CN1696137A - Red light iridium complexes with quinoline nitrogen heterocycles as ligands and their applications - Google Patents

Abstract

The invention relates to an iridium complex based on a quinoline nitrogen heterocycle as a ligand, a preparation method thereof and an application as a red light material in an organic electroluminescence device. A series of quinoline nitrogen heterocycles are selected as ligands to coordinate with iridium (III) to form iridium (III) complexes; and the iridium (III) complexes are doped on the In the host material, multi-layer devices or single-layer devices are constructed to achieve high-efficiency red light emission. Compared with other red light ligands, quinoline ligands have the characteristics of easy synthesis and purification, and the corresponding complexes maintain a short lifespan and high efficiency, which provides the possibility for the construction of high-efficiency electroluminescent devices sex.

Description

Red light iridium complexes with quinoline nitrogen heterocycles as ligands and their applications

technical field

The invention relates to an iridium complex based on a quinoline nitrogen heterocyclic ring as a ligand and its application as a red light material in an organic electroluminescent device.

technical background

Since CW Tang et al. first reported the electroluminescence phenomenon of octahydroxyquinoline aluminum (Alq ₃ ) in 1987, the research on organic light-emitting diodes has aroused widespread interest in academia and industry. According to spin statistics theory, in most organic light-emitting diodes, the ratio of singlet excitons to triplet excitons generated is 1:3. The triplet excitons exhibit non-radiative decay due to their long lifetime and spin-forbidden nature, which limits the internal quantum efficiency of devices to no more than 25%. However, due to the heavy atom effect of metal atoms, transition metal complexes lead to strong spin-orbit coupling, which increases the effective intersystem crossing between singlet and triplet states, that is, using transition metal complexes as Electroluminescent materials can make full use of all energy forms including singlet and triplet states, greatly improve the efficiency of devices, and theoretically make the internal quantum efficiency of devices reach 100%.

The transition metal complexes currently used as electroluminescent materials mainly include heavy metal complexes such as Ir(III), Pt(II), Os(II), Re(I), and Cu(I). Among them, iridium complexes are widely used in electroluminescent devices due to their short lifetime and high efficiency, and have achieved red, green and blue three-primary color luminescence.

The emission color of iridium complexes strongly depends on the structure of the ligand, therefore, we can choose the appropriate ligand to adjust the emission color. At present, the ligands used to obtain high-efficiency red light in iridium complexes mainly include 2-(2-benzothienyl)pyridine and 1-phenylisoquinoline. The synthesis methods of these ligands are complex and not easy to synthesize in large quantities. Therefore, it is necessary to design ligands that are relatively easy to synthesize and purify for efficient red-emitting iridium complexes.

Contents of the invention

The purpose of the present invention is to provide a red light iridium complex electroluminescent material based on quinoline nitrogen heterocycle as a ligand.

The present invention designs and synthesizes a series of quinoline nitrogen heterocyclic rings as ligands, coordinates with iridium (III) to form complexes; and the iridium (III) complexes are doped by vacuum evaporation or solution spin coating In the host material, multi-layer devices or single-layer devices are constructed for efficient red emission. Compared with other red light ligands, quinoline ligands have the characteristics of easy synthesis and purification, and the corresponding complexes maintain a short lifespan and high efficiency, which provides the possibility for the construction of high-efficiency electroluminescent devices sex.

The iridium (III) complexes synthesized by the present invention are all mononuclear six-coordination structures, and have the following basic structures:

In the general structure Represents a bidentate ligand with carbon and nitrogen as coordinating atoms, with the following structure:

Wherein, _R is selected from hydrogen, fluorine, trifluoromethyl, cyano, C1-C30 alkyl, C1-C20 alkoxy, C6-C30 aryl, C6-C30 fused aromatic ring group, C2-C30 heteroaryl; Ar1 is selected from one of the following aromatic structural units:

Wherein R ₂ , R ₄ , R ₆ are C1-C30 alkyl; R ₅ is hexyl or octyl; R ₃ is C1-C30 alkyl or C1-C20 alkoxy at any substitution position; R ₇ is selected From hydrogen, C1-C30 alkyl, C1-C20 alkoxy, C6-C30 aryl; R ₈ is C1-C30 alkyl or C1-C20 alkoxy; X is oxygen or sulfur atom.

