title: Relative binding affinity of thiolate, imidazolate, phenoxide, and nitrite toward the {Fe(NO)2} motif of dinitrosyl iron complexes (DNICs): the characteristic pre-edge energy of {Fe(NO)2}9 DNICs.
abstract: The synthesis, characterization, and transformation of the anionic {Fe(NO)(2)}(9) dinitrosyl iron complexes (DNICs) [(NO)(2)Fe(ONO)(2)](-) (1), [(NO)(2)Fe(OPh)(2)](-) (2), [(NO)(2)Fe(OPh)(C(3)H(3)N(2))](-) (3) (C(3)H(3)N(2) = imidazolate), [(NO)(2)Fe(OPh)(-SC(4)H(3)S)](-) (4), [(NO)(2)Fe(p-OPhF)(2)](-) (5), and [(NO)(2)Fe(SPh)(ONO)](-) (6) were investigated. The binding affinity of ligands ([SPh](-), [-SC(4)H(3)S](-), [C(3)H(3)N(2)](-), [OPh](-), and [NO(2)](-)) toward the {Fe(NO)(2)}(9) motif follows the ligand-displacement series [SPh](-) approximately [-SC(4)H(3)S](-) > [C(3)H(3)N(2)](-) > [OPh](-) > [NO(2)](-). The findings, the pre-edge energy derived from the 1s --> 3d transition in a distorted T(d) environment of the Fe center falling within the range of 7113.4-7113.8 eV for the anionic {Fe(NO)(2)}(9) DNICs, implicate that the iron metal center of DNICs is tailored to minimize the electronic changes accompanying changes in coordinated ligands. Our results bridging the ligand-substitution reaction study and X-ray absorption spectroscopy study of the electronic richness of the {Fe(NO)(2)}(9) core may point the way to understanding the reasons for nature's choice of combinations of cysteine, histidine, and tyrosine in protein-bound DNICs and rationalize that most DNICs characterized/proposed nowadays are bound to the proteins almost through the thiolate groups of cysteinate/glutathione side chains in biological systems.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Ming-Che
authors.initials: MC
authors.lastname: Tsai
authors.forename: Fu-Te
authors.initials: FT
authors.lastname: Tsai
authors.forename: Tsai-Te
authors.initials: TT
authors.lastname: Lu
authors.forename: Ming-Li
authors.initials: ML
authors.lastname: Tsai
authors.forename: Yin-Ching
authors.initials: YC
authors.lastname: Wei
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.forename: Jyh-Fu
authors.initials: JF
authors.lastname: Lee
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D007093:Imidazoles / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D007093:Imidazoles; D008024:Ligands; D009573:Nitrites; D009589:Nitrogen Oxides; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; C029899:imidazole; D007501:Iron; D010100:Oxygen