Recent Research Developments

Index of Recent Research News
May 25th, 2005
Low Temperature Trapping of a Diiron-Superoxo Intermediate

    The initial step in oxygen activation catalyzed by metalloproteins typically involves the the formation of a metal O2 adduct, often proposed to be a metal-superoxo species. For nonheme diiron enzymes, such a transient species has been proposed but not yet observed, not even for synthetic models. In a recent article published in Proc. Natl. Acad. Sci. U.S.A. (2005, 102, 5340), postdoctoral associate Xiaopeng Shan and Professor Lawrence Que, Jr. reported the successful trapping of the first example of a diiron(II,III) superoxo species in the reaction of [Fe2(μ-OH)2(6-Me3-TPA)2]2+ (6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine) with O2 in CH2Cl2 at -80 °C prior to the formation of the previously characterized [Fe2(μ-O)(μ-1,2-O2)(6-Me3-TPA)2]2+ peroxo intermediate. This superoxo species has been characterized by resonance Raman spectroscopy to show its ν(O-O) at 1310 cm-1 with a -71 cm-1 18O isotope shift. A doublet peak pattern for the 16O18O isotopomer of this species in mixed-isotope Raman experiments strongly suggests that the superoxide ligand is bound end-on. Further studies revealed that this superoxo species, unlike the subsequent peroxide, is capable to oxidize 2,4-di-tert-butylphenol through a proton coupled electron transfer mechanism.

* This page is updated every two weeks.
Next scheduled update: June 8th, 2005.
    The University of Minnesota is an equal opportunity educator and employer.

    Copyright 2005 by the Regents of the University of Minnesota.For questions or comments, contact the Chemistry Webmaster or read the University's Online Privacy Statement.