A DFT and multi-configurational perturbation theory study on O2 binding to a model heme compound via the spin-change barrier
A DFT and multi-configurational perturbation theory study on O2 binding to a model heme compound via the spin-change barrier
复制标题
DOI：
10.1039/c6cp02329k
复制
发表时间：
2016-07-21
影响因子：
3.3
通讯作者：
Hasegawa, J.
中科院分区：
文献类型：
--
作者：
Kitagawa, Y.;Chen, Y.;Hasegawa, J.
采用二阶微扰理论（MS-CASPT2）和密度泛函理论（DFT）计算的多态多构型自一致场方法研究了双氧通过系统间交叉（ISC）与模型血红素化合物的结合。在较长的Fe-O距离中，S-0和T-1态的能级被分离，这降低了这些结构中系统间交叉的概率。在DFT（B97D）计算水平上，S-0和T-1态的Fe-O距离分别为1.91和2.92埃。最小系统间能量交叉点（MEISCP）位于Fe-O距离2.17埃的过渡态，与T-1最小系统间能量势垒为1.0 kcal mol（-1）。用MS-CASPT2计算结果验证了这一结果，包括自旋轨道相互作用，也显示了在Fe-O距离为2.05埃的系统间交叉点。对反应座标的能量分解分析表明，卟啉环的缩环模式对反应座标有重要贡献，表明控制自旋态相对能级的反应座标在体系间交叉中起着关键作用。
Dioxygen binding to a model heme compound via intersystem crossing (ISC) was investigated with a multi-state multi-configurational self-consistent field method with second-order perturbation theory (MS-CASPT2) and density functional theory (DFT) calculations. In elongated Fe-O distances, the energy levels of the S-0 and T-1 states are separated, which decreases the probability of intersystem crossing in these structures. At the DFT(B97D) level of calculation, the Fe-O distances of the S-0 and T-1 states were 1.91 and 2.92 angstrom, respectively. The minimum energy intersystem crossing point (MEISCP) was located as a transition state at a Fe-O distance of 2.17 angstrom with an energy barrier of 1.0 kcal mol(-1) from the T-1 minimum. The result was verified with MS-CASPT2 calculations including the spin-orbit interaction which also showed the intersystem crossing point at a Fe-O distance of 2.05 angstrom. An energy decomposition analysis on the reaction coordinate showed the important contribution of the ring-shrinking mode of the porphyrin ring, indicating that the reaction coordinates which control the relative energy level of the spin-states play a key role in intersystem crossing.