Light conversion material containing double helix structure, its preparation method and application in preparing light yellow LED

Abstract

The application provides a light conversion material containing double helical structures, and has a chemical formula of [Cd(edd)(bpy)] n , belongs to a triclinic system, and has a space group of Pī and a cell parameter. 2‑ In the chemical formula, the component edd is obtained by removing two protons from a binary carboxylic acid H2edd, and the structure of the H2edd is shown in formula I; the structure of the bpy is shown in formula II. The light conversion material containing double helical structures prepared by the application has a yield of about 75%, and has good thermal stability. The crystal structure contains a P-M type one-dimensional infinite double helical band with a common node, the bpy bridged helical band further forms a two-dimensional metal-organic coordination polymer layer, and there are various twist angles between the internal functional groups of the organic bridged components edd 2‑ and bpy. The light conversion material is used as a non-rare earth element and single-component light conversion agent for encapsulating an LED device, and the LED can emit a characteristic light with a main wavelength of 567.8 nm under low power driving.

Description

Technical Field

[0001] This application belongs to the field of advanced luminescent materials, specifically relating to a light-converting material with a double-belt helical structure, its preparation method, and its application in the preparation of light yellow LEDs. Background Technology

[0002] According to the principle of three primary colors, red and green light combine to produce yellow light, and yellow light combined with blue light produces white light; theoretically, there could be over 16.7 million possible colors in a 256-color system. Although the currently known range of light colors is still limited, the invention of the Light Emitting Diode (LED), a revolutionary advancement in lighting technology, has opened up new avenues for enriching the variety of light colors. Currently, coating LED chips with light-converting agents is the mainstream technology for developing new light-colored LED light sources, known as "light-to-light" LEDs. However, the light-converting agents used in this technology are mainly rare-earth-containing inorganic composite luminescent materials, which are not only limited in variety but also constrained by non-renewable rare-earth strategic resources. To date, pale yellow LED devices are still rare.

[0003] Metal-organic coordination supramolecular light-converting materials constructed through coordination bonds and other interactions are a class of advanced crystalline light-emitting materials with ordered structures. These materials possess well-defined microscopic electronic structures and high purity, representing an important direction for the development of novel non-rare-earth light-converting materials. However, given the numerous factors influencing chemical reaction processes and the difficulty in predicting outcomes, obtaining new materials with novel structures and specific functions remains a challenging and cutting-edge research focus in the field of light-emitting materials. Summary of the Invention

[0004] In view of the above-mentioned shortcomings in the existing technology, the purpose of this invention is to provide a light-converting material with a double-belt helical structure, and to measure its precise electronic structure. LED devices made with this new material can emit a rare pale yellow light when operating at low power.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a light-converting material containing a double-belt helical structure, with the general chemical formula [Cd(edd)(bpy)]. n It belongs to the triclinic crystal system and has the space group [missing information]. Unit cell parameters In the general chemical formula, component edd 2- It is obtained by removing two protons from the dicarboxylic acid H2edd, the structure of which is shown in Formula I; the structure of bpy is shown in Formula II.

[0006]

[0007] Furthermore, the asymmetric unit cell of the crystal structure of the light-converting material contains one Cd atom. 2+ Ions, 1 edd 2- And 1 bpy component; the organic component edd 2- With 3 Cd 2+ Ion coordination, while the organic component bpy bridges two Cd atoms. 2+ Ions; Cd 2+ The ion adopts a seven-coordinate mode, that is, it coordinates with 2 pyridine N atoms and 5 carboxyl oxygen atoms, further forming a binuclear cluster [Cd2N4O8], Cd1···Cd1 #1 Distance is The coordination mode is shown in Equation III; in Equation III, the numbers to the right of the element symbols indicate the atom numbers in the unit cell, and the superscript # indicates crystallographic symmetry transformation (see Table 1).

