Hexagonal bipyramidal dysprosium single-ion magnet and synthesis method and application thereof

Abstract

The application discloses a hexagonal bipyramidal dysprosium single-ion magnet, a synthesis method and application thereof, a structural formula of the single-ion magnet is [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2], wherein [EO5-BPh2] ‑ a chemical structural formula of [2,6-dichloro-4-nitro-PhO] ‑ a chemical structural formula of [2,6-dichloro-4-nitro-PhO] Compared with the prior art, the application has the following advantages: (1) the hexagonal bipyramidal single-core dysprosium compound has good stability, high purity and high yield, can exhibit typical slow relaxation behavior under an applied magnetic field of 0.06 T, has the characteristics of a single-molecule magnet, and can be used as a molecular-based magnetic material in a novel high-density information storage device (such as an optical disc, a hard disc and the like); and (2) the method is safe, simple, controllable and reproducible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular-based magnetic materials, and relates to a compound with single-molecule magnet characteristics and used for a new type of high-density information storage device (such as an optical disc, a hard disc, etc.), in particular to a hexagonal bipyramidal dysprosium single-ion magnet and a synthesis method and application thereof. BACKGROUND

[0002] Magnetic materials are widely used, and their application market exceeds that of semiconductor materials; among them, information storage is one of the largest application fields of magnetic materials. With the development of information technology, the number of integrated electronic devices is exponentially increased, and the device size is continuously reduced. Such continuous development of integration and miniaturization will be limited by processing technology and cost, causing an insurmountable obstacle for modern electronic device integration technology. Therefore, the development of molecular-based magnetic materials has become a hot spot of scientists.

[0003] Single-molecule magnets (SMMs) are an important field of research on molecular-based magnetic materials. They can exhibit both the macroscopic magnetism of classical magnets and the quantum tunneling effect of microscopic particles, and have become a bridge connecting the classical theory and quantum theory of magnetism, and have great application potential in high-density information storage, quantum computers and molecular spin.

[0004] The flip energy barrier U of SMMs is determined by the ground state spin value (S) and the negative zero-field splitting energy parameter (D) of the system, and their relationship is U = S 2 |D| or (S 2 -1 / 4)|D|. Initially, researchers selected appropriate bridging ligands to adjust the magnetic interaction between the spin carriers to ferromagnetic interaction, and increased the ground state spin value (S), thereby obtaining single-molecule magnets. However, researchers found that the increase of S would decrease the value of D, and only by increasing S could not effectively increase the flip energy barrier U value. Therefore, researchers used lanthanide ions with strong magnetic anisotropy to construct single-core complexes, and obtained single-molecule magnets by increasing the value of D. Such single-molecule magnets are also called single-ion magnets (SIMs) because they only have one magnetic center in the molecular structure.

[0005] Lanthanide ions have more single electrons, and have stronger spin-orbit coupling, which is an ideal choice for designing single-ion magnets. Dy(III) has a Kramer electron layer structure (f layer has an odd number of electrons), so the ground state of dysprosium-based single-ion magnets is bistable and independent of the coordination field balance. Therefore, dysprosium-based single-ion magnets have attracted the attention of many researchers, and have become the best single-ion magnet system with an effective energy barrier and blocking temperature as high as 1540 cm -1and 80 K. However, the synthesis of these high-performance dysprosium-based single-ion magnets often needs to be carried out under extremely water-free and oxygen-free conditions, so that the synthesis is inconvenient to control, the repeatability is poor, and the yield is low. In addition, part of such materials are unstable at room temperature and in air, and are easy to decompose or weather. SUMMARY

[0006] Technical problems solved: In order to overcome the shortcomings of the prior art, obtain a mononuclear dysprosium compound with good stability, high purity and high yield, and provide a synthetic method with mild and controllable synthesis conditions and good repeatability, the hexagonal bipyramidal dysprosium single-ion magnet and a synthesis method and application thereof are provided.

[0007] Technical solutions: The hexagonal bipyramidal dysprosium single-ion magnet has a structural formula of:

[0008] [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2], wherein [EO5-BPh2] - has chemical structural formulas as follows, respectively:

[0009]

[0010] [2,6-dichloro-4-nitro-PhO] - has chemical structural formulas as follows, respectively:

[0011]

[0012] Preferably, the single-ion magnet has a chemical structural formula of:

[0013]

[0014] Preferably, the single-ion magnet has a structural unit as follows: the crystal belongs to a triclinic system, a P-1 space group, and a unit cell parameter of α = 80.6880 (10) °, β = 77.9540 (10) °, and γ = 60.9390 (10) °.

