Zinc complex and preparation method thereof

Abstract

The invention relates to the technical field of complexes, in particular to a zinc complex and a preparation method thereof, the molecular formula of the complex is Zn3 (Hbsa) 6 (4-pp) 6, Hbsa is 5-bromosalicylic acid anion, and 4-pp is 4-phenylpyridine neutral molecule; a basic structural unit of the complex is composed of three Zn (II) ions, six 5-bromosalicylic acid anions and six 4-phenylpyridine neutral molecules; the complex belongs to a monoclinic system, the space group is I2 / a, and the cell parameters of the complex are as follows: # imgabs0 # and # imgabs1 #, alpha is 90 degrees, beta is 96.393 (6) degrees, and gamma is 90 degrees; the preparation method comprises the following steps: dissolving 5-bromosalicylic acid, 4-phenylpyridine and zinc nitrate hexahydrate in a solvent to obtain a mixed solution, putting the obtained mixed solution in a reaction kettle, dropwise adding 3 drops of triethylamine, reacting under a heating condition, cooling, filtering and washing to obtain the 5-bromosalicylic acid-zinc nitrate compound. The complex has strong fluorescence emission at 430 nm under the excitation wavelength of 328 nm, which indicates that the complex has excellent fluorescence property and is a potential fluorescence detection material.

Description

Technical Field

[0001] The present invention relates to the technical field of complexes, and in particular to a zinc complex and a preparation method thereof. Background Art

[0002] Metal complexes are formed by the metal center ion and the organic ligand molecule in the form of coordination bonds. Researchers have been continuously exploring the study of complexes and are committed to developing and improving synthesis methods to obtain new complex materials with specific structures and properties. Using innovative organic ligands, metal ions and synthesis methods, researchers have successfully developed a series of complex materials with unique structures and properties.

[0003] Aromatic carboxylic acid compounds contain carboxyl groups with strong coordination ability. Depending on the number and position of carboxyl groups, transition metal complexes with different spatial structures can be constructed. Organic carboxylic acid ligands with diverse structures can react with many metal ions to form complexes with different structures and special properties. In recent years, aromatic acid complexes of zinc have been widely used in the field of luminescent materials, but there are still many problems and challenges, and further research on aromatic acid complexes of zinc is still needed. There are currently no reports on the construction of zinc complexes using 5-bromosalicylic acid (H2bsal) and 4-phenylpyridine (4-pp) as ligands. Summary of the invention

[0004] The object of the present invention is to provide a zinc complex constructed with 5-bromosalicylic acid and 4-phenylpyridine as ligands and a preparation method thereof in view of the above-mentioned problems.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A zinc complex, wherein the molecular formula of the complex is Zn3(Hbsal)6(4-pp)6, wherein Hbsal is a 5-bromosalicylic acid anion, and 4-pp is a 4-phenylpyridine neutral molecule; the basic structural unit of the complex consists of three Zn(II) ions, six 5-bromosalicylic acid anions and six 4-phenylpyridine neutral molecules; the complex belongs to the monoclinic system, the space group is I2 / a, and the unit cell parameters are: α=90°, β=96.393(6)°, γ=90°.

[0007] The present invention also provides a method for preparing the zinc complex, comprising the following steps:

[0008] Take 5-bromosalicylic acid, 4-phenylpyridine and zinc nitrate hexahydrate and dissolve them in a solvent to obtain a mixed solution, put the obtained mixed solution in a reaction kettle, add 3 to 5 drops of triethylamine, react under heating conditions, cool down, filter, wash, and obtain the product.

[0009] In the above preparation method, the molar ratio of 5-bromosalicylic acid, 4-phenylpyridine and zinc nitrate hexahydrate is 2:2:1.

[0010] In the above preparation method, the solvent is a mixture of distilled water and ethanol in a volume ratio of 5:3.

[0011] In the above preparation method, the reaction under heating conditions refers to a constant temperature reaction at 140° C. for three days.

[0012] In the above preparation method, the specific condition of the constant temperature reaction is constant temperature reaction in a hot air drying oven.

[0013] In the above preparation method, the reactor is a reactor with a polytetrafluoroethylene liner.

