Phenylphosphine dibenzofuran heat exciton compound as well as preparation method and application thereof

Abstract

The invention relates to a phenylphosphine dibenzofuran heat exciton compound as well as a preparation method and application thereof. The invention discloses an organic micromolecular photoelectric functional material based on phenyl phosphine dibenzofuran as an acceptor unit. According to the invention, phenyl phosphine dibenzofuran is used as an electron withdrawing group, and the carrier transmission capability of the device can be improved by virtue of the excellent electron transmission capability of a phosphine oxide group, so that the structure of the device is simplified, and the performance and the service life of the device are improved. The molecular weight, conjugate length, charge transfer and other inherent characteristics of the material can be effectively adjusted by regulating and controlling the variety and size of the donor connecting unit, and meanwhile, the torsion angle between the donor and the acceptor can be adjusted by introducing a benzene ring between the donor and the acceptor, so that the intramolecular hybrid local excitation charge transfer state luminescent material with a donor-acceptor structure is formed. The invention further discloses a preparation method and application of the material. The compound can be used as a novel luminescent molecule with good performance, low cost and high luminescent intensity. A non-doped device prepared from the phenyl phosphine dibenzofuran-based heat exciton compound realizes efficient blue light and sky light emission. Therefore, the molecules have remarkable economic values in the application aspects of preparing luminescent materials, luminescent devices or intelligent materials and the like, and have good application prospects in the fields of full-color display and solid-state illumination.

Description

Technical Field

[0001] The present application relates to the field of organic light-emitting materials, and more specifically, to a phenylphosphine oxide thermal exciton compound and a preparation method and application thereof. Background Art

[0002] Organic light-emitting materials used as organic light-emitting diodes (OLED) are widely used in flat panel displays, smart phones, and solid-state lighting, thanks to their significant advantages such as large area and high-quality display and lighting, ultra-high resolution, ultra-fast response speed, and flexibility. Organic light-emitting materials have great application potential in flat panel displays, smart phones, and solid-state lighting, and have attracted widespread attention from academia and industry around the world.

[0003] However, the development of blue light-emitting materials lags significantly behind that of green and red materials. This difference is mainly due to the higher band gap of blue light-emitting materials, which leads to a more unbalanced charge injection and transfer within the device. At present, commercial blue light-emitting materials mainly rely on traditional fluorescent materials, resulting in very low device efficiency. At present, both phosphorescent materials and related fluorescent materials need to be doped into the host material, which requires a host material with a higher triplet energy level, and the efficiency roll-off of the device is also large. Thermionic materials have the characteristics of high-energy triplet antisystem crossing to achieve 100% exciton utilization. Therefore, it is very important to develop new thermoexciton luminescent materials to achieve high-efficiency non-doped blue and sky-blue OLEDs. Summary of the invention

[0004] In order to overcome the problems of the above-mentioned prior art such as the lack of efficient non-doped blue light emitting materials, the present application provides a phenylphosphine oxofluorene-type thermoexciton compound with an intramolecular hybridized localized excited charge transfer state. At the same time, the phenylphosphine oxofluorene-type thermoexciton compound can be used as an organic light-emitting material, has a very high photoluminescence quantum yield in a thin film state, and can be used to prepare efficient non-doped blue light and sky blue light devices.

[0005] Another object of the present application is to provide a method for preparing the above-mentioned phenylphosphine oxide thermoexciton compound.

[0006] Another object of the present application is to provide the use of the above-mentioned phenylphosphine oxide thermoexciton compound in an organic electroluminescent device, wherein the light-emitting layer adopts the above-mentioned organic small molecule light-emitting material and has high external quantum efficiency and excellent light-emitting performance.

[0007] In order to solve the above technical problems, the technical solution adopted in this application is:

[0008] A phenylphosphine oxide thermoexciton compound can be used for organic small molecule optoelectronic functional materials, and has a molecular structure as shown in formula (I):

[0009]

[0010] Among them, D 1 , D 2 is the donor group, and the remaining phenylphosphine oxide is the acceptor group.

