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 ZnII, CdII, CoII and NiII 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 Schlafli 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 Schlafli symbol of (3.44.6)(32.44.56.63), while compound 7 has a 3D topological network with a Schlafli symbol of (412.616). Magnetic analyses indicate that compounds 5 and 7 show weak antiferromagnetic interactions.