Spin crossover complex with low-pressure sensitivity as well as preparation method and application of spin crossover complex

Abstract

The invention relates to a spin crossover complex with low-pressure sensitivity and a preparation method and application thereof, 5-chlorine-salicylaldehyde reacts with thiosemicarbazide to obtain a ligand (5-chloro-2-hydroxybenzylidene) hydrazino thioamide, the ligand is mixed with iron ions, self-assembly is performed under specific conditions to obtain the spin crossover complex, and the expression of the spin crossover complex is [Fe < III > (H-5-Cl-thsa) (5-Cl-thsa). The material can trigger a spin state transition temperature (Tc) to move to a room temperature range under micro pressure, and has high pressure sensitivity, and meanwhile, the transition temperature is close to the room temperature; the spin crossover material can be used as a piezomagnetic material, can be used for a pressure sensor device, and provides an innovative solution for developing a high-precision, low-power-consumption and miniaturized pressure sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezomagnetic materials, and in particular relates to a spin crossover complex with low-pressure sensitivity, a preparation method thereof, and an application thereof. Background Art

[0002] Spin-crossover materials are a class of molecular materials that can undergo spin state transitions in response to external stimuli. Their electronic structure undergoes reversible switching between high-spin and low-spin states. This characteristic leads to significant changes in the material's physical properties, such as optics, magnetism, and conductivity, giving it significant application potential in sensors, information storage, molecular switches, and other fields. In recent years, pressure-responsive materials based on the spin-crossover effect have attracted much attention. Due to their high sensitivity and reversibility to external pressure, they are considered ideal candidates for the development of a new generation of high-precision pressure sensors.

[0003] The spin transition temperature of existing spin-crossover materials is usually difficult to achieve efficient pressure regulation at room temperature and difficult to produce rapid and sensitive pressure response at medium and low pressures, which greatly limits the development of piezomagnetic materials. In addition, traditional pressure sensors (such as piezoresistive and piezoelectric) rely on the deformation response of semiconductor or ceramic materials, and have problems such as insufficient sensitivity, poor fatigue resistance, and difficulty in miniaturization. It is difficult to meet the demand for high-performance sensors in emerging fields such as flexible electronics and micro-electromechanical systems (MEMS). A piezomagnetic material with an operating temperature near room temperature and high sensitivity at medium and low pressures is crucial to the development of this field. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a spin crossover complex with low pressure sensitivity and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is: a spin cross complex with low pressure sensitivity, the expression is [Fe III (H-5-Cl-thsa)(5-Cl-thsa), the structural formula of which is shown in Formula 1;

[0006]

[0007] Preferably, the spin transition temperature (T c ) is T c ↑:225.46K,T c ↓:224.66K; sensitivity to pressure during heating is 43.8K kbar -1 ; The sensitivity to pressure during cooling is 45.9K kbar -1 .

[0008] Preferably, T cThey are: 220bar, T c ↑:240.36K,T c ↓:234.7K;520bar,T c ↑:250.23K,T c ↓:249.39K;770bar,T c ↑:260.24K,T c ↓:259.49K;970bar,T c ↑:270.27K,T c ↓:269.43K.

[0009] The preparation method of the spin-cross complex with low pressure sensitivity comprises the following steps:

[0010] Step 1: Add 5-chloro-salicylaldehyde and thiosemicarbazide in a molar ratio of 1:0.5-2 to an ethanol solvent, stir and reflux at 60-80°C for 4-8 hours to prepare a ligand (5-chloro-2-hydroxybenzylidene) hydrazinothioamide;

[0011] Step 2: At room temperature and pressure, methanol and isopropanol solvents are mixed to prepare a crystal culture mixture; (5-chloro-2-hydroxybenzylidene) hydrazinethioamide is added to the crystal culture mixture and allowed to stand for 10 to 30 minutes;

[0012] Step 3: adding triethylamine to the solution prepared in step 2;

[0013] Step 4: adding Fe(NO3)3·9H2O solution to the crystal culture mixed solution obtained in step 3;

[0014] Step 5: The mixed solution was allowed to react at 80-100°C for 16-24 hours, and after cooling to room temperature, black block crystals were collected and precipitated, which was the spin cross complex [Fe III (H-5-Cl-thsa)(5-Cl-thsa);

[0015] The molar ratio of (5-chloro-2-hydroxybenzylidene)hydrazinothioamide, triethylamine and Fe(NO3)3·9H2O is 0.2-0.4:0.60-0.90:0.1-0.2.

