Analyses of sizable ZFS and magnetic tensors of high spin metallocomplexes
Analyses of sizable ZFS and magnetic tensors of high spin metallocomplexes
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高自旋金属配合物的大 ZFS 和磁张量分析
DOI：
10.1039/c7cp03850j
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发表时间：
2017
影响因子：
3.3
通讯作者：
Wei-Ching L
中科院分区：
文献类型：
--
作者：
Takeshi Yamane;Kenji Sugisaki;Tomoki Nakagawa;Hideto Matsuoka;Takahisa Nishio;Shigemori Kinjyo;Nobuyuki Mori;Satoshi Yokoyama;Chika Kawashima;Naoki Yokokura;Kazunobu Sato;Yuki Kanzaki;Daisuke Shiomi;Kazuo Toyota;David H. Dolphin;Wei-Ching L
虚拟自旋-1/2哈密顿方法是分析具有相当大的零场分裂（zerofieldsplitting，简称ZF）的高自旋金属配合物的精细结构/超精细ESR谱的假定方法，因此在大多数情况下给出了远离g = 2的显著主g值，而没有明确提供它们的ZF参数。实际上，g值与g = 2的显著偏离表明它们的高自旋态的出现，但自然地，它们永远不会与通过量子化学计算（例如复杂的DFT或从头算MO计算）获得的真实g值一致。在这项工作中，我们提出了简便的方法来确定具有相当大的自旋的高自旋金属络合物的磁张量，而不是进行先进的高场/高频ESR光谱。我们重新讨论了高自旋有效g值和真实主g值之间关系的解析表达式。给出了S ≤ 7/2时geff-gtrue关系的实用解析公式。真正的塞曼微扰形式给出了S = 3/2的精确解，并且对于更高的S，它比迄今为止记录的伪塞曼微扰方法精确得多（A.亚伯拉罕和B。过渡金属离子的电子顺磁共振，1970年; Pilbrow，J. Magn. Reson.，1978，31，479; F. Trandafir等人，应用磁共振原理，2007，31，553; M. Fittipaldi等人，J. Phys. Chem. B，2008，112，3859），其中E（Sx 2-Sy 2）项被推定为二级处理。为了显示本方法的有用性，我们利用FeIII（Cl）OEP（S = 5/2）（OEP：2，3，7，8，12，13，17，18-八乙基卟啉）和CoIIOEP（S = 3/2）在NiIIOEP的抗磁性主体晶格中良好地磁性稀释。单晶ESR光谱的优点在于，在与可靠的理论结果进行比较时，磁张量主轴上的分子信息是至关重要的。在高自旋态的金属配合物与相当大的自旋在伪八面体对称，其精细结构的ESR跃迁的主z轴方向出现在较低的领域远离g = 2的X-带，不同意与假定的直观图片得到使用相关的ESR光谱。一个混合价态的ReIII，IV双核配合物的情况下，其精细结构/超精细ESR谱的净晶体已在其主轴系统进行了分析。对所有高自旋实体的磁张量进行了DFT/ab initio MO计算。
The fictitious spin-1/2 Hamiltonian approach is the putative method to analyze the fine-structure/hyperfine ESR spectra of high spin metallocomplexes having sizable zerofield splitting (ZFS), thus giving salient principal g-values far from around g = 2 without explicitly providing their ZFS parameters in most cases. Indeed, the significant departure of the g-values from g = 2 is indicative of the occurrence of their high spin states, but naturally they never agree with true g-values acquired by quantum chemical calculations such as sophisticated DFT or ab initio MO calculations. In this work, we propose facile approaches to determine the magnetic tensors of high spin metallocomplexes having sizable ZFS, instead of performing advanced high-field/high-frequency ESR spectroscopy. We have revisited analytical expressions for the relationship between effective g-values and true principal g-values for high spins. The useful analytical formulas for the geff–gtrue relationships are given for S's up to 7/2. The genuine Zeeman perturbation formalism gives the exact solutions for S = 3/2, and for higher S's it is much more accurate than the pseudo-Zeeman perturbation approach documented so far (A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Metal Ions, 1970; J. R. Pilbrow, J. Magn. Reson., 1978, 31, 479; F. Trandafir et al., Appl. Magn. Reson., 2007, 31, 553; M. Fittipaldi et al., J. Phys. Chem. B, 2008, 112, 3859), in which the E(Sx2 − Sy2) term is putatively treated to the second order. To show the usefulness of the present approach, we exploit FeIII(Cl)OEP (S = 5/2) (OEP: 2,3,7,8,12,13,17,18-octaethylporphyrin) and CoIIOEP (S = 3/2) well magnetically diluted in the diamagnetic host crystal lattice of NiIIOEP. The advantage of single-crystal ESR spectroscopy lies in the fact that the molecular information on the principal axes of the magnetic tensors is crucial in comparing with reliable theoretical results. In high spin states of metallocomplexes with sizable ZFS in pseudo-octahedral symmetry, their fine-structure ESR transitions for the principal z-axis orientation appear in the lower field far from g = 2 at the X-band, disagreeing with the putative intuitive picture obtained using relevant ESR spectroscopy. A ReIII,IV dinuclear complex in a mixed valence state exemplifies the cases, whose fine-structure/hyperfine ESR spectra of the neat crystals have been analyzed in their principal-axis system. The DFT-based/ab initio MO calculations of the magnetic tensors for all the high spin entities in this work were carried out.