In-depth exploration of polysubstituted BOPHYs Dyes: Synthesis, photophysical, electrochemical, and theoretical properties

A family of new highly substituted and symmetrical BOPHYs with modulated optoelectronic properties was synthetized. The strategy consisted in the formation of pyrroles substituted with electron-donor or -withdrawing groups through the cycloaddition reaction between Fischer carbene and oxazolones. The absorption spectra of all compounds present a main peak due to the HOMO-LUMO electronic transition, as supported by the theoretical study. The maximum has large absorption coefficient ε (∼104 M−1cm−1) and is in the green region from 514 to 531 nm, red shifted with respect to unsubstituted BOPHY. The dihedral angle between the two bridged rings in the BOPHY core affects the degree of puckering, depending on the chemical modulation. The fluorescence spectra present excitonic features and pure color according to the CIE coordinates, from green, orange to almost red. Inside the family, the Stokes shift (Δν) follows the same trend as the maxima, and inversely with the fluorescence quantum yield (φ), being the most fluorescent (φ = 85%) the BOPHY with the lowest Stokes shift (Δν) (R1 = phenyl and R2 = methyl). BOPHYs are more difficult to oxidize and reduce than BODIPYs, displaying a shift in the anodic and cathodic potentials in regard to BODIPYs. The delocalization of charges in BOPHYs does not extend with an additional = N–BF2 nucleus, thus BOPHYs rather present a higher band gap reveling that are less conjugated molecules than mononucleous = N–BF2. [Display omitted] •Synthesis of new highly substituted BOPHYs with modulated optoelectronic properties.•Absorption and emission maxima are between 514-531 nm and 543–604 nm, respectively.•The molecules are electrochemically active, even after successive cycles.•The molecules may be considered as electron acceptors in organic solar cells.•Electron Donor groups increase HOMO but not LUMO, which is in the BOPHY core.