Organic fluorescent material based on benzophenone bridging group, and preparation method and application thereof

Abstract

The application discloses a kind of organic fluorescent materials based on benzophenone bridging group and preparation method and application;The organic fluorescent material has structure shown in formula I, wherein R 1 It is nitrogen-containing heterocyclic electron donor group, and is connected with the benzene ring of benzophenone bridging group through nitrogen atom;R2 is di (mesityl) boron-based electron acceptor;The material takes the carbonyl carbon of benzophenone as bridging node, constructs space charge transfer system, realizes the fluorescence enhancement response to fluoride ion and the fluorescence quenching response to hydrogen fluoride, and first completes the signal level distinction recognition to two fluoride forms.Simultaneously, the synergistic effect of rigid nitrogen-containing heterocyclic donor and steric hindrance aryl boron acceptor effectively inhibits aggregation quenching, and gives material high solid-state fluorescence quantum yield;The material preparation method is simple, detection sensitivity is high, selectivity is excellent, and has wide application prospect in industrial fluoride leakage tracing, environmental monitoring and on-site visual detection.

Description

Technical Field

[0001] This invention relates to an organic fluorescent material based on a benzophenone bridging group, its preparation method, and its application, and relates to the field of organic fluorescent sensing materials technology, specifically to an organic fluorescent material that can distinguish and detect hydrogen fluoride and fluoride ions, its preparation method, and its application. Background Technology

[0002] Since the beginning of the 21st century, with the vigorous development of strategic emerging industries such as fluorochemicals, semiconductors, and new energy, the importance of accurate detection technology for hydrogen fluoride and fluoride ions in industrial safety, environmental monitoring, and public health has become increasingly prominent. Hydrogen fluoride (HF), as a core raw material in the fluorochemical industry chain, is colorless, highly volatile, and highly toxic. While difficult to detect at low concentrations, it can be rapidly absorbed through the respiratory tract and skin, causing serious lesions ranging from acute chemical pneumonia to chronic fluorosis. Simultaneously, the accumulation of excessive fluoride ions in water bodies can lead to endemic fluorosis diseases such as dental fluorosis and skeletal fluorosis. However, traditional detection methods such as chromatography (expensive equipment, cumbersome pretreatment, and inability to monitor in real time) and electrochemical methods (severe interference from ions, easy electrode aging, and lack of online monitoring capabilities) cannot meet the rigid demand for real-time, in-situ, and visualized detection of fluorides in industrial sites and complex environments. Therefore, the development of novel fluoride sensing technologies has become a research hotspot in analytical chemistry and public safety.

[0003] Organic fluorescent probe technology, as a new generation of chemical sensing methods, can efficiently convert molecular-level chemical recognition events into optical signals such as fluorescence intensity, wavelength, or lifetime, thereby achieving high spatiotemporal resolution in-situ visual detection of target analytes and demonstrating great application potential in the field of fluoride ion sensing. In recent years, fluoride ion fluorescent probes based on different fluorescent backbones (such as BODIPY, coumarin, naphthalimide, fluorescein, etc.) and recognition mechanisms (such as hydrogen bonding / deprotonation, Si-O bond breaking, BF coordination, etc.) have emerged continuously. The detection environment has expanded from pure organic solvents to pure aqueous phases, environmental water samples, biological fluids, and even living cell and animal systems. The detection phenomena cover various modes such as fluorescence quenching, fluorescence enhancement, ratiometric fluorescence change, and colorimetric response. These probes have advantages such as high sensitivity, high selectivity, rapid response, ease of operation, and the ability to fabricate portable solid-state sensor devices, and are considered one of the most promising technical routes for achieving real-time on-site monitoring of fluorides.

[0004] Currently, there are numerous reports on fluorescent probes for fluoride ions in the green and yellow light bands, which can basically meet the needs of quantitative detection of fluoride ions in conventional aqueous phases. However, for complex applications such as early warning of hydrogen fluoride gas leaks and tracing the source of fluoride ion pollution, existing probe systems still have a fundamental bottleneck—they cannot distinguish between hydrogen fluoride (HF) and fluoride ions. Because HF partially dissociates in aqueous solution... and Existing probes all target the dissociated state as their recognition site. Thermodynamic design is performed, and its chemical recognition events occur in HF aqueous solutions and In aqueous solutions, the "convergent pathways" result in highly homogeneous optical signals at the final output. This means that while the sensor reports the presence of fluoride, it cannot inform decision-makers whether the threat originates from dissolved HF gas leaking from the atmosphere or from pre-existing fluoride contamination in the water. In practical emergency response, this lack of information directly leads to ambiguity or even bias in the selection of response plans, severely hindering the practical application of fluorescence sensing technology from the laboratory to industrial settings. Triarylborane groups, as an effective and sensitive... Recognition motifs have garnered significant attention in the design of fluoride ion probes. However, traditional triarylborane probes inevitably suffer from limitations such as inability to distinguish between hydrogen fluoride and fluoride ions, poor solid-state processability, and insufficient photostability in biological systems. To address these issues, the design of steric hindrance around the boron acceptor, the selection of auxiliary recognition motifs, and the regulation of overall solid-state assembly of the molecule are crucial. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides an organic fluorescent material based on benzophenone bridging groups, its preparation method, and its application. The triarylboryl organic fluorescent material based on benzophenone bridging groups and nitrogen-containing heterocyclic donor groups has high sensitivity and high selectivity, and can achieve signal-level differentiation and recognition of hydrogen fluoride and fluoride ions.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an organic fluorescent material based on benzophenone bridging groups, having the structure shown in Formula I: Formula I In the formula, there are two 1,4-phenylene groups; R1 is selected from one of the following groups: 9,9-dimethyl-9,10-dihydroacrylin-10-yl, phenothiazine-10-yl, carbazole-9-yl; the structures are as follows: , , ; R2 is a bis(trimethyl)boron group; its structure is: ; Furthermore, R1 is directly connected to the para-carbon atom of the adjacent Ph group through the nitrogen atom on its ring.

