Invisible fluorescent pigments, process for their preparation and use

Abstract

The present application relates to a kind of invisible fluorescent pigments and its preparation method and application, the structural formula of the invisible fluorescent pigments is as shown in formula (I), in formula (I), Ar1 It is the five-membered heterocyclic ring as shown in formula (II-1), X is atom except carbon atom, Ar2 It is fluorine phenyl, Re is Tb or Eu.The invisible fluorescent pigments of the present application have the characteristics of high fluorescence intensity, good stability and unique spectral characteristics, and have good practical value and industrialization prospect in the field of anti-fake ink and the like.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting ink technology, and in particular to an invisible fluorescent pigment, its preparation method, and its application. Background Technology

[0002] With the rapid development of the commodity economy and science and technology, counterfeiting methods are becoming increasingly professional and covert, placing higher demands on the anti-counterfeiting technologies of paper currency, securities, and important certificates. Fluorescent anti-counterfeiting ink, as a widely used visual security technology, occupies an important position in the anti-counterfeiting field due to its convenient detection and strong concealment. However, traditional fluorescent anti-counterfeiting materials generally suffer from poor stability, susceptibility to environmental interference, excessively wide characteristic emission bands, and ease of counterfeiting, making it difficult to meet the stringent requirements of anti-counterfeiting scenarios regarding material performance and security levels. Summary of the Invention

[0003] Therefore, it is necessary to provide an invisible fluorescent pigment, its preparation method, and its application to address the above problems. The invisible fluorescent pigment has the characteristics of high fluorescence intensity, good stability, and unique spectral features.

[0004] An invisible fluorescent pigment, the structural formula of which is shown in formula (I), wherein Ar1 is a five-membered heterocycle as shown in formula (II-1), X is an atom other than carbon, Ar2 is a fluorophenyl, and Re is Tb or Eu;

[0005] , .

[0006] In one embodiment, Ar1 is at least one of a selenophene ring or a tellurene ring;

[0007] And / or, Ar2 is at least one of a 4-fluorobenzene ring, a 2,4,6-trifluorobenzene ring, or a 3,4,5-trifluorobenzene ring.

[0008] A method for preparing an invisible fluorescent pigment as described above includes the following steps:

[0009] The first compound, with the structural formula shown in formula (II), was subjected to an electrophilic acylation reaction to obtain the second compound, with the structural formula shown in formula (III). , ;

[0010] The second compound is subjected to a cross-aldollar condensation reaction to obtain a third compound, the structural formula of which is shown in formula (Ⅳ-ⅰ), formula (Ⅳ-ⅱ), or formula (Ⅳ-ⅲ). , , ;

[0011] The third compound is subjected to a Michael addition reaction to yield a fourth compound, the structural formula of which is shown in formula (V-i), (V-ii), or (V-iii). , , ;

[0012] A terbium salt or europium salt was added to the fourth compound to carry out a complexation reaction, resulting in an invisible fluorescent pigment with the structural formula shown in formula (I).

[0013] In one embodiment, the molar ratio of the electrophilic reagent to the first compound in the electrophilic acylation reaction is 1.2:1 to 2.0:1;

[0014] And / or, the molar ratio of the electrophilic reagent to the second compound in the cross-aldol condensation reaction is 1.1:1 to 1.6:1;

[0015] And / or, the molar ratio of the nucleophile to the third compound in the Michael addition reaction is 1.3:1 to 2:1;

[0016] And / or, the molar ratio of the fourth compound to the terbium salt is 2.8:1 to 3.2:1;

[0017] And / or, the molar ratio of the fourth compound to the europium salt is 2.8:1 to 3.2:1.

[0018] In one embodiment, the electrophilic reagent in the electrophilic acylation reaction is acetyl chloride;

[0019] And / or, the electrophilic reagent in the cross-aldollation reaction is fluorobenzaldehyde;

[0020] And / or, the nucleophile in the Michael addition reaction is at least one of hydrogen sulfide or sodium hydrosulfide.

[0021] In one embodiment, the first compound is selected from at least one of selenophene or tellurene;

[0022] And / or, the fluorobenzaldehyde is selected from at least one of 4-fluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde or 3,4,5-trifluorobenzaldehyde;

[0023] And / or, the terbium salt is selected from TbCl3;

[0024] And / or, the europium salt is selected from EuCl3.

