Nitrogen-containing bowl-shaped conjugated pH response fluorescent probe as well as preparation method and application thereof

Abstract

The invention relates to a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and a preparation method and application thereof, the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe is characterized in that the structural formula of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe is # imgabs0 #, and R is hydrogen, acetyl or p-toluenesulfonyl. Compared with the prior art, the nitrogen-containing bowl-shaped conjugated molecule provided by the invention shows a highly sensitive response characteristic in an acid-base medium. Due to the introduction of nitrogen atoms, the electronic structure of molecules is obviously changed, lone pair electrons of the nitrogen atoms can participate in the reaction, and the protonation behavior is obvious under the acidic condition. After protonation, the fluorescence intensity of the molecule is obviously enhanced, and the emission wavelength has obvious red shift, so that the probe has important application value in the aspect of developing a high-sensitivity acid-base sensor. In addition, the nitrogen-containing polycyclic aromatic hydrocarbon compound also shows application prospects in the fields of organic light-emitting diodes, information safety, biological imaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical fields of chemistry and acid-base pH sensor technology, and particularly relates to a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and a preparation method and application thereof. Background Art

[0002] Due to their unique electronic structures and excellent optoelectronic properties, nitrogen-doped polycyclic aromatic hydrocarbon compounds have shown broad application prospects in the field of materials science. The introduction of nitrogen atoms can effectively regulate the electronic distribution of polycyclic aromatic hydrocarbons and lower their frontier orbital energy levels, thus significantly affecting their optoelectronic properties. Such compounds have important application values in fields such as molecular electronics, field-effect transistors, solar cells, organic light-emitting diodes, and biological imaging. With the in-depth research, it has been found that the doping of nitrogen atoms in the polycyclic aromatic hydrocarbon skeleton, especially the nitrogen atoms on the pyridine ring, adopts the sp 2 hybridization mode, and their lone pair electrons are located in the sp 2 orbital, rather than in the π system. Due to the relatively high lone pair electron density and uneven electron cloud distribution of the nitrogen atoms on the pyridine ring, the pyridine nitrogen atoms are easily protonated in an acidic medium. This protonation process reduces the electron density on the ring, thereby leading to the activation of the ring and endowing the material with the characteristics of being sensitive to acid-base media. Based on these characteristics, in recent years, many simple, efficient, and innovative synthesis techniques for nitrogen-containing polycyclic aromatic hydrocarbon compounds have been developed, aiming to obtain nitrogen-containing polycyclic aromatic hydrocarbon compounds with novel structures and functions. These advancements have not only promoted the development of materials science but also provided more possibilities for applications in related fields.

[0003] Therefore, designing and synthesizing nitrogen-containing polycyclic aromatic hydrocarbon-based organic functional molecules that are sensitive to acid-base media through a concise and efficient synthesis strategy has become one of the current research hotspots. Such molecules can exhibit high sensitivity to changes in the acid-base environment and achieve precise regulation of optical, electrical, and other properties through changes in molecular structure. This unique response characteristic makes it show broad application prospects in the field of intelligent materials, especially in the development of acid-base sensors, information storage materials, and biological imaging probes, etc., and has important scientific value and practical significance. By further optimizing the molecular design and synthesis methods, such materials are expected to provide new ideas and technical support for the future development of intelligent materials.

[0004] However, most of the current fluorescence probes based on pyridine structure have the following problems: (1) low sensitivity, usually requiring the addition of more acid to produce an obvious change in fluorescence signal; (2) fluorescence quenching or weakening after acidification, rather than enhancement, belonging to the turn-off type probe, resulting in poor detection sensitivity; (3) narrow range of fluorescence wavelength change, only the intensity of fluorescence changes before and after acidification, or only a small Stokes shift; (4) most of them are single-wavelength probes, while dual-wavelength fluorescence probes have greater advantages.

[0005] Therefore, there is an urgent need for a pH probe to achieve high-sensitivity detection and response to the environmental pH value. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems by providing a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescence probe, its preparation method and application. By designing and synthesizing nitrogen-containing polycyclic aromatic hydrocarbon compounds with acid-responsive characteristics, and using their unique electronic structure and molecular configuration changes, high-sensitivity detection and response to the environmental pH value are achieved, providing an important theoretical basis and technical support for the development of new pH-sensitive materials, and having significant scientific significance and application value.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The technical concept of the present invention is as follows:

[0009] In order to solve the problems existing in most of the fluorescence probes based on pyridine structure, a unique pyridine-containing bowl-shaped molecule is designed. Due to its unique structure, the lone pair electrons on its pyridine are more exposed, making it more sensitive to protons. At the same time, since it contains both an electron-rich carbazole ring and an electron-deficient pyridine ring, stronger intramolecular charge transfer can be generated after protonation, thus achieving dual-wavelength luminescence and a large Stokes shift. Moreover, due to its unique structural characteristics, the fluorescence intensity may be greatly enhanced after protonation. These characteristics make this type of molecule a high-sensitivity and high-resolution pH probe, having broad application prospects in the fields of chemistry, medicine, environmental detection, etc.

[0010] The first object of the present invention is to provide a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescence probe, and the structural formula of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescence probe is shown in formula (I):

[0011]

[0012] Wherein, R is hydrogen, acetyl group, p-toluenesulfonyl group, etc.

[0013] Further, in an organic solvent or a mixed solution of an organic solvent and water, the fluorescence of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescence probe for pK aAcids with a pKa less than 8.5 have a dual-wavelength response.

[0014] Furthermore, the dual-wavelength response is manifested as follows:

[0015] After acidification, the original fluorescence emission wavelength of the molecule in formula (I) weakens, and at the same time, a new red-shifted fluorescence emission is generated, and the intensity of the newly generated fluorescence increases with the increase of the acid equivalent; the original fluorescence emission wavelength of the molecule is the molecular fluorescence emission wavelength of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe in an organic solvent or a mixed solution of an organic solvent and water; the new fluorescence emission wavelength of the molecule is the molecular fluorescence emission wavelength that newly appears after adding an acid with a pKa a less than 8.5 to the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe in an organic solvent or a mixed solution of an organic solvent and water.

[0016] Furthermore, after acidification, the fluorescence quantum yield is increased by 5 - 20 times compared with that before adding acid.

[0017] Furthermore, the organic solvent includes one or more of dichloromethane, acetonitrile, DMSO, and methanol; the acid with a pKa a less than 8.5 includes one or more of acetic acid, trifluoroacetic acid, hydrochloric acid, and Meldrum's acid.

