Supramolecular macrocyclic aromatic hydrocarbon constructed based on naphthalene ring and benzophenone as well as synthesis method and application of supramolecular macrocyclic aromatic hydrocarbon

Abstract

The invention discloses supramolecular macrocyclic aromatic hydrocarbon constructed on the basis of naphthalene rings and benzophenone as well as a synthesis method and application of the supramolecular macrocyclic aromatic hydrocarbon, and belongs to the technical field of supramolecular chemistry. The supramolecular macrocyclic aromatic hydrocarbon takes a naphthalene ring and benzophenone as construction units, forms a central symmetry structure through methylene bridge connection, and has the characteristics of a hexagonal electron-deficient cavity and a non-covalent bond molecular pipeline; the synthesis method comprises two steps of Friedel-Crafts acylation synthesis of an intermediate and cyclization condensation synthesis of a target product, the reaction condition is mild, the operation is simple, and the cyclization yield is high. The invention further discloses a reddish charge transfer composite material formed by the macrocyclic aromatic hydrocarbon and 1, 2, 4, 5-tetracyanobenzene, the composite material has specific gasochromic response to benzene vapor, the color of the composite material is changed from reddish to orange brown after the composite material adsorbs the benzene vapor, and the composite material has no obvious response to other benzene series pollutants such as methylbenzene and dimethylbenzene. The method can be used for rapid and visual detection of benzene steam. The method has an important application value in the fields of supramolecular sensing and environmental monitoring.

Description

Technical Field

[0001] This invention belongs to the fields of organic synthetic chemistry and supramolecular chemistry, specifically relating to a supramolecular macrocyclic aromatic hydrocarbon constructed based on a naphthalene ring and benzophenone and its synthesis method, and also relating to the application of the charge transfer composite material formed by the macrocyclic aromatic hydrocarbon in benzene vapor detection. Background Technology

[0002] Macrocyclic aromatic hydrocarbons (MAHs) have long been considered important research subjects in supramolecular chemistry due to their unique molecular recognition capabilities and host-guest complexation behavior. With the continuous deepening of related research, these compounds have shown broad application potential in functional material construction, biomedical systems, and related fields of chemistry and chemical engineering. Therefore, the design and synthesis of supramolecular macrocyclic host molecules with novel structural configurations and special physicochemical properties has become an important direction in current supramolecular chemistry research. In particular, macrocyclic aromatic hydrocarbon systems possessing large and deep cavity structures, tunable optical responses, and unique spatial configurations have received widespread attention in recent years. However, due to limitations such as structural complexity and synthetic controllability, the construction of such macrocyclic host molecules still faces certain technical challenges. In recent years, with the rapid development of supramolecular chemistry and organic macrocyclic aromatic hydrocarbon research, in addition to traditional calixarene and pillararene systems, a variety of novel macrocyclic aromatic hydrocarbon host molecules with diverse functional properties have been reported. As an extended π-conjugated unit with both suitable spatial size and good optical response characteristics, the alkoxy-substituted derivatives of the naphthalene ring have gradually developed into important structural building blocks for constructing novel supramolecular macrocycles.

[0003] Benzene, a significant and widely distributed pollutant, poses a substantial hazard. The development of highly selective sensing materials for benzene has become a research hotspot in environmental monitoring, offering irreplaceable applications in industrial waste gas treatment, indoor air purification, water quality safety monitoring, and occupational health protection. However, the simple structure of the benzene molecule, lacking conjugated chromogenic or fluorescent functional groups, presents significant challenges for its visualization, qualitative, and quantitative detection. Currently used detection techniques such as gas chromatography, gas chromatography-mass spectrometry, and high-performance liquid chromatography often rely on large, sophisticated instruments, resulting in cumbersome procedures, long detection cycles, and difficulties in rapid on-site deployment, failing to meet the practical needs of real-time emergency monitoring. In contrast, optical sensing technology based on light signal response, with its advantages of fast response, ease of operation, excellent sensitivity, low cost, and the ability to achieve in-situ real-time monitoring, effectively overcomes the bottlenecks of traditional detection methods and has become a core research direction in the field of rapid benzene pollution detection, possessing a very broad application prospect.

