X‐ray Magnetic Circular Dichroism Spectroscopy Applied to Nitrogenase and Related Models: Experimental Evidence for a Spin‐Coupled Molybdenum(III) Center

Nitrogenase enzymes catalyze the reduction of atmospheric dinitrogen to ammonia utilizing a Mo‐7Fe‐9S‐C active site, the so‐called FeMoco cluster. FeMoco and an analogous small‐molecule (Et4N)[(Tp)MoFe3S4Cl3] cubane have both been proposed to contain unusual spin‐coupled MoIII sites with an S(Mo)=1/...

Full description

Saved in:
Bibliographic Details
Published in:Angewandte Chemie 2019-07, Vol.131 (28), p.9473-9477
Main Authors: Kowalska, Joanna K., Henthorn, Justin T., Van Stappen, Casey, Trncik, Christian, Einsle, Oliver, Keavney, David, DeBeer, Serena
Format: Article
Language:English
Subjects:
Ammonia
Atmospheric models
Chemistry
Circular dichroism
Clusters
Configurations
Cubane
Dichroism
FeMo-Cofaktor
Iron
Low temperature
Magnetic fields
MoFe protein
Molybdenum
Nitrogenase
Proteins
Selectivity
Spectroscopy
Spectrum analysis
Spinkopplung
Stickstoff-Fixierung
XMCD-Spektroskopie
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Nitrogenase enzymes catalyze the reduction of atmospheric dinitrogen to ammonia utilizing a Mo‐7Fe‐9S‐C active site, the so‐called FeMoco cluster. FeMoco and an analogous small‐molecule (Et4N)[(Tp)MoFe3S4Cl3] cubane have both been proposed to contain unusual spin‐coupled MoIII sites with an S(Mo)=1/2 non‐Hund configuration at the Mo atom. Herein, we present Fe and Mo L3‐edge X‐ray magnetic circular dichroism (XMCD) spectroscopy of the (Et4N)[(Tp)MoFe3S4Cl3] cubane and Fe L2,3‐edge XMCD spectroscopy of the MoFe protein (containing both FeMoco and the 8Fe‐7S P‐cluster active sites). As the P‐clusters of MoFe protein have an S=0 total spin, these are effectively XMCD‐silent at low temperature and high magnetic field, allowing for FeMoco to be selectively probed by Fe L2,3‐edge XMCD within the intact MoFe protein. Further, Mo L3‐edge XMCD spectroscopy of the cubane model has provided experimental support for a local S(Mo)=1/2 configuration, demonstrating the power and selectivity of XMCD. Spin‐Effekte: Fe‐L2,3‐Kanten‐ und Mo‐L3‐Kanten‐XMCD‐Spektroskopie wurden kombiniert, um den FeMo‐Cofaktor des Nitrogenase‐Enzyms und einen elektronisch verwandten Modellkomplex zu untersuchen. Die experimentellen Befunde stützen eine Nicht‐Hund‐Konfiguration am Mo‐Atom. XMCD=Zirkularer magnetischer Röntgendichroismus.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201901899