Ligand compound, rare earth supramolecular sensing material, sensing film, fluorescent probe, and preparation method and use thereof

Abstract

The present invention discloses a ligand compound, a rare earth supramolecular sensing material, a sensing film, a fluorescent probe, and a preparation method and use thereof. The ligand compound has a structure as shown in formula (I), wherein R 1 is a trihalomethyl group; R 2 Selected from the structure shown in the following formula (II), where X is selected from at least one of oxygen and sulfur, and must contain oxygen. The ligand compound of the present invention can react with rare earth metal ions and be used to detect the content of heavy metal ions in water environments. #imgabs0#

Description

Technical Field

[0001] The present invention relates to a ligand compound, a rare earth supramolecular sensing material, a sensing film, a fluorescent probe, and a preparation method and application thereof. Background Art

[0002] Heavy metals include gold, silver, copper, iron, mercury, lead, and cadmium. In the context of environmental pollution, heavy metals primarily refer to heavy elements with significant biotoxicity, such as mercury, cadmium, lead, chromium, and the metalloid arsenic. Heavy metals are extremely difficult to biodegrade. Instead, they accumulate hundreds of times through biomagnification in the food chain, ultimately entering the human body. Within the body, heavy metals can strongly interact with proteins and enzymes, rendering them inactive. They can also accumulate in certain organs, causing chronic poisoning.

[0003] Cadmium is a highly toxic heavy metal, and most of its compounds are also toxic. Industrial wastewater containing cadmium pollutes rivers and farmland. Cadmium is more readily absorbed by crops, vegetables, and rice than other heavy metals. When people consume contaminated crops, cadmium enters the body through the digestive tract, where it accumulates primarily in the liver and kidneys, causing damage. Long-term exposure can affect the function of blood production, nerves, kidneys, and other organs, posing a serious health risk, especially to children. Cadmium is highly destructive to the human central nervous system. Once inside, cadmium poisoning is extremely difficult to excrete, and can easily interfere with kidney and reproductive function. Cadmium displaces calcium from bones, causing severe softening and fractures. It can also cause gastric dysfunction, reduce the zinc-to-cadmium ratio, and lead to elevated hypertension. "Itai-itai disease" is a typical example of chronic cadmium poisoning. Caused by cadmium contamination of the human living environment, it has a widespread impact, affecting numerous victims and has become recognized as a "public health hazard."

[0004] Furthermore, cadmium pollution is characterized by its long lifespan and hidden nature. Cadmium's toxicity is latent; even concentrations as low as 0.1 mg / L in drinking water can accumulate in human tissues, particularly in women, with an incubation period of 10 to 30 years, and it is difficult to detect in the early stages.

[0005] Currently, the accuracy and precision of traditional methods such as atomic absorption spectroscopy, atomic fluorescence spectroscopy, and inductively coupled plasma can meet the requirements and the technology is mature. However, the required detection is time-consuming, and the samples must be specially processed to reduce signal interference. The large experimental equipment required limits their use to scientific research institutions.

[0006] Crown ethers are a class of cyclic compounds composed of polyether units. They possess strong metal-chelating properties and can be used as metal ion scavengers. CN110394166A discloses a crown ether-based lignin-based adsorption material and its preparation method. The material is prepared using an amino crown ether compound and lignin as raw materials using a Mannich reaction. This adsorption material can be used in wastewater treatment containing heavy metal ions such as mercury, lead, and copper, as well as in water purification.

[0007] Researchers are concerned about how to capture heavy metal ions while identifying them through luminescence signals or changes in fluorescence intensity, thereby enabling qualitative or quantitative trace detection and analysis of heavy metal ions. CN109897317A discloses a cellulose nanocrystal-rare earth complex-polyvinyl alcohol composite hydrogel fluorescent probe. This patent document incorporates a rare earth europium complex into a reversibly cross-linked hydrogel to detect heavy metal ions in aqueous environments. The patent document utilizes a cellulose nanocrystal / polyvinyl alcohol composite gel to impart improved mechanical properties to the fluorescent probe and enable detection of heavy metal ions. Summary of the Invention

[0008] One object of the present invention is to provide a ligand compound that can form a rare earth supramolecular sensing material with rare earth metal ions, which is used for detecting the content of heavy metal ions in water environments, especially for trace analysis of cadmium ions with a low detection limit. Another object of the present invention is to provide a method for preparing the above-mentioned ligand compound. Another object of the present invention is to provide a rare earth supramolecular sensing material that has high sensitivity, low detection limit and good reproducibility when used for detecting the content of heavy metal ions, especially cadmium ions, in water environments. Another object of the present invention is to provide a method for preparing the rare earth supramolecular sensing material as described above. Another object of the present invention is to provide a use of the rare earth supramolecular sensing material as described above. Other objects of the present invention also include providing a sensing film and providing a fluorescent probe.

[0009] In one aspect, the present invention provides a ligand compound having a structure as shown in formula (I),

[0010]

[0011] In formula (I), R 1 is a trihalomethyl group; R 2 Selected from the structure shown in the following formula (II):

[0012]

[0013] In formula (II), X is at least one selected from oxygen and sulfur, and must contain oxygen.

