气相中Cu^+活化N_2O中N-O键反应机理的理论研究

Theoretical study of the reaction mechanism for activation N-O bond of N_2O by Cu^+ in gas phase

采用密度泛函UB3LYP/6311+G(2d)方法计算研究了Cu+在基态和激发态下与N2O的反应机理,全参数优化了反应势能面上各驻点的几何构型,用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证,并用UCCSD(T)/6311G(2d,p)、单点垂直激发、Harvey等人的方法分别进行各驻点单点能校正,单重态和三重态反应势能面交叉点CP确定,最低能量交叉点(MECP)的优化及MECP处相应的自旋轨道耦合常数(SOC)计算。计算结果表明,该反应为一步反应,SOC值为84.2 cm-1,比较大的SOC值说明了在势能面上CP点处的翻转能够有效的降低反应的活化能,降低活化能值为27.6kJ.mol,增加反应放热126.7kJ.mol,这在动力学和热力学上对反应是非常有利。

The reaction mechanism between Cu＋in ground state and excited state with N20 has been studied using the density functional theory（DFI＇） at UB3LYP/6-311 ＋G （2d）leveL The geometries for reactants, the transition states and the products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calcula- tions. For each stationary point, single-point energy calculations were carried out by UCCSD （T）/6-311 G（ 2d, p）method. The potential energy curve-crossing diagrams were investigated for state correlation between singlet and triplet state in the reaction of Cu＋with N20. There is a crossing point（CP） between the singlet and the triplet potential energy surfaces,which would play a significant rote in this catalytic reaction. The minimum energy crossing points （MECP） that obtained by the mathematical algorithm proposed by Harvey et al. has been also employed. The calculation results showed that the reaction is a one-step reaction. The values of the SOC constants is 84. 2 cm^-1 at MECP,which indicate that the spin crossing process in this reaction can occur efficiently due to the large SOC involved. This process made the wlue of activation energy reduce 27.6 kJ ·mol, the reaction heat effect increase 126. 7 kJ·mol,which are very helpful for the reaction on kinetics and thermodynamics.