In nature, manganese-dependent enzymes in bacteria and higher organisms have the ability to catalyze substrate oxidation reactions using molecular oxygen as an oxidant. The oxidation products of these reactions often serve as carbon sources, which are important for growth in nature. Two examples of such systems include manganese-dependent dioxygenase (MndD) and quercetin dioxygenase (QueD), which break down catechol and flavonoid species respectively. Recent evidence has suggested a peroxomanganese intermediate for MndD that forms when dioxygen reacts with the active-site manganese-catechol complex. This research uses synthetic models to explore these types of transformations as a means of advancing our understanding of the enzyme mechanisms. The complexes studied here are supported by polypyrazolylborate ligands (TpPh2), which serve as molecular vises, keeping the metal ion in a tridentate grip. This binding mode mimics what is seen in the active site of natural enzymes, leaving the rest of the coordination sites open for chemical operations. To study these systems, a combined approach of spectroscopic characterization, with methods such as electronic absorption and electron paramagnetic resonance spectroscopy, and reactivity studies with dioxygen were used. In addition to showing structural characterization of the [MnII(TpPh2)(3-Hfl)] complex, this poster will show evidence that these trispyrazolylborate-supported manganese complexes are O2 reactive and will aim to describe the O2 reaction products.

Characterization and oxygen reactivity of a flavonoid-bound manganese complex supported by a scorpionate ligand

251st National Meeting (2016)

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