[0014] According to the ligand compound of the present invention, preferably, it has a structure shown in the following formula:

[0015]

[0016] On the other hand, the present invention also provides a method for preparing the ligand compound as described above, comprising the following steps:

[0017] 1) subjecting the compound represented by formula (1c) to a bromine substitution reaction to obtain a compound represented by formula (1d);

[0018] 2) The compound represented by formula (1d) and HR 2 The raw materials react to obtain a compound represented by formula (1e);

[0019] 3) reacting the compound represented by formula (1e) with the compound represented by formula (IV) to obtain the ligand compound;

[0020]

[0021] In formula (IV), R 1 is a trihalomethyl group;

[0022] In formula (1e), R 2 Selected from the structure shown in the following formula (II):

[0023]

[0024] In formula (II), X is at least one selected from oxygen and sulfur, and must contain oxygen.

[0025] According to the preparation method of the present invention, preferably:

[0026] In step 1), the compound represented by formula (1c) is reacted with N-bromosuccinimide to obtain the compound represented by formula (1d);

[0027] In step 2), the compound represented by formula (1d) is reacted with HR 2 The compound is reacted in the presence of cesium carbonate to obtain a compound represented by formula (1e);

[0028] In step 3), the compound represented by formula (IV) is first reacted with sodium methoxide, and then the compound represented by formula (1e) is added to react to obtain the ligand compound.

[0029] According to the preparation method of the present invention, preferably, the following steps are further included:

[0030] i) reacting m-halotoluene with acetyl halide to form a compound represented by formula (1a);

[0031] ii) reacting acetyl-m-toluidine with acetyl halide to form a compound represented by formula (1b);

[0032] iii) reacting the compound represented by formula (1a) with the compound represented by formula (1b) to obtain the compound represented by formula (1c);

[0033]

[0034] In formula (1a), Y is bromine or iodine;

[0035] There is no particular order between step i) and step ii).

[0036] On the other hand, the present invention also provides a rare earth supramolecular sensing material, which is composed of the ligand compound as described above and rare earth metal ions RE 3+ Formation; wherein, rare earth metal ions RE 3+ Selected from Sm 3+ 、Eu 3+ , Tb 3+ 、Er 3+ He Lu 3+ At least one of .

[0037] In another aspect, the present invention further provides a method for preparing the rare earth supramolecular sensing material as described above, comprising the following steps:

[0038] The ligand compound according to claim 1 or 2 is dissolved in a C1-C3 alkyl alcohol, and then reacted with a rare earth chloride in the presence of an alkaline substance to obtain a rare earth supramolecular sensing material; wherein the alkaline substance is selected from triethylamine or pyridine.

[0039] In another aspect, the present invention further provides a use of the rare earth supramolecular sensing material as described above in detecting the content of heavy metal ions in a water environment, wherein the heavy metal ions include cadmium ions.

[0040] In yet another aspect, the present invention further provides a sensing film, which is formed by coating the rare earth supramolecular sensing material as described above on a substrate, and the thickness of the sensing film is less than 100 nm.

[0041] Finally, the present invention also provides a fluorescent probe, which is formed by the sensing film as described above.

[0042] The present invention uses tri-β-diketone with triphenylamine as a skeleton as a ligand, which can coordinate with rare earth metal ions (especially europium ions) to achieve rare earth metal ion fluorescence response, and introduces an aza-crown ether at the meta position of the amino group in the triphenylamine skeleton as a recognition group for heavy metal ions, which can capture heavy metal ions, especially cadmium ions. The coordination of nitrogen on the benzene ring and the ligand will affect the ligand's energy transfer to the rare earth metal ions (especially europium ions), resulting in fluorescence enhancement in the rare earth supramolecular sensing material of the present invention. The rare earth supramolecular sensing material of the present invention can realize the analysis of trace heavy metal ion content (especially cadmium ions) in water, can improve analysis efficiency, sensitivity and reproducibility, and has a low detection limit. The reaction conditions of the preparation method of the present invention are mild and safe. The product purity of the ligand compound and the rare earth supramolecular sensing material can reach more than 99.0%. The present invention can also prepare a nanoscale sensing film (film thickness <100 nm) by spin-coating the rare earth supramolecular sensing material onto a quartz sheet, and can utilize the gaps between the films to prepare a reversible fluorescent probe that can be used multiple times, thereby realizing the analysis of trace cadmium ion content, thereby improving efficiency and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Ultraviolet absorption spectra of the rare earth supramolecular sensing material prepared in Example 2 of the present invention capturing cadmium ions at different concentrations;

[0044] Figure 2 Fluorescence spectra of the rare earth supramolecular sensing material prepared in Example 2 of the present invention capturing cadmium ions at different concentrations;

[0045] Figure 3 This is a fluorescence intensity spectrum of the rare earth supramolecular sensing material prepared in Example 2 of the present invention at 616 nm after the concentration of different metal ions is increased 10 times under ultraviolet excitation wavelength.

