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Title: FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime

Abstract

In this paper, the iron carbene complex [FeII(btz)3](PF6)2 (where btz = 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene)) has been synthesized, isolated, and characterized as a low-spin ferrous complex. It exhibits strong metal-to-ligand charge transfer (MLCT) absorption bands throughout the visible spectrum, and excitation of these bands gives rise to a 3MLCT state with a 528 ps excited-state lifetime in CH3CN solution that is more than one order of magnitude longer compared with the MLCT lifetime of any previously reported FeII complex. The low potential of the [Fe(btz)3]3+/[Fe(btz)3]2+ redox couple makes the 3MLCT state of [FeII(btz)3]2+ a potent photoreductant that can be generated by light absorption throughout the visible spectrum. Finally, taken together with our recent results on the [FeIII(btz)3]3+ form of this complex, these results show that the FeII and FeIII oxidation states of the same Fe(btz)3 complex feature long-lived MLCT and LMCT states, respectively, demonstrating the versatility of iron N-heterocyclic carbene complexes as promising light-harvesters for a broad range of oxidizing and reducing conditions.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [1]; ORCiD logo [3]; ORCiD logo [4];  [1]; ORCiD logo [3];  [1]; ORCiD logo [1];  [5]; ORCiD logo [4]; ORCiD logo [3]
  1. Lund Univ. (Sweden). Division of Chemical Physics
  2. Lund Univ. (Sweden). Division of Chemical Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States). PULSE Inst.
  3. Lund Univ. (Sweden). Center for Analysis and Synthesis (CAS)
  4. Lund Univ. (Sweden). Division of Theoretical Chemistry
  5. Uppsala Univ. (Sweden). Dept. of Chemistry. Ångström Lab.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lund Univ. (Sweden); Uppsala Univ. (Sweden)
Sponsoring Org.:
USDOE; Knut and Alice Wallenberg Foundation (Sweden); Swedish Energy Agency (Energimyndigheten); Swedish Research Council (VR); Crafoord Foundation (Sweden); Danish Council for Independent Research (Denmark)
OSTI Identifier:
1471519
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 9; Journal Issue: 3; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Chábera, Pavel, Kjaer, Kasper S., Prakash, Om, Honarfar, Alireza, Liu, Yizhu, Fredin, Lisa A., Harlang, Tobias C. B., Lidin, Sven, Uhlig, Jens, Sundström, Villy, Lomoth, Reiner, Persson, Petter, and Wärnmark, Kenneth. FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime. United States: N. p., 2018. Web. doi:10.1021/acs.jpclett.7b02962.
Chábera, Pavel, Kjaer, Kasper S., Prakash, Om, Honarfar, Alireza, Liu, Yizhu, Fredin, Lisa A., Harlang, Tobias C. B., Lidin, Sven, Uhlig, Jens, Sundström, Villy, Lomoth, Reiner, Persson, Petter, & Wärnmark, Kenneth. FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime. United States. doi:https://doi.org/10.1021/acs.jpclett.7b02962
Chábera, Pavel, Kjaer, Kasper S., Prakash, Om, Honarfar, Alireza, Liu, Yizhu, Fredin, Lisa A., Harlang, Tobias C. B., Lidin, Sven, Uhlig, Jens, Sundström, Villy, Lomoth, Reiner, Persson, Petter, and Wärnmark, Kenneth. Wed . "FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime". United States. doi:https://doi.org/10.1021/acs.jpclett.7b02962. https://www.osti.gov/servlets/purl/1471519.
@article{osti_1471519,
title = {FeII Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime},
author = {Chábera, Pavel and Kjaer, Kasper S. and Prakash, Om and Honarfar, Alireza and Liu, Yizhu and Fredin, Lisa A. and Harlang, Tobias C. B. and Lidin, Sven and Uhlig, Jens and Sundström, Villy and Lomoth, Reiner and Persson, Petter and Wärnmark, Kenneth},
abstractNote = {In this paper, the iron carbene complex [FeII(btz)3](PF6)2 (where btz = 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene)) has been synthesized, isolated, and characterized as a low-spin ferrous complex. It exhibits strong metal-to-ligand charge transfer (MLCT) absorption bands throughout the visible spectrum, and excitation of these bands gives rise to a 3MLCT state with a 528 ps excited-state lifetime in CH3CN solution that is more than one order of magnitude longer compared with the MLCT lifetime of any previously reported FeII complex. The low potential of the [Fe(btz)3]3+/[Fe(btz)3]2+ redox couple makes the 3MLCT state of [FeII(btz)3]2+ a potent photoreductant that can be generated by light absorption throughout the visible spectrum. Finally, taken together with our recent results on the [FeIII(btz)3]3+ form of this complex, these results show that the FeII and FeIII oxidation states of the same Fe(btz)3 complex feature long-lived MLCT and LMCT states, respectively, demonstrating the versatility of iron N-heterocyclic carbene complexes as promising light-harvesters for a broad range of oxidizing and reducing conditions.},
doi = {10.1021/acs.jpclett.7b02962},
journal = {Journal of Physical Chemistry Letters},
number = 3,
volume = 9,
place = {United States},
year = {2018},
month = {1}
}

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Figures / Tables:

Figure 1. Figure 1.: ChemDraw (left) and X-ray diffraction structure (right) of [Fe(btz)3]2+ with Fe in red, N in blue, and C in gray. Hydrogen atoms and counterions are omitted for clarity.

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