Synthesis, characterization, and photophysical properties of iridium complexes with an 8-phenylquinoline framework. The first six-membered chelated iridium complexes for electroluminance

A series of six-membered chelated iridium complexes bearing an 8-phenylquinoline framework have been prepared and characterized with an X-ray diffraction study. The photophysical properties of these complexes were examined with appropriate spectroscopic methods. The results, in combination with ab initio approaches, led us to clearly assign various electronic transition states. One salient feature for these red complexes is the appearance of a dual strong absorption band around 425-500 nm, which incorporates a state mixing between (MLCT)-M-1 and pi-pi* manifolds. These complexes show deep red phosphorescent emissions (650-680 nm), with short lifetimes of 1.7-3.0 mu s and moderate quantum yields of 0.05-0.11 in deaerated CH3CN. The electroluminance performance of these species shows a promising perspective in the OLED display. One representative, Ir[8-(3,5-difluorophenyl)quinoline](2)(acac) (4c), shows a eta(ext) value of 2.04% at J = 20 mA/cm(2) and the maximum brightness is 3427 cd/m(2) (x = 0.68, y = 0.32) with a full width at half-maximum of only 60 nm at 16 V, demonstrating the first six-membered chelated iridium complexes to suit applications in OLED devices.