Thiazolothiazole-based fluorescent probe, preparation method thereof, and application in detecting sarin and its simulants

Abstract

The present invention discloses a fluorescent probe based on thiazolothiazole, a preparation method thereof, and an application for sensing and detecting sarin and its simulants. The fluorescent probe is a fluorescent molecule with a push-pull electron effect constructed by using thiazolothiazole as an electron-withdrawing group and a triphenylamine group as an electron-pushing group. The compound constructed with thiazolothiazole and triphenylamine groups in the present invention has a significant push-pull electron effect, a large Stokes shift, and a high fluorescence quantum yield, exhibiting good ICT characteristics and excellent photophysical properties, and exhibiting excellent sensing performance such as high sensitivity, fast response speed, and short recovery time for the sarin gas simulant DCP. The present invention prepares the fluorescent probe into a fluorescent sensing film with good photochemical stability by a drop coating method, converts the film into a device, and further prepares it into a film-based fluorescent sensor, which is expected to achieve high-sensitivity detection of sarin gas and has great potential and application value in practical applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent sensing films, and particularly relates to a fluorescent probe based on thiazolothiazole, and application of the fluorescent probe in sensing and detecting sarin and its analogue diethyl chlorophosphate (DCP). Background Art

[0002] Thin-film fluorescence sensors have experienced rapid development over the past decade due to their numerous advantages, including non-contamination of the analyte, reusability, and ease of device integration. Their core component is the fluorescence sensing unit that interacts with the analyte, which determines sensor performance. Therefore, the design and construction of novel fluorescent molecules is crucial. Thiazole and its derivatives, as typical p-type semiconductor materials, have been developed in the organic semiconductor field for nearly 30 years and hold a key position in fields such as organic field-effect transistors, organic light-emitting diodes, organic solar cells, and sensors.

[0003] Among them, the thiazolothiazole group has attracted widespread attention due to its simple synthesis method, unique rigid planar structure, and bicyclic heteroatom structure. The thiazolothiazole group is composed of two thiazole groups fused together, with a large rigid coplanar π-conjugated structure that enables effective intermolecular π-π stacking. It has excellent photophysical properties such as large molar absorption coefficient, high fluorescence quantum yield, and long fluorescence lifetime. Its excellent fluorescence properties can be used to construct fluorescent probes, showing great application potential in the field of fluorescence sensing.

[0004] The propeller structure of triphenylamine (TPA) not only effectively suppresses the ACQ effect caused by intermolecular π-π stacking (a phenomenon in which certain luminescent molecules emit efficiently in dilute solutions but their luminescence efficiency is reduced or even completely eliminated in concentrated solutions or when aggregated), but also offers advantages such as a large Stokes shift, high fluorescence quantum yield, and excellent photostability. As a typical electron donor, TPA is a popular group for constructing fluorescent probe molecules. TPA has long been widely used in the field of fluorescence sensing, but in the field of sarin gas detection, the sensitivity and selectivity of fluorescent probes constructed with it cannot meet the growing demand. Summary of the Invention

[0005] The present invention aims to provide a fluorescent probe with a pronounced push-pull electron effect, a large Stokes shift, a high fluorescence quantum yield, excellent ICT (Information Communication in Chemical) characteristics, and superior photophysical properties. The probe exhibits excellent sensing performance for the sarin gas simulant DCP, including high sensitivity, fast response, and short recovery time. This fluorescent probe utilizes a TPA group as an electron donor and a thiazolothiazole group as an electron acceptor, modulating the intramolecular push-pull electron effect to construct a DA system fluorescent probe with ICT characteristics, thereby improving the fluorescent probe's performance in detecting sarin gas simulants.