[0025] In one embodiment, the electrophilic acylation reaction is carried out in an acidic solvent, wherein the mass ratio of the first compound to the acidic solvent is 1:1.5 to 1:3;

[0026] And / or, the electrophilic acylation reaction further includes the addition of a Lewis acid compound, wherein the molar ratio of the first compound to the Lewis acid compound is 1:0.04 to 1:0.08;

[0027] And / or, the pH of the complexation reaction is 6 to 8.

[0028] In one embodiment, the acidic solvent is selected from at least one of acetic acid or acetic anhydride;

[0029] And / or, the Lewis acid compound is selected from at least one of iodine or anhydrous aluminum trichloride.

[0030] In one embodiment, the electrophilic acylation reaction takes 3 to 6 hours;

[0031] And / or, the temperature of the cross-aldol condensation reaction is 0℃~25℃, and the time is 12h~20h;

[0032] And / or, the Michael addition reaction is carried out at a temperature of -10°C to 0°C for a time of 3 to 8 hours;

[0033] And / or, the complexation reaction takes 3 to 10 hours.

[0034] An anti-counterfeiting ink, the anti-counterfeiting ink comprising the invisible fluorescent pigment as described above.

[0035] In this invention, the five-membered heterocycle in the ligand is connected to the benzene ring to form a planar π-conjugated system with high rigidity. Three identical ligands and two oxygen ligands coordinate around the rare earth ion, constructing a highly symmetric and structurally rigid coordination environment. This effectively suppresses non-radiative energy loss caused by molecular vibrations or solvent collisions, thereby significantly improving the fluorescence quantum yield of the complex. Furthermore, the sulfur atom in the -SH group of the ligand has a strong interaction with the rare earth ion, which not only enhances the overall stability of the complex but also helps to fine-tune the electronic energy level of the rare earth ion and can serve as an efficient channel for energy transfer from the ligand π-system to the rare earth ion. Therefore, under photoexcitation, the energy of the stealth fluorescent pigment of this invention can be transferred from the triplet state of the ligand to the excited state of the rare earth ion through a resonance mechanism, exciting the rare earth ion to undergo radiative transition and emit characteristic fluorescence with high intensity and unique spectral characteristics. In addition, the stealth fluorescent pigment prepared by this invention has excellent chemical stability and has good practical value and industrialization prospects in fields such as anti-counterfeiting inks. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The infrared spectrum of the invisible fluorescent pigment prepared in Example 1 of this invention;

[0038] Figure 2 The fluorescence excitation spectrum of the stealth fluorescent pigment prepared in Example 1 of this invention is shown.

[0039] Figure 3 This is the fluorescence emission spectrum of the stealth fluorescent pigment prepared in Example 1 of the present invention. Detailed Implementation

[0040] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0042] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0043] This invention provides an invisible fluorescent pigment with the structural formula shown in formula (I). In formula (I), Ar1 is a five-membered heterocycle as shown in formula (II-1), X is an atom other than carbon, Ar2 is a fluorophenyl, and Re is Tb or Eu.

[0044] , .

[0045] In this invention, each ligand interacts with rare earth ions (Tb) via a thiol group (-SH) and a carbonyl oxygen (C=O). 3+ Or Eu 3+ The complex forms a bidentate coordination, where three identical ligands provide three thiol groups and three carbonyl oxygen groups to coordinate with the rare earth ion. Additionally, two water molecules participate in coordination through their oxygen atoms, collectively constructing an eight-coordinate symmetrical coordination environment. The coordination structure of the stealth fluorescent pigment can be represented as [Re(L)3(H2O)2] (where L represents the bidentate ligand, and Re is Tb or Eu). The five-membered heterocycle in the ligand connects with the benzene ring to form a planar π-conjugated system with high rigidity. The three identical ligands and two oxygen ligands together construct a highly symmetrical and structurally rigid coordination environment around the rare earth ion. This coordination structure can effectively suppress non-radiative energy loss caused by molecular vibration or solvent collisions, thereby significantly improving the fluorescence quantum yield of the complex. Furthermore, there is a strong interaction between the sulfur atom of the -SH group in the ligand and the rare earth ion, which not only enhances the overall stability of the complex but also helps to fine-tune the electronic energy level of the rare earth ion and can serve as an efficient channel for energy transfer from the ligand π system to the rare earth ion. Therefore, under photoexcitation, the energy of the stealth fluorescent pigment of this invention can be transferred from the triplet state of the ligand to the excited state of the rare earth ion through a resonance mechanism, exciting the rare earth ion to undergo radiative transition and emitting characteristic fluorescence with high intensity and unique spectral characteristics. Furthermore, the stealth fluorescent pigment prepared by this invention exhibits excellent chemical stability and has good practical value and industrialization prospects in fields such as anti-counterfeiting inks.

