Iridium complexes with aza-benzo fused ligands

This application is related to U.S. patent application Ser. No. 13/928,456, filed Jun. 27, 2013 and U.S. patent application Ser. No. 13/673,338, filed Nov. 9, 2012.

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

The present invention relates to iridium complexes containing aza-benzo fused ligands. In particular, iridium complexes containing both phenylpyridine ligands and aza-benzo fused ligands were found to be useful as phosphorescent emitters when used in OLED devices. Additionally, iridium complexes containing both phenylpyridine ligands and aza-benzo fused ligands where an alkyl group is bonded to the pyridine ring of the aza-dibenzofuran moiety of the ligand were also found to be useful as phosphorescent emitters.

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when 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. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy) 3 , which has the following structure:

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

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat 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 may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, 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 are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one 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. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). 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.

As used herein, and as would be generally understood by one 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 further 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.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

A compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula I below

is provided. In the compound of Formula I, A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 comprise carbon or nitrogen, and at least one of A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 is nitrogen. Ring B is bonded to ring A through a C—C bond, the iridium is bonded to ring A through a Ir—C bond. X is O, S, or Se. R 1 , R 2 , R 3 , and R 4 independently represent mono-, di-, tri-, tetra-substitution, or no substitution, and any adjacent substitutions in R 1 , R 3 , and R 4 are optionally linked together to form a ring. R 1 , R 3 , and R 4 are 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. R 2 is selected from the group consisting of aryl, substituted aryl, heteroaryl, and substituted heteroaryl. n is an integer from 1 to 3. In one aspect, the compound has the structure according to Formula I, where n is 1.

In one aspect, the compound has the structure according to Formula II below where all variables are as defined above in connection with Formula I:

In one aspect, the compound has the structure according to Formula II where n is 1.

In one aspect of the compound according to Formula I, only one of A 1 to A 8 is nitrogen. In one aspect, only one of A 5 to A 8 is nitrogen. In one aspect, X is O.

In one aspect, R 1 , R 3 , and R 4 are independently selected from the group consisting of hydrogen, deuterium, alkyl, and combinations thereof. In one aspect, R 3 is alkyl. In one aspect, the alkyl is deuterated or partially deuterated.

According to another aspect of the present disclosure, in the compound of Formula I, A 1 -A 4 and A 6 -A 8 are C, and A 5 is N, resulting in a compound having the structure according to Formula III

wherein R is selected from the group consisting of alkyl, cycloalkyl, and combinations thereof.

In one aspect, R 1 in Formula III represents mono-, di-substitution, or no substitution; R 2 , R 3 , and R 4 independently represent mono-, di-, tri-, tetra-substitution, or no substitution; any adjacent substitutions in R 1 , R 3 , and R 4 are optionally linked together to form a ring; R 1 , R 3 , and R 4 are 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; R2 is selected from the group consisting of aryl, substituted aryl, heteroaryl, and substituted heteroaryl; and n is an integer from 1 to 3.

In one embodiment, a first device comprising a first organic light emitting device is provided. The first device further comprises an anode, a cathode, and an organic layer, disposed between the anode and the cathode. The organic layer comprises a compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula I.

According to an embodiment, the organic layer comprises a compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula III.

The inventors have discovered that addition of an aryl group to the aza ring of the specific aza-dibenzofuran ring system in the iridium complexes containing aza-benzo fused ligands results in the formation of yellow phosphorescent compounds with superior device efficiency. The inventors have discovered that conjugating the pyridine ring in the L A ligand with aryl rings result in a new class of novel efficient yellow phosphorescent emitters for PHOLEDs.

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

FIG. 3 shows structural Formula I, Formula II, and Formula III.

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 each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 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 more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100 . The figures are not necessarily drawn 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 more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F 4 -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. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport 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. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. 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 may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

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 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230 , device 200 may 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 one example of how some layers may be omitted from the structure of device 100 .

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection 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. Functional OLEDs may be achieved by combining the various layers described in different 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. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may 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. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2 .

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs 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. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2 . For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. patent application 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 carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the present invention may further optionally comprise 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, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise 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 as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.).

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 employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

A compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula I below

is provided. In the compound of Formula I, A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 comprise carbon or nitrogen, and at least one of A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 is nitrogen. Ring B is bonded to ring A through a C—C bond, the iridium is bonded to ring A through a Ir—C bond. X is O, S, or Se. R 1 , R 2 , R 3 , and R 4 independently represent mono-, di-, tri-, tetra-substitution, or no substitution, and any adjacent substitutions in R 1 , R 3 , and R 4 are optionally linked together to form a ring. R 1 , R 3 , and R 4 are 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. R 2 is selected from the group consisting of aryl, substituted aryl, heteroaryl, and substituted heteroaryl. n is an integer from 1 to 3. In one aspect, the compound has the structure according to Formula I, where n is 1.

