Reversible coordination crosslinker and wavelength / temperature orthogonal control method thereof

Abstract

The application discloses a reversible coordination crosslinking agent and a wavelength / temperature orthogonal control method thereof, wherein the structure of the reversible coordination crosslinking agent is shown in the following formula: the reversible coordination crosslinking agent is orthogonally coordinated in an aqueous solution by different temperatures and is orthogonally de-coordinated by different wavelengths of light. The application provides a new compound containing two ruthenium centers in a single molecule, can realize orthogonal control of multiple paths, provides a new multi-stimulus orthogonal strategy, is suitable for orthogonal reversible control of polymer crosslinking and de-crosslinking by light and heat, and is especially suitable for the fields of photoresponsive hydrogels, 4D printing materials and the like, and can realize programmable control of a dynamic network.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of light-responsive polymer materials, and particularly relates to a reversible coordination crosslinking agent and a wavelength / temperature orthogonal control method thereof. BACKGROUND

[0002] Multi-stimulus orthogonal control of the reversible coordination crosslinking agent is the core of realizing multi-dimensional regulation of intelligent materials, but its development is limited by insufficient stimulus orthogonality and molecular design limitations. Traditional schemes mostly rely on multi-molecular cooperative mechanisms (such as mixing two different photosensitive molecules), which can realize step-by-step response, but face inherent problems such as uneven diffusion of components, frequent interface side reactions and poor cycle stability. Single-molecule systems (such as single-core ruthenium complexes) avoid multi-component interference, but the single functionality limits them to respond to only a single stimulus (such as light or heat), which cannot meet the needs of complex scenarios. In addition, the existing light-responsive systems generally have the problem of spectral overlap (such as both azobenzene and nitrobenzyl ester responding to ultraviolet light), which makes it difficult to achieve site-specific dissociation through wavelength selection, severely limiting the spatiotemporal programming ability.

[0003] Therefore, it is of important application value and research significance to develop a single-molecule reversible crosslinking agent with orthogonal control. The crosslinking agent based on a double-core ruthenium complex can precisely construct two ruthenium centers in one molecule, completely avoiding the component competition and interface failure of multi-molecular systems, while realizing orthogonal control and dynamic reversibility, and providing a molecular-level control basis for dynamic reconstruction of complex structures. SUMMARY

[0004] In view of the problems in the prior art, the application provides a reversible coordination crosslinking agent and a wavelength / temperature orthogonal control method thereof. The reversible coordination crosslinking agent of the application solves the coordination problems of multi-stimulus orthogonality, single-molecule functional integration and high cycle stability, and provides a new multi-stimulus orthogonal control strategy.

[0005] The reversible coordination crosslinking agent of the application has the following structure:

[0006] .

[0007] The preparation method of the reversible coordination crosslinking agent of the application comprises the following steps:

[0008] Step 1: Dissolve ruthenium trichloride and 4-carboxylic acid-2,2':6,2''-terpyridine in anhydrous ethanol, and react at 70-80°C for 4-8h; after the reaction is completed, cool to room temperature to obtain a suspension, filter and collect the precipitate, wash with ethanol and diethyl ether, and vacuum dry to obtain compound 1;

[0009] Step 2: Compound 1 and biq were dissolved in a mixed solvent of anhydrous ethanol and deionized water, and reacted at 75-90°C for 18-36h under nitrogen protection in the dark; after the reaction was completed, it was filtered while hot, the filtrate was collected, and the crude product was obtained by rotary evaporation; the crude product was purified by silica gel column, and compound 2 was obtained after vacuum drying;

[0010] Step 3: Ethanolamine and potassium hydroxide were dissolved in anhydrous dimethyl sulfoxide, and after stirring at 30-60°C for 30-60min, 4-chloro-2,2':6,2''-terpyridine was added, and reacted at 30-60°C for 6-12h; after the reaction was completed, it was cooled to room temperature, deionized water was added to the reaction solution, the product was extracted with dichloromethane, and then deionized water and saturated brine were used for washing; the organic phase was collected, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation; compound 3 was obtained after vacuum drying;

[0011] Step 4: Compound 3 and di-tert-butyl dicarbonate were dissolved in dichloromethane, and reacted at 20-30°C for 2-6h; after the reaction was completed, it was washed with deionized water and saturated brine; the organic phase was collected, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation; compound 4 was obtained after vacuum drying;

