Synthesis and Characterization of Two Isomers of Th@C82: Th@C2v(9)-C82 and Th@C2(5)-C82.

Actinide endohedral fullerenes have demonstrated remarkably different physicochemical properties compared to their lanthanide analogues. In this work, two novel isomers of Th@C82 were successfully synthesized, isolated, and fully characterized by mass spectrometry, X-ray single crystallography, UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry. The molecular structures of the two isomers were determined unambiguously as Th@C2v(9)-C82 and Th@C2(5)-C82 by single-crystal X-ray diffraction analysis. Raman and UV-vis-NIR spectroscopies further confirm the assignment of the cage isomers. Electrochemical gaps suggest that both Th@C2v(9)-C82 and Th@C2(5)-C82 possess a stable closed-shell electronic structure. The computational results further confirm that Th@C2v(9)-C82 and Th@C2(5)-C82 exhibit a unique four-electron charge transfer from the metal to the carbon cage and are among the most abundant isomers of Th@C82.