[0008]

[0009] Furthermore, in the spatial structure of the light-converting material, the organic component edd 2- The internal functional groups of bpy are not completely coplanar, exhibiting significant distortion; through Cd-O coordination bonds, edd 2- With bridge Cd 2+ Ions form a PM-type one-dimensional infinite double helix with common nodes, and the helical band contains dimensions. The macrocycle is further connected to the helical band via Cd-N coordination bonds to form a two-dimensional metal-organic coordination polymer layer; the coordination polymer layers are further superimposed to form a stable three-dimensional supramolecular aggregate.

[0010] The aforementioned light-converting material with a double-belt helical structure was prepared by a solvothermal synthesis method using H2edd, bpy, Cd(NO3)2·4H2O and HNO3 as raw materials and a mixed solution of DMF and water as solvent.

[0011] Furthermore, the preparation method specifically includes the following steps:

[0012] (1) Mix the above raw materials and solvent to form a reaction system and place it in a sealed container; the molar ratio of the raw materials H2edd:bpy:Cd(NO3)2·4H2O:HNO3 is 1:1:2:0~2.45; the volume ratio of the solvent DMF to water is 2~10:2~10;

[0013] (2) Stir the reaction system at room temperature for 10-30 minutes, then raise the reaction temperature to 100-120℃ and react for 2-4 days. After that, cool naturally, filter and dry to obtain block crystals.

[0014] Furthermore, the molar ratio of H2edd:bpy:Cd(NO3)2·4H2O:HNO3 in step (1) is 1:1:2:1.75.

[0015] Furthermore, the initial molar concentration of bpy in the reaction system is 8.3 mmol / L.

[0016] Furthermore, the reaction temperature of the reaction system in step (2) is 120°C; the drying refers to the crystals being washed with distilled water and then naturally dried in the air at room temperature.

[0017] The application of the light-converting material with a double-belt helical structure prepared by the above method in the preparation of characteristic light yellow LED devices and composite fluorescent materials.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The optically convertible material with a double-belt helical structure prepared in this invention is a crystalline non-rare earth metal-organic coordination supramolecular crystalline material with a well-defined microstructure. In its periodically extended spatial structure, through Cd-O coordination bonds, edd 2- Bridge Cd 2+ Ions form a PM-type one-dimensional infinite double helix with co-nodes. The bpy-bridged helical bands further form a two-dimensional metal-organic coordination polymer layer. The organic component in the crystal structure is edd. 2- The internal functional groups of bpy are not completely coplanar, and multiple conjugated systems exist, indicating that electron transitions between energy levels may emit photons of various wavelengths or energies. These structural features provide a paradigm for the research of novel crystalline optical conversion materials.

[0020] (2) The light-converting material with a double-belt helical structure prepared by the present invention does not contain rare earth elements, has a yield of about 75%, and has good thermal stability; it exists stably in common solvents such as water and DMF; the crystal sample of this material exhibits yellow-green fluorescence under ultraviolet light excitation.

[0021] (3) The light-converting material with a double-belt helical structure provided by the present invention is used as a single-component light-converting agent. The LED encapsulated by the "light-to-light" technology emits a characteristic light yellow light under low power driving, with a correlated color temperature of 4426K and a wavelength of 567.8nm. The device spectrum has a certain intensity of violet light emission peak, with the violet light peak wavelength located at 420nm. The LED is a characteristic light yellow light device, which has application prospects in the preparation of instrument indicator lights, full-spectrum high-power light sources, etc. Attached Figure Description

[0022] Figure 1 This is the X-ray powder diffraction pattern of the optical conversion material of this invention;

[0023] Figure 2 This is a thermogravimetric curve of the optical conversion material of the present invention;

[0024] Figure 3 This is a single-crystal fluorescence photograph of the optical conversion material of this invention. The actual material emits yellow-green fluorescence under a 365nm ultraviolet lamp.

[0025] Figure 4 The infrared spectrum of the light-converting material of this invention is shown below.

[0026] Figure 5 Figure 1 shows the crystal structure of the light-converting material of the present invention, wherein Figure (a) shows the organic component edd 2- With bpy and Cd 2+ Bridged coordination modes; Figure (b) shows a binuclear polyhedron composed of [Cd₂N₄O₈]; Figure (c) shows a Cd 2+ and edd 2- A PM-type double-band helical structure is formed; Figure (d) shows a nanoscale macroring composed of [Cd2(edd)2]; Figure (e) is a simplified schematic diagram of the double-band helical structure.

