Luminescent material for miniature magnetoelectric driving element and preparation method thereof

Abstract

The invention relates to the technical field of luminescent materials, and discloses a luminescent material for a miniature magnetoelectric driving element and a preparation method of the luminescent material. The material is a micromolecular coordination compound with a general formula of X [L] 2, X is selected from Cu < + >, Ni < + >, Co < + > and Mn < + >, and a ligand L contains a carbazole rigid skeleton, a flexible alkylene connecting chain and a Schiff base chelating module. The preparation adopts a step-by-step construction strategy, and the product is obtained through N-alkylation, nucleophilic substitution and condensation, coordination reaction and purification. The material is controllable in luminescent property, sensitive in magnetic response and excellent in thermal stability and light stability, can be processed into a uniform thin film in a solution mode, can accurately reflect the working state of a miniature magnetoelectric driving element, and is suitable for large-scale application.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to a luminescent material for micro magnetoelectric drive elements and a method for preparing the same. Background Technology

[0002] With the rapid development of micro-magnetic-electric actuator technology, real-time monitoring of their operating status via optical signals has become a research hotspot. However, there is currently a lack of small-molecule luminescent materials with well-defined structures, solution-processable properties, and controllable costs, especially functional materials that can accurately reflect the driving state of micro-magnetic-electric actuators through changes in luminescence.

[0003] Existing technologies mostly use quantum dots, inorganic perovskites, or traditional organic dyes as luminescent media. Although these materials have certain luminescent capabilities, they have significant limitations when applied to micro-magnetic and electrical drive components.

[0004] On the one hand, quantum dots and perovskite materials often contain heavy metals, making their synthesis cumbersome, costly, and environmentally incompatible, while also exhibiting poor long-term stability under complex magnetic or electric fields. On the other hand, while traditional small-molecule organic dyes are less expensive, their chemical structures are typically simple, lacking specific designs for magnetoelectric driving environments, making it difficult to achieve highly sensitive optical responses to driving states, and they generally suffer from poor photostability and susceptibility to photobleaching. Furthermore, existing materials often struggle to achieve a balance between structural design and processing performance, frequently failing to simultaneously meet the stringent requirements of microdevices for solution processing and long-term device stability. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a luminescent material for micro magnetoelectric drive elements and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A luminescent material for use in micro magnetoelectric drive elements, wherein the luminescent material is a small molecule coordination compound having the following general formula (I): X[L]2; L is a ligand with the structure (II): A—N(R1)—(CH2) n1 —NH—(CH2) n2 —N=CH—Ar—OH; The groups in equations (I) and (II) are defined as follows: X is selected from Cu² + Ni² + Co² + Mn² + Cu² is preferred + ; A is selected from 9H-carbazole or a carbazole derivative, wherein the carbazole derivative is 9-ethyl-9H-carbazole, 3,6-diphenyl-9H-carbazole, 9-phenyl-carbazole or 3,3'-bicarbazole; R1 is H or a C1~C4 alkyl group; (CH2) n1 and (CH2) n2 It is a straight-chain flexible alkylene linkage, 2≤n1≤6, 2≤n2≤6; Ar is a 2-hydroxyphenyl or a derivative thereof, and its benzene ring may be optionally substituted by 1 to 3 identical or different substituents at the 3-, 4-, and 5- positions, wherein the substituents are selected from C1-C4 alkyl, C1-C4 alkoxy, F, Cl, Br, or CF3.

[0007] Preferably, X is Cu² + The compound is Cu[L]2, and its emission wavelength is 500-550 nm (green light). X=Cu 2+ Having d 9 The electronic configuration, under the influence of a ligand field, can produce significant metal-to-ligand charge transfer or ligand-centered luminescence. Cu[L]2 complexes emit green light in the 500-550 nm range after excitation, making them suitable for micro-display elements.

[0008] Preferably, X is Mn² + The compound is Mn[L]2, and the luminescent material exhibits long-lifetime phosphorescent emission with a phosphorescence lifetime ≥100 μs. 2+ Having d 5 The high-spin configuration, with its dd transition being a spin-forbidden transition, exhibits a weak radiative transition probability and a long excited-state lifetime. Mn[L]2 complexes display long-lifetime phosphorescent emission with a phosphorescence lifetime ≥100 μs. This property gives the material unique advantages in time-resolved fluorescence detection, anti-counterfeiting marking, and magnetoelectric drive applications requiring the elimination of background light interference.

[0009] A method for preparing a luminescent material for a micro magnetoelectric driving element includes the following steps: S1: 9H-carbazole or carbazole derivatives with dihaloalkane Y-(CH2) n1 -Z was subjected to N-alkylation under alkaline conditions at a reaction temperature of 80~120℃ for 6~12h to obtain N-haloalkylcarbazole intermediate M1; S2: Intermediate M1 undergoes nucleophilic substitution with salicylaldehyde precursor at 80~120℃ for 6~12h, followed by acid treatment to obtain ligand L; S3: Ligand L undergoes a coordination reaction with a metal salt at 50~80℃. After the reaction is completed, the mixture is cooled to room temperature, the solvent is concentrated under reduced pressure, a poor solvent is added to precipitate the solid, filtered, washed, and vacuum dried to obtain the purified luminescent material X[L]2.

[0010] Preferably, in step S1, Y and Z in the dihaloalkane are each independently selected from Br, Cl, and I, preferably 1-bromo-3-chloropropane; the alkaline conditions are provided by K2CO3 or Cs2CO3, and the molar amount of K2CO3 or Cs2CO3 is 1.2 to 2.0 times that of 9H-carbazole or a carbazole derivative.

[0011] Preferably, in step S2, the salicylaldehyde precursor is a 2-hydroxybenzaldehyde derivative and a diamine H2N-(CH2). n2 -NH2 is obtained by pre-condensation; the 2-hydroxybenzaldehyde derivative is obtained by selectively substituting 1 to 3 identical or different substituents at the 3-, 4-, and 5-positions of the benzene ring, and the substituents are selected from C1 to C4 alkyl, C1 to C4 alkoxy, F, Cl, Br or CF3.

[0012] Preferably, in step S2, the molar ratio of intermediate M1 to salicylaldehyde precursor is 1:(1.1~1.5).

[0013] Preferably, in step S2, the acidic conditions are provided by glacial acetic acid or p-toluenesulfonic acid.

[0014] Preferably, in step S3, the metal salt is an acetate or chloride corresponding to X, specifically copper(II) acetate, copper(II) chloride, nickel(II) acetate, nickel(II) chloride, cobalt(II) acetate, cobalt(II) chloride, manganese(II) acetate, or manganese(II) chloride. The amount of metal salt used is 0.4 to 0.6 times the molar amount of ligand L, and the reaction time is 2 to 6 hours.

[0015] Preferably, in step S3, the undesirable solvent is diethyl ether or n-hexane.

[0016] Preferably, the light-emitting material for micro magnetoelectric driving elements provided by the present invention operates on the following principle: 1. Chemical mechanism of synthesis reaction The luminescent material described in this invention is prepared using a "stepwise construction" strategy, and its chemical reaction principle is as follows: S1: (Nucleophilic substitution reaction): Under basic conditions, the nitrogen anion on 9H-carbazole acts as a nucleophile to attack the dihaloalkane Y-(CH2). n1 At one end of the -Z, an SN2 nucleophilic substitution reaction occurs, introducing a straight-chain side chain with an active halogen onto the nitrogen atom of the carbazole, yielding intermediate M1.

[0017] S2: (Chain extension and condensation reaction): The halogen atom at the end of intermediate M1 reacts with the diamine H2N-(CH2). n2 -NH2 undergoes nucleophilic substitution to achieve chain growth; subsequently, the terminal primary amino group and the aldehyde group of the salicylaldehyde precursor undergo a dehydration condensation reaction under acid catalysis to form a stable Schiff base (-C=N-) structure, completing the construction of ligand L.

