Design, preparation and application of colorimetric optical probe for detecting content of thiophenol

Abstract

The invention provides a colorimetric optical probe which is high in response speed, good in selectivity and capable of visually detecting thiophenol as well as a preparation method and application of the colorimetric optical probe. According to the probe, a dicyanoisophorone derivative is used as a chromophore, and a 2, 4-dinitrobenzene sulfonic acid group is used as a recognition group. The probe is yellow in a solvent system with the pH value of 7.4, and after thiophenol is added, the color of the solution is changed from yellow to orange red, so that the aim of detecting thiophenol by a visual method is fulfilled. The thiophenol probe disclosed by the invention is simple to synthesize and relatively simple in post-treatment; the method realizes rapid detection of thiophenol, has good selectivity, and has a wide application prospect in real-time monitoring of thiophenol in an environment.

Description

Technical Field

[0001] The invention relates to a colorimetric optical probe for detecting thiophenol, preparation and application thereof, and belongs to the field of organic small molecule optical probes. Background Art

[0002] Benzothiophenol (PhSH) is a valuable organic synthesis intermediate widely used in the preparation of drugs, pesticides and various industrial products. However, due to its high volatility, irritation and toxicity, thiophenol is listed as a priority pollutant by the U.S. Environmental Protection Agency. In biological systems, thiophenol can be auto-oxidized to aromatic disulfides and further induce oxidative stress, producing harmful superoxide radicals and hydrogen peroxide (H2O2). Prolonged exposure of organisms (>15 min) to thiophenol can cause serious health problems, including central nervous system damage, breathing difficulties, vomiting, and even death. In general, the median lethal concentration (LC50) of thiophenol for fish is 2.5 ~ 3.5. 50 ) range is 0.01 mmol·L -1 To 0.4 mmol·L -1 The median lethal concentration (LC) of 50 ) ranged from 2.15 mg / kg to 46.2 mg / kg. Therefore, it is of great significance to develop an efficient and real-time monitoring method for thiophenol in environmental and biological samples.

[0003] Due to the pollution of thiophenol to the environment, water sources, food sources and biological fluids, many researchers have begun to develop colorimetric sensors for high-sensitivity and high-selectivity detection. The main technologies for detecting thiophenol are high-performance liquid chromatography and gas chromatography. Although these methods can detect thiophenol with high sensitivity, they have disadvantages such as expensive instruments, complicated operation processes and cell protoplasm destruction. Colorimetric sensors have broad application prospects in the detection of thiophenol due to their high sensitivity, strong specificity, low cost, simplicity and the ability to provide rapid on-site response near contaminated areas. Therefore, it is of great practical significance to develop a colorimetric optical probe with fast reaction speed, good specificity and visual colorimetric detection of thiophenol, a pollutant in the environment. Summary of the invention

[0004] In view of some problems existing in the optical probes for detecting thiophenol in the prior art, such as short fluorescence emission wavelength, long reaction time and inability to be used for visual detection, the present invention aims to provide a colorimetric optical probe that can be used for visual detection of thiophenol.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned optical probe for semi-quantitative detection of thiophenol, which has readily available raw materials, simple synthesis steps and high yield.

[0006] Another object of the present invention is to provide a colorimetric optical probe that can quickly detect the content of thiophenol and can be used for on-site visual detection and efficient real-time monitoring of thiophenol in the environment and biological samples.

[0007] To achieve the above purpose, the present invention adopts the following technical solution.

[0008] A thiophenol colorimetric optical probe based on isophorone derivatives, the structural formula of which is shown in Formula I.

[0009]

[0010] A method for synthesizing a thiophenol colorimetric optical probe based on the above-mentioned dicyanoisophorone derivative comprises the following steps: (1) Take a 50 mL round-bottom flask, add p-toluene thiophenol and polyphosphoric acid into the flask, and then add ethyl acetoacetate dropwise to the mixture. After stirring the reaction at 90 °C for 0.5 h, the mixture is cooled to room temperature. The mixture is extracted with ethyl acetate and dried over anhydrous Na2SO4. After purification by column chromatography, a white solid compound 1 is obtained.

[0011]

[0012] (2) Compound 1 and malononitrile were dissolved in acetic anhydride and refluxed at 140 °C with stirring for 16 h. Afterwards, the mixture was cooled to 55 °C, and methanol was added and stirred for 3 h. After the reaction was completed, the solvent was removed under reduced pressure by a rotary evaporator, and the crude product was purified by column chromatography to obtain a yellow solid compound 2.

