Heterometallic Octanuclear NiII4LnIII4 (Ln = Y, Gd, Tb, Dy, Ho, Er) Complexes Containing NiII2LnIII2O4 Distorted Cubane Motifs: Synthesis, Structure, and Magnetic Properties

The reaction of 2-methoxy-6-[{2-(2-hydroxyethylamino)­ethylimino}­methyl] phenol (LH3) with lanthanide metal salts followed by the addition of nickel acetate allowed isolation of a family of octanuclear complexes, [Ni4Ln4(μ2-OH)2(μ3-OH)4(μ-OOCCH3)8(LH2)4]·(OH)2·xH2O. Single crystal X-ray diffraction studies of these complexes reveal that their central metallic core consists of two tetranuclear [Ni2Ln2O4] cubane subunits fused together by acetate and hydroxide bridges. The magnetic study of these complexes reveals a ferromagnetic interaction between the LnIII and the NiII center. The magnitude of exchange coupling between the NiII and LnIII center, parametrized from the magnetic data of the Gd analogue, gives J = +0.86 cm–1. The magneto caloric effect, studied for the NiII4GdIII4 complex, shows a maximum of magnetic entropy change, −ΔSm = 22.58 J kg–1 K–1 at 3 K for an applied external field of 5 T.