[0012] Step 5: Compound 4 and ruthenium trichloride were dissolved in anhydrous ethanol, and reacted at 70-80°C for 4-8h; after the reaction was completed, it was cooled to room temperature to obtain a suspension, which was filtered and the precipitate was collected, washed with ethanol and diethyl ether, and vacuum dried to obtain compound 5;

[0013] Step 6: Compound 5, 2,2'-bipyridine (bpy), triethylamine and lithium chloride were dissolved in a mixed solvent of anhydrous ethanol and deionized water, and reacted at 75-90°C for 4-12h under nitrogen protection in the dark; after the reaction was completed, it was filtered while hot, the filtrate was collected, and the crude product was obtained by rotary evaporation; the crude product was purified by neutral alumina column, and compound 6 was obtained after vacuum drying;

[0014] Step 7: Compound 6 and trifluoroacetic acid were dissolved in dichloromethane, and reacted at 20-30°C for 1-4h; after the reaction was completed, the crude product was purified by neutral alumina column, and compound 7 was obtained after vacuum drying;

[0015] Step 8: Compound 2, triethylamine, 2-(7-azabenzotriazol)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU) and 1-hydroxy-7-azabenzotriazole (HOAT) were dissolved in anhydrous dichloromethane under ice water bath conditions, and reacted for 30-60min; then compound 7 was added, and reacted at 20-30°C for 18-36h; after the reaction was completed, the crude product was purified by silica gel column, and compound 8 was obtained after vacuum drying;

[0016] Step 9: Compound 8, silver tetrafluoroborate is added to a mixed solvent of deionized water and acetone, and reacted at 50-70°C for 12-24h. After the reaction is completed, the solvent is spin-dried, recrystallized in an aqueous sodium tetrafluoroborate solution, and the solid is collected by filtration, washed with dichloromethane and diethyl ether, and dried under vacuum to obtain the target product 9.

[0017] In Step 1, the molar ratio of ruthenium trichloride to 4-carboxylic acid-2,2':6,2"-terpyridine is 1:0.8-1.2.

[0018] In Step 2, the molar ratio of compound 1 to bipyridine is 1:0.8-1.2.

[0019] In Step 3, the molar ratio of 4-chloro-2,2':6,2"-terpyridine to ethanolamine is 1:1-10, and the molar ratio of 4-chloro-2,2':6,2"-terpyridine to potassium hydroxide is 1:2-10.

[0020] In Step 4, the molar ratio of compound 3 to di-tert-butyl dicarbonate is 1:0.9-2.

[0021] In Step 5, the molar ratio of compound 4 to ruthenium trichloride is 1:0.8-1.2.

[0022] In Step 6, the molar ratio of compound 5 to 2,2'-bipyridine is 1:0.8-1.2, the molar ratio of compound 5 to triethylamine is 1:0.9-3, and the molar ratio of compound 5 to lithium chloride is 1:0.8-1.2.

[0023] In Step 7, the molar ratio of compound 6 to trifluoroacetic acid is 1:20-100.

[0024] In Step 8, the molar ratio of compound 2 to triethylamine is 1:0.9-3, the molar ratio of compound 2 to 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate is 1:0.9-2, the molar ratio of compound 2 to 1-hydroxy-7-azabenzotriazole is 1:0.9-2, and the molar ratio of compound 2 to compound 7 is 1:0.8-1.2.

[0025] In Step 9, the molar ratio of compound 8 to silver tetrafluoroborate is 1:2-5.

[0026] The reaction scheme is as follows:

[0027] .

[0028] The wavelength / temperature orthogonal control method of the reversible coordination crosslinking agent is adding acetonitrile as a ligand to the aqueous solution system of the reversible coordination crosslinking agent, coordinating acetonitrile by regulating the system temperature, and dissociating acetonitrile by regulating the wavelength of the irradiation light, so as to realize the light / heat-induced ligand exchange.

[0029] The concentration of the reversible coordination crosslinking agent in the system is 1-4 mM, and the concentration of acetonitrile is 10-100 mM.

[0030] Preferably, the concentration of the reversible coordination crosslinking agent in the system is 3.7 mM, and the concentration of acetonitrile is 37 mM.

