A Rhodamine Derivative, Its Preparation Method and Application

Abstract

This invention provides a rhodamine derivative, its preparation method, and its applications. By substituting spironolactone groups and N,N-diethyl groups, a series of rhodamine derivatives were obtained. These derivatives exhibit properties diametrically opposed to traditional rhodamine; they are fluorescent in their hydrophobic, closed-ring (lactone) form, but become almost non-fluorescent when converted to the open-ring form, making their application in hydrophobic environments possible. These rhodamine derivatives overcome the quenching caused by aggregation in rhodamine, achieving a fluorescence quantum yield of nearly 20% in the solid state. Due to their unique properties, the rhodamine dyes of this invention have great application potential in sensing, polymer labeling, and photothermal conversion.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent materials, and relates to a rhodamine derivative, its preparation method, and its application. Background Technology

[0002] Rhodamine (Rh-B) and its derivatives (hereinafter referred to as rhodamine) are among the most important organic fluorophores. Since their discovery, rhodamine has been widely used in various fields such as bioimaging, anti-counterfeiting, ion detection, toxic gas detection, and biosensing. The widespread application of rhodamine molecules is attributed to three significant characteristics: high brightness and photostability; spectral properties that are strongly dependent on molecular structure and numerous modifiable sites; and a balance between a colorless, non-fluorescent lactone form and a colored, fluorescent zwitterionic form. Although rhodamine dyes perform well in various applications, some drawbacks remain, such as low signal-to-noise ratio due to autofluorescence, weak tissue penetration, high scattering caused by excitation and emission light, single emission wavelength, photobleaching, low labeling efficiency, and poor selectivity. These limitations place higher performance demands on rhodamine fluorescent dyes. Based on the modifiability of the rhodamine molecular structure, researchers have used this to adjust its absorption and emission wavelengths, optimize its photophysical properties, and thus broaden its application range. However, a typical characteristic of rhodamine dyes is the existence of a lactone-zwitterion balance, and researchers always prefer the hydrophilic, open-ring (zwitterion) form for study, which greatly limits its application in hydrophobic environments. Therefore, it is essential to develop its closed-ring, spironolactone form for application. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a rhodamine derivative, its preparation method, and its applications. This rhodamine derivative has properties opposite to those of traditional rhodamine dyes. The rhodamine derivative exhibits bright fluorescence in the closed-ring state and almost no fluorescence in the open-ring state, showing great promise for applications in microplastic labeling and photothermal processes.

[0004] This invention is achieved through the following technical solution: A rhodamine derivative, wherein the rhodamine derivative is one of the following compounds: .

[0005] The method for preparing the rhodamine derivative includes: 4-Diethylaminoketo acid, 3-iodophenol and methanesulfonic acid were stirred evenly and heated under reflux to react and obtain compound I-RHO; I-RHO, 1,2-dichloroethane, and phosphorus oxychloride were mixed and heated under reflux to react. After the reaction was completed, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure to obtain crude acyl chloride residue. Benzenesulfonamide or p-methylbenzenesulfonamide or p-methoxybenzenesulfonamide or p-chlorobenzenesulfonamide or p-fluorobenzenesulfonamide or m-fluorobenzenesulfonamide or o-fluorobenzenesulfonamide, as well as triethylamine and acetonitrile, were added to the crude acyl chloride residue and heated under reflux to react to obtain an intermediate product. The intermediate product, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, tetrahydrofuran, and water were mixed and heated under reflux to give the rhodamine derivative.

[0006] Preferably, the molar ratio of 4-diethylaminoketo acid, 3-iodophenol and methanesulfonic acid is 1:(1-1.5):(60-90), and the first heating reflux temperature is 160-180°C.

[0007] Preferably, the molar ratio of I-RHO to phosphorus oxychloride is 1:(15-25), and the reflux temperature for the second heating is 85-105°C.

[0008] Preferably, the molar ratio of benzenesulfonamide or p-methylbenzenesulfonamide or p-methoxybenzenesulfonamide or p-chlorobenzenesulfonamide or p-fluorobenzenesulfonamide or m-fluorobenzenesulfonamide or o-fluorobenzenesulfonamide to triethylamine is 1:(15-20), and the reflux temperature for the third heating is 60-80°C.

[0009] Preferably, intermediate products, indole 2 The molar ratio of pinacol borate, potassium carbonate, and bis(triphenylphosphine)palladium dichloride is 1:(1.5–2):(1–3):(0.05–0.2).

[0010] Preferably, the reflux temperature for the fourth heating is 70–80°C.

[0011] A fluorescently labeled microplastic comprising the aforementioned rhodamine derivative.

[0012] The application of the rhodamine derivatives in microplastic labeling.

