WO2018125512A1 - High triplet energy phosphine oxide compounds for oled application - Google Patents

High triplet energy phosphine oxide compounds for oled application Download PDF

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WO2018125512A1
WO2018125512A1 PCT/US2017/064124 US2017064124W WO2018125512A1 WO 2018125512 A1 WO2018125512 A1 WO 2018125512A1 US 2017064124 W US2017064124 W US 2017064124W WO 2018125512 A1 WO2018125512 A1 WO 2018125512A1
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organic electroluminescent
heteroaryl
electroluminescent compound
formula
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French (fr)
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Kyoung Moo Koh
Mark E. Ondari
Sukrit MUKHOPADHYAY
David S. LAITAR
Timothy J. Gallagher
Kevin P. LAWRY
Hong Yeop NA
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Dow Global Technologies Llc
Rohm And Haas Electronic Materials Korea Ltd.
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/6553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having sulfur atoms, with or without selenium or tellurium atoms, as the only ring hetero atoms
    • C07F9/655345—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having sulfur atoms, with or without selenium or tellurium atoms, as the only ring hetero atoms the sulfur atom being part of a five-membered ring
    • C07F9/655354—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having sulfur atoms, with or without selenium or tellurium atoms, as the only ring hetero atoms the sulfur atom being part of a five-membered ring condensed with carbocyclic rings or carbocyclic ring systems
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/28—Phosphorus compounds with one or more P—C bonds
    • C07F9/50—Organo-phosphines
    • C07F9/53—Organo-phosphine oxides; Organo-phosphine thioxides
    • C07F9/5325—Aromatic phosphine oxides or thioxides (P-C aromatic linkage)
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
    • C07F9/572—Five-membered rings
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
    • C07F9/572—Five-membered rings
    • C07F9/5728—Five-membered rings condensed with carbocyclic rings or carbocyclic ring systems
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    • C07—ORGANIC CHEMISTRY
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
    • C07F9/576—Six-membered rings
    • C07F9/5765—Six-membered rings condensed with carbocyclic rings or carbocyclic ring systems
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
    • C07F9/576—Six-membered rings
    • C07F9/58—Pyridine rings
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/645—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having two nitrogen atoms as the only ring hetero atoms
    • C07F9/6509—Six-membered rings
    • C07F9/6512—Six-membered rings having the nitrogen atoms in positions 1 and 3
    • C—CHEMISTRY; METALLURGY
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/6515—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having three nitrogen atoms as the only ring hetero atoms
    • C07F9/6521—Six-membered rings
    • C—CHEMISTRY; METALLURGY
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    • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
    • C07F9/02—Phosphorus compounds
    • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
    • C07F9/655—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms
    • C07F9/65515—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms the oxygen atom being part of a five-membered ring
    • C07F9/65517—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms the oxygen atom being part of a five-membered ring condensed with carbocyclic rings or carbocyclic ring systems
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    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/06—Luminescent, e.g. electroluminescent, chemiluminescent materials containing organic luminescent materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/10—Triplet emission

Definitions

  • the present invention relates to phosphine oxide compounds and organic electroluminescent devices comprising the compounds. More particularly, the invention relates to phosphine oxide compounds with specific chemical structures which have a high triplet energy level suitable for an organic light emitting device (OLED) application.
  • OLED organic light emitting device
  • OLEDs are devices in which stacks of organic layers including an electron transport layer (ETL), an emission layer (EML) and a hole transport layer (HTL) are interposed between two electrodes.
  • EML contains at least one organic compound that emits light in response to an electric current between these two electrodes.
  • Such organic compounds are called electroluminescent compounds.
  • electroluminescent compounds include specific Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels, a sufficient energy gap between HOMO and LUMO, and a higher triplet energy level.
  • One embodiment of the invention is an organic electroluminescent compound represented by the following Formula (1) or Formula (2): Formula (1)
  • Ri, R 2 and R 3 are each selected from the following (a) or (b),
  • Ri is an aryl group which may be substituted by a heteroaryl group
  • R 2 and R 3 are independently selected from an aryl group which is substituted by a heteroaryl group and the substituent of R 2 and the substituent of R 3 are different heteroaryl groups
  • Ri and R 2 are each an aryl group and R 3 is a group represented by the following formula (3), formula (4) or formula (5);
  • R 4 ,R 6 and R 7 are each selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a diphenyl phosphine oxide group, a phenyl phosphine group or a carbazolyl group, R5, Rs and R9 are each selected from an alkyl group having 1 to 8 carbon atoms or a heteroaryl group, X is selected from an oxygen atom or a sulfur atom;
  • Another embodiment of the invention is an organic electroluminescent device containing the organic electroluminescent compound.
  • aryl refers to an organic radical derived from aromatic hydrocarbon by the removal of one hydrogen atom therefrom.
  • An aryl group may be a monocyclic and/or fused ring system, each ring of which suitably contains from 4 to 6, preferably from 5 or 6, atoms.
  • An aryl also comprises those where two or more aryl groups are combined through single bond(s).