[0046] To tune the triplet energy level of the ligand and better match it with the excited state energy levels of different rare earth ions, thereby optimizing energy transfer efficiency, Ar1 can optionally have the following structure: The selenophene ring or structural formula is At least one of the tellurene rings.

[0047] To modulate the electron cloud density of the ligand π-conjugated system and thus fine-tune the fluorescence emission wavelength and intensity of the complex, Ar2 can optionally be a compound with the following structure: The 4-fluorobenzene ring has the following structural formula: The 2,4,6-trifluorobenzene ring or structural formula is At least one of the 3,4,5-trifluorobenzene rings.

[0048] Understandably, the "" marked in Ar1 and Ar2 "The position is the connection point with equation (Ⅰ).

[0049] The present invention also provides a method for preparing the invisible fluorescent pigment as described above, comprising the following steps:

[0050] Step S1: The first compound, with the structural formula shown in formula (II), undergoes an electrophilic acylation reaction to obtain the second compound, with the structural formula shown in formula (III). , ;

[0051] Step S2: The second compound is subjected to a cross-aldollar condensation reaction to obtain a third compound, the structural formula of which is shown in formula (Ⅳ-ⅰ), formula (Ⅳ-ⅱ), or formula (Ⅳ-ⅲ). , , ;

[0052] Step S3: The third compound is subjected to a Michael addition reaction to obtain a fourth compound, the structural formula of which is shown in formula (V-i), (V-ii), or (V-iii): , , ;

[0053] Step S4: Add terbium salt or europium salt to the fourth compound to carry out a complexation reaction, and obtain an invisible fluorescent pigment with the structural formula shown in formula (I).

[0054] The method for preparing the invisible fluorescent pigment of the present invention can produce a novel pigment with high fluorescence intensity, unique spectral characteristics, and strong stability. Furthermore, the preparation method of the present invention differs from conventional routes, with novel ligand structures and synthetic intermediates that are not commercially available chemicals, making them difficult to obtain through simple complexation reactions, thus significantly increasing the difficulty of imitation and raising technical barriers.

[0055] In step S1, the first compound and the electrophilic reagent are heated under reflux in an acidic solvent to carry out an electrophilic acylation reaction. The reaction time is preferably 3h to 6h, and can be any value of 3h, 4h, 5h or 6h or any range between two.

[0056] Optionally, the molar ratio of the electrophilic reagent to the first compound in the electrophilic acylation reaction is preferably 1.2:1 to 2.0:1, and can be selected from any ratio of 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1 or 2.0:1.

[0057] In order to obtain a ligand with high rigidity and strength, so that the resulting stealth fluorescent pigment has high fluorescence intensity, the first compound may be selected from at least one of selenophene or tellurene, and the electrophilic agent may be selected from at least one of acetyl chloride or acetic anhydride.

[0058] To increase the reaction rate and promote the complete reaction of the first compound, a Lewis acid compound can be added as a catalyst. The molar ratio of the first compound to the Lewis acid compound is preferably 1:0.04 to 1:0.08, and can be selected from any ratio of 1:0.04, 1:0.05, 1:0.06, 1:0.07 or 1:0.08. The Lewis acid compound can be selected from at least one of iodine or anhydrous aluminum trichloride.

[0059] Optionally, the mass ratio of the first compound to the acidic solvent is preferably 1:1.5 to 1:3, and can be selected from any ratio of 1:1.5, 1:2, 1:2.5 or 1:3. The acidic solvent can be selected from at least one of acetic acid or acetic anhydride.

[0060] To obtain a high-purity second compound, the reaction solution after the electrophilic acylation reaction can be cooled, filtered, and then purified by washing with water and recrystallizing with ethanol.

[0061] In step S2, the second compound and the electrophilic reagent undergo a cross-aldol condensation reaction in a mixed solvent containing the first alcohol solvent and sodium alkoxide. The reaction temperature is preferably 0°C to 25°C, and can be any value or a range between 0°C, 5°C, 10°C, 15°C, 20°C, or 25°C. The reaction time is preferably 12h to 20h, and can be any value or a range between 12h, 14h, 16h, 18h, or 20h.

[0062] To ensure the complete reaction of the second compound, the molar ratio of the electrophilic reagent in the cross-aldol condensation reaction to the second compound is preferably 1.1:1 to 1.6:1, and can be any ratio among 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1 or 1.6:1.

