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71.
Eva Blokker Dr. Xiaobo Sun Prof. Dr. Jordi Poater Dr. Ir. J. Martijn van der Schuur Dr. Trevor A. Hamlin Prof. Dr. F. Matthias Bickelhaupt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(63):15616-15622
We have quantum chemically analyzed element−element bonds of archetypal HnX−YHn molecules (X, Y=C, N, O, F, Si, P, S, Cl, Br, I), using density functional theory. One purpose is to obtain a set of consistent homolytic bond dissociation energies (BDE) for establishing accurate trends across the periodic table. The main objective is to elucidate the underlying physical factors behind these chemical bonding trends. On one hand, we confirm that, along a period (e. g., from C−C to C−F), bonds strengthen because the electronegativity difference across the bond increases. But, down a period, our findings constitute a paradigm shift. From C−F to C−I, for example, bonds do become weaker, however, not because of the decreasing electronegativity difference. Instead, we show that the effective atom size (via steric Pauli repulsion) is the causal factor behind bond weakening in this series, and behind the weakening in orbital interactions at the equilibrium distance. We discuss the actual bonding mechanism and the importance of analyzing this mechanism as a function of the bond distance. 相似文献
72.
Stephen R. Wasserman Jordi Benach John W. Koss Laura L. Morisco 《Synchrotron Radiation News》2015,28(6):4-9
On May 11 and 12, 2000, the Stanford Synchrotron Radiation Laboratory, as it was then known, hosted a “Workshop on Techniques for Automated Mounting, Viewing and Centering Pre-Cooled Protein Crystals” [1, 2]. The 12 presentations during the meeting all focused on the impact that automation could have on the performance of synchrotron beamlines and thus on research in structural biology. Two principal themes ran through the workshop: (1) robotics to mount crystals on a diffractometer; and (2) methods to place a crystal in the X-ray beam. Five conceptual and prototype robotic systems for automated mounting were described—the original ACTOR from Abbott Laboratories, later modified and marketed by Rigaku/MSC, and the systems which in final form become the ALS [3], EMBL/ESRF SC3 [4], APS/SBC [5], and SSRL SAM robots [6]. By December of that year, the ACTOR had been installed for testing at Sector 32 of the Advanced Photon Source (Figure 1). Within three years, by the end of 2003, several of these robots, plus the commercial MARcsc from MAR Research, had been deployed to handle frozen protein crystals at beamlines for macromolecular crystallography (MX). Currently, at least 13 distinct robot types, not including variants of the ALS automounter, are employed at synchrotron beamlines to transfer crystals from storage to beam position. 相似文献
73.
Craig J. Richmond Roc Matheu Dr. Albert Poater Dr. Laura Falivene Dr. Jordi Benet‐Buchholz Dr. Xavier Sala Prof. Luigi Cavallo Prof. Antoni Llobet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17282-17286
Extremely slow and extremely fast new water oxidation catalysts based on the Ru–bda (bda=2,2′‐bipyridine‐6,6′‐dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s?1, respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π‐stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. 相似文献
74.
Cover Picture: Phosphinothiolates as Ligands for Polyhydrido Copper Nanoclusters (Chem. Eur. J. 49/2014)
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75.
Dr. Hua Dong Dr. Jordi Ignés‐Mullol Dr. Josep Claret Dr. Lourdes Pérez Dr. Aurora Pinazo Prof. Dr. Francesc Sagués 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7396-7401
A chiral selection process in a self‐assembled soft monolayer of an achiral amphiphile as a consequence of its interaction with chiral species dissolved in the aqueous subphase, is reported. The extent of the chiral selection is statistically measured in terms of the enantiomorphic excess of self‐assembled submillimeter domains endowed with well‐defined orientational chirality that is unambiguously resolved using optical microscopy. Our results show that the emergence of chirality is mediated by electrostatic interactions and significantly enhanced by hydrophobic effects. This chiral chemical effect can be suppressed and even reversed by opposing a macroscopic physical influence, such as vortical stirring. This result gives evidence for the crucial role of hydrodynamic effects in supramolecular aggregation. 相似文献
76.
