Cucurbit[7]uril stabilization of a diarylmethane carbocation in aqueous solution

The stability of the 4,4′-bis(dimethylamino)diphenylmethane carbocation is significantly enhanced in aqueous solution by its inclusion in the cucurbit[7]uril host cavity. The formation of the host–guest complex (KCB[7] = 2.0 × 104 M−1) shifts the carbinol–carbocation equilibrium, maximizing the formation of the intensely blue carbocation to 90% at pH 5.2.