Difluoroboron β-diketonate complex fluorescent probe, preparation method and application thereof

Abstract

The present invention belongs to the technical field of organic synthesis, and specifically relates to a difluoroboron β-diketonate complex fluorescent probe, a preparation method thereof, and an application. The fluorescent probe has a chemical structural formula as shown in Formula a; wherein, R has a structure of Formula b or Formula c. The fluorescent probe of the present invention has a piezochromic effect, with a wavelength change of 87 nm before and after grinding, and is expected to be applied to information encryption; at the same time, the fluorescent probe has a solvatochromic effect, AIE characteristics, and its fluorescence is highly sensitive to water below 1.0%, and can be applied to the detection of trace water in organic solvents.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a difluoroboron β-diketonate complex fluorescent probe, a preparation method thereof, and an application thereof. Background Art

[0002] Organic light-emitting materials have attracted great attention in the past few years due to their fascinating photophysical properties. Some organic light-emitting molecules can be applied to sensors and bioimaging in solution, and some organic light-emitting molecules in their solid form can be applied to optoelectronic devices or data encryption. Among them, aggregation-induced emission (AIE) molecules can emit light with high efficiency in the solid state or in the aggregated state, and are applied to biosensing, organic optoelectronic systems, diagnosis and treatment, etc. due to their unique AIE characteristics. However, most aggregation-induced emission (AIE) molecules can only emit light with high efficiency in a single phase, such as either in the solution phase, or in the solid phase or the aggregated state, etc. Therefore, despite significant progress in the development of luminescent compounds, there is an increasing demand for materials that can maintain emission in both states.

[0003] Among the numerous aggregation-induced emission (AIE) materials reported currently, TPE derivatives have received increasing attention and research due to their ease of synthesis and functionalization. For example, in the prior art, H. Sun, et al, A new AIE and TICT-active tetraphenylethene-based thiazole compound: Synthesis, structure, photophysical properties and application for water detection in organic solvents, Sensors and Actuators B, 2018, 267, 448 - 456, prepared a new AIE and TICT-active tetraphenylethene-based thiazole compound. The fluorescence of this compound is highly sensitive to water below 1.0%, so its performance as a trace water detection sensor was further tested. The detection limit (DL) and quantification limit (QL) were estimated based on the following equations: DL = 3.3σ / S and QL = 10σ / S (σ = standard deviation of blank samples), S = slope of the calibration curve at low water content (below 1.0% (v / v)). The DL and QL in tetrahydrofuran were 0.019 and 0.059% (v / v), respectively. Unfortunately, this organic compound needs to be synthesized through five-step chemical reactions, and the synthesis process is relatively complex; this study only presented the solvatochromic effect, AIE characteristics of the luminescent molecule in solution, and its application in trace water detection in organic solvents, without studying its luminescence properties in the solid state. W. J. Liu, et al, Exploration the inherent mechanism of polymorphism and mechanochromism based on isomerism and AIE theory, Dyes and Pigments, 2019, 171, 107663, designed and synthesized two new difluoroboron β-diketonate complexes TPEB2T and TPEB3T based on the isomeric effect of helical TPE units and thiophene, and showed significant AIE effects, solvatochromism, and mechanochromic fluorescence properties. However, the maximum wavelength change before and after grinding was only 66 nm, and its application in any field was not studied. Summary of the Invention

[0004] The present invention provides a difluoroboron β-diketonate complex fluorescent probe, its preparation method and application. This fluorescent probe has strong luminescence properties in solution phase, solid phase and aggregated state. This fluorescent probe has a pressure-induced color change effect, with a wavelength change of 87 nm before and after grinding, and is expected to be applied to information encryption. At the same time, this fluorescent probe has a solvatochromic effect and AIE characteristics, and its fluorescence is highly sensitive to water below 1.0%, and can be applied to the detection of trace water in organic solvents.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The first object of the present invention is to provide a difluoroboron β-diketonate complex fluorescent probe, which has a chemical structural formula as shown in formula a:

[0007]

[0008] Among them, R1 has a structure of formula b or formula c;

[0009]

[0010] The second object of the present invention is to provide a preparation method of the above difluoroboron β-diketonate complex fluorescent probe, including the following steps:

[0011] Step 1: Dissolve 1-(4-bromophenyl)-1,2,2-triphenylethylene, acetylphenylboronic acid, tetrakis(triphenylphosphine)palladium, tetrabutylammonium bromide and potassium carbonate in a solvent, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, extract, rotary evaporate and chromatograph to obtain an intermediate product S1;

[0012] Step 2: Dissolve the intermediate product S1 in tetrahydrofuran, add NaH and stir the reaction at 0-5 °C, then add methyl thiophene-2-carboxylate or methyl p-cyanobenzoate, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate and chromatograph to obtain an intermediate product S2;

[0013] Step 3: Dissolve the intermediate product S2 in dichloromethane, add triethylamine and react at room temperature, then add boron trifluoride diethyl etherate, and react in the dark at room temperature. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate and chromatograph to obtain the difluoroboron β-diketonate complex fluorescent probe.

