Fluorescent molecules, fluorescent molecule-based host-guest complexes, and preparation and use thereof

Abstract

The application discloses two types of fluorescent molecules which can be used as guest molecules, host-guest complexes formed based on the two types of fluorescent guest molecules, and a preparation method and application in luminescent materials of the host-guest complexes. The application discloses two types of fluorescent molecules with complementary colors and different fluorescent emissions. Based on the two types of fluorescent molecules, the application realizes formation of host-guest complexes in a dilute solution and further realizes fluorescence regulation, specifically including fluorescence enhancement and color adjustment, for example, white light emission can be realized by changing the concentration of host molecules. Fluorescence resonance energy transfer exists in the formation of the host-guest complexes, which provides a new idea and new selection for precise regulation of fluorescence.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials, specifically to two types of fluorescent molecules that can serve as guest molecules, host-guest complexes formed based on these two types of fluorescent guest molecules, and their preparation methods and applications. Background Technology

[0002] In recent years, stimulus-responsive fluorescent materials have been widely used in chemical sensors, biosensors, and fluorescence indicators. Common fluorescent probes have advantages such as speed, sensitivity, and ease of operation, and are widely used for the selective recognition of ions, small molecules, and biomacromolecules. However, traditional organic fluorescent molecules suffer from aggregation-induced quenching (ACQ) phenomenon. The design and synthesis of aggregation-induced emission (AIE) groups, represented by tetraphenylethylene (TPE), have greatly expanded the application range of stimulus-responsive reversible conversion materials and fluorescent probes.

[0003] Tetraphenylene (TPE) and its derivatives exhibit fluorescence emission under aggregation-induced effect (AIE) due to the intramolecular rotational restriction (RIR) effect. In solution, TPE shows almost no fluorescence. When aggregated or in the solid state, the rotation of the benzene ring is impeded, and TPE will recover its fluorescence emission. Patent specification CN116041262A discloses a TPE derivative molecule with AIE effect, whose fluorescence emission is blue, mainly concentrated in the 450-500 nm wavelength range. It can specifically recognize benzo-21-crown-7, cucurbita[7] and cucurbita[8] in the aqueous phase to form host-guest complexes, thereby achieving fluorescence enhancement.

[0004] White light-emitting materials have attracted considerable attention due to their potential applications in organic light-emitting diodes and bright sensor materials. Synthesizing a polymer that covers the entire visible light spectrum is not easy. Furthermore, the ease with which multiple emitting polymers can mix leads to unfavorable interactions between them, making it difficult for chemists to prepare materials with this type of emission. This process can be achieved by fine-tuning the primary colors—red, green, and blue—or two complementary colors, based on the principle.

[0005] The patent specification with publication number CN115595147A discloses a light-harvesting system based on columnar aromatic hydrocarbons for continuous energy transfer, its preparation method and application. The light-harvesting system uses a tetraphenylethylene compound G modified with methylpyridinium salt as a guest and energy donor, a columnar aromatic hydrocarbon compound H modified with ammonium carboxylate salt as a host, and a fluorescent dye as an energy acceptor. Compounds G and H self-assemble into nanoparticles through host-guest interactions, and together with the fluorescent dye, they construct a light-harvesting system for continuous energy transfer. The emission color of this light-harvesting system is tunable and can be used to prepare high-efficiency white light emitting devices. Summary of the Invention

[0006] This invention utilizes non-covalent interactions by combining tetraphenylethylene units with the host to design and realize target compounds with optical properties, providing a new strategy for achieving fluorescence modulation in dilute solutions and generating white light.

[0007] In a first aspect, the present invention provides a fluorescent molecule with a molecular structure as shown in formula (1):

[0008]

[0009] In formula (1), R1 is a substituent as shown in formula (3) or formula (4):

[0010]

[0011] In the first aspect, the excitation wavelength of the fluorescent molecule with the molecular structure shown in formula (1) is 400-450 nm and the fluorescence emission wavelength is 550-600 nm.

[0012] In a second aspect, the present invention provides a method for preparing the fluorescent molecule described in the first aspect, wherein compound D undergoes a nucleophilic reaction with R1Br to obtain the fluorescent molecule described in the first aspect;

[0013]

[0014] In the second aspect, the molar ratio of compound D to R1Br can be 1:4 to 12.

[0015] Thirdly, the present invention provides a fluorescent molecule with a molecular structure as shown in formula (2):

[0016]

[0017] In formula (2), R2 is a substituent as shown in formula (3) or formula (4):

[0018]

[0019] In the third aspect, the excitation wavelength of the fluorescent molecule with the molecular structure shown in formula (2) is 350-400 nm and the fluorescence emission wavelength is 400-450 nm.

