Datensatz

Zusammenfassung

Porphycene (P_C), a structural isomer of porphine, is a promising photosensitizer for photodynamic therapy. Its excited states can be quenched by molecular oxygen, generating singlet O₂. The electronic structures of P_C and of the P_C· · ·O₂ complex were investigated using complete active space perturbation theory. It is shown that singlet oxygen generation involves 12 electronic states of the complex, with singlet, triplet, and quintet multiplicities. Two scenarios for singlet-O₂ yield are analyzed: (I) quenching of triplet states of P_C and (II) quenching of singlet states of P_C. In the first scenario, which is favored under low O₂ concentration, singlet-O₂ yield is limited by the relatively low triplet quantum yield of P_C. We discuss how the singlet-O₂ yield would be busted if conditions for occurrence of the second scenario could be achieved.