Narrow-band blue-light molecule as well as preparation method and application thereof

Abstract

The invention discloses a narrow-band blue light molecule as well as a preparation method and application thereof. Two donor units are introduced into a fluorene skeleton and form a staggered structure with multiple resonance units in space to regulate and control the space charge transfer intensity, on one hand, the reverse intersystem crossing rate can be improved to improve the performance and efficiency of the device, and on the other hand, efficient light emission of a narrow band is maintained. The invention further discloses a preparation method and application of the material. The compound can be used as a novel luminescent molecule with high performance, high color purity and high quantum efficiency. The narrow-band blue-light molecule has huge application potential in the aspects of preparation of luminescent materials, luminescent devices, electronic technologies and the like, and has obvious and clear prospects in the fields of display technologies and solid-state illumination luminescence.

Description

Technical Field

[0001] The present application relates to the technical field of organic light-emitting materials, and more specifically, to a preparation method and application of narrow-band blue light molecules. Background Art

[0002] In past reports, DA-type TSCT-TADF molecules (thermally activated delayed fluorescence molecules through space charge transfer) with a narrow luminescence spectrum (half-peak width of about 50nm) generally use polycyclic aromatic hydrocarbon compounds fused with boron and oxygen atoms as acceptor units. However, the multiple resonance characteristics of the boron-oxygen unit are weak. When used as an acceptor of the TSCT-TADF molecule, it interacts with the donor unit to produce emission dominated by long-range charge transfer. Its multiple resonance characteristics are easily destroyed, and it is difficult to maintain its own narrow-band emission characteristics.

[0003] However, due to the large structural rigidity of the boron-oxygen unit, it can effectively inhibit the structural relaxation of the excited state and to a certain extent inhibit the broadening of the emission half-peak width. The existing common MR-TADF materials (multiple resonance thermally activated delayed fluorescence materials) have a large ΔE due to excessive overlap of HOMO and LUMO. ST And it makes the reverse intersystem crossing process slow down.

[0004] Application Contents

[0005] In order to overcome one of the problems existing in the above-mentioned prior art, the primary purpose of the present application is to provide a narrow-band blue light molecule, which introduces two donor units into the fluorene skeleton to form a staggered structure with the multiple resonance units in space to regulate the spatial charge transfer intensity, and has the advantages of high luminous efficiency, narrow band and high color purity.

[0006] Another object of the present application is to provide a method for preparing the above-mentioned narrow-band blue light molecule.

[0007] Another object of the present application is to provide applications of the above narrow-band blue light molecules.

[0008] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0009] A narrow-band blue light molecule can be used for organic small molecule optoelectronic functional materials, and has a molecular structure shown in the following formula (I):

[0010]

[0011] Wherein, D is an electron donating group.

[0012] Preferably, in the narrow-band blue light molecule of the present application, the D is selected from one of the following structural formulas:

[0013]

[0014] The present application also provides a method for preparing the above narrow-band blue light molecule, comprising the following steps:

[0015] S1 Preparation of Intermediate 1:

[0016] 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate were added to the reaction bottle in sequence, and after nitrogen was replaced three times, N,N-dimethylformamide was added, and reflux reaction was carried out under nitrogen conditions. After the reaction was completed, the system was restored to room temperature, and then extracted and washed with dichloromethane and saturated brine. After the organic phase was recovered and the solvent was removed, ethanol was added, heated and stirred, and filtered to obtain intermediate 1, whose structural formula is shown below;

[0017]

[0018] S2 Preparation of Intermediate 2:

[0019] The intermediate 1 obtained in step S1 is dissolved in o-xylene, and n-butyl lithium is slowly added under stirring, and then boron tribromide is continuously added under stirring, and then N,N-diisopropylethylamine is added, and stirring is continued for 5 hours; after the reaction, 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 with 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 an intermediate 2, whose structural formula is shown below;

[0020]

[0021] S3 Preparation of Intermediate 3:

[0022] The intermediate 2 prepared in step S2 is dissolved in 1,4-dioxane, and diboric acid pinacol ester, 1,1-bis(diphenylphosphino)ferrocene palladium dichloride, and potassium acetate are added. After nitrogen is replaced three times, the reaction is carried out for 24 hours. The mixture is extracted and washed with dichloromethane and saturated brine, the organic phase is recovered and dried with anhydrous magnesium sulfate, and the solvent is removed by distillation under reduced pressure. The crude product is then separated and purified by column chromatography to generate intermediate 3, the structural formula of which is shown below;

[0023]

[0024] S4. Preparation of intermediate 4:

[0025] 1-Bromo-9-fluorenone and a compound containing an electron-donating group were added to a two-necked flask, and carbon tetrachloride and methanesulfonic acid solvent were added. The nitrogen was replaced three times for 24 hours, and the mixture was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was then separated and purified by column chromatography to generate intermediate 4.

