Pulse radiolytically induced redox and alkylation processes of C70

Abstract

Redox and alkylation (radical addition) reactions with C₇₀ have been investigated by means of radiation chemical methods, particularly time-resolved pulse radiolysis measurements. All experiments were conducted in solutions (propan-2-ol, 2-methylpropan-2-ol and 1,2-dichloroethane) at room temperature. The differential spectrum obtained upon one-electron reduction of C₇₀ by (CH₃)₂C(OH)˙(k= 8 × 10⁸ dm³ mol^–1 s^–1) and attributable to the formation of C₇₀^˙– shows a relatively weak but still distinct absorption band in the IR at 880 nm. One-electron oxidation of C₇₀ by the cation of 1,2-dichloroethane (1,2-DCE^˙+) yields C₇₀^˙+ radical cations (k 2 × 10¹⁰ dm³ mol^–1 s^–1) with an even weaker but still noticable band at 925 nm. Compared with the IR-absorption bands of the analogue C₆₀^˙– and C₆₀^˙+(which exhibit relatively strong and characteristic bands at 1080 and 980 nm, respectively) those attributable to the C₇₀-derived species are considerably less intense but not absent as might have been deduced from earlier experimental and theoretical studies. IR absorptions (with maxima around 960 nm) have also been observed for (C₇₀–CH₂CH₂Cl)˙ and (C₇₀–CH₂C(CH₃)₂OH)˙ which are formed upon addition of ˙CH₂CH₂Cl (k= 1.9 × 10⁹ dm³ mol^–1 s^–1) and ˙CH₂C(CH₃)₂OH (k= 1.8 × 10⁹ dm³ mol^–1 s^–1), respectively, to C₇₀. The absolute rate constants are very similar to those measured for the corresponding radical reactions with C₆₀. In conclusion, C₇₀ exhibits rather similar features to those of C₆₀ with respect to radical and one-electron redox initiated reactions with, however, some noticeable differences.