[0018] S3: (Coordination reaction): The O,N-chelating sites in ligand L undergo a coordination reaction with the metal ion X in the metal salt. By controlling the stoichiometric ratio of the metal salt to the ligand, a self-assembly is formed to form an X[L]2 type metal complex, which is then purified by recrystallization in a poor solvent to obtain the final luminescent material.

[0019] 2. Principles of Molecular Structure Functionalization Design The luminescent material of this invention has the general formula X[L]2, and its organic ligand L adopts an asymmetric multifunctional structural design, consisting of three functional modules: Rigid framework module (A): 9H-carbazole or its derivatives are selected. The carbazole group has a large conjugated π system and good thermal stability. As a rigid framework of the molecule, it not only provides excellent hole transport capability, but also adjusts the energy level structure of the molecule through derivative substitution (such as alkyl, phenyl), thereby fine-tuning the emission color.

[0020] Flexible connecting arm module: Introducing a straight-chain alkylene chain —(CH2) n1 —NH—(CH2) n2 — The flexible chain acts as a "spacer group" to separate the rigid carbazole group from the metal chelate center, effectively reducing the steric hindrance and π-π stacking effect between intramolecular groups and avoiding fluorescence quenching (ACQ effect) caused by aggregation; at the same time, the long-chain alkyl group significantly improves the solubility of the material in organic solvents, meeting the material processability requirements of micro-component fabrication processes (such as spin coating and inkjet printing).

[0021] Metal chelating module: Based on the Schiff base structure (—N=CH—Ar—OH) formed by salicylaldehyde derivatives. The phenolic hydroxyl oxygen and imine nitrogen in this structure constitute stable O,N-bident chelating sites, which can form highly stable five- or six-membered chelating rings with transition metals, ensuring the structural stability of the complex under complex electric and thermal environments.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. By selecting different transition metal ions X, this invention can achieve different types of luminescence, such as fluorescence or long-life phosphorescence, with luminescence wavelengths covering the range from green to orange-red light, which can meet the needs of different monitoring scenarios for micro magnetoelectric drive components; at the same time, the material has good luminescence quantum efficiency and outstanding photostability, and can still maintain a high luminescence intensity after long-term irradiation, effectively overcoming the defects of traditional organic dyes that are easy to photobleach.

[0023] 2. The luminescent material prepared by this invention has precise magnetic response capability. The synergistic effect of transition metal ions and ligands enables the material to produce significant luminescence intensity modulation in a magnetic field. It has a fast response speed and can reflect the working state of micro magnetoelectric driving elements in real time through optical signals, filling the gap in high-sensitivity optical response of existing small molecule luminescent materials under magnetoelectric driving environment.

[0024] 3. The luminescent material prepared by this invention balances processing performance and structural stability. The flexible alkylene linkage in the ligand significantly improves the solubility of the material in common organic solvents, allowing for the preparation of uniform thin films through solution processing techniques such as spin coating and inkjet printing, meeting the requirements for the fabrication of micro-devices. At the same time, the stable molecular configuration formed by the rigid carbazole framework and the Schiff base chelate structure gives the material excellent thermal stability, maintaining structural stability under complex magnetic, electric, and thermal environments. This solves the problems of poor environmental compatibility and inadequate stability of existing quantum dots and perovskite materials, as well as the difficulty in balancing the structure and processing performance of traditional organic dyes.

[0025] 4. The luminescent material prepared by this invention has a simple and controllable synthesis route, adopts a stepwise construction strategy, has mild reaction conditions, readily available raw materials, does not require complex equipment, and has a simple product purification process with controllable costs. Compared with quantum dots and perovskite materials, which have complicated synthesis steps and high costs, it is more suitable for large-scale production and practical applications. Detailed Implementation

[0026] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, structure, features and effects of the present invention, in conjunction with the preferred embodiments, is provided below.

[0027] Example 1: Synthesis of complex Cu[L1]2 In the structure (I) prepared in this embodiment, X is Cu². + A is 9H-carbazole, n1=3, n2=3, and Ar is a complex of 2-hydroxyphenyl.

