Near-infrared organic free radical afterglow material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of organic light-emitting materials, and particularly discloses a near-infrared organic free radical afterglow material and a preparation method and application thereof. On the basis of a compound molecule TPP-o-3OMe-NH2-Br, a push-pull electron group 6-(dimethylamino) naphthalimide (NNI) and a push-pull electron group 6-bromonaphthalimide (NBI) are introduced, and the molecules TPP-o-3OMe-NNI-Br and TPP-o-3OMe-NBI-Br are designed and synthesized; after the TPP-o-3OMe-NNI-Br and the TPP-o-3OMe-NBI-Br are doped in the polymer PMMA, the long afterglow emission characteristic of different light activation times is achieved; the light activation time of the afterglow of the TPP-o-3OMe-NBI-Br coated PMMA film is obviously shortened, and the emission of the red afterglow is successfully realized by the TPP-o-3OMe-NNI-Br coated PMMA film; finally, the application of multi-color display and storage of optical information is achieved by combining the light-emitting characteristics of the two films, and the material is expected to provide a new thought for development of organic free radical light-emitting materials and multi-information encryption application.

Description

Technical Field

[0001] The invention belongs to the technical field of organic luminescent materials, and in particular relates to a near-infrared organic free radical afterglow material and a preparation method and application thereof. Background Art

[0002] Compared with inorganic luminescent materials, organic luminescent materials can change their luminescent properties (lifespan, color regulation, and luminescent intensity) by designing their molecular structures. They have more convenient synthesis strategies, broader application prospects, and good environmental protection. They can well solve the problems of inorganic luminescent materials in resource scarcity and environmental pollution (most inorganic luminescent materials require the introduction of rare metal elements). At present, organic luminescent materials have broad application prospects in the fields of electroluminescence, organic lasers, sensors, and bio-imaging.

[0003] Among organic light-emitting materials, those that can emit red light have excellent tissue penetration and anti-interference capabilities, which are particularly important for biological imaging, information encryption technology, information storage and other fields under extreme environments, and have very important research significance. Up to now, the red-light-emitting materials are mainly fluorescence with singlet-state radiation inactivation and phosphorescence with triplet-state inactivation in terms of luminescence mechanism. How to develop a class of free radical luminescent materials that can achieve red afterglow emission under different states is still a challenging problem. Studies have shown that organic quaternary phosphonium salts have good water solubility. In recent years, some researchers have also introduced benzene rings, carbazole and other π-conjugated groups to regulate the luminescence range and constructed many organic quaternary phosphonium salts with long afterglow materials. These studies provide new ideas for the design and regulation of quaternary phosphonium salt red fluorescence and red afterglow. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a near-infrared organic free radical afterglow material and a preparation method and application thereof.

[0005] In the first aspect, the present invention provides a near-infrared organic free radical afterglow material, the general structural formula of which is

[0006]

[0007] Wherein, the R includes

[0008]

[0009] They respectively constitute the aromatic quaternary phosphonium salt derivatives TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned near-infrared organic free radical afterglow material, comprising the following steps:

[0011] S1. Synthesis of compound TPP-o-3OMe-NH2-Br: tri(2-methoxyphenyl)phosphine and 2-bromoethylamine hydrobromide were added to a reaction flask, CH3CH2CN was added to dissolve, and the mixture was refluxed with stirring overnight. After the reaction was completed, the solvent was vacuum dried, ultrapure water was added to the obtained solid powder, and NaOH was added to adjust the pH, and then the crude product was extracted with EA. The crude product was separated and purified by silica gel column chromatography to obtain a white solid compound TPP-o-3OMe-NH2-Br;

[0012] S2, the compound TPP-o-3OMe-NH2-Br in S1, the compound 4-bromo-1,8-naphthalene dicarboxylic anhydride, and 4-dimethylaminopyridine (DMAP) are mixed and added to a reaction bottle, and after vacuum drying, an ethanol solution is added under a nitrogen atmosphere, and the mixture is stirred and refluxed. After the reaction is completed, the solvent is removed by vacuum drying, and the crude product is separated and purified by silica gel column chromatography to obtain a yellow solid compound TPP-o-3OMe-NBI-Br;

