Synthesis and photophysical properties of (post-)functionalized BOAHY dyes with strong aggregation-induced emission

A series of new difluoroboronate anchored acylhydrazone (BOAHY) derivates were prepared in good yields via a simple two-step reaction starting from commercially available reagents. The spectroscopic properties of these dyes can be easily tuned through appropriate functionalization and post-functionalization. While these BOAHYs are dim in solution, they are intensely fluorescent in the solid state, with absolute quantum yields up to 33%. By changing the solvent composition to reduce their solubility, the dyes form aggregates, thus switching on the fluorescence. Steady-state and time-resolved spectroscopy, as well as X-ray crystallography, provide a full characterization of these new BOAHYs and reveal the mechanism behind their aggregation-induced emission (AIE) behavior. BOAHY dyes are dim in solution but strongly fluorescent in the solid state, with quantum yields up to 33%. Our experiments provide a full characterization of these new dyes and reveal the mechanism behind their aggregation-induced emission behavior.