CN101161663A - Pyrazine ligand iridium complex and method for synthesizing same - Google Patents

Abstract

The present invention relates to a pyrazine-ligand iridium complex and the preparation method thereof, the technical proposal of which includes a pyrazine-ligand iridium complex with the structure shown by the formula on the right. The preparation includes the following procedures that: a) the pyrazine ligand is dissolved with glycol, into which N2 is inducted for 30 min, b) Iridium trichloride hydrate is added into the solution above, with calefaction with a microwave oven for 4-5 min, c)the mixture solution is cooled down under room temperature, and filtrated, the filter cake is rinsed with water and then with anhydrous ethanol, d) thin layer chromatography is carried out, in which the crude product is extracted with silica gel adopted as the stationary phase and chloroform adopted as the lotion and, e) the intended product is obtained through vacuum drying under 40 DEG C. The present invention accomplishes the coordination between pyrazine ligand and metal iridium under radiation of micro waves to obtain a novel tri-loop iridium complex, which is a good phosphorescence material excellent in solubility when kept in an organic solvent, and has huge potentials and applicable prospect as an electro-phosphorescence material to improve the illuminant efficacy of parts of apparatus.

Description

Pyrazine ligand iridium complex and its synthesis method

Technical field: The present invention relates to the field of a complex and its synthesis method, in particular to the field of a pyrazine iridium complex and its synthesis method.

Background technology: Since Tang of Kodak Company of the U.S. and Burroughes of University of Cambridge in 1990 introduced organic and macromolecular electroluminescent materials and devices respectively in 1987, organic light-emitting diode (hereinafter referred to as OLED) research has started in the global academic and industrial circles. upsurge. Compared with liquid crystal display, OLED has the advantages of fast response, wide viewing angle, flexible display, low temperature resistance, shock resistance, etc. Compared with cathode ray tube (CRT) technology, it has small size, light weight, high efficiency, high brightness, low Voltage DC drive, easy to realize large-area full-color display and many other advantages. The potential excellent performance of organic light-emitting diodes in the field of display technology has made it the most competitive technology in the third-generation flat panel display.

Emissive materials used in OLEDs can be divided into two categories. One is a fluorescent material, and the other is a phosphorescent material. The maximum internal quantum efficiency of the electroluminescent material is 25% because the fluorescent light-emitting material only relies on singlet exciton radiation to decay and emit light. Phosphorescent materials can achieve phosphorescence emission in which singlet and triplet luminescence are mixed through intersystem crossing. Theoretically, the internal quantum efficiency of OLEDs made of phosphorescent materials can reach 100%.

In recent years, studies have found that Ir ³⁺ complexes can produce strong spin-orbit coupling, which allows the originally forbidden triplet transition, and then can achieve strong phosphorescence emission. At present, the external quantum efficiency of tricyclic iridium complex phosphorescent devices reaches about 15%. For example, Baldo et al. doped the diphenylpyridine iridium complex Ir(ppy) ₃ (II) into the material TAZ(I), and obtained a phosphorescent device with an external quantum efficiency of (15.4±0.2)%. Tsuboyama et al. doped Ir(piq) ₃ (III) into CBP to obtain a phosphorescent device with an external quantum efficiency of 10.3%. The efficiency of phosphorescent devices depends on many factors, such as energy level matching between host and guest, excited state lifetime of host and guest, guest-guest orbital coupling, charge injection and transport, and triplet-triplet (TT) annihilation. The structure of organic ligands in metal complexes has a great influence on luminous efficiency and emission wavelength. Therefore, designing and synthesizing new metal complexes is of great significance for the development of phosphorescent materials with different luminescent colors.

SUMMARY OF THE INVENTION: The purpose of the present invention is to synthesize a new class of phosphorescent material pyrazine ligand iridium complexes with higher luminous quantum efficiency.

Another object of the present invention is to provide a method for synthesizing the iridium complex of pyrazine ligands.