[0011] The present application is based on a phenylphosphine oxide system, in which phenylphosphine oxide is an electron acceptor (A), and by introducing groups (D) with different electron donating abilities thereto, an organic light-emitting material having a D-π-A-π-D structure is formed. The phosphine oxide group of the phenylphosphine oxide group has excellent electron transport capability, which can improve the carrier transport capability of the device. In addition, the introduction of a benzene ring between D and A can reduce the torsion angle between DA, so that the molecule has an intramolecular hybridized localized excited charge transfer state, thereby increasing the partial overlap of the frontier orbitals of the molecule, improving the fluorescence quantum efficiency, and achieving a very high photoluminescence quantum yield in a thin film state, and obtaining excellent device efficiency.

[0012] Therefore, the phenylphosphine oxide thermoexciton compound provided in the present application can be used as a luminescent material or smart material, and has a good application prospect in the fields of full-color display and solid-state lighting.

[0013] Preferably, D1 and D2 are selected from the following structural formulas:

[0014]

[0015] One or more of, wherein R is selected from H, Me, MeO, t-Bu, or Ph.

[0016] Preferably, the D 1 , D 2 Selected from the following structural formula:

[0017]

[0018] One or more of, R is selected from H, Me, MeO, t-Bu, or Ph.

[0019] Preferably, the D 1 , D 2 Selected from the following structural formula:

[0020]

[0021] One or more of, R is selected from H, Me, MeO, t-Bu, or Ph.

[0022] The present application also provides a method for preparing the phenylphosphine oxide thermoexciton compound, comprising the following steps:

[0023] S1 Preparation of intermediate 1: 4,4'-dibromo-3-nitro-1,1'-biphenyl and copper powder are added to a reaction bottle in sequence, nitrogen is replaced three times, N,N-dimethylformamide is added, and reflux reaction is carried out at 110-150°C under nitrogen conditions. After the reaction is completed, the system is restored to room temperature, extracted and washed with dichloromethane and saturated brine, the organic phase is recovered and dried with anhydrous magnesium sulfate, the solvent is removed by distillation under reduced pressure, and the crude product is separated and purified by column chromatography to obtain intermediate 1;

[0024]

[0025] S2 preparation of intermediate 2: the intermediate 1 obtained in step S1 and iron powder are added to the reaction bottle in sequence, the nitrogen is replaced three times, acetic acid is added, and the reaction is heated at 40-100°C under nitrogen conditions. After the reaction is completed, the system is returned to room temperature, neutralized with sodium bicarbonate and filtered, and the solvent is removed by distillation under reduced pressure. The crude product is then separated and purified by column chromatography to obtain intermediate 2;

[0026]

[0027] S3 Preparation of Intermediate 3: Dissolve the intermediate 2 prepared in step S2 in acetic acid, add a sodium nitrite aqueous solution at -10 degrees and stir for 30 minutes, add a potassium iodide aqueous solution at -20 to 0 degrees, and continue stirring for 30 minutes. Return to room temperature, stir overnight, extract and wash with dichloromethane and saturated brine, recover the organic phase and dry it with anhydrous magnesium sulfate, distill under reduced pressure to remove the solvent, and then separate and purify the crude product by column chromatography to generate Intermediate 3;

[0028]

[0029] S4 Preparation of Intermediate 4: Under low temperature conditions of -60 to -80°C, the intermediate 3 obtained in step S3 is dissolved in tetrahydrofuran, then n-butyl lithium is slowly added and stirred for 1 hour, then phenylphosphine dichloride is added and stirring is continued for 30 minutes. Return to room temperature and stir overnight. After 12 hours, 30% hydrogen peroxide is added, and after reacting for 1 hour, water is added to quench the reaction, and the reaction is extracted and washed with dichloromethane and saturated brine, the organic phase is recovered and dried over anhydrous magnesium sulfate, and the solvent is removed by distillation under reduced pressure, and then the crude product is separated and purified by column chromatography to obtain Intermediate 4;

[0030]

[0031] Preparation of S5 phenylphosphine oxide thermoexciton compound: The intermediate 4 prepared in S4 is dissolved together with an alkaline salt, a catalyst and a donor group in an organic solvent, and subjected to heating reaction and post-treatment to obtain a phenylphosphine oxide thermoexciton compound.

[0032] Preferably, in step S1, the molar ratio of 4,4'-dibromo-3-nitro-1,1-biphenyl to copper powder is 1:(1-2), the reaction temperature is 110-150° C., and the reaction time is 1-4 h.

[0033] Preferably, in step S2, the molar ratio of the intermediate 1 to the iron powder (is 1:(10-20), the reaction temperature is 40-100° C., and the reaction time is 10-20 h.

