Photochemical reaction of gadolinium(III) tetraphenylporphyrin in toluene solution containing an electron acceptor or donor

In this paper we have studied by absorption spectroscopy the course of the steady state photolysis of gadolinium(III) complex with 5,10,15,20-tetraphenylporphyrin. The result has been compared with the photolysis of free base tetraphenylporphyrin. Irradiation of GdTPP(acac) and H₂TPP (H₂TPP ≡ tetraphenylporphyrin; Hacac ≡ acetylacetone) with visible light in the presence of triethylamine as an electron donor, leads to their photoreduction. Formation of the gadolinium tetraphenylchlorin complex and tetraphenylchlorin is observed. The process of irradiation in the presence of CCI₄ as an electron acceptor has different pathways for GdTPP(acac) and H₂TPP. The gadolinium complex is mono oxidized, giving rise to the π⁺ radical cation while, for unmetallated porphyrin, dication H₄(TPP)²⁺ formation is observed.