Su Qingqing, Li Yuanying, Wang Bin, Liu Minjuan, Wang Hongjuan, Wang Wenliang, Liu Fengyi
Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University , Xi'an, Shaanxi 710062, People's Republic of China.
J Phys Chem A. 2017 Apr 6;121(13):2588-2596. doi: 10.1021/acs.jpca.7b01674. Epub 2017 Mar 24.
We carried out CASPT2//(TD)DFT and CASPT2//CASSCF studies on the working mechanism of imine switches, including a camphorquinone-derived ketoimine (shortened as k-Imine) switch designed by Lehn as well as a model camphorquinone alkene-imine (a-Imine) proposed in this study. Under the experimental conditions (light irradiation with 455 and 365 nm for E and Z, respectively), k-Imine is excited to the S:(n,π*) state and then decays toward a perpendicular intermediate following the C═N bond rotation coordinate. During the bond rotation, a mild energy barrier caused by the strong interaction of S:(n,π*) and S:(n,π*) states will more or less slow down the rotation speed of k-Imine. The large difference in irradiation light wavelength supports k-Imine as a two-way photoswitch. The photoisomerization of a-Imine obeys a similar but fully barrierless pattern while requiring a higher excitation energy to reach the (n,π*) state. The good directionality of thermal isomerization toward E(a-Imine), plus the barrierless photoisomerization, allows for the design of a thermal and photo-operated switch. For both imines, a minimal-energy crossing point (MECI) located at the perpendicular region, with low relative energy and close to the rotary path, ensures the directionality of C═N bond rotation and confirms imines as optimal candidates for photoswitches and motors.
我们对亚胺开关的工作机制进行了CASPT2//(TD)DFT和CASPT2//CASSCF研究，其中包括勒恩设计的樟脑醌衍生的酮亚胺（简称为k-亚胺）开关以及本研究中提出的模型樟脑醌烯烃-亚胺（a-亚胺）。在实验条件下（分别用455和365 nm光照射E型和Z型），k-亚胺被激发到S:(n,π*)态，然后沿着C═N键旋转坐标向垂直中间体衰变。在键旋转过程中，由S:(n,π*)和S:(n,π*)态的强相互作用引起的适度能垒会或多或少地减慢k-亚胺的旋转速度。照射光波长的巨大差异支持k-亚胺作为一种双向光开关。a-亚胺的光异构化遵循类似但完全无势垒的模式，同时需要更高的激发能才能达到(n,π*)态。热异构化向E(a-亚胺)的良好方向性，加上无势垒的光异构化，使得热控和光控开关的设计成为可能。对于这两种亚胺，位于垂直区域、相对能量较低且靠近旋转路径的最小能量交叉点（MECI）确保了C═N键旋转的方向性，并证实亚胺是光开关和分子马达的最佳候选物。
