Preparation method and application of water-controlled reversible dysprosium-based monomolecular magnet framework material

Abstract

The invention discloses a preparation method and application of a water-controlled reversible dysprosium-based monomolecular magnet framework material, and belongs to the technical field of organic magnetic materials. The preparation method comprises the following steps: adding chemical reaction amounts of dysprosium nitrate hexahydrate and 2, 5-dihydroxy terephthalic acid into a mixed solvent formed by N, N-dimethylformamide and water, mixing, and reacting at a certain temperature; and after the reaction is finished, cooling, collecting a product and purifying to obtain the reversible dysprosium-based single-molecular magnet framework material. The method has the characteristics of lower cost, simple steps and controllable synthesis, and is suitable for large-scale production. The prepared reversible dysprosium-based single-molecular magnet framework material realizes reversible transformation of the performance of a single-molecular magnet under simple conditions, provides a way for regulating and controlling the performance of the single-molecular magnet by dynamic water molecules, and has a good application prospect in the fields of quantum calculation and the like.

Description

Technical Field

[0001] The invention relates to the technical field of organic magnetic materials, and in particular to a preparation method and application of a water-controlled reversible dysprosium-based single-molecule magnet framework material. Background Art

[0002] The quantum science revolution since the early 20th century, driven by the development of related technologies, has profoundly shaped the face of contemporary scientific frontiers and industrial applications. In recent years, with the deep accumulation and great leaps in the fields of electromechanics, optics, control and other technologies, quantum information technology is rapidly moving from theory to practice. Once a breakthrough is achieved in this important field, it will have a subversive impact on future information processing, communication security and even related industrial structures. Quantum information technology needs to rely on the development of quantum computers. Quantum computers are a type of physical device that follows the laws of quantum mechanics to perform high-speed mathematical and logical operations, store and process quantum information. When a device processes and calculates quantum information and runs quantum algorithms, it is a quantum computer. The main characteristics of quantum computers are fast running speed, strong information processing capabilities, and a wide range of applications. Compared with general computers, the more information is processed, the more advantageous it is for quantum computers to perform operations, and the more accurate the operations can be. The calculation basis of quantum computers is quantum bits. Experimental and theoretical studies have found that single-molecule magnets can be used as quantum bit carriers.

[0003] Since its discovery in 1993, single-molecule magnets (SMMs) have attracted extensive attention from disciplines such as chemistry, materials, and physics, mainly because they have great application potential in data storage, information processing, quantum computing, and spintronics devices. Inspired by the first single-molecule magnet study, the initial research focused on 3d metals, mainly by regulating the interaction between metal ions to obtain a relatively large spin value. However, there has been no major breakthrough in the effective energy barrier of the 3d-SMMs system, mainly due to the small magnetic anisotropy of transition metal ions. In 2003, the first 4f single-molecule magnet was synthesized and reported. In subsequent studies on the 4f-SMMs system, it was found that due to the large magnetic anisotropy of most rare earth ions themselves, a relatively large effective energy barrier can be obtained. Among them, rare earth dysprosium ions have become excellent carriers for constructing rare earth single-molecule magnets because of their strong magnetic anisotropy and large spin value. Therefore, more and more research groups are using metal dysprosium salts and different ligands to build single-molecule magnets with better performance. In recent years, single-molecule magnets based on rare earths have made a series of major breakthroughs, and their blocking temperature has exceeded the temperature of liquid nitrogen, taking an important step towards practical application.

[0004] At present, there are many reports on rare earth single-molecule magnets in this field. Although multi-nuclear transition metal cluster-based single-molecule magnets have been developed for many years, their preparation is still uncontrollable. This is mainly reflected in the great difficulty of synthesizing existing materials, the difficulty of preparation, and the almost impossible to achieve large-scale preparation. Designing and synthesizing rare earth framework materials is an important strategy for the controllable synthesis of single-molecule magnets. The stability and porosity of the framework structure provide a solution for the understanding and regulation of the performance of single-molecule magnets.

