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Tuning the 2LMCT Deactivation of Cyclometalated Iron Carbene Complexes with Electronic Substituent Effects

Mishra, Abhishek LU ; Sharma, Kumkum LU ; Johnson, Catherine Ellen ; Fosu, Emmanuel Adu ; Schwarz, Jesper LU ; Prakash, Om LU ; Gupta, Arvind Kumar LU ; Huang, Ping LU ; Lindgren, Fredrik and Häggström, Lennart , et al. (2025) In Chemistry - A European Journal 31(47).
Abstract

FeIII complexes based on the [FeIII(ImP)2]+ motif (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)), where the ligand contains both carbene and cyclometalated moieties, are a promising class of photoactive materials made from this abundant metal. In this work, it is shown that bromo or furanyl substituents attached to the cyclometalating moiety of the ImP ligands stabilize the 2LMCT excited state to very different extent resulting in opposing effects on the 2LMCT lifetime. For [FeIII(ImPBr)2]+, the lifetime (255 ps) of its moderately stabilized 2LMCT state (1.85 eV) is slightly increased compared to the parent... (More)

FeIII complexes based on the [FeIII(ImP)2]+ motif (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)), where the ligand contains both carbene and cyclometalated moieties, are a promising class of photoactive materials made from this abundant metal. In this work, it is shown that bromo or furanyl substituents attached to the cyclometalating moiety of the ImP ligands stabilize the 2LMCT excited state to very different extent resulting in opposing effects on the 2LMCT lifetime. For [FeIII(ImPBr)2]+, the lifetime (255 ps) of its moderately stabilized 2LMCT state (1.85 eV) is slightly increased compared to the parent complex (1.90 eV, 240 ps) pointing to an increased barrier for deactivation via the 4MC state and enabling applications as photoredox catalyst. In contrast, the 2LMCT energy of [FeIII(ImPFur)2]+ is lowered substantially to a value of 1.63 eV due to the extended π-system of the ligands and the reduced energy gap favors internal conversion directly to the ground state resulting in a considerably reduced 2LMCT lifetime of 59 ps. These findings have general implications for design of ligand modifications aiming at extended LMCT lifetimes and/or modified ground and excited state potentials.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
iron, N-heterocyclic carbene, photophysics, photoredox catalysis, Potential energy diagrams
in
Chemistry - A European Journal
volume
31
issue
47
article number
e01985
publisher
Wiley-Blackwell
external identifiers
  • scopus:105011870402
  • pmid:40711372
ISSN
0947-6539
DOI
10.1002/chem.202501985
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 The Author(s). Chemistry – A European Journal published by Wiley-VCH GmbH.
id
ab60cb71-cc85-4cd0-827f-269c77c01c44
date added to LUP
2026-01-21 13:30:31
date last changed
2026-01-22 03:00:02
@article{ab60cb71-cc85-4cd0-827f-269c77c01c44,
  abstract     = {{<p>Fe<sup>III</sup> complexes based on the [Fe<sup>III</sup>(ImP)<sub>2</sub>]<sup>+</sup> motif (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)), where the ligand contains both carbene and cyclometalated moieties, are a promising class of photoactive materials made from this abundant metal. In this work, it is shown that bromo or furanyl substituents attached to the cyclometalating moiety of the ImP ligands stabilize the <sup>2</sup>LMCT excited state to very different extent resulting in opposing effects on the <sup>2</sup>LMCT lifetime. For [Fe<sup>III</sup>(ImPBr)<sub>2</sub>]<sup>+</sup>, the lifetime (255 ps) of its moderately stabilized <sup>2</sup>LMCT state (1.85 eV) is slightly increased compared to the parent complex (1.90 eV, 240 ps) pointing to an increased barrier for deactivation via the <sup>4</sup>MC state and enabling applications as photoredox catalyst. In contrast, the <sup>2</sup>LMCT energy of [Fe<sup>III</sup>(ImPFur)<sub>2</sub>]<sup>+</sup> is lowered substantially to a value of 1.63 eV due to the extended π-system of the ligands and the reduced energy gap favors internal conversion directly to the ground state resulting in a considerably reduced <sup>2</sup>LMCT lifetime of 59 ps. These findings have general implications for design of ligand modifications aiming at extended LMCT lifetimes and/or modified ground and excited state potentials.</p>}},
  author       = {{Mishra, Abhishek and Sharma, Kumkum and Johnson, Catherine Ellen and Fosu, Emmanuel Adu and Schwarz, Jesper and Prakash, Om and Gupta, Arvind Kumar and Huang, Ping and Lindgren, Fredrik and Häggström, Lennart and Bendix, Jesper and Jakubikova, Elena and Lomoth, Reiner and Wärnmark, Kenneth}},
  issn         = {{0947-6539}},
  keywords     = {{iron; N-heterocyclic carbene; photophysics; photoredox catalysis; Potential energy diagrams}},
  language     = {{eng}},
  month        = {{08}},
  number       = {{47}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Chemistry - A European Journal}},
  title        = {{Tuning the <sup>2</sup>LMCT Deactivation of Cyclometalated Iron Carbene Complexes with Electronic Substituent Effects}},
  url          = {{http://dx.doi.org/10.1002/chem.202501985}},
  doi          = {{10.1002/chem.202501985}},
  volume       = {{31}},
  year         = {{2025}},
}