Two heptanuclear cluster-based 3D metal-organic frameworks with a good magnetocaloric effect

Two coordination polymers [Ln(7)(IDA)(3)(HCOO)(3)(mu(3)-OH)(8)(H2O)(6)]Cl-4 center dot 8H(2)O (Ln = Gd, Dy; IDA(-) = iminodiacetic anion) featuring a three-dimensional (3D) framework based on Ln(7) units were synthesized. According to X-ray structural analysis, the two compounds are isostructural; both consist of a garland-shaped Ln(7) building unit with a zigzag arrangement along the c-axis and one-dimensional round channels inside. Magnetic investigations demonstrate that 1Gd shows a good MCE with -Delta S-m(max) = 40.85 J kg(-1) K-1 at 3 K and Delta H = 7 T due to the larger mass ratio (metal/ligand) and increased magnetic density of the 3D structure.