1-carboxymethyl-1-H-pyrazole-3-formic acid Pb complex, synthetic method and application

Abstract

The invention relates to the technical field of pyrazole complexes, in particular to a 1-carboxymethyl-1-H-pyrazole-3-formic acid Pb complex, a synthesis method and application, the minimum asymmetric unit of the complex comprises a Pb (II) ion, a double deprotonated H2pzca ligand ion and two free water molecules, and a [Pb (CH3COO) 2] basic unit is formed. According to the invention, 1-carboxymethyl-1-H-pyrazole-3-formic acid is used as a pyrazole organic ligand for the first time and is subjected to a coordination reaction with lead acetate trihydrate to synthesize the novel pyrazole complex, and the complex has excellent thermal stability and fluorescence characteristic, also has excellent optical performance and chemical stability, and can be used for preparing the novel pyrazole complex. Wide application prospects are realized in the field of luminescent materials.

Description

Technical Field

[0001] The invention relates to the technical field of pyrazole complexes and also to the field of fluorescent materials, in particular to a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex, a synthesis method and an application thereof. Background Art

[0002] Pyrazolyl is an important nitrogen-containing heterocyclic structure. Its unique biological and chemical properties and various chemical reaction types make it one of the most popular heterocyclic structures in the current synthesis of organic compounds and optimization of drug molecules. Pyrazolyl derivatives refer to compounds generated by changing one or more atoms in the pyrazolyl structure. Common pyrazolyl derivatives include 2-pyrazolecarboxylic acid, pyrazolone, pyrazoline, pyrazolol, pyrazole borate, etc., which have been proven to be important candidate compounds in the fields of drugs, antibiotics, anticancer agents, photosensitizers and pesticides.

[0003] The study of pyrazolyl derivative coordination compounds is an important branch of coordination chemistry. Compounds with metal centers and pyrazolyl derivative ligands formed by the coordination of pyrazolyl derivatives with metal ions or central atoms are not only widely used in the fields of biomedicine, catalysis, electronic devices, materials science, etc., but also have important application prospects in the field of environmental science. The framework of pyrazole complexes is usually composed of a pyrazole ring as the center, and coordinated with multiple organic, inorganic or metal ions (the coordination group can be an organic bonding group such as carboxylic acid, alcohol, amine, phosphoric acid, phosphonic acid, or a metal ion such as iron, copper, nickel, silver, etc.). In these complexes, the pyrazole ring forms coordination bonds with other atoms through the lone pair of electrons on its nitrogen atom. In addition to the pyrazole ring, other groups in the complex also largely determine its physical and chemical properties and application fields. By rationally designing the type, order and structure of the coordination group, new pyrazole complexes with different properties and application values ​​can be prepared. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex, a synthesis method and an application, so as to provide a new type of pyrazole complex, and further apply it to luminescent materials.

[0005] Based on the above purpose, the present invention provides a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex, wherein the smallest asymmetric unit of the complex comprises a Pb(II) ion, a doubly deprotonated H2pzca ligand ion and two free water molecules to form a [Pb(CH3COO)2] basic unit; the structural formula of the smallest asymmetric unit is shown in formula (I):

[0006]

[0007] Preferably, the complex is crystallized in monoclinic system, β=103.464(4)°, P21 / n space group.

[0008] The present invention also provides a method for synthesizing the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex, comprising the following steps:

[0009] (1) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid:

[0010] After mixing anhydrous ethanol and 3-pyrazolecarboxylic acid, concentrated sulfuric acid was added dropwise at 80°C and stirred for 2 hours to obtain 1-H-pyrazole-3-carboxylic acid ethyl ester;

[0011] Add 1-H-pyrazole-3-carboxylate and ethyl bromoacetate to anhydrous acetone, stir at 60°C, and monitor the reaction by thin layer chromatography. When 1-H-pyrazole-3-carboxylate is consumed, concentrate the yellow-brown reaction mixture to dryness and purify to obtain 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid;

[0012] (2) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex: 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid, 95 v / v% ethanol and distilled water were mixed and placed in a reaction kettle. The mixture was magnetically stirred for 10 min, and potassium hydroxide and lead acetate trihydrate were added in sequence. The mixture was magnetically stirred for 5 min at room temperature, and then hydrothermally reacted at 120° C. for 2 d. After the mixture was naturally cooled to room temperature, it was filtered and dried to obtain 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex as white crystals.

