A multi-stimulus responsive aggregation-induced luminescence molecule and preparation method thereof

Abstract

The present invention belongs to the field of organic synthetic materials, and discloses a multi-stimulus responsive aggregation-induced luminescence molecule and a preparation method thereof. The present invention forms an electron push-pull system by introducing methoxytetraphenylethylene as an electron donor, vinylthiophene as a π bridge and indandione as an electron acceptor in the molecular structure, wherein the vinyl group in the molecular structure is sensitive to alkali, and the carbonyl group in indandione is sensitive to acid. The aggregation-induced luminescence molecule provided by the present invention exhibits aggregation-induced emission characteristics, a large Stokes shift (up to 267 nm), a maximum emission peak in the aggregated state / solid state greater than 650 nm, and high fluorescence quantum efficiency. The molecule has multi-stimulus responsive characteristics, as well as the characteristics of naked eye detection and rapid response.

Description

Technical Field

[0001] The invention belongs to the field of organic synthetic materials, and more specifically relates to a multi-stimulus responsive aggregation-induced luminescence molecule and a preparation method thereof. Background Art

[0002] Stimuli-responsive luminescent materials are materials with intelligent response characteristics. When subjected to external stimuli such as mechanical force (friction, grinding, scratching, etc.), heat, light, temperature, solvent polarity, pH value, current, magnetic field, acid and alkali, the luminescent properties (luminescent color, luminescent intensity or luminescent lifetime, etc.) change. This material has potential application value in fluorescence sensing, bioimaging, image display, information recording, ultra-high density and high-resolution information storage technology, nonlinear optoelectronic devices, pressure-sensitive elements, thermosensitive materials, reversible writing media, color-changing camouflage materials and anti-radiation protection materials, and has therefore attracted the interest of more and more scientists. Studies have shown that different stimulus factors cause changes in the molecular structure of the material or the interaction between molecules, which leads to changes in the luminescent properties. Therefore, by designing and optimizing these stimuli-responsive luminescent materials, precise control of luminescent color and luminescent intensity can be achieved.

[0003] At present, there have been many reports on luminescent materials that respond to single stimulus factors. For example, materials such as mechanoluminescence, photoluminescence, mechanoluminescence, electroluminescence, photochromism, mechanochromism and acidochromism. The luminescence range of these materials is generally between blue and red. There are few types of stimulus-responsive luminescent materials with longer emission wavelengths. At the same time, since materials with different stimulus responses have different requirements for molecular structures, the design and synthesis of organic luminescent materials with multi-stimulus responses is challenging. In addition, existing stimulus-responsive luminescent materials have disadvantages such as complex synthesis, low yield or harsh reaction conditions.

[0004] Multi-stimulus-responsive aggregation-induced luminescence materials have multi-mode transformation capabilities, can provide materials with more functions, and have wider application value in practical applications. Therefore, how to provide a multi-stimulus-responsive aggregation-induced luminescence molecule is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the present invention provides a multi-stimulus responsive aggregation-induced luminescence molecule and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A multi-stimulus responsive aggregation-induced luminescence molecule, the structural formula of which is shown below:

[0008] .

[0009] The present invention also provides a method for preparing the above-mentioned multi-stimulus responsive aggregation-induced luminescence molecule, comprising the following steps:

[0010] (1) Under nitrogen protection, bis-(4-methoxyphenyl)methanone and 4-bromobenzene-4-methoxybenzophenone were added to a reaction vessel, tetrahydrofuran solvent was added, and then zinc powder was added in a ratio of 1:0.3-1 to 4-bromobenzene-4-methoxybenzophenone. A titanium catalyst was added under ice-water bath conditions. After 30 minutes, the temperature was slowly raised to reflux temperature, the reaction was carried out for 4-5 hours, the solvent was removed under reduced pressure, and the intermediate 1 was purified by silica gel column chromatography to obtain the intermediate 1;

[0011] (2) Add intermediate 1 and 5-formyl-2-thiopheneboronic acid to a mixed solvent of ethanol and toluene, then add a palladium catalyst and an alkali solution, reflux for 8-10 hours under nitrogen, then cool the mixture to room temperature, pour it into water, extract with dichloromethane and wash with brine, combine the organic layers, dry with anhydrous magnesium sulfate, filter, evaporate the solvent, and purify by silica gel column chromatography to obtain intermediate 2;

[0012] (3) Add intermediate 2 and 1,3-indanedione to dichloromethane, then add aluminum catalyst, stir and heat to reflux for 2-3 hours, evaporate the solvent under reduced pressure, and purify by silica gel column chromatography to obtain an aggregation-induced emission molecule;

[0013] The synthesis route of the aggregation-induced emission molecule is as follows:

[0014] .

