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Has 1,3 - adamantane acid ligand coordination polymers to build the structure and properties of

Author: ZhangWeiHong
Tutor: WangYaoYu
School: Northwestern University
Course: Inorganic Chemistry
Keywords: Coordination polymers Dicarboxylate ligands Luminescence properties Magnetic properties
CLC: O631.3
Type: Master's thesis
Year: 2010
Downloads: 87
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Abstract


During the past two decades, the rational design and synthesis of metal-organic frameworks (MOFs) have made considerable progress in the fields of supramolecular chemistry and crystal engineering. The high interest to these new complexes arises not only from their intriguing ability to form variety of architectures and topologies but also because of their potential applications as in industry as zeolite-like materials, membranes for separation processes, also as luminescent and so on. The self-assembly of supramolecules and coordination polymers is influenced by many factors, such as the coordinative function of the ligands, the type of metal ions, the presence of solvent molecules, counter ion, the metal-to-ligand molar ratio, reaction temperature and pH value of the solution. It is well known that the nature of organic ligands plays an important role in the design and construction of new metal-organic frameworks. Among numerous organic ligands, the versatile ligands with two or more carboxylic functional groups can exhibit great variety of diverse coordination modes. Ligands with partially flexible carboxyl groups are under intensive study, because their flexibility and conformational freedom may provide more possibilities for the construction of frameworks with new structures. Investigation of their properties can lead to deeper understanding of the supramolecular assembly processes. For the present study we have chosen the 1,3-adamantanediacetic acid (H2ADA) for systematic investigation of its coordination ability. H2ADA contains two free independent carboxyl groups that can be completely or partially deprotonated which can be found in various coordination modes and conformations. Due to that, the carboxylic groups of H2ADA have both the hydrogen bond donor and acceptor properties, which is important for the formation of complexes with higher dimensionalities. To our knowledge, there are few examples related to the metal organic frameworks based on H2ADA present in scientific literature.Bidentate rod-like N,N’-donor ligands, like 4,4’-bipy, can have large influence on the assembly processes and have been extensively used with multi-carboxylate ligands to synthesize combined multiligand metal-organic frameworks. The use of flexible analog of 4,4’-bipy,1,2-bis(4-pyridyl)ethane (bpa), 1,3-bis(4-pyridyl)propane (bpp) in which N-donor pyridine rings are separated by alkyl (CH2)n spacers can lead to fascinating architectures with new properties. The application of these N-donor complexes in MOFs synthesis often results in new structures with unique motifs and useful functional properties.Fifteen coordination polymers have been synthesized on the basis of hydrothermal technique or diffusion methods and characterized by IR spectra, elemental analysis, X-ray single crystal analysis, thermal analysis, XRPD analysis, fluorescence spectroscopy and magnetic susceptibility measurement.We have used the combination of H2ADA with bpp/4,4’-bipy and cobalt nitrate as precursors for new MOFs. The effect of pH influence was also investigated due to possible pH-induced changes in the coordination diversity of H2ADA under hydro(solvo)thermal synthesis conditions. Five new coordination polymers [Co(HADA)2(bpp)]n (1), {[Co(ADA)(bpp)(CH3OH)]·H2O}n (2), [Co2(ADA)2(bpp)]n (3), [Co(HADA)2(4-4’-bipy)(H2O)2]n (4), and [Co(ADA)(4-4’-bipy)o.s]n (5) originated from similar systems (H2ADA/bpp, H2ADA/4,4’-bipy) are synthesized and characterized by single crystal X-Ray diffraction, X-ray powder diffraction(XRPD) and thermogravimetric analysis (TG). The magnetic properties for 3 and 5 are also been studied. A variety of possible pH dependent coordinate modes and configurations of H2ADA ligand have been found in these complexes.We intend to compare the diversification of the structures when we change the length and flexible of the pyridine containing neutral ligand within the similar system. Additionally, the influence of the centre metal (ZnⅡand CdⅡ) when using the same ligands under different synthesis condition is also been investigated. So we have used the combination of H2ADA with 4,4’-bipy/bpa/bpp and ZnⅡ/CdⅡas precursors for new MOFs. A variety of coordinate modes and configurations of ADA ligands can be found in these coordination polymers. Eight new coordination polymers [Zn3(ADA)3(H2O)2]n-5nH2O (6), [Zn(ADA)(4,4’-bipy)o.5]n (7), [Zn2(ADA)2(bpa)]n (8), [Zn2(ADA)2(bpa)]n (9), [Zn2(ADA)2(bpp)]n (10), [Cd(HADA)2((4,4’-bipy)]n (11), [Cd3(ADA)3(bpa)2(CH3OH)(H2O)]n (12), and [Cd2(ADA)2(bpp)2]n·7nH2O (13) are synthesized and characterized by single crystal X-ray diffraction, their luminescent properties, X-ray powder diffraction (XRPD) and thermo-gravimetric analysis (TGA) were also investigated in detail.The V-shaped dipyridylamine ligands, like 2,2’-dipyridylamine,2,3’-dipyridylamine and 4,4’-dipyridylamine were widely used for the assembly of new coordination polymers. The V-shaped molecule 2,4’-dipyridylamine is an isomer of the well-documented molecule 2,2’-dipyridylamine, and to the best of our knowledge no MOFs related to L has been reported before. With the above background in mind, our research has focused on designing and synthesizing a new V-shaped ligand, named 2,4’-dipyridylamine (L) and used it as ligand with H2ADA to construct new stuructures. And two coordination polymers:[Zn(ADA)(L)]n (14) and [Cd(ADA)(L)2]n (15) were obtained when employing them with d10 metal salts under hydrothermal condition.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
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