Zinc terpyridyl complex with multi-photon excitation fluorescence characteristic as well as preparation method and application of zinc terpyridyl complex
By synthesizing the tripyridine zinc complex, using its complex coordination balance in aqueous solution and multiphoton excitation fluorescence characteristics, the problem of insufficient anti-counterfeiting capabilities of traditional information encryption technology is solved, and the high security and flexible encryption of multi-level information is achieved, and the anti-counterfeiting capabilities of information is enhanced.
Patent Information
- Application Number
- CN202510531206.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-25
- Publication Date
- 2025-08-08
AI Technical Summary
Traditional information encryption technology has insufficient anti-counterfeiting capabilities and a single decoding mechanism, making it difficult to achieve high security and flexibility protection of multi-level information.
The terpyridine zinc complex is synthesized, and the complex coordination equilibrium is achieved in aqueous solution to generate reversible fluorescence emission, combined with the multi-photon excitation fluorescence characteristics, and heat erasable printing is realized, and used for the encryption and decryption of multi-level information.
High security and flexible encryption of multi-level information are realized, and the reversible display and erase of information at different excitation wavelengths is achieved through multi-photon excitation fluorescence characteristics, enhancing the anti-counterfeiting ability of information.
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Figure CN120441474A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of multi-photon excited fluorescent materials, and in particular to a terpyridine zinc complex with multi-photon excited fluorescent properties, and a preparation method and application thereof. Background Art
[0002] With the rapid development of information technology, the need to protect important information is becoming increasingly urgent. Information encryption is a key means of improving information security, and multi-level information encryption technology diversifies information encryption and effectively protects information security. Common information encryption methods use different substances to encode information. When the encrypted information is exposed to specific external conditions (such as sunlight or ultraviolet rays), the corresponding encrypted information can be decrypted. Multi-level information encryption, on the other hand, allows confidential information to be classified into several confidentiality levels according to its priority.
[0003] Currently, traditional information encryption technologies suffer from low levels of anti-counterfeiting, a single encryption method, and poor decoding mechanisms. Multi-level information encryption technology, with its diverse encryption methods and high decryption difficulty, can better protect personal privacy and enhance information security. Summary of the Invention
[0004] The technical problem to be solved by this invention is to provide a terpyridine zinc complex with multiphoton-excited fluorescence properties, its preparation method, and its application in multi-level information encryption and decryption. The complex achieves complexation equilibrium in aqueous solution, producing reversible fluorescence emission, enabling heat-erasable printing. The multiphoton-excited fluorescence properties of the complex are utilized to achieve multi-level information encryption and decryption at multiphoton excitation wavelengths. Compared to traditional information encryption, multi-level information encryption offers higher security and greater flexibility.
[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:
[0006] One of the purposes of the present invention is to provide a terpyridine zinc complex, the structural formula of which is as follows:
[0007]
[0008] Wherein, X is one of Cl and CH3COO; Y is one of NO3, CF3SO3, and ClO4.
[0009] A second object of the present invention is to provide a method for preparing the terpyridine zinc complex, comprising the following preparation steps:
[0010] S1. In the presence of a catalyst and an acid-binding agent, aniline reacts with ethyl bromoacetate to obtain compound C1;
[0011] S2 and compound C1 react with N,N-dimethylformamide (DMF) and phosphorus oxychloride (POCl3) to obtain compound C2;
[0012] S3. In the presence of a base and an amine, compound C2 reacts with 2-acetylpyridine to obtain ligand L;
[0013] S4, ligand L reacts with ZnX2 to obtain complex LZnX2;
[0014] S5. The ligand L reacts with ZnY2 to obtain the complex LZnY2.
[0015]
[0016] Wherein, X is one of Cl and CH3COO; Y is one of NO3, CF3SO3, and ClO4.
