Pyrazole group-containing salicylhydrazide derivative with optical switch performance, preparation method and application of pyrazole group-containing salicylhydrazide derivative

Abstract

The invention discloses a pyrazole group-containing salicylhydrazide derivative with photoswitch performance, a preparation method and application, the derivative can be used as a fluorescent probe to identify copper ions, sulfur ions, trifluoroacetic acid and triethylamine, and meanwhile, partial configuration transformation of the derivative can be realized by irradiation of 302-wavelength light. And the fluorescence emission intensity is enhanced, so that the detection sensitivity on the substances is enhanced. The series of fluorescent probes have the advantages of simple and convenient synthesis route, high yield, wide detection range, high sensitivity, light control and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent probes, and particularly relates to a salicylhydrazide derivative containing a pyrazole group with photoswitching performance and its use as a fluorescent probe. Background Art

[0002] Fluorescent molecules, as a classic type of intelligent material, have a wide range of applications, such as anti-counterfeiting, bioimaging, storage devices, and security inks. In addition, the emission wavelength range and intensity of some fluorescent materials can be not easily affected by different ions, acids and bases, heat, light, electricity, mechanical, and magnetic properties. These special properties have attracted the attention of researchers for intelligent fluorescent molecules and have also been widely used in fluorescent probes and information encryption.

[0003] Guo Kunpeng et al. (Journal of Materials Chemistry C, 2022, 10, 11016) reported a class of copper ion quenching probes containing Schiff base structures. Although this compound has high sensitivity, its detection target is single, which limits its application value. Despite the outstanding advantages of these fluorescent materials in identifying special substances, how to effectively organize intelligent fluorescent molecules to respond to multiple stimuli is a huge challenge and ensure the mutual independence between different stimuli, which hinders the further application and progress of fluorescent molecules. Therefore, developing new intelligent fluorescent molecules with multiple stimuli is of great significance and their action mechanisms are preliminarily explained. Summary of the Invention

[0004] To solve the problem of the single function and narrow application range of current fluorescent probes, the present invention aims to provide a salicylhydrazide derivative containing a pyrazole group, and the recognition of copper ions, sulfide ions, trifluoroacetic acid, and triethylamine by this compound as a fluorescent probe. At the same time, irradiation with light of 302 nm wavelength can achieve partial conformational transformation (E-form → Z-form) of the compound, enhance its fluorescence emission intensity, and thus enhance the detection sensitivity to the above substances.

[0005] The technical solution to achieve the object of the present invention is: a salicylhydrazide derivative containing a pyrazole group with photoswitching performance, which has the following structure:

[0006]

[0007] Wherein,

[0008] R 1 -R 4 independently is any group among a hydrogen atom, a fluorine atom, a chlorine atom, an iodine atom, and a methyl group.

[0009] Preferably, R 1 -R 4is a hydrogen atom.

[0010] The preparation method of the above-mentioned salicylhydrazide derivatives containing pyrazole groups with photoswitching performance includes: (1) a step of preparing compound 2 by subjecting compound 1 to a substitution reaction with hydrazine hydrate,

[0011]

[0012] (2) a step of reacting compound 2 with 1-methyl-1H-pyrazole-3-carbaldehyde to prepare the target compound,

[0013]

[0014] Preferably, in step (1), the substitution reaction is carried out in the presence of the organic solvent ethanol.

[0015] Preferably, in step (1), the substitution reaction temperature is 60 ± 5 °C and the reaction time is 4 hours.

[0016] Preferably, in step (1), the molar ratio of compound I to hydrazine hydrate is 1:5.

[0017] Preferably, in step (2), the reaction is carried out in the presence of the organic solvent ethanol.

[0018] Preferably, in step (2), the reaction temperature is 60 - 75 °C and the reaction time is 6 hours.

[0019] Preferably, in step (2), the molar ratio of reactant 2 to 1-methyl-1H-pyrazole-3-carbaldehyde is 1:1.5.

