화학공학소재연구정보센터
Inorganic Chemistry, Vol.51, No.23, 12729-12737, 2012
Spectroscopic and Computational Studies of a Small-Molecule Functional Mimic of Iron Superoxide Dismutase, Iron 2,6-Diacetylpyridinebis(semioxamazide)
Iron 2,6-diacetylpyridinebis(semioxamazide) (Fe(dapsox)) is a heptacoordinate pentagonal bipyramidal, functional mimic of iron-dependent superoxide dismutase that has been well-characterized on the basis of kinetics and mechanistic studies; however, prior to our studies, its electronic structure had yet to be examined. This paper details our initial characterization of Fe(dapsox) in both its reduced and oxidized states, by electronic absorption (Abs) and low-temperature magnetic circular dichroism spectroscopies. Density functional theory (DFT) geometry optimizations have yielded models in good agreement with the published crystal structures. Time-dependent DFT and INDO/S-CI calculations performed on these models successfully reproduce the experimental Abs spectra and identify intense, low-energy transitions in the reduced complex (Fe-II(H(2)dapsox)) as metal-to-ligand charge transfer transitions, suggesting the presence of pi-backbonding in this complex. This backbonding along, with the proton uptake accompanying metal ion reduction, provides a compelling mechanism by which the metal-centered redox potential is correctly tuned for catalytic superoxide disproportionation.