Synthesis of 2,7,12,17-tetraphenylporphycene (TPPo). First aryl-substituted porphycene for the photodynamic therapy of tumors

We report on the synthesis of 2,7,12,17-tetraphenylporphycene (TPPo), the first example of an aryl-substituted porphycene macrocycle. A modification of the general porphycene synthetic method has been used, thus avoiding an intermediate sublimation. TPPo has an absorption maximum at 659 nm (ε = 50.000 M^-1cm^-1), and shows good sensitizing properties: it photoproduces singlet oxygen with a quantum yield of ca. 0.25, is phototoxic to cells, and has low dark toxicity. These properties make TPPo a suitable candidate for the photodynamic therapy of tumors.