Fe(ii) spin crossover complex, crystal and preparation method and application thereof

Abstract

The application belongs to the technical field of new materials, and particularly relates to a Fe(II) spin crossover complex, a crystal and a preparation method and application thereof. The complex has a molecular formula of [Fe(L 1 )(L 2 )]2(ClO4)4·1.5H2O; a ligand L 1 is trans-4-pentylcyclohexyl-2,6-di(1H-pyrazol-1-yl)isonicotinate; a ligand L 2 is 6,6''-2,6-dimethoxyphenyl-substituted terpyridine; the ligand L 1 of the application is a unique rigid head-flexible tail structure, which is helpful to guide a more ordered packing effect; the ligand L 2 provides a highly rigid and planar structural unit, overcomes the crystallization difficulty of a flexible ligand, and stabilizes a supramolecular structure; the obtained crystal exhibits a unique crystal packing and spatial configuration in a spin state transition process at different temperatures, and realizes optimization of a molecular structure and regulation of spin transition characteristics.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to an Fe(II) spin-cross complex, crystal, its preparation method and application. Background Technology

[0002] Spin crossover (SCO) refers to the reversible transition of transition metal ions between high-spin (HS) and low-spin (LS) states under external stimuli (such as temperature, pressure, and light). Fe(II)-based spin-crossover complexes have attracted much attention due to their significant spin state changes (S = 0 to S = 2) and the accompanying changes in physical properties (such as color, conductivity, and magnetism). In recent years, researchers have explored their applications in molecular switches, information storage, and other fields by introducing flexible alkyl chains and complementary ligand strategies.

[0003] Different types of coordination compounds form different molecular stacking structures due to intermolecular hydrogen bonding. These differences in stacking structures affect the coordination synergistic effect of spin-variant centers, thereby enabling precise control of spin-variant temperature, transition type, and hysteresis loop width. However, in current research, how to rationally design and finely control these intermolecular interactions remains a major challenge that needs to be overcome in this field. Summary of the Invention

[0004] The technical problem to be solved by this invention is the difficulty in rationally designing and constructing Fe(II) spin-crossed complexes, thereby providing an Fe(II) spin-crossed complex, crystal, preparation method and application thereof.

[0005] Therefore, the present invention provides the following technical solution:

[0006] The first aspect of this invention protects a Fe(II) spin-crossed complex, wherein the molecular formula of the complex is: [Fe(L... 1 (L) 2 )]2(ClO4)4·1.5H2O; ligand L 1 It is trans-4-pentylcyclohexyl-2,6-bis(1H-pyrazol-1-yl)isonicotinic acid ester, with the structural formula shown in formula (1); (1); ligand L 2 It is a 6,6''-2,6-dimethoxyphenyl-substituted tripyridine with the structural formula shown in formula (2); (2).

[0007] A second aspect of this invention protects a method for preparing the aforementioned Fe(II) spin-crossed complex, wherein the preparation method comprises the following steps: ligand L 1 ligand L 2 Fe(ClO4)2·6H2O and the first solvent were mixed to carry out a coordination reaction, and the filtrate containing Fe(II) spin-crossed complexes was obtained after filtration.

[0008] In this invention, ligand L can be directly used. 1 ligand L 2 Fe(ClO4)2·6H2O and the first solvent are mixed, or the ligand L can be added first. 1 ligand L 2 The ligand solution is obtained by mixing Fe(ClO4)2·6H2O with methanol in the first solvent. The metal solution is obtained by mixing the ligand solution with the metal solution to make the mixture more uniform.

[0009] In this invention, the filtration method is a conventional filtration method in the field, which effectively prevents heterogeneous nucleation in order to remove insoluble impurities, microcrystalline seeds and suspended matter.

[0010] In one alternative implementation, the ligand L 1 The preparation method includes the following steps: under inert gas protection, 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid is dissolved in a second solvent, a condensing agent and a catalyst are added to carry out the first stage of the first reaction, trans-4-pentylcyclohexanol is added to carry out the second stage of the first reaction, and the first purification is performed to obtain ligand L. 1 .

[0011] In one alternative embodiment, the molar ratio of trans-4-pentylcyclohexanol to 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid is 1:(1-1.5).

[0012] In one optional embodiment, the ratio of 2,6-bis(1H-pyrazole-1-yl)isonicotinic acid to the second solvent is 5 mmol:(120-150) mL.

[0013] In one alternative embodiment, the molar ratio of 2,6-bis(1H-pyrazole-1-yl)isonicotinic acid to the condensing agent is 5:(10-12).

[0014] In one alternative embodiment, the molar ratio of 2,6-bis(1H-pyrazole-1-yl)isonicotinic acid to the catalyst is 5:(10-12).

[0015] In one alternative embodiment, the second solvent comprises N,N-dimethylformamide (DMF) and / or N,N-dimethylacetamide (DMAC).

[0016] In one alternative embodiment, the condensing agent comprises 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI) and / or dicyclohexylcarbodiimide (DCC).

[0017] In one alternative embodiment, the catalyst comprises 4-dimethylaminopyridine (DMAP) and / or 4-pyrrolidinylpyridine (PPY).

[0018] In one alternative embodiment, the reaction temperature of the first stage of the first reaction is -5 to 0°C, and the reaction time is 1-2 hours.

[0019] In one optional embodiment, the reaction temperature of the second stage of the first reaction is 20-25°C, and the reaction time is 24-36 hours.

[0020] In one alternative embodiment, the first purification includes the following steps: passing an eluent of n-hexane and ethyl acetate in a volume ratio of 10-12:1 through a silica gel column.

[0021] In one alternative implementation, the ligand L 2 The preparation method includes the following steps: S1, 2-acetyl-6-bromopyridine, benzaldehyde and a third solvent are mixed to obtain a mixed solution, and a condensation reaction base is added to carry out the first stage of the second reaction; S2, add a ring-closing alkaline medium to carry out the second stage of the second reaction, and perform the second purification to obtain the intermediate product; S3, under anhydrous and oxygen-free conditions, the intermediate product, 2,6-dimethoxyphenylboronic acid, metal catalyst, Suzuki coupling base, and fourth solvent are mixed to obtain a mixed solution, which is then used in the third stage of the second reaction, followed by a third purification to obtain ligand L. 2 .

[0022] In one alternative embodiment, the molar ratio of 2-acetyl-6-bromopyridine to benzaldehyde is 25:9-10.

[0023] In one optional embodiment, the ratio of 2-acetyl-6-bromopyridine to the third solvent is 25 mmol:(100-120) mL.

[0024] In one alternative embodiment, the molar ratio of the 2-acetyl-6-bromopyridine to the condensation reaction base is 1:(0.9-1).

[0025] In one alternative embodiment, the third solvent includes at least one of methanol and ethanol.

[0026] In one optional embodiment, the condensation reaction base includes at least one of sodium hydroxide and potassium hydroxide.

[0027] In this invention, in order to make the reaction more complete, the initiator is generally prepared as an initiator solution. The specific concentration can be adjusted according to the actual situation. Typically, without limitation, the concentration of the alkaline solution for the condensation reaction is 0.1-0.12 mol / L.

[0028] In one optional embodiment, the molar ratio of the 2-acetyl-6-bromopyridine to the cyclic alkaline medium is 1:(20-25).

[0029] In this invention, the ring-closed alkaline medium includes at least one of ammonium hydroxide and triethylamine.

[0030] In this invention, in order to make the reaction more complete, the ring-closing alkaline medium is generally prepared into a ring-closing alkaline medium solution. The specific concentration can be adjusted according to the actual situation. Typically, without limitation, when the ring-closing alkaline medium is ammonium hydroxide, the mass percentage concentration is 28-30 wt%; when the ring-closing alkaline medium is triethylamine, the mass percentage concentration is 10-11 wt%.

[0031] In one optional embodiment, the molar ratio of the intermediate product to 2,6-dimethoxyphenylboronic acid is 1:(2-2.5), optionally 1:(2.4-2.5).

