A fluorescent compound capable of naked-eye detection of semicarbazide and a preparation method and application thereof

Abstract

The application discloses a fluorescent compound capable of naked-eye detection of aminourea and a preparation method and application thereof. A PPAB compound with electron push-pull action is obtained through condensation reaction of a pyrrolopyrrolodione and a nitrogen-containing aromatic primary amine, coordination with BF3.Et2O, and [2+2] cycloaddition-anti-electric ring-opening reaction with tetracyanoethylene. In an organic solvent, the PPAB and aminourea perform irreversible chemical reaction, high-sensitivity detection of aminourea is realized, and the application has the characteristics of simple operation, rapid reaction, good selectivity, colorimetric and fluorescent dual-mode detection and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organic small molecule materials, and relates to a fluorescent small molecule compound and preparation and application thereof in semicarbazide detection. BACKGROUND

[0002] Semicarbazide (SEM) is also called carbamimidate, and is a characteristic metabolite of nitrofuran antibiotic nitrofurazone. SEM is often used as a marker for monitoring illegal use of nitrofurazone in animal-derived food. On the other hand, the sealing of canned food often adopts a "press on-twist off" (PT) sealing technology, in which an azodicarbonamide (ADC) is often used as a foaming agent in the production process of a sealing gasket, so as to achieve the sealing effect by forming a small air chamber. The gasket containing the ADC foaming agent can generate SEM through thermal decomposition during the sealing of a glass bottle and the sterilization process, and thus SEM can contaminate food. In addition, SEM is also a thermal decomposition byproduct in the baking process of food, and may be left in products such as bread and flour. Based on the wide use of nitrofurazone and ADC, SEM has been identified as a widely distributed food hazard, and canned foods such as honey, jam, tomato sauce, mayonnaise and condiments are important categories of SEM contamination.

[0003] Food is likely to be contaminated by SEM during processing and packaging. Studies have shown that SEM has potential carcinogenic, teratogenic and mutagenic effects, and can seriously affect the operation of the endocrine system and the nervous system. SEM has been proven to be toxic to multiple tissues and organs of the human body such as the thyroid, thymus, spleen, uterus and ovary. Therefore, it is of great significance to sensitively detect SEM residues in canned food and meat products for 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 instrumental detection methods have high sensitivity and accuracy, they have the disadvantages of time-consuming, need for expensive machines and professional operation. In recent years, optical detection technology (colorimetric and fluorescent analysis) has attracted much attention due to its high selectivity, fast response speed, convenient operation, low cost, intuition, real-time and other advantages. Some inorganic luminescent materials such as upconversion inorganic luminescent nanomaterials and quantum dots are used as fluorescent probes for SEM detection, but only single-mode (such as colorimetric or fluorescent) light response can be achieved for detection, and there are still some disadvantages such as slow detection speed, high detection limit, short luminescence wavelength of the probe and small spectral change, which greatly limit the application. At present, there is no literature on high-sensitivity detection of SEM. SUMMARY

[0005] The application aims at solving the problems of few kinds of SEM fluorescent probes and slow response speed, and provides a fluorescent compound PPAB with high sensitivity for naked-eye detection of SEM, and the structural formula is as follows:

[0006]

[0007] Wherein:

[0008]

[0009] The SEM contains an electron-rich amino group, and a plurality of electron-deficient cyano ethylene fragments are introduced into the probe with a large conjugated planar structure to form an electron push-pull system and prolong the absorption and emission wavelength of the probe; in addition, the introduction of the cyano ethylene fragment can improve the reaction rate of the PPAB core and the SEM and improve the detection sensitivity.

[0010] The application also provides a fluorescent compound for naked-eye detection of SEM and a preparation method thereof, and the reaction route is as follows:

[0011]

[0012] The preparation method comprises the following steps:

[0013] (1) under the protection of nitrogen, bromide and 1-3 times of molar equivalent of 5-alkynylpyridine-2-amine are dissolved with tetrahydrofuran and a base, the base is triethylamine or diisopropylamine, a catalytic amount of a palladium catalyst and a monovalent copper reagent are sequentially added, the palladium catalyst is Pd(PPh3)4, Pd(dppf)Cl2 or Pd(PPh3)2Cl2, preferably Pd(PPh3)2Cl2; the monovalent copper reagent is CuCl, CuBr or CuI, preferably CuI; stirring is carried out at 70-100 DEG C for 8-10 hours; water is added to fully shake, then ethyl acetate is used for extraction, 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.

