Organic room-temperature phosphorescent material as well as preparation method and application thereof

Abstract

The invention belongs to the field of room-temperature phosphorescent materials, and particularly discloses an organic room-temperature phosphorescent material as well as a preparation method and application thereof. The molecular formula of the compound is [X (mda) 4 (H2O) 4] n, X represents alkaline earth metal, mda represents H2mda after dehydrogenation, and H2mda is imidazole-4, 5-dicarboxylic acid. The preparation method comprises the following steps: adding H2mda and water-soluble salt of alkaline earth metal into H2O, uniformly stirring, carrying out hydrothermal reaction at 115-125 DEG C for 2.5-3.5 days, and cooling to room temperature to obtain a solid which is the target product organic room-temperature phosphorescent material. The organic room-temperature phosphorescent material is applied to anti-counterfeiting marks, data security protection or biological imaging. The method adopts a hydrothermal method, is simple and quick, is high in product purity and is suitable for industrial large-scale popularization; according to the organic room-temperature phosphorescent material, the afterglow of 3.5 s can be observed by naked eyes, and the organic room-temperature phosphorescent material has potential application prospects in the fields of anti-counterfeiting marks, data security protection or biological imaging.

Description

Technical Field

[0001] The invention belongs to the field of room temperature phosphorescent materials, and in particular relates to an organic room temperature phosphorescent material and a preparation method and application thereof. Background Art

[0002] Organic room temperature phosphorescent (RTP) materials have attracted widespread attention from the scientific community due to their unique advantages such as structural diversity, rich functionality and excellent biocompatibility. This type of material with long-life RTP characteristics has shown broad application prospects in many fields such as anti-counterfeiting labels, data security protection and bioimaging. Generally speaking, the RTP properties of pure organic molecules are largely affected by intermolecular interactions. These strong intermolecular interactions play a vital role. They can break the spin-forbidden transition barrier between the excited singlet and triplet states, thereby realizing an efficient intersystem crossing (ISC) process. At the same time, these interactions can effectively stabilize the excited triplet state, thereby promoting the lasting manifestation of the RTP effect. So far, the use of transition metal ions (such as Zn 2+ 、Cd 2+ The phosphorescence lifetime of MOFs constructed with alkaline earth metal ions (such as Sr 2+ , Ba 2+ MOFs with alkaline earth metals as the core generally show the characteristics of short phosphorescence lifetime due to the inherent weak spin-orbit coupling (SOC) of the central light metal ions. However, it cannot be ignored that alkaline earth metals are abundant in the earth's crust, and compared with transition metals and rare earth metals, they have the obvious advantage of being non-toxic or low-toxic. In view of this, alkaline earth metal ions have great potential to become an ideal choice for creating efficient luminescent MOFs. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention aims to provide an organic room temperature phosphorescent material and a preparation method and application thereof.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows: An organic room temperature phosphorescent material, the molecular formula of which is [X(mda) 4 (H 2 O) 4 ] n , where X represents alkaline earth metal and mda represents H after dehydrogenation. 2 mda,H 2 MDA is imidazole-4,5-dicarboxylic acid, H 2 The structural formula of MDA is as follows: .

[0005] Preferably, X is an alkaline earth metal Sr, and the molecular formula of the corresponding organic room temperature phosphorescent material is [Sr(mda) 4 (H 2 O) 4 ] n .

[0006] Preferably, [Sr(mda) 4 (H 2 O) 4 ] n The crystal structure is monoclinic, the space group is C2 / c, and the unit cell parameters are: a=21.033(2) Å, b=21.0179(19) Å, c=13.6696(14) Å, α=90°, β=113.100(4)°, γ=90°.

[0007] A method for preparing the organic room temperature phosphorescent material: 2 MDA and water-soluble salts of alkaline earth metals are added together with H 2 O, stir evenly, perform hydrothermal reaction at 115-125°C for 2.5-3.5 days, then cool to room temperature, and the obtained solid is the target product, an organic room temperature phosphorescent material.

[0008] Preferably, the water-soluble salt of the alkaline earth metal is measured by the alkaline earth metal element therein, in a molar ratio, H 2 mda: water-soluble salt of alkaline earth metal = 1:2, and every 0.04mmol H 2 tda, the amount of mixed solvent used is 2.5~3.5mL.

[0009] Preferably, the water-soluble salt of the alkaline earth metal is a nitrate or chloride salt.

[0010] Preferably, the cooling rate is (5-15)°C / 40min.

[0011] An application of the organic room temperature phosphorescent material in anti-counterfeiting marking, data security protection or biological imaging.

[0012] Beneficial effects: (1) The present invention adopts a hydrothermal method, which is simple and fast, has high product purity, and is suitable for large-scale industrial promotion; (2) The organic room temperature phosphorescent material of the present invention has an afterglow of 3.5 seconds that can be observed by the naked eye, and has potential application prospects in the fields of anti-counterfeiting labels, data security protection or biological imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 :[Sr(mda) prepared in Example 1 4 (H 2 O) 4 ]n Coordination environment diagram.

