Dicyanacenaphthopyrazine tsct-tadf near-infrared light-emitting material and application thereof

Abstract

The application belongs to the technical field of light emitting and display, and particularly relates to a dicyanacenaphthopyrazine TSCT-TADF near-infrared light emitting material and application thereof. The TSCT-TADF near-infrared light emitting material has a strong electron-withdrawing dicyanacenaphthopyrazine as an acceptor (A) unit, a strong electron-donating triarylamine or oxygen-bridged triphenylamine derivative as a donor (D) unit, and a 1,8-naphthyl or 5,6-acenaphthyl as a pi bridge unit. The near-infrared light emitting materials LY-1 and LY-2 with TSCT-TADF performance are obtained. The non-doped near-infrared electroluminescent devices are prepared by taking the materials LY-1 and LY-2 as light emitting layers. The maximum emission peaks of the electroluminescent devices based on the light emitting layers of LY-1 and LY-2 are located at 724 nm and 784 nm, respectively, and the corresponding maximum external quantum efficiencies (EQE) are 1.85% and 0.55%, respectively.

Description

Technical Field

[0001] This invention belongs to the field of light emission and display technology, specifically relating to a dicyanoacenaphthene TSCT-TADF near-infrared luminescent material and its application. Background Technology

[0002] Organic light-emitting diodes (OLEDs) possess excellent properties such as high resolution, light weight, and flexibility, and are currently widely used in displays, showing huge market potential. The key to improving the efficiency of OLEDs lies in the upgrading of novel luminescent materials. In OLEDs constructed from traditional fluorescent materials, 75% of triplet excitons typically fail to emit light due to transition confinement. Therefore, how to effectively utilize triplet excitons to emit light and achieve 100% internal quantum efficiency (IQE) has become a research hotspot and key scientific issue in luminescent materials. Since the Adachi team designed and developed thermally active delayed fluorescence (TADF) materials and achieved efficient green luminescence (Nature, 2012, 492, 234) in 2012, TADF-based organic luminescent materials have become an effective method for obtaining efficient luminescence. Compared with traditional fluorescent materials, TADF materials have a smaller singlet (S0) to triplet (T1) energy split (ΔE). ST By utilizing reverse intersystem crossing (RISC) to achieve energy conversion of excitons from triplet to singlet states (T1→S1), TADF molecules can achieve almost 100% exciton utilization and efficient electroluminescence, attracting significant attention in the field of OLED research (Adv. Opt. Mater., 2018, 6, 1800385; Adv. Mater., 2020, 32, 2003885). However, due to spin forbidden constraints, the spin-flipping rate between the singlet and triplet states of TADF molecules is low, thus limiting the application of this type of material in OLEDs.

[0003] Organic light-emitting materials based on space charge transfer (TSCT) avoid the aggregation quenching (ACQ) phenomenon that easily occurs in large planar conjugated near-infrared light-emitting materials in thin film state due to the face-to-face spatial arrangement between the donor and acceptor units and the twisted steric hindrance structure of the molecular structure. In particular, it not only reduces the energy level difference (ΔE) between singlet and triplet states. ST It can suppress nonradiative transitions, which is beneficial to improving fluorescence quantum yield and plays an important role in shortening exciton lifetime and maintaining a low device efficiency roll-off (Angew. Chem. Int. Ed., 2021, 60, 3994; Mater. Chem. Front., 2023, 7, 1128; J. Mater. Chem. C, 2021, 9, 4792).

[0004] Organic near-infrared luminescent materials refer to luminescent materials with emission wavelengths exceeding 700 nm. Due to their strong penetrability, low background interference, invisibility, and non-damaging properties to biological organisms, they have broad application prospects in luminescent displays, medical diagnostics, and phototherapy. In particular, compared to inorganic near-infrared luminescent materials, organic near-infrared luminescent materials have become the main development direction for near-infrared luminescent materials and OLEDs due to their abundant material sources, low cost, easily tunable optical properties, and ability to achieve flexible luminescent displays. However, due to the limitations of the bandgap law, the luminous efficiency of organic near-infrared luminescent materials generally decreases with increasing emission wavelength. Simultaneously, to reduce the bandgap, organic near-infrared luminescent materials inevitably require the grafting of large planar conjugated systems. While these materials exhibit strong luminescence in solution, they are prone to ACQ phenomena in thin films, making it difficult to achieve high-efficiency luminescence. Therefore, improving the RISC rate, suppressing nonradiative transitions, and reducing the energy level difference between singlet and triplet states are crucial problems that urgently need to be solved in near-infrared luminescent materials. Summary of the Invention

