Binuclear copper complexes, methods of making and using the same

Abstract

The present application relates to metal complexes, in particular to a kind of binuclear copper complex and its preparation method and application, the preparation method of the binuclear copper complex, comprising the following steps: Cu (CF3SO3) (CH3CN) 4 is dissolved in acetonitrile, then it is added to the acetonitrile dissolved with bis [2,6-di (N, N-di (pyridine-2-ylmethyl) amino) -4- (methyl) phenyl] disulfide, stirring reaction, then the solution is vacuum volatilized, add ether solvent and stand overnight, there are crystals to precipitate, collect crystal, the target product is obtained.The binuclear copper complex can be used as homogeneous molecular catalyst in photocatalytic carbon dioxide reduction, and shows high activity and high selectivity in photocatalytic carbon dioxide reduction.

Description

Technical Field

[0001] This invention relates to metal complexes, and more particularly to a binuclear copper complex, its preparation method, and its applications. Background Technology

[0002] Excessive atmospheric CO2 levels are a major cause of global warming, and its impact on the human environment is increasingly severe. Utilizing light energy to convert CO2 into usable carbon-containing reduction products is crucial for achieving the carbon cycle and alleviating the energy crisis and climate problems. Because CO2 is a very stable linear molecule, it is difficult to reduce to other carbon-containing compounds, and the reduction process is complex, producing a variety of products. In particular, aqueous photocatalytic systems inevitably compete with proton reduction for H2. Therefore, developing highly active, stable, and selective catalysts has become key to advancing photocatalytic CO2 reduction. Developing efficient and low-cost complex catalysts using organic ligands and non-precious metal ions has become a hot topic in homogeneous photocatalytic CO2 reduction research in recent years.

[0003] In recent years, metal complexes have been applied to the study of photocatalytic CO2 reduction. For example, invention patent No. ZL202111478010.2 discloses a complex catalyst for photocatalytic CO2 reduction, specifically a binuclear cobalt complex as shown in formula (1). When the invention uses a binuclear cobalt complex as a catalyst, the system is a highly efficient homogeneous photocatalytic system, and the binuclear cobalt complex can effectively suppress the generation of byproduct H2, greatly improving the selectivity for CO.

[0004]

[0005] Cu-based materials have been widely used in heterogeneous photocatalytic CO2 reduction research, and Cu complexes have been reported extensively as photosensitizers. However, research on Cu complexes as homogeneous molecular catalysts is scarce. Currently, no studies have been conducted on bis[2,6-di(N,N-di(pyridin-2-ylmethyl)amino)-4-(methyl)phenyl]dithion (…). Me LSSL Me Reports on the use of cobalt complexes obtained by reacting organic ligands with metal salt Cu(CF3SO3)(CH3CN)4 as homogeneous molecular catalysts in photocatalytic carbon dioxide reduction. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems by providing a binuclear copper complex that can be used as a homogeneous molecular catalyst in photocatalytic carbon dioxide reduction, exhibiting high activity and high selectivity in photocatalytic carbon dioxide reduction, along with its preparation method and applications.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The chemical formula of the binuclear copper complex described in this invention is: [Cu2( Me The structural formula of [LS)(H2O)](CF3SO3)2·2H2O is shown below:

[0009]

[0010] The complex [Cu2( Me [LS)(H2O)](CF3SO3)2·2H2O is a monoclinic crystal system, space group P21 / n, and its smallest asymmetric unit contains a Cu. + A Cu 2+ One ligand ( Me LS) - One μ2-H2O molecule, two CF3SO3 molecules - The complex contains Cu ions and two free H₂O molecules. The coordinating atoms of the two Cu ions in the complex both originate from the ligands ( Me LS) - One S atom and three N atoms, bridging the O atom in μ2-H2O, form a trigonal bipyramidal five-coordinate mode. The distance between the two Cu ions is...

[0011] The method for preparing the binuclear copper complex of the present invention includes the following steps:

[0012] Dissolve Cu(CF3SO3)(CH3CN)4 in acetonitrile, then add it to acetonitrile containing bis[2,6-bis(N,N-bis(pyridin-2-ylmethyl)amino)-4-(methyl)phenyl]dithion. Stir the reaction, then evaporate the solution under vacuum, add an ether solvent and let it stand overnight. Crystals precipitate out. Collect the crystals to obtain the target product.

[0013] The bis[2,6-bis(N,N-bis(pyridin-2-ylmethyl)amino)-4-(methyl)phenyl]dithion prepared by the above method ( Me LSSL Me Organic ligands can be found in the literature (Stephane Torelli, MO, Jacques Pecaut, Helene Jamet, Laurent Le Pape, and Stephane Menage, A{Cu2S}). 2+ The mixture-valent core featuring a Cu-Cu bond[J]. Angew. Chem. Int. Ed. 2010, 49, 8249-8252. can be prepared by mixing, valent core, and a Cu-Cu bond can be designed and synthesized independently.

