Boron difluoride hydrazone (BODIHY) complexes: A new class of fluorescent molecular rotors

Fluorescent dyes exhibiting luminescence in the solid state are crucial for the development of efficient solid-state lighting devices. Most fluorophores though do not emit in the solid state, mainly as a result of intermolecular interactions that cause emission quenching. Boron difluoride hydrazone (BODIHY) dyes are peculiar in this sense as their emission is drastically enhanced when transferred from solution to the solid state. The BODIHY dyes are easy to synthesize and derivatize, have tunable absorption and emission profiles and large Stokes shifts, which are all desirable characteristics from solid-state emitters. Here, we summarize the discovery and development of BODIHY dyes including the tuning of their photophysical properties through structure-property analyses.