternative pathway which can be harnessed to generate electricity. By decoupling the redox reactions within a single type of enzyme (e.g., Trametes versicolor laccase), we harvested electricity efficiently from unconventional fuels including recalcitrant pollutants (e.g. bisphenol-A and hydroquinon) in a single-laccase biofuel cell. The intramolecular electron-harnessing concept was further demonstrated with other enzymes, including power generation during CO2 bioconversion to formate catalyzed by formate dehydrogenase from Candida boidinii. The novel single-enzyme biofuel cell is shown to be potentially feasible utilizing wastewater as fuel as well as generating energy in tandem with driving bioconversion of chemical feedstock from CO2.
      PubDate: 2017-06-23T02:45:33.837012-05:
      DOI: 10.1002/ange.201703980
       
  • Unusual Internal Electron Transfer in Conjugated Radical Polymers
    • Authors: Fei Li; Danielle Gore, Shaoyang Wang, Jodie Lutkenhaus
      Abstract: Nitroxide-containing organic radical polymers (ORPs) have captured attention for their high power and fast redox kinetics. Yet a major challenge is the polymer's aliphatic backbone, resulting in a low electronic conductivity. Recent attempts that replace the aliphatic backbone with a conjugated one have not met with success. The reason for this is not understood until now. We examine a family of polythiophenes bearing nitroxide radical groups, showing that while both species are electrochemically active, there exists an internal electron transfer mechanism that interferes with stabilization of the polymer's fully oxidized form. This finding directs the future design of conjugated radical polymers energy storage and electronics, where careful attention to the redox potential of the backbone relative to the organic radical species is needed.
      PubDate: 2017-06-23T02:45:24.350021-05:
      DOI: 10.1002/ange.201705204
       
  • Associating and dissociating nanodimer analysis for quantifying
           ultra-small amounts of DNA
    • Authors: Keunsuk Kim; Jeong-Wook Oh, Young Kwang Lee, Jiwoong Son, Jwa-Min Nam
      Abstract: Amplification- and enzyme-free quantification of DNA at ultra-low concentrations, on the orders of 10-1,000 targets, is highly beneficial, but is extremely challenging. To address this challenge, true detection signals should be reliably discriminated from false or noise signals. Here, we developed the dynamically associating and dissociating nanodimer analysis (ADNA) method that allows for collecting maximum detection signals from true target-binding events while keeping nonspecific signals at minimum level. In the ADNA assay for ultra-low target concentrations, the whole Au nanoprobes on a lipid micropattern were simultaneously monitored and analyzed in situ, and the newly defined dissociating dimers that are eventually decoupled into monomers after dimer formation were incorporated into detection signals. 10s to 1000s of DNA copies can be reliably quantified with excellent single-base-mismatch differentiation capability using this non-enzymatic, amplification-free ADNA method.
      PubDate: 2017-06-23T01:47:31.663868-05:
      DOI: 10.1002/ange.201705330
       
  • Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO
           Tolerant Catalysts
    • Authors: Aaron Garg; Maria Milina, Madelyn Ball, Daniela Zanchet, Sean T. Hunt, James A. Dumesic, Yuriy Román-Leshkov
      Abstract: Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. The ability to control shell coverage and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.Zum Kern der Sache: Nanopartikel mit Übergangmetallnitrid-Kern (TiWN) und einer Pt-Schale wurde ausgehend von Nanopartikeln mit Metallcarbid-Kern (TiWC) hergestellt. Der Nitrid-Kern moduliert die elektronische Struktur von Pt in einer Weise, dass die CO-Toleranz während der elektrochemischen Wasserstoffoxidation deutlich erhöht ist.
      PubDate: 2017-06-23T01:34:05.937018-05:
      DOI: 10.1002/ange.201704632
       
  • Vancomycin-Dependent Response in Live Drug-Resistant Bacteria by Metabolic
           Labeling
    • Authors: Sean E. Pidgeon; Marcos M. Pires
      Abstract: The surge in drug-resistant bacterial infections threatens to overburden healthcare systems worldwide. Bacterial cell walls are essential to bacteria, thus making them unique targets for the development of antibiotics. We describe a cellular reporter to directly monitor the phenotypic switch in drug-resistant bacteria with temporal resolution. Vancomycin-resistant enterococci (VRE) escape the bactericidal action of vancomycin by chemically modifying their cell-wall precursors. A synthetic cell-wall analogue was developed to hijack the biosynthetic rewiring of drug-resistant cells in response to antibiotics. Our study provides the first in vivo VanX reporter agent that responds to cell-wall alteration in drug-resistant bacteria. Cellular reporters that reveal mechanisms related to antibiotic resistance can potentially have a significant impact on the fundamental understanding of cellular adaption to antibiotics.Können sie widerstehen' Vancomyinresistente Enterokokken exprimieren VanX-Dipeptidasen, die wirkstoffsensitive Bausteine entfernen. Eine Serie von Verbindungen wurde für die metabolische Markierung von Bakterienzellwänden lebender VRE-Zellen eingesetzt (siehe Bild), um mit Antibiotikaresistenz verbundene Strukturveränderungen zu erfassen.
      PubDate: 2017-06-23T01:33:42.006789-05:
      DOI: 10.1002/ange.201704851
       
  • Rhodium(I)-Catalyzed Bridged [5+2] Cycloaddition of
           cis-Allene-vinylcyclopropanes to Synthesize the Bicyclo[4.3.1]decane
           Skeleton
    • Authors: Cheng-Hang Liu; Zhi-Xiang Yu
      Abstract: Previously reported was that cis-ene-vinylcyclopropanes (cis-ene-VCPs) underwent Rh-catalyzed [5+2] reaction to give 5,7-fused bicyclic products, where vinylcyclopropane (VCP) acts as five-carbon synthon. Unfortunately, this reaction had very limited scope. Replacing the 2π component of cis-ene-VCPs to allene moiety, the corresponding cis-allene-VCPs did not undergo the expected normal [5+2] cycloaddition to give 5,7-fused bicyclic products. Instead, the challenging bicyclo[4.3.1]decane skeleton was obtained via an unprecedented bridged [5+2] cycloaddition. DFT calculations were applied to understand why this bridged [5+2] reaction is favored over the anticipated but not realized normal [5+2] reaction.Allen baut Brücken: Unter Rhodiumkatalyse reagieren cis-Allen-Vinylcyclopropane nicht über einen normalen [5+2]-Prozess zu den erwarteten kondensierten Bicyclen, sondern gehen eine überraschende verbrückende [5+2]-Cycloaddition ein. Durch inverse Alleninsertion entsteht auf diesem Weg ein Bicyclo[4.3.1]decan-Gerüst.
      PubDate: 2017-06-23T01:33:27.914739-05:
      DOI: 10.1002/ange.201702288
       
  • Nitrogen Photofixation over III-Nitride Nanowires Assisted by Ruthenium
           Clusters of Low Atomicity
    • Authors: Lu Li; Yichen Wang, Srinivas Vanka, Xiaoyue Mu, Zetian Mi, Chao-Jun Li
      Abstract: In many heterogeneous catalysts, the interaction of supported metal species with a matrix can alter the electronic and morphological properties of the metal and manipulate its catalytic properties. III-nitride semiconductors have a unique ability to stabilize ultra-small ruthenium (Ru) clusters (ca. 0.8 nm) at a high loading density up to 5 wt %. n-Type III-nitride nanowires decorated with Ru sub-nanoclusters offer controlled surface charge properties and exhibit superior UV- and visible-light photocatalytic activity for ammonia synthesis at ambient temperature. A metal/semiconductor interfacial Schottky junction with a 0.94 eV barrier height can greatly facilitate photogenerated electron transfer from III-nitrides to Ru, rendering Ru an electron sink that promotes N≡N bond cleavage, and thereby achieving low-temperature ammonia synthesis.III-Nitrid-Halbleiter stabilisieren Rutheniumcluster mit Beladungsdichten bis 5 Gew.-%. Der Schottky-Übergang an der Grenzfläche zwischen Metall und Halbleiter begünstigt den Transfer von Photoelektronen aus den III-Nitriden auf das Ruthenium, das dadurch die Spaltung der N≡N-Bindung in einer Niedertemperatursynthese von Ammoniak bewirken kann.
      PubDate: 2017-06-23T01:33:12.977721-05:
      DOI: 10.1002/ange.201703301
       
  • α-Radical Phosphines: Synthesis, Structure, and Reactivity
    • Authors: Lianghu Gu; Yiying Zheng, Estela Haldón, Richard Goddard, Eckhard Bill, Walter Thiel, Manuel Alcarazo
      Abstract: A series of phosphines featuring a persistent radical were synthesized in two steps by condensation of dialkyl-/diarylchlorophosphines with stable cyclic (alkyl)(amino)carbenes (cAACs) followed by one-electron reduction of the corresponding cationic intermediates. Structural, spectroscopic, and computational data indicate that the spin density in these phosphines is mainly localized on the original carbene carbon from the cAAC fragment; thus, it remains in the α-position with respect to the central phosphorus atom. The potential of these α-radical phosphines to serve as spin-labeled ligands is demonstrated through the preparation of several AuI derivatives, which were also structurally characterized by single-crystal X-ray diffraction.Da ist das Radikal! Eine Reihe von Phosphan-α-Radikalen wurde ausgehend von cyclischen Alkyl(amino)carbenen synthetisiert, strukturanalytisch charakterisiert und an Gold(I) koordiniert. Dichtefunktionalrechnungen zufolge ist die Spindichte für Phosphanliganden wie Goldkomplexe über das Carben-π-System delokalisiert, mit Schwerpunkt auf dem vormaligen Carben-Kohlenstoffatom.
      PubDate: 2017-06-23T01:33:05.674089-05:
      DOI: 10.1002/ange.201704185
       
  • Aromatic-Imide-Based Thermally Activated Delayed Fluorescence Materials
           for Highly Efficient Organic Light-Emitting Diodes
    • Authors: Meng Li; Yanwei Liu, Ruihong Duan, Xiaofang Wei, Yuanping Yi, Ying Wang, Chuan-Feng Chen
      Abstract: Aromatic-imide-based thermally activated delayed fluorescence (TADF) materials with a twisted donor–acceptor–donor skeleton were efficiently synthesized and exhibited excellent thermal stability and high photoluminescence quantum yields. The small ΔEST value (
      PubDate: 2017-06-23T01:32:46.463235-05:
      DOI: 10.1002/ange.201704435
       
  • Unraveling the Nature of Sites Active toward Hydrogen Peroxide Reduction
           in Fe-N-C Catalysts
    • Authors: Chang Hyuck Choi; Won Seok Choi, Olga Kasian, Anna K. Mechler, Moulay Tahar Sougrati, Sebastian Brüller, Kara Strickland, Qingying Jia, Sanjeev Mukerjee, Karl J. J. Mayrhofer, Frédéric Jaouen
      Abstract: Fe-N-C catalysts with high O2 reduction performance are crucial for displacing Pt in low-temperature fuel cells. However, insufficient understanding of which reaction steps are catalyzed by what sites limits their progress. The nature of sites were investigated that are active toward H2O2 reduction, a key intermediate during indirect O2 reduction and a source of deactivation in fuel cells. Catalysts comprising different relative contents of FeNxCy moieties and Fe particles encapsulated in N-doped carbon layers (0–100 %) show that both types of sites are active, although moderately, toward H2O2 reduction. In contrast, N-doped carbons free of Fe and Fe particles exposed to the electrolyte are inactive. When catalyzing the ORR, FeNxCy moieties are more selective than Fe particles encapsulated in N-doped carbon. These novel insights offer rational approaches for more selective and therefore more durable Fe-N-C catalysts.Die chemische Beschaffenheit sekundärer aktiver Zentren, die während der indirekten Reduktion von O2 gebildetes H2O2 reduzieren, wurde für Fe-N-C-Katalysatoren untersucht. Schichten aus N-dotiertem Kohlenstoff mit eingebetteten Fe-Partikeln und FeNxCy-Einheiten sind mäßige Katalysatoren der H2O2-Reduktion, Fe-freier N-dotierter Kohlenstoff und exponierte Fe-Partikel sind inaktiv. Die Resultate belegen die direkte und indirekte O2-Reduktion mit Fe-N-C-Katalysatoren.
      PubDate: 2017-06-23T01:32:37.639713-05:
      DOI: 10.1002/ange.201704356
       
  • Cofactor-Free, Direct Photoactivation of Enoate Reductases for the
           Asymmetric Reduction of C=C Bonds
    • Authors: Sahng Ha Lee; Da Som Choi, Milja Pesic, Yang Woo Lee, Caroline E. Paul, Frank Hollmann, Chan Beum Park
      Abstract: Enoate reductases from the family of old yellow enzymes (OYEs) can catalyze stereoselective trans-hydrogenation of activated C=C bonds. Their application is limited by the necessity for a continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Visible light-driven activation of OYEs through NAD(P)H-free, direct transfer of photoexcited electrons from xanthene dyes to the prosthetic flavin moiety is reported. Spectroscopic and electrochemical analyses verified spontaneous association of rose bengal and its derivatives with OYEs. Illumination of a white light-emitting-diode triggered photoreduction of OYEs by xanthene dyes, which facilitated the enantioselective reduction of C=C bonds in the absence of NADH. The photoenzymatic conversion of 2-methylcyclohexenone resulted in enantiopure (ee>99 %) (R)-2-methylcyclohexanone with conversion yields as high as 80–90 %. The turnover frequency was significantly affected by the substitution of halogen atoms in xanthene dyes.Flavin-enthaltende alte gelbe Enzyme (AGE) werden ohne NAD(P)H-Kofaktor von molekularen Photosensibilisatoren über direkten Transfer von Photoelektronen zur prosthetischen Flavin-Einheit aktiviert. Bengalrosa (4,5,6,7-Tetrachlor-2′,4′,5′,7′-tetraiodfluorescein, RB) und seine Xanthen-Derivate werden als Photosensibilisatoren der AGE-katalysierten Reduktion konjugierter C=C-Bindungen unter Bestrahlung mit sichtbarem Licht getestet.
      PubDate: 2017-06-23T01:32:30.223125-05:
      DOI: 10.1002/ange.201702461
       
  • Eine neue Raffinesse bei Oligoarylen-Architekturen
    • Authors: Graham J. Bodwell
      Abstract: In Schale geworfen: Ein atemberaubendes schalenförmiges Oligoarylen wurde jüngst hergestellt. Die Struktur ist analog zu der von Corranulen, statt aus zwanzig sp2-hybridisierten Kohlenstoffatomen ist das neue nanometergroße Molekül aber aus zwanzig 1,3,5-trisubstituierten Benzolringen aufgebaut.
      PubDate: 2017-06-23T01:32:25.971824-05:
      DOI: 10.1002/ange.201704621
       
  • “Super-reduzierende” Photokatalyse: konsekutive Energie- und
           Elektronentransfers mit polycyclischen aromatischen Kohlenwasserstoffen
    • Authors: Malte Brasholz
      Abstract: Weniger ist mehr: Aktuelle Entwicklungen in der Photokatalyse machen zunehmend negative Reduktionspotentiale synthetisch nutzbar. Feinabgestimmte Energie- und Elektronentransfers mit polycyclischen aromatischen Kohlenwasserstoffen ermöglichen die katalytische Bildung von stark reduzierenden Aren-Radikalanionen, klassischen Ein-Elektronen-Reduktionsmitteln der organischen Synthese.
      PubDate: 2017-06-23T01:32:23.208843-05:
      DOI: 10.1002/ange.201704763
       
  • One Model, Two Enzymes: Activation of Hydrogen and Carbon Monoxide
    • Authors: Seiji Ogo; Yuki Mori, Tatsuya Ando, Takahiro Matsumoto, Takeshi Yatabe, Ki-Seok Yoon, Hideki Hayashi, Masashi Asano
      Abstract: The ability to catalyze the oxidation of both H2 and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H2 supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H2 and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H2, CO, and H2/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.Enzymatische Katalyse: Könnte man die Oxidation von H2 und CO in einem einzigen Reaktionsgefäß katalysieren, wäre das ein großer Vorteil für die Wasserstofftechnologie, da CO stets als Verunreinigung in technischem Wasserstoff auftritt. Ein Katalysator wird nun vorgestellt, der die Oxidation von H2 und CO entweder einzeln oder zusammen in Abhängigkeit vom pH-Wert katalysieren kann (siehe Bild).
      PubDate: 2017-06-23T01:31:19.579318-05:
      DOI: 10.1002/ange.201704864
       
  • Tuning the Inter-nanofibril Interaction to Regulate the Morphology and
           Function of Peptide/DNA Co-assembled Viral Mimics
    • Authors: Rong Ni; Ying Chau
      Abstract: The ability to tune the inter-subunit interaction within the virus capsid may be critical to assembly and biological function. This process has been extended here with peptide/DNA co-assembled viral mimics. The resulting co-assemblies, formed and stabilized by both DNA-peptide nanofibril and peptide nanofibril-nanofibril interactions, have been tuned through hydrophobic packing interactions of the peptide sequences. By strengthening peptide side chain complementarity and/or elongating the peptide chain (from 4 to 8 residues), we report strengthening the inter-nanofibril interaction to create stable nanococoons with high gene transfection efficacy.
      PubDate: 2017-06-22T23:45:49.33649-05:0
      DOI: 10.1002/ange.201703596
       
  • A Novel Electrochemical Biosensor with Dual Signal Outputs: Toward
           Simultaneous Quantification of pH and O2 in Brain upon Ischemia and in
           Tumor during Cancer Therapy
    • Authors: Li Liu; Fan Zhao, Wei Liu, Tong Zhu, ZH John Zhang, Chen Chen, Zhihui Dai, Huisheng Peng, Jun-long Huang, Qin Hu, Wenbo Bu, Yang Tian
      Abstract: In this work, we develop a novel methodology for designing electrochemical biosensors with both current and potential signal outputs for simultaneous determination of two important species in the live systems. By designing a new molecule, Hemin-aminoferrocene (Hemin-Fc), we create a single electrochemical biosensor for simultaneous quantification of O2 and pH in brain upon ischemia and in tumor during cancer starvation therapy. The reduction peak current of Hemin group increases with rising concentrations of O2 from 1.3 to 200.6 μM. Meanwhile, this peak potential positively shifts with decreasing pH from 8.0 to 5.5, resulting in simultaneous determination of O2 and pH by monitoring both current and potential signal outputs. The developed single biosensor with high temporal and spatial resolutions, as well as remarkable selectivity and accuracy, is successfully applied in determination of O2 and pH in brain upon ischemia, as well as in tumor during cancer therapy.
      PubDate: 2017-06-22T22:45:29.705434-05:
      DOI: 10.1002/ange.201705615
       
  • Cesium's off-the-map valence orbital
    • Authors: Maarten Goesten; Martin Rahm, Matthias Bickelhaupt, Emiel Hensen
      Abstract: The Td-symmetric [CsO4]+ ion, featuring Cs in an oxidation state of 9, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygens. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only. From a Molecular Orbital perspective, the bonding scheme reminds of XeO4: an octet of electrons to bind electronegative ligands, and no low-lying acceptor orbitals on the central atom. In this sense, Cs+ resembles hypervalent Xe.
      PubDate: 2017-06-22T21:50:32.23626-05:0
      DOI: 10.1002/ange.201704118
       
  • Electrochemical TERS Elucidates Potential-Induced Molecular Reorientation
           of Adenine/Au(111)
    • Authors: Natalia Martín Sabanés; Tatsuhiko Ohto, Denis Andrienko, Yuki Nagata, Katrin F. Domke
      Abstract: Electrochemical surface activity arises from the interaction and geometric arrangement of molecules at electrified interfaces. We present a novel electrochemical tip-enhanced Raman spectroscope that can access the vibrational fingerprint of less than 100 small, non-resonant molecules adsorbed at atomically flat Au electrodes to study their adsorption geometry and chemical reactivity as a function of applied potential. Combining experimental and simulation data for showcase adenine/Au(111), we conclude that protonated physisorbed adenine adapts a tilted orientation at low potentials while it is vertically adsorbed around the potential of zero charge. Further potential increase induces adenine deprotonation and reorientation to a planar configuration. The extension of EC-TERS to the study of adsorbate reorientation significantly broadens the applicability of this advanced spectroelectrochemical tool for the nanoscale characterization of a full range of electrochemical interfaces.
      PubDate: 2017-06-22T20:52:13.690438-05:
      DOI: 10.1002/ange.201704460
       
  • Facile One Pot Synthesis of Functional Giant Polymeric Vesicles Controlled
           by Oscillatory Chemistry
    • Authors: Bishnu Bastakoti; Juan Perez-Mercader
      Abstract: We introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov-Zhabotinsky (B-Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B-Z reaction initiate the polymerization between a polyethylene glycol (PEG) macro reversible addition-fragmentation chain transfer agent and butyl acrylate monomers. The growth of the hydrophobic block on PEG undergoes self-assembly to form spherical micelles. The nanoscale micelles transform into submicron vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B-Z reaction. The one pot synthesis of an amphiphilic di-block copolymer and retention of oscillatory behavior for the B-Z reaction with the formation of giant vesicles bring a new insight into possible pathways to generate new opportunities for the synthesis of active functional microreactors in the range from 100's of nm to tens of µm.
      PubDate: 2017-06-22T20:52:03.258372-05:
      DOI: 10.1002/ange.201703816
       
  • Antimonene Quantum Dots: Synthesis and Application as Near-Infrared
           Photothermal Agents for Effective Cancer Therapy
    • Authors: Wei Tao; Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid Farokhzad
      Abstract: Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG-coated AMQDs showed a PTCE of 45.5%, which is higher than many other NMs-based PTAs such as graphene, Au, MoS2, and black phosphorus (BP).Through both in vitro and in vivo studies, the PEG-coated AMQDs demonstrated notable NIR-induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.
      PubDate: 2017-06-22T11:50:36.39735-05:0
      DOI: 10.1002/ange.201703657
       
  • Mechanistic Insights into Nanoparticle Surface Adsorption by Solution NMR
           Spectroscopy in an Aqueous Gel
    • Authors: Timothy K. Egner; Pranjali Naik, Nicholas C. Nelson, Igor I. Slowing, Vincenzo Venditti
      Abstract: Engineering nanoparticle (NP) functions at molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Here we show that the combined analysis of Dark state Exchange Saturation Transfer (DEST) and Relaxation Dispersion (RD) NMR experiments acquired on gel-stabilized samples of NP allows for accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ~200 nm ceria NP. We show that, while CA forms weak interactions with the NP, PhOH is tightly bound to the NP surface. Interestingly, we found that adsorption of PhOH proceeds through an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. We believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to characterization of nanomaterials.
      PubDate: 2017-06-22T10:45:49.466449-05:
      DOI: 10.1002/ange.201704471
       
  • Visible light photocatalysis of 6π heterocyclization
    • Authors: Martin Derwyn Smith; Niels Münster, Nicholas Parker, Lucy van Dijk, Robert Paton
      Abstract: Photo-mediated 6π cyclization is a valuable method for the formation of fused heterocyclic systems. Here we demonstrate that irradiation of cyclic 2-aryloxyketones with blue LED light in the presence of an Ir(III) complex leads to efficient and high yielding arylation across a panoply of substrates by energy transfer. 2-arylthioketones and 2-arylaminoketones also cyclize effectively under these conditions. Quantum calculation demonstrates that the reaction proceeds via conrotatory ring closure in the triplet excited state. Subsequent suprafacial 1,4-hydrogen shift and epimerization leads to the observed cis-fused products.
      PubDate: 2017-06-22T09:46:06.388904-05:
      DOI: 10.1002/ange.201705333
       
  • From Borane to Borylene without Reduction: Ambiphilic Behavior of a
           Monovalent Silylisonitrile Boron Species
    • Authors: Merle Arrowsmith; Dominic Auerhammer, Rüdiger Bertermann, Holger Braunschweig, Mehmet Ali Celik, Julian Erdmannsdörfer, Thomas Kupfer, Ivo Krummenacher
      Abstract: Deprotonation of [(cAAC)BH2(CN)] provided clean access to the stable boryl anion, [(cAAC)BH(CN)]-. Whereas the addition of soft electrophiles occurred at the nucleophilic boron center, harder silyl electrophiles added to the harder terminal cyano nitrogen. The resulting [(cAAC)BH(CNSiPh3)] species behaved both like a silylium boryl nucleophile and a neutral silylisonitrile borylene.
      PubDate: 2017-06-22T09:45:43.871163-05:
      DOI: 10.1002/ange.201705561
       
  • Organogelator - Cellulose Composite for Practical and Eco-friendly Marine
           Oil Spill Recovery
    • Authors: Kana M Sureshan; Annamalai Prathap
      Abstract: Marine oil-spills pose serious threats to the ecosystem and economy. There is much interest in developing sorbents that can tackle such spills. We have developed a novel sorbent by impregnating cellulose pulp with a sugar-derived oleogelator, 1,2:5,6-di-O-cyclohexylidene-mannitol. The gelator molecules mask the surface-exposed hydroxyl groups of cellulose fibrils by engaging them in H-bonding and expose their hydrophobic parts making the fibers temporarily hydrophobic (water contact-angle 110°). This sorbent absorbs oil effectively, selectively and instantly from oil-water mixtures due to its hydrophobicity. Then the gelator molecules get released uniformly in the oil and later self-assemble to fibers, as evident from SEM analysis, congealing the oil within the matrix. This hierarchical entrapment of the oil by non-covalent polymeric fibers within a covalent polymer matrix makes the gel very strong (230-fold increase in the yield-stress) and rigid, making it suitable for practical use.
      PubDate: 2017-06-22T08:46:48.546507-05:
      DOI: 10.1002/ange.201704699
       
