Effects of peripheral substituents and axial ligands on the electronic structure and properties of cobalt porphyrins.
Effects of peripheral substituents and axial ligands on the electronic structure and properties of cobalt porphyrins.
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DOI：
10.1021/jp058212b
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
M. Liao;J. Watts;Ming-Ju Huang
中科院分区：
文献类型：
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作者：
M. Liao;J. Watts;Ming-Ju Huang
采用密度泛函理论（DFT）方法研究了外围取代基和轴向配体（L）对四苯基钴卟啉（CoTPP）电子结构和性质的影响。测试了各种密度泛函，并通过考虑几种可能的低态来确定每个系统的基态。完全氟化的CoTPPF 28（L）2络合物（L = THF、Py和Im）的基态通过含有动能密度tau的间位-GGA官能化的tau-HCTH被鉴定为高自旋（4 E（g）），与实验测量一致。所有的纯GGA泛函，包括最近开发的mPBE，OPBE，和HCTH/407，显示或多或少高估的高自旋态的相对能量。2A（1g）和4 E（g）态之间的能隙是不显著的（大约0.1eV），并且以L = Py < L = THF < L = Im的顺序变化。结果及其趋势与19 F NMR研究一致，其显示CoTPPF 28（THF）2和CoTPPF 28（Py）2中4 E（g）态的部分布居以及CoTPPF 28（1-MeIm）2中向高自旋态的完全转化。在通过两个非常强的场轴向CO配体配位时，CoTPPF 28（CO）2变成低自旋，如在未连接的CoTPPF（x）中。研究了外围取代基和轴向配体对CoTPPF（x）-（L）2的电离能、电子亲合势和结合强度的影响。
The effects of peripheral substituents and axial ligands (L) on the electronic structure and properties of cobalt tetraphenylporphyrin (CoTPP) have been studied using DFT methods. Various density functionals were tested, and the ground state of each system was determined by considering several possible low-lying states. The ground states of the fully fluorinated CoTPPF28(L)2 complexes with L = THF, Py, and Im were identified to be high-spin (4E(g)) by the meta-GGA functional tau-HCTH, which contains the kinetic energy density tau, in agreement with experimental measurements. All the pure GGA functionals, including the recently developed mPBE, OPBE, and HCTH/407, show more or less overestimation of the relative energies of the high-spin states. The energy gap between the 2A(1g) and 4E(g) states is insignificant (approximately 0.1 eV) and varies in the order L = Py < L = THF < L = Im. The results and their trend are consistent with 19F NMR studies which show partial population of the 4E(g) state in CoTPPF28(THF)2 and CoTPPF28(Py)2 and a complete conversion to the high-spin state in CoTPPF28(1-MeIm)2. Upon coordination by two very strong field axial CO ligands, CoTPPF28(CO)2 becomes low-spin, as in unligated CoTPPF(x). The influence of the peripheral substituents and axial ligands on the ionization potentials, electron affinities, and CoTPPF(x)-(L)2 binding strength was also investigated in detail.