Preparation method and application of indazole-modified rhodamine mercury ion probe

Abstract

The present application relates to the field of optical sensing imaging detection technology, and specifically to a preparation method and application of an indazole-modified rhodamine mercury ion probe. The present application provides a compound, and a salt or solvate thereof, the chemical structure of the compound being as shown in Formula I: #imgabs0# wherein R1 and R2 are independently selected from C1 to C2 alkyl groups. The present application also provides a crystalline form, and the compound shown in Formula I and / or the crystalline form can be used to prepare an indazole-modified rhodamine mercury ion probe. Under certain conditions, the indazole-modified rhodamine mercury ion probe can achieve high selectivity, high sensitivity, in-situ, and real-time response to mercury ions, and the detection limit can reach 10 ‑10 The order of magnitude of M; its preparation method is simple and easy with low cost; a molecular fluorescent probe that can be used to detect mercury ions is designed using the dye as an optical signal reporter group.

Description

Technical Field

[0001] The present application relates to the field of optical sensing imaging detection technology, and in particular to a preparation method and application of an indazole-modified rhodamine mercury ion probe. Background Art

[0002] In recent years, the identification and detection of important substances in organisms and the environment have become important goals in the field of chemical sensors. Several detection methods, such as high-resolution liquid chromatography, mass spectrometry, atomic absorption spectroscopy, inductively coupled plasma atomic emission spectroscopy, and electrochemical sensing, have been used to analyze these targets. However, these detection methods require complex instrumentation, resulting in cumbersome procedures and time-consuming processes. Molecular fluorescent probes based on organic fluorophores offer numerous advantages, including high sensitivity, ease of operation, good reproducibility, excellent membrane permeability, and in situ detection. Furthermore, when combined with fluorescence imaging techniques, molecular fluorescent probes can be conveniently used for the timely and non-invasive in situ detection of target molecules in biological systems and can be used to monitor biomolecules and their biological processes in living cells and organisms. Therefore, molecular fluorescent probes are becoming an indispensable research tool in modern life sciences and disease diagnosis. The design, synthesis, and bioimaging applications of molecular fluorescent probes have become a cutting-edge, interdisciplinary research field.

[0003] Mercury ions, a highly toxic heavy metal ion, have attracted the attention of scientists in fields including chemistry, biology, clinical biochemistry, and environmental science. Mercury ions accumulate in the human body as methylmercury through the food chain and are difficult to decompose, causing damage to the central nervous system, the mouth, mucous membranes, and teeth. Therefore, the design of highly selective and sensitive heavy metal probes is of paramount importance.

[0004] Chemical fluorescent probes detect mercury ions by interacting with the target analyte, mercury ions, utilizing changes in fluorescence intensity or emission wavelength. These probes offer advantages such as high sensitivity and selectivity, rapid detection, and simple operation. Furthermore, due to their easily modifiable organic molecular structures and low toxicity, they hold broad application prospects in the detection of mercury ions in the environment and biological tissues. Among these chemical fluorescent probes, rhodamine-based organic fluorescent dyes, due to their large molar extinction coefficients and high fluorescence quantum yields, have attracted significant interest and have been widely developed and reported as fluorescent probes for heavy metal ions based on their "on-off" effect. Numerous experimental results have demonstrated that rhodamine-based organic fluorescent dyes are excellent organic materials for constructing heavy metal mercury ion detection probes. Although various rhodamine-based fluorescent probes have been developed and reported for mercury ion detection, these current fluorescent probes suffer from low selectivity and sensitivity, as well as structural and optical signal instability, making them inadequate for the wavelength, selectivity, and sensitivity requirements of biomolecule detection. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an indazole-modified rhodamine mercury ion probe and a preparation method and application thereof, so as to solve the problems in the prior art.

[0006] To achieve the above-mentioned and other related purposes, the present application provides, in a first aspect, a compound, and a salt or solvate thereof, wherein the chemical structure of the compound is shown in Formula I:

[0007]

[0008] Wherein, R1 and R2 are independently selected from C1-C2 alkyl groups.

