Organic super-fluorescent scintillator without heavy atom modification as well as preparation method and application of organic super-fluorescent scintillator

Abstract

The invention belongs to the field of organic luminescent materials, and discloses an organic super-fluorescent scintillator material without heavy atom modification and a preparation method thereof. Compared with the conventional common scintillator material, the material does not need the participation of heavy atoms in the molecular structure design, and has the characteristics of simplicity in preparation, good film-forming property and the like; according to the organic super-fluorescent scintillator material prepared by the invention, VQA with amine / carbonyl multiple resonance MR chromophore is selected and is covalently bound with 4-vinylpyridine, and high-efficiency radiation luminescence is realized through effective energy transfer from 4VP to VQA; meanwhile, the prepared material is doped with some commercial materials by utilizing a physical blending method, so that the radiation luminescence property of the material is further improved, and the possibility is provided for subsequently applying the material to the field of X-ray imaging.

Description

Technical Field

[0001] The invention belongs to the field of organic luminescent materials, and in particular relates to a method for preparing an organic superfluorescent scintillator without heavy atom modification. Background Art

[0002] Scintillator luminescence is a phenomenon that can convert high-energy X-ray photons into low-energy visible light, and it shows great potential in the fields of medicine, astrophysics, radiochemistry, and industrial non-destructive testing. Organic scintillators have been developed as promising scintillator materials due to their low cost, flexibility, and easy preparation process.

[0003] However, the limited atomic number of organic materials leads to poor X-ray absorption, and most known organic scintillators are fluorescent materials whose luminescence originates from singlet excited states. In fluorescent organic scintillators, only 25% of singlet excitons are used for radiative luminescence (RL), and 75% of triplet excitons are wasted. Therefore, weak X-ray absorption and inefficient exciton utilization hinder the development and commercialization of organic scintillators. This is because the triplet excited state generated by the energy deposition of incident particles in traditional fluorescent dye organic scintillators can be converted to singlet through triplet-triplet annihilation to achieve the delayed pulse tail characteristics of organic scintillators, but it is not a particularly efficient triplet-to-singlet conversion process overall. For example, the most familiar organic scintillator is anthracene-based scintillator, but its low exciton utilization limits its development in the field of X-ray detection. In response to this, we studied thermally activated delayed fluorescent materials as luminescent molecules of organic scintillators and found that the smaller singlet-triplet energy difference is conducive to the luminescence capture of radiation-induced triplet excitons. TADF scintillators significantly outperform anthracene-based scintillators due to their large Stokes shift, which reduces self-absorption, and offer tremendous new possibilities for radiation detection and imaging using highly efficient organic materials. Summary of the invention

[0004] In order to solve the above problems, the present invention discloses an organic superfluorescent scintillator material without heavy atom modification and a preparation method thereof. Compared with the currently commonly used scintillator materials, the material of the present application does not require the participation of heavy atoms in the molecular structure, and has the characteristics of simple preparation and good film-forming properties. The organic superfluorescent scintillator material prepared by the present invention selects 7-(4-vinylphenyl)quinoline [3,2,1-de] acridine-5,9-dione (VQA) with amine / carbonyl multi-resonance MR chromophore, which is covalently bonded to 4-vinylpyridine, and achieves high-efficiency radioluminescence through effective energy transfer from 4VP to VQA. At the same time, the prepared material is doped with some commercial materials by physical blending, which further improves the radioluminescence performance of the material, providing the possibility for subsequent application in the field of X-rays.

[0005] To achieve the above object, the technical solution of the present invention is as follows: The present invention provides a heavy atom-free organic superfluorescent scintillator, including P4VQA, whose structural formula is as follows: Formula I; Among them, m:n=1:0.005.

