Crystal form of macrocyclic binuclear cobalt complex as well as preparation method and application of crystal form

Abstract

The invention discloses a crystal form of a macrocyclic binuclear cobalt complex as well as a preparation method and application of the crystal form. The preparation method of the crystal form comprises the following steps: dissolving 2-hydroxy-5-methoxyisophthalein, ethylenediamine and cobalt salt in a mixed solvent composed of methanol and acetonitrile according to a volume ratio of 1: 1, and carrying out a solvothermal reaction to obtain the 2-hydroxy-5-methoxyisophthalein cobalt salt. The test result of the applicant shows that when the complex with the concentration of 0.2 [mu] M is used as a catalyst, CO2 is subjected to photocatalytic reduction to generate 2.05 [mu] mol of CO, the TON value of the selectively generated CO is 2050, and the CO selectivity reaches 96%.

Description

Technical Field

[0001] The invention relates to a metal coordination compound, in particular to a crystal form of a macrocyclic binuclear cobalt complex and a preparation method and application thereof. Background Art

[0002] At present, the content of carbon dioxide (CO2) in the atmosphere is increasing day by day. Excessive CO2 has continuously enhanced the greenhouse effect, which in turn has caused a series of environmental problems. Today, in the process of my country making high-quality economic development a top priority, CO2 emissions from industrial production and people's daily activities have increased significantly, which will seriously affect our ecological environment and living comfort, and aggravate energy shortages. Therefore, we need to take measures to reduce the concentration of CO2 in the atmosphere, and even convert it into the energy we need.

[0003] Photocatalytic decomposition of water to produce hydrogen and CO2 reduction are typical artificial photosynthesis processes that can convert solar energy into high-efficiency clean energy and are known as the "crown" reaction of mankind. At present, the efficiency of converting solar energy into chemical energy is still relatively low, and this technology is difficult to apply industrially. The main reason is that the activity, selectivity and stability of the catalyst are too low, and there is still a long way to go before production applications. Therefore, the development of new, efficient and low-cost catalysts is still the direction of efforts in the field of photocatalysis at home and abroad. Among them, metal complexes, as typical homogeneous molecular catalysts, have clear molecular structures and catalytic active sites, so it is easy to regulate the catalytic performance of the complexes from organic ligands and metal centers, which is conducive to studying the catalytic mechanism at the molecular level.

[0004] In recent years, many metal complexes have been developed and applied to photocatalytic CO2 reduction. For example, the invention patent with publication number CN114031647A previously applied by the inventor team of this application provides a binuclear cobalt complex with the chemical formula [(C 33 H 33 N6O2)Co2(CH3COO)2](CH3COO)·H2O, 2,6-bis((bis(pyridin-2-ylmethyl)amino)methyl)-4-methoxyphenol and cobaltous acetate tetrahydrate are placed in methanol and / or ethanol, the pH value of the system is adjusted to alkaline and then heated for reaction. The complex described in the invention can be used as a homogeneous molecular catalyst for CO2 reduction to convert carbon dioxide into carbon monoxide, with high selectivity, and even exhibits excellent catalytic activity under low concentration conditions of 0.1μm. For example, the invention patent with publication number CN117843694A discloses a hydroxyphenanthroline binuclear cobalt complex with a molecular formula of C 48 H 26Cl2Co2N8O6, the invention utilizes the bidentate coordination characteristics of 2,9-dichloro-1,10-phenanthroline to achieve the purpose of forming a coordination compound with cobalt ions, and the resulting binuclear cobalt complex has a certain photocatalytic effect and can convert carbon dioxide into ethylene, but the catalytic activity is not ideal. At present, there is no report on the binuclear cobalt complex with two central cobalt ions of different valence states obtained by condensing 2-hydroxy-5-methoxyisophthalide and ethylenediamine and its use as a photocatalyst to catalyze CO2 reduction. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a crystal form of a macrocyclic binuclear cobalt complex and a preparation method and application thereof.

[0006] The crystalline form of the macrocyclic binuclear cobalt complex provided by the present invention belongs to the orthorhombic system, the P212121 space group, and its unit cell parameters are: α=90.00°, β=90.00°, γ=90.00°.

