Synthesis and Luminescence Studies of Hydrocarbon-Branched Tris-Cyclometallated Iridium (III) Complexes

Abstract

We synthesized the tris-cyclometallated iridium complexes containing the substituted styryl groups and their saturated analogs. As the styryl iridium complexes, Ir(F-ppy-4-CH=CHC₆H₄R)₃ (where R = Me, NMe₂, OMe) were prepared via direct functionalization of the methyl groups in the ppy (2-phenylpyridine) ligand at the iridium complexes. The corresponding saturated analogs, Ir(F-ppy-4-CH₂CH₂C₆H₄R)₃ (where R = Me, NMe₂), were synthesized during the two step reactions of the IrCl₃·xH₂O with F-ppy-4-CH=CHC₆H₄R via in situ hydrogenation. Their photophysical properties were investigated both in solution and in film. The longer π-conjugation in the cyclometallating ligands leads to the bathochromic shift in photoluminescence of their iridium complexes. Among R groups, the NMe₂ end group had the strongest push-pull effect with the F group at the other end, and led to the effective control of the ILCT transition.

Keywords:

• Hydrocarbon-branched
• iridium complex
• OLED
• phosphorescence

Acknowledgement

This work was supported by the Korea Research Foundation (KRF-2008-531-C00036).