Syntheses, Structures And Properties Of Coordination Polymers Based On5-hydroxynicotinic Acid And Its Derivatives

Metal-organic coordination polymers based on aromatic carboxylate ligands have been focused all the time due to their fascinating structural diversity and potential applications such as catalysis, magnetism, luminescence and porosity, etc. In this thesis, thirteen new coordination complexes have been synthesized by choosing5-hydroxynicotinic acid and its derivatives as fundamental ligands. The complexes were characterized by single crystal X-ray diffraction analyses and elementary analysis, IR spectra, and thermogravimetric analyses. The topology structures, photoluminescent properties and magnetic properties have been studied and discussed. The main results are as follows:1. Four complexes were hydrothermally synthesized from5-hydroxynicotinic acid (H2L’), namely [Zn(HL’)2]n (1),[Zn(HL1)2]n·2nH2O (2),[Cd(HL1)2]n (3),[Cd(HL’)(CH3COO)(phen)]n-nH2O (4). Complexes1,2,3are all2D layered architecture which further linked into3D supramolecular networks by hydrogen bonds. Complexe4is a1D chain along the a axis, and further formed2D structure by the combined actions of π---π stacking and hydrogen bonds interactions.2. Design and synthesize a ligand, N-acetic-5-oxygen-nicotinic acid (H2L2), based on H2L1, and two new complexes were obtained, namely [Mn(L2)(H2O)2]n·nH2O (5),[Zn(L2)(phen)]n·3nH2O (6). Complexe5is a2D structure which was generated by L2linking the adjacent dinuclear{Mn2} subunits. Complexe6is a2D layered structure, in which phen modified on both sides.3. We successfully designed a new asymmetric tricarboxylate ligand which possesses both rigid and flexible carboxyl groups, N-acetic-5-oxycarboxymethyl-nicotinic acid (H2L3), based on H2L1, and seven new complexes were obtained, namely [Zn(L3)(H2O)3]n (7),[Cd(L3)(H2O)3]n (8),[Mn(L3)(H2O)3]n (9),[Co(L3)(H2O)3]n (10),[Cd(L3)(H2O)]n (11),[Cd(L3)(4,4’-bipy)]n-nH2O (12),[Ba(L3)(H2O)3]n·2.25nH2O (13). Complexes7-10are isostructural and exhibit2D helical layered structures. Complexe11is a2D folded ladder layer. Complexe12is a2D structure by the4,4’-bipy linking the adjacent folded double-chains. Complexe13is a3D netwok formed by the coordination of ligand and alkaline-earth metal barium.4. The solid-state luminescent properties of complexes7,8,11,12were investigated at room temperature under the same experimental conditions by means of the fluorescent spectrophotometer. Photoluminescence studies revealed that the fluorescent intensities of complexes7,8,11,12dramatically increase compared with the H2L3ligand and display red-shift of emission peak.5. The temperature-dependent magnetic susceptibilities for complexes9and10have been measured for polycrystalline samples at an applied magnetic field of1000Oe in the range of2-300K. Variable temperature magnetic susceptibility indicates the existence of a weak antiferromagnetic interaction in9and10, respectively.