[0013]

[0014] (3) Take a 50 mL round-bottom flask, add compound 2, dissolve it in 10 mL of anhydrous acetonitrile, add 50 μL of piperidine, and finally add 10 mL of anhydrous acetonitrile solution of 6-hydroxy-2-naphthaldehyde, and reflux for 4 h at 75 °C under Ar2 atmosphere. After the reaction is completed, the reaction solution is cooled to room temperature and filtered under reduced pressure to obtain pure compound 3.

[0015]

[0016] (4) Compound 3 and CH2Cl2 were added to a 10 mL round-bottom flask, and 5 μL of triethylamine was added dropwise. 2, 4-dinitrobenzenesulfonyl chloride was dissolved in CH2Cl2 and added dropwise. The mixture was stirred in an ice-water bath for 0.5 h, and the reaction solution was heated to 40°C and reacted for 3 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, and washed with ice acetonitrile three times to obtain a deep red probe formula I.

[0017]

[0018] The above probe is used for visual detection of thiophenol in environmental samples.

[0019] A colorimetric optical probe for rapid detection of thiophenol in the environment can perform a semi-quantitative "naked eye colorimetric" determination of thiophenol by comparing the color changes of the solution under sunlight after the probe formula I reacts with thiophenol of different concentrations. The specific detection method is as follows.

[0020] The probe type I was added to the PBS buffer (20 mmol L -1 , pH 7.4, 50% DMSO) were added with different concentrations of thiophenol (0 - 12 μmol·L -1 ), record the UV-visible absorption spectrum of the probe at 420 nm. Probe Formula I shows a maximum absorption peak at 420 nm, and its solution appears yellow under sunlight. After adding thiophenol, the UV absorption peak red-shifts to 480nm, and the color of the solution changes significantly (from yellow to orange-red), thereby achieving visual detection of thiophenol.

[0021] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects: Probe I shows a maximum absorption peak at 420 nm, and its solution appears yellow in sunlight. When different concentrations of thiophenol are added, the maximum ultraviolet absorption peak of probe I at 420 nm gradually red-shifts to 480 nm, and the color of the solution gradually changes from yellow to orange-red in sunlight. Compared with the reported optical probes for detecting thiophenol, its advantages are: by comparing the color changes of the solution under sunlight after the reaction of probe I with different thiophenols, a "naked eye colorimetric" semi-quantitative detection of thiophenol can be quickly performed; secondly, the probe has a strong ability to resist interfering substances in the environment and has a high sensitivity; finally, the probe has a simple synthesis step, high yield, and good photostability. Therefore, this probe has a broader application prospect in the future field of environmental protection and modern analytical chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the structural formula of probe type Ⅰ.

[0023] Figure 2 This is the mass spectrum of probe formula Ⅰ.

[0024] Figure 3 This is the NMR spectrum of probe formula Ⅰ.

[0025] Figure 4 This is the UV-visible absorption spectrum of probe type I that changes with time.

[0026] Figure 5It is the UV-visible absorption spectrum of the reaction of probe formula Ⅰ with thiophenol at different pH.

[0027] Figure 6 This is the UV-visible absorption spectrum of probe type I in response to thiophenol changing with time.

[0028] Figure 7 This is the UV-visible absorption spectrum of probe type I in response to different concentrations of thiophenol.

[0029] Figure 8 This is a color change diagram of probe formula I after reacting with different concentrations of thiophenol under fluorescent light.

[0030] Fig. 9 This is the response mechanism of the reaction between probe formula I and thiophenol.

[0031] Fig.10 This is the UV-visible absorption spectrum of probe formula Ⅰ and chromophore (compound 3).

[0032] Fig.11 The UV-visible absorption spectra of probe formula I reacting with various analytes in the environment. + ,Mg 2+ , Mn 2+ , K + , Cu 2+ , Fe 3+ ), anion (SO3 2− , HSO 3− , NO 3− , HS − ,CO3 2− , Cl − , SO4 2− , S2O3 2− ,Br − , ClO − ), biothiols (Cys, GSH), AA, H2O2. Among them, Cu 2+ , Fe 3+ , HS − The concentrations of Cys and GSH were both 50.0 μmol•L -1 , the concentrations of other substances were all 500.0 μmol•L -1 ).

[0033] Fig.12 This is a diagram of the color change of the solution after the probe type I reacts with different analytes under fluorescent light. Example

[0034] The present invention is further described below in conjunction with embodiments and drawings, but the present invention is not limited by the following embodiments.

[0035] Example 1 Synthesis of fluorescent probe formula Ⅰ (1) Take a 50 mL round-bottom flask, add p-toluene thiophenol (0.6229 g, 5 mmol) and polyphosphoric acid (8 mL) into the flask, and then add ethyl acetoacetate (635 μL, 5 mmol) dropwise to the mixture. After stirring the reaction at 90 °C for 0.5 h, the mixture was cooled to room temperature. The mixture was extracted with ethyl acetate and dried over anhydrous Na2SO4. After purification by column chromatography, a white solid compound 1 was obtained.

