Novel photo-responsive eutectic solvent and preparation method thereof

Abstract

The invention belongs to the technical field of eutectic solvents, and discloses a novel photo-responsive eutectic solvent and a preparation method thereof.The novel photo-responsive eutectic solvent is composed of an azobenzene compound and a quaternary ammonium salt compound, the molar ratio of the azobenzene compound to the quaternary ammonium salt compound is 1: (0.5-10), the molar ratio of the azobenzene compound to the quaternary ammonium salt compound is 1: (0.5-10), and the molar ratio of the azobenzene compound to the quaternary ammonium salt compound is 1: (0.5-10). The preparation method comprises the following steps: S1, grinding, pulverizing, mixing and heating an azobenzene compound and a quaternary ammonium salt compound to form a homogeneous liquid, and cooling to obtain a viscous liquid; and S2, carrying out vacuum drying on the viscous liquid obtained in the step S1 to obtain the novel photo-responsive eutectic solvent. The preparation method of the novel photo-responsive deep eutectic solvent is simple, reaction conditions are mild, raw materials are easy to obtain and can be recycled, the problem that other additional substances need to be introduced into temperature-responsive, CO2 / N2-adsorptive and pH-responsive deep eutectic solvents to drive responsive DES is solved, and the development requirement of the modern green chemical industry is met.

Description

Technical Field

[0001] The present invention relates to the technical field of deep eutectic solvents, and in particular to a novel photoresponsive deep eutectic solvent and a preparation method thereof. Background Art

[0002] Deep eutectic solvents (DES) are usually composed of a certain stoichiometric ratio of hydrogen bond acceptor quaternary ammonium salt (HBA) and hydrogen bond donor (HBD, such as amines, carboxylic acids and polyols). In recent years, with the gradual deepening of research, various new DES have emerged. - According to the type of hydrogen bond donor, different eutectic solvents are obtained. DES can be roughly divided into four categories: Type I DES (metal halide and choline chloride), Type II DES (water and metal halide and choline chloride), Type III DES (choline chloride and hydrogen bond donor) and Type IV DES (transition metal and urea). Since the synthetic raw materials of DES are very common compounds, they are abundant in source and inexpensive, therefore, DES is expected to achieve large-scale industrial production and is conducive to the development of modern green chemical industry.

[0003] In addition, as a compound similar to ionic liquids, deep eutectic solvents have some advantages of ionic liquids, such as lower vapor pressure, good chemical stability and thermal stability, strong solubility and strong modifiability. However, compared with ionic liquids, deep eutectic solvents are mainly formed by hydrogen bonds between hydrogen bond donors and hydrogen bond acceptors to form a homogeneous system. Its preparation process is simple, the atomic utilization rate is high, the raw material price is low, it is non-toxic and harmless, and it is biodegradable, which is conducive to large-scale production. Responsive deep eutectic solvents are deep eutectic solvents with specific functional groups. These functional groups can undergo reversible changes under external stimuli (such as temperature, pH value changes, etc.), thereby changing their physicochemical properties. This responsiveness makes different stimulus-responsive deep eutectic solvents have potential application value in the fields of smart materials and drug delivery systems. For example, by adjusting the functional groups, the drug release process can be controlled, thereby improving the bioavailability and therapeutic effect of the drug. The emergence of responsive DES has expanded and optimized the application of DES in sample preparation. With its efficient extraction and separation effect, green extraction principle and multifunctional advantages, it has become one of the most potential and valuable research topics in the sample pretreatment process.

[0004] At present, the research on responsive DES mainly focuses on three aspects: (1) CO2 / N2 adsorption. CO2 / N2 has become a recognized trigger for switchable solvents. CO2 / N2 can significantly change the properties of certain switchable materials, including solvents, surfactants, catalysts, polymers, gels, etc. The most attractive advantage of CO2 / N2-driven responsive DES is that it can be recycled. (2) pH responsiveness. By adding appropriate proton donors and deprotonating agents to the solution system containing the analyte and adjusting the pH value of the system, the switching of DES is completed. Without additional equipment, the extraction and separation of the target analyte can be continuously completed in the solution system. (3) Temperature responsiveness. In the hydrophobic DESs system, water is added to form a mixed two-phase system, and the system temperature is changed to drive the formation of a homogeneous system, which is called temperature-responsive DES.

