Sc(2)S@C(84) has recently been detected but not structurally characterized.1 Density functional theory calculations on C(84) and Sc(2)S@C(84) show that the favored isomer of Sc(2)S@C84 shares the same parent cage as Sc(2)C2@C(84), whereas Sc(2)S@C(84):51383, which violates the isolated-pentagon rule, is the second lowest energy isomer with the widest HOMO-LUMO gap and shows high kinetic stability. The analysis shows that Sc(2)S@C(84):51575 is favored when the temperature exceeds 2,800 K and it can transform into the most favorable isomer Sc(2)S@C(84):51591. Molecular orbital analysis indicates that both Sc(2)S and Sc(2)C(2) formally transfer four electrons to the cage, and quantum theory of atoms in molecules analysis demonstrates that there is a covalent interaction between Sc(2)S and C(84):51591. The IR spectra of Sc(2)S@C(84) are provided to aid future structural identification.
Keywords: density functional calculations; fullerenes; molecular orbitals; quantum chemistry; scandium.
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