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Patent US7902374 - Stability OLED materials and devices - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsOrganic light emitting materials and devices comprising phosphorescent metal complexes comprising ligands comprising aryl or heteroaryl groups substituted at both ortho positions are described. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising...http://www.google.com/patents/US7902374?utm_source=gb-gplus-sharePatent US7902374 - Stability OLED materials and devicesAdvanced Patent SearchPublication numberUS7902374 B2Publication typeGrantApplication numberUS 11/592,275Publication dateMar 8, 2011Filing dateNov 3, 2006Priority dateMay 6, 2005Fee statusPaidAlso published asUS20070088167, WO2008054584A1Publication number11592275, 592275, US 7902374 B2, US 7902374B2, US-B2-7902374, US7902374 B2, US7902374B2InventorsChun Lin, Peter B. Mackenzie, Robert W. Walters, Jui-Yi Tsai, Cory S. Brown, Jun DengOriginal AssigneeUniversal Display CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (50), Non-Patent Citations (12), Referenced by (5), Classifications (26), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetStability OLED materials and devices
US 7902374 B2Abstract
Organic light emitting materials and devices comprising phosphorescent metal complexes comprising ligands comprising aryl or heteroaryl groups substituted at both ortho positions are described. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.
This application claims the benefit of priority of provisional Application No. 60/844,636 filed on Sep. 15, 2006, and is a continuation-in-part of application Ser. No. 11/241,981, filed on Oct. 4, 2005, which claims the benefit of priority of provisional Application No. 60/678,170, filed May 6, 2005; Application No. 60/701,929, filed Jul. 25, 2005; and Application No. 60/718,336, filed Sep. 20, 2005. The contents of all five applications are herein incorporated by reference in their entirety.
The present invention generally relates to organic light emitting devices (OLEDs), and organic compounds used in these devices, as well as phosphorescent OLEDs having an electron impeding layer.
We have discovered that OLED devices that incorporate N-(2,6-disubstituted phenyl)-2-phenyl imidazole derived metal complexes can have lifetimes upwards of 5 times longer than devices incorporating the corresponding N-methyl imidazole complexes with the same R2 substituents.
This application is also related to U.S. Utility application Ser. No. 11/242,025 entitled “Electron Impeding Layer for High Efficiency Phosphorescent OLEDs,” filed on Oct. 4, 2005. The contents of these applications is herein incorporated by reference in their entirety. In one embodiment, the present invention provides an organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.
By “ortho positions,” we mean the positions on the aryl or heteroaryl group which are adjacent to the point of attachment of the second ring to the first ring. In the case of a six-membered ring aryl group attached via the 1-position, such as 2,6-dimethylphenyl, the 2-and 6-positions are the ortho positions. In the case of a 5-membered ring heteroaryl group attached via the 1-position, such as 2,5-diphenylpyrrol-1-yl, the 2-and 5-positions are the ortho positions. In the context of this invention, ring fusion at a carbon adjacent to the point of attachment, as in 2,3,4,5,7,8,9,10-ocathydroanthracen-1-yl, is considered to be a type of ortho substitution.
In the context of this invention, by “Set 1”, we mean structures d1-d19:
R1a-e are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1a-e may be linked to form a ring. By “Set 2a” we mean the group consisting of 2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,3,4,5,6-pentamethylphenyl, 2,6-dimethyl-4-phenylphenyl, 2,6-dimethyl-4-(3,5-dimethylphenyl)phenyl, 2,6-dimethyl-4-(2,6-dimethylphenyl)phenyl, 2,6-dimethyl-4-(4-pyridyl)phenyl, 2,6-dimethyl-4-(2,6-dimethyl-4-pyridyl)phenyl, 2,4-dimethyl-3-naphthyl, 2,6-dimethyl-4-cyanophenyl, 2,6-dimethyl-4-(9-carbazolyl)phenyl, 2,6-dimethyl-4-(9-phenyl-3-carbazolyl)phenyl, 2,6-dimethyl-4-(2,6-dimethyl-4-cyanophenyl)phenyl, and 1,8-dimethyl-9-carbazolyl.
