Use of a halogenated salen-type complex as a fluorescent sensor for detecting water content in ethanol or DMF

Abstract

The invention discloses a halogenated salen type complex as a fluorescent sensor for detecting water content in ethanol or DMF, the complex belongs to monoclinic system, P21 / c space group, and its adjacent molecules are connected by multiple weak interactions participated by halogen bonds, wherein χ is a halogen atom; its molecular formula is (χ-L2H2) [N,N'-bis(χ-salicylaldehyde)-m-xylene]; the detection range of the fluorescent sensor for water content in the ethanol or DMF is 0-90%vol%. The halogenated salen type complex provided by the present invention not only shows good linearity and lower detection limit as a fluorescent sensor, but also provides a wide detection range (0-90%vol%) in terms of measuring the water content in ethanol and DMF, which is wider than other water content probes, and its synthesis is simple and the preparation cost is low. In addition, the fluorescent sensor provided by the present invention uses a halogenated salen type complex as a carrier, which is different from the prior art fluorescent probes, which are mostly non-halogenated isomers, so that the development of fluorescent probes provides a new approach.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescent probes, and in particular relates to application of a halogenated salen-type complex as a fluorescent sensor for detecting water content in ethanol or DMF. Background Art

[0002] Water is commonly found in all kinds of organic solvents and is the most common impurity in all kinds of organic solvents. In the pharmaceutical and chemical industries, the presence of water can affect the production process and may also inhibit the efficacy and usability of the product. In metal organic chemistry, water can cause the inactivation of many reagents, inhibit the reaction and reduce the product recovery rate. For many sensitive chemical reactions, the water content in organic solvents plays a decisive role in the success of the experiment. Especially in the wine industry, from vodka (% water = 4%), to brandy (% water = 42%), to ordinary wine (% water = 88%), different water contents can seriously affect the quality of the product and even cause huge losses to industrial production. Therefore, the development of a water content detection probe that is simple to operate, effective, rapid, and has a wide detection range for the detection of water content in organic solvents has important practical value not only under laboratory conditions but also in actual industrial production.

[0003] So far, chromatographic spectroscopy, infrared spectroscopy, potentiometric method, Raman spectroscopy, solid phase extraction, holographic method, flm sensor based on absorbance, electrochemical method based on impedance, conductivity method and amperometric method have been used for the determination of water in organic solvents. Most of these methods have the disadvantages of complicated operation or excessively high materials and costs. Moreover, some of these methods cannot be used for the determination of water content in redox active solvents such as DMF. At present, the most widely used method for detecting water content is Karl Fischer titration. Although this method has the advantages of sensitivity and accuracy, this method requires the use of toxic and expensive reagents, and has the disadvantages of large sample demand, slow reaction speed, need for skilled operators and complex test operation, thereby limiting the application of this method.

[0004] In recent years, fluorescence sensing technology has attracted widespread attention due to its simplicity, high efficiency and intuitiveness. Based on recognition mechanisms such as intramolecular charge transfer (ICT), photoinduced electron transfer (PET), excited state intramolecular proton transfer (ESIPT), molecular aggregation, solvatochromism, and stoichiometric reaction, some fluorescence sensors have been developed for the determination of water content in organic media. For example, Yang et al. designed a dansyl-rhodamine complex fluorescent probe based on resonance energy transfer (FRET) to detect trace water in DMF; Wu et al. developed a pyrrolopyrrole dione derivative fluorescent probe using excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) to detect water content in aprotic solvents. However, these probes have the disadvantages of cumbersome synthesis methods, limited detection range, and insufficient precision. So far, there are few highly sensitive and wide-range detection methods that can detect water content in ethanol or DMF, and there are also few available fluorescent probes.

[0005] The invention aims to provide a fluorescence sensor with high sensitivity and wide detection range for detecting the water content in ethanol or DMF. Summary of the invention

[0006] The invention aims to provide a halogenated salen type complex used as a fluorescent sensor for detecting the water content in ethanol or DMF.

