Near-infrared small-molecule fluorescent dye with pentadecamethine conjugated chain, and preparation method therefor and use thereof

Abstract

The present invention relates to a near-infrared small-molecule fluorescent dye with a pentadecamethine conjugated chain, and a preparation method therefor and the use thereof. The near-infrared small-molecule dye has a structure as represented by general formula A; is a functional dye molecule which is obtained on the basis of a new dye parent comprising two benzindole structures linked via a pentadecamethine chain and by means of regulating substituents on the parent structure; and exhibits absorption and emission peak wavelengths in the near-infrared region. Different substituents can be introduced onto the pentadecamethine chain and the indole N atoms. The near-infrared small-molecule dye has absorption and emission wavelengths in the near-infrared region of 1100-1300 nm, and has the characteristics of high brightness, excellent photostability, low cytotoxicity, simple synthesis, easy structural modification, etc. After water-solubility modification, the near-infrared small-molecule dye can be widely used in biomedical fields such as tumor-targeted imaging and in-vivo vascular imaging. General formula A

Description

Near-infrared small-molecule fluorescent dye with fifteen-methine conjugated chain and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of biological materials, especially the field of biomedical imaging detection, and particularly relates to a near-infrared small-molecule fluorescent dye with fifteen-methine conjugated chain and a preparation method and application thereof. BACKGROUND

[0002] Fluorescence imaging has good applications in pathology and physiology because of its fast response, high spatial and temporal resolution, and real-time imaging characteristics, such as early diagnosis and treatment of diseases and mechanism research. Moreover, compared with other clinical imaging methods, such as Positron Emission Tomography (PET), Computed Tomography (CT), and Single-Photon Emission Computed Tomography (SPECT), fluorescence imaging has the advantage of not emitting harmful radiation. Organic small-molecule fluorescent probes have good safety and biocompatibility among many fluorescent probes such as carbon nanotubes, rare earth nanoparticles, and quantum dots, and have applications such as angiography, lymph node imaging, and targeted tumor imaging.

[0003] However, the main bottleneck of fluorescence imaging is the shallow tissue penetration depth and the low signal-to-noise ratio caused by high absorption, scattering, and autofluorescence of biological tissues. In recent years, near-infrared II region imaging (NIR-II, 1000-1700 nm), also known as shortwave infrared imaging (SWIR), has a great prospect because it avoids the autofluorescence region of living organisms and has less light scattering, compared with traditional visible light and near-infrared I region imaging, and has higher resolution and tissue penetration depth. In addition, the near-infrared II region is divided into near-infrared IIa (1300-1400 nm) and near-infrared IIb (1500-1700 nm) regions. Although the tissue absorption coefficient of the near-infrared II region is slightly higher than that of the near-infrared I region, the scattered light and autofluorescence are significantly reduced, making the near-infrared II region have higher resolution and penetration depth. Although the near-infrared II region fluorescent probe has the advantages of long wavelength and high contrast, the types of conjugated chains of the fluorescent probe molecules are few, and the molar absorption coefficient and fluorescence quantum yield are still low, and the modifiability on the conjugated chain is limited.

[0004] In the performance of fluorescent dyes, with the lengthening of the polycumulene chain, the absorption and fluorescence wavelength of the cyanine dye is significantly improved, which improves the important performance parameters of the dye molecule in biological imaging, such as the penetration depth and signal-to-background ratio. However, the method for synthesizing a long polycumulene chain is currently lacking.

[0005] However, in terms of synthesis, with the lengthening of the polycumulene chain, the synthesis of the cyanine dye becomes more difficult, and the stability of the dye is also poorer.

[0006] Therefore, it is an important goal in the field of fluorescent probe synthesis to design and synthesize a near-infrared two-region organic small-molecule fluorescent probe with high molar absorption coefficient, high brightness, excellent light stability, small cytotoxicity, simple synthesis, and novel structure that is easy to modify. SUMMARY

[0007] The purpose of the present application is to provide a near-infrared small-molecule fluorescent dye with a fifteen-membered polycumulene conjugated chain, a preparation method and application thereof, and the structure is easy to modify. The near-infrared small-molecule dye provided by the present application is a novel dye parent based on two benzindole structures connected by a fifteen-membered polycumulene chain. The functional dye molecule with an absorption and emission peak wavelength in the near-infrared region is obtained by substituting the substituents on the parent structure. Different substituents can be introduced on the fifteen-membered polycumulene chain and the indole N atom. In the process of lengthening the chain length of the polycumulene chain, the present application improves the important performance parameters of the fluorescent dye, such as the penetration depth and signal-to-background ratio. In the process of lengthening the chain length of the polycumulene chain, the present application is simple to synthesize and ensures the stability of the dye.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] The first purpose of the present application is to provide a near-infrared small-molecule fluorescent dye with a fifteen-membered polycumulene conjugated chain, which comprises one or more of the structures shown in general formula A or the solvates of the structures shown in general formula A, and the general formula A is as follows:

[0010] General formula A

[0011] In the formula, R1, R2, R3, n and X are as follows:

[0012] R1, R2 are each independently selected from C1-C6 alkyl, aromatic ring and substituted aromatic ring, chlorine atom; R3 is independently selected from C1-C6 alkyl, C1-C6 terminal alkyne, C1-C6 sulfonic acid group substituted alkane; n is independently selected from 1 or 2; X is independently selected from bromine atom, tetraphenylboric acid, tetra(pentafluorophenyl)boric acid.

[0013] Further, the near-infrared small-molecule dye has a maximum absorption wavelength of 1100-1300 nm and a maximum emission wavelength of 1150-1300 nm, and a molecular weight of 700-1300 Da.

[0014] Further, the near-infrared small molecule dye has a brightness of 4.8-115.1M -1 cm -1 , a molar extinction coefficient of 4.8x10 4 -2.6x10 5 M -1 cm -1 .

[0015] Further, the small molecule fluorescent dye has a structure shown in general formula A, or is an isomer of the structure shown in general formula A or a solvate of the structure shown in general formula A.

[0016] Further preferably, the small molecule fluorescent dye has a structure shown in general formula A.

[0017] Further, the solvate of the structure shown in general formula A is a solvate formed by general formula A and dichloromethane, methanol, dimethyl sulfoxide and the like solvents.

