First Report on the Separation of Trivalent Lanthanides from Trivalent Actinides Using an Aqueous Soluble Multiple N‑Donor Ligand, 2,6-bis(1<i>H</i>‑tetrazol-5-yl)pyridine: Extraction, Spectroscopic, Structural, and Computational Studies

A terdentate multiple N donor ligand, 2,6-bis­(1<i>H</i>-tetrazol-5-yl)­pyridine (H₂BTzP), was synthesized, and its complexation with trivalent americium, neodymium, and europium was studied using single-crystal X-ray diffraction, attenuated total reflectance-fourrier transform infrared spectroscopy, time-resolved fluorescence spectroscopy, UV–vis absorption spectrophotometry. Higher complexation strength of BTzP toward trivalent actinide over lanthanides as observed from UV–vis spectrophotometric study resulted in an effective separation of Am³⁺ and Eu³⁺ in liquid–liquid extraction studies employing <i>N,N,<i>N</i>′,N′</i>-tetra-<i>n</i>-octyl diglycolamide in the presence of BTzP as the aqueous complexant. The selectivity of BTzP toward Am³⁺ over Eu³⁺ was further investigated by DFT computations, which indicated higher metal–ligand overlap in the Am³⁺ complex as indicated from the metal–nitrogen bond order and frontier molecular orbital analysis of the BTzP complexes of Am³⁺ and Eu³⁺