Symmetrical multi-tooth schiff base trinuclear rare earth complex, preparation method and application
By preparing symmetrical multidentate Schiff base trinuclear rare earth complexes as catalysts, the problems of low catalyst efficiency and poor selectivity in existing technologies have been solved, and the efficient and high-purity cyclic carbonate production of carbon dioxide and epoxide cycloaddition reaction has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI'AN PETROLEUM UNIVERSITY
- Filing Date
- 2024-08-22
- Publication Date
- 2026-06-30
AI Technical Summary
Existing catalysts exhibit low catalytic efficiency and poor selectivity in the cycloaddition reaction of carbon dioxide and epoxides, and the reaction conditions are harsh, leading to the formation of byproducts.
A symmetrical multidentate Schiff base trinuclear rare earth complex was used as a catalyst. An intermediate was generated by reacting 3-amino-2-hydroxyacetophenone with 1,3-diamino-2-propanol. The intermediate was then reacted with o-vanillin and rare earth metal salts to form a multidentate Schiff base trinuclear rare earth complex with a cage-like structure, which was used to catalyze the synthesis of cyclic carbonates from carbon dioxide.
It improves the efficiency and purity of catalytic reactions, reduces the formation of byproducts, has good catalytic activity and selectivity, is suitable for epoxy compounds with different substituents, and achieves efficient utilization of carbon dioxide.
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Figure CN119039327B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of multifunctional new materials technology, specifically to a symmetrical multidentate Schiff base trinuclear rare earth complex, its preparation method, and its application. Background Technology
[0002] The global climate and ecosystem changes caused by greenhouse gas emissions, primarily carbon dioxide (CO2), are receiving widespread attention, with annual global CO2 emissions reaching tens of billions of tons. Controlling CO2 emissions and its recovery, fixation, utilization, and recycling have become serious concerns for countries worldwide. Simultaneously, from a resource utilization perspective, vigorously developing green CO2 utilization technologies, developing a green, high-tech, and fine chemical industry chain, and increasing product added value are of great significance. The rational and efficient utilization of CO2, directly converting it into usable materials, is an important way to reduce carbon dioxide emissions under the dual-carbon context. Converting carbon dioxide molecules into cyclic carbonates through a catalytic process via the cycloaddition reaction of epoxides is an important method for mitigating carbon dioxide emissions from industrial sources and obtaining useful chemical materials. Cyclic carbonates can be used in lithium-ion battery electrolytes, dye additives, and intermediates in fine chemical synthesis, making them a widely applicable and highly valuable organic carbonate. The cycloaddition reaction of carbon dioxide and epoxides, using carbon dioxide and epoxides as raw materials, is carried out under specific temperature, pressure, and catalyst conditions. In this process, using a highly efficient catalyst to improve the reaction conversion rate is crucial for the utilization of carbon dioxide.
[0003] To improve the reactivity of the cycloaddition reaction between carbon dioxide and epoxides, existing technologies have disclosed heterogeneous catalysts, including metal oxides, modified molecular sieves, clays, and polymers. Heterogeneous catalysts are relatively easy to remove from the products, but they suffer from low catalytic activity, low selectivity, long reaction times, and harsh reaction conditions. To achieve the cycloaddition reaction of carbon dioxide and epoxides under milder conditions, existing technologies have developed homogeneous catalysts, such as metal complexes, especially tetradentate Schiff base metal complexes with cobalt or chromium as active centers. These exhibit high catalytic activity under milder reaction conditions, but they have low selectivity, and the cycloaddition reaction products may contain byproducts such as polycarbonate. Therefore, it is necessary to research novel catalysts with high catalytic activity, good selectivity, and reduced production costs. Summary of the Invention
[0004] To address the problems of low catalytic efficiency and poor selectivity in existing technologies, this invention provides a symmetrical multidentate Schiff base trinuclear rare earth complex, its preparation method, and its application.
[0005] To achieve the above objectives, the present invention employs the following technical solution:
[0006] This invention provides a symmetrical multidentate Schiff base trinuclear rare earth complex, the molecular structure of which is as follows: , where R represents a trivalent rare earth ion.
[0007] Furthermore, R is Sc 3+ Y 3+ La 3+ Ce 3+ Pr 3+ 、Nd 3+ Pm 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ Or Lu 3+ .