[0014] Preferably, in step 1, the molar ratio of 1-(4-bromophenyl)-1,2,2-triphenylethylene, acetylphenylboronic acid, tetrakis(triphenylphosphine)palladium, tetrabutylammonium bromide and potassium carbonate is 1:1.02-1.2:0.001-0.008:0.5:1.8.

[0015] Preferably, in step 1, the solvent is toluene and water, the volume ratio of toluene to water is 4:1, the temperature of the heating reflux reaction is 80 - 85°C, and the time is 12 - 24 h.

[0016] Preferably, in step 2, the molar ratio of the intermediate S1, methyl thiophene - 2 - carboxylate and NaH is 1:3:6; the molar ratio of the intermediate S1, methyl 4 - cyanobenzoate and NaH is 1:2 - 3:4 - 6.

[0017] Preferably, in step 2, the reaction is stirred at 0°C for 0.5 - 1 h, the temperature of the heating reflux reaction is 66 - 70°C, and the time is 12 - 24 h.

[0018] Preferably, in step 3, the molar ratio of the intermediate S2, triethylamine and boron trifluoride diethyl etherate is 1:2:1.15 - 2.

[0019] Preferably, in step 3, the reaction time for adding triethylamine is 0.5 - 1 h; the reaction time for room - temperature light - avoiding reaction is 12 - 24 h.

[0020] In steps 1, 2 and 3, the solvent used for extraction is dichloromethane, and the eluent for chromatography is petroleum ether and ethyl acetate, and the volume ratio of petroleum ether to ethyl acetate is 2 - 4:1 - 2.

[0021] The third object of the present invention is to provide the application of the above - mentioned difluoroboron β - diketonate complex fluorescent probe in detecting trace water in organic solvents.

[0022] The present invention has the following beneficial effects compared with the prior art:

[0023] The present invention provides a tetraphenylethylene - based difluoroboron β - diketonate complex fluorescent probe with multiphase luminescence. This compound has strong luminescence properties in the solution phase, solid phase and aggregated state. This compound has a piezochromic effect, and the wavelength changes by 87 nm before and after grinding, and is expected to be applied to information encryption. At the same time, this organic luminescent compound has a solvatochromic effect, AIE characteristics, and its fluorescence is highly sensitive to water below 1.0%, and can be applied to the detection of trace water in organic solvents. Description of the Drawings

[0024] Figure 1 It is the structural diagram of the fluorescent probe prepared in Example 1 of the present invention;

[0025] Figure 2 It is the structural diagram of the fluorescent probe prepared in Example 2 of the present invention;

[0026] Figure 3 It is the normalized fluorescence emission spectrum of the compound prepared in Example 1 of the present invention in different solid states;

[0027] Figure 4 X-ray diffraction patterns of the compound prepared in Example 1 of the present invention in different solid states;

[0028] Figure 5 Fluorescence intensities of the compound prepared in Example 1 of the present invention in tetrahydrofuran with different water contents;

[0029] Figure 6 Variation of the fluorescence peak of the compound prepared in Example 1 of the present invention in tetrahydrofuran with water content;

[0030] Figure 7 Calibration equation for determining the water content in the fluorescence probe THF with the compound prepared in Example 1 of the present invention. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0033] A difluoroboron β-diketonate complex fluorescence probe has a chemical structural formula as shown in Formula a:

[0034]

[0035] Among them, R1 has a structure of Formula b or Formula c;

[0036]

[0037] The preparation method of the above difluoroboron β-diketonate complex fluorescence probe includes the following steps:

[0038] Step 1: Dissolve 1-(4-bromophenyl)-1,2,2-triphenylethylene, acetylphenylboronic acid, tetrakis(triphenylphosphine)palladium, tetrabutylammonium bromide and potassium carbonate in a solvent, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, extract, rotary evaporate and chromatograph to obtain an intermediate product S1;

[0039] Step 2: Dissolve the intermediate S1 in tetrahydrofuran, add NaH and stir the reaction at 0 - 5 °C, then add methyl thiophene-2-carboxylate or methyl 4-cyanobenzoate, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate, and chromatograph to obtain the intermediate S2;

[0040] Step 3: Dissolve the intermediate S2 in dichloromethane, add triethylamine and react at room temperature, then add boron trifluoride diethyl etherate and react in the dark at room temperature. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate, and chromatograph to obtain the difluoroboron β-diketonate complex fluorescent probe.

