Double-boron fluorescent dye as well as preparation method and application thereof

Abstract

The invention discloses a double-boron fluorescent dye as well as a preparation method and application thereof. Different electron-donating or electron-withdrawing groups are introduced to the periphery of an aryl diboron-nitrogen skeleton to form the organic light-emitting material with a synergistic effect of short-range charge and long-range charge transfer states, and then the intramolecular charge transfer state (ICT) is weakened through locking adjustment of an intramolecular covalent bond. The preparation method is simple, the adjustable light color can be extended from blue-green light to red light molecules, and the twisted molecular structure after closed loop is expected to be applied to the field of circularly polarized light, so that the simplification and performance of the device structure are realized.

Description

Technical Field

[0001] This application relates to the technical field of organic light-emitting materials, and more specifically, to a diboron fluorescent dye and its preparation method and application. Background Art

[0002] The technology of using organic light-emitting materials as organic light-emitting diodes (OLEDs) has great market value and application prospects in the fields of flat panel display and solid-state lighting, etc. This is attributed to the significant advantages of organic light-emitting materials such as being thin, light, low-power consumption, high contrast, self-luminous, and having flexibility, large area, high-quality display and lighting, ultra-high resolution, and ultra-fast response speed. Organic light-emitting materials have great application potential in the fields of flat panel display, smartphones, and solid-state lighting, etc., attracting extensive attention from the global academic and industrial communities.

[0003] However, in recent years, most of the studied organic light-emitting materials are green and red light materials, and there is relatively little research on deep blue-green or blue-green multi-resonance materials.

[0004] Content of the Application

[0005] To overcome one of the problems existing in the above-mentioned prior art, the primary object of this application is to provide a diboron fluorescent dye. This diboron fluorescent dye contains an electron donor, and at the same time, this diboron fluorescent dye can be used as an organic light-emitting material to regulate the charge transfer excited state of the multi-resonance emission material through intramolecular covalent bond locking. By adjusting the type of electron donor, it has the advantage of adjustable light color from deep blue-green to red light.

[0006] Another object of this application is to provide a preparation method of the above-mentioned diboron fluorescent dye.

[0007] Another object of this application is to provide an application of the above-mentioned diboron fluorescent dye.

[0008] The above objects of this application are achieved through the following technical solutions:

[0009] A diboron fluorescent dye, which can be used for organic small molecule optoelectronic functional materials, and has a molecular structure shown in the following formula (Ⅰ):

[0010]

[0011] Among them, an electron-donating group or an electron-withdrawing group, and the D is selected from one of the following structural formulas:

[0012]

[0013] Among them, the R is selected from H, CN, Me or t-Bu.

[0014] Preferably, the above-mentioned diboron fluorescent dye provided by this application has one of the following molecular structures:

[0015]

[0016] This application also provides a preparation method of the above-mentioned diboron fluorescent dye, which includes the following steps:

[0017] S1. Prepare Intermediate 1

[0018] Add 1,4-dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate into the reaction flask in sequence. After evacuating and replacing nitrogen three times, add N,N-dimethylformamide, and reflux the reaction under nitrogen atmosphere. After the reaction is completed, wait for the system to return to room temperature, extract and wash with dichloromethane and saturated brine, recover the organic phase, remove the solvent, add ethanol, heat and stir, and filter to obtain Intermediate 1. Its structural formula is as follows:

[0019]

[0020] S2. Prepare Intermediate 2

[0021] Dissolve the Intermediate 1 prepared in step S1 in dichloromethane. Add Intermediate 1 and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone into the reaction flask, evacuate with nitrogen three times at room temperature, then add methanesulfonic acid and stir at room temperature. After the reaction is completed, add triethylamine to quench the reaction, extract and wash with dichloromethane and saturated brine, recover the organic phase, dry it with anhydrous magnesium sulfate, distill off the solvent under reduced pressure, and then purify the crude product by column chromatography to obtain Intermediate 2. Its structural formula is as follows:

[0022]

[0023] S3. Prepare the diboron fluorescent dye

[0024] Dissolve the Intermediate 2 prepared in step S2 in o-xylene, slowly add n-butyllithium under stirring, then continue to add boron tribromide under stirring conditions, then add N,N-diisopropylethylamine, and continue to stir; after the solution cools, add 2-mesitylmagnesium bromide and continue to stir. After the reaction is completed, quench the reaction with methanol, extract and wash with dichloromethane and saturated brine, recover the organic phase, dry it with anhydrous magnesium sulfate, distill off the solvent under reduced pressure, and then purify the crude product by column chromatography to obtain the diboron fluorescent dye.

[0025] Preferably, in step S1, the molar ratio of 1,4-dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2.5 - 3):(2 - 3).

[0026] More preferably, the reaction temperature is 110 - 150 °C and the reaction time is 24 - 36 h.

[0027] Preferably, in step S2, the molar ratio of intermediate 1 to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1:(1.5 - 2), the reaction temperature is 0 to -10°C, and the reaction time is 2 to 4 h.

[0028] Preferably, in step S3, the molar ratio of intermediate 2, n-butyllithium, boron tribromide, and 2-mesityl magnesium bromide is 1:(3.5 - 4):(3.5 - 4.5):(8 - 9), the reaction temperature is 0 to -30°C, and the reaction time is 6 to 12 h.

[0029] Preferably, a Grignard reagent needs to be added in step S3, and the Grignard reagent is one of phenylmagnesium bromide. In this way, the phenyl donor group in phenylmagnesium bromide is conducive to a more delocalized distribution of HOMO.

[0030] Preferably, a Grignard reagent needs to be added in step S3, and the Grignard reagent is one of benzylmagnesium bromide. In this way, the benzyl group in benzylmagnesium bromide can make the molecule more twisted.

