Electrochemical properties and electropolymerization of tetrakis(para-aminophenyl)porphyrin in dichloromethane

Abstract

The study of electrochemical properties of tetrakis(p-aminophenyl)porphyrin and its electropolymerization was performed in dichloromethane solution by cyclic voltamperometry (CVA) and chronoamperometry (CA) methods. In the range of positive potentials from 0 to 0.87 V two peaks on CVA are observed and assigned to a reversible redox process. The maximum current of the oxidation increases with the number of cycles, while the minimum current of the reduction process decreases, i.e. the process of flm growth dominates the process of its dissolution. During the electrooxidation process the electroconductive poly-porphyrin flm highly adherenced with electrode surface was obtained. The potential of tetrakis(p-aminophenyl)porphyrin electropolymerization was measured by CVA and CA methods and was found to be +0.83 V. The analysis of electronic absorption spectra has shown that π-conjugated system of macroheterocycle is preserved during the electropolymerization process and the porphyrin chromophores in the polymer film do not interact. On the basis of IR spectroscopic studies it may be supposed that under the polarizing anodic potentials the polymerization of tetrakis(p-aminophenyl)porphyrin involving dihydrophenazine fragments occurs. To confirm the nature of the prepared material differential scanning calorimetry (DSC) studies of the film was carried out. The endothermic branch of the DSC curve is typical for partially crystalline polymers. The endothermic branch exhibits a low-temperature shoulder starting at -10 0C which is characteristic for polymer compounds melting in a wide temperature range. The heat of melting of the sample crystallites is 1.4 times higher than that for polyolefins (polyethelene, isotactic polypropylene). The maximum of the melting peak is found to be ~71 °C. The obtained results show that the film is a partially crystalline high-molecular compound which slowly melts in a wide temperature range. © ISUCT Publishing.