A carbonyl-modified imidazo[1,2-a]pyridine fluorescent probe molecule and a preparation method and application thereof

Abstract

The application provides a carbonyl-modified imidazo[1,2-alpha]pyridine fluorescent probe molecule and a preparation method and application thereof, and belongs to the technical field of fluorescent probes, and aims to solve the technical problem of low sensitivity of organic small-molecule fluorescent dyes in pesticide detection. The fluorescent probe molecule has good solvatochromic properties and viscosity-dependent fluorescence emission behavior, and is applied to detection of organic pesticide DCN. The preparation process is as follows: 2-aminopyridine is used as a starting material to synthesize two compounds with different conjugation degrees through a Claisen-Schmidt reaction, an iodine-catalyzed cyclization reaction and a Heck reaction, and the structural formulae are as follows: in the formula, R 1 =F, Cl, Br, I, CF3, COOMe, CN, H, Me or OMe; R 2 =Cl, Br, CF3, COOMe, H, Me or OMe; R 3 =F, Cl, Br, I, CF3, H, Me or OMe; n is a positive integer between 0 and 11. The two compounds have good light-emitting properties in tetrahydrofuran solution, and can selectively recognize organic pesticide DCN, and are expected to become probe molecules for detecting DCN residues in actual samples.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent probes, and in particular relates to a carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, pesticides have been widely used in modern agriculture, playing a crucial role in improving agricultural productivity and directly boosting agricultural output. However, inappropriate use of pesticides can pollute the soil, air, water, and even the ecological environment, increasing the risk of harmful residues in food and drinking water. Due to the high toxicity and non-degradability of pesticides, their long-term accumulation poses a serious threat to the ecological environment and human health. Among the many types of pesticides, 2,6-dichloro-4-nitroaniline (DCN) is a key raw material for the preparation of other pesticides, such as herbicides, insecticides, and disinfectants. It is often used to prevent diseases such as cotton boll blight and fruit and vegetable rot. DCN is highly toxic, causing irreversible damage to the human body even at very low concentrations. Some studies have shown that even low-concentration exposure to DCN can lead to decreased immunity, allergic reactions, renal failure, central nervous system poisoning, and even cancer. In response to this situation, fluorescence detection has attracted widespread attention due to its rapidity, sensitivity, simple detection process, and real-time monitoring capabilities. Organic small molecule fluorescent probes have attracted widespread attention due to their high sensitivity, high selectivity, simple synthesis and characterization, short reaction time, multiple modification sites, and non-destructiveness to biological samples.

[0003] Imidazolopyridine derivatives are a unique class of nitrogen-containing fused-ring compounds widely used in medicine due to their exceptional biological activity. Their pharmacological effects primarily include antimitotic, antituberculosis, and antiviral properties, and they can also act as antagonists for several receptors. Beyond their physiological significance, rational structural modification can transform them into novel fluorescent probe frameworks. For example, Patent Publication No. CN 114763353A discloses a fluorescent detection reagent based on an imidazopyridine core and its detection technology for the signal molecule H2S. Upon reaction with the signal molecule hydrogen sulfide, the 2,4-dinitrophenyl ether group of this molecular probe hydrolyzes to a hydroxyl group, emitting red fluorescence in PBS (pH = 7.4, 10 mM) buffer. Patent publication number CN 115215864A discloses a fluorescent probe for detecting beverage viscosity, its preparation method, and its application. The probe contains dual electron-withdrawing groups—bromobenzimidazole and indolium—and a methoxyphenyl group, which is an electron-donating group. The resulting "AAD" structure possesses a high polarity and relatively high electron-withdrawing properties, which facilitates good dispersibility of the probe in the highly polar aqueous environment of beverages. The free rotation of the methoxyphenyl group also helps the probe sensitively respond to changes in viscosity. The aforementioned publication demonstrates that different modification groups on the imidazopyridine core can significantly influence fluorescence properties. Summary of the Invention

[0004] In response to the technical problem of low sensitivity of organic small molecule fluorescent dyes in the detection of organic pesticides, the present invention proposes a carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule, its preparation method and application. By utilizing the good fluorescence emission ability of the compound in solution, it can achieve high-sensitivity recognition of DCN and has good anti-interference ability during the recognition process.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule having a general structural formula of N1 or N2:

[0007] Where R 1 =F, Cl, Br, I, CF3, COOMe, CN, H, Me or OMe; R 2 =Cl, Br, CF3, COOMe, H, Me or OMe; R 3 =F, Cl, Br, I, CF3, H, Me or OMe; n is a positive integer between 0 and 11; preferably n is 0, 1, 2, 3, 7 or 11.