In order to achieve the above object, the technical solution adopted in the present invention is: a pyrazine ligand iridium complex, which is characterized in that its structural formula is as follows:

Wherein, -R is -H or -CH ₃ ; -X is -H or -F.

The synthetic method of pyrazine ligand iridium complex, its synthetic steps are as follows:

a) Pyrazine ligands are dissolved in ethylene glycol and passed through N ₂ for 30 minutes;

b) Add iridium trichloride hydrate to the above solution, and microwave-assisted heating for 4 to 5 minutes;

c) The mixture is cooled at room temperature, filtered with suction, and the filter residue is washed with water and absolute ethanol successively;

d) thin-layer chromatography, using silica gel as a stationary phase and chloroform as an eluent to purify the crude product;

e) Vacuum drying at 40°C to obtain the target product.

Wherein, the proportioning of each material is:

The molar ratio of pyrazine ligands to iridium trichloride hydrate is 50-100:1;

The volume of adding 1mmol of pyrazine ligand to ethylene glycol is about 1-3mL.

The microwave-assisted heating has a temperature of 75-85°C.

The reaction mechanism is: bibenzoyl and alkyldiamine first undergo nucleophilic addition reaction to generate dihydropyrazine, and then undergo oxidation reaction under the action of tetrachlorobenzoquinone to generate pyrazine ligand.

The pyrazine ligand, in the medium of ethylene glycol, under the protection of nitrogen, undergoes coordination reaction with iridium trichloride to generate the pyrazine ligand iridium complex.

By comparing the ultraviolet absorption spectra of the pyrazine ligand and the iridium complex of the pyrazine ligand, it can be seen that the corresponding absorption peaks are all red-shifted. From this, it can be confirmed that a metal iridium complex was synthesized.

It can be seen from the fluorescence spectrum that the emission peak of the pyrazine ligand iridium complex has a larger red shift than that of the pyrazine ligand emission peak. Due to the strong orbital spin coupling of the Ir ³⁺ complex, the singlet excitons and triplet excitons of the complexes are mixed. On the one hand, triplet excitons have the properties of singlet excitons, the symmetry of triplet excitons is broken, and phosphorescence quenching is effectively suppressed; on the other hand, singlet states also have some properties of triplet states, The longer the decay time, the lower the fluorescence efficiency, which makes it possible to achieve phosphorescence at room temperature. The luminescence of iridium complexes of pyrazine ligands mainly comes from the phosphorescence emission of the triplet state of metal complexes.

The beneficial effects of the present invention are: the coordination of pyrazine ligands and metal iridium under microwave irradiation is realized through the present invention, and a novel tricyclic metal iridium complex is obtained. The complex has good solubility in common organic solvents and is a good phosphorescent material. By measuring the fluorescence spectrum, the Ir[DPP] synthesized as in Example ₂ has an excitation wavelength of 332nm, which shows a strong emission peak at 572.9nm, and is a better yellow-green phosphorescent material; synthesized as in Example 5 The Ir[MDPP] ₃ complex has an emission peak at 559nm and is a better green phosphorescent material. The complex Ir[DPP] ₃ was doped in TAZ, a small molecule material with good electron transport properties, and HMTPD was used as the hole transport layer. ^It was measured that the maximum external quantum efficiency of the device reached (16 ±0.1)%. It shows the great potential and application prospect of pyrazine ligand iridium complexes as electrophosphorescent materials in improving the luminous efficiency of devices.

Description of drawings:

Fig. 1 is the ¹ H NMR spectrogram of Ir[DPP] ₃ ;

Fig. 2 is the ¹ H NMR spectrogram of Ir[MDPP] ₃ ;

Fig. 3 is the ultraviolet absorption spectrogram of DPP and Ir[DPP] ₃ ; (wherein 1 is Ir[DPP] ₃ ; 2 is DPP)

Fig. 4 is the fluorescence spectrogram of DPP and Ir[DPP] ₃ ; (wherein 1 is Ir[DPP] ₃ ; 2 is DPP)

Fig. 5 is the fluorescence spectrogram of MDPP and Ir[MDPP] ₃ ; (wherein 3 is MDPP; 4 is Ir[MDPP] ₃ )

Detailed ways:

Material: Bibenzoyl (AR, Tianjin Guangfu Fine Chemical Research Institute)

Chlorobenzoquinone (AR, Tianjin Guangfu Fine Chemical Research Institute)

Iridium trichloride hydrate (AR, Shanghai Jiuyue Chemical Co., Ltd.)

