A donor-acceptor type compound based on pyridine derivatives, and preparation method and application thereof

Abstract

The application discloses a donor-acceptor type compound based on a pyridine derivative or a pharmaceutically acceptable salt thereof, and a structural general formula is as follows: The donor-acceptor type compound based on the pyridine derivative has the characteristics of intramolecular charge transfer and aggregation-induced emission, is very sensitive to the content of water in an organic solution, has a high fluorescence quantum yield, and is a novel fluorescent sensor which can detect the water content in the organic solvent by detecting the emission intensity.

Description

Technical Field

[0001] This invention belongs to the field of organic materials technology, specifically, it relates to a donor-acceptor compound based on pyridine derivatives, its preparation method, and its application. Background Technology

[0002] Organic fluorescent materials have wide applications in fluorescence imaging, sensing, and organic light-emitting diodes due to their simple structure and stable luminescence. Common chromophores are usually planar aromatic ring functional groups, which also readily generate strong π-π interactions, aiding in crystal formation. However, this advantage also brings a fatal problem for luminescent materials: aggregation-induced quenching (ACQ). Molecules with ACQ can emit bright emission in dilute solutions, but show almost no emission in aggregates or solid states. This is because these molecules form aggregates at high concentrations due to non-covalent intermolecular forces. Studying the single-crystal structure of these molecules usually reveals strong π-π interactions, leading to the formation of multiple metastable energy levels, resulting in increased non-radiative channels in the solid state and emission quenching. In fact, the discovery of the ACQ phenomenon can be traced back to 1954. The book *Photophysics of Aromatic Molecules*, published in 1970, summarized the effects of aggregation-induced emission (ACQ) on many aromatic luminescent agents. Despite its long history, the ACQ problem has never been fully solved. In 2001, Tang et al. unexpectedly discovered that some fluorophores with distorted conformations exhibited stronger emission in the aggregated state than in the solution state, thus proposing and creating the concept of aggregation-induced emission (AIE). AIE behavior is defined as the higher photoluminescence efficiency of luminescent materials in the aggregated state compared to in solution. Since then, extensive experimental and theoretical research has been conducted to expand the scope of AIE and explore its underlying mechanisms. Currently, the most widely accepted explanation for the AIE mechanism is the restriction of intramolecular motion (RIM), including restriction of intramolecular rotation (RIR) and restriction of intramolecular vibration (RIV). In recent years, due to the broad development prospects of AIE molecules, many researchers have devoted themselves to studying the design principles, luminescence mechanisms, and the relationship between structure and properties of AIE molecules. To this day, high-performance AIE molecules continue to attract the attention of many researchers.

[0003] Modification of AIE molecules typically employs DA or D-π-A designs. In 2012, Park et al. synthesized and characterized a novel covalently linked single-molecule material based on a DA strategy. Unlike traditional luminescent color switching, this material exhibits reversible luminescent switching behavior in the solid state in response to external mechanical stimuli, achieving a contrast ratio of up to 1000 times. Through simulation calculations and analysis based on structure, thermodynamics, electrochemistry, and photophysics, the mechanically responsive light-switching capability was derived from three aspects: first, the appropriately aligned molecular orbital energy levels between the dicyanobenzene core and carbazole provide a basis for intramolecular electron transfer; second, the ability of carbazole and dicyanobenzene to form π-π stacking; and third, the flexibility of the linking groups, allowing switching between solid-state conformations. The unique structure in the crystalline phase leads to the formation of a non-luminescent CT state; conversely, in the externally shear-induced amorphous phase, the characteristic structure is disrupted, thus significantly slowing down the eT rate and restoring fluorescence. Furthermore, this group successfully demonstrated the application of a rewritable pressure-sensitive fluorescent recording medium with high contrast, high stability, and good processing performance. This research will inspire the development of a novel class of pressure-sensitive luminescent materials and further provide important insights into the solid-state luminescence properties of covalently linked DA-type molecules. In 2015, Tian et al. proposed a novel luminescent molecule, acridine-tetraphenylene derivative, which exhibits significant on-off and color-tuned luminescence under mechanical grinding or hydrostatic pressure. Based on in-depth experimental and computational studies, they hypothesized that the origin of the mechanosensitive color-changing behavior is a change in the intramolecular geometric conformation, particularly the torsion angle between the tetraphenylene and acridine moieties. The almost orthogonal conformation between the tetraphenylene and acridine groups completely separates the electron distribution and suppresses the ICT process, leading to the emission of locally excited states in the molecular crystal. When the molecule is mechanically stimulated, the force perturbation changes the twisted conformation, causing the leading orbitals between the donor and acceptor to overlap and form an intramolecular charge-transfer state. The mechanical stimulation induces a change in luminescence from a non-emitting phase to a bright cyan emitting phase. This further provides important insights into the solid-state luminescence properties of twisted DA molecules.

