Four-core gadolinium-based magnetocaloric material and preparation method thereof

Abstract

The invention relates to the technical field of materials, in particular to a tetranuclear gadolinium-based magnetocaloric material and a preparation method thereof. The molecular formula of the tetranuclear gadolinium-based magnetocaloric material is C40H44Cl4Gd4N28O12, the chemical formula of the tetranuclear gadolinium-based magnetocaloric material is [[Gd4 (L) 4 (mu2-N3) 4 (Cl) 4], and L is (E)-2-(hydroxylamino)-N '-((6-methoxypyridine-2-yl) methylene) propanohydrazide without one proton. The tetranuclear gadolinium-based magnetocaloric material crystal disclosed by the invention belongs to a triclinic system and a P-1 space group, and cell parameters are as follows: a is equal to 11.5828 (7), b is equal to 17.3200 (10), c is equal to 18.4552 (11), alpha is equal to 86.047 (3) degrees, beta is equal to 79.424 (3) degrees, gamma is equal to 86.413 (3) degrees, and V is equal to 3626.1 (4) 3. The tetranuclear gadolinium-based magnetocaloric material has large magnetic entropy change and can be used as a magnetic refrigeration material, and the preparation method is easy and convenient to operate, good in reproducibility and high in product purity.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and particularly to a tetranuclear gadolinium-based magnetocaloric material and a preparation method thereof. Background Art

[0002] The magnetocaloric effect (MCE) refers to the temperature change that occurs when a magnetic material is magnetized by an external magnetic field under adiabatic conditions. This phenomenon usually manifests as an increase in temperature during magnetization and a decrease in temperature during demagnetization. Magnetocaloric refrigeration technology based on the magnetocaloric effect is expected to become the next-generation refrigeration technology to replace traditional refrigeration solutions. High-performance magnetocaloric materials used in magnetocaloric refrigeration can well solve the pollution problems caused by current refrigeration technologies. Compared with the current mainstream compression refrigeration technology, magnetocaloric refrigeration has the advantages of high efficiency, low energy consumption, low noise, and easy maintenance, and has attracted extensive attention from scientific workers at home and abroad.

[0003] The magnetocaloric refrigeration ability of magnetic materials depends on the magnitude of the magnetic entropy change. The larger the value of the magnetic entropy change and the wider the magnetic entropy change temperature range, the stronger the comprehensive magnetocaloric performance of the material, and the more suitable it is for use in magnetocaloric refrigeration. Since the 4f electrons of the rare earth element Gd are in a half-filled state and have a large theoretical magnetic moment, it has a relatively excellent magnetocaloric effect. In 1976, Brown et al. of NASA in the United States used the rare earth element Gd as a magnetocaloric material to achieve a temperature span change of nearly 47 K under the action of a 7T magnetic field applied by a superconducting magnet for the first time in room-temperature magnetocaloric refrigeration. At present, a large number of Gd-based alloys and Gd-based compounds have been synthesized and their properties studied, which is one of the main research directions for finding magnetocaloric materials with excellent properties.

[0004] Before the work of this patent application, there were no reports in patent literatures and scientific papers on the self-assembly of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, gadolinium chloride, sodium azide to form a magnetocaloric material in a methanol / acetonitrile mixed solvent. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a tetranuclear gadolinium-based magnetocaloric material.

[0006] Another object of the present invention is to provide a preparation method of the above-mentioned tetranuclear gadolinium-based magnetocaloric material.