[0031] The wavelength / temperature orthogonal control method of the reversible coordination crosslinking agent comprises the following steps:

[0032] The reversible coordination crosslinking agent and acetonitrile are added to deionized water, dissolved and mixed uniformly, at 20-40℃, the ruthenium containing biq can coordinate acetonitrile, while the ruthenium containing bpy is difficult to coordinate acetonitrile, at 70-90℃, all ruthenium can coordinate acetonitrile; the system is irradiated with light with a wavelength of 600-660 nm, the acetonitrile ligand on the ruthenium containing biq can dissociate, while the acetonitrile ligand on the ruthenium containing bpy cannot dissociate, and the system is irradiated with light with a wavelength of 440-500 nm, the acetonitrile ligand on all ruthenium can dissociate.

[0033] The ligand exchange reaction route of the reversible coordination crosslinking agent is as follows:

[0034] .

[0035] When the ligand exchange of the reversible coordination crosslinking agent is regulated by temperature, the system temperature is controlled at 20-40℃, the ruthenium connected with biquinoline coordinates acetonitrile, and the original water ligand is replaced by acetonitrile ligand; the system temperature is controlled at 70-90℃, all ruthenium coordinates acetonitrile, and the original water ligand is replaced by acetonitrile ligand.

[0036] Preferably, the system temperature is controlled at 25℃, the ruthenium connected with biquinoline coordinates acetonitrile, and the original water ligand is replaced by acetonitrile ligand; the system temperature is controlled at 80℃, all ruthenium coordinates acetonitrile, and the original water ligand is replaced by acetonitrile ligand.

[0037] When the ligand exchange of the reversible coordination crosslinking agent is regulated by wavelength, light with a wavelength of 600-660 nm is used to control the dissociation of the acetonitrile ligand on the ruthenium connected with biquinoline, and light with a wavelength of 440-500 nm is used to control the dissociation of the acetonitrile ligand on all ruthenium.

[0038] Preferably, the dissociation of the acetonitrile ligand on the ruthenium connected with the biquinoline is controlled by a LED light source with a wavelength of 625 nm, and the dissociation of all acetonitrile ligands on the ruthenium is controlled by a LED light source with a wavelength of 470 nm.

[0039] In order to more clearly describe the principles of the present application, it is explained herein that the reversible coordination crosslinking agent has two coordination centers of ruthenium, the ruthenium containing biq can coordinate acetonitrile at 25℃, so that the original water ligand is replaced by the acetonitrile ligand, the ruthenium containing bpy can coordinate acetonitrile at 80℃, so that the original water ligand is replaced by the acetonitrile ligand, and the influence between them is small, so that a normal coordination interval can be formed; the acetonitrile on the ruthenium containing biq can be dissociated by 625 nm light, so that the original acetonitrile ligand is replaced by the water ligand, and the acetonitrile on the ruthenium containing bpy can be dissociated by 470 nm light, so that the original acetonitrile ligand is replaced by the water ligand, so that a normal dissociation interval can be formed, thereby realizing the thermal normal coordination and the light normal dissociation of the crosslinking agent described in the present application.

[0040] Compared with the prior art, the present application provides a new compound containing two ruthenium centers in a single molecule, which can realize the normal control of multiple paths, provides a new normal strategy, and more likely, the acetonitrile ligand can be replaced by a ligand containing a cyano group, so as to realize the reversible control of the crosslinking and de-crosslinking of the polymer by light and heat, thereby providing a broader possibility for realizing the programmable control of the dynamic network. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The UV-Vis absorption spectrum of the reversible coordination crosslinking agent is shown 1 H nuclear magnetic resonance spectrum.

[0042] Figure 2 The UV-Vis absorption spectrum of the ligand exchange process ① is shown. From the Figure 2 It can be seen from the figure that the absorption peak around 550 nm is blue-shifted, indicating that the water ligand on the ruthenium containing biq is replaced by the acetonitrile ligand, and the ruthenium containing bpy is not.

[0043] Figure 3 The UV-Vis absorption spectrum of the ligand exchange process ② is shown. From the Figure 3 It can be seen from the figure that the absorption peak around 500 nm is red-shifted, indicating that the acetonitrile ligand on the ruthenium containing biq is replaced by the water ligand.