[0008] The preparation method of the above-mentioned symmetrical multidentate Schiff base trinuclear rare earth complexes includes:
[0009] 3-Amino-2-hydroxyacetophenone was reacted with 1,3-diamino-2-propanol by heating to generate an intermediate;
[0010] The intermediate was reacted with o-vanillin by heating to generate ligand L;
[0011] Ligand L was deprotonated and a rare earth metal salt was added to obtain a trinuclear rare earth complex of a polydentate Schiff base.
[0012] Furthermore, the molecular structural formula of the ligand L is as follows:
[0013] .
[0014] Furthermore, the rare earth metal salt is a rare earth chloride hexahydrate or a rare earth nitrate hexahydrate containing rare earth metal ions.
[0015] Furthermore, in the process of heating 3-amino-2-hydroxyacetophenone and 1,3-diamino-2-propanol to generate an intermediate, the heating temperature is 50℃~70℃, the reaction time is 4~12h, and the molar ratio of 3-amino-2-hydroxyacetophenone to 1,3-diamino-2-propanol is 2:(0.95~1.05).
[0016] Furthermore, in the process of heating the intermediate with o-vanillin to generate ligand L, the heating reaction temperature is 50℃~70℃, the reaction time is 3~6h, and the molar ratio of the intermediate to o-vanillin is 1:(1.95~2.05).
[0017] Furthermore, the molar ratio of the ligand L to the rare earth metal salt is 1:(3-4).
[0018] Such as the application of the above-mentioned symmetrical multidentate Schiff base trinuclear rare earth complexes in the catalytic synthesis of cyclic carbonates from carbon dioxide.
[0019] Furthermore, the application methods of symmetrical multidentate Schiff base trinuclear rare earth complexes in the catalytic synthesis of cyclic carbonates from carbon dioxide include:
[0020] A symmetrical multidentate Schiff base trinuclear rare earth complex and a co-catalyst are added to an epoxide, and carbon dioxide is introduced to react and a cyclic carbonate is obtained; wherein the co-catalyst is tetrabutylammonium bromide.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] This invention discloses a symmetrical multidentate Schiff base trinuclear rare earth complex, the molecular structural formula of which is as follows: In this complex, R represents a trivalent rare earth ion. Its molecular structure shows that the complex molecule consists of three rare earth metal ions and one ligand. Two of the rare earth metal ions form an octagonal configuration with one imine N atom, two phenolic hydroxyl O atoms, two water molecules, one methanol molecule, and two hydroxyl O atoms from the ligand, respectively. The other rare earth metal ion forms an octagonal configuration with two phenolic hydroxyl O atoms, two methoxy O atoms, two water molecules, and two hydroxyl O atoms from the ligand. After coordination, the molecule forms a cage-like structure, encapsulating reactants during the catalytic reaction, reducing side reactions, decreasing byproduct formation, and improving reaction efficiency and purity. Simultaneously, the molecular cage can selectively adsorb and directionally regulate specific types of molecules through the size and chemical properties of its channels, thereby promoting specific reaction pathways. This molecular recognition property can significantly affect the efficiency and selectivity of the catalyst, thus ensuring the catalytic efficiency and selectivity of this complex as a catalyst.
[0023] This invention provides a method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex as described above. The method involves heating 3-amino-2-hydroxyacetophenone with 1,3-diamino-2-propanol to generate an intermediate; reacting this intermediate with o-vanillin to generate ligand L; deprotonating ligand L; and adding a rare earth metal salt to obtain the symmetrical multidentate Schiff base trinuclear rare earth complex. This preparation method is simple and mild, synthesizing the Schiff base ligand in only two steps. This ligand has strong coordination ability and can react with various rare earth metal salts at room temperature to generate trinuclear rare earth complexes, enabling large-scale mass production.
[0024] This invention also provides the application of the aforementioned symmetrical multidentate Schiff base trinuclear rare earth complex in the catalytic synthesis of cyclic carbonates from carbon dioxide. The metal center in the complex, where solvent molecules participate in coordination, serves as a potential catalytic site. When used to catalyze the cycloaddition reaction of CO2 and epoxides, it exhibits high catalytic activity. The catalyst system demonstrates good catalytic activity for epoxides with different substituents, showing good versatility and significant implications for the efficient utilization of carbon dioxide. Attached Figure Description
[0025] Figure 1 This is a crystal structure diagram of a symmetrical multidentate Schiff base trinuclear rare earth complex according to the present invention.