[0005] Single-molecule magnets exhibit hysteresis effects of molecular origin and a necessary condition for data storage. Examples from the lanthanides have demonstrated this phenomenon at the highest temperatures to date. However, in the decades since the discovery of single-molecule magnets, the hysteresis temperature has only increased from 4 K to about 14 K using a consistent magnetic field sweep rate of about 20 Oersteds per second, although higher temperatures have been achieved with very fast sweep rates (e.g., 200 Oersteds per second to reach 30 K). Here, the David P. Mills team reported a hexa-tert-butyl bipyrazolone complex Dy(Cpttt)2][B(C6F5)4] in the literature (Conrad a. P. goodwin, FabrizioOrtu, Daniel Reta, Nicholas F. Chilton, David P. Mills, Molecular magnetichysteresis at 60 kelvin in dysprosocenium. Nature, 2017, 548, 439-422.), where Cpttt = {C5H2tBu3-1,2,4}; tBu = C(CH3)3. The compound can exhibit hysteresis effects at temperatures up to 60 kelvin at a scan rate of 22 oersted per second. The team found that the dynamic magnetic relaxation at this temperature changed significantly, and this change still existed in the magnetic dilution sample, indicating that the origin of the hysteresis is unique to the localized metal-ligand vibration mode of dysprosium. Its spin dynamics show that magnetic relaxation at high temperatures is caused by localized molecular vibrations. These results suggest that magnetic data storage in a single molecule above liquid nitrogen temperature should be possible by carefully designing the molecular structure. However, the compound still has an extremely obvious disadvantage, namely, it is unstable in air. In addition, the compound is very difficult to synthesize and must be synthesized in a glove box. These conditions limit the use of this material.

[0006] According to the viewpoints put forward in the literature (R. Sessoli, Magnetic molecules back in the race. Nature, 2017, 548, 400-401.), it is necessary to design and synthesize rare earth metal organic framework materials to improve stability and improve magnetic relaxation dynamics. In addition, the literature (E. Coronado, et al. Quantum coherent spin-electric control in a molecular nanomagnet at clock transitions. Nat. Phys. 2021, 17, 1205-1209.) describes the results of basic theoretical research on the application of molecular magnets as quantum storage. In general, the existing technology usually has the following technical problems to be solved: (1) The synthesis of single-molecule magnets is difficult, the preparation process is complicated, and it is difficult to mass produce; (2) The organic ligands used in single-molecule magnets are relatively complex and expensive, which brings huge financial pressure to industrial production; (3) Single-molecule magnet materials cannot achieve reversible changes in single-molecule magnet performance through simple conditions, such as humidity. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, in the first aspect of the present invention, a method for preparing a reversible dysprosium-based single-molecule magnet framework material with lower cost, simple steps and controllable synthesis is provided, comprising the following steps: A chemical reaction amount of dysprosium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are added to a mixed solvent formed by N,N-dimethylformamide and water, and the mixture is reacted at a certain temperature. After the reaction is completed, the product is cooled, collected and purified to obtain a reversible dysprosium-based single-molecule magnet framework material, which is recorded as Dy2·4H2O.

[0008] Preferably, the molar ratio of dysprosium nitrate hexahydrate to 2,5-dihydroxyterephthalic acid is 0.9-1.1:0.9-1.1.

[0009] Preferably, the mixed solvent is prepared by mixing N,N-dimethylformamide and water in a volume ratio of 0.9-1.1:0.9-1.1.

[0010] Preferably, the reaction temperature is 110-130° C. and the reaction time is 64-80 h.

[0011] Preferably, the cooling rate is 9-11°C / h.

[0012] The appropriate reaction temperature is conducive to the reaction and the product of the target structure of the present invention is efficiently synthesized. Under the above preferred temperature and time conditions, the target product can be obtained with a good yield. Controlling the cooling rate within the preferred range helps to reduce lattice defects and improve the integrity and stability of the product crystal.

