Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Thesis (M.Sc.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on July 9, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, [Department of] Earth and Atmospheric Science, University of Alberta. Includes bibliographical references.

Osmium is a hard grey brittle metal which scratches glass. It has a melting point of 2700[degree]C, and a specific gravity of 22.4, which is greater than any other known substance. The grey color of osmium resembles the grey color of iron and ruthenium. Osmium was discovered in 1803 by Tennant in the insoluble residue remaining after treating an alloy of the platinum metals with acid. Osmium occurs in nature alloyed with the other metals of the platinum group. One type of alloy includes all six of the of the platinum metals, osmium, iridium, platinum, ruthernium, rhodium and palladium. Osmium also occurs in an alloy of osmium and iridium called osmiridium. These alloys are usually recovered by placer mining methods. Canada, Russia, Colombia, South Africa and the United States are the worlds producers of platinum metals. The beds of Alaskan rivers contain platinum metals. Osmium has limited uses due in part to scarcity. Its cost is approximately fifty dollars per ounce. Haber found that osmium metal catalyzes the synthesis of ammonia from the elements. Other investigators have ranked osmium first in catalytic powers among the platinum metals. Osmium alloys are used for bearings in place of jewels in precision instruments because of their resistance to wear. Osmium alloys are also used in pen points because of their resistance to wear and corrosion Osmium tetroxide finds use as a catalyst in inorganic and organic reactions. It is employed as a catalyst in the quantitative determination of arsenic in which arsenite is titrated with ceric sulfate. Osmium tetroxide catalyzes the action of potassium permanganate on maleic acid to form meso-tartaric acid; and also catalyzes the additions of hydrogen peroxide to other ethelenic compounds to form glycols. Osmium tetroxide is used to develop fresh glycols. Osmium tetroxide is used to develop fresh finger prints. It also finds use as a hardening and staining agent in making sections for study under the microscope in biological work. Many problems were encountered in attacking the structure of the osmium thiocyanate complex. Preliminary investigations showed that the red complex could be prepared by the direct action of osmium tetroxide on solutions of sodium thiocyanate in perchloric acid. Complex colors developed in great excess of thiocyanate showed no fading over a period of a week. The complex was found to follow Beers law (See figure 1). Sulfate ions appeared as a by product of the reaction, indicating a reduction of the osmium to a lower oxidation state. The speed of the reaction appeared to be dependent on on CNS concentration. At high CNS concentrations, good colors were developed, but at lower concentrations the colors were obscured by the appearance of a dark precipitate of a colloidal nature.

No description available.

Yes / Platinum drugs are widely used for cancer treatment. Other precious metals are promising, but their clinical progress depends on achieving different mechanisms of action to overcome Pt-resistance. Here, we evaluate 13 organo-Os complexes: 16-electron sulfonyl-diamine catalysts [(η6-arene)Os(N,N′)], and 18-electron phenylazopyridine complexes [(η6-arene)Os(N,N’)Cl/I]+ (arene = p-cymene, biphenyl, or terphenyl). Their antiproliferative activity does not depend on p21 or p53 status, unlike cisplatin, and their selective potency toward cancer cells involves the generation of reactive oxygen species. Evidence of such a mechanism of action has been found both in vitro and in vivo. This work appears to provide the first study of osmium complexes in the zebrafish model, which has been shown to closely model toxicity in humans. A fluorescent osmium complex, derived from a lead compound, was employed to confirm internalization of the complex, visualize in vivo distribution, and confirm colocalization with reactive oxygen species generated in zebrafish. / Wellcome Trust (grant no. 107691/Z/15/Z), ERC (grant nos. 247450, 324594), Science City (AWM and ERDF), WCPRS and Bruker Daltonics (Studentship for JPCC), Mike and Enfys Bagguley, and EPSRC (Studentship for HEB, and grant no. EP/F034210/1)

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy