Organic fluorescent dye and preparation method thereof

Abstract

The invention relates to the technical field of fluorescent dye preparation, in particular to an organic fluorescent dye and a preparation method thereof.The preparation method comprises the following steps that m-diethylaminophenol and Meldrum's acid are catalyzed in an ethanol-water solvent through a supported catalyst and stirred to react in an oil bath, and an intermediate is obtained through acidification crystallization after cooling; and heating the intermediate, anhydrous potassium carbonate and ethyl iodoacetate in N, N-dimethylformamide under the protection of nitrogen to carry out alkylation reaction, and carrying out recrystallization, saponification hydrolysis and purification on the reaction liquid to obtain the organic fluorescent dye coumarin 343. The supported catalyst prepared by the invention shows good catalytic performance, stability and recoverability in the preparation reaction of the organic fluorescent dye.

Description

Technical Field

[0001] This invention relates to the field of fluorescent dye preparation technology, and more particularly to an organic fluorescent dye and its preparation method. Background Technology

[0002] Fluorescent dyes are an important class of optical labeling materials. Their luminescence mechanism is based on the absorption of light energy of a specific wavelength by the molecule, which excites electrons to transition to a higher energy state, and then releases energy as photons upon returning to the ground state, thereby generating a fluorescent signal. These materials have wide applications in bioimaging, disease diagnosis, and treatment monitoring. Among many fluorophores, coumarin derivatives are a class of fluorescent dyes with classic structures and excellent performance. Their main molecular structure is a benzopyranone structure (formed by the coupling of a benzene ring and a pyran ring). This type of structure has good photostability and high fluorescence quantum yield, and is the basis for the evolution of many important fluorescent dyes, such as fluorescein and rhodamine, whose structures are derived from coumarin derivatives. Currently, commonly used fluorescent dyes mainly include the following categories: fluorescein dyes have excellent water solubility and high fluorescence quantum yield; rhodamine dyes exhibit outstanding photostability and a large Stokes shift; and cyanin dyes, due to their strong fluorescence performance in the near-infrared region, are particularly suitable for imaging deep tissues in vivo.

[0003] In existing technologies, the synthesis of coumarin and its derivatives often uses homogeneous acid-base catalysts (such as concentrated sulfuric acid, p-toluenesulfonic acid, piperidine, etc.). These catalysts remain in the system after the reaction, making them difficult to separate and recover, leading to complex post-processing steps, generating large amounts of wastewater and waste residue, which does not conform to green chemistry principles. Furthermore, the catalysts cannot be recycled, resulting in high costs. In addition, traditional methods suffer from high reaction temperatures, long reaction times, and numerous side reactions, leading to low yields and low purity of the target product, coumarin 343. Fluorescent dyes are highly sensitive to impurities; even trace impurities can severely affect their fluorescence quantum yield and photostability. The crude products obtained by existing methods may have dark colors, high impurity content, and low recrystallization yields. Summary of the Invention

[0004] To address the problems mentioned in the background section, this invention provides an organic fluorescent dye and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing an organic fluorescent dye includes the following steps:

[0007] S1. Add m-diethylaminophenol and McFarland acid to a reactor pre-filled with an ethanol-water mixed solvent. Place the reaction system in an oil bath, add a supported catalyst, and react for 3-6 hours with stirring. After the reaction is complete, cool to room temperature, separate, and obtain an intermediate after acidification and crystallization.

[0008] S2. The intermediate, anhydrous potassium carbonate and ethyl iodoacetate were added to a reactor containing N,N-dimethylformamide. Under nitrogen protection, the reaction system was heated and stirred for 6-10 hours. After the reaction was completed, the mixture was cooled to room temperature and recrystallized to obtain pale yellow needle-like crystals. After saponification and hydrolysis, and purification, the organic fluorescent dye coumarin 343 was obtained.

[0009] Further, in step S1, the mass ratio of intermediate diethylaminophenol to McFarland acid is (1.29-1.58):1; in the ethanol-water mixed solvent, the volume ratio of ethanol to water is (8-10):1; the amount of supported catalyst added is 1-5% of the total mass of intermediate diethylaminophenol and McFarland acid; the ratio of the total volume of the reaction system to the total mass of intermediate diethylaminophenol and McFarland acid is 10-20 mL / g; acidification crystallization involves adding an aqueous acid solution to the reaction mixture to adjust the pH value to 1.5-3.0, preferably 2.0-2.5, to precipitate the intermediate; the acid is selected from hydrochloric acid, sulfuric acid, or phosphoric acid.

