CN110642840B

CN110642840B - Barbituric acid derivative, preparation method and application thereof in data encryption and decryption

Info

Publication number: CN110642840B
Application number: CN201910917575.2A
Authority: CN
Inventors: 崔月芝; 张汉君; 陶芙蓉; 徐进振; 李学晨
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2019-09-26
Filing date: 2019-09-26
Publication date: 2020-11-13
Anticipated expiration: 2039-09-26
Also published as: CN110642840A

Abstract

The disclosure provides a barbituric acid derivative, a preparation method and application thereof in data encryption and decryption, wherein the chemical structure of the barbituric acid derivative is shown as a formula I:

the barbituric acid derivative provided by the disclosure has the characteristic of enhanced crystallization-induced emission, and can be used for encryption and decryption of data.

Description

Barbituric acid derivative, preparation method and application thereof in data encryption and decryption

Technical Field

The disclosure belongs to the technical field of excitation response luminescent materials, and relates to a barbituric acid derivative, a preparation method and application thereof in data encryption and decryption.

Background

The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.

Excitation-responsive luminescent materials are of great interest for a wide range of applications such as data security, sensors, optical data recording and data protection. Among them, compounds that reversibly modulate between different brightness and emission color are of great interest, although many of the light-emitting compounds exhibit this property in solution. It is known that the light emitting properties of a light emitting material can be changed by changing the molecular structure, but this operation is almost irreversible or insufficient. The mode of molecular packing is changed by mechanical force, heating, solvent fuming, etc., and the emission of the light-emitting compound is reversibly adjusted without damaging the molecular structure of the light-emitting compound. However, the conventional luminescent materials have disadvantages of quenching (ACQ) caused by aggregation, and thus these disadvantages limit their practical applications. In 2001, the polymerization induced emission (AIE) studied could solve the ACQ problem.

To the best of the inventors' knowledge, some AIE compounds having a helical conformation in the aggregated state have a higher emission intensity in the crystalline state than in the amorphous state, while at the same time a blue shift of the emission wavelength in the crystalline state, which is named Crystal Induced Emission Enhancement (CIEE). Compounds with CIEE properties can be transformed in crystalline and amorphous states by mechanical stress, heating or solvent fumigation.

Disclosure of Invention

The barbituric acid derivative has the characteristics of enhanced crystallization-induced emission, and the color of the barbituric acid derivative changes during the conversion process of the compound in a crystalline state and an amorphous state through mechanical stress, heating or solvent fumigation, and the barbituric acid derivative can be applied to data encryption and decryption according to the characteristics.

In order to achieve the purpose, the technical scheme of the disclosure is as follows:

in a first aspect, a barbituric acid derivative has a chemical structure shown as formula I:

in a second aspect, a method for preparing a barbituric acid derivative comprises preparing a compound represented by formula i from a compound 1 and a compound 2 by the following reaction scheme:

in a third aspect, the barbituric acid derivative is applied to data encryption and decryption.

In a fourth aspect, the cryptographic ink is the barbituric acid derivative.

In a fifth aspect, an ink material comprises the above cipher ink and a camouflage material, wherein the chemical structure of the camouflage material is shown as formula II:

the color and the luminescence properties of the compound shown in the formula II are similar to those of the compound shown in the formula I, and the compound shown in the formula II does not have the characteristic of crystallization-induced emission enhancement, so that the compound shown in the formula I can be used for encrypting and decrypting data.

In a sixth aspect, a method for encrypting data uses the above ink material to record data on a carrier using a cryptographic ink, and then covers the carrier on which the data is recorded with a camouflage material.

In a seventh aspect, a method for decrypting data includes heating or spraying a solvent on the carrier obtained by the method for encrypting data.

The beneficial effect of this disclosure does:

the barbituric acid derivative synthesized by the method disclosed by the invention has excellent fluorescence activity and enhanced crystallization-induced emission, and can be used for data encryption-decryption. Experiments prove that when the barbituric acid derivative is used as the cipher ink, the barbituric acid derivative can be converted into a crystalline state and an amorphous state through mechanical stress, heating or solvent fumigation, so that the cipher ink generates different color changes, and further, the materials recorded by the cipher ink are encrypted and decrypted.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.

