Zinc(II), nickel(II) and cadmium(II) coordination polymers based on the ligand oxamide N,N-bis(4-phthalic acid): synthesis, structural characterization and magnetic properties

Seven new metal-organic frameworks assembled from semi-rigid polycarboxylate and auxiliary N-donor ligands: syntheses, structures and properties

Seven new metal-organic frameworks (MOFs), namely, [Zn₂(L¹)(H₂O)₃]_n (1), [Zn₂(L¹)(dib)(H₂O)₂]_n (2), {[Zn₂(L¹)(4,4'-bipy)(H₂O)₂]·H₂O}_n (3), [Cd₂(L¹)(1,10-phen)]_n (4), [Ni₂(HL¹)(4,4'-bipy)(μ₃-OH)(μ₂-H₂O)]_n (5), {[Co₄(L¹)(4,4'-bibp)₃]·(4,4'-bibp)₃}_n (6), and [Co₂(L²)(4,4'-bibp)₂(H₂O)]_n (7), where H₄L¹ and H₄L² are semi-rigid 3-(3,5-dicarboxylphenoxy)phthalic acid and 4-(3,5-dicarboxylphenoxy)phthalic acid, respectively, and 4,4'-bipy is 4,4'-bipyridine, dib is 1,4-bis(1H-imidazol-1-yl)benzene, 1,10-phen is 1,10-phenanthroline and 4,4'-bipb is 1,4-bis(pyridin-4-yl)benzene, have been prepared under solvothermal conditions with Zn^II, Cd^II, Co^II and Ni^II ions in the presence of auxiliary N-donor ligands. The crystal structures and photoluminescence and magnetic properties of these compounds have been investigated. Compound 1 displays a 3,4,6-connected two-dimensional (2D) topology with a Schläfli symbol of (4².5)₂(4³.5².7)(4⁵.5⁶.6³)₂, and the 2D structure was further assembled to form a three-dimensional (3D) framework by intermolecular O-H...O hydrogen bonds. Compound 2 features a novel 3,3,4-connected structure and the point symbol is (4.10²)(4.6.8⁴)(6².8). Compound 3 exhibits a 3,4,6-connected 3-nodal net having a 3,4,6 T53 type topology, with the point symbol (4.6²)₂(4².6⁴)₂(4².6⁸.8².10³). Compound 4 shows a 2D→3D supramolecular structure formed by π-π stacking interactions. Compound 5 possesses a 3D framework with a tfz-d net topology. Compounds 6 and 7 are constructed from the same auxiliary ligand and metal salt at the same temperature, but with different main ligands and exhibiting different topologies. Compound 6 presents a 3D 4,6-connected topological network with a Schläfli symbol of (3.4⁴.6)(3².4⁴.5⁶.6³), while compound 7 has a 3D topological network with a Schläfli symbol of (4¹².6¹⁶). Magnetic analyses indicate that compounds 5 and 7 show weak antiferromagnetic interactions.