Importance of the Liquid−Liquid Interface in Assisted Ion Extraction: New Molecular Dynamics Studies of Cesium Picrate Extraction by a Calix[4]arene

We report a molecular dynamics study of key species involved in the liquid−liquid extraction of the cesium picrate salt by an important extractant molecule L (the 1,3-alternate-dimethoxy-calix[4]arene-crown-6) at the chloroform−water interface, with the main aim being to investigate the effect of (i) the explicit representation of polarization effects, (ii) the concentration of the complexes, and (iii) the volume/interfacial area ratio on their distribution at the interface. The outcome of phase separation of randomly mixed systems, consistently simulated with a polarizable force field and with pairwise additive 1−6−12 potentials, is found to be quasi the same, indicating that explicit representation of polarization critically determines neither the formation of the liquid−liquid interface nor the partitioning of the solutes. This is found first at low concentration (3 LCs+ Pic− species per box) in a 1:1 chloroform/water mixture for the complexed and uncomplexed states of the cation, and for a more concen...