[0004] Quantitative detection of water in organic solvents is a crucial issue in both laboratory and industrial applications. With the development of organic chemistry, reaction systems requiring water have also emerged. Traditional methods typically involve the detection of trace amounts of water, but these methods may have drawbacks, such as being time-consuming and resource-intensive, requiring complex procedures, and exhibiting poor detection results, especially for water-dominant solvents. Therefore, developing a simple, rapid, and accurate method for the quantitative detection of high water content is of great significance for both laboratory and industrial applications. By designing suitable AIE (Aggregate Intramolecular Twisted Charge Transfer) and TICT (Intramolecular Twisted Charge Transfer) materials, highly sensitive detection of water content can be achieved, while also improving the accuracy and stability of the detection.

[0005] Novel AIE and TICT materials offer several advantages for the quantitative detection of water in organic solvents. First, their fluorescence properties in water are influenced by water content, enabling highly sensitive detection. Second, compared to traditional methods, the detection methods using these novel materials are simpler and faster, requiring no complex procedures and thus significantly improving detection efficiency. Furthermore, the design of these novel materials allows for accurate detection of water content in various organic solvents, thus offering broad applicability. Summary of the Invention

[0006] The first objective of this invention is to provide a donor-acceptor compound based on a pyridine derivative.

[0007] A second objective of this invention is to provide a method for preparing the donor-acceptor compound based on the pyridine derivative.

[0008] A third objective of this invention is to provide the application of the pyridine derivative-based donor-acceptor compound in the preparation of a water-content fluorescent probe.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] In a first aspect, the present invention provides a donor-acceptor compound based on a pyridine derivative or a pharmaceutical salt thereof, having one of the following general structural formulas:

[0011]

[0012] in,

[0013] X is hydrogen or nitrogen;

[0014] Y represents hydrogen or nitrogen.

[0015] Z represents hydrogen or nitrogen;

[0016] Furthermore, X and Y are not nitrogen at the same time, Y and Z are not nitrogen at the same time, and X and Z are not nitrogen at the same time.

[0017] Preferably, the structure of the pyridine derivative-based donor-acceptor compound is selected from one of the following structures:

[0018]

[0019] A second aspect of the present invention provides a method for preparing the donor-acceptor compound based on the pyridine derivative, comprising the following steps:

[0020]

[0021] 2-Naphthaldehyde and a cyano-containing compound in a molar ratio of 1:1 to 6 (preferably 1:4) are dissolved in a solvent (preferably methanol). 4-Methylpiperidine is added in an ice bath at 0°C. The molar ratio of 2-naphthaldehyde to 4-methylpiperidine is 1 to 6:1 (preferably 3:1). The mixture is stirred for 1 to 6 hours (preferably 3 hours) to obtain the donor-acceptor compound based on the pyridine derivative.

[0022] or,

[0023]

[0024] 3-(naphthyl-2-yl)propenal and a cyano-containing compound in a molar ratio of 1:1 to 6 (preferably 1:4) are dissolved in a solvent (preferably methanol). 4-methylpiperidine is added in an ice bath at 0°C. The molar ratio of 3-(naphthyl-2-yl)propenal to 4-methylpiperidine is 1 to 6:1 (preferably 3:1). The mixture is stirred for 1 to 6 hours (preferably 3) to obtain the donor-acceptor compound based on the pyridine derivative.