[0015] Preferably, the molar ratio of bis-(4-methoxyphenyl)methanone, 4-bromobenzene-4-methoxybenzophenone and zinc powder in step (1) is 1:1:0.3-1.5.

[0016] Preferably, the titanium catalyst in step (1) is selected from one of TiO2, Ti(NO3)4, and TiCl4.

[0017] Further preferably, the titanium catalyst in step (1) is TiCl4.

[0018] The beneficial effects of the above technical solution are: based on the fact that TiO2 and Ti(NO3)4 are solid, and Ti(NO3)4 catalyzes this reaction extremely violently, while TiCl4 is a liquid catalyst and the reaction proceeds gently.

[0019] Preferably, in step (2), the molar ratio of the intermediate 1, 5-formyl-2-thiopheneboronic acid and the palladium catalyst is 1:1.5:0.05-0.2.

[0020] Preferably, the palladium catalyst in step (2) is selected from one of PdCl2 and Pd(PPh3)4.

[0021] Further preferably, the palladium catalyst in step (2) is Pd(PPh3)4.

[0022] Preferably, the alkaline solution in step (2) is selected from one of Na2CO3 solution, K2CO3 solution, KOH solution and NaOH solution.

[0023] Further preferably, the alkaline solution in step (2) is a K2CO3 solution.

[0024] Preferably, in step (3), the molar ratio of the intermediate 2, 1,3-indanedione and the aluminum catalyst is 1:1:0.05-0.1.

[0025] Preferably, the aluminum catalyst in step (3) is selected from one of Al2O3 and AlCl3.

[0026] Further preferably, the aluminum catalyst in step (3) is AlCl3.

[0027] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a multi-stimulus responsive aggregation-induced luminescence molecule and a preparation method thereof, which has the following beneficial effects:

[0028] 1. The present invention forms an electron push-pull system by introducing methoxytetraphenylethylene as an electron donor, vinylthiophene as a π bridge and indandione as an electron acceptor in the molecular structure, wherein the vinyl group in the molecular structure is sensitive to alkali and the carbonyl group in indandione is sensitive to acid. The aggregation-induced luminescence molecule provided by the present invention exhibits aggregation-induced emission characteristics, large Stokes shift (up to 267 nm), a maximum emission peak in the aggregated state / solid state greater than 650 nm and high fluorescence quantum efficiency. The molecule has multi-stimulus response characteristics: (1) mechanoluminescence color change characteristics, after slight grinding, an obvious emission red shift occurs, and the wavelength ranges from 640 nm to 691 nm; (2) base response, with the addition of base, colorimetric and ratio fluorescence quenching signals appear; (3) acid response, with the addition of acid, fluorescence quenching signals appear; (4) It has the characteristics of naked eye detection and rapid response.

[0029] 2. The synthesis process of the present invention is simple, the reaction conditions are mild, the yield is high, it is soluble in a variety of organic solvents, and has good solution processability.

[0030] 3. The multi-stimulus responsive aggregation-induced luminescence molecules of the present invention have broad application prospects in many fields such as acid and alkaline gas detection, real-time monitoring of pressure changes, non-destructive detection of pressure, and structural damage detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0032] Figure 1 (a) and (b) the UV-visible absorption spectra and fluorescence emission spectra of the aggregation-induced emission molecules of the examples in different solvents.

[0033] Figure 2 The fluorescence emission spectra of the aggregation-induced emission molecule of the example in different dioxane / water mixed solvents (a) and the change of fluorescence intensity under different water content conditions (b).

[0034] Figure 3 The figure is the UV-visible absorption spectrum of the aggregation-induced emission molecule of the embodiment under alkaline conditions.

[0035] Figure 4 (a) is a fluorescence emission graph of the aggregation-induced emission molecule of the embodiment at pH 7-11 and (b) is a fluorescence emission graph at pH 11-12.5.

[0036] Figure 5 (a) and (b) the UV-visible absorption spectrum and fluorescence emission graph of the aggregation-induced emission molecule of the embodiment under acidic conditions.