[0020] Fourthly, the present invention provides a method for preparing the fluorescent molecule described in the third aspect, wherein compound E undergoes a nucleophilic reaction with R2Br to obtain the fluorescent molecule described in the third aspect;

[0021]

[0022] In the fourth aspect, the molar ratio of compound E to R2Br can be 1:2 to 8.

[0023] Fifthly, the present invention provides a host-guest complex comprising a host molecule cucurbita[8]urea (CB[8]) and a guest molecule, wherein the guest molecule is a fluorescent molecule with a molecular structure as shown in formula (1) as described in the first aspect and / or a fluorescent molecule with a molecular structure as shown in formula (2) as described in the third aspect.

[0024] In the fifth aspect, further, the guest molecule may be a fluorescent molecule with the molecular structure shown in Formula (1) as described in the first aspect and a fluorescent molecule with the molecular structure shown in Formula (2) as described in the third aspect, and R1 and R2 may not both be substituents as shown in Formula (4). Even further, R1 may be a substituent as shown in Formula (3), and R2 may be a substituent as shown in Formula (4).

[0025] In the host-guest complex described in the fifth aspect, when the guest molecule can be a fluorescent molecule with a molecular structure as shown in Formula (1) of the first aspect and a fluorescent molecule with a molecular structure as shown in Formula (2) of the third aspect, the molar ratio of the fluorescent molecule with a molecular structure as shown in Formula (1) of the first aspect and the fluorescent molecule with a molecular structure as shown in Formula (2) of the third aspect can be 1:2, and the molar ratio of the host molecule to the fluorescent molecule with a molecular structure as shown in Formula (1) of the first aspect can not exceed 6:1.

[0026] Fluorescence modulation can be achieved by placing the host-guest complex described in the fifth aspect in an aqueous phase.

[0027] In a sixth aspect, the present invention provides a method for preparing the host-guest complex described in the fifth aspect, wherein a host molecule solution is added dropwise to a guest molecule solution to obtain the host-guest complex described in the fifth aspect.

[0028] In the sixth aspect, both the guest molecule solution and the host molecule solution may be aqueous solutions.

[0029] In a seventh aspect, the present invention provides the application of fluorescent molecules with molecular structures as shown in Formula (1) in the first aspect in luminescent materials.

[0030] In an eighth aspect, the present invention provides the application of fluorescent molecules with molecular structures as shown in Formula (2) in the third aspect in luminescent materials.

[0031] In a ninth aspect, the present invention provides the application of the host-guest complex described in the fifth aspect in luminescent materials.

[0032] In the seventh to ninth aspects, the luminescent material described in the application can be a white-light-emitting material.

[0033] This invention enables fluorescence modulation and white light emission processes in dilute aqueous solutions through the regulation of host molecules.

[0034] Compared with the prior art, the beneficial effects of this invention are as follows:

[0035] The fluorescent molecules with molecular structures as shown in formula (1) and (2) provided by this invention are two types of fluorescent molecules with complementary colors and different fluorescence emissions. Based on these two types of fluorescent molecules, this invention realizes the formation of ternary complexes (host-guest complexes) in dilute solutions, thereby achieving fluorescence regulation, specifically including fluorescence enhancement and color adjustment, for example, white light emission can be achieved by changing the concentration of the host molecule.

[0036] This invention utilizes fluorescence resonance energy transfer (FRET) in the formation of ternary complexes, providing a new approach and option for precise fluorescence modulation. Attached Figure Description

[0037] Figure 1 The schematic diagram of the main molecule CB[8].

[0038] Figure 2 The diagram shows the changes in fluorescence emission due to host-guest interaction; A: several binding modes of the terminal group and the host molecule CB[8]; B: host-guest fluorescence titration results of TPE-pyFph with CB[8]; C: host-guest fluorescence titration results of TPE-pyph with CB[8]; D: after adding TPE-pyph to CB[8], pyFph is added, proving that the ternary complex of benzene-fluorobenzene-CB[8] is more stable.

[0039] Figure 3 The diagram illustrates how cross-arrangement facilitates FRET conversion results.

