An organic photochromic compound containing a b←n bond, and a preparation method and application thereof

Abstract

The application relates to an organic photochromic compound containing a B <-N bond and a preparation method and application thereof. The organic photochromic compound has a structure shown in formula I. The synthesis steps of the organic photochromic compound are simple and efficient; the photochromic ability in a solid state is good, the smart color-changing material can still maintain a large color-changing range in a pure solid state, and the organic photochromic compound has wide potential applications in the fields of organic light-emitting diodes, optical information storage, smart light switch devices and agricultural plastic films.

Description

Technical Field

[0001] This application relates to the field of photochromic materials, specifically to an organic photochromic compound containing B←N bonds, its preparation method, and its application. Background Technology

[0002] Photochromic materials undergo reversible color changes under light stimulation, accompanied by alterations in their physicochemical properties. These changes lead to a wide range of applications, such as organic light-emitting diodes (OLEDs), optical information storage, intelligent light conversion devices, and targeted biopharmaceuticals. Photochromic materials can be categorized into inorganic, organic, and organic-inorganic hybrid photochromic materials. Inorganic and organic-inorganic hybrid materials fall short in terms of color-changing range, efficiency, and controllability, while organic photochromic materials exhibit strong structural modifiability, allowing for precise control through chemical modification to enhance photoresponse speed and color-changing performance. Despite significant progress in the field of organic photochromic materials, several challenges remain. For example, high synthesis difficulty and insufficient photosensitivity limit the application of certain materials; improving their resistance to light fatigue, reversibility, and long lifespan is crucial for their application in high-end fields. Therefore, developing ideal organic photochromic compounds has become a research hotspot in the field of photochromic materials.

[0003] Boron-containing organic photochromic materials have attracted research interest due to their unique optical properties. Boron is a typical electron-deficient unit; the empty p orbitals of boron atoms can form strong p-π conjugation with π-conjugated systems, thus greatly stabilizing the LUMO orbitals on π-conjugated ligands. This gives these molecules efficient electron transport properties and effectively reduces their energy level difference, thereby achieving absorption of visible light and color change upon visible light irradiation. Therefore, introducing B←N units into the molecular framework to reduce the HOMO-LUMO energy level difference, and combining molecular units that undergo slight structural changes before and after light irradiation with B←N units, can create photochromic molecules that respond rapidly to visible light irradiation in the solid state, providing a novel strategy for developing visible light photochromic materials. However, photochromic compounds with boron-containing organic frameworks are scarce. Therefore, developing novel boron-containing photochromic materials and promoting the development of new intelligent color-changing materials through chemical regulation at the molecular level is of great significance. Summary of the Invention

[0004] To address the problems in the prior art, this application provides an organic photochromic compound containing B←N bonds, its preparation method, and its application.

[0005] In a first aspect, this application provides an organic photochromic compound containing B←N bonds, having the structure shown in Formula I:

[0006]

[0007] In Formula I, R1 is selected from C1-C4 alkyl (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl), C6-C8 aryl (e.g., phenyl, tolyl or ethylphenyl), and C1-C4 alkoxy (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy or tert-butoxy).

[0008] R2 is selected from halogens (e.g., fluorine, chlorine, or bromine), C1-C4 alkyl groups (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), C6-C8 aryl groups (e.g., phenyl, tolyl, or ethylphenyl), and C1-C4 alkoxy groups (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, or tert-butoxy).

[0009] R3 and R4 may be the same or different, each independently selected from hydrogen, C1-C4 alkyl (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl) or C1-C4 alkoxy (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy or tert-butoxy), and when R1 and R2 are both C1-C4 alkoxy, R3 and R4 are not both hydrogen.

[0010] The organic photochromic compounds provided in this application, on the one hand, are N,C-chelated tetracoordinate boron compounds containing B←N coordination units. Due to the presence of their B←N chelating units, these compounds enhance conjugation and planarity, significantly improving the photochromic performance of photochromic materials under pure solid-state conditions. This results in compounds with advantages such as high luminescence intensity, high carrier mobility, and good stability. On the other hand, compared with previously studied compounds that can only emit a single type of light, specific electron-donating substituents enable the compounds to simultaneously emit blue-violet light (400-480 nm) and red-orange light (600-680 nm). These compounds can be incorporated into agricultural films as composite light-converting agents, greatly improving the utilization rate of sunlight.

[0011] In some embodiments, R1 is selected from methyl, ethyl, phenyl, methoxy, or ethoxy.

[0012] In some embodiments, R2 is selected from fluorine, bromine, methyl, ethyl, phenyl, methoxy, or ethoxy.

[0013] In some embodiments, R3 and R4 may be the same or different, and each may be independently selected from hydrogen, methyl, ethyl, methoxy, or ethoxy.

[0014] In some embodiments, the organic photochromic compound is selected from the following compounds:

[0015]

[0016] Secondly, this application provides a method for preparing an organic photochromic compound containing a B←N bond, comprising one or more of the following steps:

[0017] Step 1: React compound a with compound b to generate compound M.

