Reduction via Cobalt centered Vitamin B12 cofactors has long been utilized by microbes as a means to mitigate the deleterious effects of halogenated organic compounds.  Research inspired by this biochemical machinery has focused mainly on chlorinated and brominated compounds, especially concerning the ethylene derived solvents containing one or more chlorine molecules, e.g. polychloroethyelene (PCE) and trichloroethyelene (TCE). In the past decade, investigations into the defluorination of fluorinated organic compounds have received some attention to remediate environmental pollutants, however, the degradation mechanisms remain largely unexplored to date. Herein, density functional theory was utilized to model and probe the Cobalt catalyzed reduction of a plethora perfluorinated substrates, encompassing a wide variety of structural and chemical motifs. Inner sphere reactivity including S<sub>N</sub>2 nucleophilic attack at various carbon centers and direct fluorine abstraction were explored in conjunction with outer-sphere electron transfer schemes and the physio-chemical properties of the substrates. Truncated Cobalt-corrin systems were used to model the various inner sphere mechanisms and were contrasted to substituted heterocyclic macrocycles to explore the effect of aromaticity and substituents on the reactivity of cobalt towards PFAS substrates.  This comprehensive investigation not only helps to elucidate the pathways involved in the defluorination of the substrates via Co catalysis but provides mechanistic insights into other reduction methods such as hydrated electrons and UV-photolysis.<br/>

Cobalt catalyzed reduction of perfluoroalkyl substances: Reactions and mechanisms

255th National Meeting (2018)

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