Solvent Modulated Assembly of Two Ni(II) Complexes: Syntheses, Structures and Magnetic Properties

A dinuclear [Ni2(L)2(DMSO)2(MeOH)2] (1) and a tetra-nuclear [Ni4(L)4(DMF)2(H2O)2].DMF (2) Ni(II) complexes have been prepared by treating nickel nitrate hexahydrate with the Schiff base ligand H2L (H2L=(E)-2-(2-hydroxybenzyliden)amino-4-nitrophenol) in a one-pot reaction. Complex 1 was obtained after recrystallization of the precipitate from the reaction with a 1:1:1 mixture of DMSO/CH2Cl2/MeOH. In contrast, the tetrameric complex 2 was obtained after slow evaporation of the filtrate. Both complexes were characterized by analytical, thermogravimetric, optical and magnetic techniques. The solid state molecular structures of 1 and 2 were determined by single crystal X-ray crystallography. Complex 1 shows a dinuclear structure whereas complex 2 shows a defective dicubane structure. The magnetic properties of complex 1 show a predominant ferromagnetic coupling between the Ni(II) ions with J=+16.1 cm−1 and 2 shows a predominant Ni−Ni antiferromangetic interaction of J=-15.5 cm−1. Both coupling constants are the expected ones from magneto-structural correlations. The thermal stability and optical properties of both complexes have also been investigated.