Nanoscience Seminar: Luis Echegoyen
- Buckyball Maracas: New Endohedral Fullerene Structures, Reactivity and Mechanistic Aspects.
- Luis Echegoyen, University of Texas at El Paso.
- Endohedral clusterfullerenes were serendipitously discovered in 1999 with the isolation of Sc3N@C80, the first member of what has become an extensive family of interesting compounds. Most of these compounds have been shown to be fairly unreactive due to their unique electronic structure, which formally contains a highly positive cluster encapsulated inside a carbon cage that is highly negatively charged (the accepted model for Sc3N@C80 involves the transfer of six electrons to form [Sc3N]6+[C80]6-).
We recently isolated and characterized two new scandium carbide endohedral structures, Sc2C2@C2v(9)-C861 and Sc2C2@Cs(hept)-C88.2 The former compound represented the first observation of the C2V(9) C86 cage and exhibited a distorted but ordered scandium cluster inside. The second compound is much more unique in that it possesses a heptagonal ring on its carbon surface, making it the only C88 endohedral cage with such a heptagon. Extensive theoretical calculations suggest that the C88 compound is formed directly by the insertion of a C2 unit into a specific location of the C86 compound, to yield a kinetically trapped compound which is not the thermodynamically favored one.
Finally, we have also been involved in the synthesis and characterization of new Uranium-based endohedral fullerenes and have obtained X-Ray crystal structures for several of these compounds. Some are monouranium species, U@C2n, while some are di-uranium compounds, U2@C2n.3 Still others are much more interesting and totally unanticipated, with formula U2X@C2n, where X= C, O, S or N and 2n= 72, 78 or 80, which reveal interesting metal-cage interactions and totally unprecedented clusters trapped inside. Some of the carbide compounds have been crystallized and the encapsulated U2C cluster (in U=C=U@C80) exhibits unprecedented bonding with totally unanticipated properties.4 The synthesis, purification and characterization of these interesting endohedral fullerenes will be presented and discussed, along with very recent results about uranium-based endohedrals.
September 13, 2018
3:00 PM — 4:00 PM
Advanced Science Research Center, GC/CUNY
85 St. Nicholas Terrace
5th Floor Data Visualization Room