Studies on the photochemical reactions catalyzed by metalloporphyrin complexes: II. Affect photosensitized reaction by aroundsubstituting group and axial coordination of metalloporphyrin complexes

The photosensitized reduction reaction of methylviologen was investigated by tetrakis [(4-trimethylamino) phenyl] metalloporphyrins [MeTPI, Me = H₂, Zn(II), Ni(II), Cu(II), MN(III), Co(III)]. The kinetic parameter a, inductive time t_i and initial rate ν₀ in photosensitized reaction were applied to measure the photosensitivity of photosensitizers. Both substituting groups and axial coordinations of metalloporphyrin can exert a great influence on the photosensitivity of photosensitizers. The experimental results domonstrated that (1) zinc porphyrin is the best photosensitizers in the same series of porphyrins and metalloporphyrins; (2) the aromatic organic bases can increase the photosensitivity through axial ligation, on the contrary, the aliphatic amines can decrease the photosensitivity; (3) the aromatic organic bases with positive charge can increase the photosensitivity considerably.