Preparation method of a new copolymer material based on coumarin and rhodamine and its application

Abstract

The present invention belongs to the technical field of organic chemistry and polymer material chemistry, and discloses a method for preparing a novel copolymer material based on coumarin and rhodamine and its application. When the pH value of the solution changes from alkaline to acidic, the solution color changes from blue to yellow-green, and the emission wavelength red-shifts from 484nm to 554nm. The material can be used as a probe to detect in the extreme acid range of 2.24-2.64, and has potential applications in environmental monitoring as a naked eye probe. The polymer material M-Z-4-D not only realizes the ratio fluorescence detection of pH, but also provides a new idea for the development of subsequent ratio fluorescence probes.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemistry and polymer material chemistry, and relates to a preparation method of a novel copolymer material based on coumarin and rhodamine and application thereof. Background Art

[0002] Fluorescence resonance energy transfer (FRET) is a highly sensitive spectroscopic technique that has been widely used in medical diagnosis, bioanalysis, and optical imaging due to its advantages of large Stokes shift, ratiometric sensing, and dual / multi-analyte response systems. FRET is often used to design ratiometric fluorescent probes by combining multiple fluorophores (donor-acceptor) with different emission bands through the synthesis of single-molecule sensors. Initially, there is almost no overlap between the absorption band of the acceptor and the emission band of the donor, but after the acceptor specifically recognizes the target analyte, its chemical structure changes from a non-fluorescent form to a fluorescent form, and the absorption band shifts, thereby increasing the overlap with the donor emission band. In addition, the donor-acceptor fluorophores should be close to each other (usually 1 / 4 of the fluorophores). ), and the donor emission moment, acceptor absorption moment and their separation vectors must be in a favorable mutual orientation state to achieve a good FRET phenomenon.

[0003] The fluorescence or absorption properties of some organic compounds change with changes in pH. Appropriate adjustments and modifications to the structures and functional groups of different fluorophores can be used to indicate changes in the acidity or alkalinity of the target medium. pH fluorescent probes are generally divided into two types based on the number of emission peaks of the probe: single-emission pH fluorescent probes and ratiometric pH fluorescent probes. Rhodamine fluorophores are often designed as ideal pH sensors due to their large molar extinction coefficient, long-wavelength emission, and high fluorescence quantum yield. They achieve significant fluorescence enhancement through structural changes from a helical ring state to an open ring state. Because their absorption and emission spectra appear in longer wavelengths, rhodamine fluorescent carriers are often used as energy acceptors in FRET systems.

[0004] Although ratiometric fluorescent probes based on the FRET mechanism have many advantages in detecting pH, the design and development of such single molecules is indeed very complicated. It is necessary to consider the recognition site of the target molecule and the connection between different fluorescent donors and acceptors. The specific implementation requires overcoming huge difficulties. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a novel copolymer material based on coumarin and rhodamine and its application. The present invention utilizes a RAFT free radical reaction to copolymerize a modified fluorescent donor coumarin and a fluorescent acceptor rhodamine with methyl methacrylate (MMA), thereby developing a novel ratiometric fluorescent polymer material, MZ-4-D, that responds to pH. The on-off fluorescence color switching of MZ-4-D in response to pH was tested using UV and fluorescence spectroscopy. When the pH value of the solution changes from alkaline to acidic, the solution color changes from blue to yellow-green, and the emission wavelength red-shifts from 484 nm to 554 nm. This material can be used as a probe for detection in the extreme acidic range of 2.24-2.64, and has potential applications as a naked-eye probe in environmental monitoring. This material not only enables ratiometric fluorescence detection of pH but also provides a new approach for the subsequent development of ratiometric fluorescent probes. Furthermore, the polymer material's inherent ease of processing will also open up possibilities for further applications of the probe in the future.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] A new polymer material MZ-4-D based on coumarin and rhodamine, its specific structural formula is shown below:

[0008]

[0009] Wherein m:n:p=93:3.6:1, Mn=17227.2g / mol.