[0005] However, although adding water, changing the pH value of the system or alternately bubbling CO2 / N2 can have a responsive effect on the properties of DES, these three response pathways require the introduction of additional substances to complete the phase change, which may have a negative impact on the analysis of certain specific targets. Summary of the invention

[0006] The present invention aims to provide a new type of light-responsive low eutectic solvent and a preparation method thereof. The preparation method is simple, the reaction conditions are mild, the raw materials are easily available, the product is recyclable, and the problem of temperature responsiveness, CO2 / N2 adsorption and pH responsive low eutectic solvents requiring the introduction of additional substances is solved, which is beneficial to the development needs of the modern green chemical industry.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A novel photoresponsive low eutectic solvent is composed of an azobenzene compound and a quaternary ammonium salt compound, wherein the molar ratio of the azobenzene compound to the quaternary ammonium salt compound is 1:0.5-10.

[0009] Furthermore, the two benzene rings of the azobenzene compound have one or more of H, hydroxyl, carboxyl, sulfonic acid and amino groups; the quaternary ammonium salt compound is one or more of monoquaternary ammonium salt, diquaternary ammonium salt, triquaternary ammonium salt and polyquaternary ammonium salt.

[0010] Furthermore, the azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetraethylammonium chloride.

[0011] Furthermore, the azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetrabutylammonium chloride.

[0012] Furthermore, the azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetrabutylammonium bromide.

[0013] The method for preparing the novel photoresponsive deep eutectic solvent as described in any one of the above items comprises the following steps:

[0014] S1. Grind and crush the azobenzene compound and the quaternary ammonium salt compound in molar ratio, mix them, gradually heat them to form a homogeneous liquid, and then cool them to obtain a viscous liquid;

[0015] S2. The viscous liquid obtained in S1 is vacuum dried to obtain a novel light-responsive low eutectic solvent.

[0016] Furthermore, in S1, the heating time is 30 to 120 minutes, and the heating temperature is 50 to 120°C.

[0017] Furthermore, in S2, the vacuum drying pressure is 10-20 kPa, the vacuum drying temperature is 50-100°C, and the vacuum drying time is 60-300 min.

[0018] The beneficial effects of the technical solution are:

[0019] 1. The present invention uses azobenzene compounds with different substituents on the benzene ring as hydrogen bond donors to form a new type of light-responsive low eutectic solvent with quaternary ammonium salt compounds. The hydrogen bonding effect of azobenzene-type responsive low eutectic solvents is stronger under ultraviolet irradiation. Compared with the three traditional responsive low eutectic solvents, no additional substances need to be introduced to drive DES, which solves the negative impact of the temperature responsiveness, CO2 / N2 adsorption and pH responsiveness of the low eutectic solvents on the solvent due to the need to introduce additional substances;

[0020] 2. The raw materials of the present invention are widely available, low in cost, simple in preparation method, mild in reaction conditions, do not require the use of inorganic acids and alkalis, can be recycled and reused, and will not cause the generation of a large amount of three wastes in the post-treatment process. Therefore, the cost can be greatly reduced and the pollution to the environment can be reduced, which is conducive to the development of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the photoisomerization of azobenzene compounds and quaternary ammonium salt compounds with different substituents on the benzene ring of the present invention after forming DES;

[0022] Figure 2 is the structural formula of 4-((4-hydroxyphenyl)diazenyl)benzoic acid (HBD) of the present invention;

[0023] Figure 3 is the structural formula of tetraethylammonium chloride, tetrabutylammonium chloride and tetrabutylammonium bromide of the present invention;

[0024] In the figure, (a) is the structural formula of tetraethylammonium chloride (TEAC) in Examples 1 and 3, (b) is the structural formula of tetrabutylammonium chloride (TBAC) in Example 2, and (c) is the structural formula of tetrabutylammonium bromide (TBAB) in Example 3;

[0025] Figure 4 In Example 1 of the present invention, HBD 1 HNMR spectrum;

[0026] Figure 5 In Example 1 of the present invention, HBD and TEAC-DES 1 HNMR comparison spectra;

[0027] Figure 6 In Example 2 of the present invention, HBD and TBAC-DES 1 HNMR comparison spectra;

[0028] Figure 7 In Example 3 of the present invention, HBD and TBAB-DES 1 HNMR comparison spectra;

[0029] Figure 8 In Example 2 of the present invention, TBAC-DES was placed under 365nm ultraviolet irradiation for 6 hours. 1 HNMR comparison spectra;

[0030] Fig. 9 In Example 3 of the present invention, TBAB-DES was exposed to 365nm ultraviolet light for 6 hours. 1 HNMR comparison spectra;

[0031] Fig.10 The results of the refractive index change test of TBAC-DES of Example 2 and TBAB-DES of Example 3 were respectively placed under 365nm ultraviolet irradiation;

[0032] Fig.11 The conductivity change test results of TBAC-DES of Example 2 and TBAB-DES of Example 3 were respectively placed under 365nm ultraviolet irradiation;

[0033] Fig.12 This is the result diagram of the photoresponse change of azobenzene (HBD);

[0034] In the figure, (A) shows the photoresponse change of HBD under 365nm light, and (B) shows the photoresponse change of HBD under 440nm light.

