A photo-regulatable azobenzene group-modified palladium catalyst and its preparation method and use

Abstract

The invention discloses a palladium catalyst modified by azobenzene group that can be light-regulated and its preparation method and use, and its preparation method comprises the following steps: under nitrogen atmosphere, reagent A and tetrahydrofuran are added to borane tetrahydrofuran at 30 DEG C, react for 3h, add water to quench the reaction, dry, remove the solvent in vacuo to obtain reagent B; methanol and concentrated hydrochloric acid are added to reagent B, react overnight, dry, remove the solvent in vacuo to obtain reagent C, add diethylamine to reflux to obtain reagent D; methyl red, 1-hydroxybenzotriazole, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, dichloromethane are added to reagent D respectively, 3h post-processing vacuum removes the solvent, and bisphosphine ligands can be obtained by column chromatography; bisphosphine ligands are mixed with reagent G to obtain the palladium catalyst modified by azobenzene group that can be light-regulated. The palladium catalyst modified by the azobenzene group prepared by the present invention is simple to synthesize, is not harsh on experimental conditions, and is easy to react.

Description

Technical Field

[0001] The invention relates to the field of chiral initiation systems and active controllable polymerization reactions, and in particular to a photo-regulatable azobenzene group-modified palladium catalyst, a preparation method and use thereof. Background Art

[0002] Polyisocyanide is one of the earliest discovered polymers with a stable helical conformation. It has stable properties, readily available monomers, simple polymerization methods, and can maintain a good helical structure in both solution and solid state, making it a very meaningful synthetic polymer. Polyisocyanide is a polymer with a stable helical conformation, which has important research significance and application prospects in the fields of chiral molecule recognition, asymmetric catalysis, enantiomer separation, drug carriers, liquid crystal display, etc.

[0003] Azobenzene is a photochromic compound that can reversibly undergo photoisomerization, resulting in structural changes. The photochromic properties of azobenzene have been used in various polymers, protein probes and molecular machines. In recent years, azobenzene derivatives as functional elements of photoswitch response have not only been used to synthesize smart polymers, liquid crystal materials, molecular switches and molecular machines, but are also rapidly penetrating into various aspects of chemical and biological system research and analysis. However, the photoisomerization ability of azobenzene in chiral ligands and catalysts has rarely been explored. Among the currently known studies, there are few reports on the use of azobenzene groups in light-regulated polymerization reactions. Summary of the invention

[0004] The purpose of the present invention is to provide a photo-regulatable azobenzene group-modified palladium catalyst and a preparation method and use thereof. The prepared ligand is simple to synthesize, has no strict requirements on experimental conditions, and is easy to react.

[0005] In one aspect of the present invention, the present invention provides a photo-regulatable azobenzene-modified bisphosphine ligand. According to an embodiment of the present invention, the general structural formula is as follows:

[0006]

[0007] In another aspect of the present invention, the present invention provides a method for preparing a photo-controllable azobenzene-modified palladium catalyst. According to an embodiment of the present invention, the method comprises the following steps:

[0008] (1) Under a N2 atmosphere, reagent A and redistilled tetrahydrofuran are stirred at -30°C, and then a borane tetrahydrofuran solution is added. After the reaction is completed, water is added to quench the reaction, and then extraction is performed with ethyl acetate, drying, and vacuum concentration to obtain reagent B;

[0009] (2) Methanol and concentrated hydrochloric acid were added to reagent B, and the reaction was stirred at room temperature overnight. The crude product was washed with saturated NaHCO3 solution and saturated NaCl solution for multiple times, and the separated organic phase was dried over anhydrous sodium sulfate and concentrated in vacuo to obtain reagent C;

[0010] (3) Add diethylamine to reagent C, reflux at 55° C. overnight, and concentrate the reaction product in vacuo to obtain reagent D;

[0011] (4) Under a nitrogen atmosphere, add dichloromethane solvent to methyl red, stir at 0°C, then add 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in sequence, continue stirring and react at 0°C for 1 hour, add reagent D, move to room temperature for reaction, treat the reaction solution after the reaction is completed, remove the solvent in vacuo, and obtain the photo-regulatable azobenzene group-modified bisphosphine ligand by column chromatography.

