Bipyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and preparation method thereof

Abstract

The invention provides a bipyridine bisamide organic ligand for adjusting soil urease activity and inhibiting nitrification and a preparation method thereof, and belongs to the technical field of coordination complexes. Chlorinated 4, 4 '-stilbene dicarboxylic acid and a halogen-containing pyridine compound are used, sulfydryl-containing sulfur quantum dots are introduced, the bipyridine bisamide organic ligand is obtained, the soil urease activity is improved, and meanwhile soil nitrate reductase can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of coordination complexes, and in particular relates to a bipyridine biamide organic ligand for regulating soil urease activity and inhibiting nitrification, and a preparation method thereof. Background Art

[0002] Coordination polymers (also called coordination polymers or complexes) are inorganic-organic hybrid materials obtained by self-assembling transition metals, such as Co, Zn, Cu, etc., and organic ligands. Due to this special composition, the coordination polymer not only combines the advantages of inorganic materials, such as high fire resistance, light weight, and environmental protection, but also has the characteristics of organic materials, such as porosity and good designability. Ligands (referred to as ligands) are divided into monodentate and polydentate according to the number of coordinating atoms. Monodentate ligands have one coordinating atom and can directly coordinate with the central atom; polydentate ligands have two or more coordinating atoms and can form a variety of coordination modes with the central atom, such as chelate coordination.

[0003] The Chinese invention patent (publication number CN103724365A) discloses a transition metal complex based on a semi-rigid bispyridine bisamide organic ligand and terephthalic acid, and its synthesis method and application. The invention uses a semi-rigid bispyridine bisamide ligand N,N'-bis(3-pyridine amide)-1,2-cyclohexane as a neutral organic amine ligand. Not only the pyridine nitrogen atom coordinates with the metal ion, but the amide oxygen atom is also a potential coordination site. The introduction of the amide group increases the hydrophilicity of the ligand, accelerates the crystallization process when synthesizing the transition metal complex, shortens the synthesis cycle, shortens the constant temperature time, and reduces power consumption. However, the patented technology still does not solve the problem that the bispyridine bisamide organic ligand cannot effectively regulate soil urease activity and inhibit nitrification when applied to soil fertilizers, thereby limiting the use of the bispyridine bisamide organic ligand.

[0004] Therefore, there is an urgent need for a bispyridine bisamide organic ligand that can effectively reduce soil nitrate reductase while increasing soil urease activity by functionalizing the raw material components and introducing modified components. Summary of the invention

[0005] The purpose of the present invention is to provide a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and a preparation method thereof. By using chlorinated 4,4'-stilbene dicarboxylic acid and halogen-containing pyridine compounds and introducing mercaptosulfur quantum dots, the bispyridine bisamide organic ligand is obtained, which can effectively reduce soil nitrate reductase while improving soil urease activity.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The first aspect of the present invention provides a method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, comprising the following steps: Step S1: adding 20 to 25 parts of 4,4'-stilbene dicarboxylic acid and 12 to 15 parts of N-chlorosuccinimide to 40 to 50 parts of dichloromethane by weight, stirring for 10 to 20 minutes, then adding 2 to 4 parts of trifluoroacetic acid and stirring for 12 to 24 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with an organic solvent, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: In parts by weight, 6 to 8 parts of the chlorinated 4,4'-stilbene dicarboxylic acid, 4 to 6 parts of pyridine compounds and 0.2 to 0.5 parts of quantum dot materials are added to 60 to 70 parts of pyridine, stirred for 30 to 60 minutes, and then 14 to 16 parts of triphenyl phosphite are added, the temperature is raised to 110 to 120°C, refluxed for 10 to 12 hours, cooled, allowed to stand, solids collected by suction filtration, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0007] Chlorinated 4,4'-stilbene dicarboxylic acid can provide chlorine to microorganisms, promote their growth and metabolism, and indirectly increase urease activity by enhancing microbial activity. At the same time, chlorine can form soluble complexes with metal ions in the soil, increase the bioavailability of these metal ions, and ensure that metal ions can serve as important cofactors for urease activity.

