Novel conducting polymers based on thieno[3,2-b]indoles: Electrochemical properties and molecular structure

The electropolymerization of thieno[3,2-b]indole (TI), 6-methoxythieno[3,2-b]indole (MeOTI) and N-methylthieno[3,2-b]indole (N-MeTI) was performed in organic solvents with the aim to prepare new conducting materials. TI and MeOTI anodic oxidation led to the formation on platinum electrodes of electroactive polymer films that were characterized by cyclic voltammetry, quartz microbalance, MALDI-TOF, FT-IR spectroscopy and scanning electron microscopy. MALDI-TOF mass spectrometry indicates that films are mainly constituted of short-chain oligomers. FT-IR studies and molecular orbital calculations show that polymers present coupling occurring on the thiophene and phenyl rings. The great differences observed between the electrochemical and physicochemical properties of the various polymer films were mainly induced by the location and electron-donating effects of substituents in the different monomers. Substitution influenced not only electroactivity, chain length and film morphology, but also the electropolymerization sites.