CN113480454B - Linear hydrogen bond type azobenzene crystal and preparation method and application thereof - Google Patents

Abstract

The invention discloses a linear hydrogen bond type azobenzene crystal and a preparation method and application thereof, wherein the crystal is ( Z )-2-(4-aminophenyl)-1-phenyldiazene-2-oxide, The molecular structure presents a trans configuration, and adjacent molecules are connected to each other through linear N-H…O linear hydrogen bonds to form an infinitely extending one-dimensional hydrogen bond chain, which makes the compound polar and extremely polar. Strong mid-infrared second-order nonlinear effects. The crystal is obtained by volatilizing crystallization at room temperature. The frequency doubling coefficient of this material is 7~8 times that of commercial KDP, and it has good thermal stability. It is used in laser frequency doubling conversion, electro-optic modulator, Q switch and shutter for high-speed photography. It has potential application value in the field of components and so on.

Description

A kind of linear hydrogen bond type azobenzene crystal and its preparation method and application

technical field

The invention belongs to an organic nonlinear optical material, in particular to a linear hydrogen bond type azobenzene second-order nonlinear optical material and a preparation method thereof.

Background technique

The nonlinear optical effect originates from the strong coherent light interaction between the laser and the medium. When the laser propagates in a medium with a non-zero second-order polarizability, effects such as optical frequency doubling, sum frequency, difference frequency and optical parametric oscillation will occur. Using 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 prepared, which are used in optical information processing, high-speed optical communication, optical storage, electronic Instruments and other high-tech fields have important application value. Nonlinear optical materials can be divided into two categories according to their chemical composition, namely inorganic nonlinear optical materials and organic nonlinear optical materials. Compared with inorganic nonlinear optical materials, organic nonlinear optical materials have the advantages of large nonlinear optical coefficient, fast nonlinear response, high damage threshold, low cost, easy processing, flexibility and other incomparable advantages of inorganic crystals. widespread attention of researchers.

Among many organic nonlinear optical materials, azobenzene organic compounds have good photosensitivity, nonlinear optical properties, good thermal stability and easy film formation. They are widely used in optical devices, optical information storage and biological applications. Materials and other fields have shown potential application prospects and have become one of the research hotspots in this field in recent years. In general, the macroscopic frequency doubling factor χ ⁽²⁾ of a crystal is the vector sum of the microscopic frequency doubling factors β of all the molecules that make up this crystal. The design ideas for traditional azobenzene-based second-order nonlinear materials mainly include the following two points: (1) Introducing electron-pushing groups and electron-withdrawing groups at both ends of azobenzene to form intramolecular charge transfer, The microscopic frequency doubling coefficient β of the molecule is increased; (2) azobenzene molecules containing chiral centers are used to form polymers, thereby showing second-order nonlinearity in the macroscopic. However, both methods have certain drawbacks. For the former, the random arrangement of molecules in the crystal may cause the dipoles to cancel each other out, eventually making the macroscopic frequency doubling coefficient χ ⁽²⁾ tend to 0; for the latter, the crystallinity of the polymer material is very poor, And the macro frequency doubling coefficient is often low, which greatly limits the application of such materials.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a linear azobenzene-based crystal in which molecules are aligned under the action of hydrogen bonds; the second purpose of the present invention is to provide a preparation method for the above-mentioned linear hydrogen-bonded azobenzene-based crystals The third object of the present invention is to provide the application of the above-mentioned linear hydrogen-bonded azobenzene-based crystal as a second-order nonlinear optical material.

α＝β＝γ＝90°、Z＝4、

含有沿晶体学c轴的氢键相互作用链。Technical solution: A linear hydrogen bond type azobenzene crystal of the present invention is characterized in that: the crystal is (Z)-2-(4-aminophenyl)-1-phenyldiazepine-2-oxidation Its molecular formula is C ₁₂ H ₁₁ N ₃ O, which belongs to the orthorhombic crystal system, the space group is Pca2 ₁ , and the unit cell parameter is

α=β=γ=90°, Z=4,

Contains chains of hydrogen bonding interactions along the crystallographic c-axis.