[0032] In one optional embodiment, the ratio of the intermediate product to the fourth solvent is 1 mmol:(45-50) mL.

[0033] In one optional embodiment, the molar ratio of the intermediate product to the metal catalyst is 1:(0.04-0.05).

[0034] In one alternative embodiment, the Suzuki coupling base includes at least one of anhydrous sodium carbonate, anhydrous potassium carbonate, and anhydrous cesium carbonate.

[0035] In one alternative embodiment, the molar ratio of the intermediate product to the Suzuki coupling base is 1:(35-40).

[0036] In one alternative embodiment, the metal catalyst comprises [1,1'-bis(diphenylphosphine)ferrocene]palladium dichloride and / or tetra(triphenylphosphine)palladium.

[0037] In one alternative embodiment, the fourth solvent is ethanol, water, and toluene in a volume ratio of 3:(0.9-1):(2.9-3).

[0038] In one optional embodiment, the reaction temperature of the first stage of the second reaction is 20-25°C, and the reaction time is 24-36 hours.

[0039] In one optional embodiment, the reaction temperature of the second stage of the second reaction is 70-80°C, and the reaction time is 24-36 hours.

[0040] In one alternative embodiment, a second purification is performed by recrystallization with dichloromethane and / or chloroform.

[0041] In one optional embodiment, the reaction temperature of the third stage of the second reaction is 70-80°C, and the reaction time is 24-36 hours.

[0042] In an alternative embodiment, a third purification is performed by recrystallization with methanol and / or chloroform.

[0043] In one alternative implementation, the ligand L 1 ligand L 2 The molar ratio of Fe(ClO4)2·6H2O is 1:1:1.

[0044] In one alternative embodiment, the first solvent comprises dichloromethane and methanol.

[0045] In one alternative implementation, the ligand L 1 L 2 The ratio of the amount of dichloromethane used is 0.05 mmol:0.05 mmol:(10-15) mL.

[0046] In one optional embodiment, the ratio of Fe(ClO4)2·6H2O to methanol is 0.05 mmol:(5-7.5) mL.

[0047] In one optional embodiment, the coordination reaction is carried out at a temperature of 20-25°C for 1-2 hours.

[0048] A third aspect of this invention protects a crystal of the aforementioned Fe(II) spin-crossed complex, wherein the crystal crystallizes at 120 K in the triclinic P space group; the cell parameters are: a = 17.8731(6) Å, b = 17.9316(6) Å, c = 21.4725(6) Å, α = 90°, β = 112°, γ = 111°, V = 5807.1(3) Å. 3Z = 2; crystallized at 300 K in triclinic space group P; cell parameters are: a = 18.345(9) Å, b = 18.208(10) Å, c = 21.065(10) Å, α = 89°, β = 111°, γ = 112°, V = 5989(5) Å 3 Z = 2.

[0049] The fourth aspect of this invention protects a method for preparing crystals of Fe(II) spin-crossed complexes, wherein the aforementioned filtrate containing Fe(II) spin-crossed complexes is volatilized to obtain crystals of Fe(II) spin-crossed complexes.

[0050] In one alternative embodiment, the evaporation conditions include: an evaporation temperature of 20-25°C, a evaporation time of 10-18 days based on 15 mL of filtrate.

[0051] The fifth aspect of this invention protects the application of the aforementioned Fe(II) spin-crossed complex crystal in information storage, molecular switches, and molecular sensors.

