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化学学报
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化学学报 ›› 2010, Vol. 68 ›› Issue (22): 2305-2311. 上一篇    下一篇

研究论文

气相中Ta＋活化分解CO2的自旋禁阻反应机理

刘玲玲1，王永成*,2，张力1   

  1. (1兰州城市学院化学与环境科学学院 兰州 730070)
    (2西北师范大学化学化工学院 兰州 730070)
  • 投稿日期:2010-02-12 修回日期:2010-05-31 发布日期:2010-07-08
  • 通讯作者: 王永成 E-mail:wangyc@nwnu.edu.cn
  • 基金资助:

    过渡金属活化小分子自旋禁阻反应动力学的理论计算研究

Spin-Forbidden Reaction Mechanism of CO2 Cleavage Activated by Ta＋ in Gas Phase

Liu Lingling1 Wang Yongcheng*,2 Zhang Li1   

  1. (1 College of Chemistry and Environment Science, Lanzhou City University, Lanzhou 730070)
    (2 College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070)
  • Received:2010-02-12 Revised:2010-05-31 Published:2010-07-08

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采用密度泛函理论中的UB3LYP方法, 对Ta 采用相对论校正赝势基组(SDD), C, O采用6-311＋G(3d)基组, 计算研究了气相中不同自旋态下Ta＋活化CO2分解反应的微观机理. 计算结果表明, Ta＋活化CO2分解反应是典型的自旋禁阻反应, 以五重态进入反应通道, 经过五重态势能面到三重态势能面的系间窜越(ISC), 最终产物TaO＋, CO以三重态离开反应通道. 运用Harvey方法优化出最低能量交叉点(MECP), 并计算了MECP处的自旋-轨道耦合(SOC)常数(204.94 cm－1), 较大的SOC值说明了在MECP处的自旋-轨道耦合作用较强, 势能面的交叉降低了自旋禁阻反应能垒, 为反应提供了一条低能反应路径. 运用Landau-Zener跃迁几率公式计算了MECP处系间窜越几率, 较大的系间窜越几率说明了该自旋禁阻反应速率较快.

关键词: 密度泛函理论, Ta＋活化, 自旋禁阻反应, 最低能量交叉点, 自旋-轨道耦合, 系间窜越几率

Spin-forbidden reaction mechanism of CO2 cleavage activated by Ta＋ in the gas phase was investigated, using density functional theory (DFT, UB3LYP) with the relativistic effective core potential (ECP) of basis sets (SDD) for Ta and the 6-311＋G(3d) basis set for C and O. The calculation results show that Ta＋ initially close to CO2 on the quintet surface, then the product, TaO＋ and CO, exit the channel on the triplet surface. The process involves an intersystem crossing (ISC) from the quintet to the triplet state. The minimum energy crossing point (3-5MECP) is located by using the methods of Harvey et al. The large spin-orbit coupling (SOC) constant (204.94 cm－1) calculated shows that the spin-forbidden reaction takes place easily. The intersystem crossing probability estimated at MECP indicate that the spin-forbidden reaction have a rapid rate.

Key words: density functional theory, Ta＋ activation, spin-forbidden reaction, minimum energy crossing point, spin-orbital coupling, intersystem crossing probability