[0063] Optionally, the electrophilic agent can be fluorobenzaldehyde, preferably at least one of 4-fluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde or 3,4,5-trifluorobenzaldehyde.

[0064] Optionally, 600 mL to 800 mL of the first alcohol solvent is added to each mole of the second compound. The first alcohol solvent may be selected from at least one of ethanol or methanol. The molar ratio of the second compound to sodium ethoxide is 1:0.8 to 1:2.0, preferably 1:1.2 to 1:1.8. The sodium ethoxide is selected from at least one of sodium ethoxide or sodium methoxide.

[0065] To obtain a high-purity third compound, the product of the cross-hydroxyl condensation reaction can be recrystallized. The specific steps are as follows: ethanol is added to the reaction product and stirred to form a slurry. The mixture is then heated in a water bath at 45℃~50℃ until the solid is completely dissolved. The mixture is then transferred to a low-temperature environment and allowed to stand overnight. After filtration, the purified third compound is obtained.

[0066] In step S3, the third compound and the nucleophile undergo a Michael addition reaction with a second alcohol solvent. Specifically, the Michael addition reaction is a thiocarbonylation reaction. The reaction temperature can be -10℃ to 10℃, and can be any value or a range between -10℃, -8℃, -6℃, -4℃, -2℃, 0℃, 2℃, 4℃, 6℃, 8℃, or 10℃. The reaction time is preferably 3h to 8h, and can be any value or a range between 3h, 4h, 5h, 6h, 7h, or 8h.

[0067] To ensure the complete reaction of the third compound, the molar ratio of the nucleophile to the third compound in the Michael addition reaction is preferably 1.3:1 to 2:1, and can be any ratio among 1.3:1, 1.5:1, 1.7:1, 1.9:1 or 2:1.

[0068] Optionally, the nucleophile in the Michael addition reaction can be at least one of hydrogen sulfide or sodium hydrosulfide. When hydrogen sulfide is used, the Michael addition reaction is preferably controlled at -10℃ to 0℃; when sodium hydrosulfide is used, the Michael addition reaction is preferably controlled at 0℃ to 10℃.

[0069] To catalyze the dissociation of hydrogen sulfide or sodium hydrosulfide to generate HS - Alkaline substances such as potassium hydroxide can be added to the reaction system to adjust it to a weakly alkaline state. This can increase the reaction rate and help the Michael addition reaction proceed more completely.

[0070] To obtain a high-purity fourth compound, the reaction solution obtained from the Michael addition reaction can be filtered, the solid collected can be dissolved in a mixed solvent containing ethanol and chloroform and recrystallized to obtain a high-purity fourth compound, wherein the volume ratio of ethanol to chloroform is preferably 1:1.

[0071] In step S4, the fourth compound undergoes a complexation reaction with a terbium salt or a europium salt in a third alcohol solvent. The reaction time is preferably 3h to 10h, and can be any value among 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, or any range between two of them.

[0072] To ensure complete reaction of the fourth compound, the molar ratio of the fourth compound to the terbium salt is preferably 2.8:1 to 3.2:1, and can be any ratio among 2.8:1, 2.9:1, 3.0:1, 3.1:1, or 3.2:1; the molar ratio of the fourth compound to the europium salt is preferably 2.8:1 to 3.2:1, and can be any ratio among 2.8:1, 2.9:1, 3.0:1, 3.1:1, or 3.2:1.

[0073] To improve the interaction between -SH and Tb in the ligand 3+ Or Eu 3+ Coordination ability, while avoiding Tb 3+ Or Eu 3+ Hydroxide precipitates form at excessively high pH levels. The pH of the complexation reaction is preferably controlled between 6.0 and 8.0, for example, any value among 6.0, 6.5, 7.0, 7.5, or 8.0, or a range between any two. Specifically, potassium hydroxide or sodium hydroxide can be used for pH adjustment.

[0074] To suppress excessively high local concentrations of rare earth ions in the reaction system, which could lead to precipitation, the fourth compound can be heated to reflux in a third alcohol solvent, followed by the addition of terbium or europium salts in batches and multiple times. For example, the terbium or europium salt can be prepared as a mixture with the third alcohol solvent and then added dropwise to the reaction system. The Tb concentration in the reaction system... 3+ Or Eu 3+ The concentration can be controlled from 0.05 mol / L to 0.2 mol / L, for example, any value or a range between 0.05 mol / L, 0.07 mol / L, 0.1 mol / L, 0.13 mol / L, 0.15 mol / L, 0.17 mol / L or 0.2 mol / L, preferably 0.1 mol / L to 0.15 mol / L.

