Intense Photoinduced Intervalence Charge Transfer in High‐Valent Iron Mixed Phenolate/Carbene Complexes

MUNZ, DOMINIK; GRAVOGL, LISA; CADRANEL, ALEJANDRO; MEYER, KARSTEN

CHEMISTRY-A EUROPEAN JOURNAL

WILEY-V C H VERLAG GMBH

Año: 2022

0947-6539

We report high-valent iron complexes, supported by N -heterocyclic carbene (NHC)-anchored, bis-phenolate pincer ligands that undergo ligand-to-metal charge transfer (LMCT) upon photoexcitation. The resulting excited states ? with a lifetime in the pico-second range ? feature a ligand-based mixed-valence system and intense inter­valence charge transfer bands in the near-infrared (NIR) region. Upon oxidation of the complex, corres­ponding intervalence charge transfer (IVCT) absorptions are also observed in the ground state. We suggest that the spectroscopic hallmarks of such LMCT states provide useful tools to decipher excited state decay mechanisms in high-valent NHC complexes. Our obser­vations further indicate that NHC-anchored, bis-phenolate pincer ligands are not sufficiently strong donors to prevent the population of excited metal-centered (MC) states in high-valent iron complexes.