Tetracarboxylate-based Co(ii), Ni(ii) and Cu(ii) three-dimensional coordination polymers: syntheses, structures and magnetic properties

Abstract

Methylenediisophthalic acid (H₄MDIP), as semi-rigid ‘V’-shaped carboxylate ligands, react with CoO, NiO and Cu(NO₃)₂·3H₂O to give three novel coordination polymers [H₃O]₂[Co₃(MDIP)₂]·2DMF (1), [Ni₂(HMDIP)(μ₂-OH)(H₂O)₃(DMF)]·4H₂O·DMF (2) and [Cu₃(MDIP)(μ₂-OH)₂(H₂O)₄]·6.5H₂O (3) (DMF = N,N′-dimethylformamide). All compounds have been characterized by thermogravimetric analysis, IR spectroscopy, elemental and single-crystal X-ray diffraction analyses. Complex 1 is an unusual open anionic framework that is defined as the metal–organic replica of fluorite. Both 2 and 3 features a 3D open framework with one-dimensional elliptical channels and R- and L-helical chains, and their resulting frameworks can be rationalized as crb and pts topology respectively. An interesting feature of complex 3 is the presence of the linear Cu₃ units that is formed by carboxylate and μ₂-hydroxyl groups linking three Cu(II) metal centers. Magnetic investigations indicate that ferromagnetic couplings are dominant in the three compounds.