[0014] (2) under the protection of nitrogen, intermediate 1 and compound 3,6-bis(3-bromo-4-(octyloxy)phenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione are dissolved in toluene, the mass ratio is 1:4, stirring is carried out at 60-80 DEG C for 0.5-2 hours, the temperature is increased to 80-100 DEG C, 6-20 times of molar equivalent of TiCl4 and 20-60 times of molar equivalent of an organic base are sequentially added, 20-40 times of molar equivalent of BF3.Et2O is added after 8h of reaction, the reaction is ended after 2h of reaction, and the temperature is reduced to room temperature. Water is added to quench the reaction, then dichloromethane is used for extraction, 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 2.

[0015] (3) Under nitrogen protection, intermediate 2 is dissolved with dichloromethane, then 2-4 equivalent of tetracyanoethylene compound is added, and stirred for 6 hours at room temperature. After the reaction is completed, the reaction is quenched with water, extracted with dichloromethane and water. 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 application, the PPAB compound with electron push-pull effect is obtained by condensation reaction of pyrrolopyrrolopyrrolidone with nitrogen-containing aromatic primary amine, coordination with BF3.Et2O, and [2+2] cycloaddition-anti-electrocyclic reaction with tetracyanoethylene.

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

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

[0019] (1) In the present application, multiple electron-deficient cyanoethylene fragments are introduced to accelerate the reaction rate of the fluorescent probe with SEM, thereby effectively improving the sensitivity of SEM detection and overcoming the shortcomings of slow response rate and low sensitivity of the current fluorescent probe for SEM.

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

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

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

[0023] Figure 1 The hydrogen spectrum of the fluorescent compound PPAB of the example.

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

[0025] Figure 3 The ultraviolet-visible spectrum of the fluorescent compound PPAB (10 -5 mol / L) prepared in the example in different solvents.

[0026] Figure 4Fluorescent compound PPAB (10 -5 Fluorescence spectra of PPAB (10

[0027] Figure 5 Fluorescent compound PPAB (10 -5 Time-dependent UV-Vis spectra of PPAB (10 -5 mol / L) in 1,4-dioxane after reaction with SEM (100 x 10

[0028] Figure 6 Fluorescent compound PPAB (10 -5 Time-dependent fluorescence emission spectra of PPAB (10 -5 mol / L) in 1,4-dioxane after reaction with SEM (100 x 10

[0029] Figure 7 Fluorescent compound PPAB (10 -5 UV-Vis spectra of PPAB (10 -5 mol / L) in 1,4-dioxane after reaction with SEM and other analytes (100 x 10

[0030] Figure 8 Fluorescent compound PPAB (10 -5 Fluorescence emission spectra of PPAB (10 -5 mol / L) in 1,4-dioxane after reaction with SEM and other analytes (100 x 10 DETAILED DESCRIPTION

[0031] EXAMPLE

[0032] (1) 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, 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 with 50 ml of toluene, and the temperature was raised to 100 °C. TiCl4(0.18 ml, 10.68 mmol) and triethylamine (0.67 ml, 30.62 mmol) were added in turn. After 8 h of reaction, BF3-Et20 (0.55 ml, 28.49 mmol) was added, and the reaction was terminated after 2 h of reaction and the temperature was lowered to room temperature. Water was added to quench the reaction, and then dichloromethane was used for extraction. 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 :1, v / v) to obtain intermediate 2 with a yield of 20%. 1 H NMR (500 MHz, Chloroform-d) δ 8.18 - 8.12 (m, 1 H), 7.57 (m, 1 H), 7.34 - 7.31 (m, 2H), 7.27 (d, J = 1.9 Hz, 1 H), 7.25 (d, J = 2.1 Hz, 2H), 7.12 - 7.03 (m, 7H), 7.00 - 6.96 (m, 2H), 6.61 - 6.55 (m, 1 H), 5.27 (d, J = 2.1 Hz, 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 with 50 ml of toluene, and the temperature was raised to 100 °C. TiCl4(0.18 ml, 10.68 mmol) and triethylamine (0.67 ml, 30.62 mmol) were added in turn. After 8 h of reaction, BF3-Et20 (0.55 ml, 28.49 mmol) was added, and the reaction was terminated after 2 h of reaction and the temperature was lowered to room temperature. Water was added to quench the reaction, and then dichloromethane was used for extraction. 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 :1, v / v) to obtain intermediate 2 with a yield of 20%. 1H NMR (400 MHz, Chloroform-d) δ 8.98 (d, J = 2.2 Hz, 2H), 8.40 - 8.26 (m, 6H), 7.68 (d, J = 9.0 Hz, 4H), 7.51 - 7.27 (m, 22H), 7.04 (d, J = 8.9 Hz, 2H), 6.98 (d, J = 9.0 Hz, 4H), 4.20 (t, J = 6.4 Hz, 4H), 1.94 (q, J = 6.9 Hz, 4H), 1.39 - 1.31 (m, 20H), 0.96 - 0.92 (t, 6H). HRMS (ESI): m / z [M + H]

