Construction Of Ratio Fluorescent Probe Based On C=N Isomerization And Its Application In Ion Detection

As an important constituent of Reactive Oxygen Species?ROS?,hypochlorite ion?ClO^-?is involved in many physiological activities in the human body.However,many studies have shown that ClO^-is closely related to many diseases.Similarly,the essential metal ions in living organisms can also adjust the dynamic balance of the physiological environment.The excessive amounts of metal ions can induce physiological dysfunction or diseases.Therefore,the rapid identification and detection of ClO^-and some ions are very important.Recently,fluorescent methodology has been gradually applied ion detection in various environmental systems and organisms due to the low cost,high selectivity,low detection limit and"naked eye"identify.In this paper,a series of small-molecule fluorescent probes with high sensitivity and great detection were constructed to detect ClO^-and two metal ions,which realized the rapid identification and detection of target ions in environmental water and biological cells.The specific response mechanism of the probe to target ion was verified by means of characterization methods.The research contents are as follows:?1?Two novel ClO^-fluorescent probes?Probe 1a and 1b?were constructed by introducing different recognition groups?p-toluenesulfonylhydrazide and diaminomaleonitrile?into coumarin.The optical response performances of the two probes were studied respectively.Probe1a exhibited a non-fluorescent state due to the isomerization of C=N bond in the structure.The C=N bond was oxidized by ClO^-and then generated a strong blue fluorescence coumarin aldehyde.The changes of fluorescence were used to achieve specific identification to ClO^-.The probe has good water solubility,low detection limit and short response time for ClO^-.Probe 1a can be successfully applied the detection of ClO^-in environmental water samples and biological cells.Probe 1b exhibited a red fluorescence due to the large conjugated system.The blue-shift of fluorescence caused by the reaction between Probe 1b and ClO^-can make the probe exhibit a ratio recognition.At the same time,the specific coordination between Probe 1b and Cu²⁺produced a fluorescence quenching.High sensitivity and strong anti-interference ability were displayed in the recognition of two target ions.In addition,the complex between EDTANa₂ and Cu²⁺can be used to realize the reversible coordination of Cu²⁺and avoid the mutual interferences of quantitative detection.Based on the combination of theoretical calculations and structural characterizations,the recognition mechanisms of two target ions were discussed,which could provide a new idea for designing and developing multifunctional and ratio fluorescent probes.?2?A dual response fluorescent probe?Probe 2?was constructed based on quinazoline,which was applied in identifying ClO^-and Al³⁺.Probe 2 exhibited a red fluorescence due to the large conjugated system.The blue-shift of fluorescent from red to blue-green appeared due to the oxidation of ClO^-.Similarly,the yellow-green fluorescence emerged by the selective coordination with aluminum ion(Al³⁺).The colour of the probe solution after adding ClO^-(Al³⁺)changed from yellow to colorless?brown?with low detection limit and strong anti-interference ability.In addition,the reaction product between Probe 2 and Al³⁺can be used to relay identification of F^-.The probe monomer was released by the strong reaction between F^-and Al³⁺to change the optical property of the system.Repeated experiments have shown that the reversible cyclic detection for Al³⁺and F^-can be achieved by Probe 2.The standard experiment of actual water samples and the fluorescence imaging of HepG2 cells further confirmed the feasibility of the probe for detecting the target in environmental water and biological cells.This work can lay the foundation for the design of fluorescence sensing technology,which has high-performance multi-functional and multi-response superiority.?3?A ratiometric fluorescent probe?Probe 3?was constructed based on naphthalimide and coumarin fluorophores to recognize the endogenous ClO^-selectively.The resonance energy transfer mechanism of the two fluorophores made Probe 3 exhibit yellow-green fluorescence.The probe can generate coumarin aldehydes by the oxidation of ClO^-,accompanied by a significant shift of fluorescence from yellow-green to blue,which showing a ratio fluorescence response.It was found from spectroscopy that the probe has strong selectivity,high sensitivity and short response time to ClO^-.In addition,the localization function of the morpholine ring was used in introducing the probe into the lysosome.Fluorescence imaging of RAW 264.7 cells confirmed that Probe 3 can be used for the ratio monitoring of endogenous ClO^-.This work provides the basic conditions for the further study of real-time monitoring of target ions within biological organelles.