A thermally stable pH-responsive "supramolecular buckle" based on the encapsulation of 4-(4-aminophenyl)-N-methylpyridinium by cucurbit[8]uril

Supramolecular building blocks that can respond to external stimuli are the basis for the fabrication of responsive materials. However, those that can be used in aqueous media and at elevated temperatures are extremely limited. In this work, a cucurbit[8]uril(CB[8])-based host-guest system has been developed. It exhibits excellent response to the change of pH by forming a thermally stable 1 : 2 host-guest complex under neutral conditions and transforming into a 1 : 1 complex by releasing one guest molecule in the presence of an acid. This transformation makes this system serve as a useful "supramolecular buckle", which can fasten and unfasten two components. These features endow it with great potential in fabricating pH-responsive materials in aqueous media over a wide temperature range.