METHOD FOR PRODUCING HALOGEN-CROSSLINKED IRIDIUM DIMER

Abstract

Provided is a method for producing a halogen-crosslinked iridium dimer, including reacting an iridium compound represented by the general formula (1) with an aromatic bidentate ligand in a solvent to produce a halogen-crosslinked iridium dimer, the solvent having a boiling point of 50 C. or higher and lower than 350 C., the reaction being carried out at a reaction temperature of 50 C. or higher and lower than 300 C., and the aromatic bidentate ligand being added in an amount of 0.5 times or more and less than 10 times the molar amount of the iridium compound. The halogen-crosslinked iridium dimer is usable as a precursor of a cyclometalated iridium complex useful as a phosphorescent material.

##STR00001##

Claims

1. A method for producing a halogen-crosslinked iridium dimer, comprising reacting an iridium compound represented by the following general formula (1) with an aromatic bidentate ligand represented by the following general formula (2) in a solvent to produce a halogen-crosslinked iridium dimer represented by the following general formula (3), the solvent having a boiling point of 50 C. or higher and lower than 350 C., the aromatic bidentate ligand being added in an amount of 0.5 times or more and less than 10 times the molar amount of the iridium compound, and the reaction being carried out at a reaction temperature of 50 C. or higher and lower than 300 C.: ##STR00048## wherein Ir represents an iridium atom, O represents an oxygen atom, X represents a halogen atom, and Y represents a counter cation; R.sup.1 to R.sup.6 each independently represent a hydrogen atom, an alkyl group, or an aryl group, and some or all of hydrogen atoms of the alkyl group or aryl group may be substituted with halogen atoms; and adjacent ones of R.sup.1 to R.sup.6 may be linked together to form a ring structure; ##STR00049## wherein N represents a nitrogen atom, C represents a carbon atom, H represents a hydrogen atom, CyA represents a five-membered or six-membered cyclic group containing nitrogen atoms, CyB represents a five-membered or six-membered cyclic group containing carbon atoms, and CyA and CyB may be linked together to form a ring structure; and ##STR00050## wherein Ir represents an iridium atom, N represents a nitrogen atom, C represents a carbon atom, X represents a halogen atom, CyA represents a five-membered or six-membered cyclic group containing nitrogen atoms, and is linked to iridium via the nitrogen atoms, and CyB represents a five-membered or six-membered cyclic group containing carbon atoms, and is linked to iridium via the carbon atoms; and CyA and CyB may be linked together to further form a ring structure.

2. The method according to claim 1, wherein CyA is one of a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a cinnoline ring, a phthalazine ring, a quinazoline ring, a naphthyridine ring, an imidazole ring, a pyrazole ring, a triazole ring, a tetrazole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, and a thiadiazole ring; and CyB is one of a benzene ring, a naphthalene ring, an anthracene ring, a carbazole ring, a fluorene ring, a furan ring, a thiophene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a cinnoline ring, a phthalazine ring, a quinazoline ring, a naphthyridine ring, an imidazole ring, a pyrazole ring, a triazole ring, a tetrazole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, and a thiadiazole ring.

3. The method according to claim 1, wherein CyA and CyB are linked together to form one of a benzoquinoxaline ring, a benzoquinoline ring, a dibenzoquinoxaline ring, a dibenzoquinoline ring, and a phenanthridine ring.

4. The method according to claim 1, wherein the aromatic bidentate ligand is a compound represented by one of the following general formulae (4) to (14): ##STR00051## ##STR00052## ##STR00053## wherein R.sup.7 to R.sup.94 each independently represent a hydrogen atom or a substituent; and adjacent substituents may be linked together to further form a ring structure.

5. The method according to claim 1, wherein the reaction of the iridium compound and the aromatic bidentate ligand is carried out under normal pressure.

6. The method according to claim 2, wherein CyA and CyB are linked together to form one of a benzoquinoxaline ring, a benzoquinoline ring, a dibenzoquinoxaline ring, a dibenzoquinoline ring, and a phenanthridine ring.

7. The method according to claim 2, wherein the aromatic bidentate ligand is a compound represented by one of the following general formulae (4) to (14): ##STR00054## ##STR00055## ##STR00056## wherein R.sup.7 to R.sup.94 each independently represent a hydrogen atom or a substituent; and adjacent substituents may be linked together to further form a ring structure.