[0008] The preparation method of carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecules comprises the following steps:

[0009] (1) 4-bromoacetophenone and R 3 The substituted benzaldehyde undergoes Claisen-Schmidt reaction to give compound 1;

[0010] (2) With R 1 or R 2 The substituted 2-aminopyridine derivative undergoes a cyclization reaction with compound 1 to obtain compound 2;

[0011] (3) Compound 2 undergoes Heck coupling reaction with aminostyrene or aminophenyl-1,3-butadiene with different alkyl chain lengths to obtain the target product.

[0012] The operation method of the Claisen-Schmidt reaction in step (1) is: 4-bromoacetophenone and a 3 The substituted benzaldehyde is dissolved in solvent I, and a basic catalyst is added, and the reaction is carried out at room temperature for 6-24 hours.

[0013] The R 3 The substituted benzaldehyde includes p-fluorobenzaldehyde, p-trifluoromethylbenzaldehyde, benzaldehyde, p-methylbenzaldehyde, p-methoxybenzaldehyde and the like.

[0014] The 4-bromoacetophenone, with R 3 The molar ratio of the substituted benzaldehyde and the alkaline catalyst is 1:(1-1.4):(1-2); the molar volume ratio of 4-bromoacetophenone and solvent I is 1:(4-6) mmoL / mL; the solvent I comprises water and ethanol in a volume ratio of 1:(4-6); and the alkaline catalyst is sodium hydroxide, potassium hydroxide or cesium carbonate.

[0015] The operation method of the cyclization reaction in step (2) is: 1 and R 2 The substituted 2-aminopyridine derivative and compound 1 are dissolved in solvent II, and a catalyst is added, and the mixture is reacted at 60-80° C. for 12-24 hours.

[0016] The R 1 and R 2 The substituted 2-aminopyridine derivatives include 2-amino-4-bromopyridine, 2-amino-4-trifluoromethylpyridine, 2-aminoisonicotinate methyl ester, 2-aminopyridine, 2-amino-5-bromopyridine, 2-amino-5-trifluoromethylpyridine, 6-aminonicotinic acid methyl ester, 2-amino-5-methylpyridine, 4,5-dibromopyridin-2-amine, and the like.

[0017] The compound 1, with R 1 and R2 The molar ratio of the substituted 2-aminopyridine derivative and the catalyst is 1:(1-4):(2-5); the molar volume ratio of compound 1 to solvent II is 1:(2-5) mmoL / mL.

[0018] The catalyst comprises ammonium acetate and I2 in a molar ratio of 2:1; and the solvent II is chloroform.

[0019] The operation method of the Heck coupling reaction in step (3) is as follows: dissolving compound 2 and aminostyrene or aminophenyl-1,3-butadiene with different nitrogen alkyl chain lengths in solvent III, adding palladium catalyst and auxiliary agent, and reacting at 70-120° C. in an inert gas atmosphere for 12-24 hours.

[0020] The aminostyrenes or aminophenyl-1,3-butadienes with different azoalkyl chain lengths are 4-dimethylaminostyrene, 4-dimethylaminophenyl-1,3-butadiene, 4-diethylaminostyrene, 4-diethylaminophenyl-1,3-butadiene, 4-dipropylaminostyrene, 4-dipropylaminophenyl-1,3-butadiene, 4-dibutylaminostyrene, 4-dibutylaminophenyl-1,3-butadiene, 4-dioctylaminostyrene, 4-dioctylaminophenyl-1,3-butadiene, 4-didodecylaminostyrene, 4-didodecylaminophenyl-1,3-butadiene,

[0021] The molar ratio of the compound 2, aminostyrene or aminophenyl-1,3-butadiene with different nitrogen alkyl chain lengths, the auxiliary agent and the palladium catalyst is 1:(1.0-1.4):(1-5):(0.01-0.1); the molar volume ratio of the compound 2 to the solvent III is 1:(4-6) mmoL / mL; the solvent III is N,N-dimethylformamide, tetrahydrofuran or dimethyl sulfoxide; the palladium catalyst is any one or more of tetrakis(triphenylphosphine)palladium, palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium or bistriphenylphosphinepalladium dichloride; and the auxiliary agent is any one or more of tetrabutylammonium bromide, sodium carbonate, potassium carbonate, cesium carbonate, sodium methoxide or potassium acetate.