[0007] The technical problem to be solved by the present invention is achieved through the following technical solutions: A tetranuclear gadolinium-based magnetocaloric material, with the chemical formula [[Gd4(L)4( μ 2-N3)4(Cl)4], and the molecular formula C 40 H 44 Cl4Gd4N28 O 12 , where L is (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide after losing one proton, and the structural formula of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide is:

[0008] The crystal of the tetranuclear gadolinium-based magnetocaloric material belongs to the triclinic system, space group P-1, and the unit cell parameters are a = 11.5828(7) Å, b = 17.3200(10) Å, c = 18.4552(11) Å, α = 86.047(3)°, β = 79.424(3)°, γ = 86.413(3)°, V = 3626.1(4) Å 3 。

[0009] Furthermore, the asymmetric structural unit of the tetranuclear gadolinium-based magnetocaloric material contains 4 independent Gd(III) metal centers (Gd1, Gd2, Gd3, and Gd4), 4 (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide anions L - 、4 μ2-N3 - and 4 Cl - The metal center Gd(III) all adopts an eight-coordinate mode to coordinate with 5 N atoms, 2 O atoms, and 1 Cl atom to form an N5O2Cl coordination environment. Gd1 and Gd3 exhibit a square antiprismatic coordination geometry, while Gd2 and Gd4 exhibit a dodecahedral coordination geometry. The four Gd(III) ions are bridged by 4 μ2-O and 4 μ3-N3 to form a quadrilateral Gd4 core. In the Gd4 core, the distances between adjacent Gd...Gd are 3.9657(5), 4.0172(5), 4.0322(5), and 4.0249(5) Å respectively, and the diagonal Gd...Gd distances are 5.6777(6) and 5.6618(5) Å respectively. The bond lengths of Gd-O / N are in the range of 2.373(5)−2.636(6) Å, and the bond length range of Gd-Cl is in the range of 2.694(2)−2.719(2) Å.

[0010] Furthermore, adjacent molecules are further assembled into a two-dimensional supramolecular structure parallel to the ab plane through hydrogen bond O-H…Cl and C-H…N interactions.

[0011] Preparation method of a kind of four-core gadolinium-based magnetocaloric material: Add (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionyl hydrazide, gadolinium chloride and sodium azide into a mixed solution of methanol and acetonitrile, dropwise add a small amount of triethylamine, stir well and then filter, and then place the filtrate in a high-pressure reaction kettle, and carry out a heating reaction under solvothermal conditions and then slowly cool to obtain the four-core gadolinium-based magnetocaloric material.

[0012] Further, the heating temperature is 70-90 °C.

[0013] Further, the heating reaction time is 48-96 hours.

[0014] Further, the temperature reduction is from 2 °C / hour to 10 °C / hour to room temperature.

[0015] Further, the volume ratio of methanol and acetonitrile in the mixed solution is 6:4.

[0016] Further, the molar ratio of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionyl hydrazide to the volume of triethylamine in the solution is 1 mmol:1 mL.

[0017] Further, the molar ratio of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionyl hydrazide, gadolinium chloride and sodium azide is 0.9-1.1:0.9-1.1:1.8-2.2.

[0018] Further, the molar ratio of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionyl hydrazide, gadolinium chloride and sodium azide is preferably 1:1:2.

[0019] Beneficial effects of the present invention: The present invention synthesizes the four-core gadolinium-based magnetocaloric material ( Figures 1-4 ) for the first time under solvothermal conditions. The four-core gadolinium-based magnetocaloric material of the present invention has high purity ( Figure 7 ); there is an antiferromagnetic coupling effect in the gadolinium magnetocaloric material based on aromatic acyl hydrazide of the present invention, which can be used as an antiferromagnetic material ( Figure 8 , 9 ); the gadolinium magnetocaloric material based on aromatic acyl hydrazide of the present invention has a large magnetic entropy change and exhibits a relatively excellent magnetocaloric effect, and can be used as a magnetic refrigeration material ( Figure 10 ); the preparation method of the four-core gadolinium-based magnetocaloric material of the present invention is simple and convenient to operate, has good reproducibility, and the product has high purity. Description of the drawings

