A Photoreactive Iron(II) Complex Luminophore

• Published in: Journal of the American Chemical Society 2022-01, Vol.144 (3), p.1169-1173
• Main Authors: Leis, Wolfgang, Argüello Cordero, Miguel A, Lochbrunner, Stefan, Schubert, Hartmut, Berkefeld, Andreas
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c13083

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 λem,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.