[0018] The second object of the present invention is to provide a preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe, including the following steps:

[0019] Step S1: Add a solvent to the compound (II) with the structural formula , then add triethylamine, add acetyl chloride AcCl or p-toluenesulfonyl chloride TsCl, and then react. After the reaction is completed, quench and purify to obtain the compound (III) with the following structure: Among them, R1 is an acetyl group (Ac) or a p-toluenesulfonyl group (Ts). When adding acetyl chloride AcCl, the corresponding R1 is an acetyl group (Ac), and when adding p-toluenesulfonyl chloride TsCl, the corresponding R1 is a p-toluenesulfonyl group (Ts);

[0020] Step S2: Mix the compound (III) obtained in step S1 with a catalyst, an oxidant , molecular sieve, and solvent, and heat and react under oxygen. After the reaction is completed, purify to obtain the compound (IV) with the following structure: Among them, R1 is an acetyl group (Ac) or a p-toluenesulfonyl group (Ts);

[0021] Step S3: Mix the compound (IV) obtained in step S2 with a solvent, add trifluoromethanesulfonic acid TfOH, carry out the reaction, alkalize the reaction system, and purify to obtain the compound (V) with the following structure: Among them, R1 is acetyl (Ac) or p-toluenesulfonyl (Ts);

[0022] Step S4: Add a solvent to the compound (V) obtained in step S3, then add pyridine, add benzoyl chloride, and then heat for reaction. After the reaction is completed, quench, and after purification, obtain compound (VI) with the following structure: Among them, R1 is acetyl (Ac) or p-toluenesulfonyl (Ts);

[0023] Step S5: Prepare a phosphorus oxychloride solution of the compound (VI) obtained in step S4, add phosphorus pentoxide, heat and stir the mixture for reaction. After the reaction is completed, cool, pour it into ice water, precipitate the product, filter the solid, and after purification, obtain compound (I-a) with the following structure: Among them, R1 is acetyl (Ac) or p-toluenesulfonyl (Ts), and compound (I-a) is the compound corresponding to R being acetyl or p-toluenesulfonyl in compound (I).

[0024] Furthermore, after step S5, the following step S6 is carried out:

[0025] Step S6: Prepare a methanol solution of the compound (I-a) obtained in step S5, add sodium hydroxide, heat the mixture for reaction. After the reaction is completed, after purification, obtain compound (I-b) with the following structure: Compound (I-b) is the compound corresponding to R being hydrogen in compound (I).

[0026] Furthermore, in step S6, the molar ratio of sodium hydroxide to compound (I-a) is 3 - 5 equivalents.

[0027] Furthermore, in step S6, the temperature of the heating reaction is 50 - 70 °C, and the time is 5 - 24 hours.

[0028] Furthermore, in step S6, the purification includes the following process: Dilute the reaction solution with dichloromethane by one time, extract with dichloromethane, wash the organic layer three times with water, then dry with anhydrous sodium sulfate, filter, concentrate under reduced pressure to obtain a crude product, and subject the crude product to column chromatography.

[0029] Furthermore, in step S1, the solvent is tetrahydrofuran or 1,2-dichloroethane.

[0030] Furthermore, in step S1, the molar ratio of the added acetyl chloride AcCl or p-toluenesulfonyl chloride TsCl to compound (II) is 1 - 6 equivalents.

[0031] Furthermore, in step S1, the temperature of the reaction is room temperature 25 °C, and the time is 18 - 24 hours.

[0032] Further, in step S1, after the reaction is completed, it is quenched with saturated sodium bicarbonate solution.

[0033] Further, in step S2, the catalyst is palladium acetate, the oxidant is copper acetate, and the solvent is dioxane.

[0034] Further, in step S2, the reaction temperature is 80–150 °C and the time is 48 - 72 hours.

[0035] Further, in step S3, the solvent is tetrahydrofuran.

[0036] Further, in step S3, trifluoromethanesulfonic acid TfOH is added at 0 °C.

[0037] Further, in step S3, the molar ratio of trifluoromethanesulfonic acid TfOH to compound (IV) added is 2 - 4 equivalents.

[0038] Further, in step S3, the reaction is carried out under nitrogen, the reaction temperature is 50 - 70 °C, and the time is 10 - 12 h.

[0039] Further, in step S3, the reaction system is alkalized with sodium hydroxide solution.

[0040] Further, in step S4, the solvent is tetrahydrofuran or dichloromethane.

[0041] Further, in step S4, benzoyl chloride is added at 0 - 25 °C.

[0042] Further, in step S4, the molar ratio of benzoyl chloride to compound (V) added is 3 - 6 equivalents.

[0043] Further, in step S4, the reaction temperature is 0 - 60 °C and the time is 12 - 14 hours.

[0044] Further, in step S4, after the reaction is completed, it is quenched with sodium bicarbonate solution.

[0045] Further, in step S5, the molar ratio of phosphorus pentoxide to compound (VI) added is 1 - 5 equivalents.

[0046] Further, in step S5, the reaction temperature is 90 - 110 °C and the time is 5 - 24 hours.

[0047] Further, in step S5, it is poured into ice water with a volume 5 - 20 times that of phosphorus oxychloride POCl3.

[0048] Further, in step S1, the purification includes the following process: the quenched solution is extracted with dichloromethane, the organic layer is washed three times with saturated brine, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography.

[0049] Further, in step S2, the purification includes the following process: the reaction solution is diluted two-fold with dichloromethane solution and filtered, extracted with dichloromethane, the organic layer is washed three times with water, then dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography.

[0050] Further, in step S3, the purification includes the following process: extracted with dichloromethane, the organic layer is washed three times with water, then dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography.

[0051] Further, in step S4, the purification includes the following process: extracted with dichloromethane, the organic layer is washed three times with brine, then dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography.

[0052] Further, in step S5, the purification includes the following process: extracted with dichloromethane, the organic layer is washed three times with brine, then dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography.

[0053] Further, steps S1 - S6 are as follows:

[0054] Among them, R1 is acetyl (Ac) or p-toluenesulfonyl (Ts).

[0055] The third object of the present invention is to provide the application of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe, and use the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe in acid-base sensor materials, organic light-emitting diodes (OLEDs), information security, biological imaging, etc.

[0056] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0057] 1) The present invention relates to a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and its preparation and application. The organic functional molecules of polycyclic aromatic hydrocarbon compounds containing nitrogen atoms exhibit highly sensitive characteristics to acidic and basic media. Due to the introduction of nitrogen atoms, the electronic structure of the compound changes significantly. The lone pair electrons of nitrogen atoms can participate in reactions, enabling it to exhibit obvious protonation behavior under acidic conditions. This protonation process will change the electronic distribution of the molecule, thereby regulating its optical, electrical and other properties. Specifically, this type of molecule emits blue fluorescence under ultraviolet light irradiation at 364 nm in the neutral state (when R is hydrogen, the wavelength is 400 - 500 nm). After protonation, its fluorescence undergoes a significant red shift, emitting green or orange fluorescence (when R is hydrogen, the wavelength is 500 - 750 nm), and the fluorescence is significantly enhanced. This characteristic makes it have important application value in the development of highly sensitive acid-base sensors. In addition, due to their excellent optoelectronic properties and tunable electronic structures, such molecules also show broad application prospects in the fields of organic light-emitting diodes (OLEDs), solar cells, biological imaging, etc. The present invention provides important theoretical basis and technical support for the development of new functional materials, and has significant scientific significance and practical application potential.

