A photochromic coordination polymer and its preparation method and application

Abstract

The present invention provides a coordination polymer with photochromic properties, as well as its preparation method and application. The chemical formula of the polymer is [Cd2(NDI-ATZ)(H2PMD)(DMF)4]; the present invention also relates to the preparation method and application of the polymer. In the present invention, naphthalene diimide, which has excellent electron-deficient properties, is used as an electron acceptor and hybridized with an aromatic carboxylic acid electron donor through the coordination of metallic cadmium to form a naphthalene diimide-based cadmium coordination polymer material with photochromic properties. Based on the intermolecular electron transfer mechanism, the color-changing material can change color under ultraviolet light. The coordination polymer prepared by the present invention produces rapid photoresponsive behavior under ultraviolet light and has excellent fatigue resistance, providing a new approach for the development of photoresponsive materials.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of organic-inorganic hybrid color-changing materials, and in particular relates to a photochromic coordination polymer and a preparation method and application thereof. Background Art

[0002] Electron donating-accepting coordination polymer photochromic materials have shown important practical application value in the fields of information storage, sensing, display and switching due to their regular and controllable structure and good visual detectable photochromic behavior. The performance indicators of electron donating-accepting coordination polymer photochromic materials mainly include the following three aspects: (1) color change rate and color contrast during the color change process; (2) reversibility of the fading process; (3) fatigue resistance during the color change and fading process during repeated use. To date, different electron donating-accepting coordination polymer photochromic materials have been constructed using excellent electron acceptors such as viologen derivatives (V), aromatic diimide derivatives (ADIs), and 2,4,6-tripyridyl-1,3,5-triazine derivatives (TPTs) as organic ligands. However, the slow photoresponse rate of these synthesized electron donating-accepting coordination polymers and their relatively poor reversibility and cyclability have become important scientific issues that limit the practical application of such materials.

[0003] Naphthalene diimide derivatives (NDIs) possess large positive quadrupole moments and strong polarizability. They are a class of colorless, conjugated π-electron-deficient organic compounds and are considered promising building blocks for the construction of electron-donating and -accepting coordination polymers. Naphthalene diimide derivatives (NDIs) possess large positive quadrupole moments and strong polarizability. They are colorless, conjugated π-electron-deficient organic compounds and are considered promising building blocks for the construction of electron-donating and -accepting coordination polymers. Anchoring two tetrazole groups on either side of the nitrogen position of NDI not only bridges multiple metal sites, but also forms strong intermolecular π…π, lone pair…π, and CH…π interactions with the aromatic carboxylic acid ligands within the NDI functionalized organic ligand, serving as effective electron transfer pathways. Therefore, the self-assembly of the naphthalene diimide ligand with excellent electron-deficiency and the aromatic carboxylic acid electron donor through metal coordination can not only achieve effective regulation of the internal electrons of the electron donating-accepting coordination polymer, but also optimize the electron donating-accepting interface relationship, thereby improving the photochromic properties of the electron donating-accepting photochromic coordination polymer material. Summary of the Invention

[0004] The purpose of the present invention is to provide a photochromic coordination polymer and a preparation method and application thereof.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a photochromic coordination polymer, which is a naphthalene diimide-based coordination polymer with the chemical formula [Cd2(NDI-ATZ)(H2PMD)(DMF)4]; wherein NDI-ATZ is a negative divalent ligand NDI-ATZ of 5-amino-1H-tetrazole-naphthalene diimide, as shown in structural formula (1); H2PMD is a negative divalent anionic ligand H2PMD of pyromellitic acid, as shown in structural formula (2); and DMF is N,N-dimethylformamide.

[0007]

[0008] Preferably, the excellent electron-deficient acceptor naphthalene diimide of the naphthalene diimide-based cadmium-based coordination polymer is hybridized with the oxygen-containing carboxylic acid electron donor through the coordination effect of metal cadmium, thereby forming a specific interface relationship between the electron donor and the acceptor.

[0009] Preferably, the naphthalene diimide functional coordination polymer is a color-changing material based on intermolecular electron transfer.

