A tetranuclear copper cluster with nitrogen-sulfur bidentate ligand protection and a preparation method thereof

Abstract

The application belongs to the field of inorganic synthetic chemistry and electrochemical new materials, and particularly relates to a kind of four-core copper cluster with nitrogen and sulfur bidentate ligand protection and a preparation method thereof.The preparation method of the application comprises the following steps: taking copper salt as metal source, taking 4,5-diphenyl-2-mercaptooxazole as protective ligand, and using a simple one-step method to prepare atomically precise nitrogen and sulfur bidentate ligand protected four-core copper cluster.The application uses 4,5-diphenyl-2-mercaptooxazole as bidentate ligand, and widens and enriches the types of copper cluster through a simple one-step method.The four-core copper cluster obtained based on the method has good application prospect in the field of energy catalysis.

Description

Technical Field

[0001] This invention belongs to the field of inorganic synthetic chemistry and electrochemical new materials, specifically relating to a tetranuclear copper cluster protected by nitrogen-sulfur bidentate ligands and its preparation method. Background Technology

[0002] Renewable energy sources are inherently intermittent and random; therefore, developing and utilizing new energy storage and conversion devices plays a crucial role in the full utilization and efficient conversion of renewable electricity. Electrocatalytic energy storage and conversion devices, such as fuel cells and water electrolysis devices, are already in the early stages of large-scale application, fully demonstrating the enormous value and potential of electrochemical devices in energy storage and conversion. The efficient operation of such electrochemical devices is based on the electrochemical catalytic process occurring at the anode and cathode. The overall performance of the device largely depends on the electrocatalytic materials at the anode and cathode. Therefore, developing highly efficient new electrocatalytic materials is a key factor and a challenging issue in promoting the industrial application of such electrochemical devices.

[0003] Precisely structured metal clusters are ultra-small nanoparticles with a core composed of several to hundreds of metal atoms, protected by organic ligands, and possessing a defined chemical composition, molecular formula, and atomic-level resolution. In recent years, precisely structured metal clusters have become a research frontier in the field of electrocatalytic materials due to their well-defined structure-property relationships. Among them, gold clusters, palladium clusters, copper clusters, and their alloys have shown performance advantages in oxygen reduction, carbon dioxide reduction, and nitrate reduction reactions. Copper clusters, in particular, as a non-precious metal element, have the advantages of abundant resources and low cost. However, currently reported copper clusters mostly use traditional monodentate ligands containing sulfur and phosphorus for protection, which greatly limits the application and development of copper clusters. Therefore, designing and preparing novel Cu clusters with well-defined structures and unique coordination structures, and developing simple and convenient preparation methods, are of great significance. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a copper cluster protected by a nitrogen-sulfur bidentate ligand, which broadens and enriches the types of copper clusters and has breakthrough significance for the application of copper clusters in electrocatalytic energy storage and conversion. At the same time, it provides a method for preparing the tetranuclear copper cluster.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows: This invention provides a tetranuclear copper cluster protected by a bidentate ligand of nitrogen and sulfur. The tetranuclear copper cluster comprises four Cu atoms and four 4,5-diphenyl-2-mercaptooxazole ligands. The center is composed of four copper atoms arranged in a tetrahedral shape. Each copper atom is coordinated with two S atoms of 4,5-diphenyl-2-mercaptooxazole and one N atom of 4,5-diphenyl-2-mercaptooxazole. The average bond length between copper atoms and sulfur atoms is 2.3 Å, and the average bond length between copper atoms and nitrogen atoms is 2.0 Å.

[0006] Furthermore, the chemical formula of the tetranuclear copper cluster is: Cu4(C 15 H 10 NOS)4.

[0007] Furthermore, the tetranuclear copper cluster belongs to the tetragonal crystal system with space group I41 / a, a = 17.27990(10) Å, b = 17.27990(10) Å, c = 18.0084(2) Å, α = 90°, β = 90°, γ = 90°.

