Synthesis and Photophysical Properties of Cationic Iridium Complexes using Oxazoline based Ancillary Ligands for Lighting Applications

Abstract

In this study, we report the design, synthesis and characterization of two new cationic iridium(III) complexes employing oxazole based ancillary ligand, namely, and [Ir(ppz)₂(mbdiho)]PF₆ (Complex 1) and [Ir(dfppy)₂(mbdiho)]PF₆ (Complex 2) and its use in light-emitting electrochemical cells (LECs). The design is based on 2-phenylpyrazole (ppz) and 2-(2,4-difluorophenyl)pyridine (dfppy) as cyclometalating ligands and 2,2-Methylenebis[3a,8a-dihydro-8H-indeno[1,2]oxazole] (mbdiho) as ancillary ligand. The effect of substituents in the cyclometalating ligands on the photophysical and electrochemical properties of the complexes has been investigated. The synthesized complexes were used for the fabrication of LEC devices and studied their electroluminescent properties. The complexes incorporated LECs resulted in a higher luminance of 2820 cd m⁻² and current efficiency of 1.04 cd A⁻¹ for Complex 2 than Complex 1. Our work suggests that the light emission of cationic iridium complexes can easily tuned by the substituents present on the cyclometalating ligands which resulted in yellow and green emission for LECs based on Complexes 1 and 2, respectively.

Keywords:

• Iridium complexes
• Photophysical properties
• Electrochemical properties
• Electroluminescence.

Funding

This work was supported by the Basic Science Research Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Education, Science and Technology (NRF-2013R1A1A4A03009795) and the Brain Korea (BK) 21 Plus project.