[0046] Figure 4 This is the hydrogen spectrum of the intermediate compound 1e obtained in Example 1 of the present invention.

[0047] Figure 5 This is the hydrogen spectrum of the ligand compound obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0049] <Term Explanation>

[0050] In the present invention, Cm-Cn represents a group having m to n carbon atoms; for example, C1-C3 alkyl represents an alkyl group having 1 to 3 carbon atoms.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present 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 the event of a conflict, this specification and the definitions included therein shall prevail. In addition, materials, methods, preparation examples, and examples are exemplary only and are not intended to be limiting.

[0052] <Ligand Compound>

[0053] The ligand compound of the present invention can form a rare earth supramolecular sensing material with rare earth metal ions. The resulting rare earth supramolecular sensing material can be used to capture heavy metal ions, particularly cadmium ions, in water. It can be used for microanalysis of heavy metal ions in aqueous environments. The fluorescence response value can be used to determine the heavy metal ion content.

[0054] The ligand compound of the present invention has a structure shown in formula (I):

[0055]

[0056] In formula (I), R 1 It is a trihalomethyl group, for example, trifluoromethyl, trichloromethyl, tribromomethyl, preferably trifluoromethyl.

[0057] R 2 Selected from the structure shown in the following formula (II):

[0058]

[0059] In formula (II), X is at least one selected from oxygen and sulfur, and must contain oxygen.

[0060] In certain embodiments, all X are oxygen. In other embodiments, some X are oxygen and some X are sulfur.

[0061] According to one embodiment of the present invention, R in the structure shown in formula (I) 1 is a trifluoromethyl group, in formula (II), all X are oxygen, and the ligand compound of the present invention has the following structure:

[0062]

[0063] After extensive research, the inventors of this application discovered that tri-β-diketones with a triphenylamine backbone can act as ligands to coordinate with rare earth metal ions (particularly europium ions) to achieve a fluorescent response. Furthermore, an azacrown ether introduced at the meta position of the amine group within the triphenylamine backbone acts as a recognition group for heavy metal ions, enabling the capture of heavy metal ions, particularly cadmium ions. The coordination of the nitrogen on the benzene ring with the ligand affects the energy transfer from the ligand to the rare earth ion, resulting in fluorescence enhancement in this rare earth supramolecular sensing material.

[0064] By introducing an azacrown ether as a heavy metal ion recognition group at the meta position of the amine group in the triphenylamine backbone synthesized by this invention, the resulting rare earth supramolecular sensing material produces a fluorescent response to heavy metal ions, particularly cadmium ions. However, when the concentration of captured heavy metal ions (especially cadmium ions) reaches a certain level, fluorescence attenuation or fluorescence quenching occurs. This rare earth supramolecular sensing material can produce fluorescence of varying intensities in samples with varying ion concentrations, which can be detected using a fluorescence instrument.

[0065] <Method for Preparing Ligand Compound>

[0066] The present invention also provides a method for preparing the above-mentioned ligand compound, which comprises: 1) a step of synthesizing a compound represented by formula (1d); 2) a step of synthesizing a compound represented by formula (1e); and 3) a step of synthesizing a ligand compound. Optionally, the method further comprises: i) a step of synthesizing a compound represented by formula (1a); ii) a step of synthesizing a compound represented by formula (1b); and iii) a step of synthesizing a compound represented by formula (1c). Steps i) and ii) are not performed in any particular order. A detailed description is provided below.

[0067] Synthesis steps of the compound represented by formula (1a)

[0068] This is the synthesis step of intermediate 1a. Meta-halotoluene is reacted with acetyl halide to form a compound represented by formula (1a).

[0069] Wherein, Y is bromine or iodine.

[0070] The m-halotoluene can be m-chlorotoluene, m-bromotoluene or m-iodotoluene, preferably m-iodotoluene. The acetyl halide can be acetyl chloride or acetyl bromide, preferably acetyl chloride.

[0071] According to one embodiment of the present invention, meta-halogenated toluene is dissolved in 1,2-dichloroethane solvent to form a first solution; acetyl halide and anhydrous aluminum chloride are added to 1,2-dichloroethane solvent to form a second solution; the second solution is added to the first solution and reacted under an ice bath. After the reaction is completed, the reaction system is quenched in ice water, allowed to stand and separate, the organic layer is collected, and the aqueous layer is extracted with dichloromethane or chloroform. The organic phases are combined. The combined organic phase is washed with water until neutral, and then the organic phase is dried and concentrated to obtain a concentrate, which is subjected to column chromatography (the eluent for column chromatography is petroleum ether / ethyl acetate) to obtain an oily liquid, which is the compound shown in formula (1a).

[0072] The molar ratio of meta-halotoluene to acetyl halide can be 1:1.9 to 2.1, preferably 1:2.0 to 2.02. The molar ratio of meta-halotoluene to anhydrous aluminum chloride can be 1:1.9 to 2.1, preferably 1:2.0 to 2.03.

