Synthesis and application of a class of aggregation-induced luminophores with mechanochromic luminescence properties

Abstract

The present invention discloses a synthesis method and application of a class of α-cyanoethylene aggregation-induced emission-type luminophores with mechanochromic luminescence properties. α-cyanoethylene mechanochromic fluorophores can trigger a transient fluorescence color response immediately after external mechanical stimulation and are therefore widely used in fields such as photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multi-color rapid response codes, and comprehensive information encryption systems. This series of compounds has a simple synthesis route, a high reaction yield, and uses inexpensive and easily synthesized raw materials. The products have good thermal stability, do not require special storage conditions, and have a high overall synthesis efficiency. This method is more easily promoted for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and specifically relates to a synthesis method and application of an aggregation-induced luminophore with mechanochromic luminescence properties. Background Art

[0002] Mechanochromic fluorescence (MFC) materials are a hot topic in the research field of new smart materials. The intelligent control of the solid-state luminescence properties of materials has always been a driving force for exploration. Studies have found that this type of color-changing materials with a special response mechanism can undergo dual changes in appearance and fluorescence color after external stimuli such as squeezing, grinding, and friction. However, most organic fluorophores will cause fluorescence quenching due to the close π-π stacking between solid molecules, which greatly limits their application prospects as solid-state emission devices. In addition, it is difficult to achieve the transition from crystalline phase to amorphous phase through molecular stacking mode. Therefore, it is still an outstanding challenge to design a class of aggregation-induced emission-type luminophores with adjustable appearance or emission color at the solid level. In 2001, Academician Tang Benzhong first proposed the concept of aggregation-induced emission (AIE), which enables solid molecules in the aggregated state to still maintain good emission characteristics. Later studies showed that fluorescence color changes can be induced by mechanical force stimulation. Based on the theoretical research on mechanochromism induced by cyanoethylene functionalization, the cyanodiphenylethylene core is used and AIE fluorophores with different color enhancement effects are introduced on both sides to effectively achieve a controllable mechanochromic effect carrying AIE characteristics, which becomes an important strategy for obtaining an ideal smart MFC material with aggregation-induced luminescent properties of mechanochromic luminescence. Summary of the Invention

[0003] The present invention aims to introduce macromolecular AIE fluorophores at the end of cyanoethylene units with excellent mechanochromic effects to achieve good solid-state color-changing properties. This design employs a typical dicyanodiphenylvinyl (DCPV)-type AIE small molecule system with tunable intramolecular charge transfer (ICT) properties between the substituent and the core. This provides a simple and effective synthetic strategy for obtaining aggregation-induced luminophores with mechanochromic luminescence properties. Because these luminophores can immediately trigger transient fluorescence color responses upon external mechanical stimulation, they are widely used in fields such as photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multicolor rapid-response codes, and comprehensive information encryption systems. The present invention uses 4,4'-dibromobenzophenone as a raw material to prepare a 4,4'-dibromodicyanophenylvinyl (BrDCPV) intermediate through a Knoevenagel condensation reaction. Under base catalysis conditions, BrDCPV is heated to reflux in a mixed system of toluene and ethanol, and a class of α-cyanoethylene mechanochromic fluorophores is prepared through a Suzuki coupling reaction, providing a new idea for the synthesis of aggregation-induced emission-type luminophores with mechanochromic luminescence properties.

[0004] In order to further optimize the traditional aggregation-induced emission small molecules and add unique mechanochromic fluorescence properties, the present invention proposes a type of aggregation-induced luminophore with mechanochromic emission properties with the structural formula:

[0005]

[0006] Here, R is one of triphenyltriazine, tetraphenylethylene, or triphenylamine. α-Cyanoethylene mechanochromic fluorophores can trigger transient fluorescence color responses immediately after mechanical stimulation. Therefore, they are widely used in photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multicolor rapid-response codes, and comprehensive information encryption systems.

[0007] In order to more efficiently prepare the above-mentioned aggregation-induced luminophore with mechanochromic luminescence properties, the technical solution of the present invention proposes a simple cyanoethylene functionalization synthesis method, which includes the following steps:

[0008] Step 1: Synthesis. Using the obtained 4,4'-dibromodicylon (BrDCPV) intermediate as the raw material, under base-catalyzed conditions, BrDCPV is heated under reflux in a mixture of toluene and ethanol to prepare a class of α-cyanoethylene mechanochromic fluorophores via a Suzuki coupling reaction. The reaction formula is:

[0009]

[0010] Step 2: Extraction. After the reaction is complete, extract the cooled reaction product 2-3 times with a good solvent, collect the organic phase solution, wash the collected organic phase solution with saturated brine 2-3 times, and then dry it with anhydrous magnesium sulfate to obtain a mixture of the crude reaction product and the good solvent;

[0011] Step 3: Purification: The mixture of the crude reaction product and a good solvent was distilled under reduced pressure until a small amount of solvent remained, and the pure product was further obtained by silica gel column chromatography using dichloromethane / petroleum ether (V / V = 1:2) as the eluent.