[0034] Preferably, the molar ratio of the intermediate 2, sodium nitrite and potassium iodide in step S3 is 1:(1-3):(2-4), the reaction temperature is -20-0°C, and the reaction time is 10-20h.

[0035] Preferably, the molar ratio of intermediate 3, n-butyl lithium (2.5M) and phenylphosphine dichloride in step S4 is 1:(2-3):(1-2), the reaction temperature is -60--80°C, and the reaction time is 1-2h. Return to room temperature and continue stirring for 12 hours. The molar ratio of intermediate 3 to hydrogen peroxide (30%) is 1:5, the reaction temperature is -10-30°C, and the reaction time is 4-6h.

[0036] Preferably, the molar ratio of the intermediate 4 to the alkaline salt, the catalyst and the donor group in step S5 is 1:(2-4):(0.03-0.05):(2-2.5), the alkaline salt of the reaction is one of sodium tert-butoxide or potassium tert-butoxide, the catalyst of the reaction is one of palladium acetate, tris(dibenzylideneacetone)dipalladium or 1,1'-bis(diphenylphosphinoferrocene)palladium dichloride, the organic solvent of the reaction is one of toluene, dimethyl sulfoxide, and N,N-dimethylformamide, and the reaction is carried out under an inert gas atmosphere at a temperature of 100°C to 120°C for 12 to 24 hours.

[0037] The phenylphosphine oxide thermoexciton compound is used as a luminescent material, a luminescent device or an intelligent material.

[0038] Compared with the prior art, the beneficial effects of this application are:

[0039] The present application provides a phenylphosphine oxide group as an acceptor, by changing the donor molecular structure, forming a coexistence of an intramolecular hybridized localized state and a charge transfer state, thereby forming a thermoexciton channel. With this type of non-doped device based on the thermoexciton luminescent material of phenylphosphine oxide, the maximum external quantum efficiency is greater than 5%. The phenylphosphine oxide thermoexciton compound has significant economic value in the preparation of luminescent materials, luminescent devices or intelligent materials, and has a good application prospect in the fields of full-color display and solid-state lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1This is the hydrogen nuclear magnetic resonance spectrum of the thermal exciton compound A1 prepared in Example 1 of the present application.

[0041] Figure 2 This is the mass spectrum of the thermal exciton compound A1 prepared in Example 1 of the present application.

[0042] Figure 3 The thermal exciton compound A1 prepared in Example 1 of the present application is 1.0×10 -5 UV absorption and fluorescence emission spectra of M in tetrahydrofuran solution.

[0043] Figure 4 This is a fluorescence emission spectrum of the thermoexciton compound A1 prepared in Example 1 of the present application in different solutions.

[0044] Figure 5 This is a relationship diagram between the Stokes shift and the solvent polarity parameter of A1 prepared in Example 1, which is drawn according to the Lippert Mataga solvatochromic model.

[0045] Figure 6 This is the thermogravimetric analysis diagram of the thermal exciton compound A1 prepared in Example 1.

[0046] Figure 7 This is the luminescence spectrum of an organic electroluminescent device using the thermoexciton compound A1 prepared in Example 1 as the luminescent layer material.

[0047] Figure 8 This is a current density-voltage-brightness curve of an organic electroluminescent device using the thermoexciton compound A1 prepared in Example 1 as the light-emitting layer material.

[0048] Fig. 9 This is a graph showing the relationship between external quantum efficiency and brightness of an organic electroluminescent device using the thermoexciton compound A1 prepared in Example 1 as the light-emitting layer material.

[0049] Fig.10 This is a variable-angle luminescence spectrum diagram of the thermal exciton compound A1 prepared in Example 1.

[0050] Fig.11 This is a graph of the absolute quantum efficiency of compound A1 prepared in Example 1 of the present application.

[0051] Fig.12 Schematic diagram of the luminescence mechanism of the thermoexciton compound A1 prepared in Example 1 of the present application through high-energy-level reverse intersystem crossing. DETAILED DESCRIPTION

[0052] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0053] It should be noted that:

[0054] In this application, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0055] In the present application, unless otherwise specified, percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0056] In the present application, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0057] In this application, unless otherwise specified, the numerical range "a-b" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6-15" means that all real numbers between "4-6" are listed in this document, and "4-6" is just an abbreviation of these numerical combinations.

[0058] The "range" disclosed in the present application is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0059] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in a sequential manner. Preferably, the reaction method herein is carried out sequentially.