[0009] In a specific embodiment of the present application, the salt of the compound is selected from the sodium salt of the compound represented by formula I and / or the potassium salt of the compound represented by formula I;

[0010] And / or, the solvate is selected from a mixture of the compound represented by Formula I and an organic solvent; the organic solvent is selected from a combination of one or more of methanol, ethanol, acetonitrile, propane, dichloromethane, chloroform, petroleum ether, and ethyl acetate.

[0011] The second aspect of the present application provides a method for preparing the compound, and a salt or solvate thereof, comprising the following steps:

[0012] 1) The compound represented by formula II is reacted with 6-hydroxyindazole by heating to prepare the compound represented by formula III:

[0013]

[0014] 2) reacting the compound represented by formula III with hydrazine hydrate, and then recrystallizing the precipitate to prepare the compound represented by formula I:

[0015]

[0016] In a specific embodiment of the present application, after the heating reaction in step 1), the compound represented by formula III is prepared by neutralization and extraction, and the organic phase is collected, dried, filtered, and chromatographed;

[0017] And / or, in step 1), the reaction is carried out in an acid; the acid is selected from concentrated sulfuric acid and / or methanesulfonic acid; preferably, the weight ratio of the total weight of the compound represented by formula II and the 6-hydroxyindazole to the weight of the acid is 1:2-8;

[0018] And / or, in step 1), the molar ratio of the compound represented by formula II to the 6-hydroxyindazole is 1:1 to 1.5;

[0019] And / or, in step 1), the reaction temperature of the heating reaction is 105-130°C,

[0020] And / or, in step 1), the reaction time is 24 to 28 hours.

[0021] In a specific embodiment of the present application, in step 2), the molar ratio of the compound represented by formula III to hydrazine hydrate is 1:4-10;

[0022] And / or, in step 2), the reaction is carried out in an organic solvent; the organic solvent is selected from a combination of one or more of methanol, ethanol, and acetonitrile; preferably, in step 2), the weight ratio of the total weight of the compound represented by formula III and hydrazine hydrate to the organic solvent is 1:0.8 to 2:10 to 25;

[0023] And / or, in step 2), the reaction temperature is 15-45°C,

[0024] and / or, in step 2), the reaction time is 12 to 48 hours;

[0025] And / or, in step 2), the recrystallization is carried out using acetonitrile.

[0026] In a third aspect, the present application provides a crystalline form, which is a crystalline form of the compound represented by Formula I, or a salt thereof, or a solvate thereof.

[0027] In a specific embodiment of the present application, the crystal form includes the following unit cell parameters: α=90°, β=115.56°, γ=90°,

[0028] and / or, the crystal space group is C2 / c, and the crystal system belongs to the monoclinic system;

[0029] And / or, the melting point of the crystalline form is 260-262°C.

[0030] The fourth aspect of the present application provides a method for preparing the crystalline form, comprising mixing the compound represented by Formula I with a saturated acetonitrile solution and allowing it to evaporate naturally at room temperature.

[0031] The fifth aspect of the present application provides the use of the compound, its salt or solvate and / or the crystalline form in an indazole-modified rhodamine mercury ion probe.

[0032] In a sixth aspect, the present application provides an indazole-modified rhodamine mercury ion probe, comprising the compound, and its salt or solvate and / or the crystalline form.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. The indazole-modified rhodamine mercury ion probe can achieve high selectivity, high sensitivity, in situ, and real-time response to mercury ions under certain conditions, and the detection limit can reach 10 -10 The order of magnitude of M.

[0035] 2. The preparation method is simple, easy and low-cost. A molecular fluorescent probe that can be used to detect mercury ions is designed using rhodamine dye as an optical signal reporter group.

[0036] 3. Rhodamine dye can also be used as a platform to design probes that recognize various molecules or ions.