In an embodiment of the compound having the structure of Formula I, R 2 is phenyl or substituted phenyl. In one embodiment, R 2 is pyridine or substituted pyridine. In one embodiment, R 2 represents mono-substitution.

In one aspect, the compound has the structure according to Formula II below where all variables are as defined above in connection with Formula I:

In one aspect, the compound has the structure according to Formula II where n is 1.

In one aspect of the compound according to Formula I, only one of A 1 to A 8 is nitrogen. In one aspect, only one of A 5 to A 8 is nitrogen. In one aspect, X is O.

In one aspect, R 1 , R 3 , and R 4 are independently selected from the group consisting of hydrogen, deuterium, alkyl, and combinations thereof. In one aspect, R 3 is alkyl. In one aspect, the alkyl is deuterated or partially deuterated.

In one aspect, in the compound of Formula I, L A is selected from the group consisting of:

In another aspect, in the compound of Formula I, L A is selected from the group consisting of

According to another aspect of the present disclosure, in the compound of Formula I, A 1 -A 4 and A 6 -A 8 are C, and A 5 is N, resulting in a compound having the structure according to Formula III

wherein R is selected from the group consisting of alkyl, cycloalkyl, and combinations thereof.

In one aspect, R 1 in Formula III represents mono-, di-substitution, or no substitution; R 2 , R 3 , and R 4 independently represent mono-, di-, tri-, tetra-substitution, or no substitution; any adjacent substitutions in R 1 , R 3 , and R 4 are optionally linked together to form a ring; R 1 , R 3 , and R 4 are 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; R 2 is selected from the group consisting of aryl, substituted aryl, heteroaryl, and substituted heteroaryl; and n is an integer from 1 to 3.

In one embodiment, the compound of formula Ir(L A )(L B ) 2 has one of the the formulas listed in Table 1 below:

In one embodiment, a first device comprising a first organic light emitting device is provided. The first device further comprises an anode, a cathode, and an organic layer, disposed between the anode and the cathode. The organic layer comprises a compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula I and the variables as defined herein.

According to an embodiment, the organic layer of the first organic light emitting device comprises a compound having the formula Ir(L A ) n (L B ) 3−n , and having the structure according to Formula III and the variables as defined herein.

In one embodiment, the first device is a consumer product. In one embodiment, the first device is an organic light-emitting device. In one embodiment, the first device comprises a lighting panel.

In another embodiment, the organic layer in the first organic light emitting device is an emissive layer and the compound is an emissive dopant. In one embodiment, the organic layer is an emissive layer and the compound is a non-emissive dopant.

In one embodiment, the organic layer further comprises a host. In one embodiment, the host comprises a triphenylene containing benzo-fused thiophene or benzo-fused furan, wherein any substituent in the host is an unfused substituent independently selected from the group consisting of C n H 2n+1 , OC n H 2n+1 , OAr 1 , N(C n H 2n+1 ) 2 , N(Ar 1 )(Ar 2 ), CH═CH—C n H 2n+1 , C≡CHC—H 2n+1 , Ar 1 , Ar 1 -Ar 2 , C n H 2n —Ar 1 , or no substitution, wherein n is from 1 to 10; and wherein Ar 1 and Ar 2 are independently selected from the group consisting of benzene, biphenyl, naphthalene, triphenylene, carbazole, and heteroaromatic analogs thereof

In one embodiment, the host comprises at least one chemical group selected from the group consisting of carbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

The “aza” designation in the fragments described above, i.e. aza-dibenzofuran, aza-dibenzonethiophene, etc. means that one or more of the C—H groups in the respective fragment can be replaced by a nitrogen atom, for example, and without any limitation, azatriphenylene encompasses both dibenzo[fh]quinoxaline and dibenzo[fh]quinoline. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.

In one embodiment, the host is selected from a group of compounds, the Host Group, consisting of:

and combinations thereof.

In one embodiment, the host comprises a metal complex.

According to another aspect, the organic layer in the first device described above can comprise a compound having the formula Ir(L A ) n (L B ) 3−n , having the structure according Formula II as defined above.

According to another aspect, a formulation comprising the compound of Formula I and/or Formula II is also within the scope of the present disclosure.

Device Examples

All example devices were fabricated by high vacuum (<10 −7 Torr) thermal evaporation. The anode electrode is 1200 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by 1,000 Å of Al. All devices are encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H 2 O and O 2 ) immediately after fabrication, and a moisture getter was incorporated inside the package.

