Photoacoustic measurements of porphyrin triplet-state quantum yields and singlet-oxygen efficiencies

Photoacoustic calorimetry was used to measure the quantum yields of singlet molecular oxygen production by the triplet states of tetraphenylporphyrin (TPP), Zn-TPP and Cu-TPP in toluene, yielding values of 0.67 &plusmn 0.14, 0.68 &plusmn 0.19 and 0.03 &plusmn 0.01, respectively. We show that a novel dichlorophenyl derivative of Zn-TPP is capable of singlet-oxygen production with a 0.90 &plusmn 0.07 quantum yield. The synthesis and characterisation of a new photostable chlorin with high absorptivity in the red that is capable of singlet-oxygen production with 0.54 &plusmn 0.06 quantum yield is described. Our results suggest that chlorinated chlorins may be interesting new sensitisers for photodynamic therapy.