Ab initio trajectory surface-hopping dynamics studies of excited-state proton-coupled electron transfer reactions in trianisoleheptazine-phenol complexes.
Ab initio trajectory surface-hopping dynamics studies of excited-state proton-coupled electron transfer reactions in trianisoleheptazine-phenol complexes.
复制标题
三茴香七嗪-苯酚复合物中激发态质子耦合电子转移反应的从头开始轨迹表面跳跃动力学研究
DOI：
10.1039/d2cp01262f
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
W. Domcke
中科院分区：
文献类型：
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作者：
X. Huang;W. Domcke
Schlenker和同事最近利用时间分辨光致发光猝灭和泵探针实验研究了三苯基异七嗪（TAHz）氢键配合物与几种苯酚衍生物的激发态质子耦合电子转移（PCET）反应。三苯基异七嗪是一种与聚合物氮化碳相关的发色团，广泛应用于析氢光催化。苯酚上的PCET反应活性明显依赖于取代基的给电子/吸电子性质，有迹象表明，对最强烈的给电子取代基甲氧基的PCET反应是无障碍或几乎无障碍的。本文采用TDDFT/ωB97X-D电子结构模型，对taz -苯酚和taz -甲氧基苯酚两种配合物的激发态PCET动力学进行了第一线原理非绝热动力学模拟。TDDFT/ωB97X-D电子结构模型的定性可靠性通过基于波函数的从头算方法(二阶代数图构造（ADC(2)）对激发能和势能分布进行广泛的基准测试来评估。非绝热动力学模拟提供了时间和结构上解决的见解范式PCET反应在taz -苯酚配合物。光激发亮1ππ*态到TAHz长寿命暗S1态的无辐射弛豫发生在100 fs以内。实验中观察到，由于h原子转移势垒较低，taz -甲氧基苯酚配合物在绝热S1表面上的PCET反应速度比taz -苯酚配合物快。在目前模拟覆盖的250 fs时间窗口内，发现配合物到电子基态的弛豫仅通过PCET发生，证实了氢键在荧光猝灭过程中的重要作用。计算的PCET时间常数的绝对值明显短于从时间分辨光致发光测量中提取的TAHz与酚醛底物在甲苯中的混合物。讨论了这种差异的可能根源。
The excited-state proton-coupled electron-transfer (PCET) reaction in hydrogen-bonded complexes of trianisoleheptazine (TAHz), a chromophore related to polymeric carbon nitrides widely used in hydrogen-evolution photocatalysis, with several phenol derivatives were recently studied by Schlenker and coworkers with time-resolved photoluminescence quenching and pump–probe experiments. A pronounced dependence of the PCET reactivity on the electron-donating/electron-withdrawing character of the substituents on phenol was found, with indications of a barrierless or nearly barrierless PCET reaction for the most strongly electron-donating substituent, methoxy. In the present work, the excited-state PCET dynamics was explored with first-principles nonadiabatic dynamics simulations using the TDDFT/ωB97X-D electronic-structure model for two selected complexes, TAHz–phenol and TAHz–methoxyphenol. The qualitative reliability of the TDDFT/ωB97X-D electronic-structure model was assessed by extensive benchmarking of excitation energies and potential-energy profiles against a wave-function-based ab initio method, the algebraic-diagrammatic construction of second order (ADC(2)). The nonadiabatic dynamics simulations provide temporally and structurally resolved insights into paradigmatic PCET reactions in TAHz–phenol complexes. The radiationless relaxation of the photoexcited bright 1ππ* state to the long-lived dark S1 state of TAHz occurs in less than 100 fs. The ensuing PCET reaction on the adiabatic S1 surface is faster in TAHz–methoxyphenol complexes than in TAHz–phenol complexes due to a lower H-atom-transfer barrier, as observed in the experiments. The relaxation of the complexes to the electronic ground state is found to occur exclusively via PCET within the 250 fs time window covered by the present simulations, confirming the essential role of the hydrogen bond for the fluorescence quenching process. The absolute values of the computed PCET time constants are significantly shorter than those extracted from time-resolved photoluminescence measurements for mixtures of TAHz with phenolic substrates in toluene. The possible origins of this discrepancy are discussed.