[0073] According to one embodiment of the present invention, the meta-halotoluene is meta-iodotoluene, and the acetyl halide is acetyl chloride, and the reaction equation is as follows:

[0074]

[0075] Synthesis steps of the compound represented by formula (1b)

[0076] This is the synthesis step of intermediate 1b: Acetyl-m-toluidine is reacted with acetyl halide to form a compound represented by formula (1b).

[0077]

[0078] The acetyl halide may be acetyl chloride or acetyl bromide, preferably acetyl chloride.

[0079] According to one embodiment of the present invention, acetyl-m-toluidine is dissolved in 1,2-dichloroethane solvent to obtain a third solution; acetyl halide and anhydrous aluminum chloride are dissolved in 1,2-dichloroethane solvent to obtain a fourth solution. The fourth solution is added to the third solution in batches, heated under reflux for reaction, and after completion of the reaction, the reaction system is poured into ice water to quench, and dilute hydrochloric acid is added to adjust the pH to 2-3, and stirred at room temperature for 1-1.5 hours. The pH is then adjusted to a weak alkaline state, the solution is allowed to stand for separation, the organic layer is collected, and the aqueous layer is extracted with dichloromethane or chloroform. The organic phases are combined. The organic phases are dried and concentrated to obtain a concentrate. The concentrate is subjected to column chromatography (the eluent used for column chromatography is petroleum ether / ethyl acetate) to obtain an oily liquid. This is the compound represented by formula (1b).

[0080] The molar ratio of acetyl-meta-toluidine to acetyl halide is 1:2.2 to 2.6, preferably 1:2.4 to 2.55. The molar ratio of acetyl halide to anhydrous aluminum chloride is 1:1.

[0081] According to a specific embodiment of the present invention, the specific reaction equation is as follows:

[0082]

[0083] Synthesis steps of the compound represented by formula (1c)

[0084] This is the synthesis step of intermediate 1c. The compound represented by formula (1a) is reacted with the compound represented by formula (1b) to obtain the compound represented by formula (1c).

[0085]

[0086] In this step, the solvent is 1,2-o-dichlorobenzene, and copper powder, 18-crown-6 and potassium carbonate are used as reaction aids. Specifically, copper powder is a catalyst, 18-crown-6 is a phase transfer catalyst, and potassium carbonate is an alkaline reagent.

[0087] In certain embodiments, intermediates 1a and 1b are dissolved in 1,2-o-dichlorobenzene under an inert gas atmosphere. Copper powder, 18-crown-6, and potassium carbonate are added to the solution and heated under reflux for 18 to 32 hours. After the reaction, the solid-liquid separation is performed, the solid is removed, and the mother liquor is washed with ammonia and then with water. The organic layer is collected. The organic layer is dried and concentrated to obtain a concentrate, which is then separated by column chromatography (eluent: petroleum ether / ethyl acetate, volume ratio = 5:1) to obtain a solid. This is the compound represented by formula (1c).

[0088] The molar ratio of intermediate 1a to intermediate 1b may be 2.1 to 2.6:1, preferably 2.4 to 2.6:1, and more preferably 2.5 to 2.55:1.

[0089] The molar ratio of copper powder to intermediate 1b can be 8 to 11:1, preferably 9.5 to 10.5:1, and more preferably 9.9 to 10.1:1. The molar ratio of 18-crown-6 to intermediate 1b can be 0.05 to 0.07:1, preferably 0.06 to 0.07:1. The molar ratio of potassium carbonate to intermediate 1b can be 1.4 to 1.6:1, preferably 1.48 to 1.55:1, and more preferably 1.49 to 1.51:1.

[0090] Synthesis steps of the compound represented by formula (1d)

[0091] This is the synthesis step of intermediate 1d. The compound represented by formula (1c) is subjected to bromine substitution reaction to obtain the compound represented by formula (1d).

[0092]

[0093] In the present invention, the bromine-substituting reagent is NBS (N-bromosuccinimide).

[0094] In certain embodiments, intermediate 1c is dissolved in acetonitrile to obtain an acetonitrile solution, to which NBS is added portionwise. After the addition is complete, the reaction is continued with stirring at room temperature for 18 to 36 hours. After the reaction is complete, the mixture is reduced with sodium thiosulfate and then extracted multiple times with ethyl acetate. The organic layer is collected, dried, filtered, and concentrated, and the concentrate is recrystallized to obtain a solid, i.e., the compound represented by formula (1d).

[0095] The molar ratio of intermediate 1c to NBS can be 1:3.1 to 3.5, preferably 1:3.2 to 3.4, and more preferably 1:3.3 to 3.35. The solvent for recrystallization is ethanol.

[0096] Synthesis steps of the compound represented by formula (1e)

[0097] That is the synthesis step of intermediate 1e. 2 Reaction to obtain the compound represented by formula (1e). Specifically, the compound represented by formula (1d) is reacted with HR 2 The reaction is carried out in the presence of cesium carbonate to obtain a compound represented by formula (1e).

[0098]

[0099] HR 2 The structural formula is as follows:

[0100]

[0101] Wherein, X is selected from at least one of oxygen and sulfur, and must contain oxygen.