[0075] Optionally, the terbium salt is preferably TbCl3, and the europium salt is preferably EuCl3.

[0076] Optionally, the third alcohol solvent may be selected from at least one of ethanol or methanol.

[0077] The present invention also provides an anti-counterfeiting ink, wherein the anti-counterfeiting ink includes the aforementioned invisible fluorescent pigment.

[0078] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0079] Example 1

[0080] Step S1: Add 0.2 mol of selenophene and 50 mL of acetic acid to a three-necked flask, stir and heat until the selenophene is completely dissolved; then add 8 mmol of iodine, stir for 5 min, and then add 0.3 mol of acetyl chloride dropwise. After the addition is complete, heat to reflux and react for 3 h, then cool to room temperature. Slowly pour the reaction solution into 400 mL of ice water with stirring, and filter. Wash the resulting filter cake with water until neutral, and recrystallize from ethanol to obtain 2-acetylselenophene, as shown in the following reaction formula:

[0081] .

[0082] Step S2: Add 160 ml of ethanol and 12 g of NaOH to a three-necked flask and stir until the solid is completely dissolved. Then add 0.2 mol of 2-acetylselenophene and 0.25 mol of 4-fluorobenzaldehyde, and stir at 20℃~25℃ for 3 h until the material becomes a paste. Add 50 ml of water, stir evenly, and place in a refrigerator to stand for 12 h. Filter the precipitated solid, and wash the filter cake with water and ethanol successively. Then add 50 ml of ethanol to slurry, heat in a water bath at 45℃~50℃ until the solid is completely dissolved, cool to room temperature, place the beaker in a refrigerator at 0℃~5℃ and stand for 12 h, filter and dry to obtain the third compound with the structural formula shown in formula (Ⅳ-ⅰ-1). The reaction formula is as follows:

[0083] .

[0084] Step S3: Place the three-necked flask in an ice-salt bath, add 200 ml of anhydrous ethanol and 0.1 mol of the third compound with the structural formula shown in formula (Ⅳ-ⅰ-1), stir until the solid is completely dissolved, add 2 ml of 50 wt.% KOH solution dropwise, control the reaction temperature at -10℃ to 0℃, and continuously pass 0.15 mol of dry H2S for 3 hours. Filter the precipitated solid and recrystallize it using a 1:1 volume ratio of ethanol and chloroform to obtain the fourth compound with the structural formula shown in formula (Ⅴ-ⅰ-1), the reaction formula of which is as follows:

[0085] .

[0086] Step S4: Add 100 mL of anhydrous ethanol to a three-necked flask, and while stirring, add 0.06 mol of the fourth compound shown in formula (V-I-1). Heat until the solid is completely dissolved, then continue heating to reflux. Add an ethanol solution containing 0.02 mol TbCl3 dropwise. After the addition is complete, adjust the pH of the reaction solution to 6-7 with 1 mol / L NaOH. Maintain the reaction temperature for 5 hours, then stop heating, cool, and filter to obtain the solid. Wash the solid with dichloromethane and dry to obtain a white solid invisible fluorescent pigment with the molecular formula C. 39 H 37O5F3S3Se3Tb, the structural formula is shown in equation (Ⅰ-1):

[0087] .

[0088] The infrared spectrum of the stealth fluorescent pigment prepared in this embodiment is as follows: Figure 1 As shown, it can be seen that at 1650cm -1 A C=O stretching vibration absorption peak appeared nearby, at 2500 cm⁻¹. -1 A weak absorption peak can be observed nearby, attributed to the stretching vibration of -SH, at 800 cm⁻¹. -1 Absorption peaks for Tb-O and Tb-S coordination bonds were observed nearby; therefore, the infrared spectrum confirms that the structure of the stealth fluorescent pigment is consistent with formula (Ⅰ-1); the fluorescence excitation spectrum is as follows. Figure 2 As shown, the complex exhibits a broad excitation band in the 300nm–400nm ultraviolet region, with the maximum excitation peak located around 350nm, indicating that it can be effectively excited by conventional ultraviolet light sources; the fluorescence emission spectrum is shown below. Figure 3 As shown, under 350nm light excitation, the complex exhibits Tb 3+ The characteristic emission peaks are located near 490nm, 545nm, 585nm, and 620nm, respectively, corresponding to... 5 D4→ 7 F6 5 D4→ 7 F5 5 D4→ 7 F4 and 5 D4→ 7 The F3 transition, with the strongest emission peak at 545 nm, exhibits bright yellow-green fluorescence, demonstrating that the ligand effectively transfers energy to Tb. 3+ ion.