  • Activation-Dependent Breathing in a Flexible Metal–Organic Framework and
           the Effects of Repeated Sorption/Desorption Cycling
    • Authors: Emile R. Engel; Abdelaziz Jouaiti, Charl X. Bezuidenhout, Mir Wais Hosseini, Leonard J. Barbour
      Abstract: A non-interpenetrated metal–organic framework with a paddle-wheel secondary building unit has been activated by direct thermal evacuation, guest exchange with a volatile solvent, and supercritical CO2 drying. Conventional thermal activation yields a mixture of crystalline phases and some amorphous content. Exchange with a volatile solvent prior to vacuum activation produces a pure breathing phase with high sorption capacity, selectivity for CO2 over N2 and CH4, and substantial hysteresis. Supercritical drying can be used to access a guest-free open phase. Pressure-resolved differential scanning calorimetry was used to confirm and investigate a systematic loss of sorption capacity by the breathing phase as a function of successive cycles of sorption and desorption. A corresponding loss of sample integrity was not detectable by powder X-ray diffraction analysis. This may be an important factor to consider in cases where flexible MOFs are earmarked for industrial applications.Tief durchatmen: Eine Metall-organische Gerüststruktur mit einem Schaufelrad-förmigen Sekundärbaustein wird durch direkte thermische Evakuierung, Gastaustausch mit einem flüchtigen Lösungsmittel und Trocknen in überkritischem CO2 aktiviert. Der Lösungsmittelaustausch erzeugt eine atmende Phase mit hoher Sorptionskapazität, Selektivität für CO2 gegenüber N2 und CH4 und erheblicher Hysterese.
      PubDate: 2017-06-22T08:31:48.036683-05:
      DOI: 10.1002/ange.201704044
       
  • Simulated isotope exchange patterns enable protein structure determination
    • Authors: Antoni James Borysik
      Abstract: Understanding the myriad protein-protein interactions required for cell function requires efficient leveraging of biophysical data to drive computational docking. The detailed insight into protein interfaces provided by isotope exchange endows this experimental technique with a unique importance for docking approaches. However, progress in coupling these methods is hindered by the inability to interpret the complex exchange patterns in relation to protein structure. A method to simulate protein isotope exchange patterns from docking outputs is described and its utility to guide the selection of native assemblies demonstrated. Unique signatures are generated for each docking pose allowing high throughput ranking of whole docking simulations by pairwise comparison to experimental outputs. Native assemblies are obtained using nothing but their simulated profiles and experimental difference-data for individual proteins are sufficient to drive structure determination for the whole complex.
      PubDate: 2017-06-22T04:51:06.808036-05:
      DOI: 10.1002/ange.201704604
       
  • Tricyanmethan und sein Ketenimin-Tautomer: Bildung aus verschiedenen
           Vorstufen sowie Analyse in Lösung, in einer Argonmatrix und im
           Einkristall
    • Authors: Klaus Banert; Madhu Chityala, Manfred Hagedorn, Helmut Beckers, Tony Stüker, Sebastian Riedel, Tobias Rüffer, Heinrich Lang
      Abstract: Lösungen von Azidomethylidenmalononitril wurden bei tiefer Temperatur photolysiert, um das entsprechende 2H-Azirin und Tricyanmethan zu bilden, was durch Tieftemperatur-NMR-Spektroskopie analysiert wurde. Das letztgenannte Produkt wurde auch nach kurzer Thermolyse einer Lösung der Azid-Vorstufe beobachtet, während die Bestrahlung des in einer Argonmatrix isolierten Azids nicht zum Tricyanmethan, sondern erstmals zum zweifelsfreien Nachweis des tautomeren Ketenimins durch IR-Spektroskopie führte. Wenn die lange bekannte, grünliche “aquoethereal” Phase, die aus Kaliumtricyanmethanid, verdünnter Schwefelsäure und Diethylether entsteht, rasch eingedampft und sublimiert wurde, resultierte statt des früher proklamierten Ketenimin-Tautomers eine Mischung aus Hydroniumtricyanmethanid und Tricyanmethan. Unter speziellen Bedingungen ergab die Sublimation Einkristalle des Tricyanmethans, was die Analyse der Molekülstruktur mithilfe der Röntgenbeugung ermöglichte.Von der Außenwelt isoliert in einer Argonmatrix kann ein lange gesuchtes Ketenimin nach der Bestrahlung eines geeigneten Vinylazids nachgewiesen werden. Dagegen führt dieselbe Vorstufe bei der Photolyse oder Thermolyse in Lösung zu Cyanoform, das auch in Form von Einkristallen aus Kaliumtricyanmethanid zugänglich ist.
      PubDate: 2017-06-22T01:52:58.110777-05:
      DOI: 10.1002/ange.201704561
       
  • Chemically Tailoring the Dopant Emission in Manganese-Doped CsPbCl3
           Perovskite Nanocrystals
    • Authors: Samrat Das Adhikari; Sumit K. Dutta, Anirban Dutta, Amit K. Guria, Narayan Pradhan
      Abstract: Doping in perovskite nanocrystals adopts different mechanistic approach in comparison to widely established doping in chalcogenide quantum dots. The fast formation of perovskites makes the dopant insertions more competitive and challenging. Introducing alkylamine hydrochloride (RNH3Cl) as a promoting reagent, precise controlled doping of MnII in CsPbCl3 perovskite nanocrystals is reported. Simply, by changing the amount of RNH3Cl, the Mn incorporation and subsequent tuning in the excitonic as well as Mn d–d emission intensities are tailored. Investigations suggested that RNH3Cl acted as the chlorinating source, controlled the size, and also helps in increasing the number of particles. This provided more opportunity for Mn ions to take part in reaction and occupied the appropriate lattice positions. Carrying out several reactions with varying reaction parameters, the doping conditions are optimized and the role of the promoting reagent for both doped and undoped systems are compared.Die kontrollierte MnII-Dotierung von CsPbCl3-Nanokristallen wird durch den Einsatz eines Alkylamin-Hydrochlorids (RNH3Cl) gefördert. Ihre Emissionsintensität richtet sich nach der Mn-Dotierung, die wiederum über die Menge an RNH3Cl eingestellt wird. Im Zuge dieses Prozesses werden die CsPbCl3-Nanokristalle zusätzlich stabilisiert.
      PubDate: 2017-06-22T01:52:17.569707-05:
      DOI: 10.1002/ange.201703863
       
  • Facile and reversible formation of Fe(III)-O-Ce(IV) adducts from nonheme
           oxoiron(IV) complexes and Ce(III)
    • Authors: Apparao Draksharapu; Waqas Rasheed, Johannes E. M. N. Klein, Lawrence Que
      Abstract: CAN or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII-O-CeIV(OH2)(NO3)4]+ (3), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv. CAN or [(N4Py)FeIV=O]2+ (2) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S = 1 FeIV in 2 to S = 5/2 in 3, which is found to be facile despite the formal spin forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.
      PubDate: 2017-06-22T01:22:10.106507-05:
      DOI: 10.1002/ange.201704322
       
  • An Activatable Photosensitizer Targeted to γ-Glutamyltranspeptidase
    • Authors: Mayumi Chiba; Yuki Ichikawa, Mako Kamiya, Toru Komatsu, Tasuku Ueno, Kenjiro Hanaoka, Tetsuo Nagano, Norbert Lange, Yasuteru Urano
      Abstract: We adopted a spirocyclization-based strategy to design γ-glutamyl-hydroxymethyl selenorhodamine green (gGlu-HMSeR) as a photo-inactive compound that would be specifically cleaved by the tumor-associated enzyme γ-glutamyltranspeptidase (GGT) to generate a potent photosensitizer, HMSeR. gGlu-HMSeR takes a colorless, spirocyclic structure, and does not show marked phototoxicity to low-GGT-expressing cells or normal tissues upon irradiation with visible light. In contrast, HMSeR predominantly takes an open colored structure, and generates reactive oxygen species upon irradiation. Thus, the γ-glutamyl group serves as a tumor-targeting moiety for photodynamic therapy (PDT), switching on tumor-cell-specific phototoxicity. Photoirradiation after gGlu-HMSeR treatment resulted in selective ablation of implanted tumor spheroids, without damage to healthy tissue. gGlu-HMSeR is the first activatable photosensitizer targeting an aminopeptidase for highly tumor-selective PDT.
      PubDate: 2017-06-21T23:45:44.33914-05:0
      DOI: 10.1002/ange.201704793
       
  • High-Field NMR Spectroscopy Reveals Aromaticity-Modulated Hydrogen Bonding
           (AMHB) in Heterocycles
    • Authors: Tayeb Kakeshpour; John P. Bailey, Madison R. Jenner, Darya E. Howell, Richard J. Staples, Daniel Holmes, Judy I. Wu, James E. Jackson
      Abstract: : From DNA base pairs to drug-receptor binding, hydrogen (H-)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored; H-bond strength modulation due to enhancement or disruption of heterocycles' aromaticity is revealed by comparing homodimer H-bond energies of aromatic heterocycles with analogues that have the same H-bonding moieties but lack cyclic π-conjugation. NMR studies of dimerization in C6D6 find aromaticity-modulated H-bonding (AMHB) energy effects of ca. ±30%, depending on whether they enhance or weaken aromatic delocalization. The attendant ring current perturbations expected from such modulation are confirmed by chemical shift changes in both observed ring C-H and calculated nucleus-independent sites. In silico modeling confirms that AMHB effects outweigh those of hybridization or dipole-dipole interaction.
      PubDate: 2017-06-21T20:45:54.883932-05:
      DOI: 10.1002/ange.201705023
       
  • Controlling Reaction Selectivity via Surface Termination of Perovskite
           Catalysts
    • Authors: Felipe Polo-Garzon; Shi-Ze Yang, Victor Fung, Guo Shiou Foo, Elizabeth Erin Bickel, Matthew F. Chisholm, De-en Jiang, Zili Wu
      Abstract: Although perovskites have been widely used in catalysis, tuning their surface terminations to control reaction selectivities has not been well established. In this work, we employ multiple surface sensitive techniques to characterize the surface termination (one aspect of surface reconstruction) of SrTiO3 (STO) after thermal pretreatment (Sr-enrichment) and chemical etching (Ti-enrichment). We show, using the conversion of 2-propanol as a probe reaction, that the surface termination of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivities in a wide range, which are inaccessible using single metal oxides, either SrO or TiO2. Density functional theory (DFT) calculations well explain the selectivity tuning and reaction mechanism on different surface terminations of STO. Similar catalytic tunability is also observed on BaZrO3, highlighting the generality of the finding from this work.
      PubDate: 2017-06-21T11:47:09.153338-05:
      DOI: 10.1002/ange.201704656
       
  • Visible Light-Driven Aza-ortho-Quinone Methide Generation Enables a
           Multicomponent Reaction
    • Authors: Wen-Jing Xiao; Yi-Ying Liu, Xiao-Ye Yu, Miao-Maio Qiao, Xiaotian Qi, Jia-Rong Chen, De-Qing Shi
      Abstract: A visible light photoredox-catalyzed and radical-mediated strategy for the in situ generation of aza-ortho-quinone methides from readily accessible alkenylanilines and alkyl radical precursors has been accomplished for the first time. This protocol enables an efficient multicomponent cascade reaction of alkenylanilines, halides and sulfur ylides, and shows wide substrate scope and high functional group tolerance with respect to each component. Treatment of the initially formed cycloaddition products with a base leads to a convergent and streamlined synthesis of densely functionalized indoles in a single flask operation.
      PubDate: 2017-06-21T11:13:11.777831-05:
      DOI: 10.1002/ange.201704690
       
  • Switch of C−H Activation Mechanism for Full Selectivity Control in
           Cobalt(III)-Catalyzed C−H Alkylations
    • Authors: Daniel Zell; Markus Bursch, Valentin Müller, Stefan Grimme, Lutz Ackermann
      Abstract: Selectivity control in hydroarylation-based C−H alkylation has been dominated by steric interactions. In contrast, we unravel a conceptually distinct strategy that exploits the programmed switch in the C−H activation mechanism by means of cobalt catalysis, setting the stage for expedient C−H alkylations with unactivated alkenes. Detailed mechanistic studies provided compelling evidence for a programmable switch in the C−H activation mechanism from a linear-selective ligand-to-ligand hydrogen transfer (LLHT) to a branched-selective base-assisted internal electrophilic-type substitution (BIES).
      PubDate: 2017-06-21T09:54:53.833572-05:
      DOI: 10.1002/ange.201704196
       
  • Decarboxylative Alkynylation
    • Authors: Joel M. Smith; Tian Qin, Rohan R. Merchant, Jacob T. Edwards, Lara R. Malins, Zhiqing Liu, Guanda Che, Zichao Shen, Scott A. Shaw, Martin D. Eastgate, Phil S. Baran
      Abstract: The development of a new decarboxylative cross-coupling protocol that affords terminal and substituted alkynes from various carboxylic acids is described using both nickel- and iron-based catalysts. The use of N-hydroxytetrachlorophthalimide (TCNHPI) esters is crucial to the success of the transformation, and the reaction is amenable to in situ carboxylic acid activation. Additionally, an inexpensive, commercially-available alkyne source is employed in this formal homologation process that serves as a surrogate for other well-established alkyne syntheses. The reaction can be conducted on a mole scale, and the conditions are mild, operationally simple, and broad in scope while providing succinct avenues to previously reported synthetic intermediates.
      PubDate: 2017-06-21T08:46:28.072616-05:
      DOI: 10.1002/ange.201705107
       
  • Phosphonium Salts as Pseudohalides: Regioselective Ni-Catalyzed
           Cross-Coupling of Complex Pyridines and Diazines.
    • Authors: Andrew McNally; Xuan Zhang
      Abstract: Heterobiaryls are important pharmacophores that are challenging to prepare by traditional cross-coupling methods. An alternative approach is presented where pyridines and diazines are converted to heteroaryl phosphonium salts and coupled with arylboronic acids. Nickel catalysts are unique for selective heteroaryl transfer, and the reaction has a broad substrate scope that includes complex pharmaceuticals. Phosphonium ions also display orthogonal reactivity in cross-couplings compared to halides enabling chemoselective palladium and nickel-catalyzed coupling sequences.
      PubDate: 2017-06-21T08:45:27.98322-05:0
      DOI: 10.1002/ange.201704948
       
  • Mechanism-Based Enantiodivergence in Manganese Reduction Catalysis: A
           Chiral Pincer Complex for the Highly Enantioselective Hydroboration of
           Ketones
    • Authors: Vladislav Vasilenko; Clemens K. Blasius, Hubert Wadepohl, Lutz H. Gade
      Abstract: A manganese alkyl complex containing a chiral bis(oxazolinyl-methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction under mild reaction conditions (TOF >450 h−1 at −40 °C). The earth-abundant base-metal catalyst operates at very low catalyst loadings (as low as 0.1 mol %) and with a high level of functional-group tolerance. There is evidence for the existence of two distinct mechanistic pathways for manganese-catalyzed hydride transfer and their role for enantiocontrol in the selectivity-determining step is presented.Zwei mechanistische Pfade werden beim mangankatalysierten Hydridtransfer im selektivitätsbestimmenden Schritt der enantioselektiven Hydroborierung von Ketonen beschritten. Die Reaktion liefert nützliche chirale Alkohole in ausgezeichneten Ausbeuten und Enantioselektivitäten bereits mit geringen Katalysatormengen bei einer hohen Verträglichkeit mit funktionellen Gruppen.
      PubDate: 2017-06-21T07:30:37.226482-05:
      DOI: 10.1002/ange.201704184
       
  • Noncovalent Immobilization of Molecular Electrocatalysts for Chemical
           Synthesis: Efficient Electrochemical Alcohol Oxidation with a
           Pyrene–TEMPO Conjugate
    • Authors: Amit Das; Shannon S. Stahl
      Abstract: Electrocatalytic methods for organic synthesis could offer sustainable alternatives to traditional redox reactions, but strategies are needed to enhance the performance of molecular catalysts designed for this purpose. The synthesis of a pyrene-tethered TEMPO derivative (TEMPO=2,2,6,6-tetramethylpiperidinyl-N-oxyl) is described, which undergoes facile in situ noncovalent immobilization onto a carbon cloth electrode. Cyclic voltammetry and controlled potential electrolysis studies demonstrate that the immobilized catalyst exhibits much higher activity relative to 4-acetamido–TEMPO, an electronically similar homogeneous catalyst. In preparative electrolysis experiments with a series of alcohol substrates and the immobilized catalyst, turnover numbers and frequencies approach 2 000 and 4 000 h−1, respectively. The synthetic utility of the method is further demonstrated in the oxidation of a sterically hindered hydroxymethylpyrimidine precursor to the blockbuster drug, rosuvastatin.Elektrisch oxidiert: Ein 2,2,6,6-Tetramethylpiperidinyl-N-oxyl(TEMPO)-Katalysator mit angebundener Pyren-Einheit wurde in situ nichtkovalent auf einer Kohlenstofffilz-Elektrode immobilisiert. Der Elektrokatalysator oxidiert effizient verschiedene substituierte Benzylalkohole.
      PubDate: 2017-06-21T07:30:25.315179-05:
      DOI: 10.1002/ange.201704921
       
  • Segmental, domain-selective perdeuteration and small angle neutron
           scattering for structural analysis of multi-domain proteins
    • Authors: Miriam Sonntag; Pravin Jagtap, Bernd Simon, Marie-Sousai Appavou, Arie Geerlof, Ralf Stehle, Frank Gabel, Janosch Hennig, Michael Sattler
      Abstract: Multi-domain proteins play critical roles in fine-tuning essential processes in cellular signaling and gene regulation. Typically, multiple globular domains that are connected by flexible linkers undergo dynamic re-arrangements upon binding to protein, DNA or RNA ligands. RNA binding proteins (RBPs) represent an important class of multi-domain proteins, which regulate gene expression by recognizing linear or structured RNA sequence motifs. Here, we employ segmental perdeuteration of the three RNA recognition motif (RRM) domains in the RBP TIA-1 using Sortase A-mediated protein ligation. We show that domain-selective perdeuteration combined with contrast-matched small-angle neutron scattering (SANS), SAXS and computational modelling provides valuable information to precisely define relative domain arrangements. The approach is generally applicable to study conformational arrangements of individual domains in multi-domain proteins and changes induced by ligand binding.
      PubDate: 2017-06-21T07:26:07.068401-05:
      DOI: 10.1002/ange.201702904
       
  • Structural Transition in Liquid Crystal Bubbles Generated from Fluidic
           Nanocellulose Colloids
    • Authors: Guang Chu; Rita Vilensky, Gleb Vasilyev, Shengwei Deng, Dan Qu, Yan Xu, Eyal Zussman
      Abstract: The structural transition in micrometer-sized liquid crystal bubbles (LCBs) derived from rod-like cellulose nanocrystals (CNCs) was studied. The CNC-based LCBs were suspended in nematic or chiral nematic liquid-crystalline CNCs, which generated topological defects and distinct birefringent textures around them. The ordering and structure of the LCBs shifted from a nematic to chiral nematic arrangement as water evaporation progressed. These packed LCBs exhibited a specific photonic cross-communication property that is due to a combination of Bragg reflection and bubble curvature and size.Flüssigkristallblasen mit aktiver Ordnung wurden aus fluidischen Nanocellulose-Kolloiden erhalten. Struktur, Textur, topologische Defekte und zeitliche Entwicklung dieser Blasen wurden in Suspension und im festen Zustand (Film) untersucht. Dabei zeigten sich interessante optische Eigenschaften.
      PubDate: 2017-06-21T07:25:59.338199-05:
      DOI: 10.1002/ange.201703869
       
  • Wet and Functional Adhesives from One-Step Aqueous Self-Assembly of
           Natural Amino Acids and Polyoxometalates
    • Authors: Jing Xu; Xiaodong Li, Jingfang Li, Xiangyi Li, Bao Li, Yang Wang, Lixin Wu, Wen Li
      Abstract: Sessile organisms have undergone long-term evolution to develop the unique ability by positioning themselves on wet solid surface through secreting adhesive proteins. The present study reveals that natural amino acid monomers can also exhibit similar adhesion capacity. This kind of biomimetic adhesives were created by the one-step aqueous assembly of basic amino acids with assistance of anionic polyoxometalates. The polyoxometalates not only serve as multivalent scaffold to initiate the supramolecular cross-linking of amino acid molecules, but also function as a redox component, bestowing the wet adhesives with electrochromic features.Perfekte Partner: Wasserstoffbrücken und elektrostatische Wechselwirkungen zwischen basischen Aminosäuren und Polyoxometallaten resultieren gemeinsam mit Zwitterionen-Selbstorganisation in der Bildung von elektrochromen Nassklebstoffen. Der einfache und nachhaltige Ansatz ebnet den Weg für neue funktionale Adhäsiva.
      PubDate: 2017-06-21T07:25:48.249981-05:
      DOI: 10.1002/ange.201703774
       
  • Dearomative Intramolecular (4+3) Cycloadditions of Arenes with Epoxy and
           Aziridinyl Enolsilanes
    • Authors: Jesse Ling; Sarah Lam, Kam-Hung Low, Pauline Chiu
      Abstract: An intramolecular (4+3) cycloaddition of epoxy and aziridinyl enolsilanes with benzene, naphthalene, and anthracene derivatives is reported. Highly functionalized polycyclic alcohols and amines are generated under relatively mild reaction conditions with yields up to 89 %. Optically enriched cycloadducts are obtained from cycloadditions of enantiomerically pure epoxides and aziridines.Den Kreis aufbrechen: Arene reagieren als Diene in intramolekularen (4+3)-Cycloadditionen mit Epoxy/Aziridinylenolsilanen. Diese stufenweise Cycloaddition läuft selbst mit Benzol schon bei niedrigen Temperaturen ab. Aus enantiomerenangereicherten Epoxiden oder Aziridinen werden optisch aktive (4+3)-Cycloaddukte erhalten.
      PubDate: 2017-06-21T07:25:34.241404-05:
      DOI: 10.1002/ange.201704155
       
  • Stretchable Electrochemical Sensor for Inducing and Monitoring Cell
           Mechanotransduction in Real-Time
    • Authors: Yan-Ling Liu; Yu Qin, Zi-He Jin, Xue-Bo Hu, Miao-Miao Chen, Rong Liu, Christian Amatore, Wei-Hua Huang
      Abstract: Existing methods offer little direct and real-time information about stretch-triggered biochemical responses during cell mechanotransduction. Herein, we report a novel stretchable electrochemical sensor that takes advantage of a hierarchical percolation network of carbon nanotubes and gold nanotubes (CNTs- Au NTs). This hybrid nano-structure provides the sensor with excellent time-reproducible mechanical and electrochemical performances while granting very good cellular compatibility, making it perfectly apt to induce and monitor simultaneously transient biochemical signals. This is validated by monitoring stretch-induced transient release of small signaling molecules by both endothelial and epithelial cells cultured on this sensor and submitted to stretching strains of different intensities. This work demonstrates that the hybrid CNTs-Au NTs platform offers a versatile and highly sensitive way to characterize and quantify short-time mechanotransduction responses.
      PubDate: 2017-06-21T05:47:03.626956-05:
      DOI: 10.1002/ange.201705215
       
  • The First Total Synthesis of Ovafolinin A and B: Unique Polycyclic
           Benzoxepin Lignans via a Cascade Cyclization
    • Authors: Samuel James Davidson; David Barker
      Abstract: Ovafolinins A and B, isolated from Lyonia ovalifolia var. elliptica, are lignans which contain a unique penta- and tetracyclic benzoxepin bridged aryl tetralin structure. We report the first total synthesis of these natural products initially utilizing an acyl-Claisen rearrangement to construct the lignan backbone with correct relative stereochemistry. Judicious use of a bulky protecting group placed reactive moieties in the correct orientation resulting in a cascade reaction forming the benzoxepin bridged aryl tetralin from a linear precursor in a single step. Modification of this route allowed an enantioselective synthesis of (+)-ovafolinin A and B which confirmed the absolute stereochemistry and comparison of optical rotation suggests these compounds are found as scalemic mixtures in nature.
      PubDate: 2017-06-21T05:46:52.943414-05:
      DOI: 10.1002/ange.201705575
       