8. The method according to claim 3, wherein the aromatic bidentate ligand is a compound represented by one of the following general formulae (4) to (14): ##STR00057## ##STR00058## ##STR00059## wherein R.sup.7 to R.sup.94 each independently represent a hydrogen atom or a substituent; and adjacent substituents may be linked together to further form a ring structure.

9. The method according to claim 2, wherein the reaction of the iridium compound and the aromatic bidentate ligand is carried out under normal pressure.

10. The method according to claim 3, wherein the reaction of the iridium compound and the aromatic bidentate ligand is carried out under normal pressure.

11. The method according to claim 4, wherein the reaction of the iridium compound and the aromatic bidentate ligand is carried out under normal pressure.

Description

DESCRIPTION OF EMBODIMENTS

[0095] Hereinafter, an embodiment of the present invention will be described in detail, but the embodiment is illustrative, and the present invention is not limited thereto. In this embodiment, first a halogen-crosslinked iridium dimer was produced by use of an iridium compound ((Ir-1), (Ir-17), or (Ir-23) in Chemical Formula 11) as a raw material (Examples 1 to 21 and Comparative Examples 1 to 5). A cyclometalated iridium complex was synthesized by use of the produced halogen-crosslinked iridium dimer. (Examples 22 and 23 and Comparative Examples 6 and 7)

[0096] First, examples and comparative examples for production of the halogen-crosslinked iridium dimer will be described. In the description below, the structures of ligands (L-1 to L-16) and halogen-crosslinked iridium dimers (D-1 to D-17: hereinafter, sometimes referred to as target compounds) are shown in reaction schemes described in examples and comparative examples. The iridium compounds (Ir-1), (Ir-17), and (Ir-23) used in this embodiment were produced by heating and reacting iridium trichloride hydrate and a -diketone ligand having necessary substituents R.sup.1 to R.sup.6 in an aqueous solution containing sodium hydrogen carbonate as described below.

[0097] [Method for Producing Iridium Compound (Ir-1)]

[0098] 37.1 g (105 mmol) of iridium trichloride trihydrate and 200 ml of pure water were added in a three-necked flask, and dissolved, 200 ml of 1 M sodium hydrogen carbonate was subsequently added, 20.5 ml (200 mmol) of acetylacetone was further added, and the mixture was reacted at 95 C. for 10 hours. After the reaction, the reaction product was dried by vacuum drying, 400 ml of methanol was subsequently added, and the mixture was refluxed for 8 hours, and filtered. The filtrate was concentrated, and cold methanol was added to obtain 13.0 g of an orange iridium compound (Ir-1) crystal. The isolation yield was 26.8%.

[0099] [Method for Producing Iridium Compound (Ir-17)]

[0100] 40.6 g (115 mmol) of iridium trichloride trihydrate and 530 ml of pure water were added in a three-necked flask, and dissolved, 45.7 g (357 mmol) of 5-methyl-2,4-hexanedione was subsequently added, the mixture was reacted at 95 C. for 1 hour, and 47.5 g (475 mmol) of potassium hydrogen carbonate was added thereto little by little to adjust the pH to about 8. Further, the mixture was heated and reacted for 5 hours. After the reaction, the reaction product was left standing overnight, unreacted 5-methyl-2,4-hexanedione was extracted and removed from the aqueous layer of the supernatant by use of hexane, an iridium compound (Ir-17) was subsequently extracted with ethyl acetate, and the extract was concentrated and dried to obtain 12 g of an orange crude crystal of the iridium compound (Ir-17). Further, the crude crystal was subjected to column purification to obtain 10.2 g of an orange crystal of the iridium compound (Ir-17). The isolation yield was 16%.

[0101] [Method for Producing Iridium Compound (Ir-23)]

[0102] 4.0 g (11.0 mmol) of iridium trichloride trihydrate and 43 ml of pure water were added in a three-necked flask, and stirred in an argon atmosphere, 5.26 g (34.11 mmol) of trifluoroacetylacetone was subsequently added, and the mixture was refluxed in an argon atmosphere for 1 hour. Further, 4.52 g (45.11 mmol) of potassium hydrogen carbonate was added, and the mixture was reacted at 90 C. for 5 hours. After the reaction, the reaction product was left standing overnight, unreacted trifluoroacetylacetone was extracted and removed from the aqueous layer of the supernatant by use of chloroform, an iridium compound (Ir-23) was subsequently extracted with ethyl acetate, and the extract was concentrated and dried to obtain 1.8 g of a brown crude material of an iridium compound (Ir-23). Further, the crude material was subjected to column purification to obtain 1.5 g of an orange solid of the iridium compound (Ir-23). The isolation yield was 20%.