[0013] Preferably, the usage ratio of anhydrous ethanol, 3-pyrazolecarboxylic acid and concentrated sulfuric acid is 50 mL:10 mmol:2 mL.

[0014] Preferably, the usage ratio of anhydrous acetone, 1-H-pyrazole-3-carboxylate and ethyl bromoacetate is 30 mL:5 mmol:0.6 mmol.

[0015] Preferably, the purification method is: purifying the crude product by column chromatography on silica gel with petroleum ether / ethyl acetate (1 / 1) as eluent to obtain a white product 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid.

[0016] Preferably, the usage ratio of 1-carboxy-1-H-pyrazole-3-carboxylic acid, 95 v / v% ethanol, distilled water, potassium hydroxide and lead acetate trihydrate is 0.1 mmol:10 mL:5 mL:0.2 mmol:0.2 mmol.

[0017] The present invention further provides application of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex in luminescent materials.

[0018] Preferably, the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex is used in photoluminescent materials.

[0019] Preferably, the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex is used in an electroluminescent material. Under the conditions of a standard three-electrode system and 0.1 mol / L K2S2O8, the luminescence intensity of the complex at 20-210 s is about 124-148 a.u.

[0020] The 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex of the present invention is also used in fluorescence sensing.

[0021] The 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex of the present invention is further applied to fluorescence detection.

[0022] Beneficial effects of the present invention:

[0023] The present invention uses 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid as a pyrazole organic ligand for the first time to carry out coordination reaction with lead acetate trihydrate to synthesize a novel pyrazole complex. The complex has excellent thermal stability and fluorescence characteristics, as well as excellent optical properties and chemical stability, and has broad application prospects in the field of luminescent materials, and can also be used for fluorescence sensing and fluorescence detection.

[0024] The structure of the complex consists of a five-membered ring formed by 1-carboxyl-1-H-pyrazole-3-carboxylic acid and a transition metal ion, the central metal ion of which is Pb 2+ , through the metal ion Pb 2+ Coordination with the organic ligand H2pzca can enhance the spin-orbit coupling effect, enhance electrochemiluminescence (ECL) emission, and has high stability. Therefore, it can provide an important theoretical basis for the design of new coordination polymer luminescent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic structural diagram of the minimum asymmetric unit of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex of the present invention;

[0027] Figure 2 is a unit coordination mode diagram of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex of the present invention, wherein a is the coordination mode diagram of the ligand in the complex, and b is the coordination octahedron diagram of Pb(II) in the complex;

[0028] Figure 3 is a three-dimensional structure diagram of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex of the present invention;

[0029] Figure 4 The coordination compound [Pb(pzca)·2H2O] prepared in Example 1 of the present invention n Infrared spectrum of

[0030] Figure 5 The coordination compound [Pb(pzca)·2H2O] prepared in Example 1 of the present invention n Thermogravimetric analysis diagram of

[0031] Figure 6 The coordination compound [Pb(pzca)·2H2O] prepared in Example 1 of the present invention n XRD analysis diagram of

[0032] Figure 7 The coordination compound [Pb(pzca)·2H2O] prepared in Example 1 of the present invention n Fluorescence analysis of

[0033] Figure 8 This is an analysis chart of the electrochemical luminescence intensity of the coordination compound [Pb(pzca)·2H2O]n prepared in Example 1 of the present invention changing with time. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0035] Example 1

[0036] (1) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid:

[0037] After mixing 50 mL of anhydrous ethanol and 10 mmol (1.112 g) of 3-pyrazolecarboxylic acid, 2 mL of concentrated sulfuric acid was added dropwise at 80°C and stirred for 2 h to obtain 1-H-pyrazole-3-carboxylic acid ethyl ester (1.350 g, 9.6 mmol, 96%);

