Carbazolyl-containing CN ring metal platinum (II) complex as well as preparation method and application thereof

Abstract

The invention relates to a carbazolyl-containing CN cyclometalated platinum (II) complex and a preparation method and application thereof.The platinum (II) complex is synergistically regulated and controlled by a bidentate ligand and two monodentate ligands, a carbazole group is introduced to a benzene ring of a main ligand phenylpyridine structure of a material, the hole injection and electron transmission performance of the platinum (II) complex can be obviously improved, and the hole injection performance and the electron transmission performance of the platinum (II) complex are improved; the efficiency of the electroluminescent device can be improved; meanwhile, alkynyl and pyridine derivatives are respectively introduced to two monodentate ligands, and the two monodentate ligands, namely alkynyl and pyridine, can reduce the molecular rigidity, so that the compound does not emit light or emits light weakly in a solution state, and is enhanced in light emission in an aggregation state; and the AIE (aggregation-induced emission means a special phenomenon that an emitter which does not emit or emits weakly in a dilute solution can emit highly in an aggregation state or a solid state) is ensured. The synthesized platinum (II) complex has good thermal stability, the synthesis method of the platinum (II) complex is simple and efficient, and the platinum (II) complex has wide application prospects in the field of organic electroluminescent materials.

Description

Technical Field

[0001] The invention relates to a carbazole-containing C^N cyclometallated platinum (II) complex and a preparation method and application thereof, and belongs to the technical field of electronic materials. Background Art

[0002] Organic Light Emitting Diode (OLED) is a new generation of display and lighting materials that is very popular at present. It has the advantages of ultra-thin, self-luminous, wide viewing angle, high brightness, foldable, low voltage drive and fast brightness adjustment. At present, OLED has been widely used in daily life, such as mobile phone screens, car displays and TVs that people use daily. OLED research is actually still in the development stage, and the research and development of luminescent materials is the key to affecting the performance of OLED devices. Therefore, it is of great significance to design and develop an efficient and stable luminescent material.

[0003] In organic light-emitting devices (OLEDs), conventional fluorescent molecules can only utilize about 25% of electroluminescent excitons to emit light, while phosphorescent organometallic complexes can fully utilize all electroluminescent excitons for emission, thereby improving the electroluminescent efficiency. Now some phosphorescent organometallic complexes, such as cyclometallic Ir(III) and platinum(II) complexes, have been successfully applied in chemical sensing, bioimaging and electroluminescence of OLEDs. Among them, platinum(II) complexes have an ordered aggregation form and good electron / hole transport ability, so metal platinum(II) complex phosphorescent materials have become an important component and future development direction of OLEDs. Therefore, platinum(II) complexes have become a phosphorescent material with great practical application value. Since the structure of C^N cyclometallic ligands has a great influence on the lowest energy emission excited state, adding electron donating / withdrawing groups at different positions of C^N ligands can increase / decrease the electron density of the metal center. The introduction of electron donating carbazole groups on the main ligand helps promote hole injection / transport. The presence of such groups can increase the highest occupied molecular orbital energy level and greatly improve the thermal stability or film durability of organic compounds. Therefore, platinum (II) complexes containing carbazole groups with good thermal stability and morphological stability are ideal materials for preparing OLED devices. The method of multi-site coordinated regulation of bidentate ligands and two monodentate ligands can increase the regulation space of the complex skeleton structure and limit the D 2d Deformation luminescence enhancement: It is easy to carry out diversified design, easy to control material properties, and can reasonably optimize its processability. The use of solution wet processing technology, such as spin coating, scraping coating and other low-cost and easy-to-operate processes, can well meet the preparation of efficient room temperature phosphorescent materials. Summary of the invention

[0004] The present invention provides a carbazolyl-containing C^N cyclometallated platinum (II) complex and its preparation method and application. The carbazolyl-containing cyclometallated platinum (II) complex designed by the present invention has excellent luminescence performance and thermal stability, and can be used as a luminescent material in organic electroluminescent devices.

[0005] The technical solution adopted by the present invention is: a platinum (II) complex containing a carbazolyl C^N ligand and two monodentate auxiliary ligands, which is formed by a C^N type cyclometal ligand synthesized from 4-(9-carbazolyl)phenylboronic acid and 2-bromopyridine and two monodentate ligands complexing platinum (II) ions, and its structure is as follows:

[0006] The aryl boronic acid compound is selected from 4-(9-carbazolyl)phenylboronic acid.

