Syntheses, Structures And Properties Of Coordination Polymers Constructed From Carboxylate Ltgands In Ionic Liquids

Ionic liquids can be used to synthesize coordination polymers as solvents, becauseof their good solubility and thermal stability. They do not produce autogenouspressure at a high temperature with the characteristics of low vapor pressure and lessvolatile, and provide the convenience and security to atmospheric pressure synthesis.Meanwhile, ionic liquids are various and versatile, so they can be used as solvents,structure-directing agents and ligands after participating in situ decompositionreaction.Coordination polymers (CPs) are a class of ordered structures constructed frominorganic metal units and organic connector with the electron donor. They have a highspecific surface area and adjustable pore size as well as application value in manyareas, such as gas adsorption and catalysis. Carboxylate ligands are often used tobuild new coordination polymers, which have a variety of interactions with the metalcenter and form different topologies. Thiophene-2,5-dicarboxylic acid (H2tdc)containing S-atom heterocyclic ring is a rigid and polycarboxylic acid ligand. Sincethe ratio of S atoms is larger than that of C, N and O atoms, the lone pair of electronsof S atoms is easy to delocalize in the heterocyclic ring. H2tdc exhibits excellentcharge transfer capacity.4-(1,2,4-triazol-1-yl) benzoic acid (Htzbc) and5-(4’-carboxyphenyl) tetrazole (H2cptta) ligand containing N-atom heterocyclic ringprovide N donor and potential coordination sites. They can coordinate to a lot ofmetal ions and show a variety of coordinating modes. The work selects H2tdc, Htzbcand H2cptta as ligands, and transition metals zinc, copper and nickel as the metalsource to build four coordination polymers. The main results are as follows:1. In this paper, the methods of alkylation and anion exchange are used to synthesize a total of fourteen kinds of imidazole ionic liquids. These methods aresimple steps, cheap and high yield (up to85%). These ionic liquids are tested byinfrared spectroscopy and1H-NMR spectroscopy in order to determ the structure andpurity (almost100%). Meanwhile, we investigate the effect of anion and the length ofcationic carbon chain on infrared absorption peaks and1H-NMR chemical shifts.2. At a low temperature and atmodpheric pressure condition, the ionic liquid[BMIM]Br as solvent, a three-dimensional supramolecular compound[Zn(tzbc)2(H2O)4](1) is constracted from rigid ligand Htzbc and Zn (II). Thezero-dimensional is connected by the π-π stacking interaction and hydrogen bondswhich are formed by four coordinated water and fully deprotonated Htzbc to form athree-dimensional supramolecular structure. On the basis of synthesis of compound1,a second ligand1,4-terephthalic acid (H2BDC) is added. We get anotherzero-dimensional compound [Zn(MIM)2Br2](2). In compound2, Zn2+is coordinatedby methylimidazole (MIM) generated by situ decomposition reaction of [BMIM]+andthe Br-of ionic liquids anion, to form a tetrahedral structure. The ligand Htzbc andH2BDC were not involved in the compound. Fluorescence spectroscopy studies haveshown that compound1exhibited a characteristic emission peak at412,464and524nm, and is attributable to the ligand to metal charge transfer (LMCT). Itsfluorescence lifetime is millisecond level, and the luminescent property is certainsmall molecules solvent-dependent properties. The luminescent property ofcompound2is also belonging to the LMCT.3. Compound [Cu(tdc)(MIM)2](3) is built with V-type ligands H2tdc and Cu2+ionsin the [EMIM]Br condition, which is a one-dimensional chain containing a (CuOCO)28-membered ring and a16-membered ring (CuOC2SC2O). Fluorescence test deteminethat fluorescence quenching phenomenon of H2tdc and MIM occurs when compound3forms. When the solvent is [BMIM]Br, ligand cptta2-connects to trinuclear [Ni3O]4+cluster to form a three-dimensional anion framework [Ni3O(cptta)3(MIM)3]2-(4).Compound4contains a hexagonal hole, each MIM points into pore. We simplify itsstructure, and get a6-connection acs (49·66) topology. Compound4has strongluminescent and antiferromagnetic properties, and can be used as potential luminescent and magnetic materials.4. Ionic liquids play a multiple role in the synthesis of compound1to4, they notonly can be used as the solvent, the structure-directing agent, but also as a ligandinvolved in the reaction. The studies have shown that the choice of solvent isimportant for the synthesis of compounds1and2. In the synthesis of compounds2,3and4, ionic liquids decompose to MIM in situ.. MIM occupy coordinate sites with Cu(II) ions and hinder the formation of higher dimensional compound in compound3. Incompound4, MIM point into the pore and is likely to expand the pore size, Therefore,compound4contains a hexagonal holes of approximately20.7. MIM induce thestructures of compounds3and4and play a role in the structure directing.