Near-infrared aggregation-induced emission molecules, methods of making and using the same

Abstract

The application belongs to the technical field of fluorescent nanomaterials, and discloses a near-infrared aggregation-induced emission molecule with a structure shown in formula I and a quaternary ammonium salt structural derivative thereof. The luminescent molecule and the quaternary ammonium salt structural derivative show weak TICT type molecular luminescence in polar organic solvents such as DMSO, and show relatively strong near-infrared aggregation-induced fluorescence in an aggregation state such as an aqueous solution and a solid state, and can be used for preparing a fluorescent probe and a biological imaging reagent.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent nanomaterials technology, specifically relating to near-infrared aggregation-induced emission materials. Background Technology

[0002] In recent years, organic optoelectronic materials have shown rapid development in fields such as bioimaging, sensing, and display lighting devices (Chemical Reviews, 2016, 116(22), 13279-13412.). As the mainstream of luminescent materials (Angew ChemInt Ed, 2021, 60(28), 15335-15339.), traditional fluorescent molecules have rigid conjugated structures that result in π-π stacking interactions. Under aggregation or high concentrations, fluorescence weakens or even stops, a phenomenon known as "concentration quenching." This phenomenon greatly limits the application performance of fluorescent molecules in the field of organic optoelectronic materials. In 2001 and 2002, the research teams of Academician Tang Benzhong and Professor Park discovered aggregation-induced emission (AIE) (Chemical Communications, 2001, 1740-1741; Journal of the American Chemical Society, 2002, 124(48), 14410-14415.) and aggregation-induced enhanced emission (AIEE). Fluorescent molecules with the above properties can emit stronger fluorescence in aggregated states (amorphous or crystalline) than in molecular states, thus overcoming the adverse effects of concentration quenching.

[0003] In recent years, fluorescent molecules exhibiting aggregation-induced emission (AIE) have attracted considerable attention due to their wide applications in fluorescent probes (Accounts of Chemical Research, 2019, 52(9):2559-2570.) and bioimaging (Advanced Science News, 2019, 6(8):1801615.). Compared to visible light, long-wavelength near-infrared light offers advantages such as less photodamage to cells, lower scattering, stronger light penetration, and better separation from media autofluorescence, leading to its wider application in bioprobes and imaging. Therefore, AIE-active molecules emitting in the near-infrared region are ideal candidates for biological applications.

[0004] Most of the near-infrared AIE molecules that have been developed so far are TICT-type molecules based on the triphenylamine series. Compared with the types of AIE molecules in the visible light region, the development of near-infrared AIE molecules is still an important challenge (Chemistry An Asian Journal, 2017, 12(16): 2134-2138.).

[0005] Currently developed naphthalimide fluorescent dyes are mostly obtained by introducing single or double electron-donating substituents (such as N, O, P, etc.) of different intensities into their 3, 4 and 5 positions to obtain naphthalimide derivatives that emit yellow-green to red light (ACS Sensors, 2019, 4(5), 1409-1416; Advanced Science, 2018, 5(1), 1700552.).

[0006] However, with the enhancement of the electron-donating group, the resulting naphthalimide derivatives exhibit twisted intramolecular charge transfer (TICT) properties, which greatly quench the fluorescence quantum efficiency of the molecules in polar solvents and aggregated states. For example, the naphthalimide molecule obtained by introducing a diphenylamine group at the 4-position emits red light at 612 nm in acetonitrile, but the quantum efficiency is only 1% (Chemistry–A European Journal, 2023, e202301597).

[0007] Further modulating the fluorescence of naphthalimide molecules into the near-infrared region (>650 nm) while maintaining their strong fluorescence quantum efficiency can provide an excellent photofunctional molecular platform for probing the microenvironment of biological systems.

