An Insight into the Complexation of Trivalent Americium Vis‐à‐Vis Lanthanides with Bis(1,2,4‐triazinyl)bipyridine Derivatives

Abstract

Complexation of Am3+ and Ln3+ (La3+, Eu3+, and Er3+) with two bis(1,2,4‐triazinyl)bipyridine (C2BTBP, C5BTBP) derivatives has been studied in acetonitrile medium with use of various experimental techniques such as electrospray ionization mass spectrometry (ESI‐MS), time‐resolved fluorescence spectroscopy (TRFS), UV/Vis spectrophotometry, and solution calorimetry. Metal–ligand stoichiometries and conditional stability constants of these complexes were determined. To the best of our knowledge, this is the first report on the complexation of Am3+ with any of the BTBP derivatives with use of UV/Vis spectrophotometric titration to determine the conditional stability constants. Density functional theory (DFT) calculations are carried out on the An3+ (U3+ and Am3+) and Ln3+ (La3+, Nd3+, Eu3+, Er3+, and Lu3+) complexes of BTBP in order to understand the difference between the bonding in actinide and lanthanide complexes. The results indicate a stronger covalent interaction in the An–N bonds as compared to the Ln–N bonds, which leads to an actinide selectivity of this class of ligands.