[0041] The specific synthesis route is as follows:

[0042]

[0043] Example 1

[0044] A preparation method of a difluoroboron β-diketonate complex fluorescent probe, comprising the following steps:

[0045] Step 1: Weigh 1.15 g of 1-(4-bromophenyl)-1,2,2-triphenylethylene, 410 mg of phenylboronic acid, 23.1 mg of tetrakis(triphenylphosphine)palladium, 451.3 mg of tetrabutylammonium bromide, and 690 mg of potassium carbonate, dissolve them in a solvent of 50 mL of toluene and water (the volume ratio of toluene to water is 4:1), introduce nitrogen, and stir and heat for a reflux reaction at 85 °C for 24 h under a nitrogen atmosphere. After the reaction is completed, cool to room temperature, extract with dichloromethane, rotary evaporate the solvent, and obtain the intermediate S1 through column chromatography (silica gel, petroleum ether:ethyl acetate = 2:1);

[0046] Step 2: Weigh 720.9 mg of the intermediate S1 and dissolve it in 5 mL of anhydrous tetrahydrofuran (THF). Add 336 mg of NaH and react for 0.5 h at 0 °C, then add 597.1 mg of methyl thiophene-2-carboxylate, introduce nitrogen, and stir and heat for a reflux reaction at 70 °C for 24 h under a nitrogen atmosphere. After the reaction is completed, cool to room temperature, adjust the pH to neutral with dilute hydrochloric acid, extract with dichloromethane, rotary evaporate the solvent, and obtain the intermediate S2 through column chromatography (silica gel, petroleum ether:ethyl acetate = 4:1);

[0047] Step 3: Weigh 1108.1 mg of the intermediate S2 and dissolve it in 5 mL of dichloromethane. Add 0.06 mL of triethylamine and react at room temperature for 0.5 h, then add 1.12 mL of boron trifluoride diethyl etherate and react in the dark at room temperature for 24 h. After the reaction is completed, adjust the pH to neutral with sodium hydroxide, extract with dichloromethane, rotary evaporate the solvent, and obtain the tetraphenylethylene difluoroboron β-diketonate complex through column chromatography (silica gel, petroleum ether:dichloromethane = 3:2), and the structural formula is asFigure 1 as shown

[0048] Example 2

[0049] A preparation method of a difluoroboron β-diketonate complex fluorescent probe, comprising the following steps:

[0050] Step 1: Weigh 1.15 g of 1-(4-bromophenyl)-1,2,2-triphenylethylene, 410 mg of acetylphenylboronic acid, 23.1 mg of tetrakis(triphenylphosphine)palladium, 451.3 mg of tetrabutylammonium bromide and 690 mg of potassium carbonate, dissolve them in a solvent of 50 mL of toluene and water (the volume ratio of toluene to water is 4:1), introduce nitrogen, stir and heat under reflux at 85 °C in a nitrogen atmosphere for 24 h. After the reaction is completed, cool to room temperature, extract with dichloromethane, spin-dry the solvent, and obtain the intermediate product S1 through column chromatography (silica gel, petroleum ether:ethyl acetate = 2:1);

[0051] Step 2: Weigh 720.9 mg of the intermediate product S1 and dissolve it in 5 mL of anhydrous tetrahydrofuran (THF). Add 336 mg of NaH at 0 °C and react for 0.5 h, then add 773.6 mg of methyl p-cyanobenzoate, introduce nitrogen, stir and heat under reflux at 70 °C in a nitrogen atmosphere for 24 h. After the reaction is completed, cool to room temperature, adjust the pH to neutral with dilute hydrochloric acid, extract with dichloromethane, spin-dry the solvent, and obtain the intermediate product S2 through column chromatography (silica gel, petroleum ether:ethyl acetate = 4:1);