The organic stack of the device examples consisted of sequentially, from the ITO surface, 100 Å of Compound A as the hole injection layer (HIL), 300 Å of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) as the hole transporting layer (HTL), 300 Å of the invention compound doped in Compound B as a host with 7 wt % of the iridium phosphorescent compound as the emissive layer (EML), 50 {acute over (Å)} of Compound B as a blocking layer (BL), 450 Å of tris-8-hydroxyquinoline aluminum (Alq) as the ETL. The comparative Example with Compound C was fabricated similarly to the Device Examples.

The device results and data from those devices are summarized in Tables 2 and 3. As used herein, NPD, Alq, Compounds A, B, and comparative Compound C, and the inventive compounds III-32, III-44, and III-74 have the following structures:

Table 3 summarizes the performance of the devices. The CIE color coordinate, driving voltage (V), luminous efficiency (LE) were measured at a fixed current density, 10 mA/cm 2 . According to the CIE color coordinate, all example devices were yellow emitting but the inventive device Examples 1, 2, and 3 exhibited better efficiencies than the comparative device Example 1 in term of LE (63.4˜73.6 cd/A vs 54.2 cd/A) and EQE (23.3˜27.7% vs 20.6%).

Combination with Other Materials

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may 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 referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

A hole injecting/transporting material to be used in the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but not limit to: a phthalocyanine or porphryin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and silane derivatives; a metal oxide derivative, such as MoO x ; a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, but not limit to the following general structures:

Each of Ar 1 to Ar 9 is selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as 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, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each Ar is further substituted by a substituent 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, Ar 1 to Ar 9 is independently selected from the group consisting of:

k is an integer from 1 to 20; X 101 to X 108 is C (including CH) or N; Z 101 is NAr 1 , O, or S; Ar 1 has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit to the following general formula:

Met is a metal; (Y 101 -Y 102 ) is a bidentate ligand, Y 101 and Y 102 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 may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, (Y 101 -Y 102 ) is a 2-phenylpyridine derivative.

In another aspect, (Y 101 -Y 102 ) is a carbene ligand.

In another aspect, Met is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fc + /Fc couple less than about 0.6 V.

Host:

The light emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as light emitting material, and may contain a host material using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant. While the Table 4 below categorizes host materials as preferred for devices that emit various colors, any host material may be used with any dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have the following general formula:

Met is a metal; (Y 103 -Y 104 ) is a bidentate ligand, 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 may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

(O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, Met is selected from Ir and Pt.

In a further aspect, (Y 103 -Y 104 ) is a carbene ligand.

Examples of organic compounds used as host are selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as 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, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atome, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each group is further substituted by a substituent 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, host compound contains at least one of the following groups in the molecule:

R 101 to R 107 is 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

k is an integer from 1 to 20; k′″ is an integer from 0 to 20.

X 101 to X 108 is selected from C (including CH) or N.

Z 101 and Z 102 is selected from NR 101 , O, or S.

A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED.

In one aspect, compound used in HBL contains the same molecule or the same functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

k is an integer from 1 to 20; L 101 is another ligand, k′ is an integer from 1 to 3.

Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

In one aspect, compound used in ETL contains at least one of the following groups in the molecule:

R 101 is 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 acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

Ar 1 to Ar 3 has the similar definition as Ar's mentioned above.

k is an integer from 1 to 20.

X 101 to X 108 is selected from C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but not limit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L 101 is another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of the OLED device, the hydrogen atoms can be partially or fully deuterated. Thus, any specifically listed substituent, such as, without limitation, methyl, phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, classes of substituents such as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also encompass undeuterated, partially deuterated, and fully deuterated versions thereof.

In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exciton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED. Non-limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 4 below. Table 4 lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

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Experimental

1. Synthesis of Compound III-32

A mixture of phenylpyridine iridium complex (2.1 g, 2.94 mmol), 8-(4-(4-isopropylphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.23 g, 5.88 mmol), 2-ethoxyethanol (60 mL) and DMF (60 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug with dichloromethane (DCM). The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 1.3 g desired product (50.3% yield) which was confirmed by LC-MS.

2. Synthesis of Compound III-44

Synthesis of 8-(4-(3-isopropylphenyl)pyridine-2-yl)-2-methylbenzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (3.15 g, 10.2 mmol), 2-chloro-4-(3-isopropylphenyl)pyridine (2.60 g, 11.2 mmol), Pd 2 (dba) 3 (0.187 g 0.204 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.335 g, 0.815 mmol), potassium phosphate (7.57 g, 35.7 mmol), toluene (90 mL) and water (9 mL) was degassed with nitrogen and then refluxed overnight. The toluene layer was dried on Na 2 SO 4 and then further purified by column chromatography using dichloromethane in hexanes and then vacuum distilled to give 8-(4-(3-Isopropylphenyl)pyridine-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.2 g, 57% yield).

