Tetranuclear beta-ketimine zinc complex and synthesis method and application thereof

Abstract

The application belongs to the field of metal complex catalyst preparation and application, and discloses a kind of tetranuclear β Zinc ketimine complex and synthesis method and application.Tetranuclear β Zinc ketimine complex is applied to catalyze caprolactone ring-opening polymerization, and tetranuclear β Zinc ketimine complex is used as catalyst, caprolactone is used as raw material, under the protection of waterless, oxygenless and inert gas, 110 ℃ bulk polymerization, without solvent and cocatalyst participation, can catalyze caprolactone ring-opening polymerization to prepare polycaprolactone.The catalyst is low toxic, the preparation method is simple, the structure is novel, has good catalytic activity to caprolactone polymerization, the catalyst consumption is low in the catalytic process, and the molecular weight of obtained polymer is high (83893~130186 g / mol).

Description

Technical Field

[0001] This invention belongs to the field of metal complex catalyst preparation and application, specifically involving tetranuclear catalysts. β - Ketoimine zinc complexes, their synthesis methods, and their application in catalyzing the ring-opening polymerization of caprolactone. Background Technology

[0002] The pervasive use of plastics in modern life has led to an exponential increase in their production, triggering significant challenges related to energy, the environment, and climate change. The transition from current petroleum-based plastics to sustainable alternatives is a crucial and challenging task for modern society. Biodegradable polymers derived from renewable resources, such as polycaprolactone (PCL) and its copolymers, offer a viable approach to addressing these issues. PCL is a widely used aliphatic polyester with a degree of crystallinity, making it easy to mold at lower temperatures. Due to its biodegradability, biocompatibility, and excellent thermomechanical properties, it has been applied in packaging, electronics, and biomedicine, including absorbable sutures to reduce scarring, orthopedic fixation devices to avoid secondary removal surgeries, drug delivery carriers for controlled release, and tissue-engineered scaffolds to support cell infiltration and tissue integration.

[0003] Polycaprolactone (PCL) can have its material properties and degradation behavior flexibly controlled through synthetic methods. Ring-opening polymerization based on metal complex catalysis is currently the main method for synthesizing PCL. Metal complex catalysts play a crucial role in ring-opening polymerization, exhibiting high activity that enables controllable regulation of polymer molecular weight, precise design of microstructure, and reduction of product dispersion (Ð), thereby modifying the chemical and physical properties of the material. Currently, the industrial production of high molecular weight PCL still relies on the reaction of Sn(Oct)₂ at high temperatures (170-190 °C) under solvent-free conditions. Although Sn(Oct)₂ has been approved by the US FDA, catalyst residues in the polymer cannot be completely removed, and toxic tin metal residues may cause problems such as cell inflammation. Therefore, developing metal complex catalysts with low toxicity, high catalytic activity, and low cost to achieve a green and environmentally friendly process for the production of PCL is of great significance. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a quad-core processor. β - Ketoimine zinc complexes, their synthesis methods and applications, with tetranuclear... β Using zinc ketimine complex as a catalyst, polycaprolactone was prepared by bulk ring-opening polymerization of caprolactone at 110 °C under anhydrous, oxygen-free, and inert gas protection, without the need for solvents or co-catalysts.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution: Quad-core βThe preparation method of the -ketimine zinc complex includes the following steps: Under inert gas protection, diethylzinc is dropped onto a material with a structure of general formula I within a temperature range of 25 ℃ to 50 ℃. β The reaction was completed by stirring in a ketimine ligand solution for 4-6 hours to obtain the tetranuclear ligand. β - Ketoimine zinc complex; the structure of general formula I is as follows: General Formula I Where R is -CH2CH2-, -CH2CH2CH2-, -CH2CH(CH3)-, -( S One of them is )-CH2CH(CH3)-.

[0006] Furthermore, the structure is as described in general formula I. β The molar ratio of ketoimine ligand to ZnEt2 is 1:1~1.6.

[0007] Furthermore, the structure is as described in general formula I. β The solvent in the -ketoimine ligand solution is one of toluene or dichloromethane.

[0008] Furthermore, the solvent in the ZnEt2 solution is one of n-hexane and toluene.

[0009] Furthermore, the inert gas is argon or nitrogen.

[0010] Another objective of this invention is to protect a quad-core... β - Ketoimine zinc complex, the tetranuclear β - Ketoimine zinc complex is obtained through the above tetranuclear... β The zinc ketimine complex was prepared using a method for preparing -CH2CH2-, -CH2CH(CH3)-, or -( S When one of the )-CH2CH(CH3)- is present, it has a structure like that of general formula II: General Formula II When R is -CH2CH2CH2-, it has a structure like that of general formula III: Formula III Another object of the present invention is to protect the quad-core. β Applications of ketoimine zinc complexes.