  • Electronically Activated Organoboron Catalysts for Enantioselective
           Propargyl Addition to Trifluoromethyl Ketones
    • Authors: Nicholas W. Mszar; Malte S. Mikus, Sebastian Torker, Fredrik Haeffner, Amir H. Hoveyda
      Abstract: A broadly applicable, practical, scalable, efficient and highly α- and enantioselective method for addition of a silyl-protected propargyl moiety to trifluoromethyl ketones has been developed. Reactions, promoted by 2.0 mol % of a catalyst that is derived in situ from a readily accessible aminophenol compound at ambient temperature, were complete after only 15 minutes at room temperature. The desired tertiary alcohols were isolated in up to 97 % yield and 98.5:1.5 enantiomeric ratio. Alkyl-, alkenyl-, alkynyl-, aryl- or heteroaryl-substituted trifluoromethyl ketones can be used. Utility is highlighted by application to a transformation that is relevant to enantioselective synthesis of BI 653048, a compound active against rheumatoid arthritis.Schnell und selektiv: Ausgestattet mit einer Trifluormethylgruppe können chirale Organoborkatalysatoren die hoch enantioselektive Addition einer Silyl-geschützten Propargylborverbindung an verschiedenste Trifluormethylketone vermitteln. Die Nützlichkeit der Methode wird in einem Prozess demonstriert, der zur enantioselektiven Synthese des Antirheumatikums BI 653048 genutzt werden könnte.
      PubDate: 2017-06-21T04:43:14.089224-05:
      DOI: 10.1002/ange.201703844
       
  • Inducing Complexity in Intermetallics through Electron–Hole Matching:
           the Structure of Fe14Pd17Al69
    • Authors: Gordon G. C. Peterson; Vincent J. Yannello, Daniel C. Fredrickson
      Abstract: We illustrate how the crystal structure of Fe14Pd17Al69 provides an example of an electron–hole matching approach to inducing frustration in intermetallic systems. Its structure contains a framework based on IrAl2.75, a binary compound that closely adheres to the 18−n rule. Upon substituting the Ir with a mixture of Fe and Pd, a competition arises between maintaining the overall ideal electron concentration and accommodating the different structural preferences of the two elements. A 2×2×2 supercell results, with Pd- and Fe-rich regions emerging. Just as in the original IrAl2.75 phase, the electronic structure of Fe14Pd17Al69 exhibits a pseudogap at the Fermi energy arising from an 18−n bonding scheme. The electron–hole matching approach's ability to combine structural complexity with electronic pseudogaps offers an avenue to new phonon glass–electron crystal materials.Die Kristall- und elektronische Struktur von Fe14Pd17Al69 illustrieren einen Ansatz für neue Verwirklichungen des Phononenglas-Elektronenkristall-Konzepts: die Strategie des Elektron-Loch-Abgleichs.
      PubDate: 2017-06-21T04:36:13.958783-05:
      DOI: 10.1002/ange.201702156
       
  • Chemical Recognition of Active Oxygen Species on the Surface of Oxygen
           Evolution Reaction Electrocatalysts
    • Authors: Chunzhen Yang; Olivier Fontaine, Jean-Marie Tarascon, Alexis Grimaud
      Abstract: Owing to the transient nature of the intermediates formed during the oxygen evolution reaction (OER) on the surface of transition metal oxides, their nature remains largely elusive by the means of simple techniques. The use of chemical probes is proposed, which, owing to their specific affinities towards different oxygen species, unravel the role played by these species on the OER mechanism. For that, tetraalkylammonium (TAA) cations, previously known for their surfactant properties, are introduced, which interact with the active oxygen sites and modify the hydrogen bond network on the surface of OER catalysts. Combining chemical probes with isotopic and pH-dependent measurements, it is further demonstrated that the introduction of iron into amorphous Ni oxyhydroxide films used as model catalysts deeply modifies the proton exchange properties, and therefore the OER mechanism and activity.Die Einführung von Eisen in Filme aus amorphem Nickeloxyhydroxid modifiziert die Protonendiffusion an deren Grenzflächen, und Tetraalkylammonium-Kationen fangen reaktive Sauerstoffspezies ein. Diese Effekte wirken sich auf die Aktivität und den Mechanismus der Sauerstoffentwicklung aus. IHP/OHP=innere/äußere Helmholtz-Schicht.
      PubDate: 2017-06-21T04:35:40.584832-05:
      DOI: 10.1002/ange.201701984
       
  • One Model, Two Enzymes: Activation of Hydrogen and Carbon Monoxide
    • Authors: Seiji Ogo; Yuki Mori, Tatsuya Ando, Takahiro Matsumoto, Takeshi Yatabe, Ki-Seok Yoon, Hideki Hayashi, Masashi Asano
      Abstract: Ein [NiIr]-basierter Katalysator bietet der CO-Vergiftung die Stirn, indem er das Gas als Brennstoff verwendet. Das Katalysatorsystem kann H2 bei niedrigen pH-Werten und CO bei hohen pH-Werten oxidieren. Bei pH 7 werden beide Oxidationen zugleich katalysiert. In ihrer Zuschrift (
      DOI : 10.1002/ange.201704864) berichten S. Ogo et al. über eine Prototyp-Brennstoffzelle, die mit einem 50:50-Vorrat an H2 und CO betrieben wurde. Die doppelte Funktion ist als zweiköpfiger Vogel dargestellt.
      PubDate: 2017-06-21T04:35:32.686447-05:
       
  • Selective CF3 Substitution for Affecting the Physical and Chemical
           Properties of Gold Corroles
    • Authors: Zeev Gross; Sudhakar Kolanu, Monica Kosa, Natalia Fridman, Boris Tumanskii, Magal Saphier, Amir Mizrahi
      Abstract: Gold corroles have been hardly accessible and display no interesting physical or chemical properties. We now introduce a facile methodology for obtaining selectively CF3-substituted gold(III) corroles and show that the introduction of these groups has immense effects on the structures of the complexes, their photophysical and redox properties, and on their ability to participate in catalytic processes.
      PubDate: 2017-06-21T03:45:34.722881-05:
      DOI: 10.1002/ange.201705007
       
  • Spectroscopic Observation of the Triplet Diradical State of a
           Cyclobutadiene
    • Authors: Arseni Kostenko; Yuzuru Kobayashi, Boris Tumanskii, Masaaki Nakamoto, Akira Sekiguchi, Yitzhak Apeloig
      Abstract: We report the first direct observation by electron paramagnetic resonance (EPR) spectroscopy of a triplet diradical state of a CBD derivative 2 which is formed by a thermal excitation of the CBD singlet 1. Both experiment and theory support a thermal equilibrium between rectangular singlet 1 and the square triplet diradical 2 with a singlet-triplet energy gap of 13.9 kcal mol−1.
      PubDate: 2017-06-21T01:25:20.553177-05:
      DOI: 10.1002/ange.201705228
       
  • A novel DNA structure containing AgI-mediated G:G and C:C Base Pairs
    • Authors: Hehua Liu; Fusheng Shen, Phensinee Haruehanroengra, Qingqing Yao, Yunshan Cheng, Yiqing Chen, Chun Yang, Jing Zhang, Baixing Wu, Qiang Luo, Ruixue Cui, Jixi Li, Jinbiao Ma, Jia Sheng, Jianhua Gan
      Abstract: Metallo-base pairs have been extensively utilized in many research fields, including genetic code extension, novel therapeutics development, and various nanodevice designs. Compared to other cations, AgI is more flexible in pairing with natural base pairs. Herein, we present a DNA structure containing two C-AgI-C pairs and one first time reported G-AgI-G pair in a short 8mer DNA strand. This structure not only discloses the detailed insights into these AgI-base pairing patterns in DNA, but also represents the first nonhelical DNA structure driven by the heavy metal ions, further contributing to the structural diversity of DNA. This unique complex structure is highly sequence dependent, implying its functional potentials as a new DNA aptamer that can bind and recognize silver ions. These results not only advance our understanding on the interactions between AgI and nucleobases, but also provide a unique structural component for the rational design of new DNA nanodevices.
      PubDate: 2017-06-20T20:51:34.437418-05:
      DOI: 10.1002/ange.201704891
       
  • The Viologen Cation Radical Pimer: A Case of Dispersion-Driven Bonding
    • Authors: Margarita Geraskina; Andrew S. Dutton, Mark Juetten, Samuel Wood, Arthur Winter
      Abstract: Pi bonds between organic radicals have generated recent excitement as an orthogonal interaction for designing self-assembling architectures in water. Here, we provide the first a systematic investigation of the effect of the viologen cation radical structure on the strength and nature of the pimer bond. A striking and unexpected feature of the this pi bond is that the bond strength is unchanged by substitution with electron-donating groups or withdrawing groups or with increased conjugation. Furthermore, the interaction is undiminished by sterically bulky N-alkyl groups. Theoretical modelling indicates that strong dispersion forces dominate the interaction between the radicals, rationalizing the insensitivity of the bonding interaction to substituents: The stacking of polarizable pi radicals leads to attractive dispersion forces in excess of typical dispersion interactions of small molecules and helps overcome the Coulombic repulsion of bringing two cationic species into contact.
      PubDate: 2017-06-20T20:51:31.065697-05:
      DOI: 10.1002/ange.201704959
       
  • Oxygen Vacancy-Mediated Photocatalysis of BiOCl: Reactivity, Selectivity
           and Perspective
    • Authors: Hao Li; Jie Li, Zhihui Ai, Falong Jia, Lizhi Zhang
      Abstract: Semiconductor photocatalysis is a trustworthy approach to harvest clean solar light for energy conversions, while state-of-the-art catalytic efficiencies are unsatisfactory because of the finite light response and/or robust charge carriers' recombination. Along with the development of modern material characterization techniques and electronic-structure computations, oxygen vacancies (OVs) on real photocatalysts surface, even in infinitesimal concentration, are found to play a more decisive role in determining the kinetics, energetics and mechanisms of photocatalytic reactions. This review endeavors to clarify the inherent functionality of OVs in photocatalysis at the surface molecular level using 2D BiOCl as the platform. Structure sensitivity of OVs on reactivity and selectivity of photocatalytic reactions is intensely discussed via confining OVs onto prototypical BiOCl surfaces of different structures. The critical understanding of OVs chemistry in this review can help to consolidate and advance the fundamental theories of photocatalysis, and also offer new perspectives and guidelines for the rational design of catalysts with satisfactory performance.
      PubDate: 2017-06-20T20:51:13.796615-05:
      DOI: 10.1002/ange.201705628
       
  • A Carbene Catalysis Strategy for the Synthesis of Protoilludane Natural
           Products
    • Authors: Karl Scheidt; Todd Hovey, Daniel Cohen, Daniel Walden, Paul Cheong
      Abstract: The Armillaria and Lactarius genera of fungi produce antimicrobial and cytotoxic mellolide, protoilludane, and marasmane sesquiterpenoids. Herein, we report a unified synthetic strategy to access the protoilludane, mellolide, and marasmane families of natural products. The significance of these syntheses lies in a) the organocatalytic, enantioselective construction of key chiral intermediates from a simple achiral precursor, b) the utility of a key 1,2-butanediol intermediate to serve as a progenitor to each natural product class, and c) a direct chemical conversion of a protoilludane to a marasmane via serendipitous ring contraction, providing experimental support for their proposed biosynthetic relationships.
      PubDate: 2017-06-20T13:23:46.167159-05:
      DOI: 10.1002/ange.201705308
       
  • Iridium(I)-Catalyzed Intramolecular Hydrocarbonation of Alkenes: Efficient
           Access to Cyclic Systems Bearing Quaternary Stereocenters
    • Authors: Fernando Lopez; David F. Fernández, Moises Gulías, Jose L. Mascareñas
      Abstract: A catalytic, versatile and atom-economical C-H functionalization process that provides a wide variety of cyclic systems featuring methyl-substituted quaternary stereocenters is described. The method relies on the use of a cationic Ir(I)-bisphosphine catalyst, which promotes a carboxamide-assisted activation of an olefinic C(sp2)-H bond followed by exo-cyclization to a tethered 1,1-disubstituted alkene. The extension of the method to aromatic and heteroaromatic C-H bonds, as well as developments on an enantioselective variant, are also described.
      PubDate: 2017-06-20T13:21:27.504604-05:
      DOI: 10.1002/ange.201705105
       
  • Switchable Access to Different Spirocyclopentane Oxindoles by
           N-Heterocyclic Carbene Catalyzed Reactions of Isatin-Derived Enals and
           N-Sulfonyl Ketimines
    • Authors: Lei Wang; Sun Li, Marcus Blümel, Rakesh Puttreddy, Anssi Peuronen, Kari Rissanen, Dieter Enders
      Abstract: A novel NHC-catalyzed annulation protocol for the asymmetric synthesis of biologically important β-lactam fused spirocyclopentane oxindoles with four contiguous stereocenters, including two quaternary carbon centers, was developed. Alternatively, spirocyclopentane oxindoles containing an enaminone moiety can be achieved using the same starting materials, isatin-derived enals, and N-sulfonyl ketimines, in the presence of a slightly different NHC catalytic system. This switchable annulation strategy enables the selective assembly of both heterocyclic scaffolds with good yields and excellent enantioselectivities for a broad range of substrates.Den Schalter umlegen: Die NHC-katalysierte schaltbare asymmetrische Reaktion zwischen Isatin-abgeleiteten Enalen und N-Sulfonylketiminen verläuft über den Homoenolatmechanismus und führt selektiv zu Spirocyclopentanoxindolen, die eine β-Lactam- oder eine Enaminongruppe enthalten. Die Reaktion liefert hohe Ausbeuten und exzellente Stereoselektivität mit einem breiten Spektrum von Substraten.
      PubDate: 2017-06-20T12:47:04.985209-05:
      DOI: 10.1002/ange.201704210
       
  • Direct Zinc(II)-Catalyzed Enantioconvergent Additions of Terminal Alkynes
           to α-Keto Esters
    • Authors: Blane P. Zavesky; Jeffrey S. Johnson
      Abstract: The addition of terminal alkynes to racemic β-stereogenic α-keto esters was achieved in high levels of stereoselectivity, affording versatile tertiary propargylic alcohols containing two stereocenters. This environmentally benign enantioconvergent reaction proceeds with perfect atom economy, requires no solvent, and is catalyzed by a non-toxic zinc salt. The alkyne moiety can be leveraged in downstream transformations including hydrogenation to the corresponding saturated tertiary alcohol, which represents the product of a formal enantioconvergent aliphatic nucleophile addition.Eine perfekte Verwandlung: Die Addition von terminalen Alkinen an racemische β-stereogene α-Ketoester gelingt mit hoher Stereoselektivität und liefert nützliche tertiäre Propargylalkohole, die zwei Stereozentren enthalten. Diese umweltschonende, enantiokonvergente Reaktion läuft mit hoher Atomökonomie ab, benötigt kein Lösungsmittel und wird durch ein ungiftiges Zinksalz katalysiert.
      PubDate: 2017-06-20T12:46:32.462352-05:
      DOI: 10.1002/ange.201704226
       
  • Catalyst-Controlled, Enantioselective and Diastereodivergent Conjugate
           Addition of Aldehydes to Electron-Deficient Olefins
    • Authors: Jennifer Kan; Hiroki Maruyama, Matsujiro Akakura, Taichi Kano, Keiji Maruoka
      Abstract: A chiral amine-catalyzed, enantioselective and diastereodivergent method for aldehyde addition to electron deficient olefins is presented. Hydrogen bonding was used as a control element to achieve unusual anti-selectivity, which was further elucidated through mechanistic and computational studies.
      PubDate: 2017-06-20T11:34:56.744626-05:
      DOI: 10.1002/ange.201705546
       
  • Von der chemischen Topologie zu molekularen Maschinen (Nobel-Aufsatz)
    • Authors: Jean-Pierre Sauvage
      Abstract: Das Gebiet der molekularen Maschinen nahm seinen Anfang, nachdem mehreren Forschungsgruppen die relativ einfache Herstellung ineinander verschlungener Ringverbindungen gelungen war. Man unterscheidet hier Catenane, als ineinander verschlungene Ringe, und Rotaxane, bei denen Ringe auf molekulare Fasern oder Achsen aufgefädelt sind. Andere Familien von molekularen Maschinen wurden ebenfalls entwickelt, die nicht in den Bereich der Catenane oder Rotaxane gehören, diese stammen aber erst aus jüngerer Zeit. Da die Erzeugung ineinander verschlungener Ringmoleküle mit Blick auf das Gebiet der molekularen Maschinen so wichtig ist, werden wir mit diesem Teil unserer Arbeiten beginnen. Der zweite Teil wird sich den dynamischen Eigenschaften solcher Systeme widmen, sowie den Verbindungen, deren Bewegung auf kontrollierte Weise “von außen” gesteuert werden kann, d. h. den molekularen Maschinen. Wir werden unsere Ausführungen auf eine sehr begrenzte Auswahl von Beispielen beschränken, die wir als besonders repräsentativ für das Forschungsgebiet erachten.Magische Ringe: Das Gebiet der molekularen Maschinen hat seinen Ursprung in der Synthese von Catenanen und Rotaxanen sowie in der chemischen Topologie. J.-P. Sauvage schildert in seinem Nobel-Aufsatz die Anfänge dieser Forschungen und die Entwicklung hin zu den ersten molekularen Muskeln und Maschinen, deren Bewegung auf kontrollierte Weise „von außen” gesteuert werden kann.
      PubDate: 2017-06-20T08:31:01.867712-05:
      DOI: 10.1002/ange.201702992
       
  • Dynamisches makromolekulares Materialdesign – die Vielseitigkeit von
           Cyclodextrin-basierter Wirt-Gast-Chemie
    • Authors: Bernhard V. K. J. Schmidt; Christopher Barner-Kowollik
      Abstract: Cyclodextrin-Wirt-Gast-Chemie ist ein leistungsfähiger Design-Ansatz für dynamische und adaptive Materialien mit einstellbaren Eigenschaften. B. V. K. J. Schmidt und C. Barner-Kowollik beschreiben in ihrem Aufsatz (
      DOI : http://doi.org/10.1002/ange.201612150), wie komplexe supramolekulare Strukturen für Anwendungen von der Biomedizin bis zu selbstheilenden Materialien erzeugt werden können. Wie Wirt-Gast-Wechselwirkungen verschiedene molekulare Stränge verbinden, so vereinigt dieses Jubiläumsheft – anlässlich des 150-jährigen Bestehens der GDCh und des 100-jährigen Bestehens der RACI – Beispiele aus verschiedenen chemischen Teilgebieten von deutschen und australischen Autoren.
      PubDate: 2017-06-20T08:16:01.942724-05:
       
  • Co-assembly of Patchy Polymeric Micelles and Protein Molecules
    • Authors: Weijing Fan; Li Liu, Hanying Zhao
      Abstract: The development in the synthesis and self-assembly of patchy nanoparticles has resulted in the creation of complex hierarchical structures. Co-assembly of polymeric nanoparticles and protein molecules combines the advantages of polymeric materials and biomolecules, and will produce new functional materials. Co-assembly of positively charged patchy micelles and negatively charged bovine serum albumin (BSA) molecules is investigated. The patchy micelles, which were synthesized using block copolymer brushes as templates, leads to co-assembly with protein molecules into vesicular structures. The average size of the assembled structures can be controlled by the molar ratio of BSA to patchy micelles. The assembled structures are dissociated in the presence of trypsin. The protein–polymer hybrid vesicles could find potential applications in medicine.Die Coaggregation positiv geladener „gefleckter” Micellen und negativ geladener Rinderserumalbumin-Moleküle zu Vesikelstrukturen wurde untersucht. Die mittlere Größe der resultierenden Strukturen lässt sich durch das Molverhältnis der beiden Komponenten steuern. In Gegenwart von Trypsin dissoziieren die Vesikel.
      PubDate: 2017-06-20T08:01:14.949907-05:
      DOI: 10.1002/ange.201704955
       
  • QM/MM Study on the Photoreactions of Dark- and Light-Adapted States of a
           Blue-Light YtvA LOV Photoreceptor
    • Authors: Xue-Ping Chang; Yuan-Jun Gao, Wei-Hai Fang, Ganglong Cui, Walter Thiel
      Abstract: The dark- and light-adapted states of YtvA LOV domains exhibit distinct excited-state behavior. We have employed high-level QM(MS-CASPT2)/MM calculations to study the photochemical reactions of the dark- and light-adapted states. The photoreaction from the dark-adapted state starts with an S1T1 intersystem crossing followed by a triplet-state hydrogen transfer from the thiol to the flavin moiety that produces a diradical intermediate, and a subsequent internal conversion that triggers a barrierless C-S bond formation in the S0 state. The energy profiles for these transformations are different for the four conformers of the dark-adapted state considered. The photochemistry of the light-adapted state does not involve the triplet state: photoexcitation to the S1 state triggers C-S bond cleavage followed by recombination in the S0 state; both these processes are essentially barrierless and thus ultrafast. The present work offers new mechanistic insights into blue-light photoreceptors.
      PubDate: 2017-06-20T07:59:37.156985-05:
      DOI: 10.1002/ange.201703487
       
  • A Unified Continuous Flow Assembly-Line Synthesis of Highly Substituted
           Pyrazoles and Pyrazolines
    • Authors: Joshua Britton; Timothy F. Jamison
      Abstract: A rapid and modular continuous flow synthesis of highly functionalized fluorinated pyrazoles and pyrazolines has been developed. Flowing fluorinated amines through sequential reactor coils mediates diazoalkane formation and [3+2] cycloaddition to generate more than 30 azoles in a telescoped fashion. Pyrazole cores are then sequentially modified through additional reactor modules performing N-alkylation and arylation, deprotection, and amidation to install broad molecular diversity in short order. Continuous flow synthesis enables the safe handling of diazoalkanes at elevated temperatures, and the use of aryl alkyne dipolarphiles under catalyst-free conditions. This assembly-line synthesis provides a flexible approach for the synthesis of agrochemicals and pharmaceuticals, as demonstrated by a four-step, telescoped synthesis of measles therapeutic, AS-136A, in a total residence time of 31.7 min (1.76 g h−1).Fließbandjob: Fertigungslinien wurden genutzt, um hoch funktionalisierte Pyrazole und Pyrazoline auf dem Weg zu Agrochemikalien und Pharmazeutika über eine mehrstufige Synthese unter kontinuierlichem Fluss herzustellen.
      PubDate: 2017-06-20T07:55:21.585023-05:
      DOI: 10.1002/ange.201704529
       
  • Controlling the α/γ-Reactivity of Vinylogous Ketone Enolates in
           Organocatalytic Enantioselective Michael Reactions
    • Authors: Igor Iriarte; Olatz Olaizola, Silvia Vera, Iñaki Gamboa, Mikel Oiarbide, Claudio Palomo
      Abstract: The first regio-, diastereo-, and enantioselective direct Michael reaction of β,γ-unsaturated ketones with nitroolefins is enabled by Brønsted base/hydrogen-bonding bifunctional catalysis. A squaramide-substituted tertiary amine catalyzes the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, giving rise to adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–98 % ee range.Umgeschaltet: In situ generierte vinyloge Enolat-Äquivalente reagieren meist unter Beibehaltung der Konjugation über das γ-Kohlenstoffatom. Ein bifunktionaler Wasserstoffbrückenkatalysator mit einer zusätzlichen tertiaren Amin-Funktion ermöglicht jedoch auch diastereo- und enantioselektive α-Additionen von β,γ-ungesättigten Ketonen an Nitroolefine.
      PubDate: 2017-06-20T07:44:11.655223-05:
      DOI: 10.1002/ange.201703764
       
  • A Modular Approach to Inorganic Phosphazane Macrocycles
    • Authors: Alex J. Plajer; Raúl García-Rodríguez, Callum G. M. Benson, Peter D. Matthews, Andrew D. Bond, Sanjay Singh, Lutz H. Gade, Dominic S. Wright
      Abstract: Union von organischer und Makrocyclenchemie: Die Bildung von großen anorganischen Makrocyclen mit über Schwefel- oder Seleniumatome verknüpften Phosphazan-Einheiten gelingt ganz einfach mit einer Eintopfmethode, die D. S. Wright et al. in ihrer Zuschrift (10.1002/ange.201702558) beschreiben. Die Methode erlaubt die Einführung vielfältiger organischer Substituenten, erleichtert so die gezielte Abstimmung der sterischen und elektronischen Eigenschaften und bedeutet einen wichtigen Schritt in der Entwicklung von Synthesewerkzeugen zum Aufbau anorganischer Makromoleküle.
      PubDate: 2017-06-20T07:42:34.566009-05:
      DOI: 10.1002/ange.201705956
       
  • A Designed Approach to Enantiodivergent Enamine Catalysis
    • Authors: Juliet Macharia; Victor Wambua, Yun Hong, Lawrence Harris, Jennifer S. Hirschi, Gary B. Evans, Mathew J. Vetticatt
      Abstract: The rational design and implementation of enantiodivergent enamine catalysis is reported. A simple secondary amine catalyst, 2-methyl-l-proline, and its tetrabutylammonium salt function as an enantiodivergent catalyst pair delivering the enantiomers of α-functionalized aldehyde products in excellent enantioselectivities. This novel concept of designed enantiodivergence is applied to the enantioselective α-amination, aldol, and α-aminoxylation/α-hydroxyamination reactions of aldehydes.Ungleiches Paar: In einer enantiodivergenten Enamin-Katalyse wirken das einfache sekundäre Amin 2-Methyl-l-prolin und sein Tetrabutylammoniumsalz als Katalysatorpaar, das die Enantiomere α-funktionalisierter Aldehyde mit ausgezeichneten Enantioselektivitäten liefert. Dieser neuartige enantiodivergente Ansatz ermöglicht enantioselektive α-Aminierungen und α-Aminoxylierungen/α-Hydroxyaminierungen sowie Aldolreaktionen von Aldehyden.
      PubDate: 2017-06-20T07:42:32.015373-05:
      DOI: 10.1002/ange.201703919
       
