中文摘要：

采用多组态CASSCF方法和MS-CASPT2方法研究了丁烯二腈中性分子及阳离子和阴离子的顺-反异构化机理.结果表明,中性分子和离子态的光顺-反异构化反应经历不同的非绝热跃迁途径：中性丁烯二腈受光激发至S1态后,需克服一个不低于19.7 k J/mol的能垒才有机会到达基态和激发态间的圆锥交叉（S1/S0-CI）,随后经非辐射跃迁回到基态,S1/S0-CI在结构上偏离C=C双键旋转路径,且能量较高,因此会降低旋转速度,阻碍旋转的单向性;丁烯二腈阳离子和阴离子自由基的D0态和D1态旋转势能面在90°处相交,优化的D1/D0-CI与D1态中间体的结构和能量均相近,因此从D1态经由D1/D0-CI无辐射跃迁到D0态的过程无势垒,在此过程中C=C旋转方向性得到最大限度的保持.研究结果证实了电子诱导不仅能降低基态热旋转势垒,而且能够调控光旋转的非绝热跃迁机理.

英文摘要：

CASSCF and MS-CASPT2 mechanistic studies were carried on the cis-trans isomerization processes of 1,2-dicyanoethylene in its neutral,cationic and anionic forms. The results confirmed the importance of electron-induction in reducing the reaction barrier,and more importantly,revealed the different nonadiabatic channels tuned by electron attachment / detachment. The S1→S0decay of neutral dicyanoethylene need overcome a mild barrier（ ≥19.7 k J / mol） to reach a H-migration-type,namely the S1/ S0-CI,which is away from the C=C torsional coordinates and may slow down the speed of C=C rotation and hurt its directionality;while in cationic and anionic isomerization processes,the D1 and D0 PESs intersect along the rotary path,therefore,the nonadiabatic D1→D0decay is barrierless,as result,the directionality of C=C rotation is maintained. The study revealed the role of electron induction in tuning the cis-trans photoisomerization,and shed light on the design of light-driven molecular rotary motors.