Our research interests are in area of synthetic inorganic and organic chemistry and are focused on creating bio-inspired oxidation catalysis. Metalloenzymes are capable of a number of remarkable catalytic oxidative transformations of organic substrates that are regiospecific and stereospecific and use dioxygen as the oxidant. Crystal structures and electronic spectroscopy of such metalloenzymes are now widely available and provide critical insights into the ligation environment necessary to form such functional catalysts. These structures are a starting point from which to construct small synthetic complexes that perform similar types of chemistry. Extending the oxidative chemistry beyond the constraints of the protein environment is the ultimate goal.

For these redox active metal sites, the ligation environment is tightly coupled to the functional chemistry. Yet, focusing solely on the immediate ligation of the metal is not generally sufficient to create efficient catalysts. Site-isolation of the active oxidant is also needed either by peripheral ligand design or by supporting the metal complex on an oxidatively stable matrix. Integrating these factors together to create a functional catalytic complex is a significant challenge.

Of all the available metals, biological systems primarily use copper or iron sites to activate dioxygen for oxidative transformations. In our lab, we have focused on functional models of several enzymes including galactose oxidase (Cu), tyrosinase (Cu), lipoxygenase (Fe, Mn), and several mononuclear non-heme enzymes that require alpha-ketoacids as co-reductants (Fe). Extensive spectroscopic and kinetic investigations, often at low temperatures, provide keen insights into these complexes and their transiently stable oxidized forms. Temporally and operationally efficient epoxidation catalysts have been resulted from such studies that are capable of oxidizing a wide range of electron deficient olefins at exceedingly fast rates. Additionally, mild alcohol to aldehyde oxidation reagents have been discovered. Movement of these complexes into silica based materials represents a direction in the development of these bio-inspired metal-based oxidants.

1) "Site-Isolation And Epoxidation Reactivity Of A Templated Bis-Phenanthroline Ferrous Site In Porous Silica," T.J. Terry, G. Dubois, A.J. Murphy Angew. Chem. (2007), in press.

2) "Reversible O-O Bond Cleavage In Copper-Dioxygen Isomers: Impact Of Anion Basicity," X. Ottenwaelder, D. Jackson Rudd, M.C. Corbett, B. Hedman B., K.O. Hodgson, T.D.P. Stack J. Am. Chem. Soc., 128 (29) 9268-9269 (2006).

3) "Discovery And Optimization Of Rapid Manganese Catalysts For The Epoxidation Of Terminal Olefins," A.J. Murphy, T.D.P. Stack J. Mol. Catal., A, 251, 78-88 (2006).

4) "C-H Activation By A Mononuclear Manganese(III) Hydroxide Complex: Synthesis And Characterization Of A Manganese-Lipoxygenase Mimic?" C. R. Goldsmith, A. P. Cole, T. D. P. Stack J. Am. Chem. Soc., 127 (27), 9904-9912 (2005).

5) "Tyrosinase Reactivity In A Model Complex: An Alternative Hydroxylation Mechanism," L. M. Mirica, M. Vance, D. Jackson-Rudd, B. Hedman, K. O. Hodgson, E. I. Solomon, T. D. P. Stack, Science, 308, 5730, 1890-1892 (2005).

6) "Structure And Spectroscopy Of Copper-Dioxygen Complexes," L. M. Mirica, X. Ottenwaelder, T. D. P. Stack, Chem. Rev., 104 (2), 1013-1045 (2004).