[0008] At present, the design strategies for near-infrared emitting naphthalene imide compounds are mostly of two types: 1) introducing fused and indole onto the aromatic ring of naphthalene imide (J. Mater. Chem. B, 2017, 5(13), 2436-2444.); 2) introducing hemine units at the 4-position of naphthalene imide through two methods of double bond connection (Dyes and Pigments, 2022, 206, 110619.).

[0009] The strategies described above resulted in either increased planarity of the aromatic rings or increased flexibility of the conjugated units in the obtained fluorescent molecules, leading to lower fluorescence quantum efficiency while achieving near-infrared fluorescence.

[0010] Therefore, developing near-infrared AIE molecules with aggregation-induced emission properties in the aggregated state, and developing near-infrared naphthalimide fluorescent materials with high quantum efficiency in this state, is of great technological significance. Summary of the Invention

[0011] The purpose of this invention is to provide a near-infrared aggregation-induced emission molecule and its derivatives with quaternary ammonium salt side chains. This invention also provides methods for preparing the above-mentioned near-infrared aggregation-induced emission molecule and its derivatives, as well as their applications.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] A near-infrared aggregation-induced emission molecule, the molecular structure of which is shown in Formula I:

[0014]

[0015] The preparation method of the above-mentioned near-infrared aggregation-induced emission molecules follows the reaction route shown in Formula II.

[0016]

[0017] The preparation method includes the following steps:

[0018] A Suzuki coupling reaction was carried out on a 4-boronate-1,8-naphthalimide derivative (NI-B) and 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline (TBZ-TPA-Br) to yield the near-infrared aggregation-induced emission molecule 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-hydroxyphenyl)-1,8-naphthalimide (J2). The catalysts used in the Suzuki coupling reaction were tetrakis(triphenylphosphine)palladium and potassium carbonate.

[0019] The molar ratio of 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline (TBZ-TPA-Br) to 4-boronate-1,8-naphthalimide derivative (NI-B) is 1:1-1.5, preferably 1:1.1-1.3; the molar ratio of 4-boronate-1,8-naphthalimide derivative (NI-B), tetrakis(triphenylphosphine)palladium and potassium carbonate is 1:0.01-0.06:4-6.

[0020] The 4-boronate-1,8-naphthalimide derivative (NI-B) is prepared by a Suzuki coupling reaction of bis(pinacol)boronate and 4-bromo-1,8-naphthalimide derivative (NI-Br); further, the catalyst used for the Suzuki coupling reaction is [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride and potassium acetate.

[0021] The molar ratio of 4-bromo-1,8-naphthylimide derivative (NI-Br) to bis-pinacol borate ester is 1:1.5-2.5, more preferably 1:2; the molar ratio of 4-bromo-1,8-naphthylimide derivative (NI-Br) to [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride and potassium acetate is 1:0.01-0.05:2-4.

[0022] Triphenylamine boric acid and 4,7-dibromo-2,1,3-benzothiadiazole undergo a Suzuki coupling reaction to yield 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline (TBZ-TPA-Br). The catalysts used are tetra(triphenylphosphine)palladium and potassium carbonate.

[0023] The molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to triphenylamine boric acid is 1:1-2, preferably 1:1.3-1.5; the molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to tetra(triphenylphosphine)palladium and potassium carbonate is 1:0.01-0.05:4-6.

[0024] The reaction pathway described above is shown in Equation II.

[0025] Furthermore, the catalysts used in the Suzuki coupling reaction in step (3) are tetra(triphenylphosphine)palladium and potassium carbonate.

[0026] Further, in step (3), the molar ratio of 4-boronate-1,8-naphthylimide derivative (NI-B), 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline (TBZ-TPA-Br), tetra(triphenylphosphine)palladium, and potassium carbonate is (15-30):(10-20):1:(75-115).

[0027] A near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure, the general molecular formula of which is shown in Formula III:

[0028]

[0029] Where n is any even value from 2 to 10, including 2 and 10; m is any value from 0 to 3, including 0 and 3.