[0007] The object of the present invention is achieved by using a halogenated salen-type complex as a fluorescent sensor for detecting the water content in ethanol or DMF, wherein the complex belongs to the monoclinic system and the P21 / c space group, and its adjacent molecules are connected by multiple weak interactions involving halogen bonds, wherein χ is a halogen atom; its molecular formula is (χ-L2H2) [N,N'-bis(χ-salicylaldehyde)-m-xylene]; and the detection range of the fluorescent sensor for the water content in ethanol or DMF is 0-90% vol%.

[0008] The principle of the invention is that in anhydrous ethanol and DMF solvents, water of different contents has a quantitative quenching effect on the fluorescence of halogenated salen-type complexes, thereby realizing rapid and sensitive detection of a wide range of water in ethanol and DMF.

[0009] The beneficial effects of the present invention are:

[0010] 1. The present invention provides a halogenated salen-type complex for detecting the water content in ethanol or DMF, which can respond to the water content in a variety of organic solvents. The halogenated salen-type complex for detecting the water content in ethanol or DMF provided by the present invention not only shows good linearity and a low detection limit, but also provides a wide detection range (0-90% vol%) in determining the water content in ethanol and DMF, which is wider than other water content probes. The fluorescent sensor provided by the present invention uses the halogenated salen-type complex as a carrier, which is different from the existing fluorescent probes, which are mostly non-halogenated isomers, and provides a new way for the development of fluorescent probes.

[0011] 2. The fluorescent sensor for detecting water content in ethanol or DMF provided by the present invention has the advantages of being applicable to a wide range of water traces in organic solvents, low cost, simple chemical synthesis, detectable by the naked eye, and fast response time.

[0012] 3. The test paper based on the halogenated salen-type complex solution provided by the present invention can qualitatively detect the water content in the organic solvent, and provides an instant detection platform for detecting the water content in the organic solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the infrared spectrum of the halogenated salen complex W7 of the present invention;

[0014] Figure 2 The halogenated salen complex W7 of the present invention 1 H nmR spectrum;

[0015] Figure 3 The halogenated salen complex W7 of the present invention 13 C nmR spectra;

[0016] Figure 4 The infrared spectrum of the halogenated salen complex S1 prepared in Example 2;

[0017] Figure 5 The infrared spectrum of the halogenated salen complex S2 prepared in Example 3;

[0018] Figure 6 In the figure, (a) is the normalized emission spectrum of W7 in different solvents; (b) is the normalized absorption spectrum of W7 in different solvents; (c) is the fluorescence spectrum of W7 in different solvents; (d) is the photo of W7 in different solvents under 365 nm UV light; (e) is the emission wavelength of W7 and the solvent parameter E T (30) is the fitting curve; (f) is the fitting curve of the emission peak of W7 and the solvent parameter ETN; (1×10 -5 mmol / mL, λex = 400 nm);

[0019] Figure 7 In the figure, (a) is the normalized fluorescence spectrum of W7 at different water contents in ethanol solution; (b) is the normalized fluorescence spectrum of W7 at different water contents in DMF solution; (c) is the fitting relationship between the emission peak of W7 in ethanol solution and water content; (d) is the fitting relationship between the emission peak of W7 in DMF solution and water content;

[0020] Figure 8 In the figure, (a) is the molar electron transition energy (E) of the ethanol-water mixture. T(m) ) and the molar fraction of water (x w ) relationship; (b) is the molar electron transition energy (E) of the aqueous solution mixture of DMF T(m) ) and the molar fraction of water (x w ) relationship;

[0021] Fig. 9 In the figure, (a) shows the W7 (1×10 -5 mol / mL) at 400 nm; (b) after adding 0, 30, 60, and 90 wt% water into DMF, the fluorescence intensity at W7 (1×10 -5 mol / mL) with time; (c) Fitting of the relationship between the emission peak of W7 in ethanol solution and water content; (d) Fitting of the relationship between the emission peak of W7 in DMF solution and water content;