[0012] The various raw materials used in the present invention are commercial reagents with low prices. The intermediates are relatively simple to prepare and have good thermal stability and do not require special storage conditions. The overall synthetic route is simple, the yield is high, and the pollution is low.

[0013] In order to better prepare α-cyanoethylene mechanical chromophore, the preferred technical solution is that the molar ratio of the first step intermediate BrDCPV and R-pinacol ester is 1:2.5, the solvent is toluene and ethanol, the reaction temperature is reflux, and the reaction time is 24h.

[0014] In order to improve the extraction efficiency of the reactants, a preferred technical solution is that the good solvent in the second step is dichloromethane.

[0015] In order to improve the purification efficiency, the preferred technical solution is that the eluent used for column chromatography purification is dichloromethane and petroleum ether (V / V=1:2), and the product and impurities can be well separated in this system.

[0016] In order to better promote the application of this type of aggregation-induced luminescent material with mechanochromic luminescence properties, it is now proposed that this aggregation-induced luminescent material be used in the fields of photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multi-color rapid response codes and comprehensive information encryption systems.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1. The present invention proposes an aggregation-induced emission-type luminophore with mechanochromic luminescence properties, further optimizing traditional aggregation-induced luminescence small molecules and adding unique mechanofluorescent color-changing properties. This series of compounds has potential application value in the fields of photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multi-color rapid response codes, and comprehensive information encryption systems.

[0019] 2. The present invention uses 4,4'-dibromodicylon as raw material, achieves heating reflux in a toluene and ethanol mixture system under base catalysis conditions, and prepares a class of α-cyanoethylene mechanochromic fluorophores through Suzuki coupling reaction, which provides a new idea for the synthesis of aggregation-induced emission-type luminophores with mechanochromic luminescence properties.

[0020] 3. The various raw materials used in the synthesis of the present invention are cheap and easily available, the intermediates are simple to prepare and have stable performance, and do not require special storage conditions; the relevant reagents and solvents are commonly used commercial reagents with low cost; the overall synthesis route is simple, the yield is high, and the pollution is small; the synthesis method includes three steps of synthesis, extraction and purification, and the purification only requires washing with a solvent. Compared with other aggregation-induced luminescence materials, the synthesis steps are simplified, making this method easier to promote industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the structure of a synthetic compound;

[0022] Figure 2 This is a comparison of the fluorescence emission spectra of TADCPV in solutions with different volume ratios (water and tetrahydrofuran).

[0023] Figure 3 It is the fluorescence emission spectrum of TADCPV raw powder after grinding-fumigation cycle.

[0024] Figure 4 It is TADCPV solid powder fatigue test. DETAILED DESCRIPTION

[0025] Below in conjunction with the accompanying drawings and Examples, the specific embodiment of the present invention is further described.The following examples are only used to more clearly illustrate technical scheme of the present invention, and can not limit protection scope of the present invention with this.The process, conditions, reagents, experimental techniques, testing methods etc. of implementing the present invention, except the content mentioned specifically below, are common knowledge and common common sense in this area, and the present invention has no particular restrictions.The data that following examples provide include specific operations and reaction conditions and product.Product purity is all through nuclear magnetic resonance, high resolution mass spectrum and PXRD powder diffraction technical analysis and identification, and structure is accurately characterized.

[0026] An α-cyanoethylene mechanochromic fluorophore, the structural formula of which is shown below:

[0027]

[0028] Wherein, R is one of triphenyltriazine, tetraphenylethylene and triphenylamine.

[0029] The above-mentioned method for synthesizing the α-cyanoethylene-based mechanochromic fluorophore comprises the following steps:

[0030] Step 1: Synthesis. Using the obtained 4,4'-dibromodicylon (BrDCPV) intermediate as the raw material, under base-catalyzed conditions, BrDCPV is heated under reflux in a mixture of toluene and ethanol to prepare a class of α-cyanoethylene mechanochromic fluorophores via a Suzuki coupling reaction. The reaction formula is:

[0031]

[0032] Step 2: Extraction. After the reaction is complete, extract the cooled reaction product 2-3 times with a good solvent, collect the organic phase solution, wash the collected organic phase solution with saturated brine 2-3 times, and then dry it with anhydrous magnesium sulfate to obtain a mixture of the crude reaction product and the good solvent;

[0033] Step 3: Purification: The mixture of the crude reaction product and a good solvent was distilled under reduced pressure until a small amount of solvent remained, and the pure product was further obtained by silica gel column chromatography using dichloromethane / petroleum ether (V / V = 1:2) as the eluent.

