Synthesis Of Water-soluble Cyclometallated Iridium Complex And Its Applications In Luminescence Analysis

Cyclometallated iridium???complexes have better photophysical and chemical properties compared to traditional organic fluorescent materials.Firstly,it exhibits stronger phosphorescence characteristics and good photothermal stability at room temperature.Secondly,this kind of complexes has larger Stokes shift and longer luminescence lifetime.The sample autofluorescence and background stray light interference can be effectively eliminated by Time-resolved spectroscopy?TRS?technology.In addition,the emission wavelength can be tuned by simple modification of the complex structure.In recent years,cyclometallated iridium complex has attracted extensive attention of researchers in the fields of organic electroluminescence devices?OLED?,electrochemical sensing,bio-optical imaging,phosphorescent probes and photocatalysis.However,most cyclometallated iridium complexes have poor water-soluble,and there is a serious phosphorescence self-quenching phenomenon,which greatly limits their application in the fields of analysis and detection.The purpose of this study is to improve the water solubility of the complex and to better avoid its phosphorescent self-quenching effect.Based on the excellent phosphorescence emission performance of water soluble cyclometallated iridium complexes,the probe for target molecule monitoring and quantitative analysis can be constructed,which has significant value in the fields of environmental protection,biology and medical research.In this paper,three phosphorescent cyclometallated iridium complexes with good water solubility and emission properties have been designed and synthesized.Different structures of the complex were characterized by nuclear magnetic resonance?NMR?,infrared spectroscopy?FT-IR?and mass spectrometry?MS?,respectively.The photophysical properties of the complex were studied in detail through ultraviolet-visible absorption spectroscopy and phosphorescence spectroscopy.Besides,we have established a method for the detection of efficient probes in environmental and biological samples.The specific contents are described below:1.A water-soluble iridium complex with carboxyl group[?fppy?₂Ir?BQCOOH?]?Ir-C?was designed and synthesized.The carboxylate group embedded in the ligand effectively improves the water solubility of Ir-C as a solubilizing group.It has been found that Ir-C can be used not only as a highly sensitive pH indicator in acidic and neutral environments,but also for the quantitative determination of nanoscale?nM?BSA with high selectivity.Firstly,the modification of Ir-C with nitrogen-doped carbon quantum dots?N-CQDs?improves the water solubility of the complex,and can effectively inhibit the phosphorescence self-quenching of Ir-C.A visible ratio phosphorescence probe for pH detection of actual drinking water samples and river sample was constructed.Besides,a"Turn-on"probes based on Ir-C was also been constructed,and been used to distinguish BSA from other significant proteins.When the signal-to-noise ratio?S/N?is 3,the detection limit of the probe's response to BSA is as low as 7.0 nM,and it has a good linear relationship in the range of 20?140 nM.The results will provide theoretical support for the development of water-soluble phosphorescent chemical probes.2.We purposefully apply water-soluble and excellent phosphorescent iridium complexes to the field of biosensing.In this chapter,a hydroxyl-type water-soluble phosphorescent iridium complex[?fppa?₂Ir?fppy?]?Ir-OH?was designed and developed.Based on the direct hydrogen-bond interaction between Ir-OH and the imidazole group pyridine nitrogen,A"Turn-on"phosphorescent probe was constructed to detect trace L-histidine and be applied in cell imaging research.The luminous intensity of the probe has a good linear relationship with the concentration of L-histidine from 5.0?M to 100?M,the detection limit of which is 1.7?M when the signal-to-noise ratio?S/N?is 3.This kind of complex is easy to prepare,has high luminous efficiency,low cytotoxicity and good biocompatibility,which can provide useful materials for biosensor applications.3.In order to further reduce the cytotoxicity of the probe and improve the biocompatibility,a new water-soluble phosphorescent iridium complex[?pq-COOH?₂Ir?his?]was designed and synthesized by introducing non-toxic L-histidine?Ir-his?as an auxiliary ligand.Based on the competitive coordination reaction of Cu²⁺with the carbonyl oxygen and the adjacent amino nitrogen atom on the Ir-his ligand,a phosphorescent probe for detecting trace Cu²⁺in domestic water was successfully constructed.The luminous intensity of the probe shows a good linear relationship with the concentration of Cu²⁺from 0.1?M to 500?M,the detection limit of which is 0.08?M when the signal-to-noise ratio?S/N?is 3.The iridium complex has high quantum yield,low cytotoxicity and good biocompatibility.The excellent performance of the iridium complex provides the possibility for its further application in biological research.