Syntheses, Structures And Property Studies Of Coordination Polymers Based On Imidazole Derivatives

Metal-organic coordination polymers (MOCPs) as a newly-identified functional molecule-based materials, have attracted much more attentions because of their flexible tailoring, various topologies and promising applications in hydrogen storage, ion-exchange, adsorption, molecular recognization, catalysts along with optics, electrics, magnetism and enantioselective separation. According to the principle of molecular engineering, it is possible that rational design and synthesis of novel multifunctional materials by selecting certain geometric metal ions and special organic ligands. At the same time, MOCPs can be endowed with multifunctional properties by selecting functional metal ions and organic ligands with functional groups.The aim of this thesis is the synthesis of new coordination compounds on the basis of imidazole derivatives ligands (4'-(imidazol-1-ylmethyl)benzonitrile, 4,4'-(1H,1'H-2,2'-biimidazole-1,1'-diylbis(methylene))dibenzoic acid, 2,2'-(1H,1'H-2,2'-biimidazole-1,1'-diyl)diacetate, and 4–((2–(pyridine–2–yl)–1H–imidazol–1–yl)methyl)benzoic acid) and metal zinc ions. The study on synthetic conditions and rules for these new compounds, topological analyses, and the exploration of relationships between structures and properties for these new compounds are also carried out. These compounds have been structurally characterized by elemental analyses, IR, XRPD, TG and single crystal X-ray diffractions. In addition, the thermal stabilities, fluorescent activity and photovoltage transients of these compounds have been studied. These results will be introduced from the following four issues:1. Five novel coordination polymers, [Zn(imbz)2]n (1), {[Zn(imbz)2]·H2O}n (2), [Zn(imbz)(μ2–OH)]n (3), [Zn3(imbt)2(p-bdc)3]n (4) and [Zn4(μ3–OH)2(imbt)2(p-bdc)3]n (5), have been hydrothermally prepared through systematically changing the pH values of reaction mixture, on the basis of 4'-(imidazol-1-ylmethyl)benzonitrile (imbt) ligands, terephthalic acid, and metal zinc ions.Compounds 1-3 were formed from imbt ligand and Zn(II) under different pH values. Compounds 1-3 exhibit very different strutures due to slightly different coordination mode of L1 ligand. Compounds 4-5 were formed from imbt ligand, Zn(II) ions and p-bdc ligands under similar reaction conditions. Investigation on their structural differences reveals that the pH values of the reaction system andμ–OH groups play important roles in modulating the architecture of coordination compounds. Moreover, compounds 1–5 all exhibit strong blue photoluminescence in the solid state at room temperature. 2. Two supramolecular isomers 6 and 7 formulated as [Zn(L1)]·2H2O, based on Zn(II) and 4,4'-(1H,1'H-2,2'-biimidazole-1,1'-diylbis(methylene))dibenzoic acid (L1), have been hydrothermally prepared through changing the pH values of reaction mixture. Complex 6 exhibits a 2D four-connected network; Complex 7 shows a twofold interpenetrated 3D framework.3. One novel compound, [Zn3(L2)2(OH)2]?3H2O (8), has been hydrothermally synthesized on the basis of 2,2'-(1H,1'H-2,2'-biimidazole-1,1'-diyl)diacetate ligands (L2), and metal zinc ions. Compound 8 exhibits an unprecedented chiral metal–organic framework, which was constructed by interweaving of three kinds of single helical chains.4. Five novel compounds, [Zn(L3)2] (9), [Zn2(μ3-OH)(L3)(m–bdc)] (10), [Zn2(μ3-OH)(L3)(p–bdc)]·H2O (11), [Zn2(L3)(btc)(H2O)]·2.5H2O (12) and [Zn4(μ3–OH)2(L3)2(btec)] (13), have been hydrothermally synthesized on the basis of 4–((2–(pyridine–2–yl)–1H–imidazol–1–yl)methyl)benzoic acid ligands, aromatic polycarboxylate ligands with different configurations, and metal zinc ions. Compound 9 exhibits a one-dimensional chain linked via double L bridges. Both MOFs in compounds 10 and 11 are 3-D networks with different topologies, which were all constructed by the tetranuclear zinc clusters as secondary building units (SBUs). Among them, 10 features a well-known pcu topology with bent dicarboxylate ligand (m-BDC) as an auxiliary ligand, while 11 has a 8-connected network with linear dicarboxylate ligand (p-BDC) as an auxiliary ligand. Compound 12 shows a novel (3, 5)-connected 3D network with (4.62)(4.64.82.10.122) topology, which was constructed by 1,3,5–benzenetricarboxylic acid and L3 ligands. Compound 13 displays an intricate (3, 4, 8)-connected network with (4.62)(42.63.8)(42.64)(42.618.7.86.10) topology based on L3 ligands, 1,2,4,5–benzenetetracarboxylic acid and metal zinc ions.