[0052] Step 3: Weigh 1108.1 mg of the intermediate product S2 and dissolve it in 5 mL of dichloromethane. Add 0.06 mL of triethylamine and react for 0.5 h, then add 1.12 mL of boron trifluoride diethyl etherate, and react at room temperature in the dark for 24 h. After the reaction is completed, adjust the pH to neutral with sodium hydroxide, extract with dichloromethane, spin-dry the solvent, and obtain the tetraphenylethylene difluoroboron β-diketonate complex through column chromatography (silica gel, petroleum ether:dichloromethane = 3:2), and the structural formula is as Figure 2 as shown

[0053] The solid powder of the tetraphenylethylene difluoroboron β-diketonate complex prepared in Example 1 was ground in an agate mortar to obtain a ground sample. A few drops of dichloromethane were added to the ground solid powder, and then heated to prepare a sample subjected to solvent fumigation; the complex was dissolved in dichloromethane, and then n-hexane was added and allowed to stand for a period of time to precipitate crystals, obtaining a crystal sample. The spectral properties of the crystal, the solid powder before and after grinding, and the sample subjected to solvent fumigation after grinding were tested.

[0054] The compound prepared in Example 1 showed yellow light emission under irradiation with a 365 nm ultraviolet lamp, and showed orange light emission under irradiation with a 365 nm ultraviolet lamp after grinding. Subsequently, its fluorescence spectrum was tested,Figure 3 Normalized fluorescence emission spectra of different solid states of the compound prepared in Example 1 of the present invention. As Figure 3 shown, in different solid states, the emission peak of the crystal sample is located at 516 nm, the emission peak of the solid powder is located at 550 nm, the emission peak of the ground sample redshifts to 637 nm, and the emission peak of the sample after solvent fumigation returns to 559 nm.

[0055] Meanwhile, to further explore the piezochromic effect, X-ray diffraction (PXRD) was tested for these four states respectively. Figure 4 X-ray diffraction patterns of different solid states of the compound prepared in Example 1 of the present invention. As Figure 4 shown, it can be seen that after the solid powder was ground, the sharp peaks disappeared and broad diffraction peaks appeared, indicating that grinding produced a new state. After the ground sample was fumigated, the disappeared peaks reappeared, indicating that the random molecular arrangement changed to an ordered aggregate.

[0056] Using the compound prepared in Example 1 as a fluorescence probe, the application of water detection in organic solvents was further explored.

[0057] Qualitative detection: Accurately weigh 0.0070 g of the fluorescence probe and dissolve it in 3 mL of ethyl acetate for standby.

[0058] Qualitative judgment is as follows: Pipette 100 μL of the above-prepared ethyl acetate solution of the fluorescence probe into two sample bottles, dry them in an oven, and then add 5 mL of the tetrahydrofuran to be tested and the tetrahydrofuran solution with 1% water content respectively. Irradiate with a 365 nm ultraviolet lamp and observe the fluorescence brightness of the tetrahydrofuran to be tested and the tetrahydrofuran solution with 1% water content; if the fluorescence brightness of the tetrahydrofuran to be tested is stronger than that of the tetrahydrofuran solution with 1% water content, the content of trace water in the tetrahydrofuran to be tested does not exceed 1%. Qualitative determination of trace water in organic solvents is achieved by visually comparing the fluorescence brightness between the organic solvent to be tested and the solvent with known water content under ultraviolet lamp irradiation.

[0059] Quantitative detection: Draw a standard curve. Accurately weigh 0.0070 g of the fluorescence probe and dissolve it in 3 mL of ethyl acetate for standby. In addition, prepare tetrahydrofuran solutions with water contents (v / v) of 0%, 0.05%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1.0%, 2.0%, 3.0%, and 5.0% for standby. Pipette 100 μL of the above-prepared ethyl acetate solution of the fluorescence probe respectively, and then add 5 mL of the tetrahydrofuran solutions with different water contents that have been prepared. Measure the fluorescence emission spectra of each solution with a fluorescence spectrophotometer and record the maximum fluorescence emission intensity of each solution.

[0060] Figure 5Fluorescence intensity of the compound prepared in Example 1 of the present invention at different water contents in tetrahydrofuran. As Figure 5 shown, where the y-axis represents fluorescence intensity and the x-axis represents the water content of the solution. As the water content increases, the fluorescence intensity gradually decreases.

[0061] Figure 6 Variation of the fluorescence peak of the compound prepared in Example 1 of the present invention in tetrahydrofuran with water content, as Figure 6 shown, where the y-axis represents fluorescence intensity and the x-axis represents the water content of the solution. When the water content is below 1%, there is an obvious linear relationship between the fluorescence intensities.

