pH controlled emission of ruthenium(II)–tris–bipyridine complexes

Ruthenium tris–2,2′-bipyridine complexes 1, 2 and 3 have additional non-coordinated basic pyridine or bipyridine moieties within their structures. Upon protonation they reversibly become suitable acceptor sites for intramolecular photoinduced electron transfer by which the ruthenium tris–2,2′-bipyridine emission is quenched. The pH dependent emission was studied in organic solvents and water.