Nonadiabatic Dynamics of Photoinduced Proton-Coupled Electron Transfer in a Solvated Phenol-Amine Complex
Nonadiabatic Dynamics of Photoinduced Proton-Coupled Electron Transfer in a Solvated Phenol-Amine Complex
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DOI：
10.1021/jp5126969
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发表时间：
2015-02-12
影响因子：
3.3
通讯作者：
Hammes-Schiffer, Sharon
中科院分区：
文献类型：
--
作者：
Goyal, Puja;Schwerdtfeger, Christine A.;Hammes-Schiffer, Sharon
光诱导协同电子-质子转移（Photo-EPT）是一种重要的能量转换过程。对硝基苯酚-叔丁胺氢键复合物的瞬态吸收和拉曼光谱实验表明，该复合物在1，2-二氯乙烷溶剂化过程中可能发生光致EPT。实验探测了两个激发的电子状态，被解释为分子内电荷转移（ICT）状态和EPT状态。本文采用混合量子力学/分子力学非绝热表面跳跃动力学方法研究了光激发后的弛豫途径。势能面是在飞行中生成的半经验浮动占领分子轨道完整的活性空间组态相互作用方法的溶质分子和分子机械力场显式溶剂分子。自由能曲线沿着质子转移坐标说明，质子转移是热力学和动力学上有利的较低能量的激发态，但不是在较高能量的激发态，支持这些状态的表征为EPT和ICT，分别。非绝热动力学模拟表明，粒子数从ICT态到EPT态的衰减时间为100 fs，从EPT态到基态的衰减时间为1 ps，与实验结果定性一致.对于54%的轨迹，质子从苯酚转移到胺在400 fs的EPT状态，然后迅速转移回苯酚后衰变到基态。因此，这些计算增加了原来的实验数据的解释提供的证据质子转移的EPT状态之前衰变到基态。从这些模拟中获得的基本见解也与其他光EPT过程有关。
Photoinduced concerted electron-proton transfer (EPT), denoted photo-EPT, is important for a wide range of energy conversion processes. Transient absorption and Raman spectroscopy experiments on the hydrogen-bonded p-nitrophenylphenol-t-butylamine complex, solvated in 1,2-dichloroethane, suggested that this complex may undergo photo-EPT. The experiments probed two excited electronic states that were interpreted as an intramolecular charge transfer (ICT) state and an EPT state. Herein mixed quantum mechanical/molecular mechanical nonadiabatic surface hopping dynamics is used to investigate the relaxation pathways following photoexcitation. The potential energy surface is generated on the fly with a semiempirical floating occupation molecular orbital complete active space configuration interaction method for the solute molecule and a molecular mechanical force field for the explicit solvent molecules. The free energy curves along the proton transfer coordinate illustrate that proton transfer is thermodynamically and kinetically favorable on the lower-energy excited state but not on the higher-energy excited state, supporting the characterization of these states as EPT and ICT, respectively. The nonadiabatic dynamics simulations indicate that the population decays from the ICT state to the EPT state in 100 fs and from the EPT state to the ground state on the slower time scale of 1 ps, qualitatively consistent with the experimental measurements. For 54% of the trajectories, the proton transfers from the phenol to the amine in 400 fs on the EPT state and then transfers back to the phenol rapidly upon decay to the ground state. Thus, these calculations augment the original interpretation of the experimental data by providing evidence of proton transfer on the EPT state prior to decay to the ground state. The fundamental insights obtained from these simulations are also relevant to other photo-EPT processes.