Thesis Ph. D., University of Hong Kong. / Includes reprints of 2 papers entitled Structural and mechanistic studies of co-ordination compounds. Part II ... by C.K. Poon and H.W. Tong, from the Journal of the Chemical Society (A), 1971, and Structural and mechanistic studies of co-ordination compounds. Part V ... by K.S. Mok and others, from the Journal of the Chemical Society (Dalton), 1972.

Thesis (M. Sc.)--University of Hong Kong, 1973. / Typewritten.

Thesis (M. Sc.)--University of Hong Kong, 1970. / Typewritten.

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The ability for megavoltage computed tomography patient setup verification using a cobalt-60 (Co–60) gamma ray source has been established in the context of cobalt tomotherapy. However, it would be beneficial to establish improved cobalt imaging that could be used on more conventional units. In terms of safety and efficiency, this imaging technique would provide the patient with less exposure to radiation. Digital tomosynthesis (DT) is an imaging modality that may provide improved depth localization and in-plane visibility compared to conventional portal imaging in modern Co–60 radiation therapy. DT is a practical and efficient method of achieving depth localization from a limited gantry rotation and a limited number of projections. In DT, each plane of the imaging volume can be brought into focus by relatively displacing the composite images and superimposing the shifted dataset according to the acquisition geometry. Digital flat-panel technology has replaced the need for multiple film exposures and therefore the speed of imaging and capabilities for image processing has put DT in the forefront of both clinical and industrial imaging applications. The objective of this work is to develop and evaluate the performance of an experimental system for megavoltage digital tomosynthesis (MVDT) imaging using a Co–60 gamma ray source. Linear and isocentric acquisition geometries are implemented using tomographic angles of 20-60° and 10-60 projections. Reconstruction algorithms are designed for both acquisition geometries. Using the backprojection approach, the data are shifted and added to reconstruct focal planes of interest. Depth localization and its dependence on tomographic angle and projection density are visualized with an anthropomorphic head phantom. High contrast resolution at localized depths is quantified using the modulation transfer function approach. Results show that focal-plane visibility is improved for larger tomographic angles and that focal-plane visibility has negligible dependence on projection density. Lastly, the presence of noise and artifacts in the resulting images are quantified in terms of the signal-to-noise ratio and the artifact spread function. The work presented here is expected to provide the justification required to proceed with a prototype Co–60 MVDT system for patient set-up verification in modern Co–60 radiation therapy. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-04-28 14:14:07.44

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This thesis focuses on the properties of the diiminepyridine (DIP) ligand and its transition metal complexes, especially cobalt complexes. Existing and new X-ray structures of five-coordinate DIP Fe and Co dihalide complexes have been analyzed using the two-angle criterion ω. Substituent effects (less than 6 kcal/mol) and metal effects (mostly less than 6 kcal/mol) on structure distortion have been explored by density functional theory (DFT). The small energy barrier indicated easy distortion of the coordination geometries. The same strategy was also applied to the analysis of iron dialkyl complexes. There seems to be no direct correlation between structural preference and catalytic activity in olefin polymerization. Ligand parameters of DIP-type ligands, which intend to measure the σ-donor and π-acceptor ability, were developed using DFT calculation. The stabilization energy of the metal complexes was decomposed assuming a linear energy relationship. The results showed that the standard DIP ligand is both a strong σ-donor and a strong π-acceptor, and inferior only to the bis(carbene)pyridine ligand. A mild way to make (DIP)CoR using labile-ligand cobalt dialkyl precursors has been explored. A simple and easy way to synthesize (Py)2Co(CH2SiMe3)2 has been developed. This compound is stable at room temperature and can be further converted to (TMEDA)Co(CH2SiMe3)2 in high yield. The X-ray structure of the analogous (Py)2Co(CH2CMe2Ph)2 showed a structure similar to its iron analog. Application to DIP ligands indicates that the π-acceptor ability of the ligand determines whether cobalt(I) or cobalt(II) dialkyl will be obtained. However, steric protection is important in obtaining stable cobalt(I) alkyl complexes. Hydrogenolysis of LCoCH2SiMe3 (L: 2,6-[2,6-Me2C6H3N=C(CH3)]2C5H3N) generated LCo(N2) complex in the presence of dinitrogen. When reacted with organic halides, especially aryl chlorides, LCo(N2) broke the carbon-halogen bond through a binuclear oxidative addition mode to generate two cobalt(I) products. The radical mechanism proposed was supported by DFT studies. The resulting cobalt(I) aryl products can further react with activated alkyl halides to generate cross-coupled products, probably also through a radical mechanism. LCo(N2) can also be used to break the acyl carbon-oxygen bond of esters, although less efficiently.

This thesis focuses on the properties of the diiminepyridine (DIP) ligand and its transition metal complexes, especially cobalt complexes. Existing and new X-ray structures of five-coordinate DIP Fe and Co dihalide complexes have been analyzed using the two-angle criterion ω. Substituent effects (less than 6 kcal/mol) and metal effects (mostly less than 6 kcal/mol) on structure distortion have been explored by density functional theory (DFT). The small energy barrier indicated easy distortion of the coordination geometries. The same strategy was also applied to the analysis of iron dialkyl complexes. There seems to be no direct correlation between structural preference and catalytic activity in olefin polymerization. Ligand parameters of DIP-type ligands, which intend to measure the σ-donor and π-acceptor ability, were developed using DFT calculation. The stabilization energy of the metal complexes was decomposed assuming a linear energy relationship. The results showed that the standard DIP ligand is both a strong σ-donor and a strong π-acceptor, and inferior only to the bis(carbene)pyridine ligand. A mild way to make (DIP)CoR using labile-ligand cobalt dialkyl precursors has been explored. A simple and easy way to synthesize (Py)2Co(CH2SiMe3)2 has been developed. This compound is stable at room temperature and can be further converted to (TMEDA)Co(CH2SiMe3)2 in high yield. The X-ray structure of the analogous (Py)2Co(CH2CMe2Ph)2 showed a structure similar to its iron analog. Application to DIP ligands indicates that the π-acceptor ability of the ligand determines whether cobalt(I) or cobalt(II) dialkyl will be obtained. However, steric protection is important in obtaining stable cobalt(I) alkyl complexes. Hydrogenolysis of LCoCH2SiMe3 (L: 2,6-[2,6-Me2C6H3N=C(CH3)]2C5H3N) generated LCo(N2) complex in the presence of dinitrogen. When reacted with organic halides, especially aryl chlorides, LCo(N2) broke the carbon-halogen bond through a binuclear oxidative addition mode to generate two cobalt(I) products. The radical mechanism proposed was supported by DFT studies. The resulting cobalt(I) aryl products can further react with activated alkyl halides to generate cross-coupled products, probably also through a radical mechanism. LCo(N2) can also be used to break the acyl carbon-oxygen bond of esters, although less efficiently.