[0010] Furthermore, the supported catalyst in step S1 is prepared by the following steps:

[0011] A1. Zinc nitrate hexahydrate and hexamethylenetetramine were dissolved in deionized water and heated for 3-8 hours for crystallization. After the reaction was completed, ZnO nanorods were obtained by separation and purification.

[0012] A2. Add γ-methacryloxypropyltrimethoxysilane (KH-570) to anhydrous ethanol, and add 1-2 drops of glacial acetic acid to catalyze hydrolysis. Stir at room temperature for 30-60 min, add ZnO nanorods, heat and stir under reflux for 2-6 h. After the reaction is complete, centrifuge to obtain modified ZnO nanorods. The amount of glacial acetic acid added is 0.5-2% of the volume of γ-methacryloxypropyltrimethoxysilane.

[0013] A3. Modified ZnO nanorods, itaconic acid, and N-vinylimidazolium were dispersed in N,N-dimethylformamide to obtain a suspension. Azobisisobutyronitrile was added, and the mixture was stirred in an oil bath for 4-10 hours. After separation and purification, a supported catalyst was obtained. The separation and purification included cooling the product after the reaction, centrifuging, washing it sequentially with N,N-dimethylformamide and ethanol, and finally drying it under vacuum.

[0014] Furthermore, in step S1, the temperature of the oil bath is 62-68℃, preferably 64-66℃; the stirring speed is 200-400 rpm; and the reaction time is preferably 4-5 h.

[0015] Further, in step S2, the mass ratio of the intermediate, anhydrous potassium carbonate, and ethyl iodoacetate is 1:(0.9-1.0):(0.75-0.85), and the amount of N,N-dimethylformamide is 8-12 mL per gram of intermediate; nitrogen protection is achieved by purging nitrogen into the reactor for 5-15 min before the reaction to replace the air.

[0016] Further, in step S2, the heating and stirring temperature is 78-82℃, preferably 80℃; the stirring speed is 300-500 rpm; the solvent used for recrystallization is a mixed solvent of ethanol and water with a volume ratio of (4-6):1; the recrystallization temperature is 0-10℃; after saponification and hydrolysis, the product is precipitated by acidification to a pH value of 2.0-3.0; the saponification and hydrolysis is to add an aqueous solution of sodium hydroxide or potassium hydroxide or an alcohol-water mixture to the recrystallized ester intermediate crystals, and heat to 40-70℃ for 1-4 hours; the acid used for acidification is hydrochloric acid or sulfuric acid.

[0017] Further, in step A1, the mass ratio of zinc nitrate hexahydrate to hexamethylenetetramine is (2.0-2.2):1; the total concentration of both in deionized water is 0.05-0.15 mol / L; the temperature of the heating crystallization reaction is 95-100℃, and the reaction time is preferably 5-7h.

[0018] Further, in step A2, the concentration of γ-methacryloxypropyltrimethoxysilane in anhydrous ethanol is 1-3% (v / v); the concentration of modified ZnO nanorods in the anhydrous ethanol reaction system is 5-20 mg / mL; the heating and stirring reflux temperature is 60-70℃, preferably 65℃; and the stirring speed is 100-400 rpm.

[0019] Further, in step A3, the molar ratio of itaconic acid to N-vinylimidazole is 1:(1.2-1.8), preferably 1:(1.4-1.6); the total mass ratio of modified ZnO nanorods to itaconic acid and N-vinylimidazole is 1:(1-5); the amount of azobisisobutyronitrile added is 0.6-1.2% of the total molar amount of itaconic acid and N-vinylimidazole; the mass ratio of itaconic acid to N-vinylimidazole is 1:(0.87-1.30); the amount of azobisisobutyronitrile added is approximately 0.9-1.8% of the total mass of itaconic acid and N-vinylimidazole; the total concentration of itaconic acid and N-vinylimidazole in the suspension is 0.5-2.0 mol / L; the oil bath reaction temperature is 70-80℃; the reaction is carried out under nitrogen or inert gas protection.