[0028] The reaction route is as follows: S1: Synthesis of intermediate M1 Under nitrogen protection, 10.0 g (59.8 mmol) of 9H-carbazole, 12.4 g (89.7 mmol) of potassium carbonate (K₂CO₃), and 150 mL of N,N-dimethylformamide (DMF) were added to a 500 mL three-necked flask. The mixture was stirred for 30 min to ensure thorough dispersion of the solid. 7.1 mL (71.4 mmol) of 1-bromo-3-chloropropane was slowly added dropwise, and the mixture was heated to 90 °C and stirred for 8 h. After the reaction was complete, the mixture was cooled to room temperature, poured into 300 mL of ice water, stirred for 10 min, and extracted with dichloromethane (100 mL × 3). The organic phases were combined, washed with deionized water (150 mL × 2), and dried over anhydrous magnesium sulfate overnight. The mixture was filtered, concentrated under reduced pressure to remove the solvent, and the residue was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 8:1) to give M1 in 83% yield. 1 H NMR analysis confirmed the compound as M1. The NMR data are as follows: 1 HNMR(500MHz,Chloroform-d)δ8.06–8.00(m,2H),7.62(dd,J=7.8,1.1Hz,2H),7.47– 2H),7.31–7.22(m,2H),4.16(t,J=4.7Hz,2H),3.66(t,J=3.1Hz,2H),2.11–2.05(m,2H).

[0029] S2: Ligand L1 synthesis (1) Preparation of salicylaldehyde precursor: 2-hydroxybenzaldehyde and 1,3-diaminopropane were refluxed in ethanol to obtain salicylaldehyde precursor.

[0030] (2) Nucleophilic substitution: Add 5.0 g (20.5 mmol) of intermediate M1, 4.4 g (24.6 mmol) of the above salicylaldehyde precursor (the molar ratio of M1 to the precursor is 1:1.2), 6.9 g (50 mmol) of potassium carbonate and 80 mL of DMF to a 250 mL three-necked flask, and stir the mixture at 90 °C for 8 h under nitrogen protection.

[0031] (3) Acidic post-treatment: Cool to 70℃, add 0.5 mL of glacial acetic acid, and continue stirring for 3 h. After the reaction is complete, cool to room temperature, pour the reaction solution into 200 mL of water, extract with dichloromethane (80 mL × 3), wash the organic phase once with saturated sodium bicarbonate solution (100 mL), wash once with deionized water (100 mL), dry with anhydrous magnesium sulfate, concentrate, and purify by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 4:1) to obtain a pale yellow solid L1, with a yield of 75%. 1 H NMR analysis, MS results, and infrared analysis confirmed it to be ligand L1, as shown below: HRMS(ESI)m / z:[M+H] + calcd for C 25 H 27 N3O 385.2154, found 386.2232; 1 HNMR(500MHz,Chloroform-d)δ8.50(t,J=1.7Hz,1H),8.06– , ,7.47–7.40(m,1H),7.40–7.33(m,2H),7.33–7.22(m,3H),6.96– ,4.13(t,J=5.6Hz,2H),3.43(td,J=6.8,1.5Hz,2H),2.92(p,J=4.1Hz,1H),2.80–2.73(m,4H),1.91–1.82(m,4H); Infrared spectrum (FT-IR, KBr pellet): 3426 cm⁻¹ - ¹ represents the stretching vibration peak of the phenolic hydroxyl group (OH), at 3056 cm⁻¹. - ¹ represents the stretching vibration peak of the aromatic ring CH, at 2938 cm⁻¹. - ¹、2864cm - ¹ represents the methylene CH stretching vibration peak, 1632 cm⁻¹ - ¹Schiff base C=N stretching vibration peak, 1598 cm⁻¹ - ¹、1492cm - ¹ represents the aromatic ring skeleton vibration peak, 1245 cm⁻¹ - ¹ represents the CO stretching vibration peak, 740 cm⁻¹ - ¹ represents the characteristic absorption peak of the carbazole ring.