[0089] Example 2

[0090] The only difference between Example 2 and Example 1 is that 2,4,6-trifluorobenzaldehyde is used instead of 4-fluorobenzaldehyde in step S2, resulting in a third compound with the structural formula shown in formula (Ⅳ-ⅰ-2), and the reaction formula is as follows:

[0091] .

[0092] In step S3, the third compound with the structural formula shown in formula (Ⅳ-ⅰ-2) is used instead of the third compound with the structural formula shown in formula (Ⅳ-ⅰ-1) to obtain the fourth compound with the structural formula shown in formula (Ⅴ-ⅰ-2), and the reaction formula is as follows:

[0093] .

[0094] In step S4, the fourth compound with the structural formula shown in formula (V-i-2) is used instead of the fourth compound with the structural formula shown in formula (V-i-1) to obtain the compound with the molecular formula C. 39 H 31 O5F9S3Se3Tb, an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-2):

[0095] .

[0096] Example 3

[0097] The only difference between Example 3 and Example 1 is that 3,4,5-trifluorobenzaldehyde is used instead of 4-fluorobenzaldehyde in step S2, resulting in a third compound with the structural formula shown in formula (Ⅳ-ⅰ-3), and the reaction formula is as follows:

[0098] .

[0099] In step S3, the third compound with the structural formula shown in formula (Ⅳ-ⅰ-3) is used instead of the third compound with the structural formula shown in formula (Ⅳ-ⅰ-1) to obtain the fourth compound with the structural formula shown in formula (Ⅴ-ⅰ-3), and the reaction formula is as follows:

[0100] .

[0101] In step S4, the fourth compound with the structural formula shown in formula (V-i-3) is used instead of the fourth compound with the structural formula shown in formula (V-i-1) to obtain the compound with the molecular formula C. 39 H 31 O5F9S3Se3Tb, an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-3): .

[0102] Example 4

[0103] The difference between Example 4 and Example 1 lies only in step S1: 0.2 mol of tellurene and 50 ml of acetic anhydride were added to a three-necked flask, and the mixture was stirred and heated until the tellurene was completely dissolved. Then, 8.0 mmol of anhydrous aluminum trichloride was added, and the mixture was stirred for 5 min. Next, 0.3 mol of acetyl chloride was added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 3 h. The mixture was then cooled to room temperature. The reaction solution was slowly poured into 400 ml of ice water with stirring, and the mixture was filtered. The resulting filter cake was washed with water until neutral, and recrystallized from ethanol to obtain 2-acetyltellurene. The reaction formula is as follows:

[0104] .

[0105] Step S2: Add 160 ml of ethanol and 12 g of NaOH to a three-necked flask and stir until the solid is completely dissolved. Then add 0.2 mol of 2-acetyltellurphene and 0.25 mol of 4-fluorobenzaldehyde, and stir at 20℃~25℃ for 4 h until the material becomes a paste. Add 50 ml of water, stir evenly, and place in a refrigerator to stand for 12 h. Filter the precipitated solid, and wash the filter cake with water and ethanol successively. Then add 50 ml of ethanol to slurry, heat in a water bath at 45℃~50℃ until the solid is completely dissolved, cool to room temperature, and place the beaker in a refrigerator at 0℃~5℃ to stand for 12 h. Filter and dry to obtain the third compound with the structural formula shown in formula (Ⅳ-ⅰ-4). The reaction formula is as follows:

[0106] .

[0107] In step S3, the third compound with the structural formula (Ⅳ-ⅰ-4) is used instead of the third compound with the structural formula (Ⅳ-ⅰ-1) to obtain the fourth compound with the structural formula (Ⅴ-ⅰ-4), and the reaction formula is as follows:

[0108] .

[0109] In step S4, the fourth compound with the structural formula shown in formula (V-i-4) is used instead of the fourth compound with the structural formula shown in formula (V-i-1) to obtain the compound with the molecular formula C. 39 H 37 O5F3S3Te3Tb, an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-4):

[0110] .

[0111] Example 5

[0112] The only difference between Example 5 and Example 4 is that 2,4,6-trifluorobenzaldehyde is used instead of 4-fluorobenzaldehyde in step S2, resulting in a third compound with the structural formula shown in formula (Ⅳ-ⅰ-5), and the reaction formula is as follows:

[0113] .

[0114] In step S3, the third compound with the structural formula shown in formula (Ⅳ-ⅰ-5) is used instead of the third compound with the structural formula shown in formula (Ⅳ-ⅰ-4) to obtain the fourth compound with the structural formula shown in formula (Ⅴ-ⅰ-5), and the reaction formula is as follows:

[0115] .