  • aryls comprise phenyl, naphthyl, biphenyl, anthryl, indenyl, fluorenyl, benzofluorenyl, phenanthryl, triphenylenyl, pyrenyl, perylenyl, chrysenyl, naphtacenyl, fluoranthenyl and the like.
  • the naphthyl may be 1 -naphthyl or 2-naphthyl.
  • the anthryl may be 1 -anthryl, 2-anthryl or 9-anthryl.
  • the fluorenyl may be any one of 1-fluorenyl, 2-fluorenyl, 3-fluorenyl, 4-fluorenyl and 9-fluorenyl.
  • the heteroaryl may be a 5- or 6- membered monocyclic heteroaryl, or a polycyclic heteroaryl which is fused with one or more benzene ring(s), and may be partially saturated.
  • the structures that one or more heteroaryl group(s) are bonded through a single bond are also comprised.
  • the heteroaryl groups comprise divalent aryl groups of which the heteroatoms are oxidized or quarternized to form N-oxides, quaternary salts, or the like.
  • Specific examples comprise monocyclic heteroaryl groups, such as furyl, thiophenyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl and pyridazinyl; polycyclic heteroaryl groups such as benzofuranyl, fluoreno[4, 3-b]benzofuranyl, benzothiophenyl, fluoreno[4, 3-b]benzothiophenyl, isobenzofurany
  • One embodiment of the present invention is the organic electroluminescent compounds having the structure represented by the following Formula (1).
  • Ri, R 2 and R 3 are each selected from Group (a) or Group (b) described below.
  • Ri is an aryl group which may be substituted by a heteroaryl group.
  • R 2 and R 3 are independently selected from an aryl group which is substituted by a heteroaryl group and the substituent of R 2 and the substituent of R 3 are different heteroaryl groups.
  • Suitable examples of Ri comprise a phenyl group and a substituted phenyl group.
  • Substituents of the phenyl group comprise a pyridinyl group, a pyrimidinyl group, a pyrazinyl group and a carbazolyl group.
  • Suitable examples of the R 2 and R 3 comprise a phenyl group which is substituted by a heteroaryl group.
  • the heteroaryl group includes a pyridinyl group, a pyrimidinyl group, a pyrazinyl group and a carbazolyl group, a diphenyl pyrimidynyl group, a diphenyl triazolyl group, a phenyl carbazolyl group, a carbazolyl group which is substituted by a phenyl carbazolyl group and a diphenyl amino group.
  • Suitable examples of the compound represented by Group (a) of Formula (1) are selected from the following structures:
  • one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) Group (a) has a pyridinyl group as its heteroaryl group.
  • Such compounds are disclosed as (A-l) to (A-5).
  • one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) Group (a) has a carbazolyl group as its heteroaryl group.
  • Such compounds are disclosed as (A-l) to (A-5) and (B-l) to (B-5).
  • one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) has both a pyridinyl group and a carbazolyl group as its heteroaryl group. Such compounds are disclosed as (A-l) to (A-5).
  • Ri and R 2 are each aryl group and R 3 is represented by the following formula (3), formula (4) or formula (5).
  • R 4 , R 6 and R 7 are each selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a heteroaryl group or a group having an aryl group and a phosphine oxide group.
  • R5, Rs and R9 are selected from an alkyl group having 1 to 8 carbon atoms or a heteroaryl group.
  • R 8 and R9 can form a ring.
  • X is selected from an oxygen atom or a sulfur atom.
  • Suitable examples of the R 4 , R 6 and R 7 comprise a hydrogen atom, a methyl group, an ethyl group, a butyl group, a hexyl group, an octyl group, a diphenyl phosphine oxide group, a phenyl phosphine group and a carbazolyl group.
  • Suitable examples of the R5 comprise a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a diphenyl pyridinyl group, a carbazolyl group, a diphenyl phosphine oxide group and a diphenyl phosphine oxide group substituted carbazolyl group.
  • Suitable examples of the compound represented by Group (b) of Formula (1) are selected from the following structures:
  • Rio to R15 are an aryl group or an aryl group substituted by an aryl group, a heteroaryl group or amine group. At least one of Rio to R15 is an aryl group which substituted by a heteroaryl group.
  • L is an alkylene group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 2 carbon atoms.
  • the phosphine oxide compounds of the present invention may have a molecular weight of 1200 Dalton or less. More preferably, the molecular weight of the compounds are 1000 Dalton or less, the most preferably 800 Dalton or less.
  • the energy of the Ti state was computed as the difference in energy between the minima of So and Ti potential energy surfaces (PES). All the calculations were performed using G09 suit of programs (Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J.
  • the HOMO values of the phosphine oxide compounds of the present invention are shallower (higher) than -7.0 eV, more preferably shallower than -6.5 eV, the most preferably shallower than -5.5eV.
  • the LUMO values of the phosphine oxide compounds of the present invention are deeper (lower) than -0.75 eV, more preferably deeper than -1.0 eV, the most preferably deeper than -1.25 eV.
