Schiff base optical switch material, preparation method thereof and bulk three-dimensional display system

Abstract

The invention provides a Schiff base photoswitch material. The chemical structural formula of the Schiff base photoswitch material is shown in the specification, wherein n is an integer from 5 to 15. The Schiff base optical switch material can have the characteristic of intersection point luminescence under common excitation of purple light and blue light, and can be used in a display space of volume three-dimensional imaging. The Schiff base optical switch material is applied to volume three-dimensional display, is high in transparency and good in stability and reversibility, and can be applied to the fields of two-dimensional, multi-security anti-counterfeiting, three-dimensional data storage and the like as a quick-response optical switch material. The invention also provides a preparation method of the Schiff base optical switch material and a volume three-dimensional display system comprising the Schiff base optical switch material.

Description

TECHNICAL FIELD

[0001] The present application relates to a Schiff base photo-switching material and a preparation method thereof, and a volume three-dimensional display system comprising the Schiff base photo-switching material. BACKGROUND

[0002] Volume three-dimensional display is a kind of stereoscopic display method of real space imaging, which utilizes the special visual mechanism of human beings to create a display object composed of voxels instead of molecular particles. In addition to the shape represented by light waves, the real existence of voxels can also be touched. Volume three-dimensional display technology constructs a series of light-emitting voxel points in the imaging space in a very short time through two light sources, and realizes display by using visual persistence. In the field of organic light-emitting materials, photochromic materials with reversible performance are expected to be used as the medium of volume three-dimensional display. Schiff base mainly refers to a kind of organic compounds containing imine or azomethine groups (-RC=N-). 1,8-naphthalimide is a kind of fluorescent material, which is used as a fluorescent probe in many detection fields due to its good molecular stability and high fluorescence brightness. However, there is little report on its application as volume three-dimensional display material. SUMMARY

[0003] In view of this, the first aspect of the present application provides a Schiff base photo-switching material, the chemical structural formula of which is as follows:

[0004] wherein n is an integer of 5-15.

[0005] The Schiff base photo-switching material has the characteristic of cross-point luminescence under the excitation of purple light and blue light, and can be used in the display space of volume three-dimensional imaging. The Schiff base photo-switching material applied in volume three-dimensional display has high transparency, good stability and reversibility, and can also be applied in the fields of two-dimensional, multi-safety anti-counterfeiting, three-dimensional data storage, etc. as a fast-response photo-switching material.

[0006] The second aspect of the present application provides a volume three-dimensional display system comprising the Schiff base photo-switching material as described above.

[0007] The third aspect of the present application provides a preparation method of the Schiff base photo-switching material, comprising:

[0008] Step one, reacting 4-bromo-1,8-naphthalic anhydride with n-butylamine to obtain intermediate one

[0009] Step two, reacting the intermediate one with sodium methoxide to obtain intermediate two

[0010] Step three, reacting the intermediate two with hydriodic acid to obtain intermediate three

[0011] Step four: react intermediate three with hexamethylenetetramine to obtain intermediate four.

[0012] Step 5: React the intermediate tetrahydropalmatus with aliphatic amines to obtain the final target product.

[0013]

[0014] This application uses 4-bromo-1,8-naphthalenedicarboxylic anhydride and aliphatic amines as raw materials, resulting in low-cost raw materials. The prepared Schiff base photoswitching material contains a naphthalimide fluorescent group, which improves the brightness of the Schiff base photoswitching material. The aliphatic amine is selected as a primary amine with a long carbon chain aliphatic hydrocarbon group, which increases molecular flexibility, reduces intermolecular π-π stacking, and reduces the fluorescence quenching phenomenon of molecular aggregates. At the same time, since the Schiff base compound formed by salicylaldehyde and its derivatives and amine compounds contains a "potential six-membered ring" structure composed of intramolecular hydrogen bonds formed by hydroxyl groups and C=N double bonds, it can also effectively reduce the fluorescence quenching phenomenon of aggregates in the material. Attached Figure Description

[0015] Figure 1 The image shows the 1H NMR spectrum of the Schiff base photoswitching material of Example 1 of this application.

