There is great interest in understanding the rules that govern the organization of single molecules into crystalline materials.  We have focused on a macrocyclic bis-urea building block that readily self-assembles through hydrogen bonding and aryl stacking interactions into columnar structures forming needle shaped crystals.  These simple bis-urea macrocycles predictably form porous crystals that can reversibly absorb guests and can be used as a confined environment for reactions.  Here we report on the limits of this supramolecular motif.  We investigate the effects that ring size, rigidity, and crystallization conditions have on the fidelity of the crystalline assembled structure. Finally, we examine the incorporation of functional groups within the macrocycle framework that could compete with the urea oxygen as hydrogen bond acceptors.  These studies indicate that urea-urea assembly motif is robust and highly conserved. 

Benzophenone macrocycle

X-ray structure of self-assembled benzophenone  (guest DMSO omitted)

Unsymmetrical bis-urea macrocycles that contains a ethyleneglycol linker.

X-ray structure of self-assembled unsymmetrical bis-urea macrocycle.

This research is funded by the National Science Foundation (CHE-0316424) and by the American Chemical Society Petroleum Research Fund (44682)