Quantitative Characterization of Fluorine-Centered Noncovalent Interactions in Crystalline Benzanilides.

Abstract

Six isomeric molecules, featuring a minimum of three fluorine atoms on either the benzoyl or aniline side, have been synthesized, crystallized and characterized through single crystal X-ray diffraction (SCXRD). In addition, two other compounds, containing six fluorine atoms, three on each of the benzoyl and aniline side of the benzanilide scaffold have also been characterized through SCXRD. This current study aims to augment the capacity for hydrogen bond formation, specifically involving organic fluorine, by elevating the acidity of the involved hydrogens through the incorporation of highly electronegative fluorine atoms, in the presence of strong N-H⋅⋅⋅O=C H-bonds. Lattice energy calculations and assessment of intermolecular interaction energies elucidate the contributions of electrostatics and dispersion forces in crystal packing. The topological analysis of the electron density is characterized by the presence of bond critical points (BCPs) involving C-H⋅⋅⋅F and F⋅⋅⋅F contacts, thus establishing the bonding nature of these interactions which play a crucial role in the crystal packing in addition to the presence of traditional N-H⋅⋅⋅O=C H-bonds.