[0058] 2) The present invention relates to a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and its preparation and application. The preparation method of the nitrogen-containing polycyclic aromatic hydrocarbon compounds provided by the present invention adopts a simple strategy of gradually constructing heterocycles. This method uses triaminotriphenylene as the starting material, first constructs a nitrogen-containing five-membered heterocycle on the triphenylene skeleton, and then further introduces a pyridine heterocycle, thereby precisely introducing heteroatoms into the polycyclic aromatic hydrocarbon skeleton. Through this series of efficient chemical reactions, nitrogen-containing polycyclic aromatic hydrocarbon organic functional molecules sensitive to acidic and basic media are successfully prepared. This method has the advantages of mild reaction conditions, simple steps, high yield, etc., and is an efficient and scalable synthesis strategy. The present invention not only provides a new technical route for the preparation of nitrogen-containing polycyclic aromatic hydrocarbon compounds, but also lays an important foundation for the development of new organic materials with specific functions. Brief Description of the Drawings

[0059] Figure 1 It is a schematic diagram of the preparation route of the organic functional molecule of the nitrogen-containing polycyclic aromatic hydrocarbon compound in Example 1 of the present invention.

[0060] Figure 2 It is the 1H NMR spectrum of Compound III in Example 1 of the present invention;

[0061] Figure 3 It is the 13C NMR spectrum of Compound III in Example 1 of the present invention;

[0062] Figure 4 It is the 1H NMR spectrum of Compound IV in Example 1 of the present invention;

[0063] Figure 5 is the carbon-13 NMR spectrum of Compound IV in Example 1 of the present invention;

[0064] Figure 6 is the proton NMR spectrum of Compound V in Example 1 of the present invention;

[0065] Figure 7 is the carbon-13 NMR spectrum of Compound V in Example 1 of the present invention;

[0066] Figure 8 is the proton NMR spectrum of Compound VI in Example 1 of the present invention;

[0067] Figure 9 is the carbon-13 NMR spectrum of Compound VI in Example 1 of the present invention;

[0068] Figure 10 is the proton NMR spectrum of Compound I-a in Example 1 of the present invention;

[0069] Figure 11 is the carbon-13 NMR spectrum of Compound I-a in Example 1 of the present invention;

[0070] Figure 12 is the proton NMR spectrum of Compound I-b in Example 1 of the present invention;

[0071] Figure 13 is the carbon-13 NMR spectrum of Compound I-b in Example 1 of the present invention;

[0072] Figure 14 is the crystal structure of Compound I-b in Example 1 of the present invention;

[0073] Figure 15 are the ultraviolet-visible absorption spectrum and fluorescence emission spectrum of Compound I-a in dichloromethane in Example 2 of the present invention, where Figure 15 (a) is the ultraviolet-visible absorption spectrum of Compound I-a in dichloromethane; Figure 15 (b) is the fluorescence emission spectrum of Compound I-a in dichloromethane;

[0074] Figure 16 are the ultraviolet-visible absorption spectrum and fluorescence emission spectrum of Compound I-b in dichloromethane in Example 2 of the present invention, where Figure 16 (a) is the ultraviolet-visible absorption spectrum of Compound I-b in dichloromethane; Figure 16 (b) is the fluorescence emission spectrum of Compound I-b in dichloromethane;

[0075] Figure 17 is the fluorescence decay curve of Compound I-a in dichloromethane in Example 2 of the present invention;

[0076] Figure 18 It is the fluorescence decay curve diagram of solid compound I-a in Example 2 of the present invention;

[0077] Figure 19 It is the fluorescence emission spectrum diagram of compound I-a in dichloromethane solutions with different concentrations in Example 2 of the present invention;

[0078] Figure 20 It is the ultraviolet absorption spectrum and fluorescence emission spectrum of compound I-a in solutions with different polarities in Example 2 of the present invention, where Figure 20 (a) is the ultraviolet absorption spectrum diagram of compound I-a in solutions with different polarities; Figure 20 (b) is the fluorescence emission spectrum diagram of I-b in solutions with different polarities;

[0079] Figure 21 It is the ultraviolet absorption spectrum and fluorescence emission spectrum of compound I-b in solutions with different polarities in Example 2 of the present invention, where Figure 21 (a) is the ultraviolet absorption spectrum diagram of compound I-b in solutions with different polarities; Figure 21 (b) is the fluorescence emission spectrum diagram of I-b in solutions with different polarities;

[0080] Figure 22 It is the ultraviolet absorption spectrum and fluorescence emission spectrum of compound I-a under the influence of different equivalents of TFA in Example 2 of the present invention, where Figure 22 (a) is the ultraviolet-visible absorption spectrum diagram of compound I-a under the influence of different equivalents of TFA; Figure 22 (b) is the fluorescence emission spectrum diagram of compound I-a under the influence of different equivalents of TFA;

[0081] Figure 23 It is the ultraviolet absorption spectrum and fluorescence emission spectrum of compound I-b under the influence of different equivalents of TFA in Example 2 of the present invention, where Figure 23 (a) is the ultraviolet-visible absorption spectrum diagram of compound I-b under the influence of different equivalents of TFA; Figure 23 (b) is the fluorescence emission spectrum diagram of compound I-b under the influence of different equivalents of TFA;

[0082] Figure 24 It is the change curve of the fluorescence intensity of compound I-b in a solution of methanol / water (volume ratio 1:99, using 0.2 M potassium dihydrogen phosphate and dipotassium hydrogen phosphate buffer solution, adjusting the pH value with hydrochloric acid) with respect to the pH value. Detailed implementation mode

[0083] The present invention will be described in detail below with reference to specific embodiments, but it is by no means a limitation of the present invention. Features such as preparation means, materials, structures or composition ratios that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0084] The present invention relates to a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and its preparation method and application. The structural formula characteristics of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe are as follows: Among them, R is hydrogen, acetyl, p-toluenesulfonyl group, etc. Compared with the prior art, the present invention relates to a bowl-shaped conjugated molecule containing a nitrogen atom, its preparation method, acid-responsive characteristics and its application in the field of acid-base sensor materials. Specifically, the nitrogen-containing bowl-shaped conjugated molecule proposed by the present invention exhibits highly sensitive response characteristics in acid-base media. Due to the introduction of nitrogen atoms, the electronic structure of the molecule changes significantly. The lone pair electrons of nitrogen atoms can participate in the reaction, making it show obvious protonation behavior under acidic conditions. After protonation, the fluorescence intensity of the molecule increases significantly, and the emission wavelength undergoes an obvious red shift. This characteristic makes it have important application value in the development of highly sensitive acid-base sensors. In addition, such nitrogen-containing polycyclic aromatic hydrocarbon compounds also show broad application prospects in the fields of organic light-emitting diodes (OLEDs), information security, biological imaging, etc.