[0013] The application of the rhodamine derivatives in photothermal conversion.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a general and simple strategy to obtain a series of rhodamine derivatives by modifying the intramolecular donor and acceptor groups and substituting spironolactone groups and N,N-diethyl groups. These rhodamine derivatives exhibit properties diametrically opposed to conventional rhodamine; they are fluorescent in their hydrophobic, closed-ring (lactone) form, but become almost non-fluorescent when converted to the open-ring form, enabling their application in hydrophobic environments. These rhodamine derivatives overcome the quenching caused by aggregation in traditional rhodamine, achieving a fluorescence quantum yield of nearly 20% in the solid state. Due to their unique properties, the rhodamine dyes of this invention hold great promise for applications in sensing, polymer labeling, and photothermal conversion. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 It is the 1H NMR spectrum of S-Rh-B; Figure 2 It is the S-Rh-B carbon NMR spectrum; Figure 3 This is the 1H NMR spectrum of Rh-In; Figure 4 It is the carbon NMR spectrum of Rh-In; Figure 5 It is the hydrogen NMR spectrum of S-Rh-In; Figure 6 It is the carbon NMR spectrum of S-Rh-In; Figure 7 This is the 1H NMR spectrum of MS-Rh-In; Figure 8 This is the MS-Rh-In carbon NMR spectrum; Figure 9 This is the 1H NMR spectrum of MOS-Rh-In; Figure 10 This is the 1H NMR spectrum of ClS-Rh-In; Figure 11 yes p -FS-Rh-In 1H NMR spectrum; Figure 12 yes p Carbon NMR spectrum of -FS-Rh-In; Figure 13 yes m -FS-Rh-In 1H NMR spectrum; Figure 14 yeso -FS-Rh-In 1H NMR spectrum; Figure 15 These are the absorption and emission spectra of Rh-B; Figure 16 These are the emission spectra of Rh-B open-ring and closed-ring; Figure 17 It is the absorption and emission spectrum of S-Rh-B; Figure 18 These are the emission spectra of S-Rh-B open-ring and closed-ring. Figure 19 These are the absorption and emission spectra of Rh-In; Figure 20 These are the emission spectra of Rh-In open-ring and closed-ring types; Figure 21 These are the absorption and emission spectra of S-Rh-In; Figure 22 These are the emission spectra of S-Rh-In open-ring and closed-ring systems; Figure 23 These are photographs of Rh-B, S-Rh-B, Rh-In, and S-Rh-In under a UV lamp (365nm); Figure 24 These are the absorption and emission spectra of MS-Rh-In; Figure 25 These are the emission spectra of MS-Rh-In open-ring and closed-ring systems; Figure 26 These are the absorption and emission spectra of MOS-Rh-In; Figure 27 These are the emission spectra of MOS-Rh-In open-loop and closed-loop systems; Figure 28 These are the absorption and emission spectra of ClS-Rh-In; Figure 29 These are the emission spectra of ClS-Rh-In open-ring and closed-ring forms; Figure 30 yes p Absorption and emission spectra of -FS-Rh-In; Figure 31 yes p -FS-Rh-In open-ring and closed-ring emission spectra; Figure 32 yes m Absorption and emission spectra of -FS-Rh-In; Figure 33 yes m -FS-Rh-In open-ring and closed-ring emission spectra; Figure 34 yes oAbsorption and emission spectra of -FS-Rh-In; Figure 35 yes o -FS-Rh-In open-ring and closed-ring emission spectra; Figure 36 These are photographs of MS-Rh-In, MOS-Rh-In, ClS-Rh-In, p-FS-Rh-In, m-FS-Rh-In, and o-FS-Rh-In under fluorescent and ultraviolet (365nm) lamps; Figure 37 The UV spectrum of the S-Rh-In-SEBS membrane after one week of diffusion in water at room temperature and 40°C is shown. Figure 38 This is the UV spectrum of the Rh-B-SEBS membrane after one week of diffusion in water at room temperature and 40°C; Figure 39 The UV spectra of Rh-B-SEBS membrane and S-Rh-In-SEBS membrane after one week of diffusion in water at room temperature and 40°C are shown. Figure 40 a) shows the temperature change of MOS-Rh-In-SEBS films with different proportions under 638nm (0.6W) laser light; b) shows the temperature change of 1.5% MOS-Rh-In-SEBS films over time under irradiation with 0.6W laser light at 450nm, 520nm, and 638nm. Figure 41 a) shows the temperature change of 1.5% MOS-Rh-In-SEBS under 450nm laser irradiation; b) shows the temperature change of 3% MOS-Rh-In-SEBS under 520nm laser irradiation; c) shows the temperature change of 3% MOS-Rh-In-SEBS under 638nm laser irradiation.

[0017] The above Figure 15 , Figure 17 , Figure 19 , Figure 21 , Figure 24 , Figure 26 , Figure 28 , Figure 30 , Figure 32 , Figure 34 In the diagram, Abs-L represents the closed-loop absorption spectrum, Abs-Z represents the open-loop absorption spectrum, Em-L represents the closed-loop fluorescence emission spectrum, and Em-Z represents the open-loop fluorescence emission spectrum. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0019] This invention discloses a series of rhodamine derivatives, including S-Rh-In, MS-Rh-In, MOS-Rh-In, ClS-Rh-In, and p -FS-Rh-In、 m -FS-Rh-In、 o -FS-Rh-In.

[0020] The structural formula of S-Rh-In is as follows: The structure of MS-Rh-In is: The structural formula of MOS-Rh-In is: The structural formula of ClS-Rh-In is: ; p The structural formula for -FS-Rh-In is: ; m The structural formula for -FS-Rh-In is: ; o The structural formula for -FS-Rh-In is: .

[0021] This invention discloses a method for synthesizing the above-mentioned rhodamine derivatives, comprising the following steps: 1) Preparation of compound I-RHO 4-Diethylaminoketoic acid, 3-iodophenol, and methanesulfonic acid were stirred until homogeneous and heated to reflux. After the reaction was complete, the mixture was cooled to room temperature, and the pH of the reaction solution was adjusted to 9. The mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain compound I-RHO.

