Anion free radical compound with stable water solubility as well as preparation method and application of anion free radical compound

Abstract

The invention discloses a water-soluble stable anion free radical compound and a preparation method and application thereof, the anion free radical compound comprises an electron donor and an electron acceptor, the electron donor is an alkali metal compound, and anions of the alkali metal compound are halide ions; moreover, electrons of halide ions are delocalized from an electron donor to an electron acceptor to form an anion free radical compound. An electron donor and an electron acceptor form a charge transfer compound, and the charge transfer compound is self-assembled to form a stable anion free radical compound. The free radical compound takes alkali metal halide salt as an electron donor, on one hand, integer charge transfer between halogen anions and an electron acceptor can be met, and F4TCNQ.-anion free radicals are rapidly generated; on the other hand, coordination bonds with moderate strength are formed between alkali metal cations and F4TCNQ.-. Therefore, the composition has excellent water solubility and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of free radical materials, and particularly relates to a water-soluble stable anion free radical complex as well as a preparation method and application thereof, in particular to an anion free radical complex taking an alkali metal compound with halogen anion as an electron donor for charge transfer as an electron donor and a preparation method and application thereof. BACKGROUND

[0002] Free radical materials are a kind of materials with unique chemical reactivity, which contain at least one unpaired electron and maintain long-term stability through space steric hindrance, electron delocalization or rigid encapsulation. They have good application value in the fields of biological imaging, biological sensing, photodynamic therapy, solid-phase free radical catalysts, energy conversion and energy storage technology (Exploration. Vol. 2. No. 2. 2022, Annu. Rev. Chem. Biomol. Eng. 2018. 9: 83-103).

[0003] At present, free radical materials are generally produced by breaking chemical bonds to generate free radicals through light / radiation-induced cleavage, thermal decomposition solid-phase reaction and the like, and the process occurs in the molecule, resulting in a very tedious and time-consuming molecular design and synthesis process. In addition, free radical materials can also be prepared through intermolecular charge transfer. Specifically, an electron donor (D) and an electron acceptor (A) molecule are co-assembled to form a charge transfer complex through intermolecular interactions (such as charge transfer, hydrogen bonding, π-π stacking, etc.), charge transfer occurs, and an ion pair containing a free radical is formed (Adv. Mater., 2020, 2001146; J. Mater. Chem. C, 2018, 6, 1884-1902). More importantly, the charge transfer complex can be prepared by a simple and low-cost one-step mechanical grinding method, thereby avoiding a complex and long-period synthesis process. At the same time, the high reactivity and short lifetime of free radicals are always problems that need to be faced in the preparation of free radical materials, and common solutions are to use space steric hindrance effect, electron delocalization, lattice constraint, charge regulation and coordination, and low-temperature solidification to stabilize free radicals. In 2024, Liao Jianzhen's group of Pingxiang University reported that naphthalene diimine derivatives (H4NDISA) or lead-based coordination polymers (Pb-NDISA) and suitable primary or tertiary amine organic molecules form a charge transfer complex at room temperature through mechanical grinding, and it is subsequently verified that NDISA anion free radicals are generated, and good stability is maintained under heating conditions (Inorg. Chem. 2024, 63, 16799-16806).

[0004] The free radical material with good water solubility can detect organic pollutants in domestic sewage, and has fast reaction and no secondary pollution, and can even degrade pollutants in a green way. However, the stability of the existing free radical material under normal temperature, normal pressure and pure water phase conditions is still insufficient to meet the actual demand, and there is still a lack of effective solutions that can exist stably in a pure water system.

[0005] Therefore, it is urgent to explore a more efficient and simple preparation method, and to develop a free radical material with good water solubility and stability, so as to meet the application requirements of the growing free radical storage field and water pollutant detection field. SUMMARY

[0006] The present application mainly aims at the technical problems of the existing free radical material preparation difficulty and poor stability, and provides a water-soluble stable anion free radical complex and a preparation method and application thereof. The anion free radical complex has excellent water solubility and stability, and is suitable for water pollutant detection.

[0007] The inventive concept of the present application is that: the present application uses an alkali metal compound MX (wherein: M represents an alkali metal cation, and X represents a halide anion) which can transfer an integer charge with halide anion as an electron donor, and selects 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano dimethyl p-benzoquinone (F4TCNQ) containing a strong electron-withdrawing group as an electron acceptor. When the above electron donor and acceptor are combined, the electrons of the halide anion can be delocalized from the donor to the acceptor, and the two form a charge transfer (CT) state, thereby widening the absorption spectrum of the system. At the same time, the electron donor and the electron acceptor form an anion free radical complex through intermolecular charge transfer interaction.