[0060] Unless otherwise specified, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present application.

[0061] The present application provides a phenylphosphine oxide thermoexciton compound, which can be used for organic small molecule optoelectronic functional materials. The phenylphosphine oxide thermoexciton compound has a molecular structure as shown in formula (I):

[0062]

[0063] Among them, D 1 , D 2 is a donor group, and the phenylphosphine oxide is an acceptor group.

[0064] The present application is based on a phenylphosphine oxide system, wherein phenylphosphine oxide is an electron acceptor (A), and by introducing groups (D) with different electron donating abilities thereto, a thermoexciton luminescent material having an intramolecular hybridized localized excited charge transfer state with a D-π-A-π-D structure is formed. The phosphine oxide group of the phenylphosphine oxide group has excellent electron transport capability, which can improve the carrier transport capability of the device. In addition, by introducing a benzene ring between the donor and the acceptor, the torsion angle between the donor and the acceptor can be adjusted, the torsion angle of the molecule can be reduced, the overlap of the frontier molecular orbitals can be increased, and the fluorescence quantum efficiency can be improved. The fluorescence quantum efficiency of A1 measured in toluene is 93.27%, which is conducive to the realization of efficient non-doped light-emitting devices, and overcomes the problems of the above-mentioned prior art lacking efficient non-doped blue light or sky blue light emitting materials.

[0065] In some embodiments, D1 and D2 are selected from the following structural formulas:

[0066]

[0067] One or more of, wherein R is selected from H, Me, MeO, t-Bu, or Ph.

[0068] Therefore, the present application is based on the phenylphosphine oxide system, in which phenylphosphine oxide is an electron acceptor (A), and by introducing groups (D) with different electron donating abilities thereinto, a variety of charge transfer organic light-emitting materials with a D-π-A-π-D structure are constructed.

[0069] In some embodiments of the present application, the D 1 , D 2 Selected from the following structural formula:

[0070]

[0071] One or more of, R is selected from H, Me, MeO, t-Bu, or Ph. For example, the following phenylphosphine oxide thermoexciton compound can be constructed:

[0072]

[0073] The phenylphosphine oxide fluorene thermoexciton compound system constructed above is diverse and can also achieve short-wave emission, for example, it can achieve blue light to sky blue light (such as Figure 7 shown).

[0074] Example 1

[0075] This embodiment provides a phenylphosphine oxide thermoexciton compound, the structural formula of which is shown in A1:

[0076]

[0077] The preparation method of the thermal exciton compound is as follows:

[0078] S1. Preparation of intermediate 1:

[0079] 4,4'-dibromo-3-nitro-1,1'-biphenyl (10mmol, 3.54g) and copper powder (15mmol, 0.95g) were added to a 100ml two-necked flask in the reaction bottle in sequence. After replacing nitrogen three times, 30mL of N,N-dimethylformamide was added through a syringe. React at 120°C for 1 hour under nitrogen conditions. After the reaction is completed, the reaction solution is cooled to room temperature and extracted with dichloromethane and saturated brine three times. Take the organic phase and evaporate dichloromethane under reduced pressure to obtain a crude product. Then separate and purify by silica gel column chromatography with dichloromethane / n-hexane as eluent to obtain intermediate 1 with a yield of 90%. The structural formula of intermediate 1 is as follows:

[0080]

[0081] The reaction equation is:

[0082]

[0083] S2. Preparation of intermediate 2;

[0084] The intermediate 1 (11.02 g, 20 mmol) and iron powder (11.4 g, 200 mmol) obtained in step S1 were added to the reaction bottle in sequence. After nitrogen was replaced three times, 30 ml of acetic acid was added and the reaction was heated at 50°C under nitrogen for 15 hours. After the reaction was completed, the system was returned to room temperature, neutralized with sodium bicarbonate and filtered, and the solvent was removed by vacuum distillation. The crude product was then recrystallized from diethyl ether to obtain intermediate 2 with a yield of 85%.

