CN113980038B - Hexagonal biconical mononuclear dysprosium compound, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a hexagonal double-cone type mononuclear dysprosium compound, a preparation method and application thereof,the structural formula of the mononuclear dysprosium compound is as follows: [ Dy (EO 5-BPh) ₂ )(2,6‑dichloro‑4‑nitro‑PhO)Cl]Wherein [ EO5-BPh ] ₂ ] ^‑ The chemical structural formulas of (a) are respectively as follows:[2,6‑dichloro‑4‑nitro‑PhO] ^‑ the chemical structural formulas of (a) are respectively as follows:compared with the prior art, the invention has the following advantages: (1) The hexagonal double-cone type mononuclear dysprosium compound has good stability, high purity and high yield, can show typical slow relaxation behavior under the condition that an external magnetic field is 0.06T, has the characteristic of a single-molecule magnet, and can be used as a molecule-based magnetic material in novel high-density information storage equipment (such as optical discs, hard magnetic discs and the like); (2) The method has the advantages of safe and simple process, high controllability and good reproducibility.

Description

Hexagonal bipyramidal mononuclear dysprosium compound and its preparation method and application

Technical field

The present invention relates to the technical field of molecular-based magnetic materials, and relates to compounds that have the characteristics of single-molecule magnets and can be used in new high-density information storage devices (such as optical disks, hard disks, etc.), specifically hexagonal bipyramidal mononuclear dysprosium compounds and their preparation methods. application.

Background technique

In recent years, the research on molecular magnets has received widespread attention. Single-molecule magnets are composed of discrete molecular units that do not interact in a magnetic sense rather than three-dimensional extended lattices (such as metals and metal oxides). It exhibits hysteresis behavior below the blocking temperature, so it shows broad application prospects in fields such as ultra-dense storage and quantum computing. To obtain a compound with "single-molecule magnet" behavior, two conditions must be met magnetically: a large ground state spin (S) and uniaxial magnetic anisotropy (D). Initially, researchers selected appropriate bridging ligands to adjust the magnetic interaction between spin carriers into ferromagnetic interactions and increase the ground state spin value (S) to obtain single-molecule magnets. However, researchers found that increasing S will reduce the D value, and simply increasing S cannot effectively increase the flipping energy barrier U value. To this end, the researchers used lanthanide ions with strong magnetic anisotropy to construct mononuclear complexes and obtained single-molecule magnets by increasing the D value.

Lanthanide ions have a large number of single electrons and stronger spin-orbit coupling, making them an ideal choice for designing single-ion magnets. Dy(III) has a Kramer electronic layer structure (the f layer has an odd number of electrons) and strong single-ion magnetic anisotropy. Therefore, dysprosium complexes have attracted the attention of many researchers and have become the single-ion magnet system with the best performance. Its effective energy barrier and blocking temperature can be as high as 1540cm ^-1 and 80K. However, the synthesis of these high-performance dysprosium-based single-ion magnets often requires extreme conditions without water and oxygen. Therefore, it is inconvenient to control the synthesis, resulting in poor repeatability and low yield. And some of these materials are unstable at room temperature and air and are prone to decomposition or weathering.

Contents of the invention

Technical problem to be solved: In order to overcome the shortcomings of the existing technology, obtain a mononuclear dysprosium compound with good stability, purity and high yield, and provide a synthesis method with mild, controllable synthesis conditions and good repeatability, the present invention Hexagonal bipyramidal mononuclear dysprosium compounds and preparation methods and applications thereof are provided.

Technical solution: hexagonal bipyramidal mononuclear dysprosium compound. The simplified structural formula of the mononuclear dysprosium compound is: [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl], where [ The chemical structural formulas of EO5-BPh ₂ ] ^- are:

The chemical structural formulas of [2,6-dichloro-4-nitro-PhO] ^- are:

Preferably, the chemical structural formula of the mononuclear dysprosium compound is:

Preferably, the structural unit of the mononuclear dysprosium compound is: the crystal belongs to the triclinic system, P-1 space group, and the unit cell parameters are α=72.842(2)°, β=89.7370(10)°, γ=85.392(2)°.

Preferably, the Dy(III) is coordinated with 1 [2,6-dichloro-4-nitro-PhO] ^- and 1 Cl ^- ion in the axial direction, and with 1 [EO5-BPh The six oxygen atoms of ₂ ] ^- are coordinated to form a hexagonal bipyramidal coordination configuration.

Preferably, the mononuclear dysprosium compound is a light yellow bulk crystal, which can exhibit typical slow relaxation behavior under the action of an external magnetic field and has the characteristics of a single molecule magnet.

