Resonance energy transfer-based red-light aggregation-induced emission molecules, their preparation methods and applications

Abstract

The present invention discloses a resonance energy transfer type red light aggregation-induced emission molecule, its preparation method and application, belonging to the technical field of fine chemical engineering. It uses a molecule with aggregation-induced emission properties as an energy donor and an aggregation quenching red light or near-infrared dye as an energy acceptor, and the two are connected by a rigid linking unit; by using an AIE molecule as an energy donor, a non-AIE type fluorophore with spectral matching is transformed into an AIE active fluorophore. The introduction of the blue light AIE molecule phenylnaphthalimide into the AIE type fluorescent molecule enables the prepared molecule to still maintain the characteristic red light emission of the cyanovinyl triphenylamine fragment in the aggregated state. And through the energy transfer mechanism, a large Stokes shift from the excitation light to the emission light is achieved, which has the characteristics of high molecular structure flexibility, simple molecular synthesis, mild reaction conditions, and good aggregation state luminescence performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemicals, and particularly relates to a resonance energy transfer type red light aggregation-induced emission molecule, a preparation method thereof, and an application thereof. Background Art

[0002] Aggregation-Induced Emission (AIE) materials are a new type of luminescent materials. Such materials can emit relatively strong fluorescence signals in the solid state or nano-aggregated state. Fluorescent materials with AIE properties show great application prospects in the fields of thin film sensors, fluorescence detection and imaging in biological and water systems, and optoelectronic functional materials such as organic light-emitting diodes. Among them, the application in the field of biological detection and diagnosis requires that the fluorescent material has long-wavelength red to near-infrared luminescence. The existing design strategies for red and near-infrared luminescent AIE molecules include: 1) introducing AIE active units (such as tetraphenylethylene) into conventional red and near-infrared luminescent molecules (Journal of the American Chemical Society, 2017, 139, 10150-10156); 2) constructing AIE-type luminescent molecules with an intramolecular proton transfer mechanism (Journal of Materials Chemistry C. 2016, 4(14): 2909-2914); 3) constructing AIE-type luminescent molecules with a twisted intramolecular charge transfer mechanism (The Journal of Physical Chemistry C. 2013, 117(44): 23117-23125).

[0003] Studies have shown that the above design strategies for long-wavelength luminescent AIE molecules still have certain disadvantages. Such as excessive increase in molecular volume, low atom economy, and low luminescence efficiency. Therefore, it is of important technical value and application value to develop a new design strategy for long-wavelength luminescent AIE through the design of a new luminescence mechanism. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention aims to provide a resonance energy transfer type red light aggregation-induced emission molecule, a preparation method thereof, and an application thereof. It has the characteristics of high design flexibility, simple synthesis, mild reaction conditions, and good long-wavelength aggregated state luminescence performance.

[0005] Specifically, the following technical solutions are adopted to achieve:

[0006] A resonance energy transfer type red light aggregation-induced emission molecule, which uses a molecule with aggregation-induced emission properties as an energy donor and a red or near-infrared dye with quenched aggregation state as an energy acceptor, and the two are connected by a rigid linking unit, as shown in formula (I):

[0007]

[0008] Preferably, the energy acceptor is a commonly used red light or near-infrared light-emitting dye.

[0009] The synthesis route of the above resonance energy transfer type red light aggregation-induced emission molecule is as follows:

[0010]

[0011] The preparation method of the above resonance energy transfer type red light aggregation-induced emission molecule includes the following steps:

[0012] (a) Catalytic synthesis of (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid from cyanoacetic acid and 4-(diphenylamino)benzaldehyde;

[0013] (b) React (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid in step (a) with 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione to obtain the target compound.

[0014] Preferably, in step (a), cyanoacetic acid and 4-(diphenylamino)benzaldehyde are dissolved in ethanol and catalytically synthesized through piperidine. The molar volume ratio of cyanoacetic acid, 4-(diphenylamino)benzaldehyde, piperidine, and ethanol is 1 mmol: 1-1.5 mmol: 0.24-0.5 mL: 20-30 mL.

