Syntheses, Structures And Properties Of The Coordination Complexes Based On Iodo-dicarboxylate Ligands

In recent years, the rational design and construction of coordination polymers based upon assembly of metal ions and various multifunctional bridging ligands has been an increasingly active research area because of many such systems representing intriguing variety of structure, useful properties and potential applications in the field of separation, absorption, catalysis, and sensing. Considering the feature of the iodine atom which has potentially capability of partaking in halogen bonding, our group regarded the combinations of iodine atoms with benzene polycarboxylate acids may introduce halogen bonding in the assembly of the metal-organic coordination complexes and furnish different intriguing structures and properties.In this paper, a series of thirteen divalent coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and ancillary nitrogen ligands (phen 1,10-phenanthroline, bpe= 1,2-bis(4-pyridyl)ethene, p-bix= 1,4-bis(imidazol-1-ylmethyl)-benzene, m-bix= 1,3-bis(imidazol-l-ylmethyl)-benzene, bbi= 1,1'-(1,4-butanediyl)bis(imidazole)), namely [Zn2(5-iipa)2(phen)2(H2O)]n (1), [Cd2(5-iipa)2(phen)2]n (2), [Cu(5-iipa)(phen)(H2O)]n (3), [Cu2(5-iipa)2(phen)2(H2O)]n (4), [Zn(5-iipa)(bpe)1.5]n (5), [Mn4(5-iipa)4(bpe)4·5H2O]n (6), [Co(5-iipa)(p-bix)]n (7), [Co(5-iipa)(m-bix)]n (8), [Ni(5-iipa)(m-bix)(H2O)]n (9), [Co(5-iipa)(bbi)·3(H2O)]n(10), [Ni(5-iipa)(bbi)]n (11), [Cu(5-iipa)(bbi)]n (12) and Cu2(5-iipa)2(bbi)·0.5H2O]n (13) have been synthesized and characterized by IR, elemental analysis, single-crystal X-ray diffraction and thermal analysis as well as luminescence for d10-metal complexes. Taking account of the halogen bonding, the changes of the 2Dâ†'3D in compound 6,7,8 and 10 make them turn into rare two-fold or three-fold interpenetrating supramolecular arrays based on such interactions, which is remarkable in the coordination polymers. Especially in complex 10, there exist rectangular channels running along the [100] direction with ca.9.318×13.472 A apertures in the 3D supramolecular frameworks. The channels are mainly occupied by the guest water molecules. The result of the XRD shows that the metal-organic framework was not destroyed by the removal of the guest water molecules. Complexes 3 and 4 were obtained under the same condition except the usage of different base, and 12 and 13 were obtained by using different ratio of the reactants, which indicates that the assembly of the coordination complexes can be influenced by these extraneous factors.A flexible iodo-dicarboxylate ligand, namely,5-iodo-benzene-1,3-dioxyacetic acid (H2L) has also been synthesized in this paper and three metal-organic frameworks {[Zn(L)(4,4'-bpy)1.5(H2O)]·H2O}n (1), [Zn(L)(bpe)]n (2), [Co(L)(bpe)0.5(H2O)2]n (3), have been hydrothermally synthesized through the reaction of this ligand with divalent zinc and cobalt salts in the presence of ancillary nitrogen ligands (4,4'-bpy= 4,4'-bipyridine, bpe= 1,2-bis(4-pyridyl)ethene) and characterized by elemental analysis, IR, X-ray diffraction and thermal analysis. The luminescences for 14 and 15 are also detected. Compound 15 features an interesting three-fold parallel interpenetrated two-dimensional (2D)â†'two-dimensional (2D) network motif. In the structure of 16, double-layer structures composed of single and triple helices with opposite chirality are associated together through bpe ligands to exhibit a (3,4)-connected 3D mesomeric network with a Schlafli symbol of (6-102)(62-104) topology.