title: A hybrid mechanism in chiral discrimination induced by crystallization of supramolecular compounds.
abstract: 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.
authors.affiliation: 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.
authors.forename: Youness
authors.initials: Y
authors.lastname: Amharar
authors.forename: Arnaud
authors.initials: A
authors.lastname: Grandeury
authors.forename: Morgane
authors.initials: M
authors.lastname: Sanselme
authors.forename: Samuel
authors.initials: S
authors.lastname: Petit
authors.forename: Gérard
authors.initials: G
authors.lastname: Coquerel