CN106832315B - A kind of two-dimentional lead coordination polymer with fluorescence property and preparation method thereof - Google Patents

Abstract

The invention discloses a two-dimensional lead coordination polymer with fluorescent properties and a preparation method thereof. The molecular formula of the coordination polymer is C ₁₀ H ₈ O ₄ Pb, the structural unit belongs to the monoclinic crystal system, and the space group is P21/c , the unit cell parameters are: a=8.6232(6)Å, b=13.2129(9)Å, c=8.6432(3)Å, α=γ=90°, β=90.001(1)°, through the bridge of the ligand The complex grows into a polymer with a two-dimensional layered framework structure in the 001 crystal direction. The preparation method of the invention has mild reaction conditions, simple preparation process and low cost, and the prepared coordination polymer not only has strong fluorescence performance, but also has good thermal stability.

Description

A two-dimensional lead coordination polymer with fluorescent properties and its preparation method

technical field

The invention relates to the technical field of synthesis of metal organic coordination polymers, in particular to a two-dimensional lead coordination polymer with fluorescent properties and a preparation method thereof.

Background technique

As one of the important research topics in inorganic and materials chemistry today, metal-organic coordination polymers not only have structural aesthetic value, but also have good application prospects in the fields of luminescence, magnetism, adsorption, hydrogen storage, catalysis, and separation. In particular, the construction of coordination polymers with highly thermally stable structures and special physicochemical properties through the coordination of metal ions and organic multifunctional ligands has attracted great interest. However, designing and constructing such materials with special structures and functions is an innovative technology, which is very challenging, especially materials with good thermal stability and fluorescent properties. In recent years, some coordination polymers with high thermal stability or fluorescent properties have been widely studied and achieved certain results, but among these coordination polymers, both good thermal stability and fluorescent properties materials are rarely reported.

Contents of the invention

The purpose of the present invention is to provide a two-dimensional lead coordination polymer with fluorescent properties and a preparation method thereof, the reaction conditions are mild, the preparation process is simple, and the cost is low, and the prepared two-dimensional lead coordination polymer has fluorescent properties and better stability.

The technical solution adopted by the present invention to achieve the above technical purpose is: a two-dimensional lead coordination polymer with fluorescent properties, the molecular formula of the coordination polymer is C ₁₀ H ₈ O ₄ Pb, and the structural unit of the coordination polymer is It belongs to the monoclinic crystal system, the space group is P21/c, and the unit cell parameters are: a=8.6232(6)Å, b=13.2129(9)Å, c=8.6432(3)Å, α=γ=90°, β =90.001(1)°; the asymmetric unit of the coordination polymer contains two Pb ions and two 1,4-diphenylacetic acid ions, each Pb ion in the crystal is five-coordinated, each Pb The ions coordinate with the O atoms [Pb-O = 2.457(5)- 2.673 (6) Å] in the five carboxyl groups, and the ligand-bridged complex grows in the 001 crystal direction to form a two-dimensional layered framework structure of polymers.

The preparation method of the above-mentioned two-dimensional lead coordination polymer with fluorescent properties: take Pb(NO ₃ ) ₂ •6H ₂ O and 1,4-diphenethylcyanide dissolved in distilled water, transfer to the reaction kettle, seal the reaction kettle The reaction is carried out under the condition of 128-130° C. After the reaction is completed, it is cooled to room temperature to obtain colorless flaky crystals. After filtering, washing and drying, a two-dimensional lead coordination polymer is obtained.

As a further optimization of the preparation method of a two-dimensional lead coordination polymer with fluorescent properties of the present invention: the following steps are included:

(1) Under the condition of stirring at room temperature, dissolve Pb(NO ₃ ) ₂ •6H ₂ O and 1,4-diphenethylcyanide in distilled water, and adjust the pH value of the solution to 1.5, and set aside;

(2) Transfer the solution obtained in step (1) to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in an oven at 128-130°C for 72-80 hours. After the reaction is completed, heat it at 5°C Slowly cool at a speed of 1/h to obtain colorless flaky crystals, filter, wash with distilled water and ethanol in turn, and dry to obtain a two-dimensional lead coordination polymer.

As a further optimization of a two-dimensional lead coordination polymer with fluorescent properties and its preparation method in the present invention: Pb(NO ₃ ) ₂ •6H ₂ O and 1,4-diphenylcyanide in the step (1) The molar ratio of adding is 1:2, and the pH value of the solution is 1.5.

Beneficial effect

First, the two-dimensional lead coordination polymer of the present invention has fluorescence. During the preparation process of the coordination polymer, the cyano group in the ligand is first converted into a carboxyl group and then coordinates with metallic lead. A strong emission peak λem = 445 nm appears under the condition of excitation spectrum λex=365nm, and its fluorescence emission may be mainly attributed to the fluorescence caused by the metal-ligand electron transfer (MLCT) effect;

Second, the two-dimensional lead coordination polymer of the present invention has good thermal stability, and the TG curve of the complex shows that the compound has good thermal stability, and the organic ligand begins to lose weight from 325 ° C, causing the structural framework to collapse . The reason why the complex has good thermal stability is due to the very close packing between the layers, and there is no solvent molecule in the crystal;

Third, the preparation process of the two-dimensional lead coordination polymer of the present invention is simple, and the production efficiency is high, the equipment investment is small, and the pollution in the whole production process is small, which meets the requirements of sustainable development.

