Cited by 105Lanthanide and Transition Metal ComplexesLuminescence and Fluorescent MaterialsOrganic Light-Emitting Diodes Research

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A Near‐Infrared‐II Emissive Chromium(III) Complex

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Abstract

The combination of π‐donating amido with π‐accepting pyridine coordination units in a tridentate chelate ligand causes a strong nephelauxetic effect in a homoleptic Cr III complex, which shifts its luminescence to the NIR‐II spectral range. Previously explored Cr III polypyridine complexes typically emit between 727 and 778 nm (in the red to NIR‐I spectral region), and ligand design strategies have so far concentrated on optimizing the ligand field strength. The present work takes a fundamentally different approach and focusses on increasing metal–ligand bond covalence to shift the ruby‐like 2 E emission of Cr III to 1067 nm at 77 K.

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Crossref · 10.1002/anie.202106398

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Figures

Figure 1 Molecular structures of (a) [Cr(bpy)3]3+ (bpy=2,2′‐bipyridine),[ 3b , 4 ] (b) [Cr(phen)3]3+ (phen=1,10‐phenanthroline),[ 3b , 4 ] (c) [Cr(tpy)2]3+ (tpy=2,2′:6′,2′′‐terpyridine),[ 3b , 4 ] (d) [Cr(ddpd)2]3+ (ddpd=N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐2,6‐diamine), [5] and (e) [Cr(dqp)2]3+ (dqp=2,6‐di(quinoline‐8‐yl)pyridine) [6] along with their luminescence quantum yields (φ) in solution at room temperature and wavelengths of emission band maxima (λem). (f) Molecular structure of the new [Cr(dpc)2]+ complex reported herein (dpc=3,6‐di‐tert‐butyl‐1,8‐di(pyridine‐2‐yl)‐carbazolato) and its emission peak wavelength.
Figure 1 Molecular structures of (a) [Cr(bpy)3]3+ (bpy=2,2′‐bipyridine),[ 3b , 4 ] (b) [Cr(phen)3]3+ (phen=1,10‐phenanthroline),[ 3b , 4 ] (c) [Cr(tpy)2]3+ (tpy=2,2′:6′,2′′‐terpyridine),[ 3b , 4 ] (d) [Cr(ddpd)2]3+ (ddpd=N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐2,6‐diamine), [5] and (e) [Cr(dqp)2]3+ (dqp=2,6‐di(quinoline‐8‐yl)pyridine) [6] along with their luminescence quantum yields (φ) in solution at room temperature and wavelengths of emission band maxima (λem). (f) Molecular structure of the new [Cr(dpc)2]+ complex reported herein (dpc=3,6‐di‐tert‐butyl‐1,8‐di(pyridine‐2‐yl)‐carbazolato) and its emission peak wavelength.CC BY-NC-ND · PubMed Central
Figure 2 (a) Tanabe–Sugano diagram for the d3 valence electron configuration in Oh symmetry. Single configurational coordinate diagrams illustrating (b) the influence of an increase in ligand field parameter (10 Dq) on the 2E, 2T1, and 4T2 energies and (c) the influence of an increase in metal–ligand bond covalence (decrease of Racah B parameter) on the respective energies.
Figure 2 (a) Tanabe–Sugano diagram for the d3 valence electron configuration in Oh symmetry. Single configurational coordinate diagrams illustrating (b) the influence of an increase in ligand field parameter (10 Dq) on the 2E, 2T1, and 4T2 energies and (c) the influence of an increase in metal–ligand bond covalence (decrease of Racah B parameter) on the respective energies.CC BY-NC-ND · PubMed Central
Scheme 1 Synthesis of the new chromium(III) complex, [Cr(dpc)2](PF6).
Scheme 1 Synthesis of the new chromium(III) complex, [Cr(dpc)2](PF6).CC BY-NC-ND · PubMed Central
Figure 3 Molecular structure of [Cr(dpc)2]+ in [Cr(dpc)2](PF6)⋅2.5(C2H4Cl2) (H atoms, the counter ion and solvent molecules are omitted for clarity, 50 % probability ellipsoids). Selected bond angles (°) and bond distances (Å): N2‐Cr1‐N5, 173.69(8); N1‐Cr1‐N3, 173.66(7); N4‐Cr1‐N6, 173.16(7); Cr1‐N2, 1.969(2); Cr1‐N5, 1.962(3); Cr1‐N1, 2.133(2); Cr1‐N3, 2.115(3); Cr1‐N4, 2.109(3); Cr1‐N6, 2.133(2). CCDC 2082071 ([Cr(dpc)2](PF6)⋅2.5(C2H4Cl2)) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre.
Figure 3 Molecular structure of [Cr(dpc)2]+ in [Cr(dpc)2](PF6)⋅2.5(C2H4Cl2) (H atoms, the counter ion and solvent molecules are omitted for clarity, 50 % probability ellipsoids). Selected bond angles (°) and bond distances (Å): N2‐Cr1‐N5, 173.69(8); N1‐Cr1‐N3, 173.66(7); N4‐Cr1‐N6, 173.16(7); Cr1‐N2, 1.969(2); Cr1‐N5, 1.962(3); Cr1‐N1, 2.133(2); Cr1‐N3, 2.115(3); Cr1‐N4, 2.109(3); Cr1‐N6, 2.133(2). CCDC 2082071 ([Cr(dpc)2](PF6)⋅2.5(C2H4Cl2)) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre.CC BY-NC-ND · PubMed Central
Figure 4 (a) Cyclic voltammogram of 1 mM [Cr(dpc)2](PF6) in acetonitrile with 0.1 M ( n Bu4N)(PF6) as supporting electrolyte, recorded at a scan rate of 100 mV s−1. (The Fc+/0 potential corresponds to 0.63 V vs. NHE). [34] (b) UV/Vis absorption spectrum of [Cr(dpc)2](PF6) in acetonitrile at 20 °C (black trace). The red trace shows the long‐wavelength part of this spectrum on a magnified ϵ‐scale (right y‐axis, recorded on a more concentrated solution, see inset). The vertical black and red bars mark the energies of DFT‐calculated vertical transitions, the heights of these bars reflect relative oscillator strengths. The heights of the vertical red bars were multiplied by a factor of 10 relative to the vertical black bars. (c) Luminescence spectrum of [Cr(dpc)2](PF6) in acetonitrile at 77 K, obtained after excitation at 450 nm.
Figure 4 (a) Cyclic voltammogram of 1 mM [Cr(dpc)2](PF6) in acetonitrile with 0.1 M ( n Bu4N)(PF6) as supporting electrolyte, recorded at a scan rate of 100 mV s−1. (The Fc+/0 potential corresponds to 0.63 V vs. NHE). [34] (b) UV/Vis absorption spectrum of [Cr(dpc)2](PF6) in acetonitrile at 20 °C (black trace). The red trace shows the long‐wavelength part of this spectrum on a magnified ϵ‐scale (right y‐axis, recorded on a more concentrated solution, see inset). The vertical black and red bars mark the energies of DFT‐calculated vertical transitions, the heights of these bars reflect relative oscillator strengths. The heights of the vertical red bars were multiplied by a factor of 10 relative to the vertical black bars. (c) Luminescence spectrum of [Cr(dpc)2](PF6) in acetonitrile at 77 K, obtained after excitation at 450 nm.CC BY-NC-ND · PubMed Central

