D-A-D type organic fluorescent probe for detecting iron ions as well as preparation method and application of D-A-D type organic fluorescent probe

Abstract

The invention relates to the field of ferric ion detection, and particularly provides a fluorescent probe for detecting ferric ions as well as a preparation method and application of the fluorescent probe. The fluorescent probe shows good performance, and is low in detection limit, high in selectivity and sensitivity and strong in anti-interference capability. The preparation method comprises the following steps: dissolving 3, 6-carbazole methyl dicarboxylate and sodium hydride in an organic solvent, stirring and heating at normal temperature, slowly dropwise adding a bis (4-fluorophenyl) sulfone solution until the bis (4-fluorophenyl) sulfone solution is completely added, reacting for a certain period of time, adding an obtained product into water, stirring, filtering to obtain a brown solid, and sequentially carrying out Soxhlet extraction, column chromatography purification, stirring reflux and vacuum drying to obtain the target product. The fluorescent probe is obtained. The powdery fluorescent probe material is dissolved in water and mixed with a solution to be detected, the fluorescence emission spectrum of the mixed solution is detected, and ferric ions in the solution are detected through the change of fluorescence intensity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organic fluorescent substance preparation, and particularly relates to a D-A-D type organic fluorescent probe for detecting trivalent iron ions and a preparation method thereof. BACKGROUND

[0002] Iron is an essential transition metal element for life system, and trivalent iron ions (Fe 3+ ) play a core role in oxygen transport, DNA synthesis and enzyme catalysis, but its excess can trigger Fenton reaction to produce hydroxyl radicals, leading to cell oxidative damage, which is closely related to Parkinson's disease, cirrhosis and cancer. The United States EPA stipulates that the upper limit of Fe 3+ in drinking water is 0.3 mg L -1 , and China's GB 5749-2022 also adopts the same standard. Therefore, it is of great significance to develop a high-selectivity and high-sensitivity Fe 3+ detection method for public health, environmental monitoring and clinical diagnosis.

[0003] Although traditional detection techniques such as atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) have high accuracy, they rely on large instruments, have complex sample pretreatment and high cost, and are difficult to realize in-situ rapid screening. Fluorescent probes have become a research hotspot for metal ion detection because of their rapid response, simple operation, naked-eye observation and compatibility with biological imaging. However, the existing Fe 3+ fluorescent probes still have the following shortcomings: (1) poor selectivity, seriously interfered by coexisting ions such as Cu 2+ , Al 3+ and Zn 2+ ; (2) low water solubility, which can only work in organic solvent / water mixed systems, limiting the application of biological samples; (3) small Stokes shift (≤30 nm), high self-absorption and background fluorescence, resulting in low signal-to-noise ratio; (4) long synthesis route and low total yield, which is difficult to scale up.

[0004] In recent years, the donor-acceptor-donor (D-A-D) structure has attracted attention in the design of Fe 3+ probes because of its strong intramolecular charge transfer (ICT) effect, which can significantly increase the Stokes shift and improve the two-photon absorption cross section. However, the existing D-A-D probes mostly rely on Schiff base or carboxylic acid groups to recognize Fe 3+ , which has weak coordination ability, slow response and poor light stability. Therefore, it is still a technical problem to be solved in the field to develop a new recognition site and optimize the D-A-D skeleton to realize a high-selectivity, high-sensitivity and water-soluble Fe 3+ fluorescent probe. SUMMARY

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing an organic fluorescent probe for detecting ferric ions, its preparation method, and its applications. Based on the excellent optical properties of carbazole / sulfone derivatives, this invention successfully synthesizes a DAD-type organic fluorescent probe by introducing a carboxyl group. This probe demonstrates high selectivity, high sensitivity, and anti-interference ability for the detection of ferric ions through fluorescence titration experiments, making it important for environmental analysis.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A DAD-type organic fluorescent probe and its preparation method, comprising the following steps:

[0008] S1, methyl 3,6-carbazole dicarboxylate and sodium hydride are dissolved in an organic solvent to obtain solution A, which is stirred at room temperature for 30 minutes and then heated to a certain temperature.

[0009] S2, dissolve bis(4-fluorophenyl) sulfone in an organic solvent to obtain solution B.

[0010] S3, slowly add solution B to solution A, and allow the reaction to proceed for a certain period of time.

[0011] S4. Add the product obtained in S3 to 500 mL of water and stir. Filter to obtain a brown solid.

[0012] S5, the brown solid obtained in S4 was subjected to Soxhlet extraction, column chromatography purification, and reflux.

[0013] S6. The pH of the solution obtained in S5 was adjusted with 1M acid, filtered to obtain a solid product, and then dried in a vacuum drying oven to obtain a yellow DAD-type organic fluorescent probe product.

[0014] Furthermore, based on the above technical solution, the organic solvent is N,N-dimethylformamide.

