Role of halogen-involved intermolecular interactions and existence of isostructurality in the crystal packing of —CF3 and halogen (Cl or Br or I) substituted benzamides

Abstract

A total of 23 benzamides are obtained through a simple reaction between chloro-/bromo-/iodoaniline and trifluoromethylbenzoyl chloride and characterized using single-crystal X-ray diffraction. Crystal structures of three series of benzamides based on N-chlorophenyl–trifluoromethyl–benzamide (nine compounds), N-bromophenyl–trifluoromethyl–benzamide (six compounds), and N-iodophenyl–trifluoromethyl–benzamide (eight compounds) are prepared to analyse the halogen-mediated noncovalent interactions. The influences of Cl/Br/I and trifluoromethyl substituents on the respective interactions are examined in the presence of a strong N—H...O hydrogen bond. This exercise has resulted in the documentation of frequently occurring supramolecular synthons involving halogen atoms in the crystal packing of benzamide molecules in the solid state. In the present study, a detailed quantitative evaluation has been performed on the nature, energetics, electrostatic contributions, and topological properties of short and directional intermolecular interactions derived from the electron density on halogenated benzamides in the solid state. Besides these, the occurrence of three-, two- and one-dimensional isostructurality in halogen (Cl or Br or I) substituted benzamide analogues is also investigated. A `region of co-existence' involving halogen-based intermolecular interactions in the vicinity of the sum of the van der Waals radii has been identified. Thus, the nature of the halogen (effective size), type of interaction and the packing characteristics via presence of additional interactions establish the subtle, yet important, role of cooperativity in intermolecular interactions in crystal packing.