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A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes

[Image: see text] A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B–N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formul...

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Autores principales: Baschieri, Andrea, Aleotti, Flavia, Matteucci, Elia, Sambri, Letizia, Mancinelli, Michele, Mazzanti, Andrea, Leoni, Enrico, Armaroli, Nicola, Monti, Filippo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2023
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9906742/
https://www.ncbi.nlm.nih.gov/pubmed/36696253
http://dx.doi.org/10.1021/acs.inorgchem.2c04449
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author Baschieri, Andrea
Aleotti, Flavia
Matteucci, Elia
Sambri, Letizia
Mancinelli, Michele
Mazzanti, Andrea
Leoni, Enrico
Armaroli, Nicola
Monti, Filippo
author_facet Baschieri, Andrea
Aleotti, Flavia
Matteucci, Elia
Sambri, Letizia
Mancinelli, Michele
Mazzanti, Andrea
Leoni, Enrico
Armaroli, Nicola
Monti, Filippo
author_sort Baschieri, Andrea
collection PubMed
description [Image: see text] A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B–N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formula [Ir(C(∧)N)(2)(N(∧)NB)], where C(∧)N indicates three different cyclometalating ligands (Hppy = 2-phenylpyridine; Hdfppy = 2-(2,4-difluoro-phenyl)pyridine; Hpqu = 2-methyl-3-phenylquinoxaline). Moreover, the azaborine-based complex 2a was compared to the isoelectronic C=C iridium(III) complex 2b, obtained using the corresponding 2-(naphthalen-2-yl)pyridine ligand 1b. Due to the dual cyclometalation mode of such C=C ligand, the isomeric complex 2c was also obtained. All new compounds have been fully characterized by NMR spectroscopy and high-resolution mass spectrometry (MS), and the X-ray structure of 2a was determined. The electronic properties of both ligands and complexes were investigated by electrochemical, density functional theory (DFT), and photophysical methods showing that, compared to the naphthalene analogues, the azaborine ligand induces a larger band gap in the corresponding complexes, resulting in increased redox gap (basically because of the highest occupied molecular orbital (HOMO) stabilization) and blue-shifted emission bands (e.g., λ(max) = 523 vs 577 nm for 2avs2b, in acetonitrile solution at 298 K). On the other hand, the (3)LC nature of the emitting state is the same in all complexes and remains centered on the pyridyl-borazaronaphthalene or its C=C pyridyl-naphthalene analogue. As a consequence, the quantum yields of such azaborine-based complexes are comparable to those of the more classical C=C counterparts (e.g., photoluminescence quantum yield (PLQY) = 16 vs 22% for 2avs2b, in acetonitrile solution at 298 K) but with enhanced excited-state energy. This proves that such type of azaborine ligands can be effectively used for the development of novel classes of photoactive transition-metal complexes for light-emitting devices or photocatalytic applications.
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spelling pubmed-99067422023-02-08 A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes Baschieri, Andrea Aleotti, Flavia Matteucci, Elia Sambri, Letizia Mancinelli, Michele Mazzanti, Andrea Leoni, Enrico Armaroli, Nicola Monti, Filippo Inorg Chem [Image: see text] A novel 1,2-azaborine (i.e., 4-methyl-2-(pyridin-2-yl)-2,1-borazaronaphthalene, 1a) has been synthesized and used for the first time as a B–N alternative to common cyclometalating ligands to obtain neutral phosphorescent iridium(III) complexes (i.e., 2a, 3, and 4) of general formula [Ir(C(∧)N)(2)(N(∧)NB)], where C(∧)N indicates three different cyclometalating ligands (Hppy = 2-phenylpyridine; Hdfppy = 2-(2,4-difluoro-phenyl)pyridine; Hpqu = 2-methyl-3-phenylquinoxaline). Moreover, the azaborine-based complex 2a was compared to the isoelectronic C=C iridium(III) complex 2b, obtained using the corresponding 2-(naphthalen-2-yl)pyridine ligand 1b. Due to the dual cyclometalation mode of such C=C ligand, the isomeric complex 2c was also obtained. All new compounds have been fully characterized by NMR spectroscopy and high-resolution mass spectrometry (MS), and the X-ray structure of 2a was determined. The electronic properties of both ligands and complexes were investigated by electrochemical, density functional theory (DFT), and photophysical methods showing that, compared to the naphthalene analogues, the azaborine ligand induces a larger band gap in the corresponding complexes, resulting in increased redox gap (basically because of the highest occupied molecular orbital (HOMO) stabilization) and blue-shifted emission bands (e.g., λ(max) = 523 vs 577 nm for 2avs2b, in acetonitrile solution at 298 K). On the other hand, the (3)LC nature of the emitting state is the same in all complexes and remains centered on the pyridyl-borazaronaphthalene or its C=C pyridyl-naphthalene analogue. As a consequence, the quantum yields of such azaborine-based complexes are comparable to those of the more classical C=C counterparts (e.g., photoluminescence quantum yield (PLQY) = 16 vs 22% for 2avs2b, in acetonitrile solution at 298 K) but with enhanced excited-state energy. This proves that such type of azaborine ligands can be effectively used for the development of novel classes of photoactive transition-metal complexes for light-emitting devices or photocatalytic applications. American Chemical Society 2023-01-25 /pmc/articles/PMC9906742/ /pubmed/36696253 http://dx.doi.org/10.1021/acs.inorgchem.2c04449 Text en © 2023 The Authors. Published by American Chemical Society https://creativecommons.org/licenses/by/4.0/Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Baschieri, Andrea
Aleotti, Flavia
Matteucci, Elia
Sambri, Letizia
Mancinelli, Michele
Mazzanti, Andrea
Leoni, Enrico
Armaroli, Nicola
Monti, Filippo
A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title_full A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title_fullStr A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title_full_unstemmed A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title_short A Pyridyl-1,2-azaborine Ligand for Phosphorescent Neutral Iridium(III) Complexes
title_sort pyridyl-1,2-azaborine ligand for phosphorescent neutral iridium(iii) complexes
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9906742/
https://www.ncbi.nlm.nih.gov/pubmed/36696253
http://dx.doi.org/10.1021/acs.inorgchem.2c04449
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