Low-potential electrochemical polymerization of 5-fluoroindole and characterization of its polymers

High-quality poly(5-fluoroindole) (P5FIn) films were synthesized electrochemically by direct oxidation of 5-fluoroindole (5FIn) in pure boron trifluoride diethyl etherate (BFEE). The oxidation potential of 5FIn in this medium was measured to be only 1.05 V vs. SCE, which was much lower than that determined in acetonitrile + 0.1 mol L−1 Bu4NBF4 (1.30 V). P5FIn films obtained from this medium showed good electrochemical behavior and good thermal stability. Dedoped P5FIn films were soluble in dimethyl sulfoxide. Fluorescent spectral studies indicate that P5FIn is a good blue-light emitter. The structure and morphology of the polymer were studied by UV–vis spectroscopy, FT-IR spectroscopy, 1H NMR spectroscopy and scanning electron microscopy, respectively. The results of the spectroscopies of dedoped P5FIn indicated the polymerization mainly occurred at C(2) and C(3) positions.