Mohamed Darari1, Antonio Francés-Monerris2,3, Bogdan Marekha4, Abdelatif Doudouh5, Emmanuel Wenger5, Antonio Monari2, Stefan Haacke6, Philippe C Gros1. 1. Université de Lorraine, CNRS, L2CM, F-54000 Nancy, France. 2. Université de Lorraine, CNRS, LPCT, F-54000 Nancy, France. 3. Departament de Química Física, Universitat de València, 46100 Burjassot, Spain. 4. Max-Planck-Institute for Medical Research, 69120 Heidelberg, Germany. 5. Université de Lorraine, CNRS, CRM2, F-54000 Nancy, France. 6. Université de Strasbourg, CNRS, IPCMS, F-67034 Strasbourg, France.
Abstract
The control of ligand-field splitting in iron (II) complexes is critical to slow down the metal-to-ligand charge transfer (MLCT)-excited states deactivation pathways. The gap between the metal-centered states is maximal when the coordination sphere of the complex approaches an ideal octahedral geometry. Two new iron(II) complexes (C1 and C2), prepared from pyridylNHC and pyridylquinoline type ligands, respectively, have a near-perfect octahedral coordination of the metal. The photophysics of the complexes have been further investigated by means of ultrafast spectroscopy and TD-DFT modeling. For C1, it is shown that-despite the geometrical improvement-the excited state deactivation is faster than for the parent pseudo-octahedral C0 complex. This unexpected result is due to the increased ligand flexibility in C1 that lowers the energetic barrier for the relaxation of 3MLCT into the 3MC state. For C2, the effect of the increased ligand field is not strong enough to close the prominent deactivation channel into the metal-centered quintet state, as for other Fe-polypyridine complexes.
The control of ligand-field splitting in iron (II) complexn class="Chemical">es is critical to slow down the metal-to-ligand charge transfer (MLCT)-excited states deactivation pathways. The gap between the metal-centered states is maximal when the coordination sphere of the complex approaches an ideal octahedral geometry. Two new iron(II) complexes (C1 and C2), prepared from pyridylNHC and pyridylquinoline type ligands, respectively, have a near-perfect octahedral coordination of the metal. The photophysics of the complexes have been further investigated by means of ultrafast spectroscopy and TD-DFT modeling. For C1, it is shown that-despite the geometrical improvement-the excited state deactivation is faster than for the parent pseudo-octahedral C0 complex. This unexpected result is due to the increased ligand flexibility in C1 that lowers the energetic barrier for the relaxation of 3MLCT into the 3MC state. For C2, the effect of the increased ligand field is not strong enough to close the prominent deactivation channel into the metal-centered quintet state, as for other Fe-polypyridine complexes.
Entities:
Keywords:
density functional theory; excited states dynamics; iron (II) complexes; octahedral geometry; time-resolved spectroscopy