Electrosyntheses of high-quality poly(5-nitroindole) films in boron trifluoride diethyl etherate containing additional diethyl ether

Abstract High‐quality poly(5‐nitroindole) (PNP) films were synthesized electrochemically by the direct anodic oxidation of 5‐nitroindole in boron trifluoride diethyl etherate (BFEE) containing additional 10% diethyl ether (EE) (by volume). The addition of EE to BFEE could improve the solubility of the monomer. The oxidation potential onset of 5‐nitroindole in this medium was measured to be only 1.04 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile and 0.1 mol L −1 tetrabutylammonium tetrafluoroborate (1.53 V vs SCE). PNP films obtained from this medium showed good electrochemical behavior and good thermal stability with a conductivity of 10 −2 S cm −1 ; this indicated that BFEE containing 10% EE was a suitable medium for the electrosyntheses of PNP films. Structural studies showed that the polymerization of the 5‐nitroindole ring occurred at the 2,3‐position. As‐formed PNP films were thoroughly soluble in the strong polar organic solvent dimethyl sulfoxide and partly soluble in tetrahydrofuran or acetone. Fluorescent spectral studies indicated that PNP was a good green‐light emitter, with excitation and emission wavelengths of 420 and 550 nm, respectively. To the best of our knowledge, this is the first time that nitro‐group‐substituted high‐quality conducting polymer films have been electrodeposited. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3986–3997, 2005