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A Near-Infrared Luminescent Cr(III) N-Heterocyclic Carbene Complex
Robert W Jones1, Rory A Cowin2, Iona I Ivalo2
1Department of Chemistry, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
Abstract:
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.
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