[0020] According to another aspect of the present invention, an organic fluorescent dye prepared by the above preparation method is provided, having the structural formula shown in formula (I):

[0021]

[0022] Equation (I)

[0023] The beneficial effects of this invention are:

[0024] 1. In the technical solution of this invention, zinc oxide nanorods are prepared by hydrothermal method as a rigid support, and a covalently bonded interface layer is constructed on its surface using a silane coupling agent. Then, polymer brushes containing carboxyl and imidazole groups are grafted via interface-initiated polymerization to form an organic-inorganic hybrid core-shell catalyst. The catalyst uses zinc oxide nanorods as a rigid support, and multifunctional polymer brushes are covalently grafted onto them. The zinc ion sites on the zinc oxide surface act as Lewis acids, preferentially activating the carbonyl group of McFarland acid. The carboxyl groups in the polymer brush provide Brønsted acid sites for catalytic dehydration and cyclization, while the imidazole groups act as weak base / nucleophilic promoters, assisting in the formation of phenoxy anions and proton transfer. This allows the multi-step condensation, addition, dehydration, and cyclization reactions involved in the synthesis of the coumarin parent ring to proceed in an orderly and rapid manner under mild conditions, significantly improving the reaction rate and selectivity, and effectively suppressing the formation of byproducts.

[0025] 2. In the technical solution of this invention, the entire synthesis route is carried out under mild temperature and normal pressure, without the need for harsh anhydrous and oxygen-free conditions. The catalyst is a solid powder, which is convenient to add, and the post-processing can be separated by simple centrifugation or filtration, which greatly simplifies the operation process and reduces the difficulty and energy consumption of industrial production.

[0026] 3. In the technical solution of this invention, the prepared coumarin 343 dye undergoes highly selective condensation promoted by a supported catalyst, followed by alkylation, saponification, and purification steps, resulting in a final product with high purity and few impurities (such as isomers and unreacted raw materials). This ensures its stable and excellent fluorescence properties, meeting its high-end application requirements in dye lasers, fluorescent probes, and biolabeling. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the present invention;

[0028] Figure 2 The scanning electron microscope image (100 nm) of the supported catalyst in Example 1 of the present invention.

[0029] Figure 3 The image shows a scanning electron microscope (SEM) image (100 nm) of the supported catalyst in Example 2 of this invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following preparation examples and embodiments, m-diethylaminophenol (analytical grade), McFarland acid (isopropyl malonate, analytical grade), and anhydrous potassium carbonate were purchased from Yuci Botong Chemical Reagent and Glassware Distribution Department; N-vinylimidazolium (chemically pure), γ-methacryloyloxypropyltrimethoxysilane (KH-570, chemically pure), hexamethylenetetramine (chemically pure), zinc nitrate hexahydrate (chemically pure), ethyl iodoacetate (analytical grade), and azobisisobutyronitrile (AIBN, chemically pure) were purchased from Taiyuan Yingze District Julian Laboratory Supplies Sales Center; and itaconic acid (chemically pure) was purchased from Shanxi Hongxinyuantai Science and Trade Co., Ltd.

[0032] Preparation Example 1

[0033] Supported catalysts are prepared by the following steps:

[0034] A1. Weigh 2.97 g of zinc nitrate hexahydrate and 1.40 g of hexamethylenetetramine, dissolve them in 200 mL of deionized water (total concentration approximately 0.05 mol / L), stir magnetically until completely dissolved, heat and stir in an oil bath at 98 °C and 300 rpm for 6 h. After the reaction is complete, allow to cool naturally to room temperature, separate the resulting white precipitate by centrifugation, and wash it three times each with deionized water and anhydrous ethanol. Dry the product in a vacuum drying oven at 60 °C for 6 h to obtain white powdered ZnO nanorods.

[0035] A2. Measure 1.5 mL of γ-methacryloxypropyltrimethoxysilane (KH-570) and 0.015 mL of glacial acetic acid, add them to 150 mL of anhydrous ethanol, and stir magnetically for 45 min at room temperature to pre-hydrolyze the solution. Weigh 1.5 g of the ZnO nanorods prepared above and add them to the solution. Heat and stir under reflux in an oil bath at 65 °C for 4 h at a stirring speed of 250 rpm. After the reaction is complete, centrifuge and wash three times with anhydrous ethanol. Dry the obtained solid under vacuum at 60 °C for 6 h to obtain modified ZnO nanorods.

[0036] A3. Weigh 1.0 g of modified ZnO nanorods, 1.30 g of itaconic acid and 1.42 g of N-vinylimidazole, add 50 mL of N,N-dimethylformamide (DMF), and ultrasonically disperse for 30 min to form a uniform suspension. Add 0.041 g of azobisisobutyronitrile (AIBN) as an initiator. Under nitrogen protection, place in an oil bath at 75 °C and stir for 8 h at a stirring speed of 300 rpm. After the reaction is completed, cool to room temperature, centrifuge the obtained solid, wash three times with N,N-dimethylformamide and ethanol, and finally vacuum dry at 60 °C for 12 h to obtain the supported catalyst.

