Construction of NiIILnIIIMIII (Ln = GdIII, TbIII; M = FeIII, CrIII) clusters showing slow magnetic relaxations

Four heterotrimetallic 3d-3d'-4f complexes, [Ni(L)Gd(H2O)(4)][Cr(CN)(6)]CH3OH center dot 2H(2)O (1), [Ni(L)Tb(H2O)(4)]-[ Cr(CN)(6)]CH3OH center dot 2H(2)O (2), [Ni(L)Gd(H2O)(4)][Fe(CN)(6)]center dot 3H(2)O (3), and [Ni(L)Tb(H2O)(4)][Fe(CN)(6)]CH3OH center dot 2H(2)O (4) (H2L = N, N-ethylenebis(3-methoxysalicylaldiimine)), were synthesized and characterized structurally and magnetically. The X-ray structural analysis revealed that these complexes are isostructural, in which Ni(II)Ln(III)M(III) (Ln = Tb-III, Gd-III; M = Fe-III, Cr-III) is arranged in trinuclear clusters. Then, these clusters further interact with each other via weak hydrogen bonds to form high dimensional supramolecular networks. Magnetic investigation indicates that the Ni(II) centers are diamagnetic. Dominant antiferromagnetic coupling is presented in complexes 1 and 3. An ac magnetic susceptibility measurement indicates that complexes 2 and 4 show typical field induced slow magnetic relaxation, which might be caused by the magnetic anisotropy of the central Tb-III ions.