[0006] Another object of the present invention is to provide a method for preparing an organic superfluorescent scintillator without heavy atom modification, comprising the following steps: S1. Under an argon atmosphere, dimethyl 5-bromo-2-iodoisophthalate, diphenylamine, activated copper powder, potassium carbonate, and cuprous iodide are dissolved in o-dichlorobenzene to react to obtain dimethyl 5-bromo-2-diphenylaminopropionate; S2. Under an argon atmosphere, sodium hydroxide and an ethanol aqueous solution are added to dimethyl 5-bromo-2-diphenylaminopropionate to react to obtain 5-bromo-2-(diphenylamino)pentanoic acid; S3. Under an argon atmosphere, N,N-dimethylformamide is added to a mixture of 5-bromo-2-(diphenylamino)pentanoic acid and dichloromethane, and then oxalyl chloride and tin chloride are added to react to obtain 7-bromoquino[3,2,1-de]acridine-5,9-dione; S4. Under an argon atmosphere, 7-bromoquinolino[3,2,1-de]acridine-5,9-dione, potassium carbonate, tetrakis(triphenylphosphine)palladium, and 4-vinylphenylboronic acid are dissolved in toluene, and deionized water is added to react to obtain 7-(4-vinylphenyl)quinolino[3,2,1-de]acridine-5,9-dione (VQA); S5. Under an argon atmosphere, VQA, 4-vinylpyridine and azobisisobutyronitrile are added to toluene to react to obtain an organic superfluorescent scintillator P4VQA powder product.

[0007] Further, in step S1, 5-bromo-2-iodoisophthalic acid dimethyl ester, diphenylamine, activated copper powder and potassium carbonate are added to ultra-dry o-dichlorobenzene, and reacted at 175-180 ° C in an argon atmosphere for 20-24 h; wherein the molar ratio of 5-bromo-2-iodoisophthalic acid dimethyl ester, diphenylamine, activated copper powder, potassium carbonate and cuprous iodide is 1:1.1-1.2:0.15-0.2:1.3-1.4:0.04-0.05; the molar ratio of 5-bromo-2-iodoisophthalic acid dimethyl ester to o-dichlorobenzene is 1:157-158.

[0008] Furthermore, in step S2, sodium hydroxide and ethanol aqueous solution are added, and the reaction is carried out at 75-80° C. for 20-24 h under an argon atmosphere; wherein the molar ratio of ethanol / water (V / V: 1 / 1); 5-bromo-2-(diphenylamino)pentanoic acid dimethyl ester to sodium hydroxide is 1:5.

[0009] Further, in step S3, N,N-dimethylformamide is added to a mixture of 5-bromo-2-(diphenylamino)pentanoic acid and dichloromethane under an ice-water bath, and then oxalyl chloride is added dropwise, the ice-water bath is removed, and the mixture is reacted at a temperature of 40-45° C. for 30 min, and then tin chloride is added dropwise and the same temperature is maintained to continue condensing and reflux for 3 h; Furthermore, the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to oxalyl chloride is 1:2.1-2.2, the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to tin chloride is 1:2.1-2.2; and the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to dichloromethane is 1:500-520.

[0010] Further, in step S4, the reaction is carried out under an argon atmosphere at 85-90° C. for 20-24 h; toluene needs to be bubbled; the molar ratio of 7-bromoquinoline [3, 2, 1-de] acridine-5, 9-dione to 4-vinylbenzeneboronic acid is 1:1.4-1.5; the molar ratio of 7-bromoquinoline [3, 2, 1-de] acridine-5, 9-dione to potassium carbonate is 1:1.4-1.5; the molar ratio of potassium carbonate to tetrakis (triphenylphosphine) palladium is 1:0.032-0.033; the molar ratio of 7-bromoquinoline [3, 2, 1-de] acridine-5, 9-dione to toluene (ultra-dry) is 1:42-45; and the volume ratio of toluene (ultra-dry) to deionized water is 2:1.

[0011] Further, in step S5, the reaction is carried out under an argon atmosphere at 65-70°C for 10-12 h; wherein the stabilizer of 4-vinylpyridine needs to be removed by reduced pressure distillation; the molar ratio of 4-vinylpyridine to VQA is 1:0.005; the molar ratio of 4-vinylpyridine to 7-(4-vinylphenyl)quino[3,2,1-de]acridine-5,9-dione is 1:0.001-0.005; the molar ratio of 4-vinylpyridine to azobisisobutyronitrile is 1:0.01-0.015; and the molar ratio of 4-vinylpyridine to toluene (super dry) is 1:2.