A mixture of iridium complex (2.0 g, 2.80 mmol), 8-(4-(3-isopropylphenyl)pyridine-2-yl)-2methylbenzofuro[2,3-b]pyridine (2.2 g, 5.81 mmol), 2-ethoxyethanol (60 mL) and DMF (60 mL) was heated at 130° C. overnight. The reaction mixture was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed to give 1.08 g desired product (44% yield).

3. Synthesis of Compound III-74

Synthesis of 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine

2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (5.96 g, 19.28 mmol), 2-chloro-4-phenylpyridine (4.39 g, 23.13 mmol), tris(dibenzylideneacetone)palladium(0) (0.353 g, 0.386 mmol) and 2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.8 g, 1.951 mmol) were charged into a 500 mL 2-neck flask. Potassium phosphate tribasic (12.26 g, 57.8 mmol) was then dissolved in 45 mL of water. This solution was charged into the reaction mixture. The reaction mixture was degassed with nitrogen then was heated to reflux overnight. The reaction mixture was cooled to room temperature. The toluene layer was separated and was dried over magnesium sulfate. These organics were filtered and concentrated under vacuum. The crude product was passed through a silica gel column using 70-99% toluene/heptanes followed by 5-15% ethyl acetate/toluene. Some of the impure product fractions were columned on silica gel using 5-15% ethyl acetate/DCM. All the clean product fractions were combined yielding 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (5.3 g, 15.76 mmol, 82% yield).

Synthesis of 2-ethyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine

2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (5.3 g, 15.76 mmol) was dissolved in 130 mL of THF. This solution was cooled in a dry ice bath to −78° C. Lithium diisopropylamide in THF (9.85 mL, 19.69 mmol) was added dropwise to the reaction mixture over a 10 minute period maintaining the temperature below −73° C. The reaction mixture was stirred at −78° C. for 2 hours. Iodomethane (3.35 g, 23.63 mmol) was dissolved in 20 mL of THF then was added dropwise via syringe to the cold reaction mixture. Stirring was continued as the reaction mixture gradually warmed to room temperature overnight. The reaction mixture was quenched with aqueous ammonium chloride then was extracted 2×300 mL ethyl acetate. The organics were combined, were washed with aqueous LiCl then were dried over magnesium sulfate. These organics were then filtered and concentrated under vacuum. The crude residue was dissolved in DCM and was loaded onto a silica gel column. The column was eluted with 5-8% ethyl acetate/DCM. The main set of product fractions were combined and concentrated under vacuum yielding 2-ethyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (5.15 g, 14.70 mmol, 93% yield)

Synthesis of 2-isopropyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine

2-ethyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (5.15 g, 14.70 mmol) was charged into the reaction mixture with 120 mL of THF. This mixture was cooled to −78° C. Lithium diisopropylamide in THF (9.19 mL, 18.37 mmol) was added dropwise to the cooled reaction mixture over a 10 minute period. The reaction mixture was then stirred for 2 hours at −78° C. Iodomethane (3.13 g, 22.05 mmol) was then dissolved in 10 mL of THF. This solution was then added via syringe to the cold reaction mixture. Stirring was continued as the reaction mixture was allowed to gradually warm to room temperature overnight. The reaction mixture was quenched with aqueous ammonium chloride then was extracted 2×300 mL ethyl acetate. The organics were combined, were washed with aqueous LiCl then were dried over magnesium sulfate. These organics were then filtered and concentrated under vacuum. The crude residue was dissolved in DCM and was loaded onto a silica gel column. The column was eluted with 3-4% ethyl acetate/DCM. Clean product fractions were combined and solvents were evaporated yielding 2-isopropyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (4.1 g, 11.25 mmol, 77% yield).

2-isopropyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (2.2 g, 6.04 mmol) and iridium complex (2.1 g, 2.94 mmol) were combined with 60 mL of DMF and 60 mL of 2-ethoxyethanol. This heterogeneous mixture was placed under a nitrogen atmosphere then was heated to reflux overnight. The reaction mixture was cooled to room temperature. The solvents were removed under vacuum. The crude residue was dissolved in 300 mL of DCM. This mixture was passed through a short silica gel plug. The plug was rinsed with 500 mL of DCM. The DCM filtrate was evaporated under vacuum then was loaded onto a silica gel column. The column was 1st eluted with 60% DCM/heptanes then 50% DCM/heptanes. The eluant was gradually increased to 57% DCM/heptanes. Clean product fractions yielded the desired product (1.4 g, 1.972 mmol, 67.0% yield).

5. Synthesis of Compound III-1604

A mixture of iridium complex (1.3 g, 1.67 mmol), 2-isopropyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (1.22 g, 3.35 mmol), 2-ethoxyethanol (35 mL) and DMF (35 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The mixture was further purified by silica gel column with DCM/heptane as elute to obtain 1.25 g desired product (83% yield).