[0013] S3. The compound TPP-o-3OMe-NH2-Br, the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride and 4-dimethylaminopyridine in S1 are mixed and added to a reaction bottle. After vacuum drying, a dry 20 mL ethanol solution is added under a nitrogen atmosphere, and the mixture is stirred and refluxed. After the reaction is completed, the solvent is removed by vacuum drying. The crude product is separated and purified by silica gel column chromatography to obtain an orange-yellow solid compound TPP-o-3OMe-NNI-Br.

[0014] Preferably, the molar ratio of the compound TPP-o-3OMe-NH2-Br, the compound 4-bromo-1,8-naphthalene dicarboxylic anhydride, and 4-dimethylaminopyridine in S2 is 3.12:3.4:3.4.

[0015] Preferably, the molar ratio of the compound TPP-o-3OMe-NH2-Br, the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride and 4-dimethylaminopyridine in S3 is 1:1.1:1.1.

[0016] Preferably, the synthesis method of the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride in S3 is: dissolving 4-bromo-1,8-naphthalene dicarboxylic anhydride in isoamyl alcohol, heating to reflux in an oil bath, then adding 3-dimethylaminopropionitrile to the mixture and reflux overnight, filtering the precipitate at room temperature, washing the precipitate with water and hexane, and drying the precipitate under reduced pressure to obtain a yellow 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride (NNI) solid powder.

[0017] Preferably, the molar ratio of the 4-bromo-1,8-naphthalene dicarboxylic anhydride to 3-dimethylaminopropionitrile is 1:4.

[0018] In a third aspect, the present invention provides an application of the above-mentioned near-infrared organic free radical afterglow material for preparing at least one of semiconductor electronic devices, biological imaging, and spin materials.

[0019] The beneficial effects of the present invention are:

[0020] The invention introduces electron-pushing and electron-pulling groups 6-(dimethylamino)naphthaleneimide (NNI) and 6-bromonaphthaleneimide (NBI) on the basis of the compound molecule TPP-o-3OMe-NH2-Br, designs and synthesizes molecules TPP-o-3OMe-NNI-Br and TPP-o-3OMe-NBI-Br; after TPP-o-3OMe-NNI-Br and TPP-o-3OMe-NBI-Br are doped in polymer PMMA, they have long afterglow emission characteristics with different light activation times; the light activation time of afterglow of TPP-o-3OMe-NBI-Br@PMMA film is significantly shortened, and TPP-o-3OMe-NNI-Br@PMMA film successfully realizes red afterglow emission; finally, the luminescent characteristics of the two films are combined to produce applications of multi-color display and storage of optical information, and such materials are expected to provide new ideas for the development of organic free radical luminescent materials and multiple information encryption applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 It is the UV absorption spectrum and HPLC spectrum of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br.

[0023] Figure 2 These are the monomer, dimer, and π···π stacking interaction diagrams of OC and YC crystals.

[0024] Figure 3 This is the Hirschfeld surface analysis diagram of PC and YC crystals.

[0025] Figure 4 Thermogravimetric analysis (a), solid UV (b), and XRD spectra (c) of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br.

[0026] Figure 5Solid-state fluorescence spectra (a), fluorescence lifetimes (b), and phosphorescence spectra (c) of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br.

[0027] Figure 6 TPP-o-3OMe-NBI-Br@PMMA and

[0028] Thermogravimetric analysis (a), solid UV (b) and XRD spectra (c) of TPP-o-3OMe-NNI-Br@PMMA.

[0029] Figure 7 These are the spectrum (a) and phenomenon diagrams (b, c) of TPP-o-33OMe-NBI-Br doped in PMMA film.

[0030] Figure 8 These are the spectrum diagram (a) and phenomenon diagrams (b, c) of TPP-o-33OMe-NNI-Br doped in PMMA film.

