Photoresponsive rare earth supramolecule, preparation method and use thereof

Abstract

The application discloses a light response type rare earth supermolecule, a preparation method and application thereof. The light response type rare earth supermolecule has a structure as shown in formula (II), wherein R1 is selected from methyl or ethyl; R2 is a substituent at any position of a benzene ring, and R2 is independently selected from hydrogen, C1-C6 alkyl or C1-C6 alkoxy; Ln is selected from one of Eu 3+ , Yb 3+ , Sm 3+ , Gd 3+ and Tb 3+ . The rare earth supermolecule of the application shows a change in luminescent intensity which can be easily captured by naked eyes during the cyclic irradiation of ultraviolet light and visible light.

Description

Technical Field

[0001] This invention relates to a photoresponsive rare earth supramolecular, its preparation method, and its uses. Background Technology

[0002] Photochromic materials have demonstrated broad potential applications in optical information storage, light-emitting switches, fluorescent chemical sensors, and optoelectronic devices. Diarylethylene, azobenzene, and spiropyran are some common photochromic units used in the preparation of photochromic materials. Among them, the diarylethylene unit (DAE) is widely used in application research and development in fields such as optical switches, molecular machines, information storage, functional vesicles, biological devices, and smart surface materials due to its excellent thermal stability and fatigue resistance.

[0003] CN102659768A discloses a method for preparing a hexafluorocyclopentene-based photochromic compound with diaromatic heterocyclic substitution. This method introduces specific functional groups, and the absorption wavelength of the prepared photochromic compound is red-shifted by 50-100 nm. It can be applied in optical information storage, anti-counterfeiting identification, covert materials, and military camouflage materials.

[0004] CN113173920A discloses a fluorescence-on-demand type diarylethene fluorescent probe, its preparation method, and its application. The probe is composed of two parts: diarylethene and paclitaxel. Under alternating irradiation with ultraviolet and visible light, it exhibits photochromic and photofluorescent color-changing behavior. After multiple light-on-off cycles, the diarylethene fluorescent probe still has good light-on-off capability.

[0005] Rare earth ions, due to their unique optical properties such as visible light emission, long-lived excited states, narrow emission bands, and large Stokes shifts, have brought new opportunities for the expansion and improvement of the performance of photochromic materials. In recent years, although there are still certain challenges in the synthesis of photochromic materials using rare earth ions, a small number of rare earth-based photochromic molecules have been synthesized and reported.

[0006] CN116332968A discloses a β-diketone multi-element rare earth complex, its preparation method, and its application. This patent document prepares a β-diketone ligand and then combines it with an o-phenanthroline ligand to prepare a rare earth complex containing two ligands. The novel rare earth complex containing two ligands obtained combines the advantages of luminescence properties and stability of both β-diketone and o-phenanthroline structures.

[0007] As photochromic materials, the modulation of luminescence intensity is one of the most useful characteristics of optical switching technology. The change in optical signal, which is easily captured by the naked eye, is a very important factor in determining whether a material can be used for application exploration. However, because the energy levels of most photochromic ligands are poorly matched with the energy levels of rare earth ions, the material is not easy to capture and detect due to the small difference in luminescence intensity before and after ring opening and closing. Summary of the Invention

[0008] In view of this, one object of the present invention is to provide a photoresponsive rare earth supramolecular that exhibits a change in luminescence intensity that is easily captured by the naked eye during cyclic irradiation with 275 nm ultraviolet light and 526 nm visible light.

[0009] Another objective of this invention is to provide a method for preparing the above-mentioned photoresponsive rare earth supramolecular material. This method is relatively simple, and the raw materials and synthetic reagents used are inexpensive and readily available, which can solve the problem of high cost.

[0010] Another object of the present invention is to provide the use of the above-mentioned photoresponsive rare earth supramolecular in the preparation of photocontrolled molecular switches.

[0011] On the one hand, the present invention provides a photoresponsive rare-earth supramolecular having a structure as shown in formula (II).

