Pyrrolidine-Derived Phenanthroline Diamides: An Influence of Fluorine Atoms on the Coordination of Lu(III) and Some Other f-Elements and Their Solvent Extraction

Abstract

Three pyrrolidine-derived phenanthroline diamides were studied as ligands for lutetium trinitrate. The structural features of the complexes have been studied using various spectral methods and X-ray. The presence of halogen atoms in the structure of phenanthroline ligands has a significant impact on both the coordination number of lutetium and the number of solvate water molecules in the internal coordination sphere. The stability constants of complexes with La(NO3)3, Nd(NO3)3, Eu(NO3)3, and Lu(NO3)3 were measured to demonstrate higher efficiency of fluorinated ligands. NMR titration was performed for this ligand, and it was found that complexation with lutetium leads to an approximately 13 ppm shift of the corresponding signal in the 19F NMR spectrum. The possibility of formation of a polymeric oxo-complex of this ligand with lutetium nitrate was demonstrated. Experiments on the liquid–liquid extraction of Am(III) and Ln(III) nitrates were carried out to demonstrate advantageous features of chlorinated and fluorinated pyrrolidine diamides.

First 4,7-oxygenated 1,10-phenanthroline-2,9-diamides: synthesis, tautomerism and complexation with REE nitrates

“…The LM 2 stoichiometry is most likely the result of the formation of complexes in the form of tight ion pairs, [LM] + M − . We have repeatedly observed this phenomenon earlier when studying the coordination chemistry of phenanthrolinediamides toward lanthanides 11,20,21 and actinides. 9,12 At the same time, the existence of L 3 M and even L 4 M complexes is more questionable.…”

“…For example, the introduction of halogen atoms at these positions affects the coordination chemistry of the ligands and the structure of the resulting complexes with rare-earth element (REE) nitrates. 20,21 Along with this, DAPhen which is functionalized at position 4 or 4,7 is still a rare specimen, especially oxygenated derivatives.…”

First 24-Membered Macrocyclic 1,10-Phenanthroline-2,9-Diamides—An Efficient Switch from Acidic to Alkaline Extraction of f-Elements

“…The extraction properties of 1,10-phenanthroline-2,9-dicarboxylic acid diamides toward f-elements can be customized by varying the structure of diamide fragments and the modification of the phenanthroline core [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. We demonstrated earlier valuable properties of diamides prepared from cyclic amines [ 40 , 41 , 42 ].…”

4-Oxo-7-fluoro-1,10-phenanthroline-2,9-diamides: Synthesis, Structural Features, Lanthanide Complexes, and Am(III)/Ln(III) Solvent Extraction

“…In this study, we aim to develop a synthesis for unsymmetrical phenanthrolines with different X and Y substituents at positions 4 and 7, which possess opposite electronic effects. Earlier we reported on the synthesis of the first diamides of 4,7-difluoro-1,10-phenanthroline-2,9-dicarboxylic acid, discussed the structure of their complexes with REE nitrates, and investigated the extraction properties in the separation of the Am­(III)/Eu­(III) pair …”

“…Earlier we reported 62 on the synthesis of the first diamides of 4,7-difluoro-1,10-phenanthroline-2,9-dicarboxylic acid, discussed the structure of their complexes with REE nitrates, and investigated the extraction properties in the separation of the Am(III)/Eu(III) pair. 63…”