A benzothiadiazole fluorescent probe molecule and a preparation method and application thereof

Abstract

The application belongs to the technical field of fluorescent sensor, and discloses a benzothiadiazole fluorescent probe molecule, a preparation method and application thereof.The structural formula of the benzothiadiazole fluorescent probe molecule is shown as follows: wherein R1 is R2 is or the R1; R3 and R4 are respectively -F, or one of the following: The benzothiadiazole fluorescent probe molecule designed and synthesized by the application has near-infrared fluorescence emission characteristics, can have good targeting for SO2, and the fluorescence intensity thereof will be enhanced with the increase of the SO2 concentration in the solution.Compared with other SO2 fluorescent probe molecules of the same type at present, the probe molecule in the application has a longer emission wavelength, a shorter response time and a more significant fluorescence intensity change.At the same time, the biological safety can be well guaranteed, so that the probe molecule can be applied to the detection of the SO2 content in actual food samples.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorescent sensors, and particularly relates to a benzothiadiazole fluorescent probe molecule and a preparation method and application thereof. BACKGROUND

[0002] At present, as the most commonly used tool for detecting the content of SO2 in food, high performance liquid chromatography can provide satisfactory accuracy, but the expensive instrument cost limits its application in ordinary families. In addition, although the commercially available detection kit based on pararosaniline spectrophotometry can carry out detection without relying on instruments and equipment, formaldehyde or mercury will be used in the use process, which will undoubtedly endanger people's health, and therefore is not suitable for home detection of ordinary people.

[0003] Using a fluorescent probe molecule as a detection means is a relatively popular method at present. An ideal SO2 fluorescent probe molecule must have a large emission wavelength, a short response time and a large fluorescence change rate, so that such a fluorescent probe molecule can exhibit excellent accuracy in actual sample detection. However, the SO2 probe molecules developed based on fluorescence spectrophotometry generally use indole, benzothiazole, quinaldine, coumarin, fluoroboropyrrole, pyrene, acridine and anthracene as a fluorescent group, which leads to the defects of these fluorescent probe molecules, such as low sensitivity, not obvious color change and short emission wavelength.

[0004] Benzothiadiazole is an extremely attractive fluorescent group, which has strong electron-withdrawing ability and is widely used in optoelectronic materials. Gao Feng team once tried to directly use benzothiadiazole as a fluorescent group and developed a new type of SO2 fluorescent probe molecule. Unfortunately, the probe molecule has excellent sensitivity, but the emission wavelength is short (520 nm) and the fluorescence change rate is small (maximum 6 times), which cannot meet the requirements of an ideal SO2 fluorescent probe molecule (Aphotostable reaction-based A-A-A type two-photon fluorescent probe for rapid detection and imaging of sulfur dioxide[J].Journal of Materials Chemistry B,2021,9.DOI:10.1039 / D1TB00433F.).

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a benzothiadiazole fluorescent probe molecule and a preparation method and application thereof, so as to solve the problems of long response time, low sensitivity, and non-obvious color change of the existing fluorescent probe molecule in detecting the concentration of sulfur dioxide.

[0007] The technical scheme adopted by the present application to solve the above technical problems is as follows:

[0008] In a first aspect of the present application, a benzothiadiazole fluorescent probe molecule is provided, which has a structure shown in formula (1):

[0009]

[0010] wherein R1 is

[0011] R2 is or R1.

[0012] R3 and R4 are -F, or one of them.

[0013] The molecular structure formula of the benzothiadiazole fluorescent probe molecule is:

[0014]

[0015]

[0016]

[0017] one of them.

[0018] In a second aspect of the present application, a preparation method of a benzothiadiazole fluorescent probe molecule is provided, which comprises:

[0019] Dispersing raw material I-A, 4-acetyl styrene, benzoic acid, Pd(OAc)2 and benzoquinone into an organic solvent, and reacting under a first predetermined reaction condition to obtain intermediate II-A;

[0020] Dispersing the intermediate II-A and phosphorus oxychloride into DMF, and reacting under a second predetermined reaction condition to obtain intermediate III-A;

[0021] Dispersing the intermediate III-A, raw material IV-A, benzoic acid, Pd(OAc)2 and benzoquinone into an organic solvent, and reacting under a third predetermined reaction condition to obtain the benzothiadiazole fluorescent probe molecule;

[0022] The structural formula of the raw material I-A is

[0023] The structural formula of the intermediate II-A is

[0024] The structural formula of the intermediate III-A is

[0025] The structural formula of the raw material IV-A is

[0026] Optionally, the reaction temperature of the first predetermined reaction condition is 90-100℃, and the reaction time is 20-25h.