[0008] Meanwhile, the free radical complex of the present application uses an alkali metal compound with halide anion (i.e. alkali metal halide) as an electron donor, which can not only meet the integer charge transfer between the halide anion and the electron acceptor, but also quickly generate F4TCNQ ·- anion free radical; on the other hand, the alkali metal cation forms a moderate strength coordination bond with F4TCNQ ·- , which is not only weaker than the coordination bond between the alkaline earth metal cation and F4TCNQ - , but also weaker than the intermolecular interaction between the existing ionic ammonium compound and F4TCNQ ·- . Therefore, the water solubility (20℃) of the free radical complex of the present application is 1.7±0.2mg / mL, which is better than that of the alkaline earth metal organic complex (such as SrI2-F4TCNQ, the water solubility is 1.1±0.2mg / mL), and is better than that of the existing water-insoluble metal organic photothermal conversion eutectic material (such as OSB-F4TCNQ and MSB-F4TCNQ, the water solubility is less than 1×10 -3mg / mL). Therefore, the radical complex of the present application has excellent water solubility and stability.

[0009] To solve the above technical problems, the first aspect of the present application provides an anionic radical complex, comprising an electron donor and an electron acceptor, the electron donor is an alkali metal compound, the anion of the alkali metal compound is a halogen ion; and the electron of the halogen ion is delocalized from the electron donor to the electron acceptor to form the anionic radical complex.

[0010] In some embodiments of the present application, the halogen ion is selected from at least one of iodine ion, bromine ion, chlorine ion, fluorine ion, the alkali metal ion in the alkali metal compound can form an ion pair balanced charge with the anionic radical, and the radical ligand can chelate with the alkali metal ion to form a stable radical metal complex.

[0011] In some embodiments of the present application, the cation of the alkali metal compound is selected from at least one of lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion. For example, the alkali metal compound is selected from at least one of lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride.

[0012] In some embodiments of the present application, the electron acceptor is 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-dimethyl-p-benzoquinone (F4TCNQ), F4TCNQ contains a strong electron-withdrawing group, which is beneficial to the transfer of the electron of the halogen anion from the donor to the acceptor when combined with the strong electron-donating group halogen anion in the electron donor, and generates F4TCNQ ·- Anionic radical.

[0013] In some embodiments of the present application, the molar ratio of the electron donor to the electron acceptor is (0.1-10):1; for example, it can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc., including but not limited to the listed values, and other values not listed in the value range are also applicable.

[0014] The second aspect of the present application provides a preparation method of the above-mentioned anionic radical complex, which is a one-step mechanical grinding method. The anionic radical complex of the present application is prepared by a mechanochemical method, i.e. a one-step mechanical grinding method, which is efficient and simple.

[0015] In some embodiments of the present application, the one-step mechanical grinding method comprises the following steps:

[0016] After mixing the electron donor and the electron acceptor, grinding is performed to obtain the anion radical complex.

[0017] Specifically, when the electron donor and the electron acceptor are mixed, the two components contact each other to form an electron donor-electron acceptor intermolecular CT complex; grinding is continued to make the two components more fully contact and orderly self-assemble in the form of the anion radical complex with the lowest energy.

[0018] In some embodiments of the present application, the grinding is pressurized grinding, and the time of the pressurized grinding is more than 1 hour; preferably 1-2 hours.

[0019] The third aspect of the present application provides application of the above-mentioned anion radical complex in detecting organic pollutants in domestic sewage.

[0020] Specifically, the anion radical complex of the present application has good water solubility and stability, can detect organic pollutants in domestic sewage, has a rapid reaction and no secondary pollution, and can even greenly degrade the pollutants. Therefore, it is suitable for detecting organic pollutants in domestic sewage.

[0021] The fourth aspect of the present application provides an amino acid sensing and detecting device, which comprises a sensing element, and the material for preparing the sensing element comprises the above-mentioned anion radical complex.

[0022] Specifically, F4TCNQ ·- The anion radical can react with amino acids such as cysteine, and therefore, the anion radical complex of the present application can be used as a raw material for preparing a sensing element of an amino acid sensing and detecting device.

