A binuclear zinc coordination polymer, its preparation method and application

Abstract

The present invention belongs to the field of zinc coordination polymers, and specifically relates to a binuclear zinc coordination polymer and its preparation method and application. The molecular formula of the coordination polymer is: {[Zn2(L)(phen)2(H2O)]·H2O} n , where L 4‑ is the deprotonated product of 1,4-bis(3,5-dicarboxyphenoxy)benzene, phen is 1,10-phenanthroline, and n represents the degree of polymerization; the structural formula is: #imgabs0# This coordination polymer is prepared by adding Zn(NO3)2·6H2O, 1,4-bis(3,5-dicarboxyphenoxy)benzene, and 1,10-phenanthroline into a mixed solvent of distilled water and acetonitrile and carrying out a hydrothermal reaction. This coordination polymer has a good fluorescence recognition effect on Cu 2+ and can be used as a fluorescence sensor for efficiently detecting Cu 2+ in aqueous solution, with a detection limit of 1.22×10 ‑8 M.

Description

Technical Field

[0001] The present invention belongs to the field of zinc coordination polymers, and particularly relates to a binuclear zinc coordination polymer, a preparation method thereof, and an application thereof. Background Art

[0002] Transition metal ions play important roles in many biological systems and ecological environments. Among them, copper is a very important metal element, which plays an important role in the normal functions of organs and the life metabolism process at low concentrations. However, when there is an excessive amount of copper ions in the body, it will lead to serious diseases, including Wilson's disease, coronary heart disease, hypertension, arteriosclerosis, etc. Therefore, the analysis and detection of copper ions in the environment have attracted much attention in recent years.

[0003] Currently, the commonly used detection methods include gas chromatography, high performance liquid chromatography, spectrophotometry, mass spectrometry, etc. Although these methods have high determination accuracy, the sample pretreatment is complex, the detection time is long, and the equipment is expensive, which limits their applications. As a fluorescent probe, coordination polymer has many advantages such as simple operation method, good stability, fast response speed, high sensitivity, low cost, etc. Therefore, it is of great significance to design and synthesize a fluorescent probe for the rapid detection of transition metal copper ions. Summary of the Invention

[0004] The object of the present invention is precisely aimed at the above technical status quo, and provides a binuclear zinc coordination polymer, a preparation method thereof, and the application of this coordination polymer as a fluorescent probe for detecting Cu 2+ in water.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] In the first aspect, the present invention provides a binuclear zinc coordination polymer, and its molecular simple formula is: {[Zn2(L)(phen)2(H2O)]·H2O} n , where L 4- is the deprotonated product of 1,4-bis(3,5-dicarboxyphenoxy)benzene, phen is 1,10-phenanthroline, and n represents the degree of polymerization; its structural formula is:

[0007]

[0008] wherein represents the coordination bond outside the asymmetric unit;

[0009] The crystal of this coordination polymer belongs to the monoclinic system, space group C2 / c, and the unit cell parameters are: α = 90.00°, β = 111.216(17)°, γ = 90.00°. In this coordination polymer, zinc ions adopt a pentacoordination mode, where Zn1 coordinates with three carboxylate oxygen atoms from three L 4- ligands and two nitrogen atoms from one 1,10-phenanthroline; Zn2 coordinates with two carboxylate oxygen atoms from two L 4- ligands, two nitrogen atoms from one 1,10-phenanthroline and one oxygen atom from one water molecule; this coordination polymer is a one-dimensional structure, and the bond lengths of Zn—O and Zn—N are in the ranges of and respectively. X-ray powder diffraction confirms that the crystal samples are homogeneous and stable.

[0010] Second, the present invention provides a preparation method of the binuclear zinc coordination polymer described in the first aspect, including the following steps: adding Zn(NO3)2·6H2O, 1,4-bis(3,5-dicarboxyphenoxy)benzene and 1,10-phenanthroline into a mixed solvent of distilled water and acetonitrile, adjusting the pH of the mixed system with dilute nitric acid, and obtaining the binuclear zinc coordination polymer through hydrothermal reaction.

[0011] Furthermore, the molar ratio of Zn(NO3)2·6H2O, 1,4-bis(3,5-dicarboxyphenoxy)benzene and 1,10-phenanthroline is 1:1:1.

[0012] Furthermore, the volume ratio of distilled water to acetonitrile is 2:1.

[0013] Furthermore, the temperature of the hydrothermal reaction is 160 °C and the time is 72 h.

[0014] Furthermore, the pH of the mixed system is 5.5 - 6.

[0015] Third, the present invention provides the application of the binuclear zinc coordination polymer described in the first aspect as a fluorescent probe for detecting Cu 2+ in water.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The binuclear zinc coordination polymer provided by the present invention is synthesized under hydrothermal conditions, with a simple preparation process, high yield and purity. Thermogravimetric analysis shows that the structure of this coordination polymer decomposes above 441 °C, and the practical temperature range is below 441 °C.

