CN114685807A

CN114685807A - Cadmium coordination polymer based on pyrazole carboxylic acid ligand and preparation method thereof

Info

Publication number: CN114685807A
Application number: CN202210421536.5A
Authority: CN
Inventors: 赵红; 张灵美
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-07-01
Anticipated expiration: 2042-04-21
Also published as: CN114685807B

Abstract

The invention discloses a cadmium coordination polymer based on a pyrazole carboxylic acid ligand, which has a chemical formula as follows: [ Cd (Hppza)^‑)(H₂O)I]_n(ii) a Wherein H₂ppza is 5- (4-pyridine) -1H-pyrazole-3-carboxylic acid. The invention also discloses a preparation method of the cadmium coordination polymer, cadmium iodide is dissolved in distilled water to obtain a cadmium iodide aqueous solution; h is to be₂ppza dissolved in acetonitrile to give H₂ppza acetonitrile solution; mixing aqueous solution of cadmium iodide with H₂Mixing ppza acetonitrile solutions, placing the mixture at a high temperature for reaction, and cooling the mixture to room temperature at a rate of 5 ℃ per half hour after the reaction to obtain yellow blocky crystals; and filtering, washing and drying the obtained product to obtain the target product. The complex with the crystal structure has good thermal stability and excellent fluorescence performance, and is expected to become a potential candidate material of a photochemical sensor; in addition, the inventionThe method is simple, easy to operate and high in yield.

Description

Cadmium coordination polymer based on pyrazole carboxylic acid ligand and preparation method thereof

Technical Field

The invention relates to a cadmium coordination polymer based on a pyrazole carboxylic acid ligand and a preparation method of the cadmium coordination polymer.

Background

CPs material (coordination polymer material) is a novel crystal material formed by self-assembling metal ions or metal clusters and multifunctional organic ligands under proper conditions, and has great application potential in the fields of fluorescence sensing, catalysis, magnetism, gas adsorption, electrochemistry and the like.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a cadmium coordination polymer based on pyrazole carboxylic acid ligand with a one-dimensional structure, and the invention also aims to provide a preparation method of the cadmium coordination polymer.

The technical scheme is as follows: the cadmium coordination polymer based on the pyrazole carboxylic acid ligand has the chemical formula as follows: [ Cd (Hppza)^-)(H₂O)I]_n(ii) a Wherein H₂ppza is 5- (4-pyridine) -1H-pyrazole-3-carboxylic acid.

Wherein the basic structural unit of the cadmium coordination polymer is as follows: cd (II) ion as central metal ion, an oxygen atom coordinating with water, and a metal ion I^-And one incompletely deprotonated Hppza^-Coordinating the ligand; wherein, pyrazole ring nitrogen atom, carboxylic acid oxygen atom and central metal ion Cd in the ligand²⁺And (4) coordination.

The pyrazole group of the 5- (4-pyridine) -1H-pyrazole-3-carboxylic acid ligand contains a proton on the N atom and a proton on the carboxyl oxygen atom, both of which may be deprotonated during the reaction, which is called deprotonation. According to the single crystal test result, the ligand in the complex is deprotonated only by carboxyl, and the proton on pyrazole is still remained, so that the complex is not completely deprotonated, and is completely deprotonated if both protons are deprotonated.

Wherein the pyridine nitrogen atom in each basic structural unit is connected to another metal central ion Cd²⁺Extended into a one-dimensional chain structure, and a carboxyl oxygen atom is simultaneously connected with another metal central ion Cd²⁺Forming a double-chain structure, and growing to obtain the one-dimensional double-chain polymer.

Wherein, the coordination polymer has a one-dimensional double-chain structure, belongs to a triclinic system, has a space group of P-1, and has the following unit cell parameters:

α＝100.353(2)°，β＝106.301(2)°，γ＝112.195(2)°，

Z＝2。

the preparation method of the cadmium coordination polymer comprises the following steps:

(1) dissolving cadmium iodide in distilled water to obtain a cadmium iodide aqueous solution;

(2) h is to be₂ppza dissolved in acetonitrile to give H₂ppza acetonitrile solution;

(3) mixing aqueous solution of cadmium iodide with H₂Mixing ppza acetonitrile solutions, placing the mixture at a high temperature for reaction, and cooling the mixture to room temperature at a rate of 5 ℃ per half hour after the reaction to obtain yellow blocky crystals;

(4) and filtering, washing and drying the obtained product.

Wherein, in the step (3), the cadmium iodide aqueous solution and H₂Cadmium iodide and H in mixed solution obtained by mixing ppza acetonitrile solution₂The molar ratio of ppza was 1: 1.

wherein, in the step (3), the reaction temperature is 120 ℃, and the reaction time is three days.

