The luminescent charge-transfer state of ruthenium-bipyrazine complexes

Using laser flash photolysis, excited-state absorption measurements on Ru(bpz)/sub 3//sup 2 +/ and (Ru(BPY)/sub 2/(bpz)/sup 2 +/ were carried out in methanol (bpy is bipyridine; bpz is bipyrazine). Pulse radiolysis was used to produce spectra of one-electron-reduced forms of bpz which were compared with excited-state spectra found in the laser flash photolysis experiments. A strong indication of the localization of the electron on one bpz ligand was observed, thus confirming a lower ..pi..* level in bpz compared to the case of bpy. Decay rate constants and O/sub 2/ quenching rate constants are also reported in water, methanol, and acetonitrile.