[0005] To overcome the problems existing in the prior art, this invention constructs a class of organic near-infrared luminescent materials based on dicyanoacenaphthene, which has dual characteristics of TSCT effect and TADF performance, structural ortho-twisted structure, and face-to-face spatial arrangement between donor and acceptor units. By utilizing the synergistic strategy of TSCT and TADF, high-efficiency luminescence of TSCT-TADF near-infrared emission is achieved and its application in organic electroluminescent diodes is realized.

[0006] This invention constructs a class of D-π-A type TSCT-TADF near-infrared luminescent materials using a strong electron-withdrawing dicyanoacenaphthene structure as the electron acceptor (A) unit, a strong electron-donating triarylamine or oxabridged triphenylamine derivative as the electron donor (D) unit, and 1,8-naphthyl or 5,6-acenaphthene as the π-bridge unit.

[0007] The TSCT-TADF near-infrared luminescent material provided by this invention has the structure shown in formula (1) or formula (2):

[0008]

[0009] Wherein: D is an independent triarylamine or oxatriarylamine derivative unit.

[0010] The specific structures of the preferred TSCT-TADF near-infrared luminescent materials are as follows; these compounds are only representative examples:

[0011]

[0012] In the more preferred TSCT-TADF near-infrared luminescent material, the D unit is a triarylamine or a benzoxopyroxazine, with molecular structural formulas named LY-1 or LY-2, respectively.

[0013]

[0014] The preparation steps of TSCT-TADF near-infrared luminescent material are as follows:

[0015] Preparation method of LY-1: Using acenaphthene as raw material, 5-bromoacenaphthene and 5,6-dibromoacenaphthene are prepared by bromination reaction; using bromotriphenylamine as donor (D) unit, 5-bromoacenaphthene is prepared by oxidation reaction as acceptor (A) unit, D / A unit is subjected to Miyaura borate esterification reaction, and then 5,6-dibromoacenaphthene is used as bridging unit to carry out Suzuki coupling reaction with borate esterified D / A unit, and Schiff base condensation cyclization reaction to prepare LY-1.

[0016] Preparation method of LY-2: The D / A unit was prepared by Miyaura borate esterification using bromooxy-bridged triphenylamine as the donor (D) unit and 5-bromoacenaphthene as the acceptor (A) unit. LY-2 was then prepared by Suzuki coupling reaction with the borate-esterified D / A unit using 1,8-dibromonaphthalene as the bridging unit, followed by Schiff base condensation cyclization.

[0017] This invention also provides the application of TAST-TADF near-infrared luminescent material, which is used as a luminescent layer material in the preparation of near-infrared OLEDs.

[0018] The near-infrared OLED structure of this invention is: ITO / PEDOT:PSS (40nm) / PVK (5nm) / LY-1 or LY-2 / TmPyPB (40nm) / LiF (1.2nm) / Al (120nm). The hole transport layer is a polyvinylcarbazole (PVK) coating; the electron transport layer is TmPyPB; the emitting layer is a coating of the TSCT-TADF near-infrared emitting material LY-1 or LY-2 of this invention; and the cathode layer is composed of lithium fluoride and aluminum.

[0019] The TSCT-TADF near-infrared luminescent materials LY-1 or LY-2 were used to prepare the luminescent layer of near-infrared OLEDs, and the maximum emission peak (corresponding external quantum efficiency) of the undoped near-infrared OLED devices were 724nm (1.85%) or 784nm (0.55%), respectively.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The TSCT-TADF near-infrared luminescent material of the present invention has a simple molecular structure and low preparation cost.

[0022] (2) The unique steric hindrance twisted structure of the TSCT-TADF near-infrared luminescent material of the present invention enables a face-to-face spatial arrangement between the donor and acceptor units, restricting the free rotation of the molecular donor and acceptor units, improving the rigidity of the molecular structure, which is beneficial to improving the oscillator strength, enhancing the intramolecular π-π interaction, and weakening the concentration-quenching effect, thereby achieving the goal of improving PLQY, which exceeds 28%. At the same time, it also obtains a shorter delayed fluorescence lifetime and maintains a low efficiency roll-off.

