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.
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.
Tsai
Ming-Che
MC
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
Tsai
Fu-Te
FT
Lu
Tsai-Te
TT
Tsai
Ming-Li
ML
Wei
Yin-Ching
YC
Hsu
I-Jui
IJ
Lee
Jyh-Fu
JF
Liaw
Wen-Feng
WF
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
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