E.s.r. determination of arrhenius parameters for two-site cation jumping in p-benzosemiquinone

Abstract

The Arrhenius parameters for the two-site jumping of the potassium cation in p-benzosemiquinone ion pairs in DME have been determined by comparing computed line width and line amplitude ratios with those derived from experimental spectra over the temperature range –10 to +90°C. The results were E= 3.4 ± 1 kcal mole^–1 and log₁₀A= 9.5 ± 0.5. The A factor indicates a negative entropy of activation for the intramolecular process and this is discussed. A study of two-site jumping of alkali metal ions in 2,5-di-tert butyl p-benzosemiquinone ion pairs in DME has been described. The rate of jumping increases along the series Na < K < Rb. An approximate value for the activation energy of the process has been determined for the potassium derivative.