Further, the crystal molecules are in a trans-azobenzene conformation, and adjacent crystal molecules are connected by N-H...O hydrogen bonds to form a one-dimensional hydrogen bond chain.

The present invention also protects the preparation method of the linear hydrogen bond type azobenzene crystal, characterized in that it comprises the following steps:

(1) Dissolve 4-aminoazobenzene in acetic anhydride, stir at room temperature until a solid appears, then add ethyl acetate to dissolve the solid, separate the organic phase, wash the organic phase with saturated aqueous sodium bicarbonate solution, then add anhydrous Sodium sulfate was allowed to stand, and finally the organic phase was filtered and spin-dried to obtain an orange solid mixture;

(2) the orange solid mixture obtained in step (1) is separated by column chromatography, and the intermediate product 4-acetamidoazobenzene is isolated;

(3) the intermediate product 4-acetamidoazobenzene obtained in step (2) is dissolved in the mixed solution of glacial acetic acid and acetic anhydride, and then H ₂ O ₂ is added to carry out the reaction, when the color of the solution changes from orange to yellow The reaction solution was placed in ice water to cool, a large amount of yellow milky suspension appeared, filtered and dried to obtain a yellow solid;

(4) dissolving the yellow solid obtained in step (3) in ethanol, adding NaOH aqueous solution, the reaction solution is refluxed and placed in an ice-water bath to cool down, and cold water is added to it, a large amount of yellow milky suspension occurs, filtered and dried to obtain yellow crude product;

(5) The yellow crude product obtained in step (4) is separated by column chromatography to obtain the product (Z)-2-(4-aminophenyl)-1-phenyldiazene-2-oxide;

(6) Dissolving the product of step (5) in a mixed solvent of dichloromethane and petroleum ether, and slowly volatilizing the solvent to obtain yellow flake crystals.

Further, in the step (1), 20-30 mmol of 4-aminoazobenzene is added to every 30-40 mL of acetic anhydride.

Further, in the step (3), 30-40 mol of 4-acetamidoazobenzene is added to every 120-140 mL of the mixed solution; wherein, the volume ratio of glacial acetic acid and acetic anhydride in the mixed solution is 10-13 : 3-5; the volume ratio of the mixed solution to H ₂ O ₂ is 13-18: 3-6; wherein, the mass percentage concentration of H ₂ O ₂ is 25-35 wt %, preferably 30 wt %.

Further, in the step (3), the reaction temperature is 40-50° C., and the reaction time is 6-8 h.

Further, the eluent adopted during the column chromatography separation in the step (2) and the step (5) is the mixed solvent of dichloromethane and methanol; in the step (2), the volume ratio of the dichloromethane and the sherwood oil is 10-15:1; in step (5), the volume ratio of dichloromethane and petroleum ether is 3-5:1.

Further, in the step (6), the volume ratio of dichloromethane and petroleum ether is 3-5:1; the volatilization temperature is 20-30°C.

The present invention further protects the application of the linear hydrogen bond type azobenzene crystal as a second-order nonlinear optical organic material. Wherein, the second-order nonlinear optical organic material is mainly used for the preparation of laser frequency doubling conversion, electro-optic modulator, Q-switch and shutter components for high-speed photography.

The structural unit diagram of the linear hydrogen-bonded azobenzene crystal prepared by the present invention is shown in FIG. 1 , wherein, for a single crystal molecule, it is in a trans-azobenzene conformation, and the molecule contains a bond of -NO=N-, so that the O atom is connected. Become a hydrogen bond acceptor, and in the process of crystal molecular stacking, the N in the substituted -NH ₂ on the benzene ring has a hydrogen atom to become a hydrogen bond donor, and -NO=N- O through linear NH...O hydrogen bonding to each other. As the hydrogen bonds extend infinitely, adjacent molecules pack into a jagged structure through intermolecular interactions. Since the group introducing hydrogen bonds into the molecules causes the molecules to be aligned under the action of hydrogen bonds, and the NO bonds all point to the same side, the vector sum of the microscopic frequency doubling coefficients β of all molecules has a maximum value in this direction, The compound has strong polarity and endows the prepared crystal with good second-order nonlinear optical properties.

