Face-to-face dinuclear cobalt complexes, methods of making and using the same

Abstract

This invention discloses a face-to-face binuclear cobalt complex, its preparation method, and its applications, belonging to the fields of organic synthesis and catalysis technology. The face-to-face binuclear cobalt complex is crystalline material A or crystalline material B, and the chemical formula of crystalline material A is C. 68 H 68 Co2N4O6, the chemical formula of crystalline material B is C 54 H 76 Co2N6O6; The face-to-face binuclear cobalt complex of the present invention includes two crystal forms: crystal material A and crystal material B. In crystal material A, the distance between the two cobalt metal centers is 4.821 Å. Ligands connect the two metal centers via bridging to form a large cavity, constituting a binuclear cobalt complex. The two cobalt metals are in the +2 valence state and are synergistically activated, capable of generating hydroxyl radicals through homolytic cleavage. In crystal material B, the ligands connect the two cobalt metal centers via carbon chain bridging. The coordination environment of each cobalt metal center exhibits an octahedral configuration, the distance between the two metal centers is 5.720 Å, and they are in the +3 valence state, forming a binuclear cobalt complex.

Description

Technical Field

[0001] This invention relates to the fields of organic synthesis and catalysis, and in particular to a face-to-face binuclear cobalt complex, its preparation method, and its application. Background Technology

[0002] Binuclear metal complexes, due to their unique electronic structure, synergistic effects, and tunable active sites, show broad application prospects in catalysis, magnetic materials, molecular recognition, and biomimicry. Among them, cobalt, with its abundant valence states and coordination modes, has become one of the ideal metal centers for constructing functional binuclear complexes. Through careful design of ligand structures, precise control over the spatial configuration, electronic properties, and reactivity of binuclear cobalt complexes can be achieved.

[0003] The "face-to-face" configuration is a special binuclear metal arrangement in which the two metal centers are not completely isolated by ligands, but are arranged in a relatively close, almost parallel manner in space, usually forming a cavity in the middle for substrate molecules to enter or interact with. This unique structure facilitates electronic communication between the metal centers and enables selective inclusion or activation of specific substrates through its cavity, thus exhibiting excellent performance in catalytic reactions, especially in degradation reactions that require bimetallic synergy or template effects.

[0004] Currently, various binuclear cobalt complexes with different structures have been reported in the literature. However, many existing binuclear cobalt complexes still face challenges in synthesis and application. First, in terms of synthesis, some complex structures have low yields and require stringent reaction conditions (such as anhydrous and oxygen-free environments and strict temperature control), resulting in complex preparation processes with poor reproducibility, making large-scale preparation difficult. Second, in terms of properties, some complexes lack stability, especially being sensitive to moisture in the air (hygroscopicity) and / or light, easily undergoing structural decomposition or transformation, leading to changes in crystal morphology and a decrease in chemical purity, which severely restricts their long-term storage and practical application. For example, some complexes with catalytic potential must be stored and used in an inert atmosphere due to their poor stability, greatly increasing application costs and operational difficulties. Therefore, developing novel binuclear cobalt complexes with simple preparation methods, good reproducibility, low requirements for preparation and storage conditions, and excellent stability (including easy solubility in organic solvents and resistance to light) and specific "face-to-face" active configurations is of great significance for promoting the practical application of such functional materials.

[0005] In summary, there is an urgent need in this field for a novel binuclear cobalt complex that not only possesses a large, face-to-face cavity structure conducive to catalysis, but also has ease of industrial production and stability suitable for practical application environments. Summary of the Invention

[0006] The purpose of this invention is to address the technical deficiencies in the prior art by providing a face-to-face binuclear cobalt complex, its preparation method, and its applications.

[0007] The technical solution adopted to achieve the purpose of this invention is:

[0008] A face-to-face binuclear cobalt complex, wherein the face-to-face binuclear cobalt complex is crystalline material A or crystalline material B, and the chemical formula of crystalline material A is C. 68 H 68 Co2N4O6, the molecular structure is:

[0009] ;

[0010] The chemical formula of the crystalline material B is C. 54 H 76 Co2N6O6, the molecular structure is:

[0011] .

