Simulating 3D Electrochemiluminescence Reveals Energy-Transfer-Driven DPA Emission in DPA/Ru(bpy)32+ Mixtures

The annihilation electrochemiluminescence (ECL) of mixed luminophore systems offers a powerful route to color-tunable emission, but its output is often governed by a complex interplay of competing reaction pathways. Herein, the classic mixed system of 9,10-diphenylanthracene (DPA) and tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+) is investigated using potential-resolved multicolor ECL (3D-ECL) spectroscopy. Despite direct formation of DPA’s emissive singlet state being thermodynamically inaccessible across most reaction pathways, the mixed system exhibits a remarkable nine-fold enhancement of its characteristic blue emission. We demonstrate that this enhancement is mechanistically driven by two sequential processes: efficient population of the DPA triplet state (3DPA*) via energy transfer (En.T.) from the excited ruthenium(II) complex, followed by triplet-triplet annihilation (TTA) to generate the emissive singlet state. For the first time, these mechanistic assignments are validated quantitatively by simulating the complete 3D-ECL matrices using KISSA-1D software. This combined experimental and computational framework confirms the dominant role of the sensitized TTA pathway and provides a powerful new strategy for elucidating the mechanisms of complex, multicolor ECL systems.