The preparation principle of the present invention is as follows: firstly, by introducing an NH ₂ group with strong electron-pushing ability on one side of the benzene ring of the azobenzene, the charge in the azobenzene molecule is transferred, and the microscopic frequency doubling of the molecule is improved. coefficient β. Secondly, by oxidizing the N=N double bond in azobenzene, a hydrogen bond acceptor is introduced to form a linear NH...O strong hydrogen bond with the H atom on the N atom in _-NH2 , which finally endows the prepared The crystal obtains good second-order nonlinear optical properties.

Beneficial effects: compared with the prior art, the present invention has the following significant advantages: the present invention obtains a linear hydrogen bond type azobenzene-based second-order nonlinear optical organic material (Z)-2-(4-aminophenyl) -1-Phenyldiazene-2-oxide, exhibits a good mid-infrared second-order nonlinear effect, and its frequency doubling coefficient χ ⁽²⁾ is 7-8 times that of commercial KDP. It is used in laser frequency doubling conversion, electro-optical Modulators, Q switches, and shutters for high-speed photography have potential applications. The product has the characteristics of simple synthesis, cheap and readily available raw materials, environmental friendliness and high stability, and is suitable for large-scale industrial production.

Description of drawings

Fig. 1 is the linear hydrogen bond type azobenzene crystal structure diagram of the present invention;

Fig. 2 is the linear hydrogen-bonded azobenzene crystal powder diffraction pattern prepared in Example 1;

Fig. 3 is the intensity contrast diagram of linear hydrogen bond type azobenzene crystal and commercial KDP frequency doubling coefficient χ ⁽²⁾ ;

Figure 4 is a comparison of the thermal stability test chart of linear hydrogen-bonded azobenzene crystals and commercial KDP;

Fig. 5 is the crystal structure diagram of 4-aminoazobenzene in Comparative Example 1;

Fig. 6 is the intensity comparison diagram of the second-order nonlinear frequency doubling coefficient χ ⁽²⁾ of 4-aminoazobenzene and commercial KDP prepared in Comparative Example 1

Detailed ways

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

Example 1

(1) Dissolve 25 mmol of 4-aminoazobenzene in 35 mL of acetic anhydride, stir at room temperature until a solid appears, then add ethyl acetate to dissolve the solid, separate the organic phase, wash the organic phase with a saturated aqueous NaHCO ₃ solution, then Add anhydrous Na ₂ SO ₄ and let stand for 30min, then the organic phase is filtered and spin-dried to obtain an orange solid mixture;

(2) the obtained orange solid mixture is separated by column chromatography, and the eluent is a mixed solvent of dichloromethane and methanol with a volume ratio of 13:1, and the intermediate product 4-acetamidoazobenzene can be isolated;

(3) 40 mmol of the obtained intermediate product 4-acetamidoazobenzene was dissolved in 100 mL of glacial acetic acid and 30 mL of acetic anhydride, then 40 mL of H ₂ O ₂ with a concentration of 30% was added, and the reaction solution was heated at 50° C. Stir at constant temperature for 4h in an oil bath, the color of the solution gradually changed from orange to yellow, then the reaction solution was cooled in ice water, a large amount of yellow milky suspension appeared, filtered and dried to obtain a yellow solid;

(4) The obtained yellow solid was dissolved in ethanol, a concentrated aqueous NaOH solution was added, the reaction solution was refluxed for 2h, then the reaction solution was placed in an ice-water bath to cool down, and cold water was added to it, a large amount of yellow milky suspension appeared, and after filtration drying to obtain a yellow crude product;

(5) the obtained yellow crude product is separated by column chromatography, and the eluent is the mixed solvent of dichloromethane and petroleum ether with a volume ratio of 3:1, and the final product (Z)-2-(4-amino can be separated out) phenyl)-1-phenyldiazene-2-oxide;

(6) Dissolve the final product in a mixed solvent of dichloromethane and petroleum ether with a volume ratio of 3:1, slowly volatilize the solvent at 25°C, stir in a 100mL beaker until uniformly dissolved, and slowly volatilize in a room temperature environment , about 1-2 days after the precipitation of yellow flaky crystals.