[0015] Preferably, the Dy(III) is coordinated with two [2,6-dichloro-4-nitro-PhO] - in the axial direction, and is coordinated with one [EO5-BPh2] - six oxygen atoms in the equatorial plane, forming a hexagonal bipyramidal coordination configuration.

[0016] Preferably, the single-ion magnet is a light yellow block crystal, and exhibits a typical slow magnetic relaxation process under the action of an applied magnetic field.

[0017] The synthesis method of any one of the above-mentioned hexagonal bipyramidal dysprosium mononuclear ion magnets comprises the following steps: dissolving DyCl3·6H2O and pentaethylene glycol (EO5) in a methanol solution, stirring and reacting for 2 hours, removing the methanol solvent by rotary evaporation to obtain anhydrous oil, adding the anhydrous oil to a mixed solution of 2,6-dichloro-4-nitro-PhOH and NaH in water and dichloromethane, stirring and reacting for 1 hour, adding NaBPh4, heating and refluxing for 1 hour, cooling to room temperature, separating the dichloromethane layer, transferring the dichloromethane layer to a test tube, slowly adding n-hexane, and standing to obtain the dysprosium mononuclear ion magnet, wherein the molar ratio of the DyCl3·6H2O to the pentaethylene glycol and 2,6-dichloro-4-nitro-PhOH is 1:1-1.5:2-2.5, 10-15 mL of methanol corresponds to 1 mmol of DyCl3·6H2O, 1 mmol of NaH corresponds to 1 mmol of 2,6-dichloro-4-nitro-PhOH, and 10-20 mL of the mixed solution of water and dichloromethane corresponds to 1 mmol of 2,6-dichloro-4-nitro-PhOH.

[0018] Preferably, the volume ratio of the mixed solution of water and dichloromethane is 1:1, and the volume of n-hexane is 3-6 times the volume of dichloromethane.

[0019] Preferably, the heating and refluxing temperature is 100°C.

[0020] Preferably, the standing time for two-phase diffusion is 2-6 days.

[0021] The hexagonal bipyramidal dysprosium mononuclear ion magnet is used in the preparation of molecular-based magnetic materials.

[0022] Beneficial effects: (1) The hexagonal bipyramidal mononuclear dysprosium compound has good stability, high purity and high yield, can exhibit typical slow relaxation behavior under an external magnetic field of 0.06 T, has the characteristics of a single-molecule magnet, and can be used as a molecular-based magnetic material in new high-density information storage equipment (such as optical discs, hard discs, etc.); (2) The method is safe, simple, controllable and reproducible. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a crystal structure diagram of the dysprosium mononuclear ion magnet [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2];

[0024] Figure 2 is a direct current magnetization test diagram of the dysprosium mononuclear ion magnet [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2];

[0025] Figure 3is a plot of the field-dependent magnetization curve of the dysprosium single-ion magnet [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2];

[0026] Figure 4 is a plot of the temperature-dependent imaginary ac susceptibility curve of the dysprosium single-ion magnet [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2]. DETAILED DESCRIPTION

[0027] The following examples further illustrate the present application but are not to be construed as limiting. Modifications and adaptations of the application methods, steps or conditions described can occur to those skilled in the art without departing from the spirit and scope of the application. If not specifically mentioned, the technical means used in the examples are conventional means known to those skilled in the art.

[0028] Example 1

[0029] The synthesis method of the hexagonal bipyramidal dysprosium single-ion magnet comprises:

[0030] Step one, DyCl3-6H2O (0.5 mmol) and pentaethylene glycol (0.5 mmol) are mixed and stirred in 10 mL of methanol solution, and allowed to react for 2 hours, and the methanol solvent is removed by rotary evaporation to obtain a colorless oil;

[0031] Step two, 2,6-dichloro-4-nitrophenol (1 mmol) and NaH (1 mmol) are dissolved in 10 mL of a mixed solvent of water-dichloromethane (1:1), and then the colorless oil obtained in step one is added, and stirred for 1 hour;

[0032] Step three, NaBPh4 (0.5 mmol) is added to the mixture of step two, heated to 100°C and refluxed for 1 hour, cooled to room temperature, the dichloromethane layer is separated out with a separatory funnel, transferred to a test tube, 20 mL of n-hexane is slowly added dropwise to form two-phase separation, and the crystal of the dysprosium single-ion magnet is obtained after 2 days.

