KR101145684B1 - Novel Iridium Complexes with Cyclometallated Imide containing Ligands and the Electrophosphorescence Containing The Same - Google Patents

Abstract

PURPOSE: An iridium complex is provided to be luminescent with an orange color, to obtain excellent chemical and electrical properties, to have superior luminous efficiency, high brightness, and high chromatic purity, and to be used as orange phosphors of an electrophosphorescent device. CONSTITUTION: An iridium(III) complex is marked by chemical formula 1. In chemical formula 1, A is a chemical bond or an alkylene group with C1-C5 and R1-R4 are hydrogen, an alkyl group with C1-C20, an alkoxyl group with C1-C20, an alkylsily group with C1-C20, an arylsilyl group with C6-C20, or an aryl group with C6-C20. R1-R4 are capable of forming a benzene ring or a naphthalene ring by being connected to substituent through alkenylene.

Description

Iridium complex having an imide group and an electrophosphorescent device comprising the same {Novel Iridium Complexes with Cyclometallated Imide containing Ligands and the Electrophosphorescence Containing The Same}

The present invention relates to a novel iridium composite having an orange phosphorescent light emitting property and an electrophosphorescent device comprising the same.

The flat panel display plays a very important role in supporting a highly visual information society, centered on the internet, which is rapidly growing in recent years. In particular, organic electroluminescent devices (organic EL devices) capable of low voltage driving with self-luminous type have superior viewing angles and contrast ratios compared to liquid crystal displays (LCDs), which are mainstream flat panel displays, and require no backlight. Light weight and thinness are possible, and it has an advantage in terms of power consumption. In addition, the fast response speed and wide color reproduction range have attracted attention as a next generation display device.

In general, an organic EL device is formed on a glass substrate in order of an anode made of a transparent electrode, an organic thin film including a light emitting region, and a metal electrode. In this case, the organic thin film may include a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), or an electron injection layer (electron) in addition to a light emitting layer (EML). injection layer (EIL), and may further include an electron blocking layer (EBL) or a hole blocking layer (HBL) due to light emission characteristics of the emission layer. When an electric field is applied to the organic EL device having such a structure, holes are injected from the anode and electrons are injected from the cathode, and the injected holes and electrons are recombined in the emission layer through the hole transport layer and the electron transport layer, respectively, and emit excitons. To form. The formed light exciton emits light while transitioning to ground states, in which a light emitting layer (dopant) is doped into the light emitting layer (host) to increase the efficiency and stability of the light emitting state.

Recently, it has been known that not only fluorescent light emitting materials but also phosphorescent light emitting materials can be used as light emitting materials of organic EL devices. Such phosphorescent light emission is carried out through intersystem crossing after electrons transfer from the ground state to the excited state. The singlet excitons are non-luminescent to triplet excitons, and then the triplet excitons are light-transmitted as they transition to the ground state. At this time, the transition to the triplet excitons does not directly transition to the ground state (spin forbidden), since the process of transition to the ground state after the flipping of the electron spin proceeds (lifetime) than fluorescence (lifetime) It has a longer characteristic. That is, the emission duration of fluorescence emission is only several nanoseconds, but the phosphorescence emission corresponds to several micro seconds, which is a relatively long time.

In addition, in quantum mechanics, when the holes injected from the anode and the electrons injected from the cathode recombine to form a light-emitting excitons, the formation ratio of the singlet and triplet is 1: 3. Antiluminescence excitons are generated about three times more than singlet excitation excitons. Therefore, in the case of using a phosphorescent light emitting material, there is an advantage that can achieve a three times higher luminous efficiency than the fluorescent light emitting material.

As a molecular structure that is easy to phosphorescence, a metal complex including a metal having a large atomic number as a molecular structure that is easy to carry out transit is applicable. Among these, iridium organic complex is attracting attention as a material having excellent phosphorescence efficiency. However, there are many problems such as luminous efficiency, color purity and electrical stability, and especially in the case of blue and red light emission, it is very urgent to develop a phosphorescent light emitting material having excellent luminous efficiency, color purity and electrical stability.

