Sc2O@C3v(8)‑C82: A Missing Isomer of Sc2O@C82

By introducing CO2 as the oxygen source during the arcing process, a new isomer of Sc2O@C82, Sc2O@C3v(8)-C82, previously investigated only by computational studies, was discovered and characterized by mass spectrometry, UV–vis–NIR absorption spectroscopy, cyclic voltammetry, 45Sc NMR, density functional theory (DFT) calculations, and single-crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C3v(8) and suggests that Sc2O cluster is disordered inside the cage. The comparative studies of crystallographic data further reveal that the Sc1–O–Sc2 angle is in the range of 131.0–148.9°, much larger than that of the Sc2S@C3v(8)-C82, demonstrating a significant flexibility of dimetallic clusters inside the cages. The electrochemical studies show that the electrochemical gap of Sc2O@C3v(8)-C82 is 1.71 eV, the largest among those of the oxide cluster fullerenes (OCFs) reported so far, well correlated with its rich abundance in the reaction mixture of OCF synthesis. Moreover, the comparative electrochemical studies suggest that both the dimetallic clusters and the cage structures have major influences on the electronic structures of the cluster fullerenes. Computational studies show that the cluster can rotate and change the Sc–O–Sc angle easily at rather low temperature.