FIG. 1 is a graph showing UV-visible absorption spectra (solution concentration: 10) of CB-1 prepared in example 1 and CB-2 prepared in example 2 in a Tetrahydrofuran (THF) solution according to the present disclosure^-4M)；

FIG. 2 is THF of CB-1 prepared in example 1 and CB-2 prepared in example 2 of the present disclosure at different water volume contentsFluorescence Spectroscopy (solution concentration: 10)^-4M), the left graph is a fluorescence curve, and the right graph is a curve of occurrence intensity and emission peak;

FIG. 3 is a simulated plot of the molecular dynamics of CB-1 prepared in example 1 and CB-2 prepared in example 2 of the present disclosure;

fig. 4 is a torsion profile of carbazole ring plane a and barbituric acid ring plane B of CB-2 prepared in example 2 of the present disclosure;

FIG. 5 is a graph of the emission spectra of CB-2 prepared in example 2 of the present disclosure after recrystallization in different ratios of ethanol to dichloromethane;

FIG. 6 is an XRD spectrum of resolidification of CB-2 prepared in example 2 of the present disclosure at different ratios of ethanol to dichloromethane;

FIG. 7 is a scanning electron micrograph of CB-2 prepared in example 2 of the present disclosure, wherein the left panel (A) is crystallized from ethanol and the right panel (B) is crystallized from dichloromethane;

FIG. 8 is a schematic diagram of encryption and decryption using CB-1 prepared in example 1 and CB-2 prepared in example 2 of the present disclosure;

FIG. 9 is an electron density distribution plot of the LUMO and HOMO molecular orbitals of CB-1 prepared in example 1 and CB-2 prepared in example 2 of the present disclosure;

FIG. 10 is a diagram of the optimized molecular ground state geometry of CB-1 prepared in example 1 and CB-2 prepared in example 2 of the present disclosure.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, 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 disclosure belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The disclosure provides a barbituric acid derivative, a preparation method and application thereof in data encryption and decryption. The barbituric acid derivative has the characteristic of crystallization-induced emission enhancement and can be used for encryption and decryption of data.

In one exemplary embodiment of the present disclosure, a barbituric acid derivative is provided, which has a chemical structure shown in formula i:

in another embodiment of the present disclosure, a method for preparing barbituric acid derivatives is provided, which comprises using compound 1 and compound 2 as starting materials to prepare a compound represented by formula i:

in one or more examples of this embodiment, compound 1 is subjected to an aldol condensation reaction with compound 2 to provide a compound of formula I.

In one or more embodiments of this embodiment, the reaction conditions are: refluxing is carried out in a solvent.

In this series of examples, the solvent is ethanol.

In the series of embodiments, the reflux time is 2.5-3.5 h.

In one or more embodiments of this embodiment, the molar ratio of compound 1 to compound 2 is 1:0.9 to 1.1.

In one or more examples of this embodiment, the reaction is followed by purification by silica gel column chromatography.

In this series of examples, the mobile phase purified by silica gel column chromatography was a mixture of ethyl acetate and petroleum ether. When the volume ratio of the ethyl acetate to the petroleum ether is 2: 0.9-1.1, the purification effect is better.

In a third embodiment of the present disclosure, an application of the barbituric acid derivative in data encryption and decryption is provided.

In a fourth embodiment of the present disclosure, there is provided a cipher ink, wherein the cipher ink is the barbituric acid derivative.

In a fifth embodiment of the present disclosure, an ink material is provided, which includes the above-mentioned cipher ink and a camouflage material, wherein the chemical structure of the camouflage material is as shown in formula ii:

in a sixth embodiment of the present disclosure, a method for encrypting data is provided, in which the ink material is used, data is recorded on a carrier by using a cipher ink, and then the carrier on which the data is recorded is covered with a camouflage material.

In one or more embodiments of this embodiment, the support is paper.

In a seventh embodiment of the present disclosure, a method for decrypting data is provided, in which a carrier obtained by the above method for encrypting data is heated or sprayed with a solvent.

