TWI651309B - A bipolar host material based on spiro [fluorene-9,2'-imidazole], synthesis method and application thereof - Google Patents

Abstract

The invention relates to a bipolar host material based on spiro[芴-9,2'-imidazole], a synthesis method and application thereof, and belongs to the field of organic electronic materials. A bipolar host material, a compound having the structure of the formula (I), wherein R ₁ -R ₃ are a C1-C4 alkyl group or an alkoxy substituted or unsubstituted acridinyl group, a phenothiazine group, an anthracene Azyl, diphenylamine, hydrogen, halogen. Experiments have shown that the bipolar host material of the present invention has a high glass transition temperature, and the bipolar host material facilitates carrier injection and transport balance.

Description

Bipolar host material based on spiro[芴-9,2'-imidazole], synthesis method and application thereof

The invention relates to a novel bipolar host material, belonging to the technical field of organic luminescent materials, in particular to a bipolar material with a snail [芴-9, 2'-imidazole] as a central core and an application thereof.

The organic light-emitting diode (OLED) has the characteristics of high speed, low energy consumption, high brightness, wide viewing angle, bendability and active illumination, and has been highly valued by the scientific community and the industry. Its application in display, lighting and other aspects has great potential. Electroluminescence and electrophosphorescence are referred to as first generation and second generation OLEDs, respectively. OLED based on fluorescent materials has high stability, but is limited by the law of quantum statistics. Under the action of electric start, the ratio of singlet excitons to triplet excitons is 1:3, so the fluorescent material The internal quantum efficiency of electroluminescence is only 25%. The phosphorescent material has a spin-orbit coupling effect of heavy atoms, which can comprehensively utilize singlet excitons and triplet excitons, and the theoretical internal quantum efficiency can reach 100%. Phosphorescent materials have become the main luminescent material in the market. However, phosphorescent-based OLEDs have a significant efficiency roll-off effect, which is a hindrance in high-brightness applications. In addition, phosphorescent materials require the use of expensive metals such as Pt, Ir, etc., so the price of phosphorescent materials is relatively high. Typically, phosphorescent materials are doped in organic host materials in OLED devices.

Phosphorescent materials can utilize singlet excitons and triplet excitons in combination to achieve 100% internal quantum efficiency. However, since the excited state exciton lifetime of the transition metal complex is relatively long, the triplet-triplet state (T ₁ -T ₁ ) is quenched in the actual operation of the device. To overcome this problem, researchers often dope phosphorescent materials into organic host materials. Therefore, for high-efficiency organic light-emitting diodes, it is important to develop high-performance host materials as well as guest materials.

At present, the main material widely used in phosphorescent devices is CBP (4,4'-bis(9-carbazolyl)biphenyl), but it requires a higher driving voltage and a lower glass transition temperature (T _g ) (T _g = 62 ° C), easy to crystallize. In addition, CBP is a P-type material, the hole mobility is much higher than the electron mobility, which is not conducive to carrier injection and transmission balance, and the luminous efficiency is low.

The present invention provides a bipolar host material with a high driving voltage, a glass transition temperature, easy crystallization, a carrier injection and a transmission imbalance, etc., which are snails [芴-9, 2'-Imidazole] As a strong-centered electron core, a derivative such as diphenylamine, carbazole or acridine having strong electron donating ability is used as a linking group to form a DA-type or DAD-type bipolar host material.

a bipolar host material based on spiro[芴-9,2'-imidazole], a compound having the structure of formula (I),

Wherein R ₁ , R ₂ , R _{3 are} represented by C1-C4 alkyl or alkoxy substituted or unsubstituted acridinyl, phenothiazine, carbazolyl, diphenylamino, hydrogen, halogen, R ₁ , At least one of R ₂ and R _{3 is} a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazolyl group, or a diphenylamino group.

Preferably, R ₁ represents a C1-C4 alkyl group or an alkoxy substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazolyl group, a diphenylamino group, and at least one of R ₂ and R ₃ is a C1-C4 alkane. Alkyl or alkoxy substituted or unsubstituted acridinyl, phenothiazine, oxazolyl, diphenylamino, the remainder being hydrogen.

Preferably, R ₁ and R ₃ are a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, an oxazolyl group, or a diphenylamino group.

Preferably, R ₁ and R _{3 are the} same.

The compound of formula (I) has the following structure:

An organic semiconductor diode device comprising a cathode, an anode and an organic layer, the organic layer being one or more of a hole transport layer, a hole blocking layer, an electron transport layer, and a light-emitting layer. It is particularly noted that the above organic layers may be present in each of the layers as needed.