[0020] The present invention also provides the use of the target compound as a fluorescent probe, which can recognize copper ions, sulfur ions, trifluoroacetic acid or triethylamine.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) The target compound involved in the present invention can be used as a fluorescent probe to realize the recognition of substances such as Cu 2+ , S 2- , trifluoroacetic acid, triethylamine, etc.

[0023] (2) This series of fluorescent probes has the advantages of simple synthesis route, high yield, wide detection range and light controllability.

[0024] (3) Irradiation with light of 302 nm wavelength can achieve the configuration transformation (E-form → Z-form) of some compounds, enhance their fluorescence emission intensity and thus enhance the detection sensitivity to the above substances. Description of the Drawings

[0025] Figure 1It is the crystal structure of the target compound 3 prepared in Example 1 of the present invention.

[0026] Figure 2 It is the crystal packing diagram of the target compound 3 prepared in Example 1 of the present invention.

[0027] Figure 3 They are the fluorescence spectra of the target compound 3 (probe 3) of the present invention titrated with different cations respectively.

[0028] Figure 4 It is Cu 2+ The fluorescence titration curve of the target compound 3 (probe 3).

[0029] Figure 5 It is Figure 4 The fitting curve.

[0030] Figure 6 It is S in Application Example 3 2- The fluorescence titration curve of 3-Cu 2+ The fluorescence titration curve of.

[0031] Figure 7 It is the fluorescence spectrum of the recognition of different anions by the probe 3-Cu in Application Example 3 2+ in Application Example 3.

[0032] Figure 8 They are the fluorescence emission spectra of the target compound 3 (probe 3) and 3-trifluoroacetic acid combined with trifluoroacetic acid and triethylamine respectively in Application Example 5.

[0033] Figure 9 It is the fluorescence emission spectrum of the target compound 3 (probe 3) under the 302 nm light steady state and after heating in Application Example 7.

[0034] Figure 10 It is the fluorescence titration fitting curve diagram of the probe 3 for Cu 2+ after being irradiated by the 302 nm light source for 90 min in Application Example 8. Detailed implementation manners

[0035] The present invention designs and synthesizes a series of novel salicylhydrazide derivatives containing pyrazole groups, and studies their fluorescence properties in various solutions. The research results show that this series of compounds have good detection effects on Cu 2+ , S 2- , trifluoroacetic acid, and triethylamine, and the irradiation of ultraviolet light can enhance the fluorescence quantum yield of some compounds and thus increase the detection sensitivity, thereby realizing the light control of the fluorescence probe.

[0036] The following implementation cases can enable those skilled in the art to understand the present invention more clearly, but do not limit the present invention in any way. Although the present invention only lists the compound 3 (probe 3), but R1 ~R 4 When they are methyl and halogen respectively, there is no influence on the detection effect. The solvents used in the fluorescence detection method include but are not limited to the following solvents (methylene chloride, acetonitrile, tetrahydrofuran and water).

[0037] In an acetonitrile solution (5×10 -5 mol), the target compound can emit blue-green light with a wavelength range of 400 - 550 nm under the excitation of a 320 nm light source. After adding an aqueous solution of copper ions, fluorescence quenching can be achieved. Moreover, with the increase of the copper ion concentration, the quenching effect enhances linearly, and the detection limit is 0.24 μM. The complex 3-Cu formed by the target compound and copper ions 2+ can be used to detect sulfide ions, and the detection limit is 1.86 μM. At the same time, this series of fluorescent probes can detect trifluoroacetic acid in methylene chloride, chloroform, tetrahydrofuran, acetonitrile, cyclohexane, methanol, ethanol or isopropanol. That is, in a 5×10 -5 mol probe solution, slowly adding trifluoroacetic acid (1 - 2 μL) can quickly quench the fluorescence of the system, and adding triethylamine again can restore the fluorescence emission intensity of the system. The test method refers to the methods reported by Nakorn Niamnont et al. in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 279(2022)121382 and Kamaljit Singh et al. in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 290(2023)122239.

