Preparation method of ion type 4-hydroxy-1,5-naphthyridine europium complex

Abstract

The application discloses a preparation method of an ionic 4-hydroxy-1,5-naphthyridine europium complex, which comprises the following steps: reacting 4-hydroxy-1,5-naphthyridine ligand, alkali and a trivalent europium salt in butanol solvent according to a molar ratio of 4:4:1. The yield of the 4-hydroxy-1,5-naphthyridine europium complex prepared by the method is close to 100%, and the product has large particles, is easy to separate and has higher purity.

Description

Technical Field

[0001] This invention belongs to the field of rare earth complex luminescent materials preparation, specifically relating to a method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes. Background Technology

[0002] Rare-earth complex luminescent materials are characterized by bright colors, high efficiency, and large Stokes shifts, making them suitable for applications such as fluorescent anti-counterfeiting, light-converting agricultural films, lighting, and displays. Incorporating rare-earth complexes into polymers can achieve high luminescence brightness and high transparency at very low doping concentrations, making them ideal for light-converting materials. However, complexes based on traditional β-diketone ligands suffer from insufficient stability and rapidly degrade under ultraviolet irradiation, exhibiting a "photobleaching" phenomenon, which limits the practical application of such materials.

[0003] In previous research, our team developed a 4-hydroxy-1,5-naphthidine (ND) rare-earth luminescent material with high luminous efficiency and excellent photostability. This type of material possesses a rigid molecular structure, which greatly enhances its resistance to photodegradation (Chinese Patent 201110139842.1; Adv. Funct. Mater. 2016, 26, 2085). Subsequently, our team successfully developed the 4-hydroxy-1,5-naphthidine europium complex Eu(ND)3L. x The production process route (Chinese Patent 202210338200.2) for (ND represents 4-hydroxy-1,5-naphthidine ligands, L is a neutral ligand) has been completed, and small-scale, pilot-scale and industrial production (hundred-ton production line) of this type of material has been completed.

[0004] Our team has also developed an ionic rare earth complex, [Eu(ND)4]M (ND represents 4-hydroxy-1,5-naphthidine ligands, and M is an antication). This type of material has advantages such as stronger light absorption, compact coordination structure, and less ligand dissociation, making it a more efficient and stable luminescent material (Chinese Patent 201510130379.2). However, during industrial production, our team found some defects in the preparation of this material. Specifically, 4-hydroxy-1,5-naphthidine europium complexes are usually prepared in methanol or ethanol solvents, with ethanol being the most commonly used. However, for this ionic rare earth complex [Eu(ND)4]M, the yield in ethanol is only 80-87% (while the ideal yield is over 95%), leading to increased production costs. In addition, when this ionic rare earth complex [Eu(ND)4]M is prepared in ethanol, the resulting product has a small particle size, causing slow filtration speed and incomplete washing.

[0005] Therefore, the preparation of this ionic 4-hydroxy-1,5-naphthidine europium complex still faces technical challenges. Solving these production difficulties is crucial for the industrial promotion of this novel rare-earth complex luminescent material. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of low yield and small product particle size in the preparation process of ionic 4-hydroxy-1,5-naphthidine europium complexes, and to provide a method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes with a yield close to 100% and larger product particles that are easier to separate.

[0007] To achieve the above-mentioned technical objectives, the technical solution of the present invention is: a method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes, comprising mixing 4-hydroxy-1,5-naphthidine ligands, a base, and a trivalent europium salt in a molar ratio of 4:4:1 in a n-butanol solution, reacting at 90-118°C for 10 minutes to 24 hours, and obtaining the 4-hydroxy-1,5-naphthidine europium complexes by filtration or centrifugation after cooling;

[0008] The structural formula of the 4-hydroxy-1,5-naphthidine ligand is shown in Formula I, and the structure of the 4-hydroxy-1,5-naphthidine europium complex is shown in Formula II.

[0009]

[0010] In Formulas I and II, R1, R2, R3, R4, and R5 are selected from any one of hydrogen atom, Cl, cyano, and methyl; M is a quaternary ammonium ion, which is selected from C1-C18 straight-chain or branched alkyl, phenyl, or benzyl-substituted quaternary ammonium ions.

[0011] The trivalent europium salt is a hydrochloride, nitrate, or acetate of trivalent europium;

[0012] The base is a C1-C18 straight-chain or branched alkyl, phenyl, or benzyl-substituted ammonium hydroxide.