[0013] In the second aspect of the present invention, a reversible dysprosium-based single-molecule magnet framework material is provided, which can realize simple guest water molecule regulation of single-molecule magnet performance. The material is prepared by the method provided in the first aspect of the present invention; the material obtained after Dy2·4H2O loses water molecules is recorded as Dy2, and Dy2 is converted into Dy2·4H2O after gaining water molecules. The reversible dysprosium-based single-molecule magnet framework material undergoes a reversible single crystal phase to single crystal phase transformation by gaining and losing water molecules.

[0014] Preferably, the crystal structure of Dy2·4H2O is triclinic. P-1 Space group; its unit cell parameters are as follows: a=10.6287(5) Å, b=11.0400(5) Å, c=13.0588(7) Å, α=73.360(2)°, β=66.472(2)°, γ=82.568(2)°, V=1345.91(12) Å 3 , Z=2.

[0015] Preferably, the crystal structure of Dy2 is triclinic. P-1 Space group; its unit cell parameters are as follows: a=10.6505(14) Å, b=11.0143(14) Å, c=13.112(2) Å, α=99.462(6)°, β=113.946(4)°, γ=98.975(4)°, V=1343.7(3) Å 3 , Z=2.

[0016] Preferably, both Dy2·4H2O and Dy2 are framework structures that are three-dimensionally extended using bridging binuclear dysprosium as secondary structural units; the dysprosium ions in Dy2·4H2O and Dy2 are in a distorted tetragonal anti-prismatic coordination environment.

[0017] Further preferably, in the reversible single crystal phase to single crystal phase transition of Dy2·4H2O and Dy2, the degree of crystal distortion ranges from 0.882 to 0.932; the average bond length varies from 2.369 to 2.372 Å; and the shortest Dy-O bond length varies from 2.280 to 2.28 Å.

[0018] Preferably, both Dy2·4H2O and Dy2 have pcu Topological structure type, point group is {4 12 .6 3}, the extended point group is [4.4.4.4.4.4.4.4.4.4.4.6(4).6(4).6(4)].

[0019] In the third aspect of the present invention, there is provided an application of the reversible dysprosium-based single-molecule magnet framework material according to the second aspect of the present invention, specifically, it is used as a single-molecule magnet material for preparing quantum computing and spin electronics devices.

[0020] Based on the above technical solutions, the design concept and principle of the present invention are as follows: The present invention uses cheap organic ligands (2,5-dihydroxyterephthalic acid) and rare earth salts (dysprosium nitrate hexahydrate) to construct rare earth dysprosium-based organic framework materials. The raw materials for preparation are simple, and the controllable synthesis and mass preparation of single-molecule magnet materials are realized. It should be noted that in the patent (CN114524831A), 2,5-dihydroxyterephthalic acid, hexahydrate dysprosium metal salt, 4,4'-dimethyl-2,2'-bipyridine, and water are used to react to prepare a dysprosium complex, which contains hydrophilic channels in its crystal structure and can maintain structural stability in an aqueous environment. Compared with the present invention, the crystal structure is significantly different. Its synthesis adds auxiliary pyridine ligands, the preparation is more complicated, and may be accompanied by the generation of by-products, and it does not have advantages in terms of cost and controllable synthesis. In addition, the dysprosium complex cannot achieve the design requirements of reversible transformation of single-molecule magnet performance.

[0021] In the present invention, the reversible dysprosium-based single-molecule magnet framework material can lose water molecules by heating to 100°C to achieve the conversion between Dy2·4H2O and Dy2; Dy2 can regain water molecules and be converted into Dy2·4H2O when placed in a water-containing environment such as air. The process of gaining and losing water is a single crystal to single crystal conversion process, and the crystalline properties of the material are not affected. Therefore, the inventors use the porosity of porous materials and a reversible transformation process controlled by water to achieve simple guest water molecules to regulate the performance of single-molecule magnets. Materials with different magnetic behaviors can be obtained according to actual application requirements, which provides an important reference scheme for the development of new dynamic single-molecule magnets and has broad application prospects.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a method for preparing a reversible dysprosium-based single-molecule magnet framework material, which has the characteristics of lower cost, simple steps, controllable synthesis, and suitability for large-scale production, and provides an important reference scheme for the development of new dynamic single-molecule magnets.

