Series of rare earth complexes constructed based on thiodihydrazide o-vanillin Schiff base ligand and synthesis method thereof

Abstract

The invention provides a series of rare earth complexes constructed based on a thiodihydrazide o-vanillin Schiff base ligand and a synthesis method of the series of rare earth complexes, and belongs to the field of rare earth complexes, and the rare earth complexes are a cluster [Dy3 (L9) 2 (L10) 2 (NO3) 2] NO3. 2CH3CN. 2CH3OH or a cluster [Dy4 (L11) 2Cl6 (CH3OH) 2 (H2O) 2]. 2CH3OH. The two Dy complexes 12-13 are synthesized from thiodihydrazide and o-vanillin with two dysprosium salts respectively under the condition of a one-pot method. The domino reaction can generate an intermediate organic ligand which is difficult to generate by a traditional method, so that the structure of the complex is regulated and controlled, the coordination environment of a Dy metal center is changed, and the magnetism is regulated and controlled.

Description

Technical Field

[0001] The present invention relates to the field of rare earth complexes, and particularly to a series of rare earth complexes constructed based on thiosemicarbazide-o-vanillin Schiff base ligands and a synthesis method thereof. Background Art

[0002] In recent years, rare earth complexes have attracted more and more attention from researchers due to their beautiful structures, excellent magnetic and optical properties, and have been widely applied to fields such as sensing, catalysis, anti-counterfeiting, storage, ion exchange, magnetic refrigeration, sterilization, and gas adsorption. Rare earth elements themselves have characteristics such as high coordination numbers and complex coordination modes, which not only result in the diversity of their structures but also bring some problems, such as difficulty in designing and synthesizing target complexes directionally, tracking the self-assembly of rare earth complexes, and exploring the assembly mechanism. How to design and synthesize rare earth complexes with beautiful structures and excellent properties has always been a challenge.

[0003] The domino reaction is abbreviated as the domino reaction, which was defined and named by Tietze in 1993. The principle of this type of reaction is similar to the domino game, that is, a series of reactions occur continuously without adding any other reagents, drugs, and catalysts. Each subsequent reaction step uses the reaction product (all or part) of the previous step as a raw material. Since this method does not require the separation and purification of intermediates, it greatly improves the atomic utilization rate and has great advantages in terms of saving raw material costs, time costs, and step design. Moreover, due to its interlocking reaction steps and complex reaction mechanism, the domino reaction can often convert simple raw materials into molecules with complex structures that are difficult to synthesize by traditional methods. Therefore, the domino reaction is widely used in fields such as photoelectrocatalysis, organic catalysis, biocatalysis, and organic synthesis. For example, in 2018, the team of Professor Zeng Minghua reported a domino tandem reaction of up to 14 steps in Angew. Chem. Int. Ed., obtaining a novel triheteroarylmethyl radical end product with high yield and exploring the reaction mechanism of each step. This work was not only the longest tandem reaction discovered at that time but also broke through the limitations of traditional methods for generating triarylmethyl radicals. With the development of coordination chemistry, more and more metal complexes with different structures have been discovered by researchers, but a problem has also emerged, that is, the available ligands are becoming increasingly scarce and difficult to synthesize or separate. The domino reaction is a new idea. The end products, intermediate products, or by-products in the tandem reaction can all be used as ligands to coordinate with metals, greatly expanding the possibilities of complex structures. Summary of the Invention

[0004] The purpose of the present invention is to provide a series of rare earth complexes constructed based on thiosemicarbazide-o-vanillin Schiff base ligands and a synthesis method thereof, so as to solve the technical problem of the limitations of existing traditional methods for generating triarylmethyl radicals.