[0012]

[0013] Wherein, R1 is selected from methyl or ethyl; R2 is a substituent at any position on the benzene ring, and R2 is independently selected from hydrogen, C1-C6 alkyl or C1-C6 alkoxy;

[0014] Wherein, Ln is selected from Eu 3+ Yb 3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them.

[0015] In the photoresponsive rare earth supramolecular according to the present invention, preferably, R1 is ethyl; R2 is independently selected from hydrogen or C1-C6 alkyl.

[0016] According to the photoresponsive rare-earth supramolecular of the present invention, preferably, Ln is Eu. 3+ .

[0017] According to the photoresponsive rare-earth supramolecular of the present invention, preferably, the compound represented by formula (II) is:

[0018]

[0019] Wherein, Ln is selected from Eu 3+ Yb3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them.

[0020] On the other hand, the present invention also provides a method for preparing a photoresponsive rare earth supramolecular as described above, comprising: reacting the compound shown in formula (I) with the compound shown in formula (E) to obtain the compound shown in formula (II);

[0021]

[0022] Wherein, R1 is selected from methyl or ethyl; R2 is a substituent at any position on the benzene ring, and R2 is independently selected from hydrogen, C1-C6 alkyl or C1-C6 alkoxy;

[0023] Wherein, Ln is selected from Eu 3+ Yb 3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them.

[0024] According to the preparation method of the present invention, preferably, it includes the following steps:

[0025] The compound shown in formula (D) is oxidized in the presence of an oxidizing agent to obtain the compound shown in formula (I);

[0026]

[0027] R1 and R2 are shown above.

[0028] According to the preparation method of the present invention, preferably, the compound represented by formula (D) is prepared by steps including the following:

[0029] (1) The compound shown in formula (A) is reacted with X-R1 in the presence of alkyllithium to give the compound shown in formula (B); wherein X is bromine or iodine, and R1 is selected from methyl or ethyl.

[0030] (2) The compound shown in formula (B) is reacted with a brominating agent or an iodizing agent to obtain the compound shown in formula (C);

[0031] (3) The compound shown in formula (C) was reacted with octafluorocyclopentene in the presence of alkyllithium to obtain the compound shown in formula (D);

[0032]

[0033] In formula (C), Y is bromine or iodine;

[0034] R1 and R2 are shown above.

[0035] According to the preparation method of the present invention, preferably, in steps (1) and (3), the alkyl lithium is n-butyllithium.

[0036] According to the preparation method of the present invention, preferably, in step (2), a mixture of glacial acetic acid and chloroalkanes is used as the reaction solvent; in steps (1) and (3), tetrahydrofuran is used as the reaction solvent.

[0037] In another aspect, the present invention also provides the use of the photoresponsive rare-earth supramolecular as described above in the preparation of a photocontrolled molecular switch.

[0038] The photoresponsive rare-earth supramolecular of this invention exhibits luminescence intensity changes that are easily detected by the naked eye during cyclic irradiation with 275nm ultraviolet light and 526nm visible light. This solves the problem that current methods struggle to detect and capture luminescence due to the small difference in intensity before and after ring opening and closing, caused by the poor energy level matching between most photochromic ligands and rare-earth ions. Furthermore, the rare-earth supramolecular structure of this invention exhibits good structural stability. In addition, it also demonstrates excellent fatigue resistance and thermal stability. Attached Figure Description

[0039] Figure 1 The image shows the one-dimensional hydrogen spectrum of the ligand compound and the photoresponsive rare earth supramolecular of Example 1.

[0040] Figure 2 This is the mass spectrum of the photoresponsive rare earth supramolecular of Example 1.

[0041] Figure 3 For the application of rare earth supramolecular acetonitrile solution (1×10) in Example 1 -5 M) Absorption trend curve in the open-loop state.

[0042] Figure 4 For the application of rare earth supramolecular acetonitrile solution (1×10) in Example 1 -5 Absorption trend curve under the closed-loop state (M).

[0043] Figure 5 For the application of rare earth supramolecular acetonitrile solution (1×10) in Example 1 -5 M) Ultraviolet absorption change curves after multiple cycles of irradiation and fatigue resistance tests.