[0011] Furthermore, the quad-core β Applications of -ketoimine zinc complexes, specifically tetranuclear... β Application of ketoimine zinc complexes in the catalytic ring-opening polymerization of caprolactone.

[0012] The advantages of this invention compared to existing technologies are: this invention develops a novel quad-core... β Preparation methods and applications of -ketimine zinc complexes. (Based on tetranuclear...) β Using a zinc ketimine complex as a catalyst and caprolactone as a raw material, bulk polymerization of caprolactone was carried out at 110 °C under anhydrous, oxygen-free, and inert gas protection. This method catalyzes the ring-opening polymerization of caprolactone to prepare polycaprolactone without the need for solvents or co-catalysts. The catalyst is low in toxicity, the preparation method is simple, the structure is novel, and the catalyst dosage is low during the catalytic process. The reaction rate is fast, and the resulting polymer has a moderate molecular weight distribution and a high molecular weight (83893~130186 g / mol). Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0014] Figure 1 Quad-core β Schematic diagram of the single-crystal molecular structure of zinc ketimine complex of general formula II; Figure 2 Quad-core β A schematic diagram of the single-crystal molecular structure of the zinc ketimine complex of general formula III. Detailed Implementation

[0015] The present invention will be described in detail below with reference to embodiments. However, the following embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention. The experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially. Ligand 1a-1c- S References ( Macromol.Rapid Commun. Synthesis, 2023, 44(3):2200663.)

