Hydroxyphenyl benzothiazole (HBT), is a well-known organic system based on its special characteristic of the excited state hydrogen transfer (ESHT) following photoexcitation. However, the capability of this system regarding photochromism and photoswitching has not been addressed yet. In this study, we have investigated this issue by the aim of the MP2, CC2, ADC(2), and CASSCF theoretical methods. Also, we have considered several electron withdrawing groups and investigated their effects on the photophysical characteristics and spectroscopic properties of the enol and keto tautomers of the titled system. It has been predicted that the main HBT and its considered substitutions fulfill the essential characteristics required for photochromism. Also, substitution is an effective idea for tuning the photophysical nature of HBT and its similar systems. Our theoretical results verify that different substitutions alter the UV absorption of HBT systems from 330 to 351 nm and also the corresponding absorption wavelength of the γ-forms of 526–545 nm.

中文翻译：

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2-（2-羟基苯基）苯并噻唑（HBT）及其衍生物的光致变色理论研究

羟苯基苯并噻唑（HBT）是一种众所周知的有机体系，基于其在光激发后的激发态氢转移（ESHT）的特殊特性。但是，该系统有关光致变色和光开关的能力尚未得到解决。在这项研究中，我们已经通过MP2，CC2，ADC（2）和CASSCF理论方法的目的研究了此问题。另外，我们考虑了几个吸电子基团，并研究了它们对标题体系的烯醇和酮互变异构体的光物理特性和光谱性质的影响。据预测，主要的HBT及其考虑的替代物满足光致变色所需的基本特征。同样，替代是调节HBT及其类似系统的光物理性质的有效想法。