Binuclear dysprosium single-molecule magnet with solvent molecule magnetic response as well as synthesis method and application of binuclear dysprosium single-molecule magnet

Abstract

The invention relates to a binuclear dysprosium single-molecular magnet with solvent molecule magnetic response as well as a synthesis method and application of the binuclear dysprosium single-molecular magnet with solvent molecule magnetic response, and a binuclear system with solvent response sites is directionally constructed by self-assembly of a nitrogen-oxygen pyridine Schiff base ligand and dysprosium ions. The single crystal of the material can be subjected to reversible single-crystal-to-single-crystal conversion in different solvent atmospheres along with reversible exchange of coordination solvent molecules. The structure change directly causes reversible switching of the macroscopic magnetic properties, and non-intrusive dynamic regulation and control of the magnetic relaxation behavior are realized.

Description

Technical Field

[0001] This invention relates to the field of molecular-based magnetic material preparation technology, specifically to a binuclear dysprosium single-molecule magnet with solvent molecular magnetic response, its synthesis method, and its application. Background Technology

[0002] Single-molecule magnets are a novel class of molecular magnetic materials exhibiting magnetic bistableness and slow magnetic relaxation at the molecular scale. Especially when dysprosium ions, with their strong magnetic anisotropy, are used as the spin source, these materials not only display outstanding magnetic properties and rich relaxation dynamics, but also show significant research potential and practical application prospects in cutting-edge fields such as high-density information storage and quantum computing. Based on the number of dysprosium spin centers, they can be classified into mononuclear dysprosium single-ion magnets, binuclear dysprosium molecular magnets, and multinuclear dysprosium molecular magnets. Among these, binuclear dysprosium single-molecule magnets possess unique structural advantages: on the one hand, the single-ion magnetic anisotropy of dysprosium ions can be precisely controlled through a ligand field; on the other hand, the magnetic exchange interaction between two dysprosium ions can be modulated by bridging ligands, thereby significantly suppressing the quantum tunneling effect and effectively optimizing magnetic relaxation behavior and overall performance.

[0003] Studies of the magneto-structure relationship in single-molecule magnet systems have revealed that the coordination environment, coordination configuration, and strength of the coordination field surrounding dysprosium ions determine the arrangement of their ground-state multilevel sub-energy levels, which is one of the causes of dysprosium ion magnetic anisotropy. The regulation of the magnetic properties of single-molecule magnets is one of the core research topics driving their practical applications. Existing methods are diverse, covering functional group modification of ligand structures, substitution of metal ion types, and even optimization of the entire molecular crystal stacking mode. Once implemented, these methods fix the molecular structure and macroscopic properties of the material, lacking dynamic tunability, and the synthesis process often requires redesign and complex steps. Despite the variety of regulation strategies, achieving precise and dynamic regulation of the structure and magnetic behavior of single-molecule magnets using mild, reversible external stimuli (such as changes in the solvent environment) remains a significant challenge. This is mainly because solvent molecules in molecular crystals are usually randomly or disorderedly encapsulated, making it difficult to achieve ordered, reversible insertion and extraction of solvent molecules, thereby triggering significant changes in the coordination environment and magnetic anisotropy. Therefore, developing a novel intelligent molecular magnet capable of generating a sensitive and reversible magnetic response to solvent environments provides a valuable opportunity to understand the relationship between structure and performance at the molecular level. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a novel intelligent molecular magnet that can produce a sensitive and reversible magnetic response to the solvent environment.

[0005] The solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A binuclear dysprosium single-molecule magnet, said binuclear dysprosium single-molecule magnet having one of the following molecular formula structures:

[0007] Complex 1: {[Dy(o-pcbs)(CH3OH)(H2O)3]·2Br·H2O}2

[0008] Complex 2: {[Dy(o-pcbs)(CH3OH)2(H2O)2]·2Br·CH3CN}2;

[0009] In this context, o-pcbs represents 2-nitropyridyl-(2-hydroxy)phenylhydrazone Schiff base.

[0010] Furthermore, the complex 1 crystallizes in space group P 21 / n, with cell parameters of... α=90°, β=95.410(3)°, γ=90°, Z = 4, μ = 6.833 mm -1 F(000) = 1378.3; the complex 2 crystallizes in P bca Space group, cell parameters are α=90°, β=90°, γ=90°, Z = 8, μ = 6.261 mm -1 F(000) = 2878.8.

[0011] Furthermore, the asymmetric unit of the complex 1 consists of a Dy 3+ It consists of an ion, an o-pcbs ligand, a coordinated methanol molecule, three coordinated water molecules, and bromide ions in two lattices and a lattice water molecule.

