Host materials for electroluminescent devices

Abstract

To provide novel organic materials that have performance advantages over conventional organic materials when used in organic optoelectronic devices, particularly, organic light emitting devices (OLEDs).SOLUTION: The invention provides carbazole derivatives represented by the compounds A and B in the figure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 772,403, filed November 28, 2018, the disclosure of which is incorporated by reference in its entirety.

[0002] The present invention relates to compounds for use as hosts and devices, such as organic light-emitting diodes, containing same. [Background technology]

[0003] Optoelectronic devices utilizing organic materials are becoming increasingly desirable for several reasons. Because many of the materials used to fabricate such devices are relatively inexpensive, organic optoelectronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as flexibility, may make them well suited for specific applications, such as fabrication on flexible substrates. Examples of organic optoelectronic devices include organic light-emitting diodes / devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic light-emitting layer emits light can generally be easily tuned with appropriate dopants.

[0004] OLEDs utilize thin organic films that emit light when a voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Patent Nos. 5,623,999; 5,723,999; and 5,723,999, which are incorporated herein by reference in their entireties.

[0005] One application of phosphorescent emissive molecules is full-color displays. Industry standards for such displays require pixels adapted to emit specific colors, referred to as "saturated" colors. In particular, these standards require saturated red, green, and blue pixels. Alternatively, OLEDs can be designed to emit white light. Conventionally, liquid crystal display emission from a white backlight is filtered with absorbing filters to produce red, green, and blue emission. Similar techniques can be used with OLEDs. White OLEDs can be either single EML devices or stacked structures. Color can be measured using CIE coordinates, which are well known in the art.

[0006] An example of a green emitting molecule has the following structure: [ka] The compound is tris(2-phenyl)iridium, denoted as Ir(ppy)3, having the formula:

[0007] In this figure and later figures herein, we depict the coordination bond from nitrogen to the metal (here Ir) as a straight line.

[0008] As used herein, the term "organic" includes polymeric and small molecule organic materials that can be used to fabricate organic optoelectronic devices. "Small molecule" refers to any organic material that is not a polymer, and "small molecules" can actually be quite large. Small molecules can contain repeating units in some circumstances. For example, using a long-chain alkyl group as a substituent does not remove a molecule from the "small molecule" class. Small molecules can be incorporated into polymers, for example, as pendant groups on a polymer backbone or as part of the backbone. Small molecules can also serve as the core moiety of dendrimers, which consist of a series of chemical shells built on the core moiety. The core moiety of a dendrimer can be a fluorescent or phosphorescent small molecule emitter. Dendrimers can be "small molecules," and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

[0009] As used herein, "top" means furthest from the substrate, while "bottom" means closest to the substrate. When a first layer is described as "disposed over" a second layer, the first layer is disposed further from the substrate. There may be other layers between the first and second layers, unless it is specified that the first layer is "in contact with" the second layer. For example, a cathode may be described as "disposed over" an anode, even though there may be various organic layers in between.

[0010] As used herein, "solution processable" means capable of being dissolved, dispersed or transported in and / or deposited from a liquid medium, either in solution or suspension form.

[0011] A ligand may be referred to as "photoactive" if it is considered to directly contribute to the photoactive properties of the emissive material. A ligand may be referred to as "ancillary" if it is considered not to contribute to the photoactive properties of the emissive material, although the ancillary ligand may modify the properties of the photoactive ligand.

[0012] As used herein, and as generally understood by those skilled in the art, a first "highest occupied molecular orbital" (HOMO) or "lowest unoccupied molecular orbital" (LUMO) energy level is "greater than" or "higher than" a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Because ionization potentials (IPs) are measured as negative energies relative to the vacuum level, a higher HOMO energy level corresponds to an IP with a smaller absolute value (a less negative IP). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) with a smaller absolute value (a less negative EA). On a conventional energy level diagram with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A "higher" HOMO or LUMO energy level appears closer to the top of such a diagram than a "lower" HOMO or LUMO energy level.

[0013] As used herein, and as generally understood by those skilled in the art, a first work function is "greater than" or "higher than" a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a "higher" work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a "higher" work function is illustrated as being farther away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

[0014] Further details on OLEDs and the above definitions can be found in US Pat. No. 6,223,999, which is incorporated herein by reference in its entirety. Summary of the Invention

[0015] A compound of formula I below. [ka] (Wherein, ring A is a 5- or 6-membered aromatic ring; R A , R B , and R C each independently represents the maximum allowable substitution from mono to no substitution; Y 1 is absent or present and, if present, is selected from the group consisting of a direct bond, O, S, Se, CRR′, NR, SiRR′, and BR; X 1 ~X 3 are N or CR, respectively; X 1 ~X 3 at least one of is N; A 1 ~A 5 are each independently C or N; The maximum number of N atoms that can be bonded to each other in each ring is 2; R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof; R, R', R A , R B , and R C are each independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; Any two substituents may be bonded or fused together to form a ring.

[0016] Also disclosed are OLEDs that include the compounds of the present disclosure in an organic layer.

[0017] Consumer products including the OLEDs are also disclosed. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows an organic light-emitting device.

[0019] [Figure 2] FIG. 2 shows an inverted organic light-emitting device that does not have a separate electron transport layer. DETAILED DESCRIPTION OF THE INVENTION

[0020] Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons migrate to the oppositely charged electrode, respectively. When an electron and hole localize on the same molecule, an "exciton," a localized electron-hole pair with an excited energy state, is formed. Light is emitted via a photoemissive mechanism when the exciton relaxes. In some cases, the exciton may be localized on an excimer or exciplex. Non-radiative mechanisms, such as thermal relaxation, can also occur but are generally considered undesirable.

[0021] Early OLEDs used emissive molecules that emitted light from their singlet state ("fluorescence"), as disclosed, for example, in U.S. Patent No. 4,769,292, which is incorporated by reference in its entirety. Fluorescence emission typically occurs in a time frame of less than 10 nanoseconds.

[0022] More recently, OLEDs have been demonstrated that have emissive materials that emit light from triplet states ("phosphorescence"). Baldo et al., "Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices," Nature, Vol. 395, No. 151-154, 1998; ("Baldo-I") and Baldo et al., "Very high-efficiency green organic light emitting devices based on electrophosphorescence," Appl. Phys. Lett., Vol. 75, No. 3, 4-6 (1999) ("Baldo-II"), which are incorporated by reference in their entireties. Phosphorescence is described in further detail in U.S. Pat. No. 7,279,704, columns 5-6, which are incorporated by reference.

[0023] FIG. 1 shows an organic light-emitting device 100. The drawing is not necessarily to scale. Device 100 may include a substrate 110, an anode 115, a hole-injection layer 120, a hole-transport layer 125, an electron-blocking layer 130, an emissive layer 135, a hole-blocking layer 140, an electron-transport layer 145, an electron-injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in further detail in U.S. Pat. No. 7,279,704, cols. 6-10, which are incorporated by reference.

