Department of Chemistry, University of Virginia, Charlottesville, VA, 22904, USA.
J Fluoresc. 2021 Jan;31(1):39-49. doi: 10.1007/s10895-020-02626-8. Epub 2020 Oct 14.
Emissive β-diketones (bdks) and difluoroboron complexes (BFbdks) exhibit multi-stimuli responsive luminescence, including solvatochromism, viscochromism, aggregation induced emission, thermal and mechanochromic luminescence, halochromism and pH sensing. In this study, a series of six-membered heterocycle-substituted (piperidine, morpholine, 1-methyl piperazine) bdk ligands and boron complexes were synthesized, and their luminescent properties were investigated. All the compounds exhibited red-shifted emission in more polar solvents due to intramolecular charge transfer as well as higher emission intensity in more viscous environments. In response to solubility changes in water/tetrahydrofuran mixtures, while the piperazine bdk ligand showed aggregation caused quenching, the piperidine and morpholine bdks displayed enhanced emission upon aggregation. In the solid state, all ligands exhibited mechanochromism. More dramatic halochromism was observed for the piperidine boron dye spin cast film. In solution, for the boron dyes under varying pH values (1-13), different protonated and deprotonated forms were analyzed according to the measured emission spectra. Graphical abstract Multi-stimuli responsive luminescent properties were investigated for the six-membered heterocycle-substituted β-diketone ligands and difluoroboron complexes.
发光β-二酮（bdks）和二氟硼配合物（BFbdks）表现出多种刺激响应发光，包括溶剂变色、粘光变色、聚集诱导发光、热和机械变色发光、卤键变色和 pH 传感。在这项研究中，合成了一系列六元杂环取代（哌啶、吗啉、1-甲基哌嗪）bdk 配体和硼配合物，并研究了它们的发光性质。所有化合物在极性更强的溶剂中由于分子内电荷转移而表现出红移发射，在更粘稠的环境中表现出更高的发射强度。在响应水/四氢呋喃混合物中溶解度的变化时，虽然哌嗪 bdk 配体表现出聚集导致的猝灭，但哌啶和吗啉 bdk 在聚集时表现出增强的发射。在固态下，所有配体均表现出机械变色。对于哌啶硼染料旋涂薄膜，观察到更剧烈的卤键变色。在溶液中，对于不同 pH 值（1-13）下的硼染料，根据测量的发射光谱分析了不同的质子化和去质子化形式。
