Cookies

We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.


Durham Research Online
You are in:

Unusual dual-emissive heteroleptic iridium complexes incorporating TADF cyclometalating ligands.

Benjamin, Helen and Zheng, Yonghao and Kozhevnikov, Valery N. and Siddle, Jamie S. and O'Driscoll, Luke J. and Fox, Mark A. and Batsanov, Andrei S. (2020) 'Unusual dual-emissive heteroleptic iridium complexes incorporating TADF cyclometalating ligands.', Dalton transactions., 49 (7). pp. 2190-2208.

Abstract

Five new neutral heteroleptic iridium(III) complexes IrL2(pic) (2–6) based on the archetypical blue emitter FIrpic have been synthesised. The cyclometallating ligands L are derived from 2-(2,6-F2-3-pyridyl)-4-mesitylpyridine (7), 2-(3-cyano-2,6-F2-phenyl)-4-mesitylpyridine (8), 2-(2,6-F2-phenyl)-4-[2,7-(HexO)2-9H-carbazol-9-yl]pyridine (9), 2-(2,6-F2-3-pyridyl)-4-[2,7-(HexO)2-9H-carbazol-9-yl]pyridine (10) and 2-(3-cyano-2,6-F2-phenyl)-4-[2,7-(HexO)2-9H-carbazol-9-yl]pyridine (11) for complexes 2, 3, 4, 5 and 6, respectively. The carbazole-functionalised ligands 9–11 show weak thermally activated delayed fluorescence (TADF) in solution. Complexes 5 and 6 reveal dual emission in polar solvents. A broad charge transfer (CT) band appears and increases in intensity relative to the higher energy emission band as solvent polarity is increased. The dual emission occurs when the energy of the ligand 3CT state is comparable to that of the 3MLCT state of the complex, resulting in fast interconversion between the two. Assignment of the ligand TADF and dual emission properties is supported by hybrid density functional theory (DFT) and time dependent DFT (TD-DFT) calculations. Phosphorescent organic light emitting devices (PhOLEDs) have been fabricated using these complexes as sky-blue emitters, and their performance is compared to devices using FIrpic and the previously reported complex IrL2(pic) 1 (L from the 2-(2,6-F2-phenyl)-4-mesitylpyridine ligand). For identical device structures, the device containing the carbazole complex 4 performs best out of the seven complexes. The dual emission observed in solution for complexes 5 and 6 is not observed in their devices.

Item Type:Article
Full text:(AM) Accepted Manuscript
Download Other (Crystal structure data)
(426Kb)
Full text:(AM) Accepted Manuscript
Download PDF
(6535Kb)
Full text:(AM) Accepted Manuscript
Download PDF (Supplementary information)
(4098Kb)
Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1039/C9DT04672K
Date accepted:23 January 2020
Date deposited:05 March 2020
Date of first online publication:31 January 2020
Date first made open access:31 January 2021

Save or Share this output

Export:
Export
Look up in GoogleScholar