Synthesis, structures and photophysical properties of boron fluorine derivatives based on pyridine/1,8-naphthyridine

Three boron fluorine complexes B1-B3 containing pyridine/1,8-naphthyridine were synthesized and structurally characterized. Compounds B1 and B2 exhibited strong fluorescence in solution and solid state. The solvent-dependent luminous properties and large Stokes shift in solution could be explained by intramolecular charge transfer, which is confirmed by time-dependent density functional theory calculation. The absolute quantum yield of B1 in powder form reached 0.48 because of inhibiting planar pi...pi stacking. Single-crystal X-ray diffraction analyses of B1 and B2 revealed that weak intermolecular C H...F and H...pi interactions hinder further stacking of pi...pi dimers, consequently preventing aggregation-induced quenching. Complex 113, composed of boron-dipyrromethene and 1,8-naphthyridine fluorophore, had potential applications as a pH ratiometric fluorescent sensor. (c) 2014 Elsevier Ltd. All rights reserved.