Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstr. 15, D-76131 Karlsruhe, Germany.
Dalton Trans. 2013 Jun 28;42(24):8926-38. doi: 10.1039/c3dt00105a. Epub 2013 May 9.
The reaction of Fe3O(O2CPh)6(H2O)3 with lanthanide/rare earth nitrate salts in the presence of triethanolamine (H3tea) in acetonitrile/methanol solution yields a series of compounds with isostructural tetranuclear core motifs [Fe(III)2Ln(III)2(μ3-OH)2(teaH)2(O2CCPh)6]·3MeCN (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Y (13)). In all cases the core topology is a defect-dicubane planar or "butterfly" Fe2Ln2 motif. Compounds 1-13 were investigated using a combination of experimental techniques and theoretical studies. Magnetic susceptibility measurements were carried out on all compounds. The magnetic coupling between the two Fe(III) centres is antiferromagnetic, with J(FeFe) ca.-6.71(4) cm(-1), while the Fe-Ln couplings are much weaker, e.g. J(FeGd) = 0.18(1) cm(-1). Compounds 6, 7, 8 and 13 were selected for Mössbauer studies in order to investigate the influence of isotropic (Gd(III)), highly anisotropic non-Kramers and Kramers (Tb(III) and Dy(III)) and diamagnetic (Y(III)) rare earth ions on the local environment of the Fe(III) centres. Compounds 3, 6, 8 and 13 were also studied using X-Band EPR spectroscopy. For 13, with the diamagnetic Y(III) ion, this made it possible to obtain the D, E, J(FeFe) and g parameters for the iron centres. It is shown that the low-temperature spectra of compounds 3, 6 and 8 are determined by magnetic properties of rare-earth ions and the dipole-dipole interactions between the Ln(III) ions. The Fe-Ln interactions were confirmed as very weak and dipolar in nature by the temperature dependence of EPR spectra at T > 20 K.
Fe3O(O2CPh)6(H2O)3与镧系/稀土硝酸盐盐在三乙醇胺（H3tea）的存在下在乙腈/甲醇溶液中反应，生成一系列具有同构四核核基序[Fe(III)2Ln(III)2(μ3-OH)2(teaH)2(O2CCPh)6]·3MeCN（Ln=Ce（1），Pr（2），Nd（3），Sm（4），Eu（5），Gd（6），Tb（7），Dy（8），Ho（9），Er（10），Tm（11），Yb（12），Y（13））的化合物。在所有情况下，核拓扑结构都是缺陷二立方烷平面或“蝴蝶”Fe2Ln2 基序。使用实验技术和理论研究相结合的方法研究了化合物 1-13。对所有化合物都进行了磁化率测量。两个 Fe(III)中心之间的磁耦合是反铁磁性的，J(FeFe)约为-6.71(4)cm(-1)，而 Fe-Ln 耦合则弱得多，例如 J(FeGd)=0.18(1)cm(-1)。选择化合物 6、7、8 和 13 进行穆斯堡尔研究，以研究各向同性（Gd(III)）、高度各向异性非克拉默斯和克拉默斯（Tb(III)和 Dy(III)）和抗磁性（Y(III)）稀土离子对 Fe(III)中心局部环境的影响。还使用 X 波段 EPR 光谱研究了化合物 3、6、8 和 13。对于 13，由于具有抗磁性 Y(III)离子，因此可以获得铁中心的 D、E、J(FeFe)和 g 参数。结果表明，化合物 3、6 和 8 的低温光谱由稀土离子的磁性和 Ln(III)离子之间的偶极-偶极相互作用决定。通过在 T>20 K 时 EPR 光谱的温度依赖性，证实了 Fe-Ln 相互作用非常弱且具有偶极子性质。
