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 (*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 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 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.