A pyrone multifunctional luminescent liquid crystal compound and a preparation method and application thereof

Abstract

The present application relates to the technical field of multifunctional light-emitting liquid crystal, and particularly relates to a pyrone multifunctional light-emitting liquid crystal compound, a preparation method and application thereof, and a structure of the compound is shown as formula (I), wherein n is 10, 12 or 14. The target product can be prepared by reacting 3,4,5-trialkoxybenzaldehyde and 2,6-dimethyl-gamma-pyrone in the presence of sodium tert-butoxide in anhydrous ethanol, and then purified by recrystallization. The method is suitable for industrial production, because raw materials are easy to obtain, reaction conditions are mild, and purification is simple. The pyrone light-emitting liquid crystal compound provided by the present application combines the excellent light-emitting performance of pyrone and the supramolecular self-assembly characteristics of liquid crystal, and can be applied to the fields of bistable light-emitting materials, ferroelectric materials, light-emitting organic gels and picric acid fluorescent probes, and shows a broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of multifunctional luminescent liquid crystal technology, specifically to a pyranone-based multifunctional luminescent liquid crystal compound, its preparation method, and its applications. Background Technology

[0002] Liquid crystal luminescent (LLCs) combine the photoluminescence properties of materials with the self-assembly capabilities of liquid crystals, showing broad application prospects in the field of optoelectronic devices and currently attracting widespread attention from researchers. In a mesocrystalline phase, this material can efficiently emit linearly or circularly polarized light based on its molecular arrangement, which helps reduce the manufacturing cost of liquid crystal displays and improve their performance.

[0003] Traditional luminescent materials exhibit strong emission in dilute solutions, but their emission is weak or nonexistent in the aggregated state due to aggregation-induced quenching (ACQ) effects, severely limiting their applications in optoelectronic devices. In contrast, aggregation-induced emission (AIE) materials, based on the restricted intramolecular motion (RIM) mechanism, achieve high luminescence efficiency in the aggregated state, but these materials emit almost no light in dilute solutions. Recently, dual-state emission (DSE) materials, by balancing aggregation-induced quenching and aggregation-induced emission, maintain high luminescence efficiency in both solution and solid states, showing promising application prospects in the field of organic optoelectronic devices.

[0004] Ferroelectric materials are a class of special dielectric materials with spontaneous polarization whose polarization direction can be reversed by an external electric field. They are widely used in non-volatile computer memory, sensors, and optics. Since the ferroelectric properties were first discovered in Rochelle salts, these materials have primarily been used by inorganic materials (such as BaTiO3 and Pb(Zr)). x Ti 1-x Liquid crystal molecules (LCMs) and polymers (such as polyvinylidene fluoride) are used in ferroelectric materials. Although some progress has been made in ferroelectric materials, the synthesis of novel liquid crystal ferroelectric materials with low cost and solution processability remains a huge challenge.

[0005] Organic gels are soft materials that can form three-dimensional luminescent network structures in organic solvents. They possess properties such as antifreeze, anti-icing, conductivity, tunable structure, and stimulus response, and have wide applications in drug delivery, flexible electronics, and biosensing. However, designing and synthesizing organic gels with luminescent properties remains challenging.

[0006] Picric acid, a polynitro aromatic compound, possesses extremely high explosive power. It is also a toxic environmental pollutant, causing eye / skin irritation and chronic diseases such as anemia, cancer, and cyanosis. Picric acid is widely used as a chemical reagent in the pharmaceutical, dye, and fireworks industries, causing serious environmental damage. Therefore, developing fluorescent probes with high sensitivity and specificity for recognizing picric acid is of paramount importance.

[0007] Pyranones, as excellent luminescent units, have been widely used to construct multicolor luminescent organic dyes for the fabrication of optoelectronic devices such as organic light-emitting diodes and fluorescent probes. Furthermore, pyranones possess large dipole moments, making them potential supramolecular self-assembly functional units. However, to date, no pyranone-based liquid crystal molecules have been reported, and their applications in supramolecular functional materials urgently need further development.