Crystals with a size of 0.20 × 0.20 × 0.20 mm ^were selected for single crystal structure analysis. The single crystal diffraction data were collected on a Rigaku Oxford Diffraction, 2020 diffractometer. The crystal structure data of the obtained compounds are shown in Table 1.

Table 1 Main crystallographic data of compound (Z)-2-(4-aminophenyl)-1-phenyldiazene-2-oxide

^[a] R ₁ =Σ||F _o |-|F _c ||/|F _o |. ^[b] wR ₂ =[Σw(F _o ² -F _c ² ) ² ]/Σw(F _o ² ) ² ] ^1/2 . ^[c] Maximum and minimum residual electron densities.

α＝β＝γ＝90°，

Z值为4。晶体在分子堆积过程中，相邻分子间通过N-H…O氢键型相互作用形成沿着晶体学c轴的一维链。由于晶体的宏观倍频系数χ⁽²⁾是组成这一晶体的所有分子的微观倍频系数β的矢量和，因此这种线性氢键型偶氮苯类化合物具有如此高的二阶非线性系数χ⁽²⁾，在强度上商业KDP的7～8倍。The obtained yellow flake-like crystal was analyzed at 293K and its crystal structure was found to be in the trans-azobenzene conformation. Orthorhombic polar crystal system, space group Pca2 ₁ ,

α=β=γ=90°,

The Z value is 4. During the molecular packing process of crystals, adjacent molecules form a one-dimensional chain along the crystallographic c-axis through NH…O hydrogen-bonding interactions. Since the macroscopic frequency doubling coefficient χ ⁽²⁾ of a crystal is the vector sum of the microscopic frequency doubling coefficients β of all the molecules that make up this crystal, this linear hydrogen-bonded azobenzene compound has such a high second-order nonlinear coefficient χ ⁽²⁾ , 7 to 8 times the commercial KDP in strength.

Referring to Fig. 2, the characteristic peak 2θ is 10.2°, 13.2°, 16.8°, 19.0°, 19.7°, 21°, 22°, 23.6°, 26°, 26.3°, 27.2°, 27.8°, 30.98°, 31.7° , indicating that the powder diffraction experimental data of the obtained yellow flake crystals are in complete agreement with the simulated data, indicating that the prepared compounds are of high purity.

The properties of the prepared yellow flake crystals (Z)-2-(4-aminophenyl)-1-phenyldiazene-2-oxide were compared with commercial KDP. First, the prepared yellow flake crystals are ground into powder with a particle size of about 200-300 μm, then a powder sample of about 3-5 mg is taken and sandwiched in a transparent glass sheet with a size of 1 cm × 1 cm, and then the glass sheet is placed On the laser light path, Nd:YAG pulsed laser was used as the light source in the experiment to generate fundamental frequency light of 1064 nm through the sample sandwiched by glass, and then the generated signal was displayed on the oscilloscope through the photomultiplier tube. Similarly, the reference KDP crystal was ground into powder with a particle size of about 200-300 μm, and the comparison test was carried out under the same experimental conditions. Referring to Figure 3, (Z)-2-(4-aminophenyl)-1-phenyldiazene-2-oxide and commercial KDP macroscopic frequency doubling coefficient χ ⁽²⁾ intensity comparison, product χ ^{(2 ) is} as high as 14-15, which is 7-8 times that of commercial KDP; meanwhile, see Figure 4, the stability test of χ ⁽²⁾ of the product with temperature, the sample temperature is gradually melted when the temperature is as high as 410K-420K, χ ⁽²⁾ Then it drops to 0.