[0007] The macrocyclic binuclear cobalt complex of the present invention is composed of a di-anionic ligand obtained by condensation of 2-hydroxy-5-methoxyisophthalide and ethylenediamine, chelating two cobalt ions, and its molecular formula is C 22 H 22 Cl3Co2N4O4, the metal center cobalt ion Co1 is +3 valence, Co2 is +2 valence, the two cobalt ions are chelated together through a macrocyclic ligand, and coordinated with one or two chloride ions at the same time to form a five-coordinate or six-coordinate geometric structure. The planar structure of the complex is shown in the following formula (I):

[0008]

[0009] The preparation method of the crystalline form of the above-mentioned macrocyclic binuclear cobalt complex is: dissolving 2-hydroxy-5-methoxyisophthalide, ethylenediamine and cobalt salt in a mixed solvent and performing a solvothermal reaction to obtain the crystalline form; wherein the mixed solvent is a composition composed of methanol and acetonitrile in a volume ratio of 1:1.

[0010] In the above preparation method, the cobalt salt can be CoCl2·6H2O or CoCl2, preferably CoCl2·6H2O. The reaction is preferably carried out at ≥50°C, more preferably at 80-100°C; when the reaction is carried out at 80-100°C, the reaction time is usually controlled at 24-48h.

[0011] The applicant has found in experiments that when other conditions are constant, the composition and ratio of the mixed solvent have an important influence on whether the target product can be obtained. When methanol or acetonitrile is used as the solvent alone, no crystal product is generated or only precipitation is formed after the reaction is completed. When the ratio of methanol and acetonitrile is changed, crystals can be obtained, but the color and shape of the obtained crystals are different from the target product described in the present invention.

[0012] The 2-hydroxy-5-methoxyisophthalide involved in the above preparation method can be prepared by referring to the existing literature (Org. Biomol. Chem., 2016, 14, 669-673; J. Org. Chem. 2023, 88 (14), 10002-10013), which will not be described in detail here.

[0013] The present invention also includes the use of the above-mentioned macrocyclic binuclear cobalt complex crystal form in a photocatalyst. Further, it is used as a photocatalyst in photocatalytic carbon dioxide reduction. During the photocatalytic carbon dioxide reduction, the photocatalytic system includes a photosensitizer, a catalyst, a sacrificial agent and a solvent, wherein the catalyst is the above-mentioned mononuclear cobalt complex or crystal form, and the selection of the photosensitizer, the sacrificial agent and the solvent is the same as the prior art. Specifically, the photosensitizer can be [Ru(phen)3](PF6)2, [Ru(phen)3]Cl2 or [Ru(bpy)3]Cl2, preferably [Ru(phen)3](PF6)2; the sacrificial agent is preferably triethanolamine (TEOA) and / or triethylamine (TEA); the solvent is preferably a mixed solution comprising water and acetonitrile, wherein the volume ratio of water to acetonitrile is preferably 1:4. In the photocatalytic system, the concentration of the photosensitizer is preferably 400-500 μM, the concentration of the catalyst is preferably 0.05-1 μM, and the concentration of the sacrificial agent is preferably 0.30-0.35M.

[0014] The present invention also provides a catalyst, which contains the crystal form of the macrocyclic binuclear cobalt complex.

[0015] Compared with the prior art, the present invention synthesizes a crystalline form of a macrocyclic binuclear cobalt complex by an in-situ method. The complex can selectively generate carbon monoxide during photocatalytic CO2 reduction as a homogeneous molecular catalyst, showing high catalytic activity, selectivity and stability. The applicant's test results show that when the concentration of the complex is 0.2 μM as a catalyst, photocatalytic CO2 reduction generates 2.05 μmol CO, the turnover number TON value of selectively generating CO is 2050, and the selectivity for CO reaches 96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the infrared spectrum of the final product obtained in Example 1 of the present invention.

[0017] Figure 2This is a crystal structure diagram of the final product obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] In order to better explain the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0019] The 2-hydroxy-5-methoxyisophthalide involved in the following examples was prepared by the following method:

[0020]

[0021] Take hexamethylenetetramine (11.2012g, 80mmol) and 4-methoxyphenol (2.1608g, 20mmol) and dissolve them in 15mL trifluoroacetic acid, and heat them in N2 atmosphere at 100℃ for 6 hours. After the reaction is completed, add 10mL ultrapure water to the reaction product, and then continue to heat and reflux for 10 minutes. After the temperature of the obtained reaction product is reduced to room temperature, add 400mL ice water, precipitate for 10 minutes, and filter to obtain a light yellow solid. The obtained light yellow solid is dissolved in ethyl acetate, and water is extracted to remove moisture, and then the ethyl acetate is removed by decompression concentration to obtain 2-hydroxy-5-methoxyisophthalide (0.32g, yield: 19%). 1 H NMR (400MHz, Chloroform-d), δ (ppm) 11.06 (2H,s), 10.15 (1H,s), 7.44 (2H,s), 3.79 (3H,s).