[0038] 0.5 mmol (0.7 g) of 1-H-pyrazole-3-carboxylate and 0.6 mmol (0.835 g) of ethyl bromoacetate were added to 30 mL of anhydrous acetone, and the mixture was stirred at 60° C. The reaction was monitored by thin layer chromatography. When the 1-H-pyrazole-3-carboxylate was consumed, the yellow-brown reaction mixture was concentrated to dryness, and the crude product was purified by column chromatography on silica gel with petroleum ether / ethyl acetate (1 / 1) as eluent to obtain a white product 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid (H2pzca) with a yield of 55% (0.622 g);

[0039] (2) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex: 0.1 mmol (0.0234 g) of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid, 10 mL of 95 v / v% ethanol, and 5 mL of distilled water were mixed and placed in a reaction kettle. The mixture was stirred magnetically for 10 min, and then 0.2 mmol (0.0112 g) of KOH and 0.2 mmol (0.0758 g) of Pb(CH3COO)2·3H2O were added in sequence. The mixture was stirred magnetically for 5 min at room temperature until all the mixture was dissolved. The mixture was then subjected to hydrothermal reaction at 120°C for 2 d. After the mixture was cooled naturally to room temperature, the mixture was filtered and dried to obtain a white crystalline 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex ([Pb(pzca)·2H2O] n ).

[0040] Example 2 Determination of the crystal structure of the complex

[0041] The crystal structure of the complex was determined by a Bruker APEX-IICCD single crystal X-ray diffractometer using graphite monochromated MoKα radiation. The ω-scan technique was used to collect data at 25 °C, and the standard crystallographic software SHELXT-2014 and SHELXL-2014 were used for crystal structure analysis and modification.

[0042] [Pb(pzca)·2H2O] n The single crystal sample of the complex was placed on an X-ray diffractometer for diffraction experiments. The structure of the crystal can be obtained by analyzing the diffraction data. After X-ray single crystal diffraction analysis, the inventors obtained [Pb(pzca)·2H2O] n The crystal structure information of the complex is provided in Table 1. n The crystallographic data of the complexes are listed in Table 2 [Pb(pzca)·2H2O] n Bond length and bond angle data of the complex.

[0043] Table 1 [Pb(pzca)·2H2O] n Crystallographic data

[0044]

[0045]

[0046] Table 2 Complex [Pb(pzca)·2H2O] n The bond length and bond angle (°) data

[0047]

[0048] Results and Analysis:

[0049] The results showed that the complex crystallized in monoclinic, β=103.464(4)°, P21 / n space group.

[0050] like Figure 1 As shown, the smallest asymmetric unit of the complex contains a Pb(II) ion, a H2pzca ligand, a doubly deprotonated H2pzca ligand ion and two free water molecules, forming the [Pb(CH3COO)2] basic unit.

[0051] like Figure 2 -a shows that the metal center Pb 2+ The coordination number is 6, and the bond length of Pb–O1 is The bond length of Pb–O2 is The bond length of Pb–O3 is The bond length of Pb–O4 is The bond length of Pb–N is The bond lengths are consistent with those reported in the literature; C3, C4, C5, N1, and N2 form a five-membered ring, and O2 and N2 chelate a Pb 2+ A five-membered ring is formed, and the complex contains a carboxyl group and a carboxymethyl group. The coordination mode of the carboxyl group is bidentate bridging, and the coordination mode of the carboxymethyl group is bridging and chelating. Through such an extended relationship, a two-dimensional plane is formed.

[0052] like Figure 2 -b, in the crystal structure of the complex, the Pb atom is connected to one N atom and four O atoms, presenting a distorted octahedral structure. Among them, O1, O2, O4, and N2 atoms form an equatorial plane (symmetry operation code: A = 3 / 2-x, 1 / 2+y, 1 / 2-z; B = 2-x, 1-y, 1-z; C = 3 / 2-x, -1 / 2+y, 1 / 2-z; D = 1-x, -y, 1-z); O2, O3, N2, and Pb1 are almost located on the same plane.

[0053] like Figure 3It can be seen that due to the presence of more O and N atoms in the complex and a large number of water molecules in the complex structure, its hydrogen bond content is rich, and adjacent two-dimensional layers are connected to each other through hydrogen bond interactions, forming a stable three-dimensional supramolecular structure.