<Example 1> Synthesis of Compound (D-1)

[0103] ##STR00020##

[0104] 290.6 mg of an iridium compound (Ir-1), 280.0 mg of a ligand (L-1), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 8 hours. After completion of the reaction, the reaction solution was cooled to room temperature, dichloromethane and water were added, the mixture was extracted, and the organic layer was recovered. The solution was filtered through a celite layer, and the filtrate was concentrated under reduced pressure. The obtained solid was recrystallized by use of dichloromethane and hexane to obtain a target compound (D-1) as a red solid. The isolation yield was 62%. The product was analyzed by .sup.1H-NMR.

<Example 2> Synthesis of Compound (D-1)

[0105] ##STR00021##

[0106] 290.6 mg of an iridium compound (Ir-1), 280.0 mg of a ligand (L-1), and 2.5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 210 C. for 1 hour. After completion of the reaction, the reaction solution was cooled to room temperature, dichloromethane and water were added, the mixture was extracted, and the organic layer was recovered. The solution was filtered through a celite layer, and the filtrate was concentrated under reduced pressure. The obtained solid was recrystallized by use of dichloromethane and hexane to obtain a target compound (D-1) as a red solid. The isolation yield was 85%. The product was analyzed by .sup.1H-NMR.

<Comparative Example 1> Synthesis of Compound (D-1) (Using Iridium Trichloride n-Hydrate as Starting Material)

[0107] ##STR00022##

[0108] 211.6 mg of iridium trichloride n-hydrate, 320.5 mg of a ligand (L-1), 17 ml of 2-ethoxyethanol, and 2 ml of water were added in a three-necked flask, and heated and reacted in an argon atmosphere at 105 C. for 17 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and concentrated to about 5 ml. Water was added to the solution to precipitate a solid. This mixture was filtered, and washed with water and hexane to obtain 360.4 mg of a blackish ocher solid. The blackish ocher solid was analyzed by .sup.1H-NMR, and the result showed that in addition to a target compound (D-1), a ligand (L-1) and unidentified impurities were contained in a large amount, and the purity of the target compound was about 50%.

<Comparative Example 2> Synthesis of Compound (D-1) (without Using Solvent)

[0109] ##STR00023##

[0110] 290.6 mg of an iridium compound (Ir-1) and 1.4 g of a ligand (L-1) were added in a three-necked flask, and heated and reacted in an argon atmosphere at 210 C. for 1 hour. After completion of the reaction, the reaction solution was cooled to room temperature, dichloromethane and water were added, the mixture was extracted, and the organic layer was recovered. The solution was filtered through a celite layer, and the filtrate was concentrated under reduced pressure. The obtained solid was recrystallized by use of dichloromethane and hexane to obtain a target compound (D-1) as a red solid. The isolation yield was 40%. The product was analyzed by .sup.1H-NMR.

<Example 3> Synthesis of Compound (D-2)

[0111] ##STR00024##

[0112] 290.6 mg of an iridium compound (Ir-1), 246.4 mg of a ligand (L-2), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 17 hours. After completion of the reaction, the reaction solution was cooled to room temperature, dichloromethane and water were added, the mixture was extracted, and the organic layer was recovered. The solution was filtered through a celite layer, and the filtrate was concentrated under reduced pressure. The obtained solid was recrystallized by use of dichloromethane and hexane to obtain a target compound (D-2) as a red solid. The isolation yield was 79%. The product was analyzed by .sup.1H-NMR.

<Comparative Example 3> Synthesis of Compound (D-2) (Using Iridium Trichloride n-Hydrate as Starting Material)

[0113] ##STR00025##

[0114] 211.6 mg of iridium trichloride n-hydrate, 271.0 mg of a ligand (L-2), 17 ml of 2-ethoxyethanol, and 2 ml of water were added in a three-necked flask, and heated and reacted in an argon atmosphere at 105 C. for 17 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and concentrated to about 5 ml. Water was added to the solution to precipitate a solid. This mixture was filtered, and washed with water and hexane to obtain 351.9 mg of a blackish red solid. The blackish red solid was analyzed by .sup.1H-NMR, and the result showed that in addition to a target compound (D-2), a ligand (L-2) and unidentified impurities were contained in a large amount, and the purity of the target compound was about 50%.

