Effective energy barrier improvement via hydroxyl-bridge in linear {Dy2IIIZn2II} clusters

Abstract

Two heterometallic tetranuclear clusters [Dy2Zn2(bipy)2(nb)10] (1) and [Dy2Zn2(bipy)2(μ−OH)2(nb)8] (2) (bipy = 2,2′-bipyridine, Hnb = m-nitrobenzoic acid) were hydrothermally prepared by the reactions of same mixed-ligands with different dysprosium sources. Structurally, the coordination environment, configuration, and the binding modes of the mixed ligands are almost similar to each other. Only a slight difference is a pair of μ-COO− moieties connecting DyIII and ZnII cations in 1 replaced by a couple of scarcely µ-OH– bridges in 2. Magnetically, complex 1 displays no slow magnetic relaxation behavior, while the complex 2 behaves as a single molecule magnet with the effective energy barrier of 78.69 K due to the large uniaxial anisotropy of DyIII ions, which is mainly originating from the strong coordination ability of hydroxide-bridges.