[0023] (3) Conjugate π-bridges are selected between the intramolecular donor and acceptor units to minimize the spatial overlap between the donor unit HOMO and the acceptor unit LUMO, thereby obtaining a smaller S1-T1 energy split (ΔE). ST This promotes reverse intersystem crossing (RISC), enabling rapid transitions from the T1 to S1 state, reducing non-radiative transitions in molecules, and improving the luminescence efficiency of materials.

[0024] (4) For the first time, near-infrared emission with a photoluminescence wavelength exceeding 800 nm was achieved using a TSCT-TADF luminescent material.

[0025] (5) The TSCT-TADF near-infrared organic light-emitting material of the present invention can be used as a light-emitting layer material and applied to near-infrared OLED devices, achieving near-infrared electroluminescence of more than 780nm for the first time.

[0026] (6) This type of TSCT-TADF near-infrared organic light-emitting small molecule material has high thermal stability and excellent carrier transport performance. Attached image description:

[0027] Figure 1 The UV-Vis absorption spectra of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention are shown in toluene solution.

[0028] Figure 2 The images show the UV-Vis absorption spectra of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention in thin films.

[0029] Figure 3 The photoluminescence spectra of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention in toluene solution are shown.

[0030] Figure 4 The photoluminescence spectra of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention are shown in thin films.

[0031] Figure 5 The low-temperature fluorescence phosphorescence spectrum of compound LY-1 obtained in Example 1 of this invention is shown at 77K.

[0032] Figure 6 The low-temperature fluorescence phosphorescence spectrum of compound LY-2 obtained in Example 2 of this invention is shown at 77K.

[0033] Figure 7 The CV diagrams are of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention.

[0034] Figure 8 This is the delayed fluorescence spectrum of compound LY-1 obtained in Example 1 of the present invention.

[0035] Figure 9 This is the delayed fluorescence spectrum of compound LY-2 obtained in Example 2 of the present invention.

[0036] Figure 10 The diagram shows the structure of undoped near-infrared light-emitting devices of compounds LY-1 and LY-2 obtained in Examples 1 and 2 of this invention.

[0037] Figure 11 The image shows the EL spectrum of compound LY-1 obtained in Example 1 of this invention in the undoped state.

[0038] Figure 12 The image shows the EQE spectrum of compound LY-1 obtained in Example 1 of this invention in the undoped state.

[0039] Figure 13 The image shows the EL spectrum of compound LY-2 obtained in Example 2 of this invention in the undoped state.

[0040] Figure 14 The image shows the EQE spectrum of compound LY-2 obtained in Example 2 of this invention in the undoped state. Detailed Implementation

[0041] The present invention will be further illustrated below by specific embodiments of dicyanoacenaphthene TSCT-TADF near-infrared luminescent materials LY-1 and LY-2, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0042] Example 1: The synthesis scheme of LY-1, a near-infrared luminescent material based on dicyanoacenaphthene TSCT-TADF, is as follows:

[0043]

[0044] The preferred synthetic route for compound LY-1

[0045] Synthesis of compound M1

[0046] In a 500 mL single-necked flask, acenaphthene (50.0 g, 324.3 mmol, 1.00 eq.) was dissolved in DMF (160 mL) under heating in air, and the resulting solution was cooled to 0 °C in an ice bath. Protected from light, N-bromosuccinimide (125 g, 716 mmol, 2.20 eq.) was added in portions over 1 hour, keeping the reaction temperature below 5 °C. The mixture was heated to room temperature overnight to give a dark solution with a pale yellow precipitate. The precipitate was separated by filtration, washed with ethanol (3 × 50 mL), and dried under vacuum. It was then resuspended in ethanol (500 mL) and heated to reflux overnight. The mixture was cooled and filtered to give 5,6-dibromoacenaphthene (M1), as pale orange / beige crystals, washed with ethanol (3 × 30 mL), and dried under vacuum (22.6 g, 22%). 1 H NMR (400MHz, CDCl3) δ (ppm) = 7.79 (d, J = 7.4Hz, 2H), 7.09 (d, J = 7.4Hz, 2H), 3.31 (s, 4H).

