In nature, some bacteria are able to efficiently produce hydrogen gas. [FeFe]-hydrogenases are the enzymes that generally catalyze the reduction of hydrogen in nature. These enzymes, which contain iron in their active site, are of great interest because of the increasing need to develop a cheaper substitute for platinum as a catalyst for hydrogen production. Symmetric model compounds containing all CO ligands or mixed CO/CN and CO/PMe3 ligands on both irons in the active site have been studied extensively. However, asymmetric compounds have not been the focus of as much work. This work examined two asymmetric molecules containing both CO and CN ligands: [Fe2(μ-S2C2H4)(CO)5(CN)1]1- (1) and [Fe2(μ-S2C3H6)(CO)5(CN)1]1− (2). The asymmetry of these model compounds makes the redox potentials of the two iron atoms different, changing the catalytic properties of the compounds. The molecules were studied using 400 nm and 266 nm UV pump-infrared probe spectroscopy in order to better understand the ultrafast dynamics of the active site. So far, 1 has been studied using 400 nm pump pulses, and 2 has been studied using 400 nm and 266 nm pump pulses. In 1, distinct bleaches are observed around 1930, 1979, 1999, and 2038 cm-1. There are also new absorptions at 1899, 1964, and 2023 cm-1. The bleaches and absorptions decay with a time constant of 23 +/- 6.6 ps. There is some evidence of residual signal remaining out to 300 ps, especially with the bleach at 1979 cm-1. Similar bleaches and absorptions are observed in 2 due to the similarity in structure. Additionally, density functional theory (DFT) calculations are being used to simulate possible photoproducts.

Ultrafast laser spectroscopy to study photodynamics of asymmetric hydrogenases

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.