<Example 4> Synthesis of Compound (D-3)

[0115] ##STR00026##

[0116] 290.6 mg of an iridium compound (Ir-1), 264.0 mg of a ligand (L-3), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was cooled to room temperature, and filtered. The obtained light yellow solid was washed with methanol to obtain a target compound (D-3) with an isolation yield of 73%. The product was analyzed by .sup.1H-NMR.

<Comparative Example 4> Synthesis of Compound (D-3) (Using Iridium Trichloride n-Hydrate as Starting Material)

[0117] ##STR00027##

[0118] 211.6 mg of iridium trichloride n-hydrate, 396.4 mg of a ligand (L-3), 10 ml of 2-ethoxyethanol, and 3 ml of water were added in a three-necked flask, and heated and reacted in an argon atmosphere at 105 C. for 17 hours. After completion of the reaction, the brown reaction solution was cooled to room temperature, and filtered. The obtained dark yellow solid was washed with methanol to obtain a target compound (D-3) with an isolation yield of 30%.

<Example 5> Synthesis of Compound (D-4)

[0119] ##STR00028##

[0120] 290.6 mg of an iridium compound (Ir-1), 314.8 mg of a ligand (L-4), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 10 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-4) with an isolation yield of 73%. The product was analyzed by .sup.1H-NMR.

<Example 6> Synthesis of Compound (D-5)

[0121] ##STR00029##

[0122] 290.6 mg of an iridium compound (Ir-1), 186.0 mg of a ligand (L-5), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 17 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-5) with an isolation yield of 97%. The product was analyzed by .sup.1H-NMR.

<Example 7> Synthesis of Compound (D-5)

[0123] ##STR00030##

[0124] 333.9 mg of an iridium compound (Ir-17), 186.0 mg of a ligand (L-5), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-5) with an isolation yield of 92%. The product was analyzed by .sup.1H-NMR.

<Example 8> Synthesis of Compound (D-5)

[0125] ##STR00031##

[0126] 182.5 mg of an iridium compound (Ir-23), 93.0 mg of a ligand (L-5), and 2.5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-5) with an isolation yield of 97%. The product was analyzed by .sup.1H-NMR.

<Comparative Example 5> Synthesis of Compound (D-5) (without Using Solvent)

[0127] ##STR00032##

[0128] 333.9 mg of an iridium compound (Ir-17) and 223.2 mg of a ligand (L-5) were added in a Schlenk flask, and heated and reacted in an argon atmosphere at 180 C. for 17 hours. After completion of the reaction, methanol was added, and the yellow reaction solution was filtered to obtain a smoky yellow solid. The smoky yellow solid was washed with methanol to obtain a target compound (D-5) with a yield of 18%.

<Example 9> Synthesis of Compound (D-6)

[0129] ##STR00033##

[0130] 290.6 mg of an iridium compound (Ir-1), 215.1 mg of a ligand (L-6), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a target compound (D-6) with an isolation yield of 91%. The product was analyzed by .sup.1H-NMR.

<Example 10> Synthesis of Compound (D-7)

[0131] ##STR00034##

[0132] 290.6 mg of an iridium compound (Ir-1), 313.6 mg of a ligand (L-7), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the red reaction solution was filtered to obtain a red solid. The red solid was washed with methanol to obtain a target compound (D-7) with an isolation yield of 92%. The product was analyzed by .sup.1H-NMR.

<Example 11> Synthesis of Compound (D-8)

[0133] ##STR00035##

[0134] 290.6 mg of an iridium compound (Ir-1), 294.4 mg of a ligand (L-8), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a target compound (D-8) with an isolation yield of 97%. The product was analyzed by .sup.1H-NMR.

<Example 12> Synthesis of Compound (D-9)

[0135] ##STR00036##

[0136] 290.6 mg of an iridium compound (Ir-1), 173.0 mg of a ligand (L-9), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the light yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-9) with an isolation yield of 83%. The product was analyzed by .sup.1H-NMR.

