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Unveiling the effect of solvent polarity on the excited state intramolecular proton transfer mechanism of new 3-hydroxy-4-pyridylisoquinoline compound.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy ( IF 4.3 ) Pub Date : 2020-01-21 , DOI: 10.1016/j.saa.2020.118082
Jiaojiao Hao 1 , Yang Yang 1
Affiliation  

The new 3-hydroxy-4-pyridylisoquinoline compound is attractive and promising lead structure in drug discovery. The pronounced sensitivity of its emission property toward solvent polarity effect was presented in experiment (J. Org. Chem, 2019, 84, 3011). Nevertheless, the experiment was lack of solvent polarity effect on the excited state intramolecular proton transfer (ESIPT) mechanism in detail. In this study, the ESIPT process of this molecule in different polarity solvents were comprehensively expounded by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. In order to ensure the accuracy of the experiment and roundly explore in theoretical level, two ESIPT pathways (1 and 2) based on the N1 and N2 forms of studied molecule were proposed, among which the ESIPT pathway 1 was derived from experiment. The calculated electronic spectrum of both N1 and N2 forms were rather comparable with the experiment. The calculated intramolecular hydrogen bond (IHB) parameters and infrared (IR) vibration spectra determined the enhancement of IHBs at the S1 state under different solvents for both N1 and N2 forms. The frontier molecular orbitals (FMOs) analysis proved that the intramolecular charge transfer (ICT) taken place during photoexcitation. The potential energy curves (PECs) at the S0 and S1 states were constructed to illustrate the solvent polarity effect on ESIPT mechanism. According to potential energy barriers (PEBs) on the PECs at S1 state, it is concluded that the ESIPT pathway 1 was forbidden with exceedingly high PEBs (24.585-25.322 kcal/mol), while the ESIPT pathway 2 was feasible with enough low PEBs (0.100-0.510 kcal/mol), which suggested the inconsequence of the experiment. Based on the PEBs of ESIPT pathway 2 in different solvent, the effect of solvent polarity on ESIPT mechanism was depicted. The results are as follows: the S1 state IHB intensity was enhanced with increasing solvent polarity; the extent of ICT was decreased with the increment of solvent polarity; the S1 state PEB was decreased as the solvent polarity increased. Indeed in short, the ESIPT reaction became more and more likely as the solvent polarity enhanced. We believe that this investigation will be useful to the utilization and development of property for such photochemical substances.

中文翻译:

揭示了溶剂极性对新型3-羟基-4-吡啶基异喹啉化合物的激发态分子内质子转移机理的影响。

新型的3-羟基-4-吡啶基异喹啉化合物在药物开发中具有诱人的前景,并具有广阔的前景。实验(J.Org.Chem,2019,84,3011)中显示了其发射性质对溶剂极性效应的显着敏感性。然而,该实验在激发态分子内质子转移(ESIPT)机理上缺乏溶剂极性的影响。在这项研究中,通过密度泛函理论(DFT)和时变DFT(TDDFT)方法全面阐述了该分子在不同极性溶剂中的ESIPT过程。为了保证实验的准确性并在理论层面进行全面探索,提出了两种基于N1和N2形式的被研究分子的ESIPT途径(1和2),其中ESIPT途径1来源于实验。N1和N2形式的计算电子光谱与实验相当。计算得出的分子内氢键(IHB)参数和红外(IR)振动光谱确定了在N1和N2形式的不同溶剂下,S1状态下IHB的增强。前沿分子轨道(FMOs)分析证明,在光激发过程中发生了分子内电荷转移(ICT)。构建了S0和S1状态下的势能曲线(PEC),以说明溶剂极性对ESIPT机理的影响。根据处于S1状态的PEC上的潜在能垒(PEB),可以得出结论,禁止使用过高的PEB(24.585-25.322 kcal / mol)禁止ESIPT途径1,而使用足够低的PEB则ESIPT途径2是可行的( 0.100-0.510 kcal / mol),这暗示了实验的不足。基于ESIPT途径2在不同溶剂中的PEB,描述了溶剂极性对ESIPT机理的影响。结果如下:随着溶剂极性的增加,S1态的IHB强度增强;ICT的程度随着溶剂极性的增加而降低;S1状态的PEB随着溶剂极性的增加而降低。简而言之,随着溶剂极性的增强,ESIPT反应变得越来越可能。我们认为,这项调查对于此类光化学物质的利用和开发将是有用的。随着溶剂极性的增加,S1态的IHB强度增强。ICT的程度随着溶剂极性的增加而降低。S1状态的PEB随着溶剂极性的增加而降低。简而言之,随着溶剂极性的增强,ESIPT反应变得越来越可能。我们相信,这项调查对于此类光化学物质的利用和开发将是有用的。随着溶剂极性的增加,S1态的IHB强度增强。ICT的程度随着溶剂极性的增加而降低;S1状态的PEB随着溶剂极性的增加而降低。简而言之,随着溶剂极性的增强,ESIPT反应变得越来越可能。我们相信,这项调查对于此类光化学物质的利用和开发将是有用的。
更新日期:2020-01-21
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