Fine tuning of crystal architecture by intermolecular interactions: synthon engineering

<p>There has been a long time effort to influence or favourably fine tune structural properties by introductionof substituents or guest molecules of different sizes, shapes and chemical composition to consequentlyalter physico-chemical properties of the respective crystals. These attempts require the recognition,understanding and application of intermolecular interactions, crystallographic and, in case of occurrence,non-crystallographic symmetries. It brings us to the field of crystal engineering, which aims to producenew substances with required properties based on the knowledge of the structural properties of alreadycharacterised solids. A series of calixarene crystal structures are presented where the crystal packing isdetermined by spatial or by electrostatic effects. A series of laterally substituted calixarenes where bothsteric requirements and electrostatic forces play a role in the crystal architecture shows how the supramolecularsynthon can be engineered.</p>