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

Abstract

A terdentate multiple N donor ligand, 2,6-bis(1 H-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 N,N, N',N'-tetra- n-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+.