[0030] The preparation method of the above-mentioned near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures follows the reaction route shown in Formula IV:

[0031]

[0032] The preparation method includes the following steps:

[0033] (1) Near-infrared aggregation-induced emission molecule (J2) and Br-(CH2) n The -Br dibromoalkane undergoes a substitution reaction, where n is any even number from 2 to 10, to give 4-(7-(4-diphenylaminophenyl)benzothiadiazol-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide (referred to as J2-R). x -Br);

[0034] (2) The 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide prepared in step (1) is reacted with tertiary amine compounds to obtain the target product, a near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure. The tertiary amine compound is one of trimethylamine, triethylamine, tripropylamine, and tributylamine.

[0035] Furthermore, the substitution reaction in step (1) is carried out in a reaction environment with the addition of cesium carbonate and potassium hydroxide.

[0036] Further, in step (1), the molar ratio of 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-hydroxyphenyl)-1,8-naphthalimide (J2) and dibromoalkane is 1:1-6, preferably 1:3-5; the molar ratio of 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-hydroxyphenyl)-1,8-naphthalimide (J2), cesium carbonate and potassium hydroxide is 1:0.5-1:1:1.5-3.

[0037] Further, in step (2), an excess of a tertiary amine compound is used, preferably 4-(7-(4-diphenylaminophenyl)benzothiadiazol-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide (J2-R) x The molar ratio of -Br) to tertiary amine compounds is 1:(1-100).

[0038] Depending on the cost, increasing the amount of tertiary amine compounds can improve the yield, ensure the complete reaction of dye intermediates, reduce costs, and simplify subsequent processing.

[0039] The aforementioned near-infrared aggregation-induced emission molecules or near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures can obtain near-infrared fluorescence. They exhibit weak TICT-type molecular luminescence in polar organic solvents such as DMSO, and strong near-infrared aggregation-induced fluorescence in aggregated states such as aqueous solutions and solids. They can be used to prepare fluorescent probes.

[0040] The aforementioned near-infrared aggregation-induced luminescent molecules or near-infrared aggregation-induced luminescent molecules containing quaternary ammonium salt structures can be used for bioimaging and for preparing bioimaging reagents.

[0041] The beneficial effects of this invention are as follows:

[0042] (1) The near-infrared aggregation-induced emission molecule or near-infrared aggregation-induced emission molecule containing quaternary ammonium salt structure of the present invention uses naphthalimide as an acceptor, and introduces benzothiadiazole as a π bridge and a second acceptor to enhance the molecule's electron-withdrawing ability and extend the delocalization range of π electrons. It uses rotor-type building block triphenylamine as an electron donor and connects the above three building blocks through single bonds to construct a non-planar molecule with a suitable degree of twist between the electron donor and acceptor, thereby realizing near-infrared emission of the molecule. At the same time, it ensures that the molecule forms a certain dihedral angle in the aggregated state, destroys the π-π stacking between molecules, and realizes aggregation-induced emission.

[0043] (2) Near-infrared aggregation-induced emission molecules or near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures exhibit weak TICT-type molecular luminescence in polar organic solvents such as DMSO, and exhibit strong near-infrared aggregation-induced fluorescence in aggregated states such as aqueous solution and solid.

[0044] (3) Near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures have a quantum efficiency of up to 3.28% in water (using NITPA2 in aqueous solution as a reference, φ = 0.6), and the emission peak is located near 680 nm;

[0045] (4) Near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures have their hydrophilic and hydrophobic properties regulated by introducing quaternary ammonium salt side chains with alkyl chains of different lengths, thus constructing AIE nanomaterials with tunable aggregation state and luminescence properties and good aqueous dispersibility. The added quaternary ammonium salt structure has a certain degree of hydrophilicity and enhances compatibility with cells, which is beneficial for cell imaging.

