High solid-state luminescence in propeller-shaped AIE-active pyridine-ketoiminate-boron complexes.

Two pyridine-ketoiminate-based organoboron complexes (2 and 3) were developed. 2 and 3 showed very weak emission in low-viscosity organic solvents because of the intramolecular rotation induced non-radiative process. Their emission can be dramatically enhanced by the increase in solvent viscosity or by molecular aggregation in the solid state. Moreover, 2 and 3 exhibited intense emission with high quantum yield of 0.53 and 0.46, respectively. X-ray crystallographic analysis showed that the weak intermolecular interactions such as C-H···F and C-H···π by fixing the molecular conformations of 2 and 3 were responsible for intense luminescence in the solid state. The large Stokes shifts and high efficient solid-state emission of 2 and 3 make them valuable AIE luminophores for further potential applications in the fields of fluorescence imaging and materials science.