[0018] Further preferably, the small molecule fluorescent dye has a structure shown in any one of the following formulae B1-B14:

[0019] A second object of the present application is to provide a preparation method of the above-mentioned near-infrared small molecule dye, comprising the following steps:

[0020] Step one, carbon-nitrogen coupling reaction of the compound shown in formula (1) with halide or sulfonic acid lactone compound to obtain the compound shown in formula (2);

[0021] Step two, dehydration condensation reaction of the compound shown in formula (2) with aldehyde compound to obtain the compound shown in formula (3);

[0022] Step three, Suzuki coupling reaction of the compound shown in formula (3) to obtain the compound shown in formula (4);

[0023] Step four, Knoevenagel condensation reaction of the compound shown in formula (3) or formula (4) with cyclopentanone to obtain the compound shown in formula (5);

[0024] Step five, nucleophilic addition reaction of the compound shown in formula (5) under the action of lithium reagent or Grignard reagent, to obtain the compound shown in general formula A after the nucleophilic addition reaction or to obtain the compound shown in general formula A after the nucleophilic addition reaction and then reacting with the corresponding anion salt;

[0025] wherein, formula (1) is formula (2) is formula (3) is formula (4) is formula (5) is

[0026] Further, the preparation method comprises the following flow:

[0027] Further, in step one, the compound shown as formula (1) is coupled with halide or sulfonic lactone compound to obtain the compound shown as formula (2), which comprises:

[0028] The compound shown as formula (1) is heated and stirred with halide or the compound shown as formula (1) is heated and stirred with sulfonic lactone compound to obtain the compound shown as formula (2) in a first organic solvent environment;

[0029] The halide is alkyl or terminal alkyne halide;

[0030] The halide or sulfonic lactone compound has any one of the following structures shown as formula C1, C2 or C3:

[0031] In formula C1, C2 or C3, R3 is independently selected from C1-C6 alkyl or C1-C6 terminal alkyne; wherein formula C1 and C2 are halide, and C3 is sulfonic lactone compound;

[0032] The first organic solvent is selected from one or more of benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, diethyl ether, 1, 4-dioxane and glacial acetic acid.

[0033] Further, in step one, the heating and stirring conditions are as follows: the heating temperature is 100-120℃, the stirring rate is 500-1000 rpm, and the heating and stirring time is 24-72 h.

[0034] Further, the molar ratio of the compound shown as formula (1) to halide or the compound shown as formula (1) to sulfonic lactone compound is 1:1.2-1:10.

[0035] Further, in step two, the compound shown as formula (2) is subjected to dehydration condensation reaction with aldehyde compound to obtain the compound shown as formula (3), which comprises:

[0036] The compound shown as formula (2) is stirred with aldehyde compound to obtain the compound shown as formula (3) in a second organic solvent environment;

[0037] The aldehyde compound has any one of the following structures shown as formula D1 or D2:

[0038] The second organic solvent is selected from one or more of one or more of benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dichloromethane, trichloromethane, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, tetrahydrofuran, diethyl ether, 1,4-dioxane, ethanol, and methanol.

[0039] Further, in step two, the stirring conditions are as follows: the stirring rate is 500-1000 rpm, and the stirring time is 9-24 h.

[0040] Further, the molar ratio of the compound of formula (2) to the aldehyde compound is 1:1-1:3.

[0041] Further, in step three, the compound of formula (3) is subjected to Suzuki coupling reaction to obtain a compound of formula (4), which includes:

[0042] In a third organic solvent environment, under inert gas protection, the compound of formula (3) is heated and stirred with a boronic acid compound using a palladium catalyst and a base as catalysts to obtain a compound of formula (4) through Suzuki coupling reaction;

[0043] The boronic acid compound has the following structure shown in formula E:

[0044] In formula E, R1 is independently selected from C1-C6 alkyl, aromatic ring, and substituted aromatic ring.

[0045] The palladium catalyst is selected from one or more of tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)dipalladium, bis(dibenzylideneacetone)palladium, and palladium acetate; the base is selected from one or more of potassium tert-butoxide, sodium tert-butoxide, potassium carbonate, cesium carbonate, and potassium phosphate; and the third organic solvent is selected from one or more of benzene, toluene, xylene, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and diethyl ether.

[0046] Further, in step three, under inert gas protection, the heating and stirring conditions are as follows: the heating temperature is 80-120°C, the stirring rate is 500-1000 rpm, and the heating and stirring time is 12-48 h.

[0047] Further, the molar ratio of the compound of formula (3) to the boronic acid compound is 1:1-1:3.

[0048] Further, in step four, the compound of formula (3) or formula (4) is subjected to Knoevenagel condensation reaction with cyclopentanone to obtain a compound of formula (5), which includes:

[0049] In the fourth organic solvent environment, the compound shown in formula (3) or formula (4) is heated and stirred with cyclopentanone and a base, wherein the base acts as a catalyst, and a Knoevenagel condensation reaction is carried out to obtain a compound shown in formula (5);

[0050] The base is selected from one or more of sodium hydroxide, sodium tert-butoxide, sodium ethoxide, and potassium hydroxide;

[0051] The fourth organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, 1,4-dioxane, ethanol, and methanol.

[0052] Further, in step four, the heating and stirring conditions are as follows: the heating temperature is 80-120°C, the stirring rate is 500-1000 rpm, and the heating and stirring time is 12-72 h.

[0053] Further, the molar ratio of the compound shown in formula (3) to cyclopentanone is 1:0.5-1:1.

[0054] Further, in step five, the compound shown in formula (5) is subjected to a nucleophilic addition reaction under the action of a lithium reagent or a Grignard reagent, and after the nucleophilic addition reaction, the compound shown in general formula A is obtained or the partial compound obtained after the nucleophilic addition reaction is reacted with a corresponding anion salt to obtain the compound shown in general formula A, including:

[0055] In the fifth organic solvent environment, under the protection of an inert gas, the compound shown in formula (5) is reacted with a lithium reagent or the compound shown in formula (5) is reacted with a Grignard reagent at low temperature to undergo a nucleophilic addition reaction, and after the nucleophilic addition reaction, the compound shown in general formula A is obtained or the partial compound obtained after the nucleophilic addition reaction is exchanged with a corresponding anion salt to obtain the compound shown in general formula A.

[0056] The lithium reagent or the Grignard reagent has a structure shown in any one of the following formulae F1 and F2:

[0057] In formulae F1 and F2, R2 is independently selected from C1-C6 alkyl, an aromatic ring, and a substituted aromatic ring.

[0058] The anion salt is selected from one or more of sodium tetraphenylborate and potassium tetra(pentafluorophenyl)borate, and the fifth organic solvent is selected from one or more of ultradry tetrahydrofuran, diethyl ether, and 1,4-dioxane.