  • the triplet energy values of the phosphine oxide compounds of the present invention are higher than 2.8 eV, more preferably higher than 2.9 eV, the most preferably higher than 2.95 eV.
  • an electroluminescent device includes a first electrode, a second electrode, and one or more organic layers interposed between the first electrode and the second electrode.
  • the organic layers include electron transport layers
  • EMLs emission layers
  • HTLs hole transport layers
  • the LUMO level of this suite of molecules ranges between -1.2 eV and -1.5 eV, which is identified as a desired range for host materials.
  • the pyridine-substituted phosphine oxides can be used in emission layer as a high triplet host materials.
  • this suite of molecules has the correct electronics for an efficient host material.
  • OLEDs were fabricated onto an ITO coated glass substrate that served as the anode, and topped with an aluminum cathode. All organic layers were thermally deposited by physical vapor deposition, in a vacuum chamber with a base pressure of less than 10 "7 torr.
  • Each cell containing HIL1, HIL2, HTL1, HTL2, EBL, EML host, EML dopant, ETL1, ETL2, or EIL, was placed inside a vacuum chamber, until it reached 10 "6 torr.
  • a controlled current was applied to the cell, containing the material, to raise the temperature of the cell. An adequate temperature was applied to keep the evaporation rate of the materials constant throughout the evaporation process.
  • N4,N4'-diphenyl-N4,N4'-bis(9-phenyl-9H-carbazol-3-yl)-[l,l'- biphenyl]-4,4'-diamine was evaporated at a constant lA/s rate, until the thickness of the layer reached 600 Angstrom.
  • the dipyrazino[2,3-f:2',3'-h]quinoxaline- 2,3,6,7,10,11-hexacarbonitrile layer was evaporated at a constant 0.5A/s rate, until the thickness reached 50 Angstrom.
  • N-([l,l'-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9- phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine was evaporated at a constant lA/s rate, until the thickness reached 150 Angstrom.
  • N,N-di([l,l'-biphenyl]-4-yl)-4'- (9H-carbazol-9-yl)-[l,l'-biphenyl]-4-amine was evaporated at a constant lA/s rate, until the thickness reached 50 Angstrom.
  • the deposition rate for host materials was 0.85A/s, and the deposition for the dopant material was 0.15 A/s, resulting in a 15% doping of the host materials.
  • 5-(4-([l,r-biphenyl]-3-yl)-6-phenyl-l,3,5-triazin-2-yl)-7,7-diphenyl-5,7- dihydroindeno[2,l-b]carbazole was evaporated at a constant lA/s rate, until the thickness reached 50 Angstrom.
  • J-V-L current- voltage-brightness
  • EL spectra of the OLED were collected by a calibrated CCD spectrograph and External Quantum Efficiency (EQE) was analyzed by spectroradiometer PR655 (PHOTO RESEARCH®, 7279 William Barry Blvd., Syracuse, NY 13212-3349, U.S.A.).
  • OLED comprising the Compound 1 or Compound 2 had a higher luminous efficiency and EQL compared to the OLED comprising reference.

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Abstract

Phosphine oxide compounds which have a high Triplet Energy used in an emission layer of Organic Light Emitting Devices (OLEDs) and OLEDs comprising the compounds are disclosed.

Description

HIGH TRIPLET ENERGY PHOSPHINE OXIDE COMPOUNDS FOR
USE IN ELECTROLUMINESCENT DEVICES
Field of the invention
The present invention relates to phosphine oxide compounds and organic electroluminescent devices comprising the compounds. More particularly, the invention relates to phosphine oxide compounds with specific chemical structures which have a high triplet energy level suitable for an organic light emitting device (OLED) application.
Background of the invention
Organic light emitting devices (OLEDs) are devices in which stacks of organic layers including an electron transport layer (ETL), an emission layer (EML) and a hole transport layer (HTL) are interposed between two electrodes. EML contains at least one organic compound that emits light in response to an electric current between these two electrodes. Such organic compounds are called electroluminescent compounds. Several properties required for such electroluminescent compounds include specific Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels, a sufficient energy gap between HOMO and LUMO, and a higher triplet energy level.
Some prior arts disclose phosphine oxide compounds used for electroluminescent devices, see JP63056610A, JP9268283A, JP4876333B, JP2004095221A, JP2004203828A, WO2005073340A, US20090167166A, JP2008244013A, US20080238307A, US20080241518A, and JP2008244012A. However, there remains a need for new compounds which have specific HOMO/LUMO levels, a sufficient HOMO/LUMO energy gap and a higher triplet energy level that are useful for OLEDs that have improved device performance.
