Acid/Base-controlled supramolecular switch

A rotaxane-like complex incorporating a hydroquinone-intercepted acyclic po lyether chain terminated by tert-butylaniline rings and encircled by cyclob is(paraquat-p-phenylene) self-assembles spontaneously in acetonitrile solut ion from which it can be crystallized. Protonation of the nitrogen atoms of the guest is accompanied by the complete dissociation of the supramolecula r complex into its free components. Addition of a base restores the origina l equilibrium affording back the rotaxane-like complex.