摘要
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.