Synthesis, characterization, and optoelectronic properties of heteroleptic iridium complexes containing substituted 1,3,4-oxadiazole and β-diketone as ligands

Abstract

The new heteroleptic iridium(III) complexes (BuOXD)₂Ir(tta) and (BuOXD)₂Ir(tmd) [BuOXD = 2-(4-butyloxyphenyl)-5-phenyl[1,3,4]oxadiazolato-N4,C2, tta = 1,1,1-trifluoro-4-thienylbutane-2,4-dionato, tmd = 2,2,6,6-tetramethylheptane-3,5-dionato] have been synthesized and characterized. These complexes have two cyclometalated ligands (C^N) and a bidentate diketone ligand (X) [C^N)₂Ir(X)], where X is a β-diketone with trifluoromethyl, theonyl or t-butyl groups. The color tuning with the change in electronegativity of substituents in the β-diketones has been studied. Photoluminescence spectra of the complexes showed peak emissions at 523 and 549 nm, respectively. The electroluminescent properties of these complexes have been studied by fabricating multi layer devices with device structure ITO/α-NPD/8% iridium complex doped CBP/BCP/Alq₃/LiF/Al. The electroluminescence spectra also showed peak emissions at 526 and 570 nm for (BuOXD)₂Ir(tta) and (BuOXD)₂Ir(tmd), respectively. These metal complexes showed good thermal stability in air to 340°C.

Keywords:

• Heteroleptic iridium complex
• β-Diketones
• Electroluminescence
• Color tuning

Acknowledgments

The authors thank the Director, National Physical Laboratory, New Delhi and Head, Department of Chemistry, M. D. University, Rohtak (Haryana) for providing the necessary facilities. The authors also gratefully recognize the financial support from the Department of Science and Technology (DST) and Council of Scientific and Industrial Research (CSIR), New Delhi, India.