The compound of the formula (I) is a material of the light-emitting layer.

The organic layer of the electronic device of the present invention has a total thickness of from 1 to 1000 nm, preferably from 1 to 500 nm, more preferably from 5 to 300 nm.

The organic layer may be formed into a film by steaming or spin coating.

As mentioned above, the compounds of formula (I) of the present invention are as follows, but are not limited to the structures listed:

The preparation method of the above bipolar material comprises the following preparation steps:

First, a halogen-substituted arylethanedione (a) is reacted with a halogen-substituted or unsubstituted 9-fluorenone (b) under ammonium acetate and acetic acid to obtain a halogen-substituted 4',5'-diaryl snail (芴-9,2'-imidazole) (c), the last halogen-substituted 4',5'-diaryl spiro (芴-9,2'-imidazole) (c) with a C1-C4 alkyl or alkoxy group The substituted or unsubstituted acridine, phenothiazine, oxazole, diphenylamine (d) is subjected to a palladium catalyzed Buchwald reaction to give the bipolar host material.

Experimental table experiments show that the bipolar host material of the present invention has a high glass transition temperature (Tg = 158 ° C), and the bipolar host material facilitates carrier injection and transport balance.

Compound a is obtained by reoxidation of phenylacetylene and p-iodo halogen benzene by Sonogashira coupling reaction; compound b is commercially available; and compound d is commercially available.

10‧‧‧ glass substrate

20‧‧‧Anode

30‧‧‧ hole injection layer

40‧‧‧ hole transport layer

50‧‧‧Lighting layer

60‧‧‧ hole blocking layer

70‧‧‧Electronic transport layer

80‧‧‧electron injection layer

90‧‧‧ cathode

Figure 1 is a DSC curve of Compound 2; 2 is a structural view of the device of the present invention, wherein 10 represents a glass substrate, 20 represents an anode, 30 represents a hole injection layer, 40 represents a hole transport layer, 50 represents a light-emitting layer, and 60 represents a hole blocking layer. 70 represents an electron transport layer, 80 represents an electron injection layer, and 90 represents a cathode.

The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Synthesis of 4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (c1)

The synthetic route is as follows:

The specific synthesis steps are:

Weigh 1-(4-bromophenyl)-2-phenylethyl-1,2-dione (14.5 g, 50 mmol) (a1) (prepared by Sonogashira coupling reaction, reoxidation), 9-fluorenone (7.2 g, 40 mmol) (b1), ammonium acetate (19.2 g, 250 mmol), 150 mL of glacial acetic acid in a 250 mL round bottom flask, warmed to reflux and stirred for 16 hours. After completion of the reaction, it was naturally cooled to room temperature, poured into 200 mL of purified water to precipitate a yellow solid. The core funnel was suction filtered and washed. Separation by gel column chromatography gave 9.9 g of a yellow solid. Yield: 55%.

(2) 9,9-Dimethyl-10-[4-[4'-phenylspiro(芴-9,2'-imidazole)-5'-yl]phenyl]-9,10-dihydroanthracene Synthesis of pyridine (1)

The synthetic route is as follows:

The specific synthesis steps are:

Weigh 4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (0.9g, 2mmol) ( c1 ),9,9-dimethyl-9,10 - Dihydroacridine (0.46 g, 2.2 mmol) ( d1 ), Pd ₂ (dba) ₃ (0.18 g, 0.2 mmol), NaOtBu (0.39 g, 4 mmol) in a 25 mL three-neck flask, and exchanged nitrogen three times. A solution of tri-tert-butylphosphine in toluene (0.15 g, 0.42 mmol) was dissolved in 10 mL of dry toluene and poured into a reaction flask. The temperature was refluxed for 16 hours. After the reaction was completed, a 5% solution of sodium hydrogensulfite was added, and the mixture was extracted with dichloromethane. The mixture was filtered through a celite funnel, and the solvent was evaporated to dryness eluting with hexane: ethyl acetate = 10:1 as eluent. Further, it was dissolved in 4 mL of dichloromethane, and 20 mL of methanol was added thereto, and the mixture was allowed to stand in a refrigerator at 5 ° C to obtain 0.85 g of a yellow crystal. Yield: 73%. The product identification data is as follows: ¹ H NMR (400 MHz, CDCl ₃ ) δ = 8.02 - 7.94 (m, J = 8.3 Hz, 2 H), 7.80 (d, J = 7.1 Hz, 2 H), 7.83 (d, J = 7.8 Hz, 2 H), 7.53 (d, J = 7.3 Hz, 1 H), 7.51-7.37 (m, 8 H), 7.30-7.22 (m, 2 H), 7.05-6.90 (m, 6 H), 6.37-6.31 (m, J = 8.1 Hz, 2 H). ¹³ C NMR (100 MHz, CDCl ₃ ) δ = 168.5, 167.9, 143.7, 142.4, 140.6, 138.7, 132.2, 132.1, 131.9, 131.5, 131.0, 130.3, 129.8, 129.2, 128.6, 128.0, 126.4, 125.4, 123.2, 121.0, 121.0, 114.1, 110.3, 53.5, 36.1, 31.2 ppm. Ms (ESI: Mz 577) (M+1)