[0012] In the above technical solution, the center-to-center distance between the two opposing +2 valence cobalt metals in the crystal material A is 4.821 Å.

[0013] In the above technical solution, the center-to-center distance between the two opposing +3 valence cobalt metals in the crystal material B is 5.720 Å.

[0014] In the above technical solution, the crystal material A is a divalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and crystallographic parameters: a = 13.7404 Å, b = 15.1843 Å, c = 15.3513 Å, α = 92.601°, γ = 113.435°, β = 97.761°, Z = 13, V = 2894.41.

[0015] In the above technical solution, the crystal material B is a trivalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and cell parameters a = 23.7300 Å, b = 8.8490 Å, c = 28.3962 Å, α = 90°, γ = 90°, β = 102.217°, Z = 25, and V = 5827.8.

[0016] Another aspect of the present invention includes a method for preparing the face-to-face binuclear cobalt complex, wherein the preparation method is a synthesis of a salon-type organic framework structure and a metallic cobalt salt.

[0017] In the above technical solution, the preparation method includes the following steps:

[0018] Step 1: 3-(tert-butyl)-2-hydroxybenzaldehyde, 2,4-diaminodiphenyl ether or diethylenetriamine are added to ethanol for reaction. After filtration and washing, the mixture is dried to obtain a salon-type organic framework structure powder.

[0019] Step 2: Add the salen-type organic framework structure powder obtained in Step 1 and cobalt acetate tetrahydrate to methanol, stir and heat, and reflux to obtain face-to-face binuclear cobalt complex.

[0020] In the above technical solution, in step 1, when the mass ratio of 3-(tert-butyl)-2-hydroxybenzaldehyde and 2,4-diaminodiphenyl ether is (2~3):1, the reaction is carried out at 20℃-30℃. In step 2, the mass ratio of the salen-type organic framework structure powder and cobalt acetate tetrahydrate is (1.2~2):1, and the reflux time is 8h, finally generating crystalline material A.

[0021] In the above technical solution, in step 1, when the mass ratio of 3-(tert-butyl)-2-hydroxybenzaldehyde and diethylenetriamine is (3~4):1, a reflux reaction is carried out at 50℃-80℃. In step 2, the mass ratio of the salen-type organic framework structure powder and cobalt acetate tetrahydrate is (1.2~2):1, and the reflux time is 12h, finally generating crystalline material B.

[0022] Another aspect of the invention includes the application of the face-to-face binuclear cobalt complex in the preparation of hydroxyl radicals.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. The face-to-face binuclear cobalt complex of the present invention has two crystal forms: crystal material A and crystal material B. In crystal material A, the distance between the two cobalt metal centers is 4.821 Å. The ligands connect the two metal centers via bridging to form a large cavity, constituting a binuclear cobalt complex. The two cobalt metals are in the +2 valence state and are synergistically activated, capable of generating hydroxyl radicals through homolytic cleavage. In crystal material B, the ligands connect the two cobalt metal centers via carbon chain bridging. The coordination environment of each cobalt metal center exhibits an octahedral configuration, the distance between the two metal centers is 5.720 Å, and they are simultaneously in the +3 valence state, forming a binuclear cobalt complex.

[0025] 2. The preparation method of this invention is simple, mild, highly reproducible, and easy to scale up. The face-to-face binuclear cobalt complexes exhibit good stability and are readily soluble in organic solvents such as dichloromethane and benzene. Furthermore, all face-to-face binuclear cobalt complexes of this invention are prepared and tested in air; therefore, the chemical purity and crystal structure of the face-to-face binuclear cobalt complexes remain stable in air, making them easy to store. This invention successfully combines novel structure, simple synthesis, and excellent stability, making it highly practical. Attached Figure Description

[0026] Figure 1 The geometric structure of crystal material A in Example 1 is characterized by X-ray single-crystal diffraction.

[0027] Figure 2 The geometry of crystal material B in Example 2 is characterized by X-ray single-crystal diffraction.

[0028] Figure 3 The above are the H NMR data of crystal material A in Example 1.

