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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 DyIII 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. [ABSTRACT FROM AUTHOR]