Low-melting-point dihydroxy heterocyclic onium cyanide-containing ionic liquid and preparation method thereof

Abstract

The invention relates to a low-melting-point dihydroxy heterocyclic onium cyanide-containing ionic liquid and a preparation method thereof, and the main method comprises the following steps: carrying out quaternization reaction on monohydroxy substituted heterocyclic onium and a dihalogenated hydrocarbon structure to obtain corresponding dihalogenated heterocyclic onium salt; furthermore, silver dicyandiamide, tricyanomethanesilver and silver thiocyanate are subjected to anion exchange reaction in a solvent, and the dihydroxyl heterocyclic onium ionic liquid compounds containing different cyanide anions are prepared. A dihydroxyl structure is introduced into a heterocyclic onium structure, cyanide-containing anions with charge delocalization and weak coordination are provided, lattice energy is reduced, and the melting point of a system is reduced through interaction of intermolecular hydrogen bonds; meanwhile, nitrogen-containing cations and cyanide-containing anions are combined to form an ionic liquid compound with high carbon yield. The ionic liquid can be used as an electrolyte solvent / additive, a flame-retardant plasticizer or a cellulose dissolving medium and the like, contains dihydroxyl, and can participate in polymer synthesis as a functional group. The material is mild in preparation process condition, short in reaction period, simple in reaction and few in by-product, and has the advantages of being green and capable of being amplified.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, specifically relating to a low-melting-point dihydroxy heterocyclic onyx cyanide-containing ionic liquid and its preparation method. Background Technology

[0002] Ionic liquids (ILs) are a class of substances that possess characteristics such as low vapor pressure, wide electrochemical and thermal stability windows, good solubility, and ion conductivity. Through programmable combinations of cationic frameworks, anionic types, and side-chain functional groups, ILs have evolved from alternative solvents into mission-specific functional media, widely used in energy, materials processing and interface control, as well as catalysis and separation processes. Among the many cationic types, heterocyclic onions (such as imidazolium, pyridinium, quinolineium, thiazolylium, triazolium, pyrrolidineonium, and pyrazinium) have become the mainstream framework for functionalized ionic liquids due to their stable charge distribution, good interfacial compatibility, and expandable side-chain chemical structures. Achieving synergistic optimization among low melting point, tunable hydrogen bonds, and reactive sites to meet practical application needs is one of the core issues in the design of single-molecule ILs.

[0003] The study of deep eutectic solvents (DES) provides clear insights into the melting point reduction and rheological regulation of liquids (ILs): when strong and multicentric hydrogen bonds and coordination interactions are formed between hydrogen bond acceptors and hydrogen bond donors, accompanied by a certain degree of charge delocalization, the effective activity and lattice energy of each component are significantly reduced, resulting in low-melting-point liquids with melting points far lower than those of the monomers. This principle can be applied to the functionalization design of heterocyclic onium ILs: introducing dihydroxyl groups into the cationic side chain to construct hydrogen bond networks between hydroxyl groups and anions, and between hydroxyl groups themselves, weakens the orderly stacking of cations and anions and the driving force for crystallization; using charge-delocalized, weakly coordinated halogen-free anions can further reduce lattice energy and improve low-temperature fluidity. Compared to halide salts, which tend to lead to strong coulombic pairing and higher melting points, using halogen-free anions with larger volume, high polarizability, or highly delocalized charge and hydrogen bond acceptor capabilities is more conducive to obtaining viscous flow ILs at or near room temperature.

[0004] The cyano structure can be thermally polymerized to form a cross-linked network structure of polytriazine. The cyano-containing anion combines with a nitrogen-containing cation to form a special ionic liquid, which can be used to prepare highly nitrogen-doped carbon materials. Using heterocyclic ononium as the backbone and introducing dihydroxyl side chains, and selecting halogen-free weakly coordinating anions such as dicyandiamide, tricyanomethane, and thiocyanate to provide hydrogen bond acceptors and simultaneously provide the cyano structure for high-temperature polymerization, this functionalized structural design can broaden the innovative applications of heterocyclic ononium ILs with reactive sites and low melting points in the fields of energy, functional material preparation, and catalysis. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-melting-point dihydroxy heterocyclic onyx cyanide-containing ionic liquid compound, thereby preparing a novel low-melting-point ionic liquid compound containing dihydroxyl groups with reactive sites.

