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

The mutual influence of OH/pi, CH/O, parallel alignment (all attractive) and lone pair/pi (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 Moller-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/pi and CH/O interactions strengthen each other for 0.42-0.44 kcal/mol. Similar effect is also present in the system containing LP/pi and OH/pi interaction, that strengthen each other for 0.42-0.46 kcal/mol. In contrast, two OH/pi interactions weaken each other for 0.40 kcal/mol, two CH/O interactions weaken each other for 0.31 kcal/mol, while two LP/pi interaction weaken each other by 0.40 kcal/mol. Weakening is also present in the system containing LP/pi 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