[0052] The technical solution of this invention has the following advantages: This invention provides a Fe(II) spin-crossed complex, wherein the molecular formula of the complex is: [Fe(L... 1 (L) 2 )]2(ClO4)4·1.5H2O; Ligand L 1 It is trans-4-pentylcyclohexyl-2,6-di(1H-pyrazol-1-yl)isonicotinic acid ester; ligand L 2 Tripyridine substituted with 6,6''-2,6-dimethoxyphenyl; ligand L of the present invention 1 It features a unique rigid head-flexible tail structure, capable of providing specific intermolecular interactions (such as π···π intramolecular and intermolecular interactions), facilitating more ordered stacking while preserving necessary conformational degrees of freedom; ligand L 2 It can provide highly rigid and planar structural units, overcome the problem of flexible ligand crystallization, and play a role in stabilizing supramolecular structures through template-based methods; At 120K, the Fe1 site exhibits a low-spin state, while the Fe2 site exhibits a high-spin state. At 240K, the Fe2 site begins to show a transition to a high-spin state. At 300K, both Fe sites exhibit a high-spin state. During the spin state transition, unique crystal packing and spatial configuration are observed, achieving optimization of molecular structure and regulation of spin-variant properties. Attached Figure Description

[0053] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0054] Figure 1 It is the ligand L of Example 1 1 The proton NMR spectrum; Figure 2 It is the ligand L of Example 1 1 The mass spectrum; Figure 3 It is the ligand L of Example 1 2 The proton NMR spectrum; Figure 4 This is a schematic diagram of the crystal stacking of Example 1 at 120K; Figure 5 This is a schematic diagram of the crystal stacking of Example 1 at 300K; Figure 6 Ligand L in Comparative Example 2 3 The proton NMR spectrum; Figure 7 Ligand L in Comparative Example 2 3 The mass spectrum; Figure 8 This is the temperature-dependent magnetic susceptibility curve of the crystal in Example 1; Figure 9 The temperature-dependent magnetic susceptibility curve of the crystal in Comparative Example 1 is shown. Figure 10 This is the temperature-dependent magnetic susceptibility curve of the crystal in Comparative Example 2. Detailed Implementation

[0055] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0056] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0057] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0058] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This range can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0060] In the description of the embodiments of the present invention, the term "at least one" refers to one or more (including two).

[0061] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0062] DMF is anhydrous DMF.