[0022] Application of a carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule in pesticide detection.

[0023] The probe molecules were dissolved in tetrahydrofuran to form a dilute solution of carbonyl-modified imidazo[1,2-α]pyridine compounds. This dilute solution exhibited strong specificity for DCN. As the DCN concentration in the solution increased, the compound's fluorescence intensity gradually decreased. Furthermore, within a low concentration range, the maximum fluorescence intensity of the compound exhibited a good linear relationship with DCN concentration.

[0024] The two carbonyl-modified imidazo[1,2-a]pyridine fluorescent probe molecules provided by the present application have good luminescence performance in tetrahydrofuran solution. The probe molecules also have good solvatochromic behavior and viscosity-dependent fluorescence emission behavior. The dilute solutions of the two molecules can specifically detect DCN molecules, and the detection process has good selectivity and anti-interference ability. This has potential application value for DCN pesticide residues in actual samples. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The nuclear magnetic resonance hydrogen spectrum of the fluorescent probe molecule N1.

[0027] Figure 2 The nuclear magnetic resonance carbon spectrum of the fluorescent probe molecule N1.

[0028] Figure 3 The high-resolution mass spectrum of the fluorescent probe molecule N1.

[0029] Figure 4 The nuclear magnetic resonance hydrogen spectrum of the fluorescent probe molecule N2.

[0030] Figure 5 The nuclear magnetic resonance carbon spectrum of the fluorescent probe molecule N2.

[0031] Figure 6 The high-resolution mass spectrum of the fluorescent probe molecule N2.

[0032] Figure 7 The fluorescence response behavior of the probe molecule N1 (10 μM) in tetrahydrofuran solution to common pesticides (100 μM) (I0 is the fluorescence intensity of the initial solution, I is the fluorescence intensity of the solution after adding pesticides).

[0033] Figure 8 The fluorescence response behavior of the probe molecule N2 (10 μM) in tetrahydrofuran solution to common pesticides (100 μM) (I0 is the fluorescence intensity of the initial solution, I is the fluorescence intensity of the solution after adding pesticides).

[0034] Figure 9 The relationship diagram of the maximum fluorescence intensity of the probe molecule N1 (10 μM) in tetrahydrofuran solution with the change of DCN concentration.

[0035] Figure 10 This is a graph showing the relationship between the maximum fluorescence intensity of the probe molecule N2 (10 μM) in tetrahydrofuran solution and the change in DCN concentration.

[0036] Figure 11 Normalized fluorescence emission spectra of fluorescent probe molecule N1 in different solvents.

[0037] Figure 12 Normalized fluorescence emission spectra of the fluorescent probe molecule N2 in different solvents.

[0038] Figure 13 is the double logarithmic fitting straight line between the maximum fluorescence intensity of the fluorescent probe molecule N1 and the solvent viscosity.

[0039] Figure 14 It is the double logarithmic fitting straight line of the maximum fluorescence intensity of the fluorescent probe molecule N2 and the solvent viscosity. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0041] Compound 2a was prepared first for use in the following examples. The structural formula of compound 2a is:

[0042]

[0043] The general reaction formula is:

[0044]

[0045] Preparation: Sodium hydroxide solid (0.44 g, 11 mol) was dissolved in 9 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (45 mL) in an ice-water bath. After stirring for 10 minutes, benzaldehyde (1.27 g, 12 mmol) was added. The reaction system was stirred at room temperature for 12 hours, and the solid was collected by filtration. The solid was washed repeatedly with ethanol and water, and dried to yield a white solid, compound 1a (4.19 g, 73%). The product was used in the next reaction without further purification.