[0046] (5) The preparation method of the present invention has the characteristics of simple synthesis, mild reaction conditions, easy preparation of nano-aggregates, good luminescence performance in aggregated state, and large Stokes shift. Attached Figure Description

[0047] Figure 1 The fluorescence emission spectra (A) and fluorescence emission intensity ratio graph (B) of compound J2 in dimethyl sulfoxide solutions with water content of 0%-99% are shown.

[0048] Figure 2 The fluorescence emission spectrum (A) and fluorescence emission intensity ratio broken line graph (B) of compound J2-R2-TR2A in dimethyl sulfoxide solution with water content of 0%-99% are shown.

[0049] Figure 3 For compound NI-B 1 H NMR spectrum;

[0050] Figure 4 For compound TBZ-TPA-Br 1 H NMR spectrum;

[0051] Figure 5 For compound J2 1 H NMR spectrum;

[0052] Figure 6 For compound J2-R2-Br 1 H NMR spectrum;

[0053] Figure 7 Compound J2-R 2- TR2A 1 H NMR spectrum;

[0054] Figure 8 For compound J2 13 C NMR spectrum;

[0055] Figure 9 For compound J2-R2-Br 13 C NMR spectrum;

[0056] Figure 10 Compound J2-R 2- TR2A 13 C NMR spectrum;

[0057] Figure 11 This is the high-resolution mass spectrum of compound J2;

[0058] Figure 12 This is the high-resolution mass spectrum of compound J2-R2-Br;

[0059] Figure 13 Compound J2-R 2- High-resolution mass spectrum of TR2A;

[0060] Figure 14 A fluorescence photograph of an aqueous solution of compound J2;

[0061] Figure 15 Compound J2-R 2- Fluorescence image of TR2A in aqueous solution;

[0062] Figure 16 Compound J2-R 2- SEM image of nanoaggregates prepared in TR2A aqueous solution;

[0063] Figure 17 Compound J2-R 2- Cellular imaging of TR2A. Detailed Implementation

[0064] Example 1: Synthesis method of NI-B

[0065]

[0066] 5 g of NI-Br (13.58 mmol), 6.90 g of bis-pinacolborate (27.16 mmol), 200 mg of Pd(dppf)Cl2 (273.34 μmol), and 4 g of potassium acetate (40.74 mmol) were dissolved in 1,4-dioxane (70 mL), and the mixture was stirred at 110 °C for 3 h under nitrogen protection. After cooling the reaction solution to room temperature, the reaction was quenched with water, and the crude product was obtained by filtration. The reaction mixture was purified by silica gel (ethyl acetate / dichloromethane = 1 / 10) column chromatography to give a pale yellow solid (3.40 g, yield 60.29%). 1 H NMR spectrum as shown Figure 3 .

[0067] 1 H NMR(400MHz,CHLOROFORM-d)δppm 1.48(s,12H),6.75(t,J=2.08Hz,1H),6.85-6.93(m,2H),7.40(t,J=8.07Hz,1H),7.83(dd,J= 8.44,7.34Hz,1H),8.34(d,J=7.21Hz,1H),8.61-8.68(m,2H),9.19(dd,J=8.50,1.04Hz,1H).

[0068] Example 2: Synthesis method of TBZ-TPA-Br

[0069]

[0070] 1 g of 4,7-dibromo-2,1,3-benzothiadiazole (3.40 mmol), 1.38 g of triphenylamine boric acid (4.76 mmol), 100 mg of Pd(PPh3)4 (86.54 μmol), and 2.35 g of K2CO3 (17.01 mmol) were dissolved in 25 mL of a tetrahydrofuran / water mixture (v / v = 40 / 10). The reaction mixture was reacted at 70 °C under a N2 atmosphere for 20 h. After cooling the reaction mixture to ambient temperature, tetrahydrofuran was removed by rotary evaporation. The mixture was then extracted with dichloromethane and water, and the organic layer was separated and dried over anhydrous Na2SO4. After evaporation of the solvent, the crude product was purified by column chromatography using petroleum ether / dichloromethane (8 / 1, v / v) as the eluent to give an orange solid TBZ-TPA-Br (1.08 g, yield 69.26%). 1 H NMR spectrum as shown Figure 4 .

