Regioselective Control of Multiple Additions to Empty and Endohedral Fullerenes

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With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Chemistry Division, Prof. Luis Echegoyen and his research team at the University of Texas at El Paso will prepare and characterize endohedral "clusterfullerenes", for potential uses as acceptor materials in high efficiency organic solar cells (OSCs). Endohedral clusterfullerenes are carbon cages that entrap a variety of clusters, resulting in unusual electronic properties. Of fundamental importance will be the interplay between the properties of the encapsulated clusters and the corresponding addition positions on the exohedral carbon surfaces. The long range goal is to control, in a predetermined way, the regiochemistry of multiple additions on the surfaces of these fullerenes. This team will explore reaction regiochemistry using independent multiple addition processes as well as tethered ones, where the adduct reagents are connected by a well-defined spacer. The properties of these compounds will be characterized using a wide variety of techniques, including X-ray crystallographic analyses, spectroscopy and electrochemistry, specifically looking for evidence of endo-exo cluster-cage interactions and their relationship to the overall chemical and electronic properties of the compounds.This project focuses mainly on two families of endohedral clusterfullerenes, the trimetallic nitrides, in which the carbon cages encapsulate M3N clusters, and the dimetallic sulfides, which entrap M2S clusters. Efforts will be devoted to entrapping mainly transition metals and avoid rare earths, including mixed metallic sulfides, M1M2S@C2n, where M1 and M2 and transition metals and n39. Intrinsic as well as chemical properties will be fully explored. An outreach program will continue to impact middle school students, primarily eighth graders of Hispanic origin, by exposing them to Energy and Nano concepts and laboratory practices. Besides this important broader impact there are potential societal benefits to be derived from the compounds and materials prepared, especially in OSCs, and from the training provided to the students involved in the project, many of whom are from Hispanic backgrounds. Because Professor Echegoyen is heavily involved in international collaborations with many scientists around the world, an additional broader impact results from these fertile intellectual interactions.