Opportunities and challenges of applying advanced X-ray spectroscopy to actinide and lanthanide N-donor ligand systems

N-donor ligands such as n-Pr-BTP [2,6-bis­(5,6-di­propyl-1,2,4-triazin-3-yl)­pyridine] preferentially bind trivalent actinides (An(3+)) over trivalent lanthanides (Ln(3+)) in liquid–liquid separation. However, the chemical and physical processes responsible for this selectivity are not yet well understood. Here, an explorative comparative X-ray spectroscopy and computational (L (3)-edge) study for the An/Ln L (3)-edge and the N K-edge of [An/Ln(n-Pr-BTP)(3)](NO(3))(3), [Ln(n-Pr-BTP)(3)](CF(3)SO(3))(3) and [Ln(n-Pr-BTP)(3)](ClO(4))(3) complexes is presented. High-resolution X-ray absorption near-edge structure (HR-XANES) L (3)-edge data reveal additional features in the pre- and post-edge range of the spectra that are investigated using the quantum chemical codes FEFF and FDMNES. X-ray Raman spectroscopy studies demonstrate the applicability of this novel technique for investigations of liquid samples of partitioning systems at the N K-edge.