The immediate goal of the proposed research is to explore and develop the chemistry of new host molecules with multiple, interactive recognition sites. Central to this purpose is the synthesis of crown ethers and cyclophanes appended to a metallocene. The free rotation of metallocenes about their central axis will allow them to communicate conformational information from one recognition site to another. This interdependence of recognition site conformations will manifest itself experimentally in allosteric binding behavior. That is, the binding of the first guest will organize the remote binding site so as to favor or disfavor the binding of the second guest; these effects are termed positive and negative cooperativity, respectively. Metallocenes will also accommodate a wide array of auxillary functional groups. Thus, electrostatic and steric forces may be exploited in the design of these allosteric systems. The findings of the proposed research will serve to delineate the concepts that underly allosteric interactions in enzymes, receptors, and other cellular machinery, as well as synthetic systems including "molecular devices."