Modeling Non-Radiative Processes in Luminescent Eu(III) Coordination Complexes

Computational tools, together with theoretical models developed by our research group and others, have been employed to investigate the non-radiative processes governing the photophysical behavior of luminescent Eu(III) coordination complexes. The study focuses on understanding the dependence of luminescence quenching on the electronic structure of the ligands, particularly the relative energies of intraligand (IL) and ligand-to-metal charge-transfer (LMCT) excited states, as well as the competition between LMCT-mediated deactivation and multiphonon relaxation. Neutral ligands, including heterobiaryls and amides derived from 2-aminopyridine and pyrimidine, together with anionic ligands such as β-diketonates, aromatic carboxylates, and NCS⁻, have been selected to systematically modulate the energetic ordering of IL and LMCT excited states. The proposed theoretical models provide plausible mechanistic interpretations of the observed photophysical properties and successfully rationalize luminescence quenching while yielding satisfactory predictions of the luminescence quantum efficiencies.