[0005] Two Dy complexes 12 - 13 were synthesized by a one - pot method using thiodihydrazide and o - vanillin with dysprosium(III) nitrate hexahydrate and dysprosium(III) chloride hexahydrate respectively. Comparing complexes 12 - 13, just because of the different anions in the reaction system, the types of Schiff base ligands formed in - situ are different, so the structures of these two complexes are different, and the coordination numbers, coordination environments and arrangements of Dy metal centers are different. Complex 12 anomalously generated H2L in the reaction. 9 Ligand and unilateral acylhydrazone HL 10 Ligand, we discussed and deduced the formation mechanism of H2L 9 Ligand. Magnetic measurements showed that complex 12 is a single - molecule magnet under zero - field, and complex 13 only showed frequency - dependent behavior in the low - temperature region. Combining the structural analysis of the two complexes, the reason for such a large difference in magnetism may be due to the different arrangements and coordination environments of the Dy metal centers in the two complexes.

[0006] To achieve the above - mentioned purpose, the technical scheme adopted in the present invention is as follows:

[0007] A series of rare - earth complexes based on thiodihydrazide - o - vanillin Schiff - base ligands, the rare - earth complexes are clusters [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH or clusters [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH.

[0008] Furthermore, the cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH crystallizes in the monoclinic system, space group C2 / c, and has a trinuclear structure.

[0009] Furthermore, the cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH contains three Dy(III) ions, two (L 9 ) 2- ligands, two (L 10 ) - ligands, two coordinated NO3 - ions, one free NO 3- ion for charge balance, two co - crystallized acetonitrile molecules and two co - crystallized methanol molecules. The three Dy(III) centers are arranged approximately linearly and are bridged by the hydroxyl groups on the benzene rings of two Schiff - base ligands. The Dy(III) ions have two coordination modes in total, and Dy1 is eight - coordinated.

[0010] Furthermore, the cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH crystallizes in the monoclinic system, space group I2 / a, with a four-core structure.

[0011] Furthermore, the cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH contains four Dy(III) ions, two (L 11 ) 3- ligands, six coordinating Cl - ions, two coordinating methanol molecules, two coordinating water molecules, and two co-crystallized methanol molecules. The four Dy(III) centers can be regarded as arranged in a trapezoid, bridged by two Schiff base ligands (L 11 ) 3- ). The Dy(III) ions have two coordination modes, and Dy1 is eight-coordinate.

[0012] Furthermore, the synthesis process of the cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH is as follows:

[0013] Weigh 0.1 mmol of thiodihydrazide, 0.1 mmol of o-vanillin, and 0.2 mmol of Dy(NO3)3·6H2O, and place them in a Pyrex tube. After cleaning and sealing the bottom, use a pipette to successively add 1.3 mL of anhydrous methanol and 0.7 mL of acetonitrile to the Pyrex tube. Finally, add 15 μL of triethylamine, shake well to mix all substances thoroughly, then immediately seal the Pyrex tube and place it in an oven at 80 °C. After 48 h, take out the Pyrex tube and place it in a cooling box to slowly cool to room temperature. Subsequently, yellow block crystals on the tube wall can be observed, which are the cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH.

[0014] Furthermore, the thiodihydrazide is 10.6 mg, the o-vanillin is 15.2 mg, and the Dy(NO3)3·6H2O is 90.2 mg.

[0015] Furthermore, the synthesis process of the cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH is as follows:

[0016] Weigh 0.1 mmol of thiodihydrazide, 0.1 mmol of o-vanillin, and 0.2 mmol of DyCl3·6H2O, place them in a Pyrex tube, which is cleaned and sealed at the bottom. Use a pipette to successively add 1.3 mL of anhydrous methanol and 0.7 mL of acetonitrile to the Pyrex tube. Finally, add 15 μL of triethylamine, shake well to fully mix all substances. Then immediately seal the Pyrex tube and place it in an oven at 80 °C. After 48 h, take out the Pyrex tube and put it in a cooling box to slowly cool to room temperature. Subsequently, yellow block crystals can be observed on the tube wall.

