Small-molecule Raman pH probe and application thereof in interface acidity measurement

Abstract

The micromolecule Raman pH probe provided by the invention has relatively strong sensitivity and an adjustable pH response range, can be anchored at an interface with relatively low loading capacity, realizes accurate measurement of interfacial acidity, is especially suitable for interfacial acidity measurement of a colored interface, and has a wide application range.

Description

Technical Field

[0001] The invention belongs to the field of analytical chemistry, and in particular relates to a small molecule Raman pH probe and application thereof in measuring interface acidity. Background Art

[0002] Interactions at interfaces catalyze fundamental reactions that are critical to various natural processes, such as the formation of soils and minerals, and the migration and transformation of chemical elements. Among them, interfacial acidity, as one of the most important interfacial properties, affects key steps such as adsorption, desorption, proton transfer, and electron transfer at energy, catalysis, and electrochemical interfaces. The chemical equilibrium and kinetics at the interface are different from those in the bulk phase, especially the molecular-scale proton transfer at the interface, which plays an important role in key processes. Therefore, detecting interfacial proton transfer is of great significance for understanding and controlling interfacial reactions.

[0003] Interfacial proton transfer brings about changes in interfacial acidity. However, there are fundamental challenges in directly detecting interfacial acidity because the interface scale is usually nanometer to sub-nanometer. As a traditional method for measuring acidity, electrochemical technology is sensitive and fast, but it is difficult to achieve the required spatial resolution even with miniaturized electrodes. Using the spatial resolution of the molecular probe's own scale, second harmonic spectroscopy and sum frequency spectroscopy are commonly used methods for measuring interfacial properties. They have strong interface specificity, but they need to rely on computational chemistry and other methods for complex calibration for quantitative measurement. In addition, the fluorescent probe method has also been used to measure interfacial acidity, but due to self-absorption problems, it cannot measure colored interfaces (such as transition metal-water interfaces).

[0004] Raman is an inelastic scattering spectroscopy technique that can detect light in a wide spectral range (~200-4000cm -1 ) presents a more characteristic fingerprint signal peak (half-peak width can reach ~10cm -1 ), and is non-destructive and photostable, making it an effective analytical measurement method. However, the sensitivity of Raman signals for interface characterization is insufficient. Surface-enhanced Raman (SERS) spectroscopy, which relies on hot spots of precious metal nanoparticles, can improve sensitivity, but the use of this technology will change the natural properties of the interface (the original binary interface becomes a ternary interface). Therefore, the measurement of interfacial acidity urgently needs to develop small molecule Raman pH probes with intramolecular enhancement. Summary of the invention

[0005] The present invention provides a compound represented by formula (I):

[0006]

[0007] Among them, P is a proton-responsive group, L is a linking group, and G is an interface anchoring group;

[0008] The proton responsive group P has the following structure:

[0009]

[0010] represents the connection site between the proton response group P and the linking group L;

[0011] A is selected from N, R1 is absent; or A is selected from C, R1 is selected from H, CN (cyano), NO2 (nitro) or SO3H (sulfonic acid);

[0012] R2, R3, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen (e.g., F, Cl, Br, I); or, R2 is selected from COOH (carboxyl), R3, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen (e.g., F, Cl, Br, I); or, R3 is selected from COOH (carboxyl), R2, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen (e.g., F, Cl, Br, I); R4 is selected from COOH (carboxyl), R2, R3, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen (e.g. F, Cl, Br, I); or, R5 is selected from COOH (carboxyl), R2, R3, R4 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen (e.g. F, Cl, Br, I);

[0013] R6, R7, R8, R9 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy; or, R6 is selected from OH (hydroxyl), R7, R8, R9 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy; or, R9 is selected from OH (hydroxyl), R6, R7, R8 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy;

[0014] R 10 Selected from H, C1-10 alkyl, C1-10 alkoxy, C1-10 alcoholic hydroxyl.

[0015] According to an embodiment of the present invention, A is selected from N, and R1 is absent. According to an embodiment of the present invention, A is selected from C, and R1 is selected from CN (cyano), NO2 (nitro) or SO3H (sulfonic acid).

