The electrocatalytic reduction of CO2 is a profoundly challenging problem that is of interest, not only as a means of counteracting unsustainable emissions of CO2, but also as a method for the development of renewable fuels and commodity chemicals. Mn(bpy-R)(CO)3Br catalysts have been shown to be viable, earth-abundant alternatives to the extensively studied Re(bpy-R)(CO)3Cl catalysts. In the presence of weak Br�nsted acids, these Mn catalysts reduce CO2 to CO at lower overpotentials with comparable activity to the Re catalysts. One distinct difference between these Mn catalysts and their Re counterparts is a higher tendency for dimerization before generating the catalytically-active state. This tendency for dimerization is thought to contribute to an overpotential for two-electron reduction, as well as to limiting the activity of these Mn catalysts. Techniques for eliminating dimerization will be discussed, including synthetic modification of the bipyridine ligand. Eliminating dimerization results in formation of the CO2-binding state at a 300 mV more positive potential than for previous Mn catalysts. Although CO2 binds at a modest potential, an �over reduction� is required to initiate catalysis. Many mechanistic tools, including IR-spectroelectrochemisty, are described that help gain insight into this unique catalysis.

Carbon dioxide reduction by manganese bipyridyl complexes: Synthetic modification and mechanistic insights

248th National Meeting (2014)

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