[0038] Irradiating the solvent system of the probe (the solvent can be solvents such as acetonitrile and methylene chloride) with a 302 nm light source until it reaches a photostationary state can increase the fluorescence intensity and the quantum yield, thus providing a premise for further improving the detection sensitivity of this series of probes and realizing the light control of the fluorescent probes. This series of fluorescent probes can also be used as fluorescent dyes, biosensors, etc.

[0039] It should be noted that based on the (E)-2-hydroxy-N'-((1-methyl-1H-pyrazol-3-yl)methylene)benzohydrazide (target compound 3) of the present invention, when the pyrazole moiety linked to the acylhydrazone changes its linkage site or is replaced with other five-membered rings, the fluorescence emission properties of the molecule significantly decrease and it does not have the function of a probe. Therefore, the present invention introduces three comparative examples including (E)-2-hydroxy-N'-((1-methyl-1H-pyrazol-4-yl)methylene)benzohydrazide (compound 4), (E)-2-hydroxy-N'-((1-methyl-1H-pyrazol-5-yl)methylene)benzohydrazide (compound 5), and (E)-N'-(cyclopentylmethylene)-2-hydroxybenzohydrazide (compound 6) to prove the outstanding performance of the target compound 3 of the present invention as a probe.

[0040]

[0041] Example 1

[0042] The synthetic route of the target compound 3 is as follows, and the synthesis and purification methods can both adopt the commonly used synthetic methods in the art.

[0043]

[0044] Methyl salicylate (1.52 g, 10 mmol), i.e., compound 1, was added to 15 mL of ethanol, and 85% hydrazine hydrate (2 g, 50 mmol) was slowly added dropwise with stirring. Subsequently, the temperature was raised to 60 °C, and the reaction progress was detected by thin-layer chromatography. After refluxing for 4 hours, the reaction was stopped and the temperature was lowered to room temperature. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography (eluent: V(ethyl acetate):V(petroleum ether) = 1:1) to obtain 1.35 g of the intermediate 2, i.e., salicylhydrazide, with a yield of 89%.

[0045] Compound 2 (0.45 g, 3 mmol) was added to 20 mL of ethanol, and 1-methyl-1H-pyrazole-3-carbaldehyde (0.5 g, 4.5 mmol) was added dropwise. The temperature was raised to 60 °C, and the reaction was carried out for 6 hours. The system was cooled to room temperature, and a solid precipitated out. The target compound 3 was obtained by recrystallization from ethanol, weighing 0.56 g, with a yield of 76%. 1 H NMR (500 MHz, DMSO) δ 11.86 (s, 1H), 11.77 (s, 1H), 8.43 (s, 1H), 7.86 (s, 1H), 7.78 (s, 1H), 7.44 (s, 1H), 6.96 (s, 2H), 6.63 (s, 1H), 3.89 (s, 3H); 13 C NMR (126 MHz, DMSO) δ 165.33,

[0046] 159.66,147.61,143.90,134.27,133.14,128.81,119.35,117.76,116.27,103.70,39.27; HRMS calcd for C 12 H 13 N 4 O 2 [M + H] + 245.1033; found 245.1039; C 12 H 12 N 4 O 2 (244.10) calculated. C, 59.01; H, 4.95; N, 22.94; found C 58.45, H 4.82, N 21.37。

[0047] The structure of the synthesized target compound was confirmed by single crystal X - ray diffraction of the target compound, Figure 1 and 2 are the single crystal structure and unit cell diagram of target compound 3, respectively.