[0059] Further, in step five, under the protection of an inert gas, the low-temperature reaction conditions are as follows: the low-temperature temperature is -87°C, the stirring rate is 500-1000 rpm, and the stirring time is 0.5-3 h.

[0060] Further, the molar ratio of the compound shown in formula (5) to the lithium reagent or the molar ratio of the compound shown in formula (5) to the Grignard reagent is 1:1-1:20.

[0061] Further, the molar ratio of the compound shown in formula (5) to the lithium reagent or the molar ratio of the compound shown in formula (5) to the Grignard reagent is 1:1-1:20.

[0062] The near-infrared small molecule dye provided by the present application is a novel dye parent molecule based on two benzindole structures connected by a fifteen-membered methine chain, and is a functional dye molecule with an absorption and emission peak wavelength in the near-infrared region obtained by regulating substituents on the parent structure. Different substituents can be introduced on the fifteen-membered methine chain and the indole N atom. The maximum absorption wavelength is between 1100-1300nm, the maximum emission wavelength is between 1150-1300nm, the molecular weight is between 700-1300Da, the brightness is high, the molar extinction coefficient is high, the light stability is excellent, the cytotoxicity is small, the synthesis is simple, and the structure is easy to modify. -1 cm -1 , the molar extinction coefficient is high, the light stability is excellent, the cytotoxicity is small, the synthesis is simple, and the structure is easy to modify. 4 -2.6×10 5 M -1 cm -1 , the light stability is excellent, the cytotoxicity is small, the synthesis is simple, and the structure is easy to modify.

[0063] The third object of the present application is to provide an application of a near-infrared small molecule fluorescent dye with a fifteen-methine conjugated chain. The near-infrared small molecule dye provided by the present application can be used for tumor targeted imaging, in vivo blood vessel imaging, fluorescence imaging, etc.

[0064] Compared with the prior art, the present application has the following advantages:

[0065] The present application provides a near-infrared small molecule fluorescent dye with a fifteen-methine conjugated chain and a preparation method thereof. The present application has a longer absorption and emission wavelength, can perform NIR-IIb imaging, has a better signal-to-noise ratio (SNR) and imaging effect compared with traditional visible and NIR-I imaging, and makes up for the shortcomings of few NIR-II imaging molecular structures and short wavelength. The maximum absorption wavelength is between 1100-1300nm, the maximum emission wavelength is between 1150-1300nm, the brightness is high, the molar extinction coefficient is high, the light stability is excellent, the cytotoxicity is small, the synthesis is simple, and the structure is easy to modify, and the present application can be used for tumor targeted imaging, in vivo blood vessel imaging, NIR-II fluorescence imaging, etc. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 is the normalized absorption spectrum and photoluminescence (PL) spectrum of the small molecule fluorescent dye B1-B10 in dichloromethane.

[0067] Figure 2 is a fluorescence imaging test photo of the small molecule fluorescent dye B3 and B7 nanoparticles and ICG respectively prepared into a PBS solution with a concentration of 0.15 mM, obtained by using a chemiluminescence fluorescence imaging analysis system under different long-pass filters LP1300 and LP1500, wherein (a) LP1300, (b) LP1500.

[0068] Figure 3 is a schematic diagram of the survival rate of 4T1 cells incubated with B3 material for 12 hours, using 4T1 cells, 8000 cells / well, and B3 material prepared into a PBS solution with a concentration of 0-150 μM nanoparticles.

[0069] Figure 4 is a schematic diagram of NIR-IIb imaging of the hindlimb blood vessels of a Balb / c-nude mouse using the small molecule fluorescent dye B3 nanoparticles prepared into a PBS solution with a concentration of 0.15 mM.

[0070] Figure 5 is a schematic diagram of NIR-II vascular imaging of a mouse using the small molecule fluorescent dye B3.

[0071] Figure 6 is a schematic diagram of NIR-II tumor imaging of a mouse using the small molecule fluorescent dye B3. DETAILED DESCRIPTION

[0072] The present application will be described in detail below with specific examples, but is by no means a limitation on the present application. If not explicitly stated in the technical solution, the preparation means, materials, structures or composition ratio of the features are considered as common technical features disclosed in the prior art.

[0073] The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These are within the scope of protection of the present application.

[0074] In this embodiment, the hydrogen nuclear magnetic resonance spectrum (1H NMR) of the compound is measured by Bruker AVANCE III HD 400 or Bruker AVANCE III HD 500; and the reagents used are commercially available reagents.

[0075] Example 1

[0076] This example provides a preparation of a fluorescent dye B1, the compound structure formula and the specific synthesis route are as follows:

[0077] (1) Synthesis of compound B1-(2)

[0078] In a 100 mL round bottom flask, add 2,3,3-trimethyl-4,5-benzo-3H indole (1.0 g, 4.8 mmol), add acetonitrile (36 mL), add 1-iodopropane (702 μL, 7.2 mmol), heat the reaction for 2 days at 110 °C with a stirring rate of 800 rpm. After cooling to room temperature, concentrate with rotary evaporation, wash the remaining oily solution with diethyl ether to obtain product B1-(2), dark brown solid 1.34 g, yield 97%.

[0079] H-NMR (400 MHz, CDC13, 25 °C) δ = 8.08 (2H, t, J = 8 Hz, ar.CH) and 8.04 (1H, d, J = 8 Hz, ar.CH) part overlapped, 7.92 (1H, d, J = 8 Hz, ar.CH), 7.83 (1H, d, J = 8 Hz, ar.CH), 7.66 (1H, t, J = 8 Hz, ar.CH), 4.80 (2H, t, J = 8 Hz, -NCH2-), 3.20 (3H, s, -CH3), 2.11-2.02 (2H, m, -NCH2CH2CH2), 1.87 (6H, s, -CH3), 1.11 (3H, t, J = 8 Hz, -NCH2CH2CH3);13C-NMR (100 MHz, CDC13, 25 °C) δ = 195.3, 189.7, 150.1, 138.5, 138.0, 136.9, 133.5, 132.1, 131.2, 130.0, 127.3, 55.8, 55.2, 22.6, 21.6, 16.8, 11.2; ESI-MS m / z calculated for C18H22N+ 252.17; obs.: 252.2

[0080] (2) Synthesis of compound B1-(3)

[0081] Weigh a mixture of compound B1-(2) (5 mmol, 1.9 g), and 2-chloro-1- formyl-3-(hydroxy methylene) cyclohexene (6 mmol, 1.0 g) in a mixture of toluene (37 mL) and acetic acid (13 mL), stir at room temperature for 12 h with a stirring rate of 800 rpm, concentrate with rotary evaporation. The resulting compound is purified by silica gel column chromatography (PE:EA = 9:1) to obtain compound B1-(3), red solid 1.0 mmol, 427 mg, separation yield 21.1%.

