Radical dinuclear rare earth single-molecule magnet complex and preparation method and application thereof

Abstract

The present application relates to the technical field of metal complex, in order to solve the problem that the conventional self-assembly strategy cannot meet the development needs of high-performance polynuclear rare earth single-molecule magnets, a free radical dinuclear rare earth single-molecule magnet complex and its preparation method and application are provided.The free radical rare earth single-molecule magnet complex bridged by hydroquinone is obtained by design and synthesis, and the complex is Ln2(L1)2(L2)(OTF)2(Py)2, wherein L1 and L2 are organic ligands, and Ln is any one of rare earth metals Dy, Gd or Y.The single-molecule magnet properties of the series of free radical dinuclear rare earth complexes prepared by the present application are mainly regulated by the rare earth metal ions and the bridging free radical ligand, wherein the rare earth metal Dy ion has significant magnetic anisotropy and large magnetization intensity, the introduction of the bridging free radical ligand can effectively enhance the magnetic interaction between the rare earth ions, and then the effective regulation of the magnetization quantum tunneling and magnetic relaxation process of the single-molecule magnet is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal complex, in particular to a free radical binuclear rare earth single-molecule magnet complex and a preparation method and application thereof. BACKGROUND

[0002] Developing new rare earth high-density magnetic storage materials has become an important issue in the future information field. The key to improving the magnetic storage capacity is to continuously reduce the size of the magnetic particles used for recording information, but when the size is reduced to a certain extent, the superparamagnetic effect will affect the stability of the magnetic recording information, greatly limiting the development of high-density information storage. In order to meet the demand for small, light, thin and high stability of magnetic storage materials, in recent years, molecular-based magnetic materials mainly based on rare earth single-molecule magnets have made up for the shortcomings of traditional synthesis methods, not only realizing true nanoscale magnetic storage, but also breaking the limit of the superparamagnetic limit of materials.

[0003] The magnetization quantum tunneling of rare earth single-molecule magnets mainly comes from the magnetic moment flip between the ground state doublet without thermal induced relaxation, so the stability of the ground state doublet is crucial to inhibit the magnetic quantum tunneling. It has been found that the strong axial ligand field can well stabilize the ground state doublet of the rare earth ion, and the ground state and the excited state are well separated, and the compound can exhibit strong magnetic anisotropy.

[0004] Professor Richard A. Layfield's research group prepared metallocene rare earth single-molecule magnets using a properly steric cyclopentadiene ligand, in which the cyclopentadiene ligand provides an axial ligand field, and due to the steric effect of the ligand, there is no coordination atom in the equatorial plane of the rare earth ion, so it exhibits strong magnetic anisotropy, and the effective energy barrier is as high as 1541 cm -1 , and the magnetic blocking temperature reaches above the liquid nitrogen temperature (80 K), which is the best single-molecule magnet so far, laying a solid foundation for the practical application of future rare earth single-molecule magnets.

[0005] However, although the magnetic blocking temperature of the cyclopentadiene sandwich rare earth single-molecule magnet has reached above the liquid nitrogen temperature, the preparation process of this kind of single-molecule magnet is mainly based on strict waterless and oxygenless operation, and its chemical and thermal stability is relatively poor, which seriously limits the wide application of future rare earth single-molecule magnets.

[0006] For polynuclear systems, it is extremely difficult to simultaneously regulate the axial ligand field of multiple rare earth ions. In recent years, Professor Selvan Demir's group has constructed several binuclear high-performance rare earth single-molecule magnets using free radicals as strong magnetic exchange connecting units. The free radicals transmit strong antiferromagnetic interaction, and the quantum tunneling effect of the compounds is completely suppressed. In 2022, Professor Jeffrey R. Long's group constructed a new mixed-valence binuclear rare earth single-molecule magnet by bridging the rare earth units with bromide ions and reducing one of the rare earth ions to divalent by KC8. Due to the 4f n 5d1 electronic structure of the divalent rare earth ion, the two rare earth ions form a stable rare earth-rare earth bond by sharing d electrons, exhibit high-spin ground state and strong magnetic anisotropy, and the quantum tunneling is effectively suppressed, with a coercive field of more than 14 T and a magnetic blocking temperature of more than 60 K. This successful example fully embodies that by increasing the magnetic coupling between rare earth ions, the magnetization quantum tunneling can be effectively suppressed, and the magnetic blocking temperature of the rare earth single-molecule magnet can be improved, which also provides an important reference for further designing polynuclear rare earth single-molecule magnets with different topological structures.

