A metal cage, ligand and preparation method and application thereof

Abstract

The application provides a metal cage, a ligand and a preparation method and application thereof, relates to the technical field of metal-organic materials, and the structural formula of the metal cage is shown as formula (II). The metal cage provided by the application is asymmetric in structure, has a large cavity size, and is stable in property. The large cavity size and good water solubility of the metal cage can efficiently and accurately recognize and effectively wrap liposoluble dyes, and then the dyes are separated and released from the main body, and the metal cage has excellent regeneration performance and cycle use stability, can realize selective capture and controllable transport of liposoluble dyes, and provides a novel and efficient molecular carrier for the fields of dye separation and purification, environmental pollutant removal and the like.

Description

Technical Field

[0001] This invention relates to the field of metal-organic materials technology, and in particular to a metal cage, ligand, preparation method and application thereof. Background Technology

[0002] Supramolecular coordination compounds have attracted much attention due to their unique structures, distinctive properties, and potential applications. Especially since the 1980s, countless supramolecular chemists have dedicated themselves to designing and synthesizing novel and functionally unique supramolecular coordination compounds. Designing and synthesizing novel and functionally unique supramolecular coordination compounds is one of the important research directions in supramolecular chemistry.

[0003] Because of their high lipid solubility, lipid-soluble dyes may cross the blood-brain barrier and affect the nervous system. If we consume these contaminated plants and animals without knowing the risks, it could have serious consequences and even pose a genetic risk.

[0004] In existing technologies, the separation and removal of lipid-soluble dyes often employs traditional adsorption materials such as activated carbon, diatomaceous earth, silica gel, and resins. However, these traditional adsorption materials suffer from inherent drawbacks in practical applications, including limited adsorption capacity, single adsorption sites, and poor selective recognition of lipid-soluble dyes. This makes it difficult to achieve specific capture and efficient enrichment of target lipid-soluble dyes in complex systems. Furthermore, traditional adsorption materials generally suffer from poor chemical stability, easily experiencing structural collapse, swelling, or decomposition in real-world environments, leading to rapid degradation of adsorption performance. In addition, after adsorption, traditional adsorption materials typically face difficulties in desorption, demanding regeneration conditions, and extremely low recycling rates, failing to meet the practical requirements for efficient, stable, green, and sustainable separation and treatment of lipid-soluble dyes. This severely limits their large-scale application in the precise removal of lipid-soluble dyes from complex systems.

[0005] Therefore, developing a new type of adsorbent material with high adsorption capacity, high selectivity, high stability, easy regeneration and recyclability to achieve specific recognition, efficient capture and complete separation of lipid-soluble dyes has become a key technical problem that urgently needs to be solved in the fields of environmental governance, food safety and separation materials. Summary of the Invention

[0006] This invention provides a metal cage, ligand, preparation method, and application thereof to address the shortcomings of traditional adsorption materials in the prior art, such as limited adsorption capacity, poor selectivity, poor stability, and low recycling rate. It provides a metal cage with asymmetrical structure, large cavity, and stable properties, thereby achieving efficient and accurate recognition and capture of dye molecules.

[0007] In a first aspect, the present invention provides a metal cage, the chemical formula of which is: L4(bpyPd)10 (X) 12 ;

[0008] The structural formula of L is shown in equation (Ⅰ):

[0009] (Ⅰ);

[0010] bpy is 2-2' bipyridine;

[0011] The structure of the metal cage is shown in the following formula (Ⅱ):

[0012] (II);

[0013] in,

[0014] X is the equilibrium anion.

[0015] The metal cage provided by this invention is a palladium-containing metal cage based on pyrazolium pyridine ligands. The transition metal palladium has a moderate atomic radius and a planar square coordination mode, giving the metal cage exceptional stability and functional diversity, largely avoiding side reactions. Furthermore, palladium has low toxicity and a relatively low price. The metal cage provided by this invention has a large cavity size and good water solubility, enabling efficient and precise identification and effective encapsulation of lipid-soluble dyes, which are then separated and released from the host.

