Assembling two Dy2 single-molecule magnets with different energy barriers via fine-tuning the geometries of DyIII sites

Abstract

The utilization of two Schiff-base ligands H₂L¹ and H₂L² (H₂L¹ = 4-chloro-2-(((3-ethoxy-2-hydroxybenzyl)imino)methyl) phenol, H₂L² = 2-(((3-ethoxy-2-hydroxybenzyl)imino)methyl)-4-methoxy-phenol) with different substituents at the backbone of phenol in the construction of dinuclear dysprosium single-molecule magnets (SMMs) is reported. Two complexes of formulae [Dy₂(L¹)₂(NO₃)₂(EtOH)(DMF)]·2EtOH (1) and [Dy₂(L²)₂(NO₃)₂(MeOH)₂] (2) have been prepared and structurally characterized. X-ray crystallographic analysis revealed that the four Dy^III ions of 1 and 2 all adopt NO₇ coordination environments. The two Dy^III centers of 1 exhibit triangular dodecahedron (D_2d) and square antiprism (D_4d) geometries, respectively, while the two Dy^III sites in 2 both show triangular dodecahedron geometry with D_2d symmetry. Magnetic analyses indicated that both complexes display SMM behavior with energy barriers of 86.91 K (1) and 93.70 K (2), respectively. The slight enhancement of the energy barrier of 2 reveals that the coordination geometries of Dy^III ions would affect the magnetic behaviors of 1 and 2. Complete Active Space Self-Consistent Field (CASSCF) calculations were conducted for 1 and 2 to illustrate the slight variation of the magnetic behaviors. The calculated results are well consistent with those of the experimental outcomes.