Chain-like core-shell structure crystal and preparation method and application thereof

Abstract

The application discloses a chain-like core-shell structure crystal and a preparation method and application thereof, the crystal is chloroethyl HDABCO-sodium bromofluoroborate, a structural formula of the crystal is [CH2ClCH2N(CH2CH2)3NH]4·[(Na6Br)(BF4) 13 ], a molecular structure presents a one-dimensional chain framework with infinite extension, adjacent chains are connected through N-H...F linear hydrogen bonds and chloroethyl-HDABCO, so that the compound has polarity and has a mid-infrared second-order nonlinear effect. In addition, the ultraviolet band edge absorption of the material is close to the near ultraviolet region, so that the material is expected to be close to inorganic ultraviolet nonlinear optical materials. The crystal is obtained through room temperature volatilization crystallization, has good thermal stability, and has potential application values in the fields of laser frequency doubling conversion, electro-optic modulators, deep ultraviolet nonlinear optics and shutter used for high-speed photography.

Description

Technical Field

[0001] This invention relates to a crystal, its preparation method, and its application, specifically to a chain-like core-shell structure crystal, its preparation method, and its application. Background Technology

[0002] Nonlinear optical effects originate from the strong coherent light interaction between laser light and a medium. When a laser propagates in a medium with a non-zero second-order polarizability, it produces effects such as optical frequency doubling, sum frequency, difference frequency, and optical parametric oscillations. Utilizing this second-order nonlinear optical effect of crystals, nonlinear optical components such as laser frequency converters, second harmonic generators, and optical parametric oscillators can be fabricated, possessing significant application value in high-tech fields such as optical information processing and optical storage. In recent years, nonlinear optical materials in the ultraviolet and near-far-infrared bands have attracted considerable attention due to their important applications in novel instruments and equipment in cutting-edge scientific fields. Currently, the most researched materials include borate, carbonate, nitrate, sulfate, and phosphate systems. However, commercially available ultraviolet nonlinear optical materials such as KBe₂BO₃F₂ (KBBF) contain highly toxic BeO during synthesis, and the preparation of inorganic nonlinear optical materials requires high costs and energy consumption. Organic nonlinear optical materials, due to their high content of organic conjugated systems, are difficult to absorb at band edges and approach the ultraviolet region, and organic substances are generally less stable.

[0003] Compared to inorganic and organic nonlinear optical materials, organic-inorganic hybrid nonlinear optical materials possess unparalleled advantages over inorganic and organic crystals, including low cost, ease of fabrication, flexibility, and stability. Furthermore, their fast nonlinear response has attracted widespread attention from researchers. While numerous organic-inorganic hybrid nonlinear optical materials have been reported to have potential applications in optical devices, optical information storage, and biomaterials, and have become a research hotspot in this field in recent years, very few materials can absorb light in the ultraviolet region. Therefore, exploring organic-inorganic hybrid materials for ultraviolet nonlinear optics remains a challenge. Summary of the Invention

[0004] Objectives of the invention: The present invention aims to provide a crystal with a chain-like core-shell structure exhibiting good mid-infrared second-order nonlinear effects; the second objective of the invention is to provide a method for preparing the above-mentioned novel chain-like core-shell structure crystal; the third objective of the invention is to provide the application of the above-mentioned novel chain-like core-shell structure crystal as a second-order nonlinear optical material.

[0005] Technical solution: The chain-like core-shell structured crystal of the present invention is sodium chloroethylHDABCO-bromofluoroborate, with the molecular formula C2. 32 H 68 Cl4N8Na6B13 F 52 Br, with the structural formula [CH2ClCH2N(CH2CH2)3NH]4·[(Na6Br)(BF4)] 13 The crystal belongs to the tetragonal crystal system, with space group I4(79) and cell parameters of . α=β=γ=90°、Z=4、 It contains a one-dimensional core-shell structure along the crystallographic c-axis.

[0006] Furthermore, in the crystal structural unit, bromide ions and sodium fluoroborate form a core-shell structure that extends infinitely along the c-axis. Organochloroethyl HDABCO cations are arranged within this structure, with their dipoles all pointing towards the c-axis, and are connected to the inorganic core-shell framework via weak van der Waals forces. This crystal molecular structure exhibits an infinitely extending one-dimensional chain framework, with adjacent chains interconnected through linear NH…F hydrogen bonds with chloroethyl-HDABCO, giving the compound polarity and exhibiting a second-order nonlinear effect in the mid-infrared range.