[0014] Figure 2 :[Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n PXRD spectrum of .

[0015] Figure 3 :[Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n Luminescence spectrum at room temperature: Fluor. is the fluorescence emission spectrum, Phos. is the phosphorescence emission spectrum.

[0016] Figure 4 :[Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n Afterglow image after irradiation with UV light at 365 nm excitation.

[0017] Figure 5 :[Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n Lifetime decay curves at room temperature: the left figure is the fluorescence lifetime decay curve, and the right figure is the phosphorescence lifetime decay curve.

[0018] Figure 6 : Crystals prepared in Example 1 [Sr (mda) 4 (H 2 O) 4 ] n The pattern changes of the "four-leaf clover" pattern under different light sources: (a) irradiation under sunlight; (b) irradiation under 365 nm ultraviolet light; (c) 0.1s after turning off the ultraviolet light; (d) 1.0s after turning off the ultraviolet light; (e) 3.0s after turning off the ultraviolet light. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0020] In the following examples: All chemical reagents used were purchased from commercial sources, their purity level was analytical grade, and no additional purification steps were performed; the drug imidazole-4,5-dicarboxylic acid (H 2 MDA) was purchased from Zhengzhou Anmusi Chemical Products Co., Ltd.; all water used in the experiments was deionized water.

[0021] Test instrument: The infrared spectroscopy (IR) analysis of the samples was carried out using a Bruker Tensor 27 infrared spectrometer. Potassium bromide was used for tableting during the test, and the test covered a wavelength range of 400 to 4000 cm -1 ; Elemental analysis (for C, H, and N elements) was performed using a FLASH EA 1112 elemental analyzer; solid-state fluorescence and phosphorescence spectra of the samples were acquired using a Hitachi F-4600 fluorescence spectrometer; powder X-ray diffraction (PXRD) analysis was performed using a PANalytical X'Pert diffractometer, using Cu-K a X-rays were used as the radiation source; the room temperature phosphorescence lifetime rate was determined by an Edinburgh FLS980 steady-state transient fluorescence spectrometer.

[0022] Data collection and analysis of crystal structure: First, carefully select the samples of appropriate size, regular shape and transparency from the crystals. Then, use Bruker APEX-II CCD diffractometer with Cu-Ka ray (λ=0.71073 Å) as the radiation source to collect the diffraction data of these crystals. The crystal structure is directly solved by SHELXS-97 program, and the SHELXL-2014 program is used to use the full matrix least squares method F 2 After structural optimization, detailed information such as crystallographic parameters, crystallization data, bond lengths, and bond angles were finally collated and listed in the attached table.

[0023] Example 1

[0024] The preparation route is as follows: .

[0025] Preparation process: Accurately weigh H 2 MDA (6.2 mg, 0.04 mmol) and Sr(NO 3 ) 2 (17.0 mg, 0.08 mmol), and 3 mL of H 2 O, stirred with a glass rod for 5 min, transferred to a 25 mL polytetrafluoroethylene liner, placed in a reactor and heated to 120 °C, kept reacting for 3 days, then cooled to room temperature at 10 °C / 40 min, and pale yellow transparent block crystals [Sr(mda) 4 (H2 O) 4 ] n , yield (based on Sr): 72%.

[0026] Molecular formula C 20 H 22 N 8 O 20 Sr (782.08), elemental analysis calculated value (%): C, 30.72; H, 2.84; N,14.33; measured value: C, 31.34; H, 2.53; N, 14.95. It can be seen that the calculated value and the measured value are basically consistent.

[0027] IR (KBr, cm -1 ): 3559.33s, 3174.69m, 2867.08w, 1941.74m, 1651.50m, 1521.54m, 1392.39m, 1242.46s, 1096.90w, 845.99m, 774.24s, 530.42m.

[0028] Example 1 Preparation of [Sr (mda) 4 (H 2 O) 4 ] n The crystallographic data are shown in Table 1.

[0029]

[0030] Example 1 Preparation of [Sr (mda) 4 (H 2 O) 4 ] n The coordination environment diagram is as follows Figure 1 As shown (for clarity, all hydrogen atoms have been omitted). It can be seen that the asymmetric unit contains a Sr 2+ , four mda 2- The metal Sr(II) is eight-coordinated, and all eight atoms are monodentate coordinated, of which (O4, O8, O11, O13) are from the ligand H. 2 The carboxylic acid oxygen atom on mda, while (O17, O18, O19, O20) atoms come from the oxygen atoms of the coordinated water molecules. Bond length Sr-O: 2.56(2) Å~2.65(2) Å, [the bond angle around Sr (II) is 70.7(8)~155.1(7)º], the above bond lengths and bond angles are consistent with those reported for Sr (II) complexes.