By “Set 2b” we mean the group consisting of 2,6-di-isopropylphenyl, 2,4,6-tri-isopropylphenyl, 2,6-di-isopropyl-4-phenylphenyl, 2,6-di-isopropyl-4-(3,5-dimethylphenyl)phenyl, 2,6-di-isopropyl-4-(2,6-dimethylphenyl)phenyl, 2,6-di-isopropyl-4-(4-pyridyl)phenyl, 2,6-di-isopropyl-4-(2,6-dimethyl-4-pyridyl)phenyl, 2,4-di-isopropyl-3-naphthyl, 2,6-di-isopropyl-4-cyanophenyl, 2,6-di-isopropyl-4-(9-carbazolyl)phenyl, 2,6-di-isopropyl-4-(9 phenyl-3-carbazolyl)phenyl, 2,6-di-isopropyl-4-(2,6-dimethyl-4-cyanophenyl)phenyl, 2,6-di-tert-butylphenyl, 2,6-di-tert-butyl-4-(3,5-dimethylphenyl)phenyl, 2,6-bis(trimethylsilyl)phenyl, 2,6-bis(dimethylphenylsilyl)phenyl, and 2,6-bis(trimethylsilyl)-4-(3,5-dimethylphenyl)-phenyl.
By “Set 2c” we mean the group consisting of 2,6-di-phenylphenyl, 2,6-di(4-isopropylphenyl)-4-isopropylphenyl, 2,6-di(4-isopropylphenyl)-4-methylphenyl, 2,6-di(4-isopropylphenyl)-4-tert-butylphenyl, 2,4,6-triphenylphenyl, 2,6-di-(4-isopropylphenyl)phenyl, 2,6-di-(3,5-dimethylphenyl)phenyl, 2,4,6-tri(4-isopropylphenyl)phenyl, 2,6-di-(4-tert-butylphenyl)phenyl, 2,6-di-(4-fluorophenyl)phenyl, 2,6-di-(9-carbazolyl)-4-isopropylphenyl, 2,6-di-(9-phenyl-3-carbazolyl)-4-isopropylphenyl, 2,6-di-(4-methoxyphenyl)phenyl, 2,6-diphenyl-4-fluorophenyl, 2,6-di-(2-triphenylenyl)phenyl, 2,6-di-(2-triphenylenyl)-4-isopropylphenyl, 2,6-di-(2,6-dimethyl-4-pyridyl)phenyl, 2,6-di-(4-cyanophenyl)-4-isopropylphenyl, 2,6-di-2-naphthylphenyl, 2,6-di-(4-phenylphenyl)-4-isopropylphenyl, 2,6-di-(3-phenylphenyl)-4-isopropylphenyl, 2,6-di-(4-diphenylaminophenyl)phenyl, 2,6-di-(4-dimethylaminophenyl)phenyl, 2,6-di-(4-trimethylsilylphenyl)phenyl, 2,6-di-(4-triphenylsilylphenyl)phenyl, and 2,6-di-(4-diphenylmethylsilylphenyl)phenyl.
By “Set 2d” we mean structures c1-c9:
R1a,e are each independently selected from the group consisting of hydrocarbyl comprising two or more carbons, heteroatom substituted hydrocarbyl, aryl, and heteroaryl; Rb-d are each independently selected from the group consisting of H, F, cyano, alkoxy, aryloxy, hydrocarbyl, heteroatom substituted hydrocarbyl, aryl, and heteroaryl; in addition, any two of R1b-d may be linked to form a ring; and Ar1,2 are each independently aryl or heteroaryl. By “Set 3a,” we mean the structures f1-f4:
Arsr is the second ring; R1a,b are each independently selected from the group consisting of hydrogen, hydrocarbyl, and heteroatom substituted hydrocarbyl, cyano, and F; in addition, R1a,b may be linked to form a ring; and R2a,b are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, R2a,b may comprise a group bonded to said metal. By “Set 3b,” we mean structures f5-f9:
Arsr is the second ring; R1a-c are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1a-c may be linked to form a ring; and R2a,b are each independently selected from the group consisting of hydrogen, hydrocarbyl, and heteroatom substituted hydrocarbyl, cyano, and F; in addition, R2a,b may comprise a group bonded to said metal. By “Set 4,” we mean structures t1-t10:
Arfr is the first ring; Ar1 is aryl or heteroaryl; and R1a-d are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1a-d may be linked to form a ring. By “Set 5a,” we mean structures 11-17:
Ar1 is aryl or heteroaryl. By “Set 5b”, we mean structures 120-122:
R1a-i are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1c-i may be linked to form a ring; and R2a,b are each independently selected from the group consisting of hydrocarbyl comprising two or more carbons, heteroatom substituted hydrocarbyl, aryl, and heteroaryl. By “Set 5c”, we mean structures 140-146:
R1a-i are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1c-i may be linked to form a ring; Ar1 is aryl or heteroaryl; Ar3a is 4-isopropylphenyl; and Ar3b is 3,5-dimethylphenyl. By “Set 6a,” we structures mc3, mc50, mc48, mc25, mc46, mc5, mc4, mc54, mc51, mc26a, mc26, mc39, mc49, mc6, mc9, mc8, mc4b, mc38b, mc15, mc26b, mc28b, mc32b, mc33b, mc34b, mc35b, mc29b, mc30b, mc31b, mc42b, mc43b, mc44b, and mc45b:
Ar3 is aryl or heteroaryl; m is 1, 2 or 3; and n is an integer selected to satisfy the valency of the metal. By “Set 6b,” we mean structures mc37, oa9, oa4, oa6, oa8, u6, and oa5:
Ar3a is 4-isopropylphenyl; and Ar3b is 3,5-dimethylphenyl. By “Set 6c,” we mean structures mc1, mc2, mc11, mc12, mc13, mc17, mc18, mc19, mc20, mc21, mc22, mc23, mc24, mc27, mc36, oa11, mc51b, mc52b, oa12, oa1, oa2, oa3, oa8b, mc14, mc16, mc46b, mc49b, mc52b, mc53b, and mc51b:
R2a-c and R1a-q are each independently selected from the group consisting of hydrogen, hydrocarbyl, and heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R2a-c and R1a-q may be linked to form a ring, provided that if R1a and R2a are linked the ring is a saturated ring; Ar1-3 are aryl or heteroaryl; Arsr is the second ring; Arc is 9-carbazolyl or substituted 9-carbazolyl; Ln are ancillary ligands, which may be the same or different; m is 1, 2 or 3; n is an integer selected to satisfy the valency of M; and M is a metal selected from the group consisting of Re, Ru, Os, Rh, Ir, Pd, Pt, and Au. It will be understood that the aryl groups may be substituted. In certain preferred embodiments, the both ortho positions of the aryl or heteroaryl group of the second ring are substituted with substituents selected from the group consisting of aryl and heteroaryl. By “Set 6d,” we mean structures mc40b and mc41b:
R1a-i are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R1a-i may be linked to form a ring; and Ar1a,b are aryl or heteroaryl. By “Set 6e,” we mean structures m1-m176 in Table 2 below, wherein gs1, gs2, gs3, gs4, and gs5 are the general structures set forth in Set 7; 3,5-Me2Ph means 3,5-dimethylphenyl; and pip means 1-piperidinyl.
By “Set 7,” we mean structures gs1-gs5:
In a fourth preferred embodiment, the second ring is substituted by an aryl, heteroaryl, or electron withdrawing group. By “electron withdrawing group,” we mean a group with a positive value for the Hammett Substituent Constant corresponding to that group. Hammett Substituent Constants are known to those skilled in the art (see, for example, Hansch, C; Leo, A.; Taft, R. W.; Chem. Rev. 1991, Vol. 91, p. 165). A number of electron withdrawing groups have been reported in the literature as being compatible with OLED devices. Such groups are preferred. Examples of such groups include cyano, 9-carbazolyl, and 1-triazolyl.
In a eleventh preferred embodiment, the compound is sublimable. By “sublimable,” we mean that the compound has sufficient volatility and thermal stability at elevated temperatures that it can be incorporated into a vapor phase processed OLED device. Typically, this means that more than about a 25% yield of greater than about 98% pure sublimed material can be recovered upon sublimation over a period of at least about several hours at temperatures between about 200 and about 400� C. In some cases, the compound may melt or soften in the process, in which case the process may resemble a distillation.
In a thirty-fourth embodiment, the triplet energy of the arene or heteroarene corresponding to the second ring is greater than about 2.5 eV. By “arene or heteroarene corresponding to the second ring”, we mean the molecule obtained by attaching a hydrogen atom to the second ring in place of the first ring. For example, when the second ring is 2,6-dimethylphenyl, the corresponding arene would be 1,3-dimethylbenzene. Similarly, when the second ring is 2,6-dimethyl-4-phenylphenyl, the corresponding arene would be 1,5-dimethyl-3-phenylbenzene. Triplet energies for common arenes and heteroarenes may be found in a variety of reference texts, including “Handbook of Photochemistry” 2nd edition (S. L. Murov, I. Carmichael, G. L. Hug, eds; Dekker, 1993, N.Y.), or may be calculated by methods known to those skilled in the art, for example, by Density Functional Theory (DFT) calculations using Gaussian 98 with the G98/B31yp/cep-31 g basis set. Triplet energies greater than about 2.5 eV correspond to triplet transition wavelengths shorter than about 500 nm. Without wishing to be bound by theory, the inventors suppose that in some cases, an excessively low triplet energy on the second ring will either red-shift the phosphorescent emission, or reduce the radiative quantum yield, or both.
