Selenium cyanide coordinated cobalt single ion magnet as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of transition metal coordination chemistry, and discloses a selenium cyanide coordinated cobalt single-ion magnet and a preparation method and application thereof, and the molecular formula of the selenium cyanide coordinated cobalt single-ion magnet is Co (bim) 4 (SeCN) 2. The preparation method of Co (bim) 4 (SeCN) 2 comprises the following steps: dissolving anhydrous cobalt chloride in absolute ethyl alcohol, adding potassium selenide, stirring, 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 Co (bim) 4 (SeCN) 2. The preparation process is safe and simple, high in controllability and good in repeatability, and the prepared complex is good in stability and relatively high in purity and yield, has the property of a field-induced single-molecule magnet, and can be used as a molecule-based magnetic material to be applied to the fields of novel high-density information storage equipment and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of transition metal complex coordination functional materials, and relates to a selenium cyanide coordinated cobalt single ion magnet and a preparation method and application thereof. Background Art

[0002] Cobalt complexes are one of the important types of transition metal complexes. As a transition metal element, cobalt has a variety of oxidation states and coordination numbers. Therefore, cobalt complexes can generate complexes with a variety of coordination numbers and geometric structures. Since cobalt complexes have good magnetic and optical properties, they are widely used in the field of materials science. For example, some cobalt complexes can be used as magnetic materials to prepare magnetic storage media or magnetic sensors.

[0003] Single-Molecule Magnets (SMMs) are truly nano-sized molecular magnets. They not only exhibit the macroscopic properties of traditional magnets, but also the quantum tunneling effect of microscopic particles. When the magnetism in a single-molecule magnet originates from a single paramagnetic ion in a molecule, it is a single-ion magnet (SIMs).

[0004] In most cases, the first-order orbital angular momentum in cobalt complexes is quenched, while the second-order spin-orbit coupling can easily lead to large magnetic anisotropy by mixing the related excited state with the ground state. Therefore, the transition metal single-ion magnets reported so far are mainly concentrated on mononuclear cobalt complexes. The cobalt ions involved in cobalt single-ion magnets mainly have two oxidation states, namely Co(I) and Co(II). Among them, Co(II) ions, as Kramers ions, have unique transverse zero-field splitting characteristics that can effectively suppress the occurrence of quantum tunneling effects. This characteristic makes Co(II) complexes occupy a dominant position in the reported cobalt-based single-ion magnet research. Cobalt single-ion magnets can be divided into many different types according to their coordination environment and structure. The coordination numbers of cobalt(II) single-ion magnets reported so far mainly include di-, tri-, tetra-, penta- and hexa-coordination.

[0005] Selenocyanate ([SeCN]-) is a multifunctional ligand with unique electron donation and bridging capabilities, as well as strong chemical stability. These properties give it potential advantages in the design of metal complexes. However, there are few studies on selenocyanate-coordinated cobalt single-ion magnets in the prior art, especially in the regulation of magnetic properties and their application development. Summary of the invention

[0006] The purpose of the present invention is to at least partially solve the above-mentioned technical problems, and to provide a selenium cyanide coordinated cobalt single ion magnet and its preparation method and application. The cobalt single ion magnet can exist stably in the air and has the properties of a single molecule magnet under an external magnetic field.

[0007] The first aspect of the present invention provides a selenium cyanide coordinated cobalt single ion magnet, the chemical formula of the cobalt single ion magnet is Co(bim)4(SeCN)2, wherein bim is 1-allylimidazole; the crystallographic parameters of the cobalt single ion magnet are: triclinic system, P-1 space group, unit cell parameters α=109.731°, β=113.791°, γ=94.205°; the cobalt ions in the cobalt single ion magnet are respectively connected with 4 bims and 2 SeCN - Ions coordinate.

[0008] In some embodiments of the present invention, the configuration of the cobalt single-ion magnet is a distorted octahedral configuration.

[0009] The second aspect of the present invention provides a method for preparing the above-mentioned cobalt single-ion magnet, which is as follows: dissolving CoCl2 in anhydrous ethanol, adding potassium selenocyanate, stirring for 20 to 40 minutes, and then adding BIM, reacting at room temperature for 2 to 4 hours, and then filtering to obtain a filtrate, placing the filtrate in an ether atmosphere, and standing for 2 to 4 days to obtain the cobalt single-ion magnet.

[0010] In some embodiments of the present invention, the molar ratio of CoCl2 to potassium selenocyanate is 1:2.

[0011] In some embodiments of the present invention, every 0.5 mmol of CoCl2 corresponds to 10-15 mL of anhydrous ethanol.

[0012] In some embodiments of the present invention, every 0.5 mmol of CoCl2 corresponds to 2.0-2.5 mmol of bim.

[0013] In a third aspect of the present invention, there is provided the use of the above-mentioned cobalt single ion magnet or the cobalt single ion magnet prepared by the above-mentioned preparation method in a molecule-based magnetic material.

[0014] In a fourth aspect of the present invention, there is provided the use of the above-mentioned cobalt single-ion magnet or the cobalt single-ion magnet prepared by the above-mentioned preparation method in high-density information storage materials.

