Photoreactions of Sc₃N@C₈₀ with Disilirane, Silirane, and Digermirane: A Photochemical Method to Separate I_h and D_5h Isomers

Under photoirradiation, Sc₃N@I_h-C₈₀ reacted readily with disilirane 1, silirane 4, and digermirane 7 to afford the corresponding 1:1 adducts, whereas Sc₃N@D_5h-C₈₀ was recovered without producing those adducts. Based on these results, we described a novel method for the exclusive separation of I_h and D_5h isomers of Sc₃N@C₈₀. The method includes three procedures: selective derivatization of Sc₃N@I_h-C₈₀ using 1, 4, and 7, facile HPLC separation of pristine Sc₃N@D_5h-C₈₀ and Sc₃N@I_h-C₈₀ derivatives, and thermolysis of Sc₃N@I_h-C₈₀ derivatives to collect pristine Sc₃N@I_h-C₈₀. In addition, laser flash photolysis experiments were conducted to elucidate the reaction mechanism. Decay of the transient absorption of ³Sc₃N@I_h-C₈₀^* was observed to be enhanced in the presence of 1, indicating the quenching process. When Sc₃N@D_5h-C₈₀ was used, the transient absorption was much less intensive. Therefore, the quenching of ³Sc₃N@D_5h-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.