[0026] S5. Preparation of narrow-band blue light molecules:

[0027] The prepared intermediate 3, intermediate 4 and potassium carbonate were added to a two-necked flask, and tetrahydrofuran and water were added as solvents. After nitrogen was replaced three times, the catalyst tetrakis(triphenylphosphine)palladium was added to react for 12 hours. After removing tetrahydrofuran, 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 obtain a narrow-band blue light molecule.

[0028] Preferably, in step S1, the molar ratio of 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2-3):(2-3), the reaction temperature is 110-150° C., and the reaction time is 24-36 h.

[0029] Preferably, in step S2, the molar ratio of the intermediate 1, n-butyl lithium (2.5 M) and boron tribromide is 1:(2-3):(1-2), the reaction temperature is 0-20° C., and the reaction time is 1-2 h.

[0030] Preferably, in step S3, the molar ratio of the intermediate 2 to bipyraclostrobin, potassium acetate, and 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride is 1:2:3:0.05, the reaction temperature is 100-140° C., and the reaction time is 12-24 h.

[0031] Preferably, in step S4, the molar ratio of 1-bromo-9-fluorenone to the donor group, carbon tetrachloride and methanesulfonic acid is 1:4, the reaction temperature is 90° C., and the reaction time is 24 h.

[0032] Preferably, the molar ratio of intermediate 3, intermediate 4, potassium carbonate, tetrahydrofuran, water and tetrakis(triphenylphosphine)palladium described in step S5 is (1-2):1:2:0.05, the reaction temperature is 70-80°C, and the reaction time is 12h.

[0033] The narrow-band blue light molecules in the present application are used as luminescent materials, luminescent devices or smart materials.

[0034] Compared with the prior art, the beneficial effects of this application are:

[0035] The narrow-band blue light molecule provided in the present application bridges the donor unit and the multiple resonance unit through the fluorene skeleton to realize the combination of two different charge transfer modes, long-range charge transfer and short-range charge transfer. While maintaining the narrow-band emission of the short-range charge transfer characteristics of the multiple resonance unit, the high-energy excited state with the long-range charge transfer property is introduced to promote multi-channel exciton spin flip coupling and achieve faster reverse intersystem crossing. At the same time, the additionally introduced donor unit can bring about a great steric hindrance effect, making it impossible to form long-range π-π stacking between molecules, which can effectively inhibit the serious aggregation-induced luminescence quenching of MR-TADF molecules, so that the EQE of the molecule reaches 33.61% at a doping concentration of 20%, which can be used as a new type of luminescent molecule with good performance, low cost and high luminescence intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound A1 prepared in Example 1 of the present application;

[0037] Figure 2 The mass spectrum of compound A1 prepared in Example 1 of the present application;

[0038] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of compound A2 prepared in Example 2 of the present application;

[0039] Figure 4 The mass spectrum of compound A2 prepared in Example 2 of the present application;

[0040] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of compound A3 prepared in Example 3 of the present application;

[0041] Figure 6 The mass spectrum of compound A3 prepared in Example 3 of the present application;

[0042] Figure 7 This is the hydrogen nuclear magnetic resonance spectrum of compound A4 prepared in Example 4 of the present application;

[0043] Figure 8 The mass spectrum of compound A4 prepared in Example 4 of the present application;

[0044] Fig. 9 Compounds A1, A2, A3, and A4 prepared in Examples 1, 2, 3, and 4 of the present application were 1.0×10 -5 UV absorption spectrum of M in toluene solution;

[0045] Fig.10 Compounds A1, A2, A3, and A4 prepared in Examples 1, 2, 3, and 4 of the present application were 1.0×10 -5 Fluorescence emission spectrum of M in toluene solution;

[0046] Fig.11 The brightness-external quantum efficiency characteristic curve and electroluminescence spectrum of the device at different doping concentrations in Example 1 of the present application are shown;

[0047] Fig.12 The three-dimensional design diagram of the narrow-band blue light molecule provided for this application and the schematic diagram of the related principles. DETAILED DESCRIPTION

[0048] 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.

[0049] It should be noted that:

[0050] 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.

[0051] In the present application, unless otherwise specified, percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0052] 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.

[0053] 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 "1-5" means that all real numbers between "1-5" are listed in this document, and "1-5" is just an abbreviation of these numerical combinations.

