College of Physics and Materials Science, Henan Normal University, Xinxiang 453007, China.
College of Physics and Materials Science, Henan Normal University, Xinxiang 453007, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jul 5;200:1-9. doi: 10.1016/j.saa.2018.04.023. Epub 2018 Apr 11.
The control of internal molecular motions by outside stimuli is a decisive task in the construction of functional molecules and molecular machines. Light-induced intramolecular rotations of photoswitches have attracted increasing research interests because of the high stability and high reversibility of photoswitches. Recently, Henry et al. reported an unprecedented two-dimensional controlled photoswitch, the hemithioindigo (HTI) derivative Z1, whose single bond rotation in dimethyl sulphoxide (DMSO) solvent and double bond rotation in cyclohexane solvent can be induced by visible light (J. Am. Chem. Soc. 2016, 138, 12,219). Here we investigate the intramolecular rotations of the HTI and Z1 in different polar solvents by time-dependent density functional theory (TDDFT) and Nonadiabatic dynamic simulations. Due to the steric hindrance between methyl and thioindigo fragment, the rotations of Z1 in the excited state are obstructed. Interestingly, the HTI exhibits two distinct rotation paths in DMSO and cyclohexane solvents at about 50fs. The intermolecular hydrogen bonds between HTI and DMSO play an important role in the rotation of HTI in DMSO solvent. Therefore, the HTI is a more promising two-dimensional photoswitch compared with the Z1. Our finding is thus of fundamental importance to understand the mechanisms of this class of photoswitches and design complex molecular behavior.
外部刺激对内部分子运动的控制是构建功能分子和分子机器的关键任务。光致分子内旋转光开关因其高稳定性和高可逆性而引起了越来越多的研究兴趣。最近，Henry 等人报道了一种前所未有的二维可控光开关——半硫靛（HTI）衍生物 Z1，其在二甲亚砜（DMSO）溶剂中单键旋转，在环己烷溶剂中双键旋转均可被可见光诱导（J. Am. Chem. Soc. 2016, 138, 12,219）。在这里，我们通过含时密度泛函理论（TDDFT）和非绝热动力学模拟研究了 HTI 和 Z1 在不同极性溶剂中的分子内旋转。由于甲基和硫靛片段之间的空间位阻，Z1 在激发态下的旋转受到阻碍。有趣的是，HTI 在 DMSO 和环己烷溶剂中大约在 50fs 时呈现出两种不同的旋转路径。HTI 与 DMSO 之间的分子间氢键在 DMSO 溶剂中 HTI 的旋转中起着重要作用。因此，与 Z1 相比，HTI 是一种更有前途的二维光开关。我们的发现对于理解这类光开关的机制和设计复杂的分子行为具有重要的基础意义。
