In-situ Synthesis Method and Application of a Dysprosium Complex of Quinazolinone Schiff Base

Abstract

The invention discloses an in-situ synthesis method and application of a dysprosium complex of quinazolinone Schiff base. The complex is prepared by a low-temperature solvothermal method in a methanol solvent using N'-(3-ethoxysalicylidene)-2-(3-ethoxysalicylideneimine) benzohydrazide and dysprosium nitrate as reaction raw materials. During the reaction process, part of the initial ligand is in-situ transformed into 3-(3-ethoxysalicylideneimine) quinazolinone. The initial ligand and the in-situ generated quinazolinone Schiff base ligand jointly construct an unprecedented dysprosium-based pentanuclear cluster structure formed by the sharing of edges of {Dy4} tetrahedral units and {Dy3} triangular units. Under zero external field, the complex exhibits obvious single-molecule magnet behavior characteristics and has application potential in the field of new molecular-based magnetic materials.

Description

Technical Field

[0001] The present invention belongs to the field of novel molecular-based magnetic materials, and particularly relates to an in-situ synthesis method of a dysprosium complex of quinazolinone Schiff base and its application in the field of molecular-based magnetic materials. Background Art

[0002] Single-molecule magnets mainly in the form of metal complexes have promising application potentials in aspects such as quantum computing and high-density information storage, and are a novel molecular-based magnetic material expected to replace existing traditional magnetic materials. In the research in this field, dysprosium ions among rare-earth ions have gradually become one of the preferred spin carriers for synthesizing high-performance single-molecule magnets due to their strong spin-orbit coupling effect and strong single-ion magnetic anisotropy. Especially in some polynuclear dysprosium-based complexes, if the dysprosium ions are arranged in a specific manner, it is expected to obtain some special magnetic behaviors and excellent single-molecule magnet properties through the cooperation of the magnetic axes of multiple dysprosium ions. Therefore, exploring polynuclear dysprosium complexes with novel topological structures is of great significance for the research and development of dysprosium single-molecule magnets.

[0003] The in-situ reaction of ligands is a special coordination synthesis reaction in which, during the coordination process, after the initial ligands undergo structural transformation, they participate in the formation of complexes with new structures. Such in-situ synthesis reactions often can obtain some products with strange topological structures. And complexes that cannot be obtained by conventional means are also expected to be realized through in-situ synthesis reactions. However, in the synthesis of single-molecule magnets, this in-situ synthesis method is currently mostly applied to transition-metal-based single-molecule magnets, but is very rare in dysprosium-based single-molecule magnets. Therefore, developing the in-situ synthesis of dysprosium-based single-molecule magnets not only highlights the characteristics and innovation in the synthesis method, but also is expected to obtain excellent single-molecule magnet properties through the construction of special topological structures. Summary of the Invention

[0004] The purpose of the present invention is precisely in view of the above situation, to provide an in-situ synthesis method of a dysprosium complex of quinazolinone Schiff base and its application in the field of single-molecule magnets.

[0005] A dysprosium complex of quinazolinone Schiff base involved in the present invention is characterized in that its chemical composition is [Dy5(eebhz)3(eqlz)(μ-CH3O)(μ3-CH3O)2(μ4-O)(CH3OH)]·2CH3OH. Among them, H3eebhz is the initial ligand N′-(3-ethoxysalicylidene)-2-(3-ethoxysalicylimino)benzohydrazide, and Heqlz represents the 3-(3-ethoxysalicylimino)quinazolinone ligand in-situ transformed from H3esshz during the reaction. This complex crystallizes in the triclinic P1 space group, and its main crystallographic parameters are: α = 86.713(2)°, β = 71.974(2)°, γ = 77.151(2)°; Z = 2, ρ calc (g / cm 3 ) = 1.803 g·cm –3 , μ = 3.845 mm –1 , F(000) = 2608.0; The specific crystallographic data are shown in Table 1 below:

[0006] Table 1. Crystallographic parameters of the magnet

[0007]

[0008] A preparation method of a quinazolinone Schiff base dysprosium complex, and its specific steps are as follows:

[0009] (1) Weigh 2-aminobenzohydrazide (6 mmol, 0.907 g) and 3-ethoxysalicylaldehyde (12 mmol, 1.994 g), and dissolve them in 40 mL of absolute ethanol. Heat under reflux for 3 h, remove the heat source, and let the reaction solution cool naturally. Filter the precipitated yellow solid by suction, and recrystallize it with ethanol to obtain the initial ligand H3eebhz for synthesizing a quinazolinone Schiff base dysprosium complex.