[0023] The present invention provides a reversible dysprosium-based single-molecule magnet framework material, which realizes the reversible transformation of the single-molecule magnet performance under simple conditions and provides a way to regulate the single-molecule magnet performance by dynamic water molecules.

[0024] The present invention provides an application of a reversible dysprosium-based single-molecule magnet framework material, which has good application prospects in fields such as quantum computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Single crystal photos of Dy2·4H2O and Dy2; Figure 2 is the powder diffraction pattern of Dy2·4H2O; Figure 3 It is the crystal structure of Dy2·4H2O; Figure 4 is the crystal structure of Dy2; Figure 5 For Dy2·4H2O and Dy2 pcu Topology; Figure 6 The temperature-dependent DC susceptibility curves of Dy2·4H2O and Dy2; Figure 7 is the AC magnetic susceptibility curve of Dy2·4H2O and Dy2; Figure 8 is the Arrhenius curve of Dy2. DETAILED DESCRIPTION

[0026] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0027] Example 1 The preparation method of the reversible dysprosium-based single-molecule magnet framework material comprises the following steps: Dysprosium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid were added to a mixed solvent of N,N-dimethylformamide and water (1:1, v / v) in a molar ratio of 1:1; stirred at room temperature for 10 min, the mixture was placed in a Teflon-coated stainless steel container, heated to 120 °C and kept for 3 days; then the container was cooled to room temperature at a rate of 10 °C / h, the product was collected and purified, and the crystalline material obtained was a yellow single crystal, that is, a reversible dysprosium-based single-molecule magnet framework material, named Dy2·4H2O, with a yield of about 52%. By heating to 100 °C, the crystal water in the material can be removed to form a new phase to obtain Dy2.

[0028] High yield of Dy2·4H2O can be obtained by adjusting parameters such as ratio, temperature, time, etc. within the scope defined by the present invention or by using a large amount of raw materials for preparation.

[0029] The single crystal photos of Dy2·4H2O and Dy2 prepared in this embodiment are as follows Figure 1 Shown (photographing instrument: Bruker D8quest). Figure 1 In the figure, Dy2·4H2O containing crystalline water is shown at 273 K, and Dy2 lost crystalline water by heating is shown at 373 K. The bulk material Dy2·4H2O was characterized by powder diffraction test (test instrument: Bruker D8 Advance). The results are shown in Figure 2. Figure 2 shown. Figure 2 It shows that the purity of Dy2·4H2O is highly consistent with the single crystal simulated diffraction peak, proving the high purity of the material.

[0030] Example 2 In this example, the prepared Dy2·4H2O and Dy2 single crystal samples were subjected to in-situ 273K and 373K variable temperature single crystal X-ray diffraction structure tests to study their crystal structures. The results are shown in Table 1.

[0031] Table 1: Crystal structure refinement parameters of Dy2·4H2O and Dy2

[0032] Single crystal tests show that Dy2·4H2O undergoes a phase transition from single crystal to single crystal due to water loss at high temperature, that is, the transformation from Dy2·4H2O to Dy2 is realized. After testing the high-temperature single crystal, the crystal was placed in air for 4 h, and the single crystal was tested again at room temperature, and it was found that Dy2 was transformed into Dy2·4H2O. Therefore, this material can achieve a reversible single crystal to single crystal phase transition controlled by water. Both Dy2·4H2O and dehydrated phase Dy2 are crystallized in triclinic P-1 Space group.