[0044] Figure 6 For the application of rare earth supramolecular acetonitrile solution (1×10) in Example 1 -5 M) Ultraviolet-visible absorption spectrum after heating to 55°C and maintaining it for 3 hours under steady light conditions.

[0045] Figure 7 For the application of rare earth supramolecular acetonitrile solution (1×10) in Example 1 -5 Emission spectrum of M under 275nm ultraviolet light irradiation. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0047] <Terminology Explanation>

[0048] In this invention, Cm-Cn represents having m to n carbon atoms; for example, C1-C6 alkyl represents having 1 to 6 carbon atoms.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although similar or equivalent methods and materials may be used in the implementation or testing of this invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety. In case of any conflict, this specification and its included definitions shall prevail. Furthermore, materials, methods, preparation examples, and embodiments are exemplary only and are not intended to be limiting.

[0050] <Photoresponsive rare earth supramolecular>

[0051] The photoresponsive rare-earth supramolecular of the present invention represents a class of substances. The photoresponsive rare-earth supramolecular of the present invention has the structure shown in formula (II):

[0052]

[0053] In the rare-earth supramolecular of this invention, the ligand compound shown in formula (I) serves as the auxiliary ligand, and the compound shown in formula (E) (i.e., Ln(hfa)3·2H2O) serves as the host ligand. Thus, this invention can regulate the energy transfer from the ligand compound to the Eu(III) ion by switching the ring-opening and ring-closed states of the ligand compound. The ring-closed diarylvinyl photochromic auxiliary ligand and the hexafluoroacetylacetone host ligand, after ring closure, enhance the energy transfer of Eu(III) ions. 3+ Ions have an effective synergistic sensitization effect.

[0054] The rare-earth supramolecular structure of this invention exhibits excellent stability. Each rare-earth ion forms a stable eight-coordinate and three-capped triangular prism coordination geometry with the two O atoms in the two sulfone coordination units of the photochromic co-ligand and the six O atoms from the three hfa ligands, resulting in strong structural stability. This provides favorable conditions for the practical application of optical switching materials.

[0055] In this invention, R1 is selected from methyl or ethyl, preferably ethyl. R2 is a substituent at any position on the benzene ring, and R2 is independently selected from hydrogen, C1-C6 alkyl, or C1-C6 alkoxy. Preferably, R2 is independently selected from hydrogen or C1-C6 alkyl. More preferably, R2 is independently selected from hydrogen or C1-C3 alkyl. According to a specific embodiment of the invention, R2 is hydrogen.

[0056] In this invention, C1-C6 alkyl groups may include, but are not limited to, straight-chain alkyl groups or branched alkyl groups; preferably, they are C1-C3 alkyl groups, more preferably C1-C3 straight-chain alkyl groups. Examples of C1-C6 alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, etc. Furthermore, the C1-C6 alkyl groups of this invention may include substituted alkyl groups or unsubstituted alkyl groups. Substituents in substituted alkyl groups may contain heteroatoms, such as O, S, N, P, or halogen atoms. Halogen atoms in this invention include, but are not limited to, fluorine, chlorine, bromine, and iodine.

[0057] In this invention, C1-C6 alkoxy groups may include, but are not limited to, straight-chain alkoxy groups or branched-chain alkoxy groups; preferably, they are C1-C3 alkoxy groups, more preferably, they are C1-C3 straight-chain alkoxy groups. Examples of C1-C6 alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, neopentoxy, hexoxy, etc.

[0058] In this invention, Ln is selected from Eu. 3+ Yb 3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them, preferably Eu 3+ .

[0059] According to a specific embodiment of the present invention, the compound represented by formula (II) is:

[0060]

[0061] Where Et is ethyl, and Ln is selected from Eu 3+ Yb 3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them, preferably Eu 3+ .

[0062] The rare-earth supramolecular of the present invention can solve the problem that the energy levels of most photochromic ligands are poorly matched with the energy levels of rare-earth ions, making the materials difficult to capture and detect due to the small difference in luminescence intensity before and after ring opening and closing.

