Lan Rui-Fang, Yang Yun-Fan, Ma Yan-Zhen, Li Yong-Qing
Department of Physics, Liaoning University, Shenyang 110036, PR China.
Department of Physics, Liaoning University, Shenyang 110036, PR China; State Key Lab of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2017 Aug 5;183:37-44. doi: 10.1016/j.saa.2017.04.018. Epub 2017 Apr 18.
The symmetrical structures 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (BBTD) can take shape two intramolecular hydrogen bonds in chloroform. In order to research the molecular dynamic behavior of BBTD upon photo-induced process, we utilize density functional theory (DFT) and time-dependent density functional theory (TDDFT) to complete theoretical calculation. Through the comparison of bond length, bond angle, IR spectra, and frontier molecular orbitals between ground state (S) and first excited state (S), it clearly indicates that photoexcitation have slightly influence for intensity of hydrogen bond. For the sake of understanding the mechanism of excited state intramolecular proton transfer (ESIPT) of BBTD in chloroform, potential energy surfaces have been scanned along with the orientation of O-H and O-H in S and S state, respectively. A intrigued hydrogen bond dynamic phenomenon has been found that ESIPT of BBTD is not a synergetic double proton transfer process, but a stepwise single proton transfer process BBTD→BBTD-S→BBTD-D. Moreover, the proton transfer process of BBTD-S→BBTD-D is easier to occur than that of BBTD→BBTD-S in S state.
对称结构2,5-双（苯并恶唑-2-基）噻吩-3,4-二醇（BBTD）在氯仿中可形成两个分子内氢键。为了研究BBTD在光诱导过程中的分子动力学行为，我们利用密度泛函理论（DFT）和含时密度泛函理论（TDDFT）完成理论计算。通过比较基态（S）和第一激发态（S）之间的键长、键角、红外光谱和前线分子轨道，清楚地表明光激发对氢键强度的影响较小。为了理解BBTD在氯仿中的激发态分子内质子转移（ESIPT）机制，分别沿着S态和S态中O-H和O-H的方向扫描了势能面。发现了一个有趣的氢键动力学现象，即BBTD的ESIPT不是协同双质子转移过程，而是分步单质子转移过程BBTD→BBTD-S→BBTD-D。此外，在S态中，BBTD-S→BBTD-D的质子转移过程比BBTD→BBTD-S的质子转移过程更容易发生。