[0007] Preferably, it has the structure shown in Formula I-1, Formula I-2 or Formula I-3: Formula I is defined as R1 being 9,9-dimethyl-9,10-dihydroacrylin-10-yl; the specific structure is as follows: Formula I-1; Formula I-2 is where R1 is phenothiazine-10-yl; the specific structure is as follows: Formula I-2; Formula I-3 is where R1 is carbazole-9-yl; the specific structure is as follows: Formula I-3.

[0008] This invention discloses a method for preparing an organic fluorescent material, comprising the following steps: S1. Bromobenzoyl chloride and fluorobenzene undergo a Friedel-Crafts acylation reaction at 110–130 °C in the presence of excess fluorobenzene as a solvent and aluminum trichloride as a catalyst to yield 4-fluoro-4'-bromobenzophenone; the specific structure is Formula A: Formula A; S2. Compounds with the structure shown in Formula A, nitrogen-containing heterocyclic compounds, and basic catalysts undergo nucleophilic substitution reactions in N,N'-dimethylformamide solvent to obtain compounds B-1, B-2, and B-3 with the structure shown in Formula B; S2.3. In N,N'-dimethylformamide, the product of S1 is reacted with 9,9-dimethyl-9,10-dihydroacridine, phenothiazine, or carbazole under alkaline catalysis at 110–130 °C to undergo a nucleophilic substitution reaction to obtain compound B; compound B is of formula B-1, B-2, or B-3; the specific structure is as follows: Formula B-1; Formula B-2; Formula B-3; S3. Under anhydrous and oxygen-free conditions, at -78°C to room temperature, the compound of formula B is reacted with bis(trimethyl)boron fluoride and n-butyllithium in ultra-dry tetrahydrofuran or n-hexane to obtain the material of formula I.

[0009] Preferably, in S1, the molar ratio of p-bromobenzoyl chloride to fluorobenzene is 1:6-8, the molar ratio of p-bromobenzoyl chloride to aluminum trichloride is 1:1-1.2, and the reaction time is 6-12 hours.

[0010] Preferably, in S2, the molar ratio of the nitrogen-containing heterocyclic compound to 4-fluoro-4'-bromobenzophenone is 1:1 to 1.2; the alkaline catalyst is cesium carbonate, potassium acetate, potassium carbonate, or sodium carbonate, and the amount used is 3 to 5 times the molar amount of the nitrogen-containing heterocyclic compound; the reaction time is 6 to 12 hours.

[0011] Preferably, in S3, the molar ratio of the compound with the structure shown in Formula B to boron bis(trimethyl)fluoride is 1:1 to 1.2; the molar ratio of the compound with the structure shown in Formula B to n-butyllithium is 1:1 to 1.2; the solvent is n-hexane or ultra-dry tetrahydrofuran; and the reaction time is 12-24 h.

[0012] This invention discloses a method for distinguishing and detecting hydrogen fluoride and fluoride ions, using the aforementioned organic fluorescent material as a probe, comprising: a. Dissolve the material in an organic solvent or an aqueous mixed solvent to prepare a detection system; b. Add the sample to be tested and record the changes in the fluorescence spectrum; c. If the fluorescence intensity increases and the emission peak shifts to blue, then it is determined to contain fluoride ions. If the fluorescence intensity is quenched and the emission peak is blue-shifted, then it is determined to contain hydrogen fluoride (HF).

[0013] Preferably, the concentration of the organic fluorescent material in the detection system is 1–20 μM, and the excitation wavelength is 350–500 nm; the organic solvent is one or more of toluene, tetrahydrofuran, or dimethyl sulfoxide.

[0014] This invention discloses the application of an organic fluorescent material in the preparation of a solid-state sensor for on-site visual detection of hydrogen fluoride gas. The solid-state sensor is a test paper, a thin film, or a nanofiber membrane. The organic fluorescent material has a fluorescence quantum yield of not less than 40% in the solid state.

[0015] The compounds of this invention introduce a nitrogen-containing heterocycle as an electron donor on the bridging group and a boron-containing group with steric hindrance as a fluoride ion recognition acceptor, forming a space charge transfer system, which is beneficial for the distinguishable detection of hydrogen fluoride and fluoride ions.

[0016] Among them, triarylboron derivatives are an important structural type for achieving highly selective recognition of fluoride ions. They utilize the empty p orbitals of boron atoms as Lewis acid recognition sites, and... BF coordination occurs, causing a significant change in the intramolecular charge transfer (ICT) state, thereby outputting a sensitive spectral response signal. To achieve the distinguishable detection of hydrogen fluoride and fluoride ions, two common fluorescent material design strategies are employed: one utilizes boron atoms and... The direct coordination effect allows for single-point identification and output of a single response signal, but these probes are only effective against the dissociated state. The response cannot distinguish between HF aqueous solution and signal at the signal dimension. Salt solutions cause a loss of distinguishing detection capabilities. An alternative strategy is to introduce proton-paired molecules into the boron-containing framework. Sensitive auxiliary recognition groups or the construction of multi-mode signal output channels enable the probe to target HF molecules (simultaneously providing...) and ) and isolation Ions produce differentiated optical responses, enabling signal-level differentiation and identification of the two analytes. By modulating the structure of the triarylboron acceptor (A), electron donor (D), and auxiliary recognition group (R), the molecular energy level, charge transfer mode, recognition thermodynamics, and signal output mode can be controlled, thereby endowing the probe with the ability to identify fluoride speciation. Such materials have broader application prospects in real-time industrial monitoring and fluoride source tracing in complex environments.

