A Near Infra-Red Luminescent Cr(III) N-Heterocyclic Carbene Complex

Robert Jones, Rory A. Cowin, Iona Ivalo, Dimitri Chekulaev, Thomas M. Roseveare, Craig Rice, Julia A. Weinstein, Paul Elliott, Paul Scattergood

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Photoluminescent coordination complexes of Cr(III) are of interest as near-infrared spin-flip emitters. Here, we explore the preparation, electrochemistry, and photophysical properties of the first two examples of homoleptic N-heterocyclic carbene complexes of Cr(III), featuring 2,6-bis(imidazolyl)pyridine (ImPyIm) and 2-imidazolylpyridine (ImPy) ligands. The complex [Cr(ImPy)3]3+ displays luminescence at 803 nm on the microsecond time scale (13.7 μs) from a spin-flip doublet excited state, which transient absorption spectroscopy reveals to be populated within several picoseconds following photoexcitation. Conversely, [Cr(ImPyIm)2]3+ is nonemissive and has a ca. 500 ps excited-state lifetime.
Original languageEnglish
Pages (from-to)8526-8530
Number of pages5
JournalInorganic Chemistry
Issue number19
Early online date2 May 2024
Publication statusPublished - 13 May 2024

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