[0085]

[0086] The reaction equation is:

[0087]

[0088] S3. Preparation of intermediate 3;

[0089] The intermediate 2 (9.83 g, 20 mmol) obtained in step S2 was dissolved in 60 ml of acetic acid, and an aqueous solution of sodium nitrite (4.20 g, 40 mmol) was added dropwise at -10°C and stirred for 30 min. An aqueous solution of potassium iodide (9.96 g, 60 mmol) was added at -10°C and stirred for 30 minutes. The mixture was restored to room temperature, stirred overnight, extracted and washed with dichloromethane and saturated brine, the organic phase was recovered and dried over anhydrous magnesium sulfate, the solvent was removed by distillation under reduced pressure, and dichloromethane / n-hexane was used as the eluent for separation and purification to obtain intermediate 1 with a yield of 55%. The structural formula of the intermediate 3 is shown below:

[0090]

[0091] The reaction equation is:

[0092]

[0093] S4. Preparation of intermediate 4;

[0094] Under low temperature -78 ° C, the intermediate 3 (10mmol, 7.13g) was dissolved in 60mL tetrahydrofuran, and then 2.5mL n-butyl lithium (2.5M) (24mmol, 9.6ml) was slowly added and stirred for 1 hour, and then phenylphosphine dichloride (15mmol, 2.66g) was added and stirred for 30 minutes. The room temperature was restored and stirred for 12 hours. After 12 hours, 5ml of 30% hydrogen peroxide was added, and water was added after 1 hour of reaction to quench the reaction, and the organic phase was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered and dried with anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The reaction solution was extracted with dichloromethane and saturated brine for 3 times. The organic phase was taken and the dichloromethane was evaporated under reduced pressure to obtain a crude product. Then, the intermediate 4 was separated and purified by silica gel column chromatography with ethyl acetate / n-hexane as eluent, and the yield was 65%.

[0095] The structural formula of the intermediate 4 is shown below:

[0096]

[0097] The reaction equation is:

[0098]

[0099] Preparation of S5.A1:

[0100] Preparation of S5 phenylphosphine oxide thermal exciton compounds:

[0101] Intermediate 4 (2mmol, 1.17g), tert-butyl carbazole (2.5mmol, 1.67g), tri-tert-butylphosphine tetrafluoroborate (0.2mmol, 58.2mg), tri(dibenzylideneacetone)dipalladium (0.2mmol, 183.0mg) and sodium tert-butoxide (4mmol, 768.8mg) were added to a 100ml two-necked flask in the reaction bottle in sequence. After replacing nitrogen three times, 30mL of toluene was added through a syringe. Reflux at 110°C under nitrogen for 24 hours. After the reaction was completed, the reaction solution was cooled to room temperature and extracted with ethyl acetate and saturated brine three times. The organic phase was taken and the dichloromethane was evaporated under reduced pressure to obtain a crude product. Then, A1 was separated and purified by silica gel column chromatography with ethyl acetate / n-hexane as eluent, and the yield was 85%. The structural formula of the final thermoexciton compound A1 is shown below:

[0102]

[0103] The reaction equation is

[0104]

[0105] Performance Testing

[0106] The phenylphosphine oxide thermal exciton compound A1 obtained in Example 1 was characterized and its performance tested.

[0107] The test method is as follows:

[0108] The structure of the thermal exciton compound was detected using a Bruker 600MHz superconducting nuclear magnetic resonance spectrometer, with deuterated chloroform or deuterated dimethyl sulfoxide as the solvent;

[0109] Mass spectrometry detection: A1 prepared in Example 1 was dissolved in dichloromethane to prepare a solution with a concentration of 1 mg / mL, and mass spectrometry was performed using a liquid spectrometer LCMS-2020.

[0110] UV absorption spectrum detection: Shimadzu UV-visible spectrophotometer UV-2700 was used with a scanning range of 200 to 550 nm;

[0111] Emission spectrum detection: using a steady-state / transient fluorescence spectrometer (FLS980), with an excitation wavelength of 310 nm,

[0112] The test temperature was 300K under nitrogen protection.

[0113] Thermogravimetric analysis test: using TGA thermogravimetric analyzer (TGA 4000), heating rate is 10℃min under nitrogen protection -1 , the heating end point is greater than 700℃.

