Homoleptic platinum metal liquid crystal luminescent materials containing triazole pyridine derivatives, their synthesis and applications

Abstract

Homoleptic platinum metal liquid crystal luminescent materials containing triazole pyridine derivatives, their synthesis and applications. Such platinum complexes use triazole pyridine derivatives with flexible long chains as cyclometalated homoleptic ligands. By introducing polyazole on the ligands, it helps with the electron transport of the materials, thereby balancing the hole and electron transport capabilities of the platinum complexes. These platinum complexes are doped into 4,4',4”-tris(carbazol-9-yl)triphenylamine (TCTA) and 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) at different mass concentrations as the light-emitting layer to prepare single-doped solution-processed organic light-emitting diodes (OLEDs), obtaining high-efficiency white light and orange-red light devices, thus further expanding the applications of OLEDs in display and lighting systems.

Description

Technical Field

[0001] The present invention relates to the field of organic electroluminescent materials, and particularly to a homoleptic platinum metal liquid crystal luminescent material containing a triazole pyridine derivative, and its synthesis and application. Background Art

[0002] Metal liquid crystal luminescent materials refer to liquid crystal materials containing metal cations; the introduction of heavy atoms strengthens the spin-orbit coupling effect (SOC) of the molecules, increases the intersystem crossing probability (ISC) of the molecules, increases the population of the excited triplet state T1, and thus enables the molecules to emit light efficiently or greatly improves the photoluminescence quantum yield of the molecules (Xiao, L.; Chen, Z.; Qu, B.; Luo, J.; Kong, S.; Gong, Q.; Kido, J. Adv. Mater. 2011, 23, 926; Choy, W. C.; Chan, W. K.; Yuan, Y. Adv. Mater. 2014, 26, 5368).

[0003] Meanwhile, except for a very small number of metal liquid crystal luminescent materials without flexible chains (Krikorian, M.; Liu, S.; Swager, T. M. J. Am. Chem. Soc. 2014, 136, 2952) or containing one flexible chain (Geng, H.; Luo, K.; Cheng, H.; Zhang, S.; Ni, H.; Wang, H.; Yu, W.; Li, Q. RSC Adv. 2017, 7, 11389), most metal liquid crystal luminescent materials contain multiple flexible long chains, making them generally have good solubility in common organic solvents, which is beneficial to the preparation of solution-processed OLEDs.

[0004] On the other hand, white organic light-emitting devices (WOLEDs) have great potential applications in the fields of large-area flexible displays and lighting systems, and solution-processed OLEDs can form films by using low-cost and process-simplified solution processing methods. The light-emitting active molecules applied in WOLEDs are generally single-doped and multi-component doped (the latter includes two dopants with complementary color lights and three-component dopants with red, green, and blue light materials respectively). The white light OLED devices with multi-component doping have the problem of more complex preparation processes. Relatively speaking, the preparation process of single-doped white light OLEDs is simpler, and the single-doped active light-emitting molecules with a wide wavelength can cover the entire light-emitting region. However, the monomer emission of most platinum metal liquid crystals is yellowish-green or yellow (Wu, X.; Zhu, M.; Bruce, D. W.; Zhu, W.; Wang, Y. J. Mater. Chem. C 2018, 6, 9848.), and their emission in the aggregated state is generally yellow or orange-red light (Cuerva, C.; Cano, M.; Lodeiro, C. Chem. Rev. 2021, 121, 12966), resulting in difficulty in formulating white light with their emissions at different doping concentrations. Combining highly efficient blue and yellow light-emitting materials together will obtain the optimal white light efficiency (Liang, A.; Huang, G.; Dong, S.; Zheng, X.; Zhu, J.; Wang, Z.; Wu, W.; Zhang, J.; Huang, F. J. Mater. Chem. C 2016, 4, 6626). Therefore, it is particularly important to seek a class of platinum complexes in which the monomer molecules emit blue light and their excimers can emit yellow or orange-red light.