[0010] Preferably, the naphthalene diimide-based coordination polymer crystallizes in the orthorhombic Cmmm space group, and the asymmetric unit consists of a crystallographically independent Cd 2+ ion, half of the deprotonated NDI-ATZ, half of the H2PMD and two coordination disordered DMF molecules, each Cd 2+ The ion adopts a 6-coordinate coordination mode, which contains 4 O atoms and 2 N atoms. The 4 O atoms come from one H2PMD ligand and two coordinated DMF molecules, and the 2 N atoms come from two NDI-ATZ ligands. Then, H2PMD and NDI-ATZ alternately connect Cd 2+ The ions form a one-dimensional chain structure, and adjacent one-dimensional chains interact through hydrogen bonds to form a three-dimensional supramolecular network.

[0011] The crystals of the naphthalene diimide-based cadmium coordination polymer were measured by a SMART APEX CCD single crystal diffractometer using a graphite monochromator Mo-Kα radiation. Data were collected in ω-scan mode and subjected to Lp factor correction and absorption correction using the SADABS program. The structure was solved using the direct method to determine the position of heavy atoms, and then the difference function method and least squares method were used to obtain the coordinates of non-hydrogen atoms. The theoretical hydrogenation method was used to obtain the position of hydrogen atoms. The structure was modified using the least squares method. All non-hydrogen atoms were anisotropic. All calculations were completed using the Olex2 program. The measured crystallographic parameters are as follows: molecular weight is 583.79, belonging to the orthorhombic system, space group Cmmm, unit cell parameters α=90°, β=90°, γ=90°, Z=4.

[0012] The present invention also relates to a method for preparing the aforementioned photochromic coordination polymer, comprising the following steps:

[0013] (1) adding cadmium nitrate tetrahydrate, 5-amino-1H-tetrazolyl-naphthalene diimide and pyromellitic acid to a solution of N,N-dimethylformamide and stirring uniformly to obtain a mixed solution;

[0014] (2) The mixture was placed in an oven at 80°C for 2-3 days to react, and crystals were precipitated. The crystals were washed with DMF, filtered, and dried to obtain light yellow rod-shaped crystals.

[0015] Preferably, in step (1), the cadmium nitrate tetrahydrate, 5-amino-1H-tetrazole-naphthalene diimide and pyromellitic acid are added to a 3-5 mL N,N-dimethylformamide solution in a molar ratio of (1.5-2.5): (0.5-1.5): (1.5-2.5) and stirred evenly.

[0016] The present invention also relates to the application of the aforementioned photochromic coordination polymer, and the application of the naphthalene diimide-based coordination polymer as a photochromic material.

[0017] The present invention has the following advantages:

[0018] (1) In the present invention, naphthalene diimide with excellent electron-deficient properties is used as an electron acceptor, and is hybridized with an aromatic carboxylic acid electron donor through the coordination effect of metal cadmium to form a naphthalene diimide-based cadmium coordination polymer material with photochromic properties, providing a photochromic coordination polymer material and expanding the application range of color-changing materials.

[0019] (2) The material based on the intermolecular electron transfer mechanism provided by the present invention can change color rapidly under ultraviolet light irradiation, thereby improving fatigue resistance and providing unique insights into the construction of photochromic materials.

[0020] (3) The preparation method of the organic-inorganic hybrid photochromic material provided by the present invention is simple, easy, low-cost, highly repeatable, safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The structure diagram of the naphthalene diimide-based cadmium coordination polymer of the present invention; from left to right are the asymmetric structural unit diagram, the 1D chain structure diagram, and the three-dimensional supramolecular network structure diagram;

[0022] Figure 2 Figure 2 is a diagram of the weak interaction between NDI-ATZ and H2PMD in the naphthalene diimide-based cadmium coordination polymer of the present invention;

[0023] Figure 3This is a color change diagram of the naphthalene diimide-based cadmium coordination polymer of the present invention under ultraviolet light;

[0024] Figure 4 The figure is a time-dependent UV-visible absorption spectrum of the naphthalene diimide-based cadmium coordination polymer during the color change process under UV light;

[0025] Figure 5 The EPR spectra of the naphthalene diimide-based cadmium coordination polymer of the present invention before and after photochromism and fading;

