One-dimensional coordination polymers with multi-stimulus responsive and long-lasting luminescence, their preparation methods and applications

Abstract

This invention belongs to the field of luminescent materials technology, specifically relating to a one-dimensional coordination polymer with multi-stimulus responsiveness and long-lasting luminescence, its preparation method, and its applications. The one-dimensional coordination polymer disclosed in this invention is prepared by a simple solvothermal method using the organic ligand 2,2-dipyridinamine DPy and cadmium chloride or cadmium bromide. The obtained one-dimensional coordination polymer exhibits excellent long-lasting luminescence performance, high thermal stability, and can emit light continuously at high temperatures. Simultaneously, it can be excited by controlling the temperature or excitation wavelength, resulting in diverse colors, a long afterglow time, and highly efficient phosphorescence emission. It can be applied in fields such as sensing and detection, information storage, and anti-counterfeiting displays.

Description

Technical Field

[0001] This invention belongs to the field of supramolecular design and synthesis technology. More specifically, it relates to one-dimensional coordination polymers with multi-stimulus responsiveness and long-lasting luminescence, their preparation methods, and applications. Background Technology

[0002] Long-lasting luminescence refers to the phenomenon where light continues to emit light for several seconds to several days after photoexcitation ceases; materials exhibiting this phenomenon are called long-afterglow materials. Long-lasting luminescence, or long-afterglow materials, as a special type of optical material, has attracted widespread research interest in recent years. Due to their unique photon absorption, storage, and release capabilities, long-lasting luminescence materials have been widely applied in numerous fields such as sensing and detection, information storage, anti-counterfeiting displays, and bioimaging (Shi H.-F., Yao W., Ye W.-P., Ma H.-L., Huang W., An Z.-F. Accounts of Chemical Research. 2022, 55:3445.).

[0003] However, the electronic transitions between singlet and triplet energy levels in organic molecules are theoretically spin-forbidden, and due to slow intersystem crossing and rapid nonradiative deactivation processes, the long-lasting luminescence of most organic materials is not significant. Furthermore, most existing luminescent materials exhibit relatively singular luminescence, and phosphorescence emission is inefficient and easily quenched at high temperatures, making it difficult to obtain long-lasting luminescent materials at high temperatures (Zhang Q.-S., Wang S.-C., Xiong X.-H., Fu P.-Y., Zhang X.-D., Fan Y.-N., Pan M. Angew. Chem. Int. Ed. 2022, 61:e202205556.). Therefore, there is an urgent need to construct a luminescent material with long-lasting luminescence and high-temperature resistance. Summary of the Invention

[0004] The technical problem this invention aims to solve is to overcome the shortcomings and deficiencies of existing technologies, such as insignificant long-lasting luminescence and easy quenching of phosphorescence emission at high temperatures. This invention provides a one-dimensional coordination polymer with multi-stimulus responsive long-lasting luminescence. The one-dimensional coordination polymer of this invention introduces halogen heavy atoms into its structure, which not only further enhances the spin-orbit coupling effect of organic molecules but also forms abundant hydrogen bonds. This results in a one-dimensional coordination polymer with multi-stimulus responsive long-lasting luminescence, capable of phosphorescence excitation by temperature and excitation wavelength, exhibiting diverse colors, a long afterglow time, and highly efficient phosphorescence emission.

[0005] The purpose of this invention is to provide a method for preparing a one-dimensional coordination polymer with multi-stimulus responsiveness and long-lasting luminescence.

[0006] Another objective of this invention is to provide the application of one-dimensional coordination polymers with multi-stimulus responsiveness and long-lasting luminescence in the preparation of luminescent materials.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A one-dimensional coordination polymer exhibiting multi-stimulus responsiveness and long-lasting luminescence, wherein the polymer is LIFM-QZ5 or LIFM-QZ6; wherein the molecular unit of LIFM-QZ5 is C 10 H9CdCl2N3 belongs to the triclinic crystal system, space group P-1, and cadmium has a six-coordinate structure; the molecular unit of LIFM-QZ6 is C. 20 H 18 Cd3Br6N6 belongs to the monoclinic crystal system, space group P21 / n, and cadmium has a six-coordinate structure.