[0054] 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.

[0055] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0056] 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.

[0057] The present applicant discovered in the study that polycyclic aromatic hydrocarbon compounds fused with boron and nitrogen atoms can be used as efficient narrow-band OLED light-emitting materials. The multiple resonance effect of boron and nitrogen atoms disperses HOMO and LUMO in different atoms, giving the molecule the characteristics of TADF. The short-range charge transfer induced by the multiple resonance effect can achieve narrow emission and extremely high color purity. The boron-nitrogen unit is not only an MR-TADF molecule, but can also act as an acceptor in a DA-type TSCT-TADF molecule. The sufficiently strong multiple resonance effect of the boron-nitrogen unit will not be destroyed by the additionally introduced donor, and it maintains the characteristics of narrow-band emission. By introducing donor units into the MR-TADF molecule to produce long-range charge transfer, the reverse intersystem crossing rate can be improved, which can effectively solve the problem of MR-TADF having a large ΔE due to excessive overlap of HOMO and LUMO. ST And it makes the reverse intersystem crossing process slow down.

[0058] The present application provides a narrow-band blue light molecule that can be used for organic small molecule optoelectronic functional materials, which has a molecular structure shown in the following formula (I):

[0059]

[0060] Wherein, D is an electron donating group.

[0061] The narrow-band blue light molecule provided by the present application bridges the donor unit and the multiple resonance unit through the fluorene skeleton to realize the combination of two different charge transfer modes, long-range charge transfer and short-range charge transfer. While maintaining the narrow-band emission of the short-range charge transfer characteristics of the multiple resonance unit, the high-energy excited state of the long-range charge transfer property is introduced to promote multi-channel exciton spin flip coupling and achieve faster reverse intersystem crossing. At the same time, the additionally introduced donor unit can bring about a huge steric hindrance effect, making it impossible to form a long-range π-π stacking between molecules, which can effectively inhibit the serious aggregation-induced luminescence quenching of MR-TADF molecules, so that the molecules maintain good luminescence performance at high doping concentrations.

[0062] In some preferred embodiments, in the narrow-band blue light molecule of the present application, the D is selected from one of the following structural formulas:

[0063]

[0064] Therefore, specifically, the structural formula of the narrow-band blue light molecule is one of the following structures:

[0065]

[0066]

[0067] Therefore, the present invention bridges the donor unit and the multiple resonance unit through the fluorene skeleton to realize the combination of two different charge transfer modes, long-range charge transfer and short-range charge transfer. While maintaining the narrow-band emission of the short-range charge transfer characteristics of the multiple resonance unit, the high-energy excited state of the long-range charge transfer property is introduced to promote multi-channel exciton spin flip coupling, achieve faster reverse intersystem crossing, and maintain good luminescence performance.

[0068] In some more preferred embodiments, in the narrow-band blue light molecule of the present application, the D is selected from one of the following structural formulas:

[0069]

[0070] More specifically, the present application can construct the narrow-band blue light molecules described below:

[0071]

[0072] The narrow-band blue light molecular system constructed in the present application is diverse, and while maintaining narrow emission, it also takes into account improving the reverse intersystem crossing rate and suppressing aggregation-induced luminescence quenching.

[0073] In some more preferred embodiments, D is selected from one of the following structural formulas:

[0074]

[0075] For example, a narrow-band blue-light molecule can be constructed as shown below:

[0076]

[0077] The narrow-band blue light molecular system constructed in the present application is diverse, and while maintaining narrow emission, it also takes into account improving the reverse intersystem crossing rate and suppressing aggregation-induced luminescence quenching.

[0078] The present application also provides a method for preparing the above narrow-band blue light molecule. The method comprises the following steps:

[0079] S1 Preparation of Intermediate 1:

[0080] 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate were added to the reaction bottle in sequence, and after nitrogen was replaced three times, N,N-dimethylformamide was added, and reflux reaction was carried out under nitrogen conditions. After the reaction was completed, the system was restored to room temperature, and then extracted and washed with dichloromethane and saturated brine. After the organic phase was recovered and the solvent was removed, ethanol was added, heated and stirred, and filtered to obtain intermediate 1, whose structural formula is shown below;

[0081]

[0082] S2 Preparation of Intermediate 2:

[0083] The intermediate 1 obtained in step S1 is dissolved in o-xylene, and n-butyl lithium is slowly added under stirring, and then boron tribromide is continuously added under stirring, and then N,N-diisopropylethylamine is added, and stirring is continued for 5 hours; after the reaction, 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 with 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 an intermediate 2, whose structural formula is shown below;

[0084]