  • Qing-Hua Fan
    • PubDate: 2017-06-20T07:01:17.321494-05:
      DOI: 10.1002/ange.201705962
       
  • Silver(III)⋅⋅⋅Silver(III) Interactions that Stabilize the syn Form
           in a Porphyrin Dimer Upon Oxidation
    • Authors: Akhil Kumar Singh; Firoz Shah Tuglak Khan, Sankar Prasad Rath
      Abstract: The interaction between two AgII porphyrins, connected covalently through a highly flexible ethane bridge, in a metalloporphyrin dimer has been investigated upon stepwise oxidation. X-ray structure determination of one and two-electron oxidized complexes has clearly revealed only metal-centered oxidation that results in short Ag−N (porphyrin) distance with large distortion in the porphyrin macrocycle. The 2e-oxidized complex exhibits significant metallophilic interaction in the form of a close AgIII⋅⋅⋅AgIII contact that brings two porphyrin rings more cofacial with syn-conformation, which would otherwise stabilize in an anti-form. The interaction also leads to an intense emission peak at 546 nm at 77 K in the photoluminescence study.Ring auf Ring: Ein Ethylen-verbrücktes AgIII-Porphyrindimer zeigt eine signifikante metallophile Wechselwirkung, die zwei Porphyrinringe übereinander zu liegen bringt. Der kleine AgIII⋅⋅⋅AgIII-Abstand wird der Überlappung von dz2-Metallorbitalen zugeschrieben. Der Komplex zeigt ein intensives Emissionssignal bei λ=546 nm bei 77 K in einer Photolumineszenzstudie.
      PubDate: 2017-06-20T07:00:21.597762-05:
      DOI: 10.1002/ange.201705108
       
  • A T-Shaped Nickel(I) Metalloradical Species
    • Authors: Changho Yoo; Yunho Lee
      Abstract: Ein T-förmiges Nickel(I)-Metalloradikal mit starrem Acridan-basierten PNP-Ligand zeigt beispiellose offenschalige Reaktivität. In ihrer Zuschrift (
      DOI : 10.1002/ange.201704487) zeigen Y. Lee und C. Yoo, dass das frei zugängliche halb gefüllte dx2−y2-Orbital der radikalischen d9-Spezies die Fähigkeit zur homolytischen Spaltung von σ-Bindungen (z. B. H−H, N−N, C−C) über einen Zwei-Elektronen-Prozess unter Beteiligung von zwei Metallzentren verleiht.
      PubDate: 2017-06-20T06:59:59.038089-05:
       
  • Crystalline Hollow Microrods for Site-Selective Enhancement of Nonlinear
           Photoluminescence
    • Authors: Bing Chen; Wei Kong, Yong Liu, Yunhao Lu, Mingyu Li, Xvsheng Qiao, Xianping Fan, Feng Wang
      Abstract: Sun Wukong, der König der Affen, lässt hohle Mikrokristalle im Nahinfrarotlicht als räumlich aufgelöste optische Codes erstrahlen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201703600) erklären F. Wang et al., wie Lichtstreuung und -reflexion durch die Innenwände der Mikrostäbe die Lichtintensität über die Struktur hinweg moduliert. Dabei wird das elektrische Feld in der Nähe der Innenwände verstärkt, und es kommt zu hellen Lichtemissionen im Bereich der Löcher.
      PubDate: 2017-06-20T06:59:56.71875-05:0
       
  • Photocatalytic Nanosheet Lithography: Photolithography based on
           Organically Modified Photoactive 2D Nanosheets
    • Authors: Pirmin Ganter; Bettina V. Lotsch
      Abstract: Harvesting the properties of nanosheets is not only crucial from a fundamental perspective, but also for the development of novel functional devices based on 2D nanosheets. Herein, we demonstrate the processing of organically modified TBAxH1−xCa2Nb3O10 nanosheets into photonic thin films and study their colorimetric sensing properties in response to various aqueous and organic solvent vapors. Building on the enhanced solvent accessibility of TBA-containing nanosheets and their photocatalytic activity under UV irradiation, we develop a new concept for photocatalytic lithography using TBAxH1−xCa2Nb3O10 nanosheets as a negative photoresist to obtain high-fidelity micron-scale patterns of robust inorganic nanosheets. Photocatalytic nanosheet lithography (PNL) therefore adds a new resist-free, resource efficient direct patterning technique to the toolbox of photolithography.Mustergültig: Die Fähigkeit organisch modifizierter TBAxH1−xCa2Nb3O10-Nanoschichten zur Aufnahme von Lösungsmitteln wurde mit ihrer inhärenten photokatalytischen Aktivität kombiniert. Dieser Ansatz macht sie zu Dampfsensoren und möglichen negativen Photolacken zum Aufbringen mikrometergroßer Muster.
      PubDate: 2017-06-20T06:59:09.916861-05:
      DOI: 10.1002/ange.201703149
       
  • A Rapid Total Synthesis of Ciprofloxacin Hydrochloride in Continuous Flow
    • Authors: Hongkun Lin; Chunhui Dai, Timothy F. Jamison, Klavs F. Jensen
      Abstract: Within a total residence time of 9 min, the sodium salt of ciprofloxacin was prepared from simple building blocks via a linear sequence of six chemical reactions in five flow reactors. Sequential offline acidifications and filtrations afforded ciprofloxacin and ciprofloxacin hydrochloride. The overall yield of the eight-step sequence was 60 %. No separation of intermediates was required throughout the synthesis when a single acylation reaction was applied to remove the main byproduct, dimethylamine.In neun Minuten wurde das Antibiotikum Ciprofloxacin aus fünf Synthesebausteinen in einem Strömungssystem hergestellt. Insgesamt sechs Reaktionen laufen in fünf Reaktoren ab und führen zum Ciprofloxacin-Natriumsalz. Einfache pH-Einstellung, Filtration und Kristallisation im Offline-Betrieb liefern Ciprofloxacin-Hydrochlorid-Kristalle.
      PubDate: 2017-06-20T06:57:32.881333-05:
      DOI: 10.1002/ange.201703812
       
  • Cold Snapshot of a Molecular Rotary Motor Captured by High-Resolution
           Rotational Spectroscopy
    • Authors: Sérgio R. Domingos; Arjen Cnossen, Wybren J. Buma, Wesley R. Browne, Ben L. Feringa, Melanie Schnell
      Abstract: We present the first high-resolution rotational spectrum of an artificial molecular rotary motor. By combining chirped-pulse Fourier transform microwave spectroscopy and supersonic expansions, we captured the vibronic ground-state conformation of a second-generation motor based on chiral, overcrowded alkenes. The rotational constants were accurately determined by fitting more than 200 rotational transitions in the 2–4 GHz frequency range. Evidence for dissociation products allowed for the unambiguous identification and characterization of the isolated motor components. Experiment and complementary quantum-chemical calculations provide accurate geometrical parameters for the C27H20 molecular motor, the largest molecule investigated by high-resolution microwave spectroscopy to date.Molekulare Motoren im Überschall: Die Struktur eines unidirektionalen künstlichen molekularen Motors im Grundzustand wurde mittels hochauflösender Mikrowellenspektroskopie und Überschallexpansionen bestimmt. So wurde eine einzigartige funktionale Nanomaschine in der Gasphase untersucht.
      PubDate: 2017-06-20T06:55:05.626963-05:
      DOI: 10.1002/ange.201704221
       
  • Iron-Catalyzed Cyclotrimerization of Terminal Alkynes by Dual Catalyst
           Activation in the Absence of Reductants
    • Authors: Davide Brenna; Matteo Villa, Tim N. Gieshoff, Fabian Fischer, Marko Hapke, Axel Jacobi von Wangelin
      Abstract: Catalyzing C−C bond-forming reactions with earth-abundant metals under mild conditions is at the heart of sustainable synthesis. The cyclotrimerization of alkynes is a valuable atom-efficient reaction in organic synthesis that is enabled by several metal catalysts, including iron. This study reports an effective iron-catalyzed cyclotrimerization for the regioselective synthesis of 1,2,4-substituted arenes (1 mol % catalyst, toluene, 20 °C, 5 min). A dual activation mechanism (substrate deprotonation, reductive elimination) renders the simple FeII precatalyst highly active in the absence of any reductant.Cyclotrimerisierungen von terminalen Alkinen gelangen mit dem einfachen Präkatalysator Fe(hmds)2 (hmds=1,1,1,3,3,3-Hexamethyldisilazid), der nicht mit einem zusätzlichen Reduktionsmittel, sondern durch das Substrat aktiviert wird. 1,2,4-Trisubstituierte Arine wurde innerhalb weniger Minuten bei 20 °C mit hoher Regioselektivität gebildet.
      PubDate: 2017-06-20T06:54:43.853119-05:
      DOI: 10.1002/ange.201705087
       
  • Mn(I)-Catalyzed Regio- and Stereoselective 1,2-Diheteroarylation of
           Allenes: Combination of C-H activation and Smiles Rearrangement
    • Authors: Shi-Yong Chen; Xiang-Lei Han, Jia-Qiang Wu, Qingjiang Li, Yunyun Chen, Honggen Wang
      Abstract: Heteroarenes are important structural motif in functional molecules. Reported herein is a Mn(I)-catalyzed 1,2-diheteroarylation of allenes via a C-H activation/Smiles rearrangement cascade. The reaction occurred under additive-free or even solvent-free conditions which allowed the creation of two C-C and one C-N bonds in a single operation. A series of structurally diverse bicyclic or tricyclic compounds bearing an exocyclic double bond were constructed in good to excellent efficiency. The decarboxylative ring-opening of the products led to the facile synthesis of vicinal biheteroaryls. Synthetic applications were demonstrated and preliminary mechanistic studies were conducted.
      PubDate: 2017-06-20T06:54:26.181388-05:
      DOI: 10.1002/ange.201704952
       
  • Maßgeschneiderte Ahp-Cyclodepsipeptide als potente, nicht-kovalente
           Serinprotease-Inhibitoren
    • Authors: Steffen Köcher; Juliana Rey, Jens Bongard, André N. Tiaden, Michael Meltzer, Peter J. Richards, Michael Ehrmann, Markus Kaiser
      Abstract: Die S1-Serinproteasen sind eine der größten und biologisch relevantesten Proteasefamilien. Trotz ihrer biomedizinischen Bedeutung gibt es bisher jedoch nur eine geringe Zahl generischer Ansätze zur Herstellung potenter, bioaktiver, S1-Enzymfamilien-spezifischer und nicht-kovalenter Inhibitoren. Hier wird gezeigt, dass Ahp-Cyclodepsipeptide geeignete Grundstrukturen zur Bildung maßgeschneiderter Serinprotease-Inhibitoren sind. Um diese möglichst effizient herzustellen, wurde eine praktikable Fest- und Flüssigphasensynthese entwickelt und mit der ersten Synthese zweier Naturstoffe, Tasipeptin A und B, validiert. Die Eignung der Ahp-Cyclodepsipeptide als Gerüststrukturen zur Herstellung maßgeschneiderter Serinprotease-Inhibitoren wird an der Entwicklung der bisher potentesten Inhibitoren für die humanen HTRA-Proteasen demonstriert. Dieser Ansatz sollte auch auf weitere Serinproteasen anwendbar sein, wodurch sich neue Möglichkeiten zur systematischen Auffindung von Serinprotease-Inhibitoren ergeben.Sonden nach Maß: Ahp-Cyclodepsipeptide, eine Naturstoffklasse mit spezifischen, nicht-kovalenten Serinprotease-Hemmeigenschaften, wurden maßgeschneidert, um chemische Sonden für das Studium der biomedizinisch relevanten HTRA-Proteasen herzustellen.
      PubDate: 2017-06-20T06:49:49.038865-05:
      DOI: 10.1002/ange.201701771
       
  • Renewable Molecular Flasks with NADH Models: Combination of Light-Driven
           Proton Reduction and Biomimetic Hydrogenation of Benzoxazinones
    • Authors: Liang Zhao; Jianwei Wei, Junhua Lu, Cheng He, Chunying Duan
      Abstract: Using small molecules with defined pockets to catalyze chemical transformations resulted in attractive catalytic syntheses that echo the remarkable properties of enzymes. By modulating the active site of a nicotinamide adenine dinucleotide (NADH) model in a redox-active molecular flask, we combined biomimetic hydrogenation with in situ regeneration of the active site in a one-pot transformation using light as a clean energy source. This molecular flask facilitates the encapsulation of benzoxazinones for biomimetic hydrogenation of the substrates within the inner space of the flask using the active sites of the NADH models. The redox-active metal centers provide an active hydrogen source by light-driven proton reduction outside the pocket, allowing the in situ regeneration of the NADH models under irradiation. This new synthetic platform, which offers control over the location of the redox events, provides a regenerating system that exhibits high selectivity and efficiency and is extendable to benzoxazinone and quinoxalinone systems.In der Tasche: Aktive Zentren von NADH-Modellen wurden zu redoxaktiven molekularen Reaktionsgefäßen umgebaut, sodass biomimetische Hydrierung und photokatalytische In-situ-Protonenreduktion im inneren bzw. äußeren Bereich der Tasche ablaufen. Bei der Ein-Topf-Umsetzung von Benzoxazinonen und Chinoxalinonen mit Licht als Energiequelle können so die Enzymeigenschaften imitiert werden.
      PubDate: 2017-06-20T06:49:37.54361-05:0
      DOI: 10.1002/ange.201702926
       
  • Synthese, Struktur und Bindungsanalyse eines homoleptischen Berylliumazids
    • Authors: Dominik Naglav; Briac Tobey, Benjamin Lyhs, Beate Römer, Dieter Bläser, Christoph Wölper, Georg Jansen, Stephan Schulz
      Abstract: [Ph4P]2[Be(N3)4] (1) und [PNP]2[Be(N3)4] (2; PNP=Ph3PNPPh3) wurden durch Reaktion von Be(N3)2 mit [Ph4P]N3 und [PNP]N3 synthetisiert. Das Tetraazidoberyllat-Dianion [Be(N3)4]2− (1′) repräsentiert das erste strukturell charakterisierte homoleptische Berylliumazid, und die elektronische Struktur und Bindungssituation in 1′ wurde mit quantenchemischen Methoden (NPA, ELF, LOL) untersucht.Stickstoffreiche Salze: Be(N3)2 reagiert mit zwei Äquivalenten [Ph4P]N3 und [PNP]N3 (PNP=Ph3PNPPh3) zu [Ph4P]2[Be(N3)4] (1) bzw. [PNP]2[Be(N3)4] (2) mit dem Tetraazidoberyllatdianion. 1 wurde durch Röntgenstrukturanalyse charakterisiert (siehe Struktur des [Be(N3)4]2−-Dianions; Be braun, N blau) und seine Bindungssituation durch quantenchemische Rechnungen studiert. Außerdem wurde die Struktur von 2 in Lösung mittels NMR-Spektroskopie untersucht.
      PubDate: 2017-06-20T06:49:04.691991-05:
      DOI: 10.1002/ange.201703147
       
  • Visible Light Irradiated Graphitic Carbon Nitride (g-C3N4) Photocatalyzed
           Cation Radical Diels-Alder Reactions with Dioxygen as Sustainable Mediator
           for Photoinduced Electrons
    • Authors: Yubao Zhao; Markus Antonietti
      Abstract: Photocatalytic Diels-Alder (D-A) reaction with electron rich olefins is realized by graphitic carbon nitride (g-C3N4) under visible light irradiation and aerobic condition. This heterogeneous photo-redox reaction system is highly efficient, and apparent quantum yield reaches a remarkable value of 47 % for the model reaction. Dioxygen plays a critical role as electron mediator, which is distinct from the previous reports in the homogeneous Ru(II) complex photo-redox system. Moreover, the reaction intermediate vinylcyclobutane is captured and monitored during the reaction, serving as a direct evidence for the proposed reaction mechanism. The cycloaddition process is thereby determined to be the combination of direct [4 + 2] cycloaddition and [2 + 2] cycloaddition followed by photocatalytic rearrangement of the vinylcyclobutane intermediate.
      PubDate: 2017-06-20T06:02:55.433608-05:
      DOI: 10.1002/ange.201703438
       
  • Mg2+ dependent high mechanical anisotropy of three-way-junction-pRNA
           revealed by single-molecule force spectroscopy
    • Authors: Yang Sun; Weishuai Di, Yiran Li, Wenmao Huang, Xin Wang, Meng Qin, Wei Wang, Yi Cao
      Abstract: Mechanical anisotropy is ubiquitous in biological tissues but remains hard to be reproduced in synthetic biomaterials. Developing molecular building blocks with anisotropic mechanical response is the key towards engineering anisotropic biomaterials. Here we report that the three-way-junction- (3WJ-) pRNA, derived from φ29 DNA packaging motor, shows strong mechanical anisotropy upon Mg2+ binding. In the absence of Mg2+, 3WJ-pRNA is mechanically weak without noticeable mechanical anisotropy. While in the presence of Mg2+, the unfolding forces can differ by more than 4 folds along different pulling directions, ranging from ~47 pN to ~219 pN. Mechanical anisotropy of 3WJ-pRNA stems from pulling direction dependent cooperativity for the rupture of two Mg2+ binding sites, which represents a novel mechanism for the mechanical anisotropy of biomacromolecules. We anticipate that 3WJ-pRNA can be used as a key element for the construction of biomaterials with controllable mechanical anisotropy.
      PubDate: 2017-06-20T04:50:55.992797-05:
      DOI: 10.1002/ange.201704113
       
  • ABi2(IO3)2F5 (A= K, Rb and Cs): Combination of Halide and Oxide Anionic
           Units to Create Large SHG Response with Wide Bandgap
    • Authors: Xingguo Chen; Hongming Liu, Qi Wu, Xingxing Jiang, Xianggao Meng, Zheshuai Lin, Jingui Qin
      Abstract: A family of nonlinear optical materials that contain the halide, oxide and oxyhalide polar units simultaneously in a single structure, namely, ABi2(IO3)2F5 (A = K, 1;Rb,2 and Cs,3), have been designed and synthesized. They crystallize in the same polar space group of P21 with a two-dimensional double-layered framework constructed by [BiF5]2- and [BiO2F4]5- units connected to each other by four F atoms, in which two [IO3]- groups are linked to [BiO2F4]5- unit on the same side, and a hanging Bi-F bond of [BiF5]2- unit is located on the other side via ionic interaction with the layer-inserted alkali metal ions to form three-dimensional structure. The well-ordered alignments of these polar units lead to a very strong second harmonic generation response of 12 (1), 9.5 (2) and 7.5 (3) times larger than that of KDP under 1064 nm laser radiation. All of them exhibited wide bandgap over 3.75 eV, indicating that they will possess high laser damage threshold.
      PubDate: 2017-06-20T04:49:15.37811-05:0
      DOI: 10.1002/ange.201705672
       
  • Frontispiz: Surprising Stability of Larger Criegee Intermediates on
           Aqueous Interfaces
    • Authors: Jie Zhong; Manoj Kumar, Chong Q. Zhu, Joseph S. Francisco, Xiao C. Zeng
      Abstract: Atmosphärenchemie J. S. Francisco, X. C. Zeng et al. zeigen in der Zuschrift auf S. 7848 ff., dass Criegee-Intermediate mit hydrophoben Substituenten (länger als C1) länger auf der Oberfläche von Wassertröpfchen überleben.
      PubDate: 2017-06-20T02:33:34.567343-05:
      DOI: 10.1002/ange.201782761
       
  • Biosynthesis of Complex Indole Alkaloids: Elucidation of the Concise
           Pathway of Okaramines
    • Authors: Chen-Yu Lai; Hsiao-Ching Lin, I-Wen Lo, Ranuka T. Hewage, Yi-Chen Chen, Chien-Ting Chen, Chi-Fang Lee, Steven Lin, Man-Cheng Tang
      Abstract: The okaramines are a class of complex indole alkaloids isolated from Penicillium and Aspergillus species. Their potent insecticidal activity arises from selectively activating glutamate-gated chloride channels (GluCls) in invertebrates, not affecting human ligand-gated anion channels. Okaramines B (1) and D (2) contain a polycyclic skeleton, including an azocine ring and an unprecedented 2-dimethyl-3-methyl-azetidine ring. Due to their complex scaffold, okaramines have inspired many total synthesis efforts, but the enzymology of the okaramine biosynthetic pathway remains unexplored. Here, we identified and characterized the biosynthetic gene cluster (oka) of 1 and 2, then elucidated the pathway with target gene inactivation, heterologous reconstitution, and biochemical characterization. Notably, we characterized an α-ketoglutarate-dependent non-heme Fe(II) dioxygenase that forged the azetidine ring on the okaramine skeleton.
      PubDate: 2017-06-20T01:40:58.436774-05:
      DOI: 10.1002/ange.201705501
       
  • Strain Stiffening Hydrogels through Self-Assembly and Covalent Fixation of
           Semi-Flexible Fibers
    • Authors: Marcos Fernandez-Castano Romera; René P. M. Lafleur, Clément Guibert, Ilja K. Voets, Cornelis Storm, Rint P. Sijbesma
      Abstract: Biomimetic, strain-stiffening materials are reported, made through self-assembly and covalent fixation of small building blocks to form fibrous hydrogels that are able to stiffen by an order of magnitude in response to applied stress. The gels consist of semi-flexible rodlike micelles of bisurea bolaamphiphiles with oligo(ethylene oxide) (EO) outer blocks and a polydiacetylene (PDA) backbone. The micelles are fibers, composed of 9–10 ribbons. A gelation method based on Cu-catalyzed azide–alkyne cycloaddition (CuAAC), was developed and shown to lead to strain-stiffening hydrogels with unusual, yet universal, linear and nonlinear stress–strain response. Upon gelation, the X-ray scattering profile is unchanged, suggesting that crosslinks are formed at random positions along the fiber contour without fiber bundling. The work expands current knowledge about the design principles and chemistries needed to achieve fully synthetic, biomimetic soft matter with on-demand, targeted mechanical properties.Biomimetische spannungsversteifende Materialien wurden durch Selbstorganisation und kovalente Fixierung kleiner Bausteine aus Bisharnstoff-Bolaamphiphilen zu faserigen Hydrogelen hergestellt. Bei Ausüben eines mechanischen Drucks versteifen sich die Gele um eine Größenordnung.
      PubDate: 2017-06-20T01:26:31.582793-05:
      DOI: 10.1002/ange.201704046
       
  • Europium Oxybromide Catalysts for Efficient Bromine Looping in Natural Gas
           Valorization
    • Authors: Vladimir Paunović; Ronghe Lin, Matthias Scharfe, Amol P. Amrute, Sharon Mitchell, Roland Hauert, Javier Pérez-Ramírez
      Abstract: The industrialization of bromine-mediated natural gas upgrading is contingent on the ability to fully recycle hydrogen bromide (HBr), which is the end form of the halogen after the activation and coupling of the alkanes. Europium oxybromide (EuOBr) is introduced as a unique catalytic material to close the bromine loop via HBr oxidation, permitting low-temperature operation and long lifetimes with a stoichiometric feed (O2:HBr=0.25)—conditions at which any catalyst reported to date severely deactivates because of excessive bromination. Besides, EuOBr exhibits unparalleled selectivity to methyl bromide in methane oxybromination, which is an alternative route for bromine looping. This novel active phase is finely dispersed on appropriate carriers and scaled up to technical extrudates, enhancing the utilization of the europium phase while preserving the performance. This catalytic system paves the way for sustainable valorization of stranded natural gas via bromine chemistry.Brom-Zyklus: Materialien auf Europiumoxybromid-Basis sind außergewöhnliche Katalysatoren für die Oxidation von HBr zu Br2 und die Oxybromierung von CH4 zu CH3Br im Sinne eines geschlossenen Brom-Zyklus für die Umwandlung von Erdgas in Brennstoffe und Chemikalien.
      PubDate: 2017-06-20T01:26:13.774967-05:
      DOI: 10.1002/ange.201704406
       
  • Stable Heterometallic Cluster Ions based on Werner's Hexol
    • Authors: David A. Marsh; William S. Elliott, Rachel M. Smith, Meredith C. Sharps, Mary K. Baumeister, Matthew E. Carnes, Lev N. Zakharov, William H. Casey, Darren W. Johnson
      Abstract: Large aqueous ions are interesting because they are useful in materials science (for example to generate thin films) but also because they serve as molecular models for the oxide–aqueous mineral interface where spectroscopy is difficult. Here we show that new clusters of the type M[(μ-OH)2Co(NH3)4]3(NO3)6 (M=Al, Ga) can be synthesized using Werner's century-old cluster as a substitutable framework. We substituted Group 13 metals into the hexol Co[(μ-OH)2Co(NH3)4]36+ ion to make diamagnetic heterometallic ions. The solid-state structure of the hexol-type derivatives were determined by single-crystal XRD and NMR spectroscopy and confirmed that the solid-state structure persists in solution after dissolution into either D2O or [D6]DMSO. Other compositions besides these diamagnetic ions can undoubtedly be made using a similar approach, which considerably expands the number of stable aqueous heteronuclear ions.Heterometallcluster: Neue, stabile Polymetallionen wurden durch gezielte Substitutionen in Werners Hexolstruktur, [Co((μ-OH)2Co(NH3)4)3]6+, hergestellt. Die Substitutionen wurden mit Metallen der Gruppe 13 vorgenommen und die Stabilität der Clusterionen durch NMR-Spektroskopie bestätigt.
      PubDate: 2017-06-20T01:25:31.537565-05:
      DOI: 10.1002/ange.201704073
       