[0006] To achieve the above-mentioned purpose, the present invention provides a thiazolothiazole-based fluorescent probe (abbreviated as TPA-TZ) having the following structural formula:

[0007]

[0008] The preparation method of the above-mentioned thiazolothiazole-based fluorescent probe comprises the following steps:

[0009] Step 1: Under anhydrous and oxygen-free conditions, dithioacetamide and 4-bromobenzaldehyde are added to DMF and refluxed at 140-160°C for 6-10 hours. After the reaction, the reaction solution is cooled to room temperature, and the product is isolated and purified to obtain compound 1. The reaction equation is as follows:

[0010]

[0011] Step 2: Under anhydrous and oxygen-free conditions, compound 1, diphenylamine, tri-tert-butylphosphine tetrafluoroborate, palladium acetate, and sodium tert-butoxide were added to toluene and stirred at 110-120°C for 24-48 hours. After the reaction, the reaction solution was cooled to room temperature, and the product was isolated and purified to obtain a thiazolothiazole-based fluorescent probe. The reaction equation is as follows:

[0012]

[0013] In the above step 1, the molar ratio of dithioacetamide to 4-bromobenzaldehyde is preferably 1:2 to 2.5.

[0014] In the above step 2, the molar ratio of the compound 1 to diphenylamine is preferably 1:2-3.

[0015] In the above step 2, the amount of tri-tert-butylphosphine tetrafluoroborate added is preferably 10% to 30% of 1 mol of the compound.

[0016] In the above step 2, the amount of palladium acetate added is preferably 5% to 10% of 1 mol of the compound.

[0017] In the above step 2, the amount of sodium tert-butoxide added is preferably 2 to 3 times the molar amount of the compound.

[0018] The present invention also provides the use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP.

[0019] The beneficial effects of the present invention are as follows:

[0020] This invention synthesized a novel thiazolylthiazolyl-based fluorescent compound, TPA-TZ. Photophysical testing of the compound in both solution and aggregate states demonstrated a pronounced push-pull electron effect, a large Stokes shift, a high fluorescence quantum yield, and excellent luminescence properties in both solution and aggregate states. Based on these excellent photophysical properties, the compound TPA-Tz was prepared into a fluorescent sensing film by drop coating. This film was then fabricated into a device to form a thin-film-based fluorescence sensor. In subsequent testing of DCP vapor, the sensor demonstrated excellent performance, including high sensitivity (detection limit as low as 100 ppb), fast response speed (less than 5 s), and short recovery time (less than 15 s), demonstrating a highly sensitive and reversible sensing effect for DCP. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The UV-visible absorption spectra of compound TPA-Tz in different solvents (concentration of 2.5×10 -5 mol / L).

[0022] Figure 2 The fluorescence emission spectra of compounds Py-Tz (a) and TPA-Tz (b) in DCM solution (concentration range 5.0×10 -7 mol / L to 1.0×10 -4 mol / L).

[0023] Figure 3 This is the photochemical stability test result of TPA-Tz film (excitation wavelength is 430 nm).

[0024] Figure 4 Sensitivity test of TPA-Tz film to different concentrations of DCP vapor (a) and response signal diagram (b) (the inset is a linear relationship diagram).

[0025] Figure 5 These are the test results of the response dynamics of TPA-Tz film to DCP vapor. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention are further illustrated below by means of the accompanying drawings and specific embodiments. Those skilled in the art should understand that the specific embodiments are intended only to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the scope of protection of the present invention shall be defined by the claims. Example 1

[0027]

[0028] Step 1: Under anhydrous and oxygen-free conditions, 0.60 g (5 mmol) of dithioacetamide and 2.00 g (11 mmol) of 4-bromobenzaldehyde were added to a 50 mL double-necked round-bottom flask. 30 mL of DMF was added and the mixture was refluxed at 150°C for 8 h. After the reaction was complete and the reaction solution was cooled to room temperature, it was extracted with dichloromethane and washed with water. Water was removed with anhydrous sodium sulfate, and the organic solvent was removed using a rotary evaporator. The product was separated and purified by column chromatography using a 1:1 mixture of petroleum ether and dichloromethane (volume ratio) as the developing solvent. Finally, the product was recrystallized from cyclohexanone and dried under vacuum at 50°C to obtain 1.20 g of yellow compound 1 in a 53% yield. Compound 1 was characterized as follows: 1 H NMR (600 MHz, CDCl3): δ (ppm) 7.88 (d, 4H),7.63 (d, 4H); APCI-HRMS: [(M+H)]+ (C 16 H8Br2N2S2): 452.8548, found 452.8547.

