Benzene-hydrogen bond (C6H6-HX) interactions: the influence of the X nature on their strength and anisotropy.

The intermolecular potential energy of the C6H6-SH2 and C6H6-NH3 dimers is formulated as combination of independent electrostatic and nonelectrostatic contributions. The relevant parameters of the nonelectrostatic terms, derived from molecular polarizability components, have been proved to be useful to describe in a consistent way both size repulsion and dispersion attraction forces. The representation adopted for the electrostatic contribution asymptotically reproduces the dipole quadrupole interaction. To test the validity of the proposed potential formulation, the features of the most stable configurations of the systems predicted have been compared with the available ab initio and experimental data. Moreover, the strength of the C6H6-HX interaction has been analyzed comparing the obtained results with the corresponding ones for the C6H6-H2O and C6H6-CH4 systems, investigated previously with the same methodology. Information on the relative orientation dependence of the partners, arising from the anisotropy of the intermolecular interaction, evaluated at different intermolecular distances, has been also obtained. Such information is crucial to evaluate sterodynamics effects in bimolecular collisions.