摘要
[PPN][Se 5 Fe(NO) 2 ] (1) and [K-18-crown-6-ether][S 5 Fe(NO) 2 ] (2′) were synthesized and characterized by IR, UV-Vis, EPR spectroscopy, magnetic susceptibility, and X-ray structure. [PPN][Se 5 Fe(NO) 2 ] easily undergoes ligand exchange with S 8 and (RS) 2 (R = C 7 H 4 SN (5), o-C 6 H 4 NHCOCH 3 (6), C 4 H 3 S (7)) to form [PPN][S 5 Fe(NO) 2 ] and [PPN][(SR) 2 Fe(NO) 2 ]. The reaction displays that [E 5 Fe(NO) 2 ] - (E = Se (3), S (4)) facilely converts to [Fe 4 E 3 (NO) 7 ] - by adding acid HBF 4 or oxidant [Cp 2 Fe][BF 4 ] in THF, respectively. Obviously, complexes 1 and 2′ serve as the precursors of the Roussin's black salts 3 and 4. The electronic structure of {Fe(NO) 2 } 9 core of [Se 5 Fe(NO) 2 ] - is best described as a dynamic resonance hybrid of {Fe +1 ( {radical dot} NO) 2 } 9 and {Fe -1 (NO + ) 2 } 9 modulated by the coordinated ligands. The findings, EPR signal of g = 2.064 for 1 at 298 K, implicate that the low-molecular-weight DNICs and protein-bound DNICs may not exist with selenocysteine residues of proteins as ligands, since the existence of protein-bound DNICs and low-molecular-weight DNICs in vitro has been characterized with a characteristic EPR signal at g = 2.03. In addition, complex 2′ treated human erythroleukemia K562 cancer cells exposed to UV-A light greatly decreased the percentage survival of the cell cultures. © 2006 Elsevier B.V. All rights reserved.