Abstract

There has been a long time effort to influence or favourably fine tune structural properties by introduction
of substituents or guest molecules of different sizes, shapes and chemical composition to consequently
alter 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 produce
new substances with required properties based on the knowledge of the structural properties of already
characterised solids. A series of calixarene crystal structures are presented where the crystal packing is
determined by spatial or by electrostatic effects. A series of laterally substituted calixarenes where both
steric requirements and electrostatic forces play a role in the crystal architecture shows how the supramolecular
synthon can be engineered.