[0015] Further, in step (a), the molar volume ratio of cyanoacetic acid, 4-(diphenylamino)benzaldehyde, piperidine, and ethanol is 1 mmol: 1 mmol: 0.24 mL: 20 mL.

[0016] Preferably, in step (a), the catalytic synthesis condition of piperidine is under an oil bath condition, and the reflux temperature is 66-80 °C for heating and reacting for 2-6 h.

[0017] Further, in step (a), the catalytic synthesis condition of piperidine is under a methyl silicone oil bath condition, and the reflux temperature is 80 °C for heating and reacting for 2 h.

[0018] Preferably, in step (b), (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid and 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione are dissolved in tetrahydrofuran, and the target product is obtained under heating conditions.

[0019] Further, in step (b), under heating conditions, a dehydrating agent and an acid-binding agent are respectively added, and the target product is obtained after post-treatment.

[0020] Preferably, in step (b), the dehydrating agent is dicyclohexylcarbodiimide and the acid-binding agent is 4-dimethylaminopyridine; the molar volume ratio of 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione, (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid, dicyclohexylcarbodiimide, 4-dimethylaminopyridine and tetrahydrofuran is 1 mmol: 1-1.1 mmol: 1.2–2.5 mmol: 0.2-0.45 mmol: 30-50 mL;

[0021] The reaction temperature is from room temperature to 50 °C, and the reaction time is 20–72 h;

[0022] The post-treatment process is as follows: after the reaction is completed, it is cooled to room temperature, the filtrate is collected by vacuum filtration, and after rotary evaporation, it is purified by column chromatography.

[0023] Furthermore, in step (b), the molar volume ratio of 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione, (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid, dicyclohexylcarbodiimide, 4-dimethylaminopyridine and tetrahydrofuran is 1 mmol: 1.07 mmol: 2.5 mmol: 0.45 mmol: 30 mL;

[0024] Furthermore, the heating reaction temperature is from room temperature to 50 °C, and the heating reaction time is 20 h.

[0025] Preferably, both steps (a) and (b) are carried out under stirring.

[0026] The above resonance energy transfer type red light aggregation-induced emission molecule is applied to the preparation of fluorescent materials;

[0027] The above luminescent molecule or the above fluorescent material is applied to the preparation of thin film sensors, fluorescent detection and imaging materials for biological or aqueous systems, and optoelectronic functional materials.

[0028] The beneficial effects of the present invention are as follows:

[0029] First, the resonance energy transfer type aggregation-induced emission molecule designed by the present invention can use an AIE molecule as an energy donor to convert a non-AIE type fluorophore with spectral matching into an AIE active fluorophore.

[0030] Second, the AIE-type fluorescent molecules prepared by the present invention introduce blue-light AIE molecule phenylnaphthalimide, so that the prepared molecules still maintain the characteristic red light emission of the cyanovinyl triphenylamine fragment in the aggregated state. And through the energy transfer mechanism, a large Stokes shift (248 nm) from the excitation light (360 nm) to the emission light (608 nm) is achieved.

[0031] Third, the energy transfer-type molecules proposed by the present invention can realize the connection of donors and acceptors through the esterification reaction of carboxyl groups and phenolic hydroxyl groups. This method has the characteristics of high molecular structure flexibility, simple molecular synthesis, mild reaction conditions, and good aggregation-induced luminescence performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the ultraviolet absorption spectra of the compound NIPTPACN (A) of the present invention and its two precursor compounds 2 (B) and compound 3 (C) in different solvents;

[0033] Figure 2 It is the fluorescence spectra of the compound NIPTPACN (C) of the present invention and its two precursor compounds 2 (A) and compound 3 (B) in different solvents;

