Hexa(1,1,3,3-tetramethyl-butyl)-hexakis(dimethylphosphinoyl-methoxy)-calix[6]arene: synthesis, characterization and implementation as a synergistic agent in the solvent extraction of lanthanoids

Abstract A new lower rim phosphorus-containing calix[6]arene with six dimethyl-methylene phosphine oxide groups, namely 5,11,17,23,29,35-hexa(1,1,3,3-tetramethyl-butyl)-37,38,39,40,41,42-hexakis-(dimethylphosphinoylmethyleneoxy)-calix[6]arene ( S ), has been synthesized and characterized. The structure of this calix[6]arene was identified and confirmed by elemental analysis, IR, 1 H and 31 P{H} NMR spectroscopy and ESI-mass-spectrometry. The 1 H and 31 P{H} NMR spectra indicate that at room temperature in DMSO- d 6 and 1,1,2,2-tetrachloroethane-d 2 solutions, S exists as a mixture of conformers. The synergistic solvent extraction of selected lanthanoid ions (La, Nd, Eu, Ho, Lu) with 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone ( HP ) and S in chloroform has been studied. It was found that in the presence of S the lanthanoid ions have been extracted as LnP 3 · S species. A very large synergistic enhancement (up to 10 5 ) was established. The stoichiometry and the structure of the solid complex of Eu(III) with HP and S (1:3:1) were proposed based on elemental analysis, IR, 1 H NMR and 31 P NMR data.