Electrolyte effects in intramolecular electron transfer

Pulse radiolijsis and laser photolysis were used to study intramolecular electron transfer (ET) reactions in solutions of electrolytes. The presence of counterions has been found to slow the rate of weakly exoergic (ΔG = 100 meV) electron transfer by as much as 3 orders of magnitude. The larger counterions resulted in a larger decrease of the ET rate, suggesting that the transfer rate is influenced by the mobility of ions. In a separate study, transient triplet charge-transfer (CT) absorption bands of p-minonitroterphemyl were used as probes of ion-pairing dynamics and energetics. It has been found that the pairing process is diffusion controlled, and that in weakly polar media, association with ions can stabilize the photoinduced charge-separated state by up to 1 eV.