[0016] Preferably, the volume ratio of methanol to isopropanol in the crystal culture mixture is 1-2:2-5;

[0017] Preferably, in the Fe(NO3)3·9H2O solution, the volume of distilled water corresponding to each millimole of Fe(NO3)3·9H2O is 4 to 7 mL.

[0018] A piezomagnetic material includes a spin-crossing complex with low pressure sensitivity.

[0019] Application of piezomagnetic materials in pressure sensors.

[0020] The advantages and positive effects of the present invention are: proposing a new type of spin-crossover material, which can trigger the spin state transition temperature to move to the room temperature range under a small pressure, has high pressure sensitivity, and the transition temperature is near room temperature; the spin-crossover material can be used as a piezomagnetic material and can be used in pressure sensor devices, providing an innovative solution for the development of high-precision, low-power, miniaturized pressure sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Spin-cross complexes [Fe III Molecular structure diagram of (H-5-Cl-thsa)(5-Cl-thsa);

[0022] Figure 2 Spin-cross complexes [Fe III Temperature-dependent magnetic susceptibility curve of (H-5-Cl-thsa)(5-Cl-thsa) measured under an external magnetic field of 1000 Oe;

[0023] Figure 3 Spin-cross complexes [Fe III Differential scanning calorimetry analysis curve of (H-5-Cl-thsa)(5-Cl-thsa);

[0024] Figure 4 Spin-cross complexes [Fe III X-ray powder diffraction data of (H-5-Cl-thsa)(5-Cl-thsa);

[0025] Figure 5 Spin-cross complexes [Fe III Normalized temperature-dependent magnetic susceptibility curves of (H-5-Cl-thsa)(5-Cl-thsa) under different applied hydrostatic pressures;

[0026] Figure 6 Spin-cross complexes [Fe III Temperature change and pressure sensitivity of (H-5-Cl-thsa)(5-Cl-thsa) spin transition driven by pressure. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0028] The present invention relates to a spin cross complex with low pressure sensitivity and its preparation method and application. The ligand (5-chloro-2-hydroxybenzylidene) hydrazinethioamide is obtained by reacting 5-chloro-salicylaldehyde with thiosemicarbazide, and the ligand is mixed with iron ions and self-assembled under specific conditions to obtain a spin cross complex. The expression is [Fe III (H-5-Cl-thsa)(5-Cl-thsa), whose structural formula is shown in Formula 1; wherein 5-Cl-thsa is (5-chloro-2-hydroxybenzylidene) hydrazinothioamide, whose structural formula is shown in Formula 2.

[0029] Complex [Fe III (H-5-Cl-thsa)(5-Cl-thsa) structural formula;

[0030] (5-chloro-2-hydroxybenzylidene) hydrazinothioamide structural formula;

[0031] The specific preparation steps are as follows:

[0032] Step 1: Add 5-chloro-salicylaldehyde and thiosemicarbazide to an ethanol solvent, stir and reflux at 60-80°C for 4-8 hours, cool, wash, filter, and dry to obtain a white powdery precipitate, which is the ligand (5-chloro-2-hydroxybenzylidene) hydrazinethioamide; wherein the molar ratio of 5-chloro-salicylaldehyde to thiosemicarbazide is 1:0.5-2, and the volume of ethanol added per millimole of 5-chloro-salicylaldehyde is 5-10 mL; the reaction equation is as follows:

[0033]

[0034] Step 2: at room temperature and pressure, methanol and isopropanol solvents are mixed to obtain a crystal culture mixture, which is a colorless and transparent solution; the prepared (5-chloro-2-hydroxybenzylidene) hydrazinethioamide is added to the crystal culture mixture, and after standing for 10 to 30 minutes, a colorless and transparent solution with a small amount of white precipitate is formed; wherein the crystal culture mixture is a mixed solution of methanol and isopropanol, and the volume ratio of methanol to isopropanol is 1 to 2:2 to 5;

[0035] Step 3: Add triethylamine to the solution prepared in step 2, and the mixed solution will turn light yellow;

[0036] Step 4: At room temperature and pressure, add Fe(NO3)3·9H2O to distilled water and fully dissolve it to obtain an orange metal salt solution. The volume of distilled water corresponding to each millimole of Fe(NO3)3·9H2O is 4-7 mL. The Fe(NO3)3·9H2O solution is added to the crystal culture mixed solution obtained in step 3. The solution turns black-green.

