Fullerene polypyridine ligands: Synthesis, ruthenium complexes, and electrochemical and photophysical properties

Fullerene coordination ligands bearing one bipyridine or terpyridine unit were synthesized, and their coordination to ruthenium(II) formed linear rod-like donor-acceptor systems. Steady-state fluorescence of [Ru(bpy)(2)-(bpy-C-60)](2+) showed a rapid solvent-dependent, intramolecular quenching of the ruthenium(II) MLCT excited state. Time-resolved flash photolysis in CH3CN revealed characteristic transient absorption changes that have been ascribed to the formation of the C-60 triplet state, suggesting that photoexcitation of [Ru(bpy)(2)(bpy-C-60)](2+) results in a rapid intramolecular transduction of triplet excited state energy. The electrochemical studies on both [Ru(bpy)(2)(bpy-C-60)](2+) and [Ru(tpy)(tPY-C-60)](2+) indicated electronic coupling between the metal center and the fullerene core.