[0037] 4. A crystalline form of an indazole-modified rhodamine mercury ion probe was obtained. Due to its single crystal form and high stability, the crystalline form of the present invention has more obvious advantages in mercury ion detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The fluorescence spectrum of the probe obtained in the present invention is obtained by gradually adding mercury ions to CH3CN-H2O (pH=6.0, v / v, 1 / 4).

[0039] Figure 2 This is a diagram of the single crystal structure of compound 2 obtained in Example 2 of the present invention.

[0040] Figure 3 It is the unit cell parameter of the single crystal product obtained in Example 2 of the present invention.

[0041] Figure 4 This is a diagram showing color changes when the probe obtained by the present invention reacts with different heavy metal ions.

[0042] Figure 5 The diagram is a color change diagram of the test strip of the probe obtained by the present invention and the test of mercury ions with different concentrations.

[0043] Figure 6 It is the reaction kinetics diagram of the probe obtained in the present invention.

[0044] Figure 7 This is a graph showing the detection limit test data of the probe obtained in the present invention.

[0045] Figure 8 It is the mass spectrum of the intermediate product 1 obtained in Example 1 of the present invention.

[0046] Figure 9 is the intermediate product 1 obtained in Example 1 of the present invention 1 H NMR (400 MHz) nuclear magnetic spectrum.

[0047] Figure 10 is the intermediate product 1 obtained in Example 1 of the present invention 13 C NMR (100 MHz) nuclear magnetic spectrum.

[0048] Figure 11 It is the mass spectrum of compound 2 obtained in Example 2 of the present invention.

[0049] Figure 12 is the compound 2 obtained in Example 2 of the present invention 1 H NMR (400 MHz) nuclear magnetic spectrum.

[0050] Figure 13 is the compound 2 obtained in Example 2 of the present invention 13 C NMR (100 MHz) nuclear magnetic spectrum. DETAILED DESCRIPTION

[0051] In order to make the invention purpose, technical scheme and beneficial effects of this application clearer, the present application is further described below with reference to the examples. It should be understood that the examples are only used to explain this application and are not used to limit the scope of the application. Unless otherwise specified, the test methods used in the following examples are all conventional methods. People familiar with this technology can easily understand other advantages and effects of this application from the content disclosed in this description.

[0052] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, but are preferably performed sequentially. For example, "the method includes steps 1) and 2)" means that the method may include steps 1) and 2) performed sequentially, or may include steps 2) and 1) performed sequentially.

[0054] After extensive research, the inventors of this application have discovered an indazole-modified rhodamine mercury ion probe, its preparation method, and application. Under certain conditions, the indazole-modified rhodamine mercury ion probe can achieve high selectivity, high sensitivity, in situ, and real-time response to mercury ions, and the detection limit can reach 10 -10 The present application was completed on the basis of the following principles: a simple, easy, and low-cost preparation method; a molecular fluorescent probe for detecting mercury ions was designed using the dye as an optical signal reporter; and the dye can also serve as a platform for designing probes that recognize various molecules or ions.

[0055] In one aspect, the present application provides a compound, and a salt or solvate thereof, wherein the chemical structural formula of the compound is shown in Formula I:

[0056]

[0057] Wherein, R1 and R2 are independently selected from C1-C2 alkyl groups.

[0058] Among the compounds, salts or solvates provided herein, the salts of the compounds are selected from the sodium salt of the compound represented by Formula I and / or the potassium salt of the compound represented by Formula I; the solvates are selected from a mixture of the compound represented by Formula I and an organic solvent; the organic solvent is selected from a combination of one or more of methanol, ethanol, acetonitrile, propane, dichloromethane, chloroform, petroleum ether, and ethyl acetate.