In the above-mentioned complexes of the present invention, Ar1 is preferably selected from one of the following fused ring aromatic structural units:

R ₃ is C1-C30 alkyl or C1-C20 alkoxy at any substitution position

The above-mentioned complex of the present invention has the following structure:

The above-mentioned complex of the present invention has the following structure:

All quinoline ligands were prepared by Friedlnder reaction. The reaction is catalyzed by concentrated H ₂ SO ₄ , and ice HAc is used as solvent, and the reaction is refluxed for 16-24 hours. The resulting product is purified by recrystallization or column separation.

配体与三氯化铱反应生成含氯桥的中间体；然后，氯桥被乙酰丙酮(acac)取代生成铱(III)配合物。All iridium(III) complexes are prepared by two-step reactions. first,

The ligand reacts with iridium trichloride to generate an intermediate containing a chlorine bridge; then, the chlorine bridge is replaced by acetylacetone (acac) to generate an iridium(III) complex.

According to the present invention, an organic electroluminescent device has one or more organic thin layers formed between the first electrode and the second electrode, wherein at least one organic layer comprises one or more of the above-mentioned compounds of the present invention. Complex

The light-emitting layer of the electroluminescent device can be prepared by vacuum co-evaporation. The process is as follows: the iridium (III) complex and the small molecule host material are evaporated simultaneously under vacuum conditions, and the two independent quartz crystal oscillators are used to Control the evaporation rate of each, so as to control the content of both. At the same time, a hole transport layer is introduced between the anode ITO and the light-emitting layer by vacuum evaporation, and one or two organic small molecule layers with hole blocking or electron transport functions are introduced between the metal cathode and the light-emitting layer to form a multilayer structure. device. Small molecules used as host materials include 4,4'-N,N'-dicarbazole biphenyl (CBP), 2-(4-diphenyl)-5-(4-tert-butylphenyl)-1 , 3,4-oxadiazole (PBD), 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI), 3-(4-diphenyl)-5-(4 -tert-butylphenyl)-4-(4-ethylphenyl)-1,2,4-triazole (TAZ) and the like. In the light-emitting layer, the weight ratio of the iridium (III) complex to the host material is 1-9:100.

The light-emitting layer of the electroluminescent device can also be prepared by solution spin coating, and the process is as follows: the iridium (III) complex and the polymer host material are blended, dissolved in chloroform CHCl ₃ , and spin-coated on the polythiophene derivative (PEDOT) modified or not modified ITO glass surface, prepared into a light-emitting layer. Polymers used as host materials include: polyphenylene, polyphenylene, polyvinylcarbazole, polycarbazole, polyfluorene or polyfluorene derivatives. The weight ratio of the iridium (III) complex to the polymer host material is 1-9:100. In addition, the light-emitting layer can be further mixed with small molecule carrier transport materials: 2-(4-diphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole ( PBD), 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI), 3-(4-diphenyl)-5-(4-tert-butylphenyl)-4 -(4-Ethylphenyl)-1,2,4-triazole (TAZ), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-1,1'-diphenyl-4,4'-diamine (TPD), or N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-diphenyl-4, 4'-diamine (NPB). In device assembly, after spin-coating the light-emitting layer, metal electrodes can be directly evaporated to form a single-layer device; vacuum evaporation can also be used to further introduce one or two layers with hole blocking or electron transport properties between the metal electrode and the light-emitting layer. Functional organic small molecule layers to construct multilayer devices.

Description of drawings

The present invention will be more clearly understood through the detailed description of exemplary embodiments in conjunction with the accompanying drawings, wherein:

Figure 1 shows the ultraviolet-visible absorption (UV-Vib) spectrum and photoluminescence (PL) fluorescence spectrum of compound (1-NAPQ) ₂ Ir (acac) and (TPAPQ) ₂ Ir (acac) in dichloromethane solution;

Fig. 2 provides the brightness-voltage curve of the organic EL device that embodiment 2 makes;

Fig. 3 provides the variation curve of the luminous efficiency and power efficiency of the organic EL device that embodiment 2 makes with brightness;

Fig. 4 provides the EL spectrum of the organic EL device that embodiment 1 and 2 manufactures

Detailed ways

The present invention is described in detail with reference to the following examples, which are for illustrative purposes and are not intended to limit the scope of the present invention.

