Two Dysprosium(III)-Based Single-Molecule Magnets Derived from 1,10-Phenanthroline Ligands and Different Anions as Bridging Groups

Two Dy compounds, [Dy-2(Phen)(2)(CH3COO)(6)] (1; Phen = 1,10-phenanthroline) and [Dy(Phen)(2)(NO3)(3)] (2), were obtained by the reactions of Phen with different dysprosium salts containing different anions, which act as bridging groups and greatly affect the coordination polyhedra of the metal ions. In the former complex, the Dy-III ions are bridged by acetate anions and adopt a spherical capped square antiprismatic (C-4v) coordination environment, whereas a bicapped square antiprism (D-4d) was observed for 2, in which the Dy-III ions are bridged by nitrate anions. Static and dynamic magnetic measurements revealed that both compounds display slow magnetic relaxation but with fast quantum tunneling of magnetization (QTM). In an applied direct-current (dc) field, the QTM was suppressed, and two slow magnetic relaxation processes occurred for both compounds. Comparative studies on the magnetic properties indicate how the ligand field and the local geometric symmetry of the magnetic anisotropy of the Dy-III center leads to differing magnetic behavior.