[0016] The reaction formulas for the following embodiments are: Example 1 Synthesis of 2a: Under argon atmosphere, 1a (0.2 g, 1.16 mmol) was dissolved in dehydrated dichloromethane. Diethylzinc (0.58 mL, 2 M in toluene, 1.16 mmol) was added dropwise to the system. After 4 hours, no bubbles were observed, indicating the reaction was complete, yielding a yellow transparent solution. The solvent was removed by cold trap to obtain a yellow crude complex powder. A mixture of hexane and pentane was added to the system, and the mixture was rapidly cooled to -20 °C, precipitating a yellow powder. The solvent was removed by filtration, and the powder was dried. The solvent was repeatedly concentrated and cooled, and the powder product was collected. The product was characterized by NMR and elemental analysis. Yield: 0.21 g (78%). 1 H NMR (500 MHz, CDCl3) δ 3.98–3.90 (m, 4H, CN(CH2C H 2 O)), 3.80–3.72 (m, 4H, CN(CH2C H 2 O), 3.50–3.39 (m, 4H, CN(C) H 2 CHO)), 3.16–3.06 (m, 4H,CN(C H 2 CHO)), 2.29–2.23 (m, 8H, C(C H 2CH3)), 2.09–2.02 (m, 24H, C H 3 C(O), CN(CH2CH2O)C H 3 ), 1.07–1.00 (m, 12H, C(CH2C H 3 )). 13 C NMR (126 MHz, CDCl3) δ 180.42,172.90, 104.16, 62.31, 51.85, 25.68, 23.46, 17.78, 14.71. Anal. calcd forC 36 H 60 N4O8Zn4·2CH2Cl2: C, 41.18; H, 5.82; N, 5.06. Found: C, 40.91; H, 6.19; N, 5.12. Example 2 Synthesis of 2b: Under argon atmosphere, 1b (0.2 g, 1.08 mmol) was dissolved in dehydrated dichloromethane. Diethylzinc (0.54 mL, 2 M in toluene, 1.08 mmol) was added dropwise to the system. After 4 hours, no bubbles were observed, indicating the reaction was complete, yielding a yellow transparent solution. The solvent was removed by cold trapping to obtain a yellow crude complex powder. A mixture of hexane and pentane was added to the system, and the mixture was rapidly cooled to -20 °C, precipitating a yellow powder. The solvent was removed by filtration, and the powder was dried. The solvent was repeatedly concentrated and cooled, and the powder product was collected. The product was characterized by NMR and elemental analysis. Yield: 0.17 g (65%). 1 H NMR (500 MHz, CDCl3) δ 4.03–3.93 (m, 8H, CN(CH2CH2C H 2 O)), 3.57–3.46 (m, 8H, CN(C H 2 CH2CH2O)), 2.25–2.19 (m, 8H, C(C H 2 CH3), 2.05–2.02 (m, 24H,C) H 3 C(O), CN(CH2CH2CH2O)C H 3 ), 1.97–1.86 (m, 8H, CN(CH2C H 2 CH2O)), 1.02–0.96 (m,12H, C(CH2C H 3 Anal. calcd for C 40 H 68 N4O8Zn4: C, 48.31; H, 6.89; N, 5.63.Found: C, 47.84; H, 6.73; N, 5.58. Example 3 Synthesis of 2c: Under argon atmosphere, 1c (0.2 g, 1.08 mmol) was dissolved in dehydrated dichloromethane. Diethylzinc (0.54 mL, 2 M in toluene, 1.08 mmol) was added dropwise to the system. After 6 hours, no more bubbles were observed, indicating the reaction was complete and a yellow transparent solution was obtained. The solvent was dried using a cold trap to obtain the crude complex. The crude complex was purified by washing with n-hexane to obtain a yellow powder product, which was characterized by NMR and elemental analysis. Yield: 0.23 g (85%).1 HNMR (500 MHz, CDCl3) δ 3.81–2.82 (m, 12H, CN(C H 2 C H (CH3)O)), 2.31–2.20 (m, 8H,C(C H 2 CH3), 2.06–2.00 (m, 24H, C) H 3 C(O), CN(CH2CH(CH3)O)C H 3 ), 1.25–1.11 (m, 12H,CN(CH2CH(C H 3 )O)), 1.03–0.99 (m, 12H, C(CH2C H 3 )). 13 C NMR (126 MHz, CDCl3) δ181.01, 172.49, 104.69, 67.39, 57.19, 25.85, 23.27, 21.49, 17.56, 14.99. Example 4 2c- S Synthesis: Under argon atmosphere, 1c- S (0.2 g, 1.08 mmol) was dissolved in dehydrated dichloromethane. Diethylzinc (0.54 mL, 2 M in toluene, 1.08 mmol) was added dropwise to the system. After 4 hours, no more bubbles were observed, indicating the reaction was complete and a yellow, transparent solution was obtained. The solvent was then removed using a cold trap to obtain a yellow crude complex powder. A mixture of hexane and pentane was added to the system, and the mixture was rapidly cooled to -20 °C, precipitating a yellow powder. The solvent was removed by filtration, and the powder was dried. The solvent was repeatedly concentrated and cooled, and the powder product was collected. The product was characterized by NMR and elemental analysis. Yield: 0.18 g (67%). 1 H NMR (500 MHz, CDCl3) δ 3.92–3.19 (m, 12H, CN(C H 2 C H (CH3)O)),2.29–2.22 (m, 8H, C(C H 2 CH3), 2.05–1.97 (m, 24H, C) H 3C(O), CN(CH2CH(CH3)O)C H 3 ),1.39–1.21 (m, 12H, CN(CH2CH(C H 3 )O)), 1.02 (t, J = 7.3 Hz, 12H, C(CH2C H 3 Anal. calcd for C 40 H 68 N4O8Zn4: C, 48.31; H, 6.89; N, 5.63. Found: C, 48.29; H, 6.89; N, 5.59. Example 5 Quad-core β A method for catalyzing the ring-opening polymerization of caprolactone using a zinc ketimine complex at 110 °C with a monomer to catalyst molar ratio of 5000:1, the method comprising the following steps: Under argon protection, 0.5 mL (3.61 mmol) of caprolactone was drawn into a Schlenk flask using a syringe and preheated in an IKA at 110°C for approximately 10 min. 2b was then added to the caprolactone mixture, and the mixture was thoroughly stirred. Samples were taken periodically. A small amount of sample was then taken out using a syringe under argon protection. 1 The conversion rate of caprolactone was detected by ¹H NMR (400 MHz, CDCl₃). After the reaction, the stopper was opened and the mixture was exposed to air. It was then cooled in an ice-water bath, and approximately 1 mL of a 5% acetic acid methanol solution was added to quench the reaction. The reaction showed that 98% monomer conversion was achieved within 12 s of catalysis. A small amount (1-2 mL) of CH₂Cl₂ was added to fully dissolve the mixture, followed by the addition of a large amount of cold methanol solution (-18 °C) while vigorous stirring to allow the polymer to settle completely. The crude polymer was repeatedly washed with cold methanol solution using a vacuum filtration device, and the residual solvent was removed at high temperature using an oil pump to obtain the pure polymer. GPC analysis revealed the polymer molecular weight (Mn) to be 130186 g / mol and its molecular weight distribution... Ð = 2.176.

[0017] Example 6 Quad-core β - A method for catalytic ring-opening polymerization of caprolactone using zinc ketimine complex 2a at a monomer to catalyst molar ratio of 10000:1, the method being the same as in Example 5. The differences from Example 5 are: catalytic reaction time t = 65 s, monomer conversion conv. = 68%, polymer molecular weight Mn = 76560 g / mol, and polymer molecular weight distribution.Ð = 1.603.

[0018] Example 7 Quad-core β - A method for catalytic ring-opening polymerization of caprolactone using zinc ketimine complex 2c at a monomer to catalyst molar ratio of 10000:1, the method being the same as in Example 5. The differences from Example 5 are: catalytic reaction time t = 200 s, monomer conversion conv. = 63%, polymer molecular weight Mn = 100167 g / mol, and polymer molecular weight distribution. Ð = 1.568.