[0016] According to an embodiment of the present invention, R2, R3, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; preferably, R2, R3, R4, and R5 are each independently selected from H, C1-3 alkyl, C1-3 alkoxy, and halogen; illustratively, R2, R3, R4, and R5 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, F, Cl, Br, and I.

[0017] According to an embodiment of the present invention, R2 is selected from COOH (carboxyl), R3, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; preferably, R3, R4, and R5 are each independently selected from H, C1-3 alkyl, C1-3 alkoxy, and halogen; illustratively, R3, R4, and R5 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, F, Cl, Br, and I.

[0018] According to an embodiment of the present invention, R3 is selected from COOH (carboxyl), R2, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; preferably, R2, R4, and R5 are each independently selected from H, C1-3 alkyl, C1-3 alkoxy, and halogen; illustratively, R2, R4, and R5 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, F, Cl, Br, and I.

[0019] According to an embodiment of the present invention, R4 is selected from COOH (carboxyl), R2, R3, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; preferably, R2, R3, and R5 are each independently selected from H, C1-3 alkyl, C1-3 alkoxy, and halogen; illustratively, R2, R3, and R5 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, F, Cl, Br, and I.

[0020] According to an embodiment of the present invention, R5 is selected from COOH (carboxyl), R2, R3, and R4 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; preferably, R2, R3, and R4 are each independently selected from H, C1-3 alkyl, C1-3 alkoxy, and halogen; illustratively, R2, R3, and R4 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, F, Cl, Br, and I.

[0021] According to an embodiment of the present invention, R6, R7, R8, and R9 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; preferably, R6, R7, R8, and R9 are each independently selected from H, C1-3 alkyl, and C1-3 alkoxy; illustratively, R6, R7, R8, and R9 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, and propoxy.

[0022] According to an embodiment of the present invention, R6 is selected from OH (hydroxyl), and R7, R8, and R9 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; preferably, R7, R8, and R9 are each independently selected from H, C1-3 alkyl, and C1-3 alkoxy; illustratively, R7, R8, and R9 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, and propoxy.

[0023] According to an embodiment of the present invention, R9 is selected from OH (hydroxyl), R6, R7, and R8 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; preferably, R6, R7, and R8 are each independently selected from H, C1-3 alkyl, and C1-3 alkoxy; illustratively, R6, R7, and R8 are each independently selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, and propoxy.

[0024] According to an embodiment of the present invention, R 10 is selected from H, C1-6 alkyl, C1-6 alkoxy, C1-6 alcohol hydroxyl; preferably, R 10 is selected from H, C1-3 alkyl, C1-3 alkoxy, C1-3 alcohol hydroxyl; illustratively, R 10 Selected from H, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH3)2OH.

[0025] According to an embodiment of the present invention, the proton response group P has a structure shown in the following formula (P-2), formula (P-3), formula (P-4), formula (P-5), and formula (P-6):

[0026]

[0027] Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A has the above definition.

[0028] According to an embodiment of the present invention, the linking group L is used to connect the proton responsive group P with the interface anchoring group G; a common linking group in the art may be selected.

[0029] According to an embodiment of the present invention, the linking group L has the following structure:

[0030] -(CH2) m -Q-(CH2) n -

[0031] (L-1)

[0032] Wherein, m and n are the same or different and are independently selected from integers of 1 to 10;

[0033] Q is selected from -NHCO-, -CONH-, -C(=O)O-, -OC(=O)-, -O-, -S- or any combination thereof.

[0034] According to an embodiment of the present invention, m and n are the same or different and are independently selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. One side of the linking group L is connected to the proton responsive group P, and the other side is connected to the interface anchoring group G.

[0035] According to an embodiment of the present invention, the interface anchoring group G is selected from:

[0036] (1) Chelating coordination group;

[0037] (2) Charged groups;

[0038] (3) Alkyl chain group.

