Quantum Chemical Insight of the Dimetallic Sulfide Endohedral Fullerene Sc2S@C70: Does It Possess the Conventional D5h Cage?

Like C60, C70 is one of the most representative fullerenes in fullerene science. Even though there are 8149 C70 isomers, only two of them have been found before: the conventional D5h and an isolated pentagon rule (IPR)-violating C2v(7854). Through the use of quantum chemical methods, we report a new unconventional C70 isomer, C2(7892), which survives in the form of dimetallic sulfide endohedral fullerene Sc2S@C70. Compared with the IPR-obeying C70 and the C2v(7854) fullerene with three pairs of pentagon adjacencies, the C2(7892) cage violates the isolated pentagon rule and has two pairs of pentagon adjacencies. In Sc2S@C2(7892)-C70, 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 Sc2S cluster to the fullerene cage, results in the stabilization of the non-IPR endohedral fullerene. The electronic structure of Sc2S@C70 can be formally described as [Sc2S]4+@[C70]4; however, a substantial overlap between the metallic orbitals and cage orbitals has also been found. Electrochemical properties and electronic absorption, infrared, and 13CNMR spectra of Sc2S@C70 have been calculated theoretically.