Department of Chemical and Biological Engineering , Princeton University , Princeton , New Jersey 08544 , United States.
Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506 , United States.
J Am Chem Soc. 2018 Jun 20;140(24):7519-7525. doi: 10.1021/jacs.8b01421. Epub 2018 Jun 8.
Polymorphism is pervasive in molecular solids. While computational predictions of the molecular polymorphic landscape have improved significantly, identifying which polymorphs are preferentially accessed and experimentally stable remains a challenge. We report a framework that correlates short intermolecular contacts with polymorphic stability. The presence of short contacts between neighboring molecules prevents structural rearrangement and stabilizes the packing arrangement, even when the stabilized polymorph is not enthalpically favored. In the absence of such intermolecular short contacts, the molecules have added degrees of freedom for structural rearrangement, and solid-solid polymorphic transformations occur readily. Starting with a series of core-halogenated naphthalene tetracarboxylic diimides, we establish this framework with the packing polymorphs of more than 20 compounds, ranging from molecular semiconductors to pharmaceutics and biological building blocks. This framework, widely applicable across molecular solids, can help refine computational predictions by identifying the polymorphs that are kinetically stable.
多晶型现象在分子固体中普遍存在。尽管对分子多晶型景观的计算预测已有显著改进，但确定哪些多晶型物优先被触及且在实验中稳定仍然是一个挑战。我们报告了一个将短分子间接触与多晶型稳定性相关联的框架。相邻分子之间短接触的存在可以防止结构重排，并稳定堆积排列，即使稳定的多晶型物在焓上不受青睐也是如此。在没有这种分子间短接触的情况下，分子具有更多的结构重排自由度，固态-固态多晶型转变很容易发生。从一系列核心卤代萘四羧酸二酰亚胺开始，我们用 20 多种化合物的堆积多晶型物来建立这个框架，范围从分子半导体到药物和生物建筑块。这个框架广泛适用于分子固体，可以通过识别动力学稳定的多晶型物来帮助改进计算预测。
