Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (08): 1673-1680.doi: 10.3866/PKU.WHXB201306041

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

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.

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