On the other hand, iridium (III) ions form C ^ N ligands and (C ^ N) ₃ Ir complexes such as dimine ligands or 2-phenylpyridyl derivative ligands, and at room temperature. It has been reported to exhibit strong phosphorescence. Iridium (III) ions not only form complexes with three metallization ligands (C ^ N), but also two ligands (C ^ N) and one anionic bidentate ligand (LX) and (C ^ N) ) ₂ IrLX complexes can be formed, and these iridium (III) complexes also exhibit strong phosphorescence.

Tris- (2-phenylpyridinato) Ir (III) [(ppy) ₃ Ir (III)] and bis- (2-phenylpyridinate) (acetoacetonate) which are representative iridium (III) complexes ) Ir (III) [(ppy) ₂ (acac) Ir (III)] is shown. It has been reported that the internal luminescence quantum efficiency of (Ppy) ₃ Ir (III) reaches about 75%. Many iridium (III) complex development studies have been conducted on the basis of the excellent phosphorescence ability and the luminous efficiency improving ability of the iridium (III) complex. As shown in the general structure of iridium (III) complexes, high luminous yields are obtained by systematically altering the structure of the ring, the C ^ N cyclometalating main ligand, and the monoanionic bidentate ancillary ligand. Phosphorescent iridium (III) complexes with a have been reported.

The flat panel display plays a very important role in supporting a highly visual information society, centered on the internet, which is rapidly growing in recent years. In particular, organic electroluminescent devices (organic EL devices) capable of low voltage driving with self-luminous type have superior viewing angles and contrast ratios compared to liquid crystal displays (LCDs), which are mainstream flat panel displays, and require no backlight. Light weight and thinness are possible, and it has an advantage in terms of power consumption. In addition, the fast response speed and wide color reproduction range have attracted attention as a next generation display device.

In general, an organic EL device is formed on a glass substrate in order of an anode made of a transparent electrode, an organic thin film including a light emitting region, and a metal electrode. In this case, the organic thin film may include a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), or an electron injection layer (electron) in addition to the light emitting layer (EML). injection layer (EIL), and may further include an electron blocking layer (EBL) or a hole blocking layer (HBL) due to light emission characteristics of the emission layer. When an electric field is applied to the organic EL device having such a structure, holes are injected from the anode and electrons are injected from the cathode, and the injected holes and electrons are recombined in the emission layer through the hole transport layer and the electron transport layer, respectively, and emit excitons. To form. The formed light exciton emits light while transitioning to ground states, in which a light emitting layer (dopant) is doped into the light emitting layer (host) to increase the efficiency and stability of the light emitting state.

Recently, it has been known that not only fluorescent light emitting materials but also phosphorescent light emitting materials can be used as light emitting materials of organic EL devices. Such phosphorescent light emission is carried out through intersystem crossing after electrons transfer from the ground state to the excited state. The singlet excitons are non-luminescent to triplet excitons, and then the triplet excitons are light-transmitted as they transition to the ground state. At this time, the transition to the triplet excitons does not directly transition to the ground state (spin forbidden), since the process of transition to the ground state after the flipping of the electron spin proceeds (lifetime) than fluorescence (lifetime) It has a longer characteristic. That is, the emission duration of fluorescence emission is only several nanoseconds, but the phosphorescence emission corresponds to several micro seconds, which is a relatively long time.

In addition, in quantum mechanics, when the holes injected from the anode and the electrons injected from the cathode recombine to form a light-emitting excitons, the formation ratio of the singlet and triplet is 1: 3. Antiluminescence excitons are generated about three times more than singlet excitation excitons. Therefore, in the case of using a phosphorescent light emitting material, there is an advantage that can achieve a three times higher luminous efficiency than the fluorescent light emitting material.

As a molecular structure that is easy to phosphorescence, a metal complex including a metal having a large atomic number as a molecular structure that is easy to carry out transit is applicable. Among these, iridium organic complex is attracting attention as a material having excellent phosphorescence efficiency. However, there are many problems such as luminous efficiency, color purity and electrical stability, and especially in the case of blue and red light emission, it is very urgent to develop a phosphorescent light emitting material having excellent luminous efficiency, color purity and electrical stability.