[0020] Figure 1The asymmetric structural unit diagram of the present invention based on a tetranuclear gadolinium-based magnetic thermal material; Figure 2 The coordination environment diagram of the metal center Gd in the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 3 The coordination environment diagram of the hydrazide ligand in the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 4 The square Gd4 nucleus diagram in the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 5 The two-dimensional supramolecular structure diagram of the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 6 The infrared spectrum diagram of the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 7 The X-ray powder diffraction pattern of the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 8 The direct current variable temperature magnetic susceptibility curve of the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 9 The Curie-Weiss law fitting curve diagram of the tetranuclear gadolinium-based magnetic thermal material of the present invention; Figure 10 The magnetic entropy change temperature curve diagram of the tetranuclear gadolinium-based magnetic thermal material of the present invention. Detailed implementation manners

[0021] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Embodiment

[0022] Dissolve 0.1 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.1 mmol of GdCl3·6H2O and 0.2 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V =6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min and then filter. Transfer the filtrate to a stainless steel reaction kettle lined with polytetrafluoroethylene. Seal the stainless steel reaction kettle and place it in an oven. Carry out a solvothermal reaction at 80 °C for 72 h, then cool to room temperature at 2 °C / hour, filter, and wash to obtain the light yellow bulk crystals of the gadolinium magnetic thermal material based on aromatic hydrazide, with a yield of 31.4% (based on Gd).

[0023] The structural characterization of the tetranuclear gadolinium-based magnetic thermal material crystal prepared in this example is as follows: The single-crystal X-ray diffraction data of the crystal were measured using a Bruker Smart Apex CCD single-crystal diffractometer. Graphite-monochromated Mo Kα radiation ( λ = 0.071073 nm) was used as the radiation source at 150 K to collect the diffraction data. The scanning mode was φ-ω scan, and Lp factor correction and empirical absorption correction were performed. The positions of metal atoms and non-hydrogen atoms were determined by the direct method, and all non-hydrogen atom coordinates and their anisotropic thermal parameters were refined by full-matrix least-squares method. The crystallographic parameters are shown in Table 1, and the structure is shown in Figures 1-4 .

[0024] Table 1 Main crystallographic data of the prepared tetranuclear gadolinium-based magnetocaloric material crystal

[0025] A tetranuclear gadolinium-based magnetocaloric material with the chemical formula [[Gd4(L)4( μ 2-N3)4(Cl)4], and the molecular formula is C 40 H 44 Cl4Gd4N 28 O 12 . where L is (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide after losing one proton. The crystal of the tetranuclear gadolinium-based magnetocaloric material belongs to the triclinic system, space group P-1, and the unit cell parameters are a = 11.5828(7) Å, b = 17.3200(10) Å, c = 18.4552(11) Å, α = 86.047(3)°, β = 79.424(3)°, γ = 86.413(3)°, V = 3626.1(4) Å 3 . The asymmetric structural unit of the tetranuclear gadolinium-based magnetocaloric material contains 4 independent Gd(III) metal centers (Gd1, Gd2, Gd3 and Gd4), 4 (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide anions L - , 4 μ2-N3 - and 4 Cl -Composition. The bond lengths of Gd−O / N are in the range of 2.373(5)−2.636(6) Å, and the bond lengths of Gd−Cl are in the range of 2.694(2)−2.719(2) Å. The metal center Gd(III) adopts an eight-coordinate mode to coordinate with 5 N atoms, 2 O atoms and 1 Cl atom, forming an N5O2Cl coordination environment. Gd1(III) and Gd3(III) exhibit a square antiprismatic coordination geometry, while Gd2(III) and Gd4(III) show a dodecahedral coordination geometry. Four Gd(III) ions are bridged by 4 μ2-O and 4 μ3-N3 to form a quadrilateral Gd4 core. In the Gd4 core, the distances between adjacent Gd…Gd are 3.9657(5), 4.0172(5), 4.0322(5) and 4.0249(5) Å respectively, and the diagonal Gd…Gd distances are 5.6777(6) and 5.6618(5) Å. Adjacent molecules are further assembled into a two-dimensional supramolecular structure parallel to the ab plane through hydrogen bonds O−H…Cl and C−H…N interactions.

