Preparation method of naphthalimide fluorescent probe and application of naphthalimide fluorescent probe in mercury ion detection

Abstract

The invention discloses a preparation method of a naphthalimide fluorescent probe and application of the naphthalimide fluorescent probe in mercury ion detection. According to the invention, 1, 8-naphthalimide is taken as an initial raw material, a novel Schiff base fluorescent probe (probe QA) taking naphthalimide as a fluorophore is designed and synthesized, and the novel Schiff base fluorescent probe is used for detecting Hg < 2 + > in an aqueous solution. In a MeOH / H2O (v / v = 4: 1, and pH = 7.0) solution, the probe QA has high sensitivity and selectivity to Hg < 2 + >, fluorescence quenching of the probe QA to Hg < 2 + > is prior to that of other competitive metal ions, and the quenching rate of Hg < 2 + > to the probe QA can reach 99%. In addition, the synthetic raw materials of the probe are low in price and easy to obtain, the probe QA is simple in preparation process and high in product yield, the green and environment-friendly requirements are met, and the probe has a very good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescent probe preparation, relates to cation selective fluorescence detection, and specifically relates to a preparation method of a naphthaleneimide probe and an application method of the probe in detecting mercury ions. Background Art

[0002] Mercury is the third most harmful element to human health. It exists in many forms, such as metallic mercury, inorganic mercury and organic mercury. The toxicity of different forms of mercury and their effects on the nervous, digestive and immune systems, as well as the lungs, kidneys, skin and eyes vary. It is generally believed that organic mercury is the most dangerous and common form of mercury exposure, especially methylmercury, which is a powerful neurotoxin that accumulates in organisms along the food chain and has certain effects on the nervous, digestive and immune systems. In addition, mercury exposure not only affects the immune status of the organism, but also causes cardiovascular diseases such as myocardial infarction, heart rate variability and hypertension. In summary, the study of a highly selective and sensitive Hg 2+ The detection method is of great significance.

[0003] As we all know, compared with the traditional Hg 2+ Compared with other detection methods, fluorescence spectroscopy has the advantages of simple operation, low cost, short response time, high sensitivity and high selectivity, and has been widely used in the field of heavy metal ion detection. In addition, the naphthalene imide fluorophore has optical properties such as large Stokes shift, good photostability, high quantum yield and easy structure modification, which is very suitable for fluorescence detection of Hg 2+ It has been widely used. Summary of the invention

[0004] The purpose of the present invention is to provide a method for detecting metal ions Hg 2+ A naphthaleneimide fluorescent probe and a preparation method thereof.

[0005] Another object of the present invention is to provide the above-mentioned naphthalene imide probe for fluorescence detection of Hg 2+ Application in.

[0006] 1. Naphthalimide fluorescent probes

[0007] The present invention is a naphthalimide fluorescent probe, the molecular formula of which is C 20 H 16 N4O3, named QA.

[0008] 2. Preparation method of naphthalimide fluorescent probe

[0009] (1) Anhydrous ethanol was used as solvent, 4-bromo-1,8-naphthalene anhydride and ethanolamine were used as substrates in a feed ratio of 1:1.2, and refluxed at 80°C for 4 hours with TLC monitoring. After the reaction was completed, the reaction was filtered and recrystallized from anhydrous ethanol to synthesize intermediate 3.

[0010] (2) Using ethylene glycol methyl ether as solvent, intermediate 3 and hydrazine hydrate as substrates, the feed ratio was 1:4, and the reaction was refluxed for 5 hours. The reaction progress was monitored by TLC. After the reaction was completed, the mixture was rinsed with distilled water 3-4 times to synthesize intermediate 2.

[0011] (3) Anhydrous ethanol was used as solvent, the intermediate 2,2-formaldehyde pyridine was used as substrate, glacial acetic acid was used as catalyst, the feed ratio was 1:1.2:1.2, the reaction was carried out at 60°C for 1.5 hours, and the reaction was monitored by TLC. After the reaction was completed, the naphthylimide probe QA was obtained. The synthetic route of QA is shown in Figure 1 The infrared spectrum and hydrogen spectrum of the naphthylimide sensor molecule QA prepared by the above method are shown in Figure 2 and Figure 3 .

