A theoretical analysis of atomic charge fluxes in chlorofluoromethanes and relationship with bonding character descriptors

Abstract

In this study, intramolecular electronic charge fluxes in chlorofluoromethanes, which take place during atomic stretching displacements, were analyzed in terms of bond character descriptors. Topological parameters of the electron density at the critical points of C–X bonds (X = H, F or Cl) and charge fluxes were obtained through the Quantum Theory of Atoms in Molecules (QTAIM). All calculations were done at the CCSD/cc-pVQZ level of theory. Thus, we have noticed that the covalent character of C–H, C–Cl and C–F bonds seems to increase as hydrogen atoms are replaced by halogens in other bonding sites of those molecules. This is attributed to polarizations induced over the carbon atom by the negatively charged substituents. It was also observed that the charge fluxes at the atoms of enlarged C–H bonds are linearly related to these bond character parameters. A similar pattern of charge fluxes is likewise seen for C–Cl and C–F bonds. However, the displacement of halogen atoms results in a larger delocalization of the charge fluxes (long range electronic charge transfers). This probably leads to a further observed separation into subgroups of molecules with appropriate linear relationships between halogen charge fluxes and bond character descriptors.