[0035] Fig.13The light response change result diagram of TBAB-DES in Example 3;

[0036] In the figure, (C) shows the photoresponse change result of TBAB-DES under 365nm illumination, and (D) shows the photoresponse change result of TBAB-DES under 440nm illumination;

[0037] Fig.14 is the IR spectrum of TBAC-DES in Example 2 of the present invention;

[0038] Fig.15 is the IR spectrum of TBAB-DES in Example 3 of the present invention;

[0039] Fig.16 TG diagram of TBAC-DES in Example 2 of the present invention;

[0040] Fig.17 This is the TG diagram of TBAB-DES in Example 3 of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0042] Example 1

[0043] A new type of photoresponsive deep eutectic solvent is composed of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetraethylammonium chloride, wherein the optimal molar ratio of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetraethylammonium chloride DES is 1:2.

[0044] A method for preparing the novel light-responsive deep eutectic solvent as described above comprises the following steps:

[0045] S1. Weigh the obtained 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetraethylammonium chloride in a molar ratio of 1:1, grind and mix them in a round-bottom flask, gradually heat under stirring, and after obtaining a mixture liquid, cool and observe the changes in the properties of the mixture. If a stable DES cannot be formed, continue to add tetraethylammonium chloride to the round-bottom flask according to the molar ratio, and heat under repeated stirring until a stable DES is formed. It was found that at a molar ratio of 1:1, HBD and HBA became unstable yellow liquids. Gradually increase the amount of quaternary ammonium salt until the molar ratio is 1:2, keep the heating temperature at 60°C and continue heating for 90 minutes to obtain an orange-red viscous liquid that can remain stable;

[0046] S2. The orange-red viscous liquid obtained in S1 was dried at 60° C. for 120 min in a vacuum drying oven at a vacuum pressure of 15 kPa to obtain a novel photoresponsive low eutectic solvent, namely, TEAC-DES photoresponsive low eutectic solvent.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is:

[0049] A new type of photoresponsive deep eutectic solvent is composed of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium chloride, wherein the optimal molar ratio of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium chloride to form DES is 1:3.

[0050] The method for preparing the novel photoresponsive deep eutectic solvent as described above comprises the following steps:

[0051] S1. Weigh the obtained 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium chloride respectively according to the molar ratio of 1:1, grind and mix them in a round-bottom flask, gradually heat under stirring, and after obtaining a mixture liquid, cool and observe the changes in the properties of the mixture. If a stable DES cannot be formed, continue to add tetrabutylammonium chloride to the round-bottom flask according to the molar ratio, and heat under repeated stirring until a stable DES is formed. It was found that at a molar ratio of 1:2, HBD and HBA became unstable yellow liquids. The amount of quaternary ammonium salt was gradually increased until the molar ratio was 1:3, and the orange-red viscous liquid obtained by maintaining the heating temperature at 60°C and heating for 90 minutes could remain stable;

[0052] S2. The orange-red viscous liquid obtained in S1 was dried at 60° C. for 120 min in a vacuum drying oven at a vacuum pressure of 15 kPa to obtain a novel photoresponsive low eutectic solvent, namely, TBAC-DES photoresponsive low eutectic solvent.

[0053] Example 3

[0054] The difference between this embodiment and embodiment 1 is:

[0055] A new type of photoresponsive deep eutectic solvent is composed of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium bromide, wherein the optimal molar ratio of 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium bromide to form DES is 1:3.

[0056] The method for preparing the novel photoresponsive deep eutectic solvent as described above comprises the following steps:

[0057] S1. Weigh the obtained 4-((4-hydroxyphenyl)diazenyl)benzoic acid and tetrabutylammonium bromide in a molar ratio of 1:1, grind and mix them in a round-bottom flask, gradually heat under stirring, and after obtaining a mixture liquid, cool and observe the changes in the properties of the mixture. If a stable DES cannot be formed, continue to add tetrabutylammonium bromide to the round-bottom flask according to the molar ratio, and heat under repeated stirring until a stable DES is formed. It was found that at a molar ratio of 1:2, HBD and HBA became unstable yellow liquids. Gradually increase the amount of quaternary ammonium salt until the molar ratio is 1:3, keep the heating temperature at 60°C and continue heating for 90 minutes to obtain an orange-red viscous liquid that can remain stable;

[0058] S2. The orange-red viscous liquid obtained in S1 was dried at 60° C. for 120 min in a vacuum drying oven at a vacuum pressure of 15 kPa to obtain a novel photoresponsive low eutectic solvent, namely, TBAB-DES photoresponsive low eutectic solvent.

