A benzothiazole salt organic second-order nonlinear optical material and a preparation method thereof

Abstract

The application belongs to the field of nonlinear optical materials, and provides a benzothiazole salt organic second-order nonlinear optical material and a preparation method thereof, so as to provide a novel organic single crystal with good second-order nonlinear optical characteristics. 25 H 25 NO5S2, belongs to a monoclinic system, a space group is P21, a cell parameter is alpha = gamma = 90 DEG, beta = 101.66809 DEG; the material has the advantages of simple synthesis method, easy operation, sufficient raw material source, low production cost, high compound crystal synthesis yield and purity, good repeatability, and meets the requirements of large-scale production, and the frequency doubling effect of the organic compound crystal is 6.9 times of that of DAST, and the organic compound crystal can be used as a potential organic second-order nonlinear optical material.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear optical materials and provides a benzothiazole salt organic second-order nonlinear optical material and its preparation method. Specifically, it is a novel organic nonlinear optical crystal material with a D-π-A configuration: 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate. Background Technology

[0002] Organic nonlinear optical materials have potential applications in high-speed information processing, optical frequency conversion, communication, electro-optic effects, terahertz spectral imaging, and optical data storage, and have therefore attracted widespread attention. Researchers are committed to developing and designing novel organic crystals with large first hyperpolarizability β, and cultivating organic single crystals with large second-order macroscopic nonlinearity for application in the field of nonlinear optics.

[0003] Compared with the widely studied inorganic electro-optic crystals (such as GaP, ZnTe, and GaAs) and semi-organic crystals, organic nonlinear optical crystal materials possess unique properties, such as high nonlinear optical efficiency, laser readout modulation, broadband strong terahertz wave generation, ultrafast response time, high laser damage threshold, low dielectric dispersion, and almost unlimited design possibilities, thus possessing greater research value. However, approximately 75% of organic chromophores crystallize in centrosymmetric space groups (see S. Kannan, J. Mater. Chem. C, 8, 16668–16690 (2020).), and do not exhibit macroscopic second-order optical nonlinear properties. Therefore, the search for novel organic chromophores with stable non-centrosymmetric orientations is of great significance.

[0004] In recent years, researchers have studied organic pyridine salts with different anionic structures to understand the role of anions in crystal structures (see Z. Yang, Adv. Funct. Mater. 15, 1072–1076 (2005).). Notably, among different types of organic materials, 4-N,N-dimethylamino-4'-N'-methylpyridine p-toluenesulfonate (DAST) crystals exhibit large molecular optical nonlinearity, low dielectric constant, large electro-optic coefficient, a bandwidth approaching 20 THz, and its powder's second harmonic generation (SHG) efficiency at 1907 nm excitation is 1000 times that of urea (see SR Marder, Science. 245, 626–628 (1989).). It is currently the most widely used organic nonlinear optical material. Although DAST and its derivatives all possess large macroscopic nonlinearity, these materials still have some shortcomings, such as long growth cycles, susceptibility to hygroscopicity, and low optical transmittance, which limit their wider application. Therefore, developing novel organic single crystals with good nonlinear optical properties is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a benzothiazole salt organic second-order nonlinear optical material and its preparation method, thereby providing a novel organic single crystal with excellent second-order nonlinear optical properties. Specifically, the organic second-order nonlinear optical crystal material provided by this invention is 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate, with the characteristic molecular formula C2. 25 H 25 NO5S2; The synthesis method of this material is simple and easy to operate, with abundant raw material sources, low production cost, high yield and purity of compound crystal synthesis, and good reproducibility, making it suitable for large-scale production; More importantly, the frequency doubling effect of this organic compound crystal is as high as 6.9 times that of DAST, making it a high-performance organic second-order nonlinear optical material with broad application prospects.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A benzothiazole salt organic second-order nonlinear optical material, characterized in that the material is specifically 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate, with the characteristic molecular formula C2. 25 H 25 NO5S2 has the characteristic molecular formula: C 25 H 25 NO5S2.