[0005] On the other hand, the reported cycloplatinum metal liquid crystal luminescent materials currently have generally low performance in white light and highly efficient orange-red OLEDs (manifested by a relatively low external quantum efficiency EQE; Wang, Y.; Fan, J.; Shi, J.; Qi, H.; Baranoff, E.; Xie, G.; Li, Q.; Tan, H.; Liu, Y.; Zhu, W. Dyes Pigments 2016, 133, 238). Considering that platinum liquid crystal complexes themselves have good hole-transporting ability (Zou, G.; Zhao, L.; Zeng, L.; Luo, K.; Ni, H.; Wang, H.; Li, Q.; Yu, W.; Li, X. Inorg. Chem. 2019, 58, 861), introducing a ligand containing a nitrogen atom with a stronger electrophilicity than carbon atoms will be more conducive to the electron transport of the target molecule, making the recombination of holes and electrons in the luminescent molecule more favorable, thereby improving its electroluminescence efficiency. Triazole pyridine and its derivatives are ligands with relatively many nitrogen atoms, and there is only one report on neutral platinum homoleptic complexes based on triazole pyridine derivatives so far (Prabhath, M. R. R.; Romanova, J.; Curry, R. J.; Silva, S. R. P.; Jarowski, P. D. Angew. Chem. Int. Ed. Engl., 2015, 54, 7949). Moreover, the reported homoleptic platinum complexes of these triazole pyridine ligands have the disadvantage of poor solubility and have never been applied to the preparation of luminescent devices. Therefore, the application research of triazole homoleptic platinum complexes in organic electroluminescent devices is still blank. In the present invention, a phenyl group modified with a flexible alkoxy long chain at the 3, 4, and 5 positions is introduced at the 5th position of the pyridine ring of the cyclometalated ligand triazole pyridine, optimizing the homoleptic platinum complexes with triazole pyridine as the core and applying them to OLEDs devices. Summary of the Invention

[0006] The purpose of the present invention is to synthesize a class of cycloplatinum homoleptic metal liquid crystal luminescent materials with triazole pyridine derivatives with peripheral flexible long chains as ligands; using these platinum complexes as single-doped luminescent active molecules to prepare highly efficient white light and orange-red organic electroluminescent devices.

[0007] The cycloplatinum homoleptic metal liquid crystal luminescent materials with triazole pyridine derivatives as ligands in the present invention are characterized in that the platinum complex uses triazole pyridine with a flexible long chain as the cyclometalated ligand; on the basis of the existing platinum metal complexes with hole-transporting ability, triazole pyridine with electron-transporting properties is introduced.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] The chemical structure of the homoleptic platinum liquid crystal luminescent material with a triazole pyridine derivative as a ligand in the present invention is as follows:

[0010]

[0011] The types of its peripheral flexible chains are as follows:

[0012] 1) When n = 3, the flexible chain is n-propyl;

[0013] 2) When n = 4, the flexible chain is n-butyl;

[0014] 3) When n = 6, the flexible chain is n-hexyl;

[0015] 4) When n = 8, the flexible chain is n-octyl;

[0016] 5) When n = 10, the flexible chain is n-decyl;

[0017] 6) When n = 12, the flexible chain is n-dodecyl.

[0018] In the platinum complex of the present invention, a triazole pyridine with a flexible long chain is used as a cyclometalating ligand, the platinum source is potassium chloroplatinate, the solvent is a mixture of organic solvents such as tetrahydrofuran, ethylene glycol monoethyl ether, methanol and water in a certain ratio (1:1 to 10:1), a weak base such as potassium carbonate or sodium carbonate is used as a deprotonating reagent, the reaction temperature is from room temperature to 100 °C, and the reaction time is 12 to 24 h.

[0019] The application of the homoleptic platinum metal liquid crystal luminescent material containing a triazole pyridine derivative in the present invention is used to prepare a light-emitting device, wherein Pt-TC8 and Pt-TC10 are particularly used for white light devices and orange-red light devices, and the white light devices and orange-red light devices both include ITO, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and an aluminum metal cathode.

[0020] The platinum complex in the device serves as a light-emitting molecule; the mass concentration of the complex as a dopant is 0.2% to 60%; the mass ratio of the components of the co-blended host of 4,4',4”-tris(carbazol-9-yl)triphenylamine (TCTA) and 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) is 0.5 to 1.5; specifically, the light-emitting layer in the white light device is composed of the platinum complex as a single dopant doped into TCTA and OXD-7 to form a light-emitting layer; the mass concentration of the single dopant doping is 0.2% to 1.5%.

[0021] Compared with the prior art, the beneficial effects obtained by the technical solution of the present invention are:

[0022] 1) The cycloplatinated metal liquid crystal luminescent materials of Pt-TC8 and Pt-TC10 with triazolopyridine derivatives as ligands have excellent electron transport properties, so they can effectively improve the electron injection and electron transport properties of platinum complexes in devices;

[0023] 2) By grafting multiple flexible long chains on the periphery of the homoleptic platinum metal liquid crystal luminescent molecules of triazolopyridine derivatives, the solubility of platinum complexes is greatly improved, which is beneficial to the preparation of solution-processed organic light-emitting devices;

[0024] 3) Using the platinum complex as a single dopant with a doping concentration of 0.2 wt% - 1.5 wt%, it can be used to prepare white light devices; when the doping concentration is 1 wt%, the performance of white light OLEDs devices reaches the optimum (the maximum external quantum efficiency is 5.08%), which is the best-performing white light OLED based on platinum metal liquid crystal complexes at present (Wang, Y.; Fan, J.; Shi, J.; Qi, H.; Baranoff, E.; Xie, G.; Li, Q.; Tan, H.; Liu, Y.; Zhu, W. Dyes Pigments, 2016, 133, 238; Wang, Y.; Fan, J.; Li, T.; Wang, Q.; Shi, J.; Qu, Z.; Tan, H.; Liu, Y.; Zhu, W. RSC Adv., 2016, 6, 45864; Yang, X.; Wu, X.; Zhou, D.; Yu, J.; Xie, G.; Bruce, D. W.; Wang, Y. Dalton Trans., 2018, 47, 13368).