[0015] The selenium cyanide coordinated cobalt single ion magnet and its preparation method and application according to the embodiment of the present invention have at least one of the following advantages:

[0016] (1) The selenium cyanide coordinated cobalt single ion magnet provided by the present invention can exist stably in the air and has the properties of a single molecule magnet under an external magnetic field, and can be widely used in the preparation of molecular-based magnetic materials.

[0017] (2) The preparation method provided by the present invention is simple to operate, has good controllability, high reproducibility, and the obtained complex has high purity and yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0019] Figure 1 The crystal structure diagram of the cobalt single ion magnet Co(bim)4(SeCN)2 provided by the present invention;

[0020] Figure 2 A powder X-ray diffraction pattern of the cobalt single ion magnet Co(bim)4(SeCN)2 provided by the present invention;

[0021] Figure 3 This is a temperature-dependent magnetic susceptibility test diagram of the cobalt single-ion magnet Co(bim)4(SeCN)2 provided by the present invention;

[0022] Figure 4 A field-dependent magnetization intensity curve of the cobalt single-ion magnet Co(bim)4(SeCN)2 provided by the present invention;

[0023] Figure 5 The AC magnetic susceptibility diagram of the cobalt single ion magnet Co(bim)4(SeCN)2 provided by the present invention under different external magnetic fields;

[0024] Figure 6 A frequency-dependent imaginary AC susceptibility diagram of the cobalt single-ion magnet Co(bim)4(SeCN)2 provided by the present invention;

[0025] Figure 7 The present invention provides a diagram of the imaginary AC magnetic susceptibility of the cobalt single-ion magnet Co(bim)4(SeCN)2 that is temperature dependent. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0027] Example 1

[0028] Take 0.5mmol CoCl2 and dissolve it in 10ml anhydrous ethanol, then add 1mmol KSeCN, stir for 30min and then add 2mmol bim. After reacting at room temperature for 3h, filter to obtain a blue-purple solution. Transfer the solution to a test tube. Move the test tube into a sealed container filled with ether reagent for diffusion. After 3 days, a purple-red block crystal product, i.e., crystals of cobalt single-ion magnet Co(bim)4(SeCN)2, is obtained with a yield of 68%.

[0029] Example 2

[0030] Take 0.5mmol CoCl2 and dissolve it in 10ml anhydrous ethanol, then add 1mmol KSeCN, stir for 30min and then add 2.5mmol bim. React at room temperature for 3h, 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 purple-red block crystal product, i.e., crystals of cobalt single ion magnet Co(bim)4(SCN)2, is obtained with a yield of 65%.

[0031] Example 3

[0032] Take 0.5mmol CoCl2 and dissolve it in 15ml anhydrous ethanol, then add 1mmol KSeCN, stir for 30min and then add 2.0mmol bim. After reacting at room temperature for 3h, 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 purple-red block crystal product, i.e., crystals of cobalt single-ion magnet Co(bim)4(SeCN)2, is obtained with a yield of 65%.

[0033] The cobalt single ion magnet Co(bim)4(SeCN)2 prepared in Example 1 was used as a sample for measurement:

[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 the structural diagram of the cobalt single-ion magnet Co(bim)4(SeCN)2. Figure 1The structure diagram proves that the cobalt single ion magnet Co(bim)4(SeCN)2 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 Crystallographic data of cobalt single ion magnet Co(bim)4(SeCN)2

[0037]

[0038]

[0039] Table 2 Coordinate bond length and bond angle data of cobalt single ion magnet Co(bim)4(SeCN)2

[0040] <![CDATA[Co1-N2 1 ]]> 2.163(3) Co1-N2 2.163(3) Co1-N4 2.131(3) <![CDATA[Co1-N4 1 ]]> 2.131(3) Co1-N3 2.149(3) <![CDATA[Co1-N3 1 ]]> 2.149(3) <![CDATA[N2 1 -Co1-N2]]> 180.0 <![CDATA[N4 1 -Co1-N2 1 ]]> 92.70(11) <![CDATA[N4 1 -Co1-N2]]> 87.30(11) N4-Co1-N2 92.70(11) <![CDATA[N4-Co1-N2 1 ]]> 87.30(11) <![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"> 89.41(12) <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"> 90.59(12) <![CDATA[N4-Co1-N3 1 ]]> 90.59(12) N4-Co1-N3 89.41(12) N3-Co1-N2 88.81(12) <![CDATA[N3 1 -Co1-N2]]> 91.19(12) <![CDATA[N3-Co1-N2 1 ]]> 91.19(12) <![CDATA[N3 1 -Co1-N2 1 ]]> 88.81(12) <![CDATA[N3-Co1-N3 1 ]]> 180.0

[0041] The central cobalt ion is bound by four bim ligands and two SeCN - The coordination is carried out to form a distorted octahedral coordination configuration, which is calculated by Shape software (Table 3).