[0026] Figure 2 This is a schematic diagram of the preparation method of a symmetrical multidentate Schiff base trinuclear rare earth complex according to the present invention.
[0027] Figure 3 This is a schematic diagram of the reaction synthesis process of a symmetrical multidentate Schiff base trinuclear rare earth complex according to the present invention.
[0028] Figure 4 The infrared spectrum of ligand L is shown during the synthesis of a symmetrical multidentate Schiff base trinuclear rare earth complex according to the present invention.
[0029] Figure 5 The images show the infrared spectra of the complexes prepared in Examples 1 to 3 of this invention.
[0030] Figure 6 The graphs show the thermal stability analysis of the complexes prepared in Examples 1 to 3 of this invention.
[0031] Figure 7 This is a schematic diagram of the catalytic reaction of the symmetrical multidentate Schiff base trinuclear rare earth complex of the present invention.
[0032] Figure 8 This is an NMR spectrum of the complex Tb3L in Example 1 of the present invention catalyzing the synthesis of cyclic carbonates from carbon dioxide and styrene oxide.
[0033] Figure 9 This is the NMR spectrum of the synthesis of cyclic carbonates from carbon dioxide and allyl glycidyl ether catalyzed by the complex Tb3L in Example 1 of this invention.
[0034] Figure 10 This is the NMR spectrum of the synthesis of cyclic carbonates from carbon dioxide and phenyl glycidyl ether catalyzed by the complex Tb3L in Example 1 of this invention.
[0035] Figure 11 This is the NMR spectrum of the synthesis of cyclic carbonate from carbon dioxide and n-butyl glycidyl ether catalyzed by the complex Tb3L in Example 1 of this invention.
[0036] Figure 12 This is a schematic diagram of the mechanism by which the complex Tb3L catalyzes the synthesis of cyclic carbonates from epoxides in Example 1 of the present invention. Detailed Implementation
[0037] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.
[0038] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.
[0039] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values (including integers and fractions) within those ranges.
[0040] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”
[0041] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.
[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.
[0044] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.
[0045] This invention discloses a symmetrical multidentate Schiff base trinuclear rare earth complex, the molecular structural formula of which is: Wherein, R represents a trivalent rare earth ion. Preferably, R is a Sc 3+ Y 3 + La 3+ Ce 3+ Pr 3+ 、Nd 3+ Pm 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ Or Lu 3+ The only slight differences in the number of free anions and water molecules in the complex molecules formed by different ions are...
[0046] See Figure 1The crystal structure diagram of this symmetrical multidentate Schiff base trinuclear rare earth complex shows that the complex molecule consists of three rare earth metal ions and one ligand. Two of the rare earth metal ions form an eight-coordinate configuration with one imine N atom, two phenolic hydroxyl O atoms, two water molecules, one methanol molecule, and two hydroxyl O atoms from the ligand, respectively. The other rare earth metal ion forms an eight-coordinate configuration with two phenolic hydroxyl O atoms, two methoxy O atoms, two water molecules, and two hydroxyl O atoms from the ligand. After coordination, the molecule forms a cage-like structure, encapsulating reactants during the catalytic reaction, reducing side reactions, decreasing byproduct formation, and improving reaction efficiency and purity. Simultaneously, the molecular cage can selectively adsorb and directionally regulate specific types of molecules through the size and chemical properties of its channels, thereby promoting specific reaction pathways. This molecular recognition property can significantly affect the efficiency and selectivity of the catalyst.
[0047] See Figure 2 and Figure 3 This invention provides a method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex as described above, comprising:
[0048] S1: 3-Amino-2-hydroxyacetophenone is reacted with 1,3-diamino-2-propanol by heating to generate an intermediate, specifically:
[0049] An alcoholic solution of 3-amino-2-hydroxyacetophenone and 1,3-diamino-2-propanol was heated under reflux and stirred at 50°C to 70°C for 4 to 12 hours. The mixture was then filtered to obtain an orange-red powder, which is the intermediate for synthesis. The alcoholic solution was a methanol solution or an ethanol solution, and the molar ratio of 3-amino-2-hydroxyacetophenone to 1,3-diamino-2-propanol was 2:(0.95 to 1.05).