In a thirty-ninth preferred embodiment, the calculated singlet-triplet gap is less than about 0.4 eV. By “calculated singlet-triplet gap” we mean the difference in energy between the lowest lying singlet excited state and the lowest lying triplet excited state of the metal complex as calculated by Density Functional Theory (DFT) methods using Gaussian 98 with the G98/B31yp/cep-31 g basis set. In a fortieth preferred embodiment, the calculated singlet-triplet gap is less than about 0.3 eV. In a forty-first preferred embodiment, the calculated singlet-triplet gap is less than about 0.2 eV. In a forty-second preferred embodiment, the calculated singlet-triplet gap is less than about 0.1 eV.
In a forty-third preferred embodiment, the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.1 V. By “reduction potential of the ligand” we mean the electrochemical reduction potential in solution for the neutral compound corresponding to the ligand. If the ligand is a monoanionic bidentate donor derived from an N-aryl-2-phenylimidazole, the “neutral compound corresponding to the ligand” is the N-aryl-2-phenylimidazole. More generally, if the ligand is a neutral donor, then the “neutral compound corresponding to the ligand” and the ligand are the same compound, or are tautomers; if the ligand is a monoanionic donor, then the “neutral compound corresponding to the ligand” is the compound wherein the atom of the ligand that is bonded to the metal and bears a formal negative charge in the metal complex has a proton in place of the metal in the neutral compound corresponding to the ligand.
Suitable materials for the electron impeding layer include mCBP, which can be used in combination with many emissive layer materials, such as an emissive layer host that is mCP or mCBP and an emissive dopant that is one of compounds 1-5. See Table 3 and FIG. 52. This application is related to U.S. Provisional Application No. 60/678,170, filed on May 6, 2005, U.S. Provisional Application No. 60/701,929, filed on Jul. 25, 2005, U.S. Provisional Application No. 60/718,336, entitled “IMPROVED STABILITY OLED MATERIALS AND DEVICES,” which was filed on Sep. 20, 2005 and U.S. Utility application Ser. No. 11/241,981, entitled “IMPROVED STABILITY OLED MATERIALS AND DEVICES,” being filed on Oct. 4, 2005. The contents of these applications is herein incorporated by reference in their entirety.
Synthesis of fac-mc3
A 50 mL Schlenk tube flask was charged with N-(2,6-dimethyl phenyl)-2-phenylimidazole (5.30 g, 21 mmol) and tris(acetylacetonate)iridium(III) (1.96 g, 4.0 mmol). The reaction mixture was stirred under a nitrogen atmosphere and heated at 240� C. for 48 hours. After cooling, the solidified mixture was washed first with absolute ethanol followed by hexane. The residue was further purified by a silica gel column to give fac-mc3 (3.10 g). The product was further purified by vacuum sublimation. 1H and MS results confirmed the desired compound. λmax of emission=476, 504 nm (CH2Cl2 solution at room temperature), CIE=(0.21, 0.43), Eox=0.05 V, irreversible reduction at Epc=−2.85 V (vs. Fc+/Fc, in 0.10M nBu4NPF6 solution (DMF) with Pt working and auxiliary electrodes and a non-aqueous Ag/Ag+ reference electrode, and scan rates of 100 mVs−).
Synthesis of fac-mc25
A 50 mL Schlenk tube flask was charged with N-(2,6-dimethyl phenyl)-2-(4-fluoro phenyl)imidazole (8.50 g, 32 mmol) and tris(acetylacetonate)iridium(III) (3.14 g, 6.4 mmol). The reaction mixture was stirred under a nitrogen atmosphere and heated at 240� C. for 48 hours. After cooling, the solidified mixture was washed first with absolute ethanol followed by hexane. The residue was further purified by a silica gel column to give fac-mc25 (1.60 g). The product was further purified by vacuum sublimation. 1H and MS results confirmed the desired compound. λmax of emission=456, 486 nm (CH2Cl2 solution at room temperature), CIE=(0.20, 0.32).
Synthesis of fac-mc6
A 50 mL Schlenk tube flask was charged with N-(2,6-diisopropyl phenyl)-2-phenylimidazole (7.60 g, 25 mmol), tris(acetylacetonate)iridium(III) (2.45 g, 5.0 mmol) and tridecane (1 mL). The reaction mixture was stirred under a nitrogen atmosphere and heated at 240� C. for 48 hours. After cooling, the solidified mixture was washed first with absolute ethanol followed by hexane. The residue was further purified by a silica gel column to give fac-mc6 (1.5 g). The product was further purified by vacuum sublimation. 1H and MS results confirmed the desired compound. λmax of emission=476, 504 nm (CH2Cl2 solution at room temperature), CIE=(0.22, 0.43).
