Predictability of Isostructurality within Monosubstituted Cinnamide Crystals

The use of isostructural crystals as a crystal engineering design tool to identify potential mixed crystals is common for inorganic materials but has not been extensive in molecular crystal engineering due to their wider variety. Therefore, it is important to develop a greater understanding of the features that promote isostructural chemical families. A series of substituted cinnamides has been investigated, experimentally and computationally, identifying five isostructural sets, which are also predicted as low-energy structures. While o- and p-substituted compounds show groupings with multiple members, the m-substituted systems have fewer groups and show a higher level of disorder in the crystal structures. All the structures comprise consistent hydrogen-bonding motifs with only differences in the packing of these components; this suggests that further isostructural polymorphs may be possible by alteration of growth conditions or the use of other phases as hetero-seeds.