[0007] The method for preparing the chain-like core-shell structured crystal includes the following steps:

[0008] (1) Dissolve DABCO (1,4-diazabicyclo[2.2.2]octane, triethylenediamine) in a solvent, stir, then add bromochloroethane and raise the temperature to dissolve and react until the solid reappears completely. Finally, filter the organic phase and evaporate it to dryness to obtain a white solid mixture. Wash the solid phase and then dry and collect it.

[0009] (2) The solid obtained in the above steps is recrystallized to obtain the product chloroethylDABCO bromide.

[0010] (3) Dissolve the above-mentioned chloroethyl DABCO bromide in an aqueous solution, then add sodium fluoroborate and fluoroboric acid solution to react, filter out the insoluble matter, the solution becomes transparent and clear, place it at room temperature to allow the solvent to evaporate, and obtain colorless transparent crystals.

[0011] Furthermore, in step (1), the molar ratio of bromochloroethane to DABCO is 1:2 to 3; 20 to 30 mmol of triethylenediamine (DABCO) is added to every 50 mL of ethyl acetate; the solvent is ethyl acetate or acetonitrile; the reaction temperature is 50 to 60 °C; and the reaction time is 20 to 24 h.

[0012] Furthermore, the solvent used for recrystallization in step (2) is a mixed solution of acetonitrile and methanol, with a volume ratio of acetonitrile to methanol of 2.5 to 3:1;

[0013] Furthermore, in step (3), the molar ratio of chloroethyl DABCO bromide to the added sodium fluoroborate and fluoroboric acid solution is 1:1:1-3; the mass fraction of the fluoroboric acid solution is 40%. The solvent evaporation temperature is 20-40℃; bromide ions cannot be removed by Ag2CO3 and need to be retained in the solution.

[0014] The chain-like core-shell structured crystal can be used as a second-order nonlinear optical organic-inorganic hybrid material with deep ultraviolet absorption. This second-order nonlinear optical organic material is mainly used in the fabrication of laser frequency doubling converters, electro-optic modulators, Q-switches, and shutter components for high-speed photography. Its band-edge absorption can be below 200 nm, showing potential for application in the near-ultraviolet and deep ultraviolet regions.

[0015] The novel chain-like core-shell structure of the crystal prepared in this invention has a core composed of bromine as the center and sodium as the ligand, with fluoroborate ions forming a shell that encapsulates BrNa6, forming a one-dimensional inorganic framework chain along the crystallographic c-axis. Organic cations are interspersed between these one-dimensional chains, and their arrangement results in a polar arrangement of the crystal, thus creating a macroscopic frequency doubling coefficient χ. (2) The special inorganic framework formed by alkali metals and fluoroboric acid gives the prepared crystals good second-order nonlinear optical properties.

[0016] The preparation principle of this invention is as follows: (1) using an alkali metal as the framework to construct the center; (2) using a compound containing polar cations to construct an organic-inorganic hybrid crystal in a non-central space group, thereby exhibiting second-order nonlinearity on a macroscopic scale. Specifically, firstly, by introducing chloroethyl into triethylenediamine, the entire molecule becomes a polar molecule. Secondly, by constructing a one-dimensional core-shell structure with bromine as the central atom, sodium ions as the secondary center, and fluoroborate ions surrounding and coordinating, a framework with absorption in the ultraviolet region is constructed. Finally, because the polar cations and the formed framework are aligned in the same direction, the prepared crystal is endowed with good second-order nonlinear optical properties.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The chain-like core-shell structure of the crystal chloroethyl HDABCO-bromofluoroborate sodium exhibits a good mid-infrared second-order nonlinear effect. Its ultraviolet spectrum can absorb in the deep ultraviolet region, which is comparable to some inorganic ultraviolet nonlinear optical materials. It breaks the past of organic materials and organic-inorganic materials having no absorption in the deep ultraviolet region, which promotes its potential application value in the fields of laser frequency doubling conversion, electro-optic modulators, Q switches and shutters for high-speed photography; (2) The product has the characteristics of simple synthesis, cheap and readily available raw materials, environmental friendliness and high stability, which are suitable for large-scale industrial production. Attached Figure Description