[0071] 1H NMR(400MHz,CHLOROFORM-d)δppm 7.07-7.14(m,2H),7.17-7.25(m,6H),7.29-7.36(m,4H),7.57(d,J=7.70Hz,1H),7.83(d,J=8.56Hz,2H),7.92(d,J=7.58Hz,1H).

[0072] Synthesis method of Example 3J2

[0073]

[0074] 1 g TBZ-TPA-Br (2.18 mmol), 1.09 g NI-B (2.62 mmol), 150 mg Pd(PPh3)4 (129.8 μmol), and 1.81 g K2CO3 (13.09 mmol) were dissolved in 25 mL of a tetrahydrofuran / water mixture (v / v = 40 / 10). The reaction was carried out at 70 °C for 5 hours under a nitrogen atmosphere. After cooling the reaction mixture to ambient temperature, tetrahydrofuran was removed by rotary evaporation. The mixture was then extracted with dichloromethane and water, the organic layer was separated, and dried over anhydrous Na2SO4. After solvent evaporation, the crude product was purified by column chromatography using dichloromethane as eluent to give a red solid J2 (1.22 g, yield 83.87%). 1 H NMR spectrum and 13 The C NMR spectrum is as follows Figure 5 , 8 High-resolution mass spectra as follows Figure 11 .

[0075] 1 H NMR(400MHz,CHLOROFORM-d)δppm 6.79(t,J=1.96Hz,1H),6.90-6.97(m,2H),7.10-7.16(m,2H),7.21-7. 27(m,6H),7.32-7.38(m,4H),7.45(t,J=8.07Hz,1H),7.68-7.73(m,1H) ,7.80-7.84(m,1H),7.87-7.91(m,1H),7.97(dd,J=8.07,3.18Hz,3H),8.09(d,J=7.82Hz,1H),8.72(d,J=6.60Hz,1H),8.80(d,J=7.58Hz,1H).

[0076] 13C NMR(100MHz,CHLOROFORM-d)δppm 116.1,116.5,120.2,122.5,122.6,123,123.6,125.2,126.6,127,129,129.2,129.5,129.8,130,130.1,1 30.4,130.6,131,131.4,132,133.2,134.7,136,142.9,147.3,148.6,153.5,154.8,157.4,164.4,164.6.

[0077] HRMS[M] + m / z:Cald.666.1726;Found:666.1721.

[0078] Example 4

[0079]

[0080] 1 g J2 (1.50 mmol), 390 mg cesium carbonate (1.20 mmol), and 170 mg potassium hydroxide (3.03 mmol) were placed in a 100 mL two-necked flask. 1.30 g dibromobutane liquid (6.00 mmol) was added, dissolved in 45 mL DMF, and stirred at room temperature for 6 h. After the reaction was complete, water was added to quench the reaction, and the crude product was obtained by filtration. The crude product was then purified by silica gel column chromatography (200-300 mesh) using petroleum ether:dichloromethane eluent = 2:1 to obtain a red solid (950 mg, yield 79%). 1 H NMR spectrum and 13 The C NMR spectrum is as follows Figure 6 , 9 High-resolution mass spectra as follows Figure 12 .

[0081] 1H NMR(400MHz,CHLOROFORM-d)δppm 1.95-2.04(m,2H),2.07-2.16(m,2H),3.53(t,J=6.54Hz,2H),4.07(t,J=5.93Hz,2H),6.91(s,1H), 6.97(d,J=7.82Hz,1H),7.06(dd,J=8.38,2.14Hz,1H),7.10-7.15(m,2H),7.22-7.28(m,6H),7.32-7 .38(m,4H),7.50(t,J=8.13Hz,1H),7.72(t,J=7.89Hz,1H),7.82-7.86(m,1H),7.89-7.92(m,1H),7. 98(dd,J=7.95,4.52Hz,3H),8.11(d,J=8.44Hz,1H),8.72(d,J=7.09Hz,1H),8.81(d,J=7.46Hz,1H).

