Laser flash photolysis of IrCl62− in aqueous solutions

The method of laser flash photolysis (308 nm) is used to study the photochemistry of IrCl 6 2− complex in aqueous solutions with and without free Cl − ions. Photolysis in aqueous solutions lead to photoaquation of initial complex within less than 20 ns with a quantum yield of 0.01. In aqueous solutions containing free Cl − ions, the photoreduction of IrCl 6 2− and the appearance of an absorption band of Cl 2 •− radical ion with a maximum at 350 nm are observed. An increase in the Cl − ion concentration causes an increase in both the quantum yield of photoreduction and Cl 2 •− yield. These results allow one to conclude that a chlorine atom, precursor of Cl 2 •− radical ion, arises due to the electron transfer from an outerspheric Cl − ion to the excited complex. The obtained experimental data have made it possible to estimate the rate constants of direct and back electron transfer in the (IrCl 6 2− ) ∗ –Cl − pair.