Singlet oxygen quantum yields of potential porphyrin-based photosensitisers for photodynamic therapy

Abstract

The singlet oxygen formation quantum yield (ΦΔ) for solutions of the di-cation, free-base and metallated forms of hematoporphyrin derivative (HpD), hematoporphyrin IX (Hp9) and a boronated protoporphyrin (BOPP) are reported using the method of direct detection of the characteristic phosphorescence following polychromatic excitation. Values of ΦΔ for the free-base form of all the porphyrins and the di-cation forms of Hp9 and HpD are in the range of 0.44 to 0.85 in the solvents investigated. Incorporation of zinc ions into the macrocycle reduces ΦΔ for all three porphyrins. BOPP facilitates the coordination of certain transition metals (Mn, Co and Cu) compared to Hp9 and HpD and results in a d..