Synthesis of fac-mc4
A 2-neck 50 mL round bottom flask was charged with N-(2,6-dimethyl-4-phenylbenzene)-2-phenylimidazole (4.95 g, 15.3 mmol) and tris(acetylacetonate)iridium(III) (1.25 g, 2.54 mmol). The reaction mixture was stirred under a light nitrogen purge and heated at 230� C. for 20 hours. After cooling, the solidified mixture was dissolved with methylene chloride, transferred to a 100 mL flask, and evaporated without exposure to light. The residue was further purified by silica gel (treated with triethylamine) chromatography using 20% EtOAc/Hexanes as eluent to give fac-mc4 (˜1.0 g). This product was then recrystallized from diethyl ether. Attempts at sublimation of the dopant were unsuccessful to the thermal properties of the compound. 1H and MS results confirmed the structure of the compound. λmax of emission=475, 505 nm (methylene chloride solution at room temperature), CIE=(0.20, 0.41), Eox=0.05 V, quasi-reversible reduction at Epc=−2.9 V (vs. Fc+/Fc, in 0.10M Bun 4NPF6 solution (DMF) with Pt working and auxiliary electrodes and a non-aqueous Ag/Ag+ reference electrode, and scan rates of 100 mVs−1).
Synthesis of mc3-Cl
A 50 ml rounded flask was charged with 1.26 g of 2-phenyl-3-(2,6-dimethylphenyl)-imidazoline, 938 mg of IrCl3, and a mixture of 2-ethoxyethanol (24 mL) and water (6 mL). The reaction mixture was heated at 100� C. for 24 hrs. The reaction mixture was cooled to ambient temperature and the desired product was isolated by filtration.
Synthesis of mc26
A 25 ml rounded flask was charged with 57 mg of silver (I) oxide, 82 mg of 1-(3,4-dimethylphenyl)-3-methyl-benzimidazolate iodide, 118 mg of hi1 and 10 ml of dichloroethane. The reaction was stirred and heated with a heating mantle at 75� C. for 6 hours in the dark under nitrogen while protected from light with aluminum foil. The reaction mixture was cooled to ambient temperature and concentrated under reduced pressure. Filtration through Celite using dichloromethane as the eluent was performed to remove the silver(I) salts. A yellow solution was obtained and further purified by flash column chromatography on silica gel using dichloromethane as the eluent; the desired product was isolated.
Synthesis of fac-mc46
Synthesis of mc47
A 50 mL round bottom flask was charged mc3-Cl (162 mg, 1.12 mmol), silver trifluoromethansulfonate (576 mg, 2.24 mmol), 10 ml of methanol and 10 ml of dichloromethane. The reaction mixture was stirred at room temperature for 2 hours. The reaction mixture was filtered and the filtrate was concentrated to dryness. The residue was transfer to a 50 mL round bottom flask which was charged with 2-pyrazopyridine (325 mg, 2.24 mmole), Sodium hydride (94.2 mg for 60% in mineral oil, 2.35 mmole) and 20 ml of anhydrous acetontrile. The reaction mixture was stirred under a light nitrogen purge and heated at 81� C. for 20 hours. After cooling, the reaction mixture was concentrated to dryness. The residue was further purified by silica gel (treated with triethylamine) chromatography using 40% EtOAc/methylene chloride as eluent to give mc47 (700 mg). 1H and MS results confirmed the structure of the compound. λmax of emission=467, 494 nm (methylene chloride solution at room temperature), CIE=(0.20, 0.40), Eox=0.38 V(i), irreversible reduction at Epc=−3.06 V (vs. Fc+/Fc, in 0.10M Bun 4NPF6 solution (DMF) with Pt working and auxiliary electrodes and a non-aqueous Ag/Ag+ reference electrode, and scan rates of 100 mVs−1).
Synthesis of mc54
A 1-neck 50 mL round bottom flask was charged with N-(2,6-dimethyl-4-(3,5-dimethylphenyl)benzene)-2-phenylimidazole (4.5 g, 12.8 mmol) and tris(acetylacetonate)iridium(III) (1.57 g, 3.2 mmol). The reaction mixture was stirred under a nitrogen atmosphere and heated at 200� C. for 60 hours. After cooling, the solidified mixture was dissolved with methylene chloride and purified by silica gel (treated with triethylamine) chromatography using 20% dichloromethane/hexanes as eluent. The solvent was removed and the product was then recrystallized from dichloromethane/methanol and filtered yielding 1.4 grams. The material was slurried in hot ethyl acetate and filtered to yield 1.2 grams of bright yellow solid. The material was further purified by sublimation. 1H and MS results confirmed the structure of the compound. λmax of emission=476 nm (methylene chloride solution at room temperature), CIE=(0.23, 0.43).
