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

Abstract

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 (−ΔS_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 ΔE/k_B = 54.3 K and the preexponential factor τ₀ = 4.77 × 10⁻⁶ s.