[0082] 13 C NMR(100MHz,CHLOROFORM-d)δppm 27.89,29.48,33.51,66.97,114.9,115.14,120.91,122.55,122.78,123.13,123.63,125.16,126.62,126.99,129.06,129.15,129.46,129.91,130.11,130.67,131.07,131.15,131.8,132.98,134.72,136.48,142.7,147.35,148.6,153.55,154.8,159.77,164.11,164.34.

[0083] HRMS[M] + m / z: Cald.800.1457; Found:800.1445.

[0084] Example 5

[0085]

[0086] J2-R2-Br (600 mg, 733.67 μmol) and 9 mL of excess triethylamine were dissolved in 18 mL of DMF, and the mixture was heated to 90 °C and stirred for 24 h. After the reaction was completed, diethyl ether was added, and a solid precipitated. The solid was filtered, and then dissolved in ethyl acetate. The insoluble residue was the desired product, which was filtered to give a red solid (400 mg, yield 60.38%). 1 H NMR spectrum and 13The C NMR spectrum is as follows Figure 7 , 10 High-resolution mass spectra as follows Figure 13 .

[0087] 1 H NMR(400MHz,CHLOROFORM-d)δppm 1.39(t,J=7.15Hz,9H),1.99(br.s.,4H),3.47(q,J=7.01Hz,8H),4.15(br.s.,2H),6.91(s,1H) ,6.95(d,J=8.07Hz,1H),7.07(d,J=8.07Hz,1H),7.11(t,J=7.34Hz,2H),7.27(br.s.,6H),7.31-

[0088] 7.36(m,4H),7.48(t,J=8.01Hz,1H),7.67(t,J=7.89Hz,1H),7.79-7.82(m,1H)7.88(d,J=7.21Hz,1 H),7.96(d,J=8.19Hz,3H),8.08(d,J=8.44Hz,1H),8.66(d,J=7.09Hz,1H),8.74(d,J=7.46Hz,1H).

[0089] 13 C NMR(100MHz,CHLOROFORM-d)δppm 8.1,19.2,26,57.3,58.4,67.1,114.9,115.4,121.3,122.5,122.9,123.6,125.2,126.6,127,129,129.2,129.4,129.7 ,130,130.1,130.3,130.6,131.1,131.7,133.1,134.7,136.6,142.8,147.3,148.6,153.5,154.7,159.4,164.1,164.3.

[0090] HRMS[M] + m / z: Cald.822.3473; Found:822.3463.

[0091] Example 6 Fluorescence Analysis

[0092] 1. Fluorescence analysis of near-infrared aggregation-induced emission molecules J2 fluorescence analysis

[0093] Fluorescence emission experiments of compound J2 in dimethyl sulfoxide solutions with a water content of 0%–99% were conducted, with an excitation wavelength of 476 nm and a slit width of 5 / 5 nm. The spectrum (A) and the fluorescence emission intensity ratio line graph (B) are shown below. Figure 1 As shown, the fluorescence image of the aqueous solution is as follows: Figure 14 As shown. Figure 1 In the middle (A) diagram, as the water content increases, the peak value first rises and then falls. Between 0-40% water content, J2 is in a molecular state with almost no emission. Between 40-60% water content, the fluorescence intensity increases sharply, indicating that J2 changes from a non-luminescent molecular state to a luminescent aggregated state. When the water content increases to above 60%, due to the excessive hydrophobicity of J2, the fluorescence intensity increases at higher f values. w The nucleation rate is faster at higher water content, resulting in smaller J2 aggregates and a gradual decrease in fluorescence. This indicates that compound J2 possesses aggregation-induced emission properties.

