Structures and magnetic properties of novel Ln()-based pentanuclear clusters: magnetic refrigeration and single-molecule magnet behavior

Six new and novel polynuclear Ln III 5 clusters, formulated as [Ln 5 (L) 4 (acac) 7 ]·solvents (Ln( iii ) = Sm ( 1 ), Eu ( 2 ), Gd ( 3 ), Tb ( 4 ), Dy ( 5 ) and Ho ( 6 ), Hacac = acetylacetone, and H 2 L = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-5-hydroxymethyl-2-furancarboxylic acid) have been successfully obtained through the reaction of a polydentate Schiff base ligand (H 2 L) and Ln(acac) 3 ·2H 2 O. Single crystal X-ray diffraction data indicate that clusters 1-6 are isostructural and their central Ln( iii ) ions have a Ln( iii ) 5 chain arrangement. Magnetic property investigations show that the Gd( iii )-based cluster ( 3 ) exhibits a significant and larger MCE with the maximum −Δ S m value of 34.02 J kg −1 K −1 (Δ H = 7.0 T and T = 2.0 K). Alternating current (ac) susceptibility measurements of the Dy( iii )-based cluster (5) display remarkable slow magnetic relaxation behaviors at zero applied direct current (dc) magnetic field (Δ E / k B = 17.47 K and τ 0 = 1.52 × 10 −6 s). Furthermore, studies on the solid-state fluorescence properties show that clusters 2 , 4 , and 5 display the characteristic lanthanum luminescence at room temperature. The Gd 5 cluster displays significant magnetic refrigeration properties, whereas the Dy 5 cluster exhibits remarkable SMM behavior. Clusters 2 , 4 , and 5 display the characteristic lanthanum luminescence.