Laser flash photolysis of IrCl62- in aqueous solutions

The method of laser flash photolysis (308 nm) is used to study the photoche mistry of IrCl62- complex in aqueous solutions with and without free Cl- io ns. Photolysis in aqueous solutions lead to photoaquation of initial comple x within less than 20 ns with a quantum yield of 0.01. In aqueous solutions containing free Cl- ions, the photoreduction of IrCl62- 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 b oth the quantum yield of photoreduction and Cl-2(.-) yield. These results a llow one to conclude that a chlorine atom, precursor of Cl- radical ion, ar ises due to the electron transfer from an outerspheric Cl- ion to the excit ed complex. The obtained experimental data have made it possible to estimat e the rate constants of direct and back electron transfer in the (IrCl62-)* -Cl- pair. (C) 2000 Published by Elsevier Science B.V. All rights reserved.