Theoretical Study Of The Isomerization Mechanism Of Push-Pull P,P'-disubstituted Stilbene Derivatives

In this dissertation,we studied three typical materials of push-pull stilbene derivatives employing CASSCF method.The main content of this article includes two parts.In the first part.We introduce research background of push-pull stilbene derivatives and methods breifly.In the second part.we optimized Conical Intersections(CI)and intersystem crossing points(ISC)of DNS,ANS and NS at CASSCF level in Photoisomerization,studing photochemical reaction mechanism.In the first chapter,we introduce main features and applications of push-pulll stilbene derivatives,the research background and methodology involved in this work.In the second chapter,the main conical intersections(CI)and intersystem crossing points(ISC)in photoisomerization of DNS are exhibited.Results show that the trans?cis isomerization reaction of DNS is fulfilled by the singlet and triplet two mixed path.And N,N-dimethylamino,C=C bond and nitro substituents torsion are involved in isomerization reaction of DNS.The three chapter shows,the main conical intersections(CI)and intersystem crossing points(ISC)of ANS are exhibited.By Compared with DNS,We found that ANS has a similar mechanism.But the only difference is that ISC between S1 and T1 in the trans configuration have not be optimized.That is to say,Different substituents of stilbene in photochemical reaction have little effect for the singlet isomerization reaction,however,donor has the certain influence for the triplet isomerization reaction.The stronger capacity of donor is,the stronger ISC between Si and Ti is.Similarly,the main conical intersections(CI)and intersystem crossing points(ISC)of NS in photoisomerization are displayed in the fourth chapter.Compared with the computational results of ANS and DNS,we found that NS have shown a similar mechanism with other two.But the only difference is that no ISCl geometry has been searched between S1 and T1.The results show that the donor substituent has little effect for the singlet isomerization reaction,but,for the triplet isomerization reaction,the donor enhance the quantum yield of triplet path.