Local Coordination Geometry Perturbed β‑Diketone Dysprosium Single-Ion Magnets

A series of three β-diketone mononuclear dysprosium complexes, namely, Dy­(TFI)₃(H₂O)₂ (1), Dy­(TFI)₃(bpy) (2), and [Dy­(TFI)₃(Phen)]·0.02CHCl₃ (3) (TFI = 2-(2,2,2-trifluoroethyl)-1-indone, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been designed and synthesized. Crystal structure analysis reveals that complexes 1–3 have haveisomorphic structures in which the central Dy­(III) ion is eight-coordinated by six oxygen atoms from three TFI ligands and two O/N atoms from auxiliary ligands, forming a distorted bicapped trigonal prismatic geometry for 1, a distorted dodecahedral geometry for 2, and a distorted square antiprismatic geometry for 3, respectively. Magnetic studies indicate that complex 2 with D_2d symmetry and 3 with D_4d symmetry exhibit slow magnetic relaxation with barrier heights (U_eff/k_B) of 48.8 K for 2 and 57.9 K for 3. Strikingly, the relaxation time (τ) of 0.0258 s for 3 is about 20 times that for 2, which is presumably associated with larger rotation of the SAP surroundings for 3. Further, complexes 2 and 3 exhibit essential magnetic hysteresis loops at 1.8 K. These extend the recent reports of the single-ion magnets (SIMs) of β-diketone mononuclear dysprosium complexes.