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 is a compound with a general formula (I-a) or (I-b), as follows: The dichroic dye disclosed in this invention has good dichroism and photothermal stability. The disclosed preparation method is characterized by 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, characterized in that the dichroic dye is a compound having a general formula (Ia) or (Ib), wherein the general formulas (Ia) and (Ib) are as follows:

[0006]

[0007] Wherein, R1 is selected from H, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms; X1 is selected from -CH2- or -N-; n is selected from 0 to 2;

[0008] express The =CH- on the benzene ring can be replaced by N, and the H on the benzene ring can be replaced by F.

[0009] According to another aspect of the present invention, a method for preparing a dichroic dye having a general formula (Ia) structure is provided, the method comprising the following steps:

[0010] Will have a formula The compound was fully dissolved in an organic solvent with 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, and then a weak base dissolved in pure water and a coupling catalyst were added. The dichroic dye with the general formula (Ia) was prepared by the Suzuki coupling reaction at 20-100℃. Hal is a boric acid or borate ester substituent.

[0011] According to another aspect of the present invention, a method for preparing a dichroic dye having a general formula (Ib) structure is provided, the method comprising the following steps:

[0012] Will have a 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. The mixture was then subjected to a Suzuki coupling reaction at 20-100°C to prepare a dichroic dye with the general formula Ib, wherein Hal is a boric acid or borate ester substituent.

[0013] 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.

[0014] 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.

[0015] 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. Detailed Implementation Plan

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preparation process of the compounds having general formulas (Ia) to (Ib) is as follows:

[0017]

[0018] The beneficial effects of the present invention will be further illustrated below with reference to embodiments.

[0019] The following examples are for illustrative purposes only and not for limiting the invention. All percentages mentioned in the examples are by mass, and temperatures are expressed in degrees Celsius. The measured physicochemical parameters are expressed as follows: T NIK represents the clearing point; Δn represents optical anisotropy (Δn = ne - no, 589 nm, measurement temperature 25℃); Δε represents dielectric anisotropy (Δε = ε∥ - ε⊥, 25℃); K11 represents the stretch elastic coefficient (measurement temperature 25℃); K33 represents the bending elastic coefficient (measurement temperature 25℃).

[0020] 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:

[0021] Table 1

[0022]

[0023]

[0024] 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. C n 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.

[0025] Table 2

[0026]

[0027]

[0028] Example 1: Preparation of M001

[0029]

[0030] Under nitrogen protection, 48.7 g of propylcyclopentylphenylboronic acid and 29.4 g of 4,7-dibromo-2,1,3-benzothiadiazole were dissolved in 500 ml of toluene and stirred. The mixture was heated to approximately 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, 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 41g of pure product M001, HPLC > 99.85%, yield 80.7%;

[0031] Example 2, Preparation of M002

[0032]

[0033] Under nitrogen protection, 45 g of cyclopentylphenylboronic acid and 45.8 g of 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole dissolved in 500 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 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 maintained 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, recrystallization, and drying to obtain 48g of pure M002, with a yield of 81.5%.

[0034] Example 3, Preparation of M003

[0035]

[0036] Under nitrogen protection, 43.8 g of 4-pyrrolidinyl phenylboronic acid ester and 45.8 g of 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole dissolved in 500 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 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, 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 47g of pure M003, with a yield of 79.7%.

[0037] Example 4: Preparation of M004

[0038]

[0039] Under nitrogen protection, 56.8 g of 4-(4-cyclopentylphenyl)-2-fluorophenylboronic acid and 29.4 g of 4,7-dibromo-2,1,3-benzothiadiazole were dissolved in 500 ml of toluene and stirred. The mixture was heated to approximately 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, 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 52g of pure product M001, HPLC > 99.85%, yield 84.9%;

[0040] The performance testing methods for compounds M001 to M004 are as follows:

[0041] 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.

[0042] Table 3

[0043]

[0044] 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 ⊥

[0045] The optical performance of M001 to M004 was measured and calculated according to the above test method. The performance parameters are shown in Table 4 below:

[0046] Table 4

[0047] Product Name Maximum absorption peak (nm) Maximum absorbance Two-color ratio M001 426 0.29 13.71 M002 538 0.43 9.68 M003 548 0.38 14.69 M004 424 0.27 14.21

[0048] The colorimetric performance of horizontally oriented liquid crystal cells with a thickness of 9 μm filled with MA001 to MA004 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.

[0049] The mixture MA001-004 obtained by mixing compounds M001-004 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.

[0050] Table 4

[0051]

[0052] As can be seen from Examples 1 to 4 above, the method provided by the present invention can achieve the goal of preparing photosensitive 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.

[0053] Using a similar preparation method as in Examples 1-4, the following dye compounds can be easily prepared:

[0054]

[0055]

[0056] In addition to the above, although the embodiments of the present invention do not exhaustively cover all the claimed dichroic dyes with benzothiadiazole structures, 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.

[0057] 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, characterized in that, The dichroic dye is a compound having a general formula (Ia) or (Ib), as follows: Wherein, R1 is selected from H, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms; X1 is selected from -CH2- or -N-; n is selected from 0 to 2; 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 (Ia) structure, the method comprising the following steps: Will have a formula The compound (Ia-1) was fully dissolved in an organic solvent with 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole. Then, a weak base dissolved in pure water and a coupling catalyst were added, and the mixture was prepared by a Suzuki coupling reaction at 20-100°C to obtain a dichroic dye with the general formula (Ia), wherein Hal is a boric acid or borate ester substituent.

3. A method for preparing a dichroic dye having a general formula (Ib) structure, the method comprising the following steps: Will have a formula The compound (Ia-1) 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. The mixture was then subjected to a Suzuki coupling reaction at 20-100°C to prepare a dichroic dye with the general formula (Ib), wherein Hal is a boric acid or borate ester substituent.

4. The preparation method according to claims 2-3, 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.

5. The preparation method according to claims 2-3, characterized in that, The weak base is selected from one or more of sodium carbonate, potassium carbonate, sodium acetate, and potassium acetate.

6. The preparation method according to claims 2-3, 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.

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

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