Quantum Chemical Insight of the Dimetallic Sulfide Endohedral Fullerene Sc 2 S@C 70 : Does It Possess the Conventional D 5 h Cage?

Like C 60 , C 70 is one of the most representative fullerenes in fullerene science. Even though there are 8149 C 70 isomers, only two of them have been found before: the conventional D 5 h and an isolated pentagon rule (IPR)‐violating C 2 v (7854). Through the use of quantum chemical methods, we report a new unconventional C 70 isomer, C 2 (7892), which survives in the form of dimetallic sulfide endohedral fullerene Sc 2 S@C 70 . Compared with the IPR‐obeying C 70 and the C 2 v (7854) fullerene with three pairs of pentagon adjacencies, the C 2 (7892) cage violates the isolated pentagon rule and has two pairs of pentagon adjacencies. In Sc 2 S@ C 2 (7892)‐C 70 , two scandium atoms coordinate with two pentalene motifs, respectively, presenting two equivalent ScS bonds. The strong coordination interaction, along with the electron transfer from the Sc 2 S cluster to the fullerene cage, results in the stabilization of the non‐IPR endohedral fullerene. The electronic structure of Sc 2 S@C 70 can be formally described as [Sc 2 S] 4+ @[C 70 ] 4− ; however, a substantial overlap between the metallic orbitals and cage orbitals has also been found. Electrochemical properties and electronic absorption, infrared, and 13 C NMR spectra of Sc 2 S@C 70 have been calculated theoretically.