A Theoretical Study of X-H⋯C and X-H⋯π Interactions Between Substituted Benzene Derivatives and HF, HCl and HBr: AIM, NBO and NMR Analyses

The effects of X-H⋯C and X–H⋯π interactions are considered where the hydrogen acids act as a proton donor and the different π-systems such as para-substituted (H, F, Cl, OH, SH, CH3, and NH2) benzene derivatives act as a proton acceptor. The influence of substituents on the strength of interactions indicates that the electron-withdrawing groups weaken the interaction while electron-donating ones strengthen it. Topological properties of charge density show low ρ and positive 2ρBCP values and these properties are typical for closed-shell interactions. Based on the obtained natural bond orbital analysis results, the greatest charge transfer occurs in the HF complexes, while the smallest of that belongs to the HBr ones. The aromaticity indicators are also examined upon complexation. Finally, the NMR data results exhibit that the maximum and minimum isotropic value of the proton shielding tensor corresponds to the HBr and HF complexes, respectively.