  • A Generalized Strategy for the Synthesis of Large-Size Ultrathin
           Two-Dimensional Metal Oxide Nanosheets
    • Authors: Hewei Zhao; Yujie Zhu, Fengshi Li, Rui Hao, Shaoxiong Wang, Lin Guo
      Abstract: Two-dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large-size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet-chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main-group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state.Einfach und allgemein ist ein nasschemischer Syntheseansatz für große Metalloxid-Nanoschichten an Graphenoxid (GO) als Templat. Produkte zeigen eine einzigartige Oberflächenchemie, und sie können mit vorgegebener Dicke erzeugt werden.
      PubDate: 2017-06-19T08:46:43.480378-05:
      DOI: 10.1002/ange.201703871
       
  • 1-Substituted 2-Azaspiro[3.3]heptanes: Overlooked Motifs for Drug
           Discovery
    • Authors: Alexander A. Kirichok; Iryna Shton, Maria Kliachyna, Iryna Pishel, Pavel K. Mykhailiuk
      Abstract: The 2-substituted piperidine core is found in drugs (18 FDA-approved drugs), however, their spirocyclic analogues remain unknown. Described here is the synthesis of spirocyclic analogues for 2-substituted piperidines and a demonstration of their validation in drug discovery.Fitness-Prüfung: 2-substituiertes Piperidin findet sich als Gerüst in vielen Wirkstoffen, seine spirocyclischen Analoga hingegen nicht. Einige dieser Analoga wurden nun synthetisiert und in der Wirkstoffentwicklung validiert.
      PubDate: 2017-06-19T08:46:22.985099-05:
      DOI: 10.1002/ange.201703801
       
  • Studying the Conformation of a Receptor Tyrosine Kinase in Solution by
           Inhibitor-Based Spin Labeling
    • Authors: Dongsheng M. Yin; Jeffrey S. Hannam, Anton Schmitz, Olav Schiemann, Gregor Hagelueken, Michael Famulok
      Abstract: The synthesis of a spin label based on PD168393, a covalent inhibitor of a major anticancer drug target, the epidermal growth factor receptor (EGFR), is reported. The label facilitates the analysis of the EGFR structure in solution by pulsed electron paramagnetic resonance (EPR) spectroscopy. For various EGFR constructs, including near-full-length EGFR, we determined defined distance distributions between the two spin labels bound to the ATP binding sites of the EGFR dimer. The distances are in excellent agreement with an asymmetric dimer of the EGFR. Based on crystal structures, this dimer had previously been proposed to reflect the active conformation of the receptor but structural data demonstrating its existence in solution have been lacking. More generally, our study provides proof-of-concept that inhibitor-based spin labeling enables the convenient introduction of site-specific spin labels into kinases for which covalent or tight-binding small-molecule modulators are available.Synthese und Anwendung eines spinmarkierten kovalenten Inhibitors führten zu einer vielseitigen, leicht anwendbaren Methode für die Einführung paramagnetischer Reste an einer definierten Proteinposition für EPR-Studien. Die Sonde ermöglicht, die Konformation des Inhibitor-gebundenen Fast-Volllängen-EGF-Rezeptors in Lösung zu bestimmen. Diese Studie ist ein wichtiger Fortschritt für die EPR-Analyse komplexer Proteine. EGF=Epidermaler Wachstumsfaktor.
      PubDate: 2017-06-19T08:45:53.141926-05:
      DOI: 10.1002/ange.201703154
       
  • Frozen Acrylamide Gels as Dynamic Nuclear Polarization Matrices
    • Authors: Jasmine Viger-Gravel; Pierrick Berruyer, David Gajan, Jean-Marie Basset, Anne Lesage, Paul Tordo, Olivier Ouari, Lyndon Emsley
      Abstract: Aqueous acrylamide gels can be used to provide dynamic nuclear polarization (DNP) NMR signal enhancements of around 200 at 9.4 T and 100 K. The enhancements are shown to increase with crosslinker concentration and low concentrations of the AMUPol biradical. This DNP matrix can be used in situations where conventional incipient wetness methods fail, such as to obtain DNP surface enhanced NMR spectra from inorganic nanoparticles. In particular, we obtain 113Cd spectra from CdTe-COOH NPs in minutes. The spectra clearly indicate a highly disordered cadmium-rich surface.Wässrige Acrylamidgele lassen sich zur Verstärkung von DNP-NMR-Signalen um ca. 200 bei 9.4 und 100 K verwenden. Diese neue DNP-Matrix kann eingesetzt werden, wenn herkömmliche Methoden versagen, z. B. der Erhalt von Spektren aus der DNP-SENS von CdTe-COOH-Nanopartikeln mit stark fehlgeordneter, Cadmium-reicher Oberfläche. DNP=Dynamische Kernpolarisation, SENS=oberflächenverstärkte NMR-Spektroskopie.
      PubDate: 2017-06-19T08:45:30.320858-05:
      DOI: 10.1002/ange.201703758
       
  • Divergent Synthesis of Disulfanes and Benzenesulfonothioates Bearing
           2-Aminofurans From N-Tosylhydrazone-Bearing Thiocarbamates
    • Authors: Shaoyu Mai; Qiuling Song
      Abstract: An efficient and convenient synthesis of valuable disulfanes and benzenesulfonothioates, having a 2-aminofuran framework, has been developed by employing a copper-catalyzed transformation of readily available N-tosylhydrazone-bearing thiocarbamates. This method features an inexpensive metal catalyst, mild reaction conditions, good functional-group tolerance, short reaction times, and delivers valuable and complex products. A copper carbene generated from an N-tosylhydrazone-bearing thiocarbamate is proposed as the key intermediate for the transformation and it triggers the subsequent cascade. Remarkably, the Ts anion released from N-tosylhydrazone further serves as a nucleophile, thus rendering the formation of benzenesulfonothioates under controlled conditions.Nichts verschwendet: Mit N-Tosylhydrazon funktionalisierte Thiocarbamate erweisen sich als wertvolle Substrate für die kupferkatalysierte Synthese komplexer Disulfane und Benzolsulfonothioate mit 2-Aminofuran-Gerüst. Bemerkenswerterweise dient die 4-Toluolsulfonyl(Ts)-Gruppe, deren Abspaltung als Abfallprodukt man erwarten würde, als Nukleophil für die Bildung der Benzolsulfonothioate.
      PubDate: 2017-06-14T02:20:51.057035-05:
      DOI: 10.1002/ange.201704091
       
  • Bioinspired Total Synthesis of Homodimericin A
    • Authors: Jun Huang; Yueqing Gu, Kai Guo, Lei Zhu, Yu Lan, Jianxian Gong, Zhen Yang
      Abstract: Homodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels–Alder reaction, and an ene reaction.Doppelt hält besser: Der hoch oxygenierte und racemische pilzliche Metabolit Homodimericin A (1), der einen dichten käfigartigen Kern mit acht aufeinanderfolgenden stereogenen Zentren aufweist, wurde in nur sieben Stufen synthetisiert. Die Syntheseroute wurde in Anlehnung an die biogenetische Synthese von 1 entworfen und enthält eine doppelte Michael-Reaktion und eine intramolekulare Diels-Alder-Reaktion (siehe Schema).
      PubDate: 2017-06-12T14:11:14.254575-05:
      DOI: 10.1002/ange.201702768
       
  • Gewählt …
    • PubDate: 2017-06-12T14:10:28.235205-05:
      DOI: 10.1002/ange.201705180
       
  • Titelbild: Superelektrophiles Verhalten eines Anions demonstriert durch
           spontane Bindung von Edelgasen an [B12Cl11]− (Angew. Chem. 27/2017)
    • Authors: Markus Rohdenburg; Martin Mayer, Max Grellmann, Carsten Jenne, Tobias Borrmann, Florian Kleemiss, Vladimir A. Azov, Knut R. Asmis, Simon Grabowsky, Jonas Warneke
      Pages: 7789 - 7789
      Abstract: Das Ion [B12Cl11]− … …hat Eigenschaften, die nicht vereinbar zu sein scheinen – eine positive und eine negative Seite wie die Göttin Helja aus der altnordischen Mythologie: Physikalisch ist [B12Cl11]− ein Anion, es geht jedoch für stark elektrophile Kationen typische Reaktionen ein. In der Zuschrift auf S. 8090 ff. berichten S. Grabowsky, J. Warneke et al., dass die Elektrophilie von [B12Cl11]− so hoch ist, dass sogar die Edelgase Kr und Xe spontan bei Raumtemperatur gebunden werden – eine typische Reaktion von Superelektrophilen.
      PubDate: 2017-06-09T05:01:38.910125-05:
      DOI: 10.1002/ange.201703996
       
  • Innentitelbild: Lithiophilic Sites in Doped Graphene Guide Uniform Lithium
           Nucleation for Dendrite-Free Lithium Metal Anodes (Angew. Chem. 27/2017)
    • Authors: Rui Zhang; Xiao-Ru Chen, Xiang Chen, Xin-Bing Cheng, Xue-Qiang Zhang, Chong Yan, Qiang Zhang
      Pages: 7790 - 7790
      Abstract: Lithiummetallanoden versprechen die besten Ergebnisse für eine neue Generation von Batterien mit hoher Energiedichte. In der Zuschrift auf S. 7872 ff. nutzen Q. Zhang et al. eine stickstoffdotierte Graphen-Matrix (als Lotus-Blätter dargestellt) mit lithiophilen Nukleationszentren (der Frosch), um Li (die Kaulquappen) gleichmäßig verteilt auf der Anodenoberfläche anzulagern. Die Leistungsfähigkeit dieser dendritfreien Lithiummetallanoden ist bemerkenswert.
      PubDate: 2017-05-09T07:25:26.428193-05:
      DOI: 10.1002/ange.201704344
       
  • Editorial: Den Pulsschlag der Chemie fühlen – schon im
           Grundpraktikum
    • Authors: Roland A. Fischer
      Pages: 7792 - 7793
      Abstract: Diese Erfahrungen aus Anfängerpraktika sind, wie ich finde, einzigartig im ganzen weiteren Studienverlauf. Wertvoll ist auch die schonungslose Offenlegung des Zusammenhangs von zumutbarer Aneignung von Wissen, sorgfältiger Beobachtung, logischem Denken im Umgang mit Fakten, selbstkritischer Hartnäckigkeit und Belastbarkeit mit dem Erfolg im und durch das Experiment. Als Lohn winkt Befriedigung ...” Lesen Sie mehr im Editorial von Roland A. Fischer.
      PubDate: 2017-06-08T07:05:41.983544-05:
      DOI: 10.1002/ange.201704760
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 27/2017
    • Pages: 7795 - 7810
      PubDate: 2017-06-20T02:33:29.078584-05:
      DOI: 10.1002/ange.201782711
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 27/2017
    • Pages: 7814 - 7817
      PubDate: 2017-06-20T02:33:35.100649-05:
      DOI: 10.1002/ange.201782713
       
  • Gareth A. Morris
    • Pages: 7818 - 7818
      Abstract: „Mein Rat für Studenten: Sie sollen meinen Rat ignorieren – was sie üblicherweise tun. Mein erstes Experiment war vermutlich etwas aus dem Ladybird-Buch Magnets, Bulbs and Batteries, als ich etwa sieben war. Heute spiele ich einfach mit größeren Magneten ...“ Dies und mehr von und über Gareth A. Morris finden Sie auf Seite 7818.
      PubDate: 2017-03-01T02:10:42.89373-05:0
      DOI: 10.1002/ange.201701095
       
  • Effects of Nanoconfinement on Catalysis. Herausgegeben von Rinaldo Poli.
    • Authors: Pablo Ballester
      Pages: 7821 - 7822
      Abstract: Springer International Publishing, 2017. 266 S., geb., 155.99 €.—ISBN 978-3319502052
      PubDate: 2017-05-05T06:47:40.97507-05:0
      DOI: 10.1002/ange.201704055
       
  • Photokatalyse ermöglicht die akzeptorfreie Dehydrierung von
           benzanellierten gesättigten Ringen bei Raumtemperatur
    • Authors: Qin Yin; Martin Oestreich
      Pages: 7824 - 7826
      Abstract: Sonnenverbrannt: Sichtbares Licht ermöglicht die akzeptorfreie Dehydrierung von gesättigten Hetero- und Carbocyclen mit anelliertem Benzolring bei Raumtemperatur (siehe Schema, X=N und CH2). Die neuen Reaktionsvorschriften sind nicht nur nützlich für die Synthese bicyclischer (Hetero)Arene mit vielfältigen Substitutionsmustern, sondern unter Umständen auch für die Wasserstoffspeicherung attraktiv.
      PubDate: 2017-05-02T10:58:06.272758-05:
      DOI: 10.1002/ange.201703536
       
  • Katalytische Desaromatisierung von N-Heteroarenen mit Silicium- und
           Borverbindungen
    • Authors: Sehoon Park; Sukbok Chang
      Pages: 7828 - 7847
      Abstract: Desaromatisierte N-Heterocyclen sind als Strukturmotive für die organische Synthese und die chemische Biologie von Bedeutung. Die katalytische desaromatisierende Reduktion von nicht aktivierten N-Heteroarenen mit Silicium- und/oder Borverbindungen als Reduktionsmittel ist eine der direktesten Alternativen zur Hydrierung. Bisher wurden jedoch nur vereinzelte Beispiele zur katalytischen Reduktion von N-Heteroarenen mit Silan- oder Boranreduktionsmitteln beschrieben. In diesem Aufsatz wird über jüngste Fortschritte bei der katalytischen Reduktion von nicht aktivierten N-Heteroarenen mit Hydrosilanen, Hydroboranen, Silaboranen und Diboranen berichtet. Dabei wird vor allem auf die chemische Reaktivität und Selektivität von Übergangsmetallkatalysatoren und metallfreien Organokatalysatorsystemen eingegangen. Des Weiteren werden die Funktionsweisen dieser Katalysatoren insbesondere auf der Basis experimenteller mechanistischer Erkenntnisse beschrieben.Alternative zur Hydrierung: Die katalytische desaromatisierende Reduktion von nichtaktivierten N-Heteroarenen mit Silicium- und/oder Borverbindungen als Reduktionsmittel ist eine der direktesten Alternativen zur Hydrierung. Dieser Aufsatz befasst sich mit der chemischen Reaktivität und der Selektivität homogener Katalysesysteme in solchen Transformationen.
      PubDate: 2017-06-06T02:30:35.508172-05:
      DOI: 10.1002/ange.201612140
       
  • Surprising Stability of Larger Criegee Intermediates on Aqueous Interfaces
    • Authors: Jie Zhong; Manoj Kumar, Chong Q. Zhu, Joseph S. Francisco, Xiao C. Zeng
      Pages: 7848 - 7852
      Abstract: Criegee intermediates have implications as key intermediates in atmospheric, organic, and enzymatic reactions. However, their chemistry in aqueous environments is relatively unexplored. Herein, Born–Oppenheimer molecular dynamics (BOMD) simulations examine the dynamic behavior of syn- and anti-CH3CHOO at the air–water interface. They show that unlike the simplest Criegee intermediate (CH2OO), both syn- and anti-CH3CHOO remain inert towards reaction with water. The unexpected high stability of C2 Criegee intermediates is due to the presence of a hydrophobic methyl substituent on the Criegee carbon that lowers the proton transfer ability and inhibits the formation of a pre-reaction complex for the Criegee–water reaction. The simulation of the larger Criegee intermediates, (CH3)2COO, syn- and anti-CH2C(CH3)C(H)OO on the water droplet surface suggests that strongly hydrophobic substituents determine the reactivity of Criegee intermediates at the air–water interface.Reaktivitätsabfall: Ein hydrophober Methylsubstituent am Kohlenstoffatom von Criegee-Zwischenstufen vermindert die Fähigkeit zur Protonenübertragung und behindert die Bildung eines Präreaktionskomplexes für die Reaktion mit Wasser. Criegee-Zwischenstufen mit noch größeren hydrophoben Substituenten sind an der Oberfläche von Wassertröpfchen länger beständig.
      PubDate: 2017-05-04T05:05:34.392781-05:
      DOI: 10.1002/ange.201702722
       
  • Unclicking the Click: Metal-Assisted Mechanochemical Cycloreversion of
           Triazoles Is Possible
    • Authors: Martin Krupička; Przemyslaw Dopieralski, Dominik Marx
      Pages: 7853 - 7857
      Abstract: The mechanochemical cycloreversion of 1,2,3-triazole compounds, which serve as unusually stable building blocks in materials and biomolecular chemistry as a result of mild “click chemistry”, remains puzzling. We show that the hitherto discussed straight-forward retro-click mechanism of the 1,4-disubstituted isomer, even if CuI catalyzed, can be ruled out in view of more favorable activation free energies of destructive pathways. In stark contrast, the 1,5-regioiomer can undergo cycloreversion under rather mild mechanochemical conditions owing to its favorable response to the external force in conjunction with standard RuII catalysis.Das mechanochemische Öffnen von 1,2,3-Triazol ist ein kontroverses Thema. Quantenchemische Rechnungen unter konstanter Zugspannung zeigen, dass die 1,5-Regioisomere unter Standard-Ultraschallbedingungen leicht Cycloreversionen eingehen, sofern diese RuII-katalysiert sind.
      PubDate: 2017-04-24T03:10:52.825802-05:
      DOI: 10.1002/ange.201612507
       
  • Ultrasensitive Measurement of Ca2+ Influx into Lipid Vesicles Induced by
           Protein Aggregates
    • Authors: Patrick Flagmeier; Suman De, David C. Wirthensohn, Steven F. Lee, Cécile Vincke, Serge Muyldermans, Tuomas P. J. Knowles, Sonia Gandhi, Christopher M. Dobson, David Klenerman
      Pages: 7858 - 7862
      Abstract: To quantify and characterize the potentially toxic protein aggregates associated with neurodegenerative diseases, a high-throughput assay based on measuring the extent of aggregate-induced Ca2+ entry into individual lipid vesicles has been developed. This approach was implemented by tethering vesicles containing a Ca2+ sensitive fluorescent dye to a passivated surface and measuring changes in the fluorescence as a result of membrane disruption using total internal reflection microscopy. Picomolar concentrations of Aβ42 oligomers could be observed to induce Ca2+ influx, which could be inhibited by the addition of a naturally occurring chaperone and a nanobody designed to bind to the Aβ peptide. We show that the assay can be used to study aggregates from other proteins, such as α-synuclein, and to probe the effects of complex biofluids, such as cerebrospinal fluid, and thus has wide applicability.Ein Hochdurchsatzassay, der den induzierten Ca2+-Einstrom in immobilisierte Lipidvesikel misst, wurde entwickelt, um Membran-zerstörende Proteinaggregate, die mit neurodegenerativen Erkrankungen in Verbindung stehen, zu quantifizieren und zu charakterisieren. Pikomolare Konzentrationen von Aβ42-Oligomeren induzieren einen Ca2+-Einstrom, der durch Zusatz eines Chaperons und eines Nanokörpers unterbunden werden kann.
      PubDate: 2017-05-05T06:48:00.796345-05:
      DOI: 10.1002/ange.201700966
       
  • The Nature of Ion Conduction in Methylammonium Lead Iodide: A Multimethod
           Approach
    • Authors: Alessandro Senocrate; Igor Moudrakovski, Gee Yeong Kim, Tae-Youl Yang, Giuliano Gregori, Michael Grätzel, Joachim Maier
      Pages: 7863 - 7867
      Abstract: By applying a multitude of experimental techniques including 1H, 14N, 207Pb NMR and 127I NMR/NQR, tracer diffusion, reaction cell and doping experiments, as well as stoichiometric variation, conductivity, and polarization experiments, iodine ions are unambiguously shown to be the mobile species in CH3NH3PbI3, with iodine vacancies shown to represent the mechanistic centers under equilibrium conditions. Pb2+ and CH3NH3+ ions do not significantly contribute to the long range transport (upper limits for their contributions are given), whereby the latter exhibit substantial local motion. The decisive electronic contribution to the mixed conductivity in the experimental window stems from electron holes. As holes can be associated with iodine orbitals, local variations of the iodine stoichiometry may be fast and enable light effects on ion transport.NMR/NQR-Techniken, verfolgte Diffusion, Reaktionszell- und Dotierungsexperimente, Variation der stöchiometrischen Zusammensetzung, Leitfähigkeits- und Polarisationsexperimente identifizieren Iodidionen als bewegliche Spezies in CH3NH3PbI3 und Iod-Leerstellen als mechanistische Zentren unter Gleichgewichtsbedingungen. Der elektronische Anteil der Mischleitfähigkeit beruht maßgeblich auf Löchern.
      PubDate: 2017-05-30T14:06:40.540684-05:
      DOI: 10.1002/ange.201701724
       
  • High-Flux Carbon Molecular Sieve Membranes for Gas Separation
    • Authors: Hannes Richter; Hartwig Voss, Nadine Kaltenborn, Susanne Kämnitz, Alexander Wollbrink, Armin Feldhoff, Jürgen Caro, Stefan Roitsch, Ingolf Voigt
      Pages: 7868 - 7871
      Abstract: Carbon membranes have great potential for highly selective and cost-efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp2 hybridized carbon sheets as well as sp3 hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m3(STP)/(m2hbar). Furthermore, by a post-synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide.Oxidation ändert Selektion: Die kontrollierte Carbonisierung einer dünnen Polymerblend-Beschichtung auf einem keramischen Träger liefert eine 125 nm dünne Kohlenstoffmembran, die wie ein Molekularsieb wirkt und Wasserstoff mit hoher Selektivität durchlässt. Eine Oxidation nach der Synthese überführt diese Membran in eine Kohlenstoffmembran mit selektivem Oberflächenfluss und Kohlendioxid-Selektivität.
      PubDate: 2017-06-01T13:41:22.943316-05:
      DOI: 10.1002/ange.201701851
       
  • Lithiophilic Sites in Doped Graphene Guide Uniform Lithium Nucleation for
           Dendrite-Free Lithium Metal Anodes
    • Authors: Rui Zhang; Xiao-Ru Chen, Xiang Chen, Xin-Bing Cheng, Xue-Qiang Zhang, Chong Yan, Qiang Zhang
      Pages: 7872 - 7876
      Abstract: Lithium (Li) metal is the most promising electrode for next-generation rechargeable batteries. However, the challenges induced by Li dendrites on a working Li metal anode hinder the practical applications of Li metal batteries. Herein, nitrogen (N) doped graphene was adopted as the Li plating matrix to regulate Li metal nucleation and suppress dendrite growth. The N-containing functional groups, such as pyridinic and pyrrolic nitrogen in the N-doped graphene, are lithiophilic, which guide the metallic Li nucleation causing the metal to distribute uniformly on the anode surface. As a result, the N-doped graphene modified Li metal anode exhibits a dendrite-free morphology during repeated Li plating and demonstrates a high Coulombic efficiency of 98 % for near 200 cycles.Stickstoffdotiertes Graphen als Matrix für die Li-Abscheidung reguliert die Keimbildung von Li-Metall und unterdrückt das Wachstum von Dendriten. Die N-haltigen funktionellen Gruppen im N-dotierten Graphen sind lithiophil und sorgen für eine einheitliche Verteilung des Li-Metalls auf der Anodenoberfläche. Die dendritfreien Lithiummetallanoden zeigen ein beeindruckendes elektrochemisches Verhalten.
      PubDate: 2017-05-03T02:55:42.84417-05:0
      DOI: 10.1002/ange.201702099
       
  • Phase-Selective Syntheses of Cobalt Telluride Nanofleeces for Efficient
           Oxygen Evolution Catalysts
    • Authors: Qiang Gao; Chuan-Qi Huang, Yi-Ming Ju, Min-Rui Gao, Jian-Wei Liu, Duo An, Chun-Hua Cui, Ya-Rong Zheng, Wei-Xue Li, Shu-Hong Yu
      Pages: 7877 - 7881
      Abstract: Cobalt-based nanomaterials have been intensively explored as promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. Herein, we report phase-selective syntheses of novel hierarchical CoTe2 and CoTe nanofleeces for efficient OER catalysts. The CoTe2 nanofleeces exhibited excellent electrocatalytic activity and stablity for OER in alkaline media. The CoTe2 catalyst exhibited superior OER activity compared to the CoTe catalyst, which is comparable to the state-of-the-art RuO2 catalyst. Density functional theory calculations showed that the binding strength and lateral interaction of the reaction intermediates on CoTe2 and CoTe are essential for determining the overpotential required under different conditions. This study provides valuable insights for the rational design of noble-metal-free OER catalysts with high performance and low cost by use of Co-based chalcogenides.So flauschig: Hierarchische flauschige CoTe2-Nanofasern wurden an Te-Nanodraht-Templaten aufgebaut. Sie sind aktive und stabile Elektrokatalystoren für die Sauerstoffentwicklung (OER) in alkalischem Medium. Bezüglich ihrer OER-Aktivität übertreffen sie CoTe und reichen an gängige RuO2-Katalysatoren heran.
      PubDate: 2017-06-01T13:41:16.764858-05:
      DOI: 10.1002/ange.201701998
       