[0027] Optionally, the reaction temperature of the second predetermined reaction condition is 80-100℃, and the reaction time is 9-16h.

[0028] Optionally, the reaction temperature of the third predetermined reaction condition is 90-100℃, and the reaction time is 20-25h.

[0029] It is easy to understand that under the first predetermined reaction condition, the second predetermined reaction condition and the third predetermined reaction condition, the reaction can be more thorough.

[0030] Optionally, the molar ratio of the raw material I-A to the 4-acetyl styrene is 1:0.8-0.9; by adding the raw material I-A in excess, the 4-acetyl styrene can only be substituted at the 4th position of the benzene ring of the raw material I-A, and the 7th position of the benzene ring is reserved, and then reacted with the raw material IV with a strong electron-donating group.

[0031] Optionally, the molar ratio of the intermediate II-A to the phosphorus oxychloride is 1:2-3; by adding the phosphorus oxychloride in excess, the volatilization and hydrolysis of the phosphorus oxychloride can be avoided, so that the intermediate II-A cannot be fully reacted.

[0032] Optionally, the molar ratio of the intermediate III-A to the raw material IV-A is 1:1-1.2; by adding the cheap and readily available raw material IV-A in excess, the intermediate III-A can be fully reacted.

[0033] Optionally, the organic solvent is one or more of toluene, acetonitrile and DMF; the organic solvent only plays the role of a reaction medium.

[0034] In a third aspect, the present application provides a preparation method of a benzothiadiazole fluorescent probe molecule, which comprises:

[0035] The raw material I-B, 4-acetyl phenylboronic acid, tetrabutylammonium bromide and Pd(PPh3)4 are dispersed into a mixed solvent, and reacted under a fourth predetermined reaction condition to obtain an intermediate II-B.

[0036] The intermediate II-B, phosphorus oxychloride is dispersed in DMF, and reacted under the fifth predetermined reaction condition to obtain the intermediate III-B;

[0037] The intermediate III-B, the raw material IV-B, benzoic acid, Pd(OAc)2 and benzoquinone are dispersed in an organic solvent, and reacted under the sixth predetermined reaction condition to obtain the benzothiadiazole fluorescent probe molecule;

[0038] The structure of the raw material I-B is

[0039] The structure of the intermediate II-B is

[0040] The structure of the intermediate III-B is

[0041] The structure of the raw material IV-B is

[0042] Optionally, the reaction temperature of the fourth predetermined reaction condition is 80-100°C, the reaction time is 96-100h, and the reaction system is protected in an inert gas;

[0043] Optionally, the reaction temperature of the fifth predetermined reaction condition is 80-100°C, and the reaction time is 9-16h;

[0044] Optionally, the reaction temperature of the sixth predetermined reaction condition is 90-100°C, and the reaction time is 20-25h;

[0045] It is easy to understand that under the fourth predetermined reaction condition, the fifth predetermined reaction condition and the sixth predetermined reaction condition, the reaction can be more thorough; the inert gas can protect the catalyst Pd(PPh3)4 from being oxidized and inactivated.

[0046] Optionally, the mixed solvent includes an organic solvent and a saturated inorganic weak base solution; that is, the reaction is carried out in a two-phase system. Due to the existence of the two-phase system, the catalyst Pd(PPh3)4 can be transferred between the organic phase and the aqueous phase, promoting the progress of the reaction. This transfer can make Pd(PPh3)4 better contact with 4-acetylphenylboronic acid and the raw material I-B, thereby increasing the reaction rate.

[0047] Optionally, the molar ratio of the raw material I-B to the 4-acetylphenylboronic acid is 1:2-3; by excessive addition of cheap and readily available 4-acetylphenylboronic acid, the raw material I-B can be fully reacted.

