Different single-molecule magnets behaviors of carboxyl bridged dinuclear Dy(III) complexes induced by charged and neutral ligand

Abstract

Three dinuclear dysprosium complexes, namely, Dy2(DBM)4L2(CH3CH2OH)2·2CH2Cl2(1), Dy2(DBM)4L2(CH3OH)2·2CH2Cl2(2), Dy2(BAC)4L2(CH3CH2OH)2 (3) and yttrium compound Y2(BAC)4L2(CH3CH2OH)2 (3Y) (L = 2,6-dimethoxybenzoic acid, DBM = dibenzoyl methane, BAC = Benzoylacetone), were structurally and magnetically characterized. The single-crystal structures showed that L serves as an effective bridge to link two Dy(III) centers with μ2-η1:η2-O2 coordination mode. Each Dy(III) ion was chelated by two bidentate β-diketonate co-ligands and a methanol or ethanol molecule, leading to an eight-coordinated geometry. The magnetic measurements revealed that all the complexes behaved as field-induced single-molecule magnets, and the ferromagnetic intramolecular interactions between Dy(III) ions are apparent. Strikingly, the alteration of neutral ligands between 1 and 2 did not result in a significant change of their relaxation energy barriers (Ueff/kB = 25.6 K and 26.1 K respectively), while the dramatically enhancement of energy barrier by nearly triple (91.6 K) increase was observed in 3 when modulating the terminal of β-diketonate anion and the open butterfly-shaped hysteresis loop was also observed at 1.8 K in 10% diluted samples of 3. The electrostatic model for the determination of the magnetic anisotropy in Dy complexes implemented by the Magellan program revealed that the dynamic magnetic relaxation is dominated by the charged β-diketonate ligand much more than the neutral ligand in this case.