A chiral schiff base zinc(ii) binuclear complex, a preparation method and application of an organic circularly polarized white light device (CP-WOLED)

Abstract

A chiral Schiff base zinc(II) binuclear complex, its preparation method, and its application in organically electro-polarized white light devices (CP-WOLEDs) are disclosed. The visible light color changes with alterations in the substituents of the chiral Schiff base ligand; a color compensation strategy can be employed for use as an organically circularly polarized photoluminescent / electroluminescent material in CP-WOLEDs. At room temperature, the chiral Schiff base zinc(II) binuclear complex exhibits blue light emission in CH2Cl2 solution, with maximum emission peaks at 462 nm and 461 nm, and displays strong ground-state chirality and the Cotton effect, with an asymmetry factor of | g PL |~10 ‑4 Using this blue chiral Schiff base zinc(II) binuclear complex as a dopant material, and through color compensation with its blue light as the primary color, an organic electro-polarized white light-emitting device was developed, achieving excellent luminescence performance.

Description

Technical Field

[0001] This invention relates to an organic light-emitting material based on a chiral Schiff base zinc(II) binuclear complex, specifically to a novel chiral Schiff base zinc(II) binuclear complex, its preparation method, and its application in an organic electro-polarized circularly polarized white light device (CP-WOLED), belonging to the field of organic optoelectronic functional materials. Background Technology

[0002] White organic light-emitting diodes (WOLEDs) possess advantages such as soft and uniform light emission, self-emission, and surface light source characteristics, and are considered a new generation of lighting sources. The realization of white light relies on the emission of three primary colors or complementary colors; efficient monochromatic light is a prerequisite for achieving high-level white light. Based on excimer complexes involving intermolecular charge transfer, it is only necessary to select suitable donor and acceptor materials and utilize their intrinsically small Δ... EST Triple-state excitons can be utilized through reverse system-to-system crossing (RISC) processes, theoretically achieving 100% internal quantum efficiency. Furthermore, the broad-band luminescence of the exciton complex itself is beneficial for improving the color and light quality of WOLEDs. However, current fully exciton complex WOLEDs still suffer from structural complexity and relatively low efficiency.

[0003] Currently, white OLEDs are achieved through dual emission of complementary colors or triple emission of the three primary colors, which inevitably requires a large amount of luminescent material, resulting in high costs. However, utilizing excimer light emission can reduce the amount of luminescent material used, and the device efficiency is superior to that of ordinary fluorescent WOLEDs, representing a new approach to reducing the cost of WOLEDs. Furthermore, the broad-spectrum emission of excimer light emission is more conducive to achieving high color rendering index WOLEDs.

[0004] Therefore, this patent focuses on the research and development of monochromatic and white light OLEDs based on fully excimer-based excitation complex luminescence. By selecting a highly efficient monochromatic excimer-based excimer complex, employing a complementary color strategy, controlling the exciton recombination region, balancing carrier injection, and rationally designing the device structure, the aim is to fabricate a high-efficiency, high-brightness, and high-color-quality WOLED. Two chiral Schiff base zinc(II) complexes are synthesized through a self-assembly reaction, further enabling the realization of CP-WOLED devices that emit organically electro-polarized circularly polarized white light. Summary of the Invention

[0005] Technical Problem: The purpose of this invention is to provide a novel chiral Schiff base zinc(II) binuclear complex. The chiral Schiff base chelates zinc atoms, and the acetate group also provides the coordination environment, thereby improving the performance of the zinc(II) complex, resulting in a material with good emission wavelength and excellent luminescence properties. Furthermore, this invention provides a method for preparing the chiral Schiff base zinc(II) complex, and the application of this blue light-emitting material in organic electroluminescent white light-emitting devices.