[0014] The zinc complex prepared by the present invention can be used as a fluorescent material in fluorescence detection.

[0015] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0016] 1. The present invention synthesized a novel complex Zn3(Hbsal)6(4-pp)6 by a solvothermal method, and determined its crystal structure by an X-ray single crystal diffractometer. The complex belongs to the monoclinic system, the space group is I2 / a, and the unit cell parameters are: α=90°, β=96.393(6)°, γ=90°. The complex exhibits strong fluorescence emission at 430nm under an excitation wavelength of 328nm, indicating that the complex has excellent fluorescence properties and is a potential fluorescence detection material.

[0017] 2. The zinc complex prepared by the present invention exhibits strong fluorescence when dissolved in water. The test results show that the zinc complex prepared by the present invention has specificity for the detection of CRO in aqueous solution. At the same time, in order to detect the fluorescence anti-interference ability of the complex to CRO, the test was carried out under the condition of coexistence of CRO and other antibiotics. The test results show that under the condition of coexistence of other antibiotics, the complex still has specific selectivity for CRO, and can achieve a quenching effect on the fluorescence intensity of the solution without interference from other antibiotics. In addition, the reusability test shows that the fluorescence intensity of the complex can be fully restored after immersion, and the fluorescence luminescence intensity remains basically unchanged after 4 cycles, indicating that the complex can be used as a fluorescent sensor for detecting CRO and has good recyclability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 4 is a basic structural unit diagram of the zinc complex prepared by the present invention.

[0019] Figure 2 It is a one-dimensional chain diagram of the zinc complex prepared by the present invention.

[0020] Figure 3 The three-dimensional framework structure diagram of the zinc complex prepared by the present invention.

[0021] Figure 4 The present invention provides a solid-state luminescence spectrum of the zinc complex prepared by the present invention and the ligand used.

[0022] Figure 5 The fluorescence intensity of the zinc complex prepared by the present invention in different solvents.

[0023] Figure 6 In the figure, (a) is the fluorescence intensity of the zinc complex prepared by the present invention in different antibiotics; (b) is the fluorescence graph of the zinc complex prepared by the present invention in the presence of different concentrations of CRO.

[0024] Figure 7 is the linear fitting curve of CRO and I0 / I concentration.

[0025] Figure 8 In the figure, (a) is the fluorescence spectrum of the zinc complex prepared by the present invention in the presence of different antibiotics at the same concentration; (b) is the cycle diagram of the zinc complex prepared by the present invention detecting CRO.

[0026] Fig. 9 The figure is the PXRD pattern of the zinc complex prepared by the present invention after fluorescence detection.

[0027] Fig.10 The UV-visible spectra of various antibiotics and the emission spectrum of the zinc complex prepared by the present invention. DETAILED DESCRIPTION

[0028] In order to express the present invention more clearly, the present invention is further described below through specific examples.

[0029] Example 1

[0030] This embodiment prepares a zinc complex, and the specific preparation steps are as follows:

[0031] 5-bromosalicylic acid (0.3 mmol, 0.0651 g), 4-phenylpyridine (0.3 mmol, 0.0465 g) and zinc nitrate hexahydrate (0.15 mmol, 0.0445 g) were weighed respectively, placed in a 50 mL beaker, 10 mL of distilled water and 6 mL of ethanol were added, and then stirred with a magnetic stirrer at room temperature until completely dissolved to obtain a mixed solution; the mixed solution was transferred to a reactor equipped with a polytetrafluoroethylene liner, 3 drops of triethylamine were added dropwise, and then the closed reactor was placed in a hot air drying oven at 140° C. for constant temperature reaction for three days. After the reaction was completed, the temperature was gradually lowered to room temperature, the reactor was opened for filtration and washed several times to obtain white needle-shaped crystals, i.e., the zinc complex.

[0032] Example 2

[0033] In this example, the crystal structure of the zinc complex obtained in Example 1 (hereinafter referred to as the zinc complex) was tested by X-ray single crystal diffractometer. The crystal structure of the complex Zn3(Hbsal)6(4-pp)6 is shown in the attached figure. Figure 1-3 The crystal diffraction results show that the complex belongs to the monoclinic system, the space group is I2 / a, and its unit cell parameters are: α=90°, β=96.393(6)°, γ=90°.