  • Interprotein Electron Transfer between FeS-Protein Nanowires and
           Oxygen-Tolerant NiFe Hydrogenase
    • Authors: Saravanan Rengaraj; Raoudha Haddad, Elisabeth Lojou, Nicolas Duraffourg, Michael Holzinger, Alan Le Goff, Vincent Forge
      Pages: 7882 - 7886
      Abstract: Self-assembled redox protein nanowires have been exploited as efficient electron shuttles for an oxygen-tolerant hydrogenase. An intra/inter-protein electron transfer chain has been achieved between the iron-sulfur centers of rubredoxin and the FeS cluster of [NiFe] hydrogenases. [NiFe] Hydrogenases entrapped in the intricated matrix of metalloprotein nanowires achieve a stable, mediated bioelectrocatalytic oxidation of H2 at low-overpotential.Selbstorganisierte Redoxprotein-Nanodrähte bewirken den effizienten Elektronentransport in einer sauerstoffverträglichen Hydrogenase. In einem Geflecht aus Metalloprotein-Nanodrähten eingebettete [NiFe]-Hydrogenasen vermitteln stabil die bioelektrokatalytische H2-Oxidation bei geringem Überpotential.
      PubDate: 2017-06-06T08:20:22.76463-05:0
      DOI: 10.1002/ange.201702042
       
  • Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective
           Hydroxylation of Benzene to Phenol with Hydrogen Peroxide
    • Authors: Tomokazu Tsuji; Antonius Andre Zaoputra, Yutaka Hitomi, Kaoru Mieda, Takashi Ogura, Yoshihito Shiota, Kazunari Yoshizawa, Hiroyasu Sato, Masahito Kodera
      Pages: 7887 - 7890
      Abstract: A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu2(μ-OH)(6-hpa)]3+, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H2O2, thus attaining large turnover numbers (TONs) and high H2O2 efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N2, the highest value reported for benzene hydroxylation with H2O2 catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H2O2 activation and benzene hydroxylation is proposed.Günstige Rahmenbedingungen: Ein Dikupferkomplex mit verbrückendem Liganden, der die zweikernige Struktur spezifisch stabilisiert, erhöht die Aktivität, Selektivität und H2O2-Effizienz in der katalytischen Hydroxylierung von Benzol zu Phenol mit H2O2. Die zweikernige Struktur begünstigt die Bildung der aktiven Spezies.
      PubDate: 2017-05-31T08:56:49.675473-05:
      DOI: 10.1002/ange.201702291
       
  • Lanthanide Complexes that Respond to Changes in Cyanide Concentration in
           Water
    • Authors: Jack D. Routledge; Xuejian Zhang, Michael Connolly, Manuel Tropiano, Octavia A. Blackburn, Alan M. Kenwright, Paul D. Beer, Simon Aldridge, Stephen Faulkner
      Pages: 7891 - 7894
      Abstract: Cyanide ions are shown to interact with lanthanide complexes of phenacylDO3A derivatives in aqueous solution, giving rise to changes in the luminescence and NMR spectra. These changes are the consequence of cyanohydrin formation, which is favored by the coordination of the phenacyl carbonyl group to the lanthanide center. These complexes display minimal affinity for fluoride and can detect cyanide at concentrations less than 1 μm. By contrast, lanthanide complexes with DOTAM derivatives display no affinity for cyanide in water, but respond to changes in fluoride concentration.Lanthanoidkomplexe von Phenacyl-DO3A-Derivaten zeigen das Vorliegen von Cyanid in wässrigen Lösungen durch Änderungen ihrer Lumineszenz und NMR-Spektren an. Da dieser Effekt auf die Bildung eines Cyanhydrins zurückgeht, haben die Komplexe eine minimale Fluoridaffinität, während sie Cyanid in Konzentrationen unter 1 μm detektieren.
      PubDate: 2017-06-05T13:16:28.268136-05:
      DOI: 10.1002/ange.201702296
       
  • From Discrete Molecular Cages to a Network of Cages Exhibiting Enhanced
           CO2 Adsorption Capacity
    • Authors: Lei Zhang; Long Xiang, Cheng Hang, Wenlong Liu, Wei Huang, Yichang Pan
      Pages: 7895 - 7899
      Abstract: We have adopted the concept of “cage to frameworks” to successfully produce a Na–N connected coordination networked cage Na-NC1 by using a [3+6] porous imine-linked organic cage NC1 (Nanjing Cage 1) as the precursor. It is found that Na-NC1 exhibits hierarchical porosity (inherent permanent voids and interconnected channel) and gas sorption measurements reveal a significantly enhanced CO2 uptake (1093 cm3 g−1 at 23 bar and 273 K) than that of NC1 (162 cm3 g−1 under the same conditions). In addition, Na-NC1 exhibits very low CO2 adsorption enthalpy making it a good candidate for porous materials with both high CO2 storage and low adsorption enthalpy.Netzwerker: Hierarchische poröse Strukturen entstehen durch Vernetzung einzelner formstabiler poröser organischer Käfige über Natriumionen. Das resultierende Käfig-Netzwerk ist ein CO2-Speicher mit hervorragender Kapazität und niedriger Adsorptionsenthalpie verglichen mit der isolierten Vorstufe.
      PubDate: 2017-05-30T14:06:38.876624-05:
      DOI: 10.1002/ange.201702399
       
  • Photocatalytic Self-Doped SnO2−x Nanocrystals Drive
           Visible-Light-Responsive Color Switching
    • Authors: Dan Han; Baolai Jiang, Ji Feng, Yadong Yin, Wenshou Wang
      Pages: 7900 - 7904
      Abstract: Visible-light-responsive reversible color-switching systems are attractive to many applications because visible light has superior penetration and causes far less damage to organic molecules than UV. Herein, we report that self-doping of SnO2−x nanocrystals with Sn2+ red-shifts their absorption to the visible region and simultaneously produces oxygen vacancies, which can effectively scavenge photogenerated holes and thus enable the color switching of redox dyes using visible light. Wavelength-selective switching can also be achieved by coupling the photocatalytic activity of the SnO2−x NCs with the color-switching kinetics of different redox dyes. The fast light response enables the further fabrication of a solid film that can be repeatedly written on using a visible laser pen or projection printing through a photomask. This discovery represents a big step forward towards practical applications, especially in areas in which safety issues and photodamage by UV light are of concern.Sichtbares Licht erzeugt Farbwechsel: Die Selbstdotierung von SnO2−x-Nanokristallen mit Sn2+ verschiebt deren Absorptionsbanden in den sichtbaren Spektralbereich und erzeugt gleichzeitig Sauerstoff-Fehlstellen, die einen durch sichtbares Licht stimulierten Farbwechsel von Redox-Farbstoffen ermöglichen. Das System kann in Medien verwendet werden, die sich durch einen Laser oder durch Photomaskendruck mehrfach beschreiben lassen.
      PubDate: 2017-06-05T13:20:35.657312-05:
      DOI: 10.1002/ange.201702563
       
  • One-Dimensionally Disordered Chiral Sorting by Racemic Tiling in a
           Surface-Confined Supramolecular Assembly of Achiral Tectons
    • Authors: Yi-Qi Zhang; Tao Lin, Borja Cirera, Raphael Hellwig, Carlos-Andres Palma, Zhi Chen, Mario Ruben, Johannes V. Barth, Florian Klappenberger
      Pages: 7905 - 7910
      Abstract: The aggregation of (pro)chiral/achiral molecules into crystalline structures at interfaces forms conglomerates, racemates, and solid solutions, comparable to known bulk phases. Scanning tunneling microscopy and Monte Carlo simulations were employed to uncover a distinct racemic phase, expressing 1D disordered chiral sorting through random tiling in surface-confined supramolecularly assembled achiral 4,4′′-diethynyl-1,1′:4′,1′′-terphenyl molecules. The configurational entropy of the 1D disordered racemic tiling phase was verified by analytical modeling, and found to lie between that of a perfectly ordered 2D racemate and a racemic solid solution.Kampf der Tektone: Rastertunnelmikroskopie und Monte-Carlo-Simulationen mit analytischer Modellierung visualisieren eine besondere racemische Phase in supramolekularen Anordnungen achiraler Tektone auf Oberflächen. Die racemische Phase zeigt 1D-fehlgeordnete Chiralitätssortierung durch zufällige Parkettierung.
      PubDate: 2017-06-07T06:40:48.129064-05:
      DOI: 10.1002/ange.201702771
       
  • AJIPHASE®: A Highly Efficient Synthetic Method for One-Pot Peptide
           Elongation in the Solution Phase by an Fmoc Strategy
    • Authors: Daisuke Takahashi; Tatsuji Inomata, Tatsuya Fukui
      Pages: 7911 - 7915
      Abstract: We previously reported an efficient peptide synthesis method, AJIPHASE®, that comprises repeated reactions and isolations by precipitation. This method utilizes an anchor molecule with long-chain alkyl groups as a protecting group for the C-terminus. To further improve this method, we developed a one-pot synthesis of a peptide sequence wherein the synthetic intermediates were isolated by solvent extraction instead of precipitation. A branched-chain anchor molecule was used in the new process, significantly enhancing the solubility of long peptides and the operational efficiency compared with the previous method, which employed precipitation for isolation and a straight-chain aliphatic group. Another prerequisite for this solvent-extraction-based strategy was the use of thiomalic acid and DBU for Fmoc deprotection, which facilitates the removal of byproducts, such as the fulvene adduct.Extrahiert statt gefällt: AJIPHASE® ist eine neue Eintopfmethode für die Peptidsynthese, die während der Peptidverlängerung Lösungsmittelextraktion anwendet und keine Isolierungsschritte beinhaltet. Dieser effiziente Ansatz ermöglicht die Synthese von Peptiden mit hoher Reinheit und zeichnet sich durch einen deutlich reduzierten Lösungsmittelverbrauch aus.
      PubDate: 2017-06-01T13:40:54.547394-05:
      DOI: 10.1002/ange.201702931
       
  • Iridium-Catalyzed Formyl-Selective Deuteration of Aldehydes
    • Authors: William J. Kerr; Marc Reid, Tell Tuttle
      Pages: 7916 - 7920
      Abstract: We report the first direct catalytic method for formyl-selective deuterium labeling of aromatic aldehydes under mild conditions, using an iridium-based catalyst designed to favor formyl over aromatic C−H activation. A good range of aromatic aldehydes is selectively labeled, and a one-pot labeling/olefination method is also described. Computational studies support kinetic product control over competing aromatic labeling and decarbonylation pathways.Al-D-hyde: Ein Iridiumkatalysator wurde entwickelt, der in aromatischen Aldehyden die Formyl- statt der Aryl-C-H-Bindungen aktiviert. Rechnungen zufolge ist die Produktbildung gegenüber einer Markierung am aromatischen System und der Decarbonylierung kinetisch begünstigt.
      PubDate: 2017-06-07T06:40:52.15265-05:0
      DOI: 10.1002/ange.201702997
       
  • Strain Coupling of Conversion-type Fe3O4 Thin Films for Lithium Ion
           Batteries
    • Authors: Sooyeon Hwang; Qingping Meng, Ping-Fan Chen, Kim Kisslinger, Jiajie Cen, Alexander Orlov, Yimei Zhu, Eric A. Stach, Ying-Hao Chu, Dong Su
      Pages: 7921 - 7924
      Abstract: Lithiation/delithiation induces significant stresses and strains into the electrodes for lithium ion batteries, which can severely degrade their cycling performance. Moreover, this electrochemically induced strain can interact with the local strain existing at solid–solid interfaces. It is not clear how this interaction affects the lithiation mechanism. The effect of this coupling on the lithiation kinetics in epitaxial Fe3O4 thin film on a Nb-doped SrTiO3 substrate is investigated. In situ and ex situ transmission electron microscopy (TEM) results show that the lithiation is suppressed by the compressive interfacial strain. At the interface between the film and substrate, the existence of LixFe3O4 rock-salt phase during lithiation consequently restrains the film from delamination. 2D phase-field simulation verifies the effect of strain. This work provides critical insights of understanding the solid–solid interfaces of conversion-type electrodes.Ein dynamischer Lithiierungsprozess unter Einwirkung von Grenzflächenspannung wurde mit In-situ-Rastertransmissionselektronenmikroskopie und Phasenfeldsimulationen untersucht. Als Modellsystem diente ein dünner Fe3O4-Film, der heteroepitaktisch auf einem SrTiO3(STO)-Substrat abgeschieden wurde.
      PubDate: 2017-05-29T11:10:46.853556-05:
      DOI: 10.1002/ange.201703168
       
  • Chemically Controlled Spatiotemporal Oscillations of Colloidal Assemblies
    • Authors: Alicia Altemose; María Antonieta Sánchez-Farrán, Wentao Duan, Steve Schulz, Ali Borhan, Vincent H. Crespi, Ayusman Sen
      Pages: 7925 - 7929
      Abstract: We report an autonomous oscillatory micromotor system in which active colloidal particles form clusters, the size of which changes periodically. The system consists of an aqueous suspension of silver orthophosphate microparticles under UV illumination, in the presence of varying concentrations of hydrogen peroxide. The colloid particles first attract each other to form clusters. After a short delay, these clusters abruptly disperse and oscillation begins, alternating between clustering and dispersion of particles. After a cluster oscillation initiates, the oscillatory wave propagates to nearby clusters and eventually all the clusters oscillate in phase-shifted synchrony. The oscillatory behavior is governed by an electrolytic self-diffusiophoretic mechanism which involves alternating electric fields generated by the competing reduction and oxidation of silver. The oscillation frequency is tuned by changing the concentration of hydrogen peroxide. The addition of inert silica particles to the system results in hierarchical sorting and packing of clusters. Densely packed Ag3PO4 particles form a non-oscillating core with an oscillating shell composed largely of silica microparticles.Durchstimmbare Kolloidoszillationen: Ein autonom oszillierendes System bestehend aus Ag3PO4-Kolloidpartikeln unter UV-Licht und Wasserstoffperoxid wurde entwickelt. Die Partikel oszillieren zwischen geclusterten und dispergierten Zuständen, die Signalausbreitung und Synchronisierung aufweisen. Das Verhalten folgt einem selbstdiffusionsphoretischen, auf der Redoxchemie von Silber basierenden Mechanismus.
      PubDate: 2017-05-30T14:06:24.331208-05:
      DOI: 10.1002/ange.201703239
       
  • Enzymatic Engineering of Live Bacterial Cell Surfaces Using
           Butelase 1
    • Authors: Xiaobao Bi; Juan Yin, Giang K. T. Nguyen, Chang Rao, Nurashikin Bte Abdul Halim, Xinya Hemu, James P. Tam, Chuan-Fa Liu
      Pages: 7930 - 7933
      Abstract: Butelase-mediated ligation (BML) can be used to modify live bacterial cell surfaces with diverse cargo molecules. Surface-displayed butelase recognition motif NHV was first introduced at the C-terminal end of the anchoring protein OmpA on E. coli cells. This then served as a handle of BML for the functionalization of E. coli cell surfaces with fluorescein and biotin tags, a tumor-associated monoglycosylated peptide, and mCherry protein. The cell-surface ligation reaction was achieved at low concentrations of butelase and the labeling substrates. Furthermore, the fluorescein-labeled bacterial cells were used to show the interactions with cultured HeLa cells and with macrophages in live transgenic zebrafish, capturing the latter's powerful phagocytic effect in action. Together these results highlight the usefulness of butelase 1 in live bacterial cell surface engineering for novel applications.Butelase-vermittelte Ligation (BML) wird verwendet, um lebende Bakterienzellen an der Oberfläche mit diversen Frachtmolekülen für verschiedene Anwendungen zu modifizieren. Die fluoresceinmarkierten Bakterienzellen wurden zur Visualisierung der Pathogen-Wirt-Wechselwirkungen mit kultivierten HeLa-Zellen und mit Makrophagen in lebenden Zebrafischen genutzt.
      PubDate: 2017-06-09T01:35:41.560139-05:
      DOI: 10.1002/ange.201703317
       
  • Visible-Light Photocatalytic Intramolecular Cyclopropane Ring Expansion
    • Authors: Javier Luis-Barrera; Víctor Laina-Martín, Thomas Rigotti, Francesca Peccati, Xavier Solans-Monfort, Mariona Sodupe, Rubén Mas-Ballesté, Marta Liras, José Alemán
      Pages: 7934 - 7938
      Abstract: Described herein is a new visible-light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ring expansion reaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ring expansion reaction, and the need for the nitro group on the cyclopropane.Auf Expansionskurs: Durch Photokatalyse mit sichtbarem Licht wurden durch Ringerweiterung enantiomerenangereicherte Dihydrofurane und Cyclopentene synthetisiert. Mechanistische Studien und Rechnungen zeigen die Schlüsselfaktoren der Reaktion auf.
      PubDate: 2017-06-06T07:45:27.046334-05:
      DOI: 10.1002/ange.201703334
       
  • Intermolecular Charge-Transfer Interactions Facilitate Two-Photon
           Absorption in Styrylpyridine–Tetracyanobenzene Cocrystals
    • Authors: Lingjie Sun; Weigang Zhu, Wei Wang, Fangxu Yang, Congcong Zhang, Shufeng Wang, Xiaotao Zhang, Rongjin Li, Huanli Dong, Wenping Hu
      Pages: 7939 - 7943
      Abstract: Cocrystals of 4-styrylpyridine and 1,2,4,5-tetracyanobenzene were successfully prepared by supramolecular self-assembly. Donor–acceptor interactions between the molecular components are the main driving force for self-assembly and contribute to intermolecular charge transfer. The cocrystals possess two-photon absorption properties that are not observed in the individual components; suggesting that two-photon absorption originates from intermolecular charge-transfer interactions in the donor–acceptor system. The origin of two-photon absorption in multichromophore systems remains under-researched; thus, the system offers a rare demonstration of two-photon absorption by cocrystallization. Cocrystal engineering may facilitate further design and development of novel materials for nonlinear optical and optoelectronic applications.Kokristalle aus 4-Styrylpyridin und 1,2,4,5-Tetracyanbenzol (STC) werden vorgestellt. Dank eines intermolekularen Ladungstransfers zwischen den beiden Komponenten in der supramolekularen Anordnung zeigen die Kristalle eine Zwei-Photonen-Absorption.
      PubDate: 2017-06-01T13:40:42.207584-05:
      DOI: 10.1002/ange.201703439
       
  • Layer-by-Layer Motif Architectures: Programmed Electrochemical Syntheses
           of Multilayer Mesoporous Metallic Films with Uniformly Sized Pores
    • Authors: Bo Jiang; Cuiling Li, Huayu Qian, Md. Shahriar A. Hossain, Victor Malgras, Yusuke Yamauchi
      Pages: 7944 - 7949
      Abstract: Although multilayer films have been extensively reported, most compositions have been limited to non-catalytically active materials (e.g. polymers, proteins, lipids, or nucleic acids). Herein, we report the preparation of binder-free multilayer metallic mesoporous films with sufficient accessibility for high electrocatalytic activity by using a programmed electrochemical strategy. By precisely tuning the deposition potential and duration, multilayer mesoporous architectures consisting of alternating mesoporous Pd layers and mesoporous PdPt layers with controlled layer thicknesses can be synthesized within a single electrolyte, containing polymeric micelles as soft templates. This novel architecture, combining the advantages of bimetallic alloys, multilayer architectures, and mesoporous structures, exhibits high electrocatalytic activity for both the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR).Filmreif: Mesoporöse Pd-, Pt- und PdPt-Filme mit kontrollierter Dicke wurden durch elektrochemische Abscheidung erzeugt. Insbesondere der PdPt-Mehrschichtfilm war hoch aktiv in der elektrochemischen Oxidation von Ethanol und Methanol.
      PubDate: 2017-06-05T13:21:10.174687-05:
      DOI: 10.1002/ange.201703609
       
  • Preparation of Ultrathin Two-Dimensional TixTa1−xSyOz Nanosheets as
           Highly Efficient Photothermal Agents
    • Authors: Chaoliang Tan; Lingzhi Zhao, Peng Yu, Ying Huang, Bo Chen, Zhuangchai Lai, Xiaoying Qi, Min Hao Goh, Xiao Zhang, Shikui Han, Xue-Jun Wu, Zheng Liu, Yanli Zhao, Hua Zhang
      Pages: 7950 - 7954
      Abstract: Although two-dimensional (2D) metal oxide/sulfide hybrid nanostructures have been synthesized, the facile preparation of ultrathin 2D nanosheets in high yield still remains a challenge. Herein, we report the first high-yield preparation of solution-processed ultrathin 2D metal oxide/sulfide hybrid nanosheets, that is, TixTa1−xSyOz (x=0.71, 0.49, and 0.30), from TixTa1−xS2 precursors. The nanosheet exhibits strong absorbance in the near-infrared region, giving a large extinction coefficient of 54.1 L g−1 cm−1 at 808 nm, and a high photothermal conversion efficiency of 39.2 %. After modification with lipoic acid-conjugated polyethylene glycol, the nanosheet is a suitable photothermal agent for treatment of cancer cells under 808 nm laser irradiation. This work provides a facile and general method for the preparation of 2D metal oxide/sulfide hybrid nanosheets.Heizdecke: Dünne 2D-Metalloxid/sulfid-Hybridnanoblätter der allgemeinen Zusammensetzung TixTa1−xSyOz wurden ausgehend von TixTa1−xS2-Schichtkristallen durch elektrochemische Li-Interkalation hergestellt. Die Nanoblätter absorbieren stark im Nahinfrarot und eignen sich aufgrund dieser Eigenschaft – nach Modifizierung mit Liponsäure-konjugiertem Polyethylenglykol – für die photothermische Behandlung von Krebszellen.
      PubDate: 2017-06-05T13:21:08.030658-05:
      DOI: 10.1002/ange.201703597
       
  • Efficient Electrocatalytic Reduction of CO2 by Nitrogen-Doped Nanoporous
           Carbon/Carbon Nanotube Membranes: A Step Towards the Electrochemical CO2
           Refinery
    • Authors: Hong Wang; Jia Jia, Pengfei Song, Qiang Wang, Debao Li, Shixiong Min, Chenxi Qian, Lu Wang, Young Feng Li, Chun Ma, Tom Wu, Jiayin Yuan, Markus Antonietti, Geoffrey A. Ozin
      Pages: 7955 - 7960
      Abstract: Herein we introduce a straightforward, low cost, scalable, and technologically relevant method to manufacture an all-carbon, electroactive, nitrogen-doped nanoporous-carbon/carbon-nanotube composite membrane, dubbed “HNCM/CNT”. The membrane is demonstrated to function as a binder-free, high-performance gas diffusion electrode for the electrocatalytic reduction of CO2 to formate. The Faradaic efficiency (FE) for the production of formate is 81 %. Furthermore, the robust structural and electrochemical properties of the membrane endow it with excellent long-term stability.Kohlenstoff im Kohlenstoff: Nach einem direkten Verfahren werden N-dotierte hierarchische Kohlenstoff/Kohlenstoff-Nanoröhren-Membranen aufgebaut, die sich als hoch aktive, selektive und beständige Diffusionselektroden für die Reduktion von CO2 zu Formiat in wässriger Lösung eignen.
      PubDate: 2017-06-01T13:36:28.604717-05:
      DOI: 10.1002/ange.201703720
       
  • Lanthanide Metal–Organic Framework Microrods: Colored Optical Waveguides
           and Chiral Polarized Emission
    • Authors: Xiaogang Yang; Xianqing Lin, Yibing Zhao, Yong Sheng Zhao, Dongpeng Yan
      Pages: 7961 - 7965
      Abstract: Lanthanide metal–organic frameworks (Ln-MOFs) have received much attention owing to their structural tunability and widely photofunctional applications. However, successful examples of Ln-MOFs with well-defined photonic performances at micro-/nanometer size are still quite limited. Herein, self-assemblies of 1,3,5-benzenetricarboxylic acid (BTC) and lanthanide ions afford isostructural crystalline Ln-MOFs. Tb-BTC, Eu@Tb-BTC, and Eu-BTC have 1D microrod morphologies, high photoluminescence (PL) quantum yields, and different emission colors (green, orange, and red). Spatially PL resolved spectra confirm that Ln-MOF microrods exhibit an optical waveguide effect with low waveguide loss coefficient (0.012≈0.033 dB μm−1) during propagation. Furthermore, these microrods feature both linear and chiral polarized photoemission with high anisotropy.Leuchtstäbe: Drei kristalline isostrukturelle Lanthanoid-organische Gerüste (Ln-MOFs) mit der Form von Mikrostäben ergeben hohe Photolumineszenz-Quantenausbeuten und strahlen in verschiedenen Farben. Die Ln-MOFs sind Wellenleiter mit geringem Verlust sowie hoch anisotroper linearer und chiraler Polarisation.
      PubDate: 2017-05-31T08:56:34.362554-05:
      DOI: 10.1002/ange.201703917
       
