Easily planar magnetic anisotropy cobalt single ion magnet and preparation method and application thereof

Abstract

The invention belongs to the technical field of transition metal coordination chemistry, and relates to an easy-surface magnetic anisotropy cobalt single-ion magnet and a preparation method and application thereof, and the simple structural formula of the cobalt single-ion magnet is Co (bim) 4 (SCN) 2. The preparation method comprises the following steps: dissolving anhydrous cobalt chloride in absolute ethyl alcohol, adding potassium thiocyanate, stirring for 30 minutes, adding bim, fully reacting, and filtering to obtain a bluish violet solution; and placing the solution in a diethyl ether atmosphere, and standing for several days to obtain the cobalt single-ion magnet with easy surface magnetic anisotropy. The preparation method is safe and simple in preparation process, high in controllability, good in repeatability and high in yield. The prepared cobalt single-ion magnet is good in stability and high in purity, shows a slow magnetic relaxation behavior under an external magnetic field, and can be applied to the fields of novel high-density information storage equipment and the like as a molecule-based magnetic material.

Description

Technical Field

[0001] The invention belongs to the technical field of transition metal complex coordination functional materials, and relates to a cobalt single-ion magnet with easy-face magnetic anisotropy, and a preparation method and application thereof. Background Art

[0002] Single molecule magnets (SMMs) have attracted much attention as candidate materials for advanced materials such as ultra-high-density information storage, quantum computing, and molecular devices due to their unique magnetic and quantum properties. The magnetism of single-molecule magnets is generated within a single molecule rather than determined by the interaction between lattices, which makes single-molecule magnets truly nanoscale molecular magnets. It is very easy to prepare and purify single-molecule magnets, and their magnetic properties are closely related to the molecular structure. By changing the ligands and central metal atoms, single-molecule magnets with different properties can be obtained. At present, there are two important challenges: synthesizing single-molecule magnets with excellent performance and deeply studying the magnetic structure relationship of single-molecule magnets. Single-ion magnets contain only one magnetic center and are very suitable for studying the magnetic structure relationship of single-molecule magnets.

[0003] Compared with lanthanide complexes, the first-order orbital angular momentum of transition metal ion complexes is quenched in most cases, and the resulting axial anisotropy is mostly caused by second-order spin-orbit coupling. Therefore, the synthesis of transition metal single-ion magnets is conducive to our deeper research and exploration of spin, magnetic anisotropy and slow magnetic relaxation behavior in metal complexes. Among transition metal complexes, the second-order spin-orbit coupling of cobalt complexes easily leads to large magnetic anisotropy by mixing the relevant excited state with the ground state. Therefore, the number of cobalt single-ion magnets reported so far is the largest among transition metal single-ion magnets. Due to the diversity of ligands, the coordination environment is varied, so many cobalt single-ion magnets with different structures and different magnetic properties have been obtained, which has also prompted people to continue to study and explore cobalt single-ion magnets. Summary of the invention

[0004] The purpose of the present invention is to provide a cobalt single-ion magnet with easy-face magnetic anisotropy and a preparation method and application thereof. The cobalt single-ion magnet can exist stably in the air and has slow magnetic relaxation behavior under an external magnetic field.

[0005] In the first aspect of the present invention, there is provided a cobalt single ion magnet with anisotropic magnetic field, the molecular formula of which is Co(bim) 4 (SCN) 2 , where bim is 1-allylimidazole. The crystallographic parameters of cobalt single ion magnet are: the crystal belongs to the triclinic system, the space group is P-1, and the unit cell parameters are α=

[0006] 69.923(7)°,β=65.435(6)°,γ=65.435(6)°. In this cobalt single ion magnet, the cobalt ions are respectively connected with 4 bims and 2 SCNs. - The ions are coordinated to form a hexacoordinated complex.

[0007] In some embodiments, the configuration of the easy face magnetic anisotropic cobalt single ion magnet is a distorted octahedral configuration.

[0008] The second aspect of the present invention discloses a method for preparing the above-mentioned easy-face magnetic anisotropy cobalt single-ion magnet, comprising the following steps:

[0009] S1. CoCl 2 Dissolve in anhydrous ethanol, add potassium thiocyanate (KSCN), stir for 20-60 min, add 1-allylimidazole (BIM), react at room temperature for 2-5 h, and filter to obtain a blue-purple solution;

[0010] S2. placing the blue-purple solution in an ether atmosphere and leaving it to stand for 2 to 4 days to obtain red block crystals, namely the easy-face magnetic anisotropic cobalt single-ion magnet.