[0085] The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0086] In this embodiment, unless otherwise specified, all reagents used are commercially available reagents. Triaminotriphenylene can be a commercially available product, but for cost considerations and the need for large-scale use, the preferred synthesis method includes the following steps: Dissolve 2,3-dichloronitrobenzene (30 g) in a flask containing 240 mL of DMF, add 60 g of copper powder, stir and reflux at 180 °C for 6 - 10 hours. Cool slightly to below the boiling point and filter while hot, wash with a small amount of DMF. Slowly pour the filtrate into 700 mL of ammonia water diluted three times with stirring. A solid precipitates. Pour out the supernatant, filter the solid by suction, wash with dilute ammonia water, wash with water until the water is colorless. Add 500 ml of CH2Cl2 (the specific amount depends on the dissolution situation), 50 ml of ammonia water, and 100 ml of water, stir for fifteen minutes, separate the layers, wash again with dilute ammonia water, wash the organic phase once with brine, dry, evaporate to dryness, suction dry, add 50 mL of acetone, heat and stir for 30 min, cool and filter by suction, and wash with a small amount of acetone (5 - 10 mL) to obtain 9.5 - 10 g of solid with a purity > 90%; Dissolve the nitro compound (6 g) in 600 mL of ethyl acetate and 30 mL of ethanol, add 0.8 g of 10% palladium on carbon under nitrogen. After replacing with hydrogen three times, hydrogenate at room temperature with a hydrogen balloon (it may be necessary to replace the balloon in the middle according to the size of the balloon), and track the reaction with a thin-layer plate until the raw materials are consumed (the end point of the reaction can probably be judged by the color changing from yellow to colorless or gray). The reaction must be complete. After the reaction is completed, filter off the palladium on carbon, wash with a small amount of ethyl acetate, and evaporate to dryness to obtain 4.52 g of a pale yellow syrupy solid. As long as the purity of the nitro compound in the previous step > 90%, the product of this step does not need to be purified. The reaction processes involved are as follows:

[0087]

[0088] Example 1

[0089] This example provides a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe and its preparation method, specifically a polycyclic aromatic hydrocarbon-based organic functional molecule I-a (where R in formula (I) is p-toluenesulfonyl) and I-b (where R in formula (I) is hydrogen) containing nitrogen atoms and their preparation methods.

[0090] Figure 1 It is a schematic diagram of the preparation route of the polycyclic aromatic hydrocarbon-based organic functional molecule containing nitrogen atoms in Example 1 of the present invention (the raw material for step S1 corresponding to Example 1 is p-toluenesulfonyl chloride TsCl, and R1 is Ts).

[0091] As Figure 1 shown, the preparation method of the polycyclic aromatic hydrocarbon-based organic functional molecule I-a and I-b containing nitrogen atoms includes the following steps:

[0092] Step S1, Preparation of Compound III: Put Compound II (triaminotriphenylene) (2.740 g, 10 mmol, 1 eq.) shown in the following structural formula II into a 250 mL three-necked flask equipped with a stir bar. Under a nitrogen atmosphere, add tetrahydrofuran (THF) (30 mL). After Compound II is fully dissolved, add triethylamine Et3N (21 mL, 150 mmol, 15.0 eq.) and stir for 20 minutes to obtain a mixed solution. Then, dissolve p-toluenesulfonyl chloride TsCl (12 g, 60 mmol, 6.0 eq.) in tetrahydrofuran (THF (70 mL)) to obtain a tetrahydrofuran solution of p-toluenesulfonyl chloride. At 0 °C, slowly add the prepared tetrahydrofuran solution of p-toluenesulfonyl chloride dropwise to the mixed solution, and finally continue to stir at room temperature for 18 hours to complete the reaction. After the reaction is completed, quench with saturated sodium bicarbonate solution, adjust the pH of the mixture in the system to 6 - 8, and extract with dichloromethane:methanol = 10:1 (60 mL * 3, that is, repeat three times). The organic layer is washed three times with saturated brine, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, and the crude product is further purified by precipitation in dichloromethane (DCM):petroleum ether (PE) = 1:10 to provide an analytically pure product, obtaining a white solid. The obtained white solid includes the compound shown in the following formula III.

[0093]

[0094] The reaction formula is as follows:

[0095]

[0096] Figure 2 is the 1H NMR spectrum of Compound III in Example 1 of the present invention.

[0097] Figure 3 is the 13C NMR spectrum of Compound III in Example 1 of the present invention.

[0098] As Figure 2 、 3 shown, Compound III (4.40 g, yield: 60%) was obtained. M.p. 153 - 154 °C. 1 1H NMR (400 MHz, DMSO-d6): δ 10.05 (s, 3H), 9.28 (d, J = 8.4 Hz, 3H), 7.43 (d, J = 7.9 Hz, 6H), 7.32 - 7.27 (m, 9H), 6.77 (d, J = 7.6 Hz, 3H), 2.36 (s, 9H); 1313C NMR(101MHz, DMSO-d6): δ 143.42, 137.45, 132.90, 131.84, 129.91, 128.83, 128.19, 127.39, 126.94, 126.08, 21.51; HRMS (ESI Positive Ion Mode) m / z calculated for C 39 H 33 N3O6S3 [M + NH4] + : 753.1869, found: 753.1860.

[0099] Step S2, preparation of Compound IV: Put Compound III (1.5 g, 2.0 mmol, 1.0 eq.) from Step S1 into a 100 mL Schlenk tube equipped with a magnetic stirrer, add the catalyst palladium acetate (Pd(OAc)2) (67.9 mg, 0.3 mmol, 15 mol%), the oxidant copper acetate (Cu(OAc)2) (1.6 g, 9.0 mmol, 4.5 eq.), add molecular sieve (1.2 g) in the glove box, add the solvent dioxane (20 mL) under an oxygen atmosphere, and heat to 100 °C for reaction for 48 hours. After the reaction is completed, cool to room temperature, dilute and filter the reaction solution, extract with dichloromethane:methanol = 10:1 (40 mL * 3, that is, repeat three times), wash the organic layer with water three times, then dry with anhydrous sodium sulfate, filter, concentrate under reduced pressure, and purify the crude product by column chromatography (dichloromethane:petroleum ether = 30:1) to obtain a white solid. The obtained white solid includes the compound shown in Formula IV below.

