Synthesis and characterization of Zn and Co monocarboxy-phthalocyanines and investigation of their photocatalytic efficiency as TiO₂composites

In this study, synthesis of a group of novel A₃B-type non-symmetrically tetrasubstituted zinc(II) and cobalt(II) phthalocyanines bearing one carboxy group (4-mercaptobenzoic acid/4-hydroxybenzoic acid) and three 4-tert-butylphenoxy substituents was achieved by a statistical condensation reaction of the corresponding two phthalonitriles. These four new phthalocyanines have been characterized by using elemental analyses, UV–vis, FT-IR,¹H NMR and mass spectroscopic techniques. MPcs were incorporated into TiO₂semiconductors to prepare TiO₂-MPc composites as heterogeneous catalysts. The novel composites were characterized by X-ray diffraction (XRD), infrared (FTIR) and diffuse reflectance analysis. The characterization results show that MPcs are anchored on the surface of TiO₂through CO[sbnd]O[sbnd]TiO₂bonds and anatase structure of TiO₂remains unchanged after the sensitization process. The optimum loading of the dyes on TiO₂(ca. 8.4 μmol/g TiO₂) was almost independent of the amount of TiO₂used. The new TiO₂-MPc composites were used to test their photocatalytic activity on decomposition of 4-chlorophenol under visible light. In contrast to untreated TiO₂, all photocatalysts prepared in this study were highly effective on 4-chlorophenol under visible light and almost total photodegradation was accomplished.