[0011] In some embodiments, in step S1 of the above preparation method, CoCl 2 , KSCN and 1-allylimidazole in a molar ratio of 1:2:(4-5).

[0012] In some embodiments, in step S1 of the above preparation method, each 0.5 mmol of CoCl 2 Corresponds to 10-15mL of anhydrous ethanol.

[0013] The third aspect of the present invention provides a use of the above-mentioned easy-face magnetic anisotropy cobalt single-ion magnet or the cobalt single-ion magnet prepared by the above-mentioned preparation method in the preparation of molecule-based magnetic materials.

[0014] The fourth aspect of the present invention provides a use of the above-mentioned easy-face magnetic anisotropy cobalt single-ion magnet or the cobalt single-ion magnet prepared by the above-mentioned preparation method in the preparation of high-density information storage materials.

[0015] Compared with the existing technology, it has the following technical effects:

[0016] (1) The easy-face magnetic anisotropy cobalt single-ion magnet prepared by the present invention has easy-face magnetic anisotropy, exhibits single-ion magnet properties under an external magnetic field, has slow magnetic relaxation behavior, and is stable in air at room temperature.

[0017] (2) The preparation method of the present invention is easy to operate, has good controllability, high reproducibility, and the purity and yield of the prepared product are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention provides a cobalt single ion magnet Co(bim) with anisotropic magnetic field. 4 (SCN) 2 The crystal structure diagram of

[0019] Figure 2 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 Powder X-ray diffraction pattern of

[0020] Figure 3 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 Temperature-dependent magnetic susceptibility test diagram;

[0021] Figure 4 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 Field dependence of magnetization intensity curve;

[0022] Figure 5 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 AC susceptibility diagram under different external magnetic fields;

[0023] Figure 6 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 Plot of frequency-dependent imaginary AC susceptibility;

[0024] Figure 7 The easy-face magnetic anisotropy cobalt single ion magnet Co(bim) provided in Example 1 of the present invention 4 (SCN) 2 Plot of the temperature dependence of the imaginary AC magnetic susceptibility. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The reagents used in the present invention are all commercially available and of analytical grade.

[0027] Example 1

[0028] Take 0.5mmol CoCl 2 Dissolve in 10 ml of anhydrous ethanol, add 1 mmol KSCN, stir for 30 min, and then add 2 mmol bim. React at room temperature for 3 h and filter to obtain a blue-purple solution. Transfer the solution to a test tube. Transfer the test tube to a sealed container filled with ether reagent for diffusion. After 3 days, a red block crystal product is obtained, namely, the easy-face magnetic anisotropic cobalt single ion magnet Co(bim). 4 (SCN) 2 The yield of crystals was 76%.

[0029] Example 2

[0030] Take 0.5mmol CoCl 2 Dissolve in 10 ml of anhydrous ethanol, add 1 mmol KSCN, stir for 30 min, and then add 2.5 mmol bim. React at room temperature for 3 h, filter to obtain a blue-purple filtrate, and transfer the filtrate to a test tube. Finally, move the test tube into a sealed container filled with ether reagent for diffusion. After 2 days, a red block crystal product is obtained, namely, the easy-face magnetic anisotropic cobalt single ion magnet Co(bim). 4 (SCN) 2 The yield of crystals was 70%.

[0031] Example 3

[0032] Take 0.5mmol CoCl 2 Dissolve in 15 ml of anhydrous ethanol, add 1 mmol KSCN, stir for 30 min, and then add 2.0 mmol bim. React at room temperature for 3 h and filter to obtain a blue-purple solution. Transfer the solution to a test tube, and move the test tube into a sealed container filled with ether reagent for diffusion. After 4 days, a red block crystal product is obtained, namely, the easy-face magnetic anisotropic cobalt single ion magnet Co(bim). 4 (SCN) 2 The yield of crystals was 72%.

