‘Windmill’-shaped Ln III4 (LnIII = Gd and Dy) clusters: magnetocaloric effect and single-molecule-magnet behavior†
Abstract
Two new tetranuclear lanthanide clusters with the formula [Ln4(L)4(μ2-CH3O)4]·4CH3OH·xC2H5OH (LnIII = Gd (1) and Dy (2), H2L = N′-(4-diethylamino-2-hydroxybenzylidene)-6-(hydroxymethyl)picolinohydrazide, x = 0 for 1 and x = 4 for 2) were assembled by using a polydentate ligand (H2L) reacting with β-diketonate salts (Ln(acac)3·2H2O, LnIII = Gd (1) and Dy (2)). Single-crystal X-ray structures reveal that clusters 1 and 2 are mainly composed of four LnIII ions that are interconnected through eight μ2-O bridging oxygen atoms, and the Ln4 clusters show a ‘windmill’-shaped arrangement. The magnetic investigations reveal that cluster 1 displays a cryogenic magnetic refrigeration property with a large magnetic entropy (−ΔSm = 29.0 J kg−1 K−1, ΔH = 7.0 T and T = 2.0 K); meanwhile, alternating current (ac) magnetic susceptibility measurement reveals that 2 exhibits typical SMM behavior with a Ueff/kB of 42.4 K and pre-exponential factor τ0 = 1.2 × 10−6 s.