title: Synthesis, X-ray crystal structure, and redox and electronic properties of iron(III)-polyimidazole complexes relevant to the metal sites of iron proteins.
abstract: A new tripod N(3) ligand (L), containing three imidazole rings, was synthesized in good yield. At variance with usual aromatic ligands with N(2) or N(3) donor sets such as pyridine or pyrazole derivatives, L stabilizes the Fe(III) oxidation state. The corresponding iron(III) complexes [Fe(L)Cl(3)] (1) and [Fe(L)(2)](ClO(4))(3) (2) were prepared and characterized by X-ray structural analysis and spectroscopic methods. The coordination environment around all the Fe(III) centers has a distorted octahedral geometry. [Fe(L)Cl(3)] (1) belongs to the monoclinic system, space group P2(1)/n, a = 9.7406(5) A, b = 17.207(2) A, c = 14.615(2) A, beta = 104.448(9)(o) Z = 4, V = 2372.1(4) A(3); R = 0.044, R(w) = 0.055. [Fe(L)(2)](ClO(4))(3) (2) belongs to the monoclinic system, space group P2(1)/c, a = 16.1057(15) A, b = 11.1079(12) A, c = 26.283(2) A, beta = 102.062(10)(o), Z = 4, V = 4598.2(8) A(3); R = 0.0465, R(w) = 0.0902. The Fe-N((i)PrIm) bond lengths are systematically longer than the Fe-N(MeIm) ones. Compound 2 is a highly anisotropic low-spin Fe(III) complex displaying a rather unusual EPR spectrum with a sharp signal at g = 3.5 and a broad one at g approximately 1.6. The fitting of this EPR spectrum is discussed.
authors.affiliation: Laboratoire de chimie et biochimie pharmacologiques et toxicologiques (CNRS UMR8601), Université René Descartes, 45, rue des Saints Pères, 75270 Paris Cedex 06, France.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Chauvin
authors.forename: Yves-Michel
authors.initials: YM
authors.lastname: Frapart
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Vaissermann
authors.forename: Bruno
authors.initials: B
authors.lastname: Donnadieu
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Tuchagues
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Chottard
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008667:Metalloproteins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011506:Proteins
chemical_list: D005290:Ferric Compounds; D007093:Imidazoles; D008024:Ligands; D008667:Metalloproteins; D011506:Proteins; D007501:Iron