[0017] Furthermore, the catalyst includes, but is not limited to, at least one of potassium iodide (KI) and cuprous iodide (CuI). Iodide ion is both a good nucleophile and a good leaving group. In the present invention, when performing the nucleophilic substitution reaction between aniline and ethyl bromoacetate, KI or CuI is added as a catalyst. The bromide ion of ethyl bromoacetate is easily attacked by the iodide ion and lost, forming an iodide. The iodine in the iodide is easily attacked by the nucleophile aniline and lost, thereby accelerating the reaction rate.
[0018] Furthermore, the acid binding agent is potassium carbonate (K2CO3). The function of the acid binding agent is to neutralize the hydrogen bromide generated during the reaction of aniline and ethyl bromoacetate, thereby increasing the reaction rate.
[0019] Furthermore, the molar ratio of aniline to ethyl bromoacetate is 1:(2.1-2.3).
[0020] Furthermore, the molar ratio of compound C1 to DMF and POCl3 is 1:(4.9-5.1):(4.9-5.1). Compound C1, DMF, and POCl3 undergo a Vilsmeier-Haack reaction, using DMF as a formylating agent and catalyzed by POCl3 to introduce an aldehyde group onto the benzene ring.
[0021] Furthermore, the base includes, but is not limited to, at least one of potassium hydroxide (KOH) and sodium hydroxide (NaOH); the amine is, but is not limited to, aqueous ammonia (NH3·H2O). Furthermore, the molar ratio of the compound C2 to 2-acetylpyridine is 1:(1.9-2.1).
[0022] Furthermore, the molar ratio of the ligand L to ZnX2 is 1:(0.9-1.1); the molar ratio of the ligand L to ZnY2 is 1:(0.4-0.6).
[0023] Furthermore, the ZnX2 is one of zinc chloride (ZnCl2) and zinc acetate (Zn(CH3COO)2); the ZnY2 is one of zinc nitrate (Zn(NO3)2), zinc trifluoromethanesulfonate (Zn(CF3SO3)2), and zinc perchlorate (Zn(ClO4)2).
[0024] A third object of the present invention is to provide an application of the terpyridine zinc complex in multi-level information encryption and decryption.
[0025] The beneficial effects of the present invention are:
[0026] 1. The present invention synthesizes a novel terpyridine zinc complex, in which terpyridine has a strong coordination ability for metal ions; the benzene ring enhances the degree of conjugation of the molecule; the electron-withdrawing effect of terpyridine makes it easier for electrons on the electron-donating group (ester group) to flow toward the terpyridine, which is beneficial for intramolecular charge transfer and regulates the luminescence of the complex; the introduction of a Zn(II) center helps to enhance the charge transfer from the central ion to the ligand, thereby improving the multi-photon excitation fluorescence performance of the complex.
[0027] 2. The coordination bonds of the terpyridine zinc complex described in the present invention can be destroyed by polar solvents such as water. As the water content increases, the fluorescence intensity of the complex gradually decreases. After the complex solution is heated, the solvent evaporates, the ligand and the metal ion are re-coordinated, and the fluorescence is restored, which can achieve heat-erasable printing.
[0028] 3. The terpyridine zinc complexes described herein exhibit strong three-photon fluorescence at near-infrared (NIR) II excitation wavelengths. Compared to traditional fluorescent materials, the terpyridine zinc complexes described herein offer long-wavelength excitation, short-wavelength emission, and high contrast, enabling multi-level information encryption and decryption. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 The crystal structure diagram of the complex LZn(ClO4)2 in the present invention;
[0030] Figure 2 The two-photon / multi-photon fluorescence spectra of the ligand L and the complex LZn(ClO4)2 in the present invention at different excitation wavelengths; the two-photon fluorescence spectrum of LZn(ClO4)2 at an excitation wavelength of 720-920 nm (a); the multi-photon fluorescence spectrum of LZn(ClO4)2 at an excitation wavelength of 1200-1500 nm (b); the two-photon fluorescence spectrum of L at an excitation wavelength of 720-920 nm (c);
[0031] Figure 3 The UV-visible absorption spectra of the ligand L and the complex LZn(ClO4)2 in the present invention are shown;
[0032] Figure 4 The fluorescence intensity change of the complex LZn(ClO4)2 in the present invention at a water content of 0 to 20%;
[0033] Figure 5 Schematic diagram of the structure of the four-layer anti-counterfeiting paper based on the complex LZn(ClO4)2 of the present invention;
[0034] Figure 6 This is a demonstration diagram of anti-counterfeiting paper achieving repeated printing under ultraviolet light;
[0035] Figure 7 The emission color diagram of the complexes LZnX2 (X = Cl, CH3COO) and LZnY2 (Y = NO3, CF3SO3, ClO4) in the present invention at excitation wavelengths of 800nm and 1300nm;
[0036] Figure 8 Schematic diagram of the multi-level information encryption and decryption process based on the complex LZnY2 (Y = NO3, ClO4) of the present invention as the initial filling material. DETAILED DESCRIPTION
[0037] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific embodiments and illustrations.