[0008] Furthermore, the single crystal of the benzothiazole salt organic second-order nonlinear optical material belongs to the monoclinic crystal system, with space group P21 and cell parameters of [missing information]. α=γ=90°, β=101.66809°.

[0009] Furthermore, the preparation method of the above-mentioned benzothiazole salt organic second-order nonlinear optical material is characterized by comprising the following steps:

[0010] Step 1. Prepare the crude crystal product;

[0011] Step 1-1. First, use ethylene glycol dimethyl ether as the reaction solvent and pour it into a reaction vessel equipped with a reflux condenser. Then, add 2-methylbenzothiazole powder and methyl p-toluenesulfonate solution to the reaction vessel sequentially, wherein the molar ratio of 2-methylbenzothiazole to methyl p-toluenesulfonate is 1:1. When the amount of 2-methylbenzothiazole is 0.01-0.05 mol, use 50-100 ml of ethylene glycol dimethyl ether solvent. Next, add a magnetic rotor and seal the reaction vessel. Turn on the constant temperature magnetic stirrer and set the reaction conditions to 60-100℃ oil bath heating. After reacting for 36-48 hours, filter to obtain the intermediate product. Finally, add ethylene glycol dimethyl ether solvent and wash and filter repeatedly.

[0012] Steps 1-2. Add the intermediate product back into the reaction vessel, add 3,4-dimethoxybenzaldehyde, then pour in methanol solvent, and then add piperidine solution as a catalyst. The molar ratio of 3,4-dimethoxybenzaldehyde to 2-methylbenzothiazole is equimolar. When the amount of 3,4-dimethoxybenzaldehyde is 0.01-0.05 mol, take 50-100 ml of methanol solvent and 1-2 ml of piperidine solution. After adding the magnetic rotor, seal the reaction vessel, turn on the constant temperature heating magnetic stirrer, and set the reaction conditions to oil bath heating at 60-100℃. React for 36-48 hours, then evaporate and dry the solvent to obtain 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder.

[0013] Step 2. Crystal growth;

[0014] Step 2-1. Dissolve 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder in methanol solvent and stir for 2-8 hours to obtain a supersaturated solution. When the amount of 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder is 0.01-0.05 mol, the amount of methanol solvent should be 30-50 ml.

[0015] Step 2-2. Add a crystal growth slant to the supersaturated solution, keep the supersaturated solution at 50-60℃ for 12-24 hours, and then place it at room temperature for spontaneous nucleation.

[0016] After steps 2-3.5-7 days, benzothiazole salt organic second-order nonlinear optical crystal material is obtained.

[0017] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0018] The organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate provided by this invention has excellent second-order nonlinear optical properties. Its second harmonic generation signal is up to 6.9 times that of DAST, a commercially widely used second-order nonlinear optical material. It can also solve the problem of DAST's water absorption and deliquescence, and can be used as a potential candidate material for applications such as frequency conversion. Moreover, the synthesis method of this organic compound is simple, easy to operate, has abundant raw material sources, low production cost, high yield, high purity and good reproducibility, making it suitable for large-scale production. Attached Figure Description

[0019] Figure 1 This is a synthetic route diagram of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiments of the present invention.

[0020] Figure 2 This is a diagram of the crude product of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in an embodiment of the present invention.

[0021] Figure 3 This is a crystallographic diagram of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate grown in an embodiment of the present invention.

[0022] Figure 4 The crystal structure of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiments of the present invention is shown.

[0023] Figure 5 This is a frontier molecular orbital diagram of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiments of the present invention.

[0024] Figure 6 This is a comparison chart of the second harmonic signal intensity of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder and DAST powder in an embodiment of the present invention.

[0025] Figure 7 This is a high-resolution mass spectrometry characterization of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiments of the present invention.