[0014] In the above preparation method, acetonitrile is used as a solvent. The amount of solvent can be determined as needed, and it is usually appropriate to dissolve the raw materials participating in the reaction.

[0015] In the above preparation method, the reaction solution obtained after the reaction is a dark green solution, and an ether solvent needs to be added for product precipitation. The selection and amount of the ether solvent are the same as in the prior art; specifically, the ether solvent can be diethyl ether and / or petroleum ether.

[0016] This invention also includes the application of the aforementioned binuclear copper complex in catalyst preparation, specifically its application as a catalyst in photocatalytic CO2 reduction. In this specific application, the photocatalytic system includes a photosensitizer, a catalyst, a sacrificial agent, and a solvent. The catalyst is the aforementioned cobalt complex, and the selection of the photosensitizer, sacrificial agent, and solvent is the same as in the prior art. Specifically, the photosensitizer is preferably [Ru(phen)3](PF6)2; the sacrificial agent is preferably triethylamine (TEA); and the solvent is preferably an acetonitrile / water (4:1, v / v) mixture. In the photocatalytic system, the concentration of the photosensitizer is preferably 400–500 μM, the concentration of the catalyst is preferably 0.05 μM–1 μM, and the concentration of the sacrificial agent is preferably 0.30 M–0.35 M.

[0017] The present invention also provides a catalyst containing the above-mentioned binuclear copper complex.

[0018] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0019] Compared with the prior art, the present invention provides a novel example of a bis[2,6-bis(N,N-bis(pyridin-2-ylmethyl)amino)-4-(methyl)phenyl]dithion ( Me LSSL Me The present invention relates to a binuclear copper complex with organic ligands and its preparation method. The applicant's experimental results show that when using a 1 μM complex 1 as a catalyst, photocatalytic CO2 reduction produces 10.51 μmol formic acid. The TON value for photocatalytic CO2 reduction to selectively produce formic acid reaches 2120, and the selectivity for formic acid reaches 98%. This indicates that the binuclear copper complex prepared in this invention, as a homogeneous molecular catalyst, exhibits high catalytic activity and selectivity in photocatalytic CO2 reduction, and can efficiently photocatalyze CO2 reduction to selectively produce formic acid. Attached Figure Description

[0020] Figure 1 This is the mass spectrum of the final product obtained in Example 1 of the present invention.

[0021] Figure 2 This is a mass spectrometry fitting diagram of the final product obtained in Example 1 of the present invention.

[0022] Figure 3 This is the high-resolution XPS spectrum of the final product obtained in Example 1 of this invention.

[0023] Figure 4 This is the electron paramagnetic resonance (EPR) spectrum of the final product obtained in Example 1 of this invention.

[0024] Figure 5 It is the complex [Cu2(] obtained in Example 1 Me Crystal structure diagram of LS)(H2O)](CF3SO3)2·2H2O. Detailed Implementation

[0025] To more clearly illustrate the present invention, the following specific embodiments will be used to further explain the invention.

[0026] The following examples involve bis[2,6-bis(N,N-bis(pyridin-2-ylmethyl)amino)-4-(methyl)phenyl]dithion ( Me LSSL Me Organic ligands are prepared according to the following method:

[0027]

[0028] Synthesis of B: Substance A, 2,6-dicarboxy-4-methylphenol (635 mg, 3.87 mmol), was dissolved in dry DMF (25 mL) under an inert atmosphere. Solid 1,4-diazabicyclo[2.2.2]octane (DABCO, 867 mg, 7.74 mmol) was added, and the solution turned orange. After 15 min, solid dimethylthiocarbamoyl chloride (715.5 mg, 5.8 mmol) was added, and the mixture was stirred for 18 hours. Then, 100 mL of water was added, and the solution was cooled to 0 °C. After filtration, a beige powder was obtained, which was dissolved in CHCl3 and dried over anhydrous Na2SO4. After filtration and evaporation, the crude product was purified by silica gel column chromatography (1 / 3-1 / 5, dichloromethane / n-hexane) to give a pale yellow solid B (820 mg, 84%).

[0029] Synthesis of C: Compound B (860 mg, 3.15 mmol) was dissolved in 1,2-dichloroethane (20 mL) under an inert atmosphere. The solution was stirred and boron trifluoride diethyl ether (BF3·Et2O) (500 μL, 4.05 mmol) was added. The temperature was raised to 80 °C and the reaction was carried out for 3 hours. The resulting orange solution was cooled to 0 °C and 20 mL of water was added. After allowing the two phases to come into full contact, the mixture was allowed to stand and separate into layers. The aqueous layer was extracted with CH2Cl2 (3 × 30 mL). The combined organic layers were dried over anhydrous Na2SO4. After evaporating the solvent, the crude product was purified by silica gel column chromatography (1 / 4–3 / 4, ethyl acetate / n-hexane) to obtain a light pink solid C (803 mg, 93%).

