Preparation, room temperature phosphorescence and anti-counterfeiting performance of carbazolyl 3,5-dicyanopyridine derivatives

Abstract

The application discloses preparation of carbazolyl 3,5-dicyanopyridine derivatives, room temperature phosphor and anti-counterfeiting performance thereof. The preparation method comprises the following steps: adding ortho-, meta- or para-carbazolyl benzaldehyde and malononitrile into a reaction bottle, stirring and reacting under room temperature conditions with sodium hydroxide as a catalyst and anhydrous methanol as a solvent, and obtaining ortho-, meta- or para-carbazolyl 3,5-dicyanopyridine by separating and purifying the reaction crude product. Crystals of the three compounds are obtained by a solvent diffusion method with dichloromethane-petroleum ether as a solvent, and the crystal state room temperature phosphor material is obtained. The crystals are doped with urea / triphenylphosphine at a weight ratio of 1:100, the doped crystals are uniformly ground and mixed, and then heated to be molten, so that the host-guest doped phosphor material is obtained, and the novel material is used in the field of anti-counterfeiting patterns.

Description

Technical Field

[0001] This invention belongs to the field of organic functional materials, specifically relating to the preparation of carbazolyl 3,5-dicyanopyridine derivatives and the optimization method for room temperature phosphorescence properties. Background Technology

[0002] Ultralong organic room-temperature phosphorescent (UORTP) materials are inexpensive, biocompatible, and low in toxicity, showing broad application prospects in high-tech fields such as data storage, bioimaging, sensors, and anti-counterfeiting. Generally, the construction of phosphors mainly involves two aspects: promoting intersystem transitions and suppressing the nonradiative decay of triplet excitons. The former relies on introducing carbonyl groups, heteroatoms, and heavy atoms, as well as reducing the band gap (ΔE) between the singlet (S1) and triplet (T1) states. ST The molecular design of α-donor-acceptor (DA or DAD / ADA) luminescent materials relies on crystal engineering and host-guest doping. Therefore, many distorted donor-acceptor (DA or DAD / ADA) luminescent materials exhibit small ΔE values. ST These materials exhibit excellent room-temperature phosphorescence (RTP) properties. Carbazole, triphenylamine, and phenothiazine are frequently used as electron donors, forming a distorted DA molecular configuration through conjugation of the nitrogen atom with electron acceptors such as benzoic acid, benzaldehyde, and cyanobenzene. However, 3,5-dicyanopyridine (DCP) units are rarely used as electron acceptors in DA phosphorescent materials. Furthermore, DCP units contain multiple electron-withdrawing and electron-donating groups, such as cyano, pyridine, methoxy, and amino groups, which, in addition to producing intrinsic phosphorescence, hold promise for generating cluster phosphorescence through spatial conjugation of functional groups. Moreover, DCP is characterized by its simple preparation, high yield, and mild reaction conditions.

[0003] Besides suppressing the nonradiative decay of triplet excitons, crystal engineering plays a crucial role in exploring the intrinsic mechanisms of photophosphorescent phosphors (RTPs). Crystals possess ordered molecular arrangements and stacking patterns, and precise molecular conformations and stacking methods can be easily obtained through single-crystal X-ray diffraction. Combining crystal analysis with theoretical calculations can reveal key parameters of photophysical properties, thus identifying crucial factors influencing RTP performance. Isomers with the same molecular formula but different molecular configurations, as well as intermolecular arrangement and stacking patterns, often lead to high-contrast optical performance. Therefore, a series of isomers with excellent crystallinity helps to construct structure-function relationships, thereby revealing the intrinsic mechanisms behind RTPs. Furthermore, the poor reproducibility and demanding growth conditions of crystals greatly limit their applications. Therefore, exploring amorphous RTP systems has become a hot topic in the research of pure organic room-temperature phosphorescent materials. In particular, using low-melting-point small molecules as host materials and doping these host materials with organic phosphorescent small molecules can provide a rigid environment that allows for a qualitative leap in the performance of organic phosphorescent small molecule RTPs, while also offering advantages such as flexibility and ease of processing, facilitating the application of various technologies. Summary of the Invention

[0004] The purpose of this invention is to explore and investigate the structure-performance relationship of pure organic room temperature phosphorescent materials, obtain long-lifetime and time-dependent room temperature phosphorescent materials, and increase the difficulty of counterfeiting anti-counterfeiting materials.

