CHEMICAL CONTROL OF INTERMOLECULAR INTERACTIONS IN PORPHYRIN-BASED HOST MATERIALS. Charles E. Strouse and Marianne K. Byrn, Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095-1569, USA

The remarkable versatility of metallotetraarylporphyrins as clathrate hosts is the result of several molecular characteristics which are subject to chemical modification. Unlike host materials that possess a complementarity with favored guests, or a self-complementarity that dictates crystal packing, tetraarylporphyrin molecules, for the most part, interact in a non-specific way with both guest molecules and each other. As a result, the crystal packing in these materials is strongly influenced by entropic factors. The driving force for guest incorporation in these materials is the fact that these large, rigid, highly symmetric molecules cannot pack efficiently in three dimensions. Incorporation of guest molecules provides the additional degrees of freedom required for efficient packing. This talk will explore various modifications of the host molecules, and their influence on clathrate thermodynamics. The phase equilibria of these systems, and the importance of these equilibria in technological applications, will also be discussed.