[0012] The general synthesis reaction formula of the photo-regulatable azobenzene-modified bisphosphine ligand is:

[0013]

[0014] In addition, the method for preparing a photo-regulatable azobenzene-modified bisphosphine ligand according to the above embodiment of the present invention may also have the following additional technical features:

[0015] In some embodiments of the present invention, in step (1), the reagent A is a phosphine ligand, the molar ratio of the reagent A to borane tetrahydrofuran is 1.0:4.0, the reaction time is 2-3h, and the general structural formula of the reagent A is as follows:

[0016]

[0017] In the step (2), the molar ratio of reagent B to methanol and concentrated hydrochloric acid is 1.0:5.0:12.0;

[0018] In the step (3), the molar ratio of reagent C to diethylamine is 1.0:5.0;

[0019] In the step (4), the molar ratio of reagent D to methyl red, 1-hydroxybenzotriazole, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1.0:1.2:0.1:1.2; the reaction solution is treated as follows: washing three times with a saturated NH4Cl solution, combining the organic phases, drying the organic phases with anhydrous Na2SO4 and then filtering, concentrating the filtrate under reduced pressure to obtain a crude product, separating the crude product using column chromatography, and collecting the product; the eluent used in the column chromatography is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the petroleum ether to ethyl acetate is 9:1.

[0020] In another aspect of the present invention, the present invention provides a method for preparing a photo-regulatable azobenzene-modified palladium catalyst.

[0021] According to an embodiment of the present invention, under a nitrogen atmosphere, the photo-regulatable azobenzene-modified bisphosphine ligand, reagent G, and tetrahydrofuran are stirred for reaction at room temperature, and the solvent is removed in vacuo to obtain the photo-regulatable azobenzene-modified palladium catalyst.

[0022] In addition, the method for preparing a photo-regulatable azobenzene-modified palladium catalyst according to the above embodiment of the present invention may also have the following additional technical features:

[0023] In some embodiments of the present invention, the reagent G is a methoxypalladium catalyst, and the molar ratio of the photo-regulatable azobenzene-modified bisphosphine ligand to the reagent G is 1.0:1.0.

[0024] Reagent G is a methoxypalladium catalyst, and the general structural formula is as follows:

[0025]

[0026] In another aspect of the present invention, the present invention provides a method for preparing the photo-regulatable azobenzene-modified palladium catalyst to obtain the photo-regulatable azobenzene-modified palladium catalyst.

[0027] In addition, the photo-controllable azobenzene group-modified palladium catalyst according to the above embodiment of the present invention may also have the following additional technical features:

[0028] In some embodiments of the present invention, the general structural formula is as follows:

[0029]

[0030] The general synthesis reaction formula of the photo-regulatable azobenzene-modified palladium catalyst is:

[0031]

[0032] In another aspect of the present invention, the present invention provides a use of a photo-controllable azobenzene group-modified palladium catalyst. According to an embodiment of the present invention, the photo-controllable azobenzene group-modified palladium catalyst is used to catalyze the polymerization of isonitrile monomers and to control the polymerization of isonitrile monomers under ultraviolet light and visible light.

[0033] In addition, the use of a photo-controllable azobenzene group-modified palladium catalyst according to the above embodiment of the present invention may also have the following additional technical features:

[0034] In some embodiments of the present invention, the steps are specifically included: using reagent F to dissolve the isonitrile monomer and the palladium catalyst modified with an azobenzene group, reacting them under ultraviolet light or visible light at 55°C, respectively, obtaining a reaction mixture after the reaction is completed, adding the reaction mixture to methanol, centrifuging to obtain a yellow solid, washing the obtained product with methanol and then vacuum drying it until the mass remains unchanged to obtain a polyisocyanate polymer.

[0035] In some embodiments of the present invention, reagent F is one or more of tetrahydrofuran, chloroform, and toluene, and the molar ratio of the photo-regulatable azobenzene-modified palladium catalyst to reagent F is 1.0:10.0; the isonitrile monomer is one of isonitrile monomer A-1, isonitrile monomer D-1 or isonitrile monomer L-1, and the molar ratio of the azobenzene-modified palladium catalyst to the isonitrile monomer is 1:20-200.

