Chiral Schiff base zinc (II) binuclear complex, preparation method and application of organic electroluminescence circular polarization white light device (CP-WOLED)

Abstract

The invention discloses a chiral Schiff base zinc (II) binuclear complex, a preparation method and application of the chiral Schiff base zinc (II) binuclear complex. Light color change in a visible region is realized along with change of chiral Schiff base ligand substituent. The organic circularly polarized electroluminescent / electroluminescent material can be applied to an organic circularly polarized white light device by adopting a color compensation strategy. At room temperature, the chiral Schiff base zinc (II) binuclear complex shows blue light emission in a CH2Cl2 solution, the maximum emission peaks are located at 462 nm and 461 nm, and the chiral Schiff base zinc (II) binuclear complex shows a strong ground state chiral signal, a Cotton effect and an asymmetric factor gPL-10-4. The blue light chiral Schiff base zinc (II) binuclear complex is used as a doping guest material, and an organic electroluminescent circularly polarized white light emitting device is developed through color compensation with blue light as a primary color and has good light emitting performance.

Description

Technical Field

[0001] The invention relates to an organic luminescent material of a chiral Schiff base zinc (II) binuclear complex, in particular to a novel chiral Schiff base zinc (II) binuclear complex, a preparation method and an application of an organic electro-induced circularly polarized white light device (CP-WOLED), belonging to the field of organic photoelectric functional materials. Background Art

[0002] White organic light emitting diodes (WOLEDs) have the advantages of soft and uniform light emission, self-luminescence, and surface light sources, and are considered to be a new generation of lighting sources. The realization of white light depends on the emission of three primary colors or complementary colors. Efficient monochromatic light is the prerequisite for achieving high-level white light. Based on the intermolecular charge transfer exciplex, it is only necessary to select suitable donor and acceptor materials and utilize their intrinsically small Δ EST , triplet excitons can be utilized through the reverse intersystem crossing (RISC) process, and theoretically 100% internal quantum efficiency can be achieved. Moreover, the wide-band luminescence of the exciplex itself is conducive to improving the light color quality of WOLED. However, the current all-exciplex WOLED still has problems such as complex structure and low efficiency.

[0003] At present, the realization of white light OLED is dual emission of complementary colors or triple emission of three primary colors, which inevitably uses a large amount of luminescent materials and is costly. However, the use of luminescence from exciplexes can reduce the use of luminescent materials, and the efficiency of the device is better than that of ordinary fluorescent WOLED, which is a new idea for reducing the cost of WOLED. In addition, the wide spectrum emission of exciplexes is more conducive to the realization of WOLED with a high color rendering index.

[0004] Therefore, this patent is based on the research and development of monochromatic and white light OLEDs based on the emission of all-exciton complexes. By selecting efficient monochromatic light exciton complexes, adopting complementary color strategies, regulating the exciton recombination area, balancing carrier injection, and rationally designing the device structure, it aims to prepare WOLEDs with high efficiency, high brightness, and high color quality. Two chiral Schiff base zinc (II) complexes are synthesized through self-assembly reactions, and the CP-WOLED device of organic electro-induced circularly polarized white light is further realized. Summary of the invention

[0005] Technical problem: The purpose of the present invention is to provide a new type of binuclear complex of chiral Schiff base zinc (II) configuration, which improves the performance of zinc (II) complex by chelating zinc atom with chiral Schiff base and providing coordination environment with acetate group, so that the material has good emission wavelength and excellent luminescence performance. In addition, the present invention provides a preparation method of chiral Schiff base zinc (II) complex, and the application of this blue light material in organic electroluminescent white light emitting device.

[0006] Technical solution: In the first aspect, the present invention provides a novel chiral Schiff base zinc (II) binuclear complex, characterized in that metal zinc is used as the luminescent center, and is formed by chelating the acetate provided by the chiral Schiff base ligand and zinc acetate with metal zinc, and has the following general structural formula 1:

[0007]

[0008] Among them, 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 increase the LUMO energy level of the material and blue-shift its luminescent wavelength, and is beneficial to reduce the HOMO energy level of the material and blue-shift its luminescent wavelength.

[0009] An acetate ion is coordinated by two oxygen atoms on it, and two zinc atoms are bridged by acetate to form a stable octahedral structure.

[0010] In a second aspect, the present invention provides a method for preparing a novel chiral Schiff base zinc (II) binuclear complex, and the synthesis method thereof is as follows:

[0011]

[0012] The synthesis steps include:

[0013] Step 1, preparation of chiral Schiff base ligand: Add salicylaldehyde (977 mg, 837 μL) to a 50 mL round-bottom flask, add 20 mL of ethanol and stir at room temperature, the solution is clear and transparent. Then, continue to add (1R, 2R)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL) / (1S, 2S)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL), the solution immediately turns brown, and after 4 hours of reaction, the solution is brown. After the reacted solution is left to stand at -10 ° C for one week, a large amount of yellow solid precipitates from the solution. Filter to obtain a yellow solid and wash with ethanol.