[0015] Furthermore, based on the above technical solution, the mass ratio of methyl 3,6-carbazole dicarboxylate: sodium hydride: bis(4-fluorophenyl) sulfone is 3:1:1.

[0016] Furthermore, based on the above technical solution, the reaction conditions for the mixed solution include:

[0017] The reaction temperature is 100-150℃, preferably 130℃, and the reaction time is 18-32h, preferably 24h.

[0018] Furthermore, based on the above technical solution, the reaction products are extracted using dichloromethane and methanol using a Soxhlet extraction method for 4-12 hours, preferably 8 hours.

[0019] Furthermore, based on the above technical solution, the Soxhlet extract was purified by column chromatography using ethyl acetate:dichloromethane in a volume ratio of 1:1 as the eluent.

[0020] Furthermore, based on the above technical solution, the alkali used during the stirring and reflux of the purified product is potassium hydroxide.

[0021] Furthermore, based on the above technical solution, the pH value of the solution is adjusted to 1 using 1M hydrochloric acid.

[0022] Furthermore, based on the above technical solution, the drying conditions include:

[0023] The drying temperature is 40-80℃, and the drying time is 12-16h.

[0024] Furthermore, based on the above technical solution, this application also proposes an application of the above-mentioned fluorescent probe for detecting iron ions, wherein the solid fluorescent probe is dissolved in water, mixed with the solution to be detected, and the fluorescence emission spectrum of the mixed solution is detected, and the iron ions in the solution are detected by the change in fluorescence intensity.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention provides a carbazole-based DAD-type fluorescent material for detecting ferric ions. The electron-withdrawing effect of the sulfone group in the probe synergistically interacts with the electron-donating unit of the carbazole, enabling the detection of Fe... 3+ The recognition sites form a unique tetrahedral coordination configuration, which not only provides excellent thermal stability and mechanical strength, but also endows the material with excellent fluorescence properties;

[0027] This invention provides a method for preparing a carbazole-based DAD-type fluorescent material for detecting ferric ions, which simplifies the synthesis steps, reduces production costs, and facilitates the large-scale application of the material.

[0028] This invention provides a carbazole-based DAD-type fluorescent material for detecting ferric ions as a fluorescent probe in the detection of ferric ions, exhibiting high sensitivity and high selectivity. Attached Figure Description

[0029] Figure 1 (a) Fluorescence emission spectra of SPC under different metal ions (λex = 340 nm); (b) Fluorescence emission spectra of SPC-dtb under different metal ions (λex = 355 nm); (c) Fluorescence emission spectra of SPC-dca under different metal ions (λex = 335 nm); (d) Fluorescence emission spectra of SPC-dca under different Fe ions (λex = 335 nm); 3+ (e) Fluorescence emission spectrometer of SPC at different concentrations (λex = 340 nm); 3+(f) Fluorescence emission spectrometry of SPC-dtb at different concentrations (λex = 355 nm); 3+ At the specified concentration, the fluorescence emission spectrometer of SPC-dca (λex = 335 nm).

[0030] Figure 2 Detection limit diagram of probe SPC-dca (a) Fluorescence intensity of probe SPC-dca at 406 nm and Fe 3+ (a) Linear relationship of concentration; (b) Different Fe 3+ Stern-Volmer plot of probe SPC-dca at the specified concentration.

[0031] Figure 3 The probe SPC-dca was added with Fe in the presence of different metal ions 3+ The fluorescence intensity diagram afterward.

[0032] Figure 4 probe SPC-dca for Fe 3+ The effect of cyclic detection is shown in Figure (a) on Fe using the SPC-dca probe. 3+ (a) Fluorescence emission spectrum of reversibility; (b) Fe3+ and EDTA were added alternately to the SPC-dca solution for 5 cycles. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0037] Example 1

[0038] A method for preparing SPC-dca, a DAD-type organic fluorescent probe material for detecting iron ions, includes the following steps:

[0039] Step 1: Dissolve 3.54g of methyl 3,6-carbazole dicarboxylate and 1.2g of sodium hydride in 40mL of DMF solution, stir at room temperature for 30min, heat to 130℃, and continue stirring for 10min.

[0040] Step 2: Dissolve 1.58 g of bis(4-fluorophenyl) sulfone in 25 mL of DMF solution, and then slowly add it dropwise to the mixed solution prepared in Step 1. React for 24 h.

[0041] Step 3: Add the product obtained in Step 2 to 500 mL of water and stir. Filter to obtain a brown solid, and extract with dichloromethane and methanol for 8 h respectively.

[0042] Step 4: The solid obtained in Step 3 is purified by column chromatography using ethyl acetate:dichloromethane 1:1 as the eluent.

[0043] Step 5: Dissolve the solid obtained in Step 4 in a mixed solution of 75 mL water and 75 mL tetrahydrofuran, add 1.5 g potassium hydroxide, and stir under reflux for 18 h.

