Rhodamine-pyrazole Schiff base multi-metal ion response fluorescent probe and preparation method thereof

Abstract

The invention relates to a rhodamine-pyrazole Schiff base multi-metal ion response fluorescent probe, which is obtained by carrying out nucleophilic addition-elimination reaction on amino-functionalized rhodamine B hydrazide and aldehyde group modified aryl pyrazole aldehyde, and the chemical structural formula of the probe molecule is as shown in the specification: # imgabs0 #. The probe disclosed by the invention shows specific recognition capability on trivalent metal ions Fe < 3 + >, Al < 3 + > and Cr < 3 + > and divalent metal ions Cu < 2 + >. The probe realizes selective recognition of target metal ions in a fluorescence'opening 'mode, and shows double recognition signals along with obvious solution color change.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent probe preparation, and specifically relates to a multi-metal ion responsive fluorescent probe based on a rhodamine-pyrazole Schiff base structure and a preparation method thereof. The present invention synthesizes a novel fluorescent probe RAP containing an imine structure by subjecting amino-functionalized rhodamine B hydrazide to a nucleophilic addition-elimination reaction with an aldehyde-modified aryl pyrazole aldehyde. The probe is responsive to trivalent metal ions Fe 3+ 、Al 3+ and Cr 3+ and divalent metal ions Cu 2+ The probe achieves selective recognition of target metal ions by means of fluorescence “turning on”, accompanied by obvious solution color changes, showing dual recognition signals. Background Art

[0002] Transition metal ions are closely related to fields such as medicine, environmental science, and life science, and are crucial to the regulation of growth, development, and physiological functions of living organisms. However, some high-concentration and non-degradable heavy metal ions such as Cr 6+ , Cu 2+ Such metal ions can cause electrolyte disturbances by destroying intracellular ion homeostasis, thereby causing organ damage and interfering with enzymatic reactions. 3+ Cr 3+ and Fe 3+ And divalent Cu 2+ The impact on the body is particularly significant.

[0003] Rhodamine B is widely used as a fluorescent group for "on" chemical sensors due to its high fluorescence quantum yield, large Stokes shift, excellent photostability, and long absorption and emission wavelengths. The detection mechanism of Rhodamine B is based on the transformation of the lactone ring structure: when the Rhodamine B derivative exists in the form of a closed-ring lactone, the sample appears colorless and non-fluorescent; after coordination with the target metal ion, the lactone ring opens with obvious color and fluorescence changes. On the other hand, pyrazole compounds are often introduced as fluorescent groups in the design of chemical sensors due to their unique structural characteristics, excellent optical activity, and tunable chemical properties.

[0004] Chemical sensors based on pyrazole and its derivatives have attracted much attention due to their significant fluorescence "on-off" effect and visual colorimetric response. 3+ 、Al 3+ and Cr 3+ and divalent metal ions Cu 2+, a novel rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP was designed and synthesized in this application. The obtained probe RAP of this application shows excellent selectivity for target metal ions (M 3+ and Cu 2+ ). While achieving the "turn-on" of the probe fluorescence, it is accompanied by a significant change in the solution color. Summary of the Invention

[0005] The object of the present invention is to overcome the defects of the prior art and provide a rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe, which can specifically recognize and effectively detect trivalent metal ions Fe 3+ 、Al 3+ and Cr 3+ as well as divalent metal ions Cu 2+ and so on.

[0006] The present invention also provides a preparation method and application of the above rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe.

[0007] In order to achieve the above object of the invention, the solutions adopted in this application are as follows: A rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe, the structural formula of which is shown as follows: .

