Dichroic dye having a benzothiadiazole structure, method for preparing the same, and use thereof

Abstract

This invention discloses a dichroic dye with a benzothiadiazole structure, its preparation method, and its application. The dichroic dye with the benzothiadiazole structure is a compound with general formula I. General formula I is the dichroic dye disclosed in this invention, which has good dichroism and photothermal stability. The disclosed preparation method has the characteristics of simple operation, low pollution, and high yield, and is particularly suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a dye compound, its preparation method, and its application. Background Technology

[0002] Dye-based liquid crystal materials are guest-host liquid crystal materials in which a small amount of dichroic dyes are doped into the host liquid crystal. Due to the guest-host effect, under the drive of an external electric field, the dichroic dye molecules, as guests, rotate with the host liquid crystal. Since dichroic dye molecules are usually rod-shaped, their long and short axes have different light absorption capabilities. When the dichroic dye molecules rotate, the light absorption capability of the guest-host liquid crystal as a whole also changes accordingly, thereby inducing changes in color and light transmittance, achieving the purpose of color display.

[0003] Common dichroic dye molecules fall into two main categories: azo and anthraquinone. Azo dyes possess strong optical properties and excellent solubility, but their poor light and heat stability limits their prospects for commercial applications. Anthraquinone dyes exhibit good light and heat stability and produce vibrant colors, but their absorption capacity is relatively weak, their dichroic ratio is low, and they suffer from solubility issues. Therefore, a novel dye that simultaneously possesses good light and heat stability, high absorption capacity and dichroic ratio, and good solubility is what we need. Summary of the Invention

[0004] The purpose of this invention is to provide a benzothiadiazole-structured dichroic dye that has both good dichroism and photothermal stability, and to provide a method for preparing the benzothiadiazole-structured dichroic dye that is simple to operate, has low pollution, high yield and is easy to purify.

[0005] Technical Solution: To achieve the above objective, according to one aspect of the present invention, a dichroic dye having a benzothiadiazole structure is provided, wherein the dichroic dye is a compound having a general formula I structure, and the compound of general formula I is:

[0006]

[0007] R1 and R2 are each independently selected from H, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms; X1 and X2 are each independently selected from either -CH2- or -N-.

[0008] a and b are each independently 0 or 1, and a and b are not both 0 at the same time;

[0009] c and d are each independently 0, 1 or 2, and c and d are not both 0 at the same time;

[0010] express The =CH- on the benzene ring can be replaced by N, and the H on the benzene ring can be replaced by F;

[0011] express The =CH- on the benzene ring can be replaced by N, and the H on the benzene ring can be replaced by F.

[0012] According to one aspect of the present invention, a method for preparing a dichroic dye having a general formula I structure is provided, the method comprising the following steps:

[0013] (1) Having the formula The compound was fully dissolved in an organic solvent with 4,7-dibromo-2,1,3-benzothiadiazole, and then a weak base dissolved in pure water and a coupling catalyst were added. A coupling reaction was carried out at 20–100 °C to obtain the compound of formula (I-2), wherein Hal is a boric acid or borate ester substituent. The compound of formula (I-2) is:

[0014]

[0015] (2) The compound of formula (I-2) is fully dissolved in an organic solvent with 2-thiopheneboronic acid, and then a weak base dissolved in pure water and a coupling catalyst are added. A coupling reaction is carried out at 20–100 °C to obtain the compound of formula (I-3), wherein the compound of formula (I-3) is:

[0016]

[0017] (3) The compound of formula (I-3) is fully dissolved in an organic solvent, and then a brominating agent is added. A substitution reaction is carried out at room temperature to obtain the compound of formula (I-4), wherein the compound of formula (I-4) is:

[0018]

[0019] (4) The compound of formula (I-4) is combined with a compound having the formula The compound is fully dissolved in an organic solvent, and then a weak base dissolved in pure water and a coupling catalyst are added. The coupling reaction is carried out at 20–100 °C to obtain the compound of formula I, wherein Hal is a boric acid or borate ester substituent.

[0020] According to another aspect of the present invention, the organic solvent used in the above preparation method is selected from one or more of toluene, tetrahydrofuran, DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), ethanol, chloroform, acetonitrile, and dichloromethane.

[0021] According to another aspect of the present invention, the weak base mentioned in the above preparation method is selected from one or more of sodium carbonate, potassium carbonate, sodium acetate, and potassium acetate.

[0022] According to another aspect of the present invention, the catalyst used in the above preparation method is selected from PdCl2, palladium acetate, PdCl2(PPh3)2, Pd(PPh3)4, Pd 132 One or more of them.

[0023] According to another aspect of the present invention, the brominating agent described in the above preparation method is selected from one or more of 1,3-dibromo-5,5-dimethylhydantoin, N-bromoacetamide, and N-bromosuccinimide. Detailed Implementation Plan

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other, and the preparation method of the compound having general formula I is as follows:

[0025]

[0026] The beneficial effects of the present invention will be further illustrated below with reference to embodiments.

[0027] The following examples are for illustrative purposes only and not for limiting the invention. All percentages mentioned are by mass, and temperatures are expressed in degrees Celsius. The measured physical and chemical parameters are as follows: TNI represents the clearing point; Δn represents optical anisotropy (Δn = ne - no, 589 nm, measurement temperature 25°C); Δε represents dielectric anisotropy (Δε = ε∥ - ε⊥, 25°C); K11 represents the flexural elasticity coefficient (measurement temperature 25°C); K33 represents the bending elasticity coefficient (measurement temperature 25°C).

[0028] In various embodiments of the present invention, the liquid crystal molecule backbone is named as: cyclohexyl Represented by the letter C; phenyl Represented by the letter P; the phenyl group on the left is monofluorinated. Represented by the letter H2, the phenyl group on the right side is monofluorinated. Represented by the letter H1; the corresponding codes for specific group structures are shown in Table 1:

[0029] Table 1

[0030]

[0031] The side chains of each compound are converted into chemical formulas according to Table 2 below, with the left-side branch denoted by R1 and the right-side branch by R2. Among them, the group C... n H 2n+1 and C m H 2m+1 They are straight-chain alkyl groups having n and m carbon atoms respectively, and Cp represents cyclopentyl. Cn H 2n+1 Cp represents a cyclopentyl alkyl group with n carbon atoms in a straight chain. The main chain and branches, as well as the branches themselves, are separated by a hyphen ("-"). In naming, the main chain comes first, followed by the branch. For example, Represented as CMPP-2-N; Represented as CPP-3-N, Represented as PH1P-3-N; It is represented by CC-3-V.

[0032] Table 2

[0033]

[0034]

[0035] Example 1, Preparation of M001

[0036]

[0037] Step 1: Preparation of M001-1

[0038]

[0039] Under nitrogen protection, 57.2 g of pentylbiphenyl-m-fluorophenylboronic acid and 58.8 g of 4,7-dibromo-2,1,3-benzothiadiazole dissolved in 2000 ml of toluene were added to the system and stirred. The mixture was heated to approximately 45 °C, and then Pd was added to the system. 132 The temperature was further increased to slight reflux, and then an aqueous solution of 84.8 g sodium carbonate and pure water was added dropwise to the system while maintaining slight reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, filtration, concentration, recrystallization, and drying to obtain 82 g of M001-1.

[0040] Step 2: Preparation of M001-2

[0041]

[0042] Under nitrogen protection, 56g of the product from the previous step, M001-1, and 17.3g of 2-thiopheneboronic acid were added to the system, dissolved in 500ml of toluene. The mixture was heated to approximately 45°C and stirred. Pd was then added to the system. 132 Continue heating to a slight reflux, then add alkaline water dropwise to the system while maintaining slight reflux. After the addition is complete, heat to 80°C and keep warm overnight. After overnight, cool to room temperature, then add water for layer extraction. Wash with water until neutral, then dry with anhydrous magnesium sulfate, filter, concentrate, recrystallize and dry to obtain 50g of M001-2.