[0006] The above-mentioned objective of this invention is achieved by the following technical solution: a low-melting-point dihydroxy heterocyclic onyx cyanide-containing ionic liquid compound, characterized in that: the heterocyclic onyx is imidazolium (Im + ), Pyridium (Py + ), Quinolinetonium (Qn) + ), thiazolyl (Thz) + Triazoline (Tz) + ), Pyrrolidineonium (Pyr + ) and pyrazine (Pyz) + The negative ions are dicyandiamide anions (DCA). - ), Tricyanomethane anion (TCM) - ) and thiocyanate anion (SCN) - The dihydroxy heterocyclic onium ionic liquid compound has the following structure:

[0007]

[0008] Among them, heterocyclic onium Im + ,Py + Qn + ,Thz + Tz + Pyr + Pyz + The structural formula is

[0009] A - Selected from

[0010] R1 and R2 are selected from C1 to C2, respectively. 16 Alkyl groups.

[0011] The present invention achieves the above technical solution by comprising the following steps:

[0012] (a) Quaternization reaction: The hydroxyl-containing heterocyclic compounds shown in formulas (1) to (7) are dissolved in an organic solvent and reacted with the dihalogenated organic compounds of formulas (8) to (10); after the reaction is completed, the mixture is purified to obtain a dihydroxyl-containing haloanion heterocyclic onion liquid compound.

[0013] (b) Anion exchange reaction: The dihydroxyl-containing halide-containing heterocyclic onion ionic liquid obtained in step (a) is subjected to anion exchange reaction with silver dicyandiamide, silver tricyanomethyl and silver thiocyanate as shown in formula (11) to (13) in a solvent to generate silver halide precipitate. The silver halide precipitate is removed by filtration, and the solution is rotary evaporated and dried to obtain a dihydroxyl-containing heterocyclic onion ionic liquid compound containing dicyandiamide, tricyanomethane and thiocyanate anions.

[0014] The structural formulas of compounds (1) to (7) are as follows:

[0015]

[0016] The structural formulas of compounds (8) to (10) are as follows:

[0017]

[0018] The structural formulas of compounds (11) to (13) are as follows:

[0019]

[0020] Among them, R1 and R2 are selected from C1 to C2 respectively. 16 Alkyl groups.

[0021] In the above technical solutions, the (a) quaternization reaction: the molar ratio of the hydroxyl-containing heterocyclic compound to the dihalogenated organic compound is (2-2.2):1.

[0022] In the above technical solutions, (a) the quaternization reaction is carried out in a polar aprotic solvent, such as one or more of acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N,N-dimethylacetamide.

[0023] In the above technical solution, the molar ratio of the reaction of the dihydroxy halogenated anionic heterocyclic onium liquid with silver dicyandiamide, silver tricyanomethyl methyl ether and silver thiocyanate is 1:(2-2.5).

[0024] In the above technical solution, the anion exchange reaction (b) is carried out by a polar solvent selected from one or more of alcohols, nitriles, ketones, and water.

[0025] In the above technical solution, the preparation method of (b) anion exchange reaction of silver dicyandiamide, silver tricyanomethyl, and silver thiocyanate is as follows: the preparation method of silver dicyandiamide, silver tricyanomethyl, and silver thiocyanate is as follows: silver nitrate reacts with sodium dicyandiamide, potassium tricyanomethyl, and potassium thiocyanate in a solvent to generate silver salt precipitates, which are then washed, filtered, and dried to obtain the products.

[0026] In the above technical solutions, in the preparation of (b) anion exchange reaction of silver dicyandiamide, silver tricyanomethyl and silver thiocyanate, the molar ratio of silver nitrate to sodium dicyandiamide, potassium tricyanomethyl and potassium thiocyanate is 1:(1-1.5).