[0048] Comparative Example 1

[0049] The synthetic route of compound 4 is as follows. The synthesis and purification methods are both common synthetic methods in the art. Methyl salicylate (1.52 g, 10 mmol), namely compound 1, was added to 15 mL of ethanol, and 85% hydrazine hydrate (2 g, 50 mmol) was slowly added dropwise with stirring. Subsequently, the temperature was raised to 60 °C, and the reaction progress was monitored by thin - layer chromatography. After refluxing for 4 hours, the reaction was stopped and cooled to room temperature. The solvent was concentrated by distillation under reduced pressure, and the product was purified by column chromatography (eluent: V(ethyl acetate):V(petroleum ether) = 1:1) to obtain 1.35 g of intermediate 2, namely salicylhydrazide, with a yield of 89%.

[0050] Compound 2 (0.45 g, 3 mmol) was added to 20 mL of ethanol, and 1 - methyl - 1H - pyrazole - 4 - carbaldehyde (0.5 g, 4.5 mmol) was added dropwise. The temperature was raised to 60 °C and the reaction was carried out for 6 hours. The system was cooled to room temperature, and a solid precipitated. The target compound 4 was obtained by recrystallization from ethanol, weighing 0.48 g with a yield of 66%. 1 H NMR (500 MHz, DMSO) δ12.01 (s, 1H), 11.63 (s, 1H), 8.36 (s, 1H), 8.15 (s, 1H), 7.87 (dd, J = 7.8, 1.2 Hz, 1H), 7.79 (s, 1H), 7.46–7.38 (m, 1H), 6.99–6.91 (m, 2H), 3.88 (s, 3H); 13¹³C NMR (126 MHz, DMSO) δ 165.04, 159.79, 143.10, 138.26, 134.21, 131.63, 128.68, 119.30, 117.77, 116.07, 39.19; HRMS calcd for C 12 H 13 N 4 O 2 [M + H] + 245.1033, found 245.1036; C 12 H 12 N 4 O 2 (244.10) calculated. C, 59.01; H, 4.95; N, 22.94; found C 58.04, H 4.79, N 21.84。

[0051] Comparative Example 2

[0052] Methyl salicylate (1.52 g, 10 mmol), which is Compound 1, was added to 15 mL of ethanol, and 85% hydrazine hydrate (2 g, 50 mmol) was slowly added dropwise with stirring. Subsequently, the temperature was raised to 60 °C, and the reaction progress was monitored by thin-layer chromatography. After refluxing for 4 hours, the reaction was stopped and the mixture was cooled to room temperature. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography (eluent: V(ethyl acetate):V(petroleum ether) = 1:1) to obtain 1.35 g of Intermediate 2, namely salicylhydrazide, with a yield of 89%.

[0053] Compound 2 (0.45 g, 3 mmol) was added to 20 mL of ethanol, and 1-methyl-1H-pyrazole-5-carbaldehyde (0.5 g, 4.5 mmol) was added dropwise. The temperature was raised to 60 °C, and the reaction was carried out for 6 hours. The system was cooled to room temperature, and a solid precipitated out. The solid was recrystallized from ethanol to obtain 0.40 g of the target compound 5, with a yield of 55%. 1 ¹H NMR (500 MHz, DMSO) δ 11.88 (s, 1H), 11.75 (s, 1H), 8.55 (s, 1H), 7.88 (d, J = 7.7 Hz, 1H), 7.50 (t, J = 7.0 Hz, 1H), 7.45 (dd, J = 11.3, 4.1 Hz, 1H), 6.98 (dd, J = 13.7, 7.7 Hz, 2H), 6.69 (d, J = 1.5 Hz, 1H), 4.06 (s, 3H); 1313C NMR (126 MHz, DMSO) δ 165.12, 159.35, 139.05, 138.74, 136.89, 134.37, 129.09, 119.50, 117.76, 116.41, 108.19, 38.77; HRMS calcd for C 12 H 13 N 4 O 2 [M + H] + 245.1033, found 245.1033; C 12 H 12 N 4 O 2 (244.10) calculated. C, 59.01; H, 4.95; N, 22.94; found C 58.73, H 4.82, N 21.21。

[0054] Comparative Example 3

[0055] Compound 1, methyl salicylate (1.52 g, 10 mmol), was added to 15 mL of ethanol, and 85% hydrazine hydrate (2 g, 50 mmol) was slowly added dropwise with stirring. Subsequently, the temperature was raised to 60 °C, and the reaction progress was monitored by thin-layer chromatography. After refluxing for 4 hours, the reaction was stopped and cooled to room temperature. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography (eluent: V(ethyl acetate):V(petroleum ether) = 1:1) to obtain 1.35 g of intermediate 2, salicylhydrazide, with a yield of 89%.

