Spectroscopic and electrochemical properties of ruthenium(II) polypyridyl complexes

Luminescent mixed-ligand ruthenium(II) complexes of type [Ru(bpy)2L]2+ (where bpy = 2,2′-bipyridine, L = 3,3′-dicarboxy-2,2′-bipyridine 1; 4,4′-dicarboxy-2,2′-bipyridine 2; or 5,5′-dicarboxy-2,2′-bipyridine 3) were synthesized. Their photophysical, acid–base and electrochemical properties were investigated. The emission lifetime for 2 was the longest, and the emission quantum yield was the highest for 2. This reveals that the positions of the carboxylic acids in the 2,2′-bipyridine ligand had an important influence on the photophysical and electrochemical properties of the complexes.