[0023] The above technical solutions of the present application have at least the following technical effects or advantages relative to the prior art:

[0024] (1) The present application uses an alkali metal compound capable of transferring an integer charge with a halogen anion as an electron donor, and selects F4TCNQ containing a strong electron-withdrawing group as an electron acceptor, so that the electron donor and the electron acceptor form a charge transfer complex and self-assemble to form a stable anion radical complex. The radical complex uses an alkali metal halide as an electron donor, which can satisfy the integer charge transfer between the halogen anion and the electron acceptor, and quickly generate F4TCNQ ·- anion radical; on the other hand, the alkali metal cation forms a moderate coordination bond with F4TCNQ ·- Therefore, it has excellent water solubility and stability.

[0025] (2) The anion radical complex of the present application can be prepared by a one-step mechanical grinding process, without strict control of conditions, and is suitable for wide promotion and use. Meanwhile, the anion radical complex prepared by the present application is formed by self-assembly of inorganic alkali metal halide and organic small molecules, and has the advantages of mild and simple preparation conditions and low cost, and thus has good application prospects in the field of radical storage.

[0026] (3) The solubility of the anion radical complex of the present application in water at 20℃ can reach 1.7±0.2 mg / mL, and has good application value in the field of water pollutant detection, and can be used for preparing a sensing element of an amino acid sensing and detection device. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A process flow diagram for preparing the anion radical complex by the one-step mechanical grinding method used in the embodiments of the present application;

[0028] Figure 2 A molecular structure of the electron donor and electron acceptor F4TCNQ used in the embodiments of the present application;

[0029] Figure 3 A charge transfer process diagram of the anion radical complex prepared by the present application;

[0030] Figure 4 An infrared spectrum of the solid powder of the anion radical complex prepared in Examples 1-5;

[0031] Figure 5 An ultraviolet-visible-near infrared absorption spectrum of the solid powder of the anion radical complex prepared in Examples 1-5 and F4TCNQ;

[0032] Figure 6 An infrared spectrum of the anion radical complex prepared in Examples 1-5 and F4TCNQ in acetone solution;

[0033] Figure 7 An ultraviolet-visible-near infrared absorption spectrum of the aqueous solution of the anion radical complex prepared in Examples 1-5 and the single-component electron donor and electron acceptor;

[0034] Figure 8 An electron paramagnetic resonance spectrum of the solid powder of the anion radical complex prepared in Examples 1-5;

[0035] Figure 9 An EDS spectrum of the solid powder of the anion radical complex prepared in Example 2;

[0036] Figure 10UV-Vis-NIR absorption spectra of aqueous solutions of the anionic radical complex prepared for Example 3-5, freshly prepared and aged for 18 months;

[0037] Figure 11 UV-Vis absorption spectra of the composites prepared for Example 4 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0038] The application will be described in conjunction with the following examples in order to facilitate the understanding of the application by those skilled in the art. It is necessary to point out here that the examples are only used to further illustrate the application and cannot be understood as limiting the scope of protection of the application. Non-essential improvements and adjustments to the application made by those skilled in the art based on the above description of the application shall still fall within the scope of protection of the application. Meanwhile, the raw materials mentioned below which are not described in detail are all commercially available products; the process steps or preparation methods which are not mentioned in detail are all known to those skilled in the art.

[0039] Example 1

[0040] A method for preparing an anionic radical complex by one-step mechanical grinding, a schematic diagram of the preparation process is shown as follows Figure 1 and specifically includes the following steps:

[0041] (1) LiI solid 13.39 mg and F4TCNQ solid 27.62 mg were weighed respectively, and then the two solids were mixed uniformly to form an intermolecular charge transfer complex;

[0042] (2) The intermolecular charge transfer complex prepared in step (1) was transferred to a grinder for pressurized grinding for 1 hour to obtain the anionic radical complex of the present example, denoted as LiI-F4TCNQ.

[0043] Example 2

[0044] A method for preparing an anionic radical complex by one-step mechanical grinding, specifically including the following steps:

[0045] (3) NaI solid 14.99 mg and F4TCNQ solid 27.62 mg were weighed respectively, and then the two solids were mixed uniformly to form an intermolecular charge transfer complex;

[0046] (4) The intermolecular charge transfer complex prepared in step (1) was transferred to a grinder for pressurized grinding for 1 hour to obtain the anionic radical complex of the present example, denoted as NaI-F4TCNQ.

