Rong Chunying, Lian Shixun, Yin Dulin, Shen Bin, Zhong Aiguo, Bartolotti Lee, Liu Shubin
College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, Hunan 410081, People's Republic of China.
J Chem Phys. 2006 Nov 7;125(17):174102. doi: 10.1063/1.2378830.
Density functional theory has been widely used to investigate the structural and electronic properties of heme-containing proteins such as cytochrome P450. Nevertheless, recent studies have shown that approximate exchange-correlation energy density functionals can incorrectly predict the stability order of spin states in, for instance, iron-containing pyridine and imidazole systems. This raises questions about the validity of earlier theoretical studies. In this work, we systematically investigate a few typical inorganic and organic iron-containing complexes and try to understand the performance difference of various density functionals. Two oxidation states of iron, Fe(II) and Fe(III), with different spin states and both adiabatic and vertical structures are considered. A different description of the outmost molecular orbital is found to play the crucial role. Local density and generalized gradient based functionals bias the lower spin state and produce a more localized frontier orbital that is higher in energy than the hybrid functionals. Energy component analysis has been performed, together with comparison of numerous structural and electronic properties. Implications of the present work to the theoretical study of heme-containing biological molecules and other spin-related systems are discussed.
密度泛函理论已被广泛用于研究含血红素蛋白质（如细胞色素P450）的结构和电子性质。然而，最近的研究表明，近似交换关联能量密度泛函可能会错误地预测含铁吡啶和咪唑体系中自旋态的稳定性顺序。这引发了对早期理论研究有效性的质疑。在这项工作中，我们系统地研究了一些典型的无机和有机含铁配合物，并试图了解各种密度泛函的性能差异。考虑了铁的两种氧化态Fe(II)和Fe(III)，具有不同的自旋态以及绝热和垂直结构。发现对最外层分子轨道的不同描述起着关键作用。基于局域密度和广义梯度的泛函偏向于较低自旋态，并产生一个能量高于杂化泛函的更局域化的前沿轨道。进行了能量成分分析，并比较了众多结构和电子性质。讨论了本工作对含血红素生物分子和其他自旋相关体系理论研究的意义。
