螺吡喃光控转变的半经验动力学研究

Semi-classical molecular dynamics of photo induced isomerization of spiropyran

采用半经典的电子-辐射-离子动力学模拟(SERID)研究了螺吡喃分子开环反应的非绝热动力学过程.采用简化模型的螺吡喃(mSP)简化计算.开环过程中mSP分子首先经过一个圆锥相交点后变为顺式-反式-顺式-模型部花青(CTC-mMC)继而又变为顺式-反式-反式-模型部花青(CTT-mMC).这与实验中螺吡喃分子开环后由于第一个异构体顺式-顺式-顺式-模型部花青(CCC-mMC)不稳定而在很短时间内转变为CTC-mMC基本一致.模拟过程中亦发现CTC-mMC不如CTT-mMC稳定,体系经CTT-mMC后回到能量较低的CTT-mMC构型.mSP的3个C—C—C—C二面角随时间扭转的实时动力学过程验证了以前理论推测的反应机理,模拟得到的激发态寿命与实验值基本一致.

A semi-classical electron-radiation-ion dynamics simulation （SERID） has been employed to research the non-adiabatic dynamics process of the ring opening reaction of spiropyran molecule. The simplified model spiropyran （mSP） to simplify the calculation was used. The results show that raSP first passes through a conical intersecting （CI） point into CTC-mMC （MC is the abbreviation of merocyanine, mMC is its simplified model） and then into the CTT-mMC, and the conversion reaction of the two isomers is the excited state reaction. These results is consistent with the fact that the first isomer formed after ring opening reaction of SP molecule is unstable and converts to CTC-mMC in a very short period of time. Simulation results indicate that CTT-mMC is more stable than CTC-mMC, so that the latter is rapidly back to lower energy CTT-mMC configuration on the excited state. The present results provide the real-time dynamics process of three C-C-C-C dihedral angle of raSP molecule turning around with the time, which verifies the reaction mechanism of theoretical speculation, and the lifetime of excited state on the typical trajectory is rou^hlv consistent with the experimental result.