Dinuclear Ln(iii) complexes constructed from an 8-hydroxyquinoline Schiff base derivative with different terminal groups show differing slow magnetic relaxation

Abstract

Two series of dinuclear Ln^III complexes, namely, [Ln(tfa)₂(L)]₂ (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)) and [Ln(tfa)₂(L′)]₂ (Ln = Gd (6), Tb (7), Dy (8), Ho (9), Er (10)) (tfa = trifluoroacetylacetonate, HL = 2-[[(4-methylphenyl)imino]methyl]-8-hydroxyquinoline and HL′ = 2-[[(4-ethylphenyl)imino]methyl]-8-hydroxyquinoline), were synthesized, and structurally and magnetically characterized. Measurements of alternating-current (ac) susceptibility revealed that complexes 3 and 8 display significant zero-field single-molecule magnetic (SMM) behaviors with barrier energies of U_eff/k_B = 9.14 K, τ₀ = 4.76 × 10⁻⁶ s and U_eff/k_B = 17.50 K, τ₀ = 3.96 × 10⁻⁶ s, respectively. The magnetic studies also revealed that 1 and 6 feature a magnetocaloric effect with magnetic entropy change of −ΔS_m values for 1 and 6 of 19.72 J kg⁻¹ K⁻¹ and 19.37 J kg⁻¹ K⁻¹ at T = 2 K and ΔH = 7 T, respectively.