Chapter 2. Energetic and Kinetic Aspects of ECL Generation

Strongly exergonic electron transfer annihilation processes between electrochemically generated oxidant D+ and reductant A− are able to produce electronically excited *D and/or *A species. Depending on the energy released in the A−+D+ reaction, the excited triplet states (3*D or 3*A) as well as the excited singlet states, (1*D or 1*A) can be populated. An intrinsic electron transfer step within [A−⋯D+] pair is additionally preceded/followed by diffusion of reactants/products from/into the bulk solutions as well as associated with spin up-conversion processes between different spin forms of an activated complex 1[A−⋯D+] and 3[A−⋯D+]. All of these processes are implementable in the mechanistic description of the ECL phenomena with formulation of the ECL excitation schemes. The presented qualitative as well quantitative discussion of the resulting schemes may allow deeper insight into mechanisms and efficiencies of the ECL excitation.