single-crystal X-ray diffraction

单晶 X射线衍射
  • 文章类型: Journal Article
    利用结晶海绵{[(ZnI2)3(tpt)2·x(溶剂)]n}方法可以表征新型合成有机油。13种相关分子吸附物提供的系统的结构差异和官能团的多样性提供了对客体结构之间关系的详细定量理解,它的构象,以及与相邻客人和宿主框架采用的分子间相互作用的类型。此分析扩展为评估这些因素与特定分子结构阐明的所得质量指标的联系。
    Utilization of the crystalline sponge {[(ZnI2)3(tpt)2·x(solvent)]n} method has enabled characterization of a novel family of synthetic organic oils. The systematic structural differences and diversity of functional groups offered by 13 related molecular adsorbates provide a detailed quantitative understanding of the relationship between the guest structure, its conformation, and the type of intermolecular interactions adopted with neighbouring guests and the host framework. This analysis is extended to assess the connection of these factors to the resulting quality indicators for a particular molecular structure elucidation.
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  • 文章类型: Journal Article
    通常使用单独的样品收集单晶X射线和中子衍射数据。当在高压下研究样品时,这是一个缺点,因为在两个单独的实验中很难达到完全相同的压力,特别是如果中子数据是使用劳厄方法收集的,其中无法测量晶胞尺寸的精确绝对值来检查压力的接近程度。在这项研究中,衍射数据已收集在相同的条件下对硫酸铜(II)五水合物的相同样品,使用常规的实验室衍射仪和X射线源进行X射线测量,并在ANSTO设施中使用Koala单晶Laue衍射仪进行中子测量。样本,尺寸为0.40×0.22×0.20mm3,并保持在0.71GPa的压力下,包含在一个微型的美林-巴西特钻石砧座细胞中。通过微型电池的金属体以及钻石的高穿透性衍射中子束产生了适合结构细化的数据,并补偿了X射线测量的低完整性,由于样品的三斜对称和细胞对倒数空间的遮蔽,这一比例仅为24%。这两个数据集组合在一个单一的“XN”结构细化中,其中所有原子,包括H原子,用各向异性位移参数进行了细化。与分别使用X射线或中子数据进行细化相比,在XN细化中,结构参数的精度提高了50%。
    Single-crystal X-ray and neutron diffraction data are usually collected using separate samples. This is a disadvantage when the sample is studied at high pressure because it is very difficult to achieve exactly the same pressure in two separate experiments, especially if the neutron data are collected using Laue methods where precise absolute values of the unit-cell dimensions cannot be measured to check how close the pressures are. In this study, diffraction data have been collected under the same conditions on the same sample of copper(II) sulfate pentahydrate, using a conventional laboratory diffractometer and source for the X-ray measurements and the Koala single-crystal Laue diffractometer at the ANSTO facility for the neutron measurements. The sample, of dimensions 0.40 × 0.22 × 0.20 mm3 and held at a pressure of 0.71 GPa, was contained in a miniature Merrill-Bassett diamond-anvil cell. The highly penetrating diffracted neutron beams passing through the metal body of the miniature cell as well as through the diamonds yielded data suitable for structure refinement, and compensated for the low completeness of the X-ray measurements, which was only 24% on account of the triclinic symmetry of the sample and the shading of reciprocal space by the cell. The two data-sets were combined in a single \'XN\' structure refinement in which all atoms, including H atoms, were refined with anisotropic displacement parameters. The precision of the structural parameters was improved by a factor of up to 50% in the XN refinement compared with refinements using the X-ray or neutron data separately.
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  • 文章类型: Journal Article
    A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3 perovskite was carried out over the wide temperature range 298-928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \\bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetric P4mm symmetry group, the difference in relative displacement between Pb and O along the c-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye-Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factor Ueq for O is observed in the vicinity of the transition point, while Ueq values for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘD for Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.
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  • 文章类型: Journal Article
    On the way towards the development of a synthetic route aimed at obtaining new methylsilanediol derivatives with an aminocarbonyl group in β to silicon (which may have a potential biological interest), we have synthesized, isolated and purified five diphenylic possible precursors, namely chloromethyl(methyl)diphenylsilane, 2-{[methyl(diphenyl)silyl]methyl}-1H-isoindole-1,3(2H)-dione, N-[(methyl(diphenyl) silanyl)-methyl]-benzamide, N-[(methyl(diphenyl)silyl)-methyl]-acetamide and N-[(methyl(diphenyl)silyl)-methyl]-formamide. The conformational landscape of the five species in this study are explored by means of DFT calculations at the B3LYP/6-311++G(∗∗) level. The theoretical molecular structures predicted are confirmed by the reproduction of their respective IR and Raman spectral profiles, that are completely assigned. Some evidence in the vibrational spectra points to the occurrence of conformational mixtures in the samples. Further, single-crystal X-ray diffraction has allowed the elucidation of the crystalline structure of 2-{[methyl(diphenyl)silyl]methyl}-1H-isoindole-1,3(2H)-dione.
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