[0008] As a preferred solution, the organic solvent in step S1 is diethyl ether or ethyl acetate.

[0009] As a preferred solution, the pyridine compound in step S2 is a halogen-containing pyridine compound.

[0010] As a preferred solution, the halogen-containing pyridine compound is 2-fluoro-3-amino-4-methylpyridine and 2-bromo-3-amino-4-methylpyridine.

[0011] As a preferred solution, the mass ratio of 2-fluoro-3-amino-4-methylpyridine to 2-bromo-3-amino-4-methylpyridine is (1~2):1.

[0012] The halogens in pyridine compounds can bind to the key amino acid residues of nitrifying enzymes, interfering with the active sites of the enzyme, thereby reducing the activity of nitrifying enzymes. At the same time, halogens can also interfere with the cell membrane structure and function of nitrifying bacteria, inhibiting their growth and metabolism. The combined effect affects the activity of nitrifying bacteria and inhibits nitrification.

[0013] As a preferred solution, the quantum dot material in step S2 is mercaptosulfur-containing quantum dots.

[0014] As a preferred scheme, the preparation method of the mercaptosulfur quantum dots comprises: dispersing 5 to 10 parts of sulfur quantum dots in 40 to 50 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then subjecting the sulfur quantum dot mixed solution to plasma treatment, adding 1 to 3 parts of thioglycolic acid and 0.2 to 0.5 parts of 1-hydroxybenzotriazole to the sulfur quantum dot mixed solution after the plasma treatment, stirring the reaction for 2 to 4 hours, centrifuging after the reaction is completed, washing, and drying to obtain mercaptosulfur quantum dots.

[0015] As a preferred scheme, the preparation method of the sulfur quantum dots comprises: adding 4 to 6 parts of sodium hydroxide and 3 to 5 parts of polyethylene glycol to 40 to 50 parts of deionized water by weight, stirring evenly, adding 1 to 2 parts of sulfur powder, stirring at 70 to 75° C. for 2 to 4 hours to obtain an orange-red solution; using a peristaltic pump to pass air into the orange-red solution and continue to react for 20 to 24 hours, after the reaction is completed, adding 10 to 12 parts of a 35% mass concentration of hydrogen peroxide solution dropwise to react for 40 to 60 minutes, cooling to room temperature after the reaction is completed to obtain a light yellow solution, dialyzing, rotary evaporation, and freeze-drying to obtain sulfur quantum dots.

[0016] As a preferred solution, the average particle size of the sulfur powder is 0.5 μm.

[0017] The charge on the surface of the thiolsulfur quantum dots can form a complex with the positively charged metal ions in the soil through electrostatic attraction, thereby increasing the utilization rate of soil urease for metal ions in the form of a complex, thereby increasing the activity of soil urease.

[0018] The second aspect of the present invention provides a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, which is prepared by the preparation method described in the first aspect.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The thiol group of the sulfur quantum dots of the present invention forms a covalent bond with the key amino acid residues of nitrase, interfering with the active site of nitrase, while the halogen in the pyridine compound can bind to the active site of nitrase, further reducing the activity of nitrase, thereby inhibiting nitrification.

[0020] 2. The chlorinated 4,4'-stilbene dicarboxylic acid of the present invention can provide chlorine element for microorganisms, promote the growth and metabolism of microorganisms, and indirectly improve the urease activity by virtue of the improvement of microbial activity; at the same time, the chlorine element can form a soluble complex with the metal ions in the soil, increase the bioavailability of these metal ions, and ensure that the metal ions can serve as an important auxiliary factor for urease activity.

[0021] 3. The halogens in the pyridine compounds of the present invention can bind to the key amino acid residues of nitrifying enzymes, interfere with the active sites of the enzyme, and thus reduce the activity of nitrifying enzymes; at the same time, the halogens can also interfere with the cell membrane structure and function of nitrifying bacteria, inhibit their growth and metabolism, and the combined effect affects the activity of nitrifying bacteria and inhibits nitrification.