[0016] Figure 2 The absorption spectrum is that of the Schiff base photoswitching material of Example 1 of this application.

[0017] Figure 3 This is a schematic diagram illustrating the application of the Schiff base photo-switching material in a three-dimensional display system according to Embodiment 1 of this application.

[0018] Explanation of key component symbols:

[0019] 3D display system 100

[0020] Imaging space 10

[0021] First excitation light 21

[0022] Second excitation light 22 Detailed Implementation

[0023] The embodiments of this application are described below with reference to the accompanying drawings. Unless otherwise specified, the data ranges involved in this application shall include end values.

[0024] This application provides a novel Schiff base photoswitching material with the following chemical structural formula:

[0025] Where n is an integer between 5 and 15.

[0026] This Schiff base photo-switching material can be used in organic solvents. It can be excited by two light sources of different wavelengths. The intersection of the two light sources can emit yellow fluorescence, and it can recover quickly after being stimulated by visible light, thus having a three-dimensional display effect.

[0027] This Schiff base optical switch material has high transparency, good stability and reversibility. As a fast-response optical switch material, it can also be applied to two-dimensional, multi-layer security anti-counterfeiting, three-dimensional data storage and other fields.

[0028] The above chemical structural formula represents the Schiff base photoswitching material in its natural state. The structure of the Schiff base photoswitching material produced in Example 1 below was characterized using 1H NMR spectroscopy, and the results are as follows: Figure 1 .according to Figure 1 The position (chemical shift) and area (number of hydrogen atoms) of the middle peak can be used to determine the chemical shift of the middle peak. Figure 1 The hydrogen peak in the sample corresponds to the hydrogen-containing functional group in the molecular structure of the Schiff base photoswitch material, verifying that the Schiff base photoswitch material with this molecular structure can be formed.

[0029] Please see Figure 2 As can be seen from the absorption spectrum of the Schiff base photoswitch material, the Schiff base photoswitch material of this application has two obvious absorption peaks in the wavelength range of 200nm to 700nm. It has obvious absorption in the ultraviolet region of wavelength 225nm to 310nm and the region of wavelength 350nm to 440nm, but its light absorption ability in the region of wavelength 450nm to 700nm is relatively weak.

[0030] Based on the principle of excited-state proton transfer, this Schiff base photoswitch material can rapidly transform from the enol form (initial state) to the keto isomer under violet light irradiation with wavelengths of 365 nm to 410 nm. Without irradiation with violet light of wavelengths of 365 nm to 410 nm, the keto isomer will transform into the enol form of the Schiff base photoswitch material. That is, the enol form and the keto form are interconvertible, as shown in the following reaction formula.

[0031]

[0032] Another beam of visible light (blue light with a wavelength of 440nm to 470nm) intersects with violet light with a wavelength of 365nm to 410nm, exciting the ketone isomer to produce a yellow fluorescence under laser light.

[0033] The Schiff base photo-switching material provided in this application embodiment can be converted into an isomer under the irradiation of a first excitation light. The isomer generates a laser beam under the irradiation of a second excitation light, exhibiting a fast overall response speed and applicable to various scenarios, such as two-dimensional display devices, three-dimensional display devices, light-controlled switching elements, or multi-emissivity anti-counterfeiting materials.

[0034] The preparation method of this Schiff base photoswitching material includes:

[0035] Step 1: React 4-bromo-1,8-naphthalenedicarboxylic anhydride with n-butylamine to obtain intermediate 1.

[0036] Specifically, the process involves adding 4-bromo-1,8-naphthalenedicarboxylic anhydride and an organic solvent (one or more of the following organic solvents: glacial acetic acid, formic acid, acetic acid, dimethyl sulfoxide, dimethylformamide, acetonitrile, methanol, ethanol, tetrahydrofuran, toluene, dichloroethane, etc.) to a reaction flask, stirring, and then adding n-butylamine dropwise. After the addition is complete, the mixture is heated to reflux for 8 hours, for example, heated to 120°C and refluxed. The mixture is then cooled to room temperature, deionized water is added dropwise, and the mixture is filtered. The filter cake is washed with water and dried to obtain intermediate one. The reaction formula is as follows.