Instrument: CXM-300 Precision Microscopic Melting Point Tester

FLASH EA1112 Elemental Analyzer

Varian Mercury-300 superconducting NMR instrument

Cary100-300 Fluorescence Spectrometer

Perkin Elmer Lambda 25 UV Spectrophotometer

Embodiment 1 2, the synthesis of 3-diphenylpyrazine ligand (DPP)

Weigh 10 g of bibenzoyl into a 100 mL round bottom flask, add 3.84 mL of ethylenediamine and 45 mL of absolute ethanol. Magnetic stirring, reflux for 30min, stop the reaction. After cooling at room temperature, pale yellow needle crystals were precipitated, recrystallized with absolute ethanol to obtain light yellow needle crystals as 2,3-dihydro-5,6-diphenylpyrazine (DPPH), dried in vacuo to obtain 5.33g, Yield 48.6%. m.p 162.5-163.5°C (literature value 166-167°C).

Weigh 4.4g DPPH and 4.62g chloranil in a 100mL round bottom flask, add 50mL xylene. Magnetic stirring, reflux for 7h to stop the reaction. The reaction mixture was cooled to room temperature, diluted with 40 mL of anhydrous ether, then treated with sodium hydroxide solution, and then the organic phase was treated with hydrochloric acid, and the acid layer was neutralized to neutral with sodium hydroxide solution, and light yellow-brown crystals were precipitated. That is 2,3-diphenylpyrazine (DPP). Vacuum dried to obtain 3.89 g, yield 87.6%. m.p.121.3-122.2°C (literature value 123-124°C).

The pyrazine ligand is characterized by measuring its melting point; as shown in Figure 3, DPP shows three absorption peaks at 224nm, 272nm and 286nm in the ultraviolet absorption spectrum.

Example 2 Synthesis of 2,3-diphenylpyrazine iridium complex (Ir[DPP] ₃ )

Weigh 1.760g (7.580mmol) of DPP into a 100mL three-necked flask, and add 10mL of ethylene glycol. Nitrogen was then passed for 30 min to remove the oxygen in the flask. Another 0.053 g (0.152 mmol) IrCl ₃ ·3H ₂ O was added rapidly. Under the protection of N ₂ , microwave heating (80° C.) and reflux for 4 min. Cool at room temperature, and filter the precipitate with suction. Wash with water and ethanol respectively. The crude product was purified by thin-layer chromatography using silica gel as the stationary phase and chloroform as the expanding agent. After vacuum drying, 0.036 g of an orange-red solid was obtained, with a yield of 51%.

Element test results (theoretical value): C: 64.58% (65.07%); H: 4.03% (3.75%); N: 9.25% (9.49%).

As shown in Figure 1, ¹ HNMR analysis shows that δ=9.1ppm is the proton absorption peak (3H) on the pyrazine ring at a, and δ=8.0ppm is the proton absorption peak (3H) on the pyrazine ring at b; δ=7.8 ppm is the proton absorption peak (6H) on the benzene ring coordinated with iridium at c place; δ=7.5ppm is the proton absorption peak (9H) on the benzene ring not coordinated with iridium at d place; δ=6.1ppm, δ =6.5ppm, δ=6.6ppm, δ=6.9ppm are respectively the absorption peaks of protons on the benzene ring at e, f, g, and h (both are 3H).

The obtained compound was confirmed to be the target product by elemental analysis and NMR methods.

