The Nonadiabatic Dynamic Research Of Hemithioindigo-hemistilbene Photoisomerization Mechanism

This dissertation is divided into three parts.The first part includes the dominant mechanism of Z?E isomerism,which plays an important role in the research of hemithioindigo hemistilbene(HTI).The second part introduces the method to study photoisomerization mechanism of E-HTI and Z-HTI.The third part is the most important part,which describes the study of photoisomerization mechanism of E-HT1 and Z-HTI employing the surface hopping molecular dynamic simulations.The former part of chapter 1 is the introduction section,which includes the dominant mechanism of Z?E isomerism and relevant compounds of Z?E isomerism.The latter part of chapter 1 mainly introduces methods applied on this dissertation,a new method based on the improved Zhu-Nakamura formula makes the dynamics smoothly and then gets the right result.The second part mainly displays the S1 excitation E?Z photoisomerization mechanisms of hemithioindigo hemistilbene(HTI).First,we employ static electronic structure computations in optimizing geometries and obtain seven conical intersections(CI).Then we have employed the two-state-averaged CASSCF calculations together with the Zhu-Nakamura formulas based on-the-fly trajectory surface hopping dynamics simulations to investigate the E?Z photoisomerization mechanisms of HTI upon S1 excitation.In the process,we think the major isomerization pathway is central double bond torsion and the final product is reactive trajectories.However,the nonreactive trajectories involve the conical zones lie in vicinity of E-form Franck-Condon region and mix central double bond and benzene ring torsion route,which leads to only yield to E products.Only 66 among 332 simulated trajectories hopping to the ground state and in which only 19 of them switch to Z product.Finally,we have obtained quantum yield of 0.057(19 in 332)is in good agreement with the experimental value of 0.053 ± 0.016.The proposed reaction pathways would be beneficial guidance to the future experiments on photoisomerization of HTI.The third chapter mainly introduces the Si excitation Z?E photoisomerization mechanisms of hemithioindigo hemistilbene(HTI),the adopted method is same as that described in third chapter.We only obtained elementary dynamic results that isomerization of Z-HTI mainly passes through the CI which is similar with that of E-HTI and photoproduct is E-HTI.