The influence of bridging ligand (BL), spectator ligand (LL), and solvent on the photophysical properties of the MLCT state has been assessed in a series of mono- and binuclear polypyridyl complexes of Ru(II); {[(LL)2Ru]n(BL)}2,n+ (n = 1, 2; BL = 2,2′- bipyrimidine (bpym), 2,3-bis(2-pyridyl)pyrazine (dpp); LL = a substituted 2,2′-bipyridine (bpy), 1, 10-phenanthroline (phen)). A comparative study of the two series of complexes with dpp or bpym as the bridging ligand allows some of the reported anomalies in the behavior of the latter series of complexes to be explained. Features in the excited-state absorption spectra of the ligand-bridged binuclear complexes are also reported. Chemical and photochemical oxidation of the binuclear complexes from the (II, II) state to (II, III) and (III, III) states are examined. Complexes in the (III, III) state are unstable and rapidly cleave into monomeric components. © 1990, American Chemical Society. All rights reserved.