Structures, stabilities, electronic, and optical properties of C64 fullerene isomers, anions (C<STACK>642-</STACK> and C644-), metallofullerene Sc2@C64, and Sc2C2@C64

The 3465 classical isomers of C₆₄ fullerene have been investigated by quantum chemical methods PM3, and the most stable isomers have been refined with HCTH/3-21G//SVWN/STO-3G, B3LYP/6-31G(d)//HCTH/3-21G, and B3LYP/6-311G(d)//B3LYP/6-31G(d) level. C₆₄(D₂:0003) with the lowest e₅₅ (e₅₅ = 2), the number of pentagon-pentagon fusions, is predicted to be the most stable isomer and it is followed by the C₆₄(C_s:0077) and C₆₄(C₂:0103) isomers within relative energy of 20.0 kcal/mol. C₆₄(D₂:0003) prevails in a wide temperature range according to energy analysis with entropy contribution at B3LYP/6-31G(d) level. The simulated IR spectra and electronic spectra help to identify different fullerene isomers. All the hexagons in the isomers with e₅₅ = 2 display local aromaticity. The relative stabilities of C₆₄ isomers change with charging in ionic states. Doping also affects the relative stabilities of fullerene isomers as demonstrated by Sc₂@C₆₄(D₂:0003) and Sc₂@C₆₄(C_s:0077). The bonding of Sc atoms with C₆₄ elongates the C&bond;C bond of two adjacent pentagons and enhances the local aromaticity of the fullerene cages. Charging, doping, and derativization can be utilized to isolate C₆₄ isomers through differentiating the electronic and steric effects. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 [ABSTRACT FROM AUTHOR]