[0085] S3 Preparation of Intermediate 3:

[0086] The intermediate 2 prepared in step S2 is dissolved in 1,4-dioxane, and diboric acid pinacol ester, 1,1-bis(diphenylphosphino)ferrocene palladium dichloride, and potassium acetate are added. After nitrogen is replaced three times, the reaction is carried out for 24 hours. The mixture is extracted and washed with dichloromethane and saturated brine, the organic phase is recovered and dried with anhydrous magnesium sulfate, and the solvent is removed by distillation under reduced pressure. The crude product is then separated and purified by column chromatography to generate intermediate 3, the structural formula of which is shown below;

[0087]

[0088] S4. Preparation of Intermediate 4:

[0089] 1-Bromo-9-fluorenone and a compound containing an electron-donating group were added to a two-necked flask, and carbon tetrachloride and methanesulfonic acid solvent were added. The nitrogen was replaced three times and reacted for 24 hours. 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 separated and purified by column chromatography to generate intermediate 4.

[0090] S5. Preparation of narrow-band blue light molecules:

[0091] The prepared intermediate 3, intermediate 4 and potassium carbonate were added to a two-necked flask, and tetrahydrofuran and water were added as solvents. After nitrogen was replaced three times, the catalyst tetrakis(triphenylphosphine)palladium was added to react for 12 hours. After removing tetrahydrofuran, 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 obtain a narrow-band blue light molecule.

[0092] In some preferred embodiments, in step S1 of the method for preparing narrow-band blue light molecules of the present application, the molar ratio of 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2-3):(2-3), the reaction temperature is 110-150°C, and the reaction time is 24-36h.

[0093] In some preferred embodiments, in step S2 of the method for preparing narrow-band blue light molecules of the present application, the molar ratio of intermediate 1, n-butyl lithium (2.5 M) and boron tribromide is 1:(2-3):(1-2), the reaction temperature is 0-20°C, and the reaction time is 1-2h.

[0094] In some preferred embodiments, in the preparation method described in the present application, in step S3, the molar ratio of the intermediate 2 to diboric acid pinacol ester, potassium acetate, and 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride is 1:2:3:0.05, the reaction temperature is 100-140°C, and the reaction time is 12-24h.

[0095] In some preferred embodiments, in the preparation method described in the present application, the molar ratio of 1-bromo-9-fluorenone to the donor group, carbon tetrachloride and methanesulfonic acid described in step S4 is 1:4, the reaction temperature is 90° C., and the reaction time is 24 h.

[0096] In some preferred embodiments, in the preparation method described in the present application, the molar ratio of intermediate 3, intermediate 4, potassium carbonate, tetrahydrofuran, water and tetrakis(triphenylphosphine)palladium described in step S5 is (1-2):1:2:0.05, the reaction temperature is 70-80°C, and the reaction time is 12h.

[0097] The present application also provides the application of narrow-band blue light molecules as luminescent materials, luminescent devices or smart materials, etc.

[0098] The following will describe in detail the preparation method of the narrow-band blue light compound of formula (I) by taking A1, A2, A3 and A4 as examples.

[0099] Example 1

[0100] This embodiment provides a narrow-band blue light molecule, the structural formula of which is shown in A1:

[0101]

[0102] The preparation method of the compound is as follows:

[0103] S1. Preparation of intermediate 1:

[0104] 2,6-difluoro-4-bromoiodobenzene (20mmol, 6.38g), 3,6-di-tert-butylcarbazole (25mmol, 13.97g) and cesium carbonate (30mmol, 19.55g) were added to a 250mL two-necked flask in sequence. After nitrogen was replaced three times, 80mL of N,N-dimethylformamide was added through a syringe. The mixture was reacted at 150°C for 24 hours under nitrogen. After the reaction was completed, the system was restored to room temperature, extracted and washed with dichloromethane and saturated brine, the organic phase was recovered and the solvent was removed, ethanol was added, heated and stirred, and filtered to obtain intermediate 1; the yield was 75%, and the structural formula of the intermediate 1 is as follows:

[0105]

[0106] The reaction equation in the above preparation method is as follows:

[0107]

[0108] S2. Preparation of intermediate 2;

[0109] Under low temperature -10°C, the intermediate 1 (1mmol, 837.7mg) was dissolved in 20mL o-xylene, and 2.1mL n-butyl lithium (2.5M) (1.8mmol, 0.4ml) was slowly added under stirring. After stirring for 1 hour, boron tribromide (1.5mmol, 375mg) was continuously added under stirring. After two hours, N,N-diisopropylethylamine (2.0mmol, 258.48mg) was added, and the mixture was heated to 120°C for 12h. After the reaction, water was added to quench the reaction, and the mixture 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. Then, the crude product was separated and purified by column chromatography to obtain the intermediate 2; the yield was 30%, and the structural formula of the intermediate 2 was as follows:

[0110]

[0111] The reaction equation in the above preparation method is:

[0112]

[0113] S3. Preparation of intermediate 3;

[0114] The intermediate 2 (1 mmol, 719.6 mg) was dissolved in 1,4-dioxane, and diboric acid pinacol ester (2 mmol, 507.88 mg), 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride (0.05 mmol, 36.59 mg), and potassium acetate (3 mmol, 294.42 mg) were added. The nitrogen was replaced three times, and the reaction was carried out at 110° C. for 24 hours. The mixture was extracted and washed with dichloromethane and saturated brine, and 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 separated and purified by column chromatography to generate the intermediate 3; the yield was 60%, and the structural formula of the intermediate 3 is as follows:

[0115]

[0116] The reaction equation involved in the above preparation steps is:

[0117]

[0118] S4. Preparation of intermediate 4:

[0119] 1-Bromo-9-fluorenone (1mmol, 260mg) and N-phenylcarbazole (4mmol, 970mg) were dissolved in carbon tetrachloride and methanesulfonic acid solvents, and nitrogen was replaced three times. After reacting at 90°C for 24 hours, the mixture was extracted and washed with dichloromethane and saturated brine, and 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 separated and purified by column chromatography to generate intermediate 4; the yield was 63%. The structural formula of intermediate 4 is shown below:

[0120]

[0121] The reaction equation in the above preparation method is:

[0122]

[0123] Preparation of S5.A1:

[0124] Intermediate 4 (1 mmol, 730 mg) and intermediate 3 (1.2 mmol, 920 mg) and potassium carbonate (2 mmol, 280 mg) were dissolved in tetrahydrofuran and water (1:8) solvent, and the nitrogen was replaced three times, and then a catalyst tetrakis(triphenylphosphine)palladium (0.05 mmol, 60 mg) was added to react at 75° C. for 24 hours. After removing tetrahydrofuran, the mixture was extracted and washed with dichloromethane and saturated brine, and the organic phase was recovered and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure, and then the crude product was separated and purified by column chromatography with a yield of 71%. The final compound A1 was obtained with the following structural formula:

[0125]

[0126] The reaction equation in the above preparation method is:

[0127]

[0128] Example 2

[0129] This embodiment provides another narrow-band blue light molecule, and its preparation method is basically the same as that of embodiment 1, except that, unlike embodiment 1, the group of R1 is The narrow-band blue light molecule A2 is obtained, and the structural formula of A2 is shown below:

[0130]

[0131] Example 3

[0132] This embodiment provides another narrow-band blue light molecule, and its preparation method is basically the same as that of embodiment 1, except that, unlike embodiment 1, the group of R1 is The narrow-band blue light molecule A3 is obtained, and the structural formula of A3 is shown below:

[0133]

[0134] Example 4

[0135] This embodiment provides another narrow-band blue light molecule, and its preparation method is basically the same as that of embodiment 1, except that, unlike embodiment 1, the group of R1 is The narrow-band blue light molecule A4 is obtained, and the structural formula of A4 is shown below:

[0136]

[0137] Performance Testing

[0138] The narrow-band blue light molecules A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 were characterized and their performances were tested.

[0139] The test method is as follows:

[0140] Compound structure detection: using a Bruker 400MHz superconducting nuclear magnetic resonance spectrometer, the solvent is deuterated chloroform or deuterated dimethyl sulfoxide;

[0141] Mass spectrometry detection: A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 were dissolved in dichloromethane to prepare a solution with a concentration of 1 mg / mL, and mass spectrometry was performed using a liquid chromatography-mass spectrometer LCMS-2020;

[0142] UV absorption spectrum detection: Shimadzu UV-visible spectrophotometer UV-2700 was used with a scanning range of 310 to 650 nm;

[0143] Emission spectrum detection: using a steady-state / transient fluorescence spectrometer (FLS980), the excitation wavelength is 365nm, under nitrogen protection, the test temperature is 300K.

