Office: Clark Hall Room 210
Our major research activities continue to focus on detailed spectroscopic and computational studies related to 1) understanding electronic structure contributions to reactivity in pyranopterin Mo/W enzymes and S-Ribosylhomocysteinase (LuxS), and 2) understanding electronic communication in donor-bridge-acceptor (D-B-A) biradicals, magnetic interactions between f-electrons and delocalized electrons, and electron transport in molecular wires with an internally biased electronic structure.
Spectroscopic studies of pyranopterin molybdenum active sites (sulfite oxidase, DMSO reductase, xanthine oxidase) and LuxS (an enzyme involved in bacterial interspecies communication) are coupled with parallel studies on small molecule analogs in order to understand their mechanism of activity. We employ a combined spectroscopic approach utilizing multifrequency EPR, MCD, resonance Raman, and electronic/X-ray absorption spectroscopies, coupled with the results of detailed bonding calculations, to provide comprehensive information regarding electronic structure contributions to catalysis. The bonding descriptions that we develop for these active sites provide deep insight into numerous fundamental biological processes including electron transfer, atom transfer, catalytic hydroxylations, water activation, electronic delocalization, enzyme-substrate interactions, and the nature of the transition state; all key to understanding the mechanism of activity in metalloenzymes.
D-B-A Biradicals. Donor-Bridge-Acceptor systems have been suggested as components of molecular wire devices including those that promote unidirectional electron flow. We wish to understand how the unique electronic structure of the bridge, its geometry, and the nature of D and A conspire to allow facile control of electron transport, and even spin-polarized electron transport when the bridge moiety possesses uncompensated spin. Recently, we have observed direct evidence for electronic correlation over distances of 2nm in extended systems.
Magnetic Interactions in Ln-radical Systems. We use MCD spectroscopy, electronic absorption spectroscopy, and magnetic susceptibility to probe the ground and excited state electronic structures of unusual lanthanide-radical complexes, including lanthanides connected by extended bridges. The impetus for this work has been to determine the degree of electronic interaction between localized f-states and delocalized ligand π-electrons.