[0007] The nitrogen heteroaromatic ring compound is selected from 2-bromopyridine.

[0008] The monodentate ligand "square" structure is selected from pyridine, 2-fluoropyridine, 2-chloropyridine, 3-chloropyridine, 4-bromopyridine, 4-methylpyridine, and 2-chloro-3-trifluoromethylpyridine.

[0009] The monodentate ligand "circular" structure is selected from -Cl, 1-ethynyl-3-fluorobenzene, 2-fluorophenylacetylene, 1-chloro-2-ethynylbenzene, 3-chloro-1-ethynylbenzene, 4-ethynylaniline, 4-fluorophenylacetylene, 4-ethynylbiphenyl, 2-ethynylthiophene, 4-ethynyltriphenylamine, and 9-(4-ethynylphenyl)carbazole.

[0010] (1) Synthesis of carbazolyl C^N ligands: 1.0 mmol 2-bromopyridine, 2.0 mmol potassium carbonate, 0.015 mmol palladium acetate and 4-(9-carbazolyl)phenylboronic acid were added to a round-bottom flask in air, and then 12 ml of a 3:1 ethanol / water mixed solution was added. The mixture was stirred magnetically at 80 °C for 30 min. Suzuki cross-coupling reaction occurred in air. The reaction progress was tracked by thin layer chromatography. After the reaction was complete, 25 ml of saturated brine was added. The reaction product was extracted three times with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the product was separated by chromatography after rotary evaporation to obtain the target product. The analytically pure compound was obtained. The product structure was determined by 1 H NMR, 13 C NMR and mass spectrometry identification; (2) Synthesis of platinum (II) complex intermediates: Under nitrogen atmosphere, C^N ligand (2.58 mmol) and K2PtCl4 (2.36 mmol) were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL). The reaction mixture was heated to 85°C and stirred for 18 h. After cooling to room temperature, it was poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with a pyridine derivative (7.59 mmol) in CHCl3 (20 mL) at 45°C for 18 h. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography using dichloromethane and ethyl acetate (v / v, 5:1).

[0011] (3) Under nitrogen atmosphere, potassium hydroxide (2.0 eq) was added to a methanol solution (15 ml) containing an acetylene compound (2.0 eq). Pt1 (1.0 eq) was added to the mixture which was stirred at 70 °C for 1.0 h. The mixture was then stirred at 50 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into 100 mL of H2O and extracted several times with CH2Cl2. The mixed organic layers were dried and concentrated. The crude product was precipitated from hexane. The filtered precipitate was washed several times with methanol, n-hexane and ether to obtain the target product. The product structure was determined by 1 H NMR, 13 C NMR and mass spectrometry identification.

[0012] The platinum (II) complex is used as an electroluminescent material.

[0013] Pt1: The "circular" structure is selected from -Cl, and the "square" structure is selected from pyridine.

[0014] Pt2: The "circular" structure is selected from 9-(4-ethynylphenyl)carbazole, and the "square" structure is selected from pyridine.

[0015] Pt3: The "circular" structure is selected from 1-ethynyl-3-fluorobenzene, and the "square" structure is selected from pyridine.

[0016] Pt4: The "circular" structure is selected from 2-ethynylthiophene, and the "square" structure is selected from pyridine.

[0017] Pt5: The "circular" structure is selected from 4-ethynyltriphenylamine, and the "square" structure is selected from pyridine.

[0018] Pt6: The "circular" structure is selected from -Cl, and the "square" structure is selected from 2-fluoropyridine.

[0019] Pt7: The "round" structure is selected from 2-fluorophenylacetylene, and the "square" structure is selected from 2-fluoropyridine.

[0020] Pt8: The "circular" structure is selected from -Cl, and the "square" structure is selected from 4-bromopyridine.

[0021] Pt9: The "circular" structure is selected from 1-chloro-2-ethynylbenzene, and the "square" structure is selected from 4-bromopyridine.

[0022] Pt10: The "circular" structure is selected from 3-chloro-1-ethynylbenzene, and the "square" structure is selected from 4-bromopyridine.

[0023] Pt11: The "circular" structure is selected from 4-ethynylaniline, and the "square" structure is selected from 4-bromopyridine.