[0008] Therefore, this invention aims to develop a pyranone-based multifunctional luminescent liquid crystal material. Furthermore, this invention provides a simple preparation method, making the preparation process of this luminescent liquid crystal more convenient and economical. In addition, this invention explores the multifunctional applications of this luminescent liquid crystal in the fields of dual-state luminescent materials, ferroelectric materials, luminescent organogels, and fluorescent probes, providing new solutions for the application of luminescent liquid crystals in the field of novel multifunctional materials. Summary of the Invention

[0009] The present invention aims to provide a pyranone-based multifunctional luminescent liquid crystal compound, its preparation method, and its applications. The compound Py-n exhibits a hexagonal columnar liquid crystal phase. Furthermore, Py-n possesses dual-state luminescence properties and can form luminescent organic gels in specific organic solvents. Under an applied electric field, Py-n can achieve self-assembly and orientation, making it suitable as a ferroelectric material. Simultaneously, Py-n can serve as a highly sensitive fluorescent probe for recognizing picric acid. The multifunctional properties of this type of material hold promise for widespread application in novel optoelectronic materials.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: A pyranone-based multifunctional luminescent liquid crystal compound, the structure of which is shown in formula (I): (I) Where n is any integer among 10, 12, or 14.

[0011] On the other hand, the present invention proposes a method for preparing the above-mentioned pyranone-based multifunctional luminescent liquid crystal compounds, the chemical reaction equation of which is as follows: Includes the following steps: 3,4,5-trialkoxybenzaldehyde and 2,6-dimethyl-γ-pyranone were dissolved in anhydrous ethanol, stirred and mixed, and sodium tert-butoxide was added. The mixture was reacted at 50-70°C until complete, and then post-treated to obtain the compound shown in formula (Ⅰ). Wherein, the number of carbon atoms of the alkoxy group in the 3,4,5-trialkoxybenzaldehyde is 10, 12 or 14, so as to obtain compounds of formula (Ⅰ) with n=10, 12 or 14 respectively.

[0012] Furthermore, the molar ratio of 3,4,5-trialkoxybenzaldehyde, 2,6-dimethyl-γ-pyranone and sodium tert-butoxide is 2:1:(1-2).

[0013] Further, the post-processing includes: after the reaction is complete, removing the solvent by vacuum distillation, and purifying the resulting solid residue by recrystallization to obtain the compound shown in formula (I); and / or The solvent system used for recrystallization is dichloromethane and methanol.

[0014] On the other hand, the present invention proposes a light-emitting device or optoelectronic material comprising the above-mentioned pyranone-based multifunctional light-emitting liquid crystal compound.

[0015] On the other hand, the present invention proposes an electric field-responsive optoelectronic material comprising the above-mentioned pyranone-based multifunctional luminescent liquid crystal compound.

[0016] On the other hand, the present invention proposes a luminescent organic gel comprising the above-mentioned pyranone-based multifunctional luminescent liquid crystal compound and a solvent.

[0017] Furthermore, the solvent for the luminescent organogel is n-butanol.

[0018] On the other hand, this invention proposes the application of the above-mentioned pyranone-based multifunctional luminescent liquid crystal compounds as fluorescent probes in the detection of picric acid.

[0019] Furthermore, the detection is a fluorescence quenching detection.

[0020] The beneficial effects of this invention are: This invention successfully synthesized a novel class of pyranone-based luminescent liquid crystal compounds. These molecules use pyranone as the core luminescent unit, and by introducing three long alkoxy chains on both sides, a target compound with the structure shown in formula (I) is constructed. Pyranone itself, as an excellent luminescent unit, has been widely used to construct multicolor luminescent organic dyes, but its application in the field of liquid crystal materials has not been previously reported. This invention combines the luminescent properties of pyranone with the self-assembly capability of liquid crystals through molecular design, resulting in compounds that exhibit a typical birefringent texture under a polarizing microscope. X-ray diffraction analysis confirmed the formation of a hexagonal columnar liquid crystal phase. Simultaneously, fluorescence spectroscopy tests showed that these compounds maintain strong fluorescence emission in both pure solution and aggregated states, exhibiting bi-state luminescence characteristics. This design concept, which successfully integrates the pyranone luminescent unit with the ordered structure of liquid crystals, provides a feasible solution for developing novel multifunctional luminescent materials.