[0031] Fig. 9 These are the low-temperature spectra (77K) of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br in 2-Me-THF solution, where ad is the low-temperature spectrum of TPP-o-3OMe-NBI-Br (a is the steady-state spectrum, c is the transient spectrum; b is the lifetime at 428nm, and d is the lifetime at 450nm); eh is the low-temperature spectrum of TPP-o-3OMe-NNI-Br (e is the steady-state spectrum, g is the transient spectrum; f is the lifetime at 500nm, and h is the lifetime at 450nm).

[0032] Fig.10 This is the luminescence mechanism diagram of TPP-o-3OMe-NNI-Br, where a is the EPR diagram of singlet oxygen before and after illumination, b is the EPR diagram of free radicals before and after illumination, c is the doublet electrostatic potential, and d is the theoretical calculation of the luminescence mechanism study.

[0033] Fig.11 TPP-o-3OMe-NBI-Br@PMMA and

[0034] Optical information anti-counterfeiting application diagram prepared by TPP-o-3OMe-NNI-Br@PMMA. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Main experimental drugs and reagents

[0037] Sodium hydroxide (CAS: 1310-73-2), tri(2-methoxyphenyl)phosphine (CAS: 4731-65-1), 2-bromoethylamine hydrobromide (CAS: 2576-47-8), 4-dimethylaminopyridineacetonitrile (CAS: 1122-58-3), 4-bromo-1,8-naphthalene dicarboxylic anhydride (CAS: 81-86-7), isopentanol (CAS: 123-51-3) N, N-dimethylaminoacetonitrile (CAS: 926-64-7), methanol, n-hexane. Commonly used analytical grade solvents include methanol, dichloromethane, ethyl acetate, petroleum ether, etc. Ultrapure water was prepared by Mili-Q ultrapure water machine, silica gel powder (200-300 mesh) and silica gel plate.

[0038] Main experimental instruments

[0039] 1 H NMR, 13 C NMR and 31 P NMR nuclear magnetic resonance spectrum was measured using a Bruker AVANCE-600 nuclear magnetic resonance instrument. High-resolution mass spectra were measured by an Agilent 6540Q-TOF mass spectrometer, and high-performance liquid chromatography (HPLC) was measured by an Agilent 1260 Infinity high-performance liquid chromatograph, using a 4.6 mm × 250 mm C18 reversed-phase column. UV-visible absorption spectrum data were measured by a UV-2600 UV-visible spectrophotometer. Thermogravimetric analysis data were measured by a Mettler TGA / DSC / 1600LF instrument with a heating rate of 10 K / min. Steady-state and transient spectra, lifetimes, and quantum yields were measured using a Horiba Jobin Yvon Fluorolog-3. Electron spin resonance (EPR) spectra were measured by a Bruker Emxplus-6 / 1. In the theoretical calculation part, Gaussian 09 software was used for time-dependent density functional theory (TD-DFT) calculation, orca software was used for spin-orbit coupling constant calculation, and Crystal explorer software was used for Hirschfeld surface analysis.

[0040] Example 1

[0041] The method for preparing a near-infrared organic free radical afterglow material comprises the following steps:

[0042] S1, synthesis of compound TPP-o-3OMe-NH2-Br: tri(2-methoxyphenyl)phosphine (1g, 2.8mmol) and 2-bromoethylamine hydrobromide (0.63g, 4.4mmol) were added to a 50ml Schlenk reaction bottle, 20ml CH3CH2CN was added to dissolve, refluxed and stirred overnight (12h), and TCL was used to detect whether the reaction was complete. After the reaction was completed, the solvent was vacuum-dried, 30ml ultrapure water was added to the obtained solid powder, and NaOH was added to adjust the pH, and then EA was extracted to obtain a crude product, and the crude product was separated and purified by silica gel column chromatography (eluent: MeOH:DCM=1:5) to obtain a white solid compound TPP-o-OM e-NH2-Br (1.02g, 2.12mmol) with a yield of 74%, and the synthesis route is as follows:

[0043]

