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Electronic characterization of redox (non)-innocent Fe 2 S 2 reference systems: a multi K-edge X-ray spectroscopic study

DOI: 10.1039/C9RA08903A DOI Help

Authors: J. P. H. Oudsen (University of Amsterdam) , B. Venderbosch (University of Amsterdam) , T. J. Korstanje (University of Amsterdam) , M. Tromp (Zernike Institute for Advanced Materials)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Rsc Advances , VOL 10 , PAGES 729 - 738

State: Published (Approved)
Published: January 2020
Diamond Proposal Number(s): 13069

Open Access Open Access

Abstract: Di-iron dithiolate hydrogenase model complexes are promising systems for electrocatalytic production of dihydrogen and have therefore been spectroscopically and theoretically investigated in this study. The direct effect of ligand substitution on the redox activity of the complex is examined. In order to understand and eventually optimize such systems, we characterised both metal and ligand in detail, using element specific X-ray absorption Fe- and S-K edge XAS. The (electronic) structure of three different [Fe2S2] hydrogenase systems in their non-reduced state was investigated. The effect of one- and two-electron reduction on the (electronic) structure was subsequently investigated. The S K-edge XAS spectra proved to be sensitive to delocalization of the electron density into the aromatic ring. The earlier postulated charge and spin localization in these complexes could now be measured directly using XANES. Moreover, the electron density (from S K-edge XANES) could be directly correlated to the Fe–CO bond length (from Fe K-edge EXAFS), which are in turn both related to the reported catalytic activity of these complexes. The delocalization of the electron density into the conjugated π-system of the aromatic moieties lowers the basicity of the diiron core and since protonation occurs at the diiron (as a rate determining step), lowering the basicity decreases the extent of protonation and consequently the catalytic activity.

Subject Areas: Materials, Chemistry

Instruments: B18-Core EXAFS