[0010] The specific preparation method of the novel polymer material MZ-4-D based on coumarin and rhodamine is as follows:

[0011] S1.2mmol of rhodamine 6G and 3mL of hydrazine hydrate were heated under reflux in 15-30mL of ethanol solution for five hours to obtain the compound rhodamine hydrazine hydrate;

[0012] S2.500 mg of rhodamine hydrazine hydrate was further reacted with 1.5 times the molar amount of p-allyloxybenzaldehyde and two drops of glacial acetic acid in 25 mL of ethanol solution and heated under reflux for four hours to produce a Schiff base reaction to obtain compound MS6.

[0013] S3.500 mg of coumarin hydrazine hydrate, one molar amount of p-allyloxybenzaldehyde, and two drops of glacial acetic acid were stirred in 15-30 mL of anhydrous ethanol and heated under reflux for four hours to obtain MS5. 5 mmol of methyl methacrylate, 0.125 mmol of MS5, 0.125 mmol of MS6, and 0.066 mmol of the chain transfer agent 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were heated to 70 degrees in 4 mL of tetrahydrofuran (THF) under the initiation of 0.026 mmol of azobisisobutyronitrile. After 24 hours of polymerization, polymer MZ-4-D was obtained. The reaction formula is shown below:

[0014]

[0015] The novel polymer material MZ-4-D based on coumarin and rhodamine prepared by the above preparation method changes the color of the solution from blue to yellow-green and the emission wavelength red-shifts from 484 nm to 554 nm when the pH value of the solution changes from alkaline to acidic.

[0016] The present invention also seeks to protect the use of the novel coumarin and rhodamine-based polymer material MZ-4-D as a fluorescent probe for pH detection, which can detect in the extreme acidic range of 2.24-2.64 and be used as a naked eye probe in environmental monitoring.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] The present invention successfully developed a new color-adjustable polymer pH detection material by introducing coumarin and rhodamine derivatives with excellent photophysical properties into a methyl methacrylate polymer platform. In alkaline and neutral environments, only blue light is emitted from MS5, while in acidic environments, the spiral closed-loop structure of MS6 opens. At this time, the overlapping area of ​​the coumarin blue light emission band in MS5 and the rhodamine red light absorption band in MS6 increases, promoting the occurrence of fluorescence resonance energy transfer, causing the fluorescence color of MZ-4-D to change from blue to yellow-green, achieving visualization of the probe. The copolymer MZ-4-D can be prepared by RAFT free radical reaction of coumarin fluorophore, rhodamine fluorophore and methyl methacrylate, and the synthesis is simple and easy. The development of this copolymer also makes its later application in flexible nanomaterials possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the H NMR spectrum of compound MS6 in Example 2 of the present invention in DMSO-d6;

[0020] Figure 2 is the carbon NMR spectrum of compound MS6 in Example 2 of the present invention in DMSO-d6;

[0021] Figure 3 This is the H NMR spectrum of MZ-4-D in CDCl3 in Example 3 of the present invention;

[0022] Figure 4 It is the ultraviolet spectrum of MZ-4-D in Example 3 of the present invention;

[0023] Figure 5 is a graph showing the change in the absorption intensity ratio of MZ-4-D at 529 nm and 436 nm as a function of pH in Example 3 of the present invention;

[0024] Figure 6 This is the fluorescence spectrum of MZ-4-D at different pH values ​​in Example 3 of the present invention;

[0025] Figure 7 3 is a graph showing the change in the ratio of the fluorescence intensity of MZ-4-D at 554 nm and 484 nm as a function of pH in Example 3 of the present invention;

[0026] Figure 8 is a graph showing the change in CIE coordinates of MZ-4-D in Example 3 of the present invention with pH;

[0027] Figure 9 This is a graph showing the fluorescence color change of MZ-4-D at different pH values ​​in Example 3 of the present invention;

[0028] Figure 10 This is the infrared spectrum of MZ-4-D in Example 3 of the present invention;

[0029] Figure 11 is the X-ray diffraction pattern of MZ-4-D in Example 3 of the present invention;

[0030] Figure 12 This is a scanning electron microscope image of MZ-4-D in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0032] Example 1 Synthesis of Compound Rhodamine 6G Hydrazine Hydrate

[0033]

[0034] Rhodamine 6G (0.958 g, 2 mmol) was dissolved in 30 mL of ethanol, and 80% hydrazine hydrate (3 mL) was added. The solution was refluxed for 5 hours until the red color disappeared. After cooling to room temperature, a light red precipitate was obtained. This was filtered, washed twice with 15 mL of ethanol-water mixture, and dried under vacuum to obtain 0.78 g of the product (91.2% yield).

