Electrophilicity Indices and Halogen Bonds: Some New Alternatives to the Molecular Electrostatic Potential.

We assess the ability of various atomic and molecular electrophilicity descriptors to predict the strength of halogen bonds. To this aim, several physicochemical quantities rooted within the framework of conceptual density functional theory were derived using second and third order Taylor expansions of the electronic energy, and their correlation to binding energies were compared with those obtained for more usual electronic descriptors. This benchmark was performed for a large and representative database of noncovalent complexes involving fluorine, chlorine, and bromine atoms, and showed that some of these new quantities, in particular the atomic cubic electrophilicity index, exhibited more transferability and broadness of application than did more common descriptors such as the molecular electrostatic potential.