[0037] Step 5: Place the reaction vessel into a reactor, and place the reaction vessel in an oven at 80-100°C for 16-24 hours. After the reactor is completely cooled to room temperature, the reaction vessel is taken out. Black block crystals are observed on the inner wall of the reaction vessel. The product is obtained after washing, filtering, and drying. The prepared spin cross complex [Fe III (H-5-Cl-thsa)(5-Cl-thsa);

[0038] The molar ratio of (5-chloro-2-hydroxybenzylidene)hydrazinothioamide, triethylamine and Fe(NO3)3·9H2O is 0.2-0.4:0.60-0.90:0.1-0.2.

[0039] Spin-cross complexes [Fe III (H-5-Cl-thsa)(5-Cl-thsa), the magnetic test results under normal pressure show that the compound has a one-step mutation spin crossover behavior, and the spin transition temperature is T c ↑:225.46K,T c ↓:224.66K.

[0040] In the hydrostatic pressure range of 1bar-1000bar, the product shows a one-step mutation spin crossover at different pressures. As the pressure increases, the transition temperature (T c ) moves to the room temperature range, T c They are: 220bar, T c ↑:240.36K,T c ↓:234.7K;520bar,T c ↑:250.23K,T c ↓:249.39K;770bar,T c ↑:260.24K,T c ↓:259.49K;970bar,T c ↑:270.27K,T c ↓:269.43K. After the pressure is released, the spin transition temperature of the product can be restored to the initial level, and dT c / dP is defined as T c Sensitivity to pressure, the sensitivity of the product to pressure during the heating and cooling process (dT c / dP) are 43.8K kbar -1 and 45.9K kbar -1 , this compound is a new type of spin-crossover compound with ultra-high pressure sensitivity.

[0041] Spin-cross complexes [Fe III(H-5-Cl-thsa)(5-Cl-thsa) minimum asymmetric unit such as Figure 1 As shown, its center is a trivalent Fe hexacoordinated by N2O2S2, and the metal center is coordinated by two Schiff base ligands. Applying pressure will shorten the bond length between the metal center and the ligand, resulting in an increase in the crystal field splitting energy, which is more favorable for the low spin state. Therefore, a higher temperature is required to trigger the transition from the LS state to the HS state, resulting in a spin transition temperature T c Increased; In addition, the complex [Fe III (H-5-Cl-thsa)(5-Cl-thsa) is a typical two-dimensional layered structure, with the halogen Cl located between layers. The layers are interconnected by halogen-related hydrogen bonds, resulting in minimal steric hindrance. The applied pressure causes a significant volume contraction, leading to significant structural changes and, therefore, significant pressure sensitivity. The complex was synthesized using a heating reaction, simplifying the reaction process. The introduction of heat rapidly breaks down the potential barriers required for synthesis, enabling stable and rapid nucleation growth. The resulting crystals exhibit excellent crystallinity and morphology.

[0042] Spin-cross complexes [Fe III (H-5-Cl-thsa)(5-Cl-thsa) has low pressure sensitivity and can be used in many fields. In particular, in the field of pressure sensors, the spin temperature T is changed by pressure as the driving force. c The spin transition temperature can be controlled even at low pressures of several hundred bar, with the transition temperature remaining near room temperature. These properties make it suitable for use as a piezomagnetic material in pressure sensor devices. The complex also features a simple synthesis scheme, minimal equipment requirements, and universal applicability, making it suitable for industrial deployment.

[0043] The present invention is described below with reference to the accompanying drawings. Experimental methods without specific operating steps are carried out in accordance with the corresponding product specifications. Unless otherwise specified, the instruments, reagents, and consumables used in the examples can be purchased from commercial companies.

[0044] Example 1:

[0045] A mixture of 5-chloro-salicylaldehyde (1.5657 g, 10 mmol) and thiosemicarbazide (0.9114 g, 10 mmol) was added to 60 mL of ethanol solvent and stirred at 75°C for 8 h. After cooling, washing, filtering, and drying, a white powdery precipitate was obtained, which was the ligand (5-chloro-2-hydroxybenzylidene) hydrazinothioamide.

