The effect of central metal on the photodynamic properties of silylated tetraphenylporphyrin derivative

Abstract We have introduced central metal to 5,10,15,20-tetrakis(3′-trimethylsilyl-5′-carboxyphenyl)porphyrin tetrasodium ( 1 ), which shows high photodynamic activity. As central metals, Zn and Pd have been studied, and Zn and Pd improved the quantum yield of intersystem crossing by the heavy atom effect. Pd improved the quantum yield of singlet oxygen sensitization, but Zn decreased the quantum yield. The difference in the quantum yield has been discussed. Cytotoxicity has been evaluated by using a HeLa cell line, and cytotoxicity of metal complexes of 1 were sufficiently low. Pd also improved concentration of photosensitizers in cells, and thus Pd enhanced photodynamic activity. The difference of the photodynamic activity induced by the complexation could be explained by the quantity of singlet oxygen produced in cells, which was evaluated by using the quantum yield of singlet oxygen sensitization, a concentration of photosensitizers in cells, and absorption spectrum of photosensitizers.