Electrochemical Generation of Aza-BODIPY Polymers as NIR-Absorbing Electrochromic Materials

A new aza-BODIPY derivative substituted at its periphery with triphenylamine (TPA) units was synthesized in high yield on a preparative scale. The first step involved a Claisen–Schmidt condensation between commercially available 6′-methoxy-2′-acetonaphthone and 4-(diphenylamino)benzaldehyde, affording the corresponding chalcone derivative. This α,β-unsaturated ketone was then subjected to a Michael addition in the presence of CH₃NO₂, yielding diaryl-4-nitrobutan-1-ones. Subsequent treatment with NH₄OAc in refluxing butanol afforded the corresponding tetraarylazadipyrromethene intermediate. Finally, complexation with BF₃·OEt₂ and N,N-diisopropylethylamine in dry dichloroethane led to the target aza-BODIPY bearing two TPA moieties. These substituents were introduced to enable radical coupling reactions under electrochemical conditions. The monomer was electropolymerized onto Pt and ITO electrodes via cyclic voltammetry within an appropriate potential window. During electrochemical cycling, a progressive increase in the redox currents was observed with each scan, indicating the growth of a polymer film on the electrode surface. Polymer formation was confirmed by CV and UV–Vis spectroscopy. Spectroelectrochemical studies revealed changes in the absorption spectra at different wavelengths as a function of the applied potential. These optical transitions, occurring in both the visible and near-infrared regions of the electromagnetic spectrum. Our outcome highlight that this new aza-BODIPY-based electropolymer is a promising candidate for application in electrochromic devices, particularly those requiring NIR absorption capabilities