[0044] Graph information: 1 H NMR (500MHz, MeOD) δ7.95–7.89 (m, 3H), 7.49–7.44 (m, 3H), 7.29–7.23 (m, 3H), 7.15 (dd, J=15.5, 9.5Hz, 3H), 3.93 (s, 9H), 3.69–3.59 (m, 4H), 3.33 (s, 1H), 3.29–3.22 (m, 2H).ppm 13 C NMR (126MHz, MeOD) δ161.77, 137.69, 134.65, 122.30, 112.95, 104.81, 104.06, 56.94, 55.91, 47.82, 34.98, 24.40, 23.91.ppm 31 P NMR (202MHz, MeOD) δ21.83ppm.[M+H] + Calcd.for C 23 H 27 NO3PBr, 476.0898, found, 476.0892;

[0045] S2, synthesis of TPP-o-3OMe-NBI-Br: Compound TPP-o-3OMe-NH2-Br (1.5 g, 3.12 mmol) in S1, compound 4-bromo-1,8-naphthalene dicarboxylic anhydride (0.95 g, 3.43 mmol) and 4-dimethylaminopyridine (DMAP) (0.42 g, 3.43 mmol) were mixed and added to a dry Schlenk reaction bottle (50 ml), vacuum dried for 30 min, 20 ml of dry ethanol solution was added under nitrogen atmosphere, stirred and refluxed for 7 h, and after the reaction was completed, the solvent was removed by vacuum drying, and the crude product was separated and purified by silica gel column chromatography (eluent: MeOH:DCM=1:5) to obtain a yellow solid compound TPP-o-3OMe-NBI-Br (1.24 g, 1.70 mmol) with a yield of 61%; the synthesis route is as follows:

[0046]

[0047] Graph information: 1 H NMR (600MHz, MeOD) δ8.49 (dd, J=17.7, 7.9Hz, 2H), 8.24 (d, J=7.9Hz, 1H), 8.06 (d, J=7.9Hz, 1H), 7.92–7.83 (m, 4H), 7.5 2–7.45 (m, 3H), 7.41–7.36 (m, 3H), 7.33–7.28 (m, 3H), 4.24 (d, J = 11.2Hz, 2H), 3.85 (s, 9H), 3.60 (d, J = 18.2Hz, 2H).ppm. 13 C NMR (151MHz, MeOD) δ163.00, 161.86, 137.15, 134.74, 133.10, 131.64, 131.09, 130.28, 130.01, 128.51, 128.06, 122.48, 121.94, 112.53, 105

[0048] .65, 105.03, 55.57, 35.16, 22.06.ppm. 31 P NMR (243 MHz, MeOD) δ 20.08

[0049] .ppm.HRMS m / z:[M+H] + Calcd.for C 35 H 30 NBr2O5P, 736.0329, found 736.0322;

[0051] S3. Synthesis of compound TPP-o-3OMe-NNI-Br: 4-bromo-1,8-naphthalene dicarboxylic anhydride (1 g, 2 mmol) was dissolved in isoamyl alcohol and heated to reflux in an oil bath. Then 3-dimethylaminopropionitrile (1.4 g, 8 mmol) was added to the mixture and refluxed overnight. The precipitate was filtered at room temperature, washed with water and hexane, and dried under reduced pressure to obtain a yellow NNI solid powder with a yield of 90%. The synthesis route is as follows:

[0052]

[0053] Graph information: 1 H NMR(400MHz, CDCl3)δ8.50(d,1H)8.46(d,1H)8

[0054] .37(d,1H)7.65(t,1H)7.06(d,1H)3.18(s,6H). 13 C NMR (400MHz, CDCl3) δ161.76, 160.78, 157.98, 135.03, 133.20, 133.00, 125.02, 124.83, 119.19, 113.18, 109.30, 44.69;

[0055] Then compound TPP-o-3OMe-NH2-Br (1.2 g, 2.50 mmol), compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride (0.67 g, 2.75 mmol) and DMAP (0.34 g, 2.75 mmol) were added.