[0046]

[0047] The preparation method is as follows: 1a (2.87 g, 10 mmol), 2-aminopyridine (1.16 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol) and I2 (2.53 g, 10 mmol) are dissolved in 30 mL of chloroform, and the system is reacted at 70°C for 16 h. After the reaction is completed, it is cooled to room temperature, poured into 50 mL of saturated Na2S2O3 aqueous solution, and extracted with dichloromethane (20 mL x 3 times). The combined organic phase is dried with anhydrous NaSO4, and then separated by a silica gel chromatographic column (petroleum ether: ethyl acetate = 3:1) to obtain a yellow solid, which is compound 2a (0.9 g, 24%).

[0048] Example 1

[0049] The structural formula of the compound of the example is:

[0050]

[0051] The reaction formula is:

[0052]

[0053] The preparation method is as follows: compound 2a (3.76 g, 10 mmol), 4-dimethylaminostyrene (1.84 g, 12.5 mmol), palladium acetate (0.11 g, 0.5 mmol), potassium carbonate (3.46 g, 25 mmol) and tetrabutylammonium bromide (3.84 g, 12 mmol) are placed in a Schlenk flask, and 50 mL of DMF solution is added under an argon atmosphere. The system is reacted at 100°C for 12 h. After the reaction is completed, it is cooled to room temperature, poured into 300 mL of water to precipitate a solid. The precipitate is collected by filtration, dried, and then separated by a silica gel chromatographic column (ethyl acetate: petroleum ether = 1:1) to obtain a yellow solid, which is compound N1 (2.97 g, 67%). The nuclear magnetic resonance spectrum is as shown in Figure 1 and 2 , 1 H NMR (600 MHz, CDCl3) δ 8.17 (d, J = 8.4 Hz, 2H), 8.10 (dd, J = 7.0, 1.2 Hz, 1H), 7.79-7.69 (m, 1H), 7.57-7.54 (m, 2H), 7.51 (dd, J = 8.2, 6.5 Hz, 4H), 7.48-7.41 (m, 3H), 7.29 (ddd, J = 9.2, 6.6, 1.2 Hz, 1H), 7.15 (d, J = 16.2 Hz, 1H), 6.93 (d, J = 16.2 Hz, 1H), 6.84 (td, J = 6.8, 1.2 Hz, 1H), 6.72 (d, J = 8.8 Hz, 2H), 3.00 (s, 6H). 13C NMR (151 MHz, CDCl3) δ 40.4, 112.3, 113.6, 119.1, 123.4, 124.0, 125.2, 125.5, 125.8, 128.0, 128.4, 128.7, 129.0, 129.1, 130.4, 131.3, 131.4, 135.8, 140.5, 142.6, 143.9, 150.5, 189.4. High resolution mass spectrometry Figure 3 As shown, HRMS (ESI) m / z calculated for [C 30 H 26 N3O + ]444.2070([M+H] + ),found444.2069.

[0054] Example 2

[0055] The structural formula of the compound of this embodiment is:

[0056]

[0057] The general reaction formula is:

[0058]

[0059] The preparation method is as follows: Compound 2a (3.76 g, 10 mmol), 3a (2.16 g, 12.5 mmol), palladium acetate (0.11 g, 0.5 mmol), potassium carbonate (3.46 g, 25 mmol) and tetrabutylammonium bromide (3.84 g, 12 mmol) are placed in a Schlenk flask, and 50 mL of DMF solution is added under an argon atmosphere. The system is reacted at 100 ° C for 12 hours. After the reaction is completed, it is cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate is collected by filtration, dried, and separated using a silica gel column (ethyl acetate: petroleum ether = 2:3) to obtain a red solid, which is compound N2 (4.13 g, 88%). The nuclear magnetic resonance spectrum is as follows Figure 4 and 5 As shown, 1HNMR (600MHz, CDCl3) δ8.16(d,J=8.2Hz,2H),8.10(d,J=6.9Hz,1H),7.74(d,J=9. 2Hz,1H),7.57-7.54(m,2H),7.51(t,J=7.5Hz,2H),7.46(dd,J=7.8,5.2Hz,3H),7 .35(d,J=8.7Hz,2H),7.29(ddd,J=9.2,6.6,1.3Hz,1H),7.05(dd,J=15.5,10.5Hz ,1H),6.87-6.76(m,2H),6.72-6.63(m,3H),6.59(d,J=15.5Hz,1H),2.99(s,6H). 13 C NMR (151 MHz, CDCl3) δ 40.4, 112.4, 113.6, 119.1, 124.0, 124.8, 125.5, 125.6, 125.9, 127.8, 128.4, 128.8, 129.0, 129.2, 129.4, 130.4, 131.3, 132.6, 134.9, 136.0, 140.5, 142.2, 143.9, 150.3, 189.3. High resolution mass spectrometry Figure 6 As shown, HRMS (ESI) m / z calculated for [C 32 H 28 N3O + ]470.2227([M+H] + ),found470.2222.

