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

Abstract

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 (An³⁺) over trivalent lanthanides (Ln³⁺) 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 (L₃-edge) study for the An/Ln L₃-edge and the N K-edge of [An/Ln(n-Pr-BTP)₃](NO₃)₃, [Ln(n-Pr-BTP)₃](CF₃SO₃)₃ and [Ln(n-Pr-BTP)₃](ClO₄)₃ complexes is presented. High-resolution X-ray absorption near-edge structure (HR-XANES) L₃-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.

Keywords: CC-RIXS; HR-XANES; X-ray Raman; actinides; lanthanides; partitioning.