Photochemistry of group IV porphyrin halides

The photochemistry of early transition metal porphyrins (TPP)ZrX2 and (TTP)TiCl (TPP=tetraphenylporphyrin, TTP=tetratolylporphyrin, X=Br, Cl) was investigated. Chemical reduction and electrochemical studies indicated that the porphyrin macrocycle is more easily reduced than the metal centers. The same trend is observed under photochemical conditions of UV and near-UV excitation, where photoreduction of the porphyrin macrocycle is observed, as opposed to MX photoelimination.