[0034] Depend on Figure 1 It can be seen that the basic structural unit of the zinc complex consists of three Zn(Ⅱ) ions, six Hbsal - anion and six 4-pp neutral molecules. Each zinc ion Zn1, Zn2 and Zn3 is respectively connected with two Hbsal - The oxygen atoms (O1, O4), (O7, O7A) and (O10, O10A) of the two 4-pp molecules and the nitrogen atoms (N1, N2), (N3, N3A) and (N4, N4A) of the two 4-pp molecules form coordination bonds.

[0035] like Figure 2 As shown, the metal central ion Zn(Ⅱ) is four-coordinated, and the four surrounding atoms form an irregular trigonal pyramid configuration.

[0036] In addition, if Figure 3 As shown, the molecules of the zinc complex interact with each other through hydrogen bonds (such as O3-H3...O2 and O6-H6...O5, etc.) to form a three-dimensional stacking structure.

[0037] Example 3

[0038] In this example, the two ligands used in Example 1 and the zinc complexes constructed therefrom were subjected to solid-state fluorescence testing. The test results are shown in FIG. Figure 4 shown.

[0039] Due to the π-π * The ligand 5-bromosalicylic acid (H2bsal) has fluorescence emission at 445nm under the excitation wavelength of 331nm; the ligand 4-phenylpyridine (4-pp) has fluorescence emission at 524nm under the excitation wavelength of 263nm; the zinc complex Zn3(Hbsal)6(4-pp)6 has a more obvious fluorescence emission peak at 430nm under the excitation wavelength of 328nm. Compared with the ligands H2bsal and 4-pp, due to the Zn 2+ After the metal central ion coordinates with H2bsal, the rigidity of the H2bsal molecular structure changes, resulting in a red shift in the fluorescence emission peak of the zinc complex, indicating that the zinc complex has excellent fluorescence properties and is a potential fluorescence detection material.

[0040] Example 4

[0041] This example tests the solvent selectivity of the zinc complex.

[0042] Some common solvents were selected, namely water (H2O), acetonitrile (CH3CN), methanol (CH3OH), ethanol (EtOH), dichloromethane (CH2Cl2), chloroform (CHCl3), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and acetone (ACETONE). The fine powder sample (2 mg) of the zinc complex was dispersed in 5 mL of different solvents and ultrasonically treated for 30 min until a stable suspension was formed, and then the fluorescence intensity was tested. The results are shown in Figure 2. Figure 5 shown.

[0043] Depend on Figure 5 It can be seen that when the zinc complex is dissolved in water, its fluorescence intensity is the strongest, followed by acetonitrile and ethanol. On the contrary, when chloroform is used as a solvent, the fluorescence intensity is significantly weakened, showing a strong fluorescence quenching effect. Therefore, it was decided to carry out the detection of antibiotics in an aqueous solution environment.

[0044] Example 5

[0045] This example tests the performance of zinc complexes on antibiotics.

[0046] At room temperature, a series of 3 × 10 -3mol / L antibiotic solution was tested, and the antibiotics used included 7-aminocephalosporin (7-AP), erythromycin (ERY), ampicillin (AMP), penicillin potassium (PEN), metronidazole (MTR), ofloxacin (OLA), omeprazole (PPI), cefazolin sodium (CSS), gentamicin (GEN), cephalexin (LEX), fudaxin (CAG) and ceftriaxone sodium (CRO). Each antibiotic aqueous solution (20 μL) was mixed with a well-dispersed zinc complex suspension to obtain a zinc complex antibiotic mixture, which was then subjected to fluorescence detection. The results are shown in FIG. Figure 6 shown.

[0047] Figure 6 .(a) shows that CRO has a higher quenching efficiency towards zinc complexes compared with other antibiotics, indicating that zinc complexes are specific for the detection of CRO in aqueous solution.

