Soft X-ray emission and absorption—a comparative study on the sensitivity to oxidation state and ligand environment of transition metal complexes

In order to understand the function of transition metals, which are a necessary part of many catalytic cycles, it is necessary to obtain information about oxidation states, ligand environment, and local structure surrounding the metal centers. L-Edge X-ray absorption spectroscopy, which probes the unoccupied 3d levels, has been shown to be a sensitive probe of the oxidation and spin state of transition metal sites. As soft X-ray fluorescence (SXF) instead probes the occupied states, an investigation of how this complementary technique can be used to probe transition metal centers was conducted and the results are presented here. SXF is found to be very sensitive to ligand environment and relatively insensitive to electronic geometry and metal oxidation state. Potential applications of this technique to systems such as metalloproteins and manganese–lithium batteries are discussed.