[0056] The mixture was added to a dry Schlenk reaction bottle (50 ml), vacuum dried for 30 min, and 20 ml of dry ethanol solution was added under nitrogen atmosphere, stirred and refluxed for 7 h. After the reaction was completed, the solvent was removed by vacuum drying. The crude product was separated and purified by silica gel column chromatography (eluent: MeOH:DCM=1:5); the orange-yellow solid compound TPP-o-3OMe-NNI-Br (700) (1.10 g 2.50 mmol) had a yield of 63%;

[0057] The synthetic route is as follows:

[0058]

[0059] Graph information: 1H NMR (600MHz, MeOD) δ8.47 (d, J=9.7Hz, 1H), 8.36 (d, J=8.4Hz, 1H), 8.24 (d, J=8.3Hz, 1H), 7.89–7.84 (m, 3H), 7.64–7.60 (m, 1H), 7.53 (dd, J=15.3 , 7.8Hz, 3H), 7.38–7.32 (m, 3H), 7.32–7.26 (m, 3H), 7.10 (d, J=8.3Hz, 1H ), 4.20–4.14(m, 2H), 3.82(s, 9H), 3.60–3.53(m, 2H), 3.15(s, 6H).ppm. 13 C NMR (151MHz, MeOD) δ164.06, 163.43, 161.86, 157.56, 137.03, 134.70, 132.56, 131

[0060] .93, 130.72, 130.11, 124.67, 124.37, 122.02, 121.88, 121.80, 113.01, 1 12.65, 112.45, 105.77, 105.15, 55.50, 43.66, 34.76, 21.83, 21.47.ppm. 31 P NMR(243MHz, MeOD)δ19.65.ppm.HRMS m / z:[M+H] + Calcd.for C 37 H 36 N2O5PBr, 699.1544; found, 699.1541.

[0061] The purity of the compounds was verified by high performance liquid chromatography (HPLC) (the mobile phase was pure methanol), as Figure 1 As shown, each ultraviolet absorption band in the HPLC of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br shows only one peak signal, indicating that the purity of the compounds TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br is high, and the effect of impurities on their long afterglow emission is almost negligible.

[0062] Single crystal structure analysis:

[0063] The compound TPP-o-3OMe-NNI-Br molecules were slowly evaporated from a mixed solution of ethyl acetate / dichloromethane to obtain orange fluorescent crystals (OC), and from a mixed solvent of n-hexane / methanol / dichloromethane to obtain yellow fluorescent crystals (YC). Crystallographic data showed that the OC crystal system was monoclinic with a space group of C1 2 / c 1, and the YC crystal system was orthorhombic with a space group of P bc a. There are 7 molecules in the unit cell of OC and 5 molecules in the unit cell of YC, among which YC (ρ

[0064] =1.442g.cm -3 ) than OC (ρ = 1.427 g.cm -3 ) are arranged more closely, and the volume YC OC The volume is larger (Table 1). The molecular crystals of the compound TPP-o-3OMe-NBI-Br were obtained by slow evaporation of the solvent (ethyl acetate / dichloromethane), and there was no fluorescence emission at room temperature. The crystallographic data showed that the crystal system was triclinic, the space group was P-1, and there were only two molecules in the unit cell.

[0065] Table 1 Crystal data of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br

[0066]

[0067] like Figure 2 As shown in the figure, the two fluorescence color crystal data of TPP-o-3OMe-NNI-Br molecule were analyzed. For the molecular monomer, taking the NNI group as the reference plane, we found that all the dimethylamino atoms of the OC crystal are almost coplanar with the NNI, while the plane formed by the NN-2-methyl group of the YC crystal is almost perpendicular to the NNI plane. This results in that the charge transfer efficiency of the OC crystal is higher than that of the YC crystal when the molecule is excited, which can effectively enhance the fluorescence enhancement of the π···π interaction formed by the crystal stacking. Therefore, we analyzed the interaction between the two crystal dimers, OC crystal Compared with YC crystal It has a stronger CH···O interaction and is relatively Crystal, OC crystal It has a larger π···π overlap, and the coplanarity of the dimethylamino group and NNI in the OC crystal greatly enhances the π-conjugated electron transfer, causing the crystal luminescence to red-shift.

