Theoretical investigation the selective separation of Am(III)/Eu(III) by bis-succinamides ligands

The selective separation of Am(III) over Eu(III) from high-level radioactive liquid waste using four bis-succinamide ligands (THE-BisSCA, L¹; THDM-BisSCA, L²; THDPh-BisSCA, L³; THDⁱ⁻P-BisSCA, L⁴) was explored with density functional theory. Ligands with phenyl groups near the nitrogen, particularly L³, showed the highest Eu(III) affinity. The π bonds orbitals of the benzene ring may conjugate with the long pair N-2p orbital, and this special p-π conjugation effect can lead to charge transfer from benzene ring to the donor N atoms on L³ ligand, resulting a lower energy and more stable structure of the complex formed with the L³ ligand compared to other complexes. Thermodynamic analysis corroborates L³ has Eu(III) preference, offering valuable guidance for efficient Am(III) and Eu(III) separation with these ligands.