Fluorescent compound capable of detecting semicarbazide with naked eyes as well as preparation method and application of fluorescent compound

Abstract

The invention discloses a fluorescent compound capable of detecting semicarbazide with naked eyes as well as a preparation method and application of the fluorescent compound. The preparation method comprises the following steps: carrying out condensation reaction on diketopyrrolopyrrole and nitrogen-containing aromatic primary amine, carrying out coordination with BF3. Et2O, and carrying out [2 + 2] cycloaddition-counter electrocyclization reaction with tetracyanoethylene to obtain the PPAB compound with the electronic push-pull effect. In an organic solvent, PPAB and semicarbazide are subjected to irreversible chemical reaction, high-sensitivity detection of semicarbazide is achieved, and the method has the advantages of being easy and convenient to operate, rapid in reaction, good in selectivity, capable of achieving colorimetric and fluorescent dual-mode detection and the like.

Description

Technical Field

[0001] The invention belongs to the field of organic small molecule materials and relates to a fluorescent small molecule compound and its preparation and application in semicarbazide detection. Background Art

[0002] Semicarbazide (SEM), also known as aminocarbamoyl hydrazide, is a characteristic metabolite of the nitrofuran antibiotic furazolidone and is often used as a residual marker for monitoring the illegal use of furazolidone in animal-derived foods. On the other hand, canned foods are often sealed using the "press on-twist off" (PT) sealing technology, in which azodicarbonamide (ADC) is often used as a foaming agent in the production process of sealing gaskets to achieve a sealing effect by forming a tiny air chamber. Gaskets containing ADC foaming agents can generate SEM through thermal decomposition during the sealing of glass bottles and disinfection processes, which enter the food and cause SEM contamination. In addition, SEM is also a thermal decomposition byproduct of food baking processing and may remain in products such as bread and flour. Based on the widespread use of furazolidone and ADC, SEM has been identified as a widely distributed food hazard, among which canned foods such as honey, jam, ketchup, mayonnaise, and condiments are important categories of SEM contamination.

[0003] Food may be contaminated by SEM during processing and packaging. Studies have shown that SEM has potential carcinogenic, teratogenic and mutagenic effects. In severe cases, it can also affect the functioning of the endocrine system and nervous system. It has been proven to be toxic to multiple tissues and organs in the human body, such as the thyroid gland, thymus, spleen, uterus and ovaries. Therefore, sensitive detection of SEM residues in canned foods and meat products is of great significance to human health and food safety.

[0004] SEM detection usually adopts methods such as high performance liquid chromatography, enzyme-linked immunosorbent assay, immunochromatographic analysis and electrochemical analysis. Although these instrument detection methods have high sensitivity and accuracy, they are time-consuming and require expensive machines and professionals to operate. In recent years, optical detection technology (colorimetric and fluorescence analysis) has attracted much attention due to its high selectivity, fast response speed, convenient operation, low cost, intuitiveness and real-time. Some inorganic luminescent materials such as up-conversion inorganic luminescent nanomaterials and quantum dots are used as fluorescent probes for SEM detection, but they can only be detected through single-mode (such as colorimetric or fluorescence) light response. There are also shortcomings such as slow detection speed, high detection limit, short luminescent wavelength of the probe and small spectral change, which greatly limits its application. At present, there is no literature to achieve high-sensitivity detection of SEM. Summary of the invention

[0005] The purpose of the present invention is to provide a fluorescent compound PPAB with high sensitivity and naked eye detection of SEM, in view of the shortage of SEM fluorescent probes and slow response speed, and the structural formula is:

[0006]

[0007] in:

[0008]

[0009] SEM contains electron-rich amino groups, and multiple electron-deficient cyanoethylene fragments are introduced into the probe with a large conjugated planar structure to form an electron push-pull system, which extends the absorption and emission wavelengths of the probe; in addition, the introduction of cyanoethylene fragments can increase the reaction rate between the PPAB core and SEM and improve the detection sensitivity.

[0010] The present invention also provides a fluorescent compound capable of detecting SEM with naked eyes and a preparation method thereof, and the reaction scheme is as follows:

[0011]

[0012] The preparation method thereof comprises the following steps:

[0013] (1) Under nitrogen protection, the bromide and 1-3 times the molar equivalent of 5-alkynepyridine-2-amine are dissolved in tetrahydrofuran and a base, wherein the base is triethylamine or diisopropylamine. A catalytic amount of a palladium catalyst and a monovalent copper reagent are added in sequence, wherein the palladium catalyst is Pd(PPh 3 ) 4 、Pd(dppf)Cl 2 、Pd(PPh 3 ) 2 Cl 2 , preferably Pd(PPh 3 ) 2 Cl 2 The monovalent copper reagent is CuCl, CuBr, CuI, preferably CuI. Stir at 70-100°C for 8-10 hours. Add water and shake thoroughly, then extract with ethyl acetate, combine the organic phases, remove the solvent by rotary evaporation, and separate and purify the crude product by column chromatography to obtain intermediate 1.