(Z)-2-(4-aminophenyl)-1-phenyldiazene-2-oxide can exhibit such a strong macroscopic frequency doubling coefficient χ ⁽²⁾ and high thermodynamic temperature properties, which are completely beneficial Due to the strong hydrogen bonding interaction of NH...O formed during the crystallization of the compound. The NH...O hydrogen bond not only makes the molecules neatly arranged in the same direction during the stacking process, and makes the macroscopic frequency doubling coefficient χ ⁽²⁾ to show a maximum value; but also makes the bonding between molecules more closely, which greatly improves the compound of thermal stability.

Example 2

(1) Dissolve 30 mmol of 4-aminoazobenzene in 40 mL of acetic anhydride, stir at room temperature until a solid appears, then add ethyl acetate to dissolve the solid, separate the organic phase, wash the organic phase with a saturated aqueous NaHCO ₃ solution, then Add anhydrous Na ₂ SO ₄ and let stand for 30min, then the organic phase is filtered and spin-dried to obtain an orange solid mixture;

(2) the obtained orange solid mixture is separated by column chromatography, and the eluent is a mixed solvent of dichloromethane and methanol with a volume ratio of 15:1, and the intermediate product 4-acetamidoazobenzene can be isolated;

(3) 35 mmol of 4-acetamidoazobenzene obtained as an intermediate product was dissolved in 110 mL of glacial acetic acid and 40 mL of acetic anhydride, then 60 mL of H ₂ O ₂ with a concentration of 30% was added, and the reaction solution was heated at 40° C. Stir at constant temperature for 5h in an oil bath, the color of the solution gradually changed from orange to yellow, then the reaction solution was cooled in ice water, a large amount of yellow milky suspension appeared, filtered and dried to obtain a yellow solid;

(4) The obtained yellow solid was dissolved in ethanol, a concentrated aqueous NaOH solution was added, the reaction solution was refluxed for 2h, then the reaction solution was placed in an ice-water bath to cool down, and cold water was added to it, a large amount of yellow milky suspension appeared, and after filtration drying to obtain a yellow crude product;

(5) The obtained yellow crude product is separated by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether with a volume ratio of 4:1, and the final product (Z)-2-(4-amino can be separated out) phenyl)-1-phenyldiazene-2-oxide;

(6) Dissolve the final product in a mixed solvent of dichloromethane and petroleum ether with a volume ratio of 4:1, slowly volatilize the solvent at 20°C, stir in a 100mL beaker until it is uniformly dissolved, and slowly volatilize in a room temperature environment , about 1-2 days after the precipitation of yellow flaky crystals.

Example 3

(1) Dissolve 20 mmol of 4-aminoazobenzene in 30 mL of acetic anhydride, stir at room temperature until a solid appears, then add ethyl acetate to dissolve the solid, separate the organic phase, wash the organic phase with a saturated aqueous NaHCO ₃ solution, then Add anhydrous Na ₂ SO ₄ and let stand for 30min, then the organic phase is filtered and spin-dried to obtain an orange solid mixture;

(2) the obtained orange solid mixture is separated by column chromatography, and the eluent is a mixed solvent of dichloromethane and methanol with a volume ratio of 10:1, and the intermediate product 4-acetamidoazobenzene can be isolated;

(3) 30 mmol of 4-acetamidoazobenzene obtained as an intermediate product was dissolved in 130 mL of glacial acetic acid and 50 mL of acetic anhydride, then 50 mL of H ₂ O ₂ with a concentration of 30% was added, and the reaction solution was heated at 45° C. Stir for 8h at constant temperature in an oil bath, the color of the solution gradually changed from orange to yellow, then the reaction solution was cooled in ice water, a large amount of yellow milky suspension appeared, filtered and dried to obtain a yellow solid;

(4) The obtained yellow solid was dissolved in ethanol, a concentrated aqueous NaOH solution was added, the reaction solution was refluxed for 2h, then the reaction solution was placed in an ice-water bath to cool down, and cold water was added to it, a large amount of yellow milky suspension appeared, and after filtration drying to obtain a yellow crude product;

(5) the obtained yellow crude product is separated by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether with a volume ratio of 5:1, and the final product (Z)-2-(4-amino can be separated out) phenyl)-1-phenyldiazene-2-oxide;

(6) Dissolve the final product in a mixed solvent of dichloromethane and petroleum ether with a volume ratio of 5:1, slowly volatilize the solvent at 30°C, stir in a 100mL beaker until uniformly dissolved, and slowly volatilize in a room temperature environment , about 1-2 days after the precipitation of yellow flaky crystals.

