Poly(5-bromoindole) (PBrI) films were synthesized electrochemically by direct oxidation of 5-bromoindole in pure boron trifluoride diethyl etherate. The oxidation potential of 5-bromoindole in this medium was measured to be only 0.97 V vs. saturated calomel electrode, which was lower than that determined in acetonitrile + 0.1 mol L-1 Bu4NBF4 (1.08 V). PBrI films obtained from this medium showed good electrochemical behavior and good thermal stability. Structural studies showed that the polymerization of 5-bromoindole ring occurred at 2,3 position. As-formed PBrI films were thoroughly soluble in strong polar solvent dimethylsulfoxide and partly soluble in tetrahydrofuran. Fluorescent spectral studies indicated that PBrI was a good blue-light emitter. The excitation and emission spectra of PBrI showed a significant shift to longer wavelength compared with that of the monomer, consistent with the greater extent of electron delocalization. (c) 2006 Wiley Periodicals, Inc.