Colorimetric probe for detecting cyanide as well as preparation method and application of colorimetric probe

Abstract

The invention discloses a colorimetric probe for detecting cyanide and a preparation method and application thereof, and the structural formula of the colorimetric probe is as follows: 4-cyano-2-pyridine-2-acetonitrile-1, 8-naphthalimide.

Description

Technical Field

[0001] This application relates to the field of cyanide detection, and in particular to a colorimetric probe for detecting cyanide, its preparation method, and its uses. Background Technology

[0002] Cyanide ions (CN-) are highly toxic substances that pose a serious threat to human health. Their toxicity mechanism primarily stems from their efficient binding to cytochrome oxidases, inhibiting cellular oxidative metabolism and causing cytotoxic hypoxia. Symptoms of poisoning exhibit a cascade effect with increasing exposure dose, including vomiting, convulsions, coma, and even death. Environmental cyanide pollution mainly originates from industrial activities, including electroplating, gold mining, steel production, and chemical synthesis, which generate cyanide waste. Given the high toxicity of cyanide ions, establishing accurate detection methods for cyanide in environmental and biological systems is of particular significance, as concentrations exceeding safe thresholds can cause irreversible damage to ecosystems and human health. Among numerous detection technologies, fluorescent chemical sensors have attracted considerable attention due to their unique molecular recognition characteristics, real-time visualization capabilities, and advantages such as biocompatibility and imaging capabilities.

[0003] Naphthalimide, as a classic fluorophore, is highly favored in anion probe design due to its rigid π-conjugated framework and excellent photophysical properties. Currently, research on cyanide ion (CN-) probes based on naphthalimide mainly focuses on the functionalization modification of the 3- and 4-positions. This is closely related to the electron distribution characteristics caused by the electron-withdrawing ability of its dicarbonyl group: the 3- and 4-positions are the main electron-deficient sites of naphthalimide and are more susceptible to attack by nucleophiles.

[0004] In contrast, there are relatively few reports on chemical modifications at the 2-position, mainly due to steric hindrance, hydrocarbon reactivity, and synthetic challenges. Therefore, constructing a novel colorimetric CN-probe that introduces a recognition site at the 2-position of naphthalimide via an aromatic hydrogen nucleophilic substitution reaction is of great significance. Summary of the Invention

[0005] To address the above technical problems, this application provides a colorimetric probe for detecting cyanide ions, the structural formula of which is as follows:

[0006] It is 4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

[0007] According to another aspect of this application, this application provides a method for preparing a colorimetric probe for detecting cyanide ions, the preparation method comprising the following steps:

[0008] S101, 4-bromo-1,8-naphthylimide was dissolved in the first solvent, and n-butylamine was slowly added dropwise after stirring at room temperature. The system was heated to 80°C and refluxed. After the reaction was completed, the reaction solution was cooled and poured into ice water to precipitate a pale yellow solid. The product was then collected by vacuum filtration, the filter cake was washed with water, and the dried solid was further recrystallized with ethyl acetate to finally obtain white solid N-n-butyl-4-bromo-1,8-naphthylimide.

[0009] In S102, N-n-butyl-4-bromo-1,8-naphthalimide prepared in S101 was dissolved together with cuprous cyanide in a second solvent. After being replaced with nitrogen or a rare gas, the mixture was stirred in an oil bath at 120°C. After the raw material disappeared, the mixture was cooled to room temperature and then slowly poured into water to quench the reaction. The mixture was extracted with dichloromethane, and the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was then purified by silica gel column chromatography to finally obtain a pale yellow solid N-n-butyl-4-cyano-1,8-naphthalimide.

