Tailoring the Emission of Fluorinated Bipyridine-Chelated Iridium Complexes.

New functionalized tris(2',6'-difluoro-2,3'-bipyridinato-,C4')iridium(III) ((dfpypy)Irs) complexes, including small molecules and their dendrimer embedded analogoues, were synthesized and characterized. It is demonstrated that both the -(dfpypy)Ir-based polyphenylene dendrimers and (triisopropylsilyl)ethynyl (TIPSE)-substituted (dfpypy)Ir complexes induce large bathochromic shifts (∼50 nm) of emission bands compared with -(dfpypy)Ir. This is due to the pronounced π-π* character of emissive excited states and the extended conjugation. A further remarkable feature is the small bathochromic shift of the emissions of -tris(2-phenylpyridine)iridium (-(ppy)Ir)-based polyphenylene dendrimers when compared to those of the iridium (Ir) complex core. Obviously, the triplet metal-to-ligand charge transfer makes emission less sensitive to extended conjugation than the π-π* transition. This finding suggests new concepts for designing blue phosphorescent dendrimer emitters. Both the dendrimers and the TIPSE-substituted (dfpypy)Ir complexes represent new green and the trimethylsilyl-functionalized (dfpypy)Ir new blue phosphorescent emitters. Incorporation of TIPSE moieties into the ligands of iridium complex gives rise to enhanced phosphorescence.