In one or more embodiments of this embodiment, the solvent utilized for spraying the solvent is dichloromethane. Dichloromethane enables the compound shown in the formula I of the disclosure to change from a crystalline state to an amorphous structure, thereby realizing data decryption.

In order to make the technical solutions of the present disclosure more clearly understood by those skilled in the art, the technical solutions of the present disclosure will be described in detail below with reference to specific embodiments.

Example 1

Synthesis of the Compound represented by formula II (denoted as CB-1):

adding 9-phenylcarbazole-3-formaldehyde and 1, 3-dimethyl barbituric acid (the molar ratio is 1:1) into ethanol (10mL), heating and refluxing for 3 hours, after the reaction is finished, carrying out rotary evaporation on the material after the reaction is finished to obtain a solid, and purifying the solid by using a silica gel column chromatography (ethyl acetate: petroleum ether 2: 1) to obtain a product, namely CB-1, with the yield of 90%.

¹H NMR(400MHz,Chloroform-d)9.34(d,J＝1.7Hz,1H),8.81(s,1H),8.40(d,J＝8.9,1.8Hz,1H),8.26(d,J＝7.7Hz,1H),7.66(t,J＝7.7Hz,2H),7.60–7.53(m,3H),7.51–7.46(m,1H),7.41(t,J＝5.4Hz,3H),3.46(d,J＝1.5Hz,6H)(Fig.S1).FT-IR(KBr,cm-1):1722(C＝O)。

Example 2

Synthesis of a Compound of formula I (designated as CB-2):

adding 9-phenylcarbazole-3-formaldehyde and 1, 3-diphenyl barbituric acid (the molar ratio is 1:1) into ethanol (10mL), heating and refluxing for 3 hours, after the reaction is finished, performing rotary evaporation on the material after the reaction is finished to obtain a solid, and purifying the solid by using a silica gel column chromatography (ethyl acetate: petroleum ether 2: 1) to obtain a product, namely CB-2, with the yield of 90%.

¹H NMR(400MHz,Chloroform-d)9.32(s,1H),8.95(s,1H),8.49(d,J＝9.6Hz,1H),8.23(d,J＝7.7Hz,1H),7.69–7.61(m,3H),7.53(d,J＝11.4Hz,6H),7.47(t,J＝7.6Hz,4H),7.37(d,J＝8.0Hz,6H)(Fig.S3).FT-IR(KBr,cm^-1):1737(C＝O)。

The synthetic routes of CB-1 and CB-2 are as follows:

the properties of CB-1 and CB-2 prepared in examples 1 and 2 are characterized as follows:

the UV-visible absorption spectra of CB-1 and CB-2 in Tetrahydrofuran (THF) solutions are shown in FIG. 1, and the absorption spectra of CB-1 and CB-2 in THF solutions are similar and have two types of characteristic peaks, wherein 250 to 350nm is the pi-pi electron transition of the corresponding benzene ring unit, and the other is the ICT from the carbazole unit to the barbiturate moiety at 425 and 455nm (CB-1 and CB-2, respectively). It was also found therein that the absorption wavelength was changed due to different substituents in barbituric acid. When the substituent on the N-atom of barbituric acid is benzene, which expands the conjugation and reduces the energy gap between HOMO and LUMO, the absorption spectrum of CB-2 shows a red shift compared to CB-1.

When four is usedThe fluorescence intensities of CB-1 and CB-2 are shown in FIG. 2 when the volume content of water in the solution of Tetrahydrofuran (THF) is increased, and when f is_w(Water content is H)₂O to THF volume ratio) increased from 0% to 90%, the emission intensity of CB-1, -2 increased 14-fold and 22-fold, respectively, under the same conditions. In addition to observing the change in fluorescence intensity, the emission wavelength (. lamda.) was also noted_em) With f_wAnd (4) changing. For CB-1, when f_wIncreasing from 0% to 70%, the intermolecular forces increase with increasing water content, λ_emA red shift occurs. When f is_wWhen increasing from 70% to 80%, lambda_emA blue shift occurs due to the slow accumulation of molecules in solution to form nanoparticles and the decrease in internal micropolarity of the molecules. With f of CB-2_wThe emission wavelength is red-shifted because the pi-pi interactions between neighborhoods enhance the planarity of the molecule.