[0022] The structural formula of the compound I-RHO is as follows: .

[0023] 2) Preparation of compound S-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. Benzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed homogeneously and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain compound S-Rh.

[0024] The structural formula of the compound S-Rh is as follows: .

[0025] 3) Preparation of compound S-Rh-In S-Rh, potassium carbonate, indole-2-borate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain compound S-Rh-In.

[0026] 4) Preparation of compound MS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. p-Toluenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain compound MS-Rh.

[0027] The structural formula of the compound MS-Rh is as follows: .

[0028] 5) Preparation of compound MS-Rh-In MS-Rh, potassium carbonate, indole-2-borate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the product MS-Rh-In.

[0029] 6) Preparation of compound MOS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. p-Methoxybenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the compound MOS-Rh.

[0030] The structural formula of the compound MOS-Rh is as follows:

[0031] 7) Preparation of compound MOS-Rh-In MOS-Rh, potassium carbonate, indole-2-borate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the product MOS-Rh-In.

[0032] 8) Preparation of compound ClS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. p-Chlorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain compound ClS-Rh.

[0033] The structural formula of the compound ClS-Rh is as follows:

[0034] 9) Preparation of compound ClS-Rh-In ClS-Rh, potassium carbonate, indole-2-borate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the product ClS-Rh-In.

[0035] 10) Preparation of compounds p- FS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. p-Fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the compound. p- FS-Rh.

[0036] Wherein, the compound p- The structural formula of FS-Rh is:

[0037] 11) Preparation of compounds p -FS-Rh-In Will p- FS-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the final product. p -FS-Rh-In.

[0038] 12) Preparation of compounds m- FS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. m-Fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the compound. m- FS-Rh.

[0039] Wherein, the compound m- The structural formula of FS-Rh is:

[0040] 13) Preparation of compounds m -FS-Rh-In Will m- FS-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the final product. m -FS-Rh-In.

[0041] 14) Preparation of compounds o- FS-Rh I-RHO, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were stirred until homogeneous and heated to reflux. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. o-Fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed until homogeneous and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was added, and the mixture was heated to reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the compound. o- FS-Rh.

[0042] Wherein, the compound o- The structural formula of FS-Rh is:

[0043] 16) Preparation of compounds o -FS-Rh-In Will o- FS-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were mixed thoroughly and heated to reflux. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected and the solvent was removed by rotary evaporation under reduced pressure. The crude product was purified by column chromatography to obtain the final product. o -FS-Rh-In.

[0044] The amounts of reactants used in each step of the above method are as follows: In step 1), the molar ratio of 4-diethylaminoketo acid, 3-iodophenol and methanesulfonic acid is 1:(1~1.5):(60~90), and the specific reaction temperature is 160~180℃.

[0045] In step 2), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380~420):(15~25), and the specific reaction temperature is 85~105℃; the molar ratio of benzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15~20):(170~190), and the specific reaction temperature is 60~80℃.

[0046] In step 3), S-Rh, indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0047] In step 4), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of p-toluenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0048] In step 5), MS-Rh, indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0049] In step 6), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of p-methoxybenzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0050] In step 7), MOS-Rh, indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0051] In step 8), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of p-chlorobenzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0052] In step 9), ClS-Rh, indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0053] In step 10), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of p-fluorobenzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0054] In step 11), p- FS-Rh, Indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0055] In step 12), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of m-fluorobenzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0056] In step 13), m- FS-Rh, Indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0057] In step 14), the molar ratio of I-RHO, 1,2-dichloroethane and phosphorus oxychloride is 1:(380-420):(15-25), and the specific reaction temperature is 85-105℃; the molar ratio of o-fluorobenzenesulfonamide, triethylamine and ultra-dry acetonitrile is 1:(15-20):(170-190), and the specific reaction temperature is 60-80℃.

[0058] In step 15), o- FS-Rh, Indole 2 The molar ratio of pinacol borate, potassium carbonate, bis(triphenylphosphine) palladium dichloride, tetrahydrofuran, and water is 1:(1.5–2):(1–3):(0.05–0.2):(250–500):(1000–1200), and the specific reaction temperature is 70–80℃.

[0059] The above method uses column chromatography as the actual purification operation. Column chromatography uses petroleum ether-ethyl acetate, dichloromethane-n-hexane, or dichloromethane-ethyl acetate systems as eluents. In step 9), the volume ratio of petroleum ether to ethyl acetate is 10:1; in step 1), the volume ratio of petroleum ether to ethyl acetate is 15:1; in step 8), the volume ratio of petroleum ether to ethyl acetate is 1:2; in step 2), the volume ratio of dichloromethane to n-hexane is 2:1; in steps 3) and 6), the volume ratio of dichloromethane to n-hexane is 5:1; in steps 4), 10), 13), 14), and 15), the volume ratio of dichloromethane to n-hexane is 1:1; in steps 5) and 11), the volume ratio of dichloromethane to n-hexane is 4:1; in step 7), the volume ratio of dichloromethane to ethyl acetate is 100:1; and in step 12), the volume ratio of dichloromethane to n-hexane is 1:2.