[0044] Figure 4 The UV-Vis absorption spectrum of the ligand exchange process ③ is shown. From the Figure 4 It can be seen from the figure that the absorption peak around 500 nm continues to be blue-shifted, indicating that the water ligand on the ruthenium containing bpy is replaced by the acetonitrile ligand at this time.

[0045] Figure 5The UV-Vis absorption spectra of the ligand exchange process 4 are shown. It can be seen from the Figure 5 that the absorption peak around 460nm does not change, and the absorption peak around 500nm red shifts, indicating that the acetonitrile ligand on the biq-containing ruthenium is replaced by a water ligand, while the bpy-containing ruthenium is not.

[0046] Figure 6 The UV-Vis absorption spectra of the ligand exchange process 5 are shown. It can be seen from the Figure 6 that the absorption peak around 550nm blue shifts, indicating that the water ligand on the biq-containing ruthenium is replaced by an acetonitrile ligand.

[0047] Figure 7 The UV-Vis absorption spectra of the ligand exchange process 6 are shown. It can be seen from the Figure 7 that the absorption peak around 460nm red shifts, indicating that the acetonitrile ligand on the bpy-containing ruthenium is replaced by a water ligand.

[0048] Figure 8 The UV-Vis absorption spectra of the ligand exchange process 7 are shown. It can be seen from the Figure 8 that the absorption peaks around 460nm and 500nm red shifts, indicating that the acetonitrile ligand on the biq- and bpy-containing ruthenium is replaced by a water ligand.

[0049] Figure 9 The UV-Vis absorption spectra of the ligand exchange process 8 are shown. It can be seen from the Figure 9 that the absorption peaks around 550nm and 500nm blue shifts, indicating that the water ligand on the biq- and bpy-containing ruthenium is replaced by an acetonitrile ligand.

[0050] Figure 10 The reversible cycle results of the reversible coordination crosslinker are shown, where Figure A is the cycle chemical reaction formula, Figure B is the 1 H nuclear magnetic resonance spectrum, and Figure C is the proportion of ruthenium-acetonitrile bond in the total ruthenium in the cycle. It can be seen from the Figure 10 that in the 10 cycles of the ligand exchange processes 7 and 8, the proportion of ruthenium-acetonitrile bond does not change significantly with the increase of the cycle number, which reflects good reversible cycle stability. DETAILED DESCRIPTION

[0051] In order to further illustrate the present application, the method provided by the present application is described in detail below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not limitations on the present application.

[0052] Example 1: Synthesis of reversible coordination crosslinker

[0053] 1. Synthesis of compound 1

[0054] Ruthenium trichloride (784.41 mg, 3.00 mmol) and 4-carboxylic acid-2,2’:6,2’’- terpyridine (831.84, 3.00 mmol) were dissolved in anhydrous ethanol (30 mL) and reacted at 80 °C for 6 h; after the reaction was completed, it was cooled to room temperature to obtain a suspension, which was suction filtered and the precipitate was collected and washed with ethanol, diethyl ether, and dried in vacuum to obtain a brownish yellow solid (1.29 g, yield 86%), which was compound 1.

[0055] 2. Synthesis of compound 2

[0056] Compound 1 (751.13 mg, 1.50 mmol) and bipyridine (384.47 mg, 1.50 mmol) were dissolved in a mixed solvent of anhydrous ethanol (60 mL) and deionized water (20 mL) and reacted at 85 °C for 24 h in the dark under a nitrogen atmosphere; after the reaction was completed, it was filtered while hot, the filtrate was collected, and rotary evaporation was performed to obtain a crude product, which was purified by a silica gel column (eluent: dichloromethane / methanol = 10 / 1), and dried in vacuum to obtain a blue-violet solid (656.17 mg, yield 62%), which was compound 2.

[0057] 3. Synthesis of compound 3

[0058] Ethanolamine (305.42 mg, 5 mmol) and potassium hydroxide (1.40 g, 25 mmol) were dissolved in anhydrous dimethyl sulfoxide (10 mL), after stirring at 40 °C for 30 min, 4-chloro-2,2’:6,2’’-terpyridine (1.34 g, 5 mmol) was added, and reacted at 40 °C for 9 h; after the reaction was completed, it was cooled to room temperature, deionized water was added to the reaction solution, the product was extracted with dichloromethane, and then washed with deionized water and saturated brine; the organic phase was collected, dried over anhydrous sodium sulfate, rotary evaporation was performed to remove the solvent, and dried in vacuum to obtain a light yellow liquid (1.36 g, yield 93%), which was compound 3.