[0027] In the above technical solutions, in the preparation of dicyandiamide silver, tricyanomethyl silver and thiocyanate silver by the anion exchange reaction (b), the solvent is a polar solvent, preferably one or more of water, methanol or ethanol.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) By utilizing the interaction mechanism between components to lower the melting point of deep eutectic solvent (DES), the structure of ionic liquids is designed to prepare novel heterocyclic onium ionic liquid compounds with reactive sites and low melting points, thus broadening the application field of ionic liquid compounds.

[0030] (2) The synthesis method provided by the present invention is simple, has a short reaction cycle, low process cost, and can be further scaled up. Attached Figure Description

[0031] Figure 1 DSC curves of the dihydroxyl-containing heterocyclic onium ionic liquid compounds with different anions prepared in Examples 1-3;

[0032] Figure 2 Thermogravimetric curves of the bihydroxyl-containing heterocyclic onium ionic liquid compounds prepared in Examples 1-3. Detailed Implementation

[0033] To better illustrate the objectives, technical solutions, and advantages of this invention, the technical solutions of this invention will be described in detail below with reference to specific embodiments. This invention can be implemented in different forms and is not to be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make this disclosure thorough and complete, and to fully convey the inventive concept to those skilled in the art. This invention will be defined only by the claims.

[0034] In the technical solution of this application, 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzene dibromide (Br2IL) is a pre-prepared intermediate, which can be prepared according to the following reference examples. All Br2IL used in the following examples were prepared according to the reference examples.

[0035] Reference Example

[0036] Raw materials: 1-(2-hydroxyethyl)imidazole, Shanghai Maclean Biochemical Technology Co., Ltd.; 1,3-di(bromomethyl)benzene, Shanghai Aladdin Biochemical Technology Co., Ltd.; acetonitrile, methanol, Beijing Tongguang Fine Chemical Co., Ltd.

[0037] Preparation of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzene dibromide (Br2IL):

[0038] 9.748 g (0.087 mol) of 1-(2-hydroxyethyl)imidazolium was dissolved in a 100 mL three-necked flask containing acetonitrile. Then, 11.46 g (0.043 mol) of 1,3-di(bromomethyl)benzene was dissolved in 50 mL of acetonitrile and added dropwise to the flask. The mixture was refluxed at 60 °C under nitrogen protection and mechanically stirred for 8 h. A white solid product was retained. The product was dissolved in 8 mL of methanol and precipitated in 160 mL of acetonitrile. Recrystallization twice yielded 13.24 g of white crystalline 1,3-bis[(1-(2-hydroxyethyl)imidazolium-onyl)methyl]benzene dibromosalt (Br2IL), with a yield of 62.8%. The chemical structure of Br2IL is as follows:

[0039]

[0040] Example 1

[0041] Raw materials: Br2IL prepared according to the reference example; silver nitrate (AgNO3), methanol, Beijing Tongguang Fine Chemical Co., Ltd.; sodium dicyandiamide, Shanghai Mairui Chemical Technology Co., Ltd.; distilled water.

[0042] Preparation of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(dicyanamide) salt (DCA2IL):

[0043] (1) Dissolve 6.8g (0.04mol) AgNO3 in 200ml of distilled water and 5.4g (0.06mol) sodium dicyandiamide in 200ml of distilled water. Add the sodium dicyandiamide aqueous solution to the AgNO3 aqueous solution under magnetic stirring. React for 5h under light-protected conditions. Filter, wash with water and dry to obtain silver dicyandiamide (AgDCA) white powder compound.

