Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Tailoring the Photophysical Properties of a Homoleptic Iron(II) Tetra N-Heterocyclic Carbene Complex by Attaching an Imidazolium Group to the (C∧N∧C) Pincer Ligand─A Comparative Study

Prakash, Om LU ; Lindh, Linnea LU orcid ; Gupta, Arvind Kumar LU ; Hoang Hai, Yen Tran LU ; Kaul, Nidhi ; Chábera, Pavel LU ; Lindgren, Fredrik ; Ericsson, Tore ; Häggström, Lennart and Strand, Daniel LU , et al. (2024) In Inorganic Chemistry 63(6). p.2909-2918
Abstract

We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)2](PF6)4 (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)2](PF6)2 (pbmi =... (More)

We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)2](PF6)4 (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)2](PF6)2 (pbmi = (pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) as well as a stronger MLCT absorption band extending more toward the red spectral region. However, compared to the carboxylic acid derivative [Fe(cpbmi)2](PF6)2 (cpbmi = 1,1′-(4-carboxypyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)), the excited-state lifetime of [Fe(miHpbmi)2](PF6)4 is the same, but both the extinction and the red shift are more pronounced for the former. Hence, this makes [Fe(miHpbmi)2](PF6)4 a promising pH-insensitive analogue of [Fe(cpbmi)2](PF6)2. Finally, the excited-state dynamics of the title compound [Fe(miHpbmi)2](PF6)4 was investigated in solvents with different viscosities, however, showing very little dependency of the depopulation of the excited states on the properties of the solvent used.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; ; ; ; ; ; and , et al. (More)
; ; ; ; ; ; ; ; ; ; ; ; and (Less)
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Inorganic Chemistry
volume
63
issue
6
pages
10 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:38301278
  • scopus:85184825680
ISSN
0020-1669
DOI
10.1021/acs.inorgchem.3c02890
language
English
LU publication?
yes
id
8f4113b6-4e18-4224-801f-5e26a06c07f5
date added to LUP
2024-02-27 14:55:00
date last changed
2024-04-26 18:39:53
@article{8f4113b6-4e18-4224-801f-5e26a06c07f5,
  abstract     = {{<p>We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>4</sub> (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>2</sub> (pbmi = (pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) as well as a stronger MLCT absorption band extending more toward the red spectral region. However, compared to the carboxylic acid derivative [Fe(cpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>2</sub> (cpbmi = 1,1′-(4-carboxypyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)), the excited-state lifetime of [Fe(miHpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>4</sub> is the same, but both the extinction and the red shift are more pronounced for the former. Hence, this makes [Fe(miHpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>4</sub> a promising pH-insensitive analogue of [Fe(cpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>2</sub>. Finally, the excited-state dynamics of the title compound [Fe(miHpbmi)<sub>2</sub>](PF<sub>6</sub>)<sub>4</sub> was investigated in solvents with different viscosities, however, showing very little dependency of the depopulation of the excited states on the properties of the solvent used.</p>}},
  author       = {{Prakash, Om and Lindh, Linnea and Gupta, Arvind Kumar and Hoang Hai, Yen Tran and Kaul, Nidhi and Chábera, Pavel and Lindgren, Fredrik and Ericsson, Tore and Häggström, Lennart and Strand, Daniel and Yartsev, Arkady and Lomoth, Reiner and Persson, Petter and Wärnmark, Kenneth}},
  issn         = {{0020-1669}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{2909--2918}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Inorganic Chemistry}},
  title        = {{Tailoring the Photophysical Properties of a Homoleptic Iron(II) Tetra N-Heterocyclic Carbene Complex by Attaching an Imidazolium Group to the (C<sup>∧</sup>N<sup>∧</sup>C) Pincer Ligand─A Comparative Study}},
  url          = {{http://dx.doi.org/10.1021/acs.inorgchem.3c02890}},
  doi          = {{10.1021/acs.inorgchem.3c02890}},
  volume       = {{63}},
  year         = {{2024}},
}