<Example 13> Synthesis of Compound (D-9)

[0137] ##STR00037##

[0138] 333.9 mg of an iridium compound (Ir-17), 173.0 mg of a ligand (L-9), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the light yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol to obtain a target compound (D-9) with an isolation yield of 92%. The product was analyzed by .sup.1H-NMR.

<Example 14> Synthesis of Compound (D-10)

[0139] ##STR00038##

[0140] 290.6 mg of an iridium compound (Ir-1), 277.6 mg of a ligand (L-10), and 5 ml of diethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a target compound (D-10) with an isolation yield of 87%. The product was analyzed by .sup.1H-NMR.

<Example 15> Synthesis of Compound (D-11)

[0141] ##STR00039##

[0142] 290.6 mg of an iridium compound (Ir-1), 278.7 mg of a ligand (L-11), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a compound (D-11) with an isolation yield of 90%. The product was analyzed by .sup.1H-NMR.

<Example 16> Synthesis of Compound (D-12)

[0143] ##STR00040##

[0144] 290.6 mg of an iridium compound (Ir-1), 329.1 mg of a ligand (L-12), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a target compound (D-12) with an isolation yield of 93%. The product was analyzed by .sup.1H-NMR.

<Example 17> Synthesis of Compound (D-13)

[0145] ##STR00041##

[0146] 290.6 mg of an iridium compound (Ir-1), 361.7 mg of a ligand (L-13), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the reaction solution was cooled to room temperature, dichloromethane and water were added, and the mixture was extracted. The organic layer was recovered, and concentrated under reduced pressure. The obtained yellow solid was recrystallized by use of dichloromethane and hexane to obtain a target compound (D-13) with an isolation yield of 80%. The product was analyzed by .sup.1H-NMR.

<Example 18> Synthesis of Compound (D-14)

[0147] ##STR00042##

[0148] 290.6 mg of an iridium compound (Ir-1), 253.5 mg of a ligand (L-14), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a yellow solid. The yellow solid was washed with methanol to obtain a target compound (D-14) with an isolation yield of 73%. The product was analyzed by .sup.1H-NMR.

<Example 19> Synthesis of Compound (D-15)

[0149] ##STR00043##

[0150] 290.6 mg of an iridium compound (Ir-1), 253.5 mg of a ligand (L-15), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the reddish brown reaction solution was filtered to obtain a reddish brown solid. The reddish brown solid was washed with methanol to obtain a target compound (D-15) with an isolation yield of 87%. The product was analyzed by .sup.1H-NMR.

<Example 20> Synthesis of Compound (D-16)

[0151] ##STR00044##

[0152] 290.6 mg of an iridium compound (Ir-1), 207.8 mg of a ligand (L-16), and 5 ml of ethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 180 C. for 5 hours. After completion of the reaction, the yellow reaction solution was filtered to obtain a light yellow solid.

[0153] The yellow solid was washed with methanol to obtain a target compound (D-16) with an isolation yield of 90%. The product was analyzed by .sup.1H-NMR.

<Example 21> Synthesis of Compound (D-17)

[0154] ##STR00045##

[0155] 333.9 mg of an iridium compound (Ir-17), 292.8 mg of a ligand (L-17), and 5 ml of diethylene glycol were added in a three-necked flask, and heated and reacted in an argon atmosphere at 210 C. for 5 hours. After completion of the reaction, the light yellow reaction solution was filtered to obtain a light yellow solid. The light yellow solid was washed with methanol, and then recrystallized with dichloromethane and methanol to obtain a target compound (D-17) with an isolation yield of 61%. The product was analyzed by .sup.1H-NMR.

[0156] The results of Examples 1 to 21 revealed that it was possible to produce a halogen-crosslinked iridium dimer with a favorable yield by using the production method of the present invention. On the other hand, it was apparent from Comparative Examples 1, 3, and 4 that when iridium chloride was used as a starting material, it was not possible to produce a halogen-crosslinked iridium dimer with a favorable yield. Comparative Examples 2 and 5 revealed that the yield of a halogen-crosslinked iridium dimer synthesized in the absence of a solvent was lower as compared to a case where the reaction was carried out in a solvent.

[0157] The results of Examples 7, 13, and 21 show that the iridium compound (Ir-17) as a raw material is an iridium compound, the ligand of which has substituents satisfying the relationship of R.sup.1 0 R.sup.3 and R.sup.4 0 R.sup.6. A favorable yield is also obtained from this iridium compound. In addition, the result of Example 8 showed that an alkyl group substituted with fluorine as a substituent was also useful.