[0059] 4. Synthesis of compound 4

[0060] Compound 3 (1.17 g, 4 mmol) and di-tert-butyl dicarbonate (873.00 mg, 4 mmol) were dissolved in dichloromethane (20 mL) and reacted at 25 °C for 4 h; after the reaction was completed, it was washed with deionized water and saturated brine; the organic phase was collected, dried over anhydrous sodium sulfate, rotary evaporation was performed to remove the solvent, and dried in vacuum to obtain a white solid (1.48 g, yield 94%), which was compound 4.

[0061] 5. Synthesis of compound 5

[0062] Compound 4 (1.18 g, 3.00 mmol) and ruthenium trichloride (784.41 mg, 3.00 mmol) were dissolved in anhydrous ethanol (30 mL) and reacted at 80°C for 6 h. After the reaction was completed, the suspension was cooled to room temperature, filtered, and the precipitate was collected and washed with ethanol and diethyl ether. The brownish yellow solid (1.49 g, 83% yield) was obtained after drying under vacuum, which was compound 5.

[0063] 6. Synthesis of compound 6

[0064] Compound 5 (1.20 g, 2 mmol), 2,2'-dipyridyl (312.38 mg, 2 mmol), triethylamine (556 μL, 4.00 mmol), and lithium chloride (89.02 mg, 2.10 mmol) were dissolved in a mixed solvent of anhydrous ethanol (75 mL) and deionized water (25 mL) and reacted at 85°C for 12 h in the dark under a nitrogen atmosphere. After the reaction was completed, the filtrate was collected by filtering while hot, and the crude product was obtained by rotary evaporation. The crude product was purified by passing through a neutral alumina column (eluent: dichloromethane / methanol = 10 / 1), and the purple red solid (850.33 mg, 50% yield) was obtained after drying under vacuum, which was compound 6.

[0065] 7. Synthesis of compound 7

[0066] Compound 6 (720.62 mg, 1 mmol) and trifluoroacetic acid (4.46 mL, 60 mmol) were dissolved in dichloromethane (5 mL) and reacted at 25°C for 2 h. The crude product was purified by passing through a neutral alumina column (eluent: dichloromethane / methanol = 6 / 1), and the purple red solid (570.86 mg, 92% yield) was obtained after drying under vacuum, which was compound 7.

[0067] 8. Synthesis of compound 8

[0068] Compound 2 (70.56 mg, 0.10 mmol), triethylamine (28 μL, 0.20 mmol), 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (57.04 mg, 0.15 mmol), and 1-hydroxy-7-azabenzotriazole (20.42 mg, 0.15 mmol) were dissolved in anhydrous dichloromethane (5 mL) and reacted for 60 min under an ice water bath. Compound 7 (62.05 mg, 0.1 mmol) was then added, and the reaction was carried out at 25°C for 24 h. The crude product was purified by passing through a silica gel column (eluent: dichloromethane / methanol = 10 / 1), and the purple solid (60.17 mg, 46% yield) was obtained after drying under vacuum, which was compound 8.

[0069] 9. Synthesis of reversible coordination crosslinker, i.e., compound 9

[0070] Compound 8 (52.32 mg, 0.04 mmol), silver tetrafluoroborate (19.47 mg, 0.10 mmol) were added into the mixed solvent of deionized water (5 mL) and acetone (5 mL), and reacted at 60 °C for 12 h. After the reaction, the solvent was spin-dried, and the solid was collected by recrystallization in a saturated aqueous sodium tetrafluoroborate solution, washed with dichloromethane and diethyl ether, and dried under vacuum to obtain a red solid (47.10 mg, yield 76%), which was a reversible coordination crosslinker compound 9. The nuclear magnetic resonance spectrum is shown in Figure 1 .