[0024] Further examples are available for each of these layers. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Patent No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole-transporting layer is m-MTDATA doped with F4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003 / 0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Patent No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron-transporting layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003 / 0230980, which is incorporated by reference in its entirety. U.S. Patent Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes, including composite cathodes with a thin layer of metal, such as Mg:Ag, with an overlying transparent, conductive, sputter-deposited ITO layer. The theory and use of blocking layers are described in more detail in U.S. Patent No. 6,097,147 and U.S. Patent Application Publication No. 2003 / 0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004 / 0174116, which is incorporated by reference in its entirety. A description of protective layers can be found in U.S. Patent Application Publication No. 2004 / 0174116, which is incorporated by reference in its entirety.

[0025] FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole-transport layer 225, and an anode 230. Device 200 can be fabricated by depositing the layers described, in order. Because the most common OLED configuration has the cathode disposed above the anode, and device 200 has cathode 215 disposed below anode 230, device 200 can be referred to as an "inverted" OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides an example of how some layers can be omitted from the structure of device 100.

[0026] The simple layer structures illustrated in Figures 1 and 2 are provided as non-limiting examples, and it is understood that embodiments of the present invention can be used in conjunction with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. A functional OLED may be achieved by combining the various layers described in various ways, or layers may be omitted entirely based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. While many of the examples provided herein describe the various layers as including a single material, it is understood that combinations of materials, such as a mixture of a host and a dopant, or more generally, a mixture, may be used. Layers may also have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole-transport layer 225 transports holes and injects holes into emissive layer 220 and may be described as a hole-transport layer or a hole-injection layer. In one embodiment, an OLED may be described as having an "organic layer" disposed between a cathode and an anode. The organic layer may include a single layer, or may further include multiple layers of different organic materials, such as those described with respect to Figures 1 and 2.

[0027] Structures and materials not specifically described may also be used, such as OLEDs (PLEDs) composed of polymeric materials, such as those disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. As a further example, an OLED having a single organic layer may be used. OLEDs may be stacked, for example, as described in U.S. Pat. No. 5,707,745 to Forrest et al., which is incorporated by reference in its entirety. OLED structures may deviate from the simple layered structures illustrated in FIGS. 1 and 2. For example, the substrate may include angled reflective surfaces to improve outcoupling, such as the mesa structure described in U.S. Pat. No. 6,091,195 to Forrest et al. and / or the recessed structure described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entirety.

[0028] Unless otherwise specified, any of the layers of the various embodiments can be deposited by any suitable method. For organic layers, preferred methods include deposition by thermal evaporation, such as those described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties; inkjet deposition; organic vapor phase deposition (OVPD), such as that described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety; and organic vapor jet printing (OVJP), such as that described in U.S. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin-coating and other solution-based processes. Solution-based processes are preferably performed in a nitrogen or inert atmosphere. For other layers, preferred methods include thermal evaporation. Preferred patterning methods include patterning via masks, such as those described in U.S. Patent Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, deposition via cold welding, and patterning associated with some deposition methods, such as inkjet and organic vapor jet printing (OVJP). Other methods may also be used. The material to be deposited may be modified to be compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, preferably containing at least three carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents with 20 or more carbons may be used, with 3 to 20 carbons being a preferred range. Materials with asymmetric structures may have better solution processability than those with symmetric structures, because asymmetric materials may be less prone to recrystallization. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

[0029] Devices fabricated according to embodiments of the present invention may further include a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment, including moisture, vapors, and / or gases. The barrier layer may be deposited over, under, or adjacent to the substrate, the electrode, or any other portion of the device, including the edges. The barrier layer may include a single layer or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase and compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate inorganic or organic compounds, or both. Preferred barrier layers include mixtures of polymeric and non-polymeric materials, as described in U.S. Pat. No. 7,968,146 and PCT Patent Application Nos. PCT / US2007 / 023098 and PCT / US2009 / 042829, which are incorporated herein by reference in their entireties. To be considered a "mixture," the polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and / or simultaneously. The weight ratio of polymeric to non-polymeric materials can be in the range of 95:5 to 5:95. The polymeric and non-polymeric materials can be made from the same precursor materials. In one example, the mixture of polymeric and non-polymeric materials consists essentially of polymeric silicon and inorganic silicon.

[0030] Devices made according to embodiments of the present invention can be incorporated into a wide variety of electronic component modules (or units) that can be incorporated into various electronic products or intermediate components. Such electronic products or intermediate components include display screens, lighting devices (such as discrete light source devices or lighting panels), and the like, which can be utilized by end-user product manufacturers. Such electronic component modules can optionally include drive electronics and / or power sources. Devices made according to embodiments of the present invention can be incorporated into a wide variety of consumer products having one or more electronic component modules (or units) incorporated therein. Consumer products are disclosed that include OLEDs that include compounds of the present disclosure in the organic layer of the OLED. Such consumer products include any type of product that includes one or more light sources and / or one or more display devices of some kind. Some examples of such consumer products include flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for indoor or outdoor illumination and / or signaling, head-up displays, fully or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, mobile phones, tablets, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, microdisplays (displays less than 2 inches diagonal), 3-D displays, virtual reality or augmented reality displays, vehicles, video walls including multiple displays aligned together, theater or stadium screens, phototherapy devices, and signage. A variety of control mechanisms, including passive matrix and active matrix, can be used to control devices fabricated according to the present invention. Many of the devices are intended for use within a temperature range comfortable to humans, such as 18°C ​​to 30°C, and more preferably room temperature (20-25°C), but they can also be used outside this temperature range, e.g., between -40°C and +80°C.

[0031] The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may use the materials and structures. More generally, organic devices such as organic transistors may use the materials and structures.

[0032] The terms "halo," "halogen," or "halide" are used interchangeably and refer to fluorine, chlorine, bromine, and iodine.

[0033] The term "acyl" refers to a substituted carbonyl group (C(O)-R s ) refers to

[0034] The term "ester" refers to a substituted oxycarbonyl (-OC(O)-R s or -C(O)-OR s ) group.

[0035] The term "ether" means -OR s Refers to the base.

[0036] The terms "sulfanyl" and "thioether" are used interchangeably, and -SR s Refers to the base.

[0037] The term "sulfinyl" refers to -S(O)-R s Refers to the base.

[0038] The term "sulfonyl" means -SO2-R s Refers to the base.

[0039] The term "phosphino" refers to -P(R s ) refers to three groups, each R s may be the same or different.

[0040] The term "silyl" refers to -Si(R s ) refers to three groups, each R smay be the same or different.

[0041] In each of the above, R s is hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, and combinations thereof. s is selected from the group consisting of alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

[0042] The term "alkyl" refers to and includes both straight-chain and branched-chain alkyl groups. Preferred alkyl groups contain from 1 to 15 carbon atoms and include methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, and 2,2-dimethylpropyl. Furthermore, the alkyl groups can be optionally substituted.

[0043] The term "cycloalkyl" refers to and includes monocyclic, polycyclic, and spiroalkyl groups. Preferred cycloalkyl groups are those containing 3 to 12 ring carbon atoms and include cyclopropyl, cyclopentyl, cyclohexyl, bicyclo[3.1.1]heptyl, spiro[4.5]decyl, spiro[5.5]undecyl, adamantyl, and the like. Furthermore, the cycloalkyl groups can be optionally substituted.

