Fluorophores that respond to external stimuli, such as changes in pH, have utility in bio-imaging and sensing applications. Almost all pH-responsive fluorophores rely on complex syntheses and the use of pH-responsive functional groups that are peripheral to the fluorophore framework. In this work, pH-responsive boron-containing heterocycles based on tridentate acyl pyridylhydrazone ligands were prepared. These non-emissive heterocycles were synthesized in three steps from inexpensive, commercially available reagents without the use of chromatography or air-sensitive reagents. Treatment with acid resulted in protonation of the boron-bound methylamine donor and efficient blue photoluminescence. Experimental and computational analysis revealed that protonation resulted in a change in molecular structure and prevented photoluminescence quenching associated with photoinduced electron transfer. This work demonstrates a new approach for the design of fluorophores with potential applications in biological imaging.

中文翻译：

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配体质子化导致高荧光硼阳离子


对外部刺激（如 pH 值变化）做出反应的荧光团在生物成像和传感应用中具有实用性。几乎所有的 pH 响应性荧光基团都依赖于复杂的合成和荧光基团框架外围的 pH 响应官能团的使用。在本工作中，制备了基于三齿酰基吡啶酰腙配体的 pH 响应性含硼杂环。这些非发射杂环是用廉价的市售试剂分三步合成的，无需使用色谱或空气敏感试剂。用酸处理导致硼结合的甲胺供体的质子化和高效的蓝色光致发光。实验和计算分析表明，质子化导致分子结构发生变化，并阻止了与光诱导电子转移相关的光致发光猝灭。这项工作展示了一种在生物成像中具有潜在应用的荧光团设计新方法。