A pH-responsive organic fluorescent probe, its preparation method and application

Abstract

This invention provides a pH-responsive organic fluorescent probe, its preparation method, and its applications. This probe exhibits excellent pH responsiveness, with a linear pH response range of 4.0 to 8.0, covering the entire pH range of the physiological environment. The pH-responsive fluorescent probe P-pH provided by this invention responds rapidly to acidic pH in the environment; it can be specifically activated in acidic pH environments; and it can specifically respond to acidic pH without interference from related ions. The pH-responsive fluorescent probe P-pH provided by this invention also exhibits good pH response stability and a long response time.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a pH-responsive organic fluorescent probe (P-pH), its preparation method, and its application. Background Technology

[0002] Small-molecule organic fluorescent materials have attracted widespread attention in optical imaging and information encryption due to their advantages such as modifiable structure, tunable color and luminescence intensity, diverse synthesis methods, and excellent photophysical properties. However, due to the aggregation-induced quenching effect of traditional organic fluorescent materials, their fluorescence is easily quenched under physiological conditions, limiting their further application in the chemical industry. In recent years, pH-responsive organic fluorescent probes for environmental monitoring have been increasingly widely used in the chemical field.

[0003] Currently, most developed pH organic fluorescent probes exhibit poor photostability and selectivity, making them highly susceptible to interference from other related substances. Therefore, establishing a pH-responsive signal amplification strategy to achieve accurate detection and response to pH in environmental monitoring is a key area of ​​current research. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a pH-responsive organic fluorescent probe (P-pH) with good pH responsiveness, and its linear pH response range is 4.0 to 8.0, covering the entire pH range of the physiological environment.

[0005] The present invention also provides a method for preparing the pH-responsive organic fluorescent probe P-pH.

[0006] This invention also provides the application of the pH-responsive organic fluorescent probe P-pH in environmental detection.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A pH-responsive organic fluorescent probe, P-pH, has the following structural formula:

[0009]

[0010] Where R = H.

[0011] A further design feature of this invention is that the linear pH response range of the organic fluorescent probe P-pH is 4.0 to 8.0.

[0012] A further design feature of this invention is that the organic fluorescent probe P-pH can be specifically activated in an acidic environment with a pH value of 4-8.

[0013] A further design feature of this invention is that the organic fluorescent probe P-pH exhibits a good linear response in the pH range of 4-8.

[0014] This invention discloses a method for preparing a pH-responsive organic fluorescent probe, comprising the following steps:

[0015] Step 1, Synthesis of the first intermediate: o-phenanthroline was added to a mixed solvent of appropriate amounts of sulfuric acid and nitric acid, and a small amount of potassium bromide was added. The mixture was refluxed at 100-120℃ for 6-12 h to obtain the first intermediate 1,10-o-phenanthroline-5,6-dione.

[0016] Step 2, Synthesis of the auxiliary ligand: The first intermediate prepared in Step 1, diphenylamino-4-benzaldehyde, and ammonium acetate were dissolved in glacial acetic acid and refluxed at 60-70℃ for 12-24 h. After the reaction, the mixture was neutralized with ammonia water, then filtered and dried. The purified product was purified by silica gel column chromatography to obtain the crude product and the auxiliary ligand. The molar ratio of the first intermediate, diphenylamino-4-benzaldehyde, and ammonium acetate was 1:1:0.01.

[0017] Step 3, Synthesis of the second intermediate: Methoxynaphthylpropionic acid impurity, dipentanoyl diboron, ferrocene palladium dichloride, and potassium acetate were dissolved in an appropriate amount of dioxane solvent. After nitrogen was introduced into the system, the reaction was carried out for more than 24 hours. After the reaction was completed, the product was filtered and extracted, the organic phase was collected, dried, and purified by column chromatography to obtain the second intermediate 2-(6-methoxynaphth-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane, wherein the molar ratio of methoxynaphthylpropionic acid impurity, dipentanoyl diboron, ferrocene palladium dichloride, and potassium acetate was (1.4-2.25):(1.4-2.25):0.1:(14-22.5);

[0018] Step 4, Synthesis of the third intermediate: The second intermediate obtained in step 3, 1-chloroisoquinoline, and tetra-triphenylphosphine palladium were dissolved in a suitable amount of toluene and a mixed solvent of ethanol and water. The mixture was purged with nitrogen and reacted at 90-100℃ for 12-24 h. The product was filtered and extracted, the organic phase was collected and dried, and then purified by column chromatography to obtain the third intermediate 1-(6-methoxynaphthyl-2-yl)isoquinoline. The molar ratio of the second intermediate, 1-chloroisoquinoline, and tetra-triphenylphosphine palladium to potassium carbonate was 1:1:(0.06-0.08):(40-50).