[0004] The emergence of each new type of macrocyclic host has enriched the research of host-guest chemistry and supramolecular chemistry. However, there are currently no reports on supramolecular acceptor macrocycles constructed by linking naphthalene rings and benzophenone units through methylene bridges, and their use as selective gas-induced colorimetric detection materials for benzene vapor. Therefore, the design, synthesis, and application of macrocyclic aromatic hydrocarbons based on naphthalene rings and benzophenone are still of great research value. Summary of the Invention

[0005] The purpose of this invention is to provide a supramolecular macrocyclic aromatic hydrocarbon based on a naphthalene ring and benzophenone. This macrocyclic aromatic hydrocarbon has a specific cavity structure and non-covalent molecular channel characteristics, providing a novel host molecule for supramolecular assembly, adsorption separation and sensing material development.

[0006] Another objective of this invention is to provide a method for synthesizing the above-mentioned supramolecular macrocyclic aromatic hydrocarbons, which has mild reaction conditions, simple operation, and high cyclization yield, overcoming the shortcomings of traditional macrocyclic aromatic hydrocarbon synthesis with harsh conditions and cumbersome steps.

[0007] Another objective of this invention is to provide a charge transfer composite material based on the aforementioned macrocyclic aromatic hydrocarbons, and the application of this composite material in the detection of benzene vapor color change, thereby achieving high selectivity in distinguishing benzene from other benzene-related pollutants and solving the technical problems of poor selectivity, indistinct color change, and slow detection speed of existing benzene detection materials.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A supramolecular macrocyclic aromatic hydrocarbon constructed based on a naphthalene ring and benzophenone, with the following structural formula: .

[0009] The macrocyclic aromatic hydrocarbon uses naphthalene rings and benzophenone as building blocks, connected by methylene bridges to form a centrosymmetric structure with nanoscale electron-deficient cavities. The cavities are hexagonal in shape, with a major axis of 13.53 Å and a minor axis of 10.09 Å. The units connected by methylene bridges are staggered and not in the same plane. There are C−H•••π interactions between the methyl groups of adjacent moieties and the naphthalene ring, which can form non-covalent molecular channels. This structural characteristic gives it excellent molecular recognition and adsorption capabilities.

[0010] The above-mentioned method for synthesizing supramolecular macrocyclic aromatic hydrocarbons includes the following steps: a. Synthesis of intermediate fragments via Friedel-Crafts acylation reaction: Alkoxynaphthalene and terephthaloyl chloride were subjected to a Friedel-Crafts acylation reaction in an organic solvent in the presence of a catalyst. After the reaction, post-treatment yielded an intermediate fragment. The structural formula of the intermediate fragment is as follows: ; The alkoxynaphthalene is 2,6-dimethoxynaphthalene, the catalyst is aluminum trichloride, and the organic solvent is dichloromethane; the molar ratio of terephthaloyl chloride to alkoxynaphthalene is 1:4 to 1:5, the molar amount of catalyst is 1.3 to 1.4 times the molar amount of terephthaloyl chloride, the reaction temperature is 30 to 50°C, and the reaction time is 5 to 6 hours; the post-treatment steps include: quenching the reaction with water, stirring for 30 to 60 minutes, washing with distilled water, and separation and purification by column chromatography.

[0011] b. Cyclocondensation reaction to synthesize the target product: The intermediate fragment obtained in step a is subjected to a cyclization condensation reaction with paraformaldehyde in a Lewis acid catalyst and an organic solvent. After the reaction is completed, the supramolecular macrocyclic aromatic hydrocarbon is obtained by post-treatment.

[0012] The Lewis acid catalyst is boron trifluoride diethyl ether, and the organic solvent is 1,2-dichloroethane; the molar ratio of the intermediate fragment to paraformaldehyde is 1:2 to 1:4, the molar amount of the Lewis acid catalyst is twice the molar amount of the intermediate fragment, the reaction temperature is 40 to 60°C, and the reaction time is 10 to 20 min; the post-treatment steps include: terminating the reaction with water, washing with saturated sodium chloride solution, drying with anhydrous sodium sulfate, filtration, evaporation under reduced pressure, and separation and purification by column chromatography.

[0013] The synthesis route is as follows: .

