Triple state properties of tetrasubstituted zinc phthalocyanine derivatives

Photophysical properties of zinc phthalocyanine and its three novel tetrasubstituted derivatives were determined with laser flash photolysis. The substituents containing either glycol ether groups or benzene rings with different functions are attached to the aromatic nuclei of phthalocyanines (Pcs) through ether bonds. The triplet lifetimes in deoxygenated solutions in ethanol and toluene are around 300 ms while in air saturated solutions between 0.2 and 0.4 ms. Oxygen quenching rate constants are between 1 and 2 £ 109 M21s21 and the quantum yields of singlet oxygen formation are between 0.4 and 0.6. Oxygen quenching of a Pc derivative embedded in phospholipid vesicles shows strong temperature dependence below the main phase transition temperature of the phospholipid, with activation energy of 61 kJ mol21. The triplet state parameters obtained in this study, together with the ground state absorption properties suggest that the new compounds may be tested as photosensitizers in photodynamic therapy. q 2004 Elsevier B.V. All rights reserved