Zero-field mononuclear cobalt monomolecular magnet and preparation method and application thereof

Abstract

The invention discloses a zero-field mononuclear cobalt single-molecular magnet and a preparation method and application thereof, the simple structural formula of the mononuclear cobalt single-molecular magnet is [Co (L) (dhbq)]. 2CH3OH. H2O, the chemical structural formula of L is # imgabs0 # dhbq, and the structural formula of L is # imgabs1 #. Compared with the prior art, the mononuclear cobalt single-molecular magnet has the following advantages: (1) the mononuclear cobalt single-molecular magnet is relatively high in purity and yield; the magnetic material can show typical slow relaxation behaviors in a zero field and an external magnetic field, has the characteristics of a single-molecule magnet, and can be used as a molecule-based magnetic material in novel high-density information storage equipment (such as an optical disk and a hard disk); (2) the mononuclear cobalt monomolecular magnet is not weathered in air and has good stability; and (3) the method is safe and simple in process, high in controllability and good in reproducibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and relates to a single-molecule magnet material, specifically a zero-field mononuclear cobalt single-molecule magnet and its preparation method and application. Background Art

[0002] With the development of information technology, the demand for the number of integrated electronic devices has increased exponentially while the device size has been continuously reduced. The continuous development of this integration and miniaturization will be restricted by processing technology and cost, creating an insurmountable obstacle for modern electronic device integration technology. Therefore, the research and development of molecular-based magnetic materials has become a hot topic of concern for scientists. Single-ion magnets (SIMs) are an important field in the research of molecular-based magnetic materials. Moreover, they have great application potential in the fields of high-density information storage, quantum computers, and molecular spintronics.

[0003] Since Long et al. reported the first mononuclear transition metal single-molecule magnet K[(tpaMes)Fe II in 2010, mononuclear single-molecule magnets based on 3d transition metals have attracted the attention of researchers and have developed rapidly. Currently, mononuclear single-molecule magnets based on magnetic centers such as Mn(III), Fe(I / II / III), Co(II), Ni(I), Cr(II), and Re(IV) have been reported. Due to its Kramer electron structure (S = 3 / 2), the ground state of the mononuclear cobalt single-molecule magnet is bistable. Therefore, mononuclear cobalt single-molecule magnets have attracted the attention of many researchers and have become the mononuclear transition metal single-molecule magnet system with the best performance. However, most mononuclear cobalt complexes only have corresponding properties under an applied magnetic field, while zero-field mononuclear cobalt single-molecule magnets are less and air-unstable. Summary of the Invention

[0004] Technical problems to be solved: In order to overcome the deficiencies of the prior art, obtain a stable cobalt complex with excellent single-molecule magnet properties, and provide a synthesis method with mild and controllable synthesis conditions and good repeatability, the present invention provides a mononuclear cobalt single-molecule magnet and its preparation method and application.

[0005] Technical solution: A zero-field mononuclear cobalt single-molecule magnet, the structural formula of the single-molecule magnet is: [Co(L)(dhbq)]·2CH3OH·H2O, where the chemical structural formula of L is:

[0006]

[0007] The structural formula of dhbq is:

[0008]

[0009] Preferably, the chemical structural formula of the single-molecule magnet is:

[0010]

[0011] Preferably, the structural unit of the single-molecule magnet is: The crystal belongs to the triclinic system, space group P-1, and the unit cell parameters are α = 94.555(6) o , β = 90.894(7) o , γ = 109.837(6) o .

[0012] Preferably, Co(II) coordinates with four nitrogen atoms of a ligand L and two oxygen atoms of the divalent negative ion of 2,5-dihydroxy-1,4-benzoquinone to form a six-coordinate trigonal prism configuration.

[0013] Preferably, the single-molecule magnet is a red block crystal, which can exhibit typical slow relaxation behavior under zero field and external magnetic field, and has the characteristics of a single-molecule magnet.

[0014] The preparation method of any one of the above-mentioned mononuclear cobalt single-molecule magnets, the method includes the following steps:

[0015] Dissolve CoCl2·6H2O and 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane in acetonitrile, stir for 4 h to obtain a purple suspension, add a methanol solution containing triethylamine and 2,5-dihydroxy-1,4-benzoquinone (H2dhbq) thereto, heat under reflux for 1 h, and filter. Let the filtrate stand for evaporation, and red block crystals slowly crystallize out, which are the mononuclear cobalt single-molecule magnets. The molar ratio of CoCl2·6H2O to 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane and 2,5-dihydroxy-1,4-benzoquinone is 1:1 to 1.5:1 to 1.5. For every 1 mmol of CoCl2·6H2O, it corresponds to 20 - 40 mL of acetonitrile, for every 1 mmol of CoCl2·6H2O, it corresponds to 20 - 40 mL of acetonitrile, and for every 1 mmol of 2,5-dihydroxy-1,4-benzoquinone, it corresponds to 2 - 3 mmol of triethylamine.