[0017] Further, the thiodihydrazide is 10.6 mg, the o-vanillin is 15.2 mg, and the DyCl3·6H2O is 71.5 mg.

[0018] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0019] The present invention synthesizes two Dy complexes 12 - 13 by using thiodihydrazide and o-vanillin respectively with two dysprosium salts under the condition of one-pot method. The domino reaction can generate intermediate organic ligands that are difficult to generate by traditional methods to regulate the structure of the complex, and then change the coordination environment of the Dy metal center, thereby regulating the magnetism. Combining structural and magnetic analyses, comparing complexes 12 - 13, only because the anions in the system are different, resulting in different types of Schiff base ligands generated by in-situ reaction, the regulation of the structure and magnetism of the complex is realized. Complex 12 generates the H2L 9 ligand and the unilateral acylhydrazone HL 10 ligand. We deduced the possible formation mechanism of the H2L 9 ligand. Observing the structure of complex 12, it can be found that the arrangement of the three Dy metal centers is linear, which may cause their magnetic axes not to be parallel and there is no complete cancellation, so it shows good magnetism under zero field. Magnetic tests show that there is a peak in the ac susceptibility curve, and as the frequency increases, the peak moves towards higher temperature, indicating that complex 12 is a single-molecule magnet under zero field; complex 13 generates the bilateral acylhydrazone H3L 11 ligand in the reaction. The four Dy(III) metal centers are pairwise symmetric, which may cause their magnetic axes to be parallel and the magnetism to cancel, so it shows poor magnetism under zero field. Only frequency-dependent behavior is observed in the low-temperature region during magnetic tests. Finally, the effective energy barriers U eff and relaxation times τ0 of complexes 12 - 13 are calculated according to the Arrhenius equation. The effective energy barriers U eff of complexes 12 - 13 are 44.7 K and 15.8 K respectively, and the relaxation times τ0 are 1.97×10 -6 s and 1.27×10 -13 s respectively. Brief Description of the Drawings

[0020] Figure 1 is the synthetic route of Complex 12-13 of the present invention and the in-situ generated Schiff base ligand diagram;

[0021] Figure 2 is the structural diagram of Complex 12 of the present invention (a); ligand coordination mode diagram (b); Dy1 coordination environment diagram (c); Dy2 coordination environment diagram (d);

[0022] Figure 3 is the ligand H2L of the present invention 9 possible formation mechanism diagram;

[0023] Figure 4 is the structural diagram of Complex 13 of the present invention (a); ligand coordination mode diagram (b); Dy1 coordination environment diagram (c); Dy2 coordination environment diagram (d);

[0024] Figure 5 is the TG / DTG diagram of Complex 12-13 of the present invention;

[0025] Figure 6 is the PXRD diffraction diagram of Complex 12-13 of the present invention (red is the theoretical value; black is the measured value);

[0026] Figure 7 is the χ m T-T curve diagram of the present invention;

[0027] Figure 8 is the M-H curve diagram and M-HT -1 curve diagram of Complex 12-13 of the present invention;

[0028] Figure 9 is the Loop curve diagram of Complex 12-13 of the present invention;

[0029] Figure 10 is the zero-field ac susceptibility vs. temperature curve diagram of Complex 12-13 of the present invention;

[0030] Figure 11 is the Cole-Cole diagram of Complex 12-13 of the present invention;

[0031] Figure 12 is the ln(τ0)-T -1 curve diagram of Complex 12-13 of the present invention. Detailed Description of the Invention

[0032] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the following preferred embodiments are given with reference to the accompanying drawings to further elaborate on the present invention. However, it should be noted that many details listed in the specification are only for enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be realized even without these specific details.

