Combined X-ray Absorption and X-ray Emission Spectroscopy Study of Synthetic [Fe4S4] Cubane Complexes at the S K-edge

Iron-sulfur (FeS) clusters are ubiquitous metallocofactors, which drive the crucial biological processes to enable life on earth, ranging from iron homeostasis and gene regulation to multielectron transfer and enzymatic catalysis. Among them, cuboidal Fe4S4 clusters bearing cysteine ligands are the most represented structures and are found in a large number of biological systems as mediators of long-range electron transfers or directly as catalytic active sites of enzymes. It has been reported that the redox processes in mono- and multinuclear iron thiolate and sulfide complexes involve extensive electronic relaxations that are greatly affected by the ligand, which can contribute significantly to the thermodynamics and kinetics of the electron transfer. Therefore, in the current study we aim to investigate the sulfur ligand spectra of our Fe4S4 complexes, which can be used to gauge the contributions of super- and double-exchange to the valence delocalization in these systems.