[0034] In order to better prepare α-cyanoethylene mechanical chromophore, the preferred technical solution is that the molar ratio of the first step intermediate BrDCPV and R-pinacol ester is 1:2.5, the solvent is toluene and ethanol, the reaction temperature is reflux, and the reaction time is 24h.

[0035] In order to improve the extraction efficiency of the reactants, a preferred technical solution is that the good solvent in the second step is dichloromethane.

[0036] In order to improve the purification efficiency, the preferred technical solution is that the eluent used for column chromatography purification is dichloromethane and petroleum ether (V / V=1:2), and the product and impurities can be well separated in this system.

[0037] In order to better promote the application of this type of aggregation-induced luminescent material with mechanochromic luminescence properties, it is now proposed that this aggregation-induced luminescent material be used in the fields of photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multi-color rapid response codes and comprehensive information encryption systems.

[0038] Example 1

[0039] Taking the synthesis of compound TADCPV as an example, the chemical reaction formula is as follows:

[0040]

[0041] The intermediate BrDCPV (388.3 mg, 1 mmol), 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine (1.305 g, 3 mmol), K2CO3 (11.4 g / 40 mL, 2 M), and Pd(PPh3)4 (115.6 mg, 0.1 mmol) were added to toluene (40 mL), and ethanol (20 mL) was added to the mixture. The reaction mixture was then heated to reflux under N2 protection for 24 hours. The crude product was cooled to room temperature and quenched with water (60 mL). The mixture was extracted with dichloromethane (3 × 80 mL), and the combined extracts were washed with water and brine, dried over MgSO4, and concentrated. The crude product was further purified by silica gel column chromatography using DCM / PE (1:2) as eluent. 548 mg of light yellow solid TADCPV was obtained (yield: 64.6%); melting point was 137-139°C.

[0042] 1 H NMR (400 MHz, CDCl3, ppm) δ H =7.04–7.14(m,17H,TPE–H),7.38–7.43(t,4H,TPE–H)7.48–7.51(d,2H,J=8.4Hz,Ar–H),7.65–7.68(m,4H,Ar-H),7.85–7.87(d,J=8.4Hz,2H,Ar–H); 13 C NMR (100 MHz, CDCl3, ppm): δ C=80.2,114.3,126.4,126.5,126.3,126.9,127.1,127.7,127.9,130.7,131.3,13 1.4,132.0,132.1,136.2,136.9,137.6,140.2,140.3,143.5,143.6,143.7,143.9 144.7,145.1,174.0,196.0; FAB-MS:m / z calcd for C 52 H 36 N4890.3661[M + ]; found 890.3651[M + ].

[0043] Example 2

[0044] The difference between Example 2 and Example 1 is that the molar ratio of the intermediate BrDCPV and 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine is 1:2, while that of Example 1 is 1:3. The yield of the isolated target compound TADCPV is 45.2%, and some raw material BrDCPV remains in the middle. The test data is the same as that of Example 1.

[0045] Example 3

[0046] The difference between Example 3 and Example 1 is that the molar ratio of the intermediate BrDCPV and 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine is 1:2.5, while that of Example 1 is 1:3. The yield of the isolated target compound TADCPV is 60.2%, and the test data is the same as that of Example 1.

[0047] Example 4

[0048] The difference between Example 4 and Example 1 is that the reaction temperature is room temperature, while the reaction temperature in Example 1 is reflux. The yield of the isolated target compound TADCPV is 18%, and the test data is the same as that of Example 1.

[0049] Example 5

[0050] The difference between Example 5 and Example 1 is that the reaction temperature is 60° C., while the reaction temperature in Example 1 is reflux. The yield of the isolated target compound TADCPV is 32.6%, and the test data is the same as that in Example 1.

[0051] Example 5

[0052] The difference between Example 5 and Example 1 is that the reaction time is 12 hours, while the reaction time in Example 1 is 24 hours. The yield of the isolated target compound TADCPV is 40.2%, and the test data is the same as that in Example 1.

[0053] Example 6

[0054] The difference between Example 6 and Example 1 is that the reaction time is 36 hours, while the reaction time in Example 1 is 24 hours. The yield of the isolated target compound TADCPV is 66.2%. The test data is the same as that in Example 1.

[0055] The drugs used in this embodiment are all commercially available chemical reagents.