[0018] Figure 1This is a crystal structure diagram of sodium chloroethyl HDABCO-bromofluoroborate of the present invention;

[0019] Figure 2 The powder diffraction pattern of sodium chloroethyl HDABCO-bromofluoroborate crystals prepared in Example 1;

[0020] Figure 3 The frequency doubling coefficient χ of sodium chloroethyl HDABCO-bromofluoroborate crystals and commercial KDP (2) Intensity comparison chart;

[0021] Figure 4 The image shows the ultraviolet diffuse reflectance of sodium chloroethyl HDABCO-bromofluoroborate crystals;

[0022] Figure 5 The second-order nonlinear harmonic coefficient χ of the chloroethyl DABCO-bromine salt prepared in Comparative Example 1 (2) The intensity signal diagram;

[0023] Figure 6 The second-order nonlinear harmonic coefficient χ of the chloroethyl HDABCO-dibromo salt prepared in Comparative Example 2 (2) The intensity signal diagram. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1

[0026] (1) Dissolve 20 mmol DABCO in 50 mL ethyl acetate, stir at room temperature, then add 10 mmol bromochloroethane and mix. Increase the temperature to 60 °C to dissolve and react for about 20 h until the solid reappears completely. Finally, filter the organic phase and evaporate to dryness to obtain a white solid mixture. Wash the solid phase with acetonitrile solvent, then dry and collect.

[0027] (2) Dissolve the solid obtained in step (1) in 40 mL of a mixed solution of acetonitrile and methanol, and recrystallize the product chloroethyl DABCO bromide at a volume ratio of 2.5:1 to obtain the product.

[0028] (3) Dissolve 5 mmol of the intermediate product obtained in step (2) in 25 mL of aqueous solution, then add 5 mmol of sodium fluoroborate and 37.5 mmol of 40 wt% fluoroboric acid solution in a molar ratio of 1:1:1.5 to react. Filter out the insoluble matter; the solution becomes transparent and clear. Place it in a 50 mL plastic beaker at room temperature and allow it to evaporate at 20°C for about one week to obtain colorless and transparent crystals. See the structural unit diagram of the crystals. Figure 1In this structure, bromine forms the core, sodium the ligand, and fluoroborate ions encapsulate BrNa6, forming a one-dimensional inorganic framework chain along the crystallographic c-axis. Organic cations intersect within these one-dimensional chains, resulting in a polar arrangement within the crystal. Therefore, the macroscopic doubling frequency coefficient χ of the crystal is... (2) The special inorganic framework formed by alkali metals and fluoroboric acid gives the prepared crystals good second-order nonlinear optical properties.

[0029] Select a size of 0.20×0.20×0.20mm. 3 The crystals were used for single-crystal structure analysis. Single-crystal diffraction data were collected on a Rigaku Oxford Diffraction diffractometer. The crystal structure data of the obtained compounds are shown in Table 1.

[0030] Table 1. Main crystallographic data of the compound sodium chloroethylHDABCO-bromofluoroborate.

[0031]

[0032] [a] R1=Σ||F o |-|F c || / |F o | [b] wR2=[Σw(F o 2 -F c 2 ) 2 ] / Σw(F o 2 ) 2 ] 1 / 2 [c] Maximum and minimum residual electron densities.

[0033] The obtained colorless, transparent, bulk crystals, analyzed at 300K, exhibited a one-dimensional core-shell structure. A tetragonal chiral crystal system, space group I4, was adopted. α=β=γ=90°, The Z-value is 2. During the molecular packing process, the crystal forms a one-dimensional inorganic framework along the crystallographic c-axis, with bromine as the center, sodium as the ligand, and fluoroborate ions encapsulating BrNa6. Organic cations intersect between these one-dimensional chains, resulting in a polar arrangement within the crystal. Therefore, the macroscopic doubling frequency coefficient χ of the crystal is significant. (2) It was thus able to come into being.

