1,10-Phenanthroline and Non-Symmetrical 1,3,5-Triazine Dipicolinamide-Based Ligands For Group Actinide Extraction

The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5-triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza-heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non-symmetric 2-substituted-4,6-di(6-picolin-2-yl)-1,3,5-triazines from the 1,3,5-triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (U-VI, Np-V,Np-VI, Am-III, Cm-III, and Pu-IV) from an acidic solution (3 M HNO3). Phenanthroline-based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre-organization of the dipicolinamide-1,10-phenanthroline architecture.