Synthesis of mc48
Synthesis of mc49i-1
A 1-neck 50 mL round bottom flask was charged with N-(2,6-dimethyl-4-bromobenzene)-2-phenylimidazole (3.0 g, 9.2 mmol) and tris(acetylacetonate)iridium(III) (1.12 g, 2.3 mmol). The reaction mixture was stirred under a light nitrogen purge and heated at 200� C. for 48 hours. After cooling, the solidified mixture was dissolved with methylene chloride and purified by silica gel (treated with triethylamine) chromatography using 20% dichloromethane/hexanes as eluent. The good fractions were combined and the solvent removed by rotary evaporation. The product was then recrystallized from dichloromethane/methanol and filtered yielding 0.17 grams of fac mc49i-1.
Synthesis of mc49
A 1-neck 100 ml round bottom flask was charged with mc49i-1 (0.15 g, 0.13 mmol), 4-pyridineboronic acid, (0.06 g, 0.0.39 mmol), palladium acetate (2 mg, 9�10−6 mol), triphenylphosphine (10 mg, 4�10−5 mmol), potassium carbonate (0.14 g, 1 mmol), 20 ml 1,2-dimethoxyethane, and 10 ml water. The mixture was heated to reflux for 6 hours and then allowed to cool to room temperature. The mixture was extracted with dichloromethane and water. The organic layer was dried with magnesium sulfate and filtered. The solvent was removed and the product was purified by silica gel column (treated with triethylamine) using 95% ethyl acetate/methanol as the eluent. The product was crystallized from dichloromethane/hexanes.
Synthesis of mc50
A 50 mL round bottom flask was charged with N-(2,6-dimethylphenyl)-2-(p-tolylimidazole (4.50 g, 19 mmol) and tris(acetylacetonate)iridium(III) (1.87 g, 3.81 mmol). The reaction mixture was stirred under a light nitrogen purge and heated in a sand bath at 200� C. for 96 hours. After cooling, the solidified mixture was dissolved with methylene chloride, transferred to a 100 mL flask, and evaporated without exposure to light. The residue was further purified by silica gel (treated with triethylamine) chromatography using 10% methyelene chloride/hexanes as eluent to give fac-tris[N-(2,6-dimethyl phenyl)-2-p-tolylimidazole]iridium(III) (1.2 g). This product was then recrystallized from methylene chloride/hexanes to give 0.80 g as yellow crystals. Sublimation of the product yielded 0.42 g as yellow crystals. NMR and MS results confirmed the structure of the compound. λmax of emission=472, 502 nm (methylene chloride solution at room temperature), CIE=(0.21, 0.40), Tg=363.8� C. Eox=0.04 V, Ered=Not Detected (vs. Fc+/Fc, in 0.10M Bun 4NPF6 solution (DMF) with Pt working and auxiliary electrodes and a non-aqueous Ag/Ag+ reference electrode, and scan rates of 100 mVs−1).
Synthesis of mc51
Synthesis of mc52
In a 100 mL round bottom flask was dissolved 3.0 g (1.62 mmol) chloro-bridged dimer in 60 mL 1,2-dichloroethane. 1.12 g (4.83 mmol) silver oxide was then added and the mixture was allowed to reflux for 10 minutes under N2 atmosphere. 1.08 g (3.22 mmol) 1-phenyl-3-methyl-benzimidazolate iodide was added to the mixture and the mixture was heated for 1 minute at reflux followed by cooling. The mixture was then filtered and the solids rinsed with methylene chloride. The filtrate was then evaporated down and the residue purified on a silica gel column (treated with triethylamine) using 40% methylene chloride/hexanes. The pure fractions were evaporated of solvent and the solids recrystallized from methylene chloride/hexanes to give ˜1.8 g er-bis[N-(2,6-dimethyl-4-{2,5-dimethylphenyl}phenyl)-2-phenylimidazole]-N-phenyl-3-methylbenzimidazole iridium(III). The solids were then stirred in 1.5 L acetonitrile in a quartz chamber and photoisomerized with 254 nm UV light in a rayonet under N2 atmosphere. After 72 hours, photoisomerization to the fac isomer was complete to afford mc52.
