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Microwave-assisted one-pot synthesis of new ionic cyclometalated iridium complexes of [Ir(bzq)2(N^N)]+A- type and their selected electroluminescent properties

Abstract

Iridium C,N-cyclometalated complexes of ionic structure are considered to be promising candidates for application in the host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility to reduce their concentration in organic matrices as well as allows to obtain organic light emitting devices (OLEDs) with interesting emission parameters. We report herein the methodology enabling the synthesis of cyclometalated ionic iridium(III) complexes of the type [Ir(C^N)2(N^N)]+A- according to three-component one-pot strategy, involving acceleration of the reaction via microwave irradiation. The developed protocol allowed the efficient synthesis of a series of new cationic iridium(III) coordination derivatives, which were isolated and spectroscopically characterized, besides the structures of two of them were determined by X-Ray method. Moreover, the iridium(III) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme, that was used to predict HOMO-LUMO gaps for the studied Ir(III) complexes, showed a good correlation between the experimental and calculated values. In order to determine the influence of structure and nature of the ancillary ligand on location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on poly(N-vinylcarbazole)/2–(4–tert–butylphenyl)–5–(4–biphenyl)–1,3,4–oxadiazole (PVK/PBD) matrix. The highest luminance, above 10000 cd/m2 was recorded for the device containing only 1.0 wt% of the [Ir(bzq)2(1,10-phenantroline)]+PF6- in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range from 1.0 to 2.2 cd/A.

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Supplementary files

Publication details

The article was received on 15 Apr 2017, accepted on 16 Jun 2017 and first published on 19 Jun 2017


Article type: Paper
DOI: 10.1039/C7DT01372H
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Microwave-assisted one-pot synthesis of new ionic cyclometalated iridium complexes of [Ir(bzq)2(N^N)]+A- type and their selected electroluminescent properties

    B. Orwat, E. Witkowska, I. Kownacki, M. Oh, M. Hoffmann, M. Kubicki, I. Grzelak, B. Marciniec, I. Głowacki, B. Luszczynska, G. Wiosna-Sałyga, J. Ulanski, P. Ledwon and M. Lapkowski, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01372H

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