[0007] At present, the effective energy barrier of air-stable rare earth single-molecule magnets can already be comparable to that of single-core rare earth single-molecule magnets, but the blocking temperature is still far apart. Through structure comparison, we found that: on the basis of maintaining the coordination configuration of the rare earth ion D 5h / D 6h By introducing magnetic interaction, arranging the magnetic anisotropy of the rare earth ions in the same direction, and using strong magnetic coupling, it is expected to further suppress the quantum tunneling, and at the same time improve the blocking temperature of the rare earth single-molecule magnet.

[0008] However, due to the high coordination number and variable coordination configuration of the rare earth ion, it is extremely difficult to simultaneously regulate the magnetic anisotropy of multiple rare earth ions in the same system, and the conventional self-assembly strategy cannot meet the development needs of high-performance polynuclear rare earth single-molecule magnets. SUMMARY

[0009] In order to comprehensively solve the above problems, the present application aims to provide a free radical binuclear rare earth single-molecule magnet complex and a preparation method and application thereof. The series of complexes provided by the present application all have clear single crystal structure, high thermal stability and different single-molecule magnet properties.

[0010] Technical idea: The idea of the present application is to design and synthesize a hydroquinone-bridged free radical rare earth single-molecule magnet complex, and to regulate the magnetization quantum tunneling and relaxation time of the series of free radical rare earth single-molecule magnets by regulating the type of rare earth ion and the redox degree of the bridging ligand.

[0011] The present application proposes to design and synthesize hydroquinone ligands, to improve the chemical and thermal stability of rare earth single-molecule magnets, to enhance the magnetic anisotropy of rare earth ions by enhancing the axial ligand field, and to arrange the magnetic anisotropy axes of the rare earth ions in the same direction. At the same time, by the characteristics of generating free radicals after the oxidation and reduction of hydroquinone, the magnetic quantum tunneling is suppressed by intramolecular magnetic coupling, the blocking temperature of the rare earth single-molecule magnet is effectively improved, and the controllable assembly and performance regulation of high-performance double-core rare earth single-molecule magnets are realized.

[0012] In order to achieve the above-mentioned purpose and technical idea, the first aspect of the present application provides a free radical double-core rare earth single-molecule magnet complex, and the chemical expression is as follows:

[0013] Ln2(L1)2(L2)(OTF)2(Py)2;

[0014] Wherein, L1 and L2 are organic ligands, and Ln is any one of rare earth metals Dy, Gd or Y.

[0015] ;

[0016] The structural formula of the ligand L2 is as follows:

[0017] .

[0018] Preferably, Ln is the rare earth metal Dy, and the free radical double-core rare earth single-molecule magnet complex is Dy2(L1)2(L2)(OTF)2(Py)2, and the structural formula is as follows:

[0019] .

[0020] Preferably, Ln is the rare earth metal Gd, and the free radical double-core rare earth single-molecule magnet complex is Gd2(L1)2(L2)(OTF)2(Py)2, and the structural formula is as follows:

[0021] .

[0022] Preferably, Ln is the rare earth metal Y, and the free radical double-core rare earth single-molecule magnet complex is Y2(L1)2(L2)(OTF)2(Py)2, and the structural formula is as follows:

[0023] .