[0022] 4. The surface charge of the mercaptosulfur quantum dots of the present invention can form a complex with positively charged metal ions in the soil through electrostatic attraction, thereby increasing the utilization rate of soil urease for metal ions in the form of the complex, thereby increasing the activity of soil urease. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The sources of some components in the embodiments and comparative examples are as follows: 4,4'-Stilbene dicarboxylic acid, CAS No. 100-31-2, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 3-Amino-4-methylpyridine, CAS No. 3430-27-1, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Pyridine, CAS No. 110-86-1, was purchased from Sinopharm Chemical Reagent Co., Ltd.; Triphenyl phosphite, CAS No. 101-02-0, purchased from Nantong Runzhou Chemical Co., Ltd.; N-chlorosuccinimide, CAS No. 128-09-6, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Dichloromethane, CAS No. 75-09-2, was purchased from Sinopharm Chemical Reagent Co., Ltd.; Trifluoroacetic acid, CAS No. 76-05-1, was purchased from Sinopharm Chemical Reagent Co., Ltd.; Anhydrous ethanol, CAS No. 64-17-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.; Ethyl acetate, CAS No. 141-78-6, was purchased from Sinopharm Chemical Reagent Co., Ltd.; Diethyl ether, CAS No. 60-29-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.; 2-Fluoro-3-amino-4-methylpyridine, CAS No. 173435-32-0, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 2-Bromo-3-amino-4-methylpyridine, CAS No. 126325-50-6, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Polyethylene glycol, product number 202398-250G, was purchased from Sigma-Aldrich; Sulfur powder I, with an average particle size of 0.5 μm, was purchased from Anaiji (Shanghai) Pharmaceutical Chemical Co., Ltd.; Sulfur powder II, with an average particle size of 45 μm, was purchased from Sigma-Aldrich; Hydrogen peroxide solution, product number H433859-250ml, mass concentration 35%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Thioglycolic acid, CAS No. 68-11-1, purchased from Shandong Jinghao Chemical Co., Ltd.; 1-Hydroxybenzotriazole, CAS No. 2592-95-2, was purchased from Shanghai Anaiji Chemical Reagent Company.

[0025] Example 1 This embodiment provides a method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, comprising the following steps: Preparation of mercaptosulfur quantum dots: (1) In parts by weight, 6 parts of sodium hydroxide and 5 parts of polyethylene glycol are added to 50 parts of deionized water, stirred evenly, and then 2 parts of sulfur powder (sulfur powder I, average particle size of 0.5 μm) are added, and stirred at 75°C for 2 hours to obtain an orange-red solution; air is introduced into the orange-red solution using a peristaltic pump and the reaction is continued for 24 hours, and after the reaction is completed, 12 parts of a 35% mass concentration of hydrogen peroxide solution are added dropwise to react for 60 minutes, and after the reaction is completed, the solution is cooled to room temperature to obtain a light yellow solution, dialyzed, rotary evaporated, and freeze-dried to obtain sulfur quantum dots. (2) In parts by weight, 10 parts of sulfur quantum dots are dispersed in 50 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then the sulfur quantum dot mixed solution is subjected to plasma treatment. After the plasma treatment is completed, 3 parts of thioglycolic acid and 0.5 parts of 1-hydroxybenzotriazole are added to the sulfur quantum dot mixed solution, and the reaction is stirred for 4 hours. After the reaction is completed, the solution is centrifuged, washed, and dried to obtain mercaptosulfur quantum dots.