[0025] The cyano-containing compound is selected from one of the following structures:

[0026]

[0027] A third aspect of the present invention provides the use of the pyridine derivative-based acceptor compound or its pharmaceutical salt in the preparation of a water-content fluorescent probe.

[0028] In this application, a pyridine derivative-based donor-acceptor compound is dissolved in water and an organic solvent (tetrahydrofuran), and the fluorescence emission intensity is measured. The water content in the organic solvent is determined by comparing the measured fluorescence emission intensity with a standard curve.

[0029] In a fourth aspect, the present invention provides the use of the pyridine derivative-based donor-acceptor compound or a pharmaceutical salt thereof in the preparation of a fluorescent sensor.

[0030] By adopting the above technical solution, the present invention has the following advantages and beneficial effects:

[0031] The donor-acceptor compounds based on pyridine derivatives of the present invention have a simple synthesis method, low raw material cost, easy industrial production process, and efficient and convenient product purification, playing an important role in practical applications such as organic fluorescent probes.

[0032] The preparation method of this invention is simple, efficient, economical, and has value for large-scale production, while also being environmentally friendly. The main intermediates are fully commercialized, inexpensive, and readily available, possessing significant economic value. The pyridine derivative-based donor-acceptor compounds of this invention are easily modified, and different donor-acceptor compounds can be obtained through molecular engineering design.

[0033] The donor-acceptor compound based on pyridine derivatives provided by this invention solves the technical problems of complex synthesis routes and high costs in the prior art, and fills the gap for fluorescent probes with high water content.

[0034] The donor-acceptor compound based on pyridine derivatives provided by this invention has torsional intramolecular charge transfer and aggregation-induced emission properties, is highly sensitive to the water content in organic solutions, and has a high fluorescence quantum yield. It is a novel fluorescent sensor that can detect the water content in organic solvents by detecting the emission intensity. Attached Figure Description

[0035] Figure 1 The fluorescence emission spectra of compound 1-1 prepared in Example 1 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0036] Figure 2 This is a working curve of compound 1-1 prepared in Example 1 of the present invention in tetrahydrofuran solutions with different water contents.

[0037] Figure 3 The fluorescence emission spectra of compounds 1-2 prepared in Example 2 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0038] Figure 4 The graphs show the working curves of compounds 1-2 prepared in Example 2 of this invention in tetrahydrofuran solutions with different water contents.

[0039] Figure 5 The fluorescence emission spectra of compounds 1-3 prepared in Example 3 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0040] Figure 6 The graphs show the working curves of compounds 1-3 prepared in Example 3 of this invention in tetrahydrofuran solutions with different water contents.

[0041] Figure 7 The fluorescence emission spectra of compound 2-1 prepared in Example 4 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0042] Figure 8 This is a working curve of compound 2-1 prepared in Example 4 of the present invention in tetrahydrofuran solutions with different water contents.

[0043] Figure 9 The fluorescence emission spectra of compound 2-2 prepared in Example 5 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0044] Figure 10This is a working curve of compound 2-2 prepared in Example 5 of the present invention in tetrahydrofuran solutions with different water contents.

[0045] Figure 11 The fluorescence emission spectra of compounds 2-3 prepared in Example 6 of this invention in tetrahydrofuran solutions with different water contents are shown.

[0046] Figure 12 The graphs show the working curves of compounds 2-3 prepared in Example 6 of this invention in tetrahydrofuran solutions with different water contents. Detailed Implementation

[0047] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0048] The raw materials and reagents used in the embodiments of this invention are all commercially available products or prepared using conventional methods described in the literature.