[0021] The preparation method disclosed in this invention is characterized by its simplicity, mild conditions, and ease of purification. The synthetic route uses 3,4,5-trialkoxybenzaldehyde and 2,6-dimethyl-γ-pyranone as starting materials, undergoing a one-step condensation in anhydrous ethanol with sodium tert-butoxide to obtain the target product. The reaction temperature is controlled between 50 and 70 degrees Celsius, requiring no inert gas protection or harsh conditions such as anhydrous and oxygen-free environments. After the reaction, only vacuum distillation is needed to remove the solvent, and the resulting solid can be recrystallized from dichloromethane and methanol to obtain the pure product, with a yield of 89% to 93%. The starting material 3,4,5-trialkoxybenzaldehyde can be prepared by conventional methods, 2,6-dimethyl-γ-pyranone is a commercially available reagent, and sodium tert-butoxide and anhydrous ethanol are both commonly used and inexpensive reagents. The entire preparation process does not require column chromatography separation, avoiding large amounts of solvent consumption and complex post-processing operations, and possesses good prospects for industrial production.

[0022] The pyranone-based multifunctional luminescent liquid crystals provided by this invention demonstrate potential value in multiple application fields. Regarding dual-state luminescent materials, these compounds maintain strong fluorescence emission in both pure tetrahydrofuran solution and aqueous tetrahydrofuran solutions with high water content. This characteristic of efficient luminescence in both dilute solutions and aggregated states makes them promising for the fabrication of light-emitting devices. Regarding ferroelectric materials, after encapsulating these compounds in an ITO liquid crystal cell and applying a DC voltage, polarized light microscopy revealed that the columnar liquid crystal regions changed from multiaxial orientation to uniaxial orientation, indicating that the large dipole moment of the pyranone core can undergo directional alignment under an external electric field. This electric field response behavior is a key characteristic of ferroelectric materials. Regarding luminescent organic gels, these compounds can spontaneously form stable luminescent organic gels in n-butanol. Scanning electron microscopy revealed that their microstructure is a three-dimensional layered network structure. This soft matter material, possessing both luminescent and gel properties, has research value in drug delivery, flexible electronics, and other fields. In the area of ​​picric acid fluorescent probes, the electron-rich properties and strong luminescence of these compounds enable highly selective fluorescence quenching detection of picric acid, with no significant interference from other structurally similar nitroaromatic compounds. Fluorescent titration experiments show that the detection limit can reach the nanomolar level, providing a new probe molecule for the rapid detection of picric acid in the environment. The exploration of these multiple application directions demonstrates the broad application prospects of the compounds of this invention as multifunctional materials.

[0023] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is the synthetic route diagram for compound Py-n; Figure 2 This is the 1H NMR spectrum of compound Py-12; Figure 3 This is the carbon NMR spectrum of compound Py-12; Figure 4 This is a hexagonal columnar liquid crystal texture pattern of compound Py-12 observed under POM. Figure 5 This is the XRD pattern of compound Py-12 at 40 °C; Figure 6 This is the two-state emission fluorescence spectrum of compound Py-12; Figure 7This is a POM (Polymer Oxidation Membrane) pattern of liquid crystal texture observed in a liquid crystal cell prepared with compound Py-12 after applying voltage; Figure 8 This is a SEM image of the organic gel formed by compound Py-12 in n-butanol; Figure 9 These are fluorescence spectra of compound Py-12 after different nitroaromatic explosives were added to the solution. Figure 10 This is a graph showing the detection limit of compound Py-12 for PA. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0027] As described in this embodiment, the pyranone-based multifunctional luminescent liquid crystal compound has the following general structural formula: Where n is 10, 12, 14, and the luminescent liquid crystal compound is Py-n.

[0028] The method for synthesizing Py-n includes: 3,4,5-trialkoxybenzaldehyde (3.0 mmol) and 2,6-dimethyl-γ-pyranone (0.12 g, 1.0 mmol) were dissolved in 10 mL of anhydrous ethanol in a 50 mL single-necked round-bottom flask. After stirring at room temperature for 5 minutes, sodium tert-butoxide (0.1 g, 1.0 mmol) was added, and the temperature was raised to 50-70 °C. The reaction was stirred, and the reaction was stopped when the 2,6-dimethyl-γ-pyranone was completely converted by TLC. Excess ethanol solvent was removed by vacuum distillation, and the pure compound Py-n (yield: 89-93%) was obtained by recrystallization from dichloromethane and methanol. Its NMR spectrum data are as follows.