[0006] Technical solution: In a first aspect, the present invention provides a novel chiral Schiff base zinc(II) binuclear complex, characterized in that it is formed by the chelation of metallic zinc with a chiral Schiff base ligand and an acetate ion provided by zinc acetate, and has the following general structural formula:

[0007]

[0008] In the chiral Schiff base zinc(II) binuclear complex, the hydroxyl group of the chiral Schiff base ligand is an electron-donating group, which is beneficial to increasing the LUMO energy level of the material and causing its emission wavelength to blue shift, and is also beneficial to decreasing the HOMO energy level of the material and causing its emission wavelength to blue shift.

[0009] An acetate ion coordinates with its two oxygen atoms, and two zinc atoms are bridged by the acetate ion, forming a stable octahedral structure.

[0010] Secondly, the present invention provides a method for preparing novel chiral Schiff base zinc(II) binuclear complexes, the synthesis method of which is as follows:

[0011]

[0012] The synthesis steps include the following:

[0013] Step 1, Preparation of chiral Schiff base ligands: Salicylic aldehyde (977 mg, 837 μL) was added to a 50 mL round-bottom flask, and 20 mL of ethanol was added and stirred at room temperature. The solution was clear and transparent. Then, (1R,2R)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL) / (1S,2S)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL) were added. The solution immediately turned brown, and after 4 hours of reaction, the solution remained brown. After standing at -10℃ for one week, a large amount of yellow solid precipitated from the solution. The solid was filtered and washed with ethanol.

[0014] Step 2, Preparation of chiral Schiff base zinc(II) complex: Zn(OAc)₂·2H₂O (65.8 mg) and R,RI (32.2 mg) / S,SI (32.2 mg) were added to a 50 mL flask. At room temperature, 25 mL of ethanol was added and stirred for 3 min, resulting in a pale yellow solution. The solution was then heated under reflux at 70 °C with stirring for 24 h. After cooling to room temperature, the resulting solution was filtered, and after standing at room temperature for one week, needle-like, light white crystals were obtained.

[0015] In step 1 above, the molar ratio of salicylaldehyde to (1R,2R)-(-)-1,2-cyclohexanediamine is 2:1, and the molar ratio of salicylaldehyde to (1S,2S)-(-)-1,2-cyclohexanediamine is 2:1.

[0016] In step 2 above, the molar ratio of Zn(OAc)2·2H2O to R and RI is 3:1, and the molar ratio of Zn(OAc)2·2H2O to S and SI is 3:1.

[0017] Thirdly, the present invention provides a chiral Schiff base zinc(II) binuclear complex organic electroluminescent device, wherein the light-emitting layer is doped with the chiral Schiff base zinc(II) binuclear complex provided by the present invention, the structural formula of which is shown below:

[0018]

[0019] The organic electroluminescent device provided by this invention has good white light emission performance, such as luminous efficiency and brightness.

[0020] Beneficial effects of the present invention

[0021] (1) This invention provides a novel organic electroluminescent circularly polarized light-emitting material—a chiral Schiff base zinc(II) binuclear complex, which achieves color change in the visible light region as the substituent of the chiral Schiff base ligand changes; it is a type of organic circularly polarized photoluminescent / electroluminescent material that can be applied to organic electroluminescent circularly polarized white light devices using a color compensation strategy, and has the advantages of simple preparation method, high yield, excellent photophysical properties, circular polarization activity and low cost.

[0022] (2) The chiral Schiff base zinc(II) binuclear complexes provided by this invention introduce chirality through chiral Schiff base ligands, giving them a more sensitive molecular structure design. In the chiral Schiff base zinc(II) complexes provided by this invention, circularly polarized (CPL) signals can be generated due to chiral injection; compared to non-chiral Schiff base zinc(II) complexes, chiral Schiff base zinc(II) complexes possess circular polarization activity. Therefore, the circularly polarized luminescence of chiral Schiff base Zn(II)-complexes can inevitably be utilized to realize CP-WOLEDs that cater to 3D displays.

[0023] (3) The organic electro-polarized white light device provided by the present invention has a low start-up voltage and good circularly polarized white light emission performance.