[0068] In order to further analyze the difference in chemical bonding between the two crystals, we performed Hirschfeld surface analysis calculations on the two crystal monomer molecules, such as Figure 3 As shown in the figure, in OC crystal, six interactions dominate, namely H···H (54.5%), C···H (19.2%), H···Br (10.5%), H···O (8.0%), C···C (1.2%), and C···O (1.0%). In YC crystal, H···H (54.5%) is not much different from OC, C···H (12.4%) is weakened by 6.4%, H···Br (12.4%) is enhanced by 1.9%, and H···O (5.6%) is weakened by 2.4%. This indicates that in the crystal stacking structure, OC crystal has stronger weak interactions.

[0069] Characterization of photophysical properties:

[0070] The photophysical properties of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br in solid and solution states were systematically studied. Figure 4 As shown in the figure, both TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br molecules showed good thermal stability, and the ultraviolet absorption of TPP-o-3OMe-NNI-Br molecules in the solid state reached 500nm, indicating that the introduction of electron-donating groups may enable TPP-o-3OMe-NNI-Br molecules to have better intramolecular charge transfer. Powder single crystal diffraction shows that both solid powders maintain a good crystal shape.

[0071] like Figure 5 As shown, TPP-o-3OMe-NBI-Br solid powder exhibits red fluorescence emission (650nm) under 365nm ultraviolet light, and TPP-o-3OMe-NNI-Br molecules exhibit bright yellow fluorescence emission (580nm). Unfortunately, long afterglow emission from TPP-o-3OMe-NBI-Br molecules cannot be observed at room temperature, and long afterglow emission cannot be detected by instruments. Although the two crystals of TPP-o-3OMe-NNI-Br molecules have no afterglow emission to the naked eye, afterglow emission signals are detected at 680nm by instruments.

[0072] Photoactivated long afterglow properties:

[0073] In order to obtain red long afterglow emission visible to the naked eye at room temperature, TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br molecules were doped into PMMA at a mass ratio of 0.5%, and two organic long afterglow materials TPP-o-3OMe-NBI-Br@PMMA and TPP-o-3OMe-NNI-Br@PMMA films with light-activated properties were obtained. The obtained films were analyzed by thermogravimetric experiments, as shown in Figure 2. Figure 6 As shown in the figure, both doped polymers show good thermal stability. UV absorption was performed on TPP-o-3OMe-NBI-Br@PMMA and TPP-o-3OMe-NNI-Br@PMMA films. Both films showed a wide absorption band, which provided a basis for the selection of excitation light sources. At the same time, both doping systems maintained a good amorphous structure.

[0074] like Figure 7 As shown in the transient spectrum, the TPP-o-3OMe-NBI-Br@PMMA film has three emission peaks before activation, namely 420nm, 570nm, and 610nm. After activation, the emission peak intensities at 570nm and 610nm increase, while the emission peak intensity at 420nm tends to weaken, making the fluorescence color of the TPP-o-3OMe-NBI-Br@PMMA film change from purple to pink before and after photoactivation. In the steady-state spectrum after a delay of 0.1ms, no fluorescence peak at 420nm can be detected before and after activation. Moreover, unlike the TPP-o-3OMe-NMI-Br@PMMA film in Chapter 3, although no afterglow emission is observed before photoactivation, the afterglow emission signal can be monitored by the instrument. This is because the introduction of heavy atom bromine enhances spin-orbit coupling and improves the intersystem crossing efficiency (ISC) from singlet to triplet.

[0075] The luminescence phenomenon of TPP-o-3OMe-NNI-Br@PMMA film is different from the previous doping system, such as Figure 8 Due to the introduction of dimethylamino, the TPP-o-3OMe-NNI-Br@PMMA film successfully achieved red afterglow emission. By detecting the transient spectrum and steady-state spectrum before and after activation, we found that the fluorescence of the TPP-o-3OMe-NNI-Br@PMMA film would also weaken after activation, indicating that the TPP-o-3OMe-NNI-Br@PMMA film may also have a similar luminescence mechanism during the activation process.

