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991.
Three‐Dimensional Branched and Faceted Gold–Ruthenium Nanoparticles: Using Nanostructure to Improve Stability in Oxygen Evolution Electrocatalysis
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Dr. Lucy Gloag Dr. Tania M. Benedetti Dr. Soshan Cheong Dr. Yibing Li Dr. Xuan‐Hao Chan Prof. Lise‐Marie Lacroix Prof. Shery L. Y. Chang Dr. Raul Arenal Dr. Ileana Florea Dr. Hector Barron Dr. Amanda S. Barnard Dr. Anna M. Henning Prof. Chuan Zhao Prof. Wolfgang Schuhmann Prof. J. Justin Gooding Prof. Richard D. Tilley 《Angewandte Chemie (International ed. in English)》2018,57(32):10241-10245
Achieving stability with highly active Ru nanoparticles for electrocatalysis is a major challenge for the oxygen evolution reaction. As improved stability of Ru catalysts has been shown for bulk surfaces with low‐index facets, there is an opportunity to incorporate these stable facets into Ru nanoparticles. Now, a new solution synthesis is presented in which hexagonal close‐packed structured Ru is grown on Au to form nanoparticles with 3D branches. Exposing low‐index facets on these 3D branches creates stable reaction kinetics to achieve high activity and the highest stability observed for Ru nanoparticle oxygen evolution reaction catalysts. These design principles provide a synthetic strategy to achieve stable and active electrocatalysts. 相似文献
992.
Enzymatic or In Vivo Installation of Propargyl Groups in Combination with Click Chemistry for the Enrichment and Detection of Methyltransferase Target Sites in RNA
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993.
Yu‐Hao Li Shaoping Zheng Dr. Yves‐Marie Legrand Dr. Arnaud Gilles Dr. Arie Van der Lee Dr. Mihail Barboiu 《Angewandte Chemie (International ed. in English)》2018,57(33):10520-10524
Self‐assembled alkyl‐ureido‐benzo‐15‐crown‐5‐ethers are selective ionophores for K+ cations, which are preferred to Na+ cations. The transport mechanism is determined by the optimal coordination rather than classical dimensional compatibility between the crown ether hole and the cation diameter. Herein, we demonstrate that systematic changes of the structure lead to unexpected modifications in the cation‐transport activity and suffice to produce adaptive selection. We show that the main contribution to performance arises from optimal constraints on the conformational freedom, which are determined by the binding macrocycles, the nature of the hydrogen‐bonding groups, and the hydrophobic tails. Simple changes to the flexible 15‐crown‐5‐ether lead to selective carriers for Na+. Hydrophobic stabilization of the channels through mutual interactions between lipids and variable hydrophobic tails appears to be an important cause of increased activity. Oppositely, restricted translocation is achieved when constrained hydrogen‐bonded macrocyclic relays are less dynamic in a pore superstructure. 相似文献
994.
The Molecular Structure of gauche‐1,3‐Butadiene: Experimental Establishment of Non‐planarity
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Dr. Joshua H. Baraban Dr. Marie‐Aline Martin‐Drumel P. Bryan Changala Dr. Sandra Eibenberger Dr. Matthew Nava Prof. David Patterson Prof. John F. Stanton Prof. G. Barney Ellison Dr. Michael C. McCarthy 《Angewandte Chemie (International ed. in English)》2018,57(7):1821-1825
The planarity of the second stable conformer of 1,3‐butadiene, the archetypal diene for the Diels–Alder reaction in which a planar conjugated diene and a dienophile combine to form a ring, is not established. The most recent high level calculations predicted the species to adopt a twisted, gauche structure owing to steric interactions between the inner terminal hydrogens rather than a planar, cis structure favored by the conjugation of the double bonds. The structure cis‐1,3‐butadiene is unambiguously confirmed experimentally to indeed be gauche with a substantial dihedral angle of 34°, in excellent agreement with theory. Observation of two tunneling components indicates that the molecule undergoes facile interconversion between two equivalent enantiomeric forms. Comparison of experimentally determined structures for gauche‐ and trans‐butadiene provides an opportunity to examine the effects of conjugation and steric interactions. 相似文献
995.
Andrzej Wolan Justyna A. Kowalska-Six Holisoa Rajerison Michèle Césario Marie Cordier Yvan Six 《Tetrahedron》2018,74(38):5248-5257
Two types of bicyclic N-cyclopropyl glycine ester derivatives have been prepared and put under scrutiny as possible precursors of azomethine ylides. The results demonstrate that they can indeed participate in 1,3-dipolar cycloaddition reactions with dipolarophiles, as illustrated in the cases of phenyl vinyl sulfone, N-phenylmaleimide, diethyl fumarate and diethyl maleate. The relative configurations of the major diastereoisomers produced are consistent with the predicted generation of azomethine ylide species, reacting in concerted cycloaddition processes. This unprecedented way of generating such 1,3-dipoles provides access to functionalised pyrrolizidine and pyrrolidine derivatives, that would be difficult to make directly by more classic methods. It was also found that using phenyl vinyl sulfone or N-phenylmaleimide as the dipolarophile reactant, a domino nucleophilic conjugate addition/1,3-dipolar cycloaddition process may operate competitively. 相似文献
996.
Fr. Stolba 《Fresenius' Journal of Analytical Chemistry》1869,8(1):63-64
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