[0026] Step S1: adding 25 parts of 4,4'-stilbene dicarboxylic acid and 15 parts of N-chlorosuccinimide to 50 parts of dichloromethane by weight, stirring for 20 minutes, then adding 4 parts of trifluoroacetic acid and stirring for 24 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with ethyl acetate, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: In parts by weight, 8 parts of the chlorinated 4,4'-stilbene dicarboxylic acid, 4 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine and 0.5 parts of mercaptosulfur quantum dots are added to 70 parts of pyridine, stirred for 60 minutes, and then 16 parts of triphenyl phosphite are added, the temperature is raised to 120°C, refluxed for 10 hours, cooled, allowed to stand, solids collected by suction filtration, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0027] Example 2 This embodiment provides a method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, comprising the following steps: Preparation of mercaptosulfur quantum dots: (1) In parts by weight, 4 parts of sodium hydroxide and 3 parts of polyethylene glycol are added to 40 parts of deionized water, stirred evenly, and then 1 part of sulfur powder (sulfur powder I, average particle size of 0.5 μm) is added, and stirred at 70°C for 4 hours to obtain an orange-red solution; air is introduced into the orange-red solution using a peristaltic pump and the reaction is continued for 20 hours, and after the reaction is completed, 10 parts of a 35% mass concentration of hydrogen peroxide solution are added dropwise to react for 40 minutes, and after the reaction is completed, the solution is cooled to room temperature to obtain a light yellow solution, dialyzed, rotary evaporated, and freeze-dried to obtain sulfur quantum dots. (2) In parts by weight, 5 parts of sulfur quantum dots are dispersed in 40 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then the sulfur quantum dot mixed solution is subjected to plasma treatment. After the plasma treatment is completed, 1 part of thioglycolic acid and 0.2 parts of 1-hydroxybenzotriazole are added to the sulfur quantum dot mixed solution, and the reaction is stirred for 2 hours. After the reaction is completed, the solution is centrifuged, washed, and dried to obtain mercaptosulfur quantum dots.

[0028] Step S1: adding 20 parts of 4,4'-stilbene dicarboxylic acid and 12 parts of N-chlorosuccinimide to 40 parts of dichloromethane by weight, stirring for 10 minutes, then adding 2 parts of trifluoroacetic acid and stirring for 12 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with ether, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: In parts by weight, 6 parts of the chlorinated 4,4'-stilbene dicarboxylic acid, 2 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine and 0.2 parts of mercaptosulfur quantum dots are added to 60 parts of pyridine, stirred for 30 minutes, and then 14 parts of triphenyl phosphite are added, the temperature is raised to 110°C, refluxed for 12 hours, cooled, allowed to stand, solids collected by suction filtration, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0029] Example 3 This embodiment provides a method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, comprising the following steps: Preparation of mercaptosulfur quantum dots: (1) In parts by weight, 5 parts of sodium hydroxide and 4 parts of polyethylene glycol are added to 45 parts of deionized water, stirred evenly, and then 2 parts of sulfur powder (sulfur powder I, average particle size of 0.5 μm) are added, and stirred at 72°C for 3 hours to obtain an orange-red solution; air is introduced into the orange-red solution using a peristaltic pump and the reaction is continued for 22 hours, and after the reaction is completed, 11 parts of a 35% mass concentration of hydrogen peroxide solution are added dropwise to react for 50 minutes, and after the reaction is completed, the solution is cooled to room temperature to obtain a light yellow solution, dialyzed, rotary evaporated, and freeze-dried to obtain sulfur quantum dots. (2) In parts by weight, 8 parts of sulfur quantum dots are dispersed in 45 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then the sulfur quantum dot mixed solution is subjected to plasma treatment. After the plasma treatment is completed, 2 parts of thioglycolic acid and 0.4 parts of 1-hydroxybenzotriazole are added to the sulfur quantum dot mixed solution, and the reaction is stirred for 3 hours. After the reaction is completed, the solution is centrifuged, washed, and dried to obtain mercaptosulfur quantum dots.

[0030] Step S1: adding 24 parts of 4,4'-stilbene dicarboxylic acid and 14 parts of N-chlorosuccinimide to 45 parts of dichloromethane by weight, stirring for 15 minutes, then adding 3 parts of trifluoroacetic acid and stirring for 20 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with ethyl acetate, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: In parts by weight, 7 parts of the chlorinated 4,4'-stilbene dicarboxylic acid, 3 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine and 0.4 parts of mercaptosulfur quantum dots are added to 65 parts of pyridine, stirred for 50 minutes, and then 15 parts of triphenyl phosphite are added, the temperature is raised to 115°C, refluxed for 11 hours, cooled, allowed to stand, solids collected by suction, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0031] Comparative Example 1 The present comparative example provides a method for preparing a bispyridine bisamide organic ligand, comprising the following steps: in parts by weight, 8 parts of 4,4'-stilbene dicarboxylic acid and 6 parts of 3-amino-4-methylpyridine are added to 70 parts of pyridine, stirred for 60 minutes, and then 16 parts of triphenyl phosphite are added, the temperature is raised to 120°C, refluxed for 10 hours, cooled, allowed to stand, solids collected by suction filtration, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand.