[0036] The polymerization process and the structure of isonitrile monomer A-1, D-1 or L-1 are as follows:

[0037]

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The photo-regulatable azobenzene group-modified palladium catalyst of the present invention is simple to synthesize, has no strict requirements on experimental conditions, and is easy to react;

[0040] (2) Use azobenzene-modified palladium catalysts for the coordination polymerization of isonitrile monomers and study the effects of ultraviolet and visible light on the polymerization of isonitrile monomers, providing new strategies for photo-regulated polymerization.

[0041] (3) The azobenzene group-modified palladium catalyst of the present invention utilizes the azobenzene group to undergo cis-trans isomerization under ultraviolet light or visible light, thereby changing the steric hindrance of the catalyst and thus changing the catalyst activity. The catalyst activity is reduced under ultraviolet light, while the catalyst activity is not affected under visible light, thereby being able to well control the alternating polymerization of isonitrile monomers under ultraviolet light and visible light. Light-controlled polymerization technology has great application value in the fields of nanotechnology, smart materials, optoelectronic materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the H NMR spectrum of the photo-regulatable azobenzene-modified bisphosphine ligand in Example 1 of the present invention

[0043] Figure 2 This is the ultraviolet change spectrum of the photo-regulatable azobenzene-modified bisphosphine ligand under 365nm ultraviolet light in Example 1 of the present invention;

[0044] Figure 3This is the H NMR spectrum of the photo-regulatable azobenzene group-modified palladium catalyst in Example 2 of the present invention;

[0045] Figure 4 It is the gel permeation chromatogram of the polymer prepared in Example 3 and Example 4 of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example 1

[0048] A method for preparing a photo-regulatable azobenzene-modified bisphosphine ligand comprises the following steps:

[0049] (1) Take 2.0g of reagent A in a 100mL two-necked bottle, replace the reaction system with N2 atmosphere, inject 5mL of redistilled tetrahydrofuran into the reaction bottle with a syringe, place the reaction bottle in a -30℃ ice bath and stir, add 7.0mL of borane tetrahydrofuran solution, use TLC to track the reaction progress, and after about 3h, the raw material reaction is complete and the reaction is stopped. Add water to the reaction solution to quench the reaction, then extract with ethyl acetate, dry, and concentrate in vacuo to obtain reagent B, which is directly used for the next step. The general structural formula of the reagent A is as follows:

[0050]

[0051] (2) Reagent B, 10 mL of methanol, and 25 mL of concentrated hydrochloric acid were added to a 100 mL round-bottom flask, and the mixture was stirred and reacted overnight at room temperature. The crude product was washed with a saturated NaCl solution for several times, and the separated organic phase was dried over anhydrous sodium sulfate and concentrated in vacuo to obtain reagent C.

[0052] (3) Reagent C and 15 mL of diethylamine were added to a 100 mL round-bottom flask and refluxed at 55 °C overnight. The reaction product was concentrated in vacuo to obtain reagent D, which was used directly in the next step.

[0053] (4) Methyl Red was added to a 100 mL round-bottom flask, nitrogen was replaced, 30 mL of dichloromethane was added, and the mixture was stirred at 0° C. 1-hydroxybenzotriazole (HOBt) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) were added in sequence, and the mixture was stirred at 0° C. for 1 h. Reagent D was added, and the mixture was moved to room temperature for reaction. The reaction progress was tracked by TLC. The reaction mixture was washed three times with saturated NH4Cl solution, and the organic phases were combined. The organic phases were dried over anhydrous Na2SO4 and then filtered. The filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was separated by column chromatography, and the product was collected and dried by an oil pump to obtain 950 mg of a red solid, which was the photo-regulatable azobenzene-modified bisphosphine ligand, with a yield of 70%.