[0037] Preparation Example 2

[0038] Supported catalysts are prepared by the following steps:

[0039] A1. Weigh 4.46g of zinc nitrate hexahydrate and 1.96g of hexamethylenetetramine, dissolve them in 100mL of deionized water, stir to dissolve, and crystallize the solution at 100℃ for 5h. The subsequent separation, washing and drying operations are the same as in Preparation Example 1 to obtain ZnO nanorods.

[0040] A2. Measure 3.0 mL of KH-570 and 0.03 mL of glacial acetic acid, add them to 100 mL of anhydrous ethanol, stir and pre-hydrolyze for 30 min, add 2.0 g of ZnO nanorods (concentration 20 mg / mL), reflux at 70 °C for 3 h, stirring at 150 rpm, and then perform the same separation, washing and drying operations as in Preparation Example 1 to obtain modified ZnO nanorods;

[0041] A3. Weigh 1.0 g of modified ZnO nanorods, 1.30 g of itaconic acid and 1.18 g of N-vinylimidazole, add 40 mL of DMF and 0.025 g of AIBN, and react at 70 °C for 10 h. The subsequent treatment is the same as in Preparation Example 1 to obtain the supported catalyst.

[0042] Preparation Example 3

[0043] Supported catalysts are prepared by the following steps:

[0044] A1. Weigh 5.94g of zinc nitrate hexahydrate and 2.66g of hexamethylenetetramine, dissolve them in 200mL of deionized water, and crystallize them at 95℃ for 7h. The remaining operations are the same as in Preparation Example 1.

[0045] A2. Measure 0.75 mL of KH-570 and 0.015 mL of glacial acetic acid, add them to 75 mL of anhydrous ethanol, stir for 60 min, add 0.375 g of ZnO nanorods, reflux at 60 °C for 6 h, stirring at 400 rpm, and perform the remaining operations as in Preparation Example 1.

[0046] A3. Weigh 0.5g of modified ZnO nanorods, 0.65g of itaconic acid and 1.65g of N-vinylimidazole, add 50ml of LDMMF and 0.045g of AIBN, and react at 80℃ for 4h. The remaining operations are the same as in Preparation Example 1 to obtain the supported catalyst.

[0047] Example 1

[0048] A method for preparing an organic fluorescent dye includes the following steps:

[0049] S1. Weigh 1.81 g of m-diethylaminophenol and 1.26 g of McFarland acid, add them to a 30 mL ethanol-water mixed solvent, add 0.092 g of the supported catalyst prepared in Preparation Example 1, place the reaction system in a 65 °C oil bath, and react for 4 h with stirring at 300 rpm. After the reaction is complete, cool to room temperature, filter the reaction solution to remove the solid catalyst, and slowly adjust the pH of the filtrate to 2.2 with 2 M hydrochloric acid aqueous solution in an ice-water bath. A large amount of solid precipitates out. Continue stirring in an ice bath for 30 min to allow complete crystallization, filter, wash the filter cake with a small amount of ice water, recover the catalyst, and vacuum dry to obtain an orange-red solid intermediate.

[0050] S2. Weigh 3.0 g of the intermediate obtained in step S1, 2.82 g of anhydrous potassium carbonate and 2.25 g of ethyl iodoacetate, add 30 mL of N,N-dimethylformamide, and heat and stir in an oil bath at 80 °C for 8 h under nitrogen protection at a stirring speed of 400 rpm. After the reaction is completed, cool to room temperature, pour the reaction solution into 200 mL of ice water, and precipitate the solid with stirring. Filter the solid and recrystallize the crude product with an ethanol-water mixed solvent (V(ethanol):V(water)=5:1) at 5 °C to obtain pale yellow needle-like crystals.

[0051] S3. Place the crystals in a 100mL round-bottom flask, add 30mL of ethanol and 15mL of 2M sodium hydroxide aqueous solution, and stir at 60℃ for 2h to carry out saponification and hydrolysis. After the reaction is completed, cool and acidify with 2M hydrochloric acid solution to pH=2.5 under ice-water bath. A bright yellow solid precipitates out. Filter and wash the filter cake with a small amount of cold water and cold ethanol in sequence. Purify the crude product by silica gel column chromatography (eluent: dichloromethane / methanol, gradient elution). Collect the main fraction, remove the solvent by rotary evaporation, and dry under vacuum to obtain the final product coumarin 343.

[0052] Example 2

[0053] A method for preparing an organic fluorescent dye includes the following steps:

[0054] S1. Weigh 1.81 g of m-diethylaminophenol and 1.40 g of McFarland acid, add them to 50 mL of ethanol-water (V:V=8:1) solvent, add 0.064 g of the supported catalyst prepared in Example 2, and react at 62 °C and 200 rpm for 5 h. Acidification is performed using sulfuric acid to adjust the pH to 1.8. The remaining treatment is the same as in Example 1.

