The adiabatic ionization potential (AIP), electron affinity (AEA), and relative reduction potential (E0) of fullerene C60 and fullerenols C60(OH)n (n=12, 22, 24, and 36) were calculated to determine the effect of increasing hydroxylation on antioxidant activity. Then, electrostatic potential maps were generated for the fullerenols to determine how positive centers relate to hydroxylation. Additionally, six conformations of C60(OH)22 were studied to determine the effect of hydroxyl distribution on fullerenol stability. All structures were generated using the Gaussian ’09 software package. The neutral, cation, and anion states of the fullerenols were optimized without constraint using the B3LYP method with a 6-31G** basis set. The AIP, AEA, and E0 of gas phase fullerenols (n=12, 22, 24, and 36) were calculated by applying the Born-Haber Cycle. Electrostatic potential maps were generated in Spartan 14 using the same method and basis set. Fullerenols C60(OH)22 and C60(OH)36 proved to be the most effective at scavenging negative charge with AEA values of 0.125 and 0.175 eV and E0 values of 2.69 and 4.03 eV respectively. The relative neutral optimization energies of n=22 conformations revealed that fullerenol stability is heavily dependent upon hydroxyl distribution. The electrostatic maps supported this finding and revealed that n=22 and n=36 had the most positive centers. The combination of these results revealed that the relative positioning of hydroxyl groups determines the reactivity and stability of fullerenols. As such, it was determined that the propensity to scavenge negative charge, stability, and formation of positive centers on fullerenols is determined by hydroxyl interaction on the fullerene cage. This yielded high electron affinities, high reduction potentials, and low ionization potentials for n=22 and 36 making the two fullerenols the most promising antioxidants.

New metrics for the reactivity and stability of antioxidant fullerenols found using the Born-Haber cycle

255th National Meeting (2018)

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