[0031] The diboron fluorescent dye in the present application is used in applications such as luminescent materials, light-emitting devices, or intelligent materials.

[0032] Compared with the prior art, the beneficial effects of the present application are:

[0033] In the present application, by introducing different electron-donating or electron-withdrawing groups around the aryl diboron nitride skeleton, an organic luminescent material with the synergistic effect of short-range charge and long-range charge transfer states is formed. Then, through the regulation of intramolecular covalent bond locking, the intramolecular charge transfer state (ICT) is weakened, realizing a hybrid emission material mainly based on short-range charge transfer state and supplemented by long-range charge transfer state. The preparation method is simple, the adjustable light color can extend from deep blue-green light to red light molecules, and the twisted molecular structure after ring closure is also expected to be applied in the field of circularly polarized light, thereby simplifying the device structure and improving the performance. Description of the Drawings

[0034] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of compound A1 prepared in Example 1 of the present application.

[0035] Figure 2 It is the mass spectrum of compound A1 prepared in Example 1 of the present application.

[0036] Figure 3 It is the nuclear magnetic resonance hydrogen spectrum of compound A2 prepared in Example 2 of the present application.

[0037] Figure 4 It is the mass spectrum of compound A2 prepared in Example 2 of the present application.

[0038] Figure 51H NMR spectrum of Compound A3 prepared in Example 3 of this application.

[0039] Figure 6 Mass spectrum of Compound A3 prepared in Example 3 of this application.

[0040] Figure 7 1H NMR spectrum of Compound A4 prepared in Example 4 of this application.

[0041] Figure 8 Mass spectrum of Compound A4 prepared in Example 4 of this application.

[0042] Figure 9 UV absorption spectra of Compounds A1, A2, A3, and A4 prepared in Examples 1, 2, 3, and 4 of this application in a toluene solution of 1.0×10 -5 M.

[0043] Figure 10 Fluorescence emission spectra of Compounds A1, A2, A3, and A4 prepared in Examples 1, 2, 3, and 4 of this application in a toluene solution of 1.0×10 -5 M.

[0044] Figure 11 Lifetime diagrams of Compounds A1 and A2 prepared in Examples 1 and 2 of this application when doped at a ratio of 3% in the PhCzBCz host material.

[0045] Figure 12 Schematic diagram of the luminescence principle of the diboron molecule involved in this application.

[0046] Figure 13 Schematic diagram of the design concept of the diboron molecule involved in this application.

[0047] Figure 14 Fluorescence quantum yield (PLQY) diagrams of Compounds A1 and A2 prepared in Examples 1 and 2 of this application in a toluene solution. Detailed implementation mode

[0048] The implementation schemes of this application will be described in detail below in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate this application and should not be regarded as limiting the scope of this application. For those conditions not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0049] It should be noted that:

[0050] In this application, if there is no special indication, all the implementation modes and preferred implementation methods mentioned in this article can be combined with each other to form a new technical solution.

[0051] In this application, unless otherwise specified, percentages (%) or parts refer to weight percentages or parts by weight relative to the composition.

[0052] In this application, unless otherwise specified, the various components involved or their preferred components can be combined with each other to form new technical solutions.

[0053] In this application, unless otherwise stated, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "1 to 5" means that all real numbers between "1 to 5" are fully listed herein, and "1 to 5" is just an abbreviated representation of these numerical combinations.

[0054] The "ranges" disclosed in this application can be in the form of lower limits and upper limits, which can be one or more lower limits and one or more upper limits, respectively.

[0055] In this application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in sequence. Preferably, the reaction methods herein are carried out sequentially.

[0056] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to persons skilled in the art. In addition, any methods or materials similar or equivalent to the described content can also be applied to this application.

[0057] The applicant found in the research that: However, due to the coupling of the MR-TADF structure with the short-range charge transfer (SRCT) state and the twisted D-A structure with the long-range charge transfer (LRCT) state, when the molecule contains a twisted D-A structure or the bond / bridge connecting the D and A groups can rotate freely, strong charge delocalization may occur in the excited state, followed by charge separation, thereby generating a strong / twisted ICT state, which can be stabilized by polar solvent molecules.

[0058] However, if the planarity of the D-A structure is increased and / or the distortion or internal rotation of the excited group is prevented, it is easy to form a weak ICT property. There is an obvious difference in the energy gap between the strong / twisted ICT state and the weak ICT state. The former leads to orbital decoupling and complete charge transfer, manifested as redshift and broadband emission. Based on this concept, this application proposes a method for modulating the charge transfer excited state of MR emitters through intramolecular covalent bond locking, tying the rotatable-attached 3,6-di-tert-butyl-9-carbazole (tCz) to BNCz in m-Cz-BNCz, thereby promoting the transition from the strong ICT state to the weak ICT state, and thus achieving blueshift emission and spectral narrowing. At the same time, a reasonable redshift emission is obtained compared with the parent molecule BNCz.

[0059] The present application provides a diboron fluorescent dye, which can be used in organic small molecule optoelectronic functional materials and has a molecular structure as shown in the following formula (I):

[0060]

[0061] Among them, the electron-donating group or electron-withdrawing group, and the D is selected from one of the following structural formulas:

[0062]

[0063] Among them, the R is selected from H, CN, Me or t-Bu.