On the other hand, iridium (III) ions form C ^ N ligands and (C ^ N) ₃ Ir complexes such as dimine ligands or 2-phenylpyridyl derivative ligands, and at room temperature. It has been reported to exhibit strong phosphorescence. Iridium (III) ions not only form complexes with three metallization ligands (C ^ N), but also two ligands (C ^ N) and one anionic bidentate ligand (LX) and (C ^ N) ) ₂ IrLX complexes can be formed, and these iridium (III) complexes also exhibit strong phosphorescence.

Tris- (2-phenylpyridinato) Ir (III) [(ppy) ₃ Ir (III)] and bis- (2-phenylpyridinate) (acetoacetonate) which are representative iridium (III) complexes ) Ir (III) [(ppy) ₂ (acac) Ir (III)] is shown. It has been reported that the internal luminescence quantum efficiency of (Ppy) ₃ Ir (III) reaches about 75%. Many iridium (III) complex development studies have been conducted on the basis of the excellent phosphorescence ability and the luminous efficiency improving ability of the iridium (III) complex. As shown in the general structure of iridium (III) complexes, high luminous yields are obtained by systematically altering the structure of the ring, the C ^ N cyclometalating main ligand, and the monoanionic bidentate ancillary ligand. Phosphorescent iridium (III) complexes with a have been reported.

Accordingly, an object of the present invention is to introduce an imide group into the ligand of the iridium complex to change the electrical properties of the iridium complex due to the electron-pulling properties of the imide group to provide excellent electrical stability, high luminous efficiency and luminous luminance, and high color purity. It is possible to provide an iridium-based orange phosphorescent material and an electrophosphorescent device comprising the same.

The present invention relates to a novel iridium complex represented by the following formula (1) and an electrophosphorescent device comprising the same.

[Formula 1]

[In Formula 1, A is a chemical bond or (C1-C5) alkylene;

R ₁ to R ₄ are each independently hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl, and R ₁ to R ₄ may be connected to an adjacent substituent with an alkenylene to form a benzene or naphthalene ring, wherein the alkenylene is (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl, May be further substituted with (C6-C20) arylsilyl or (C6-C20) aryl;

R ₅ is (C 1 -C 20) alkyl, halo (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl or (C 6 -C 20) aryl, wherein the aryl of R ₅ is (C 1 -C 20) C20) alkyl, (C1-C20) alkoxy, halo (C1-C20) alkyl, (C1-C20) alkylsilyl, (C6-C20) arylsilyl and halogen may be further substituted with one or more substituents selected from the group consisting of There is;

Ar is a monocyclic or polycyclic aromatic ring;

R ₆ is hydrogen, hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl;

L is acetylacetone or picolinamide; And

n is 2 or 3.]

Ar is benzene or naphthalene, and R ₁ to R ₄ are each independently hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, Octyl, ethylhexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, triphenylsilyl, phenyl or naphthyl R ₅ is methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, trifluoromethyl, perfluoroethyl, perfluor Propyl, perfluorobutyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, triphenylsilyl, phenyl thuryl, trifluoro-phenyl, phenyl trialkylsilyl, triphenylsilyl, phenyl, fluorinated phenyl or naphthyl, R ₆ is Bovine, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, methoxy, ethoxy, propoxy, butoxy, pen Methoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, triphenylsilyl, phenyl or naphthyl.

The iridium complex according to Chemical Formula 1 of the present invention may be more specifically a compound represented by Chemical Formulas 2 to 13.

[Formula 2]

(3)

[Formula 4]

[Chemical Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

[Formula 10]

[Formula 11]

[Chemical Formula 12]

[Formula 13]

[In Formulas 2 to 13, Ar, R ₁ to R ₅ and L are the same as defined in Formula 1, R ₁₁ is hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20 ) Alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl.]

Iridium complex of the present invention may be selected from the following compounds, but is not limited thereto.

The compound of Formula 1 according to the present invention may be prepared according to a known method using a bridged iridium. That is, a compound having an imide group having the following structure as a main ligand substance and iridium trichloride hydrate (IrCl ₃ -nH ₂ O) are reacted under an organic solvent such as ethoxyethanol to synthesize a crosslinked iridium complex, and then the crosslinked An iridium compound of Formula 1 may be prepared by reacting an iridium compound in the presence of a base such as sodium carbonate with acetylacetone or picolinamide as an auxiliary ligand material.