[0033] As Figure 1 shown, the synthesis of cluster 12-13

[0034] Cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH(12) synthesis

[0035] Precisely weigh 0.1 mmol (10.6 mg) of thiodihydrazide, 0.1 mmol (15.2 mg) of o-vanillin, and 0.2 mmol (90.2 mg) of Dy(NO3)3·6H2O, put them into a Pyrex tube about 18 cm long (cleaned and sealed at the bottom), use a pipette to successively add 1.3 mL of anhydrous methanol and 0.7 mL of acetonitrile into the Pyrex tube, and finally add 15 μL of triethylamine, shake well to fully mix all substances, then immediately seal the Pyrex tube and place it in an oven at 80 °C. After 48 h, take out the Pyrex tube and put it into a cooling box to slowly cool to room temperature. Subsequently, yellow block crystals can be observed on the tube wall. The yield of this product is about 45.32% (calculated based on Dy(NO3)3·6H2O). Elemental analysis (%) (Dy3C 56 H 62 N 17 O 23 S2), found: C, 35.42; H, 3.05; N, 12.45, theoretical: C, 35.53; H, 3.30; N, 12.58. IR (KBr, cm -1 ) : 3435(s), 2936(m), 2359(w), 1603(s), 1459(s), 1384(s), 1220(s), 961(m), 849(w), 737(s).

[0036] Cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH(13) synthesis

[0037] Accurately weigh 0.1 mmol (10.6 mg) of thiodihydrazide, 0.1 mmol (15.2 mg) of o-vanillin, and 0.2 mmol (71.5 mg) of DyCl3·6H2O, and place them in a Pyrex tube about 18 cm long (cleaned and sealed at the bottom). Use a pipette to successively add 1.3 mL of anhydrous methanol and 0.7 mL of acetonitrile to the Pyrex tube. Finally, add 15 μL of triethylamine, shake well to fully mix all substances, then immediately seal the Pyrex tube and place it in an oven at 80 °C. After 48 h, take out the Pyrex tube and place it in a cooling box to slowly cool to room temperature. Subsequently, yellow block crystals can be observed on the tube wall. The yield of this product is approximately 65.23% (calculated based on DyCl3·6H2O). Elemental analysis (%) (Dy4C 38 H 50 Cl6N8O 14 S2), found: C, 25.65; H, 2.76; N, 6.17, calculated: C, 25.79; H, 2.85; N, 6.33. IR (KBr, cm -1 ) : 3404(s), 2943(m), 2366(w), 1606(s), 1455(s), 1363(s), 1265(s), 1020(m), 949(m), 736(s), 573(w).

[0038] Structural analysis of complex 12 - 13

[0039] Tested by X-ray single crystal diffractometer, the results show that complex 12 crystallizes in the monoclinic system, space group C2 / c. Complex 12 has a trinuclear structure (as shown in Figure 2 a), including three Dy(III) ions, two (L 9 ) 2- ligands, two (L 10 ) - ligands, two coordinated NO3 - ions, one free NO3 - ion for charge balance, two co-crystallized acetonitrile molecules and two co-crystallized methanol molecules. The three Dy(III) centers are approximately linearly arranged and bridged by the hydroxyl groups on the benzene rings of two Schiff base ligands. The Dy(III) ions have two coordination modes. Dy1 is eight-coordinated (as shown in Figure 2 c), and its configuration is D 2d , Triangular dodecahedron configuration. The eight coordinating atoms come from two N atoms, two O atoms of two Schiff base ligands (L 9 ) 2- and two N atoms, two O atoms of two Schiff base ligands (L 10) - The four O atoms of; Dy2 is nine-coordinate, and its configuration is C after analysis (calculated by SHAPE software) s , Muffin configuration (as Figure 2 shown in d), and the nine coordinating atoms come from two Schiff base ligands (L 9 ) 2- One N atom, three O atoms of, one Schiff base ligand (L 10 ) - Two N atoms, one O atom of and two O atoms of one coordinating NO3 - ion. The coordination mode of the Schiff base ligand (L 9 ) 2- has only one kind, that is, μ3-η 1 :η 2 :η 1 :η 1 :η 1 . The coordination mode of the Schiff base ligand (L 10 ) - has only one kind, that is, μ2-η 1 :η 2 :η 1 :η 1 (as Figure 2 shown in b).