[0064] The diboron fluorescent dye provided by the present application, based on the multiple resonance properties of the aryl diboron nitride group, connects an electron-donating group or an electron-withdrawing group through a covalent bond to achieve effective charge transfer to regulate the excited state properties of the molecule. This hybrid emission material with a short-range charge transfer state (SRCT) mainly composed of a multiple resonance structure, i.e., an MR structure, and a long-range charge transfer state (LRCT) of a twisted donor-acceptor structure, i.e., a D-A structure, further locks and adjusts the charge transfer excited state of the material through an intramolecular covalent bond, making the intramolecular charge transfer state (ICT) weaker. Because the aryl boron nitride group has the properties of high luminescence efficiency and high color purity luminescence, it can improve the external quantum efficiency of the device. By locking and fixing the structure through a covalent bond, the molecular rigidity is increased, the long-range charge transfer state of the molecule is weakened, so that the molecular ICT becomes weaker, and the excited state properties of the molecule are regulated, which effectively promotes the reverse intersystem crossing process and improves the performance of thermally activated delayed fluorescence. It can be used as a new type of luminescent molecule with good performance, low cost and high luminescence intensity.

[0065] In some preferred embodiments, the diboron fluorescent dye of the present application has one of the following molecular structures:

[0066]

[0067] Therefore, specifically, the structural formula of the above diboron fluorescent dye is one of the following structures:

[0068]

[0069] Among them, the above R is selected from H, CN, Me or t-Bu.

[0070] The blue-green light compound provided by this application is an organic light-emitting material with a synergistic effect of short-range charge transfer state and long-range charge transfer state formed by introducing groups with different electron-donating or electron-withdrawing abilities to its periphery. Then, the charge transfer excited state of the multi-resonance emission material is regulated by intramolecular covalent bond locking, weakening the intramolecular charge transfer state (ICT). A mixed emission material of short-range charge transfer state (MR-TADF structure) and long-range charge transfer state (twisted D-A structure) is realized. Since the aryl boron nitride group has the property of high luminous efficiency, it can improve the external quantum efficiency of the device. Then, through intramolecular covalent bond locking, the long-range charge transfer state of the molecule is realized and the excited state properties of the molecule are regulated, enabling the realization of an organic light-emitting material with a synergistic effect mainly based on the short-range charge transfer state and supplemented by the long-range charge transfer state, which can effectively promote the reverse intersystem crossing process and improve the performance of thermally activated delayed fluorescence, thereby reducing the serious problem of device roll-off and overcoming the problems such as the lack of efficient low-roll-off emission materials in the above-mentioned prior art.

[0071] In some more preferred embodiments, for the diboron fluorescent dye in this application, D is selected from one of the following structural formulas:

[0072]

[0073] Among them, R is selected from H, CN, Me or t-Bu.

[0074] More specifically, this application can construct the diboron fluorescent dye as described below:

[0075]

[0076] The diboron fluorescent dye system constructed in this application is diverse and can simultaneously achieve short-wave emission, for example, blue-green light emission can be achieved.

[0077] In some more preferred embodiments, D is selected from one of the following structural formulas:

[0078]

[0079] Among them, R is selected from H, CN, Me or t-Bu. For example, the diboron fluorescent dye shown below can be constructed:

[0080]

[0081] The above-constructed diboron fluorescent dye system is diverse and can simultaneously achieve short-wave emission, for example, blue-green light emission can be achieved.

[0082] In some more preferred embodiments, the diboron fluorescent dye in this application has one of the following molecular structures:

[0083]

[0085] This application is based on aryl boron-nitrogen system molecules, where the aryl boron-nitrogen group is a multiple resonance luminescence core. By locking through intramolecular covalent bonds, the charge transfer excited state of the multi-resonance emission material is regulated (see Figure 13 ), and groups with different electron-donating or electron-withdrawing abilities are introduced to its periphery to form an organic luminescent material with the synergistic effect of short-range charge transfer state and long-range charge transfer state.

[0086] This application also provides a preparation method of the above-mentioned diboron fluorescent dye. The method includes the following steps:

[0087] S1. Prepare Intermediate 1

[0088] Add 1,4-dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate into the reaction flask in sequence. After evacuating and replacing nitrogen three times, add N,N-dimethylformamide, and reflux the reaction under nitrogen. After the reaction is completed, wait for the system to return to room temperature, extract and wash with dichloromethane and saturated brine, recover the organic phase, remove the solvent, add ethanol, heat and stir, and filter to obtain Intermediate 1. Its structural formula is as follows:

[0089]

[0090] S2. Prepare Intermediate 2

[0091] Dissolve the Intermediate 1 prepared in step S1 in dichloromethane. Add Intermediate 1 and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone into the reaction flask, evacuate with nitrogen three times at room temperature, then add methanesulfonic acid and stir at room temperature. After the reaction is completed, add triethylamine to quench the reaction, extract and wash with dichloromethane and saturated brine, recover the organic phase, dry with anhydrous magnesium sulfate, distill off the solvent under reduced pressure, and then purify the crude product by column chromatography to obtain Intermediate 2. Its structural formula is as follows:

[0092]

[0093] S3. Prepare the diboron fluorescent dye

[0094] Dissolve the Intermediate 2 prepared in step S2 in o-xylene, slowly add n-butyllithium under stirring, then continue to add boron tribromide under stirring, and then add N,N-diisopropylethylamine and continue to stir; after the solution is cooled, add 2-mesitylmagnesium bromide and continue to stir. After the reaction is completed, quench the reaction with methanol, extract and wash with dichloromethane and saturated brine, recover the organic phase, dry with anhydrous magnesium sulfate, distill off the solvent under reduced pressure, and then purify the crude product by column chromatography to obtain the diboron fluorescent dye.

[0095] In some preferred embodiments, in step S1 of the preparation method of the diboron fluorescent dye of the present application, the molar ratio of 1,4-dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2.5-3):(2-3).

[0096] In some preferred embodiments, in step S1 of the preparation method of the diboron fluorescent dye of the present application, the reaction temperature is 110-150 °C and the reaction time is 24-36 h.

[0097] In some preferred embodiments, in the preparation method of the present application, in step S2, the molar ratio of intermediate 1 and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1:(1.5-2), the reaction temperature is 0--10 °C, and the reaction time is 2-4 h.