[0032] Comparative Example 2 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 1 is that chlorinated 4,4'-stilbene dicarboxylic acid is used instead of 4,4'-stilbene dicarboxylic acid.

[0033] Comparative Example 3 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 1 is that 4 parts of 2-fluoro-3-amino-4-methylpyridine and 2 parts of 2-bromo-3-amino-4-methylpyridine are used to replace 6 parts of 3-amino-4-methylpyridine.

[0034] Comparative Example 4 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 3 is that the amount of 2-bromo-3-amino-4-methylpyridine is changed from 2 parts to 1 part.

[0035] Comparative Example 5 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 3 is that the amount of 2-fluoro-3-amino-4-methylpyridine is changed from 4 parts to 1 part, and the amount of 2-bromo-3-amino-4-methylpyridine is changed from 2 parts to 4 parts.

[0036] Comparative Example 6 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 1 is that 0.5 parts of mercaptosulfur quantum dots are added.

[0037] Comparative Example 7 This comparative example provides a method for preparing a bispyridine bisamide organic ligand. The difference between this comparative example and comparative example 6 is that sulfur powder II (average particle size of 45 μm) is used instead of sulfur powder I (average particle size of 0.5 μm) to prepare mercapto-containing sulfur quantum dots.

[0038] Performance Testing The bispyridine bisamide organic ligands prepared in the above examples and comparative examples were subjected to the following tests: soil urease was tested according to the requirements of "TNAIA 011-2020 Sodium phenol-sodium hypochlorite colorimetric method for determination of soil urease activity"; soil nitrate reductase was determined by phenol disulfonic acid colorimetric method. The test results are shown in Table 1.

[0039] Table 1 Performance test results

[0040] From the above performance test results, it can be seen that the comprehensive performance of the bispyridine bisamide organic ligand of Examples 1-3 is the most outstanding. The tested soil urease is 156.97~158.82 IU / g, and the soil nitrate reductase is 2.66~2.78 IU / g. This is mainly because it uses chlorinated 4,4'-stilbene dicarboxylic acid and halogen-containing pyridine compounds, and introduces thiol-containing sulfur quantum dots, which effectively reduces soil nitrate reductase while improving soil urease activity.

[0041] However, because the necessary technical solution was not adopted in Comparative Example 1, the corresponding performance tests were significantly worse than those of the embodiment. The soil urease tested was 134.06 IU / g, and the soil nitrate reductase was 4.23 IU / g. IU / g; compared with comparative example 1, comparative example 2 uses chlorinated 4,4'-stilbene dicarboxylic acid instead of 4,4'-stilbene dicarboxylic acid, and the soil urease increases; compared with comparative example 1, comparative example 3 uses 4 parts of 2-fluoro-3-amino-4-methylpyridine and 2 parts of 2-bromo-3-amino-4-methylpyridine to replace 6 parts of 3-amino-4-methylpyridine, and the soil nitrate reductase decreases; compared with comparative example 3, comparative example 4 changes the amount of 2-bromo-3-amino-4-methylpyridine from 2 parts to 1 part, that is, the mass ratio of 2-fluoro-3-amino-4-methylpyridine to 2-bromo-3-amino-4-methylpyridine is greater than 2. Due to the excessive amount of 2-fluoro-3-amino-4-methylpyridine, the composite effect is not good, so the soil nitrate reductase increases; compared with comparative example 1, comparative example 5 changes 2 -The amount of fluoro-3-amino-4-methylpyridine was changed from 4 parts to 1 part, and the amount of 2-bromo-3-amino-4-methylpyridine was changed from 2 parts to 4 parts, that is, the mass ratio of 2-fluoro-3-amino-4-methylpyridine and 2-bromo-3-amino-4-methylpyridine was less than 1. Due to the small amount of 2-fluoro-3-amino-4-methylpyridine, the composite effect was poor, so the soil nitrate reductase increased; compared with comparative example 1, comparative example 6 added 0.5 parts of thiol-containing sulfur quantum dots, and the soil urease increased; compared with comparative example 6, comparative example 7 used sulfur powder II (particle size of 45 μm, purchased from Sigma-Aldrich) instead of sulfur powder I (particle size of 0.5 μm, purchased from Anaiji) to prepare thiol-containing sulfur quantum dots. Due to the large particle size of sulfur powder II, the preparation effect of sulfur quantum dots was poor, so the soil urease decreased. The above experimental results further prove the importance of the technical scheme defined in the present invention for its technical effect.