[0063] Example 1 This embodiment provides a crystal of Fe(II) spin-crossed complex, and the preparation method includes the following steps: ligand L 1 Synthesis Under nitrogen protection, 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid (5 mmol) was dissolved in anhydrous DMF (120 mL), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (10 mmol) and 4-dimethylaminopyridine (10 mmol) were added. The mixture was stirred at 0 °C for 1 h to carry out the first stage of the first reaction. Then, trans-4-pentylcyclohexanol (5 mmol) was added, and the mixture was stirred at 25 °C for 24 h to carry out the second stage of the first reaction. Hexane and ethyl acetate in a volume ratio of 12:1 were used as eluents, and the mixture was passed through a silica gel column to obtain ligand L. 1 ; ligand L 1 The proton NMR spectrum is shown below. Figure 1 The specific data is as follows: 1 H NMR (500 MHz, Chloroform-d) δ8.57 (d, J = 2.5 Hz, 2H), 8.37 (s, 2H), 7.80 (s, 2H), 6.52 (d, J = 2.2 Hz,2H), 4.99 (s, 1H), 2.13 (d, J = 4.1 Hz, 2H), 1.86 (d, J = 13.4 Hz, 2H), 1.63 1.47 (m, 2H), 1.3 1.21 (m, 9H), 1.11 (d, J = 3.1 Hz, 2H), 0.88 (s, 3H); ligand L 1 The mass spectrum can be found in Figure 2 The specific data is: MS (ESI) m / z [M+H] + Calculated value C 23 H 29 N5O2: 408.23, Measured value: 408.09, MS (ESI) m / z [M+Na] + Theoretical value: 430.23; Experimental value: 430.10. The high degree of agreement between the measured and calculated values ​​indicates that the synthesized product is indeed the target molecule we designed. ligand L 2 Synthesis S1, 2-acetyl-6-bromopyridine (25 mmol), benzaldehyde (9.6 mmol), and methanol (100 mL) were mixed to form a mixed solution, and then NaOH aqueous solution (concentration of 0.1 mol / L, total volume of 24 mL) was added dropwise. The mixture was reacted at 25 °C for 24 h to carry out the first stage of the second reaction. S2, 36 mL of a 28 wt% ammonium hydroxide aqueous solution was slowly added, and the reaction was carried out at 75 °C for 24 h to proceed to the second stage of the second reaction. Recrystallization was then performed using dichloromethane (solid to dichloromethane ratio of 1 g: 20 mL) to obtain the intermediate product. (Molecular weight 466.95); S3, under an anhydrous and oxygen-free environment, the intermediate product (1.1 mmol), 2,6-dimethoxyphenylboronic acid (2.7 mmol), [1,1′-bis(diphenylphosphine)ferrocene]palladium dichloride (0.05 mmol), and anhydrous sodium carbonate (42.0 mmol) were added to 50 mL of a fourth solvent (ethanol, water, and toluene in a volume ratio of 3:1:3). The reaction was carried out at 78 °C for 24 h to proceed to the third stage of the second reaction. The solid was removed from the solvent under reduced pressure and recrystallized using chloroform (the ratio of solid to chloroform was 1 g:15 mL) to obtain ligand L. 2 ; ligand L 2 The proton NMR spectrum is shown below. Figure 3 The specific data is as follows: 1 H NMR (600 MHz, Chloroform-d) δ8.68 (s, 2H), 8.61 (d, J = 7.8 Hz, 2H), 7.91 (t, J = 7.7 Hz, 2H), 7.79 (d, J=7.2 Hz, 2H), 7.43 (t, J = 7.6 Hz, 2H), 7.38 (s, 1H), 7.36 (d, J = 6.8 Hz, 2H), 7.34 (d, J = 7.9Hz, 2H), 6.70 (d, J = 7.3 Hz, 4H), 3.76 (s, 12H); Synthesis of Fe(II) spin-crossed complexes ligand L 1 (0.05 mmol) and ligand L 2 (0.05 mmol) was mixed with 10 mL of dichloromethane to obtain a ligand solution. Fe(ClO4)2·6H2O (0.05 mmol) was mixed with 5 mL of methanol to obtain a metal solution. The ligand solution and metal solution were stirred at 25 °C for 1 h. The reaction mixture was filtered to obtain a filtrate containing Fe(II) spin-crossed complexes. The filtrate was collected and placed at 25 °C to evaporate the solvent. Crystals were obtained after 14 days based on 15 mL of filtrate, with a yield of 27% (based on Fe(ClO4)2·6H2O). The crystals were analyzed using a Vario EL III elemental analyzer from Elementar, Germany: Calculated values ​​(%) (C) 120 H 123Cl4Fe2N 16 O 29.5 ): C, 57.30; H, 4.89; N, 8.91; Measured values: C, 57.54; H, 4.87; N, 8.89. The high degree of agreement between the measured values ​​and the calculated values ​​indicates that the synthesized product is the target molecule we designed. Crystal data were collected using a Bruker D8 VENTURE CMOS single-crystal X-ray diffractometer (Mo-Kα radiation, λ = 0.71073 Å); Crystallized at 120K in the triclinic system, space group P; cell parameters are: a = 17.8731(6) Å, b = 17.9316(6) Å, c = 21.4725(6) Å, α = 90°, β = 112°, γ = 111°, V = 5807.1(3) Å 3 Z = 2; Crystallized at 300 K in the triclinic system, space group P; cell parameters are: a = 18.345(9) Å, b = 18.208(10) Å, c = 21.065(10) Å, α = 89°, β = 111°, γ = 112°, V = 5989(5) Å 3 Z = 2; Table 1. Average bond lengths and structural distortion parameters of Fe sites in the crystal.

