Design,Synthesis And Properties Of Fluorescent Probes Based On Nitrogen- And Oxygen-Containing Heterocyclic Micromolecules

Mercury ion,hydrogen sulfide?H₂S?and biothiols?GSH,Hcy,Cys?play important roles in both environmental and physiological activities,and their imbalances can lead to adverse physiological reactions.For example,Hg²⁺is not easily degraded and tends to accumulate,causing environmental pollution.It can enters the human body by the food chain,excessive Hg²⁺may cause damage to the central nervous system,kidneys and brain,and even cause death;the imbalance of hydrogen sulfide concentration may result in Down syndrome,high blood pressure and other diseases;the abnormalities in bio-thiol concentrations are directly related to cardiovascular diseases and cancer.Therefore,the detection of ions and small biomolecules is of great significance to both the environment and the organism.Fluorescence probe analysis is widely used in the detection of ions and biological small molecules because of its high sensitivity,simple operation,high selectivity and real-time dynamic detection.In this paper,we synthesized four kinds of fluorescent probes based on nitrogen-oxygen heterocyclic small molecules,and studied their optical properties,they are as follows:1.Utilizing dicyanoisophorone derivative as a fluorophore,NBD as a responsive group and a quenching group,a near-infrared fluorescent probe HZ-NBD was designed and synthesized,which is capable of selectively detecting H₂S/GSH.The probe HZ-NBD shows high sensitivity,strong anti-interference ability and short response time.In addition,due to the low toxicity of the probe and wide pH application range,it has been successfully applied to fluorescence imaging in cells and zebrafish,which laid a foundation for its practical application.2.A near-infrared fluorescent probe AZ-NO₂ with dicyanoisophorone derivative as the fluorescent precursor was designed and synthesized.By introducing the 2,4-dinitrophenyl group with a strong electron withdrawing effect to the hydroxyl group,inhibiting intramolecular charge transfer leads to fluorescence quenching.When adding H₂S,the thiol-induced aromatic nucleophilic substitution reaction causes the removal of2,4-dinitrobenzene,thereby releasing a near-infrared fluorescent signal.The experimental results show that the probe AZ-NO₂ can achieve specific detection of H₂S,high sensitivity?16.3 nM?,strong anti-interference ability,rapid response,low toxicity,and can be applied to exogenous and endogenous H₂S in cells and zebrafish fluorescence imaging.3.Exploring fluorescein as a fluorescent platform,two kinds of fluorescent probes HSFH?5-hydroxy salicylaldehyde fluorescein? and HQAFH?8-hydroxyquinolin-2-fluorescein?for detecting Hg²⁺were synthesized based on Schiff base reaction.Both of these fluorescent probes are based on the fluorescein-based lactam spiro switch recognition mechanism,and the mercury ions and the spirohydrazide are coordinated to open-loop,thereby achieving specific recognition of Hg²⁺.In addition,the probes have a high sensitivity and a wide pH range.Finally,HSFH is also used in the detection of actual water samples.