SOLID PHASE PHOTOREDUCTION OF METHYLVIOLOGEN ON CELLULOSE SENSITIZED BY TRIS(2,2'-BIPYRIDYL)RUTHENIUM COMPLEX

–Methylviologen (MV²⁺) adsorbed on cellulose could be reduced photochemically in the solid phase sensitized by tris(2,2'-bipyridyl)ruthenium(II) complex, Ru(II)(bpy)₃], using disodium ethylene-diaminetetraacetic acid (Na₂EDTA) as a reducing agent. Formation of the cation radical (MV ⁺.) was confirmed by visible and EPR spectra. The MV⁺. formed on cellulose was remarkably stable against air oxidation and rapidly accumulated even by the irradiation under air. Water adsorbed on the cellulose greatly retarded the photoreaction. Action spectrum showed that the excitation of Ru(II)(byp)₃ is responsible for the photochemical reaction. The quenching of the emission from Ru(II)(bpy)*₃ by MV²⁺. indicated that a primary photochemical reaction occurs between Ru(II)(bpy)*₃ and MV²⁺. The main reaction path is the reduction of MV²⁺ by Ru(II)(bpy)₃, giving MV⁺. and Ru(III)(bpy)₃, followed by the reduction of Ru(III)(bpy)₃ to Ru(II)(bpy)₃ with Na₂EDTA, which in turn is oxidized to give carbon dioxide.