Studies of Ruthenium Complexes. VII. Photochemical Reactions of cis -Dihalogenotetraammineruthenium(III) Complexes in Aqueous Solutions

Studies have been made of the photochemistry of cis-dihalogenotetraammineruthenium(III) in aqueous solutions. For the cis-dichlorocomplex, no photochemical reaction has been observed by the irradiation of the visible light region. For cis-dibromo- and cis-diiodo-complexes, a simple aquation of halide ligand seems to occur in a solution with a pH lower than 2.5. The typical values of the quantum yields for the cis-[RuX2(NH3)4] ++H2O\xrightarrowhν cis-[RuX(OH2)(NH3)4]2+X− reaction were 0.27×10−2 (382 nm light) and 0.82×10−2(408 nm light) for dibromo- and dichloro-complexes respectively. The quantum yield was dependent on the wavelength of light, but was independent of the concentrations of halide and hydrogen ions. The quantum yield seems to depend on the oxidizability of the ligand or on probability of the deactivation process in the primary excited state. In accounting for the low quantum yield, it seems most probable that the photoexcited complex species is converted to the ground state by non-radiative ...