[0046] At room temperature and pressure, a mixed solution of 4 mL of methanol and 8 mL of isopropanol was added to the inner container of the hydrothermal synthesis reactor to prepare a crystal culture solution. (5-chloro-2-hydroxybenzylidene) hydrazinothioamide (0.0918 g, 0.4 mmol) was added to the crystal culture solution and allowed to stand for 10 minutes. Triethylamine (112 μL, 0.8 mmol) was added to the above mixed solution, and the solution turned yellow.

[0047] Fe(NO₃)₃·9H₂O (0.0808 g, 0.2 mmol) was added to 1 mL of distilled water and fully dissolved to obtain an orange metal salt solution. This solution was then added dropwise to the crystal culture mixture described above, resulting in a dark green solution. The reactor liner was placed into the outer shell and placed in an 85°C oven for 20 hours. The oven was then removed and allowed to stand for 24 hours, allowing the reactor to completely cool to room temperature. Black block crystals adhered to the walls of the reactor liner, representing the target spin-crossover compound. After washing, filtration, and drying, a novel spin-crossover compound with low-pressure sensitivity and room-temperature operation was obtained with a yield of 62.8%.

[0048] The obtained product was tested, and the magnetic test results under normal pressure showed that the compound has a one-step mutation spin crossover behavior. The temperature-dependent magnetic susceptibility curve of the new spin crossover complex measured under an external magnetic field of 1000Oe is as follows: Figure 2 The differential scanning calorimetry analysis curve is shown in Figure 3 As shown, the spin transition temperature of the complex is T c ↑:225.46K,T c ↓:224.66K. XRD data as follows Figure 4 As shown in Figure 3, the measured data are well fitted with the simulated data, proving that the sample has a high degree of crystallinity.

[0049] Example 2:

[0050] A mixture of 5-chloro-salicylaldehyde (0.7829 g, 5 mmol) and thiosemicarbazide (0.4557 g, 5 mmol) was added to 25 mL of ethanol solvent and stirred at 75°C for 8 h. After cooling, washing, filtering and drying, a white powdery precipitate was obtained, which was the ligand: (5-chloro-2-hydroxybenzylidene) hydrazinothioamide;

[0051] At room temperature and pressure, a mixed solution of 2 mL of methanol and 10 mL of isopropanol was added to the inner container of the hydrothermal synthesis reactor to prepare a crystal culture solution. (5-chloro-2-hydroxybenzylidene) hydrazinothioamide (0.0918 g, 0.4 mmol) was added to the crystal culture solution and allowed to stand for 10 minutes. Triethylamine (120 μL, 0.86 mmol) was added to the above mixed solution, and the solution turned yellow.

[0052] Fe(NO₃)₃·9H₂O (0.0808 g, 0.2 mmol) was added to 1 mL of distilled water and fully dissolved to obtain a metal salt solution, which appeared orange. The metal salt solution was then added dropwise to the crystal culture mixture, resulting in a dark green solution. The reactor liner was placed into the reactor shell and placed in a 90°C oven for 20 hours. The oven was then removed and allowed to stand for 24 hours, allowing the reactor to completely cool to room temperature. Black block crystals adhered to the walls of the reactor liner, representing the target spin-crossover compound. After washing, filtration, and drying, a novel spin-crossover compound with low-pressure sensitivity and room-temperature operation was obtained in a yield of 54.3%.

[0053] Example 3:

[0054] A mixture of 5-chloro-salicylaldehyde (1.5657 g, 10 mmol) and thiosemicarbazide (0.9114 g, 10 mmol) was added to 60 mL of ethanol solvent and stirred at 75°C for 8 h. After cooling, washing, filtering and drying, a white powdery precipitate was obtained, which was the ligand: (5-chloro-2-hydroxybenzylidene) hydrazinothioamide;

[0055] At room temperature and pressure, a mixed solution of 4 mL of methanol and 8 mL of isopropanol was added to the inner container of the hydrothermal synthesis reactor to prepare a crystal culture solution. (5-chloro-2-hydroxybenzylidene) hydrazinothioamide (0.0918 g, 0.4 mmol) was added to the crystal culture solution and allowed to stand for 10 minutes. Triethylamine (120 μL, 0.86 mmol) was added to the above mixed solution, and the solution turned yellow.

