FORMATION FEATURES AND ELECTROCHROMIC PROPERTIES OF POLYPORPHYRIN FILMS BASED ON Zn-TETRAKIS(3-(HYDROXYPHENYL)PORPHYRIN

Abstract

This paper presents the results of electrochemical deposition and the redox behavior of polyporphyrin films based on Zn(II) tetrakis(3–(hydroxyphenyl)porphyrin (ZnT(3–OHPh)P). It has been shown that electrochemical deposition initiated by superoxide anion–radical can be used to form films based on ZnT(3–OHPh)P. The potential ranges at which the electrochemical deposition of poly–ZnT(3–OHPh)P occurs on ITO electrodes were determined. The thickness of the obtained films based on ZnT(3–OHPh)P was determined by atomic force microscopy (AFM) and is about 90 nm. The presented results of studying the electronic absorption spectra of films based on ZnT(3–OHPh)P showed that the tetrapyrrole macrocycle is not destroyed during electrochemical deposition. The paper presents the results of Raman spectroscopy, which confirm that the main reason for the binding of hydroxyphenylporphyrin molecules in a polyporphyrin film is the formation of C–O–C bridges between side substituents. The redox processes in poly–ZnT(3–OHPh)P were studied by the spectroelectrochemical method. Electrochromic responses of films based on ZnT(3–OHPh)P have been determined in a wide range of potentials. Process of electroreduction leads to a decrease and a shift to the short–wavelength region of the Soret band. Electrooxidation of films based on ZnT(3–OHPh)P leads to a decrease in the intensity of the Soret band and the disappearance of the Q bands. It is shown that the observed spectral changes are in good agreement with the known literature data and indicate the localization of excess negative or positive charges on the macrocycle. Due to the change in their optical properties depending on the applied voltage, films based on ZnT(3–OHPh)P can be recommended as a promising electrochromic coating.