Electrochemical behavior of the monomeric and polymeric forms of N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine

Electrochemical behavior of new phenothiazine derivative, N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine (PhTz) and of the product of its electropolymerization has been investigated on glassy carbon electrode using electrochemical techniques. Monomeric PhTz is involved in quasi-reversible electron transfer complicated with adsorption of oxidized form. The transfer coefficient and standard heterogeneous constant were estimated in a wide pH range. In multiple cycling of the potential, the PhTz was oxidized to the polymeric film, which growth was confirmed by electrochemical impedance spectroscopy. Maximal deposition of the product was found for application of the upper potential of 1.3 V. Sulfate and nitrate anions promote electropolymerization whereas chloride ions inhibit the reaction. The reduction of polyPhTz depended on the number of the potential scans because of the increase of diffusional permeability with the number of cycles. A broad pH dependency of the potential, reversibility of the redox reactions and similarity of the behavior of monomeric and polymeric forms of PhTz make them attractive for future application in the assembly of electrochemical (bio)sensors. It was shown on the example of application of appropriately modified electrodes in acid-base and redox titration and in discrimination of native and damaged DNA adsorbed onto the polyPhTz layer based on the changes in the impedance parameters.