[0014] Step 2, preparation of chiral Schiff base zinc (II) complex: Add Zn(OAc)2·2H2O (65.8 mg) and R,RI (32.2 mg) / S,SI (32.2 mg) to a 50 mL flask. Add 25 mL of ethanol and stir for 3 min at room temperature, and the solution turns light yellow. Then heat the solution under reflux at 70 ° C and stir for 24 h. After cooling to room temperature, filter the resulting solution, and after standing at room temperature for one week, obtain needle-shaped light white crystals.

[0015] In the above 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.

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

[0017] In a third aspect, 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, and its structural formula is as follows:

[0018]

[0019] The organic electroluminescent device provided by the present invention has good white light emitting performance, such as luminous efficiency, brightness and the like.

[0020] Beneficial effects of the present invention

[0021] (1) The present invention provides a novel organic electro-induced circularly polarized luminescent material, a chiral Schiff base zinc (II) binuclear complex, which realizes the change of light color in the visible light region with the change of the chiral Schiff base ligand substituent. It is a type of organic circularly polarized photoluminescent / electroluminescent material that can be applied to organic electro-induced circularly polarized white light devices using a color compensation strategy, and has the advantages of simple preparation method, high yield, excellent photophysical properties, circularly polarized activity and low cost.

[0022] (2) The chiral Schiff base zinc (II) binuclear complex provided by the present invention introduces chirality through the chiral Schiff base ligand, giving it a more sensitive molecular structure design. In the chiral Schiff base binuclear zinc (II) complex provided by the present invention, a circular polarization (CPL) signal can be generated due to chiral injection; compared with the achiral Schiff base zinc (II) complex, the chiral Schiff base zinc (II) complex has circular polarization activity. Therefore, the circularly polarized luminescence of the chiral Schiff base Zn (II)-complex is bound to be able to be utilized to realize CP-WOLED that caters to 3D display.

[0023] (3) The organic electro-induced circularly polarized white light device provided by the present invention has a lower starting voltage and better circularly polarized white light emitting performance.

[0024] A chiral Schiff base zinc (II) binuclear complex organic circularly polarized luminescent material, specifically a novel chiral Schiff base zinc (II) binuclear complex constructed based on a chiral Schiff base ligand, and the light color changes in the visible light region with the change of the chiral Schiff base ligand substituent; it is a first-of-its-kind organic circularly polarized photoluminescent / electroluminescent material that can be applied to organic electro-circularly polarized white light devices using a color compensation strategy. The present invention provides a chiral Schiff base zinc (II) binuclear complex, a preparation method and its application in organic electro-circularly polarized white light devices (CP-WOLED). At room temperature, the chiral Schiff base zinc (II) binuclear complex (Example 1) exhibits blue light emission in a CH2Cl2 solution, with maximum emission peaks at 462nm and 461nm, and exhibits a strong ground state chiral signal and Cotton effect, and an asymmetry factor |g PL |~10 -4 The blue light-emitting chiral Schiff base zinc (II) binuclear complex was used as a doping guest material, and an organic electro-induced circularly polarized white light emitting device was developed through color compensation with blue light as the primary color, which achieved good luminescence performance, such as a lower starting voltage (V on =6.5V), high electroluminescent efficiency (maximum current efficiency of 0.63cd / A, maximum power efficiency of 0.44lm / W and maximum external quantum efficiency of 0.67%) and good electro-circularly polarized white light (CIE: x = 0.35-0.38, y = 0.32-0.36; asymmetry factor |g EL |~10 -4 )wait. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0030] Figure 6 Schematic diagram of the structure of the electroluminescent devices of chiral Schiff base zinc (II) binuclear complex [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 Description

[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) and bond angles (°). DETAILED DESCRIPTION

[0035] The technical solution of this solution will be further explained below through specific examples so as to more fully understand the content of the patent of this invention.

[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 a chiral Schiff base ligand substituted with an H atom, and its structural formula is as follows:

[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 Ligand R,R / S,S-H2Salen:

[0040] Add salicylaldehyde (977 mg, 837 μL, 8 mmol) to a 50 mL round-bottom flask, add 20 mL of ethanol and stir at room temperature, the solution is clear and transparent. Then, continue to add (1R, 2R)-(-)-1,2-cyclohexanediamine (0.456 g, 500 μL, n = 4 mmol), the solution immediately turns brown, and after 4 hours of reaction, the solution is brown. After the solution after the reaction is left to stand at -10 ° C for one week, a large amount of yellow solid precipitates from the solution. Filter to obtain a yellow solid and wash 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. At room temperature, add 25 mL of ethanol and stir for 3 min. The solution turns light yellow. Then heat the solution under reflux at 70 °C and stir for 24 h. After cooling to room temperature, filter the resulting solution and let it stand at room temperature for one week to obtain needle-shaped light white crystals. The target complex (1) was subjected to H NMR spectrum test. 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 new chiral Schiff base zinc (II) binuclear complexes (1) and (2) (10 -5 M) In CH2Cl2 solution, under the excitation condition of 394nm, the maximum emission peaks of the emission spectrum are at 462nm and 461nm. The blue light chiral Schiff base zinc (II) binuclear complex is used as a doping guest material, and an organic electro-induced circularly polarized white light emitting device is developed through color compensation with its blue light as the primary color.