[0036]

[0037] (2) Solid compound 1 (0.3506 g, 2 mmol) and malononitrile (1.3226 g, 20 mmol) were dissolved in 7 mL of acetic anhydride and refluxed at 140 °C with stirring for 16 h. Afterwards, the mixture was cooled to 55 °C, and 11 mL of methanol was added and stirred for 3 h. After the reaction was completed, the solvent was removed under reduced pressure by a rotary evaporator, and the crude product was purified by column chromatography to obtain a yellow solid compound 2.

[0038]

[0039] (3) Add compound 2 (0.0485 g, 0.2 mmol) to a 50 mL round-bottom flask, dissolve it in 10 mL of anhydrous acetonitrile, add 50 μL of piperidine, and finally add 10 mL of anhydrous acetonitrile solution of 6-hydroxy-2-naphthaldehyde (0.0345 g, 0.2 mmol), and reflux for 4 h at 75 °C under Ar2 atmosphere. After the reaction is completed, the reaction solution is cooled to room temperature and filtered under reduced pressure to obtain pure compound 3.

[0040]

[0041] (4) Compound 3 (0.0119 g, 0.03 mmol) and 1 mL CH2Cl2 were added to a 10 mL round-bottom flask, 5 μL triethylamine was added dropwise, and 2, 4-dinitrobenzenesulfonyl chloride (0.016 g, 0.06 mmol) was dissolved in 1 mL CH2Cl2 and added dropwise, and then stirred in an ice-water bath for 0.5 h, and the reaction solution was heated to 40 °C and reacted for 3 h. After the reaction was completed, it was cooled to room temperature, filtered under reduced pressure, and washed with ice acetonitrile 3 times to obtain a deep red compound probe formula I.

[0042]

[0043] Example 2 Study on the photostability of fluorescent probe formula I The probe formula I was dissolved in dimethyl sulfoxide to obtain 50 μL of 1 mmol·L -1 The stock solution was sealed and refrigerated for later use. -1 ), different volumes of thiophenol solution (1 mmol·L -1 ) was added to PBS buffer (20 mmol·L -1 , pH = 7.4, 50% DMSO) was used for UV-visible absorption spectrum measurement. It was found that when only probe formula I was contained, there was an obvious absorption peak at 420 nm, and the maximum absorption peak of probe formula I at 420 nm hardly changed within 2 h, indicating that the probe had good photostability. The results are shown in Figure 4 shown.

[0044] Example 3 Response of probe type I to thiophenol at different pH values We studied the response of probe type I to thiophenol at different pH values, and adjusted the pH value by adding PBS buffer of different pH values ​​to the reaction solution. When the pH value was 2.0, 3.0, 4.0, 5.0, 6.0, and 8.0, the ultraviolet absorption peak of the probe after reacting with thiophenol showed almost no change. Only when the pH value was 7.4, the ultraviolet absorption peak of probe type I at 420 nm showed an obvious red shift to 480 nm. The results are shown in Figure 2. Figure 5 As shown, it is shown that the reaction effect of probe formula I and thiophenol is best under neutral conditions.

[0045] Example 4 Study on the response time of probe type I to thiophenol At room temperature, we investigated the response time of probe I to thiophenol. Figure 6 As shown, before the addition of thiophenol, probe formula I showed an absorption peak at 420 nm. After the addition of thiophenol, the ultraviolet absorption peak showed a red shift. With the increase of reaction time, the red shift of the ultraviolet absorption peak of probe formula I at 420 nm increased, and finally stabilized at 10 min.

[0046] Example 5 Response of Probe Formula I to Thiophenol We then studied the response of probe I to different concentrations of thiophenol. -1 , pH 7.4, 50% DMSO) were added with different concentrations of thiophenol (0 - 12 μmol·L -1 ), record the UV-visible absorption spectrum of probe formula I at 420 nm, the results are as follows Figure 7When different concentrations of thiophenol were added, the maximum ultraviolet absorption peak of probe formula I at 420 nm gradually red-shifted to 480 nm, and the color of the solution gradually changed from yellow to orange-red under sunlight. Figure 8 It is shown that after the probe formula I reacts with thiophenol, by comparing the solution color changes after the probe formula I reacts with different thiophenols under sunlight, a "naked eye colorimetric" semi-quantitative detection of thiophenol can be performed.

