Studies On Crystal Structure And Properties Of Coordination Polymers With N-Heterocycle Ligands

The research of coordination polymer(metal-organic frameworks,MOFs) remains one of the an extremely active fields of material chemistry, coordination chemistry and crystal chemistry in recent years. The construction of metal-organic frameworks is of great interest due to their intriguing network topologies and their potential applications as catalysts, ion exchange, gas storage, electrochemistry and magnetism. Crystal engineering based on organic linkers and metal centers with specific coordination geometries is an important approach in the preparation of coordination materials with desired functions. In addition to coordinative covalent bonding which is most important in constructing coordination polymer, hydrogen bonding,π-πstacking interaction and other weak intermolecular interactions have attracted considerable interest in the construction of supramolecular coordination framework. Generally speaking, the generation of self-assembling coordination architectures depends on the combined effect of several factors, such as:the coordination geometry of the metal ions, the feature of the organic ligands, the coordinated and/or non-coordinated counter ions, the solvent systems, the reaction conditions, and so on. Among these factors, beyond doubt, the ligand is one of the most important factors for fabricaing the structure of coordination polymer. Therefore, the application of well-designed ligands to control the assembly of molecular architectures has become a popular and rapidly growing discipline.In the thesis, we have adopted four ligands with N or O heteroatoms (1,10-phenroline-5,6-dione,4-amino-3,5-dimethyl-1,2,4-triazole,2,6-pyridine-dicarboxylic acid and 1H-1,2,4-triazole-3,5-dicarboxylic acid), The crystal structures and properties of these complexes have also been investigated.(ⅰ). Development and assembly of coordination polymers are concisely introduced, and classification of coordination polymers according to the different ligands(such as: 4,4-bipyridine, 1H-1,2,4-triazole and 2,6-pyridine-dicarboxylic acid) is summarized. And then, we introduce our research topic.(ⅱ). Six complexes were synthesized and characterized through the self-assembly of pdon ligand and d10 or d5 metal ions, compex 1 is a one-dimensional zigzag chain connected byμ-Cl bridge, complex 2 is a one-dimensional molecular helix chain bridged by doubleμ1,3-SCN bridge,3-5 are mononuclear complexes, in 6, we observed hydroxylation of pdon ligand. Electrochemistry, UV-vis, Fluorescent and CD properties of complexes 1-4 were in detail studied. Result indicates that the CD spectrum of complex 2 shows positive Cotton effect in the wavelength range of 200-360 nm in DMSO solution, while it was not found in acetonitrile solution. Complex 2 crystallized in P21/c space group with racemic mixtures with zero CD intensity in the solid state, powder XRD pattern of 2 shows phase purity. So we think that these positive Cotton effects may come from complex 2 with some degree of enantiomeric excess, the average degree of twisting between left-hand and right-hand helical forms. Although Zn2+, Cd2+, and Hg2+ are elements of the same group, their self-assembly behaviors were essentially different. The architectures may relate to crystal and ionic radii (A, C.N.6) of metal ions, Mn (0.81,0.67), Zn (0.88,0.74), Cd(1.09,0.95), and Hg (1.16,1.02). Part work has been published in Crystal Growth & Design,2010,10,1706-1714.(ⅲ). Based on colorful coordinaton modes of the 1H-1,2,4-triazole-3,5-dicarboxylic acid ligand, we proposed a pattern designator(Mhijknlm) to specify coordination modes of H3dctrz(Scheme 3.2). Eight polymers were successfully designed and synthesized by solution evaporation and hydrothermal technique, and characterized by IR, element analysis and single crystal X-ray diffraction. Complex 7 is a 1D chain consisting of trinuclear Mn2+ cluster basic units,8 and 9 being a 1D chain and a 2D (4,4) topology structure, repectively. Magnetic properties of two complexes 7 and 8 indicate that two polymers exhibit antiferromagnetic interaction between metal ions.10 is a mononuclear complex. Complexes 7-10 have different coordination modes 32001110 (7),21001001 (8),31011001(9), 10001001(10) respectively. Complexes 12-14 were hydrothermally synthesized. X-Ray diffraction analysis shows that H3dctrz ligand was unexpectedly decarboxylated under hydrothermal conditions. This part of work has been published in Dalton Trans,2010,39, 5877-5884.(iv). We adopted three kinds of bridging ligands (KSCN, NaN3,4-amino-3,5-dimethyl-1,2,4-triazole) with transition metal ions to synthesize two new complexes and studied their magnetic properties. The results show that two complexes exhibit antiferromagnetic interaction. Complex 16 is a 2D layer (4,4) topology structure consisting of trinuclear (Mn2+)3 building units. To our surprise, there are three kinds of coordination modes for N3- in the trinuclear building units respectively, namely μ-1,1-N3-(EO),μ-1,3-N3·(EE) and terminal N3-. The most interesting feature of this structure is that this two-dimensional layer represents a wave shape along b-axis direction. The period is ca.17.4668 A. Complex 17 is only a trinuclear structure, SCN- adoptedμ-1,1-SCN-(EO) and terminal N-coordination modes. In the two complexes structures, admtrz ligand adoptedμ-1,2-triazole bridging mode.(v). Four new complexes were synthesized by using 2,6-pyridine-dicarboxylic acid ligand, La(NO3)3, Ce(NO3)3 and transition metal ions. Complex 18 is a 1D linear structure and the main feature of its structure is to build tetranuclear units throughμ-1,1-O bridge with a one-dimensional chain structure.19 is a 2D layer structure consisting of 1D chain forming by La(PDA)2 units along a axis and 1D chain by [AgLa (μ-1,4-PDA)2] building units along b axis.20 and 21 are the two different crystal structures obtained in the same solution.20 is a hexanuclear clusters forming by the two trinuclear units bridged byμs-O atoms.21 is a six-core structure connected into sub-structure of two trinuclear units throughμ1,3-COO carboxyl-bridged mode.In this thesis, we in detail described synthesis, crystal structure, and properties containing N-hetercycle metal-organic coordination polymers. By studying the relationship between structure and function, our work not only enriched and developed synthesis chemistry and structural chemistry of metal organic coordination polymer, but also accumulated the valuable experimental data for the synthesis and property development of the materials.