[0024] The second aspect of the present application provides a preparation method of the free radical double-core rare earth single-molecule magnet complex, comprising the following steps:

[0025] S1: 2-(1-pyrazole)-pyridine is heated and reacted with potassium borohydride to synthesize ligand L1;

[0026] S2: 2,5-diformyl-p-xylylene ether is dissolved in dichloromethane, then boron tribromide is added to react at room temperature, then ammonium chloride is added to quench the reaction, and a ligand L2 is synthesized;

[0027] S3: a rare earth metal salt is dissolved in pyridine to react, then the ligand L2 is added, and the reaction is continued, and a radical dinuclear rare earth single-molecule magnet complex is synthesized.

[0028] Preferably, in S1, the molar ratio of 2-(1-pyrazole)-pyridine to potassium borohydride is 5:1.

[0029] Preferably, in S2, the molar ratio of 2,5-diformyl-p-xylylene ether to boron tribromide is 1:3.

[0030] Preferably, in S3, the molar ratio of the ligand L1, the ligand L2 to the rare earth metal is 2:2:1.

[0031] Preferably, in S3, the rare earth metal salt is any one of Dy(OTF)3, Gd(OTF)3 or Y(OTF)3.

[0032] The third aspect of the present application provides an application of the radical dinuclear rare earth single-molecule magnet complex prepared according to the above scheme, as a preparation of a molecular magnetic storage device.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] The present application synthesizes two examples of multidentate ligands, and assembles them with rare earth ions, and effectively regulates the magnetization quantum tunneling and magnetic relaxation of the series of radical dinuclear rare earth single-molecule magnet complexes by changing the oxidation state of the rare earth ions and the bridging radical ligands, specifically:

[0035] (1) The dinuclear rare earth single-molecule magnet complex [Y2(L1)2(L2)(OTF)2(Py)2] obtained by using the ligands L1 and L2 and Y(OTF)3 in the present application, and the magnetic test shows that the complex exhibits paramagnetism, and since the rare earth element Y and the ligand L2 do not contribute to the magnetic moment, it is shown that the bridging ligand is a radical;

[0036] (2) The dinuclear rare earth single-molecule magnet complex [Gd2(L1)2(L2)(OTF)2(Py)2] obtained by using the ligands L1 and L2 and Gd(OTF)3 in the present application, and the magnetic test shows that the magnetization significantly increases in the low temperature region, indicating that there is a radical transfer ferromagnetic interaction in the compound;

[0037] (3) The bimetallic rare earth single-molecule magnet complex [Dy2(L1)2(L2)(OTF)2(Py)2] obtained by the ligands L1 and L2 and Dy(OTF)3 is used in the application, the magnetic test shows that the magnetization significantly decreases in the low temperature zone, indicating that the compound has obvious magnetic blocking, the hysteresis loop test shows that the compound has obvious hysteresis loop opening in the non-zero field, confirming that the compound has the magnetization slow relaxation phenomenon, and the magnetization quantum tunneling is well inhibited, and the effective energy barrier reaches 223.8 K.

[0038] The above results show that the single-molecule magnet properties of the series of free radical bimetallic rare earth complex prepared by the application are mainly regulated by the rare earth metal ions and the bridging free radical ligand, wherein the rare earth metal Dy ion has significant magnetic anisotropy and large magnetization, and the introduction of the bridging free radical ligand can effectively enhance the magnetic interaction between the rare earth ions, thereby realizing the effective regulation of the magnetization quantum tunneling and the magnetic relaxation process of the single-molecule magnet. BRIEF DESCRIPTION OF DRAWINGS

[0039] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, illustrate the application together with the embodiments of the application, and do not constitute a limitation on the application.