[0022] Fig.10 In the figure, (a) shows the change of fluorescence intensity of W7 in ethanol with different water contents; (b) shows the change of fluorescence intensity of W7 in DMF with different water contents; (c) shows the linear fitting of fluorescence intensity of W7 in ethanol and water content; (d) shows the linear fitting of fluorescence intensity of W7 in DMF and water content (W7 = 1×10 -5 mmol / mL; ex = 400 nm; % water = 0-90%, v / v); (e) is a photograph of the water content of W7 increased in ethanol under 365 nm UV light; (f) is a photograph of the water content of W7 increased in DMF under 365 nm UV light;

[0023] Fig.11 Schematic diagram of the working principle of sensor W7 for visual detection of water content through TE signal (red light path);

[0024] Fig.12In the figure, (a) is a photo of the fluorescence intensity of W7 at different water contents in ethanol and the corresponding Tyndall phenomenon; (b) is a photo of the fluorescence intensity of W7 at different water contents in DMF and the corresponding Tyndall phenomenon (λ ex = 365 nm; % water = 0%, 30%, 60%, 90%);

[0025] Fig.13 In the figure, (a) is a photo of the W7 sensor paper dripped into ethanol with different water contents; (b) is a photo of the W7 sensor paper dripped into DMF with different water contents (λ ex = 365 nm; % water = 0-90%);

[0026] Fig.14 Figure S4 is the normalized emission spectra of non-halogenated isomers in different solvents; Figure S5 is the normalized absorption spectra of non-halogenated isomers in different solvents; Figure S6 is the emission wavelength of non-halogenated isomers and solvent parameter E T (30); Figure S7 shows the emission peaks of the non-halogenated isomers and the solvent parameter E T N ; S8 is a comparison diagram of the linear change of the emission wavelength of W7 and non-halogenated isomers in ethanol solution with the change of water content; S9 is a comparison diagram of the linear change of the emission wavelength of W7 and non-halogenated isomers in DMF solution with the change of water content. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention fall within the protection scope of the present invention.

[0028] The present invention discloses a use of a halogenated salen-type complex as a fluorescent sensor for detecting the water content in ethanol or DMF, characterized in that the complex belongs to the monoclinic system and the P21 / c space group, and its adjacent molecules are connected by multiple weak interactions involving halogen bonds, wherein χ is a halogen atom; its molecular formula is (χ-L2H2) [N,N'-bis(χ-salicylaldehyde)-m-xylene]; and the detection range of the fluorescent sensor for the water content in ethanol or DMF is 0-90% vol%.

[0029] The detection limit of the fluorescent sensor for water content in ethanol is 0.0524% (v / v), and the quantification limit is 0.1747% (v / v).

[0030] The detection limit of the fluorescent sensor for water content in DMF is 0.0512% (v / v), and the quantification limit is 0.1707% (v / v).

[0031] The matrix of the fluorescent sensor for detecting the water content in ethanol or DMF is filter paper.

[0032] The halogenated salen type complex is prepared according to the following steps:

[0033] 1) Dissolve halogenated salicylaldehyde and m-xylylenediamine in ethanol and stir for 1.5-3 hours, then filter and collect the filtrate;

[0034] 2) drying the filtrate in a rotary evaporator at 110° C. in vacuum to obtain a light green powder;

[0035] 3) The light green powder is washed with a polar solvent for multiple times and filtered, and finally the organic solvent is slowly evaporated for 6-8 days to obtain the target complex.

[0036] In step 1, the molar ratio of halogenated salicylaldehyde to the m-xylylenediamine solution is 2:1, and the volume ratio of m-xylylenediamine to ethanol is 1:800-80000.

[0037] In step 2, the vacuum drying time is 4-5 hours.

[0038] In step 3, the polar solvent is ethanol, DMF, DMSO, methanol, acetonitrile or tetrahydrofuran.

[0039] The present invention will be further described below with reference to the embodiments.

[0040] All reagents used in the examples of the present invention are commercially available and are of analytical grade. Meta-phenylenediamine and 5-Cl salicylaldehyde were purchased from Aladdin Reagent Co., Ltd. (Shanghai, China); anhydrous ethanol (99.7%), methanol (99.5%), acetonitrile (99.5%), dimethyl sulfoxide (DMSO) (99.5%), tetrahydrofuran (99.5%), and N,N-dimethylformamide (DMF) (99.5%) were purchased from Tianjin Damao Company; ultrapure water was used throughout the experiment; all reagents were used without further purification.