[0059] The schematic diagram of the photoisomerization of azobenzene compounds and quaternary ammonium salt compounds with different substituents on the benzene ring after forming DES is shown in the figure. Figure 1 As shown;

[0060] In Examples 1 to 3, the structural formula of 4-((4-hydroxyphenyl)diazenyl)benzoic acid (HBD) is as follows Figure 2 As shown, the structural formulas of tetraethylammonium chloride, tetrabutylammonium chloride and tetrabutylammonium bromide are as follows Figure 3 The stable low eutectic solvents obtained in Examples 1, 2 and 3 were dissolved in deuterated dimethyl sulfoxide and subjected to nuclear magnetic resonance hydrogen spectroscopy ( 1 HNMR) detection, the results are as follows Figure 4-7 As shown, it can be seen that the "-OH" peak area of ​​the three DESs is reduced. After HBD forms TEAC-DES, the chemical shift of "-OH" increases from 10.455ppm to 11.016ppm, after forming TBAC-DES, the chemical shift of "-OH" increases from 10.455ppm to 10.802ppm, and after forming TBAB-DES, the chemical shift of "-OH" increases from 10.455ppm to 10.480ppm. TBAC-DES and TBAB-DES dissolved in deuterated dimethyl sulfoxide light-responsive low eutectic solvents were placed under 365nm ultraviolet irradiation for 6 hours and then subjected to nuclear magnetic resonance hydrogen spectroscopy again ( 1 HNMR) detection, the results are as follows Figure 8-9As shown, it can be seen that the peak area of ​​"-OH" decreases after 365nm illumination for 6 hours, and after illumination, the chemical shift of "-OH" of TBAC-DES (6h) increases from 10.802ppm to 11.233ppm, and the chemical shift of "-OH" of TBAB-DES (6h) increases from 10.480ppm to 10.521ppm. The changes in the chemical shift and peak area of ​​"-OH" before and after illumination prove that the hydrogen bonding effect of DESs is enhanced after 365nm illumination.

[0061] The TBAC-DES low eutectic solvent of Example 2 and the TBAB-DES low eutectic solvent of Example 3 were respectively placed under 365 nm ultraviolet irradiation to detect the refractive index change. The results are as follows: Fig.10 As shown in the figure, after irradiation with 365nm light, the hydrogen bonding effect of DES is stronger, the refractive index of TBAC-DES decreases from 1.4781 to 1.3949, and the refractive index of TBAB-DES decreases from 1.4541 to 1.3813. Under irradiation with 365nm, the refractive index of DESs gradually decreases.

[0062] The TBAC-DES low eutectic solvent of Example 2 and the TBAB-DES low eutectic solvent of Example 3 were respectively placed under 365 nm ultraviolet irradiation to detect the conductivity change. The results are as follows: Fig.11 As shown in the figure, after irradiation with 365nm light, the hydrogen bonding effect of the DES mixture becomes stronger, the refractive index of TBAC-DES decreases from 4.95μS / cm to 4.31μS / cm, and the refractive index of TBAB-DES decreases from 2.38μS / cm to 1.71μS / cm. The conductivity of DESs gradually decreases with the irradiation of 365nm light.

[0063] HBD and the TBAB-DES low eutectic solvent of Example 3 were dissolved in tetrahydrofuran respectively, and the change of photoisomerization rate of azobenzene (HBD) before and after forming DES was investigated. The photoresponse change results are shown in FIG. Figure 12-13 As shown in the figure, the photoisomerization rate of azobenzene before and after forming DESs was compared. It was found that when irradiated at 365 nm, the photoisomerization rate of HBD increased from 5.03×10 -2 s is reduced to 2.32×10 -2 s, when illuminated at 440 nm: the photoisomerization rate of HBD increased from 5.24×10 -2 s increases to 6.4×10 -2 s, proving that the hydrogen bonding effect of DES has a great influence on the photoisomerization rate of azobenzene, and the DES photoisomerization process can be cycled many times;