[0010] (2) Add the weighed H3eebhz ligand (0.10 mmol, 0.015 g) and Dy(NO3)3·6H2O (0.15 mmol, 0.0685 g) into the polytetrafluoroethylene inner liner of a 25 mL high-temperature reaction kettle. Then add 7 mL of methanol and 7 drops of triethylamine, stir for 5 min and then seal. Place the reaction kettle in an 80 °C oven and react for 72 h, and then cool it to room temperature at a cooling rate of 10 °C / hour to obtain yellow prismatic crystals of the dysprosium complex.

[0011] A quinazolinone Schiff base dysprosium complex, and its in-situ synthesis reaction characteristics are as follows:

[0012] During the reaction process, some of the initial H3eebhz ligands successively undergo hydrolysis, condensation, and cyclization reaction processes, and are in-situ transformed into the quinazolinone Schiff base ligand Heqlz. The new ligand Heqlz, together with the initial H3eebhz ligand, participates in the construction of the quinazolinone Schiff base dysprosium complex.

[0013] A quinazolinone Schiff base dysprosium complex, and the spatial structure characteristics of its molecule are as follows:

[0014] 5 Dy III ions are composed of 1 μ-CH3O - ion, 2 μ3-CH3O - ions and 1 μ4-O2- The ion bridging forms [Dy5(μ4-O)(μ3-CH3O)2(μ-CH3O)] 10+ the cluster core. This core can be regarded as an assembly formed by the edge-sharing of one {Dy4} tetrahedral unit and one {Dy3} triangular unit. Two eebhz 3- ligands wind around the waist of this [Dy5(μ4-O)(μ3-CH3O)2(μ-CH3O)] 10+ core. One of them bridges Dy1, Dy2, Dy4 and Dy5, while the other bridges Dy2, Dy3, Dy4 and Dy5, thus further strengthening this core. Another eebhz 3- and one in-situ generated eqlz - ligands are located at the bottom and top of the core respectively, acting as terminal protecting ligands.

[0015] The innovation of the present invention lies in:

[0016] The in-situ synthesis reaction of ligands is very helpful for obtaining complexes with special topological structures and excellent properties. However, such a reaction is rarely applied in the synthesis of dysprosium-based complexes, especially in the synthesis of dysprosium-based single-molecule magnets. The present invention provides here an unprecedented method for the in-situ synthesis of a dysprosium complex of quinazolinone Schiff base from hydrazone ligands. The dysprosium complex synthesized by this method not only has a cluster topology that has not been reported in previous literature, but also exhibits excellent magnetic properties and has the potential to be developed into a molecular-based magnetic material. Brief Description of the Drawings

[0017] Figure 1 It is the structural diagram of the H3eebhz ligand used in the present invention.

[0018] Figure 2 It is the structural diagram of the in-situ generated Heqzl ligand in the present invention..

[0019] Figure 3 It is the molecular structure diagram of the dysprosium complex of quinazolinone Schiff base described in the present invention.

[0020] Figure 4 It is the X-ray powder diffraction pattern of the dysprosium complex of quinazolinone Schiff base described in the present invention.

[0021] Figure 5 It is the variable-temperature magnetic susceptibility diagram of the dysprosium complex of quinazolinone Schiff base described in the present invention.

[0022] Figure 6 It is the magnetization intensity curve diagram of the dysprosium complex of quinazolinone Schiff base described in the present invention.

[0023] Figure 7AC susceptibility real part plot of the quinazolinone Schiff base dysprosium complex of the present invention under zero field.

[0024] Figure 8 AC susceptibility imaginary part plot of the quinazolinone Schiff base dysprosium complex of the present invention under zero field.

[0025] Figure 9 Cole-Cole plot of the quinazolinone Schiff base dysprosium complex of the present invention under zero field. Detailed implementation manners

[0026] Example:

[0027] 1. An in-situ synthesis method of a quinazolinone Schiff base dysprosium complex, and the specific steps are as follows:

[0028] (1) Add 2-aminobenzohydrazide (6 mmol, 0.907 g) and 3-ethoxysalicylaldehyde (12 mmol, 1.994 g) into a 100 mL flask, and then add 40 mL of absolute ethanol. After the reaction solution is stirred and refluxed for 3 h under water bath heating, remove the water bath pot and let it cool naturally in the air. As the temperature decreases, a yellow precipitate gradually precipitates in the reaction solution. Filter by suction, and recrystallize the yellow precipitate with ethanol to obtain the H3eebhz ligand, and the yield is about 77%.

