Chiral dinuclear zn(ii)-complexes based on chiral salen-type schiff base ligands (r,r / s,s-l) and preparation method and electroluminescent applications

Abstract

A chiral dinuclear Zn(II)-complex based on chiral Salen-type Schiff base ligands (R, R / S, S-L) and its preparation method, along with its application in electro-induced circularly polarized luminescence, were presented. With changes in the configuration of the chiral Salen-type Schiff base ligands, this type of chiral dinuclear Zn(II)-complex exhibited different light colors in the visible region. At room temperature, the chiral dinuclear Zn(II)-complex developed based on chiral Salen-type Schiff base ligands introduced by the methoxy (-OMe) functional group showed maximum emission peaks of 467 and 462 nm in CH2Cl2 solution, with CIE coordinates of (0.156, 0.192) and (0.158, 0.190), respectively, located in the blue light emission region. It exhibited a strong ground-state chiral signal and Cotton effect, with an asymmetry factor |g PL |~10 ‑4 The electroluminescent devices CP-OLED-R,R-II and CP-OLED-S,S-II all have a start-up voltage of 6V. Their maximum emission wavelengths for electro-polarized emission are 488nm and 496nm, respectively, with CIE coordinates located in the blue light region at (0.288, 0.305) and (0.283, 0.304), respectively. The maximum current efficiency of CP-OLED-R,R-II is 0.90cd / A, the maximum power efficiency is 0.47lm / W, and the maximum external quantum efficiency is 0.43%. The maximum current efficiency of CP-OLED-S,S-II is 0.83cd / A, the maximum power efficiency is 0.40lm / W, and the maximum external quantum efficiency is 0.38%. The asymmetry factor |g EL |~10 ‑4 .

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic functional materials technology. It relates to a chiral metal-organic photo- / electro-polarized circularly polarized luminescent material, specifically a chiral dinuclear Zn(II)-complex [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] constructed based on chiral Salen-type Schiff base ligands (R,R / S,SL), its preparation method, and its application in an electro-polarized circularly polarized luminescent device. Background Technology

[0002] Early applications of chiral Salen-like Schiff base-Zn(II)-complexes primarily focused on chiral catalysis. However, the emergence and development of CD spectroscopy, especially CPL spectroscopy, spurred interest in the chiral photoelectronic properties of chiral Salen-like Schiff base-Zn(II)-complexes in both the ground and excited states. This is particularly evident in the recent surge in CPL-OLEDs (circularly polarized organic light-emitting diodes) for 3D displays. Consequently, relatively little research has been conducted on electroluminescent visible-light and even white-light circularly polarized organic light-emitting devices (CPL-OLEDs / CPL-WOLEDs) based on chiral-Zn(II)-complexes as the host light-emitting material. Tang et al. obtained chiral R,R / S,S-Salen-Zn(II)-monuclear complexes by reacting (1R,2R)-(-)-1,2-cyclohexanediamine or (1S,2S)-(+)-1,2-cyclohexanediamine with vanillin via an aldehyde-amine condensation reaction and further coordination self-assembly with Zn(OAc)2·2H2O. Their photo-induced circularly polarized luminescence properties showed that the photo-induced blue-green light exhibited an asymmetry factor (gPL) of 10 in THF solution. -3 Furthermore, through the design of a device structure of ITO / PEDOT:PSS / TAPC / R,R / S,S-Salen-Zn(II) / TPBi / Ca / Ag with chiral R,R / S,S-Salen-Zn(II)-formed separately, its electroluminescent CPL-OLED device was realized. Its shortcomings are: 1) Due to the light color interference of the TAPC and TPBi auxiliary layer materials, the blue-green light of R,R / S,S-Salen-Zn(II)-recombines into yellow light; 2) Electroluminescence performance: such as 1000 cd / m² 2 At this point, the current efficiency is only 0.181 cd / A, and the power efficiency is only 0.074 lm / W.