[0044] Step 6: The product obtained in Step 5 was rotary evaporated to remove tetrahydrofuran. The pH of the solution was adjusted to 1 with 1M hydrochloric acid. The solid product was filtered and placed in a vacuum drying oven at 60℃ for 12 hours to obtain 1.97 g of yellow fluorescent probe compound with a yield of 45.4%, which was labeled as SPC-dca.

[0045] Example 2

[0046] A method for preparing SPC-dtb, a DAD-type organic fluorescent probe material for detecting iron ions, includes the following steps:

[0047] Step 1: Dissolve 3.49g of 3,6-di-tert-butylcarbazole and 1.2g of sodium hydride in 40mL of DMF solution, stir at room temperature for 30min, heat to 100℃, and continue stirring for 10min.

[0048] Step 2: Dissolve 1.58 g of bis(4-fluorophenyl) sulfone in 25 mL of DMF solution, and then slowly add it dropwise to the mixed solution prepared in Step 1. React for 10 h.

[0049] Step 3: Add the product obtained in Step 2 to 500 mL of water and stir. Filter to obtain a solid product.

[0050] Step 4: Recrystallize the solid obtained in Step 3 with methanol.

[0051] Step 5: Place the solid obtained in Step 4 into a vacuum drying oven at 60℃ for 12 hours to obtain 3.59 g of grayish-white solid product with a yield of 74.4%, labeled as SPC-dtb.

[0052] Example 3:

[0053] A method for preparing a DAD-type organic fluorescent probe material SPC for detecting iron ions includes the following steps:

[0054] Step 1: Dissolve 2.09g carbazole and 1.2g sodium hydride in 40mL DMF solution, stir at room temperature for 30min, heat to 100℃, and continue stirring for 10min.

[0055] Step 2: Dissolve 1.58 g of bis(4-fluorophenyl) sulfone in 25 mL of DMF solution, and then slowly add it dropwise to the mixed solution prepared in Step 1. React for 10 h.

[0056] Step 3: Add the product obtained in Step 2 to 500 mL of water and stir. Filter to obtain a solid product.

[0057] Step 4: The solid obtained in Step 3 is purified by column chromatography using petroleum ether:dichloromethane in a volume ratio of 1:1 as the eluent.

[0058] Step 5: The organic matter in the product obtained in step 4 was removed by rotary evaporation and then placed in a vacuum drying oven at 50°C for 12 hours to obtain 2.66 g of white fluorescent probe compound with a yield of 77.6%, which was labeled as SPC.

[0059] In Examples 1-3, the DAD-type organic fluorescent probe material obtained through the technical solution of this invention can be used as a fluorescent probe to detect ferric ions. Specific analysis is as follows:

[0060] The probe stock solutions were all 50 μM DMF solutions of probe molecules. 10 mM solutions of various metal ion nitrates (Fe) were prepared using distilled water. 3+ Co 2+ Ni 2+ Zn 2+ pb 2+ Cu 2+ Cd 2+ Al 3+ Ag + Mg 2+ In 3+ Sn 4+ Cr 3+ Zr 4 + Mn 2+ K + Na +The working solution was prepared with a solution of diethylamine dioxate and disodium oxalate. During the experiment, the solution was diluted with the mother liquor to the specified concentration to ensure the water content was below 5%, thus avoiding aggregation that could lead to fluorescence quenching (ACQ effect) and negatively impact the experimental results. The probe molecule suspension was sonicated until homogeneous, and then quickly pipetted into 1 mL colorimetric tubes. 5 μL of metal ion solutions of different concentrations were added for fluorescence testing.

[0061] like Figure 1 As shown in Figure ac, under the same conditions, adding Co... 2+ Ni 2+ Zn 2+ Pb 2+ Cu 2+ Cd 2+ Al 3+ Ag + Mg 2+ In 3+ Sn 4+ Cr 3+ Zr 4+ Mn 2+ K + and Na + At that time, the fluorescence intensity of the working solutions of probes SPC, SPC-dtb, and SPC-dca did not change significantly, while the fluorescence intensity of the working solutions after the addition of Fe... 3+ At that time, the fluorescence intensity of the working solution decreased significantly. This indicates that the fluorescent probes SPC, SPC-dtb, and SPC-dca have a significant effect on Fe. 3+ The detection exhibits good selectivity. For example... Figure 1 As shown in df, also at 100μM Fe 3+ At the specified concentration, the quenching rate of probe SPC-dca was 85.05%, significantly higher than that of probes SPC (31.69%) and SPC-dtb (24.64%). These results indicate that, as a fluorescent probe targeting Fe3+, SPC-dca exhibits significantly higher sensitivity than SPC and SPC-dtb.

