A viologen coordination compound crystal and preparation method thereof

Abstract

A viologen coordination compound crystal and a preparation method thereof, wherein the structural formula of the crystal is shown in formula (I): wherein BTC is pyromellitic acid. The present invention uses viologen molecules (Bcnbpy·2Cl) as a guest and the oxygen atom of the carboxyl group of pyromellitic acid as an electron donor to provide a multifunctional color-changing material that can respond to ultraviolet light and blue light and also has an organic amine-induced color-changing function. The preparation method of the present invention has non-toxic raw materials, a simple method, no pollutant emissions, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to a novel viologen color-changing crystalline material and a preparation method thereof, in particular to a coordination compound material synthesized based on electron transfer between viologen ligands and electron donor molecules. Background Art

[0002] In recent years, the storage of chemical information in molecules, detection at the molecular level, and conversion into analyzable and detectable signals have attracted increasing research interest. Chemical information analytical sensing materials can detect and identify analytes through color changes, fluorescence properties, photosensitivity, and conductivity. However, some analytes, such as explosives, chemicals, toxic or corrosive gases, radioactive and biologically active agents, can still cause serious damage to human skin and respiratory system at low concentrations. In order to avoid and prevent their potential or actual harm to humans, these substances should be identified or detected at the lowest possible concentration. Based on the actual situation and the problems we face, cationic coordination polymer materials and two-dimensional and three-dimensional metal organic framework materials have entered our sight. These materials generally have pores of a certain size, which are formed by connecting metal centers and organic linking ligands, and have cationic sites. Due to the special and novel structural characteristics of these materials, as well as their excellent reversibility and recyclability in the detection process, they are synthesized and studied by more and more researchers. Cationic coordination polymers are materials with excellent sensing and detection properties. They can identify and detect analytes stored inside compounds through fluorescence detection or color changes of materials. This ability is mainly based on the role played by the functional units provided by organic ligands. In recent years, based on some organic ligands with color-changing properties, such as piperazines, diarylethenes and viologen cations, the synthesized coordination polymers or metal organic frameworks have been increasingly used in light, electricity and thermochemistry. Organic ligands have a real impact on the properties of the complexes, especially as the introduction of functional units or sites, which is decisive for the functionality and potential applications of the synthesized compounds. Therefore, the solubility, stability and functionality of organic ligands are the focus of researchers.

[0003] Viologen cationic ligands / 4,4-bipyridine derivatives are a class of excellent organic ligands that are electron-deficient and can be regarded as Lewis acids. They have good responses to stimuli such as light, electricity, heat, pressure and X-rays and undergo corresponding color changes. In recent reports, viologen cationic ligands, as organic linking media and transition metals, rare earth metals and polyionic metal oxyacids (POM), have been increasingly studied in the field of multifunctional detection materials, and can detect and identify hazardous analytes through visible color changes or changes in fluorescence intensity.

[0004] Organic amines (methylamine, ethylamine, aniline, triethylamine, etc.) have lone pairs of electrons on the nitrogen atom of the amino group, which can act as electron donors to provide electrons to electron acceptors. Such substances can be regarded as a type of Lewis base. The introduction of viologen organic ligands into metal coordination polymers or polyacid compounds can be used as functional units to encapsulate and identify small molecules of organic amines. However, for most coordination polymers, metal organic frameworks, including polyacid compounds, they play the role of "storage" and "detector". During the detection process, some performance has always troubled researchers. This is because most of these materials have irreversible structural collapse after detection or are only one-time detection and cannot be reused multiple times. These two problems have hindered the development of such materials and their further application, which has substantially questioned and affected the value of such materials. Therefore, in the current work, it is a huge and meaningful challenge to synthesize multifunctional and stable crystalline materials based on viologen that can be detected cyclically. Summary of the invention

[0005] The object of the present invention is to provide a novel viologen color-changing crystalline material and a preparation method thereof. The compound can be used as a multifunctional color-changing material, can respond to ultraviolet light and blue light, and also has an organic amine-induced color-changing function.

[0006] In order to achieve the above object, the present invention includes the following technical solutions:

[0007] A viologen coordination compound crystal, the structural formula of which is shown in formula (I):

[0008] Among them, BTC is pyromellitic acid.