Summary of the invention
One embodiment of the invention is an organic electroluminescent compound represented by the following Formula (1) or Formula (2):
Figure imgf000003_0001
Formula (1)
wherein Ri, R2 and R3 are each selected from the following (a) or (b),
(a) Ri is an aryl group which may be substituted by a heteroaryl group, R2 and R3 are independently selected from an aryl group which is substituted by a heteroaryl group and the substituent of R2 and the substituent of R3 are different heteroaryl groups,
(b) Ri and R2 are each an aryl group and R3 is a group represented by the following formula (3), formula (4) or formula (5);
Figure imgf000003_0002
wherein R4 ,R6 and R7 are each selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a diphenyl phosphine oxide group, a phenyl phosphine group or a carbazolyl group, R5, Rs and R9 are each selected from an alkyl group having 1 to 8 carbon atoms or a heteroaryl group, X is selected from an oxygen atom or a sulfur atom;
Figure imgf000003_0003
Formula (2) wherein Rio to R15 are an aryl group or an aryl group substituted by an aryl group, a heteroaryl group or an amine group, at least one of Rio to R15 are an aryl group which is substituted by a heteroaryl group, L is an alkylene group having 1 to 4 carbon atoms.
Another embodiment of the invention is an organic electroluminescent device containing the organic electroluminescent compound.
Detailed description of the invention
As used throughout this specification, the term "aryl" refers to an organic radical derived from aromatic hydrocarbon by the removal of one hydrogen atom therefrom. An aryl group may be a monocyclic and/or fused ring system, each ring of which suitably contains from 4 to 6, preferably from 5 or 6, atoms. An aryl also comprises those where two or more aryl groups are combined through single bond(s). Examples of aryls comprise phenyl, naphthyl, biphenyl, anthryl, indenyl, fluorenyl, benzofluorenyl, phenanthryl, triphenylenyl, pyrenyl, perylenyl, chrysenyl, naphtacenyl, fluoranthenyl and the like. The naphthyl may be 1 -naphthyl or 2-naphthyl. The anthryl may be 1 -anthryl, 2-anthryl or 9-anthryl. The fluorenyl may be any one of 1-fluorenyl, 2-fluorenyl, 3-fluorenyl, 4-fluorenyl and 9-fluorenyl.
As used throughout this specification, the term "heteroaryl" refers to an aryl group, in which at least one carbon atom, CH group or CH2 group within the ring is replaced with a heteroatom (for example, B, N, O, S, P(=0), Si and P). The heteroaryl may be a 5- or 6- membered monocyclic heteroaryl, or a polycyclic heteroaryl which is fused with one or more benzene ring(s), and may be partially saturated. The structures that one or more heteroaryl group(s) are bonded through a single bond are also comprised. The heteroaryl groups comprise divalent aryl groups of which the heteroatoms are oxidized or quarternized to form N-oxides, quaternary salts, or the like. Specific examples comprise monocyclic heteroaryl groups, such as furyl, thiophenyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl and pyridazinyl; polycyclic heteroaryl groups such as benzofuranyl, fluoreno[4, 3-b]benzofuranyl, benzothiophenyl, fluoreno[4, 3-b]benzothiophenyl, isobenzofuranyl, benzimidazolyl, benzothiazolyl, benzisothiazolyl, benzisoxazolyl, benzoxazolyl, isoindolyl, indolyl, indazolyl, benzothiadiazolyl, quinolyl, isoquinolyl, cinnolinyl, quinazolinyl, quinoxalinyl, carbazolyl, phenanthridinyl and benzodioxolyl; and corresponding N-oxides (for example, pyridyl N-oxide, quinolyl N-oxide) and quaternary salts thereof.
One embodiment of the present invention is the organic electroluminescent compounds having the structure represented by the following Formula (1).
O
P.
Rf I R3
Formula (1)
In Formula (1), Ri, R2 and R3 are each selected from Group (a) or Group (b) described below.
Group (a)
In Formula (1), Ri is an aryl group which may be substituted by a heteroaryl group. R2 and R3 are independently selected from an aryl group which is substituted by a heteroaryl group and the substituent of R2 and the substituent of R3 are different heteroaryl groups.
Suitable examples of Ri comprise a phenyl group and a substituted phenyl group. Substituents of the phenyl group comprise a pyridinyl group, a pyrimidinyl group, a pyrazinyl group and a carbazolyl group. Suitable examples of the R2 and R3 comprise a phenyl group which is substituted by a heteroaryl group. The heteroaryl group includes a pyridinyl group, a pyrimidinyl group, a pyrazinyl group and a carbazolyl group, a diphenyl pyrimidynyl group, a diphenyl triazolyl group, a phenyl carbazolyl group, a carbazolyl group which is substituted by a phenyl carbazolyl group and a diphenyl amino group.
Suitable examples of the compound represented by Group (a) of Formula (1) are selected from the following structures:
Figure imgf000005_0001
Figure imgf000006_0001
Figure imgf000007_0001
Figure imgf000008_0001
Figure imgf000009_0001
Preferably, one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) Group (a) has a pyridinyl group as its heteroaryl group. Such compounds are disclosed as (A-l) to (A-5).
Preferably, one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) Group (a) has a carbazolyl group as its heteroaryl group. Such compounds are disclosed as (A-l) to (A-5) and (B-l) to (B-5).
More preferably, one embodiment of the invention for the organic electroluminescent compounds disclosed in Formula (1) Group (a) has both a pyridinyl group and a carbazolyl group as its heteroaryl group. Such compounds are disclosed as (A-l) to (A-5). Group (b)
In Formula (1), Ri and R2 are each aryl group and R3 is represented by the following formula (3), formula (4) or formula (5).