[0114] Electroluminescence test: Indium tin oxide (ITO) glass substrates with a resistance of 15Ω / square were cleaned with optical cleaner, deionized water, acetone, and isopropyl alcohol, followed by a 5-minute plasma treatment. After treatment, the substrates were transferred to a vacuum chamber. Under high vacuum conditions (<8×10 -5 Pa), organic materials After the deposition of the organic layer, the ITO glass substrate was patterned using a light shield with an array of 2.0 mm × 2.5 mm openings. Subsequently, LiF and Al were deposited at a rate of and The OLEDs were deposited successively at a rate of 100 nm. In the experiment, the electroluminescence spectrum, CIE coordinates and brightness intensity of the OLEDs were recorded using Photo Research PR655, and the current density and driving voltage were recorded using Keithley2400. Assuming a Lambertian distribution, the external quantum efficiency was estimated by the brightness, electroluminescence spectrum and current density. The organic electroluminescent device of this embodiment was obtained. Device structure: glass substrate / indium tin oxide (125 nm) / HATCN (10 nm) / TAPC (40 nm) / TCTA (10 nm) / A1 / TmPyPB (40 nm) / lithium fluoride (1 nm) / aluminum (100 nm). Among them, indium tin oxide is the anode, HATCN is the hole injection layer, TAPC is the hole transport layer, TCTA is the exciton blocking layer, TmPyPB is the electron transport layer, lithium fluoride is the electron injection layer, aluminum is the cathode, and A1 is the light-emitting layer.

[0115] The molecular hydrogen spectrum of the phenylphosphine oxide thermoexciton compound A1 prepared in Example 1 is as follows: Figure 1 As shown. It can be seen that: 1 H NMR(600MHz,Chloroform-d)δ8.15(d,J=1.9Hz,4H),8.08(dd,J=10.3,1.8Hz,2H),8.01(dd,J=8.0,3.0Hz,2H),7.97(t,J=1.5Hz,2H),7.86-

[0116] 7.81 (m, 4H), 7.81-7.76 (m, 2H), 7.67-7.63 (m, 4H), 7.56-7.51 (m, 1H), 7.47 (td, J = 9.0, 2.5Hz, 6H), 7.40 (d, J = 8.6Hz, 4H), 1.47 (s, 36H), the molecular hydrogen spectrum peaks can correspond to the target product one by one, and the number is reasonable; from the mass spectrum (i.e. Figure 2) can be seen in the figure, the relative molecular mass is 983.5064, minus one H, which is consistent with the relative molecular mass of the synthesized A1. Combining the above NMR and mass spectrometry results, it can be seen that the product obtained in Example 1 is A1.

[0117] Using Shimadzu UV-2700 ultraviolet visible spectrophotometer, A1 prepared in Example 1 was dissolved in dichloromethane solution to prepare 1×10 -3 mol / L stock solution, diluted to 1×10 -5 mol / L. Using fluorescence emission spectroscopy: FLS980 fluorescence instrument, A1 prepared in Example 1 was dissolved in dichloromethane solution to prepare 1×10 -3 mol / L stock solution, when testing, dilute to 1×10 -5 mol / L.

[0118] Figure 3 A1 prepared in Example 1 is 1×10 -5 mol / L tetrahydrofuran UV-visible absorption and fluorescence emission spectra. Figure 3 It can be seen that the main absorption peak positions of A1 are 372nm, the main emission peak positions are 452nm, and it has blue light emission.

[0119] Figure 4 The fluorescence emission spectra of A1 prepared in Example 1 in different solutions are shown in FIG. Figure 4 It can be seen that with the increase of polarity of the solvent from n-hexane to acetone, an obvious solvatochromism is presented, that is, the fluorescence emission gradually red-shifts, which is a typical sign of the CT characteristics of the corresponding excited state molecules.

[0120] Figure 5 The relationship between the Stokes shift and the solvent polarity parameter of A1 prepared in Example 1 is plotted according to the Lippert Mataga solvatochromic model, as shown in FIG. Figure 5 As shown, all the thermoexciton compounds exhibit two linear fits in low-polarity solvents and high-polarity solvents, respectively, indicating the existence of two different excited states.

[0121] Thermogravimetric analysis test: using TGA thermogravimetric analyzer (TGA 4000), heating rate is 10℃min under nitrogen protection -1 , the heating end point is greater than 700℃.

[0122] Figure 6 This is the thermogravimetric analysis diagram of the thermal exciton compound A1 prepared in Example 1. Figure 6 It can be seen that the thermal decomposition temperature of A1 is 513.7°C. This molecule has a very high decomposition temperature and can be easily obtained through gradient sublimation to obtain high-purity optoelectronic materials for use, and is suitable for use in electroluminescent devices.

[0123] Figure 7 The luminescence spectrum of the organic electroluminescent device using the thermoexciton compound A1 prepared in Example 1 as the luminescent layer material. Figure 7 It can be seen that the electroluminescence peak of A1 is 460 nanometers, which makes it possible to realize efficient non-doped blue light-emitting devices.