[0047] Synthesis of compound M2

[0048] In a 1.0 L flask, 20 g (64.1 mmol, 1.00 eq.) of 5,6-dibromo-1,2-dihydroacenaphthene (M1) was dissolved in 500 mL of 1,4-dioxane under heating. The resulting mixture was degassed for 30 min while cooling to room temperature. Triphenylamine boric acid (22.24 g, 76.92 mmol, 1.20 eq.) and Pd(PPh3)4 (740 mg, 0.64 mmol, 0.01 eq.) were then added, along with 128 mL of degassed aqueous solution of K2CO3 (35.4 g, 256.4 mmol, 4.00 eq.). The reaction mixture was then degassed again for 5 min. The mixture was then heated under reflux for 12 h (preheated to 110 °C oil bath) under argon atmosphere. The resulting deep red mixture was cooled to room temperature and poured into a mixture of 500 mL of CHCl3 and 500 mL of 1 M HCl. The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The resulting solid was subjected to column chromatography to give the target intermediate as a bright yellow solid (6.72 g, 14.1 mmol, 22%). 1 H NMR (400MHz, CDCl3) δ (ppm) = 8.28 (d, J = 7.3Hz, 1H), 8.23 ​​(d, J = 7.3Hz, 1H), 8.14 (d, J = 7.3H) z,1H),7.94(d,J=7.3Hz,1H),7.34–7.27(m,6H),7.25–7.21(m,6H),7.08(t,J=7.3Hz,2H).

[0049] Synthesis of compound M3

[0050] In a 500 mL single-necked flask, acenaphthene (50.0 g, 324.3 mmol, 1.00 eq.) was dissolved in 160 mL of DMF under heating in air, and the resulting solution was cooled to 0 °C in an ice bath. Protected from light, N-bromosuccinimide (62.5 g, 358 mmol, 1.10 eq.) was added in portions over 1 hour, keeping the reaction temperature below 5 °C. The mixture was warmed to room temperature overnight to give a pale yellow solution. The precipitate was separated by filtration in ice water, dissolved in DCM, and the mixture was subjected to column chromatography to give 5-bromoacenaphthene (M3) as a pale yellow solid (72.5 g, 96%). 1 H NMR (400MHz, CDCl3) δ (ppm): 7.77 (dd, J=8.4, 0.8Hz, 1H), 7.66 (d, J=7.0Hz, 1H), 7.55 (dd, J=8.4, 6. 9Hz, 1H), 7.33 (dd, J=6.9, 0.8Hz, 1H), 7.14 (d, J=7.0Hz, 1H), 3.44–3.41 (m, 2H), 3.36–3.33 (m, 2H).

[0051] Synthesis of compound M4

[0052] M3 (6.36 g, 27.3 mmol) was dissolved in acetic anhydride (1 L) at 110 °C. CrO3 (21.1 g, 211 mmol) was carefully added to the stirred solution over 2 hours. The resulting green suspension was heated to 160 °C and stirred for 30 minutes. The solution was then poured hot onto crushed ice (1 kg), HCl (20 mL) was added, and the precipitate was filtered off. The brown precipitate was washed with water, dried under vacuum, and recrystallized from acetic anhydride (2 L) to give a light brown solid, 1,8-dibromoacenaphthene-dione (4.44 g, 67%). 1 H NMR (400MHz, DMSO) δ (ppm) = 8.41 (d, 1H), 8.23 ​​(d, 1H), 8.16 (d, 1H), 8.06 (t, 1H), 7.97 (d, 1H).

[0053] Synthesis of compound M5

[0054] In a 100 mL single-necked flask, M4 (1.3 g, 4.98 mmol), potassium acetate (0.687 g, 7.00 mmol), and bis[pinacolyl]diborane (0.762 g, 3.00 mmol) were dissolved in dry 1,4-dioxane (13 mL). The catalyst [1,1'-bis(diphenylphosphine)ferrocene]palladium(II) chloride was added under a nitrogen atmosphere, and the reaction mixture was heated at 110 °C for 12 h. The reaction mixture was diluted with water and the suspension was extracted with ethyl acetate (3x). The combined organic layers were washed with brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The mixture was subjected to column chromatography to give M5 (1.216 g, 79.3%) as a brownish-yellow solid. 1 H NMR (400MHz, CDCl3) δ (ppm) = 9.14 (dd, J = 63.9, 8.5Hz, 1H), 8.60 (dd, J = 16.5, 7.2Hz, 1H), 8.37 (d d,J=18.1,7.0Hz,1H),8.09(dd,J=21.8,7.0Hz,1H),7.86(dt,J=15.7,7.7Hz,1H),1.46(s,12H).

