Construction, Structure And Characterization Of Coordination Molecules Of Azacyclocarboxylic Acid Ligands

Coordination polymers (CPs) and metal-organic frameworks (MOFs) represent a unique class of highly ordered crystalline materials originated through the self-assembly of polytopic organic struts coordinated by inorganic nodes (metal ions or metal-ion clusters) resulting in the formation of well-defined low density networks. They have been extensively studied for their exceptional chemical and structural diversity and potential applications in numerous areas. Especially, as a new class of highly ordered crystalline materials, MOFs have attracted tremendous interest over the last two decades because of their structure variety, low solubility, and their enormously high surface areas with tailorable pore size and surface functionality. A noteworthy aspect in MOF chemistry is the direct structure-property relationship, which is a hallmark of this research area. Although various diverse CP/MOF structures have been reported and studied up to now, controllable design and construction of coordination polymers is still challenging. Because both ligands/metal ions and many external factors impose crucial influences on the structures and properties of the compounds. Beyond the main efforts should be centered on the design of suitable organic ligands for constructing coordination architectures, it is necessary to research how to build different MOFs from the same reactants by controlling these external factors. To our knowledge, N-heterocyclic carboxylic acid ligands with functional groups have less been researched, compared with phenyl aromatic carboxylic acid ligands. Taking these into consideration, we chose four N-heterocyclic carboxylic acid ligands with different functional groups and size to build CPs/MOFs with fascinating structures and interesting properties through the reasonable control of reaction conditions under the guidance of coordination chemistry, supramolecular chemistry and crystal engineering principle.In the first chapter, five new CPs based on 4-((2-methyl-1H-midazol-1-yl)methyl) benzoic acid (HL1),[Zn(L1)2]n (1),{[Zn(L1)2]·(H2O)}n (2),{[Cd(Ll)2]·(H2O)}n (3), {[Co(L1)2]·(H2O)2}n (4), [Cu(L1)2]n (5), have been synthesized under hydro(solvo) thermal conditions by adjusting the reaction conditions.the single crystal structure analyses indicate that complex 1 is in chiral space group and displays a rare 2D→2D 2-fold parallel interpenetrated layer network with two types of chiral double helixes, whereas the bulk crystallization of 1 are racemic mixtures based on the CD measurement.2 and 3 are isostructural and also 2D chiral helical-layer while the overall structure are mesomer and achiral.4 and 5 are different string chains. More importantly,1 has been successfully applied in the detection of Cu2+ ions in aqueous media and nitrobenzene.In the second chapter, eight new coordination polymers, [Cd(L2)2(bpe)]n (6), [Ag(L2)]n (7),{[Cu(L3)2(H2O)]·H2O}n (8), [Cu(L3)2]n (9), [Cu2(L3)4(bpy)(H2O)2]n (10), [Co(L3)2(H2O)4]n (11), [Co(L3)2(bpe)]n (12) and [Co(L3)2(bpp)2(H2O)]n (13) (HL2= 2-fluoroisonicotinic acid, HL3= 5-fluoronicotinic acid, bpe=1,2-di(4-pyridyl) ethylene, bpy =4,4’-bipyridine, bpp=1,3-bi(4-pyridyl)propane), have been synthesized using different methods. Single crystal X-ray analysis revealed that compound 6 and 12 shows a one-dimensional (1D) ladder like structure consisting of a dinuclear [M(COO)2] which is bridged by two bpe ligand in parallel arrangement, whereas compound 7 is a linear chain structure; 8 and 9 are 3D frameworks; 10 is 2D network; 11 is a mononuclear and 13 is bent chain. All of them have been characterized by IR spectroscopy, powder X-ray diffraction and thermogravimetric analysis. Furthermore, solid state photoluminescence properties of compounds 6 and 7 at room temperature and magnetic properties of 9 and 12 were also discussed.By reacting 5,5’-(pyridine-2,6-diyl)diisophthalic acid (H4L4) with Zn(NO3)2 or MnCl2 under solvothermal conditions, two unprecedented (3,4,6)-connected twf-d topological nanocage-based MOFs with very rare two or three types of cluster SBUs which include an interesting bi-paddle-wheel tetranuclear cluster,{[Zn2(L4) (H2O)1.5]-(xGUEST)}n (14) and {[H2N(CH3)2]0.25[Mn3.75(L4)1.5(Cl)0.75(HCOO)(DMF) (H2O)0.675]·(xGUEST)}n(15), were successfully constructed.Interestingly, two nanocages based on the mixed-cluster SBUs are formed in the two compounds. This work not only could provide a facile route to design and synthesize novel cage-based MOFs as promising functional materials, but also could rich the coordination frameworks with cages and multinuclear cluster SBUs. Complex 14 showed different luminescence in solid state and solvent, respectively, due to different luminescence mechanism. Both of them reveal highly selective CO2 capture.