Varbanov S.Tashev E.Vassilev N.Atanassova M.Lachkova V.Tosheva T.Shenkov S.Dukov I.2024-07-102024-07-102024-07-102024-07-102017-01-010277-538710.1016/j.poly.2017.06.013SCOPUS_ID:85021369490https://rlib.uctm.edu/handle/123456789/433A 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, 1H and 31P{H} NMR spectroscopy and ESI-mass-spectrometry. The 1H and 31P{H} NMR spectra indicate that at room temperature in DMSO-d6 and 1,1,2,2-tetrachloroethane-d2 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 LnP3·S species. A very large synergistic enhancement (up to 105) 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, 1H NMR and 31P NMR data.enArticle