1991 Volume 64 Issue 6 Pages 1866-1871
In the presence of a sacrificial donor (such as ethylenediaminetetraacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid or oxalic acid in a deaerated aqueous solution) [Co(edta)]− is reduced to [Co(edta)]2− by quenching oxidatively the photo-excited [Ru(bpy)3]2+ ([Ru(bpy)3]2+*). The reduction rate for the [Co(edta)]− increases with an increase in the concentration of the sacrificial donor, and is kept constant at [EDTA] ≥ 0.03 mol dm−3, [CDTA] ≥ 0.01 mol dm−3, or [C2O42−] ≥ 0.07 mol dm−3 at pH 4.6. The ratio [[Co(edta)]−]reacted : [EDTA]reacted : [[Co(edta)]2−]formed=2 : 1 : 2 is obtained at pH 5.2. The reaction rates were examined as a function of the concentrations of [Co(edta)]− and [Ru(bpy)3]2+ as well as the pH, ionic strength, and temperature of the solution, and the intensity of the incident light. In the presence of oxygen, the decrease of [Co(edta)]− is greatly suppressed and the formation of the hydrogen peroxide is appreciable. The reaction mechanism is presented in order to account for the obtained results.
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