[0063] <Preparation Method>

[0064] The preparation method of the photoresponsive rare earth supramolecular of the present invention includes the following steps:

[0065] (1) The synthetic steps of the compound shown in formula (B);

[0066] (2) The synthetic steps of the compound shown in formula (C);

[0067] (3) The synthetic steps of the compound shown in formula (D);

[0068] (4) The steps for synthesizing the ligand compound (i.e., the compound shown in formula (I));

[0069] (5) The synthetic steps of the compound shown in formula (II) (i.e., the photoresponsive rare earth supramolecular). The following is a detailed description.

[0070] Synthetic steps of the compound shown in formula (B)

[0071] In step (1) of the present invention, the compound shown in formula (A) is reacted with X-R1 in the presence of alkyllithium to obtain the compound shown in formula (B).

[0072]

[0073] R2 is a substituent at any position on the benzene ring, and R2 is independently selected from hydrogen, C1-C6 alkyl, or C1-C6 alkoxy. Preferably, R2 is independently selected from hydrogen or C1-C6 alkyl. More preferably, R2 is independently selected from hydrogen or C1-C3 alkyl.

[0074] In this invention, C1-C6 alkyl groups may include, but are not limited to, straight-chain alkyl groups or branched alkyl groups; preferably, they are C1-C3 alkyl groups, more preferably C1-C3 straight-chain alkyl groups. Examples of C1-C6 alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, etc. Furthermore, the C1-C6 alkyl groups of this invention may include substituted alkyl groups or unsubstituted alkyl groups. Substituents in substituted alkyl groups may contain heteroatoms, such as O, S, N, P, or halogen atoms. Halogen atoms in this invention include, but are not limited to, fluorine, chlorine, bromine, and iodine.

[0075] In this invention, C1-C6 alkoxy groups may include, but are not limited to, straight-chain alkoxy groups or branched-chain alkoxy groups; preferably, they are C1-C3 alkoxy groups, more preferably, they are C1-C3 straight-chain alkoxy groups. Examples of C1-C6 alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, neopentoxy, hexoxy, etc.

[0076] In step (1), X-R1 is a halomethane or haloethane, and X is selected from bromine or iodine.

[0077] In step (1), the alkyl lithium can be isopropyl lithium, isobutyl lithium or n-butyl lithium, preferably n-butyl lithium.

[0078] The molar ratio of alkyllithium to the compound shown in formula (A) can be 1 to 1.2:1, preferably 1.05 to 1.15:1, and more preferably 1.08 to 1.1:1. The molar ratio of X-R1 to the compound shown in formula (A) can be 1.1 to 1.8:1, preferably 1.3 to 1.7:1, and more preferably 1.5 to 1.7:1.

[0079] In step (1), tetrahydrofuran is used as the reaction solvent, and the reaction temperature is -78℃ to -45℃, preferably -78℃ to -60℃.

[0080] According to a specific embodiment of the present invention, under nitrogen protection, the compound shown in formula (A) was dissolved in tetrahydrofuran, cooled to -78°C to -60°C, and then a n-butyllithium solution was added dropwise. After the addition was complete, a tetrahydrofuran solution of X-R1 was added dropwise. After the addition was complete, the mixture was stirred at -78°C to -45°C for 20 to 30 minutes, then heated to room temperature and stirred for 10 to 16 hours. After the reaction was complete, the reaction was quenched with water. The mixture was extracted multiple times with ethyl acetate, the organic layer was washed with Na2S2O3 solution, and then the organic layer was dried and concentrated to remove the ethyl acetate, yielding the compound shown in formula (B).

[0081] Synthetic steps of the compound shown in formula (C)

[0082] The compound shown in formula (B) is reacted with a brominating or iodizing reagent to give the compound shown in formula (C).

[0083] In formula (C), Y is bromine or iodine.

[0084] In step (2), the brominating agent can be N-bromosuccinimide (NBS). The iodizing agent can be N-iodosuccinimide. It is preferred to use a brominating agent. The molar ratio of the brominating agent to the compound shown in formula (B) can be 0.8–1:1, preferably 0.85–0.95:1, and more preferably 0.86–0.9:1.

