Synthesis and characterization of a green-light-emitting (pbi-Br)2 Ir (acac) metal complex for OLEDs.

Abstract

We designed and synthesized a 2-(4-bromophenyl)-1-phenyl-1H-benzimidazole (pbi-Br) ligand, which was then employed to create an innovative phosphorescent cyclometallated iridium(III) (pbi-Br)2 Ir(acac) metal complex with acetyl acetone as an ancillary ligand using the Suzuki coupling reaction. The complex was then characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra and thermogravimetric analysis (TGA)/differential thermal analysis (DTA) for structural and thermal analysis, respectively. XRD confirmed its amorphous nature and the FTIR spectrum revealed the molecular structure confirmation of the metal complex. The TGA/DTA curve disclosed its thermal stability up to 310°C. Ultraviolet (UV)-vis absorption and photoluminescence (PL) spectra were measured to explore the photo-physical properties of the (pbi-Br)2 Ir(acac) complex in basic and acidic media respectively. With the variation in solvent from acidic to basic media, optical absorption peaks blue shifted with variation in optical densities. These results facilitated the calculation of various photo-physical parameters. When excited at 379nm in the solid state, the synthesized complex gave out a green light emission, peaking at λemi =552nm. Staggering differences in optical density were observed in the PL spectra of the solvated complex. A Stokes' shift of 7140.45cm-1 and 7364.94cm-1 was observed when the complex was solvated in acetic acid and chloroform, respectively. Hence the synthesized iridium metal complex can be considered as promising green emissive material for optoelectronic applications.