Surface Hopping Excited-State Dynamics Study of the Photoisomerization of a Light-Driven Fluorene Molecular Rotary Motor
Surface Hopping Excited-State Dynamics Study of the Photoisomerization of a Light-Driven Fluorene Molecular Rotary Motor
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DOI：
10.1021/ct200199w
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发表时间：
2011-07-01
影响因子：
5.5
通讯作者：
Filatov, Michael
中科院分区：
文献类型：
--
作者：
Kazaryan, Andranik;Lan, Zhenggang;Filatov, Michael
我们报告了一个典型的基于芴的分子旋转马达（1）的工作循环中的光异构化步骤的理论研究。采用正交化修正的OM 2哈密顿量结合多参考组态相互作用（MRCI）处理，通过半经验量子化学计算，研究了基态电子态（S-0）和第一单重激发态（S-1）的势能面. OM 2/MRCI的结果为相关的1-P和1-M异构体和相应的S-0过渡态的SO和Si的最小值是在良好的协议与更高层次的计算，无论是在几何和能量。通过定位两个S-0-S-1最小能量锥形交叉点和交叉缝上的附近点，并通过计算朝向这些MECIs的路径的能量分布，在OM 2/MRCI水平上表征S-1表面。利用半经典Tully型轨道表面跳跃（TSH）方法和OM 2/MRCI方法研究了光激发到S-1态后的激发态动力学.通过锥形交叉区域观察到快速弛豫到基态，主要是通过具有强烈扭曲的中心C=C双键和平行化的中心碳原子的最低能量区域。从TSH-OM 2模拟的直接和逆光异构化反应的激发态寿命（1.40和1.79 ps）和光稳态比（2.7：1）与现有的实验数据（约1.50 ps）吻合得很好。1.7 PS和3：1）。激发态寿命，光稳态比，和动力学的细节的TSH-OM 2模拟也同意经典的分子动力学模拟使用重新参数化的优化势液体模拟（OPLS）的所有原子力场与ad-hoc表面跳跃在预定义的圆锥形交叉点。后一种方法允许更广泛的统计抽样。
We report a theoretical study of the photoisomerization step in the operating cycle of a prototypical fluorene-based molecular rotary motor (1). The potential energy surfaces of the ground electronic state (S-0) and the first singlet excited state (S-1) are explored by semiempirical quantum-chemical calculations using the orthogonalization-corrected OM2 Hamiltonian in combination with a multireference configuration interaction (MRCI) treatment. The OM2/MRCI results for the So and Si minima of the relevant 1-P and 1-M isomers and for the corresponding S-0 transition state are in good agreement with higher-level calculations, both with regard to geometries and energetics. The S-1 surface is characterized at the OM2/MRCI level by locating two S-0-S-1 minimum-energy conical intersections and nearby points on the intersection seam and by computing energy profiles for pathways toward these MECIs. Semiclassical Tully-type trajectory surface hopping (TSH) simulations with on-the-fly OM2/MRCI calculations are carried out to study the excited-state dynamics after photoexcitation to the S-1 state. Fast relaxation to the ground state is observed through the conical intersection regions, predominantly through the lowest-energy one with a strongly twisted central C=C double bond and pyramidalized central carbon atom. The excited-state lifetimes for the direct and inverse photoisomerization reactions (1.40 and 1.79 ps) and the photostationary state ratio (2.7:1) from the TSH-OM2 simulations are in good agreement with the available experimental data (ca. 1.7 ps and 3:1). Excited-state lifetimes, photostationary state ratio, and dynamical details of the TSH-OM2 simulations also agree with classical molecular dynamics simulations using a reparametrized optimized potentials for liquid simulations (OPLS) all-atom force field with ad-hoc surface hops at predefined conical intersection points. The latter approach allows for a more extensive statistical sampling.