[0017] The nitrogen-containing heterocyclic electron-donating group and benzophenone bridging group provided in this invention have rigid structures, which helps reduce non-radiative transition paths and improve the fluorescence quantum yield of the probe. The introduction of a boron-containing acceptor group with steric hindrance provides high selective recognition by utilizing the empty p orbitals of boron atoms to specifically coordinate with fluoride ions, and by modulating the steric environment around the acceptor, enables the probe to target hydrogen fluoride molecules (while simultaneously providing...). and The probe exhibits differentiated optical responses to isolated fluoride ions, enabling distinguishable detection of both. Furthermore, by modulating the electron cloud distribution of the molecular frontier orbitals, the probe possesses suitable HOMO and LUMO energy levels, which facilitates optimization of photoinduced electron transfer (PET) and intramolecular charge transfer (ICT) processes, improving the detection signal-to-noise ratio and response sensitivity. As shown in the test results of the examples, the organic fluorescent material provided by this invention exhibits fluorescence response wavelengths of fluoride ions in the range of 510–535 nm, with a detection limit as low as 162 nM; fluorescence response wavelengths of hydrogen fluoride aqueous solutions in the range of 528–537 nm, with a detection limit as low as 838 nM; and a fluorescence quantum yield of 40.2–50.6%. It also demonstrates clearly distinguishable fluorescence response signals to hydrogen fluoride aqueous solutions and fluoride salt aqueous solutions.

[0018] The organic fluorescent material provided by this invention uses a nitrogen-containing heterocycle as an electron donor group, introduces benzophenone as a bridging group on the nitrogen atom of the nitrogen-containing heterocycle, and introduces an arylboron derivative with steric hindrance as a fluoride ion recognition acceptor to form a space charge transfer system. The nitrogen-containing heterocycle electron donor group provided by this invention has a rigid structure, which is beneficial to reduce non-radiative transition paths and improve the fluorescence quantum yield of the probe. The carbonyl carbon atom with sp² electron structure on the benzophenone serves as a connecting node, effectively regulating the intramolecular charge transfer between the electron donor and acceptor, so that the probe maintains a low background fluorescence when it is not bound to fluoride ions. The arylboron derivative acceptor utilizes the empty p orbital of the boron atom to conduct specific BF coordination with fluoride ions, providing high selective recognition ability. At the same time, it has a large steric hindrance, which can suppress intermolecular π-π stacking, avoid luminescence quenching due to probe aggregation, and improve the luminescence efficiency of the probe in the solid state. Furthermore, by modulating the electron cloud distribution of the molecular frontier orbitals, the probe possesses suitable HOMO and LUMO energy levels, which is beneficial for optimizing photoinduced electron transfer and intramolecular charge transfer processes, thereby improving the sensitivity and signal-to-noise ratio for distinguishing between hydrogen fluoride and fluoride ions. The method for preparing organic fluorescent materials provided by this invention has readily available starting materials, mild reaction conditions, and simple operation steps, which helps to reduce preparation costs. The probe can be used for the distinguishing detection of fluoride ions and hydrogen fluoride in solution phase, and has high sensitivity and selectivity.

[0019] Compared with the prior art, the present invention has the following beneficial effects.

[0020] 1. This invention is the first to achieve distinguishable fluorescence detection of fluoride ions and hydrogen fluoride, and the material is effective against... It exhibits a fluorescence "on" response and a fluorescence "quenching" response for HF, with opposite signal directions, providing clear traceability information for emergency decision-making.

[0021] 2. In this invention, the carbonyl sp² carbon node of the benzophenone bridging group effectively regulates the intramolecular charge transfer process, maintaining low background fluorescence when unbound and generating a high signal-to-noise ratio signal after binding. The rigid nitrogen-containing heterocyclic donor reduces non-radiative transition paths, endowing the material with high fluorescence quantum yield (40.2–50.6% in solution).

[0022] 3. The acceptor portion of this invention employs a sterically hindered di(trimethylyl)boron group, which can interact with... It exhibits highly selective BF coordination and effectively suppresses intermolecular π-π stacking, overcoming the aggregation quenching problem of traditional fluorescent probes and improving the luminescence efficiency in the solid state, making it suitable for solid-state sensor devices such as test paper and thin film.

[0023] 4. The preparation method of this invention uses readily available raw materials, has mild reaction conditions, is simple to operate, and the product is easy to purify, thus possessing good prospects for industrial application. Attached Figure Description

[0024] The present invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 The fluorescence spectrum of Example 1 in toluene solution is shown.

[0026] Figure 2 This is the fluorescence spectrum of Example 2 in toluene solution.

[0027] Figure 3 This is the fluorescence spectrum of Example 3 in toluene solution.

[0028] Figure 4 The fluorescence spectrum of Example 1 under TBAF titration (0-10 eq) is shown.

[0029] Figure 5 The image shows the UV-Vis absorption spectrum of Example 1 under TBAF titration (0-10 eq).

[0030] Figure 6 The fluorescence spectrum of Example 1 under HF titration (0-10 eq) is shown.

[0031] Figure 7 The image shows the UV-Vis absorption spectrum of Example 1 under HF titration (0-10 eq). Detailed Implementation

[0032] This invention provides an organic fluorescent material based on a benzophenone bridging group, having the structure shown in Formula I: Formula I; In equation I, R1 is... , or ; In equation I, R2 is... ; In this invention, the organic fluorescent material has the structure shown in any one of Formula I-1, Formula I-2, and Formula I-3: Formula I-1 Formula I-2 Formula I-3 This invention provides a method for preparing the organic fluorescent material described above, comprising the following steps: (1) A Friedel-Crafts acylation reaction was carried out in a solvent with bromobenzoyl chloride, fluorobenzene, and aluminum trichloride catalyst to obtain a compound with the structure shown in Formula A; Formula A (2) Compounds with the structure shown in Formula A, nitrogen-containing heterocyclic compounds, and basic catalysts undergo nucleophilic substitution reactions in N,N'-dimethylformamide (DMF) solvent to obtain compounds with the structure shown in Formula B (B-1, B-2 and B-3); Formula B-1 Formula B-2 Type B-3 (3) The compound shown in Formula B, bis(trimethylyl)boron fluoride, and n-butyllithium undergo a nucleophilic substitution reaction in a solvent to obtain an organic fluorescent material with the structure shown in Formula I.