[0008] This invention also provides a method for preparing the above-mentioned nitrogen-sulfur bidentate ligand-protected tetranuclear copper cluster, which mainly includes the following steps: Step 1: Dissolve the copper salt in acetonitrile and stir until completely dissolved; Step 2: Add 4,5-diphenyl-2-mercaptooxazole to the solution from Step 1 and continue stirring to fully dissolve and mix the raw materials; Step 3: Add sodium borohydride to the solution from step 2 and stir to obtain a reddish-brown solution; Step 4: Centrifuge the reddish-brown solution from Step 3, collect the supernatant, and perform single-crystal culture to obtain tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands. 15 H 10 NOS)4.

[0009] Preferably, in step 1, the copper salt is one or a combination of copper chloride, cuprous iodide, and copper trifluoroacetate.

[0010] Preferably, in step 1, the concentration of copper salt in acetonitrile is 0.01-0.05 mol / L.

[0011] Preferably, in step 1, the stirring rate is 300-1000 rpm and the stirring time is 5-60 min.

[0012] Preferably, in step 2, the molar ratio of 4,5-diphenyl-2-mercaptooxazole to copper ions is (0.5~3):1.

[0013] Preferably, in step 2, the stirring rate is 300-1000 rpm and the stirring time is 5-60 min.

[0014] Preferably, in step 3, the molar ratio of sodium borohydride to copper ions is (1~5):1.

[0015] Preferably, in step 3, the stirring rate is 300-1000 rpm and the stirring time is 2-12 h.

[0016] Preferably, in step 4, the centrifugation speed is 2000-12000 rpm / min.

[0017] Preferably, in step 4, the single crystal culture time is 3-5 days.

[0018] This invention provides a tetranuclear copper cluster Cu4(C) protected by a bidentate nitrogen-sulfur ligand. 15 H 10 The application of NOS)4 in electrocatalytic reactions, wherein the tetranuclear copper cluster is used as an electrode material for electrocatalytic reactions; the electrocatalytic reactions are oxygen reduction reactions, carbon dioxide reduction reactions, or nitrate reduction reactions.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The tetranuclear copper cluster Cu4(C) protected by the nitrogen-sulfur bidentate ligand disclosed in this invention 15 H 10 NOS)4, the core framework of this cluster consists of four copper atoms arranged in a tetrahedral shape, with four dehydrogenated ligands bonded to the outer layer. Each 4,5-diphenyl-2-mercaptooxazole ligand is bidentately coordinated with nitrogen, sulfur, and copper atoms. This cluster is uncharged, allowing for the resolution of its precise crystal structure. This enables a precise correlation between structure and properties, broadening and enriching the variety of copper clusters.

[0020] (2) The preparation method disclosed in this invention adopts a simple one-step method, which is convenient for synthesis, simple for separation and purification, and has good reproducibility.

[0021] (3) The obtained tetranuclear copper cluster Cu4(C) 15 H 10 NOS)4 was prepared as an electrode and used as a cathode for various electrocatalytic reactions. The test results showed that the cluster exhibited significant electrocatalytic activity in oxygen reduction, carbon dioxide reduction and nitrate reduction reactions, providing a theoretical and material basis for research on electrocatalytic energy storage and conversion. Attached Figure Description

[0022] Figure 1 Example 1: Tetranuclear copper cluster Cu4(C) protected by nitrogen-sulfur bidentate ligands15 H 10 Crystal structure diagram of NOS4; Figure 2 Example 1: Tetranuclear copper cluster Cu4(C) protected by nitrogen-sulfur bidentate ligands 15 H 10 The UV-Vis absorption spectrum of NOS)4; Figure 3 Example 1: Tetranuclear copper cluster Cu4(C) protected by nitrogen-sulfur bidentate ligands 15 H 10 ESI-MS mass spectrum of NOS4. Detailed Implementation

[0023] 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. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope of protection of the claims of this application.

[0024] Example 1 (1) Dissolve copper trifluoroacetate in acetonitrile at a concentration of 0.02 mol / L, and stir at 800 rpm for 20 min until completely dissolved; (2) Add 4,5-diphenyl-2-mercaptooxazole (molar ratio of 1:1 to copper ions) to the above solution, stir at 800 rpm, and continue stirring for 20 min to fully dissolve and mix the raw materials; (3) Add sodium borohydride (molar ratio of 2:1 to copper ions) to the above solution, stir at 800 rpm for 4 h to obtain a reddish-brown solution; (4) The above reddish-brown solution was centrifuged at 3000 rpm, and the supernatant was collected for single-crystal culture. After 4 days, tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands were obtained. 15 H 10 NOS)4 crystals.