[0010] In step S103, under nitrogen or rare gas protection, pyridine-2-acetonitrile, sodium hydride, and a third solvent are added sequentially to the reaction vessel. After stirring at room temperature, N-n-butyl-4-bromo-1,8-naphthalimide prepared in step S102 is added. The reaction continues at room temperature until the starting material spot completely disappears. Then, saturated citric acid aqueous solution is slowly added dropwise to the reaction solution to adjust the pH of the mixture to 5-6. The reaction solution is then transferred to a separatory funnel, extracted with dichloromethane, and washed with saturated sodium chloride solution. The combined organic phases are dried with anhydrous sodium sulfate, concentrated under reduced pressure to remove the solvent, mixed with silica gel, and further purified by column chromatography to obtain the white solid product N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

[0011] In a preferred embodiment, it satisfies at least one of the following conditions:

[0012] The first solvent is anhydrous ethanol;

[0013] The second solvent is anhydrous dimethyl sulfoxide;

[0014] The third solvent is anhydrous tetrahydrofuran solvent.

[0015] In a preferred embodiment, the ratio of 4-bromo-1,8-naphthimide: n-butylamine: anhydrous ethanol is 10–20 mmol: 15–30 mmol: 30–50 mL.

[0016] In a preferred embodiment, the ratio of N-n-butyl-4-bromo-1,8-naphthalimide:cuprous cyanide:anhydrous dimethyl sulfoxide is 2–3.5 mmol:6–12 mmol:5–15 mL.

[0017] In a preferred embodiment, the ratio of N-n-butyl-4-cyano-1,8-naphthalimide:pyridine-2-acetonitrile:sodium hydride:anhydrous tetrahydrofuran is 1–2.5 mmol:1.5–3 mmol:5–15 mmol:20–40 mL.

[0018] According to another aspect of this application, this application also provides the use of a colorimetric probe for detecting cyanide ions in a mixed solution.

[0019] In a preferred embodiment, it is used to detect cyanide ions in a 9:1 volume ratio of acetonitrile to water solution.

[0020] In a preferred embodiment, when using ultraviolet absorption spectroscopy for detection, the probe is dissolved in a 9:1 volume ratio of acetonitrile to water solution to test for cyanide ions. Attached Figure Description

[0021] Figure 1 A schematic diagram of the synthetic route for preparing a colorimetric probe for detecting cyanide ions.

[0022] Figure 2 The probe of this application (20 μmol·L) -1 Acetonitrile and water mixed solutions with a volume ratio of 9:1 in different cyanide concentrations (0-840 μmol·L⁻¹) -1 (Ultraviolet absorption spectrum)

[0023] Figure 3 The probe of this application (20 μmol·L) -1 Add different ions (840 μmol·L⁻¹) to a 9:1 volume ratio mixture of acetonitrile and water. -1 The ultraviolet absorption spectrum at that time;

[0024] Figure 4 The probe of this application (20 μmol·L) -1 ) in relation to other interfering substances (840 μmol·L -1 When coexisting, it affects cyanide (840 μmol·L⁻¹) -1 A bar graph showing the change in UV absorption at 630 nm during the response;

[0025] Figure 5 The probe and fluorescent probe of this application were subjected to ultraviolet absorption at 630 nm in a pH 0-12 system by adding cyanide ions. Detailed Implementation

[0026] The preferred embodiments described below are merely examples, and other obvious variations will be apparent to those skilled in the art. The basic principles of this application defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of this application.

[0027] like Figure 1 As shown, a preferred embodiment of this application describes a method for preparing a fluorescent probe for detecting hypochlorous acid, wherein the fluorescent probe for detecting hypochlorous acid has the following structural formula:

[0028] The preparation method includes the following steps:

[0029] S101, 4-bromo-1,8-naphthylimide was dissolved in the first solvent, and n-butylamine was slowly added dropwise after stirring at room temperature. The system was heated to 80°C and refluxed. After the reaction was completed, the reaction solution was cooled and poured into ice water to precipitate a pale yellow solid. The product was then collected by vacuum filtration, the filter cake was washed with water, and the dried solid was further recrystallized with ethyl acetate to finally obtain white solid N-n-butyl-4-bromo-1,8-naphthylimide.