[0032] S3: Synthesis of complex Cu[L1]2 To a 250 mL round-bottom flask, add 3.50 g (9.1 mmol) of ligand L1, 60 mL of ethanol, and 20 mL of DMF. After stirring to dissolve, add 0.84 g (4.6 mmol) of copper(II) acetate. Heat to 70 °C and stir for 4 h. Cool to room temperature and concentrate under reduced pressure to approximately 20 mL. Slowly add 150 mL of n-hexane and stir for 30 min to precipitate a solid. Filter, wash the filter cake with cold n-hexane (20 mL × 2), and vacuum dry (60 °C, 4 h) to obtain a dark green solid Cu(L1)2 with a yield of 82%. Infrared spectroscopy confirmed it to be the complex Cu[L1]2, as shown below: Infrared spectrum (FT-IR, KBr pellet): 3426 cm⁻¹ - The stretching vibration peak of the phenolic hydroxyl group (OH) at point ¹ was significantly weakened, at 1632 cm⁻¹. - The C=N stretching vibration peak at point ¹ shifted to 1620 cm⁻¹. - ¹, This is because N reacts with Cu² + Coordination leads to a change in the polarity of the C=N bond, resulting in an additional 528 cm⁻¹. - ¹Cu-O coordination bond stretching vibration peak, 492 cm⁻¹ - The stretching vibration peak of the Cu-N coordination bond at position ¹ directly proves the formation of the complex.

[0033] Example 2: Synthesis of complex Cu[L2]2 In the structure (I) prepared in this embodiment, X is Cu². + Ar is a complex of 2-hydroxy-5-methoxyphenyl.

[0034] The synthesis steps are similar to those in Example 1, except that: In step S2, 2-hydroxybenzaldehyde is replaced with 2-hydroxy-5-methoxybenzaldehyde to prepare salicylaldehyde precursor.

[0035] The final complex Cu[L2]2 was obtained with a yield of 78%.

[0036] pass 1 H NMR analysis, MS results, and infrared analysis confirmed it to be ligand L2, as shown below: HRMS(ESI)m / z:[M+H] + calcd for C 26 H 29 N3O2 415.2260, found 416.2338; 1 HNMR(500MHz,Chloroform-d)δ8.49(t,J=1.7Hz,1H),8.06– , ,7.46–7.41(m,1H),7.38(ddd,J=7.8,7.2,1.4Hz,1H),7.30– H), 6.91– (p,J=4.1Hz,1H),2.76(tdd,J=5.3,4.2,3.4Hz,4H),1.89–1.83(m,4H).

[0037] The infrared spectroscopy results confirmed it to be a complex Cu[L2]2, as shown below: 1268cm in ligand L2 - ¹(Ar-O-CH3 stretching vibration), 3430 cm⁻¹ in the complex - ¹(OH) decreases, 1625cm - ¹(C=N) shifts towards lower wavenumbers, adding 532 cm⁻¹ - ¹(Cu-O), 495cm - ¹(Cu-N).

[0038] Example 3: Synthesis of complex Mn[L1]2 In the structure (I) prepared in this embodiment, X is Mn² + Complexes.

[0039] The synthesis steps are similar to those in Example 1, except that manganese(II) acetate is used as the metal salt in step S3.

[0040] The final complex Mn[L1]2 was obtained in 75% yield. Infrared spectroscopy confirmed it as Mn[L1]2, as shown below: FT-IR (KBr tablet): 3428cm - ¹(OH) decreases, 1622cm - ¹(C=N) shifts towards lower wavenumbers, adding 545cm - ¹(Mn-O), 508cm - ¹(Mn-N).

[0041] Example 4: Synthesis of complex Ni[L1]2 In the structure (I) prepared in this embodiment, X is Ni². + Complexes.

[0042] The synthesis steps are similar to those in Example 1, except that nickel(II) acetate is used as the metal salt in step S3.

[0043] The final product was the complex Ni[L1]2, with a yield of 80%. Infrared spectroscopy confirmed it as the complex Ni[L1]2, as shown below: FT-IR (KBr tablet): 3425cm - ¹(OH) decreases, 1618cm - ¹(C=N) shifts towards lower wavenumbers, adding 538 cm⁻¹ - ¹(Ni-O), 502cm - ¹(Ni-N).