[0054] Example 3 Complex [Pb(pzca)·2H2O] n IR infrared spectrum analysis

[0055] The complex [Pb(pzca)·2H2O] was detected by Fourier transform infrared spectrometer n , KBr was used to press the tablet and its infrared spectrum was measured.

[0056] like Figure 4 As shown, 1500-1600cm -1 is the peak on carbonyl oxygen, which is the absorption of carbonyl; 1450cm -1 Some peaks at 700-830cm are stretching vibrations of NN. Due to hydrogen bonding, the absorption peak of -OH migrates to the low frequency region, and the peak intensity becomes broader. -1 The absorption peak inside should be caused by the vibration of CH on the pyrazole five-membered ring. Therefore, it can be seen that Example 1 successfully prepared [Pb(pzca)·2H2O] by hydrothermal method. n At the same time, by comparing the synthesized complexes, it can be found that there are deviations in the positions of some peaks in the spectrum, which is due to the influence of the coordination bonds produced by the organic ligands and transition metal ions.

[0057] Example 4 Complex [Pb(pzca)·2H2O] n Thermogravimetric analysis

[0058] In order to explore the complex [Pb(pzca)·2H2O] n The thermal stability of the complex [Pb(pzca)·2H2O] was determined by thermogravimetric analysis in a nitrogen atmosphere at a heating rate of 10°C / min in the temperature range of 30-900°C. n The TG curve is as follows Figure 5 As shown:

[0059] Depend on Figure 5 It can be seen that the thermogravimetric image clearly shows three weight loss stages. Complex [Pb(pzca)·2H2O] n The weight loss was 2.89% in the temperature range of 34–94°C, and the disappearance was mainly due to free water molecules and attached small molecules. Complex [Pb(pzca)·2H2O] nIt can remain stable in the range of 94-270℃, and then the temperature gradually increases in the range of 270℃-430℃, thus exceeding [Pb(pzca)·2H2O] n The maximum temperature that can be tolerated causes the structure of the complex to slowly collapse, and the random material will decompose, and further lose weight by 20.31% in the temperature range of 270-430℃; finally, after 430℃, the mass of the complex continues to decrease and the skeleton gradually decomposes. Figure 5 From the TG diagram, we can see that [Pb(pzca)·2H2O] n The maximum thermal stability temperature is 270℃. At the same time, its thermal stability range is relatively narrow. Finally, it is inferred that PbO is stable after 900℃.

[0060] Example 5 Complex [Pb(pzca)·2H2O] n XRD analysis

[0061] In order to verify the purity of the complex, powder X-ray diffraction (PXRD) was carried out at room temperature with a step size of 0.02°, a scanning speed of 20° / min, and a 2θ angle range of 5°-50°.

[0062] like Figure 6 As shown, the comparison complex [Pb(pzca)·2H2O] n The experimental XRD spectrum (black spectrum) and the single crystal structure XRD spectrum (red spectrum) simulated by computer show that the diffraction peaks at 8.757°, 17.579°, 18.983°, 27.321°, 34.138°, and 38.772° are similar in height, indicating that the synthesized polycrystalline product is a single pure phase with very little impurity content. The difference in the intensity of individual diffraction peaks and the peak shift may be due to the preferred orientation effect of the crystal during the measurement. It can be seen that [Pb(pzca)·2H2O] n The XRD patterns of the synthesized crystals match the simulated single crystal data, proving that the synthesized crystals have a high phase purity.

[0063] Example 6 Complex [Pb(pzca)·2H2O] n Photoluminescence analysis

[0064] For free ligand H2pzca and [Pb(pzca)·2H2O] n The complex was subjected to fluorescence analysis, where H2pzca was excited at 298 nm, [Pb(pzca)·2H2O] n The complexes were excited at 372 nm, and their solid-state fluorescence emission spectra were recorded at room temperature.

[0065] like Figure 7As shown, H2pzca ligand and [Pb(pzca)·2H2O] n The complexes all exhibited photoluminescence properties. Among them, the luminescence spectrum of H2pzca showed that under 298nm excitation, the maximum emission peak of the ligand was 327nm, which may be due to the electron migration of the semi-rigid ligand π–π*; [Pb(pzca)·2H2O] n The maximum emission wavelength of the complex under 372nm excitation is 407nm. Compared with the ligand, the maximum emission peak of the complex has an obvious red shift of 80nm, which may be due to the increase of hydrogen bonding and rigidity of the ligand after coordination with Pb(II) ions.

