Syntheses and photophysical properties of cyclometallated iridium (III) acetylide complexes

A series of cyclometallated iridium(III) acetylide complexes Ir(ppy)2(PPh3)(Ctriple bond; length of mdashCR) (R = C6H5 3, C6H4But-4 4, C6F5 5, C6H4COMe-4 6, SiMe3 7) were synthesized by substitution of coordination chloride in precursor Ir(ppy)2(PPh3)Cl (2, ppy = 2-phenylpyridine) with an acetylide ligand. These complexes are brightly luminescent in fluid dichloromethane at ambient temperature, originating from 3MLCT/3LLCT/3IL states as supported by TD-DFT studies. It is demonstrated that substitution of coordination chloride in precursor 2 (λem = 456 and 485 nm, Φem = 1.6%) with an acetylide ligand results in obvious red-shift of the emission as well as significant enhancement of the luminescence efficiency in 3–7 (λem = 480–510 nm, Φem = 9.5%–19%) since the energy level of non-emissive d–d transition is highly raised and thus d–d state deactivation is significantly suppressed.