[0056] Fe(NO₃)₃·9H₂O (0.0808 g, 0.2 mmol) was added to 1 mL of distilled water and fully dissolved to obtain a metal salt solution, which appeared orange. The metal salt solution was then added dropwise to the crystal culture mixture, resulting in a dark green solution. The reactor liner was placed into the reactor shell and placed in a 90°C oven for 20 hours. The oven was then removed and allowed to stand for 24 hours, allowing the reactor to completely cool to room temperature. Black block crystals adhered to the walls of the reactor liner, representing the target spin-crossover compound. After washing, filtration, and drying, a novel spin-crossover compound with low-pressure sensitivity and room-temperature operation was obtained in a yield of 36.3%.

[0057] Example 4:

[0058] The spin crossover compounds prepared in Examples 1-3 were tested by applying an external magnetic field of 1000 Oe and performing temperature-dependent magnetic susceptibility tests on the complexes at different pressures:

[0059] At 220 bar, the transition temperature during heating is T c↑: 240.36K, the cooling process transition temperature is T c ↓: 234.7K. Under 520bar, the transition temperature during heating is T c ↑: 250.23K, the cooling process transition temperature is T c ↓: 249.39 K. Under 770 bar, the transition temperature during heating is T c ↑: 260.24K, the cooling process transition temperature is T c ↓:259.49K. Under 970bar, the transition temperature during heating is T c ↑: 270.27K, the cooling process transition temperature is T c ↓:269.43K. After the pressure is released, the spin transition temperature of the product can be restored to the initial level, such as Figure 6 As shown, dT c / dP is defined as T c Sensitivity to pressure, the sensitivity of the product to pressure during the heating and cooling process (dT c / dP) are 43.8K kbar -1 and 45.9K kbar -1 , this compound is a new type of spin-crossover compound with ultra-high pressure sensitivity.

[0060] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A spin-cross complex with low pressure sensitivity, characterized in that: The expression is [Fe III (H-5-Cl-thsa)(5-Cl-thsa), the structural formula of which is shown in Formula 1; 2. The spin-cross complex with low pressure sensitivity according to claim 1, characterized in that: Spin transition temperature (T c ) is T c ↑:225.46K,T c ↓:224.66K; sensitivity to pressure during heating is 43.8K kbar -1 ; The sensitivity to pressure during cooling is 45.9K kbar -1 .

3. The spin-cross complex with low pressure sensitivity according to claim 1, characterized in that: T under different pressures c They are: 220bar, T c ↑:240.36K,T c ↓:234.7K;520bar,T c ↑:250.23K,T c ↓:249.39K;770bar,T c ↑:260.24K,T c ↓:259.49K;970bar,T c ↑:270.27K,T c ↓:269.43K.

4. The method for preparing the low-pressure-sensitive spin crossover complex according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: Step 1: Add 5-chloro-salicylaldehyde and thiosemicarbazide in a molar ratio of 1:0.5-2 to an ethanol solvent, stir and reflux at 60-80°C for 4-8 hours to prepare a ligand (5-chloro-2-hydroxybenzylidene) hydrazinothioamide; Step 2: At room temperature and pressure, methanol and isopropanol solvents are mixed to prepare a crystal culture mixture; (5-chloro-2-hydroxybenzylidene) hydrazinethioamide is added to the crystal culture mixture and allowed to stand for 10 to 30 minutes; Step 3: adding triethylamine to the solution prepared in step 2; Step 4: adding Fe(NO3)3·9H2O solution to the crystal culture mixed solution obtained in step 3; Step 5: The mixed solution was allowed to react at 80-100°C for 16-24 hours, and after cooling to room temperature, black block crystals were collected and precipitated, which was the spin cross complex [Fe III (H-5-Cl-thsa)(5-Cl-thsa); The molar ratio of (5-chloro-2-hydroxybenzylidene)hydrazinothioamide, triethylamine and Fe(NO3)3·9H2O is 0.2-0.4:0.60-0.90:0.1-0.

2.

5. The method for preparing a spin-cross complex with low pressure sensitivity according to claim 4, wherein: The volume ratio of methanol to isopropanol in the crystal culture mixture is 1-2:2-5.

6. The method for preparing a spin-cross complex with low pressure sensitivity according to claim 4, wherein: In the Fe(NO3)3·9H2O solution, the volume of distilled water corresponding to each millimole of Fe(NO3)3·9H2O is 4 to 7 mL.

7. A piezomagnetic material, characterized in that: The invention comprises the spin cross complex with low pressure sensitivity as described in any one of claims 1 to 3.

8. Use of the piezomagnetic material according to claim 7 in a pressure sensor.

Images