Synthesis and Characterization of Boron Difluoride Complexes Bearing π-Expanded Pyridine Ligands as Organic Fluorochromes

Novel boron complexes bearing pyrrole and π-expanded pyridine structures, such as quinoline, isoquinoline, and phenanthridine, were prepared. These compounds showed the fluorescence emission characters in both solution and solid state. Particularly, several complexes in solution exhibited high fluorescence quantum yield with Stokes shift values being four to five times larger than that of boron dipyrromethenes (BODIPYs). The present paper describes the optical properties of these novel boron complexes as well as their halogenated derivatives from the results of both experimental and computational studies.