[0031] Figure 2 [Sr(mda) prepared in Example 14 (H 2 O) 4 ] n From the PXRD spectrum analysis, all the main strong diffraction peaks are consistent with the single crystal structure simulation results.

[0032] Figure 3 [Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n The emission spectrum at room temperature: Fluor. is the fluorescence emission spectrum, Phos. is the phosphorescence emission spectrum. Figure 3 It can be observed that the maximum fluorescence emission (Em) wavelength is 464nm, and at the same time, the corresponding maximum fluorescence excitation (Ex) wavelength of the crystal is 375nm; the maximum phosphorescence emission (Em) wavelength is 504nm, and at the same time, the corresponding maximum phosphorescence excitation (Ex) wavelength of the crystal is 291nm.

[0033] Figure 4 [Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n Afterglow image after irradiation with ultraviolet light at 365nm excitation. Figure 4 As shown: when the UV lamp is turned off, yellow light is emitted first and then turns into green light. This transformation and the subsequent green light emission process last for a total of about 3.5 seconds.

[0034] In order to understand the luminescence of the crystal more accurately, we tested its transient lifetime using a double exponential fitting mode. I 0 = I+A 1 exp( t / τ 1 )+ A 2 exp( t / τ 2 )( I 0 and I They are τ =0 and τ = t Fluorescence or phosphorescence intensity at ; τ 1 and τ 2 Represents the fluorescence or phosphorescence decay lifetime; A 1 and A 2 is the amplitude of each component) to fit the crystal. Figure 5 [Sr(mda) prepared in Example 1 4 (H 2 O) 4 ] n Lifetime decay curves at room temperature: the left figure is the fluorescence lifetime decay curve, and the right figure is the phosphorescence lifetime decay curve. Figure 5 As shown, when the fluorescence emission wavelength of the crystal is 464 nm, the fluorescence lifetime of the crystal is 3.52 ns, and when the phosphorescence emission wavelength of the crystal is 504 nm, the phosphorescence lifetime of the crystal is 255.82 ms.

[0035] Application of crystals in anti-counterfeiting A self-made pattern, which consists of a group of crystals prepared in Example 1 [Sr (mda) 4 (H 2 O) 4 ] n The image of a "four-leaf clover". Figure 6 a. Under natural light, the “four-leaf clover” appears white as a whole, but when it is illuminated by a 365nm ultraviolet excitation light source, the pattern turns blue ( Figure 6 b); 0.1s after the UV light is turned off, the "four-leaf clover" first shows yellow phosphorescence ( Figure 6 c), and then when the UV light is turned off 1.0s later, the "four-leaf clover" turns into green phosphorescence ( Figure 6 d), and then 3.0s after the UV lamp is turned off, the light of the "four-leaf clover" gradually becomes blurred ( Figure 6 e) and finally disappear.

Claims

1. An organic room temperature phosphorescent material, characterized in that: Its molecular formula is [X(mda)4(H2O)4] n , wherein X represents an alkaline earth metal, mda represents H2mda after dehydrogenation, and H2mda is imidazole-4,5-dicarboxylic acid.

2. The organic room temperature phosphorescent material according to claim 1, characterized in that: X is an alkaline earth metal Sr, and the molecular formula of the corresponding organic room temperature phosphorescent material is [Sr(mda)4(H2O)4] n .

3. The organic room temperature phosphorescent material according to claim 2, characterized in that: [Sr(mda)4(H2O)4] n The crystal structure is monoclinic, the space group is C2 / c, and the unit cell parameters are: a=21.033(2) Å, b=21.0179(19) Å, c=13.6696(14) Å, α=90°, β=113.100(4)°, γ=90°.

4. A method for preparing an organic room temperature phosphorescent material as claimed in any one of claims 1 to 3, characterized in that: Add H2MDA and water-soluble salt of alkaline earth metal into H2O, stir evenly, perform hydrothermal reaction at 115-125°C for 2.5-3.5 days, then cool to room temperature, and the obtained solid is the target product, organic room temperature phosphorescent material.

5. The method for preparing an organic room temperature phosphorescent material as claimed in claim 4, characterized in that: The water-soluble salt of alkaline earth metal is measured based on the alkaline earth metal element therein, and the molar ratio of H2mda: water-soluble salt of alkaline earth metal is 1:2, and the amount of mixed solvent used is 2.5-3.5 mL for every 0.04 mmol H2tda.

6. The method for preparing an organic room temperature phosphorescent material according to claim 4, characterized in that: The water-soluble salts of alkaline earth metals are nitrates or chlorides.

7. The method for preparing an organic room temperature phosphorescent material according to claim 4, characterized in that: The cooling rate is (5~15)℃ / 40min.

8. Use of the organic room temperature phosphorescent material as claimed in any one of claims 1 to 3 in anti-counterfeiting labels, data security protection or biological imaging.

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