[0037]

[0038] In step one, the molar ratio of 4-bromo-1,8-naphthalenedicarboxylic anhydride to n-butylamine is 1:(2-3), and the mass ratio of 4-bromo-1,8-naphthalenedicarboxylic anhydride to organic solvent and deionized water is 1:(6-10):(6-10). In step one, the reflux temperature varies depending on the organic solvent. For example, if glacial acetic acid is used, the reflux temperature can be raised to 115–125°C; if ethanol is used, the reflux temperature can be raised to 80–90°C.

[0039] Step two: Intermediate one is reacted with sodium methoxide to obtain intermediate two.

[0040] Specifically, the process involves adding intermediate one, anhydrous copper sulfate (as a catalyst), and an alcoholic organic solvent (which can be one or more of methanol, ethanol, isopropanol, ethylene glycol, etc.) to a reaction flask, stirring, and then adding a sodium methoxide organic solvent solution (e.g., sodium methoxide with a mass percentage concentration of 30%) dropwise to the reaction flask. After the addition is complete, the temperature is raised to 60℃~70℃ and refluxed for reaction, for example, raised to 65℃ and refluxed for 6 hours. The temperature is then lowered to room temperature, filtered, and the filter cake is washed with 5% hydrochloric acid, then washed with water until neutral, and dried to obtain intermediate two. The reaction formula is as follows.

[0041]

[0042] In step two, the mass ratio of intermediate one to anhydrous copper sulfate and sodium methoxide is 10:(1-3):(7.5-10.5). The mass ratio of intermediate one to organic solvent and 5% hydrochloric acid solution is 10:(70-80):(25-35).

[0043] Step 3: Intermediate 2 is reacted with hydroiodic acid to obtain intermediate 3.

[0044] Specifically, the process involves adding intermediate II and hydroiodic acid (e.g., at a concentration of 57%) to a reaction flask, stirring and heating to 125°C–140°C for reflux reaction, for example, heating to 130°C for reflux reaction for 16 hours, cooling to room temperature, filtering, dissolving the filter cake in a 5% sodium hydroxide solution, extracting with dichloroethane, acidifying the aqueous phase with concentrated hydrochloric acid dropwise to pH 5, filtering, washing the filter cake with water, and drying to obtain intermediate III. The reaction equation is as follows.

[0045]

[0046] In step three, the mass ratio of intermediate two to hydrogen iodide is 1:(4.56-6.84); the mass ratio of intermediate two to 5% sodium hydroxide aqueous solution and dichloromethane is 1:(4-6):(2-4).

[0047] Step four: Intermediate three is reacted with hexamethylenetetramine to obtain intermediate four.

[0048] Specifically, the process involves adding intermediate three and an organic solvent (one or more of trifluoroacetic acid, acetic acid, polyphosphoric acid, dimethyl sulfoxide, methanol, ethanol, and acetone) to a reaction flask, stirring, adding hexamethylenetetramine in batches, heating to 70°C–80°C and refluxing, for example, heating to 72°C and refluxing for 12 hours, cooling to room temperature, adding deionized water dropwise, filtering, washing the filter cake with water, and drying to obtain intermediate four. The reaction equation is as follows.

[0049]

[0050] In step four, the molar ratio of intermediate three to hexamethylenetetramine is 1:(1.5-2). In some embodiments, the mass ratio of intermediate four to trifluoroacetic acid and deionized water is 1:(8-12):(10-20).

[0051] Step 5: React intermediate 4 with aliphatic amines to obtain the final target product.

[0052]

[0053] Specifically, the process involves adding intermediate tetrahydropalmatine, aliphatic amine, and solvent S to a reaction flask, stirring, and refluxing at 70°C to 100°C, for example, refluxing at 78°C for 2 hours, followed by cooling to allow crystallization, filtration, washing, and drying to obtain the Schiff base material. The reaction equation is as follows.

