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

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