[0029] Figure 4 The image shows the ultraviolet light spectrum of crystal material B in Example 1.

[0030] Figure 5 The image shows the LC spectrum of hydroxy terephthalic acid, a product of crystal material A in Example 1, which is obtained by capturing hydroxyl radicals using terephthalic acid.

[0031] Figure 6 The image shows the GC spectrum of benzyl alcohol oxidized from crystal material A in Example 1.

[0032] Figure 7 The image shows the ultraviolet-visual spectra of carbon monoxide oxidized by crystal material A in Example 1.

[0033] Figure 8 The image shows the UV-Vis spectra of crystalline material A, ethylene oxide, from Example 1.

[0034] Figure 9 The image shows the LC spectrum of hydroxy terephthalic acid, a product of crystal material B in Example 2, which is obtained by capturing hydroxyl radicals using terephthalic acid.

[0035] Figure 10 The image shows the GC spectrum of benzyl alcohol oxidized from crystal material B in Example 2.

[0036] Figure 11 The image shows the GC spectrum of cyclohexanol oxidized from crystal material A in Example 1.

[0037] Figure 12 The image shows the GC spectrum of cyclohexanol oxidation of crystal material B in Example 2.

[0038] Figure 13 The image shows the GC spectrum of Co-oxidized cyclohexanol in Comparative Example 2. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0040] Example 1

[0041] A method for preparing a face-to-face binuclear cobalt complex (crystal material A), the chemical reaction formula of which is as follows:

[0042] ;

[0043] Includes the following steps:

[0044] Step 1: 3.56 g of 3-(tert-butyl)-2-hydroxybenzaldehyde and 1.61 g of 2,4-diaminodiphenyl ether were added to a round-bottom flask containing 20 mL of anhydrous ethanol. The mixture was stirred continuously in air at room temperature (25±5°C) for 4 hours. A solid gradually precipitated during the reaction. After the reaction was complete, the mixture was filtered under reduced pressure (using a Buchner funnel or a sintered glass funnel). The flask was thoroughly washed with a small amount of anhydrous ethanol (approximately 5 mL × 2) to completely remove residual reactants and byproducts. Finally, the obtained solid was vacuum dried at 40°C for 2 hours to obtain a bright yellow powder, which is the Salophen organic framework powder. t-Bu (Ligand powder), denoted as Salophen t-Bu L1 ligand;

[0045] Step 2, administer 520.1 mg and 1.0 mmol of Salophen obtained in Step 1. t-Bu Ligand powder, 298.9 mg, 1.2 mmol cobalt acetate tetrahydrate (Co(OAc)). •4H O) Add 20 mL of anhydrous methanol to a 50 mL double-necked round-bottom flask, and then place it under an oxygen atmosphere (by continuously introducing oxygen or using an oxygen bulb for protection), and stir and reflux in an oil bath at 50 °C for 8 hours. During the reaction, the color of the solution in the double-necked round-bottom flask gradually changes from the initial mixed color to a deep red. After the reaction is completed, the resulting reaction solution is naturally cooled to room temperature and allowed to stand for 1 hour. A large amount of red solid precipitates out. The solid product is collected by vacuum filtration (Buchner funnel) and thoroughly washed with anhydrous methanol (0-4 °C, about 5 mL × 2) and pre-cooled anhydrous diethyl ether (about 5 mL × 2) to completely remove residual methanol, unreacted raw materials and possible byproducts. Finally, the obtained solid is dried in a vacuum drying oven at room temperature for 6 hours to obtain a red face-to-face binuclear cobalt complex (crystal material A).

[0046] Under nitrogen protection, the crystal material A of Example 1 was sealed in a capillary tube. Diffraction intensity data of the crystal was collected using an Xtalab PRO MM007 DW diffractometer under monochromatic Mo-Ka irradiation with graphite. Figure 1 And as shown in Table 1:

[0047] Table 1

[0048] ;

[0049] ;

[0050] The crystal material A is a divalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and crystallographic parameters: a = 13.7404 Å, b = 15.1843 Å, c = 15.3513 Å, α = 92.601°, γ = 113.435°, β = 97.761°, Z = 13, V = 2894.41.