[0055] S2. Weigh 2.5g of intermediate, 2.38g of anhydrous potassium carbonate and 2.04g of ethyl iodoacetate, add them to 20mL of DMF, and react at 78℃ and 300 rpm for 10h. After treating the reaction solution, recrystallize it at 0℃ with ethanol-water (4:1). The remaining treatment is the same as in Example 1.

[0056] S3. Saponification and hydrolysis were carried out using 1M KOH ethanol-water solution (1:1) at 50°C for 3 hours. After acidification to pH=3.0, a solid was precipitated. After filtration, the solid was directly purified by recrystallization with hot ethanol once. The remaining treatments were the same as in Example 1 to obtain the product.

[0057] Example 3

[0058] A method for preparing an organic fluorescent dye includes the following steps:

[0059] S1. Weigh 1.99 g of m-diethylaminophenol and 1.26 g of McFarland acid, add them to 30 mL of ethanol-water (V:V=10:1) solvent, add 0.065 g of the supported catalyst prepared in Preparation Example 3, react at 68 °C and 400 rpm for 3 h, adjust the pH to 2.5 with phosphoric acid, and perform the remaining treatment as in Example 1.

[0060] S2. Weigh 3.0 g of intermediate, 3.0 g of anhydrous potassium carbonate and 2.55 g of ethyl iodoacetate, add them to 36 mL of DMF, and react at 82 °C and 500 rpm for 6 h. The recrystallization solvent is ethanol-water (V:V=6:1) and the temperature is 10 °C. The remaining treatment is the same as in Example 1.

[0061] S3. Saponification and hydrolysis were performed using 0.5M NaOH aqueous solution at 70°C for 1 hour. After acidification to pH=2.0, a solid was precipitated. The product was purified by column chromatography (eluent: ethyl acetate / petroleum ether system). The remaining treatments were the same as in Example 1 to obtain the product.

[0062] Example 4

[0063] A method for preparing an organic fluorescent dye includes the following steps:

[0064] S1. Weigh 1.85 g of m-diethylaminophenol and 1.40 g of McFarland acid, add them to 35 mL of ethanol-water (V:V=9:1) solvent, add 0.098 g of the supported catalyst prepared in Example 1, and react at 64 °C and 350 rpm for 5 h. After filtering the reaction solution, adjust the pH to 2.0 with 2 M sulfuric acid. The remaining treatment is the same as in Example 1.

[0065] S2. Weigh 2.8g of intermediate, 2.66g of anhydrous potassium carbonate and 2.24g of ethyl iodoacetate, add them to 25mL of DMF, and react at 80℃ and 400rpm for 9h. The recrystallization solvent is ethanol-water (V:V=5:1), the temperature is 2℃, and the rest of the treatment is the same as in Example 1.

[0066] S3. Saponification and hydrolysis were performed using a 1.5M NaOH solution in ethanol-water (V:V=2:1) ​​at 60°C for 2 hours. The solution was then acidified to pH=2.8 with 2M hydrochloric acid, filtered, and purified by silica gel column chromatography (ethyl acetate / petroleum ether = 1 / 1 to 2 / 1 gradient). The remaining treatments were the same as in Example 1 to obtain the product.

[0067] Example 5

[0068] A method for preparing an organic fluorescent dye includes the following steps:

[0069] S1. Weigh 1.78 g of m-diethylaminophenol and 1.26 g of McFarland acid, add them to 25 mL of ethanol-water (V:V=8.5:1) solvent, add 0.061 g of the supported catalyst prepared in Example 2, and react at 66 °C and 250 rpm for 4.5 h. After filtering the reaction solution, adjust the pH to 2.4 with 1 M hydrochloric acid. The rest of the treatment is the same as in Example 1.

[0070] S2. Weigh 3.2g of intermediate, 3.04g of anhydrous potassium carbonate and 2.72g of ethyl iodoacetate, add them to 32mL of DMF, and react at 79℃ and 350rpm for 7h. The recrystallization solvent is ethanol-water (V:V=4.5:1), the temperature is 8℃, and the rest of the treatment is the same as in Example 1.

[0071] S3. Saponification and hydrolysis were performed using 2M KOH aqueous solution at 45°C for 3.5 hours. The reaction was then acidified with 1M sulfuric acid to pH 2.2. The remaining treatments were the same as in Example 1 to obtain the product.