[0100] The reaction formula is as follows:

[0101]

[0102] Figure 4 is the 1H NMR spectrum of Compound IV in Example 1 of the present invention.

[0103] Figure 5 is the 13C NMR spectrum of Compound IV in Example 1 of the present invention.

[0104] As Figure 4 、 5 shown, the prepared Compound IV (500 mg, yield: 34%). M.p. > 300 °C; 1HNMR(400MHz, DMSO-d6): δ 10.46 (s, 1H), 8.80 (d, J = 8.0 Hz, 1H), 8.20 - 8.15 (m, 3H), 7.99 (d, J = 8.3 Hz, 1H), 7.92 - 7.86 (m, 5H), 7.59 (d, J = 7.8 Hz, 2H), 7.35 (d, J = 7.9 Hz, 2H), 7.26 - 7.21 (m, 4H), 7.03 (d, J = 8.2 Hz, 1H), 2.36 (s, 3H), 2.16 (d, J = 4.8 Hz, 6H); 13 C NMR(101MHz, DMSO-d6): δ 146.22, 146.13, 143.80, 141.38, 139.98, 137.25, 135.00, 134.40, 134.29, 134.16, 131.75, 130.73, 130.73, 130.14, 129.69, 128.85, 128.74, 127.45, 127.04, 126.96, 126.95, 126.77, 125.72, 124.27, 122.65, 122.07, 116.99, 116.36, 115.38, 115.19, 21.48, 21.37; HRMS(ESI Positive Ion Mode) m / z calculated for C 39 H 29 N3O6S3 [M + H] + : 732.1291, found: 732.1288.

[0105] Step S3, prepare compound V: Put the compound IV (732 mg, 1.0 mmol, 1.0 eq.) prepared in step S2 into a 50 mL Schlenk tube equipped with a magnetic stirrer. Under a nitrogen atmosphere, add the solvent tetrahydrofuran THF (10 mL). Slowly add trifluoromethanesulfonic acid TfOH (0.2 mL, 3.0 eq.) at 0 °C. After restoring to room temperature, heat the reaction to 60 °C and react for 10 hours. The system turns black. After the reaction is completed, alkalize with 20% sodium hydroxide solution, extract with dichloromethane (30 mL * 3, that is, repeat three times). Wash the organic layer with water three times, then dry with anhydrous sodium sulfate, filter, concentrate under reduced pressure, and purify the crude product by column chromatography (dichloromethane: petroleum ether = 2:1) to obtain a pale yellow solid. The obtained pale yellow solid includes the compound shown in the following formula V.

[0106] The reaction formula is as follows:

[0107]

[0108] Figure 6 1H NMR spectrum of Compound V in Example 1 of the present invention.

[0109] Figure 7 13C NMR spectrum of Compound V in Example 1 of the present invention.

[0110] As Figure 6 、 7 shown, the prepared Compound V (404 mg, yield: 70%). M.p. 268 - 269 °C; 1 H NMR (400 MHz, DMSO-d6): δ8.49 (d, J = 7.9 Hz, 1H), 8.10 - 8.04 (m, 3H), 7.92 - 7.78 (m, 6H), 7.21 - 7.16 (m, 5H), 6.22 (s, 2H), 2.12 (d, J = 9.3 Hz, 6H); 13 C NMR (101 MHz, DMSO-d6): δ146.19, 145.99, 145.63, 141.33, 134.63, 134.39, 134.26, 133.58, 132.34, 130.66, 130.48, 129.84, 129.67, 127.00, 126.85, 126.80, 124.58, 123.22, 122.47, 122.44, 117.09, 117.02, 115.98, 115.62, 113.59, 112.95, 21.35, 21.31; HRMS (ESI Positive Ion Mode) m / z calculated for C 32 H 23 N3O4S2 [M + H] + : 578.1203, found: 578.1197.

[0111] Step S4, Preparation of Compound VI: Put V (1.2 g, 2.0 mmol, 1.0 eq.) prepared in Step S3 into a 100 mL round-bottom flask equipped with a stir bar. Under a nitrogen atmosphere, add dichloromethane CH₂Cl₂ (30 mL). After Compound V is fully dissolved, add pyridine (0.5 mL, 6.0 mmol, 3.0 eq.) and stir for 15 minutes to obtain a mixed solution. Then, dissolve benzoyl chloride (0.9 mL, 8.0 mmol, 4.0 eq.) in dichloromethane (10 mL) to obtain a dichloromethane mixed solution of benzoyl chloride. Slowly add the prepared dichloromethane mixed solution of benzoyl chloride dropwise to the mixed solution, and finally stir at room temperature for 14 hours for complete reaction. After the reaction is completed, quench with saturated sodium bicarbonate solution, adjust the pH of the mixture in the system to 6 - 8, and extract with dichloromethane (30 mL * 3, that is, repeat three times). The organic layer is washed three times with brine, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, and the crude product is purified by column chromatography (dichloromethane: petroleum ether = 1:1) to obtain a pale yellow solid. The obtained pale yellow solid includes the compound shown in Formula VI below.

[0112] The reaction formula is as follows:

[0113]

[0114] Figure 8 is the ¹H NMR spectrum of Compound VI in Example 1 of the present invention.

[0115] Figure 9 is the ¹³C NMR spectrum of Compound VI in Example 1 of the present invention.

[0116] As Figure 8 、 9 shown, Compound VI (1.0 g, yield: 75%) was obtained. M.p. 189 - 190 °C; 1 ¹H NMR (400 MHz, DMSO-d₆): δ 11.08 (s, 1H), 8.22 - 8.16 (m, 5H), 8.11 (d, J = 7.7 Hz, 1H), 8.05 (d, J = 7.9 Hz, 1H), 7.94 - 7.89 (m, 4H), 7.83 - 7.77 (m, 2H), 7.69 - 7.63 (m, 3H), 7.28 - 7.24 (m, 4H), 2.18 (d, J = 6.3 Hz, 6H). 1313C NMR(101MHz, DMSO-d6): δ 166.51, 146.22, 146.15, 141.51, 139.39, 134.81, 134.44, 134.41, 134.29, 134.26, 133.08, 132.61, 130.79, 130.75, 130.00, 129.24, 128.87, 128.70, 128.38, 126.96, 126.93, 126.39, 125.50, 125.25, 123.14, 122.48, 122.34, 116.76, 116.69, 115.57, 115.01, 21.41, 21.39. HRMS(ESI Positive Ion Mode) m / z calculated for C 39 H 27 N3O5S2 [M + H] + : 682.1465, found: 682.1462.