[0008] A preparation method of the above rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe, which specifically includes the following steps: 1) Dissolve phenylhydrazine and 1,1,3,3-tetramethoxypropane in the solvent methanol, and heat and reflux with constant stirring at 75 - 85 °C for 1 - 2 h under the action of the catalyst hydrochloric acid. After the reaction is completed, evaporate the solvent, adjust the pH to neutral, extract with ethyl acetate to obtain 1-phenyl-1H-pyrazole (Compound 1); 2) Mix the 1-phenyl-1H-pyrazole, phosphorus oxychloride (POCl3) and N,N-dimethylformamide (DMF) obtained in step 1), and then heat and reflux with constant stirring at 70 - 85 °C for 3 - 5 h. After the reaction is completed, pour it into ice water, extract with dichloromethane, and separate by column chromatography to obtain 1-phenyl-1H-pyrazole-4-carbaldehyde (Compound 2); 3) Dissolve rhodamine B and hydrazine hydrate in absolute ethanol, and heat and reflux with constant stirring at 70 - 80 °C for 4 - 6 h. After the reaction is completed, cool to room temperature, concentrate the solvent, adjust the pH to weakly alkaline 9 - 10 with hydrochloric acid and sodium hydroxide solution, precipitate solids, and filter, wash and dry to obtain rhodamine B hydrazide (Compound 3); 4) Dissolve the 1-phenyl-1H-pyrazole-4-carbaldehyde obtained in step 2) and the rhodamine B hydrazide obtained in step 3) in an anhydrous ethanol solvent, and stir and heat under reflux at a constant temperature of 70 - 80 °C for 6 - 8 h under the action of a catalyst, glacial acetic acid. After the reaction is completed, cool to room temperature, precipitate a solid, and after suction filtration, washing, drying, and recrystallization, the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP (compound 4) is obtained.

[0009] The synthetic route of the above rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe is as follows: .

[0010] Specifically, the molar ratio of phenylhydrazine to 1,1,3,3-tetramethoxypropane described in step 1) is preferably 1:1 - 1.2.

[0011] Further, the hydrochloric acid described in step 1) is preferably an HCl solution with a concentration of 0.7 - 0.9 mol·L -1 ; the hydrazine hydrate described in step 3) is preferably an N2H4·H2O solution with a mass concentration of 80%. The molar ratio of the hydrochloric acid used as the catalyst in step 1) to 1,1,3,3-tetramethoxypropane is 0.4 - 0.6:1.

[0012] Specifically, the molar ratio of 1-phenyl-1H-pyrazole, phosphorus oxychloride (POCl3), and N,N-dimethylformamide (DMF) described in step 2) is preferably 1:1 - 2:1 - 2.

[0013] Specifically, the molar ratio of rhodamine B to hydrazine hydrate described in step 3) is preferably 1:5 - 10. The hydrochloric acid used to adjust the pH in step 3) is an HCl solution with a concentration of 1 - 2 mol·L -1 ; the sodium hydroxide solution used is an NaOH solution with a concentration of 1 - 2 mol·L -1 .

[0014] Specifically, the molar ratio of rhodamine B hydrazide to 1-phenyl-1H-pyrazole-4-carbaldehyde described in step 4) is preferably 1:1 - 1.2. The molar ratio of 1-phenyl-1H-pyrazole-4-carbaldehyde to the catalyst glacial acetic acid is preferably 1:0.2 - 0.5.

[0015] Further, the eluent used for column chromatography separation in step 2) is preferably composed of a mixture of petroleum ether and ethyl acetate with a volume ratio of 7 - 9:1.

[0016] The present invention also provides the above rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe for specifically recognizing and detecting Fe 3+ , Al 3+ , Cr 3+ , Cu2+ The application of at least one of the following.

[0017] In this application, a novel rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP was designed and synthesized, which can specifically recognize and effectively detect trivalent metal ions Fe 3+ 、Al 3+ and Cr 3+ as well as divalent metal ions Cu 2+ etc. The probe RAP described in this application shows excellent selectivity for target metal ions (M 3+ and Cu 2+ ). While realizing the "turn-on" of the probe fluorescence, it is accompanied by a significant change in the solution color.

