Th@Td(19151)-C76: A Highly Symmetric Fullerene Cage Stabilized by a Tetravalent Actinide Metal Ion.

For the first time, Th@Td(19151)-C76, a highly symmetric C76 cage encapsulating an actinide metal ion, has been synthesized and characterized by single-crystal X-ray crystallography, mass spectrometry, UV-vis-NIR spectroscopy, and cyclic voltammetry. The single-crystal crystallographic analysis unambiguously assigned the fullerene cage as Td(19151)-C76 and confirmed Th@Td(19151)-C76 as the first IPR (isolated-pentagon rule) C76-based monometallofullerene. The crystallographic results further revealed that the optimal Th site resides over a sumanene-type hexagon, similar to that of the Th@C1(11)-C86 but different from the previously reported Th@C3v(8)-C82. In addition, electrochemical study found that Th@Td(19151)-C76 processes an unusually low first oxidation potential (0.03 V), suggesting its strong electron donating ability.