[0018]

[0019] Step 2: React compound M with 9-boron bicyclo[3.3.1]nonane dimer to generate compound I.

[0020]

[0021] R1 is selected from C1-C4 alkyl (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl), C6-C8 aryl (e.g., phenyl, tolyl or ethylphenyl), and C1-C4 alkoxy (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy or tert-butoxy).

[0022] R2 is selected from halogens (e.g., fluorine, chlorine, or bromine), C1-C4 alkyl groups (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), C6-C8 aryl groups (e.g., phenyl, tolyl, or ethylphenyl), and C1-C4 alkoxy groups (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, or tert-butoxy).

[0023] R3 and R4 may be the same or different, each independently selected from hydrogen, C1-C4 alkyl (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl) or C1-C4 alkoxy (e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy or tert-butoxy), and when R1 and R2 are both C1-C4 alkoxy, R3 and R4 are not both hydrogen;

[0024] R5 is selected from halogens.

[0025] The method provided in this application can significantly improve the color-changing performance of photochromic materials containing B←N bonds, and also enhance the color-changing responsiveness and reversibility of the materials. It also leads to the formation of novel organic smart color-changing materials containing B←N bonds with tunable color-changing range, ensuring the color-changing ability of these materials under pure solid-state conditions. By studying the characteristics of vacant p orbitals of boron atoms and lone pair electrons of nitrogen atoms, and rationally combining these two to design a compound synthesis method, a series of novel B←N bond-containing materials with strong photochromic responsiveness, significantly enhanced solid-state color-changing ability, and novel color-changing properties have been developed. Furthermore, the method provided in this application, by first constructing the molecular framework and then coordinating the vacant orbitals of boron with the lone pair electrons of nitrogen through a borohydride reaction, can efficiently improve the material synthesis efficiency and greatly reduce the synthesis cost of photochromic materials.

[0026] In some embodiments, R1 is selected from methyl, ethyl, phenyl, methoxy, or ethoxy.

[0027] In some embodiments, R2 is selected from fluorine, bromine, methyl, ethyl, phenyl, methoxy, or ethoxy.

[0028] In some embodiments, R3 and R4 may be the same or different, and each may be independently selected from hydrogen, methyl, ethyl, methoxy, or ethoxy.

[0029] In some embodiments, R5 is selected from fluorine, chlorine, or bromine.

[0030] In some embodiments, compound a is

[0031] In some embodiments, compound b is

[0032] In some embodiments, the compound of formula M is

[0033] In some embodiments, in step 1, the molar ratio of compound a to compound b is 1:0.8 to 1:1.2, for example, 1:0.9, 1:1.0 or 1:1.1.

[0034] In some embodiments, the reaction temperature in step 1 is 70°C-90°C, for example 75°C, 80°C or 85°C.

[0035] In some implementations, the reaction time in step 1 is 24-48 hours, for example, 30 hours, 36 hours, or 42 hours.

[0036] In some embodiments, step 1 is carried out in a mixed solution of water and tetrahydrofuran. In some embodiments, step 1 further includes tetra(triphenylphosphine)palladium and potassium carbonate.

[0037] In some embodiments, in step 1, the reaction is carried out in an inert atmosphere, such as an argon atmosphere.

[0038] In some embodiments, in step 2, the molar ratio of the compound of formula M to the 9-boron bicyclo[3.3.1]nonane dimer is 1:1.1 to 1:1.6, for example, 1:1.2, 1:1.3, 1:1.4 or 1:1.5.

[0039] In some embodiments, the reaction temperature in step 2 is 80°C-100°C, for example, 85°C, 90°C or 95°C.

[0040] In some implementations, the reaction time in step 2 is 12h-48h, for example 18h, 24h, 30h, 36h or 42h.

[0041] In some embodiments, step 2 is carried out in 1,2-dichloroethane. In some embodiments, step 2 further includes ferric tribromide.

[0042] In some embodiments, step 2 is carried out in an inert atmosphere, such as an argon atmosphere.

[0043] In some embodiments, the method for preparing the organic photochromic compound includes the following steps:

[0044]

[0045] Step S11: Compound a and compound b are coupled via an organic Suzuki coupling reaction to construct nitrogen-containing aromatic heterocyclic molecular intermediate M;

[0046] Step S12: The nitrogen-containing aromatic heterocyclic molecular intermediate M is converted into the target molecule through a hydroboration reaction.

[0047] In some embodiments, the preparation method of the organic photochromic compound includes the following specific steps:

[0048] Step A: Compounds a, b, and tetra(triphenylphosphine)palladium were placed in a 250 mL three-necked flask, dissolved in a mixed solution of degassed and deoxygenated distilled water and tetrahydrofuran, and refluxed at 80 °C for 24 h under Ar protective gas. After the reaction was complete, the tetrahydrofuran was removed by vacuum distillation, and the mixture was extracted with ethyl acetate. The combined ethyl acetate organic phases were dried over anhydrous magnesium sulfate, and then the ethyl acetate was removed by vacuum distillation. The crude product was treated with dichloromethane and petroleum ether (V... DCMV PE The product was purified by column chromatography using a 1:1 eluent to obtain a white solid intermediate product M.

