Role of Hetero-Halogen (F···X, X = Cl, Br, and I) or Homo-Halogen (X···X, X = F, Cl, Br, and I) Interactions in Substituted Benzanilides

A series of halogen-substituted benzanilides have been synthesized and characterized, and crystallization studies directed toward generation of polymorphs have been performed to delineate the importance of interactions involving halogens. The effect of halogen substitution on the molecular conformation and supramolecular packing has been investigated. The N−H···O H-bond is a key structure-directing element acting in conjunction with C−H···O and C−H···π interactions. In addition, it is of importance to note that organic fluorine prefers Type I F···F contacts, whereas Cl, Br, and I prefer Type II contacts. Hetero-halogen···halogen interactions on the other hand are predominately of Type II geometry, and this is due to the greater polarizability of the electron density associated with the heavier halogens. It is of importance to evaluate the contributing role of these interactions in crystal structure packing and the co-operativity associated with such interactions in the solid state.