[0025] Example 2 (1) Dissolve copper chloride in acetonitrile at a concentration of 0.02 mol / L, and stir at 1000 rpm for 30 min until completely dissolved; (2) Add 4,5-diphenyl-2-mercaptooxazole (molar ratio of 2:1 to copper ions) to the above solution, stir at 1000 rpm, and continue stirring for 30 min to fully dissolve and mix the raw materials; (3) Add sodium borohydride (molar ratio of 2:1 to copper ions) to the above solution, stir at 1000 rpm for 4 h to obtain a reddish-brown solution; (4) The above reddish-brown solution was centrifuged at 5000 rpm, the supernatant was collected, and single crystal culture was performed. After 3 days, tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands were obtained. 15 H 10 NOS)4 crystals.

[0026] Example 3 (1) Dissolve copper trifluoroacetate in acetonitrile at a concentration of 0.01 mol / L, and stir at 1000 rpm for 30 min until completely dissolved; (2) Add 4,5-diphenyl-2-mercaptooxazole (molar ratio of 1:1 to copper ions) to the above solution, stir at 1000 rpm, and continue stirring for 30 min to fully dissolve and mix the raw materials; (3) Add sodium borohydride (molar ratio of 3:1 to copper ions) to the above solution, stir at 1000 rpm for 3 h to obtain a reddish-brown solution; (4) The above reddish-brown solution was centrifuged at 7000 rpm, the supernatant was collected, and single crystal culture was performed. After 5 days, tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands were obtained. 15 H 10 NOS)4 crystals.

[0027] Example 4 (1) Dissolve cuprous iodide in acetonitrile at a concentration of 0.05 mol / L, and stir at 1000 rpm for 30 min until completely dissolved; (2) Add 4,5-diphenyl-2-mercaptooxazole (molar ratio of 0.5:1 to copper ions) to the above solution, stir at 1000 rpm, and continue stirring for 30 min to fully dissolve and mix the raw materials; (3) Add sodium borohydride (molar ratio of 5:1 to copper ions) to the above solution, stir at 1000 rpm for 10 h to obtain a reddish-brown solution; (4) The above reddish-brown solution was centrifuged at 7000 rpm, the supernatant was collected, and single crystal culture was performed. After 5 days, tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands were obtained. 15 H 10 NOS)4 crystals.

[0028] Crystal characterization: The tetranuclear copper cluster obtained in Example 1 was further characterized as follows: The crystals were tested under an optical microscope in a nitrogen atmosphere. Data were collected using a Bruker D8 Venture diffractometer equipped with a Ga-Kα light source, and then integrated and restored using APEX 3 software. The structure was then solved and refined using the She1XT and She1XL programs in Olex2 software. All Cu, N, and S atoms were directly discovered, and the remaining non-hydrogen atoms were generated through differential Fourier synthesis. All non-hydrogen atoms were anisotropically refined. The positions of all hydrogen atoms were determined by geometric calculations and then isotropically refined. The electron density generated by residual solvent molecules was removed from the data using the SQUEEZE method in PLATON, and the resulting data was further refined. The crystal data obtained in Example 1 are shown in Table 1 below: Table 1. Main crystallographic data of the tetranuclear copper cluster obtained in Example 1 Data collection and structural analysis were performed using X-ray single-crystal diffraction techniques, yielding the precise crystal structure of the copper cluster. The crystal structure of the nitrogen-sulfur bidentate ligand-protected copper cluster prepared in Example 1 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the copper cluster is a copper cluster protected by 4,5-diphenyl-2-mercaptooxazole ligands, containing four Cu atoms and four 4,5-diphenyl-2-mercaptooxazole ligands, with the center composed of four copper atoms arranged in a tetrahedral shape. Each copper atom is coordinated with two S atoms of 4,5-diphenyl-2-mercaptooxazole and one N atom of 4,5-diphenyl-2-mercaptooxazole; the average bond length between copper atoms and sulfur atoms is 2.3 Å, and the average bond length between copper atoms and nitrogen atoms is 2.0 Å. Therefore, the molecular formula of the tetranuclear copper cluster is Cu4(C 15 H 10 NOS)4.