[0082] 1H NMR (400 MHz, Chloroform-d) δ 10.30 (s, 1H), 8.07 (d, J = 8.6 Hz, 1H), 8.00 (d, J = 12.6 Hz, 1H), 7.85 (d, J = 8.2 Hz, 1H), 7.80 (d, J = 8.7 Hz, 1H), 7.56 - 7.46 (m, 1H), 7.36 - 7.29 (m, 1H), 7.13 (d, J = 8.7 Hz, 1H), 5.57 (d, J = 12.8 Hz, 1H), 3.79 (t, J = 6.0 Hz, 2H), 2.61 (t, J = 5.9 Hz, 2H), 2.52 (t, J = 6.0 Hz, 2H), 2.01 (s, 6H), 1.89 - 1.78 (m, 4H), 1.06 (t, J = 7.2 Hz, 3H). 13 C NMR (101 MHz, Chloroform-d) δ 190.8, 164.3, 148.8, 141.6, 131.3, 130.1, 129.9, 129.6, 129.5, 128.9, 128.3, 127.0, 122.8, 122.7, 121.7, 109.4, 92.5, 48.6, 44.2, 27.5, 26.7, 24.6, 21.0, 20.1, 11.7. HRMS: calculated for C 26 H 28 ClNO[M+H] + 406.1932, found 406.1942.

[0083] Synthesis of compound B1-(4)

[0084] A mixture of B1-(3) (1 mmol, 410 mg), phenylboronic acid (2 mmol, 250 mg), K2CO3(2.2 mmol, 300 mg), and Pd(PPh3)4(tetrakis triphenylphosphine palladium) (0.06 mmol, 60 mg) was added to a Schlenk flask under argon protection. Dry DMF (0.1 mmol, 8.5 mL) and deionized water (0.08 mmol, 1.5 mL) were added to the flask, stirred at 90 °C for 24 h, the stirring rate was 800 rpm, after cooling to room temperature, the reaction mixture was poured into brine, extracted with ethyl acetate. The organic phase was dried over Na2SO4, filtered, concentrated by rotary evaporation. Purified by silica gel column chromatography (PE:EA = 9:1) to give compound B1-(4), red solid 0.87 mmol, 389 mg, separation yield 87.0%.

[0085] 1H NMR (400 MHz, Chloroform-d) δ 9.26 (s, 1H), 7.85 (d, J = 8.6 Hz, 1H), 7.83 (d, J = 8.1 Hz, 1H), 7.76 (d, J = 8.7 Hz, 1H), 7.47 - 7.37 (m, 4H), 7.25 - 7.19 (m, 3H), 7.01 (d, J = 8.7 Hz, 1H), 6.57 (d, J = 12.9 Hz, 1H), 5.55 (d, J = 12.9 Hz, 1H), 3.69 (t, J = 7.2 Hz, 2H), 2.59 (t, J = 5.8 Hz, 2H), 2.52 (t, J = 6.1 Hz, 2H), 1.92 - 1.83 (m, 2H), 1.82 - 1.70 (m, 2H), 1.43 (s, 6H), 1.00 (t, J = 7.4 Hz, 3H). 13 C NMR (101 MHz, Chloroform-d) δ 193.1, 162.7, 158.5, 141.7, 137.6, 133.9, 131.1, 130.3, 129.9, 129.8, 129.4, 129.1, 128.8, 128.6, 127.9, 127.5, 126.7, 122.4, 121.6, 109.3, 92.5, 47.8, 44.1, 27.0, 25.4, 22.5, 21.5, 20.0, 11.7. HRMS: calculated for C 32 H 33 NO[M+H] + 448.2635, found 448.2638.

[0086] Synthesis of compound B1-(5)

[0087] A mixture of B1-(4) (0.5 mmol, 225 mg), cyclopentanone (0.25 mmol, 23 μL) and NaOH (2 mmol, 80 mg) was added to a round bottom flask. 0.2 mmol, 4 mL of anhydrous ethanol (EtOH) was added to the flask, stirred at 80 °C for 48 h, the stirring rate was 800 rpm, after cooling to room temperature, filtration and washing with ethanol, compound B1-(5) was obtained as a blue solid, 0.19 mmol 183 mg, separation yield was 77%.

[0088] 1H NMR (400 MHz, Chloroform-d) δ 7.85 (d, J = 8.4 Hz, 2H), 7.75 (d, J = 8.0 Hz, 2H), 7.68 (d, J = 8.7 Hz, 2H), 7.43 - 7.35 (m, 8H), 7.22 - 7.18 (m, 2H), 7.14 - 7.08 (m, 4H), 7.02 - 6.96 (m, 4H), 6.23 (d, J = 12.8 Hz, 2H), 5.48 (d, J = 12.8 Hz, 2H), 3.65 (t, J = 7.0 Hz, 4H), 3.05 - 2.97 (m, 4H), 2.78 (t, J = 5.9 Hz, 4H), 2.58 (t, J = 5.6 Hz, 4H), 1.98 - 1.90 (m, 4H), 1.80 - 1.72 (m, 4H), 1.43 (s, 12H), 1.00 (t, J = 7.4 Hz, 6H). 13 C NMR (101 MHz, Chloroform-d) δ 159.5, 150.0, 142.1, 140.1, 135.0, 134.4, 131.1, 130.5, 130.1, 129.7, 129.5, 129.2, 129.1, 129.0, 128.7, 128.0, 127.0, 126.5, 122.0, 121.7, 109.1, 92.8, 47.4, 44.0, 28.7, 26.9, 16.7, 25.0, 22.5, 20.0, 11.7. MALDI-FT ICR MS: calculated for C 69 H 70 N2O[M] + 942.5488, found 942.5444.

[0089] (5) Synthesis of compound B1

[0090] In a Schlenk flask was added B1-(5) (0.02 mmol, 20 mg) and argon protection. The flask was added with super dry THF (2 mL) and cooled to 0 °C with ice water bath. Then phenyl magnesium bromide 1M (0.04 mmol, 40 μL) was added dropwise into the solution. Stirring at 800 rpm for 0.5 h in a low temperature reactor, 2 mL of methanol was added to quench the reaction. The remaining liquid was purified with alumina (300-400 mesh) chromatography (DCM:MeOH = 25:1) to obtain compound B1, black solid 0.004 mmol, 4.2 mg, separation yield 19.3%.

