title: Insight into the dinuclear {Fe(NO)2}10{Fe(NO)2}10 and mononuclear {Fe(NO)2}10 dinitrosyliron complexes.
abstract: The reversible redox transformations [(NO)(2)Fe(S(t)Bu)(2)](-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2)(2-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2)(-) ⇌ [Fe(μ-S(t)Bu)(NO)(2)](2) and [cation][(NO)(2)Fe(SEt)(2)] ⇌ [cation](2)[(NO)(2)Fe(SEt)(2)] (cation = K(+)-18-crown-6 ether) are demonstrated. The countercation of the {Fe(NO)(2)}(9) dinitrosyliron complexes (DNICs) functions to control the formation of the {Fe(NO)(2)}(10){Fe(NO)(2)}(10) dianionic reduced Roussin's red ester (RRE) [PPN](2)[Fe(μ-SR)(NO)(2)](2) or the {Fe(NO)(2)}(10) dianionic reduced monomeric DNIC [K(+)-18-crown-6 ether](2)[(NO)(2)Fe(SR)(2)] upon reduction of the {Fe(NO)(2)}(9) DNICs [cation][(NO)(2)Fe(SR)(2)] (cation = PPN(+), K(+)-18-crown-6 ether; R = alkyl). The binding preference of ligands [OPh](-)/[SR](-) toward the {Fe(NO)(2)}(10){Fe(NO)(2)}(10) motif of dianionic reduced RRE follows the ligand-displacement series [SR](-) > [OPh](-). Compared to the Fe K-edge preedge energy falling within the range of 7113.6-7113.8 eV for the dinuclear {Fe(NO)(2)}(9){Fe(NO)(2)}(9) DNICs and 7113.4-7113.8 eV for the mononuclear {Fe(NO)(2)}(9) DNICs, the {Fe(NO)(2)}(10) dianionic reduced monomeric DNICs and the {Fe(NO)(2)}(10){Fe(NO)(2)}(10) dianionic reduced RREs containing S/O/N-ligation modes display the characteristic preedge energy 7113.1-7113.3 eV, which may be adopted to probe the formation of the EPR-silent {Fe(NO)(2)}(10)-{Fe(NO)(2)}(10) dianionic reduced RREs and {Fe(NO)(2)}(10) dianionic reduced monomeric DNICs in biology. In addition to the characteristic Fe/S K-edge preedge energy, the IR ν(NO) spectra may also be adopted to characterize and discriminate [(NO)(2)Fe(μ-S(t)Bu)](2) [IR ν(NO) 1809 vw, 1778 s, 1753 s cm(-1) (KBr)], [Fe(μ-S(t)Bu)(NO)(2)](2)(-) [IR ν(NO) 1674 s, 1651 s cm(-1) (KBr)], [Fe(μ-S(t)Bu)(NO)(2)](2)(2-) [IR ν(NO) 1637 m, 1613 s, 1578 s, 1567 s cm(-1) (KBr)], and [K-18-crown-6 ether](2)[(NO)(2)Fe(SEt)(2)] [IR ν(NO) 1604 s, 1560 s cm(-1) (KBr)].
authors.affiliation: Department of Chemistry and Frontier Research Center of Fundamental and Applied Science of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Shih-Wey
authors.initials: SW
authors.lastname: Yeh
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Lin
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Li
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Chen
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Jang
authors.forename: Jyh-Fu
authors.initials: JF
authors.lastname: Lee
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D043844:Crown Ethers / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D058085:Iron Compounds / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D009603:Nitroso Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011789:Quantum Theory; D013816:Thermodynamics; D056928:X-Ray Absorption Spectroscopy
chemical_list: D043844:Crown Ethers; D058085:Iron Compounds; D008024:Ligands; D009603:Nitroso Compounds; D009569:Nitric Oxide; C015762:18-crown-6