[0024] A novel chiral Schiff base zinc(II) binuclear complex organic circularly polarized luminescent material is disclosed, specifically relating to a novel chiral Schiff base zinc(II) binuclear complex constructed based on a chiral Schiff base ligand, which exhibits visible light color variation with changes in the substituents of the chiral Schiff base ligand. This is a pioneering organic circularly polarized photoluminescent / electroluminescent material that can be applied to organic electro-polarized white light devices using a color compensation strategy. This invention provides a chiral Schiff base zinc(II) binuclear complex, its preparation method, and its application in organic electro-polarized white light devices (CP-WOLED). At room temperature, the chiral Schiff base zinc(II) binuclear complex (Example 1) exhibits blue light emission in CH2Cl2 solution, with maximum emission peaks at 462 nm and 461 nm, and displays a strong ground-state chiral signal and Cotton effect, with an asymmetry factor |g PL |~10 -4 Using this blue chiral Schiff base zinc(II) binuclear complex as the dopant guest material, and through color compensation with blue light as the primary color, an organic electro-polarized white light-emitting device was developed, achieving good luminescent performance, such as a low start-up voltage (V). on =6.5V), high electroluminescence efficiency (maximum current efficiency of 0.63 cd / A, maximum power efficiency of 0.44 lm / W and maximum external quantum efficiency of 0.67%) and good electroluminescent circularly polarized white light (CIE: x = 0.35-0.38, y = 0.32-0.36; asymmetry factor |g EL |~10 -4 )wait. Attached Figure Description

[0025] Figure 1 The 1H NMR spectra of the chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) are shown.

[0026] Figure 2 X-ray single-crystal structures of chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1)(left) and (2)(right).

[0027] Figure 3 For chiral ligands R, RI / S, SI and chiral Schiff base zinc(II) binuclear complexes [Zn2(R, RL / S, SL)(μ1-OAc)(μ2-OAc)] (1) and (2) at 10 -5 The ultraviolet-visible absorption spectrum of M dichloromethane solution.

[0028] Figure 4The chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) at room temperature at 10 -5 Fluorescence emission spectrum of M dichloromethane solution.

[0029] Figure 5 The chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) at room temperature at 10 -5 Circular dichroism spectroscopy in M ​​dichloromethane solution.

[0030] Figure 6 Schematic diagram of the structure of electroluminescent devices for chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)](1) and (2).

[0031] Figure 7 Electroluminescence spectra of chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2).

[0032] Appendix Explanation

[0033] Table 1 shows the crystal data and structural refinement of the chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2);

[0034] Table 2 shows the main bond lengths of the chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)](1) and (2). Bond angle (°). Detailed Implementation

[0035] The following specific examples will further illustrate the technical solution of this invention to provide a more comprehensive understanding of the content of this patent.

[0036] Example 1: This example provides a novel chiral Schiff base zinc(II) binuclear complex [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) based on H-atom substituted chiral Schiff base ligands, with the following structural formulas:

[0037]

[0038] The preparation steps of the above-mentioned chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) are as follows:

[0039] Step 1, Synthesis of chiral Schiff base ligands R,R / S,S-H2Salen:

[0040] Salicylic aldehyde (977 mg, 837 μL, 8 mmol) was added to a 50 mL round-bottom flask, followed by stirring with 20 mL of ethanol at room temperature. The solution was clear and transparent. Then, (1R,2R)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL, n = 4 mmol) was added. The solution immediately turned brown, and after 4 hours of reaction, the solution remained brown. After standing at -10°C for one week, a large amount of yellow solid precipitated from the solution. The solid was filtered and washed with ethanol.