[0018] In the EtOH / H2O solvent, the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP in this application coordinates with the target metal ions in a 1:1 binding ratio, resulting in the opening of its lactone ring and the "turn-on" of fluorescence, realizing the specific recognition of trivalent metal ions M 3+ (Fe 3+ 、Al 3+ and Cr 3+ )and divalent metal ions Cu 2+ etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the 1H nuclear magnetic resonance spectrum ( 1 1H NMR) of the probe RAP of the present invention; Figure 2 is the 13C nuclear magnetic resonance spectrum ( 13 13C NMR) of the probe RAP of the present invention; Figure 3 is the ultraviolet absorption spectrum of the selectivity of the probe RAP of the present invention for metal ions (the abscissa is the wavelength and the ordinate is the absorbance); Figure 4 is the fluorescence emission spectrum of the selectivity of the probe RAP of the present invention for metal ions (the abscissa is the wavelength and the ordinate is the fluorescence intensity, and the excitation wavelength is 510 nm); Figure 5 In, a) is a photo of the solution color change after adding different metal ions of the probe RAP of the present invention under natural light; b) is a photo of the solution fluorescence change after adding different metal ions of the probe RAP of the present invention under irradiation with a 365 nm ultraviolet lamp; Figure 6 is the probe RAP of the present invention in an EtOH / H2O (v / v = 7 / 3) solution, with the increase of Cu 2+Increase in concentration, change in fluorescence emission spectrum (abscissa is wavelength, ordinate is fluorescence intensity, excitation wavelength is 510 nm); the inset in the figure is the probe RAP of the present invention with the increase of Cu 2+ Increase in concentration, change trend of fluorescence intensity at 578 nm (abscissa is Cu 2+ concentration, ordinate is fluorescence intensity); Figure 7 For the probe RAP of the present invention in an EtOH / H2O (v / v = 7 / 3) solution, with the increase of Fe 3+ Increase in concentration, change in fluorescence emission spectrum (abscissa is wavelength, ordinate is fluorescence intensity, excitation wavelength is 510 nm); the inset in the figure is the probe RAP of the present invention with the increase of Fe 3+ Increase in concentration, change trend of fluorescence intensity at 578 nm (abscissa is Fe 3+ concentration, ordinate is fluorescence intensity); Figure 8 For the probe RAP of the present invention in an EtOH / H2O (v / v = 7 / 3) solution, with the increase of Al 3+ Increase in concentration, change in fluorescence emission spectrum (abscissa is wavelength, ordinate is fluorescence intensity, excitation wavelength is 510 nm); the inset in the figure is the probe RAP of the present invention with the increase of Al 3+ Increase in concentration, change trend of fluorescence intensity at 578 nm (abscissa is Al 3+ concentration, ordinate is fluorescence intensity); Figure 9 For the probe RAP of the present invention in an EtOH / H2O (v / v = 7 / 3) solution, with the increase of Cr 3+ Increase in concentration, change in fluorescence emission spectrum (abscissa is wavelength, ordinate is fluorescence intensity, excitation wavelength is 510 nm); the inset in the figure is the probe RAP of the present invention with the increase of Cr 3+ Increase in concentration, change trend of fluorescence intensity at 578 nm (abscissa is Cr 3+ concentration, ordinate is fluorescence intensity). Detailed implementation mode

[0020] The technical solutions of the present invention are further introduced in detail below in combination with embodiments, and the protection scope of the present invention is not limited thereto.

[0021] In the following embodiments, the raw materials used are all ordinary commercially available products that can be directly purchased.

[0022] Room temperature refers to 25 ± 5°C.

