The molybdenum cofactor (Moco) is necessary for survival within all eukaryotic cells. This research focuses on the molybdopterin, which names the one or two conserved pyranopterin dithiolene ligands on Moco. Without the molybdopterin, Moco loses its catalytic efficiency, but there is little known about the relationship between molybdopterin and the catalytic function of Moco. Molybdopterin is additionally one of the most redox active ligands in all of biology and is energetically expensive to create, making it of significant focus to our research. Several crystal structures of bacterial molybdoenzymes suggest that this ligand can exist in an open or closed pyran structure, and the interconversion between these states is believed to play a significant role in its catalytic system. To date, the Burgmayer lab group has created the model system [TEA][Tp*Mo(X)pterin-C(CH3)2R-dithiolene], where TEA is tetraethylammonium, Tp* is tris(3,5-dimethylpyrazolyl)hydroborate, X is either oxygen or sulfur, Mo exists in the Mo(IV) or Mo(V) oxidation state, and R can be a hydroxyl or methyl. When R is a hydroxyl group, the complex experiences reversible intramolecular cyclization that is dependent upon the dielectric constant of the solvent, producing a pyran ring. The focus of this poster is on the [Tp*Mo4+(O)S2BDMPP]- system, where the hydroxyl group involved in pyran formation is isosterically replaced with a methyl group, thus preventing intramolecular cyclization. Through investigating the synthesis and isolation of this complex in this system, we have learned more about the efficiency and the electronics that it may exhibit compared to other model systems the Burgmayer group has previously developed.

Molybdenum pyranopterin dithiolene complexes: Investigating the steric effects on molybdenum cofactor models

251st National Meeting (2016)

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