[0016] Preferably, X is hexafluorophosphate.

[0017] A second aspect of the present invention provides a method for preparing a metal cage, comprising:

[0018] Will The metal cage was prepared by solution self-assembly of the (2-2'-bipyridine)palladium complex;

[0019] The structural formula of the (2-2'-bipyridine)palladium complex is shown in the following formula (Ⅲ):

[0020] (III);

[0021] in,

[0022] Y represents the equilibrium anion.

[0023] As a preferred option The molar ratio of the (2-2'-bipyridine)palladium complex is 2:(4.8~5.5), for example, it can be 2:4.8, 2:4.9, 2:5.0, 2:5.1, 2:5.2, 2:5.3, 2:5.4, 2:5.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable; more preferably, it is 2:(4.8~5.2).

[0024] More preferably, The molar ratio of the (2-2'-bipyridine)palladium complex is 2:5.

[0025] Preferably, when the equilibrium anion of the metal cage is hexafluorophosphate, Y is nitrate, and the solution undergoes an anion exchange reaction after self-assembly to obtain a metal cage with hexafluorophosphate as the equilibrium anion.

[0026] Preferably, the solvent used in the solution self-assembly reaction is water, and the temperature of the solution self-assembly reaction is 45~65℃, for example, 45℃, 47℃, 50℃, 52℃, 55℃, 57℃, 60℃, 63℃, 65℃, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the method for preparing the metal cage includes:

[0028] Will The (2-2'-bipyridine)palladium complex was reacted with water in a molar ratio of 2:(4.8~5.5) at 45~65°C via solution self-assembly followed by an anion exchange reaction to obtain a metal cage with hexafluorophosphate as the equilibrium anion.

[0029] The structural formula of the (2-2'-bipyridine)palladium complex is shown in the following formula (Ⅲ):

[0030] (III);

[0031] in,

[0032] Y represents nitrate.

[0033] Preferably, the solution self-assembly reaction time is 3 to 5 hours, for example, 3 hours, 3.3 hours, 3.5 hours, 3.7 hours, 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the solution self-assembly reaction is carried out at a temperature of 45°C for 4 hours.

[0035] Preferably, the solvent used in the solution self-assembly reaction is deionized water or deuterated water.

[0036] A third aspect of the present invention provides a ligand having the structural formula shown in formula (Ⅰ):

[0037] (I).

[0038] A fourth aspect of the present invention provides a method for preparing a ligand, comprising the following steps:

[0039] S1. Compound A was prepared by coupling 2,4,6-tribromopyridine and 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole (1-THP-4-pyrazoleboronic acid pinacol ester, CAS No.: 1003846-21-6) via the Suzuki–Miyaura reaction;

[0040] S2. The ligand is prepared by coupling compound A with 4-pyridineboronic acid pinacol ester via a Suzuki–Miyaura coupling reaction followed by hydrolysis protection.

[0041] The synthetic route for the ligand is as follows:

[0042] .

[0043] Preferably, the molar ratio of 2,4,6-tribromopyridine to 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole is 1:(2~2.2), which can improve the yield of the ligand.

[0044] More preferably, the molar ratio of 2,4,6-tribromopyridine to 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole is 1:2.

[0045] Preferably, the molar ratio of compound A to pinacol 4-pyridineboronic acid is 1:(1.1~1.2).

[0046] More preferably, the molar ratio of compound A to pinacol 4-pyridineboronic acid is 1:1.1.

[0047] Preferably, the solvent used in the Suzuki–Miyaura coupling reaction is selected from a mixed solvent of 1,4-dioxane and water, or a mixed solvent of n-butanol and water.

[0048] Preferably, the volume ratio of 1,4-dioxane to water in the mixed solvent of 1,4-dioxane and water is (6~8):1.

[0049] Preferably, the volume ratio of n-butanol to water in the mixed solvent of n-butanol and water is (6~8):1.

[0050] Preferably, the temperature of the Suzuki–Miyaura coupling reaction is 100~120°C. Controlling the reaction temperature within this range can improve the yield of the ligand.