[0014] This invention also provides a charge-transfer composite material, comprising the aforementioned supramolecular macrocyclic aromatic hydrocarbon as the host and 1,2,4,5-tetracyanobenzene (TCNB) as the guest, wherein the host and guest form a reddish host-guest complex through charge transfer. The molar ratio of the supramolecular macrocyclic aromatic hydrocarbon to 1,2,4,5-tetracyanobenzene is 1:2.

[0015] The application of the above-mentioned charge transfer composite material in the detection of benzene vapor color change is as follows: the composite material is exposed to the test gas environment and its color change is observed; if the material color changes from reddish-brown to orange-brown, it indicates that benzene vapor is present in the test gas environment; if there is no significant color change, it indicates that there is no benzene vapor or only other benzene-related pollutants are present in the test gas environment.

[0016] The gas environment to be tested is a gas environment containing benzene-based pollutants, including one or more of benzene, toluene, o-xylene, m-xylene, and p-xylene; the composite material has specific selectivity for benzene, and only undergoes a significant color change after adsorbing benzene vapor, while showing no significant color response to toluene, o-xylene, m-xylene, and p-xylene.

[0017] Compared with the prior art, the present invention has the following advantages: 1. Structural novelty: This invention designs and synthesizes a supramolecular macrocyclic aromatic hydrocarbon with naphthalene ring and benzophenone as building units and methylene bridges. This macrocyclic aromatic hydrocarbon has specific hexagonal electron-deficient cavities and non-covalent molecular channel characteristics. Its centrosymmetric structure and unique spatial configuration give it excellent molecular recognition, adsorption and supramolecular assembly capabilities, providing a novel host molecule for supramolecular chemistry research.

[0018] 2. Advantages of the synthesis method: This invention uses a two-step method to synthesize the target macrocyclic aromatic hydrocarbons. Compared with the harsh conditions (such as high temperature, high pressure, inert gas protection, and complicated steps) of traditional macrocyclic aromatic hydrocarbon preparation, this method has mild reaction conditions, does not require inert gas protection, is simple to operate, has a short reaction time, high cyclization yield, and is easy to scale up for industrial production, thus reducing the preparation cost of macrocyclic aromatic hydrocarbons.

[0019] 3. Excellent detection performance: Based on the charge transfer composite material formed by macrocyclic aromatic hydrocarbons and TCNB of this invention, highly selective gas-induced color change detection of benzene vapor is achieved, with the following advantages: ① High selectivity: It only produces a color response to benzene, which can effectively distinguish benzene from other benzene-related pollutants; ② Rapid response: A significant color change can be observed within 30 minutes after benzene vapor adsorption; ③ High visualization: The color changes from reddish-brown to orange-brown, with a significant change, without relying on precision instruments, enabling rapid on-site qualitative detection.

[0020] 4. Broad application prospects: The supramolecular macrocyclic aromatic hydrocarbons of this invention have potential application value in supramolecular assembly, adsorption separation, fluorescent probes, functional materials and other fields; the charge transfer composite materials constructed therefrom can be widely used for rapid on-site detection of benzene vapor in industrial waste gas, indoor air and occupational environment scenarios, providing new technical means for environmental monitoring and occupational health protection. Attached Figure Description

[0021] Figure 1 The 1H NMR spectrum of intermediate fragment (2) is shown.

[0022] Figure 2 The NMR carbon spectrum of intermediate fragment (2) is shown.

[0023] Figure 3 The mass spectrum of intermediate fragment (2) is shown.

[0024] Figure 4 The 1H NMR spectrum of macrocyclic aromatic hydrocarbon (1) is shown.

[0025] Figure 5 This is the mass spectrum of macrocyclic aromatic hydrocarbon (1).

[0026] Figure 6 The crystal structure diagram of macrocyclic aromatic hydrocarbon (1) is shown.

[0027] Figure 7 The following are the crystal structure diagrams of F-CLP@TCNB: a) is the packing diagram of F-CLP@TCNB crystal along the a-axis; b) is the packing diagram of F-CLP@TCNB crystal along the b-axis; c) is the packing diagram of F-CLP@TCNB crystal along the b-axis.

