Electrosyntheses of high quality poly (5-nitroindole) films

Abstract

High quality poly (5-nitroindole) (PNP) films were synthesized electrochemically by direct anodic oxidation of 5-nitroindole in boron trifluoride diethyl etherate (BFEE) containing additional 10% diethyl ether (by volume). The additional diethyl ether improved the solubility of the monomer in BFEE. In this medium, the oxidation potential onset of 5-nitroindole was measured to be only 1.04 V vs. SCE. PNP films obtained from this medium showed good electrochemical behavior with conductivity of 10−2 S cm−1. Structural studies showed that the polymerization of 5-nitroindole ring occurred at 2,3 position. As-formed PNP films could be dissolved in acetone, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), etc. Fluorescent spectral studies indicated that PNP was a good green light emitter with the best excitation and emission wavelength 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 can be electrodeposited. These results will be greatly helpful for the understanding of the synthesis and properties of nitro-substituted conducting polymers and provide a new route for the post-functionalization of nitro-substituted conducting polymers through the reduction of nitro group.