Cooperative binding of cucurbit[n]urils and β-cyclodextrin to heteroditopic imidazolium-based guests

Abstract

Imidazolium-based guests containing two distinct binding epitopes are capable of binding beta-cyclodextrin and cucurbit[6/7]uril (CB) simultaneously to form heteroternary 1:1:1 inclusion complexes. In the final the hosts occupy binding sites disfavored in the binary complexes because of the chemically induced reorganization of the intermediate 1:1 aggregate. In addition, the reported guests are capable of binding two CBs to form either 1:2 or 1:1:1 ternary assemblies despite consisting of a single cationic moiety. Whereas the adamantane site binds CB solely via hydrophobic interactions, the CB unit at the butyl site is stabilized by a combination of hydrophobic and ion-dipole interactions.