[0035] Example 2 Synthesis of Compound MS6

[0036]

[0037] 500 mg of rhodamine 6G hydrazine hydrate and 1.5 times the molar amount of p-allyloxybenzaldehyde were placed in a 50 ml flask. 25 ml of anhydrous ethanol was added, and two drops of glacial acetic acid were added to promote the reaction. The mixture was heated under reflux with stirring for 4 hours, cooled and filtered, and the filter cake was washed three times with a small amount of ethanol and filtered to obtain 200 mg of the product with a yield of 30%. The developing solvent was CH2Cl2:CH4O (v / v) = 50:1, R f =0.46.

[0038] 1 H-NMR (500MHz, DMSO-d6): δ(ppm)8.68(s,1H,-CH=N-),7.88(d,1H,J=8.0Hz,-ArH-),7.57(m,2H,- ArH-),7.32(d,2H,J=8.6Hz,-ArH-),7.02(d,1H,J=7.2Hz,-ArH-),6.93(d,2H,J=8.6Hz,-ArH-),6. 32(s,2H,-ArH-),6.16(s,2H,-ArH-),6.00(m,1H,-CH=CH2),5.25(m,2H,-CH=CH2),5.06(s,2H,-C H2-),4.56(s,2H,-NH-),3.12(m,4H,-CH2CH3),1.84(d,6H,-CH3),1.20(t,6H,J=7.0Hz,-CH2CH3). 13 C-NMR (125MHz, DMSO-d6): δ (ppm) 163.95, 160.25, 151.83, 151.43, 148.19, 147.68, 134.09, 133.75, 129.40, 129.11, 128.78,127.70,127.35,124.20,118.62,118.14,115.46,105.58,96.18,68.71,65.94,55.39,37.94,17.48,14.64.

[0039] Example 3 Synthesis of polymer MZ-4-D

[0040]

[0041] Free radical polymerization of MZ-4-D:

[0042] 500 mg of coumarin hydrazine hydrate and one molar amount of p-allyloxybenzaldehyde were placed in a 50 ml flask. 25 ml of anhydrous ethanol was added, and two drops of glacial acetic acid were added to promote the reaction. The mixture was heated under reflux and stirred for four hours. TLC confirmed the reaction was complete. The mixture was cooled and filtered. The filter cake was washed three times with a small amount of ethanol and then filtered to obtain 450 mg of the product MS5, with a yield of 60%. The developing solvent was CH2Cl2:CH4O (v / v) = 50:1, R f =0.46.

[0043] Using the RAFT method, purified MMA (500 mg, 5 mmol), MS5 (52.58 mg, 0.125 mmol), and MS6 (71.8 mg, 0.125 mmol) were dissolved in 4 ml of THF at a ratio of 40:1:1. 0.066 mmol of chain transfer agent 2-(dodecyltrithiocarbonate)-2-methylpropionic acid (24.3 mg) and 4.4 mg of initiator AIBN (0.026 mmol) were added. After complete dissolution, the reaction system was replaced with a nitrogen atmosphere by three cycles of nitrogen insufflation, vacuum pump evacuation, and nitrogen insufflation. Subsequently, the sealed mixture was heated in a 70°C oil bath for condensation reaction for 24 hours. After the reaction, the polymerization reaction was quenched with an ice-water mixture, the reaction solution was concentrated, and the mixture was poured into methyl tert-butyl ether for precipitation three times. Dissolution and precipitation were repeated three times with THF and methyl tert-butyl ether, and then filtered and dried in a vacuum drying oven at 30°C for 24 hours to obtain 196.6 mg of product. Mn = 17227.2 g / mol, PDI = 1.59. The hydrogen spectrum is as follows Figure 3 shown.

