Electrocatalytic amplification of coreactant electrochemiluminescence using redox mediators

Electrochemiluminescence (ECL) has emerged as a sensitive analytical technique with a wide range of applications. While recent studies have begun to explore the role of redox mediators to facilitate ECL systems, this work extends these foundational insights by developing a comprehensive theoretical framework that supports, generalizes, and rationalizes mechanistic pathways borrowed from molecular electrocatalysis. This advancement is demonstrated through the electrocatalytic amplification of coreactant ECL within the [Ru(bpy)3]2+/TPrA system, utilizing a water-soluble redox-active Ir(III) complex as an electrocatalyst. Our investigation unveils previously uncharted mechanisms that enable the enhancement of Ru complex ECL at low electrode potentials, crucially without requiring the direct oxidation of [Ru(bpy)3]2+ or TPrA at the electrode, thus offering a deeper understanding of ECL activation through moelcular electrocatalysis. Through an integrated approach combining electrochemical analysis, spectroscopic investigation, and finite element modeling, we elucidate how the redox mediator critically modulates ECL efficiency by controlling the kinetics of radical species production and decay. The mediation by the Ir(III) complex not only governs the generation of TPrA radicals and excited [Ru(bpy)3]2+ states, thereby enhancing ECL intensity, but also the conditions under which ECL can be quenched. Further exploration of the mediator's redox characteristics provides predictive insights into ECL behavior, underscoring the mediator's redox potential as pivotal in determining ECL onset, peak potential, and intensity. This refined understanding paves the way for tailoring ECL systems for enhanced performance in analytical, imaging, and biomedical applications through the judicious selection of redox mediators.