[0050] S2: The intermediate is reacted with o-vanillin by heating to generate ligand L, specifically as follows:
[0051] The intermediate and an alcoholic solution of o-vanillin were heated and stirred under reflux at 50°C to 70°C for 3 to 6 hours to react completely. The mixture was then filtered to obtain a red powder, thus synthesizing ligand L. The alcoholic solution was a methanol solution or an ethanol solution, and the molar ratio of the intermediate to o-vanillin was 1:(1.95 to 2.05).
[0052] S3: Ligand L is deprotonated and a rare earth metal salt is added to obtain a trinuclear rare earth complex of a polydentate Schiff base, specifically:
[0053] Ligand L is uniformly dispersed in the reaction solvent. After deprotonation, rare earth metal salts are added and stirred until the solution is clear. The solution is filtered, and the resulting filtrate is allowed to stand at 15℃–40℃ for 12–72 hours. After filtration and drying, the obtained crystals are symmetrical multidentate Schiff base trinuclear rare earth complexes, denoted as R3L. The rare earth metal salts are hexahydrate rare earth chlorides or hexahydrate rare earth nitrates of rare earth metal ions. The reaction solvent is one or more of methanol, ethanol, and acetonitrile mixed in any proportion. The base used for deprotonation is one or two of sodium hydroxide, triethylamine, potassium hydroxide, and lithium hydroxide.
[0054] The molecular structure of the ligand L is as follows:
[0055] The molar ratio of the ligand L to the rare earth metal salt is 1:(3-4).
[0056] Example 1
[0057] 3.56 g of 3-amino-2-hydroxyacetophenone and 1.06 g of 1,3-diamino-2-propanol were added to 80 mL of methanol solution. After stirring until completely dissolved, the solution was heated under reflux at 70 °C for 12 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 3.43 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 81.76%.
[0058] 3.41 g of the intermediate and 2.91 g of o-vanillin were added to 80 mL of methanol solution. The mixture was heated under reflux at 50 °C and stirred for 6 h to obtain a red solution. The solution was filtered and dried under vacuum to obtain a red powder, i.e., ligand L 5.48 g. The yield was calculated to be 91.00%.
[0059] 0.031 g of ligand L and 0.074 g of TbCl3·6H2O were placed in a beaker, and 4 mL of methanol solution and 4 mL of acetonitrile solution were added. After adding 50 μL of triethylamine and stirring, the solution turned clear yellow. The solution was filtered into a 20 mL sample vial, sealed with plastic wrap with a small hole, and allowed to stand at room temperature for 48 h to obtain yellow cuboid crystals. This crystal belongs to the monoclinic crystal system, space group C2 / c Its unit cell parameters are: a=15.2015(6)Å, b=19.0699(6)Å, c=17.3445(6)Å, α=90°, β=91.0867(18)°, γ=90°, V=5027.1(3)Å. 3 Dc = 1.959 g / cm³ 3 , Z=4, F(000)=2896.0, μ(MoKa)=4.461mm -1GooF = 1.043, crystal size: 0.20mm × 0.15mm × 0.14mm, R1 = 0.0588, wR2 = 0.0687 [I>=2σ(I)]; detailed crystallographic data are shown in Table 1 below:
[0060] Table 1 Crystallographic data of complex Tb3L
[0061]
[0062] Example 2
[0063] 3.59 g of 3-amino-2-hydroxyacetophenone and 1.07 g of 1,3-diamino-2-propanol were added to 80 mL of methanol solution. After the solution was completely dissolved, it was heated under reflux at 65 °C for 12 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 3.62 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 85.58%.
[0064] 3.62 g of the intermediate and 3.09 g of o-vanillin were added to 80 mL of methanol solution. The mixture was heated under reflux at 50 °C and stirred for 6 h to obtain a red solution. The solution was filtered and dried under vacuum to obtain a red powder, i.e., ligand L 5.87 g. The yield was calculated to be 92.63%.
