NON-COVALENT SYNTHESIS OF HOST GUEST ASSEMBLIES THROUGH MOLECULAR RECOGNITION. V. R. Pedireddi, W. Jones, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 lEW, UK

The creation of supramolecular structures requires an appreciation of the types of intermolecular interactions which can be reliably used to create ordered arrays. The nature of the assemblies thus formed also depends upon the position of the substituents on the molecule(s) under consideration.

It is interesting that within certain crystals potential cavities for guest inclusion may exist but because of catenation or interpenetration of the adjacent layers (for reasons of efficient close packing) guests are not incorporated. The crystal structures of trimesic acid and adamantanetetra-carboxylic acid are representative examples.

Another example of a system which contains potential guest cavities is 3,5-dinitro-4-methylbenzoic acid, 1. It adopts a layered structure such that in every layer, six molecules are connected through O-H...O and C-H...O Hydrogen bonds to create 7 x 13 Å voids. The voids are subsequently filled by groups from adjacent layers. We wished to discover whether these cavities could be filled by guests of appropriate dimension. When 1 is co-crystallised with 2,6-dimethylnaphthalene, 2, the molecules of 2 in fact fit into the cavity through the formation of C-H...O H-bonds. The structure of the complex, the underlying supramolecular chemistry and further implications will be discussed with respect to 2 and other guest molecules.