[0019] Step 5, Synthesis of iridium chloride bridged dimer: Iridium chloride trihydrate and the third intermediate prepared in step 4 are dissolved in a mixed solution of water and ethylene glycol ethyl ether under nitrogen protection and reacted at 110-120℃ for 40-60 h; after the reaction is completed, the mixture is filtered and dried to obtain iridium chloride bridged dimer, wherein the molar ratio of iridium chloride trihydrate to the third intermediate is (0.9-1):2;

[0020] Step 6, Synthesis of P-pH: Dissolve the iridium chloride bridged dimer, auxiliary ligand, and potassium hexafluorophosphate obtained in step 5 in a suitable amount of methanol and dichloromethane mixed solvent, purge the system with nitrogen, and react at 20-30℃ for 8-24 h; after the reaction, purify the crude product by silica gel column chromatography to obtain the complex P-pH, wherein the molar ratio of the iridium chloride bridged dimer, auxiliary ligand, and potassium hexafluorophosphate is 0.5:1:4.

[0021] The present invention is further designed in that, in step 1, the volume ratio of sulfuric acid to nitric acid in the mixed solvent of sulfuric acid and nitric acid is 1:1; in step 4, the volume ratio of toluene to ethanol in the mixed solvent of toluene, ethanol and water is 2:1; and in step 6, the volume ratio of methanol to dichloromethane in the mixed solvent of methanol and dichloromethane is 2:1.

[0022] A further design feature of this invention is that, in step 3, the solvent used for column chromatography purification is water.

[0023] A further design of this invention is that, in step 6, the solvent used for the silica gel column chromatography purification is methanol or anhydrous dichloromethane.

[0024] The above-mentioned pH-responsive organic fluorescent probe P-pH is used in environmental monitoring.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The pH-responsive organic fluorescent probe P-pH provided by this invention, due to the excellent photophysical and photochemical properties and superior photostability of iridium transition metal complexes, is widely used in optical imaging, photocatalysis, and information encryption. However, research on iridium complexes in pH-responsive detection is still in its early stages. Therefore, studying the application of iridium complexes in pH-responsive environments is of great significance and promising development potential.

[0027] The pH-responsive organic fluorescent probe P-pH exhibits excellent pH responsiveness, with a linear pH response range of 4.0 to 8.0, covering the entire pH range of the physiological environment and possessing the potential for environmental detection.

[0028] The pH-responsive organic fluorescent probe P-pH synthesized in this invention exhibits pH responsiveness, with a linear pH response range of 4.0 to 8.0, covering the entire pH range of the physiological environment, and possesses the potential for environmental detection.

[0029] The pH-responsive organic fluorescent probe material P-pH of this invention enables fluorescence on / off detection at different pH levels. The luminescence performance of the fluorescent probe P-pH under different pH, metal ion, redox substances, temperatures, and viscosities was investigated. This invention lays a foundation for advancing the application of metal-based organic materials in relevant pH detection and further developing environmental monitoring materials.

[0030] The pH-responsive fluorescent probe P-pH provided by this invention can rapidly respond to acidic pH in the environment; it can be specifically activated in acidic pH environments; and it can specifically respond to acidic pH without being affected by related ions. The pH-responsive fluorescent probe P-pH provided by this invention also has good pH response stability and a long response time. Attached Figure Description

[0031] Figure 1 Here is a synthetic route diagram for the pH-responsive organic fluorescent probe in the examples:

[0032] Figure 2 Synthetic route diagram for auxiliary ligands:

[0033] Figure 3 Synthetic route diagram for the second intermediate:

[0034] Figure 4 Synthetic route diagram for the third intermediate:

[0035] Figure 5 Synthetic route diagram for iridium chloride bridged dimers;

[0036] Figure 6 Synthetic route diagram for P-pH:

[0037] Figure 7 This is a schematic diagram of the mechanism of P-pH response to pH in this invention;

[0038] Figure 8 This is the 1H NMR spectrum of the probe P-pH of the present invention;

[0039] Figure 9 This is the fluorescence spectrum of the P-pH response to pH of the present invention;

[0040] Figure 10 This is the ion interference spectrum of the P-pH response to pH of the present invention;

[0041] Figure 11 The fluorescence spectra of the time stability of P-pH to different pH responses of the present invention;

[0042] Figure 12 The fluorescence spectra of the temperature stability of P-pH in response to different pH values ​​are shown in the present invention.