[0009] Furthermore, in LIFM-QZ5, the six-coordinate structure of cadmium forms an octahedral structure with two nitrogen atoms and four chlorine atoms on a ligand, and then extends infinitely to form a one-dimensional network; in LIFM-QZ6, the six-coordinate structure of cadmium has two coordination modes, one of which forms an octahedral structure with two nitrogen atoms and four bromine atoms on a ligand, and the other is that cadmium is directly coordinated with six bromine atoms, which also extends infinitely to form a one-dimensional network.

[0010] This invention utilizes the heavy atom effect and nodal interactions to construct one-dimensional coordination polymers with long-lasting, multi-stimulus luminescence through ligands. On one hand, the strong heavy atom effect enhances the spin-orbit coupling of organic molecules, promoting their phosphorescence emission. On the other hand, the nodal interactions of metal ions induce the organic ligands to form a more compact stacking structure, resisting the intrusion of external quenchers. Furthermore, introducing halogen heavy atoms into the structure not only further enhances the spin-orbit coupling effect of organic molecules but also forms abundant hydrogen bonds, resulting in one-dimensional coordination polymers with long-lasting, multi-stimulus luminescence.

[0011] 2,2-Dipyridinamine (DPy) has a DA structure with a significant electronic push-pull configuration, which is highly favorable for luminescence. Furthermore, after forming a coordination polymer, the two pyridine rings on the ligands are almost in the same plane, allowing for robust π…π interactions between the ligand molecules. This can anchor each one-dimensional coordination polymer chain together through π…π interactions, leading to the formation of a bulk single crystal. On the other hand, the abundant π…π interactions can greatly stabilize triplet excitons, thereby enhancing phosphorescence emission. Moreover, the crystal structure of these materials may exhibit multiple aggregation forms, further influencing the triplet excited-state energy level distribution and resulting in multicolor tunable ultralong room-temperature phosphorescence.

[0012] The present invention also protects a method for preparing the one-dimensional coordination polymer, specifically comprising the following steps: mixing DPy and CdX2·nH2O in a molar ratio of 0.06–0.09:0.11–0.13 mmol and adding the mixture to a solvent, performing a solvothermal reaction at 130–160 °C, and then cooling the mixture to obtain the desired product; wherein, n = 2.5–4; and X in CdX2·nH2O is chlorine or bromine.

[0013] Preferably, DPy and CdX2·nH2O are mixed and added to the solvent at a molar ratio of 0.08:0.12 mmol.

[0014] Preferably, the temperature of the solvothermal reaction is 140–150°C; more preferably, the temperature of the solvothermal reaction is 150°C.

[0015] Further, the solvent is a mixed solution of acetonitrile and water; preferably, the volume ratio of acetonitrile to water is 6-4:2-0.

[0016] Furthermore, the solvothermal time is 50-72 hours; preferably, the solvothermal time is 60-72 hours; more preferably, the solvothermal time is 72 hours.

[0017] The growth rate of a crystal is closely related to the cooling rate. During crystal growth, the temperature of its surrounding environment decreases. If the cooling is too rapid, the crystal will be too small, or even fail to grow into a complete crystal. Conversely, if the cooling is too slow, large crystals will form. A suitable cooling rate results in regular crystals with smooth crystal faces and relatively regular crystal morphology, thus leading to better material properties. Therefore, the cooling rate described in this application is 2–10 °C / h; preferably, the cooling rate is 5 °C / h.

[0018] Meanwhile, this invention also protects the application of one-dimensional coordination polymers with multi-stimulus responsiveness and long-lasting luminescence in the preparation of luminescent materials.

[0019] Preferably, the luminescent material includes bioimaging materials, optical sensing materials, information storage materials, and anti-counterfeiting detection materials.

[0020] The present invention has the following beneficial effects:

[0021] The one-dimensional coordination polymers prepared by this invention exhibit long-lasting luminescence that is both excitation-dependent and temperature-dependent. The afterglow luminescence gradually shows a redshift transition with increasing excitation wavelength or temperature. It also possesses high-temperature long-lasting luminescence characteristics and high thermal stability, maintaining its crystal structure even at nearly 600℃. The one-dimensional coordination polymer LIFM-QZ6, under 365nm excitation, can withstand an afterglow temperature of 477K, which is significantly higher than that reported in existing technologies (not exceeding 450K). Furthermore, the preparation method of this invention is simple and easy to operate, and it shows great promise for applications in luminescent technologies such as sensing and detection, information storage, anti-counterfeiting displays, and bioimaging. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the crystal structure of LIFM-QZ5; in the diagram, the blue spheres represent nitrogen atoms and the green spheres represent chlorine atoms.