[0059] Another aspect of the present application provides a method for preparing the compound, and a salt or solvate thereof, comprising the following steps:

[0060] 1) The compound represented by formula II is reacted with 6-hydroxyindazole by heating to prepare the compound represented by formula III:

[0061]

[0062] 2) reacting the compound represented by formula III with hydrazine hydrate, and then recrystallizing the precipitate to prepare the compound represented by formula I:

[0063]

[0064] In the method for preparing the compound, salt, or solvate thereof provided herein, the heating reaction in step 1) is followed by neutralization and extraction, and the organic phase is collected, dried, filtered, and chromatographed to prepare the compound represented by Formula III. The neutralizing agent is selected from sodium bicarbonate. Preferably, the neutralizing agent is saturated sodium bicarbonate. The extraction agent is selected from ethyl acetate. After extraction, the organic phase is collected and dried over anhydrous sodium sulfate to obtain a crude product, which is then chromatographed using a dichloromethane / ethyl acetate column. The volume ratio of dichloromethane to ethyl acetate is 1:20-40, specifically 1:20-25, 1:25-30, or 1:30-40. After chromatography, separation is performed using a silica gel column to obtain a solid of the compound represented by Formula III. The silica gel in the silica gel column is 200 mesh. The crude product is separated to obtain a compound represented by Formula III with a purity of 95-99%.

[0065] In the method for preparing the compound, salt or solvate thereof provided herein, in step 1), the reaction is carried out in an acid. The acid is selected from concentrated sulfuric acid and / or methanesulfonic acid. Preferably, the weight ratio of the total weight of the compound represented by formula II and the 6-hydroxyindazole to the acid is 1:2 to 8, specifically, 1:2 to 4, 1:4 to 6, or 1:6 to 8. More preferably, the weight ratio of the total weight of the compound represented by formula II and the 6-hydroxyindazole to the concentrated sulfuric acid is 1:2 to 8, specifically, 1:2 to 4, 1:4 to 6, or 1:6 to 8.

[0066] In the method for preparing the compound, salt, or solvate thereof provided herein, in step 1), the molar ratio of the compound represented by Formula II to the 6-hydroxyindazole is 1:1-1.5, specifically 1:1-1.1, 1:1.1-1.2, 1:1.2-1.3, or 1:1.3-1.5. The compound represented by Formula II can specifically be 2-(2,4-dihydroxybenzoyl)benzoic acid or 2-(2,4-dihydroxybenzoyl)phenylacetic acid.

[0067] In the method for preparing the compound, salt, or solvate thereof provided herein, in step 1), the reaction temperature of the heating reaction is 105-130° C., specifically, 105-110° C., 110-120° C., or 120-130° C., etc. Those skilled in the art can adjust the reaction time according to the progress of the reaction. For example, the reaction time is 24-28 hours, specifically, 24-25 hours, 25-26 hours, or 26-28 hours, etc.

[0068] In the method for preparing the compound, salt or solvate thereof provided herein, in step 2), the molar ratio of the compound represented by formula III to hydrazine hydrate is 1:4-10, specifically, 1:4-6, 1:6-17, 1:7-8, or 1:8-10. The reaction is carried out in an organic solvent. The organic solvent is selected from a combination of one or more of methanol, ethanol, and acetonitrile. Preferably, the weight ratio of the total weight of the compound represented by formula III and hydrazine hydrate to the organic solvent is 1:0.8-2:10-25, specifically, 1:0.8-1:10-12, 1:1-1.2:12-20, or 1:1.2-2:20-25. More preferably, the weight ratio of the total weight of the compound represented by formula III and hydrazine hydrate to the methanol is 1:0.8-2:10-25, specifically, 1:0.8-1:10-12, 1:1-1.2:12-20, or 1:1.2-2:20-25, etc.

[0069] In the method for preparing the compound, salt, or solvate thereof provided herein, in step 2), the reaction temperature is 15-45° C., specifically, 15-20° C., 20-35° C., or 35-45° C., etc. Those skilled in the art can adjust the reaction time according to the progress of the reaction. For example, the reaction time is 12-48 h, specifically, 12-16 h, 16-24 h, or 24-48 h, etc.

[0070] In the method for preparing the compound, salt, or solvate thereof provided herein, in step 2), the recrystallization is performed using acetonitrile. Preferably, the acetonitrile is saturated acetonitrile. Saturated acetonitrile refers to a solution obtained by adding acetonitrile to water until the acetonitrile can no longer dissolve.