[0049] Step B: Weigh intermediate product M, 9-boronbicyclo[3.3.1]nonane dimer, and ferric bromide into a side-necked flask, add 1,2-dichloroethane, and react at 90℃ for 24 h; after the reaction, wash repeatedly with 100 mL of dichloromethane, filter, and collect the crude product, a pale yellow solid. Use dichloromethane and petroleum ether (V... DCM V PE The final product was obtained by column chromatography using a 1:4 ratio as the eluent.

[0050] Thirdly, this application provides an organic photochromic material, which includes the organic photochromic compound containing B←N bonds as described in the first aspect or the organic photochromic compound containing B←N bonds prepared according to the preparation method described in the second aspect.

[0051] Alternatively, its raw materials may include the organic photochromic compound containing B←N bonds as described in the first aspect or the organic photochromic compound containing B←N bonds prepared by the preparation method described in the second aspect.

[0052] In some embodiments, the organic photochromic material includes the product of the organic photochromic compound containing B←N bonds after irradiation with visible or ultraviolet light.

[0053] Fourthly, this application provides the application of the organic photochromic compound containing B←N bonds described in the first aspect, or the organic photochromic compound containing B←N bonds prepared by the preparation method described in the second aspect, or the organic photochromic material described in the third aspect, in organic light-emitting diodes, optical information storage, intelligent optical switching devices, and plastic films.

[0054] Fifthly, this application provides a light-converting thin film comprising a base film and an organic photochromic compound containing B←N bonds as described in the first aspect, or an organic photochromic compound containing B←N bonds prepared by the preparation method described in the second aspect, or an organic photochromic material as described in the third aspect.

[0055] In some embodiments, the organic photochromic compound or organic photochromic material is doped in the light-converting film at an amount of 0.5 wt% to 1 wt%, for example, 0.6 wt%, 0.7 wt%, 0.8 wt%, or 0.9 wt%.

[0056] In some embodiments, the base film is selected from one or more of polyethylene film, polypropylene film, and polymethyl methacrylate film.

[0057] Compared with the prior art, the beneficial effects of this application are as follows:

[0058] (1) The N,C-chelated tetracoordinate boron compounds containing B←N coordination units in the organic photochromic compounds provided in this application enhance the conjugation and planarity of the compounds due to the presence of their chelating units. This can greatly improve the photochromic performance of the photochromic materials under pure solid conditions, giving the compounds advantages such as high luminous intensity, high carrier mobility and good stability. They have a wide range of potential applications in the fields of organic light-emitting diodes, optical information storage, intelligent optical switching devices and agricultural plastic films.

[0059] (2) Compared with the compounds that can only emit a single light in previous studies, the specific electron-donating substituents can enable the compounds to emit blue-violet light of 400-480nm and red-orange light of 600-680nm at the same time. They can be used as composite light-converting agents and incorporated into agricultural films, etc., to greatly improve the utilization rate of sunlight.

[0060] (3) The method provided in this application can efficiently improve the synthesis efficiency of materials by first constructing a molecular skeleton and then coordinating the empty orbitals of boron with the lone pair electrons of nitrogen through a borohydride reaction, which greatly reduces the synthesis cost of photochromic materials. Attached Figure Description

[0061] Figure 1 For the compound OMeBr 1 H NMR spectrum.

[0062] Figure 2 For the compound OMeBr 13 C10 NMR spectrum.

[0063] Figure 3 For the compound OMeBr 11 B NMR spectrum.

[0064] Figure 4 For compound 2Me 1 H NMR spectrum.

[0065] Figure 5 For compound 2Me 13 C10 NMR spectrum.

[0066] Figure 6 For compound 2Me 11 B NMR spectrum.

[0067] Figure 7 For compound 2Ph 1 H NMR spectrum.

[0068] Figure 8 For compound 2Ph 13 C10 NMR spectrum.

[0069] Figure 9 For compound 2Ph 11 B NMR spectrum.

[0070] Figure 10 For compound 4OMe 1 H NMR spectrum.

[0071] Figure 11 For compound 4OMe 13 C10 NMR spectrum.

[0072] Figure 12 For compound 4OMe 11 B NMR spectrum.

[0073] Figure 13 The UV absorption spectra of the solid compounds OMeBr, 2Me, 2Ph, and 4OMe before illumination are shown.

[0074] Figure 14 The ultraviolet absorption spectra of compounds OMeBr-R, 2Me-R, 2Ph-R, and 4OMe-R obtained after irradiation of solid compounds OMeBr, 2Me, 2Ph, and 4OMe are shown.

[0075] Figure 15 The fluorescence spectra (15a) and corresponding CIE coordinate plots (15b) of the solid compounds OMeBr, 2Me, 2Ph and 4OMe in dilute dichloromethane solution are shown.

