Probing the Electron-Accepting Reactivity of Isomeric Bis(pyrrolidinium) Fullerene Salts in Aqueous Solutions

Abstract

A series of water-soluble isomer bis(pyrrolidinium) salts, with C60(C4H10N+)2 as cationic moiety (2a−2d), were probed in radical- and light-induced reduction studies and compared to bis(carboxylates) C60[C(COO-)2]2 and to γ-CD-encapsulated C60. Pulse radiolytic reduction of 2a−2d with hydrated electrons and (CH3)2•COH radicals leads to the formation of the fullerene π-radical anion, exhibiting fingerprint absorption characteristics in the near-IR region. Because of the electron-withdrawing nature of the pyrrolidinium groups the electron-acceptor properties of the investigated bis(pyrrolidinium) salts are markedly improved relative to the bis(carboxylates) (C60[C(COO-)2]2) and also relative to C60. For example, the rate constants for the fullerene reduction of 2a−2d with hydrated electrons ((0.88−2.2) × 1010 M-1 s-1) and (CH3)2•COH radicals ((4.7−7.1) × 108 M-1 s-1) are clearly faster than those noted for C60[C(COO-)2]2 (eaq-: (0.19−0.34) × 1010 M-1 s-1; (CH3)2•COH: (0.9−2.2) × 108 M-1 s-1), and C60 (eaq...