[0072] Example 6

[0073] A method for preparing an organic fluorescent dye includes the following steps:

[0074] S1. Weigh 1.90 g of m-diethylaminophenol and 1.26 g of McFarland acid, add them to 32 mL of ethanol-water (V:V=10:1) solvent, add 0.095 g of the supported catalyst prepared in Preparation Example 3, and react at 62 °C and 380 rpm for 6 h. After filtering the reaction solution, adjust the pH to 1.8 with 3 M phosphoric acid. The remaining treatment is the same as in Example 1.

[0075] S2. Weigh 2.0 g of intermediate, 1.80 g of anhydrous potassium carbonate and 1.50 g of ethyl iodoacetate, add them to 20 mL of DMF, and react at 81 °C and 450 rpm for 6 h. The recrystallization solvent is ethanol-water (V:V=6:1), the temperature is 0 °C, and the rest of the treatment is the same as in Example 1.

[0076] S3. Saponification and hydrolysis were performed using a 0.8M NaOH methanol-water (V:V=1:1) solution at 70°C for 1.5 hours. The solution was then acidified to pH=3.0. The remaining treatments were the same as in Example 1 to obtain the product.

[0077] Example 7

[0078] A method for preparing an organic fluorescent dye includes the following steps:

[0079] S1. Weigh 1.81 g of m-diethylaminophenol and 1.33 g of McFarland acid, add them to 30 mL of ethanol-water (V:V=8:1) solvent, add 0.078 g of the supported catalyst prepared in Example 1, and react at 68 °C and 300 rpm for 3.5 h. After filtering the reaction solution, adjust the pH to 2.5 with 2 M hydrochloric acid. The remaining treatment is the same as in Example 1.

[0080] S2. Weigh 3.5g of intermediate, 3.5g of anhydrous potassium carbonate and 2.98g of ethyl iodoacetate, add them to 35mL of DMF, and react at 78℃ and 500rpm for 10h. The recrystallization solvent is ethanol-water (V:V=4:1), the temperature is 5℃, and the rest of the treatment is the same as in Example 1.

[0081] S3. Saponification and hydrolysis were performed using 1M NaOH aqueous solution at 50°C for 4 hours, followed by acidification to pH=2.0. The remaining treatments were the same as in Example 1 to obtain the product.

[0082] Example 8

[0083] A method for preparing an organic fluorescent dye includes the following steps:

[0084] S1. Weigh 1.99 g of m-diethylaminophenol and 1.40 g of McFarland acid, add them to 38 mL of ethanol-water (V:V=9:1) solvent, add 0.102 g of the supported catalyst prepared in Example 2, and react at 65 °C and 400 rpm for 4 h. After filtering the reaction solution, adjust the pH to 2.6 with 1.5 M sulfuric acid. The remaining treatment is the same as in Example 1.

[0085] S2. Weigh 4.0 g of intermediate, 3.60 g of anhydrous potassium carbonate and 3.20 g of ethyl iodoacetate, add them to 40 mL of DMF, and react at 82 °C and 300 rpm for 8 h. The recrystallization solvent is ethanol-water (V:V=5:1) and the temperature is 10 °C. The remaining treatment is the same as in Example 1.

[0086] S3. Saponification and hydrolysis were performed using a 1.2M KOH ethanol-water (V:V=3:1) solution at 65°C for 2 hours. The solution was then acidified with 2M hydrochloric acid to pH=2.4. The remaining treatments were the same as in Example 1 to obtain the product.

[0087] Example 9

[0088] A method for preparing an organic fluorescent dye includes the following steps:

[0089] S1. Weigh 1.72 g of m-diethylaminophenol and 1.26 g of McFarland acid, add them to 28 mL of ethanol-water (V:V=8:1) solvent, add 0.075 g of the supported catalyst prepared in Preparation Example 3, and react at 63 °C and 200 rpm for 5.5 h. After filtering the reaction solution, adjust the pH to 2.1 with 2 M hydrochloric acid. The rest of the treatment is the same as in Example 1.

[0090] S2. Weigh 2.2g of intermediate, 2.20g of anhydrous potassium carbonate and 1.83g of ethyl iodoacetate, add them to 22mL of DMF, and react at 80℃ and 320rpm for 7.5h. The recrystallization solvent is ethanol-water (V:V=4.5:1), the temperature is 3℃, and the rest of the treatment is the same as in Example 1.