[0024] Pt12: The "circular" structure is selected from -Cl, and the "square" structure is selected from 4-trifluoromethylpyridine.

[0025] Pt13: The "circular" structure is selected from 4-fluorophenylacetylene, and the "square" structure is selected from 4-trifluoromethylpyridine.

[0026] Pt14: The "circular" structure is selected from 4-ethynylbiphenyl, and the "square" structure is selected from 4-trifluoromethylpyridine.

[0027] Beneficial effects of the present invention: This carbazole-based C^N ring metal platinum (II) complex can greatly increase the space for the structural design of the organic platinum (II) complex by using a carbazole-based C^N ligand and two monodentate ligands for coordinated deployment, that is, the properties of the organic platinum (II) complex can be more finely controlled, and it is easier to meet the special requirements of new application scenarios for materials. The introduction of a carbazole group on the benzene ring of the main ligand phenylpyridine structure of the material can not only improve the hole injection and electron transport properties of the platinum (II) complex, but also greatly improve the thermal stability or film durability of the organic compound. By changing the type and position of the two monodentate ligand substituents, the emission wavelength of the complex can be adjusted. Compared with tetradentate and tertiary ligands, the platinum (II) complex synthesized by the present invention is easier to synthesize and purify, has good solubility in common organic solvents, has good solution processing performance, can emit strong room temperature phosphorescence, and has good thermal stability, and has broad application prospects in the field of OLED materials. It is used as a guest luminescent material in an organic light-emitting device with good luminescent properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the TGA diagram of the platinum (II) complex Pt1 of the present invention, T g =242.30 ℃.

[0029] Figure 2 It is the UV-visible absorption diagram of the solution of the platinum (II) complex Pt1 of the present invention.

[0030] Figure 3 It is a photoluminescence image of the platinum (II) complex Pt1 of the present invention in a dichloromethane solution.

[0031] Figure 4 This is a photoluminescence image of the platinum (II) complex Pt1 of the present invention in a 1w% doped PMMA film.

[0032] Figure 5 It is the H NMR spectrum of the platinum (II) complex Pt1 of the present invention.

[0033] Figure 6 It is a JVL diagram of an OLED device using the platinum (II) complex Pt1 of the present invention as a light-emitting material.

[0034] Figure 7 It is a schematic diagram of the single crystal structure of the platinum (II) complex Pt1 of the present invention. DETAILED DESCRIPTION

[0035] The above technical scheme is to achieve the coupling of halogenated nitrogen heteroaromatic compounds with 4-(9-carbazolyl)phenylboronic acid in an air atmosphere through a palladium-catalyzed Suzuki cross-coupling reaction without an external ligand, to prepare a C^N type cyclometal ligand biaryl compound, and then the biaryl compound is used as a cyclometal ligand to react with K2PtCl4 to prepare a cyclometal ligand-yam complex. The C^N type cyclometal ligand biaryl compound is prepared by adding 2-bromopyridine, 4-(9-carbazolyl)phenylboronic acid, potassium carbonate, and palladium acetate in a molar ratio of 1:1.5:2.0:0.015 to 12 ml of a 3:1 ethanol / water mixed solution, stirring magnetically at 80 ° C for 30 min, adding saturated brine after the reaction is complete, extracting the reaction product with ethyl acetate, combining the organic phases, drying over anhydrous sodium sulfate, filtering, rotary evaporation, and using ethyl acetate and petroleum ether as eluents to obtain the target product by chromatography separation, thereby obtaining an analytically pure compound. After that, C^N ligand and K2PtCl4 were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL) under nitrogen atmosphere. The reaction mixture was heated to 85°C, stirred for 18 h, and after cooling to room temperature, poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with a pyridine derivative in CHCl3 for 18 h at 45 °C. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography with dichloromethane and ethyl acetate. 2 equivalents of potassium hydroxide were added to a methanol solution containing 2 equivalents of acetylene compound. 1 equivalent of Pt1 was added to the mixture stirred at 70 °C for 1.0 h. Then, the mixture was stirred at 50 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into 100 mL of H2O and extracted several times with CH2Cl2. The mixed organic layer was dried and concentrated. The crude product was precipitated from hexane. The filtered precipitate was washed several times with methanol, n-hexane and ether to obtain the target product.