The preparation method of any of the above hexagonal bipyramidal mononuclear dysprosium compounds, the method includes the following steps: adding DyCl ₃ ·6H ₂ O and pentaethylene glycol (EO5) to a solution containing 2,6-dichloro-4- Nitrophenol (2,6-dichloro-4-nitro-PhOH) and NaH in a mixed solution of water and methylene chloride, stir for 1 hour, then add NaBPh ₄ , heat to reflux for 4 hours, cool to room temperature, and remove the dichloromethane The methane layer is separated, transferred to a test tube, n-hexane is slowly added, and allowed to stand for two-phase diffusion to obtain a mononuclear dysprosium compound, wherein the DyCl ₃ ·6H ₂ O is mixed with pentaethylene glycol and 2,6-dichloro-4 -The molar ratio of nitrophenol is 1:1~1.5:0.3~0.5. Each 1mmol of DyCl ₃ ·6H ₂ O corresponds to 1mmol of NaBPh ₄ , and each 1mmol of 2,6-dichloro-4-nitrophenol corresponds to For 1 mmol of NaH, each 1 mmol of 2,6-dichloro-4-nitrophenol corresponds to 10 to 20 mL of a mixed solution of water and methylene chloride.

Preferably, the volume ratio of the mixed solution of water and methylene chloride is 1:1.

Preferably, the volume of n-hexane is 3 to 6 times the volume of methylene chloride.

Preferably, the heating and refluxing temperature is 100°C, and the two-phase diffusion time is 2 to 6 days.

Application of any of the above hexagonal bipyramidal mononuclear dysprosium compounds in the preparation of molecular-based magnetic materials.

Beneficial effects: (1) The hexagonal bipyramidal mononuclear dysprosium compound of the present invention has good stability, high purity and yield, can exhibit typical slow relaxation behavior under an external magnetic field of 0.06T, and has single-molecule properties. The characteristics of the magnet can be used as a molecular-based magnetic material in new high-density information storage devices (such as optical disks, hard disks, etc.); (2) the method is safe and simple, has high controllability and good reproducibility.

Description of drawings

Figure 1 is the crystal structure diagram of [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl];

Figure 2 is the DC magnetic susceptibility test chart of [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl];

Figure 3 is a field-dependent magnetization curve of [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl];

Figure 4 is a temperature-dependent imaginary part AC magnetic susceptibility curve of [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl].

Detailed ways

The following examples further illustrate the content of the present invention, but should not be understood as limiting the present invention. Without departing from the spirit and essence of the present invention, any modifications and substitutions made to the method, steps or conditions of the present invention shall fall within the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

Example 1

A method for synthesizing hexagonal bipyramidal mononuclear dysprosium compounds with single-molecule magnet behavior, including:

Step 1. Dissolve 2,6-dichloro-4-nitrophenol (0.5mmol) and NaH (0.5mmol) in 15mL water-dichloromethane (1:1) mixed solvent, and then add DyCl ₃ ·6H ₂ O (0.5mmol) and pentaethylene glycol (0.5mmol) were added, and the reaction was stirred for 1 hour to obtain a yellow suspension.

Step 2: Add NaBPh ₄ (0.5mmol) to the above suspension, heat to 100°C and reflux for 4 hours, cool to room temperature, separate the methylene chloride layer using a separatory funnel, transfer to a test tube, and slowly drip. Add 30 mL of n-hexane to form a two-phase layer, and obtain the crystal of dysprosium single ion magnet after 4 days.

The yield of the dysprosium single-ion magnet prepared in this example is 41.8%, and the purity is above 99%.

Example 2

A method for synthesizing hexagonal bipyramidal mononuclear dysprosium compounds with single-molecule magnet behavior, including:

Step 1. Dissolve 2,6-dichloro-4-nitrophenol (0.3mmol) and NaH (0.3mmol) in 10mL water-dichloromethane (1:1) mixed solvent, and then add DyCl ₃ ·6H ₂ O (0.5mmol) and pentaethylene glycol (0.7mmol) were added, and the reaction was stirred for 1 hour to obtain a yellow suspension.

Step 2: Add NaBPh ₄ (0.5mmol) to the above suspension, heat to 100°C and reflux for 4 hours, cool to room temperature, separate the methylene chloride layer using a separatory funnel, transfer to a test tube, and slowly drip. Add 20 mL of n-hexane to form a two-phase layer, and obtain the crystal of dysprosium single ion magnet after 3 days.

The yield of the dysprosium single-ion magnet prepared in this example is 38.5%, and the purity is above 99%.

The characteristics of the dysprosium single molecule magnet prepared in this example are as follows:

(1) Crystal structure determination

Select a single crystal of appropriate size under a microscope, and use the graphite monochromatized molybdenum target Mo Kα on a Bruker SMART Apex II CCD single crystal instrument at room temperature. Test structure. Use the APEXII program to collect data and determine unit cells. Structural data were normalized and corrected for absorption using the SAINT and SADABS programs. Structural analysis was performed using the SHELXTL-97 program. The coordinates of all non-hydrogen atoms are obtained by the difference Fourier synthesis method. The full matrix least squares method is applied to correct the atomic coordinates and anisotropic temperature factors. All hydrogen atoms are hydrogenated using theory. The structural diagram is shown in Figure 1, the crystallographic data are shown in Table 1, and the coordination bond lengths are shown in Table 2.

Table 1 Crystallographic data of the complexes

Table 2 Coordination bond length data of complexes

The structural diagram in Figure 1 shows that Dy(III) is coordinated with two [2,6-dichloro-4-nitro-PhO] ^- in the axial direction and with one [EO5-BPh ₂ ] ^- in the equatorial plane. Oxygen atoms are coordinated to form a hexagonal bipyramidal coordination configuration.