[0025] 4) By increasing the doping concentration of the platinum complex to 10 wt% - 60 wt%, a highly efficient orange-red light device can be obtained. When the doping concentration is 10 wt%, the maximum external quantum efficiency of the prepared orange-red light OLED is 20.24%, comparable to the reported high-performance orange-red light OLEDs based on thermally activated delayed fluorescence materials (TADF) (EQE ≈ 20%) (Chen, J.-X.; Tao, W.-W.; Xiao, Y.-F.; Wang, K.; Zhang, M.; Fan, X.-C.; Chen, W.-C.; Yu, J.; Li, S.; Geng, F.-X.; Zhang, X.-H.; Lee, C.-S., ACS Appl. Mater. Inter., 2019, 11, 29086; Xie, F.-M.; Li, H.-Z.; Dai, G.-L.; Li, Y.-Q.; Cheng, T.; Xie, M.; Tang, J.-X.; Zhao, X., ACS Appl. Mater. Inter., 2019, 11, 26144), and it is also the best-performing OLED based on metal liquid crystal complexes currently (the highest EQE of the reported OLEDs based on metal liquid crystals is 11.3%, Qian, G.; Yang, X.; Wang, X.; Herod, J.D.; Bruce, D.W.; Wang, S.; Zhu, W.; Duan, P.; Wang, Y. Adv. Opt. Mater., 2020, 8, 2000775). Description of the Drawings

[0026] Figure 1 It is the UV-visible absorption spectrum of the platinum complex Pt-TC8 in dichloromethane solution;

[0027] Figure 2 It is the photoluminescence spectrum of the platinum complex Pt-TC8 in dichloromethane solution;

[0028] Figure 3 It is the photoluminescence spectrum of the platinum complex Pt-TC8 in the solid state;

[0029] Figure 4 It is the photoluminescence spectrum of the platinum complex Pt-TC8 in the liquid crystal state;

[0030] Figure 5 It is the thermogravimetric analysis (TGA) spectrum of the platinum complex Pt-TC8;

[0031] Figure 6 It is the birefringence texture (POM) diagram of the platinum complex Pt-TC8;

[0032] Figure 7 It is the X-ray diffraction (XRD) spectrum of the platinum complex Pt-TC8;

[0033] Figure 8 It is the device structure of the platinum complexes Pt-TC8 and Pt-TC10 and the energy level of related materials;

[0034] Figure 9 It is the electroluminescence spectrum of the device when the doping concentration of the platinum complex Pt-TC8 is 1 wt%;

[0035] Figure 10 It is the current density-voltage-luminance spectrum of the device when the doping concentration of the platinum complex Pt-TC8 is 1 wt%;

[0036] Figure 11 It is the graph of the current efficiency and power efficiency varying with luminance of the device when the doping concentration of the platinum complex Pt-TC8 is 1 wt%;

[0037] Figure 12 It is the external quantum efficiency and luminance curve of the device when the doping concentration of the platinum complex Pt-TC8 is 1 wt%;

[0038] Figure 13 It is the electroluminescence spectrum of the device when the doping concentration of the platinum complex Pt-TC8 is 10 wt%;

[0039] Figure 14 It is the current density-voltage-luminance spectrum of the device when the doping concentration of the platinum complex Pt-TC8 is 10 wt%;

[0040] Figure 15 It is the graph of the current efficiency and power efficiency varying with luminance of the device when the doping concentration of the platinum complex Pt-TC8 is 10 wt%;

[0041] Figure 16 It is the external quantum efficiency and luminance curve of the device when the doping concentration of the platinum complex Pt-TC8 is 10 wt%. Detailed implementation mode

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to the drawings and embodiments, specifically including the synthesis, characterization, preparation and testing of the target molecule.

[0043] Example 1

[0044] Synthesis of 2-(5-1,2,3-triazolyl)-5-(3,4,5-tri-n-octyloxy)phenyl-pyridine

[0045]

[0046] 1) Synthesis of 3,4,5-trihydroxybromobenzene

[0047]

[0048] Add dichloromethane (DCM, 15 mL) and 3,4,5-trimethoxybromobenzene (3 g, 12.14 mmol) into a 100 mL one-neck round-bottom flask with a side arm. Purge with argon three times and place it in a cold trap at -78 °C and stir for 15 min. Then, dropwise add a dichloromethane solution of boron tribromide (10.00 g, 40.06 mmol; in 5 mL DCM) to this solution over 30 min. After the addition is complete, remove the reaction flask from the cold trap, allow it to return to room temperature naturally and stir overnight. Then pour the reaction solution into a beaker containing a large amount of ice-water mixture (100 mL), and extract it three times with ethyl acetate (EA) (3 × 50 mL). Dry the combined organic layers with anhydrous sodium sulfate and filter by suction. Then, perform rotary evaporation under reduced pressure in a water bath to remove the organic solvent, and obtain 3,4,5-trihydroxybromobenzene as an off-white solid (2.35 g, 94%).