[0065] 0.031 g of ligand L and 0.075 g of DyCl3·6H2O were placed in a beaker, and 4 mL of methanol solution and 4 mL of acetonitrile solution were added. After adding 50 μL of triethylamine and stirring, the solution turned clear yellow. The solution was filtered into a 20 mL sample vial, sealed with plastic wrap with a small hole, and allowed to stand at room temperature for 48 h to obtain yellow cuboid crystals. This crystal belongs to the monoclinic crystal system, space group C2 / c Its unit cell parameters are: a=15.2130(7)Å, b=19.0520(7)Å, c=17.3083(7)Å, α=90°, β=91.1002(18)°, γ=90°, V=5015.7(3)Å. 3 Dc = 1.975 g / cm³ 3 , Z=4, F(000)=2900.0, μ(MoKa)=4.711mm -1 GooF = 1.057, crystal size: 0.15mm × 0.14mm × 0.12mm, R1 = 0.0217, wR2 = 0.0659 [I>=2σ(I)]; detailed crystallographic data are shown in Table 2 below:
[0066] Table 2 Crystallographic data of complex Dy3L
[0067]
[0068] Example 3
[0069] 3.02 g of 3-amino-2-hydroxyacetophenone and 0.91 g of 1,3-diamino-2-propanol were added to 60 mL of methanol solution. After the solution was completely dissolved by stirring, the solution was heated under reflux at 70 °C for 8 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 2.96 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 83.25%.
[0070] 2.96 g of the intermediate and 2.53 g of o-vanillin were added to 60 mL of methanol solution. The mixture was heated under reflux and stirred at 50 °C for 6 h to obtain a red solution. The solution was filtered, vacuum dried, and a red powder, i.e., ligand L, was obtained. The yield was calculated to be 93.55%.
[0071] 0.031 g of ligand L and 0.061 g of YCl3·6H2O were placed in a beaker, and 4 mL of methanol solution and 4 mL of acetonitrile solution were added. After adding 50 μL of triethylamine and stirring, the solution turned clear yellow. The solution was filtered into a 20 mL sample vial, sealed with plastic wrap with a small hole, and allowed to stand at room temperature for 48 h to obtain yellow cuboid crystals. This crystal belongs to the monoclinic crystal system, space group C2 / c Its unit cell parameters are: a=15.2235(6)Å, b=18.9525(6)Å, c=17.2788(6)Å, α=90°, β=91.0539(18)°, γ=90°, V=4993.1(3)Å 3 Dc = 1.685 g / cm³ 3 , Z=4, F(000)=2560.0, μ(MoKa)=3.746mm -1 GooF = 1.054, crystal size: 0.17mm × 0.13mm × 0.12mm, R1 = 0.0383, wR2 = 0.0673 [I>=2σ(I)]; detailed crystallographic data are shown in Table 3 below:
[0072] Table 3 Crystallographic data of complex Y3L
[0073]
[0074] Example 4
[0075] 3.02 g of 3-amino-2-hydroxyacetophenone and 0.90 g of 1,3-diamino-2-propanol were added to 50 mL of methanol solution. After stirring until completely dissolved, the solution was heated under reflux at 70 °C for 8 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 2.99 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 84.13%.
[0076] 2.99 g of the intermediate and 2.55 g of o-vanillin were added to 60 mL of methanol solution. The mixture was heated under reflux at 50 °C and stirred for 6 h to obtain a red solution. The solution was filtered, vacuum dried, and a red powder, i.e., ligand L, was obtained. The yield was calculated to be 95.49%.
[0077] 0.031 g of ligand L and 0.077 g of ErCl3·6H2O were placed in a beaker, and 4 mL of methanol solution and 4 mL of acetonitrile solution were added. After adding 50 μL of triethylamine and stirring, the solution turned clear yellow. The solution was filtered into a 20 mL sample vial, sealed with plastic wrap with a small hole, and allowed to stand at room temperature for 48 h to obtain yellow cuboid crystals. This crystal belongs to the monoclinic crystal system, space group C2 / c Its unit cell parameters are: a=15.2215(7)Å, b=18.9623(7)Å, c=17.2521(7)Å, α=90°, β=91.061(2)°, γ=90°, V=4978.7(4)Å. 3 Dc = 2.024 g / cm³ 3 , Z=4, F(000)=2940.0, μ(MoKa)=5.303mm -1 GooF = 1.029, crystal size: 0.2mm × 0.14mm × 0.12mm, R1 = 0.0234, wR2 = 0.1206 [I>=2σ(I)].