[0042] Table 3 CShM values ​​of cobalt single ion magnet Co(bim)4(SeCN)2

[0043] Configuration CShM value HP-6(Hexagonal) 31.610 PPY-6(Pentagonal Pyramid) 29.490 OC-6(octahedron) 0.050 TPR-6(Triangular Prism) 16.390 JPPY-6(Pentagonal Pyramid) 32.881

[0044] (2) Powder X-ray diffraction determination of phase purity

[0045] The phase purity of the purple-red blocky crystalline product obtained in this example was characterized using a Bruker D8 Advance powder X-ray diffractometer. Figure 2 As shown, the theoretical data is obtained by simulating the single crystal structure data using Mercury software. The results show that the hexacoordinated cobalt single ion magnet material has reliable phase purity, which provides a guarantee for its application in molecular-based magnetic materials.

[0046] (3) Characterization of magnetic properties

[0047] The magnetic measurement uses the superconducting quantum interference device Quantum Design MPMS 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 2.5K and 5K, and the magnetic field is 0~7T. The frequency range of AC magnetic susceptibility is 1~1000Hz, the temperature range is 2.0~5.0K, and the external DC magnetic field is 1000Oe.

[0048] like Figure 3As shown in Figure 2, under an external DC magnetic field of 1000 Oe, when the temperature reaches 300 K, the χ M T value is 3.55cm 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 K mol -1 ), which indicates that there is a large magnetic anisotropy in the cobalt single-ion magnet Co(bim)4(SeCN)2. As the temperature decreases, the χ M The T value gradually decreases. When the temperature drops to 2K, χ M T drops to 2.20cm 3 ·Kmol -1 Since the shortest distance between Co…Co in the cobalt single-ion magnet Co(bim)4(SeCN)2 is relatively long, the χ M The sharp drop in T value is mainly caused by the larger zero-field splitting inside the cobalt single-ion magnet Co(bim)4(SeCN)2 rather than the intermolecular interaction. The axial zero-field splitting parameter D value obtained by PHI fitting is +65.12cm -1 , indicating that the cobalt single ion magnet Co(bim)4(SeCN)2 has a large easy-face magnetic anisotropy. The magnetization intensity curve is shown in Figure 4 As shown, with the increase of magnetic field strength, the magnetization intensity continues to increase, reaching a maximum value of 2.64Nβ at 2.5K and 7T, and has not yet reached saturation, indicating that there is a large magnetic anisotropy in the cobalt single-ion magnet Co(bim)4(SeCN)2.

[0049] The AC magnetic susceptibility test shows that at 2.0K, the cobalt single-ion magnet Co(bim)4(SeCN)2 exhibits a frequency-dependent imaginary magnetic susceptibility signal under an external magnetic field ( Figure 5 ). Under an external magnetic field of 1000Oe, the imaginary AC magnetic susceptibility of the cobalt single-ion magnet Co(bim)4(SeCN)2 shows a significant frequency dependence ( Figure 6 ) and temperature dependence ( Figure 7 ).

[0050] Based on the above phenomena, the cobalt single-ion magnet Co(bim)4(SeCN)2 prepared by the present invention can exhibit the properties of a single-molecule magnet under an external magnetic field and can be used as a molecular-based magnetic material in high-density information storage devices.

[0051] The selenium cyanide coordinated cobalt single ion magnet and its preparation method and application according to the embodiment of the present invention have at least one of the following advantages:

[0052] (1) The selenium cyanide coordinated cobalt single ion magnet provided by the present invention can exist stably in the air and has the properties of a single molecule magnet under an external magnetic field, and can be widely used in the preparation of molecular-based magnetic materials.

[0053] (2) The preparation method provided by the present invention is simple to operate, has good controllability, high reproducibility, and the obtained complex has high purity and yield.

Claims

1. A selenium cyanide coordinated cobalt single ion magnet, characterized in that: The chemical formula of the cobalt single ion magnet is Co(bim)4(SeCN)2, wherein bim is 1-allylimidazole; The crystallographic parameters of the cobalt single ion magnet are: triclinic system, P-1 space group, unit cell parameters are α=109.731°, β=113.791°, γ=94.205°; The cobalt ions in the cobalt single ion magnet are respectively connected with 4 bims and 2 SeCN - Ions coordinate.

2. The cobalt single ion magnet according to claim 1, characterized in that The configuration of the cobalt single-ion magnet is a distorted octahedral configuration.

3. A method for preparing the cobalt single ion magnet according to claim 1, characterized in that: The preparation method comprises the following steps: dissolving CoCl2 in anhydrous ethanol, adding potassium selenocyanate, stirring for 20 to 40 minutes, then adding BIM, reacting at room temperature for 2 to 4 hours, filtering to obtain a filtrate, placing the filtrate in an ether atmosphere, and standing for 2 to 4 days to obtain the cobalt single ion magnet.

4. The preparation method according to claim 3, characterized in that: The molar ratio of CoCl2 to potassium selenocyanate is 1:

2.

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

6. The preparation method according to claim 4, characterized in that: Every 0.5 mmol of CoCl2 corresponds to 2.0-2.5 mmol of BIM.

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

8. Use of the cobalt single ion magnet according to claim 1 or 2 or the cobalt single ion magnet prepared by the preparation method according to any one of claims 3 to 6 in high-density information storage materials.

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