[0085] The solvent used is a mixed solvent. Specifically, a mixture of glacial acetic acid and chloroalkanes is used as the reaction solvent. The chloroalkanes can be dichloromethane, chloroform, or carbon tetrachloride, preferably chloroform. The volume ratio of glacial acetic acid to chloroalkanes can be 0.9 to 1:1, for example, 1:1. The reaction temperature can be 0 to 10°C.

[0086] According to a specific embodiment of the present invention, the compound shown in formula (B) was dissolved in a mixed solvent of V(glacial acetic acid):V(CHCl3) = 1:1 at 0–10 °C. Then, the brominating agent NBS was added in portions, and the mixture was stirred in the dark for 1–3 h (to prevent NBS decomposition). After the reaction was complete, a weakly alkaline aqueous solution was added to adjust the pH to 7. The mixture was then extracted multiple times with ethyl acetate, and the organic layer was washed with Na2S2O3 solution. The organic layers were combined, dried, and concentrated to remove ethyl acetate, yielding a crude product. Column chromatography was performed using petroleum ether as the eluent to obtain the compound shown in formula (C).

[0087] Synthetic steps of the compound shown in formula (D)

[0088] In step (3), the compound shown in formula (C) is reacted with octafluorocyclopentene in the presence of alkyllithium to obtain the compound shown in formula (D).

[0089]

[0090] The alkyllithium can be isopropyllithium, isobutyllithium, or n-butyllithium, preferably n-butyllithium. The reaction solvent is tetrahydrofuran. The reaction temperature can be -78℃ to -45℃, preferably -78℃ to -60℃.

[0091] The molar ratio of alkyllithium to the compound shown in formula (C) can be 1.2 to 1.5:1, preferably 1.3 to 1.5:1, and more preferably 1.4 to 1.45:1. The molar ratio of octafluorocyclopentene to the compound shown in formula (C) can be 0.5 to 0.51:1, for example, 0.5:1.

[0092] According to a specific embodiment of the present invention, the compound shown in formula (C) was dissolved in anhydrous tetrahydrofuran, cooled to -78°C to -60°C, and n-butyllithium was added dropwise. After the addition was complete, stirring was continued for 20 to 30 minutes, followed by the dropwise addition of octafluorocyclopentene. After the addition was complete, the reaction was continued at -78°C to -60°C for 1 to 2 hours, then the temperature was raised to room temperature, and stirring was continued for 1 to 2 hours. After the reaction was complete, water was added to quench the reaction. The mixture was extracted multiple times with ethyl acetate, and the organic layer was washed with brine. The organic layers were combined. The organic layer was dried, concentrated to remove ethyl acetate, and the crude product was obtained. Column chromatography was performed using petroleum ether as the eluent to obtain the compound shown in formula (D).

[0093] Synthetic steps of ligand compounds (i.e., compounds represented by formula (I))

[0094] In step (4), the compound shown in formula (D) is oxidized in the presence of an oxidizing agent to obtain the compound shown in formula (I).

[0095] The ligand compounds of the present invention have the structure shown in formula (I):

[0096]

[0097] Preferably, the ligand compound of the present invention is selected from the following compounds:

[0098] Et stands for ethyl group.

[0099] The oxidant is preferably m-chloroperoxybenzoic acid. The molar ratio of the oxidant to the compound shown in formula (D) can be 10–25:1, preferably 18–25:1, and more preferably 20–22:1. The solvent is dichloromethane or chloroform, preferably dichloromethane.

[0100] According to a specific embodiment of the present invention, the compound shown in formula (D) was dissolved in dichloromethane at 20–35°C. m-chloroperoxybenzoic acid was added, and the mixture was stirred for 10–20 h. After the reaction was complete, the dichloromethane was removed by concentration, and the solution was dissolved in water. Then, NaHSO3 was added, and stirring was continued for 18–24 h. The mixture was then extracted multiple times with dichloromethane, the organic layers were combined, washed with water, dried, and concentrated to remove dichloromethane. The crude product was recrystallized using a mixed solvent V(CH2Cl2):V(n-hexane) = 1:3. The compound shown in formula (I) was obtained.

