Syntheses and electrochromic and fluorescence properties of three double dithienylpyrroles derivatives

Three double dithienylpyrroles derivatives have been successfully prepared by performing a Knorr–Paal condensation between 1,4-di(thiophen-2-yl) butane-1,4-dione and various aromatic diamines. Additionally, their corresponding polymer films were synthesized via electropolymerization. Their electrochemical, spectroelectrochemical and electrochromic behaviors were further investigated by thermogravimetric analysis, scanning electron microscopy, cyclic voltammetry, UV–vis absorption and fluorescence emission spectra. Scanning electron microscopy and thermogravimetric analysis demonstrated that the polymer films possessed homogeneous, compact and smooth layer structures and thermal stabilities (up to nearly 180   °C). Cyclic voltammograms and UV–vis absorption spectra studies showed that the polymer films have stable, well-defined, reversible redox processes, low optical band gaps ( E g   <   2.2   eV) and multicolor electrochromic behaviors. Additionally, the fluorescence spectra study showed that all of the monomers and polymers exhibited different intensity emission bands at different wavelengths.