Proton coupled electron transfer reaction of phenols with excited state ruthenium(II) - Polypyridyl complexes

Abstract

The reaction of phenols with the excited state,*[Ru(bpy) 3]2+ (E0=0.76 V) and*[Ru(H 2dcbpy)3]2+, (dcbpy=4,4′-dicarboxy-2, 2′-bipyridine) (E0=1.55 V vs. SCE) complexes in CH 3CN has been studied by luminescence quenching technique and the quenching is dynamic. The formation of phenoxyl radical as a transient is confirmed by its characteristic absorption at 400 nm. The kq value is highly sensitive to the change of pH of the medium and ΔG0 of the reaction. Based on the treatment of kq data in terms of energetics of the reaction and pH of the medium, proton coupled electron transfer (PCET) mechanism has been proposed for the reaction. © 2010 John Wiley & Sons, Ltd.