The influence of dimerization of water-soluble metalloporphyrins as photosensitizers on the efficiency of generation of singlet oxygen

Quantum yields (Phi(Delta)) for the generation of singlet oxygen sensitized by Pd(II) complexes of watersoluble porphyrins: meso-tetrakis(4-N-methylpyridyl)porphine [PdTMPyP](4+) (Phi(Delta) = 0.9), meso-tetrakis(4-N,N,N-trimethylaminophenyl)porphine [PdTTMAPP](4+) (Phi(Delta) = 0.8), meso-tetrakis(4-carboxyphenyl)porphine [PdTCPP](4-) (Phi(Delta) = 0.7), and meso-tetrakis(4-sulfonatophenyl)porphine [PdTSPP](4-) (Phi(Delta) = 0.5) were determined using a chemical method. It was found that the dimerization and aggregation of metalloporphyrins greatly influence the Phi(Delta) value. The quantum yields evaluated for the formation of singlet oxygen sensitized by metalloporphyrin monomeric and dimeric forms are Phi(Delta), (M) approximate to 0.9 and Phi(Delta), (D) approximate to 0.2, respectively, and do not depend on the porphyrin nature.