Spectroscopy and photophysics of chloro-bis-bipyridyl complexes of ruthenium(II) with pyridine ligands

The absorption, luminescence, and luminescence excitation spectra of ruthenium(II) complexes cis-[Ru(bPY)(2)(L)Cl](+) [bpy = 2,2'-bipyridyl; L = NH3, pyrazine, pyridine, 4-aminopyridine, 4-picoline, isonicotinamide, 4-cyanopyridine, 4,4'-bipyridyl, or trans-1,2-bis(4-pyridyl)ethylene] in alcoholic (4:1 EtOH-MeOH) solutions are studied. At 77 K, the quantum yields and decay times of the luminescence of the complexes are measured and the deactivation rate constants of the lowest electronically excited metal-to-ligand charge transfer state ((MLCT)-M-3) are determined. The linear correlation between the energy of the lowest state (MLCT)-M-3 d(pi)(Ru) > pi*(bpy) of the cis-[Ru(bpy)(2)(L)Cl](+) complexes and the parameter pK(a) of the free 4-substituted pyridines and pyrazine used as ligands is established. (C) 2003 MAIK Nauka/Interperiodica.