[0019] Example 8 Quad-core β -Ketoimine zinc complex 2c- S The method for catalytic ring-opening polymerization of caprolactone under a monomer to catalyst molar ratio of 10000:1 is the same as in Example 5. The differences from Example 5 are: catalytic reaction time t = 233 s, monomer conversion conv. = 94%, polymer molecular weight Mn = 83893 g / mol, and polymer molecular weight distribution. Ð =1.987.

[0020] The above embodiment has four cores. β -Ketoimine zinc complexes 2a, 2b, 2c, 2c- S Table 1 shows the test data for the preparation of polycaprolactone by catalytic ring-opening polymerization of caprolactone.

[0021] Table 1 Quad-core β Data table of caprolactone ring-opening polymerization catalyzed by zinc ketimine complex. Note: 1 Monomer conversion rate through 1 H NMR spectroscopy determination.

[0022] 2 The molecular weight was determined by gel permeation chromatography (GPC) using polystyrene as a standard and tetrahydrofuran as the eluent.

[0023] 3 The formula for calculating the conversion frequency (TOF) is: TOF = conversion × ([M]:[Cat]) / time.

[0024] As shown in Table 1, the quad-core prepared by this invention... βThe zinc ketimine complex catalyzes the polymerization of caprolactone at 110 °C with a monomer conversion rate of 63%–98%, yielding polycaprolactone with a number-average molecular weight of 76,560–130,186 g / mol. Complex 2c, in particular, can produce polycaprolactone with a molecular weight as high as 100,000 under low catalyst dosage conditions, and exhibits a relatively low molecular weight distribution. Compared with existing methods for catalytic polymerization of caprolactone to prepare polycaprolactone, this invention significantly improves polymerization rate, monomer conversion rate, and polymer molecular weight. Furthermore, the tetranuclear polymer prepared in this invention… β - Ketoimine zinc complexes can catalyze without the participation of a co-catalyst. The catalyst preparation method is simple, the structure is novel, and zinc metal is non-toxic. It still has high catalytic activity under the condition of low catalyst dosage (monomer to catalyst molar ratio of 10000:1) and can catalyze the production of polymers with higher molecular weights.

[0025] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. Quad-core β A method for preparing -ketimine zinc complexes, characterized in that the step include: Under inert gas protection, diethylzinc is dropped onto a material with a structure of general formula I within a temperature range of 25 ℃ to 50 ℃. β The reaction was completed by stirring in a ketimine ligand solution for 4-6 hours to obtain the tetranuclear ligand. β - Ketoimine zinc complex; the structure of general formula I is as follows: General Formula I Where R is -CH2CH2-, -CH2CH2CH2-, -CH2CH(CH3)-, -( S One of them is )-CH2CH(CH3)-.

2. The quad-core according to claim 1 β The method for preparing the -ketoimine zinc complex is characterized by... The structure is as described in general formula I. β The molar ratio of ketoimine ligand to ZnEt2 is 1:1~1.

6.

3. The quad-core according to claim 1 β The method for preparing the -ketoimine zinc complex is characterized by... The structure is as described in general formula I. β The solvent in the -ketoimine ligand solution is one of toluene or dichloromethane.

4. The quad-core according to claim 1 β The method for preparing the -ketoimine zinc complex is characterized by... The solvent in the ZnEt2 solution is either hexane or toluene.

5. The quad-core according to claim 1 β The method for preparing the -ketoimine zinc complex is characterized by... The inert gas is argon or nitrogen.

6. A quad-core β - Ketoimine zinc complex, characterized in that The quad-core as described in claim 1 β The tetranuclear ketimine zinc complex was prepared by a specific method. β - Ketoimine zinc complexes have structures like those of general formula II: General Formula II Where R = -CH2CH2-, -CH2CH(CH3)-, -( S One of them is )-CH2CH(CH3)-.

7. A quad-core β - Ketoimine zinc complex, characterized in that The quad-core as described in claim 1 β The tetranuclear zinc ketimine complex was prepared by a method for preparing -ketoimine zinc complexes, wherein R in general formula I is -CH2CH2CH2-, and the tetranuclear... β - Ketoimine zinc complexes have structures like those of general formula III: General Formula III.

8. Quad-core β The application of -ketoimine zinc complexes, the tetranuclear β The structure of the -ketoimine zinc complex is as described in claim 6 or 7.

9. The quad-core according to claim 8 β The application of -ketoimine zinc complexes is characterized by... Specifically, it is a quad-core processor. β Application of ketoimine zinc complexes in the catalytic ring-opening polymerization of caprolactone.

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