[0071] On the other hand, the present application provides a crystalline form, which is a crystalline form of a compound represented by Formula I, or a salt thereof, or a solvate thereof. Figure 2 As shown, the crystal form is a single crystal structure. Figure 4 As shown, the crystal form includes the following unit cell parameters: α=90°, β=115.56°, γ=90°, The crystal space group is C 2 / c, and the crystal system belongs to the monoclinic system. The melting point of the crystal is 260-262°C, specifically, 260-261°C, or 261-262°C. The determination of single crystal data is not particularly limited, and a single crystal testing instrument known to those skilled in the art can be used. In a specific embodiment, the single crystal data of the crystal is obtained by collecting single crystal X-ray diffraction data of the crystal at 293K on a BRUKER SMART APEX-II CCD diffractometer.

[0072] Another aspect of the present application provides a method for preparing the crystalline form, comprising mixing the compound of Formula I with a saturated acetonitrile solution and allowing the mixture to evaporate naturally at room temperature. The saturated acetonitrile solution is a solution obtained by adding acetonitrile to water until the acetonitrile can no longer dissolve.

[0073] On the other hand, the present application provides the use of the compound, its salt or solvate and / or the crystalline form in an indazole-modified rhodamine mercury ion probe.

[0074] On the other hand, the present application provides an indazole-modified rhodamine mercury ion probe, including the compound, and its salt or solvate and / or the crystalline form.

[0075] The above content is a further detailed description of the present invention in conjunction with specific embodiments. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, all of which should be deemed to fall within the scope of protection of the present invention. Being a fluorescent dye is one use of the new compound of the present invention, and it cannot be determined that the compound of the present invention is only used for fluorescent dyes. For ordinary technicians in the technical field to which the present invention belongs, based on the same mechanism of action of the compound of the present invention as a fluorescent dye, they can make several simple inferences to derive other application uses of the compound of the present invention, all of which should be deemed to fall within the scope of protection of the present invention.

[0076] The present application is further described below by way of examples, but the scope of the present application is not limited thereby.

[0077] Example 1

[0078] Preparation of intermediate product 1

[0079]

[0080] 1) 2-(2,4-Dihydroxybenzoyl)benzoic acid (3.13 g, 10 mmol) and 6-hydroxyindazole (1.34 g, 10 mmol) were added to 8 mL of concentrated sulfuric acid, stirred, and heated in an oil bath at 110°C for 24 h.

[0081] 2) The reaction solution was added to 100 mL of water and neutralized with saturated sodium bicarbonate until neutral. Ethyl acetate (50 mL x 3) was added for extraction. The organic phases were combined, dried, filtered, and the solvent was evaporated under reduced pressure. The residue was separated by silica gel chromatography using dichloromethane / ethyl acetate (v / v = 1:30) as eluent to obtain intermediate 1 as an off-white solid (3.53 g). The yield was 82.8%. MP: 273-275°C. The mass spectrum of the obtained intermediate 1 is shown below. Figure 8 shown.

[0082] like Figure 9 and Figure 10 As shown, intermediate product 1: 1 H NMR(400MHz,CD3Cl)δ(ppm))8.53(s,1H,broad),8.19-8.17(m,1H),7.93(s,1H),7.77-7.71(m,3H),7.35-7.30(m,1H),7.16( d,J=8.8Hz,1H),6.57(d,J=8.9Hz,1H),6.52(s,1H),6.41(dd,J=8.8,2.1Hz,1H),3.38(q,J=7.1Hz,6H),1.19(t,J=7.1Hz,8H). 13 C NMR(100MHz,CD3Cl)δ(ppm)168.79,152.66,152.24,152.12,149.87,137.82,135.66,135.33,130.71,128.30,127.06,126.02, 124.65,123.53,120.40,113.36,109.04,104.92,100.20,97.75,83.82,44.65,12.62.ESI-HRMS:calcd.m / z412.1656for[M+H] + , found m / z 412.1655for[M+H] + .

