The ability to mimic the chemistry of mononuclear non-heme iron oxygenases using small molecule complexes is of great importance to both synthetic chemists and biochemists alike owing to the vast array of transformations performed by this class of enzymes.  Taurine dioxygenase (TauD), an a-ketoglutarate (a-KG) dependent enzyme, catalyzes the hydroxylation of taurine to sulfite and aminoacetaldehyde via an Fe(IV)=O moiety with concomitant oxidative decarboxylation of a-ketoglutarate to produce succinate.  We report the structural, electronic and reactivity properties of a fully functional TauD synthetic analog containing a facially-coordinated N2O1 ligand system, [Na+][FeII(N2O1)(a-KG)(MeOH)-]. A combined approach utilizing experimental (mechanistic and spectroscopic) data and computational (DFT) simulations will be presented in order to describe the dynamic solution behavior of this system.   A discussion of the solution speciation that results from the binding of an asymmetric bidentate ligand (a-KG) to the fac-[FeII(N2O1)(MeOH)3]+ complex and the resulting reactivity properties of these adducts will be presented.  Kinetic characterizations, based on low-temperature stopped-flow spectroscopic data, will be described in order to identify coordination geometry changes that occur during O2 utilization and substrate oxidation.  Insights into the chemical basis for the selection of the appropriate isomer(s) in the TauD metalloenzyme active sites will be presented.

Utilizing iron(II)-coenzyme oxygen activation in catalysis: How close is close enough?

246th National Meeting (2013)

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