物理化学学报 >> 2013, Vol. 29 >> Issue (08): 1673-1680.doi: 10.3866/PKU.WHXB201306041

理论与计算化学 上一篇    下一篇

非血红素铁(III)活化氧分子反应的自旋轨道耦合和零场分裂

吕玲玲1, 王小芳1, 朱元成1, 刘新文1, 袁焜1, 王永成2   

  1. 1 天水师范学院生命科学与化学学院, 甘肃 天水 741001;
    2 西北师范大学化学化工学院, 兰州 730070
  • 收稿日期:2013-02-27 修回日期:2013-06-03 发布日期:2013-07-09
  • 通讯作者: 吕玲玲 E-mail:lvling100@163.com
  • 基金资助:

    国家自然科学基金(21263022)和甘肃省财政厅高校科研项目基金资助

Spin-Orbit Coupling and Zero-Field Splitting in Dioxygen Activation by Non-Heme Iron(III)

LV Ling-Ling1, WANG Xiao-Fang1, ZHU Yuan-Cheng1, LIU Xin-Wen1, YUAN Kun1, WANG Yong-Cheng2   

  1. 1 College of Life science and Chemistry, Tianshui Normal University, Tianshui 741001, Gansu Province, P. R. China;
    2 College of Chemistry and Chemical Engineering, Northwest Normal University, LanZhou 730070, P. R. China
  • Received:2013-02-27 Revised:2013-06-03 Published:2013-07-09
  • Contact: LV Ling-Ling E-mail:lvling100@163.com
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21263022) and University Research Fund of Gansu Province Financial Department, China.

摘要:

采用密度泛函理论对原儿茶酚3,4-双加氧酶(3,4-PCD)活化O2分子的反应机理进行了探讨. 初始复合物, 六重态61的超快形成主要归因于电子交换诱导系间穿越(EISC), Fe dz:O2 π*(z)是主要的交换通道, 在Fe―O键长为0.2487 nm处, 交换重叠积分Sij=ádz α|π*(z) β>=0.3758. 从六重态61 形成四重态中间体41, 有两种效应共存, 即电子交换耦合作用和自旋轨道耦合(SOC)作用, 且相互竞争. 计算结果表明, 自旋轨道耦合(SOC)作用起主导因素(SOC=353.16 cm-1). 至于O―O键的解离主要取决于儿茶酚(PCA)最高占据分子轨道(HOMO)的电子转移, 非血红素酶的铁中心仅承担PCA向O2电子转移的缓冲作用.22

关键词: 原儿茶酚3,4-双加氧酶, 自旋轨道耦合, 零场分裂, 反应机理

Abstract:

The mechanism of the O2 activation by the protocatechuate 3,4-dioxygenase was investigated using density functional calculations. In the initial complex, the ultrafast formation of the sextet 61 was probably the result of electron-exchange-induced intersystem crossing, and Fe dz:O2 π*(z) was the dominant exchange pathway, with an overlap of dz: O2π*(z) was dominant exchange pathway with the overlap of Sijdz α|π*(z) β>=0.3758 at an Fe―O bond length of 0.2487 nm. Two coexisting effects, electron spin exchange coupling and spin-orbit coupling (SOC) in the sextet 61, are responsible for formation of the quartet state 41 from the sextet 61. The exchange interaction competes with the SOC interaction as a driving force for spin conversion. The calculated results show that the latter is the dominant factor, because of the larger SOC constant (353.16 cm-1). In cleavage of the O― O bond, electron transfer from the protocatechuate (PCA) highest occupied molecular orbital (HOMO) plays a vital role. The Fe center of the non-heme enzyme is a buffer to transfer an electron pair from the PCA HOMO to O2.222

Key words: Protocatechuate 3,4-dioxygenase, Spin-orbit coupling, Zero-field splitting, Reaction mechanism

MSC2000: 

  • O641