Valence-to-Core X-ray Emission Spectroscopy: A Sensitive Probe of the Nature of a Bound Ligand

The sensitivity of iron K beta X-ray emission spectroscopy (XES) to the nature of the bound ligands (sigma-donating, pi-donating, and pi-accepting) has been explored. A combination of experiment and theory has been employed, with a DFT approach being utilized to elucidate ligand effects on the spectra and to assign the spectral intensity mechanisms. Knowledge of the various contributions to the spectra allows for a deeper understanding of spectral features and demonstrates the sensitivity of this method to the identity of the interacting ligands. The potential of XES for identifying intermediate species in nonheme iron enzymes is highlighted.