Pulse radiolysis studies of aqueous [Ir(C3,N'Hbpy)(bpy)2]3+ and its basic form. Mechanism of H2 formation

The decay of iridium species produced by reduction of [Ir(C3,N'Hbpy)(bpy)2]3+ (hereafter referred to as Ir(III)3+) and [Ir(C3,N'bpy)(bpy)2]2+ (Ir(III)2+ hereafter) is reported. At strongly acidic pH (<1.7), the species produced by one-electron reduction (Ir(II)2+) react with h+ by a pseudo-first-order reaction. Hydrogen is the final product. At higher pH's, such as about 4, Ir(II)2+ disproportionates, and the product Ir(I) (presumably in the protonated form [Ir(I)H]2+) produces Ir(III)2+ and hydrogen. The mechanism of these processes is discussed, and equilibrium as well as reaction rate constants are reported. Ir(III)3+, Ir(II)2+, etc. represent the appropriate formal oxidation states. The reduction site in Ir(II)is not necessarily at the Ir