Molecular assemblies from linear-shaped Ln clusters to Ln clusters using different β-diketonates: disparate magnetocaloric effects and single-molecule magnet behaviours.

A series of tetranuclear lanthanide-based clusters [Ln(dbm)(L)(CHOH)]·2CHOH (Ln(III) = Gd (1), Dy (2), and Ho (3); HL = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-2,3-dihydroxybenzaldehyde, Hdbm = dibenzoylmethane) and octanuclear lanthanide-based clusters [Ln(HL)(CHO)(CHOH)]·6CHOH (Ln(III) = Gd (4), Dy (5)) were assembled using a polydentate Schiff-base ligand HL and two different β-diketone salts a solvothermal method, and their structures and magnetic properties have been characterized. Interestingly, β-diketones play an important role in assembling and affecting the structures of Ln to Ln clusters. This is the first use of β-diketone to affect the structures of polynuclear Ln(III)-based clusters from linear-shaped Ln clusters to Ln clusters. Magnetic studies revealed that antiferromagnetic interactions exist in clusters 1-Gd4 and 4-Gd8. More importantly, clusters 1-Gd4 and 4-Gd8 display significant cryogenic magnetic refrigeration properties (-Δ = 24.88 J kg K for 1-Gd4 and -Δ = 32.52 J kg K for 4-Gd8); the results show that cluster 4-Gd8 exhibits a larger magnetocaloric effect than 1-Gd4. Cluster 2-Dy4 shows remarkable single-molecule magnet (SMM) behavior (Δ/ = 67.5 K and = 3.06 × 10 s) under a zero dc field, and 5-Dy8 exhibits a field-induced SMM-like behavior (Δ/ = 39.83 K and = 2.12 × 10 s) under a 5000 Oe dc field.