Electron transfer within 1,3-dinitrobenzene radical anions: electron hopping or superexchange?

The intramolecular electron transfer on several 1,3‐dinitrobenzene radical anions with different substituents on position 5 was studied by electron paramagnetic resonance and optical spectroscopies in MeCN. The radical anions are all charge‐localized mixed valence species, as is common for meta‐substituted dinitrobenzenes. Rate constants for the electron transfer reaction were obtained by the Marcus–Hush analysis of the intervalence optical bands assuming quartic‐augmented energy surfaces and solvent‐controlled dynamics. These calculated rate constants match quite well the experimental ones obtained by simulation of the electron paramagnetic resonance spectra, which rules out bridge‐reduced states as intermediates in the reaction path and confirms the superexchange mechanism. Copyright © 2012 John Wiley & Sons, Ltd. The rates of intramolecular electron transfer in a series of 1,3‐dinitrobenzene radical anions calculated by the Marcus–Hush analysis of the intervalence optical bands (kopt) match quite well the experimental rates obtained by simulation of the dynamical linebroadening effects induced by the reaction on the EPR spectra (kepr), confirming the superexchange mechanism.