title: X-ray emission spectroscopy: a spectroscopic measure for the determination of NO oxidation states in Fe-NO complexes.
abstract: Extensive study of the electronic structure of Fe-NO complexes using a variety of spectroscopic methods was attempted to understand how iron controls the binding and release of nitric oxide. The comparable energy levels of NO π* orbitals and Fe 3d orbitals complicate the bonding interaction within Fe-NO complexes and puzzle the quantitative assignment of NO oxidation state. Enemark-Feltham notation, {Fe(NO)x}(n), was devised to circumvent this puzzle. This 40-year puzzle is revisited using valence-to-core X-ray emission spectroscopy (V2C XES) in combination with computational study. DFT calculation establishes a linear relationship between ΔE(σ2s*-σ2p) of NO and its oxidation state. V2C Fe XES study of Fe-NO complexes reveals the ΔE(σ2s*-σ2p) of NO derived from NO σ(2s)*/σ(2p)→Fe(1s) transitions and determines NO oxidation state in Fe-NO complexes. Quantitative assignment of NO oxidation state will correlate the feasible redox process of nitric oxide and Fe-nitrosylation biology.
authors.affiliation: Department of Chemistry, Chung Yuan Christian University, No. 200, Chung Pei Rd. Chungli, 32023 (Taiwan). TTLu@cycu.edu.tw.
authors.forename: Tsai-Te
authors.initials: TT
authors.lastname: Lu
authors.forename: Tsu-Chien
authors.initials: TC
authors.lastname: Weng
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D007501:Iron / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D013052:Spectrometry, X-Ray Emission / Q000379:methods*
chemical_list: D009569:Nitric Oxide; D007501:Iron
keywords: X-ray emission spectroscopy; bioinorganic chemistry; iron; nitrosyl complexes