[0060] The present invention will be further described below with reference to specific embodiments: Example 1: Synthesis of compound S-Rh-B (used as a control) Rhodamine B, ultra-dry 1,2-dichloroethane, and phosphorus oxychloride were added to a two-necked flask, stirred until homogeneous, and heated under reflux for 8 h. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding crude acyl chloride residue. The crude acyl chloride was used directly in the next reaction without purification. Benzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed homogeneously in a round-bottom flask and transferred to the crude acyl chloride residue. An additional 24 mL of ultra-dry acetonitrile was then quickly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound S-Rh-B was obtained by column chromatography using petroleum ether:ethyl acetate = 8:1 as the eluent. Three sets of experiments were conducted, and the different material ratios are shown in Table 1 below. The structure of S-Rh-B obtained in the second set of experiments was characterized as [C]. 30 H 36 N3O2] + Calculated value: 582.2430; Measured value: 582.2348. The 1H and 1C NMR spectra are shown below. Figure 1 and Figure 2 .

[0061] Table 1. Experimental conditions for three groups in Example 1

[0062] The reaction equation is as follows:

[0063] Example 2: Synthesis of compound I-RHO 4-Diethylaminoketoic acid, 3-iodophenol, and methanesulfonic acid were added to a round-bottom flask, stirred thoroughly, and heated under reflux for 8 hours. After the reaction was complete, the mixture was cooled to room temperature, and the pH of the reaction solution was adjusted to 9 using saturated Na₂CO₃. The mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound I-RHO was obtained by column chromatography using petroleum ether:ethyl acetate = 15:1 as the eluent. Three sets of experiments were conducted, and the different material ratios are shown in Table 2 below.

[0064] Table 2. Experimental conditions for three groups in Example 2

[0065] The reaction equation is as follows:

[0066] Example 3: Synthesis of compound Rh-In (used as a control) Compound I-RHO obtained from the second group of experiments in Example 2, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and refluxed for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound Rh-In was obtained by column chromatography using petroleum ether:ethyl acetate = 8:1 as the eluent. Three groups of experiments were conducted, and the different material ratios are shown in Table 3 below. The structure of Rh-In obtained from the second group of experiments is characterized as [C]. 32 H 27 N2O3] + Calculated value: 487.2016; Measured value: 487.2021. See the 1H and 1C NMR spectra. Figure 3 and Figure 4 .

[0067] Table 3. Experimental conditions for three groups in Example 3

[0068] The reaction equation is as follows:

[0069] Example 4: Synthesis of compound S-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 h. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, benzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed homogeneously and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then quickly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound S-Rh was obtained by column chromatography using dichloromethane:n-hexane as the eluent at a ratio of 2:1. Three groups of experiments were conducted, and the different material ratios are shown in Table 4 below.

[0070] Table 4. Experimental conditions for three sets of examples in Example 4

[0071] The reaction equation is as follows:

[0072] Example 5: Synthesis of compound S-Rh-In Compound S-Rh obtained from the second group of experiments in Example 4, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and refluxed for 12 hours under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. Column chromatography was performed using dichloromethane:n-hexane = 5:1 as the eluent to obtain compound S-Rh-In. Three groups of experiments were conducted, and the different material ratios are shown in Table 5 below. The structure of S-Rh-In obtained from the second group of experiments is characterized as [C]. 38 H 32 N3O4S] + Calculated value: 626.2106; Measured value: 626.2102. The 1H and 1C NMR spectra are shown below. Figure 5 and Figure 6 .

[0073] Table 5. Experimental conditions for three groups in Example 5

[0074] The reaction equation is as follows:

[0075] Example 6: Synthesis of compound MS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 h. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, p-toluenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then rapidly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound MS-Rh was obtained by column chromatography using dichloromethane:n-hexane as the eluent (1:1). Three groups of experiments were conducted, and the different material ratios are shown in Table 6 below.

[0076] Table 6. Experimental conditions for three groups in Example 6

[0077] The reaction equation is as follows:

[0078] Example 7: Synthesis of compound MS-Rh-In Compound MS-Rh obtained from the second group of experiments in Example 6, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and heated to reflux for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. Column chromatography was performed using dichloromethane:n-hexane = 4:1 as the eluent to obtain compound MS-Rh-In. Three groups of experiments were conducted, and the different material ratios are shown in Table 7 below. The structure of MS-Rh-In obtained from the second group of experiments is characterized as [C]. 39 H 34 N3O4S] + Calculated value: 640.2192; Measured value: 640.2261. The 1H and 1C NMR spectra are shown below. Figure 7 and Figure 8 .

[0079] Table 7. Experimental conditions for three groups in Example 7

[0080] The reaction equation is as follows:

[0081] Example 8: Synthesis of compound MOS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 h. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, p-methoxybenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then rapidly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound MOS-Rh was obtained by column chromatography using dichloromethane:n-hexane as the eluent at a ratio of 5:1. Three groups of experiments were conducted, and the different material ratios are shown in Table 8 below.

[0082] Table 8. Experimental conditions for three groups in Example 8

[0083] The reaction equation is as follows:

[0084] Example 9: Synthesis of compound MOS-Rh-In Compound MOS-Rh obtained from the second group of experiments in Example 8, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and refluxed for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. Column chromatography was performed using dichloromethane:ethyl acetate = 100:1 as the eluent to obtain compound MOS-Rh-In. Three groups of experiments were conducted, and the different material ratios are shown in Table 9 below. The structure of MOS-Rh-In obtained from the second group of experiments is characterized as [C]. 39 H 34 N3O5S] + Calculated value: 655.2141; Measured value: 655.2141. The 1H NMR spectrum is shown below. Figure 9 .