[0030] In S102, N-n-butyl-4-bromo-1,8-naphthalimide prepared in S101 was dissolved together with cuprous cyanide in a second solvent. After being replaced with nitrogen or a rare gas, the mixture was stirred in an oil bath at 120°C. After the raw material disappeared, the mixture was cooled to room temperature and then slowly poured into water to quench the reaction. The mixture was extracted with dichloromethane, and the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was then purified by silica gel column chromatography to finally obtain a pale yellow solid N-n-butyl-4-cyano-1,8-naphthalimide.

[0031] In step S103, under nitrogen or rare gas protection, pyridine-2-acetonitrile, sodium hydride, and a third solvent are added sequentially to the reaction vessel. After stirring at room temperature, N-n-butyl-4-bromo-1,8-naphthalimide prepared in step S102 is added. The reaction continues at room temperature until the starting material spot completely disappears. Then, saturated citric acid aqueous solution is slowly added dropwise to the reaction solution to adjust the pH of the mixture to 5-6. The reaction solution is then transferred to a separatory funnel, extracted with dichloromethane, and washed with saturated sodium chloride solution. The combined organic phases are dried with anhydrous sodium sulfate, concentrated under reduced pressure to remove the solvent, mixed with silica gel, and further purified by column chromatography to obtain the white solid product N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

[0032] Preferably, the first solvent is anhydrous ethanol.

[0033] Preferably, the second solvent is anhydrous dimethyl sulfoxide;

[0034] Preferably, the third solvent is anhydrous tetrahydrofuran solvent.

[0035] Example 1

[0036] I. Synthesis of Colorimetric Probe Molecule 1 for Detecting Cyanide

[0037] Specifically, the synthesis of the colorimetric probe molecule for detecting cyanide in this application involves using 4-bromo-1,8-naphthalene anhydride, n-butylamine, and cuprous cyanide as raw materials to synthesize an intermediate, which is then reacted with pyridine-2-acetonitrile in an aromatic hydrogen nucleophilic substitution reaction to finally obtain the target probe.

[0038] (1) Synthesis of N-n-butyl-4-bromo-1,8-naphthalimide

[0039] Specifically, commercially available 4-bromo-1,8-naphthimide (5.00 g, 16.76 mmol) was dissolved in 50 mL of anhydrous ethanol. After stirring at room temperature for 10 min, n-butylamine (1.84 g, 25.14 mmol) was slowly added dropwise. The system was heated to 80 °C and refluxed for 3.5 h. The reaction was considered complete by TLC monitoring. After cooling, the reaction solution was poured into ice water, precipitating a large amount of pale yellow solid. The product was collected by vacuum filtration, and the filter cake was washed three times with water. The dried solid was further recrystallized from ethyl acetate. Finally, white solid 4 (4.30 g, 86%) was obtained.

[0040] The white solid powder product obtained above was measured using a nuclear magnetic resonance instrument (Bruker AVANCE III 400MHz), and the data are shown below:

[0041] 1 H NMR (400MHz, CDCl3) δ [ppm]: 8.64 (d, J = 9.6Hz, 1H), 8.54 (d, J = 8.8Hz, 1H), 8.39 (d, J = 8.4Hz, 1H), 8.02 (d, J =8.0Hz,1H),7.83(t,J=8.8Hz,1H),4.17(t,J=8.0Hz,2H),1.71(m,2H),1.45(m,2H),0.98(t,J=6.8Hz,3H).

[0042] Analysis of the nuclear magnetic resonance spectroscopy data of the white solid powder product obtained above showed that the white solid powder product obtained above is N-n-butyl-4-bromo-1,8-naphthalimide.

[0043] (2) N-n-butyl-4-cyano-1,8-naphthalimide:

[0044] The N-n-butyl-4-cyano-1,8-naphthalimide (1.00 g, 3.01 mmol) prepared in step (1) and cuprous cyanide (0.91 g, 10.17 mmol) were dissolved in 5 mL of dimethyl sulfoxide (DMSO). After three nitrogen purgings, the mixture was stirred in an oil bath at 120 °C for 14 h. TLC (developing solvent: petroleum ether / ethyl acetate = 3:1) showed that the starting material disappeared. After the reaction solution was cooled to room temperature, it was slowly poured into 100 mL of water to quench the reaction. The mixture was extracted with dichloromethane (3 × 30 mL), and the organic phases were combined and washed with saturated brine (50 mL), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain the crude product. The crude product was then purified by silica gel column chromatography (petroleum ether / dichloromethane = 1:1) to finally obtain a pale yellow solid compound 5 (0.56 g, yield 66.8%).