[0098] In some preferred embodiments, in the preparation method of the present application, in step S3, the molar ratio of intermediate 2, n-butyllithium, boron tribromide and 2-mesityl magnesium bromide is 1:(3.5-4):(3.5-4.5):(8-9), the reaction temperature is 0--30 °C, and the reaction time is 6-12 h.

[0099] In some preferred embodiments, in the preparation method of the present application, a Grignard reagent needs to be added in step S3, and the Grignard reagent is one of phenylmagnesium bromide.

[0100] In some preferred embodiments, in the preparation method of the present application, a Grignard reagent needs to be added in step S3, and the Grignard reagent is one of benzylmagnesium bromide.

[0101] The present application also provides the application of the diboron fluorescent dye as a luminescent material, a light-emitting device or a smart material, etc.

[0102] Hereinafter, the preparation method of the diboron fluorescent dye compound of formula (I) will be described in detail by taking A1, A2, A3 and A4 as examples.

[0103] Example 1

[0104] This example provides a diboron fluorescent green light-emitting compound, and the structural formula is as shown in A1:

[0105]

[0106] The preparation method of this compound is as follows:

[0107] S1. Preparation of intermediate 1:

[0108] In a 250 mL three-necked flask, 3,6-di-tert-butylcarbazole (7.71 g, 27.6 mmol) and Cs 2 CO3 (10.78 g, 33.1 mmol) was dissolved in ultradry DMF (80 mL), and the mixture was stirred at room temperature under nitrogen for 30 min. Then 1,4-dibromo-2,3-difluorobenzene (3 g, 11.0 mmol) was added. After purging with nitrogen three times, the reaction was carried out at 150 °C for 24 h under nitrogen. After the reaction was completed and the system returned to room temperature, it was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered, the solvent was removed, ethanol was added, and the mixture was heated and stirred. Then it was filtered to obtain Intermediate 1 with a yield of 94.1%. The structural formula of Intermediate 1 is shown below:

[0109]

[0110] The reaction equation in the above preparation method is as follows:

[0111]

[0112] Preparation of S2.A1:

[0113] In a 250 mL two-necked flask, compound 2 (2 g, 2.5 mmol) was dissolved in 100 mL of ultradry o-xylene. Under nitrogen, the solution was cooled to -30 °C, and then n-butyllithium (3.6 mL, 2.50 M n-hexane solution, 8.9 mmol) was added and stirred for 30 min. Then the temperature was raised to 50 °C and stirred for 4 h. Subsequently, the solution was cooled to -40 °C, and BBr 3 (1.7 mL, 17.7 mmol) was added and stirred for 30 min. Then it was transferred to room temperature and stirred for 4 h. Then, at -30 °C, N,N-diisopropylethylamine (4.0 mL, 25.3 mmol) was added and stirred for 30 min. Next, the temperature was raised to 120 °C and stirred for 12 h. After the solution was cooled to 0 °C, 2-mesitylmagnesium bromide (2.5 mL, 1.0 M tetrahydrofuran solution, 25.3 mmol) was added and stirred for 2 h. Finally, the reaction mixture was stirred at room temperature for 24 h. After the reaction was completed, the reaction solution was quenched with methanol. The mixture was dissolved in dichloromethane and extracted with a large amount of saturated brine. The organic phase was dried over anhydrous MgSO 4 and the organic solvent was removed by a rotary evaporator. Then, through silica gel column chromatography with dichloromethane / petroleum ether as the eluent, separation and purification were carried out to obtain the final compound A1 with a yield of 65%. The structural formula of the final compound A1 is shown below:

[0114]

[0115] The reaction equation in the above preparation method is:

[0116]

[0117] Example 2

[0118] This embodiment provides another kind of diboron nitride-based blue light-emitting compound, and its preparation method is basically the same as that of Embodiment 1. The structural formula of A2 is as follows:

[0119]

[0120] S1. Preparation of Intermediate 1:

[0121] In a 250 mL three-necked flask, 3,6-di-tert-butylcarbazole (7.71 g, 27.6 mmol) and Cs 2 CO 3 (10.78 g, 33.1 mmol) were dissolved in ultra-dry DMF (80 mL), and stirred at room temperature under nitrogen for 30 min. Then 1,4-dibromo-2,3-difluorobenzene (3 g, 11.0 mmol) was added. After purging with nitrogen three times, the reaction was carried out at 150 °C for 24 hours under nitrogen. After the reaction was completed, when the system returned to room temperature, it was extracted and washed with dichloromethane and saturated brine. The organic phase was recovered, the solvent was removed, and ethanol was added and heated with stirring. After suction filtration, Intermediate 1 was obtained; the yield was 94.1%. The structural formula of the Intermediate 1 is as follows:

[0122]

[0123] The reaction equation in the above preparation method is as follows:

[0124]

[0125] S2. Preparation of Intermediate 2;

[0126] Under the condition of low temperature -10 °C, in a 250 mL two-necked flask, Intermediate 1 (3 g, 3.8 mmol) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (1.30 g, 3.0 mmol, 1.5 eq) were dissolved in ultra-dry CH 2 Cl 2 (100 mL), and stirred at room temperature under nitrogen for 10 min. Then methanesulfonic acid (MSA) (1.85 mL, 29.1 mmol) was added. Stirred at room temperature for 6 h, and triethylamine was added to quench the reaction. After the reaction was completed, water was added to quench the reaction, and it 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 reduced pressure distillation. Then the crude product was separated and purified by column chromatography to obtain Intermediate 2; the yield was 60%. The structural formula of the Intermediate 2 is as follows:

[0127]

[0128] The reaction equation in the above preparation method is:

[0129]

[0130] Preparation of S3.A2:

