Radoń Mariusz
Faculty of Chemistry, Jagiellonian University in Kraków , ul. Ingardena 3, 30-060 Kraków, Poland.
J Chem Theory Comput. 2014 Jun 10;10(6):2306-21. doi: 10.1021/ct500103h. Epub 2014 May 21.
Spin-state energetics of metalloporphyrins and heme groups is elucidated by performing high-level coupled cluster calculations for their simplified mimics. An efficient computational protocol is proposed-based on the mix of extrapolation to complete basis set and explicitly correlated (F12) methodology-which retains the high accuracy of the CCSD(T) method at a cost that makes it applicable also to relatively large models, e.g., FeP and FeP(Cl) (P = porphin). Adequacy of CCSD(T) is supported by analysis of multireference character and comparison with the completely renormalized CR-CC(2,3) method. The high-level coupled cluster results are used for assessment of density functional theory (DFT) methods, for which an accurate description of the spin-state energetics is recognized as a major challenge. Although the DFT results are highly functional-dependent, it is shown that the spin-state energetics of a full heme model and its simplified mimic remain in a good linear correlation. This makes it possible to estimate the spin-state energetics of full heme models based on the accurate CCSD(T) results for their mimics, as illustrated for porphyrin complexes of Fe(II), Mn(II), and Co(II); pentacoordinate heme complexes of Fe(II) and Fe(III); and a ferryl heme model. Comparison with the available experimental data is also presented.
通过对金属卟啉和血红素基团的简化模型进行高水平耦合簇计算，阐明了它们的自旋态能量学。基于外推到完备基组和显式相关（F12）方法的混合，提出了一种有效的计算方案，该方案以一种使其也适用于相对较大模型（例如FeP和FeP(Cl)，P = 卟吩）的成本保留了CCSD(T)方法的高精度。通过对多参考特征的分析以及与完全重整化的CR-CC(2,3)方法的比较，支持了CCSD(T)的适用性。高水平耦合簇结果用于评估密度泛函理论（DFT）方法，准确描述自旋态能量学被认为是DFT方法的一项重大挑战。尽管DFT结果高度依赖于泛函，但结果表明完整血红素模型及其简化模型的自旋态能量学保持良好的线性相关性。这使得基于其简化模型的精确CCSD(T)结果来估计完整血红素模型的自旋态能量学成为可能，如对Fe(II)、Mn(II)和Co(II)的卟啉配合物；Fe(II)和Fe(III)的五配位血红素配合物；以及一个高铁血红素模型的说明。还给出了与现有实验数据的比较。