[0091] 1H NMR (400 MHz, Chloroform-d) δ 8.00 - 7.79 (m, 6H), 7.52 - 7.49 (m, 2H), 7.41 - 7.28 (m, 11H), 7.05 - 6.87 (m, 11H), 6.61 (d, J = 7.1 Hz, 2H), 6.17 (d, J = 14.2 Hz, 1H), 4.42 (t, J = 6.5 Hz, 3H), 3.00 - 2.65 (m, 9H), 2.08 - 1.98 (m, 8H), 1.91 - 1.82 (m, 4H), 1.41 (s, 12H), 1.03 (t, J = 7.3 Hz, 6H). MALDI-FT ICR MS: calculated for C 75 H 75 BrN2[M-Br] + 1003.5925, found 1003.5925, [M-2H-Br] + 1001.5768, found 1001.5726.

[0092] Example 2

[0093] This example provides a preparation of fluorescent dye B3, the compound structure and specific synthesis route are as follows:

[0094] (1) The same as B1-(2) in the synthesis of compound B1.

[0095] (2) Synthesis of compound B3-(3)

[0096] A mixture of B1-(2) (10 mmol, 3.8 g) and 2-chloro-1-formyl-3- (hydroxymethylene) cyclopentene (15 mmol, 2.4 g) was dissolved in a mixture of toluene (347 mmol, 37 mL) and acetic acid (209 mmol, 13 mL), stirred at room temperature for 12 h at a stirring rate of 800 rpm, and concentrated by rotary evaporation. The residual organic matter was purified by silica gel column chromatography (PE:EA = 9:1) to obtain compound B1-(3), red solid 1.6 mmol 636.2 mg, separation yield 16.3%.

[0097] 1H NMR (400 MHz, Chloroform-d) δ 10.01 (s, 1H), 8.02 (d, J = 8.5 Hz, 1H), 7.81 (d, J = 8.2 Hz, 1H), 7.76 (d, J = 8.7 Hz, 1H), 7.50 - 7.39 (m, 2H), 7.31 - 7.26 (m, 1H), 7.08 (d, J = 8.7 Hz, 1H), 5.31 (d, J = 12.9 Hz, 1H), 3.75 (t, J = 6.2 Hz, 2H), 2.80 - 2.73 (m, 4H), 1.94 (s, 6H), 1.84 - 1.77 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13 C NMR (101 MHz, Chloroform-d) δ 186.7, 162.5, 149.4, 141.8, 135.6, 133.9, 130.0, 129.8, 129.6, 129.2, 129.0, 126.9, 125.0, 122.7, 121.7, 109.4, 93.4, 48.4, 27.6, 26.2, 24.9, 20.0, 11.7. HRMS: calculated for C 25 H 26 ClNO[M+H] + 392.1776, found 392.1776.

[0098] Synthesis of compound B3-(4)

[0099] A mixture of B1-(3) (0.5 mmol, 200 mg), 4-methoxybenzeneboronic acid (1 mmol, 152 mg), K2CO3 (1 mmol, 138 mg) and Pd(PPh3)4 (0.2 mmol, 231 mg) was added to a Schlenk flask, which was protected by argon. Dry DMF (0.1 mmol, 8.5 mL) and deionized water 0.08 (mmol, 1.5 mL) were added to the flask, which was stirred at 90 °C for 24 h at a stirring rate of 800 rpm. After cooling to room temperature, the reaction mixture was poured into brine and extracted with ethyl acetate. The combined organic layers were dried over Na2SO4, filtered and concentrated in vacuo. Purification by silica gel flash chromatography (PE:EA = 6:1) gave compound B3-(4) as a red solid, 0.39 mmol, 179 mg, in a separation yield of 77.4%

[0100] 1H NMR (400 MHz, Chloroform-d) δ 9.57 (s, 1H), 7.92 (d, J = 8.6 Hz, 1H), 7.77 (d, J = 8.2 Hz, 1H), 7.71 (d, J = 8.7 Hz, 1H), 7.44 - 7.37 (m, 1H), 7.31 (d, J = 8.6 Hz, 2H), 7.25 - 7.20 (m, 1H), 7.06 - 7.00 (m, 3H), 6.94 (d, J = 12.8 Hz, 1H), 5.38 (d, J = 12.8 Hz, 1H), 3.92 (s, 3H), 3.70 (t, J = 7.2 Hz, 2H), 2.89 - 2.80 (m, 4H), 1.83 - 1.74 (m, 2H), 1.71 (s, 6H), 1.01 (t, J = 7.4 Hz, 3H). 13 C NMR (101 MHz, Chloroform-d) δ 189.6, 162.4, 160.9, 160.0, 142.0, 140.5, 140.0, 131.0, 129.8, 129.7, 129.4, 129.0, 128,7, 126.7, 126.2, 125.4, 122.3, 121.6, 116.1, 114.8, 113.8, 109.3, 94.2, 55.4, 47.8, 44.0, 27.7, 27.2, 26.5, 20.0, 11.7. MALDI-FT ICR MS: calculated for C 32 H 33 NO2[M] + 463.2511, found 463.2495.

[0101] Synthesis of compound B3-(5)

[0102] A mixture of B3-(4) (0.1 mmol, 46 mg), cyclopentanone (0.05 mmol, 4.5 μL) and NaOH (0.2 mmol, 8 mg) was added in a round bottom flask. Ethanol (1 mL) was added in the flask, stirred at 80 °C for 48 h at a stirring rate of 800 rpm, after cooling to room temperature, the reaction mixture was filtered, washed with ethanol to give compound B3-(5) as a blue solid, 0.04 mmol, 41 mg, isolated yield 85%.

[0103] 1H NMR (400 MHz, Chloroform-d) δ 7.90 (d, J = 8.5 Hz, 2H), 7.74 (d, J = 8.1 Hz, 2H), 7.67 (d, J = 8.7 Hz, 2H), 7.41 - 7.35 (m, 2H), 7.22 - 7.15 (m, 6H), 7.05 - 6.87 (m, 8H), 6.68 (d, J = 12.6 Hz, 2H), 5.36 (d, J = 11.8 Hz, 2H), 3.94 - 3.85 (m, 6H), 3.70 - 3.62 (m, 4H), 3.17 - 2.99 (m, 4H), 2.90 - 2.78 (m, 4H), 1.82 - 1.73 (m, 16H), 1.00 (t, J = 7.4 Hz, 6H). MALDI-FT ICR MS: calculated for C 69 H 70 N2O3[M] + 974.5386, found 974.5343.