[0117] Step S5, Preparation of the polycyclic aromatic hydrocarbon-based organic functional molecular compound I-a containing a nitrogen atom: Put the compound VI (68 mg, 0.1 mmol, 1.0 eq.) prepared in step S4 into a 25 mL Schlenk tube equipped with a magnetic stirrer, add phosphorus pentoxide P2O5 (42.6 mg, 0.3 mmol, 3.0 eq.), replace the nitrogen, and then add phosphorus oxychloride POCl3 (2 mL). Under a nitrogen atmosphere, the reaction mixture is stirred at 100 °C for 18 hours. After the reaction is completed, it is cooled, poured into ice water (20 mL), the product precipitates, alkalized with 20% sodium hydroxide solution, the solid is filtered, the solid is dissolved in dichloromethane and extracted (20 mL * 3, that is, repeated three times), the organic layer is washed three times with brine, then dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The crude product is purified by column chromatography (dichloromethane: petroleum ether = 1:3) to obtain a yellow solid. The obtained yellow solid includes the compound shown in formula I-a below.

[0118] The reaction formula is as follows:

[0119]

[0120] Figure 10 is the 1H NMR spectrum of the polycyclic aromatic hydrocarbon-based organic functional molecular compound I-a containing a nitrogen atom in Example 1 of the present invention.

[0121] Figure 11 is the 13C NMR spectrum of the polycyclic aromatic hydrocarbon-based organic functional molecular compound I-a containing a nitrogen atom in Example 1 of the present invention.

[0122] Such as Figure 10 、11 As shown, the obtained compound I-a (25 mg, yield: 38%). M.p. 171 - 172 °C; 1 1H NMR (400 MHz, CDCl3): δ 8.35 (d, J = 8.8 Hz, 1H), 8.21 - 8.15 (m, 2H), 8.13 - 8.10 (m, 3H), 8.04 - 7.99 (m, 4H), 7.95 (d, J = 8.1 Hz, 2H), 7.66 - 7.57 (m, 3H), 7.27 (d, J = 8.6 Hz, 2H), 7.22 (d, J = 8.1 Hz, 2H), 2.32 (d, J = 12.1 Hz, 6H). 13 13C NMR (101 MHz, CDCl3): δ 161.05, 145.53, 145.33, 144.67, 143.14, 141.86, 141.35, 140.88, 138.96, 135.73, 135.48, 134.03, 131.08, 130.59, 130.29, 130.21, 130.18, 129.97, 129.22, 128.96, 128.19, 128.06, 127.18, 127.09, 127.03, 123.84, 123.05, 120.92, 120.71, 119.94, 118.73, 21.74, 21.73. HRMS (ESI Positive Ion Mode) m / z calculated for C 39 H 25 N3O4S2 [M + H] + : 664.1359, found: 664.1350.

[0123] Step S6, preparation of the nitrogen - atom - containing polycyclic aromatic hydrocarbon organic functional molecule compound I - b: Put the I - a (130 mg, 0.2 mmol, 1.0 eq.) prepared in step S4 into a 50 mL Schlenk tube equipped with a magnetic stirrer, add sodium hydroxide NaOH (40 mg, 1.0 mmol, 5.0 eq.), displace nitrogen and then add methanol MeOH (4 mL). Under a nitrogen atmosphere, the reaction mixture is stirred at 70 °C for 12 hours. After the reaction is completed, it is cooled to room temperature, the reaction solution is diluted with twice the volume of dichloromethane, and extracted with dichloromethane: methanol = 10:1 (20 mL * 3, that is, repeated three times). The organic layer is washed three times with saturated brine, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, and the crude product is purified by column chromatography (dichloromethane: methanol = 300:1) to obtain an orange - red solid. The obtained orange - red solid includes the compound shown in formula I - b as follows.

[0124] The reaction formula is as follows:

[0125]

[0126] Figure 12 1H NMR spectrum of the nitrogen-containing polycyclic aromatic hydrocarbon organic functional molecular compound I-b in Example 1 of the present invention.

[0127] Figure 13 13C NMR spectrum of the nitrogen-containing polycyclic aromatic hydrocarbon organic functional molecular compound I-b in Example 1 of the present invention.

[0128] As Figure 12 、 13 shown, the prepared compound I-b (45 mg, yield: 63%). M.p. > 300 °C; 1 1H NMR (400 MHz, DMSO-d6): δ 11.79 (s, 1H), 11.63 (s, 1H), 8.16 - 8.12 (m, 2H), 7.99 (d, J = 8.9 Hz, 1H), 7.88 (d, J = 2.4 Hz, 2H), 7.74 (d, J = 8.8 Hz, 1H), 7.64 - 7.54 (m, 5H); 13 13C NMR (101 MHz, DMSO-d6): δ 157.10, 147.47, 145.43, 143.19, 141.94, 140.71, 140.04, 136.40, 131.16, 131.14, 130.41, 129.50, 129.06, 128.17, 127.18, 126.18, 125.61, 125.2 25 H 13 N3 [M + H] + : 356.1182, found: 356.1179.

[0129] Example 2

[0130] This example provides the characterization and performance testing of the products I-a and I-b prepared in Example 1.

[0131] The organic functional molecules of nitrogen-containing polycyclic aromatic hydrocarbons prepared in Example 1 were characterized by single crystal X-ray diffraction, high resolution mass spectrometry, 1H nuclear magnetic resonance spectrum, and 13C nuclear magnetic resonance spectrum. The crystal structure of compound I-b is shown in Figure 14 .

[0132] Figure 15The UV-visible absorption spectrum and fluorescence emission spectrum of Compound I-a in Example 2 of the present invention in dichloromethane, where Figure 15 (a) is the UV-visible absorption spectrum of Compound I-a in dichloromethane; Figure 15 (b) is the fluorescence emission spectrum of Compound I-a in dichloromethane. It can be seen from Figure 15 that the wavelength range of the UV-visible absorption spectrum of Compound I-a in dichloromethane is 283 - 409 nm, and the fluorescence emission wavelength range in dichloromethane is 395 - 560 nm.

[0133] Figure 16 The UV-visible absorption spectrum and fluorescence emission spectrum of Compound I-b in Example 2 of the present invention in dichloromethane, where Figure 16 (a) is the UV-visible absorption spectrum of Compound I-b in dichloromethane; Figure 16 (b) is the fluorescence emission spectrum of Compound I-b in dichloromethane. It can be seen from Figure 16 that the wavelength range of the UV-visible absorption spectrum of Compound I-b in dichloromethane is 294 - 425 nm, and the fluorescence emission wavelength range in dichloromethane is 408 - 650 nm.

[0134] Figure 17 is the fluorescence decay curve of Compound I-a in dichloromethane in Example 2 of the present invention.

[0135] Figure 18 is the fluorescence decay curve of solid Compound I-a in Example 2 of the present invention.

[0136] It can be seen from Figure 17 and 18 that the paths of the fluorescence decay curves of the solid and the compound dissolved in dichloromethane have not changed.