(2) Magnetic performance characterization:

The magnetic measurement uses a superconducting quantum interferometer Quantum Design MPMS SQUID VSM magnetic measurement system. The test temperature of DC magnetic susceptibility is 2.0~300K, and the magnetic field is 0.1T. The test temperature of magnetization strength is 2.0K, and the magnetic field is 0~7T. The frequency range used for the imaginary AC magnetic susceptibility and the real AC magnetic susceptibility is 1~999Hz, the temperature range is 2.0~8.0K, and the external DC magnetic field is 0.06T.

As shown in Figure 2, when the temperature is 300K, the product of DC magnetic susceptibility (χ) and temperature (T) is 14.69cm ³ mol ^{- 1} K, which is close to spin-only Dy(III) (S=5/2 , L=5, ⁶ H _15/2 , g=4/3), the theoretical value is 14.17cm ³ k mol ^-1 . When the temperature starts to decrease, this product remains constant, while when the temperature is below 10 K, the value starts to decrease sharply due to the presence of important magnetic anisotropy in the system. The magnetization curve (Figure 3) shows that at a temperature of 2K, when the magnetic field reaches 7T, the magnetization of the complex is 5.89Nβ, which does not reach the saturation value of 10Nβ, indicating that the complex has strong magnetic anisotropy. When an external DC field is 0.06T, the imaginary AC magnetic susceptibility χ” of the complex shows obvious temperature dependence and frequency dependence (Figure 4), resulting in slow magnetic relaxation behavior.

Based on the above phenomena, the rare earth complex prepared in the present invention can exhibit typical slow relaxation behavior under an external magnetic field of 0.06T, 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 CD, hard disk, etc.).

Claims (8)

1. Hexagonal bipyramidal mononuclear dysprosium compound, characterized in that the simplified structural formula of the mononuclear dysprosium compound is: [Dy(EO5-BPh ₂ )(2,6-dichloro-4-nitro-PhO)Cl], where the chemical structural formula of [EO5-BPh ₂ ] ^- is: The chemical structural formula of [2,6-dichloro-4-nitro-PhO] ^- is: The structural unit of the mononuclear dysprosium compound is: the crystal belongs to the triclinic system, P-1 space group, and the unit cell parameters are α=72.842(2)°, β=89.7370(10)°, γ=85.392(2)°; The Dy(III) is coordinated with 1 [2,6-dichloro-4-nitro-PhO] ^- and 1 Cl ^- ion in the axial direction, and with 1 [EO5-BPh ₂ ] ^- on the equatorial plane The six oxygen atoms are coordinated to form a hexagonal bipyramidal coordination configuration. 2. The hexagonal bipyramidal mononuclear dysprosium compound according to claim 1, wherein the chemical structural formula of the mononuclear dysprosium compound is: 3. The hexagonal bipyramidal mononuclear dysprosium compound according to claim 1, characterized in that the mononuclear dysprosium compound is a light yellow bulk crystal and can exhibit typical slow relaxation behavior under the action of an external magnetic field. , with single-molecule magnet characteristics. 4. The preparation method of the hexagonal bipyramidal mononuclear dysprosium compound of any one of claims 1-3, characterized in that the method includes the following steps: DyCl ₃ ·6H ₂ O and pentaethylene glycol are added to a solution containing 2, 6-Dichloro-4-nitrophenol (2,6-dichloro-4-nitro-PhOH) and NaH in a mixed solution of water and dichloromethane, stir and react for 1 hour, then add NaBPh ₄ and heat to reflux for 4 hours. Cool to room temperature, separate the dichloromethane layer, transfer to a test tube, slowly add n-hexane, let it stand, and obtain a mononuclear dysprosium compound through two-phase diffusion, wherein the DyCl ₃ ·6H ₂ O and pentaethylene glycol, 2 , the molar ratio of 6-dichloro-4-nitrophenol is 1:1～1.5:0.3～0.5, every 1mmol of DyCl ₃ ·6H ₂ O corresponds to 1mmol of NaBPh ₄ , every 1mmol of 2,6-dichloro -4-nitrophenol corresponds to 1 mmol of NaH, and each 1 mmol of 2,6-dichloro-4-nitrophenol corresponds to 10 to 20 mL of a mixed solution of water and methylene chloride. 5. The preparation method of the hexagonal bipyramidal mononuclear dysprosium compound according to claim 4, characterized in that the volume ratio of the water and methylene chloride mixed solution is 1:1. 6. The method for preparing a hexagonal bipyramidal mononuclear dysprosium compound according to claim 4, wherein the volume of n-hexane is 3 to 6 times the volume of methylene chloride. 7. The preparation method of the hexagonal bipyramidal mononuclear dysprosium compound according to claim 4, characterized in that the heating and refluxing temperature is 100°C, and the two-phase diffusion time is 2 to 6 days. 8. Application of the hexagonal bipyramidal mononuclear dysprosium compound of any one of claims 1 to 3 in the preparation of molecular-based magnetic materials.