[0038] Example 1
[0039] Preparation of complex LZn(ClO4)2:
[0040] (1) Preparation of Compound C1
[0041] Aniline (0.61 g, 0.0066 mol), 25 mL of dry acetonitrile, K2CO3 (2.5 g, 0.018 mol), and KI (2.4 g, 0.014 mol) were added to the reactor and stirred at room temperature for 10 min under nitrogen protection. Ethyl bromoacetate was then added dropwise and the temperature was raised to 95°C for 12 h. After the reaction, the reaction solution was cooled to room temperature and the acetonitrile was removed by distillation under reduced pressure. 15 mL of dichloromethane was added to the residue and extracted with 20 mL of water twice. The organic phase was collected and dried over anhydrous sodium sulfate. Dichloromethane was removed by distillation under reduced pressure and the mixture was purified by silica gel column chromatography (V 石油醚 :V 乙酸乙酯 =10:1) to obtain a colorless or light yellow liquid, namely compound C1, with a yield of 90%.
[0042] (2) Preparation of Compound C2
[0043] DMF (2.1 g, 0.029 mol) and compound C1 (1.5 g, 0.0056 mol) were added to the reactor, cooled to 0-5°C, and POCl3 (4.4 g, 0.029 mol) was slowly added dropwise. After the addition was complete, the mixture was kept at 0-5°C for 30 min, heated to 65°C for reaction for 3 h, and stirred at room temperature for 12 h. After the reaction was completed, 20 mL of dichloromethane was added to the reaction solution, and the resulting mixed solution was slowly poured into a 0°C aqueous sodium hydroxide solution (50 mL, 0.1 M), stirred for 2 min, extracted with dichloromethane, and the organic phase was taken, washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered, and dichloromethane was removed by vacuum distillation. The mixture was then purified by silica gel column chromatography (V 石油醚 :V 乙酸乙酯 =5:1), and dried to obtain a light yellow solid, namely compound C2, with a yield of 80%.
[0044] (3) Preparation of ligand L
[0045] 150 mL of ethanol, compound C2 (2.9 g, 0.010 mol), 2-acetylpyridine (2.4 g, 0.020 mol), NH3·H2O (20 mL, 25%) and KOH (2.2 g, 0.040 mol) were added to the reactor and the temperature was raised to 75°C for 6 h. After the reaction, the reaction solution was cooled to room temperature and the pH was adjusted to neutral with ice water to precipitate a yellow solid. After drying, an esterification reaction was carried out (50 mL of ethanol and 1.5 mL of concentrated sulfuric acid, condensed and refluxed for 6 h), and the solid was separated by chromatographic column (V 石油醚 :V 乙酸乙酯 =20:1) to obtain ligand L with a yield of 29%.
[0046] (4) Preparation of complex LZn(ClO4)2
[0047] Weigh the ligand L (0.090 g, 0.19 mmol) and heat it to dissolve in 20 mL of ethanol. Slowly add the ethanol solution of Zn(ClO4)2 (0.10 mmol) dropwise and heat to reflux for 2 h to generate a precipitate. Filter it, wash it with a small amount of ethanol, and dry it to obtain the complex LZn(ClO4)2 with a yield of 90%.
