A solution-processable light-stimulus-responsive cadmium coordination polymer and its preparation and application

Abstract

This invention relates to a metal Cd(II) coordination polymer containing a mixture of ligands of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine, its preparation method, and its photostimulation-responsive application. The chemical formula of the coordination polymer of this invention is [Cd(TFBA)2(Thpz)2], where TFBA represents the monovalent anion of 2,4,6-trifluorobenzoic acid, and Thpz represents 2-(2-thienyl)vinyl)pyrazine. This coordination polymer material can undergo a [2+2] cycloaddition reaction under 450 nm blue light or 365 nm ultraviolet light irradiation, accompanied by mechanical movement of the crystals under light irradiation. It can be used to prepare photoactuators under 450 nm blue light or 365 nm ultraviolet light irradiation.

Description

Technical Field

[0001] This invention relates to the field of photostimulation-responsive materials technology, specifically to photostimulation-responsive coordination polymers and their preparation and application. Background Technology

[0002] Stimulus-responsive materials are smart materials whose physical or chemical properties change in response to external stimuli, such as temperature, pH, light, electric fields, and magnetic fields. Stimulus-responsive materials have shown great application potential in biomimetic actuators, optoelectronic devices, artificial intelligence, and sensors. Photomechanical behavior, on the other hand, arises from photochemical reactions that alter the internal structure of molecules, generating forces that bind them together. The release of these forces leads to a series of energy conversions, transforming light energy into kinetic energy. These mechanical movements are largely caused by the anisotropy generated in single crystals during photoreaction processes.

[0003] Among these, the mechanical behavior driven by illumination [2+2] ring addition is influenced by the wavelength of the incident light and the crystal properties. Most reported photoactuators require short-wavelength light sources, which pose potential health risks to humans (e.g., high-energy ultraviolet light). Blue light is inherently green, clean, and abundant. The design and synthesis of photoactuators and related devices that capture blue light and generate continuous motion remain challenging. Summary of the Invention

[0004] This invention relates to Cd(II) coordination polymers containing a mixture of ligands of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine, their preparation methods, and photostimulation-responsive applications. The coordination polymer material can undergo a [2+2] cycloaddition reaction under blue or ultraviolet light irradiation, accompanied by mechanical movement of the crystals under light irradiation. To achieve the above objectives, this invention provides the following technical content:

[0005] A Cd(II) coordination polymer having the following general molecular formula with mixed ligands of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine: [Cd(TFBA)2(Thpz)2]; where TFBA represents the monovalent anion of 2,4,6-trifluorobenzoic acid, and Thpz represents 2-(2-thienyl)vinyl)pyrazine. The molecular formula is as follows:

[0006]

[0007] This invention further discloses a single crystal of a photostimulated responsive Cd(II) coordination polymer containing a mixed ligand of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine, characterized in that the coordination polymer crystallizes in a monoclinic crystal system with space group P21 / c and cell parameters of [missing information]. Z = 2; the basic structure is a one-dimensional network of infinite structures formed by 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine connected together with a central cadmium ion.

[0008] This invention also discloses a method for preparing a photostimulated responsive Cd(II) coordination polymer containing a mixed ligand of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine. The method involves adding 2,4,6-trifluorobenzoic acid, 2-(2-thienyl)vinyl)pyrazine, and cadmium nitrate tetrahydrate to a mixed solvent of methanol and 0.1M sodium hydroxide aqueous solution, and allowing the mixture to stand at room temperature to obtain the photostimulated responsive Cd(II) coordination polymer. The molar ratio of 2,4,6-trifluorobenzoic acid, 2-(2-thienyl)vinyl)pyrazine, and cadmium nitrate tetrahydrate is 1–2:1–2:0.5–1, and the volume ratio of methanol to 0.1M sodium hydroxide aqueous solution in the mixed solvent is 2–3:1–2, resulting in light yellow needle-like crystals.

[0009] 3. This invention further discloses the preparation and photo-driven application of a photostimulated responsive Cd(II) coordination polymer containing a mixed ligand of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine. The composite membrane substrate is selected from one or more of PVA, polyvinylidene fluoride, and polypropylene.

[0010] The significant feature of the photostimulation-responsive Cd(II) coordination polymer containing a mixture of 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine ligands prepared in this invention is that:

[0011] (1) The coordination polymer material prepared by the present invention can undergo a [2+2] cycloaddition reaction under 450nm blue light or 365nm ultraviolet light, and the crystal moves mechanically under light.

[0012] (2) Compared with the complex steps of grinding and ultrasonication of large and non-uniform single crystal samples to prepare small-sized composite membrane fillers, the present invention can easily prepare composite membranes by adding the reactant solution to the base liquid at room temperature.

[0013] (3) Compared with the preparation of coordination polymers by heating methods such as hydrothermal or solvothermal methods, the present invention can be synthesized at room temperature. Attached Figure Description

[0014] Figure 1 Infrared spectrum of coordination polymer [Cd(TFBA)2(Thpz)2].