[0027] Figure 6 This is a three-dimensional supramolecular structure diagram of the light-converting material of the present invention, with the cylindrical bridging component being bpy;

[0028] Figure 7 The images show the emission spectrum, colorimetric diagram, and photographs of an LED device encapsulated with the light-converting material of this invention as a single-component light-converting agent during operation. Detailed Implementation

[0029] The method of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The present invention uses X-ray single-crystal diffraction to analyze the crystalline product, obtaining its precise electronic structure, and performs a series of characterizations on the final product, determining its general chemical formula as [Cd(edd)(bpy)]. n The yield is calculated based on the amount of bpy used. That is, based on the molar percentage of bpy in the product composition, the theoretically expected mass of the target material is calculated, and the ratio of the actual product mass to the former is the yield. In this invention, the Chinese name for H2edd is (2E,2'E)-3,3-((ethyl-1,2-dimethylbis(oxy))bis(2,1-phenylene))diacrylic acid, and the Chinese name for bpy is 4,4'-bipyridine.

[0030] I. Preparation of the light-converting material containing a double-belt helical structure according to the present invention

[0031] Example 1

[0032] Take the following materials by specific mass or volume: H2edd (35.4 mg, 0.1 mmol), bpy (15.6 mg, 0.1 mmol), Cd(NO3)2·4H2O (61.8 mg, 0.2 mmol), DMF (2 mL), H2O (10 mL), and HNO3 solution (7 mol / L, 25 μL, 0.175 mmol). The molar ratio of H2edd:bpy:Cd(NO3)2·4H2O:HNO3 is 1:1:2:1.75. Place the above materials in a 25 mL polytetrafluoroethylene-lined container, stir for about 15 min, seal in a stainless steel reactor, place the reactor in an electric heating oven and heat to 120°C. After heating for one hour, remove and cool (optional). Add HNO3 and continue the reaction for 3 days. After naturally cooling to room temperature, obtain a strip-shaped crystal sample. Filter it from the mother liquor, wash with distilled water, and air dry naturally at room temperature.

[0033] The prepared crystal samples were subjected to powder diffraction tests using a Shimadzu XRD-6100 X-ray diffractometer (see...). Figure 1 (x-axis—angle; y-axis—diffraction intensity). The peaks of the test spectrum match well with the peaks of the simulated crystal structure spectrum (mercury software), indicating that the structure of the obtained crystalline sample is the same as the structure analyzed from the single crystal data, suggesting that the crystalline sample has high phase purity.

[0034] Figure 2 Thermogravimetric curve of an optically convertible material containing a double-belt helical structure, from Figure 2 It can be seen that the thermogravimetric data analysis of the obtained crystalline samples shows (see...) Figure 2 (Under nitrogen atmosphere, x-axis—temperature; y-axis—residue). The crystalline sample of the optically converting material showed no significant weight loss before 240℃, indicating that the sample did not contain solvent molecules. Significant weight loss occurred after 240℃, possibly due to framework collapse or decomposition. This indicates that the optically converting material with a double-belt helical structure prepared in this invention has good thermal stability.

[0035] like Figure 3 As shown in the photograph, the bulk single crystal sample of the light-converting material exhibits yellow-green fluorescence under a 365nm ultraviolet lamp. The photograph indicates that the new material is a crystalline solid material with downward light-converting properties.

[0036] Determination of single crystal structure: Select a suitable single crystal and perform the determination on a SMARTAPEXIIC ZN single crystal diffractometer (Mo-Ka, X-ray diffraction data were collected at room temperature using a graphite monochromator and corrected for the Lp factor. The crystal structure was solved directly, and the analytical and refinement of the structure were performed using the SHELXTL-97 package, followed by full-matrix least squares F-method. 2Anisotropic refinement was performed on all non-hydrogen atoms. The hydrogen atom coordinates of the organic ligands were obtained by theoretical hydrogen addition. Crystallographic data are shown in Table 1; coordinate bond lengths are shown in Table 2.

