Charge‐Recombination Fluorescence from Push–Pull Electronic Systems Constructed around Amino‐Substituted Styryl–BODIPY Dyes

A small series of donor–acceptor molecular dyads has been synthesized and fully characterized. In each case, the acceptor is a dicyanovinyl unit and the donor is a boron dipyrromethene (BODIPY) dye equipped with a single styryl arm bearing a terminal amino group. In the absence of the acceptor, the BODIPY‐based dyes are strongly fluorescent in the far‐red region and the relaxed excited‐singlet states possess significant charge‐transfer character. As such, the emission maxima depend on both the solvent polarity and temperature. With the corresponding push–pull molecules, there is a low‐energy charge‐transfer state that can be observed by both absorption and emission spectroscopy. Here, charge‐recombination fluorescence is weak and decays over a few hundred picoseconds or so to recover the ground state. Overall, these results permit evaluation of the factors affecting the probability of charge‐recombination fluorescence in push–pull dyes. The photophysical studies are supported by cyclic voltammetry and DFT calculations.