Six New Co-Coordination Polymers Based on a Tripodal Carboxylate Ligand

Six new compounds of partially or wholly deprotonated 3,5-bi­(4-carboxy-phenoxy)-benzoic acid (H3BCPBA), namely, {[Co­(H2BCPBA)2(H2O)4]}n (1), {[Co­(HBCPBA)­(bipy0.5)2·(H2O)]}n (bipy = 4,4′-bipyridine) (2), {[Co3(BCPBA)2(dpe)·(μ2-H2O)4]·2H2O·2DMF}n (dpe = 1,2-di-4-pyridyleth-ene) (3), {[Co3(BCPBA)2(pdp)·(μ2-H2O)4]·2DMF}n (pdp = 4-[(E)-4-pyridinylazo]­pyridine) (4), {[Co3(BCPBA)2(bpe)·(μ2-H2O)4]·2DMF}n (bpe = 1,2-bis­(4-pyridyl)­ethane) (5), {[Co2(HBCPBA)2 (bpp)·(μ2-H2O)2]·H2O·2DMF}n (bpp = 1, 3-bis­(4-pyridyl)­propane) (6) were synthesized in the presence or absence of auxiliary ligand. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Compound 1 is a zero-dimensional structure. Compound 2 is a two-dimensional (2D) sheet structure with two 2D → 2D interpenetration frameworks. Compounds 3–5 are similar and possess three-dimensional (3D) networks with two 3D → 3D interpenetration frameworks. In compound 6, H3BCPBA and bpp ligands link Co centers to generate a 2D sheet structure which is further connected by intermolecular hydrogen bonds to form a 3D supramolecular structure. The photochemical properties are performed in the solid state at room temperature. Magnetic susceptibility measurements indicate that compounds 2–6 exhibit antiferromagnetic coupling between adjacent Co­(II) ions.