Preparation method of optical / thermal dual-mode switchable monomolecular magnet material

Abstract

The invention belongs to the technical field of magnetic materials, and particularly relates to a preparation method of a light / heat dual-mode switchable monomolecular magnet material, which comprises the following steps: uniformly mixing dysprosium chloride hexahydrate, 9-anthracarboxylic acid, N, N-dimethylformamide and deionized water, putting the mixture into a 20mL glass bottle, carrying out hydrothermal reaction, and naturally cooling to room temperature, thereby obtaining the light / heat dual-mode switchable monomolecular magnet material. Filtering and washing to obtain a monomolecular magnet material; according to the present invention, by using the dual optical activity characteristic of the 9-anthracene formic acid ligand, through the photo-induced cycloaddition and electron transfer dual regulation and control mechanism, on the premise of maintaining the integrity of the single crystal, the 0-dimensional to 1-dimensional structure conversion of the single-molecule magnet is achieved, and the light-controlled and thermal-controlled dual magnetic switch functions are provided; a new way is opened up for intelligent regulation and control and high-performance application of the molecule-based magnetic material; the preparation method is simple in process and efficient, and the obtained substance is high in stability, easy to produce on a large scale and wide in market prospect.

Description

Technical field:

[0001] The invention belongs to the technical field of magnetic materials, and in particular relates to a method for preparing a light / heat dual-mode switchable single-molecule magnetic material. Background technology:

[0002] In the field of molecular-based magnetic materials, single-molecule magnets (SMMs) are considered to be potential key materials in the future fields of information storage, quantum computing, and spin electronics due to their unique magnetic properties, such as significant hysteresis effect, quantum tunneling effect, and high spin state stability. However, the magnetic regulation of traditional single-molecule magnets mostly relies on macroscopic means such as external magnetic field or temperature, and their response speed and reversibility are difficult to meet the needs of practical applications. Therefore, the development of new, efficient and reversible magnetic regulation methods has become an important direction of current research on molecular-based magnetic materials.

[0003] In recent years, photo-controlled and thermal-controlled magnetic materials have attracted much attention because they can achieve remote, non-contact magnetic control. These materials introduce photosensitive or thermal-sensitive groups to change the molecular structure or electronic arrangement under light or temperature changes, thereby achieving reversible magnetic control. However, most existing photo-controlled or thermal-controlled magnetic materials are often accompanied by crystal structure destruction or phase change during the magnetic control process, resulting in instability or loss of material properties.

[0004] As an important branch of molecular nanomagnets, single-molecule magnets (SMMs) have attracted extensive attention from the scientific community due to their unique magnetic properties and potential application value, such as high-density information storage, complex logic gates, and advanced device architectures. However, achieving reversible regulation of SMMs remains a very challenging task. Summary of the invention:

[0005] The purpose of the present invention is to solve the problem that the prior art cannot realize the dual photoactive response of photoinduced cycloaddition and photogenerated free radicals to regulate the performance of single-molecule magnets, and provide a method for preparing a light / thermal dual-mode switchable single-molecule magnet material. 9-Anthracenecarboxylic acid is used as an organic ligand to achieve a structural transition from zero dimension to one dimension and from single crystal to single crystal (SC-SC), and through the dual regulation mechanism of light-induced cycloaddition and electron transfer, the reversible on / off switching of SMMs behavior is successfully achieved.

[0006] In order to achieve the above object, the present invention provides a method for preparing a light / heat dual-mode switchable single-molecule magnet material, which realizes light / heat switching on / off of the single-molecule magnet material through cycloaddition and electron transfer. The specific steps are as follows:

[0007] (1) Add dysprosium salt (0.035-0.040 g), organic acid (0.025-0.03 g), N,N-dimethylformamide (DMF) (1 mL) and deionized water (5 mL) into a reaction glass bottle;

[0008] (2) The mixture obtained in step (1) is ultrasonicated at room temperature for 20-30 minutes, mixed evenly, and then subjected to solvent thermal reaction, heated to 90°C for 12-14 hours, taken out, naturally cooled to room temperature, filtered, washed, and dried to obtain yellow block crystals, which are optical / thermal dual-mode switchable single-molecule magnet materials.