[0078] Example 5
[0079] 3.28 g of 3-amino-2-hydroxyacetophenone and 0.97 g of 1,3-diamino-2-propanol were added to 50 mL of methanol solution. After stirring until completely dissolved, the solution was heated under reflux at 70 °C for 8 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 3.18 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 82.41%.
[0080] 3.18 g of the intermediate and 2.71 g of o-vanillin were added to 60 mL of methanol solution. The mixture was heated under reflux and stirred at 50 °C for 6 h to obtain a red solution. The solution was filtered, vacuum dried, and a red powder, i.e., ligand L, was obtained. The yield was calculated to be 93.29%.
[0081] 0.031 g of ligand L and 0.076 g of YbCl3·6H2O were placed in a beaker, and 4 mL of methanol solution and 4 mL of acetonitrile solution were added. After adding 50 μL of triethylamine and stirring, the solution turned clear yellow. The solution was filtered into a 20 mL sample vial, sealed with plastic wrap with a small hole, and allowed to stand at room temperature for 48 h to obtain yellow cuboid crystals. This crystal belongs to the monoclinic crystal system, space group C2 / cIts unit cell parameters are: a=15.2526(15)Å, b=18.9104(15)Å, c=17.1936(14)Å, α=90°, β=91.313(4)°, γ=90°, V=4957.9(7)Å. 3 Dc = 2.058 g / cm³ 3 , Z=4, F(000)=2976.0, μ(MoKa)=5.904mm -1 GooF = 1.041, crystal size: 0.2mm × 0.14mm × 0.12mm, R1 = 0.064, wR2 = 0.0776 [I>=2σ(I)].
[0082] Example 6
[0083] 3.18 g of 3-amino-2-hydroxyacetophenone and 0.95 g of 1,3-diamino-2-propanol were added to 50 mL of methanol solution. After stirring until completely dissolved, the solution was heated under reflux at 70 °C for 8 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 3.01 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 80.37%.
[0084] 3.01 g of the intermediate and 2.57 g of o-vanillin were added to 60 mL of methanol solution. The mixture was heated under reflux and stirred at 50 °C for 6 h to obtain a red solution. The solution was filtered, vacuum dried, and a red powder, i.e., ligand L, was obtained. The yield was calculated to be 95.15%.
[0085] Take 0.031 g of ligand L and 0.074 g of GdCl3·6H2O in a beaker, add 4 mL of methanol solution and 4 mL of acetonitrile solution, and then add 50 μL of triethylamine. After stirring, the solution turns clear yellow. Filter into a 20 mL sample bottle, seal with plastic wrap and make a small hole, and let stand at room temperature for 48 h to obtain yellow cuboid crystals.
[0086] Example 7
[0087] 3.03 g of 3-amino-2-hydroxyacetophenone and 0.90 g of 1,3-diamino-2-propanol were added to 50 mL of methanol solution. After stirring until completely dissolved, the solution was heated under reflux at 70 °C for 8 h to obtain a reddish-brown solution. The solution was filtered and dried under vacuum to obtain 3.04 g of orange-red powder, i.e., the intermediate. The yield was calculated to be 85.26%.
[0088] 3.04 g of the intermediate and 2.60 g of o-vanillin were added to 60 mL of methanol solution. The mixture was heated under reflux and stirred at 50 °C for 6 h to obtain a red solution. The solution was filtered, vacuum dried, and a red powder, i.e., ligand L, was obtained. The yield was calculated to be 94.23%.
[0089] Take 0.031 g of ligand L and 0.073 g of EuCl3·6H2O in a beaker, add 4 mL of methanol solution and 4 mL of acetonitrile solution, and then add 50 μL of triethylamine. After stirring, the solution turns clear yellow. Filter into a 20 mL sample bottle, seal with plastic wrap and make a small hole, and let stand at room temperature for 48 h to obtain yellow cuboid crystals.
