Photosensitized oxidation of 4-nitrophenol was studied in organic solutions with seven octasubstituted thio and aryloxy palladium and platinum phthalocyanines acting as photosensitizers. Kinetic studies conducted also showed that the complexes have different singlet oxygen quenching constants with direct implication on the quantum yield of photodegradation of 4-nitrophenol (Phi(4-NP)). Palladium analogues gave better results than the platinum analogues in terms of Phi(4-NP) with palladium(dodecylthio)phthalocyanine giving the highest yield of 1.8 x 10(-3). Gas chromatography (GC) and liquid chromatography connected to a mass spectrometer (LC-MS) were used to confirm the photodegradation products which were hydroquinone and 1,4-benzoquinone. (C) 2010 Elsevier B.V. All rights reserved.