[0076] Figure 16 The fluorescence spectra (16a) and corresponding CIE coordinate diagrams (16b) of the solid compounds OMeBr, 2Me, 2Ph and 4OMe before illumination are shown.

[0077] Figure 17 The fluorescence spectra (17a) and corresponding CIE coordinate diagrams (17b) of compounds OMeBr-R, 2Me-R, 2Ph-R and 4OMe-R obtained after irradiation of solid compounds OMeBr, 2Me, 2Ph and 4OMe are shown.

[0078] Figure 18 Fluorescence spectra of solid compounds OMeBr, 2Me, 2Ph and 4OMe before illumination (18a) and fluorescence spectra of compounds OMeBr-R, 2Me-R, 2Ph-R and 4OMe-R after illumination (18b) when 550nm yellow light is used as the excitation source.

[0079] Figure 19 The fluorescence spectra of light-converting films doped with the light-irradiated compounds OMeBr-R, 2Me-R, 2Ph-R, and 4OMe-R are shown. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and technologies have also been described in numerous publications.

[0081] The present application will be further described below through specific embodiments.

[0082] Example 1

[0083]

[0084] Under argon protection, tetra(triphenylphosphine)palladium (730 mg, 0.63 mmol) was weighed into a two-necked flask, and 4-methoxyphenylboronic acid (2.12 g, 13.93 mmol), 2,5-dibromopyridine (3.0 g, 12.66 mmol), and anhydrous potassium carbonate (K₂CO₃, 5.25 g, 37.99 mmol) were added. Then, degassed tetrahydrofuran (100 mL) and distilled water (50 mL) were added. The reaction mixture was heated under reflux at 85 °C for 36 h. After the reaction was complete, the solution was cooled to room temperature. Tetrahydrofuran was removed by vacuum distillation, and the mixture was extracted with ethyl acetate (3 × 50 mL). The organic phases were combined, dried over anhydrous magnesium sulfate, allowed to stand for 2 h, and then filtered. The filtrate was distilled under vacuum to remove the solvent. The resulting solid was purified by silica gel column chromatography using dichloromethane and petroleum ether (1:3 v / v) to give the white target product M4. Yield: 2.44g, yield: 71%.

[0085] Under argon protection, anhydrous FeBr3 (56 mg, 0.19 mmol) was weighed into a double-necked side-mounted flask, and raw material M4 (1.0 g, 3.79 mmol) and 9-boron bicyclo[3.3.1]nonane dimer (646.7 mg, 2.65 mmol) were added. Then, 100 mL of 1,2-dichloroethane solution dried with calcium hydride was added, resulting in a mixed orange-yellow suspension. The reaction mixture was heated under reflux at 90 °C for 24 h. After the reaction was complete, the system was cooled to room temperature, the reaction was quenched with distilled water, filtered, and the solid phase was collected to obtain a pale yellow crude product. The crude product was dissolved in dichloromethane and recrystallized to obtain the white target product OMeBr, yield: 0.945 g, 65%.

[0086] compound OMeBr 1 H-NMR nuclear magnetic resonance hydrogen spectrum, 13C1-NMR carbon-12 NMR spectrum and 11 B-NMR boron spectrum as follows Figure 1 , Figure 2 and Figure 3 As shown.

[0087] 1 H NMR (400MHz, CDCl3, ppm): δ9.06 (s, 1H), 7.99 (dd, J=8.7, 1.8Hz, 1H), 7.79 (dd, J=8.5, 6.3Hz, 2H), 7.50 (d, J=2.2Hz, 1H), 6 .87(dd,J=8.5,2.3Hz,1H),3.92(s,3H),2.39(s,2H),2.30–2.00(m,4H),1.85(ddd,J=21.4,13.5,6.8Hz,6H),0.60(s,2H);

[0088] 13 C NMR (101MHz, CDCl3, ppm): δ160.92,156.55,145.93,141.31,128.24,123.20,117.84,117.24,113.74,112.11,55.37,32.51,29.42,24.40,23.30;

[0089] 11 B NMR (128.3MHz, CDCl3, ppm): δ3.46.

[0090] Example 2

[0091]

[0092] Under argon protection, tetra(triphenylphosphine)palladium (1.0 g, 0.87 mmol) was weighed into a two-necked side-necked flask, and 4-methylphenylboronic acid (2.61 g, 19.18 mmol), 2-bromo-5-methylpyridine (3.0 g, 17.44 mmol), and anhydrous potassium carbonate (K₂CO₃, 7.23 g, 52.32 mmol) were added. Then, degassed tetrahydrofuran (100 mL) and distilled water (50 mL) were added. The reaction mixture was heated under reflux at 85 °C for 36 h. After the reaction was complete, the solution was cooled to room temperature. Tetrahydrofuran was removed by vacuum distillation, and the mixture was extracted with ethyl acetate (3 × 50 mL). The organic phases were combined, dried over anhydrous magnesium sulfate, allowed to stand for 2 h, and then filtered. The filtrate was distilled under vacuum to remove the solvent. Using dichloromethane and petroleum ether (1:1 v / v) as eluents, the resulting solid was purified by silica gel column chromatography to give the white target product M5. Yield: 2.33g, yield: 73%.

