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

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-methyl-phenyl)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, tau(0) = 4.76 x 10(-6) s and U-eff/k(B) = 17.50 K, tau(0) = 3.96 x 10(-6) s, respectively. The magnetic studies also revealed that 1 and 6 feature a magnetocaloric effect with magnetic entropy change of -Delta S-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 Delta H = 7 T, respectively.