[0030] Synthesis of D: Bis(2-pyridylmethyl)amine (1.4 g, 7.05 mmol) was dissolved in 1,2-dichloroethane (20 mL) and added dropwise to a solution of compound C (874 mg, 3.2 mmol) and CH3COOH (300 μL, 5.17 mmol) in dichloroethane (20 mL). The resulting mixture was stirred for 10 min, and NaHB(OAc)3 (2.04 g, 9.6 mmol) was added in three portions over 1 hour. After 48 hours, the reaction was quenched with semi-saturated NaHCO3 (30 mL), and the layers were separated. The aqueous phase was then extracted with CH2Cl2 (3 × 30 mL), and the combined organic layers were dried over anhydrous Na2SO4. After evaporation of the solvent, the mixture was dissolved and refluxed in diethyl ether for 3 h. The clear supernatant was ground to obtain a beige solid, washed with water, and centrifuged. The solid was dried under vacuum to obtain pure product D (1.25 g, 64%).

[0031] Synthesis of E: KOH (910 mg, 16 mmol) and compound D (500 mg, 0.811 mmol) were added to 20 mL of degassed methanol. The mixture was refluxed for 18 h, cooled to room temperature, and I2 (103 mg, 0.405 mmol) was added in solid form. The mixture was then stirred for 2 h. After vacuum evaporation of the solvent, the resulting solid was reacted thoroughly with saturated NaHCO3 (25 mL) in 25 mL of CH2Cl2, centrifuged, and the combined organic layers were extracted. After drying with anhydrous Na2SO4, a yellow hygroscopic foam was obtained, which was the target ligand E. Me LSSL Me (1.25g, 64%).

[0032] Example 1

[0033] Weigh out Cu(CF3SO3)(CH3CN)4 (74.7 mg, 0.198 mmol) and dissolve it in 1 mL of acetonitrile. Add this solution to the solution containing the dissolved ligand. Me LSSL MeIn 4 mL of acetonitrile (54 mg, 0.0495 mmol), the solution immediately turned dark green; after stirring for 10 min, the total volume of the solution was evaporated under vacuum to 2 mL, and ether was added until the solution became turbid. After standing overnight, dark green crystals were obtained, which were the target metal complex (15 mg, 20%, calculated as metal Cu salt).

[0034] The product obtained in this embodiment was characterized as follows:

[0035] (1) Mass spectrometry, its spectrum is as follows Figure 1 As shown.

[0036] According to high-resolution mass spectrometry, the complex exhibits two main peaks ( Figure 1 The peaks at +2 valence (365.0582) and +1 valence (879.0637) are respectively. The composition of the +2 valence peak at 365.0582 is {[Cu2( Me LS)(H2O)] 2+ +CH3CN} 2+ It contains a coordination framework and an acetonitrile molecule. The +1 valence peak at 879.0637 is composed of {[Cu2( Me LS)(H2O)] 2+ +CF3SO3 - +CH3CN} + It contains a coordination framework, an acetonitrile molecule, and a trifluoromethanesulfonate ion.

[0037] (2) Mass spectrometry fitting diagram as shown in the figure Figure 2 As shown.

[0038] Fitting the target peak revealed that it was identical to the molecular weight of the target complex.

[0039] (3) XPS spectrum as shown Figure 3 As shown.

[0040] The XPS plot of the complex showed four main peaks and four satellite peaks. The main peak 2P³ / ² = 932.38 eV and its satellite peak 2P³ / ² = 941.28 eV, and the main peak 2P¹ / ² = 952.18 eV and its satellite peak 2P¹ / ² = 961.48 eV belonged to +1 valent copper ions; the main peak 2P³ / ² = 934.08 eV and its satellite peaks 2P³ / ² = 944.28 eV, 2P¹ / ² = 954.08 eV and 2P¹ / ² = 962.88 eV belonged to +2 valent copper ions.

[0041] (4) Electron paramagnetic resonance (EPR) spectrum as shown in the figure Figure 4 As shown.

[0042] At a low temperature of 77 K, the electron paramagnetic spectrum of the complex consists of four peaks, indicating that the unpaired electron spin (S = 1 / 2) is mainly concentrated in the Cu(II) ion (nuclear spin I = 3 / 2) in the complex. At 200 K, the original quartet splits into a septet, indicating that the EPR of the binuclear copper complex exhibits temperature-dependent behavior. According to literature reports, this indicates that the two copper ions in the synthesized binuclear copper complex have valence states of +1 and +2, respectively. This result is consistent with the results of high-resolution mass spectrometry and XPS analysis.