[0051] Preferably, the Suzuki–Miyaura coupling reaction takes 48–72 h. Controlling the reaction time within this range can improve the yield of the ligand.

[0052] Preferably, the palladium catalyst used in the Suzuki–Miyaura coupling reaction is tetrakis(triphenylphosphine)palladium, the base is potassium carbonate, and the temperature is 110°C.

[0053] A fifth aspect of the invention provides the application of a metal cage prepared by the method described in the first aspect or the method described in the second aspect in the separation of dye molecules.

[0054] Preferably, the dye molecule is a fat-soluble dye molecule.

[0055] Preferably, the dye molecule is a boron fluoride dipyrrole dye molecule.

[0056] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0057] The palladium-containing metal cage structure based on pyrazolpyridine ligands provided by this invention is asymmetrical, has a large cavity size, and is stable.

[0058] The Pd metal-organic cage based on pyrazole-pyridine ligands provided by this invention has the characteristics of large cavity size and good water solubility, which can efficiently and accurately identify and effectively encapsulate lipid-soluble dyes, and then separate and release them from the host. It also has excellent regeneration performance and recycling stability, enabling selective capture and controllable transport of lipid-soluble dyes, providing a novel and efficient molecular carrier for dye separation and purification, environmental pollutant removal and other fields. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0060] Figure 1 This is a crystal structure diagram of the metal cage provided in Embodiment 1 of the present invention.

[0061] Figure 2 The 1H NMR spectrum of the ligand provided in Example 1 of this invention.

[0062] Figure 3 The nuclear magnetic resonance hydrogen spectrum of the metal cage provided in Embodiment 1 of the present invention.

[0063] Figure 4 The fluorescence image is of the metal cage-like structure BODIPY provided in Embodiment 1 of the present invention.

[0064] Figure 5 This is a repeatability test diagram of the release of BODIPY by the metal cage in Test Example 2 of the present invention. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0066] The following examples are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the examples, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased from legitimate channels.

[0067] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0068] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0069] Example 1

[0070] 1. This embodiment provides a metal cage, the chemical formula of which is: L4(bpyPd) 10 (X) 12 ;

[0071] The structural formula of L is shown in equation (Ⅰ) below:

[0072] (Ⅰ);

[0073] bpy is 2-2' bipyridine;

[0074] The structure of the metal cage is shown in the following formula (Ⅱ):

[0075] (II);

[0076] in,

[0077] X stands for hexafluorophosphate.

[0078] 2. The method for preparing the metal cage provided in this embodiment includes the following steps:

[0079] (1) Synthesis of ligand L, the synthetic route is as follows:

[0080] ;

[0081] S1. Weigh 2,4,6-tribromopyridine (1 g, 3.17 mmol) and 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole (1.76 g, 6.33 mmol) and add them to a mixed solution of 1,4-dioxane (50 mL) and water (8 mL). Under a nitrogen atmosphere, add potassium carbonate (2.18 g, 15.8 mmol) and tetra(triphenylphosphine)palladium (100 mg, 0.0950 mmol). After refluxing at 110 °C for 72 h, remove the solvent. Dissolve the residue in dichloromethane (120 mL) and extract three times with water (30 mL). After extraction, dry with anhydrous magnesium sulfate, filter, concentrate, and purify the crude product by silica gel column chromatography (silica, ethyl acetate / petroleum ether 2:1) to obtain compound A (200 mg).

[0082] S2. Compound A (200 mg, 0.436 mmol) and pinacol 4-pyridineboronic acid (98.68 mg, 0.479 mmol) were dissolved in a mixed solution of 1,4-dioxane (30 mL) and water (5 mL). Potassium carbonate (1 g, 7.25 mmol) and tetrakis(triphenylphosphine)palladium (30 mg, 0.026 mmol) were added under a nitrogen atmosphere. The mixture was refluxed at 110 °C for 48 h. The solvent was removed, and the residue was dissolved in dichloromethane (60 mL). The mixture was extracted three times with water (15 mL). After extraction, anhydrous magnesium sulfate was added and dried. The mixture was filtered, and hydrochloric acid was added to the filtrate while stirring to adjust the pH to 1. After stirring for 6 h, saturated sodium bicarbonate solution was added to adjust the pH to 7. At this point, a precipitate was formed. After filtration and drying, ligand L was obtained with a yield of 50%.