[0023] Example 1 A preparation method of a rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe, which specifically includes the following steps: 1) Weigh 12.98 g (120 mmol) of phenylhydrazine and 19.70 (120 mmol) of 1,1,3,3-tetramethoxypropane into a 300 mL round-bottom flask, add 80 mL of methanol solvent, 80 mL of 0.8 mol·L -1 hydrochloric acid catalyst, and heat under constant stirring and reflux at 75 °C for 1.5 h. After the reaction is completed, rotate and evaporate to remove the solvent, adjust the pH of the reaction system to neutral with saturated NaOH solution, and extract with ethyl acetate (5×30 mL) to obtain a transparent brown liquid, which is 1-phenyl-1H-pyrazole; 2) Weigh 4.82 g (66 mmol) of DMF into a 100 mL three-necked flask, cool it to 0-5 °C in an ice-water bath, slowly add 10.12 g (66 mmol) of POCl3 dropwise with a constant-pressure dropping funnel and stir for 1 h. Add 6.97 g (60 mmol) of 1-phenyl-1H-pyrazole to the three-necked flask, and then transfer it to an oil bath at 80 °C for reaction for 4 h. After the reaction is completed, pour the reaction system into 100 mL of ice water, let it stand, and extract with dichloromethane (5×30 mL) to obtain a black-brown liquid. Perform column chromatography separation with petroleum ether and ethyl acetate (v / v = 8 / 1) to obtain a white solid, which is 1-phenyl-1H-pyrazole-4-carbaldehyde; 3) Weigh 4.790 g (10 mmol) of rhodamine B into a 300 mL round-bottom flask, add 180 mL of anhydrous ethanol solvent, slowly add 5.001 g of 80% N2H4·H2O solution (80 mmol) dropwise with a constant-pressure dropping funnel, and heat under constant stirring and reflux at 80 °C for 6 h. After the reaction is completed, cool the system to room temperature, first filter off the insoluble impurities by suction, and then remove the solvent by rotary evaporation. Subsequently, in order to remove the excessive hydrazine hydrate in the reaction system and precipitate the product as a solid, add 80 mL of 1 mol·L - 1 HCl solution, and adjust the pH to about 9.5 with 1 mol·L -1 NaOH solution. A large amount of light pink solid precipitates. After suction filtration, washing with distilled water, and vacuum drying at 60 °C for 24 h, it is rhodamine B hydrazide; 4) Weigh 0.913 g (2 mmol) of rhodamine B hydrazide and 0.361 g (2.2 mmol) of 1-phenyl-1H-pyrazole-4-carbaldehyde into a 100 mL round-bottom flask, add 20 mL of anhydrous ethanol solvent and 0.05 mL of glacial acetic acid catalyst, and stir and heat under reflux at 80 °C for 8 h. After the reaction is completed, cool to room temperature, and a large amount of white solid will precipitate. Filter it by suction, wash it with anhydrous ethanol, dry it in vacuo at 60 °C for 12 h, and recrystallize it with anhydrous ethanol to obtain the target product, rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP.

[0024] The spectral data of the target product, rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP, are as follows. For details, see Figure 1 and Figure 2 : 1 H NMR (400 MHz, DMSO- d 6 ) δ : 8.76 (s, 1H), 8.61 (s, 1H), 7.89 (d, J = 8.0 Hz, 1H), 7.78 - 7.75 (m, 3H), 7.59 - 7.51 (m, 2H), 7.44 (t, J = 8.0 Hz, 2H), 7.28 (t, J = 8.0 Hz, 1H), 7.05 (d, J = 8.0 Hz, 1H), 6.46 - 6.43 (m, 4H), 6.32 (dd, J 1 = 8.0 Hz, J 2 = 4 Hz, 2H), 3.28 (q, J 1 = 12.0 Hz, J 2 = 4 Hz, 8H), 1.05 (t, J = 4.0 Hz, 12H); 13 C NMR (100 MHz, DMSO- d 6 ) δ: 164.1, 153.0, 152.0, 148.9, 142.2, 139.5, 139.2, 134.1, 130.0, 129.1, 128.9, 128.4, 127.9, 127.2, 124.0, 123.4, 120.8, 119.0, 108.4, 105.9, 98.0, 65.7, 44.1, 12.9. FT-IR (KBr cm -1 ) ν : 2970, 1691, 1616, 1516, 1306. HRMS ( m / z ): 611.3145 [M+H] + (calcd 611.3129).

[0025] From the above spectral information, the structure of the target product rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP prepared can be deduced as follows: .

[0026] Use test of the probe RAP of the present invention.