[0033] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0034] In this invention, p-bromobenzoyl chloride, fluorobenzene, and aluminum trichloride are subjected to a Friedel-Crafts acylation reaction in a solvent to obtain a compound with the structure shown in Formula A.

[0035] In this invention, the solvent is an excess of fluorobenzene solvent; the molar mass ratio of benzoyl chloride to fluorobenzene is 1:6 to 8; and the molar ratio of p-bromobenzoyl chloride to aluminum trichloride is 1:1 to 1.2.

[0036] In this invention, the mixing of p-bromobenzoyl chloride, fluorobenzene, and aluminum trichloride in an excess of fluorobenzene solvent preferably includes thoroughly mixing p-bromobenzoyl chloride with an excess of fluorobenzene, evacuating the system and purging nitrogen three times, adding the aluminum trichloride catalyst, and stirring at the reaction temperature.

[0037] In this invention, the addition temperature of the aluminum trichloride catalyst is preferably 0°C, the temperature at which the catalyst and reactants are fully mixed is preferably room temperature 25-30°C, and the time is preferably 1-2 h; the reaction temperature of p-bromobenzoyl chloride with fluorobenzene is preferably 85-90°C, and the time is preferably 6-8 h.

[0038] In this invention, the equation for the Friedel-Crafts acylation reaction is as follows:

[0039] After completing the Friedel-Crafts acylation reaction, the present invention preferably adds 30 mL of deionized water to the reaction system, raises the temperature of the reaction system to a preferred temperature of 100–130 °C, and removes excess fluorobenzene through a Dean-Stark hydrophobic valve with a condenser for a preferred time of 5–6 h. After completing the removal of fluorobenzene, the present invention preferably cools to room temperature, adds the obtained Friedel-Crafts acylation reaction product to ice water, precipitates a white solid, extracts it with dichloromethane, and purifies the crude product by column chromatography (petroleum ether: ethyl acetate = 4:1) to obtain a white solid product, which is the compound with the structure shown in Formula A.

[0040] After obtaining the compound with the structure shown in Formula A, the present invention carries out a nucleophilic substitution reaction of the compound with the structure shown in Formula A, a basic catalyst, and a nitrogen-containing heterocyclic compound in DMF solvent to obtain the compound with the structure shown in Formula B (B-1, B-2, B-3).

[0041] In this invention, the alkaline catalyst is cesium carbonate, potassium acetate, potassium carbonate, or sodium carbonate; the molar ratio of the nitrogen-containing heterocyclic donor group to A is 1:1 to 1.2; and the molar ratio of the nitrogen-containing heterocyclic donor group to the alkaline catalyst is 1:3 to 5.

[0042] In this invention, the preferred method of mixing the compound with the structure shown in Formula A, the nitrogen-containing heterocyclic compound, and the basic catalyst in a DMF solvent includes: adding the compound with the structure shown in Formula A, the nitrogen-containing heterocyclic compound, and the basic catalyst into an ultra-dry DMF solvent, evacuating the vacuum and purging nitrogen three times, and stirring and heating to the temperature of the nucleophilic substitution reaction.

[0043] In this invention, the nucleophilic substitution reaction is carried out at a temperature of 110–130 °C for 6–12 h; the equation for the nucleophilic substitution reaction is as follows: B-1 B-2 B-3 In this invention, after the nucleophilic substitution reaction is completed, the reaction is preferably cooled to room temperature, ice water is added to the reaction system to quench the reaction, dichloromethane is used for extraction, the organic phase is washed with saturated sodium chloride solution and dried with anhydrous magnesium sulfate, filtered, and the organic solvent in the organic phase is distilled under reduced pressure. The crude product is purified by column chromatography (petroleum ether: ethyl acetate) to obtain the compound with the structure shown in Formula B.

[0044] After obtaining the compound with the structure shown in Formula B, the present invention carries out a nucleophilic substitution reaction between the compound with the structure shown in Formula B and bis(trimethylyl)boron fluoride and n-butyllithium at -78 °C to obtain an organic fluorescent material with the structure shown in Formula I.

[0045] In this invention, the molar ratio of the compound of formula B to boron bis(trimethyl)fluoride is 1:1 to 1.2; the molar ratio of the compound of formula B to n-butyllithium is 1:1 to 1.2; the solvent is n-hexane or ultra-dry tetrahydrofuran; this invention does not have special requirements on the amount of solvent used, as long as it is sufficient to dissolve the compound of formula B.

[0046] In this invention, there are no special requirements for the mixing process; any mixing process well known in the art can be used.

[0047] In this invention, the nucleophilic substitution reaction is carried out at a temperature of -78 °C; the reaction time is 12-24 h; and the nucleophilic reaction is carried out under a nitrogen atmosphere.

[0048] In this invention, the reaction equation for the nucleophilic substitution reaction is as follows: Formula I-1 Formula I-2 Formula I-3 After the affinity substitution reaction is completed, the present invention preferably pours the obtained reaction solution into ice water, extracts it with dichloromethane, concentrates it under reduced pressure, and purifies it by column chromatography (petroleum ether: ethyl acetate) to obtain an organic fluorescent material with the structure shown in Formula I based on the benzophenone bridging group.

[0049] This invention provides the application of the organic fluorescent material described in the above-described scheme, or the organic fluorescent material prepared by the above-described method, in the fluorescence detection of hydrogen fluoride and fluoride ions.

[0050] This invention provides a method for detecting fluoride ions using fluorescence, with an organic fluorescent material as the fluorescence sensing material. The organic fluorescent material is either the organic fluorescent material described in the above-described scheme or an organic fluorescent material prepared by the preparation method described in the above-described scheme.