[0036] Example 1 Synthesis of Platinum (II) Complex Pt1 Chemical formula: PtC 28 H 20 ClN3 Synthesis of ligands

[0037] 1.0 mmol 2-bromopyridine, 2.0 mmol potassium carbonate, 0.015 mmol palladium acetate and 4-(9-carbazolyl)phenylboronic acid were added to a round-bottom flask in air, and then 12 ml of a mixed solution of ethanol / water with a volume ratio of 3:1 was added. The mixture was stirred magnetically at 80 °C for 30 min. Suzuki cross-coupling reaction occurred in air. The reaction progress was tracked by thin layer chromatography. After the reaction was complete, 25 ml of saturated brine was added. The reaction product was extracted three times with ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the product was separated by chromatography after rotary evaporation to obtain the target product. An analytically pure compound was obtained. The product structure was confirmed by the method of the intermediate. 1 H NMR, 13 C NMR and mass spectrometry identification.

[0038] Synthesis of Platinum(II) Complexes

[0039] Under nitrogen atmosphere, C^N ligand (2.58 mmol) and K2PtCl4 (2.36 mmol) were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL). The reaction mixture was heated to 85 °C, stirred for 18 h, cooled to room temperature, and poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with pyridine (7.59 mmol) in CHCl3 (20 mL) for 18 h at 45 °C. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography with dichloromethane and ethyl acetate (v / v, 5:1). The TGA diagram of the platinum (II) complex Pt1 was obtained by thermogravimetric analysis (see Appendix Figure 1 ). The absorption spectrum of Pt1 in dichloromethane solution was obtained by UV-Vis absorption spectrophotometer and fluorescence spectrophotometer respectively (see Appendix Figure 2 )、Emission Spectrum (Attached Figure 3 ) and the emission spectra in PMMA films (Appendix Figure 4 Its H NMR spectrum is shown in the attached Figure 5 As shown. Take ITO glass with good conductivity and transmittance of 25mm×25mm, clean, dry, and treat with ozone, and then vacuum-deposit each functional layer in sequence to obtain a device. Test the performance of the device.

[0040] Example 2 Synthesis of Platinum (II) Complex Pt5 Chemical formula: PtC 48 H 34N4, molecular structure is as follows:

[0041] The synthesis steps are as follows: Under nitrogen atmosphere, C^N ligand (2.58 mmol) and K2PtCl4 (2.36 mmol) were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL). The reaction mixture was heated to 85 °C, stirred for 18 h, cooled to room temperature, and poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with pyridine (7.59 mmol) in CHCl3 (20 mL) for 18 h at 45 °C. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography with dichloromethane and ethyl acetate (v / v, 5:1). Under nitrogen atmosphere, potassium hydroxide (2.0 eq) was added to a methanol solution (15 ml) containing 4-ethynyltriphenylamine (2.0 eq). Pt1 (1.0 eq) was added to the mixture which was stirred at 70 °C for 1.0 h. The mixture was then stirred at 50 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into 100 mL of H2O and extracted several times with CH2Cl2. The mixed organic layers were dried and concentrated. The crude product was precipitated from hexane. The filtered precipitate was washed several times with methanol, n-hexane and ether to obtain the target product. The product structure was determined by 1 H NMR, 13 C NMR and mass spectrometry identification.

[0042] Example 3 Synthesis of platinum (II) complex Pt13 Chemical formula: PtC 37 H 23 F4N3, the molecular structure is as follows:

[0043] The synthesis steps are as follows: Under nitrogen atmosphere, C^N ligand (2.58 mmol) and K2PtCl4 (2.36 mmol) were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL). The reaction mixture was heated to 85 °C, stirred for 18 h, cooled to room temperature, and poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with 4-trifluoromethylpyridine (7.59 mmol) in CHCl3 (20 mL) for 18 h at 45 °C. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography with dichloromethane and ethyl acetate (v / v, 5:1). Under nitrogen atmosphere, potassium hydroxide (2.0 eq) was added to a methanol solution (15 ml) containing 4-fluorophenylacetylene (2.0 eq). Pt1 (1.0 eq) was added to the mixture which was stirred at 70 °C for 1.0 h. The mixture was then stirred at 50 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into 100 mL of H2O and extracted several times with CH2Cl2. The mixed organic layers were dried and concentrated. The crude product was precipitated from hexane. The filtered precipitate was washed several times with methanol, n-hexane and ether to obtain the target product. The product structure was determined by 1 H NMR, 13 C NMR and mass spectrometry identification.

