[Spectral analysis of the effect of different polymerization potential on electrosynthesized poly (5-nitroindole) films].

High quality poly (5-nitroindole) (PNI) films can be synthesized electrochemically by direct anodic oxidation of 5-nitroindole (NI) in boron trifluoride diethyl etherate (BFEE) at different polymerization potential in the range of 1.23-2.23 V (vs. SCE). To the best of our knowledge, this is the first time that high quality polymer films of nitro group substituted conducting polymers were electrodeposited. The oxidation onset potential of NI was only 1.04 V vs. SCE in this medium. Chronoamperometric response of NI, FTIR and 1H NMR indicated that the polymerization potential had a great effect on the quality of PNI films. Lower potential is helpful for the electrochemical polymerization of NI and the extension of the conjugation length of PNI. On the other hand, a higher potential led to side reactions and poor polymer film quality. The structural characterization of PNI films by FTIR and 1H NMR indicated that the electrochemical polymerization of NI occurred at C2 and C3 positions.