Bonding Study on the Chemical Separation of Am(III) from Eu(III) by S‑, N‑, and O‑Donor Ligands by Means of All-Electron ZORA-DFT Calculation

We
performed a theoretical investigation for the selectivity of Eu­(III)/Am­(III)
ions depending on the donor atoms by means of all-electron ZORA-DFT
calculation. We estimated their selectivity as the relative stability
in the complex formation reaction. The B2PLYP functional reproduced
the experimental selectivity in which S- and N-donor ligands favor
Am­(III) ion, but O-donor ligand favors Eu­(III) ion. Mulliken’s
bond overlap population analysis revealed that the contribution of
the f orbital to the bonding was small or zero for Eu complex, whereas
it was large for Am complex. The bonding nature of the f orbital for
Am ion was the bonding type to S- and N-donor ligands, while it was
the antibonding type to O-donor ligand. It was suggested that the
difference in the bonding nature between the f orbital in the metal
and the donor atoms determines the selectivity of Eu­(III)/Am­(III)
by donor ligands.