[0116] In step S4, the fourth compound with the structural formula shown in formula (V-i-5) is used instead of the fourth compound with the structural formula shown in formula (V-i-4) to obtain the compound with the molecular formula C. 39 H 31 O5F9S3Te3Tb, an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-5): .

[0117] Example 6

[0118] The only difference between Example 6 and Example 4 is that 3,4,5-trifluorobenzaldehyde is used instead of 4-fluorobenzaldehyde in step S2, resulting in a third compound with the structural formula shown in formula (Ⅳ-ⅰ-6), and the reaction formula is as follows:

[0119] .

[0120] In step S3, the third compound with the structural formula (Ⅳ-ⅰ-6) is used instead of the third compound with the structural formula (Ⅳ-ⅰ-4) to obtain the fourth compound with the structural formula (Ⅴ-ⅰ-6), and the reaction formula is as follows:

[0121] .

[0122] In step S4, the fourth compound with the structural formula shown in formula (V-i-6) is used instead of the fourth compound with the structural formula shown in formula (V-i-4) to obtain the compound with the molecular formula C. 39 H 31 O5F9S3Te3Tb, an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-6): .

[0123] Example 7

[0124] The difference between Example 7 and Example 1 lies only in step S4: 100 mL of anhydrous ethanol is added to a three-necked flask, followed by the addition of 0.06 mol of the fourth compound as shown in formula (V-I-1) with stirring. The mixture is heated until the solid is completely dissolved, and then the temperature is raised to reflux. An ethanol solution containing 0.02 mol EuCl3 is added dropwise. After the addition is complete, the pH of the reaction solution is adjusted to 6-7 with 1 mol / L NaOH. The reaction is maintained at this temperature for 5 hours. Heating is then stopped, and the mixture is cooled and filtered to obtain a solid. The solid is washed with dichloromethane and dried to obtain a white solid invisible fluorescent pigment with the molecular formula C. 39 H 37 O5F3S3Se3Eu, the structural formula is shown in equation (Ⅰ-7):

[0125] .

[0126] Example 8

[0127] The difference between Example 8 and Example 4 lies only in step S4: 100 mL of anhydrous ethanol is added to a three-necked flask, and 0.06 mol of the fourth compound as shown in formula (V-I-4) is added while stirring. The mixture is heated until the solid is completely dissolved, and then the temperature is raised to reflux. An ethanol solution containing 0.02 mol EuCl3 is added dropwise. After the addition is complete, the pH of the reaction solution is adjusted to 6-7 with 1 mol / L NaOH. The reaction is maintained at this temperature for 5 hours. Heating is stopped, the mixture is cooled, and filtered to obtain a solid. The solid is washed with dichloromethane and dried to obtain a white solid invisible fluorescent pigment with the molecular formula C. 39 H 37 O5F3S3Te3Eu, the structural formula is shown in equation (Ⅰ-8):

[0128] .

[0129] Example 9

[0130] The only difference between Example 9 and Example 1 is that thiophene is used instead of selenophene in step S1, and the corresponding intermediate products are obtained in steps S2 and S3. In step S4, an invisible fluorescent pigment with the structural formula shown in formula (I-9) is obtained.

[0131] .

[0132] Comparative Example 1

[0133] The only difference between Comparative Example 1 and Example 1 is that benzaldehyde is used instead of 4-fluorobenzaldehyde in step S2, and the corresponding intermediate product is obtained in step S3. In step S4, the invisible fluorescent pigment with the structural formula shown in formula (I-10) is obtained.

[0134] .

[0135] Comparative Example 2

[0136] The only difference between Comparative Example 2 and Example 1 is that in step S4, an ethanol solution of LaCl3 was used instead of an ethanol solution of TbCl3 to prepare an invisible fluorescent pigment with the structural formula shown in formula (Ⅰ-11):

[0137] .

[0138] The carbon and hydrogen ratios in the stealth fluorescent pigments prepared in the above examples and comparative examples were tested using an elemental analyzer, and their molecular weights were determined using an ESI-MS mass spectrometer. The results are shown in Table 1.

[0139] Table 1

[0140]

[0141] The colorant properties of the invisible fluorescent pigments prepared in the above examples and comparative examples were tested according to the national standard GB 1708-1719-79; and their solvent resistance in solvents such as 2% NaOH, ethanol, acetone, butanone, and acetic acid was tested. The results are shown in Table 2.

