Cocrystal of 1,1-Dicyano-2-(4-hydroxyphenyl)-ethene with l-Proline and Induced Conformational Polymorphism of 1,1-Dicyano-2-(4-hydroxy- 3-methoxyphenyl)-ethene

Crystallization of 1,1-dicyano-2-(4-hydroxyphenyl)-ethene (I) and 1,1-dicyano-2-(4-hydroxy-3-methoxyphenyl)-ethene (II) with l-proline (III) and l-tartaric acid (IV) was carried out. Compound I formed cocrystals
with l-proline I·III. However, cocrystallization of II was unsuccessful; instead in the presence of III or IV formation
of two conformational polymorphs IIa and IIb was observed. In cocrystals I·III, hydrogen bonded chains of proline
molecules with molecules of I attached to them were found. Similar synthons were found in the literature in other
proline-containing crystals, and we believe that it is possible to use these acentric supramolecular associates in
crystal engineering of nonlinear optical materials. Possible reasons for the formation of two conformational polymorphs
of compound II are discussed based on the results of X-ray analysis, molecular and crystal structure energy
calculations, and thermal behavior of compound II.

本研究成功实现了1,1-二氰基-2-(4-羟基苯基)-乙烯（I）及1,1-二氰基-2-(4-羟基-3-甲氧基苯基)-乙烯（II）与L-脯氨酸（III）和L-酒石酸（IV）的结晶过程。化合物I与L-脯氨酸形成了I·III共结晶。然而，化合物II的共结晶未能实现；相反，在III或IV的存在下，观察到了IIa和IIb两种构象多形体的形成。在I·III共结晶中，发现了脯氨酸分子的氢键链与附着其上的I分子。在文献中，其他含脯氨酸的晶体中也发现了类似的合成子，我们相信，可以利用这些非中心超分子配位体在非线性光学材料的晶体工程中发挥重要作用。基于X射线分析、分子及晶体结构能量计算以及化合物II的热行为结果，讨论了化合物II形成两种构象多形体的可能原因。