Near-infrared two-region fluorescent molecule and preparation method thereof

Abstract

The invention discloses a near-infrared two-region fluorescent molecule and a preparation method thereof. The 4, 8-bis [5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-dithiadiazole near-infrared two-region fluorescent molecular contrast agent is prepared by using the method, and is based on 4, 8-bis [5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-dithiadiazole. The fluorescent molecule is formed by coupling reaction of a near-infrared second-region fluorescent molecule taking 2, 8-bis [5-bromo-3-(2-ethylhexyl)-2-thienyl]-dithiadiazole as an electron acceptor structural unit and 2-ethylhexyl-5-trimethyltin thiophene Stille, so that the obtained fluorescent molecule has high penetration depth and high-resolution fluorescence imaging capability in a near-infrared second region (NI R-I, 1000-1700 nm).

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescence imaging, and in particular relates to a near-infrared second-zone fluorescent molecule and a preparation method thereof. Background Art

[0002] Fluorescence microscopy is one of the most widely used technologies in current optical imaging. Near-infrared fluorescence in vivo imaging, which is also fluorescence imaging, is also gaining more and more attention in the biomedical field. Traditional fluorescence imaging is mainly concentrated in the near-infrared region I (NIR-I), with a fluorescence emission wavelength range of 650-950nm. The short wavelength (<1000nm) and poor photon penetration depth have become the main obstacles to the application of in vivo biomedical fluorescence imaging. Compared with visible light and NIR-I light, the wavelength is 1000-1700nm, that is, near-infrared region II (NIR-II) fluorescence imaging, which can penetrate deeper into biological tissues and has less scattered light in this wavelength window. Since NIR-II light has the advantages of deeper penetration into biological tissues (about 5-20mm), reduced background autofluorescence and improved signal-to-noise ratio, the newly emerging fluorescence imaging in the NIR-II region is gaining more and more attention.

[0003] There are many NIR-II fluorescence imaging agents based on inorganic materials, organic small molecules and conjugated polymers. Among them, organic small molecules have the advantages of good biocompatibility and easy metabolism in the body and are widely concerned. However, at present, NIR-II fluorescence contrast agents based on organic conjugated small molecules are mainly based on quinoxaline electron acceptors, and the quinoxaline acceptor structure has the disadvantages of large molecular weight and low penetration depth. Therefore, it is becoming more and more urgent to develop a new type of organic conjugated NIR-II fluorescent small molecule for the preparation of contrast agents. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a near-infrared second-zone fluorescent molecule and a preparation method thereof, aiming to solve the technical problem of providing an organic fluorescent molecule with high penetration depth and high resolution.

[0005] To achieve the above object, the present invention provides the following technical solution: a near-infrared second-zone fluorescent molecule, the structural formula of which is:

[0006]

[0007] Further, 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole is used as an electron acceptor structural unit to carry out Stille coupling reaction with a donor unit, wherein the donor unit is:

[0008]

[0009] Furthermore, the synthetic route of the fluorescent molecule is:

[0010]

[0011] Furthermore, the near-infrared region II fluorescent molecule is the near-infrared region II fluorescent molecule as described above, comprising the following steps:

[0012] S01: dissolving a certain mass ratio of 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene in an anhydrous toluene solution;

[0013] SO2: Add a certain amount of catalyst to the mixed solution in step SO1, mix well and pour into the reaction bottle for vacuum treatment;

[0014] S03: Stir the mixed solution in step SO2 at 110° C. for 12-14 h and cool to room temperature;

[0015] S04: extracting, drying, filtering and purifying the mixture cooled to room temperature in step S03 to obtain the final product.

[0016] Further, the vacuum treatment in step SO2 includes:

[0017] The reaction bottle was vacuumed with a water pump, ultrasonicated in an ultrasonic cleaner for 1-2 minutes, repeated 3-10 times, and finally filled with inert gas.

[0018] Furthermore, the mass ratio of the 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene is 1:2.

[0019] Furthermore, the catalyst in step S02 is Pd(PPh3)4.

[0020] Further, the step S04 comprises:

[0021] A: Add potassium fluoride solution to the mixture cooled to room temperature and stir for 3-6 hours;

[0022] B: adding dichloromethane and saturated sodium chloride solution to step A for extraction treatment;

[0023] C: Add anhydrous magnesium sulfate to step B, dry for 1-1.5 hours, filter, and rotary evaporate to obtain oily crystals;

[0024] D: The obtained oily crystals were purified by silica gel column chromatography.

