Photoreduction of quinones by thiols sensitized by phthalocyanines.

Under the irradiation of red light (690 nm), quinones were converted to hydroquinones by thiols in the presence of metallophthalocyanines. The reaction proceeded via the charge separation between the triplet state of phthalocyanine and the quinone. The product determining step was protonation of the quinone anion radical, as indicated by the fact that the reaction was accelerated by the use of more acidic thiols or addition of an acid.