Browsing by Author "Varbanov S."
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Item Are fancy acidic or neutral ligands really needed for synergism in ionic liquids? A comparative study of lanthanoid extraction in CHCl3 and an ionic liquid(2015-07-27) Atanassova M.; Kurteva V.; Lubenov L.; Varbanov S.; Billard I.The study of trivalent lanthanoid (La, Nd, Eu, Ho and Lu) extraction by two individual ligands, one acidic such as a pyrazolone derivative, 3-methyl-1-phenyl-4-(4-phenylbenzoyl)-pyrazol-5-one (HL), and one neutral such as 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(dimethylphosphinoylmethoxy)calix[4]arene (SIV), was performed in CHCl3 and in one ionic liquid, IL 1-methyl-1,3-butylimidazolium-bis(trifluoromethanesulfonyl)imide ([C1C4im][Tf2N]), in order to establish and examine the impact of the diluent on individual and synergistic extraction processes. Chloride aqueous medium and constant ionic strength μ = 0.1 M were set in both cases. The parameters of the extraction processes were determined. Comparison between the two diluents was made on the basis of (i) composition of the extracted species: LnL3·HL in CHCl3vs. LnL3 in IL with HL as a single extractant (L- represents the HL anion), and LnL3·SIV in the presence of the phosphorus-containing calix[4]arene in both diluents; and (ii) values of the equilibrium constants and the synergistic enhancements; the separation factors between metals were evaluated as well. The IL medium appears far superior to the molecular solvent in terms of individual and overall synergistic extraction efficiencies. However, the huge differences in extraction efficiencies observed in CHCl3 for chemically different ligands are erased in the IL medium, thus modifying the lever arms on which chemists should rely in order to obtain even better extracting systems in ionic liquid media.Item 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(2017-01-01) Varbanov S.; Tashev E.; Vassilev N.; Atanassova M.; Lachkova V.; Tosheva T.; Shenkov S.; Dukov I.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, 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.Item Zinc Complexes of Dimethyl(phthalimidomethyl)phosphine Oxide(1994-02-01) Varbanov S.; Russeva E.; Ganchev A.