[0025] Furthermore, the mass ratio of the 2-ethylhexyl-5-trimethyltinthiophene to the Pd(PPh3)4 is 15:1.

[0026] The beneficial effect of the present invention is that: compared with the prior art, the present invention designs, synthesizes and prepares a 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole near-infrared second region fluorescent molecular contrast agent, which is formed by a near-infrared second region fluorescent molecule based on 4,8-bis[5-bromo-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole as an electron acceptor structural unit and 2-ethylhexyl-5-trimethyltinthiophene Stille coupling reaction, so that the obtained fluorescent molecule has high penetration depth and high-resolution fluorescence imaging ability in the near-near infrared second region (NIR I, 1000-1700nm).

[0027] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0029] Figure 1 The synthetic route of the near-infrared second-region fluorescent molecule BETETD of the present invention is as follows;

[0030] Figure 2 This is a nuclear magnetic resonance hydrogen spectrum characterization diagram of the near-infrared second-zone fluorescent molecule BETETD of the present invention;

[0031] Figure 3 This is a mass spectrum characterization diagram of the near-infrared second-region fluorescent molecule BETETD of the present invention;

[0032] Figure 4 It is a fluorescence emission curve diagram of the near-infrared second-zone fluorescent molecule BETETD of the present invention under 660nm excitation;

[0033] Figure 5 It is a fluorescence emission curve diagram of the near-infrared second-zone fluorescent molecule BETETD of the present invention under 808nm excitation;

[0034] Figure 6 This is an AI E special effect diagram of the near-infrared second-zone fluorescent molecule BETETD of the present invention under 808nm excitation. DETAILED DESCRIPTION

[0035] A near-infrared second-zone fluorescent molecule is synthesized by using 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole as an electron acceptor structural unit and carrying out Stille coupling reaction with a donor unit. The preparation method comprises:

[0036] S01: dissolving a certain mass ratio of 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene in an anhydrous toluene solution;

[0037] SO2: Add a certain amount of catalyst to the mixed solution in step SO1, mix well and pour into the reaction bottle for vacuum treatment;

[0038] S03: Stir the mixed solution in step SO2 at 110° C. for 12-14 h and cool to room temperature;

[0039] S04: extracting, drying, filtering and purifying the mixture cooled to room temperature in step S03 to obtain the final product.

[0040] Furthermore, the catalyst in step S02 is Pd(PPh3)4.

[0041] Its synthetic route is:

[0042]

[0043] Among them, the structural formula of 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole is:

[0044]

[0045] Among them, the structural formula of 2-ethylhexyl-5-trimethyltinthiophene is:

[0046]

[0047] In the present application, the above-mentioned polymer is referred to as BETETD for short. The full chemical name of BETETD is 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole (4,8-bis[5-(2-ethy l hexyl)-2-th ieny l-3-(2-ethy l hexy l)-2-th ieny l]-d ith iad iazo le, BETETD).

[0048] In this embodiment, if Figure 2As shown, it is the nuclear magnetic resonance hydrogen spectrum characterization diagram of the near-infrared second-zone fluorescent molecule BETETD obtained in this example. Figure 3 As shown, it is the mass spectrum characterization diagram of the near-infrared second-region fluorescent molecule BETETD obtained in this example. Figure 4 and Figure 5 As shown, this is the fluorescence performance diagram of the near-infrared second-zone fluorescent molecule BETETD obtained in this example, Figure 4 is the fluorescence emission curve of BETETD under 660nm excitation; Figure 5 This is the fluorescence emission curve of BETETD under 808nm excitation. It can be seen from the above fluorescence emission curve that when the wavelength is 1100nm, the fluorescence value reaches the maximum; Figure 6 This is the AIE special effect diagram of BETETD under 808nm excitation. It can be seen that the AIE special effect of BETETD under 808nm excitation can reach 90%.

