排序方式: 共有27条查询结果,搜索用时 125 毫秒
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We have applied crystal structure prediction methods to understand and predict the formation of a DMSO solvate of the anti-convulsant drug carbamazepine (CBZ), in which the DMSO molecules are disordered. Crystal structure prediction calculations on the 1:1 CBZ:DMSO solvate revealed the generation of two similar low energy structures which differ only in the orientation of the DMSO molecules. Analysis of crystal energy landscapes generated at 0 K suggests the possibility of solvent disorder. A combined computational and experimental study of the changes in the orientation of the DMSO within the crystal structure revealed that the nature of the disorder changes with temperature. At low temperature, the DMSO disorder is static whilst at high temperature the DMSO configurations can interconvert by a 180° rotation of the DMSO molecules within the lattice. This 180° rotation of the DMSO molecules drives a phase change from a high temperature dynamically disordered phase to a low temperature phase with static disorder. Crystallisation of a DMSO solvate of the related molecule epoxycarbamazepine resulted in a different degree of DMSO disorder in the crystal structure, despite the similarity of the carbamazepine and epoxycarbamazepine molecules. We believe consideration of disorder and its contribution to entropy and crystal free energies at temperature other than 0 K is fundamental for the accuracy of future energy rankings in crystal structure prediction calculations of similar solvated structures. 相似文献
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Cruz-Cabeza AJ Day GM Jones W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(29):8830-8836
We report on the crystal structure of urea (U) with acetic acid (A), its physical stability and its predictability using computational methods. The crystal structure of urea:acetic acid (U:A) shows hydrogen-bond ribbons and a 1:2 stoichiometry. Crystal structure prediction calculations are presented for two sets of U:A stoichiometries: 1:1 and 1:2. A 1:3 stoichiometry is also partially explored by means of a synthon approach. The calculated lattice energies, along with hydrogen-bond patterns, of crystal structures predicted with the three stoichiometries are presented and analysed to provide a rationalisation for the stoichiometry observed. Exploring stoichiometric diversity using computational methods provides a tool for the rationalisation of stoichiometry preferences in crystalline multicomponent systems and a first step towards their prediction. 相似文献
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CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Transforming Computed Energy Landscapes into Experimental Realities: The Role of Structural Rugosity
Dr. Riccardo Montis Prof. Roger J. Davey Sarah E. Wright Dr. Grahame R. Woollam Dr. Aurora J. Cruz-Cabeza 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20537-20540
We exploit the possible link between structural surface roughness and difficulty of crystallisation. Polymorphs with smooth surfaces may nucleate and crystallise more readily than polymorphs with rough surfaces. The concept is applied to crystal structure prediction landscapes and reveals a promising complementary way of ranking putative crystal structures. 相似文献
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A procedure is explained to determined the amount of several pairs of diametrical loads applied to the outside boundary of
a ring when stresses at selected points of the inside or outside boundaries are known. Coefficients of influence are used,
following an approach similar to the one presented in a previous paper. Examples of application are given and the possible
increase in precision is shown when the number of points of measurements is larger than the number of loads to be determined. 相似文献