[0022] Example 1

[0023] 2-Hydroxy-5-methoxyisophthalide (0.0180 g, 0.1 mmol), ethylenediamine (0.1 mmol, 3.33 μL) and CoCl2·6H2O (0.1 mmol, 0.0237 g) were placed in a heat-resistant glass tube with one end sealed and about 20 cm long, and 2 mL of a mixed solvent consisting of methanol and acetonitrile (the volume ratio of methanol to acetonitrile was 1:1) was added, and then vacuumed and sealed, and the sealed thick-walled glass tube was placed in an oven at 80°C for 48 hours. After stopping the reaction, the temperature was slowly lowered to room temperature. Square block black-red crystals were observed to precipitate in the glass tube, and the crystals were collected and dried. The yield was 37% (0.0088 g, calculated based on the amount of Co).

[0024] The product obtained in this example was characterized:

[0025] (1) Infrared spectrum, its spectrum is as follows Figure 1 shown.

[0026] IR(KBr,cm -1):3211w,2935m,1637vs,1583s,1557vs,1478s,1437s,1341s,1295vs,1229vs,1156s,1090s,1031s,942m,876m,803m,757m,634m,522w.

[0027] (2) Crystal structure analysis:

[0028] A square block of black-red crystals of moderate size was selected and placed on a Bruker SMART CCD diffractometer. The initial crystal structures of the products obtained in this example were solved by the SHELXS-97 direct method, and the geometric hydrogenation, non-hydrogen atomic coordinates and anisotropic thermal parameters were refined by the full matrix least squares method using SHELXL-97. The obtained crystallographic and structural refinement data are shown in Table 1 below, and some bond length and bond angle data are shown in Table 2 and Table 3 below, respectively. The structure of the obtained square block black-red crystal is shown in Figure 2 As shown, the obtained square block-shaped black-red crystals are determined to be the target product of the present invention.

[0029] Table 1 Crystallographic data of the cobalt complex of the present invention

[0030]

[0031] Table 2 Partial bond length data of cobalt complexes of the present invention

[0032]

[0033] Table 3 Partial bond angle data of the cobalt complex of the present invention (°)

[0034]

[0035] Comparative Example 1-1

[0036] Example 1 was repeated, except that the volume ratio of methanol to acetonitrile was changed to 1:3.

[0037] After the reaction was stopped, the temperature was slowly lowered to room temperature, and spherical brown crystals were observed to precipitate in the glass tube. After testing, it was found that the crystals were not the target product of the present invention.

[0038] Comparative Example 1-2

[0039] Example 1 was repeated, except that the solvent was changed to methanol only.

[0040] After the reaction was stopped, the temperature was slowly lowered to room temperature, and the glass tube contained a clear liquid without crystals or precipitation. The liquid in the glass tube was further concentrated under reduced pressure, but still no crystals or precipitation were observed.

[0041] Comparative Examples 1-3

[0042] Example 1 was repeated except that the solvent was changed to acetonitrile only.

[0043] After the reaction was stopped, the temperature was slowly lowered to room temperature, and a black precipitate was precipitated in the glass tube. After testing, it was found that the precipitate was not the target product of the present invention.

[0044] Comparative Examples 1-4

[0045] Example 1 was repeated, except that the solvent was changed to ethanol only.

[0046] After stopping the reaction, the temperature was slowly lowered to room temperature, and a brown-yellow emulsion appeared in the glass tube.

[0047] Example 2

[0048] Example 1 was repeated, except that the reaction was carried out at 100° C. and the reaction time was controlled to 36 h.

[0049] As a result, square block-shaped black-red crystals were precipitated, with a yield of 23% (0.0055 g, calculated based on the amount of Co).

[0050] The product obtained in this example was subjected to single crystal diffraction analysis, and it was determined that the obtained square block-shaped black-red crystals were the target product of the present invention.

[0051] Example 3

[0052] Example 1 was repeated, except that the reaction was carried out at 50° C. and the reaction time was controlled to 72 h.

[0053] As a result, square block-shaped black-red crystals were precipitated, with a yield of 26% (0.0062 g, calculated based on the amount of Co).

[0054] The product obtained in this example was subjected to single crystal diffraction analysis, and it was determined that the obtained square block-shaped black-red crystals were the target product of the present invention.

[0055] Experimental Example 1: The macrocyclic binuclear cobalt complex crystal form of the present invention was used as a homogeneous molecular catalyst to test its photocatalytic CO2 reduction performance in an aqueous mixed solvent system.

[0056] (1) Materials used:

[0057] Photosensitizer: [Ru(phen)3](PF6)2, catalyst: macrocyclic binuclear cobalt complex prepared according to Example 1 of the present invention (hereinafter referred to as complex 1), sacrificial agent: TEOA, LED light source (wavelength 450nm, light intensity 100mW·cm -2 , the irradiation area is 0.8cm 2 ), a 15-20 mL quartz reactor, CO2 gas, rubber tube, analytical balance, stirrer and gas chromatograph.