[0049] Further, the vacuum treatment in step SO2 includes:

[0050] The reaction bottle is evacuated with a water pump, ultrasonicated in an ultrasonic cleaner for 1-2 minutes, repeated 3-10 times, and finally filled with an inert gas. Preferably, the inert gas is argon. This ensures that the reaction must be carried out in an inert environment without water and oxygen to avoid the presence of oxygen which may cause oxidation of the catalyst and thus cause self-coupling of the organic compound.

[0051] Furthermore, the mass ratio of the 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene is 1:2.

[0052] Furthermore, the mass ratio of the 2-ethylhexyl-5-trimethyltinthiophene to the Pd(PPh3)4 is 15:1.

[0053] Embodiment 1:

[0054] 4,8-bis[5-bromo-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole (150 mg, 0.2 mmol) and 2-ethylhexyl-5-trimethyltinthiophene (300 mg, 0.5 mmol) were subjected to still coupling reaction under the conditions of catalyst Pd(PPh3)4 (20 mg, 0.02 mmol) and anhydrous toluene (10 mL), and then the reaction mixture was stirred at 110°C for 12 hours. After cooling to room temperature, the mixture cooled to room temperature was extracted, dried, filtered, and purified to obtain the final product. The final product BETETD has the following advantages and characteristics:

[0055] (1) Excellent photostability: Compared with traditional fluorescent materials, this fluorescent molecule can still maintain a high fluorescence intensity in the aggregated state, avoiding the problem of aggregation-induced fluorescence quenching (ACQ);

[0056] (2) High quantum yield: The fluorescent molecule has a high fluorescence quantum yield and can more efficiently convert the absorbed light energy into fluorescent emission;

[0057] (3) Good biocompatibility: The fluorescent molecule has good biocompatibility, reducing toxicity and side effects in the body;

[0058] (4) Multifunctionality: Through molecular design, the fluorescent molecule can realize the multifunctionality of the NIRI IAI E molecule, such as combining with targeting molecules to achieve targeted imaging and treatment;

[0059] (5) Broad application prospects: With the unique properties and advantages of this fluorescent molecule, it has broad application prospects in many fields such as biomedicine, materials science, and environmental monitoring.

[0060] Embodiment 2:

[0061] 4,8-bis[5-bromo-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole (75 mg, 0.1 mmol) and 2-ethylhexyl-5-trimethyltinthiophene (150 mg, 0.25 mmol) were subjected to still coupling reaction in the presence of catalyst Pd(PPh3)4 (10 mg, 0.01 mmol) and anhydrous toluene (10 mL), and the reaction mixture was stirred at 110°C for 12 hours. After cooling to room temperature, the mixture cooled to room temperature was extracted, dried, filtered, and purified to obtain the final product BETETD.

[0062] Embodiment 3:

[0063] 4,8-bis[5-bromo-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole (225 mg, 0.3 mmol) and 2-ethylhexyl-5-trimethyltinthiophene (450 mg, 0.75 mmol) were subjected to still coupling reaction in the presence of catalyst Pd(PPh3)4 (30 mg, 0.03 mmol) and anhydrous toluene (10 mL), and the reaction mixture was stirred at 110°C for 12 hours. After cooling to room temperature, the mixture cooled to room temperature was extracted, dried, filtered, and purified to obtain the final product BETETD.

[0064] Further, the step S04 comprises:

[0065] A: Add potassium fluoride solution to the mixture cooled to room temperature and stir for 3-6 hours;

[0066] B: adding dichloromethane and saturated sodium chloride solution to step A for extraction treatment;

[0067] C: Add anhydrous magnesium sulfate to step B, dry for 1-1.5 hours, filter, and rotary evaporate to obtain oily crystals;

[0068] D: The obtained oily crystals were purified by silica gel column chromatography.

[0069] Embodiment 4:

[0070] On the basis of Example 1, potassium fluoride solution was added to the mixture cooled to room temperature and stirred for 3 hours, and then dichloromethane and saturated sodium chloride solution were added for extraction, and then anhydrous magnesium sulfate was added, dried for 1 hour, filtered, and rotary evaporated to obtain oily crystals. Finally, the obtained oily crystals were purified by silica gel column chromatography (PE:DCM=v / v10 / 1) to obtain a blue solid product BETETD, and the reaction yield was 82%.

[0071] In the present application, the reaction yield refers to the ratio of the actual production output of the product obtained by inputting a unit amount of raw materials into a chemical reaction to the theoretically calculated product output.