[0049] Example 1

[0050] The preparation method of donor-acceptor compound 1-1 based on pyridine derivative includes the following steps:

[0051]

[0052] 2-Naphthaldehyde (25 mmol, 3.90 g), 2-(pyridin-2-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-Methylpiperidine (8 mmol, 1 mL) was added to the mixture under an ice bath at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 3-(naphth-2-yl)-2-(pyridin-2-yl)acrylonitrile, i.e., compound 1-1 (5.20 g, 81% yield). 1 HNMR (400MHz, DMSO-d6) δ8.71(ddd,J=4.8,1.8,0.9Hz,1H),8.64(s,1H),8.54–8.49(m,1H),8.21(dd,J=8.7,1.8Hz,1H),8.09( d,J=8.7Hz,1H),8.04–7.96(m,3H),7.90(dt,J=8.0,1.1Hz,1H),7.64(pd,J=6.9,1.6Hz,2H),7.47(ddd,J=7.5,4.7,1.1Hz,1H). 13CNMR(151MHz,DMSO)δ151.09,149.72,144.96,137.92,133.90,132.60,131.51,130.76,128.82,128.6 8,128.18,127.77,127.15,124.95,124.01,120.67,117.63,110.65.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2 + [M+H] + :257.1073; found:257.1069.

[0053] Compound 1-1 was prepared into a 0.01 mol / L tetrahydrofuran solution. 30 μL of the compound 1-1 tetrahydrofuran solution was then added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0054] Figure 1 The fluorescence emission spectra of compound 1-1 prepared in Example 1 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 2 This is a graph showing the working curves of compound 1-1 prepared in Example 1 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 1 As shown, the fluorescence emission intensity of compound 1-1 significantly increases with increasing water content, reaching 4.20 × 10⁻⁶ at 99% water content. 6 .Depend on Figure 1 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 2 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0055] A 30 μL solution of compound 1-1 in tetrahydrofuran (0.01 mol / L) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 1-1 in tetrahydrofuran (0.01 mol / L) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 2.31 × 10⁻⁶. 6 B = 4.20 × 10 6 Therefore, A divided by B equals 0.55. Substituting the vertical axis 0.55 into the working curve graph, we get the horizontal axis as 0.97, which indicates a water content of 97%.

[0056] Example 2

[0057] Synthesis and Application of Pyridine Derivative-Based Donor-Acceptor Compounds 1-2

[0058]

[0059] 2-Naphthaldehyde (25 mmol, 3.90 g), 2-(pyridin-3-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-Methylpiperidine (8 mmol, 1 mL) was added to the mixture under an ice bath at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 3-(naphth-2-yl)-2-(pyridin-3-yl)acrylonitrile, i.e., compounds 1-2 (4.44 g, 69% yield). 1 HNMR(400MHz, DMSO-d6)δ9.02(dd,J=2.5,0.8Hz,1H),8.66(dd,J=4.8,1.5Hz,1H),8.48–8.43(m,1H),8.34(s,1H),8.20(ddd ,J=8.1,2.5,1.6Hz,1H),8.14(dd,J=8.7,1.8Hz,1H),8.09(d,J=8.7Hz,1H),8.01(td,J=7.5,1.9Hz,2H),7.69–7.54(m,3H). 13 CNMR(151MHz,DMSO)δ149.98,146.83,144.55,133.76,133.36,132.54,131.13,130.76,130.02,128.7 3,128.65,128.06,127.78,127.16,124.84,124.00,117.47,107.47.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2+ [M+H] + :257.1073; found:257.1070.

[0060] Compounds 1-2 were prepared into tetrahydrofuran solutions with a concentration of 0.01 mol / L. 30 μL of each tetrahydrofuran solution was added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0061] Figure 3 The fluorescence emission spectra of compounds 1-2 prepared in Example 2 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 4 This is a graph showing the working curves of compounds 1-2 prepared in Example 2 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 3 As shown, the fluorescence emission intensity of compounds 1-2 significantly increased with increasing water content, reaching 1.23 × 10⁻⁶ at 99% water content. 6 .Depend on Figure 3 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 4 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0062] A 30 μL solution of compound 1-2 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 1-2 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 4.63 × 10⁻⁶. 5 B = 1.23 × 10 6Therefore, A divided by B equals 0.38. Substituting the vertical axis 0.38 into the working curve graph, we get the horizontal axis as 0.92, which indicates a water content of 92%.

