Two Discrete Ln12 Shelf-Shaped Clusters: Magnetic Studies Reveal a Significant Cryogenic Magnetocaloric Effect and Slow Magnetic Relaxation

Two unique dodecanuclear lanthanide clusters, [LnIII12Na3(µ3-OH)2(hmmp)6(piv)12(CO3)6(MeOH)6]OH·5MeOH {Ln = Gd3+, Dy3+; hmmpH2 = 2-[(2-hydroxyethylimino)methyl]-6-methoxyphenol}, have been synthesized by treating the simple Schiff-base ligand hmmpH2 with the relevant lanthanide chloride and sodium pivalate (NaPiv). Single-crystal X-ray diffraction analysis revealed that the central cores of Gd12 and Dy12 are unprecedented and composed of a distorted four-layer triangular shelf-like molecular structure, which can be broken down into two types of four parallel triangular layers with an ABBA arrangement. Magnetic investigations revealed that the Gd12 cluster is a good candidate for magnetic refrigeration with a significant entropy change (–ΔSm) of 30.99 J kg–1 K–1 for H = 7 T at 4 K, whereas the Dy12 cluster shows single-molecule magnet behavior.