[0012] 3. Naphthalimide fluorescent probes for Hg 2+ Selective research applications

[0013] In the (MeOH / H2O (v:v=4:1)) solution of probe QA, 10 eq of 1.0×10 -2 mol / L metal ion aqueous solution (Al 3+ , Ca 2+ , Cu 2+ 、Co 2+ Cr 3+ 、Cd 2+ , Fe 3+ , K + 、Na + Mg 2+ 、Zn 2+ 、Ni 2+ and Hg 2+ ), and measured the UV absorption spectrum and fluorescence spectrum. The results showed that only Hg 2+ The UV absorption spectrum of the metal ions was significantly changed, resulting in the disappearance of the absorption peak at 458 nm, while the other metal ions did not cause significant changes in the absorption spectrum (see Figure 4 ). It can be seen from the fluorescence spectrum (see Figure 5 ), except Fe 3+ and Hg 2+ Except for Fe, no obvious fluorescence spectra changes were observed at 545 nm for other metal ions. 3+ To some extent, the fluorescence intensity of probe QA will be weakened, but it does not reach quenching. 2+ When the fluorescence emission intensity of the mixed solution was significantly quenched, the quenching rate was 99%. Therefore, these results show that probe QA can be used as a Hg2+ Highly selective fluorescent probe.

[0014] 4. Naphthalimide probes for Hg 2+ Interference research applications

[0015] To further verify the probe's sensitivity to Hg 2+ Compared with other metal ions, Hg 2+ With other metal cations (Al 3+ , Ca 2+ , Cu 2+ 、Co 2+ Cr 3+ 、Cd 2+ , Fe 3+ , K + 、Na + Mg 2+ 、Zn 2+ and Ni 2+ ) for the competitive experiment of probe QA, and based on the experimental results, a bar graph of the probe QA detection process was drawn (see Figure 6 ) It can be seen more intuitively that the probe QA is sensitive to Hg 2+ It has high specific detection ability.

[0016] 5. Naphthalimide probe QA for metal ion Hg 2+ Determination of the limit of detection (LOD)

[0017] UV titration was used to determine the Hg 2+ The lowest detection limit (LOD) of aqueous solution was obtained, and the data were linearly fitted (see UV titration diagram for details). Figure 7 , LOD linear fitting diagram see Figure 8 ), the probe QA is calculated to be Hg by the formula LOD = 3σ / k 2+ The LOD is 8.87×10 -6 mol / L.

[0018] VI. Naphthalimide probe QA for metal ion Hg 2+ Determination of the complex constant (Ka)

[0019] The probe QA was tested with different concentrations of Hg 2+ Fluorescence titration spectra in the presence of Fig. 9 ) was analyzed using the Benesi-Hildebrand equation:

[0020]

[0021] The relationship between probe QA and Hg 2+ The complex constant ( Fig.10 ), and the Ka is calculated to be 1.71×10 4 M -1 .

[0022] VII. Naphthalimide probe QA for metal ion Hg 2+ Determination of binding stoichiometry

[0023] To further determine the relationship between probe QA and Hg 2+ The binding stoichiometry of the probe QA and Hg 2+ The total concentration of the system is constant at 100 μM, and the probe QA and Hg 2+ Concentration ratio, measuring the fluorescence emission intensity as [QA] / ([Hg 2+ ]+[QA]) concentration, and the fluorescence emission intensity at 545nm was plotted as Job'plot ( Fig.11 ). The fluorescence intensity is [QA] / ([Hg 2+ ]+[QA]) reaches a maximum when it is 0.326, indicating that the probe QA and Hg 2+ The combination ratio is 1:2, which is consistent with the above fluorescence titration experiment results.

