Unique Four-Electron Metal-to-Cage Charge Transfer of Th to a C82 Fullerene Cage: Complete Structural Characterization of Th@C3v(8)‑C82

Endohedral metallofullerenes (EMFs) containing lanthanides have been intensively studied in recent years. By contrast, actinide endohedral fullerenes remain largely unexplored. Herein, for the first time, we report the single crystal structure and full characterization of an actinide endohedral fullerene, Th@C82, which exhibits remarkably different electronic and spectroscopic properties compared to those of lanthanide EMFs. Single crystal X-ray crystallography unambiguously established the molecular structure as Th@C3v(8)-C82. Combined experimental and theoretical studies reveal that Th@C3v(8)-C82 is the first example of an isolated monometallofullerene with four electrons transferred from the metal to the cage, with a surprisingly large electrochemical band gap of 1.51 eV. Moreover, Th@C3v(8)-C82 displays a strong vibrationally coupled photoluminescence signal in the visible region, an extremely rare feature for both fullerenes and thorium compounds.近年来，含镧系元素的内嵌金属富勒烯（Endohedral metallofullerenes, EMFs）已得到广泛深入的研究。与之形成鲜明对比的是，锕系内嵌富勒烯至今仍未得到充分探索。本研究首次报道了一种锕系内嵌富勒烯Th@C82的单晶结构与全面表征，该化合物展现出与镧系EMFs截然不同的电子与光谱性质。单晶X射线衍射明确确定其分子结构为Th@C₃ᵥ(8)-C₈₂。结合实验与理论研究表明，Th@C₃ᵥ(8)-C₈₂是首例分离得到的单金属内嵌富勒烯，其金属向碳笼转移了四个电子，且拥有令人惊异的宽达1.51 eV的电化学带隙。此外，Th@C₃ᵥ(8)-C₈₂在可见光区域展现出强烈的振动耦合光致发光信号，这一特性在富勒烯与钍类化合物中均极为罕见。