Excited state intramolecular proton transfer (ESIPT) of organic molecules has been drawing continuously considerable interests. It is not only one of the most basic processes in life but also exists in wide of application fields. In this work, we theoretically make a thorough inquiry about molecular excited state trends and ESIPT procedures for the novel highly miscible 2,5-bis (benzoxazol-2-yl)thiophene-3,4-diol-ethyl (BBTE) molecule. Based on DFT and TDDFT means, we first examine and certify hydrogen bond O1–H2···N3 role in BBTE. Probing into molecular structure and infrared (IR) vibrational behaviors, we validate O1–H2···N3 of BBTE is enhanced in S1 state via photo-induced excitation. Accessorial negative electronic densities over N3 atom facilitate attracting hydrogen proton, which caters to the truth of strengthening hydrogen bond in S1. In addition, frontier orbital gap indicates the solvent polarity plays vital roles in affecting excited state courses for BBTE. By means of potential energy curves (PECs) in three kinds of solvents, we propose the ultrafast ESIPT mechanism for BBTE with explaining previous experimental characteristics. Along the way of ESIPT, we present the regulation mechanism for BBTE via solvent polarities.

中文翻译：

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2,5-双（苯并恶唑-2-基）噻吩-3,4-二醇-乙基化合物在不同溶剂中的详细激发态质子转移机制的理论揭示

有机分子的激发态分子内质子转移 (ESIPT) 一直备受关注。它不仅是生命中最基本的过程之一，而且存在于广泛的应用领域。在这项工作中，我们从理论上对新型高度混溶的 2,5-双 (苯并恶唑-2-基)噻吩-3,4-二醇-乙基 (BBTE) 分子的分子激发态趋势和 ESIPT 程序进行了彻底调查。基于 DFT 和 TDDFT 手段，我们首先检查和证明氢键 O1–H2...N3 在 BBTE 中的作用。探究分子结构和红外 (IR) 振动行为，我们验证了 BBTE 的 O1–H2...N3 通过光诱导激发在 S1 状态下增强。N3 原子上的辅助负电子密度有助于吸引氢质子，这迎合了加强 S1 中氢键的事实。此外，前沿轨道间隙表明溶剂极性在影响 BBTE 的激发态过程中起着至关重要的作用。通过三种溶剂中的势能曲线（PEC），我们提出了 BBTE 的超快 ESIPT 机制，并解释了先前的实验特性。在 ESIPT 的过程中，我们通过溶剂极性展示了 BBTE 的调节机制。