[0044] The terms "heteroalkyl" or "heterocycloalkyl" refer to an alkyl or cycloalkyl group, respectively, having at least one carbon atom replaced by a heteroatom. Optionally, the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably O, S, or N. Furthermore, the heteroalkyl or heterocycloalkyl group is optionally substituted.

[0045] The term "alkenyl" refers to and includes both straight-chain and branched-chain alkene groups. An alkenyl group is essentially an alkyl group containing at least one carbon-carbon double bond in the alkyl chain. A cycloalkenyl group is essentially a cycloalkyl group containing at least one carbon-carbon double bond in the cycloalkyl ring. As used herein, the term "heteroalkenyl" refers to an alkenyl group having at least one carbon atom replaced by a heteroatom. Optionally, the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably O, S, or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups are those containing 2 to 15 carbon atoms. Furthermore, the alkenyl, cycloalkenyl, or heteroalkenyl group is optionally substituted.

[0046] The term "alkynyl" refers to and includes both straight-chain and branched-chain alkyne groups. Preferred alkynyl groups are those containing 2 to 15 carbon atoms. Furthermore, such alkynyl groups are optionally substituted.

[0047] The terms "aralkyl" and "arylalkyl" are used interchangeably and refer to an alkyl group substituted with an aryl group. In addition, said aralkyl group is optionally substituted.

[0048] The term "heterocyclic group" refers to and includes aromatic and non-aromatic cyclic groups containing at least one heteroatom. Optionally, the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably O, S, or N. Heteroaromatic cyclic groups may be used interchangeably with heteroaryl. Preferred heteroaromatic cyclic groups contain 3 to 7 ring atoms and include at least one heteroatom, including cyclic amines such as morpholino, piperidino, and pyrrolidino, and cyclic ethers / thioethers such as tetrahydrofuran, tetrahydropyran, and tetrahydrothiophene. Furthermore, the heterocyclic groups may be optionally substituted.

[0049] The term "aryl" refers to and includes both monocyclic aromatic hydrocarbyl groups and polycyclic aromatic ring systems. A polycyclic ring can have two or more rings in which two carbon atoms are shared between two adjacent rings (the rings are "fused"), at least one of which is an aromatic hydrocarbyl group, and the other rings can be, for example, a cycloalkyl, cycloalkenyl, aryl, heterocyclic, and / or heteroaryl. Preferred aryl groups contain 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Aryl groups having 6 carbons, 10 carbons, or 12 carbons are particularly preferred. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, and are preferably phenyl, biphenyl, triphenyl, triphenylene, fluorene, and naphthalene. Furthermore, the aryl group may be optionally substituted.

[0050] The term "heteroaryl" refers to and includes both monocyclic heteroaromatic groups and polycyclic aromatic ring systems containing at least one heteroatom. Heteroatoms include, but are not limited to, O, S, N, P, B, Si, and Se. In many instances, O, S, or N are preferred heteroatoms. Heteromonocyclic aromatic systems are preferably monocyclic rings having 5 or 6 ring atoms, and the rings can have 1 to 6 heteroatoms. Heteropolycyclic ring systems can have two or more rings in which two atoms are common to two adjacent rings (the rings are "fused"), and at least one of the rings is heteroaryl; for example, the other rings can be cycloalkyl, cycloalkenyl, aryl, heterocyclic, and / or heteroaryl. Heteropolycyclic aromatic ring systems can have 1 to 6 heteroatoms per ring of the polycyclic aromatic ring system. Preferred heteroaryl groups are those containing 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benziso ... Examples of heteroaryl groups include benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, with dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and their aza analogs being preferred. Furthermore, the heteroaryl group can be optionally substituted.

[0051] Of the aryl and heteroaryl groups listed above, triphenylene, naphthalene, anthracene, dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, pyrazine, pyrimidine, triazine, and benzimidazole groups, and their respective aza analogues, are of particular interest.

[0052] As used herein, the terms alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aralkyl, heterocyclic, aryl, and heteroaryl are independently unsubstituted or substituted with one or more common substituents.

[0053] In many instances, the common substituents are selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

[0054] In some instances, preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

[0055] In some instances, preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, alkoxy, aryloxy, amino, silyl, aryl, heteroaryl, sulfanyl, and combinations thereof.

[0056] In still other instances, more preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

[0057] The terms "substituted" and "substituted" refer to a substituent other than H attached to the relevant position (e.g., carbon or nitrogen). For example, R 1 If represents a mono-substitution, one R 1 must be other than H (i.e., a substitution). Similarly, R 1 If represents a di-substitution, R 1 must be other than H. Similarly, R 1 If represents unsubstituted, R 1can be a hydrogen at an available valence of a ring atom, as in the case of a carbon atom in benzene and a nitrogen atom in pyrrole, or simply represent nothing in the case of a ring atom with a fully satisfied valence (e.g., nitrogen in pyridine). The maximum number of substitutions possible in a ring structure depends on the total number of available valences on the ring atoms.

[0058] As used herein, "combinations thereof" refers to one or more members of the applicable list being combined to form known or chemically stable configurations that one skilled in the art can conceive of from the applicable list. For example, alkyl and deuterium can be combined to form a partially or fully deuterated alkyl group; halogen and alkyl can be combined to form a halogenated alkyl substituent; halogen, alkyl, and aryl can be combined to form a halogenated arylalkyl. In one example, the term "substituted" includes combinations of 2 to 4 of the listed groups. In another example, the term "substituted" includes combinations of 2 to 3 groups. In yet another example, the term "substituted" includes combinations of 2 groups. Preferred combinations of substituents are those containing up to 50 atoms that are not hydrogen or deuterium, or those containing up to 40 atoms that are not hydrogen or deuterium, or those containing up to 30 atoms that are not hydrogen or deuterium. In many examples, preferred combinations of substituents include up to 20 atoms that are not hydrogen or deuterium.

[0059] The designation "aza" in the fragments described herein, such as aza-dibenzofuran, aza-dibenzothiophene, etc., means that one or more of the C—H groups in each aromatic ring can be replaced by a nitrogen atom; for example, but not by way of limitation, azatriphenylene encompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Those skilled in the art can readily envision other nitrogen analogs of the above-described aza derivatives, and all such analogs are intended to be encompassed by the terms described herein.

[0060] As used herein, "deuterium" refers to an isotope of hydrogen. Deuterated compounds can be readily prepared using methods known in the art. For example, U.S. Pat. No. 8,557,400, International Publication No. WO 2006 / 095951, and U.S. Patent Application Publication No. 2011 / 0037057, the entire contents of which are incorporated by reference, describe the preparation of deuterium-substituted organometallic complexes. Further reference is made to Tetrahedron 2015, 71, 1425-30 (Ming Yan et al.) and Angew. Chem. Int. Ed. (Reviews) 2007, 46, 7744-65 (Atzrodt et al.), the entire contents of which are incorporated by reference, which describe efficient routes for deuteration of methylene hydrogens in benzylamines and substitution of aromatic ring hydrogens with deuterium, respectively.