[0034] See Figure 2The powder diffraction patterns obtained showed characteristic peaks of 2θ of 8.6°, 13.45°, 16.37°, 19.95°, 21.53°, 22.56°, 23.30°, 23.95°, 26.18°, 26.65°, 27.21°, 28.18°, 29.08°, and 32.65°, indicating that the powder diffraction experimental data of the obtained colorless flaky crystals were in perfect agreement with the simulated data, demonstrating the high purity of the prepared compound.

[0035] The performance of the prepared colorless and transparent bulk crystal sodium chloroethyl HDABCO-bromofluoroborate was compared with that of commercial KDP. First, the prepared colorless and transparent bulk crystal was ground into powder with a particle size of approximately 200–300 μm. Then, approximately 3–5 mg of the powder sample was sandwiched in a 1 cm × 1 cm transparent glass slide. This glass slide was then placed in the laser path. An Nd:YAG pulsed laser was used as the light source to generate 1064 nm fundamental frequency light, which was transmitted through the sample sandwiched in the glass. The generated signal was then displayed on an oscilloscope via a photomultiplier tube. Similarly, the reference KDP crystal was ground into powder with a particle size of approximately 200–300 μm and compared under the same experimental conditions. See [link to relevant documentation]. Figure 3 Macroscopic octave coefficient χ of sodium chloroethyl HDABCO-bromofluoroborate with commercial KDP (2) Intensity comparison, χ² of the product (2) The value is as high as 14-15, which is 7-8 times that of commercial KDP. Due to the unique nature of the inorganic framework, for measuring the crystal's ultraviolet diffuse reflectance properties, please refer to [reference needed]. Figure 4 It was found that its absorption is <200nm, indicating that it has absorption capability in the near-ultraviolet region, thus making it a nonlinear optical material in the near-ultraviolet region.

[0036] Sodium chloroethyl HDABCO-bromofluoroborate can exhibit a macroscopic octave coefficient χ. (2) The near-ultraviolet nonlinear optics are entirely due to the formation of core-shell one-dimensional chains and the arrangement of polar organic cations during the crystallization of this compound. This arrangement of polar cations ensures that the molecules are neatly aligned in the same direction during the stacking process, contributing to the macroscopic frequency doubling coefficient χ. (2) The inorganic one-dimensional chain with a special core-shell structure provides the basis for its absorption properties in the near-ultraviolet region.

[0037] Example 2

[0038] (1) Dissolve 30 mmol DABCO in 60 mL acetonitrile, stir at room temperature, then add 10 mmol bromochloroethane and mix. Increase the temperature to 50 °C to dissolve and react for about 24 h until the solid reappears completely. Finally, filter the organic phase and evaporate to dryness to obtain a white solid mixture. Wash the solid phase with acetonitrile solvent, then dry and collect.

[0039] (2) Dissolve the solid obtained in step (1) in 40 mL of a mixed solution of acetonitrile and methanol, and recrystallize the product chloroethyl DABCO bromide at a volume ratio of 2.5:1 to obtain the product.

[0040] (3) Dissolve 5 mmol of the intermediate product obtained in step (2) in 25 mL of aqueous solution, then add 5 mmol of sodium fluoroborate and 50 mmol of 40 wt% fluoroboric acid solution in a molar ratio of 1:1:2 to carry out the reaction. Filter out the insoluble matter, and the solution becomes transparent and clear. Place it in a 50 mL plastic beaker at room temperature and volatilize at 30 °C for about 1 week to obtain colorless and transparent crystals.

[0041] Example 3

[0042] (1) Dissolve 30 mmol DABCO in 60 mL acetonitrile, stir at room temperature, then add 10 mmol bromochloroethane and mix. Increase the temperature to 60 °C to dissolve and react for about 20 h until the solid reappears completely. Finally, filter the organic phase and evaporate to dryness to obtain a white solid mixture. Wash the solid phase with acetonitrile solvent, then dry and collect.

[0043] (2) Dissolve the solid obtained in step (1) in 40 mL of a mixed solution of acetonitrile and methanol, and recrystallize the product chloroethyl DABCO bromide at a volume ratio of 3:1 to obtain the product.