[0054]

[0055] In step five, solvent S is one of methanol, ethanol, toluene, and tetrahydrofuran, and the molar ratio of intermediate four to aliphatic amine is 1:(0.9-1.3). In some embodiments, the mass ratio of intermediate four to solvent S is 1:(4-6).

[0056] Please see Figure 3 This application also provides a volumetric 3D display system 100, including the aforementioned Schiff base photo-switching material. The Schiff base photo-switching material is dispersed in an organic solvent to form a transparent solution, which serves as the imaging space 10 for the volumetric 3D display.

[0057] The 3D display system 100 also includes an excitation light source (not shown) for illuminating the imaging space 10. The excitation light source includes a first excitation light 21 and a second excitation light 22. The two light sources intersect at a point in the imaging space 10 to generate luminescent voxel dots. When the excitation light source moves rapidly, multiple intersection points are formed in the imaging space 10, which, as voxels, constitute a 3D stereoscopic image. The first excitation light 21 is violet light with a wavelength of 365nm to 410nm, and the second excitation light 22 is blue light with a wavelength of 440nm to 470nm.

[0058] The first excitation beam 21 and the second excitation beam 22 intersect at a point in the imaging space 10, generating luminous voxel dots. By controlling the scanning paths and speeds of the first and second excitation beams 21 and 22 respectively via a computer connected to an optical scanning mirror, the luminous point at the intersection of the two laser beams is scanned rapidly at a speed exceeding the refresh rate of the human eye, forming an array of multiple voxel dots, thus creating a three-dimensional spatial image within the imaging space 10. The voxel dots generated and disappeared at speeds lower than the limit of human eye resolution using this Schiff base photo-switching material have a fast response speed, enabling dynamic refreshing of the three-dimensional image.

[0059] The specific method for preparing the solution for the imaging space 10 is as follows: dissolve the Schiff base photoswitch material in dichloromethane to obtain a dichloromethane solution, pour the dichloromethane solution into solvent V and mix evenly to obtain a solution of the Schiff base photoswitch material.

[0060] In some embodiments, solvent V is at least one selected from hexane, heptane, cyclohexane, methyl tert-butyl ether, and toluene. In some embodiments, the mass ratio of solvent V to dichloromethane and Schiff base photoswitching material is (9000-9800):(1000-200):1.

[0061] This application uses 4-bromo-1,8-naphthalenedicarboxylic anhydride and aliphatic amines as raw materials, resulting in low-cost raw materials. The prepared Schiff base photoswitching material contains a naphthalimide fluorescent group, which improves the brightness of the Schiff base photoswitching material. The aliphatic amine is selected as a primary amine with a long carbon chain aliphatic hydrocarbon group, which increases molecular flexibility, reduces intermolecular π-π stacking, and reduces the fluorescence quenching phenomenon of molecular aggregates. At the same time, since the Schiff base compound formed by salicylaldehyde and its derivatives and amine compounds contains a "potential six-membered ring" structure composed of intramolecular hydrogen bonds formed by hydroxyl groups and C=N double bonds, it can also effectively reduce the fluorescence quenching phenomenon of aggregates in the material.

[0062] The preparation of Schiff base photoswitching materials will be specifically described below through Examples 1 to 3.

[0063] Example 1

[0064] The specific synthesis steps of intermediate one are as follows:

[0065] Weigh 27.7 g of 4-bromo-1,8-naphthalenedicarboxylic anhydride and 221.6 g of glacial acetic acid into a reaction flask, stir, and add 21.9 g of n-butylamine dropwise. After the addition is complete, heat to 120 °C and reflux for 8 h. Cool to room temperature, add 221.6 g of deionized water dropwise, filter, wash the filter cake with water, and dry to obtain intermediate one.

[0066] The specific synthesis steps of intermediate 2 are as follows:

[0067] Weigh 33.2g of intermediate one, 3.3g of anhydrous copper sulfate, and 265.6g of methanol into a reaction flask, stir, and add 99.6g of 30% sodium methoxide methanol solution dropwise. After the addition is complete, heat to 65℃ and reflux for 6 hours. Cool to room temperature, filter, wash the filter cake with 99.69g of 5% hydrochloric acid, wash with water, and dry to obtain intermediate two.

