Peripheral octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines bearing coumarin and chloro groups: Synthesis, characterization, spectral and electrochemical properties

Novel octa-substituted metal-free, cobalt(II) and zinc(II) phthalocyanines have been synthesized by using chloro and/or coumarin substituted phthalonitrile derivatives. The compounds were characterized by UV–Vis, IR, 1H NMR, and MALDI-TOF mass spectrometry and elemental analysis. The effects of substituents, metals, solvents and concentration on spectroscopic properties and aggregation behaviour of the novel Pcs were investigated. Furthermore, the redox properties of the octa-4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin-substituted compounds were examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. Metal-free phthalocyanine and zinc phthalocyanine displayed ligand-based one-electron redox processes whereas cobalt phthalocyanine showed both ligand- and metal-based processes. A couple corresponding to the reduction of 4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin substituents was also detected. The redox processes of the compounds in dimethylsulfoxide were observed to be broad or split, due to the association of electron transfer processes by aggregation–deaggregation equilibrium.

Graphical abstractNovel octa-substituted phthalocyanines have been synthesized by using chloro and/or coumarin substituted phthalonitrile derivatives. The effects of substituents, metals, solvents and concentration on spectroscopic properties and aggregation behaviour of the novel Pcs were investigated. Furthermore, the redox properties of the compounds were examined by voltammetry and in situ spectroelectrochemistry in nonaqueous medium. Metal-free phthalocyanine and zinc phthalocyanine displayed ligand-based one-electron redox processes whereas cobalt phthalocyanine showed both ligand- and metal-based processes. A couple corresponding to the reduction of 4-(4-methoxyphenyl)-7-oxo-8-methylcoumarin substituents was also detected. The redox processes of the compounds in dimethylsulfoxide were observed to be broad or split, due to the association of electron transfer processes by aggregation–deaggregation equilibrium.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of the octa-substituted phthalocyanines bearing coumarin and chloro groups. ► Investigation of spectroscopic properties of the phthalocyanines in different solvents. ► Aggregation behaviour of the phthalocyanines in different solvents. ► Investigation of the redox properties of the compounds.