[0040] In the drawings:

[0041] Figure 1 is the H-NMR spectrum of the ligand L1 in DMSO-d 6 1 H-NMR spectrum;

[0042] Figure 2 is the H-NMR spectrum of the ligand L2 in DMSO-d 6 1 H-NMR spectrum;

[0043] Figure 3 is the single crystal structure diagram of the complex Ln2(L1)2(L2)(OTF)2(Py)2;

[0044] Figure 4 is the infrared spectrum diagram of the complex Ln2(L1)2(L2)(OTF)2(Py)2: (a) is the infrared spectrum of Dy2(L1)2(L2)(OTF)2(Py)2, (b) is the infrared spectrum of Gd2(L1)2(L2)(OTF)2(Py)2, and (c) is the infrared spectrum of Y2(L1)2(L2)(OTF)2(Py)2;

[0045] Figure 5 ​​is the thermal gravimetric curve of complex Ln2(L1)2(L2)(OTF)2(Py)2, (a) is the thermal stability result of Dy2(L1)2(L2)(OTF)2(Py)2, (b) is the thermal stability result of Gd2(L1)2(L2)(OTF)2(Py)2, (c) is the thermal stability result of Y2(L1)2(L2)(OTF)2(Py)2

[0046] Figure 6 is the magnetization curve of complex Ln2(L1)2(L2)(OTF)2(Py)2;

[0047] Figure 7 is the hysteresis loop diagram of complex Ln2(L1)2(L2)(OTF)2(Py)2;

[0048] Figure 8 is the relaxation time diagram of complex Ln2(L1)2(L2)(OTF)2(Py)2;

[0049] Figure 9 is the preparation method flow chart of the application. DETAILED DESCRIPTION

[0050] The following Figures 1-9 The preferred embodiments of the application are described, it should be understood that the preferred embodiments described herein are only used to illustrate and explain the application, and are not used to limit the application.

[0051] The raw materials and reagents involved in the application are as follows:

[0052] The solvents used in the application are all commercially available analytical reagents, wherein dichloromethane, ammonium chloride, 2,5-diformyl-p-xylenol, pyridine are purchased from Anjie (Shanghai) Pharmaceutical Chemical Co., Ltd., boron tribromide, 2-(1-pyrazole)-pyridine, Dy(OTF)3, Gd(OTF)3, Y(OTF)3 are purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd., potassium borohydride is purchased from China National Pharmaceutical Group Corporation.

[0053] Example 1:

[0054] The free radical binuclear rare earth single-molecule magnet complex has a chemical formula of:

[0055] Ln2(L1)2(L2)(OTF)2(Py)2;

[0056] Wherein, L1 and L2 are organic ligands, and Ln is any one of rare earth metals Dy, Gd or Y (Y corresponds to the rare earth element yttrium, which is a rare earth element other than lanthanide series elements);

[0057] The structural formula of ligand L1 is:

[0058] ;

[0059] The structural formula of the ligand L2 is:

[0060] .

[0061] When Ln is a rare earth metal Dy, the free radical dinuclear rare earth single-molecule magnet complex is Dy2(L1)2(L2)(OTF)2(Py)2, belongs to a triclinic system, a space group is P-1, and cell parameters are a = 12.319(3) Å, b = 14.053(4) Å, c = 14.775(3) Å, α = 75.993(6) °, β = 66.199(4) °, γ = 84.748(6) °, ν = 2270.7(10) Å 3 , and a structural formula is:

[0062] .

[0063] When Ln is a rare earth metal Gd, the free radical dinuclear rare earth single-molecule magnet complex is Gd2(L1)2(L2)(OTF)2(Py)2, belongs to a triclinic system, a space group is P-1, and cell parameters are a = 12.462(2) Å, b = 14.014(3) Å, c = 14.839(3) Å, α = 76.262(6) °, β = 65.843(4) °, γ = 84.820(5) °, ν = 2296.7(7) Å 3 , and a structural formula is:

[0064] .

[0065] When Ln is a rare earth metal Y, the free radical dinuclear rare earth single-molecule magnet complex is Y2(L1)2(L2)(OTF)2(Py)2, belongs to a triclinic system, a space group is P-1, and cell parameters are a = 12.4471(18) Å, b = 14.335(2) Å, c = 15.018(2) Å, α = 75.784(2) °, β = 65.611(2) °, γ = 84.809(3) °, ν = 2365.6(6) Å 3 , and a structural formula is:

[0066] .