[0094] The enhancement of fluorescence intensity of J2 at 665 nm was plotted, as shown in the figure. Figure 1 (B) It can be found that when the water content in the DMSO-H2O mixture reaches 60%, the fluorescence intensity (I) of J2 is about 54 times stronger than its fluorescence intensity (I0) in pure DMSO solution.

[0095] 2. Fluorescence analysis of near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures

[0096] Fluorescence emission experiments of compound J2-R2-TR2A in dimethyl sulfoxide solutions with an water content of 0%–99% were conducted, with an excitation wavelength of 450 nm and a slit width of 5 / 5 nm. The spectrum (A) and the fluorescence emission intensity ratio line graph (B) are shown below. Figure 2 As shown, the fluorescence image of the aqueous solution is as follows: Figure 15 As shown. Figure 2 In the middle (A), as the water content increases, the peak value first increases (20-70%) and then decreases (70-99%). There is almost no emission in the water content range of 0-20%. In the range of 20-70%, the fluorescence intensity gradually increases. When the water content increases to more than 70%, the fluorescence gradually weakens due to the increase in the aggregate size of J2-R2-TR2A and the decrease in dispersibility. This indicates that the compound J2-R2-TR2A has aggregation-induced emission properties.

[0097] Example 7: Preparation of nanoscale dispersions of near-infrared aggregation-induced luminescent molecules containing quaternary ammonium salts

[0098] 1. First, dissolve 10 mg J2-R2-TR2A in 10 mL THF and stir until completely dissolved. After passing through a 0.22 μm polyethersulfone filter membrane, a completely dissolved stock solution with a concentration of 1 mg / mL is obtained.

[0099] 2. Add 10 mL of deionized water and a suitable-sized magnetic stir bar to a 25 mL beaker. Using a 1000 μL microsyringe, take 637 μL of the above stock solution and inject it into the vigorously stirred deionized water.

[0100] 3. Continue stirring the above mixed solution overnight at room temperature to obtain a red solution in which THF has completely evaporated.

[0101] 4. Filter the above solution through a 0.22μm water-soluble filter membrane to obtain J2-R. 2- TR2A nanoaggregate solution was used for subsequent experiments.

[0102] Compound J2-R 2- SEM images of nanoaggregates prepared in TR2A aqueous solution are shown below. Figure 16 As shown in the figure, the aggregates exhibit a uniformly dispersed spherical nanostructure with a particle size distribution around 50 nm. This demonstrates that uniformly sized nanoparticles can be prepared using a simple recrystallization method by controlling the side chains.

[0103] Example 8: Cell imaging experiment of compound J2-R2-TR2A

[0104] 1. Prepare a stock solution of J2-R2-TR2A (1 mmol / L).

[0105] 2. Take MCF-7 cells that have adhered for 24 hours, aspirate the culture medium, wash three times with PBS buffer, and add 2 mL of culture medium without fetal bovine serum. Then, add compound J2-R2-TR2A (2 μL) using a pipette, gently shake to mix, and incubate at 37°C for different times.

[0106] 3. Aspirate the culture medium from the above culture dish, rinse three times with PBS buffer to remove unstained dye adhering to the cells, add 2 mL of PBS buffer, and then place the dish under a laser confocal fluorescence microscope for imaging. The excitation wavelength of the laser confocal microscope should be set to 458 nm, and the collection channel to 600-700 nm.

[0107] Compound J2-R 2- Cellular imaging image of TR2A as shown Figure 17 As shown in the figure. The compound J2-R can be seen in the figure. 2- TR2A can enter cells, and noticeable fluorescence is visible after 2 hours of incubation. The fluorescence intensity increases with increasing incubation time. The added quaternary ammonium salt structure has a certain degree of hydrophilicity, enhancing its compatibility with cells and facilitating cell imaging.

[0108] Example 9: Detection and Analysis of Quantum Efficiency

[0109] The near-infrared aggregation-induced emission molecule J2-Rx-TRx'A containing a quaternary ammonium salt structure exhibits weak TICT-type molecular luminescence in polar organic solvents such as DMSO, but strong near-infrared aggregation-induced fluorescence in aggregated states such as aqueous solution and solid. With NITPA2 in aqueous solution as a reference, φ=0.6, the quantum efficiency in water can reach 3.28%, and the emission peak is located near 680nm.