[0005] The invention involves adding sodium hydroxide as a catalyst and anhydrous methanol as a solvent to a reaction flask. Carbazole benzaldehyde and malononitrile react under sodium hydroxide catalysis at room temperature with stirring until complete. The crude product is then separated and purified to obtain a carbazole-3,5-dicyanopyridine derivative. Crystals of the three compounds are obtained using a solvent diffusion method with dichloromethane-n-hexane as the solvent. Through host-guest doping and pattern design and drawing, advanced anti-counterfeiting patterns are constructed using different fluorescence and phosphorescence emission methods.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] A method for synthesizing a carbazolyl-3,5-dicyanopyridine derivative, comprising the following preparation process:

[0008] Carbazole benzaldehyde, malononitrile, sodium hydroxide and solvent were added to the reaction vessel under atmospheric conditions. The mixture was stirred and reacted at room temperature for 2 hours. The crude product was purified by column chromatography to obtain the carbazole 3,5-dicyanopyridine derivative.

[0009] Furthermore, the general formula for the preparation of carbazolyl-3,5-dicyanopyridine derivatives is shown below:

[0010]

[0011] In the above preparation method, the molar ratio of carbazole benzaldehyde, malononitrile, and sodium hydroxide is 1:2:1.2.

[0012] In the above preparation method, the organic solvent is anhydrous methanol, and the volume ratio is 10:1.

[0013] The principle of this invention is as follows: 3,5-Dicyanopyridine is selected as the electron-withdrawing group, and carbazole as the electron-donating group. A twisted donor (D)-π-acceptor (A) molecular configuration is constructed through benzene linkage. Different substitution positions are used to adjust the band gap and spin-orbit coupling constant between the lowest singlet and triplet states. The twisted molecular conformation helps to reduce the band gap between the lowest singlet and triplet states, thereby accelerating the formation of triplet excitons. Simultaneously, urea and triphenylphosphine have low melting points and good crystallinity. Host-guest doping can reduce the non-radiative transition of triplet excitons in the luminescent material, enhancing room-temperature phosphorescence performance. The melt dispersion of the luminescent material with urea and triphenylphosphine can simultaneously form monomolecular and aggregate dispersions of the luminescent material. Furthermore, the heteroatoms on the 3,5-dicyanopyridine units in the luminescent material can form spatial interactions with the amino and carbonyl groups of the urea molecule, further generating clustered triplet luminescent centers. Single-molecule, aggregate, and cluster luminescent centers have different phosphorescence lifetimes, thus producing time-dependent room-temperature phosphorescence, enhancing its application value in anti-counterfeiting and encryption fields.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] (1) In different doping matrices of urea and triphenylphosphine, this invention achieves different fluorescence and phosphorescence emission of the same compound, and simultaneously forms binary phosphorescence emission of single molecules and aggregates. In the urea matrix, it forms ternary phosphorescence emission of single molecules, aggregates and clusters, with different room temperature phosphorescence lifetimes, thus exhibiting time-dependent phosphorescence emission. Currently, ternary phosphorescence emission generated by host-guest doping is rarely reported, which helps to increase the difficulty of counterfeiting anti-counterfeiting materials;

[0016] (2) The present invention synthesized three isomers. Only the ortho-isomer doped in the urea matrix can produce visible afterglow under excitation at 380 nm and 400 nm, and the afterglow under 400 nm excitation is as long as 0.5 s. Therefore, in addition to time-dependent room temperature phosphorescence, a higher level of encryption can be achieved by using different excitation wavelengths. Attached Figure Description

[0017] Figure 1 , Figure 2 and Figure 3 These are the proton, carbon, and mass spectra of the target product o-CzAD obtained in Example 1;

[0018] Figure 4 , Figure 5 and Figure 6 These are the proton, carbon, and mass spectra of the target product m-CzAD obtained in Example 1;

[0019] Figure 7 , Figure 8 and Figure 9These are the proton, carbon, and mass spectra of the target product p-CzAD obtained in Example 1;

[0020] Figure 10 The fluorescence and room-temperature phosphorescence spectra of the three crystals of the target product obtained in Example 1 are shown.

