(57)Fe Mössbauer isomer shifts of heme protein model systems: electronic structure calculations.
(57)Fe Mössbauer isomer shifts of heme protein model systems: electronic structure calculations.
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(57)血红素蛋白模型系统的Fe穆斯堡尔异构体位移：电子结构计算。
DOI：
10.1021/ja011583v
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发表时间：
2002
影响因子：
15
通讯作者：
Oldfield,Eric
中科院分区：
文献类型：
--
作者：
Zhang,Yong;Mao,Junhong;Oldfield,Eric
用密度泛函理论（DFT）计算了24个无机、有机金属和金属蛋白质/金属卟啉模型体系在S = 0、1/2、1、3/2、2和5/2自旋态下的57 Fe穆斯堡尔同分异构位移（δFe）.我们发现，在整个2.34 mm s-1的异构体位移范围内，计算值和实验值之间有很好的相关性：计算值和实验值之间的均方根偏差为0.07 - 0.08 mm s-1（相当于总δ费朗的3 - 4%，取决于所用的泛函），R2值为0.973和0.981（p< 0.0001）。最好的结果是通过使用混合交换相关功能B3 LYP，以前用于57 Fe穆斯堡尔四极分裂和57 Fe NMR化学位移和化学屏蔽各向异性。α的相对论修正值αrel在本研究中使用的大基组下收敛，但精确值因所用方法而有所不同：−0.253a03mm s-1（Hartree−Fock; HF）; −0.316a03mm s-1（混合HF-DFT; B3 LYP）或−0.367a03mm s-1（纯DFT; BPW 91）。正常和中间自旋态的异构体位移都可以通过计算很好地再现，δ F值的范围也很宽：从[FeVIO 4]2-（−0.90 mm s-1 expt; −1.01 mm s-1calc）到KFeIIF 3（1.44 mm s-1 expt; 1.46 mm s-1calc）。对所有无机固体以及所研究的所有有机金属和金属卟啉体系的分子轨道分析表明，对铁核处的总电荷密度ρtot（0）有三个主要的核心MO贡献（因此δFe），不随化学变化而变化，而价态MO贡献与δFe高度相关（R2= 0.915 - 0.938，取决于所使用的泛函），并且价MO贡献和总MO贡献之间的相关性甚至更好（R2= 0.965 - 0.976，取决于所使用的泛函）。这些结果是普遍感兴趣的，因为它们表明，DFT方法现在能够在所有自旋状态和非常宽的δ Fvalues范围内以非常小的均方根误差准确预测无机，有机金属和金属卟啉体系中的δ Fvalues。
We report the results of density functional theory (DFT) calculations of the57Fe Mössbauer isomer shifts (δFe) for a series of 24 inorganic, organometallic, and metalloprotein/metalloporphyrin model systems inS= 0,1/2, 1,3/2, 2, and5/2spin states. We find an excellent correlation between calculation and experiment over the entire 2.34 mm s-1range of isomer shifts: a 0.07−0.08 mm s-1rms deviation between calculation and experiment (corresponding to 3−4% of the total δFerange, depending on the functionals used) withR2values of 0.973 and 0.981 (p< 0.0001). The best results are obtained by using the hybrid exchange-correlation functional B3LYP, used previously for57Fe Mössbauer quadrupole splittings and57Fe NMR chemical shifts and chemical shielding anisotropies. The relativistically corrected value of α, αrel, converges with the large basis set used in this work, but the exact values vary somewhat with the methods used: −0.253a03mm s-1(Hartree−Fock; HF); −0.316a03mm s-1(hybrid HF-DFT; B3LYP), or −0.367a03mm s-1(pure DFT; BPW91). Both normal and intermediate spin state isomer shifts are well reproduced by the calculations, as is the broad range of δFevalues: from [FeVIO4]2-(−0.90 mm s-1expt; −1.01 mm s-1calc) to KFeIIF3(1.44 mm s-1expt; 1.46 mm s-1calc). Molecular orbital analyses of all inorganic solids as well as all organometallic and metalloporphyrin systems studied reveal that there are three major core MO contributions to ρtot(0), the total charge density at the iron nucleus (and hence δFe), that do not vary with changes in chemistry, while the valence MO contributions are highly correlated with δFe(R2= 0.915−0.938, depending on the functionals used), and the correlation between the valence MO contributions and the total MO contribution is even better (R2= 0.965−0.976, depending on the functionals used). These results are of general interest since they demonstrate that DFT methods now enable the accurate prediction of δFevalues in inorganic, organometallic, and metalloporphyrin systems in all spin states and over a very wide range of δFevalues with a very small rms error.