Cd (II) and H₂The complex obtained after the ppza self-assembly has excellent fluorescence performance, on one hand, the used 5- (4-pyridine) -1H-pyrazole-3-formic acid ligand has a large conjugated pi-electron system, which is beneficial to the transmission of electrons in the complex and further obtains a material with good optical performance; on the other hand because of 3d¹⁰The configured Cd (II) ions do not have d-d electron transition and do not consume energy, so that the quantization efficiency of the organic ligand is improved, and the cadmium complex obtained by the method can show stronger fluorescence. The complex obtained by self-assembling Cd (II) and a 5- (4-pyridine) -1H-pyrazole-3-formic acid ligand has good thermal stability, and on the one hand, the overall structural stability is stronger because a new five-membered ring structure is formed after coordination; on the other hand, because a large number of coordination bonds, hydrogen bonds and pi … pi stacking effects exist in the complex, the rigidity of the whole complex is enhanced, the structure is firmer, the thermal stability of the complex is effectively improved, and the structure is stable at high temperature.

Has the advantages that: the complex with the crystal structure has good thermal stability and excellent fluorescence performance, and is expected to become a potential candidate material of a photochemical sensor; in addition, the synthesis method is simple, easy to operate and high in yield.

Drawings

FIG. 1 is a schematic diagram of an asymmetric unit of Cd (II) coordination polymer;

FIG. 2 shows Cd (II) coordination polymer Cd²⁺Schematic diagram of the coordination environment of (a);

FIG. 3 is a schematic diagram of one-dimensional double-stranded chain of Cd (II) coordination polymer along the a-axis direction;

FIG. 4 is a three-dimensional supramolecular stacking diagram of Cd (II) coordination polymers along the a-axis direction;

FIG. 5 shows [ Cd (Hppza)^-)(H₂O)I]_nA PXRD pattern of the complex;

FIG. 6 shows [ Cd (Hppza)^-)(H₂O)I]_nTG plot of the complex;

FIG. 7 shows [ Cd (Hppza)^-)(H₂O)I]_nAnd (3) solid fluorescence emission diagram of the complex.

Detailed Description

The technical solution of the present invention is further described with reference to the following specific embodiments.

Example 1

The Cd (II) coordination polymer has a chemical formula as follows: [ Cd (Hppza)^-)(H₂O)I]_n(ii) a Wherein H₂ppza is 5- (4-pyridine) -1H-pyrazole-3-carboxylic acid.

The Cd (II) coordination polymer is prepared by the following method: mixing CdI₂(0.3mmol, 0.1098g) was dissolved in 15mL of distilled water to obtain an aqueous solution of cadmium iodide; will H₂ppza (0.3mmol, 0.0567g) was dissolved in 15mL acetonitrile to give H₂ppza in acetonitrile; mixing aqueous solution of cadmium iodide with H₂Mixing ppza acetonitrile solutions, placing the mixture into a sealed reaction kettle, heating the mixture in a forced air drying oven at 120 ℃ for three days, cooling the mixture to room temperature at a rate of 5 ℃ per half hour after heating, and separating out yellow blocky crystals in the kettle; filtering, washing and drying the obtained product at room temperature to obtain the target product with the yield of58％。

The infrared absorption peak of the obtained Cd (II) coordination polymer comprises: 3442(s),1623(m),1383(w),1306(w),1108(m),813(w),714(w),622(w),516(w),495 (w). The elemental analysis data were: c, 39.22; h, 3.35; n,18.54 (theoretical); c, 39.12; h, 3.41; n,18.55 (experimental values). The crystallographic data of the complex are as follows: triclinic, P-1 space group,

α＝100.353(2)°，β＝106.301(2)°，γ＝112.195(2)°，

Z＝2。

as shown in FIG. 1, the asymmetric unit of the complex of the present invention comprises a Cd (II) ion, an incompletely deprotonated Hppza^-A ligand anion, one iodide ion and one coordinating water molecule. As shown in FIG. 2, each Cd (II) is centered in the N2O2 coordination environment of the ligand (each Cd²⁺The metal center is hexacoordinated, i.e., coordinated to six atoms, four of which are derived from ligands, O2, O2B, N1A, N3, two carboxylic acid oxygen atoms (O2, O2B), one pyridine nitrogen atom (N1A), one pyrazole nitrogen atom (N3), one oxygen atom coordinating water (O3), and one I^-Coordination; the resulting CdN2O3I polyhedral geometry can therefore be regarded as a distorted octahedron, with the equatorial positions occupied by atoms N1A, O2B, N3, O3 and the axial positions occupied by atoms I1, O2 (symmetrical operating code: A ═ 1+ x,1+ y,1+ z; B ═ 2-x,3-y,2-z), and with the conventional Cd-O (2.3664 (19))

) Cd-N (2.307 (2)) and

)、Cd–I

the bond length. As shown in FIG. 3, the deprotonated ligand binds Cd (II) into a one-dimensional double-stranded structure. As shown in FIG. 4, adjacent one-dimensional chains are connected into a two-dimensional layered structure through hydrogen bonds formed between oxygen atoms of coordinated water molecules and iodide ions, and the layers are stacked into a three-dimensional supramolecular structure through hydrogen bonds formed between oxygen atoms of coordinated water molecules and carboxylic acid oxygen atoms of ligands. As shown in FIG. 5, the powder diffraction pattern of the solid was determined and [ Cd (Hppza)^-)(H₂O)I]_nThe simulation patterns of the single crystal structure analysis are basically consistent, which indicates that the complex is crystallized in a pure phase.