[0054] The structural formula of the photo-regulatable azobenzene-modified bisphosphine ligand is shown below:

[0055]

[0056] Figure 1 This is the H NMR spectrum of the azobenzene group-modified bisphosphine ligand prepared in this example. By identifying the signal peak, it is determined that the structure of the prepared product is correct.

[0057] Figure 2 This is the ultraviolet change spectrum of the photo-regulatable azobenzene-modified bisphosphine ligand under 365nm ultraviolet light in an embodiment of the present invention. Through the identification of the absorption peaks, it was found that it has ultraviolet absorption peaks at 426nm and 335nm, and under 365nm ultraviolet light irradiation, the absorption peak at 426nm decreases, and the absorption peak at 335nm increases. It is judged that the molecule can undergo cis-trans isomerization changes under 365nm ultraviolet light.

[0058] Example 2

[0059] A method for preparing a photo-regulatable azobenzene-modified palladium catalyst comprises the following steps:

[0060] Under a nitrogen atmosphere, the photo-regulatable azobenzene group-modified bisphosphine ligand prepared in Example 1, reagent G, and tetrahydrofuran were stirred at room temperature for reaction, and the solvent was removed in vacuo to obtain the photo-regulatable azobenzene group-modified palladium catalyst. Among them, reagent G is a methoxy palladium catalyst, and the general structural formula is as follows:

[0061]

[0062] The general structure of the photo-regulatable azobenzene-modified palladium catalyst is as follows:

[0063]

[0064] Figure 3This is the H NMR spectrum of the photo-regulatable azobenzene group-modified palladium catalyst in the embodiment of the present invention. By identifying the signal peak, it is determined that the structure of the prepared product is correct.

[0065] Example 3

[0066] Weigh an appropriate amount of a photo-regulatable azobenzene group-modified palladium catalyst into a 10 mL polymerization bottle, add tetrahydrofuran to the polymerization bottle to dissolve the catalyst in a water-free and oxygen-free nitrogen environment, stir at room temperature for 2.5 hours under visible light, then dissolve the isonitrile monomer A-1 in chloroform and add it to the catalyst, react under visible light at 55°C, after the reaction is completed, add the reaction mixture into methanol, centrifuge to obtain a yellow solid, wash the obtained product with methanol, and vacuum dry until the mass remains unchanged to obtain the polyisocyanate polymer with a yield of 92%.

[0067] Example 4

[0068] Weigh an appropriate amount of a photo-regulatable azobenzene group-modified palladium catalyst into a 10 mL polymerization bottle, add tetrahydrofuran to the polymerization bottle to dissolve the catalyst in a water-free and oxygen-free nitrogen environment, stir at room temperature for 2.5 h under ultraviolet light, then dissolve the isonitrile monomer A-1 in chloroform and add it to the catalyst, react at 55°C and 365 nm ultraviolet light, after the reaction is completed, add the reaction mixture into methanol, centrifuge to obtain a yellow solid, wash the obtained product with methanol, and vacuum dry until the mass remains unchanged to obtain the polyisocyanate polymer with a yield of 2%.

[0069] Figure 4 This is the gel permeation chromatogram of the polymer prepared in the example of the present invention. Through the identification of signal peaks, it is found that the molecular weight of the polymer during visible light polymerization is larger and the yield is higher; while the molecular weight of the polymer during polymerization under 365nm ultraviolet light is smaller and the yield is lower. It is judged that ultraviolet light can reduce the activity of the catalyst, while the catalyst activity is not affected under visible light, thereby achieving the purpose of light-regulated polymerization.

[0070] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A photo-regulatable azobenzene-modified bisphosphine ligand, characterized in that: The general structure is as follows:

2. A method for preparing a photo-controllable azobenzene-modified bisphosphine ligand according to claim 1, characterized in that: The method comprises the following steps: (1) Under a N2 atmosphere, reagent A and redistilled tetrahydrofuran are stirred at -30°C, and then a borane tetrahydrofuran solution is added. After the reaction is completed, water is added to quench the reaction, and then extraction is performed with ethyl acetate, drying, and vacuum concentration to obtain reagent B; Wherein, the general structural formula of the reagent A is as follows: (2) Methanol and concentrated hydrochloric acid were added to reagent B, and the reaction was stirred at room temperature overnight. The crude product was washed with saturated NaHCO3 solution and saturated NaCl solution for multiple times, and the separated organic phase was dried over anhydrous sodium sulfate and concentrated in vacuo to obtain reagent C; (3) Add diethylamine to reagent C, reflux at 55° C. overnight, and concentrate the reaction product in vacuo to obtain reagent D; (4) Under a nitrogen atmosphere, add dichloromethane solvent to methyl red, stir at 0°C, then add 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in sequence, continue stirring and react at 0°C for 1 hour, add reagent D, move to room temperature for reaction, treat the reaction solution after the reaction is completed, remove the solvent in vacuo, and obtain the photo-regulatable azobenzene group-modified bisphosphine ligand by column chromatography.

3. The method for preparing a photo-regulatable azobenzene-modified bisphosphine ligand according to claim 2, characterized in that: In the step (1), the molar ratio of reagent A to borane tetrahydrofuran is 1.0:4.0, and the reaction time is 2-3h; In the step (2), the molar ratio of reagent B to methanol and concentrated hydrochloric acid is 1.0:5.0:12.0; In the step (3), the molar ratio of reagent C to diethylamine is 1.0:5.0; In the step (4), the molar ratio of reagent D to methyl red, 1-hydroxybenzotriazole, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1.0:1.2:0.1:1.2; the reaction solution is treated as follows: washing three times with a saturated NH4Cl solution, combining the organic phases, drying the organic phases with anhydrous Na2SO4 and then filtering, concentrating the filtrate under reduced pressure to obtain a crude product, separating the crude product using column chromatography, and collecting the product; the eluent used in the column chromatography is a mixture of petroleum ether and ethyl acetate, and the volume ratio of the petroleum ether to ethyl acetate is 9:

1.

4. A method for preparing a photo-regulatable azobenzene-modified palladium catalyst, characterized in that: Under a nitrogen atmosphere, the photo-regulatable azobenzene group-modified bisphosphine ligand according to claim 1, reagent G, and tetrahydrofuran are stirred at room temperature for reaction, and the solvent is removed in vacuo to obtain the photo-regulatable azobenzene group-modified palladium catalyst, wherein the reagent G is a methoxypalladium catalyst, and its general structural formula is as follows:

5. The method for preparing a photo-regulatable azobenzene-modified palladium catalyst according to claim 4, characterized in that: The molar ratio of the photo-regulatable azobenzene-modified bisphosphine ligand to the reagent G is 1.0:1.

0.

6. A photo-controllable azobenzene-modified palladium catalyst prepared according to the method for preparing a photo-controllable azobenzene-modified palladium catalyst according to claim 4.

7. A photo-controllable azobenzene-modified palladium catalyst according to claim 6, characterized in that: The general structure is as follows:

8. Use of the photo-controllable azobenzene-modified palladium catalyst according to claim 6, characterized in that: The photo-regulatable azobenzene group-modified palladium catalyst is used for catalyzing the polymerization of isonitrile monomers and regulating the polymerization of isonitrile monomers under ultraviolet light and visible light.

9. The use of a photo-controllable azobenzene group-modified palladium catalyst according to claim 8, characterized in that: The specific steps include: Reagent F is used to dissolve an isonitrile monomer and a palladium catalyst modified with a photo-regulatable azobenzene group, and the reaction is carried out under ultraviolet light or visible light at 55°C. After the reaction is completed, a reaction mixture is obtained, the reaction mixture is added into methanol, and a yellow solid is obtained by centrifugation. The obtained product is washed with methanol and then vacuum dried until the mass remains unchanged to obtain a polyisocyanate polymer, wherein the reagent F is one or more of tetrahydrofuran, chloroform, and toluene.

10. The use of a photo-controllable azobenzene group-modified palladium catalyst according to claim 9, characterized in that: The molar ratio of the photo-regulatable azobenzene group-modified palladium catalyst to the reagent F is 1:20-200; the isonitrile monomer is one of isonitrile monomer A-1, isonitrile monomer D-1 or isonitrile monomer L-1.

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