[0013] Preferably, the quaternary ammonium ion is selected from any one of tetramethylammonium, tetraethylammonium, tetrabutylammonium, phenyltrimethylammonium, benzyltrimethylammonium, and hexadecyltrimethylammonium.

[0014] Preferably, the alkali is selected from any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, phenyltrimethylammonium hydroxide, benzyltrimethylammonium hydroxide, and hexadecyltrimethylammonium hydroxide.

[0015] Preferably, the ratio of the 4-hydroxy-1,5-naphthidine ligand to the base can be 1:1 to 1:1.05. The ratio of the base to the 4-hydroxy-1,5-naphthidine ligand can be equivalent or slightly excess (1 to 1.05 equivalents), but not too much excess, otherwise the hydroxyl group will also participate in competitive coordination, resulting in the inability to form a complex with the ideal ratio.

[0016] In the above-mentioned method for producing europium complexes, 4-hydroxy-1,5-naphthidine ligands, bases, and trivalent europium salts are mixed in a molar ratio of 4:4:1. It should be noted that this ratio is only approximate, and any technical solution approaching this molar ratio is within the scope of protection of this invention patent; or, if the feeding ratio is intentionally deviated from this ratio (for example, increased to 5:5:1), but the three raw materials still react in this molar ratio (4:4:1) during the actual reaction process, it is also within the scope of protection of this invention.

[0017] Preferably, in the above-mentioned method for producing europium complexes, the amount of n-butanol is 5 to 20 times the mass of the 4-hydroxy-1,5-naphthidine ligand. More preferably, the amount of n-butanol is 5 to 10 times the mass of the 4-hydroxy-1,5-naphthidine ligand.

[0018] Preferably, the n-butanol solution can be n-butanol, or a mixture of n-butanol and methanol / ethanol, wherein the mass percentage of n-butanol in the mixture is 50% or more. When the n-butanol solution is a mixture of n-butanol and methanol / ethanol, the methanol / ethanol is distilled off as the temperature rises during heating, and the residual amount of methanol / ethanol in the final reaction system is less than 10% of the mass of n-butanol.

[0019] In the above-mentioned method for producing europium complexes, the reaction temperature is further preferably 100-110℃. Excessively high temperatures may cause partial decomposition of the organic quaternary ammonium base or the quaternary ammonium salt of the ligand.

[0020] As a variation of the technical solution of this invention, the preparation of the ionic rare earth complex [Eu(ND)4]M can also involve dissolving the alkali and / or rare earth salt in methanol or ethanol, then mixing the 4-hydroxy-1,5-naphthidine ligand, the methanol / ethanol solution of the alkali, and the methanol / ethanol solution of the trivalent europium salt in a molar ratio of 4:4:1, and further mixing with n-butanol, or directly mixing in n-butanol to form a n-butanol / methanol / ethanol mixed solution (n-butanol mass percentage of more than 50%). During the reaction, as the temperature rises, the low-boiling-point methanol / ethanol is distilled off, so that the reaction system is ultimately dominated by n-butanol (methanol and ethanol residual mass ratio less than 10%), thus achieving the technical effect described in this invention. This variation is also within the protection scope of this invention.

[0021] The present invention is proposed to improve the difficulties in the industrial preparation process of the ionic rare earth complex [Eu(ND)4]M (4-hydroxy-1,5-naphthidine europium complex). Specifically, the difficulties include: (1) low yield. Ethanol is usually used as a solvent in the preparation of 4-hydroxy-1,5-naphthidine rare earth complexes. After testing, the ionic rare earth complex [Eu(ND)4]M has a high solubility in ethanol solvent (about 10-20 g / L). There is a dissolution loss (about 10%) during the reaction and washing processes, resulting in a low product yield of only 80-87% (while the ideal yield is over 95%), which increases the production cost. (2) The complex product particles are fine, making separation difficult, filtration slow, and the product is not easy to wash clean. After drying, agglomeration occurs.

