Thermally Robust and Tuneable Phosphorescent Gold(III) Complexes Bearing (N^N)‐Type Bidentate Ligands as Ancillary Chelates. Issue 14 (7th February 2019)

• Record Type: Journal Article
• Authors: Malmberg, Robert; Bachmann, Michael; Blacque, Olivier; Venkatesan, Koushik
• Is Part Of: Chemistry. Volume 25:Issue 14(2019)
• Page Start: 3627
• Page End: 3636
• Publication Date: 2019-02-07
• Subjects: gold -- metallacycles -- nitrogen heterocycles -- N, N ligands -- OLED -- phosphorescence; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201805486
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Phosphorescent mono‐cyclometalated gold(III) complexes and their possible applications in organic light emitting diodes (OLEDs) can be significantly enhanced with their improved thermal stability by suppressing the reductive elimination of the respective ancillary ligands. A rational tuning of the π‐conjugation of the cyclometalating ligand in conjunction with the non‐conjugated 5, 5′‐(1‐methylethylidene)bis(3‐trifluoromethyl)‐1 H ‐pyrazole were used as a strategy to achieve room‐temperature phosphorescence emission in a new series of gold(III) complexes. Photophysical studies of the newly synthesised and characterised complexes revealed phosphorescent emission of the complexes at room temperature in solution, thin films when doped in poly(methyl methacrylate) (PMMA) as well as in 2‐Me‐THF at 77 K. The complexes exhibit highly tuneable emission behaviour with photoluminescent quantum efficiencies up to 22 % and excited state lifetimes in the range of 63–300 μs. Detailed photophysical investigations in combination with DFT and TD‐DFT calculations support the conclusion that the emission properties are strongly dictated by both the cyclometalating ligand and the ancillary chelating ligand. Thermogravimetric studies further show that the thermal stability of the Au III complexes has been drastically enhanced, making these complexes more attractive for OLED applications. Abstract : Shining gold ! Room‐temperature emission from mono‐cyclometalated Au III complexes bearing dianionic (N^N)‐type chelates with also significantly improved thermal stability has been achieved by tuning the triplet excited state through the judicious combination of both the cyclometalating ligand and the ancillary ligand dianionic (N^N) chelate.