Recent Progress in Trivalent Actinide and Lanthanide Solvent Extraction and Coordination Chemistry with Triazinylpyridine N Donor Ligands

Abstract

A follow up to an earlier review on the coordination and extraction of trivalent actinide and lanthanide ions with triazinylpyridine N-donor ligands is presented. It reviews the recent development in the fields of ligand modifications and improvements, considering both hydrophobic compounds (to be used as extracting agents) and hydrophilic compounds (to be used as stripping agents), with a focus on fundamental studies.

Spectroscopic investigation of the covalence of An(iii) complexes with tetraethylcarboxamidopyridine

“…these ions (see the ESI †). Besides the speciation, 1 H NMR delivers information on the complex structure and insights into the bonding properties between the ligand and metal ion.…”

“…Soft N-donor ligands such as bis(triazinyl)pyridine (BTP) or bis (triazinyl)bipyridine (BTBP) are known for their selectivity towards trivalent actinide ions, An(III), over their lanthanide counterparts, Ln(III). 1,2 The molecular origin of this selectivity remains a topic of fundamental scientific interest. Generally speaking, the interaction of organic ligands with An(III) and Ln (III) is mainly driven by electrostatic forces.…”

Influence of a N-Heterocyclic Core on the Binding Capability of N,O-Hybrid Diamide Ligands toward Trivalent Lanthanides and Actinides

“…However, on the basis of the hard–soft acid–base theory, trivalent actinide ions are relatively softer than lanthanide ions and are inclined to form more stable covalent complexes with softer N- or S-donor ligands. ,− Therefore, the highly efficient separation of trivalent actinides over lanthanides can be achieved using those N- or S-donor ligands, and various kinds of extractants for the separation of trivalent lanthanides and actinides have been developed. − Compared with S-containing ligands, those N- and/or O-donor ligands only contain C, H, O, and N elements (the so-called CHON principle) , are completely incinerable and would produce much less solid radioactive waste during the solvent extraction process and thus became the more ideal extractants for the separation of trivalent actinides over lanthanides. ,, …”

Innovative Separations Research and Development Needs for Advanced Fuel Cycles

“…An 80-year evolution of coordination chemistry in actinide separation science has identified six essential pillars that serve as a foundation for a successfully applied ligand (Geist and Panak 2021). Pillar 1 is compatibility.…”