[0029] Step 2: Under anhydrous and oxygen-free conditions, 0.90 g (2 mmol) of compound 1, 0.85 g (5 mmol) of diphenylamine, 0.09 g (0.30 mmol) of tri-tert-butylphosphine tetrafluoroborate, 0.023 g (0.10 mmol) of palladium acetate, and 0.45 g (4.69 mmol) of sodium tert-butoxide were added to a 50 mL Shrek flask and completely dissolved in 30 mL of freshly distilled toluene. The mixture was stirred at 110°C for 48 h. After the reaction was complete, the reaction solution was cooled to room temperature and quenched with saturated brine. Extraction was performed with chloroform, and the solvent was removed by rotary evaporation. The product was purified by column chromatography using a 1:1 mixture of petroleum ether and dichloromethane (volume ratio) as the developing solvent. Finally, the product was recrystallized from dichloromethane / n-hexane and dried under vacuum at 50°C to obtain 0.34 g of the yellow target compound, TPA-Tz, in a 26% yield. Characterization of TPA-Tz was as follows: 1 H NMR (600 MHz, CDCl3): δ (ppm)7.82 (d, 4H), 7.31 (t, 8H), 7.16 (d, 8H), 7.15 (d, 4H), 7.10 (d, 4H); APCI-HRMS: [(M+H)]+ (C 40 H 28 N4S2): 629.1828, measured value 629.1826.

[0030] Comparative Example 1

[0031]

[0032] Under anhydrous and oxygen-free conditions, 0.60 g (5 mmol) of dithioacetamide and 1.20 g (11 mmol) of 4-pyridinecarboxaldehyde were added to a 50 mL double-necked round-bottom flask, along with 30 mL of DMF. The mixture was refluxed at 150°C for 8 h. After the reaction was complete and cooled to room temperature, the solution was extracted with dichloromethane and washed with water. Water was removed with anhydrous sodium sulfate, and the organic solvent was removed using a rotary evaporator. Finally, the product was separated and purified by column chromatography using a mixture of petroleum ether and dichloromethane in a 1:2 volume ratio as the developing solvent. After vacuum drying at 50°C, 0.70 g of the white compound Py-Tz was obtained with a yield of 39%. Characterization of Py-Tz was as follows: 1 H NMR (600 MHz, CDCl3): δ (ppm) 8.79 (d, 4H), 7.88 (d, 4H); APCI-HRMS: [(M+H)]+ (C 14 H8N4S2): 297.0263, measured value 297.0264. Example 2

[0033] Application of the prepared thiazolothiazole fluorescent probe (TPA-Tz) in sensing and detecting sarin gas and its simulant DCP

[0034] TPA-TZ was added to toluene to prepare 1×10 -4 mol / L TPA-TZ toluene solution. 30 μL 1×10 -4 A 10 mol / L TPA-TZ toluene solution was drop-coated on a 1 cm × 1 cm glass plate and dried to obtain a TPA-TZ fluorescent sensing film. A comparative experiment was also conducted using Py-Tz from Comparative Example 1.

[0035] like Figure 1 As shown, TPA-Tz exhibits two distinct absorption bands at 300 nm and 430 nm in different solvents, both attributable to the π-π* transition of TPA-Tz. Furthermore, in terms of photophysical properties, the shape and position of the characteristic UV absorption peak of TPA-Tz do not change significantly with increasing solvent polarity, demonstrating that solvent polarity has little effect on the electronic structure of the ground state of the compound TPA-Tz.