[0037] Table 1. Main crystallographic data

[0038]

[0039] *R1=Σ||F o |-|F c || / Σ|F o |,wR2=[Σ w (F o 2 -F c 2 ) 2 / Σ w (F o 2 ) 2 ] 1 / 2

[0040] Table 2 Coordination bond lengths

[0041]

[0042] Symmetrical transformations: #1 -x+2, -y+1, -z+1; #2 x, y-1, z; #3 -x+1, -y, -z+1; #4 x, y+1, z

[0043] Based on the above characterization data, the general formula of the optically convertible material containing a double-belt helical structure is [Cd(edd)(bpy)]. n The chemical formula of the asymmetric unit is C 30 H 24 N2O6Cd has a chemical formula weight of 620.92. Elemental analysis of C, H, and N shows the following calculated values ​​(%): C 58.03, H 3.90, N 4.51; and the actual measured values ​​(%): C 58.01, H 3.88, N 4.47. Figure 4 The infrared spectrum of the novel substance of this invention (x-axis—wavenumber; y-axis—transmittance). FT-IR (KBr, cm⁻¹) -1 3045(w), 2929(w), 1636(m), 1545(s), 1389(vs), 1238(s), 975(m), 761(vs), 626(s). Note: Elemental analysis values ​​were obtained using a Perkin-Elmer 2400 elemental analyzer; infrared spectra were obtained using a Perkin-Elmer FT-IR Spectrometer with KBr as the base, ranging from 400 to 4000 cm⁻¹. -1 Measured within the range.

[0044] The precise electronic structure was obtained by analyzing its X-ray single-crystal diffraction data. The coordination mode and partial crystal structure are shown below. Figure 5 As shown in figure a, the asymmetric unit cell of the crystal structure of the optically convertible material contains one Cd atom. 2+ Ions, 1 edd 2- And 1 bpy component; the organic component edd 2- With 3 Cd 2+ In ion coordination, the twist angle between the functional groups aromatic ring (C4) and -CH=CH-(C3) is 20°, and the twist angle between -CH=CH(C3)- and -COO-(O1) is 9°, indicating a conjugation effect among the three groups. Meanwhile, the twist angle between aromatic ring (C17) and -CH=CH-(C19) is 34°, and the twist angle between -CH=CH(C19)- and -COO- is... - The twist angle between the (O5) groups is 18°, indicating that the conjugation effect among the three groups is reduced; the organic component 4,4'-bipyridine (bpy) bridges two Cd groups. 2+ The ion, with a twist angle of approximately 28° between the two aromatic rings in its structure, indicates a significant reduction in conjugation compared to coplanarity. (Cd) 2+ The ion adopts a seven-coordinate mode, that is, it coordinates with 2 pyridine N atoms and 5 carboxyl oxygen atoms, further forming a binuclear cluster [Cd2N4O8], Cd1···Cd1 #1 Distance is Coordination mode such as Figure 5 As shown in b. As shown in Table 1, the Cd-O / N bond length is... The range refers to common coordination bond lengths. Organic components edd 2- The multiple twist angles present in the bpy structure, i.e. the existence of complex molecular orbital energy levels, indicate that electron transitions between energy levels may emit photons of multiple wavelengths or energies.

[0045] like Figure 5 As shown in c and 5e, in the spatially extended structure of the light-converting material, the organic component edd 2- With bridge Cd 2+ Ions form a PM-type one-dimensional infinite double helix with common nodes, and the helical band contains dimensions. Large ring ( Figure 5 d). For example Figure 6 As shown, the organic component bpy bridges the double-banded helices through Cd-N coordination bonds, further forming a two-dimensional metal-organic coordination polymer layer; the two-dimensional layer is further superimposed through interlayer supramolecular interactions to form a stable three-dimensional supramolecular aggregate, in which the interlayer P-helical structure and M-helical structure are adjacent.

[0046] This embodiment was repeated multiple times, and the actual mass of the light-converting material containing the double-belt helical structure remained at 43.7–46.4 mg, with a yield of 70.4%–74.7% calculated based on bpy.