[0048] Optionally, the molar ratio of the intermediate II-B to the phosphorus oxychloride is 1:2-3; by adding excess phosphorus oxychloride, the volatilization and hydrolysis of phosphorus oxychloride can be avoided, so that the intermediate II-B cannot be fully reacted.

[0049] Optionally, the molar ratio of the intermediate III-B to the raw material IV-B is 1:1-1.2; by adding excess cheap and readily available raw material IV-B, the intermediate III-B can be fully reacted.

[0050] Optionally, the organic solvent is one or more of toluene, acetonitrile, DMF; the organic solvent only plays the role of a reaction medium.

[0051] Optionally, the saturated inorganic weak base solution is one or more of saturated sodium bicarbonate solution, saturated sodium carbonate solution, saturated potassium carbonate solution.

[0052] In a fourth aspect, the present application provides a preparation method of a benzothiadiazole fluorescent probe molecule, which comprises:

[0053] The raw material I-C, 4-acetylphenylacetylene, cuprous iodide and Pt2Cl2(PPh3)2 are dispersed in an organic solvent to react under seventh predetermined reaction conditions to obtain an intermediate II-C;

[0054] The intermediate II-C and phosphorus oxychloride are dispersed in DMF to react under eighth predetermined reaction conditions to obtain the benzothiadiazole fluorescent probe molecule;

[0055] The raw material I-C has a structural formula of

[0056] The intermediate II-C has a structural formula of

[0057] Optionally, the reaction temperature of the seventh predetermined reaction condition is 80-100℃, the reaction time is 20-25h, and the reaction system is protected in an inert gas;

[0058] Optionally, the reaction temperature of the eighth predetermined reaction condition is 80-100℃, and the reaction time is 9-16h;

[0059] It is easy to understand that under the seventh predetermined reaction condition and the eighth predetermined reaction condition, the reaction can be more thorough; the inert gas can protect the catalyst Pt2Cl2(PPh3)2 from oxidation failure.

[0060] Optionally, the molar ratio of the raw material I-C to the 4-acetylphenylacetylene is 1:2-3; by adding an inexpensive and readily available 4-acetylphenylacetylene in excess, the 4th and 7th positions of the raw material I-C can be reacted under the catalysis of cuprous iodide and Pt2Cl2(PPh3)2.

[0061] Optionally, the molar ratio of the intermediate II-C to the phosphorus oxychloride is 1:2-3; by adding phosphorus oxychloride in excess, the volatilization and hydrolysis of phosphorus oxychloride can be avoided, so that the intermediate II-C cannot be fully reacted.

[0062] Optionally, the organic solvent is one or more of toluene, acetonitrile, and DMF; the organic solvent only serves as a reaction medium.

[0063] In a fifth aspect of the present application, the application of the above-mentioned benzothiadiazole fluorescent probe molecule is provided, wherein the benzothiadiazole fluorescent probe molecule is used for detecting the content of sulfur dioxide in food.

[0064] Optionally, the benzothiadiazole fluorescent probe molecule is used for detecting the content of sulfur dioxide in food, which comprises: diluting a liquid food sample 10 times directly in a PBS solution. After grinding, a solid food sample is mixed with a PBS solution to a concentration of 5 mg / mL. The mixture is soaked for 30 min. Then, 3 mL of the supernatant is transferred to a test tube. Then, 3 μM of one or more of the above-mentioned benzothiadiazole fluorescent probe molecules is added to the test tube, and mixed thoroughly to ensure complete interaction. After the reaction is completed, 200 μL of the mixture is carefully transferred to a designated well of a 96-well plate for subsequent high-throughput analysis. Finally, the measured fluorescence intensity is combined with the standard curve to calculate the concentration of SO2.

[0065] Optionally, the benzothiadiazole fluorescent probe molecule is used for detecting the content of sulfur dioxide in food, which comprises: preparing a colorimetric test paper or solution for rapid detection of SO2 in food, wherein one or more of the above-mentioned benzothiadiazole fluorescent probe molecules is contained; the color of the test paper or solution can change significantly with the increase of the concentration of SO2, which can be directly observed by the naked eye.