[0144] The test results are as follows:

[0145] The nuclear magnetic resonance hydrogen spectrum of the narrow-band blue light molecule A1 prepared in Example 1 is as follows: Figure 1 As shown. Figure 1 It can be seen that: 1 HNMR(400MHz,Methylene Chloride-d2)δ8.94(d,J=2.0Hz,2H),8.29(d,J=1.9Hz,2H),8.05(dd,J=7.7,1.2Hz,1H),7.96(d,J=2.1Hz,2H),7.84(dt,J= 7.7,1.0Hz,1H),7.80(d,J=2.0Hz,2H),7.64(d,J=7.8Hz,2H),7.58(d,J=2.9Hz,1H),7.52(s,2H),7.35(dd,J=8.7,1.9Hz,2H ),7.27(dd,J=7.5,1.1Hz,1H),7.23(dt,J=8.7,1.2Hz,2H),7.19(d,J=6.3Hz,1H),7.16-7.10(m,8H),7.08(dd,J=7.5,1.2Hz,1H),6.98(t,J=8.3Hz,4H),6.92(t,J=7.5Hz,2H),6.80(d,J=8.9Hz,5H),6.12(d,J=8.9Hz,2H),1.58(s,18H),1.10(s,18H). The peaks of the molecular hydrogen spectrum of nuclear magnetic resonance can correspond to the target product one by one, and the number is reasonable; the mass spectrum of compound A1 prepared in Example 1 of the present application is as follows Figure 2 As shown. Figure 2 As can be seen in the figure, the relative molecular mass is 1287.65, which is consistent with the relative molecular mass of the synthesized A1. Combining the results of the above nuclear magnetic resonance hydrogen spectrum and mass spectrum, it can be seen that the product prepared in Example 1 is A1.

[0146] The nuclear magnetic resonance hydrogen spectrum of the narrow-band blue light molecule A2 prepared in Example 2 is as follows: Figure 3 As shown. Figure 3 It can be seen that: 1HNMR(400MHz,Chloroform-d)δ9.10(d,J=2.0Hz,2H),8.38(d,J=1.8Hz,2H),8.10(d, J=2.0Hz,2H),7.93-7.80(m,3H),7.77-7.68(m,3H),7.52(t,J=7.5Hz,1H),7.49-7.36 (m, 3H), 7.33-7.21 (m, 3H), 7.15-7.02 (m, 3H), 6.76-6.72 (m, 8H), 6.72-6.69 (m, 5H), 6.69-6.66 (m, 2H), 6.41-6.36 (m, 5H), 6.36-6.34 (m, 5H), 1.64 (s, 18H), 1.31 (s, 18H). The peaks of the nuclear magnetic resonance molecular hydrogen spectrum can correspond to the target product one by one, and the number is reasonable; the mass spectrum of compound A2 prepared in Example 2 of the present application is as follows Figure 4 As shown. Figure 4 As can be seen in the figure, the relative molecular mass is 1292.68, which is consistent with the relative molecular mass of the synthesized A2. Combining the above NMR and mass spectrometry results, it can be seen that the product obtained in Example 2 is A2.

[0147] The nuclear magnetic resonance hydrogen spectrum of the narrow-band blue light molecule A3 prepared in Example 3 is as follows: Figure 5 As shown. Figure 5 It can be seen that: 1 HNMR (400MHz, Chloroform-d) δ9.12 (d, J = 1.9Hz, 3H), 8.43 (d, J = 1.8Hz, 3H), 8.17 (d, J = 2.1Hz, 3H), 7.98 (d, J = 8.8Hz, 4H), 7.81 (d, J = 9.3Hz, 3H), 7.65 (dd, J = 8.8, 2.1Hz, 4H), 7.32 (t, J = 7.5Hz, 2H), 7.24-6.91 (m, 8H), 6.42 (s, 13H), 1.70 (s, 18H), 1.22 (s, 18H). The peaks of the hydrogen spectrum of the nuclear magnetic resonance molecule can correspond to the target product one by one, and the number is reasonable; the mass spectrum of compound A3 prepared in Example 3 of the present application is as follows Figure 6 As shown. Figure 6 As can be seen in the figure, the relative molecular mass is 1319.63, which is consistent with the relative molecular mass of the synthesized A3. Combining the above NMR and mass spectrometry results, it can be seen that the product obtained in Example 3 is A3.