[0012] The present invention also provides an application of the organic superfluorescent scintillator without heavy atom modification as described above in the field of X-rays.

[0013] The beneficial effects of the present invention are: (1) The present invention specifically designs and prepares an organic superfluorescent scintillator, which, compared with the existing scintillator materials, does not contain halogen, is simple to prepare, has good film-forming properties, and can emit green light under ultraviolet excitation in the thin film state.

[0014] (2) No harmful substances such as halogen need to be added during the preparation process of the present invention, which greatly reduces the damage of the reaction to the human body and the environment. At the same time, the product of the present invention can be prepared on a large scale, the preparation process is simple, and the preparation cost is greatly reduced, which is conducive to the subsequent investment in the organic scintillator market.

[0015] (3) The present invention utilizes the characteristics of the amine / carbonyl multi-resonance MR chromophore of the VQA material to covalently bind it to 4-vinylpyridine as a narrow-band emitter to achieve efficient energy transfer from 4VP to VQA. At the same time, 4VP is used as a host material because it promotes the generation of triplet excitons through efficient n-π* transitions and high triplet energy levels, which helps to support efficient energy transfer from the host to the guest to sensitize the triplet excitons of the guest. The above materials provide a new research strategy for the development and design of efficient organic fluorescent scintillators.

[0016] (4) The organic superfluorescent scintillator material prepared by the present invention uses VQA with amine / carbonyl multi-resonance MR chromophores to covalently bind it to 4-vinylpyridine, and achieves high-efficiency radiative luminescence through effective energy transfer from 4VP to VQA. At the same time, the prepared material is doped with some commercial materials by physical blending, which further improves the radiative luminescence performance of the material, providing the possibility for subsequent application in the field of X-ray imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The middle is the steady-state spectra of P4VQA at different ratios; Figure 2 The absorption spectrum of P4VQA in solution and the steady-state spectrum of P4VQA under excitation of different wavelengths are shown in the figure. Figure 3 The UV excitation spectra of P4VQA (m:n=1:0.005) after physical blending with each guest material and the UV excitation spectra of P4VQA (m:n=1:0.005) with each guest material at different doping ratios. DETAILED DESCRIPTION

[0018] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Example 1

[0019] Synthesis of Dimethyl 5-Bromo-2-Diphenylaminopropionate Dimethyl 5-bromo-2-iodoisophthalate (3.93 g, 9.85 mmol), diphenylamine (2.00 g, 11.82 mmol), activated copper (0.13 g, 1.97 mmol), copper (I) iodide (0.09 g, 0.49 mmol), potassium carbonate (1.77 g, 12.80 mmol) and 30 mL of 1,2-dichlorobenzene (o-DCB) were stirred and refluxed for 24 h under an argon atmosphere. After cooling to room temperature, 100 mL of dichloromethane (DCM) was added to the mixture, which was then stirred for 10 min. After filtering the mixture with a glass filter funnel, the filtrate was concentrated under reduced pressure. The residue given was purified by silica gel column chromatography using ethyl acetate (EA) / petroleum ether (PE) (V / V: 1 / 50) as the eluent to obtain the product as a light green solid product, 1 H NMR (400 MHz, CDCl3) δ = 7.86(s, 2H), 7.21-7.17 (m, 4H), 6.97-6.94(m, 6H), 3.45 (s, 6H). 13 C NMR (101 MHz, CDCl3) δ = 166.26, 146.74, 143.57, 136.59, 134.17,129.03, 122.73, 122.55,118.01, 52.56. MALDI-TOF: m / z calcd for C 22 H 18 BrNO4 [M] + : 440.19; Found:440.29. The structure is as follows: . Example 2