[0104] (5) Synthesis of compound B3

[0105] B3-(5) (0.02 mmol, 20 mg) was added to a Schlenk flask, which was protected by argon. The flask was added with super dry THF (2 mL), and cooled to 0 °C in an ice water bath. Then 1 M 4-methoxyphenyl magnesium bromide (0.2 mmol, 0.2 mL) was added dropwise into the solution. The reaction was stirred in a low temperature reactor for 0.5 h at a stirring rate of 800 rpm, and 2 mL of methanol was added to quench the reaction. Compound 4c was obtained by purification with basic alumina 300-400 mesh column chromatography (DCM:MeOH = 25:1), as a black solid (0.009 mmol, 9.7 mg), with a separation yield of 41.2%.

[0106] 1 H NMR (400 MHz, Chloroform-d) δ 7.98 - 7.77 (m, 6H), 7.49 - 7.30 (m, 6H), 7.15 - 7.08 (m, 4H), 6.95 - 6.88 (m, 8H), 6.82 - 6.75 (m, 4H), 6.68 - 6.64 (m, 1H), 6.07 (d, J = 13.8 Hz, 1H), 4.69 - 4.12 (m, 4H), 3.75 - 3.60 (m, 9H), 3.25 - 3.00 (m, 8H), 2.05 - 1.78 (m, 8H), 1.67 (s, 12H), 0.97 (t, J = 7.2 Hz, 6H). MALDI-FT ICR MS: calculated for C 66 H 67 BrN2O3[M-Br]+ 1065.5929, found 1065.5929, [M-2H-Br] + 1063.5772, found 1063.5616.

[0107] Example 3

[0108] This example provides a preparation of fluorescent dye B13, the compound structure and specific synthetic route are as follows:

[0109] (1) The same as in the synthesis of compound B1-(2) and B1.

[0110] (2) The same as in the synthesis of compound B3-(3) and B3.

[0111] (3) Synthesis of compound B13-(4)

[0112] A mixture of B3-(3) (0.5 mmol, 197 mg), phenylboronic acid (1 mmol, 122 mg), K2CO3, (1 mmol, 138 mg) and Pd(PPh3)4(0.05 mmol, 50 mg) was added to a Schlenk flask under argon protection. Dry DMF (0.05 mmol, 4 mL) and deionized water (0.04 mmol, 0.8 mL) were added to the flask, stirred at 90°C for 24 h at a stirring rate of 800 rpm, cooled to room temperature, and then the reaction mixture was poured into brine and extracted with ethyl acetate. The organic phase was dried over Na2SO4, filtered, and concentrated by rotary evaporation. The resulting organic matter was purified by column chromatography on silica gel (PE:EA = 6:1) to obtain compound B13-(4), red solid 0.45 mmol, 197 mg, separation yield 90.9%.

[0113] 1 H NMR (400 MHz, Chloroform-d) δ 9.55 (s, 1H), 7.90 (d, J = 8.4 Hz, 1H), 7.77 (d, J = 8.4 Hz, 1H), 7.71 (d, J = 8.8 Hz, 1H), 7.53 - 7.44 (m, 3H), 7.42 - 7.33 (m, 3H), 7.25 - 7.20 (m, 1H), 7.03 (d, J = 8.7 Hz, 1H), 6.88 (d, J = 12.1 Hz, 1H), 5.37 (d, J = 13.1 Hz, 1H), 3.69 (t, J = 6.7 Hz, 2H), 2.92 - 2.81 (m, 4H), 1.83 - 1.72 (m, 2H), 1.68 (s, 6H), 1.01 (t, J = 6.8 Hz, 3H). 13C NMR (101 MHz, Chloroform-d) δ 189.6, 163.0, 161.2, 141.9, 140.5, 140.2, 133.3, 129.8, 129.8, 129.7, 129.6, 129.5, 128.9, 128.8, 128.7, 128.3, 126.7, 126.6, 122.4, 121.6, 115.4, 109.3, 94.2, 47.9, 44.0, 27.8, 27.2, 26.5, 11.7. HRMS: calculated for C 31 H 31 NO[M+H] + 434.2478, found 434.2494.

[0114] (4) Synthesis of compound B13-(5)

[0115] A mixture of B13-(4) 0.2 mmol, 87 mg, cyclopentanone, 0.1 mmol, 8.9 μL, and NaOH, 4 mmol, 32 mg was added in a round bottom flask. Ethanol 2 mL was added in the flask, stirred at 80 °C for 48 h at a stirring rate of 800 rpm, after cooling to room temperature, the reaction mixture was filtered, washed with ethanol to give compound B13-(5), blue solid 0.08 mmol, 76 mg, isolated yield 83%.

[0116] 1 H NMR (400 MHz, Chloroform-d) δ 7.89 (d, J = 9.0 Hz, 2H), 7.74 (d, J = 8.1 Hz, 2H), 7.67 (d, J = 8.7 Hz, 2H), 7.46 - 7.33 (m, 8H), 7.25 - 7.14 (m, 8H), 6.99 (d, J = 8.8 Hz, 2H), 6.62 (d, J = 12.6 Hz, 2H), 5.35 (d, J = 11.4 Hz, 2H), 3.75 - 3.58 (m, 4H), 3.21 - 2.97 (m, 8H), 2.94 - 2.77 (m, 4H), 1.80 - 1.72 (m, 4H), 1.68 (s, 12H), 1.00 (t, J = 7.4 Hz, 6H). MALDI-FT ICR MS: calculated for C 67 H 66 N2O[M] + 914.5175, found 914.5050.

[0117] (5) Synthesis of compound B13

[0118] B13-(5), 0.01 mmol, 9 mg was added into a Schlenk flask, which was protected by argon. The flask was cooled to 0 °C with an ice-water bath. Then phenylmagnesium bromide 1 M (0.2 mmol, 0.2 mL) was added dropwise into the solution. The mixture was stirred in the ice-water bath for 0.5 h at a stirring rate of 800 rpm. Methanol 2 mL was added to quench the reaction. The resulting organic matter was purified by column chromatography (DCM:MeOH = 25:1) with basic alumina (300-400 mesh) to obtain compound 4 mg, black solid (0.004 mmol, 4.0 mg), with a separation yield of 41.0%. The obtained solid was dissolved in acetonitrile, and sodium tetraphenylborate (0.2 mmol, 68 mg) was added. The mixture was stirred at room temperature for 5 h at a stirring rate of 800 rpm. The resulting organic matter was purified by column chromatography (DCM:MeOH 99:1) with basic alumina (300-400 mesh) to obtain compound B13, 2.4 mg, black solid (0.002 mmol, 2.4 mg), with a separation yield of 46.3%.