[0048] Example 2
[0049] Single crystal cultivation of complex LZn(ClO4)2:
[0050] 10 mg of ligand L was dissolved in 8 mL of dichloromethane and filtered into a 25 mL colorimetric tube. Subsequently, 5 cm thick ethanol was added as a buffer layer, and then 3 mg of Zn(ClO4)2 dissolved in 10 mL of ethanol was slowly added dropwise as the upper layer. The tube mouth was covered with filter paper and slowly evaporated for several days to obtain yellow needle-shaped crystals. The size of the single crystal was 0.1×0.11×0.13 mm. The crystal structure of the single crystal was determined by X-ray single crystal diffractometer.
[0051] The crystal structure of LZn(ClO4)2 is as follows Figure 1 As shown. To clearly show the crystal structure, hydrogen atoms have been deleted. Crystal analysis shows that the crystal belongs to the triclinic system, P-1 space group. Among them, Zn(II) coordinates with the six N atoms in the terpyridine groups in the two ligands to form a hexacoordinated distorted octahedral configuration; terpyridine acts as the main ligand and coordinates with the central Zn(II) to form a conjugated system, which is conducive to charge exchange and enhances the charge transfer from the central ion to the ligand.
[0052] Example 3
[0053] Multiphoton excitation fluorescence properties of the complex LZn(ClO4)2:
[0054] from Figure 2 It can be seen that the strongest two-photon fluorescence of the complex at an excitation wavelength of 840nm covers an emission band of 470-690nm; the strongest three-photon fluorescence of the complex at an excitation wavelength of 1300nm covers an emission band of 450-680nm; and the strongest two-photon fluorescence of the ligand at an excitation wavelength of 720nm covers an emission band of 380-510nm. This shows that both ligand L and the complex LZnCl2 can achieve two-photon excitation, and the fluorescence intensity of the complex LZnCl2 is significantly higher than that of the ligand L.
[0055] from Figure 3 It can be seen that the ligand L has two absorption peaks at 290nm and 330nm; the complex LZn(ClO4)2 has an obvious absorption peak at 400nm. With the addition of water, the absorption peak intensity of LZn(ClO4)2 weakens.
[0056] from Figure 4 It can be seen that at 550 nm, as the water content increases, the fluorescence intensity gradually decreases; when the water content is 10%, the fluorescence intensity is half of the initial fluorescence intensity.
[0057] Example 4
[0058] Heating erasable printing of the complex LZn(ClO4)2:
[0059] Using printing paper as a substrate, a 1mm thick layer of commercial PEG-PPG-PEG was applied as a passivation layer. A mixture of equal volumes of LZn(ClO4)2 and PEG-PPG-PEG was then applied as an imaging layer. Finally, a 1mm thick layer of PEG-PPG-PEG was applied as a protective layer. Heat-erasable printing was performed using a commercially available inkjet printer, using water as the ink.
[0060] Figure 6 This image demonstrates the reproducible printing of security paper under UV light. Confidential information is printed on the paper using water as the ink, initially invisible to the naked eye. After UV exposure, the confidential information becomes clearly visible. Heating the paper causes the confidential information pattern to disappear. This phenomenon occurs because the coordination bonds between LZnX2 and LZnY2 can be disrupted by aqueous polar solvents, reducing fluorescence intensity. Upon heating, the solvent evaporates, freeing the metal ions to re-coordinate with the ligand L, restoring fluorescence and extinguishing the pattern.
[0061] Example 5
[0062] Preparation of complexes LZnX2 (X = Cl, CH3COO) and LZnY2 (Y = NO3, CF3SO3):
[0063] The preparation method is the same as that of Example 1, except that zinc perchlorate is replaced by ZnCl2, Zn(CH3COO)2, Zn(NO3)2, and Zn(CF3SO3)2, respectively, and reacts with ligand L in the form of an aqueous solution.