[0028] Figure 8 For density functional theory (DFT) calculations: (a) TCNB, (b) F-CLP and (c) F-CLP@TCNB frontier molecular orbitals and corresponding first band gap differences.

[0029] Figure 9 The solid-state UV-Vis spectra of F-CLP, F-CLP@TCNBα, and TCNB are shown.

[0030] Figure 10 The infrared spectrum of F-CLP@TCNB.

[0031] Figure 11 The image shows the gas-induced color change response of F-CLP@TCNBα in the vapors of benzene series pollutants (benzene, toluene, ortho-, meta-, and para-xylene).

[0032] Figure 12 The solid-state UV-Vis diffuse reflectance spectra of F-CLP@TCNBα adsorbing benzene series pollutants (benzene, toluene, ortho-, meta-, and para-xylene) vapors are shown in Figure 1. (a) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα; (b) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα after adsorbing Tol vapor; (c) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα after adsorbing mXL vapor; (d) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα after adsorbing Bz vapor; (e) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα after adsorbing oXL vapor; (f) Solid-state UV-Vis diffuse reflectance spectrum of F-LP@TCNBα after adsorbing pXL vapor.

[0033] Figure 13 This is a schematic diagram of the crystal structure of F-CLP@TCNBα after benzene adsorption and TCNB removal. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the instruments and reagents used are all commercially available conventional products; unless otherwise specified, the experimental methods used are all conventional experimental methods.

[0035] Example 1: Synthesis of supramolecular macrocyclic aromatic hydrocarbons a. In a 100 mL round-bottom flask, 2,6-dimethoxynaphthalene (2.78 g, 14.78 mmol), terephthaloyl chloride (1.00 g, 4.93 mmol), AlCl3 (1.44 g, 10.84 mmol), and dry CH2Cl2 (80 mL) were added sequentially. The reaction mixture was stirred at 40 °C for 6 hours, followed by quenching with water. The organic layer was washed with saturated NaCl solution and dried over anhydrous Na2SO4. Purification by silica gel thin-layer chromatography (mobile phase: petroleum ether / dichloromethane, polarity increasing ratio 1:1 to 1:5) yielded 1 g of a yellow solid intermediate fragment (compound 2), in 40% yield.

[0036] 1 H NMR (400 MHz, CDCl3, 298 K) δ (ppm):δ 7.86 (s, 6H), 7.41 (s, 2H),7.29 (s, 2H), 7.14 (s, 2H), 7.08 (dd, J = 9.2, 2.6 Hz, 2H), 3.89 (s, 6H),3.77 (s, 6H).13C NMR spectrum of2 is shown in Figure S2. 13C NMR (100 MHz, CDCl3, 298 K) δ (ppm): 155.81, 153.48, 139.96, 138.51, 130.31, 128.77, 128.49, 126.90, 126.85, 125.42, 122.04, 119.23, 114.34, 106.39, 55.89, 55.26, 30.34. Simulated molecular weight: m / z 507.1802, High-resolution mass spectrometry measured value: m / z 507.1806. b. The intermediate compound (100 mg, 0.197 mmol), paraformaldehyde (118 mg, 3.39 mmol), and dried 1,2-dichloroethane (50 mL) were added to a 100 mL round-bottom flask. Then, boron trifluoride diethyl ether (0.5 mL, 4.00 mmol) was added as a catalyst, and the reaction mixture was stirred at 60 °C for 10 min. The reaction was then terminated with water. The organic layer was washed with saturated NaCl solution and dried over anhydrous sodium sulfate. The organic layer was filtered and evaporated under reduced pressure. The residue was purified by silica gel column chromatography using a mobile phase of petroleum ether / dichloromethane (10:1 to 1:1) with gradually increasing polarity to give 62 mg of the target product, a supramolecular macrocyclic aromatic hydrocarbon (compound 1, F-CLP), in 30% yield.