[0055] Synthesis of compound M6

[0056] In a 100 mL single-necked flask, M5 (1 g, 3.25 mmol, 1.00 eq.) was dissolved in 1,4-dioxane (30 mL). The resulting mixture was degassed for 30 min, and then M2 (1.548 g, 3.25 mmol, 1 eq.) and Pd(PPh3)4 (187.8 mg, 0.1625 mmol, 0.05 eq.) were added. A degassed aqueous solution of K2CO3 (1.8 g, 13 mmol, 4.00 eq.) (6.5 mL) was added, and the reaction mixture was degassed again for 5 min. The mixture was then heated under reflux for 12 h (preheated to 110 °C oil bath). The resulting deep red mixture was cooled to room temperature and poured into a mixture of CHCl3 (50 mL) and 1 M HCl (50 mL). The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The obtained solid was subjected to column chromatography to obtain the target intermediate M6, which was a brownish-red solid (1.27 g, 2.21 mmol, 68.1%). 1H NMR (400MHz, CDCl3) δ (ppm) = 7.97 (dd, J = 13.1, 7.1Hz, 2H), 7.78 (d, J = 8.5Hz, 1H), 7.63-7.52 (m, 2H), 7.46 (dd, J = 12.1, 6.5Hz, 3H), 7.34 (d, J =7.1Hz,1H),7.18(t,J=7.0Hz,4H),6.98(t,J=7.4Hz,2H),6.71(d,J=7.7Hz,4H),6.41(t,J=9.1Hz,2H),6.01(d,J=8.4Hz,1H),3.57(s,4H).

[0057] Synthesis of compound LY-1

[0058] In a 50 mL single-necked flask, M6 (1 g, 1.73 mmol, 1 eq) and 2,3-diaminomaleonitrile (280 mg, 2.6 mmol, 1.5 eq) were added and dissolved in AcOH. The mixture was heated to 125 °C and refluxed for 12 hours under a nitrogen atmosphere. The mixture was poured into water, cooled to room temperature, and poured into a mixture of CHCl3 (50 mL) and water (50 mL). The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The resulting solid was subjected to column chromatography to give the target product LY-1 as a reddish-brown solid (1 g, 1.55 mmol, 89.6%). 1 H NMR (400MHz, CDCl3) δ (ppm) = 8.44 (d, J = 7.0Hz, 1H), 8.30 (d, J = 7.3Hz, 1H), 7.93 (d, J = 8 .4Hz,1H),7.73–7.67(m,1H),7.64(d,J=7.3Hz,1H),7.47(dd,J=10.7,4.3Hz,3H),7.36 (d,J=7.1Hz,1H),7.10(t,J=7.8Hz,4H),6.95(t,J=7.2Hz,2H),6.82(d,J=8.1Hz,1H),6 .53(d,J=7.9Hz,4H),6.40(dd,J=36.5,8.0Hz,2H),5.90(d,J=8.0Hz,1H),3.58(s,4H).

[0059] Example 2: The synthesis scheme of LY-2, a near-infrared luminescent material based on dicyanoacenaphthene TSCT-TADF, is as follows:

[0060]

[0061] Preferred synthetic route for compound LY-2

[0062] Synthesis of compound M7

[0063] In a 250 mL single-necked flask, M5 (2 g, 6.5 mmol, 1.00 eq.) was dissolved in 1,4-dioxane (60 mL). The resulting mixture was degassed for 30 min, and then 1,8-dibromonaphthalene (1.859 g, 6.5 mmol, 1 eq.) and Pd(PPh3)4 (187.8 mg, 0.1625 mmol, 0.025 eq.) were added. A degassed aqueous solution of K2CO3 (3.6 g, 26 mmol, 4.00 eq.) (13 mL) was added, and the reaction mixture was degassed again for 5 min. The mixture was then heated under reflux for 12 h (preheated to 110 °C oil bath). The resulting deep red mixture was cooled to room temperature and poured into a mixture of CHCl3 (80 mL) and 1 M HCl (80 mL). The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The obtained solid was subjected to column chromatography to obtain the target intermediate M7, which was a yellow solid (1.794 g, 4.635 mmol, 71.31%). 1 H NMR (400MHz, CDCl3) δ8.11(d,J=7.2Hz,1H),8.05-7.99(m,2H),7.94(d,J=8.1Hz,1H),7.74(d,J=7.2Hz,1H),7 .69(d,J=7.4Hz,1H),7.61(dd,J=7.5,5.1Hz,2H),7.59-7.54(m,1H),7.46-7.44(m,1H),7.32(t,J=7.8Hz,1H).