[0014] (2) Under nitrogen protection, the intermediate 1 and the compound 3,6-bis(3-bromo-4-(octyloxy)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione were dissolved in toluene in a mass ratio of 1:4, stirred at 60-80°C for 0.5-2 hours, heated to 80-100°C, and 6-20 times the molar equivalent of TiCl4 and 20-60 times the molar equivalent of an organic base were added in sequence. After reacting for 8 hours, 20-40 times the molar equivalent of BF 3·Et 2 O, the reaction was terminated after 2 hours of reaction and cooled to room temperature. Water was added to quench the reaction, and then extracted with dichloromethane, the organic phases were combined, the solvent was removed by rotary evaporation, and the crude product was separated and purified by column chromatography to obtain intermediate 2.

[0015] (3) Under nitrogen protection, the intermediate 2 is dissolved in dichloromethane, and then 2 to 4 equivalents of tetracyanoethylene compound are added and stirred at room temperature for 6 hours. After the reaction is completed, the reaction is quenched with water, and dichloromethane and water are extracted. The solvent is removed by rotary evaporation, and the crude product is separated and purified by column chromatography to obtain the fluorescent compound PPAB.

[0016] In the present invention, pyrrolopyrrole diketo and nitrogen-containing aromatic primary amine undergo condensation reaction with BF 3 .Et 2 O coordinates and undergoes a [2+2] cycloaddition-reverse electrocyclization reaction with tetracyanoethylene to obtain a PPAB compound with electron push-pull effect.

[0017] The present invention also provides an application of a fluorescent compound PPAB that can detect SEM with naked eyes: the PPAB is reacted with SEM in 1,4-dioxane, and then ultraviolet or fluorescence spectrum detection is performed. The PPAB concentration is 10 μmol / L, the upper limit of SEM detection is 1000 μmol / L, and the reaction time is 2 to 30 minutes.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention introduces multiple electron-deficient cyanoethylene fragments to accelerate the reaction rate between the fluorescent probe and SEM, thereby effectively improving the sensitivity of SEM detection, overcoming the shortcomings of the current SEM fluorescent probe, which has a slow response rate and low sensitivity.

[0020] (2) The fluorescent compound provided by the present invention has the characteristics of simple operation, rapid reaction and good selectivity in SEM detection.

[0021] (3) The fluorescent compound provided by the present invention has the characteristics of colorimetric and fluorescent dual-mode detection in SEM amine detection.

[0022] (4) This method has practical application value in the field of SEM detection research and can be used for food safety testing, environmental monitoring, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the hydrogen spectrum of the fluorescent compound PPAB in the example.

[0024] Figure 2 It is the high-resolution mass spectrum of the fluorescent compound PPAB in the example.

[0025] Figure 3 The fluorescent compound PPAB (10 -5 mol / L) in different solvents.

[0026] Figure 4 The fluorescent compound PPAB (10 -5 mol / L) in different solvents.

[0027] Figure 5 The fluorescent compound PPAB (10 -5 mol / L) in 1,4-dioxane and SEM (100×10 -5 mol / L) time-dependent UV-visible spectrum of the solution after the reaction.

[0028] Figure 6 The fluorescent compound PPAB (10 -5 mol / L) in 1,4-dioxane and SEM (100×10 -5 mol / L) time-dependent fluorescence emission spectrum of the solution after the reaction.

[0029] Figure 7 The fluorescent compound PPAB (10 -5 mol / L) in 1,4-dioxane and SEM and other analytes (100×10 -5 mol / L) after the reaction.

[0030] Figure 8 The fluorescent compound PPAB (10 -5 mol / L) in 1,4-dioxane and SEM and other analytes (100×10 -5 mol / L) after the reaction. DETAILED DESCRIPTION

[0031] Example

[0032] (1) The compound 3,6-bis(3-bromo-4-(octyloxy)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione was synthesized according to the method disclosed in the literature (The Journal of Physical Chemistry C 2009, 114(2):1343-1349).

[0033] (2) Compound 5-ethynylpyridin-2-amine was synthesized according to the method disclosed in the literature (Journal of Materials Chemistry B 2018, 6: 5570-5581).

