Professor Armstrong’s research focuses on transition metal catalysis of multi-electron reactions at the oxidizing and reducing limits of the redox scale. Transition metal complexes function as homogeneous catalysts in a wide variety of systems of biological and industrial importance. Professor Armstrong is involved with the development of catalytically-active species with emphasis on those that operate at the oxidizing and reducing extremes of the redox scale. He is particularly interested in multi-electron transformations. An example of a process of interest that requires a highly oxidizing species is the conversion of water to dioxygen, as carried out in photosynthetic organisms at a tetranuclear manganese center. At the other extreme of the redox scale, Professor Armstrong seeks highly educing species capable of fixation of small molecules such as N2, H2, CO, CO2, and CH4. Nitrogenase is an enzyme that employs a metal cluster to catalyze the conversion of dinitrogen to ammonia. His approach to elucidation of the enzyme active site structures involves synthesis of novel transition metal clusters whose properties may be compared to those of the native system. An ideal bio-mimetic complex will not only reproduce the structural and spectroscopic properties of the enzyme but will also e able to function as the enzyme does. Once more is understood about the enzyme-active site structure and function via the bio-mimetic approach, Professor Armstrong hopes to optimize the performance of artificial catalysts and to extend, or in some cases restrict, their substrate specificities.
Representative Key Publications:
"Manganese clusters with relevance to Photosystem II" Mukhopadhyay, S.; Mandal, S. K.; Bhaduri, S.; Armstrong, W. H. Chem. Rev. 2004, 104, 3981.
"Shape-Shifting Tetranuclear Oxo-Bridged Manganese Cluster: Relevance to Photosystem II Water Oxidase Active Site" Mukhopadhyay, S.; Mok, H. J.; Staples, R. J.; Armstrong, W. H. J. Am. Chem. Soc. 2004, 126, 9202.
"A New Class of Oxo-Bridged High-Valent Hexamanganese Clusters Supported by Sterically Hindered Carboxylate Ligands" Mukhopadhyay, S.; Gandhi, B. A.; Kirk, M. L.; Armstrong, W. H. Inorg. Chem. 2003, 42, 8171.