Synthesis and characterization of a series of conducting polymers based on indole and carbazole

A series of indole (In) and carbazole (Cz) derivative monomers have been synthesized, such as 4-[3-carbazolyl] indole (4In-3Cz), 5-[3-carbazolyl] indole (5In-3Cz), 6-[3-carbazolyl] indole (6In-3Cz), 7-[3-carbazolyl] indole (7In-3Cz). The comonomers synthesized by Stille coupling reaction were characterized by ¹H-NMR and elemental analysis. Potentiodynamic method was used for electropolymerization of comonomers, Indole, Cz, and the mixture of In and Cz. Electrochemical activities of resulting P[4In-3Cz], P[5In-3Cz], P[6In-3Cz], P[7In-3Cz], polyindole (PIn), polycarbazole (PCz) and P[In-co-Cz] films were investigated comparatively by CV at different scan rates, electrochemical impedance spectroscopy (EIS) and spectroelectrochemical measurements. The ionization potentials, I_p, specific capacitance, C_sp, and optical band gap, E_g, of copolymers were obtained from these measurements. In order to gain some preliminary information on the structure of the copolymers, DFT analysis was performed and dimers and tetramers were optimized. Results suggested that, in order to obtain an In-Cz copolymer with low oxidation potential and band gap, indole ring should be substituted through 5 position to the 3 position of Cz. If high specific capacitance value or high conductivity are desired, P[4In-3Cz] and P[6In-3Cz] are the best copolymers, respectively.