[0044] 1H-NMR(500MHz, CDCl3): δ(ppm)11.79(a,1H,-NH-),8.85(b,1H,-CH=N-),8.75(c,1H,-CH=N-),6.0-8.0(aromatic hydrogens,20H),4.0-6.0(alkyl hydrogens,10H),3.6(m,3H,-O-CH3),3.48-3.45(d,4H,-N-CH2-),3.21(g,4H,-N-CH2-CH3 ),1.7-2.2(f+p,8H,-CH3,-CH2-),1.25(e+h,12H,-CH2-CH3),1.02-0.85(n,3H,-C-CH3-).

[0045] Example 4M-Z-4-D UV Spectrometry

[0046] Figure 4 It shows that in acetonitrile-water solution (V 乙腈 :V 水 =8:2) in the pH sensor MZ-4-D. When the pH is 2.74, MZ-4-D exhibits a broad absorption peak characteristic of coumarin at 436nm and a characteristic absorption peak of a rhodamine derivative at 528nm. As the pH value of the solution increases, the absorption peak at 528nm gradually decreases, indicating that the open-ring rhodamine in MZ-4-D is converted to a closed-ring form as the pH increases. As the pH changes from acidic to neutral to weakly alkaline, the absorbance of the rhodamine portion gradually decreases. We use the absorption peak ratio of 528nm to 436nm as the value A 528 / A 436 As the vertical axis, pH as the horizontal axis, observe A 528 / A 436 The value of pH changes, and it is found that when the pH reaches 7, A 529 / A 436 tends to balance (see Figure 5 ).

[0047] Example 5 Fluorescence Spectral Response of M-Z-4-D to pH

[0048] Figure 6 The fluorescence emission changes of MZ-4-D at different pH values ​​are shown. 乙腈 :V 水=8:2) solution, with an excitation wavelength of 465 nm to excite MZ-4-D (0.052 g / L). When pH = 7.26, only the coumarin portion emits blue light at 484 nm. However, as the pH decreases, the non-fluorescent spirocyclic form of rhodamine is converted to an open ring form, and the fluorescence intensity at 554 nm gradually increases. The ratio of the fluorescence intensity at 554 nm to that at 484 nm is F 554 / F 484 As the pH decreases, it gradually increases (see Figure 7 The study showed that when MZ-4-D is exposed to acidic conditions, the non-fluorescent helical ring form of rhodamine transforms into an open ring, and the fluorescence of the solution gradually shifts from blue to yellow-green, enabling naked-eye pH recognition. This suggests that the polymer sensor MZ-4-D can be used to detect pH in an environment.

[0049] CIE Coordinates of Example 6M-Z-4-D

[0050] Figure 8 The CIE coordinates of the fluorescence spectrum of MZ-4-D change with pH. When the pH decreases from 11.78 to 2.24, the CIE coordinates shift significantly from the blue region to the yellow-green region, moving from (0.18, 0.44) (pH = 11.78) to (0.36, 0.51) (pH = 2.24). At pH 11.78, MZ-4-D exhibits light blue emission (excitation at 465 nm) due to the non-fluorescent helical ring structure of the MS5 moiety and MS6. When the pH decreases from 11.78 to 2.24, the fluorescence color changes from light blue to yellow-green (excitation at 465 nm) due to energy transfer between the MS5 moiety and the open-ring MS6 moiety. Figure 9 The corresponding fluorescence photograph shows that the color change of MZ-4-D can well achieve visual color change of pH.