Figure imgf000010_0001
In the formulas (3) to (5), R4, R6 and R7 are each selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a heteroaryl group or a group having an aryl group and a phosphine oxide group. R5, Rs and R9 are selected from an alkyl group having 1 to 8 carbon atoms or a heteroaryl group. R8 and R9 can form a ring. X is selected from an oxygen atom or a sulfur atom.
Suitable examples of the R4, R6 and R7 comprise a hydrogen atom, a methyl group, an ethyl group, a butyl group, a hexyl group, an octyl group, a diphenyl phosphine oxide group, a phenyl phosphine group and a carbazolyl group. Suitable examples of the R5 comprise a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a diphenyl pyridinyl group, a carbazolyl group, a diphenyl phosphine oxide group and a diphenyl phosphine oxide group substituted carbazolyl group.
Suitable examples of the compound represented by Group (b) of Formula (1) are selected from the following structures:
Figure imgf000011_0001
10
Figure imgf000012_0001
11
Figure imgf000013_0001
Figure imgf000014_0001
Formula (2)
In Formula (2), Rio to R15 are an aryl group or an aryl group substituted by an aryl group, a heteroaryl group or amine group. At least one of Rio to R15 is an aryl group which substituted by a heteroaryl group. L is an alkylene group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 2 carbon atoms.
Examples of Formula (2) compounds include:
Figure imgf000014_0002
Figure imgf000015_0001

Figure imgf000016_0001
Figure imgf000017_0001
The phosphine oxide compounds of the present invention may have a molecular weight of 1200 Dalton or less. More preferably, the molecular weight of the compounds are 1000 Dalton or less, the most preferably 800 Dalton or less.
Modeling Methodology:
The ground-state (So) and first excited triplet-state (Ti) configurations of the molecules were computed using Density Functional Theory (DFT). For this purpose, B3LYP is used as the functional ((a) Becke, A.D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C; Yang, W.; Parr, R.G. Phys. Rev. B 1988, 37, 785. (c) Miehlich, B.; Savin, A.; Stall, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200.) and 6-3 lg* is used as basis set ((a) Ditchfield, R.; Hehre, W.J.; Pople, J.A. J. Chem. Phys. 1971, 54, 724. (b) Hehre, W.J.; Ditchfield, R.; Pople, J.A. J. Chem. Phys. 1972, 56, 2257. (c) Gordon, M.S. Chem. Phys. Lett. 1980, 76, 163.). The energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were obtained from the So configuration. The energy of the Ti state was computed as the difference in energy between the minima of So and Ti potential energy surfaces (PES). All the calculations were performed using G09 suit of programs (Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2009.). The energies of HOMO, LUMO and Ti are reported in eVs.
The HOMO values of the phosphine oxide compounds of the present invention are shallower (higher) than -7.0 eV, more preferably shallower than -6.5 eV, the most preferably shallower than -5.5eV.
The LUMO values of the phosphine oxide compounds of the present invention are deeper (lower) than -0.75 eV, more preferably deeper than -1.0 eV, the most preferably deeper than -1.25 eV.
The triplet energy values of the phosphine oxide compounds of the present invention are higher than 2.8 eV, more preferably higher than 2.9 eV, the most preferably higher than 2.95 eV.
The organic compounds of the present invention can be used in organic layers of an organic electroluminescent device. Normally, an electroluminescent device includes a first electrode, a second electrode, and one or more organic layers interposed between the first electrode and the second electrode. The organic layers include electron transport layers
(ETLs), emission layers (EMLs) and hole transport layers (HTLs). The organic compounds of the present invention can be used especially for EMLs.
Examples
The following examples illustrate embodiments of the present invention. All parts and percentages are by weight unless otherwise indicated.
Pre aration of (2-bromophenyl)(3-bromophenyl)(phenyl)phosphine oxide
Figure imgf000019_0001
Molecular Weight 235 91 Molecular Weight: 420.08 Molecular Weight: 436.08 ft-Butyllithium (15.9 mL of 1.6 M in tetrahydrofuran (THF) solution, 0.0254 mol) was added dropwise to a solution of 1,4-dibromobenzene (6.00 g, 0.0254 mol) in anhydrous THF (100 mL) at -78 °C. The reaction mixture was kept at this temperature for 1 h, and then chlorophenylphosphine (1.73 mL, 0.0127 mol) was added at - 78 °C. The resulting mixture was stirred for a further 2 h at room temperature before quenching with 5 mL of methanol. Water was added, and the mixture was extracted with CH2CI2, washed with water and Brine. After the solvent had been completely removed, 30% hydrogen peroxide (30 mL) and CH2CI2 (60 mL) were added to the obtained residue and the mixture stirred overnight at room temperature. The organic layer was separated and washed with water and then brine. The extract was evaporated to dryness, and the residue was purified with reverse phase column separation. After purification, 2.01g of (2-bromophenyl)(3-bromophenyl)(phenyl)phosphine oxide (purity was higher than 99.5 %) and 0.7 g of by-product were obtained after the purification. (48.82 % for overall yield)
Preparation of (3-(9H-carbazol-9-yl)phenyl)(3-bromophenyl)(phenyl)phosphine oxide
Figure imgf000019_0002
Molecular Weight: 522.38
In a glovebox, Cul (5 mol %), (2-bromophenyl)(3-bromophenyl)(phenyl)phosphine oxide (1 eq), and K3P04 (2.1 eq) was added to a 40 mL vial. Carbazole (1 eq.), trans-N,N- dimethyl- 1,2-cyclohexanediamine (10 mol %), and toluene (15 mL) were then successively added in a glove box. The reaction mixture was heated at 100 C for 24 h. After the reaction, the mixture solution was cooled to ambient temperature, diluted with methyl chloride (100 mL), and washed with water (100 mL) and brine (100 mL). The organic phase was concentrated and the resulting residue was purified by column chromatography to provide 0.80 g of the desired product. Purity of the product was higher than 99.5%, and overall yield was 48.3%.