[0044] Example 5: Synthesis of Co[L1]2 complex In the structure (I) prepared in this embodiment, X is Co²⁺ + Complexes.

[0045] The synthesis steps are similar to those in Example 1, except that cobalt(II) acetate is used as the metal salt in step S3.

[0046] The final compound, Co[L1]2, was obtained in 82% yield. Infrared spectroscopy confirmed it as Co[L1]2, as shown below: FT-IR (KBr tablet): 3427cm - ¹(OH) decreases, 1621cm - ¹(C=N) shifts towards lower wavenumbers, adding 540cm - ¹(Co-O), 505cm - ¹(Co-N).

[0047] Comparative Example 1: Based on Example 2, the difference is that the 9H-carbazole group in ligand L is replaced with a non-conjugated simple amine such as aniline, and the rest is the same as in Example 2.

[0048] Comparative Example 2: Based on Example 2, the difference is that the flexible alkylene linker "—(CH2)" in ligand L is added. n 1—NH—(CH2) n2 The "-" is removed and replaced with a direct connection (i.e., n1=n2=0). That is, ligand L2 is prepared by reacting 9H-carbazole and 2-hydroxy-5-methoxybenzaldehyde, and then coordinated with copper acetate (II) for coordination reaction. The rest is the same as in Example 2.

[0049] Comparative Example 3: Based on Example 2, the difference is that the "salicylaldehyde derivative (Schiff base structure)" at the end of ligand L2 is replaced with a simple aliphatic amine without a chelating group, that is, the ligand end has no -N=CH-Ar-OH structure. In other words, n-propylamine is reacted with intermediate M1 and then coordinated with copper acetate (II). The rest is the same as in Example 2.

[0050] Comparative Example 4: Based on Example 2, the difference is that the metal salt "copper acetate (II)" is replaced with a non-transition metal salt that does not have the ability of d-electron transition, namely zinc acetate (II), and the rest is the same as Example 2.

[0051] Test Example: The complexes prepared in Examples 1-5 and Comparative Examples 1-4, as well as the commercially available control sample (Rhodamine B), were subjected to the above-mentioned performance tests. The results are shown in the table below: 1. Testing Method (1) Photoluminescence performance test: The excitation and emission spectra of the sample were tested using a fluorescence spectrophotometer; the luminescence quantum efficiency (PLQY) of the sample was determined using the integrating sphere method.

[0052] (2) Luminescence lifetime test: A time-resolved fluorescence spectrometer was used to measure the luminescence decay curve of the sample by pulsed laser excitation, and the luminescence lifetime was obtained by fitting (for example 3, which is phosphorescence).

[0053] (3) Magnetic response performance test: The sample is placed in an adjustable magnetic field (0-5T) generated by a superconducting magnet, the change of the sample luminescence intensity with the magnetic field strength is monitored, the luminescence intensity modulation amplitude (ΔI / I0) is calculated, and the response time is tested using a pulsed magnetic field.

[0054] (4) Thermal stability test: The thermal decomposition temperature of the sample was tested using a thermogravimetric analyzer (TGA) under a nitrogen atmosphere at a heating rate of 10℃ / min.

[0055] (5) Photostability test: Simulate sunlight irradiation in a xenon lamp aging chamber with an irradiation intensity of 100mW / cm² for 24 hours, and test the retention rate of the luminous intensity of the sample.

[0056] (6) Processing performance test: Solubility test: Take 20mg of sample, add 1mL of solvent, sonicate for 30min, let stand for 24h, observe whether it is completely dissolved (no precipitate), and record the maximum solubility; Film-forming test: A 10 mg / mL sample solution was spin-coated onto a silicon wafer (3000 rpm, 30 s), and vacuum dried at 60 °C for 4 h. The film surface was then observed using an optical microscope (100x) to determine if it was uniform, free of cracks, and free of pinholes.