[0026] Figure 8The infrared spectrum characterization of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiments of the present invention is shown. Detailed Implementation

[0027] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] This embodiment provides a benzothiazole salt organic second-order nonlinear optical material, specifically 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate, with the characteristic molecular formula: C 25 H 25 NO5S2

[0029] The synthetic route for 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate described in this embodiment is as follows: Figure 1 As shown, the specific process is as follows:

[0030] Step 1-1. First, measure 50 ml of ethylene glycol dimethyl ether solvent and pour it into a round-bottom flask equipped with a reflux condenser as the reaction solvent. Then, weigh 5.27 g (0.035 mol) of 2-methylbenzothiazole powder and 6.68 g (0.035 mol) of p-toluenesulfonate solution separately using an electronic balance and add them to the flask in sequence. Next, add a conical magnetic rotor and seal the mouth of the flask with a sealing film. Turn on the constant temperature magnetic stirrer and set the reaction conditions to 60°C oil bath heating. After reacting for 48 hours, stop heating. A large amount of pale yellow precipitate can be seen precipitating at the bottom of the flask. Pour the reaction solution in the flask into a vacuum filtration device to obtain a pale yellow intermediate product. Finally, add a large amount of ethylene glycol dimethyl ether solvent to the obtained intermediate product for washing and filtration to remove unreacted reactants. Repeat the washing and filtration 2-3 times.

[0031] Steps 1-2. The intermediate product was added back to the reaction flask, and 5.81 g (0.035 mol) of the cation donor 3,4-dimethoxybenzaldehyde was slowly added to the flask. Then, 40 ml of methanol solvent was added. The precipitate in the flask completely dissolved, and the solution became clear. 1 ml of piperidine solution was then added dropwise as a catalyst to accelerate the reaction. The clear solution gradually turned red with the addition of the catalyst. The reaction conditions were set to 60°C oil bath heating, and heating was stopped after 48 hours of complete reaction. Due to the high solubility of the product, the final product was a deep red solution without precipitation. After evaporating and drying the solvent, a low-purity orange powder was obtained. This powder is the crude product of 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate crystals. Figure 2 As shown.

[0032] The crystal growth process of 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate described in this embodiment is as follows:

[0033] Step 2-1. Weigh 2g of recrystallized 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder and dissolve it in 100ml of methanol solution, stirring thoroughly for 2h.

[0034] After the powder of 2,3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate is completely dissolved, it is added to an inclined plate. The beaker is placed in a constant temperature oven at 50°C for 12 hours and then removed and placed at room temperature to allow it to evaporate slowly and spontaneously nucleate.

[0035] Steps 2-3. Five days later, small crystals, approximately 2×3×1mm in size, can be seen at the bottom of the beaker and on the inclined plate. 3 ,like Figure 3 As shown.

[0036] like Figure 4 The crystal structure of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in this embodiment is shown. Figure 4 The results show that the crystal structure parameters are: belonging to the monoclinic crystal system, space group P21, and unit cell parameters are... α=γ=90°, β=101.66809°.

[0037] like Figure 5 This is the frontier molecular orbital diagram of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in this embodiment, derived from... Figure 5 The results show that the charge on the HOMO orbital is mainly distributed on the sulfonic acid group of the anion, while the charge on the LUMO orbital is mainly located on the benzothiazole group and the π-conjugated bridge of the cation. The HOMO-LUMO orbital transition indicates that the intramolecular charge transfer occurs in the chromophore of 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate.

[0038] like Figure 6 The image shown is a comparison of the second harmonic signal intensity between the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder and the DAST powder in this embodiment. Figure 6 The experimental results show that its second harmonic generation signal (shown by the dashed line) is 6.9 times that of DAST (shown by the solid line), a commercially widely used second-order nonlinear optical material, indicating that this organic material can serve as a high-performance new second-order nonlinear optical material.