[0039] According to an embodiment of the present invention, when the interface anchoring group G is a chelating coordination group, it can be anchored at the metal-based mineral-water solid-liquid interface (through coordination). According to an embodiment of the present invention, the chelating coordination group is selected from catechol groups, octahydroxyquinoline groups, dicarboxylic acids and polycarboxylic acids, diamines and polyamines, etc. According to an embodiment of the present invention, the metal-based mineral or material-water solid-liquid interface is selected from: iron-water interface, such as zero-valent iron-water interface, nano zero-valent iron-water interface, oxalated nano zero-valent iron-water interface. The molecular structure of the dicarboxylic acid group can be expressed as -R(COOH)2; wherein R represents an optionally substituted or unsubstituted carbon chain (e.g., C1-20, C1-10, C1-6 alkyl carbon chain) or a cyclic structure (e.g., C3-20 cycloalkyl, C3-10 cycloalkyl, C3-20 heterocycloalkyl, C3-10 heterocycloalkyl, C6-20 aryl, C6-10 aryl, 5-20 membered heteroaryl, 5-10 membered heteroaryl).

[0040] According to an embodiment of the present invention, when the interface anchoring group G is a charged group, it can be anchored at the silica-water solid-liquid interface (through electrostatic interaction). According to an embodiment of the present invention, the charged group is selected from: -N + R a (R b )(Rc )X - 、-N + H3X - etc.; among them, R a , R b , R c are the same or different and are independently selected from H, C1-10 alkyl; X is selected from halogen (e.g. fluorine, chlorine, bromine, iodine); preferably, R a , R b , R c are the same or different and are independently selected from H, C1-6 alkyl, C1-3 alkyl; illustratively, R a , R b , R c Can be independently selected from H, methyl, ethyl, propyl, isopropyl.

[0041] According to an embodiment of the present invention, when the interface anchoring group G is an alkyl chain group, it can be anchored at the polymer resin-water interface (through intermolecular van der Waals forces). According to an embodiment of the present invention, the interface anchoring group G is selected from C1-20 alkyl; preferably, the alkyl chain group is selected from C2-16 alkyl; illustratively, the alkyl chain group is C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, C10 alkyl, C11 alkyl, C12 alkyl, C13 alkyl, C14 alkyl, C15 alkyl, C16 alkyl.

[0042] According to an embodiment of the present invention, the compound represented by formula (I) is selected from the following structures:

[0043] (i) Formula (I-1), Formula (I-2), Formula (I-3) for the metal-based mineral or material-water solid-liquid interface,

[0044]

[0045] Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L have the above definitions;

[0046] (ii) Formula (I-4) for the silica-water solid-liquid interface,

[0047]

[0048] Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L, R a , R b , R c has the above definition; X is selected from halogen;

[0049] (iii) Formula (I-5) for the polymer resin-water solid-liquid interface,

[0050]

[0051] Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L have the above definitions, and E is selected from C1-20 alkyl.

[0052] According to an embodiment of the present invention, E is selected from C2-16 alkyl; illustratively, E is selected from C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, C10 alkyl, C11 alkyl, C12 alkyl, C13 alkyl, C14 alkyl, C15 alkyl, C16 alkyl.

[0053] According to an embodiment of the present invention, the compound represented by formula (I) is selected from the following structures:

[0054]

[0055]

[0056] The present invention also provides the use of the compound represented by the above formula (I) in the preparation of a pH probe.

[0057] The present invention also provides the use of the compound represented by the above formula (I) in measuring the acidity of the interface.

[0058] The present invention also provides the use of the compound represented by the above formula (I) in the preparation of a product or reagent for measuring interfacial acidity.

[0059] According to an embodiment of the present invention, the interface is a solid-liquid interface.

[0060] According to an embodiment of the present invention, the solid-liquid interface is selected from:

[0061] Metal-based mineral or material-water solid-liquid interface, such as iron-water interface, such as zero-valent iron-water interface, nano zero-valent iron-water interface, oxalated nano zero-valent iron-water interface;

[0062] Silica-water solid-liquid interface;

[0063] Polymer resin-water interface.

