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

A series of cyclometallated iridium(III) acetylide complexes Ir(ppy)2(PPh3)(CCR) (R=C6H5 3, C6H4Bu^t-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 (λ em =456 and 485nm, Φ em =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 (λ em =480–510nm, Φ em =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.
Graphical abstract Highlights Substitution of coordination chloride in precursor Ir(ppy)2(PPh3)Cl with a strong-field acetylide ligand causes an obvious red-shift of the emission as well as significant enhancement of luminescent quantum yields in complexes Ir(ppy)2(PPh3)(CCR) (R=C6H5, C6H4Bu^t-4, C6F5, C6H4COMe-4, SiMe3).