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Angewandte Chemie

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https://www.readbyqxmd.com/read/28345296/boosting-the-energy-density-of-carbon-based-aqueous-supercapacitors-by-optimizing-the-surface-charge
#1
Minghao Yu, Dun Lin, Haobin Feng, Yinxiang Zeng, Yexiang Tong, Xihong Lu
The voltage of carbon-based aqueous supercapacitors is limited by the water splitting reaction occurring in one electrode, generally resulting in the promising but unused potential range of the other electrode. Exploiting this unused potential range provides the possibility for further boosting their energy density. An efficient surface charge control strategy was developed to remarkably enhance the energy density of multiscale porous carbon (MSPC) based aqueous symmetric supercapacitors (SSCs) by controllably tuning the operating potential range of MSPC electrodes...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345286/highly-selective-synthesis-of-cis-enediyne-on-a-ag-111-surface
#2
Tao Wang, Haifeng Lv, Qitang Fan, Lin Feng, Xiaojun Wu, Junfa Zhu
Cis-enediyne-type compounds have received much attention as potent antitumor antibiotics. The conventional synthesis of cis-enediynes in solution typically involves multiple steps and various side reactions. For the first time, selective one-step synthesis of cis-enediyne from a single reactant is reported on a Ag(111) surface with a yield up to 90 %. High selectivity for the formation of cis-enediyne originates from the steric effect posed by weak intermolecular interactions, which protect the cis-enediyne from further reaction...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345283/oxygen-incorporated-amorphous-cobalt-sulfide-porous-nanocubes-as-high-activity-electrocatalysts-for-the-oxygen-evolution-reaction-in-an-alkaline-neutral-medium
#3
Pingwei Cai, Junheng Huang, Junxiang Chen, Zhenhai Wen
A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6 O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6 O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345220/boosting-the-performance-of-the-nickel-anode-in-the-oxygen-evolution-reaction-by-simple-electrochemical-activation
#4
Tatsuya Shinagawa, Marcus Tze-Kiat Ng, Kazuhiro Takanabe
The development of cost-effective and active water-splitting electrocatalysts that work at mild pH is an essential step towards the realization of sustainable energy and material circulation in our society. Its success requires a drastic improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. A simple electrochemical protocol has been developed to activate Ni electrodes, by which a stable NiOOH phase was formed, which could weakly bind to alkali-metal cations...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345208/increased-synthetic-control-gaining-access-to-predicted-mg2-si5-n8-and-%C3%AE-ca2-si5-n8
#5
Philipp Bielec, Wolfgang Schnick
Nitridosilicates represent an intriguing class of materials and are typically made up of highly condensed tetrahedral network structures. Alkaline-earth nitridosilicates emerged as unique host materials for Eu(2+) doped luminophores which found broad application in phosphor-converted (pc)-LEDs. In contrast to common strategies of preparing nitridosilicates by bottom-up syntheses, we have now succeeded to post-synthetically design nitridosilicates by ion exchange in metal halide melts. We describe the syntheses of hitherto unknown but predicted alkaline-earth nitridosilicates, Mg2 Si5 N8 and β-Ca2 Si5 N8 ...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345205/para-selective-c-h-borylation-of-hetero-arenes-by-cooperative-iridium-aluminum-catalysis
#6
Lichen Yang, Kazuhiko Semba, Yoshiaki Nakao
para-Selective C-H borylation of benzamides and pyridines has been achieved by cooperative iridium/aluminum catalysis. A combination of iridium catalysts commonly employed for arene C-H borylation and bulky aluminum-based Lewis acid catalysts provides an unprecedented strategy for controlling the regioselectivity of C-H borylation to give variously substituted (hetero)arylboronates, which are versatile synthetic intermediates for complex multi-substituted aromatic compounds.
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345204/insight-into-ion-transfer-through-the-sub-nanometer-channels-in-zeolitic-imidazolate-frameworks
#7
Ze-Yu Jiang, Hai-Ling Liu, Saud Asif Ahmed, Sumaira Hanif, Shi-Bin Ren, Jing-Juan Xu, Hong-Yuan Chen, Xing-Hua Xia, Kang Wang
A crack-free sub-nanometer composite structure for the study of ion transfer was constructed by in situ growth of ZIF-90 [Zn(ICA)2 , ICA=Imidazole-2-carboxaldehyde] on the tip of a glass nanopipette. The potential-driven ion transfer through the sub-nanometer channels in ZIF-90 is strongly influenced by the pH of the solution. A rectification ratio over 500 is observed in 1 m KCl solution under alkaline conditions (pH 11.58), which is the highest value reported under such a high salt concentration. Fluorescence experiments show the super-high rectification ratio under alkaline conditions results from the strong electrostatic interaction between ions and the sub-nanometer channels of ZIF-90...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345175/enantioselective-palladium-catalyzed-carbonylative-carbocyclization-of-enallenes-via-cross-dehydrogenative-coupling-with-terminal-alkynes-efficient-construction-of-%C3%AE-chirality-of-ketones
#8
Bin Yang, Youai Qiu, Tuo Jiang, William D Wulff, Xiaopeng Yin, Can Zhu, Jan-E Bäckvall
An enantioselective Pd(II) /Brønsted acid-catalyzed carbonylative carbocyclization of enallenes ending with a cross-dehydrogenative coupling (CDC) with a terminal alkyne was developed. VAPOL phosphoric acid was found as the best co-catalyst among the examined 28 chiral acids, for inducing the enantioselectivity of α-chiral ketones. As a result, a number of chiral cyclopentenones were easily synthesized in good to excellent enantiomeric ratio with good yields.