[0119] 1 H NMR (400 MHz, Chloroform-d) δ 7.96 - 7.92 (m, 2H), 7.90 - 7.81 (m, 4H), 7.49 - 7.39 (m, 13H), 7.08 - 6.99 (m, 10H), 6.89 - 6.82 (m, 3H), 5.84 (d, J = 14.0 Hz, 1H), 3.79 (t, J = 7.2 Hz, 2H), 3.67 (t, J = 6.8 Hz, 2H), 3.49 - 2.88 (m, 8H), 1.79 - 1.62 (m, 20H), 0.91 (t, J = 7.2 Hz, 6H). HRMS: calculated for C 73 H 71 BrN2[M-Br] + 975.5612, found 975.5620.

[0120] Example 4

[0121] This example provides a preparation of fluorescent dye B7, the compound structure formula and specific synthesis route are as follows:

[0122] (1) The same as in the synthesis of compound B1-(2) and B1.

[0123] (2) The same as in the synthesis of compound B3-(3) and B3.

[0124] (3) The same as in the synthesis of compound B13-(4) and B13.

[0125] (4) The synthesis of compound B13-(5) is the same as B13.

[0126] (5) The synthesis of compound B7

[0127] B13-(5) (0.01 mmol, 9 mg) was added into a Schlenk flask, which was protected by argon. Ultradry THF (200 mmol, 2 mL) was added into the flask, which was cooled to 0 °C in an ice-water bath. Then phenylmagnesium bromide 1 M (0.2 mmol, 0.2 mL) was added dropwise into the solution. The stirring rate was 800 rpm in the ice-water bath. Methanol 2 mL was added to quench the reaction. The resulting organic matter was purified by column chromatography (300-400 mesh) with basic alumina (DCM:MeOH = 25:1) to obtain compound B7, 4 mg, black solid (0.004 mmol, 4.0 mg), with a separation yield of 41.0%.

[0128] 1 H NMR (400 MHz, Chloroform-d) δ 7.96 - 7.92 (m, 2H), 7.90 - 7.81 (m, 4H), 7.49 - 7.39 (m, 13H), 7.08 - 6.99 (m, 10H), 6.89 - 6.82 (m, 3H), 5.84 (d, J = 14.0 Hz, 1H), 3.79 (t, J = 7.2 Hz, 2H), 3.67 (t, J = 6.8 Hz, 2H), 3.49 - 2.88 (m, 8H), 1.79 - 1.62 (m, 20H), 0.91 (t, J = 7.2 Hz, 6H). HRMS: calculated for C 73 H 71 BrN2[M-Br] + 975.5612, found 975.5620.

[0129] The preparation method of B2, B4-B12 in general formula A dyes B1-B12 is basically the same as the reaction condition of example 1, and the difference lies in the corresponding reactants used.

[0130] The preparation method of general formula A dyes B13-B14 is basically the same as the reaction condition of example 3, and the difference lies in the corresponding reactants used.

[0131] Test example

[0132] The general formula A dyes B1-B10 prepared in the above examples were respectively prepared into a DCM solution with a concentration of 1 x 10 -5 M, and the ultraviolet-visible-near infrared absorption spectrum and fluorescence emission spectrum were scanned and drawn, as shown in FIG. 1. The related optical physical properties are shown in Table 1. It can be seen that the maximum absorption wavelength (λabs ) between 1100-1300 nm, the maximum emission wavelength (λ em ) between 1150-1300 nm, the molar extinction coefficient (ε) is 4.8 x 10 4 -2.6 x 10 5 M -1 cm -1 , the brightness is between 4.8-115.1 M -1 cm -1 , and the fluorescence quantum yield (Φ) is high.

[0133] Photophysical data of the dyes in Table 1 Part A.

[0134] The dye B3 and B7 of general formula A prepared in the above examples and ICG (indocyanine green) were respectively prepared into a PBS solution with a concentration of 0.15 mM. The chemical luminescence fluorescence imaging analysis system was used to obtain the fluorescence imaging test photos under different long-pass filters LP1300 and LP1500. As shown in FIG. 2, the brightness of B3 and B7 under LP1300 was 5.1 and 4.1 times that of ICG with the same concentration. The brightness of B3 and B7 under LP1500 was 9.6 and 5.1 times that of ICG with the same concentration.

[0135] The dye B3 of general formula A prepared in the above examples was respectively prepared into a PBS solution of nanoparticles with a concentration of 0-150 μM. 4T1 cells, 8000 cells / well, were incubated with B3 material for 12 hours. The survival rate of 4T1 cells is shown in FIG. 3. As shown in FIG. 3, the B3 nanoparticles had no obvious cytotoxicity at a concentration of 150 μM.

[0136] The dye B3 of general formula A prepared in the above examples was prepared into a PBS solution with a concentration of 0.15 mM. The NIR-IIb imaging of the hind limb blood vessels of a Balb / c-nude mouse is shown in FIG. 4. As shown in FIG. 4, the B3 nanoparticles can clearly distinguish the femoral artery, vein and multiple calf blood vessels, and the signal-to-background ratio can reach 6.8.

[0137] The NIR-II vascular imaging of a mouse using the dye B3 of general formula A prepared in the above examples is shown in FIG. 5. As shown in FIG. 5, B3 can clearly distinguish the thoracic and abdominal blood vessels of a mouse.

[0138] The NIR-II tumor imaging of a mouse using the dye B3 of general formula A prepared in the above examples is shown in FIG. 6. As shown in FIG. 6, B3 is enriched in the orthotopic breast tumor of a mouse, and the tumor background signal ratio with normal tissue can reach 4.8.

[0139] The foregoing description of specific embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed, and various modifications and variations are possible in light of the above teachings. It is intended that the application embrace all alternatives, modifications and variations as can befall within the scope of the description.

Claims

1. A near-infrared small-molecule fluorescent dye having a fifteen-methine-conjugated chain, characterized in that, The small molecule fluorescent dye includes one or more of a structure represented by general formula A, a solvate of the structure represented by general formula A, the general formula A being as follows: In the formula: R1, R2are each independently selected from C1-C6 alkyl, aromatic ring and substituted aromatic ring, chlorine atom; R3is independently selected from C1-C6 alkyl, C1-C6 terminal alkyne, C1-C6 sulfonic acid group substituted alkane; n is independently selected from 1 or 2; X is independently selected from bromine atom, tetraphenylboric acid, tetra(pentafluorophenyl)boric acid.

