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

Three square-shape tetranuclear lanthanide complexes: {[Ln(4)(L)(4)(CH3O)(4)]center dot 4CH(3)OH} (Ln = Gd (1), Tb(2), Dy (3); L = N '-(2-hydroxy-5-methylbenzylidene)-6-(hydroxymethyl)picolinohydrazide) were fabricated and structurally characterized. The [Ln(4)O(8)] core of complexes 1-3 was held together by four mu(2) carbonyl oxygen atoms from the L2- ligands and four mu(2) methanol oxygen atoms. Magnetic studies reveal that compound 1 exhibits cryogenic magnetic refrigeration property (-Delta S-m = 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 Delta E/k(B) = 54.3 K and the preexponential factor tau(0) = 4.77 x 10(-6) s.