[0064] Beneficial Effects

[0065] The present invention provides a small molecule Raman pH probe, which has strong sensitivity and an adjustable pH response range, can be anchored at an interface with a low load, and can achieve accurate measurement of interfacial acidity. The probe is particularly suitable for interfacial acidity measurement of colored interfaces and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 : Properties of compound 1 for quantitative detection of pH. (a) Raman spectra of compound 1 solutions at different pH conditions. (b) Raman peak area ratio (peak area 1380cm-1 / Peak Area 1325cm-1 ) and pH. (c) Reversibility test. (d) Selectivity test when adding different ions.

[0067] Figure 2 :Interfacial acidity measurement of nano-zero-valent iron / oxalated nano-zero-valent iron-water. (a) Schematic diagram and physical image of compound S1 and compound 1 adsorbed on the surface of nano-zero-valent iron in deionized water. (b) Interfacial acidity measurement of nano-zero-valent iron and oxalated nano-zero-valent iron in deionized water.

[0068] Figure 3 : Properties of silica interfacial acidity probe and interfacial acidity measurement. (a) Raman spectra of compound 2 solution under different pH conditions. (b) Raman peak area ratio (peak area 1355cm -1 / Peak Area 1315cm -1 ) and pH. (c) Schematic diagram and physical image of compound S2 and compound 2 adsorbed on the surface of hydrophilic silica in deionized water. (d) Interfacial acidity measurement of hydrophilic nanosilica in deionized water. DETAILED DESCRIPTION

[0069] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0070] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0071] Example 1 Measurement of zero-valent iron-water interface acidity

[0072] Synthesis steps and characterization of probes

[0073]

[0074] Synthesis of compound S1. Weigh 2,6-dimethyl-4-aminopyridine (122.7 mg, 1.0 mmol) and fluoroboric acid (873 μL, 13 mmol) in a 50 mL eggplant-shaped bottle, stir for 10 min under ice-salt bath conditions, then add sodium nitrite (103.5 mg, 1.5 mmol) and continue stirring for 1 h under ice-salt bath conditions. Then, add sodium acetate solution to adjust the pH value of the mixture to 5.0. Weigh 3-(ethyl(phenyl)amino)propionic acid (193.3 mg, 1.0 mmol) and dissolve it in 1 mL of acetonitrile, cool to 0 ° C, add the above reaction solution, and continue to react for 3 h under ice bath conditions. After the reaction is complete, extract it twice with ethyl acetate and dry it with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry it, dry column, remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound S1 (176 mg, 51%) as a red solid. The characterization data of compound S1 are as follows: 1 H NMR(400MHz,DMSO-d6)δ12.45(s,1H),7.80(d,J=9.1Hz,2H),7.30(s,2H),6.85-6.83(m,2H) ,3.67(s,2H),3.49(s,2H),2.58(d,J=8.4Hz,2H),2.50(s,6H),1.13(dd,J=9.3,4.5Hz,3H); 13 C NMR(101MHz,DMSO-d6)δ172.95,171.98,171.25,158.63,158.26,150.95,150.87,142.55,1 42.48,125.90,112.18,111.41,45.79,44.69,33.24,32.16,23.98,12.18; HRMS(ESI):calcd for C 18 H 22 N4O2 + [M+H] + 327.1816, found 327.1812.