[0016] Preferably, the temperature of heating under reflux is 70 °C.

[0017] Preferably, the standing evaporation time is 3 - 4 days.

[0018] The application of any one of the above-mentioned mononuclear cobalt single-molecule magnets in the preparation of molecular-based magnetic materials.

[0019] Advantages: (1) The mononuclear cobalt single-molecule magnet of the present invention can exhibit typical slow relaxation behavior even in zero field, has the characteristics of a single-molecule magnet, and can be used as a molecular-based magnetic material in new high-density information storage devices (such as optical discs, hard disks, etc.); (2) The mononuclear cobalt single-molecule magnet does not weather in air and has good stability; (3) The method has simple and safe process, high controllability and good reproducibility. Description of the Drawings

[0020] Figure 1 is the crystal structure diagram of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O;

[0021] Figure 2 is the powder X-ray diffraction pattern of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O;

[0022] Figure 3 is the DC magnetic susceptibility test diagram of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O;

[0023] Figure 4 is the magnetization intensity curve diagram of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O;

[0024] Figure 5 is the field-dependent imaginary part AC magnetic susceptibility diagram of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O;

[0025] Figure 6 is the imaginary part AC magnetic susceptibility diagram of the zero-field mononuclear cobalt single-molecule magnet [Co(L)(dhbq)]·2CH3OH·H2O at 800 Oe. Detailed Embodiments

[0026] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all belong to the scope of the present invention. If not specifically indicated, the technical means used in the examples are conventional means well known to those skilled in the art.

[0027] Example 1

[0028] Preparation method of zero-field mononuclear cobalt single-molecule magnet, comprising: dissolving CoCl2·6H2O (1 mmol) and 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane (1 mmol) in acetonitrile (20 mL), stirring for 4 h to obtain a purple suspension, adding thereto a methanol (20 mL) solution containing triethylamine (2 mmol) and 2,5-dihydroxy-1,4-benzoquinone (1 mmol), heating under reflux for 1 h, and filtering. The filtrate was left to evaporate, and after 3 days, red block crystals were crystallized out, which were the mononuclear cobalt single-molecule magnet.

[0029] The yield of the mononuclear cobalt single-molecule magnet prepared in this example was 56.2%.

[0030] Example 2

[0031] Preparation method of zero-field mononuclear cobalt single-molecule magnet, comprising: dissolving CoCl2·6H2O (1 mmol) and 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane (1.5 mmol) in acetonitrile (25 mL), stirring for 4 h to obtain a purple suspension, adding thereto a methanol (30 mL) solution containing triethylamine (3 mmol) and 2,5-dihydroxy-1,4-benzoquinone (1.5 mmol), heating under reflux for 1 h, and filtering. The filtrate was left to evaporate, and after 3 days, red block crystals were crystallized out, which were the mononuclear cobalt single-molecule magnet.

[0032] The yield of the mononuclear cobalt single-molecule magnet prepared in this example was 63.8%.

[0033] The characterization of the dysprosium single-ion magnet prepared in this example is as follows:

[0034] (1) Crystal structure determination

[0035] Select single crystals of appropriate size under a microscope. At room temperature, on a Bruker SMART Apex II CCD single-crystal diffractometer, use graphite-monochromated molybdenum target Mo Kα to test the structure. Use the APEXII program to collect data and determine the unit cell. The structure data is normalized and absorption-corrected using the SAINT and SADABS programs. Use the SHELXTL-2016 program for structure analysis. The coordinates of all non-hydrogen atoms are obtained by difference Fourier synthesis method, and the atomic coordinates and anisotropic temperature factors are corrected using full-matrix least-squares method. All hydrogen atoms are added theoretically. The coordination structure diagram is shown in Figure 1 , and the crystallographic data is shown in Table 1, and the coordination bond lengths are shown in Table 2.

[0036] Table 1 Crystallographic data of the complex

[0037]

[0038]

[0039] Table 2 Coordination bond lengths and bond angle data of the complex

[0040]

[0041] Figure 1 The structure diagram shows that Co(II) coordinates with four nitrogen atoms of a ligand L and two oxygen atoms of the divalent negative ion of 2,5-dihydroxy-1,4-benzoquinone to form a six-coordinate trigonal prism configuration.

[0042] (2) Powder X-ray diffraction for phase purity determination

[0043] The phase purity of the bulk crystal product obtained in this example was characterized using a Bruker D8 Advance powder X-ray diffractometer. As Figure 2 shown, the simulated curve was obtained by simulating the single crystal structure data using Mercury software. The results show that the cobalt single-ion magnet material has reliable phase purity, providing guarantee for its application in molecular-based magnetic materials.

