Counter anions influence the relaxation dynamics of phenoxy-bridged Dy2 single molecule magnets

Abstract

The syntheses, structures and magnetic properties of a series of dimeric dysprosium(III) complexes [Dy₂L₂(CH₃OH)(H₂O)]·2X·solvent {X = Cl (1), NO₃ (2), ClO₄ (3)} and [Dy₂L₂(CH₃OH)₂]·2X·solvent {X = CF₃SO₃ (4)}, formed from the 1 : 1 reactions of the H₂L ligand with the corresponding dysprosium salts, are reported. Structural and magnetic studies reveal that counter anions on the periphery play a significant role in determining the dynamic magnetic relaxation process of these complexes. The coordination geometries of the Dy(1)(III) centers are eight-coordinate triangular dodecahedra in 1–4. All compounds exhibit single-molecule magnet (SMM) behavior under a zero dc field and optimal applied dc field except 3, which displays only slow relaxation of magnetization. A comparison of the magnetic properties and structural parameters of the four compounds shows that the short Dy–O_phen distances and the large O_phen–Dy–O_phen angles create an axial ligand field in which dysprosium(III) complexes exhibit magnetic anisotropy and SMM properties.