[0003] This invention introduces functional groups (-OMe, -OH, -OPr, etc.) onto chiral Salen-type Schiff bases (R, RL / S, SL), and further obtains chiral binuclear Zn(II)-complexes by using an excess of Zn(OAc)2·2H2O, and uses them as guest materials for CP-OLEDs devices. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a chiral binuclear Zn(II)-complex based on chiral Salen-type Schiff base ligands (R,R / S,SL), its preparation method, and its application in electro-induced circularly polarized luminescence. Two asymmetric Schiff bases, R,RI and S,SI, are synthesized by aldehyde-amine condensation reaction of salicylaldehyde with (1R,2R)-(-)-cyclohexanediamine or (1S,2S)-(-)-cyclohexanediamine, respectively. Subsequently, R,RI and S,SI are further coordinated with Zn(OAc)2·2H2O to self-assemble into Zn(II)-complexes [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(CH3OH)](R,R-II) and [Zn2(S,SL)(μ1-OAc)(μ2-OAc)(CH3OH)](S,S-II).

[0005] A [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type chiral Zn(II)-complex, characterized by a binuclear metal-zinc(II) as the luminescent center, formed by the chelation of a chiral Schiff base ligand with zinc metal, having the following general structural formula:

[0006]

[0007] Secondly, a method for preparing a chiral Zn(II)-complex with the configuration [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] is described below:

[0008]

[0009]

[0010] The synthesis steps include the following:

[0011] Step 1, Preparation of chiral Schiff base ligands: First, salicylaldehyde is weighed into a round-bottom flask, methanol is added to dissolve it and the mixture is stirred continuously. Then, (1R,2R)-(-)-1,2-cyclohexanediamine / (1S,2S)-(-)-1,2-cyclohexanediamine is added dropwise at room temperature and stirred at 70°C for 5 hours.

[0012] Step 2, Preparation of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type chiral Zn(II)-complex: Add the chiral Schiff base ligand prepared in Step 1 and Zn(OAc)2·2H2O to the flask, then add methanol and stir. Heat and reflux at 70℃ for 2.5 h, then add a small amount of DMF (volume ratio of 1:20 with the previously added methanol), and finally reflux and stir for 24 h to finish.

[0013] In step 1 above, the molar ratio of salicylaldehyde to cyclohexanediamine is 2:1.

[0014] In step 2 above, the molar ratio of the chiral Schiff base ligand to Zn(OAc)2·2H2O is 1:3.

[0015] Thirdly, the present invention provides an electro-polarized light-emitting device of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type blue Zn(II)-complexes, wherein the light-emitting layer is doped with two [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type blue Zn(II)-complexes (R,R-II and S,S-II) provided by the present invention, the structural formulas of which are shown below:

[0016]

[0017] Beneficial effects of the present invention

[0018] (1) This invention provides a novel chiral Schiff base dinuclear zinc(II) complex, and this type of chiral dinuclear Zn(II)-complex exhibits different light colors in the visible light region depending on the configuration of the chiral Salen-type Schiff base ligand. This type of material has the advantages of low cost, easy synthesis, excellent photophysical properties and circular polarization activity based on chiral Schiff base ligand modification.

[0019] (2) The organic electro-polarized light-emitting device prepared by the present invention has the advantages of low start-up voltage, high luminous efficiency and good environmental stability, and occupies an important position in the research field of organic electro-polarized light emission. Attached Figure Description

[0020] Figure 1 For the [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type chiral Zn(II)-complex (R,R-II) 1 HNMR spectrum;

[0021] Figure 2 For the [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type chiral Zn(II)-complex (S,S-II) 1HNMR spectrum;

[0022] Figure 3 X-ray single-crystal structure diagram of chiral Zn(II)-complexes (R,R-II and S,S-II) of type [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)];

[0023] Figure 4 Emission spectra of chiral Zn(II)-complexes (R,R-II and S,S-II) of the [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type in dichloromethane;

[0024] Figure 5 The absorption spectra of chiral Zn(II)-complexes (R,R-II and S,S-II) of the [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type in dichloromethane are shown.