[0131] In a 250 mL two-necked flask, dissolve intermediate 2 (2 g, 2.2 mmol) in 100 mL of ultradry o-xylene. After cooling the solution to -10 °C under nitrogen, add n-butyllithium (3.7 mL, 2.50 M n-hexane solution, 9.0 mmol) and stir for 30 min. Then, warm the mixture to 50 °C and stir for 2 h. Next, cool the solution to -30 °C and add BBr 3 (1.6 mL, 17.8 mmol), stir for 30 min, then transfer to room temperature and stir for 1 h. Then, add N,N-diisopropylethylamine (4.1 mL, 25.5 mmol) at -20 °C and stir for 30 min. Subsequently, warm the mixture to 120 °C and stir for 24 h. After cooling the solution to 0 °C, add 2-mesitylmagnesium bromide (2.5 mL, 1.0 M tetrahydrofuran solution, 25.5 mmol) and stir for 2 h. Then, stir the reaction mixture at room temperature for 24 h and quench the reaction with methanol. Dissolve the mixture in dichloromethane and extract with a large amount of saturated brine. Dry the organic phase over anhydrous MgSO 4 and remove the organic solvent by rotary evaporation. Further purify by silica gel column chromatography using dichloromethane / petroleum ether as the eluent to obtain the final compound A2 with a yield of 20%. The structural formula of the final compound A2 is as follows:

[0132]

[0133] The reaction equation in the above preparation method is:

[0134]

[0135] Example 3

[0136] This example provides another boron-nitrogen-based red-emitting compound. The structural formula of A3 is as follows:

[0137]

[0138] S1. Preparation of intermediate 3:

[0139] In a 250 mL three-necked flask under a nitrogen atmosphere, 3,6-di-tert-butylcarbazole (12.25 g, 43.84 mmol) was added to a two-necked round-bottom flask. Cesium carbonate (15.87 g, 48.71 mmol) was added, followed by DMF (100 mL) to form a suspension, which was stirred at room temperature for 30 min. Then, 1,4-dibromo-2,3,5,6-tetrafluorobenzene (3.00 g, 9.74 mmol) was added all at once, and the reaction mixture was stirred at 155 °C for 24 h. The mixture was extracted with water, and the crude product was recrystallized from hot ethanol. The intermediate 3 product (12.10 g, 8.39 mmol, 92%) was obtained as a pale yellow solid. The structural formula of the intermediate 1 is as follows:

[0140]

[0141] The reaction equation in the above preparation method is as follows:

[0142]

[0143] S2. Preparation of intermediate 4;

[0144] In a 250 mL two-necked flask, compound 5 (3 g, 2.23 mmol) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (0.76 g, 3.45 mmol, 1.5 eq) were dissolved in ultradry CH 2 Cl 2 (60 mL), and the mixture was stirred at room temperature under nitrogen for 10 min. Then, methanesulfonic acid (MSA) (1.85 mL, 16.73 mmol) was added. The mixture was stirred at room temperature for 4 h, and the reaction was quenched by adding triethylamine. The solvent in the mixture was removed by a rotary evaporator, and the residue was purified by silica gel column chromatography using PE:DCM = 5:1 as the eluent. The obtained crude product was recrystallized from DCM / PE to obtain a yellow powder product 3 (1.78 g, yield 59.4%). The structural formula of the intermediate 4 is as follows:

[0145]

[0146] The reaction equation in the above preparation method is:

[0147]

[0148] S3. Preparation of A3:

[0149] In a 250 mL two-necked flask, dissolve compound 3 (2 g, 2.2 mmol) in 100 mL of ultradry o-xylene. After cooling the solution to -10 °C under nitrogen, add n-butyllithium (3.7 mL, 2.50 M n-hexane solution, 9.0 mmol) and stir for 30 min. Then, warm the temperature to 50 °C and stir for 2 h. Next, cool the solution to -30 °C and add BBr 3 (1.6 mL, 17.8 mmol), stir for 30 min, then transfer to room temperature and stir for 1 h. Then, add N,N-diisopropylethylamine (4.1 mL, 25.5 mmol) at -20 °C and stir for 30 min. Next, warm the temperature to 120 °C and stir for 24 h. After cooling the solution to 0 °C, add 2-mesitylmagnesium bromide (2.5 mL, 1.0 M tetrahydrofuran solution, 25.5 mmol) and stir for 2 h. Then, stir the reaction mixture at room temperature for 24 h and quench the reaction with methanol. Dissolve the mixture in dichloromethane and extract with a large amount of saturated brine. Dry the organic phase over anhydrous MgSO 4 and remove the organic solvent by rotary evaporation. Purify the crude product by silica gel column chromatography and purify the product by flash chromatography using PE:DCM = 9:1 as the eluent. Recrystallize the crude product several times from dichloromethane / n-hexane to obtain the blue solid product A3 (267 mg, yield 23%). The structural formula of the final compound A3 is shown below:

[0150]

[0151] The reaction equation in the above preparation method is as follows:

[0152]

[0154] Example 4

[0155] This example provides another boron nitride-based red-light emitting compound. Its preparation method is basically the same as that of Example 3. The structural formula of A4 is shown below:

[0156]

[0157] S1. Preparation of A4:

[0158] In a 250 mL two-necked flask, dissolve compound 2 (2 g, 2.5 mmol) in 100 mL of ultradry o-xylene. After cooling the solution to -30 °C under nitrogen, add n-butyllithium (3.6 mL, 2.50 M n-hexane solution, 8.9 mmol) and stir for 30 min. Then, warm the temperature to 50 °C and stir for 4 h. Next, cool the solution to -40 °C and add BBr 3(1.7 mL, 17.7 mmol) was stirred for 30 min, then transferred to room temperature and stirred for 4 h. Then, at -30 °C, N,N-diisopropylethylamine (4.0 mL, 25.3 mmol) was added and stirred for 30 min. Subsequently, the temperature was raised to 120 °C and stirred for 12 h. After the solution was cooled to 0 °C, 2-mesitylmagnesium bromide (2.5 mL, 1.0 M solution in tetrahydrofuran, 25.3 mmol) was added and stirred for 2 h. Finally, the reaction mixture was stirred at room temperature for 24 h. After the reaction was completed, the reaction solution was quenched with methanol. The mixture was dissolved in dichloromethane and extracted with a large amount of saturated brine. The organic phase was dried over anhydrous MgSO 4 and the organic solvent was removed by a rotary evaporator. The crude product was purified by silica gel column chromatography, and the product was purified by flash chromatography using PE:DCM = 6:1 as the eluent. The crude product was further purified by recrystallization from dichloromethane / n-hexane multiple times to obtain an orange solid product A4 with a yield of 26%. The structural formula of the final compound A4 is shown below:

[0159]

[0160] The reaction equation in the above preparation method is as follows:

[0161]

[0162] Performance Test

[0163] The boron-nitrogen compounds A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 were characterized and their performance was tested.

[0164] The test methods are as follows:

[0165] Compound structure detection: A Bruker 400 MHz superconducting nuclear magnetic resonance spectrometer was used, and the solvent was deuterated chloroform or deuterated dichloromethane;

[0166] 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 tests were carried out using a liquid chromatography-mass spectrometry instrument LCMS-2020.

[0167] Ultraviolet absorption spectrum detection: A Shimadzu ultraviolet-visible spectrophotometer UV-2700 was used, and the scanning range was 350 - 800 nm;

[0168] Emission spectrum detection: A steady-state / transient fluorescence spectrometer (FLS980) was used, and the excitation wavelength was 360 nm,

[0169] Under nitrogen protection, the test temperature was 300 K.

[0170] Lifetime decay curve detection: Using a steady-state / transient fluorescence spectrometer (FLS980), the excitation wavelength of A1 is 520 nm, and the excitation wavelength of A2 is 480 nm. The doped host material PhCzBCz thin film is vacuum-evaporated on a quartz wafer at a ratio of 3 wt%, and measured in air.

[0171] Fluorescence quantum yield detection: Using a steady-state / transient fluorescence spectrometer (FLS980), under nitrogen protection, measured by the absolute photoluminescence quantum yield in an integrating sphere.

[0172] The test results are as follows:

[0173] The 1H NMR spectrum of the diboron-nitrogen-based green-emitting compound A1 prepared in Example 1 is as Figure 1 shown. From Figure 1 it can be seen that: 1 H NMR (400 MHz, Chloroform-d) δ 8.57 (s, 2H), 8.14 (s, 2H), 7.91 (d, J = 2.5 Hz, 2H), 7.79 (s, 2H), 7.00 (s, 2H), 6.96 (s, 2H), 6.71 (d, J = 10.8 Hz, 2H), 6.19 (d, J = 8.1 Hz, 2H), 2.43 (s, 6H), 2.23 (s, 6H), 1.92 (s, 6H), 1.55 (s, 18H), 1.22 (s, 18H). The peaks of this 1H NMR spectrum of the molecule can correspond one by one to the target product, and the quantity is reasonable; The mass spectrum of the compound A1 prepared in Example 1 of this application is as Figure 2 shown. From Figure 2 it can be seen that the relative molecular mass in the figure is 889.48, which is consistent with the relative molecular mass of the synthesized A1. Combining the results of the above 1H NMR spectrum and mass spectrum, it can be known that the product prepared in Example 1 is A1.

[0174] The 1H NMR spectrum of the diboron-nitrogen-based blue-emitting compound A2 prepared in Example 2 is as Figure 3 shown. From Figure 3 it can be seen that: 11H NMR (400 MHz, Chloroform-d) δ 8.76 (d, J = 1.9 Hz, 2H), 8.25 (d, J = 1.9 Hz, 2H), 8.11–8.10 (m, 2H), 7.90 (s, 2H), 7.15 (s, 2H), 7.11 (d, J = 1.8 Hz, 2H), 6.86 (dd, J = 8.8, 2.0 Hz, 2H), 2.55 (s, 6H), 2.35 (s, 6H), 2.06 (s, 6H), 1.68 (s, 18H), 1.35 (s, 18H). The peaks in the 1H NMR spectrum can correspond one by one to the target product, and the quantity is reasonable; The mass spectrum of compound A2 prepared in Example 2 of this application is as Figure 4 shown. It can be seen from Figure 4 that the relative molecular mass in the figure is 886.62, which is consistent with the relative molecular mass of the synthesized A2. Combining the above results of NMR and mass spectrometry, it can be known that the product obtained in Example 2 is A2.

[0175] The 1H NMR spectrum of the double boron-nitrogen red-emitting compound A3 prepared in Example 3 is as Figure 5 shown. It can be seen from Figure 5 that: 1 1H NMR (400 MHz, Methylene Chloride-d 2 ) δ 7.41 (d, J = 1.9 Hz, 2H), 6.90 (s, 2H), 6.75 (s, 2H), 6.55 (s, 2H), 5.78 (d, J = 14.4 Hz, 4H), 5.50 (s, 2H), 5.49 (s, 2H), 4.94 (d, J = 8.6 Hz, 2H), 0.33 (d, J = 8.6 Hz, 72H). The peaks in the 1H NMR spectrum can correspond one by one to the target product, and the quantity is reasonable; The mass spectrum of compound A3 prepared in Example 3 of this application is as Figure 6 shown. It can be seen from Figure 6 that the relative molecular mass in the figure is 1200.46, which is consistent with the relative molecular mass of the synthesized A3. Combining the above results of NMR and mass spectrometry, it can be known that the product obtained in Example 3 is A3.

