A new conducting polymer was synthesized by electrochemical polymerization of 4-(2,5-di-2-thiophen-2-yl-pyrrol-1-yl)-2-phthalonitrile (SNS-PN). Electrochemical polymerization of SNS-PN was performed in acetonitrile/0.2M LiClO4 solvent/electrolyte couple. Characterizations of the resulting polymer P(SNS-PN) were carried out by cyclic voltammetry, UV-vis, and Fourier transform infrared (FTIR) spectroscopic techniques. Spectroelectrochemical studies revealed that P(SNS-PN) has an electronic band gap of 2.45 eV and exhibits electrochromic behavior. The switching ability of polymer was also monitored and the percentage transmittance change (Delta T%) was found as 24%. It is also found that P(SNS-PN) is fluorescent and its fluorescence intensity enhances in the presence of cations. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2685-2690, 2009