Example 1
Figure imgf000020_0001
Chemical Formula: C35H25N2OP Chemical Formula: C30H21 BrNOP Molecular Weight: 520.57
Molecular Weight: 522.38
In a 250 mL flask, (3-(9H-carbazol-9-yl)phenyl)(3-bromophenyl)(phenyl)phosphine oxide (2.83 g, 5.42 mmol), 4-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)pyridine (1.33 g, 6.50 mmol), K3P04 (2.50 g, 10.8 mmol) , and [1,1 '- Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.44 g, 5.4 mmol) were dissolved in 150 mL of mixture of dioxane and water(120:30) in N2 atmosphere. The solution was heated at 90 °C overnight. After the reaction, aliquot of sample was characterized by LC/MS. The solvent was evaporated with a rotavap and the solid was redispersed in CH2CI2. The mixture was washed with water. The further purification was applied using a reverse column separation and sublimation. After the purification, 0.70 g of pure compound was obtained (yield was 24.82 %, purity was 99.98%).
lH NMR (400 MHz, Chloroform- ) δ 8.66 - 8.60 (m, 2H), 8.15 - 8.04 (m, 3H), 7.90 - 7.68 (m, 8H), 7.62 - 7.53 (m, 2H), 7.53 - 7.45 (m, 2H), 7.45 - 7.41 (m, 2H), 7.32 - 7.21 (m, 6H).
13C NMR (101 MHz, Chloroform- ) δ 150.39, 146.96, 140.29, 138.86 (d, = 11.9 Hz), 138.15 (d, = 14.8 Hz), 135.33, 134.31, 133.89, 132.86, 132.56 - 132.40 (m), 132.36, 132.12, 132.06, 131.96, 131.07, 130.77 (t, = 1.5 Hz), 130.68, 130.56 (d, = 1.3 Hz), 130.47, 130.43 (d, = 1.8 Hz), 130.17, 130.06, 129.51, 129.38, 128.90, 128.78, 126.08, 123.55, 121.63, 120.42, 109.34. Example 2
Figure imgf000021_0001
Chemical Formula: C35H25N2OP
Chemical Formula: C30H2i BrNOP Molecular Weight: 520.57
Molecular Weight: 522.38
In a 250 mL flask, (3-(9H-carbazol-9-yl)phenyl)(3-bromophenyl)(phenyl)phosphine oxide (2.40 g, 4.59 mmol), 3-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)pyridine (1.13 g, 5.51 mmol), K3P04 (2.12 g, 9.19 mmol) , and [1,1 '- Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.38 g, 4.59 mmol) were dissolved in 150 mL of mixture of dioxane and water(120:30) in N2 atmosphere. The solution was heated at 90 °C overnight. After the reaction, aliquot of sample was characterized by LC/MS. The solvent was evaporated with a rotavap and the solid was redispersed in CH2CI2. The mixture was washed with water. The further purification was applied using a reverse column separation and sublimation. After the purification, 1.30 g of pure compound was obtained (Yield was 60.20 %, purity was 99.77%).
lH NMR (400 MHz, Methanol-^) δ 8.75 (dd, / = 2.4, 0.9 Hz, 1H), 8.51 (dd, / = 4.9, 1.6 Hz, 1H), 8.08 - 8.01 (m, 3H), 8.00 (m, 1H), 7.95 - 7.90 (m, 1H), 7.88 - 7.62 (m, 9H), 7.61 - 7.53 (m, 2H), 7.47 (ddd, = 8.0, 4.9, 0.9 Hz, 1H), 7.28 - 7.23 (m, 4H), 7.20 (m, 2H).