[0029] The molecular structure of the H3eebhz ligand is shown in Figure 1 . The 1H NMR data thereof are as follows: 1 1H NMR (500 MHz, DMSO- d6 ): δ 11.33 (s, 1H), 9.22 (s, 1H), 8.40 (s, 1H), 7.79 (d, J = 6.3 Hz, 1H), 7.43 (d, J = 2.7 Hz, 1H), 7.34 - 7.25 (m, 1H), 7.04 - 6.94 (m, 2H), 6.89 (dd, J = 8.0, 1.6 Hz, 1H), 6.85 (d, J = 2.7 Hz, 1H), 6.79 (t, J = 7.8 Hz, 2H), 6.75 (t, J = 7.0 Hz, 1H), 6.64 (t, J = 7.9 Hz, 1H), 6.59 (d, J = 8.0 Hz, 1H), 4.03 (dt, J = 11.8, 7.1 Hz, 4H), 1.33 (dt, J = 14.3, 7.0 Hz, 6H).

[0030] (2) Weigh out the H3eebhz ligand (0.10 mmol, 0.015 g) and Dy(NO3)3·6H2O (0.15 mmol, 0.0685 g) according to a molar ratio of 2:3, and place them in the PVC inner liner of a 25 mL high-temperature reaction kettle. Then add 7 mL of methanol and 7 drops of triethylamine. After magnetic stirring for 5 min, seal the reaction kettle. Subsequently, place the reaction kettle in an 80 °C oven, maintain the reaction for 72 h, and cool it to room temperature at a cooling rate of 10 °C / h. Yellow prismatic crystals of the dysprosium complex are obtained at the bottom of the kettle. Based on the ligand, the yield is approximately 46%.

[0031] 2. Crystal Structure Characterization of a Quinazolinone Schiff Base Dysprosium Complex:

[0032] The single-crystal structure diffraction data of this magnet were collected using an Agilent Supernova single-crystal diffractometer with graphite-monochromated Mo-Kα radiation in the scanning mode. The calculation work was completed on a PC using the SHELXS and SHELXL programs embedded in the Olex2 software. All data were corrected for empirical absorption. The structure of the complex was solved by the heavy-atom method, hydrogen atoms were added, and the structure was refined by full-matrix least squares.

[0033] As Figure 3 shown, this quinazolinone Schiff base dysprosium complex consists of 5 Dy III ions, 3 eebhz 3- ligands, 1 eqlz - ligand ( Figure 2 ), 1 μ-CH3O - ion, 2 μ3-CH3O - ions, 1 μ4-O 2- ion, and 1 coordinated methanol molecule. There are also 2 free methanol molecules in the crystal lattice. The 5 Dy III ions it contains are bridged by 1 μ-CH3O - , 2 μ3-CH3O - and 1 μ4-O 2- ions to form a [Dy5(μ4-O)(μ3-CH3O)2(μ-CH3O)] 10+ cluster core. Overall, this core can be regarded as a combination formed by a {Dy4} tetrahedral unit composed of Dy1, Dy2, Dy3, and Dy4, and a {Dy3} triangular unit composed of Dy3, Dy4, and Dy5, through sharing Dy3 and Dy4 atoms.

[0034] In this [Dy5(μ4-O)(μ3-CH3O)2(μ-CH3O)] 10+The waist is wound with 2 eebhz 3- ligands. One of them bridges and chelates Dy1, Dy2, Dy4 and Dy5 in a coordination mode of μ4-η 2 :η 3 η 3 :η 1 ; while the other bridges and chelates Dy2, Dy3, Dy4 and Dy5 in a mode of μ4-η 2 :η 3 η 3 :η 2 The eebhz at the bottom of the tetrahedron bridges the Dy1 and Dy2 ions in a μ-η 3- :η 3 :η 3 mode. For the eqlz - ligand generated in-situ during the reaction, together with another methanol molecule, respectively perfect the coordination geometries of the Dy5 and Dy4 ions in a terminal coordination manner. The 5 Dy III ions exhibit 4 kinds of coordination geometries. Among them, Dy1 has an eight-coordinate trigonal dodecahedron geometry, Dy2 and Dy5 have an eight-coordinate square antiprism geometry, Dy3 has an eight-coordinate bicapped trigonal prism geometry, and Dy4 has a nine-coordinate monocapped square antiprism geometry.

[0035] 3. X-ray powder diffraction characterization of a quinazolinone Schiff base dysprosium complex:

[0036] As Figure 4 shown, the powder diffraction curve obtained by testing the complex is in good agreement with the curve simulated from single crystal data, indicating that the sample of the complex is a pure phase.

[0037] 4. Application of a quinazolinone Schiff base dysprosium complex:

[0038] One example of the quinazolinone Schiff base dysprosium complex described in the present invention is mainly characterized by its single molecule magnet behavior without an external magnetic field.

[0039] Figure 5 is the variable temperature magnetic susceptibility of the complex measured in the temperature range of 300 - 2 K under an external magnetic field of 1.0 kOe. At room temperature, the χ M T value of this magnet is 70.14 cm 3 K mol -1 , which is close to the corresponding theoretical value (70.85 cm III Kmol 3 ) of 5 independent Dy -1 ions. As the temperature decreases, its χ M T value gradually begins to decrease and finally reaches the lowest value of 48.4 cm at 2 K 3Kmol -1 .