[0064] Synthesis of compound M8

[0065] In a 100 mL single-necked flask, 7-bromobenzo[5,6][1,4]oxazino[2,3,4-kl]phenyloxazine (2 g, 5.68 mmol), potassium acetate (1.374 g; 14.00 mmol), and bis[pinacolyl]diborane (1.524 g, 6 mmol) were dissolved in dry 1,4-dioxane (30 mL). The catalyst [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) chloride was added under a nitrogen atmosphere, and the reaction mixture was heated at 110 °C for 36 h. The reaction mixture was diluted with water and the suspension was extracted with DCM (3x). The combined organic layers were washed with brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The mixture was subjected to column chromatography to give M8 (2.127 g, 93.8%) as a white solid. 1H NMR (400MHz, CDCl3) δ7.36-7.28(m,2H),6.97-6.82(m,8H),1.31(s,12H).

[0066] Synthesis of compound M9

[0067] In a 200 mL single-necked flask, M7 (1.5 g, 3.87 mmol, 1.00 eq.) was dissolved in 1,4-dioxane (50 mL). The resulting mixture was degassed for 30 min, and then M8 (1.699 g, 4.26 mmol, 1.1 eq.) and Pd(PPh3)4 (187.8 mg, 0.1625 mmol, 0.025 eq.) were added. A degassed aqueous solution of K2CO3 (2.14 g, 15.48 mmol, 4.00 eq.) (8 mL) was added, and the reaction mixture was degassed again for 5 min. The mixture was then heated under reflux at nitrogen for 24 h (preheated to 110 °C in an oil bath). The resulting deep red mixture was cooled to room temperature and poured into a mixture of CHCl3 (80 mL) and 80 mL of water. The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The obtained solid was subjected to column chromatography to obtain the target intermediate M9 (1.46 g, 65.2%), which was a red solid. 1 H NMR (400MHz, CDCl3) δ8.11(d,J=8.0Hz,1H),8.04(d,J=8.1Hz,1H),7.96(d,J=7. 2Hz,1H),7.84(d,J=6.8Hz,1H),7.70-7.55(m,4H),7.51(dd,J=15.4,6.8Hz,2H) ,7.32(d,J=7.0Hz,1H),7.16(t,J=8.4Hz,2H),6.98-6.87(m,4H),6.83-6.78(m, 1H), 6.48 (t, J = 12.3Hz, 1H), 5.95 (t, J = 5.6Hz, 1H), 5.53 (dd, J = 16.9, 5.2Hz, 1H).

[0068] Synthesis of compound LY-2

[0069] In a 100 mL single-necked flask, M9 (1 g, 1.725 mmol, 1 eq) and 2,3-diaminomaleonitrile (280 mg, 2.6 mmol, 1.5 eq) were added and dissolved in AcOH. The mixture was heated to 125 °C and refluxed for 12 hours under a nitrogen atmosphere. The mixture was poured into water, cooled to room temperature, and poured into a mixture of CHCl3 (50 mL) and water (50 mL). The layers were separated, and the aqueous layer was further extracted with DCM (4 × 100 mL). The organic layers were combined, dried over MgSO4, filtered, and the solvent was removed under reduced pressure. The resulting solid was subjected to column chromatography to give the target intermediate LY-2 as a dark green solid (1.08 g, 1.67 mmol, 92.6%). 1 H NMR (400MHz, CD2Cl2) δ8.33(d,J=6.1Hz,2H),8.13(d,J=7.9Hz,1H),8.05(d,J=7.9Hz,1H),7.68(dt,J=25.0,9.3Hz,4H), 7.61-7.50(m,2H),7.28(t,J=7.8Hz,1H),6.85(dt,J=14.2,9.5Hz,7H),6.39(d,J=7.0Hz,1H),5.92(s,1H),5.33(s,1H).

[0070] Example 3: UV Testing of Near-Infrared Emitting Materials LY-1 and LY-2 Based on Dicyanoacenaphthene Space Charge Transfer

[0071] Compounds LY-1 and LY-2 were dissolved in chloroform solution, and thin films of LY-1 and LY-2 were prepared by spin coating. The UV-Vis absorption spectra of the thin films and toluene were then measured. Figure 1 and Figure 2 It can be seen that the UV-Vis absorption spectra of compounds LY-1 and LY-2 in thin films and toluene have two absorption peaks: the absorption bands of the two compounds at around 330 nm are attributed to π-π transitions, and the absorption bands at around 400-550 nm are attributed to intramolecular charge transfer (ICT).

