Solvent induced intramolecular electron exchange kinetics in 1,3‐isodisubstituted aromatic radical anions I. ESR‐measurements at 280 K

The rate constants of the intramolecular solvent induced electron transfer in 1,3‐dinitrobenzene and benzene‐1,3‐dicarbaldehyde radical anions were measured in different solvents by means of ESR‐spectroscopy using the alternating linewidth effect. At 280 K, for benzene‐1,3‐dicarbaldehyde the rate constants are 0.89–1.52·10 9 s −1 in several alcohols, whereas for the 1,3‐dinitrobenzene radical they are 1.16–2.19–10 6 s −1 in alcohols and 2.8–4.2·10 9 s −1 in aprotic solvents. The reactions were found to be adiabatic and uniform in the sense of classical transition state theory. From the solvent dependence of the rate constants, the transferred charge was determined applying Marcus theory as being z = 0.31 for the benzene‐1,3‐dicarbaldehyde, z = 0.84 for the 1,3‐dinitrobenzene radical anion in alcohols and z = 0.51 in aprotic solvents. The ellipsoidal cavity model was employed for evaluating the outer sphere reorganization energy λ 0 .