[0043] (5) Crystal structure analysis: The obtained crystallographic and structural refinement data are shown in Table 1 below, and the obtained dark green crystal is determined to be the target product of this invention.

[0044] Table 1. Crystallographic parameters of binuclear complexes

[0045]

[0046] Example 2

[0047] Repeat Example 1, except that petroleum ether is used instead of diethyl ether.

[0048] The result was dark green crystals.

[0049] The dark green crystals obtained in this embodiment were characterized and analyzed, and it was determined that they were all the target products of this invention.

[0050] Experimental Example 1: The photocatalytic CO2 reduction performance of the binuclear copper complex described in this invention as a homogeneous molecular catalyst was tested in an aqueous mixed solvent system.

[0051] (1) Materials used:

[0052] Photosensitizer: [Ru(phen)3](PF6)2, catalyst: a dinuclear copper complex prepared according to Example 1 of this invention (hereinafter referred to as complex 1), sacrificial agent: TEA, solvent: a mixture of acetonitrile and water in a volume ratio of 4:1, LED light source (wavelength 450nm, light intensity 100mW·cm). -2 The irradiated area is 0.8 cm². 2 The equipment includes a 15-20 mL quartz reactor, CO2 gas, rubber tubing, an analytical balance, a stirrer, and a gas chromatograph.

[0053] (2) Specific experimental steps:

[0054] Weigh out photosensitizer [Ru(phen)3](PF6)2 (2 mg, 0.4 mM), sacrificial agent TEA (200 μL, 0.3 M), and complex 1 (5 μL, 1 μM) sequentially into a quartz glass tube. Add 4 mL of ultra-dry acetonitrile and 1 mL of water, seal tightly with a rubber tube, and introduce CO2 gas. After 10–20 min, irradiate with the LED light source at a constant temperature of 25 °C for 10 h, stirring simultaneously. After completing the above operations, inject the gas sample into a gas chromatograph for detection of formic acid, the CO2 reduction product. The detection results are shown in Table 2 below.

[0055] Table 2. Experimental data on photocatalytic CO2 reduction using the binuclear copper complex described in this invention as a catalyst.

[0056]

[0057] Reaction conditions: Under constant temperature of 25℃, using an LED lamp (wavelength 450nm, 100mW·cm²). -2 Irradiated area 0.8cm 2 Irradiate the lower part of the quartz tube for 10 hours. Serial number 1: Complex 1 (1 μM); Serial number 2: No catalyst added; Serial number 3: No CO2, N2 passed through.

[0058] As shown in Table 2, in the photocatalytic system constructed in this invention, when using 1 μM complex 1 as a catalyst, photocatalytic CO2 reduction produces 10.51 μmol formic acid (HCOOH), and no CO, CH4, or CH2=CH2 products are detected. The totient number (TON) for the photocatalytic CO2 reduction to formic acid reaches 2120, with a selectivity of 98%. However, when complex 1 is not used as a catalyst or when there is no CO2 in the system, no formic acid is generated in the reaction system, indicating that the formic acid produced in this reaction does indeed originate from the photocatalytic CO2 reduction of complex 1.

[0059] To further investigate the catalytic performance of complex 1, the inventors also conducted photocatalytic tests on it under different concentration conditions. The catalytic effects of complex 1 at concentrations of 10 μM, 1 μM, 0.1 μM and 0.05 μM are shown in Table 3.

[0060] Table 3 Effect of different concentrations of binuclear copper complex on catalytic performance

[0061]

[0062] Reaction conditions: Under constant temperature of 25℃, using an LED lamp (wavelength 450nm, 100mW·cm²). -2 Irradiated area 0.8cm 2The lower part of the quartz tube was irradiated for 10 hours. The photosensitizer [Ru(phen)3](PF6)2 concentration was 0.4 mM, the sacrificial agent concentration was 0.3 M, and 5 mL of CH3CN / H2O (4:1, v / v) was used as the solvent in the reaction system.

[0063] As shown in Table 3, the conversion number TON for the selective production of formic acid in the catalytic system decreases with decreasing catalyst concentration. HCOOH The value gradually increased. When the catalyst concentration was reduced to 0.05 μM, the conversion number for the selective formation of formic acid in the catalytic system increased to 8920. This shows that the catalyst exhibits very high catalytic activity even under low concentration conditions.

[0064] The above experimental results show that the binuclear copper complex of the present invention, as a homogeneous molecular catalyst, has very good photocatalytic CO2 reduction activity and selectivity in aqueous systems.

[0065] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. Application of binuclear copper complexes in the preparation of catalysts, wherein the chemical formula of the binuclear copper complex is: [Cu2( Me The structural formula of [LS)(H2O)](CF3SO3)2·2H2O is shown below: ； The application is as a catalyst in photocatalytic CO2 reduction.

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