[0090] See Figure 4 Infrared spectroscopy analysis was performed on the ligand L prepared in Example 1, at 3411 cm⁻¹. -1 Attributable to the stretching vibration of the OH structure in the ligand, 2931 cm⁻¹ -1 With 2824cm -1 This is attributed to the stretching vibrations of CH on the methyl and methylene groups in the ligands, with 1603 cm⁻¹ being the most significant. -1 The C=N classification indicates that 1,3-diamino-2-propanol and 3-amino-2-hydroxyacetophenone underwent a condensation reaction, 1522 cm⁻¹ -1 With 1447cm -1 This can be attributed to the stretching vibration of the aromatic ring skeleton in the ligand, 1238 cm⁻¹ -1 This can be attributed to the stretching vibration of CN bound to the aromatic ring in the ligand, 1151 cm. -1 This vibration can be attributed to the stretching vibration of CO in the methoxy group attached to the aromatic ring of the ligand, at 1062 cm⁻¹. -1 The position can be attributed to the stretching vibration of CO in the hydroxyl group attached to the aromatic ring in the ligand, 735 cm⁻¹ -1 The vibrations in the vicinity can be attributed to the out-of-plane bending vibrations of the CH group in the trisubstituted benzene ring of the ligand. Infrared spectroscopy characterization confirmed the successful synthesis of the ligand.
[0091] See Figure 5 The infrared spectra of the trinuclear rare earth complexes prepared in Examples 1, 2, and 3 were measured and compared with ligand L. The infrared spectra of the three complexes were consistent with those of the ligand, indicating that they had the same coordination mode. Compared with ligand L, the infrared spectra of the three complexes at 1600 cm⁻¹ were significantly different. -1 The characteristic peak of the imine C=N group near the 735 cm⁻¹ exhibits a blue shift. -1 The characteristic peak of CH in the nearby trisubstituted benzene ring undergoes a red shift, indicating that the N atom in ligand L and the O atom in the benzene ring substituent have coordinated with the metal ion.
[0092] See Figure 6 Thermogravimetric analysis (TGA) was performed on the trinuclear rare earth complexes prepared in Examples 1, 2, and 3 using a TGA / NETZSCHSTA449C thermogravimetric analyzer. Under nitrogen protection, the temperature ranged from room temperature to 800°C. The experimental results showed that the trinuclear rare earth complexes prepared in Examples 1, 2, and 3 all exhibited good stability up to 100°C.
[0093] This invention provides an application of a symmetrical multidentate Schiff base trinuclear rare earth complex as a catalyst for the synthesis of cyclic carbonates from carbon dioxide. By investigating the temperature, pressure, type and amount of co-catalyst, the optimal reaction conditions were determined to be: 0.1 mol% of the symmetrical multidentate Schiff base trinuclear rare earth complex (denoted as R3L) and 0.8 mol% of the co-catalyst TBAB, reacted at 80°C and 1 MPa CO2 for 3 h. See also... Figure 7 This is a schematic diagram of the reaction between epoxide and carbon dioxide to form cyclic carbonates.
[0094] Example 8
[0095] 10 mmol of styrene oxide was placed in a 30 ml high-pressure reactor as a substrate, along with 0.1 mol% of the complex Tb3L prepared in Example 1 and 0.8 mol% of the co-catalyst TBAB. The reaction was carried out at 80 °C and 1 MPa CO2 for 3 h. See [link to relevant documentation] Figure 8 ,pass 1 HNMR analysis showed a conversion rate of 98% and a selectivity of over 99% for cyclic carbonates.
[0096] Example 9
[0097] 10 mmol of allyl glycidyl ether was placed in a 30 mL high-pressure reactor as a substrate. 0.1 mol% of the complex Tb3L prepared in Example 1 and 0.8 mol% of the co-catalyst TBAB were added. The reaction was carried out at 80 °C and 1 MPa CO2 for 3 h. (See also...) Figure 9 ,pass 1 HNMR analysis showed a conversion rate of 99% and a selectivity of over 99% for cyclic carbonates.
[0098] Example 10
[0099] 10 mmol of phenyl glycidyl ether was placed in a 30 ml high-pressure reactor as the substrate, along with 0.1 mol% of the complex Tb3L prepared in Example 1 and 0.8 mol% of the co-catalyst TBAB. The reaction was carried out at 80 °C and 1 MPa CO2 for 3 h. (See also...) Figure 10 ,pass 1 HNMR analysis showed a conversion rate of 99% and a selectivity of over 99% for cyclic carbonates.
[0100] Example 11
[0101] 10 mmol of n-butyl glycidyl ether was placed in a 30 ml high-pressure reactor as the substrate. 0.08 mol% of the complex Tb3L prepared in Example 1 and 0.8 mol% of the co-catalyst tetrabutylammonium bromide (TBAB) were added. The reaction was carried out at 80 °C and 1 MPa CO2 for 3 h. (See also...) Figure 11 ,pass1 HNMR analysis showed a conversion rate of 93% and a selectivity of over 99% for cyclic carbonates.