[0009] The dysprosium salt used in the present invention is dysprosium chloride hexahydrate, the organic acid is 9-anthracenecarboxylic acid, and the volume of the reaction glass bottle is 20 mL.

[0010] The present invention also provides a light / heat dual-mode switchable single-molecule magnet material prepared by the above method, the molecular formula of which is C 126 H 88 Dy2N2O 18 , as yellow block crystals.

[0011] The light / heat dual-mode switchable single-molecule magnetic material of the present invention has dual magnetic switching functions of light control and heat control. Illumination causes the material to produce magnetic behavior, and heating causes the magnetic behavior to disappear.

[0012] The illumination parameters of the present invention are: irradiation under a xenon lamp (320-780nm, 300W) at room temperature for 120-150min.

[0013] The heating parameters of the present invention are: heating at 120° C. for 48-50 hours.

[0014] The chemical formula of the light / heat dual-mode switchable single-molecule magnet material prepared by the present invention is [Dy2(DMF)2(HAC)2(AC)6]. The magnet material has a light / heat reversible switchable magnet behavior. Specifically, after being irradiated by a xenon lamp (320-780nm, 300W), the magnet material undergoes a dual structural change in the molecular and electronic structures. Under the interaction of stacking and hydrogen bonding, the sample after illumination generates anthracenecarboxylic acid free radicals through an electron transfer process assisted by metal ions inside the ligand. Due to the unique π The conjugated structure undergoes a [4+4] cycloaddition reaction under the action of π-π stacking between anthracene rings, realizes the transformation from single crystal to single crystal (SC-SC), forms a one-dimensional chain complex, and exhibits the photochromism and fluorescence quenching phenomenon induced by free radicals at room temperature; at the same time, through the coordinated regulation of photoinduced cycloaddition and photogenerated free radicals, it exhibits significant single-molecule magnet behavior after the structural transformation; the sample is heated after illumination, and the sample structure is restored to the original state, that is, heating causes the cycloaddition caused by illumination to open the ring and restore to the original monomer structure. The single-molecule magnet material of the present invention can realize the reversible regulation of the magnet by illumination and heating.

[0015] The present invention realizes the SC-SC structural transformation of magnetic materials from 0D to 1D through cycloaddition reaction, and connects isolated molecular units into a one-dimensional chain structure without destroying the crystal structure, thereby changing the interaction between molecules and magnetic behavior. At the same time, combined with the electron transfer mechanism, the electronic arrangement and spin coupling state of the magnetic center can be further regulated to achieve fine control of magnetism.

[0016] Compared with the prior art, the present invention uses 9-anthracenecarboxylic acid as a ligand and prepares a light / heat dual-mode switchable single-molecule magnet material through self-assembly technology. The dual photoactive properties of the 9-anthracenecarboxylic acid ligand are utilized. Through the dual control mechanism of light-induced cycloaddition and electron transfer, the structural transformation of the single-molecule magnet from 0 dimension to 1 dimension is achieved while maintaining the integrity of the single crystal, and the dual magnetic switching functions of light control and heat control are given to it, which opens up a new path for the intelligent control and high-performance application of molecular-based magnetic materials and provides a new idea for designing functional molecules with complex light response behaviors. The preparation method is simple and efficient, and the obtained material has strong stability, is easy to mass produce, and has broad market prospects. Description of the drawings:

[0017] Figure 1 This is a schematic diagram of the molecular structure principle of the single-molecule magnetic material involved in the present invention.

[0018] Figure 2 This is a schematic diagram of the reversible [4+4] cycloaddition principle of the single-molecule magnetic material involved in the present invention under the action of light and temperature.

