STACKED OR T-SHAPED BENZENE DIMER IN AQUEOUS-SOLUTION - A MOLECULAR-DYNAMICS STUDY

An aqueous solution of a benzene dimer has been investigated by means of molecular dynamics simulations. The potential of mean force as a function of the benzene separation for stacked and T-shaped configurations has been calculated. The close-contact T-shaped dimer was found to possess the lowest free energy. The more favorable benzene-benzene and benzene-water interaction present for the T-shaped geometry exceeds the increase in the hydrophobic surface free energy as compared to the close-contact stacked dimer. Moreover, a well-defined solvent-separated stacked minimum with a similar potential of mean force as the close-contact stacked minimum was obtained. The hydration of the benzene dimer is very similar to that of a single benzene molecule. The main exception occurs for the solvent-separated stacked dimer where water molecules located between the benzene dimer display a weaker preferential orientation with respect to the benzene molecules and a moderately enhanced water structure.