[0033] The yield of the dysprosium single-ion magnet prepared in this example is 31.8%, and the purity is more than 99%.

[0034] Example 2

[0035] The synthesis method of the hexagonal bipyramidal dysprosium single-ion magnet comprises:

[0036] Step one, DyCl3-6H2O (0.5 mmol) and pentaethylene glycol (0.7 mmol) are mixed and stirred in 15 mL of methanol solution, and allowed to react for 2 hours, and the methanol solvent is removed by rotary evaporation to obtain a colorless oil;

[0037] Step two, 2,6-dichloro-4-nitrophenol (1.2 mmol) and NaH (1.2 mmol) were dissolved in 15 mL of water-dichloromethane (1:1) mixed solvent, then the colorless oil obtained in step one was added, and stirred for 1 hour;

[0038] Step three, NaBPh4(0.5 mmol) was added to the mixture of step two, heated to 100°C and refluxed for 1 hour, cooled to room temperature, the dichloromethane layer was separated out with a separatory funnel, transferred to a test tube, 25 mL of n-hexane was slowly added to form two-phase separation, and the crystal of dysprosium single ion magnet was obtained after 2 days.

[0039] The yield of the dysprosium single molecule magnet prepared in this example was 33.8%, and the purity was more than 99%.

[0040] Example 3

[0041] The synthesis method of the hexagonal bipyramidal dysprosium single ion magnet comprises:

[0042] Step one, DyCl3·6H2O (0.5 mmol) and pentaerythritol (0.5 mmol) were stirred and mixed in 15 mL of methanol solution, and reacted for 3 hours, and the methanol solvent was removed by rotary evaporation to obtain a colorless oil;

[0043] Step two, 2,6-dichloro-4-nitrophenol (1.2 mmol) and NaH (1.2 mmol) were dissolved in 20 mL of water-dichloromethane (1:1) mixed solvent, then the colorless oil obtained in step one was added, and stirred for 1 hour;

[0044] Step three, NaBPh4(0.5 mmol) was added to the mixture of step two, heated to 100°C and refluxed for 1 hour, cooled to room temperature, the dichloromethane layer was separated out with a separatory funnel, transferred to a test tube, 30 mL of n-hexane was slowly added to form two-phase separation, and the crystal of dysprosium single ion magnet was obtained after 3 days.

[0045] The yield of the dysprosium single molecule magnet prepared in this example was 31.0%, and the purity was more than 99%.

[0046] The dysprosium single ion magnet prepared in this example was characterized as follows:

[0047] (1) Crystal structure determination

[0048] Under a microscope, a single crystal of appropriate size was selected, and at room temperature, a graphite monochromated molybdenum target Mo Kα Test structure. The data were collected and the unit cell was determined using the APEXII program. The structure data were normalized and absorption corrected using the SAINT and SADABS programs. The structure was solved using the SHELXTL-2016 program. All non-hydrogen atom coordinates were obtained by difference Fourier synthesis, and the atomic coordinates and anisotropic thermal factors were corrected using full-matrix least squares, and all hydrogen atoms were theoretically added. The structure diagram is shown in Figure 1 , the crystallographic data are shown in Table 1, and the coordination bond length is shown in Table 2.

[0049] Table 1 Crystallographic data of the complex

[0050]

[0051] Table 2 Coordination bond length data of the complex

[0052]

[0053] Figure 1 The structure diagram shows that the Dy(III) is coordinated with two [2,6-dichloro-4-nitro-PhO] - in the axial direction, and with one [EO5-BPh2] - in the equatorial plane, and is coordinated with six oxygen atoms, forming a hexagonal bipyramidal coordination configuration.

[0054] (2) Magnetic performance characterization:

[0055] The magnetic measurement was performed using a superconducting quantum interference device Quantum Design MPMS SQUID VSM magnetic measurement system. The test temperature of the direct current magnetic susceptibility was 2.0-300K, and the magnetic field was 0.1T. The test temperature of the magnetization was 2.0K, and the magnetic field was 0-7T. The frequency range used for the imaginary part of the alternating current magnetic susceptibility and the real part of the alternating current magnetic susceptibility was 1-999Hz, the temperature range was 2.0-12K, and the applied direct current magnetic field was 0.06T.