To better explain the aggregation-induced emission of CB-2 is stronger than that of CB-1, molecular dynamics simulations were performed on the systems of CB-1 and CB-2 in the BIOVIA Materials Studio 2017Forcite package, with 8 molecules of each compound (CB-1, CB-2) randomly dissolved in 400 water molecules, respectively, to form 2 different initial systems with the same cubic simulated lattice

The single-point charge (SPC) model can accurately describe the environment of the aqueous solution and is suitable for all water molecules.

MD simulation employs COMPASS force fields, which are force fields for atomic simulation of common organic molecules based on state-of-the-art de novo calculation and empirical parameterization techniques. All simulations were equilibrated at constant temperature (298.15K) and volume (NPT) for 30 ns. Atomic coordinates are saved every 200 ps.

For CB-2, its AIE activity is higher than that of CB-1. As a result of molecular dynamics simulation, as shown in fig. 3, the carbazole assumes a bent configuration because a sub-group of a benzene ring of a substituent on the N-atom of the carbazole has a repulsive effect on the carbazole. Meanwhile, the N-atom on the barbituric acid and the benzene ring of the substituent are perpendicular to each other. Thus, the conformation of CB-2 is a rigid structure in the shape of a propeller, molecules interpenetrate, and intramolecular rotation is restricted. Furthermore, the present disclosure also calculates the twist distribution of the carbazole ring plane a and the barbituric acid ring plane B (fig. 4) of the two compounds during the simulation. As shown below, the twist of the carbazole ring plane a and the barbituric acid ring plane B is quite different for the two systems: the corresponding dihedral angles of these two compounds were 60 ° for CB-1 and 53 ° for CB-2, respectively.

However, for CB-1, its three-dimensional structure is large and the combination is relatively loose. In addition, the dihedral angle between the carbazole ring plane A and the barbituric acid ring plane B of CB-1 is large, which easily causes the generation of TICT and decreases the fluorescence intensity.

The present disclosure calculates the binding energy of each system after self-assembly by equation (1),

ΔE_binding＝E_total–(E_solution+8E_compound)(1)

results are shown in Table 1, when 8 represents the number of molecules per compound, E_bindingIs the binding energy of each system after simulation, E_totalIs the potential energy of each energy minimizing system in equilibrium, E_solutionIs the potential energy of a single aqueous solution without any compound, E_compoundIs the potential energy of each compound. E_tolIs the total enthalpy of each system after 30ns simulation.

TABLE 1 binding energy of the Compounds

It is known that the binding energy is the energy released when several particles are combined from a free state into one composite particle, and the larger the binding energy value is, the more stable the molecular structure is and the more compact the composite aggregate is. As can be seen from Table 1, the binding energy of CB-2 is much greater than that of CB-1, indicating that CB-2 is more tightly bound, which also provides evidence that the AIE activity of CB-2 is greater than that of CB-1.

That is, the colour of CB-2 crystallized from ethanol (orange) changed significantly after recrystallization from dichloromethane (orange-red). The emission spectra of CB-2 recrystallized from a mixture of ethanol and dichloromethane in different proportions are shown in FIG. 5. It was observed that the emission spectrum gradually red-shifted with increasing dichloromethane content.

To further understand the CIEE mechanism of CB-2, XRD of CB-2 recrystallized from mixtures of ethanol and dichloromethane in different ratios was measured. It was found that as the content of methylene chloride was increased, the intensity of XRD diffraction peaks was gradually decreased as shown in fig. 6, and even some peaks were disappeared, which means that as the content of methylene chloride was increased, the CB-2 powder was changed from a crystalline state to an amorphous structure. At the same time, the scanning electron microscope further demonstrates this conclusion, as shown in fig. 7. Therefore, compound CB-2 has CIEE activity.