[0049] 2) Synthesis of 3,4,5-tris(n-octyloxy)bromobenzene

[0050]

[0051] Add 3,4,5-trihydroxybromobenzene (2.00 g, 9.76 mmol), 1-bromooctane (6.22 g, 32.21 mmol) and potassium carbonate (8.09 g, 58.56 mmol) into a 200 mL eggplant-shaped one-neck flask with a side arm. After purging with argon three times, add 30 mL of N,N-dimethylformamide (DMF). Place the sealed eggplant-shaped flask in an oil bath at 80 °C and react for 36 h. After the reaction is completed, cool it to room temperature, add 100 mL of water to the reaction flask, and extract it three times with DCM (3 × 20 mL). Then combine the organic layers, dry with anhydrous sodium sulfate and filter by suction. Then, perform rotary evaporation under reduced pressure in a water bath to remove the organic solvent. The obtained crude product is purified by silica gel (200 - 300 mesh) column chromatography, and the eluent is petroleum ether (PE) / EA = 20:1 (v / v). Finally, obtain 3,4,5-tris(n-octyloxy)bromobenzene as a white solid (4.76 g, 90%). 11H NMR (500 MHz, CDCl3) δ 6.67 (s, 2H), 3.93 (t, J = 6.3 Hz, 4H), 3.90 (t, J = 6.3 Hz, 2H), 1.79 (quintet, J = 7.0 Hz, 4H), 1.72 (quintet, J = 7.0 Hz, 2H), 1.45 (quintet, J = 7.2 Hz, 6H), 1.36 - 1.25 (m, 24H), 0.89 (t, J = 6.5 Hz, 9H).

[0052] 3) Synthesis of 3,4,5-tris(n - octyloxy)phenylboronic acid pinacol ester

[0053]

[0054] Add 3,4,5-tris(n - octyloxy)bromobenzene (3.00 g, 5.54 mmol), bis(pinacolato)diboron (1.69 g, 6.65 mmol), potassium acetate (1.63 g, 16.62 mmol), 1,4 - dioxane (70 mL) and Pd(dppf)Cl2·CH2Cl2 (228 mg, 0.28 mmol) into a 200 mL round - bottomed flask with a side - arm. Place the sealed round - bottomed flask in an oil bath at 85 °C and react for 24 h. After the reaction is completed, cool it to room temperature, then pour the reaction solution into a beaker containing water (100 mL) and extract it with DCM three times (3×50 mL). Combine the organic layers, dry them over anhydrous sodium sulfate and filter by suction. Then, carry out rotary evaporation under reduced pressure in a water bath to remove the organic solvent. The obtained crude product is purified by silica gel (200 - 300 mesh) column chromatography, and the eluent is PE / EA = 15:1 (v / v). Finally, 3,4,5 - tris(n - octyloxy)phenylboronic acid pinacol ester is obtained as a gray - brown waxy solid (2.64 g, 81%). 1 1H NMR (500 MHz, CDCl3) δ 6.99 (s, 2H), 4.01 (t, J = 6.5 Hz, 4H), 3.97 (t, J = 6.5 Hz, 2H), 1.79 (quintet, J = 7.1 Hz, 4H), 1.74 (quintet, J = 7.1 Hz, 2H), 1.46 (quintet, J = 7.4 Hz, 6H), 1.33 (s, 12H), 1.34 - 1.25 (m, 24H), 0.884 (t, J = 6.8 Hz, 6H), 0.879 (t, J = 6.8 Hz, 3H).

[0055] 4) Synthesis of 5 - bromo - 2 - ((isopropylsilyl)ethynyl)pyridine

[0056]

[0057] Add 2-iodo-3-bromopyridine (10 g, 35.22 mmol), tris(isopropyl)silylacetylene (6.49 g, 35.57 mmol), Pd(PPh3)2Cl2 (1.24 g, 1.76 mmol) and copper(I) iodide (335 mg, 1.76 mmol) into a 200 mL eggplant-shaped single-neck flask with a side arm. After purging with argon three times, add triethylamine (TEA, 60 mL) and acetonitrile (MeCN, 60 mL). React at room temperature for 12 h, then rotary evaporate to remove the solvent. Add DCM (100 mL) to the solid mixture, wash with water three times (3×50 mL). Dry the organic layer with anhydrous sodium sulfate and filter by suction. Then rotary evaporate the obtained filtrate under reduced pressure in a water bath to remove the organic solvent. Purify the obtained crude product by column chromatography on silica gel (200-300 mesh), and the eluent is n-hexane to obtain 5-bromo-2-((isopropylsilyl)ethynyl)pyridine as a colorless oil (11.92 g, 100%). 1 1H NMR (500 MHz, CDCl3) δ 8.63 (dd, J = 2.3, 0.6 Hz, 1H), 7.76 (dd, J = 8.3, 2.4 Hz, 1H), 7.34 (dd, J = 8.3, 0.7 Hz, 1H), 1.15–1.12 (m, 21H)