[Where A is a chemical bond or (C1-C5) alkylene; R ₁ to R ₄ are each independently hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl, and R ₁ to R ₄ may be connected to an adjacent substituent with an alkenylene to form a benzene or naphthalene ring, wherein the alkenylene is (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl, May be further substituted with (C6-C20) arylsilyl or (C6-C20) aryl; R ₅ is (C 1 -C 20) alkyl, halo (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl or (C 6 -C 20) aryl, wherein the aryl of R ₅ is (C 1 -C 20) C20) alkyl, (C1-C20) alkoxy, halo (C1-C20) alkyl, (C1-C20) alkylsilyl, (C6-C20) arylsilyl and halogen may be further substituted with one or more substituents selected from the group consisting of There is; R ₆ is hydrogen, hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl; Ar is a monocyclic or polycyclic aromatic ring.]

In another aspect, the present invention provides an electrophosphor device, the electrophosphor device according to the invention is an electrophosphor device comprising at least one organic layer interposed between the anode, the cathode and the positive electrode, the organic layer is the iridium of the formula At least one complex.

In the electrophosphorescent device according to the present invention, the organic material layer may include a light emitting layer, and the light emitting layer may include one or more of the iridium complex of Formula 1 as a light emitting material, and other compounds known in the art, for example For example, 4,4-dicarbazole bisphenyl (CBP) may be included by doping the compound of Chemical Formula 1 as a host.

The electrophosphorescent device can be formed by a conventional deposition method.

Since the iridium complex of the present invention is an orange phosphorescent compound having excellent chemical and electrical stability, luminous efficiency, high luminance and excellent color purity, it can be usefully used as an orange phosphorescent material of an electrophosphorescent device.

The iridium complex of the present invention is a compound having orange phosphorescence emission characteristics, and by introducing imide groups into the ligand, the electron-pulling properties of the imide groups change the electrical properties of the iridium complex, thereby providing excellent chemical and electrical stability, luminous efficiency, high luminance emission and Since it shows excellent color purity, it can be usefully used as the orange phosphorescent material of the electrophosphorescent device. In addition, the iridium complex of the present invention can be used as a very important material for white light expression.

1-Structure of organic electroluminescent device
2-UV / PL spectrum of compound (4) according to the invention
3-DSC curve of compound (4) according to the present invention
4-EL spectrum of the organic electroluminescent device of Example 1 employing compound (4) according to the present invention in a light emitting layer
5-Current efficiency and power efficiency curves for the current density of the organic electroluminescent device of Example 1 employing the compound (4) according to the invention in the light emitting layer

Hereinafter, a novel iridium (III) complex according to the present invention according to the present invention and on the basis of the production examples, a method for manufacturing the same and the light emitting characteristics of the device, but the following examples are provided to help the understanding of the present invention The scope of the present invention is not limited to the following examples.

[ Example  One] Phthalimide Pyridine Juri Gand  Acetylacetone Secondary ligand  Preparation of Iridium Complexes Having Compound (4)

Synthesis of Compound (1)

4-bromophthalic anhydride (10.0 g, 44.05 mmol) was added to distilled m -cresol (20 mL), followed by isopropylamine (3.1 g, 52.86 mmol) and catalyst isoquinoline under a stream of nitrogen. (0.5 g) was added at room temperature. It was slowly heated to 200 ° C. for 2 hours and stirred at reflux for 8 hours. After 8 hours, the temperature was lowered to room temperature and m -cresol was removed by vacuum distillation, and then 4-bromo-N-isopropyl as a white solid using a silica column (EA: Hexane = 1: 10, v / v). Phthalimide (Compound 1) was obtained (10.7 g, 91%). ¹ H NMR (300 MHz, CDCl ₃ , δ): 7.93 (s, 1H), 7.83 (d, 1H), 7.67 (d, 1H), 4.55-4.47 (m, 1H), 1.48 (d, 6H)

Synthesis of Compound (2)