[0083] The results of the nuclear magnetic resonance analysis are ( Figure 2 ): 1H NMR (400MHz, DMSO-d6, 298 K): δ(ppm) =13.09 (s, 1H), 8.76 (dd, 1H), 8.51 (s, 1H), 8.26 (s, 1H),7.97(dd,1H),7.91(s,1H).

[0084] (2) Synthesis of the metal cage, the synthetic route is as follows:

[0085]

[0086] Ligand L (8 mg, 0.028 mmol) and the metal assemblagem bpyPd(NO3)2 (27.1 mg, 0.07 mmol) were weighed into a 5 mL assembly tube, with a molar ratio of ligand L to bpyPd(NO3)2 of 2:5. 1 mL of deionized water was added to the assembly tube, and the mixture was stirred at 45 °C for 4 h, eventually yielding a pale yellow clear solution. Ethyl acetate was then added to the clear solution, resulting in the precipitation of a yellow solid. The solid was separated by centrifugation and dried under vacuum to obtain the palladium-containing metal cage of the pyrazolpyridine ligand.

[0087] The obtained palladium-containing metal cage was dissolved in dimethyl sulfoxide (DMSO), and nitrate (NO3) was added. - Ten molar amounts of KPF6 were stirred at room temperature for 4 hours, then washed with deionized water and centrifuged to dry, yielding a palladium metal cage with hexafluorophosphate as the equilibrium anion.

[0088] The nuclear magnetic resonance analysis results of the palladium metal cage with hexafluorophosphate as the equilibrium anion prepared in this embodiment are as follows: Figure 3 ): 1 H NMR (600 MHz, CD3CN, 298 K): δ(ppm)= 9.05 (d, 4H),8.58 (s, 4H), 8.49 (m,22H),8.45 (dd, 6H), 8.33 (d, 4H),8.25 (d, 4H), 8.07 (d, 3H), 7.92 (s, 4H), 7.89 (m, 7H), 7.77 (m, 6H).

[0089] By growing the metal cage sample provided in Example 1 into a single crystal and characterizing its structure using single-crystal X-ray diffraction, it was found that the metal cage crystal belongs to the monoclinic crystal system, space group P1(2), and the cell parameters are a (Å) = 22.8660(12), b (Å) = 24.5415(18), c (Å) = 32.033(2), α (°) = 88.109(2), β (°) = 85.420(2), γ (°) = 65.973(2), and the unit cell volume V (Å) is... 3 = 16366(2), the structural composition of the metal cage is C 164 H 120 N 56 P 12 F 72 Pd 10 A cationic three-dimensional cage-like structure, with hexafluorophosphate ions as the balancing charge ion, has a relative molecular mass Mr = 5799.09. Its structure is formed by the connection of four organic ligands L and ten (bpy)Pd assembly units. Crystal structure diagram of the metal cage provided in Example 1 (dark green: Pd) 2+ Gray: C; Blue: N; Orange: P; Fluorescent Green: F; White: H) Figure 1 As shown.

[0090] Test Example 1

[0091] Example 1: Inclusion release test of the metal cage provided in Example 1 on BODIPY:

[0092] BODIPY (4,4-difluoro-1,3,5,7,8-pentamethyl-4-boron-3A,4A-diaza-S-indenene, CAS No.: 121207-31-6) molecules are insoluble in water but soluble in organic solvents such as DMF and DMA, and the solutions exhibit strong fluorescence intensity. In contrast, the metal cage alone is soluble in water, and the solution is non-fluorescent. This invention uses changes in fluorescence spectra to demonstrate that the metal cage can encapsulate BODIPY molecules. The specific operation is as follows: Prepare 1×10 -5 The fluorescence intensity was tested using a mol / L aqueous solution of a metal cage. 20 mg of BODIPY powder was added to 3 mL of the above 1×10⁻⁶ solution. -5 After sonicating with an aqueous solution of metal cages for 3 hours, the solution was centrifuged and the fluorescence intensity of the clear solution was tested. 2 mL of a 1×10⁻⁶ mol / L solution was prepared. -5 A mol / L solution of BODIPY in DMF was prepared and its fluorescence intensity was tested.