[0018] The binuclear zinc coordination polymer provided by the present invention has good stability in aqueous solution. It can detect Cu 2+ in the aqueous phase through specific fluorescence quenching, and the detection limit is 1.22×10 -8 M. Brief Description of the Drawings

[0019] Figure 1 This is the crystal structure diagram of the binuclear zinc coordination polymer of the present invention (solvent water molecules are omitted, ellipsoidity is 30%, where the symmetry codes: (i) -x, -y, -z + 1; (ii) -x, y, -z + 1 / 2; (iii) x, -y, z + 1 / 2).

[0020] Figure 2 This is the X-ray powder diffraction pattern (experimental and simulated) of the binuclear zinc coordination polymer of the present invention at 298K.

[0021] Figure 3 This is the thermogravimetric analysis diagram of the binuclear zinc coordination polymer of the present invention.

[0022] Figure 4 This is the fluorescence spectrum diagram of the binuclear zinc coordination polymer of the present invention at 298K.

[0023] Figure 5 This is the bar chart of fluorescence intensity when various different metal cations are added to the water suspension of the binuclear zinc coordination polymer of the present invention.

[0024] Figure 6 This is for the binuclear zinc coordination polymer of the present invention in the water suspension with the addition of different concentrations of Cu 2+ The fluorescence spectrum diagram (a) and fluorescence linear calibration curve (b).

[0025] Figure 7 This is when other metal cations are present, the bar chart of fluorescence intensity after adding Cu 2+ to the water suspension of the binuclear zinc coordination polymer of the present invention. Detailed Embodiments

[0026] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Example 1

[0028] Preparation of the Binuclear Zinc Coordination Polymer in Example 1

[0029] 0.1 mmol of Zn(NO3)2·6H2O, 0.1 mmol of H4L (H4L is 1,4-bis(3,5-dicarboxyphenoxy)benzene), and 0.1 mmol of 1,10-phenanthroline were added to 6 mL of distilled water and 3 mL of acetonitrile. Then, 0.05 mL of 1 M HNO3 solution was added. After stirring at room temperature for 30 min, the mixture was placed in a reaction kettle and reacted at 160 °C for 72 h. It was naturally cooled to room temperature to obtain a large amount of colorless strip crystals, and the yield was about 68.7%. Elemental analysis (%) : theoretical value (calculated according to the molecular formula C 46 H 30 Zn2N4O 12 ) : C 57.46, H 3.15, N 5.83; measured value: C 57.14, H 3.28, N 5.89.

[0030] Example 2 Structure determination of the binuclear zinc coordination polymer

[0031] Single crystal X-ray diffraction data were collected on a Bruker Apex II diffractometer, with graphite monochromator Mo-Kα as the radiation source The crystal was tested at room temperature. The cell parameters were determined using SMART software, and absorption correction was carried out through the SADABS program. The structure was solved using the SHELXS-97 program and refined by full-matrix least squares based on F 2 For the structure refinement, C and O atoms were theoretically hydrogenated and fixed on the parent atoms. The detailed crystal determination data are shown in Table 1, and the crystal structure is shown in Figure 1 .

[0032] Table 1 Crystallographic data of the coordination polymer

[0033]

[0034]

[0035] Example 3 Analysis of the phase by powder diffraction method

[0036] Using a D8 type tester from Bruker Company, Germany, the test conditions were: the radiation source was Cu-Kα, the scanning rate was 2° / min, and the scanning range was 5 - 50°.

[0037] The X-ray powder diffraction results showed that the measured values of the polycrystalline sample and the simulated values of the single crystal structure were almost identical, indicating that the phase of the zinc coordination polymer crystal sample of the present invention was uniform, as shown in Figure 2 .

[0038] Example 4 Thermogravimetric analysis of the binuclear zinc coordination polymer of the present invention

[0039] Thermogravimetric analysis was carried out on a Dupont thermogravimeter at a heating rate of 10 °C / min under nitrogen protection, and the temperature range of the test was 25 - 800 °C. The results are as Figure 3 shown. The coordination polymer loses two free water molecules in the range of 142 - 441 °C (the theoretical value and the experimental value are 3.75% and 3.28% respectively). When the temperature is higher than 441 °C, the main structure begins to decompose and collapse. This indicates that the framework structure of the coordination polymer has good thermal stability below 441 °C.

[0040] Example 5 Fluorescence spectrum of the binuclear zinc coordination polymer of the present invention at 298K

[0041] The luminescence properties of the sample were tested using a Spectrofluorometer FS5 fluorescence spectrometer.

[0042] The fluorescence emission spectrum of the coordination polymer aqueous suspension was measured at room temperature. The results show that the fluorescence intensity of the binuclear zinc coordination polymer of the present invention is stable in aqueous solution, with an excitation wavelength of 269 nm and emission wavelengths of 365 and 382 nm ( Figure 4 ).