[0062] Figure 2 This is the detection limit diagram for the SPC-dca probe. With Fe... 3+ With increasing concentration, the fluorescence intensity of the SPC-dca solution at 406 nm tends to decrease, especially in Fe... 3+ It exhibits a good linear relationship in the concentration range of 10-80 μM. Figure 2 a, R 2 =0.9991), which indicates that within this concentration range, SPC-dca has a significant effect on Fe. 3+ It possesses quantitative detection capabilities. The quenching constant Ksv of SPC-dca is obtained from the Stern-Volmer plot as 45185.49 M. -1 According to the 3σ rule, SPC-dca affects Fe.3+ The limit of detection (LOD) was calculated to be 9.86 × 10⁻⁶. -7 M.

[0063] Figure 3 The probe SPC-dca is added with Fe in the presence of different metal ions. 3+ The subsequent fluorescence intensity diagram, i.e., the anti-interference effect diagram. At the same concentration of other related cations (Co... 2+ Ni 2+ Zn 2+ pb 2+ Cu 2+ Cd 2+ Al 3+ Ag + Mg 2+ In 3+ Sn 4 + Cr 3 +、Zr 4+ Mn 2+ K + Na + In the presence of ), 1.0 equivalent of Fe was added to the SPC-dca solution. 3+ The probe's anti-interference capability was tested. The fluorescence intensity at 406 nm was measured when the excitation wavelength was 335 nm, as shown in the figure. The addition of other metal ions had little effect on the fluorescence intensity of the SPC-dca solution. The addition of Fe... 3+ Subsequently, the fluorescence intensity decreased significantly. This indicates that the probe SPC-dca is effective against Fe... 3+ Its recognition is unaffected by other metal cations, exhibiting good selectivity and anti-interference properties.

[0064] Figure 4 probe SPC-dca for Fe 3+ The effect of cyclic detection is shown in the figure. To study the reversibility and regenerability of the probe SPC-dca, ethylenediaminetetraacetic acid (EDTA) was used as a chelating agent to chelate the metal ions that form a complex with the probe, and the fluorescence intensity before and after chelation was measured. From Figure 4 a can be seen that Fe was added to the probe solution. 3+ Fluorescence quenching occurred subsequently after the addition of Fe. 3+ After shaking an equal amount of EDTA, the fluorescence intensity recovered after a period of time. Figure 4 b is Fe 3+ The EDTA cycle was added to the test system and looped 5 times. This led to the conclusion that SPC-dca and Fe... 3+ The interaction is reversible, and the fluorescent probe is regenerable.

[0065] The above-described embodiments are merely preferred experimental schemes of the present invention. It should be noted that, for those skilled in the art, the experimental schemes may be described in different ways, and appropriate modifications may be made to the embodiments of the present invention, but all of these modifications are within the protection scope of the present invention.

Claims

1. A DAD-type organic fluorescent probe, its preparation method, and its application in the detection of iron ions, characterized in that, The preparation method includes the following steps: methyl 3,6-carbazole dicarboxylate and sodium hydride are dissolved in an organic solvent and stirred at room temperature for 30 minutes. After heating, bis(4-fluorophenyl)sulfone solution is slowly added dropwise until completely added, and the reaction is allowed to proceed for a certain period of time. The resulting product is added to water and stirred, filtered to obtain a brown solid, and purified by column chromatography after Soxhlet extraction. The purified solid is dissolved in a mixture of water and organic solvent, alkali is added, and the mixture is stirred and refluxed for 18 hours. Tetrahydrofuran is removed by rotary evaporation. The pH of the solution is adjusted with acid, and the solid product is filtered and placed in a vacuum drying oven at 60°C for 12 hours to obtain a yellow fluorescent probe compound, labeled SPC-dca.

2. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The organic solvent is N,N-dimethylformamide.

3. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The mass ratio of methyl 3,6-carbazole dicarboxylate:sodium hydride:bis(4-fluorophenyl)sulfone is 3:1:

1.

4. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The reaction temperature of the mixed solution is 100-150℃, and the reaction time is 18-32h.

5. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The reaction products were first extracted with dichloromethane and methanol using a Soxhlet extraction method for 4-12 hours.

6. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The Soxhlet extract was purified by column chromatography using ethyl acetate:dichloromethane in a volume ratio of 1:1 as the eluent.

7. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, The alkali used during the stirring and reflux of the purified product is potassium hydroxide.

8. The DAD-type organic fluorescent probe and its preparation method according to claim 1, characterized in that, Adjust the pH of the solution to 1 using 1M hydrochloric acid.

9. An application of the DAD-type organic fluorescent probe for detecting iron ions as described in claim 1, characterized in that, The solid fluorescent probe is dissolved in DMF and mixed with the solution to be tested. The fluorescence emission spectrum of the mixed solution is detected, and the iron ions in the solution are detected by the change in fluorescence intensity.

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