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首页> 外文期刊>The Journal of Chemical Physics >Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study
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Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study

机译：氢键引起的三重态激发电子态转换：瞬态吸收光谱和随时间变化的DFT研究

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The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T-1 and T-2 states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S-0 state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S-0, T-1, and T-2 states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the n pi* triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents. (C) 2016 AIP Publishing LLC.
机译：溶剂在芳族酮的光化学和光物理中起决定性作用。黄酮（XT）就是这样一种芳香族酮，其三重态-三重态（T-T）吸收光谱显示出有趣的溶剂变色行为。而且，XT对H原子抽象的反应性表明，质子溶剂相对于非质子溶剂前所未有的降低。因此，结合时间依赖的密度泛函理论，使用特设的显式溶剂模型方法对XT的三重态-三重态-三重态吸收光谱进行了溶剂溶变色分析。 XT的T-T吸收带的详细溶剂变色分析表明，氢键相互作用在相应的三重态激发态中是不同的。此外，发现非特异性和氢键相互作用对质子溶剂中三重态的不同溶剂化的贡献具有相同的大小。 XT的T-1和T-2状态的前沿分子轨道和电子密度差分析表明，相对于S-0状态，这些状态下的电荷重新分布分别导致分子间氢键增强和减弱。 XT-甲醇超分子复合物的垂直激发能计算进一步支持了这一点。在S-0，T-1和T-2状态下，针对该配合物获得的分子间氢键势能曲线支持该模型。总之，我们认为XT的两个最低三重态激发态表现出的不同氢键机制导致n pi *三重态的作用降低，因此导致其在质子溶剂中对H原子抽象的反应性降低。 （C）2016 AIP出版有限责任公司。

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