[0033] Combined with the results in Table 1, the structure was analyzed (measured by Bruker D8 quest), and the crystal structure of Dy2·4H2O is as follows Figure 3 As shown, the crystal structure of Dy2 is Figure 4 As shown. Structural analysis found that both Dy2·4H2O and Dy2 are framework structures with three-dimensional extension of bridging binuclear dysprosium as secondary structural units. The dysprosium ions in the material are all in a distorted square antiprism coordination environment, but the degree of distortion changes from 0.932 to 0.882, the average bond length changes from 2.369 to 2.372 Å, and the shortest Dy-O bond length also changes from 2.286 to 2.280 Å. 8 Changes in the coordination environment (structural distortion and bond length changes, the shorter the bond length, the more conducive to improving magnetic anisotropy) directly affect the magnetic anisotropy of the dysprosium ion. The magnitude of the magnetic anisotropy has a great influence on the behavior of single-molecule magnets, thereby achieving the regulation of magnetic properties.

[0034] Example 3 In this example, TOPOSPro software was used to analyze the structure of Dy2·4H2O and Dy2. The topological structure is shown in Figure 5 shown. Figure 5 The analysis results show that both Dy2·4H2O and Dy2 have pcu Topological structure type. The point group is {4 12 .6 3}, the extended point group is [4.4.4.4.4.4.4.4.4.4.4.6(4).6(4).6(4)].

[0035] Example 4 This example characterizes the magnetic properties of Dy2·4H2O and Dy2 to study the performance of reversible dysprosium-based single-molecule magnet framework materials in applications. The direct current (DC) magnetic susceptibility of the ground powder samples of the two crystalline materials was measured in the range of 2-300 K using a Quantum Design SQUID VSM magnetometer under an applied DC field of 1000 Oe. All magnetic data have been corrected for the contribution of sample diamagnetism and corrected using the Pascal constant.

[0036] The temperature-dependent DC susceptibility curves of Dy2·4H2O and Dy2 are shown in Figure 6 As shown. Figure 6 The temperature-dependent DC magnetic susceptibility measurements show that the room temperature magnetic χ M T is 14.24 cm 3 mol -1 K, while the room temperature of Dy2 χ M T is 14.45 cm 3 mol -1 K. These room temperature values ​​are slightly higher than the theoretical value of 14.17 cm 3 mol -1 K, proving that the dysprosium ions in the material have a certain magnetic anisotropy.

[0037] The alternating current (AC) magnetic susceptibility data were collected in the case of zero DC field or with a 1000 Oe DC field applied, over the temperature range of 2-25 K, an AC field of 2 Oe, and a frequency range of 1-1000 Hz. The AC magnetic susceptibility curves of Dy2·4H2O and Dy2 are shown in Figure 2. Figure 7As shown. Water loss has a certain effect on magnetic anisotropy. The variable temperature and variable frequency AC magnetic susceptibility test did not observe the frequency-dependent slow magnetic relaxation behavior of Dy2·4H2O, but Dy2 showed obvious temperature- and frequency-dependent slow magnetic relaxation behavior. Therefore, the reversible transformation of Dy2·4H2O to Dy2 realizes the transformation from non-single-molecule magnet to single-molecule magnet, and this material can be used for quantum information storage at extremely low temperatures.

[0038] The relaxation time at each temperature is obtained by fitting the cole-cole curve, which is obtained at each temperature with the real and imaginary AC signals as the xy axes. The Arrhenius curve of Dy2 is shown in Figure 8 The relaxation time (τ) at each test temperature was extracted by fitting the Argand plot of χ'' versus χ' using the generalized Debye model. The Arrhenius formula (τ = τ0exp(U eff / k B T) fitting, and estimate the effective relaxation energy barrier of the material U eff 300.6 cm -1 , the pre-exponential factor τ0 is 1.9×10 -6 s. This result reflects the single-molecule magnetic properties of the dehydrated material and confirms its potential as a quantum information material.