[0020] Synthesis of 5-bromo-2-(diphenylamino)pentanoic acid Under argon atmosphere, dimethyl 5-bromo-2-(diphenylamino)pentanoate (3.50 g, 7.95 mmol) and sodium hydroxide (1.59 g, 39.75 mmol) were added to a solution of ethanol / water (V / V: 1 / 1, 50 mL). The mixture was stirred and refluxed for 24 h. After cooling to room temperature, it was acidified with concentrated hydrochloric acid to precipitate a yellow solid, which was filtered with a glass filter funnel, washed with deionized water and dried in a vacuum oven overnight. The yellow solid product (yield: 3.11 g, 95%) was used directly without further purification. The structure is as follows: . Example 3

[0021] Synthesis of 7-bromoquino[3,2,1-de]acridine-5,9-dione Under argon atmosphere, two drops of N,N-dimethylformamide (DMF) were added to a mixture of 5-bromo-2-(diphenylamino)pentanoic acid (2.60 g, 6.31 mmol) in anhydrous DCM (100 mL). After adding oxalyl chloride (1.18 mL, 13.88 mmol), the mixture was refluxed for 30 min. Then, tin (IV) chloride DCM solution (6.94 mL, 2 M, 13.88 mmol) was added and the mixture was refluxed for 3 h. After cooling to room temperature, the mixture was added dropwise to 1 M sodium hydroxide aqueous solution and extracted three times with DCM. The organic layer was dried over anhydrous magnesium sulfate. After filtering and evaporating the solvent, the given residue was purified by silica gel column chromatography using DCM / PE (V / V: 3 / 1) as eluent to obtain the product as an orange-yellow solid product, 1 H NMR (400MHz, CDCl3) δ = 8.81 (s, 2H), 8.48 (dd, J = 7.9, 1.7 Hz, 2H), 8.13 (d,J = 8.6Hz, 2H), 7.72 (ddd, J = 8.8, 7.2, 1.7 Hz, 2H), 7.53~7.49 (m, 2H). 13 C NMR (101MHz, CDCl3) δ = 117.97, 140.16, 138.41, 135.60, 133.54, 128.47, 126.79,125.97, 125.49, 120.78,117.92. MALDI-TOF: m / z calcd for C 20 H 10 BrNO2 [M] + :376.16; Found: 376.20. The structure is as follows: . Example 4

[0022] Synthesis of 7-(4-vinylphenyl)quinolino[3,2,1-de]acridine-5,9-dione (VQA) Into a 50 mL round-bottom flask charged with 7-bromoquinolino[3,2,1-de]acridine-5,9-dione (3) (1.00 g, 2.66 mmol), 4-vinylbenzeneboronic acid under argon atmosphere, Pd(PPh3)4 (0.15 g, 0.13 mmol), potassium carbonate (0.55 g, 3.99 mmol), toluene (12 mL) and deionized water (2 mL) were mixed by using a syringe. Then, the mixture was heated to 90 °C and refluxed for 24 h. After the mixture was cooled, 20 mL of deionized water was added to the resulting solution, and the mixture was extracted several times with DCM. The organic phase was dried over anhydrous magnesium sulfate. After filtration and solvent evaporation, the given residue was purified by silica gel column chromatography using DCM / PE (V / V: 4 / 1) as eluent to obtain the product (VQA) as a light yellow solid. 1 H NMR(400 MHz, CDCl3) δ = 8.99 (s,2H), 8.52 (dd, J = 7.9, 1.7 Hz, 2H), 8.16 (d, J= 8.6 Hz, 2H), 7.79 (d, J = 8.3 Hz, 2H), 7.71 (ddd, J= 8.7, 7.0, 1.7 Hz, 2H),7.56 (d, J = 8.3 Hz, 2H), 7.50 (t, J = 7.3 Hz, 2H), 6.79 (dd, J = 17.6,10.9Hz, 1H), 5.87~5.83 (d, 1H), 5.33 (d, J = 11.0 Hz, 1H). 13 C NMR (101 MHz, CDCl3) δ = 178.79,139.86, 138.52, 137.77, 137.62, 136.33, 136.22, 132.93,130.71, 128.08, 127.35, 127.15, 126.56,125.41, 124.04, 120.40, 114.72. MALDI-TOF: m / z calcd for C 28 H 17 NO2 [M] + : 399.10; Found:398.96. The structure is as follows: . Example 5