[0043] Step 3: Preparation of M001-3

[0044]

[0045] Add 19.2g M002-2, 8g NBS, and 350ml chloroform to the system. Stir overnight at room temperature. Pour the reaction solution into ethanol and slurry. Filter, wash, and dry the filter cake to obtain 21g, yield 93.3%.

[0046] Step 4: Preparation of M001

[0047]

[0048] Under nitrogen protection, 4.2 g of cyclopentylphenylboronic acid and 10.75 g of M001-3 dissolved in 250 ml of toluene were added to the system and stirred. The temperature was raised to about 45 °C, and Pd was added to the system. 132 The temperature was further increased to micro-reflux, and then alkaline water was added dropwise to the system while maintaining micro-reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, filtration, concentration, and column chromatography to collect 8.5 g of M001, with a yield of 70.8%.

[0049] Example 2, Preparation of M002

[0050]

[0051] Step 1: Preparation of M002-1

[0052]

[0053] Under nitrogen protection, 46.4 g of 4-(3-propylcyclopentyl)phenylboronic acid and 58.8 g of 4,7-dibromo-2,1,3-benzothiadiazole dissolved in 2000 ml of toluene were added to the system and stirred. The mixture was heated to approximately 45 °C, and then Pd was added to the system. 132 The temperature was further increased to slight reflux, and then an aqueous solution of 84.8 g sodium carbonate and pure water was added dropwise to the system while maintaining slight reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, filtration was performed, concentration was achieved, recrystallization was performed, and drying was completed to obtain 70 g of M002-1.

[0054] Step 2: Preparation of M002-2

[0055]

[0056] Under nitrogen protection, 40g of the product from the previous step, M002-1, and 17.3g of 2-thiopheneboronic acid were added to the system, dissolved in 500ml of toluene. The mixture was heated to approximately 45°C and stirred. Pd was then added to the system.132 Continue heating to a slight reflux, then add alkaline water dropwise to the system while maintaining slight reflux. After the addition is complete, heat to 80°C and keep warm overnight. After overnight, cool to room temperature, then add water for layer extraction. Wash with water until neutral, then dry with anhydrous magnesium sulfate, filter, concentrate, recrystallize and dry to obtain 38g of M002-2.

[0057] Step 3: Preparation of M002-3

[0058]

[0059] 20.2g M002-2, 8g NBS, and 350ml chloroform were added to the system. After stirring at room temperature overnight, the reaction solution was poured into ethanol and stirred. The mixture was then filtered, washed, and the filter cake was dried to obtain 21.8g M002-3, with a yield of 90.3%.

[0060] Step 4: Preparation of M002

[0061]

[0062] Under nitrogen protection, 4.2 g of cyclopentylphenylboronic acid and 9.64 g of M002-3 dissolved in 250 ml of toluene were added to the system and stirred. The temperature was raised to about 45 °C, and Pd was added to the system. 132 The temperature was further increased to slight reflux, and then alkaline water was added dropwise to the system while maintaining slight reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight incubation, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, filtration, concentration, and column chromatography to collect 7.9 g of M002, with a yield of 72.3%.

[0063] Example 3, Preparation of M003

[0064]

[0065] Step 1: Preparation of M003-1

[0066]

[0067] Under nitrogen protection, 46.6 g of 4-(3-propylpyrrolyl)phenylboronic acid and 58.8 g of 4,7-dibromo-2,1,3-benzothiadiazole dissolved in 2000 ml of toluene were added to the system and stirred. The mixture was heated to approximately 45 °C, and then Pd was added to the system. 132 The temperature was further increased to slight reflux, and then an aqueous solution of 84.8 g sodium carbonate and pure water was added dropwise to the system while maintaining slight reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, and the mixture was filtered, concentrated, recrystallized, and dried to obtain 68 g of M003-1.