[0064] A schematic diagram of a 120K crystal stack is shown below. Figure 4 As shown, a schematic diagram of the 300K crystal stack is as follows. Figure 5 As shown in Table 1, the average bond lengths and structural distortion parameters of Fe sites in the crystal under 120K and 300K conditions are as follows. Combining the figure and the table, it can be seen that the Fe(II) ion is six-coordinated. The average Fe-N bond lengths of Fe1 and Fe2 sites are 1.977 Å (120 K) and 2.180 Å (300 K), respectively. This indicates that the Fe1 site undergoes a transition from a low-spin state to a high-spin state during the heating process, while the Fe2 site remains in a high-spin state. The distance between the intermolecular π…π interactions between pyridinium groups at the Fe2 site is 3.967 Å, ​​indicating that the Fe2 site is in a relatively stable and confined local crystal environment. This provides a structural explanation for its maintenance of a high-spin (HS) state throughout the entire temperature range.

[0065] Comparative Example 1 This comparative example provides a crystal of a Co(II) spin-crossed complex, the preparation method of which includes the following steps: ligand L1 The synthesis was carried out according to the method described in Example 1; ligand L 2 The synthesis was carried out according to the method described in Example 1; Synthesis of Co(II) spin-crossed complexes ligand L 1 (0.05 mmol) and L 2 (0.05 mmol) was mixed with 10 mL of dichloromethane to obtain a ligand solution, and Co(ClO4)2 was added. 6H2O (0.05 mmol) was mixed with 5 mL of methanol to obtain a metal solution. The ligand solution and the metal solution were stirred at 25 °C for 1 h. After filtering the reaction mixture, a filtrate containing Co(II) spin-crossed complex was obtained. The Co(II) spin-crossed complex crystals were synthesized according to the method described in Example 1, and the crystals were obtained.

[0066] Comparative Example 2 This comparative example provides a crystal of Fe(II) spin-crossed complex, and the preparation method includes the following steps: ligand L 3 Synthesis Under nitrogen protection, 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid (5 mmol) was dissolved in anhydrous DMF (120 mL), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (10 mmol) and 4-dimethylaminopyridine (10 mmol) were added. The mixture was stirred at 0 °C for 1 h to carry out the first stage of the first reaction. Then, 1-octanol (5 mmol) was added, and the mixture was stirred at 25 °C for 24 h to carry out the second stage of the first reaction. Hexane and ethyl acetate in a volume ratio of 12:1 were used as eluents, and the mixture was passed through a silica gel column to obtain ligand L. 3 ,for ; ligand L 3 The proton NMR spectrum is shown below. Figure 6 The specific data is as follows: 1 H NMR (500 MHz, Chloroform-d) δ8.57 (d, J = 3.7 Hz, 2H), 8.39 (d, J = 1.3 Hz, 2H), 7.80 (s, 2H), 6.53 (d, J= 1.8 Hz, 2H), 4.40 (d, J = 1.3 Hz, 2H), 1.82 (d, J = 7.4 Hz, 2H), 1.45 (d, J= 7.6 Hz, 2H), 1.39 1.31 (m, 4H), 1.30 (d, J = 5.8 Hz, 4H), 0.89 0.88 (m, 3H); ligand L 3 The mass spectrum can be found in Figure 7 The specific data is: MS (ESI) m / z [M+H] + Theoretical value: 368.20; Experimental value: 368.03. MS (ESI) m / z [M+Na] + Theoretical value: 390.20; Experimental value: 390.02; The high degree of agreement between the measured value and the calculated value indicates that the synthesized product is the target molecule we designed. ligand L 2 The synthesis was carried out according to the method described in Example 1; The Fe(II) spin-crossed complex was synthesized according to the method described in Example 1; The Fe(II) spin-crossed complex crystals were synthesized according to the method described in Example 1, and the crystals were obtained.

[0067] Test case Spin-variant behavior analysis The crystals prepared in Example 1 and Comparative Examples 1-2 were subjected to variable-temperature magnetic susceptibility testing using a Quantum Design PPMS-9 physical property measurement system (test conditions: 1000 Oe, 2K-300 K).

[0068] Example 1: Specific test results are as follows Figure 8 As shown in the curve, the χT value of the crystal is 7.62 cm at 300 K. 3 mol –1 K, as the temperature decreases, the χT value gradually decreases, reaching 4.49 cm at 150 K. 3 mol –1 The value of χT is K, and then tends to plateau, indicating that incomplete spin transition occurs around 240 K; at 120 K, the χT value is 0.77 cm. 3 mol –1 K indicates that some Fe(II) ions are still in a high-spin state, corresponding to the Fe2 site being in a high-spin state.

