Integration of EXAFS, Spectroscopic, and DFT Techniques for Elucidation of the Structure of Reactive Diiron Compounds

Mark I. Bondin; Stacey J. Borg; Mun Hon Cheah; Garry Foran; Stephen P. Best

doi:10.1071/CH06022

RESEARCH ARTICLE

Previous Next Contents Vol 59(4)

Integration of EXAFS, Spectroscopic, and DFT Techniques for Elucidation of the Structure of Reactive Diiron Compounds

Mark I. Bondin ^A , Stacey J. Borg ^A , Mun Hon Cheah ^A , Garry Foran ^B and Stephen P. Best ^A ^C

+ Author Affiliations

- Author Affiliations

^A School of Chemistry, University of Melbourne, Parkville VIC 3010, Australia.

^B Australian Nuclear Science and Technology Organisation (ANSTO), Menai NSW 2234, Australia.

^C Corresponding author. Email: spbest@unimelb.edu.au

Australian Journal of Chemistry 59(4) 263-272 https://doi.org/10.1071/CH06022
Submitted: 19 January 2006 Accepted: 12 April 2006 Published: 1 May 2006

Abstract

Strategies for modelling the EXAFS of a range of compounds with structural features common to the diiron subsite of the [FeFe] hydrogenase H-centre are compared, and this has allowed identification of highly constrained models that still permit expression of the main structural characteristics of the compounds. Despite giving self-consistent values of the iron–scatterer distances, the EXAFS analysis fails to give unambiguous identification of the stereochemistry and composition of the compounds, and this necessitates the integration of results obtained using other spectroscopic and computational approaches. The combination of infrared spectroscopy, EXAFS, and ab initio DFT calculations are shown to provide a particularly potent approach for the study of metal carbonyl compounds of this class. In this case the EXAFS-derived iron–scatterer distances provide the basis of the starting point for DFT geometry optimization calculations, and the final distances together with the calculated infrared spectrum provides a means of validating the computed geometry. The approach is applied both to compounds of known structure and to the examination of the unstable products of chemical or electrochemical reduction.

Acknowledgments

S.P.B. gratefully acknowledges the Australian Research Council for funding this research. M.I.B. acknowledges the award of an Australian Postgraduate Research Award. Dr Harry Quiney is thanked for the invaluable assistance given in the setting up and evaluation of the ab initio calculations. This work was performed at the Australian National Beamline Facility with support from the Australian Synchrotron Research Program, which is funded by the Commonwealth of Australia under the Major National Research Facilities Program. Support of the Victorian Institute for Chemical Sciences High Performance Computing Facility is gratefully acknowledged.

References

Integration of EXAFS, Spectroscopic, and DFT Techniques for Elucidation of the Structure of Reactive Diiron Compounds

Abstract

Acknowledgments

Subscriber Login