[0051] In air, the 1H NMR data of the crystal material A prepared in this embodiment were tested, as follows: Figure 3 As shown, 1 The H NMR (400MHz, CH3Cl, 25℃) image shows a clear paramagnetic signal, indicating that the cobalt center is in the +2 valence state.

[0052] Example 2

[0053] A method for preparing a face-to-face binuclear cobalt complex (crystal material B), the chemical reaction formula of which is as follows:

[0054]

[0055] Includes the following steps:

[0056] Step 1: 3.56 g of 3-(tert-butyl)-2-hydroxybenzaldehyde and 1 g of diethylenetriamine were added to a round-bottom flask containing 20 mL of anhydrous ethanol. The mixture was stirred continuously in air and refluxed for 4 hours at 50 °C. A solid gradually precipitated during the reaction. After the reaction was complete, the mixture was filtered under reduced pressure (using a Buchner funnel or a sintered glass funnel). The filtration was thoroughly washed with a small amount of anhydrous ethanol (approximately 5 mL × 2) to completely remove residual reactants and byproducts. Finally, the obtained solid was vacuum dried at 40 °C for 2 hours to obtain a bright yellow powder, which is the Salophen organic framework powder. t-Bu (Ligand powder), denoted as Salophen t-Bu L2 ligand.

[0057] Step 2, add 423.1 mg and 1.0 mmol of Salophen obtained in Step 1. t-Bu Ligand powder, 298.9 mg, 1.2 mmol cobalt acetate tetrahydrate (Co(OAc)). •4H O) Add 20 mL of anhydrous methanol to a 50 mL double-necked round-bottom flask, and then place it under an oxygen atmosphere (by continuously introducing oxygen or using an oxygen bulb for protection), and stir and reflux in an oil bath at 50 °C for 12 hours. During the reaction, the color of the solution in the double-necked round-bottom flask gradually changes from the initial mixed color to brownish-yellow. After the reaction is completed, the resulting reaction solution is naturally cooled to room temperature and allowed to stand for 1 hour. A large amount of red solid precipitates out. The solid product is collected by vacuum filtration (Buchner funnel) and thoroughly washed with anhydrous methanol (0-4 °C, about 5 mL × 2) and pre-cooled anhydrous diethyl ether (about 5 mL × 2) to completely remove residual methanol, unreacted raw materials and possible byproducts. Finally, the obtained solid is dried in a vacuum drying oven at room temperature for 6 hours to obtain a brownish-yellow face-to-face binuclear cobalt complex with an octahedral configuration as the central metal (crystalline material B).

[0058] The face-to-face binuclear cobalt complex in this embodiment was subjected to low-temperature single-crystal X-ray diffraction on an Xtalab PROMM007 DW diffractometer. Under monochromatic Cu-Ka radiation from graphite, diffraction intensity data of the crystal were collected using an Xtalab PRO MM007 DW diffractometer, and the unit cell parameters were measured, as follows: Figure 2 And as shown in Table 2:

[0059] Table 2

[0060] ;

[0061] ;

[0062] The crystal material B is a trivalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and cell parameters a = 23.7300 Å, b = 8.8490 Å, c = 28.3962 Å, α = 90°, γ = 90°, β = 102.217°, Z = 25, and V = 5827.8.

[0063] The ultraviolet spectrum of the crystal material B prepared in this embodiment was measured in air, as shown below. Figure 4 As shown, there is an absorption peak at 399 nm, indicating that the cobalt metal in crystal material B is +3 and can exist stably in air.

[0064] Example 3

[0065] 6 mg of crystalline material A obtained in Example 1 and 1.82 mg of terephthalic acid were added to the reaction vessel, along with 10 ml of benzene solution. Oxygen was bubbled through at 1 atm, and the mixture was stirred at room temperature for 1 hour under xenon lamp illumination. After extraction and filtration, the mixture was subjected to qualitative analysis using LC. The results were compared with the standard hydroxyterephthalic acid. Figure 5 The LC spectrum shows that hydroxyl terephthalic acid is produced during the reaction, proving that crystalline material A can generate hydroxyl radicals.

