Photophysical Investigation of Iron(II) Complexes Bearing Bidentate Annulated Isomeric Pyridine-NHC Ligands
Kévin Magra, Mohamed Darari, Edoardo Domenichini, Antonio Francés‐Monerris, Cristina Cebrián, Marc Beley, Mariachiara Pastore, Antonio Monari, Xavier Assfeld, Stefan Haacke, Philippe C. Gros
Abstract
The possibility of achieving luminescent and photophysically active metal–organic compounds relies on the stabilization of charge transfer states and kinetically and thermodynamically blocking non-radiative dissipative channels. In this contribution, we explore the behavior of bidentate iron complexes bearing N-heterocyclic carbene ligands with extended conjugation systems by a multidisciplinary approach combining chemical synthesis, ultrafast time-resolved spectroscopy, and molecular modeling. Lifetimes of the metal-to-ligand charge transfer and metal-centered states reaching up to ≈20 ps are evidenced, while complex decay mechanisms are pointed out, together with a possible influence of the facial and meridional isomerism. The structural degrees of freedom driving the non-radiative processes are highlighted, and their rigidification is suggested as an effective way to further increase the lifetimes.