[0060] Example 3

[0061] The structural formula of the compound of this embodiment is:

[0062]

[0063] The general reaction formula of compound 1b is:

[0064]

[0065] Preparation: Potassium hydroxide solid (0.62 g, 11 mol) was dissolved in 9 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (45 mL) in an ice-water bath. After stirring for 10 minutes, p-trifluoromethylbenzaldehyde (2.09 g, 12 mmol) was added. The reaction system was stirred at room temperature for 12 hours, and the solid was collected by filtration. The solid was washed repeatedly with ethanol and water, and dried to yield a white solid, compound 1b (2.04 g, 58%). The product was used in the next reaction without further purification.

[0066] The general reaction formula of compound 2b is:

[0067]

[0068] Preparation: 1b (3.54 g, 10 mmol), 2-aminopyridine (1.16 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol), and I2 (2.53 g, 10 mmol) were dissolved in 30 mL of chloroform and reacted at 70°C for 16 h. After cooling to room temperature, the reaction mixture was poured into 50 mL of saturated aqueous Na2S2O3 and extracted with dichloromethane (20 mL x 3). The combined organic phases were dried over anhydrous NaSO4 and separated by silica gel chromatography (petroleum ether:ethyl acetate = 3:1) to yield compound 2b (0.8 g, 18%) as a yellow solid.

[0069] The general reaction formula of compound N3 is:

[0070]

[0071] Preparation method: Compound 2b (4.44 g, 10 mmol), 4-dimethylaminostyrene (1.84 g, 12.5 mmol), tetrakis(triphenylphosphine)palladium (0.58 g, 0.5 mmol), sodium carbonate (2.65 g, 25 mmol), and tetrabutylammonium bromide (3.84 g, 12 mmol) were placed in a Schlenk flask. Under an argon atmosphere, 50 mL of DMF solution was added. The system was reacted at 100°C for 12 h. After the reaction, the mixture was cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate was collected by filtration, dried, and separated by silica gel chromatography (ethyl acetate:petroleum ether = 1:1) to yield a yellow solid, compound N3 (3.94 g, 77%).

[0072] Example 4

[0073]

[0074] The general reaction formula of compound 1a is:

[0075]

[0076] Preparation: Sodium hydroxide solid (0.44 g, 11 mol) was dissolved in 9 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (45 mL) in an ice-water bath. After stirring for 10 minutes, benzaldehyde (1.27 g, 12 mmol) was added. The reaction system was stirred at room temperature for 12 hours, and the solid was collected by filtration. The solid was washed repeatedly with ethanol and water, and dried to yield a white solid, compound 1a (4.19 g, 73%). The product was used in the next reaction without further purification.

[0077] The general reaction formula of compound 2c is:

[0078]

[0079] Preparation: 1a (2.87 g, 10 mmol), 2-amino-5-cyanopyridine (1.43 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol), and I2 (2.53 g, 10 mmol) were dissolved in 30 mL of chloroform and reacted at 70°C for 16 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 50 mL of saturated aqueous Na2S2O3. The mixture was extracted with dichloromethane (20 mL x 3). The organic phases were combined, dried over anhydrous NaSO4, and separated by silica gel chromatography (petroleum ether:ethyl acetate = 3:1) to yield compound 2c (1.1 g, 27%) as a yellow solid.

[0080] The general reaction formula of compound N4 is:

[0081]

[0082] The preparation method is as follows: Compound 2c (4.01 g, 10 mmol), 3a (2.16 g, 12.5 mmol), palladium acetate (0.11 g, 0.5 mmol), potassium carbonate (3.46 g, 25 mmol), and tetrabutylammonium bromide (3.84 g, 12 mmol) were placed in a Schlenk flask. Under an argon atmosphere, 50 mL of DMF solution was added. The system was reacted at 100°C for 12 h. After the reaction, the mixture was cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate was collected by filtration, dried, and separated by silica gel chromatography (ethyl acetate:petroleum ether = 2:3) to yield a red solid, compound N4 (3.71 g, 75%).

