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 int erface to produce an electrode/thin layer organic phase/aqueous solution co nfiguration, the electrogenerated radical species formed in the PhCN phase (C12-Ru(bpy)(3)(3+), DPA(+), or TH+) diffused to the liquid/ liquid interfa ce to react with (oxidize) a coreactant (C2O42-) soluble only in the aqueou s solution, leading to the formation of a strongly reducing radical species (CO2.-). The electron transfer from CO2.- in the aqueous solution to the o xidized species in the organic phase across the liquid/liquid interface pro duced an electronically excited state which then emitted light. The appeara nce of an ECL signal in these systems supports: the suggestion of Marcus in verted region behavior in very exothermic heterogeneous electron-transfer r eactions at the liquid/ liquid interface.