[0061] It is understood that when a molecular fragment is described as being a substituent or as being attached to another moiety, the name may be described as being the fragment (e.g., phenyl, phenylene, naphthyl, dibenzofuryl) or the entire molecule (e.g., benzene, naphthalene, dibenzofuran). Different designations of substituents or attached fragments are considered equivalent herein.

[0062] In some instances, adjacent substituents in a pair can be optionally bonded or fused to form a ring. Preferred rings are 5-, 6-, or 7-membered carbocyclic or heterocyclic rings, including both cases where the portion of the ring formed by the pair of substituents is saturated and cases where the portion of the ring formed by the pair of substituents is unsaturated. As used herein, "adjacent" means that the two related substituents can be adjacent to each other on the same ring, or can be adjacent to each other on two rings that have the two nearest available substitutable positions, such as the 2- and 2'-positions in biphenyl and the 1- and 8-positions in naphthalene, as long as a stable fused ring system can be formed.

[0063] In one aspect, the present invention includes compounds of Formula I: [ka] (Wherein, ring A is a 5- or 6-membered aromatic ring; R A , R B , and R C each independently represents the maximum allowable substitution from mono to no substitution; Y 1 is absent or present and, if present, is selected from the group consisting of a direct bond, O, S, Se, CRR′, NR, SiRR′, and BR; X 1 ~X 3 are N or CR, respectively; X 1 ~X 3 at least one of is N; A 1 ~A 5 are each independently C or N; The maximum number of N atoms that can be bonded to each other in each ring is 2; R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof; R, R', R A , R B , and R C are each independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; Any two substituents may be bonded or fused together to form a ring.

[0064] In one embodiment, R, R', R A , R B , and R C are each independently hydrogen or a substituent selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

[0065] In one embodiment, X 1 ~X 3 are each N. In one embodiment, X 1 is CR and X 2 and X 3 is N. In one embodiment, X 2 is CR and X 1 and X 3 is N. In one embodiment, X 1 is N and X 2 and X 3 is CR.

[0066] In one embodiment, each R is H.

[0067] In one embodiment, each R A is H.

[0068] In one embodiment, each R B is H.

[0069] In one embodiment, each R C is H.

[0070] In one embodiment, R 1 , R 2 , R 3 , and R 4are each aryl or heteroaryl.

[0071] In one embodiment, R 1 and R 2 are bonded to form a carbazole group.

[0072] In one embodiment, R 3 and R 4 are bonded to form a carbazole group.

[0073] In one embodiment, R 1 and R 2 are bonded to form a carbazole group, and R 3 and R 4 are bonded to form a carbazole group.

[0074] In one embodiment, A 1 ~A 5 are each C. In one embodiment, A 5 is C and ring A is a 6-membered aromatic ring. 5 is N, and ring A is a five-membered aromatic ring.

[0075] In one embodiment, the compound is selected from the group consisting of: [ka] [ka] (In the formula, R D , R E , R F , R G , and R H represents the maximum allowable substitution from mono to no substitution; Y 2 and Y 3 are each independently selected from the group consisting of a direct bond, O, S, Se, CRR′, NR, SiRR′, and BR, or absent: A 6~A 25 are each independently C or N; The maximum number of N atoms that can be bonded to each other in each ring is 2; Z 1 ~Z 3 are each independently selected from the group consisting of O, S, Se, CRR′, NR, SiRR′, or BR; R D , R E , R F , R G , and R H are each independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; Any two substituents may be bonded or fused together to form a ring.

[0076] In one embodiment, the compound is selected from the group consisting of compounds H1-B1-B1-B1 through H50-B60-B60-B60, based on the numbered formula Hn-Bi-Bj-Bk, where n is an integer from 1 to 50, i, j, and k are each independently integers from 1 to 60, and H1 through H50 have the following structures: [ka] [ka] [ka] Alternatively, the compound is selected from the group consisting of compounds H51-B1-B1 to H70-B60-B60 based on the numbered formula Hm-Bi-Bj, where m is an integer from 51 to 70, i and j are each independently an integer from 1 to 60, and H51 to H70 have the following structure: [ka] [ka] In the formula, B1 to B60 have the following structures: [ka] [ka] [ka] [ka]

[0077] In one embodiment, the compound is selected from the group consisting of: [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0078] In another aspect, the present invention includes an organic light-emitting device (OLED) comprising an anode, a cathode, and an organic layer disposed between the anode and the cathode, the organic layer comprising a compound according to Formula I.

[0079] In one embodiment, the OLED further comprises a sensitizer, and the organic layer comprises an acceptor and a host; the acceptor is selected from the group consisting of fluorescent emitters, delayed fluorescent emitters, and combinations thereof; and the host is a compound of Formula I.

[0080] In some embodiments, the OLED has one or more properties selected from the group consisting of flexible, rollable, foldable, stretchable, and bendable. In some embodiments, the OLED is transparent or translucent. In some embodiments, the OLED further comprises a layer comprising carbon nanotubes.

[0081] In some embodiments, the OLED further comprises a layer comprising a delayed fluorescent emitter. In some embodiments, the OLED comprises an RGB pixel array or a white and color filter pixel array. In some embodiments, the OLED is a mobile device, a handheld device, or a wearable device. In some embodiments, the OLED is a display panel having a diagonal of less than 10 inches or an area of ​​less than 50 square inches. In some embodiments, the OLED is a display panel having a diagonal of at least 10 inches or an area of ​​at least 50 square inches. In some embodiments, the OLED is a lighting panel.

[0082] The emitter dopant can be a phosphorescent dopant and / or a fluorescent dopant.The organic layer can comprise a compound according to Formula I, and variants thereof, as described herein, as a host.

[0083] In one embodiment, the organic layer is an emissive layer, and the compound is an emissive or non-emissive dopant.

[0084] In one embodiment, the organic layer is an emissive layer, and the compound is an emissive or non-emissive dopant.

[0085] In one embodiment, the organic layer is an emissive layer comprising an emitter and a host; the emitter is selected from the group consisting of a phosphorescent emitter, a fluorescent emitter, a delayed fluorescent emitter, and combinations thereof; and the host is a compound of Formula I.

[0086] In one embodiment, the phosphorescent emitter is a transition metal complex having at least one ligand, or a portion of said ligand if said ligand is more than bidentate, selected from the group consisting of: [ka] [ka] (In the formula, Y 1 ~Y 13 are each independently selected from the group consisting of carbon and nitrogen; Y' is BR e , N.R. e , PR e , O, S, Se, C=O, S=O, SO2, CR e R f , SiR e R f , and GeR e R f selected from the group consisting of: R e and Rf may be fused or linked to form a ring; R a , R b , R c , and R d may each independently represent mono-substitution to the maximum possible number of substitutions, or no substitution; R a , R b , R c , R d , R e , and R f are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; R a , R b , R c , and R d Any two adjacent substituents of may be fused or linked to form a ring or to form a multidentate ligand.

[0087] In another aspect, the present invention includes a consumer product comprising an organic light emitting device (OLED) comprising an anode, a cathode, and an organic layer disposed between the anode and the cathode, the organic layer comprising a compound according to Formula I.