[0058] 5) Synthesis of 5-((3,4,5-trioctyloxy)phenyl)-2-((isopropylsilyl)ethynyl)pyridine

[0059]

[0060] Add 3,4,5-tris(n-octyloxy)phenylboronic acid pinacol ester (2.50 g, 4.25 mmol), 5-bromo-2-((isopropylsilyl)ethynyl)pyridine (1.44 g, 4.25 mmol), potassium carbonate (1.76 g, 12.75 mmol) and tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) into a 100 mL reaction tube with a side arm. After purging with argon three times, add toluene (30 mL), ethanol (15 mL) and water (15 mL) to the reaction tube in sequence, then reflux the reaction for 24 h. After the reaction is completed, cool to room temperature, pour the reaction solution into water (200 mL) and extract with DCM three times (3×50 mL). Combine the organic layers, dry with anhydrous sodium sulfate and filter by suction. Then rotary evaporate the obtained filtrate under reduced pressure in a water bath to remove the organic solvent. Purify the obtained crude product by column chromatography on silica gel (200-300 mesh), and the eluent is PE / EA = 30:1 (v / v) to obtain 5-((3,4,5-trioctyloxy)phenyl)-2-((isopropylsilyl)ethynyl)pyridine as a white solid (2.64 g, 86%). 11H NMR (500 MHz, CDCl3) δ 8.76 (s, 1H), 7.79 (d, J = 7.1 Hz, 1H), 7.51 (d, J = 8.1 Hz, 1H), 6.71 (s, 2H), 4.03 (t, J = 6.5 Hz, 4H), 3.99 (t, J = 6.5 Hz, 2H), 1.83 (quintet, J = 7.1 Hz, 4H), 1.77 (quintet, J = 7.1 Hz, 2H), 1.49 (quintet, J = 7.3 Hz, 6H), 1.38–1.26 (m, 24H), 1.19 - 1.13 (m, 21H), 0.88 (t, J = 6.7 Hz, 9H)

[0061] 6) Synthesis of 5 - ((3,4,5 - trioctyloxy)phenyl)-2 - ethynylpyridine

[0062]

[0063] Add 5 - ((3,4,5 - trioctyloxy)phenyl)-2 - ((isopropylsilyl)ethynyl)pyridine (2.00 g, 2.78 mmol), tetrabutylammonium fluoride (TBAF 1.09 g, 4.17 mmol), tetrahydrofuran (THF) and methanol (MeOH 2 mL) into a 100 mL single - necked flask. React at room temperature under an air atmosphere and monitor the reaction by TLC spotting. After 5 min, the reaction is complete. Rotavaporize to remove the solvent, and purify the crude product by silica gel (200 - 300 mesh) column chromatography. The eluent is PE / EA = 10:1 (v / v) to obtain 5 - ((3,4,5 - trioctyloxy)phenyl)-2 - ethynylpyridine as a white solid (1.55 g, 99%). 1 1H NMR (500 MHz, CDCl3) δ 8.78 (s, 1H), 7.84 (d, J = 7.8 Hz, 1H), 7.55 (d, J = 8.0 Hz, 1H), 6.73 (s, 2H), 4.03 (t, J = 6.5 Hz, 4H), 4.00 (t, J = 6.5 Hz, 2H), 3.25 (s, 1H), 1.83 (quintet, J = 6.9 Hz, 4H), 1.77 (quintet, J = 6.9 Hz, 2H), 1.49 (quintet, J = 7.1 Hz, 6H), 1.37 - 1.27 (m, 24H), 0.88 (t, J = 6.8 Hz, 9H).

[0064] 7) Synthesis of methyl pivaloylazide

[0065]

[0066] Sodium azide (NaN3, 20.00 g, 307.64 mmol) and chloroformate pivalate (42.12 g, 279.68 mmol) were added to a 500 mL single-necked flask. After purging with argon three times, deionized water (160 mL) was added. The reaction was carried out overnight at 90 °C. After the reaction was completed, the temperature was lowered to room temperature. The reaction solution was extracted three times with EA (3 × 100 mL), and the combined organic layers were dried over anhydrous sodium sulfate and filtered by suction. The solvent was removed by rotary evaporation of the filtrate to obtain methyl azide pivalate as a colorless liquid (35.00 g, 80%). 1 1H NMR (500 MHz, CDCl3) δ 5.14 (s, 2H), 1.25 (s, 9H).

