title: Magnetic interactions in the high-spin iron(III) oxooctaethylchlorinato derivative [Fe(oxoOEC)(Cl)] and its pi-cation radical [Fe(oxoOEC.)(Cl)]SbCl6.
abstract: The preparation and characterization of the beta-oxochlorin derivative [3,3,7,8,12,13,17,18-octaethyl-(3H)-porphin-2-onato(2-)]iron(III) chloride, [Fe(oxoOEC)(Cl)], and its pi-cation radical derivative [Fe(oxoOEC.)(Cl)]SbCl6 is described. Both compounds have been characterized by single-crystal X-ray structure determinations, IR, UV/vis/near-IR, and Mössbauer spectroscopies, and temperature-dependent magnetic susceptibility measurements. The macrocycles of [Fe(oxoOEC)(Cl)] and [Fe(oxoOEC.)(Cl)]SbCl6 are both saddled, and [Fe(oxoOEC.)(Cl)]-SbCl6 is slightly ruffled as well. [Fe(oxoOEC)(Cl)] shows a laterally shifted dimeric unit in the solid state, with a mean plane separation of 3.39 A and a lateral shift of 7.39 A. Crystal data for [Fe(oxoOEC)(Cl)]: triclinic, space group P1, Z = 2, a = 9.174(2) A, b = 13.522(3) A, c = 14.838(3) A, alpha = 95.79(3) degrees, beta = 101.46(2) degrees, gamma = 104.84(3) degrees. Upon oxidation, the inter-ring geometric parameters increase; the mean plane separation and the lateral shift of the dimeric unit of [Fe(oxoOEC.)(Cl)]SbCl6 are 4.82 and 8.79 A, respectively. Crystal data for [Fe(oxoOEC.)(Cl)]SbCl6: monoclinic, space group Cc, Z = 4, a = 19.8419(13) A, b = 10.027(2) A, c = 22.417(4) A, beta = 96.13(2) degrees. A broad near-IR absorption band appears at 1415 nm for the pi-cation radical, [Fe(oxoOEC.)(Cl)]SbCl6. Zero-field Mössbauer measurements at 4.2 K for both [Fe(oxoOEC)(Cl)] and [Fe(oxoOEC.)(Cl)]SbCl6 confirmed that the oxidation state of the iron atom did not change upon chemical oxidation. Solid-state magnetic susceptibility measurements for [Fe(oxoOEC.)(Cl)]SbCl6 resulted in a large temperature dependence of the magnetic moment that can best be fit with a model that includes a zero-field splitting parameter of D = 6 cm-1, antiferromagnetic intermolecular iron-iron coupling (2JFe-Fe = -0.14 cm-1), antiferromagnetic intramolecular iron-radical coupling (2JFe-r = -76 cm-1), and antiferromagnetic radical-radical coupling (2Jr-r = -13 cm-1).
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Neal
authors.forename: S J
authors.initials: SJ
authors.lastname: Kang
authors.forename: I
authors.initials: I
authors.lastname: Turowska-Tyrk
authors.forename: C E
authors.initials: CE
authors.lastname: Schulz
authors.forename: W R
authors.initials: WR
authors.lastname: Scheidt
mesh_terms: D000465:Algorithms; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D008280:Magnetics; D008665:Metalloporphyrins / Q000138:chemical synthesis* / Q000737:chemistry*; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: C471211:(3,3,7,8,12,13,17,18-octaethyl-(3H)-porphin-2-onato(2-))iron(III) chloride; D005290:Ferric Compounds; D008665:Metalloporphyrins