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

A series of cyclometallated iridium(III) acetylide complexes Ir(PPY)(2)(PPh3)(C equivalent to CR) (R=C6H5 3, C6H4Bu1-4 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 (MLCT)-M-3/(LLCT)-L-3/(IL)-I-3 states as supported by TD-DFT studies. It is demonstrated that substitution of coordination chloride in precursor 2 (lambda(em) = 456 and 485 nm, Phi(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 (lambda(em) = 480-510 nm, (Phi(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. (C) 2012 Elsevier B.V. All rights reserved.