[0110] The quantum efficiency is measured using the relative quantum efficiency method of a reference compound, and is calculated using the formula:

[0111] The fluorescence intensity (I / I) of the analyte and the reference (NITPA2) was obtained separately. R ) and absorbance (OD / OD R ), through the quantum efficiency (Q) of the reference material R ) Calculate the quantum efficiency Qn and nn of the measured object. R The solvent refractive indices of the two samples are shown in Table 1, as they are both water samples and thus cancel each other out. The measured quantum efficiency of the J2-Rx-TRx'A compound in water is shown in Table 1.

[0112]

[0113] Table 1

[0114] n m Quantum efficiency Φ 2 0 3.14％ 2 1 3.53％ 4 0 3.01％ 4 1 3.28％ 6 0 1.68％ 6 1 2.03％

Claims

1. A near-infrared aggregation-induced emission molecule, the molecular structure of which is shown in Formula I: Formula I.

2. The method for preparing near-infrared aggregation-induced emission molecules according to claim 1, characterized in that, step include: The 4-boronate-1,8-naphthalimide derivative shown in formula (B) and 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline were subjected to a Suzuki coupling reaction to obtain the near-infrared aggregation-induced emission molecule 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-hydroxyphenyl)-1,8-naphthalimide.

3. The method for preparing near-infrared aggregation-induced emission molecules according to claim 2, characterized in that, The bis-pinacol borate ester and the 4-bromo-1,8-naphthalimide derivative shown in formula (A) were subjected to a Suzuki coupling reaction to obtain the 4-boronate-1,8-naphthalimide derivative shown in formula (B).

4. The method for preparing near-infrared aggregation-induced emission molecules according to claim 2, characterized in that, Triphenylamine boric acid and 4,7-dibromo-2,1,3-benzothiadiazole undergo a Suzuki coupling reaction to yield 4-(7-bromobenzothiadiazole-4-yl)-N,N-diphenylaniline.

5. A near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure, the general molecular formula of which is shown in Formula III: Where n is any even number from 2 to 10; m is any integer from 0 to 3.

6. The method for preparing near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures according to claim 5, characterized in that, step include: (1) The near-infrared aggregation-induced emission molecule of claim 1 and the Br-(CH2) structural formula n The dibromoalkane of -Br undergoes a substitution reaction, where n is any even number from 2 to 10, to give 4-(7-(4-diphenylaminophenyl)benzothiadiazol-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide; (2) The 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide prepared in step (1) is reacted with tertiary amine compounds to obtain the target product, a near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure. The tertiary amine compound is one of trimethylamine, triethylamine, tripropylamine, and tributylamine.

7. The method for preparing near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures according to claim 6, characterized in that, Step (1) The substitution reaction is carried out in a reaction environment with the addition of cesium carbonate and potassium hydroxide, and the molar ratio of the near-infrared aggregation-induced luminescent molecule to the dibromoalkane described in claim 1 is 1:1-6.

8. The method for preparing near-infrared aggregation-induced emission molecules containing quaternary ammonium salt structures according to claim 6, characterized in that, In step (2), the molar ratio of 4-(7-(4-diphenylaminophenyl)benzothiadiazole-4-yl)-N-(3-(n-bromoalkoxy)phenyl)-1,8-naphthalimide and tertiary amine compounds is 1:(1-100).

9. The application of the near-infrared aggregation-induced emission molecule of claim 1 or the near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure of claim 5 in the preparation of fluorescent probes.

10. The application of the near-infrared aggregation-induced emission molecule of claim 1 or the near-infrared aggregation-induced emission molecule containing a quaternary ammonium salt structure of claim 5 in the preparation of bioimaging reagents.

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