Energetics and kinetics of homogeneous electrochemiluminescent electron transfer reactions in naphthalimide solutions

Free activation energies and rate constants for bimolecular reactions of electron transfer (RET) between electrogenerated radical ions A(-.) and A(+.) of electrochemiluminophores A (substituted naphthalimides) are calculated. A correlation analysis is conducted for the first time, yielding mechanisms and kinetics of RET that occur in an anomalous (in terms of formation of nonexcited products) region of electron transitions. The correlation dependences of the electrochemiluminescence (ECL) intensity on the free activation energy of RET are plotted. The correlation coefficients pertaining to each series of naphthalimide compounds under study are found for different electrolysis conditions. Comparing the above dependences and coefficients shows adequacy of the expressions proposed for the calculation of rate constants inherent in homogeneous RET. The calculations are made in the framework of the known theories, describing intermolecular exothermic electron transitions, which most closely coincide with the experimental dependences of the ECL intensity on the free activation energy.