Multiple Triplet Metal‐Centered Jahn‐Teller Isomers Determine Temperature‐Dependent Luminescence Lifetimes in [Ru(bpy)3]2+

Abstract

AbstractUnderstanding the factors that determine the luminescence lifetime of transition metal compounds is key for applications in photocatalysis and photodynamic therapy. Here we show that for (bpy = 2,2’‐bipyridine), the generally accepted idea that emission lifetimes can be controlled optimizing the energy barrier from the emissive triplet metal‐to‐ligand charge‐transfer (3MLCT) state to the thermally‐activated triplet metal‐centered (3MC) state or the energy gap between both states is a misconception. Further, we demonstrate that considering a single relaxation pathway determined from the minimum that is lowest in energy leads to wrong temperature‐dependent emission lifetimes predictions. Instead, we obtain excellent agreement with experimental temperature‐dependent lifetimes when an extended kinetic model that includes all the pathways related to multiple Jahn–Teller isomers and their effective reaction barriers is employed. These concepts are essential to correctly design other luminescent transition metal complexes with tailored emission lifetimes based on theoretical predictions.