Photophysical properties and oxygen sensitivity of phenylpyridine-type iridium(Ⅲ) complexes with electron-withdrawing groups in the cyclometalating ligand
Photophysical properties and oxygen sensitivity of phenylpyridine-type iridium(Ⅲ) complexes with electron-withdrawing groups in the cyclometalating ligand
To evaluate the effect of electron-withdrawing groups on iridium(Ⅲ) complexes,three cationic iridium(Ⅲ) complexes Ir1-Ir3 were synthesized by using 1,10-phenanthroline as the N^N ancillary ligand and 2-phenylpyridine (ppy) or two ppy derivatives as the C^N cyclometalating ligand. The two derivatives are a ppy molecule containing fluorine and a ppy molecule containing both fluorine and diphenyl-phosphoryl unit,respectively,corresponding to Ir2 and Ir3. The photophysical and electrochemical properties of the ppy-type complexes were studied by UV-Vis absorption spectra,emission spectra and cyclic voltammetry along with theoretical calculations. The oxygen sensitivity was tested in acetonitrile solution with different oxygen concentrations. The results show that the emission peaks of complexes Ir1-Ir3 in dichloromethane solution are 570,506 and 470 nm,respectively,with a quantum yield of 23％,35％ and 56％. The onset oxidation potentials were measured to be 1.20,1.51 and 1.87 V. The introduction of electron-withdrawing fluorine and diphenylphosphoryl groups affects the HOMO energy level of the corresponding complexes Ir2 and Ir3,showing a larger energy gap than Ir1 and resulting in the blue-shifted emission. The emission of complexes Ir1-Ir3 can be quenched by oxygen,and the introduction of electron-withdrawing groups enhances the quenching effect. For Ir3,the Stern-Volmer quenching constant Ksv value is 0.14 Torr-1,suggesting the complex has the potential application as a blue-green type oxygen probe.
关键词
铱(Ⅲ)配合物/吸电子基团/光电性能/密度泛函理论/氧敏感性
Key words
Iridium(Ⅲ) complexes/electron-withdrawing group/photophysical and electrochemical properties/theoretical calculations/oxygen sensitivity
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