[0051] In this invention, the organic fluorescent material is preferably used for the distinguishing detection of fluoride ions and hydrogen fluoride in a solution phase. In this invention, the system for solution phase detection preferably includes pure water, a mixed aqueous solution containing an organic solvent (such as DMSO / H₂O), or... The detection system can be prepared using solutions such as 2O, DMF / H2O, THF / H2O, etc.), PBS buffer solution, or HEPES buffer solution. This invention does not impose any special limitations on the detection system; an aqueous phase or mixed solvent system familiar to those skilled in the art can be used. In this invention, the concentration of the organic fluorescent material in the detection system is preferably 1–20 μM, and the detection concentration range of the fluoride ions is preferably 0–100 μM.

[0052] In this invention, the optical response mode of the organic fluorescent material preferably includes one or more of fluorescence intensity variation type, ratiometric fluorescence variation type, or colorimetric response type. In this invention, the excitation wavelength for fluorescence detection is preferably located in the ultraviolet-visible region of 350-500 nm. In this invention, the detection limit of the organic fluorescent material for fluoride ions can be as low as the nanomolar level, and the response time is preferably from several seconds to several minutes.

[0053] This invention also provides a method for using the organic fluorescent material described in the above technical solution to distinguish between hydrogen fluoride and fluoride ions, comprising the following steps: contacting the organic fluorescent material with an aqueous solution of hydrogen fluoride and an aqueous solution of a fluoride salt, respectively, and distinguishing between hydrogen fluoride and fluoride ions by comparing the differential fluorescence spectral responses produced by the two (such as changes in emission peak position shift direction, peak intensity ratio, or response rate differences). This invention does not impose special requirements on the specific operating conditions of each detection step, all of which are well-known fluorescence sensing experimental operations in the art.

[0054] The organic fluorescent materials, their preparation methods, and applications provided by this invention are described in detail below with reference to embodiments. However, these should not be construed as limiting the scope of protection of this invention. Various modifications and variations can be made to this invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0055] The present invention will be further described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0056] Example 1: Synthesis of Formula I-1 This embodiment provides an organic fluorescent material based on a benzophenone bridging group, having the structure shown in Formula I-1 below (R1 = 9,9-dimethyl-9,10-dihydroacryl-10-yl).

[0057] Formula I-1; (1) Synthesis of 4-fluoro-4'-bromobenzophenone (A) A; p-Bromobenzoyl chloride (2 g, 9.1 mmol) and fluorobenzene (5.6 mL, approximately 60 mmol) were added to a 50 mL three-necked flask and stirred in an ice-water bath. After the solution was cooled to 0 °C, anhydrous aluminum chloride (1.56 g, 11.65 mmol) was slowly added. The mixture was stirred at room temperature for 2 h, then heated to reflux for 6 h. After cooling to room temperature, 30 mL of ultrapure water was added, and the mixture was stirred and heated to reflux. The fluorobenzene was removed by passing the mixture through a Dean-Stark hydrophobic valve with a condenser. The reaction was completed after 5 h. The reaction solution was poured into 100 mL of ice water to precipitate the product. The precipitate was filtered and washed twice with 0.5 M NaOH solution and water. The crude product was recrystallized in ethanol to give compound A, which was a white crystal (2.03 g, 7.27 mmol, 80%). ¹H NMR (600 MHz, Chloroform-d, ppm) δ 7.84 (m, 1H), 7.66 (d, J = 0.9 Hz, 2H), 7.19 (m, 1H). MS (MALDI-TOF, m / z): [M]+ calculated value 279.01, measured value 280.03.

[0058] (2) Synthesis of 4-(9,9-dimethyl-9,10-dihydroacrylin-10-yl)-4'-bromobenzophenone (B-1) B-1; 9,9-Dimethyl-9,10-dihydroacridine (0.82 g, 3.9 mmol) was added to 25 mL of ultra-dry DMF, and the mixture was evacuated and purged with nitrogen three times. The mixture was stirred and heated to 60°C for 5 min. Cs₂CO₃ (4.10 g, 12.6 mmol) was added to the reaction system in three portions, and the mixture was stirred for 30 min. 4-Fluoro-4'-bromobenzophenone (A) (1 g, 3.6 mmol) was added to the reaction solution, and the mixture was stirred and heated to reflux. The reaction ended after 15 h. After cooling to room temperature, the reaction solution was poured into 100 mL of ice water and stirred with a glass rod. A gray precipitate was formed. The precipitate was filtered and washed three times with saturated NaCl solution. The organic phase was extracted with dichloromethane. The combined organic layers were dried over MgSO4, filtered, and distilled under reduced pressure. The crude product was purified by column chromatography (eluent: n-hexane / ethyl acetate = 4 / 1 v / v) to obtain compound B-1 as a yellow solid (0.95 g, 2.03 mmol, 56%). ¹H NMR (600 MHz,Chloroform-d, ppm) δ 8.04(m, 2H), 7.78 (m, 2H), 7.69 (m, 2H), 7.48 (m, 4H),7.00(m, 4H), 6.33 (dd, J = 8.1, 1.5 Hz, 2H), 1.70 (s, 6H). MS (MALDI-TOF, m / z): The calculated value is 467.09, and the measured value is 468.09.