[0101] Synthetic steps of photoresponsive rare earth supramolecular (i.e., the compound represented by formula (II))

[0102] The compound of formula (I) prepared above is reacted with the compound of formula (E) to obtain the compound of formula (II).

[0103]

[0104] Wherein, Ln is selected from Eu 3+ Yb 3+ 、Sm 3+ Gd 3+ and Tb 3+ One of them, preferably Eu 3+ In this invention, the compound represented by formula (E) can be abbreviated as Ln(hfa)3·2H2O.

[0105] According to a specific embodiment of the present invention, Ln(hfa)3·2H2O is dissolved in acetonitrile, and then the compound shown in formula (I) is added. The mixture is heated under reflux for 10 to 16 hours. After the reaction is completed, the acetonitrile is removed by concentration to obtain the compound shown in formula (II), which is a photoresponsive rare earth supramolecular.

[0106] The molar ratio of the compound shown in formula (I) to Ln(hfa)3·2H2O can be 1 to 1.02:1.

[0107] <Application>

[0108] The present invention also provides the use of the photoresponsive rare earth supramolecular as described above in the preparation of photocontrolled molecular switches.

[0109] When testing the properties of rare earth supramolecular molecules, they can be mixed with acetonitrile to obtain a rare earth supramolecular solution. The concentration of the rare earth supramolecular solution can be 1×10⁻⁶. -6 ~1×10 -3 M.

[0110] After repeated irradiation cycles, the rare-earth supramolecular material of this invention exhibited excellent fatigue resistance. Furthermore, when an acetonitrile solution of the rare-earth supramolecular material was heated to 55°C and held at that temperature for 3 hours under photosteady conditions, its UV-Vis absorption spectrum showed no significant change, indicating that the rare-earth supramolecular material possesses excellent thermal stability. This excellent fatigue resistance and thermal stability enable its widespread application in the research and development of optical switching materials.

[0111] It exhibits changes in luminescence intensity that are easily detected by the naked eye during cyclic irradiation with 275nm ultraviolet light and 526nm visible light.

[0112] <Testing Methods>

[0113] 1 ¹H NMR: Measurements were performed using an Avance III 400 nuclear magnetic resonance spectrometer from Bruker, Switzerland, with deuterated acetonitrile as the solvent.

[0114] MS: Measured using a liquid chromatography-mass spectrometry system manufactured by Shimadzu Corporation, Japan.

[0115] Ultraviolet-visible absorption spectra: measured using a Lambda 25 ultraviolet spectrometer from PerkinElmer, USA.

[0116] Example 1

[0117] Reaction equation:

[0118]

[0119] Where Ln is Eu 3+ .

[0120] Step (1): Synthesis of compound (B) (i.e., 2-ethylbenzo[b]thiophene)

[0121] Benzothiophene (5.95 g, 45.0 mmol) was dissolved in a Schlenk flask containing 100 mL of anhydrous THF under N2 protection and cooled to -78 °C. n-Butyllithium was then added dropwise to the reaction system.

[0122] (32 mL, 50.0 mmol), maintained for 30 min, then iodoethane (6 mL, containing 5 mL THF) was added.

[0123] 76.0 mmol) was added dropwise to the reaction system. After the addition was complete, the mixture was stirred at -78°C for 20 min, then slowly brought to room temperature and stirred overnight. After the reaction was complete, water was added dropwise to quench the reaction. 25 mL of water was added to the reaction solution, and the mixture was extracted with ethyl acetate (25 mL × 3). The organic layers were washed with Na₂S₂O₃ solution (25 mL × 3), combined, and dried over anhydrous sodium sulfate. Ethyl acetate was removed by vacuum distillation to give 5.6 g of a colorless liquid, with a yield of 93%.

