Bridge Orientation as a Selector of Intermolecular Interactions in a Series of Crystalline Isomeric Benzylideneanilines

Comparison of the crystal structures of compounds we have designated "bridge-flipped isomers," which on the molecular level differ only in the orientation of a bridge of atoms connecting two larger parts of the molecule, otters a useful context for the examination and evaluation of intermolecular interactions and their robustness as supramolecular synthons. Intermolecular interactions in the crystal structures of five pairs of bridge-flipped isomeric benzylideneanilines are examined here, including interactions between nitrile groups and ring hydrogen atoms, between halogen atoms, and between nitrile groups and halogen atoms. Of these, only the halogen-nitrile interaction in which the halogen is iodine is present in both bridge-flipped isomers of the pair, although its influence on the molecular packing arrangement is insufficient to compel the two isomers to assume identical packing arrangements. Pairwise analysis of crystal structures of bridge-flipped isomers thus provides a perspective beyond that provided by the isolated analysis of the structures of the individual compounds.