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345159/stereoselective-catalytic-synthesis-of-active-pharmaceutical-ingredients-in-homemade-3d-printed-mesoreactors
#9
Sergio Rossi, Riccardo Porta, Davide Brenna, Alessandra Puglisi, Maurizio Benaglia
3D-printed flow reactors were designed, fabricated from different materials (PLA, HIPS, nylon), and used for a catalytic stereoselective Henry reaction. The use of readily prepared and tunable 3D-printed reactors enabled the rapid screening of devices with different sizes, shapes, and channel dimensions, aimed at the identification of the best-performing reactor setup. The optimized process afforded the products in high yields, moderate diastereoselectivity, and up to 90 % ee. The method was applied to the continuous-flow synthesis of biologically active chiral 1,2-amino alcohols (norephedrine, metaraminol, and methoxamine) through a two-step sequence combining the nitroaldol reaction with a hydrogenation...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338296/photochromism-and-dual-color-fluorescence-in-a-polyoxometalate-benzospiropyran-molecular-switch
#10
Arnaud Parrot, Aurélie Bernard, Aurélie Jacquart, Stefano Artin Serapian, Carles Bo, Etienne Derat, Olivier Oms, Anne Dolbecq, Anna Proust, Rémi Métivier, Pierre Mialane, Guillaume Izzet
The photophysical properties of a Keggin-type polyoxometalate (POM) covalently bounded to a benzospiropyran (BSPR) unit have been investigated. These studies reveal that both closed and open forms are emissive with distinct spectral features (λem (closed form)=530 nm, λem (open form)=670 nm) and that the fluorescence of the BSPR unit of the hybrid is considerably enhanced compared to BSPR parent compounds. While the fluorescence excitation energy of the BSPR reference compounds (370 nm) is close to the intense absorption responsible of the photochromic character (350 nm), the fluorescence excitation of the hybrid is shifted to lower energy (400 nm), improving the population of the emissive state...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338289/a-sodium-ion-conducting-direct-formate-fuel-cell-generating-electricity-and-producing-base
#11
Yinshi Li, Ying Feng, Xianda Sun, Yaling He
A barrier that limits the development of the conventional cation-exchange membrane direct liquid fuel cells (CEM-DLFCs) is that the CEM-DLFCs need additional base to offer both alkaline environment and charge carriers. Herein, we propose a Na(+) -conducting direct formate fuel cell (Na-DFFC) that is operated in the absence of added base. A proof-of-concept Na-DFFC yields a peak power density of 33 mW cm(-2) at 60 °C, mainly because the hydrolysis of sodium formate provides enough OH(-) and Na(+) ions, proving the conceptual feasibility...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338287/synthesis-of-rationally-halogenated-buckybowls-by-chemoselective-aromatic-c-f-bond-activation
#12
Olena Papaianina, Vladimir A Akhmetov, Alexey A Goryunkov, Frank Hampel, Frank W Heinemann, Konstantin Y Amsharov
Halogenated buckybowls or bowl-shaped polycyclic aromatic hydrocarbons (BS-PAHs) are key building blocks for the "bottom-up" synthesis of various carbon-based nanomaterials with outstanding potential in different fields of technology. The current state of the art provides quite a limited number of synthetic pathways to BS-PAHs; moreover, none of these approaches show high selectivity and tolerance of functional groups. Herein we demonstrate an effective route to BS-PAHs that includes directed intramolecular aryl-aryl coupling through C-F bond activation...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338284/palladium-catalyzed-enantioselective-synthesis-of-2-aryl-cyclohex-2-enone-atropisomers-platform-molecules-for-the-divergent-synthesis-of-axially-chiral-biaryl-compounds
#13
Chongqing Pan, Zixi Zhu, Mingkai Zhang, Zhenhua Gu
The palladium-catalyzed asymmetric synthesis of enone-based atropisomers from 2-iodo-3-methylcyclohex-2-enones and aryl boronic acid is reported. BoPhoz-type phosphine-aminophosphine ligands showed superior enantioselectivity over other ligands. These cyclohexenone-based atropisomers are useful compounds for further elaboration. The divergent synthesis of biaryl atropisomers with different ortho substituents was demonstrated.