[0023] Figure 2 This is a schematic diagram of the crystal structure of LIFM-QZ6; in the diagram, the blue spheres represent nitrogen atoms and the red spheres represent bromine atoms.

[0024] Figure 3 Thermogravimetric curves for LIFM-QZ5 and LIFM-QZ6.

[0025] Figure 4 The steady-state photoluminescence spectrum and delayed photoluminescence spectrum of LIFM-QZ5 and LIFM-QZ6 are shown.

[0026] Figure 5 Phosphorescence lifetime diagrams for LIFM-QZ5 and LIFM-QZ6.

[0027] Figure 6 The images show the variable excitation and variable temperature spectra of LIFM-QZ5.

[0028] Figure 7 The images show the variable excitation and variable temperature spectra of LIFM-QZ6.

[0029] Figure 8 Afterglow images for LIFM-QZ5 and LIFM-QZ6.

[0030] Figure 9 Scintillation emission spectra of LIFM-QZ5 and LIFM-QZ6

[0031] Figure 10 This is an illustration of the anti-counterfeiting detection application of LIFM-QZ5. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0033] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0034] Example 1: Synthesis of LIFM-QZ5

[0035] 0.08 mmol (13.7 mg) of DPy and 0.12 mmol (27.4 mg) of CdCl2·2.5H2O were mixed in 6 mL of a mixture of acetonitrile and water (5:1), and the mixture was sonicated for 10 minutes to ensure thorough mixing. The mixture was then heated at 150 °C for 72 hours. The cooling rate was controlled at 5 °C / h, and the mixture was allowed to cool to room temperature for 24 hours to obtain colorless needle-like crystals LIFM-QZ5 (yield 83%).

[0036] Figure 1 This is a schematic diagram of the LIFM-QZ5 crystal structure. CdX4N2 Octahedron represents the octahedral structure formed after cadmium coordination. Cadmium forms an octahedral structure with two nitrogen atoms from one ligand and four chlorine atoms from the cadmium halide. The diagram shows that the ligand DPy reacts with CdCl2·2.5H2O to form a one-dimensional chain structure, with abundant π-π interactions and hydrogen-halogen (hydrogen-chlorine) interactions between the chains.

[0037] Table 1 shows the relevant data for the single crystal structure of LIFM-QZ5.

[0038] Table 1 Single crystal structure data of LIFM-QZ5

[0039]

[0040]

[0041] Example 2: Synthesis of LIFM-QZ6

[0042] 0.08 mmol (13.7 mg) of DPy and 0.12 mmol (41.3 mg) of CdBr2·4H2O were mixed in acetonitrile (6 mL), and the mixture was sonicated for 10 minutes to ensure thorough mixing. The mixture was then heated at 150 °C for 72 hours. The cooling rate was controlled at 5 °C / h, and the mixture was allowed to cool to room temperature for 24 hours to obtain yellow needle-like crystals LIFM-QZ6 (yield 78%).

[0043] Figure 2The diagram shows the crystal structure of LIFM-QZ6. As can be seen from the diagram, the ligand DPy reacts with CdBr2·4H2O to form a one-dimensional chain structure. There are abundant π-π interactions between the chains (π-π interactions are formed between all ligand molecules, but only two are shown in the diagram as representatives) and hydrogen-halogen bonds (hydrogen-bromine bonds).

[0044] Table 2 shows the relevant data for the single crystal structure of LIFM-QZ6.

[0045] Table 2 Single crystal structure data of LIFM-QZ6

[0046]

[0047]

[0048] Example 3: Synthesis of LIFM-QZ5

[0049] 0.08 mmol (13.7 mg) of DPy and 0.12 mmol (27.4 mg) of CdCl2·2.5H2O were mixed in 6 mL of a mixture of acetonitrile and water (4:2), and the mixture was sonicated for 10 minutes to ensure thorough mixing. The mixture was then heated at 140 °C for 60 hours. The cooling rate was controlled at 5 °C / h, and the mixture was allowed to cool to room temperature for 24 hours to obtain colorless needle-like crystals LIFM-QZ5 (yield 57%).

[0050] Example 4: Synthesis of LIFM-QZ6

[0051] 0.08 mmol (13.7 mg) of DPy and 0.12 mmol (41.3 mg) of CdBr2·4H2O were mixed in a mixture of acetonitrile and water (5:1), and the mixture was sonicated for 10 minutes to ensure thorough mixing. The mixture was then heated at 140 °C for 60 hours. The cooling rate was controlled at 5 °C / h, and the mixture was allowed to cool to room temperature for 24 hours to obtain yellow needle-like crystals LIFM-QZ6 (yield 43%).

