Furan and pyridinechalcogenodiazole-based π-conjugated systems via a donor-acceptor approach

Two novel furan and pyridinechalcogenodiazole based monomers, namely 4,7-di(furan-2-yl)-[1, 2, 5]thiadiazolo[3,4-c]pyridine (Fu-S-Fu) and 4,7-di(furan-2-yl)-[1, 2, 5]selenadiazolo [3,4-c]pyridine (Fu-Se-Fu), where a single atom in the pyridinechalcogenodiazole unit is varied from S to Se, were designed and synthesized via a donor-acceptor approach, and then the corresponding polymers, P(Fu-S-Fu) and P(Fu-Se-Fu), were electrosynthesized. Also, structure characterization and optoelectronic properties, including FTIR, SEM, DFT theoretical calculations, intramolecular charge transfer nature, optical and electrochemical behaviors, and electrochromic performance, were systematically investigated and comparatively discussed. The obtained monomers exhibited lower oxidation potential (Fu-S-Fu: 1.12 V; Fu-Se-Fu: 1.09 V), leading to the facile electrodeposition of uniform hybrid polymer films with outstanding electroactivity at low oxidation potentials. Optical spectroscopy of corresponding polymers showed that Se substitution led to a red-shift in the low-energy transition, while the high-energy band remains relatively constant in energy.