[0026] Figure 6 This is a cycle diagram of the naphthalene diimide-based cadmium coordination polymer of the present invention before and after photochromism for 10 cycles;

[0027] Figure 7 The X-ray powder diffraction patterns of the naphthalene diimide-based cadmium coordination polymer of the present invention before and after discoloration under ultraviolet light;

[0028] Figure 8 The infrared spectra of the naphthalene diimide-based cadmium coordination polymer of the present invention before and after discoloration under ultraviolet light;

[0029] Figure 9 This is a diagram showing the application of five-ink erasable printing of the naphthalene diimide-based cadmium coordination polymer of the present invention;

[0030] Figure 10 The figure is a time-dependent UV-visible absorption spectrum of the naphthalene diimide-based cadmium coordination polymer of the present invention during the color change process of light in different wavelength bands;

[0031] Figure 11 The diagram shows the color change of the naphthalene diimide-based cadmium coordination polymer of the present invention during the color change process under illumination of different wavelengths. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only for further explanation of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] This embodiment relates to the synthesis of a naphthalene diimide-based cadmium coordination polymer [Cd2(NDI-ATZ)(H2PMD)(DMF)4]: The specific method is as follows:

[0035] A mixture of Cd(NO₃)₂·4H₂O (30.9 mg, 0.1 mmol), H₂NDI-ATZ (20.0 mg, 0.05 mmol), and H₄PMD (24.50 mg, 0.1 mmol) in DMF (3 mL) was mixed and sonicated at room temperature for 10 min. The mixture was placed in a 10 mL screw-cap glass bottle and heated at 80°C for 48 h to yield pale yellow rod-shaped crystals. These crystals were collected, washed with DMF, and stored in a sealed container protected from light. The yield was 56.3% (based on H₂NDI-ATZ).

[0036] Example 2

[0037] Photochromic experiment

[0038] The naphthalene diimide-based cadmium coordination polymer prepared in Example 1 was subjected to a photochromic experiment. The specific steps were as follows: the light source used was a 300W high-pressure mercury lamp. The sample was placed on a glass slide and placed on a constant-temperature metal plate 30 cm away from the light source. After irradiation with ultraviolet light, the sample changed color from light yellow to dark yellow within 1 second. As the irradiation time increased, the color gradually deepened and finally turned brown. The sample reached saturation within 4 seconds. The original sample was represented by compound 1, and the sample after irradiation was represented by 1P (see Figure 3 and Figure 4 The color change of the sample is due to the generation of colored free radical signals by photoinduced electron transfer, which is confirmed by EPR. Figure 5 It can be faded by placing it in the dark for 2 hours or heating it at 140℃ for 5 minutes. This reversible color change can be cycled at least 10 times. Figure 6 The structural integrity is good and has not been damaged, and it has strong anti-fatigue performance and stability. Figure 7 and Figure 8 .

[0039] Example 3

[0040] Inkless erasable printing experiment

[0041] The naphthalene diimide-based cadmium coordination polymer obtained in Example 1 was subjected to an inkless erasable printing experiment. The specific steps were as follows: the light source used was a 300W high-pressure mercury lamp. After a sample was evenly coated on paper into a specific pattern, it was placed on a constant-temperature metal plate 30 cm away from the light source. When irradiated with ultraviolet light, the sample changed from yellow to brown within 4 seconds. It faded after being placed in the dark for 2 hours or heated at 140°C for 5 minutes. Figure 9 .

[0042] Example 4

[0043] Ultraviolet light detection experiment

[0044] The naphthalene diimide-based cadmium coordination polymer obtained in Example 1 was subjected to an inkless erasable printing experiment. The specific steps were as follows: a 30W xenon lamp equipped with a bandpass filter was used as the light source. The sample was placed on a glass slide and placed on a constant temperature metal plate 30 cm away from the light source. The sample was irradiated with light of different wavelengths. Within the same irradiation time, the color change of the sample irradiated with 400nm wavelength violet light was significantly greater than that of the sample irradiated with other wavelengths. Figure 10 and Figure 11 The color change of the naphthalene diimide-based cadmium coordination polymer obtained in Synthesis Example 1 under 400 nm violet light is significantly different from the color change under irradiation with light of other wavelengths, and can be used for violet light detection.