[0040] The formation of the ligand H2L 9 is abnormal, so we speculated on the reaction mechanism of the ligand H2L 9 . The ligand H2L 9 may have two formation mechanisms: The first is as Figure 3 shown. First, the amino group on thiodihydrazide acts as a nucleophile to perform nucleophilic addition with the aldehyde group. After proton transfer, a Schiff base is formed. Subsequently, under the action of a strong base, the amino group removes an H and undergoes an addition reaction with the Schiff base to form an intermediate ammonium salt. After proton transfer and the nucleophilic attack of water, an elimination reaction occurs to form an imine system. Finally, under the action of a strong base, dehydration forms the ligand H2L 9 ; The second is that thiodihydrazide decomposes to form hydrazine under the alkaline condition of triethylamine, and then hydrazine forms the ligand H2L 9 .

[0041] Complex 13 crystallizes in the monoclinic system, space group I2 / a. Complex 13 has a tetranuclear structure (as Figure 4 shown in a), including four Dy(III) ions, two (L 11 ) 3- ligands, and six coordinating Cl -ions, two methanol molecules involved in coordination, two water molecules involved in coordination and two methanol molecules involved in co-crystallization. The four Dy(III) centers can be viewed as a ladder arrangement, with two Schiff base ligands (L 11 ) 3- Bridged, Dy (III) ions have two coordination modes, Dy1 is eight-coordinated (such as Figure 4 c), after analysis (calculated by SHAPE software), its configuration is D 2d , Snub diphenoid J84 configuration, the eight coordinated atoms come from two Schiff base ligands (L 11 ) 3- The Dy2 is seven-coordinated, and its configuration is D after analysis (calculated by SHAPE software). 5h , Pentagonal bipyramid configuration (such as Figure 4 d), the seven coordinated atoms come from two Schiff base ligands (L 11 ) 3- The four O atoms and three coordinated Cl - Ion. Schiff base ligand (L 11 ) 3- There is only one coordination mode, namely μ4-η 1 :η 2 :η 1 :η 1 :η 1 :η 1 :η 2 :η 1 (like Figure 4 b), and the specific structural data are shown in Table 1.

[0042] Table 1 Crystallographic data of complexes 12-13

[0043]

[0044]

[0045] Thermogravimetric (TG) analysis of complexes 12-13

[0046] In order to study the thermal stability of complexes 12-13, we conducted thermogravimetric (TG) tests on them respectively. The test conditions were selected in a flowing N2 atmosphere, with the temperature rising from 35°C to 1000°C (heating rate was 5°C / min). Figure 5 As shown, complex 12 has a major weight loss process. At 35℃-177℃, the weight loss rate of complex 12 is 11.03%, which can be corresponding to the loss of a free NO3- There are two co-crystallized acetonitrile molecules and two co-crystallized methanol molecules (the theoretical value is 10.99%). As the temperature continues to rise, a plateau appears in the weight loss curve, indicating that the complex can remain stable. When the temperature exceeds 245 °C, the weight loss curve drops rapidly, and its framework begins to collapse. Finally, the remaining mass at 1000 °C is 43.47%, and the residue may be Dy oxide. The thermogravimetric behavior of complex 12 is consistent with its molecular formula. Complex 13 has a main weight loss process. The structure of the complex remains stable at 35 °C - 205 °C. The weight loss rate of complex 13 is 6.53%, which can correspond to the loss of two coordinated methanol molecules, two co-crystallized methanol molecules and two co-crystallized water molecules (the theoretical value is 7.34%). When the temperature exceeds 205 °C, the weight loss curve drops rapidly, and its framework begins to collapse. Finally, the remaining mass at 1000 °C is 27.07%, and the residue may be Dy oxide. The thermogravimetric behavior of complex 13 is consistent with its molecular formula.

