FACULTY & STAFF

Cather (left) and current graduate students

M. Cather Simpson

Associate Professor of Chemistry (Effective July 2005)

E-mail

Simpson Research Group Web Site

Chem 111: Web resources for the Fall, 2005

Cather's Spring, 2005 SAGES class
 Gods, Monsters or Innocents?
 Check out the final poster session!

Physical Chemistry

B.A., University of Virginia, 1987
Ph.D., University of New Mexico, 1994
Howard Hughes Predoctoral Fellow, 1989-1994
Department of Energy Distinguished Postdoctoral Research Fellow, 1994-1996


Laser Directed Chemistry in Biological Molecules

The research in Dr. Simpson's group focuses upon the characterization and control of events immediately subsequent to excitation of large, biological molecules in solution. State-of-the-art transient and time resolved spectroscopic methods that use tunable visible and infrared pulses are employed. Intramolecular vibrational energy redistribution (IVR) and intermolecular vibrational energy relaxation (VR) are directly monitored as the initially excited molecule evolves on femtosecond to nanosecond timescales. The goals of this research are to understand these processes, and the influences of structural and environmental factors upon them, and then to use this knowledge to direct chemical reactions.

Metalloporphyrins

Metalloporphyrins catalyze a variety of biological reactions, including electron and energy transfer, O2 transport and storage, oxidation reactions, and the conversion of light energy to chemical energy. Technological applications also increasingly exploit the useful properties of porphyrins. These molecules are becoming prevalent as active materials in fuel cells, alkane oxidation processes, chiral synthesis and separation methods, and as the binary switch elements in sensors and molecular memory devices. The structural variability inherent in porphyrin systems allows catalyst specificity, efficiency, and stability to be tuned. These properties give porphyrins the potential to play pivotal roles as future catalysts designed to perform selected tasks.

Vibrational energy dynamics in metalloporphyrins are not well understood. However, nonthermal vibrational energy distributions have been observed in these molecules. Some modes couple quite poorly to the other modes and to the solvent. The energy flow through these degrees of freedom is retarded. Such bottleneck modes can be used to funnel energy into desired reaction coordinates and away from those leading to unwanted products. An understanding of the vibrational behavior in metalloporphyrins will lend insight into the detailed mechanisms that determine catalytic efficiency and specificity in natural systems, and will allow the rational design of porphyrin-based catalysts to carry out particular functions.