[0083] Example 2

[0084] Preparation of mercury ion probe 2

[0085]

[0086] 1) The intermediate product 1 (0.41 g, 1 mmol) prepared in Example 1 and hydrazine hydrate (0.16 g, 5 mmol) were stirred in 8 mL of methanol at room temperature until a large amount of precipitate appeared.

[0087] 2) The precipitate was collected and the crude precipitate was recrystallized from acetonitrile to obtain pure compound 2, i.e., mercury ion probe 2, as a white solid powder (0.29 g, yield 68.5%). Compound 2 is a compound of formula I wherein R1 and R2 are independently selected from methyl groups.

[0088] 3) Single crystals of compound 2 were obtained by naturally evaporating a saturated acetonitrile solution of the pure compound of formula I at room temperature.

[0089] The obtained single crystal structure is as follows Figure 2As shown, the unit cell parameters of the obtained single crystal are as follows Figure 3 The mass spectrum of the obtained compound 2 is shown as Figure 11 shown.

[0090] like Figure 12 and Figure 13 As shown, compound 2: 1 H NMR (400MHz, CD3Cl) δ (ppm) 8.87 (s, 1H, broad), 8.09 (d, J = 7.4Hz, 1H), 7.92 (s, 1H), 7.71 (d, J = 8.7Hz, 1H), 7.61-7.51 (m, 2H), 7.20 (d, J = 7.5Hz, 1H), 7.1 4(d,J=8.7Hz,1H),6.49(d,J=2.0Hz,1H),6.42(d,J=8.8Hz,1H),6.35(dd,J =8.8,2.2Hz,1H),3.68(s,2H),3.36(q,J=7.0Hz,4H),1.13(t,J=7.0Hz,6H). 13 CNMR(100MHz,CD3Cl)δ(ppm)166.03,153.23,152.62,149.32,149.21,137.42,135.21,133.54,129.77,129.52,127.3 3,124.38,124.05,122.59,120.29,113.37,108.93,104.00,99.86,98.19,65.08,44.52,12.68.ESI-HRMS:calcd.m / z 426.1925for[M+H] + ,found m / z426.1923for[M+H] + .

[0091] Example 3

[0092] Determination of optical properties of mercury ion probe 2

[0093] The mercury ion probe 2 prepared in Example 2 was prepared to a concentration of 5×10 -3 mol / L DMF solution and save for future use.

[0094] Determination of the optical properties of mercury ion probe 2 in different concentrations of mercury ions: Mercury ion probe 2 was dissolved in CH3CN-H2O (pH=6.0, v / v, 1 / 4) solvent to prepare 5×10 -6 mol / L test solution 3mL, gradually add Hg 2+ ions (0~1.5×10 -4 mol / L), and record the fluorescence emission spectrum. Figure 1 shown.

[0095] Example 4

[0096] Ion selectivity of mercury ion probe 2 and determination of different concentrations of compounds using test strips

[0097] The mercury ion probe 2 prepared in Example 2 was dissolved in CH3CN-H2O (pH=6.0, v / v, 1 / 4) solvent to prepare 3 mL of 10.0 μM test solution. 100 μM of different heavy metal ions were gradually added and the color changes were observed by taking pictures. The results are shown in FIG. Figure 4 .

[0098] Preparation of test strips: Immerse the test strips in a dichloromethane solution of mercury ion probe 2 (1mM) and then dry in air. Add different concentrations of mercury ions to the test strips in sequence, from right to left: 0, 1.0×10 -6 M,1.0×10 - 5 M,1.0×10 -4 M,1.0×10 -3 M,1.0×10 -2 M, take pictures to observe the color change, the results are shown in Figure 5 .

[0099] Example 5

[0100] Determination of the kinetics of mercury ion probe 2

[0101] The mercury ion probe 2 prepared in Example 2 was dissolved in CH3CN-H2O (pH=6.0, v / v, 1 / 4) solvent to prepare 3 mL of 10.0 μM test solution. The test compound and the compound were added with Hg 2+ The fluorescence emission spectrum of mercury ions at 100.0 μM was tested from 0 to 40 minutes after the addition of mercury ions. Figure 6 .

