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.