摘要
The reaction of [PPN][Fe(CO) 3 (NO)] and S 8 in a 1:1 molar ratio in THF proceeded to give the dinitrosyl iron complex [PPN][S 5 Fe(NO) 2 ] (1) and the known [PPN] 2 [S 5 Fe(μ-S) 2 FeS 5 ] (2). EPR signals of g values g z = 2.0148, g x = 2.0270, and g y = 2.0485 at 77 K confirmed the existence of the unpaired electron in compound 1. The temperature-dependent magnetic moment of complex 1 indicates that the ground state is one unpaired electron with (S t , S L ) = (1/2, 1) at very low temperature (S t is the total spin quantum number of the system; S L is the sum of the spin quantum numbers of two NO ligands). The O K-edge absorptions of complex 1 and [(NO)Fe(S 2 CNEt 2 ) 2 ] at 532.1 and 532.5 eV are assigned to the transition of 1s → π*(NO) and 1S → π*(NO + ), respectively. For the electronic structure of the {Fe(NO) 2 } core, DFT calculations, magnetic susceptibility measurement, EPR, and Fe K-/L-edge XAS spectroscopy of complex 1 lead to a description of {Fe 1+ (•NO) 2 } 9 . [2Fe-2S] cluster 2 treated with nitric oxide in THF shows that cluster 2 is transformed into the dinitrosyl iron complex 1 identified by IR, UV-vis, and X-ray diffraction analysis. The reaction may be reversed by the photolysis of the THF solution of 1 in the presence of the NO-accepting reagent [(C 4 H 8 O)Fe(S,S-C 6 H 4 ) 2 ] - to reform 2. This result demonstrates a successful biomimetic reaction cycle of the degradation and reassembly of [2Fe-2S] cluster [S 5 Fe(μ-S) 2 FeS 5 ] 2- relevant to the repair of nitric oxide-modified [2Fe-2S] ferredoxin by cysteine desulfurase and L-cysteine in vitro.