[0124] Figure 8 A current density-voltage-brightness curve of an organic electroluminescent device using the thermal exciton compound A1 prepared in Example 1 as a light-emitting layer material;

[0125] Fig. 9 This is a graph showing the relationship between external quantum efficiency and brightness of an organic electroluminescent device using the thermal exciton compound A1 prepared in Example 1 as the light-emitting layer material. Fig. 9 It can be seen that the maximum external quantum efficiency of A1 is 7.3% and 5.5% respectively.

[0126] Meanwhile, the starting voltage, maximum current efficiency, maximum external quantum efficiency, CIE coordinates and other data of the non-doped organic electroluminescent device prepared in Example 1 with the thermoexciton compound A1 as the light-emitting layer material are summarized as shown in the following table.

[0127]

[0128] As can be seen from the above table, the obtained non-doped organic electroluminescent device has a lower starting voltage, better external quantum efficiency, and emits blue light and sky blue light.

[0129] Fig.10 This is a variable angle luminescence spectrum diagram of the thermal exciton compound A1 prepared in Example 1. Fig.10 It can be seen that the orientation factor of the A1 film is 90%. Therefore, this method of connecting the donor at the meta position of the benzene ring of phenylphosphine oxide as the main core makes the molecules have a long axis linear arrangement, which is beneficial to improving the light extraction efficiency of the device.

[0130] Fig.11 The thermal exciton compound A1 prepared in Example 1 is 1×10 -5 The fluorescence quantum efficiency measured in mol / L toluene is 93.27%, achieving efficient luminescence. This is due to the fact that the phenylphosphine oxide thermoexciton compound A1 can adjust the torsion angle between the donor and the acceptor by introducing a benzene ring between the donor and the acceptor, reduce the torsion angle of the molecule, increase the overlap of the frontier molecular orbitals, and improve the fluorescence quantum efficiency.

[0131] Fig.12 Schematic diagram of the luminescence mechanism of the thermoexciton compound prepared from the thermoexciton compound A1 prepared in Examples 1 and 2 through high-energy level reverse intersystem crossing.

[0132] In summary, the multi-electron donor phenylphosphine oxide thermoexciton compound provided in the present application exhibits blue light and sky blue light emission, and the maximum external quantum efficiency of the non-doped device prepared by this type of molecule is 7.3% and 5.5% respectively, breaking through the theoretical limit of 5% of the external quantum efficiency of traditional fluorescent materials. The molecule can be used as a new type of OLED light-emitting molecule with good performance and low cost. The phenylphosphine oxide thermoexciton compound is conducive to the formation of long-axis linear molecules and is conducive to improving the light extraction efficiency of the device because the donor is connected to the benzene ring meta position of the phenylphosphine oxide as the main core. Therefore, it has significant economic value in the preparation of luminescent materials, luminescent devices or smart materials, and has good application prospects in the fields of full-color display and solid-state lighting.

[0133] At the same time, the present application realizes the controllable preparation of multi-donor phenylphosphine oxide thermoexciton compounds; the preparation cost is low, the raw material source is wide, large-scale production can be achieved, and it has broad commercial prospects.

[0134] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0135] Although several embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A phenylphosphine oxide thermoexciton compound, which can be used for organic small molecule optoelectronic functional materials, characterized in that: It has a molecular structure as shown in formula (I): Wherein, D1 and D2 are donor groups, phenylphosphine oxide is an acceptor group, and D1 and D2 are selected from any one of the following structural formulas: The R is selected from H, Me, t-Bu, MeO, or Ph.

2. The phenylphosphine oxide thermoexciton compound according to claim 1, characterized in that: The D1 and D2 are selected from the following structural formula: One or more of, R is selected from H, Me, MeO, t-Bu, or Ph.