[0027] Test Example 1 Take the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP (0.0305 g, 0.05 mmol) prepared in Example 1, dissolve it with DMSO (10 mL), and prepare a probe mother liquor of 5×10 -3 mol·L -1 ; Take 0.2 mL of the 5×10 - 3 mol·L -1 probe mother liquor, dilute it with EtOH / H2O (v / v = 7 / 3), and make up to the mark in a 100 mL volumetric flask to prepare a 1×10 -5 mol·L -1 probe solution. Dissolve different metal salts in 10 mL of deionized water to prepare a 1×10 -2 mol·L -1 metal ion stock solution. Use a microsyringe to take 2 μL of the 1×10 -2 mol·L -1 metal ion stock solution into 2 mL of the 1×10 -5 mol·L -1 blank probe solution to prepare a probe solution containing different metal ions. Use a UH4150 ultraviolet-visible-near-infrared spectrophotometer to measure the blank probe solution and add 1 equivalent concentration of different interfering substances Li+ , Na + , Mg 2+ , Al 3+ , K + , Ca 2+ , Cr 3+ , Mn 2+ , Fe 3 + , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Ba 2+ , Pb 2+ probe solution of, the ultraviolet absorption spectra are shown in Figure 3 .

[0028] As Figure 3 shown, with the addition of Fe 3+ , Al 3+ , Cr 3+ and Cu 2+ , new absorption peaks appeared in the ultraviolet absorption spectrum of the probe solution at 560 nm. Compared with M 3+ (Fe 3+ , Al 3+ , Cr 3+ ), the addition of Cu 2+ made the absorption peak at 560 nm more obvious. 560 nm is the ultraviolet absorption characteristic peak of the ring-opening of rhodamine B, indicating that during the process of the probe RAP recognizing the target metal ions, its lactone ring opened. The probe RAP can specifically recognize M 3+ and Cu 2+ .

[0029] Test Example 2 Take the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP (0.0305 g, 0.05 mmol) prepared in Example 1, dissolve it in DMSO (10 mL), and prepare a probe mother liquor of 5×10 -3 mol·L -1 ; take 0.2 mL of the 5×10 - 3 mol·L -1 probe mother liquor, dilute it with EtOH / H2O (v / v = 7 / 3), and make up to the mark in a 100 mL volumetric flask to prepare a 1×10 -5 mol·L -1 probe solution. Dissolve different metal salts in 10 mL of deionized water to prepare a 1×10 -2 mol·L -1Metal ion stock solution. Use a micro-syringe to take 2 μL of 1×10 -2 mol·L -1 metal ion stock solution and add it to 2 mL of 1×10 -5 mol·L -1 blank probe solution to prepare probe solutions containing different metal ions. Use an F7000 fluorescence spectrophotometer with an excitation wavelength of 510 nm to measure the fluorescence emission spectra of the blank probe solution and the probe solutions added with 1 equivalent concentration of different interfering substances Li + , Na + , Mg 2+ , Al 3+ , K + , Ca 2+ , Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Ba 2+ , Pb 2+ . The results are shown in Figure 4 .

[0030] As Figure 4 shown, after adding M 3+ (Fe 3+ , Al 3+ , Cr 3+ ) and Cu 2+ , the fluorescence emission peaks of the probe solution at 578 nm are all significantly enhanced. Among them, the most significant increase in fluorescence intensity is Fe 3+ , followed by Al 3+ , and finally Cr 3+ and Cu 2+ . The intensity of the fluorescence "turn-on" of Cu 2+ is relatively weak compared with that of the trivalent metal ion M 3+ , which may be due to the paramagnetism of Cu 2+ causing fluorescence quenching of the ring-opening rhodamine. RAP shows good specific recognition ability for M 3+ and Cu 2+ .