[0051] Infrared spectrum analysis of Example 7M-Z-4-D

[0052] In order to preliminarily confirm that MS5 and MS6 were successfully copolymerized onto PMMA, infrared spectroscopy was used for analysis and comparison, such as Figure 10 As shown in the figure, PMMA curve can be seen at 1732cm -1 The characteristic vibration peak of C=O appeared at 2996cm -1 、2951cm -1 The CH bond stretching vibration absorption peaks of methoxy and methyl appeared at 1449 and 1159, 1190, 1240, and 1268 cm -1 The characteristic peaks are the absorption peaks of methyl CH bond bending vibration and COC stretching vibration; from the curve MS6 in the figure, it can be seen that the peaks are located at 1715cm -1C=O stretching vibration peak at 1715 cm -1 The C=O stretching vibration peak at 1689cm is shown in the curve MS5. -1 C=N stretching vibration peak at 1720cm -1 The C=O stretching vibration peak at the bottom of the column; the absorption peak positions of each monomer almost correspond to the position of the main absorption peak of MZ-4-D. Combined with the NMR spectrum, it can be inferred that MZ-4-D was successfully prepared by RAFT.

[0053] Example 8 Crystallization Performance Analysis of the Product of M-Z-4-D

[0054] Figure 11 The X-ray powder diffraction (XRD) patterns of PMMA and MZ-4-D show that within the 2θ angle range of 5-80°, PMMA exhibits two major diffraction peaks at 2θ = 14.16° and 2θ = 30.35°, respectively. MZ-4-D, on the other hand, exhibits a sharp MS5 characteristic diffraction peak at 2θ = 7.14°, and sharp MS6 characteristic diffraction peaks at 2θ = 8.96°, 2θ = 11.75°, 2θ = 16.17°, and 2θ = 22.36°. The relative intensity of the corresponding diffraction peaks for MZ-4-D is 1.46 times that of PMMA, indicating an increase in the crystalline phase.

[0055] Surface morphology analysis of the product of Example 9

[0056] Figure 12 This is a scanning electron microscope image of MZ-4-D. A small amount of MZ-4-D powder was evenly applied to a metal plate and then sprayed with gold for several minutes before scanning with an electron microscope. The image shows the free dispersion of the product blocks, which appear as fine particles of relatively uniform size and good surface morphology. Agglomeration is caused by precipitation polymerization.

[0057] The above embodiments are merely examples and illustrations of the present invention and are not intended to limit the present invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the above embodiments and that various variations and modifications may be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention.

Claims

1. A polymer material based on coumarin and rhodamine, characterized in that The specific structural formula is shown below: Wherein m:n:p=93:3.6:1, Mn=17227.2g / mol.

2. A polymer material based on coumarin and rhodamine as claimed in claim 1, characterized in that: When the pH value of the solution changes from alkaline to acidic, the solution color changes from blue to yellow-green, and the emission wavelength red-shifts from 484 nm to 554 nm.

3. Use of a coumarin and rhodamine-based polymer material as claimed in any one of claims 1 to 2 as a fluorescent probe for pH detection.

4. A method for preparing a polymer material based on coumarin and rhodamine according to any one of claims 1 to 2, characterized in that: S1.2mmol of rhodamine 6G and 3mL of hydrazine hydrate were heated under reflux in 15-30mL of ethanol solution for five hours to obtain the compound rhodamine hydrazine hydrate; S2.500 mg of rhodamine hydrazine hydrate was further reacted with 1.5 times the molar amount of p-allyloxybenzaldehyde and two drops of glacial acetic acid in 25 mL of ethanol solution and heated under reflux for four hours to produce a Schiff base reaction to obtain compound MS6; S3.500 mg of coumarin hydrazine hydrate, one molar amount of p-allyloxybenzaldehyde, and two drops of glacial acetic acid were heated under reflux with stirring in 15-30 ml of anhydrous ethanol for four hours to obtain 450 mg of MS5; 5 mmol of methyl methacrylate, 0.125 mmol of MS5, 0.125 mmol of MS6, and 0.066 mmol of the chain transfer agent 2-(dodecyltrithiocarbonate)-2-methylpropionic acid were heated to 70 degrees in 4 mL of tetrahydrofuran under the initiation of 0.026 mmol of azobisisobutyronitrile, and polymerized for 24 hours to obtain the polymer material MZ-4-D; The reaction formula is as follows:

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