Electrogenerated chemiluminescence. XV. On the formation of excimers and exciplexes in ECL

The emission resulting from the reaction of electrogenerated radical anions ((A-+) and cations (D-+) (ECL) for four systems which provide evidence for the intermediacy of excimers or exciplexes is described. The effect of solvent and supporting electrolyte concentration and the energetics of the radical ion reaction on the nature of the emission is discussed and the results are compared with previous chemiluminescence studies of Weller and Zachariasse. For one system involving trans-stilbene radical anion and tri-p-tolylamine radical cation, only radiation attributable to an exciplex formed in the initial cation-anion encounter, is observed.