[0041] Step 2, synthesis of chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2):

[0042] Add Zn(OAc)2·2H2O (65.8 mg, 0.3 mmol) and R,R-H2Salen / S,S-H2Salen (32.2 mg, 0.1 mmol) to a 50 mL flask. Add 25 mL of ethanol at room temperature and stir for 3 min; the solution turns pale yellow. Then heat the solution under reflux at 70 °C for 24 h with stirring. After cooling to room temperature, filter the resulting solution and allow it to stand at room temperature for one week to obtain needle-like, light white crystals. The target complex (1) is then subjected to 1H NMR spectroscopy, as shown... Figure 1 As shown, the analysis results are: [Zn2(R,RL)(μ1-OAc)(μ2-OAc)](1): 1 H NMR (400MHz, DMSO-d6): δ(ppm)8.32(2H,s,-CH=N),7.21(2H,d,Ph),7.12(2H,t,-Ph),6.60(2H,d,-Ph),6.42(2H,t,-Ph),3.19(2H,d,-Ch),2.46(6H,d,-CH3 of OAc),1.91(2H,s,-Ch),1.80(6H,s,-Ch).[Zn2(S,SL)(μ1-OAc)(μ2-OAc)](2): 1H NMR (400MHz, DMSO-d6): δ(ppm)8.33(2H,s,-CH=N),7.21(2H,d,Ph),7.14(2H,t,-Ph),6.62(2H,d,-Ph),6.42(2H,t,-Ph),3.20(2H,d,-Ch),2.46(6H,d,-CH3 of OAc),1.91(2H,s,-Ch),1.80(6H,s,-Ch).

[0043] like Figure 4 As shown, at room temperature, the novel chiral Schiff base zinc(II) binuclear complexes (1) and (2)(10) -5 In CH2Cl2 solution, under excitation conditions of 394 nm, the maximum emission peaks of the emission spectrum are at 462 nm and 461 nm. Using this blue chiral Schiff base zinc(II) binuclear complex as a dopant material, an organic electro-polarized white light emitting device was developed through color compensation with its blue light as the primary color.

[0044] like Figure 5 As shown, at room temperature, the novel chiral Schiff base zinc(II) binuclear complexes (1) and (2)(10) -5 In CH2Cl2 solution, the chiral Schiff base zinc(II) binuclear complexes (1) and (2) exhibit strong Cotton peaks at (-)290, (+)335, (-)370 and (+)294, (-)335, (+)370, respectively. These two sets of peaks are almost completely symmetrical about the X-axis, indicating that the chiral characteristics of the chiral Schiff base ligand are perfectly preserved in the chiral Schiff base zinc(II) binuclear complexes (1) and (2). Furthermore, the circularly polarized spectra show an asymmetry factor |g PL |~10 -4 This provides a source of chirality for the subsequent development of CP-WOLED.

[0045] Example 2

[0046] In this embodiment, the chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) provided in Example 1 above are used as doped guest materials for the emitting layer to prepare an organic electroluminescent circularly polarized light-emitting device, such as... Figure 5 As shown, the structure of this organic electroluminescent circularly polarized light-emitting device includes a transparent anode material, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode material.

[0047] The fabrication process of this organic electroluminescent circularly polarized light-emitting device includes:

[0048] When the pressure is less than 10 -4Under Torr conditions, a 5 nm thick MoO3 layer was successively deposited on a pre-cleaned ITO glass substrate as a hole injection layer, a 40 nm thick TAPC layer as a hole transport layer, a 20 nm thick mCP layer doped with 5 wt% of the chiral Schiff base zinc(II) binuclear complexes [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) prepared in Example 1 as a light-emitting layer, a 40 nm thick TPBi layer as an electron transport layer, a 1 nm thick LiF layer as an electron injection layer, and a 100 nm thick metallic Al layer as a cathode material. The specific structure of the device is as follows: ITO / MoO3 (5 nm) / TAPC (40 nm) / mCP:5 wt% Zn-Complex I-II (20 nm) / TPBi (40 nm) / LiF (1 nm) / Al (100 nm).