[0083] Example 5

[0084]

[0085] The general reaction formula of compound 1a is:

[0086]

[0087] Preparation: Sodium hydroxide solid (0.44 g, 11 mol) was dissolved in 9 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (45 mL) in an ice-water bath. After stirring for 10 minutes, benzaldehyde (1.27 g, 12 mmol) was added. The reaction system was stirred at room temperature for 12 hours, and the solid was collected by filtration. The solid was washed repeatedly with ethanol and water, and dried to yield a white solid, compound 1a (4.19 g, 73%). The product was used in the next reaction without further purification.

[0088] The general reaction formula of compound 2d is:

[0089]

[0090] Preparation: 1a (2.87 g, 10 mmol), 2-amino-4-methoxypyridine (1.49 g, 12 mmol), ammonium acetate (1.44 g, 20 mmol), and I2 (2.53 g, 10 mmol) were dissolved in 30 mL of chloroform and reacted at 70°C for 16 h. After the reaction was completed, the mixture was cooled to room temperature and poured into 50 mL of saturated aqueous Na2S2O3. The mixture was extracted with dichloromethane (20 mL x 3). The organic phases were combined, dried over anhydrous NaSO4, and separated by silica gel chromatography (petroleum ether:ethyl acetate = 3:1) to yield compound 2d (0.8 g, 20%) as a yellow solid.

[0091] The general reaction formula of compound N5 is:

[0092]

[0093] Preparation method: Compound 2d (4.06 g, 10 mmol), 4-diethylaminostyrene (2.19 g, 12.5 mmol), 4-vinylaniline (1.49 g, 12.5 mmol), tetrakis(triphenylphosphine)palladium (0.58 g, 0.5 mmol), sodium carbonate (2.65 g, 25 mmol), and tetrabutylammonium bromide (3.84 g, 12 mmol) were placed in a Schlenk flask. Under an argon atmosphere, 50 mL of DMF solution was added. The system was reacted at 100°C for 12 h. After the reaction, the mixture was cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate was collected by filtration, dried, and separated by silica gel chromatography (ethyl acetate:petroleum ether = 1:1) to yield a yellow solid, compound N5 (3.31 g, 66%).

[0094] Example 6

[0095] The structural formula of the compound of this embodiment is:

[0096]

[0097] The general reaction formula of compound 1a is:

[0098]

[0099] The preparation method is as follows: Sodium hydroxide solid (0.4 g, 10 mol) is dissolved in 12 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (48 mL) in an ice-water bath. After stirring for 10 minutes, benzaldehyde (1.06 g, 10 mmol) is added. The reaction system is stirred at room temperature for 24 hours, then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, compound 1a. The product can be used in the next reaction without further purification.

[0100] The general reaction formula of compound 2a is:

[0101]

[0102] Preparation method: 1a (2.87 g, 10 mmol), 2-aminopyridine (0.97 g, 10 mmol), ammonium acetate (0.96 g, 13.3 mmol), and I2 (1.67 g, 6.7 mmol) were dissolved in 20 mL of chloroform and reacted at 60°C for 24 h. After cooling to room temperature, the reaction mixture was poured into 50 mL of saturated aqueous Na2S2O3 and extracted with dichloromethane (20 mL x 3). The combined organic phases were dried over anhydrous NaSO4 and separated by silica gel chromatography (petroleum ether:ethyl acetate = 3:1) to yield a yellow solid.

[0103] The general reaction formula of compound N1 is:

[0104]

[0105] The preparation method is as follows: Compound 2a (3.76 g, 10 mmol), 4-dimethylaminostyrene (1.47 g, 10 mmol), palladium acetate (0.022 g, 0.1 mmol), and potassium carbonate (1.38 g, 10 mmol) are placed in a Schlenk flask. Under an argon atmosphere, 40 mL of DMF solution is added. The system is reacted at 70°C for 24 h. After the reaction is completed, the mixture is cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate is collected by filtration, dried, and separated using a silica gel column (ethyl acetate:petroleum ether = 1:1) to obtain a yellow solid, which is compound N1.

