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961.
Christian Logemann Daniel Gunzelmann Prof. Dr. Thorsten Klüner Prof. Dr. Jürgen Senker Prof. Dr. Mathias S. Wickleder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15495-15503
The reactions of group 14 tetrachlorides MCl4 (M=Si, Ge, Sn) with oleum (65 % SO3) at elevated temperatures lead to the unique complex ions [M(S2O7)3]2?, which show the central M atoms in coordination with three chelating S2O72? groups. The mean distances M? O within the anions increase from 175.6(2)–177.5(2) pm (M=Si) to 186.4(4)–187.7(4) pm (M=Ge) to 201.9(2)–203.5(2) pm (M=Sn). These distances are reproduced well by DFT calculations. The same calculations show an increasing positive charge for the central M atom in the row Si, Ge, Sn, which can be interpreted as the decreasing covalency of the M? O bonds. For the silicon compound (NH4)2[Si(S2O7)3], 29Si solid‐state NMR measurements have been performed, with the results showing a signal at ?215.5 ppm for (NH4)2[Si(S2O7)3], which is in very good agreement with theoretical estimations. In addition, the vibrational modes within the [MO6] skeleton have been monitored by Raman spectroscopy for selected examples, and are well reproduced by theory. The charge balance for the [M(S2O7)3]2? ions is achieved by monovalent A+ counter ions (A=NH4, Ag), which are implemented in the syntheses in the form of their sulfates. The sizes of the A+ ions, that is, their coordination requirements, cause the crystallographic differences in the crystal structures, although the complex [M(S2O7)3]2? ions remain essentially unaffected with the different A+ ions. Furthermore, the nature of the A+ ions influences the thermal behavior of the compounds, which has been monitored for selected examples by thermogravimetric differential thermal analysis (DTA/TG) and XRD measurements. 相似文献
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Dr. Michael L. Lejkowski Dr. Ronald Lindner Dr. Takeharu Kageyama Dr. Gabriella É. Bódizs Dipl.‐Chem. Philipp N. Plessow Dr. Imke B. Müller Dr. Ansgar Schäfer Dr. Frank Rominger Prof. Dr. Peter Hofmann Dr. Cornelia Futter Dr. Stephan A. Schunk Dr. Michael Limbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(44):14017-14025
For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C1 building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO2, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal. 相似文献
966.
Dr. Andreas Kafizas Prof. Claire J. Carmalt Prof. Ivan P. Parkin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13048-13058
It has often been suggested that anatase–rutile mixtures/composites synergistically enhance photocatalysis. However, in the case of dense thin‐films containing an intimate mix of both anatase and rutile phases, such an effect has not been observed. In synthesising combinatorial films with graded film thickness and phase, and applying established photocatalytic mapping methods, we were able to assess how dense thin‐films of intimately mixed anatase–rutile mixtures affect photocatalytic performance. We found that no photocatalytic synergy between anatase–rutile composites (29≤rutile %≤83) within such dense thin‐film systems exists. In fact, an increased presence of rutile caused the photocatalytic activity to fall. This was explained by the unfavourable energetics in the multiple electron transfers required between several neighbouring rutile and anatase sites for the photo‐generated electron to reach the material’s surface; encouraging the trapping of electrons within the bulk and increasing the likelihood of charge recombination. The decrease in photocatalytic activity was found to vary linearly with rutile component. 相似文献
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Dr. Tana Koudelakova Dr. Radka Chaloupkova Dr. Jan Brezovsky Dr. Zbynek Prokop Dr. Eva Sebestova Dr. Martin Hesseler Dr. Morteza Khabiri Maryia Plevaka Daryna Kulik Dr. Ivana Kuta Smatanova Dr. Pavlina Rezacova Dr. Rudiger Ettrich Prof. Uwe T. Bornscheuer Prof. Jiri Damborsky 《Angewandte Chemie (International ed. in English)》2013,52(7):1959-1963
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Nanorod‐assembled FHA microspheres with different F contents were for the first time prepared through a facile one‐step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self‐assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self‐assembled into sphere‐like sturctures at high pH conditions and rod‐like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca2+ release kinetics from EDTA‐Ca‐Na2 at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self‐assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability. 相似文献