Three bis-cyclometalated cationic Ir(III) complexes Ir1, Ir2 and Ir3 with an ester substituent at the 4-position of the phenyl ring on the 2-phenylpyridine (ppy) have been synthesized and fully characterized. The emission maxima of ester-substituted Ir(III) complexes show a notable blue-shift compared to the parent complex Ir0 [Ir(ppy)2(phen)]+PF6− (phen = 1,10-phenanthroline). The influence of an ester group on the photoelectric properties of the Ir(III) complexes has been investigated systematically. The oxygen sensing films prepared from ethyl cellulose immobilized with Ir(III) complexes exhibit excellent operational stability, high photostability and a quick response to oxygen. Ir1–Ir3 show extended luminescence lifetimes relative to Ir0, and display better sensitivity to changes in oxygen partial pressure.