6. Synthesis of Compound III-35

A mixture of iridium complex (2.3 g, 3.22 mmol), 8-(4-(4-isobutylphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.53 g, 6.44 mmol), 2-ethoxyethanol (60 mL) and DMF (60 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 1.8 g desired product (62.6% yield).

7. Synthesis of Compound III-50

A mixture of iridium complex (2.3 g, 3.22 mmol), 8-(4-(4-fluorolphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.28 g, 6.44 mmol), 2-ethoxyethanol (60 mL) and DMF (60 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 1.6 g desired product (56.1% yield) which was confirmed by LC-MS.

8. Synthesis of Compound III-38

Synthesis of 2-Chloro-4-(4-cyclopentylphenyl)pyridine

A mixture of 2-chloro-4-iodopyridine (6.43 g, 26.3 mmol), (4-cyclopentylphenyl)boronic acid (5.0 g, 26.3 mmol), Pd(Ph 3 P) 4 (0.0.91 g 0.79 mmol), sodium carbonate (8.37 g, 79 mmol), DME (257 mL) and water (64 mL) was degassed with nitrogen and then refluxed overnight. The reaction mixture was concentrated and extracted with ethyl acetate. The the ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using dichloromethane in hexanes and then vacuum distilled to give 2-Chloro-4-(4-cyclopentylphenyl)pyridine (4.6 g, 68% yield).

Synthesis of 8-(4-(4-cyclopentylphenyl)pyridine-2-yl)-2-methylbenzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (2.5 g, 8.09 mmol), 2-chloro-4-(4-cyclopentylphenyl)pyridine (2.29 g, 8.89 mmol), Pd 2 (dba) 3 (0.148 g 0.162 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.266 g, 0.647 mmol), potassium phosphate (6.01 g, 28.3 mmol), DME (70 mL) and water (7 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in hexanes to give 8-(4-(4-cyclopentylphenyl)pyridine-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.4 g, 73% yield).

A mixture of iridium complex (1.2 g, 1.68 mmol), 8-(4-(4-cyclopentylphenyl)pyridine-2-yl)-2methylbenzofuro[2,3-b]pyridine (1.36 g, 3.36 mmol), ethoxyethanol (40 mL) and DMF (40 mL) was heated at 130° C. overnight. The reaction mixture was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed to give 0.60 g product. After sublimation, it yielded the product (0.4 g, 27% yield).

9. Synthesis of Compound III-1738

A mixture of iridium complex (1.257 g, 1.68 mmol), 8-(4-(4-cyclopentylphenyl)pyridine-2-yl)-2methylbenzofuro[2,3-b]pyridine (1.36 g, 3.36 mmol), ethoxyethanol (40 mL) and DMF (40 mL) was heated at 130° C. overnight. The reaction was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed. After sublimation, it gave the product (0.45 g, 29% yield).

10. Synthesis of Compound III-5979

Synthesis of 2-Chloro-4-(p-tolyl)pyridine

A mixture of 2-chloro-4-iodopyridine (10.0 g, 41.8 mmol), p-tolylphenylboronic acid (5.68 g, 41.8 mmol), Pd(Ph 3 P) 4 (1.45 g 1.25 mmol), sodium carbonate (13.3 g, 125 mmol), DME (300 mL) and water (75 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and the extracted with ethyl acetate. The the ethyl acetate layer was dried on Na 2 SO 4 , vacuum distilled and recrystalized to give 2-chloro-4-(p-tolyl)pyridine (3.75 g, 18.4 mmol, 44% yield).

Synthesis of 2-methyl-8-(4-(p-tolyl)(pyridin-2-yl)benzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (2.5 g, 8.03 mmol), 2-chloro-4-(p-tolyl)pyridine (1.80 g, 8.83 mmol), Pd 2 (dba) 3 (0.147 g 0.161 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.264 g, 0.642 mmol), potassium phosphate (5.96 g, 28.1 mmol), toluene (100 mL) and water (10 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in hexanes and washed with methanol to give 2-methyl-8-(4-(p-tolyl)pyridin-2-yl)benzofuro[2,3-b]pyridine (2.0 g, 5.71 mmol, 71% yield).

To a 250 mL flask, the two starting materials, solvents 2-ethoxyethanol 50 mL and DMF 50 mL were charged. The reaction mixture was heated up to 130° C. under N 2 for 27 hours. The reaction was cooled down and solvents were evoparted and run silica gel column with DCM/heptane to obtain about 0.68 g desired product which is confirmed by LC-MS and sublimed to get 0.38 g.