[0067] 8) Synthesis of 1-(pivaloyloxymethyl)-4-(2-(5-((3,4,5-tri-n-octyloxy)phenyl))pyridin-1-yl)-1,2,3-triazole

[0068]

[0069] 5-((3,4,5-Tri-n-octyloxy)phenyl)-2-ethynylpyridine (1.25 g, 2.22 mmol), methyl azide pivalate (523 mg, 3.33 mmol), THF (15 mL), copper sulfate pentahydrate (28 mg, 0.11 mmol), sodium ascorbate (145 mg, 0.73 mmol), deionized water (5 mL) and tert-butanol (1 mL) were added to a 100 mL single-necked flask. The reaction was carried out overnight at room temperature under an air atmosphere. After the reaction was completed as detected by TLC, the reaction solution was extracted three times with EA (3 × 20 mL), and then the combined organic layers were washed three times with water (3 × 50 mL). The organic layer was dried over anhydrous sodium sulfate and filtered by suction to obtain the crude product, which was further purified by silica gel (200 - 300 mesh) column chromatography. The eluent was PE / EA = 4:1 (v / v) to obtain 1-(pivaloyloxymethyl)-4-(2-(5-((3,4,5-tri-n-octyloxy)phenyl))pyridin-1-yl)-1,2,3-triazole as a white waxy solid (1.41 g, 88%). 11H NMR (500 MHz, CDCl3) δ 8.79 (s, 1H), 8.42 (s, 1H), 8.22 (d, J = 7.8 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H), 6.77 (s, 2H), 6.32 (s, 2H), 4.05 (t, J = 6.5 Hz, 4H), 4.00 (t, J = 6.5 Hz, 2H), 1.83 (quintet, J = 7.1 Hz, 4H), 1.77 (quintet, J = 7.1 Hz, 2H), 1.49 (quintet, J = 7.4 Hz, 6H), 1.36 - 1.26 (m, 24H), 1.21 (s, 9H), 0.89 (t, J = 7.0 Hz, 3H), 0.88 (t, J = 7.0 Hz, 6H).

[0070] 9) Synthesis of 2-(5-1,2,3-triazolyl)-5-(3,4,5-tri-n-octyloxy)phenyl-pyridine

[0071]

[0072] Add 1-tert-butoxycarbonylmethyl-4-(2-(5-((3,4,5-tri-n-octyloxy)benzene))pyridyl)-1,2,3-triazole (800 mg, 1.11 mmol), THF (15 mL) and MeOH (5 mL) into a 100 mL single-necked flask, and add potassium hydroxide solution (KOH, 137 mg, 2.44 mmol; 2 M in water). React at room temperature for 15 min under an air atmosphere. After detecting the completion of the reaction by TLC, extract the reaction solution with EA three times (3 × 20 mL), then wash the combined organic layers with water three times (3 × 20 mL), dry the organic layer with anhydrous sodium sulfate and filter by suction to obtain 4-(2-(5-((3,4,5-tri-n-octyloxy)phenyl))pyridyl)-1,2,3-triazole as a gray viscous solid (432 mg, 64%). The product of this step can be used for the next reaction feeding without further purification.

[0073] Example 2

[0074] Synthesis of Complex Pt-TC8

[0075]

[0076] Add 2-(4-1,2,3-triazolyl)-5-(3,4,5-trioctyloxy)phenyl-pyridine (200 mg, 0.32 mmol), potassium tetrachloroplatinate (K2PtCl4 66 mg, 0.16 mmol), sodium carbonate (102 mg, 0.96 mmol), ethylene glycol monoethyl ether (3 mL) and deionized water (1 mL) into a 100 mL reaction tube. Under an argon atmosphere, place it in an oil bath at 60 °C and stir for 10 min. Then raise the temperature to 100 °C and react for 24 h. After the reaction is completed, cool it to room temperature, extract it three times with DCM (3×20 mL), dry the combined organic layer with anhydrous sodium sulfate and filter it to obtain the crude product. Then purify it by silica gel (200-300 mesh) column chromatography, and the eluent is DCM / THF = 2:1 (v / v) to obtain the complex Pt-TC8 as an orange-red viscous solid (195 mg, 85%). 1 H NMR (500 MHz, CDCl3) δ 10.40 (s, 2H), 7.79 (d, J = 8.2 Hz, 2H), 7.66 (s, 2H), 7.28 (d, J = 8.2 Hz, 2H), 6.74 (s, 4H), 4.07 (t, J = 6.2 Hz, 8H), 4.03 (t, J = 6.5 Hz, 4H), 1.88 (quintet, J = 7.0 Hz, 8H), 1.81 (quintet, J = 7.1 Hz, 4H), 1.59 - 1.50 (m, 12H), 1.43 - 1.31 (m, 48H), 0.92 (t, J = 6.0 Hz, 6H), 0.91 (t, J = 6.0 Hz, 12H). 13 C NMR (126 MHz, CDCl3) δ 153.64, 150.84, 149.24, 144.08, 138.97, 135.38, 134.55, 131.03, 128.91, 118.67, 104.18, 73.56, 69.24, 32.00, 31.97, 30.54, 29.70, 29.65, 29.48, 29.47, 26.35, 26.25, 22.75, 14.14. Elemental analysis theoretical calculated values: C 74 H 114 N8O6Pt: C, 63.18; H, 8.17; N, 7.96; Found: C, 63.28; H, 8.24; N, 7.98.

