Haberhauer Julia, Mai Sebastian, González Leticia, Hättig Christof
Institute of Theoretical Chemistry I, Faculty of Chemistry, Ruhr University Bochum, Universitätsstraße 150, 44780 Bochum, Germany.
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstrasse 17, 1090 Vienna, Austria.
Phys Chem Chem Phys. 2025 Jul 17;27(28):14985-14998. doi: 10.1039/d5cp00889a.
Nonadiabatic surface hopping simulations are used to investigate the relaxation pathways after photoexcitation of 4-(indol-1-ylamino)benzonitrile, a prototypical example of -aryl-substituted 1-aminoindoles. This molecule combines functional groups that can undergo in the excited state twisted as well as planarized intramolecular charge transfer and are potential building blocks for molecular motors. The results of the nonadiabatic dynamics simulation show that after excitation with light in the range of 4.2-4.8 eV, the -aryl-substituted 1-aminoindole decays rapidly from S and S into the S state. On the S potential energy surface, the system relaxes then to one of the charge-transfer minima with twisted amino-phenyl and planarized amino-indole torsional angles. The twist and the planarization occur nearly synchronously, with a slight advance of the twist. The geometric relaxation is accompanied by a change of the electronic structure from a ππ* excitation localized on indole to a charge transfer excitation from the indole and amino groups into the benzonitrile moiety. The simulated time-resolved fluorescence spectrum exhibits a bright band from a locally excited state and a weaker charge-transfer band. The transition energies suggest that the experimentally observed emission happens from the S minima. After transition to the ground state, half of the trajectories relax back to the original minimum and half of the trajectories to its enantiomer. The twist and planarization occur nearly synchronously, with planarization slightly leading. The combination of preference to rotate over twisted intermediate structure in the excited state and over more twisted structures in the ground state indicates that some kinetic work is done during a full cycle. Even though the kinetic work done per cycle is small, this might be increased by introducing substituents.
非绝热表面跳跃模拟被用于研究4-(吲哚-1-基氨基)苯甲腈光激发后的弛豫途径，4-(吲哚-1-基氨基)苯甲腈是芳基取代的1-氨基吲哚的典型例子。该分子结合了在激发态可发生扭曲以及平面化分子内电荷转移的官能团，是分子马达的潜在构建模块。非绝热动力学模拟结果表明，在4.2 - 4.8 eV范围内的光激发后，芳基取代的1-氨基吲哚迅速从S1和S2态衰减到S0态。在S0势能面上，系统随后弛豫到电荷转移极小值之一，此时氨基苯基扭曲且氨基吲哚扭转角平面化。扭转和平坦化几乎同步发生，扭转略有提前。几何弛豫伴随着电子结构的变化，从吲哚上局域化的ππ*激发转变为从吲哚和氨基基团到苯甲腈部分的电荷转移激发。模拟的时间分辨荧光光谱显示出一个来自局域激发态的亮带和一个较弱的电荷转移带。跃迁能量表明实验观察到的发射发生在S0极小值处。跃迁到基态后，一半的轨迹弛豫回到原始极小值，另一半弛豫到其对映体。扭转和平坦化几乎同步发生，平坦化略领先。在激发态优先在扭曲的中间结构上旋转以及在基态优先在更扭曲的结构上旋转，这表明在一个完整循环中做了一些动力学功。尽管每个循环所做的动力学功很小，但通过引入取代基可能会增加。