Comparative Example 1

Directly select 4-aminoazobenzene, dissolve it in absolute ethanol, stir in a 100ml beaker until it dissolves evenly, slowly volatilize at room temperature, and precipitate orange-yellow strip-shaped crystals after about 1-2 days.

Crystals with a size of 0.20 × 0.20 × 0.20 mm ³ were selected for single crystal structure analysis, and the single crystal diffraction data were collected on a Rigaku Oxford Diffraction, 2020 diffractometer. The crystal structure data of the obtained compounds are shown in Table 2.

Table 2 Main crystallographic data of compound 4-aminoazobenzene

β＝98.369(6)°，

Z值为2。晶体在分子堆积过程中，没有形成明显的氢键相互作用。The obtained orange-yellow strip-shaped crystal was analyzed at 293K for its crystal structure, see Figure 5, and it was found that it also had a trans-azobenzene conformation, but during the molecular stacking process, the crystals did not form obvious hydrogen bond interactions. Monoclinic polar crystal system, space group Pn,

β=98.369(6)°,

The Z value is 2. During the molecular packing process of the crystal, no obvious hydrogen bond interaction is formed.

The second-order nonlinear coefficient χ ⁽²⁾ test was performed on it. Similarly, according to the above preparation method, the 4-aminoazobenzene crystals are ground into powder with a particle size of about 200-300 μm, and then a powder sample of about 3-5 mg is taken and sandwiched in a transparent glass sheet with a size of 1 cm × 1 cm After that, the glass piece was placed on the laser light path. The Nd:YAG pulsed laser was used as the light source in the experiment to generate fundamental frequency light of 1064 nm, which was transmitted through the sample sandwiched by the glass, and the generated signal was displayed on the oscilloscope through the photomultiplier tube. . Referring to Fig. 6, the macroscopic second-order nonlinear frequency doubling coefficient χ ⁽²⁾ of the 4-aminoazobenzene compound is about 1.3-1.4, which is only 0.7-0.8 times that of commercial KDP, which is far lower than the linearity of Example 1. Hydrogen-bonded azobenzene-based second-order nonlinear optical organic materials. It is indicated that the directional arrangement of molecules under the action of hydrogen bonds by introducing hydrogen-bonded groups into the molecules is the key to endow the linear hydrogen-bonded azobenzene crystals prepared by the present invention to obtain good second-order nonlinear optical properties.

Claims (3)

1. the application of a linear hydrogen-bonded azobenzene crystal as a second-order nonlinear optical organic material, is characterized in that: the crystal is ( Z )-2-(4-aminophenyl)-1-phenyldicarbonate Nitriene-2-oxide, whose molecular formula is C ₁₂ H ₁₁ N ₃ O, belongs to orthorhombic crystal system, space group is Pca 2 ₁ , and unit cell parameters are a = 17.8186(9) Å, b = 5.5378(3) Å, c = 10.6729(6) Å, α = β = γ = 90 ^° , Z = 4, V = 1053.16(10) Å ³ , containing hydrogen-bonding interaction chains along the crystallographic c -axis. 2 . The application according to claim 1 , wherein the crystal molecules are in a trans-azobenzene conformation, and adjacent crystal molecules are connected by N-H...O hydrogen bonding to form a one-dimensional hydrogen bonding chain. 3 . 3 . The application according to claim 1 , wherein the second-order nonlinear optical organic material is used to prepare laser frequency doubling conversion, electro-optic modulators, Q switches and shutter components for high-speed photography. 4 .

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