[0077] Photophysics and liquid crystallinity of complex Pt-TC8:

[0078] The UV-visible absorption spectrum of platinum complex Pt-TC8 in dichloromethane solution ( Figure 1), showing two main absorption bands at 258 - 361 and 361 - 426 nm respectively. The former is attributed to the π-π* charge transfer transition in the ligand; the latter is attributed to the metal-to-ligand (MLCT) and intra-ligand (ILCT) charge transfer transitions. The photoluminescence spectrum of platinum complex Pt-TC8 in dichloromethane solution ( Figure 2 ), with the maximum emission wavelength at 492 nm, originating from the luminescence of the monomer complex. The photoluminescence spectrum of platinum complex Pt-TC8 in the solid state ( Figure 3 ), with the maximum emission wavelength at 622 nm, attributed to the metal-metal-ligand charge transfer transition (MMLCT). The photoluminescence spectrum of platinum complex Pt-TC8 in the liquid crystal state ( Figure 4 ), with the maximum emission wavelength at 624 nm, also attributed to MMLCT. The thermogravimetric analysis (TGA) pattern of platinum complex Pt-TC8 ( Figure 5 ), indicating a thermal decomposition temperature of 340 °C. The birefringence texture (POM) pattern of platinum complex Pt-TC8 ( Figure 6 ), showing a fan-shaped texture; the X-ray diffraction (XRD) spectrum of platinum complex Pt-TC8 ( Figure 7 ), having five groups of peaks with the spacing ratio satisfying 1:1 / √3:1 / 2:1 / √7:1 / 3, indicating its hexagonal columnar liquid crystal structure.

[0079] Example 3

[0080] Preparation of a white light device using a platinum complex as a doping material and device testing

[0081] See Figure 8 , the structure of the white light device is ITO / PEDOT:PSS(50 nm) / Poly-TPD(30 nm) / 99 wt% TCTA:OXD-7(1:1):1 wt% Pt-TC8 / BmPyPb(50 nm) / LiF(1 nm) / Al(100 nm).

[0082] Among them, ITO is indium tin oxide, PEDOT:PSS is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), Poly-TPD is poly[bis(4-phenyl)(4-butylphenyl)amine, TCTA is 4,4',4”-tris(carbazol-9-yl)triphenylamine, OXD-7 is 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole], and BmPyPb is 1,4-bis(3,5-bis(3-pyridyl)phenyl)benzene.

[0083] First, during the ultrasonic process, the indium tin oxide (ITO) glass substrates were successively washed with glass detergent, acetone, isopropyl alcohol, and deionized water, and then the solvents were dried. PEDOT:PSS was microporous filtered with 0.22 μm and spin-coated onto the pretreated ITO substrates, and dried at 130 °C for 15 min to form a 50-nm-thick hole injection layer. A chlorobenzene solution of Poly-TPD was spin-coated onto PEDOT:PSS to serve as a hole transport layer (with a thickness of 30 nm). TCTA, OXD-7, and Pt-TC8 were dissolved in DCM (5 mg mL -1 ) in a mass ratio of 49.5%:49.5%:1%, microporous filtered with 0.22 μm, and spin-coated onto the hole transport layer to prepare a 50-nm-thick light-emitting layer. Then, under the condition that the base pressure was lower than 4.0×10 -4 Pa, BmPyPb, lithium fluoride, and aluminum were respectively evaporated onto the light-emitting layer as an electron transport layer, an electron injection layer, and a metal cathode, with their thicknesses being 50 nm, 1 nm, and 100 nm respectively. Their current density-voltage-luminance properties were measured on a Keithley 2400 source meter and a calibrated silicon photodiode. The electroluminescence spectrum was measured by a HORIBA Jobin-Yvon FluoroMax-4 fluorescence spectrometer.

[0084] The electroluminescence spectrum of the single-doped (1 wt%) electroluminescent device based on Pt-TC8 is as Figure 9 shown. The maximum emission wavelength of the device is 567 nm, and the full width at half maximum is 204 nm. The current density-voltage-luminance of the device is as Figure 10 shown, indicating that the turn-on voltage is 3.40 V. The current efficiency and power efficiency curves are as Figure 11 shown. The maximum current efficiency and power efficiency are 11.7 cd A -1 and 9.4 lm W -1 respectively. The maximum luminance is 1220 cd m -2 . The external quantum efficiency spectrum is as Figure 12 shown, and the maximum external quantum efficiency is 5.08%. The CIE coordinates are (0.35, 0.38), which are very close to the CIE coordinates (0.33, 0.33) of standard white light.