[0029] Cu4(C 15 H 10 The UV spectrum of the NOS4 cluster is as follows: Figure 2 As shown, an absorption peak appears at 326 nm.

[0030] Cu4(C 15 H 10 The ESI-MS results of the NOS4 cluster are as follows: Figure 3 As shown, a molecular ion peak was observed at a mass-to-charge ratio (m / z) of 1263.90 Da, corresponding to the molecular formula [Cu4(C 15 H 10 NOS)4+ H] + .

[0031] application: The obtained Cu4(C 15 H 10 NOS)4 clusters were mixed and loaded with conductive carbon powder at a mass ratio of 3:10 to obtain Cu4(C)4 clusters. 15 H 10 NOS)4 / C. Cu4(C) 15 H 10 NOS)4 / C and perfluorosulfonic acid polymer (Nafion) were mixed in ethanol at a mass ratio of 50:1 and sonicated for 1 h to obtain a catalyst slurry. The resulting slurry was used as a working electrode and as a cathode for various electrocatalytic reactions. The electrocatalytic performance was evaluated using an electrochemical workstation (Chenhua 760E). The test results showed that the cluster exhibited significant electrocatalytic activity in oxygen reduction, carbon dioxide reduction, and nitrate reduction reactions.

Claims

1. A tetranuclear copper cluster protected by a nitrogen-sulfur bidentate ligand, characterized in that, The tetranuclear copper cluster contains four Cu atoms and four 4,5-diphenyl-2-mercaptooxazole ligands. The center consists of four copper atoms arranged in a tetrahedral shape. Each copper atom is coordinated with two S atoms of 4,5-diphenyl-2-mercaptooxazole and one N atom of 4,5-diphenyl-2-mercaptooxazole. The average bond length between copper atoms and sulfur atoms is 2.3 Å, and the average bond length between copper atoms and nitrogen atoms is 2.0 Å.

2. The tetranuclear copper cluster according to claim 1, characterized in that, The chemical formula of the tetranuclear copper cluster is: Cu4(C 15 H 10 NOS)4.

3. The tetranuclear copper cluster according to claim 1 or 2, characterized in that, The tetragonal copper cluster belongs to the tetragonal crystal system, space group I41 / a, a = 17.27990(10) Å, b = 17.27990(10) Å, c = 18.0084(2) Å, α = 90°, β = 90°, γ = 90°.

4. A method for preparing a tetranuclear copper cluster as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Dissolve the copper salt in acetonitrile and stir until completely dissolved; Step 2: Add 4,5-diphenyl-2-mercaptooxazole to the solution from Step 1 and continue stirring to fully dissolve and mix the raw materials; Step 3: Add sodium borohydride to the solution from step 2 and stir to obtain a reddish-brown solution; Step 4: Centrifuge the reddish-brown solution from Step 3, collect the supernatant, and perform single-crystal culture to obtain tetranuclear copper clusters Cu4(C) protected by nitrogen-sulfur bidentate ligands. 15 H 10 NOS)4.

5. The method for preparing a tetranuclear copper cluster according to claim 4, characterized in that, The copper salt mentioned in step 1 is one or a combination of copper chloride, cuprous iodide, and copper trifluoroacetate.

6. The method for preparing a tetranuclear copper cluster according to claim 4, characterized in that, The concentration of the copper salt in acetonitrile in step 1 is 0.01-0.05 mol / L.

7. The method for preparing a tetranuclear copper cluster according to claim 4, characterized in that, The molar ratio of 4,5-diphenyl-2-mercaptooxazole to copper ions in step 2 is (0.5~3):

1.

8. The method for preparing a tetranuclear copper cluster according to claim 4, characterized in that, The molar ratio of sodium borohydride to copper ions in step 3 is (1~5):

1.

9. The method for preparing a tetranuclear copper cluster according to claim 4, characterized in that, The single crystal culture time mentioned in step 4 is 3-5 days.

10. The application of the tetranuclear copper cluster as described in any one of claims 1-3 in electrocatalytic reactions, characterized in that, The tetranuclear copper cluster is used as an electrode material for electrocatalytic reactions; the electrocatalytic reactions are oxygen reduction, carbon dioxide reduction, or nitrate reduction.

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