is award from the Inorganic, Bioinorganic and Organo- metallic Program to Professor Jerry Atwood of the University of Alabama will fund continued studies of guest-host chemistry involving calixarenes. Calixarenes are flexible, macrocycles (hosts) that can incorporate smaller molecules (guests) with multiple non-covalent interactions. Emphasis will be on: 1) interactions with metal complexes as primary and second sphere ligands, 2) inclusion of water in the hydrophobic cavity of water soluble calix?4!arenes, 3) conformation and complexation of higher (n=5-8) calix?n!arenes, and 4) further characterization of bilayer solid state structures found for caliz?4!arene sulfonates and related compounds. Information obtained from these studies on the nature of guest-host interactions will impact on separation science and biological chemistry. %%% This study is expected to provide important fundamental information about multiple, but highly specific, non-covalent interactions of molecules. Such interactions are responsible for recognition of substrates by enzymes in biological systems and allow for the separation of mixtures of very similar molecules when appropriate hosts can be designed and synthesized.