[0062] Based on the recorded maximum fluorescence emission intensities of each solution, a standard curve of fluorescence intensity versus water content v / v is made. The standard curve is: y = -4318.8x + 8859.5, Figure 7 which is the calibration equation for determining the water content in the fluorescence probe THF of the compound prepared in Example 1 of the present invention, as Figure 7 shown, where the y-axis represents the fluorescence intensity measured by the instrument and the x-axis (v / v) represents the water content of the tetrahydrofuran solution.

[0063] Determination of trace water in the tetrahydrofuran organic solvent to be tested: Pipette 100 μL of the above-mentioned ethyl acetate solution of the fluorescence probe prepared into a sample bottle, dry it in an oven, and then add 5 mL of the tetrahydrofuran organic solvent to be tested. Measure its maximum fluorescence emission intensity with a fluorescence spectrophotometer, substitute this value into the standard curve, and calculate that the content of trace water in the tetrahydrofuran organic solvent to be tested is 0.36%.

[0064] The estimation of the detection limit (DL) and quantification limit (QL) is based on the following equations: DL = 3.3σ / S and QL = 10σ / S (σ = standard deviation of the blank sample, S = slope of the calibration curve at low water content (below 1.0% (v / v)). The DL and QL in tetrahydrofuran are 0.0005 and 0.15% (v / v), respectively.

[0065] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step methods are the same as those in the examples, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications therein.

Claims

1. A difluoroboron β-diketonate complex fluorescent probe, characterized in that, It has a chemical structural formula shown in Formula a: wherein, R has a structure of Formula b or Formula c; * is the connection site.

2. A method for preparing a difluoroboron β-diketonate complex fluorescent probe according to claim 1, characterized in that, It includes the following steps: Step 1: Dissolve 1-(4-bromophenyl)-1,2,2-triphenylethylene, acetylphenylboronic acid, tetrakis(triphenylphosphine)palladium, tetrabutylammonium bromide and potassium carbonate in a solvent, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, extract, rotary evaporate and chromatograph to obtain the intermediate S1; Step 2: Dissolve the intermediate S1 in tetrahydrofuran, add NaH and stir the reaction at 0-5 °C, then add methyl thiophene-2-carboxylate or methyl 4-cyanobenzoate, and carry out a heating reflux reaction under a protective gas atmosphere. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate and chromatograph to obtain the intermediate S2; Step 3: Dissolve the intermediate S2 in dichloromethane, add triethylamine and react at room temperature, then add boron trifluoride diethyl ether and react in the dark at room temperature. After the reaction is completed, adjust the pH to neutral, extract, rotary evaporate and chromatograph to obtain the difluoroboron β-diketonate complex fluorescent probe.

3. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, characterized in that, In Step 1, the molar ratio of 1-(4-bromophenyl)-1,2,2-triphenylethylene, acetylphenylboronic acid, tetrakis(triphenylphosphine)palladium, tetrabutylammonium bromide and potassium carbonate is 1:1.02-1.2:0.001-0.008:0.5:1.

8.

4. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, wherein, In Step 1, the solvent is toluene and water, the volume ratio of toluene and water is 4:1, the temperature of the heating reflux reaction is 80-85 °C, and the time is 12-24 h.

5. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, wherein In Step 2, the molar ratio of the intermediate S1, methyl thiophene-2-carboxylate and NaH is 1:3:6; the molar ratio of the intermediate S1, methyl 4-cyanobenzoate and NaH is 1:2-3:4-6.

6. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, wherein, In Step 2, the stirring reaction is carried out at 0-5 °C for 0.5-1 h, the temperature of the heating reflux reaction is 66-70 °C, and the time is 12-24 h.

7. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, wherein, In Step 3, the molar ratio of the intermediate S2, triethylamine and boron trifluoride diethyl ether is 1:2:1.15-2.

8. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, characterized in that, In Step 3, the reaction time for adding triethylamine is 0.5-1 h; the reaction time for reacting in the dark at room temperature is 12-24 h.

9. The preparation method of the difluoroboron β-diketonate complex fluorescent probe according to claim 2, characterized in that, In Steps 1, 2 and 3, the solvent used for extraction is dichloromethane, and the eluent in chromatography is petroleum ether and ethyl acetate, and the volume ratio of petroleum ether and ethyl acetate is 2-4:1-2.

10. Application of the difluoroboron β-diketonate complex fluorescent probe described in Claim 1 in detecting trace water in organic solvents.

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