STRUCTURAL ASPECTS OF UREA INCLUSION-COMPOUNDS AND THEIR INVESTIGATION BY X-RAY-DIFFRACTION - A GENERAL DISCUSSION
STRUCTURAL ASPECTS OF UREA INCLUSION-COMPOUNDS AND THEIR INVESTIGATION BY X-RAY-DIFFRACTION - A GENERAL DISCUSSION
复制标题
DOI：
10.1039/ft9908602985
复制
发表时间：
1990-09-07
期刊：
影响因子：
--
通讯作者：
THOMAS, JM
中科院分区：
文献类型：
--
作者：
HARRIS, KDM;THOMAS, JM
主要通过单晶 X 射线衍射研究了几种脲包合物（“客体”物种的身份不同）的结构方面。本文讨论了这些不同系统共有的一般结构特征。由于主体（脲）和客体分子的结构周期性通常不相称，因此可以方便地认为脲包合物由可区分的（尽管不是独立的）主体和客体子结构组成。例如，主体子结构用不相称调制的“基本主体结构”来表示。基本结构具有三维周期性，可以使用常规晶体学原理进行处理。不相称的调制描述了由主客体相互作用引起的对基本主体结构的结构扰动。类似地，客体子结构被认为是“基本客体结构”，它经历了由主体子结构介导的不相称的调制。这些基本的结构概念被开发并用作合理化脲包合物的 X 射线衍射图的基础。平均基本主体结构是通过常规衍射技术在室温下测量的单晶 X 射线衍射数据确定的。这种结构在所研究的每种化合物中本质上是相同的，并且包含客体分子位于其中的线性、平行、不相交的通道（隧道）。另一方面，基本客体结构的晶体学特征主要取决于客体的特性。不同脲包合物中客体子结构的完整结构细节将在未来的出版物中给出。
Structural aspects of several urea inclusion compounds (differing in the identity of the ‘guest’ species) have been investigated, principally by single-crystal X-ray diffraction. This paper discusses the general structural features that are common to these different systems. Since the structural periodicities of the host (urea) and guest molecules are generally incommensurate, it is convenient to consider the urea inclusion compound to be composed of distinguishable, although not independent, host and guest substructures. The host substructure, for example, is represented in terms of an incommensurately modulated ‘basic host structure’. The basic structure possesses three-dimensional periodicity, and can be treated using conventional crystallographic principles. The incommensurate modulation describes structural perturbations to the basic host structure which arise from host–guest interaction. Similarly, the guest substructure is considered in terms of a ‘basic guest structure’ which experiences an incommensurate modulation mediated by the host substructure. These fundamental structural concepts are developed and used as a basis for rationalizing the X-ray diffraction patterns of urea inclusion compounds.The average basic host structure has been determined from single-crystal X-ray diffraction data measured, at room temperature, via conventional diffractometric techniques. This structure is essentially the same in each compound studied, and contains linear, parallel, non-intersecting channels (tunnels) within which the guest molecules are located. The crystallographic characteristics of the basic guest structure, on the other hand, depend critically upon the identity of the guest. Full structural details of the guest substructures in the different urea inclusion compounds will be given in future publications.