INOR 608 |
| In photosynthesis, water is the ultimate source of electrons required for CO2 reduction. In turn, the 4e- oxidation of water results in the formation of dioxygen. The active site of the Photosystem II water oxidase contains a Mn4Ca cluster. It is thought that the substrate water molecules bind to this cluster and are transformed into dioxygen by a mechanism that is as yet poorly understood. Several hypothetical mechanisms for enzymatic water oxidation invoke a reactive manganyl (Mn=O) intermediate. We are engaged in testing such hypotheses by generating well defined manganyl species and characterizing their spectral and reaction characteristics. Several well characterized manganyl complexes have been reported, yet they are relatively stable and have not been shown to oxidize water. We are examining reactions between oxygen atom transfer agents and L2MnX species, where L is a bidentate Schiff base ligand and X is an anion such as chloride, nitrate, or triflate. We will describe the results of stopped-flow kinetics experiments that were followed by UV-vis spectroscopy and mass spectrometry. A reactive intermediate whose properties are consistent with a manganyl formulation has been discovered. A proposed mechanism of the oxygen atom transfer reaction will be provided. Finally, we will describe experiments aimed at probing the reactivity of our putative manganyl intermediate. |
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Inorganic Modeling of Biological Systems
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster
Sci-Mix
Division of Inorganic Chemistry |