[0106] Example 7

[0107] The structural formula of the compound of this embodiment is:

[0108]

[0109] The general reaction formula of compound 1a is:

[0110]

[0111] The preparation method is as follows: Sodium hydroxide solid (0.4 g, 10 mol) is dissolved in 12 mL of water and slowly added dropwise to a solution of 4-bromoacetophenone (2 g, 10 mmol) in ethanol (48 mL) in an ice-water bath. After stirring for 10 minutes, benzaldehyde (1.06 g, 10 mmol) is added. The reaction system is stirred at room temperature for 24 hours, then the solid is collected by filtration, washed repeatedly with ethanol and water, and dried to obtain a white solid, compound 1a. The product can be used in the next reaction without further purification.

[0112] The general reaction formula of compound 2a is:

[0113]

[0114] Preparation method: 1a (2.87 g, 10 mmol), 2-aminopyridine (0.97 g, 10 mmol), ammonium acetate (0.96 g, 13.3 mmol), and I2 (1.67 g, 6.7 mmol) were dissolved in 20 mL of chloroform and reacted at 60°C for 24 h. After cooling to room temperature, the reaction mixture was poured into 50 mL of saturated aqueous Na2S2O3 and extracted with dichloromethane (20 mL x 3). The combined organic phases were dried over anhydrous NaSO4 and separated by silica gel chromatography (petroleum ether:ethyl acetate = 3:1) to yield a yellow solid.

[0115] The general reaction formula of compound N1 is:

[0116]

[0117] The preparation method is as follows: Compound 2a (3.76 g, 10 mmol), 4-dimethylaminostyrene (2.06 g, 14 mmol), palladium acetate (0.22 g, 1 mmol), and tetrabutylammonium bromide (16 g, 50 mmol) are placed in a Schlenk flask. Under an argon atmosphere, 60 mL of DMF solution is added. The system is reacted at 120°C for 16 hours. After the reaction is completed, the mixture is cooled to room temperature and poured into 300 mL of water to precipitate a solid. The precipitate is collected by filtration, dried, and separated using a silica gel column (ethyl acetate:petroleum ether = 1:1) to obtain a yellow solid, which is compound N1.

[0118] The following application examples all use N1 and N2 prepared in Example 1 and Example 2 as test objects.

[0119] Application Example 1

[0120] Common organic pesticide interferers are: Glufosinate, Atrazine, Bisphenol A (BPA), Glyphosate, 3,4-Dichlorophenol (DCP), Trichlorobenzene (1,2,3-Trichlorobenzene, TriCB), 2,4-Dichlorophenoxyacetic acid (2,4-D), Carbaryl, Pentachloronitrobenzene (PCNB), Thiamethoxam (TMX), 2,4,6-Trichloroaniline (TCA) and 2,4-Dichloro-4'-nitrodiphenyl ether (Nitrofen, NF). The fluorescence intensity of the two carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecules in tetrahydrofuran solution is greatly affected by DCN, but is basically not affected by other organic pesticides ( Figure 7 and Figure 8 When the concentration of DCN in the tetrahydrofuran solution reached 100 μM, the fluorescence intensity of compounds N1 and N2 (10 μM) decreased by 99% and 98%, respectively.

[0121] Application Example 2

[0122] The probe molecule N1 or N2 was dissolved in a tetrahydrofuran solution to prepare a dilute solution of biphenyl imidazole [1,2-α] pyridone compounds of different concentrations. When the DCN concentration in the above solution (respectively 0μM, 5μM, 10μM, 15μM, 20μM, 25μM, 30μM, 35μM, 40μM, 45μM, 50μM, 55μM, 60μM, 70μM, 80μM, 90μM, 100μM) gradually increased, the fluorescence intensity of compound N1 or N2 (the total concentration was 10μM and the slit width was 2) gradually decreased. And in the range of 0μM to 40μM, there was a good linear relationship between the maximum fluorescence intensity of compound N1 or N2 and the DCN concentration ( Figure 9 and Figure 10 ).

[0123] Application Example 3

[0124] Prepare a 1 mM stock solution of compound N1 or N2 in THF and set aside. Use a pipette to transfer 50 μL of each solution into a 5 mL volumetric flask. After complete evaporation of the solvent, add the required test solvent to the volume and shake well to obtain a 10 μM test solution.