[0033] The cobalt single ion magnet Co(bim) provided in Example 1 of the present invention is 4 (SCN) 2 The samples were assayed and characterized as follows:

[0034] (1) Crystal structure determination

[0035] Single crystals of appropriate size were selected under a microscope, and the structure was tested at room temperature on a Bruker SMARTApex IICCD single crystal instrument using a graphite-monochromatized molybdenum target. The APEXII program was used to collect data and determine the unit cell. The structural data were normalized and absorption corrected using the SAINT and SADABS programs. The SHELXTL-97 program was used for structural analysis. All non-hydrogen atomic coordinates were obtained by the difference Fourier synthesis method, and the atomic coordinates and anisotropic temperature factors were corrected using the full matrix least squares method, and all hydrogen atoms were hydrogenated using theory. Figure 1 Shown is a cobalt single ion magnet Co(bim) 4 (SCN) 2 Structure diagram of . Figure 1 The structure of the complex shows that the complex presents a distorted octahedral coordination configuration. The crystallographic data are shown in Table 1, and the coordination bond lengths are shown in Table 2.

[0036] Table 1 Cobalt single ion magnet Co(bim) 4 (SCN) 2 Crystallographic data

[0037]

[0038] Table 2 Cobalt single ion magnet Co(bim) 4 (SCN) 2 Coordination bond length and bond angle data

[0039] <![CDATA[Co1-N2 1 ]]> 2.1656(18) Co1-N2 2.1656(18) Co1-N4 2.140(2) <![CDATA[Co1-N4 1 ]]> 2.1401(19) Co1-N3 2.163(2) <![CDATA[Co1-N3 1 ]]> 2.163(2) <![CDATA[N2 1 -Co1-N2]]> 180.0 <![CDATA[N4 1 -Co1-N2 1 ]]> 87.23(7) <![CDATA[N4 1 -Co1-N2]]> 92.77(7) N4-Co1-N2 87.23(7) <![CDATA[N4-Co1-N2 1 ]]> 92.77(7) <![CDATA[N4 1 -Co1-N4]]> 180.0 <h2 style=";text-align:left;direction:ltr"><![CDATA[N4 <h2 style=";text-align:left;direction:ltr"> 1 <h2 style=";text-align:left;direction:ltr"> -Co1-N3<h2 style=";text-align:left;direction:ltr"> 1 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 89.32(8) <h2 style=";text-align:left;direction:ltr"><![CDATA[N4 <h2 style=";text-align:left;direction:ltr"> 1 <h2 style=";text-align:left;direction:ltr"> -Co1-N3]]><h2 style=";text-align:left;direction:ltr"> 90.68(8) <![CDATA[N4-Co1-N3 1 ]]> 90.68(8) N4-Co1-N3 89.32(8) N3-Co1-N2 91.29(8) <![CDATA[N3 1 -Co1-N2]]> 88.71(8) <![CDATA[N3-Co1-N2 1 ]]> 88.70(8) <![CDATA[N3 1 -Co1-N2 1 ]]> 91.30(8) <![CDATA[N3-Co1-N3 1 ]]> 180.0

[0040] The central cobalt ion is bound by four BIM ligands and two SCN - The coordination is carried out to form a distorted octahedral coordination configuration, which is calculated by Shape software (Table 3).

[0041] Table 3 Cobalt single ion magnet Co(bim) 4 (SCN) 2 CShM value

[0042] Configuration CShM value HP-6(Hexagonal) 31.497 PPY-6(Pentagonal Pyramid) 29.442 OC-6(Octahedron) 0.053 TPR-6(Triangular Prism) 16.382 JPPY-6(Pentagonal Pyramid) 32.828

[0043] (2) Powder X-ray diffraction determination of phase purity

[0044] The cobalt single ion magnet Co(bim) was measured using a Bruker D8 Advance powder X-ray diffractometer. 4 (SCN) 2 The phase purity of Figure 2As shown, the theoretical data is obtained by simulating the single crystal structure data using Mercury software. The results show that the cobalt single ion magnet material has reliable phase purity, which provides a guarantee for its application in molecular-based magnetic materials.

[0045] (3) Magnetic properties characterization

[0046] The magnetic measurement uses the superconducting quantum interference device QuantumDesignMPMS SQUID VSM magnetic measurement system. The test temperature of DC magnetic susceptibility is 2.0~300K, and the magnetic field is 1000Oe. The test temperature of magnetization intensity is 2K, 3K and 5K, and the magnetic field is 0~7T. The frequency range of AC magnetic susceptibility is 1~1000Hz, the temperature range is 2.0~5.5K, and the external DC magnetic field is 1000Oe.