[0075] Synthesis of compound 1. Weigh S1 (326.4 mg, 1.0 mmol), 6-chloro-1-hydroxybenzotriazole (508.7 mg, 3.0 mmol), N,N-diisopropylethylamine (129.2, 1.0 mmol) and N,N'-diisopropylcarbodiimide (378.4 mg, 3.0 mmol) in a 50 mL eggplant-shaped bottle, add 5 mL of dimethylformamide to dissolve and stir at room temperature for 15 min; finally weigh dopamine hydrochloride (284.5 mg, 1.5 mmol) and add it to the above reaction solution, and stir the mixture at room temperature for 3 hours. After the reaction is complete, extract with ethyl acetate twice, and dry with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry, dry column, remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound 1 (378.5 mg, 82%), which is a red solid. The characterization data of compound 1 are as follows: 1 H NMR (400MHz, DMSO-d6) δ8.72(d,J=36.4Hz,2H),7.80(d,J=9.0Hz,2H),7.30(s,2H),6.83(d ,J=9.1Hz,2H),6.43-6.41(m,2H),6.42(d,J=7.9Hz,1H),3.64(dd,J=16.1,9.2Hz,2H),3.47 -3.43(m,2H),3.19(dd,J=13.2,6.6Hz,2H),2.53-2.2.46(m,8H),2.40(dd,J=14.3,7.2Hz,2H),1.12(t,J=6.8Hz,3H); 13 C NMR (101MHz, DMSO-d6) δ170.02,158.72,158.20,150.96,145.06,143.53,142.39,130.14,125.83,119. 21,115.96,115.43,112.08,111.34,46.56,44.65,40.59,34.59,33.74,24.09,12.17; HRMS(ESI):calcd for C 26 H 31 N5O3 + [M+H] + 462.2500, found 462.2459.

[0076] Test Results

[0077] (1) pH response properties of compound 1

[0078] In order to quantitatively detect pH, solutions of compound 1 under different pH conditions were prepared using phosphate buffer and their Raman spectra were measured respectively. The results showed that with the increase of pH value, the Raman spectra at ∼1380 cm -1 The characteristic peak at 1320 cm -1 The peak at becomes stronger ( Figure 1 a), with a pH response range of 6.6-8.8 ( Figure 1 b), meeting the detection requirements. In principle, the process of protonation and deprotonation is reversible. In order to prove that compound 1 has good reversibility, compound 1 was first dissolved in a phosphate buffer solution with a pH of 6.0, and then sodium hydroxide and hydrochloric acid were added dropwise to adjust the pH to 9.0. This adjustment was repeated 20 times, and a portion of each sample was taken out for Raman spectroscopy testing, and the relative Raman intensity was calculated. The results showed that the relative Raman intensity after repeated adjustment was basically consistent with the initial value, indicating that the probe maintained good reversibility during the repeated protonation and deprotonation process of compound 1 ( Figure 1 c). In addition, in order to ensure the accuracy of the test, compound 1 should not be disturbed by the outside world during the test. Here, the commonly used anions and cations (Cl - 、CO3 2- 、HCO3 - 、SO4 2- 、Na + , K + , Ca 2+ and Mg 2+ ) were added to the solutions of compound 1 at pH = 6.0 and pH = 9.0, and their Raman spectra were tested. The results showed that there was no substantial interference during the addition of interfering ions ( Figure 1 d).

[0079] (2) Measurement of the acidity of nano-zero-valent iron / oxalated nano-zero-valent iron-water interface

[0080] Nano zero-valent iron and oxalated nano zero-valent iron were prepared by sodium borohydride reduction method. The specific method is to weigh 6.0g sodium borohydride and 3.0g ferric chloride hexahydrate solid and dissolve them in 400mL and 1000mL deionized water respectively. After fully dissolved, the sodium borohydride solution is added dropwise to the ferric chloride hexahydrate solution at a uniform speed. During the process of adding sodium borohydride, a large amount of gas will be generated in the solution, accompanied by the formation of black fluffy solids. After all the sodium borohydride solution is dripped, the mixed solution is placed for 2h. After the solid samples are filtered, washed with water and washed with ethanol, the samples are dried in a vacuum dryer, and the samples are collected for standby use. This sample is marked as nano zero-valent iron. When oxalated nano zero-valent iron is synthesized, 0.189g sodium oxalate dihydrate solid (molar modification ratio is 10%, oxalate: iron ion = 1:10) needs to be added to the initial ferric chloride solution, and the rest of the steps are the same. This sample is marked as oxalated nano zero-valent iron.

