First- and second-electron affinities of ${\text{C}}_{60}$ and ${\text{C}}_{70}$ isomers

We present density functional theory calculations of ${\text{C}}_{60}^{q-}$ and ${\text{C}}_{70}^{q-}$ $\left(q=0-2\right)$ isomers that contain zero to three pairs of adjacent pentagons. The first- and second-electron affinities for the archetype structures of ${\text{C}}_{60}$ and ${\text{C}}_{70}$ are close to the experimental results, while isomers with pentagon adjacencies have significantly higher values. The results are rationalized in view of the numbers and locations of pentagon adjacencies in the fullerene cages and the spherical aromaticity for the magic number ${\text{C}}_{70}^{2-}$ with a closed $\left(\text{l}=5\right)$ electronic shell in the spherical gas model.

Figure 1

(Color online) Schlegel diagrams of the ${\text{C}}_{60}$ isomers studied in the present work. Pairs of adjacent pentagons are shown in blue (dark shading), isolated pentagons in yellow (light shading), pyrene bonds in red (dark shading), and hexagons in white.

Figure 2

(Color online) Left: The relative energies (with respect to the energy of the neutral IPR fullerene) of the ${\text{C}}_{60}$ isomers studied in the present work. Right: The first- and second-electron affinities.

Figure 3

(Color online) Schlegel diagrams of the ${\text{C}}_{70}$ isomers studied in the present work. Pairs of adjacent pentagons are shown in blue (dark shading), isolated pentagons in yellow (light shading), pyrene bonds in red (dark shading), and hexagons in white.

Figure 4

(Color online) Left: The relative energies (with respect to the energy of the neutral IPR fullerene) of the ${\text{C}}_{70}$ isomers studied in the present work. Right: The first- and second-electron affinities.