[0015] Figure 2Crystal structure diagram of coordination polymer [Cd(TFBA)2(Thpz)2], where (a) is the coordination environment of Cd(II) center and (b) is a one-dimensional chain structure diagram.

[0016] Figure 3 Powder diffraction pattern of the prepared [Cd(TFBA)2(Thpz)2].

[0017] Figure 4 Mechanical motion behavior of single crystals under ultraviolet light irradiation. (a) before irradiation, (b) after irradiation.

[0018] Figure 5 shows the dimer formed after [2+2] cycloaddition under 450nm blue light irradiation. 1 HNMR spectrum.

[0019] Figure 6 The deformation behavior of the composite film under 365nm ultraviolet light irradiation, where (a) is before irradiation and (b) is after irradiation.

[0020] Figure 7 A schematic diagram of a photoactuator for a composite film under 365nm ultraviolet light irradiation.

[0021] Figure 8 The deformation behavior of the composite film under 450nm blue light irradiation, where (a) is before irradiation and (b) is after irradiation.

[0022] Figure 9 A schematic diagram of a photoactuator for a composite film under 450nm blue light irradiation.

[0023] Figure 10 Crystals on the water surface are driven by ultraviolet light, where (a) is before the light is applied and (b) is after the light is applied. Detailed Implementation

[0024] The present invention will be further described below with reference to preferred embodiments and accompanying drawings, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0025] Example 1: Synthesis of coordination polymer [Cd(TFBA)2(Thpz)2]

[0026] 2,4,6-Trifluorobenzoic acid (0.1 mmol, 17.6 mg) was dissolved in a mixture of 0.1 M sodium hydroxide solution (0.1 mmol, 1 mL) and methanol (2.0 mL). Then, 2-(2-thienyl)vinyl)pyrazine (0.1 mmol, 18.8 mg) and cadmium nitrate tetrahydrate (0.05 mmol, 15.4 mg) were added. The mixture was left to stand at room temperature to obtain light yellow crystals, which were then washed with water and dried in air.

[0027] The characterization of the coordination polymer [Cd(TFBA)2(Thpz)2] prepared in this invention (Example 1) is as follows:

[0028] (1) Infrared spectroscopy determination

[0029] Infrared spectroscopy was performed using the potassium bromide pellet method on a Nicolet FT-IR-200 infrared spectrometer. Figure 1 As shown, the main infrared absorption peak of the coordination polymer described in this invention is 3419 cm⁻¹. -1 3104cm -1 1629cm -1 1580cm -1 1518cm -1 1489cm -1 1407cm -1 1359cm -1 1334cm-1, 1137cm -1 1115cm -1 1036cm -1 1023cm -1 1008cm -1 998cm -1 859cm -1 833cm -1 745cm -1 618cm -1 .

[0030] (2) Crystal structure determination

[0031] Some parameters from crystallographic data collection and structural refinement are shown in Table 1. This compound crystallizes in a monoclinic system with space group P21 / c. Figure 2 As shown in (a), the central metal ion Cd 2+ It coordinates with oxygen atoms from four TFBA ligands and nitrogen atoms from two Thpz ligands. The Thpz ligands act as end-capping ligands, and the metal ions extend and form a one-dimensional, infinite network structure through TFBA ligand bridging. Figure 2 b).

[0032] Table 1. Main crystallographic data and refinement parameters of [Cd(TFBA)2(Thpz)2]

[0033]

[0034]

[0035] Example 2: Preparation of composite membrane from original liquid sample

[0036] The reactant solution synthesized in Example 1 was added to 3.0 g of 10 wt% PVA aqueous solution, mixed, and stirred for 6 hours to obtain a homogeneous viscous liquid. This viscous liquid was dropped into a clean, dry polytetrafluoroethylene mold, dried at room temperature for 12 hours, and then peeled off to obtain a composite film.

[0037] Example 3: Preparation of composite film from crystal sample

[0038] 0.045 g of the crystals prepared in Example 1 were dissolved in 2 mL of methanol solution, and then added to 3.0 g of 10 wt% PVA aqueous solution. The mixture was stirred for 6 hours to obtain a homogeneous viscous liquid. The viscous liquid was dropped into a clean, dry polytetrafluoroethylene mold and dried at room temperature for 12 hours. The resulting composite film was then peeled off.

[0039] Example 4: Optomechanical behavior of crystals

[0040] When the crystal of Example 1 is irradiated with 365nm ultraviolet light, the rapid release of photogenerated stress causes the crystal to exhibit mechanical behaviors such as cracking and jumping. Figure 4 ).

[0041] Example 5: [2+2] cycloaddition reaction of crystals under 450 nm blue light irradiation

[0042] The crystal prepared in Example 1 was placed under 450 nm light for 2 hours. 1 ¹H NMR characterization showed characteristic peaks at 4.72–4.95 ppm attributed to cyclobutane. Figure 5 ).

