Scientific article

Additional Insights into the Design of Cr(III) Phosphorescent Emitters Using 6-Membered Chelate Ring Bis(imidazolyl) Didentate Ligands

Published inInorganic chemistry, vol. 63, no. 8, p. 3617-3629
Publication date2024-01-11
First online date2024-01-11

The interest in Cr(III) complexes has been rejuvenated over the past decades for building practical guidelines in the design of efficient earth-abundant phosphorescent near-infrared emitters. In that context, we report the first family of homoleptic tri(didentate) Cr(III) complexes [CrL3 ]3+ based on polyaromatic ligands inducing 6-membered chelate rings, namely: the bis(1-methylimidazol-2- yl)ketone (L = bik), bis(1-methylimidazol-2-yl)methane (L = bim) and bis(1-methylimidazol-2- yl)ethane (L = bie) ligands. The programmed close-to-perfect octahedral micro-symmetry of {Cr III N6 } chromophores found in [Cr(bik)3 ](OTf) 3 (1), [Cr(bim) 3 ](OTf) 3 (2) and [Cr(bie)3 ](BF4 )3 (3) ensures a ligand-field strength large enough to induce intense and long-lived Cr-based phosphorescence. Impressive excited-state lifetimes (5.0-8.2 ms) were obtained at low temperature for the [Cr(L) 3 ]3+ series. Additionally, the photoluminescent quantum yield climbs to 0.8% for (1) in deaerated solutions. Moreover, the photophysical features of the three homoleptic complexes are barely influenced by the presence of dioxygen presumably because of the poor overlap between the Cr-based phosphorescence spectra (c.a. 14100 cm-1 ) and the 1g+3g- transition in the absorption spectrum of dioxygen (13100 cm-1 ). The multiredox electrochemical pattern of (1) is evidenced by cyclic-voltammetry as well as its strong photo-oxidant behavior. The pH-sensitivity of (2) and (3) luminescence is discussed along with the reactivity of their β-diketiminate derivatives.

  • Homoleptic chromium(III) complexes
  • Spin-flip phosphorescence
  • Ix-membered chelate ring
  • Luminescent molecular materials
  • Multifunctional chromium(III) complexes
Citation (ISO format)
BENCHOHRA, Amina et al. Additional Insights into the Design of Cr(III) Phosphorescent Emitters Using 6-Membered Chelate Ring Bis(imidazolyl) Didentate Ligands. In: Inorganic chemistry, 2024, vol. 63, n° 8, p. 3617–3629. doi: 10.1021/acs.inorgchem.3c03422
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Article (Accepted version)
accessLevelRestrictedaccessLevelPublic 01/12/2025
ISSN of the journal0020-1669

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