title: S K-edge X-ray absorption spectroscopy and density functional theory studies of high and low spin {FeNO}7 thiolate complexes: exchange stabilization of electron delocalization in {FeNO}7 and {FeO2}8.
abstract: S K-edge X-ray absorption spectroscopy (XAS) is a direct experimental probe of metal ion electronic structure as the pre-edge energy reflects its oxidation state, and the energy splitting pattern of the pre-edge transitions reflects its spin state. The combination of sulfur K-edge XAS and density functional theory (DFT) calculations indicates that the electronic structures of {FeNO}(7) (S = 3/2) (S(Me2)N4(tren)Fe(NO), complex I) and {FeNO}(7) (S = 1/2) ((bme-daco)Fe(NO), complex II) are Fe(III)(S = 5/2)-NO(-)(S = 1) and Fe(III)(S = 3/2)-NO(-)(S = 1), respectively. When an axial ligand is computationally added to complex II, the electronic structure becomes Fe(II)(S = 0)-NO•(S = 1/2). These studies demonstrate how the ligand field of the Fe center defines its spin state and thus changes the electron exchange, an important factor in determining the electron distribution over {FeNO}(7) and {FeO2}(8) sites.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305, United States.
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.forename: Lei V
authors.initials: LV
authors.lastname: Liu
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dey
authors.forename: Gloria
authors.initials: G
authors.lastname: Villar-Acevedo
authors.forename: Julie A
authors.initials: JA
authors.lastname: Kovacs
authors.forename: Marcetta Y
authors.initials: MY
authors.lastname: Darensbourg
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D007202:Indicators and Reagents; D008958:Models, Molecular; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
chemical_list: D005296:Ferrous Compounds; D007202:Indicators and Reagents; D013438:Sulfhydryl Compounds; D013455:Sulfur; C034236:ferrous oxide