[0052] Experimental Example 1: Thermogravimetric Characterization of LIFM-QZ5 and LIFM-QZ6

[0053] Experimental samples: LIFM-QZ5 prepared in Example 1 and LIFM-QZ6 prepared in Example 2.

[0054] 5 mg of sample powder was placed under 1 atmosphere of nitrogen atmosphere and the thermogravimetric curves of 30–800 °C were tested on a TG209F3 thermal analyzer at a heating rate of 10 °C / min.

[0055] Experimental results are as follows Figure 3As shown in the thermogravimetric curves, there is a weight decrease around 250℃, which is due to a small amount of acetonitrile remaining inside the crystal. The weight remains stable around 350℃, with LIFM-QZ5 and LIFM-QZ6 maintaining 50% and 68% of their original weights, respectively. Therefore, the structures of LIFM-QZ5 and LIFM-QZ6 are relatively stable, and their crystal structure remains intact even when heated to nearly 600℃.

[0056] Experimental Example 2: Steady-state photoluminescence and delayed photoluminescence spectra of LIFM-QZ5 and LIFM-QZ6

[0057] Experimental samples: LIFM-QZ5 prepared in Example 1 and LIFM-QZ6 prepared in Example 2.

[0058] Steady-state photoluminescence and delayed photoluminescence spectra of LIFM-QZ5 and LIFM-QZ6 were measured on a spectrometer using xenon lamps and microsecond lamps, respectively.

[0059] Experimental results are as follows Figure 4 As shown in the spectrum, the fluorescence peak (prompt) of LIFM-QZ5 is located at around 400 nm, and the phosphorescence peak (delayed) is located at 500 nm, while the fluorescence peak of LIFM-QZ6 is located at 390 nm, and the phosphorescence peak is located between 550 and 600 nm. Figure 5 As can be seen, the blue dots are from the sample, and the red dots are from the instrument's own light spectrum. After fitting and automatically subtracting the light spectrum, the phosphorescence lifetime obtained is about 400ms. This is attributed to the heavy atom effect of chlorine and bromine, as well as the formation of a more compact stacking form through the metal framework network.

[0060] Experimental Example 3: Variable excitation and variable temperature spectra of LIFM-QZ5 and LIFM-QZ6

[0061] Experimental samples: LIFM-QZ5 prepared in Example 1 and LIFM-QZ6 prepared in Example 2.

[0062] To investigate the reasons for the changes in the emission color of LIFM-QZ5 and LIFM-QZ6, their variable excitation and variable temperature spectra were tested by changing the temperature and excitation wavelength on a FLS980 fluorescence spectrometer.

[0063] Experimental results are as follows Figures 6-7 As shown, the emission peaks of both LIFM-QZ5 and LIFM-QZ6 gradually redshift with increasing excitation wavelength. In the temperature-varying spectrum, the intensity of LIFM-QZ5 gradually decreases with increasing temperature, while LIFM-QZ6 shows a continuous increase in fluorescence peak (395 nm) and a continuous decrease in phosphorescence peak (550 nm) with increasing temperature – a typical characteristic of TADF.

[0064] Afterglow images of LIFM-QZ5 and LIFM-QZ6 in Experiment Example 4

[0065] Experimental samples: LIFM-QZ5 prepared in Example 1 and LIFM-QZ6 prepared in Example 2.

[0066] To investigate the long-lasting emission time of LIFM-QZ5 and LIFM-QZ6, we recorded long-lasting emission videos using a Canon camera and used a 365nm ultraviolet flashlight as the excitation source to detect the long-lasting emission time of LIFM-QZ5 and LIFM-QZ6 at different temperatures.

[0067] from Figure 8 As can be seen, LIFM-QZ5 can maintain an afterglow time of 11s under 365nm excitation at 77K, while LIFM-QZ6 can maintain it for 40s. Their tolerance temperatures are 457K and 477K, respectively, which are the highest values ​​reported in the literature to date, proving that the afterglow has good high temperature tolerance.

[0068] Experimental Example 5: Scintillation emission spectra of LIFM-QZ5 and LIFM-QZ6

[0069] Experimental samples: LIFM-QZ5 prepared in Example 1, LIFM-QZ6 prepared in Example 2, and ligand Dpy.

