PHOTOCATALYTIC REDUCTION OF PHENACYL HALIDES BY 9,10-DIHYDRO-10-METHYLACRIDINE - CONTROL BETWEEN THE REDUCTIVE AND OXIDATIVE QUENCHING PATHWAYS OF TRIS(BIPYRIDINE)RUTHENIUM COMPLEX UTILIZING AN ACID CATALYSIS

The photoreductions of phenacyl halide derivatives [YC6H4COCH2X (X = Br, Cl; Y = p-CN, p-Br, H, p-Me, p-MeO)] by 9,10-dihydro-10-methylacridine (AcrH2) in both the absence and presence of perchloric acid in acetonitrile proceed efficiently under irradiation of visible light of λ = 450 nm at 298 K with [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) as a photocatalyst to yield 10-methylacridinium ion (AcrH+) and the corresponding acetophenone derivatives. The dependences of the quantum yields for the [Ru(bpy)3]2+-sensitized photoreduction of phenacyl halides by AcrH2 on the HClO4 concentration have been examined. The reductive and oxidative quenching of the excited state [Ru(bpy)3]2+* by AcrH2 and phenacyl halides in the absence and presence of HClO4 have also been studied, respectively. The results indicate that the reaction in the absence of HClO4 proceeds via the reductive quenching of [Ru(bpy)3]2+ by AcrH2, followed by the reduction of phenacyl halides by [Ru(bpy)3]+, while the reaction in the strongly acidic media proceeds via the oxidative quenching of [Ru(bpy)3]2+ by phenacyl halides, followed by the oxidation of AcrH2 by [Ru(bpy)3]3+. © 1990 American Chemical Society.