[0019] Figure 3It is the ultraviolet-visible spectrum diagram of the single-molecule magnetic material involved in the present invention under different conditions.

[0020] Figure 4 The EPR spectra of the single-molecule magnetic material involved in the present invention under different conditions.

[0021] Figure 5 IR spectra of the single-molecule magnetic material involved in the present invention under different conditions.

[0022] Figure 6 The nuclear magnetic resonance hydrogen spectra of the single-molecule magnet material involved in the present invention in 0.6 mL DMSO-d6 and 0.5 μL DCI under different conditions.

[0023] Figure 7 The figure is a schematic diagram of the temperature-dependent DC magnetic susceptibility of the single-molecule magnetic material involved in the present invention before and after illumination in a 1000Oe DC magnetic field at an environment of 2 to 300K.

[0024] Figure 8 It is a schematic diagram of the change of field magnetization intensity of the single-molecule magnetic material involved in the present invention at 2K before and after illumination.

[0025] Fig. 9 The figure is a schematic diagram of AC magnetic susceptibility curves of the single-molecule magnetic material involved in the present invention in 0Oe DC field, 5Oe AC magnetic field, χ' (real part) and χ" (imaginary part).

[0026] Fig.10 The diagram is a schematic diagram of AC magnetic susceptibility curves of the single-molecule magnetic material involved in the present invention in 0Oe DC field, 5Oe AC magnetic field, χ' (real part) and χ" (imaginary part) after illumination.

[0027] Fig.11 It is a schematic diagram of AC magnetic susceptibility curves of the sample of the single-molecule magnet material involved in the present invention after heating in 0Oe DC field, 5Oe AC magnetic field, χ' (real part) and χ" (imaginary part). Specific implementation method:

[0028] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0029] Embodiment 1:

[0030] This embodiment relates to a method for preparing a light / thermal dual-mode switchable single-molecule magnetic material [Dy2(DMF)2(HAc)2(AC)6], and the specific steps are as follows:

[0031] (1) Mix 0.037 g of dysprosium trichloride hexahydrate, 0.03 g of 9-anthracenecarboxylic acid, 1 mL of N,N-dimethylformamide (DMF), and 5 mL of deionized water, transfer to a 20 mL glass bottle, and sonicate for 20 min;

[0032] (2) Seal the glass bottle containing the reactants in step (1), react in an oven at 90°C for 12 hours, take out the glass bottle after the reaction is completed, cool naturally at room temperature, filter, and rinse the obtained crystals repeatedly with distilled water for 3-4 times to obtain yellow block crystals, which are light / thermal dual-mode switchable single-molecule magnet materials.

[0033] The structural formula of the 9-anthracenecarboxylic acid is:

[0034]

[0035] The single-molecule magnet prepared in this example was subjected to single crystal X-ray diffraction test. The data showed that the single-molecule magnet was crystallized in the monoclinic P21 / c space group, and the asymmetric unit consisted of a Dy 3+ ions, three 9-anthracenecarboxylate ions, one 9-anthracenecarboxylic acid and one DMF. The Dy atom adopts the eight-coordination mode of [DyO8], presenting a square antiprism (D 4d ) shape (CShM = 1.418). Four 9-AC bridges two Dy atoms to form a zero-dimensional binuclear structure ( Figure 1 ).

[0036] Embodiment 2:

[0037] This example relates to a magnet test of the single-molecule magnetic material prepared in Example 1 under light switching. The single-molecule magnetic material (original sample) obtained in Example 1 is irradiated under a room temperature xenon lamp (320-780nm, 300W). After 120 minutes, the crystal changes from yellow to brown. The obtained brown sample is recorded as the sample after illumination. After illumination, the C2 and C9 atoms in the adjacent molecules of the sample form covalent bonds, and the C2-C9A / C9-C2A distance of the sample after illumination changes to 1.642 (7). This indicates that the binuclear structure of the original sample of the single-molecule magnetic material undergoes a transformation from 0D to 1D and from single crystal to single crystal, becoming a one-dimensional chain structure in which [4+4] cycloaddition occurs between adjacent anthracene groups. The inter-planar π-π distance between adjacent anthracene rings is The distance between molecules C2···C9A is The overlapping area is about 61.9%, indicating the presence of a strong π–π interaction. The self-chromic properties of the 9-anthracenecarboxylic acid molecule are conducive to the occurrence of electron transfer photochromism, and the intermolecular interaction between the anthracene rings conforms to the Schmidt rule of the [4+4] photocycloaddition reaction. Therefore, the single-molecule magnet material prepared in Example 1 can exhibit dual photoresponsive behavior after light irradiation.

[0038] At the same time, the original samples (before illumination) and the samples after illumination of the single-molecule magnet material were tested by UV-visible spectroscopy, electron paramagnetic resonance spectroscopy (EPR), infrared spectroscopy (IR) and nuclear magnetic resonance hydrogen spectroscopy. The results are as follows: Figure 3-Figure 6 As shown, Figure 3 From the UV-visible spectrum, we can see that there is a broad absorption peak at 450-550nm. As the illumination time increases, the absorption peak intensity increases. This process is due to the continuous generation of free radicals, and the color of the sample gradually deepens. In addition, a new absorption appeared at 325nm, indicating that the AC component underwent a photocycloaddition reaction to form a dimer product. Figure 4 From the EPR spectrum, it can be seen that there is a weak free radical signal before illumination, and after illumination, a sharp and strong free radical signal appears at around g = 2.0047. The intensity change of the signal peak before and after illumination confirms the generation of free radicals. Figure 5 From the infrared spectrum of 2-hydroxy-1-nitro-2-nitro-4-thiocyanate, three new peaks appeared at 608.7, 686.7 and 812.1 cm, corresponding to the out-of-plane deformation vibration of CH of 2-hydroxy-1-nitro-2-thiocyanate caused by photocycloaddition. Figure 6 Analysis of the H NMR spectrum revealed two new chemical shifts at 5.63 ppm and 6.75 ppm, which can be attributed to the H atoms of the dianthracene unit. These spectral analyses provide strong support for the occurrence of photoinduced anthracene [4+4] cycloaddition and the generation of free radicals.

[0039] In order to further explore the photoradical and cycloaddition of Dy 3+ The magnetic relaxation performance of the complex was regulated. The curve of the molar magnetic susceptibility multiplied by the temperature at 2-300K of the complex was tested under a 1000Oe DC magnetic field. Figure 7 As shown in Figure 2, the χT value of the single-molecule magnet material at 300K is 13.92 cm 3 mol -1 K, lower than an uncoupled Dy 3+ Theoretical value (14.17cm 3 mol -1 K), due to the deoccupancy of the Stark level, the χT value decreases as the temperature decreases, reaching a minimum value of 9.04 cm at 2 K. 3 mol -1K, indicating that there is a weak antiferromagnetic coupling between metal ions; the χT value of the sample at 300K after illumination is 14.30cm 3 mol -1 K, in the process of decreasing with temperature, drops to the lowest value of 10.69cm at 6K 3 mol -1 K, and then rose slightly, reaching 10.97cm at 2K 3 mol -1 K, which proves that the metal ion center produces ferromagnetic coupling after illumination. The curve of magnetic susceptibility changing with magnetic field was studied at 2K ( Figure 8 ) found that with the increase of magnetic field, the M value increased linearly in low field, gradually reached a maximum value of 5.5Nβ at 50kOe, and increased to 5.6Nβ after illumination. The original sample and the illuminated sample were tested for variable temperature AC magnetic susceptibility at 100Hz, 500Hz, and 1000Hz under 0 DC field and 5Oe AC field. The results are as follows Fig. 9 and Fig.10 shown. Fig. 9 No AC signal was observed for the single-molecule magnet material, which may be due to the existence of the magnetization quantum tunneling effect. However, after illumination, the peak values ​​of the real part (χ') and imaginary part (χ") of the sample at 100-10000Hz frequency in zero DC field changed significantly ( Fig.10 ), showing a frequency dependence at different temperatures, which is characteristic of magnetic relaxation phenomena, indicating that light-induced single-molecule magnetic behavior.

