The productive, controlled activation of O2 via small-molecule catalysts remains a significant challenge in the field of bioinorganic chemistry. Unlike metalloenzymes, that can gate electron/proton flow, homogeneous solutions of reductants, proton sources, and synthetic iron complexes with open or labile coordination sites frequently follow Fenton-like chemistry to generate hydroxyl radical-based reaction chemistry. In order to minimize the possibility of generating free peroxide/hydroxyl radical, we developed a synthetic model for the 2-oxoglutarate-dependent oxygenases, [FeII(N2O1)(Cl)2(MeOH)]- (2-((2-dimethylamino)ethyl)(methyl)amino)acetic acid), which contains an equivalent 2-His-1-carboxylate motif, and which readily facilitates the 1:1 coupled decarboxylation of coordinated α-keto acids with substrate C-H bond oxidation (C-OH) in the presence of O2. Mechanistic studies differentiating between a metal-based oxidant versus freely diffusing oxygen-based radicals will be presented. The examination of the relationship between the MLCT band energies for various α-keto acid adducts and their corresponding ?-to-?* energy gaps (DFT simulations) with catalytic efficiency will be described. Insights into the differential electronic structures of a subset of these adducts (MCD) will be correlated to low-temperature stopped-flow kinetic measurements for single turnover studies. Additional insights defining the ability of a range of α-keto acids to support catalytic oxidation of a common substrate in the presence of O2 will be presented.

Mechanistic studies of a biomimetic small-molecule catalyst capable of O2-dependent alkane oxidations

256th National Meeting (2018)

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