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Synthesis and characterization of the asymmetrically coordinated dinuclear complex [{L(Ph2acac)FeIII}(μ-O){FeIII(Cl4-cat)L}](ClO4) and its one-electron reduced and oxidized forms. Models for dinuclear non-heme active sites

Authors
  • Müller, Michael1
  • Weyhermüller, Thomas1
  • Bill, Eckhard1
  • Wieghardt, K.1
  • 1 Max-Planck-Institut für Strahlenchemie, P. O. Box 10 13 65, D-45413 Mülheim an der Ruhr, Germany Tel.: +49-208-306-3609; Fax: +49-208-3063952; e-mail: [email protected], DE
Type
Published Article
Journal
JBIC Journal of Biological Inorganic Chemistry
Publisher
Springer-Verlag
Publication Date
Feb 01, 1998
Volume
3
Issue
1
Pages
96–106
Identifiers
DOI: 10.1007/s007750050211
Source
Springer Nature
Keywords
License
Yellow

Abstract

The asymmetrically coordinated complex [{L(Ph2acac)FeIII}(μ-O){FeIII(Cl4-cat)L}](BPh4)·1.5toluene has been synthesized and structurally characterized (Ph2acac–=1,3-diphenylpropane-1,3-dionate, Cl4-cat2–=tetrachlorocatecholate, L=1,4,7-trimethyl-1,4,7-triazacyclononane). This species can be electrochemically oxidized and reduced by one electron, respectively, yielding two species which both have an S=1/2 ground state. It is shown that the oxidation is ligand-centered, affording a coordinated semiquinonate(1–) ligand with S=1/2 which is antiferromagnetically coupled to a high-spin FeIII ion (S=5/2) yielding an S=2 state which, in turn, is antiferromagnetically coupled (through the oxo bridge) to the second high-spin FeIII ion (S=5/2) yielding the observed S=1/2 ground state. In contrast, the reduction is metal-centered generating a mixed-valent species with an [FeIII-O-FeII]3+ core; intramolecular antiferromagnetic coupling again produces an S=1/2 ground state. The symmetrical complex [{LFeIII(Ph2acac)}2(μ-O)](ClO4)2 has also been synthesized, as have the mononuclear species [LFeII(Ph2acac)Cl] and [LFeIII(aacac)Cl](ClO4)·1 mesitylene [aacac–=3-(9-anthryl)acetylacetonate(1–)], all of which have been characterized by X-ray crystallography. The magnetism, the Mössbauer-, EPR-, and UV-VIS-spectra and the electrochemistry of complexes are reported.

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