Magnetic anisotropy and exchange coupling in a family of isostructural Fe(2)(III)Ln(2)(III) complexes

作者：Baniodeh Amer; Lan Yanhua; Novitchi Ghenadie; Mereacre Valeriu; Sukhanov Andrey; Ferbinteanu Marilena; Voronkova Violeta; Anson Christopher E; Powell Annie K^*

来源：Dalton Transactions, 2013, 42(24): 8926-8938.

DOI：10.1039/c3dt00105a

The reaction of [Fe3O(O2CPh)(6)(H2O)(3)](O2CPh) with lanthanide/rare earth nitrate salts in the presence of triethanolamine (H(3)tea) in acetonitrile/methanol solution yields a series of compounds with isostructural tetranuclear core motifs [Fe(2)(III)Ln(2)(III)(mu(3)-OH)(2)(teaH)(2)(O2CCPh)(6)]center dot 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 %26quot;butterfly%26quot; Fe(2)Ln(2) 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 Mossbauer 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 %26gt; 20 K.

• 出版日期2013