title: Insight into one-electron oxidation of the {Fe(NO)2}9 dinitrosyl iron complex (DNIC): aminyl radical stabilized by [Fe(NO)2] motif.
abstract: A reversible redox reaction ({Fe(NO)(2)}(9) DNIC [(NO)(2)Fe(N(Mes)(TMS))(2)](-) (4) ⇄  oxidized-form DNIC [(NO)(2)Fe(N(Mes)(TMS))(2)] (5) (Mes = mesityl, TMS = trimethylsilane)), characterized by IR, UV-vis, (1)H/(15)N NMR, SQUID, XAS, single-crystal X-ray structure, and DFT calculation, was demonstrated. The electronic structure of the oxidized-form DNIC 5 (S(total) = 0) may be best described as the delocalized aminyl radical [(N(Mes)(TMS))(2)](2)(-•) stabilized by the electron-deficient {Fe(III)(NO(-))(2)}(9) motif, that is, substantial spin is delocalized onto the [(N(Mes)(TMS))(2)](2)(-•) such that the highly covalent dinitrosyl iron core (DNIC) is preserved. In addition to IR, EPR (g ≈ 2.03 for {Fe(NO)(2)}(9)), single-crystal X-ray structure (Fe-N(O) and N-O bond distances), and Fe K-edge pre-edge energy (7113.1-7113.3 eV for {Fe(NO)(2)}(10) vs 7113.4-7113.9 eV for {Fe(NO)(2)}(9)), the (15)N NMR spectrum of [Fe((15)NO)(2)] was also explored to serve as an efficient tool to characterize and discriminate {Fe(NO)(2)}(9) (δ 23.1-76.1 ppm) and {Fe(NO)(2)}(10) (δ -7.8-25.0 ppm) DNICs. To the best of our knowledge, DNIC 5 is the first structurally characterized tetrahedral DNIC formulated as covalent-delocalized [{Fe(III)(NO(-))(2)}(9)-[N(Mes)(TMS)](2)(-•)]. This result may explain why all tetrahedral DNICs containing monodentate-coordinate ligands isolated and characterized nowadays are confined in the {Fe(NO)(2)}(9) and {Fe(NO)(2)}(10) DNICs in chemistry and biology.
authors: Department of Chemistry, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors: Chih-Chin
authors: CC
authors: Tsou
authors: Fu-Te
authors: FT
authors: Tsai
authors: Huang-Yeh
authors: HY
authors: Chen
authors: I-Jui
authors: IJ
authors: Hsu
authors: Wen-Feng
authors: WF
authors: Liaw
mesh_terms: D000588:Amines / Q000737:chemistry*; D004583:Electrons; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D012821:Silanes / Q000737:chemistry*
chemical_list: D000588:Amines; D005296:Ferrous Compounds; D005609:Free Radicals; D012821:Silanes; D009569:Nitric Oxide