The oxidative ring cleavage of aromatic compounds, such as o-aminophenols, is typically performed in biological systems by mononuclear non-heme iron dioxygenases.  Despite extensive study, the mechanism of these enzymes remains under debate.  A central question is the identity of the initial dioxygen-bound intermediate, which some believe consists of a substrate radical bound to an Fe(II) center.  We have prepared several monoiron(II) complexes that faithfully model the enzyme-substrate intermediates of o-aminophenol dioxygenases (APDO).  Treatment with a phenoxyl radical results in formation an unprecedented complex containing an iron(II) center coordinated to an iminobenzosemiquinonate radical.  This complex has been extensively characterized with crystallographic, spectroscopic, and electrochemical techniques, in conjunction with computational methods. We have also explored the reactivity of our APDO models with dioxygen and nitric oxide.   Collectively, our results demonstrate the viability of radical-containing intermediates in the catalytic cycles of certain non-heme iron dioxygenases.

Small molecule mimics of o-aminophenol dioxygenases

246th National Meeting (2013)

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