[0137] Figure 19 is the fluorescence emission spectrum of Compound I-a in dichloromethane at different concentrations in Example 2 of the present invention. As the concentration of Compound I-a in dichloromethane increases, the fluorescence emission wavelength range remains basically unchanged, and the emission intensity weakens (because the data has been normalized, so Figure 19 the intensity change is not obvious in

[0138] Figure 20 The UV absorption spectrum and fluorescence emission spectrum of Compound I-a in different polar solvents in Example 2 of the present invention, where Figure 20 (a) is the UV absorption spectrum of Compound I-a in different polar solvents; Figure 20 (b) is the fluorescence emission spectrum of I-a in different polar solvents. It can be seen from Figure 20It can be seen that as the solvent polarity increases, the absorbance of Compound I-a changes little, and the absorption wavelength remains basically unchanged; as the solvent polarity increases, the emission wavelength of Compound I-a shows a red-shift trend.

[0139] Figure 21 are the ultraviolet absorption spectra and fluorescence emission spectra of Compound I-b in Example 2 of the present invention in solutions with different polarities, where Figure 21 (a) is the ultraviolet absorption spectrum of Compound I-b in solutions with different polarities; Figure 21 (b) is the fluorescence emission spectrum of I-b in solutions with different polarities. From Figure 21 It can be seen that as the solvent polarity increases, the absorbance of Compound I-b gradually increases, and the absorption wavelength remains basically unchanged; as the solvent polarity increases, the emission wavelength of Compound I-b shows a red-shift trend.

[0140] Figure 22 are the ultraviolet absorption spectra and fluorescence emission spectra of Compound I-a in Example 2 of the present invention under the influence of different equivalents of trifluoroacetic acid (TFA) (a solution obtained by dissolving different equivalents of trifluoroacetic acid (TFA) in dichloromethane (DCM)), where Figure 22 (a) is the ultraviolet-visible absorption spectrum of Compound I-a under the influence of different equivalents of TFA; Figure 22 (b) is the fluorescence emission spectrum of Compound I-a under the influence of different equivalents of TFA. From Figure 22 It can be seen that as the content of trifluoroacetic acid in the system increases, the absorption peak of Compound I-a near 364 nm in the ultraviolet absorption spectrum disappears, and at the same time, new absorption peaks appear near 345 nm and 425 nm, and the absorption peaks at 345 nm and 425 nm gradually increase. In addition, as the content of trifluoroacetic acid increases, the emission peaks of Compound I-a near 408 nm and 430 nm decrease, while a new strong green fluorescence emission peak appears near 510 nm, and an isointensity point at 440 nm is observed. The fluorescence spectra of Compound I-a before and after acidification Figure 22 (b), the fluorescence quantum yield before acidification was measured to be 0.41%, and the fluorescence quantum yield after acidification (adding 50 equivalents of TFA) was 9.65%. Comparison of the fluorescence quantum yields before adding acid (i.e., before adding acid) and after acidification (i.e., after adding acid). Figure 23 are the ultraviolet absorption spectra and fluorescence emission spectra of Compound I-b in Example 2 of the present invention under the influence of different equivalents of trifluoroacetic acid (TFA) (a solution obtained by dissolving different equivalents of trifluoroacetic acid (TFA) in dichloromethane (DCM)), where Figure 23 (a) is the ultraviolet-visible absorption spectrum of Compound I-b under the influence of different equivalents of TFA; Figure 23(b) is the fluorescence emission spectrum of Compound I-b under the influence of different equivalents of TFA. From Figure 22 it can be seen that as the content of trifluoroacetic acid in the system increases, the absorption peak of Compound I-b in the ultraviolet absorption spectrum near 383 nm disappears, and at the same time, new absorption peaks appear near 357 nm and 445 nm. In addition, as the content of trifluoroacetic acid increases, the blue fluorescence intensity of Compound I-b near 450 nm weakens, a new orange fluorescence emission peak appears near 560 nm and its emission intensity gradually increases, the position of the new emission peak is approximately redshifted by nearly 110 nm, and an isointensity point is also observed at 507 nm. The fluorescence spectra of Compound I-b before and after acidification Figure 23 (b), and the fluorescence quantum yield before acidification is measured to be 1.8%, and the fluorescence quantum yield after acidification (adding 5 equivalents of TFA) is 8.39%.

[0141] Figure 24 is the curve of the fluorescence intensity of Compound I-b in Example 2 of the present invention against the change of pH value in a solution of methanol and water (volume ratio 1:99, using 0.2 M potassium dihydrogen phosphate and dipotassium hydrogen phosphate buffer solution, and adjusting the pH value with hydrochloric acid). From Figure 24 it can be seen that as the pH decreases (from 7.73 to 4.15), the emission peak near 630 nm gradually increases. From the S-shaped curve of the fluorescence intensity at 630 nm against the pH value, the pKa value is obtained as 4.97, and the fluorescence intensity and the pH value show a linear relationship in the range of 4.67 - 5.11 (R 2 = 0.9919), and the regression equation is I(630 nm) = 23589 - 4456.07pH, indicating that I-b can be used for quantitative detection of pH value.

[0142] Functions and Effects of the Examples

[0143] The above-mentioned nitrogen-containing polycyclic aromatic hydrocarbon-based organic functional molecules in the examples show very sensitive characteristics to acid-base media. Due to the introduction of nitrogen atoms, the electronic structure changes, and the lone pair electrons of nitrogen atoms can participate in reactions, making it show significant protonation behavior under acidic conditions. This protonation process will change the electron distribution of the molecule, thereby affecting its optical, electrical and other properties. After protonation, the fluorescence intensity of the molecule increases and the emission wavelength is significantly redshifted, which can be used to develop acid-base sensors. Moreover, such molecules also have broad application prospects in the fields of organic light-emitting diodes, solar cells, biological imaging, etc.

[0144] The above embodiments provide a simple and efficient method for preparing organic functional molecules of nitrogen-containing polycyclic aromatic hydrocarbons. This method uses triaminotriphenylene as the starting material, and through the strategy of gradually constructing heterocycles, a nitrogen-containing five-membered heterocycle is first constructed on the triphenylene skeleton, and then a pyridine six-membered heterocycle is introduced, thereby introducing heteroatoms simultaneously on the polycyclic aromatic hydrocarbon skeleton. This method is not only simple and efficient, but also can accurately prepare organic functional molecules of nitrogen-containing polycyclic aromatic hydrocarbons that are sensitive to acid-base media, providing strong support for research and applications in related fields.

[0145] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above description of the embodiments. The description is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe, characterized in that, The structural formula of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe is shown in Formula (I): Wherein, R is hydrogen, acetyl or p-toluenesulfonyl.

2. The nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 1, wherein In an organic solvent or a mixed solution of an organic solvent and water, the fluorescence of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe has a dual-wavelength response to acids with a pK a less than 8.

5.