<Reaction 1>

Synthesis Example 1: Synthesis of Complex (1-NAPQ) ₂ Ir(acac)

(1) Synthesis of Ligand 1-NAPQ

Dissolve 1.97g (10mmol) o-aminobenzophenone and 1.70g (10mmol) 1-naphthophenone in 15ml glacial acetic acid, slowly add 0.1ml concentrated sulfuric acid dropwise, stir, and heat to reflux. After reacting for 18 hours, it was cooled to room temperature. The reaction mixture was slowly poured into a mixed solution consisting of 40 ml of water and 15 ml of concentrated ammonia water. The precipitate was sticky, extracted with dichloromethane, washed repeatedly with water, dried over anhydrous Na ₂ SO ₄ , filtered, the solvent was evaporated by rotary evaporation, and purified by column separation to obtain 2.85 g of the product (yield 86%).

(2) Synthesis of chlorine-bridged dimers

Take 1.46g (4.4mmol) of ligand 1-NAPQ and 0.705g (2mmol) of IrCl ₃ 3H ₂ O into a 50ml round-bottomed flask, then add 30ml of ethylene glycol monoethyl ether, 10ml of distilled water, and repeatedly ventilate 3 times. Stir and heat under the protection of argon, raise the temperature to 130-140 ° C, reflux for 36 hours, filter, and wash the obtained precipitate with ethanol and distilled water, dry, and column separation and purification to obtain 1.28 g of dimer (yield 72%)

(3) Synthesis of complex (1-NAPQ) ₂ Ir(acac)

Take dimer 0.89g (0.5mmol), acetylacetone (acac) 0.20g (2mmol), anhydrous sodium carbonate 0.53g (5mmol), ethylene glycol monomethyl ether 30ml, add to a 50ml round bottom flask, and ventilate repeatedly 3 times, stirred and heated under argon protection, raised the temperature to 130-140°C, refluxed for 24 hours, filtered, and the obtained solid was separated by column chromatography using a mixed solvent (petroleum ether/dichloromethane=2/1) to obtain the final Product 500 mg. (yield 53%)

(4) Structural analysis of complex (1-NAPQ) ₂ Ir(acac)

The structure of the compound was confirmed by NMR and elemental analysis.

¹ H NMR (300MHz, CDCl ₃ ): δ1.54(s, 6H), 4.60(s, 1H), 6.88(d, J=8.2Hz, 2H), 7.04(d, J=8.4Hz, 2H), 7.29(t, J=7.4Hz, 2H), 7.37-7.40(m, 4H), 7.50(t, J=7.6Hz, 2H), 7.56-7.75(m, 12H), 7.85(d, J=7.2Hz , 2H), 8.38(d, J=8.6Hz, 2H), 8.62(s, 2H), 8.72(d, J=8.5Hz, 2H).

Theoretical (C ₅₅ H ₃₉ N ₂ O ₂ Ir): C, 69.38; H, 4.13; N, 2.94. Found: C, 69.30; H, 4.38; N, 2.69.

<Reaction 2>

Synthesis Example 2: Synthesis of Complex (TPAPQ) ₂ Ir(acac)

The synthesis method is similar to Synthesis Example 1.

(1) Synthesis of Ligand TPAPQ

Dissolve 1.97g (10mmol) of o-aminobenzophenone and 2.87g (10mmol) of 4-diphenylaminoacetophenone in 15ml of glacial acetic acid, slowly add 0.1ml of concentrated sulfuric acid dropwise, stir, and heat to reflux. After reacting for 20 hours, it was cooled to room temperature. The reaction mixture was slowly poured into a mixed solution consisting of 40 ml of water and 15 ml of concentrated ammonia water. The precipitate was sticky, extracted with dichloromethane, washed repeatedly with water, dried over anhydrous Na ₂ SO ₄ , filtered, the solvent was removed by rotary evaporation, and purified by column separation to obtain 3.59 g of the product (yield 80%).

(2) Synthesis of chlorine-bridged dimers

Take 1.97g (4.4mmol) of ligand 1-NAPQ and 0.705g (2mmol) of IrCl ₃ 3H ₂ O into a 50ml round bottom flask, then add 30ml of ethylene glycol monoethyl ether, 10ml of distilled water, and repeatedly ventilate 3 times. Stir and heat under the protection of argon, raise the temperature to 130-140°C, reflux for 48 hours, filter, and wash the obtained precipitate with ethanol and distilled water, dry, and column separation and purification to obtain dimer 1.46g (yield 65%)

(3) Synthesis of complex (TPAPQ) ₂ Ir(acac)

Take dimer 1.12g (0.5mmol), acetylacetone (acac) 0.20g (2.0mmol), anhydrous sodium carbonate 0.53g (5mmol), ethylene glycol monomethyl ether 30ml, put into a 50ml round bottom flask, and change repeatedly Gas 3 times, stirred and heated under the protection of argon, the temperature was raised to 130-140 ° C, refluxed for 24 hours, filtered, and the obtained solid was separated and purified by column separation to obtain 530 mg of the final product (yield 45%).