[0021] Figure 11 Phosphorescence spectra of Urea / o-CzAD at different delay times;

[0022] Figure 12 Phosphorescence spectra of Urea / p-CzAD at different delay times;

[0023] Figure 13 Phosphorescence spectra of PPh3 / o-CzAD at different delay times;

[0024] Figure 14 Phosphorescence spectra of PPh3 / p-CzAD at different delay times;

[0025] Figure 15 Afterglow images of four doped systems

[0026] Figure 16 Anti-counterfeiting encryption pattern, and attached as a summary diagram. Detailed Implementation

[0027] The present invention will be further described below through specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0028] Example 1

[0029] In a two-necked flask, o- / m- / p-carbazolebenzaldehyde (1 g, 3.7 mmol), malononitrile (0.49 g, 7.4 mmol), sodium hydroxide (0.18 g, 4.4 mmol), and anhydrous methanol (20 mL) were added. The mixture was stirred at room temperature for 2 hours. The mixture was then transferred to water and extracted with ethyl acetate (30 × 3 mL). The organic phases were then combined and dried over anhydrous Na₂SO₄. The solvent was removed by rotary evaporation under reduced pressure, using petroleum ether / ethyl acetate (3:1, v / v) as eluent. The product was purified by column chromatography to give 0.92 g of a yellow solid. Yield: 60%.

[0030] Crystals of three compounds were successfully cultured by slowly diffusing a saturated solution of carbazole-3,5-dicyanopyridine derivatives in dichloromethane (DCM) into n-hexane using a solvent diffusion method.

[0031] 0.1 g of product o- / p-carbazolyl-3,5-dicyanopyridine (o-CzAD / p-CzAD) was added to 10 g of triphenylphosphine / urea, dispersed by grinding with a glass rod, and then heated to the melting temperature of triphenylphosphine / urea to obtain urea / o-CzAD, urea / p-CzAD, PPh3 / o-CzAD, and PPh3 / p-CzAD host-guest doping systems.

[0032] Two sheets of filter paper were soaked in molten urea and PPh3, respectively. o-CzAD and p-CzAD were then dissolved in ethyl acetate to be used as ink. Using the same template and treated filter paper, a series of maple leaves were drawn, cut and arranged in an appropriate order. Under sunlight, only white maple leaves are visible because the main absorption bands of the host and guest are below 400 nm. However, under 365 nm ultraviolet light, they exhibit deep blue or light blue fluorescence. When the ultraviolet light is turned off, three different afterglows are observed: orange, deep blue, and yellow, which represent "level," "dot," and "blank," respectively. Therefore, the correct information cannot be obtained under either sunlight or ultraviolet light. Taking the first row as an example, when the ultraviolet light is off, we can obtain the information "level," "dot," "level," and "dot," which is the correct reading information. Comparing the correct information with the international cipher table, the first row can be interpreted as the letter "C." Using the same strategy, the remaining four rows are decrypted sequentially as "H," "I," "N," and "A." Finally, the complete encrypted information is decrypted as "CHINA."

[0033] The structural characterization data of the target product o-CzAD are shown below:

[0034] 1 H NMR (500 MHz, d6-DMSO) δ / ppm = 8.15 (d, J = 5 Hz, 2H), 7.84~7.77(m, 4H), 7.63 (d, J = 5 Hz, 1H), 7.34~7.23 (m, 7H), 3.77 (s, 3H); 13C NMR (500MHz, d6-DMSO) δ / ppm =165.63, 161.02, 158.79, 141.09, 141.08, 135.71, 133.82,132.72, 131.70, 130.17, 129.67, 126.01, 123.35, 120.77, 115.73, 115.33,111.27, 111.18, 84.45, 84.34, 55.11; HRMS (MALDI-TOF): m / z 416.1506 [[M +H] + , calculated 416.1504].