13C NMR (101 MHz, Methanol-^) δ 148.13, 147.03, 140.14, 138.82 - 137.97 (m), 135.78, 135.23, 134.24, 133.21, 132.76 (d, J = 2.7 Hz), 132.63, 131.76, 131.66, 131.59, 131.54, 131.43, 131.26 (d, J = 2.7 Hz), 131.00, 130.82, 130.67 (d, J = 3.4 Hz), 130.34, 130.24, 130.05, 129.94 (d, J = 1.4 Hz), 129.71 (d, J = 2.8 Hz), 129.60, 128.89, 128.77, 125.81, 124.15, 123.50, 120.18, 119.94 Triplet energy measurement
Table 1 . PL results of compound 1 and 2
Figure imgf000022_0002
Computational Finding:
Figure imgf000022_0001
Compound 1 Compound 2
Molecular Weight: 520.57 Molecular Weight: 520.57
HOMO: -5.41 HOMO: -5.37
LUMO: -1.44 LUMO: -1.27
T1 : 3.08 T1 : 3.02
Figure 1 . Calculation values of compound 1 and 2.
The electronic properties of all the molecules, whose structures are designed by attaching different substituents with the core structure, are computed using methodology mentioned above.
The LUMO level of this suite of molecules ranges between -1.2 eV and -1.5 eV, which is identified as a desired range for host materials. Thus, the pyridine-substituted phosphine oxides can be used in emission layer as a high triplet host materials. Thus, this suite of molecules has the correct electronics for an efficient host material.
Other compounds were calculated same as above, and listed Table 2 below. Table 2
Molecules HOMO (eV) LUMO (eV) Tl (eV) MW (Dalton)
c-i -5.14 -1.20 3.18 557.66 ! j 1) 1 -5.74 -1.07 3.18 643.65 I
b-2 -5.86 -1.91 2.89 797.82 I
D-3 -6.08 -2.08 3.12 798.80 !
B-i -5.31 -1.85 2.99 673.74 ! j B-2 -5.35 -2.02 3.11 674.73 1
A-4 -5.47 -1.99 2.98 674.73 I
B-3 -4.94 -1.84 2.92 915.03 !
B-4 -4.98 -2.02 2.92 916.01 !
B-5 -5.38 -2.08 3.11 839.92 1
b-4 -5.93 -2.02 3.11 598.63 I
A-3 ' -5.30 -1.33 2.97 520.56 !
Λ-1 -5.37 -1.27 3.02 520.56 !
Λ-2 -5.41 -1.44 3.08 520.56 !
b-5 -5.77 -1.08 3.17 581.58 1
A-5 ' -5.45 -1.50 3.09 685.75 !
b-7 -6.38 -1.36 3.17 568.54 !
b-6 -5.95 -1.25 3.12 492.51 ! j E-9 -4.98 -1.45 3.15 812.87 I
E-4 -4.89 -1.42 3.08 852.93 I
E-3 -5.35 -1.44 3.08 810.86 !
E-5 -4.98 -1.58 3.02 813.86 !
I E-7 -4.84 -1.61 3.02 853.92 I
E- l -5.30 -1.63 3.02 811.84 I
K-6 -5.03 -1.34 3.02 827.89 !
E-8 -4.88 -1.36 3.02 867.95 !
! E-2 -5.35 -1.38 3.02 825.87 1
I)- 10 -5.81 -1.21 2.89 516.57 I
b-8 -5.32 -1.35 3.09 533.56 !
b-9 -6.21 -1.23 3.12 368.36 !
PLED Fabrication and Testing
All organic materials were purified by sublimation before deposition. OLEDs were fabricated onto an ITO coated glass substrate that served as the anode, and topped with an aluminum cathode. All organic layers were thermally deposited by physical vapor deposition, in a vacuum chamber with a base pressure of less than 10"7 torr. Each cell, containing HIL1, HIL2, HTL1, HTL2, EBL, EML host, EML dopant, ETL1, ETL2, or EIL, was placed inside a vacuum chamber, until it reached 10"6 torr. To evaporate each material, a controlled current was applied to the cell, containing the material, to raise the temperature of the cell. An adequate temperature was applied to keep the evaporation rate of the materials constant throughout the evaporation process.
