Interplay between packing, dimer interaction energy and morphology in a series of tricyclic imide crystals

Crystal morphology is a very important feature in many industrial applications. Tricyclic imides, derivatives of 10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione with differing small hydrophobic groups (Me, Et), were studied and grouped based on Etter's rule. Using experimental X-ray studies, dimer energy calculations, framework analysis and periodic DFT-D calculations, it is shown that knowledge of the hydrogen-bond pattern can be used to determine the final crystal shape. Molecules forming a ring hydrogen-bond motif crystallize as plate crystals with the {100} facet as the slowest growing, whereas those molecules forming an infinite hydrogen-bond motif in the crystal structure crystallize as needles with the {101} facet having the largest surface area.