[0068] Step 2: Preparation of M003-2

[0069]

[0070] Under nitrogen protection, 40.5 g of the product from the previous step, M003-1, and 17.3 g of 2-thiopheneboronic acid were added to the system, dissolved in 500 ml of toluene. The mixture was heated to approximately 45°C and stirred. Pd was then added to the system. 132 Continue heating to a slight reflux, then add alkaline water dropwise to the system while maintaining slight reflux. After the addition is complete, heat to 80°C and keep warm overnight. After overnight, cool to room temperature, then add water for layer extraction. Wash with water until neutral, then dry with anhydrous magnesium sulfate, filter, concentrate, recrystallize and dry to obtain 39.2g of M003-2.

[0071] Step 3: Preparation of M003-3

[0072]

[0073] 20.3 g M003-2, 8 g NBS, and 350 ml chloroform were added to the system. After stirring at room temperature overnight, the reaction solution was poured into ethanol and stirred. The mixture was then filtered, washed, and the filter cake was dried to obtain 21.4 g M003-3, with a yield of 88.6%.

[0074] Step 4: Preparation of M002

[0075]

[0076] Under nitrogen protection, 4.2 g of cyclopentylphenylboronic acid and 9.7 g of M002-3 dissolved in 250 ml of toluene were added to the system and stirred. The temperature was raised to about 45 °C, and Pd was added to the system. 132 The temperature was further increased to micro-reflux, and then alkaline water was added dropwise to the system while maintaining micro-reflux. After the addition was complete, the temperature was increased to 80°C and kept at that temperature overnight. After overnight, the temperature was lowered to room temperature, and then water was added for layer extraction. After washing with water until neutral, anhydrous magnesium sulfate was added for drying, filtration, concentration, and column chromatography to collect 7.6 g of M003, with a yield of 69.2%.

[0077] The performance testing methods for compounds M001 to M003 are as follows:

[0078] Taking compound M001 as an example, 1% by mass of compound M001 and 99% by mass of the liquid crystal composition HOST-1 shown in Table 3 were thoroughly mixed and stirred until compound M001 was fully dissolved to obtain mixture MA001. Mixture MA001 was poured into a horizontally aligned liquid crystal cell with a cell thickness of 9 μm. The absorption spectrum of mixture MA001 was tested with incident light parallel to the long axis of compound M001 molecules and incident light perpendicular to the long axis of compound M001 molecules. The instrument used for testing was a Shimadzu UV-2600 spectrophotometer. In order to eliminate the influence of absorption or reflection caused by the liquid crystal composition itself and the liquid crystal cell, a horizontally aligned liquid crystal cell with a cell thickness of 9 μm filled with 100% by mass of liquid crystal composition HOST-1 was used as a reference during the test. That is, the absorption spectrum of the obtained mixture MA001 was subtracted from the absorption spectrum of HOST-1.

[0079] Table 3

[0080]

[0081] According to the definition of the dichroism ratio of dyes, the dichroism ratio of a dye is determined by its absorption intensity A under incident light parallel to the long axis of the dye molecule. ∥ Its absorption intensity A under incident light perpendicular to the long axis of the dye molecule ⊥ The dichroism ratio is calculated. Discussions of the dichroism ratio of dyes are usually conducted at the dye's maximum absorption wavelength. If the dye has multiple absorption peaks, the peak with the strongest absorption is typically chosen. Dichroism ratio D A =A ∥ / A ⊥

[0082] The optical performance of M001 to M003 was measured and calculated according to the above test method. The performance parameters are shown in Table 4 below:

[0083] Table 4

[0084] Product Name Maximum absorption peak (nm) Maximum absorbance Two-color ratio M001 458 0.32 14.81 M002 421 0.48 12.48 M003 415 0.47 12.99

[0085] The colorimetric performance of horizontally oriented liquid crystal cells with a thickness of 9 μm filled with MA001 to MA003 was measured using a CS826 spectrophotometer. A D65 standard light source was used as the light source. The photothermal stability of the sample was measured by the color difference ΔE before and after light / heat treatment. The color difference was defined in accordance with the CIELAB standard.