[0102] In certain embodiments, HR 2 A mixture of the raw materials and cesium carbonate is heated to reflux in anhydrous acetone under inert gas protection for 1 to 1.5 hours, and then the compound represented by formula (1d) is added to the reaction system, and the reflux reaction is continued for 24 to 38 hours. After the reaction is completed, the temperature is lowered, and the reaction solution is poured into ice water for quenching, and solid-liquid separation is performed to obtain a solid crude product. The solid crude product is separated by column chromatography (petroleum ether / ethyl acetate, volume ratio of the two = 1:3) to obtain a solid product, that is, the compound represented by formula (1e).

[0103] The compound represented by formula (1d) and HR 2 The molar ratio of the raw materials may be 1:3-15, preferably 1:3.2-10, and more preferably 1:3.5-5.

[0104] According to a specific embodiment of the present invention, HR2 The starting material is aza-15-crown-5.

[0105] Synthesis steps of ligand compounds

[0106] The compound represented by formula (1e) is reacted with the compound represented by formula (IV) to obtain the ligand compound. Specifically, the compound represented by formula (IV) is first reacted with sodium methoxide, and then the compound represented by formula (1e) is added to react to obtain the ligand compound.

[0107]

[0108] In formula (IV), R 1 It is a trihalomethyl group, preferably a trifluoromethyl group.

[0109] In certain embodiments, sodium methoxide and the compound represented by formula (IV) are dissolved in DME (N,N-dimethylacetamide) to obtain a DME solution; the compound represented by formula (1e) is added to the DME solution and reacted at room temperature for 18 to 36 hours. After the reaction is completed, the pH value of the reaction system is adjusted to 2 to 3 with dilute hydrochloric acid, and a precipitate is precipitated. The precipitate is filtered, and the filter cake is washed with water. The washed filter cake is dried to obtain a ligand compound.

[0110] In the present invention, the molar ratio of the compound represented by formula (1e) to the compound represented by formula (IV) may be 1:3.5 to 6.5, preferably 1:4.5 to 6.5, and more preferably 1:5.5 to 6.0.

[0111] The molar ratio of the compound represented by formula (IV) to sodium methoxide may be 1:1.0 to 1.2, preferably 1:1.0 to 1.1, and more preferably 1:1.0 to 1.05.

[0112] In the present invention, anhydrous sodium sulfate can be used to dry the organic phase.

[0113] <Rare Earth Supramolecular Sensing Materials>

[0114] The rare earth supramolecular sensing material of the present invention is composed of the ligand compound and the rare earth metal ion RE 3+ Formation; among them, RE 3+ Selected from Sm 3+ 、Eu 3+ , Tb 3+ 、Er 3+ He Lu 3+ At least one of. Preferably, RE 3+ Selected from Sm 3+ 、Eu 3+ 、Tb 3+ 、Er 3+ He Lu 3+More preferably, RE 3+ Selected from Sm 3+ 、Eu 3+ 、Tb 3+ 、Er 3+ More preferably, RE 3+ For Eu 3 + .

[0115] The rare earth supramolecular sensing material of the present invention can capture heavy metal ions, particularly cadmium ions, in water. It can analyze trace amounts of cadmium ions, significantly improving efficiency, sensitivity, and reproducibility. Heavy metal ions can be identified and trace amounts detected through changes in fluorescence intensity. The rare earth supramolecular sensing material of the present invention has excellent applicability for detecting heavy metal ions, particularly cadmium ions.

[0116] According to a specific embodiment of the present invention, R 1 is trifluoromethyl, R 2 is an aza-15-crown-5 substituent, RE 3+ For Eu 3+ The rare earth supramolecular sensing material of the present invention has the structure shown below (simulated tetrahedral structure):

[0117]

[0118] <Preparation Method of Rare Earth Supramolecular Sensing Material>

[0119] The preparation method of the rare earth supramolecular sensing material of the present invention comprises the following steps: dissolving the rare earth supramolecular sensing material ligand described above in C1-C3 alkyl alcohol, and then reacting with rare earth chloride in the presence of an alkaline reagent to obtain the rare earth supramolecular sensing material.

[0120] In the present invention, the C1-C3 alkyl alcohol may be methanol, ethanol or isopropanol, preferably ethanol. The alkaline agent may be triethylamine or pyridine, preferably triethylamine. The rare earth chloride may be a rare earth chloride containing water of crystallization.

[0121] <Purpose>

[0122] The present invention also provides a use of the rare earth supramolecular sensing material described above in detecting the content of heavy metal ions in a water environment, wherein the heavy metal ions include cadmium ions.

[0123] Preferably, the heavy metal ions are cadmium ions.

[0124] <Sensing Film>

[0125] The present invention also provides a sensing film, which is formed by coating (preferably spin-coating) the rare earth supramolecular sensing material described above on a substrate, wherein the thickness of the sensing film is less than 100 nm. The substrate may be a quartz sheet.

