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
(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)
- author
- organization
- publishing date
- 2024-02
- 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
-
- scopus:85184825680
- pmid:38301278
- 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
- 2024-06-21 23:39:14
@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}}, }