[0044] (3) Magnetic property characterization

[0045] Magnetic measurements were carried out using a superconducting quantum interference device Quantum Design MPMS SQUID VSM magnetic measurement system. The test temperature for the dc magnetic susceptibility was 2.0 - 300 K and the magnetic field was 0.1 T. The test temperature for the magnetization intensity was 2 - 6 K and the magnetic field was 0 - 7 T. The frequency range for the imaginary part and real part of the ac magnetic susceptibility was 1 - 999 Hz and the temperature range was 2 - 10 K.

[0046] As Figure 3 shown, when the temperature was 300 K, the product of the molar magnetic susceptibility (χ) and the temperature (T) was 2.68 cm 3 mol -1 K, higher than the theoretical value of 1.875 cm 3 k mol -1 for spin-only Co(II) (g = 2, S = 3 / 2). Therefore, the complex not only has a spin magnetic moment but also a significant orbital contribution. In the range of 300 - 50 K, this product remains basically unchanged, while when the temperature is below 50 K, this value begins to drop sharply, which is due to the presence of important magnetic anisotropy in the system. The magnetization intensity curve ( Figure 4 ) shows that at a temperature of 2 K, when the magnetic field reaches 7 T, the magnetization intensity of the complex is 2.13 Nβ, not reaching the theoretical saturation value of 3 Nβ, confirming that the complex has strong magnetic anisotropy. Under different applied magnetic fields, the imaginary part of the ac magnetic susceptibility χ of the complexM ”All exhibit obvious frequency-dependent phenomena ( Figure 5 ), resulting in slow magnetic relaxation behavior. In the case of an applied DC field of 800 Oe, the imaginary part of the AC magnetic susceptibility χ of this complex M ” exhibits strong temperature-dependent and frequency-dependent relaxation peaks ( Figure 6 ), further confirming that this substance belongs to a typical single-molecule magnet.

[0047] Based on the above phenomena, the cobalt single-ion magnet prepared in the present invention exhibits typical slow relaxation behavior both in zero field and in an applied field, has the characteristics of a single-ion magnet, and can be used as a molecular-based magnetic material in new high-density information storage devices (such as optical discs, hard disks, etc.).

Claims

1. Zero-field single-nuclear cobalt single-molecule magnet, characterized in that, The structural formula of the single-molecule magnet is as follows: [Co(L)(dhbq)]·2CH3OH·H2O, where the chemical structural formula of L is: The structural formula of dhbq is:

2. The zero-field single-core cobalt single-molecule magnet according to claim 1, wherein The chemical structural formula of the single-molecule magnet is:

3. The zero-field single-nuclear cobalt single-molecule magnet according to claim 1, wherein The structural unit of the single-molecule magnet is as follows: The crystal belongs to the triclinic system, space group P-1, and the unit cell parameters are α = 94.555(6) o , β = 90.894(7) o , γ = 109.837(6) o .

4. The zero-field single-core cobalt single-molecule magnet according to claim 1, characterized in that The Co(II) coordinates with four nitrogen atoms of one ligand L and two oxygen atoms of the divalent negative ion of 2,5-dihydroxy-1,4-benzoquinone to form a six-coordinate trigonal prism configuration.

5. The zero-field single-nuclear cobalt single-molecule magnet according to claim 1, wherein The single-molecule magnet is a red block crystal, which can exhibit typical slow relaxation behavior under zero field and external magnetic field, and has the characteristics of a single-molecule magnet.

6. The synthesis method of the zero-field cobalt single-ion magnet according to any one of claims 1-5, characterized in that, The method includes the following steps: Dissolve CoCl2·6H2O and 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane in acetonitrile, stir for 4 h to obtain a purple suspension, add a methanol solution containing triethylamine and 2,5-dihydroxy-1,4-benzoquinone (H2dhbq) thereto, heat under reflux for 1 h, and filter. Leave the filtrate to volatilize, and slowly crystallize out red block crystals, which are the mononuclear cobalt single-molecule magnet. Among them, the molar ratio of CoCl2·6H2O to 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacyclododecane and 2,5-dihydroxy-1,4-benzoquinone is 1:1 to 1.5:1 to 1.

5. For every 1 mmol of CoCl2·6H2O, it corresponds to 20 - 40 mL of acetonitrile, for every 1 mmol of CoCl2·6H2O, it corresponds to 20 - 40 mL of acetonitrile, and for every 1 mmol of 2,5-dihydroxy-1,4-benzoquinone, it corresponds to 2 - 3 mmol of triethylamine.

7. The synthesis method of the mononuclear cobalt single-molecule magnet according to claim 6, characterized in that, The temperature of heating under reflux is 70 °C.

8. The synthesis method of the mononuclear cobalt single-molecule magnet according to claim 6, characterized in that, The volatilization time is 3 - 4 days.

9. Use of the mononuclear cobalt single-molecule magnet according to any one of claims 1 - 5 in the preparation of a molecular-based magnetic material.

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