Janus-type emission from a cyclometalated iron(III) complex

Jakob Steube; Ayla Kruse; Olga S Bokareva; Thomas Reuter; Serhiy Demeshko; Roland Schoch; Miguel A Argüello Cordero; Athul Krishna; Stephan Hohloch; Franc Meyer; Katja Heinze; Oliver Kühn; Stefan Lochbrunner; Matthias Bauer

doi:10.1038/s41557-023-01137-w

Janus-type emission from a cyclometalated iron(III) complex

Nat Chem. 2023 Apr;15(4):468-474. doi: 10.1038/s41557-023-01137-w. Epub 2023 Feb 27.

Authors

Jakob Steube^{1

2}, Ayla Kruse^{3

4}, Olga S Bokareva^{4

5}, Thomas Reuter⁶, Serhiy Demeshko⁷, Roland Schoch^{1

2}, Miguel A Argüello Cordero^{3

4}, Athul Krishna^{1

2}, Stephan Hohloch⁸, Franc Meyer⁷, Katja Heinze⁶, Oliver Kühn^{3

4}, Stefan Lochbrunner^{3

4}, Matthias Bauer^{9

10}

Affiliations

¹ Institute of Inorganic Chemistry, Paderborn University, Paderborn, Germany.
² Center for Sustainable Systems Design, Paderborn University, Paderborn, Germany.
³ Department of Life, Light and Matter, University of Rostock, Rostock, Germany.
⁴ Institute for Physics, University of Rostock, Rostock, Germany.
⁵ Institute of Physics, University of Kassel, Kassel, Germany.
⁶ Department of Chemistry, Johannes Gutenberg University, Mainz, Germany.
⁷ Institute of Inorganic Chemistry, University of Göttingen, Göttingen, Germany.
⁸ Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria.
⁹ Institute of Inorganic Chemistry, Paderborn University, Paderborn, Germany. matthias.bauer@uni-paderborn.de.
¹⁰ Center for Sustainable Systems Design, Paderborn University, Paderborn, Germany. matthias.bauer@uni-paderborn.de.

Abstract

Although iron is a dream candidate to substitute noble metals in photoactive complexes, realization of emissive and photoactive iron compounds is demanding due to the fast deactivation of their charge-transfer states. Emissive iron compounds are scarce and dual emission has not been observed before. Here we report the Fe^III complex [Fe(ImP)₂][PF₆] (HImP = 1,1'-(1,3-phenylene)bis(3-methyl-1-imidazol-2-ylidene)), showing a Janus-type dual emission from ligand-to-metal charge transfer (LMCT)- and metal-to-ligand charge transfer (MLCT)-dominated states. This behaviour is achieved by a ligand design that combines four N-heterocyclic carbenes with two cyclometalating aryl units. The low-lying π* levels of the cyclometalating units lead to energetically accessible MLCT states that cannot evolve into LMCT states. With a lifetime of 4.6 ns, the strongly reducing and oxidizing MLCT-dominated state can initiate electron transfer reactions, which could constitute a basis for future applications of iron in photoredox catalysis.

Abstract

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