Red‐to‐NIR Iridium(III) Emitters: Synthesis, Photophysical and Computational Study, the Effects of Cyclometallating and β‐Diketonate Ligands. Issue 22 (19th May 2021)

• Record Type: Journal Article
• Authors: Kuznetsov, Kirill M.; Kritchenkov, Ilya S.; Shakirova, Julia R.; Gurzhiy, Vladislav V.; Pavlovskiy, Vladimir V.; Porsev, Vitaly V.; Sokolov, Viktor V.; Tunik, Sergey P.
• Is Part Of: European journal of inorganic chemistry. Issue 22(2021)
• Page Start: 2163
• Page End: 2170
• Publication Date: 2021-05-19
• Subjects: Iridium -- Diketonate ligands -- Cyclometalated ligands -- Ligand impact -- Phosphorescence; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.202100189
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: In this work nine novel heteroleptic Ir(III) complexes of general formulae [Ir( N ∧ C # )2 ( O ∧ O # )] containing four different cyclometallating and four β‐diketonate ligands were synthesized and fully characterized. Six of them display phosphorescence in the deep red and NIR regions with quantum yields reaching 24.6 % in degassed solution for one of the NIR emitters. Variation in the nature of orthometalating ligands results in dramatic changes in photophysical behavior: the compounds containing 2‐phenylpyridine ( N ∧ C 1 ) and 2‐(benzo[b]thiophen‐2‐yl)pyridine ( N ∧ C 2 ) ligands give non‐emissive complexes, whereas those with methyl 2‐phenylquinoline‐4‐carboxylate ( N ∧ C 3 ) and 6‐(benzo[b]thiophen‐2‐yl)phenanthridine) ( N ∧ C 4 ) are luminescent, but display different character of electronic transitions responsible for absorption and emission. Complexes with the N ∧ C 3 ligand luminesce from 3 LC excited state and do not change their emission characteristics upon variations in the nature of β‐diketonates. On the contrary, the compounds based on the N ∧ C 4 cyclometalating ligand emit from the excited state with considerable contribution of 3 MLCT character and show systematic bathochromic shift of absorption and emission bands upon increase in electron donicity of O ∧ O # ligands. This conclusion was supported by DFT and TD‐DFT calculations and by the analysis of correlations between the 13 C chemical shift of the diketonate C(H) carbon and emission maxima of the compounds under study. Abstract : Orthometalated iridium [Ir( N ∧ C )2 ( O ∧ O )] complexes containing developed aromatic systems in the N ∧ C ligands display emission in the red‐to‐NIR spectral region with unusually high quantum yields up to 24.6 %. Noninnocent role of β‐diketonate O ∧ O ligands was demonstrated, which allows fine tuning of emission wavelength through variations in donor properties of these ligands.