[0067] Example 2:

[0068] The principle of the application is:

[0069] The magnetism of rare earth single-molecule magnets originates from the molecule itself, has the advantages of single size, easy processing and strong chemical modification, and especially, the existence of large ground state magnetic moment and unquenched orbital angular momentum of rare earth ions can exhibit strong magnetic anisotropy, which is an ideal choice for preparing high-performance single-molecule magnets. The research on rare earth single-molecule magnets has been expanded from the early single-core system to high-core, heterometal and radical coupling systems. However, the magnetization quantum tunneling phenomenon often accompanies the rare earth single-molecule magnets, which seriously affects the further improvement of the magnetic blocking temperature. How to effectively prepare high-performance multi-core rare earth single-molecule magnets has become an important issue in the field of molecular magnets. And the present application designs and synthesizes a series of radical dinuclear rare earth single-molecule magnet complexes, uses the radical bridging ligand to transfer the magnetic interaction, so as to realize the effective regulation of the single-molecule magnet magnetization quantum tunneling and magnetic relaxation process.

[0070] Based on the above technical principle, as Figure 9 A flow chart of a preparation method of a radical dinuclear rare earth single-molecule magnet complex provided by the present application is shown in the figure Figure 9 The preparation method comprises the following steps:

[0071] S1: 2-(1-pyrazole)-pyridine is heated and reacted with potassium borohydride to synthesize ligand L1.

[0072] Specifically, 2-(1-pyrazole)-pyridine is mixed with potassium borohydride at a molar ratio of 5:1 under vacuum-nitrogen circulation for 3 times, reacted at 210℃ for 12 hours, and then cooled. Toluene is added, ultrasonic is performed at room temperature for 3 hours, filtration is performed, and the solid powder is collected to obtain ligand L1.

[0073] S2: 2,5-diformyl-p-xylylene ether is dissolved in dichloromethane, then boron tribromide is added and reacted at room temperature, and then ammonium chloride is added to quench the reaction to synthesize ligand L2.

[0074] Specifically, 2,5-diformyl-p-xylylene ether is dissolved in dichloromethane, then boron tribromide (the molar ratio of 2,5-diformyl-p-xylylene ether to boron tribromide is 1:3) is added, and reacted at room temperature for 24 hours. Then, ammonium chloride is added to quench the reaction (the molar ratio of boron tribromide to ammonium chloride is 1:3), the reaction solution is extracted with water, the organic phase is concentrated, recrystallized in ethanol, filtered, and the yellow solid powder is collected to obtain ligand L2.

[0075] S3: The rare earth metal salt is dissolved in pyridine and reacted with ligand L1, then ligand L2 is added and continued to react to synthesize the radical dinuclear rare earth single-molecule magnet complex.

[0076] Specifically, the rare earth metal salts dysprosium trifluoromethanesulfonate Dy(OTF)3, gadolinium trifluoromethanesulfonate Gd(OTF)3, or yttrium trifluoromethanesulfonate Y(OTF)3 and ligand L1 obtained in step S1 are dissolved in pyridine and stirred at room temperature for 2 hours. Then, ligand L2 obtained in step S2 is added and stirred at room temperature for another 2 hours. After the reaction is completed, the mixture is filtered and the filtrate is diffused in the gas phase for 8 days to obtain a free radical binuclear rare earth monomolecular magnet complex.

[0077] The molar ratio of ligands L1 and L2 to any one of dysprosium trifluoromethanesulfonate Dy(OTF)3, gadolinium trifluoromethanesulfonate Gd(OTF)3, or yttrium trifluoromethanesulfonate Y(OTF)3 is 2:2:1.

[0078] Example 3:

[0079] The application of the free radical binuclear rare earth single-molecule magnet complex in Example 1 is used for the preparation of molecular magnetic storage devices.

[0080] Experimental Analysis:

[0081] 1. NMR characterization and analysis of ligands L1 and L2:

[0082] The NMR spectra of ligands L1 and L2 were measured using a Bruker Avance 500 MHz NMR spectrometer with DMSO-d6 as the deuterated reagent.