[0047] Powder diffraction analysis of complexes 12 - 13

[0048] At room temperature, we selected clean crystals of complexes 12 - 13, ground them into powders, and performed X-ray powder diffraction tests (PXRD) on them to detect their purity. As Figure 6 shown, the red line is the theoretical value (simulated from single crystal data), and the black line is the measured value. After comparison, the coincidence degree of the theoretical peaks and the measured peaks is relatively high, proving that complexes 12 - 13 are pure phases.

[0049] Magnetic property studies of complexes 12 - 13

[0050] To explore the static magnetic behavior of complexes 12 - 13, we selected clean high-purity crystals and measured the molar magnetic susceptibility of complexes 12 - 13 under an applied direct current magnetic field (1000 Oe) and variable temperature conditions (2 K - 300 K). As Figure 7 shown, when the temperature is 300 K, the χ m T values of complexes 12 - 13 are 41.94 cm 3 ³ K⁻¹ mol⁻¹ -1 and 56.46 cm 3 ³ K⁻¹ mol⁻¹ -1 , which are close to the theoretical values of three / four free Dy(III) ions (g = 4 / 3, S = 5 / 2, L = 5) of 42.51 cm 3 ³ K⁻¹ mol⁻¹ -1 / 56.68 cm 3 ³ K⁻¹ mol⁻¹ -1 For complex 12, in the process of the temperature decreasing from room temperature 300 K to 55 K in the molar magnetic susceptibility - temperature curve, χ mThe T value decreases slowly. During the process of the temperature continuing to drop to 2 K, χ m The T value decreases rapidly and reaches the lowest value of 30.64 cm at 2 K 3 Kmol -1 , and χ m The magnetic behavior of the decreasing T value may be attributed to the antiferromagnetic interaction between metals, the crystal field effect, and the decrease of the metal Stark sublevel. For complex 13, the molar susceptibility-temperature curve decreases slowly in the temperature range from room temperature 300 K to 90 K. When the temperature drops below 90 K, χ m The T value decreases rapidly and reaches the minimum value of 48.70 cm at a temperature of 2 K 3 Kmol -1 , and χ m The magnetic behavior of the decreasing T value may be attributed to the antiferromagnetic interaction between metals, the crystal field effect, or / and the decrease of the metal Stark sublevel

[0051] The field-dependent magnetization intensities of complexes 12 - 13 were measured at temperatures of 2 K, 3 K, and 5 K respectively, and the M-H curves and M-HT -1 curves were plotted. As Figure 8 shown, after analyzing the data, it is shown that with the change of the external magnetic field from 0 - 7 T, the trends of their M-H curves are the same, first rising rapidly and then slowly rising, and reaching the maximum values at the highest magnetic field strength (7 T) and the lowest temperature (2 K), which are 30.01 μ B and 40.27 μ B , which are close to the theoretical values (30 μ B / 40 μ B ). When the temperature is different, the M-H curves and M-HT -1 curves of complexes 12 - 13 do not overlap, indicating that there may be low-lying excited states or / and magnetic anisotropy in their central metal ions

[0052] At a temperature of 2 K, the hysteresis loops of complexes 12 - 13 were measured. As Figure 9 shown, only very small hysteresis loops can be observed, which may be attributed to the quantum tunneling effect existing in complexes 12 - 13