[0040] Figure 4 The image shows the white light produced by the ternary complex under the control of the host molecule. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] Example 1

[0043] Synthesis method of compound D (i.e., TPE-py):

[0044]

[0045] In a three-necked flask, dry tetrahydrofuran (THF, 80 mL) and zinc powder (7.18 g, 109.8 mmol) were added and the mixture was placed at 0 °C under nitrogen for 10 minutes. Titanium tetrachloride (6 mL, 54.9 mmol) was slowly added dropwise to the reaction flask, and the mixture was then refluxed and heated for 2 hours. A solution of benzophenone (5.0 g, 2.74 mmol) in THF (20 mL) was then slowly added. The mixture was refluxed again for 12 hours. The reaction mixture was quenched with a 10 wt% aqueous solution of potassium carbonate and extracted with ethyl acetate (EA, 3 × 200 mL). The organic compound was washed with water, dried over anhydrous magnesium sulfate, and then filtered. The solvent was removed using a rotary evaporator. The crude product was washed with ethanol and filtered to give TPE molecules as a white solid.

[0046] TPE (5.0 g, 7.7 mmol) was dissolved in dichloromethane (DCM, 100 mL) in a round-bottom flask, and then liquid bromine (3 mL) was slowly added. After stirring at room temperature for 12 h, the reaction was quenched by adding ethanol (200 mL) and sodium sulfite (3.0 g). Sodium hydroxide (10.0 M) was added to pH 7, and the mixture was extracted with dichloromethane (3 × 100 mL). The organic phase was dried over anhydrous magnesium sulfate. After rotary evaporation, the target compound C, TPE-Br, with para-bromine substitution was obtained.

[0047] In a 100 mL Schlenk flask, compound TPE-Br (450 mg, 0.69 mmol), pyridine-4-boronic acid (679 mg, 5.5 mmol), palladium(II) acetate (162 mg, 0.73 mmol), K₂CO₃ (3.93 g, 18.5 mmol), and tricyclohexylphosphine (204 mg, 0.72 mmol) were added. Then, N,N-dimethylformamide (DMF, 30 mL) was added using a syringe, and the solution was refluxed at 100 °C under an inert atmosphere for 48 hours. After cooling to room temperature, the product was first evaporated under high vacuum, followed by extraction with chloroform. The organic phase was then washed with water, dried over anhydrous sodium sulfate, and concentrated. The final product was purified by column chromatography to give TPE-py as a yellow solid.

[0048] Example 2

[0049] Synthesis method of fluorescent molecules with molecular structures as shown in formula (1):

[0050]

[0051] In a round-bottom flask equipped with a magnetic stir bar, compound D (0.05 g, 0.08 mmol) and benzyl bromide (0.06 g, 0.35 mmol) or pentafluorobenzyl bromide (0.09 g, 0.35 mmol) were dissolved in DMF (20 mL), and the solution was heated to 100 °C. The reaction was stirred for another 12 hours. After cooling, the DMF was removed using an evaporator, and then H2O and excess potassium hexafluorophosphate were added. The precipitate was filtered off. The solid was redissolved in a small amount of acetone. Excess tetrabutylammonium bromide was added, and the resulting precipitate was filtered off to obtain the target product TPE-pyph or TPE-pyFph, as a yellow solid (TPE-pyph: 89%, 0.09 g; TPE-pyFph: 86%, 0.11 g).

[0052] The characterization data of the product prepared in this embodiment are as follows:

[0053] The product when R is phenyl in formula (1) is denoted as TPE-py-ph. 1H NMR (600MHz, D2O) δ (ppm): 8.73 (d, J = 6, 8H), 8.13 (d, J = 6, 8H), 7.67 (d, J = 6, 8H), 7.39-7.42 (m, 20H), 7.35 (d, J = 6, 8H).

[0054] The product when R is pentafluorophenyl in formula (1) is denoted as TPE-py-Fph. 1H NMR (600MHz, D2O) δ (ppm): 8.78 (d, J = 6, 8H), 8.20 (d, J = 6, 8H), 7.72 (d, J = 6, 8H), 7.38 (d, J = 6, 8H), 5.89 (s, 8H).

[0055] Example 3

[0056] Synthetic method of compound E (i.e., An-im)

[0057]

[0058] Under nitrogen atmosphere, 9,10-dibromoanthracene (2 g, 6 mmol), imidazole (2.028 g, 30 mmol), 1,10-phenanthroline (0.2 g, 0.892 mmol), Cu₂O (0.2 g, 0.892 mmol), cesium carbonate (5.432 g, 16.68 mmol), and polyethylene glycol (1.2 g) were added to a 50 mL flask equipped with a magnetic stirrer, followed by DMF (30 mL). The reaction mixture was stirred at 110 °C for 48 hours. The solvent in the reaction mixture was removed under vacuum. The residue was diluted with water and extracted with CH₂Cl₂. The organic layer was separated and dried over anhydrous Na₂SO₄. The mixture was purified by gel permeation chromatography (DCM / methanol, 20:1 v / v) to give the target product An-im (1.33 g, 72%) as an orange solid. The characterization data of the product prepared in this example are as follows:

[0059] An-im:

[0060] 1H NMR (600MHz, CDCl3) δ (ppm): 7.83 (s, 2H), 7.52–7.57 (m, 8H), 7.50 (s, 2H), 7.33 (s, 2H).