As shown in Figure 3, the UV absorption spectrum of Ir[DPP] ₃ shows three absorption peaks at 227nm, 283nm and 343nm.

As shown in Figure 4, the excitation wavelength in the fluorescence spectrum of Ir[DPP] ₃ is 332nm, which shows a strong phosphorescent emission of the metal complex triplet state at 572.9nm.

Example 3

Weigh 1.760g (7.580mmol) of DPP into a 100mL three-necked flask, and add 10mL of ethylene glycol. Nitrogen was then passed for 30 min to remove the oxygen in the flask. Then 0.030 g (0.085 mmol) IrCl ₃ ·3H ₂ O was added rapidly. Under the protection of N ₂ , microwave heating (80° C.) and reflux for 4 min. Cool at room temperature, and filter the precipitate with suction. Wash with water and ethanol respectively. The crude product was purified by thin-layer chromatography using silica gel as the stationary phase and chloroform as the expanding agent. Vacuum drying gave 0.035 g of orange-red solid Ir[DPP] ₃ with a yield of 47%.

Embodiment 4 5-methyl-2, the synthesis of 3-diphenylpyrazine ligand (MDPP)

Weigh 10g of bibenzoyl into a 100mL reaction bottle, add 45mL of fresh absolute ethanol, slowly add 4.89mL of 1,2-propylenediamine dropwise to the above reaction solution under stirring at room temperature, and then reflux for 0.5h The reaction mixture was cooled to room temperature, the precipitate was filtered, and recrystallized with absolute ethanol. Washed with absolute ethanol and dried under vacuum to obtain 7.55 g of 2-methyl-2,3-dihydro-5,6-diphenylpyrazine (MDPPH) as a light yellow solid, with a yield of 64.9%. m.p.121～122℃

Weigh 5.0g MDPPH, 5.29g chloranil and measure 47mL xylene in a 100mL reaction flask, stir and reflux for 7h, cool the reaction mixture to room temperature, dilute with anhydrous ether, and then treat with sodium hydroxide solution , and then treat the organic phase with hydrochloric acid, and the acid layer is neutralized to neutral. The precipitate was filtered and vacuum-dried to obtain 4.08 g of the product (MDPP) as a light pink solid, with a yield of 82.3%. m.p.91～92℃.

Example 5 Synthesis of 5-methyl-2,3-diphenylpyrazine iridium complex (Ir[MDPP] ₃ )

Weigh 3.00g (12.18mmol) of MDPPH into a 100mL three-necked flask, and add 15mL of ethylene glycol. Nitrogen was then passed for 30 min to remove the oxygen in the flask. Another 0.049 g (0.14 mmol) IrCl ₃ ·3H ₂ O was added rapidly. Under the protection of N ₂ , microwave heating (80° C.) and reflux for 5 min. Cool at room temperature, filter the precipitate with suction, and wash with water and absolute ethanol respectively. The crude product was purified by thin-layer chromatography using silica gel as the stationary phase and chloroform as the expanding agent. After vacuum drying, 0.068 g of an orange solid was obtained, with a yield of 52%.

As shown in Figure 2, ¹ HNMR analysis shows that δ=9.0ppm is the proton absorption peak (3H) on the pyrazine ring at a, and δ=2.3ppm is the methyl proton absorption peak (9H) on the pyrazine ring at b; δ =7.7ppm is the proton absorption peak (6H) on the benzene ring coordinated with iridium at c place; δ=7.6ppm is the proton absorption peak (9H) on the benzene ring not coordinated with iridium at d place; δ=6.0ppm , δ=6.4ppm, δ=6.6ppm, δ=6.7ppm are the absorption peaks of protons on the benzene ring at e, f, g, and h respectively (both are 3H).

As shown in Figure 5, the excitation wavelength in the fluorescence spectrum of Ir[MDPP] ₃ is 346nm, which shows a strong phosphorescent emission of the metal complex triplet state at 559nm.