In a 250 ml three-necked flask, compound (1) (5.0 g, 18.65 mmol) and 2- (tributyltin) pyridine (9.6 g, 26.10 mmol) were added to purified toluene (100 mL) and the catalyst Pd (PPh ₃ ) ₄ (1.1 g) was added thereto, and the mixture was stirred at 110 ° C. for 18 hours. After the reaction, the mixture was cooled to room temperature, extracted with water and EA, and the organic layer was removed with water using MgSO ₄ , and distilled under reduced pressure to remove the solvent. A silica column (EA: Hexane = 3: 10, v / v) was used to obtain 4- (2-pyridyl) -N-isopropylphthalimide (Compound 2) as a white solid (4.4 g, 88%). ). ¹ H NMR (300 MHz, CD ₃ COCD ₃ , δ): 8.78 (d, 1H), 8.58 (d, 1H), 8.53 (s, 1H), 8.18 (d, 1H), 8.03 (t, 1H), 7.93 (d, 1H), 7.51 (t, 1H), 4.58-4.48 (m, 1H), 1.50 (d, 6H)

 Synthesis of Compound (4)

To a solvent of 2-ethoxyethanol (30 mL) and water (10 mL), add IrCl ₃ nH ₂ O (1.6 g, 5.36 mmol) and compound (2) (3.0 g, 11.26 mmol) under a nitrogen stream. Stir at 120 ° C. for 20 hours. The color of the solution changed to orange during the stirring. The orange solution was poured into water (200 mL) to precipitate, washed with ethanol and hexane and dried to give Ir (III) -μ-chloro-bridged dimer (Compound 3) (2.7 g, 68%).

Dissolve compound (3) (2.7 g, 1.78 mmol) in 2-ethoxyethanol (25 mL), mix acetylacetone (0.5 mL, 4.87 mmol) with Na ₂ CO ₃ (1.9 g, 17.80 mmol) and mix with nitrogen stream. Stir at 120 ° C. for 24 h. After the temperature was cooled down to room temperature, the reaction was poured into water (200 mL) to precipitate, filtered off, washed with water and the solvent removed. Compound (4) was obtained as an orange-red solid using a silica column (DCM: MeOH = 20: 1, v / v) (0.7 g 48%). ¹ H NMR (300 MHz, CDCl ₃ , δ): 8.49 (d, 2H), 8.08 (d, 2H), 7.97 (s, 2H), 7.93 (d, 2H), 7.36 (t, 2H), 6.70 ( s, 2H), 5.28 (s, 1H), 4.43-4.38 (m, 2H), 1.81 (s, 6H), 1.37 (d, 12H)

Example 2 Characterization of Organic Electroluminescent Devices Using Iridium (III) Complexes According to the Present Invention

The light emitting area of the indium tin oxide (ITO) substrate (glass) was patterned to have a size of 3 mm × 3 mm and then cleaned. After mounting the substrate in the vacuum chamber, the basic pressure is 1 × 10 ^-6 torr, and the organic material is placed on the ITO NPB: ReO ₃ (80 nm), NPB (20 nm), the light emitting layer [CBP + 4% by weight of the present invention Iridium (III) complex] (20 nm), Bphen (40 nm), Bphen: RbCO ₃ (15 nm) and Al (100 nm) were formed in the order of fabrication of the organic electroluminescent device of the present invention [FIG. 1]. .

NPB: 1,4-bis [N- (1-naphthyl) -N'-phenylamino] -4,4'-diamine

ReO ₃ : rhenium oxide

Bphen: 4,7-diphenyl-1,10-phenanthroline

RbCO ₃ : rubidium carbonate

CBP: 4,4'-N, N'-dicarbazole-biphenyl

FIG. 2 is a graph showing UV / PL characteristics of compound (4) which is an iridium (III) complex of the present invention, FIG. 3 is a graph showing DSC of compound (4), and FIGS. 4 and 5 are compound (4). Is a graph showing the characteristics of the organic light emitting device employing the light emitting layer, wherein the light emitting layer is deposited by doping the compound (4) of the iridium (III) complex of the present invention to 4% by weight of CBP with CBP as a host. The maximum current efficiency was 37.4 cd / A, the maximum power efficiency was 32.7 lm / W, and the color coordinates (0.52, 0.47).