[0047] Example 6 Reaction Mechanism of Probe Formula I According to the results reported in previous literature, there is an intramolecular charge transfer (ICT) process between the fluorophore DCS-OH and the 2, 4-dinitrobenzenesulfonic acid group, which leads to fluorescence quenching. The reaction mechanism is as follows Fig. 9 As shown in the figure, after adding thiophenol, the probe formula I reacts with thiophenol to undergo a nucleophilic substitution reaction, causing the 2, 4-dinitrobenzenesulfonic acid group to leave, blocking the ICT process and releasing DCS-OH. However, there are S atoms in the fluorophore molecule, which will increase the non-radiative transition channel of the molecule, reduce the fluorescence intensity, and ultimately make the fluorophore DCS-OH almost non-fluorescent. Based on this, we compared the UV-visible absorption spectra of the probe formula I before and after the addition of thiophenol, as shown in the figure. Fig.10 As shown in the figure, when thiophenol is not added, the maximum absorption peak of probe formula I is at 420 nm. After adding thiophenol, its maximum absorption peak red-shifts to 480 nm, and the maximum ultraviolet absorption peak of the chromophore DCS-OH also appears at 480 nm. In summary, thiophenol reacts with the optical probe formula I to generate the chromophore DCS-OH.

[0048] Example 7 Selectivity Study of Probe Formula I To investigate the specificity of probe type I, we measured the expression of several common analytes (Na + ,Mg 2+ , Mn 2+ , K + , Cu 2+ , Fe 3+ , SO3 2− , HSO3 − , NO3 − , HS − ,CO3 2− , Cl − , SO4 2− , S2O3 2− ,Br − , ClO − , AA, H2O2, Cys, GSH) interfere with the detection of thiophenol. Fig.11As shown in the figure, only when benzenethiol was added, the position of the absorption peak changed significantly, while other analytes had almost no effect on it. At the same time, we detected the solution color changes of the probe and different analytes under sunlight conditions. Fig.12 It can be seen that only the probe solution with thiophenol added changes from yellow to orange-red. In summary, probe formula I can be used to determine thiophenol by visual detection and has the characteristics of high selectivity.

Claims

1. A colorimetric optical probe for detecting thiophenol, the structural formula of which is shown in Formula I: 。 2. The method for preparing a colorimetric optical probe for detecting thiophenol according to claim 1, characterized in that: The following steps are involved: (1) dissolving p-toluenethiophenol in polyphosphoric acid, adding ethyl acetoacetate to the mixture, heating and stirring to react for a period of time, extracting, drying and desolventizing the mixture after the reaction is completed, and separating and purifying the mixture by column chromatography to obtain a white solid compound 1, ， (2) Compound 1 and malononitrile are dissolved in an organic solvent, heated and stirred to react for a period of time, the mixture is cooled to a certain temperature, an alcohol organic solvent is added, and the mixture is heated and stirred to react for a period of time. After the reaction is completed, the solvent is evaporated under reduced pressure, and the yellow solid compound 2 is obtained after separation and purification by column chromatography. ， (3) Compound 2 and 6-hydroxy-2-naphthaldehyde are dissolved in an organic solvent, and piperidine is added thereto. The mixture is heated and stirred under an Ar2 atmosphere for a period of time. After the reaction is completed, the reaction solution is cooled to room temperature and filtered under reduced pressure to obtain pure compound 3; ， (4) Dissolve compound 3 in an organic solvent, add triethylamine, then add 2, 4-dinitrobenzenesulfonyl chloride, heat and stir to react for a period of time. After the reaction is completed, filter under reduced pressure to obtain a colorimetric optical probe formula I; 。 3. The method according to claim 2, characterized in that The method has the following characteristics: The reaction heating temperature of step (1) is 90°C; The reaction time of step (1) is 0.5 hours; The reaction in step (2) is carried out in an organic solvent of acetic anhydride; The reaction in step (2) is carried out in methanol, an alcohol organic solvent; In step (2), compound 1 and malononitrile are first dissolved in acetic anhydride, and refluxed and stirred at 140° C. for 16 hours; then, the mixture is cooled to 55° C., methanol is added, and the mixture is stirred for 3 hours; The reaction in step (3) is carried out in anhydrous acetonitrile as the organic solvent; The reaction heating temperature of step (3) is 75°C; The reaction time of step (3) is 4 hours; The reaction in step (4) is carried out in dichloromethane as the organic solvent; In step (4), compound 3 is dissolved in dichloromethane, and triethylamine is added dropwise, then a dichloromethane solution of 2, 4-dinitrobenzenesulfonyl chloride is added dropwise to the mixture, and the mixture is stirred for 0.5 hour in an ice-water bath, and the reaction solution is heated to 40° C. and reacted for 3 hours.

4. Use of a colorimetric optical probe for detecting thiophenol as claimed in claim 1 in preparing a reagent for efficiently and in real time monitoring the content of thiophenol in environmental and biological samples.

Images