[0047] Example 3

[0048] A method for preparing an anion radical complex by one-step mechanical grinding method, specifically comprising the following steps:

[0049] (1) respectively take KI solid 16.60 mg and F4TCNQ solid 27.62 mg, then mix the two solids uniformly to form an intermolecular charge transfer complex;

[0050] (2) transfer the intermolecular charge transfer complex prepared in step (1) to a grinder, and perform pressurized grinding for 1 hour to obtain the anion radical complex of the present example, denoted as KI-F4TCNQ.

[0051] Example 4

[0052] A method for preparing an anion radical complex by one-step mechanical grinding method, specifically comprising the following steps:

[0053] (1) respectively take RbI solid 21.24 mg and F4TCNQ solid 27.62 mg, then mix the two solids uniformly to form an intermolecular charge transfer complex;

[0054] (2) transfer the intermolecular charge transfer complex prepared in step (1) to a grinder, and perform pressurized grinding for 1 hour to obtain the anion radical complex of the present example, denoted as RbI-F4TCNQ.

[0055] Example 5

[0056] A method for preparing an anion radical complex by one-step mechanical grinding method, specifically comprising the following steps:

[0057] (1) respectively take CsI solid 25.98 mg and F4TCNQ solid 27.62 mg, then mix the two solids uniformly to form an intermolecular charge transfer complex;

[0058] (2) transfer the intermolecular charge transfer complex prepared in step (1) to a grinder, and perform pressurized grinding for 1 hour to obtain the anion radical complex of the present example, denoted as CsI-F4TCNQ.

[0059] Comparative Example 1

[0060] A method for preparing a metal-organic complex photothermal material by one-step mechanical grinding method, specifically comprising the following steps:

[0061] (1) respectively take SrI2 solid 102.43 mg and F4TCNQ solid 165.66 mg, then mix the two solids uniformly to form an intermolecular charge transfer complex;

[0062] (2) The intermolecular charge transfer complex prepared in step (1) is transferred to a grinder, and pressure grinding is performed for 0.5 hours to obtain a metal-organic complex photothermal material of the present comparative example, denoted as SrI2-F4TCNQ.

[0063] Comparative Example 2

[0064] A method for preparing a photothermal conversion eutectic material by one-step mechanical grinding, specifically comprising the following steps:

[0065] (1) 87.06 mg of MSB solid and 82.85 mg of F4TCNQ solid are weighed respectively, and then the two solids are uniformly mixed to form an intermolecular charge transfer complex;

[0066] (2) The intermolecular charge transfer complex prepared in step (1) is transferred to a grinder, and pressure grinding is performed for 1 hour to obtain a photothermal conversion eutectic material of the present comparative example, denoted as MSB-F4TCNQ.

[0067] Comparative Example 3

[0068] A method for preparing a photothermal conversion eutectic material by one-step mechanical grinding, a preparation process schematic diagram thereof is as shown in Figure 1 , specifically comprising the following steps:

[0069] (1) 118.29 mg of OSB solid and 154.386 mg of F4TCNQ solid are weighed respectively, and then the two solids are uniformly mixed to form an intermolecular charge transfer complex;

[0070] (2) The intermolecular charge transfer complex prepared in step (1) is transferred to a grinder, and pressure grinding is performed for 1 hour to obtain a photothermal conversion eutectic material of the present comparative example, denoted as OSB-F4TCNQ.

[0071] Performance test

[0072] 1. Molecular structure and charge transfer process

[0073] Figure 2 The electron donor used in the present application is an alkali metal halide salt, and the alkali metal iodide salt (LiI, NaI, KI, RbI, CsI) is selected as the molecular structure of the electron donor and the electron acceptor F4TCNQ for preparing anion radical complex of preparation examples 1-5.

[0074] Figure 3 The charge transfer process schematic diagram of the anion radical complex prepared in the present application can be seen from Figure 3 , it can be seen that the present application uses halogen ions (X - ) as an electron source and an alkali metal halide salt (M + [X -As an electron donor, F4TCNQ, containing a strong electron-withdrawing group, acts as an electron acceptor. When the electron donor and acceptor bind (mechanics), electrons can transfer from the donor to the acceptor, forming a charge-transfer (CT) state, which broadens the absorption spectrum of the system. When alkali metal ions chelate with metal ions to form complexes, they can form ion pairs with the anionic radicals to balance the charge and stabilize the radicals.

