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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Definitive structural characterization of the conventional low-temperature host structure in urea inclusion compounds
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Definitive structural characterization of the conventional low-temperature host structure in urea inclusion compounds

机译：尿素夹杂物中常规低温主体结构的确定结构表征

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摘要

Structural properties of the 1,10-dibromodecane/urea and 1,12-dibromododecane/urea inclusion compounds have been determined by single crystal X-ray diffraction for both the high-and low-temperature phases. In the high-temperature phase both inclusion compounds have the conventional hexagonal urea tunnel structure, with substantial orientational disorder of the guest molecules. In the low-temperature phase the urea tunnel structure distorts to an orthorhombic structure, based on a distorted form of the orthohexaganol cell of the high-temperature structure and with the loss of the C centre. Within this tunnel structure there is evidence that the guest molecules have a narrow distribution of orientations (with respect to rotation about the tunnel axis) and the preferred orientation of the guest molecules correlates well with the observed distortion of the host tunnel. This represents the first accurate and reliable report of the conventional low-temperature structure of urea inclusion compounds. Previous powder X-ray diffraction studies have confirmed that the host structure in the low-temperature phase of 1,10-dibromodecane/urea is the same as that in the low-temperature phase of the alkane/urea inclusion compounds.
机译：通过高温和低温相的单晶X射线衍射已确定了1,10-二溴代甘蔗/脲和1,12-二溴十二烷/脲包合物的结构性质。在高温相中，两种包合物均具有常规的六边形尿素隧道结构，且客体分子的取向紊乱。在低温阶段，尿素隧道结构基于高温结构的原六醇单元的变形形式和C中心的损失而变形为正交结构。在该隧道结构内，有证据表明，客体分子的取向分布较窄（相对于围绕隧道轴线的旋转），并且客体分子的优选取向与所观察到的主体隧道的畸变良好相关。这是尿素夹杂物的常规低温结构的第一个准确而可靠的报告。先前的粉末X射线衍射研究已经证实，在1,10-二溴代甘蔗/尿素的低温相中的主体结构与在烷烃/尿素夹杂物的低温相中的主体结构相同。

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