[0064] 5 mg of the stable deep eutectic solvents obtained in Examples 2 and 3 were weighed and analyzed by infrared spectrum (IR). The results are as follows: Figure 14-15 As shown in the figure, the “-OH” stretching vibration of HBD after forming TBAC-DES increases from 3240 cm -1 Increased to 3394cm -1 ; “-COOH” stretching vibration, at 2661cm -1 , 2542cm -1 The two small peaks of -1 , 2432cm -1 The “C=O” in “-COOH” is 1685cm -1 Increased to 1705cm -1 The bending vibration of the fingerprint region “CH” of HBD is from 1141cm -1 Reduced to 1134cm -1 The “-OH” stretching vibration of HBD after forming TBAB-DES increases from 3240cm -1 Increased to 3396cm -1 ; “-COOH” stretching vibration, at 2661cm -1 , 2542cm -1 The two small peaks of -1 , 2441cm -1 The “C=O” in “-COOH” is 1685cm -1 Increased to 1710cm -1 The bending vibration of the fingerprint region “CH” of HBD is from 1141cm -1 Reduced to 1136cm -1 , proving the existence of hydrogen bond network in DESs.

[0065] 10 mg of the stable low eutectic solvents obtained in Examples 2 and 3 were weighed for thermogravimetric analysis (TG), with the heating rate set at 10°C / min and the maximum temperature set at 600°C. The results are as follows: Figure 16-17 As shown in the figure, the first stage of DESs is the breaking of hydrogen bonds, the second stage is the decomposition of HBA, and the third stage is the decomposition of HBD. Hydrogen bonds are a weak intermolecular force, and when the temperature rises to a certain level, hydrogen bonds will break.

[0066] From the above H NMR spectrum ( 1 The results of HNMR (HNMR) detection, infrared spectrum analysis (IR) and thermogravimetric analysis (TG) show that ultraviolet irradiation can drive changes in the hydrogen bonding effect of the solvent, avoiding the negative effects caused by the introduction of additional substances.

[0067] In summary, the present invention uses azobenzene compounds with different substituents on the benzene ring as hydrogen bond donors to form a new type of light-responsive low eutectic solvent with quaternary ammonium salt compounds. The hydrogen bonding effect of the azobenzene responsive low eutectic solvent is stronger under ultraviolet irradiation. Compared with the traditional three types of responsive low eutectic solvents, no additional additives need to be introduced to drive DES, which solves the problem that the temperature responsiveness, CO2 / N2 adsorption and pH responsiveness of the low eutectic solvents need to introduce additional substances that may have a negative impact on the solvent. The raw material source of the present invention is wide, the cost is low, the preparation method is simple, and the reaction method conditions are mild. It does not require the use of inorganic acids and alkalis, can be recycled and reused, and will not cause the generation of a large amount of three wastes in the post-treatment process. Therefore, it can greatly reduce costs and reduce pollution to the environment, which is conducive to the development of green chemistry.

[0068] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A new type of photoresponsive deep eutectic solvent, characterized in that: The invention is composed of an azobenzene compound and a quaternary ammonium salt compound, wherein the molar ratio of the azobenzene compound to the quaternary ammonium salt compound is 1:0.5-10.

2. The novel photoresponsive deep eutectic solvent according to claim 1, characterized in that: The two benzene rings of the azobenzene compound both have one or more of H, hydroxyl, carboxyl, sulfonic acid and amino groups; the quaternary ammonium salt compound is one or more of monoquaternary ammonium salt, diquaternary ammonium salt, triquaternary ammonium salt and polyquaternary ammonium salt.

3. The novel photoresponsive deep eutectic solvent according to claim 2, characterized in that: The azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetraethylammonium chloride.

4. The novel photoresponsive deep eutectic solvent according to claim 2, characterized in that: The azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetrabutylammonium chloride.

5. The novel photoresponsive deep eutectic solvent according to claim 2, characterized in that: The azobenzene compound is 4-((4-hydroxyphenyl)diazenyl)benzoic acid, and the quaternary ammonium salt compound is tetrabutylammonium bromide.

6. The method for preparing the novel photoresponsive deep eutectic solvent according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Grind and crush the azobenzene compound and the quaternary ammonium salt compound in molar ratio, mix them, gradually heat them to form a homogeneous liquid, and then cool them to obtain a viscous liquid; S2. The viscous liquid obtained in S1 is vacuum dried to obtain a novel light-responsive low eutectic solvent.

7. The method for preparing the novel photoresponsive deep eutectic solvent according to claim 6, characterized in that: In S1, the heating time is 30 to 120 minutes, and the heating temperature is 50 to 120°C.

8. The method for preparing the novel photoresponsive deep eutectic solvent according to claim 6, characterized in that: In S2, the vacuum drying pressure is 10-20 kPa, the vacuum drying temperature is 50-100° C., and the vacuum drying time is 60-300 min.

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