[0041] The 1H-NMR spectra were recorded using a Bruker 600 MHz digital NMR spectrometer (AVANCE III 600 MHz). The Fourier transform infrared spectra were recorded at 400–4000 cm −1 The scanning range is 4cm with a resolution of −1, samples were measured using the conventional KBr particle method with a Thermo Scientific Nicolet 6700DTSG-KBr detector (USA). Fluorescence spectra were measured using an Edinburgh FS5 fluorescence spectrometer (UK). Laser pointer (650 nm). All fluorescence photos were taken under 365 nm UV light using a smartphone (Oppo Reno Ace) in a dark box with a ZF-1 UV lamp (Jiapeng Technology Co., Ltd., Shanghai, China).

[0042] Example 1 Synthesis of halogenated salen complex W7

[0043]

[0044] 0.157 g (1 mmol) of 5-Cl salicylaldehyde was weighed and dissolved in 50 mL of ethanol solution and stirred continuously until completely dissolved. 62 μL (0.5 mmol) of m-phenylenediamine solution was added and stirred continuously for 2 h at room temperature and pressure until a large amount of light green precipitate was produced. After the reaction was completed, impurities were filtered out using a membrane filter to obtain a light green transparent liquid, which was vacuum dried at 110 °C for 4 h in a rotary evaporator to obtain a light green powder. The light green powder was washed with ethanol several times and filtered. Finally, the organic solvent was slowly evaporated for 7 days to obtain a halogenated salen-type complex ( 5Cl -L2H2) [N,N'-bis(5-chlorosalicylaldehyde)-m-xylene], named W7. Yield: 68.3%.

[0045] FT-IR (KBr, cm -1 ): 2873, 2821(CH), 1635(C=N), 1371(CO), 1270(CN),832(C-Cl)( Figure 1 ); 1 H nmR (600 MHz, Chloroform-d) δ 13.34 (s, 2H, OH), 8.38 (s,2H, CH), 7.38 (t, J = 7.6 Hz, 1H, Ar-H), 7.30 – 7.22 (m, 7H, Ar-H), 6.93 (d, J= 8.6 Hz, 2H, Ar-H), 4.83 (s, 4H, CH2)( Figure 2 ). 13C nmR (151 MHz, Chloroform-d) δ164.61, 159.68,138.32, 132.27, 130.60, 129.23, 127.26, 127.04, 123.25,119.54, 118.63, 63.02( Figure 3 ).

[0046] Example 2 Synthesis of halogenated salen complex S1

[0047]

[0048] 0.201 g (1 mmol) of 5-Br salicylaldehyde was weighed and dissolved in 50 mL of ethanol solution and stirred continuously until completely dissolved. 62 μL (0.5 mmol) of m-phenylenediamine solution was added and stirred continuously at room temperature and pressure until a large amount of brown-green precipitate was produced. After the reaction was completed, impurities were filtered out using a membrane filter to obtain a brown-green transparent liquid, which was vacuum dried at 110 °C in a rotary evaporator to obtain a brown-green powder. The brown-green powder was washed with ethanol several times and filtered. Finally, the organic solvent was slowly evaporated to obtain a halogenated salen-type complex ( 5Br -L2H2) [N,N'-bis(5-chlorosalicylaldehyde)-m-xylene], named S1. Yield: 71.6%.

[0049] FT-IR (KBr, cm -1 ): 2818, 2736(CH), 1633(C=N), 1352(CO), 1193(CN),762(C-Br)( Figure 4 ).

