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Exploring the effect of the cyclometallating ligand in 2-(pyridine-2-yl)benzo[d]thiazole-containing iridium(III) complexes for stable light-emitting electrochemical cells

Momblona, Cristina and Ertl, Cathrin D. and Pertegás, Antonio and Junquera-Hernández, José M. and Bolink, Henk J. and Constable, Edwin C. and Sessolo, Michele and Ortí, Enrique and Housecroft, Catherine E.. (2018) Exploring the effect of the cyclometallating ligand in 2-(pyridine-2-yl)benzo[d]thiazole-containing iridium(III) complexes for stable light-emitting electrochemical cells. Journal of Materials Chemistry C, 6 (46). pp. 12679-12688.

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Abstract

The preparation and characterization of a series of iridium(III) ionic transition-metal complexes for application in light-emitting electrochemical cells (LECs) are reported. The complexes are of the type [Ir(C^N) 2 (N^N)][PF 6 ] in which C^N is one of the cyclometallating ligands 2-(3-( tert -butyl)phenyl)pyridine (tppy), 2-phenylbenzo[ d ]thiazole (pbtz), 1-phenyl-1 H -pyrazole (ppz) and 1-phenylisoquninoline (piq), and N^N is 2-(pyridine-2-yl)benzo[ d ]thiazole (btzpy). The variation in the C^N ligands allows the HOMO energy level to be tuned, leading to HOMO−LUMO gaps in the range 2.76‒3.01 eV and values of of 0.81‒1.11 V. In solution, the complexes are orange to deep-red emitters ( λ max in the range 600-660 nm), with quantum yields between 2% for [Ir(tppy) 2 (btzpy)][PF 6 ] to 41% for [Ir(pbtz) 2 (btzpy)][PF 6 ]. Similar trends for the emission maxima and photoluminescence quantum yields are observed in the solid state. Density functional theory (DFT) calculations support the charge transfer nature of the emission. Very bright electroluminescence was observed for LECs containing [Ir(pbtz) 2 (btzpy)][PF 6 ], although the device was not stable under continuous operation; this is attributed to an unbalanced charge distribution and/or to a fast ionic migration. Significantly, LECs fabricated with [Ir(tppy) 2 (btzpy)][PF 6 ] in the active layer are very stable, produce pure red emission and show no signs of degradation over a period of 5 days of continuous operation.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Constable)
05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Housecroft)
UniBasel Contributors:Housecroft, Catherine Elizabeth and Constable, Edwin Charles and Ertl, Cathrin
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Royal Society of Chemistry
ISSN:2050-7526
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
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Last Modified:24 Apr 2019 08:05
Deposited On:05 Dec 2018 09:44

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