A brief comparison of seven straightforward methods for molecular crystal-volume estimation revealed that their precisions are comparable. A chiral diamine, N
2,N
3-bis[2,6-bis(propan-2-yl)phenyl]butane-2,3-diamine, C28H44N2, has been used to illustrate the application of the methods. Three stereoisomers of the diamine cocrystallize in the centrosymmetric space group P21/c with Z′ = 1.5. The molecules occupying general positions are RR and SS, whereas that residing on an inversion center is meso. This is one of only ten examples of three stereoisomers with two asymmetric atoms cocrystallizing together reported to the Cambridge Structural Database (CSD). The conformations of the SS/RR and meso molecules differ considerably and lead to statistically significantly different C(asymmetric)—C(asymmetric) bond lengths in the diastereomers. An advanced Python script-based CSD searching technique for chiral compounds is presented.
对七种直接估算分子晶体体积的方法进行简要比较后发现,它们的精确度相当。一种手性二胺 N
2,N
3-双[2,6-双(丙-2-基)苯基]丁烷-2,3-二胺(C28H44N2)的手性二胺来说明这些方法的应用。二胺的三种立体异构体在 Z′ = 1.5 的中心对称空间群 P21/c 中共晶。占据一般位置的分子为 RR 和 SS,而位于反转中心的分子为 meso。这是剑桥结构数据库(CSD)中仅有的十个含有两个不对称原子的三种立体异构体结晶在一起的例子之一。SS/RR 和中间分子的构象差异很大,导致非对映异构体中的 C(不对称)-C(不对称)键长度在统计上有显著差异。本文介绍了一种基于 Python 脚本的手性化合物 CSD 高级搜索技术。