[0023] Synthesis of P4VQA Purify the 4-vinylpyridine solution by vacuum distillation technology to remove the stabilizer. Treat the toluene solution by bubbling experimental operation to obtain ultra-dry toluene. In an argon atmosphere, dissolve 0.01 equivalents (eq) of AIBN and 0.005 equivalents (eq) of VQA in 15 mL of freshly distilled toluene and stir for about 30 min. S4. Add 4-vinylpyridine to the reaction bottle and react at 70 °C for 12 h. After the reaction is completed, cool to room temperature, filter the precipitated solid, and then dissolve it in methanol (10 mL). The resulting solution is added dropwise to anhydrous ether (300 mL), and the precipitated polymer is filtered and collected to obtain a green powder. The structure is as follows: ; Among them, m=1, n=0.005.

[0024] Performance characterization of organic superfluorescent scintillators without heavy atom modification: This embodiment determines the molecular structure of the synthetic material through ultraviolet-visible absorption spectroscopy, powder X-ray diffraction, and nuclear magnetic resonance testing; determines the luminescence peak of the synthetic material molecules and the absorption peak of the doped guest material through steady-state spectroscopy; and determines the luminescence intensity of the synthetic material molecules through ultraviolet excitation spectroscopy. Figure 1 Part (a) shows the steady-state spectra of P4VQA with m:n=1:0.001 and m:n=1:0.01; Figure 2 Part (a) is the absorption spectrum of P4VQA in solution state; Figure 2 Part (b) shows the steady-state spectrum of P4VQA under excitation at 257 nm and 425 nm wavelengths; Figure 3 Part (a) is the UV excitation spectrum of P4VQA (m:n=1:0.005) physically blended with PS and PSF; Figure 3 Part (b) shows the UV excitation spectra of P4VQA (m:n = 1:0.005) with respect to each guest material at a mass ratio of 3:1 and 10:1.

[0025] It can be seen from the above test results that the heavy atom-free organic superfluorescent scintillator prepared in the above embodiment can be applied to the X-ray field.

[0026] Through reasonable molecular design, the above embodiments have obtained a new type of organic superfluorescent scintillator material. This material uses the characteristics of VQA material with amine / carbonyl multi-resonance MR chromophore to make it covalently bonded to 4-vinylpyridine as a narrow-band emitter to achieve effective energy transfer from 4VP to VQA. At the same time, 4VP can promote intersystem crossing (ISC) through effective n-π *Transitions and high triplet energy levels promote the generation of triplet excitons, which helps support efficient energy transfer from the host to the guest to sensitize the triplet excitons of the guest. In order to solve the problem of low luminescence intensity of P4VQA, P4VQA and polystyrene or polysulfone (mass ratio of 10:1) were weighed and doped respectively, and dissolved in chloroform to form a film. In the end, the film successfully avoided the problem of low luminescence intensity of single P4VQA material, effectively promoted energy transfer efficiency, and improved the luminescence intensity of the synthetic material, which provided the possibility for subsequent application in the field of X-rays.

[0027] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. An organic superfluorescent scintillator without heavy atom modification, characterized in that: The structure of the organic superfluorescent scintillator is shown in Formula I: Formula I; Among them, m:n=1:0.

005.