[0040] Figure 6 is the magnetization intensity diagram of the magnet at different temperatures. At each test temperature, the magnetization intensity (M) of the magnet increases rapidly with the increase of the external field (H), and the rising trend slows down after 1.5 T. Finally, the magnetization intensity reaches the maximum value of 26.30 Nμ at 1.8 K and 7 T B , and the magnetization intensity curves at each temperature do not coincide.

[0041] Figure 7 and Figure 8 are the diagrams of the real part (χ′) and the imaginary part (χ″) of the AC magnetic susceptibility measured for the complex at zero external field, respectively. As can be seen from the figure, both the real part (χ′) and the imaginary part (χ″) of the AC magnetic susceptibility of the magnet show obvious dependence on the frequency in the temperature range of 1.8 - 14 K, showing obvious slow magnetic relaxation behavior, which has the typical characteristics of a single-molecule magnet.

[0042] Figure 9 Shows the Cole-Cole diagram obtained by fitting the above AC magnetic susceptibility data based on the Debye model. The obtained Cole-Cole curve fits well with the AC magnetic susceptibility data, and each Cole-Cole curve is approximately semicircular. Based on this data, the ln(τ)-T of the relaxation process is fitted using the Arrhenius formula -1 data, and the single-molecule magnet performance parameters of the complex at zero field can be obtained: effective energy barrier (U eff ) = 77.98 cm -1 , relaxation time (τ0) = 8.76×10 -6 s.

Claims

1. A dysprosium complex of quinazolinone Schiff base, characterized in that, Its chemical formula is [Dy5(eebhz)3(eqlz)(μ-CH3O)(μ3-CH3O)2(μ4-O)(CH3OH)]·2CH3OH; where H3eebhz is N′-(3-ethoxysalicylidene)-2-(3-ethoxysalicylimino)benzohydrazide, and Heqlz represents 3-(3-ethoxysalicylimino)quinazolinone. The molecular structural formulas of the two ligands are as follows:

2. A dysprosium complex of quinazolinone Schiff base according to claim 1, characterized in that, The Heqlz mentioned above is in-situ transformed from the initial H3eebhz ligand through hydrolysis, condensation, and cyclization reaction processes successively during the reaction.

3. A dysprosium complex of quinazolinone Schiff base according to claim 1, characterized in that, It crystallizes in the triclinic P1 space group, and its main crystallographic parameters are as follows: α = 86.713(2)°, β = 71.974(2)°, γ = 77.151(2)°; Z = 2, ρ calc (g / cm 3 ) = 1.803 g·cm –3 , μ = 3.845 mm –1 , F(000) = 2608.

0.

4. A dysprosium complex of quinazolinone Schiff base according to claim 1, characterized in that Its structural characteristics are as follows: a [Dy5(μ4-O)(μ3-CH3O)2(μ-CH3O)] formed by sharing a side between one {Dy4} tetrahedral unit and one {Dy3} triangular unit 10+ core; three eebhz 3- ligands, one bridging Dy1 and Dy2, the second bridging Dy1, Dy2, Dy4 and Dy5, and the third bridging Dy2, Dy3, Dy4 and Dy5; one in-situ generated eqlz - ligand coordinates with Dy5 in a tridentate chelating form.

5. An in-situ synthesis method of a dysprosium complex of quinazolinone Schiff base as described in any one of claims 1-4, characterized in that, The specific steps are as follows: Weigh 0.10 mmol of the H3eebhz ligand and 0.15 mmol of Dy(NO3)3·6H2O, and place them in the polyvinyl chloride inner liner of a 25 mL high-temperature reaction kettle. Then add 7 mL of methanol and 7 drops of triethylamine, stir for 5 min and then seal it; Place the reaction kettle in an 80 °C oven for reaction for 72 h, and then cool it to room temperature at a cooling rate of 10 °C / hour.

6. The in-situ synthesis method according to claim 5, characterized in that, The initial ligand is N′-(3-ethoxysalicylidene)-2-(3-ethoxysalicylimino)benzohydrazide (H3eebhz).

7. The in-situ synthesis method according to claim 5, characterized in that, The molar ratio of the initial ligand to Dy(NO3)3·6H2O is 2:3; the reaction solvent is a methanol solution with a dosage of 7 mL; the reaction temperature is 80 °C; and the dosage of triethylamine as a deprotonating base is 7 drops.

8. Use of a dysprosium complex of a quinazolinone Schiff base as described in any one of claims 1-4, characterized in that, Its alternating magnetic susceptibility under zero field has an obvious frequency-dependent behavior, showing typical single-molecule magnet behavior characteristics, and can be used as a potential molecular-based magnetic material.

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