[0043] Example 6: Photoresponse of the composite film under 365nm ultraviolet light irradiation

[0044] The composite film prepared in Example 2 was cut into rectangles of 0.5 × 2 cm and exposed to a 365 nm ultraviolet light source. The photomechanical deformation behavior was recorded. Figure 6 Under 365nm ultraviolet irradiation, the composite film rapidly bent.

[0045] Example 7: Photodriven behavior of the composite film under 365nm ultraviolet light irradiation

[0046] The composite film prepared in Example 2 was cut into rectangles of 0.5 × 2 cm, fixed at one end, and an object was placed at the other end. The object was then exposed to a 365 nm ultraviolet light source, and its photomechanical deformation behavior was recorded. Figure 7 Under 365nm ultraviolet irradiation, the composite film rapidly bent and lifted the placed items.

[0047] Example 8: Photoresponse of the composite film under 450nm blue light irradiation

[0048] The composite film prepared in Example 2 was cut into rectangles of 0.5 × 2 cm and exposed to a 450 nm blue light source. The photomechanical deformation behavior was recorded. Figure 8 Under blue light irradiation, the composite membrane rapidly bent.

[0049] Example 9: Photodriven behavior of the composite film under 450nm blue light irradiation

[0050] The composite film prepared in Example 2 was cut into rectangles of 0.5 × 2 cm, fixed at one end, and an object was placed at the other end. The object was then exposed to a 450 nm blue light source, and its photomechanical deformation behavior was recorded. Figure 9 Under blue light, the composite film quickly bent and lifted the placed items.

[0051] Example 10: Light-driven behavior of crystal

[0052] The crystal from Example 1 was placed in water and allowed to float on the surface, then exposed to a 365nm ultraviolet light source. Figure 10 Due to the accumulation of photogenerated stress, the crystal moves on the water surface, thus changing the position of the crystal.

[0053] This demonstrates that the material can exhibit photomechanical behavior under ultraviolet and blue light stimulation, thus providing a new approach for constructing novel photostimulation-responsive materials.

Claims

1. A photostimulation-responsive Cd(II) coordination polymer, characterized in that, It has the following general molecular formula: [Cd(TFBA)2(Thpz)2]; where TFBA represents the monovalent anion of 2,4,6-trifluorobenzoic acid, and Thpz represents 2-(2-thienyl)vinyl)pyrazine, with the following molecular formula:

2. A single crystal of the photostimulation-responsive Cd(II) coordination polymer as described in claim 1, characterized in that, This coordination polymer crystallizes in a monoclinic system with space group P21 / c and cell parameters of [missing information]. α=90°, β=115.964(2)°, γ=90°, Z = 2; The basic structure is a one-dimensional network of infinite structures formed by 2,4,6-trifluorobenzoic acid and 2-(2-thienyl)vinyl)pyrazine linked together by a central cadmium ion.

3. A method for preparing the photostimulation-responsive Cd(II) coordination polymer as described in claim 1, characterized in that, 2,4,6-trifluorobenzoic acid, 2-(2-thienyl)vinyl)pyrazine, and cadmium nitrate tetrahydrate were dissolved in a mixed solvent of methanol and 0.1M sodium hydroxide aqueous solution, transferred to a reaction vessel, and allowed to react at room temperature to obtain the photostimulation-responsive Cd(II) coordination polymer.

4. The preparation method according to claim 3, characterized in that, The molar ratio of 2,4,6-trifluorobenzoic acid, 2-(2-thienyl)vinyl)pyrazine, and cadmium nitrate tetrahydrate is 1-2:1-2:0.5-1, and the volume ratio of methanol and 0.1M sodium hydroxide aqueous solution in the mixed solvent is 2-3:1-2.

5. The preparation method according to claim 3, characterized in that, The reaction vessel can be open or sealed, and the reaction time is 1 to 7 days.

6. A method for preparing a composite membrane, characterized in that, The photostimulation-responsive Cd(II) coordination polymer of claim 3 is added to the base liquid and stirred and dispersed thoroughly. The mixture is then poured into a mold, dried, and peeled off to obtain a composite film.

7. A method for preparing a composite membrane, characterized in that, The reactant solution of the photostimulation-responsive Cd(II) coordination polymer described in claim 3 is added to the base liquid and stirred and dispersed thoroughly. The mixture is then poured into a mold, dried, and peeled off to obtain a composite film.

8. The preparation method according to any one of claims 6 and 7, characterized in that, The substrate is selected from one or more of PVA, polyvinylidene fluoride, and polypropylene.

9. The application of the photostimulation-responsive Cd(II) coordination polymer as described in claim 1 or the composite film as described in claim 6 or claim 7 in a photoactuator under 450 nm or 365 nm illumination.

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