Identification and characterization of redox sites in supramolecular systems and their relevance for the design of photoactive devices. Ru(II)/C-60-based donor-acceptor dyads

Two dyads consisting of a mononuclear or a dinuclear ruthenium complex cova lently linked to a fullerenopyrrolidine through a rigid androstane spacer, have been prepared through azomethine ylide cycloaddition to C-60. Electroc hemical and photophysical studies revealed that ground-state electronic int eractions between the dinuclear ruthenium chromophore and the fullerenopyrr olidine moiety are small. The redox series observed for the dyads correspon d to the superimposition of the reduction patterns of the fullerene core an d of the Ru(II)-bipyridine moieties. The results of the electrochemical inv estigation allow us to rationalize the photophysical behaviour of the two s pecies by identifying the thermodynamically allowed and forbidden routes fo r the deactivation of the Ru-based metal-to-ligand charge transfer (MLCT) e xcited state.