TDDFT study on aluminum and fluoride dual-sensing mechanism of a Schiff-Base sensor.
TDDFT study on aluminum and fluoride dual-sensing mechanism of a Schiff-Base sensor.
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DOI：
10.1016/j.saa.2018.11.043
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
Dong Liu;Jieping Wang;Guang-Yue Li;Canhua Zhou
中科院分区：
文献类型：
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作者：
Dong Liu;Jieping Wang;Guang-Yue Li;Canhua Zhou
研究了先前报道的具有席夫碱部分的传感器的铝和氟化物双重传感机理。用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)方法对其进行了研究。目前的计算再现了传感器及其铝和氟化物络合物的光性质，这表明DFT和TDDFT是揭示不同电子态下详细的基于荧光的传感机制的可靠工具。理论计算结果表明，传感器中存在两个单键H-⋯-N氢键和F‘-络合物中的两个单键-H-⋯-F氢键。这些氢键引起的不同程度的共面导致了它们不同的吸收波长。然而，激发态几何构型优化和势能面扫描表明，传感器分子中的C双键N键发生了扭曲的分子内电荷转移，并发生了激发态质子从氟离子向邻近N原子的转移过程，从而使荧光猝灭。与铝传感器络合物相关的螯合增强荧光效应显示了不同的激发态过程。局部激发和发射仅发生在平面荧光团中，铝传感器络合物激发时结构的微小变化导致其强烈的荧光。从而从理论上解释了该传感器可以成功地用于氟离子的吸收光谱分析和铝阳离子的发射光谱分析。
The aluminum and fluoride dual-sensing mechanism of a previously reported sensor with a Schiff-base moiety (Spectrochim. Acta A, 2017, 183, 267–274) has been investigated by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The present calculations reproduce the photoproperties of the sensor as well as its aluminum and fluoride complexes, which illustrates that DFT and TDDFT constitute a reliable tool for uncovering detailed fluorescence-based sensing mechanisms in diverse electronic states. Theoretical results indicate that there are two Osingle bondH⋯N hydrogen bonds in the sensor and two Osingle bondH⋯F hydrogen bonds in its F¯ complex. Different degrees of coplanarity caused by these hydrogen bonds are responsible for their distinct absorption wavelengths. However, excited-state geometry optimization and a scan of the potential-energy surface show that there is twisted intramolecular charge transfer about the Cdouble bondN bond in the sensor molecule and an excited-state proton-transfer process from the fluoride anion to the neighboring N atom in the fluoride–sensor complex, whereby the fluorescence is quenched. A chelation-enhanced fluorescence effect associated with the aluminum–sensor complex shows a different excited-state process. The local excitation and emission occur exclusively within the planar fluorophore, and negligible structural change upon excitation of the aluminum–sensor complex leads to its strong fluorescence. Therefore, it is theoretically explained why the sensor may be successfully used to analyze the fluoride anion by absorption spectroscopy and the aluminum cation by emission spectroscopy.