[0176] The 1H NMR spectrum of the double boron-nitrogen red-emitting compound A4 prepared in Example 4 is as Figure 7 shown. It can be seen from Figure 7 that: 11H NMR (500 MHz, Chloroform-d) δ 9.61 (s, 4H), 8.57 (s, 4H), 8.14 (s, 4H), 7.91 (s, 4H), 6.71 (d, J = 8.8 Hz, 4H), 6.19 (d, J = 8.7 Hz, 4H), 1.92 (s, 36H), 1.22 (s, 36H). The peaks in the 1H NMR spectrum can correspond one by one to the target product, and the quantity is reasonable; The mass spectrum of compound A4 prepared in Example 4 of this application is as shown in Figure 8 shown. As can be seen from Figure 8 , the relative molecular mass in the figure is 1202.70, which is consistent with the relative molecular mass of the synthesized A4. Combining the above results of NMR and mass spectrometry, it can be known that the product obtained in Example 4 is A4.

[0177] Using a Shimadzu UV-visible spectrophotometer UV-2700, dissolve A1, A2, A3, and A4 prepared in the examples in toluene solution to prepare a stock solution of 1×10 -3 mol / L, and then dilute it into a toluene solution of 1×10 -5 mol / L for testing.

[0178] Figure 9 are the UV-visible absorption spectra of A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 in toluene at 1×10 -5 mol / L. As can be seen from Figure 9 , the main absorption peak position of this A1 is 501 nm, the main absorption peak position of A2 is 422 nm, the main absorption peak position of A3 is 648 nm, and the main absorption peak position of A4 is 660 nm.

[0179] Using fluorescence emission spectroscopy: FLS980 fluorescence spectrometer, dissolve A1, A2, A3, and A4 prepared in the examples in toluene solution to prepare a stock solution of 1×10 -3 mol / L, and when testing, dilute it into a solution of 1×10 -5 mol / L.

[0180] Figure 10 are the fluorescence emission spectra of A1, A2, A3, and A4 prepared in Example 1, Example 2, Example 3, and Example 4 in toluene solution at 1×10 -5 mol / L. As can be seen from Figure 10It can be seen that the main emission peak positions of A1 and A2 are 528 nm and 461 nm respectively, emitting blue-green light. The full width at half maximum (FWHM) of A1 is 53 nm, and the FWHM of A2 is 50 nm. The main emission peak positions of A3 and A4 are 668 nm and 680 nm respectively, emitting orange-red light. The FWHM of A3 is 62 nm, and the FWHM of A4 is 54 nm. That is, the dual-boron fluorescent dye system provided by this application is diverse, and the regulation from blue-green light to orange-red light can be achieved simultaneously.

[0181] Figure 11 For the compounds A1 ( Figure 11 the left figure in Figure 11 ) and A2 (

[0182]

[0183] ) prepared in Examples 1 and 2 of this application, when the doping ratio in the PhCzBCz host material is 3%, the lifetime diagram and the summary of photophysical property data are as follows in the table: Figure 11 It can be seen from

[0184] Figure 12 that there is almost no TADF phenomenon in A1, and the delayed component is less. After covalent bond connection, the performance of thermally activated delayed fluorescence of A2 is significantly improved, and the delayed component increases. It can be seen that at this time, the MR-TADF performance of the short-range charge transfer state can increase the reverse intersystem crossing rate, effectively promoting the reverse intersystem crossing process and thus reducing the serious problem of device roll-off, overcoming the problems such as the lack of efficient low-roll-off emission materials in the above-mentioned prior art. Figure 13 This is the schematic diagram of the principle involved in this application. The dual-boron fluorescent dye provided by this application, based on the multiple resonance properties of the aryl diboron nitride group, realizes the effective charge transfer to regulate the excited state properties of the molecule by covalently bonding an electron-donating group or an electron-withdrawing group. This short-range charge transfer state (abbreviation: SRCT) mainly based on the multiple resonance structure, that is, the MR structure (refer to the part shown by the red solid line box in Figure 12 A2 and A3) and the long-range charge transfer state (abbreviation: LRCT) of the twisted donor-acceptor structure, that is, the D-A structure (refer to the part shown by the blue dashed line box in Figure 12 A2 and A3) of the hybrid emission material, and then through the intramolecular covalent bond (refer to Figure 13The charge transfer excited state of the regulating material is locked as shown by the red dotted line and the red circle in the lower right figure, weakening the intramolecular charge transfer state (ICT). Since the aryl boron nitride group has the properties of high luminescence efficiency and high color purity luminescence, it can improve the external quantum efficiency of the device. By covalently bonding to lock the fixed structure, the molecular rigidity is increased, making the molecular structure change from a helical curved surface structure to a rigid planar structure, weakening the long-range charge transfer state of the molecule, thereby weakening the molecular ICT, and thus regulating the excited state properties of the molecule. This is different from the original situation that can effectively promote the reverse intersystem crossing process (as Figure 12 shown in the right figure), improving the performance of thermally activated delayed fluorescence, and can be used as a new type of luminescent molecule with good performance, low cost, and high luminescence intensity.

