CN112608466A

CN112608466A - Monomer compound, preparation method thereof, water-soluble fluorescent conjugated molecule and preparation method thereof

Info

Publication number: CN112608466A
Application number: CN201911261252.9A
Authority: CN
Inventors: 丛海林; 于冰; 朱耀威; 申有青; 谷传涛
Original assignee: Qingdao University
Current assignee: Qingdao University
Priority date: 2019-12-10
Filing date: 2019-12-10
Publication date: 2021-04-06
Anticipated expiration: 2039-12-10
Also published as: CN112608466B

Abstract

The invention provides a monomer compound, a preparation method thereof, a water-soluble fluorescent conjugated molecule and a preparation method thereof, and belongs to the field of water-soluble fluorescent organic micromolecules. The preparation method comprises the steps of synthesizing a compound shown as a formula (1) by polyethylene glycol monomethyl ether and p-toluenesulfonyl chloride, synthesizing a compound shown as a formula (2) by the compound shown as the formula (1) and 2-bromofluorene, and coupling the compound shown as the formula (2) and 2, 5-di (2-ethylhexyl) -3, 6-di (5-trimethyltin) -pyrrolopyrrole diketone to obtain the water-soluble fluorescent conjugated molecule. The water-soluble fluorescent conjugated molecule has excellent biological tissue penetration depth and is easy to dissolve in water.

Description

Monomer compound, preparation method thereof, water-soluble fluorescent conjugated molecule and preparation method thereof

Technical Field

The invention relates to the field of water-soluble fluorescent organic micromolecules, in particular to a monomer compound for preparing a water-soluble fluorescent conjugated molecule, a preparation method of the monomer compound, and further relates to the water-soluble fluorescent conjugated molecule prepared by the monomer compound and the preparation method of the water-soluble fluorescent conjugated molecule.

Background

In the past decades, the rapid development of nanotechnology has prompted the emergence and development of nanotechnology, making possible the integration of nanotechnology and nanomedicine. Medical imaging has become a clinically important diagnostic technique including Computed Tomography (CT), among others. However, the conventional imaging technology still has the disadvantages of long time for acquiring images, high cost and the like. In Fluorescence (FL) imaging, the camera can quickly collect the fluorescence of the target, even within milliseconds.

The fluorescence imaging technology is concerned by the biomedical field because of short image acquisition time, high detection sensitivity, environmental protection and economy. In recent years, fluorescent materials have been developed rapidly, and many kinds such as organic dyes, quantum dots, rare earth complexes, and the like have been produced. Compared with other fluorescent materials, the organic material has good biocompatibility, and eliminates biotoxicity caused by heavy metal from the root, so that the organic material has great potential in life science. The design and synthesis of novel conjugated molecules have almost unlimited variability, and the optical properties of the conjugated molecules can be adjusted by adjusting the type and number of fluorophores and changing the length of the conjugated structure, and the novel conjugated molecules have the advantages of convenient preparation and low processing temperature (0-120 ℃). In the Near Infrared (NIR) region, in particular in the second near infrared window (1000-1700nm, NIR-II), the absorption, scattering and autofluorescence of biological tissues are relatively low. Near-infrared light can achieve greater penetration depths and imaging of deep tissue in biological tissue. However, since fluorophores are mainly hydrophobic groups, hydrophobic fluorescent molecules are often not directly applicable for biological imaging and can reduce biocompatibility. This presents great difficulties in the biological application of fluorescent materials.

Disclosure of Invention

In order to overcome the defects of poor water solubility and short fluorescence emission wavelength of organic fluorescent dyes in the prior art, the invention provides a monomer compound capable of being used for preparing a water-soluble fluorescence conjugated molecule and the water-soluble fluorescence conjugated molecule, wherein the water-soluble fluorescence conjugated molecule has excellent biological tissue penetration depth and is easy to dissolve in water.

Further, the invention provides a preparation method of 2-bromo-9, 9-dipolyethylene glycol monomethyl ether fluorene shown in a formula (2).

Furthermore, the invention also provides a near-infrared two-region conjugated fluorescent molecule prepared by taking 2-bromine-9, 9-dipolyethylene glycol monomethyl ether fluorene shown in a formula (2) as one of raw materials, namely a water-soluble fluorescent conjugated molecule shown in a formula (3) and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a monomer compound having a structure represented by formula (2):

n is an integer of 10 to 50, preferably 20.