[0063] Example 3

[0064] Synthesis and application of donor-acceptor compounds 1-3 based on pyridine derivatives

[0065]

[0066] 2-Naphthaldehyde (25 mmol, 3.90 g), 2-(pyridin-4-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-Methylpiperidine (8 mmol, 1 mL) was added to the mixture under an ice bath at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 3-(naphth-2-yl)-2-(pyridin-4-yl)acrylonitrile, i.e., compounds 1-3 (5.06 g, 79% yield). 1 HNMR(400MHz,DMSO-d6)δ8.76–8.70(m,2H),8.50(d,J=4.0Hz,2H),8.17(dd,J=8.7,1.8Hz,1H), 8.09(d,J=8.8Hz,1H),8.02(ddd,J=9.5,7.6,1.7Hz,2H),7.82–7.76(m,2H),7.70–7.58(m,2H). 13 CNMR(151MHz,DMSO)δ150.57,146.18,141.17,133.98,132.49,131.52,130.76,128.86,128.7 4,128.33,127.81,127.24,124.85,119.88,117.21,108.16.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2 + [M+H] + :257.1073; found:257.1069.

[0067] Compounds 1-3 were prepared into tetrahydrofuran solutions with a concentration of 0.01 mol / L. 30 μL of each tetrahydrofuran solution was then added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0068] Figure 5 The fluorescence emission spectra of compounds 1-3 prepared in Example 3 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 6 This is a graph showing the working curves of compounds 1-3 prepared in Example 3 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 5 As shown, the fluorescence emission intensity of compounds 1-3 significantly increased with increasing water content, reaching 9.98 × 10⁻⁶ at 99% water content. 5 .Depend on Figure 5 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 6 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0069] A 30 μL solution of compound 1-3 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 1-3 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 6.17 × 10⁻⁶. 5 B = 9.98 × 10 5 Therefore, A divided by B equals 0.62. Substituting the vertical axis 0.62 into the working curve graph, we get the horizontal axis as 0.94, which indicates a water content of 94%.

[0070] Example 4

[0071] Synthesis and application of donor-acceptor compound 2-1 based on pyridine derivatives

[0072]

[0073] 3-(naphth-2-yl)propenal (25 mmol, 4.56 g), 2-(pyridin-2-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-methylpiperidine (8 mmol, 1 mL) was added to the mixture under an ice bath at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 5-(naphth-2-yl)-2-(pyridin-2-yl)pent-2,4-dienenitrile, i.e., compound 2-1 (5.50 g, 78% yield). 1 HNMR (600MHz, DMSO-d6) δ8.65(dt,J=4.8,1.3Hz,1H),8.32(d,J=11.3Hz,1H),8.12(d,J=1.8Hz,1H),7.98(dd,J=6.0,3.5Hz,1H),7.95( d,J=8.6Hz,1H),7.91(td,J=7.9,2.1Hz,2H),7.84(dd,J=8.6,1.8Hz,1H),7.76(d,J=7.9Hz,1H),7.60–7.53(m,3H),7.47–7.38(m,2H). 13 CNMR(151MHz,DMSO)δ150.64,149.75,145.20,144.08,137.65,133.58,133.04,132.98,129.01,128.71,128.4 9,127.69,127.25,126.81,124.47,123.70,123.67,120.44,116.44,112.09.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2 + [M+H] + :283.1230; found:283.1230.

[0074] Compound 2-1 was prepared into a 0.01 mol / L tetrahydrofuran solution. 30 μL of the tetrahydrofuran solution of compound 2-1 was then added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0075] Figure 7 The fluorescence emission spectra of compound 2-1 prepared in Example 4 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 8 This is a graph showing the working curves of compound 2-1 prepared in Example 4 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 7 As shown, the fluorescence emission intensity of compound 2-1 significantly increases with increasing water content, reaching 3.41 × 10⁻⁶ at 99% water content. 5 .Depend on Figure 7 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 8 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0076] A 30 μL solution of compound 2-1 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 2-1 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 2.76 × 10⁻⁶. 5 B = 3.41 × 10 5 Therefore, A divided by B equals 0.81. Substituting the vertical axis 0.81 into the working curve graph, we get the horizontal axis as 0.98, which indicates a water content of 98%.