[0045] Example 5

[0046] The crystal structure of the naphthalene diimide-based cadmium coordination polymer obtained in Example 1 was determined by the following steps:

[0047] Select crystals suitable for single crystal X-ray diffractometer data collection under a microscope, see Figure 1-Figure 5 The single crystal of suitable size was subjected to X-ray single crystal structure analysis. The X-ray diffraction data of the crystal was measured by SMART APEX CCD single crystal diffractometer and graphite monochromator Mo-Kα radiation. Data were collected using the ω scan mode and corrected for Lp factors and absorption using the SADABS program. The structure was solved using the direct method to determine the positions of heavy atoms. Non-hydrogen atomic coordinates were then determined using the difference function method and least-squares method. The positions of hydrogen atoms were determined using the theoretical hydrogenation method, and the structure was modified using the least-squares method. All non-hydrogen atoms were anisotropic. All calculations were performed using the Olex2 program. Key crystallographic data for the coordination polymer are shown in Table 1.

[0048] Table 1

[0049]

[0050] In the present invention, naphthalene diimide with excellent electron-deficient properties is used as an electron acceptor, and is hybridized with an aromatic carboxylic acid electron donor through the coordination effect of metal cadmium to form a naphthalene diimide-based cadmium coordination polymer material with photochromic properties. Based on the intermolecular ET mechanism, the color-changing material can change color under ultraviolet light irradiation. The coordination polymer prepared by the present invention produces rapid photoresponse behavior under ultraviolet light and has excellent anti-fatigue performance, providing a new idea for the development of new photoresponsive materials.

[0051] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A photochromic coordination polymer, characterized in that: The polymer is a naphthalene diimide-based cadmium coordination polymer, and its chemical formula is [Cd2(NDI-ATZ)(H2PMD)(DMF)4]; wherein NDI-ATZ is a negative divalent anion ligand of 5-amino-1H-tetrazolyl-naphthalene diimide, H2PMD is a negative divalent anion ligand of pyromellitic acid, and DMF is N,N-dimethylformamide. The structural formula of NDI-ATZ is shown in formula (1), and the structural formula of H2PMD is shown in formula (2): 。 2. The photochromic coordination polymer according to claim 1, wherein: The naphthalene diimide-based cadmium coordination polymer is in the orthorhombic crystal system Cmmm In the space group, the asymmetric unit consists of a crystallographically independent Cd 2+ ion, half of NDI-ATZ ligand, half of H2PMD ligand and two coordinated DMF molecules. 2+ The ion adopts a 6-coordinate coordination mode with 4 O atoms and 2 N atoms, of which 2 O atoms come from DMF molecules and 2 O atoms come from H2PMD ligands; 2 N atoms come from NDI-ATZ ligands, Cd 2+ The ions are alternately connected by NDI-ATZ and H2PMD ligands to form a one-dimensional chain structure, and adjacent one-dimensional chains interact through hydrogen bonds to form a three-dimensional supramolecular network.

3. A method for preparing a photochromic coordination polymer according to claim 1, characterized in that: The following steps are involved: (1) Add cadmium nitrate tetrahydrate, 5-amino-1H-tetrazolyl-naphthalene diimide and pyromellitic acid to a solution of N,N-dimethylformamide and stir evenly to obtain a mixed solution; (2) The mixture was placed in an oven at 80°C for 2-3 days to allow crystals to precipitate. The crystals were washed with DMF, filtered, and dried to obtain light yellow rod-shaped crystals.

4. The method for preparing a photochromic coordination polymer according to claim 3, wherein: In step (1), the cadmium nitrate tetrahydrate, 5-amino-1H-tetrazolyl-naphthalene diimide and pyromellitic acid are added to a 3-5 mL N,N-dimethylformamide solution in a molar ratio of (1.5-2.5): (0.5-1.5): (1.5-2.5) and stirred evenly.

5. A use of the photochromic coordination polymer according to claim 1, characterized in that: The naphthalene diimide-based coordination polymer is used in preparing photochromic materials.

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