[0083] Test results are as follows Figures 1-2 As shown, through Figures 1-2 The results show that the proton NMR spectra of the two ligands correspond on the spectrum, and there are no other impurity peaks besides the solvent peak, indicating that the synthesized ligand is the target ligand with high purity and accurate structure, and the corresponding hydrogen atom chemical shifts have been marked on the spectrum. Figures 1-2 The chemical shifts of the two ligands in the proton NMR spectra are as follows: Ligand L1 δ = 8.50 (dd, J = 5.1, 1.8 Hz, 1H), 7.94 (d, J = 7.9 Hz, 1H), 7.73 (tt, J = 7.9, 2.4 Hz, 1H), 7.54 (d, J = 2.3 Hz, 1H), 7.18 (ddd, J = 7.6, 4.8, 1.3 Hz, 1H), 6.68 (d, J = 2.2 Hz, 1H); Ligand L2 δ = 10.31 (s, 1H), 10.29 (s, 1H), 7.23 (s, 1H).

[0084] 2. Single-crystal structure testing and analysis of single-molecule magnetic complexes:

[0085] Single-crystal X-ray diffraction data were collected using a Bruker Apex II CCD diffractometer with monochromatic Mo-Kα radiation of graphite (λ = 0.71073 Å). The structure was solved using the SHELXT (direct method) in the Olex2 package, and all non-hydrogen atoms were refined for anisotropic thermal parameters of F2 using SHELXL (full matrix least squares technique). All hydrogen atoms were incorporated into the calculation positions and refined with a fixed geometry relative to their carrier atoms. The single-crystal structure of the complex was obtained using the Olex2 structure analysis program with the direct Patterson method and refined using the SHELX crystal package with full matrix least squares. The coordinates of non-hydrogen atoms and the anisotropic temperature coefficients were corrected to least squares using the full matrix method.

[0086] Test results are as follows Figure 3 As shown, through Figure 3 Structural analysis revealed that all three complexes possess a binuclear linear structure. Two ligands, L1, are located at either end of the structure and coordinate with two rare-earth ions, respectively. The two pyridine molecules further coordinate with rare-earth ions to form rare-earth coordination units. A ligand, L2, is located in the center of the structure, connecting the two rare-earth coordination units to form a linear binuclear host structure. Since the host molecule carries two positive charges, two negatively charged trifluoromethanesulfonate anions are located in the crystal lattice to balance the positive charge of the host molecule.

[0087] Furthermore, due to the similar ionic radii and coordination characteristics of the three rare earth ions, the structures of the three rare earth complexes are also similar, with only minor differences in cell parameters and coordination bond lengths. Among them, the complex Dy2(L1)2(L2)(OTF)2(Py)2 belongs to the triclinic crystal system, space group P-1, and its cell parameters are a = 12.319(3)Å, b = 14.053(4)Å, c = 14.775(3)Å, α = 75.993(6)°, β = 66.199(4)°, γ = 84.748(6)°, ν = 2270.7(10)Å. 3 The complex Gd2(L1)2(L2)(OTF)2(Py)2 belongs to the triclinic crystal system, space group P-1, and its cell parameters are a = 12.462(2)Å, b = 14.014(3)Å, c = 14.839(3)Å, α = 76.262(6)°, β = 65.843(4)°, γ = 84.820(5)°, ν = 2296.7(7)Å. 3; Complex Y2(L1)2(L2)(OTF)2(Py)2 belongs to triclinic system, space group P-1, cell parameters a = 12.4471(18) Å, b = 14.335(2) Å, c = 15.018(2) Å, α = 75.784(2) °, β = 65.611(2) °, γ = 84.809(3) °, V = 2365.6(6) Å3, Z = 2, F(000) = 1268, Rint = 0.0301, R = 0.0301, wR = 0.0701, S = 1.000, R indices all reflections, observed reflections with I > 2σ(I), wR indices all reflections, observed reflections with I > 2σ(I) 3 .

