Reactivity of redox-active guests trapped inside molecular capsules

Abstract

Inclusion of guests inside molecular capsules may have pronounced effects on their chemical reactivity. This article provides a quick summary of research on the electrochemical reactivity of encapsulated redox-active guests. A brief account of the results obtained with simple hosts, such as cyclodextrins and cucurbiturils, starts the article. However, these hosts can only provide partial encapsulation. Most of the article is devoted to the results obtained by the authors' group on the inclusion of ferrocene, cobaltocenium, and tetrathiafulvalene in molecular capsules formed by cavitand-type ligands, which give rise to supramolecular assemblies that provide full encapsulation. In general terms, trapping of redox-active centers inside molecular capsules leads to a substantial attenuation of their electrochemical kinetics, which results in electrochemically silent properties in extreme cases. However, the magnitude of this kinetic attenuation cannot be rationalized by simple criteria based on the overall size of the supramolecular assembly. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.