[0075] 2. Analysis of the degree of solid-phase charge transfer

[0076] Figure 4 The images show the infrared spectra of the anionic radical complex solid powders prepared in Examples 1-5. Figure 4 The horizontal axis represents wavenumber, and the vertical axis represents transmittance. The method reported in the reference (Anal. Chem. 2020, 92, 10, 7154–7161) uses... Figure 4 The charge transfer degree of the anionic radical complexes (LiI-F4TCNQ / NaI-F4TCNQ / KI-F4TCNQ / RbI-F4TCNQ / CsI-F4TCNQ) prepared in Examples 1-5 was calculated from the cyano stretching vibration frequency of F4TCNQ in the infrared spectrum. The values ​​were 0.03 / 0.21 / 0.49 / 0.49 / 0.55, respectively. The charge transfer degree in the complexes increased with increasing alkali metal radius. Simultaneously, the stretching vibration characteristics of the F4TCNQ backbone in the complexes tended towards those of F4TCNQ. ·- .

[0077] Figure 5 The UV-Vis-NIR absorption spectra of the anionic radical complex solid powders prepared in Examples 1-5 and F4TCNQ are shown. Figure 5 The horizontal axis represents wavelength, and the vertical axis represents normalized absorption. Figure 5 It is evident that the anionic radical complexes prepared in Examples 1-5 exhibit a narrowing band gap and broadening absorption spectra due to charge transfer. Specifically, LiI-F4TCNQ, NaI-F4TCNQ, and KI-F4TCNQ do indeed show an increase in alkali metal radius, with a corresponding increase in charge transfer, resulting in a more pronounced broadening of the absorption spectrum. However, RbI-F4TCNQ and CsI-F4TCNQ do not show further broadening of their absorption spectra despite the simultaneous increase in charge transfer. This is essentially because the absorption characteristics are influenced by a series of different intermolecular interactions, and the effect of charge transfer on compressing electron energy levels is limited.

[0078] 3. Analysis of the degree of charge transfer in the liquid phase

[0079] Figure 6 IR spectra of the anionic radical complexes prepared in Examples 1-5 and the acetone solution of F4TCNQ (Solvent: Ace) were measured in order to investigate the specific composition of the complexes by destroying the intermolecular interactions, where Figure 6 a, 6b and 6c are the spectra in different wave bands, respectively. The method reported in the reference (Anal. Chem. 2020, 92, 10, 7154-7161) was used to calculate the degree of charge transfer in the complexes by using the cyanide stretching vibration frequency of F4TCNQ in the IR spectrum of a as a probe. Figure 6 The degree of charge transfer in the acetone solution of Examples 1-5 was calculated to be 1, i.e. integer charge transfer occurred, using the cyanide stretching vibration frequency of F4TCNQ in the IR spectrum of a as a probe of the degree of charge transfer. Not only the cyanide stretching vibration frequency at both ends of F4TCNQ ·- The anionic radical is consistent, the stretching vibration frequencies of the carbon-carbon double bond and the carbon-fluorine bond on the skeleton of F4TCNQ ·- The anionic radical is consistent, the stretching vibration frequencies of the carbon-carbon double bond and the carbon-fluorine bond on the skeleton of F4TCNQ ·- The anionic radical is consistent, the stretching vibration frequencies of the carbon-carbon double bond and the carbon-fluorine bond on the skeleton of F4TCNQ

[0080] Figure 7 UV-Vis-NIR absorption spectra of the anionic radical complexes prepared in Examples 1-5 and the aqueous solutions of the single-component electron donor and electron acceptor were measured, and the F4TCNQ ·- The anionic radical solution in acetonitrile has characteristic absorption peaks at 410 nm, 754 nm and 856 nm (J. Chem. Phys. 2007, 127, 124301). After comparison, it was found that Figure 7 The anionic radical has similar absorption characteristics to those in the literature, which also indicates the presence of F4TCNQ ·- The anionic radical, further verifying that the anionic radical complexes prepared in Examples 1-5 have integer charge transfer in nature and generate F4TCNQ ·- The anionic radical. In contrast, the anionic radical complexes prepared in Examples 1-5 exhibit partial charge transfer in the solid phase, which is believed to be due to the coordination of the metal coordination center with the cyanide group, which restricts the stretching vibration of the cyanide group, resulting in apparent charge transfer.

