Synthesis, Spectroscopic and Electrochemical Characterization of Carbazole and Triphenylamine BOPHY Derivatives. Electrochemical Generation of an Optoelectronic Polymeric Film

In this study, two new BOPHY-based derivatives were efficiently synthesized with high yields and characterized by using spectroscopic, electrochemical, and spectroelectrochemical techniques. The introduction of non-conjugated (carbazole (CBZ)) and conjugated (triphenylamine (TPA)) donor groups into the BOPHY macrocycle imparted different electrochemical and spectroscopic properties. Oxidation of BP-2CBZ led to the formation of unstable CBZ radical cations, which further reacted to generate dicarbazole (DCBZ) units, allowing the formation of a polymeric film during anodic cycling. In contrast, BP-2TPA exhibited a reversible oxidation process, generating stable BOPHY and TPA radical cations which inhibited the polymerization process. Spectroscopic differences were also observed, with BP-2CBZ displaying a high fluorescence quantum yield (Φ_f), while BP-2TPA emission was nearly quenched, exhibiting solvent-dependent fluorescence with a large Stokes shift (~160 nm). BP-2TPA also demonstrated aggregation-induced emission (AIE) properties, showing an increase in fluorescence intensity of around 12 times when the water content changes from 0 to 90 %. These experimental findings were further corroborated by DFT and TDDFT calculations. The BP-2CBZ polymer presented electrochromic properties, showing color changes upon oxidation. This work represents the first report of a BOPHY-based polymer synthesized through electrochemical methods.