A method for preparing the monomer compound, comprising the steps of:

s1, synthesizing polyethylene glycol monomethyl ether sulfonyl phenylmethane shown in the formula (1) by using polyethylene glycol monomethyl ether and p-toluenesulfonyl chloride:

n is an integer from 10 to 50, preferably 20;

s2, synthesizing 2-bromo-9, 9-dipolyethylene glycol monomethyl ether fluorene shown in the formula (2) by using the compound shown in the formula (1) and 2-bromofluorene.

Preferably, in step S1, polyethylene glycol monomethyl ether and p-toluenesulfonyl chloride are dissolved in dichloromethane, the temperature of the ice water bath is maintained at 0 ℃, sodium hydroxide is added in batches under vigorous stirring, the reaction is stopped for 5 to 7 hours, after the reaction is finished, the sodium hydroxide is removed by filtration, and the obtained solution is distilled under reduced pressure to obtain the compound represented by formula (1).

Further preferably, the molar ratio of the polyethylene glycol monomethyl ether, the p-toluenesulfonyl chloride and the sodium hydroxide in the step S1 is 1: (1-1.2): (8-12), adding sodium hydroxide 3-4 times at intervals of 2-5 minutes, and reacting at 0-5 ℃ for 5-7 hours.

Preferably, the step S2 is: dissolving 2-bromofluorene and a phase transfer catalyst in dimethyl sulfoxide, stirring and mixing uniformly, adding a potassium hydroxide aqueous solution, and finally adding a compound shown in the formula (1) for reaction; and (3) after the reaction is finished, washing the extracted reaction solution by using dichloromethane for 3 times, taking an organic layer, carrying out reduced pressure distillation to remove dichloromethane, dissolving the rest solution by using a small amount of distilled water, dialyzing, and freeze-drying the obtained solution after the dialysis is finished to obtain the compound shown in the formula (2), wherein the phase transfer catalyst is tetrabutylammonium bromide or 18 crown ether 6.

Further preferably, the step S2 is: the molar ratio of the 2-bromofluorene to the compound shown in the formula (1) to tetrabutylammonium bromide is 1: (2-2.2): (0.01-0.03), the concentration of the potassium hydroxide solution is 40-50 wt%, the volume ratio of the dimethyl sulfoxide to the potassium hydroxide solution is (3-5) to 1, the reaction temperature is 60-80 ℃, and the reaction time is 6-10 hours; the passage molecular weight of the dialysis bag used for dialysis was 3000.

A water-soluble fluorescent conjugated molecule having a structure represented by formula (3):

wherein n is an integer of 10 to 50, preferably 20.

A preparation method of the water-soluble fluorescent conjugated molecule comprises the following steps:

step S3, dissolving 2, 5-di (2-ethylhexyl) -3, 6-di (5-trimethyltin) -pyrrolopyrrole-dione, the compound shown in formula (2) in claim 1 and a coupling agent in toluene, and reacting under anhydrous and oxygen-free conditions to obtain the compound.

Preferably, 2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrroledione, the compound of formula (2) according to claim 1 and a coupling agent are dissolved in toluene and reacted in the absence of water and oxygen; and after the reaction is finished, cooling the reaction solution to room temperature, carrying out reduced pressure distillation to obtain a crude product, and further separating and purifying to obtain the compound shown in the formula (3), wherein the coupling agent is tetratriphenylphosphine palladium and/or bis-triphenylphosphine palladium dichloride.

Further preferably, in step S3, the molar ratio of the compound represented by formula (2) to the coupling agent in 2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrrole-dione is 1: (1-2.4): (0.01-0.05), the reaction temperature is 110-120 ℃, and the reaction time is 30-50 hours; the coupling agent is tetratriphenylphosphine palladium and/or bis-triphenylphosphine palladium dichloride.

The further separation and purification method comprises the following steps: distilling the reaction solution under reduced pressure to obtain a crude product, pouring the crude product into 100-200mL anhydrous n-hexane for sedimentation, and then performing suction filtration to obtain the crude product; the crude product was dissolved in chloroform and purified on a silica gel column (silica gel 80-100 mesh); distilling the collected chloroform solution under reduced pressure, and then distilling under reduced pressure and drying in vacuum to obtain the final product.

Compared with the prior art, the invention has the following beneficial effects:

1. the water-soluble fluorescent conjugated molecule shown in the formula (3) comprises two parts: one part is a conjugated main chain of a structure shown in a formula (4) in a fluorene-containing pi-pi conjugated system, and the structure ensures the optical property of the fluorescent molecule; the other part is water-soluble side group polyethylene glycol monomethyl ether 2000, thereby meeting the solubility of fluorescent molecules in water phase.

