Redox mediated enhancement and quenching of co-reactant electrochemiluminescence by iridium(III) complexes

Enhancement of the electrochemiluminescence (ECL) of tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) and tri-n-propylamine by redox mediators has emerged as a new approach to maximise the sensitivity of this mode of detection. Herein, we examine the influence of six water-soluble iridium(III) complexes on this widely used ECL system by deconvoluting their respective contributions to the overall ECL intensity over a range of applied potentials. The interconnected co-reactant ECL of these metal complexes, eliciting enhancement or quenching of the [Ru(bpy)3]2+ emission, can be understood by considering the available reaction pathways under different conditions and the disparate electrochemical and photophysical properties of the reactants. The ideal properties for enhancement are established, which will inform the future design and application of redox mediators in this ECL system.