11. Synthesis of Compound III-53

To a 1 liter, 3-necked flask added sodium carbonate (18.18 g, 172 mmol), 2-chloro-4-iodopyridine (13.69 g, 57.2 mmol), (3-fluorophenyl)boronic acid (8 g, 57.2 mmol), DME (400 mL), water (100 mL). The reaction was degassed with N 2 for 30 minutes and added with palladiumtetrakistriphenylphosphine (1.982 g, 1.715 mmol) and again degassed with N 2 . The reaction was heated at reflux under N 2 overnight and worked up with silica gel chromatographed using 50-65% DCM/heptane and got about 11.09 g product (93% yield).

To a 250 mL flask added 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (3.0 g, 9.70 mmol), 2-chloro-4-(3-fluorophenyl)pyridine (2.216 g, 10.67 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.319 g, 0.776 mmol), Pd 2 (dba) 3 (0.178 g, 0.194 mmol), potassium phosphate (7.21 g, 34.0 mmol) and followed by water 7 mL) and toluene (70 mL) and degassed with N 2 and heated at reflux under N 2 overnight. Reaction was worked up with silica gel column to obtain a white solid 2.15 g (63% yield) product.

To a 250 mL flask added iridium complex (2.16 g, 3.03 mmol) and 8-(4-(3-fluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.15 g, 6.07 mmol) and followed by 2-ethoxyethanol (50 mL) and DMF (50 mL). The reaction was heated at 130° C. overnight. An aliquot by HPLC showed completion. The reaction was worked up with silica gel column with 50% DCM in heptane as elute then followed by 100% DCM to get 1.45 g (67% yield) orange solid which LC/MS showed desired MS.

12. Synthesis of Compound III-25

Synthesis of 2-Chloro-5-phenylpyridine

A mixture of 2-chloro-5-iodopyridine (5.0 g, 20.9 mmol), phenylboronic acid (2.6 g, 20.9 mmol), Pd(Ph 3 P) 4 (1.45 g 1.25 mmol), sodium carbonate (6.64 g, 62.6 mmol), DME (20 mL) and water (5 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then vacuum distilled to give 2-chloro-5-phenylpyridine (2.79 g, 14.71 mmol (70.5% yield).

Synthesis of 2-methyl-8-(5-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (3.0 g, 9.70 mmol), 2-chloro-5-phenylpyridine (2.024 g, 10.67 mmol), Pd 2 (dba) 3 (0.178 g 0.192 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.319 g, 0.776 mmol), potassium phosphate (7.21 g, 34.0 mmol), toluene (70 mL) and water (7 mL) was degassed with nitrogen and then refluxed overnight. It was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in hexanes to give 2-methyl-8-(5-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (1.38 g, 4.10 mmol, 42.3% yield).

A mixture of iridium complex (1.6 g, 2.28 mmol),1 2-methyl-8-(5-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (1.38 g, 4.10 mmol),),2-ethoxyethanol (40 mL) and DMF (40 mL) was heated at 130° C. overnight. The reaction mixture was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed (1:1 heptane:DCM) to give 0.60 g and sublimed to give the desired product (0.41 g, 21.5% yield).

13. Synthesis of Compound III-62

Synthesis of 8-(4-(3,4-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (3.0 g, 9.70 mmol), 2-chloro-4-(3,4-difluorophenyl)pyridine (2.41 g, 10.67 mmol), Pd 2 (dba) 3 (0.178 g 0.194 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.319 g, 0.776 mmol), potassium phosphate (7.21 g, 34.0 mmol), toluene (70 mL) and water (7 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in dichloromethane to give 8-(4-(3,4-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.36 g, 6.34 mmol, 65.3% yield).

A mixture of iridium complex (2.26 g, 3.17 mmol), 8 8-(4-(3,4-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.36 g, 6.34 mmol), 2-ethoxyethanol (70 mL) and DMF (70 mL) was heated at 130° C. overnight. It was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed (1:1 heptane:DCM) to give 0.9 g and sublimed to give the desired product (0.75 g, 27% yield).

14. Synthesis of Compound III-68

To a 1 liter 3-necked flask added sodium carbonate (10.62 g, 100 mmol), 2-chloro-4-iodopyridine (8.0 g, 33.4 mmol), (3,4,5-trifluorophenyl)boronic acid (5.88 g, 33.4 mmol), DME (300 mL), water (75 mL). The mixture was degassed with N 2 for 30 minutes and added palladiumtetrakistriphenylphosphine (1.158 g, 1.002 mmol) and again degassed with N 2 . Then the reaction was heated at reflux under N 2 overnight and cooled down to workup to give 4.5 g (55% yield) light yellow solid after column.