[0077] Example 5

[0078] Synthesis and Application of Pyridine Derivative-Based Donor-Acceptor Compound 2-2

[0079]

[0080] 3-(naphth-2-yl)propenal (25 mmol, 4.56 g), 2-(pyridin-3-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-methylpiperidine (8 mmol, 1 mL) was added to the mixture under ice bath conditions at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 5-(naphth-2-yl)-2-(pyridin-3-yl)pent-2,4-dienenitrile, i.e., compound 2-2 (4.94 g, 70% yield). 1 HNMR(600MHz, DMSO-d6)δ8.93(dd,J=2.5,0.9Hz,1H),8.60(dd,J=4.7,1.5Hz,1H),8.16–8.12(m,2H),8.09(ddd,J=8.1,2.5,1.6H z,1H),8.02–7.91(m,3H),7.86(dd,J=8.7,1.8Hz,1H),7.57–7.51(m,3H),7.49(d,J=15.3Hz,1H),7.43(dd,J=15.3,10.5Hz,1H). 13 CNMR(151MHz,DMSO)δ149.75,146.44,144.44,143.16,133.56,133.09,132.94,132.77,129.01,128.87,128.7 4,128.50,127.70,127.24,126.83,124.83,124.03,123.71,116.16,108.44.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2 + [M+H] + :283.1230; found:283.1228.

[0081] Compound 2-2 was prepared into a 0.01 mol / L tetrahydrofuran solution. 30 μL of the tetrahydrofuran solution was then added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0082] Figure 9 The fluorescence emission spectra of compound 2-2 prepared in Example 5 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 10 This is a graph showing the working curves of compound 2-2 prepared in Example 5 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 9 As shown, the fluorescence emission intensity of compound 2-2 significantly increases with increasing water content, reaching 8.37 × 10⁻⁶ at 99% water content. 4 .Depend on Figure 9 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 10 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0083] A 30 μL solution of compound 2-2 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 2-2 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 4.11 × 10⁻⁶. 4 B = 8.37 × 10 4 Therefore, A divided by B equals 0.49. Substituting the ordinate 0.49 into the working curve graph, we get the abscissa 0.91, which indicates a water content of 91%.

[0084] Example 6

[0085] Synthesis and application of donor-acceptor compounds 2-3 based on pyridine derivatives

[0086]

[0087] 3-(naphth-2-yl)propenal (25 mmol, 4.56 g), 2-(pyridin-4-yl)acetonitrile (100 mmol, 11.81 g), and methanol (100 mL) were added to a reaction vessel. 4-methylpiperidine (8 mmol, 1 mL) was added to the mixture under ice bath conditions at 0 °C, and the mixture was stirred for 3 hours. The reaction solution was filtered, and the solid was washed three times with 50 mL of methanol to give the product 5-(naphth-2-yl)-2-(pyridin-4-yl)pent-2,4-dienenitrile, i.e., compound 2-3 (5.79 g, 82% yield). 1 HNMR(600MHz, DMSO-d6)δ8.69–8.66(m,2H),8.30(d,J=11.0Hz,1H),8.19(d,J=1.8Hz,1H),8.04–8.00(m,1H),7.98(d,J=8.6 Hz,1H),7.96–7.93(m,1H),7.88(dd,J=8.6,1.7Hz,1H),7.69–7.66(m,2H),7.60–7.55(m,3H),7.46(dd,J=15.2,11.0Hz,1H). 13 CNMR(151MHz,DMSO)δ150.53,146.39,144.80,140.22,133.71,133.06,132.79,129.32,128.80,128.5 9,127.72,127.43,126.89,124.66,123.79,119.42,115.95,109.17.HR-MS(ESI):m / zcalculatedforC 20 H 15 N2 + [M+H] + :283.1230; found:283.1229.

