Department of Chemistry, School of Chemical Sciences, University Sains Malaysia, 11800, Minden, Penang, Malaysia.
J Fluoresc. 2022 May;32(3):937-948. doi: 10.1007/s10895-021-02782-5. Epub 2022 Feb 4.
Acid-responsive fluorescent compounds were prepared by introducing an ortho-hydroxyphenyl to pyrazoline with a benzothiazole backbone. These compounds demonstrated normal fluorescence photoinduced electron transfer (PET) under neutral conditions but the addition of trifluoroacetic acid showed an arctic blue fluorescence, we verified that a protonation process of nitrogen in the thiazole ring which weakened the ability of thiazole to donate electrons to the pyrazoline and changed the photoinduced electron transfer led to photoinduced electron transfer (PET), which was the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. The photophysical properties of Benzothiazole pyrazoline exhibited blue emission at 421 nm in aqueous DMSO. The blue shift in the emission was switched by acid in DMSO, showing the compound's distinct fluorescence peak at 554 nm. To investigate solvatochromism, eight different solvents were used. The red-shift emission observed in enhancing the polarity of solvents and emission in DMSO suggested the conformation of the molecule which led to the intramolecular charge transfer by color and emission changes. Furthermore, the probe was also applied using the High-performance liquid chromatography (HPLC) with a UV detector to determine the trifluoroacetic acid in water samples. Interestingly, the method was found to be linear over the range of 10.0 µg L to 250.0 µg L (0.999). Under the optimum condition, the separation of trifluoroacetic acid was achieved in 20 min with the LOD of 1.3 µg L and LOQ of 5.1 µg L. This proposed method also showed satisfactory results when applied for the analysis of trifluoroacetic acid in a water sample.
酸响应荧光化合物是通过在苯并噻唑骨架的吡唑啉中引入邻羟基苯来制备的。这些化合物在中性条件下表现出正常的荧光光诱导电子转移（PET），但加入三氟乙酸后则显示出极蓝光荧光，我们验证了噻唑环中氮的质子化过程削弱了噻唑向吡唑啉供电子的能力，并改变了光诱导电子转移，导致光诱导电子转移（PET），这是在强酸性条件下荧光猝灭现象的机制。苯并噻唑吡唑啉的光物理性质在水-DMSO 中表现出 421nm 的蓝色发射。在 DMSO 中，通过酸将发射蓝移，显示出化合物在 554nm 处有明显的荧光峰。为了研究溶剂化变色，使用了八种不同的溶剂。在增强溶剂极性时观察到的发射红移表明，分子的构象通过颜色和发射变化导致分子内电荷转移。此外，还使用带有紫外检测器的高效液相色谱（HPLC）将探针用于测定水样中的三氟乙酸。有趣的是，该方法在 10.0µg L 至 250.0µg L（0.999）的范围内呈线性。在最佳条件下，在 20min 内实现了三氟乙酸的分离，LOD 为 1.3µg L，LOQ 为 5.1µg L。该方法还用于水样中三氟乙酸的分析，结果令人满意。
