Construction And Properties Of Iridium Complex Reactive Molecular Probes

In recent years,with the rapid development of science and the awareness of environmental protection and healthy life,various techniques for detecting physical diseases and environmental management have been developed.It is well known that the abnormal levels of some substances and ions in nature,such as SO₂,CO,Hg²⁺and Cl^-,will not only pollute the environment,but also cause serious harm to human health.Therefore,the development of techniques for accurately detecting these substances and ions has become a research hotspot.Optical sensing techniques,such as luminous（fluorescence or phosphorescence）molecular probes,have been widely concerned by researchers because of their low cost,simple operation and strong visibility.In this paper,three kinds of transition metal iridium（III）complexes have been designed and synthesized,which have the advantages of long luminescence lifetime,large Stokes shift,good optical stability,easy modification and high quantum yield.The phosphorescent probes of cyclometalated iridium（III）complexes detected different substances（or ions）,and their structures and properties were characterized.The research work mainly includes:1.A phosphorescent probe Ir1 of"Turn-on"cyclometalated iridium（III）complex based on Photo-induced eletron transfer（PET）mechanism was synthesized by introducing electron-withdrawing nitroolefin into the ligand of cyclometalated iridium（III）complex.As an electrophilic group,nitroolefin can not only quench phosphorescence emission of cyclocmetalated iridium（III）complex,but also be used as recognition group for the selective detection of biothiols.The luminescence response of probe Ir1 to biothiols was orange light.In order to apply it to cell-imaging,the structure of probe Ir1 was optimized,that is,introducing ester groups to reduce the orbital energy gap,so as to change the luminescence emission wavelength of the probe.The probe Ir2 was synthesized successfully.The emission of the probe Ir2 to biothiols is deep red light at 643 nm.The experiments show that the probe Ir1 and Ir2 can selectively detect biothiols in complex solvent environment.Finally,the probe Ir2 is successfully used in cell-imaging.2.According to the characteristic of the specific nucleophilic reaction between the aldehyde group and HSO₃^-/SO₃^2-,a phosphorescent probe IrCHO for selective detection of HSO₃^-/SO₃^2-was synthesized by introducing the aldehyde group into the ligand of the cyclometalated iridium（III）complex.The structure of IrCHO was proved to be correct by ¹H NMR spectra,¹³C NMR spectra and HRMS spectra.Then the titration response experiment,selective response experiment,pH experiment and so on for IrCHO with HSO₃^-/SO₃^2-were carried out.It lays a foundation for the application of probe IrCHO in cell-imaging.3.A water-soluble phosphorescent probe Ir-C=N-OH of cyclometalated iridium（III）complex for detection of ClO^-/HClO was synthesized on account of the specific oxidation reaction of ClO^-/HClO and oxime groups.The experimental results show that Ir-C=N-OH exhibited very weak emisson in PBS buffer solution.After addition of ClO^-,the emission of Ir-C=N-OH was red light at 600 nm.And the probe can effectively recognize ClO^-/HClO in the presence of various interference ions.The correctness of the detection mechanism was verified by the comprehensive analysis of density functional theory（DFT）,¹H NMR and mass spectrometry.By titration response to ClO^-,interference ion test,pH test and so on,it can be inferred that the probe is expected to be used to detect ClO^-/HClO in biological cells.The response experiments in three water samples show that Ir-C=N-OH can be used to detect ClO^-/HClO in aqueous solution.