Reversible photo-oxidation of zinc tetraphenylporphine by benzo-1,4-quinone

Abstract

Zinc tetraphenylporphine shows fairly weak fluorescence and phosphorescence but intense, long-lived triplet absorption. Benzo-1,4-quinone quenches the singlet and triplet excited states of ZnTPP and the quenching probability increases with increased polarity of the solvent. Quenching leads to formation of a complex which, for the triplet reaction in toluene, is sufficiently long-lived to be observed by flash spectroscopy. In polar solvents, quenching leads to production of separated ions, the yield being a function of the solvent dielectric constant.