[0049] The EL spectrum of the device was measured vertically using a spectrometer (Ocean Optics USB 2000). Current-luminance-voltage (JVL) characteristics were measured using a single-chamber ten-source resistive evaporation apparatus (ZD-400) and an FPD (Fiber Optic Properties Automated Measurement System) (FS-1000IVL). The electroluminescence spectrum showed a maximum emission peak at 468 nm, originating from the chiral Zn(II)-complex I-II; an electroluminescence spectrum was present at 592 nm, presumably due to the excimer complex. The maximum current efficiency of the CP-OLED-I device was 0.63 cd / A, the maximum power efficiency was 0.44 lm / W, and the maximum external quantum efficiency was 0.67%. The maximum current efficiency of the CP-OLED-II device was 0.63 cd / A, the maximum power efficiency was 0.23 lm / W, and the maximum external quantum efficiency was 0.39%. As the voltage increases, the CIE coordinates of CP-OLED-I and CP-OLED-II gradually shift from the green-blue light region to the white light region. When the voltage is greater than 14.5V, the CIE coordinates of CP-OLED-I and CP-OLED-II are located in the white light region (x = 0.35-0.38, y = 0.32-0.36), and the asymmetry factor |g EL |~10 -4 By using the blue light as the primary color of the chiral schifffuran zinc(II) binuclear complex, the application of organic electro-polarized white light devices was realized.

[0050] The specific examples described above are merely preferred embodiments of the present invention. Therefore, any equivalent substitutions and improvements made under the technical support of the present invention should fall within the protection scope of the present invention.

[0051] Table 1 Crystal data and structural refinement of chiral zinc(II)-complexes I and II

[0052]

[0053]

[0054] Table 2. Main bond lengths of chiral Zn(II) complexes I and II Bond angle (°)

[0055]

[0056]

Claims

1. A chiral Schiff base zinc(II) binuclear complex, characterized in that, It has the following general structural formula:

2. The chiral Schiff base zinc(II) binuclear complex according to claim 1, characterized in that, The general formula for its synthesis is as follows:

3. The method for preparing the chiral Schiff base zinc(II) binuclear complex according to claim 2, characterized in that, Includes the following steps: Step 1, Preparation of chiral Schiff base ligands: Add salicylaldehyde to a 50 mL round-bottom flask, add 20 mL of ethanol at room temperature and stir. The solution is clear and transparent. Then, continue to add (1R,2R)-(-)-1,2-cyclohexanediamine or (1S,2S)-(-)-1,2-cyclohexanediamine. The solution immediately turns brown. After reacting for 4 hours, the solution is brown. After standing at -10℃ for one week, a large amount of yellow solid precipitates from the solution. Filter to obtain the yellow solid and wash with ethanol. Step 2, Preparation of chiral Schiff base zinc(II) complex: Add Zn(OAc)2·2H2O and R,R-H2Salen or S,S-H2Salen to a 50mL flask. Add 25mL of ethanol at room temperature and stir for 3min. The solution is pale yellow. Then heat the solution at 70℃ under reflux and stir for 24h. After cooling to room temperature, filter the obtained solution. After standing at room temperature for one week, needle-like light white crystals are obtained.

4. The method for preparing the chiral Schiff base zinc(II) binuclear complex according to claim 3, characterized in that, In step 1, the molar ratio of salicylaldehyde to (1R,2R)-(-)-1,2-cyclohexanediamine is 2:1, and the molar ratio of salicylaldehyde to (1S,2S)-(-)-1,2-cyclohexanediamine is 2:

1.

5. The method for preparing the chiral Schiff base zinc(II) binuclear complex according to claim 3, characterized in that... In step 2, the molar ratio of Zn(OAc)2·2H2O to R,R-H2Salen is 3:1, and the molar ratio of Zn(OAc)2·2H2O to S,S-H2Salen is 3:

1.

6. The chiral Schiff base zinc(II) binuclear complex according to claim 1 is used as a chiral emitting layer material in an organic electro-polarized white light device.

7. A chiral Schiff base zinc(II) binuclear complex according to claim 1, characterized in that, This technology is applied to organic electroluminescent devices, where the emitting layer is doped with a chiral Schiff base zinc(II) binuclear complex, the structural formula of which is shown below:

Images