A theoretical study on the relationship between the excited states and the photochemical behavior of stilbene and its derivatives

二苯乙烯及其衍生物的光化学行为一直是光化学研究的热点。尽管在实验和理论上付出了很大努力来阐明它，但还没有被广泛接受的图景。本研究采用从头算分子轨道方法研究了二苯乙烯及其衍生物（类二苯乙烯）的激发态电子结构和动力学。我们减少了完全的计算量。基于初步组态相互作用计算的活性空间自洽场计算. 1）二苯乙烯在反式二苯乙烯的Franck-Condon（FC）区的光化学行为我们计算了FC区的势能面，了解了反式二苯乙烯的初始过程.在第一激发流形S_0-S_3电子激发后，2）苯乙烯的光化学行为我们对苯乙烯的势能面进行了全局扫描，其中包括了S_1/S_0-和S_2/S_1-锥形交叉点（CIXs）的重要成分。3）苯乙烯衍生物的S_1/S_0-CIX_s计算了苯乙烯衍生物的S_1/S_0-CIX_s。发现它们的特征是在两性离子和共价双自由基状态之间存在一个交叉区域。4）4-二甲氨基的光化学行为。4 '-氰基二苯乙烯（DCS）在极性溶剂中的自由能面的计算，探讨了扭曲内电荷转移态的形成机理。计算了光聚合反应的S_1/S_0-CIX。

The photochemical behavior of stilbene and its derivatives has been of great interest in photochemistry. In spite of much effort to elucidate it both experimentally and theoretically, there is no widely accepted picture. In this research project, we examined the electronic structures and dynamics in the excited states of stilbene and its derivatives (stilbenoids) by means of ab initio molecular orbital (MO) method. We reduced the computational labor of complete. active space self-consistent field calculations based on preliminary configuration interaction calculations.1) the photochemical behavior of stilbene in the Franck-Condon (FC) region of teans-stilbeneWe calculated the potential energy surfaces in the FC region to know the initial process of trans-stilbene. Right after electronic excitation of S_0-S_3 which is main transition in the first excited manifold, a planar delocalized quinoid structure is preferable so as for the photoisomerization to take place.2) the photochemical behavior of stvreneWe globally scanned the potential energy surfaces of styrene including the important ingredients of the S_1/S_0- and S_2/S_1-conical intersections (CIXs) so as to present a new and reasonable picture of the photochemistry of styrene.3)the S_1/S_0-CIX_s of styrene derivativesWe calculated the S_1/S_0-CIX_s of styrene derivatives. It is found that they are characterized by a crossing region between zwitterionic and covalent diradical states.4) the photochemical behavior of 4-dimethylamino. 4'-cyanostilbene (DCS)We calculated the free energy surface of DCS in polar solvent to discuss the formation mechanism of the twisted internal charge transfer state. We also calculated the S_1/S_0-CIX for the photosiomerization.