Variability in halogen interactions: In situ cryocrystallization of low melting substituted trifluoroacetophenones

Crystal and molecular structures of four low melting halogenated trifluoroacetophenones along with the corresponding nitro derivative have been determined to understand the nature of short halogen-halogen and halogen-oxygen intermolecular contacts. The first four compounds, which are liquids at room temperature, have been analyzed using the technique of in situ cryocrystallography. The basic building block in the crystal lattice is invariant because of an intramolecular C-H center dot center dot center dot F contact, which locks the molecular conformation. The supramolecular assembly in all these structures is stabilized with additional C-H center dot center dot center dot O, C-H center dot center dot center dot F, and aromatic pi center dot center dot center dot pi intermolecular interactions. The nitro derivative is further stabilized by intramolecular C-H center dot center dot center dot O contacts.