Structure and Properties of Modular Components for Applications in Topological Supramolecular Chemistry

As a practical application of the structure of products derived from simple reactions of modular components, the background to a system for topological supramolecular assembly is introduced. Familiar base-catalyzed carbonyl condensation chemistry, acting on combinations of cyclic 1,3-diketones and aromatic aldehydes, provides thermodynamically controlled access to molecular entities of appropriate bulk to act as stoppers in rotaxane structures. Under acid-catalyzed reaction conditions, an additional, irreversible, dehydration step is introduced, thereby providing a putative mechanism for locking in place a specified topology. These ideas are illustrated with the preparation and X-ray structures of model systems derived from 5,5-dimethylcyclohexane-1,3-dione and two model aromatic dialdehydes, representing the results of the application of both reversible and irreversible reaction conditions. Additional model compounds are employed to demonstrate reaction reversibility in the former case.