Department of Medicinal Chemistry, Copenhagen University, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
J Phys Chem A. 2009 Oct 29;113(43):11949-53. doi: 10.1021/jp9035716.
Iron porphyrin complexes are cofactors in many important proteins such as cytochromes P450, hemoglobin, heme peroxidases, etc. Many computational studies on these systems have been done over the past decade. In this study, the performance of some of the most commonly used density functional theory functionals is evaluated with regard to how they reproduce experimental structures. Seven different functionals (BP86, PBE, PBE0, TPSS, TPSSH, B3LYP, and B97-D) are used to study eight different iron porphyrin complexes. The results show that the TPSSH, PBE0, and TPSS functionals give the best results (absolute bond distance deviations of 0.015-0.016 A), but the geometries are well-reproduced by all functionals except B3LYP. We also test four different basis sets of double-zeta quality, and we find that a combination of double-zeta basis set of Schafer et al. on the iron atom and the 6-31G* basis set on the other atoms performs best. Finally, we remove the porphyrin side chains and increase the basis set size systematically to see if this affects the results. We show that basis sets larger than double-zeta quality are not necessary to get accurate geometries, and nonaromatic side chains do not affect the geometries.
铁卟啉配合物是细胞色素 P450、血红蛋白、血红素过氧化物酶等许多重要蛋白质的辅因子。在过去的十年中，对这些系统进行了许多计算研究。在这项研究中，评估了一些最常用的密度泛函理论函数在重现实验结构方面的性能。使用了七种不同的函数（BP86、PBE、PBE0、TPSS、TPSSH、B3LYP 和 B97-D）来研究八个不同的铁卟啉配合物。结果表明，TPSSH、PBE0 和 TPSS 函数给出了最好的结果（绝对键距偏差为 0.015-0.016A），但除了 B3LYP 之外，所有函数都能很好地重现几何形状。我们还测试了四种不同的双 ζ 质量基组，发现铁原子采用 Schafer 等人的双 ζ 基组，其他原子采用 6-31G*基组的组合效果最好。最后，我们去除卟啉侧链并系统地增加基组大小，以观察这是否会影响结果。我们表明，不需要大于双 ζ 质量的基组来获得准确的几何形状，并且非芳香侧链不会影响几何形状。