[0037] 1 ¹H NMR (600 MHz, Chloroform-d) δ 8.17 (s, 4H), 7.34 (d, J = 9.3 Hz, 5H), 7.28 (s, 3H), 6.99 (d, J = 9.5 Hz, 5H), 4.92 (s, 5H), 4.10 (s, 16H), 3.64 (s, 16H); Molecular weight simulation: m / z 1037.3532, High-resolution mass spectrometry measured value: m / z 1037.3529. Example 2: Cultivation of Macrocyclic Aromatic Hydrocarbon Single Crystals Single-crystal culture of macrocyclic aromatic hydrocarbons (F-CLPs) constructed from naphthalene rings and benzophenone: 6 mg of pure macrocyclic aromatic hydrocarbons (F-CLPs) was weighed. Place the solution in a 4 mL glass vial, add 2.5 mL of analytical grade dichloromethane, and stir until completely dissolved to obtain a colorless and transparent solution. Place the vial open into a 15 mL glass vial containing 4 mL of analytical grade n-hexane, tighten the cap, and place in a cool, ventilated place to allow the poor solvent (n-hexane) to slowly evaporate into the good solvent (dichloromethane) system for single crystal cultivation. Avoid shaking the glass vial during cultivation. After 3 days of standing, a single crystal suitable for X-ray diffraction testing is obtained. The single crystal structure is as follows... Figure 6 The macrocyclic cavity is hexagonal in shape. The major axis of the cavity is 13.53 Å, and the minor axis is 10.09 Å. The entire single crystal exhibits centrosymmetry, but the units connected by methylene bridges are staggered and not on the same plane. Due to the C−H···π interaction between the methyl and naphthalene rings of adjacent units, the macrocyclic aromatic hydrocarbon possesses the ability to form non-covalent molecular channels, showing potential applications in supramolecular assembly and adsorption separation.

[0038] Example 3: Preparation of charge transfer composite material (F-CLP@TCNB) Supramolecular macrocyclic aromatic hydrocarbons (F-CLP, 0.048 mmol) and 1,2,4,5-tetracyanobenzene (TCNB, 0.096 mmol) were placed in a 50 mL flask, and 1 mL of analytical grade dichloromethane was added. The mixture was sonicated for 10 minutes until completely dissolved. The solvent was removed using a rotary evaporator to obtain a reddish-brown solid powder, which is the charge-transfer composite material (F-CLP@TCNB). Crystal structure analysis (…) Figure 7 ) and infrared spectroscopy testing ( Figure 10 This confirms that F-CLP and TCNB form a stable host-guest complex through charge transfer.

[0039] Figure 7The stacking diagrams of F-CLP@TCNB crystals along the a, b, and c axes are shown, demonstrating that the channels still exist after the host and guest components are combined. Figure 8 The LOMO and HOMO orbital energy levels and energy ranges of TCNB, F-CLP, and F-CLP@TCNB were calculated using density functional theory. After host-guest combination, the energy range decreased significantly, indicating a significant charge transfer interaction between F-CLP and TCNB. Figure 9 The figures show the solid-state UV-Vis diffuse reflectance spectra of F-CLP, TCNB, and F-CLP@TCNBα. As can be seen from the figures, after F-CLP and TCNB are prepared into host-guest composite materials, a charge transfer absorption band appears in the 400-600 nm range, which proves the charge transfer interaction between the two. Figure 10 These are Fourier transform infrared (FTIR) spectra of F-CLP@TCNBα, TCNB, and F-CLP. It can be seen that after F-CLP binds to TCNB, the cyano absorption peak changes from 2244 cm⁻¹. -1 up to 2246cm -1 The slight blue shift also demonstrates the interaction between the two.

[0040] Example 4: Gas-induced colorimetric detection experiment of composite materials for benzene series pollutants Take 50 mg of F-CLP@TCNB solid powder into a 20 mL glass bottle, place it in a vacuum oven at 70 °C for 6 hours to activate it and completely remove the solvent. Take 5 portions of the activated F-CLP@TCNB composite material, 5.00 mg each, and place them into 5 5.00 mL open vials respectively; at the same time, prepare 5 20.00 mL sealed vials, adding 1.00 mL of benzene, toluene, o-xylene, m-xylene, and p-xylene respectively as the gas source to be tested. Place the open vials containing the composite material into the corresponding sealed vials, seal them, and place them in a room temperature environment to observe the color change of the composite material, while simultaneously performing solid-state UV-Vis diffuse reflectance spectroscopy (UV-Vis). Figure 12 ).

