含BN旋转轴的光驱动分子马达的理论设计和机理研究  

Theoretical Design and Mechanistic Study on a Light-Driven Molecular Rotary Motor with B=N Axis

作　　者：郭妮 王斌 刘峰毅 Guo, Ni Wang, Bin Liu, Fengyi(School of Chemistry and Chemical Engineering, Shaanxi Normal University, Key Laboratory for Macromolecular Science of Shaanxi Province, Xi＇an 710119, Chin)

机构地区：[1]陕西师范大学化学化工学院陕西省大分子科学重点实验室,西安710119

出　　处：《化学学报》2018年第3期196-201,共6页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.21473107;21636006);中央高校基本科研业务费(No.GK201502002)专项资金资助~~

摘　　要：依据B=N键与C=C键的电子结构相似性,以Feringa型二苯乙烯型光驱动分子马达(CC-stilbene)为母体,设计了含极性旋转轴的模型马达BN-stilbene.CASPT2//CASSCF计算结果表明,优化所得的BN-stilbene分子的基态存在四个与CC-stilbene马达结构相似、相对能量一致的螺旋异构体;B=N极性共价双键对BN-stilbene的基态和激发态电子结构有显著影响.对BN-stilbene模型马达的工作机理研究表明,极性旋转轴的引入使得BN-stilbene中S_1/S_0-CI与激发态中间体构型更加相似且能量更低,同时可增加旋转的驱动力,起到改进分子马达光异构化过程的单向性的目的.Light-driven molecular motors have attracted overwhelming attention due to their potential applications in a wide range of fields. Despite of the great successes obtained in alkene-based light-driven molecular motors and switches, scientists pursuing high-efficient alternatives with superior working mechanisms have never suspended. In this report, a promising model of light-driven rotary motor, namely BN-stilbene motor, constructed by replacing the central C =C axis of a CC-stilbene rotary motor with a polar B=N bond, was rationally designed. Multireference Complete Active Space Self-Consistent Field （CASSCF） method and Time-Dependent Density Functional （TDDFT） theory were applied to study the mechanism of BN-stilbene, along with the Complete Active Space Second-Order Perturbation Theory （CASPT2） energy corrections. Our calculations show that the B =N axis well preserves the conjugation of between the rotor and stator, leading to four ground-state helical conformers （i.e., cis-stable, trans-unstable, trans-stable and cis-unstable）, whose geometries and energies are in line with their counterparts in CC-stilbene motor; in addition, BN-stilbene has similar absorption spectra and more slopped excited-state potential energy curves at Franck-Condon region, which can fascinate a spontaneous rotary mo- tion around B=N axis, thus generates directional photo-induced isomerization from cis-stable to trans-unstable （or from trans-stable to cis-unstable）. Moreover, the barriers for helical inversions （trans-unstable ~ trans-stable or cis-unstable cis-stable） are found to be lower than those of the reversed thermal rotations （i.e., cis-stable --~ trans-unstable and trans-stable ---, cis-unstable）, which further insures the unidirectionality of rotation. These features sufficiently allow BN-stilbene to serve as a candidate for light-driven molecular rotary motor. Finally and most importantly, as compared with that of CC-stilbene, the photoisomerization mechanism of BN-stilbene motor shows advantages

关 键 词：光异构化 分子马达 圆锥交叉 无辐射跃迁 极性旋转轴 

分 类 号：O621.13[理学—有机化学]