3. The method for preparing the phenylphosphinofluorene thermoexciton compound according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1 Preparation of Intermediate 1 4,4'-dibromo-3-nitro-1,1'-biphenyl and copper powder are added to a reaction bottle in sequence, and after nitrogen is replaced three times, N,N-dimethylformamide is added, and reflux reaction is carried out at 110-150°C under nitrogen conditions. After the reaction is completed and the system returns to room temperature, extraction and washing are performed with dichloromethane and saturated brine, and the organic phase is recovered and dried with anhydrous magnesium sulfate. The solvent is removed by distillation under reduced pressure, and then the crude product is separated and purified by column chromatography to obtain intermediate 1: S2 Preparation of Intermediate 2 The intermediate 1 obtained in step S1 and iron powder were added to the reaction bottle in sequence. After nitrogen was replaced three times, acetic acid was added and heated to 40-100°C under nitrogen conditions for reaction. After the reaction was completed, the system was restored to room temperature, neutralized with sodium bicarbonate and filtered, and the solvent was removed by distillation under reduced pressure. The crude product was then separated and purified by column chromatography to obtain intermediate 2: S3 Preparation of Intermediate 3 The intermediate 2 prepared in step S2 was dissolved in acetic acid, and a sodium nitrite aqueous solution was added at -10 degrees and stirred for 30 minutes. A potassium iodide aqueous solution was added at -20 to 0 degrees Celsius, and the stirring was continued for 30 minutes. The mixture was returned to room temperature and stirred overnight. The mixture was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and the crude product was then separated and purified by column chromatography to generate intermediate 3: S4 Preparation of Intermediate 4 At a low temperature of -60 to -80°C, the intermediate 3 obtained in step S3 is dissolved in tetrahydrofuran, and then n-butyl lithium is slowly added and stirred for 1 hour, and then phenylphosphine dichloride is added, and stirring is continued for 30 minutes. After returning to room temperature, 30% hydrogen peroxide is added after stirring overnight, and water is added to quench the reaction after 1 hour of reaction. The reaction is extracted and washed with dichloromethane and saturated brine, the organic phase is recovered and dried over anhydrous magnesium sulfate, and the solvent is removed by distillation under reduced pressure, and then the crude product is separated and purified by column chromatography to obtain intermediate 4: S5 Preparation of Phenylphosphinofluorene Thermal Exciton Compounds The intermediate 4 prepared from S4 is dissolved together with an alkaline salt, a catalyst and a donor group in an organic solvent, and subjected to a heating reaction and post-treatment to obtain a phenylphosphine oxide thermoexciton compound.

4. The method for preparing the phenylphosphinofluorene thermoexciton compound according to claim 3, characterized in that: In step S1, the molar ratio of 4,4'-dibromo-3-nitro-1,1-biphenyl to copper powder is 1:(1-2).

5. The method for preparing the phenylphosphinobenzofuran-based thermoexciton compound according to claim 4, characterized in that: The reaction temperature of step S1 is 120° C., and the reaction time is 1 to 4 hours.

6. The method for preparing the phenylphosphinofluorene thermoexciton compound according to claim 3, characterized in that: In step S2, the molar ratio of the intermediate 1 to the iron powder is 1:(10-20), the reaction temperature is 50° C., and the reaction time is 10-20 h.

7. The method for preparing the phenylphosphinofluorene thermoexciton compound according to claim 3, characterized in that: In step S3, the molar ratio of the intermediate 2, sodium nitrite and potassium iodide is 1:(1-3):(2-4), and the reaction temperature is -15°C.

8. The method for preparing the phenylphosphinofluorene thermoexciton compound according to claim 3, characterized in that: In step S4, the molar ratio of intermediate 3, n-butyl lithium and phenylphosphine dichloride is 1:(2-3):(1-2), the reaction temperature is -78°C, the reaction time is 1-2h, the temperature is restored to room temperature, and stirring is continued for 12 hours; the molar ratio of intermediate 3 to hydrogen peroxide is 1:5, the reaction temperature is -10-30°C, and the reaction time is 4-6h.

9. The method for preparing the phenylphosphinofluorene thermoexciton compound according to claim 3, characterized in that: The molar ratio of the intermediate 4 to the alkaline salt, the catalyst and the donor group described in step S5 is 1:(2-4):(0.03-0.05):(2-2.5), the alkaline salt used in the reaction is one of sodium tert-butoxide or potassium tert-butoxide, the catalyst used in the reaction is one of palladium acetate, tris(dibenzylideneacetone)dipalladium or 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride, the organic solvent used in the reaction is one of toluene, dimethyl sulfoxide and N,N-dimethylformamide, and the reaction is carried out under an inert gas atmosphere at a temperature of 100°C to 120°C for 12 to 24 hours.

10. Use of the phenylphosphinophene oxide thermoexciton compound according to claim 1 or 2 as a light-emitting material or a light-emitting device.

Images