While the development of red and green phosphorescent organic light-emitting diodes (OLEDs) has seen rapid progress, that of efficient blue phosphorescent OLEDs remains a challenge. In the present report, the introduction of a bulky substituent on the pyridyl rings of a cycloplatinated 1,3-bis(pyridine-2-yl)-4,6-difluoro-benzene appears as a facile strategy to hinder strong Pt⋯Pt interactions, allowing the fabrication of efficient blue OLEDs. Thus, the preparation and characterization of a chlorido platinum(II) complex bearing a well-designed new N^C^N-cyclometalating ligand, namely 1,3-bis(4-mesityl-pyridin-2-yl)-4,6-difluoro-benzene, are reported. Its structure, along with that of the related pro-ligand, is determined by X-ray diffraction studies on a single crystal. The shortest Pt⋯Pt distance is much longer (8.59 Å) than that observed for other N^C^N-platinum(II) chlorido complexes including one with the bulky mesityl group on the cyclometalated benzene ring (4.4 Å). This new complex exhibits intense blue phosphorescence (470–471 nm) in dichloromethane solution (Φlum = 0.97) and in the PMMA film (1 wt% complex, Φlum = 0.95) whereas red phosphorescence (672 nm) is observed in a neat film (Φlum = 0.72). Even in the solid state, the novel complex is highly luminescent suggesting that the introduction of mesityl groups on the pyridine rings is a way to inhibit self-quenching both in the PMMA matrix and in neat films. It represents a useful tool for the fabrication of efficient blue OLEDs (8% wt complex) with CIE coordinates (0.13, 0.29) approaching true blue. The molecular geometry, ground state, electronic structure, and excited electronic states of the complex, both as a monomer and dimer aggregate in solution, are calculated using density functional theory (DFT) and time-dependent (TD) DFT approaches, giving insight into the electronic origin of the absorption spectra.

Introduction of a mesityl substituent on pyridyl rings as a facile strategy for improving the performance of luminescent 1,3-bis-(2-pyridyl)benzene platinum(ii) complexes: a springboard for blue OLEDs / A. Colombo, G. De Soricellis, C. Dragonetti, F. Fagnani, D. Roberto, B. Carboni, V. Guerchais, T. Roisnel, M. Cocchi, S. Fantacci, E. Radicchi, D. Marinotto. - In: JOURNAL OF MATERIALS CHEMISTRY. C. - ISSN 2050-7526. - 12:26(2024 Jul 14), pp. 9702-9715. [10.1039/d4tc01458h]

Introduction of a mesityl substituent on pyridyl rings as a facile strategy for improving the performance of luminescent 1,3-bis-(2-pyridyl)benzene platinum(ii) complexes: a springboard for blue OLEDs

A. Colombo
Primo
;
G. De Soricellis
Secondo
;
C. Dragonetti;F. Fagnani
;
D. Roberto;D. Marinotto
Ultimo
2024

Abstract

While the development of red and green phosphorescent organic light-emitting diodes (OLEDs) has seen rapid progress, that of efficient blue phosphorescent OLEDs remains a challenge. In the present report, the introduction of a bulky substituent on the pyridyl rings of a cycloplatinated 1,3-bis(pyridine-2-yl)-4,6-difluoro-benzene appears as a facile strategy to hinder strong Pt⋯Pt interactions, allowing the fabrication of efficient blue OLEDs. Thus, the preparation and characterization of a chlorido platinum(II) complex bearing a well-designed new N^C^N-cyclometalating ligand, namely 1,3-bis(4-mesityl-pyridin-2-yl)-4,6-difluoro-benzene, are reported. Its structure, along with that of the related pro-ligand, is determined by X-ray diffraction studies on a single crystal. The shortest Pt⋯Pt distance is much longer (8.59 Å) than that observed for other N^C^N-platinum(II) chlorido complexes including one with the bulky mesityl group on the cyclometalated benzene ring (4.4 Å). This new complex exhibits intense blue phosphorescence (470–471 nm) in dichloromethane solution (Φlum = 0.97) and in the PMMA film (1 wt% complex, Φlum = 0.95) whereas red phosphorescence (672 nm) is observed in a neat film (Φlum = 0.72). Even in the solid state, the novel complex is highly luminescent suggesting that the introduction of mesityl groups on the pyridine rings is a way to inhibit self-quenching both in the PMMA matrix and in neat films. It represents a useful tool for the fabrication of efficient blue OLEDs (8% wt complex) with CIE coordinates (0.13, 0.29) approaching true blue. The molecular geometry, ground state, electronic structure, and excited electronic states of the complex, both as a monomer and dimer aggregate in solution, are calculated using density functional theory (DFT) and time-dependent (TD) DFT approaches, giving insight into the electronic origin of the absorption spectra.
Settore CHIM/03 - Chimica Generale e Inorganica
Settore CHEM-03/A - Chimica generale e inorganica
14-lug-2024
6-giu-2024
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1062708
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