[0031] Test Example 3 Take the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe RAP (0.0305 g, 0.05 mmol) prepared in Example 1 and dissolve it in DMSO (10 mL) to prepare a 5×10 -3 mol·L -1Probe stock solution; Take 0.2 mL of 5×10 - 3 mol·L -1 probe stock solution, dilute it with EtOH / H2O (v / v = 7 / 3), and make up to the mark in a 100 mL volumetric flask to prepare a 1×10 -5 mol·L -1 probe solution. Dissolve different metal salts in 10 mL of deionized water to prepare a 1×10 -2 mol·L -1 metal ion stock solution. Use a microsyringe to take 2 μL of 1×10 -2 mol·L -1 metal ion stock solution into 2 mL of 1×10 -5 mol·L -1 blank probe solution to prepare probe solutions containing different metal ions. Record the color of the blank probe solution and the fluorescence changes of the probe solutions added with 1 equivalent concentration of different interfering substances Li + , Na + , Mg 2+ , K + , Al 3+ , Ca 2+ , Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Ba 2+ , Pb 2+ under natural light and the fluorescence changes under irradiation with a 365 nm ultraviolet lamp. The results are shown in Figure 5 .

[0032] As Figure 5 shown, under natural light, the probe solutions added with other metal ions are colorless and transparent, and after adding M 3+ (Fe 3+ , Al 3+ , Cr 3+ ), the solution turns light pink; after adding Cu 2+ , the solution turns rose red. Under irradiation with a 365 nm ultraviolet lamp, the probe solution itself has no fluorescence, and the addition of trivalent metal ions M 3+ (Fe 3+ , Al 3+ , Cr 3+ ) and Cu 2+ makes the probe RAP solution "turn on" orange-red fluorescence. The target metal ions Fe 3+ , Al3+ , Cr 3+ and Cu 2+ The addition of... causes the lactone ring of the probe RAP molecule to open, resulting in changes in the color and fluorescence of its solution.

[0033] Test Example 4 Take the rhodamine-pyrazole Schiff base polymetal ion-responsive fluorescent probe RAP (0.0305 g, 0.05 mmol) prepared in Example 1, dissolve it in DMSO (10 mL), and prepare a probe mother liquor of 5×10 -3 mol·L -1 Take 0.2 mL of the 5×10 - 3 mol·L -1 probe mother liquor, dilute it with EtOH / H2O (v / v = 7 / 3), and make up to the mark in a 100 mL volumetric flask to prepare a probe solution of 1×10 -5 mol·L -1 Dissolve different metal salts in 10 mL of deionized water to prepare a metal ion stock solution of 1×10 -2 mol·L -1 Use a microsyringe to take 2 μL of the 1×10 -2 mol·L -1 metal ion stock solution and add it to 2 mL of the 1×10 -5 mol·L -1 blank probe solution to prepare a probe solution containing different metal ions. Explore the sensing characteristics of the probe RAP with the target metal ions through fluorescence titration experiments. Take the titration of Cu 2+ as an example for discussion. Use a microsyringe to gradually add 1×10 -5 mol·L -1 probe solution with 1×10 -2 mol·L -1 Cu 2+ stock solution. Use an F7000 fluorescence spectrophotometer to measure the changes in the fluorescence emission spectrum of the probe solution with an excitation wavelength of 510 nm. The results are shown in Figure 6 . As Figure 6 shown, as the concentration of Cu 2+ increases, the fluorescence intensity of the solution gradually increases. It can be observed from the Figure 6 inset that when the concentration of Cu 2+ is 0 - 3 equivalents, the change trend of the fluorescence intensity of the system is obvious; when the concentration of Cu 2+ exceeds 3 equivalents, the increase in its fluorescence intensity is slow; when the concentration of Cu 2+ reaches 10 equivalents, the fluorescence intensity reaches the maximum. When performing M 3+ (Fe 3+, Al 3+ , Cr 3+ ) during the titration experiment, the same experimental results as above were obtained. Based on this, it was selected to carry out the fluorescence titration experiment and result discussion of RAP with M 3+ within the range of 0 - 3 equivalent concentrations. The results are shown in Figure 7 , 8 and 9. As shown in Figure 7 , 8 and 9, within the range of 0 - 3 equivalent concentrations, as the concentration of M 3+ (Fe 3+ , Al 3+ , Cr 3+ ) target metal ions increases, the fluorescence intensity of the RAP - M 3+ solution shows an obvious upward trend; when the concentration of M 3+ reaches 3 equivalents, the fluorescence intensity of the system reaches the maximum value. In addition, as shown in Figure 7 , Figure 8 and Figure 9 the inset shows that the concentration of the probe and M 3+ (Fe 3+ , Al 3+ , Cr 3 + ) target metal ions shows a good linear change trend within the range of 0 - 3 equivalents.