[0064] Example 6
[0065] Multiphoton excitation fluorescence properties of the complexes LZnX2 (X = Cl, CH3COO) and LZnY2 (Y = NO3, CF3SO3, ClO4):
[0066] from Figure 7 It can be seen that after the ligand L reacts with ZnX2 (X = Cl, CH3COO) or ZnY2 (Y = NO3, CF3SO3, ClO4) aqueous solution, the emission band at excitation wavelengths of 800nm and 1300nm covers 490~650nm, showing colors such as cyan, green, yellow-green and yellow.
[0067] Example 7
[0068] Application of complex LZnY2 (Y=NO3, ClO4) in multi-level information encryption and decryption:
[0069] A glass plate was used as the matrix, a mixture of ligand L and PEG-PPG-PEG was used as the imaging layer, and a ZnY2 (Y=NO3, ClO4) aqueous solution was used as the ink for multi-level encrypted information engraving.
[0070] exist Figure 8 In the figure, the black numbers are engraved with L or ZnY2 (Y = NO3, ClO4) as ink, and the purple numbers are engraved with FeSO4 as ink. Since L and LZnY2 do not emit light in sunlight, the information of the black digital part is invisible to the naked eye, while LFeSO4 (obtained by the coordination of the ligand L and FeSO4) emits light, and information appears. In this case, it is error information; after ultraviolet irradiation, engraving with L or ZnY2 (Y = NO3, ClO4) as ink will emit light. When Zn(NO3)2 is used as ink, a green pattern appears; when Zn(ClO4)2 is used as ink, a yellow pattern appears; and when L is used as ink alone on PEG-PPG-PEG, blue appears, which is still error information; under multi-photon excitation wavelength laser irradiation, only LZnY2 (Y = NO3, ClO4) emits light. When Zn(NO3)2 is used as ink, a green pattern appears, and when Zn(ClO4)2 is used as ink, a yellow pattern appears, and the real information appears. From this we can see that information is encrypted under the conditions of naked eye and ultraviolet radiation, and the real information can only appear under the irradiation of laser with multi-photon excitation wavelength.
[0071] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.
Claims
1. An asymmetric terpyridine zinc complex having the following structural formula: in, X is one of Cl and CH3COO; Y is one of NO3, CF3SO3, and ClO4.
2. The method for preparing the asymmetric terpyridine zinc complex according to claim 1, characterized in that: The following steps are involved: S1. In the presence of a catalyst and an acid-binding agent, aniline reacts with ethyl bromoacetate to obtain compound C1; S2, compound C1, N,N-dimethylformamide, and phosphorus oxychloride to obtain compound C2; S3. In the presence of a base and an amine, compound C2 reacts with 2-acetylpyridine to obtain ligand L; S4, ligand L reacts with ZnX2 to obtain complex LZnX2; S5, ligand L reacts with ZnY2 to obtain complex LZnY2; Wherein, X is one of Cl and CH3COO; Y is one of NO3, CF3SO3, and ClO4.
3. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The catalyst is at least one of potassium iodide and cuprous iodide.
4. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The acid binding agent is K2CO3.
5. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The molar ratio of the aniline to ethyl bromoacetate is 1:(2.1-2.3).
6. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The molar ratio of the compound C1 to N,N-dimethylformamide and phosphorus oxychloride is 1:(4.9-5.1):(4.9-5.1).
7. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The alkali is at least one of potassium hydroxide and sodium hydroxide; and the amine is aqueous ammonia.
8. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The molar ratio of the compound C2 to 2-acetylpyridine is 1:(1.9-2.1).
9. The method for preparing the asymmetric terpyridine zinc complex according to claim 2, wherein: The molar ratio of the ligand L to ZnX2 is 1:(0.9-1.1); the molar ratio of the ligand L to ZnY2 is 1:(0.4-0.6).
10. Use of the asymmetric terpyridine zinc complex according to claim 1 in multi-level information encryption and decryption.