Skip to content

Research at St Andrews

Blue-emitting cationic iridium(III) complexes featuring pyridylpyrimidine cyclometalating ligands and their use in sky-blue and blue-green light-emitting electrochemical cells (LEECs) and organic light-emitting diodes (OLEDs)

Research output: Research - peer-reviewArticle

DOI

Open Access permissions

Open

Author(s)

Adam Francis Henwood, Amlan Kumar Pal, David Bradford Cordes, Alexandra Martha Zoya Slawin, Tomas W. Rees, Cristina Momblona, Azin Babaei, Antonio Pertegás, Enrique Orti, Henk J. Bolink, Etienne Baranoff, Eli Zysman-Colman

School/Research organisations

Abstract

The synthesis, structural and photophysical characterisation of four novel, cationiciridium(III) complexes is reported. These complexes were designed to emit in the blue region of the visible spectrum, without employing sp2 carbon-fluorine bonds, which have been shownto be electrochemically unstable. Two different C^N (where C^N is a bidentate cyclometalating ligand possessing an nitrogen-carbon chelate) ligands [5-(4-methylpyridin-2-yl)-2,4-dimethoxypyrimidine (Mepypyrm) and 5-(5-(trifluoromethyl)pyridine-2-yl)-2,4-dimethoxypyrimidine (CF3pypyrm)] combine electron-withdrawing pyrimidyl nitrogen atoms (in a para relationship with respect to the metal) with methoxy groups in meta relationship with respect to the metal, which both inductively withdraw electron density from the metal centre,stabilizing the highest occupied molecular orbital. The result is highly efficient (φPL = 73 –81%) green to blue (λPL = 446 – 515 nm) emission for complexes 1 – 4 in MeCN solution.Complex 1 exhibits a broad, unstructured charge transfer (CT) emission profile, while complexes 2 – 4 exhibit structured, vibronic emission profiles. Density Functional Theory (DFT) calculations corroborate these findings, with spin density calculations predicting a T1 state that is metal-to-ligand and ligand-to-ligand (C^N to N^N) charge transfer (3MLCT/3LLCT) in nature for complex 1, while complexes 2 – 4 are predicted to exhibit ligand-centred (3LC) states with spin density localised exclusively on the C^N ligands. These complexes were used as emitters in sky-blue and blue-green light-emitting electrochemical cells (LEECs). The bluest of these devices (CIE: 0.23, 0.39) is among the bluest reported for any iridium-based LEEC. Noteworthy is that although the electroluminescence intensity decreases rapidly with time (t1/2 = 0.1 – 20 min), as is typical of blue-green LEECs, for devices L1, L3 and L4 we have observed for the first time that this decay occurs without an accompanying red-shift in the CIE coordinates over time, implying that the emitter does not undergo any chemical degradation processes in the non-doped zones of the device.
Close

Details

Original languageEnglish
Pages (from-to)9638-9650
JournalJournal of Materials Chemistry C
Volume5
Issue number37
Early online date29 Aug 2017
DOIs
StatePublished - 7 Oct 2017

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. Synthesis, characterization and optoelectronic properties of iridium complexes bearing nonconjugated six-membered chelating ligands

    Hierlinger, C., Pal, A. K., Stella, F., Lebl, T., Cordes, D. B., Slawin, A. M. Z., Jacquemin, D., Guerchais, V. & Zysman-Colman, E. 30 Jan 2018 In : Inorganic Chemistry. Articles ASAP

    Research output: Research - peer-reviewArticle

  2. Near-infrared fluorescence of silicon phthalocyanine carboxylate esters

    Pal, A. K., Varghese, S., Cordes, D. B., Slawin, A. M. Z., Samuel, I. D. W. & Zysman-Colman, E. 25 Sep 2017 In : Scientific Reports. 7, 14 p., 12282

    Research output: Research - peer-reviewArticle

Related by journal

  1. An efficient synthetic strategy for uniform perovskite core-shell nanocubes NaMgF3:Mn2+, Yb3+@NaMgF3:Yb3+ with enhanced near infrared upconversion luminescence

    Ding, S., Yang, X. F., Song, E. H., Liang, C. L., Zhou, B., Wu, M. M., Zhou, W. & Zhang, Q. Y. 31 Jan 2018 In : Journal of Materials Chemistry C. Recent articles

    Research output: Research - peer-reviewArticle

  2. Superexchange-mediated negative thermal expansion in Nd-doped BiFeO3

    Kavanagh, C. M., Lightfoot, P. & Morrison, F. D. 14 Dec 2017 In : Journal of Materials Chemistry C. In press

    Research output: Research - peer-reviewArticle

  3. Polymer colour converter with very high modulation bandwidth for visible light communications

    Vithanage, D. A., Kanibolotsky, A. L., Rajbhandari, S., Manousiadis, P. P., Sajjad, M. T., Chun, H., Faulkner, G., O'Brien, D. C., Skabara, P. J., Samuel, I. D. W. & Turnbull, G. A. 21 Sep 2017 In : Journal of Materials Chemistry C. 5, 35, p. 8916-8920 5 p.

    Research output: Research - peer-reviewArticle

  4. Intermolecular states in organic dye dispersions: excimers vs aggregates

    Musser, A. J., Rajendran, S. K., Georgiou, K., Gai, L., Grant, R. T., Shen, Z., Cavazzini, M., Ruseckas, A., Turnbull, G. A., Samuel, I. D. W., Clark, J. & Lidzey, D. G. 7 Sep 2017 In : Journal of Materials Chemistry C. 5, 33, p. 8380-8389 10 p.

    Research output: Research - peer-reviewArticle

ID: 250951492