Dinuclear iridium(iii) complexes of cyclometalated fluorenylpyridine ligands as phosphorescent dopants for efficient solution-processed OLEDsElectronic supplementary information (ESI) available: Synthetic details and characterisation data for the ligands and complexes; cyclic voltammograms; X-ray crystal structures of 2a, 2d, 2e, 3a, 3b and 4e and computational data. CCDC 869121-869126. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2jm31143g

• Main Authors: M'hamedi, Ahmed, Batsanov, Andrei S, Fox, Mark A, Bryce, Martin R, Abdullah, Khalid, Al-Attar, Hameed A, Monkman, Andrew P
• Format: Article
• Language: English
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm31143g

Phosphorescent cyclometalated dinuclear iridium( iii ) complexes of fluorenylpyridine ligands bridged by bis(μ-Cl) and bis(μ-NCO) units have been synthesised and characterised by NMR, UV-vis absorption and emission spectroscopy, cyclic voltammetry, spectroelectrochemistry and X-ray diffraction. The complexes display green luminescence in solution from mixed 3 π-π*/ 3 MLCT (metal-to-ligand-charge transfer) states in the range of λ max 542-552 nm. The solution PL quantum yields of 21-41% are remarkably high for diiridium complexes. Cyclic voltammetric and UV-visible spectroelectrochemical studies establish that the mixed valence cations are stable with the two Ir 3+ /Ir 4+ centres interacting strongly. DFT/TD-DFT calculations provide further insights into the electronic and photophysical properties of the complexes, with good agreement between computed and experimental data. Solution-processed organic light emitting devices (OLEDs) using the diiridium complexes as the emissive dopants in poly(9-vinylcarbazole) (PVK) host polymer exhibit performances of up to 12 cd A −1 and external quantum efficiencies of up to 4%. The device architecture is: ITO/PEDOT:PSS/PVK-complex (5 wt%)-PBD (40 wt%)/Ba/Al. These electroluminescence efficiency values are unusually high for dinuclear metal complexes and confirm that dinuclear iridium complexes are suitable phosphors for OLEDs using simple device architectures. Analogous mononuclear fac -Ir( iii ) complexes of fluorenylpyridine ligands are reported for comparison. They have PL quantum yields of 30-43%, device performances of up to 26 cd A −1 and external quantum efficiencies of up to 8.6%. Dinuclear iridium( iii ) complexes display phosphorescence in solution ( λ max 542-552 nm) with PL quantum yields of 21-41%. Solution-processable OLEDs using PVK as the host exhibit performances of up to 12 cd A −1 , EQE 4%.