[0057] Table 1. Test results of photoluminescence and magnetic response properties Note: "-" indicates that no valid signal was detected. Table 2 Results of stability and processability tests Data Analysis: Analysis of the data in Tables 1 and 2 shows that the complexes prepared in Examples 1-5 (Cu[L1]2, Cu[L2]2, Mn[L1]2, Ni[L1]2, and Co[L1]2, respectively) all exhibit luminescence and magnetic response capabilities, good thermal and photostability, and suitable solubility in common organic solvents. After film formation, the surface is uniform, without cracks, pinholes, or agglomeration. Examples 1, 2, 4, and 5 show fluorescence emission characteristics, Example 3 shows long-lifetime phosphorescence emission characteristics, and Example 2 exhibits particularly outstanding luminescence efficiency and magnetic response sensitivity, with a more regular film formation. While commercially available Rhodamine B boasts a luminescence quantum efficiency as high as 95%, it completely lacks magnetic response capability, has extremely poor photostability, and suffers from severe film agglomeration. The material of this invention comprehensively surpasses it in magnetic response sensitivity, photothermal stability, solution processing film formation, and luminescence controllability, precisely meeting the operational status monitoring requirements of micro-magnetic-electric drive components.

[0058] Compared with Example 2, Comparative Example 1 replaced the 9H-carbazole group in the ligand with a non-conjugated simple amine. Its luminescence performance, magnetic response performance, thermal stability and photostability were significantly reduced, and the film uniformity was poor. This is because the carbazole group has a large conjugated π system and good thermal stability. As a rigid framework of the molecule, it can provide excellent hole transport capability and regulate the molecular energy level structure. In contrast, the conjugated system of simple amines is small and the electron transport efficiency is low, which leads to luminescence quenching and the related performance is impaired.

[0059] Compared to Example 2, Comparative Example 2 removed the flexible alkylene linking chain in the ligand and replaced it with a direct linking chain. This resulted in impaired luminescence performance, significantly reduced solubility in organic solvents, severe aggregation, cracking, and dense pinholes after film formation, and decreased magnetic response sensitivity. This is because the flexible alkylene linking chain can act as a spacer to separate the rigid carbazole group from the metal chelate center, reducing steric hindrance and π-π stacking within the molecule, avoiding fluorescence quenching caused by aggregation, and simultaneously improving the solubility of the material in organic solvents. After removal, the molecules are prone to aggregation, and all properties are adversely affected.

[0060] Compared to Example 2, Comparative Example 3 replaced the salicylaldehyde derivative Schiff base structure at the ligand end with a simple aliphatic amine without chelating groups. It exhibited no luminescence, lacked magnetic response, had extremely poor thermal stability, and could not form a film. This is because the phenolic hydroxyl oxygen and imine nitrogen in the Schiff base structure constitute a stable O,N-bident chelating site, which can form a highly stable chelating ring with transition metals. This is the key to constructing the luminescent core and maintaining the stability of the molecular structure. Without chelating groups, metal ions cannot co-emitte with the ligands, resulting in insufficient molecular structural stability and complete loss of related functions.

[0061] Compared with Example 2, Comparative Example 4 replaced the metal salt with a non-transition metal salt, resulting in a significant decrease in magnetic response performance, photostability, and film formation effect. This is because transition metal ions have unpaired electrons, which can split energy levels in a magnetic field, causing the luminescence intensity to change with the magnetic field and thus generating a magnetic response. In contrast, non-transition metal ions have a fully filled electron configuration and no unpaired electrons, so they cannot generate a magnetic response. At the same time, the strong coordination between transition metal ions and ligands can better improve photostability and film formation effect.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A luminescent material for use in micro magnetoelectric driving elements, characterized in that, The luminescent material is a small molecule coordination compound with the following general formula (I): X[L]2; L is a ligand with the structure (II): A—N(R1)—(CH2) n1 —NH—(CH2) n2 —N=CH—Ar—OH; The groups in equations (I) and (II) are defined as follows: X is selected from Cu² + Ni² + Co² + Mn² + Cu² is preferred + ; A is selected from 9H-carbazole or a carbazole derivative, wherein the carbazole derivative is 9-ethyl-9H-carbazole, 3,6-diphenyl-9H-carbazole, 9-phenyl-carbazole or 3,3'-bicarbazole; R1 is H or a C1~C4 alkyl group; (CH2) n1 and (CH2) n2 It is a straight-chain flexible alkylene linkage, 2≤n1≤6, 2≤n2≤6; Ar is a 2-hydroxyphenyl or a derivative thereof, and its benzene ring may be optionally substituted by 1 to 3 identical or different substituents at the 3-, 4-, and 5- positions, wherein the substituents are selected from C1-C4 alkyl, C1-C4 alkoxy, F, Cl, Br, or CF3.

