N. Muzet et al., Demixing of binary water-chloroform mixtures containing ionophoric solutesand ion recognition at a liquid-liquid interface: A molecular dynamics study, J PHYS CH B, 102(52), 1998, pp. 10772-10788
We report a series of molecular dynamics simulations on the demixing of "ho
mogeneous" binary water-chloroform mixtures containing species involved in
the assisted ion extraction process. We consider an ionophore: L (L = 1,3-a
lternate calix4arene-crown6), uncomplexed salts of Cs+ and the LCs+ and LNa
+ cation complexes with a lipophilic (Pic(-)) and a hydrophilic (Cl-) count
erion, respectively, as being solutes. In all cases, the liquids separate r
apidly, leading to two solvent slabs separated by a well-defined interface.
However, the final state is very different, depending on the hydrophilic/h
ydrophobic balance of the solutes: the Cs+ and NO3- ions of the CsNO3 salt
are completely immersed in the aqueous phase, whereas Pic(-) anions display
a strong adsorption at the interface. The LCs+ complex and the free ligand
L, although more soluble in the organic phase than in water, also display
a surfactant like behavior. Similar conclusions are obtained when L, LCs+,
Cs+ Pic(-), and Cs+ NO3- ions are simultaneously present in the solution. O
n the basis of free energy perturbation calculations on LM+ complexes, we c
alculate a marked Cs+/Na+ recognition by L at the interface. These results
have important implications concerning the mechanism of ionophore assisted
liquid-liquid ion extraction and recognition processes at the interface.