Enhancing Magnetic Behaviors of Dysprosium Single-Molecule Magnets from Crystal Field Perturbation by Deprotonating Schiff-Base Ligand

Abstract

For studying how crystal field perturbation influence magnetic relaxation behaviors of Ln-SMMs, four complexes of [Ln(H2L)(NO3)(H2O)(EtOH)](NO3)2·H2O (Ln = Dy (1), Tb (2)) and [Ln(L)(NO3)(MeOH)2] (Ln = Dy (3), Tb (4)) were synthesized by utilizing planar pentadentated Schiff-base ligand H2L [2,6-diylbis(ethan-1-yl-1-ylidene)di(isonicotinohydrazide)] under different alkaline conditions. They all have similar mononuclear structures with LnIII ion in nine-coordinated muffin geometry. Crystal field was slightly perturbed by deprotonating H2L ligand and using different solvent molecules in DyIII complex 3, which result in field-induced two-step relaxation processes with almost 3-fold increase in Ueff of 57.52 K (SR) and 28.49 K (FR) than 20.63 K for complex 1 showing one-step relaxation process. This work gives another example of improving SMM behavior simply by subtle crystal field perturbation.