[0026] The magnetic properties of the tetranuclear gadolinium-based magnetic refrigeration material prepared in this example are studied as follows: Magnetic measurements were carried out using a superconducting quantum interference device Quantum Design MPMS SQUID VSM magnetic measurement system. The test temperature of the DC susceptibility was 2.0–300 K, the magnetic field was 0.1 T, and the DC variable-temperature susceptibility curve is as Figure 8 shown. When T = 300 K, its χ M T value is 31.55 cm 3 3 K mol −1 , which is consistent with the theoretical value of 31.52 cm 8 S 7 / 2 3, L χm = 0, g g = 2) corresponding to 4 free Gd(III) ions 3 3 K mol −1 . As the temperature decreases, the χ M T χm value remains constant in the temperature range of 300–50 K, and then χ M T the χm value drops rapidly. When it drops to 2 K, the χ M T χm value reaches a minimum of 24.72 cm 3 3 K mol −1 . χM T The downward trend of the χ-T plot indicates the existence of antiferromagnetic interactions between Gd(III) ions in the gadolinium-based magnetic refrigerant material based on aromatic hydrazide described in the present invention. As Figure 9 shown, χ M T Curie-Weiss law fitting curve of χ-T: χ M -1 χ = ( T - θ) / C , two important parameters θ θ = −1.55 K, C C = 37.73 cm 3 K mol −1 were obtained. The negative θ θ parameter also proves the existence of antiferromagnetic coupling among Gd(III) ions in the tetranuclear gadolinium-based magnetic refrigerant material.

[0027] Furthermore, the magnetic refrigeration performance of the tetranuclear gadolinium-based magnetic refrigerant material prepared in this example was studied. The magnetocaloric effect of the material can be evaluated by the magnetic entropy change, and the magnetic entropy change (−Δ S m S) can be obtained according to the Maxwell equation: Δ S m S( T) H = ∫[∂ M S( T , H ) / ∂ T H] H d H H. From the magnetic entropy change-temperature curve ( Figure 10 −ΔS-T curve) of the tetranuclear gadolinium-based magnetic refrigerant material prepared in this example, it can be seen that the value of the magnetic entropy change (−Δ S m S) increases with the decrease of temperature, and the maximum value of −Δ S m S is 32.72 J kg −1 −1 −1 K T ( H = ΔH = 2.0 K and Δ

[0028] H = 7.0 T), showing an excellent magnetocaloric effect. Example

[0029] Dissolve 0.09 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.1 mmol of GdCl3·6H2O, and 0.22 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V = 6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min, then filter. Transfer the filtrate to a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the stainless-steel autoclave and place it in an oven. Carry out a solvothermal reaction at 70 °C for 48 h. Then cool it to room temperature at a rate of 10 °C / hour, filter, and wash to obtain the light yellow bulk crystals of the gadolinium magnetothermal material based on aromatic hydrazide, with a yield of 28.3% (based on Gd). Example

[0030] Dissolve 0.11 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.11 mmol of GdCl3·6H2O, and 0.2 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V = 6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min, then filter. Transfer the filtrate to a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the stainless-steel autoclave and place it in an oven. Carry out a solvothermal reaction at 90 °C for 96 h. Then cool it to room temperature at a rate of 5 °C / hour, filter, and wash to obtain the light yellow bulk crystals of the gadolinium magnetothermal material based on aromatic hydrazide, with a yield of 31.7% (based on Gd). Example

[0031] Dissolve 0.1 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.11 mmol of GdCl3·6H2O, and 0.2 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V = 6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min, then filter. Transfer the filtrate to a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the stainless-steel autoclave and place it in an oven. Carry out a solvothermal reaction at 80 °C for 96 h. Then cool it to room temperature at a rate of 10 °C / hour, filter, and wash to obtain the light yellow bulk crystals of the gadolinium magnetothermal material based on aromatic hydrazide, with a yield of 32.1% (based on Gd). Example