Example 6

Weigh 3.00 g (12.18 mmol) of 5-methyl-2,3-diphenylpyrazine into a 100 mL three-necked flask, and add 15 mL of ethylene glycol. Nitrogen was then passed for 30 min to remove the oxygen in the flask. Then 0.043 g (0.12 mmol) IrCl ₃ ·3H ₂ O was added rapidly. Under the protection of N ₂ , microwave heating (80° C.) and reflux for 5 min. Cool at room temperature, filter the precipitate with suction, and wash with water and absolute ethanol respectively. The crude product was purified by thin-layer chromatography using silica gel as the stationary phase and chloroform as the expanding agent. After vacuum drying, 0.053 g of an orange solid (Ir[MDPP] ₃ ) was obtained, with a yield of 50%.

Example 7 Synthesis of 4,4'-difluoro-2,3-diphenylpyrazine (DPPF)

Weigh 2.4g of 4,4'-difluorobibenzoyl into a 100mL reaction bottle, add 20mL of fresh absolute ethanol, slowly add 1.0mL of ethylenediamine dropwise to the above reaction solution at room temperature with stirring, Then reflux for 0.5h. The reaction mixture was cooled to room temperature, then poured into distilled water to obtain 2.04 g of yellow crystals as 4,4'-difluoro-2,3-dihydro-5,6-diphenylpyrazine (DPPFH), yield 78% . m.p.108-113°C.

Weigh 2.04g of 4,4′-difluoro-2,3-dihydro-5,6-diphenylpyrazine, 2.0g of chlorobenzoquinone and 25mL of xylene in a 100mL reaction flask, and stir and reflux for 7h. The reaction mixture was cooled to room temperature, diluted with anhydrous ether, then treated with sodium hydroxide solution, and the upper layer was separated. The organic phase was treated with hydrochloric acid, and the acid layer was neutralized to neutrality. The precipitate was filtered and vacuum-dried to obtain 1.68 g of the product (DPPF) as a yellow-brown solid, with a yield of 82%. m.p.121-122°C.

Preparation of Example 8 Complex [Ir(DPPF) ₃ ]

Weigh 0.966g (3.60mmol) of 4,4'-difluoro-2,3-diphenylpyrazine (DPPF) into a 100mL three-necked flask, and add 10mL of ethylene glycol. Then pass nitrogen gas for 30min. Then 0.0169 g (0.048 mmol) IrCl ₃ ·3H ₂ O was added rapidly. Under the protection of N ₂ , microwave heating (80° C.) and reflux for 5 min. Cool at room temperature, filter with suction, and wash with water and absolute ethanol respectively. The crude product was purified by thin-layer chromatography using silica gel as the stationary phase and chloroform as the expanding agent. After vacuum drying, 0.026 g of a brick red solid was obtained, with a yield of 54%.

Claims (4)

1. pyrazine ligand iridium complex is characterized in that its structural formula is as follows:

Wherein ,-R is-H or-CH ₃-X is-H or-F.

2. the synthetic method of the described pyrazine ligand iridium complex of claim 1 is characterized in that synthesis step is as follows:

A) pyrazine ligand is dissolved in the ethylene glycol, logical N ₂30min;

B) in above-mentioned solution, add the hydration iridous chloride, microwave-assisted heating 4～5min;

C) mixed solution room temperature cooling, suction filtration, filter residue is water, absolute ethanol washing successively;

D) tlc is that stationary phase, trichloromethane are the leacheate thick product of purifying with silica gel;

E), get target product 40 ℃ of following vacuum-dryings.

3. the synthetic method of pyrazine ligand iridium complex according to claim 2, it is characterized in that: the proportioning of each material is:

The mol ratio of pyrazine ligand and hydration iridous chloride is 50～100: 1;

The volume that the 1mmol pyrazine ligand adds ethylene glycol is 1～3mL.

4. the synthetic method of pyrazine ligand iridium complex according to claim 2 is characterized in that described microwave-assisted heating, and temperature is 75～85 ℃.

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