[0076] like Fig. 9As shown in the figure, TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br were dissolved in dimethyltetrahydrofuran at very low concentrations (0.001mM), and their transient / steady-state spectra at 77K were detected. The spectral data showed that both TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br had afterglow emission at 450nm, with lifetimes of 0.95ms and 0.86ms, respectively. The results show that the room temperature long afterglow emission of TPP-o-3OMe-NBI-Br@PMMA and TPP-o-3OMe-NNI-Br@PMMA does not originate from the monomer molecules of TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br, which is consistent with our research conclusions in the previous two chapters.

[0077] In order to further prove whether the luminescence mechanism is consistent with the previous study, we took the TPP-o-3OMe-NNI-Br molecule as an example (because its afterglow emission is red) to detect the oxygen vacancy electron paramagnetic resonance spectrum and singlet oxygen electron paramagnetic resonance spectrum (EPR) of the TPP-o-3OMe-NNI-Br@PMMA film. Before activation, no signal was detected. After 30 seconds of activation, the EPR signal of singlet oxygen was significantly enhanced, indicating that TPP-o-3OMe-NNI-Br@PMMA can also convert triplet oxygen into singlet oxygen during the photoactivation process. During the 30 seconds of UV lamp activation, the oxygen diffused into the PMMA film was consumed, and the quenching effect of triplet oxygen on triplet excitons was weakened, thereby releasing triplet excitons.

[0078] At the same time, oxygen vacancy free radicals (such as Fig.10 ), and the TPP-o-3OMe-NNI-Br@PMMA molecule has a strong absorption at 420nm, which has a large overlap with the phosphorescence peak (450nm) of its monomer molecule at low temperature, indicating that phosphorescence energy transfer (PRET) can be formed between the monomer triplet state and the radical doublet state.

[0079] like Fig.10 As shown in Figure 2, by performing TD-DF calculations on the monomer and dimer of TPP-o-3OMe-NNI-Br molecules, it was found that in the long afterglow emission spectrum, the emission peak around 650nm is close to the emission band generated by the transition of the free radical doublet state D8→D0 (f=0.036), and the emission peak at 570nm is close to the emission band generated by the transition of the triplet state T2→S0 (<T2|HSO|S0> =0.8717cm -1), indicating that the organic long afterglow comes from the synergistic effect of the doublet state of the free radical and the triplet state of the dimer. Therefore, combining experiments and theoretical calculations, we successfully obtained a red organic long afterglow material with the synergistic effect of triplet and doublet states.

[0080] Optical information anti-counterfeiting application:

[0081] like Fig.11 As shown, using the light-activated fluorescence changes and long afterglow characteristics of TPP-o-3OMe-NBI-Br@PMMA film and TPP-o-3OMe-NNI-Br@PMMA film in this chapter, a luminescent anti-counterfeiting material with light-activated time dependence was successfully prepared. As shown in Figure 4-14, a multi-color emission flower pattern was prepared, using TPP-o-3OMe-NNI-Br@PMMA film with a doping ratio of 0.5% as petals, TPP-o-3OMe-NBI-Br@PMMA (0.5%) film as leaves, and TPP-o-3OMe-NBI-Br@PMMA (1.0%) film as branches. Before light activation, the color of the petals was green, the color of the leaves was blue, and the branches were purple. After light activation, the color of the leaves was purple, while the branches became pink, and the fluorescence of the petals did not change. After turning off the ultraviolet light, a long afterglow flower with yellow branches and leaves and red petals appeared. The multi-color luminescence changes show good optical anti-counterfeiting ability.