[0047] Example 2

[0048] Take the following materials by specific mass or volume: H2edd (35.4 mg, 0.1 mmol), bpy (15.6 mg, 0.1 mmol), Cd(NO3)2·4H2O (61.8 mg, 0.2 mmol), DMF (6 mL), H2O (6 mL), and HNO3 solution (7 mol / L, 35 μL, 0.245 mmol). The molar ratio of H2edd:bpy:Cd(NO3)2·4H2O:HNO3 is 1:1:2:2.45. Place the above materials in a 25 mL polytetrafluoroethylene-lined container, stir for about 10 min, seal in a stainless steel reactor, place the reactor in an electric heating oven and heat to 100 °C. After reacting for 4 days, allow to cool naturally to room temperature to obtain strip-shaped crystal samples. Filter from the mother liquor, wash with distilled water, and air dry naturally at room temperature. Characterize the product powder by X-ray diffraction (see...). Figure 1 The data obtained were similar to those of Example 1. This indicates that the crystal structure obtained using Example 2 remained unchanged, and the product had high purity.

[0049] This embodiment was repeated multiple times, and the actual mass of the light-converting material containing the double-belt helical structure was maintained at 26.4–36.5 mg, with a yield of 42.5%–58.8% calculated based on bpy.

[0050] Example 3

[0051] Take the following materials by specific mass or volume: H2edd (35.4 mg, 0.1 mmol), bpy (15.6 mg, 0.1 mmol), Cd(NO3)2·4H2O (61.8 mg, 0.2 mmol), DMF (10 mL), and H2O (2 mL). The molar ratio of H2edd:bpy:Cd(NO3)2·4H2O is 1:1:2. Place the above materials in a 25 mL polytetrafluoroethylene-lined container, stir for about 30 min, seal in a stainless steel reactor, place the reactor in an electric heating oven and heat to 110°C. After reacting for 2 days, allow it to cool naturally to room temperature to obtain a fine crystalline sample. Filter the sample from the mother liquor, wash with distilled water, and allow it to air dry naturally at room temperature.

[0052] Powder X-ray diffraction characterization of the product (see Figure 1 The data obtained were similar to those of Example 1. This indicates that the crystal structure obtained using Example 3 remained unchanged, and the product had high purity.

[0053] This embodiment was repeated multiple times, and the actual mass of the light-converting material containing the double-belt helical structure was maintained at 12.1–25.2 mg, with a yield of 19.5%–40.6% calculated based on bpy.

[0054] II. Preliminary Application of the Optical Conversion Material Containing a Double-Belt Helical Structure of the Invention

[0055] Example 4: Fabrication of a light yellow LED device

[0056] In the experiment, a standard capped 390nm wavelength violet LED chip was used for encapsulation, with a chip power of approximately 1W. A light-converting material with a double-belt helical structure was encapsulated onto the LED chip and cured for 72 hours to obtain the LED device.

[0057] The emission spectrum of the LED was tested under a constant current of 20mA (voltage 3V). Figure 7 This diagram shows the emission spectrum and chromaticity coordinates of the LED device during operation, along with photographs of the device before and after emission (horizontal axis—wavelength, vertical axis—intensity). Data analysis indicates that the LED device emits a correlated color temperature of 4426K, a dominant wavelength of 567.8nm, and a color purity of 62.4%. In the 2-degree field-of-view CIE 1931 chromaticity diagram, the color coordinates (0.3852, 0.4793) place it in the intermediate color region, where yellow light approaches white light.

[0058] The emission spectrum of the encapsulated LED device shows that the strongest peak wavelength is at 559nm (normalized intensity 100%); there is also a violet emission peak of a certain intensity, with a wavelength at 420nm and a normalized intensity of approximately 50%. The spectral chromaticity coordinates of the device indicate a color consistent with the actual photograph, which is either light yellow or warm white. Although it is difficult for the human eye to distinguish between light yellow and warm white light, according to the principle of three primary colors composite, the spectrum contains less blue light and has higher color purity. Therefore, classifying the light color as light yellow is more reasonable. The encapsulated LED is a unique light yellow light device with promising applications in the manufacture of instrument indicator lights and full-spectrum high-power light sources.

