Viologen-cucurbituril host/guest chemistry - redox control of dimerizationversusinclusion

Abstract

Two calix[4]arene systems,C234+andC244+- where 2 corresponds to the number of viologen units and 3-4 corresponds to the number of carbon atoms connecting the viologen units to the macrocyclic core - have been synthesized and led to the formation of [3]pseudorotaxanes when combined with eitherCB[7]orCB[8]. The [3]pseudorotaxanes spontaneously dissociate upon reduction of the bipyridinium units as the result of intramolecular dimerization of the two face-to-face viologen radical cations.CB[7]andCB[8]-based [2]pseudorotaxanes containing monomeric viologen guest model compounds,MC32+andMC4+, do not undergo decomplexation and dimerization following electrochemical reduction of their bipyridinium units.