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

Methylenediisophthalic acid (H(4)MDIP), as semi-rigid 'V'-shaped carboxylate ligands, react with CoO, NiO and Cu(NO(3))(2)·3H(2)O to give three novel coordination polymers [H(3)O](2)[Co(3)(MDIP)(2)]·2DMF (1), [Ni(2)(HMDIP)(μ(2)-OH)(H(2)O)(3)(DMF)]·4H(2)O·DMF (2) and [Cu(3)(MDIP)(μ(2)-OH)(2)(H(2)O)(4)]·6.5H(2)O (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 Cu(3) units that is formed by carboxylate and μ(2)-hydroxyl groups linking three Cu(II) metal centers. Magnetic investigations indicate that ferromagnetic couplings are dominant in the three compounds.