[0034] In summary, the probe of the present invention shows specific recognition ability for trivalent metal ions Fe 3+ , Al 3+ and Cr 3+ and divalent metal ion Cu 2+ . The probe realizes the selective recognition of target metal ions through the fluorescence "turn - on" method, and at the same time is accompanied by an obvious change in the solution color, showing a dual recognition signal.

Claims

1. A rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe, characterized in that, The structural formula is as follows: 。 2. The preparation method of the rhodamine-pyrazole Schiff base polymetal ion-responsive fluorescent probe according to claim 1, characterized in that, Specifically, it includes the following steps: 1) Dissolve phenylhydrazine and 1,1,3,3-tetramethoxypropane in methanol, and under the action of the catalyst hydrochloric acid, stir and heat under reflux at 75 - 85 °C for 1 - 2 h. After the reaction is completed, evaporate the solvent, adjust the pH to neutral, extract with ethyl acetate to obtain 1-phenyl-1H-pyrazole; 2) Mix the 1-phenyl-1H-pyrazole obtained in step 1), phosphorus oxychloride and N,N-dimethylformamide, and then heat under reflux with constant stirring at 70 - 85 °C for 3 - 5 h. After the reaction is completed, pour it into ice water, extract with dichloromethane, and separate by column chromatography to obtain 1-phenyl-1H-pyrazole-4-carbaldehyde; 3) Dissolve rhodamine B and hydrazine hydrate in absolute ethanol, and heat under reflux with constant stirring at 70 - 80 °C for 4 - 6 h. After the reaction is completed, cool to room temperature, concentrate the solvent, adjust the pH to 9 - 10, precipitate solids, and obtain rhodamine B hydrazide through suction filtration, washing, and drying; 4) Dissolve the 1-phenyl-1H-pyrazole-4-carbaldehyde obtained in step 2) and the rhodamine B hydrazide obtained in step 3) in absolute ethanol, and under the action of the catalyst glacial acetic acid, stir and heat under reflux at 70 - 80 °C for 6 - 8 h. After the reaction is completed, cool to room temperature, precipitate solids, and obtain the product through suction filtration, washing, drying, and recrystallization.

3. The preparation method of the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe according to claim 2, characterized in that, In step 1), the molar ratio of phenylhydrazine to 1,1,3,3-tetramethoxypropane is 1∶1 - 1.

2.

4. The preparation method of the rhodamine-pyrazole Schiff base polymetal ion-responsive fluorescent probe according to claim 2, characterized in that, The hydrochloric acid described in step 1) is a HCl solution with a concentration of 0.7 - 0.9 mol·L -1 ; the hydrazine hydrate described in step 3) is an N2H4·H2O solution with a mass concentration of 80%.

5. The preparation method of the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe according to claim 2, characterized in that, In step 2), the molar ratio of 1-phenyl-1H-pyrazole to phosphorus oxychloride is 1∶1 - 2.

6. The preparation method of the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe according to claim 2, wherein, In step 3), the molar ratio of rhodamine B to hydrazine hydrate is 1∶5 - 10.

7. The preparation method of the rhodamine-pyrazole Schiff base multi-metal ion-responsive fluorescent probe according to claim 2, wherein, In step 4), the molar ratio of rhodamine B hydrazide to 1-phenyl-1H-pyrazole-4-carbaldehyde is 1∶1 - 1.

2.

8. The preparation method of the rhodamine-pyrazole Schiff base polymetal ion-responsive fluorescent probe according to claim 2, wherein, In step 2), the eluent used for column chromatography separation is composed of petroleum ether and ethyl acetate mixed in a volume ratio of 7 - 9∶1.

9. Use of the rhodamine-pyrazole Schiff base polymetal ion-responsive fluorescent probe according to claim 1 for specifically recognizing at least one of Fe 3+ , Al 3 + , Cr 3+ , Cu 2+ .

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