[0012] Furthermore, in the complex 1, Dy 3+ The ion is octetally coordinated, with two coordinated water molecules, one coordinated methanol molecule, and an imine nitrogen atom in the equatorial plane; the phenolic hydroxyl oxygen atom, the carbonyl oxygen atom, and an oxygen atom from a water molecule are located in the axial direction.

[0013] Furthermore, the difference between complex 2 and complex 1 is that one methanol molecule replaces the water molecule and Dy in complex 1. 3+ Ion coordination, and an acetonitrile molecule replaces a water molecule in the lattice of complex 1.

[0014] Furthermore, the Dy-O bond length of the complex 1 is in Range; the Dy-O bond length of the complex 2 is within scope.

[0015] Furthermore, the complex 1 is a yellow blocky crystal; the complex 2 is a red blocky crystal.

[0016] Furthermore, the complex 1 and complex 2 can undergo reversible interconversion under different solvent environments.

[0017] Furthermore, complex 1 can be converted into complex 2 in CH3OH solvent, and complex 2 can be converted into complex 1 in CH3CN solvent.

[0018] Furthermore, the complexes 1 and 2 exhibit typical slow relaxation behavior under zero field conditions, and possess single-molecule magnet characteristics.

[0019] This invention also provides a method for preparing the above-mentioned binuclear dysprosium single-molecule magnet, comprising the following steps:

[0020] The o-pcbs ligand was dissolved in CH3CN, and then alkali or an alkali solution and DyBr3·6H2O were added in sequence. After the reaction, a yellow solution was obtained. The yellow solution was filtered and volatilized at room temperature until yellow blocky crystals precipitated, which is complex 1.

[0021] Add CH3CN solvent to the solution containing yellow blocky crystals or directly immerse the yellow blocky crystals in CH3CN solvent until the yellow crystal blocks turn into red crystal blocks, i.e., complex 2.

[0022] Furthermore, the molar ratio of the o-pcbs ligand, DyBr3·6H2O, and base is 1:(1~1.2):(1~1.2).

[0023] Furthermore, the alkali is selected from one or more of potassium hydroxide, sodium hydroxide, triethylamine, ammonium hydroxide (Et3N), etc.; the solvent in the alkali solution is selected from CH3OH, diethyl ether, or CH3CN.

[0024] This invention also provides the application of the above-mentioned binuclear dysprosium single-molecule magnet in the preparation of dynamic smart materials with external solvent response.

[0025] Compared with existing technologies, the present invention has the following advantages:

[0026] (1) This invention is the first to successfully construct a solvent-responsive binuclear system using pyridine-nitrogen ligands and dysprosium ions. The single crystal of this material can undergo a reversible single-crystal-to-single-crystal transformation in different solvent atmospheres, accompanied by a reversible exchange of coordinating solvent molecules. This structural change directly leads to a reversible switching of its macroscopic magnetic properties (such as magnetization reversal barrier and relaxation time), realizing "non-invasive" dynamic control of magnetic relaxation behavior.

[0027] (2) Simple and efficient synthesis method: The synthesis method of this material is simple, with high yield and good reproducibility. High-quality single crystals can be obtained by conventional solution method, which facilitates subsequent structural and performance characterization and large-scale preparation. Attached Figure Description

[0028] Figure 1 This is a single-crystal structure diagram of complex 1 obtained in Example 1 of the present invention, wherein the lower right corner represents Dy. 3+ A schematic diagram of the eight-coordinate structure of an ion. In the diagram, green represents the dysprosium ion, blue represents the nitrogen atom, gray represents the carbon atom, and red represents the oxygen atom.

[0029] Figure 2 This is a single-crystal structure diagram of the complex 2 obtained in Example 1 of the present invention, where the lower right corner represents Dy. 3+ Schematic diagram of the eight-coordinate structure of an ion;

[0030] Figure 3 and Figure 4 χ² values ​​for complex 1 and complex 2, respectively M The relationship between T value and temperature;

[0031] Figure 5 and Figure 6 The M vs. H / T curves for complex 1 and complex 2 at different temperatures are shown below.

[0032] Figure 7 and Figure 8 The results of hysteresis loop tests for complex 1 and complex 2 are shown below;

[0033] Figure 9 and Figure 10 χ² values ​​for complex 1 and complex 2 below 20 K, respectively. M′ and χ M" Experimental results on the dependence of temperature and frequency;

[0034] Figure 11 and Figure 12 The real part (χ²) of the AC magnetic susceptibility diagram of complex 1 was measured under zero field. M′ ) and the imaginary part (χ) M" );

[0035] Figure 13 Cole-Cole plots of complex 1 at different temperatures;

[0036] Figure 14 The graph shows the relaxation time of complex 1 as a function of temperature, where the solid line represents the Arrhenius fitting result.