[0045] The yellow solid powder product obtained above was measured using a nuclear magnetic resonance instrument (Bruker AVANCE III 400MHz), and the data are shown below:

[0046] 1 H NMR (400MHz, CDCl3) δ [ppm]: 8.70 (d, J = 5.6Hz, 1H), 8.61 (d, J = 7.6Hz, 1H), 8.56 (d, J = 8.4Hz, 1H), 8.14 (d, J =8.8Hz,1H),7.96(t,J=3.6Hz,1H),4.16(t,J=6.8Hz,2H),1.69(m,2H),1.43(m,2H),0.97(t,J=3.2Hz,3H).

[0047] Analysis of the nuclear magnetic resonance spectroscopy data of the yellow solid powder product obtained above showed that the yellow solid powder product obtained above is N-n-butyl-4-cyano-1,8-naphthalimide.

[0048] (3) Synthesis of N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide:

[0049] Under nitrogen protection, pyridine-2-acetonitrile (0.28 g, 2.37 mmol), sodium hydride (60%, 0.52 g, 12.94 mmol), and 20 mL of anhydrous tetrahydrofuran (THF) were added sequentially to a 50 mL three-necked flask. After stirring at room temperature for 30 min, N-n-butyl-4-bromo-1,8-naphthalimide (0.60 g, 2.16 mmol) prepared in step (2) was added. The reaction continued at room temperature, and the reaction progress was monitored in real time by thin-layer chromatography (TLC) until the starting material spot completely disappeared. Subsequently, saturated citric acid aqueous solution was slowly added dropwise to the reaction solution to adjust the pH of the mixture to 5-6. The reaction solution was transferred to a separatory funnel, extracted with dichloromethane (3 × 20 mL), and washed with saturated sodium chloride solution. The combined organic phases were dried with anhydrous sodium sulfate, concentrated under reduced pressure to remove the solvent, mixed with silica gel, and further purified by column chromatography (PE / EA = 20:1) to obtain a white solid product N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide (0.45 g, yield 52.9%).

[0050] The white solid powder product obtained above was measured using a nuclear magnetic resonance instrument (Bruker AVANCE III 400MHz), and the data are shown below:

[0051] 1 H NMR (400MHz, CDCl3) δ [ppm]: 8.78 (d, J = 7.6Hz, 1H), 8.59 (d, J = 8.0Hz, 1H), 8.55 (d, J = 4.8Hz, 1H), 8.50 (s, 1H), 8.00 (t, J = 8.0Hz, 1H), 7.76 (t, J =7.2Hz,1H),7.72(d,J=7.6Hz,1H),7.65(s,1H),7.28(t,J=6.4Hz,1H),4.17(t,J=7.6Hz,2H),1.68(m,2H),1.43(m,2H),0.98(t,J=7.2Hz,3H).

[0052] Analysis of the nuclear magnetic resonance spectroscopy data of the white solid powder product obtained above showed that the white solid powder product obtained above is N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

[0053] II. Recognition performance of colorimetric probe 1 for detecting cyanide ions

[0054] 1. Ultraviolet titration experiment of cyanide ions using a colorimetric probe

[0055] Probe 1 was dissolved in acetonitrile to prepare a solution of 5000 μmol·L⁻¹. -1The cyanide stock solution was prepared in acetonitrile to a concentration of 50,000 μmol·L⁻¹. -1 Measure 100 μL of 5000 μmol·L⁻¹ -1 The probe was dissolved in a 25 mL volumetric flask and diluted to 25 mL with a 9:1 mixture of acetonitrile and water to prepare a 25 mL probe solution of 20 μM acetonitrile. Titration experiment: 25 mL of the 20 μM acetonitrile probe solution was poured into a 250 mL wide-mouth conical flask, and 10.0 μL of 50000 μmol·L⁻¹ was added dropwise each time. -1 Add 1.0 equivalent of cyanide solution, shake well, and then measure its ultraviolet absorption spectrum. Repeat this operation until 42.0 equivalents of cyanide solution are added.