[0025] Figure 6 Circular dichroism spectroscopy for chiral Zn(II)-complexes (R,R-II and S,S-II) of type [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] in dichloromethane;

[0026] Figure 7 A schematic diagram of the structure of an electroluminescent device for [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)]-type chiral Zn(II)-complexes (R,R-II and S,S-II);

[0027] Figure 8 Electroluminescence spectra of chiral Zn(II)-complexes (R,R-II and S,S-II) of the [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type;

[0028] Table 1 shows the crystal data and structural refinement of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)] type chiral Zn(II)-complexes (R,R-II and S,S-II);

[0029] Table 2 shows the main bond lengths of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)]-type chiral Zn(II)-complexes (R,R-II and S,S-II). Bond angle (°). Detailed Implementation

[0030] Example 1:

[0031] (1) Synthesis of chiral Schiff base ligands R, RI and S, SI containing R1=H and R2=CH3 substituents

[0032] First, 1.216 g (8 mmol) of 3-methoxysalicylaldehyde was weighed into a 50 mL round-bottom flask. 25 mL of methanol was added to dissolve it while stirring continuously. Next, (1R,2R)-(-)-1,2-cyclohexanediamine (0.456 g, 4 mmol) was added dropwise at room temperature. The solution rapidly changed from bright yellow to brown, and the color deepened with the addition of cyclohexanediamine. After all the reactants were added, the mixture was stirred at 70 °C for 5 h. After the reaction was complete, the solution was allowed to stand at low temperature for one week, resulting in the precipitation of a large amount of yellow solid. The solid was filtered and washed with a small amount of methanol to obtain 1.10 g of yellow needle-like solid. Yield: 65.79%. Fourier transform infrared absorption spectrum, FT-IR (KBr, cm⁻¹). -1 ):3450(m),2927(w),2858(w),2355(w),1622(s),1463(s),1369(w),13 44(w),1273(m),1249(vs),1207(m),1188(s),1168(w),1138(w),1085(m ),1043(w),968(s),933(m),854(m),837(m),800(w),783(s),742(s),64 6(w),580(m),563(w),551(w),532(w),518(w),491(w),443(w),420(w). 1 H NMR (CDCl3, 400MHz): δ (ppm) 13.88 (s, 2H, -OH), 8.26 (s, 2H, -HC=N), 6.87 (m, 2H, -Ph), 6.80 (m, 2H, -Ph), 6. 74(t,2H,-Ph),3.88(s,6H,-OCH3),3.33(m,2H,-Ch),1.91(m,4H,-Ch),1.73(m,2H,-Ch),1.49(t,2H,-Ch).

[0033] The synthesis of chiral ligands S and SI is similar to that of R and RI, except that (1R,2R)-(-)-1,2-cyclohexanediamine is replaced with (1S,2S)-(-)-1,2-cyclohexanediamine; all other conditions are the same. Yield: 65.79%. Fourier transform infrared absorption spectrum: FT-IR (KBr, cm⁻¹). -1):3452(m),2926(w),2854(w),2358(w),1622(w),1463(s),1371(w),13 44(w),1273(m),1249(vs),1207(m),1188(w),1168(w),1138(w),1085(m ),1043(w),968(s),933(m),854(m),839(m),800(w),783(s),742(s),64 8(w),580(w),563(w),553(w),530(w),518(w),491(w),443(w),418(w). 1 H NMR (CDCl3, 400MHz): δ (ppm) 13.88 (2H, s, -OH), 8.25 (2H, m, -CH = N), 6.87 (2H, m, -Ph), 6.80 (2H, m, -Ph), 6. 75(2H,t,-Ph),3.87(6H,s,-OCH3),3.34(2H,m,-Ch),1.90(2H,m,-Ch),1.74(2H,m,-Ch),1.46(2H,t,-Ch).

[0034]

[0035] (2) Synthesis of chiral Zn(II)-complexes R,R-II and S,S-II

[0036] Chiral Zn(II)-complex R,R-II: R,RI (38.2 mg, 0.1 mmol) and Zn(OAc)₂·2H₂O (65.8 mg, 0.3 mmol) were added to a flask, followed by the addition of 10 mL of methanol. The mixture did not completely dissolve, resulting in a pale bright yellow solution. Upon reflux and stirring at 70 °C, the Schiff base gradually dissolved completely, and the solution remained pale yellow. After reflux for 2.5 h, 0.5 mL of DMF was added, and the solution remained yellow. After heating and stirring for 14 h, the solution turned orange. Crystals were cultured by allowing the solvent to evaporate naturally at room temperature. After standing for one week, bright yellow granular crystals were produced. Yellow granular crystals: 0.416 g, yield: 78.78%. Fourier transform infrared absorption spectrum: FT-IR (KBr, cm⁻¹). -1):3321(w),3057(w),2928(w),2859(w),1630(s),1570(s),1438(s),1415( s),1394(s),1351(w),1304(m),1284(m),1242(s),1217(s),1174(w),1106 (w),1082(s),1047(m),1014(m),968(s),918(w),879(w),853(m),782(w), 744(vs),662(s),618(s),586(m),552(s),510(m),469(m),441(s),413(s). 1 HNMR (400MHz, DMSO-d6): δ(ppm)8.33(2H,s,-CH=N),6.80(4H,m,-Ph),6.38(2H,m,-Ph),4.12(1H,- OH),3.71(6H,s,-OCH3),3.21(2H,m,-Ch),3.17(3H,d,-CH3),2.45(6H,d,-OAc),1.80(8H,d,-Ch).