For the HIL1 layer, N4,N4'-diphenyl-N4,N4'-bis(9-phenyl-9H-carbazol-3-yl)-[l,l'- biphenyl]-4,4'-diamine was evaporated at a constant lA/s rate, until the thickness of the layer reached 600 Angstrom. For the HIL2 layer, the dipyrazino[2,3-f:2',3'-h]quinoxaline- 2,3,6,7,10,11-hexacarbonitrile layer was evaporated at a constant 0.5A/s rate, until the thickness reached 50 Angstrom. For the HTL1 layer, N-([l,l'-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9- phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine was evaporated at a constant lA/s rate, until the thickness reached 150 Angstrom. For the HTL2 layer, N,N-di([l,l'-biphenyl]-4-yl)-4'- (9H-carbazol-9-yl)-[l,l'-biphenyl]-4-amine was evaporated at a constant lA/s rate, until the thickness reached 50 Angstrom. For the EBL layer, l,3-di(9H-carbazol-9-yl)benzene was evaporated at a constant lA/s rate, until the thickness reached 50 Angstrom. For the EML layer, 9,9'-(6-phenyl-l,3,5-triazine-2,4-diyl)bis(9H-carbazole) (reference), Compound 1 or Compound 2 (these are host materials) and 5-(5-(4,6-diphenyl-l,3,5-triazin-2-yl)pyridin-2-yl)- 7-phenyl-5,7-dihydroindolo[2,3-b]carbazole (dopant) were co-evaporated, until the thickness reached 400 Angstrom. The deposition rate for host materials was 0.85A/s, and the deposition for the dopant material was 0.15 A/s, resulting in a 15% doping of the host materials. For the ETL1 layer, 5-(4-([l,r-biphenyl]-3-yl)-6-phenyl-l,3,5-triazin-2-yl)-7,7-diphenyl-5,7- dihydroindeno[2,l-b]carbazole was evaporated at a constant lA/s rate, until the thickness reached 50 Angstrom. For the ETL2 layer, 2,4-bis(9,9-dimethyl-9H-fluoren-2-yl)-6- (naphthalen-2-yl)-l,3,5-triazine was co-evaporated with lithium quinolate (Liq), until the thickness reached 300 Angstrom. The evaporation rate for the ETL compounds and Liq was 0.5 A/s. Finally, 20 Angstrom of a thin electron injection layer (Liq) was evaporated at a 0.5 A/s rate. See Table 3.
The current- voltage-brightness (J-V-L) characterizations for the OLED were performed with a source measurement unit (KEITHLY 238, (Keithley Instruments, Inc., 28775 Aurora Road 1 Cleveland, OH 44139, U.S.A) and a luminescence meter (MINOLTA CS-100A, (KONICA MINOLTA, INC. , JP TOWER, 2-7-2 Marunouchi, Chiyoda-ku, Tokyo 100-7015, Japan). EL spectra of the OLED were collected by a calibrated CCD spectrograph and External Quantum Efficiency (EQE) was analyzed by spectroradiometer PR655 (PHOTO RESEARCH®, 7279 William Barry Blvd., Syracuse, NY 13212-3349, U.S.A.).
Table 3: Device Materials
Figure imgf000025_0001
Device result
Table 4
Figure imgf000026_0002
Figure imgf000026_0001
reference Dopant Compound 1 Compound 2
As shown in Table 4, OLED comprising the Compound 1 or Compound 2 had a higher luminous efficiency and EQL compared to the OLED comprising reference.

Claims

What is claimed is:
1. An organic electroluminescent compound represented by the following Formula (1) or (2): o p.
Ri R^
R Formula (1)
wherein Ri, R2 and R3 are each selected from the following (a) or (b),
(a) Ri is an aryl group which may be substituted by a heteroaryl group, R2 and R3 are independently selected from an aryl group which is substituted by a heteroaryl group and the substituent of R2 and the substituent of R3 are different heteroaryl groups,
(b) Ri and R2 are each an aryl group and R3 is a group represented by the following formula (3), formula (4) or formula (5);
Figure imgf000027_0001
wherein R4 ,R6 and R7 are each selected from a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a diphenyl phosphine oxide group, a phenyl phosphine group or a carbazolyl group, R5, Rs and R9 are each selected from an alkyl group having 1 to 8 carbon atoms or a heteroaryl group, X is selected from an oxygen atom or a sulfur atom; 0 0
Figure imgf000028_0001
Formula (2)
wherein Rio to R15 are an aryl group or an aryl group substituted by an aryl group, a heteroaryl group or an amine group, at least one of Rio to R15 are an aryl group which is substituted by a heteroaryl group, L is an alkylene group having 1 to 4 carbon atoms.
2. The organic electroluminescent compound of claim 1, wherein Ri is a phenyl group which may be substituted by a pyrrolyl group or a carbazolyl group, R2 and R3 are independently selected from a phenyl group which is substituted by a group comprising a heteroaryl group and the substituent of R2 and the substituent of R3 are different groups.
3. The organic electroluminescent compound of claim 2, wherein one of the heteroaryl groups is a pyridinyl group.
4. The organic electroluminescent compound of claim 2, wherein one of the heteroaryl groups is a carbazolyl group.
5. The organic electroluminescent compound of claim 1, wherein the molecular weight of the organic electroluminescent compound is lower than 800 Dalton.
6. The organic electroluminescent compound of claim 1, wherein the organic
mpound is selected from the following compounds:
Figure imgf000028_0002
an
Figure imgf000029_0001
7. The organic electroluminescent compound of claim 1, characterized by having a Triplet Energy greater than 2.8 eV.
8. The organic electroluminescent compound of claim 1, characterized by having a Highest Occupied Molecular Orbital (HOMO) energy level higher than -7.0 eVand a Lowest Unoccupied Molecular Orbital (LUMO) energy level lower than -0.75 eV.
9. An organic electroluminescent device containing the organic electroluminescent compound of any of claims 1 to 8.
10. The organic electroluminescent device comprising a first electrode, a second electrode and one or more organic layers interposed between the first electrode and the second electrode, wherein the organic layer comprises one or more organic electroluminescent compounds of any of claims 1 to 8.
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