Thermal-lensing and phosphorescence studies of the quantum yield and lifetime of singlet molecular oxygen (1 delta g) sensitized by hematoporphyrin and related porphyrins in deuterated and non-deuterated ethanols

Time-resolved thermal-lensing was used to measure the absolute quantum yield (φ_Δ) of singlet molecular oxygen, O₂(¹Δ_g), produced by hematoporphyrin photosensitization in ethanol. Deuteration of the solvent did not affect the value of φ_Δ. The value of φΔ= 0.53 was then used as reference to evaluate φΔ in O₂ (¹Δ_g) phosphorescence experiments with the related porphyrins, monohydroxyethylvinyl deuteroporphyrin and dihematoporphyrin ether. The φ_Δ values, in conjunction with the respective quantum yields of intersystem crossing (measured using a nanosecond laser flash photolysis technique) served to evaluate efficiencies, S_Δ, of O₂ (¹Δ_g) production from the porphyrin triplet states. The lifetime T_Δ in monodeuterated ethanol was measured as 29 ± 3 μs and 30 ± 1 (xs by time-resolved thermal lensing and phosphorescence detection, respectively. T_Δ in ethanol and fully deuterated ethanol were in good agreement with values reported in the literature.