A Photoreactive Iron(II) Complex Luminophore

Wolfgang Leis; Miguel A Argüello Cordero; Stefan Lochbrunner; Hartmut Schubert; Andreas Berkefeld

doi:10.1021/jacs.1c13083

A Photoreactive Iron(II) Complex Luminophore

J Am Chem Soc. 2022 Jan 26;144(3):1169-1173. doi: 10.1021/jacs.1c13083. Epub 2022 Jan 13.

Authors

Wolfgang Leis¹, Miguel A Argüello Cordero², Stefan Lochbrunner², Hartmut Schubert¹, Andreas Berkefeld¹

Affiliations

¹ Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, 72076 Tübingen, Germany.
² Institute for Physics and Department of Life, Light and Matter, University of Rostock, 18051 Rostock, Germany.

PMID: 35025493
DOI: 10.1021/jacs.1c13083

Abstract

Controlling the order and lifetimes of electronically excited states is essential to effective light-to-potential energy conversion by molecular chromophores. This work reports a luminescent and photoreactive iron(II) complex, the first performant group homologue of prototypical sensitizers of ruthenium. Double cyclometalation of a phenylphenanthroline framework at iron(II) favors the population of a triplet metal-to-ligand charge transfer (³MLCT) state as the lowest energy excited state. Near-infrared (NIR) luminescence exhibits a monoexponential decay with τ = 2.4 ns in the solid state and 1 ns in liquid phase. Lifetimes of 14 ns at 77 K are in line with a narrowing of the NIR emission band at λ_em,max = 1170-1230 nm. Featuring a ³MLCT excited-state redox potential of -2 V vs the ferrocene/ferrocenium couple, the use of the Fe(II) chromophore as a sensitizer for light-driven synthesis is exemplified by the radical cross-coupling of 4-chlorobromobenzene and benzene.