Synthesis, characterization and electrochemical properties of novel β 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituted metal-free, Zn(II) and Co(II) phthalocyanines

Novel metal-free (4), Co(II) (5) and Zn(II) (6) phthalocyanines bearing four 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituents at peripheral (p) positions have been prepared by cyclotetramerization of 4-(4-(4-methoxyphenyl)-8-methylcoumarin-7-oxy)phthalonitrile. The compounds have been characterized by elemental analysis and IR, UV-Vis and MALDI-TOF mass spectroscopies. H-aggregation behaviour of the compounds has been investigated in different solvent media. Furthermore, the redox properties of the complexes were examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. In general, compounds 4 and 6 displayed ligand-based one-electron redox processes, while compound 5 showed both ligand- and metal-based processes, in addition to a couple corresponding to the reduction of the 7-hydroxy-4-(4-methoxyphenyl)-8-methylcoumarin substituents. Both electrochemical and in situ spectroelectrochemical data showed that the redox processes of these complexes are complicated by their high aggregation tendency. (C) 2012 Elsevier Ltd. All rights reserved.