Near-infrared-emitting difluoroboron β-diketonate dye with AIE characteristics for cellular imaging

Abstract Near-infrared (NIR) fluorophores have promoted the development of materials for bioimaging and therapy, but traditional NIR dyes usually suffer from aggregation-caused quenching (ACQ), impeding their applications. Herein, we propose a difluoroboron β-diketonate complex TTBE, consisting a donor-acceptor (D-A) structure with difluoroboron moiety as an electron acceptor and N, N-diethylaniline as well as triphenylamine (TPA)-thiophene building block as two electron donors. TTBE exhibited both solvatochromism and aggregation-induced emission (AIE) characteristics. In polar solvent DMSO, the emission maxima of TTBE were observed at 680 nm with low fluorescence quantum yield (ΦF = 0.01%), while in less polar solvent CH2Cl2, its emission maxima blue-shifted to 666 nm with increased fluorescence quantum yield (ΦF = 0.41%). The fluorescence of TTBE could be enhanced 650-fold in 90% hexane/THF mixture solution relatively to that in pure THF. Moreover, the fabricated F127/TTBE nanoparticles (NPs) showed NIR emission at 735 nm in water and excellent cytocompatibility even at high concentration (100 μg/mL). According to the results of cell imaging and flow cytometry, NPs were easily internalized into cells and distributed in the cytoplasm with strong red fluorescence. Therefore, this research inspires more insight into development of NIR AIE luminogens for biomedical imaging.