[0037] Figure 15 and Figure 16 χ² values ​​of complex 2 at different temperatures and frequencies are shown below. M′ and χM" data;

[0038] Figure 17 Cole-Cole plots of complex 2 at different temperatures;

[0039] Figure 18 The graph shows the relaxation time of complex 2 as a function of temperature, where the solid line represents the Arrhenius fitting result. Detailed Implementation

[0040] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0041] Example 1: Synthesis of coordination compounds

[0042] Weigh out 0.05 mmol (12.8 mg) of the o-pcbs ligand and dissolve it in 9.5 mL of CH3CN. Then add 0.25 mL (0.2 mol / L) of Et3N in CH3OH solution and stir for 5 min. Add DyBr3·6H2O (0.05 mmol, 18.8 mg) and continue stirring for 20 min. Filter the yellow solution into a 20 mL beaker and allow it to slowly evaporate at room temperature for 5 days, after which yellow blocky crystals precipitate, which is complex 1. Add 2 mL of CH3OH to the above system and allow it to stand at room temperature for 2 days. The yellow blocky crystals turn into red blocky crystals, which is complex 2. Immerse the red blocky crystals in 2 mL of CH3CN solvent for 2 days, and they revert to yellow blocky crystals.

[0043] Example 2: Determination of Crystal Structure

[0044] Single-crystal structure analysis: The instrument used for single-crystal X-ray diffraction experiments was a Rigaku SuperNova, Dual, Atlas S2 diffractometer. Raw data were acquired using the CrysAlisPro software package. The initial structure was obtained using the chargeflipping method or the direct method, refined using the least squares method, and the structure was calculated using the olex2 program. The single-crystal analytical data are shown in Table 1 below.

[0045] Table 1. Test results of crystal structure parameters of complex 1 and complex 2 obtained in Example 1.

[0046]

[0047] Based on the single-crystal test results, the single-crystal structure diagrams of coordination compound 1 and coordination compound 2 are shown below. Figure 1 and Figure 2 Complex 1 crystallizes in the monoclinic P 21 / n space group, and its asymmetric unit consists of a Dy 3+The ion consists of an o-pcbs ligand, a coordinated methanol molecule, three coordinated water molecules, and bromide ions in two lattices and one lattice water molecule. Dy 3+ The ion is octetally coordinated, with two coordinated water molecules (O3 and O5), one coordinated methanol molecule (O6), and an imine nitrogen atom (N1) in the equatorial plane. In addition, a phenolic hydroxyl oxygen atom (O1), a carbonyl oxygen atom (O2), and an oxygen atom from a water molecule (O7) are located axially. The Dy-O bond length is... Range. The stable coordination of ONO in the ligands and the short Dy-O1 bond length help maintain the strong magnetic anisotropy in the complex. The nitroxypyridine atoms on the two o-pcbs ligands connect two dysprosium ions to form a binuclear unit.

[0048] Complex 2 has a similar structure to complex 1, the difference being that a methanol molecule replaces the water molecule and Dy in complex 1. 3+ In addition to ionic coordination, water molecules in the lattice of complex 1 are replaced by acetonitrile molecules. The Dy-O bond length is 2.189- Range. This indicates that the solvent molecules significantly altered the coordination environment of the complex.

[0049] Example 3: Determination of Magnetic Properties

[0050] (1) Determination of variable temperature magnetic susceptibility

[0051] like Figure 3 and Figure 4 As shown, at room temperature (300 K), the χ² values ​​of complex 1 and complex 2 are... M The value of T is 28.53 cm. 3 mol -1 K and 28.34cm 3 mol -1 K, and two Dy 3+ ground state ( 6 H 15 / 2 The theoretical value (28.34 cm) is given by the formula: S = 5 / 2, J = 15 / 2, g = 4 / 3. 3 mol - 1 K) are comparable. From 300K to 25K, the χ² of both is similar. M The value of T decreases slowly, likely due to a reduction in the number of hot particles at the Stark sublevel below 25 K. M The rapid decrease in the T value suggests the possible existence of antiferromagnetic interactions between dysprosium ions. For example... Figure 5 and Figure 6 As shown, the M vs. H / T curves of the two complexes do not overlap at six temperatures: 2K, 5K, 10K, 15K, 20K, and 25K, indicating that their Dy 3+Ions have strong magnetic anisotropy.

[0052] (2) Measurement of hysteresis loop

[0053] We performed hysteresis loop tests on complexes 1 and 2 at low temperatures, such as... Figure 7 and Figure 8 As shown, at a sweep field velocity of 500 Oe / s, complex 1 exhibits significant hysteresis behavior below 7 K, while complex 2 only exhibits significant hysteresis behavior below 6 K. The hysteresis loop has the widest opening at 2 K and a large step at zero field, indicating that it also exhibits significant quantum tunneling behavior.