[0035] The structural characterization data of the target product m-CzAD are shown below:

[0036] 1 H NMR (500 MHz, d6-DMSO) δ / ppm = 8.23 ​​(d, J = 5 Hz, 2H), 7.81 (d, J =15 Hz, 4H), 7.64 (d, J = 5 Hz, 1H), 7.56 (d, J = 5 Hz, 2H), 7.40 (t, J = 15Hz, 2H), 7.29 (t, J = 5 Hz, 2H), 3.96 (s, 3H); 13 C NMR (500 MHz, d6-DMSO) δ / ppm = 166.20, 161.63, 159.90, 140.39, 137.64, 131.16, 127.02, 126.80, 13.39,121.05, 120.86, 110.25, 83.89, 55.28; HRMS (MALDI-TOF): m / z 416.1506 [[M +H] + , calculated 416.1512].

[0037] The structural characterization data of the target product p-CzAD are shown below:

[0038] 1 H NMR (500 MHz, d6-DMSO) δ / ppm = 8.27 (d, J = 5 Hz, 2H), 7.87~7.83(m, 5H), 7.49~7.44 (m, 5H), 7.32 (t, J = 10 Hz, 2H), 4.00 (s, 3H);13 C NMR(500 MHz, d6-DMSO) δ / ppm =166.33, 161.75, 160.39, 140.23, 139.08, 133.34,130.96, 127.03, 126.93, 123.50, 121.14, 120.95, 116.01, 110.08, 83.95, 83.75,55.29; HRMS (MALDI-TOF): m / z 416.1506 [[M +H] + , calculated 416.1507].

[0039] Based on the above characterization data, the structure of the target compound is inferred as follows:

[0040]

Claims

1. A method for synthesizing carbazolyl-3,5-dicyanopyridine derivatives, characterized in that, The specific steps are as follows: o- / m- / p-carbazolylbenzaldehyde and malononitrile were added to a reaction flask, with sodium hydroxide as a catalyst and anhydrous methanol as a solvent. The reaction was stirred at room temperature for 2 hours. The crude product was separated and purified to obtain o- / m- / p-carbazolyl 3,5-dicyanopyridine derivatives. Crystals of the three compounds were obtained by solvent diffusion using dichloromethane-n-hexane as a solvent. The crystals were doped with urea / triphenylphosphine at a weight ratio of 1:

100. After grinding and mixing evenly, the mixture was heated to 90-140℃ to obtain host-guest doped long-lifetime phosphorescent materials. Two filter papers were soaked in molten urea and PPh3, respectively. Then, o-CzAD and p-CzAD were dissolved in ethyl acetate to be used as inks. A series of maple leaves were drawn using the same template and the treated filter paper. These maple leaves were cut and arranged in an appropriate order to obtain an encrypted pattern. The general structural formula of the above carbazolyl-3,5-dicyanopyridine derivatives is as follows: .

2. The method for synthesizing the carbazolyl-3,5-dicyanopyridine derivative as described in claim 1, characterized in that, The molar ratio of ortho / meta / p-carbazole benzaldehyde to sodium hydroxide catalyst is 1:1.

2.

3. The method for synthesizing the carbazolyl-3,5-dicyanopyridine derivative as described in claim 1, characterized in that, The molar ratio of ortho / meta / p-carbazole benzaldehyde to malononitrile is 1:

2.

4. The method for synthesizing the carbazolyl-3,5-dicyanopyridine derivative as described in claim 1, characterized in that, The solvent is anhydrous methanol.

5. The method for synthesizing the carbazolyl-3,5-dicyanopyridine derivative as described in claim 1, characterized in that, The crude product was separated by column chromatography, using ethyl acetate and petroleum ether as eluents.

6. The method for synthesizing carbazolyl-3,5-dicyanopyridine derivatives as described in claim 1, characterized in that the mixed solvent for culturing the crystals is dichloromethane-n-hexane.

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