Photocatalytic degradation of chloroform by bis (bipyridine)dichlororuthenium(III/II)

Abstract

Broadband (λ > 320 nm) irradiation of chloroform solutions of either [Ru(bpy)2Cl2] or [Ru(bpy)2Cl2]Cl exposed to air led to a photostationary state, in which [Ru(bpy)2Cl2]+ predominated, and to the continuous decomposition of CHCl3, as evidenced by the accumulation of HCl, hydroperoxides (CCl3OOH and CHCl2OOH), and tetra-, penta-, and hexachloroethane. The addition of Cl− increased the rate of photodecomposition, while the replacement of Cl− by F− greatly decreased the rate. The observations are consistent with a photocatalytic cycle in which [Ru(bpy)2Cl2]+ is photochemically reduced to [Ru(bpy)2Cl2], which is thermally reoxidized by CCl3OO or CCl3OOH. In the absence of air a much slower photodecomposition reaction takes place leading to continuously increasing concentrations of chloroethanes. The data are consistent with a catalytic cycle in which [Ru(bpy)2Cl2]+ is photoreduced, as in aerated solutions, while [Ru(bpy)2Cl2] is photooxidized with chloroform as the substrate.