Ab initio calculations on C6H6•••(HF)n clusters - X-H•••π hydrogen bond

MP2/6-311++G(d,p) calculations on C6H6(HF)(n) clusters were performed and full optimizations were carried out for systems containing up to four HF molecules (n = 4) and calculations on the systems of C-6v symmetry were carried out for up to six HF molecules (n = 6). Cooperativity effects were analyzed for these molecular aggregates. It was found that F-H p and F-H F hydrogen bonds exist for these complexes and those interactions are enhanced as the number of HF molecules increases. The cooperativity effects cause numerous changes in geometrical, energetic, and topological parameters, the latter ones derived from the quantum theory of atoms in molecules. Various correlations between the analyzed parameters are presented. There are meaningful differences between the molecular graphs for the fully optimized complexes and those for the linear complexes of C-6v symmetry (for the latter, the linear chain of HF molecules is attached to a benzene molecule acting as the Lewis base). For the linear complexes, unique bond paths connect the H-attractor of the HF molecule and the ring critical point of the benzene molecule.