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. (c) 2005 Wiley Periodicals, lnc.