[0032] Dissolve 0.11 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.1 mmol of GdCl3·6H2O and 0.2 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V = 6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min, then filter. Transfer the filtrate to a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the stainless-steel autoclave and place it in an oven. Carry out a solvothermal reaction at 80 °C for 48 h, then cool to room temperature at 5 °C / hour. Filter and wash to obtain the light yellow block crystals of the gadolinium magnetocaloric material based on aromatic hydrazide, with a yield of 31.0% (based on Gd). Example

[0033] Dissolve 0.09 mmol of (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide, 0.11 mmol of GdCl3·6H2O and 0.22 mmol of NaN3 in 20 mL of a mixed solution of methanol and acetonitrile ( V : V = 6:4), add 0.1 mL of triethylamine dropwise, stir well at room temperature for 60 min, then filter. Transfer the filtrate to a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the stainless-steel autoclave and place it in an oven. Carry out a solvothermal reaction at 80 °C for 96 h, then cool to room temperature at 2 °C / hour. Filter and wash to obtain the light yellow block crystals of the gadolinium magnetocaloric material based on aromatic hydrazide, with a yield of 29.1% (based on Gd).

[0034] The above embodiments only represent the implementation modes of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. Any technical solutions obtained by means of equivalent substitution or equivalent transformation should fall within the protection scope of the present invention.

Claims

1. A quad-core gadolinium-based magnetocaloric material with the chemical formula [[Gd4(L)4( μ (2-N3)4(Cl)4], and the molecular formula C 40 H 44 Cl4Gd4N 28 O 12 , where L is (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide with one proton lost, and it is characterized in that The crystal of the tetranuclear gadolinium-based magnetocaloric material belongs to the triclinic system, space group P-1, with unit cell parameters a = 11.5828(7) Å, b = 17.3200(10) Å, c = 18.4552(11) Å, α = 86.047(3)°, β = 79.424(3)°, γ = 86.413(3)°, V = 3626.1(4) Å 3 . The asymmetric structural unit of the tetranuclear gadolinium-based magnetocaloric material contains 4 independent Gd(III) metal centers (Gd1, Gd2, Gd3 and Gd4), 4 (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionohydrazide anions L - , 4 μ2-N3 - and 4 Cl - ; the Gd(III) metal centers all adopt an eight-coordinate mode to coordinate with 5 N atoms, 2 O atoms and 1 Cl atom to form an N5O2Cl coordination environment; Gd1 and Gd3 exhibit a square antiprismatic coordination geometry, while Gd2 and Gd4 exhibit a dodecahedral coordination geometry; the four Gd(III) ions are bridged by 4 μ2-O and 4 μ3-N3 to form a quadrilateral Gd4 nucleus; adjacent tetranuclear gadolinium-based magnetocaloric material molecules are further assembled into a two-dimensional supramolecular structure parallel to the ab plane.

2. Preparation method of the tetranuclear gadolinium-based magnetocaloric material according to claim 1: Add (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionylhydrazine, gadolinium chloride, and sodium azide into a mixed solution of methanol and acetonitrile, dropwise add a small amount of triethylamine, stir well and then filter, and then place the filtrate in a high-pressure reaction kettle, and carry out a heating reaction under solvothermal conditions and then slowly cool to obtain the tetranuclear gadolinium-based magnetocaloric material.

3. The preparation method of the quad-core gadolinium-based magnetocaloric material according to claim 2, wherein The molar ratio of the (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionylhydrazine, gadolinium chloride, and sodium azide is 0.9~1.1 : 0.9~1.1 : 1.8~2.2; further, the molar ratio of the (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionylhydrazine, gadolinium chloride, and sodium azide is preferably 1 : 1 :

2.

4. The preparation method of the four-core gadolinium-based magnetocaloric material according to claim 2, characterized in that, The volume ratio of methanol and acetonitrile in the mixed solution of methanol and acetonitrile is 6 :

4.

5. The preparation method of the quad-core gadolinium-based magnetocaloric material according to claim 2, characterized in that, The volume ratio of the molar number of the (E)-2-(hydroxyamino)-N'-((6-methoxypyridin-2-yl)methylene)propionylhydrazine to triethylamine is 1 mmol : 1 mL.

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