[0102] Example 6

[0103] Determination of detection limit data for mercury ion probe 2

[0104] The mercury ion probe 2 prepared in Example 2 was dissolved in CH3CN-H2O (pH=6.0, v / v, 1 / 4) solvent to prepare 3 mL of 10.0 μM test solution, and different concentrations of mercury ions 0.1 to 3 μM were added in sequence. The fluorescence emission spectrum was recorded and the detection limit was calculated. Figure 7 .

[0105] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein shall be covered by the claims of this application.

Claims

1. A compound or a salt thereof, wherein the chemical structural formula of the compound is as shown in Formula I: in, R1 and R2 are independently selected from C1-C2 alkyl groups.

2. The compound or salt thereof according to claim 1, wherein The salt of the compound is selected from the sodium salt of the compound shown in Formula I and / or the potassium salt of the compound shown in Formula I.

3. A method for preparing the compound or salt thereof according to claim 1 or 2, comprising the following steps: 1) The compound represented by formula II is reacted with 6-hydroxyindazole by heating to prepare the compound represented by formula III: 2) reacting the compound represented by formula III with hydrazine hydrate, and then recrystallizing the precipitate to prepare the compound represented by formula I:

4. The preparation method according to claim 3, wherein After the heating reaction in step 1), the mixture is neutralized and extracted, and the organic phase is collected, dried, filtered, and chromatographed to prepare the compound represented by formula III; And / or, in step 1), the heating reaction is carried out in an acid; the acid is selected from concentrated sulfuric acid and / or methanesulfonic acid; And / or, in step 1), the molar ratio of the compound represented by formula II to the 6-hydroxyindazole is 1:1 to 1.5; And / or, in step 1), the reaction temperature of the heating reaction is 105-130°C; And / or, in step 1), the reaction time is 24 to 28 hours.

5. The preparation method according to claim 4, wherein In step 1), the heating reaction is carried out in an acid; the acid is selected from concentrated sulfuric acid and / or methanesulfonic acid; and the weight ratio of the total weight of the compound represented by formula II and the 6-hydroxyindazole to the acid is 1:2 to 8.

6. The preparation method according to claim 3, wherein In step 2), the molar ratio of the compound represented by formula III to hydrazine hydrate is 1:4-10; And / or, in step 2), the reaction is carried out in an organic solvent; the organic solvent is selected from a combination of one or more of methanol, ethanol, and acetonitrile; and / or, in step 2), the reaction temperature is 15-45° C.; and / or, in step 2), the reaction time is 12 to 48 hours; And / or, in step 2), the recrystallization is carried out using acetonitrile.

7. The preparation method according to claim 6, wherein In step 2), the reaction is carried out in an organic solvent; The weight ratio of the total weight of the compound represented by formula III and hydrazine hydrate to the organic solvent is 1:0.8 to 2:10 to 25.

8. A crystalline form, the chemical structure of which is as follows: It is characterized by: The crystal form includes the following unit cell parameters: α=90°, β=115.56°, γ=90°, 9. The crystalline form according to claim 8, wherein The crystal space group is C2 / c, and the crystal system belongs to the monoclinic system; And / or, the melting point of the crystalline form is 260-262°C.

10. A method for preparing the crystalline form according to any one of claims 8 to 9, comprising mixing the compound represented by formula I with a saturated acetonitrile solution and allowing the mixture to evaporate naturally at room temperature.

11. Use of the compound or salt thereof according to any one of claims 1 to 2 and / or the crystalline form according to any one of claims 8 to 9 in the preparation of an indazole-modified rhodamine mercury ion probe.

12. An indazole-modified rhodamine mercury ion probe comprising the compound or salt thereof according to any one of claims 1 to 2 and / or the crystal form according to any one of claims 8 to 9.

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