Structures, stabilities, electronic, and optical properties of C 64 fullerene isomers, anions (C 64 2− and C 64 4− ), metallofullerene Sc 2 @C 64 , and Sc 2 C 2 @C 64

The 3465 classical isomers of C 64 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. C 64 ( D 2 :0003) with the lowest e 55 ( e 55 = 2), the number of pentagon‐pentagon fusions, is predicted to be the most stable isomer and it is followed by the C 64 ( C s :0077) and C 64 ( C 2 :0103) isomers within relative energy of 20.0 kcal/mol. C 64 ( D 2 :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 e 55 = 2 display local aromaticity. The relative stabilities of C 64 isomers change with charging in ionic states. Doping also affects the relative stabilities of fullerene isomers as demonstrated by Sc 2 @C 64 ( D 2 :0003) and Sc 2 @C 64 ( C s :0077). The bonding of Sc atoms with C 64 elongates the CC bond of two adjacent pentagons and enhances the local aromaticity of the fullerene cages. Charging, doping, and derativization can be utilized to isolate C 64 isomers through differentiating the electronic and steric effects. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008