[0043] Example 6 Selective recognition of Cu 2+ by the binuclear zinc coordination polymer aqueous suspension of the present invention

[0044] 5 mg of the zinc coordination polymer was dissolved in 50 mL of distilled water. After standing for three days, the upper suspension was taken for fluorescence detection experiments. 200 μL (1×10 -4 M) of different metal cation (M n+ ) solutions (M n+ = Na + , K + , Mn 2+ , Ca 2+ , Ba 2+ , Co 2+ , Ni 2+ , Fe 2+ , Fe 3+ , Cu 2+ , Zn 2+ , Cd 2+ , Ag + , Cr 3+ ) were added to 2 mL of the zinc coordination polymer aqueous suspension and their fluorescence intensities were detected. It can be seen from Figure 5 that the addition of other metal cations will cause the fluorescence intensity of the zinc coordination polymer to decrease to varying degrees, but only when Cu 2+ is added, the fluorescence of the zinc coordination polymer is completely quenched, indicating that the zinc coordination polymer has fluorescence selectivity for Cu 2+ .

[0045] Example 7 Detection of Cu by the aqueous suspension of the binuclear zinc coordination polymer of the present invention 2+ sensitivity

[0046] To 2 mL of the above-mentioned aqueous suspension of zinc coordination polymer, Cu 2+ solution was added dropwise and its fluorescence intensity was detected. The experimental results are as Figure 6 shown in a. As Cu 2+ was continuously added, the fluorescence of the zinc coordination polymer gradually weakened. When the concentration of Cu 2+ was 5 μM, the fluorescence intensity of the zinc coordination polymer was completely quenched. At low concentrations, the Cu 2+ ion concentration showed a good linear relationship with I0 / I. The detection limit was calculated by the method of LOD = 3σ / K, where σ is the standard deviation of measuring five blank samples, and K is the slope of the linear curve plotted at lower concentrations. The calculated detection limit LOD = 1.22×10 -8 M ( Figure 6 b).

[0047] Example 8 Anti-interference experiment of the aqueous suspension of the binuclear zinc coordination polymer of the present invention for detecting Cu 2+ anti-interference experiment

[0048] To 2 mL of the above-mentioned zinc coordination polymer suspension, 100 μL (1×10 -4 M) of metal cation interference reagents (Na + , K + , Mn 2+ , Ca 2+ , Ba 2+ , Co 2+ , Ni 2+ , Fe 2+ , Fe 3+ , Zn 2+ , Cd 2+ , Ag + , Cr 3+ ) were added respectively and their fluorescence intensities were detected. Then 100 μL (1×10 -4 M) of Cu 2+ ions were added and their fluorescence intensities were detected. The experimental results are as Figure 7 shown. After adding other cations and then adding Cu 2+ ions, the fluorescence of the zinc coordination polymer was quenched, indicating that the presence of other cations did not affect the detection of Cu 2+ by this coordination polymer.

[0049] The above-described embodiments merely represent specific examples of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A binuclear zinc coordination polymer, characterized in that, Its molecular formula is: {[Zn2(L)(phen)2(H2O)]·H2O} n , where L 4- is the deprotonated product of 1,4-bis(3,5-dicarboxyphenoxy)benzene, phen is 1,10-phenanthroline, and n represents the degree of polymerization; its structural formula is: Among them represents the coordination bond outside the asymmetric unit; The crystal of this coordination polymer belongs to the monoclinic system, space group C2 / c, and the unit cell parameters are as follows: α = 90.00°, β = 111.216(17)°, γ = 90.00°.

2. The preparation method of the binuclear zinc coordination polymer according to claim 1, characterized in that, It includes the following steps: adding Zn(NO3)2·6H2O, 1,4-bis(3,5-dicarboxyphenoxy)benzene and 1,10-phenanthroline into a mixed solvent of distilled water and acetonitrile, adjusting the pH of the mixed system with dilute nitric acid, and obtaining the binuclear zinc coordination polymer through hydrothermal reaction.

3. The preparation method of a binuclear zinc coordination polymer according to claim 2, wherein, The molar ratio of the Zn(NO3)2·6H2O, 1,4-bis(3,5-dicarboxyphenoxy)benzene and 1,10-phenanthroline is 1:1:

1.

4. The preparation method of a binuclear zinc coordination polymer according to claim 2, wherein, The volume ratio of the distilled water to the acetonitrile is 2:

1.

5. The preparation method of a binuclear zinc coordination polymer according to claim 2, characterized in that, The temperature of the hydrothermal reaction is 160 °C and the time is 72 h.

6. The preparation method of a binuclear zinc coordination polymer according to claim 2, characterized in that, The pH of the mixed system is 5.5 - 6.

7. Use of the binuclear zinc coordination polymer according to claim 1 as a fluorescent probe for detecting Cu in water 2+ .

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