Advanced Magnetic Resonance Studies of Tetraphenylporphyrinatoiron(III) Halides
Advanced Magnetic Resonance Studies of Tetraphenylporphyrinatoiron(III) Halides
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DOI：
10.1007/s00723-020-01236-8
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发表时间：
2020-10
影响因子：
1
通讯作者：
Pagnareach Tin;Shelby E. Stavretis;M. Ozerov;J. Krzystek;A. Ponomaryov;S. Zvyagin;J. Wosnitza;
中科院分区：
文献类型：
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作者：
Pagnareach Tin;Shelby E. Stavretis;M. Ozerov;J. Krzystek;A. Ponomaryov;S. Zvyagin;J. Wosnitza;
Fe(Tpp)X(X = F，Cl，Br；通过对Fe(Tpp)BR和Fe(Tpp)I的−和Fe(Tpp)I的远红外磁谱研究，探索了这些= 5/2金属卟啉配合物的磁性Kramers内和Kramers间的双重态跃迁，得到了配合物的零场分裂和参数：Fe(Tpp)F，D= +4.67(1)cm−1，E= 0.00(1)cm−1，g⊥= 1.97(1)，g|= 2.000(5)；Fe(Tpp)Cl，D= +6.458(2)cm−1，E= +0.015(5)cm−1，E/D= 0.002，g⊥= 2.004(3)，g|= 2.02(1)；Fe(Tpp)Br，D= +9.03(5)cm−1，E= +0.047(5)cm−1，E/D= 0.005，GISO= 1.99(1)；Fe(Tpp)i，D= +13.84亿cm−1，E= +0.07亿cm−1，E/D= 0.005，Giso= 2.0HEPR和d= +13.95百万cm−1，Giso= 2.0(E的符号在每种情况下被任意指定为Ofd)。这些结果表明，场-频域磁共振实验在高精度、高精度地提取 1/2金属络合物的自旋哈密顿参数方面具有互补性。从这些实验获得的自旋哈密顿参数与其他物理方法如磁化率、磁穆斯堡尔谱、非弹性中子散射(INS)和变温变场磁圆二向色性(VT-VH MCD)实验得到的结果进行了比较。INS、Mössbauer和MCD对HFEPR/公司的结果给予了很好的一致性；其他人则不是那么一致。用多重参考从头算方法研究了Fe(Tpp)X(X = F，Cl，Br，I)的电子结构，探讨了大的正D值的来源，再现了实验数据的变化趋势。在本工作中，基于配位场理论的一个更简单的模型定性地解释了ZF从X = F到Cl再到Br再到I作为轴向配体的趋势。四方拉长的高自旋d5体系如Fe(Tpp)X表现出D>； 0，但X起着关键作用。X上的自旋离域意味着X·对D有自旋-轨道耦合贡献，而闭壳层X−则没有贡献。在X = 范围内，F、Cl、Br、I、X·字符随着X·的本征SOC值的增加而增加，因此D在该范围内相应地增加。
High-Frequency and -Field EPR (HFEPR) studies of Fe(TPP)X (X = F, Cl, Br; I, TPP2−=meso-tetraphenylporphyrinate dianion) and far-IR magnetic spectroscopic (FIRMS) studies of Fe(TPP)Br and Fe(TPP)I have been conducted to probe magnetic intra- and inter-Kramers doublet transitions in theseS= 5/2 metalloporphyrin complexes, yielding zero-field splitting (ZFS) andgparameters for the complexes: Fe(TPP)F,D= +4.67(1) cm−1,E= 0.00(1) cm−1,g⊥= 1.97(1),g||= 2.000(5) by HFEPR; Fe(TPP)Cl,D= +6.458(2) cm−1,E= +0.015(5) cm−1,E/D= 0.002,g⊥= 2.004(3),g||= 2.02(1) by HFEPR; Fe(TPP)Br,D= +9.03(5) cm−1,E= +0.047(5) cm−1,E/D= 0.005,giso= 1.99(1) by HFEPR andD= +9.05 cm−1,giso= 2.0 by FIRMS; Fe(TPP)I,D= +13.84 cm−1,E= +0.07 cm−1,E/D= 0.005,giso= 2.0 by HFEPR andD= +13.95 cm−1,giso= 2.0 by FIRMS (the sign ofEwas in each case arbitrarily assigned as that ofD). These results demonstrate the complementary nature of field- and frequency-domain magnetic resonance experiments in extracting with high accuracy and precision spin Hamiltonian parameters of metal complexes withS> 1/2. The spin Hamiltonian parameters obtained from these experiments have been compared with those obtained from other physical methods such as magnetic susceptibility, magnetic Mössbauer spectroscopy, inelastic neutron scattering (INS), and variable-temperature and -field magnetic circular dichroism (VT-VH MCD) experiments. INS, Mössbauer and MCD give good agreement with the results of HFEPR/FIRMS; the others not as much. The electronic structure of Fe(TPP)X (X = F, Cl, Br, I) was studied earlier by multi-referenceab initiomethods to explore the origin of the large and positiveD-values, reproducing the trends ofDfrom the experiments. In the current work, a simpler model based on Ligand Field Theory (LFT) is used to explain qualitatively the trend of increasing ZFS from X = F to Cl to Br and to I as the axial ligand. Tetragonally elongated high-spin d5systems such as Fe(TPP)X exhibitD> 0, but X plays a key role. Spin delocalization onto X means that there is a spin–orbit coupling (SOC) contribution toDfrom X•, as opposed to none from closed-shell X−. Over the range X = F, Cl, Br, I, X•character increases as does the intrinsic SOC of X•so thatDincreases correspondingly over this range.