Tetranuclear lanthanide complexes showing magnetic refrigeration and single molecule magnet behavior

Abstract

Three tetranuclear lanthanide complexes: {[Ln₄(L)₆(pbd)₄(μ₃-OH)₂]·2CH₃CN} (Ln = Gd (1), Tb (2), Dy (3); HL = 5-(benzylideneamino)quinolin-8-ol, pbd = 1-phenylbutane-1,3-dione) were fabricated and structurally characterized. Compounds 1–3 are isostructural belonging to the triclinic system with space group P. The core of the complexes contains a tetranuclear arrangement of Ln^III ions which is held together by two pyramidal μ₃-OH⁻ ions and six μ₂ phenol hydroxyl oxygen atoms derived from six L⁻ ligands. Magnetic studies indicated that 1 exhibits cryogenic magnetic refrigeration properties (maximum −ΔS_m = 21.41 J K⁻¹ kg⁻¹, ΔH = 7 T at 2.0 K), whereas compound 3 exhibits slow relaxation of the magnetization with an energy barrier (ΔE/k_B) of 81.48 K and τ₀ = 6.48 × 10⁻⁸ s.