Copper(II)-assisted charge transfer quenching of the excited state of a zinc(II) porphyrin complex bearing a peripheral bipyridine moiety

A zinc(II) porphyrin complex bearing a bipyridine moiety at the periphery was synthesized. The singlet excited state of the complex was found to be quenched by Cu2 + in methanol, and the photoinduced electron transfer from the excited state of the porphyrin to the bipyridine moiety in the presence of excess Cu2 + ion was observed using a transient absorption technique. The relatively long lifetime of the charge-separated state was ascribed to the slow electron exchange reaction of Cu(II)/Cu(I) couple bound to the bipyridine unit.