Multiple noncovalent interaction constructed polymeric supramolecular crystals: recognition of butyl viologen by para-dicyclohexanocucurbit[6]uril and α,α′,δ,δ′-tetramethylcucurbit[6]uril

Abstract

Binding interactions of butyl viologen (BV⁺) with para-dicyclohexanocucurbit[6]uril (Cy2Q[6]) and α,α′,δ,δ′-tetramethyl cucurbit[6]uril (TMeQ[6]) were investigated by ¹H NMR spectroscopy, isothermal titration calorimetry (ITC) and X-ray crystallography. In the solid state, the BV⁺ guest and both hosts form polymeric supramolecular crystals through multiple noncovalent interactions, including host–guest interaction, π–π stacking interaction, and metal–host coordination. In the aqueous solution, the butyl chain of BV⁺ was selectively encapsulated into the hosts Cy2Q[6] and TMeQ[6], while the bipyridinium group resides outside of the host portals, forming [2]pseudorotaxane. The ITC experiment indicates that the host–guest binding processes are exclusively enthalpy driven.