[0066] Optionally, the benzothiadiazole fluorescent probe molecule is used for detecting the content of sulfur dioxide in food, which comprises: preparing a kit for rapid detection of SO2 in food, wherein one or more of the above-mentioned benzothiadiazole fluorescent probe molecules is contained; the kit can directly observe or detect the change of the concentration of SO2 in food through an instrument.

[0067] Beneficial effects: compared with the A-A of the previous fluorescent probe molecule (弱) -A→D (弱)-A-D (弱) In summary, the present application achieves the following: (1) the introduction of an electron-withdrawing group at the 5,6 position of benzothiadiazole to modify the molecule, which not only enhances the electronegativity of benzothiadiazole but also expands the conjugated system of the molecule, making the emission wavelength move to the near-infrared direction; (2) the connection of different groups at the 4,7 position of benzothiadiazole, with beta-chlorovinylaldehyde as a specific SO2 recognition group on one side to ensure the excellent targeting of the fluorescent probe molecule, and the direct introduction of a strong electron-donating group on the other side to greatly enhance the intramolecular charge transfer (ICT) process, making the fluorescence intensity change rate larger and the color change more obvious; (3) the use of double or triple bonds to connect the SO2 recognition group, which further expands the conjugated system of the entire molecule and makes it in the same plane, avoiding the out-of-plane of benzothiadiazole and the two side substituents due to mutual repulsion between groups; D (强) -π-A (强) -π-A→D (强) -π-A (强) -π-D (弱) The present application achieves the transformation of -π-A→D, which endows the fluorescent probe molecule with near-infrared fluorescence emission performance (703 nm) and a large fluorescence change rate (maximum 20 times). The benzothiadiazole fluorescent probe molecule of the present application has a near-infrared fluorescence emission wavelength, and also has specific fluorescence enhancement response performance to SO2. The fluorescence intensity of the fluorescent probe molecule and the concentration of SO2 in the solution can present a good linear change, and the response time to SO2 is within 10 seconds, with good water solubility and biological safety. Therefore, it can be used for rapid detection of the content of SO2 in food. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 NMR spectrum of compound H5;

[0069] Figure 2 UV absorption spectrum of compound H5;

[0070] Figure 3 Fluorescence emission and linear relationship diagram of compound H5;

[0071] Figure 4 Quantum chemical calculation energy level diagram of compound H5;

[0072] Figure 5 Zwitterion resonance diagram of compound H5;

[0073] Figure 6 Selective test diagram of compound H5;

[0074] Figure 7 Response time diagram of compound H5;

[0075] Figure 8 Color change chart for the PBS solution of compound H5;

[0076] Figure 9 Operation schematic diagram for detecting SO2 in food by using compound H5. DETAILED DESCRIPTION

[0077] The present application provides a benzothiadiazole fluorescent probe molecule and a preparation method and application thereof. In order to make the purpose, technical scheme and effect of the present application more clear and definite, the present application is further described in detail below in combination with specific examples and drawings. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0078] The reagents used in the examples can be purchased from the market conventionally if not specifically mentioned. The process parameters not specifically mentioned can be carried out according to conventional techniques.

[0079] Example 1: Synthesis of compound H5

[0080] The synthesis route of compound H5 is as follows:

[0081]

[0082] 1.2g of raw material I-1 was dissolved in 10mL of DMF solvent, then 4mL of 4-acetyl styrene and a small amount of benzoic acid, Pd(OAc)2 and benzoquinone were added, and stirring was carried out at 100℃ for 24h under nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, then extraction, water washing and concentration were carried out to obtain the crude product, and finally column chromatography was carried out to obtain intermediate II-1.

[0083] 1.3g of intermediate II-1 was dissolved in 5mL of DMF, then 4mL of POCl3 was added at 0℃, and stirring was continued for 1h. Then the reaction was carried out at 80℃ for 12h. After cooling to room temperature, the pH was adjusted to neutral, then water washing and drying were carried out, and finally purification was carried out to obtain intermediate III-1.

[0084] 900mg of intermediate III-1 was dissolved in toluene, then 440mg of raw material IV-1 and a small amount of benzoic acid, Pd(OAc)2 and benzoquinone were added, and stirring was carried out at 100℃ for 24h under nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, then extraction, water washing and concentration were carried out to obtain the crude product, and finally column chromatography was carried out to obtain compound H5.

