The reactions of novel S‐heterocyclic carbenes (SHCs), which were prepared by the cycloaddition of disilenes and digermenes to CS2, with C60 and Sc3N@Ih‐C80 afforded the corresponding methano‐bridged fullerenes. The [6,6]‐closed and [6,6]‐open structures were characterized for the SHC adducts of C60 and Sc3N@Ih‐C80, respectively. These derivatives exhibited relatively low oxidation potentials, indicative of the electron‐donating effects of the SHC addends. The electronic properties of the SHC derivatives were clarified by the density functional theory calculations.

The photolysis of Sc3N@Ih‐C80 with disilirane (1,2‐disilacyclopropane) afforded the corresponding 1,2‐ and 1,4‐adducts. The relatively unstable 1,2‐product was characterized using spectroscopic and electrochemical analyses, and theoretical calculations. The relative energies of the optimized structures are consistent with the experimentally observed isomerization of the 1,2‐adduct to the 1,4‐adduct. The electron‐donating effects of the silyl groups in these products were confirmed by comparing the redox potentials of the related Sc3N@Ih‐C80 derivatives. The relative stabilities and electronic properties of the 1,2‐ and 1,4‐adducts of Lu3N@Ih‐C80 show similar aspects to those obtained for the corresponding Sc3N@Ih‐C80 derivatives.

Under photoirradiation, Sc3N@Ih-C80 reacted readily with disilirane 1, silirane 4, and digermirane 7 to afford the corresponding 1:1 adducts, whereas Sc3N@D5h-C80 was recovered without producing those adducts. Based on these results, we described a novel method for the exclusive separation of Ih and D5h isomers of Sc3N@C80. The method includes three procedures: selective derivatization of Sc3N@Ih-C80 using 1, 4, and 7, facile HPLC separation of pristine Sc3N@D5h-C80 and Sc3N@Ih-C80 derivatives, and thermolysis of Sc3N@Ih-C80 derivatives to collect pristine Sc3N@Ih-C80. In addition, laser flash photolysis experiments were conducted to elucidate the reaction mechanism. Decay of the transient absorption of 3Sc3N@Ih-C80* was observed to be enhanced in the presence of 1, indicating the quenching process. When Sc3N@D5h-C80 was used, the transient absorption was much less intensive. Therefore, the quenching of 3Sc3N@D5h-C80* by 1 could not be confirmed. Furthermore, we applied time-dependent density functional theory (TD-DFT) calculations of the photoexcited states of Sc3N@C80 to obtain insights into the reaction mechanism.