[0024] In summary, the present invention has the following advantages:

[0025] 1. The design route of the present invention is simple. 4-bromo-1,8-naphthalene anhydride is selected as the main starting material to successfully synthesize a new type of Schiff base fluorescent probe, which realizes the specific metal ion Hg 2+ Sensitive and specific detection.

[0026] 2. The fluorescent probe of the present invention is based on the naphthalimide fluorophore, has stable performance and excellent fluorescence characteristics; and the fluorescent probe detects the metal ion Hg 2+ The method has high sensitivity, high specificity, simple operation and low cost. Therefore, naphthylimide probe QA has a good application prospect in the detection of heavy metal ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The synthetic route of the naphthylimide fluorescent probe QA of the present invention is shown in FIG.

[0028] Figure 2 is the infrared spectrum of the naphthalimide fluorescent probe QA of the present invention;

[0029] Figure 3 This is the hydrogen spectrum of the naphthylimide fluorescent probe QA of the present invention;

[0030] Figure 4 The ultraviolet absorption spectra of various metal ions added to the solution of the naphthylimide fluorescent probe QA (MeOH / H2O (v:v=4:1)) of the present invention;

[0031] Figure 5 is the naphthalimide fluorescent probe QA (MeOH / H2O (v:v=4:1) of the present invention, λ ex =460nm, slit: 5nm / 5nm) Fluorescence spectra of various metal ions added to the solution;

[0032] Figure 6 Hg is added to the naphthalene imide fluorescent probe QA and other interfering ions of the present invention. 2+ Fluorescence value before and after (λ ex =460nm,λ em =545nm, slit: 5nm / 5nm). The orange bar graph represents the fluorescence intensity of the probe QA after adding the interfering ions, and the green bar graph represents the fluorescence intensity of the probe QA after adding the interfering ions and then adding Hg 2+ The fluorescence intensity of

[0033] Figure 7 Different concentrations of Hg 2+ UV titration diagram after

[0034] Figure 8 This is the UV titration fitting curve diagram of the naphthylimide fluorescent probe QA of the present invention;

[0035] Fig. 9 Different concentrations of Hg 2+ Fluorescence titration diagram after

[0036] Fig.10 The Benesi-Hildebrand plot of the naphthylimide fluorescent probe QA of the present invention is drawn according to the fluorescence titration results;

[0037] Fig.11 For [Hg 2+ ]+[QA]=100μM, the probe QA and Hg 2+ Job'plot graph; DETAILED DESCRIPTION

[0038] Example 1: Preparation of probe QA

[0039] (1) Dissolve 4-bromo-1,8-naphthalene anhydride (15mmol, 4.1565g) in 150ml of anhydrous ethanol, add 2-aminoethanol (18mmol, 1.099ml) dissolved in 15ml of anhydrous ethanol, heat the suspension to reflux for 4 hours, and monitor the reaction by TLC (PE:EA=1:2). After the reaction is completed, cool to room temperature, filter under reduced pressure, wash the filter cake with distilled water 3-4 times, recrystallize with ethanol, and place in an oven to dry to obtain compound 3 as a white solid (3.8219g, 79.88%). IR (KBr; ν, cm –1 ):3396,1697,1661,1366,1051,778.

[0040] (2) Compound 3 (7.5 mmol, 2.3917 g) and hydrazine hydrate (30 mmol, 1.876 ml) were dissolved in 45 ml of 2-methoxyethanol, heated to reflux at 125°C, reacted for 5 hours, and monitored by TLC (DCM: MeOH = 5:1). The reaction solution was cooled to room temperature and filtered, the filter cake was washed with distilled water, and vacuum dried at 105°C to obtain compound 2 as a yellow solid (1.8787, 92.40%). IR (KBr; ν, cm –1 ):3462,3374,1635,1587,1390,1069,777.