[0085] 1H NMR (400 MHz, CDC13) δ 10.43 (s, 1H), 8.40 (d, J = 6.7 Hz, 2H), 8.26 (t, J = 8.8 Hz, 2H), 8.21 (t, J = 7.2 Hz, 4H), 7.42 (s, H), 7.36 (s, H), 7.21 (s, J = 4.1 Hz, 2H), 7.04 (s, H), 4.11 (d, J = 8.2 Hz, 2H), 3.65 (dd, J = 4.5 Hz, 4.9 Hz, 4H), 2.89 (t, J = 7.8 Hz, 2H), 2.64 (t, J = 8.8 Hz, 4H); 13 C NMR (101 MHz, CDC13) δ 192.45, 183.74, 169.41, 158.76, 149.99 (2C), 136.76, 135.67, 131.94 (2C), 129.67 (4C), 129.16 (2C), 128.31 (2C), 127.06 (4C), 126.37 (2C), 123.52, 114.38 (2C), 112.61 (2C), 76.96, 66.78 (2C), 57.29, 56.91 (2C). HRMS: Calcd. [M+H] + : 596.0886; found value [M+H] + : 596.0894.

[0086] The nuclear magnetic hydrogen spectrum of compound H5 is shown in Figure 1

[0087] Example 2: Synthesis of compound F2

[0088] The synthesis route of compound F2 is as follows:

[0089]

[0090] 840 mg of raw material I-2 was dissolved in 8 mL of toluene solvent, then 4 mL of 4-acetyl phenylboronic acid and a small amount of aqueous potassium carbonate, tetrabutylammonium bromide and Pd(PPh3)4 were added, and stirred at 95°C under nitrogen atmosphere for 24h. After the reaction was completed, the mixture was cooled to room temperature, then extracted, washed with water and concentrated to obtain the crude product, and finally purified by column chromatography to obtain the intermediate II-2.

[0091] 940 mg of intermediate II-2 was dissolved in 10 mL of DMF, then 5 mL of POCl3 was added at 0°C, and stirring was continued for 1 hour. Then the reaction was carried out at 80°C for 12 hours. After cooling to room temperature, the pH was adjusted to neutral, dried by water washing, and finally purified to obtain the intermediate III-2. ​

[0092] To 900 mg of intermediate III-2 was dissolved in acetonitrile, then 440 mg of raw material IV-2 and a small amount of benzoic acid, Pd(OAc)2 and benzoquinone were added, and stirred at 100°C for 24 h under nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, then extracted, washed with water and concentrated to obtain the crude product, and finally compound F2 was obtained by column chromatography. C )2 and benzoquinone were added, and stirred at 100°C for 24 h under nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, then extracted, washed with water and concentrated to obtain the crude product, and finally compound F2 was obtained by column chromatography.

[0093] 1 H NMR (400 MHz, CDC13) δ 10.45 (s, 1H), 8.55 (d, J = 5.9 Hz, H), 7.86 (d, J = 8.1 Hz, 2H), 7.51 (t, J = 8.8 Hz, 4H), 7.22 (s, H), 7.06 (t, J = 8.1 Hz, 3H), 4.18 (d, J = 4.4 Hz, 2H), 3.84 (d, J = 4.7 Hz, 2H), 3.61 (d, J = 7.1 Hz, 2H), 3.55 (d, J = 4.9 Hz, 2H), 3.38 (s, 3H); 13 C NMR (101 MHz, CDC13) δ 189.85, 161.44, 156.73, 155.46, 150.99, 148.46 (2C), 138.13, 137.04, 134.18, 133.16 (2C), 131.81, 130.11 (2C), 127.92 (2C), 126.52 (3C), 124.41, 116.61 (2C), 72.22, 71.13, 70.54, 68.21, 57.11. HRMS: Calcd. [M+H] + : 579.0849; found value [M+H] + : 579.0888.

[0094] Example 3: Synthesis of compound A3

[0095] The synthesis route of compound A3 is as follows:

[0096]

[0097] To 990 mg of raw material I-3 was dissolved in 10 mL of DMF solvent, then 5 mL of 4-acetylphenylacetylene and a small amount of CuI and Pt2Cl2(PPh3)2 were added, and stirred at 80°C for 24 h under nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, then extracted, washed with water and concentrated to obtain the crude product, and finally intermediate II-2 was obtained by column chromatography.

