This talk will focus on recent work aimed at determining how a metal ion’s electronic structure and ligand environment can tune the energetics of O-H and O-O bond cleavage versus formation. Most of the O2 on our planet is derived from Mn-catalyzed H2O oxidation, the first step of which involves the endothermic cleavage of a strong O-H bond (BDFE= 122.7 kcal/mol). By binding H2O to a metal ion, and by coupling electron transfer to proton transfer (PCET) this process is both thermodynamically and kinetically more favorable. We also report an exceedingly rare case in which more than one intermediate is observed in a transition-metal promoted O2 reaction, and describe a series of structurally characterized metastable Mn-peroxo compounds. We show that the relative stability of dioxygen intermediates is ligand-dependent, and that the peroxo O-O bond length can be tuned by systematically varying the metal ion coordination sphere. Strong correlations between structural, spectroscopic, and kinetic parameters are observed.

Correlation between the structural, spectroscopic, and kinetic parameters of reactive Mn-peroxo complexes

251st National Meeting (2016)

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