[0059] (3) Synthesis of 4-(9,9-dimethyl-9,10-dihydroacrylin-10-yl)-4'-bis(trimethylyl)boron benzophenone (Ⅰ-1) Ⅰ-1 The three-necked reaction flask, condenser, and other glass containers were dried in a 150°C oven for 2 hours. The reaction apparatus was then assembled in the oven, and the system was evacuated and purged with nitrogen three times. B-1 (1 g, 1.95 mmol) and di(trimethyl)boron fluoride (784.40 mg, 2.92 mmol) were added to 10 mL of THF, and the system was evacuated and purged with nitrogen three times again. The reaction system was placed in a Dewar flask and stirred. Dry ice and acetone solution were introduced into the Dewar flask to lower the reaction temperature to -78°C. 1.71 mL (175 mg, 2.74 mmol) of a 1.6 M solution of n-butyllithium in n-hexane was drawn using a glass syringe and slowly injected into the reaction system. The mixture was stirred at -78°C for 1 hour, then heated to room temperature and stirred for 2 hours to complete the reaction. The reaction solution was quenched in 100 mL of ice water. The organic phase was extracted with dichloromethane. The combined organic solutions were dried over MgSO4, filtered, and distilled under reduced pressure. The crude product was purified by column chromatography (eluent: n-hexane / ethyl acetate = 30 / 1 v / v) to give compound I-1 as a white solid (598.22 mg, 0.88 mmol, 45%). ¹H NMR (400 MHz, Chloroform-d, ppm) δ 7.85 (d, J = 8.0 Hz, 2H), 7.74 (d, J = 8.0 Hz, 2H), 7.71 (d, J = 8.2 Hz, 2H), 7.18 (m, 2H), 7.14 (d, J= 8.2 Hz, 2H), 7.11 (m, 2H), 7.07 (m, 2H), 6.89 (m, 2H), 6.72 (s, 4H), 2.31 (s, 3H), 2.27 (s, 6H), 1.69 (s, 6H). ¹³C NMR (150 MHz, Chloroform-d, ppm) δ195.4, 149.6, 144.9, 143.6, 142.6, 141.3, 140.4, 138.4, 137.3, 135.5, 134.8,133.0, 132.6, 132.6, 131.2, 130.5, 125.4, 124.7, 123.6, 36.9, 30.9, 23.4,21.1. MS (MALDI-TOF, m / z): The calculated value was 661.35, and the measured value was 661.42. The emission peak of Ⅰ-1 in toluene solution was located at 438 nm (ΦPL=40.2%).

[0060] Example 2: Synthesis of Formula I-2 This embodiment provides an organic fluorescent material based on a benzophenone bridging group, having the structure shown in Formula I-2 below (R1 = phenthiazine-10-yl).

[0061] Ⅰ-2 (1) The synthesis of compound A is the same as in Example 1. A

[0062] (2) Synthesis of 4-phenthiazin-10-yl-4'-bromobenzophenone (B-2) B-2 Phenothiazine (0.78 g, 3.9 mmol) was added to 25 mL of ultra-dry DMF, and the mixture was evacuated and purged with nitrogen three times. The mixture was stirred and heated to 60°C for 5 min. Cs₂CO₃ (4.10 g, 12.6 mmol) was added to the reaction system in three portions, and the mixture was stirred for 30 min. A (1 g, 3.6 mmol) was added to the reaction solution, and the mixture was stirred and heated to reflux. After 15 h, the reaction was completed. The mixture was cooled to room temperature, and the reaction solution was poured into 100 mL of ice water. The mixture was stirred with a glass rod, and a gray precipitate was formed. The precipitate was filtered, washed three times with saturated NaCl solution, and the organic phase was extracted with dichloromethane. The combined organic layers were dried over MgSO₄, filtered, and distilled under reduced pressure. The crude product was purified by column chromatography (eluent: n-hexane / ethyl acetate = 4 / 1 v / v) to obtain compound B-2 as a yellow solid (0.88 g, 1.92 mmol, 53%). ¹H NMR (600 MHz, Chloroform-d) δ 7.85 (m, 1H), 7.77(m, 1H), 7.69 (m, 1H), 7.34 (m, 3H), 7.18 (m, 1H). MS (MALDI-TOF, m / z): The calculated value is 458.37, and the measured value is 458.45.

[0063] (3) Synthesis of 4-phenthiazin-10-yl-4'-bis(trimethylyl)boron benzophenone (I-2) Ⅰ-2 The synthesis method was the same as step (3) in Example 1, except that B-1 was replaced with B-2 (1 g, 1.99 mmol), bis(trimethyl)boron fluoride (795.96 mg, 2.97 mmol), and a hexane solution of n-butyllithium (1.74 mL, 2.79 mmol). The rest of the operation was the same, and compound I-2 was obtained as a white solid (534.19 mg, 0.80 mmol, 40%). ¹H NMR (400 MHz, Chloroform-d, ppm) δ 7.85 (d, J = 8.0 Hz, 2H), 7.74 (d, J = 8.0 Hz, 2H), 7.21(m, 2H), 7.20 (m, 2H), 7.18 (m, 2H), 7.16 (m, 2H), 6.97 (m, 2H), 6.72 (s, 4H), 2.31 (s, 3H), 2.27 (s, 6H). ¹³C NMR (150 MHz, Chloroform-d, ppm) δ 195.8, 149.3, 144.9, 143.6, 142.7, 141.6, 140.4, 138.2, 137.5, 135.2, 134.8, 133.3, 131.2, 128.1, 127.1, 23.4, 21.1. MS (MALDI-TOF, m / z): [M]⁺ Calculated value 627.28, measured value 627.25. The emission peak of Ⅰ-2 in toluene solution is located at 459 nm (ΦPL=48.9%).

[0064] Example 3: Synthesis of Formula I-3 This embodiment provides an organic fluorescent material based on a benzophenone bridging group, having the structure shown in Formula I-3 below (R1 = carbazole-9-yl).

