气相中CrO2+活化甲烷C—H键的理论研究

用密度泛函UB3LYP/6-311＋＋G**方法计算研究了气相中CrO₂⁺ (²A₁/⁴A")活化甲烷C—H键的微观机理, 找到了四条反应通道. 对其中涉及的两态反应(TSR)进行了分析, 并对影响反应机理和反应速率的势能面交叉现象(potential energy surfaces crossing)进行了详细讨论, 进而运用Hammond假设和Yoshizawa等的内禀坐标单点垂直激发计算的方法找出了一系列势能面交叉点crossing points (CPs)], 并作了相应的讨论. 进一步用碎片分子轨道理论fragment molecular orbital (FMO)]对TS1中的轨道相互作用进行了分析, 解释了CrO₂⁺活化甲烷C—H键的机理.

Theoretical Study of Gas Phase Activation of C—H Bond of Methane by CrO2+

The gas phase reaction of oxo-species CrO₂⁺ (²A₁/⁴A") with CH₄ was selected as a system of C—H bond activation by CrO₂⁺. The reaction mechanism has been investigated with density functional theory at the B3LYP/6-311＋＋G** level. Four reaction path channels have been studied on both the doublet and quartet potential energy surfaces. 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 (IRC) calculations. The potential energy curve-crossing dramatically affecting reaction mechanism and reaction rate has been discussed detailedly. The Hammond postulate and the IRC analyses used by Yoshizawa et al. have been used to locate and character a series of crossing points involving the structures and energy values. In addition, the orbital analysis of C—H bond activation has been carried out by fragment molecular orbital.