[0040] Embodiment 3:

[0041] This example involves a thermal switching magnet test of the single-molecule magnet material prepared in Example 1. The sample after illumination in Example 2 was heated at 120°C for 48 hours, and the resulting crystal was recorded as the heated sample. The heated sample was subjected to a single crystal X-ray diffraction test, and the data obtained from the test were the same as those of the single-molecule magnet material in Example 1, proving the completion of the dedimerization process ( Figure 2 ). This indicates that the sample recovered to its original structure after being heated after being exposed to light.

[0042] This embodiment adopts 1 This remarkable reversibility was closely followed by H NMR, IR, UV, and EPR spectroscopy, and the results are as follows Figure 3-6 These results verify that the photocycloaddition product returns to its original monomer configuration upon heating. However, UV-visible and EPR spectra show that the photogenerated radicals of the heated sample exhibit remarkable stability, indicating that the heat treatment selectively quenches the photodimerization reaction, while the photoinduced electron transfer process is unaffected.

[0043] This example also measures the magnetic susceptibility of the heated sample to further study its reversibility. The results are as follows: Fig.11 As shown. Fig.11 It can be seen that the frequency dependence of χ’ and χ” almost disappears, returning to the initial state shown by the original sample. This observation indicates that the SMMs behavior is effectively eliminated by heat treatment.

Claims

1. A method for preparing a light / thermal dual-mode switchable single-molecule magnetic material. It is characterized in that The specific steps are as follows: The dysprosium salt, organic acid, N,N-dimethylformamide and deionized water are mixed evenly, and then a solvent thermal reaction is carried out; after filtering, washing and drying, a yellow block crystal is obtained, which is a light / thermal dual-mode switchable single-molecule magnet material.

2. The method for preparing the optical / thermal dual-mode switchable single-molecule magnetic material according to claim 1, It is characterized in that The dysprosium salt is dysprosium trichloride hexahydrate; and the organic acid is 9-anthracenecarboxylic acid.

3. The method for preparing the optical / thermal dual-mode switchable single-molecule magnetic material according to claim 1, It is characterized in that The mass volume ratio of the dysprosium salt, anthracenecarboxylic acid, dimethylformamide and deionized water is (0.035-0.040) g: (0.025-0.03) g: 1 mL: 5 mL.

4. The method for preparing the optical / thermal dual-mode switchable single-molecule magnetic material according to claim 1, It is characterized in that The mixing method is ultrasound, and the ultrasound time is 20-30 minutes.

5. The method for preparing the optical / thermal dual-mode switchable single-molecule magnetic material according to claim 1, It is characterized in that The temperature of the solvothermal reaction is 90°C and the time is 12-14 hours.

6. A light / thermal dual-mode switchable single-molecule magnetic material prepared by the preparation method according to any one of claims 1 to 5, It is characterized in that The molecular formula of the material is C 126 H 88 Dy 2 N 2 O 18 , as yellow block crystals.

7. The optical / thermal dual-mode switchable single-molecule magnetic material according to claim 6, It is characterized in that The material has dual magnetic switch functions of light control and heat control. Light causes the material to produce magnetic behavior, and heating causes the magnetic behavior to disappear.

8. The optical / thermal dual-mode switchable single-molecule magnetic material according to claim 6, It is characterized in that The illumination parameters are: irradiation under a xenon lamp at room temperature for 120-150 minutes.

9. The optical / thermal dual-mode switchable single-molecule magnetic material according to claim 6, It is characterized in that The heating parameters are: heating at 120° C. for 48-50 hours.

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