[0044] (3) Dissolve 5 mmol of the intermediate product obtained in step (2) in 30 mL of aqueous solution, then add 5 mmol of sodium fluoroborate and 75 mmol of 40 wt% fluoroboric acid solution in a molar ratio of 1:1:3 to carry out the reaction. Filter out the insoluble matter, and the solution becomes transparent and clear. Place it in a 50 mL plastic beaker at room temperature and evaporate it on a heating table at 40 °C for about 5 days to obtain colorless and transparent crystals.

[0045] Comparative Example 1

[0046] The chloroethyl DABCO bromide obtained in step (2) of Example 1 was directly dissolved in anhydrous ethanol. The solution was stirred in a 50 ml beaker until homogeneous and dissolved. It was then slowly evaporated at room temperature, resulting in the re-precipitation of colorless crystals. The obtained crystals showed zero signal in a nonlinear optical test, indicating that the substance crystallized in a centrosymmetric structure, such as... Figure 5 .

[0047] Comparative Example 2

[0048] 5 mmol of chloroethyl DABCO bromide obtained in step (2) of Example 1 was directly dissolved in anhydrous ethanol, and 5 mmol of HBr (40% solution) was added. The solution was stirred in a 50 ml beaker until homogeneous and dissolved. The solution was then slowly evaporated at room temperature, and colorless crystals were re-precipitated. The obtained chloroethyl-HDABCO dibromide crystals showed zero signal in a nonlinear optical test, indicating that the substance also crystallizes in a centrosymmetric structure, such as... Figure 6 .

Claims

1. A crystal of chain core-shell structure, characterized by: The crystal is chloroethyl HDABCO-sodium bromofluoroborate, with a structural formula of [CH2ClCH2N(CH2CH2)3NH]4·[(Na6Br)(BF4) 13 ], containing a one-dimensional core-shell structure along the crystallographic c-axis, the crystal belongs to the tetragonal system, the space group is I4(79), the cell parameters are α = β = γ = 90°, Z = 4, 2. The chain-like core-shell structured crystal according to claim 1, characterized by: The bromine ion and sodium fluoroborate in the crystal structure unit form an inorganic core-shell structure, which extends infinitely along the c-axis, and the organic chloroethyl HDABCO cation is arranged therein, and the dipole thereof is directed toward the c-axis and is connected to the inorganic core-shell skeleton through van der Waals weak force.

3. The method of producing a crystal of a chain core-shell structure according to claim 1 or 2, characterized by, The method comprises the following steps: (1) dissolving DABCO in a solvent, stirring, then adding bromo-chloroethane to increase the temperature to dissolve, reacting until solid appears again, finally filtering the organic phase and drying to obtain a white solid mixture, washing the solid phase, and then drying and collecting; (2) recrystallizing the solid obtained in the above step to obtain the product chloroethyl DABCO bromide salt; (3) dissolving the chloroethyl DABCO bromide salt in an aqueous solution, then adding sodium fluoroborate and fluoroboric acid solution, filtering the insoluble substance, and placing the solution with transparent and clear color at room temperature to evaporate the solvent to obtain colorless transparent crystals.

4. The method for preparing a crystal of a chain-type core-shell structure according to claim 3, characterized by: The molar ratio of bromo-chloroethane to DABCO in step (1) is 1:2-3; 20-30 mmol of DABCO needs to be added per 50 mL of solvent.

5. The method for preparing a chain-like core-shell structured crystal according to claim 3, characterized in that: The reaction temperature in step (1) is 50-60°C, and the reaction time is 20-24 h.

6. The method for preparing a chain-like core-shell structured crystal according to claim 3, characterized in that: The recrystallization solvent used in step (2) is a mixed solution of acetonitrile and methanol, and the volume ratio of acetonitrile to methanol is 2.5-3:

1.

7. The method for preparing a chain-like core-shell structured crystal according to claim 3, characterized in that: The solvent evaporation temperature in step (3) is 20-40°C.

8. The method for preparing a chain-like core-shell structured crystal according to claim 3, characterized in that: The molar ratio of chloroethyl DABCO bromide salt, sodium fluoroborate and fluoroboric acid solution in step (3) is 1:1:1-3.

9. Use of the chain core-shell structure crystal of claim 1 or 2 as a second-order nonlinear optical organic-inorganic hybrid material.

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