[0066] Example 4

[0067] Under an oxygen atmosphere, 6 mg of the crystalline material A obtained in Example 1, 32 μL of benzyl alcohol, and 10.00 mL of benzene were added to a reaction vessel. The mixture was then stirred at room temperature for 6 hours under xenon lamp illumination. After filtration, the mixture was introduced for GC analysis. Figure 6 It can be seen that benzyl alcohol is oxidized in the reaction, with a conversion rate of 88%, proving that crystalline material A can generate hydroxyl radicals.

[0068] Example 5

[0069] Under an oxygen atmosphere, 6 mg of the crystalline material A obtained in Example 1 and 5.00 mL of dichloromethane were added to the reaction vessel, and 1 atm of carbon monoxide was introduced. The mixture was then stirred at room temperature for 8 hours under xenon lamp illumination. After filtration, the solution was introduced into a UV spectrophotometer for measurement. Figure 7 The ultraviolet spectrophotometer spectrum shows that the reaction occurred clearly. The peak of crystal material A at 431 nm disappeared significantly, and the product changed from the original red powder to black powder, proving that crystal material A can generate hydroxyl radicals.

[0070] Example 6

[0071] Under an oxygen atmosphere, 6 mg of the crystalline material A obtained in Example 1 and 5.00 mL of dichloromethane were added to the reaction vessel, and 1 atm of ethylene was introduced. The mixture was then stirred at room temperature for 8 hours under xenon lamp illumination. After filtration, the solution was introduced into a UV spectrophotometer for measurement. Figure 8 The ultraviolet spectrophotometer spectrum shows that the reaction occurred clearly. The peak of crystal material A at 291 nm disappeared significantly, a new peak appeared at 343 nm, and the peak at 436 nm red-shifted. The product also changed from the original red powder to black powder, proving that crystal material A can generate hydroxyl radicals.

[0072] Example 7

[0073] 6 mg of crystalline material B obtained in Example 2 and 1.82 mg of terephthalic acid were added to the reaction vessel, along with 10 ml of benzene solution. Oxygen was bubbled through at 1 atm, and the mixture was stirred at room temperature for 1 hour under xenon lamp illumination. After extraction and filtration, qualitative analysis was performed using liquid chromatography (LC). The result was compared with the standard hydroxyterephthalic acid. Figure 9 The LC spectrum shows that hydroxyl terephthalic acid is produced during the reaction, proving that crystalline material A can generate hydroxyl radicals.

[0074] Example 8

[0075] 6 mg of the crystalline material B obtained in Example 2, 32 μL of benzyl alcohol, and 10.00 ml of benzene were added to the reaction vessel. Oxygen was then introduced at 1 atm, and the mixture was stirred at room temperature for 6 hours under xenon lamp illumination. After filtration, the mixture was subjected to GC analysis. The results are as follows: Figure 10 It can be seen that benzyl alcohol is oxidized to benzoic acid in the reaction, and the conversion rate of benzyl alcohol is 79%, which proves that crystalline material B can generate hydroxyl radicals.

[0076] Example 9

[0077] 6 mg of the crystalline material A obtained in Example 1 and 5 ml of cyclohexanol were added to the reaction vessel, 2 atm of oxygen was introduced, and then the mixture was stirred at 120°C for 6 hours. After filtration, the mixture was introduced into the GC for determination. In the reaction, cyclohexanol was oxidized to cyclohexanone, and the ton number was 86, which proved that the crystalline material A can generate hydroxyl radicals.

[0078] Example 10

[0079] 6 mg of crystalline material B obtained in Example 2 and 5 ml of cyclohexanol were added to the reaction vessel, and oxygen was bubbled through at 1 atm. The mixture was then stirred at room temperature for 6 hours under xenon lamp illumination. After filtration, the mixture was subjected to GC analysis. The reaction showed that cyclohexanol was oxidized to cyclohexanone. The results are as follows: Figure 12 It can be seen that the transformation number Ton is 12, which proves that crystalline material B can generate hydroxyl radicals.