[0093] Under argon protection, anhydrous FeBr3 (8 mg, 0.27 mmol) was weighed into a double-necked side-mounted flask, and raw material M5 (1.0 g, 5.46 mmol) and 9-boron bicyclo[3.3.1]nonane dimer (0.93 g, 3.82 mmol) were added. Then, 100 mL of 1,2-dichloroethane solution dried with calcium hydride was added, resulting in a mixed orange-yellow suspension. The reaction mixture was heated under reflux at 90 °C for 24 h. After the reaction was complete, the system was cooled to room temperature, the reaction was quenched with distilled water, filtered, and the solid phase was collected to obtain a pale yellow crude product. The crude product was dissolved in dichloromethane and recrystallized to obtain the white target product 2Me, yield: 1.0 g, 60%.

[0094] Compound 2Me 1 H-NMR nuclear magnetic resonance hydrogen spectrum, 13 C1-NMR carbon-12 NMR spectrum and 11 B-NMR boron spectrum as follows Figure 4 , Figure 5 and Figure 6 As shown.

[0095] 2Me: 1 H NMR (400MHz, CDCl3, ppm): δ8.83(s,1H),7.87(d,J=8.2Hz,1H),7.80(s,1H),7.75(d,J=7.6Hz,2H) ,7.12(d,J=7.8Hz,1H),2.45(d,J=15.8Hz,8H),2.31–2.01(m,4H),1.95–1.71(m,6H),0.59(s,2H);

[0096] 13 C NMR (101MHz, CDCl3, ppm): δ155.61,144.65,139.79,138.72,133.45,129.56,126.20,121.05,116.98,32.93,29.59,24.71,23.60,22.42,18.85;

[0097] 11 B NMR (128.3MHz, CDCl3, ppm): δ2.71.

[0098] Example 3

[0099]

[0100] Under argon protection, tetra(triphenylphosphine)palladium (0.67 g, 0.58 mmol) was weighed into a two-necked side-necked flask, and phenylboronic acid (3.12 g, 25.58 mmol), 2-bromo-5-phenylpyridine (2.0 g, 8.54 mmol), and anhydrous potassium carbonate (K₂CO₃, 8.03 g, 58.13 mmol) were added. Then, degassed tetrahydrofuran (100 mL) and distilled water (50 mL) were added. The reaction mixture was heated under reflux at 85 °C for 36 h. After the reaction was complete, the solution was cooled to room temperature. Tetrahydrofuran was removed by vacuum distillation, and the mixture was extracted with dichloromethane. The organic phases were combined, dried over anhydrous magnesium sulfate, allowed to stand for 2 h, and then filtered. The filtrate was distilled under vacuum to remove the solvent. The obtained solid was purified by silica gel column chromatography (dichloromethane:petroleum ether = 1:1) to give the white target product M6. Yield: 2.5 g, 70%.

[0101] Under argon protection, anhydrous FeBr3 (4 mg, 0.16 mmol) was weighed into a double-necked side-mounted flask, and raw material M6 (1.0 g, 3.25 mmol) and 9-boron bicyclo[3.3.1]nonane dimer (0.56 g, 2.28 mmol) were added. Then, a solution of 1,2-dichloroethane dried with calcium hydride (100 mL) was added, resulting in a mixed orange-yellow suspension. The reaction mixture was heated under reflux at 90 °C for 24 h. After the reaction was complete, the system was cooled to room temperature, the reaction was quenched with distilled water, filtered, and the solid phase was collected to obtain a pale yellow crude product. The crude product was dissolved in dichloromethane and recrystallized to obtain the white target product 2Ph, yield: 0.74 g, 56%.

[0102] Compound 2Ph 1 H-NMR nuclear magnetic resonance hydrogen spectrum, 13 C1-NMR carbon-12 NMR spectrum and 11 B-NMR boron spectrum as follows Figure 7 , Figure 8 and Figure 9 As shown.

[0103] 2Ph: 1H NMR (400MHz, CDCl3, ppm): δ9.30(s,1H),9.30(s,1H),8.25(s,1H),8.19(d,J= 8.4Hz,1H),8.11(d,J=8.5Hz,1H),8.00(d,J=7.9Hz,1H),7.72(d,J=7.4Hz,2H ),7.65(d,J=7.5Hz,2H),7.56(t,J=7.5Hz,3H),7.48(t,J=6.6Hz,3H),7.39(d ,J=7.0Hz,1H),2.55(s,2H),2.21(d,J=52.8Hz,4H),1.86(s,6H),0.71(s,2H);

[0104] 13 C NMR (101MHz, CDCl3, ppm): δ156.19,143.37,142.36,141.85,137.34,136.56,134.95,133.66,131. 58,129.63,128.81,127.77,127.34,126.97,124.75,121.92,117.83,33.07,29.75,24.64,23.48;

[0105] 11 B NMR (128.3MHz, CDCl3, ppm): δ2.5.