[0058] (2) Photocatalytic experimental steps:

[0059] Weigh 2 mg of photosensitizer [Ru(phen)3](PF6)2, transfer 200 μL of sacrificial agent TEOA and complex 1 (0.5 μM) into a quartz glass tube, add 4 mL of ultra-dry acetonitrile and 1 mL of water, seal it tightly with a rubber tube, and then pass CO2 gas for 10 to 20 minutes at a fixed wavelength of 450 nm and a light intensity of 100 m W cm -2 , irradiation area is 0.8cm 2 Under the LED light, irradiate for 10 hours while stirring. After completing the above operations, take a gas sample and inject it into the gas chromatograph to detect the CO2 reduction product CO. The results are as follows: when 0.5μM complex 1 is used, catalytic CO2 reduction produces 8.49μmol CO, the catalytic conversion number TON value is 1698, and the selectivity for CO is as high as 96%.

[0060] Different parallel experiments were conducted on the above method (as shown in Table 4). As shown in Table 4, under different catalytic system conditions, the catalytic effect of the macrocyclic binuclear cobalt complex crystal form of the present invention in photocatalytic CO2 reduction is significantly higher than that of most reported photocatalytic systems.

[0061] Table 4 Experimental data of photocatalytic CO2 reduction using the cobalt complex of the present invention as a catalyst

[0062]

[0063] Reaction conditions: At 25°C, LED light (450nm, 100mW·cm -2 , illumination time 10h, illumination area 0.8cm 2) irradiated a mixed solution of H2O / CH3CN (v / v 1:4) containing 5 mL of catalyst, photosensitizer [Ru(phen)3](PF6)2 (0.4 mM), and sacrificial agent TEOA (0.3 M). No. 1: complex 1 (0.5 μM); No. 2: complex 1 (0.2 μM); No. 3: no catalyst; No. 4: no sacrificial agent; No. 5: no photosensitizer; No. 6: no light; No. 7: no CO2, N2 atmosphere; No. 8: Xe lamp instead of LED lamp; No. 9: 0.1 mL Hg(0) was added.

[0064] As shown in Table 4, the complex crystal form of the present invention has a good photocatalytic CO2 reduction effect as a homogeneous catalyst in an aqueous system. In the photocatalytic system constructed by the present invention, when 0.2μM complex 1 is used, the catalytic conversion number TON value reaches 2050, and the selectivity of catalyzing CO is greater than 96%. However, when there is no catalyst 1 (Table 4, sequence number 2) or no CO2 (Table 4, sequence number 6) in the system, no CO is generated in the reaction system, indicating that the CO produced in this reaction does come from the photocatalytic CO2 reduction of complex 1. Experimental tests show that when a Xe lamp is used instead of an LED, the photocatalysis of complex 1 decreases and the CO selectivity decreases slightly (Table 4, sequence number 8), indicating that the light source has a significant effect on the catalytic performance. In addition, the Hg(0) poisoning experiment shows that the addition of Hg(0) to the reaction has a negligible effect on the photocatalytic activity, indicating that the photocatalytic CO2 reduction to generate CO is achieved by the complex molecular catalyst, further indicating that complex 1 is an example of a stable molecular catalyst.

Claims

1. A crystalline form of a macrocyclic binuclear cobalt complex, which belongs to the orthorhombic system, P212121 space group, and its unit cell parameters are: α=90.00°, β=90.00°, γ=90.00°.

2. The method for preparing the crystalline form of the macrocyclic binuclear cobalt complex according to claim 1, characterized in that: The method comprises dissolving 2-hydroxy-5-methoxyisophthalide, ethylenediamine and cobalt salt in a mixed solvent and performing a solvothermal reaction to obtain the product; wherein the mixed solvent is a composition composed of methanol and acetonitrile in a volume ratio of 1:

1.

3. The preparation method according to claim 1, characterized in that: The cobalt salt is CoCl2·6H2O or CoCl2.

4. The preparation method according to claim 1, characterized in that: The reaction was carried out at ≥50°C.

5. The preparation method according to claim 1, characterized in that: The reaction is carried out at 80-100°C.

6. Use of the crystalline form of the macrocyclic binuclear cobalt complex according to claim 1 in photocatalysis.

7. The use according to claim 6, characterized in that: Application as photocatalyst in photocatalytic carbon dioxide reduction.

8. A catalyst comprising the crystalline form of the macrocyclic binuclear cobalt complex according to claim 1.

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