[0185] Figure 13 The upper left dotted box is a multiple resonance structure, namely the MR structure (SRCT). In this structure, by introducing an electron donor N atom and an electron acceptor B atom at the distribution positions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the multiple resonance skeleton respectively, the HOMO-LUM electron cloud separation is achieved. Figure 13 The upper right dotted box is a twisted D-A structure (LRCT). In addition, TADF represents thermally activated delayed fluorescence. When coupling the MR-TADF structure (SRCT) state and the twisted D-A structure (LRCT) state, when the molecule contains a twisted D-A structure or a bond / bridge connecting the D and A groups, since the single bond is not locked and its angle can rotate freely, strong charge delocalization may occur in the excited state, followed by charge separation, thereby generating a strongly twisted ICT state (as Figure 13 shown in the lower left figure). At this time, the fluorescence efficiency of the compound will be reduced. The diboron fluorescent dye in this application is locked by covalent bonds to increase the planarity of the D-A structure, prevent distortion or internal rotation, and form a weak ICT property (as Figure 13 shown in the lower right figure). Based on this concept, that is, a brand-new method of modulating the charge transfer excited state of the MR emission material through intramolecular covalent bond locking, the diboron fluorescent dye compound of this patent application is proposed.

[0186] Figure 14 This is the fluorescence quantum yield (PLQY) graph of compounds A1 and A2 prepared in Examples 1 and 2 of this application in toluene solution. From Figure 14 it can be seen that the fluorescence quantum yield of the diboron fluorescent dye A1 is 89.74%; while the fluorescence quantum yield of the diboron fluorescent dye A2 is as high as 98.42%. This shows that the diboron fluorescent dye provided in this application improves the performance of thermally activated delayed fluorescence and can be used as a new type of luminescent molecule with good performance, low cost, and high luminescence intensity.

[0187] In summary, the dual-boron fluorescent dye provided by the present application exhibits short-wave blue-green light emission and orange-red light emission, and can be used as a new type of luminescent molecule with high performance and high quantum efficiency. The dual-boron fluorescent dye has great application potential in the preparation of luminescent materials, light-emitting devices or intelligent materials, etc., and has good application prospects in the fields of full-color display and solid-state lighting.

[0188] Meanwhile, the present application realizes the controllable preparation of the dual-boron fluorescent dye; the preparation cost is low, the raw materials are widely available, large-scale production can be achieved, and it has broad commercial prospects.

[0189] Based on the dual-boron nitride system molecules, the present application weakens the intramolecular charge transfer state (ICT) through intramolecular covalent bond locking regulation, and realizes an emission material jointly regulated by short-range charge transfer state and long-range charge transfer state. Among them, aryl boron nitride is the multiple resonance core of short-range charge transfer, and different electron-donating groups are introduced peripherally as the long-range charge transfer part, realizing the long-range charge transfer state of the molecule and regulating the excited state properties of the molecule, which can effectively promote the reverse intersystem crossing rate and improve the performance of thermally activated delayed fluorescence, thereby reducing the serious problem of device roll-off.

[0190] Therefore, the dual-boron fluorescent dye provided by the present application can be used as a luminescent material or an intelligent material, and has good application prospects in the fields of full-color display and solid-state lighting.

[0191] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0192] Although several embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. A diboron fluorescent dye, 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 or an electron withdrawing group, and the D is selected from one of the following structural formulas: Wherein, said R is selected from H, CN, Me or t-Bu.

2. The double boron fluorescent dye according to claim 1, characterized in that: Has one of the following molecular structures:

3. The method for preparing the diboron fluorescent dye according to claim 1 or 2, characterized in that: The following steps are involved: S1. Preparation of Intermediate 1 1,4-Dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate were added to the reaction bottle in sequence. After nitrogen was replaced three times, N,N-dimethylformamide was added and refluxed 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, and ethanol was added and heated and stirred, and filtered to obtain intermediate 1, whose structural formula is shown below: S2. Preparation of Intermediate 2 The intermediate 1 obtained in step S1 was dissolved in dichloromethane, and the intermediate 1 and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone were added to the reaction bottle, and nitrogen was pumped three times at room temperature. Then, methanesulfonic acid was added and stirred at room temperature. After the reaction was completed, triethylamine 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 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 obtain intermediate 2, whose structural formula is shown below: S3. Preparation of diboron fluorescent dye The intermediate 2 obtained in step S2 is dissolved in o-xylene, and n-butyl lithium is slowly added under stirring, and then boron tribromide is continuously added under stirring, followed by N,N-diisopropylethylamine, and stirring is continued; after the solution is cooled, 2-mesitylmagnesium bromide is added and stirred, and after the reaction is completed, methanol is used to quench the reaction, and 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, and then the crude product is separated and purified by column chromatography to obtain a diboron fluorescent dye.

4. The method for preparing the diboron fluorescent dye according to claim 3, characterized in that: In step S1, the molar ratio of 1,4-dibromo-2,3-difluorobenzene, 3,6-di-tert-butylcarbazole and cesium carbonate is 1:(2.5-3):(2-3).

5. The method for preparing the diboron fluorescent dye according to claim 4, characterized in that: In step S1, the reaction temperature is 110-150° C., and the reaction time is 24-36 hours.

6. The method for preparing the diboron fluorescent dye according to claim 3, characterized in that: In step S2, the molar ratio of the intermediate 1 to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1:(1.5-2), the reaction temperature is 0--10°C, and the reaction time is 2-4h.

7. The method for preparing the diboron fluorescent dye according to claim 3, characterized in that: In step S3, the molar ratio of the intermediate 2, n-butyl lithium, boron tribromide and 2-mesityl magnesium bromide is 1:(3.5-4):(3.5-4.5):(8-9), the reaction temperature is 0--30°C, and the reaction time is 6-12h.

8. The method for preparing the diboron fluorescent dye according to claim 3, characterized in that: In step S3, a Grignard reagent needs to be added, and the Grignard reagent is one of phenylmagnesium bromide.

9. The method for preparing the diboron fluorescent dye according to claim 3, characterized in that: In step S3, a Grignard reagent needs to be added, and the Grignard reagent is one of benzylmagnesium bromide.

10. Use of the diboron fluorescent dye according to claim 1 or 2 as a luminescent material, a luminescent device or a smart material.

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