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651.
Oliver Clemens Melanie Kuhn Robert Haberkorn 《Journal of solid state chemistry》2011,184(11):2870-2876
The oxyfluorides La1−xSrxFeO3−xFx have been prepared by fluorination of the precursor oxides La1−xSrxFeO3−δ via a low temperature route using poly(vinylidene fluoride) (PVDF). The structures of the oxides and oxyfluorides were investigated in detail by the Rietveld analysis of powder diffraction data. The oxyfluorides crystallize in the space group Pnma for 0<x≤0.9 (SrFeO2F itself is cubic, space group Pm-3m) and show a sort of two-step structural distortion for decreasing x. Furthermore, a structural comparison of the oxyfluorides with the oxides is given, revealing an increase of the volume per La1−xSrxFeX3 unit during fluorination, of which the magnitude highly depends on the value of x. 相似文献
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Achim Weber Melanie Dettling Herwig Brunner Günter E. M. Tovar 《Macromolecular rapid communications》2002,23(14):824-828
Ultrasensitive isothermal titration calorimetry was used to generate thermodynamic data to assess the binding properties of molecularly imprinted polymer microgels. Microgels were imprinted using L ‐boc‐phenylalanine anilide (L ‐BFA) and then utilized in binding experiments with a variety of probe molecules, structurally closely related to the template molecule. Significant differences were observed between the binding enthalpy of the original template L ‐BFA and those of D ‐BFA, L ‐boc‐phenylalanine, L ‐boc‐tryptophane, and L ‐boc‐tyrosine. 相似文献
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Reinhold Tacke Rüdiger Bertermann Andreas Biller Olaf Dannappel Martin Penka Melanie Pülm Reiner Willeke 《无机化学与普通化学杂志》2000,626(5):1159-1173
The syntheses of the zwitterionic spirocyclic λ5Si‐silicates 7–14 are described. The chiral zwitterions contain a pentacoordinate (formally negatively charged) silicon atom and a tetracoordinate (formally positively charged) nitrogen atom, the ate and onium center being connected by an alkylene group. The zwitterions each contain two identical bidentate diolato(2–) ligands that formally derive from acetohydroximic acid or benzohydroximic acid. The stereochemistry and dynamic behavior of these compounds were investigated by experimental and theoretical methods. For this purpose, the zwitterionic λ5Si‐silicates 7–14 were studied by solution (1H, 13C, 29Si) and solid‐state (13C, 15N, and 29Si CP/MAS) NMR experiments. In addition, compounds 7 , 8 , 10 , 11 , and 13 were structurally characterized by single‐crystal X‐ray diffraction. The dynamic behavior (intramolecular enantiomerization) of 7 and 13 in solution was studied by VT 1H NMR experiments. These experimental studies were completed by ab initio investigations of the related anionic model species 15 . The chiral compounds 7–14 exist as (λ)‐ and (δ)‐enantiomers in the solid state and in solution. The trigonal‐bipyramidal structure of the respective Si‐coordination polyhedra, with the two carbon‐linked oxygen atoms in the axial sites, is the energetically most favorable one. The (λ)‐ and (δ)‐enantiomers of 7–14 are configurationally stable in solution on the NMR time scale ([D6]DMSO, room temperature). They undergo an intramolecular (λ)/(δ)‐enantiomerization (twist‐type mechanism), with an activation free enthalpy of δG{ = 72–73 kJ mol–1 (experimentally established for 7 and 13 ; calculated energy barrier for the model species 15 : 66.0 kJ mol–1). 相似文献
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