[0050] Example 3 Synthesis of halogenated salen complex S2

[0051]

[0052] 0.248 g (1 mmol) of 5-I salicylaldehyde was weighed and dissolved in 50 mL of ethanol solution and stirred continuously until completely dissolved. 62 μL (0.5 mmol) of m-phenylenediamine solution was added and stirred continuously at room temperature and pressure until a large amount of brown-yellow precipitate was produced. After the reaction was completed, impurities were filtered out using a membrane filter to obtain a brown-yellow transparent liquid, which was vacuum dried at 110 °C in a rotary evaporator to obtain a brown-yellow powder. The brown-yellow powder was washed with ethanol several times and filtered. Finally, the organic solvent was slowly evaporated to obtain a halogenated salen-type complex ( 5I-L2H2) [N,N'-bis(5-chlorosalicylaldehyde)-m-xylene], named S2. Yield: 73.1%.

[0053] FT-IR (KBr, cm -1 ): 2817, 2778(CH), 1631(C=N), 1278(CO), 1107(CN),615(CI)( Figure 5 ).

[0054] Experimental Example 4 Detection of optical properties of halogenated salen-type complexes

[0055] The optical properties of the halogenated salen-type complex of the present invention were tested by taking the complex W7 prepared in Example 1 as an example.

[0056] 1. Fluorescence spectra of W7 in solvents of different polarity

[0057] Experimental method: Prepare 10 ml of 0-90 vol.% ethanol and DMF aqueous solution in a reagent bottle, then add the prepared W7 to the above solution to a concentration of 1×10 -5 mmol / ml, and then shaken for 10s at room temperature to ensure sufficient mixing. Fluorescence emission spectra from 400 to 700 nm were collected using a fluorescence spectrometer (Edinburgh FS-5), with an excitation wavelength of 400 nm and a slit width of 1.5 nm. Photos of the above solutions were taken under 365 nm UV light using a smartphone (Oppo Reno Ace). The water content of other organic solvents was detected in the same way as above.

[0058] Results and analysis: The maximum excitation wavelength and emission wavelength of W7 were 405 nm and 482 nm (MeOH) respectively, which has a good effect on the polarity of the solvent. Figure 6 As shown in a, with the gradual increase of polarity, the emission wavelength of W7 also begins to red-shift. Generally, the maximum emission peak position (λ max ) are 401 nm and 399 nm respectively. However, for water, the λ of W7 max The value is red-shifted to around 520 nm.

[0059] In order to more clearly understand the law of solvent reaction, the present invention introduces the non-halogenated isomer of W7 shown in formula (I) for comparative experiment, and uses E T (30) (a parameter describing the solvent polarity) to fit the emission peak. Figure 6 As shown in e, the fluorescence λ of the halogenated Schiff base W7 max With E T(30) has a good linear relationship (R 2 = 0.97258), but the fluorescence λ of the non-halogenated isomers max With E T (30) The linear relationship between 2 = 0.92223) is poor (Table 1, Fig.14 -S6). Then use E T N The PL emission properties of W7 were investigated, which is a normalized polarity parameter measuring the overall solvating power of a solvent in terms of specific hydrogen bonding and nonspecific (e.g., dipolar solute-dipole) solvent interactions.

[0060] It was found experimentally that the emission peak position of the non-halogenated isomer is similar to that of E T N The linear correlation (R 2 = 0.83865) is worse ( Fig.14 -S7), while the emission peak positions of W7 dispersed in different solvents are different from those of E T N The linear correlation (R 2 = 0.96756) is better, such as Figure 6 f, and is fitted using equation (1), where E p is the energy corresponding to the peak position of the PL emission spectrum of W7 dispersed in different solvents (Table 1). These results highlight the possible application of the synthesized halogenated Schiff bases in fluorescence sensing of organic solvents in the form of pure solutions and binary water mixtures. In addition, the absorption and emission spectra of W7 in different alcohol solvents show the same trend, which can be explained by the formation of hydrogen bonds between W7 and the solvent, thereby stabilizing the energy level of the excited state. By introducing non-halogenated isomers for comparative experiments, we found that for non-halogenated Schiff bases ( Fig.14 -S4, S5), the emission spectrum and absorption spectrum of the halogenated Schiff base W7 have a small solvent-induced color shift ( Figure 6 a, 6b), indicating that due to the relatively small dipole moment, the solvent polarity has little effect on the charge transfer of the ground state molecule, and the introduction of halogen atoms reduces the interaction between Schiff base molecules. It is worth noting that as the polarity of the solvent increases from THF to DMF, the emission intensity of the halogenated Schiff base W7 changes significantly ( Figure 6 c). For example, strong fluorescence emission is shown in strong polar organic solvents such as DMF. In contrast, in weak polar organic solvents such as THF, the fluorescence intensity is very weak, which may be due to the formation of hydrogen bonds between the highly electronegative oxygen atoms in the solvent molecules and the -OH in W7, thereby inhibiting the ESIPT process. Figure 6d is a picture of W7 in different organic solvents under 365 nm ultraviolet light. It can be seen that W7 in DMF exhibits strong blue fluorescence, but under the same conditions, the blue-green fluorescence of W7 in ethanol is weak, and there is almost no fluorescence in THF. These experimental results are in good agreement with the spectral data.

