Mutual influence of parallel, CH/O, OH/π and lone pair/π interactions in water/benzene/water system

The mutual influence of OH/π, CH/O, parallel alignment (all attractive) and lone pair/π (repulsive) water/benzene interactions was studied with ab initio calculations on water/benzene/water systems. The energies of the systems containing two water molecules on the opposite sides of benzene molecule or as far as possible from each other were calculated using Møller–Plesset perturbation theory of the second order and cc-pVTZ and cc-pVQZ basis sets. The synergetic effects in those systems were shown to be related to direction and amount of electron transfer. The results showed that OH/π and CH/O interactions strengthen each other for 0.42–0.44 kcal/mol. Similar effect is also present in the system containing LP/π and OH/π interaction, that strengthen each other for 0.42–0.46 kcal/mol. In contrast, two OH/π interactions weaken each other for 0.40 kcal/mol, two CH/O interactions weaken each other for 0.31 kcal/mol, while two LP/π interaction weaken each other by 0.40 kcal/mol. Weakening is also present in the system containing LP/π and CH/O interaction, that weaken each other by 0.43 kcal/mol. Parallel alignment water/benzene interactions, where one water OH bond is parallel to benzene ring and out of benzene ring and C–H bond region, do not have a significant influence on the energy of other interactions or on each other.