The long-term objective of this research is to synthesize and characterize metal complexes that will provide physical description for the factors that contribute to the properties of Lewis acid metalloenzymes. A significant feature of this work targets a strategy for ligand synthesis and design to qualify the structure-reactivity relationships in model complexes. These structural components include steric effects and non-covalent intramolecular interactions. These synthetic models will qualify in particular the regiochemistry that is relevant in molecular recognition and stereochemical orientation of substrate mimics. In addition to the biological relevance, these structure-reactivity relationships have application in the development of stereospecific Lewis acid catalysts. The proposed polydentate ligands offer an opportunity to systematically investigate the coordination behavior for a series of similar chelating agents. Notwithstanding the contributions that have been made by inorganic research in this area, this proposed investigation is intended to expand upon these efforts to include variations in the electronic and geometric properties of the primary coordination sphere. Chiral zinc complexes will be synthesized and characterized to explore the relationship between steric and intramolecular forces as they govern the ability and the polarizability of the metal center. These relationship will be explored utilizing a variety of analytical methods: X-ray crystallography, electron, vibration and NMR spectroscopy. The contrast of the various structures will provide a basis for examining structure-reactivity relationships. Attempts will be made to relate structural parameters with spectroscopic properties and with metal ion affinity. The complexes will be examined for hydrolytic activity with appropriate stereochemical adducts. It is proposed that varying the structural features associated with the coordination environment can optimize reactivity in these compounds. The results of this investigation re anticipate as well to shed light on the structure-reactivity relationships that are prevalent in Lewis acid enzymes that contain metals other than zinc.
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