[0081] Next, the interfacial acidity of the two zero-valent iron materials synthesized above was measured. The results of the adsorption of the parent structure without chelating groups (catechol groups) and the interfacial acidity probe with chelating groups on nano-zero-valent iron in water are shown in Figure 2. Figure 2 a. The parent structure without chelating groups is dispersed in the bulk water, while the interfacial acidity probe is quickly fixed on the surface of nano-zero-valent iron due to the chelation of catechol. In order to measure the interfacial acidity of nano-zero-valent iron, 1 mg of solid material was ultrasonically dispersed in deionized water, a certain amount of compound 1 was added, and the mixture was adsorbed for 5 minutes before washing away the unadsorbed probe. The solid suspension was used for Raman testing. Raman spectroscopy showed that the interfacial pH of nano-zero-valent iron was 8.61 (P < 0.05), compared with the pH of 6.73 in the bulk water. Figure 2 b), the interfacial pH of oxalated nano-zero-valent iron is 8.04 ( Figure 2 b), which is quite different from the bulk phase.

[0082] Example 2 Measurement of Acidity at the Silica-Water Interface

[0083] Synthesis steps and characterization of probes

[0084]

[0085] Synthesis of compound S2. Weigh p-aminobenzonitrile (118.1 mg, 1.0 mmol) and fluoroboric acid (873 μL, 13 mmol) in a 50 mL eggplant-shaped bottle, stir for 10 min under ice-salt bath conditions, then add sodium nitrite (103.5 mg, 1.5 mmol) and continue stirring for 1 h under ice-salt bath conditions. Then, add sodium acetate solution to adjust the pH value of the mixture to 5.0. Weigh 2,5-dimethoxyaniline (193.3 mg, 1.0 mmol) and dissolve it in 1 mL of acetonitrile, cool to 0 ° C, add the above reaction solution, and continue to react for 3 h under ice bath conditions. After the reaction is complete, extract it twice with ethyl acetate and dry it with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry it, dry column, and remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound S2 (140 mg, 50%) as a red solid. The characterization data of compound S2 are as follows: 1 HNMR (400MHz, CDCl3) δ7.87 (d, J = 8.5Hz, 2H), 7.72 (d, J = 8.4Hz, 2H), 7.39 (s, 1H), 6.35 (s, 1H), 4.57 (s, 2H), 3.93 (d, J = 31.0Hz, 6H); 13 C NMR(101MHz, CDCl3)δ155.87,143.97,141.85,133.64,133.01,122.71,119.10,111.37,97.76,97.42,56.71,55.80; HRMS(ESI):calcd for C 15 H 14 N4O2 + [M+H] + 283.1190, found 283.1180.

[0086] Synthesis of compound S3. Weigh S2 (282.3 mg, 1.0 mmol), potassium carbonate (1382.1 mg, 10.0 mmol), potassium iodide (16.6 mg, 0.1 mmol) and bromopropionic acid (229.5, 1.5 mmol) in a 50 mL eggplant-shaped bottle, add 5 mL N, N-dimethylformamide to dissolve, and reflux at 90 ° C for 12 h. After the reaction is complete, extract with ethyl acetate twice, and dry with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry, dry column, and remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound S3 (230.3 mg, 65%), which is a red solid. The characterization data of compound S3 are as follows: 1HNMR(400MHz, CDCl3)δ7.90-7.87(m,2H),7.75-7.73(m,2H),7.40(s,1H),6.25(s,1H),4.0 5(s,3H),3.91(s,3H),3.64(d,J=5.5Hz,2H),2.77(d,J=17.8Hz,2H); HRMS(ESI):calcdfor C 18 H 18 N4O4 - [MH] - 353.1255, found 353.1244.

