Stability of Water-Stable C60 Clusters to OH Radical Oxidation and Hydrated Electron Reduction

Reactions of water-stable C-60 clusters (nC(60)) in water with OH radicals (center dot OH) and hydrated electrons (e(aq)(-)), generated by steady-state gamma-radiation, were observed and characterized. Ordered C-60 clusters were relatively recalcitrant to highly reactive center dot OH and e(aq)(-) species, with only a fraction of carbons oxidized and reduced, respectively. Pulse radiolysis suggested that the reactions of nC(60) with OH center dot and e(aq)(-) were diffusion limited, with rate constants of (7.34 +/- 0.31) X 10(9) M-1 s(-1) and (2.34 +/- 0.02) x 10(10) M-1 s(-1), respectively. Quantum mechanical calculations of binding energy of the C-60-OH adduct as a function of C-60 clustering degree indicate, despite an initial fast reaction, a slower overall conversion due to thermodynamic instability of C-60-OH intermediates. The results imply that ordered clustering of C-60 in the aqueous phase significantly hinders C-60's fundamental reactivity with radical species.