[0106] Example 4

[0107]

[0108] Under argon protection, tetra(triphenylphosphine)palladium (1.23 g, 1.06 mmol) was weighed into a two-necked side-mounted flask, and 3,4,5-trimethoxyphenylboronic acid (4.96 g, 23.40 mmol), 2-bromo-5-methoxypyridine (4.0 g, 21.27 mmol), and anhydrous potassium carbonate (K₂CO₃) (8.82 g, 63.82 mmol) were added. Then, degassed tetrahydrofuran (150 mL) and distilled water (75 mL) were added. The reaction mixture was heated under reflux at 85 °C for 36 h. After the reaction was complete, the solution was cooled to room temperature. Tetrahydrofuran was removed by vacuum distillation, and the mixture was extracted with ethyl acetate (3 × 50 mL). The organic phases were combined, dried over anhydrous magnesium sulfate, allowed to stand for 2 h, and then filtered. The filtrate was then distilled under vacuum to remove the solvent. The obtained solid was purified by silica gel column chromatography using dichloromethane and petroleum ether (volume ratio 1:1) as eluents to obtain the white target product M7. Yield: 4.18 g, yield: 71%.

[0109] Under argon protection, anhydrous FeBr3 (0.2 g, 0.72 mmol) was weighed into a double-necked side-mounted flask, and raw material M7 (2.0 g, 7.26 mmol) and 9-boron bicyclo[3.3.1]nonane dimer (1.24 g, 5.09 mmol) were added. Then, 100 mL of 1,2-dichloroethane solution dried with calcium hydride was added, resulting in a mixed orange-yellow suspension. The reaction mixture was heated under reflux at 90 °C for 24 h. After the reaction was complete, the system was cooled to room temperature, the reaction was quenched with distilled water, filtered, and the solid phase was collected to obtain a pale yellow crude product. The crude product was dissolved in dichloromethane and recrystallized to obtain the white target product 4OMe, yield: 1.77 g, 58%.

[0110] Compound 4OMe 1 H-NMR nuclear magnetic resonance hydrogen spectrum, 13 C1-NMR carbon-12 NMR spectrum and 11 B-NMR boron spectrum as follows Figure 10 , Figure 11 and Figure 12 As shown.

[0111] 4OMe: 1 H NMR (400MHz, CDCl3, ppm): δ8.73(d,J=2.3Hz,1H),7.80(d,J=9.0Hz,1H),7.51(dd,J=8.9,2.5Hz,1H),7.11(s,1H),3.98– 3.86(m,12H),2.68–2.45(m,2H),2.35–2.13(m,3H),2.02(ddd,J=19.6,13.1,6.4Hz,1H),1.90–1.63(m,6H),0.62(s,2H);

[0112] 13 C NMR (101MHz, CDCl3, ppm): δ156.61,152.99,152.53,150.51,144.26,132.04,131.83,1 25.54,117.22,100.05,60.50,60.37,58.38,56.16,34.09,30.52,25.17,22.96,18.42;

[0113] 11 B NMR (128.3MHz, CDCl3, ppm): δ5.62.

[0114] Test Example 1

[0115] The compounds 2Me, OMeBr, 2Ph and 4OMe synthesized in Examples 1-4 were subjected to ultraviolet light irradiation tests.

[0116] Figure 13 and 14 The UV absorption spectra of solid compounds OMeBr, 2Me, 2Ph, and 4OMe before and after illumination are shown.

[0117] like Figure 13 As shown, compounds 2Me, OMeBr, 2Ph, and 4OMe exhibit the strongest absorption peaks at 356 nm, 377 nm, 386 nm, and 388 nm, respectively. Furthermore, the absorption peaks red-shift as the electron-donating ability of the substituents increases; compared to 2Me, the absorption peak of 4OMe red-shifts by 32 nm. This is because compound 4OMe has three methoxy groups on its benzene ring, and methoxy groups have a stronger electron-donating ability than methyl groups.

[0118] like Figure 14 As shown, the compounds irradiated with ultraviolet light were named 2Me-R, OMeBr-R, 2Ph-R, and 4OMe-R. Ultraviolet absorption spectroscopy revealed that the absorption peak around 350 nm for all four compounds (2Me-R, OMeBr-R, 2Ph-R, and 4OMe-R) did not change significantly after irradiation. However, all compounds developed new absorption peaks in the 450-600 nm wavelength range. Specifically, the new absorption peak for 2Me-R was located at 535 nm, while the new absorption peaks for OMeBr-R, 2Ph-R, and 4OMe-R were located at 532 nm, 560 nm, and 539 nm, respectively. It is speculated that this phenomenon is caused by structural changes in the compounds after irradiation, resulting in photoisomerization and significant changes in their color and ultraviolet absorption spectra.

[0119] Test Example 2

[0120] Compounds 2Me, OMeBr, 2Ph, and 4OMe from Examples 1-4 were tested in dilute dichloromethane solution (1×10⁻⁶). -5 The fluorescence emission spectrum of mo1).