[0126] <Fluorescent Probe>

[0127] The present invention also provides a fluorescent probe, which is formed by the above-mentioned sensing film. The gaps between the films can be used to make a reversible fluorescent probe that can be used multiple times and is suitable for continuous detection of heavy metal ion concentrations in various environments.

[0128] Example 1

[0129] Reaction equation:

[0130]

[0131] The structural formula of Aza-15-Crown-5 (Chinese name: Aza-15-Crown-5) is as follows:

[0132]

[0133] Synthesis of intermediate 1a:

[0134] Dissolve meta-iodotoluene (5.00 g, 22.93 mmol) in 120 mL of 1,2-dichloroethane, then add acetyl chloride (3.60 g, 45.86 mmol) and anhydrous aluminum chloride (6.12 g, 45.86 mmol) to 60 mL of 1,2-dichloroethane. Stir at room temperature for 10 minutes until the anhydrous aluminum chloride is completely dissolved, then slowly add it dropwise to the meta-iodotoluene solution. Stir in an ice bath for 12 hours. After the reaction is completed by monitoring by TLC, the reaction solution is poured into ice water and allowed to stand for separation. The aqueous layer is extracted with dichloromethane, the organic phases are combined, washed repeatedly with water until neutral, and then dried over anhydrous sodium sulfate. The solvent is removed and the residue is separated by silica gel column chromatography. 2.88 g of a light yellow oily liquid is obtained with a yield of 48.37%. The compound represented by formula (1a) is obtained.

[0135] Synthesis of intermediate 1b:

[0136] Acetyl-m-toluidine (4.00 g, 26.81 mmol) was dissolved in 150 mL of 1,2-dichloroethane. Acetyl chloride (5.26 g, 67.02 mmol) and anhydrous aluminum chloride (8.94 g, 67.02 mmol) were then added to 80 mL of 1,2-dichloroethane. The mixture was stirred at room temperature for 10 minutes until the anhydrous aluminum chloride was completely dissolved, after which it was added portionwise to the acetyl-m-toluidine solution. The mixture was heated under reflux for 4 hours. The reaction solution was poured into ice water, and dilute hydrochloric acid was added to adjust the pH of the mixture to 2-3. The mixture was stirred at room temperature for 1 hour. The pH of the mixture was then adjusted to a weak alkaline state. The mixture was allowed to stand and separate. The aqueous layer was extracted with dichloromethane, and the organic phases were combined and dried over anhydrous sodium sulfate. The solvent was removed, and the residue was separated by silica gel column chromatography. 2.12 g of a light yellow oily liquid was obtained with a yield of 53.00%. This gave the compound represented by formula (1b).

[0137] Synthesis of intermediate 1c:

[0138] The resulting intermediate 1a compound (17.44 g, 67.07 mmol) and the resulting intermediate 1b compound (4.00 g, 26.83 mmol) were dissolved in 100 mL of 1,2-o-dichlorobenzene under nitrogen. Copper powder (17.05 g, 268.28 mmol), 18-crown-6 (0.43 g, 1.61 mmol), and K2CO3 (5.56 g, 40.24 mmol) were added to the solution and heated under reflux for 24 h. After the reaction, the solid was removed by filtration, and the filtrate was washed with dilute ammonia until colorless, then repeatedly washed with water several times. The organic layer was dried over anhydrous sodium sulfate, and the solvent was removed by distillation under reduced pressure to obtain a brown-black solid. The crude product was separated by silica gel column chromatography (petroleum ether / ethyl acetate volume ratio = 5:1) to obtain 8.78 g of a white solid. The yield was 79.22%. This gave the compound represented by formula (1c).

[0139] Synthesis of intermediate 1d:

[0140] The resulting intermediate 1c (5.00 g, 12.10 mmol) was dissolved in 150 mL of acetonitrile. 7.11 g (39.93 mmol) of NBS (N-bromosuccinimide) reagent was added portionwise to the stirring reaction mixture at room temperature. The reaction was stirred at room temperature for 24 hours. After the reaction was complete, sodium thiosulfate solution was added to reduce the Br2 produced. The mixture was then extracted with ethyl acetate (4 x 50 mL), and the organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated. The crude product was recrystallized from ethanol to obtain 4.86 g of a light yellow solid. The yield was 61.73%. This gave the compound represented by formula (1d).

[0141] Synthesis of intermediate 1e:

[0142] A mixture of aza-15-crown-5 (1.00 g, 4.56 mmol) and Cs2CO3 (2.23 g, 6.84 mmol) was heated to reflux for 1 h in 320 mL of anhydrous acetone under nitrogen protection. The obtained intermediate 1d compound (0.74 g, 1.10 mmol) was then added and refluxed for 36 h. After reflux, the reaction temperature was lowered and the reaction solution was poured into ice water to obtain a large amount of off-white solid, which was filtered off under reduced pressure to obtain an off-white solid. The crude product was separated by silica gel column chromatography (volume ratio of petroleum ether / ethyl acetate = 1:3) to obtain 0.66 g of a light yellow solid. The yield was 54.31%. The hydrogen spectrum of intermediate 1e is shown in FIG. Figure 4 .

