Molecular mechanism of transporting a polarizable iodide anion across the water-CCl4 liquid/liquid interface

Abstract

The result of transferring a polarizable iodide anion across the H2O-CCl4 liquid/liquid interface was investigated in this study. The computed transfer-free energy profile or potential of mean force exhibits a minimum near the Gibbs dividing surface. These system characteristics are similar to those found in a corresponding study of iodide transfer across the H2O-vapor interface; however, the free energy minimum was lower at the H2O-vapor interface. Molecular dynamics simulations were also carried out to compare the concentrations of NaCl, NaBr, and NaI at the H2O-vapor and H2O-CCl4 interfaces. While the concentration of bromide and iodide ions were lower at the H2O-CCl4 interface when compared to the H2O-vapor interface, the chloride ion concentrations were similar at both interfaces. Analysis of the solvation structures of iodide and chloride ions revealed that the more polarizable iodide ion was less solvated than the chloride ion at the interface. This characteristic brought the iodide ion into greater contact with CCl4, resulting in repulsive interactions with CCl4 and reducing its tendency to move to the interface.