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338279/elemental-boron-for-efficient-carbon-dioxide-reduction-under-light-irradiation
#14
Guigao Liu, Xianguang Meng, Huabin Zhang, Guixia Zhao, Hong Pang, Tao Wang, Peng Li, Tetsuya Kako, Jinhua Ye
The photoreduction of CO2 is attractive for the production of renewable fuels and the mitigation of global warming. Herein, we report an efficient method for CO2 reduction over elemental boron catalysts in the presence of only water and light irradiation through a photothermocatalytic process. Owing to its high solar-light absorption and effective photothermal conversion, the illuminated boron catalyst experiences remarkable self-heating. This process favors CO2 activation and also induces localized boron hydrolysis to in situ produce H2 as an active proton source and electron donor for CO2 reduction as well as boron oxides as promoters of CO2 adsorption...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338268/chiral-amino-alcohol-accelerated-and-stereocontrolled-allylboration-of-iminoisatins-highly-efficient-construction-of-adjacent-quaternary-stereogenic-centers
#15
Qiuyuan Tan, Xinqiao Wang, Yang Xiong, Zimeng Zhao, Lu Li, Pei Tang, Min Zhang
We have developed a highly efficient asymmetric allylboration of ketimines with nonchiral γ,γ-disubstituted allylboronic acids by using a chiral amino alcohol as the directing group, which is otherwise challenging. The amino alcohol not only serves as a cheap source of nitrogen and chirality, but also dramatically enhances the reactivity. The versatility of this method was demonstrated by its ability to access all four stereoisomers with adjacent quaternary carbon centers. A reaction model was proposed to explain the diastereoselectivity and the rate-accelerating effect...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338266/accelerated-oxygen-atom-transfer-and-c-h-bond-oxygenation-by-remote-redox-changes-in-fe3-mn-iodosobenzene-adducts
#16
Graham de Ruiter, Kurtis M Carsch, Sheraz Gul, Ruchira Chatterjee, Niklas B Thompson, Michael K Takase, Junko Yano, Theodor Agapie
We report the synthesis, characterization, and reactivity of [LFe3 (PhPz)3 OMn((s) PhIO)][OTf]x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene-metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, (57) Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe(III)2 Fe(II) Mn(II) vs...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338264/engineering-high-energy-interfacial-structures-for-high-performance-oxygen-involving-electrocatalysis
#17
Chunxian Guo, Yao Zheng, Jingrun Ran, Fangxi Xie, Mietek Jaroniec, Shi-Zhang Qiao
Engineering high-energy interfacial structures for high-performance electrocatalysis is achieved by chemical coupling of active CoO nanoclusters and high-index facet Mn3 O4 nano-octahedrons (hi-Mn3 O4 ). A thorough characterization, including synchrotron-based near edge X-ray absorption fine structure, reveals that strong interactions between both components promote the formation of high-energy interfacial Mn-O-Co species and high oxidation state CoO, from which electrons are drawn by Mn(III) -O present in hi-Mn3 O4 ...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338263/synthesis-of-poly-arylene-vinylene-s-with-different-end-groups-by-combining-acyclic-diene-metathesis-polymerization-with-wittig-type-couplings
#18
Tomonari Miyashita, Mikiko Kunisawa, Shunsuke Sueki, Kotohiro Nomura
A series of end-functionalized poly(9,9'-di-n-octylfluorene vinylene)s (EF-PFVs) with different end groups were obtained by 1) synthesizing EF-PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig-type coupling with another aldehyde. The exclusive formation of EF-PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338262/steering-on-surface-reactions-by-a-self-assembly-approach
#19
Qiwei Chen, Jacob R Cramer, Jing Liu, Xin Jin, Peilin Liao, Xiang Shao, Kurt V Gothelf, Kai Wu
4,4'-Bis(2,6-difluoropyridin-4-yl)-1,1':4',1''-terphenyl (BDFPTP) molecules underwent dehydrocyclization and covalent coupling reactions on Au(111) according to scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Self-assembly of the reactants in well-defined molecular domains prior to reaction could greatly enhance the regioselectivity of the dehydrocyclization reaction and suppress defluorinated coupling, demonstrating that self-assembly can efficiently steer on-surface reactions...
March 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28338260/iron-ii-catalyzed-hydrophosphination-of-isocyanates
#20
Helen R Sharpe, Ana M Geer, William Lewis, Alexander J Blake, Deborah L Kays
The first transition metal catalyzed hydrophosphination of isocyanates is presented. The use of low-coordinate iron(II) precatalysts leads to an unprecedented catalytic double insertion of isocyanates into the P-H bond of diphenylphosphine to yield phosphinodicarboxamides [Ph2 PC(=O)N(R)C(=O)N(H)R], a new family of derivatized organophosphorus compounds. This remarkable result can be attributed to the low-coordinate nature of the iron(II) centers whose inherent electron deficiency enables a Lewis-acid mechanism in which a combination of the steric pocket of the metal center and substrate size determines the reaction products and regioselectivity...
March 24, 2017: Angewandte Chemie
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