[0091] S3. Saponification and hydrolysis were performed using 1M NaOH aqueous solution at 55°C for 2.5 hours, followed by acidification to pH 2.7. The remaining treatments were the same as in Example 1 to obtain the product.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that no catalyst is added, while the remaining steps are the same as in Example 1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that 0.092g of p-toluenesulfonic acid (PTSA) was added as a catalyst; the remaining steps are the same as in Example 2.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 1 is that 0.092g of the unmodified ZnO nanorods from step A1 of Preparation Example 3 were added as a catalyst; the remaining steps are the same as in Example 3.

[0098] Collect the products from Examples 1-9 and Comparative Examples 1-3, and calculate the yield and purity. Yield (%) = [actual mass of coumarin 343 obtained (g) / theoretical yield (g)] × 100%, where the theoretical yield is calculated with McFlurry's acid (9.0 mmol) as the limiting reactant (M). 香豆素343 =365.4 g / mol), yielding a theoretical yield of ≈3.29 g. Chromatographic conditions were: C18 column; mobile phase: methanol / 0.1% phosphoric acid aqueous solution (70:30, v / v); flow rate: 1.0 mL / min; detection wavelength: 430 nm; column temperature: 30 °C. Results are shown in Table 1.

[0099] Table 1. Yield and purity results of Examples 1-9 and Comparative Examples 1-3

[0100]

[0101] In Examples 1-9 and Comparative Examples 2-3, after the reaction in step S1, the entire reaction mixture was transferred to a pre-weighed Buchner funnel lined with filter paper for filtration. The reaction flask and filter cake were washed with 10 mL of ethanol (5 mL × 2 times) to ensure complete catalyst transfer. The filtrate and washings were combined to obtain a crude intermediate solution. The filter paper containing the catalyst cake was carefully transferred to a pre-weighed watch glass, and the initial catalyst mass and the mass of the watch glass + filter paper + wet catalyst were recorded. The watch glass was dried in a vacuum drying oven at 60°C for 4 hours until constant weight. It was then removed, cooled to room temperature in a desiccator, and accurately weighed, recording the mass of the watch glass + filter paper + dry catalyst. The catalyst recovery rate was calculated. Dry catalyst mass = (watch glass + filter paper + dry catalyst mass) - (watch glass + filter paper mass). Recovery rate (%) = (dry catalyst mass / actual mass of catalyst added in each group) × 100%. The recovered, dried, and weighed catalyst was collected. Following the steps and feed amounts in Example 1, a secondary catalytic experiment was conducted, and the yield and purity of the secondary product were calculated. The results are shown in Tables 2 and 3:

[0102] Table 2. Catalyst recovery results of Examples 1-9 and Comparative Examples 2-3

[0103]

[0104] Table 3. Performance evaluation of the recycled catalyst in Example 1 for secondary use

[0105]

[0106] As shown in Table 1, the yields of Examples 1-9 were between 83.1% and 89.7%, and the purity was between 95.9% and 97.6%. This indicates that the supported catalysts prepared in Examples 1-3 exhibit good catalytic activity and selectivity in the organic fluorescent dye preparation reaction, and can effectively promote the reaction to obtain products with high yields and purity.

[0107] Comparative Example 1, without a catalyst, achieved a yield of only 24.5% and a purity of 69.1%, significantly lower than the examples. This indicates that the catalyst plays a crucial role in the reaction; without it, the reaction is difficult to proceed effectively, resulting in low product yield and purity. Comparative Example 2, using p-toluenesulfonic acid (PTSA) as a catalyst, achieved a yield of 78.5% and a purity of 91.3%. While it also showed some catalytic effect, both the yield and purity were lower than the examples, demonstrating that supported catalysts exhibit better catalytic performance than traditional acid catalysts. Comparative Example 3, using unmodified ZnO nanorods as a catalyst, achieved a yield of 58.6% and a purity of 87.7%, lower than the examples. This indicates that the modified supported catalyst possesses superior catalytic activity, and the modification process may have enhanced the interaction between the catalyst and reactants, thereby improving catalytic efficiency.

[0108] As shown in Table 2, the catalyst recovery rates in Examples 1-9 were between 95.5% and 97.5%, indicating that the prepared supported catalysts have good stability and recyclability. They are not easily lost during the reaction process and can be easily separated from the reaction system for reuse, thus reducing production costs.

[0109] Comparative Example 2, p-toluenesulfonic acid, is a liquid acid catalyst, which is difficult to separate and recover from the reaction system, with a recovery rate of 0%. This further demonstrates the advantages of supported catalysts in terms of recycling. Comparative Example 3, with its unmodified ZnO nanorod catalyst, had a recovery rate of 91.2%, lower than the examples. This may be due to the poor dispersibility and stability of the unmodified nanorods in the reaction system, leading to the loss of some catalyst during separation.