[0039] like Figure 7The image shown is a high-resolution mass spectrometry characterization of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in an embodiment of the present invention. Figure 7 (a) is the positive spectrum, with a distinct strong peak at a molecular weight of 312.1048, corresponding to the cation; Figure 7 (b) is a negative spectrum, with the strongest peak at a molecular weight of 171.0113, corresponding to the anion.

[0040] like Figure 8 The infrared spectrum characterization of the organic compound 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate in the embodiment of the present invention is shown in the figure. As can be seen from the figure, the vibrational modes of the chemical bonds in the molecule correspond to the wavenumbers as follows: 1586.09 cm⁻¹ -1 The corresponding C=N stretching vibration in the benzothiazole ring is 1512.88 cm⁻¹. -1 The corresponding C=C stretching vibration in the benzothiazole ring is 1512.88 cm⁻¹. -1 The point is the C=N stretching vibration in the benzothiazole ring, 1450.32 cm. -1 The corresponding C=C stretching vibration in the benzene ring is 1265.85 cm⁻¹. -1 The point is the CN stretching vibration in the benzothiazole ring, 1196.12 cm. -1 and 1027.53cm -1 Corresponding to SO3 - Stretching vibrations of functional groups, 1000-500 cm⁻¹ -1 Peaks in the wavenumber range correspond to the vibrational modes of the substituent groups on the benzene ring.

[0041] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A benzothiazolium salt organic second-order nonlinear optical material, characterized by, The material is specifically 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate, with a characteristic molecular formula of: C 25 H 25 NO5S2; The single crystal of the benzothiazole salt organic second-order nonlinear optical material belongs to monoclinic system, space group P21, and cell parameters are a = 11.332273 Å, b = 14.725604 Å, c = 20.623528 Å, α = γ = 90°, β = 101.66809°.

2. The method for preparing the benzothiazole salt organic second-order nonlinear optical material according to claim 1, characterized in that, Includes the following steps: Step 1. Prepare the crude crystal product; Step 1-1. First, ethylene glycol dimethyl ether is used as the reaction solvent and poured into a reaction vessel equipped with a reflux condenser. Then, 2-methylbenzothiazole powder and methyl p-toluenesulfonate solution are added to the reaction vessel sequentially, wherein the molar ratio of 2-methylbenzothiazole to methyl p-toluenesulfonate is 1:1, specifically 0.01–0.05 mol, and the amount of ethylene glycol dimethyl ether solvent is 50–100 ml. Next, a magnetic rotor is added, and the reaction vessel is sealed. The constant temperature magnetic stirrer is turned on, and the reaction conditions are set to oil bath heating at 60–100℃. After reacting for 36–48 hours, the intermediate product is obtained by filtration. Finally, the intermediate product is repeatedly washed and filtered multiple times with ethylene glycol dimethyl ether solvent. Steps 1-2. The intermediate product is added back to the reaction vessel, along with 3,4-dimethoxybenzaldehyde, followed by methanol solvent, and then piperidine solution is added dropwise as a catalyst. The molar ratio of 3,4-dimethoxybenzaldehyde to 2-methylbenzothiazole is equimolar, with 50-100 ml of methanol solvent and 1-2 ml of piperidine solution. After adding a magnetic rotor, the reaction vessel is sealed, and the constant-temperature heating magnetic stirrer is turned on. The reaction conditions are set to oil bath heating at 60-100℃, and the reaction is carried out for 36-48 hours. The solvent is then evaporated and dried to obtain 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder. Step 2. Crystal growth; Step 2-1. Dissolve 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder in methanol solvent and stir for 2–8 h to obtain a supersaturated solution, wherein 0.01–0.05 mol of 3,4-dimethoxystyryl-3-methylbenzothiazole p-toluenesulfonate powder and 30–50 ml of methanol solvent are used. Step 2-2. Add a crystal growth slant to the supersaturated solution, keep the supersaturated solution at 50-60℃ for 12-24 h, and then place it at room temperature for spontaneous nucleation. Steps 2-3. After 5–7 days, benzothiazole salt organic second-order nonlinear optical crystal material is obtained.

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