Synthesis of mc37
Synthesis of oa9
Synthesis of oa8
Synthesis of ii1
Synthesis of mc46a
Synthesis of mc48f
Synthesis of oa8c
Step 1: Synthesis of N-(2-chloroethyl)-4-fluorobenzamide
In a 1 L round bottom flask, 50.4 g sodium hydroxide (1.26 mol) was dissolved in 500 mL water (˜10% solution). 66.6 g (0.574 mol) 2-chloroethylamine hydrochloride was then added and the solution stirred in an ice bath at 0� C. until the salt was completely dissolved. 100 g (0.631 mol) 4-fluorobenzoyl chloride was then added dropwise via an addition funnel into the vigorously stirred solution. After addition, the solution stirred at 0� C. for 1 hour followed by stirring at room temperature for 1 hour. The cloudy mixture was then filtered to remove the water and the solids washed with ether and then filtered to give 118 g crude (slightly wet) benzamide (Alternatively, the solids could be dissolved in methylene chloride, dried with magnesium sulfate, filtered and evaporated to completely remove water from the solids). These solids were recrystallized from 120 ml EtOAc/200 mL hexanes to give 88.2 g crystalline N-(2-chloroethyl)-4-fluorobenzamide after hexanes wash and drying (an additional 6.22 g benzamide recrystallized from the original water mother liquor). NMR confirmed the structure of this compound (81.4% total yield).
Step 2: Synthesis of N-(2,4,6-tribromophenyl)-2-(4-fluorophenyl)imidazoline
To a dried 3 L round bottom flask equipped with stirbar was added 55.6 g (0.276 mol) N-(2-chloroethyl)-4-fluorobenzamide. This solid was then dissolved in 600 mL anhydrous m-xylene under N2 atmosphere and light heat. 86.1 g (0.413 mol) phosphorus pentachloride was then added and the mixture was allowed to reflux under N2 for 2 hours (completely dissolving the PCl5). The solution was then cooled whereupon 100 g (0.303 mol) tribromoaniline was added (Additionally, a base trap was attached to the condenser to neutralize generating HCl gas). This mixture was allowed to reflux for 20 hours. The solution was then allowed to cool and the imidazoline collected on a filter and washed with toluene followed by hexanes. The solids were then dissolved in methylene chloride and extracted with diluted NH4OH twice. The organic layer was dried over MgSO4, filtered and evaporated of solvent to give ˜65 g imidazoline. Recrystallization was achieved from methylene chloride/hexanes. NMR confirmed the structure of this compound.
Step 3: Aromatization of N-(2,4, 6-tribromophenyl)-2-(4-fluorophenyl)imidazoline
59.2 g (0.124 mol) N-(2,4,6-tribromophenyl)-2-(4-fluorophenyl)imidazoline was added to a 2 L flask equipped with stirbar. ˜1 L MeCN was added and the mixture stirred at room temperature until the solids were dissolved. 33% KMnO4/Montmorillonite was added in portions (0.248 mol) to the stirred mixture over a period of a few hours. After stirring overnight, the mixture was quenched with 200 mL EtOH and then poured over a celite mat to remove the oxidant. The filtrate was evaporated of solvent and the residue purified on a silica gel column using 20% EtOAc/MeCl2 as eluent. The product fractions were evaporated of solvent to give 18.8 g crude imidazole recrystallized from MeCl2/Hexanes (17.4 g, 29.4% yield). The product was confirmed by NMR.
Step 4: Synthesis of N-(2,4,6-triphenylphenyl)-2-(4-fluorophenyl)imidazole
13.36 g (28.1 mmol) N-(2,4,6-tribromophenyl)-2-(4-fluorophenyl)imidazole, 14.1 g (104 mmoL) phenylboronic acid, 2.21 g (8.40 mmol) triphenylphosphine, 0.63 g (2.81 mmol) Pd(II) acetate, and 31.4 g (228 mmol) potassium carbonate were added to a 2 L round bottom flask equipped with stir bar and refluxed in 800 mL DME/400 mL water overnight under N2 atmosphere. The mixture was then cooled, added to a separatory funnel and the water removed. The organic mixture was then enriched with 800 mL EtOAc and extracted with 2�400 mL portions of water. The organic layer was then dried over MgSO4, filtered and evaporated of solvent. Next, the residue was solubilized with 200 mL MeCl2 and dried on silica. This silica was then layered on top of a silica gel column that was eluted with a gradient of 30% EtOAc/hexanes-50% EtOAc/hexanes. The pure fractions, after evaporation of solvent, gave 9.3 g N-(2,4,6-triphenylphenyl)-2-(4-fluorophenyl)imidazole upon recrystallization from CH2Cl2/hexanes (71.0% yield). The product was confirmed by NMR.
