Stability of water-stable C₆₀ clusters to OH radical oxidation and hydrated electron reduction

Reactions of water-stable C₆₀ clusters (nC₆₀) in water with OH radicals (•OH) and hydrated electrons (e_aq ^-), generated by steady-state γ-radiation, were observed and characterized. Ordered C₆₀ clusters were relatively recalcitrant to highly reactive •OH and e_aq^- species, with only a fraction of carbons oxidized and reduced, respectively. Pulse radiolysis suggested that the reactions of nC₆₀ with OH• and e _aq^- were diffusion limited, with rate constants of (7.34 ± 0.31) - 10⁹ M^-1 s^-1 and (2.34 ± 0.02) - 10¹⁰ M^-1 s^-1, respectively. Quantum mechanical calculations of binding energy of the C₆₀-OH adduct as a function of C₆₀ 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 C₆₀ in the aqueous phase significantly hinders C₆₀s fundamental reactivity with radical species.