Magnetic anisotropy and exchange coupling in a family of isostructural FeIII2LnIII2 complexes
作者:Amer Baniodeh、Yanhua Lan、Ghenadie Novitchi、Valeriu Mereacre、Andrey Sukhanov、Marilena Ferbinteanu、Violeta Voronkova、Christopher E. Anson、Annie K. Powell
DOI:10.1039/c3dt00105a
日期:——
The reaction of [Fe3O(O2CPh)6(H2O)3](O2CPh) 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 [FeIII2LnIII2(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 FeIII centres is antiferromagnetic, with JFeFeca. −6.71(4) cm−1, while the Fe–Ln couplings are much weaker, e.g. JFeGd = 0.18(1) cm−1. Compounds 6, 7, 8 and 13 were selected for Mössbauer studies in order to investigate the influence of isotropic (GdIII), highly anisotropic non-Kramers and Kramers (TbIII and DyIII) and diamagnetic (YIII) rare earth ions on the local environment of the FeIII centres. Compounds 3, 6, 8 and 13 were also studied using X-Band EPR spectroscopy. For 13, with the diamagnetic YIII ion, this made it possible to obtain the D, E, JFeFe 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 LnIII 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.
在
乙腈/
甲醇溶液中,[Fe3O(O2CPh)6(
H2O)3](O2CPh)与
镧系元素/稀土
硝酸盐在
三乙醇胺(H3tea)存在下发生反应,生成一系列具有等结构四核核心图案的化合物[FeIII2LnIII2(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))。在所有情况下,核心拓扑结构都是缺陷-二ubane 平面或 "蝴蝶 "Fe2Ln2图案。对 1-13 号化合物的研究结合了实验技术和理论研究。对所有化合物都进行了磁感应强度测量。两个 FeIII 中心之间的磁耦合是反
铁磁性的,JFeFeca.-6.71(4) cm-1,而 Fe-Ln 耦合要弱得多,例如 JFeGd = 0.18(1) cm-1。为了研究各向同性(GdIII)、高度各向异性的非克拉默和克拉默(TbIII 和 DyIII)以及二磁性(YIII)稀土离子对 FeIII 中心局部环境的影响,我们选择了化合物 6、7、8 和 13 进行莫斯鲍尔研究。还利用 X 波段 EPR 光谱对化合物 3、6、8 和 13 进行了研究。对于含有 YIII 二磁性离子的 13 号化合物,可以获得
铁中心的 D、E、JFeFe 和 g 参数。研究表明,化合物 3、6 和 8 的低温光谱是由稀土离子的磁性和 LnIII 离子之间的偶极-偶极相互作用决定的。在温度大于 20 K 时,EPR 光谱的温度依赖性证实了
铁-
镧之间的相互作用非常微弱且具有偶极性质。