[0044] like Figure 5 As shown, at room temperature, the new chiral Schiff base zinc (II) binuclear complexes (1) and (2) (10 -5 M) In CH2Cl2 solution, the chiral Schiff base zinc (II) binuclear complexes (1) and (2) have strong Cotton peaks at (-)290, (+)335, (-)370 and (+)294, (-)335, (+)370, respectively. These two groups 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). The circular polarization spectra show that the asymmetry factor |g PL |~10 -4 , providing a chiral source for the subsequent development of CP-WOLED.

[0045] Example 2

[0046] In this embodiment, the chiral Schiff base zinc (II) binuclear complex [Zn2(R,RL / S,SL)(μ1-OAc)(μ2-OAc)] (1) and (2) provided in the above embodiment 1 are used as the doping guest material of the light-emitting layer to prepare an organic electro-induced circularly polarized light-emitting device, such as Figure 5 As shown, the structure of the organic electro-induced 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 preparation process of the organic electro-induced circular polarization light emitting device comprises:

[0048] At pressure less than 10 -4Torr, 5 nm thick MoO3 was deposited as a hole injection layer, 40 nm TAPC was deposited as a hole transport layer, 20 nm mCP doped with 5 wt% chiral Schiff base zinc (II) binuclear complex [Zn2 (R, RL / S, SL) (μ1-OAc) (μ2-OAc)] (1) and (2) prepared in Example 1 was deposited as a light-emitting layer, 40 nm TPBi was deposited as an electron transport layer, 1 nm LiF was deposited as an electron injection layer, and 100 nm metal Al was deposited as a cathode material on a pre-cleaned ITO glass substrate. 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 in the vertical direction by a spectral detector (Ocean Optics USB 2000), and the current-luminance-voltage (JVL) characteristics were measured using a single-chamber ten-source resistive evaporation device (ZD-400) and an FPD optical property automatic measurement system (FS-1000IVL). The maximum emission peak of the electroluminescence spectrum is located at 468nm, which originates from the chiral Zn(II)-complex I-II; the 592nm electroluminescence spectrum exists, which is speculated to be caused by the exciplex. The maximum current efficiency of the CP-OLED-I device is 0.63cd / A, the maximum power efficiency is 0.44lm / W and the maximum external quantum efficiency is 0.67%; the maximum current efficiency of the CP-OLED-II device is 0.63cd / A, the maximum power efficiency is 0.23lm / W and the maximum external quantum efficiency is 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 14.5 V, 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 The application of organic electro-induced circularly polarized white light devices was realized through color compensation of blue light as the primary color of chiral zinc(II) schifrolidine binuclear complex.

[0050] The contents included in the above specific examples are only preferred implementation modes of the present invention. Therefore, equivalent replacements and several improvements made with the technical support of the present invention should all fall within the protection scope of the present invention.

[0051] Table 1 Crystal data and structure 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 and bond angle (°)

[0055]

[0056]

Claims

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

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

3. The method for preparing a chiral Schiff base zinc (II) binuclear complex according to claim 2, characterized in that: The following steps are involved: Step 1, preparation of chiral Schiff base ligand: salicylaldehyde (977 mg, 837 μL) was added to a 50 mL round-bottom flask, 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) was added, the solution immediately turned brown, after reacting for 4 hours, the solution was brown, the solution after the reaction was allowed to stand at -10°C for one week, a large amount of yellow solid precipitated from the solution, filtered to obtain a yellow solid, and washed with ethanol; Step 2, preparation of chiral Schiff base zinc (II) complex: Zn (OAc) 2 · 2H 2 O (65.8 mg) and R, R-H 2 Salen (32.2 mg) / S, S-H 2 Salen (32.2 mg) were added to a 50 mL flask, 25 mL of ethanol was added and stirred for 3 min at room temperature, the solution turned light yellow, and then the solution was heated to reflux and stirred at 70 ° C for 24 h. After cooling to room temperature, the obtained solution was filtered and allowed to stand at room temperature for one week to obtain needle-shaped light white crystals.

4. The method for preparing a chiral Schiff base zinc (II) binuclear complex according to claim 3, characterized in that: In the 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 a chiral Schiff base zinc (II) binuclear complex according to claim 3, characterized in that In the 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. A chiral Schiff base zinc (II) binuclear complex according to claim 1 used as a chiral light-emitting layer material of an organic electro-induced circularly polarized white light device.

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

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