Accurate Thermochemical and Kinetic Stabilities of C84 Isomers

Abstract

Accurate double-hybrid density functional theory and isodesmic-type reaction schemes are utilized to report accurate estimates of the heats of formation (Δf H) 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 ( Pcleav) 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 [ D2 d(II)], 19 [ D3 d], 24 [ D6 h], 11 [ C2(IV)], and 4 [ D2 d(I)] are consistent with the relative Δf H and Pcleav 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 Δf H and Pcleav.