[0143] Synthesis of ligand compound Ⅰ:

[0144] Sodium methoxide (0.30 g, 5.64 mmol) and ethyl trifluoroacetate (i.e., the compound represented by Formula IV, 0.80 g, 5.64 mmol) were dissolved in 30 mL of DME. The resulting intermediate 1e compound (1.00 g, 0.94 mmol) was then added to the above solution and stirred at room temperature for 24 hours. After the reaction was complete, the pH of the reaction solution was adjusted to 2-3 with dilute hydrochloric acid to produce a large amount of yellow precipitate. The precipitate was filtered and washed with water several times, and then dried to obtain 1.21 g of a yellow solid. The product did not require further purification. The yield was 95.23%. The ligand compound I was obtained. Its hydrogen spectrum is shown in FIG. Figure 5 .

[0145] Example 2

[0146] Reaction equation:

[0147]

[0148] The resulting ligand compound represented by formula (I) (0.68 g, 0.50 mmol) was added to 20 mL of methanol, followed by triethylamine (0.20 g, 2.00 mmol). The mixture was stirred thoroughly until the ligand was completely dissolved. A methanol solution of europium chloride hexahydrate (EuCl3·6H2O) (0.06 g, 0.17 mmol) was then added, and the mixture was allowed to react at room temperature for 24 hours. After the reaction was complete, the reaction solution was filtered, and the resulting filtrate was added to water to precipitate a yellow precipitate, which was then filtered and dried under vacuum to obtain a rare earth supramolecular sensing material.

[0149] Application Example 1-Ultraviolet absorption spectrum test

[0150] Prepare 9 different concentrations (10 -9 M to 10 -1M) cadmium ion solution. Take 0.02g of the rare earth supramolecular sensing material prepared in Example 2 above and dissolve it in 2ml of N,N-dimethylformamide (DMF) solution. 3mL of several cadmium ion solutions were mixed with the DMF solution of the rare earth supramolecular sensing material and ultrasonicated for 20min. Ultraviolet absorption spectrum test was performed on 9 solutions with different concentrations. The test results are as follows Figure 1 As shown. Figure 1 It can be seen that the rare earth supramolecular sensing material of the present invention has the ability to capture cadmium ions. The absorbance at a wavelength of 260nm is related to the concentration of cadmium ions. The higher the concentration of cadmium ions, the higher the absorbance at a wavelength of 260nm. Overall, the absorption intensity of cadmium ions is very low, with a very weak absorption peak near 260nm only when the concentration of the prepared cadmium ion solution reaches 0.1M. This may be the main reason why cadmium ions are not easily affected by the fluorescence of rare earth supramolecular sensing materials.

[0151] Application Example 2-Fluorescence Test

[0152] Prepare 9 different concentrations (10 -9 M to 10 -1 M) cadmium ion solution. Take 0.02g of the rare earth supramolecular sensing material prepared in Example 2 above and dissolve it in 2ml of N,N-dimethylformamide solution. 3mL of the several cadmium ion solutions were mixed with the DMF solution of the rare earth supramolecular sensing material and ultrasonicated for 20min. Fluorescence capture tests were performed on 9 solutions of different concentrations. The test results are shown in Figure 2. Figure 2 As shown in the figure, the present invention specifically lists the highest fluorescence intensities corresponding to different concentrations of cadmium ion solutions, as shown in Table 1. The results show that only when the concentration of the prepared cadmium ion solution reaches 0.1M will cadmium ions significantly weaken the fluorescence of the rare earth supramolecular sensing material.

[0153] Table 1

[0154] <![CDATA[10 -1 M]]> <![CDATA[10 -2 M]]> <![CDATA[10 -3 M]]> <![CDATA[10 -4 M]]> <![CDATA[10 -5 M]]> <![CDATA[10 -6 M]]> <![CDATA[10 -7 M]]> <![CDATA[10 -8 M]]> <![CDATA[10 -9 M]]> Wavelength / nm 611.97 610.81 611.43 611.97 611.97 611.43 611.43 611.43 611.97 Maximum strength 21533.57 116050.58 115611.48 115172.37 114952.82 116526.27 115611.48 114294.17 114952.82

[0155] Application Example 3-Fluorescence Test under Different Metal Ions

[0156] Prepare 1×10 -23 ml of each of the N,N-dimethylformamide solutions of various metal hydrochlorides (including AlCl, CdCl, CoCl, LaCl, MnCl, NiCl, PbCl, and ZnCl) was added to 5 mg of the rare earth supramolecular sensing material solid prepared according to Example 2 to obtain a solution of the rare earth supramolecular sensing material and metal ions. The solution was sonicated for 20 minutes and then allowed to stand for 12 hours. Fluorescence measurements were performed at an excitation wavelength of 298 nm, with an excitation slit of 2.5 nm and an emission slit of 1.5 nm. The results showed that, with the exception of the cadmium ion solution, all other metal ions significantly weakened or even quenched the fluorescence of the rare earth supramolecular sensing material. Therefore, the rare earth supramolecular sensing material of the present invention exhibited a significant fluorescence detection effect for the severely toxic heavy metal cadmium ion. This demonstrates that the rare earth supramolecular sensing material prepared by the present invention can achieve the function of fluorescent recognition of heavy metal cadmium ions.