[0034] (3) Preparation of intermediate 1:

[0035]

[0036] Under nitrogen protection, 4-bromotriphenylamine (1.96 g, 6.04 mmol) and 5-pyridin-2-amine (1 g, 8.46 mmol) were dissolved in tetrahydrofuran (10 mL) and triethylamine (10 mL), and Pd(PPh 3 ) 2 Cl 2 (0.12 g, 0.17 mmol) and CuI (0.34 g, 0.17 mmol) were stirred at 70 °C for 10 hours. Water was added to quench the reaction and extracted with ethyl acetate. The solvent was removed by rotary evaporation and the crude product was separated and purified by column chromatography (petroleum ether: ethyl acetate = 3:1, v / v) to obtain intermediate 1 with a yield of 60%. 1 H NMR(500MHz,Chloroform-d)δ8.18–8.12(m,1H),7.57(m,1H),7.34–7.31(m,2H),7.27(d,J=1.9Hz,1H) ,7.25(d,J=2.1Hz,2H),7.12–7.03(m,7H),7.00–6.96(m,2H),6.61–6.55(m,1H),5.27(d,J=2.1Hz,2H).

[0037] (4) Preparation of intermediate 2:

[0038]

[0039] Under nitrogen protection, compound 3,6-bis(3-bromo-4-(octyloxy)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (0.50 g, 0.71 mmol) and intermediate 1 (1.54 g, 4.27 mmol) were dissolved in 50 ml of toluene, heated to 100 °C, and TiCl 4 (0.18 mL, 10.68 mmol), triethylamine (0.67 mL, 30.62 mmol), and BF was added after 8 h of reaction. 3 ·Et 2O (0.55 mL, 28.49 mmol), the reaction was terminated after 2 h, and the temperature was cooled to room temperature. Water was added to quench the reaction, and then extracted with dichloromethane, the organic phases were combined, the solvent was removed by rotary evaporation, and the crude product was separated and purified by column chromatography (petroleum ether: dichloromethane = 1:1, v / v) to finally obtain intermediate 2 with a yield of 20%. 1 H NMR(500MHz,Chloroform-d)δ9.00(d,J=2.1Hz,2H),8.40(d,J=8.9Hz,4H),7.89–7.83(m,2H),7.37–7.34(m,4H),7.30(m,8H), 7.16–7.06(m,14H),7.03–6.97(m,6H),4.17(t,J=6.2Hz,4H),1.91(t,J=7.5Hz,4H),1.40–1.28(m,20H),0.91(t,J=6.6Hz,6H).

[0040] (5) Preparation of compound PPAB:

[0041]

[0042] Under nitrogen protection, intermediate 2 (50 mg, 0.03 mmol) was dissolved in dichloromethane, and then tetracyanoethylene (17 mg, 0.13 mmol) was added and stirred at room temperature for 6 hours. After the reaction was completed, the reaction was quenched with water, and then extracted with dichloromethane, the organic phases were combined, and the solvent was removed by rotary evaporation. The crude product was separated and purified by column chromatography (petroleum ether: dichloromethane = 1:3, v / v) to finally obtain compound PPAB with a yield of 50%. 1 H NMR(400MHz,Chloroform-d)δ8.98(d,J=2.2Hz,2H),8.40–8.26(m,6H),7.68(d,J=9.0Hz,4H),7.51–7.27(m,22H),7.04(d,J=8.9Hz, 2H),6.98(d,J=9.0Hz,4H),4.20(t,J=6.4Hz,4H),1.94(q,J=6.9Hz,4H),1.39–1.31(m,20H),0.96–0.92(t,6H).HRMS(ESI):m / z[M+H] + Calculate for C 96 H 74 B 2 Br 2 F 4 N 16 O 2 :1741.18, found:1741.47. Its hydrogen spectrum and high-resolution mass spectrum are as follows Figure 1 , 2 shown.

[0043] The UV absorption and fluorescence emission spectra of PPAB in different solvents are shown in Figure 2. Figure 3 and 4 As shown, the maximum absorption peak in the near-infrared region is between 705-734 nm, and the maximum emission peak is between 737-772 nm, both showing solvent dependence. The Stokes shift is between 32-45 nm, which is much larger than the common PPAB molecules (Stokes shift <15 nm), indicating that PPAB with an electron push-pull system has a strong solvent effect.

[0044] The present invention is further described below in conjunction with the embodiments. Some specific embodiments are listed below, but the scope of the present invention is not limited to the scope described in the embodiments.

[0045] Detection performance test

[0046] (1) Dissolve PPAB in 1,4-dioxane to obtain a probe mother solution (10 -3 mol / L), then 1,4-dioxane was added to dilute to obtain 10 -5 mol / L PPAB solution, add SEM solution (100×10 -5 mol / L), and tested the changes in its UV spectrum at different reaction times. Figure 5 It can be seen that the absorption peak intensity at 717nm decreases rapidly, the absorption peak at 464nm remains unchanged, a new absorption peak appears at 419nm, equilibrium is reached in 15 minutes, and the color of the solution changes from green to yellow.