[0098] Compound A3 was obtained by dissolving 920 mg of intermediate II-3 in 10 mL of DMF, then adding 5 mL of POCl3 at 0 °C, and continuing stirring for 1 hour. After that, the reaction was carried out at 80 °C for 12 hours. After cooling to room temperature, the pH was adjusted to neutral, washed with water, dried, and finally purified.

[0099] 1 H NMR (400 MHz, CDC13) δ 10.37 (s, 1H), 8.55 (d, J = 5.9 Hz, H), 7.66 (d, J = 7.3 Hz, 4H), 7.59 (d, J = 8.4 Hz, 4H), 6.82 (s, 2H); 13 C NMR (101 MHz, CDC13) δ 190.15 (2C), 156.14 (2C), 152.16 (2C), 150.36 (2C), 136.11 (2C), 132.64 (4C), 129.98 (4C), 127.15 (2C), 124.02 (2C), 113.02 (2C), 96.14 (2C), 84.71 (2C). HRMS: Calcd. [M+H] + : 548.9965; found value [M+H] + : 549.0011.

[0100] Example 4: Detection of UV spectrum of compound H5 after reaction with SO2

[0101] Compound H5 was dissolved in PBS solution, then different concentrations of SO2 were added for UV determination, and the results are shown in Figure 2 .

[0102] From the results shown in Figure 2 , it can be seen that after the reaction of compound H5 with SO2, the UV spectrum of compound H5 will have a slight blue shift (525 nm to 508 nm).

[0103] Example 5: Detection of relationship between fluorescence intensity of compound H5 and SO2 concentration

[0104] Compound H5 was dissolved in PBS solution, then different concentrations of SO2 solution were titrated under excitation at a wavelength of 525 nm, and the results are shown in Figure 3 .

[0105] From the results shown in Figure 3The results shown can be seen that when the fluorescence intensity of compound H5 at 703 nm presents a significant enhancement with the increase of SO2 concentration in the solution, when 200 μM of SO2 is added, its fluorescence intensity can be enhanced to more than 20 times of the original. And through the analysis, it is found that its fluorescence intensity and the concentration of SO2 present a satisfactory linear relationship (R 2 = 0.9864) in a certain range.

[0106] Example 6: Calculation of LUMO and HOMO of compound

[0107] The LUMO and HOMO of compounds H5, F2 and A3 are calculated by quantum chemistry, and the results are shown in Figure 4 It is found that the energy gap of all the compounds in the application is significantly lower than that of the previously reported same type of fluorescent probe molecules before reacting with SO2, wherein the LUMO energy level of the compound is significantly reduced compared with the LUMO energy level of the fluorescent probe molecule reported by Gao Feng team, which shows that the strategy of enhancing the electronegativity of benzothiadiazole by introducing electron-withdrawing groups at the 5,6 position of benzothiadiazole in the application is successful.

[0108] Example 7: Analysis of the conjugated structure of compound H5

[0109] By analyzing the conjugated structure formed by benzothiadiazole and 2-(1,3-dithiol-2-ethyl) malononitrile group in the structure of compound H5, the feasibility of the design strategy of the fluorescent probe molecule in the application is further proved, and the results are shown in Figure 5 It can be found from the zwitterion resonance structure of compound H5 that the 2-(1,3-dithiol-2-ethyl) malononitrile group has a strong electron-withdrawing effect, wherein the anion is stabilized by two electron-withdrawing groups, and the cation is stabilized by the adjacent electron-donating sulfide group. The cyclic structure formed by 2-(1,3-dithiol-2-acyl) malononitrile group has an additional benefit, that is, the electron-accepting subunit is locked in a planar configuration with the rest of the molecule, thereby enhancing the orbital overlap and conjugation of the entire molecular structure. This feature is a significant difference between the application and other same type of SO2 fluorescent probe molecules.

[0110] Example 8: Determination of the targeting performance of compound H5

[0111] The targeting performance of the compound is analyzed by determining the selectivity of compound H5. Compound H5 is reacted with various common cations and anions, and the change of its fluorescence intensity at 703 nm is determined. The related results are shown in Figure 6 .

