Stability Trend Analysis of Light Lanthanide Complexes with a Fluorophenyl-dipicolinamide: A Quantum Chemical Study

Abstract

Abstract Context Extracting actinides from lanthanides is a crucial step in the reprocessing of spent nuclear fuel, and inevitably the interaction of ligands with lanthanides needs to be considered either. N,N'-diethyl-N,N'-di(para)fluorophenyl-2,6-dipicolinamid (FDPA) has been identified as a promising ligand in lanthanide-actinide separation. In this work, the stability trend of light lanthanide (Ln(III), from La(III) to Eu(III)) complexes with FDPA were theoretically analyzed using density functional theory (DFT). The bond strength, nature of bonding and thermodynamic properties were investigated in an attempt to reveal the affinities for Ln(III). Based on our calculations, the FDPA binds to Ln(III)s via closed-shell interactions. The bond strength for most Ln(III) complexes gradually decreases, which trend consistent with water, making them extractable with little selectivity. Exceptionally, FDPA shows significant selectivity for Ce(III) and Nd(III) due to energetical exclusion.Methods All the DFT calculations were carried out by Gaussian 09 E.01 program suite. The SC-ECP and ECP28MWB-SEG basis sets were used for all the Ln(III)s, and the 6-311g(d,p) basis set was used for other atoms. Vibrational frequency calculations can ensure the structure obtained are minimized on the potential energy surface. The QTAIM parameters were measured by Multiwfn 3.8.