[0041] (3) Weigh compound 2 (3 mmol, 0.8133 g) and dissolve it in 65 ml of anhydrous ethanol. Add 3.6 mmol of acetic acid and 3.6 mmol of 2-pyridinecarboxaldehyde in turn. Heat in a water bath at 60 degrees Celsius. After 1.5 hours, the reaction is terminated. The reaction process is monitored by TLC (DCM: MeOH = 7: 1). Cool and filter. Wash the filter cake with ethanol 3-4 times and dry it in a vacuum at 60 degrees Celsius to obtain probe 1 as an orange-red solid (1.075 g, 99.5%). IR (KBr; ν, cm –1 ):3422,3292,1685,1637,1277,1046,769. 1 H NMR (300MHz, DMSO) δ11.63(s,1H),8.79(d,J=8.5Hz,1H),8.62(dt,J=4.7,1 .3Hz,1H),8.53–8.44(m,2H),8.39(d,J=8.5Hz,1H),8.10(d,J=8.0Hz,1H), 7.88(td,J=7.8,1.8Hz,1H),7.84–7.75(m,2H),7.39(ddd,J=7.4,4.8,1.2H z, 1H), 4.80 (t, J = 5.9Hz, 1H), 4.14 (t, J = 6.7Hz, 2H), 3.61 (q, J = 6.5Hz, 2H).

[0042] Example 2: Detection of Hg by Probe QA 2+

[0043] (1) Weigh an appropriate amount of probe QA and dissolve it in MeOH / H2O system to prepare a probe stock solution with a concentration of 0.1 mM.

[0044] (2) Weigh an appropriate amount of metal nitrate solid and dissolve it in H2O to prepare a 10 mM metal ion stock solution.

[0045] (3) Transfer 3 mL of the probe stock solution from step (1) to a small reagent bottle and add 300 μL of 10 mM concentration of each metal ion (Al 3+ , Ca 2+ , Cu 2+ 、Co 2+ Cr 3+ 、Cd 2+ , Fe 3+ , K + 、Na + Mg 2+ 、Zn 2+ 、Ni 2+ and Hg 2+ ) aqueous solution, and tested the UV absorption spectrum and fluorescence spectrum of the system. In the fluorescence spectrum test, the excitation wavelength of QA was 460nm and the emission wavelength was 545nm. Figure 4 and 5 As shown in the figure, QA exhibits a broad absorption band at 460 nm in its absorption spectrum, and the typical emission peak of the probe is around 545 nm in the emission spectrum. 2+ After that, the fluorescence of the probe solution was observed to change from yellow to colorless under ultraviolet light, and fluorescence quenching occurred, indicating that the system contained Hg 2+ In addition, the broad absorption peak and main emission peak of the probe were significantly weakened, which shows that probe QA can effectively detect Hg by fluorescence quenching. 2+ .

Claims

1. A naphthalimide probe, the structural formula of which is:

2. A method for preparing a naphthalimide probe as claimed in claim 1, characterized in that: (1) Using anhydrous ethanol as solvent, 4-bromo-1,8-naphthalene anhydride and ethanolamine as substrates, the reaction mixture was refluxed at 80°C for 4 hours and monitored by TLC to synthesize intermediate 3. (2) Using ethylene glycol methyl ether as solvent, intermediate 3 and hydrazine hydrate as substrates, reflux reaction was performed for 5 hours to synthesize intermediate 2. (3) Using anhydrous ethanol as solvent, the intermediate 2,2-formaldehyde pyridine as substrate, and glacial acetic acid as catalyst, the reaction was carried out at 60° C. for 1.5 hours to obtain the naphthylimide probe QA.

3. The method for preparing a naphthalimide probe according to claim 2, characterized in that: The molar ratio of intermediate 2, 2-formaldehyde pyridine and glacial acetic acid is 1:1.2:1.

2.

4. The naphthalene imide fluorescent probe prepared by the method according to claim 2 and 3 is used to detect Hg 2+ Application in.

5. The naphthalimide probe according to claim 4 for fluorescence detection of Hg 2+ The application is characterized by: Hg was added to the methanol / water solution of naphthalimide probe. 2+ After that, the fluorescence of the probe is quenched.

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