Example 2

(1) Synthesis of 2-bromo-4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (c2)

The synthetic route is as follows:

Weigh 1-(4-bromophenyl)-2-phenylethyl-1,2-dione (4.34 g, 15 mmol) (a1) (prepared by Sonogashira coupling reaction, reoxidation), 2-bromo- 9-fluorenone (3.89 g, 15 mmol), ammonium acetate (5.8 g, 75 mmol), 30 mL of glacial acetic acid in a 50 mL round bottom flask, warmed to reflux and stirred for 16 hours. After completion of the reaction, it was naturally cooled to room temperature, poured into 100 mL of purified water to precipitate a yellow solid. The core funnel was suction filtered and washed. Separation by gel column chromatography gave 4.1 g of a yellow solid. Yield: 52%.

(2) 10-(4-(2-(9,9-Dimethylacridin-10(9H)-yl)-4'-phenylspiro(芴-9,2'-imidazole)-5'- Synthesis of phenyl]-9,9-dimethyl-9,10-dihydroacridine (2)

The synthetic route is as follows:

The specific synthesis steps are:

Weigh 2-bromo-4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (1g, 1.9mmol) ( c2 ),9,9-dimethyl -9,10-Dihydroacridine (0.79 g, 3.8 mmol) ( d1 ), Pd ₂ (dba) ₃ (0.18 g, 0.2 mmol), NaOtBu (0.73 g, 7.6 mmol) in a 25 mL three-neck flask, with nitrogen three times. A solution of tri-tert-butylphosphine in toluene (0.12 g, 0.6 mmol) was dissolved in 10 mL of dry toluene and poured into a reaction flask. The temperature was refluxed for 16 hours. After the reaction was completed, a 5% solution of sodium hydrogensulfite was added, and the mixture was extracted with dichloromethane. The mixture was filtered through a celite funnel, and the solvent was evaporated to dryness eluting with hexane: ethyl acetate = 10:1 as eluent. Further, it was dissolved in 4 mL of dichloromethane, and 20 mL of methanol was added thereto, and the mixture was allowed to stand in a refrigerator at 5 ° C to obtain 1.1 g of yellow crystals. Yield: 73%. The product identification data are as follows: ¹ H NMR (400 MHz, CDCl ₃ ) δ = 8.08 (d, J = 7.9 Hz, 1 H), 7.95-7.87 (m, 3 H), 7.72 (d, J = 7.2 Hz, 2 H ), 7.56-7.48 (m, 2 H), 7.48-7.41 (m, 7 H), 7.38 (d, J = 8.3 Hz, 2 H), 7.32 (s, 1 H), 7.04-6.86 (m, 10) H), 6.43-6.36 (m, 2 H), 6.34-6.27 (m, 2 H), 1.67 (s, 12 H) ppm. ¹³ C NMR (100 MHz, CDCl ₃ ) δ = 168.9, 168.3, 143.8, 142.5 , 141.7, 141.5, 140.8, 140.7, 140.5, 139.1, 133.1, 131.9, 131.7, 131.5, 131.1, 130.3, 130.1, 129.9, 129.2, 128.6, 128.4, 126.5, 126.5, 126.4, 125.4, 125.3, 123.3, 123.1, 121.3 , 120.9, 120.7, 114.3, 114.1, 110.0, 53.5, 36.0, 36.0, 31.6, 31.2 ppm. Ms (ESI: Mz 784) (M+1). T _g = 158 ° C.

Example 3

Glass transition temperature test

The glass transition temperature of Compound 2 was tested by differential scanning calorimetry (DSC) at a heating and cooling rate of 20 ° C/min under nitrogen atmosphere. The glass transition temperature T _g of Compound 2 was measured to be 158 ° C ( FIG. 1 ). The glass transition temperature of CBP reported in the literature is only 62 °C.