[0142] Table 2

[0143]

[0144] As can be seen from Examples 1, 4 and 9, when Ar1 in the stealth fluorescent pigment is a selenophene ring or a tellurene ring, its fluorescence intensity is better than that of a thiophene ring, indicating that the selenophene and tellurene structures are more conducive to improving the luminescence performance of the pigment.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An invisible fluorescent pigment, characterized in that, The structural formula of the invisible fluorescent pigment is shown in formula (I). In formula (I), Ar1 is a five-membered heterocycle as shown in formula (II-1), X is an atom other than carbon, Ar2 is a fluorophenyl, and Re is Tb or Eu. ， 。 2. The invisible fluorescent pigment according to claim 1, characterized in that, Ar1 is at least one of the selenophene ring or tellurophene ring; And / or, Ar2 is at least one of a 4-fluorobenzene ring, a 2,4,6-trifluorobenzene ring, or a 3,4,5-trifluorobenzene ring.

3. A method for preparing an invisible fluorescent pigment as described in claim 1 or 2, characterized in that, Includes the following steps: The first compound, with the structural formula shown in formula (II), was subjected to an electrophilic acylation reaction to obtain the second compound, with the structural formula shown in formula (III). , ; The second compound is subjected to a cross-aldollar condensation reaction to obtain a third compound, the structural formula of which is shown in formula (Ⅳ-ⅰ), formula (Ⅳ-ⅱ), or formula (Ⅳ-ⅲ). , , ; The third compound is subjected to a Michael addition reaction to yield a fourth compound, the structural formula of which is shown in formula (V-i), (V-ii), or (V-iii). , , ; A terbium salt or europium salt was added to the fourth compound to carry out a complexation reaction, resulting in an invisible fluorescent pigment with the structural formula shown in formula (I).

4. The method for preparing the invisible fluorescent pigment according to claim 3, characterized in that, The molar ratio of the electrophilic reagent to the first compound in the electrophilic acylation reaction is 1.2:1 to 2.0:1; And / or, the molar ratio of the electrophilic reagent to the second compound in the cross-aldol condensation reaction is 1.1:1 to 1.6:1; And / or, the molar ratio of the nucleophile to the third compound in the Michael addition reaction is 1.3:1 to 2:1; And / or, the molar ratio of the fourth compound to the terbium salt is 2.8:1 to 3.2:1; And / or, the molar ratio of the fourth compound to the europium salt is 2.8:1 to 3.2:

1.

5. The method for preparing the stealth fluorescent pigment according to claim 4, characterized in that, The electrophilic reagent in the electrophilic acylation reaction is acetyl chloride; And / or, the electrophilic reagent in the cross-aldollation reaction is fluorobenzaldehyde; And / or, the nucleophile in the Michael addition reaction is at least one of hydrogen sulfide or sodium hydrosulfide.

6. The method for preparing the stealth fluorescent pigment according to claim 5, characterized in that, The first compound is selected from at least one of selenophene or tellurene; And / or, the fluorobenzaldehyde is selected from at least one of 4-fluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde or 3,4,5-trifluorobenzaldehyde; And / or, the terbium salt is selected from TbCl3; And / or, the europium salt is selected from EuCl3.

7. The method for preparing the stealth fluorescent pigment according to claim 3, characterized in that, The electrophilic acylation reaction is carried out in an acidic solvent, and the mass ratio of the first compound to the acidic solvent is 1:1.5 to 1:

3. And / or, the electrophilic acylation reaction further includes the addition of a Lewis acid compound, wherein the molar ratio of the first compound to the Lewis acid compound is 1:0.04 to 1:0.08; And / or, the pH of the complexation reaction is 6 to 8.

8. The method for preparing the stealth fluorescent pigment according to claim 7, characterized in that, The acidic solvent is selected from at least one of acetic acid or acetic anhydride; And / or, the Lewis acid compound is selected from at least one of iodine or anhydrous aluminum trichloride.

9. The method for preparing the stealth fluorescent pigment according to any one of claims 3 to 8, characterized in that, The electrophilic acylation reaction takes 3 to 6 hours. And / or, the temperature of the cross-aldol condensation reaction is 0℃~25℃, and the time is 12h~20h; And / or, the Michael addition reaction is carried out at a temperature of -10°C to 0°C for a time of 3 to 8 hours; And / or, the complexation reaction takes 3 to 10 hours.

10. An anti-counterfeiting ink, characterized in that, The anti-counterfeiting ink includes the invisible fluorescent pigment as described in claim 1 or 2.

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