Magnetic properties and structure of tetranuclear lanthanide complexes based on 8-hydroxylquinoline Schiff base derivative and β-diketone coligand

Abstract

Five tetranuclear lanthanide complexes [Gd₄(dbm)₄(L)₆(μ₃-OH)₂]·5CH₃CN (1), [Tb₄(dbm)₄(L)₆(μ₃-OH)₂]·2CH₃CH₂OH·4CH₃CN (2), [Dy₄(dbm)₄(L)₆(μ₃-OH)₂]·4CH₃CN·2H₂O (3), [Ho₄(dbm)₄(L)₆(μ₃-OH)₂]·CH₃CH₂OH·4CH₃CN·2H₂O (4) and [Er₄(dbm)₄(L)₆(μ₃-OH)₂] (5) are obtained from the reaction of 5-(4-pyridinecarboxaldehyde)amino-8-hydroxylquinoline (HL) and Ln(dbm)₃·2H₂O (dbm = 1,3-diphenyl-1,3-propanedione). Complexes 1–5 are isomorphous and crystallize in the monoclinic space group P2₁/c. The metal ions in 1–5 adopt an approximately square-antiprismatic coordination environment. Magnetic studies indicate that complex 1 features a magnetocaloric effect (MCE) with the magnetic entropy change of −ΔS_m(T) = 16.35 J kg⁻¹ K⁻¹ at 3 K for ΔH = 7 T. Additionally, complex 3 displays single molecule magnet (SMM) behavior, exhibiting an effective energy barrier of the relaxation of magnetization U_eff/k_B = 89.38 K and pre-exponential factor τ₀ = 3.32 × 10⁻⁸ s.