[0082] In summary, the introduction of NBI molecules enables the detection of afterglow signals in TPP-o-3OMe-NBI-Br@PMMA film before light activation, which is due to the enhanced ISC by the introduction of heavy atoms. The introduction of NNI molecules enhances the charge transfer capability within the molecule, enabling the TPP-o-3OMe-NNI-Br@PMMA film to successfully achieve red afterglow emission. Thus, two free radical luminescent materials that can achieve red afterglow emission under different environmental conditions have been successfully obtained through the design of molecular structures. Such molecules have broad application prospects in the fields of optical anti-counterfeiting and information encryption under extreme conditions.

[0083] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all details in detail, nor do they limit the invention to only the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification.

Claims

1. A near-infrared organic free radical afterglow material, characterized in that: The general structural formula is Wherein, the R includes They respectively constitute the aromatic quaternary phosphonium salt derivatives TPP-o-3OMe-NBI-Br and TPP-o-3OMe-NNI-Br.

2. The method for preparing the near-infrared organic free radical afterglow material according to claim 1, characterized in that: The following steps are involved: S1. Synthesis of compound TPP-o-3OMe-NH2-Br: tri(2-methoxyphenyl)phosphine and 2-bromoethylamine hydrobromide were added to a reaction flask, CH3CH2CN was added to dissolve, and the mixture was refluxed with stirring overnight. After the reaction was completed, the solvent was vacuum dried, ultrapure water was added to the obtained solid powder, and NaOH was added to adjust the pH, and then the crude product was extracted with EA. The crude product was separated and purified by silica gel column chromatography to obtain a white solid compound TPP-o-OMe-NH2-Br; S2, the compound TPP-o-3OMe-NH2-Br in S1, the compound 4-bromo-1,8-naphthalene dicarboxylic anhydride, and 4-dimethylaminopyridine (DMAP) are mixed and added to a reaction bottle, and after vacuum drying, an ethanol solution is added under a nitrogen atmosphere, and the mixture is stirred and refluxed. After the reaction is completed, the solvent is removed by vacuum drying, and the crude product is separated and purified by silica gel column chromatography to obtain a yellow solid compound TPP-o-3OMe-NBI-Br; S3. The compound TPP-o-3OMe-NH2-Br, the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride and 4-dimethylaminopyridine in S1 are mixed and added to a reaction bottle. After vacuum drying, a dry 20 mL ethanol solution is added under a nitrogen atmosphere, and the mixture is stirred and refluxed. After the reaction is completed, the solvent is removed by vacuum drying. The crude product is separated and purified by silica gel column chromatography to obtain an orange-yellow solid compound TPP-o-3OMe-NNI-Br.

3. The method for preparing the near-infrared organic free radical afterglow material according to claim 2, characterized in that: The molar ratio of the compound TPP-o-3OMe-NH2-Br, the compound 4-bromo-1,8-naphthalene dicarboxylic anhydride, and 4-dimethylaminopyridine in S2 is 3.12:3.4:3.

4.

4. The method for preparing the near-infrared organic free radical afterglow material according to claim 2, characterized in that: The molar ratio of the compound TPP-o-3OMe-NH2-Br, the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride and 4-dimethylaminopyridine in S3 is 1:1.1:1.

1.

5. The method for preparing the near-infrared organic free radical afterglow material according to claim 2, characterized in that: The synthesis method of the compound 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride in S3 is as follows: 4-bromo-1,8-naphthalene dicarboxylic anhydride is dissolved in isoamyl alcohol, heated to reflux in an oil bath, and then 3-dimethylaminopropionitrile is added to the mixture and refluxed overnight, and the precipitate is filtered at room temperature, and the precipitate is washed with water and hexane, and the precipitate is dried under reduced pressure to obtain a yellow 4-dimethylamino-1,8-naphthalene dicarboxylic anhydride (NNI) solid powder.

6. The method for preparing the near-infrared organic free radical afterglow material according to claim 5, characterized in that: The molar ratio of the 4-bromo-1,8-naphthalene dicarboxylic anhydride to 3-dimethylaminopropionitrile is 1:

4.

7. The use of the near-infrared organic free radical afterglow material according to claim 1, characterized in that: Used to prepare at least one of semiconductor electronic devices, biological imaging, and spin materials.

Images