[0043] Figure 13 The fluorescence spectra of the viscosity stability of P-pH in response to different pH values ​​are shown in the present invention. Detailed Implementation

[0044] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. For those skilled in the art, any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the invention are all within the scope of the present invention.

[0045] The reagents used in this invention are described as follows: All raw materials used in this invention are purchased from suppliers such as Sinopharm and Aladdin. The raw materials are used directly without any special treatment.

[0046] The synthetic route of the pH-responsive organic fluorescent probe (referred to as fluorescent probe P-pH) in this invention is shown in Figure 1:

[0047] Among them, the synthetic route of the auxiliary ligand is as follows Figure 2 As shown:

[0048] The synthetic route of the second intermediate is as follows: Figure 3 As shown:

[0049] The synthetic route of the third intermediate is as follows: Figure 4 As shown:

[0050] Synthetic routes for iridium-chloride bridged dimers are as follows: Figure 5 As shown;

[0051] The synthetic route of P-pH is as follows: Figure 6 As shown.

[0052] Example 1:

[0053] The synthesis of the pH-responsive organic fluorescent probe P-pH in this example:

[0054] Step 1, Synthesis of the first intermediate 1,10-o-diaphenanthrene-5,6-dione: o-diaphenanthrene (2.7 g, 15 mmol) was added to a mixed solvent of sulfuric acid and nitric acid in 30 mL, a small amount of potassium bromide was added, and the mixture was heated to 110 °C in an oil bath and refluxed for 12 h to obtain the first intermediate 1,10-o-diaphenanthrene-5,6-dione; wherein the volume ratio of sulfuric acid to nitric acid in the mixed solvent of sulfuric acid and nitric acid was 1:1.

[0055] Step 2, Synthesis of Auxiliary Ligands: Weigh the first intermediate prepared in Step 1, 1,10-o-phenanthroline-5,6-dione (1.95 g, 9 mmol), diphenylamino-4-benzaldehyde (2.55 g, 9 mmol), and ammonium acetate (6.9 g, 0.09 mol), and dissolve them in 30 mL of glacial acetic acid. Reflux the mixture in an oil bath at 60 °C for 12 h. After the reaction, neutralize the mixture with ammonia in an ice bath. Once the pH in the reaction flask reaches 6 and no solid precipitates, filter the mixture using a funnel, washing continuously with water during this process. After filtration, dry the mixture in an oven. Then, purify the product using petroleum ether and ethyl acetate in a volume ratio of 6:1.

[0056] Step 3, Synthesis of the second intermediate 2-(6-methoxynaphthyl-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane: 0.1 g (0.45 mmol) of methoxynaphthylpropionic acid impurity, 0.15 g (0.45 mmol) of dipentanoyl diboron, 0.02 mmol of (diphenylphosphino)ferrocene palladium dichloride, and 0.85 g (4.5 mmol) of potassium acetate were dissolved in 6 mL of dioxane solvent. The system was purged with nitrogen and reacted for 12 h. After the reaction was completed, the product was filtered and extracted. The organic phase was collected, dried, and purified by column chromatography. The solvents used for column chromatography purification were petroleum ether and dichloromethane, with a volume ratio of petroleum ether to dichloromethane of 3:1.

[0057] Step 4, Synthesis of the third intermediate 1-(6-methoxynaphth-2-yl)isoquinoline: The second intermediate 2-(6-methoxynaphth-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane (0.4 g, 1.5 mmol), 1-chloroisoquinoline (0.3 g, 1.5 mmol), and tetra-triphenylphosphine palladium (0.1 g, 0.09 mmol) prepared in Step 3 were dissolved in 30 mL of a mixed solvent of toluene, ethanol, and water. Nitrogen gas was introduced, and the mixture was reacted at 96 °C for 24 h. The product was then filtered and extracted. The organic phase was collected, dried, and purified by column chromatography. The purification solvent ratio was petroleum ether to dichloromethane (volume ratio 3:1). The volume ratio of toluene to ethanol in the mixed solvent of toluene, ethanol, and water was 2:1.

[0058] Step 5, Synthesis of iridium chloride bridged dimer: Weigh iridium chloride trihydrate (0.4 g, 1.4 mmol) and the third intermediate prepared in step 4 (0.8 g, 3 mmol), dissolve them in a mixed solution of ethylene glycol ethyl ether and water, purge with nitrogen, and react at 120 °C for 48 h. Filter and dry in an oven.