The x-ray diffraction data of the Cd (II) coordination polymer is collected by a Bruker Smart Apex CCD single crystal diffractometer, and Mo-Kalpha ray monochromatized by graphite is adopted

Diffraction point data were collected at low temperature by means of the ω -scan technique. And (3) analyzing the crystal structure by using SHELXS-97 software through a direct method, and refining by using a full matrix least square method to perform anisotropic displacement parameter refining on all non-hydrogen atoms. The crystallographic parameters of the complex are shown in table 1:

TABLE 1 is a table of the crystallographic parameters of Cd (II) coordination polymers

Thermal stability test of Cd (II) coordination polymer prepared in example 1:

in N₂Heating a sample (Cd (II) coordination polymer prepared in example 1) in an alumina crucible at a rate of 10 ℃/min in an atmosphere in the range of 30 to 800 ℃ C. As shown in FIG. 6, the complex maintains its structure at 273 ℃ or lower, and the complex begins to lose weight rapidly (removal of coordinated water) by further heating, and the skeleton completely collapses at 900 ℃ in response to the decomposition of the organic ligand.

Fluorescence performance test of Cd (II) coordination polymer prepared in example 1:

free ligand H was tested at room temperature₂Solid state fluorescence emission spectra of ppza and complex. As shown in FIG. 7, H at 324nm excitation₂The ppza ligands show weak luminescence with a maximum emission wavelength of 351nm, probably due to the semi-rigid ligands pi-pi^*Due to electron migration. The maximum emission wavelength of the complex under 317nm excitation is 347 nm. The maximum emission peak of the complex is slightly blue-shifted compared to the ligand. This is due to d¹⁰The Cd (II) ions in the configuration are difficult to oxidize or reduce, so the fluorescence emission of the complex is the result of charge transfer between ligands. In addition, the fluorescence intensity of the complex is far greater than that of a free ligand, particularly a Cd (II) complex, so that on one hand, the introduction of a transition metal can effectively enhance the rigidity of the ligand, thereby being beneficial to the migration of electrons, further reducing the energy loss caused by radiationless decay and enhancing the luminous intensity, and on the other hand, the introduction of the transition metal is d¹⁰The configured metal ions are good luminescent centers.

Claims

1. The cadmium coordination polymer based on the pyrazole carboxylic acid ligand is characterized in that the chemical formula of the cadmium coordination polymer is as follows: [ Cd (Hppza)^-)(H₂O)I]_n(ii) a Wherein H₂ppza is 5- (4-pyridine) -1H-pyrazole-3-carboxylic acid.

2. The cadmium coordination polymer based on pyrazole carboxylic acid ligand according to claim 1, characterized in that the basic structural unit of the cadmium coordination polymer is: cd (II) ion as central metal ion, oxygen atom of coordinated water, I^-And Hppza^-Coordinating the ligand; wherein, pyrazole ring nitrogen atom, carboxylic acid oxygen atom and central metal ion Cd in the ligand²⁺And (4) coordination.

3. The cadmium coordination polymer based on pyrazole carboxylic acid ligand according to claim 2, characterized in that: the pyridine nitrogen atom in each basic structural unit is connected to another metal central ion Cd²⁺Extended into a one-dimensional chain structure, and a carboxyl oxygen atom is simultaneously connected with another metal central ion Cd²⁺Forming a double-chain structure, and growing to obtain the one-dimensional double-chain polymer.

4. The cadmium coordination polymer based on pyrazole carboxylic acid ligands according to claim 3, wherein the coordination polymer has a one-dimensional double-chain structure, belongs to a triclinic system, has a space group of P-1, and has unit cell parameters of:

α＝100.353(2)°，β＝106.301(2)°，γ＝112.195(2)°，

Z＝2。

5. the method of preparing a cadmium coordination polymer according to claim 1, comprising the steps of:

(2) h is to be₂ppza was dissolved in acetonitrile to give H₂ppza acetonitrile solution;

(4) and filtering, washing and drying the obtained product to obtain the target product.

6. The method of claim 5, wherein the cadmium coordination polymer is prepared by: in the step (3), the cadmium iodide aqueous solution and H₂Cadmium iodide and H in mixed solution obtained by mixing ppza acetonitrile solution₂Mole of ppzaThe molar ratio is 1: 1.

7. the method of claim 5, wherein the cadmium coordination polymer is prepared by: in the step (3), the reaction temperature is 120 ℃ and the reaction time is three days.