Guidelines to calculate non-radiative deactivation mechanisms of ruthenium tris(bipyridine) derivatives
David Hernández‐Castillo, Isabel Eder, Leticia González
Abstract
The applicability of ruthenium tris(bipyridine) complexes in fields like photoactivated chemotherapy or photocatalysis requires in-depth understanding of their excited state deactivation mechanism. In particular, the quenching of luminescence from the lowest triplet metal-to-ligand charge-transfer () excited state or the ligand photorelease relies on the fine-tuning of the energetics of the higher-lying metal-centered excited states (). In this contribution, we critically review different kinetic models commonly used to interpret the thermal activation of the excited states from the lowest minimum. Further, we extend our recently introduced kinetic model (Angew. Chem. Int. Ed. 2023, 62, e202308803) for (bpy = 2,2'-bipyridine) to a set of homoleptic tris(bipyridine)ruthenium (II) derivatives. This set has been selected to cover a wide range of electron -withdrawing/-donating substituents in the periphery of the bipyridyl ligands (4,4'--2,2'-bpy; R= , , , , , and ), on the basis of the Hammett's constant of the R functional group. Our calculations show that complexes with electron donating groups decay predominantly via one Jahn-Teller isomer (the so-called -trans conformation), while those with electron withdrawing ligands tend to decay through a different one (the -cis Jahn-Teller isomer). We discuss structure/property relationships with focus on how to steer the energetics of the excited states. This work opens the pathway to rationally use ligand substitution to enhance or quench the lifetimes of the state and also provides guidelines to understand better non-radiative deactivation mechanisms in metal complexes.