[0042] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, characterized in that: The following steps are involved: Step S1: adding 20 to 25 parts of 4,4'-stilbene dicarboxylic acid and 12 to 15 parts of N-chlorosuccinimide to 40 to 50 parts of dichloromethane by weight, stirring for 10 to 20 minutes, then adding 2 to 4 parts of trifluoroacetic acid and stirring for 12 to 24 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with an organic solvent, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: In parts by weight, 6 to 8 parts of the chlorinated 4,4'-stilbene dicarboxylic acid, 4 to 6 parts of pyridine compounds and 0.2 to 0.5 parts of quantum dot materials are added to 60 to 70 parts of pyridine, stirred for 30 to 60 minutes, and then 14 to 16 parts of triphenyl phosphite are added, the temperature is raised to 110 to 120°C, refluxed for 10 to 12 hours, cooled, allowed to stand, solids collected by suction filtration, washed with anhydrous ethanol, and dried to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

2. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 1, characterized in that: The organic solvent in step S1 is ether or ethyl acetate.

3. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 1, characterized in that: The pyridine compound in step S2 is a halogen-containing pyridine compound.

4. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 3, characterized in that: The halogen-containing pyridine compounds are 2-fluoro-3-amino-4-methylpyridine and 2-bromo-3-amino-4-methylpyridine.

5. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 4, characterized in that: The mass ratio of the 2-fluoro-3-amino-4-methylpyridine to the 2-bromo-3-amino-4-methylpyridine is (1-2):

1.

6. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 1, characterized in that: The quantum dot material in step S2 is mercaptosulfur-containing quantum dots.

7. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 6, characterized in that: The preparation method of the mercaptosulfur quantum dots comprises: dispersing 5 to 10 parts of sulfur quantum dots in 40 to 50 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then subjecting the sulfur quantum dot mixed solution to plasma treatment, adding 1 to 3 parts of thioglycolic acid and 0.2 to 0.5 parts of 1-hydroxybenzotriazole to the sulfur quantum dot mixed solution after the plasma treatment, stirring and reacting for 2 to 4 hours, and centrifuging, washing, and drying after the reaction is completed to obtain the mercaptosulfur quantum dots.

8. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 7, characterized in that: The preparation method of the sulfur quantum dots comprises: adding 4 to 6 parts of sodium hydroxide and 3 to 5 parts of polyethylene glycol to 40 to 50 parts of deionized water by weight, stirring evenly, adding 1 to 2 parts of sulfur powder, stirring at 70 to 75° C. for 2 to 4 hours to obtain an orange-red solution; using a peristaltic pump to introduce air into the orange-red solution and continue to react for 20 to 24 hours, after the reaction is completed, dripping 10 to 12 parts of a 35% hydrogen peroxide solution and reacting for 40 to 60 minutes, cooling to room temperature after the reaction is completed to obtain a light yellow solution, dialysis, rotary evaporation, and freeze-drying to obtain the sulfur quantum dots.

9. The method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 8, characterized in that: The average particle size of the sulfur powder is 0.5 μm.

10. A bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

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