Tetrachlorobenzenes represent one of the best known, but not yet fully understood, group of isomers of the structure–melting point relationship. The differences in melting temperatures of these structurally related compounds were rationalized in terms of the hierarchy and nature of formed noncovalent interactions, and the molecular aggregation that is influenced by molecular symmetry. The highest melting point is associated with the highly symmetric 1,2,4,5‐tetrachlorobenzene isomer. The structures of less symmetrical 1,2,3,4‐tetrachlorobenzene and 1,2,3,5‐tetrachlorobenzene, determined at 270 and 90 K, show a distinct pattern of halogen bonds, characterized by the different numbers and types of interactions. The evolution of Cl…Cl/H distances with temperature indicates the attractive character of intermolecular interactions and their importance to the structural and thermodynamic parameters of isomeric compounds. The favoured Cl…Cl halogen bonds were found to play a decisive role in differentiating the melting temperatures of tetrachlorobenzene isomers. It was also found that, besides the molecular symmetry and ability to form specific intermolecular interactions, both the type and the distribution of interactions are the important factors responsible for the melting behaviour of the studied isomers. The observed preferences, in tetrachlorobenzenes, for the formation of specific noncovalent interactions correspond to the distribution of calculated partial atomic charges and to the magnitudes of electrostatic potential on the molecular surfaces as well as correlate with the enthalpy of melting parameters.

中文翻译：

---

四氯苯异构体的熔点，分子对称性和聚集性：卤素键的作用。

四氯苯代表结构-熔点关系的最著名但尚未完全理解的异构体之一。根据所形成的非共价相互作用的层次和性质以及受分子对称性影响的分子聚集，可以合理化这些结构相关化合物的熔融温度差异。最高熔点与高度对称的1,2,4,5-四氯苯异构体有关。在270和90 K下测定的不太对称的1,2,3,4-四氯苯和1,2,3,5-四氯苯的结构表现出独特的卤素键模式，其特征是相互作用的数量和类型不同。Cl…Cl / H距离随温度的变化表明分子间相互作用的诱人特性及其对异构化合物的结构和热力学参数的重要性。发现偏爱的Cl…Cl卤素键在区分四氯苯异构体的熔融温度方面起决定性作用。还发现，除了分子对称性和形成特定分子间相互作用的能力以外，相互作用的类型和分布都是导致所研究的异构体的熔融行为的重要因素。在四氯苯中观察到的偏好