[0056] As shown in Figure 2 , when the temperature was 300K, the product of the direct current magnetic susceptibility (χ) and the temperature (T) was 12.5cm 3 mol -1 K, which was less than the theoretical value 14.17cm 6 k mol 15 / 2 of the spin-only Dy(III) (S=5 / 2, L=5, 3 H -1 , g=4 / 3). When the temperature began to drop, the product gradually decreased, which was due to the presence of important magnetic anisotropy in the system. The magnetization curve Figure 3The results show that at a temperature of 2 K, when the magnetic field reaches 7 T, the magnetization of the complex is 4.40 Nβ, which does not reach the theoretical saturation value of 10 Nβ, confirming that the complex has strong magnetic anisotropy. Under an applied DC field of 0.06 T, the imaginary AC magnetic susceptibility χ” of the complex exhibits significant temperature and frequency dependence. Figure 4 This resulted in slow magnetic relaxation behavior.

[0057] In summary, the rare earth complexes prepared by this invention exhibit typical slow relaxation behavior under an applied magnetic field of 0.06T, possessing the characteristics of single-ion magnets, and can be used as molecular-based magnetic materials in novel high-density information storage devices (such as optical discs, hard disks, etc.).

Claims

1. A hexagonal bipyramidal dysprosium single-ion magnet, characterized in that, The structural formula of the single-ion magnet is: [Dy(EO5-BPh2)(2,6-dichloro-4-nitro-PhO)2], wherein [EO5-BPh2] - has the chemical structure: [2,6-dichloro-4-nitro-PhO] - the chemical structural formula of which is: The chemical structural formula of the single-ion magnet is: The structure unit of the single-ion magnet is: the crystal belongs to triclinic system, P-1 space group, and the cell parameter is α = 80.6880(10)°, β = 77.9540(10)°, γ = 60.9390(10)°; The Dy(III) is coordinated axially to two [2,6-dichloro-4-nitro-PhO] - in the equatorial plane to one [EO5-BPh2] - six oxygen atoms, forming a hexagonal bipyramidal coordination geometry.

2. The hexagonal bipyramidal dysprosium single-ion magnet of claim 1, wherein The single-ion magnet is a light yellow block crystal, and shows a typical slow magnetic relaxation process under the action of an applied magnetic field.

3. The method of synthesizing the hexagonal double- bipyramidal dysprosium single-ion magnet according to claim 1 or 2, characterized in that, The method comprises the following steps: dissolving DyCl3·6H2O and pentaethylene glycol in a methanol solution, stirring and reacting for 2 hours, removing the methanol solvent by rotary evaporation to obtain anhydrous oil, adding the anhydrous oil into a mixed solution of water and dichloromethane containing 2,6-dichloro-4-nitrophenol and NaH, stirring and reacting for 1 hour, adding NaBPh4, heating and refluxing for 1 hour, cooling to room temperature, separating the dichloromethane layer, transferring the dichloromethane layer into a test tube, slowly adding n-hexane, standing, and obtaining the dysprosium single-ion magnet through diffusion of two phases, wherein the molar ratio of DyCl3·6H2O to pentaethylene glycol and 2,6-dichloro-4-nitrophenol is 1:1-1.5:2-2.5, 10-15 mL of methanol corresponds to 1 mmol of DyCl3·6H2O, 1 mmol of NaH corresponds to 1 mmol of 2,6-dichloro-4-nitrophenol, and 10-20 mL of the mixed solution of water and dichloromethane corresponds to 1 mmol of 2,6-dichloro-4-nitrophenol.

4. The method of synthesizing a hexagonal double- bipyramidal dysprosium single-ion magnet according to claim 3, wherein, The volume ratio of the mixed solution of water and dichloromethane is 1:1, and the volume of n-hexane is 3-6 times the volume of dichloromethane.

5. The method of synthesizing a hexagonal double- tapered dysprosium single-ion magnet of claim 3, wherein, The heating and refluxing temperature is 100℃.

6. The method of synthesizing a hexagonal double- tapered dysprosium single-ion magnet of claim 3, wherein, The standing time for diffusion of two phases is 2-6 days.

7. Use of the hexagonal bipyramidal dysprosium single-ion magnet in claim 1 or 2 in the preparation of molecular-based magnetic materials.

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