[0061]

[0062] Table 1 Solvents and parameters of non-halogenated isomers in different solvents

[0063]

[0064] The above optical characterizations indicate that W7 provided by the present invention can be used as a potential probe of solvent polarity.

[0065] 2. Sensing experiment of EtOH and DMF in binary mixed aqueous solution

[0066] like Figure 7 As shown in a, with the increase of water content in ethanol, the emission position of W7 gradually red-shifts. And the emission peak linear region in the water content of 0-90% has good linearity 0-90%, R 2 = 0.94218. Among them, 0-30%, R 2 = 0.99677; 30%-90%, R 2 = 0.97052;( Figure 7 c). The red shift of the emission position in DMF is similar to that in ethanol ( Figure 7 b), the difference is that there are two 0-20% (R 2 = 0.99482) and 20-90% (R 2 = 0.93223) has a different linear region from that of ethanol, but both have good linearity ( Figure 7 d) This can be explained by the solvation properties in binary mixtures. E was calculated using Eq. (2) T(m) Theoretical value, at the same time, use formula (1) and formula (3) to calculate E T(m) The experimental value of E T(OS) is the molar electron transition energy of the organic solvent (kcal / mol), E for water T(W) are the same, and the corresponding values ​​are shown in Table 2.

[0067] Table 2 Solvents and parameters of W7 in different solvents

[0068]

[0069] from Figure 8 a and Figure 8 b It can be seen that in the case of two water binary mixtures, E T(m)Not with x w This mixed solvent system E estimated by the solvent color spectrum shift of traditional dyes T(m) This unusual variation in the experimental values ​​is a common feature that has been reported by many other research groups, including Dawber et al. This is due to the preferential solvation effect of the solute molecules on the more polar component in the binary mixture. In order to estimate the degree of preferential solvation, we calculated the solvation factor η of W7 at different water contents in ethanol and DMF using equation (4) (Tables 3 and 4), where x w is the mole fraction of water, E T1(m) and E T2(m) are the molar electron transition energies obtained at two different mole fractions of water / organic solvent, respectively. η = 1 corresponds to a binary solvent mixture with random solvation or non-specific solvation, η>1 means that more polar components prefer solvation, and η<1 means that less polar components prefer solvation in the binary mixture. Calculations show that η is greater than 1 when the ethanol water content is between 0-20%. Water, as a more polar component, preferentially solvates W7 before reaching 20%, while ethanol, as a less polar component, preferentially solvates W7 above 20%. The behavior in DMF is exactly the same as that of a binary mixture of water and ethanol.

[0070] The above results confirm that the halogenated salen complex W7 provided by the present invention is preferentially solvated by different polar components in a binary solvent mixture.

[0071]

[0072]

[0073]

[0074]

[0075] Table 3 Calculation of the solvation coefficient of water-ethanol mixture at different volume ratios

[0076]

[0077] Table 4 Calculation of the solvation coefficient of water-DMF mixture at different volume ratios

[0078]

[0079] 3. Fluorescence quenching caused by aggregation

[0080] The above experiments show that W7 exhibits strong fluorescence in pure ethanol and DMF, but the fluorescence intensity gradually weakens with the increase of water content ( Fig.12 These phenomena can confirm that W7 has the characteristics of aggregation-induced emission quenching (ACQ). Fig.11 Schematic diagram of the working principle of fluorescence quenching caused by aggregation. As the water content gradually increases, the ACQ characteristics of W7 prompt molecular aggregation, thereby promoting intermolecular π-π interactions, forming an aggregated state while the fluorescence weakens.

