Mechanical Flexibility of Molecular Crystals Achieved by Exchanging Hydrogen Bonding Synthons

Tuning the mechanical properties of crystalline materials is alluring and has captivated the interest of material scientists. Here, we have demonstrated a crystal engineering approach to introduce mechanical flexibility in molecular crystals by exchanging hydrogen bonding synthons. Earlier reports suggested that the molecular crystals of probenecid are plastically deformable due to the presence of a n-propyl chain mediated slip system. This structural feature inspired us to investigate the mechanical property of the molecular crystals of the corresponding carboxamide and acid hydrazide derivatives. When a mechanical force is applied, crystals of probenecid hydrazide deform irreversibly; however, crystals of probenecid amide break. The mechanical flexibility and brittleness displayed by the crystals of probenecid hydrazide and probenecid amide are attributed to the arrangement of the n-propyl chains in the crystal structures of these compounds. The topology of the energy framework in the crystal structures of acid and hydrazide illustrated the presence of anisotropic intermolecular interactions.