A new record excited state 3MLCT lifetime for metalorganic iron(II) complexes

Herein we report the synthesis and time-resolved spectroscopic characterization of a homoleptic Fe(II) complex exhibiting a record (MLCT)-M-3 lifetime of 26 ps promoted by benzimidazolylidene-based ligands. Time dependent density functional molecular modeling of the triplet excited state manifold clearly reveals that, at equilibrium geometries, the lowest (MC)-M-3 state lies higher in energy than the lowest (MLCT)-M-3 one. This unprecedented energetic reversal in a series of iron complexes, with the stabilization of the charge-transfer state, opens up new perspectives towards iron-made excitonic and photonic devices, hampering the deactivation of the excitation via metal centered channels.