Claims

1. A carbazolyl-containing C^N cyclometallated platinum (II) complex characterized by: a carbazolyl-containing C^N cyclometallated ligand, a pyridine derivative and an alkynyl group are jointly complexed with a platinum (II) metal ion, and the structure thereof is as follows:

2. The carbazole-containing C^N cyclometallated platinum (II) complex according to claim 1, characterized in that: The carbazolyl-containing C^N ligand was synthesized by the substitution reaction of 4-(9-carbazolyl)phenylboronic acid and 2-bromopyridine.

3. The carbazole-containing C^N cyclometallated platinum (II) complex according to claim 1, characterized in that: The monodentate ligand "square" structure is selected from pyridine, 2-fluoropyridine, 2-chloropyridine, 3-chloropyridine, 4-bromopyridine, 4-methylpyridine, and 2-chloro-3-trifluoromethylpyridine.

4. The carbazole-containing C^N cyclometallated platinum (II) complex according to claim 1, characterized in that: The monodentate ligand "circular" structure is selected from -Cl, 1-ethynyl-3-fluorobenzene, 2-fluorophenylacetylene, 1-chloro-2-ethynylbenzene, 3-chloro-1-ethynylbenzene, 4-ethynylaniline, 4-fluorophenylacetylene, 4-ethynylbiphenyl, 2-ethynylthiophene, 4-ethynyltriphenylamine, and 9-(4-ethynylphenyl)carbazole.

5. The carbazole-containing C^N cyclometallated platinum (II) complex according to claim 1, characterized in that: The platinum (II) complex synthesis steps are as follows: (1) Synthesis of carbazolyl C^N ligands: 1.0 mmol 2-bromopyridine, 2.0 mmol potassium carbonate, 0.015 mmol palladium acetate and 4-(9-carbazolyl)phenylboronic acid were added to a round-bottom flask in air, and then 12 ml of a 3:1 ethanol / water mixed solution was added. The mixture was stirred magnetically at 80 °C for 30 min. Suzuki cross-coupling reaction occurred in air. The reaction progress was tracked by thin layer chromatography. After the reaction was complete, 25 ml of saturated brine was added. The reaction product was extracted three times with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the product was separated by chromatography after rotary evaporation to obtain the target product. The analytically pure compound was obtained. The product structure was determined by 1 H NMR, 13 C NMR and mass spectrometry identification; (2) Synthesis of platinum (II) complex intermediate Pt1: Under nitrogen atmosphere, C^N ligand (2.58 mmol) and K2PtCl4 (2.36 mmol) were added to a mixed solvent of 2-ethoxyethanol / H2O (v / v, 3:1, 40 mL). The reaction mixture was heated to 85 °C and stirred for 18 h. After cooling to room temperature, it was poured into 100 mL of water to precipitate Pt(II)-dichloro-bridged dimer. Without purification, the dimer was stirred with a pyridine derivative (7.59 mmol) in CHCl3 (20 mL) at 45 °C for 18 h. After cooling to room temperature, the reaction mixture was poured into 30 mL of water and extracted three times with CH2Cl2. The organic layers were combined, dried over anhydrous Na2SO4, and concentrated. Finally, the compound was purified by silica gel column chromatography using dichloromethane and ethyl acetate (v / v, 5:1).

6. (3) Under nitrogen atmosphere, potassium hydroxide (1.0 eq) was added to a methanol solution (15 ml) containing an acetylene compound (2.0 eq). Pt1 (1.0 eq) was added to the mixture which was stirred at 70 °C for 1.0 h. The mixture was then stirred at 50 °C for 12 h. After cooling to room temperature, the reaction mixture was poured into 100 mL of H2O and extracted with CH2Cl2 several times. The mixed organic layer was dried and concentrated, and hexane was added to precipitate the crude product. The filtered precipitate was washed several times with methanol, n-hexane and ether to obtain the target product.

7. The carbazole-containing C^N cyclometallated platinum (II) complex according to claim 1, characterized in that: The platinum (II) complex is used as an electroluminescent material.

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