[0061] Example 4

[0062] Synthesis method of fluorescent molecules with molecular structures as shown in formula (2):

[0063]

[0064] Compound E (1 equivalent, 0.2 g, 0.64 mmol) dissolved in acetonitrile (MeCN, 10 mL) and benzyl bromide (2 equivalents, 0.22 g, 1.29 mmol) or pentafluorobenzyl bromide (2 equivalents, 0.34 g, 1.28 mmol) were heated at 80 °C in a round-bottom flask equipped with a magnetic stir bar. The mixture was then stirred for 12 hours. After cooling, the mixture was evaporated under vacuum, and the residue was washed with DCM to give the target product An-ph or An-Fph as a white solid (An-ph: 0.39 g, 93%; An-Fph: 0.48 g, 89%).

[0065] The characterization data of the product prepared in this embodiment are as follows:

[0066] An-ph: 1 H NMR (600MHz, D2O) δ (ppm): 7.99 (s, 2H), 7.89 (s, 2H), 7.66-7.69 (m, 4H), 7.54-7.56 (m, 4H), 7.44-7.50 (m, 10H), 5.62 (s, 4H).

[0067] An-Fph: 1 H NMR (600MHz, D2O) δ (ppm): 8.06 (s, 2H), 7.98 (s, 2H), 7.73-7.75 (m, 4H), 7.52-7.54 (m, 4H), 5.88 (s, 4H).

[0068] Example 5

[0069] like Figure 2 As shown, we first demonstrate the identification of the corresponding end groups and the main molecule CB[8]. Figure 2 B shows the fluorescence changes of the host molecule CB[8] when equivalent amounts of our prepared TPE-pyFph solution (10 μM) are added. Similarly, Figure 2 C is the fluorescence change diagram of TPE-pyph (10 μM) added to the host molecule CB[8]. It is worth noting that the fluorescence is greatly enhanced here, and the reason for this phenomenon is that aggregation promotes fluorescence enhancement. Figure 2 D is the fluorescence titration diagram we performed to demonstrate the greater stability of the ternary complex. First, a TPE-pyph solution of the same concentration as described above was added. Then, the addition of 4 equivalents of CB8 resulted in a significant enhancement of fluorescence. Subsequently, due to the small molecule pyFph (its structure is shown below), the fluorescence was further enhanced. Figure 2 The addition of the D illustration (the molecule itself can be obtained through existing technology) causes the originally aggregated state to dissociate, thereby weakening the fluorescence.

[0070] See Figure 1 , Figure 2 The main molecule CB[8] and fluorescent molecules with molecular structures as shown in formula (1) can exhibit rich recognition modes. For example Figure 2 As shown in Figure A, the host molecule CB[8] has a large cavity size, which can accommodate two guest units. Driven by hydrophobic interactions, the host molecule CB[8] can simultaneously encapsulate two benzene units, or it can encapsulate one pentafluorobenzene unit and one benzene unit, and the latter has a higher ternary complex binding energy with the host molecule CB[8] due to the dipole interaction between benzene and fluorobenzene. It is worth mentioning that the repulsion between fluorobenzenes means that the cavity of CB[8] cannot simultaneously accommodate two fluorobenzene units. This binding mode provides us with a convenient way to further understand the fluorescence effect of the host molecule on the guest molecule. For example, as Figure 2As shown in Figure C, when the guest molecule TPE-pyph is mixed with the host molecule CB[8], TPE-pyph forms a two-dimensional supramolecular network in solution through the complex. This larger assembly structure has a more significant restrictive effect on the movement of TPE units, and the fluorescence of TPE-pyph is greatly enhanced. The arrangement mode of benzene-fluorobenzene units in the cavity of the host molecule CB[8] provides a more effective means to precisely control the arrangement of guest molecules and thus controllably regulate the fluorescence of guest molecules. See also Figure 2 D. When the small molecule pyFph is added to the mixed solution of guest molecule TPE-pyph and host molecule CB[8], the original two-dimensional network is replaced by the pyFph-TPE-pyph-CB[8] ternary complex, the restriction effect is weakened, the fluorescence intensity of the solution is reduced, and thus the continuous regulation of TPE fluorescence is achieved.