2. The water-soluble fluorescent conjugated molecule can emit near-infrared two-region fluorescence under the excitation of 808nm laser, the emission wavelength is 900nm-1300nm, and the fluorescence under the wavelength has better penetrating property on biological tissues compared with the near-infrared one-region fluorescence.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 shows the absorption spectra of the fluorescent molecules obtained in examples 1, 2 and 3 in water and chloroform.

FIG. 2 shows fluorescence spectra of the fluorescent molecules obtained in examples 1, 2 and 3 in water and chloroform.

FIG. 3 is a nuclear magnetic spectrum of the fluorescent molecule obtained in examples 1, 2 and 3.

Fig. 4 is a comparison of the imaging effect of the near-infrared two-region and the near-infrared one-region in application example 1.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a water-soluble fluorescent conjugated molecule, which is obtained by coupling a monomer compound 2-bromo-9, 9-dipolyethylene glycol monomethyl ether fluorene shown in a formula (2) with 2, 5-di (2-ethylhexyl) -3, 6-di (5-trimethyltin) -pyrrolopyrrole-dione. The reaction formula is as follows:

the preparation method of the water-soluble fluorescent conjugated molecule of the invention has the following examples:

example 1:

s1, preparing polyethylene glycol monomethyl ether sulfonyl phenylmethane shown in the formula (1):

polyethylene glycol monomethyl ether 2000(4g, 2mmol) and p-toluenesulfonyl chloride (0.3812g, 2mmol) were dissolved in dichloromethane (50ml), sodium hydroxide (0.96g, 24mmol) was added in portions with vigorous stirring in an ice water bath maintained at 0 ℃, the sodium hydroxide was added in 4 portions at 3 minute intervals, and the reaction was stopped for 6 hours. After the reaction, sodium hydroxide was removed by filtration, and the obtained solution was distilled under reduced pressure to obtain a white powdery polyethylene glycol monomethyl ether sulfonyl phenylmethane represented by the formula (1) in a yield of about 90%.

S2, preparing 2-bromo-9, 9-dipolyethylene glycol monomethyl ether fluorene shown in formula (2):

2-bromofluorene (0.324g, 1mmol) and tetrabutylammonium bromide (7.8mg, 0.024mmol) were dissolved in dimethyl sulfoxide, stirred, added with an aqueous solution of potassium hydroxide (5ml, 45 wt%), and finally added with the compound represented by formula (1) (4.8192g, 2.2mmol) to carry out a reaction at 75 ℃ for 8 hours. After the reaction, the reaction mixture was washed with dichloromethane 3 times, the organic layer was distilled under reduced pressure to remove dichloromethane, and the remaining solution was dissolved in a small amount of distilled water and dialyzed. After the dialysis was completed, the resulting solution was freeze-dried to obtain 2-bromo-9, 9-dimer ethylene glycol monomethyl ether fluorene represented by formula (2) as a yellow powder with a yield of about 30%. The passage molecular weight of the dialysis bag used for dialysis was 3000.

S3 synthesis of water-soluble fluorescent conjugated molecule

2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrroledione (50mg, 0.042mmol), the compound represented by the formula (2) (420mg, 0.1mmol), tetrakistriphenylphosphine palladium (2.4mg, 0.002mmol) were dissolved in toluene and reacted in the absence of water and oxygen. The reaction temperature was 120 ℃ and the reaction time was 36 hours. After completion of the reaction, the reaction solution was cooled to room temperature. Distilling the reaction solution under reduced pressure to obtain a crude product, pouring the crude product into 100-200mL anhydrous n-hexane for sedimentation, and then performing suction filtration to obtain the crude product; the crude product was dissolved in chloroform and purified on a silica gel column (silica gel 80-100 mesh); the collected chloroform solution was distilled under reduced pressure, and then distilled under reduced pressure and dried in vacuum to obtain 260mg of a dark green solid of the water-soluble fluorescent conjugated molecule represented by the formula (3) in a yield of about 55%.

