The Nonadiabatic Dynamic Research Of Diphenylbutadiene Photoisomerization Mechanism

The dissertation mainly introduce that applied high accuracy algorithms combined improved Zhu-Nakamura formula to study the mechanism of ?,?-diphenylpolyenes. The first part includes the properties of ?,?-diphenylpolyenes and the methods that we used to investigate the photoisomerization of diphenylbutadiene. The second part describes that we used the surface hopping molecular dynamic simulations to study photoisomerization mechanism of tt-DPB and cc-DPB.The first chapter mainly introduced the application of diphenylpolyenes, then presents its photochemical and photophysical properties, and introduces the following theories briefly:a new trajectory surface hopping method based on the improved Zhu-Nakamura formula; internal contracted multi-reference configuration interaction with single and double excitations ?ic-MRCISD?; configuration based multi-reference second order perturbation theory?CB-MRPT2?.In the second chapter, we introduced the photoisomerization mechanism of tt-DPB employing trajectory surface hopping method based on the improved Zhu-Nakamura formula. Static electronic structure computations indicate that the photo excitation makes tt-DPB easy to populate S₁ state in Frank-Condon region and the excited tt-DPB may decay directly to the more stable species of DPB which is proceed via two S₁/S₀ conical intersection zones. After internal conversion to S₀, the species may turn back to the original tt-DPB or rapidly towards to ct-DPB or cc-DPB. The nonadiabatic dynamic simulations verify the mechanistic picture and provide more details on the reaction processes. We have simulated 610 trajectories. Particularly, the present simulation results show that approximately 9.0% trajectories can decay forward to ct-DPB by one bond twist ?OBT? mechanism and about 4.5% of trajectories arrive at cc-DPB by bicycle pedal ?BP? mechanism, which are in good agreement with the experimental value of 7%?25% and 2%, respectively. Based the results of dynamic simulation, the lifetime of S1 state we fitted is 678.5fs, the lifetime to ct-DPB or cc-DPB are 692.5fs and 586.5fs, respectively. We found two conical intersections in the process of tt-DPB photoisomerization. According to the simulated results, the photoisomerization mainly went through CI1.The third chapter used the same method to preliminary study mechanism of cc-DPB isomerization reaction, and found that the difference from tt-DPB, in which isomerization of cc-DPB mainly through CI2 and the primary photoproduct is ct-DPB.