Description of drawings

Fig. 1 is the crystal structure figure of two-dimensional lead coordination polymer of the present invention;

Fig. 2 is the two-dimensional plane view of the growth of the two-dimensional lead coordination polymer of the present invention in the 001 crystal direction;

Fig. 3 is the TG curve of the product prepared in the embodiment of the present invention 1;

Fig. 4 is a fluorescence spectrum diagram of the product prepared in Example 1 of the present invention, wherein Ex represents the excitation spectrum, and Em represents the emission spectrum.

Detailed ways

The present invention will be described in further detail below through examples, and these examples are only used to illustrate the present invention, and do not limit the scope of the present invention.

Example 1:

Weigh 0.3312g (1mmol) Pb(NO ₃ ) ₂ •6H ₂ O and 0.3122g (2mmol) 1,4-diphenethylcyanide dissolved in 40ml of distilled water, stir at room temperature for 30min, then transfer to a liner lined with polytetrafluoroethylene In a high-pressure reaction kettle of ethylene, seal it and react at a high temperature of 130°C in an oven for 72 hours. After the reaction is completed, slowly cool to room temperature at a rate of 5°C/h, open the reaction kettle, obtain colorless flaky crystals, filter, and use Wash with distilled water and ethanol, and dry to obtain pure product. Based on the starting amount of Pb(NO ₃ ) ₂ •6H ₂ O, the yield was 75%.

Example 2

Weigh 0.3312g (1mmol) Pb(NO ₃ ) ₂ •6H ₂ O and 0.3122g (2mmol) 1,4-diphenethylcyanide dissolved in 35ml of distilled water, stir at room temperature for 30min, then transfer to a liner lined with polytetrafluoroethylene In a high-pressure reaction kettle of ethylene, seal it and react at a high temperature of 128°C in an oven for 80 hours. After the reaction is completed, slowly cool to room temperature at a rate of 5°C/h, open the reaction kettle, obtain colorless flaky crystals, filter, and use Wash with distilled water and ethanol, and dry to obtain pure product. Based on the starting amount of Pb(NO ₃ ) ₂ •6H ₂ O, the yield was 78%.

The characterization detection of the coordination polymer prepared in embodiment 1, 2:

(1) Crystal structure

Select a single crystal of appropriate size under a microscope, place it on a Bruker SMART CCD AREA DETECTOR single crystal X-diffraction instrument, and use graphite monochromatization of Mo-Ka rays (λ= 0.71073 Å). At 273(2)K, on the BrukerP4 four-circle diffractometer, the diffraction points were collected in the range of 3.083°< θ <27.596° with the Mo-Kα ray monochromated by the graphite monochromator at 298K 2158, of which 1869 independent diffraction points; all diffraction data were corrected for absorption using the SADABS program; unit cell parameters were determined by the least square method; data reduction and structure unwrapping were completed using the SAINT and SHELXTL programs, respectively. The coordinates of all non-hydrogen atoms are first determined by the difference function method and the least square method, and the positions of the hydrogen atoms are obtained by the theoretical hydrogenation method, and then the crystal structure is refined by the least square method. The schematic diagrams of the crystal structure and close-packed structure of the coordination polymer are shown in Fig. 1 and Fig. 2 . Some parameters of crystallographic diffraction point data collection and structure refinement are shown in the table below:

(2) Differential thermal gravimetric analysis and characterization

German NETZSCH TG-DSC STA 449 F1 synchronous thermal analyzer was used to measure the composition under the conditions of 200ml/min _N2 flow protection and a heating rate of 5°C/min with α-Al ₂ O ₃ as reference substance. TG-DSC curves of polymers. The TG curve of the coordination polymer is shown in Figure 3. The polymer has high stability, and the organic ligand loses weight from 325°C, which leads to the collapse of the framework structure.

(3) Fluorescence characterization

Fluorescence spectra were measured with a BCEIA 2015 FS5 integrated fluorescence spectrometer in Edinburgh. The coordination polymer was measured in DMF solution (concentration: 1.0×10 ^-6 mol/L) at room temperature. The fluorescence spectrum of the coordination polymer is shown in Fig. 4 .

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the technical content disclosed above to make some changes or modify equivalent embodiments with equivalent changes, but as long as they do not depart from the technical solution of the present invention, according to the technical content of the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solution of the present invention.

Claims (1)

1. A preparation method of a two-dimensional lead coordination polymer with fluorescent properties, the molecular formula of the coordination polymer is C ₁₀ H ₈ O ₄ Pb, the structural unit of the coordination polymer belongs to the monoclinic system, and the space The group is P21/c, and the unit cell parameters are: a=8.6232(6)Å, b=13.2129(9)Å, c=8.6432(3)Å, α=γ=90°, β=90.001(1)°; The asymmetric unit of the coordination polymer contains two Pb ions and two 1,4-diphenylacetic acid ions, and each Pb ion in the crystal is five-coordinated, and each Pb ion is connected to one of the five carboxyl groups The O atom coordinates to form a polymer with a two-dimensional layered frame structure through the bridging of ligands, which is characterized in that it includes the following steps: (1) Under stirring at room temperature, dissolve Pb(NO ₃ ) ₂ •6H ₂ O and 1,4-diphenethylcyanide in distilled water, and adjust the pH value of the solution to 1.5, for later use, Pb(NO ₃ ) ₂ • The molar ratio of 6H ₂ O and 1,4-diphenethyl cyanide is 1:2; (2) Transfer the solution obtained in step (1) to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in an oven at 128-130°C for 72-80 hours. After the reaction is completed, heat it at 5°C Slowly cool at a speed of 1/h to obtain colorless flaky crystals, filter, wash with distilled water and ethanol in turn, and dry to obtain a two-dimensional lead coordination polymer.