[0085] Table 9. Experimental conditions for three groups in Example 9

[0086] The reaction equation is as follows:

[0087] Example 10: Synthesis of compound ClS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 h. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, p-chlorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then quickly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound ClS-Rh was obtained by column chromatography using petroleum ether:ethyl acetate = 1:2 as the eluent. Three groups of experiments were conducted, and the different material ratios are shown in Table 10 below.

[0088] Table 10 Experimental conditions for Example 10

[0089] The reaction equation is as follows:

[0090] Example 11 Synthesis of compound ClS-Rh-In Compound ClS-Rh obtained from the second group of experiments in Example 10, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and refluxed for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound ClS-Rh-In was obtained by column chromatography using petroleum ether:ethyl acetate = 10:1 as the eluent. Three groups of experiments were conducted, and the different material ratios are shown in Table 11 below. The structure of ClS-Rh-In obtained from the second group of experiments is characterized as [C...]. 38 H 30 ClN3O4SNa] + Calculated value: 682.1538; Measured value: 682.1548. The 1H NMR spectrum is shown below. Figure 10 .

[0091] Table 11 Three sets of experimental conditions in Example 11

[0092] The reaction equation is as follows:

[0093] Example 12 Synthesis of Compounds p -FS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 hours. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, p-fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then rapidly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound was separated by column chromatography using dichloromethane:n-hexane = 1:1 as the eluent. p -FS-Rh. Three sets of experiments were conducted, and the different material ratios are shown in Table 12 below.

[0094] Table 12 Experimental conditions for three groups in Example 12

[0095] The reaction equation is as follows:

[0096] Example 13: Synthesis of Compounds p -FS-Rh-In The compound obtained from the second group of experiments in Example 12 p -S-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and heated to reflux for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound was then separated by column chromatography using dichloromethane:n-hexane = 4:1 as the eluent. p -FS-Rh-In. Three sets of experiments were conducted, with different material ratios as shown in Table 13 below. The results of the second set of experiments... p The -FS-Rh-In characterization structure is [C 38 H 31 FN3O4S] + Calculated value: 644.1941; Measured value: 644.2009. The 1H and 1C NMR spectra are shown below. Figure 11 and Figure 12 .

[0097] Table 13 Experimental conditions for Example 13

[0098] The reaction equation is as follows:

[0099] Example 14 Synthesis of Compounds m -FS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 hours. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, m-fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then rapidly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound was separated by column chromatography using dichloromethane:n-hexane = 1:2 as the eluent. m -FS-Rh. Three sets of experiments were conducted, and the different material ratios are shown in Table 14 below.

[0100] Table 14. Experimental conditions for three sets of examples 14

[0101] The reaction equation is as follows:

[0102] Example 15: Synthesis of Compounds m -FS-Rh-In The compound obtained from the second group of experiments in Example 14 m -S-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and heated to reflux for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound was separated by column chromatography using dichloromethane:n-hexane = 1:1 as the eluent. m -FS-Rh-In. Three sets of experiments were conducted, with different material ratios as shown in Table 15 below. The results of the second set of experiments... m The -FS-Rh-In characterization structure is [C 38 H 31 FN3O4S] + Calculated value: 644.2014; Measured value: 644.2018. The 1H NMR spectrum is shown below. Figure 13 .

[0103] Table 15. Experimental conditions for three groups in Example 15

[0104] The reaction equation is as follows:

[0105] Example 16: Synthesis of Compounds o -FS-Rh Compound I-RHO obtained from the second group of experiments in Example 2, along with ultra-dry 1,2-dichloroethane and phosphorus oxychloride, were added to a two-necked flask and stirred until homogeneous. The mixture was then heated under reflux for 8 hours. After the reaction was complete, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure, yielding a crude acyl chloride residue. This crude acyl chloride was used directly in the next reaction without purification. In a round-bottom flask, o-fluorobenzenesulfonamide, triethylamine, and ultra-dry acetonitrile were mixed thoroughly and transferred to the crude acyl chloride residue. Additional ultra-dry acetonitrile was then rapidly added, and the mixture was heated under reflux overnight. After the reaction was complete, the solvent was removed by rotary evaporation under reduced pressure. The compound was then separated by column chromatography using dichloromethane:n-hexane = 1:1 as the eluent. o -FS-Rh. Three sets of experiments were conducted, and the different material ratios are shown in Table 16 below.

[0106] Table 16 Experimental conditions for Example 16

[0107] The reaction equation is as follows:

[0108] Example 17 Synthesis of Compounds o -FS-Rh-In The compound obtained from the second group of experiments in Example 16 o -S-Rh, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, ultra-dry tetrahydrofuran, and water were sequentially added to a flask. The mixture was stirred and heated to reflux for 12 h under an inert gas atmosphere. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was collected. The solvent was removed by rotary evaporation under reduced pressure. The compound was separated by column chromatography using dichloromethane:n-hexane = 1:1 as the eluent. o -FS-Rh-In. Three sets of experiments were conducted, with different material ratios as shown in Table 17 below. The results of the second set of experiments... o The -FS-Rh-In characterization structure is [C 38 H 31 FN3O4S] + Calculated value: 644.2014; Measured value: 644.2009. The 1H NMR spectrum is shown below. Figure 14 .