[0029] Compound Py-10: 1H NMR (CDCl3;400 MHz): δ = 7.3 (d, 2 H, 1 CH=CH), 6.75(s, 4 H, 2 ArH), 6.62 (d, 2 H, 1 CH=CH), 6.34 (s, 2 H, 2 CH), 4.03 (m, 12 H,6 ArOCH2), 1.71-1.78 (m, 12 H, 6 OCH2CH2), 1.47 (m, 12 H, 6 CH2CH2CH2), 1.26-1.29 (s, 72 H, 36 CH2), 0.88 (t, J = 6.4 Hz, 36 H, 6 CH3). 13 C NMR (CDCl3;400MHz): 180.5, 161.5, 153.5 140.1, 136.3, 130.1, 118.9, 113.5, 106.4, 73.6,69.0, 31.9, 26.6-29.8, 26.1, 22.7, 14.1.

[0030] Compound Py-12: 1 H NMR (CDCl3;400 MHz): δ = 7.3 (d, 2 H, 1 CH=CH), 6.75 (s, 4 H, 2 ArH), 6.62 (d, 2 H, 1 CH=CH), 6.28 (s, 2 H, 2 CH), 4.03 (m, 12 H, 6 ArOCH2), 1.71-1.78 (m, 12 H, 6 OCH2CH2), 1.47 (m, 12 H, 6 CH2CH2CH2), 1.26-1.29 (s, 96 H, 48 CH2), 0.88 (t, J = 6 Hz, 36 H, 6 CH3). 13 C NMR (CDCl3;400MHz): 180.7, 161.8, 153.6, 140.3, 136.5, 130.3, 119.1, 113.7, 106.4, 73.8,69.5, 32.1, 26.6-29.8, 26.3), 22.8, 14.1.

[0031] Compound Py-14: 1H NMR (CDCl3; 400 MHz): δ = 7.3 (d, 2 H, 1 CH=CH), 6.75 (s, 4 H, 2 ArH), 6.61 (d, 2 H, 1 CH=CH), 6.26 (s, 2 H, 2 CH), 4.03 (m, 12 H, 6ArOCH2), 1.71-1.78 (m, 12 H, 6 OCH2CH2), 1.47 (m, 12 H, 6 CH2CH2CH2), 1.26-1.29(s, 120 H, 60 CH2), 0.88 (t, J = 6.4 Hz, 36 H, 6 CH3). 13 C NMR (CDCl3; 600 MHz): 180.6, 161.7, 153.7, 140.3, 136.5, 130.3, 119.1, 113.8, 106.5, 73.8, 69.6,32.1, 26.6-29.8, 26.3, 22.9, 14.3. Example 2

[0032] Study on the liquid crystal properties of compound Py-n Compound Py-n exhibited a distinct, typical columnar birefringent liquid crystal texture under a polarizing microscope. Figure 4 The phase transition temperature of compound Py-n was obtained by differential scanning calorimetry (Table 1). Further X-ray diffraction analysis showed that compound Py-n formed a hexagonal columnar liquid crystal phase. Figure 5 ).

[0033] Table 1. Phase transition temperatures and lattice constants of compound Py-n Note: Cr: crystal; Col h = Hexagonal columnar phase; Iso: Isotropic liquid. Example 3

[0034] Study on the two-state luminescence properties of compound Py-n Compound Py-n was dissolved in tetrahydrofuran aqueous solutions with different water contents, where tetrahydrofuran was a good solvent for compound Py-n and water was a poor solvent for compound Py-n. Figure 6 It can be seen that compound Py-10 exhibits the strongest fluorescence emission in both pure tetrahydrofuran solution and tetrahydrofuran aqueous solution with 80% water content, indicating that compound Py-n has strong fluorescence emission (i.e., dual-state emission characteristics) in both pure solution and aggregated state, and can be used as a dual-state emission liquid crystal material. Example 4

[0035] Study on the electric field orientation properties of compound Py-n The compound Py-n was heated above the clearing point, and then encapsulated within an etched ITO glass liquid crystal cell via capillary action. A 50 V DC voltage was then applied to the top and bottom of the cell, and the liquid crystal texture of the compound was observed using a polarizing microscope. Figure 7 It can be seen that compound Py-10 exhibits a distinct columnar liquid crystal texture in the etched ITO glass region, while the liquid crystal texture disappears in the unetched ITO glass region. This indicates that under the action of a DC electric field, the columnar liquid crystal orientation of compound Py-10 changes from multi-axis to uni-axis. This electric field orientation capability may be caused by the polarization of the pyranone nucleus along the long axis of the column, suggesting that compound Py-n can serve as a potential ferroelectric material. Example 5

[0036] Study on the luminescent organogel properties of compound Py-n Compound Py-n was dissolved in different organic solvents (5.0 mg / mL), and its gelation ability was tested. Table 2 shows that compound Py-10 can form a stable yellow-green fluorescent organic gel in n-butanol. SEM analysis showed that the organic gel has a layered structure. Figure 8 ).

