Structures and magnetic properties of cyclic heterometallic tetranuclear clusters

A new salicylamide Salen-like multidentate ligand, 1-(2-hydroxy-3-methoxy-benzamido)-2-(2-hydroxy-3-methoxy-benzylideneamino)-ethane (H3L), was synthesised and used to build up heterometallic magnetic clusters. As a result, four new highly thermal stable cyclic tetranuclear heterometallic clusters which were characterized by elemental analysis, X-ray diffraction, IR and TGA measurements, [M(2)Ln(2)L(2)(NO3)(4)](M(2)Ln(2), where M-II = Cu-II, Ni-II and Ln(III) = Tb-III, Dy-III) were successfully obtained with high yield under solvothermal conditions. Temperature-dependent magnetic susceptibility measurements exhibit strong ferromagnetic interactions between Cu-II and Ln(III) in Cu(2)Ln(2) which were evaluated by comparing their magnetic susceptibilities with those of the isostructural Ni(2)Ln(2) clusters containing diamagnetic Ni-II ions. Furthermore, alternating-current magnetic susceptibility studies carried out for the four tetranuclear compounds indicate that Cu(2)Ln(2) exhibit interesting slow relaxation of magnetization of the SMM behavior and the effective energy barriers for Cu2Tb2 can be obtained from alternating-current susceptibility measurements by applying an external 2000 Oe direct-current field. (C) 2017 Elsevier Ltd. All rights reserved.