Example 2:

polyethylene glycol monomethyl ether 2000(8g, 4mmol) and p-toluenesulfonyl chloride (0.762g, 4.8mmol) were dissolved in dichloromethane (50ml), sodium hydroxide (0.64g, 16mmol) was added in portions with vigorous stirring while maintaining an ice-water bath at 0 ℃, the sodium hydroxide was added in 3 portions at 2 minute intervals, and the reaction was stopped for 6 hours. After the reaction was completed, sodium hydroxide was removed by filtration, and the obtained solution was distilled under reduced pressure to obtain polyethylene glycol monomethylether sulfonylphenylmethane represented by the formula (1) as a white powder with a yield of about 86%.

2-Bromofluorene (0.648g, 2mmol) and 18 crown ether 6(10.7mg, 0.02mmol) were dissolved in dimethyl sulfoxide, stirred, and an aqueous solution of potassium hydroxide (10ml, 40 wt%) was added, and finally the compound represented by the formula (1) (8.758g, 4.0mmol) was added to conduct a reaction at 70 ℃ for 7 hours. After the reaction, the reaction mixture was washed with dichloromethane 3 times, the organic layer was distilled under reduced pressure to remove dichloromethane, and the remaining solution was dissolved in a small amount of distilled water and dialyzed. After the completion of dialysis, the resulting solution was freeze-dried to obtain 2-bromo-9, 9-dimer ethylene glycol monomethyl ether fluorene represented by formula (2) as a yellow powder. The yield was about 25%. The passage molecular weight of the dialysis bag used for dialysis was 3000.

S3 synthesis of water-soluble fluorescent conjugated molecule

2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrroledione (50mg, 0.042mmol), the compound represented by the formula (2) (336mg, 0.1mmol), tetrakistriphenylphosphine palladium (1.2mg, 0.001mmol) were dissolved in toluene and reacted in the absence of water and oxygen. The reaction temperature was 120 ℃ and the reaction time was 36 hours. After completion of the reaction, the reaction solution was cooled to room temperature. Distilling the reaction solution under reduced pressure to obtain a crude product, pouring the crude product into 100-200mL anhydrous n-hexane for sedimentation, and then performing suction filtration to obtain the crude product; the crude product was dissolved in chloroform and purified on a silica gel column (silica gel 80-100 mesh); the collected chloroform solution was distilled under reduced pressure, and then distilled under reduced pressure and dried in vacuum to obtain 213mg of a dark green solid of the water-soluble fluorescent conjugated molecule represented by the formula (3) in a yield of about 45%.

Example 3:

polyethylene glycol monomethyl ether 2000(4g, 2mmol) and p-toluenesulfonyl chloride (0.3812g, 2mmol) were dissolved in dichloromethane (50ml), sodium hydroxide (0.64g, 16mmol) was added in portions with vigorous stirring in an ice water bath maintained at 0 ℃, the sodium hydroxide was added in 4 portions at 3 minute intervals, and the reaction was stopped for 6 hours. After the reaction was completed, sodium hydroxide was removed by filtration, and the obtained solution was distilled under reduced pressure to obtain polyethylene glycol monomethyl ether sulfonyl phenylmethane represented by formula (1) as a white powder with a yield of about 88%.

2-Bromofluorene (0.324g, 1mmol) and tetrabutylammonium bromide (6.5mg, 0.02mmol) were dissolved in dimethyl sulfoxide, stirred, and an aqueous solution of potassium hydroxide (5ml, 40 wt%) was added, and finally the compound represented by the formula (1) (4.8192g, 2.2mmol) was added to conduct a reaction at a reaction temperature of 75 ℃ for 8 hours. After the reaction, the reaction mixture was washed with dichloromethane 3 times, the organic layer was distilled under reduced pressure to remove dichloromethane, and the remaining solution was dissolved in a small amount of distilled water and dialyzed. After the completion of dialysis, the resulting solution was freeze-dried to obtain 2-bromo-9, 9-dimer ethylene glycol monomethyl ether fluorene represented by formula (2) as a yellow powder with a yield of about 33%. The passage molecular weight of the dialysis bag used for dialysis was 3000.

S3 synthesis of water-soluble fluorescent conjugated molecule

2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrroledione (60mg, 0.05mmol), the compound represented by the formula (2) (420mg, 0.1mmol), and bis (triphenylphosphine) palladium dichloride (2.2mg, 0.001mmol) were dissolved in toluene and reacted without water and oxygen. The reaction temperature was 120 ℃ and the reaction time was 36 hours. After completion of the reaction, the reaction solution was cooled to room temperature. Distilling the reaction solution under reduced pressure to obtain a crude product, pouring the crude product into 100-200mL anhydrous n-hexane for sedimentation, and then performing suction filtration to obtain the crude product; the crude product was dissolved in chloroform and purified on a silica gel column (silica gel 80-100 mesh); the collected chloroform solution was distilled under reduced pressure, and then distilled under reduced pressure and dried under vacuum to obtain 235mg of a dark green solid of a water-soluble fluorescent conjugated molecule represented by the formula (3). The yield was about 50%.

