A recent crystal engineering project in Nijmegen involved the study of inclusion compounds of cephalosporin antibiotics. Inclusion compounds, like clathrates, only exist in the solid state. X-ray diffraction (on powders and single crystals) is a very powerful tool to examine this type of compounds and in combination with molecular modelling and chemometrical approaches it was possible to find new non-toxic guest molecules which form complexes with the antibiotics very efficiently and selective. An efficient complexation of host molecules is an important technique in the isolation of chemical compounds from mixtures of molecules.
Research on co-crystallizing compounds is a good strategy for obtaining insight into molecular interactions and molecular recognition. Such insight may be of significant interest for co-crystallization of supramolecular compounds in order to obtain a crystalline state which would otherwise not be accessible. The approach we have chosen for studying a specific group of complexes can easily be applied to other systems and therefore we wish to continue this theme in the future.