[0072] Embodiment 5:

[0073] On the basis of Example 2, potassium fluoride solution was added to the mixture cooled to room temperature and stirred for 4 hours, and then dichloromethane and saturated sodium chloride solution were added for extraction, and then anhydrous magnesium sulfate was added, dried for 1.5 hours, filtered, and rotary evaporated to obtain oily crystals, and finally the obtained oily crystals were purified by silica gel column chromatography (PE:DCM=v / v10 / 1) to obtain a blue solid product BETETD.

[0074] Embodiment 6:

[0075] On the basis of Example 3, potassium fluoride solution was added to the mixture cooled to room temperature and stirred for 5 hours, and then dichloromethane and saturated sodium chloride solution were added for extraction, and then anhydrous magnesium sulfate was added, dried for 1.5 hours, filtered, and rotary evaporated to obtain oily crystals, and finally the obtained oily crystals were purified by silica gel column chromatography (PE:DCM=v / v10 / 1) to obtain a blue solid product BETETD.

[0076] In the present application, the amount of anhydrous magnesium sulfate added is determined according to the actual situation, that is, if the solution does not immediately become clear after shaking the reaction bottle.

[0077] In the present application, a 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole near-infrared region II fluorescent molecular contrast agent is designed, synthesized and prepared. The near-infrared region II fluorescent molecule based on 4,8-bis[5-bromo-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole as an electron acceptor structural unit is reacted with 2-ethylhexyl-5-trimethyltinthiophene Stille coupling reaction, so that the fluorescent molecule has high penetration depth and high-resolution fluorescence imaging capability in the near-near infrared region II (NIR-II, 1000-1700nm).

[0078] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A near-infrared second region fluorescent molecule, characterized in that: The structural formula is:

2. A near-infrared second region fluorescent molecule according to claim 1, characterized in that: 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole is used as an electron acceptor structural unit to carry out Stille coupling reaction with a donor unit, wherein the donor unit is:

3. A near-infrared second region fluorescent molecule according to claim 2, characterized in that: The synthetic route of the fluorescent molecule is:

4. A method for preparing a near-infrared second-region fluorescent molecule, characterized in that: The near-infrared second region fluorescent molecule is the near-infrared second region fluorescent molecule as claimed in claim 1, comprising the following steps: S01: dissolving a certain mass ratio of 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene in an anhydrous toluene solution; SO2: Add a certain amount of catalyst to the mixed solution in step SO1, mix well and pour into the reaction bottle for vacuum treatment; S03: Stir the mixed solution in step SO2 at 110° C. for 12-14 h and cool to room temperature; S04: extracting, drying, filtering and purifying the mixture cooled to room temperature in step S03 to obtain the final product.

5. The method for preparing a near-infrared second region fluorescent molecule according to claim 4, characterized in that: The vacuum treatment in step SO2 comprises: The reaction bottle was vacuumed with a water pump, ultrasonicated in an ultrasonic cleaner for 1-2 minutes, repeated 3-10 times, and finally filled with inert gas.

6. The method for preparing a near-infrared second-region fluorescent molecule according to claim 4, characterized in that: The mass ratio of the 4,8-bis[5-(2-ethylhexyl)-2-thienyl-3-(2-ethylhexyl)-2-thienyl]-bithiadiazole and 2-ethylhexyl-5-trimethyltinthiophene is 1:

2.

7. The method for preparing a near-infrared second region fluorescent molecule according to claim 4, characterized in that: The catalyst in step S02 is Pd(PPh3)4.

8. The method for preparing a near-infrared second region fluorescent molecule according to claim 7, characterized in that: The step S04 comprises: A: Add potassium fluoride solution to the mixture cooled to room temperature and stir for 3-6 hours; B: adding dichloromethane and saturated sodium chloride solution to step A for extraction treatment; C: Add anhydrous magnesium sulfate to step B, dry for 1-1.5 hours, filter, and rotary evaporate to obtain oily crystals; D: The obtained oily crystals were purified by silica gel column chromatography.

9. The method for preparing a near-infrared second region fluorescent molecule according to claim 7, characterized in that: The mass ratio of the 2-ethylhexyl-5-trimethyltinthiophene to the Pd(PPh3)4 is 15:1.

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