[0053] The study of the dynamic magnetic behavior is a powerful method to verify whether a complex is a single-molecule magnet. The zero-field AC susceptibilities of complexes 12 - 13 were measured at different temperature ranges (2 - 8 K, 2 - 15 K, 2 - 20 K) and different vibration frequencies (1 - 1000 Hz). As Figure 10As shown, the experimental data indicate that there are obvious peaks in the real and imaginary part signals of complex 12, and as the frequency increases, the peaks shift towards higher temperatures, suggesting that complex 12 is a single-molecule magnet under zero field. In the figure, there are no peaks in the curve of complex 13, and the imaginary part signal only shows a weak frequency-dependent behavior in the low-temperature region. These results may be due to the symmetry (cancellation) of the magnetic axes of the Dy centers in complex 13 or / and the influence of quantum tunneling effects. Generally speaking, an external magnetic field has an obvious effect on suppressing quantum tunneling effects. A dynamic optimal field search test was carried out on complex 13, and the results show that there is no suitable external field that can effectively shield the interference of quantum tunneling effects. Under the same reaction conditions, only by changing the type of anions in the system, complexes 12 and 13 exhibit different structures, resulting in different magnetic properties. This result may be not only because of the different coordination environments of their spin centers, but also because the structure of complex 13 is relatively symmetric and the magnetic axes of the spin centers cancel each other out, so the magnetic properties are not good, while the structure of complex 12 has low symmetry and the magnetic axes are not parallel, so it can exhibit good magnetic properties under zero field.

[0054] To study the relaxation mechanisms of complexes 12 - 13 and calculate their effective energy barriers and relaxation times, we plotted the Cole - Cole diagrams (plots of the real part signal against the imaginary part signal at constant temperature) of complexes 12 - 13 under zero field based on the ac susceptibility data, as Figure 11 shown. Complexes 12 - 13 both exhibit only a single relaxation process. After fitting with the Debye model, we plotted the ln(τ0)-T -1 curves of complexes 12 - 13, as Figure 12 shown. The curves show an obvious linear relationship. According to the Arrhenius equation (τ = τ0exp(U eff / k B T)), the effective energy barriers U eff and relaxation times τ0 of complexes 12 - 13 were calculated. The effective energy barriers U eff of complexes 12 - 13 are 44.7 K and 15.8 K respectively, and the relaxation times τ0 are 1.97×10 -6 s and 1.27×10 -13 s respectively.

[0055] Two Dy complexes 12 - 13 were synthesized by using thiosemicarbazide and o - vanillin respectively with two dysprosium salts under the one - pot method. The domino reaction can generate intermediate organic ligands that are difficult to generate by traditional methods to regulate the structure of the complex, and then change the coordination environment of the Dy metal center, thereby regulating the magnetic properties. Combining structural and magnetic analyses, comparing complexes 12 - 13, only because of the different anions in the system, different types of Schiff base ligands are generated in - situ, realizing the regulation of the structure and magnetic properties of the complexes. Complex 12 generates H2L in the reaction9 Ligand and unilateral acylhydrazone HL 10 For the ligand, we deduced H2L 9 Possible formation mechanism of the ligand. By observing the structure of complex 12, it can be found that the arrangement of the three Dy metal centers is linear, which may lead to non-parallel magnetic axes and incomplete cancellation, so it shows good magnetism under zero field. Magnetic measurements show that there is a peak in the ac susceptibility curve, and as the frequency increases, the peak shifts to higher temperatures, indicating that complex 12 is a single-molecule magnet under zero field; In the reaction, complex 13 generated bilateral acylhydrazone H3L 11 Ligand. The four Dy(III) metal centers are pairwise symmetric, which may lead to parallel magnetic axes and magnetic cancellation, so it shows poor magnetism under zero field. Only frequency-dependent behavior was observed in the low-temperature region during magnetic measurements. Finally, the effective energy barriers U eff and relaxation times τ0 of complexes 12 - 13 were calculated according to the Arrhenius equation. The effective energy barriers U eff of complexes 12 - 13 are 44.7 K and 15.8 K respectively, and the relaxation times τ0 are 1.97×10 -6 s and 1.27×10 -13 s respectively.

[0056] Matters not covered by this invention are well-known technologies.

[0057] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands, characterized by: Rare earth complexes are clusters [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH or cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH.

