title: One Electron Makes Differences: From Heme {FeNO}(7) to {FeNO}(8).
abstract: The first X-ray single-crystal structure of a {FeNO}(8) porphyrin complex [Co(Cp)2][Fe(TFPPBr8)(NO)], and the structure of the {FeNO}(7) precursor [Fe(TFPPBr8)(NO)] are determined at 100 K. The two complexes are also characterized by FTIR and UV/Vis spectroscopy. [Fe(TFPPBr8)(NO)](-) shows distinct structural features in contrast to a nitrosyl iron(II) porphyrinate on the Fe-N-O(-) moiety, which include a much more bent Fe-N-O(-) angle (122.4(3)°), considerably longer Fe-NO(-) (1.814(4)) and N-O(-) (1.194(5) Å) bond distances. These and the about 180 cm(-1) downshift ν(N-O) stretch (1540 cm(-1)) can be understood by the covalently bonding nature between the iron(II) and the NO(-) ligand which possesses a two-electron-occupied π* orbital as a result of the reduction. The overall structural features of [Fe(TFPPBr8)(NO)](-) and [Fe(TFPPBr8)(NO)] suggest a low-spin state of the iron(II) atom at 100 K.
authors.affiliation: College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Yanqi Lake, Huairou District, Beijing, 101408 (China).
authors.forename: Bin
authors.initials: B
authors.lastname: Hu
authors.affiliation: College of Materials Science and Opto-electronic Technology, University of Chinese Academy of Sciences, Yanqi Lake, Huairou District, Beijing, 101408 (China). jfli@ucas.ac.cn.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Li
mesh_terms: D018360:Crystallography, X-Ray; D004583:Electrons; D006418:Heme / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D006418:Heme
keywords: X-ray diffraction; crystal structure; enzymes; iron; porphyrins