[0102] See Figure 12 This paper describes the catalytic mechanism of the synthesis of cyclic carbonates from carbon dioxide using the Tb3L complex. The epoxide is activated by the Schiff base ligand in the Tb3L complex and the synergistic effect of the metal Tb acid-base reaction. The bromide anion in the co-catalyst TBAB then attacks the less hindered side of the epoxide, generating a terminal alkoxide (A). Carbon dioxide then inserts into the Tb-O bond, forming a carbonate intermediate (B). Finally, a nucleophilic attack occurs within the cyclic carbonate molecule, releasing the Tb3L complex for the next catalytic cycle. This catalyst system exhibits good catalytic activity for epoxides with different substituents, demonstrating good versatility and significant implications for the efficient utilization of carbon dioxide.
[0103] In summary, this invention provides a symmetrical multidentate Schiff base trinuclear rare earth complex, its preparation method, and its application. The method involves heating 3-amino-2-hydroxyacetophenone with 1,3-diamino-2-propanol to generate an intermediate. This intermediate is then reacted with o-vanillin to generate ligand L. Ligand L is deprotonated, and a rare earth metal salt is added to obtain the symmetrical multidentate Schiff base trinuclear rare earth complex. This complex has a cage-like molecular structure, which encapsulates reactants during catalytic reactions, reducing side reactions and byproduct formation, and improving reaction efficiency and purity. Furthermore, the molecular cage can selectively adsorb and directionally regulate specific types of molecules through the size and chemical properties of its channels, thereby promoting specific reaction pathways. This molecular recognition property can significantly affect the efficiency and selectivity of the catalyst, thus ensuring the catalytic efficiency and selectivity of this complex as a catalyst.
[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.
Claims
1. A symmetrical multidentate Schiff base trinuclear rare earth complex, characterized in that, Its cationic molecular structure is: , where R represents a trivalent rare earth ion.
2. The symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 1, characterized in that, R is Sc 3 + Y 3+ La 3+ Ce 3+ Pr 3+ 、Nd 3+ Pm 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ Or Lu 3+ .
3. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex as described in claim 1 or 2, characterized in that, include: 3-Amino-2-hydroxyacetophenone was reacted with 1,3-diamino-2-propanol by heating to generate an intermediate; The intermediate was reacted with o-vanillin by heating to generate ligand L; Ligand L was deprotonated and a rare earth metal salt was added to obtain a trinuclear rare earth complex of a polydentate Schiff base.
4. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 3, characterized in that, The molecular structural formula of the ligand L is: 。 5. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 3, characterized in that, The rare earth metal salt is a rare earth chloride hexahydrate or a rare earth nitrate hexahydrate containing rare earth metal ions.
6. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 3, characterized in that, In the process of heating 3-amino-2-hydroxyacetophenone and 1,3-diamino-2-propanol to generate an intermediate, the heating temperature is 50℃~70℃, the reaction time is 4~12h, and the molar ratio of 3-amino-2-hydroxyacetophenone to 1,3-diamino-2-propanol is 2:(0.95~1.05).
7. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 3, characterized in that, In the process of heating the intermediate with o-vanillin to generate ligand L, the heating temperature is 50℃~70℃, the reaction time is 3~6h, and the molar ratio of the intermediate to o-vanillin is 1:(1.95~2.05).
8. The method for preparing the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 3, characterized in that, The molar ratio of the ligand L to the rare earth metal salt is 1:(3-4).
9. The application of the symmetrical multidentate Schiff base trinuclear rare earth complex as described in claim 1 or 2 in the catalytic synthesis of cyclic carbonates from carbon dioxide.
10. The application of the symmetrical multidentate Schiff base trinuclear rare earth complex according to claim 9 in the catalytic synthesis of cyclic carbonates from carbon dioxide, characterized in that, include: A symmetrical multidentate Schiff base trinuclear rare earth complex and a co-catalyst are added to an epoxide, and carbon dioxide is introduced to react and a cyclic carbonate is obtained; wherein the co-catalyst is tetrabutylammonium bromide.