Density functional theoretical study on the preferential selectivity of macrocyclic dicyclohexano-18-crown-6 for Sr+2 ion over Th+4 ion during extraction from an aqueous phase to organic phases with different dielectric constants

作者：Boda A; Joshi J M; Ali Sk M^*; Shenoy K T; Ghosh S K

来源：Journal of Molecular Modeling, 2013, 19(12): 5277-5291.

DOI：10.1007/s00894-013-2015-5

• DFT
• Dicyclohexano-18-crown-6 ether
• Solvent extraction
• Strontium
• Thorium
• Distribution
• Selectivity

The preferential selectivity of dicyclohexano-18-crown-6 (DCH18C6) for bivalent Sr+2 ion over tetravalent Th+4 ion was investigated using generalized gradient approximated (GGA) BP86 and the hybrid B3LYP density functional, employing split valence plus polarization (SV(P)) and triple-zeta valence plus polarization (TZVP) basis sets in conjunction with the COSMO (conductor-like screening model) solvation approach. The calculated theoretical selectivity of DCH18C6 for Sr+2 ion over Th+4 ion was found to be in accord with the selectivity for Sr+2 ion over Th+4 ion observed when performing liquid-liquid extraction experiments in different organic solvents. While 1: 1(M: L) stoichiometric complexation reactions can be used to predict the preferential selectivity of Sr2+ ion over Th4+ ion, the results obtained are not consistent with the experimental results observed upon increasing the dielectric constant of the solvent. The calculated theoretical gas-phase data for the free energy of complexation, Delta G, fail to explain the selectivity for Sr+2 ion over Th+4 ion. However, when 1: 2 (M: L) stoichiometric complexation reactions (reported in previous X-ray crystallography studies) are considered, correct and consistent results for the selectivity for Sr+2 ion over a wide range of dielectric constants are predicted. The distribution constant for Sr2+ and Th4+ ions was found to gradually increase with increasing dielectric constant of the organic solvent, and was found to be highest in nitrobenzene. The selectivity data calculated from Delta Delta G(ext) are in excellent agreement with the results obtained from solvent extraction experiments.

• 出版日期2013-12