[0088] Compound 2-3 was prepared into a 0.01 mol / L tetrahydrofuran solution. 30 μL of the tetrahydrofuran solution of compound 2-3 was then added to different water concentrations (specifically: ① 2970 μL tetrahydrofuran + 0 μL water; ② 2670 μL tetrahydrofuran + 300 μL water; ③ 2370 μL tetrahydrofuran + 600 μL water; ④ 2070 μL tetrahydrofuran + 900 μL water; ⑤ 1770 μL tetrahydrofuran + 1200 μL water; ⑥ 1470 μL tetrahydrofuran + 1500 μL water; ⑦ 1170 μL tetrahydrofuran + 1800 μL water; ⑧ 870 μL tetrahydrofuran + 2100 μL water; ⑨ 570 μL tetrahydrofuran + 2400 μL water; ⑩ 270 μL tetrahydrofuran + 2700 μL water). Prepare a 3 ml standard by mixing 0 μL tetrahydrofuran with 2970 μL water. Place the standard in a 1 cm × 1 cm × 4 cm quartz cuvette, excite at a wavelength of 365 nm, and measure the fluorescence emission curve of the sample. Plot the measured data as a reference standard.

[0089] Figure 11 The fluorescence emission spectra of compounds 2-3 prepared in Example 6 of this invention in tetrahydrofuran solutions with different water contents are shown. Figure 12 This is a graph showing the working curves of compounds 2-3 prepared in Example 6 of this invention in tetrahydrofuran solutions with different water contents. The horizontal axis represents water content, and the vertical axis represents fluorescence intensity / maximum fluorescence intensity. Figure 11 As shown, the fluorescence emission intensity of compounds 2-3 significantly increased with increasing water content, reaching 1.13 × 10⁻⁶ at 99% water content. 6 .Depend on Figure 11 The maximum fluorescence emission intensity data obtained was normalized to obtain the following: Figure 12 The working curve shown is used to determine the water content in a solvent. The specific procedure is as follows:

[0090] A 30 μL solution of compound 2-3 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of tetrahydrofuran solvent with unknown water content. The fluorescence emission intensity was measured, yielding data A. Another 30 μL solution of compound 2-3 in tetrahydrofuran (0.01 mol / L concentration) was added to 2970 μL of water, and the fluorescence emission intensity was measured, yielding data B. The water content was obtained by dividing A by B and comparing the result with a standard curve. The measured data A = 6.93 × 10⁻⁶. 5 B = 1.13 × 10 6 Therefore, A divided by B equals 0.62. Substituting the vertical axis 0.62 into the working curve graph, we get the horizontal axis as 0.93, which indicates a water content of 93%.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A donor-acceptor compound based on a pyridine derivative, characterized in that, The structure of the pyridine derivative-based donor-acceptor compound is selected from one of the following structures:

2. A method for preparing a donor-acceptor compound based on a pyridine derivative, characterized in that, Includes the following steps: 2-Naphthoaldehyde and a cyano-containing compound in a molar ratio of 1:1 to 6 were dissolved in a solvent, and 4-methylpiperidine was added in an ice bath at 0°C. The molar ratio of 2-naphthoaldehyde to 4-methylpiperidine was 1 to 6:

1. The mixture was stirred for 1 to 6 hours to obtain the donor-acceptor compound based on the pyridine derivative. The pyridine derivative-based acceptor compound is selected from one of the following compounds: The cyano-containing compound is selected from one of the following structures:

3. A method for preparing a donor-acceptor compound based on a pyridine derivative, characterized in that, Includes the following steps: 3-(naphthyl-2-yl)propenal and a cyano-containing compound in a molar ratio of 1:1 to 6 were dissolved in a solvent. 4-methylpiperidine was added in an ice bath at 0°C. The molar ratio of 3-(naphthyl-2-yl)propenal to 4-methylpiperidine was 1 to 6:

1. The mixture was stirred for 1 to 6 hours to obtain the donor-acceptor compound based on the pyridine derivative. The pyridine derivative-based acceptor compound is selected from one of the following compounds: The cyano-containing compound is selected from one of the following structures:

4. The use of the pyridine derivative-based donor-acceptor compound of claim 1 in the preparation of a fluorescent probe for water content in the organic solvent tetrahydrofuran.

5. The application of the pyridine derivative-based donor-acceptor compound of claim 1 in the preparation of a fluorescence sensor for water content in the organic solvent tetrahydrofuran.

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