Solvent dynamical effects on the electron self-exchange rate of the TEMPO˙/TEMPO⁺couple (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyloxy radical) : Part I. ESR-linebroadening measurements at T = 298 K

Abstract

Rate constants of the electron self-exchange for the TEMPO˙/TEMPO+ couple were measured in acetonitrile, benzonitrile, deuterium oxide, propylene carbonate, THF and water at T = 298 K. The experimental rate constants cover a range of 0.88 × 108 ⩽ ket ⩽ 5.0 × 108 M−1 s−1 and clearly show a solvent dynamical “friction” effect controlled by the longitudinal relaxation time of the solvent τL.