Structures and magnetic property studies of four copper(II) and nickel(II) supramolecular complexes derived from diphenic acid constructed by C–H⋯π and π–π interactions

Four one-dimensional metal–organic polymers derived from diphenic acid (H2dpa) were synthesized in the presence of auxiliary ligands, [Cu(dpa)CH3OH](1), [Ni(dpa)CH3OH] (2), [Cu(bipy)2(Hdpa)2(H2O)2] (3) and [Ni(bipy)2(Hdpa)2(H2O)2] (4) (bipy = 4, 4′-bipyridine). The dinuclear paddle–wheel second building units (SBUs) constructed by four dpa2− ligands in complexes 1 and 2 are linked by dpa2− into double chains, which are connected by C–H⋯π interactions forming a two-dimensional rhombic porous structure. In complexes 3 and 4, the metal ions are connected by bipy ligands, and the grid-like network was formed with the π–π interactions between the adjacent phenyl rings of Hdpa−. For 1 and 2, there are strong antiferromagnetic interactions within Cu–Cu and Ni–Ni dimers. It is also strong antiferromagnetic interactions between the dimmers of Cu2 in 1, while it is weaker of those of Ni2 in 2. Weaker antiferromagnetic interactions exist among Cu–Cu and Ni–Ni in 3 and 4, in which bipy is the effective coupling media. Thermally gravimetric analyses and differential thermal analyses indicate that the four complexes are all thermal stable.