Four Ln2 compounds constructed by a polydentate Schiff base ligand: Gd2 compound displaying large magnetocaloric effect and Dy2 compound showing single-molecule magnet behavior

Abstract Four new acyloxy bridged LnIII2 compounds [Ln2(L)2(acac)2(EtOH)2] (Ln(III) = Gd (1), Tb (2), Dy (3), and Ho (4), Hacac = acetylacetone, and H2L = pyridine-2-carboxylic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide) have been prepared by a polydentate Schiff base ligand under solvothermal condition. The single-crystal X-ray structure study reveals that 1-4 are isostructural and contain a parallelogram Ln2O2 core. Magnetic study reveals that antiferromagnetic interaction exists in compound 1. More importantly, compound 1 displays well cryogenic magnetic refrigeration property (−ΔSm = 28.2 J kg−1 K−1, T = 2.0 K and ΔH =70 kOe); while compound 3 exhibits evident single-molecule magnet behavior under zero-field condition (ΔE/kB = 26.8 K, τ0 = 1.05 × 10−7 s).