[0088] 3. Infrared spectrum test and analysis:

[0089] Infrared spectrum was tested on Nicolet 6700 Fourier transform infrared spectrometer, which was equipped with iTR™-ATR accessory, and the test wavelength range was 4000-500 cm -1 . The test results are shown in Figure 4 , in which (a) is the infrared spectrum of Dy2(L1)2(L2)(OTF)2(Py)2, Figure 4 (b) is the infrared spectrum of Gd2(L1)2(L2)(OTF)2(Py)2, Figure 4 (c) is the infrared spectrum of Y2(L1)2(L2)(OTF)2(Py)2, and it is shown by Figure 4 that the infrared data of the three complexes are basically similar, in which 3000-3500 cm -1 is the stretching vibration peak of benzene ring C-H; the strong absorption of 1500-1700 cm -1 is the vibration peak of C=O; and 650-800 cm -1 is the bending vibration peak of C-H. Figure 4

[0090] 4. Thermogravimetric test and analysis:

[0091] Thermal stability data were obtained by testing carbon thermal loss and thermal stability of the sample by HCT-1 type thermogravimetric analyzer. Before testing, the sample was dried in a vacuum drying box at 70°C for 12 h, 5-10 mg was weighed and placed in a crucible, and the test was carried out under N2 atmosphere, the temperature range was 35-800°C, and the heating rate was 10°C / min. The test results are shown in Figure 5 , in which (a) is the thermal stability result of Dy2(L1)2(L2)(OTF)2(Py)2, Figure 5 (b) is the thermal stability result of Gd2(L1)2(L2)(OTF)2(Py)2, Figure 5 (c) is the thermal stability result of Y2(L1)2(L2)(OTF)2(Py)2, and it is shown by Figure 5 Figure 5 ​​It can be seen that the three complexes all show weak weight loss below 100℃, which is mainly due to the loss of part of the solvent molecules in the complex during heating; the complexes show a platform in the thermogravimetric analysis at 100-360℃, indicating that the complexes are stable in this temperature range; after 360℃, the compound slowly loses weight, indicating that the complex begins to decompose, until 450℃ completely converted into rare earth oxide.

[0092] 5. DC magnetic susceptibility test and analysis:

[0093] The magnetic properties of the complexes were tested by Quantum Design MPMS-XL-7 SQUID magnetometer instrument. The working temperature of the instrument is 1.8-300 K, and the direct current field strength is-7~7 T. Before detailed measurement, the magnetic intensity of all polycrystalline samples was measured below 100 K to check the ferromagnetic impurities. All data were corrected according to the Pascal constant table.

[0094] The magnetic test results are shown in Figure 6 , which show that: Figure 6

[0095] The room temperature χ M T (molar susceptibility) value of the complex Dy2(L1)2(L2)(OTF)2(Py)2 is 27.43 cm 3 K mol -1 , which is slightly lower than the theoretical value of 28.69 cm 3 K mol -1 , indicating that there may be paramagnetic impurities in the molecule. As the temperature decreases, the χ M T value gradually decreases, and suddenly decreases at 20 K, indicating that the compound has magnetic blocking phenomenon at low temperature, indicating that the complex has potential single-molecule magnet characteristics.

[0096] The room temperature χ M T value of the complex Gd2(L1)2(L2)(OTF)2(Py)2 is 17.56 cm 3 K mol -1 , which is slightly higher than the theoretical value of 16.76 cm 3 K mol -1 , indicating that there may be ferromagnetic interaction in the molecule. As the temperature decreases, the χ M T value remains unchanged, indicating that the compound has obvious isotropic characteristics, and the χ M T value increases significantly at 19 K, indicating that the compound indeed has ferromagnetic interaction.

[0097] The room temperature χ M ​The T value is 0.45 cm. 3 K mol -1 Slightly higher than the theoretical value by 0.375 cm 3 K mol -1 This indicates the possible existence of weak ferromagnetic interactions within the molecule. Since the rare earth element Y lacks a magnetic quantum number and exhibits diamagnetism, the magnetic moment contribution of the compound originates from the single-electron behavior of the radical of the L2 ligand.