[0056] The results show that the UV absorption spectrum of probe 1 is affected by the cyanide concentration, with reference... Figure 2 With the gradual addition of cyanide, probe 1 exhibited three new absorption peaks at 297 nm, 354 nm, and 391 nm, and simultaneously showed a broad absorption band at 630 nm. When CN... - The equivalent amount was added dropwise to 840 μmol·L⁻¹ -1 At that time, the ultraviolet absorption spectrum of probe 1 no longer changed, and the system reached saturation.

[0057] 2. Selectivity study of colorimetric probes for cyanide ions

[0058] Probe 1 was prepared to a concentration of 20 μmol·L⁻¹ -1 Acetonitrile solution; prepare CN - ,Br - ,ClO - ,DTT,F - NaHS, HSO4 - ,I - NO3 - 5000 μmol·L⁻¹ of glycine and leucine -1 Acetonitrile solution, measure 0.4 mL of 5000 μmol·L⁻¹ -1 The probe solution was prepared by diluting the volume of acetonitrile and water in a 9:1 ratio to 100 mL to make a 20 μM probe 1 solution. The solution was divided into 11 groups (5 mL per group). The first group was a blank experiment. 42 equivalents of various ion solutions were added to the other groups respectively. The response of fluorescent probe 1 to various ions was observed by ultraviolet absorption spectroscopy.

[0059] The results showed that, with acetonitrile and water in a 9:1 volume ratio as the solvent, probe 1 exhibited a broad absorption band at 630 nm upon the addition of cyanide ions. However, the addition of other ions did not significantly change the UV absorption spectrum of the probe. Figure 2This indicates that the probe can specifically detect cyanide ions.

[0060] 3. Anti-interference capability test

[0061] 25 mL of the probe solution, prepared from a mixture of 20 μM water and acetonitrile (v / v = 1:9), was poured into 11 separate 15 mL test tubes, 5 mL in each tube. The first tube served as a blank control. 84 μL of different interfering substances (Br1, 50000 μmol·L-1) were added to the remaining tubes. - ,ClO - ,DTT,F - NaHS, HSO4 - ,I - NO3 - (glycine, leucine) Shake thoroughly, perform ultraviolet absorption spectroscopy detection, and finally add 84 μL of 50000 μmol·L⁻¹ to each test tube. -1 The cyanide ions were removed, shaken well, and their ultraviolet absorption spectra were measured again.

[0062] Experiments show that even in the presence of other interfering substances, cyanide ions can still significantly increase the absorption peak of probe 1 at 630 nm. Therefore, probe 1 has excellent anti-interference ability for cyanide detection, while other interfering substances do not interfere with the detection results. (Reference) Figure 4 .

[0063] 4. Detection capability of probe 1 for cyanide in different pH systems

[0064] Add 20 μL of 5000 μmol·L⁻¹ to each of the 15 test tubes. -1 Add 4.5 mL of acetonitrile to the probe solution, then add 0.5 mL of aqueous solution with pH values ​​from 0 to 12, shake for 30 s, and detect the UV absorption spectrum. Then add 84 μL of 50000 μmol·L⁻¹. -1 The cyanide ion was then analyzed, and its ultraviolet absorption spectrum was measured again.

[0065] like Figure 5 The experimental results show that when the pH is in the range of 4-12, the UV absorption peak shift of probe 1 is significant and stable, which shows that probe 1 can effectively identify cyanide ions in the pH range of 4-12.

[0066] Those skilled in the art should understand that the embodiments of this application described above are merely examples and do not limit the scope of this application. The purpose of this application has been fully and effectively achieved. The functions and structural principles of this application have been shown and explained in the embodiments, and any variations or modifications can be made to the implementation of this application without departing from the stated principles.