[0037] Figure 6 The fluorescence emission diagram of the aggregation-induced emission molecule of the embodiment before and after grinding. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example

[0040] A method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule comprises the following steps:

[0041] (1) Preparation of intermediate 1

[0042] Under nitrogen protection, bis(4-methoxyphenyl)methanone (242 mg, 1 mmol) and 4-bromobenzene-4-methoxybenzophenone (291 mg, 1 mmol) and 50 mg of zinc powder were added to a dry three-necked flask, and tetrahydrofuran solvent was added. Titanium tetrachloride (9.49 mg, 0.05 mmol) was added dropwise under ice-water bath conditions. After 30 min, the temperature was slowly raised to reflux temperature. After reacting for 4 h, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (v / v=10:1) as eluent to obtain white intermediate 1 with a yield of 75%;

[0043] (2) Preparation of intermediate 2

[0044] Accurately weigh intermediate 1 (1000 mg, 2 mmol) and 5-formyl-2-thiopheneboronic acid (468 mg, 3 mmol) and add 40 mL of a mixed solvent of ethanol and toluene (V 乙醇 :V 甲苯 =3:1), then Pd(PPh3)4 (100 mg, 0.1 mmol), 3 mL K2CO3 aqueous solution (2 mol / L) were added, and refluxed under nitrogen for 8 h. After the reaction was completed, the mixture was cooled to room temperature, then poured into water, extracted with dichloromethane and washed with brine, and the combined organic layers were dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (v / v=10:1) as the eluent to obtain a yellow intermediate 2 with a yield of 66%. 1 H NMR (400 MHz, CDCl3): δ 9.86 (s, 1H), 7.70 (d, 1H), 7.42 (d, 2H), 7.08 (d, 6H), 6.99-6.91 (m, 6H), 6.66 (dd, 3H), 3.75 (s, 9H). 13 C NMR (101MHz, CDCl3): δ 182.71, 158.30, 158.16, 158.08, 154.40,146.27, 141.98, 140.42, 137.82, 137.50, 136.34, 136.25, 132.66, 132.60,132.25, 130.45, 125.64, 123.75, 113.31, 113.28, 113.25, 113.14, 55.14. HRMS(ESI): m / z [M+Na] + Calculate for C 34 H 28O4S: 555.1700, found: 555.1605. mp:193.5-194.0℃.

[0045] (3) Preparation of aggregation-induced emission molecules

[0046] Intermediate 2 (532 mg, 1 mmol) and 1,3-indanedione (146 mg, 1 mmol) and aluminum chloride (6.67 mg, 0.05 mmol) were added to 20 mL of dry dichloromethane, stirred and heated to reflux for 2 hours, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (v / v=10:1) as the eluent to obtain a yellow aggregation-induced emission molecule with a yield of 68%. m / z [M] + Calculate for C 43 H 32 O5S: 660.1970, found: 660.1925. Elemental Analysis calcd: C, 78.16; H, 4.88; O, 12.11; S, 4.85, found: C, 78.21; H, 4.90; O, 12.09; S, 4.81. 1 H NMR (400 MHz, CDCl3): δ8.22 (s, 1H), 7.92 (d, 1H), 7.62 (d, 2H), 7.08 (d, 6H), 6.91-6.87 (m, 7H), 6.68 (dd, 6H), 3.75 (s, 9H).

[0047] The synthesis route of the aggregation-induced emission molecule is as follows:

[0048] .

[0049] Performance Testing

[0050] In order to study the effect of solvent polarity on the UV-visible absorption and fluorescence emission of the aggregation-induced emission molecule obtained in the example, different polar solvents were selected, including n-hexane, toluene, tetrahydrofuran, dichloromethane, acetone, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide. The maximum absorption peak of the aggregation-induced emission molecule in different solvents is around 470 nm, and it does not show solvent dependence, but its fluorescence emission spectrum shows strong solvent dependence. It does not emit color and fluorescence in a strong polar solvent, and emits strong fluorescence in a weak polar solvent (n-hexane, toluene, tetrahydrofuran), with emission peaks at 571, 631 and 737 nm, respectively, and the Stokes shift in tetrahydrofuran is 267 nm. The results of the UV-visible absorption spectrum and fluorescence emission spectrum are shown in the attached Figure 1 .

[0051] In addition, the fluorescence emission spectra of the aggregation-induced luminescence molecule in different proportions of dioxane / water mixed solvents and the changes in fluorescence intensity under different water content conditions were also studied. With the addition of poor solvent water, the fluorescence intensity of the aggregation-induced luminescence molecule continued to increase. When the water content was 70%, the fluorescence increased to 24 times the original, showing the aggregation-induced luminescence characteristics. The results are attached. Figure 2 .