[0070] A Newton Scientific MINI-X2 miniature X-ray tube (gold transmission target; target thickness 1.0 ± 0.1 μm; voltage: 35–70 kV; current: 5–200 μA) was used as the X-ray excitation source. The X-ray dose rate was modulated by changing the X-ray tube current and transmitted through a Radcal ionization chamber (model: 10X6-6M; effective area = 7.54 cm²). 2 The X-ray tube was calibrated and placed in an FLS 980 to test the scintillation emission spectrum.

[0071] from Figure 9 As can be seen, under different X-ray dose rates, the scintillation intensity of LIFM-QZ5 and LIFM-QZ6 increases with increasing dose rate, and their peak positions are located at the phosphorescence peak of the sample. Compared with ligands, the phosphorescence of LIFM-QZ5 and LIFM-QZ6 can be well excited by X-rays, indicating their potential as wide-range X-ray dose detection sensors.

[0072] Experimental Example 6: Anti-counterfeiting Detection Application of LIFM-QZ5 and LIFM-QZ6

[0073] Experimental samples: LIFM-QZ5 and ligand Dpy prepared in Example 1.

[0074] The ligand crystal also exhibits excellent long-lasting luminescence at 77K, but its afterglow tolerance cannot even extend to room temperature. Therefore, the ligand and LIFM-QZ5 were arranged in an "8880" pattern, with the ligand placed within the red frame and the remaining portion being LIFM-QZ5. After the light source was removed, the portion containing the ligand showed no afterglow, thus displaying the "SYSU" logo. Figure 10 This type of material displays its true pattern only after the light source is turned off, due to the afterglow emitting light, thus providing good anti-counterfeiting functionality.

[0075] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A one-dimensional coordination polymer exhibiting multi-stimulus responsiveness and long-lasting luminescence, characterized in that, The polymer is LIFM-QZ5 or LIFM-QZ6; wherein, the LIFM-QZ5 molecular unit is C 10 H9CdCl2N3 belongs to the triclinic crystal system. P Space group -1, cadmium has a six-coordinate structure; the LIFM-QZ6 molecular unit is C. 20 H 18 Cd3Br6N6 belongs to the monoclinic crystal system and has space group 1. P 21 / n, cadmium has a six-coordinate structure; The LIFM-QZ5 has the following parameters: a=7.05640(10)Å, b=9.0913(2)Å, c=10.1639(2)Å, α=68.130(2)°, β=71.297(2)°, γ=83.064(2)°, and volume=573.15(2)Å; The LIFM-QZ6 has the following parameters: a=7.0394(2)Å, b=17.4953(4)Å, c=11.6023(3)Å, α=90°, β=102.331(2)°, γ=90°, and volume=1395.93(6)Å.

2. The one-dimensional coordination polymer according to claim 1, characterized in that, In LIFM-QZ5, cadmium has a six-coordinate structure that forms an octahedral structure with two nitrogen atoms and four chlorine atoms. In LIFM-QZ6, cadmium has two coordination modes: one is that it forms an octahedral structure with two nitrogen atoms and four bromine atoms, and the other is that cadmium is directly coordinated with six bromine atoms.

3. The method for preparing the one-dimensional coordination polymer according to claim 1 or 2, characterized in that, Specifically, the following steps are included: 2,2-Dipyridinamide and CdX2·nH2O are mixed in a molar ratio of 0.06~0.09:0.11~0.13 and added to a solvent. The mixture is subjected to a solvothermal reaction at 130~160℃ and then cooled to obtain the product. In this mixture, n=2.5~4. X in CdX2·nH2O is chlorine or bromine.

4. The preparation method according to claim 3, characterized in that, The solvent is a mixed solution of acetonitrile and water.

5. The preparation method according to claim 4, characterized in that, The volume ratio of acetonitrile to water is 6~4:2~0.

6. The preparation method according to claim 3, characterized in that, The cooling rate is 2~10 ℃ / h.

7. The preparation method according to claim 3, characterized in that, The solvothermal reaction takes 50-72 hours.

8. The preparation method according to claim 3, characterized in that, The temperature of the solvothermal reaction is 140~150 ℃.

9. The application of the one-dimensional coordination polymer according to claim 1 or 2 in the field of luminescence technology.

10. The application according to claim 9, characterized in that, The field of light-emitting technology includes bio-imaging, optical sensing, information storage, and anti-counterfeiting detection.

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