Syntheses And Properties Of Metal-Organic Frameworks Constructed With Mixed-Ligands

Metal-Organic Frameworks (MOFs) have attracted intense interest for their various intriguing topologies and the potential applications such as magnetism, luminescence, catalysis, gas storage and ion exchange, etc. The main strategy used in this area is crystal engineering approach, which provides a facile way to imitate the structure of natural minerals by replacement of the bonds with organic bridges so as to control the assembly of various frameworks. Aliphatic polycarboxylic acids, being very flexible when they involve long carbon chains, have been widely used for the synthesis of coordination polymers. In general, long ligands will lead to larger voids that may result in multi-fold interpenetrating structures. However, we present some different cases where the secondary ligands chosen are classical bipyridine pillars4,4’-bipyridine (bpy),1,2-bis(4-pyridyl) ethylene (bpe) and1,3-bis(4-pyridyl)propane (bpp). There are five chapters in all papers.In Chapter1, the main content is the background task organometallic polymers, synthetic methods and properties of the role, but also introduces a guiding role in crystal engineering and molecular research in topology, and significance of the topic of this paper.In Chapter2, In this research, three coordination polymers,[Co2(ceta)(bpy)1.5(H2O)3]·4H2O (1) with pcu topology,[Ni2(ceta)(bpe)2(H2O)3]·11H2O (2) with1D circular channels and [Ni2(ceta)(bpp)2(H2O)2]·2H2O (3) with2D structure,were obtained as their single crystals. Through the experimental comparison and crystal structure of several compounds are described, it is easy to find ceta (bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylate) contains four carboxylic groups and an interesting riding alkenyl group, as well as the different lengths and conformations of the bipyridine ligands play cooperativel roles in modulating the structures of the coordination polymers. we successfully synthesized coordination polymers constructed from a tetracarboxylate ligand with the assistance of selective bipyridine ligands of increased length. The length of bpe match the coordination span of the primary ligand, when connecting the rings, both to strengthen the stability of the structure, without blocking the one-dimensional channel, the overall structure is very unique and wonderful. From the results, neither the longer ligand bpp nor the shorter ligand bpy could synthesis coordination polymers with6-membered metallocycle and1D circular channels, and these proved that the bpe ligands play crucial roles in modulating the structures of the coordination polymers. We have published the results of the study in the Polyhedron.In Chapter3, two coordination polymers Cd5(OH)2(psa)4(bpe)(H2O)2(4) and [Cd5(psa)5(bpp)]-2H2O (5) with different cluster-based building blocks were obtained as their single crystals. The details of structures show the side group effects of the psa ligands on the conformations of frameworks. We have published the results of the study in the Journal of Molecular Structure.In Chapter4, in this work we chose1,4-benzenediacetic acid and3.5-di(1H-imidazol-1-yl)benzoic acid as linkers to construct metal-organic frameworks.1.4-benzenediacetic acid ligand may show a variety of coordinationmodes and conformations because of the increased flexibility of two carboxylate groups. thus make it easier to form polynuclear cluster.In Chapter5, a novel coordination polymers [Zn(bba)(bpt)]·0.5H2O have been synthesized under hydrothermal conditions. Benzophenone-2,4’-dicarboxylic acid is a polycarboxylate ligand, it is L-shaped structure process must play a regulatory role of stereochemistry and distinctive in the assembly. We also choose3,5-bis(4-pyridyl)-1,2,4-triazole as the auxiliary bridging ligand, it plays a vital role in improving the stability of the compounds and the terms of demensions.Finally, brief conclusions on these work and an outlook are provided.