[0081] Fig.12 The fluorescence intensity of W7 in ethanol and DMF solutions at different water contents and the corresponding photos of the Tyndall phenomenon are shown. No red pathway appears at 0% water content. When the water content reaches 30%, the pathway begins to appear, and as the water content increases, the red pathway becomes clearer and broader. It can be clearly seen that as the fluorescence intensity decreases, the red pathway gradually increases. This is due to the hydrophobicity of the halogen atoms on the surface of W7 and its ACQ characteristics, which causes W7 to aggregate continuously as the water content gradually increases. This shows that the halogenated salen complex W7 has great potential for detecting water content using TE signals.

[0082] Example 5 Detection of trace water content in EtOH and DMF by W7

[0083] Experimental method: Prepare ethanol solutions and DMF solutions with different water contents (0-90 vol.%), and then add the prepared W7 to the above solutions to a concentration of 1×10 -5 mmol / ml, and then shaken for 10 s at room temperature to ensure sufficient mixing. Fluorescence spectra were collected using a fluorescence spectrometer (Edinburgh FS-5) with an excitation wavelength of 400 nm. The fluorescence intensity peaks of W7 at different water contents in ethanol and DMF were fitted. Photos of the above solutions were taken under 365 nm UV light using a smartphone with a 7 nm Qualcomm Snapdragon 855 Plus. The water content of other organic solvents was detected in the same way as above.

[0084] Test results:

[0085] 1. Response time: Fig. 9 As shown, in ethanol and DMF with a certain amount of water added, the fluorescence intensity of W7 decreased immediately, remained stable in less than 10 seconds, and remained basically stable after a period of time (15 min), indicating that W7 shows a rapid response to water and can be used in practical applications.

[0086] 2. Sensitivity: Fig.10 As can be seen from a, with the increase of water content in ethanol (% water = 0-90%), the fluorescence intensity of the solution (W7 = 1×10-5 mmol / mL) was significantly reduced. In addition, with the gradual increase of water content in anhydrous ethanol, the changes of strong blue-green to weak yellow-green to colorless can be easily observed by naked eyes under ultraviolet 365 nm excitation at different water contents ( Fig.10 e);

[0087] from Fig.10 As shown in Figures b and 10f, similar to the water content detection of anhydrous ethanol, the fluorescence intensity of the DMF water content detection gradually weakened with the increase of water content (% water = 0-90%), and the change from strong dark blue to dark green to colorless can be more clearly observed under ultraviolet 365 nm excitation. These results are consistent with the photos taken under 365 nm ultraviolet light. This may be because the solution forms an aggregated state as the water content gradually increases, and the fluorescence emission is suppressed in the aggregated state, resulting in fluorescence quenching.

[0088] from Fig.10 c and 10d, it can be seen that with the change of water content, the fluorescence intensity of W7 decreases gradually: the fluorescence intensity peaks of W7 with different water contents in ethanol and DMF were fitted, and R 2 = 0.99299, R in DMF 2 = 0.99697, which indicates that W7 has a good linear relationship in different water contents of ethanol and DMF (0%~90%). Then, according to the equation of D = 3s / ms, Q =10s / ms (D is the detection limit, Q is the quantification limit, s is the standard deviation, and ms is the slope of the regression line), the detection limits of ethanol and DMF were calculated to be 0.0524% (v / v) and 0.0512% (v / v), respectively; the quantification limits were 0.1747% (v / v) and 0.1707% (v / v), respectively, indicating that probe W7 is very sensitive to water around ethanol and DMF.

[0089] Summary: The above results show that W7 can be used as an ideal and practical fluorescence sensor to quantitatively and accurately analyze the water content in anhydrous ethanol or DMF solvents. In addition, W7 shows a good linear relationship between its fluorescence intensity and the content of aqueous solution in a wide range, indicating that W7 can also be used for accurate detection of water content in a wide range.