Claims

1. A colorimetric probe for detecting cyanide ions, characterized in that, Its structural formula is as follows: It is 4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

2. A method for preparing a colorimetric probe for detecting cyanide, characterized in that, The preparation method includes the following steps: S101, 4-bromo-1,8-naphthylimide was dissolved in the first solvent, and n-butylamine was slowly added dropwise after stirring at room temperature. The system was heated to 75-80℃ and refluxed. After the reaction was completed, the reaction solution was cooled and poured into ice water to precipitate a pale yellow solid. The product was then collected by vacuum filtration, the filter cake was washed with water, and the dried solid was further recrystallized with ethyl acetate to finally obtain white solid N-n-butyl-4-bromo-1,8-naphthylimide. In S102, N-n-butyl-4-bromo-1,8-naphthalimide prepared in S101 was dissolved together with cuprous cyanide in a second solvent. After being replaced with nitrogen or a rare gas, the mixture was stirred in an oil bath at 110–120 °C. After the raw material disappeared, the mixture was cooled to room temperature and then slowly poured into water to quench the reaction. The mixture was extracted with dichloromethane, and the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain a crude product. The crude product was then purified by silica gel column chromatography to finally obtain a pale yellow solid N-n-butyl-4-cyano-1,8-naphthalimide. In step S103, under nitrogen or rare gas protection, pyridine-2-acetonitrile, sodium hydride, and a third solvent are added sequentially to the reaction vessel. After stirring at room temperature, N-n-butyl-4-bromo-1,8-naphthalimide prepared in step S102 is added. The reaction continues at room temperature until the starting material spot completely disappears. Then, saturated citric acid aqueous solution is slowly added dropwise to the reaction solution to adjust the pH of the mixture to 5-6. The reaction solution is then transferred to a separatory funnel, extracted with dichloromethane, and washed with saturated sodium chloride solution. The combined organic phases are dried with anhydrous sodium sulfate, concentrated under reduced pressure to remove the solvent, mixed with silica gel, and further purified by column chromatography to obtain the white solid product N-n-butyl-4-cyano-2-pyridine-2-acetonitrile-1,8-naphthalimide.

3. The method for preparing the colorimetric probe for detecting cyanide ions according to claim 2, characterized in that, It satisfies at least one of the following conditions: The first solvent is anhydrous ethanol; The second solvent is anhydrous dimethyl sulfoxide; The third solvent is anhydrous tetrahydrofuran solvent.

4. The method for preparing the colorimetric probe for detecting cyanide ions according to claim 2, characterized in that, The ratio of 4-bromo-1,8-naphthimide: n-butylamine: anhydrous ethanol is 10–20 mmol: 15–30 mmol: 30–50 mL.

5. The method for preparing the colorimetric probe for detecting cyanide ions according to claim 2, characterized in that, The ratio of N-n-butyl-4-bromo-1,8-naphthalimide:cuprous cyanide:anhydrous dimethyl sulfoxide is 2–3.5 mmol:6–12 mmol:5–15 mL.

6. The method for preparing the colorimetric probe for detecting cyanide ions according to claim 2, characterized in that, N-n-Butyl-4-cyano-1,8-naphthalimide: Pyridine-2-acetonitrile: Sodium hydride: Anhydrous tetrahydrofuran: 1–2.5 mmol: 1.5–3 mmol: 5–15 mmol: 20–40 mL.

7. Use of a colorimetric probe for detecting cyanide ions based on claim 1 or any one of claims 2-6, characterized in that, It is used to detect cyanide ions in mixed solutions.

8. The use of the colorimetric probe for detecting cyanide ions according to claim 7, characterized in that, It is used to detect cyanide ions in a 9:1 volume ratio of acetonitrile to water solution.

9. The use of the colorimetric probe for detecting cyanide ions according to claim 7 or 8, characterized in that, When using ultraviolet absorption spectroscopy for detection, the probe is dissolved in a 9:1 volume ratio of acetonitrile to water solution to test for cyanide ions.

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