Bis-cyclometalated Ir(III) complexes with a diphenylamino group: design, synthesis, and application in oxygen sensing

Abstract A series of CˆN type bis-cyclometalated Ir(III) complexes ( Ir1 - Ir4 ) with a diphenylamino group at the 4-position of the phenyl ring of 2-phenylpyridine (ppy) have been prepared and fully characterized. The influences of substituents (-H, -CH 3 , -F, -CF 3 ) at the pyridyl moiety of ppy on the photophysical and electrochemical properties of these Ir(III) complexes have been investigated systematically by comparison with the model complex Ir(ppy) 2 (acac). The Ir(III) complexes ( Ir1 - Ir4 ) show phosphorescence with emission maxima in the range of 530–558 nm, which are all red-shifted relative to Ir(ppy) 2 (acac) (λ max = 518 nm). These Ir(III) complexes demonstrate longer phosphorescence lifetimes and better oxygen-sensitivity than Ir(ppy) 2 (acac). It is remarkable that introduction of both diphenylamino and trifluoromethyl groups into the cyclometalating ligand enhances the photostability of the corresponding Ir(III) complexes efficiently. The results reveal that the bulky and electron-donating characteristics of the diphenylamino group enhance the performances of the Ir(III) complexes in oxygen sensing.