[0109] Table 17 Experimental conditions for Example 17

[0110] The reaction equation is as follows:

[0111] To verify the effectiveness of this invention, numerous laboratory experiments were conducted on the novel rhodamine derivative fluorescent molecules prepared according to the above synthesis method. The experimental results are as follows: 1. Characterization of basic fluorescence behavior The prepared compounds were characterized by excitation and emission spectra using an Edinburgh Instruments FLS 980 fluorescence spectrometer. UV-Vis absorption spectra were measured using a U-3900 (Hitachi) spectrophotometer. Fluorescence quantum yields were obtained using a quantum efficiency measurement system (Hamamatsu, Quantaurus-QY).

[0112] Depend on Figure 15 , 16 It can be seen that in dichloromethane, the maximum absorption wavelength of the Rh-B closed-ring state (with 3 μL of triethylamine added) is 246 nm, the maximum emission wavelength is 557 nm, and the Stokes shift is 311 nm; the maximum absorption wavelength of the Rh-B open-ring state is 561 nm, the maximum emission wavelength is 576 nm, and the Stokes shift is 15 nm. Figure 17 , 18 It can be seen that in dichloromethane, the maximum absorption wavelength of the S-Rh-B closed-ring state is 317 nm, the maximum emission wavelength is 562 nm, and the Stokes shift is 245 nm; the maximum absorption wavelength of the S-Rh-B open-ring state (with 3 μL of trifluoroacetic acid added) is 563 nm, the maximum emission wavelength is 587 nm, and the Stokes shift is 24 nm. Figure 19 , 20 It can be seen that in dichloromethane, the maximum absorption wavelength of Rh-In in the closed-ring state is 329 nm, the maximum emission wavelength is 600 nm, and the Stokes shift is 271 nm. The maximum absorption wavelength of Rh-In in the open-ring state (with 3 μL of trifluoroacetic acid added) is 587 nm, the maximum emission wavelength is 666 nm, and the Stokes shift is 79 nm. Figure 21 , 22 It can be seen that in dichloromethane, the maximum absorption wavelength of the closed-ring S-Rh-In is 328 nm, the maximum emission wavelength is 611 nm, and the Stokes shift is 283 nm; the maximum absorption wavelength of the open-ring S-Rh-In (with 40 μL of trifluoroacetic acid added) is 590 nm, the maximum emission wavelength is 658 nm, and the Stokes shift is 68 nm. The maximum emission wavelength of the S-Rh-In solid is 604 nm. Figure 23 It is known that Rh-B, S-Rh-B, and Rh-In solids exhibit almost no fluorescence, while S-Rh-In solid displays bright fluorescence, and its quantum yield is 18.2%. This means that S-Rh-B and Rh-In have properties similar to conventional Rhodamine Rh-B, while S-Rh-In exhibits properties opposite to conventional Rhodamine. This indicates that modifying only one site cannot achieve the desired property change; only when both sites are modified simultaneously does the resulting compound exhibit properties opposite to those of conventional Rhodamine. Figure 24 , 25 It can be seen that in dichloromethane, the maximum absorption wavelength of MS-Rh-In in the closed-ring state is 328 nm, the maximum emission wavelength is 610 nm, and the Stokes shift is 282 nm; the maximum absorption wavelength of MS-Rh-In in the open-ring state (with 40 μL of trifluoroacetic acid added) is 590 nm, the maximum emission wavelength is 655 nm, and the Stokes shift is 65 nm. The maximum emission wavelength of MS-Rh-In solid is 612 nm. Figure 26 , 27 It can be seen that in dichloromethane, the maximum absorption wavelength of MOS-Rh-In in the closed-ring state is 328 nm, the maximum emission wavelength is 610 nm, and the Stokes shift is 282 nm; the maximum absorption wavelength of MOS-Rh-In in the open-ring state (with 40 μL of trifluoroacetic acid added) is 591 nm, the maximum emission wavelength is 663 nm, and the Stokes shift is 72 nm. The maximum emission wavelength of the MOS-Rh-In solid is 648 nm. Figure 28 , 29 It can be seen that in dichloromethane, the maximum absorption wavelength of the closed-ring ClS-Rh-In is 328 nm, the maximum emission wavelength is 618 nm, and the Stokes shift is 290 nm; the maximum absorption wavelength of the open-ring ClS-Rh-In (with 40 μL of trifluoroacetic acid added) is 594 nm, the maximum emission wavelength is 663 nm, and the Stokes shift is 69 nm. The maximum emission wavelength of the ClS-Rh-In solid is 623 nm. Figure 30 , 31 It can be seen that in dichloromethane, p The maximum absorption wavelength of the -FS-Rh-In closed-loop state is 328 nm, the maximum emission wavelength is 614 nm, and the Stokes shift is 286 nm. p The maximum absorption wavelength of -FS-Rh-In in the open-ring state (with 40 μL of trifluoroacetic acid added) is 592 nm, the maximum emission wavelength is 664 nm, and the Stokes shift is 72 nm. p The maximum emission wavelength of the -FS-Rh-In solid is 612 nm. Figure 32 , 33 It can be seen that in dichloromethane, m The maximum absorption wavelength of the -FS-Rh-In closed-loop state is 328 nm, the maximum emission wavelength is 615 nm, and the Stokes shift is 287 nm. m The maximum absorption wavelength of -FS-Rh-In in the open-ring state (with 40 μL of trifluoroacetic acid added) is 592 nm, the maximum emission wavelength is 663 nm, and the Stokes shift is 71 nm. mThe maximum emission wavelength of the -FS-Rh-In solid is 617 nm. Figure 34 , 35 It can be seen that in dichloromethane, o The maximum absorption wavelength of the -FS-Rh-In closed-loop state is 328 nm, the maximum emission wavelength is 612 nm, and the Stokes shift is 284 nm. o The maximum absorption wavelength of -FS-Rh-In in the open-ring state (with 40 μL of trifluoroacetic acid added) is 591 nm, the maximum emission wavelength is 661 nm, and the Stokes shift is 70 nm. o The maximum emission wavelength of the -FS-Rh-In solid is 621 nm. Figure 36 For MS-Rh-In, MOS-Rh-In, ClS-Rh-In, p -FS-Rh-In、 m -FS-Rh-In、 o The images of FS-Rh-In under fluorescent and ultraviolet (365 nm) lamps show that all six compounds exhibit red (or pink) fluorescence in their solid forms. Table 18 shows that the quantum yield of MS-Rh-In solid is 3.6%; the quantum yield of MOS-Rh-In solid is 6.9%; and the quantum yield of ClS-Rh-In solid is 2.5%. p The quantum yield of -FS-Rh-In solid is 14.1%; m The quantum yield of FS-Rh-In solid is 25.7%; o The quantum yield of -FS-Rh-In solid is 7.6%.