To a 250 ml flask added 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (3.0 g, 9.70 mmol), 2-chloro-4-(3,4,5-trifluorophenyl)pyridine (2.60 g, 10.67 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.319 g, 0.776 mmol), Pd 2 (dba)3 (0.178 g, 0.194 mmol), potassium phosphate (7.21 g, 34.0 mmol) followed by water (7 mL) and toluene (70 mL). The reaction was degassed with N 2 and heated at reflux under N 2 overnight. An aliquot by GC shows completion. The reaction mixture was worked up to give 2.35 g white solid (62% yield) product.

To a 250 mL flask added iridium complex (2.148 g, 3.01 mmol) and 2-methyl-8-(4-(3,4,5-trifluorophenyl)pyridin-2-yl)benzofuro[2,3-b]pyridine (2.35 g, 6.02 mmol) followed by 2-ethoxyethanol (50 mL) and DMF (50 mL) and heated at 130° C. overnight. The reaction was allowed to cool down and evaporated the solvents. It was dissolved in DCM and passed through a short silica gel plug eluted with DCM and then run a silica gel column to give a 1.25 g (47% yield) orange solid which LC/MS shows desired mass.

15. Synthesis of Compound III-4640

A mixture of iridium complex (2.7 g, 3.33 mmol), 8-(4-(4-fluorolphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.35 g, 6.65 mmol), 2-ethoxyethanol (50 mL) and DMF (50 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 2.3 g desired product (73% yield) which was confirmed by LC-MS.

16. Synthesis of Compound III-4622

A mixture of phenylpyridine iridium complex (2.4 g, 2.96 mmol), 8-(4-(4-isopropylphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.237 g, 5.91 mmol), 2-ethoxyethanol (50 mL) and DMF (50 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug with dichloromethane (DCM). The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 2.4 g desired product (83% yield), which was confirmed by LC-MS.

17. Synthesis of Compound III-56

Synthesis of 8-(4-(2-fluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine

2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (2.8 g, 9.06 mmol), 2-chloro-4-(2-fluorophenyl)pyridine (2.25 g, 10.84 mmol), tris(dibenzylideneacetone) palladium(0) (0.166 g, 0.181 mmol) and 2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.297 g, 0.725 mmol) were charged into the reaction vessel with 200 mL of toluene. Potassium phosphate tribasic (6 g, 28.3 mmol) was then dissolved in 25 mL of water and was added to the reaction mixture. The reaction mixture was degassed with nitrogen then was heated to reflux overnight. The reaction mixture was cooled to room temperature. The toluene layer was separated and was dried over magnesium sulfate. This mixture was filtered and concentrated under vacuum. The crude residue was passed through a silica gel column using 15-22.5% ethyl acetate/heptanes. The clean product fractions were evaporated under reduced pressure yielding 8-(4-(2-fluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.247 g, 6.34 mmol, 70% yield) as a white solid.

8-(4-(2-fluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.9 g, 5.36 mmol) and Iridium complex (1.913 g, 2.68 mmol) were charged into the reaction mixture with 50 mL of DMF and 50 mL of 2-ethoxyethanol. This reaction mixture was degassed with nitrogen then was heated at an oil bath temperature of 130° C. for 18 hours. The reaction mixture was cooled to room temperature then was evaporated under reduced pressure. The crude product was dissolved in 300 mL of DCM then was passed through a silica gel plug eluting the plug with 1.5 L of DCM. This DCM filtrated was evaporated and the crude product was passed through a silica gel column eluting the column with 55-65% DCM/heptanes. Clean product fractions yielded 1.2 g (32% yield) of the desired product.

18. Synthesis of Compound III-59

To a 250 mL flask added 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzofuro[2,3-b]pyridine (3.0 g, 9.70 mmol), 2-chloro-4-(2,4-difluorophenyl)pyridine (2.63 g, 11.64 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.319 g, 0.776 mmol), Pd 2 (dba) 3 (0.178 g, 0.194 mmol), potassium phosphate (7.21 g, 34.0 mmol) followed by water (7 mL) and toluene (volume: 70 mL). The reaction was degassed with N 2 and heated at reflux under N 2 overnight. The reaction was worked up with silica gel column to give 2.45 g (68%) clean product.

To a 250 mL flask added iridium complex (2.348 g, 3.29 mmol), 8-(4-(2,4-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (2.45 g, 6.58 mmol), 2-ethoxyethanol (60 mL), DMF (60 mL). The mixture was heated in an oil bath at 130° C. overnight under N 2 and allowed to cool and evaporated the solvents to leave a red/orange solid which was further purified by silica gel column to give orange solid 1.7 g (61% yield) desired product which was confirmed by LC-MS.