[0009] The viologen coordination compound crystal as described above, preferably, the crystallographic parameters of the crystal are as follows: molecular weight is 674.61, belongs to the triclinic system, space group is P-1, unit cell parameters are: α(°)=72.060(3), β(°)=77.983(3), γ(°)=81.530(3), Z=1.

[0010] On the other hand, the present invention provides a method for preparing the viologen coordination compound crystal as described above, the method comprising the following steps:

[0011] I. Preparation of 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride;

[0012] II. Dissolve pyromellitic acid and 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride in a solution of deionized water and N,N-dimethylformamide at a molar ratio of (1-3):1, and dissolve by stirring; place the dissolved solution in a reaction kettle lined with polytetrafluoroethylene, and synthesize by a solvent thermal method. After maintaining a constant temperature at 80-100°C for 72-120 hours, cool to room temperature, wash with deionized water, and then obtain orange-yellow block crystals, which are viologen coordination compound crystals.

[0013] In the preparation method as described above, preferably, in step II, the volume ratio of water to N,N-dimethylformamide is (1-3):1.

[0014] The preparation method as described above, preferably, comprises the following steps:

[0015] I. Preparation of 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride;

[0016] II. Dissolve pyromellitic acid and 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride in a solution of deionized water and N,N-dimethylformamide at a molar ratio of 2:1, wherein the volume ratio of water to N,N-dimethylformamide is 2:1, and dissolve by stirring; place the dissolved solution in a reaction kettle lined with polytetrafluoroethylene, and synthesize by a solvent thermal method, keep a constant temperature of 90°C for 4 days, cool to room temperature, wash with deionized water, and then obtain orange-yellow block crystals, which are viologen coordination compound crystals.

[0017] In the preparation method described above, preferably, the 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride is prepared by the following method:

[0018] Add 4,4'-bipyridine and 3-chloromethylbenzidine cyanide in a molar ratio of 1:(2-3) to N,N-dimethylformamide, heat and reflux at 100-120°C for 4-8h under the protection of N2 gas, then cool to room temperature, filter to obtain a yellow-white precipitate, wash, dry, and recrystallize in an alcohol solution to obtain 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride.

[0019] In the preparation method described above, preferably, the 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride is prepared by the following method:

[0020] Add 4,4'-bipyridine and 3-chloromethylbenzidine in a molar ratio of 1:(2-3) to N,N-dimethylformamide, heat and reflux at 100-120°C for 4-8h under the protection of N2 gas, then cool to room temperature, filter to obtain a yellow-white precipitate, wash three times with a hot DMF solution, then wash three times with ethanol, and vacuum dry at 70-80°C for 6-8h; recrystallize with a solution of methanol and deionized water in a volume ratio of 1:(1-2) to obtain 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride.

[0021] The 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride (bcnbpy·2C1) used in the present invention is preferably prepared by the following method:

[0022] The method comprises adding 4,4'-bipyridine and 3-chloromethylbenzoic acid in a molar ratio of 1:(2-3) to N,N-dimethylformamide, heating and reflux at a temperature of 110-130° C. for 6-10 minutes under the protection of N2 gas, then cooling to room temperature, filtering to obtain a yellow precipitate, washing it three times with a hot DMF solution, then washing it three times with ethanol, and vacuum drying it at 60-80° C. for 10-15 hours; and recrystallizing it with a methanol and deionized water solution in a volume ratio of 1:(1-2) to obtain a bcnbpy·2Cl viologen compound with high purity.

[0023] The beneficial effects of the present invention are:

[0024] (1) The present invention adopts a simple solvent thermal synthesis method. The viologen ligand, solvent and metal salt used are all non-toxic and harmless. The method is economical and environmentally friendly.

[0025] (2) The viologen coordination compound crystal of the present invention has the property of photochromism, can sense different light sources at extremely low concentrations, and changes color quickly.

[0026] (3) The viologen coordination compound crystal of the present invention can absorb and reflect blue light and ultraviolet light, and can be used as an optical material for protecting against blue light and ultraviolet light.

[0027] (4) The viologen coordination compound crystals of the present invention change color when encountering amine compounds, and change color rapidly at low concentrations, and can be used as a material for adsorbing and detecting amine compounds, for example, to make test strips for detecting amine compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1This is a diagram of the asymmetric structural unit of the compound prepared in Example 1.

