Nature of the Water/Aromatic Parallel Alignment Interactions

Abstract

The water/aromatic parallel alignment interactions are interactions where the water molecule or one of its OH bonds is parallel to the aromatic ring plane. The calculated energies of the interactions are significant, up to E-CCSD(T)(limit) = -2.45 kcal mol(-1) at large horizontal displacement, out of benzene ring and CH bond region. These interactions are stronger than CHO water/benzene interactions, but weaker than OH interactions. To investigate the nature of water/aromatic parallel alignment interactions, energy decomposition methods, symmetry-adapted perturbation theory, and extended transition state-natural orbitals for chemical valence (NOCV), were used. The calculations have shown that, for the complexes at large horizontal displacements, major contribution to interaction energy comes from electrostatic interactions between monomers, and for the complexes at small horizontal displacements, dispersion interactions are dominant binding force. The NOCV-based analysis has shown that in structures with strong interaction energies charge transfer of the type sigma*(OH) between the monomers also exists.