[0041] Experimental results: After standing for 30 minutes, the composite material placed in a benzene vapor environment changed color from reddish-brown to orange-brown, showing a significant color change; while the composite material placed in toluene, o-xylene, m-xylene, and para-xylene vapor environments did not show significant color changes. Figure 11 Solid-state UV-Vis diffuse reflectance spectroscopy showed that the spectral curve of the composite material after adsorbing benzene vapor changed significantly, while the spectral curves after adsorbing other benzene-related pollutants did not change significantly, confirming that the composite material has a specific and selective detection capability for benzene vapor.

[0042] Mechanism analysis: combined with changes in crystal structure ( Figure 13 ) and DFT calculation results ( Figure 8After the composite material adsorbs benzene vapor, benzene molecules enter the cavity of F-CLP, disrupting the charge transfer between F-CLP and TCNB, causing TCNB to be removed from the composite, which in turn causes the material to change color; while other benzene-based pollutant molecules are not sized to fit the cavity and cannot effectively enter the cavity to disrupt the charge transfer, so they do not have a color response.

Claims

1. A supramolecular macrocyclic aromatic hydrocarbon constructed from a naphthalene ring and benzene, with the following structural formula: 。 2. The supramolecular macrocyclic aromatic hydrocarbon according to claim 1, characterized in that, This macrocyclic aromatic hydrocarbon uses a naphthalene ring and benzophenone as building blocks, which are connected by methylene bridges to form a nanoscale electron-deficient cavity with a centrosymmetric structure. The cavity is hexagonal in shape, with a major axis of 13.53 Å and a minor axis of 10.09 Å. The units connected by the methylene bridges are interleaved and not in the same plane. There are C−H···π interactions between the methyl groups of adjacent moieties and the naphthalene ring, which can form non-covalent molecular channels.

3. The method for synthesizing supramolecular macrocyclic aromatic hydrocarbons according to claim 1 or 2, characterized in that, Includes the following steps: a. In the presence of a catalyst, alkoxynaphthalene is subjected to a Friedel-Crafts acylation reaction with terephthaloyl chloride in an organic solvent to obtain an intermediate fragment; The structural formula of the intermediate fragment is: ; b. The intermediate fragment obtained in step a is subjected to a cyclization condensation reaction with paraformaldehyde in a Lewis acid catalyst and an organic solvent to obtain a supramolecular macrocyclic aromatic hydrocarbon.

4. The synthesis method according to claim 3, characterized in that, In step a, the alkoxynaphthalene is 2,6-dimethoxynaphthalene; the catalyst is aluminum trichloride; and the organic solvent is dichloromethane.

5. The synthesis method according to claim 3, characterized in that, In step a, the molar ratio of terephthaloyl chloride to alkoxynaphthalene is 1:4 to 1:5; the molar amount of the catalyst is 1.3 to 1.4 times the molar amount of terephthaloyl chloride; and the Friedel-Crafts acylation reaction is carried out at 30 to 50°C for 5 to 6 hours.

6. The synthesis method according to claim 3, characterized in that, In step b, the Lewis acid catalyst is boron trifluoride diethyl ether; the organic solvent is 1,2-dichloroethane; the molar ratio of the intermediate fragment to paraformaldehyde is 1:2 to 1:4; the molar amount of the Lewis acid catalyst is twice the molar amount of the intermediate fragment; and the cyclization condensation reaction is carried out at 40 to 60 °C for 10 to 20 min.

7. A charge transfer composite material, characterized in that, The supramolecular macrocyclic aromatic hydrocarbon described in claim 1 or 2 serves as the host, and 1,2,4,5-tetracyanobenzene serves as the guest. The host and guest form a reddish-brown host-guest complex through charge transfer interaction.

8. The application of the composite material according to claim 7 in the gas-induced color change detection of benzene vapor.

9. The application according to claim 8, characterized in that, Expose the composite material to the test gas environment and observe its color change; if the material color changes from reddish-brown to orange-brown, it indicates the presence of benzene vapor in the test gas environment.

10. The application according to claim 9, characterized in that, The gas environment to be tested is a gas environment containing benzene-based pollutants, which include one or more of benzene, toluene, o-xylene, m-xylene, and p-xylene; and the color change is selective for benzene.

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