Effect of substituents on the photoluminescent and electroluminescent properties of substituted cyclometalated iridium(III) complexes

The photophysics of octahedral 4d6 and 5d6 complexes has been studied extensively. The d6 iridium(III) complexes show intense phosphorescence at room temperature. Our goal of this research is to study the synthesis, characterization and applications of the light emitting dopants based on iridium(III) complexes. We have prepared and characterized a series of substituted (4-CF3, 4-Me, 4-OMe, 4-F, 3-F) 2-phenylbenzoxazole ligand. The intermediate di-irrido and the six-coordinated mononuclear iridium(III) dopants of the above ligands have been synthesized and characterized. These complexes are thermally stable between 280–320 °C depending upon the substituents and sublimable. They emit bright yellow to green light. The peak emission wavelengths of the dopants can be finely tuned depending upon the electronic properties of the substituents as well as their positions in the ring. The emission spectral diagrams show that the emissive states of the complexes have major contribution of MLCT state. In the absorption spectra, the 1MLCT and 3MLCT transitions have been resolved in the range, 385–500 nm. The physical parameters of the electroluminescent devices for the substituted and the unsubstituted complexes has been compared and discussed.