(4) Structural analysis of complex (TPAPQ) ₂ Ir(acac)

The structure of the compound was confirmed by NMR and elemental analysis.

¹ H NMR (300MHz, CDCl ₃ ): δ1.62(s, 6H), 4.77(s, 1H), 6.25(d, J=2.1Hz, 2H), 6.55(dd, J=8.5, 2.0Hz, 2H ), 6.80-6.91(m, 20H), 7.42-7.59(m, 16H), 7.68(s, 2H), 7.74(d, J=8.1Hz, 2H), 8.58(d, J=8.6Hz, 2H)

Theoretical (C ₇₁ H ₅₃ N ₄ O ₂ Ir): C, 71.88; H, 4.50; N, 4.72. Found: C, 71.10; H, 4.49; N, 4.52.

Example 1:

For the given examples, organic EL devices were fabricated in CBP host materials using complex (1-NAPQ) ₂ Ir(acac) doping. First, 50 nm of N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-diphenyl-4,4'- Diamine (NPB) serves as the hole transport layer. Then, CBP was deposited on the hole transport layer to form a 30nm light-emitting layer, which was doped with 3% (1-NAPQ) ₂ Ir(acac). Finally, an upper hole blocking layer (BCP: 10mm), an electron transport layer (Alq ₃ : 40nm), an interface layer (LiF: 1nm) and a cathode (Al: 100nm) were deposited in sequence.

The resulting EL device has a luminous efficiency of 2.2cd/A at a brightness of 100cd/ ^m2 , an external quantum efficiency of 3.0%, an emission peak at 642nm, a half-maximum width of 35nm, and a color coordinate CIE value of x=0.71, y=0.29 .

Example 2:

For this example, an organic EL device was fabricated in a CBP host material using complex (TPAPQ) ₂ Ir(acac) doping. First, 50 nm of N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-diphenyl-4,4'- Diamine (NPB) serves as the hole transport layer. Then, CBP was deposited on the hole transport layer to form a 30nm light-emitting layer, which was doped with 7% (TPAPQ) ₂ Ir(acac). Finally, an upper hole blocking layer (BCP: 10nm), an electron transport layer (Alq ₃ : 40nm), an interface layer (LiF: 1nm) and a cathode (Al: 100nm) were deposited in sequence.

The resulting EL device has a luminous efficiency of 12.2cd/A at a brightness of 100cd/ ^m2 , an external quantum efficiency of 9.0%, an emission peak at 616nm, a half-maximum width of 48nm, and a color coordinate CIE value of x=0.67, y=0.32 .

Claims (5)

1. complexes of red light iridium that nitrogen heterocycles in quinoline is a part has following basic structure:

In the general structure

Representative is the bidentate ligand of ligating atom with carbon and nitrogen, has following structure:

Wherein, R ₁Be selected from aryl, the C6-C30 condensed aromatic ring yl of alkoxyl group, the C6-C30 of alkyl, the C1-C20 of hydrogen, fluorine, trifluoromethyl, cyano group, C1-C30, the heteroaryl of C2-C30; Ar1 is selected from a kind of in the following aromatic structure unit:

R wherein ₂, R ₄, R ₆Alkyl for C1-C30; R ₅Be hexyl or octyl group; R ₃Be the arbitrarily alkyl of the C1-C30 of the position of substitution or the alkoxyl group of C1-C20; R ₇Be selected from the alkyl of hydrogen, C1-C30, the alkoxyl group of C1-C20, the aryl of C6-C30; R ₈Be the alkyl of C1-C30 or the alkoxyl group of C1-C20; X is oxygen or sulphur atom.

2. an organic electroluminescence device has one or more layers organic thin layer that forms between first electrode and second electrode, and wherein one deck organic layer comprises one or more title complexs as claimed in claim 1 at least.

3. title complex as claimed in claim 1, Ar1 preferentially are selected from a kind of in the following condensed ring aromatic structure unit:

R ₃Be the arbitrarily alkyl of the C1-C30 of the position of substitution or the alkoxyl group of C1-C20.

4. title complex as claimed in claim 1 has following structure:

5. title complex as claimed in claim 1 has following structure:

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