This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports work on Group 5 and 6 metal clusters with labile ligands by Dr. Duward F. Shriver, Department of Chemistry, Northwestern University. The overall goal of the work is to synthesize extended solids and large molecular clusters containing redox and photoredox active early d-block metal clusters. New compounds will be synthesized and characterized photochemically and electrochemically, and used as the basis for preparation of micro- and mesoporous solids and for markers in electron microscopy. These compounds will serve as precursors to: (1) mixed clusters with potentially interesting bonding, reactivity, electrochemistry and photochemistry; (2) clusters containing atypical ligands for these metals; and (3) solids consisting of clusters of clusters with size and shape selectivity for small molecules and redox or photoelectrochemical activity. A number of possibilities for interaction of clusters with functional groups on solids will be investigated. For example, silica-supported molybdenum clusters will be investigated as a solid medium for photochemical or photoelectrochemical transformations of small molecules. Heavy metal clusters will be employed as markers for functional groups on polycarbon species. Also, some clusters, which can be readily imaged by high resolution electron microscopy and analyzed by electron nanodiffraction and spectroscopy, will be utilized to differentiate between competing structural models for carbon nanotubes. Molybdenum, tungsten, niobium, and tantalum form "clusters" in which six metal atoms form an octahedral core around which are associated ions, such as chloride. In this project easily exchangeable ions will be associated with some of these clusters so that they can be attached to surfaces of novel materials. The size, photochemistry, and electrochemistry of these clusters can then be used to determine the shape of the support material t o which they are attached, or to increase the chemical capabilities of both the cluster and the surface. The results could be helpful in characterizing known materials or in synthesizing new materials.
