AbstractPhotochemical properties of Ru(bpy)2(poly‐4‐methyl‐4′‐vinyl‐2,2′‐bipyridine)Cl2 (2) were studied and compared with that of Ru(bpy)3Cl2. Continuous irradiation of a solution, which contains polymer 2 as a photosensitizer, methylviologen (MV2+) or 4,4′‐bipyridinium‐1,1′‐bis(trimethylenesulfonate) (SPV) as an electron acceptor and triethanolamine (TEOA) as a sacrificial donor, resulted in the formation of viologen radical ion (MV+ or SPV−). The rate of formation of MV+ or SPV− for the polymer 2 system was smaller than that for the Ru(bpy)3 Cl2 systems. The reason for this fact was kinetically analyzed by quenching experiments of excited Ru(II) complexes by MV2+ or SPV, the photosensitized reactions of the TEOA–Ru(II) complex–MV2+ or ‐SPV systems, and the dye laser photolysis of the Ru(II) complex–MV2+ or ‐SPV systems.