Claims (10)

Iridium (III) complexes represented by the following formula (1).
[Formula 1]

[In Formula 1, A is a chemical bond or (C1-C5) alkylene;
R ₁ to R ₄ are each independently hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl, and R ₁ to R ₄ may be connected to an adjacent substituent with an alkenylene to form a benzene or naphthalene ring, wherein the alkenylene is (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl, May be further substituted with (C6-C20) arylsilyl or (C6-C20) aryl;
R ₅ is (C 1 -C 20) alkyl, halo (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl or (C 6 -C 20) aryl, wherein the aryl of R ₅ is (C 1 -C 20) C20) alkyl, (C1-C20) alkoxy, halo (C1-C20) alkyl, (C1-C20) alkylsilyl, (C6-C20) arylsilyl and halogen may be further substituted with one or more substituents selected from the group consisting of There is;
Ar is a monocyclic or polycyclic aromatic ring;
R ₆ is hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl;
L is acetylacetone or picolinamide; And
n is 2 or 3.] The method of claim 1,
And Ar is benzene or naphthalene. The method of claim 2,
An iridium (III) complex selected from formulas (2) to (13).
(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Formula 6]

[Formula 7]

[Chemical Formula 8]

[Chemical Formula 9]

[Formula 10]

(11)

[Formula 12]

[Chemical Formula 13]

[In Formulas 2 to 13, R ₁ to R ₅ and L are the same as defined in claim 1, R ₁₁ is hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20 ) Alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl.] The method of claim 3, wherein
R ₁ to R ₄ are each independently hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, methoxy, Ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, triphenylsilyl, phenyl or naphthyl, R ₅ is methyl, ethyl , n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, methoxy , Ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, phenyl tolyl, trifluoromethylphenyl, trialkylsilylphenyl, triphenylsilyl Iridium (III) complexes which are phenyl, fluorophenyl or naphthyl. The method of claim 4, wherein
Iridium (III) complexes selected from the following compounds.

An electrophosphorescent device comprising a light emitting layer between an anode, a cathode and a positive electrode, wherein the light emitting layer comprises the iridium complex according to any one of claims 1 to 5. Ligand which has imide group represented by the following compound.

[Where A is a chemical bond or (C1-C5) alkylene; R ₁ to R ₄ are each independently hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl, and R ₁ to R ₄ may be connected to an adjacent substituent with an alkenylene to form a benzene or naphthalene ring, wherein the alkenylene is (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl, May be further substituted with (C6-C20) arylsilyl or (C6-C20) aryl; R ₅ is (C 1 -C 20) alkyl, halo (C 1 -C 20) alkyl, (C 1 -C 20) alkoxy, (C 1 -C 20) alkylsilyl or (C 6 -C 20) aryl, wherein the aryl of R ₅ is (C 1 -C 20) C20) alkyl, (C1-C20) alkoxy, halo (C1-C20) alkyl, (C1-C20) alkylsilyl, (C6-C20) arylsilyl and halogen may be further substituted with one or more substituents selected from the group consisting of There is; R ₆ is hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20) arylsilyl or (C6-C20) aryl; Ar is a monocyclic or polycyclic aromatic ring.] The method of claim 7, wherein
Ligands selected from the following compounds.

[Wherein R ₁ to R ₅ are the same as defined in claim 7, R ₁₁ is hydrogen, (C1-C20) alkyl, (C1-C20) alkoxy, (C1-C20) alkylsilyl, (C6-C20 ) Arylsilyl or (C6-C20) aryl.] The method of claim 8,
R ₁ to R ₄ are each independently hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, methoxy, Ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, triphenylsilyl, phenyl or naphthyl, R ₅ is methyl, ethyl , n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, methoxy , Ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, trimethylsilyl, triethylsilyl, dimethylethylsilyl, tributylsilyl, phenyl tolyl, trifluoromethylphenyl, trialkylsilylphenyl, triphenylsilyl Ligands that are phenyl, fluorophenyl or naphthyl. The method of claim 9,
Ligand, characterized in that it is selected from the following compounds.

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