激发态质子转移分子2-（2′-羟基苯基）苯并噻唑在不同溶剂中的光谱特性

观测了2-（2′-羟基苯基）苯并噻唑（HBT）在不同极性溶剂中的吸收光谱和荧光光谱，详细研究了溶剂极性对HBT发生激发态分子内质子转移（ESWT）影响的机制。吸收光谱表明在常态条件下，HBT在各种溶剂中都以烯醇式构型和酮式构型共同存在，但以烯醇式构型占绝大多数。荧光光谱表明在纯环己烷溶剂中，HBT被紫外光激发时，绝大多数烯醇式构型发生ESIPPT转变为酮式构型，分子的ESIPT效率最大。在含有乙醇的极性溶剂中，HBT烯醇式会形成溶剂化的烯醇式构型，阻碍分子发生ESIPT反应。溶剂中乙醇含量愈多极性愈强，溶剂化烯醇式的成份就愈多，HBT的ESIPT效率就愈低。以400nm光激发HBT溶液时，在510nm处发现酮式构型荧光，从而确认了400nm处的弱吸收是酮式构型的吸收；且在436和456nm处还有新的荧光峰，分析其可能来源于酮式构型去质子化阴离子的发射。

The Spectra Properties of 2-(2'-hydroxyphenyl)benzothiazole in Different Solvents

2-(2 -hydroxyphenyl)benzothiazole (HBT) is a typical compound with excited--state intramolecular proton transfer (ESIPT) effect. The mechanism of the influence of the solvent polarity on the ESIPT effect of HBT was investigated by means of absorption and fluorescence spectra in different polar solvents. The absorption spectra of HBT molecule in all solvents have the similar configuration and are mainly situated in the UV region from 260 to 370 nm. The absorption peaks are located at 287 and 335 nm and have the decline trend with the increase in the solvent polarity. In addition, there is a very weak absorption band at 400 nm and it is attributable to the absorption from the keto form of HBT. Under UV excitation at 335 nm, the fluorescence spectra in all the solvents were obtained. All the fluorescence spectra exhibit dual fluorescence peaks, which are located at 385 and 512 nm respectively. The former is attributed to the emission from the HBT enol forms, named the normal fluorescence, and the latter the emission from the keto tautomer emission, named ESIPT fluorescence. The fluorescence spectra of HBT show that the intensity of the normal fluorescence is obviously increased and the intensity of the ESIPT fluorescence is decreased with enhancing the polarity of the solvents. This indicates that the strong polar solvents are not favorable to the ESIPT of HBT. Because the solvated enols in the polar solvent prevent the ESIPT from happening, the ESIPT efficiency of HBT in cyclohexane is the largest and that of HBT in ethanol is the smallest. The three fluorescence bands of HBT in different polarity solvents were observed with 400 nm excitation. One fluorescence band at ca. 510 nm is referred to as the ESIPT fluorescence. This confirms that the weak absorption at 400 nm results from the keto tautomer and the enol and keto forms can coexist under the normal condition, but the enol form is the absolutely predominant. In addition, the other two unknown fluorescent emission bands appear at 436 and 456 nm respectively. Their possible origin is the emission from the deprotonated anion of HBT keto tautomer.