Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Aug 14;129:280-4. doi: 10.1016/j.saa.2014.03.078. Epub 2014 Apr 2.
Time-dependent density functional theory method was performed to investigate the excited state intramolecular hydrogen bond dynamics of salicylaldehyde (SA). The geometric structures and IR spectra in the ground state S0 state and the excited state S1 state of SA are calculated using the density functional theory (DFT) and the time-dependent density functional theory (TDDFT) methods, respectively. In addition, the absorption and fluorescence peaks are also calculated using TDDFT methods. It is noted that the calculated large Stokes shift is in good agreement with the experimental results. Furthermore, our results have demonstrated that the excited state intramolecular proton transfer (ESIPT) process happens upon photoexcitation, which are distinct monitored by the formation and disappearance of the characteristic peaks of IR spectra involved in the formation of hydrogen bonds in different states and in the potential energy curves. We find that the hydrogen bonded quasi-aromatic chelating ring in the excited state becomes smaller which can facilitate the ESIPT process. The results presented here suggest that the ESIPT process of the SA molecule in the excited state can be attributed to the electronegativity change of O1 induced by excitation.
采用含时密度泛函理论方法研究了水杨醛（SA）分子内氢键的激发态动力学。利用密度泛函理论（DFT）和含时密度泛函理论（TDDFT）方法分别计算了 SA 在基态 S0 态和激发态 S1 态的几何结构和红外光谱。此外，还使用 TDDFT 方法计算了吸收和荧光峰。值得注意的是，计算出的大斯托克斯位移与实验结果吻合较好。此外，我们的结果表明，在光激发下会发生激发态分子内质子转移（ESIPT）过程，这可以通过不同状态下形成氢键的红外光谱特征峰的形成和消失以及势能曲线来明显监测到。我们发现，在激发态中氢键准芳香螯合环变小，这有利于 ESIPT 过程。这里的结果表明，SA 分子在激发态中的 ESIPT 过程可以归因于激发引起的 O1 电负性变化。
