My research interests include laser spectroscopy, applications of science in art and archaeology, and improving the integration of advanced instrumentation in the undergraduate chemistry curriculum.
Current and Former Research Group Members
Ultrafast Time-Resolved Spectroscopy of [FeFe]-Hydrogenase Model Compounds
My current research program involves the spectroscopic study of novel bio-mimetic catalysts for the production of hydrogen gas. These compounds are analogs to the [FeFe]-hydrogenases found in certain archaebacteria. A general structure of the active site of the [FeFe]-hydrogenases is shown in Figure 1. The [FeFe]-hydrogenases contain two iron atoms (shown in purple) bonded to two sulfur atoms (shown in yellow). The sulfurs are bridged by a CH2NCH2 bridge. The two irons have three C≡O (carbonyl) ligands and two C≡N ligands. Depending on the particular state of the enzyme, the last position can be open or contain another ligand. The active site is bound to the rest of the protein by a cysteine ligand, which also connects the active site to a Fe4S4 cluster (only one of the iron atoms from this cluster is shown in Figure 1).
The model compounds that we study are similar di-iron, di-thiol compounds based on Fe(μ-S2C3H6)(CO)6 (1), shown in Figure 2. Variants of this model compound include changing the bridge from C3H6 to C2H4 and replacing one or two of the C≡O ligands with either C≡N or P(CH3)3 (PMe3).
This project has two components. The first part of the project involves the synthesis and characterization of these model compounds. In particular, we are using mid-IR, Far-I R (THz), and Raman spectroscopies to assign the vibrational spectra of these compounds. For more details on this aspect of the project, click here.
In addition, we are using ultrafast time-resolved vibrational spectroscopy to study the redistribution of energy in these molecules when pumped with UV or visible light. A number of groups are working on model compounds that include active sites similar to those above, tied to a photosensitizer. The idea is to develop a light-driven catalysis mechanism similar to Photosynthesis II. Unfortunately, very little is currently known about the reaction of these active sites to UV and visible light. By studying the ultrafast behavior after excitation with UV or visible light, we can better understand such light-driven mechanisms. For more information about this aspect of the project, click here.
The results of the time-resolved spectroscopy project were recently featured in the Journal of Physical Chemistry A.[Link to http://pubs.acs.org/doi/full/10.1021/jp2121774] The work was also featured on the cover of that issue.
These projects are done in collaboration with Dr. Edwin Heilweil at the National Institute of Standards and Technology (NIST) [Link to www.nist.gov] in Gaithersburg, Maryland. This work has been funded by NIST through Cooperative Agreement Numbers 70NANBH9125, 70NANB7H6135, and 60NANB12D272, and through Hood College's Summer Research Institute program.
Interfacial Chemical Properties of Gels Used for Preservation and Conservation of Cultural Heritage
I have recently begun a second project involving the application of spectroscopy to the intersection of art, archaeology, and chemistry. This project is being done in conjunction with Barbara Berrie at the National Gallery of Art and will involve studying the properties of gel systems for cleaning artwork and archaeological artifacts.
Introduction of Raman Spectroscopy to the Undergraduate Curriculum
This project involved the purchase of a Raman spectrometer for use throughout the undergraduate chemistry curriculum. We developed or adapted six separate experiments involving Raman spectroscopy for courses from General Chemistry to Physical Chemistry. The experiments increase in complexity, with different experiments emphasizing different aspects of Raman spectroscopy. For more information about this project, including copies of the lab experiments, click here.