[0037] Chiral Zn(II)-complexes S,S-II: The synthesis method of chiral Zn(II)-complexes S,S-II is similar to that of chiral Zn(II)-complexes R,R-II, except that the chiral ligands R,RI are replaced with S,SI. Yellow granular crystals: 0.428 g, yield: 81.06%. Fourier transform infrared absorption spectrum: FT-IR (KBr, cm⁻¹) -1 ):3321(w),3057(w),2928(w),2859(w),1630(s),1570(s),1438(s),1415( s),1394(s),1351(w),1304(m),1284(m),1242(s),1217(s),1174(w),1106 (w),1082(s),1047(m),1014(m),968(s),918(w),879(w),853(m),782(w), 744(vs),662(s),618(s),586(m),552(s),510(m),469(m),441(s),413(s). 1H NMR (400MHz, DMSO-d6): δ(ppm)8.33(2H,s,-CH=N),6.82(4H,m,-Ph),6.43(2H,m,-Ph),4.12(1H,m, -OH),3.72(6H,s,-OCH3),3.23(2H,s,-Ch),3.17(3H,d,-CH3),2.47(6H,d,-OAc),1.80(8H,d,-Ch).

[0038]

[0039] (3) Photophysical properties analysis of chiral Zn(II)-complexes R,R-II and S,S-II

[0040] At room temperature, chiral Zn(II)-complexes R,R-II and S,S-II at 10 -5 The UV absorption peaks in the M dichloromethane solution were 235, 277, 359 nm and 235, 278, 356 nm, respectively, with maximum emission peaks at 467 and 462 nm, corresponding to CIE coordinates of (0.156, 0.192) and (0.158, 0.190), respectively, located in the blue light emission region. Circular dichroism chromatograms showed that at 10... -5 In M dichloromethane solution, R,R-II and S,S-II all exhibited strong ground-state chiral signals, with multiple Cotton peaks on both sides of the x-axis and the curves being mirror-symmetric about the x-axis: the Cotton peaks of chiral Zn(II)-complexes R,R-II were (-)-296, (+)-342, and (-)-380 nm, respectively; the Cotton peaks of chiral Zn(II)-complexes S,S-II were (+)-295, (-)-343, and (+)-380 nm, respectively. Circular polarization spectroscopy revealed their asymmetry factor |g PL |~10 -4 .

[0041] (4) Fabrication of organic electro-polarized light-emitting devices

[0042] The chiral Zn(II)-complex obtained in step (2) was used as an electroluminescent material to fabricate an electroluminescent circularly polarized light-emitting device. The devices CP-OLEDs-R,R-II and CP-OLEDs-S,S-II were developed by vacuum evaporation. The device structure is ITO / MoO3 (5nm) / TAPC (40nm) / mCP:5wt%Zn-Complex R,R-II / S,S-II (20nm) / TPBI (40nm) / LiF (1nm) / Al (100nm). Indium tin oxide (ITO) sheet resistors with a resistance of 20 Ω were used as the anodes of the CP-OLEDs. Their surfaces were cleaned using deionized water, acetone, trichloroethylene, and isopropanol, and each sheet was ultrasonically treated. TAPC (4-[1-[4-[di(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline) was used for hole transport, and TPBI (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) was used as the electron transport layer. The maximum emission wavelengths of the CP-OLEDs-R,R-II and CP-OLEDs-S,S-II devices were located at 488 nm and 496 nm, respectively. When the driving voltage is 6V, devices CP-OLEDs-R,R-II and CP-OLEDs-S,S-II begin to light up. When the voltage reaches 17.5V, the luminous intensity of devices CP-OLEDs-R,R-II and CP-OLEDs-S,S-II reaches its maximum, at 99.81 cd / cm². 2 and 102.27 cd / cm 2 The CP-OLED-R,R-II device exhibits a maximum current efficiency of 0.90 cd / A, a maximum power efficiency of 0.47 lm / W, and a maximum external quantum efficiency of 0.43%; the CP-OLED-S,S-II device exhibits a maximum current efficiency of 0.83 cd / A, a maximum power efficiency of 0.40 lm / W, and a maximum external quantum efficiency of 0.38%, with an asymmetry factor |g EL |~10 -4 .