[0113] Table 18 Quantum Yields of Various Solids

[0114] 2. Preparation of polymer membranes Weigh 0.099 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 1 mL of toluene to prepare a 10% (w / w) SEBS solution. Add 1 mg of compound Rh-B and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a 2 × 2 cm glass plate and let it stand overnight to obtain a nearly transparent Rh-B-SEBS membrane.

[0115] Weigh 0.099 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 1 mL of toluene to prepare a 10% (w / w) SEBS solution. Add 1 mg of compound S-Rh-In and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a 2×2 cm glass plate and let it stand overnight to obtain a nearly transparent S-Rh-In-SEBS membrane.

[0116] Weigh 0.199 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 2 mL of toluene to prepare an SEBS solution. Add 0.4 mg of compound MOS-Rh-In (containing trifluoroacetic acid) and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a glass plate (2 × 2 cm) and let it stand overnight to obtain a nearly transparent 0.2% MOS-Rh-In-SEBS membrane.

[0117] Weigh 0.199 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 2 mL of toluene to prepare an SEBS solution. Add 1 mg of compound MOS-Rh-In (containing trifluoroacetic acid) and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a glass plate (2×2 cm) and let it stand overnight to obtain a light blue 0.5% MOS-Rh-In-SEBS membrane.

[0118] Weigh 0.198 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 2 mL of toluene to prepare an SEBS solution. Add 2 mg of compound MOS-Rh-In (containing trifluoroacetic acid) and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a glass plate (2×2 cm) and let it stand overnight to obtain a blue 1% MOS-Rh-In-SEBS membrane.

[0119] Weigh 0.197 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) and dissolve it in 2 mL of toluene to prepare an SEBS solution. Add 3 mg of compound MOS-Rh-In (containing trifluoroacetic acid) and sonicate for 15 minutes to mix thoroughly. Evenly drop the mixture onto a glass plate (2×2 cm) and let it stand overnight to obtain a blue-purple 1.5% MOS-Rh-In-SEBS membrane.

[0120] 0.196 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) was dissolved in 2 mL of toluene to prepare an SEBS solution. 4 mg of compound MOS-Rh-In (containing trifluoroacetic acid) was added, and the mixture was sonicated for 15 minutes to ensure homogeneity. The mixture was then evenly drop-coated onto a 2 × 2 cm glass plate and allowed to stand overnight to obtain a purple 2% MOS-Rh-In-SEBS membrane.

[0121] 0.194 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) was dissolved in 2 mL of toluene to prepare an SEBS solution. 6 mg of compound MOS-Rh-In (containing trifluoroacetic acid) was added, and the mixture was sonicated for 15 minutes to ensure homogeneity. The mixture was then evenly drop-coated onto a 2×2 cm glass plate and allowed to stand overnight to obtain a purplish-black 3% MS-Rh-In-SEBS membrane.

[0122] 0.190 g of poly(styrene)-block-poly(ethylene-ran-butene)-block-poly(styrene) (SEBS) was dissolved in 2 mL of toluene to prepare an SEBS solution. 10 mg of compound MOS-Rh-In (containing trifluoroacetic acid) was added, and the mixture was sonicated for 15 minutes to ensure homogeneity. The mixture was then evenly drop-coated onto a 2 × 2 cm glass plate and allowed to stand overnight to obtain a purplish-black 5% MS-Rh-In-SEBS membrane.

[0123] 3. Microplastic labeling Depend on Figures 37-39 It was found that after immersing the membranes in water at room temperature and 40°C for one week, respectively, the absorption of the Rh-B-SEBS membrane increased significantly, with more severe diffusion in water at 40°C. In contrast, the absorption of the S-Rh-In-SEBS membrane remained almost unchanged. These results indicate that Rh-B in the Rh-B-SEBS membrane exhibits significant diffusion in water, while S-Rh-In in the S-Rh-In-SEBS membrane shows almost no diffusion. Therefore, the S-Rh-In-SEBS membrane possesses great labeling potential.

