Issue 47, 2023

Ultrafast 3MLCT quenching and vibrational coherence: excited-state dynamics of the first-discovered Fe(ii)–carbene sensitiser resolved

Abstract

The application of N-heterocyclic carbene (NHC) ligands represents a groundbreaking advance towards environment-friendly light-harvesting complexes, yet, even the excited-state dynamics of the first-discovered Fe–NHC photosensitiser [Fe(bmip)2]2+ (bmip = 2,6-bis(3-methyl-imidazole-1-ylidine)-pyridine) remain controversial. Using full-dimensional trajectory surface hopping (TSH) spin-vibronic dynamics simulations, we fully resolve and clarify the deactivation mechanism of [Fe(bmip)2]2+. In agreement with the most recent fs-resolved X-ray experiments, we find that the excited-state population branches into triplet metal-to-ligand charge transfer (3MLCT) and metal-centered states (3MC) on early sub-ps timescales (∼200 fs). The ultrafast 3MLCT quenching by 3MC is driven by multidimensional excited-state ligand motion; it is this deactivation process that ultimately weakens the photosensitising efficiency of [Fe(bmip)2]2+. Crucially, the preservation of vibrational coherence along the covalent Fe–C bonds (∼300 fs vibrational period) and the appearance of resulting coherent oscillations in various time-resolved experimental data unambiguously evidence the presence of the early sub-ps 3MC component.

Graphical abstract: Ultrafast 3MLCT quenching and vibrational coherence: excited-state dynamics of the first-discovered Fe(ii)–carbene sensitiser resolved

Supplementary files

Article information

Article type
Paper
Submitted
02 Okt. 2023
Accepted
12 Nov. 2023
First published
13 Nov. 2023
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2023,11, 25955-25962

Ultrafast 3MLCT quenching and vibrational coherence: excited-state dynamics of the first-discovered Fe(II)–carbene sensitiser resolved

M. Pápai, T. Rozgonyi and G. Vankó, J. Mater. Chem. A, 2023, 11, 25955 DOI: 10.1039/D3TA05985E

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