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Science Highlight
Neese Faculty Page


30 June 2005


  Super Oxidized Iron

summary written by Heather Woods, SLAC Communication Office

Núria Aliaga-Alcalde,1 Serena DeBeer George,2 Bernd Mienert,1 Eckhard Bill,1 Karl Wieghardt1 and Frank Neese1

1Max Planck Institut für Bioanorganische Chemie, Mülheim an der Ruhr, Germany
2Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, CA


Iron metals oxidize to rust, losing electrons and gaining positive charge. Iron metals typically exist in an oxidation state of +2 or +3 (2 or 3 electrons less than a neutral iron atom). However, chemists have long thought that iron compounds with even higher oxidation states play important roles in enabling chemical reactions in metal-containing proteins. In recent years, scientists have been able to synthesize and characterize numerous iron +4 compounds [written Fe(IV)], but knew little about iron +5, Fe(V), compounds. Now researchers, using facilities at SSRL, have characterized a genuine Fe(V) species, which is even more oxidized and more positively charged than the iron in rust [Fe(III)] or Fe(IV).

Frank Neese (Muelheim), Karl Wieghardt (Muelheim), Serena DeBeer George (SSRL) and co-workers, used x-ray absorption spectroscopy (XAS), combined with other spectroscopic and computational results, to study the properties of the compound. Tuned to be sensitive to iron, XAS can provide direct information about the charge of the iron atom. The XAS "K-edge" corresponds to the excitation of the most tightly bound electrons in the iron atom. As the iron atom becomes more oxidized, the energy position of the K-edge increases, providing a signature for Fe(V). This study represents the first characterization of an Fe(V) species by XAS and serves as an important experimental marker for characterization of other Fe(V) species.