Ruthenium tris(bipyridine) complexes: Interchange between photons and electrons in molecular-scale devices and machines

This review deals with a very peculiar molecule, [Ru(bpy)3]2+ (bpy: 2,2′-bipyridine), and its interaction with photons and electrons. We summarize the properties that make [Ru(bpy)3]2+ and related compounds a unique family of “clever” molecules which find application as components of chemical species capable of processing optical and electrical signals to perform a variety of interesting functions. Examples discussed in the article, that showcase the realization of these concepts with molecular and supramolecular systems, include molecular wires, switches, antennas and mechanical machines.