[0124] 4. Photothermal Applications Photothermal experiment: The membrane was placed under a laser lamp for 1 minute, and the temperature change of the membrane was recorded during the 1 minute. After 1 minute, the membrane was removed from the laser lamp, and the temperature change of the membrane was monitored for another 1 minute after removal.

[0125] Depend on Figure 40 a) It can be seen that when irradiated with a 638 nm laser, the temperature of the MOS-Rh-In-SEB film increases more significantly with the increase of the MOS-Rh-In ratio, and the photothermal effect becomes more pronounced. From Figure 40a) It can be seen that the temperature of the 1.5% MOS-Rh-In-SEBS film under irradiation with 0.6 W laser light at 450 nm, 520 nm, and 638 nm varies with time. The temperature increase is highest under 450 nm laser irradiation, while the temperature changes are approximately the same under 520 nm and 638 nm laser irradiation. Since the melting point of SEBS is around 120℃, photothermal experiments were conducted on the 3% MOS-Rh-In-SEBS film at 520 nm and 638 nm; photothermal experiments were conducted on the 1.5% MOS-Rh-In-SEBS film at 450 nm. Figure 41 a) It can be seen that as the 450 nm laser power increases, the maximum temperature reached by the 1.5% MOS-Rh-In-SEBS film also increases. Figure 41 (b) It can be seen that with the increase of laser power at 520 nm and 638 nm, the maximum temperature reached by the 3% MOS-Rh-In-SEBS film also increases. The results indicate that the photothermal effect of the MOS-Rh-In-SEBS film is more significant with the increase of laser power.

[0126] This invention uses Rhodamine B as the parent compound and synthesizes a series of novel Rhodamine derivatives with completely altered properties by substituting spironolactone and N,N-diethyl. These molecules exhibit bright fluorescence in the lactone (closed-ring) state and almost no fluorescence in the zwitterionic (open-ring) state. The lactone-state Rhodamine derivatives possess an exceptionally large Stokes shift (>280 nm), while the zwitterionic Rhodamine derivatives exhibit relatively long absorption (>590 nm). The hydrophobic, closed-ring, spironolactone Rhodamine derivatives have relatively short absorption and bright fluorescence, making them suitable for microplastic labeling. The open-ring, zwitterionic Rhodamine derivatives exhibit longer absorption and excellent photothermal effects. Therefore, these Rhodamine derivatives have great potential in microplastic labeling and photothermal applications.

Claims

1. A rhodamine derivative, characterized in that, The rhodamine derivative is one of the following compounds: 。 2. The method for preparing the rhodamine derivative according to claim 1, characterized in that, include: 4-Diethylaminoketoic acid, 3-iodophenol, and methanesulfonic acid were stirred until homogeneous, and then heated under reflux to react and obtain compound I-RHO; the structural formula of compound I-RHO is: ; I-RHO, 1,2-dichloroethane, and phosphorus oxychloride were mixed and heated under reflux to react. After the reaction was completed, 1,2-dichloroethane and phosphorus oxychloride were removed by rotary evaporation under reduced pressure to obtain a crude acyl chloride residue. Benzenesulfonamide or p-methylbenzenesulfonamide or p-methoxybenzenesulfonamide or p-chlorobenzenesulfonamide or p-fluorobenzenesulfonamide or m-fluorobenzenesulfonamide or o-fluorobenzenesulfonamide, as well as triethylamine and acetonitrile, were added to the crude acyl chloride residue and heated under reflux to react to obtain an intermediate product; the intermediate product is one of the following compounds: The intermediate product, potassium carbonate, indole-2-boronate pinacol ester, bis(triphenylphosphine)palladium dichloride, tetrahydrofuran, and water were mixed and heated under reflux to give the rhodamine derivative.

3. The method for preparing rhodamine derivatives according to claim 2, characterized in that, The molar ratio of 4-diethylaminoketo acid, 3-iodophenol and methanesulfonic acid is 1:(1~1.5):(60~90), and the first heating reflux temperature is 160~180℃.

4. The method for preparing rhodamine derivatives according to claim 2, characterized in that, The molar ratio of I-RHO to phosphorus oxychloride is 1:(15~25), and the reflux temperature for the second heating is 85~105℃.

5. The method for preparing rhodamine derivatives according to claim 2, characterized in that, The molar ratio of benzenesulfonamide or p-methylbenzenesulfonamide or p-methoxybenzenesulfonamide or p-chlorobenzenesulfonamide or p-fluorobenzenesulfonamide or m-fluorobenzenesulfonamide or o-fluorobenzenesulfonamide to triethylamine is 1:(15-20), and the reflux temperature for the third heating is 60-80℃.

6. The method for preparing rhodamine derivatives according to claim 2, characterized in that, The molar ratio of the intermediate product, indole-2-boronate pinacol ester, potassium carbonate, and bis(triphenylphosphine)palladium dichloride is 1:(1.5–2):(1–3):(0.05–0.2).

7. The method for preparing rhodamine derivatives according to claim 2, characterized in that, The fourth reflow temperature is 70-80℃.

8. A fluorescently labeled microplastic, characterized in that, The microplastic contains the rhodamine derivative of claim 1.

9. The use of the rhodamine derivative of claim 1 in the preparation of microplastic labeling reagents.

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