Synthesis, structures, and magnetic properties of butterfly-shaped hexanuclear [FeIII4LnIII2] single-molecule magnets

Abstract

Two new Fe^III₄Ln^III₂ complexes, [Fe^III₄Ln^III₂(μ₃-OH)₂(mdea)₆(NO₃)₄(H₂O)₂]·4MeOH (Ln = Y (1); Dy (2)), and their diluted analogs with a Y^III_1.83Dy^III_0.17 ratio (3) were synthesized and characterized. In the absence of carboxylate ancillary ligands, the hexanuclear cores of all three compounds possess a unique centrosymmetric chair-like topology. DC magnetic susceptibility measurements revealed the dominant antiferromagnetic interactions between Fe^III centers. Compounds 2 and 3 containing Dy^III ions display single-molecule magnet behavior with the effective energy barrier U_eff increasing from 39.7 K (for 2) to 101.5 K (for 3). The off-diagonal ligand field terms and the very weak magnetic interaction between Dy^III centers in compound 2 enhance the QTM effect at 0 dc field, which can be suppressed by performing a magnetic dilution.