[0059] Step 6, Synthesis of P-pH: The above-mentioned iridium chloride bridged dimer (0.32 g, 0.2 mmol), the above-mentioned auxiliary ligand (0.18 g, 0.4 mmol), and potassium hexafluorophosphate (0.3 g, 1.6 mmol) were dissolved in 10 mL of a mixed solvent of methanol and dichloromethane, with a volume ratio of methanol to dichloromethane of 2:1. The reaction system was purged with nitrogen and reacted at 25 °C for 12 h. The product was purified by column chromatography using dichloromethane and methanol to obtain the pH-responsive organic fluorescent probe P-pH, abbreviated as fluorescent probe P-pH.

[0060] The response mechanism of the fluorescent probe P-pH prepared in this example is as follows: Figure 7 As shown in the figure, the fluorescence intensity of the probe is significantly enhanced and the red light intensity is significantly increased under acidic conditions.

[0061] Example 2:

[0062] The method for preparing the pH-responsive organic fluorescent probe of the present invention includes the following steps:

[0063] Step 1, Synthesis of the first intermediate: 6 mmol of o-phenanthroline was added to a mixed solvent of sulfuric acid and nitric acid in 15 mL. A small amount of potassium bromide was added and the mixture was refluxed at 110 °C for 6 h to obtain the first intermediate 1,10-o-phenanthroline-5,6-dione. The volume ratio of sulfuric acid to nitric acid in the mixed solvent of sulfuric acid and nitric acid was 1:1.

[0064] Step 2, Synthesis of the auxiliary ligand: The first intermediate (7 mmol), diphenylamino-4-benzaldehyde (7 mmol), and ammonium acetate (0.07 mol) prepared in Step 1 were dissolved in 10 mL of glacial acetic acid and refluxed at 70 °C for 15 h. After the reaction, the mixture was neutralized with ammonia water, and then filtered and dried. The crude product was purified by silica gel column chromatography to obtain the auxiliary ligand; the molar ratio of the first intermediate, diphenylamino-4-benzaldehyde, and ammonium acetate was 1:1:0.01.

[0065] Step 3, Synthesis of the second intermediate: 0.7 mmol of methoxynaphthylpropionic acid impurity, 0.7 mmol of dipentanoyl diboron, 0.05 mmol of (bisphenylphosphino)ferrocene palladium dichloride, and 7 mmol of potassium acetate were dissolved in 5 mL of dioxane solvent. The system was purged with nitrogen and reacted for more than 24 h. After the reaction was completed, the product was filtered and extracted, the organic phase was collected, dried, and purified by column chromatography to obtain the second intermediate 2-(6-methoxynaphth-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxoborane, wherein the molar ratio of methoxynaphthylpropionic acid impurity, dipentanoyl diboron, ferrocene palladium dichloride, and potassium acetate was 0.7:0.7:0.05:7.

[0066] Step 4, Synthesis of the third intermediate: The second intermediate (1 mmol), 1-chloroisoquinoline (1 mmol), and tetra-triphenylphosphine palladium (0.08 mmol) obtained in step 3 were dissolved in 20 mL of a mixed solvent of toluene, ethanol, and water. The mixture was purged with nitrogen and reacted at 98 °C for 15 h. The product was filtered and extracted, and the organic phase was collected, dried, and purified by column chromatography to obtain the third intermediate 1-(6-methoxynaphthyl-2-yl)isoquinoline. The molar ratio of the second intermediate, 1-chloroisoquinoline, and tetra-triphenylphosphine palladium to potassium carbonate was 1:1:0.08:50. The volume ratio of toluene to ethanol in the mixed solvent of toluene, ethanol, and water was 2:1.

[0067] Step 5, Synthesis of iridium chloride bridged dimer: Iridium chloride trihydrate (0.9 mmol) and the third intermediate prepared in step 4 (1.8 mmol) were dissolved in a mixed solution of water and ethylene glycol ethyl ether. The reaction was carried out under nitrogen protection at 115 °C for 48 h. After the reaction was completed, the mixture was filtered and dried to obtain the iridium chloride bridged dimer. The molar ratio of iridium chloride trihydrate to the third intermediate was 1:2.