2. A method for preparing an organic superfluorescent scintillator without heavy atom modification, characterized in that: The following steps are involved: S1. Under an argon atmosphere, dimethyl 5-bromo-2-iodoisophthalate, diphenylamine, activated copper powder, potassium carbonate, and cuprous iodide are dissolved in o-dichlorobenzene to react to obtain dimethyl 5-bromo-2-diphenylaminopropionate; S2. Under an argon atmosphere, sodium hydroxide and an ethanol aqueous solution are added to dimethyl 5-bromo-2-diphenylaminopropionate to react to obtain 5-bromo-2-(diphenylamino)pentanoic acid; S3. Under an argon atmosphere, N,N-dimethylformamide is added to a mixture of 5-bromo-2-(diphenylamino)pentanoic acid and dichloromethane, and then oxalyl chloride and tin chloride are added to react to obtain 7-bromoquino[3,2,1-de]acridine-5,9-dione; S4, under an argon atmosphere, dissolving 7-bromoquinolino[3,2,1-de]acridine-5,9-dione, potassium carbonate, tetrakis(triphenylphosphine)palladium, and 4-vinylphenylboronic acid in toluene, adding deionized water, and reacting to obtain 7-(4-vinylphenyl)quinolino[3,2,1-de]acridine-5,9-dione; S5. Under an argon atmosphere, 7-(4-vinylphenyl)quinoline[3,2,1-de]acridine-5,9-dione, 4-vinylpyridine and azobisisobutyronitrile are added to toluene to react and obtain an organic superfluorescent scintillator P4VQA powder product.

3. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S1, the molar ratio of 5-bromo-2-iodoisophthalic acid dimethyl ester, diphenylamine, activated copper powder, potassium carbonate, and cuprous iodide is 1:1.1-1.2:0.15-0.2:1.3-1.4:0.04-0.05; the molar ratio of 5-bromo-2-iodoisophthalic acid dimethyl ester to o-dichlorobenzene is 1:157-158, the reaction temperature is 175-180°C, and the reaction time is 20-24h.

4. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S2, the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid dimethyl ester to sodium hydroxide is 1:5; the volume ratio of ethanol to water in the ethanol aqueous solution is 1:1, and the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid dimethyl ester to ethanol is 1:53-54; the reaction temperature is 75-80°C, and the reaction time is 20-24 h.

5. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S3, the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to oxalyl chloride is 1:2.1-2.2; the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to tin chloride is 1:2.1-2.2; the volume ratio of N,N-dimethylformamide to dichloromethane is 1.5:80; the molar ratio of 5-bromo-2-(diphenylamino)pentanoic acid to dichloromethane is 1:500-520.

6. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: Step S3 also includes the following steps: adding N,N-dimethylformamide to a mixture of 5-bromo-2-(diphenylamino)pentanoic acid and dichloromethane under an ice-water bath, and then adding oxalyl chloride dropwise, removing the ice-water bath and reacting at a temperature of 40-45° C. for 30 minutes, then adding tin chloride dropwise and maintaining the same temperature to continue condensing and reflux for 3 hours.

7. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S4, the molar ratio of 7-bromoquinoline [3,2,1-de] acridine-5,9-dione to 4-vinylbenzene boronic acid is 1:1.4-1.5, the molar ratio of 7-bromoquinoline [3,2,1-de] acridine-5,9-dione to potassium carbonate is 1:1.4-1.5; the molar ratio of potassium carbonate to tetrakis (triphenylphosphine) palladium is 1:0.032-0.033; the molar ratio of 7-bromoquinoline [3,2,1-de] acridine-5,9-dione to toluene is 1:42-45; the volume ratio of toluene to deionized water is 2:1; the reaction temperature is 85-90°C, and the reaction time is 20-24 h.

8. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S5, the molar ratio of 4-vinylpyridine to 7-(4-vinylphenyl)quinolino[3,2,1-de]acridine-5,9-dione is 1:0.001-0.005; the molar ratio of 4-vinylpyridine to azobisisobutyronitrile is 1:0.01-0.015; and the molar ratio of 4-vinylpyridine to toluene is 1:

2.

9. The method for preparing an organic superfluorescent scintillator without heavy atom modification according to claim 2, characterized in that: In step S5, the reaction temperature is 65-70° C., and the reaction time is 10-12 h.

10. Use of the organic superfluorescent scintillator without heavy atom modification as claimed in claim 1 in the field of X-rays.

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