Browsing by Author "Szilagyi, Robert"

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Copying Nature: Chemical Synthesis of a Possible Catalytic Compound for H2 Generation
(2013-03) Ural, Hazal; Szilagyi, Robert
The catalytic active iron-sulfur cluster of FeFe-hydrogenase can product hydrogen gas close to 10,000 molecules of H2 per second per enzyme molecule. None of the currently known synthetic iron-sulfur cluster can even come close to this reactivity. A recent computer modeling study indicated that there is a new compound that may be able to meet this record activity. I propose to make this compound. The innovative part of the work is the attachment of a unsaturated ligand (olefinic and/or allylic) to the Fe2S2(CO)6 'parent' compound. I will use infrared and visible/ultraviolet spectroscopic techniques to characterize the compounds I will make. Using analytical techniques I will determine the reduction potential and protonation constant of the new compounds and will compare to other iron-sulfur compounds. The proposed work will be carried out with the help of a graduate student and with the guidance of faculty mentor, who has already secured funding for material and supplies related expenses.
Electronic Structure Determination of [Fe]-hydrogenase model complexes
(2013-03) Murray, Kevin; Szilagyi, Robert
Hydrogenases are a class of metalloenzymes that catalyze the reversible oxidation of dihydrogen to protons. The mononuclear [Fe]-hydrogenases form a unique family of hydrogenase enyzmes in that they function as hydrogen forming methylene-tetrahydromethanopterin dehydrogenases (Hmd). They catalyze the reversible reduction of N5,N10-methyltetrahydromethanopterin with H2 to N5,N10-methylenetetrahydromethanopterin and a proton. In order to understand the electronic structure of the active site of this enzyme, which features a single low-spin iron center, we have studied a series of [Fe]-hydrogenase model complexes provided by a collaborator from Switzerland. X-ray absorption spectroscopy (XAS) data were taken at the S K- and Fe L-edges in order to investigate the electronic structure of these compounds. The studies complexes allowed for a comparative analysis that provided us with how distinct structural elements of the complexes determine overall electronic structure. We utilize calibrated Density Functional Theory-based (DFT) calculations to aid the interpretation of our spectroscopic results. The XAS results allow us to determine the total S 3p and Fe 3d character of the unoccupied frontier orbitals and calculations will allow us to complete the orbital composition so that the total electronic structure is defined.