Self-assembly of [2]pseudorotaxanes based on pillar[5]arene and bis(imidazolium) cations

A simple bis(imidazolium) dication, 1,4-bis[N-(N'-hydroimidazolium)] butane, can act as a new template for formation of [2] pseudorotaxane with pillar[5] arene, in which the dethreading/rethreading process can be controlled by addition of base and acid. The effect on the association constant of both the solvent and counterion is also described.