Light-Emitting Electrochemical Cells Based on Oxazoline-Iridium(III) Complexes

Herein, we report two new cationic iridium(III) complexes using oxazoline based ancillary ligand, namely, [Ir(ppy)(2)(mdpox)]PF6 (Complex 1) and [Ir(dfppy)(2)(mdpox)]PF6 (Complex 2), where ppy is 1-phenyl pyridine, dfppy is 2-(2,4-difluorophenyl) pyridine, and mdpox is 2,2-methylenebis(4,5-diphenyl- 2-oxazoline). The solution photoluminescence (PL) emission spectra shows structured emission bands for both complexes which emit blue-green and blue phosphorescence for Complex 1 and 2, respectively. To gain an insight into the photophysical and electrochemical features of the iridium complexes, DFT calculations were performed, which shows the highest occupied molecular orbital (HOMO) is located on d orbitals of iridium center and pi orbitals of the phenyl group of cyclometalated ligands, whereas the lowest unoccupied molecular orbital (LUMO) is distributed on iridium atom and one of the cyclometalated ligand. Light-emitting electrochemical cells (LECs) were fabricated employing these complexes and investigated their electroluminescent properties. LECs based on these complexes resulted yellow and green electrolunescence for Complex 1 and 2, respectively. A high luminance of 838 cd m(-2) and a current density of 486 mA cm(-1) has achieved for Complex 1 owing to the more balanced charge carrier injection and recombination.