[0056] Compound 2 (0.45 g, 3 mmol) was added to 20 mL of ethanol, and cyclopentanecarbaldehyde (0.44 g, 4.5 mmol) was added dropwise. The temperature was raised to 60 °C, and the reaction was carried out for 5 hours. The system was cooled to room temperature, and a solid precipitated. The solid was recrystallized from ethanol to obtain 0.41 g of the target compound 6, with a yield of 59%. 1 1H NMR (500 MHz, DMSO) δ 11.98 (s, 1H), 11.46 (s, 1H), 7.83 (d, J = 7.6 Hz, 1H), 7.71 (d, J = 6.3 Hz, 1H), 7.42 (t, J = 7.7 Hz, 1H), 6.93 (dd, J = 13.9, 7.7 Hz, 2H), 2.76–2.67 (m, 1H), 1.86–1.79 (m, 2H), 1.66–1.53 (m, 6H); 13C NMR (126 MHz, DMSO) δ 165.18, 159.83, 157.25, 134.16, 128.65, 119.24, 117.82, 115.91, 42.66, 30.50, 25.50; HRMS calcdfor C 13H 17 N 2 O 2 [M+H]+233.1285, found 233.1285; C 13 H 16 N 2 O 2 (232.12) calculated. C 67.22, H 6.94, N 12.06; found C 66.52, H 7.49, N 10.14。

[0057] Application Example 1

[0058] Prepare an acetonitrile stock solution of Probe 3 with a concentration of 1×10 -3 mol. At the same time, prepare aqueous stock solutions of the ions to be measured, Li -3 , Na + , K + , Ag + , Mg + , Ni 2+ , Mn 2+ , Sn 2+ , Fe 2+ , Ga 2+ , and Cu 2+ with a concentration of 1×10 2+ mol respectively, a total of 11 kinds.

[0059] Add 100 μL of the acetonitrile stock solution of Probe 3 to a fluorescence cuvette and dilute it to 2 mL. Use 320 nm as the excitation light source to measure the fluorescence emission spectrum, record the spectrum, and there is an obvious fluorescence emission peak near 450 nm. Then add 100 μL of the stock solution of the ion to be measured, Li + . Shake it evenly and let it stand for 3 minutes. Then record the fluorescence spectrum again under the same conditions and compare the difference with the original spectrum.

[0060] Replace the remaining ions to be measured and repeat the above operations in turn to obtain the fluorescence spectra of the titration of Probe 3 with different cations (ions to be measured), as shown in Figure 3 . The titration results show that only Cu 2+ achieves fluorescence quenching of Probe 3. Therefore, it shows that Probe 3 can specifically recognize Cu 2+ by fluorescence quenching (as shown in Figure 3 ), and the response to other cations is not obvious.

[0061] Add 100 μL of the acetonitrile stock solution of Probe 3 to a fluorescence cuvette and dilute it to 2 mL. Prepare seven portions, and then add 0, 20, 40, 60, 80, 100, 150 μL of the ion to be measured, Cu 2+Stock solution, shake until uniform, let stand for 3 minutes, use 320 nm as the excitation light source to measure the fluorescence emission spectrum, and obtain different concentrations of Cu 2+ The fluorescence titration curve of probe 3 is as Figure 4 shown. Fit Figure 4 it, and the obtained fitting curve is as Figure 5 . Use the detection limit calculation formula (detection limit = 3 × systematic error / detector sensitivity) to calculate the detection limit to be 0.24 μL.

