A homochiral hexagadolinium phosphonate cluster with a large magnetocaloric effect

Abstract

A homochiral hexagadolinium phosphonate cluster designated as R/S-[Gd6(pmhpH)8(NO3)2(H2O)8]·19H2O (R/S-1) was successfully obtained and analyzed using single crystal X-ray diffraction crystallography, IR spectrum, TG analysis and magnetic testing. The cluster, shaped like a lantern, is constructed from {GdO8} polyhedra and {PO3C} tetrahedra surrounded by eight pmhpH2- ligands. Within the structure, two types of gadolinium ions with different coordination modes are observed. Each Gd(III) ion is bound to two carboxylate oxygens and six phosphonate oxygens from the coordinated pmhpH2- ligands. Circular dichroism spectra comfirmed that R/S-1 exists as a pair of enantiomers. Moreover, the cluster exhibits high thermal stability, decomposing at temperatures exceeding 335°C. Notably, the magnetic measurements revealed that compound R-1 exhibits a good magnetocaloric effect (MCE) with a maximum entropy change of − ΔSmmax =36.84 Jkg− 1 K− 1 at T = 2K and ΔH = 7 T.