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Metadata

Authors
Sinha, N., Jiménez, J., Pfund, B., Prescimone, A., Piguet, C., & Wenger, O. S.
Affiliations
  • University of Basel (CH)
  • University of Geneva (CH)
Corresponding author
  • Piguet, Claude
  • Wenger, Oliver S.
Venue
Angewandte Chemie International Edition
Publisher
Wiley
Published
2021-07-12
Volume
60
Issue
44
Pages
23722-23728
ISSN
  • 1433-7851 (ISSN-L)
  • 1521-3773
OpenAlex
W3168007982
Cited by
105
References
76
Citations by year
2026: 17 · 2025: 15 · 2024: 19 · 2023: 21 · 2022: 29 · 2021: 4
FWCI
5.54
Type
journal article
Language
en
Open access
Locations
  • Angewandte Chemie International Edition (publishedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • edoc (University of Basel) (acceptedVersion)
  • Archive ouverte UNIGE (University of Geneva) (acceptedVersion, other-oa)
  • Archive ouverte UNIGE (University of Geneva) (submittedVersion, cc-by)
  • edoc (University of Basel)
Funders
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (200021_178760, 200020_178758)
  • Fonds National de la Recherche Luxembourg
Topics
  • Physical Sciences › Materials Science › Materials Chemistry › Lanthanide and Transition Metal Complexes
  • Physical Sciences › Materials Science › Materials Chemistry › Luminescence and Fluorescent Materials
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Organic Light-Emitting Diodes Research
Keywords
chromium(III) complexes, NIR-II emission, nephelauxetic effect, luminescence shift, low-temperature luminescence

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