[0039] In summary, the present invention uses relatively cheap 2,5-dihydroxyterephthalic acid and dysprosium nitrate hexahydrate to construct rare earth dysprosium-based organic framework materials, and realizes the controllable synthesis and mass preparation of single-molecule magnet materials. The reversible transformation of single-molecule magnet properties is achieved under simple conditions, providing a way for dynamic water molecules to regulate the performance of single-molecule magnets, and has good application prospects in fields such as quantum computing.

[0040] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a reversible dysprosium-based single-molecule magnet framework material, characterized in that: The steps include: A chemical reaction amount of dysprosium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid are added to a mixed solvent formed by N,N-dimethylformamide and water, and the mixture is reacted at a certain temperature. After the reaction is completed, the product is cooled, collected and purified to obtain a reversible dysprosium-based single-molecule magnet framework material, which is recorded as Dy2·4H2O.

2. The method for preparing the reversible dysprosium-based single-molecule magnet framework material according to claim 1, characterized in that: The molar ratio of dysprosium nitrate hexahydrate to 2,5-dihydroxyterephthalic acid is 0.9-1.1:0.9-1.1; the mixed solvent is prepared by mixing N,N-dimethylformamide and water in a volume ratio of 0.9-1.1:0.9-1.

1.

3. The method for preparing the reversible dysprosium-based single-molecule magnet framework material according to claim 1, characterized in that: The reaction temperature is 110-130°C, the reaction time is 64-80 h; the cooling rate is 9-11°C / h.

4. A reversible dysprosium-based single-molecule magnet framework material, characterized in that: The material is prepared by the preparation method according to any one of claims 1 to 3. The material obtained after Dy2·4H2O loses water molecules is recorded as Dy2. Dy2 is converted into Dy2·4H2O after obtaining water molecules. The reversible dysprosium-based single-molecule magnet framework material undergoes a reversible single crystal phase to single crystal phase transformation by gaining and losing water molecules.

5. The reversible dysprosium-based single-molecule magnet framework material according to claim 4, characterized in that: The crystal structure of Dy2·4H2O is triclinic. P-1 Space group; its unit cell parameters are as follows: a=10.6287(5) Å, b=11.0400(5) Å, c=13.0588(7) Å, α=73.360(2)°, β=66.472(2)°, γ=82.568(2)°, V=1345.91(12) Å 3 , Z=2.

6. The reversible dysprosium-based single-molecule magnet framework material according to claim 4, characterized in that: The crystal structure of Dy2 is triclinic. P-1 Space group; its unit cell parameters are as follows: a=10.6505(14) Å, b=11.0143(14) Å, c=13.112(2) Å, α=99.462(6)°, β=113.946(4)°, γ=98.975(4)°, V=1343.7(3) Å 3 , Z=2.

7. The reversible dysprosium-based single-molecule magnet framework material according to claim 4, characterized in that: Both Dy2·4H2O and Dy2 are framework structures that are three-dimensionally extended using bridging binuclear dysprosium as secondary structural units; the dysprosium ions in Dy2·4H2O and Dy2 are in a distorted tetragonal anti-prismatic coordination environment.

8. The reversible dysprosium-based single-molecule magnet framework material according to claim 7, characterized in that: In the reversible single crystal phase to single crystal phase transformation of Dy2·4H2O and Dy2, the degree of crystal distortion ranges from 0.882 to 0.932; the average bond length varies from 2.369 to 2.372 Å; and the shortest Dy-O bond length varies from 2.280 to 2.28 Å.

9. The reversible dysprosium-based single-molecule magnet framework material according to claim 4, characterized in that: Both Dy2·4H2O and Dy2 have pcu Topological structure type, point group is {4 12 .6 3 }, the extended point group is [4.4.4.4.4.4.4.4.4.4.4.6(4).6(4).6(4)].

10. An application of the reversible dysprosium-based single-molecule magnet framework material according to any one of claims 4 to 9, characterized in that: As a single-molecule magnetic material, it is used to prepare quantum computing and spin electronics devices.

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