[0029] Figure 2 This is the electron transfer diagram of the compound prepared in Example 1.

[0030] Figure 3 This is the UV solid diffuse reflectance image of the compound prepared in Example 1.

[0031] Figure 4 This is the PXRD pattern of the compound prepared in Example 1.

[0032] Figure 5 This is the photoswitchable fluorescence image of the compound prepared in Example 1.

[0033] Figure 6 This is a photochromic photograph of the compound prepared in Example 1.

[0034] Figure 7 a is a photograph of the color change of the crystalline compound in detecting organic amines in Experimental Example 2.

[0035] Figure 7 b is a photograph of the color change of the crystalline compound in experimental example 2 when detecting low concentration of aniline.

[0036] Figure 8 These are photos of the color change of the test paper in Experimental Example 2 in different organic amine vapors. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer, we will describe the technical solutions and tests of the present invention in more detail. Obviously, the described embodiments are only part of the present invention, not all embodiments.

[0038] Example 1 Viologen coordination compound crystal (I)

[0039] 1. Preparation of the viologen compound 1,1-bis(3-cyanobenzyl)-[4,4′-bipyridine]-1,1′-diium chloride (abbreviated as bcnbpy·2Cl)

[0040] 4,4'-bipyridine (1.56g, 10mmol) and 3-chloromethylbenzyl cyanide (3.79g, 25mmol) were added to a 50mL round-bottom flask containing 25mL N,N-dimethylformamide. Under the protection of nitrogen, the mixture was heated to reflux at 110°C for 4-8h, then cooled to 25°C and filtered to obtain a yellow-white precipitate. The precipitate was washed three times with hot DMF solution, then washed three times with ethanol, and vacuum dried at 75°C for 12h. The Bcnbpy·2C1 viologen compound with a high purity was obtained by recrystallization with a methanol and deionized water solution in a volume ratio of 1:1. The hydrogen spectrum and carbon spectrum NMR data are as follows: 1 H-NMR (600MHz, D2o): δ=5.96 (s, 4H), 7.61 (t, J=18Hz, 2H), 7.75 (d, J=6Hz, 2H), 7.82 (d, J=6Hz, 4H), 8.51 (d, J=6Hz, 4H), 9.11 (d, J=6Hz, 4H); 13 C-NMR (600MHz, D2O): δ=63.1, 112.5, 118.2, 127.4, 130.5, 132.9, 133.5, 134.0, 145.8, 190.5.

[0041] 2. Preparation of Viologen Coordination Compound Crystals [(BTC)(bcnbpy)2Cl]·2H2O

[0042] Dissolve pyromellitic acid (50.8 mg, 0.2 mmol) and bcnbpy·2Cl (45.9 mg, 0.1 mmol) in a mixed solution of 2 ml deionized water and 4 ml N, N-dimethylformamide, and dissolve by stirring. Place the dissolved solution in a 20 ml polytetrafluoroethylene liner and synthesize by a solvent thermal method. After being kept at 90° C. for 4 days, cool to room temperature, wash with deionized water, and then obtain orange-yellow block crystals, which are viologen coordination compound crystals, with a yield of 73%.

[0043] 3. Crystal detection

[0044] (1) X-ray single crystal diffraction

[0045] The product obtained in step 2 was analyzed on a Gemini R Ultra diffractometer using the Oxford diffraction method at 296 K and absorption correction using a multi-scan technique with a Mo-Kα ray from a graphite monochromator. Crystal data was collected for the radiation source. Its crystal structure was crystallographically resolved using SHELXTL-2014 and Olex2 programs. Anisotropic refinement was performed on the thermal parameters of all non-hydrogen atoms in the compound, and the positions of hydrogen atoms on the viologen ligands were fixed. The crystallographic parameters were measured as follows: molecular weight is 674.61, belongs to the triclinic system, space group is P-1, unit cell parameters: α(°)=72.060(3), β(°)=77.983(3), γ(°)=81.530(3), Z = 1. Its crystal structure data is shown in Table 1.

[0046] Table 1

[0047]

[0048] Figure 1 is the asymmetric structural unit diagram of the compound, Figure 2 The electron transfer diagram of the compound can be determined as follows:

[0049] BTC is pyromellitic acid (C 10 H208) 4- .