[0088] According to another aspect, formulations including the compounds described herein are also disclosed.

[0089] The OLEDs disclosed herein can be incorporated into one or more of consumer products, electronic component modules, and lighting panels.

[0090] In yet another aspect of the present disclosure, formulations are described that include the novel compounds disclosed herein. The formulations may also include one or more components selected from the group consisting of solvents, hosts, hole injection materials, hole transport materials, electron blocking materials, hole blocking materials, and electron transport layer materials disclosed herein.

[0091] The present disclosure encompasses any chemical structure comprising the novel compounds of the present disclosure, or monovalent or polyvalent variants thereof. In other words, the compounds of the present invention, or monovalent or polyvalent variants thereof, can be part of a larger chemical structure. Such chemical structures can be selected from the group consisting of monomers, polymers, macromolecules, and supramolecules (also known as supermolecules). As used herein, a "monovalent variant of a compound" refers to a moiety that is identical to the compound except that one hydrogen has been removed and replaced with a bond to the rest of the chemical structure. As used herein, a "polyvalent variant of a compound" refers to a moiety that is identical to the compound except that more than one hydrogen has been removed and replaced with bonds to the rest of the chemical structure. In the example of a supramolecule, the compounds of the present invention can also be incorporated into the supramolecular complex without covalent bonds. Combination with other materials

[0092] The materials described herein as useful for a particular layer in an organic light-emitting device can be used in combination with a wide variety of other materials present in the device. For example, the emissive dopants disclosed herein can be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes, and other layers that may be present. The materials described or referenced below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and those skilled in the art can readily consult the literature to identify other materials that may be useful in combination. Conductive dopants:

[0093] The charge transport layer is doped with a conductive dopant to significantly change the density of charge carriers and thereby its conductivity. The conductivity can be increased by generating charge carriers in the matrix material or, depending on the type of dopant, a change in the Fermi level of the semiconductor can also be achieved. The hole transport layer can be doped with a p-type conductive dopant, and n-type conductive dopants are used in the electron transport layer.

[0094] Non-limiting examples of conductive dopants that can be used in OLEDs in combination with the materials disclosed herein are illustrated below, along with references that disclose these materials. EP01617493, EP01968131, EP2020694, EP2684932, US20050139810, US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455, WO2009008277, WO2009011327, WO2014009310, US2007252140, US2015060804, US20150123047, and US2012146012 [ka] [ka] HIL / HTL:

[0095] The hole injection / transport material used in the present invention is not particularly limited, and any compound may be used as long as it is a compound typically used as a hole injection / transport material. Examples of such materials include phthalocyanine or porphyrin derivatives; aromatic amine derivatives; indolocarbazole derivatives; polymers containing fluorocarbons; polymers with conductive dopants; conductive polymers such as PEDOT / PSS; self-assembly monomers derived from compounds such as phosphonic acid and silane derivatives; MoO xp-type semiconducting organic compounds such as 1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile; metal complexes, and crosslinkable compounds.

[0096] Examples of aromatic amine derivatives used in the HIL or HTL include, but are not limited to, the following general structures: [ka]

[0097] Ar 1 From Ar 9each of which is a group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazole, and aromatic heterocyclic compounds such as benzothiazole, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and aromatic hydrocarbon cyclic groups and aromatic heterocyclic groups, which may be the same or different groups and which are bonded to each other directly or via at least one of an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, a phosphorus atom, a boron atom, a chain structural unit, and an aliphatic cyclic group. Each Ar can be unsubstituted or substituted with a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

[0098] In one embodiment, Ar 1 From Ar9 teeth, [ka] are independently selected from the group consisting of: where k is an integer from 1 to 20; X 101 From X 108 is C (including CH) or N; Z 101 is NAr 1 , O, or S; Ar 1 has the same radical as defined above.

[0099] Examples of metal complexes used in the HIL or HTL include, but are not limited to, those of the following general formula: [ka] where Met is a metal that may have an atomic weight greater than 40; (Y 101 -Y 102 ) is a bidentate ligand, and Y 101 and Y 102 are independently selected from C, N, O, P, and S; L 101 is an ancillary ligand; k' is an integer value from 1 to the maximum number of ligands that can be bound to the metal; and k'+k'' is the maximum number of ligands that can be bound to the metal.

[0100] In one embodiment, (Y 101 -Y 102 ) is a 2-phenylpyridine derivative. 101 -Y 102 ) is a carbene ligand. In another embodiment, Met is selected from Ir, Pt, Os, and Zn. In a further embodiment, the metal complex is + For the / Fc couple, it has a minimum oxidation potential of less than about 0.6 V in solution.

[0101] Non-limiting examples of HIL and HTL materials that can be used in OLEDs in combination with the materials disclosed herein are exemplified below along with references that disclose these materials. CN102702075、DE102012005215、EP01624500、EP01698613、EP01806334、EP01930964、EP01972613、EP01997799、EP02011790、EP02055700、EP02055701、EP1725079、EP2085382、EP2660300、EP650955、JP07-073529、JP2005112765、JP2007091719、JP2008021687、JP2014-009196、KR20110088898、KR20130077473、TW201139402、US06517957、US20020158242、US20030162053、US20050123751、US20060182993、US20060240279、US20070145888、US20070181874、US20070278938、US20080014464、US20080091025、US20080106190、US20080124572、US20080145707、US20080220265、US20080233434、US20080303417、US2008107919、US20090115320、US20090167161、US2009066235、US2011007385、US20110163302、US2011240968、US2011278551、US2012205642、US2013241401、US20140117329、US2014183517、US5061569、US5639914、WO05075451、WO07125714、WO08023550、WO08023759、WO2009145016、WO2010061824、WO2011075644、WO2012177006、WO2013018530、WO2013039073、WO2013087142、WO2013118812、WO2013120577、WO2013157367、WO2013175747、WO2014002873、WO2014015935、WO2014015937、WO2014030872、WO2014030921、WO2014034791、WO2014104514、WO2014157018 [ka] [ka] [ka] [ka] [ka] [ka] [ka] EBL:

[0102] An electron blocking layer (EBL) can be used to reduce the number of electrons and / or excitons that leave the emissive layer. The presence of such a blocking layer in a device can result in significantly higher efficiency and / or longer lifetime compared to a similar device lacking a blocking layer. Blocking layers can also be used to confine emission to a desired region of an OLED. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and / or a higher triplet energy than the emitter closest to the EBL interface. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and / or a higher triplet energy than one or more of the hosts closest to the EBL interface. In one aspect, the compound used in the EBL contains the same molecule or the same functional group used as one of the hosts described below. Additional hosts:

[0103] The light-emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as a light-emitting dopant material, and may contain one or more additional host materials using the metal complex as a dopant material. The host material is not particularly limited, and any metal complex or organic compound can be used as long as the triplet energy of the host is higher than that of the dopant. Any host material can be used with any dopant as long as the triplet criterion is met.