[0148] The nuclear magnetic resonance hydrogen spectrum of the narrow-band blue light molecule A4 prepared in Example 4 is as follows: Figure 7 As shown. Figure 7 It can be seen that: 1HNMR(400MHz,Chloroform-d)δ9.10(d,J=1.9Hz,2H),8.34(d,J=1.8Hz,2H),8.04-7.97(m,3H),7.86(d, J=7.6Hz,1H),7.80-7.71(m,4H),7.58(t,J=7.6Hz,1H),7.47(dd,J=8.8,2.1Hz,2H),7.37(t,J=6.8Hz,1 H), 7.24-7.17 (m, 3H), 6.89 (d, J = 8.5 Hz, 2H), 6.76 (dd, J = 8.5, 2.2 Hz, 2H), 6.66 (d, J = 3.4 Hz, 4H), 6.59-6.52 (m, 4H), 6.37-6.29 (m, 4H), 6.16 (d, J = 7.0 Hz, 2H), 5.95 (d, J = 6.9 Hz, 2H), 1.69 (s, 18H), 1.17 (s, 18H). The peaks of the molecular hydrogen spectrum of nuclear magnetic resonance can correspond to the target product one by one, and the number is reasonable; the mass spectrum of compound A4 prepared in Example 4 of the present application is as follows Figure 8 As shown. Figure 8 As can be seen in the figure, the relative molecular mass is 1347.59, which is consistent with the relative molecular mass of the synthesized A4. Combining the above NMR and mass spectrometry results, it can be seen that the product obtained in Example 4 is A4.

[0149] Using Shimadzu UV-2700 ultraviolet visible spectrophotometer, A1, A2, A3, and A4 prepared in Example 1 were dissolved in dichloromethane solution to prepare 1×10 -3 mol / L stock solution, and then diluted to 1×10 -5 mol / L toluene solution was used for testing.

[0150] Fig. 9 A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 were 1×10 -5 mol / L UV-visible absorption spectrum in toluene. Fig. 9 It can be seen that the main absorption peak positions of A1, A2, A3 and A4 are all 472 nm.

[0151] Using fluorescence emission spectroscopy: FLS980 fluorescence instrument, A1, A2, A3, and A4 prepared in Example 1 were dissolved in dichloromethane solution to prepare 1×10 -3 mol / L stock solution, when testing, dilute to 1×10 -5 mol / L solution.

[0152] Fig.10 A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 were 1×10-5 mol / L toluene solution. Fig.10 It can be seen that the main emission peak positions of A1, A2, A3, and A4 are around 486nm, all of which are blue light emissions, and the half-peak widths of A1, A2, A3, and A4 are in the range of 22nm-25nm, which means that short-wave emission is achieved and good luminescence performance is maintained.

[0153] Fig.11 The brightness-external quantum efficiency characteristic curve and electroluminescence spectrum of the device with different doping concentrations in Example 1 of the present application are shown in the figure. As can be seen from the figure, the maximum EQE obtained in Example 1 of the present application is 33.61% when the doping concentration is 20wt%. Fig.12 The three-dimensional design diagram of the narrow-band blue light molecule provided by the present application and the related principle schematic diagram are shown. This is attributed to the narrow-band blue light molecule provided by the present application, which bridges the donor unit and the multiple resonance unit through the fluorene skeleton to achieve a combination of two different charge transfer modes, long-range charge transfer and short-range charge transfer. While maintaining the narrow-band emission with the short-range charge transfer characteristics of the multiple resonance unit, the high-energy excited state with the long-range charge transfer property is introduced to promote multi-channel exciton spin flip coupling, achieve faster reverse intersystem crossing, and maintain good luminescence performance.

[0154] At the same time, with the increase of doping concentration, there is no phenomenon of significant decrease in efficiency similar to most MR-TADF devices. On the contrary, with the increase of doping concentration, the maximum EQE also gradually increases, and the maximum EQE does not change significantly between 5wt% and 20wt% doping concentration, showing an excellent characteristic of insensitivity to doping concentration. This is mainly because the additionally introduced donor units can bring great steric hindrance effect, which makes it impossible to form long-range π-π stacking between molecules, and can effectively inhibit the serious aggregation-induced luminescence quenching of MR-TADF molecules, so that the molecules maintain good luminescence performance at high doping concentrations.

[0155] In summary, the narrow-band blue light molecule provided in this application can be used as a new type of luminescent molecule with high performance, high color purity and high quantum efficiency. The narrow-band blue light molecule has great application potential 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.

[0156] At the same time, the present application realizes the controllable preparation of narrow-band blue light molecules; the raw materials are widely available, large-scale production can be achieved, and it has broad commercial prospects.

[0157] The narrow-band blue light molecule provided by the present application bridges the donor unit and the multiple resonance unit through the fluorene skeleton to realize the combination of two different charge transfer modes, long-range charge transfer and short-range charge transfer. While maintaining the narrow-band emission of the short-range charge transfer characteristics of the multiple resonance unit, the high-energy excited state of the long-range charge transfer property is introduced to promote the exciton spin flip coupling of multiple channels, thereby realizing faster reverse intersystem crossing.