[0050] (2) UV solid diffuse reflection

[0051] Figure 3 This is the UV solid diffuse reflectance diagram of the compound. The test results show that the compound responds quickly to both UV light and blue light, and generates responsive viologen free radicals through photoinduced electron transfer. The color change process is a process of electron transfer, and the structure of the compound has hardly changed.

[0052] (3) Powder X-ray diffraction

[0053] Figure 4 The PXRD diagram of the compound proves the stability of the compound after discoloration under blue light and UV irradiation. It can be seen from the figure that the PXRD of the compound after light irradiation has almost no change, which shows that the color change response of the compound is caused by the generation of free radicals to change the color of the compound, rather than the result of photoisomerization and photodecomposition. This result supports the potential application prospects of this compound in optical materials.

[0054] (4) Light-controlled fluorescence images

[0055] Figure 5This is the photo-controlled fluorescence diagram of the compound. It can be seen from the figure that no matter under the induction of ultraviolet light or blue light, the fluorescence intensity of the compound increases with the irradiation time, the color of the compound changes, and the fluorescence intensity decreases. Moreover, the compound can respond to light quickly, and the fluorescence change occurs within one second. This fast-response material is suitable for application as a photo-controlled fluorescent material.

[0056] Example 2 Viologen coordination compound crystal (II)

[0057] The bcnbpy·2Cl (45.9 mg, 0.1 mmol) prepared in Example 1 and pyromellitic acid (76.2 mg, 0.3 mmol) were dissolved in a mixed solution of 4 ml deionized water and 4 ml N, N-dimethylformamide, and dissolved by stirring. The dissolved solution was placed in a 20 ml polytetrafluoroethylene liner and synthesized by a solvent thermal method. After being kept at 100°C for 5 days, it was cooled to room temperature and washed with deionized water to obtain orange-yellow block crystals, which were viologen coordination compound crystals with a yield of 75%. Elemental analysis C36 H26 N4O10 (%): Theoretical value: C, 64.09; H, 3.85; N, 8.30%. Experimental value: C, 63.88; H, 3.88; N, 8.27%.

[0058] Example 3 Viologen coordination compound crystal (III)

[0059] The pyromellitic acid and bcnbpy·2C1 prepared in Example 1 were dissolved in a mixed solution of deionized water and N,N-dimethylformamide in a volume ratio of 1:1 in a molar ratio of 3:1, and dissolved by stirring. The dissolved solution was placed in a 20ml polytetrafluoroethylene liner and synthesized by a solvent thermal method. After being kept at 100°C for 5 days, it was cooled to room temperature and washed with deionized water to obtain orange-yellow block crystals, which were viologen coordination compound crystals with a yield of 75%. Elemental analysis C36 H26N4010 (%): Theoretical value: C, 64.09; H, 3.85; N, 8.30%. Experimental value: C, 63.62; H, 3.90; N, 8.24%.

[0060] Experimental Example 1 Photochromic Experiment

[0061] The viologen compound crystals prepared in Example 1 were irradiated with a 300W xenon lamp as the light source, and filters of the ultraviolet band 200-400nm and the blue light band 400-480nm were installed respectively for irradiation, the wavelengths of ultraviolet light and blue light respectively covered, and the radiation intensity was 100Lux.

[0062] Photos of the crystal before and after color change Figure 6As shown, the original crystal is orange-yellow. When 200-400nm ultraviolet light is irradiated to the crystal, it turns to medium gray after 5 seconds, and the color recovers 120 minutes after the light source is removed. When 400-480nm blue light is irradiated to the crystal, it turns to camel after 5 seconds, and the color recovers 90 minutes after the light source is removed. After the color returns to the original color, it will change color again when irradiated with the corresponding light source again, which shows that the color change of the compound material is reversible.

[0063] Experimental Example 2 Amine adsorption color change experiment

[0064] 1. Crystal adsorption color change experiment

[0065] Weigh ethylamine, mono-n-propylamine, di-n-propylamine, diethylamine, tert-butylamine, and diisopropylamine to a concentration of 100 mg / m 3 Amine ethanol solution; take aniline and prepare 10M, 1M, 10 -1 M, 10 -2 M, 10 -3 M, 10 -4 Each solution was placed in a beaker, and the amine solution was evaporated by slight heating. The viologen coordination compound crystal prepared in Example 1 was placed on top of the beaker. The adsorption test results are shown in Figure 7 As shown, Figure 7 a is a photo of the color change of crystals in different organic amine vapors when the experiment was carried out for 5 seconds; Figure 7 b is a photo of the color change of the crystal at different aniline concentrations. -4 The crystals can still respond to aniline under the condition of M concentration. In each test, the crystals can return to their original color (cp) about 1-2 minutes after leaving the gas environment.