[0071] Based on the regulatory capabilities of the aforementioned ternary complex, we further introduced a fluorobenzene-modified An-Fph molecule with anthracene as the emitting group. The choice of this molecule is advantageous because, on the one hand, its fluorescence emission wavelength is complementary to that of TPE-pyph, potentially leading to white light emission; on the other hand, the emission wavelength of An-Fph matches the excitation wavelength of TPE-pyph, which may result in FRET (fluorescence resonance energy transfer), thus better highlighting the role of the alternating network in fluorescence regulation.

[0072] like Figure 3 As shown, we selected two guest molecule structures, TPE-pyph and An-Fph, for investigation. We first confirmed that the excitation and emission of the two overlapped, satisfying the fluorescence resonance energy transfer (FRET) phenomenon. When the host molecule CB[8] was added to a mixture of TPE-pyph and An-Fph guest molecules with a molar ratio of 1:2, see Figure 3 The upper right figure (the concentration of TPE-pyph in the aqueous solution is 25 μM, and the host molecule CB[8] is added based on the equivalent amount of TPE-pyph molar amount as 1 equivalent) shows that the emission intensity of anthracene decreased after the addition of the host molecule CB[8]. This is because the alternating arrangement of benzene and fluorobenzene makes the spacing between the TPE-pyph unit and the anthracene unit more regular, effectively improving the FRET conversion between the two. However, in the latter system with anthracene-modified benzene-containing structure (i.e., the two guest molecules have the structures TPE-pyph and An-ph, and the molar ratio of TPE-pyph:An-ph is 1:2), see Figure 3The lower right figure (the concentration of TPE-pyph in the aqueous solution is 25 μM, and the amount of the host molecule CB[8] added is based on a TPE-pyph molar amount of 1 equivalent) shows that, due to the random arrangement (the two benzene ring structures included in the host molecule CB[8] may come from the same guest molecule or different guest molecules), the emission intensity of anthracene did not change significantly under the action of the host molecule CB[8]. This result indicates that the ternary complex system of the present invention has a certain possibility of fluorescence regulation.

[0073] Under the influence of the above effects, the TPE-pyph / AnFph / CB[8] ternary complex can achieve near-standard white light emission in aqueous solution. Specifically, we prepared a mixed solution with a TPE-pyph:An-Fph molar ratio of 1:2 (where the TPE-pyph concentration was 25 μM), and then gradually added the host molecule CB[8] (from 0 to 6 equivalents). Figure 4 The main molecule CB[8] was added in equivalent amounts (with the molar amount of TPE-pyph being 1 equivalent). The results showed that with the addition of the main molecule CB[8], the emission intensity of TPE-pyph molecules was significantly enhanced due to the formation of the network structure, and the emission intensity of anthracene gradually decreased with the formation of the network structure (the FRET effect was more significant). The corresponding CIE diagrams showed that the addition of the main molecule CB[8] caused the fluorescence of the solution to gradually shift from violet to yellow light. When 3 equivalents of the main molecule CB[8] were added, the corresponding solution exhibited near-standard white light emission, with CIE coordinates of (0.32, 0.31).

[0074] Therefore, this invention enables precise tuning of the fluorescence emission color of the FRET system, particularly white light emission. More importantly, these host-guest complexes can be used to manufacture white fluorescent films and can also be integrated with 365nm LEDs to create white LED devices.

[0075] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A host-guest complex, characterized in that, It includes the host molecule cucurbita[8]urea and the guest molecule, wherein the guest molecule is a fluorescent molecule with a molecular structure as shown in formula (1) and a fluorescent molecule with a molecular structure as shown in formula (2); ， In formula (1), R1 is a substituent as shown in formula (3) or formula (4); ， In formula (2), R2 is a substituent as shown in formula (3) or formula (4); 。 2. The host-guest complex according to claim 1, characterized in that, R1 and R2 are not simultaneously substituents as shown in formula (4).

3. The host-guest complex of claim 2, wherein, R1 is a substituent as shown in formula (3), and R2 is a substituent as shown in formula (4).

4. The method for preparing the host-guest complex according to any one of claims 1 to 3, characterized in that, The host molecule solution is added dropwise to the guest molecule solution to obtain the host-guest complex.

5. The application of the host-guest complex according to any one of claims 1 to 3 in luminescent materials.

6. The application according to claim 5, characterized in that, The luminescent material is a white-light-emitting material.

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