2. The luminescent material for a micro magnetoelectric drive element according to claim 1, characterized in that, X is Cu² + The compound is Cu[L]2, and the emission wavelength is 500~550nm (green light).

3. The luminescent material for a micro magnetoelectric drive element according to claim 1, characterized in that, X is Mn² + The compound is Mn[L]2, and the luminescent material exhibits long-lifetime phosphorescent emission with a phosphorescence lifetime of ≥100μs.

4. A method for preparing a luminescent material for a micro magnetoelectric driving element as described in claim 1, characterized in that, Includes the following steps: S1: 9H-carbazole or carbazole derivatives with dihaloalkane Y-(CH2) n1 -Z was subjected to N-alkylation under alkaline conditions at a reaction temperature of 80~120℃ for 6~12h to obtain N-haloalkylcarbazole intermediate M1; S2: Intermediate M1 undergoes nucleophilic substitution with salicylaldehyde precursor at 80~120℃ for 6~12h, followed by acid treatment to obtain ligand L; S3: Ligand L undergoes a coordination reaction with a metal salt at 50~80℃. After the reaction is completed, the mixture is cooled to room temperature, the solvent is concentrated under reduced pressure, a poor solvent is added to precipitate the solid, filtered, washed, and vacuum dried to obtain the purified luminescent material X[L]2.

5. The method for preparing the luminescent material for a micro magnetoelectric driving element as described in claim 4, characterized in that, In step S1, Y and Z in the dihaloalkane are each independently selected from Br, Cl, and I, preferably 1-bromo-3-chloropropane; the alkaline conditions are provided by K2CO3 or Cs2CO3, and the molar amount of K2CO3 or Cs2CO3 is 1.2 to 2.0 times that of 9H-carbazole or a carbazole derivative.

6. The method for preparing the luminescent material for a micro magnetoelectric drive element as described in claim 4, characterized in that, In step S2, the salicylaldehyde precursor is a 2-hydroxybenzaldehyde derivative and a diamine H2N-(CH2). n2 -NH2 is obtained by pre-condensation; the 2-hydroxybenzaldehyde derivative is obtained by selectively substituting 1 to 3 identical or different substituents at the 3-, 4-, and 5-positions of the benzene ring, and the substituents are selected from C1 to C4 alkyl, C1 to C4 alkoxy, F, Cl, Br or CF3.

7. The method for preparing the luminescent material for a micro magnetoelectric driving element as described in claim 4, characterized in that, In step S2, the molar ratio of intermediate M1 to salicylaldehyde precursor is 1:(1.1~1.5).

8. The method for preparing the luminescent material for a micro magnetoelectric driving element as described in claim 4, characterized in that, In step S2, the acidic conditions are provided by glacial acetic acid or p-toluenesulfonic acid.

9. The method for preparing the luminescent material for a micro magnetoelectric driving element as described in claim 4, characterized in that, In step S3, the metal salt is an acetate or chloride corresponding to X, specifically copper(II) acetate, copper(II) chloride, nickel(II) acetate, nickel(II) chloride, cobalt(II) acetate, cobalt(II) chloride, manganese(II) acetate, or manganese(II) chloride. The amount of metal salt used is 0.4 to 0.6 times the molar amount of ligand L, and the reaction time is 2 to 6 hours.

10. The method for preparing the luminescent material for a micro magnetoelectric driving element as described in claim 4, characterized in that, In step S3, the undesirable solvent is diethyl ether or n-hexane.

Images