[0068] Step 6, Synthesis of P-pH: Iridium chloride bridged dimer (0.15 mmol), auxiliary ligand (0.3 mmol), and potassium hexafluorophosphate (1.2 mmol) were dissolved in 30 mL of a mixed solvent of methanol and dichloromethane, with a volume ratio of methanol to dichloromethane of 2:1. Nitrogen gas was introduced into the system, and the reaction was carried out at 25 °C for 12 h. The crude product was then purified by silica gel column chromatography to obtain the organic fluorescent probe P-pH. Methanol or dichloromethane was used as the solvent for silica gel column chromatography purification, and the molar ratio of the main ligand, auxiliary ligand 1, and potassium hexafluorophosphate was 0.5:1:4.

[0069] Test Example 1: 1H NMR spectrum of P-pH

[0070] The following are the analytical data of the proton NMR spectrum of the fluorescent probe P-pH prepared in Example 1, such as... Figure 8 shown. 1HNMR(500MHz,Chloroform-d)δ12.26(s,1H),9.22(d,J=73.8Hz,2H),9.13(d,J=7.8Hz,2H),8.78(s,2H),8.11(dd,J=32.8,13.3Hz,4H),7.92-7.75 (m,8H),7.65(s,2H),7.32(d,J=6.0Hz,2H),7.13(d,J=7.7Hz,6H),7.07(t ,J=7.5Hz,2H),7.05-6.96(m,2H),6.72(d,J=33.0Hz,2H),6.56(d,J=6.2H z,2H),3.76(s,6H).

[0071] Test Example 2: pH Response of Iridium Complexes

[0072] The fluorescent probe P-pH prepared in Example 1 was dissolved in dimethyl sulfoxide (DMSO) to obtain a 1 mM stock solution. Then, a 10 mM detection solution was prepared using buffer solutions of different pH values. The changes in absorption and emission spectra under different pH conditions were detected using a UV-Vis spectrophotometer and a fluorescence spectrometer, respectively. The results showed that P-pH exhibited a significant pH response; the fluorescence intensity gradually increased as the pH value decreased, and a good linear relationship was observed within the pH range of 4-8. Figure 9 As shown.

[0073] Test Example 3: Selective Detection of P-pH

[0074] A stock solution of interfering ions with a concentration of 1 mM was prepared, consisting of aluminum chloride, calcium chloride, copper chloride, ferric chloride, ferrous chloride, potassium chloride, magnesium chloride, sodium chloride, zinc chloride, hydrogen peroxide, glutathione, cysteine, and homocysteine. A stock solution of the fluorescent probe P-pH prepared in Example 1 with a concentration of 1 mM was also prepared. In the test solution, the concentration of the interfering ions was 100 μM, and the concentration of the complex was 10 μM. After adding the interfering ions for 5 min, the fluorescence intensity of the sample was detected. Figure 10 As shown, the detection results indicate that the fluorescent probe P-pH exhibits specificity in its response to pH, effectively eliminating interference from the aforementioned ions.

[0075] Test Example 4: pH Response Stability under Different P-pH Conditions

[0076] The fluorescent probe P-pH prepared in Example 1 was dissolved in DMSO to prepare a 1 mM stock solution. Subsequently, detection solutions with a concentration of 10 μM were prepared using PBS (phosphate buffered saline) at pH 4 and 8. The changes in emission spectra at different times, temperatures, and viscosities were detected using a UV-Vis spectrophotometer and a fluorescence spectrometer, respectively. The detection results demonstrate that the probe exhibits good stability under different conditions.

[0077] Test Example 5: P-pH Photostability Test

[0078] The fluorescent probe P-pH prepared in Example 1 was prepared into a 10 μM detection solution using PBS (phosphate buffer) at pH 7. To simulate the pH responsiveness under physiological conditions, such as... Figure 11 , Figure 12 ,and Figure 13As shown, the stability of the pH response of the fluorescent probe P-pH under different times (0-24 hours), temperatures (20-42 degrees), and viscosities (0-glycerol 20%) was investigated. The results indicate that the fluorescent probe P-pH has good stability under different conditions, specifically in terms of time stability at different pH responses, temperature stability at different pH responses, and viscosity stability at different pH responses.