2. The near-infrared small molecule dye having a fifteen-methine conjugated chain according to claim 1, characterized in that, The maximum absorption wavelength of the near-infrared small molecule dye is between 1100-1300nm, the maximum emission wavelength is between 1150-1300nm, and the molecular weight is between 700-1300Da; The near infrared small molecule dye has a brightness of 4.8-115.1M -1 cm -1 , a molar extinction coefficient of 4.8x10 4 -2.6x10 5 M -1 cm -1 .

3. The near-infrared small molecule dye having a fifteen-methine conjugated chain according to claim 1, characterized in that, The structure of the small molecule fluorescent dye is any one of the following formulas B1-B14:

4. A process for the preparation of a near infrared small molecule dye having a fifteen-methine conjugated chain according to any one of claims 1 to 3, characterized in that, It comprises the following steps: Step one, the compound represented by formula (1) is coupled with halide or sulfonic acid lactone compound to obtain the compound represented by formula (2); Step two, the compound represented by formula (2) is subjected to dehydration condensation reaction with aldehyde compound to obtain the compound represented by formula (3); Step three, the compound represented by formula (3) is subjected to Suzuki coupling reaction to obtain the compound represented by formula (4); Step four, the compound represented by formula (3) or formula (4) is subjected to Knoevenagel condensation reaction with cyclopentanone to obtain the compound represented by formula (5); Step five, the compound represented by formula (5) is subjected to nucleophilic addition reaction under the action of lithium reagent or Grignard reagent to obtain the compound represented by general formula A or further subjected to reaction with corresponding anion salt to obtain the compound represented by general formula A; wherein formula (1) is Formula (2) is Formula (3) is Formula (4) is Formula (5) is 5. The method for preparing a near-infrared small molecule dye with a pentadecylamine conjugated chain according to claim 4, characterized in that, In step one, the compound represented by formula (1) is coupled with halide or sulfonic acid lactone compound to obtain the compound represented by formula (2), which comprises the following process: In a first organic solvent environment, the compound represented by formula (1) is heated and stirred with halide or the compound represented by formula (1) is heated and stirred with sulfonic acid lactone compound to obtain the compound represented by formula (2); The halide or sultone compound has any of the structures shown in Formulas CI, C2, C3: In formula C1-C3: R3is independently selected from C1-C6 alkyl, C1-C6 terminal alkyne; The first organic solvent is selected from one or more of benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, diethyl ether, 1,4-dioxane, glacial acetic acid.

6. The method for preparing a near-infrared small molecule dye with a pentadecylamine conjugated chain according to claim 4, characterized in that, In step two, the compound represented by formula (2) is subjected to dehydration condensation reaction with aldehyde compound to obtain the compound represented by formula (3), which comprises the following process: In a second organic solvent environment, the compound represented by formula (2) is stirred with aldehyde compound to obtain the compound represented by formula (3); The aldehyde compound has any one of the structures shown in the following Formula D1 and D2: The second organic solvent is selected from one or more of benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, tetrahydrofuran, diethyl ether, 1,4-dioxane, ethanol, methanol.

7. The method for preparing a near-infrared small molecule dye with a pentadecylamine conjugated chain according to claim 4, characterized in that, In step three, the compound represented by formula (3) is subjected to Suzuki coupling reaction to obtain the compound represented by formula (4), which comprises the following process: In a third organic solvent environment, the compound represented by formula (3) is heated and stirred with boric acid compound under the protection of inert gas, using palladium catalyst and base as catalyst to obtain the compound represented by formula (4) through Suzuki coupling reaction; The boronic acid compound has the following structure as shown in Formula E: In the formula: R1is each independently selected from C1-C6 alkyl, aromatic ring and substituted aromatic ring; The palladium catalyst is selected from one or more of tetraphenylphosphine palladium, tris(dibenzylideneacetone)dipalladium, bis(dibenzylideneacetone)palladium, palladium acetate; The base is selected from one or more of potassium tert-butoxide, sodium tert-butoxide, potassium carbonate, cesium carbonate, potassium phosphate; The third organic solvent is selected from one or more of benzene, toluene, xylene, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, diethyl ether.

8. The method for preparing a near-infrared small molecule dye with a pentadecylamine conjugated chain according to claim 4, characterized in that, In step four, the compound shown as formula (3) or formula (4) is subjected to Knoevenagel condensation reaction with cyclopentanone to obtain the compound shown as formula (5), including the following process: In the fourth organic solvent environment, the compound shown as formula (3) or formula (4) is heated and stirred with cyclopentanone and a base as a catalyst to obtain the compound shown as formula (5) through Knoevenagel condensation reaction; The base is selected from one or more of sodium hydroxide, sodium tert-butoxide, sodium ethoxide, potassium hydroxide; The fourth organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, 1,4-dioxane, ethanol, methanol.

9. The method for preparing a near-infrared small molecule dye with a pentadecylamine conjugated chain according to claim 4, characterized in that, In step five, the compound shown as formula (5) is subjected to nucleophilic addition reaction under the action of a lithium reagent or a Grignard reagent to obtain the compound shown as general formula A or further react with a corresponding anion salt to obtain the compound shown as general formula A, including the following process: In the fifth organic solvent environment, under the protection of inert gas, the compound shown as formula (5) is reacted with a lithium reagent or a Grignard reagent at low temperature to obtain the compound shown as general formula A through nucleophilic addition reaction or further exchange anion with a corresponding anion salt to obtain the compound shown as general formula A; The lithium reagent or Grignard reagent has a structure represented by any one of the following formulas F1 and F2: In the formula: R2 is independently selected from C1-C6 alkyl, aromatic ring and substituted aromatic ring; The anion salt is selected from one or more of sodium tetraphenylborate, potassium tetra(pentafluorophenyl)borate; The fifth organic solvent is selected from one or more of super-dry tetrahydrofuran, diethyl ether, 1,4-dioxane.

10. Use of a near-infrared small dye having a fifteen-methine conjugated chain according to any one of claims 1 to 3 or a near-infrared small dye having a fifteen-methine conjugated chain prepared by the production method according to any one of claims 4 to 9, characterized in that, The near-infrared small molecule dye is used for tumor targeting imaging, in vivo blood vessel imaging and fluorescence imaging.

Images