[0124] Step (2): Synthesis of compound (C) (i.e., 3-bromo-2-ethylbenzo[b]thiophene)

[0125] 2-Ethylbenzo[b]thiophene (10.00 g, 67.5 mmol) was dissolved in 100 mL of a mixed solvent of V(glacial acetic acid):V(CHCl3) = 1:1 at 0 °C. The brominating agent NBS (10.44 g, 58.6 mmol) was added to the reaction system, and the mixture was stirred in the dark for 2 h (to prevent NBS decomposition). After the reaction was complete, a weakly alkaline aqueous solution was added to adjust the pH to 7. The mixture was extracted with ethyl acetate (25 mL × 3), and the organic layer was washed with Na2S2O3 solution (25 mL × 3). The organic layers were combined and dried with anhydrous sodium sulfate. Ethyl acetate was removed by vacuum distillation to obtain a yellow oily liquid. Petroleum ether was used as the eluent, and the liquid was purified by column chromatography to obtain 12.0 g of a colorless liquid, with a yield of 81%.

[0126] Step (3): Synthesis of compound (D)

[0127] 3-Bromo-2-ethylbenzo[b]thiophene (5.00 g, 22.0 mmol) was dissolved in 100 mL of anhydrous THF. After cooling to -78 °C, n-butyllithium (12.50 mL, 31.3 mmol, 2.5 M) was added dropwise. After stirring continuously for 30 min, octafluorocyclopentene (1.40 mL, 11.0 mmol) was slowly added dropwise to the reaction system. The mixture was then stirred at -78 °C for 1 h, followed by stirring at room temperature for another 1 h. After the reaction was complete, 5 mL of water was added for hydrolysis. The mixture was extracted with ethyl acetate (25 mL × 3), and the organic phases were combined and washed with brine. The combined organic layers were dried over anhydrous sodium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified by column chromatography (petroleum ether as the eluent) to give 4.8 g of a white solid, which is the compound shown in formula (D), with a yield of 47%.

[0128] Step (4): Synthesis of compound (I)

[0129] At room temperature, the compound shown in formula (D) (3.00 g, 6.0 mmol) was dissolved in a round-bottom flask containing 150 mL of dichloromethane and stirred for 10 min until the solid was completely dissolved. m-chloroperoxybenzoic acid (22.12 g, 128.0 mmol) was added to the reaction system and stirred overnight. After the reaction was complete, dichloromethane was removed by vacuum distillation. 200 mL of water was added to the crude product, and NaHSO3 (13.32 g, 128.0 mmol) was added to the reaction system, and stirring was continued for 24 h. The reaction solution was extracted with dichloromethane (25 mL × 3), the combined organic layers were washed with water (25 mL × 3), dried over anhydrous sodium sulfate, and dichloromethane was removed by vacuum distillation. The crude product was recrystallized in a mixed solvent V(CH2Cl2):V(n-hexane) = 1:3 to give 2.5 g of white crystals, which is the ligand compound shown in formula (I), with a yield of approximately 75%. Its proton NMR spectrum is shown below. Figure 1 .

[0130] Step (5): Synthesis of photoresponsive rare earth supramolecular

[0131] The compound shown in formula (E) (which can be abbreviated as Ln(hfa)3·2H2O, 0.39 g, 0.5 mmol) was dissolved in a reaction flask containing 20 mL of anhydrous acetonitrile. The compound shown in formula (I) (0.28 g, 0.5 mmol) was added to this solution, and the mixture was heated under reflux for 12 h. After the reaction was complete, the acetonitrile was removed by distillation to obtain the target compound, namely the compound shown in formula (II). The yield was approximately 97%. Its proton NMR spectrum is shown below. Figure 1 Mass spectrometry results are available. Figure 2 The calculated molecular weight is 1334.5624, and the measured value is 1334.6783.

[0132] Application Example 1 - Performance Study of the Obtained Photoresponsive Rare Earth Supramolecular

[0133] 1.1 The compound shown in formula (II) (i.e., rare earth supramolecular, denoted as Eu(hfa)3L) and the solvent acetonitrile were mixed to obtain a photoresponsive rare earth supramolecular solution, and the ultraviolet-visible absorption spectrum of the photoresponsive rare earth supramolecular solution was detected.

