Ion Pair Formation between Organic Cations and Nitrobenzene and Nitrosobenzene Redox Species and Its Effects Upon Voltammetric Behavior

It has been known for many years that the voltammetric behavior of polycyclic aromatic hydrocarbons (PAHs) in aprotic solvents is dependent upon the nature of the supporting electrolyte. 1,2 We have shown that this is due to ion pairing of the PAH dianion to the cation of the supporting electrolyte, which has the effect of moving the second voltammetric wave to more positive potentials. 3 That is, one cannot describe the system simply by equations 1 and 2 in Scheme 1; one must include the effect of ion-pair association between the cation of the electrolyte and the dianion of the PAH (Equation 3). We have shown that the ion-pairing association constant Kassoc between the two species can be computed to excellent accuracy by a density functional theory (DFT) quantum chemical technique and that the cyclic voltammogram of several PAHs in the presence of several tetraalkylammonium ions can be simulated 4 very closely when the computed Kassoc for each particular cation is included in the simulation. 5,6