[0048] Then, the fluorescence titration method was used to test the change of the fluorescence of the zinc complex with the concentration of CRO, such as Figure 6 As shown in (b), with the increase of CRO concentration, its fluorescence intensity shows a significant downward trend. The relationship between fluorescence intensity and CRO concentration is close to the Stern–Volmer equation, and the quenching constant K is obtained after fitting. SV Value 3.63×10 5 M -1 (R 2 =0.9769), the detection limit of the complex for CRO was calculated to be 2.315×10 -6 M(such as Figure 7 shown).

[0049] At the same time, in order to detect the anti-interference ability of zinc complexes on CRO fluorescence, tests were carried out under the condition of coexistence of CRO and other antibiotics. The test results show that in the condition of coexistence of other antibiotics, zinc complexes still have specific selectivity for CRO and can achieve quenching effect on the fluorescence intensity of the solution without interference from other antibiotics, such as Figure 8 As shown in (a), the fluorescence quenching of the zinc complex by CRO is almost unaffected by other antibiotics.

[0050] In addition, in order to evaluate the reusability of the zinc complex, it was added to the CRO solution and the fluorescence intensity was detected. Figure 8 As shown in (b), the fluorescence intensity of the zinc complex can be completely restored after immersion, and the fluorescence intensity remains basically unchanged after 4 cycles. This shows that the zinc complex can be used as a fluorescent sensor for detecting CRO and has good recyclability.

[0051] Example 6

[0052] This example analyzes the fluorescence quenching mechanism of the zinc complex.

[0053] Fluorescence quenching in complexes is usually caused by the following factors: (1) structural destruction of the complex; (2) charge migration between ions and the complex; (3) fluorescence resonance energy transfer between ions and the complex.

[0054] The zinc complex detected by fluorescence was collected, filtered, washed and dried. Then it was analyzed by PXRD (see Fig. 9 ), the results showed that the PXRD spectrum of the zinc complex after fluorescence testing was highly similar to the diffraction peak of the single crystal model, which proved that the fluorescence quenching of the solution was not caused by the destruction of the coordination framework. In other words, the fluorescence quenching after adding the antibiotic (CRO) may be due to resonance energy transfer or photoinduced electron transfer. If the absorption band of the analyte effectively overlaps with the emission band of the complex, the resonance energy is transferred from the complex to the analyte, resulting in fluorescence quenching. Fig.10 The emission spectrum of the zinc complex overlaps with the UV-visible absorption spectrum of CRO, indicating that the quenching mechanism of the zinc complex prepared by the present invention on CRO can be attributed to resonance energy transfer.

[0055] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A zinc complex, characterized in that The molecular formula of the complex is Zn3(Hbsal)6(4-pp)6, wherein Hbsal is a 5-bromosalicylic acid anion and 4-pp is a 4-phenylpyridine neutral molecule; the basic structural unit of the complex consists of three Zn(II) ions, six 5-bromosalicylic acid anions and six 4-phenylpyridine neutral molecules; the complex belongs to the monoclinic system, the space group is I2 / a, and the unit cell parameters are: α=90°, β=96.393(6)°, γ=90°.

2. The method for preparing a zinc complex according to claim 1, characterized in that: The following steps are involved: Take 5-bromosalicylic acid, 4-phenylpyridine and zinc nitrate hexahydrate and dissolve them in a solvent to obtain a mixed solution, put the obtained mixed solution in a reaction kettle, add 3 to 5 drops of triethylamine, react under heating conditions, cool down, filter, wash, and obtain the product.

3. The preparation method according to claim 2, characterized in that: The molar ratio of 5-bromosalicylic acid, 4-phenylpyridine and zinc nitrate hexahydrate is 2:2:

1.

4. The preparation method according to claim 2, characterized in that: The solvent is a mixture of distilled water and ethanol in a volume ratio of 5:

3.

5. The preparation method according to claim 2, characterized in that: The reaction under heating conditions refers to a constant temperature reaction at 140° C. for three days.

6. The preparation method according to claim 5, characterized in that: The specific condition of the constant temperature reaction is constant temperature reaction in a hot air drying oven.

7. The preparation method according to claim 2, characterized in that: The reactor is a reactor with a polytetrafluoroethylene liner.

8. Use of the zinc complex according to claim 1 in fluorescence detection.

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