PHOTOOXIDATION OF RU(BPY)(CN)(4)(2-) AND RU(DMBPY)(CN)(4)(2-)

The photophysical and photochemical properties of Ru(bpy) (CN)(4)(2-) and Ru(DMbpy) (CN)(4)(2-) are reported, where bpy = 2,2'-bipyridine and DMbpy = 4,4'-dimethyl-2,2'-bipyridine. The luminescence quantum yields of the lowest energy d-pi* state are (8 +/- 1) x 10(-3) and (7 +/- 1) x 10(-3) for the bpy and DMbpy complex, respectively, in aqueous solution at ambient temperature. Under these conditions the lifetimes are 125 and 115 ns. The luminescence lifetimes increase approximately threefold in D2O. The emission is quenched by methylviologen at diffusion controlled rate (k(q(bpy)) = (1.95 +/- 0.4) x 10(10) M(-1) s(-1), k(q(DMbpy)) = (1.85 +/- 0.5) x 10(10) M(-1) s(-1)), and the cage escape efficiencies of MV(+) are found to be 0.24 +/- 0.02 and 0.25 +/- 0.03 for the bpy and DMbpy derivatives, respectively. Photolysis of Ru(bpy) (CN)(4)(2-) was also studied in chloroform and was compared with that of Fe(bpy) (CN)(4)(2-). UV irradiation of the Fe(bpy) (CN)(4)(2-) complex in chloroform results in the iron(III) complex in anaerobic conditions, while the mixed ligand ruthenium(III) complex forms only in the presence of oxygen.