Energetic and topological supramolecular study and nucleation proposal for halogenated aryl amides

Abstract

A supramolecular study of 12 halogenated aryl amides (F, Cl, Br, I) in the ortho, meta, or para positions was realized. From single crystal X-ray diffraction data and theoretical calculations of molecular orbitals, energetic and topological parameters of the intermolecular interactions were determined. The contact area between the molecules was determined by the Voronoi–Dirichlet polyhedron (VDP) method. The energy of intermolecular interactions between molecules was obtained from density functional theoretical calculations. From these data, all intermolecular interactions were classified, and the robustness of the interactions was evaluated. These data were used to propose a crystal growth path for these compounds. Strong hydrogen bonds N–H⋯O have been found in the form of supramolecular dimers and in the form of infinite chains along a plane in these structures. These interactions showed greater stabilization energy contributing to the beginning of the crystal formation. The angle between the plane of the benzene ring and the CONH₂ fragment allowed the formation of N–H⋯O and π⋯π interactions simultaneously with a large contact surface and amount of stabilization energy. Intermolecular interactions considered as weak such as C–H⋯O, C–H⋯X, and halogen bonds demonstrated an essential role in the later stages of nucleation. Furthermore, the total energy of the intermolecular interactions of the first coordination sphere was estimated and a remarkable correlation with experimental data of the melting point and crystalline packing density was verified.