[0158] Next, a cyclometalated iridium complex (C-1 or C-2) was synthesized from the halogen-crosslinked iridium dimer obtained by the production method in each of examples and comparative examples.

<Example 22> Synthesis of Cyclometalated Iridium Complex (C-1)

[0159] ##STR00046##

[0160] 6.0 mg of the chlorine-crosslinked iridium dimer (D-1) obtained in Example 2, and 6.0 mg of sodium acetylacetonate hydrate were dissolved in DMSO-d.sub.6 (0.75 ml) by heating, and the solution was then added in a NMR tube. The reaction solution was analyzed by .sup.1H-NMR, and the result showed that the chlorine-crosslinked iridium dimer (D-1) completely disappeared, and a cyclometalated iridium complex (C-1) was quantitatively produced. This revealed that the chlorine-crosslinked iridium dimer (D-1) obtained in Example 2 had an extremely high purity.

<Comparative Example 6> Synthesis of Cyclometalated Iridium Complex (C-1)

[0161] 6.0 mg of the chlorine-crosslinked iridium dimer (D-1) obtained in Comparative Example 1, and 6.0 mg of acetylacetone sodium were dissolved in DMSO-d.sub.6 (0.75 ml) by heating, and the solution was then added in a NMR tube. The reaction solution was analyzed by .sup.1H-NMR, and the result showed that in addition to a cyclometalated iridium complex (C-1), an unreacted ligand (L-1) and unidentified impurities were contained in an amount of 50% or more. This revealed that the chlorine-crosslinked iridium dimer (D-1) obtained in Comparative Example 1 had a low purity.

<Example 23> Synthesis of Cyclometalated Iridium Complex (C-2)

[0162] ##STR00047##

[0163] 6.0 mg of the chlorine-crosslinked iridium dimer (D-2) obtained in Example 3, and 6.0 mg of acetylacetone sodium were dissolved in DMSO-d.sub.6 (0.75 ml) by heating, and the solution was then added in a NMR tube. The reaction solution was analyzed by .sup.1H-NMR, and the result showed that the chlorine-crosslinked iridium dimer (D-2) completely disappeared, and a cyclometalated iridium complex (C-2) was quantitatively produced. This revealed that the chlorine-crosslinked iridium dimer (D-2) obtained in Example 3 had an extremely high purity.

<Comparative Example 7> Synthesis of Cyclometalated Iridium Complex (C-2)

[0164] 6.0 mg of the chlorine-crosslinked iridium dimer (D-2) obtained in Comparative Example 3, and 6.0 mg of acetylacetone sodium were dissolved in DMSO-d.sub.6 (0.75 ml) by heating, and the solution was then added in a NMR tube. The reaction solution was analyzed by .sup.1H-NMR, and the result showed that in addition to a cyclometalated iridium complex (C-2), an unreacted ligand (L-2) and unidentified impurities were contained in an amount of 50% or more. It was revealed that the chlorine-crosslinked iridium dimer (D-2) obtained in Comparative Example 3 had a low purity.

[0165] Examples 22 and 23 revealed that it was possible to produce a desired cyclometalated iridium complex with a high purity by using the halogen-crosslinked dimer obtained by the production method of the present invention. The results of Comparative Examples 6 and 7 showed that a halogen-crosslinked iridium dimer obtained by a previously known method using chlorine iridium as a starting material contained an unreacted ligand and black decomposed products in a large amount, and when the halogen-crosslinked iridium dimer was used, the yield and purity of a desired cyclometalated iridium complex were extremely reduced.

INDUSTRIAL APPLICABILITY

[0166] The present invention allows a halogen-crosslinked iridium dimer as a precursor of a cyclometalated iridium complex to be produced with a favorable yield and with a favorable purity. The cyclometalated iridium complex can be produced with a favorable yield and with a favorable purity by using the halogen-crosslinked iridium dimer produced according to the present invention. The present invention provides a raw material for production of a cyclometalated iridium complex that is used as a phosphorescent material to be used for organic electroluminescent (EL) devices, organic electrochemiluminescent (ECL) devices, luminescent sensors, photosensitizing pigments, photocatalysts, luminescent probes, various light sources, and the like.