[0044] (2) 4.197 g (8.6 mmol) of Br2IL was dissolved in a 100 mL methanol single-necked flask. 3 g (17.2 mmol) of AgDCA was added to the Br2IL methanol solution under magnetic stirring. The reaction was carried out for 48 h in the dark. The AgBr precipitate was removed by suction filtration, and the methanol was removed by rotary evaporation and dried to obtain 2.966 g of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(dicyanamide) salt (DCA2IL), with a yield of 75.0%. Figure 1 As shown in the DSC curve, the melting point of the product is -26.7℃; Figure 2 In the thermogravimetric analysis (TGA) curves, the initial decomposition temperature corresponding to a 5 wt% weight loss of the product is 245.8℃, and the char residue corresponding to 800℃ is 32.15%. The chemical structural formula of the product is as follows:

[0045]

[0046] Example 2

[0047] Raw materials: Br2IL prepared according to the reference example; silver nitrate (AgNO3), methanol, Beijing Tongguang Fine Chemical Co., Ltd.; potassium tricyanomethyl, Beijing Mairuida Technology Co., Ltd.; distilled water.

[0048] Preparation of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(tricyanomethyl)salt (TCM2IL):

[0049] (1) Dissolve 6.8g (0.04mol) AgNO3 in 200ml of distilled water and 5.16g (0.045mol) potassium tricyanomethyl in 200ml of distilled water. Add the potassium tricyanomethyl aqueous solution to the AgNO3 aqueous solution under magnetic stirring. React for 5h in the dark, filter, wash with water and dry to obtain silver tricyanomethyl (AgTCM) white powder compound.

[0050] (2) 3.7 g (7.58 mmol) of Br2IL was dissolved in a 100 mL methanol single-necked flask. Under magnetic stirring, 3 g (15.2 mmol) of AgTCM was added to the Br2IL methanol solution. The reaction was carried out in the dark for 48 h. The AgBr precipitate was removed by suction filtration, and the methanol was removed by rotary evaporation and dried to obtain 3.4 g of light brown transparent liquid 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(tricyanomethyl)salt (TCM2IL), with a yield of 88.3%. Figure 1 As shown in the DSC curve, the melting point of the product is -28.2℃; Figure 2 In the thermogravimetric analysis (TGA) curves, the initial decomposition temperature corresponding to a 5 wt% weight loss of the product is 260.2℃, and the char residue corresponding to 800℃ is 41.8%. The chemical structural formula of the product is as follows:

[0051]

[0052] Example 3

[0053] Raw materials: Br2IL prepared according to the reference example; silver nitrate (AgNO3), methanol, Beijing Tongguang Fine Chemical Co., Ltd.; potassium thiocyanate, Beijing Mairuida Technology Co., Ltd.; distilled water.

[0054] Preparation of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(thiocyanate) salt (SCN2IL):

[0055] (1) Dissolve 6.8g (0.04mol) AgNO3 in 200ml of distilled water and 3.88g (0.04mol) potassium thiocyanate in 200ml of distilled water. Add the potassium thiocyanate aqueous solution to the AgNO3 aqueous solution under magnetic stirring. React for 5h under dark conditions. Filter, wash with water and dry to obtain silver thiocyanate (AgSCN) white powder compound.

[0056] (2) 4.42 g (9.05 mmol) of Br2IL was dissolved in a 100 mL methanol single-necked flask. 3 g (18.1 mmol) of AgSCN was added to the Br2IL methanol solution under magnetic stirring. The reaction was carried out for 48 h in the dark. The AgBr precipitate was removed by suction filtration, and the methanol was removed by rotary evaporation and dried to obtain 2.90 g of 1,3-bis[(1-(2-hydroxyethyl)imidazolium)methyl]benzenebis(thiocyanate) salt (SCN2IL) product, with a yield of 67.2%. Figure 1 As shown in the DSC curve, the melting point of the product is -57.1℃; Figure 2 In the thermogravimetric analysis (TGA) curves, the initial decomposition temperature corresponding to a 5 wt% weight loss of the product is 244.2℃, and the char residue corresponding to 800℃ is 22.49%. The chemical structural formula of the product is as follows:

[0057]

[0058] The melting point and thermal stability data of the dihydroxy heterocyclic cyanide-containing ionic liquids prepared in Reference Examples and Examples 1-3 are shown in Table 1:

[0059] Table 1. Melting point and thermal stability test data of dihydroxy heterocyclic cyanide-containing liquids prepared in Reference Examples and Examples 1-3