[0068] The specific synthesis steps of intermediate 3 are as follows:

[0069] Weigh 28.3 g of intermediate II and 283.0 g of 57% hydroiodic acid into a reaction flask, stir and heat to 130 °C, reflux for 16 h, cool to room temperature, filter, weigh 141.5 g of 5% sodium hydroxide aqueous solution, add to the obtained filter cake, stir to dissolve, add 56.6 g of dichloromethane for extraction, take the upper aqueous phase, add concentrated hydrochloric acid dropwise to pH 5, filter, wash with water and dry to obtain intermediate III.

[0070] The specific synthesis steps of intermediate four are as follows:

[0071] Weigh 26.9 g of intermediate tetrahydroquinone and 269 g of trifluoroacetic acid into a reaction flask, stir, add 28.0 g of hexamethylenetetramine in portions, heat to 72 °C, reflux for 12 h, cool to room temperature, add 28.0 g of deionized water dropwise, filter, wash the filter cake with water, and dry to obtain intermediate tetrahydroquinone.

[0072] The specific synthesis steps of the Schiff base photoswitching material are as follows:

[0073] Weigh 2.9 g of intermediate tetramethylamine, 2.8 g of n-hexadecylamine, and 14.5 g of ethanol and add them to a reaction flask. Stir and heat to 78 °C, reflux for 2 h, cool to crystallize, filter, wash with cold ethanol, and dry to obtain Schiff base photoswitching material.

[0074] Example 2

[0075] In Example 2, the synthesis of intermediate one, intermediate two, intermediate three, and intermediate four is exactly the same as that in Example 1.

[0076] The specific synthesis steps of the Schiff base photoswitching material are as follows:

[0077] 2.9 g of intermediate tetrahydropalmatine, 1.18 g of n-hexylamine, and 14.5 g of ethanol were weighed and added to a reaction flask. The mixture was stirred and heated to 78 °C, refluxed for 2 h, cooled to crystallize, filtered, washed with cold ethanol, and dried to obtain the Schiff base photoswitching material.

[0078] Application Example 1

[0079] Volumetric 3D Display Application: Weigh 5 mg of the Schiff base photoswitch material from Example 1, add it to 1 g of dichloromethane, dissolve it completely, then add it to 49 g of cyclohexane and mix thoroughly to obtain a Schiff base photoswitch material solution. A 405 nm light source is selected as the wavelength of the photochromic light source, and 450 nm is selected as the wavelength of the excitation light source for the photochromic isomer. The two beams of light converge within the solution to form voxel dots, achieving a volumetric 3D display effect.

[0080] Application Example 2

[0081] Volumetric 3D Display Application: Weigh 5 mg of the Schiff base photoswitch material from Example 2, add it to 1 g of dichloromethane, dissolve it completely, then add it to 49 g of cyclohexane and mix thoroughly to obtain a Schiff base photoswitch material solution. A 365 nm light source is selected as the wavelength of the photochromic light source, and 450 nm is selected as the wavelength of the excitation light source for the photochromic isomer. The two beams of light converge within the solution to form voxel dots, achieving a volumetric 3D display effect.

[0082] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A Schiff base photo-switching material, characterized in that, Its chemical structural formula is: Where n is an integer between 5 and 15.

2. The Schiff base photoswitching material according to claim 1, characterized in that, The Schiff base photoswitch material absorbs light with wavelengths from 225 nm to 440 nm.

3. The Schiff base photoswitching material according to claim 1, characterized in that, The Schiff base photoswitch material can be transformed from an enol form to a keto isomer under ultraviolet light irradiation with a wavelength of 365 nm to 410 nm; and when not irradiated by ultraviolet light, the keto isomer will transform into the enol form of the Schiff base photoswitch material.

4. A volumetric three-dimensional display system, characterized in that, Includes Schiff base photoswitching materials as described in any one of claims 1 to 3.