[0134] In the open-ring state, the absorbance gradually decreases with time, as shown in the results. Figure 3 In the closed-loop state, the absorbance gradually increases with time, as shown in the following results. Figure 4 .

[0135] Furthermore, the maximum absorbance of the rare-earth supramolecular light is 392 nm. Upon irradiation with 275 nm ultraviolet light, the absorbance of the rare-earth supramolecular light at 303 nm gradually decreases, while a new absorption peak appears at 392 nm, and the absorbance gradually increases. Subsequently, after continuous irradiation with 526 nm visible light for 50 minutes, the absorption spectrum of the rare-earth supramolecular light can still return to its initial state.

[0136] The open-ring and closed-ring states refer to different conformations of the same molecule. The closed-ring state refers to the molecule's conformation forming a ring-like structure.

[0137] 1.2. After repeated irradiation cycles, the changes in the ultraviolet-visible absorption spectrum of the photoresponsive rare-earth supramolecular molecules were detected to study their fatigue resistance. Results are shown below. Figure 5 It can be seen that no significant compatibility was observed in the UV spectrum after 10 ring switching conversions, indicating that the ligand compound of the present invention has good fatigue resistance.

[0138] 1.3. The photoresponsive rare-earth supramolecular solution was heated to 55℃ under light-steady conditions and held for 3 hours. The changes in the UV-Vis absorption spectrum were detected to study its stability. The results are shown in […]. Figure 6 As can be seen, its ultraviolet-visible absorption spectrum did not show significant changes, indicating that rare earth supramolecular molecules also have good thermal stability.

[0139] 1.4. A solution of the photoresponsive rare-earth supramolecular material was obtained by mixing it with acetonitrile. The emission spectrum change under 275 nm ultraviolet light irradiation was detected at the maximum excitation wavelength of 330 nm. The results are shown in […]. Figure 7 It can be seen that Eu 3+ The five characteristic emission peaks of the ions at 576, 592, 611, 651, and 702 nm correspond to... 5 D0 - 7 F J The transition (J=0-4) was observed, and after the solution was continuously irradiated with 275nm ultraviolet light for 15 minutes, the emission spectrum of the rare earth supramolecular showed a trend of gradually increasing emission, and the maximum value of the emission peak at 612nm reached about 1.7 times the initial emission intensity.

[0140] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing a photoresponsive rare-earth supramolecular, characterized in that, The photoresponsive rare-earth supramolecular has the structure shown in formula (II). Where Ln is Eu 3+ , The preparation method includes the following steps: 0.5 mmol of the compound represented by formula (E) was dissolved in a reaction flask containing 20 mL of anhydrous acetonitrile. 0.5 mmol of the compound represented by formula (I) was added to the solution, and the mixture was heated under reflux for 12 h. After the reaction was completed, the acetonitrile was removed by distillation to obtain the target compound, namely the compound represented by formula (II), with a yield of approximately 97%. （I）； （E）； In equation (E), Ln represents Eu. 3+ .

2. The preparation method according to claim 1, characterized in that, It also includes the following steps: The compound shown in formula (D) is oxidized in the presence of an oxidizing agent to obtain the compound shown in formula (I); （D）。 3. The preparation method according to claim 2, characterized in that, The compound represented by formula (D) is prepared by the following steps: (1) The compound shown in formula (A) is reacted with X-R1 in the presence of alkyllithium to give the compound shown in formula (B); wherein X is bromine or iodine and R1 is ethyl; (2) The compound shown in formula (B) is reacted with a brominating agent to obtain the compound shown in formula (C); (3) The compound shown in formula (C) was reacted with octafluorocyclopentene in the presence of alkyllithium to obtain the compound shown in formula (D); (A); (B); （C）。 4. The preparation method according to claim 3, characterized in that, In steps (1) and (3), the alkyl lithium is n-butyllithium.

5. The preparation method according to claim 3, characterized in that, In step (2), a mixture of glacial acetic acid and chloroalkanes is used as the reaction solvent; in steps (1) and (3), tetrahydrofuran is used as the reaction solvent.

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