[0093] Fluorescence changes are shown Figure 4 ,from Figure 4It can be seen that the fluorescence intensity of pure BODIPY in DMF solution is very strong, while the fluorescence of pure metal cage aqueous solution is almost non-existent. The fluorescence intensity of BODIPY solid added to metal cage aqueous solution is between the two.

[0094] Test Example 2

[0095] Repeatability test of the inclusion release of the metal cage provided in Example 1 for BODIPY:

[0096] To further investigate the reproducibility of the metal cage provided in Example 1 of this invention, the fluorescence intensity changes after multiple BODIPY release and inclusion processes were tested. The specific method was as follows: 2 mL of the metal cage aqueous solution was taken to test its fluorescence value. 20 mg of solid BODIPY was added, and the mixture was ultrasonically vibrated for 3 hours. After centrifugation, the supernatant was collected and its fluorescence value was tested. After the test, 30 mL of ethyl acetate organic solvent was added to the supernatant, and then the ethyl acetate solution was removed. The resulting metal cage aqueous solution was then subjected to fluorescence testing again. After repeating the above steps four times, the test results were as follows: Figure 5 As shown, by Figure 5 It can be seen that the metal cage provided in Example 1 can undergo at least 4 encapsulation and release cycles. This demonstrates the repeatability and stability of the metal cage provided by the present invention.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metal cage, characterized in that, The chemical formula for the metal cage is: L4(bpyPd) 10 (X) 12 ; The structural formula of L is shown in equation (Ⅰ): (Ⅰ)； bpy is 2-2' bipyridine; The structure of the metal cage is shown in the following formula (Ⅱ): (Ⅱ)； in, X is the equilibrium anion; X is hexafluorophosphate.

2. A method for preparing a metal cage as described in claim 1, characterized in that, include: Will The metal cage was prepared by solution self-assembly of the (2-2'-bipyridine)palladium complex; The structural formula of the (2-2'-bipyridine)palladium complex is shown in the following formula (Ⅲ): (Ⅲ)； in, Y represents the equilibrium anion.

3. The method for preparing the metal cage according to claim 2, characterized in that, The molar ratio of the (2-2'-bipyridine)palladium complex is 2:(4.8~5.5).

4. The method for preparing the metal cage according to claim 2 or 3, characterized in that, When the equilibrium anion of the metal cage is hexafluorophosphate, Y is nitrate, and the metal cage with the equilibrium anion of hexafluorophosphate is obtained by an anion exchange reaction after the solution self-assembly reaction.

5. The method for preparing the metal cage according to claim 4, characterized in that, The solvent used in the solution self-assembly reaction is water, and the temperature of the solution self-assembly reaction is 45~65℃.

6. A ligand, characterized in that, The structural formula of the ligand is shown in the following formula (Ⅰ): (Ⅰ)。 7. A method for preparing a ligand, characterized in that, Includes the following steps: S1. Compound A was prepared by coupling 2,4,6-tribromopyridine and 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole via the Suzuki–Miyaura reaction. S2. The ligand is prepared by coupling compound A with 4-pyridineboronic acid pinacol ester via a Suzuki–Miyaura coupling reaction followed by hydrolysis protection. The synthetic route for the ligand is as follows: ； The molar ratio of 2,4,6-tribromopyridine to 1-(tetrahydro-2H-pyran-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-yl)-1H-pyrazole is 1:(2~2.2).

8. The application of a metal cage as described in claim 1 or a metal cage prepared by any one of claims 2 to 5 in the separation of dye molecules.

9. The application according to claim 8, characterized in that, The dye molecule is a boron fluoride dipyrrole dye molecule.

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