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Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
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Gauging Iron-Sulfur Cubane Reactivity from Covalency: Trends with Oxidation State
Liam Grunwald1, Daniel F Abbott1, Victor Mougel1
1Department of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
JACS Au
|April 26, 2024
Summary
Iron-sulfur cubane clusters reveal Fe K-edge X-ray absorption (XAS) as a key indicator for oxidation states. Sulfur K-edge HERFD-XAS tracks Fe-S bond covalency changes with redox state.
Area of Science:
- Inorganic Chemistry
- Bioinorganic Chemistry
- Materials Science
Background:
- Cubane-type iron-sulfur clusters are vital in biological electron transfer and catalysis.
- Understanding their electronic structure is crucial for elucidating their function.
- Traditional methods for determining oxidation states can be complex.
Purpose of the Study:
- To explore X-ray absorption spectroscopy (XAS) for characterizing iron-sulfur cubanes.
- To establish the Fe K-edge position as a reliable indicator of oxidation states.
- To quantify Fe-S bond covalency and its relationship with redox changes.
Main Methods:
- Room-temperature metal and ligand K-edge X-ray absorption spectroscopy (XAS).
- High energy resolution fluorescence detected XAS (HERFD-XAS) at the S K-edge.
- Analysis of a complete redox series of cubane-type iron-sulfur clusters.
Main Results:
- Fe K-edge position serves as a convenient descriptor for iron oxidation states in these clusters.
- Fe-S(thiolate) covalency increases linearly with hole addition (11 ± 0.4% per hole).
- Fe-S(μ3) covalency shows non-linear changes linked to magnetic exchange, with a distinct electronic structure in the all-ferric state.
Conclusions:
- XAS provides powerful insights into the electronic structure and redox properties of iron-sulfur cubanes.
- Fe K-edge XAS offers a practical alternative for oxidation state determination.
- Variations in Fe-S covalency highlight the complex interplay between electronic structure, magnetism, and reactivity.
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