[0121] Figure 15 The true fluorescence spectrum of the compound in dilute dichloromethane solution (15a) and the corresponding CIE coordinate plot (15b) are shown. From Figure 15As can be seen, compounds OMeBr and 2Ph have the maximum emission peak at 497 nm, with CIE coordinates of (0.241, 0.369) and (0.2320, 0.371), respectively, and emit a cyan light. Compounds 2Me and 4OMe, on the other hand, have the maximum emission peak at 477 nm, exhibiting blue light emission, with CIE coordinates of (0.194, 0.287) and (0.205, 0.303), respectively.

[0122] Test Example 3

[0123] The fluorescence emission spectra of compounds 2Me, OMeBr, 2Ph and 4OMe in Examples 1-4 were tested before and after illumination.

[0124] Figure 16 The fluorescence spectra (16a) and corresponding CIE coordinate plots (16b) of compounds 2Me, 2Ph, and 4OMe before illumination are shown. Figure 16 As can be seen, when 380 nm light is used as the excitation source, all three compounds exhibit single emission behavior, with the wavelengths of the maximum emission peaks being 453 nm, 445 nm, and 424 nm, respectively. Among them, the emission peak of compound 4OMe shows a blue shift relative to 2Me. This is because the oxygen atom of the methoxy group in compound 4OMe forms a p-π conjugated structure with phenylbipyridine, allowing the lone pair electrons on the oxygen atom to delocalize onto the phenylbipyridine backbone. This increases the electron cloud density on the phenylbipyridine backbone, releasing shorter wavelength light during the radiative transition back to the ground state, thus causing the blue shift in emission. The CIE coordinates of the three compounds are shown in the figure. The CIE coordinates of 2Me are (0.204, 0.212), 2Ph are (0.198, 0.233), and 4OMe are (0.192, 0.121), all exhibiting blue light emission.

[0125] Figure 17 The fluorescence spectra (17a) and corresponding CIE coordinate diagrams (17b) of the photoisomerization products OMeBr-R, 2Me-R, 2Ph-R, and 4OMe after irradiation of compounds 2Me, OMeBr, 2Ph, and 4OMe are shown. Figure 16As can be seen, similar to the UV absorption spectrum, compared with the colorless solid fluorescence spectrum, the fluorescence emission spectrum of the photoisomerization products shows a new emission peak in the 550-750 nm range. Before illumination, the maximum emission peak wavelength of the solid compound 2Me was 453 nm, while after illumination, a new emission peak appeared at 602 nm. Simultaneously, the compound's emission changed from blue to red-orange, and the CIE coordinates were (0.569, 0.362). Before illumination, the maximum emission peak wavelength of the solid compound 2Ph was 445 nm, while after illumination, a new emission peak appeared at 617 nm. The maximum emission peak wavelength showed a red shift relative to 2Me-R, and the compound's CIE coordinates changed to (0.476, 0.296), with the emission color changing from blue to red-orange. Furthermore, after illumination, compound 4OMe-R showed a new emission peak at 636 nm, and the compound's emission color changed from blue to red-orange, with the CIE coordinates changing to (0.591, 0.287). Furthermore, the compound OMeBr is highly sensitive to light stimulation. When 380 nm light was used as the excitation source, photoisomerization occurred during the fluorescence spectrum testing, and the compound's color changed from colorless to red. Based on the ultraviolet absorption spectroscopy data, it is inferred that the orbital energy levels of the red compound have changed compared to the colorless compound.

[0126] Further investigation of the compound's fluorescence spectrum revealed that when 550 nm yellow light was used as the excitation source, such as Figure 18 As shown, the compounds 2Me, 2Ph, and 4OMe do not change color, and the white compounds 2Me, 2Ph, and 4OMe have no emission peaks in the wavelength range of 565-900 nm. However, under the same excitation conditions, the red compounds OMeR, 2Me-R, 2Ph-R, and 4OMe-R exhibit obvious emission peaks in the red light region, with the wavelengths of the maximum emission peaks being 630 nm, 595 nm, 600 nm, and 610 nm, respectively. However, compound OMeBr-R is highly sensitive to visible light; even when excited by a 550 nm light source, the compound undergoes a color change during the test, thus exhibiting an emission peak at 600 nm. Therefore, it is inferred that blue-violet and ultraviolet light can induce isomerization of these compounds.

