Modulation of the oxygen sensing properties of iridium (III) complexes by changing their substitution groups

In this study, new bis-cyclometalated iridium (III) complexes bearing different ligated groups (-H, -OCH3, -F, -CH3) at the aryl moiety (Ir-1, Ir-2, Ir-3 and Ir-4) were synthesized and characterized. Then oxygen sensing properties of corresponding complexes were investigated in EC film. The complexes showed room temperature phosphorescence spectra in the range of 562-590 nm in THF and 546-554 nm in ethyl cellulose (EC) matrix. When they were incorporated in an ethyl cellulose matrix, the probes showed optimal dynamics of luminescence for oxygen monitoring in the range from 0 % to 100 % air saturation. The I-0/I-100 values of Ir-1, Ir-2, Ir-3 and Ir-4 in EC thin film were calculated as 10.9, 5.0, 7.3 and 22.7, respectively. The results showed that the oxygen sensitivity accomplishment of the complex core can be fine-tuned by varying these ligated groups, and the weak electron-donating properties of the methyl groups at the aryl moiety improve remarkably the optical oxygen sensing abilities of the Iridium (III) complexes.