[0034] Figure 3 It is the aggregation-induced fluorescence spectra (A - C) and fluorescence peak ratio diagrams (D - F) of the compound NIPTPACN (C, F) of the present invention and its two precursor compounds 2 (A, D) and compound 3 (B, E) in an aqueous solution of tetrahydrofuran;

[0035] In Figures 1 to 3 them, the solvent symbols are: toluene (tol), tetrahydrofuran (THF), ethyl acetate (EA), ethanol (ACN), dichloromethane (DCM), dimethyl sulfoxide (DMSO), methanol (MeOH), ethanol (EtOH), and water (H2O);

[0036] Figure 4 It is the 1H NMR spectrum of the compound NIPTPACN of the present invention;

[0037] Figure 5 It is the 1C NMR spectrum of the compound NIPTPACN of the present invention;

[0038] Figure 6 It is the high-resolution mass spectrum of the compound NIPTPACN of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] In order to facilitate the understanding of the technical means, creative features, achieved purposes and effects of the present invention, the present invention will be further described below with reference to specific illustrations.

[0040] Example 1

[0041] (1) Synthesis method of (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid (i.e., cyano-triphenylaminoacrylic acid)

[0042] The synthesis route is as follows:

[0043]

[0044] Dissolve compound 1 (500 mg, 1.83 mmol) and cyanoacetic acid (156 mg, 1.83 mmol) in 36 mL of ethanol, then add them into a 100 mL three-necked flask. Then add 0.43 mL of piperazine to the flask. Heat the reaction system in an oil bath to reflux and react for 2 hours under nitrogen protection. After the reaction is completed, cool the reaction system to room temperature, remove the solvent by rotary evaporation, and then purify it by recrystallization with ethanol to obtain an orange powder solid, which is compound 2 (yield: 430 mg, yield rate: 69%).

[0045] (2) Synthesis method of AIE molecule NIPTPACN

[0046]

[0047] Put compound 2 (340 mg, 1 mmol) and compound 3 (365 mg, 1 mmol) into a 50 mL Schlenk tube; add 30 mL of tetrahydrofuran; after complete dissolution, add 515 mg (2.5 mmol) of dicyclohexylcarbodiimide (DCC) and 55 mg (0.45 mmol) of 4-dimethylaminopyridine (DMAP). Place the reaction tube in an oil bath and react at 50 °C for 20 hours. After the reaction is completed, cool it to room temperature, filter and then rotary evaporate. Purify the obtained crude product by silica gel column chromatography (200 - 300 mesh) to obtain a red fluorescent substance, which is the target compound 4 NIPTPACN (yield 605 mg, yield rate: 88%).

[0048] 13 C{H}NMR (100 MHz, CDCl3) ppm 96.4, 116.2, 119.0, 119.2, 121.6, 121.8, 122.2, 123.0, 123.3, 123.9, 125.7, 126.6, 126.9, 127.9, 128.5, 128.7, 129.1, 129.7, 129.8, 130.3, 131.2, 131.6, 133.0, 133.6, 136.3, 138.8, 145.6, 147.4, 151.2, 153.0, 155.2, 161.3, 162.8, 163.9, 164.1;

[0049] HRMS: calcd. [C 46 H 29 N3O4Na] + 710.2056, found 710.2050.

[0050] As can be seen from Figure 1 it, NIPTPACN shows dual absorption bands in the above solvents, located at 350 - 365 nm and 427 - 440 nm respectively.

[0051] The above absorption bands are respectively attributed to the chromophore fragments of compound 2 and compound 3, indicating that in the NIPTPACN molecule, the frontier orbitals of the two chromophores are independent of each other and no charge transfer occurs.

[0052] As shown by Figure 2 it, the emission spectra of compound 2 and compound 3 are respectively in the ranges of 410 - 472 nm and 520 - 608 nm.

