Syntheses, Structures, And Properties Of Coordination Polymers Based On L，2，4-triazole

Coordination polymers (or metal-organic frameworks, MOFs) have attractedconsiderable research interest in the past decade, not only due to their intriguing variety ofstructures but also to their potential application in many fields such as luminescence,magnetism, catalysis, and gas adsorption. So it is still a great challenge to synthesizecoordination polymers with predictable structures and properties through the selection ofreaction pathways. It is well known that the structures and properties of the MOFs are mainlydependent on two facts, organic ligands and metal atoms, which are main constructingelements of MOFs. The reaction conditions used also usually result in completely differentframework structures in the assemble process of complexes. The primary purpose of the paperis to explore the coordination behavior of a kind of1,2,4-triazole ligand, synthetic conditionsand rules of their coordination polymers, and the influence of different conditions on thestructures and properties of the final MOFs. Then some helpful disciplinary conclusionsshould be summarized. Finally, some coordination polymers with excellent properties andgood application prospect were constructed.An effective approach for building novel coordination polymers is the rational design ofnovel organic ligands at present.1,2,4-Triazole and its derivatives are of particular interest incoordination chemistry, since they are effective bridging ligands combing the coordinationmodes of both imidazoles and pyrazoles. In this paper, coordination polymers based on twonew1,2,4-triazole ligands and different transition metal ions have been studiede. The mainresults are as follows:1.1,3-di(1,2,4-triazole-4)benzene (L1) and3,5-di(1,2,4-triazole-4)benzenecarboxylicacid (L2) were designed and prepared. And the ligands have been characterized by elementalanalysis, IR, and1H NMR.2. Twelve coordination polymers of L1and d10metal ions with1D,2D, and3Dstructures have been synthesized under hydrothermal/solvothermal conditions with differentsecond ligands, temperature, solvent, pH, ratios of ligand and metal, and so on. Allcompounds were characterized by single-crystal X-ray diffraction, IR, XRD, and thermogravimetric analysis. The luminescent properties were also investigated. Among which,compound2is a novel3-fold3Dâ†'3D interpenetrated framework with1D nanochannel (10.5×11.2), there is still some void ration even after interpenetrating. Compound7and9have similar2-fold3Dâ†'3D interpenetrated structure, in which2D sheets are pillared bycyanide anions. Compound12shows a complicated hexanuclear3D framework with unusualfour-coordinated cyanide anions which are generated from in-situ reaction. The differentcoordination modes of L1have been studied. The influence of inorganic anions and multiplearomatic carboxylic acids as the second ligands on the structures of coordination polymershave also been considered. It is believed that the results present here may provide a potentialpathway to rational design of novel MOFs. All compounds exihibt strong luminescence withdifferent emitting mechanism, and the structure-luminescence relationship was also discussed.The luminescent behaviors of the compound1-12imply that they can be good opticalmaterials.3. Six coordination polymers of L1and Cu(II)/Co(II) ions with1D,2D, and3Dstructures have been synthesized under different conditions. Different second ligands in thefive Cu(II) coordination polymers cause different frameworks. Compound18is a novelhexanuclear3D framework including two trinuclear second building units. Interestingly,1,3,5-benzenetricarboxylic acid show four different coordination modes in18, which is notcommon. The magnetic measurements show antiferromagnetic coupling interactions incomplexes17and18.4. Five coordination polymers of L2and Cu(II)/Co(II) ions with1D, and2D structureshave been synthesized under different conditions. Compound19,20, and22show novel2Dpolythreading structure, uncoordinated carboxyl in L2inserted each other of the adjacent2Dlayers. The2D structure of compound21includes interesting left/right handed helix chains.Compound23shows an unusual1D nanotube structure, the regular hexagon channel isconstructed by six L2molecules and six Cu(II) ions. The carboxyl group of L2does notcoordinate to metal atoms in19,20,22, and23. While in compound21, L2has twocoordination modes and in which the carboxyl group coordination to one or two metal atoms,respectively. Magnetic data indicate weak antiferromagnetic coupling interactions incomplexes20and21.