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(Invited) Actinide Endohedral Fullerenes: Uranium-Based Systems with Unique Bonding Motifs

Monday, 29 May 2017: 10:20
Churchill A2 (Hilton New Orleans Riverside)
L. Echegoyen (The University of Texas at El Paso), W. Cai, J. Murillo (Univ. of Texas at El Paso), N. Chen (Soochow University), D. Najera (Univ. of Teaxs at El Paso), and S. Fortier (Univ. of Texas at El Paso)
Endohedral fullerenes, which are carbon cages that encapsulate atoms, ions or clusters have been known since the early days immediately following the discovery of the fullerenes in 1985 by Smalley, Kroto and Curl. A wide range of cages, varying in size, shape and electronic properties have been observed which encapsulate individual atomic or ionic species or clusters that possess complementary characteristics. Of the many endohedral fullerenes that have been characterized and reported, lanthanide endofullerenes have received a lot of attention but the corresponding actinide systems have not been extensively investigated experimentally, although theoretical calculations have been reported, especially after the original report by Smalley et al in 1992 of the mass spectral observation of mono- and di-metallic Uranium endohedrals with formulas U@C2n (n=14-36) and U2@C2m (m=25-30). The latter species containing two U ions inside have been the subject of multiple theoretical calculations using multiple cages, mainly C60, C70, C80 and C90. However, experimental reports of these exotic compounds are limited to three and only one involved purification using a two-stage HPLC protocol and presented the UV-Vis spectra for U@C82 and U2@C80.

We have undertaken a systematic study of U endohedrals and have succeeded in identifying many different compounds using HRMS, and have succeeded in purifying and characterizing several mono-metallic endohedrals, including their x-ray single crystal structures, specifically U@C74 and two different isomers of U@C82.

Of particular interest for this presentation are totally unexpected Uranium endohedrals with formula U2C(2n+1), where n=39, 40 which correspond to carbides containing single C atoms encapsulated with two Us inside C78 and C80 cages. More interestingly, U2X@C2n compounds have also been detected, where X=N and O, besides C. These latter compounds will be described and their properties will be presented and discussed.