3. The nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 2, wherein The dual-wavelength response is manifested as follows: after acidification, the original fluorescence emission wavelength of the molecule in Formula (I) weakens, and at the same time, a new red-shifted fluorescence emission is generated, and the intensity of the newly generated fluorescence increases with the increase of the equivalent amount of acid; The original fluorescence emission wavelength of the molecule is the molecular fluorescence emission wavelength of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe in an organic solvent or a mixed solution of an organic solvent and water; The new fluorescence emission wavelength of the molecule is the fluorescence of the nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe that newly appears after adding an acid with a pK a less than 8.5 in an organic solvent or a mixed solution of an organic solvent and water.

4. A nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 2, characterized in that, The organic solvent includes one or more of dichloromethane, acetonitrile, DMSO, and methanol; The pK a Acids with a pK less than 8.5 include one or more of acetic acid, trifluoroacetic acid, hydrochloric acid, and Meldrum's acid.

5. A preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe as described in any one of claims 1-4, characterized in that, It includes the following steps: Step S1: Add a solvent to the compound (II) with the structural formula , then add triethylamine, add acetyl chloride AcCl or p-toluenesulfonyl chloride TsCl, and then carry out a reaction. After the reaction is completed, quench it, and obtain the compound (III) after purification. The structure is as follows: wherein, R1 is an acetyl group or a p-toluenesulfonyl group; Step S2: Mix the compound (III) obtained in Step S1 with a catalyst, an oxidizing agent molecular sieve, and a solvent, heat the mixture under oxygen, and after the reaction is completed, purify it to obtain the compound (IV) with the following structure: wherein, R1 is an acetyl group or a p-toluenesulfonyl group; Step S3: Mix the compound (IV) obtained in Step S2 with a solvent, add trifluoromethanesulfonic acid TfOH, carry out a reaction, basify the reaction system, and obtain compound (V) after purification, with the structure as follows: wherein, R1 is an acetyl group or a p-toluenesulfonyl group; Step S4: Add a solvent to the compound (V) obtained in Step S3, then add pyridine, add benzoyl chloride, and then heat for reaction. After the reaction is completed, quench the reaction, and after purification, obtain the compound (VI) with the following structure: wherein, R1 is an acetyl group or a p-toluenesulfonyl group; Step S5: Prepare a phosphorus oxychloride solution of the compound (VI) obtained in Step S4, add phosphorus pentoxide, heat and stir the mixture for reaction. After the reaction is completed, cool it, pour it into ice water, precipitate the product, filter the solid, and obtain compound (I-a) after purification. The structure is as follows: Among them, R1 is an acetyl group or a p-toluenesulfonyl group, and compound (I-a) is the compound corresponding to the case where R in compound (I) is an acetyl group or a p-toluenesulfonyl group.

6. The preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 5, characterized in that, After step S5, the following step S6 is carried out: Step S6: Prepare a methanol solution of the compound (I-a) obtained in Step S5, add sodium hydroxide, heat the mixture for reaction, and after the reaction is completed, purify to obtain the compound (I-b) with the following structure: Compound (I-b) is the compound corresponding to the case where R in compound (I) is hydrogen.

7. The preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 6, characterized in that, In step S6, the molar ratio of sodium hydroxide to compound (I-a) is 3-5 equivalents; In step S6, the temperature of the heating reaction is 50-70 °C, and the time is 5-24 hours; In step S6, the purification includes the following process: dilute the reaction solution by one time, extract with dichloromethane, wash the organic layer with water three times, then dry with anhydrous sodium sulfate, filter, concentrate under reduced pressure to obtain a crude product, and the crude product is subjected to column chromatography.

8. The preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 5, characterized in that, In step S1, the solvent is tetrahydrofuran or 1,2-dichloroethane; In step S1, the molar ratio of acetyl chloride AcCl or p-toluenesulfonyl chloride TsCl added to compound (II) is 1-6 equivalents; In step S1, the reaction temperature is 25 °C at room temperature, and the time is 18-24 hours; In step S1, after the reaction is completed, it is quenched with saturated sodium bicarbonate solution; In step S2, the catalyst is palladium acetate, the oxidant is copper acetate, and the solvent is dioxane; In step S2, the reaction temperature is 80–150 °C, and the time is 48-72 hours; In step S3, the solvent is tetrahydrofuran; In step S3, trifluoromethanesulfonic acid TfOH is added at 0 °C; In step S3, the molar ratio of trifluoromethanesulfonic acid TfOH added to compound (IV) is 2-4 equivalents; In step S3, the reaction is carried out under nitrogen, the reaction temperature is 50-70 °C, and the time is 10-12 h; In step S3, the reaction system is alkalized with sodium hydroxide solution; In step S4, the solvent is tetrahydrofuran or dichloromethane; In step S4, benzoyl chloride is added at 0-25 °C; In step S4, the molar ratio of benzoyl chloride added to compound (V) is 3-6 equivalents; In step S4, the reaction temperature is 0-60 °C, and the time is 12-14 hours; In step S4, after the reaction is completed, it is quenched with sodium bicarbonate solution; In step S5, the molar ratio of phosphorus pentoxide to compound (VI) is 1-5 equivalents; In step S5, the reaction temperature is 90-110 °C, and the time is 5-24 hours; In step S5, it is poured into ice water with a volume 5-20 times that of phosphorus oxychloride.

9. The preparation method of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to claim 5, wherein In step S1, the purification includes the following process: the quenched solution is extracted with dichloromethane, the organic layer is washed with saturated brine three times, dried with anhydrous sodium sulfate, filtered, concentrated under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography; In step S2, the purification includes the following process: diluting the reaction solution two times with dichloromethane solution and filtering, extracting with dichloromethane, washing the organic layer three times with water, drying with anhydrous sodium sulfate, filtering, concentrating under reduced pressure to obtain a crude product, and purifying the crude product by column chromatography; In step S3, the purification includes the following process: extracting with dichloromethane, washing the organic layer three times with water, drying with anhydrous sodium sulfate, filtering, concentrating under reduced pressure to obtain a crude product, and purifying the crude product by column chromatography; In step S4, the purification includes the following process: extracting with dichloromethane, washing the organic layer three times with brine, drying with anhydrous sodium sulfate, filtering, concentrating under reduced pressure to obtain a crude product, and purifying the crude product by column chromatography; In step S5, the purification includes the following process: extracting with dichloromethane, washing the organic layer three times with brine, drying with anhydrous sodium sulfate, filtering, concentrating under reduced pressure to obtain a crude product, and purifying the crude product by column chromatography.

10. Use of a nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe according to any one of claims 1-4, characterized in that, The nitrogen-containing bowl-shaped conjugated pH-responsive fluorescent probe is used for acid-base sensor materials, organic light-emitting diodes, information security or bioimaging.

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