It can be seen that the compound of the present invention has a higher glass transition temperature than the conventional host material CBP, and the present invention remarkably improves the thermal stability of the host material.

Example 4

Preparation of electroluminescent device

The device structure is ITO/MoO ₃ (10 nm) / NPB (40 nm) / compound 2 : Ir (ppy): (7 wt%, 30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / AL (100 nm ) (see Figure 2)

The device preparation method is described as follows:

First, the transparent conductive ITO glass substrate (including 10 and 20) was treated as follows: previously washed with a detergent solution, deionized water, ethanol, acetone, deionized water, and then subjected to oxygen plasma treatment for 30 seconds.

Then, 10 nm thick MoO ₃ was vapor-deposited on the ITO as the hole injection layer 30.

Then, a 40 nm-thick NPB was vapor-deposited on the hole injection layer as the hole transport layer 40.

Then, a compound 2 of 2 nm thick: Ir(ppy): (7 wt%) was vapor-deposited on the hole transport layer as the light-emitting layer 50.

Then, a BCP having a thickness of 10 nm was vapor-deposited on the light-emitting layer as the hole blocking layer 60.

Then, 30 nm thick Alq ₃ was vapor-deposited on the hole blocking layer as the electron transport layer 70.

Then, 1 nm thick Alq ₃ was vaporized on the electron transport layer as the electron injection layer 80.

Finally, 100 nm thick aluminum was vaporized on the electron injecting layer as the device cathode 90.

Devices prepared in operating current density 20mA / cm ^2, the luminance of 5224cd / m ^2, the current efficiency was 26.12cd / A, green light emission of CIEx 0.307, CIEy of 0.620.

Comparative example

Preparation of electroluminescent device

The device structure is ITO/MoO ₃ (10 nm) / NPB (40 nm) / CBP: Ir (ppy): (7 wt%, 30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / AL (100 nm)

The method was the same as in Example 4 except that a commonly used commercially available compound CBP was used as a host material to prepare a comparative electroluminescent organic semiconductor diode device.

Devices prepared in operating current density 20mA / cm ^2, the luminance of 3875cd / m ^2, the current efficiency was 19.38cd / A, green light emission of CIEx 0.312, CIEy of 0.620.

By comparing the experimental results of Example 4 and the comparative example, it can be seen that the bipolar host material of the present invention is more advantageous for carrier injection and transport balance than the widely used host material CBP, and the device prepared using the organic material of the present invention. It has better electroluminescence properties and is more in line with the requirements of high performance organic semiconductor devices for host materials.

Claims (10)

A bipolar host material, which is a compound having the structure of formula (I), Wherein R ₁ , R ₂ , R _{3 are} represented by C1-C4 alkyl or alkoxy substituted or unsubstituted acridinyl, phenothiazine, carbazolyl, diphenylamino, hydrogen, halogen; R ₁ , At least one of R ₂ and R _{3 is} a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazolyl group, or a diphenylamino group. The bipolar host material according to claim 1, wherein R ₁ represents a C1-C4 alkyl group or an alkoxy substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazolyl group, a diphenylamine group. The group, at least one of R ₂ and R ₃ is a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazolyl group, a diphenylamino group, and the balance is hydrogen. The bipolar host material according to claim 2, wherein R ₁ and R ₃ are a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, an oxazolyl group, Diphenylamine group. The bipolar host material according to claim 3, wherein R ₁ and R _{3 are the} same. The bipolar host material as described in claim 4 is the following structural compound: The bipolar host material as described in claim 5, which is a compound of the following structure: A method for preparing a bipolar material according to any one of claims 2 to 6, which is obtained by the following steps: (1) providing a halogen-substituted 4',5'-diaryl snail (芴) -9,2'-imidazole) compound; (2) halogen-substituted 4',5'-diaryl spiro (芴-9,2'-imidazole) substituted or unsubstituted with C1-C4 alkyl or alkoxy The acridine, phenothiazine, oxazole, and diphenylamine are subjected to a palladium-catalyzed Buchwald reaction to obtain the bipolar host material. The preparation method according to claim 7, wherein the compound in the step (1) is prepared by: halogen-substituted arylethanedione and halogen-substituted or unsubstituted 9-fluorenone in ammonium acetate and acetic acid conditions. The next reaction gave a halogen-substituted 4',5'-diaryl spiro (芴-9,2'-imidazole). The preparation method as described in claim 8 of the patent application, wherein the preparation reaction step is: The bipolar host material according to any one of claims 1 to 6, which is used in an organic electroluminescent device.