[0072] Example 4: Toluene solution PL test of near-infrared luminescent materials LY-1 and LY-2 based on dicyanoacenaphthene-pyrazine space charge transfer.

[0073] Photoluminescence properties of compound LY-1 in Example 1 and compound LY-2 in Example 2 were tested. Compounds LY-1 and LY-2 were dissolved in toluene to prepare a 10... -5 Solution M was tested, and its photoluminescence spectrum was measured. Figure 3As shown, under photoexcitation, all compounds are in the near-infrared region. Among them, compound LY-1 has a maximum emission peak of 731 nm, and compound LY-2 has an emission peak of 790 nm, thus meeting the near-infrared requirement.

[0074] Example 5: Thin Film PL Testing Based on Dicyanoacenaphthene-based Space Charge Transfer Near-Infrared Emitting Materials LY-1 and LY-2

[0075] Photoluminescence properties of compound LY-1 in Example 1 and compound LY-2 in Example 2 were tested. Compounds LY-1 and LY-2 were dissolved in a chloroform solution, and thin films of LY-1 and LY-2 were prepared by spin coating. The photoluminescence spectra of the thin films were then tested. Figure 4 As shown, under photoexcitation, all compounds are in the near-infrared region. Compound LY-1 has a maximum emission peak at 742 nm, and compound LY-2 has an emission peak at 806 nm, achieving the near-infrared requirement. This is the first TSCT-TADF near-infrared material with a photoluminescence wavelength exceeding 800 nm.

[0076] Example 6: CV testing of near-infrared luminescent materials LY-1 and LY-2 based on dicyanoacenaphthene-pyrazine space charge transfer.

[0077] CV tests were performed on compound LY-1 from Example 1 and compound LY-2 from Example 2. Figure 7 As shown, cyclic voltammetry (CV) was performed in a nitrogen atmosphere in anhydrous acetonitrile solution using a CHI 620 voltammeter at a scan rate of 50 mV / s. A platinum disk working electrode, a platinum wire counter electrode, and an Ag / AgCl electrode were used as the working, counter, and reference electrodes, respectively. An acetonitrile solution of tetrabutylammonium hexafluorophosphate (Bu4NPF6, 0.1 M) was used as the reference for all measurements. Ferrocene / ferrocene cations (Fc / Fc) were used as the reference. + The redox couple was used as a reference. The oxidation potential of LY-1 was measured to be 1.13 eV, and the oxidation potential of LY-2 was measured to be 1.11 eV. Ferrocene / ferrocene cations (Fc / Fc) + The potential of ) is 0.43 eV. The HOMO level of LY-1 can be calculated to be -5.55 eV, and the HOMO level of LY-2 can be calculated to be -5.48 eV. The LUMO level can be calculated from the optical band gap.

[0078] Example 7: Low-temperature fluorescence and phosphorescence testing of LY-1, a space charge transfer near-infrared luminescent material based on dicyanoacenaphthene-pyrazine.

[0079] Compound LY-1 from Example 1 was doped into CBP, and the low-temperature fluorescence and phosphorescence of its 10 wt% doped film were tested at 77 K. Figure 5 As shown. According to the fitted measurements, the singlet level and triple singlet level of LY-1 are 1.92 eV and 1.87 eV, respectively, with ΔE... ST =0.05eV, much less than 0.2eV.

[0080] Example 8: Low-temperature fluorescence and phosphorescence testing of LY-2, a space charge transfer near-infrared luminescent material based on dicyanoacenaphthene-pyrazine.

[0081] Compound LY-2 from Example 1 was doped into CBP, and the low-temperature fluorescence and phosphorescence of its 10% wt doped film were tested at 77 K. Figure 6 As shown. According to the fitted measurements, the singlet level and triple singlet level of LY-2 are 1.766 eV and 1.758 eV, respectively, ΔE ST =0.008eV, much less than 0.2eV.

[0082] Example 9: Delayed fluorescence lifetime test of LY-1, a space charge transfer near-infrared luminescent material based on dicyanoacenaphthene pyrazine.

