PHOTOELECTROCHEMICAL AND QUENCHING STUDIES OF TRIS(2,2'-BIPYRIDINE)RUTHENIUM(II) BOUND TO NAFION-COATED AND CLAY-COATED ELECTRODES

The photosensitizer [Ru(bipy)3]2+ (bipy = 2.2'-bipyridine) was adsorbe d on Nafion(nf)- and bentonite clay(bt)-coated electrodes. Photoelectr ochemical cells were constructed using Pt-nf-[Ru(bipy)3]2+ and Pt-bt-[ Ru(bipy)3]2+ electrodes with cobalt(III) complexes and Fe3+ ion as ele ctron relays. At appropriate applied potentials, anodic and cathodic p hotocurrents were induced when the electrodes were irradiated with vis ible light in solutions containing a mixture of a cobalt(III) complex and HClO4. The photoresponse could be switched between anodic and cath odic by controlling the applied electrode potential. The origin of the photocurrent is explained by an oxidative quenching by the cobalt(III ) complex of the photoexcited [Ru(bipy)3]2+ complex confined at the e lectrode, followed by electrochemical reduction or oxidation of the re sulting [Ru(bipy)3]3+ and cobalt(II) complex respectively. The quenchi ng rate constants, k(q) for the reaction of [Ru(bipy)3]2+ with three different cobalt(III) complexes and Fe3+ ion were determined by photoe lectrochemical methods.