[0060]

[0061] As shown in Table 1, compared with the higher melting point of Br2IL (128.1℃), the ionic liquids DCA2IL, TCM2IL, and SCN2IL prepared in Examples 1-3 all exhibited lower melting points, corresponding to -26.7℃, -28.2℃, and -57.1℃, respectively. The initial decomposition temperatures corresponding to 5 wt% weight loss were all above 240℃, and the char residue at 800℃ was all above 20%, demonstrating relatively high char-forming properties. This achieved the single-molecule structure design of low-melting-point heterocyclic onium ionic liquids containing reactive sites.

Claims

1. A low-melting-point dihydroxy heterocyclic onyx cyanide-containing ionic liquid compound, characterized in that: The heterocyclic onions are imidazolium (Im + ), Pyridium (Py + ), Quinolinetonium (Qn) + ), thiazolyl (Thz) + Triazoline (Tz) + ), Pyrrolidineonium (Pyr + ) and pyrazine (Pyz) + The negative ions are dicyandiamide anions (DCA). - ), Tricyanomethane anion (TCM) - ) and thiocyanate anion (SCN) - ).

2. The method for preparing the low-melting-point dihydroxy heterocyclic onyx cyanide-containing ionic liquid compound according to claim 1, characterized in that, include: (a) Quaternization reaction: The hydroxyl-containing heterocyclic compounds shown in formulas (1) to (7) are dissolved in an organic solvent and reacted with the dihalogenated organic compounds of formulas (8) to (10); after the reaction is completed, the mixture is purified to obtain a dihydroxyl-containing haloanion heterocyclic onion liquid compound. (b) Anion exchange reaction: The dihydroxyl-containing halide-containing heterocyclic onion ionic liquid obtained in step (a) is subjected to anion exchange reaction with silver dicyandiamide, silver tricyanomethyl and silver thiocyanate as shown in formula (11) to (13) in a solvent to generate silver halide precipitate. The silver halide precipitate is removed by filtration, and the solution is rotary evaporated and dried to obtain a dihydroxyl-containing heterocyclic onion ionic liquid compound containing dicyandiamide, tricyanomethane and thiocyanate anions. The structural formulas of compounds (1) to (7) are as follows: The structural formulas of compounds (8) to (10) are as follows: The structural formulas of compounds (11) to (13) are as follows: R1 and R2 are selected from alkyl groups of C1 to C16, respectively.

3. The preparation method according to claim 2, characterized in that: In the quaternization reaction described in (a), the molar ratio of the hydroxyl-containing heterocyclic compound to the dihalogenated organic compound is (2–2.2):

1.

4. The preparation method according to claim 2, characterized in that: In the quaternization reaction described in (a), the solvent is a polar aprotic solvent, such as one or more of acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N,N-dimethylacetamide.

5. The preparation method according to claim 2, characterized in that: In the anion exchange reaction described in (b), the molar ratio of the dihydroxy halogenated anionic heterocyclic onium liquid to silver dicyandiamide, silver tricyanomethyl methyl ether, and silver thiocyanate is 1:(2-2.5).

6. The preparation method according to claim 2, characterized in that: In the anion exchange reaction described in (b), the solvent is a polar solvent selected from one or more of alcohols, nitriles, ketones, and water.

7. The preparation method according to claim 2, characterized in that: The preparation methods of silver dicyandiamide, silver tricyanomethyl phosphate and silver thiocyanate are as follows: silver nitrate reacts with sodium dicyandiamide, potassium tricyanomethyl phosphate and potassium thiocyanate in solvent to form silver salt precipitates, which are then washed, filtered and dried to obtain the products.

8. The preparation method according to claim 7, characterized in that: The molar ratios of silver nitrate with sodium dicyandiamide, potassium tricyanomethyl, and potassium thiocyanate are 1:(1-1.5).

9. The preparation method according to claim 7, characterized in that: The solvent is a polar solvent, preferably one or more of water, methanol, or ethanol.

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