[0083] The compound LY-1 from Example 1 was doped into CBP at a mass percentage of 10 wt%, and the delayed lifetime spectrum of the 10 wt% film was tested. Figure 8 As shown. The lifetime measured by fitting is 2.46 μs, and the microsecond-level lifetime proves that LY-1 is a TADF material.

[0084] Example 10: Delayed fluorescence lifetime test of LY-2, a space charge transfer near-infrared luminescent material based on dicyanoacenaphthene pyrazine.

[0085] The compound LY-2 from Example 2 was doped into CBP at a mass percentage of 10 wt%, and the delayed lifetime spectrum of the 10 wt% film was tested. Figure 9 As shown. The lifetime measured by fitting is 1.89 μs, and the microsecond-level lifetime proves that LY-2 is a TADF material.

[0086] Example 11: Fabrication scheme and luminescence performance testing of near-infrared light-emitting devices based on dicyanoacenaphthene TSCT-TADF material.

[0087] The near-infrared TSCT-TADF undoped organic electroluminescent device has the following structure: ITO / PEDOT:PSS (40nm) / PVK (5nm) / LY-1 or LY-2 (40nm) / TmPyPB (40nm) / LiF (1.2nm) / Al (120nm). Figure 10As shown. The hole transport layer is a polyvinylcarbazole (PVK) coating; the electron transport layer is TmPyPB; the light-emitting layer is LY-1 or LY-2; and the cathode layer is composed of lithium fluoride and aluminum.

[0088] The device fabrication process is as follows: On treated ITO glass, a 40nm poly(ethylene thiophene) / poly(p-phenylene sulfonate) (PEDOT-PSS) (Bayer Batron P4083) hole injection layer, a 5nm PVK hole transport layer, and a 40nm emissive layer are spin-coated, followed by a 40nm electron transport layer (TmPyPB). Then, a 1.2nm lithium fluoride layer and a 120nm aluminum (Al) layer are sequentially deposited. The device's light-emitting area is 0.15cm². 2 .

[0089] The thicknesses of the hole injection layer, hole transport layer, and luminescent layer were measured using a surface profilometer (Tencor, ALFA-Step500). The thicknesses and deposition rates of Ba and Al were measured using a thickness / velocity meter (Sycon STM-100 thickness / velocity meter), with deposition rates of 0.05–0.1 nm / s for Ba and 1–2 nm / s for Al. All operations were performed in a nitrogen glove box.

[0090] Electroluminescence (EL) spectra were measured using an Instaspec 4CCD grating spectrometer from Oriel Corporation; luminous efficiency was measured using a standard silicon photodiode; electroluminescence efficiency was measured using an S80 integrator (US Labshere Corporation) in conjunction with a UDT3 digital photometer; the laser source was a He-Cd laser with spectral lines of 325 and 442 nm (USDmni Chrone Corporation); current-voltage (IV) curves, luminous intensity-voltage (LV) curves, and external quantum efficiency were measured using a Keithley source analyzer.

[0091] The electroluminescence spectrum and EQE curve of the TSCT-TADF near-infrared light-emitting device based on LY-1 and LY-2 materials are shown in the figure. Figures 11-14 As shown. By Figure 11 , Figure 12 , Figure 13 , Figure 14 It is evident that undoped pure film devices based on LY-1 and LY-2 exhibit near-infrared spectra, displaying strong luminescence in the 650 nm to 900 nm range. When these two materials were used to fabricate near-infrared organic light-emitting diode (OLED) devices, the emission wavelength and external quantum efficiency of the LY-1 pure film device were 724 nm and 1.85%, respectively; while the emission wavelength and external quantum efficiency of the LY-2 undoped pure film device were 784 nm and 0.55%, respectively. This is the first near-infrared emitting device with an emission peak close to 800 nm using TSCT-TADF electroluminescent materials.

[0092] Although the invention has been described in conjunction with preferred embodiments, the invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the invention. Guided by the inventive concept, those skilled in the art should recognize that any modifications made to the various embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. A type of dicyanoacenaphthene TSCT-TADF near-infrared luminescent material, characterized in that, The molecular structural formula of the luminescent material is: 。 2. The application of the TSCT-TADF near-infrared luminescent material according to claim 1, characterized in that, The near-infrared luminescent material is used to prepare organic light-emitting diodes.

3. The application of the TSCT-TADF near-infrared luminescent material according to claim 1, characterized in that, The near-infrared luminescent material serves as the luminescent layer material for near-infrared OLEDs.

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