[0104] Examples of metal complexes used as host materials preferably have the following general formula: [ka] where Met is a metal; 103 -Y 104 ) is a bidentate ligand, and Y 103 and Y 104 are independently selected from C, N, O, P, and S; L 101 is another ligand; k' is an integer value from 1 to the maximum number of ligands that can be bound to the metal; and k'+k'' is the maximum number of ligands that can be bound to the metal.

[0105] In one embodiment, the metal complex is: [ka] where (ON) is a bidentate ligand with the metal coordinated to atoms O and N.

[0106] In another embodiment, Met is selected from Ir and Pt. 103 -Y 104 ) is a carbene ligand.

[0107] In one embodiment, the host compound is a compound selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, and indole. The compound includes at least one member selected from the group consisting of aromatic heterocyclic compounds such as doxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and the compound includes at least one member selected from the group consisting of 2 to 10 cyclic structural units of the same or different types selected from aromatic hydrocarbon cyclic groups and aromatic heterocyclic groups, which are bonded to each other directly or via at least one of an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, a phosphorus atom, a boron atom, a chain structural unit, and an aliphatic cyclic group. Each group may be further substituted with substituents selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

[0108] In one embodiment, the host compound contains at least one of the following groups in the molecule: [ka] (In the formula, R 101 is selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, and when it is aryl or heteroaryl, has the same definition as that of Ar mentioned above. k is an integer from 0 to 20 or from 1 to 20. X 101 ~X 108 is independently selected from C (including CH) or N. Z 101 and Z 102 is independently, NR 101 , O, or S.

[0109] Non-limiting examples of additional host materials that can be used in OLEDs in combination with the host compounds disclosed herein are exemplified below, along with references that disclose these materials. EP2034538, EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644, KR20120129733, KR20130115564 , TW201329200, US20030175553, US20050238919, US20060280965, US20090017330, US20090030202, US20090167162, US2 0090302743, US20090309488, US20100012931, US20100084966, US20100187984, US2010187984, US2012075273, US2012 126221, US2013009543, US2013105787, US2013175519, US2014001446, US20140183503, US20140225088, US2014034914, US7154114, WO2001039234, WO2004093207, WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO200706375 4. WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778, WO2009066779, WO2009086028, WO20100 56066, WO2010107244, WO2011081423, WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649, WO 2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472, US20170263869, US20160163995, US9466803

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[0110] Examples of emitters are not particularly limited, and any compound that is typically used as an emitter material can be used. Suitable emitter materials include, but are not limited to, compounds that can generate light emission through phosphorescence, fluorescence, thermally activated delayed fluorescence (TADF) (also known as E-type delayed fluorescence; see, for example, U.S. Patent Application Publication No. 15 / 700,352, the entire contents of which are incorporated by reference), triplet-triplet annihilation, or a combination of these processes. In some embodiments, the emissive dopant can be a racemic mixture or can be enriched in one enantiomer.

[0111] Non-limiting examples of emitter materials that can be used in OLEDs in combination with the materials disclosed herein are exemplified below along with references that disclose these materials. CN103694277、CN1696137、EB01238981、EP01239526、EP01961743、EP1239526、EP1244155、EP1642951、EP1647554、EP1841834、EP1841834B、EP2062907、EP2730583、JP2012074444、JP2013110263、JP4478555、KR1020090133652、KR20120032054、KR20130043460、TW201332980、US06699599、US06916554、US20010019782、US20020034656、US20030068526、US20030072964、US20030138657、US20050123788、US20050244673、US2005123791、US2005260449、US20060008670、US20060065890、US20060127696、US20060134459、US20060134462、US20060202194、US20060251923、US20070034863、US20070087321、US20070103060、US20070111026、US20070190359、US20070231600、US2007034863、US2007104979、US2007104980、US2007138437、US2007224450、US2007278936、US20080020237、US20080233410、US20080261076、US20080297033、US200805851、US2008161567、US2008210930、US20090039776、US20090108737、US20090115322、US20090179555、US2009085476、US2009104472、US20100090591、US20100148663、US20100244004、US20100295032、US2010102716、US2010105902、US2010244004、US2010270916、US20110057559、US20110108822、US20110204333、US2011215710、US2011227049、US2011285275、US2012292601, US20130146848, US2013033172, US2013165653, US2013181190, US2013334521, US20140246656, US 2014103305, US6303238, US6413656, US6653654, US6670645, US6687266, US6835469, US6921915, US7279704, US73 32232, US7378162, US7534505, US7675228, US7728137, US7740957, US7759489, US7951947, US8067099, US8592586 , US8871361, WO06081973, WO06121811, WO07018067, WO07108362, WO07115970, WO07115981, WO08035571, WO200201 5645, WO2003040257, WO2005019373, WO2006056418, WO2008054584, WO2008078800, WO2008096609, WO2008101842 , WO2009000673, WO2009050281, WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO2010118029, WO20 11044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471, WO2013094620, WO2013107487, WO201317 4471, WO2014007565, WO2014008982, WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450,

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[0112] A hole-blocking layer (HBL) can be used to reduce the number of holes and / or excitons that escape from the emissive layer. The presence of such a blocking layer in a device can result in significantly higher efficiency and / or longer lifetime compared to a similar device lacking a blocking layer. A blocking layer can also be used to confine emission to a desired region of an OLED. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and / or a higher triplet energy than the emitter closest to the HBL interface. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and / or a higher triplet energy than one or more of the hosts closest to the HBL interface.

[0113] In one embodiment, the compounds used in the HBL contain the same molecules or the same functional groups as those used in the hosts described above.

[0114] In another embodiment, the compound used in the HBL comprises at least one of the following groups in the molecule: [ka] where k is an integer from 1 to 20; L 101 is another ligand, and k' is an integer from 1 to 3. ETL:

[0115] The electron transport layer (ETL) may include a material capable of transporting electrons. The electron transport layer may be intrinsic (undoped) or doped. Doping may be used to enhance conductivity. Examples of ETL materials are not particularly limited, and any metal complex or organic compound typically used to transport electrons may be used.

[0116] In one embodiment, the compound used in the ETL contains at least one of the following groups in the molecule: [ka] [ka] In the formula, R 101 is selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, and when it is aryl or heteroaryl, has the same definition as that of Ar mentioned above. 1 From Ar 3 has the same definition as that of Ar mentioned above. k is an integer from 1 to 20. X 101 From X 108 is selected from C (including CH) or N.

[0117] In another embodiment, the metal complex used in the ETL comprises, but is not limited to, the following general formula: [ka] where (ON) or (NN) is a bidentate ligand with the metal coordinated to atoms O, N or N, N; 101is another ligand; and k' is an integer value between 1 and the maximum number of ligands that can be bound to the metal.