[0065] Ⅰ-3 (1) The synthesis of compound A is the same as in Example 1. A (2) Synthesis of 4-carbazole-9-yl-4'-bromobenzophenone (B-3) B-3 Carbazole (0.65 g, 3.9 mmol) was added to 25 mL of ultra-dry DMF, and the mixture was evacuated and purged with nitrogen three times. The mixture was stirred and heated to 60°C for 5 min. Cs₂CO₃ (4.10 g, 12.6 mmol) was added to the reaction system in three portions, and the mixture was stirred for 30 min. A (1 g, 3.6 mmol) was added to the reaction solution, and the mixture was stirred and heated to reflux. After 15 h, the reaction was completed. The mixture was cooled to room temperature, and the reaction solution was poured into 100 mL of ice water. The mixture was stirred with a glass rod, and a gray precipitate was formed. The precipitate was filtered, washed three times with saturated NaCl solution, and the organic phase was extracted with dichloromethane. The combined organic layers were dried over MgSO₄, filtered, and distilled under reduced pressure. The crude product was purified by column chromatography (eluent: n-hexane / ethyl acetate = 4 / 1 v / v) to obtain compound B-3 as a yellow solid (0.95 g, 2.21 mmol, 61%). ¹H NMR (600 MHz, Chloroform-d) δ 8.17 (d, J = 7.7Hz, 2H), 7.92–7.86 (m, 2H), 7.83–7.77 (m, 2H), 7.71–7.66 (m, 2H), 7.48–7.42 (m, 4H), 7.36–7.30 (m, 2H). MS (MALDI-TOF, m / z): [M]+ calculated value 430.35, measured value 430.45.

[0066] (3) Synthesis of 4-carbazole-9-yl-4'-bis(trimethylyl)boron benzophenone (I-3) Ⅰ-3 The synthesis method was the same as step (3) in Example 1, except that B-1 was replaced with B-3 (1 g, 2.12 mmol), bis(trimethyl)boron fluoride (853.32 mg, 3.19 mmol), and a hexane solution of n-butyllithium (1.86 mL, 2.97 mmol). The rest of the operation was the same, and compound I-3 was obtained as a white solid (569.54 mg, 0.89 mmol, 42%). ¹H NMR (400 MHz, Chloroform-d, ppm) δ 8.55 (d, J = 7.8 Hz, 1H), 8.19 (d, J = 7.7 Hz, 1H), 7.88(d, J = 8.2 Hz, 2H), 7.85 (d, J = 8.0 Hz, 2H), 7.83 (d, J = 8.2 Hz, 2H), 7.52(d, J = 8.2 Hz, 1H), 7.20 (m, 2H), 7.18 (m, 2H), 7.16 (m, 2H), 7.11 (m, 2H), 6.72 (s, 4H), 2.31 (s, 3H), 2.27 (s, 6H). ¹³C NMR (150 MHz, Chloroform-d, ppm) δ 195.5, 143.6, 140.4, 139.7, 138.4, 138.2, 137.9, 136.9, 135.2, 134.0, 133.1, 132.3, 131.3, 130.9, 130.3, 129.1, 128.4, 127.9, 126.6, 122.7, 121.4, 119.8, 109.5, 22.7, 21.9. MS (MALDI-TOF, m / z): [M]⁺ Calculated value 595.30, measured value 595.34. The emission peak of Ⅰ-3 in toluene solution is located at 418 nm (ΦPL=50.6%).

[0067] The organic fluorescent materials prepared in Examples 1-3 were formulated into... The toluene solution of M was tested for UV-Vis absorption spectra using a HITACHI U-3900 UV-Vis spectrophotometer, and the fluorescence spectra of the compound were measured using a HITACHI-4700 fluorescence spectrophotometer. Figures 1-3 The fluorescence spectrum of the material in toluene solution indicates that compounds I-1 to I-3 are all blue-emitting compounds; Figures 4-7 The spectral response diagrams of the material under TBAF and HF titrations are shown below. Figure 4 and Figure 5The fluorescence spectrum and UV-Vis absorption spectrum are respectively obtained from TBAF titration (0-10 equivalents). Figure 6 and Figure 7 The fluorescence spectrum and UV-Vis absorption spectrum are respectively obtained from HF titration (0-10 equivalents). This invention uses a concentration of 10⁻ 5 The organic fluorescent material solution of M was used as the detection system. Different equivalents of TBAF (as a fluoride ion source) and HF aqueous solution were added, and the spectral changes were recorded at room temperature.

[0068] like Figure 4 As shown, during TBAF titration, as the TBAF equivalent number gradually increased from 0 to 10 equivalents, the fluorescence intensity of the organic fluorescent material exhibited a significant gradient enhancement trend, demonstrating a typical "on" type fluorescence on-response. The fluorescence enhancement exceeded 130%. Simultaneously, the position of the fluorescence emission peak showed a regular blue shift with increasing TBAF concentration, indicating... After specific BF coordination with the boron acceptor group in the organic fluorescent material, the intramolecular charge transfer state changes, leading to an increase in the excited state energy level. The detection limit of this organic fluorescent material for TBAF was calculated to be [insert value here]. mol / L.

[0069] like Figure 5 As shown, in the UV-Vis absorption spectrum, the organic fluorescent material exhibits a bidirectional spectral change with a clear isoabsorption point under TBAF titration. With increasing TBAF equivalent number, the absorption peak intensity in the long-wavelength direction gradually decreases, while the absorption peak intensity in the short-wavelength direction gradually increases. The absorption spectrum intersects at the isoabsorption point, indicating that the organic fluorescent material and... A definite stoichiometric reaction occurred between them, generating a BF coordination product with a defined structure.

[0070] like Figure 6 As shown, during HF titration, the fluorescence of the organic fluorescent material exhibits a completely opposite trend to that of the TBAF system. As the HF equivalent number increases from 0 to 10 equivalents, the fluorescence intensity continuously decreases, exhibiting a typical "quenching" type fluorescence quenching response. The fluorescence intensity quenching amplitude exceeds 95%. Simultaneously, the emission peak position also shows a blue shift trend. The detection limit of this organic fluorescent material for HF is calculated to be... mol / L. This fluorescence response direction, which is completely opposite to that of the TBAF system, constitutes the core optical readout feature of this organic fluorescent material for distinguishing between fluoride ions and hydrogen fluoride.

