Competitive Interactions in the Crystal Structures of Benzils Effected by Different Halogen Substitution

To understand the consequences of halogen substitutions on the crystalline packing behavior of benzils, benzil itself and its derivatives with fluorine, chlorine, bromine, and iodine substituents in the p-position of the phenyl rings were studied and compared with respect to their crystal structures, which are new for the chloro, bromo, and iodo derivatives. While the molecular structures in the crystal are relatively unaffected by the substitution, this is not the case for their packing. In particular, in the chloro, and seemingly in some weaker tendency also in the bromo and iodo derivatives, a leading influence of the halogen atoms to cause specific halogen···halogen contact modes is shown, whereas the influence of the fluorine atom is minor.