Intermolecular interactions and molecular packing in isomeric benzylideneanilines

CHED 412

Jill M. Spude, jmspude@stthomas.edu and William H. Ojala, whojala@stthomas.edu. Department of Chemistry, University of St. Thomas, 2115 Summit Avenue, St. Paul, MN 55105
Pairs of benzylideneanilines we have designated “bridge-flipped isomers” differ only in the orientation of the chain or bridge of atoms connecting the two aryl groups; the isomerism is Ar-CH=N-Ar' vs. Ar-N=CH-Ar'. Our goal is to prepare new solid materials having properties that can be controlled or modified by co-crystallizing various proportions of bridge-flipped benzylideneaniline isomers. Mutual solid-state solubility is most extensive for components that have the same molecular packing arrangement in their respective crystals, so we are preparing benzylideneaniline bridge-flipped isomeric pairs and determining their crystal structures to identify isostructural pairs that would be especially suitable for co-crystallization. Among these structures we have recently discovered our first isostructural pair: 2-trifluoromethyl-N-(2-methylbenzylidene)aniline and 2-methyl-N-(2-trifluoromethylbenzylidene)aniline. Unlike the only other isostructural bridge-flipped benzylideneanilines of which we are currently aware, 4-chloro-N-(4-methylbenzylidene)aniline and 4-methyl-N-(4-chlorobenzylidene)aniline, our compounds assume an ordered molecular packing arrangement in the solid state.