p-tert-Butylcalix[4]arene (1) crystals can selectively include one regioisomer from a mixture of the three regioisomers for eight kinds of disubstituted benzenes. In this study, the mechanisms for the guest selectivity in the inclusion of nitrotoluene, xylene, and cresol isomers, which were chosen as representative guests showing different guest selectivity, were investigated in detail. In the competitive inclusion of three regioisomers of nitrotoluene, xylene, and cresol, crystals of compound 1 selectively include p-nitrotoluene, p-xylene, and o-cresol, respectively. Time course of the change in isomer selectivity in the competitive inclusion experiment and comparison of thermogravimetric analysis profiles of the inclusion crystals with each of the isomers revealed that the selectivity for p-nitrotoluene and o-cresol was achieved under kinetic control, whereas the selectivity for p-xylene was achieved under thermodynamic control. X-ray crystallography of the inclusion crystals revealed that p-nitrotoluene and o-cresol form type A (host/guest = 1:1) inclusion crystals, in which a guest molecule is included in the cavity of a host molecule. On the other hand, o- and m-nitrotoluene and m- and p-cresol form thermodynamically stable type B (host/guest = 2:1) inclusion crystals, in which a guest molecule is included in a capsule constructed by gathering of two host molecules in a head to head manner. The selectivity for p-nitrotoluene and o-cresol could be explained by the effective host–guest interaction during the formation of type A inclusion crystals, which tends to be kinetically favored over the formation of type B inclusion crystals. X-ray structure analysis and Hirshfeld surface analysis of the inclusion crystals revealed that the inclusion of xylene isomers in the crystals of compound 1 resulted in the formation of type B inclusion crystals for all the three isomers. The CH−π interaction between the two methyl groups of the p-isomer and the benzene rings of the two host molecules encapsulating the isomer is the most effective. Therefore, the inclusion crystal with p-xylene is the most stable among the three isomers, resulting in p-isomer selectivity. In this way, the crystals of compound 1 precisely distinguish different disubstituted benzene isomers under kinetic or thermodynamic control by the virtue of various host–guest interactions with the guest substituents in the cavities of type A and type B inclusion crystals.

中文翻译：

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对叔丁基杯[4]芳烃晶体选择性包含双取代苯异构体的机理考虑

p -叔-Butylcalix [4]芳烃（1）的晶体可以选择性地包括从三个位置异构体的对8种二取代的苯的混合物中的一种区域异构体。在这项研究中，详细研究了包含硝基甲苯、二甲苯和甲酚异构体的客体选择性机制，这些异构体被选为具有不同客体选择性的代表性客体。在硝基甲苯、二甲苯和甲酚三种区域异构体的竞争包合物中，化合物1的晶体选择性地包括对硝基甲苯、对二甲苯和邻-甲酚，分别。竞争包合物实验中异构体选择性变化的时间过程以及包合物与每种异构体的热重分析曲线的比较表明，对硝基甲苯和邻甲酚的选择性是在动力学控制下实现的，而对于对二甲苯是在热力学控制下实现的。包合物的 X 射线晶体学显示对硝基甲苯和邻甲酚形成 A 型（主体/客体 = 1:1）包合物，其中客体分子包含在主体分子的空腔中。在另一方面，ö -和米硝基甲苯和米- 和对甲酚形成热力学稳定的 B 型（主客体 = 2:1）包合物，其中客体分子包含在由两个主体分子以头对头方式聚集而成的胶囊中。对硝基甲苯和邻甲酚的选择性可以通过在 A 型包合物形成过程中有效的主客体相互作用来解释，这在动力学上往往比 B 型包合物的形成更有利。包合物的X射线结构分析和Hirshfeld表面分析表明，化合物1的晶体中含有二甲苯异构体导致所有三种异构体都形成 B 型包合物。p-异构体的两个甲基与包裹该异构体的两个主体分子的苯环之间的 CH-π 相互作用是最有效的。因此，含有对二甲苯的包合物在三种异构体中最稳定，从而导致对异构体的选择性。通过这种方式，化合物1的晶体在动力学或热力学控制下，通过与 A 型和 B 型包合物空腔中客体取代基的各种主客体相互作用，精确区分不同的二取代苯异构体。