[0022] The reason n-butanol was chosen as the solvent in this invention is that it has lower polarity than commonly used methanol and ethanol, resulting in lower solubility (<1 g / L) for the ionic rare earth complex [Eu(ND)4]M. No published literature has ever reported the synthesis of similar rare earth complexes using butanol as a solvent. Unexpectedly, experiments revealed that the yield of the ionic rare earth complex [Eu(ND)4]M prepared in n-butanol can approach 100%. Furthermore, n-butanol (boiling point 118℃) has a higher boiling point than ethanol (boiling point 78℃). Experiments showed that the solubility of the ionic rare earth complex [Eu(ND)4]M in n-butanol solution increases significantly above 90℃, allowing the initially small particles to rapidly grow, precipitating into larger particles upon cooling. This makes final product separation easier and ensures that the washed product is free of impurities.

[0023] The beneficial effects of this invention are as follows: Using n-butanol as a solvent, the yield of the ionic rare earth complex [Eu(ND)4]M can be increased to nearly 100%, and the product has larger particles, is easier to separate, and has higher quality. The technical solution of this invention can significantly improve the yield and quality of the ionic rare earth complex [Eu(ND)4]M product, which is conducive to its large-scale industrial application. Attached Figure Description

[0024] Figure 1 This is a micrograph of the 4-hydroxy-1,5-naphthyl fluorine complex prepared using n-butanol in Example 1 of this invention.

[0025] Figure 2 This is a micrograph of the 4-hydroxy-1,5-naphthidine europium complex prepared using ethanol in Comparative Example 1 of this invention. Detailed Implementation

[0026] The product and preparation method of the present invention will be further described below through specific embodiments, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0027] A method for preparing a 4-hydroxy-1,5-naphthidine europium complex includes the following steps: mixing a 4-hydroxy-1,5-naphthidine ligand, a base, and a trivalent europium salt in a molar ratio of 4:4:1 in n-butanol solvent, or using a mixed solvent of n-butanol and methanol / ethanol, after distilling off the low-boiling methanol / ethanol, with the remaining n-butanol accounting for more than 90% by mass, reacting at 90-118°C for 10 minutes to 24 hours, and then filtering or centrifuging after cooling to obtain the 4-hydroxy-1,5-naphthidine europium complex.

[0028] <Preparation of Complexes from Butanol>

[0029] Example 1.

[0030] Europium complex [Eu(8mCND)4](NMe4) was prepared using n-butanol as a solvent. The structure of the europium complex in this embodiment is shown below:

[0031]

[0032] In 5 kg of n-butanol, 740 g (4 mol) of ligand 3-cyano-4-hydroxy-8-methyl-1,5-naphthidine (H8mCND), 724 g (4 mol) of organic base tetramethylammonium hydroxide pentahydrate, and 366 g (1 mol) of europium trichloride hexahydrate were added. The mixture was heated to 100 °C and reacted for 2 hours. The product gradually changed from a paste-like state to loose granules. After cooling, it was directly filtered and separated, washed with butanol, and vacuum dried to obtain 960 g of a light yellow europium complex product, with a yield of 99.7%. Mass spectrometry analysis (m / z, ESI): theoretical value 962.8, molecular ion peak measured M / Z = 889.1, [M-NMe4] - .

[0033] Example 2.

[0034] Europium complex [Eu(8mCND)4](PhNMe3) was prepared using n-butanol as a solvent. The structure of the europium complex in this embodiment is shown below:

[0035]

[0036] In 120 g of n-butanol, 7.40 g (0.04 mol) of ligand 3-cyano-4-hydroxy-8-methyl-1,5-naphthidine (H8mCND), 30.6 g of phenyltrimethylammonium hydroxide methanol solution (20% w / w @ MeOH, 0.04 mol), and 3.66 g (0.01 mol) of europium trichloride hexahydrate were added. The mixture was heated to 110 °C and reacted for 2 hours. During the heating process, methanol was gradually distilled off, leaving butanol as the reaction solvent (approximately 100 g of butanol remained). The product gradually changed from a paste-like consistency to loose granules. After cooling, the mixture was filtered, washed with butanol, and vacuum dried to obtain 10.23 g of a pale yellow europium complex product, with a yield of 99.8%. Mass spectrometry analysis (m / z, ESI): theoretical value 1025.2, molecular ion peak M / Z = 889.1, [M-PhNMe3] - .

[0037] Example 3.