[0087] Synthesis of compound S4. Weigh S3 (354.3 mg, 1.0 mmol), 6-chloro-1-hydroxybenzotriazole (508.7 mg, 3.0 mmol), N,N-diisopropylethylamine (129.2, 1.0 mmol) and N,N'-diisopropylcarbodiimide (378.4 mg, 3.0 mmol) in a 50 mL eggplant-shaped bottle, add 5 mL N,N-dimethylformamide to dissolve and stir at room temperature for 15 min; finally weigh dopamine hydrochloride (284.5 mg, 1.5 mmol) and add to the above reaction solution, and stir the mixture at room temperature for 3 hours. After the reaction is complete, extract with ethyl acetate twice, and dry with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry, dry column, remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound S4 (288.2 mg, 70%), which is a red solid. The characterization data of compound S4 are as follows: 1 H NMR(400MHz,MeOD)δ7.78(dd,J=28.4,8.6Hz,4H),7.32(s,1H),6.35(s,1H),4.00(s,3H),3.84(s,3H) ,3.61(d,J=6.4Hz,2H),3.37(d,J=6.5Hz,2H),2.58(dd,J=23.2,6.5Hz,4H),2.42(s,6H),1.92(s,1H); 13 C NMR(101MHz,MeOD)δ174.34,158.64,157.56,147.04,143.48,134.17,133.28,123.53,120.00,1 11.59,97.57,93.86,58.84,57.36,56.22,49.53,44.93,40.04,37.35,36.55; HRMS(ESI):calcd for C 22 H 28 N6O3+ [M+H] + 425.2293, found 425.2279.

[0088] Synthesis of compound 2. Weigh S4 (411.4 mg, 1.0 mmol) and CH3I (264.6 mg, 1.5 mmol) in a 50 mL eggplant-shaped bottle, add 5 mL of butanone to dissolve, and reflux at 90 ° C for 12 h. After the reaction is complete, extract twice with ethyl acetate, and dry with anhydrous sodium sulfate for 30 min. After removing most of the solvent by vacuum distillation, add an appropriate amount of silica gel and spin dry, dry column, and remove impurities with a mixed solvent of ethyl acetate and 1% acetic acid to obtain compound 2 (313 mg, 50%), which is a red solid. The characterization data of compound 2 are as follows: 1 H NMR(400MHz,MeOD)δ7.78(dd,J=23.0,8.5Hz,4H),7.31(s,1H),6.38(s,1H),4.03(s,3H),3.85(s,3H),3.67(t ,J=6.2Hz,4H),3.47(t,J=6.4Hz,2H),3.16(d,J=15.8Hz,9H),3.00(s,1H),2.86(s,1H),2.63(t,J=6.3Hz,2H); 13 C NMR (101MHz, MeOD) δ174.50,147.40,143.63,134.22,133.16,123.30,119.99,111.47,97.69,94.02,65.83,57.66,56.41,54.22,54.18 54.15,40.07,36.52,34.73; HRMS(ESI):calcd for C 23 H 31 N6O3 + [M] + 439.2452, found 439.2435.

[0089] Test Results

[0090] In order to quantitatively detect pH, solutions of compound 2 at different pH conditions were prepared using phosphate buffer and their Raman spectra were measured respectively. -1 The characteristic peak at 1315 cm -1 The peak at becomes stronger ( Figure 3 a), its pH response range is 3.0-5.2, which meets the detection requirements ( Figure 3 b).

[0091] In order to measure the interfacial acidity of hydrophilic silica, 1 mg of hydrophilic silica was ultrasonically dispersed in deionized water, a certain amount of compound 2 was added, mixed and adsorbed for 30 min, and then the unadsorbed probe was washed away. The solid suspension was used for Raman testing. Figure 3 c It can be seen that compared with the probe parent structure S2, the probe (compound 2) bonded with the anchoring group can be well anchored on the silica surface. Raman spectroscopy shows that compared with bulk water (pH>5.0), the interface pH of hydrophilic nanosilica is 4.09, which is significantly different from the acidity of bulk water.

[0092] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A compound represented by formula (I) or a salt thereof: in, P is a proton-responsive group, L is a linking group, and G is an interface anchoring group; The proton responsive group P has the following structure: represents the connection site between the proton response group P and the linking group L; A is selected from N, R1 is absent; or A is selected from C, R1 is selected from H, -CN, -NO2 or -SO3H; R2, R3, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen; or, R2 is selected from COOH, R3, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen; or, R3 is selected from COOH, R2, R4, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen; or, R4 is selected from COOH, R2, R3, R5 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen; or, R5 is selected from COOH, R2, R3, R4 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy, halogen; R6, R7, R8, R9 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy; or, R6 is selected from OH, R7, R8, R9 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy; or, R9 is selected from OH, R6, R7, R8 are each independently selected from H, C1-10 alkyl, C1-10 alkoxy; R 10 Selected from H, C1-10 alkyl, C1-10 alkoxy, C1-10 alcoholic hydroxyl.