[0112] From Figure 6As can be seen from the results of the compound H5, there is no obvious response to other substances except SO2, which shows that the compound of the present application has good targeting.

[0113] Example 9: Determination of the response time of compound H5 to SO2

[0114] By continuously determining the change of fluorescence intensity of compound H5 after reacting with SO2, the response time of compound H5 was detected, and the experimental results are shown in Figure 7 After adding 100 μM of HSO3 - , the fluorescence intensity of compound H5 at 703 nm reached a maximum value within 10 seconds, which indicates that the response time of compound H5 to SO2 is within 10 seconds. Compared with other SO2 fluorescent probe molecules of the same type reported before, the response time of compound H5 is the fastest.

[0115] Example 10: Determination of the ability of compound H5 to detect the content of SO2 in actual food

[0116] The ability of compound H5 to detect the content of SO2 in actual food was determined by the method of sample recovery. All the food was purchased from a supermarket. The liquid food was diluted 10 times, and the solid food was ground into powder and then added to PBS solution to prepare a sample of 5 mg / mL. After the sample was fully soaked, the supernatant was taken for determination. 0, 10, and 20 μM of HSO3 - were added in turn, and then compound H5 was added for determination, and the change of fluorescence intensity at 525 nm was collected. Finally, according to the standard curve, the concentration of SO2 determined by fluorescence intensity was calculated, and compared with the actual concentration of SO2 added. The results are shown in Table 1, which shows that compound H5 has a satisfactory recovery rate, and the error fluctuation of multiple determination results is small, which indicates that the present application can accurately check the content of SO2 in food.

[0117] Table 1

[0118]

[0119]

[0120] Example 11: Determination of the change of visible color of compound H5 in PBS solution with the concentration of SO2

[0121] By adding different concentrations of SO2 to the PBS solution of compound H5, the color change of the PBS solution of compound H5 was determined. The related results are shown in Figure 8 .

[0122] From Figure 8As can be seen in the results of compound H5, the color of the PBS solution of the compound changed significantly with the increase of the concentration of SO2 added, and the red color gradually deepened, which indicated that the compound of the application had good visible color change response to SO2, and had the potential to detect the concentration of SO2 by colorimetry of solution or test paper.

[0123] From the above experimental results, it can be seen that the benzothiadiazole compound of the application has the characteristics of near-infrared fluorescence emission, and has excellent targeting property to SO2, and the change of its fluorescence intensity can well change with the change of the content of SO2 in the solution, which is first discovered in such compounds.

[0124] It should be understood that the application of the application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the application.

Claims

1. A benzothiadiazole-based fluorescent probe molecule, characterized by, having a structure represented by formula (1): wherein R1 is R2 is R3 and R4 are 2. A method for preparing a benzothiadiazole fluorescent probe molecule, characterized by, comprising: dispersing raw material I-A, 4-acetyl styrene, benzoic acid, Pd(OAc)2 and benzoquinone into an organic solvent, reacting under a first predetermined reaction condition to obtain intermediate II-A; dispersing the intermediate II-A and phosphorus oxychloride into DMF, reacting under a second predetermined reaction condition to obtain intermediate III-A; dispersing the intermediate III-A, raw material IV-A, benzoic acid, Pd(OAc)2 and benzoquinone into an organic solvent, reacting under a third predetermined reaction condition to obtain the benzothiadiazole fluorescent probe molecule; The structural formula of the raw material I-A is The structural formula of the intermediate II-A is The structural formula of the intermediate III-A is The structural formula of the raw material IV-A is 3. The method for preparing benzothiadiazole fluorescent probe molecules according to claim 2, characterized in that, the reaction temperature of the first predetermined reaction condition is 90-100 DEG C, and the reaction time is 20-25 h; the reaction temperature of the second predetermined reaction condition is 80-100 DEG C, and the reaction time is 9-16 h; the reaction temperature of the third predetermined reaction condition is 90-100 DEG C, and the reaction time is 20-25 h.

4. The use of the benzothiadiazole fluorescent probe molecule according to claim 1, characterized in that, The benzothiadiazole fluorescent probe molecule is used for detecting the content of sulfur dioxide in food.

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