[0069] Comparative Example 1: Specific Tests as follows Figure 9 As shown in the curve, the χT value of the crystal is 3.72 cm at 300 K. 3 mol –1 K, the χT value gradually decreases as the temperature decreases, and the χT value is 1.81 cm at 2K. 3 mol –1K, the curve shows that the Co(II) ions in Comparative Example 1 maintained a high spin state throughout the process and no spin crossing phenomenon occurred.

[0070] Comparative Example 2: Specific Tests as follows Figure 10 As shown by the curve, the χT value of the crystal is 3.8 cm at 300 K. 3 mol –1 At K, when cooled to 50 K, the χT value remains almost unchanged; upon further decreasing the temperature to 2 K, the χT value decreases rapidly, reaching a minimum of 1.2 cm. 3 mol –1 The K curve shows that the Fe(II) ions in Comparative Example 2 maintained a high spin state throughout the process and no spin crossing phenomenon occurred.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A Fe(II) spin-crossed complex, characterized in that, The molecular formula of the complex is: [Fe(L 1 (L) 2 )]2(ClO4)4·1.5H2O; ligand L 1 It is trans-4-pentylcyclohexyl-2,6-bis(1H-pyrazol-1-yl)isonicotinic acid ester, with the structural formula shown in formula (1); （1）； ligand L 2 It is a 6,6''-2,6-dimethoxyphenyl-substituted tripyridine with the structural formula shown in formula (2); （2）。 2. A method for preparing the Fe(II) spin-crossed complex as described in claim 1, characterized in that, The preparation method includes the following steps: ligand L 1 ligand L 2 Fe(ClO4)2·6H2O and the first solvent were mixed to carry out a coordination reaction, and the filtrate containing Fe(II) spin-crossed complexes was obtained after filtration.

3. The preparation method according to claim 2, characterized in that, The ligand L 1 The preparation method includes the following steps: under inert gas protection, 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid is dissolved in a second solvent, a condensing agent and a catalyst are added to carry out the first stage of the first reaction, trans-4-pentylcyclohexanol is added to carry out the second stage of the first reaction, and the first purification is performed to obtain ligand L. 1 ; Optionally, the molar ratio of trans-4-pentylcyclohexanol to 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid is 1:(1-1.5); Optionally, the ratio of 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid to the second solvent is 5 mmol:(120-150) mL; Optionally, the molar ratio of 2,6-bis(1H-pyrazole-1-yl)isonicotinic acid to the condensing agent is 5:(10-12); Optionally, the molar ratio of 2,6-bis(1H-pyrazol-1-yl)isonicotinic acid to the catalyst is 5:(10-12); Optionally, the second solvent includes N,N-dimethylformamide and / or N,N-dimethylacetamide; Optionally, the condensing agent comprises 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and / or dicyclohexylcarbodiimide; Optionally, the catalyst comprises 4-dimethylaminopyridine and / or 4-pyrrolidinylpyridine.

4. The preparation method according to claim 3, characterized in that, The reaction temperature of the first stage of the first reaction is -5 to 0°C, and the time is 1-2 hours. And / or, the reaction temperature of the second stage of the first reaction is 20-25°C and the time is 24-36h; Optionally, the first purification includes the following steps: passing an eluent of n-hexane and ethyl acetate in a volume ratio of 10-12:1 through a silica gel column.