2. The compound according to claim 1, characterized in that A is selected from N, R1 is absent; or A is selected from C, R1 is selected from -CN, -NO2 or -SO3H; Preferably, R2, R3, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; Preferably, R2 is selected from COOH, and R3, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; Preferably, R3 is selected from COOH, and R2, R4, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; Preferably, R4 is selected from COOH, and R2, R3, and R5 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; Preferably, R5 is selected from COOH, and R2, R3, and R4 are each independently selected from H, C1-6 alkyl, C1-6 alkoxy, and halogen; Preferably, R6, R7, R8, and R9 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; Preferably, R6 is selected from OH, and R7, R8, and R9 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; Preferably, R9 is selected from OH, and R6, R7, and R8 are each independently selected from H, C1-6 alkyl, and C1-6 alkoxy; Preferably, R 10 Selected from H, C1-6 alkyl, C1-6 alkoxy, C1-6 alcohol hydroxyl.

3. The compound according to claim 1 or 2, characterized in that The proton response group P has the structures shown in the following formula (P-2), formula (P-3), formula (P-4), formula (P-5), and formula (P-6): Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A has the definition as described in claim 1 or 2.

4. The compound according to any one of claims 1 to 3, characterized in that The linking group L has the following structure: -(CH2) m -Q-(CH2) n - (L-1) Wherein, m and n are the same or different and are independently selected from integers of 1 to 10; Q is selected from -NHCO-, -CONH-, -C(=O)O-, -OC(=O)-, -O-, -S- or any combination thereof.

5. The compound according to any one of claims 1 to 4, characterized in that The interface anchoring group G is selected from: (1) Chelating coordination group; (2) Charged groups; (3) alkyl chain groups; Preferably, the chelating coordination group is selected from catechol groups, octahydroxyquinoline groups, dicarboxylic acid and polycarboxylic acid groups, diamines and polyamine groups; Preferably, the charged group is selected from: -N + R a (R b )(R c )X - 、-N + H3X - ; Among them, R a , R b , R c are the same or different and are independently selected from H, C1-10 alkyl; X is selected from halogen; Preferably, the alkyl chain group is selected from C1-20 alkyl groups.

6. The compound according to any one of claims 1 to 4, characterized in that The compound represented by formula (I) is selected from the following structures: (i) Formula (I-1), Formula (I-2), Formula (I-3) for the metal-based mineral or material-water solid-liquid interface, Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L have the definitions in any one of claims 1-4; (ii) Formula (I-4) for the silica-water solid-liquid interface, Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L, R a , R b , R c It has the definition as described in any one of claims 1 to 4; X is selected from halogen; (iii) Formula (I-5) for the polymer resin-water solid-liquid interface, Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , A, L have the definitions as described in any one of claims 1-4, and E is selected from C1-20 alkyl.

7. The compound according to any one of claims 1 to 6, characterized in that The compound represented by formula (I) is selected from the following structures:

8. Use of the compound represented by formula (I) according to any one of claims 1 to 7 in the preparation of a pH probe.

9. Use of the compound represented by formula (I) according to any one of claims 1 to 7 in determining interfacial acidity; Preferably, the interface is a solid-liquid interface; more preferably, the solid-liquid interface is selected from a metal-based mineral or material-water solid-liquid interface, a silica-water solid-liquid interface, and a polymer resin-water interface.

10. Use of the compound represented by formula (I) according to any one of claims 1 to 7 in the preparation of a product or reagent for measuring interfacial acidity; Preferably, the interface is a solid-liquid interface; more preferably, the solid-liquid interface is selected from: a metal-based mineral or material-water solid-liquid interface, a silicon dioxide-water solid-liquid interface, and a polymer resin-water interface.

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