published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Abstract This study elucidates the processes that may determine the distributions of Mn and other trace metals on the slope of the southern Okinawa Trough. In addition to salinity and temperature, large-volume seawater samples were collected for analyzing dissolved manganese (DMn), particulate manganese (PMn), suspended, particulate organic carbon (POC), pH and dissolved CO2 (TCO2 ) during June-July of 1998, 1999 and 2000. Concentrations of DMn and PMn in a transect decrease generally seaward from the shelf break. However, anomalous distributions of DMn and PMn occur usually between 600 m and 900 m in many deep profiles. Such distribution patterns are probably influenced by the lateral transport of metals released from slope sediments or from the plumes of submarine venting systems. For example, dissolved manganese generally decreases with depth in the oxygenated condition, but in the study area unusual high DMn concentrations were observed commonly at depth 400 m, 600 m, 800 m and 1200 m. The unusual Mn signals become weak, in general, from the South Mien-Hua Canyon to the North Mien-Hua Canyon. The higher concentration of PMn sometimes was observed in deep stations than in shallow stations at the same depth implying that processes other than lateral transport may account for the distributions. Images obtained from EK-500 showed that submarine venting systems exist in anomalous Mn distribution areas. Anomalous distributions of PMn and Kd match DMn unusual distributions very well. Besides, the distribution of TSM is closely related to PMn distributions (R=0.433, p=0.01). Although the distribution of pH data appears to be normal, total alkalinity and total CO2 display anomalous distributions coincidently with those Mn unusual distributions. Meanwhile, the ratio (PMn/PAl) is higher for those unusual Mn distributions, and this is likely the effect of submarine venting.

Selective oxidations are important for the functionalization of compounds in organic synthesis and chemical industry. Using O2 as a terminal e- acceptor would be ideal because it is cheap and environmentally friendly, but aerobic oxidations are often prone to unselective free radical autoxidation. Recently developed palladium catalysts use O2 as a selective multi-electron oxidant for various organic transformations. Although these methods are powerful and sophisticated, the lower cost of base metals makes them attractive as potential alternatives. The challenge is to develop methods for effecting multi-electron transformations at metals that typically prefer one electron changes. To this end, the development of manganese(III) complexes containing redox-active ligands as catalysts for selective oxidase-type oxidation of organic substrates was pursued. Bis(tetrabromocatecholato) manganese(III) complexes were shown to aerobically oxidize catechols to form quinones and H2O2. This reactivity was extended to other alcohol and amine substrates. In these reactions, the non-innocent tetrabromocatecholate ligands may impart a multi-electron character to the metal. To directly probe the intermediacy of ligand-centered radicals in catalytic turnover, a series of structurally similar manganese(III) complexes with aminophenol-derived ligands were prepared and characterized. The capacity of these ligands to undergo low-energy redox changes, allowed for isolation of an electron transfer series spanning two redox states without a change in oxidation state at the metal center. The ligand-centered redox events were a key feature in aerobic homocoupling of Grignard reagents.

No description available.

No description available.

No description available.

No description available.

Thesis (M.S.)--The University of North Carolina at Greensboro, 2009. / Directed by Keith Erikcon; submitted to the Dept. of Nutrition. Title from PDF t.p. (viewed Jun. 4, 2010). Includes bibliographical references (p. 65-86).

Thesis (Ph. D.)--University of London, 1967. / Bibliography: leaves 285-307.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 167-176). Also available via World Wide Web.