[0118] Non-limiting examples of ETL materials that can be used in OLEDs in combination with the materials disclosed herein are exemplified below along with references that disclose these materials. CN103508940, EP01602648, EP01734038, EP01956007, JP2004-022334, JP2 005149918, JP2005-268199, KR0117693, KR20130108183, US20040036077, U S20070104977, US2007018155, US20090101870, US20090115316, US20090140637, US20090179554, US2009218940, US2010108990, US2011156017, US20 11210320, US2012193612, US2012214993, US2014014925, US2014014927, US20140284580, US6656612, US8415031, WO2003060956, WO2007111263, WO20 09148269, WO2010067894, WO2010072300, WO2011074770, WO2011105373, W O2013079217, WO2013145667, WO2013180376, WO2014104499, WO2014104535 [ka] [ka] [ka] [ka] Charge generation layer (CGL)

[0119] In tandem or stacked OLEDs, the CGL plays a key role in performance and consists of an n-doped layer and a p-doped layer for electron and hole injection, respectively. Electrons and holes are supplied from the CGL and the electrodes. Consumed electrons and holes in the CGL are replenished by electrons and holes injected from the cathode and anode, respectively, until the bipolar current gradually reaches a steady state. Typical CGL materials contain n-type and p-type conductivity dopants used in the transport layers.

[0120] In any of the above-mentioned compounds used in each layer of an OLED device, the hydrogen atoms may be partially or fully deuterated. Thus, any specifically recited substituent, such as, but not limited to, methyl, phenyl, pyridyl, etc., includes undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, substituent classes, such as, but not limited to, alkyl, aryl, cycloalkyl, heteroaryl, etc., also include undeuterated, partially deuterated, and fully deuterated versions thereof.

[0121] It is understood that the various embodiments described herein are by way of example only and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein can be substituted with other materials and structures without departing from the spirit of the invention. Thus, the present invention as claimed may include variations from the specific examples and preferred embodiments described herein, as will be apparent to those skilled in the art. It is understood that various theories as to why the invention works are not intended to be limiting. Experimental Section [ka] Synthesis of Compound A Synthesis of 9,9'-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole): [ka]

[0122] A flame-dried 2 L flask was charged with 9H-carbazole (54.4 g, 325 mmol) and anhydrous THF (1 L) under nitrogen. The resulting solution was cooled to -70 °C, and n-BuLi (130 mL, 325 mmol) was added dropwise. The resulting mixture was allowed to warm to room temperature and then slowly transferred via intubation under nitrogen to a three-necked 3 L flask containing a solution of 2,4,6-trichloro-1,3,5-triazine (30 g, 163 mmol) in THF (200 mL). The resulting mixture was then heated to 60 °C overnight. The reaction mixture was cooled to room temperature and quenched with water. The resulting precipitate was filtered, washed with water, then with warm EtOH (ca. 500 mL), and dried to give 9,9′-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (53.8 g, 121 mmol, 74.2% yield) as a yellow solid. Synthesis of 9-(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole: [ka]

[0123] To a flame-dried 1 L three-neck flask equipped with a stirrer bar and a thermowell under nitrogen was added 9-(2-bromophenyl)-9H-carbazole (40 g, 124 mmol) and anhydrous THF (621 mL). The resulting solution was cooled to −72°C, and sec-butyllithium (155 mL, 217 mmol) was added dropwise over 40 minutes. The mixture was allowed to warm to −40°C over 90 minutes. After TLC confirmed complete consumption of 9-(2-bromophenyl)-9H-carbazole, the mixture was cooled to −78°C, and 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (44.3 mL, 217 mmol) was added dropwise. The reaction mixture was allowed to gradually warm to room temperature and stirred overnight. The reaction mixture was then cooled in an ice bath and carefully quenched with saturated aqueous ammonium chloride (100 mL) followed by 100 mL of water. The organic phase was separated and the aqueous phase was extracted with CHCl. ​​The combined organic phases were dried over NaSO, concentrated, and dried to give 9-(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (44.3 g, 120 mmol, 97% yield) as an off-white solid. Synthesis of 9,9'-(6-(2-(9H-carbazol-9-yl)phenyl)-1,3,5-triazine2,4-diyl)bis(9H-carbazole) (Compound A): [ka]

[0124] A pressure vial was charged with 9,9'-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (18.11 g, 40.6 mmol), 9-(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (15 g, 40.6 mmol), and K2CO3 (16.84 g, 122 mmol). THF (148 mL) and water (55.4 mL) were added, and the mixture was degassed with nitrogen for 10 minutes. Pd(Ph3P)4 (4.69 g, 4.06 mmol) was then added, and the resulting mixture was further degassed with nitrogen. The reaction mixture was sealed and heated at 90 °C for 72 hours. The reaction was cooled to room temperature and then quenched with water (100 mL). The resulting gray precipitate was filtered and washed with MeOH. The solid was then dissolved in DCM (1 L), passed through a short silica plug, and reprecipitated with MeOH (1 L). Trituration with acetone (750 mL) and filtration overnight afforded 23.1 g (87% yield) of 9,9'-(6-(2-(9H-carbazol-9-yl)phenyl)-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (Compound A). Synthesis of Compound B Synthesis of 9,9'-(2-chloropyrimidine-4,6-diyl)bis(9H-carbazole): [ka]

[0125] A flame-dried 5 L flask was charged with sodium hydride (60 wt%, 80 g, 2009 mmol) and THF (1605 mL). The mixture was stirred under nitrogen and cooled to -5 °C. 9H-Carbazole (112 g, 670 mmol) was then added portionwise, and the resulting mixture was stirred for 15 minutes. A solution of 2,4,6-trichloropyrimidine (82 g, 447 mmol) in THF (1958 mL) was added dropwise at -5 °C and then allowed to warm to room temperature. After stirring at room temperature overnight, the reaction mixture was cooled to 0 °C and quenched with water (250 mL). The resulting solid was filtered and then triturated with heptane (1 L) followed by EtOAc (1 L). Further trituration with THF and EtOH gave 9,9'-(2-chloropyrimidine-4,6-diyl)bis(9H-carbazole) (57 g, 128 mmol, 38.3% yield) as a white solid. Synthesis of 9,9'-(6-(2-(9H-carbazol-9-yl)phenyl)-1,3,5-triazine2,4-diyl)bis(9H-carbazole) (Compound B): [ka]

[0126] A pressure vial was charged with 9,9'-(2-chloropyrimidine-4,6-diyl)bis(9H-carbazole) (21.57 g, 48.5 mmol), 9-(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (20 g, 48.5 mmol), and K2CO3 (20.10 g, 145 mmol). THF (176 mL) and water (66 mL) were added, and the mixture was degassed with nitrogen for 10 minutes. Pd(Ph3P)4 (5.6 g, 4.85 mmol) was then added, and the resulting mixture was then degassed with nitrogen. The reaction mixture was sealed and heated at 90 °C for 72 hours. The reaction mixture was cooled to room temperature and then quenched with water (100 mL). The resulting gray precipitate was filtered and washed with water and MeOH to give 30 g (95% yield) of 9,9'-(2-(2-(9H-carbazol-9-yl)phenyl)pyrimidine-4,6-diyl)bis(9H-carbazole). Device Compound: [ka]

[0127] Materials with this formula were observed to provide significantly increased stability. Table 1 compares the device performance of the electron-type hosts E-host-1 and Compound A. Compound A was found to be 16.7 times more stable than E-host-1. [Table 1]

[0128] Compound B was also found to have significantly increased stability compared to E-host-2 (see Table 2). Note that the energy levels of the E-hosts compared in each table are nearly identical. [Table 2]

[0129] OLED devices were grown on glass substrates precoated with an indium tin oxide (ITO) layer having a sheet resistance of 15 Ω / sq. Prior to the deposition or application of the organic layers, the substrates were degreased with solvent and then treated with oxygen plasma for 1.5 minutes and UV ozone for 5 minutes at 50 W at 100 mTorr.