[0080] Comparative Example 1

[0081] Under an oxygen atmosphere, 3 mg CoCl2·6H2O, 32 μL benzyl alcohol, and 10.00 mL benzene were added to the reaction vessel. The mixture was then stirred at room temperature for 6 hours under xenon lamp illumination. After filtration, the mixture was subjected to GC analysis. Benzyl alcohol was oxidized in the reaction, with a conversion rate of 35%. Compared to Example 8, it is evident that crystalline material B exhibits better catalytic efficiency.

[0082] Comparative Example 2

[0083] 3 mg CoCl₂·6H₂O and 5 ml cyclohexanol were added to the reaction vessel, and oxygen was bubbled through at 1 atm. The mixture was then stirred at room temperature for 6 hours under xenon lamp illumination. After filtration, the mixture was subjected to GC analysis. A trace amount of cyclohexanol was oxidized to cyclohexanone in the reaction. The results are as follows: Figure 13 It is known that Ton cannot be calculated, and the product cyclohexanone is at the trace level.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A face-to-face binuclear cobalt complex, characterized in that, The face-to-face binuclear cobalt complex is either crystal material A or crystal material B, wherein the chemical formula of crystal material A is C. 68 H 68 Co2N4O6, molecular structure is: ； The chemical formula of the crystalline material B is C. 54 H 76 Co2N6O6, the molecular structure is: 。 2. The face-to-face binuclear cobalt complex according to claim 1, characterized in that, The center-to-center distance between the two opposing +2 valence cobalt metals at the center of the crystalline material A is 4.821 Å.

3. The face-to-face binuclear cobalt complex according to claim 1, characterized in that, The center-to-center distance between the two opposing +3 valence cobalt metals at the center of the crystalline material B is 5.720 Å.

4. The face-to-face binuclear cobalt complex according to claim 1, characterized in that, The crystal material A is a divalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and crystallographic parameters: a = 13.7404 Å, b = 15.1843 Å, c = 15.3513 Å, α = 92.601°, γ = 113.435°, β = 97.761°, Z = 13, V = 2894.

41.

5. The face-to-face binuclear cobalt complex according to claim 1, characterized in that, The crystal material B is a trivalent dinuclear cobalt complex with a monoclinic crystal system, space group C2, and cell parameters a = 23.7300 Å, b = 8.8490 Å, c = 28.3962 Å, α = 90°, γ = 90°, β = 102.217°, Z = 25, and V = 5827.

8.

6. The method for preparing the face-to-face binuclear cobalt complex according to any one of claims 1 to 5, characterized in that, The preparation method involves the synthesis of a salon-type organic framework structure and a cobalt metal salt.

7. The preparation method according to claim 6, characterized in that, Includes the following steps: Step 1: 3-(tert-butyl)-2-hydroxybenzaldehyde, 2,4-diaminodiphenyl ether or diethylenetriamine are added to ethanol for reaction. After filtration and washing, the mixture is dried to obtain a salon-type organic framework structure powder. Step 2: Add the salen-type organic framework structure powder obtained in Step 1 and cobalt acetate tetrahydrate to methanol, stir and heat, and reflux to obtain face-to-face binuclear cobalt complex.

8. The preparation method according to claim 7, characterized in that, In step 1, the mass ratio of 3-(tert-butyl)-2-hydroxybenzaldehyde and 2,4-diaminodiphenyl ether is (2~3):1, and the reaction is carried out at 20℃-30℃. In step 2, the mass ratio of the salen-type organic framework structure powder and cobalt acetate tetrahydrate is (1.2~2):1, and the reflux time is 8h, finally generating crystalline material A.

9. The preparation method according to claim 7, characterized in that, In step 1, when the mass ratio of 3-(tert-butyl)-2-hydroxybenzaldehyde to diethylenetriamine is (3~4):1, a reflux reaction is carried out at 50℃-80℃. In step 2, the mass ratio of the salen-type organic framework structure powder to cobalt acetate tetrahydrate is (1.2~2):1, and the reflux time is 12h, finally generating crystalline material B.

10. The use of the face-to-face binuclear cobalt complex as described in any one of claims 1 to 5 in the preparation of hydroxyl radicals.

Images