Inverted region electron transfer demonstrated by electrogenerated chemiluminescence at the liquid/liquid interface

We describe several transinterface electron-transfer processes occurring at the benzonitrile (PhCN)/water interface that produce excited states. When an electrode was moved very close to the inter face or even through the interface to produce an electrode/thin layer organic phase/aqueous solution configuration, the electrogenerated radical species formed in the PhCN phase (C12-Ru(bpy)(3)(3+), DPA(+), or TH+) diffused to the liquid/ liquid interface to react with (oxidize) a coreactant (C2O42-) soluble only in the aqueous solution, leading to the formation of a strongly reducing radical species (CO2.-). The electron transfer from CO2.- in the aqueous solution to the oxidized species in the organic phase across the liquid/liquid interface produced an electronically excited state which then emitted light. The appearance of an ECL signal in these systems supports: the suggestion of Marcus inverted region behavior in very exothermic heterogeneous electron-transfer reactions at the liquid/ liquid interface.