[0081] 4. Electron paramagnetic resonance spectrum analysis

[0082] Figure 8 The electron paramagnetic resonance spectrum of the anionic radical complex prepared in Example 1-5 is shown in Figure 4. Figure 8 The horizontal axis Magetic field represents the magnetic field, and the vertical axis Normalized intensity represents the normalized intensity. From Figure 8It can be seen that there is a free electron signal, which verifies the generation of free radicals in the anion radical complex.

[0083] 5. EDS spectrum analysis

[0084] Figure 9 The EDS spectrum of the anion radical complex solid powder prepared in Example 2 mainly contains C, N, F, Na elements, and a small amount of I element, indicating that the alkali metal iodine salt in the anion radical complex prepared in Example 2 acts as an electron donor, and the I - The anion transfers electrons to F4TCNQ as an electron acceptor, and then generates I2 elemental gas which diffuses in the air. Therefore, there is only a small amount of I element in the powder, which verifies that the integer charge transfer occurs in the anion radical complex solid powder, and F4TCNQ ·- anion radical.

[0085] 6. Radical stability analysis

[0086] Figure 10 a, 10b, 10c are the UV-Vis-near infrared absorption spectra of the aqueous solutions of the anion radical complexes prepared in Examples 3-5 before and after being placed for a period of time. From Figure 10 It can be seen that the absorption spectra of the three groups have little change before and after being placed for 18 months, and the F4TCNQ ·- The characteristic absorption of the anion radical still exists, and no new peak is generated, which verifies that the prepared anion radical complex has good stability.

[0087] 7. Water solubility

[0088] Figure 11 The UV-Vis absorption spectra of the saturated aqueous solutions of the composite materials prepared in Example 4 and Comparative Examples 1-3 at 20°C are shown in Figure 11 It can be seen that the UV absorption spectra of the saturated aqueous solutions of the OSB-F4TCNQ and MSB-F4TCNQ eutectic materials prepared in Comparative Examples 2-3 do not have obvious F4TCNQ ·- characteristic absorption peaks of the anion radical, so it can be estimated that their water solubility is less than 1 x 10 -3 mg / mL. The water solubility of the alkaline earth metal halide complex (SrI2-F4TCNQ) prepared in Comparative Example 1 is about 1.1 ± 0.2 mg / mL, and the water solubility of the anion radical complex prepared in Example 4 (1.7 ± 0.2 mg / mL) is the highest.

[0089] For those skilled in the art of the present application, without departing from the concept of the present application, can make several simple deductions or substitutions, without having to go through the creative labor. Therefore, the simple improvements made by the person skilled in the art according to the disclosure of the present application, should be within the scope of protection of the present application. The above examples are the preferred embodiments of the present application, any similar process and equivalent changes made, should belong to the protection scope of the present application.

Claims

1. An anionic free radical complex, characterized in that, It includes an electron donor and an electron acceptor, wherein the electron donor is an alkali metal compound and the anion of the alkali metal compound is a halide ion; and the electrons of the halide ion are delocalized from the electron donor to the electron acceptor to form the anion radical complex.

2. The anionic radical complex according to claim 1, characterized in that, The halide ion is selected from at least one of iodide ion, bromide ion, chloride ion, and fluoride ion.

3. The anionic radical complex according to claim 1 or 2, characterized in that, The cation of the alkali metal compound is selected from at least one of lithium ion, sodium ion, potassium ion, rubidium ion, and cesium ion.

4. The anionic radical complex according to claim 1, characterized in that, The electron acceptor is 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone.

5. The anionic radical complex according to claim 1, characterized in that, The molar ratio of the electron donor to the electron acceptor is (0.1-10):

1.

6. A method for preparing an anionic free radical complex as described in any one of claims 1 to 5, characterized in that, The preparation method is a one-step mechanical grinding method.

7. The method for preparing the anionic free radical complex according to claim 6, characterized in that, The one-step mechanical grinding method includes the following steps: The electron donor and electron acceptor are mixed and then ground to obtain the anionic radical complex.

8. The method for preparing the anionic free radical complex according to claim 7, characterized in that, The grinding is pressure grinding, and the pressure grinding time is more than 1 hour.

9. The application of the anionic radical complex according to any one of claims 1 to 5 in the detection of organic pollutants in domestic sewage.

10. An amino acid sensing and detection device, characterized in that, The invention includes a sensing element, wherein the material used to prepare the sensing element comprises the anionic radical complex according to any one of claims 1 to 5.

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