5. The preparation method according to any one of claims 2-4, characterized in that, The ligand L 2 The preparation method includes the following steps: S1, 2-acetyl-6-bromopyridine, benzaldehyde and a third solvent are mixed to obtain a mixed solution, and a condensation reaction base is added to carry out the first stage of the second reaction; S2, add a ring-closing alkaline medium to carry out the second stage of the second reaction, and perform the second purification to obtain the intermediate product; S3, under anhydrous and oxygen-free conditions, the intermediate product, 2,6-dimethoxyphenylboronic acid, metal catalyst, Suzuki coupling base, and fourth solvent are mixed to obtain a mixed solution, which is then used in the third stage of the second reaction, followed by a third purification to obtain ligand L. 2 ; Optionally, the molar ratio of 2-acetyl-6-bromopyridine to benzaldehyde is 25:9-10; Optionally, the ratio of 2-acetyl-6-bromopyridine to the third solvent is 25 mmol:(100-120) mL; Optionally, the molar ratio of 2-acetyl-6-bromopyridine to the condensation reaction base is 1:(0.9-1); Optionally, the third solvent includes at least one of methanol and ethanol; Optionally, the condensation reaction base includes at least one of sodium hydroxide and potassium hydroxide; Optionally, the molar ratio of the 2-acetyl-6-bromopyridine to the cyclic alkaline medium is 1:(20-25); Optionally, the molar ratio of the intermediate product to 2,6-dimethoxyphenylboronic acid is 1:(2-2.5); Optionally, the ratio of the intermediate product to the fourth solvent is 1 mmol:(45-50) mL; Optionally, the molar ratio of the intermediate product to the metal catalyst is 1:(0.04-0.05); Optionally, the Suzuki coupling base includes at least one of anhydrous sodium carbonate, anhydrous potassium carbonate, and anhydrous cesium carbonate; Optionally, the molar ratio of the intermediate product to the Suzuki coupling base is 1:(35-40); Optionally, the metal catalyst comprises [1,1'-bis(diphenylphosphine)ferrocene]palladium dichloride and / or tetra(triphenylphosphine)palladium; Optionally, the fourth solvent is ethanol, water, and toluene in a volume ratio of 3:(0.9-1):(2.9-3).

6. The preparation method according to claim 5, characterized in that, The first stage of the second reaction is carried out at a temperature of 20-25°C for 24-36 hours. And / or, the reaction temperature of the second stage of the second reaction is 70-80℃, and the time is 24-36h; And / or, a second purification is performed by recrystallization from dichloromethane and / or chloroform; And / or, the reaction temperature of the third stage of the second reaction is 70-80℃, and the time is 24-36h; And / or, a third purification is performed by recrystallization from methanol and / or chloroform.

7. The preparation method according to any one of claims 2-6, characterized in that, The ligand L 1 ligand L 2 The molar ratio of Fe(ClO4)2·6H2O is 1:1:1; And / or, the first solvent includes dichloromethane and methanol; Optionally, the ligand L 1 L 2 The ratio of the amount of dichloromethane used is 0.05 mmol:0.05 mmol:(10-15) mL; Optionally, the ratio of Fe(ClO4)2·6H2O to methanol is 0.05 mmol:(5-7.5) mL; Optionally, the coordination reaction is carried out at a temperature of 20-25°C for 1-2 hours.

8. A crystal of the Fe(II) spin-crossed complex as described in claim 1, characterized in that, The crystal crystallized at 120 K in the triclinic system, space group P; the cell parameters are: a = 17.8731(6) Å, b = 17.9316(6) Å, c = 21.4725(6) Å, α = 90°, β = 112°, γ = 111°, V = 5807.1(3) Å. 3 Z = 2; crystallized at 300 K in triclinic P space group; cell parameters are: a = 18.345(9) Å, b = 18.208(10) Å, c = 21.065(10) Å, α = 89°, β = 111°, γ = 112°, V = 5989(5) Å 3 Z = 2.

9. A method for preparing a crystal of Fe(II) spin-crossed complex, characterized in that, The filtrate containing the Fe(II) spin-crossed complex as described in claim 2 was volatilized to obtain crystals of the Fe(II) spin-crossed complex; Optionally, the evaporation conditions include: an evaporation temperature of 20-25°C, a evaporation time of 10-18 days based on 15 mL of filtrate.

10. The application of a crystal of the Fe(II) spin-crossed complex as described in claim 8 in information storage, molecular switches, and molecular sensors.

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