Efficient enhancement of magnetic anisotropy by optimizing the ligand-field in a typically tetranuclear dysprosium cluster

Abstract

The perturbation to the ligand field around the lanthanide ion may significantly contribute to the magnetic dynamics of single molecule magnets. This can be demonstrated by two typical Dy₄ cluster-based single molecular magnets (SMMs), [Dy₄X₂(μ₃-OH)₂(μ-OH)₂(2,2-bpt)₄(H₂O)₄]X₂·2H₂O·4EtOH (X = Cl and Br for 1 and 2, respectively), which were constructed by using 3,5-bis(pyridin-2-yl)-1,2,4-triazole (2,2-bptH) as the polynuclear-chelating ligand. Alternating-current (ac) magnetic susceptibility measurements show that the energy barriers in complexes 1 and 2 were immensely enhanced by comparing with our previous work due to the optimization of the ligand field around Dy^III ions. Remarkably, their high thermal active barriers at 190 K (1) and 197 K (2) under a zero applied external dc magnetic field are also among the highest within the reported tetranuclear lanthanide-based SMMs.