title: Structure/function correlations over binuclear non-heme iron active sites.
abstract: Binuclear non-heme iron enzymes activate O2 to perform diverse chemistries. Three different structural mechanisms of O2 binding to a coupled binuclear iron site have been identified utilizing variable-temperature, variable-field magnetic circular dichroism spectroscopy (VTVH MCD). For the μ-OH-bridged Fe(II)2 site in hemerythrin, O2 binds terminally to a five-coordinate Fe(II) center as hydroperoxide with the proton deriving from the μ-OH bridge and the second electron transferring through the resulting μ-oxo superexchange pathway from the second coordinatively saturated Fe(II) center in a proton-coupled electron transfer process. For carboxylate-only-bridged Fe(II)2 sites, O2 binding as a bridged peroxide requires both Fe(II) centers to be coordinatively unsaturated and has good frontier orbital overlap with the two orthogonal O2 π* orbitals to form peroxo-bridged Fe(III)2 intermediates. Alternatively, carboxylate-only-bridged Fe(II)2 sites with only a single open coordination position on an Fe(II) enable the one-electron formation of Fe(III)-O2 (-) or Fe(III)-NO(-) species. Finally, for the peroxo-bridged Fe(III)2 intermediates, further activation is necessary for their reactivities in one-electron reduction and electrophilic aromatic substitution, and a strategy consistent with existing spectral data is discussed.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA, 94305-5080, USA. edward.solomon@stanford.edu.
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
authors.affiliation: Department of Chemistry, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon, 34141, Republic of Korea.
authors.forename: Kiyoung
authors.initials: K
authors.lastname: Park
mesh_terms: D020134:Catalytic Domain; D019159:Nonheme Iron Proteins / Q000737:chemistry* / Q000378:metabolism*; D011789:Quantum Theory
chemical_list: D019159:Nonheme Iron Proteins
keywords: Binuclear non-heme iron enzymes; Frontier molecular orbitals; O2 activation; Peroxide activation; Variable-temperature, variable-field magnetic circular dichroism