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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 (-Δ Sm) of 30.99 J kg-1 K-1 for H = 7 T at 4 K, whereas the Dy12 cluster shows single-molecule magnet behavior. [ABSTRACT FROM AUTHOR]

The syntheses, crystal structures, and magnetic properties of a novel family of heterometallic aggregates [CuII9LnIII2(μ3-OH)8(mea)4(C3H7COO)4(NO3)2Cl6(MeOH)4(H2O)2] ·3MeOH ·2H2O [Ln = Eu ( 1), Gd ( 2), Tb ( 3), Dy ( 4)] are reported. The compounds were obtained by the direct reaction of monoethanolamine (Hmea) with CuCl2 ·2H2O and Ln(NO3)3 ·6H2O in the presence of sodium butyrate (C3H7COONa) in MeOH/MeCN solution. Compounds 1- 4 are isomorphous and have an intriguing heterometallic undecanuclear [Cu9Ln2] core that contains a [3 × 3] [Cu9] grid and two [LnCu4] tetragonal pyramids that share a common [Cu4] vertex. Compounds 1- 4 are the first high-nuclearity 3d-4f aggregates bearing a monoethanolamine (Hmea) ligand to be reported. The magnetic properties of 1- 4 have been investigated by dc and ac susceptibility measurements. A detailed magnetic analysis revealed that antiferromagnetic Cu ···Cu interactions and ferromagnetic Cu ···Gd couplings exist in [Cu9Gd2] ( 2), which exhibits a significant magnetocaloric effect. Furthermore, [Cu9Tb2] ( 3) and [Cu9Dy2] ( 4) display slow relaxation of the magnetization. [ABSTRACT FROM AUTHOR]