[0127] In summary, compounds 2Me, OMeBr, 2Ph, and 4OMe, when irradiated, all exhibit the potential to act as light-converting agents: OMeBr-R, 2Me-R, 2Ph-R, and 4OMe-R. For example, the solid compound OMeBr-R shows significant maximum absorption peaks at 375 nm and 531 nm, the ranges of which match the wavelengths of ultraviolet and yellow-green light, respectively. It also exhibits dual emission peaks at 437 nm and 635 nm, the ranges of which match the wavelengths of red-orange and blue-violet light readily absorbed by plants. Similarly, compounds 2Me-R, 2Ph-R, and 4OMe-R absorb ultraviolet light in the 280-380 nm range and yellow-green light in the 500-600 nm range, while the maximum wavelengths of their first emission peaks are 442 nm, 460 nm, and 440 nm, respectively—wavelengths that coincide with the wavelength range of blue-violet light (400-480 nm) readily absorbed by plants. The wavelengths of the second emission peaks are 601 nm, 616 nm, and 636 nm, which are consistent with the wavelength range of red-orange light required by plants. Therefore, compounds OMeBr-R, 2Me-R, 2Ph-R, and 4OMe-R are a class of light-converting agents with dual light conversion capabilities, capable of simultaneously absorbing ultraviolet and yellow-green light and emitting blue-violet and red-orange light.

[0128] Test Example 4

[0129] Compounds OMeBr-R, 2Me-R, 2Ph-R, and 4OMe-R, obtained by irradiation with compounds 2Me, OMeBr, 2Ph, and 4OMe, were incorporated into polyethylene (PE) powder at a doping concentration of 5% to obtain optically convertible films. The fluorescence emission spectra of the optically convertible films were investigated. Figure 19 ).

[0130] like Figure 19 As shown, OMeBr-PE, 2Me-PE, 2Ph-PE and 4OMe-PE all exhibit dual emission, and the wavelength of their maximum emission peak is consistent with the wavelength range of red-orange and blue-violet light.

[0131] The preferred embodiments of this application have been described in detail above; however, this application is not limited thereto. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this application and are all within the protection scope of this application.

Claims

1. An organic photochromic compound containing B←N bond, having a structure shown in formula I: wherein R 1 is selected from methyl, ethyl, phenyl, methoxy or ethoxy; R 2 is selected from fluorine, bromine, methyl, ethyl, phenyl, methoxy or ethoxy; R 3 and R 4 are the same or different, each independently selected from hydrogen, methyl, ethyl, methoxy or ethoxy; and when R 1 and R 2 are both C 1-C 4 alkoxy, R 3 and R 4 are not hydrogen at the same time. The organic photochromic compound is selected from the following compounds: 3.A method for preparing an organic photochromic compound containing B←N bond, comprising one or more of the following steps: Step 1: reacting a compound of formula a with a compound of formula b to form a compound of formula M, 2. The organic photochromic compound according to claim 1, characterized in that, Step 2: reacting the compound of formula M with 9-borabicyclo[3.3.1]nonane dimer to form a compound of formula I, R 1 is selected from methyl, ethyl, phenyl, methoxy or ethoxy; R 2 is selected from fluorine, bromine, methyl, ethyl, phenyl, methoxy or ethoxy; R 3 and R 4 are the same or different, each independently selected from hydrogen, methyl, ethyl, methoxy or ethoxy; and when R 1 and R 2 are both C 1-C 4 alkoxy, R 3 and R 4 are not hydrogen at the same time. wherein R 5 is selected from halogen. 4.The method according to claim 3, wherein R 5 is selected from fluorine, chlorine or bromine. 6.The method according to claim 3, wherein in step 1, the molar ratio of the compound of formula a to the compound of formula b is 1:0.8-1:1.2, the reaction temperature is 70-90℃, and the reaction time is 24-48h; in step 2, the molar ratio of the compound of formula M to 9-borabicyclo[3.3.1]nonane dimer is 1:1.1-1:1.6, the reaction temperature is 80-100℃, and the reaction time is 12-48h. 9.An organic photochromic material comprising the organic photochromic compound containing B←N bond according to any one of claims 1-2 or prepared by the method according to any one of claims 3-8; or raw materials thereof comprising the organic photochromic compound containing B←N bond according to any one of claims 1-2 or prepared by the method according to any one of claims 3-8. The organic photochromic material comprises a product of the organic photochromic compound containing B←N bond after irradiation by visible light or ultraviolet light. 11.Use of the organic photochromic compound containing B←N bond according to any one of claims 1-2 or prepared by the method according to any one of claims 3-8 or the organic photochromic material according to claim 9 or 10 in organic light-emitting diodes, optical information storage, smart light switch devices and plastic films.

5. The preparation method according to claim 3, characterized in that, Compounds of formula a are ​ Compounds of formula b are 7. The preparation method according to claim 3, characterized in that, The compound of formula M is 8. The production method according to any one of claims 3 to 7, characterized by, ​ ​ ​ ​ 10. The organic photochromic material according to claim 9, wherein, ​ ​ 12. A light conversion film comprising a base film and the B←N bond-containing organic photochromic compound according to any one of claims 1-2 or the B←N bond-containing organic photochromic compound prepared according to the preparation method of any one of claims 3-8 or the organic photochromic material according to claim 9 or 10.

13. The light conversion film according to claim 12, wherein, The doping amount of the B←N bond-containing organic photochromic compound or the organic photochromic material in the light conversion film is 0.5 wt% to 1 wt%.

14. The light conversion film according to claim 12, wherein, The base film is selected from one or more of a polyethylene film, a polypropylene film, a polymethyl methacrylate film.

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