Example 4:

polyethylene glycol monomethyl ether 2000(4g, 4mmol) and p-toluenesulfonyl chloride (0.831g, 4.8mmol g) were dissolved in dichloromethane (50ml), sodium hydroxide (1.92g, 48mmol) was added in portions with vigorous stirring while maintaining an ice-water bath at 0 ℃, the sodium hydroxide was added in 4 portions at 5 minute intervals, and the reaction was stopped for 6 hours. After completion of the reaction, sodium hydroxide was removed by filtration, and the obtained solution was distilled under reduced pressure to obtain polyethylene glycol monomethyl ether sulfonyl phenylmethane represented by the formula (1) as a white powder with a yield of about 93%.

2-Bromofluorene (0.324g, 1mmol) and tetrabutylammonium bromide (9.7mg, 0.03mmol) were dissolved in dimethyl sulfoxide, stirred, and an aqueous solution of potassium hydroxide (5ml, 50 wt%) was added, and finally the compound represented by the formula (1) (4.381g, 2.2mmol) was added to conduct a reaction at a reaction temperature of 75 ℃ for 8 hours. After the reaction, the reaction mixture was washed with dichloromethane 3 times, the organic layer was distilled under reduced pressure to remove dichloromethane, and the remaining solution was dissolved in a small amount of distilled water and dialyzed. After the completion of dialysis, the resulting solution was freeze-dried to obtain 2-bromo-9, 9-dimer ethylene glycol monomethyl ether fluorene represented by formula (2) as a yellow powder with a yield of about 37%. The passage molecular weight of the dialysis bag used for dialysis was 3000.

S3 synthesis of water-soluble fluorescent conjugated molecule

2, 5-bis (2-ethylhexyl) -3, 6-bis (5-trimethyltin) -pyrrolopyrroledione (120mg, 0.1mmol), the compound represented by the formula (2) (1g, 0.24mmol), tetrakistriphenylphosphine palladium (5.8mg, 0.005mmol) were dissolved in toluene and reacted in the absence of water and oxygen. The reaction temperature was 120 ℃ and the reaction time was 36 hours. After completion of the reaction, the reaction solution was cooled to room temperature. The reaction solution was poured into 150mL of anhydrous methanol, followed by suction filtration to obtain a crude product. The crude product was dissolved in chloroform and purified on a silica gel column (silica gel 80-100 mesh). The collected chloroform solution was distilled under reduced pressure, and the obtained solid was dissolved in chloroform as little as possible, and then added to 120mL of anhydrous methanol, followed by suction filtration and vacuum drying to obtain 283mg of a dark green solid of a water-soluble fluorescent conjugated molecule represented by the formula (3) in a yield of about 60%.

FIG. 1 is an absorption spectrum of a fluorescent molecule obtained in examples 1, 2, 3 and 4 in water and chloroform, FIG. 2 is a fluorescence spectrum of a fluorescent molecule obtained in examples 1, 2, 3 and 4 in water and chloroform, and FIG. 3 is a nuclear magnetic spectrum of a fluorescent molecule obtained in examples 1, 2, 3 and 4. Fig. 1, 2 show the optical properties of the fluorescent molecule, and fig. 3 demonstrates the successful synthesis of the fluorescent molecule.

Application example 1

Covering a capillary tube filled with a fluorescent molecular aqueous solution with pork slices, and then carrying out near-infrared first-region imaging and near-infrared second-region imaging on the capillary tube. The two imaging modes are compared by increasing the thickness of the biological tissue by increasing the number of pork slices. The results show that the tissue penetration depth using the near infrared two-zone imaging mode is above 5mm, whereas the tissue penetration depth using the near infrared one-zone imaging mode is only 3 mm. The thickness of the pork slices was averaged over ten total slices, averaging 1mm per slice. Fig. 4 is a comparison of the imaging effect of the near-infrared two-region and the near-infrared one-region in application example 1, and illustrates the superiority of the fluorescent molecules of the present application in imaging the near-infrared two-region, i.e. deeper tissue penetration.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims

1. a monomeric compound is characterized in that, has the structure shown in formula (2):

n is an integer of 10-50.

