Wide bandgap iridium complexes varying by their ancillary ligands: Influence on their electroluminescence properties

Lepeltier, Marc; Xiao, Pu; Graff, Bernadette; Morlet‐Savary, Fabrice; Gigmès, Didier; Lalevée, Jacques; Dumur, Frédéric

doi:10.1016/j.synthmet.2015.03.016

Cited by 4 publications

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References 37 publications

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“…Reports of heteroleptic complexes with 1,2,4-triazole or NHC cyclometalating ligands are rare, − despite the potential advantage of these compounds using the ancillary ligand(s) to tune the luminescence color, improve the stability, and/or impart additional functionality. Employing a strong σ-donor as an ancillary ligand would destabilize the ligand-field d – d excited states that are populated as a common nonradiative deactivation, which we have recently shown in a series of complexes partnering a strong σ-donor acyclic diamino carbene (ADC) ancillary ligand with two cyclometalated NHCs, producing blue phosphors with good color purity and quantum yields .…”

Section: Introductionmentioning

confidence: 99%

Cyano-Isocyanide Iridium(III) Complexes with Pure Blue Phosphorescence

et al. 2021

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In this paper, we report a series of six neutral, bluephosphorescent cyclometalated iridium complexes of the type Ir(C^Y) 2 (CNAr)(CN). The cyclometalating ligands in these compounds (C^Y) are either aryl-substituted 1,2,4-triazole or NHC ligands, known to produce complexes with blue phosphorescence. These cyclometalating ligands are paired with π-acidic, strongly σdonating cyano and aryl isocyanide (CNAr) ancillary ligands, the hypothesis being that these ancillary ligands would destabilize the higher-lying ligand-field (d−d) excited states, allowing efficient blue photoluminescence. The compounds are prepared by substituting the cyanide ancillary ligand onto a chloride precursor and are characterized by NMR, mass spectrometry, infrared spectroscopy, and, for five of the compounds, by X-ray crystallography. Cyclic voltammetry establishes that these compounds have large HOMO− LUMO gaps. The mixed cyano-isocyanide compounds are weakly luminescent in solution, but they phosphoresce with moderate to good efficiency when doped into poly(methyl methacrylate) films, with Commission Internationale de L'Eclairage coordinates that indicate deep blue emission for five of the six compounds. The photophysical studies show that the photoluminescence quantum yields are greatly enhanced in the cyano complexes relative to the chloride precursors, affirming the benefit of strong-field ancillary ligands in the design of blue-phosphorescent complexes. Density functional theory calculations confirm that this enhancement arises from a significant destabilization of the higher-energy ligand-field states in the cyanide complexes relative to the chloride precursors.

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