3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item The selective complexation of metal ions by ligands bearing cyclohexyl substituents(1991) Croft, Graeme John BruceThe addition of cyclohexyl substituents to existing ligands was investigated for its potential use as a factor in ligand design for achieving high specificity for particular metal ions, (Abbreviation abstract)Item A molecular mechanics study for selective complexation of metal ions in medical applications(1994) Chantson, Tracy, ElizabethMolecular mechanics calculations are used to interpret and predict metal ion discrimination by coordinating ligands. Of particular interest are chelates exhibiting characteristics that Single them out for potential medical application; Selectivity patterns for several series of ligands are investigated with the help of strain energy profiles as a function of metal-donor atom bond distance. Ligands include simple; open-chain oxygen- and nitrogen-donors ana triaza- and tetraazamacrocyeles. Results are compared with X-ray crystallographic and solution data. Factors such as chelate ring size, conformational flexibility and preferred metal coordination geometry are found to influence metal specificity. Addition of pendent donor groups to macrocyoles leads to rigid structures and selectivity predictions according to cavity size. Interpretation of specific. metal ion recognition by polyetner antibiotics is attempted. Structural and steric factors are probed as possible determinants of metal choice. both covalent and ionic bonding models are explored. The covalent approach results in predictions of metal selectivity which correlate with mown selectivity patterns. Unfortunately, inability to optimise force field parameters in the ionic bonding approach forced us to abandon this model. The main force field used is the TRIPOS (1992,1993) force field. It performs well in calculations involving a univariate scanning technique but has to be modified to obtain reasonable structure reproduction with the large antibiotics, Errors in thermodynamic data predictions are obtained, nonbonding parameters have yet to be properly parameterized and the allocation of partial atomic charges warrants closer examination . All of these factors contribute to the poor performance of the force field when ionic interactions between metal and donor atoms of the polyethers are assumed.Item CVD synthesis of nitrogen doped carbon nanotubes using iron pentacarbonyl as catalyst(2012-02-24) Ghadimi, NafiseIn this dissertation, the synthesis of nitrogen doped carbon nanotubes (N-CNTs) was performed successfully, using a floating catalyst chemical vapour deposition (CVD) method. Fe(CO)5 was utilized as the catalyst and acetonitrile and toluene as nitrogen and carbon sources respectively. Two different procedures were used to add reagents to the reactor: an injection method and a bubbling method. The effect of nitrogen concentration and physical parameters such as reaction temperature, gas flow rate on the morphology, crystallinity and thermal stability of the tubes was studied. The synthesized materials were characterized by means of Raman spectroscopy, TGA and TEM analyses. The presence of nitrogen was confirmed by the presence of the bamboo formations in the tubes by TEM. A comparison of the data from the numerous reactions revealed that N-CNTs can be made from Fe(CO)5 and acetonitrile. Further the main conclusions achieved using the injection method were: i) the maximum number of tubes with bamboo structure were made using on acetonitrile concentration of 15%, ii) The best growth temperature to make N-CNTs was 850 oC, iii) An increase in acetonitrile concentration decreased the yield of NCNTs and iv) Tubes with the narrowest outer diameters were made using an acetonitrile concentration of 15%.