  • A Tetracyclic Octaphosphane by Successive Addition, Inversion, and
           Condensation Reactions
    • Authors: Felix Hennersdorf; Jan J. Weigand
      Pages: 7966 - 7970
      Abstract: An example of an octaphosphane of type R2P8 (R=(DDP)Ga) was isolated by treatment of cage compound (DDP)GaP4 (2, DDP=(2,6-diisopropylphenyl)(4-((2,6-diisopropylphenyl)imino)pent-2-en-2-yl)amide) with (C6F5)2PBr. The initially formed endo-exo butterfly shaped pentaphosphane 7 rapidly rearranges to the more stable exo–exo isomer 8, which undergoes dimerization to decaphosphane 11. Compound 11 unexpectedly eliminates tetraaryldiphosphane 13 to give tetracyclo[3.3.0.02,7.04,6]octaphosphane [(DDP)GaBr]2P8 (12). The reaction steps were confirmed by crystal structure analysis of the key intermediates and supported by kinetic studies using NMR techniques.Das neutrale tetracyclische Polyphosphan R2P8 (mit R=DDPGa und DDP=N-Donor-Chelatligand) wurde nach Zusatz von Halogenphosphanen zu Hauptgruppenelement-funktionalisiertem weißem Phosphor isoliert. Zunächst wird ein Pentaphosphan gebildet, das über Inversion, Dimerisierung und Abspaltung eines Diphosphans selektiv R2P8 liefert.
      PubDate: 2017-06-01T13:36:20.475232-05:
      DOI: 10.1002/ange.201703953
       
  • Harnessing [1,4], [1,5], and [1,6] Anionic Fries-type Rearrangements by
           Reaction-Time Control in Flow
    • Authors: Heejin Kim; Keita Inoue, Jun-ichi Yoshida
      Pages: 7971 - 7974
      Abstract: A series of anionic Fries-type rearrangements of carbamoyl-substituted aryllithium intermediates were controlled by using flow microreactor systems. For the [1,4] and [1,5] rearrangements, the aryllithium intermediate formed before carbamoyl migration and the lithium alkoxide formed after carbamoyl migration can be selectively subjected to subsequent reactions with electrophiles by precisely controlling the residence time and temperature (−25 to −50 °C). In contrast, the [1,6] rearrangement is rather slow even at −25 °C. The absence of crossover products indicates the intramolecular nature of the carbamoyl group migration.Unter Kontrolle: Mehrere Fries-Umlagerungen von Carbamoyl-substituierten Aryllithium-Verbindungen wurden in Durchflussmikroreaktoren durchgeführt. Bei den [1,4]- und [1,5]-Umlagerungen konnten die Aryllithium- und Alkoxylithium-Intermediate, die vor bzw. nach der Carbamoyl-Verschiebung vorliegen, durch das Justieren von Verweilzeit und Temperatur selektiv mit Elektrophilen abgefangen werden.
      PubDate: 2017-06-01T13:36:16.916434-05:
      DOI: 10.1002/ange.201704006
       
  • Hyperconjugation Is the Source of Helicity in Perfluorinated n-Alkanes
    • Authors: Rodrigo A. Cormanich; David O'Hagan, Michael Bühl
      Pages: 7975 - 7978
      Abstract: Hyperconjugative, steric, and electrostatic effects were evaluated as possible sources of the helicity in linear perfluorinated alkanes through analysis of natural bond orbitals and classical electrostatics. Contrary to previous rationalizations, which indicate dominating steric or electrostatic effects, this analysis indicates that hyperconjugative stabilization through σCCσ*CF interactions are the underlying driving force for the origin of the observed helicity in perfluoroalkanes.Quantenmechanik – in Form von Hyperkonjugation –, und nicht reine Elektrostatik, verleiht Perfluoralkanen ihre helikale Form. Diese Schlussfolgerung widerspricht früheren Erklärungsversuchen, die auf dominante sterische oder elektrostatische Effekte setzten.
      PubDate: 2017-05-31T08:56:26.72562-05:0
      DOI: 10.1002/ange.201704112
       
  • A Smart Flexible Zinc Battery with Cooling Recovery Ability
    • Authors: Jingwen Zhao; Keval K. Sonigara, Jiajia Li, Jian Zhang, Bingbing Chen, Jianjun Zhang, Saurabh S. Soni, Xinhong Zhou, Guanglei Cui, Liquan Chen
      Pages: 7979 - 7983
      Abstract: Flexible batteries are essential for wearable electronic devices. To meet practical applications, they need to be mechanically robust and stable. However, strong or multiple bending may sever the interfacial contact between electrode and electrolyte, causing capacity fading or even battery failure. Herein we present a new cooling-recovery concept for flexible batteries, which involves a temperature-sensitive sol–gel transition behavior of the thermoreversible polymer hydrogel electrolyte. Once a battery has suffered from strong mechanical stresses, a simple cooling process can refresh the electrode–electrolyte interface. The energy-storage capability can be recovered with a healing efficiency higher than 98 %. It is believed that this study not only offers new valuable insights, but also opens up new perspectives to develop functional wearable devices.Regenerierbare flexible Batterien könnten auf der Grundlage der thermisch reversiblen Hydrogelbildung des Elektrolyts Pluronic entworfen werden. Einfaches Kühlen repariert Schäden und Risse, die an der Grenzfläche zwischen Elektrode und Elektrolyt infolge mechanischer Beanspruchung entstehen, mit Heilungsraten bis 98 %.
      PubDate: 2017-06-06T02:25:37.757893-05:
      DOI: 10.1002/ange.201704373
       
  • Self-Assembled Zinc/Cystine-Based Chloroplast Mimics Capable of
           Photoenzymatic Reactions for Sustainable Fuel Synthesis
    • Authors: Kai Liu; Chengqian Yuan, Qianli Zou, Zengchun Xie, Xuehai Yan
      Pages: 7984 - 7988
      Abstract: Prototypes of biosystems provide good blueprints for the design and creation of biomimetic systems. However, mimicking both the sophisticated natural structures and their complex biological functions still remains a great challenge. Herein, chloroplast mimics have been fabricated by one-step bioinspired amino acid mineralization and simultaneous integration of catalytically active units. Hierarchically structured crystals were obtained by the metal-ion-directed self-assembly of cystine (the oxidized dimer of the amino acid cysteine), with a porous structure and stacks of nanorods, which show similar architectural principles to chloroplasts. Porphyrins and enzymes can both be encapsulated inside the crystal during mineralization, rendering the crystal photocatalytically and enzymatically active for an efficient and sustainable synthesis of hydrogen and acetaldehyde in a coupled photoenzymatic reaction.Chloroplast-Mimetika wurden durch Metallionen-gesteuerte Selbstorganisation von Cystin unter gleichzeitiger Verkapselung von Gastmolekülen wie Porphyrinen (z. B. TPPS) und Enzymen (ADH) erhalten. Photokatalytische und enzymatische Reaktionen können in diesen biomimetischen Systemen gekoppelt werden, wodurch sie die Struktur und Funktion natürlicher Chloroplasten nachahmen und für die Produktion nachhaltiger Brennstoffe eingesetzt werden können.
      PubDate: 2017-06-05T13:21:17.992228-05:
      DOI: 10.1002/ange.201704678
       
  • Transformation of Rusty Stainless-Steel Meshes into Stable, Low-Cost, and
           Binder-Free Cathodes for High-Performance Potassium-Ion Batteries
    • Authors: Yun-hai Zhu; Yan-bin Yin, Xu Yang, Tao Sun, Sai Wang, Yin-shan Jiang, Jun-min Yan, Xin-bo Zhang
      Pages: 7989 - 7993
      Abstract: To recycle rusty stainless-steel meshes (RSSM) and meet the urgent requirement of developing high-performance cathodes for potassium-ion batteries (KIB), we demonstrate a new strategy to fabricate flexible binder-free KIB electrodes via transformation of the corrosion layer of RSSM into compact stack-layers of Prussian blue (PB) nanocubes (PB@SSM). When further coated with reduced graphite oxide (RGO) to enhance electric conductivity and structural stability, the low-cost, stable, and binder-free RGO@PB@SSM cathode exhibits excellent electrochemical performances for KIB, including high capacity (96.8 mAh g−1), high discharge voltage (3.3 V), high rate capability (1000 mA g−1; 42 % capacity retention), and outstanding cycle stability (305 cycles; 75.1 % capacity retention).Neue Aufgabe für altes Eisen: Korrodierte Drahtgewebe aus rostfreiem Stahl wurden als Quelle für Eisen mit exzellenter Leitfähigkeit zur Herstellung stabiler, kostengünstiger und flexibler Binder-freier Elektroden für Kaliumionenbatterien verwendet. Die Elektroden mit beispielloser Struktur und einem Überzug aus reduziertem Graphenoxid zeigen hohe Kapazitäten, überlegene Entladungsgeschwindigkeiten und eine hervorragende Zyklierbarkeit.
      PubDate: 2017-06-05T13:20:37.777016-05:
      DOI: 10.1002/ange.201702711
       
  • Biomimetic Total Synthesis of (±)-Homodimericin A
    • Authors: Donghui Ma; Yangbin Liu, Zhang Wang
      Pages: 7994 - 7997
      Abstract: A biomimetic total synthesis of racemic homodimericin A was achieved in seven steps, including two cascade reactions. Aqueous buffer solutions are found to help both the oxidative dimerization cascade and the intramolecular Diels–Alder cascade. This synthetic sequence validates key steps in the biogenetic proposal of homodimericin A.Sieben als Glückszahl: Eine biomimetische Synthese von Homodimericin A in sieben Stufen beruht auf zwei Reaktionskaskaden. Der vorgeschlagene Biosyntheseweg wurde experimentell bestätigt.
      PubDate: 2017-06-05T13:21:02.936892-05:
      DOI: 10.1002/ange.201702775
       
  • Total Synthesis of Homodimericin A
    • Authors: Juan Feng; Xiaoqiang Lei, Zhen Guo, Yefeng Tang
      Pages: 8003 - 8007
      Abstract: We report the concise total synthesis of homodimericin A (1), a recently identified fungal metabolite bearing an unprecedented molecular architecture. The success of the approach hinges on a series of rationally designed and bioinspired transformations, including a Moore rearrangement to assemble the monomeric hydroquinone precursor, homodimerization through double Michael addition to construct the planar A/B/C tricyclic framework, and a tandem Diels–Alder reaction/carbonyl–ene cyclization to forge the congested D/E/F tricyclic cage motif. Unequivocal evidence for the elucidated structure of homodimericin A was also provided by this study.Anregungen aus der Natur: Homodimericin A, ein hochkomplexer Pilzmetabolit, wurde aus drei einfachen Bausteinen in zehn Schritten synthetisiert (siehe Schema). Schlüsselschritte der Synthese sind eine gezielt entworfene Moore-Umlagerung zum Aufbau der monomeren Vorstufe und eine Sequenz aus bioinspirierten Transformationen, einschließlich Homodimerisierung, Diels-Alder- und Carbonyl-En-Reaktionen, zum Aufbau des hexacyclischen Grundgerüsts.
      PubDate: 2017-05-16T08:26:26.251533-05:
      DOI: 10.1002/ange.201702893
       
  • Significant Enhancement of C2H2/C2H4 Separation by a Photochromic
           Diarylethene Unit: A Temperature- and Light-Responsive Separation Switch
    • Authors: Cong Bin Fan; Le Le Gong, Ling Huang, Feng Luo, Rajamani Krishna, Xian Feng Yi, An Min Zheng, Le Zhang, Shou Zhi Pu, Xue Feng Feng, Ming Biao Luo, Guo Cong Guo
      Pages: 8008 - 8014
      Abstract: A dual temperature- and light-responsive C2H2/C2H4 separation switch in a diarylethene metal–organic framework (MOF) is presented. At 195 K and 100 kPa this MOF shows ultrahigh C2H2/C2H4 selectivity of 47.1, which is almost 21.4 times larger than the corresponding value of 2.2 at 293 K and 100 kPa, or 15.7 times larger than the value of 3.0 for the material under UV at 195 K and 100 kPa. The origin of this unique control in C2H2/C2H4 selectivity, as unveiled by density functional calculations, is due to a guest discriminatory gate-opening effect from the diarylethene unit.Photochrome Diarylethen-Einheiten wurden eingesetzt, um C2H2 zu identifizieren und hohe Selektivitäten bei der Trennung von C2H2 und C2H4 bei tiefen Temperaturen zu erzielen. Das photochrome Material kann als temperatur- und lichtresponsiver Schalter bei diesem Trennprozess genutzt werden.
      PubDate: 2017-04-24T03:26:03.16844-05:0
      DOI: 10.1002/ange.201702484
       
  • Selective and Reversible Fluoride Complexation from Water by a Cyclic
           Tri(phosphonio)methanide Dication
    • Authors: Sivathmeehan Yogendra; Felix Hennersdorf, Antonio Bauzá, Antonio Frontera, Roland Fischer, Jan J. Weigand
      Pages: 8015 - 8019
      Abstract: Tri(phosphonio)methanide dication 32+, prepared from a trifluoromethylsulfanylphosphonium dication (12+) via an intramolecular electrophilic aromatic substitution reaction, is an unexpected P-based, water-resistant Lewis acid that is capable to selectively and reversibly bind fluoride ions from organic/aqueous biphasic solution. The formed complex is an unusual fluorophosphorane ([3-F]OTf). The multiple donor–acceptor interactions of 32+ that are crucial for the fluoride fixation have been elucidated by quantum chemical calculation. Compound [3-F]OTf can also be used as a convenient anhydrous fluoride ion source and was probed as a suitable catalyst of the silylotrifluoromethylation of various aldehydes.Ein hoch fluorophiles Tri(phosphonio)methanid-Salz komplexiert Fluoridionen in organisch-wässrigen Zweiphasensystemen selektiv und reversibel. Das resultierende Fluorophosphoran-Salz ist ein hervorragender Katalysator für die Silyltrifluormethylierung von Aldehyden.
      PubDate: 2017-06-05T13:11:04.577854-05:
      DOI: 10.1002/ange.201701570
       
  • Native Mass Spectrometry from Common Buffers with Salts That Mimic the
           Extracellular Environment
    • Authors: Anna C. Susa; Zijie Xia, Evan R. Williams
      Pages: 8020 - 8023
      Abstract: Nonvolatile salts are essential for the structures and functions of many proteins and protein complexes but can severely degrade performance of native mass spectrometry by adducting to protein and protein complex ions, thereby reducing sensitivity and mass measuring accuracy. Small nanoelectrospray emitters are used to form protein and protein complex ions directly from high-ionic-strength (>150 mm) nonvolatile buffers with salts that mimic the extracellular environment. Charge-state distributions are not obtained for proteins and protein complexes from six commonly used nonvolatile buffers and ≥150 mm Na+ with conventionally sized nanoelectrospray emitter tips but are resolved with 0.5 μm tips. This method enables mass measurements of proteins and protein complexes directly from a variety of commonly used buffers with high concentrations of nonvolatile salts and eliminates the need to buffer exchange into volatile ammonium buffers traditionally used in native mass spectrometry.Kleine Nanoelektrosprayemitter werden genutzt, um Protein- und Proteinkomplexionen direkt aus nichtflüchtigen Salzpuffern hoher Ionenstärke (>150 mm) zu bilden, welche die extrazelluläre Umgebung nachahmen. Mit 0.5 μm großen Spitzen werden Ladungszustandsverteilungen spektral aufgelöst, die mit Nanosprayemitterspitzen üblicher Größe nicht zugänglich sind.
      PubDate: 2017-06-05T13:20:33.771193-05:
      DOI: 10.1002/ange.201702330
       
  • Iron-Catalyzed Intermolecular 1,2-Difunctionalization of Styrenes and
           Conjugated Alkenes with Silanes and Nucleophiles
    • Authors: Yuan Yang; Ren-Jie Song, Xuan-Hui Ouyang, Cheng-Yong Wang, Jin-Heng Li, Shenglian Luo
      Pages: 8024 - 8027
      Abstract: The first iron-catalyzed 1,2-difunctionalization of styrenes and conjugated alkenes with silanes and either N or C, using an oxidative radical strategy, is described. Employing FeCl2 and di-tert-butyl peroxide allows divergent alkene 1,2-difunctionalizations, including 1,2-aminosilylation, 1,2-arylsilylation, and 1,2-alkylsilylation, which rely on a wide range of nucleophiles, namely, amines, amides, indoles, pyrroles, and 1,3-dicarbonyls, thus providing a powerful platform for producing diverse silicon-containing alkanes.FeCl2 und Di-tert-butylperoxid (DTBP) vermitteln divergente 1,2-Difunktionalisierungen von Alkenen, wie 1,2-Aminosilylierungen, 1,2-Arylsilylierungen und 1,2-Alkylsilylierungen, mit verschiedenen Nukleophilen. Auf diesem Weg sind 1-Amino-2-silylalkane und andere Alkane mit Siliciumfunktionen in großer Vielfalt direkt und hoch selektiv zugänglich.
      PubDate: 2017-05-29T11:11:01.776851-05:
      DOI: 10.1002/ange.201702349
       
  • Phosphoribosyl Pyrophosphate: A Molecular Vestige of the Origin of Life on
           Minerals
    • Authors: Mariame Akouche; Maguy Jaber, Marie-Christine Maurel, Jean-Francois Lambert, Thomas Georgelin
      Pages: 8028 - 8031
      Abstract: In this contribution, we report the formation under prebiotic conditions of phosphoribosyl pyrophosphate (PRPP) as a molecular precursor in the one-pot synthesis of a canonical nucleotide, namely adenosine monophosphate (AMP) from its building blocks (KH2PO4 or Pi, adenine, and d-ribose), on a fumed silica surface. The on-the-rocks approach has been successfully applied to the simultaneous phosphorylation and glycosylation of ribose. The one-pot formation mechanism of AMP involves a two-step pathway via an activated intermediate, namely PRPP, obtained by multiple ribose phosphorylations upon mild thermal activation.AMP auf Siliciumoxid: Unter präbiotischen Bedingungen wird Phosphoribosylpyrophosphat (PRPP) gebildet. Diese Verbindung diente als molekulare Zwischenstufe in einer Eintopfsynthese des kanonischen Nukleotids Adenosinmonophosphat (AMP) aus den Bausteinen KH2PO4, Adenin und d-Ribose auf der Oberfläche von pyrogenem Siliciumdioxid.
      PubDate: 2017-05-30T14:06:30.696602-05:
      DOI: 10.1002/ange.201702633
       
  • Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the
           Oxidizing Power of Fluorine by Strong Lewis Acids
    • Authors: Karl O. Christe; Ralf Haiges, Monica Vasiliu, David A. Dixon
      Pages: 8032 - 8037
      Abstract: Although the existence of the NF4+ cation has been known for 51 years, and its formation mechanism from NF3 , F2 , and a strong Lewis acid in the presence of an activation energy source had been studied extensively, the mechanism had not been established. Experimental evidence had shown that the first step involves the generation of F atoms from F2 , and also that the NF3+ cation is a key intermediate. However, it was not possible to establish whether the second step involved the reaction of a F atom with either NF3 or the Lewis acid (LA). To distinguish between these two alternatives, a computational study of the NF4 , SbF6 , AsF6 , and BF4 radicals was carried out. Whereas the heats of reaction are small and similar for the NF4 and LAF radicals, at the reaction temperatures, only the LAF radicals possess sufficient thermal stability to be viable species. Most importantly, the ability of the LAF radicals to oxidize NF3 to NF3+ demonstrates that they are extraordinary oxidizers. This extraordinary enhancement of the oxidizing power of fluorine with strong Lewis acids had previously not been fully recognized.Die Gegenwart starker Lewis-Säuren (LAs) verstärkt die Oxidationskraft von elementarem Fluor (3.08 eV) um bis zu 6.7 eV, wodurch die entstehenden LAF-Radikale zu den stärksten bekannten neutralen Ein-Elektronen-Oxidantien werden. In Kombination mit der Gitterenergie des festen Produkts von ungefähr 6 eV kann LAF leicht Verbindungen wie NF3 zu NF3+ oxidieren.
      PubDate: 2017-05-04T05:10:48.18274-05:0
      DOI: 10.1002/ange.201701784
       
  • Zinc-Catalyzed Synthesis of Allylsilanes by Si−H Bond Insertion of Vinyl
           Carbenoids Generated from Cyclopropenes
    • Authors: Sergio Mata; Luis A. López, Rubén Vicente
      Pages: 8038 - 8042
      Abstract: Allylsilanes have long been recognized as valuable building blocks for organic synthesis. A zinc-catalyzed reaction of cyclopropenes and hydrosilanes provides a convenient route to these versatile unsaturated organosilanes. In this transformation, ZnBr2 serves as an efficient catalyst, allowing the generation of a zinc vinyl carbenoid intermediate, which is subsequently involved in a Si−H bond insertion. The process shows broad scope, and is amenable to substituted and functionalized cyclopropenes or the functionalization of polysiloxanes. Moreover, zinc-catalyzed carbene insertion into a Ge−H bond is reported for the first time.Ungesättigte Organosilane: Allylsilane resultieren aus atomökonomischen regioselektiven zinkkatalysierten Reaktionen von Cyclopropenen mit Hydrosilanen. Dabei wird die Insertion eines Zink-Vinylcarbenoids in die Si-H-Bindung vermutet. Das Verfahren eignet sich auch für Germanium-Analoga sowie für vielfältige Cyclopropene und oligomere Siloxane.
      PubDate: 2017-06-05T13:21:04.636676-05:
      DOI: 10.1002/ange.201703319
       
  • Carbonyl Activation in Electrophilic Polyene Cyclizations: A Toolbox for
           the Design of Isoprenoid Libraries
    • Authors: Alberto Minassi; Federica Pollastro, Giuseppina Chianese, Diego Caprioglio, Orazio Taglialatela-Scafati, Giovanni Appendino
      Pages: 8043 - 8046
      Abstract: An approach to biogenetically overlooked areas of the isoprenoid chemical space is presented. This strategy is based on the generation of a cationic center in functionalized polyolefins by Lewis acid activation of a carbonyl group, rather than by electrophilic attack at a double bond. Starting from the monocyclic humulane trienone zerumbone, polycyclic sesquiterpenoid skeletons which are either not reported as natural products or biogenetically enigmatic in terms of the isoprenoid rule, were obtained by modulating the Lewis acid catalyst. In the course of these studies, the surprising formation of a strained E-cyclooctene motif was observed in a cyclization reaction.Der riesige chemische Raum der Isoprenoide wurde anhand der Cyclisierung des Humulandienons Zerumbon unter Carbonyl- statt Olefin-Aktivierung untersucht. Dabei wurden neue biogenetische Reaktionspfade entdeckt und relevante mechanistische Beobachtungen gemacht, die die Herkunft des rätselhaften Stenotarsan-Gerüsts und die Bildung des gespannten E-Cycloocten-Motivs erklären.
      PubDate: 2017-06-05T13:21:06.117363-05:
      DOI: 10.1002/ange.201703455
       
  • Triggering Redox Activity in a Thiophene Compound: Radical Stabilization
           and Coordination Chemistry
    • Authors: Massimiliano Curcio; James R. Pankhurst, Stephen Sproules, Dimitri Mignard, Jason B. Love
      Pages: 8047 - 8051
      Abstract: The synthesis, metalation, and redox properties of an acyclic bis(iminothienyl)methene L− are presented. This π-conjugated anion displayed pronounced redox activity, undergoing facile one-electron oxidation to the acyclic, metal-free, neutral radical L. on reaction with FeBr2. In contrast, the reaction of L− with CuI formed the unique, neutral Cu2I2(L.) complex of a ligand-centered radical, whereas reaction with the stronger oxidant AgBF4 formed the metal-free radical dication L.2+.Radikalische Verwandte: Das Bis(iminothienyl)methen L− zeigt eine ausgeprägte Redoxaktivität mit Metallsalzen (siehe Schema). Solche Reaktionen lieferten das acyclische neutrale Radikal L., den neutralen Cu2I2(L.)-Komplex eines ligandenzentrierten Radikals und das metallfreie Radikaldikation L.2+, die alle mit kristallographischen, spektroskopischen und computergestützten Techniken charakterisiert wurden.
      PubDate: 2017-06-01T13:40:38.913474-05:
      DOI: 10.1002/ange.201703576
       
  • The EPR Spectrum of Triplet Mesitylphosphinidene: Reassignment and New
           Assignment
    • Authors: Alexander V. Akimov; Yulia S. Ganushevich, Denis V. Korchagin, Vasili A. Miluykov, Eugenii Y. Misochko
      Pages: 8052 - 8055
      Abstract: Low-temperature UV-photolysis of mesitylphosphiranes under highly anaerobic conditions leads to the formation of the triplet mesitylphosphinidene (MesP). The recorded X-band EPR spectrum of triplet MesP and the derived zero-field splitting parameter D=4.116 cm−1 differ significantly from those reported previously for this intermediate. New magnetic parameters of mesitylphosphinidene are discussed along with the results of DFT calculations.Endlich erwischt: Das EPR-Spektrum von Mesitylphosphiniden und der Nullfeldaufspaltungsparameter D aus diesem Spektrum unterscheiden sich deutlich von literaturbekannten Vorgängern. Das Vorliegen eines Hyperfein-Dubletts identifiziert den Triplettzustand für Mesitylphosphiniden eindeutig.
      PubDate: 2017-05-31T03:05:38.142205-05:
      DOI: 10.1002/ange.201703629
       