[0043] Table 1 shows the crystal data and structural refinement of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)]-type chiral Zn(II)-complexes (R,R-II and S,S-II).

[0044]

[0045] Table 2 shows the main bond lengths of [Zn2(R,R / S,SL)(μ1-OAc)(μ2-OAc)]-type chiral Zn(II)-complexes (R,R-II and S,S-II). Bond angle (°)

[0046]

Claims

1. A chiral binuclear Zn(II)-complex based on the [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(MeOH)] configuration, characterized in that, It has the following general structural formula: 。 2. A chiral binuclear Zn(II)-complex based on the [Zn2(S,SL)(μ1-OAc)(μ2-OAc)(MeOH)] configuration, characterized in that, It has the following general structural formula: 。 3. The method for preparing a chiral dinuclear Zn(II)-complex based on the [Zn2(R,R-L)(μ1-OAc)(μ2-OAc)(MeOH)] configuration according to claim 1, wherein the synthesis method is as follows: 。 4. The method for preparing a chiral dinuclear Zn(II)-complex based on the [Zn2(S,S-L)(μ1-OAc)(μ2-OAc)(MeOH)] configuration according to claim 2, wherein the synthesis method is as follows: 。 5. The method for synthesizing the chiral binuclear Zn(II)-coordination with the configuration [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(MeOH)] according to claim 3, characterized in that, The preparation method is as follows: First, a chiral Salen-type Schiff base ligand R,R-H2L was prepared by using ortho-substituted salicylaldehydes and chiral (1R,2R)-(-)-1,2-cyclohexanediamine. Then, the prepared chiral Salen-type Schiff base ligand R,R-H2L and Zn(OAc)2·2H2O were added to a flask, followed by the addition of methanol and stirring. The mixture was then heated under reflux at 70 °C for 2.5 h. After reflux, a small amount of DMF was added, and the mixture was finally refluxed and stirred for 24 h.

6. The method for preparing a chiral dinuclear Zn(II)-complex with the configuration [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(MeOH)] according to claim 5, characterized in that, In step 2, the molar ratio of the chiral Salen-type Schiff base ligand R,R-H2L and Zn(OAc)2·2H2O is 1:

3.

7. The method for synthesizing the chiral binuclear Zn(II)-coordination with the [Zn2(S,SL)(μ1-OAc)(μ2-OAc)(MeOH)] configuration according to claim 4, characterized in that, The preparation method is as follows: First, chiral Salen-type Schiff base ligands R,R-H2L were prepared by using ortho-substituted salicylaldehydes and chiral (1S,2S)-(-)-1,2-cyclohexanediamine. Then, the prepared chiral Salen-type Schiff base ligands R,R-H2L and Zn(OAc)2·2H2O were added to a flask, followed by the addition of methanol and stirring. The mixture was heated to reflux at 70 °C for 2.5 h, and then a small amount of DMF was added. Finally, the mixture was refluxed and stirred for 24 h.

8. An organic electroluminescent circularly polarized light-emitting device based on a chiral dinuclear Zn(II)-complex with the configuration [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(MeOH)], wherein the light-emitting layer uses the chiral dinuclear Zn(II)-complex (R,R-II) with the configuration [Zn2(R,RL)(μ1-OAc)(μ2-OAc)(MeOH)] as the guest material, the structure of which is shown below: 。 9. An organic electroluminescent circularly polarized light-emitting device based on a chiral dinuclear Zn(II)-complex with the configuration [Zn2(S,SL)(μ1-OAc)(μ2-OAc)(MeOH)], wherein the light-emitting layer uses a chiral dinuclear Zn(II)-complex (S,S-II) with the configuration [Zn2(S,SL)(μ1-OAc)(μ2-OAc)(MeOH)] as the guest material, the structure of which is shown below: 。

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