[0054] (3) Determination of AC magnetic susceptibility

[0055] like Figure 9 and Figure 10 As shown, the χ² of complex 1 and complex 2 below 20K M′ and χ M" Both exhibit significant temperature and frequency dependence, with peak values ​​indicating slow magnetic relaxation behavior. However, the peak temperature of complex 1 at 1 kHz is 14 K, and that of complex 2 at 1 kHz is 11.5 K, suggesting that solvent molecules influence the coordination environment around dysprosium ions, thereby affecting the magnetic properties of the complexes. Time (τ) can be obtained by fitting the AC magnetic susceptibility data at different temperatures using the Debye model. Figure 11-13 , Figure 15-17 Considering the Aubach process with respect to lnτ-T -1 By fitting the curve, we obtain Ea = 82.7K and τ0 = 3.7 × 10⁻¹⁰ for 1. -7 s( Figure 14 ), 2 of Ea = 31.5K, τ0 = 2.2 × 10 -5 s( Figure 18 ).

[0056] As can be seen, the novel binuclear dysprosium single-molecule magnet provided by this invention exhibits a reversible transformation of its crystal structure and magnetic properties in response to changes in the external solvent atmosphere, achieving a leap from a "static" material to a "dynamic" smart material. This overcomes the limitation of existing technologies where magnet properties are fixed once synthesized, providing a new method for "writing" and "erasing" properties without altering the chemical structure of the parent molecule. Furthermore, this invention provides a simple and efficient synthesis method for this magnetically responsive single-molecule magnet, particularly utilizing the self-assembly of pyridine-nitrogenate Schiff base ligands with dysprosium ions to directionally construct structures with solvent-responsive sites. The unique magnetic relaxation behavior of this material under solvent stimulation is also elucidated, revealing its structure-property relationship.

[0057] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A dual-core dysprosium single-molecule magnet, characterized in that, The binuclear dysprosium single-molecule magnet has one of the following molecular formula structures: Complex 1: {[Dy(o-pcbs)(CH3OH)(H2O)3]·2Br·H2O}2 Complex 2: {[Dy(o-pcbs)(CH3OH)2(H2O)2]·2Br·CH3CN}2; In this context, o-pcbs represents 2-nitropyridyl-(2-hydroxy)phenylhydrazone Schiff base.

2. The dual-nuclear dysprosium single-molecule magnet according to claim 1, characterized in that, The complex 1 crystallizes in space group P 21 / n, with unit cell parameters of […]. α=90°, β=95.410(3)°, γ=90°, Z = 4, μ = 6.833 mm -1 F(000) = 1378.3; the complex 2 crystallizes in P bca Space group, cell parameters are α=90°, β=90°, γ=90°, Z = 8, μ = 6.261 mm -1 F(000) = 2878.

8.

3. The dual-nuclear dysprosium single-molecule magnet according to claim 1, characterized in that, The Dy-O bond length of the complex 1 is at... Range; the Dy-O bond length of the complex 2 is within scope.

4. The dual-nuclear dysprosium single-molecule magnet according to claim 1, characterized in that, Complex 1 is a yellow blocky crystal, and complex 2 is a red blocky crystal.

5. The dual-nuclear dysprosium single-molecule magnet according to claim 1, characterized in that, The complex 1 and complex 2 can undergo reversible interconversion under different solvent environments.

6. The dual-nuclear dysprosium single-molecule magnet according to claim 1, characterized in that, Complex 1 can be converted into complex 2 in CH3OH solvent, and complex 2 can be converted into complex 1 in CH3CN solvent.

7. The method for preparing the binuclear dysprosium single-molecule magnet according to any one of claims 1 to 6, characterized in that, Includes the following steps: The o-pcbs ligand was dissolved in CH3CN, and then alkali or an alkali solution and DyBr3·6H2O were added in sequence. After the reaction, a yellow solution was obtained. The yellow solution was filtered and volatilized at room temperature until yellow blocky crystals precipitated, which is complex 1. Add CH3CN solvent to the solution containing yellow blocky crystals or directly immerse the yellow blocky crystals in CH3CN solvent until the yellow crystal blocks turn into red crystal blocks, i.e., complex 2.

8. The method for preparing a binuclear dysprosium single-molecule magnet according to claim 7, characterized in that, The molar ratio of the o-pcbs ligand, DyBr3·6H2O, and base is 1:(1~1.2):(1~1.2).

9. The method for preparing a dual-nuclear dysprosium single-molecule magnet according to claim 7, characterized in that, The alkali is selected from one or more of potassium hydroxide, sodium hydroxide, triethylamine, ammonium hydroxide, etc.; the solvent in the alkali solution is selected from CH3OH, diethyl ether, or CH3CN.

10. An application of the binuclear dysprosium single-molecule magnet as described in claims 1-6, characterized in that, Used to prepare dynamic smart materials that respond to external solvents.

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