[0053] Among them, compound 2 shows obvious AIE properties. In aqueous solution, it emits strong aggregated fluorescence at 461 nm; in highly polar organic solvents such as ethanol, ethanol, and methanol, it also shows obvious fluorescence emission; while compound 3 shows obvious solvent effect in organic solvents. As the solvent polarity increases, the spectrum redshifts and obvious quenching occurs, indicating that compound 3 has strong intramolecular charge transfer properties.

[0054] In addition, in DMSO and EtOH solvents, its emission wavelength and intensity are reversed, which is caused by the influence of its highly polar carboxyl unit.

[0055] The fluorescence spectrum of compound NIPTPACN, as Figure 2 shown by it, its behavior in organic solvents is similar to that of the two fragments in the organic phase, basically being the superposition of the emission peaks of the two fluorophore fragments. And NIPTPACN shows different AIE luminescence phenomena in aqueous solution from compound 3. It shows dual AIE emission peaks at 461 nm and 608 nm. Especially at the long - wave 608 nm, its AIE luminescence is significantly stronger than the emission at 461 nm, indicating that after compound 2 fragment is excited, most of the energy is transferred to compound 3 fragment and drives it to emit AIE fluorescence signal.

[0056] Figure 3 As shown in

[0057] With the increase in water content in the aqueous solution of compound 3 in tetrahydrofuran, the emission spectrum gradually decreases. When the water content reaches 40%, its fluorescence intensity is only 5% of that in the pure tetrahydrofuran solution, showing obvious ACQ properties.

[0058] The compound NIPTPACN of the present invention does not emit light in the range of 0 - 30% water content, indicating that no effective energy transfer process occurs between the fragments of 2 and 3 at this stage. When the water content reaches 40 - 60%, the fluorescence at 608 nm increases rapidly. When the water content is 60%, the luminescence intensity at 608 nm is 165 times stronger than that in pure tetrahydrofuran. Continuing to increase the water content, the luminescence of NIPTPACN decreases. When the water content is 99%, the fluorescence enhancement multiple is 105.6 times that in pure tetrahydrofuran.

[0059] The above results prove that an AIE - type donor can drive an aggregation - quenching long - wave dye to achieve AIE red luminescence. It shows that the design strategy of the energy - transfer - type AIE long - wave luminescent molecules mentioned in the present invention is effective.

[0060] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above - mentioned embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements will occur to the present invention, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. Resonance energy transfer type red light aggregation-induced emission molecule, characterized in that: The luminescent molecule is shown as formula (I):

2. The preparation method of the resonance energy transfer type red light aggregation-induced emission molecule according to claim 1, characterized in that, It includes the following steps: (a) Catalytically synthesize (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid from cyanoacetic acid and 4-(diphenylamino)benzaldehyde; (b) React (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid obtained in step (a) with 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione to obtain the target compound.

3. The preparation method according to claim 2, wherein, The reaction conditions for step (a) are: cyanoacetic acid and 4-(diphenylamino)benzaldehyde are dissolved in ethanol, and piperidine is used for catalytic synthesis. The molar volume ratio of cyanoacetic acid, 4-(diphenylamino)benzaldehyde, piperidine and ethanol is 1 mmol: 1-1.5 mmol: 0.24-0.5 mL: 20-30 mL.

4. The preparation method according to claim 3, characterized in that, The catalytic synthesis condition of piperidine is to heat and react for 2-6 h at the reflux temperature.

5. The preparation method according to claim 2, characterized in that, The reaction conditions for step (b) are: (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid and 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione are dissolved in tetrahydrofuran, and the target product is obtained under heating conditions.

6. The preparation method according to claim 5, wherein The molar volume ratio of 2-(3-hydroxyphenyl)-6-phenyl-1H-benzo[de]isoquinoline-1,3-(2H)-dione, (Z)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid, and tetrahydrofuran is 1 mmol: 1-1.1 mmol: 30-50 mL; the heating reaction temperature is from room temperature to 50 °C, and the heating reaction time is 20-72 h.

7. Use of the resonance energy transfer type red light aggregation-induced emission molecule described in claim 1 in the preparation of fluorescent materials.

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