This research is supported by the Organic and Macromolecular Chemistry Program. The research involves building molecules that mimic nature's ability to selectively complex and carry out highly selective reactions. The model molecules are relatively small compared to enzymes but are built to simulate their selective behavior, based upon an understanding of the responsible factors. Dr. Cram has been a pioneer in this work, it having culminated in his being awarded a Nobel Prize. The goal is to understand structural recognition in complexation between organic compounds. Molecular traffic control in biological systems depends centrally on structural recognition in complexation, and inspires study of complexation with simple non-biological systems. Organic compounds with convergent binding sites (hosts) are designed and prepared to complex other organic compounds with complementary, divergent binding sites (guests). The hypothesis is being tested "that stronger and more specific complexation applies to host-guest partners whose intrinsic structures enforce an organization for binding prior to complexation (preorganization)." Structures of hosts and complexes derive from crystal structures, nuclear magnetic and mass spectra, and elemental analyses. Free energies of complexation are correlated with host and guest structures. Preorganization in hosts is obtained through assembly of rigid molecular modules to form enforced concave surfaces of molecular dimensions with saucer, bowl, cup, or vase-like shapes (cavitands). Binding or solubilizing groups compose or protrude from their surfaces. Molecular cells are constructed by multiply bonding at their rims two or more cavitands to give carcerands, whose enforced interiors imprison organic or inorganic guests, whose properties change with encapsulation.
