Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2’:6’,2’’-terpyridine ligand: implications for actinide(III) /lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of the 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO22+) ion were obtained by X-ray crystallographic analysis, and showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligand

Dendronized Polymers with Peripheral Oligo(ethylene oxide) Chains: Thermoresponsive Behavior and Shape Anisotropy in Solution

International audienc

Lanthanide cation binding properties of homooxacalixarene diethylamide derivatives

International audienceThe binding properties of two homooxacalixarene diethylamides (1b and 2b) , in the cone conformation, for lanthanide cations were investigated. These properties were assessed by extraction studies and stability constant measurements in methanol, using spectrophotometric and potentiometric techniques. Microcalorimetric studies of La3+, Pr3+, Eu3+ and Gd3+ complexes in the same solvent were also performed. Proton NMR titrations with the representative lanthanides La3+, Eu3+ and Yb3+ were also carried out to establish the sites of interaction of the ligands with the cations. The analogous derivative (3b) of p-tert-butylcalix[4]arene was also studied and the results of the three compounds are compared. Diethylamide 1b is the strongest binder, showing some preference for the light lanthanides in extraction, but exhibiting practically no selectivity in complexation. 1b displays the highest stability constant values ever found with this ligand (log β = 8.6 - 9.2). In contrast, 2b shows lower extraction and stability constant values, but it is a more selective ligand, showing a clearer preference for the light lanthanides. Proton NMR titrations confirm the formation of 1:1 complexes between the amides and the cations studied, also indicating that they should be located inside the cavity defined by the phenoxy and the carbonyl oxygen atoms

Model studies toward trivalent cation binding by appropriately functionalized calix[4]arenes

Molecular modeling and molecular dynamics of a series of calix[4]arene tetracarboxylic acids and tricarboxylic acid monoamides revealed that in an aqueous environment the phenolic oxygen atoms do not participate in the complexation of Ac3+. This observation led to the design and synthesis of new calix[4]arene based ionophores, containing multiple glycine units, having an increased number of potential donor sites. Potentiometric titrations in methanol with La3+ as a non-radioactive model for Ac3+ indicated that, although the level of complexation is high for all ligands, a new calix[4]arene derivative 5 is superior at pH < 4. \u