[0066] 2. Test paper adsorption color change experiment

[0067] Take 0.05g of the viologen coordination compound crystal prepared in Example 1, dissolve it with 5ml of water and 5ml of DM, and ultrasonicate it for 30 minutes. Then add 1g of polystyrene sulfonic acid and stir it evenly. Then add 0.5g of polyethyleneimine and continue stirring until it becomes a pale yellow-white gel. Apply it evenly on the filter paper for 3 times. The total amount of application is 10mg / cm 2 , and dried to obtain a rapid organic amine detection test paper.

[0068] The beaker experiment under the condition of slight heating and evaporation of amines was carried out by the same method as the above crystal adsorption color change experiment. Figure 8 The following is a photo of the color change of the test paper in different organic amine vapors at 5 seconds of the experiment. The test paper can return to its original color (cp) about 1-2 minutes after leaving the gas environment. The color change of the test paper is reversible and can be used repeatedly.

[0069] The above experimental results indicate that the compounds of the present invention are sensitive to primary amines and therefore have potential applications in leak detection and adsorption of toxic gases.

Claims

1. A viologen coordination compound crystal, characterized in that: Its structural formula is shown in formula (I): Among them, BTC is pyromellitic acid; The crystallographic parameters of the crystal are as follows: molecular weight is 674.61, belongs to the triclinic system, space group is P-1, unit cell parameters: α(°)=72.060(3), β(°)=77.983(3), γ(°)=81.530(3), Z=1.

2. The method for preparing the viologen coordination compound crystal according to claim 1, characterized in that: The method comprises the following steps: I. Preparation of 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride; II. Dissolve pyromellitic acid and 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride in a solution of deionized water and N,N-dimethylformamide at a molar ratio of (1 to 3):1, and dissolve by stirring; place the dissolved solution in a reaction kettle lined with polytetrafluoroethylene, and synthesize by a solvent thermal method. After constant temperature at 80 to 100°C for 72 to 120 hours, cool to room temperature, wash with deionized water, and then obtain orange-yellow block crystals, which are viologen coordination compound crystals.

3. The preparation method according to claim 2, characterized in that: The volume ratio of water to N,N-dimethylformamide in step II is (1-3):

1.

4. The preparation method according to claim 2, characterized in that: The method comprises the following steps: I. Preparation of 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride; II. Dissolve pyromellitic acid and 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride in a solution of deionized water and N,N-dimethylformamide at a molar ratio of 2:1, wherein the volume ratio of water to N,N-dimethylformamide is 2:1, and dissolve by stirring; place the dissolved solution in a reaction kettle lined with polytetrafluoroethylene, and synthesize it by a solvent thermal method. After being kept at a constant temperature of 90°C for 4 days, cool it to room temperature, wash it with deionized water, and then obtain orange-yellow block crystals, which are viologen coordination compound crystals.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride is prepared by the following method: Add 4,4'-bipyridine and 3-chloromethylbenzidine cyanide in a molar ratio of 1:(2-3) to N,N-dimethylformamide, heat and reflux at 100-120°C for 4-8h under the protection of N2 gas, then cool to room temperature, filter to obtain a yellow-white precipitate, wash, dry, and recrystallize in an alcohol solution to obtain 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride.

6. The preparation method according to claim 5, characterized in that: The 1,1-bis(3-cyanophenyl)-4,4-bipyridyl dichloride is prepared by the following method: Add 4,4'-bipyridine and 3-chloromethylbenzidine in a molar ratio of 1:(2-3) to N,N-dimethylformamide, heat and reflux at 100-120°C for 4-8h under the protection of N2 gas, then cool to room temperature, filter to obtain a yellow-white precipitate, wash three times with a hot DMF solution, then wash three times with ethanol, and vacuum dry at 70-80°C for 6-8h; recrystallize with a solution of methanol and deionized water in a volume ratio of 1:(1-2) to obtain 1,1-bis(3-cyanophenyl)-4,4-bipyridine dichloride.

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