[0079] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pH-responsive organic fluorescent probe P-pH, characterized in that, The structural formula is as follows: Wherein R = H. 2.The preparation method of the pH-responsive organic fluorescent probe P-pH according to claim 1, characterized in that, Comprise the following steps: Step 1, the synthesis of the first intermediate: the o-bisphenyl hydrazine is added to a mixed solvent of appropriate amount of sulfuric acid and nitric acid, a small amount of potassium bromide is added, and the reaction is carried out at 100-120 DEG C under reflux for 6-12h, to obtain the first intermediate with the following structural formula: Step 2, the synthesis of auxiliary ligand: the first intermediate prepared in step 1, diphenyl amino-4-benzaldehyde and ammonium acetate are dissolved in glacial acetic acid, and the reaction is carried out at 60-70 DEG C under reflux for 12-24h, after the reaction, ammonia is neutralized, then filtered and dried, and the product is purified by silica gel column chromatography to obtain the auxiliary ligand; the molar ratio of the first intermediate, diphenyl amino-4-benzaldehyde and ammonium acetate is 1:1:0.01; the structural formula of the auxiliary ligand is as follows: wherein R = H; Step 3, the synthesis of the second intermediate: methoxynaphtalene propionic acid impurity, bis (pivaloyl) diboron, ferrocene dichloropalladium and potassium acetate are dissolved in appropriate amount of dioxane solvent, nitrogen is filled in the system, and the reaction is carried out for more than 24h, after the reaction, the product is filtered and extracted, the organic phase is collected, dried and then purified by column chromatography to obtain the second intermediate, wherein the molar ratio of methoxynaphtalene propionic acid impurity, bis (pivaloyl) diboron, ferrocene dichloropalladium and potassium acetate is (1.4-2.25):(1.4-2.25):0.1:(14-22.5); the structural formula of the second intermediate is as follows: Step 4, the synthesis of the third intermediate: the second intermediate prepared in step 3, 1-chloroisoquinoline and tetrakis (triphenylphosphine) palladium and potassium carbonate are dissolved in appropriate amount of mixed solvent of toluene, ethanol and water, nitrogen is filled in the system, and the reaction is carried out at 90-100 DEG C for 12-24h, the product is filtered and extracted, the organic phase is collected and dried, and then purified by column chromatography to obtain the third intermediate, the molar ratio of the second intermediate, 1-chloroisoquinoline and tetrakis (triphenylphosphine) palladium and potassium carbonate is 1:1:(0.06-0.08):(40-50); the structural formula of the third intermediate is as follows: Step 5, the synthesis of iridium chloride bridge dimer: chloro iridium trihydrate and the third intermediate prepared in step 4 are dissolved in a mixed solution of water and ethylene glycol ethyl ether, and the reaction is carried out at 110-120 DEG C under nitrogen protection for 40-60h; after the reaction is completed, it is filtered and dried to obtain the iridium chloride bridge dimer, the molar ratio of chloro iridium trihydrate and the third intermediate is (0.9-1):2; the structural formula of the iridium chloride bridge dimer is as follows: Step 6, the synthesis of P-pH: the iridium chloride bridge dimer prepared in step 5, the auxiliary ligand and potassium hexafluorophosphate are dissolved in appropriate amount of mixed solvent of methanol and dichloromethane, nitrogen is filled in the system, and the reaction is carried out at 20-30 DEG C for 8-24h; after the reaction, the crude product is purified by silica gel column chromatography to obtain the complex P-pH, the molar ratio of the iridium chloride bridge dimer, the auxiliary ligand and potassium hexafluorophosphate is 0.5:1:

4. 3.The preparation method of the pH-responsive organic fluorescent probe P-pH according to claim 2, characterized in that, The volume ratio of sulfuric acid to nitric acid in the mixed solvent of sulfuric acid and nitric acid in step 1 is 1:1; the volume ratio of toluene to ethanol in the mixed solvent of toluene and ethanol and water in step 4 is 2:1; the volume ratio of methanol to dichloromethane in the mixed solvent of methanol and dichloromethane in step 6 is 2:

1. 4.The preparation method of the pH-responsive organic fluorescent probe P-pH according to claim 2, characterized in that, In step 3, the solvent used for column chromatography purification is water. 5.The preparation method of the pH-responsive organic fluorescent probe P-pH according to claim 2, characterized in that, In step 6, the solvent used for silica gel column chromatography purification is methanol or anhydrous dichloromethane.

6. The use of the pH-responsive organic fluorescent probe P-pH in environmental detection according to claim 1.

7. Use according to claim 6, characterized in that: The linear pH response range of the pH-responsive organic fluorescent probe P-pH is 4.0 to 8.

0.

8. Use according to claim 6, characterized in that: The pH-responsive organic fluorescent probe P-pH is specifically activated in an acidic environment with a pH value of 4-8.

9. Use according to claim 6, characterized in that: The pH-responsive organic fluorescent probe P-pH has a good linear response in the range of pH value of 4-8. The pH-responsive organic fluorescent probe P-pH has a good linear response in the range of pH value of 4-8.

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