  • Facile Phenylphosphinidene Transfer Reactions from
           Carbene–Phosphinidene Zinc Complexes
    • Authors: Tetiana Krachko; Mark Bispinghoff, Aaron M. Tondreau, Daniel Stein, Matthew Baker, Andreas W. Ehlers, J. Chris Slootweg, Hansjörg Grützmacher
      Pages: 8056 - 8059
      Abstract: Phosphinidenes [R-P] are convenient P1 building blocks for the synthesis of a plethora of organophosphorus compounds. Thus far, transition-metal-complexed phosphinidenes have been used for their singlet ground-state reactivity to promote selective addition and insertion reactions. One disadvantage of this approach is that after transfer of the P1 moiety to the substrate, a challenging demetallation step is required to provide the free phosphine. We report a simple method that enables the Lewis acid promoted transfer of phenylphosphinidene, [PhP], from NHC=PPh adducts (NHC=N-heterocyclic carbene) to various substrates to produce directly uncoordinated phosphorus heterocycles that are difficult to obtain otherwise.PPh-Quelle: Die ZnCl2-vermittelte Phosphiniden-Übertragung von dem sterisch kaum befrachteten Carben-Phosphiniden-Addukt MeNHC=PPh auf verschiedene Substrate S bietet Zugang zu nichtkomplexierten Phosphorheterocyclen, die auf anderem Wege schwer erhältlich sind.
      PubDate: 2017-06-08T04:40:37.625506-05:
      DOI: 10.1002/ange.201703672
       
  • Silver-Catalyzed Three-Component 1,1-Aminoacylation of
           Homopropargylamines: α-Additions for Both Terminal Alkynes and
           Isocyanides
    • Authors: Shuo Tong; Cyril Piemontesi, Qian Wang, Mei-Xiang Wang, Jieping Zhu
      Pages: 8066 - 8070
      Abstract: The reaction of secondary homopropargylamines, isocyanides, and water in the presence of a catalytic amount of silver acetate and subsequent purification by chromatography on silica gel afforded substituted proline amides in good to excellent yields. Primary homopropargylamines underwent a cyclizative Ugi–Joullié three-component reaction with isocyanides and carboxylic acids to afford functionalized N-acyl proline amides. High diastereoselectivity was observed in the synthesis of 4-alkoxy and 4,5-disubstituted proline derivatives. This work represents the first examples of a three-component cyclizative 1,1-aminoacylation of terminal alkynes.Kein Atom geht verloren: Homopropargylamine reagieren mit Isocyaniden und entweder Carbonsäuren oder Wasser unter Silberacetat-Katalyse zu substituierten Prolinamiden. Diese Dreikomponentenreaktion verläuft als 1,1-Aminoacylierung des terminalen Alkins mit Cyclisierung und liefert gute bis hervorragende Ausbeuten. Boc=tert-Butoxycarbonyl.
      PubDate: 2017-05-31T08:56:38.961458-05:
      DOI: 10.1002/ange.201704727
       
  • Correlation between Chiral Modifier Adsorption and Enantioselectivity in
           Hydrogenation Catalysis
    • Authors: Yufei Ni; Alexander D. Gordon, Florisa Tanicala, Francisco Zaera
      Pages: 8071 - 8074
      Abstract: Infrared absorption spectroscopy performed in situ at the solid–liquid interface revealed that the adsorption on platinum supported catalysts of 1-(1-naphthyl)-ethylamine, which is used as a chiral modifier in hydrogenation catalysis, occurs through the amine group, not the aromatic ring as is widely believed. Comparisons were performed against a set of related modifier compounds with targeted substitutions to help identify the key moiety involved in the adsorption. It was determined that neither naphthalene-based modifiers without amine groups nor those with tertiary amine moieties are capable of adsorbing on the metal surface to any significant extent. A direct correlation was also found between the ability of the amines to adsorb on the platinum surface and their performance as chiral modifiers that impart enantioselectivity to the hydrogenation of α-keto esters such as ethyl pyruvate.Der chirale Modifikator 1-(1-Naphthyl)ethylamin adsorbiert über das Amin-Stickstoffatom auf Platin-Hydrierkatalysatoren, und nicht, wie weithin angenommen, über den aromatischen Ring. Die Notwendigkeit der NH2-Gruppe wurde anhand von In-situ-Infrarot-Absorptionsspektroskopie für eine Familie verwandter Verbindungen etabliert. Ihr Vorliegen korreliert mit der Enantioselektivität des Katalysators.
      PubDate: 2017-06-06T02:25:39.18703-05:0
      DOI: 10.1002/ange.201704880
       
  • Katalytische asymmetrische konjugierte Addition von Indolizinen an
           α,β-ungesättigte Ketone
    • Authors: José Tiago Menezes Correia; Benjamin List, Fernando Coelho
      Pages: 8075 - 8078
      Abstract: Beschrieben wird eine katalytische asymmetrische konjugierte Addition von Indolizinen an Enone. Die chirale Phosphorsäure (S)-TRIP aktiviert dabei α,β-ungesättigte Ketone und ermöglicht die enantioselektive Addition. Unter Verwendung der beschriebenen Methode wurden verschiedene alkylierte Indolizine in guten Ausbeuten und Enantiomerenverhältnissen von bis zu 98:2 synthetisiert.Alkylierte Indolizine: Unter Verwendung von (S)-TRIP als monofunktionellem Katalysator konnten alkylierte Indolizine in guten Ausbeuten und in Enantiomerenverhältnissen bis 98:2 synthetisiert werden.
      PubDate: 2017-06-01T13:40:52.187492-05:
      DOI: 10.1002/ange.201700513
       
  • Privilegierte Strukturen neu betrachtet
    • Authors: Petra Schneider; Gisbert Schneider
      Pages: 8079 - 8083
      Abstract: Privilegierte Strukturen inspirieren den Entwurf von Substanzbibliotheken für die medizinische Chemie. Wir haben 1.4 Millionen bioaktive Substanzen hinsichtlich der Dominanz bestimmter chemischer Grundgerüste (“frameworks”) untersucht. Dabei diente die Shannon-Entropie als ein quantitatives Maß für deren Promiskuität bezüglich der verschiedenen Targetfamilien. Diese Analyse offenbarte eine inverse Beziehung zwischen der Zahl an Wasserstoffbrückenakzeptoren und der beobachteten Promiskuität des Grundgerüsts. Des Weiteren scheinen sich strukturell einfache Gerüste besonders für Substanzbibliotheken mit unterschiedlichem Promiskuitätsgrad zu eignen, wohingegen sp3-reiche heterozyklische Grundgerüste den Entwurf von Target-fokussierten Bibliotheken ermöglichen. Die Resultate unserer Studie erlauben ein kritisches Hinterfragen von oft nur vermuteten besonderen Eigenschaften so genannter privilegierter Strukturen und weisen einen Weg zu deren systematischer Nutzung in der medizinischen Chemie.Wirkstoffdesign: Eine Analyse von 1.4 Millionen biologisch aktiven Substanzen offenbarte eine inverse Beziehung zwischen der Zahl an sp3-hybridisierten Atomen und der Zahl an Wasserstoffbrückenakzeptoren eines chemischen Grundgerüstes mit dessen Bindungsverhalten gegenüber vielen unterschiedlichen Zielproteinen.
      PubDate: 2017-05-30T14:06:25.710337-05:
      DOI: 10.1002/ange.201702816
       
  • Synthese und Nachweis von Iminoboranen durch M=B/C=N-Bindungsmetathese
    • Authors: Marco Nutz; Bitupon Borthakur, Rian D. Dewhurst, Andrea Deißenberger, Theresa Dellermann, Marius Schäfer, Ivo Krummenacher, Ashwini K. Phukan, Holger Braunschweig
      Pages: 8084 - 8089
      Abstract: Während die Metathese von Metall-Bor-Doppelbindungen mit elementaren Chalkogeniden gut beschrieben ist, kann keine vergleichbare Reaktivität für Element-Stickstoff-Bindungen beobachtet werden. Solche Reaktionen würden einen neuen Zugang zu Iminoboranen (RB≡NR′) eröffnen, die seit kurzem wieder Interesse auf sich ziehen. Im Nachfolgenden stellen wir die erstmalige Beobachtung von M=B/C=N-Metathesereaktionen vor, die zur Bildung eines stabilen Iminoborans sowie zu weiteren Iminoboran-Cycloadditionsprodukten führen.B,N-Alkin: Eine M=B/C=N-Metathese führte zur Isolierung eines stabilen Iminoborans und ferner zu weiteren Iminoboran-Cycloadditionsprodukten. Dieses Iminoboran ist das erste BspEsp-hybridisierte Produkt, das durch eine Metathesereaktion erhalten werden konnte.
      PubDate: 2017-06-01T13:40:44.971223-05:
      DOI: 10.1002/ange.201703324
       
  • Superelektrophiles Verhalten eines Anions demonstriert durch spontane
           Bindung von Edelgasen an [B12Cl11]−
    • Authors: Markus Rohdenburg; Martin Mayer, Max Grellmann, Carsten Jenne, Tobias Borrmann, Florian Kleemiss, Vladimir A. Azov, Knut R. Asmis, Simon Grabowsky, Jonas Warneke
      Pages: 8090 - 8096
      Abstract: Es entspricht der chemischen Intuition, Kationen elektrophile und Anionen nukleophile Reaktivität zuzuweisen. Wir demonstrieren hier einen bemerkenswerten Bruch mit diesem Konzept: Das Anion [B12Cl11]− bindet die Edelgase (Ngs) Xenon und Krypton spontan bei Raumtemperatur – eine Reaktion, die typisch für “superelektrophile” Dikationen ist. [B12Cl11Ng]−-Addukte mit Bindungsenergien von 80–100 kJ mol−1 enthalten B-Ng-Bindungen mit erheblichen kovalenten Anteilen. Der elektrophile Charakter des Anions [B12Cl11]− wird spektroskopisch anhand der beobachteten Blauverschiebung der CO-Streckschwingung in [B12Cl11CO]− sowie theoretisch mithilfe von Untersuchungen zur elektronischen Struktur nachgewiesen. Die Ausrichtung des elektrischen Felds an der reaktiven Stelle von [B12Cl11]− führt zu einer Energiebarriere für die Annäherung von polaren Molekülen und erleichtert die Bildung von Ng-Addukten, die mit reaktiven Kationen wie [C6H5]+ nicht beobachtet werden. Daher wird das neue chemische Konzept der “Dipol-diskriminierenden elektrophilen Anionen” eingeführt.Entgegen der Intuition: Das Binden der Edelgase Xe und Kr durch das Anion [B12Cl11]− wird durch die ungewöhnlichen Eigenschaften des elektrischen Feldes in der Umgebung des sub-koordinierten Boratoms bestimmt. Während polare Nukleophile wie Wasser einer Barriere begegnen, werden unpolare Bindungspartner wie N2 oder Edelgase bevorzugt. [B12Cl11]− ist daher ein „Dipol-diskriminierendes elektrophiles Anionen.”
      PubDate: 2017-05-31T03:05:49.070137-05:
      DOI: 10.1002/ange.201702237
       
  • Energieresonanzkreuzung steuert die Photolumineszenz von
           Europium-Antennensonden
    • Authors: Qiangqiang Zhang; Liangliang Wu, Xiaoyan Cao, Xuebo Chen, Weihai Fang, Michael Dolg
      Pages: 8097 - 8101
      Abstract: Die Energietransferpfade in Lanthanoid-Antennensonden können im Rahmen der gegenwärtig verfügbaren Modelle nicht vollständig berechnet werden; ihre Aufklärung bleibt daher eine Herausforderung. Auf Grundlage quantenchemischer Ab-initio-Berechnungen typischer Eu-Antennenkomplexe wird ein neuartiges Energieresonanzmodell vorgeschlagen, das von einer umfassenden Nonett-Quintett-Intersystemkreuzung aufgrund von Spin-Bahn-Kopplung in den Unterniveaus der beteiligten Zustände gesteuert wird.Resonanzkreuzung im Blickpunkt: Ein neuartiges Energietransfermodell steuert die Photolumineszenz von Eu-Antennensonden. Die Antenne bringt ihre adiabatische Anregungsenergie ein, um auf einem energetisch bevorzugten Nonett-Quintett-Kreuzungspfad die f-Elektronenpaarung von Eu3+ zu bewirken. Die Effizienz der Photolumineszenz wird durch Spin-Bahn-Kopplung zwischen den Unterniveaus der beteiligten Zustände gelenkt.
      PubDate: 2017-04-07T02:46:54.028194-05:
      DOI: 10.1002/ange.201701575
       
  • Selektive Si-C(sp3)-Bindungsspaltung in (Aminomethyl)silanen durch
           carbanionische Nucleophile und ihr stereochemischer Verlauf
    • Authors: Stephan G. Koller; Jonathan O. Bauer, Carsten Strohmann
      Pages: 8102 - 8106
      Abstract: Die Nutzbarmachung von Tetraorganosilanen durch gezielte Spaltung einer Si-C-Bindung ist noch immer eine anspruchsvolle Aufgabe. Nun wurde ein neuer Typ von Si-C(sp3)-Bindungsspaltungen in stabilen (Aminomethyl)silanen mit gewöhnlichen Organolithiumreagentien als Nucleophilen gefunden. Als Abgangsgruppen eignen sich Benzyl-, Allyl- und Phenylthiomethylgruppen. Ein β-ständiges Donoratom und polare Lösungsmittel sind essenziell für die Reaktion. Durch eine einfache Änderung der Reaktionsbedingungen kann zwischen einer α-Deprotonierung und einer Substitution umgeschaltet werden. Anhand eines siliciumchiralen Benzylsilans wurde der stereochemische Verlauf der Reaktion aufgeklärt. Die neue Umsetzung verläuft stereospezifisch unter Inversion der Konfiguration und eignet sich für eine zielgerichtete Synthese schwer zugänglicher, enantiomerenreiner Tetraorganosilane. Quantenchemische Rechnungen liefern einen Einblick in den Mechanismus der neuartigen Substitution.Vielseitige Reaktivität: Zusätzlich zur gängigen α-Deprotonierung wurde nun ein weiterer Reaktionspfad von (Aminomethyl)silanen aufgezeigt, der es ermöglicht, auch all-C-substituierte Silane präparativ zu nutzen. Durch einfache Veränderung der Reaktionsbedingungen lassen sich durch carbanionische Nucleophile (Nu) aktivierte Alkylgruppen am Si-Zentrum substituieren. So gelingt auch die Synthese sonst schwer zugänglicher, enantiomerenreiner Organosilane.
      PubDate: 2017-06-06T08:21:25.720661-05:
      DOI: 10.1002/ange.201702410
       
  • Elektronische Struktur und magnetische Anisotropie eines ungesättigten
           Cyclopentadienyleisen(I)-Komplexes mit 15 Valenzelektronen
    • Authors: Uttam Chakraborty; Serhiy Demeshko, Franc Meyer, Christophe Rebreyend, Bas de Bruin, Mihail Atanasov, Frank Neese, Bernd Mühldorf, Robert Wolf
      Pages: 8107 - 8112
      Abstract: Der 15-Valenzelektronen-Komplex [CpArFe(IiPr2Me2)] (1, CpAr=C5(C6H4-4-Et)5; IiPr2Me2=1,3-Diisopropyl-4,5-dimethylimidazolin-2-yliden) ist ausgehend von der Eisen(II)-Vorstufe [CpArFe(μ-Br)]2 in hohen Ausbeuten zugänglich. 57Fe-Mößbauer- und EPR-Daten, magnetische Messungen und Ab-initio-Ligandenfeldrechnungen deuten auf einen S=3/2-Grundzustand mit einer großen negativen Nullfeldaufspaltung hin. Infolgedessen weist 1 magnetische Anisotropie mit einer effektiven Spinumkehrbarriere von Ueff=64 cm−1 auf. Zudem katalysiert 1 die Dehydrierung von Dimethylamin-Boran unter Bildung von Tetramethyl-1,3-diaza-2,4-diboretan unter milden Bedingungen.Eisen(I) in Aktion: Der 15-Valenzelektronen-Komplex [CpArFe(IiPr2Me2)] wird durch den Pentaaryl-substituierten Cyclopentadienyl-Liganden C5(C6H4-4-Et)5 (CpAr) und das N-heterocyclische Carben 1,3-Diisopropyl-4,5-dimethylimidazolin-2-yliden (IiPr2Me2) stabilisiert. Diese Verbindung repräsentiert einen neuen Typ von eisenbasierten Einzelmolekülmagneten aufgrund einer ungewöhnlichen Konfiguration der 3d-Orbitale im Grundzustand.
      PubDate: 2017-05-30T05:10:45.576531-05:
      DOI: 10.1002/ange.201702454
       
  • Isomerenselektive Erzeugung und spektroskopische Charakterisierung der
           Picolyl-Radikale
    • Authors: Engelbert Reusch; Fabian Holzmeier, Philipp Constantinidis, Patrick Hemberger, Ingo Fischer
      Pages: 8113 - 8116
      Abstract: Stickstoff-haltige resonanzstabilisierte Radikale wie Picolyl spielen eine wichtige Rolle in Verbrennungsprozessen und in der Astrochemie. Sie wurden jedoch bislang kaum untersucht, da es schwierig ist, sie isomerenselektiv zu erzeugen. Schwellenphotoelektronenspektren der drei Isomere des Picolyl-Radikals, C6H6N, wurden mit Synchrotronstrahlung aufgenommen. Die Radikale wurden selektiv durch Pyrolyse aus Aminomethylpyridinen hergestellt. Ionisierungsenergien von 7.70, 7.59 und 8.01 eV wurden für 2-, 3- bzw. 4-Picolyl gemessen. Die beobachtete Schwingungsstruktur wurde einer Deformationsschwingung des aromatischen Rings zugeordnet. Die gewonnenen spektroskopischen Daten ermöglichen es, die verschiedenen Picolyl-Isomere selektiv nachzuweisen, beispielsweise in der Flammenanalytik.Die drei Isomere des Picolyl-Radikals, C6H6N, wurden durch Pyrolyse aus Aminomethylpyridin generiert und durch Schwellenphotoelektronenspektroskopie mit Synchrotronstrahlung charakterisiert.
      PubDate: 2017-06-06T02:25:29.015129-05:
      DOI: 10.1002/ange.201703433
       
  • Kooperative Licht-aktivierte Iod- und Photoredox-Katalyse zur Aminierung
           von Csp3 -H-Bindungen
    • Authors: Peter Becker; Thomas Duhamel, Christopher J. Stein, Markus Reiher, Kilian Muñiz
      Pages: 8117 - 8121
      Abstract: Ein neuartiges Verfahren zum kooperativen Zusammenspiel eines molekularen Iod- und eines Photoredox-Katalysators in einer dualen photo-induzierten intramolekularen benzylischen C-H-Aminierung wird beschrieben. In dieser Reaktion agiert Iod als Katalysator zur Bildung einer neuen C-N-Bindung unter photochemischer Aktivierung einer Csp3-H-Bindung (1,5-HAT-Prozess), während der organische Photoredox-Katalysator TPT auf effiziente Weise den molekularen Iod-Katalysator reoxidiert. Die Vereinbarkeit der beiden photochemischen Reaktionsschritte wurde mithilfe computerchemischer Berechnungen des Schlüsselschritts – der Aktivierung der N-I-Bindung – untersucht. Diese neuartige kooperative Katalyse bietet wichtige Anhaltspunkte für die Kombination von nicht-metallischen Hauptgruppenkatalysatoren mit Photoredox-Katalyse.Mehr Licht, mehr Möglichkeiten! Ein dualer Licht-aktivierter Prozess mit verflochtener Iod- und Photoredox-Katalyse für die Aminierung von entfernten Csp3-H-Bindungen wurde entwickelt. Während das Iod die Aktivierung der Csp3-H-Bindung initiiert, wirkt der Farbstoff TPT auf effiziente Weise als Photoredox-Katalysator zur Regenerierung des molekularen Iod-Katalysators. Die Vereinbarkeit der beiden Prozesse wird mit theoretischen Studien erklärt.
      PubDate: 2017-06-01T13:40:35.577666-05:
      DOI: 10.1002/ange.201703611
       
  • Generierung einer kleinen HOMO-LUMO-Lücke und intramolekulare
           C-H-Borylierung durch Diboren-Anthracen-Orbitalinterkalation
    • Authors: Sunewang R. Wang; Merle Arrowsmith, Julian Böhnke, Holger Braunschweig, Theresa Dellermann, Rian D. Dewhurst, Hauke Kelch, Ivo Krummenacher, James D. Mattock, Jonas H. Müssig, Torsten Thiess, Alfredo Vargas, Jiji Zhang
      Pages: 8122 - 8126
      Abstract: Diboren 1 wurde durch Reduktion einer Mischung aus 1,2-Di-9-anthryl-1,2-dibromdiboran(4) (6) und Trimethylphosphan mit Kaliumgraphit dargestellt. Die Molekülstruktur von 1 zeigt, dass die Anthrylringe zueinander parallel und in Bezug auf das Diboren-π(B=B)-System orthogonal angeordnet sind. Diese verdrehte Konformation ohne signifikante Konjugation erlaubt eine Interkalation des relativ hoch liegenden π(B=B)-Orbitals mit dem tief liegenden π*-Orbital der Anthryl-Einheit, was zu einer kleinen HOMO-LUMO-Lücke und letztlich zur C-H-Borylierung des Anthryl-Liganden führt. Die HOMO-LUMO-Energielücke wurde durch den Beginn der Absorptionsbande bei der längsten Wellenlänge im UV-vis-Spektrum auf 1.57 eV geschätzt (THF, λonset=788 nm). Mit elementarem Selen ließ sich Verbindung 1 quantitativ zum Diboraseleniran 8 umsetzen. Durch ein weiteres Äquivalent Selen wird unter oxidativer Abspaltung eines Phosphan-Liganden und Spaltung der B-B- und C1-H-Bindungen das cyclische 1,9-Diborylanthracen 9 erhalten.HOMO-Engineering: Ein Anthryl-substituiertes Diboren wurde als tiefgrüner kristalliner Feststoff mit einer bemerkenswert kleinen HOMO-LUMO-Lücke (HLG) von 1.57 eV isoliert. Unter oxidativer Abspaltung eines Phosphan-Liganden erfolgt eine beispiellose intramolekulare C-H-Borylierung mit der B-B-Bindung zum entsprechenden Diboraseleniran.
      PubDate: 2017-06-05T13:11:01.077829-05:
      DOI: 10.1002/ange.201704063
       
  • Innenrücktitelbild: Significant Enhancement of C2H2/C2H4 Separation by a
           Photochromic Diarylethene Unit: A Temperature- and Light-Responsive
           Separation Switch (Angew. Chem. 27/2017)
    • Authors: Cong Bin Fan; Le Le Gong, Ling Huang, Feng Luo, Rajamani Krishna, Xian Feng Yi, An Min Zheng, Le Zhang, Shou Zhi Pu, Xue Feng Feng, Ming Biao Luo, Guo Cong Guo
      Pages: 8127 - 8127
      Abstract: Selektive Adsorption und Trennung durch photochrome Metall-organische Gerüste (MOFs) lässt sich bisher nur selten allein durch externe Reize einstellen. In der Zuschrift auf S. 8008 ff. setzen F. Luo, G.-C. Guo et al. eine photochrome Diarylethen-Einheit zur lichtresponsiven Steuerung von Selektivität und Trennverhalten ein. Dadurch erhalten sie eine hoch selektive Adsorption, zum Beispiel im System C2H2/C2H4.
      PubDate: 2017-05-19T07:06:21.96921-05:0
      DOI: 10.1002/ange.201704765
       
  • Rücktitelbild: Formation Mechanism of NF4+ Salts and Extraordinary
           Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids
           (Angew. Chem. 27/2017)
    • Authors: Karl O. Christe; Ralf Haiges, Monica Vasiliu, David A. Dixon
      Pages: 8128 - 8128
      Abstract: Die stärksten neutralen Ein-Elektronen-Oxidantien …… werden von K. O. Christe et al. in der Zuschrift auf S. 8032 ff. beschrieben. Die Gegenwart starker Lewis-Säuren verstärkt die Oxidationskraft von elementarem Fluor um bis zu 6.7 eV, und Sb2F11 hat eine Elektronenaffinität von 9.78 eV (PtF6: 7.09 eV). Kombiniert mit einer typischen Gitterenergie von etwa 6 eV für ein festes Produkt können diese Lewis-Säure/Fluor-Addukte auch unreaktiven Verbindungen ein Elektron “stehlen” und beispielsweise NF3 zu NF3+ oxidieren.
      PubDate: 2017-06-05T13:21:19.958267-05:
      DOI: 10.1002/ange.201705291
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.81.113.71
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016