Solvent extraction of metal picrates by phosphoryl-containing podands
- Taras Shevchenko Univ., Kiev (Ukraine). Analytical Chemistry Dept.
- Russian Academy of Sciences, Chernogolovka (Russian Federation). Inst. of Physiologically Active Substances
- Brigham Young Univ., Provo, UT (United States). Dept. of Chemistry and Biochemistry
- Univ. Louis Pasteur, Strasbourg (France). Lab. MSM
Using UV spectroscopy, the authors have studied the thermodynamics of extraction of metal picrates M{sup +}Pic{sup {minus}} (M{sup +} = Li{sup +}, Na{sup +} K{sup +}, Rb{sup +}, Cs{sup +}, Tl{sup +} and Ag{sup +}) and M{sup 2+} (Pic{sup {minus}}){sub 2} (M{sup 2+} = Ca{sup 2+}, Sr{sup 2+}, Ba{sup 2+}, Pb{sup 2+} and UO{sub 2}{sup 2+}) from water to a chloroform or to a dichloromethane solution. The extractant molecules are mono-podands R-O-(CH{sub 2}-O-CH{sub 2}-){sub n}-O-R containing an ether chain and terminal phosphoryl groups: R = (Ph){sub 2}P(O)-C{sub 6}H{sub 4}-; n = 3, 4 (I--II) and R = (Ph){sub 2}P(O)-CH{sub 2}-C{sub 6}H{sub 4}-, n = 1, 3, 4 (III--V). The authors found that podand I displays a remarkable Ba{sup 2+}/Ca{sup 2+} extraction selectivity. All podands extract alkali and alkaline earth picrates in dichloromethane (as dissociated ion pairs) better than in chloroform (as non-dissociated ion pairs). Based on Molecular Dynamics simulations of the complexes I{sup {sm_bullet}}M{sup 2+} and I{sup {sm_bullet}}M{sup 2+} (Pic{sup {minus}}){sub 2} in the gas phase and in chloroform the authors suggest that the high selectivity of I for Ba{sup 2+} is due to (1) the formation of the complex with an optimal pseudocavity for Ba{sup 2+}, in which six donor atoms of the ligand and four oxygens of the Pic{sup {minus}} counter-ion coordinate to the cation, and (2) the smaller dehydration energy of Ba{sup 2+} compared to other alkaline earth cations. The relative free energies of extraction obtained from simulations on the I{sup {sm_bullet}} M{sup 2+} (Pic{sup {minus}}){sub 2} complexes are in good agreement with the experimental data.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 343800
- Journal Information:
- Solvent Extraction and Ion Exchange, Vol. 17, Issue 3; Other Information: PBD: May 1999
- Country of Publication:
- United States
- Language:
- English
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