[0062] Application Example 2

[0063] Change the acetonitrile stock solution of probe 3 to the dichloromethane stock solution of probe 3, and the other procedures are the same as in Application Example 1. The detection results show that probe 3 also exhibits specific recognition of Cu 2+ in the dichloromethane solution. The LOD value of the detection limit is 0.31 μL.

[0064] Application Example 3

[0065] Prepare an acetonitrile stock solution of probe 3 with a concentration of 1×10 -3 mol and an aqueous solution stock solution of Cu -3 with a concentration of 1×10 2+ mol. Add 100 μL of the acetonitrile stock solution of probe 3 and 100 μL of the Cu 2+ aqueous solution stock solution to a 1.5 mL centrifuge tube, shake well, transfer to a fluorescence cuvette, and dilute to 2 mL. Prepare 8 portions. Sequentially add 0, 20, 40, 60, 80, 100, 120, and 140 μL of an aqueous solution of Na -3 S with a concentration of 1×10 2 mol to them. Use 320 nm as the excitation light source to record the fluorescence emission spectrum. The results are as Figure 6 shown, and the fluorescence intensity gradually recovers. Use the detection limit calculation formula (detection limit = 3 × systematic error / slope) to calculate the detection limit to be 1.86 μL.

[0066] Using the same method as above, detect several other common anions OH - , CO 3 2- and F - , Cl - , Br - and other halogens. The experimental results are as Figure 7 shown, and the results show that there is no fluorescence response to these anions.

[0067] Application Example 4

[0068] Change the acetonitrile stock solution of probe 3 to the tetrahydrofuran stock solution of probe 3. The other procedures are the same as those in Application Example 3. The results show that changing the solvent to tetrahydrofuran can also achieve probe 3-Cu 2+ For S 2- detection, use the detection limit calculation formula (detection limit = 3 × systematic error / slope) to calculate that the detection limit is 2.35 μL.

[0069] Application Example 5

[0070] Prepare an acetonitrile stock solution of probe 3 with a concentration of 1×10 -3 mol, dilute it to 2 mL, use 320 nm as the excitation light source to record the fluorescence spectrum, add 5 μL of trifluoroacetic acid (TFA) to it, record the fluorescence emission spectrum, then add 10 μL of triethylamine (TEA) to it, and record the fluorescence emission spectrum. Finally, the obtained fluorescence emission spectrum is as Figure 8 shown. From Figure 8 it can be seen that when trifluoroacetic acid is added, the fluorescence emission intensity of the probe 3 system decreases, and when triethylamine is added, the fluorescence emission intensity of the probe 3 system increases, indicating that probe 3 can effectively and specifically recognize trifluoroacetic acid and triethylamine respectively.

[0071] Application Example 6

[0072] Change the acetonitrile stock solution of probe 3 to the tetrahydrofuran stock solution of probe 3. The other procedures are the same as those in Application Example 5. The results show that when the solvent is changed to tetrahydrofuran, probe 3 can also achieve the recognition of trifluoroacetic acid and triethylamine.

[0073] Application Example 7

[0074] Prepare an acetonitrile stock solution of probe 3 with a concentration of 1×10 -3 mol, dilute the sample to 2 mL, use 320 nm as the excitation light source to record the fluorescence spectrum, irradiate the sample with 302 nm ultraviolet light for 30 min, record the fluorescence emission spectrum, continue to irradiate the sample with 302 nm ultraviolet light for 60 min (a total of 90 min), record the fluorescence emission spectrum, heat the sample irradiated for 90 min to 50 - 60 °C, and record the fluorescence emission spectrum. Finally, the obtained fluorescence emission spectrum is as Figure 9 shown. From Figure 9 it can be seen that irradiation with 302 nm ultraviolet light can enhance the fluorescence emission intensity of probe 3, and heating restores the fluorescence emission intensity.