[0052] Using dioxane as solvent and adjusting pH value with base, the effect of aggregation-induced emission molecules on UV-visible absorption under alkaline conditions was studied. As the pH value increased from 7 to 12.5, the absorption peak intensity at 470 nm decreased continuously, while the absorption peak intensity at 370 nm increased, indicating that the conjugated structure of the aggregation-induced emission molecules was destroyed under alkaline conditions and had the characteristics of base response. The results are attached. Figure 3 Under this condition, as the pH value increases from 7 to 11.5, the fluorescence emission peak of 663 nm continuously red-shifts to 696 nm, accompanied by a decrease in fluorescence intensity, and 95% of the fluorescence is quenched; when the pH value further increases from 11.5 to 12.5, the fluorescence emission peak of 696 nm continuously blue-shifts to 596 nm, and the fluorescence intensity increases, showing alkaline color characteristics. The results are attached. Figure 4 .

[0053] Using dioxane as solvent and HCl to adjust the pH value, the changes in the UV-visible absorption of the aggregation-induced luminescence molecule under acidic conditions were studied. As the pH value decreased from 7 to 1, the UV absorption spectrum did not change, but its fluorescence emission peak at 663 nm continued to red-shift to 699 nm, and 87% of the fluorescence was quenched, showing acid-induced color change characteristics. The results are shown in the attached Figure 5 .

[0054] A certain amount of aggregation-induced emission molecule samples were ground and the changes in the fluorescence emission wavelength before and after grinding were compared. The emission peak of the solid powder before grinding was located at 640 nm, and the emission peak was red-shifted to 691 nm after grinding, indicating that the aggregation-induced emission molecule has a strong mechanochromic property. The results are shown in the attached Figure 6 .

[0055] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-stimulus responsive aggregation-induced luminescence molecule, characterized in that: The structural formula is as follows: 。 2. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 1, characterized in that: The following steps are involved: (1) Under nitrogen protection, bis-(4-methoxyphenyl)methanone and 4-bromobenzene-4-methoxybenzophenone were added to a reaction vessel, tetrahydrofuran solvent was added, and zinc powder was added. A titanium catalyst was added under ice-water bath conditions. After 30 minutes, the temperature was slowly raised to reflux temperature, and the reaction was carried out for 4-5 hours. The solvent was removed under reduced pressure, and the reaction was purified by silica gel column chromatography to obtain intermediate 1; (2) Add intermediate 1 and 5-formyl-2-thiopheneboronic acid to a mixed solvent of ethanol and toluene, then add a palladium catalyst and an alkali solution, reflux for 8-10 hours under nitrogen, then cool the mixture to room temperature, pour it into water, extract with dichloromethane and wash with brine, combine the organic layers, dry with anhydrous magnesium sulfate, filter, evaporate the solvent, and purify by silica gel column chromatography to obtain intermediate 2; (3) Add intermediate 2 and 1,3-indanedione to dichloromethane, then add aluminum catalyst, stir and heat to reflux for 2-3 hours, evaporate the solvent under reduced pressure, and purify by silica gel column chromatography to obtain an aggregation-induced emission molecule; The synthesis route of the aggregation-induced emission molecule is as follows: 。 3. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: The molar ratio of bis-(4-methoxyphenyl)methanone, 4-bromobenzene 4-methoxybenzophenone and zinc powder in step (1) is 1:1:0.3-1.

5.

4. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: The titanium catalyst in step (1) is selected from one of TiO2, Ti(NO3)4, and TiCl4.

5. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: In step (2), the molar ratio of the intermediate 1, 5-formyl-2-thiophene boronic acid and palladium catalyst is 1:1.5:0.05-0.

2.

6. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: The palladium catalyst in step (2) is selected from one of PdCl2 and Pd(PPh3)4.

7. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: The alkaline solution in step (2) is selected from one of Na2CO3 solution, K2CO3 solution, KOH solution and NaOH solution.

8. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: The aluminum catalyst in step (3) is selected from one of Al2O3 and AlCl3.

9. The method for preparing a multi-stimulus responsive aggregation-induced luminescence molecule according to claim 2, characterized in that: In step (3), the molar ratio of the intermediate 2, 1,3-indanedione and the aluminum catalyst is 1:1:0.05-0.

1.

10. Application of the aggregation-induced emission molecule according to claim 1 in the fields of acidic and alkaline gas detection, real-time monitoring of pressure changes, and non-destructive detection of pressure.

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