[0059] The preliminary data of the LED devices prepared by this invention show that the light-converting material with a double-belt helical structure, as a single-component light-converting agent, can efficiently convert the purple light of the LED chip into a distinctive light yellow light, saving rare earth resources and providing experimental data for the development of new non-rare earth, single-component advanced light-emitting materials.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A light-converting material containing a double-belt helical structure, characterized in that, Its general chemical formula is [Cd(edd)(bpy)] n It belongs to the triclinic crystal system and has the space group [missing information]. P ī, cell parameters a =9.746(5)Å, b =11.663(6) Å, c = 15.525(9)Å, V =1485.9(14) Å 3 In the general chemical formula, component edd 2- It is obtained by removing two protons from the dicarboxylic acid H2edd, the structure of which is shown in Formula I; the structure of bpy is shown in Formula II. The asymmetric unit cell of the crystal structure of the optically convertible material contains one Cd atom. 2+ Ions, 1 edd 2- and 1 bpy component; the edd 2- With 3 Cd 2+ Ion coordination, while the organic component bpy bridges two Cd atoms. 2+ Ions; Cd 2+ The ion adopts a seven-coordinate mode, that is, it coordinates with 2 pyridine N atoms and 5 carboxyl oxygen atoms, further forming a binuclear cluster [Cd2N4O8], Cd1···Cd1 #1 The distance is 4.023 Å, and the coordination mode is shown in Equation III; in Equation III, the numbers to the right of the element symbols indicate the atom numbers in the unit cell, and the superscript # sign indicates a crystallographic symmetry transformation. 。 2. The light-converting material with a double-belt helical structure according to claim 1, characterized in that, In the spatial structure of the light-converting material, the organic component edd 2- The internal functional groups of bpy are not completely coplanar, exhibiting significant distortion; through Cd-O coordination bonds, edd 2- With bridge Cd 2+ Ions forming common nodes PM The helical ribbon is a one-dimensional infinite double helix containing a macrocycle with dimensions of 10 Å × 12 Å. Through Cd-N coordination bonds, the bpy bridges the helical ribbon to further form a two-dimensional metal-organic coordination polymer layer. The coordination polymer layers are further superimposed to form a stable three-dimensional supramolecular aggregate.

3. A method for preparing a light-converting material containing a double-belt helical structure as described in any one of claims 1 to 2, characterized in that, The light-converting material is prepared by a solvothermal synthesis method using H2edd, bpy, Cd(NO3)2·4H2O and HNO3 as raw materials and a mixed solution of DMF and water as solvent.

4. The method for preparing the optically convertible material containing a double-belt helical structure according to claim 3, characterized in that, The preparation method specifically includes the following steps: (1) Mix the above raw materials and solvent to form a reaction system and place it in a sealed container; the molar ratio of the raw materials H2edd:bpy:Cd(NO3)2·4H2O:HNO3 is 1:1:2:0~2.45; the volume ratio of the solvent DMF to water is 2~10:2~10; (2) Stir the reaction system at room temperature for 10-30 min, then raise the reaction temperature to 100-120℃ and react for 2-4 days. After that, cool naturally, filter and dry to obtain strip-shaped crystals.

5. The method for preparing the optically convertible material containing a double-belt helical structure according to claim 4, characterized in that, The molar ratio of H2edd:bpy:Cd(NO3)2·4H2O:HNO3 in step (1) is 1:1:2:1.

75.

6. The method for preparing a light-converting material with a double-belt helical structure according to claim 4, characterized in that, The initial molar concentration of bpy in the reaction system was 8.3 mmol / L.

7. The method for preparing the optically convertible material containing a double-belt helical structure according to claim 4, characterized in that, The reaction temperature of the reaction system in step (2) is 120°C; the drying refers to the crystals being washed with distilled water and then naturally dried in the air at room temperature.

8. An application of a light-converting material containing a double-belt helical structure, characterized in that, Application of light-converting materials with a double-belt helical structure prepared by any of the methods described in claims 3 to 7 in the preparation of light yellow LED devices and composite fluorescent materials.

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