The Modulation of Structural Components in Metallosupramolecular Assemblies and Metal-Organic Frameworks
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis details the design and preparation of novel metallosupramolecular assemblies and metal-organic framework materials. This is achieved through the investigation of three families of ligand systems in combination with transition metal salts through solid state analysis. Experiments seeking to determine the effect of modulation of the structural components within these families are examined in each case. The first of such families consist of ligands containing the N1-acylamidrazone functional group in its neutral state and is described in Chapter 2. In addition to the coordination properties of these ligands being investigated, the hydrogen bonding motifs with a range of counter ions are described. The systematic variation of these anions allows for the modulation of the resultant supramolecular architectures. Chapter 3 describes a series of complexes based upon ligands containing the N1-acylamidrazone functional group in a twofold deprotonated state. Deprotonation of these ligands produces an additional bidentate coordination domain which allows the ligand to bridge metal ions. This leads to the formation of a series of octanuclear metal-organic macrocycles when reacted with zinc(II) carboxylate salts. It is shown that the modulation of the carboxylate co-ligands can be achieved with the retention of a conserved macrocyclic motif. The crystal packing of the macrocycles with respect to the carboxylate co-ligands are analysed. The use of these compounds as building units in the synthesis of metal-organic frameworks is investigated. The second family of ligands is based upon 2,2':6',2''-terpyridine-4,4''-dicarboxylic acid derivatives. A series of nine ligands, each containing an aromatic functional group at the 4'-position were synthesised. Seven of these were used in the synthesis of metal-organic frameworks with zinc(II) and were observed to form isoreticular frameworks based upon a zeolitic gis-c topology. The conserved topology and similarity of the size of the internal cavities mean the differences in properties can be attributed to the functional group at the 4'-position of the ligand. The effect of the appended functional group on the structure and their sorption properties of nitrogen, hydrogen, methane and carbon dioxide gases is discussed. The third family of ligands are based upon the phenolic oxime coordination group and are described in Chapter 5. This functional group is known to reproducibly form a pseudomacrocyclic ring around coordinated metal ions due to hydrogen bonding of the oxime proton to the phenolate oxygen atom. The functionalisation of the periphery of these complexes with carboxylic acid functional groups for their use as metalloligands in the synthesis of MOFs is investigated. This study is primarily concerned with the solid-state structural chemistry of metallosupramolecular assemblies and metal-organic frameworks. Particular attention is paid, however, to solution-based measurements such as NMR spectroscopy for elucidation of dynamic behaviour, and thermogravimetric analysis and gas uptake studies for potential void-containing materials. Twenty three ligands (twenty of which have not previously been reported) have been prepared and characterised during the course of this study. Forty two coordination complexes are also reported along with their single crystal X-ray crystal structures.