Mössbauer quadrupole splittings and electronic structure in heme proteins and model systems: a density functional theory investigation.
Mössbauer quadrupole splittings and electronic structure in heme proteins and model systems: a density functional theory investigation.
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血红素蛋白和模型系统中的穆斯堡尔四极分裂和电子结构：密度泛函理论研究。
DOI：
10.1021/ja020298o
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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;Godbout,Nathalie;Oldfield,Eric
我们报道了一系列密度泛函理论(DFT)计算的结果，旨在预测57Fe穆斯堡尔电场梯度(EFG)张量(四极分裂和不对称参数)及其取向INS=0，1/2，1，3/2，2和5/2金属蛋白和/或模型体系。对铁原子采用Wachter全电子基组，对其他重原子采用6-311G*基组，对氢原子采用6-31G*基组，对顺磁体系采用BPW91和B3LYP交换关联泛函和自旋无限制方法，得到了很好的结果。对于理论与实验的关联，我们发现当使用BPW91泛函时R2=0.975，斜率=0.99，截距=−0.08 mm秒-1，RMSD=0.30 mm秒-1(N=23分)覆盖5.63 mm S-1的Δ方程范围。当使用B3LYP泛函时，R2=0.978，斜率=1.12，截距=−0.26 mm秒-1，RMSD=0.31 mm秒-1。成功地预测了下列体系的Δ方程：(1) (1)铁的低自旋(S=1/2)体系，包括一个具有通常的(Dxy)2(Dxzdyz)3电子构型的铁卟啉和两个具有较不寻常的(Dxzdyz)4(Dxy)1电子构型的铁卟啉；(2)铁的非血红素模型化合物(S=1/2)；(3)铁的中间自旋(S=1)四苯基卟啉铁(II)；(4)铁的中间自旋(S=3/2)铁卟啉；(5)铁的高自旋(S=2)脱氧肌球蛋白和脱氧血红蛋白；(6)高铁自旋(S=5/2)高铁肌红蛋白加上两个五配位和一个六配位的铁卟啉。此外，用与顺磁体系相同的泛函和基组方案重新研究了以前研究过的7个抗磁体系(S=0，d6和d8)。所有计算的不对称参数和电场梯度张量取向都与实验数据吻合较好。此外，我们还研究了几个体系的电子结构，包括(Dxy)2(dxz，dyz)3和(dxz，dyz)4(Dxy)1[Fe(III)/卟啉]+阳离子以及Fe(II)(八乙基卟啉)的NO加合物，从计算的波函数可以很容易地获得关于自旋密度分布的有趣信息。
We report the results of a series of density functional theory (DFT) calculations aimed at predicting the57Fe Mössbauer electric field gradient (EFG) tensors (quadrupole splittings and asymmetry parameters) and their orientations inS= 0,1/2, 1,3/2, 2, and5/2metalloproteins and/or model systems. Excellent results were found by using a Wachter's all electron basis set for iron, 6-311G* for other heavy atoms, and 6-31G* for hydrogen atoms, BPW91 and B3LYP exchange-correlation functionals, and spin-unrestricted methods for the paramagnetic systems. For the theory versus experiment correlation, we foundR2= 0.975, slope = 0.99, intercept = −0.08 mm sec-1, rmsd = 0.30 mm sec-1(N= 23 points) covering a ΔEQrange of 5.63 mm s-1when using the BPW91 functional andR2= 0.978, slope = 1.12, intercept = −0.26 mm sec-1, rmsd = 0.31 mm sec-1when using the B3LYP functional. ΔEQvalues in the following systems were successfully predicted: (1) ferric low-spin (S=1/2) systems, including one iron porphyrin with the usual (dxy)2(dxzdyz)3electronic configuration and two iron porphyrins with the more unusual (dxzdyz)4(dxy)1electronic configuration; (2) ferrous NO-heme model compounds (S=1/2); (3) ferrous intermediate spin (S= 1) tetraphenylporphinato iron(II); (4) a ferric intermediate spin (S=3/2) iron porphyrin; (5) ferrous high-spin (S= 2) deoxymyoglobin and deoxyhemoglobin; and (6) ferric high spin (S=5/2) metmyoglobin plus two five-coordinate and one six-coordinate iron porphyrins. In addition, seven diamagnetic (S= 0, d6and d8) systems studied previously were reinvestigated using the same functionals and basis set scheme as used for the paramagnetic systems. All computed asymmetry parameters were found to be in good agreement with the available experimental data as were the electric field gradient tensor orientations. In addition, we investigated the electronic structures of several systems, including the (dxy)2(dxz,dyz)3and (dxz,dyz)4(dxy)1[Fe(III)/porphyrinate]+cations as well as the NO adduct of Fe(II)(octaethylporphinate), where interesting information on the spin density distributions can be readily obtained from the computed wave functions.