[0085] Example 4

[0086] Preparation and device testing of an orange-red light device with a platinum complex as a doping material

[0087] The structure of the orange-red light-emitting device is ITO / PEDOT:PSS(50nm) / Poly-TPD(30nm) / 90wt%TCTA:OXD-7(1:1):10wt%Pt-TC8 / BmPyPb(50nm) / LiF(1nm) / Al(100nm).

[0088] The related materials used are similar to those in Example 3.

[0089] First, during the ultrasonic process, the indium tin oxide (ITO) glass substrate was successively washed with glass detergent, acetone, isopropyl alcohol, and deionized water, and then the solvent was dried. PEDOT:PSS was filtered through a 0.22μm microporous filter and spin-coated onto the pretreated ITO substrate, and dried at 130°C for 15 min to form a 50nm-thick hole injection layer. The chlorobenzene solution of Poly-TPD was spin-coated onto PEDOT:PSS to serve as the hole transport layer (with a thickness of 30nm). TCTA, OXD-7, and Pt-TC8 were dissolved in DCM (5mg mL -1 ) in a mass ratio of 45%:45%:10%, filtered through a 0.22μm microporous filter, and spin-coated onto the hole transport layer to prepare a 50nm-thick light-emitting layer. Then, under the condition that the base pressure is lower than 4.0×10 -4 Pa, BmPyPb, lithium fluoride, and aluminum were respectively evaporated onto the light-emitting layer as the electron transport layer, electron injection layer, and metal cathode, with their thicknesses being 50, 1, and 100nm respectively. Their current density-voltage-brightness properties were measured on a Keithley 2400 source meter and a calibrated silicon photodiode. The electroluminescence spectrum was measured by a HORIBA Jobin-Yvon FluoroMax-4 fluorescence spectrometer.

[0090] The electroluminescence spectrum of the single-doped (10wt%) electroluminescent device based on Pt-TC8 is as Figure 13 shown. The maximum emission wavelength of the device is 615nm, and the full width at half maximum is 91nm. The current density-voltage-brightness of the device is as Figure 14 shown, indicating that the turn-on voltage is 3.40V. The current efficiency and power efficiency curves are as Figure 15 shown. The maximum current efficiency and power efficiency are 40.3cd A -1 and 23.0lm W -1 . The maximum luminous brightness is 11592cd m -2 . The external quantum efficiency spectrum is as Figure 16 shown. The maximum external quantum efficiency is 20.24%. The CIE coordinates are (0.57, 0.42), which are typical orange-red light chromaticity coordinates.

Claims

1. A homoleptic platinum metal liquid crystal luminescent material containing a triazole pyridine derivative, characterized in that, Based on a platinum metal complex with hole-transporting ability, a triazole pyridine unit with electron-transporting ability is introduced, and the structural formula is as follows:

2. Synthesis of the homoleptic platinum metal liquid crystal luminescent material containing triazole pyridine derivatives according to claim 1, characterized in that: Using an organic solvent and water as a mixed solvent, a weak base as a deprotonating reagent, and triazole pyridine with a flexible long chain as a cyclometalating ligand to react with a platinum source.

3. The synthesis according to claim 2, characterized in that: The platinum source includes potassium chloroplatinate; the organic solvent includes at least one of tetrahydrofuran, ethylene glycol monoethyl ether, and methanol.

4. The synthesis according to claim 2, wherein: The weak base includes at least one of potassium carbonate and sodium carbonate.

5. The synthesis according to claim 2, wherein: The volume ratio of the organic solvent to water is 1:1 to 10:

1.

6. The synthesis according to claim 2, characterized in that: The reaction temperature is from room temperature to 100 °C; the reaction time is 12 to 24 h.

7. Use of the homoleptic platinum metal liquid crystal luminescent material containing triazole pyridine derivatives as claimed in claim 1, characterized in that: Applied to light-emitting devices.

8. The application according to claim 7, wherein: Pt-TC8 and Pt-TC10 are used to prepare white light devices and orange-red light devices.

9. The application according to claim 7, characterized in that: The light-emitting device includes an indium tin oxide anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and an aluminum metal cathode arranged in sequence.

10. The application according to claim 7, characterized in that: In the light-emitting device, a homoleptic platinum metal liquid crystal luminescent material containing a triazole pyridine derivative is doped into 4,4',4''-tris(carbazol-9-yl)triphenylamine and 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] to form a light-emitting layer, and the doping mass concentration is 0.2% to 60%; the mass ratio of 4,4',4''-tris(carbazol-9-yl)triphenylamine to 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] is 0.5 to 1.5.

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