Preparation, characterization, electrochemistry and in situ spectroelectrochemistry of novel α-tetra[7-oxo-3-(2-chloro-4-fluorophenyl)coumarin]-substituted metal-free, cobalt and zinc phthalocyanines

In this study, a novel ligand, 7-(2,3-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin was synthesized by the reaction of 3-(2-chloro-4-fluorophenyl)-7-hydroxycoumarin with 1,2-dicyano-3-nitrobenzen in dry DMF as the solvent in the presence of K2CO3 as the base. The preparation of the corresponding phthalocyanines H2Pc, CoPc and ZnPc, substituted with 7-oxo-3-(2-chloro-4-fluorophenyl)coumarin functional groups at α positions of the Pc ring, was achieved by the cyclotetramerization of the coumarin ligand without any metal salts or with the relevant metal(II) acetates in 2-N,N-dimethylaminoethanol. The structures of the compounds were confirmed by elemental analysis, UV–vis, IR, MALDI-TOF mass and 1H NMR spectra. In addition, aggregation and redox properties of the novel phthalocyanines with four halogenated coumarinoxy substituents at α positions of the phthalocyanine ring were compared with those of previously reported corresponding ones with β-substitution, by UV–vis spectroscopy, in situ spectroelectrochemistry and voltammetry. Remarkable differences in these properties between α- and β-substituted compounds were detected, and discussed in detail.