Synthesis, structures and magnetism of a series of dinuclear and one-dimensional Ni-Ln complexes: single-molecule magnetic behavior in one-dimensional nitrate-bridged Dy analogue

摘要

By diffusion of methyl tert-butyl ether vapor into an acetonitrile solution containing [Ni(L)(H2O)(2)] (L = 1,2-bis(3-methoxy-salicylideneaminooxy) ethane) and Ln(NO3)(3)center dot 6H(2)O, three Ni-Ln heterometallic complexes, [Ni(mu-L)(MeCN)(2)Ln(NO3)(3)] (Ln = Gd for 1, Tb for 2), and [Ni(mu-L)(MeCN) Dy(NO3)(2)(mu-NO3)center dot MeCN](n) (3) were obtained. When the reaction was carried out in methanol/chloroform (2 : 1) containing H2L, Ni(Ac)(2)center dot 4H(2)O and Ln(NO3)(3)center dot 6H(2)O with diffusion of diethyl ether vapor, two Ni-Ln heterometallic complexes [Ni(mu-L)(CH3OH)(mu-NO3) Ln(NO3)(2)] (Ln = Tb for 4, and Dy for 5) were synthesized. The X-ray analyses demonstrated that complexes 1, 2, 4 and 5 display 3d-4f heterodinuclear structures, and that the Ni-II and Ln(III) ions are bridged by diphenolato atoms for 1 and 2, and by a syn-syn nitrate group and diphenolato atoms for 4 and 5. Compound 3 is made of a rare anti-anti nitrate-and phenolate-bridged Ni-Dy heterometallic chain. All complexes exhibit a net ferromagnetic interaction between the NiII and LnIII ions. Alternating current susceptibility measurements demonstrated that compound 3 behaved as a single-molecule magnet with an effective energy barrier of 15.8 K under a zero direct current field, however, 5 only displayed slow magnetic relaxation under a 2000 Oe direct current field.