5. The volumetric three-dimensional display system according to claim 4, characterized in that, The Schiff base photo-switching material is dissolved and dispersed in an organic solvent to form a transparent solution, which serves as the imaging space of the volumetric 3D display system. The volumetric 3D display system also includes an excitation light source, which emits excitation light to illuminate the imaging space. The excitation light includes a first excitation light and a second excitation light.

6. The volumetric three-dimensional display system according to claim 5, characterized in that, The first excitation light is violet light with a wavelength of 365nm to 410nm, and the second excitation light is blue light with a wavelength of 440nm to 470nm.

7. The volumetric three-dimensional display system according to claim 5, characterized in that, The organic solvent includes solvent V and dichloromethane, wherein solvent V is at least one of n-hexane, n-heptane, cyclohexane, methyl tert-butyl ether, and toluene; the mass ratio of solvent V to dichloromethane and the Schiff base photoswitching material is (9000-9800):(1000-200):

1.

8. A method for preparing a Schiff base photoswitching material, characterized in that, include: Step 1: React 4-bromo-1,8-naphthalenedicarboxylic anhydride with n-butylamine to obtain intermediate 1. Step two: react intermediate one with sodium methoxide to obtain intermediate two. Step 3: React intermediate 2 with hydroiodic acid to obtain intermediate 3. Step four: react intermediate three with hexamethylenetetramine to obtain intermediate four. Step 5: React the intermediate tetrahydropalmatus with aliphatic amines to obtain the final target product.

9. The method for preparing the Schiff base photoswitching material according to claim 8, characterized in that, Step one includes: adding 4-bromo-1,8-naphthalenedicarboxylic anhydride, an organic solvent, and n-butylamine to a reaction flask, stirring, heating to reflux, cooling to room temperature, adding deionized water dropwise, filtering, washing the filter cake with water, and drying to obtain intermediate one, wherein the molar ratio of 4-bromo-1,8-naphthalenedicarboxylic anhydride to n-butylamine is 1:(2-3), and the organic solvent is one or more selected from glacial acetic acid, formic acid, acetic acid, dimethyl sulfoxide, dimethylformamide, acetonitrile, methanol, ethanol, tetrahydrofuran, toluene, and dichloroethane; and / or, Step two includes: adding intermediate one, anhydrous copper sulfate, an alcoholic organic solvent, and sodium methoxide to a reaction flask, stirring, heating to 60℃~70℃ and refluxing, cooling to room temperature, filtering, washing the filter cake, washing with water until neutral, and drying to obtain intermediate two, wherein the mass ratio of intermediate one to anhydrous copper sulfate and sodium methoxide is 10:(1-3):(7.5-10.5); and / or, Step three includes: adding intermediate two and hydroiodic acid to a reaction flask, stirring and heating to 125℃~140℃ under reflux, cooling to room temperature, filtering to obtain a filter cake, dissolving the filter cake, extracting, acidifying, filtering, washing with water, and drying to obtain intermediate three, wherein the mass ratio of intermediate two to hydrogen iodide is 1:(4.56-6.84); and / or, Step four includes: adding the intermediate tri and trifluoroacetic acid to a reaction flask, stirring, adding hexamethylenetetramine, heating to 70℃~80℃ to reflux reaction, cooling to room temperature, adding deionized water dropwise, filtering, washing the filter cake with water, and drying to obtain the intermediate four, wherein the molar ratio of the intermediate tri to hexamethylenetetramine is 1:(1.5-2).

10. The method for preparing the Schiff base photoswitching material according to claim 8, characterized in that, Step five includes: adding the intermediate tetra, the fatty amine, and solvent S into a reaction flask, stirring, heating to 70℃~100℃ and refluxing, cooling to crystallize, filtering, washing, and drying to obtain the Schiff base photoswitching material, wherein the solvent S is one of methanol, ethanol, toluene, and tetrahydrofuran, and the molar ratio of the intermediate tetra to the fatty amine is 1:(0.9-1.3).

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