[0038] Europium complex [Eu(8mND)4](NEt4) was prepared using n-butanol as a solvent. The structure of the europium complex in this embodiment is shown below:

[0039]

[0040] To 120 g of n-butanol, 6.40 g (0.04 mol) of ligand 4-hydroxy-8-methyl-1,5-naphthidine (H8mND), 24.7 g of tetraethylammonium hydroxide methanol solution (25% w / w @ MeOH, 0.042 mol; H8mND is relatively weakly acidic, requiring slightly more base), and 3.66 g (0.01 mol) of europium trichloride hexahydrate were added. The mixture was heated to 110 °C for 2 hours. During heating, methanol was gradually distilled off, leaving butanol as the reaction solvent (approximately 100 g of butanol remained). The product gradually changed from a paste-like consistency to loose granules. After cooling, the mixture was filtered, washed with butanol, and vacuum dried to obtain 9.11 g of a pale yellow europium complex product, with a yield of 99.2%. Mass spectrometry analysis (m / z, ESI): theoretical value 919.3, measured molecular ion peak M / Z = 789.1, [M-NMe4] - .

[0041] Comparative Example 1.

[0042] The europium complex [Eu(8mCND)4](NMe4) was prepared using ethanol as a solvent. Its structure is shown in Formula III, as in Example 1.

[0043] In 50 g of anhydrous ethanol, 7.40 g (0.04 mol) of ligand 3-cyano-4-hydroxy-8-methyl-1,5-naphthidine (H8mCND), 7.24 g (0.04 mol) of organic base tetramethylammonium hydroxide pentahydrate, and 3.66 g (0.01 mol) of europium trichloride hexahydrate were added. The mixture was heated to reflux for 2 hours to form a viscous, paste-like europium complex solid. After cooling, the mixture was filtered, washed with ethanol, and dried under vacuum to obtain 8.12 g of a white, agglomerated europium complex product, with a yield of 84.4%. Mass spectrometry analysis (m / z, ESI): theoretical value 962.8, molecular ion peak measured M / Z = 889.1, [M-NMe4] - .

[0044] Comparative Example 2.

[0045] The europium complex [Eu(8mCND)4](PhNMe3) was prepared using ethanol as a solvent. Its structure is shown in Formula IV, the same as in Example 2.

[0046] In 70 g of anhydrous ethanol, 7.40 g (0.04 mol) of ligand 3-cyano-4-hydroxy-8-methyl-1,5-naphthidine (H8mCND), 30.6 g (20% w / w @ MeOH, 0.04 mol) of phenyltrimethylammonium hydroxide methanol solution, and 3.66 g (0.01 mol) of europium trichloride hexahydrate were added. The mixture was heated under reflux for 2 hours to form a viscous, paste-like europium complex solid. After cooling, the mixture was filtered, washed with ethanol, and dried under vacuum to obtain 8.92 g of a white, agglomerated europium complex product, with a yield of 87.1%. Mass spectrometry analysis (m / z, ESI): theoretical value 1025.2, molecular ion peak measured M / Z = 889.1, [M-PhNMe3] - .

[0047] Comparative Example 3.

[0048] The europium complex [Eu(8mND)4](NEt4) was prepared using ethanol as a solvent. Its structure is shown in Formula V, as in Example 3.

[0049] In 75 g of anhydrous ethanol, 6.40 g (0.04 mol) of ligand 4-hydroxy-8-methyl-1,5-naphthidine (H8mND), 24.7 g of tetraethylammonium hydroxide methanol solution (25% w / w @ MeOH, 0.042 mol), and 3.66 g (0.01 mol) of europium trichloride hexahydrate were added. The mixture was heated under reflux for 2 hours to form a viscous, paste-like europium complex solid. After cooling, the mixture was filtered, washed with ethanol, and dried under vacuum to obtain 7.38 g of a white, hard, blocky europium complex product, with a yield of 80.3%. Mass spectrometry analysis (m / z, ESI): theoretical value 919.3, molecular ion peak measured M / Z = 789.1, [M-NMe4] - .

[0050] Example 4.

[0051] Product property characterization

[0052] (1) Photoluminescence quantum efficiency

[0053] The photoluminescence quantum efficiency is the absolute quantum efficiency measured using the integrating sphere of an FLS1000 spectrometer. Using 350 nm as the excitation wavelength and a blank quartz cell as a reference, the background signal in the 340–750 nm range is scanned. An appropriate amount of europium complex powder is placed in the quartz sample cell to scan the absorption and emission signals of the sample. The spectra from the two scans are processed. The difference in the area of ​​the integrated peak in the 340–360 nm range is the absorption value of the excitation light, and the difference in the area of ​​the integrated peak in the 500–750 nm range is the emission intensity value. The ratio between the emission intensity value and the absorption value is the photoluminescence quantum efficiency.