2. The series of rare earth complexes constructed based on thiodihydrazide-conjugated o-vanillin Schiff base ligand according to claim 1, characterized in that: Cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH crystallizes in the monoclinic system, C2 / c space group, and has a trinuclear structure.

3. The series of rare earth complexes constructed based on thiodihydrazide-conjugated o-vanillin Schiff base ligand according to claim 2, characterized in that: Cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH includes three Dy(III) ions, two (L 9 ) 2- Ligand, two (L 10 ) - Ligand, two NO involved in coordination 3- ion, a free NO to balance the charge 3- ion, two cocrystallized acetonitrile molecules and two cocrystallized methanol molecules. The three Dy(III) centers are arranged in an approximately linear manner and are bridged by the hydroxyl groups on the benzene rings of the two Schiff base ligands. The Dy(III) ion has two coordination modes, and Dy1 is eight-coordinated.

4. The method of constructing a series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands according to claim 1, characterized in that: Cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH crystallizes in the monoclinic system, I2 / a space group, and has a tetranuclear structure.

5. The series of rare earth complexes constructed based on thiodihydrazide-conjugated o-vanillin Schiff base ligand according to claim 1, characterized in that: Cluster [Dy4(L 11 )2Cl6(CH3OH)2(H2O)2]·2CH3OH contains four Dy(III) ions, two (L 11 ) 3- Ligand, six Cl involved in coordination - ions, two methanol molecules involved in coordination, two water molecules involved in coordination and two methanol molecules involved in co-crystallization. The four Dy(III) centers can be viewed as a ladder arrangement, with two Schiff base ligands (L 11 ) 3- Bridged, Dy(III) ions have two coordination modes, Dy1 is eight-coordinated.

6. The method for synthesizing a series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands according to claim 1, characterized in that: Cluster [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH synthesis process is: Weigh 0.1mmol thiodihydrazide, 0.1mmol o-vanillin and 0.2mmol Dy(NO3)3·6H2O, put them into a Pyrex tube, wash and seal the bottom, use a pipette to draw 1.3mL of anhydrous methanol and 0.7mL of acetonitrile and add them into the Pyrex tube in sequence, finally add 15μL of triethylamine, shake and mix all the substances thoroughly, then seal the Pyrex tube immediately and place it in an oven at 80℃. After 48h, take out the Pyrex tube and put it into a cooling box to slowly cool to room temperature. Then, yellow block crystals can be observed on the tube wall, which are clusters [Dy3(L 9 )2(L 10 )2(NO3)2]NO3·2CH3CN·2CH3OH.

7. The method for synthesizing a series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands according to claim 6, characterized in that: Thiodihydrazide was 10.6 mg, o-vanillin was 15.2 mg, and Dy(NO3)3·6H2O was 90.2 mg.

8. The method for synthesizing a series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands according to claim 1, characterized in that: Cluster [Dy4(L 11 The synthesis process of )2Cl6(CH3OH)2(H2O)2]·2CH3OH is: Weigh 0.1 mmol of thiodihydrazide, 0.1 mmol of o-vanillin and 0.2 mmol of DyCl3·6H2O, place them in a Pyrex tube, wash and seal the bottom, use a pipette to draw 1.3 mL of anhydrous methanol and 0.7 mL of acetonitrile into the Pyrex tube in sequence, finally add 15 μL of triethylamine, shake to mix all the substances thoroughly, then immediately seal the Pyrex tube and place it in an oven at 80°C. After 48 hours, take out the Pyrex tube, put it in a cooling box and slowly cool it to room temperature, then yellow block crystals can be observed on the tube wall.

9. The method for synthesizing a series of rare earth complexes based on thiodihydrazide-conjugated o-vanillin Schiff base ligands according to claim 8, characterized in that: Thiodihydrazide was 10.6 mg, o-vanillin was 15.2 mg, and DyCl3·6H2O was 71.5 mg.

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