[0075] The reason why irradiation with 302 nm ultraviolet light can enhance the fluorescence emission intensity of probe 3 is that irradiation with 302 nm ultraviolet light can achieve the conformational transformation of this compound (E form → Z form), specifically as follows:

[0076]

[0077] Application Example 8

[0078] Add 100 μL of the acetonitrile stock solution of Probe 3 into a fluorescence cuvette and dilute it to 2 mL. Irradiate the sample with 302 nm ultraviolet light for 90 min, then add 0, 20, 40, 60, 80, 100, 150 μL of the ion Cu to be measured 2+ stock solution, shake until homogeneous, let stand for 3 minutes, use 320 nm as the excitation light source to measure the fluorescence emission spectrum, obtain the fluorescence titration curve, and after fitting, the fitting curve is as Figure 10 shown. When the Probe 3 solution system is irradiated with a 302 nm light source for 90 minutes, the detection limit of this probe for Cu 2+ is 0.18 μM. Compared with 0.24 μM in its initial state, the detection sensitivity is significantly improved.

[0079] Comparative Application Example 1

[0080] Successively use Compounds 4, 5, and 6 in Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention to perform a fluorescence titration experiment on Cu 2+ . The process is the same as that in Application Example 1. The titration results show that the fluorescence response is not obvious. Therefore, the detection effects of Compounds 4, 5, and 6 on Cu 2+ are not good.

[0081] Comparative Application Example 2

[0082] Successively use Fluorescent Probes 4, 5, and 6 in Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention to perform a fluorescence titration experiment on S 2- . The process is the same as that in Application Example 3. The titration results show that the fluorescence response is not obvious. Therefore, the detection effects of Compounds 4, 5, and 6 on S 2- are not good.

[0083] Comparative Application Example 3

[0084] Successively use Fluorescent Probes 4, 5, and 6 in Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention to perform a fluorescence titration experiment on trifluoroacetic acid and triethylamine. The process is the same as that in Application Example 5. The titration results show that the fluorescence response is not obvious. Therefore, the detection effects of Compounds 4, 5, and 6 on trifluoroacetic acid and triethylamine are not good.

Claims

1. A salicylhydrazide derivative containing a pyrazole group with optical switching performance, characterized in that, it has the following structure: wherein, R 1 -R 4 Independently any one of a hydrogen atom, a fluorine atom, a chlorine atom, an iodine atom, and a methyl group; R 1 -R 4 Preferably a hydrogen atom.

2. The preparation method of the salicylhydrazide derivative according to claim 1, characterized in that, it includes: (1) The step of preparing compound 2 by carrying out a substitution reaction between compound 1 and hydrazine hydrate, (2) The step of reacting compound 2 with 1-methyl-1H-pyrazole-3-carbaldehyde to prepare the target compound, 3. The method according to claim 2, characterized in that, in step (1) and step (2), the reactions are both carried out in the presence of the organic solvent ethanol.

4. The method according to claim 2, characterized in that, in step (1), the substitution reaction temperature is 60±5°C and the reaction time is 4 hours.

5. The method according to claim 2, characterized in that, in step (1), the molar ratio of compound I to hydrazine hydrate is 1:

5.

6. The method according to claim 2, characterized in that, in step (2), the reaction temperature is 60-75°C and the reaction time is 6 hours.

7. The method according to claim 2, characterized in that, in step (2), the molar ratio of reactant 2 to 1-methyl-1H-pyrazole-3-carbaldehyde is 1:1.

5.

8. The use of the salicylhydrazide derivative according to claim 1 as a fluorescent probe, characterized in that, this salicylhydrazide derivative can recognize copper ions, sulfide ions, trifluoroacetic acid or triethylamine.

9. The use according to claim 8, characterized in that, the fluorescence emission intensity of the salicylhydrazide derivative can be obtained under 302 nm ultraviolet light irradiation.

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