[0036] like Figure 2 As shown, Py-Tz and TPA-Tz are 5×10 -7 mol / L to 1×10 -4Within the 100 mol / L concentration range, the excitation wavelengths were 355 nm and 430 nm, respectively. Within this concentration range, the emission peak intensities of both compounds increased with increasing compound concentration, but the shape and position of their fluorescence emission spectra remained unchanged, indicating that neither Py-Tz nor TPA-Tz exhibited an ACQ effect within this concentration range. Furthermore, the characteristic absorption peak of TPA-Tz exhibited a significant red shift compared to that of Py-Tz, attributed to the strong electron-donating group triphenylamine increasing the degree of π-conjugation in the TPA-Tz molecule.

[0037] like Figure 3 As shown in the figure, in terms of photochemical stability, the fluorescence intensity of the TPA-Tz fluorescent film decays very little. After continuous irradiation for 8 hours, the fluorescence intensity decay is only 7.9%, indicating that the TPA-Tz fluorescent film has good photochemical stability and can be used for long-term stable practical applications in gas phase sensing. Figure 4 As shown, DCP vapor can significantly quench the fluorescence of the TPA-TZ fluorescent sensor film. As the DCP vapor concentration continues to increase, the quenching rate of the TPA-Tz fluorescent sensor film continues to increase. The quenching rate of saturated DCP vapor on the TPA-Tz sensor film can reach 44%. The sensing sensitivity test of the TPA-TZ fluorescent sensor film shows that the TPA-Tz fluorescent sensor film shows a good linear response to DCP concentration at least in the concentration range of 100 ppb to 5 ppm, with a correlation coefficient (R 2 ) is 0.997, and the minimum detection limit is as low as 100 ppb, indicating that the TPA-Tz fluorescent sensing film is expected to be used in the detection of ultra-low concentration DCP vapor.

[0038] The response kinetics of TPA-Tz fluorescent sensing film to DCP vapor were further analyzed in detail, the sensing process was indexed and quantified, and the sensing performance of TPA-Tz fluorescent sensing film was evaluated in depth. The results are as follows: Figure 5 The results showed that the response time of the TPA-Tz fluorescent sensing film to DCP vapor was less than 5 s. When the injection was stopped, the signal began to decrease, and the recovery time of the fluorescent sensing film (defined as the duration for the output to recover from the maximum intensity to 90% of the initial intensity) was less than 15 s.

[0039] In summary, the TPA-TZ fluorescent sensing film prepared in the present invention has good performance in the detection of DCP vapor in terms of response speed, selectivity and reusability, and the detection limit can be as low as 100 ppb, which is much lower than the detection limit reported in previous studies.

Claims

1. Application of a thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP, characterized in that: The structural formula of the fluorescent probe is shown below: 。 2. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 1, characterized in that: The preparation method of the fluorescent probe comprises the following steps: Step 1: Under anhydrous and oxygen-free conditions, dithioacetamide and 4-bromobenzaldehyde were added to DMF and refluxed at 140-160°C for 6-10 hours. After the reaction, the reaction solution was cooled to room temperature, and the product was isolated and purified to obtain compound 1. Step 2: Under anhydrous and oxygen-free conditions, compound 1, diphenylamine, tri-tert-butylphosphine tetrafluoroborate, palladium acetate, and sodium tert-butoxide are added to toluene and stirred at 110-120°C for 24-48 hours. After the reaction, the reaction solution is cooled to room temperature, and the product is isolated and purified to obtain a thiazolothiazole-based fluorescent probe. 。 3. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 2, characterized in that: In step 1, the molar ratio of dithioacetamide to 4-bromobenzaldehyde is 1:2 to 2.

5.

4. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 2, characterized in that: In step 2, the molar ratio of compound 1 to diphenylamine is 1:2-3.

5. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 2, characterized in that: In step 2, the amount of tri-tert-butylphosphine tetrafluoroborate added is 10% to 30% of 1 mole of the compound.

6. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 2, characterized in that: In step 2, the amount of palladium acetate added is 5% to 10% of 1 mol of the compound.

7. The use of the thiazolothiazole-based fluorescent probe in sensing and detecting sarin gas and its simulant DCP according to claim 2, characterized in that: In step 2, the amount of sodium tert-butoxide added is 2 to 3 times the molar amount of compound 1.

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