The proposed research describes the development of a mononuclear iron catalyst for the oxidation of water to molecular oxygen. Inspiration for elements of catalyst design are drawn from enzymes for which molecular oxygen is a natural substrate. In particular, it is hypothesized that initial O-O bond formation should be possible by nucleophilic attack of an activated water molecule on a highly oxidizing and electrophilic oxometal unit. Two factors are critical for realizing this reaction: 1) generation of a sufficiently reactive electron-deficient oxometal unit, and 2) management of protons during the key O-O bond forming event. The proposed catalyst addresses these concerns by suggesting that an appropriately ligated Fe(V)- oxo unit will be energetically disposed to undergo O-O bond formation with water. The reactivity of the Fe (V)-oxo species will be tuned using a new class of corrole-derived 'hangman'ligands, which position hydrogen bonding functionality above the plane of a tetrapyrrolic equatorial environment. The synthesized structures will be evaluated in two stages for initial Fe(V)-oxo generation and then subsequent O-O bond formation and O2 liberation. In this regard, the proposed mechanism resembles the microscopic reverse of cytochrome P450 function, where O2 is cleaved to furnish water and a high-valent iron-oxo intermediate. As such, it is expected that the proposed research will offer perspectives on the mechanism and energetic requirements of the cytochrome P450 monooxygenases. Additionally, long-term success of the proposed research represents an introduction to the possibility of converting water to molecular oxygen and hydrogen for use as fuels. Such a scheme would help reduce global dependence on fossil fuel combustion which would dramatically improve public health, especially in urban areas, by reducing environmental pollution. The risks associated with chronic exposure to pollution from fossil fuel combustion are a major and increasing public health concern. Consequently, the adoption of new non-carbon based energy sources is expected to directly improve human health, especially in urban areas. This proposal describes the design and evaluation of a water oxidation catalyst that could be used as part of a scheme to produce hydrogen, a non-polluting fuel.