[0071] like Figure 7As shown, in the UV-Vis absorption spectrum, HF titration caused an overall decrease in the absorption intensity of the organic fluorescent material, which is significantly different from the bidirectional change and isoabsorption point characteristics exhibited by the TBAF system. This further confirms that the interaction mode between HF and organic fluorescent materials differs from that of simple HF titration. Coordination—in HF aqueous solution It can additionally protonate with nitrogen-containing donor groups in organic fluorescent material molecules, forming a cooperative recognition mechanism different from TBAF.

[0072] As shown in the test results of the examples, the organic fluorescent material of the present invention exhibits a fluorescence "on" response in the TBAF system, with fluorescence intensity increasing with increasing F⁻ concentration, a blue shift in the emission peak, and a detection limit of [missing information]. mol / L; in the HF system, it exhibits a fluorescence "quenching" response, with fluorescence intensity quenching as HF concentration increases, and the emission peak also shows a blue shift trend, with a detection limit of [missing value]. mol / L. Based on the completely opposite fluorescence response directions and the differential evolution characteristics of the ultraviolet absorption spectrum, this organic fluorescent material successfully achieved the targeting of fluoride ions. The signal level can be distinguished from that of hydrogen fluoride (HF).

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An organic fluorescent material based on a benzophenone bridging group, characterized in that, It has the structure shown in Equation I: Equation I; In the formula, there are two 1,4-phenylene groups; R1 is selected from one of the following groups: 9,9-dimethyl-9,10-dihydroacrylin-10-yl, phenothiazine-10-yl, carbazole-9-yl; the structures are as follows: 、 、 ； R2 is a bis(trimethyl)boron group; its structure is: ； Furthermore, R1 is directly connected to the para-carbon atom of the adjacent Ph group through the nitrogen atom on its ring.

2. The organic fluorescent material based on benzophenone bridging groups according to claim 1, characterized in that, It has the structure shown in Formula I-1, Formula I-2 or Formula I-3: Formula I is defined as R1 being 9,9-dimethyl-9,10-dihydroacrylin-10-yl; the specific structure is as follows: Formula I-1; Formula I-2 is where R1 is phenothiazine-10-yl; the specific structure is as follows: Formula I-2; Formula I-3 is where R1 is carbazole-9-yl; the specific structure is as follows: Formula I-3.

3. The method for preparing the organic fluorescent material according to claim 1 or 2, characterized in that, Includes the following steps: S1. Bromobenzoyl chloride and fluorobenzene undergo a Friedel-Crafts acylation reaction at 110–130 °C in the presence of excess fluorobenzene as a solvent and aluminum trichloride as a catalyst to yield 4-fluoro-4'-bromobenzophenone; the specific structure is Formula A: Formula A; S2. Compounds with the structure shown in Formula A, nitrogen-containing heterocyclic compounds, and basic catalysts undergo nucleophilic substitution reactions in N,N'-dimethylformamide solvent to obtain compounds B-1, B-2, and B-3 with the structure shown in Formula B; S2.

3. In N,N'-dimethylformamide, the product of S1 is reacted with 9,9-dimethyl-9,10-dihydroacridine, phenothiazine, or carbazole under alkaline catalysis at 110–130 °C to undergo a nucleophilic substitution reaction to obtain compound B; compound B is of formula B-1, B-2, or B-3; the specific structure is as follows: Formula B-1; Formula B-2; Formula B-3; S3. Under anhydrous and oxygen-free conditions, at -78°C, the compound of formula B is reacted with bis(trimethyl)boron fluoride and n-butyllithium in ultra-dry tetrahydrofuran or n-hexane to obtain the material of formula I.

4. The method for preparing the organic fluorescent material according to claim 3, characterized in that, In S1, the molar ratio of p-bromobenzoyl chloride to fluorobenzene is 1:6-8, and the molar ratio of p-bromobenzoyl chloride to aluminum trichloride is 1:1-1.2, with a reaction time of 6-12 hours.

5. The method for preparing the organic fluorescent material according to claim 3, characterized in that, In S2, the molar ratio of the nitrogen-containing heterocyclic compound to 4-fluoro-4'-bromobenzophenone is 1:1 to 1.2; the basic catalyst is cesium carbonate, potassium acetate, potassium carbonate, or sodium carbonate, and the amount used is 3 to 5 times the molar amount of the nitrogen-containing heterocyclic compound; the reaction time is 6 to 12 hours.

6. The method for preparing the organic fluorescent material according to claim 3, characterized in that, In S3, the molar ratio of the compound with the structure shown in Formula B to boron bis(trimethyl)fluoride is 1:1 to 1.2; the molar ratio of the compound with the structure shown in Formula B to n-butyllithium is 1:1 to 1.2; the solvent is n-hexane or ultra-dry tetrahydrofuran; and the reaction time is 12-24 h.

7. A method for distinguishing and detecting hydrogen fluoride and fluoride ions, characterized in that, Using the organic fluorescent material of claim 1 or 2 as a probe, comprising: a. Dissolve the material in an organic solvent or an aqueous mixed solvent to prepare a detection system; b. Add the sample to be tested and record the changes in the fluorescence spectrum; c. If the fluorescence intensity increases and the emission peak shifts to blue, it is determined to contain fluoride ions; if the fluorescence intensity is quenched and the emission peak shifts to blue, it is determined to contain hydrogen fluoride.

8. The method according to claim 7, characterized in that, The concentration of the organic fluorescent material in the detection system is 1–20 μM, and the excitation wavelength is 350–500 nm; the organic solvent is one or more of toluene, tetrahydrofuran, or dimethyl sulfoxide.

9. The application of the organic fluorescent material according to claim 1 or 2 in the preparation of a solid-state sensor for on-site visual detection of hydrogen fluoride gas, characterized in that, The solid-state sensor is a test paper, a thin film, or a nanofiber membrane, and the organic fluorescent material has a fluorescence quantum yield of not less than 40% in the solid state.

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