2. the preparation method of the described monomeric compound of claim 1, is characterized in that, comprises the following steps:

S1, polyethylene glycol monomethyl ether and p-toluenesulfonyl chloride synthetic polyethylene glycol monomethyl ether sulfonyl benzene methane shown in formula (1):

n is an integer from 10 to 50;

S2. The compound represented by formula (1) and 2-bromofluorene synthesize 2-bromo-9,9-diethylene glycol monomethyl ether fluorene represented by formula (2).

3. the preparation method of monomer compound according to claim 2 is characterized in that,

In the step S1, the polyethylene glycol monomethyl ether and p-toluenesulfonyl chloride are dissolved in dichloromethane, the ice water bath is kept at 0°C, and sodium hydroxide is added in batches under vigorous stirring, the reaction is stopped for 5-7 hours, and the reaction After completion, sodium hydroxide was removed by filtration, and the obtained solution was distilled under reduced pressure to obtain a compound represented by formula (1).

4. the preparation method of monomer compound according to claim 3, is characterized in that,

In the step S1, the molar ratio of polyethylene glycol monomethyl ether, p-toluenesulfonyl chloride and sodium hydroxide is 1:(1-1.2):(8-12), and sodium hydroxide is added in 3-4 times , each interval is 2-5 minutes, and the reaction is carried out at 0°C-5°C for 5-7 hours.

5. the preparation method of monomer compound according to claim 4 is characterized in that,

The step S2 is as follows: dissolving 2-bromofluorene and the phase transfer catalyst in dimethyl sulfoxide, stirring and mixing evenly, adding potassium hydroxide aqueous solution, and finally adding the compound represented by formula (1) for reaction; The reaction solution was washed with dichloromethane three times, and the organic layer was distilled under reduced pressure to remove dichloromethane. The remaining solution was dissolved in a small amount of distilled water and dialyzed. After the dialysis, the resulting solution was freeze-dried to obtain the compound represented by formula (2).

6. the preparation method of monomeric compound according to claim 5 is characterized in that,

The step S2 is: the 2-bromofluorene, the molar ratio of the compound represented by the formula (1) and the phase transfer catalyst is 1:(2-2.2):(0.01-0.03), and the concentration of the potassium hydroxide solution is 40- 50wt%, the volume ratio of dimethyl sulfoxide and potassium hydroxide solution is (3-5):1, the reaction temperature is 60-80 DEG C, and the reaction time is 6-10 hours; the passing molecular weight of the dialysis bag used for dialysis is 3000.

7. A water-soluble fluorescent conjugated molecule, characterized in that it has the structure shown in formula (3):

Wherein, n is an integer of 10-50.

8. a preparation method of the described water-soluble fluorescent conjugated molecule of claim 6, is characterized in that, comprises the following steps:

In step S3, 2,5-bis(2-ethylhexyl)-3,6-bis(5-trimethyltin)-pyrrolopyrrole dione, the compound represented by the formula (2) of claim 1 and The coupling agent is dissolved in toluene, and the reaction is carried out under anhydrous and oxygen-free conditions.

9. The method according to claim 8, wherein the step S3 is:

In step S3, 2,5-bis(2-ethylhexyl)-3,6-bis(5-trimethyltin)-pyrrolopyrrole dione, the compound represented by the formula (2) of claim 1 and The coupling agent is dissolved in toluene, and the reaction is carried out under anhydrous and oxygen-free conditions; after the reaction is completed, the reaction solution is cooled to room temperature, and the crude product is obtained by distillation under reduced pressure, and the compound represented by formula (3) is obtained by further separation and purification.

10. The method according to claim 8, wherein the step S3 is:

Step S3, the 2,5-bis(2-ethylhexyl)-3,6-bis(5-trimethyltin)-pyrrolopyrrole dione, the compound represented by the formula (2), tetrakistriphenyl The molar ratio of base phosphorus palladium is 1:(1-2.4):(0.01-0.05), the reaction temperature is 110-120°C, and the reaction time is 30-50 hours;

The method for further separation and purification is as follows: the reaction solution is distilled under reduced pressure to obtain the crude product, poured into 100-200 mL of anhydrous n-hexane for sedimentation, and then suction filtered to obtain the crude product; the crude product is dissolved in chloroform and placed in a silica gel column. (Silica gel 80-100 mesh); chloroform solution collected under reduced pressure distillation, then under reduced pressure distillation and vacuum drying to obtain.