[0125] The carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule of the present invention has a good solvatochromic effect. Using 403nm and 416nm as the excitation wavelength, the compound N1 ( Figure 11 ) and N2( Figure 12 ) Fluorescence emission spectra in different solvents.

[0126] Application Example 4

[0127] Prepare a 1 mM stock solution of compound N1 or N2 using dimethyl sulfoxide (DMSO) and set aside. Use a pipette to transfer 50 μL of each stock solution to a 5 mL volumetric flask. Add a mixture of ethylene glycol and glycerol (with 0%, 20%, 30%, 40%, 60%, and 80% glycerol, respectively) to the final volume. Shake vigorously to mix the solution thoroughly.

[0128] In the above system, as the viscosity of the mixed solvent increased from 20.8 cP to 620.7 cP, the fluorescence intensities of probe molecules N1 and N2 increased by 2.83 times and 2.62 times, respectively, and both probe molecules showed good quantitative viscosity-dependent fluorescence emission behavior ( Figure 13 and Figure 14 ).

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule, characterized in that: The probe molecule has the structural formula of N1 or N2: ， Where R 1 :H, CN or Me; R 2 :H, Me or OMe; R 3 : H, CF3 or Me; n is 0, 1 or 2.

2. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 1, characterized in that: The following steps are involved: (1) 4-bromoacetophenone and R 3 The substituted benzaldehyde undergoes Claisen-Schmidt reaction to give compound 1; (2) With R 1 and R 2 The substituted 2-aminopyridine derivative undergoes a cyclization reaction with compound 1 to obtain compound 2; Compound 2 undergoes Heck coupling reaction with aminostyrene or aminophenyl-1,3-butadiene with different azoalkyl chain lengths to obtain the target product.

3. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 2, characterized in that: The operation method of the Claisen-Schmidt reaction in step (1) is: 4-bromoacetophenone and a 3 The substituted benzaldehyde is dissolved in solvent I, and a basic catalyst is added, and the reaction is carried out at room temperature for 6-24 hours.

4. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 3, characterized in that: The 4-bromoacetophenone, with R 3 The molar ratio of the substituted benzaldehyde and the alkaline catalyst is 1:(1-1.4):(1-2); the molar volume ratio of 4-bromoacetophenone and solvent I is 1:(4-6) mmoL / mL; the solvent I is water and / or ethanol; and the alkaline catalyst is sodium hydroxide, potassium hydroxide or cesium carbonate.

5. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 2, characterized in that: The operation method of the cyclization reaction in step (2) is: 1 or R 2 The substituted 2-aminopyridine derivative and compound 1 are dissolved in solvent II, and a catalyst is added, and the mixture is reacted at 60-80° C. for 12-24 hours.

6. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 5, characterized in that: The compound 1, with R 1 and R 2 The molar ratio of the substituted 2-aminopyridine derivative and the catalyst is 1:(1-4):(2-5); the molar volume ratio of compound 1 to solvent II is 1:(2-5) mmoL / mL.

7. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 6, characterized in that: The catalyst is ammonium acetate and I2 in a molar ratio of 2:1; the solvent II is chloroform.

8. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 2, characterized in that: The operation method of the Heck coupling reaction in step (3) is as follows: dissolving compound 2 and aminostyrene or aminophenyl-1,3-butadiene with different nitrogen alkyl chain lengths in solvent III, adding palladium catalyst and auxiliary agent, and reacting at 70-120 ° C in an inert gas atmosphere for 12-24 h.

9. The method for preparing the carbonyl-modified imidazo[1,2-α]pyridine fluorescent probe molecule according to claim 8, characterized in that: The molar ratio of the compound 2, aminostyrene or aminophenyl-1,3-butadiene with different nitrogen alkyl chain lengths, the auxiliary agent and the palladium catalyst is 1:(1.0-1.4):(1-5):(0.01-0.1); the molar volume ratio of the compound 2 to the solvent III is 1:(4-6) mmoL / mL; the solvent III is N,N-dimethylformamide, tetrahydrofuran or dimethyl sulfoxide; the palladium catalyst is any one or more of tetrakis(triphenylphosphine)palladium, palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium or bistriphenylphosphinepalladium dichloride; the auxiliary agent is any one or more of tetrabutylammonium bromide, sodium carbonate, potassium carbonate, cesium carbonate, sodium methoxide or potassium acetate.

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