Chemical transformations involving the oxides of nitrogen (NOx) and sulfur (SOx) are of considerable environmental and biological importance. Industrial and other combustion (e.g., auto) processes result in the production of large quantities of these compounds, which threaten our environment by contributing to air pollution, acid rain and unacceptable """"""""greenhouse"""""""" gas effects. Biological systems are known to effect many reactions involving NOx (or SOx) compounds, and global biological cycles of sulfur and nitrogen involve many transition-metal enzyme catalyzed reactions. Denitrification is the dissimilatory reduction of nitrate to nitrogen gas, an important anaerobic bacterial process which returns considerable quantities of fixed nitrogen (fertilizer) to the atmosphere. The focus of the proposed research involves studies of the chemistry of copper ion catalyzed processes, known to effect the reduction of nitrite ion to nitrous oxide (possibly through nitric oxide, NO) and N2O to dinitrogen. The objective of the research program is to examine and establish fundamental aspects of Cu-NOx chemistry. The investigations will include structural and spectroscopic characterization and studies involving the mechanisms of copper ion mediated redox reactions using these substrates. The research plan involves the use of polydentate ligands capable of binding one or more copper(I) or copper(II) ions in a known and/or controlled variable environment, one that is also capable of stabilizing both copper redox states. Preliminary studies have shown that copper nitrosyl complexes can be prepared and structurally characterized and that systems capable of biomimetic reactivity can be established (e.g. the reaction of NO2- or NO to give N2O). Further characterization and mechanistic investigations are proposed, along with detailed examination of copper ion interactions and reactivity with nitrite, nitric oxide and nitrous oxide. New ligands for copper ion interactions and reactivity with nitrite, nitric oxide and nitrous oxide. New ligands for copper and complexes will be synthesized; these are designed to address questions concerning already proposed reaction intermediates or allow for further studies involving atom transfer reactions or reduction of bound NOx species. Longer term objectives include the development of catalysts for NOx reduction and analogous chemical studies with SOx substrates.
| Karlin, K D (1993) Metalloenzymes, structural motifs, and inorganic models. Science 261:701-8 |
