Photodegradation of 4-nitrophenol (4-Np) in the presence of zinc tetrasulfophthalocyanine (ZnPcS4), zinc octacarboxyphthalocyanine (ZnPc(COOH)(8)) and a sulfonated ZnPc containing a mixture of differently sulfonated derivatives (ZnPcSmix), as photocatalysts is reported. ZnPcSmix is the most effective catalyst in terms of a high quantum yield for 4-Np degradation and the stability of the catalyst. However ZnPc(COOH)(8) degrades readily during the catalysis, but it has a higher quantum yield (Phi(4-Np)) for 4-Np degradation than the rest of the complexes. The Phi(4-Np) values were closely related to the singlet oxygen quantum yields Phi(Delta) and hence aggregation. The rate constants for the reaction with 4-Np were k(r) = 0.67 x 10(6) mol(-1) dm(3) s(-1) for ZnPcSmix and 2.8 x 10(8) mol(-1) dm(3) s(-1) for ZnPc(COOH)(8). (c) 2006 Elsevier B.V. All rights reserved.