[0090] Example 6 Preparation of fluorescent sensor test paper for water content detection based on W7

[0091] A circular filter paper with a radius of 4 cm was placed in the ethanol solution of W7 (concentration of 1×10 -2 mmol / ml) for 24 h to ensure that the halogenated salen complex W7 can be fully absorbed onto the surface and enter the pores of all test papers, and then dried in an oven at 80 °C for 30 min to obtain the content detection fluorescent sensor test paper.

[0092] Example 7

[0093] A circular filter paper with a radius of 4 cm was placed in the ethanol solution of W7 (concentration of 1.5×10 -2 mmol / ml) for 28 h to ensure that the halogenated salen complex W7 can be fully absorbed onto the surface and enter the pores of all test papers, and then dried in an oven at 60 °C for 60 min to obtain the content detection fluorescent sensor test paper.

[0094] Example 8

[0095] A circular filter paper with a radius of 4 cm was placed in the ethanol solution of W7 (concentration of 0.8×10 -2 mmol / ml) for 20 h to ensure that the halogenated salen complex W7 can be fully absorbed onto the surface and enter the pores of all test papers, and then dried in an oven at 70 °C for 50 min to obtain the content detection fluorescent sensor test paper.

[0096] Example 9

[0097] A circular filter paper with a radius of 4 cm was placed in the ethanol solution of W7 (concentration of 2×10 -2 mmol / ml) for 18 h to ensure that the halogenated salen complex W7 can be fully absorbed onto the surface and enter the pores of all test papers, and then dried in an oven at 90 °C for 20 min to obtain the content detection fluorescent sensor test paper.

[0098] Example 10

[0099] The test paper prepared in Example 4 was placed under a 365 nm ultraviolet lamp, and then ethanol solutions (50 μL) with different water contents (0%-90%) were added. The detection of the water content of DMF was the same as the above steps.

[0100] Test results: Observe the changes of the test paper in the dark, such as Fig.13 As shown: When anhydrous ethanol is added to the dry ethanol sample, the test paper produces a light blue fluorescent spot ( Fig.13 a). As the water content increases, the fluorescence intensity gradually decreases; in DMF, similar to ethanol, as the water content increases, the fluorescence intensity gradually weakens, and the spot color gradually changes from blue to dark blue and finally to black, which is consistent with the change in water concentration, indicating that the use of W7 to detect the water content in organic solvents is effective in the naked eye effect, and also provides a basis for the use of simple UV to detect water in ethanol and DMF. It also shows that the change in fluorescence intensity is visible to the naked eye when using filter paper added with W7, which shows that the colorimetric sensing test paper based on W7 can provide a convenient fluorescence platform for on-site water detection.

[0101] Embodiment 11

[0102] Take a standard solvent (such as anhydrous ethanol), drop the ethanol solution to be tested and the standard solvent on the test paper prepared in Example 4, and compare the fluorescence intensity on the test paper after 15 seconds. If the fluorescence intensity of the ethanol to be tested is weaker than that of the standard solvent, it means that the water content of the ethanol solution to be tested is higher than that of the standard solvent.

Claims

1. A halogenated salen-type complex as a fluorescent sensor for detecting water content in ethanol or DMF, characterized in that: The structural formula of the halogenated salen type complex is as follows: ， Wherein χ is Cl, Br or I; the detection range of the fluorescent sensor for water content in ethanol or DMF is 0~90vol.%.

2. The use according to claim 1, characterized in that The detection limit volume ratio v / v of the fluorescent sensor for water content in ethanol is 0.0524%, and the quantitative limit volume ratio v / v is 0.1747%.

3. The use according to claim 1, characterized in that The detection limit volume ratio v / v of the fluorescent sensor for water content in DMF is 0.0512%, and the quantitative limit volume ratio v / v is 0.1707%.

4. The use according to claim 1, characterized in that The matrix of the fluorescent sensor for detecting the water content in ethanol or DMF is filter paper.

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