[0056] The experimental results showed that Example 1 was the optimal reaction synthesis condition. Although Example 3 had a yield close to that of Example 1 and used less raw materials, some intermediate BrDCPV remained in Example 3, indicating incomplete reaction. Example 6 had a slightly higher yield than Example 1, but suffered from a longer reaction time. Therefore, the optimal reaction conditions were determined to be Example 1: a 1:3 molar ratio of the main reactants, reflux temperature, and a reaction time of 24 h.

[0057] Example 7

[0058] The aggregation-induced luminescence and mechanochromic properties of the target compound TADCPV in Test Example 1 were as follows:

[0059] Step 1: The target compound TADCPV of Example 1 was prepared at a concentration of 1×10 -7 mol / L of 11 solutions, the solvent is a mixture of water (poor solvent) and tetrahydrofuran (good solvent), wherein the volume ratios of tetrahydrofuran to water are 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, and 1:99 respectively;

[0060] Step 2: Use a fluorescence spectrometer to perform fluorescence tests on 11 solutions of the target compound TADCPV.

[0061] The experimental results show that: Figure 3As shown, the peak value of the maximum fluorescence emission intensity of the target compound TADCPV shows a trend of increasing with the increase of the water volume content in the solvent, and when the water content reaches 99%, a sudden increase in fluorescence is observed, and the maximum peak value of the maximum fluorescence emission intensity appears at the same time. Compared with the THF solution with an initial water content of 0%, the fluorescence ratio increases by about 4 times. The peak values ​​of the maximum fluorescence emission intensity of the target compounds TPEDCPV and TPADCPV measured by the same method also increase with the increase of the water volume content in the solvent, and both reach the maximum fluorescence emission intensity at a water content of 99%, and the fluorescence ratio increases by about 20 times and 330 times, respectively. This shows that the three target compounds prepared by the synthesis method of the present invention all exhibit significant aggregation-induced emission enhancement effects.

[0062] Step 3: Prepare the original powder samples of the three target products, the sample powder after mechanical grinding, and the samples obtained by dispersion and evaporation of dichloromethane solvent after grinding, respectively. Use a fluorescence spectrometer to test the fluorescence emission wavelength of the solid samples in the three states. The maximum fluorescence emission peaks of the three target compounds all showed a blue shift first and then returned to the initial state, realizing a perfect reversible cycle of mechanical color change. Afterwards, 10 anti-fatigue tests were carried out, and all showed excellent reversibility, indicating that the three target compounds prepared by the synthesis method of the present invention all exhibit reversible mechanical color change behavior.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A class of α-cyanoethylene compounds, the structural formula of which is shown below: in, R is one of triphenyltriazine, tetraphenylethylene, and triphenylamine.

2. The synthesis method of the aforementioned α-cyanoethylene-based mechanochromic fluorophore comprises the following steps: Step 1: Synthesis: Using the obtained 4,4'-dibromodicyanophenylvinyl (BrDCPV) intermediate as the raw material, under base catalysis, BrDCPV is heated under reflux in a mixed system of toluene and ethanol to prepare a class of α-cyanoethylene mechanochromic fluorophores through Suzuki coupling reaction. The reaction formula is: Step 2: Extraction: After the reaction is completed, the cooled reaction product is extracted with a good solvent 2 to 3 times, and the organic phase solution is collected. The collected organic phase solution is washed with saturated brine 2 to 3 times in sequence, and then dried with anhydrous magnesium sulfate to obtain a mixture of the crude reaction product and the good solvent; Step 3: Purification: The mixture of the crude reaction product and a good solvent is distilled under reduced pressure until a small amount of solvent remains, and the pure product is further obtained by silica gel column chromatography using dichloromethane / petroleum ether as eluent.

3. The method for synthesizing an α-cyanoethylene mechanochromic fluorophore according to claim 2, wherein the molar ratio of the first intermediate BrDCPV to R-pinacol ester in step 1 is 1:2-3, the solvent is toluene and ethanol, the reaction temperature is reflux, and the reaction time is 12-36 hours.

4. The method according to claim 2, wherein the molar ratio of the intermediate BrDCPV and 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1,3,5-triazine is 1:3, the reaction temperature is reflux, the reaction time is 24h, and the yield of the target product is the highest.

5. The method for synthesizing an α-cyanoethylene mechanochromic fluorophore according to claim 2, wherein: The good solvent in step 2 is dichloromethane.

6. The use of the compound according to claim 1, characterized in that The compound is used in photosensors, organic light-emitting diodes (OLEDs), fluorescent probes, multi-color rapid response codes and a full range of information encryption systems.

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