PHOTOCHEMICAL CO2 REDUCTION CATALYZED BY [RU(BPY)2(CO)2]2+ USING TRIETHANOLAMINE AND 1-BENZYL-1,4-DIHYDRONICOTINAMIDE AS AN ELECTRON-DONOR

Irradiation with visible light of a CO2-saturated triethanolamine (TEOA)/N,N′-dimethylformamide (DMF) solution (1:4 v/v) containing [Ru(bpy)3]2+ and [Ru(bpy)2(CO)2]2+ (bpy = 2,2′-bipyridine) selectively produced HCOO− with a maximum quantum yield of 14%. On the other hand, the photochemical CO2 reduction in CO2-saturated H2O/DMF (1:9 v/v) containing [Ru(bpy)3]2+, [Ru(bpy)2(CO)2]2+, and 1-benzyl-1,4-dihydronicotinamide (BNAH) gave not only CO but also HCOO− with maximum quantum yields of 14.8 and 2.7%, respectively. In those photochemical CO2 reductions, the luminescent-state [Ru(bpy)3]2+* was quenched reductively by TEOA and BNAH, affording [Ru(bpy)3]+, which functioned as a reductant of [Ru(bpy)2(CO)2]2+, and the change in the main product from HCOO− in TEOA/DMF to CO in H2O/DMF can be explained in terms of the acid-base equilibria among [Ru(bpy)2(CO)2]2+, [Ru(bpy)2(CO)(C(O)OH)]+, and [Ru(bpy)2(CO)(COO−)]+. © 1990, American Chemical Society. All rights reserved.