[0066] Example 7 Complex [Pb(pzca)·2H2O] n Electrochemiluminescence analysis

[0067] Complex [Pb(pzca)·2H2O] n The electrochemiluminescence analysis was carried out in a standard three-electrode system, in which the reference electrode was an Ag / AgCl electrode, the Pt wire electrode was an auxiliary electrode, the glassy carbon electrode was a working electrode, and the co-reactant was 0.1 mol / L K2S2O8.

[0068] Depend on Figure 8 It can be seen that for the complex [Pb(pzca)·2H2O] n The luminescence intensity at the 10th, 50th, 80th, 110th, 140th, 180th, and 210th seconds was about 124, 147, 146, 146, 146, 148, and 148 a.u., respectively. After multiple cycles, the luminescence intensity remained relatively stable. Experiments show that the coordination of metal ions Pb and organic ligands H2pzca can enhance the spin-orbit coupling effect and electrochemiluminescence (ECL) emission, and has high stability. Therefore, it can provide an important theoretical basis for the design of new coordination polymer luminescent materials.

[0069] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0070] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex, characterized in that: The smallest asymmetric unit of the complex contains a Pb(II) ion, a doubly deprotonated H2pzca ligand ion and two free water molecules to form a [Pb(CH3COO)2] basic unit; the structural formula of the smallest asymmetric unit is shown in formula (I):

2. A 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 1, characterized in that: The complex crystallizes in monoclinic system, β=103.464(4)°, P21 / n space group.

3. A method for synthesizing the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 1 or 2, characterized in that: The following steps are involved: (1) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid: After mixing anhydrous ethanol and 3-pyrazolecarboxylic acid, concentrated sulfuric acid was added dropwise at 80°C and stirred for 2 hours to obtain 1-H-pyrazole-3-carboxylic acid ethyl ester; Add 1-H-pyrazole-3-carboxylate and ethyl bromoacetate to anhydrous acetone, stir at 60°C, and monitor the reaction by thin layer chromatography. When 1-H-pyrazole-3-carboxylate is consumed, concentrate the yellow-brown reaction mixture to dryness and purify to obtain 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid; (2) Synthesis of 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex: 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid, 95 v / v% ethanol and distilled water were mixed and placed in a reaction kettle. The mixture was magnetically stirred for 10 min, and potassium hydroxide and lead acetate trihydrate were added in sequence. The mixture was magnetically stirred for 5 min at room temperature, and then hydrothermally reacted at 120° C. for 2 d. After the mixture was naturally cooled to room temperature, it was filtered and dried to obtain 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex as white crystals.

4. The method for synthesizing a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 3, characterized in that: The usage ratio of anhydrous ethanol, 3-pyrazolecarboxylic acid and concentrated sulfuric acid is 50mL:10mmol:2mL.

5. The method for synthesizing a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 3, characterized in that: The usage ratio of anhydrous acetone, 1-H-pyrazole-3-carboxylate and ethyl bromoacetate is 30 mL:5 mmol:0.6 mmol.

6. The method for synthesizing a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 3, characterized in that: The purification method is: the crude product is purified by column chromatography on silica gel using petroleum ether / ethyl acetate (1 / 1) as an eluent to obtain a white product 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid.

7. The method for synthesizing a 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to claim 3, characterized in that: The usage ratio of the 1-carboxy-1-H-pyrazole-3-carboxylic acid, 95 v / v% ethanol, distilled water, potassium hydroxide, and lead acetate trihydrate is 0.1 mmol:10 mL:5 mL:0.2 mmol:0.2 mmol.

8. Use of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex according to any one of claims 1, 2, 4-7 in luminescent materials.

9. The use according to claim 8, characterized in that: The invention relates to application of the 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex in photoluminescent materials.

10. The use according to claim 8, characterized in that: The 1-carboxymethyl-1-H-pyrazole-3-carboxylic acid Pb complex is used in electroluminescent materials. Under the conditions of a standard three-electrode system and 0.1 mol / L K2S2O8, the luminescence intensity of the complex is about 124-148 a.u. at 20-210 s.

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