[0040] (5) Preparation of compound PPAB:

[0041]

[0042] Intermediate 2 (50 mg, 0.03 mmol) was dissolved in dichloromethane under nitrogen protection, 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, 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 = 1:3, v / v) to finally obtain compound PPAB with a yield of 50%. 1 H NMR (400 MHz, Chloroform-d) δ 8.98 (d, J = 2.2 Hz, 2H), 8.40 - 8.26 (m, 6H), 7.68 (d, J = 9.0 Hz, 4H), 7.51 - 7.27 (m, 22H), 7.04 (d, J = 8.9 Hz, 2H), 6.98 (d, J = 9.0 Hz, 4H), 4.20 (t, J = 6.4 Hz, 4H), 1.94 (q, J = 6.9 Hz, 4H), 1.39 - 1.31 (m, 20H), 0.96 - 0.92 (t, 6H). HRMS (ESI): m / z [M + H] + calcd for C 96 H 74 B2Br2F4N 16 O2:1741.18, found:1741.47. Its hydrogen spectrum and high resolution mass spectrum are shown in Figure 1 、 2 and

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

[0044] The application will be further described below in conjunction with examples. Some specific examples are listed below, but the scope of protection claimed by the application is not limited to the range expressed in the examples.

[0045] Detection performance test

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

[0047] (2) PPAB was dissolved in 1,4-dioxane to obtain a probe stock solution (10 -3 mol / L), and then diluted with 1,4-dioxane to obtain a 10 -5 mol / L PPAB solution, and then SEM solution (100×10 -5 mol / L) was added, and the change in the fluorescence spectrum was tested at different reaction times. Figure 6 It can be seen that the fluorescence intensity at 755 nm decreases and blue shifts to 731 nm, and no new emission peak appears at short wavelengths. After 15 minutes, the fluorescence is completely quenched.

[0048] (3) PPAB was dissolved in 1,4-dioxane to obtain a probe stock solution (10 -3 mol / L), and then diluted with 1,4-dioxane to obtain a 10 -5 mol / L PPAB solution, and then SEM solution or other analytes (100×10 -5 mol / L) was added, and the change in the UV spectrum was tested. Figure 7 It can be seen that only the addition of SEM can cause significant changes in the UV spectrum of PPAB, indicating that PPAB has high selectivity for SEM detection.

[0049] (4) PPAB was dissolved in 1,4-dioxane to obtain a probe mother liquor (10 -3 mol / L), then diluted with 1,4-dioxane to obtain a 10 -5 mol / L PPAB solution, and SEM solution or other analytes (100×10 -5 mol / L) was added, and the change in the emission spectrum was as shown in Figure 8 It can be seen that only the addition of SEM can cause a significant change in the fluorescence spectrum of PPAB, indicating that PPAB has high selectivity for the detection of SEM.

[0050] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be within the scope of protection of the present application.

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, wherein The reaction process is as follows:

3. The method for preparing the fluorescent compound according to claim 2, wherein: The steps include: (1) Under nitrogen protection, the bromide and 1-3 times the molar equivalent of 5-ynylpyridin-2-amine are dissolved in tetrahydrofuran and a base, and a catalytic amount of palladium catalyst and 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 are 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 are added in sequence. After reacting for 8 hours, 20-40 times the molar equivalent of BF3·Et2O are added. After reacting for 2 hours, the reaction is terminated and cooled to room temperature. Water is added to quench the reaction, and then extracted with dichloromethane. 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 the intermediate; (3) Under nitrogen protection, the intermediate 2 was dissolved in dichloromethane, and then 2 to 4 equivalents of tetracyanoethylene were added and stirred at room temperature for 6 hours. After the reaction was completed, the reaction was quenched with water, and extracted with dichloromethane and water. The solvent was removed by rotary evaporation, and the crude product was 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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