Unité de Cristallogenèse, Sciences et Méthodes Séparatives-UPRES EA 3233, IRCOF IMR 4114, Université de ROUEN, Rue Tesnière, F-76821 Mont Saint-Aignan Cedex, France.
J Phys Chem B. 2012 May 24;116(20):6027-40. doi: 10.1021/jp301708v. Epub 2012 May 10.
Host-guest complexes formed in aqueous medium between permethylated β-cyclodextrin (TMβ-CD) and racemic 1-(p-fluorophenyl)ethanol (p-F-PE) are studied. The crystalline complexes are characterized and their crystal structures are determined, revealing two sets of solid phases with specific abilities for chiral discrimination: on the one hand, a stable complete solid solution with two independent complexes per asymmetric unit exhibits a limited chiral recognition, and on the other hand, two metastable partial solid solutions with unusual 1:2 host-guest stoichiometries behave as diastereomeric complexes. The structural features of the 1:2 complexes and their study by means of molecular modeling show that these solid phases, described as cocrystals formed between one host-guest inclusion complex and one non-engulfed p-F-PE molecule, present a significant chiral discrimination occurring both inside the cyclodextrin and outside the macrocycle in a crystal lattice cavity. Therefore, the enantioselectivity observed in this system results from an interplay between molecular inclusion in the cyclodextrin and lattice inclusion. To our knowledge, it is the first report of such a hybrid mechanism. An overview of the crystal structures of the literature containing TMβ-CD is also achieved and allows their classification in four structural groups in relation to their crystal packing features.
在水相中形成的主客体配合物，在全甲基化β-环糊精（TMβ-CD）和外消旋 1-（对氟苯基）乙醇（p-F-PE）之间进行研究。对结晶配合物进行了表征，并确定了它们的晶体结构，揭示了两种具有特定手性识别能力的固相：一方面，每个不对称单元具有两个独立配合物的稳定完全固溶体表现出有限的手性识别，另一方面，两种具有不寻常 1:2 主客体化学计量比的亚稳部分固溶体表现为非对映异构体配合物。1:2 配合物的结构特征及其通过分子建模的研究表明，这些固相，被描述为在一个主客体包合物和一个未被包合的 p-F-PE 分子之间形成的共晶，在环糊精内部和大环外部的晶格空腔中都表现出显著的手性识别。因此，在该体系中观察到的对映选择性是分子包合在环糊精和晶格包合之间相互作用的结果。据我们所知，这是首次报道这种混合机制。还实现了包含 TMβ-CD 的文献的晶体结构概述，并根据其晶体堆积特征将它们分类为四个结构组。