[0037] Table 2: Gel test results of compound Py-10 in different organic solvents Note: S represents solution; P represents precipitate; G represents gel; IS represents partial dissolution. Example 6

[0038] Research on compound Py-n as a fluorescent probe for picric acid Due to the excellent two-state luminescence and electron-rich properties of compound Py-n, it holds promise for the fluorescence detection of electron-deficient picric acid explosives. Ten equivalents of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 3-nitrotoluene (3-NT), 4-nitrotoluene (4-NT), 2,4-dinitrotoluene (2,4-DNT), and picric acid (PA) were added to a tetrahydrofuran solution of compound Py-10 (1 × 10⁻⁶). -6 M), to test its recognition ability. From Figure 9 As can be seen, the addition of PA effectively quenched the fluorescence of the Py-10 solution by 90.8%, indicating that Py-10 has a specific fluorescent recognition effect on PA. Further fluorescence titration showed that the detection limit of Py-10 for PA was 7.21 × 10⁻⁶. -9 M (Figure 10 This indicates that compound Py-n can serve as a highly sensitive and specific fluorescent probe for detecting PA.

[0039] In summary, this invention proposes a pyranone-based multifunctional luminescent liquid crystal compound, its preparation method, and its applications. The compound structure is shown in formula (Ⅰ), where n is 10, 12, or 14. The target product is obtained by reacting 3,4,5-trialkoxybenzaldehyde with 2,6-dimethyl-γ-pyranone in anhydrous ethanol under the action of sodium tert-butoxide, followed by recrystallization purification. The method of this invention uses readily available raw materials, has mild reaction conditions, and is simple to purify, making it suitable for industrial production. The pyranone-based luminescent liquid crystal compound provided by this invention combines the excellent luminescent properties of pyranone with the supramolecular self-assembly characteristics of liquid crystals, and can be applied to the fields of dual-state luminescent materials, ferroelectric materials, luminescent organogels, and picric acid fluorescent probes, showing broad application prospects.

[0040] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A pyranone-based multifunctional luminescent liquid crystal compound, characterized in that, Its structure is shown in equation (Ⅰ): （Ⅰ） Where n is any integer among 10, 12, or 14.

2. A method for preparing the pyranone-based multifunctional luminescent liquid crystal compound of claim 1, characterized in that, Includes the following steps: 3,4,5-trialkoxybenzaldehyde and 2,6-dimethyl-γ-pyranone were dissolved in anhydrous ethanol, stirred and mixed, and sodium tert-butoxide was added. The mixture was reacted at 50-70°C until the 2,6-dimethyl-γ-pyranone was completely converted. After post-treatment, the compound shown in formula (I) was obtained. Wherein, the number of carbon atoms of the alkoxy group in the 3,4,5-trialkoxybenzaldehyde is 10, 12 or 14, so as to obtain compounds of formula (Ⅰ) with n=10, 12 or 14 respectively.

3. The preparation method according to claim 2, characterized in that, The molar ratio of 3,4,5-trialkoxybenzaldehyde, 2,6-dimethyl-γ-pyranone and sodium tert-butoxide is 2:1:(1-2).

4. The preparation method according to claim 2 or 3, characterized in that, The post-processing includes: after the reaction is complete, removing the solvent by vacuum distillation, and purifying the resulting solid residue by recrystallization to obtain the compound shown in formula (I); and / or The solvent system used for recrystallization is dichloromethane and methanol.

5. A light-emitting device or optoelectronic material, characterized in that, It includes the pyranone-based multifunctional luminescent liquid crystal compound as described in claim 1.

6. A photoelectric material with electric field responsiveness, characterized in that, It includes the pyranone-based multifunctional luminescent liquid crystal compound as described in claim 1.

7. A luminescent organic gel, characterized in that, It comprises the pyranone-based multifunctional luminescent liquid crystal compound of claim 1 and a solvent.

8. The luminescent organogel as described in claim 7, characterized in that, The solvent is n-butanol.

9. The application of the pyranone-based multifunctional luminescent liquid crystal compound as described in claim 1 as a fluorescent probe in the detection of picric acid.

10. The application as described in claim 9, characterized in that, The detection method is fluorescence quenching detection.

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