[0071] Example 2: UV-Vis spectrum test of reversible coordination crosslinker

[0072] 1. Ligand exchange process ①

[0073] Compound 9 (11.47 mg, 0.0074 mmol) and acetonitrile (4 μL, 0.074 mmol) were added into deionized water (2 mL) to prepare a solution A with a ruthenium complex concentration of 3.7 mM, which was placed in a constant temperature water bath at 25 °C. Then, the UV-Vis absorption spectrum of the solution was tested by a UV-Vis spectrophotometer, the wavelength range of the test scan was 370 nm-750 nm, and the UV-Vis absorption spectrum was tested again every certain time as the standing time was prolonged, and finally a solution B was obtained, as shown in Figure 2 .

[0074] 2. Ligand exchange process ②

[0075] Solution B was irradiated with a LED lamp with a wavelength of 625 nm (light intensity 10 mW / cm 2 ), and then the UV-Vis absorption spectrum of the solution was tested by a UV-Vis spectrophotometer, the wavelength range of the test scan was 370 nm-750 nm, and the UV-Vis absorption spectrum was tested again every certain time as the irradiation time was prolonged, as shown in Figure 3 .

[0076] 3. Ligand exchange process ③

[0077] Solution B was placed in a constant temperature water bath at 80 °C, and then the UV-Vis absorption spectrum of the solution was tested by a UV-Vis spectrophotometer, the wavelength range of the test scan was 370 nm-750 nm, and the UV-Vis absorption spectrum was tested again every certain time as the standing time was prolonged, and a solution C was obtained, as shown in Figure 4 .

[0078] 4. Ligand exchange process ④

[0079] Solution C was irradiated with a LED lamp with a wavelength of 625 nm (light intensity 10 mW / cm 2irradiation, then the UV-Vis absorption spectrum of the solution was tested by using UV-Vis spectrophotometer, the wavelength range of the test scanning was 370nm-750nm, and with the extension of irradiation time, the UV-Vis absorption spectrum was tested again every certain time, finally the solution D was obtained, as shown in Figure 5 .

[0080] 5. Ligand exchange process V

[0081] The solution D was placed in a 25°C constant temperature water bath, then the UV-Vis absorption spectrum of the solution was tested by using UV-Vis spectrophotometer, the wavelength range of the test scanning was 370nm-750nm, and with the extension of placing time, the UV-Vis absorption spectrum was tested again every certain time, as shown in Figure 6 .

[0082] 6. Ligand exchange process VI

[0083] The solution D was irradiated by using a LED lamp with a wavelength of 470nm (light intensity 50mW / cm 2 ), then the UV-Vis absorption spectrum of the solution was tested by using UV-Vis spectrophotometer, the wavelength range of the test scanning was 370nm-750nm, and with the extension of irradiation time, the UV-Vis absorption spectrum was tested again every certain time, as shown in Figure 7 .

[0084] 7. Ligand exchange process VII

[0085] The solution A was placed in an 80°C constant temperature water bath, then the UV-Vis absorption spectrum of the solution was tested by using UV-Vis spectrophotometer, the wavelength range of the test scanning was 370nm-750nm, and with the extension of placing time, the UV-Vis absorption spectrum was tested again every certain time, as shown in Figure 8 .

[0086] 8. Ligand exchange process VIII

[0087] The solution C was irradiated by using a LED lamp with a wavelength of 470nm (light intensity 50mW / cm 2 ), then the UV-Vis absorption spectrum of the solution was tested by using UV-Vis spectrophotometer, the wavelength range of the test scanning was 370nm-750nm, and with the extension of irradiation time, the UV-Vis absorption spectrum was tested again every certain time, as shown in Figure 9 .

[0088] Example 3: Reversible cycle of reversible coordination crosslinker 1 H nuclear magnetic resonance spectrum

[0089] Compound 9 (1.39 mg, 0.0009 mmol) and acetonitrile (2 μL, 0.036 mmol) were added to deionized water (0.6 mL) to make a solution of 1.5 mM ruthenium complex, which was added to an NMR tube and placed in a constant temperature water bath at 80 °C for about 1 h to allow complete coordination, after which it was de-coordinated completely by irradiation with a LED lamp (light intensity 50 mW / cm 2 ) at a wavelength of 470 nm for about 20 min. The procedure was repeated 10 times, and the 1 H NMR spectroscopy was used to test the ligand exchange yield, and the results are shown in Figure 10 .