[0047] (2) Dissolve PPAB in 1,4-dioxane to obtain a probe mother solution (10 -3 mol / L), then 1,4-dioxane was added to dilute to obtain 10 -5 mol / L PPAB solution, add SEM solution (100×10 -5 mol / L), and tested the changes in fluorescence spectra at different reaction times. Figure 6 It can be seen that the fluorescence intensity at 755 nm decreased and blue-shifted to 731 nm, no new emission peak appeared at the short wavelength, and the fluorescence was completely quenched after 15 minutes.

[0048] (3) Dissolve PPAB in 1,4-dioxane to obtain a probe mother solution (10 -3 mol / L), then 1,4-dioxane was added to dilute to obtain 10 -5 mol / L PPAB solution, add SEM solution or other analytes (100×10 -5 mol / L), the changes of its UV spectrum are as follows Figure 7 As shown, it can be seen that only the addition of SEM can cause a significant change in the UV spectrum of PPAB, indicating that PPAB has high selectivity for SEM detection.

[0049] (4) Dissolve PPAB in 1,4-dioxane to obtain a probe mother solution (10 -3 mol / L), then 1,4-dioxane was added to dilute to obtain 10 -5 mol / L PPAB solution, add SEM solution or other analytes (100×10 -5 mol / L), the emission spectrum changes as follows Figure 8 As shown, it can be seen that only the addition of SEM can lead to a significant change in the fluorescence spectrum of PPAB, indicating that PPAB has high selectivity for the detection of SEM.

[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A fluorescent compound of semicarbazide that can be detected by naked eyes, characterized in that: Its structural formula is:

2. The method for preparing the fluorescent compound according to claim 1, characterized in that The reaction process is as follows:

3. The method for preparing a fluorescent compound according to claim 2, characterized in that: The steps include: (1) Under nitrogen protection, the bromide and 1-3 times the molar equivalent of 5-alkynepyridine-2-amine are dissolved in tetrahydrofuran and a base, and a catalytic amount of a palladium catalyst and a monovalent copper reagent are added in sequence, and stirred at 70-100° C. for 8-10 hours. After the reaction is completed, water is added and shaken thoroughly, and then extracted with ethyl acetate, the organic phases are combined, the solvent is removed by rotary evaporation, and the crude product is separated and purified by column chromatography to obtain intermediate 1. (2) Under nitrogen protection, the intermediate 1 and the compound 3,6-bis(3-bromo-4-(octyloxy)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione were dissolved in toluene in a mass ratio of 1:4, stirred at 60-80°C for 0.5-2 hours, heated to 80-100°C, and 6-20 times the molar equivalent of TiCl4 and 20-60 times the molar equivalent of an organic base were added in sequence. After reacting for 8 hours, 20-40 times the molar equivalent of BF3·Et2O were added. After reacting for 2 hours, the reaction was terminated and cooled to room temperature. Water was added to quench the reaction, and then extracted with dichloromethane. The organic phases were combined, the solvent was removed by rotary evaporation, and the crude product was separated and purified by column chromatography to obtain the intermediate 2. (3) Under nitrogen protection, the intermediate 2 is dissolved in dichloromethane, and then 2 to 4 equivalents of tetracyanoethylene are added and stirred at room temperature for 6 hours. After the reaction is completed, the reaction is quenched with water, and dichloromethane and water are extracted. The solvent is removed by rotary evaporation, and the crude product is separated and purified by column chromatography to obtain the fluorescent compound PPAB.

4. The method for preparing a fluorescent compound according to claim 3, wherein the palladium catalyst in step (1) is Pd(PPh3)4, Pd(dppf)Cl2 or Pd(PPh3)2Cl2.

5. The method for preparing a fluorescent compound according to claim 3, wherein the copper reagent in step (1) is CuCl, CuBr or CuI.

6. The method for preparing a fluorescent compound according to claim 3, wherein the base in step (1) is triethylamine or diisopropylamine.

7. The use of the fluorescent compound according to claim 1, characterized in that: Semicarbazide can be detected with the naked eye in organic solvents.

8. The use of the fluorescent compound according to claim 7, characterized in that: The concentration of the fluorescent compound is 10 μmol / L, the upper limit of detection of semicarbazide is 1000 μmol / L, and the reaction time is 2-30 minutes.

9. The use of the fluorescent compound according to claim 7, characterized in that: The solvent is 1,4-dioxane.

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