Step 5: Ligation to Form oa8b
The ligand from the preceding step was used to prepare oa8b following the procedure of Example 20.
Synthesis of oa10
fac-tris[N-(2,4,6-triphenylphenyl)-2-phenylimidazole]
Step 1: Synthesis of Intermediate #1
To a dried 2 L round bottom flask equipped with mechanical stirring was added N-(2-chloroethyl)benzamide (59.4 g, 0.32 mol). The solid was dissolved in 600 mL anhydrous m-xylene under nitrogen. Phosphorus pentachloride (100.8 g, 0.484 mol) was added and the mixture heated to reflux under nitrogen for 2 h (completely dissolving the PCl5). The solution was cooled and 117.37 g (0.35 mol) tribromoaniline was added, after which the mixture was heated to reflux for 20 h. After cooling, the mixture was filtered and the solid imidazoline product was collected and washed with toluene followed by hexanes. The resultant crude product was dissolved in methylene chloride and washed twice with dilute aq NH4OH. The organic layer was dried over MgSO4, filtered and concentrated under reduced pressure to afford 106 g of Intermediate #1 (71%).
Step 2: Synthesis of Intermediate #2
Potassium permanganate (43.6 g) and basic aluminum oxide (65 g) were ground together in a mortar until a fine homogeneous power was obtained. To a solution of Intermediate #1 (55.73 g, 0.121 mol) in CH3CN, KMnO4-Al2O3 (108.6 g) was added portion-wise and the mixture stirred at room temperature for 24 h. Ethanol (500 mL) was added to reduce excess oxidant. After stirring for an additional 1 h, the mixture was filtered through a short pad of Celite and the solid washed with CH3CN (500 mL). The filtrate was evaporated and the resulting crude material was purified by chromatography on SiO2 to obtain Intermediate #2, N-(2,4,6-tribromophenyl)-2-phenylimidazole (18.2 g, 33%).
Step 3: Synthesis of Intermediate #3
To a 500 mL flask was added above Intermediate #2 (18.25 g, 39.93 mmol), phenylboronic acid (19.47 g, 159.7 mmol), palladium (II) acetate (873 mg, 3.89 mmol), triphenylphosphine (4.084 g, 15.57 mmol), potassium carbonate (212 mL of a 2 M aqueous solution, 425 mmol), and 240 mL of dimethoxyethane. The reaction was heated to reflux and stirred under a nitrogen atmosphere for 12 h. The mixture was extracted with ethyl acetate and further purified by a silica gel column. Yield was 17 g (95%). GC-MS and NMR analyses confirmed the structure.
Step 4: Synthesis of fac-tris[N-(2,4,6-triphenylphenyl)-2-phenylimidazole]
The synthesis, isolation, purification, sublimation and subsequent handling of fac-tris[N-(2,4,6-triphenylphenyl)-2-phenylimidazole] is conducted in dim room light or with yellow filters over the lights and windows to minimize decomposition. To a 100 mL round bottom flask were added Intermediate #3 (4 g, 8.92 mmol), tris(acetylacetonate)iridium (III) (1.24 g, 2.55 mmol) and ethylene glycol (40 mL). The mixture was heated to reflux and stirred under a nitrogen atmosphere for 48 h. After cooling, the precipitate which formed was isolated by filtration and washed with ethanol. The crude product was further purified by a silica gel column, using silica gel that had been washed with a solution of triethylamine in hexanes (20:80), and recrystallized from dichloromethane/methanol to afford fac-tris[N-(2,4,6-triphenylphenyl)-2-phenylimidazole.
Device Fabrication Examples
OLED devices were prepared with compounds listed in FIG. 3 using the following general procedures.
The definitions for materials CuPc, NPD, CBP, HPT, and BAlq2 have been given above; the structure of Compound A (abbreviated as “cmpd A”) is given in FIG. 3. The numbers in parentheses refer to the thickness of the layer in Angstroms, and the percentage after cmpd A refers to the weight percent of compound A in that layer.
Specific exemplary devices of the invention (numbered in bold) as well as comparative devices are listed in Table 3. It is understood that the specific methods, materials, conditions, process parameters, apparatus and the like do not necessarily limit the scope of the invention. All thicknesses are measured in angstroms, and dopant concentration are in wt %.
CuPc (100)/NPD (300)/mCBP: compound “oa10”
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