title: Successful stabilization of the elusive species {FeNO}8 in a heme model.
abstract: Nitroxyl (HNO/NO(-)) heme-adducts have been postulated as intermediates in a variety of catalytic processes carried out by different metalloenzymes. Hence, there is growing interest in obtaining and characterizing heme model nitroxyl complexes. The one-electron chemical reduction of the {FeNO}(7) nitrosyl derivative of Fe(III)(TFPPBr(8))Cl, Fe(II)(TFPPBr(8))NO (1) (TFPPBr(8) = 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-[Tetrakis-(pentafluorophenyl)]porphyrin) with cobaltocene yields the significantly stable {FeNO}(8) complex, [Co(C(5)H(5))(2)](+)[Fe(TFPPBr(8))NO](-) (2). Complex 2 was isolated and characterized by UV-vis, FTIR, (1)H and (15)N NMR spectroscopies. In addition, DFT calculations were performed to get more insight into the structure of 2. According to the spectroscopic and DFT results, we can state unequivocally that the surprisingly stable complex 2 is the elusive {FeNO}(8) species. Both experimental and computational data allow to assign the electronic structure of 2 as intermediate between Fe(II)NO(-) and Fe(I)NO, which is contrasted with the predominant Fe(II)NO(-) character of known nonheme {FeNO}(8) complexes. The enhanced stability achieved for a heme model {FeNO}(8) is expected to allow further studies related to the reactivity of this elusive species.
authors.affiliation: Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, INQUIMAE-CONICET, Ciudad Universitaria, Pab. 2, C1428EHA Buenos Aires, Argentina.
authors.forename: Juan
authors.initials: J
authors.lastname: Pellegrino
authors.forename: Sara E
authors.initials: SE
authors.lastname: Bari
authors.forename: Damián E
authors.initials: DE
authors.lastname: Bikiel
authors.forename: Fabio
authors.initials: F
authors.lastname: Doctorovich
mesh_terms: D003198:Computer Simulation; D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006418:Heme / Q000737:chemistry*; D008956:Models, Chemical; D009589:Nitrogen Oxides / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D009589:Nitrogen Oxides; D011166:Porphyrins; D006418:Heme; C039900:nitroxyl