Synthesis and Photophysical Studies of New Blue Phosphorescent Iridium Complexes of Fluorinated 2-phenyl-4-methoxypyridine

Abstract

In this study, a new Ir(III) complex containing 2-(3′,5′-bistrifluoromethyl phenyl)-4-methoxypyridine have been synthesized and characterized for efficient blue organic light-emitting diodes (OLEDs). In order to tune photoluminescence (PL) spectra to a shorter wavelength, ppy ligand was fluorinated by –;CF₃ and substituted by –OCH₃ group. The methoxy group substituted on the 4-position of pyridyl ring as electron donating group strongly affected the lowest unoccupied molecular orbital (LUMO) and it raised the LUMO energy and increased the energy gap. The trifluoromethyl group substituted on the 3′,5′-position of phenyl ring as electron withdrawing group decreased the highest occupied molecular orbital (HOMO), and bulky CF₃ groups occurs a steric hindrance of iridium complex helps decrease of self-quenching. As a result, Ir[(CF₃)₂OMeppy]₂(acac) is more blue-shifted emission at 471 nm and strong luminescence efficiency.

Keywords:

• 2-(3′,5′-bis-trifluoromethylphenyl)-4-metoxypyridine
• blue
• iridium complex
• OLED
• phosphorescence

Acknowledgments

This work was supported by Seoul R&D Program (10555) and 2008 Hongik University Research Funds.