[0098] The above tests show that for different rare earth elements, χ M The T-curves show different patterns. The complex Y2(L1)2(L2)(OTF)2(Py)2, containing diamagnetic Y, exhibits paramagnetism, indicating that the ligand L2 has single-electron radical properties. The isotropic complex Gd2(L1)2(L2)(OTF)2(Py)2 shows ferromagnetic interactions at low temperatures, indicating that the radical ligand L2 can effectively transmit ferromagnetic interactions. The anisotropic complex Dy2(L1)2(L2)(OTF)2(Py)2 exhibits magnetic blocking at low temperatures, indicating that this compound has single-molecule magnetic properties.

[0099] To investigate the single-molecule magnetic behavior of the complex Dy2(L1)2(L2)(OTF)2(Py)2, we performed low-temperature hysteresis loop tests on the complex. The test results are as follows: Figure 7 As shown, through Figure 7 The results show that the complex exhibits a distinct butterfly-shaped hysteresis loop at 1.9 K, indicating that the compound possesses unimolecular magnetic properties. The zero-field hysteresis loop has a closed opening, indicating that the complex exhibits significant zero-field magnetization quantum tunneling behavior. This is attributed to the fact that the magnetic interaction transmitted by the free radical ligand L2 is insufficient to suppress the intrinsic magnetization quantum tunneling relaxation process of rare earth ions.

[0100] pass Figure 7 It can also be seen that this radical binuclear rare earth single-molecule magnet complex can be used to prepare molecular magnetic storage devices.

[0101] 6. AC magnetic susceptibility testing and analysis:

[0102] To further investigate the relaxation mechanism of the complex Dy2(L1)2(L2)(OTF)2(Py)2, we conducted AC magnetic susceptibility tests on the complex and obtained the temperature-dependent relaxation time by extracting the relaxation times at different temperatures. Figure 8 By fitting Figure 8 The curves show that the effective energy barrier of this complex is 223.8 K, and the pre-exponential factor is 1.0 × 10⁻⁶. -7s. The relaxation time shows a temperature-independent relaxation term in the low-temperature region, which is mainly caused by the magnetization quantum tunneling behavior, and the quantum tunneling relaxation time is 2.6 × 10 -3 s, which again indicates that the ligand L2 radical transfer magnetic interaction is not enough to inhibit the intrinsic magnetization quantum tunneling of rare earth elements.

[0103] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A radical dinuclear rare earth single-molecule magnet complex, characterized in that, The structural formula is: 。 2. The method for preparing the free radical binuclear rare earth single-molecule magnet complex as described in claim 1, characterized in that, The method comprises the following steps: S1: 2-(1-pyrazole)-pyridine is reacted with potassium borohydride to synthesize ligand L1, and the structural formula of the ligand L1 is: ； S2: 2,5-diformyl-p-xylylene ether is dissolved in dichloromethane, then boron tribromide is added to react at room temperature, and then ammonium chloride is added to quench the reaction to synthesize ligand L2, and the structural formula of the ligand L2 is: ； S3: Rare earth metal salt Dy(OTF)3 is dissolved in pyridine to react with the ligand L1, then the ligand L2 is added to continue the reaction to synthesize a free radical binuclear rare earth single-molecule magnet complex.

3. The method for preparing the free radical binuclear rare earth single-molecule magnet complex according to claim 2, characterized in that, In S1, the molar ratio of 2-(1-pyrazole)-pyridine to potassium borohydride is 5:

1.

4. The method for preparing the free radical binuclear rare earth single-molecule magnet complex according to claim 3, characterized in that, In S2, the molar ratio of 2,5-diformyl-p-xylylene ether to boron tribromide is 1:

3.

5. The method for preparing the free radical binuclear rare earth single-molecule magnet complex according to claim 4, characterized in that, In S3, the molar ratio of the ligand L1, the ligand L2 and the rare earth metal salt is 2:2:

1.

6. Use of a radical dinuclear rare earth single-molecule magnet complex according to claim 1, characterized in that, The use for preparing a molecular magnetic memory device.

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