[0158] At the same time, the additional donor unit can bring about a great steric hindrance effect, which prevents long-range π-π stacking between molecules, effectively inhibits the serious aggregation-induced luminescence quenching of MR-TADF molecules, and makes the EQE of the molecule reach 33.61% at a doping concentration of 20%, which can be used as a new type of luminescent molecule with good performance, low cost and high luminescence intensity. It overcomes the problems of the above-mentioned existing technologies lacking high-efficiency, high-color-purity, low-roll-off narrow-spectrum blue light emitting materials.

[0159] Therefore, the narrow-band blue light molecules provided in the present application can be used as luminescent materials or smart materials, and have good application prospects in the fields of full-color display and solid-state lighting.

[0160] 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.

[0161] 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 narrow-band blue light molecule, which can be used for organic small molecule optoelectronic functional materials, characterized in that: It has a molecular structure as shown in the following formula (I): Wherein, D is an electron-donating group, and the D is selected from one of the following structural formulas: 。 2. The method for preparing narrow-band blue light molecules according to claim 1, characterized in that: The following steps are involved: S1. Preparation of Intermediate 1 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate were added to the reaction bottle in sequence, and after nitrogen was replaced three times, N,N-dimethylformamide was added, and reflux reaction was carried out under nitrogen conditions. After the reaction was completed, the system was restored to room temperature, extracted and washed with dichloromethane and saturated brine, and the organic phase was recovered to remove the solvent, and ethanol was added to heat and stir, and filtered to obtain intermediate 1, whose structural formula is shown below: S2. Preparation of Intermediate 2 The intermediate 1 obtained in step S1 is dissolved in o-xylene, and n-butyl lithium is slowly added under stirring, and then boron tribromide is continuously added under stirring, and then N,N-diisopropylethylamine is added, and stirring is continued; after the reaction, 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 with 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 an intermediate 2, whose structural formula is shown below; S3. Preparation of Intermediate 3 The intermediate 2 prepared in step S2 is dissolved in 1,4-dioxane, and diboric acid pinacol ester, 1,1-bis(diphenylphosphino)ferrocene palladium dichloride, and potassium acetate are added. After nitrogen is replaced three times for reaction for 12 to 24 hours, it 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. Then, the crude product is separated and purified by column chromatography to generate intermediate 3, whose structural formula is shown below: S4. Preparation of Intermediate 4 1-Bromo-9-fluorenone and a compound containing an electron-donating group were added to a two-necked flask, and carbon tetrachloride and methanesulfonic acid solvent were added. The nitrogen was replaced three times for 24 hours, and the mixture was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was then separated and purified by column chromatography to generate intermediate 4, whose structural formula is shown as follows: S5. Preparation of narrow-band blue light molecules: The prepared intermediate 3, intermediate 4 and potassium carbonate were added to a two-necked flask, and tetrahydrofuran and water were added as solvents. After nitrogen was replaced three times, the catalyst tetrakis(triphenylphosphine)palladium was added to react for 12 hours. After removing tetrahydrofuran, 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 obtain a narrow-band blue light molecule.

3. The method for preparing narrow-band blue light molecules according to claim 2, characterized in that: In step S1, the molar ratio of 2,6-difluoro-4-bromoiodobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2-3):(2-3).

4. The method for preparing narrow-band blue light molecules according to claim 3, characterized in that: In step S1, the reaction temperature is 110-150° C., and the reaction time is 24-36 hours.

5. The method for preparing narrow-band blue light molecules according to claim 2, characterized in that: In step S2, the molar ratio of the intermediate 1, n-butyl lithium and boron tribromide is 1:(2-3):(1-2), the reaction temperature is 0-20°C, and the reaction time is 1-2h.

6. The method for preparing narrow-band blue light molecules according to claim 2, characterized in that: In step S3, the molar ratio of the intermediate 2 to diboric acid pinacol ester, potassium acetate, and 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride is 1:2:3:0.05, the reaction temperature is 100-140° C., and the reaction time is 24 h.

7. The method for preparing narrow-band blue light molecules according to claim 2, characterized in that: In step S4, the molar ratio of 1-bromo-9-fluorenone to the compound containing an electron-donating group is 1:4, and the reaction temperature is 90°C.

8. The method for preparing narrow-band blue light molecules according to claim 2, characterized in that: In step S5, the molar ratio of intermediate 3, intermediate 4, potassium carbonate and tetrakis(triphenylphosphine)palladium is (1-2):1:2:0.05, and the reaction temperature is 70-80°C.

9. Use of the narrow-band blue light molecule according to claim 1 as a light-emitting material or a light-emitting device.

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