Single molecule magnet behavior and magnetic refrigeration of carbonyl oxygen-bridged tetranuclear lanthanide complexes

Three square-shape tetranuclear lanthanide complexes: {[Ln4(L)4(CH3O)4]·4CH3OH} (Ln = Gd (1), Tb(2), Dy (3); L = N′-(2-hydroxy-5-methylbenzylidene)-6-(hydroxymethyl)picolinohydrazide) were fabricated and structurally characterized. The [Ln4O8] core of complexes 1–3 was held together by four μ2 carbonyl oxygen atoms from the L2− ligands and four μ2 methanol oxygen atoms. Magnetic studies reveal that compound 1 exhibits cryogenic magnetic refrigeration property (−ΔSm = 30.20 J K−1 kg−1), and 3 shows ferromagnetic interactions. Slow magnetic relaxation behaviors are observed in 3. Also, compound 3 exhibits an energy barrier of ΔE/kB = 54.3 K and the preexponential factor τ0 = 4.77 × 10−6 s.