[0086] The mixture MA001-003 obtained by mixing compounds M001-003 with HOST-1 was subjected to light / heat treatment, and the chromaticity values ​​of the samples before and after treatment were compared. The results are shown in Table 4.

[0087] Table 4

[0088]

[0089] As can be seen from Examples 1 to 3 above, the method provided by the present invention can achieve the goal of preparing dichroic dye compounds with benzothiadiazole structure using relatively simple operation techniques, easily achievable reaction conditions, and common organic reagents. The resulting dichroic dye compounds have good dichroism and photothermal stability.

[0090] Using a similar preparation method as in Examples 1-3, the following dye compounds can be easily prepared:

[0091]

[0092] In addition to the above, although the embodiments of the present invention do not exhaustively list all the dichroic dye compounds with the benzothiadiazole structure claimed, those skilled in the art will foresee that, based on the disclosed embodiments described above, other similar compounds can be prepared simply by combining their own professional knowledge without any inventive effort. Only representative embodiments are listed here.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dichroic dye having a benzothiadiazole structure, wherein the dichroic dye is a compound having a general formula I, and the compound of general formula I is: in, R1 and R2 are each independently selected from H, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms; X1 and X2 are each independently selected from either -CH2- or -N-. a and b are each independently 0 or 1, and a and b are not both 0 at the same time; c and d are each independently 0, 1 or 2, and c and d are not both 0 at the same time; express The =CH- on the benzene ring can be replaced by N, and the H on the benzene ring can be replaced by F; express The =CH- on the benzene ring can be replaced by N, and the H on the benzene ring can be replaced by F.

2. A method for preparing a dichroic dye having a general formula I structure, the method comprising the following steps: (1) Having the formula The compound was fully dissolved in an organic solvent with 4,7-dibromo-2,1,3-benzothiadiazole, and then a weak base dissolved in pure water and a coupling catalyst were added. A coupling reaction was carried out at 20–100 °C to obtain the compound of formula (I-2), wherein Hal is a boric acid or borate ester substituent. The compound of formula (I-2) is: (2) The compound of formula (I-2) is fully dissolved in an organic solvent with 2-thiopheneboronic acid, and then a weak base dissolved in pure water and a coupling catalyst are added. A coupling reaction is carried out at 20–100 °C to obtain the compound of formula (I-3), wherein the compound of formula (I-3) is: (3) The compound of formula (I-3) is fully dissolved in an organic solvent, and then a brominating agent is added. A substitution reaction is carried out at room temperature to obtain the compound of formula (I-4), wherein the compound of formula (I-4) is: (4) The compound of formula (I-4) is combined with a compound having the formula The compound is fully dissolved in an organic solvent, and then a weak base dissolved in pure water and a coupling catalyst are added. The coupling reaction is carried out at 20–100 °C to obtain the compound of formula I, wherein Hal is a boric acid or borate ester substituent.

3. The preparation method according to claim 2, characterized in that, The organic solvent is selected from one or more of toluene, tetrahydrofuran, DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), ethanol, chloroform, acetonitrile, and dichloromethane.

4. The preparation method according to claim 2, characterized in that, The weak base is selected from one or more of sodium carbonate, potassium carbonate, sodium acetate, and potassium acetate.

5. The preparation method according to claim 2, characterized in that, The catalyst is selected from PdCl2, palladium acetate, PdCl2(PPh3)2, Pd(PPh3)4, and Pd 132 One or more of them.

6. The preparation method according to claim 2, characterized in that, The brominating agent is selected from one or more of 1,3-dibromo-5,5-dimethylhydantoin, N-bromoacetamide, and N-bromosuccinimide.

7. The application of the dichroic dye as described in claim 1 in light valves, switchable windows, switchable mirrors, and host-guest displays.

Images