[0130] The devices in Tables 1 and 2 were fabricated by thermal evaporation under high vacuum (<10-6 Torr). The anode electrode was 750 Å of indium tin oxide (ITO). The example device had organic layers consisting of, from the ITO surface, a 100 Å thick layer of compound 1 (HIL), a 250 Å layer of compound 2 (HTL), a 50 Å layer of compound 3 (EBL), a 300 Å layer of compound 3 (EML) doped with 60% E-type host and 12% compound 4, a 50 Å layer of E-type host (BL), a 300 Å layer of compound 5 (ETL) doped with 35% compound 6, a 10 Å layer of compound 5 (EIL), and a 1,000 Å layer of Al (cathode). All devices were immediately encapsulated with a glass lid sealed with epoxy resin in a nitrogen glove box (<1 ppm HO and O) after fabrication, and a moisture getter was packaged. The doping rate is in volume percent. 2 Device performance at 1000 nits and 1000 nits was referenced to that of comparative compounds E-host-1 and E-host-2. [Prior art documents] [Patent documents]

[0131] [Patent Document 1] U.S. Patent No. 5,844,363 [Patent Document 2] U.S. Patent No. 6,303,238 [Patent Document 3] U.S. Patent No. 5,707,745 [Patent Document 4] U.S. Patent No. 7,279,704 [Explanation of symbols]

[0132] 100 Organic Light-Emitting Devices 110 Substrate 115 Anode 120 Hole injection layer 125 Hole transport layer 130 Electron Blocking Layer 135 Light-emitting layer 140 Hole Blocking Layer 145 Electron transport layer 150 Electron injection layer 155 Protective layer 160 cathode 162 first conductive layer 164 Second conductive layer 170 Barrier Layer 200 Inverted OLED, device 210 Substrate 215 cathode 220 Light-emitting layer 225 Hole transport layer 230 Anode

Claims

1. A composition comprising a compound of formula I: 【Chemical 1】 (Wherein, ring A is a 5- or 6-membered aromatic ring; R Ａ , R Ｂ , and R Ｃ each independently represents the maximum allowable substitution from mono to no substitution; Y １ is absent or present and, if present, is selected from the group consisting of a direct bond, O, S, Se, CRR′, NR, SiRR′, and BR; X １ ~X ３ are each N or CR; X １ ~X ３ at least one of is N; A １ ~A ５ are each independently C or N; The maximum number of N atoms that can be bonded to each other in each ring is 2; R １ , R ２ , R ３ , and R ４ are each independently selected from the group consisting of alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof; R, R', R Ａ , R Ｂ , and R Ｃ are each independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; Any two substituents may be bonded or fused together to form a ring.

2. R, R', R Ａ , R Ｂ , and R Ｃ 10. The composition of claim 1, wherein each independently is hydrogen or a substituent selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

3. X １ ~X ３ are N respectively; X １ is CR and X ２ and X ３ is N; X ２ is CR and X １ and X ３ is N; or X １ is N and X ２ and X ３ The composition of claim 1 wherein

4. R １ , R ２ , R ３ , and R ４ are each aryl or heteroaryl; R １ and R ２ are linked to form a carbazole group; or The following conditions (a) to (e): (a) R ３ and R ４ are linked to form a carbazole group; (b) R １ and R ２ are bonded together to form a carbazole group, and R ３ and R ４ are linked to form a carbazole group; (c) A ５ is C and ring A is a 6-membered aromatic ring; (d) R ３ and R ４ are bonded to form a carbazole group, and A ５ is C and ring A is a 6-membered aromatic ring; and (e) R １ and R ２ are bonded to form a carbazole group, and R ３ and R ４ are bonded together to form a carbazole group, and A ５ is C and ring A is a 6-membered aromatic ring; The composition according to claim 1, wherein at least one selected from the following holds true:

5. A ５ is N and ring A is a 5-membered aromatic ring; or A １ ~A ５ The composition of claim 1 , wherein each is C.

6. 2. The composition of claim 1, wherein the compound is selected from the group consisting of: 【Chemistry 2】 (In the formula, R Ｄ , R Ｅ , R Ｆ , R Ｇ , and R Ｈ represents the maximum allowable substitution from mono to no substitution; Y ２ and Y ３ are each independently selected from the group consisting of a direct bond, O, S, Se, CRR′, NR, SiRR′, and BR, or absent: A ６ ~A ２５ are each independently C or N; The maximum number of N atoms that can be bonded to each other in each ring is 2; Z １ ~Z ３ are each independently selected from the group consisting of O, S, Se, CRR′, NR, SiRR′, or BR; R Ｄ , R Ｅ , R Ｆ , R Ｇ , and R Ｈ are each independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; Any two substituents may be bonded or fused together to form a ring.

7. The compound is selected from the group consisting of compounds H1-B1-B1-B1 through H50-B60-B60-B60 based on the numbered formula Hn-Bi-Bj-Bk, where n is an integer from 1 to 50, and i, j, and k are each independently integers from 1 to 60, and H1 to H50 have the following structures: 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 or the composition of claim 1, wherein the compound is selected from the group consisting of compounds H51-B1-B1 through H70-B60-B60, based on the numbered formula Hm-Bi-Bj, where m is an integer from 51 to 70, and i and j are each independently integers from 1 to 60, and H51 to H70 have the following structure: 【Chemistry 7】 【Chemistry 8】 (Wherein, B1 to B60 have the following structure.) 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】

8. 2. The composition of claim 1, wherein the compound is selected from the group consisting of: 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 【Chemistry 18】 【Chemistry 19】 【Chemistry 20】 【Chemical 21】 【Chemical 22】

9. 10. The composition of claim 1, further comprising an emitter selected from the group consisting of a phosphorescent emitter, a fluorescent emitter, a delayed fluorescent emitter, and combinations thereof.

10. 10. The composition of claim 9, wherein the illuminant is a transition metal complex having at least one ligand, or a portion of said ligand if said ligand is more than bidentate, selected from the group consisting of: 【Chemistry 24】 【Chemistry 25】 (In the formula, Y １ ~Y １３ are each independently selected from the group consisting of carbon and nitrogen; Y' is BR ｅ , N.R. ｅ , P.R. ｅ , O, S, Se, C=O, S=O, SO ２ , C.R. ｅ R ｆ , SiR ｅ R ｆ , and GeR ｅ R ｆ selected from the group consisting of: R ｅ and R ｆ may be fused or linked to form a ring; R ａ , R ｂ , R ｃ , and R ｄ may each independently represent mono-substitution to the maximum possible number of substitutions, or no substitution; R ａ , R ｂ , R ｃ , R ｄ , R ｅ , and R ｆ are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; R ａ , R ｂ , R ｃ , and R ｄ Any two adjacent substituents of may be fused or linked to form a ring or to form a multidentate ligand.

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