Accurate Thermochemical and Kinetic Stabilities of C84 Isomers

Accurate double-hybrid density functional theory and isodesmic-type reaction schemes are utilized to report accurate estimates of the heats of formation (Δ_fH) for all 24 isolated-pentagon-rule isomers of the third most abundant fullerene, C₈₄. Kinetic stabilities of these C₈₄ isomers are also considered via C-C bond cleavage rates (P_cleav) calculated using density functional theory. Our results show that the relative abundance of C₈₄ fullerene isomers observed in arc discharge synthesis is the result of both thermochemical and kinetic factors. This provides timely insight regarding the characterization of several C₈₄ isomers that have been obtained experimentally to date. For instance, the established assignments of C₈₄ isomers of (using the Fowler-Manolopoulos numbering scheme) 22 [D₂(IV)], 23 [D_2d(II)], 19 [D_3d], 24 [D_6h], 11 [C₂(IV)], and 4 [D_2d(I)] are consistent with the relative Δ_fH and P_cleav values for these structures. However, our thermochemical and kinetic stabilities of C_s isomers 14, 15, and 16 indicate that the two experimentally isolated C_s isomers are 15 and 16, contrary to some previous assignments. Of the remaining isolated isomers of symmetry C₂ and D₂, definitive assignment was not possible with consideration of only Δ_fH and P_cleav.