Hydrothermal Synthesis Of Coordination Polymers Constructed With Flexible Ligands

Metal-organic coordination polymers, new kind of functional molecule materials, have attracted much more attentions for their flexible tailoring, various topologies and promising application in ion-exchange, adsorption, molecular recognization, catalysts along with optics, electrics, magnetism and enantioselective separation. According to the principle of crystal engineering, it is possible that rational design and synthesis of porous crystalline materials by selecting certain geometric metal ions and special organic ligands. At the same time, coordination polymers can be endowed with optics, electric, magnetism, enantioselective separation and catalysis by selecting functional metal ions and organic ligands with functional groups. As the properties of the coordination polymers is determined by their chemical constituents and framework topologies, seeking the coordination polymers with the novel topology has been considered as the exploiting the functional properties of the coordination polymers. Therefore, it has been a challengeable work to rationally design and synthesize the coordination polymers with predetermined structures. Latest years, many research groups at home and abroad get a lot of great fruits in design, synthesis and functional development according to the principle of the crystal engineering. However, the synthesis mechanism is still not known due to the terrible complexity of the synthesis-chemistry in coordination polymer, especially, in the coordination polymers constructed with the flexible ligands. So it is need to deeply research and accumulate abundant experimental facts, finally to achieve the aims of molecular design and directional synthesis. In the last few years, large amounts of coordination polymers based on metal ions and rigid spacer ligands have been successfully synthesized. Interestingly, compared to a lot of attempt aimed at the development of compounds containing rigid ligands, the use of flexible ligands offers a greater degree of structural diversity that are more difficult to predict and conformational flexibility to enhance the possibility of forming supramolecular isomers. In fact, it is possible to construct the novel structures with the flexible ligands because the distances and angles between functional groups and forms of linkers of flexible ligands can be adjusted to fit the coordination surroundings, not to mention the flexible ligands with the aromatic rings. The flexible ligands with aromatic rings have enough rigidity to prevent the binding-sites from coordinating to one single metal center that may results to some novel structures with large pores; and these ligands have flexible units which can entangle or entwine, as a result, it is prone to form interpenetrating or helical structures. So these properties of the flexible ligand can lead to some novel structural coordination polymers.The aim of this thesis is to utilize the principles of crystal engineer to design and synthesize the metal-organic coordination polymers constructed from metal ions and organic ligands in order to find the new synthetic pathways of novel metal-organic coordination polymer and explore their structural characters and their physical properties.In chapter two, employed the flexible pyridyl ligand----1,3-bis(4-pyridyl)propane (bpp) as a bridging ligand, five novel coordination polymers were prepared and structurally characterized. Compound 1 exhibits a 1-D helical structures via the 1,3-bis(4-pyridyl)propane ligands linking the Mn2+ metal cations, the 1-D helical structures are interlaced; Compound 2 exhibits a 1-D pillar structure via the 1,3-bis(4-pyridyl)propane and terephthalic acid ligands linking the Ni2+ metal cations, the 1-D pillar structures of compound 2 are interpenetrated; Compound 3 exhibits a 2-D layer structure via the 1,3-bis(4-pyridyl)propane and terephthalic acid ligands linking the Zn2+ metal cations, the 2-D layer structures of compound 3 are interpenetrated; Compound 4 exhibits a 2-D layer structure via the 1,3-bis(4-pyridyl)propane and terephthalic acid ligands linking the Co2+ metal cations, the 2-D layer structures of compound 4 are interpenetrated; Compound 5 exhibits an unusual distorted noninterpenetrated (10,3) framework based on Zn2+ metal cations coordination with the mixed ligands of 1,3-bis(4-pyridyl)propane and 1,3,5-Benzenetricarboxylic acid.In chapter three, we synthesized a series of coordination polymers with novel structure using the O-bondingsites flexible ligand----4,4'-oxybis(benzoicacid) (H2oba). Compound 6 is a 3-D supramolecular structure via the hydrongen-bond interaction linking the 2-D layers which are formed through the oba ligands bridging the [Co(-CO2)2(H2O)2]n layers; Compound 7 is a 3-D supramolecular structure via the hydrongen-bond interaction linking the 2-D layers which are formed through the oba ligands bridging the [Zn(-CO2)2(H2O)]n chains; Compound 8 is a 3-D network via the oba ligands supporting the [Cd3Cl2]n4n+ inorganic layers with 6-rings windows formed with the Cd2+ metal cations and Cl- ions; Compound 9 is a 3-D network via the oba ligands supporting the [Mn(OH)]nn+ inorganic layers with 4-, 8-rings windows formed with the Mn2+ and the hydroxy; Compound 10 display 1-D chains through the ligands (4,4'-oxybis(benzoicacid) and 2,2'-bpy) bridging Co2+ metal cations. The lateral 2,2'-bpy ligands from adjacent chains are paired to furnish moderately strongπ-πstacking interactions, which extend the 1-D chains into 3-D supramolecular frameworks; Compound 11 display 1-D chains through the ligands (4,4'-oxybis(benzoicacid) and 1, 10-phen) bridging Ni2+ metal cations. The lateral 1, 10-phen ligands from adjacent chains are paired to furnish moderately strongπ-πstacking interactions, which extend the 1-D chains into 3-D supramolecular frameworks; Compound 5 is a 3-D network via the 4,4'-bipyridine ligands supporting the [Co(oba)] organic-inorganic hybrid layers formed with the Co2+ and 4,4'-oxybis(benzoicacid) ligands.These crystal compounds in this thesis are analyzed by X-ray diffraction in detail. Besides the studies on structures and properties of these newly synthesized materials, it is also explored in this research that how the reagents affect on structures and properties of crystal products; furthermore the effects of various experimental conditions, the reaction temperature, the reaction time, the PH, the mole ratio of reactants, and the like, on syntheses and the phase of synthetic products are investigated. Moreover, the related theories and principles of molecular rational design, molecular structural design, and hybrid synthetic methods of coordination polymers with both organic and inorganic molecules are summarized; the experimental conditions and causes of specific structural frameworks are exploited, and effects of organic components on inorganic micro-structure are discussed.