Synergistic effect of mixed ligands on the anisotropy axis of two dinuclear dysprosium complexes

Abstract

We present the syntheses, crystal structures, magnetic properties and theoretical calculations performed on two dinuclear dysprosium complexes with formulas Dy₂(L₁)₂(L₂)₂(CH₃CH₂OH)(CH₃OH) (1) and Dy₂(L₁)₂(L₃)₂(CH₃OH)₂·1.5CH₃OH (2). Single-crystal X-ray structural data analyses showed that both complexes contain two nonequivalent dysprosium ions bridged by two phenolate oxygen atoms. In both complexes, each dysprosium site adopts a N₂O₆ coordination constitution and triangular dodecahedron (D_2d) configuration geometry with different distortion degree. Both complexes display single-molecule magnet behavior manifested by frequency-dependent out-of-phase alternating current susceptibility signal peaks under a zero-applied dc field. The effective energy barrier of the magnetization reversal and relaxation time values are 61 K, 7.1 × 10⁻⁶ s (1) and 51 K, 1.9 × 10⁻⁶ s (2), respectively. Theoretical calculations revealed a drastic discrepancy between the orientations of the anisotropy axis of the Dy2 ion observed in these two dinuclear complexes, resulting from the different spatial arrangements of the mixed ligands in the core structure.