A solid-state red-emitting dye (1) containing 2-(2′-hydroxyphenyl)benzothiazole (HBT) group at the 8-position of BODIPY was designed and synthesized. The emission peak of 1 in powder was located at 607 nm, and it exhibited a 59 nm red-shift than that in THF (548 nm). The increasing solvent viscosity and solution concentration induced fluorescent enhancement. Because of the phenolic hydroxyl group as pH-sensitive moiety, 1 could be used as a fluorescent and colorimetric probe for the determination of pH. When the pH was increased from 4.5 to 9.8, 1 displayed a remarkable emission quenching at 528 nm as well a red-shift from 455 nm to 484 nm, simultaneously exhibiting a significant fluorescence color change from bright green to blackish green. The dye 1 responded linearly to minor pH fluctuations within the range of 6.8–8.5. The pK_a value was 7.32. In addition, 1 could be utilized in pH-dependent fluorescence imaging in HeLa cells. The CCK-8 assay showed that the cytotoxicity of 1 was low.

中文翻译：

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具有固态发射的BODIPY–2-（2'-羟基苯基）苯并噻唑共轭物的合成及其在荧光pH探针中的应用†

设计并合成了在BODIPY的8位上含有2-（2'-羟基苯基）苯并噻唑（HBT）基团的固态红色发射染料（1）。粉末中的1的发射峰位于607 nm处，与THF（548 nm）相比显示出59 nm的红移。溶剂粘度和溶液浓度的增加引起荧光增强。由于酚羟基是pH敏感部分，因此1可用作荧光和比色法测定pH的探针。当pH从4.5提高到9.8，1在528 nm处显示出显着的发射猝灭以及从455 nm到484 nm的红移，同时显示出从亮绿色到黑绿色的显着荧光颜色变化。染料1对6.8-8.5范围内的较小pH波动具有线性响应。p K _a值为7.32。此外，1可用于HeLa细胞的pH依赖性荧光成像。CCK-8分析显示1的细胞毒性很低。