[0054] (2) Product particle size characterization

[0055] Take 10 mg of the europium complex product obtained from the examples and comparative examples, disperse it in 1 mL of petroleum ether (add 2-3 drops of ethanol to aid dispersion), and sonicate for 10 min to disperse it as much as possible. Take a drop of the well-mixed liquid onto a glass slide and observe the particle size under a microscope.

[0056] Table 1. Performance statistics of europium complex products

[0057]

[0058]

[0059] Table 1 shows that Comparative Examples 1-3, using ethanol or an ethanol / methanol mixture as solvents to prepare ionic europium complexes [Eu(8mND)4](NEt4), [Eu(8mCND)4](PhNMe3), and [Eu(8mND)4](NEt4), achieved product yields of 80-87%. This was mainly due to the high solubility of the complexes in the solvents, resulting in dissolution losses. In contrast, Examples 1-3, using butanol with lower polarity as a solvent, achieved product yields exceeding 99%, demonstrating that the change in solvent significantly improved yields. Furthermore, regarding particle size, the ligands and europium salts formed numerous fine particles (1-3 micrometers, such as…) in ethanol. Figure 2 As shown), while in butanol, the particles rapidly grow to tens of micrometers at high temperatures (e.g. Figure 1 As shown in the figure, the final product is easier to separate, washes thoroughly, and is less prone to clumping after drying. Regarding luminescence efficiency, the complexes prepared by the two solvents have similar luminescence efficiencies.

[0060] The technical solution of this invention uses n-butanol as a solvent, which can increase the yield of ionic rare earth complex [Eu(ND)4]M to nearly 100%, and the product has large particles, is easy to separate, and has higher quality, which is conducive to its large-scale industrial application.

[0061] The above-described embodiments are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing an ionic 4-hydroxy-1,5-naphthidine europium complex, characterized in that, The 4-hydroxy-1,5-naphthidine ligand, base, and trivalent europium salt are mixed in a molar ratio of 4:4:1 in a n-butanol solution or a mixed solution of n-butanol and methanol / ethanol, and reacted at 90~118℃ for 2 hours to 24 hours. After cooling, the mixture is filtered or centrifuged to obtain the 4-hydroxy-1,5-naphthidine europium complex. The structural formula of the 4-hydroxy-1,5-naphthidine ligand is shown in Formula I, and the structure of the 4-hydroxy-1,5-naphthidine europium complex is shown in Formula II. ； In Formulas I and II, R1, R2, R3, R4, and R5 are selected from any one of hydrogen atom, Cl, cyano, and methyl; M is a quaternary ammonium ion, which is selected from C1-C18 straight-chain or branched alkyl, phenyl, or benzyl-substituted quaternary ammonium ions. The trivalent europium salt is a hydrochloride, nitrate, or acetate of trivalent europium; The base is a C1-C18 straight-chain or branched alkyl, phenyl, or benzyl-substituted ammonium hydroxide; In the mixed solution of n-butanol and methanol / ethanol, the mass percentage of n-butanol is more than 50%.

2. The method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes as described in claim 1, characterized in that, The quaternary ammonium ion is selected from any one of tetramethylammonium, tetraethylammonium, tetrabutylammonium, phenyltrimethylammonium, benzyltrimethylammonium, and hexadecyltrimethylammonium.

3. The method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes as described in claim 1, characterized in that, The base is selected from any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, phenyltrimethylammonium hydroxide, benzyltrimethylammonium hydroxide, and hexadecyltrimethylammonium hydroxide.

4. The method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes as described in claim 1, characterized in that, The amount of n-butanol is 5 to 20 times the mass of the 4-hydroxy-1,5-naphthidine ligand.

5. The method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes as described in claim 1, characterized in that, When the n-butanol solution is a mixture of n-butanol and methanol / ethanol, the methanol / ethanol is distilled off as the temperature rises during the heating process, and the residual amount of methanol / ethanol in the final reaction system is less than 10% of the mass of n-butanol.

6. The method for preparing ionic 4-hydroxy-1,5-naphthidine europium complexes as described in claim 1, characterized in that, The reaction temperature is 100-110℃.

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