S=1/2 One‐Dimensional Random‐Exchange Ferromagnetic Zigzag Ladder,Which Exhibits Competing Interactions in a Critical Regime
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Susan N. Herringer Dr. Mercè Deumal Dr. Jordi Ribas‐Arino Prof. Juan J. Novoa Prof. Christopher P. Landee Prof. Jan L. Wikaira Prof. Mark M. Turnbull 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8355-8362
The synthesis, crystal structure, and magnetic properties (from a combined experimental and First‐Principles Bottom‐Up theoretical study) of the new compound catena‐dichloro(2‐Cl‐3Mpy)copper(II), 1 , [2‐Cl‐3Mpy=2‐chloro‐3‐methylpyridine] are described and rationalized. Crystals of 1 present well isolated magnetic 1D chains (no 3D order was experimentally observed down to 1.8 K) and magnetic frustration stemming from competing ferromagnetic nearest‐neighbor (JNN) interactions and antiferromagnetic next‐nearest neighbor (JNNN) interactions, in which α=JNNN/JNN <?0.25. These magnetic interactions give rise to a unique magnetic topology: a two‐leg zigzag ladder composed of edge‐sharing up‐down triangles with antiferromagnetic interactions along the rails and ferromagnetic interactions along the zigzag chain that connects the rails. Crystals of 1 also present a random distribution of the 2‐Cl‐3Mpy groups, which are arranged in two different orientations, each with a 50 % occupancy. This translates into a random static structural disorder within each chain by virtue of which the value of the JNN magnetic interactions can randomly take one of the following three values: 53, 36, and 16 cm?1. The structural disorder does not affect the JNNN value, which in all cases is approximately ?9 cm?1. A proper statistical treatment of this disorder provides a computed magnetic susceptibility curve that reproduces the main features of the experimental data. 相似文献
77.
Dr. Jordi Poater Prof. Dr. Miquel Solà Prof. Dr. Clara Viñas Prof. Dr. Francesc Teixidor 《Angewandte Chemie (International ed. in English)》2014,53(45):12191-12195
A bridge between classical organic polycyclic aromatic hydrocarbons (PAH) and closo borohydride clusters is established by showing that they share a common origin regulated by the number of valence electrons in an electronic confined space. Application of the proposed electronic confined space analogy (ECSA) method to archetypal PAHs leads to the conclusion that the 4n+2 Wade–Mingos rule for three‐dimensional closo boranes is equivalent to the (4n+2)π Hückel rule for two‐dimensional PAHs. More importantly, use of ECSA allows design of new interesting fused closo boranes which can be a source of inspiration for synthetic chemists. 相似文献
78.
Zihui Li Hiroaki Sai Kwan Wee Tan Tobias N. Hoheisel Sol M. Gruner Ulrich Wiesner 《Journal of Sol-Gel Science and Technology》2014,70(2):286-291
A novel strategy for fabrication of ordered ceramic–metal nanocomposites was demonstrated by multifunctional block copolymer/metal nanoparticle self-assembly. Hybrid organic–inorganic block copolymer poly(3-methacryloxypropyl-T8-heptaisobutyl-polyhedral oligomeric silsesquioxane-block-N,N-dimethylaminoethyl methacrylate) was synthesized and used as a bi-functional structure directing agent for ligand-stabilized platinum nanoparticles to form ordered organic–inorganic nanocomposites with dense loading of inorganic species in both microphase separated domains. Subsequently, thin films of the hybrid material were converted to ordered silica (ceramic)–platinum (metal) nanocomposites via UV-assisted ozonolysis. This is the first time ordered ceramic–metal nanocomposites were achieved through a bottom-up approach, opening up opportunities for the design and synthesis of a broad range of ordered inorganic–inorganic nanocomposites. 相似文献
79.
Solène Béchu Muriel Bouttemy Jackie Vigneron Daniel Lincot Jean-François Guillemoles Arnaud Etcheberry 《Surface and interface analysis : SIA》2020,52(12):975-979
Cu(In,Ga)Se2 absorbers were immerged in deionized water for different times, and specific chemical evolutions were monitored thanks to X-ray photoemission spectroscopy. Cu(In,Ga)Se2 related dissolution products were studied in water through induced coupled plasma optical emission spectroscopy. From those analyses, specific surface network disorganization was observed, with Cu migration towards the surface, leading to different kinetics of oxidation and dissolution for each element that could be quantified. 相似文献
80.
Zghal Imen Farjas Jordi Camps Jaume Sánchez-Rodríguez D. Dammak Mohamed Roura-Grabulosa Pere 《Journal of Thermal Analysis and Calorimetry》2020,140(5):2087-2096
Journal of Thermal Analysis and Calorimetry - Thermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are... 相似文献