[0047] like Figure 3 As shown in Figure 2, under an external DC magnetic field of 1000 Oe, when the temperature reaches 300 K, the cobalt single ion magnet Co(bim) 4 (SCN) 2 χ M The T value is 3.92cm 3 ·Kmol -1 , which is much larger than the theoretical value (1.875 cm) when only the spin of Co(II) ions is considered (S = 3 / 2, g = 2). 3 ·Kmol -1 ), which indicates that the cobalt single-ion magnet Co(bim) 4 (SCN) 2 There is a large magnetic anisotropy in the complex. As the temperature decreases, the χ M The T value gradually decreases. When the temperature drops to 2K, χ M T drops to 2.29cm 3 ·Kmol -1 . Due to the cobalt single ion magnet Co(bim) 4 (SCN) 2 The shortest distance between Co…Co is relatively long, so the cobalt single ion magnet Co(bim) at low temperature 4 (SCN) 2 χ M The sharp drop in T value is mainly caused by the magnetic anisotropy of the molecule itself rather than the interaction between molecules. The axial zero-field splitting parameter D value obtained by PHI fitting is +68.86cm -1 , indicating that the cobalt single-ion magnet Co(bim) 4 (SCN) 2 It has a large easy-face magnetic anisotropy. The magnetization intensity curve is as follows Figure 4As shown in Figure 3, with the increase of magnetic field strength, the magnetization intensity continues to increase and reaches a maximum value of 3Nβ at 2K and 7T.

[0048] The AC magnetic susceptibility test shows that at 2.0K, the cobalt single ion magnet Co(bim) 4 (SCN) 2 The imaginary susceptibility signal ( Figure 5 ). Under an external magnetic field of 1000Oe, the cobalt single ion magnet Co(bim) 4 (SCN) 2 The imaginary AC susceptibility shows a significant frequency dependence ( Figure 6 ) and temperature dependence ( Figure 7 ).

[0049] Based on the above phenomena, the cobalt single ion magnet Co(bim) prepared by the present invention 4 (SCN) 2 It can exhibit slow relaxation behavior under an external magnetic field and has the characteristics of a single-ion magnet. It can be used as a molecular-based magnetic material in high-density information storage devices.

[0050] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A cobalt single-ion magnet with easy-face magnetic anisotropy, characterized in that: The cobalt single-ion magnet with easy-face magnetic anisotropy is a hexacoordinated complex with a molecular formula of Co(bim)4(SCN)2, wherein bim is 1-allylimidazole. The crystallographic parameters of the cobalt single-ion magnet are: the crystal belongs to the triclinic system, the space group is P-1, and the unit cell parameters are α=69.923(7)°, β=65.435(6)°, γ=65.435(6)°.

2. The easy-face magnetic anisotropic cobalt single-ion magnet according to claim 1, characterized in that: The configuration of the cobalt single-ion magnet is a distorted octahedron.

3. A method for preparing the easy-face magnetic anisotropic cobalt single-ion magnet according to claim 1, characterized in that: The following steps are involved: S1. Dissolve CoCl2 in anhydrous ethanol, add potassium thiocyanate, stir for 20-60 min, add 1-allylimidazole, react at room temperature for 2-5 h, and then filter to obtain a blue-purple solution; S2. placing the blue-purple solution in an ether atmosphere and leaving it to stand for 2 to 4 days to obtain the easy-face magnetic anisotropic cobalt single-ion magnet.

4. The preparation method according to claim 3, characterized in that: In step S1, the molar ratio of CoCl2, potassium thiocyanate and 1-allylimidazole is 1:2:(4-5).

5. The preparation method according to claim 4, characterized in that: In step S1, every 0.5 mmol of CoCl2 corresponds to 10-15 mL of anhydrous ethanol.

6. Use of the cobalt single ion magnet according to claim 1 or 2 or the easy-face magnetic anisotropic cobalt single ion magnet prepared by the preparation method according to any one of claims 3 to 5 in the preparation of molecule-based magnetic materials.

7. Use of the cobalt single ion magnet according to claim 1 or 2 or the easy-face magnetic anisotropy cobalt single ion magnet prepared by the preparation method according to any one of claims 3 to 5 in the preparation of high-density information storage materials.

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