N,O-bidentate BF2-enaminone complexes: Synthesis, electronic structure, photophysical properties, and biological behaviour

Abstract

Twenty-six examples of 2,2-difluoro-3,6-diaryl-2,3-dihydro-1,3,2-oxazaborinines were synthesised at 42–98% yield from commercially available reagents with a set of simple procedures and were structurally fully characterised by 1H, 13C, 19F, and 11B NMR spectroscopy and single-crystal X-ray diffraction. Quantum chemical calculations at (Time-Dependent) Density Functional Theory ((TD)-DFT) level were performed to study structural and electronic properties of these new N,O-boron complexes with variable structures. A comprehensive experimental and computational investigation of the photophysical properties of these BF2-complexes showed that they are emissive in solutions and have a pronounced fluorescence in the solid state (up to 100%). They also demonstrated aggregation-induced emission enhancement (AIEE) effect, with a quantum yield up to 29%, blue–green-yellow emissions and good photostability. The dynamic light scattering (DLS) experiments confirmed the formation of nanoparticles in DMSO-water and EtOH-water mixtures. Confocal laser detection revealed that these BF2-complexes may penetrate living cells and accumulate in the endoplasmic reticulum.