[0157] Application Example 4-Fluorescence Test under Different Concentrations of Metal Ions

[0158] Prepare 1×10 -1 N,N-dimethylformamide solution of various metal hydrochlorides of M, including AlCl3, CdCl2, CoCl2, LaCl3, MnCl2, NiCl2, PbCl2, and ZnCl2, was taken. 3 ml of each solution was added to 5 mg of the rare earth supramolecular sensing material solid prepared in Example 2 to obtain a solution of rare earth supramolecular sensing material and metal ions. The solution was ultrasonicated for 20 minutes and then allowed to stand for 12 hours. Fluorescence testing was carried out at an excitation wavelength of 298 nm, an excitation slit of 2.5 nm, and an emission slit of 1.5 nm. The results are shown in FIG. Figure 3 (The left column of the same metal ion represents 10 -2 The fluorescence intensity of M, the right column represents 10 -1 The results show that when the concentration of each metal ion increases 10 times (1×10 -1 M), except for cadmium ions, other metal ions quench the fluorescence of the rare earth supramolecular sensing material. The rare earth supramolecular sensing material of the present invention realizes the function of fluorescent recognition of cadmium ions.

[0159] Based on the above analysis, the trace concentration of cadmium ions has little effect on the fluorescence intensity of the rare earth supramolecular sensing material, while the other metal ions significantly reduce or quench the fluorescence of the rare earth supramolecular sensing material. When the concentration of the prepared metal ions increases by 10 times (from 10 -2 M increased to 10 -1 M), except for cadmium ions, all other metal ions quench the fluorescence of the rare earth supramolecular sensing material. This phenomenon shows that the rare earth supramolecular sensing material prepared by the present invention can realize the function of fluorescent recognition of heavy metal cadmium ions, and the detection limit is low, which can reach 10-9 Below M.

[0160] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A ligand compound, characterized in that It has a structure as shown in formula (I), In formula (I), R 1 is a trihalomethyl group; R 2 Selected from the structure shown in the following formula (II): In formula (II), X is at least one selected from oxygen and sulfur, and must contain oxygen.

2. The ligand compound according to claim 1, characterized in that It has the structure shown below:

3. The method for preparing the ligand compound according to claim 1, wherein The steps include: 1) subjecting the compound represented by formula (1c) to a bromine substitution reaction to obtain a compound represented by formula (1d); 2) The compound represented by formula (1d) and HR 2 The raw materials react to obtain a compound represented by formula (1e); 3) reacting the compound represented by formula (1e) with the compound represented by formula (IV) to obtain the ligand compound; In formula (IV), R 1 is a trihalomethyl group; In formula (1e), R 2 Selected from the structure shown in the following formula (II): In formula (II), X is at least one selected from oxygen and sulfur, and must contain oxygen.

4. The preparation method according to claim 3, wherein: In step 1), the compound represented by formula (1c) is reacted with N-bromosuccinimide to obtain the compound represented by formula (1d); In step 2), the compound represented by formula (1d) is reacted with HR 2 The compound is reacted in the presence of cesium carbonate to obtain a compound represented by formula (1e); In step 3), the compound represented by formula (IV) is first reacted with sodium methoxide, and then the compound represented by formula (1e) is added to react to obtain the ligand compound.

5. The preparation method according to claim 3, characterized in that The following steps are also included: i) reacting m-halotoluene with acetyl halide to form a compound represented by formula (1a); ii) reacting acetyl-m-toluidine with acetyl halide to form a compound represented by formula (1b); iii) reacting the compound represented by formula (1a) with the compound represented by formula (1b) to obtain the compound represented by formula (1c); In formula (1a), Y is bromine or iodine; There is no particular order between step i) and step ii).

6. A rare earth supramolecular sensing material, characterized in that: The ligand compound according to claim 1 or 2 and the rare earth metal ion RE 3+ Formation; wherein, rare earth metal ions RE 3+ For Eu 3+ .

7. The method for preparing the rare earth supramolecular sensing material according to claim 6, wherein: The steps include: The ligand compound according to claim 1 or 2 is dissolved in a C1-C3 alkyl alcohol, and then reacted with a rare earth chloride in the presence of an alkaline substance to obtain a rare earth supramolecular sensing material; wherein the alkaline substance is selected from triethylamine or pyridine.

8. Use of the rare earth supramolecular sensing material according to claim 6 for detecting the content of heavy metal ions in a water environment, characterized in that: The heavy metal ions are cadmium ions.

9. A sensing film, characterized in that: It is formed by coating the rare earth supramolecular sensing material according to claim 6 on a substrate, and the thickness of the sensing film is less than 100 nm.

10. A fluorescent probe, characterized in that The sensor film is formed by the sensor film according to claim 9.

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