[0090] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A reversible coordination cross-linking agent, characterized in that Its structure is as follows: 。 2. The method for preparing the reversible coordination cross-linking agent according to claim 1, characterized in that The steps include: Step 1: Dissolve ruthenium trichloride and 4-carboxylic acid-2,2':6,2''-terpyridine in anhydrous ethanol and react at 70-80°C for 4-8 hours; after the reaction, cool to room temperature to obtain a suspension, and separate and purify to obtain compound 1; Step 2: Dissolve compound 1 and bisquinoline in a mixed solvent of anhydrous ethanol and deionized water, and react in a nitrogen environment at 75-90°C in the dark for 18-36 hours; after the reaction, separate and purify to obtain compound 2; Step 3: Dissolve ethanolamine and potassium hydroxide in anhydrous dimethyl sulfoxide, stir at 30-60°C for 30-60 minutes, then add 4-chloro-2,2':6,2''-terpyridine, and react at 30-60°C for 6-12 hours. After the reaction, separate and purify to obtain compound 3; Step 4: Dissolve compound 3 and di-tert-butyl dicarbonate in dichloromethane, react at 20-30°C for 2-6 hours, and separate and purify after the reaction to obtain compound 4; Step 5: Dissolve compound 4 and ruthenium trichloride in anhydrous ethanol and react at 70-80°C for 4-8 hours; after the reaction, separate and purify to obtain compound 5; Step 6: Dissolve compound 5, 2,2'-bipyridine, triethylamine, and lithium chloride in a mixed solvent of anhydrous ethanol and deionized water, and react in a nitrogen environment at 75-90°C in the dark for 4-12 hours; after the reaction, separate and purify to obtain compound 6; Step 7: Dissolve compound 6 and trifluoroacetic acid in dichloromethane, react at 20-30°C for 1-4 hours, and separate and purify after the reaction to obtain compound 7; Step 8: Dissolve compound 2, triethylamine, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and 1-hydroxy-7-azabenzotriazole in anhydrous dichloromethane in an ice-water bath, react for 30-60 min, then add compound 7, react at 20-30°C for 18-36 h, and separate and purify to obtain compound 8. Step 9: Add compound 8 and silver tetrafluoroborate to a mixed solvent of deionized water and acetone, react at 50-70°C for 12-24 hours, and separate and purify after the reaction to obtain the target product; The reaction route is as follows: 。 3. The wavelength / temperature orthogonal control method of the reversible coordination crosslinker according to claim 1, characterized in that: Acetonitrile is added as a ligand to the aqueous solution system of the reversible coordination crosslinker, the acetonitrile is coordinated by regulating the system temperature, and the acetonitrile is decoordinated by regulating the wavelength of the irradiated light to achieve photo / thermoinduced ligand exchange.

4. The wavelength / temperature orthogonal control method according to claim 3, wherein: The concentration of the reversible coordination cross-linking agent in the system is 1-4 mM, and the concentration of acetonitrile is 10-100 mM.

5. The wavelength / temperature orthogonal control method according to claim 4, characterized in that: The concentration of the reversible coordination cross-linking agent in the system is 3.7 mM, and the concentration of acetonitrile is 37 mM.

6. The wavelength / temperature orthogonal control method according to claim 4, wherein: When the ligand exchange of the reversible coordination cross-linker is regulated by temperature, the system temperature is controlled at 20-40°C, and the ruthenium connected to the biquinoline is coordinated with acetonitrile, so that the original water ligand is replaced by the acetonitrile ligand; when the system temperature is controlled at 70-90°C, all ruthenium is coordinated with acetonitrile, so that the original water ligand is replaced by the acetonitrile ligand.

7. The wavelength / temperature orthogonal control method according to claim 6, characterized in that: When wavelength-controlled ligand exchange of the reversible coordination crosslinker is used, light with a wavelength of 600-660 nm is used to control the dissociation of the acetonitrile ligand on the ruthenium connected to the bisquinoline, and light with a wavelength of 440 nm-500 nm is used to control the dissociation of the acetonitrile ligand on all ruthenium.

8. The wavelength / temperature orthogonal control method according to claim 6 or 7, characterized in that The ligand exchange reaction route of the reversible coordination cross-linker is as follows: 。

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