According to the CIEE attribute, the method designs a new information encryption and decryption technology. As shown in FIG. 8, CB-2 is used as a cipher ink, while CB-1 is used to form a camouflage material because CB-1 has no CIEE effect and exhibits the same color as CB-2. The process of encryption and decryption is as follows: in the encrypted state, the ZHJ is written on the test paper with a cipher ink and then covered with a camouflage material, resulting in an invisible state of the word ZHJ. The next step is to obtain a decrypted state, the orange color of the word ZHJ becomes orange-red and becomes visible after spraying with dichloromethane. Obviously, CB-2 has good CIEE characteristics and has potential application value in the aspect of data encryption-decryption.

The structure-property relationship at the molecular level was understood by calculating the leading molecular orbitals at the level of B3LYP/6-31G using the Density Functional Theory (DFT). The optimized geometries of CB-1 and CB-2, and the energy levels of HOMO and LUMO are shown in FIGS. 9 and 10. As shown in FIG. 9, the electrons of the LUMO molecular orbitals of CB-1 and CB-2 are mainly localized on barbituric acid. In contrast, the electrons of the HOMO molecular orbital are predominantly localized to the carbazole group. Therefore, it can be concluded that an Intramolecular Charge Transfer (ICT) process exists between barbituric acid as the electron accepting moiety and carbazole as the electron donating unit. As shown in FIG. 10, it can be seen that the optimized geometries of CB-1 and CB-2 exhibit highly distorted conformations. The reason for the non-emission in pure THF is that the highly distorted conformation efficiently dissipates the exciton energy.

In summary, the present disclosure synthesizes two barbituric acid derivatives with AIE properties. Molecular dynamics simulations show that CB-2 has the best fluorescence activity, while CB-1 ranks only second. The unexpected CB-2 of the present disclosure has the CIEE property and has potential application in data encryption-decryption. The XRD pattern demonstrates that the mechanism of CIEE is the interconversion of crystalline and amorphous states.

The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A barbituric acid derivative is characterized in that the chemical structure of the barbituric acid derivative is shown as a formula I:

2. a preparation method of barbituric acid derivatives is characterized by comprising the following steps of preparing a compound shown as a formula I by taking a compound 1 and a compound 2 as raw materials through the following reaction route:

3. the method for producing a barbituric acid derivative as claimed in claim 2, wherein the compound 1 is subjected to aldol condensation with the compound 2 to obtain a compound represented by the formula I.

4. The method for producing a barbituric acid derivative as claimed in claim 3, wherein the reaction conditions are: refluxing is carried out in a solvent.

5. The method for producing a barbituric acid derivative as claimed in claim 4, wherein the solvent is ethanol.

6. The method for producing a barbituric acid derivative as claimed in claim 4, wherein the reflux time is 2.5 to 3.5 hours.

7. The method for producing a barbituric acid derivative as claimed in claim 3, wherein the molar ratio of the compound 1 to the compound 2 is 1:0.9 to 1.1.

8. The process for producing a barbituric acid derivative as claimed in claim 3, wherein the reaction is followed by purification by silica gel column chromatography.

9. The process for producing a barbituric acid derivative as claimed in claim 8, wherein the mobile phase purified by silica gel column chromatography is a mixture of ethyl acetate and petroleum ether.

10. The method of producing a barbituric acid derivative as claimed in claim 9, wherein the volume ratio of ethyl acetate to petroleum ether is 2:0.9 to 1.1.

11. Use of the barbituric acid derivative of claim 1 in data encryption and decryption.

12. A cipher ink, characterized in that the cipher ink is the barbituric acid derivative of claim 1.

13. An ink material comprising the cryptographic ink of claim 12 and a camouflage material, wherein the chemical structure of the camouflage material is represented by formula ii:

14. a method of encrypting data using the ink material of claim 13, wherein the data is recorded on a carrier using a cryptographic ink and the carrier on which the data is recorded is covered with a camouflage material.

15. The method of data encryption according to claim 14, wherein said carrier is paper.

16. A method for decrypting data, characterized in that the carrier obtained by the method for encrypting data according to claim 14 or 15 is subjected to a heating or solvent spraying treatment.

17. The method for decrypting data as claimed in claim 16, wherein the solvent used for spraying the solvent is dichloromethane.