[0110] As shown in Table 3, the secondary product yield of the recovered catalyst in Example 1 was 86.2% and the purity was 97.1%. Compared with the yield of 89.7% and the purity of 97.6% when it was used for the first time, the change was not significant, indicating that the recovered catalyst still maintained high catalytic activity and selectivity, further proving that the supported catalyst has good reusability.

[0111] In summary, the prepared supported catalyst exhibits good catalytic performance, stability, and recyclability in the preparation reaction of organic fluorescent dyes.

[0112] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0113] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing an organic fluorescent dye, characterized by, The method comprises the following steps: S1, adding m-diaminoethyl phenol and mesitylic acid into a reactor pre-loaded with an ethanol-water mixed solvent, placing the reaction system in an oil bath, adding a supported catalyst, and reacting for 3-6 hours under stirring, after the reaction is completed, cooling to room temperature, separating, and obtaining an intermediate after acidification and crystallization; S2, adding the intermediate, anhydrous potassium carbonate, and ethyl iodoacetate into a reactor loaded with N,N-dimethylformamide, heating and stirring the reaction system under nitrogen protection for 6-10 hours, after the reaction is completed, cooling to room temperature, recrystallizing to obtain crystals, saponifying and hydrolyzing, and obtaining the organic fluorescent dye coumarin 343 after purification.

2. The method for preparing an organic fluorescent dye according to claim 1, characterized in that, In step S1, the mass ratio of m-diaminoethyl phenol and mesitylic acid is (1.29-1.58):1, the volume ratio of ethanol to water in the ethanol-water mixed solvent is (8-10):1, and the addition amount of the supported catalyst is 1-5% of the total mass of m-diaminoethyl phenol and mesitylic acid.

3. The method for preparing an organic fluorescent dye according to claim 1, characterized in that, The supported catalyst in step S1 is prepared by the following steps: A1, dissolving zinc nitrate hexahydrate and hexamethylenetetramine in deionized water, heating and crystallizing for 3-8 hours, after the reaction is completed, separating and purifying to obtain ZnO nanorods; A2, adding γ-methacryloyloxypropyltrimethoxysilane into anhydrous ethanol, stirring for 30-60 minutes at room temperature, adding ZnO nanorods, heating and stirring under reflux for 2-6 hours, after the reaction is completed, centrifugal separation is performed to obtain modified ZnO nanorods; A3, dispersing the modified ZnO nanorods, itaconic acid, and N-vinylimidazole in N,N-dimethylformamide to obtain a suspension, adding azobisisobutyronitrile, and reacting for 4-10 hours under stirring and oil bath heating, after separating and purifying, a supported catalyst is obtained.

4. The method for preparing an organic fluorescent dye according to claim 1, characterized in that, In step S1, the temperature of the oil bath is 62-68℃, and the stirring speed is 200-400 rpm.

5. The method for preparing an organic fluorescent dye according to claim 1, characterized in that, In step S2, the mass ratio of the intermediate, anhydrous potassium carbonate, and ethyl iodoacetate is 1:(0.9-1.0):(0.75-0.85), and the amount of N,N-dimethylformamide used is 8-12 mL per gram of the intermediate.

6. The method for preparing an organic fluorescent dye according to claim 1, characterized in that, In step S2, the heating and stirring reaction temperature is 78-82℃, and the stirring speed is 300-500 rpm; the recrystallization solvent is an ethanol-water mixed solvent with a volume ratio of (4-6):1; after saponification and hydrolysis, the product is precipitated by acidification to a pH value of 2.0-3.

0.

7. The method for preparing an organic fluorescent dye according to claim 3, characterized in that, In step A1, the mass ratio of zinc nitrate hexahydrate to hexamethylenetetramine is (2.0-2.2):1; and the heating and crystallization reaction temperature is 95-100℃.

8. The method for preparing an organic fluorescent dye according to claim 3, characterized in that, In step A2, the concentration of γ-methacryloyloxypropyltrimethoxysilane in anhydrous ethanol is 1-3% (v / v); the heating and stirring reflux temperature is 60-70℃, and the stirring speed is 100-400 rpm.

9. The method for preparing an organic fluorescent dye according to claim 3, characterized in that, In step A3, the molar ratio of itaconic acid to N-vinylimidazole is 1:(1.2-1.8), and the addition amount of azobisisobutyronitrile is 0.6-1.2% of the total moles of itaconic acid and N-vinylimidazole; and the oil bath reaction temperature is 70-80℃.

10. An organic fluorescent dye prepared according to the process of any one of claims 1 to 9.

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