title: Iron complexes of new pentadentate ligands containing the 1,4,7-triazacyclononane-1,4-diacetate motif. spectroscopic, electro-, and photochemical studies.
abstract: Three new pentadentate, pendent arm macrocycles containing the 1,4,7-triazacyclononane-1,4-diacetate motif have been synthesized, and their coordination chemistry with Fe(III) has been investigated. Eight new octahedral Fe(III) complexes containing chloro, azido, or mu-oxo ligands have been synthesized, five of which have been characterized by X-ray crystallography. Spectroscopic characterization of these octahedral Fe(III) complexes by UV-vis, IR, electrochemistry, EPR, magnetic susceptibility, and zero-field Mössbauer measurements firmly establishes the high-spin state of the iron in all complexes. Electrochemistry studies of the azido-Fe(III) complexes show that they can be reversibly oxidized to the corresponding Fe(IV) species at -20 degrees C, and Fe(II), Fe(III), and Fe(IV) species show characteristic IR and UV-vis profiles. Photolysis of one of the azido complexes was studied as a function of temperature (room temperature vs 77 K) and wavelength (480, 419, and 330 nm). Photoreduction to a high-spin Fe(II) species occurs under all conditions, which is proposed to be the dominant photochemical pathway generally available to high-spin ferric azido complexes.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany. ysong@chem.gla.ac.uk
authors.forename: Yu-Fei
authors.initials: YF
authors.lastname: Song
authors.forename: John F
authors.initials: JF
authors.lastname: Berry
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Eberhard
authors.initials: E
authors.lastname: Bothe
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Karl
authors.initials: K
authors.lastname: Wieghardt
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D010777:Photochemistry / Q000379:methods*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: C519451:1,4,7-triazacyclononane-1,4-diacetate; D005290:Ferric Compounds; D006571:Heterocyclic Compounds; D008024:Ligands