19. Synthesis of Compound III-65

Synthesis of: 8-(4-(2,3-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine

2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (2.8 g, 9.06 mmol), 2-chloro-4-(2,3-difluorophenyl)pyridine (2.452 g, 10.87 mmol), tris(dibenzylideneacetone)palladium(0) (0.166 g, 0.181 mmol) and 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.297 g, 0.725 mmol) were charged into the reaction mixture with 200 mL of toluene. Potassium phosphate tribasic (5.76 g, 27.2 mmol) was dissolved in 25 mL of water then was charged into the reaction mixture. This mixture was degassed then heated to reflux for 18 hours. The reaction mixture was cooled to room temperature. The toluene layer was separated and was dried over magnesium sulfate. This mixture was filtered and concentrated under vacuum. The crude residue was passed through a silica gel column using 15-22.5% ethyl acetate/heptanes. The clean product fractions were evaporated under reduced pressure yielding 8-(4-(2,3-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.2 g, 3.22 mmol, 35.6% yield) as a white solid.

8-(4-(2,3-difluorophenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.2 g, 3.22 mmol) and iridium complex (2.30 g, 3.22 mmol) were charged into the reaction mixture with 30 mL of DMF and 30 mL of 2-ethoxyethanol. This reaction mixture was degassed with nitrogen then was heated at an oil bath temperature of 130° C. for 18 hours. The reaction mixture was cooled to room temperature then was evaporated under reduced pressure. The crude product was dissolved in 300 mL of DCM then was passed through a silica gel plug eluting the plug with 1.5 L of DCM. This DCM filtrated was evaporated and the crude product was passed through a silica gel column eluting the column with 55-65% DCM/heptanes. Clean product fractions yielded 0.69 g (30% yield) of the desired product.

20. Synthesis of Compound III-1750

A mixture of iridium complex (2.1 g, 2.81 mmol), 8-(4-(4-fluorolphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.99 g, 5.62 mmol), 2-ethoxyethanol (50 mL) and DMF (50 mL) was heated at 130° C. overnight under nitrogen. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 2.1 g desired product (84% yield) which was confirmed by LC-MS.

21. Synthesis of Compound III-1559

A mixture of iridium complex (2.214 g, 2.58 mmol), 8-(4-(4-methylphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.8 g, 5.14 mmol), 2-ethoxyethanol (50 mL) and DMF (50 mL) was heated at 130° C. overnight. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug. The reaction mixture was further purified by silica gel column to give 1.8 g (71% yield) desired product which was confirmed by LC-MS.

22. Synthesis of Compound III-26

Synthesis of 2-Chloro-4-phenylpyridine

A mixture of 2-chloro-4-iodopyridine (20.0 g, 82 mmol), phenylboronic acid (10.2 g, 82 mmol), Pd(Ph 3 P) 4 (2.84 g 2.46 mmol), sodium carbonate (26.0 g, 246 mmol), DME (600 mL) and water (150 mL) was degassed with nitrogen and then refluxed overnight. The reaction was concentrated and the extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then vacuum distilled to give 2-chloro-4-phenylpyridine (2.79 g. 12.7 mmol. 82% yield).

Synthesis of 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (4.34 g, 14.03 mmol), 2-chloro-4-phenylpyridine (2.66 g, 14.03 mmol), Pd 2 (dba) 3 (0.257 g 0.281 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.582 g, 1.42 mmol), potassium phosphate (8.93 g, 42.1 mmol), toluene (180 mL) and water (28 mL) was degassed with nitrogen and then refluxed overnight. The mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in hexanes to give 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (3.66 g, 10.88 mmol, 78% yield).

A mixture of iridium complex (2 g, 2.8 mmol),1 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (1.89 g, 5.60 mmol),), ethoxyethanol (40 ml) and DMF (40 mL) was heated at 130° C. overnight. The reaction mixture was concentrated to remove solvents and filtered through a small plug of silica gel and further chromatographed to give 0.98 g product. After sublimation, it gave the desired product (0.85 g, 36.3% yield).

23. Synthesis of Compound III-196

A mixture of iridium complex (2.0 g, 2.69 mmol),), 2-methyl-8-(4-phenylpyridin-2-yl)benzofuro[2,3-b]pyridine (1.807 g, 5.37 mmol), 2-ethoxyethanol (50 mL) and DMF (50 mL) was heated at 130° C. overnight under nitrogen. The solvent mixture was evaporated under vacuum. The residue was run through a short silica plug with DCM as elute. The reaction mixture was further purified by silica gel column with DCM/heptane as elute to obtain 1.1 g desired product (47% yield) which was confirmed by LC-MS.

24. Synthesis of Compound III-220

A mixture of iridium complex (2.0 g, 2.70 mmol), 8-(4-(4-fluorolphenyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (1.911 g, 5.39 mmol), 2-ethoxyethanol 60 mL was heated at 130° C. overnight under nitrogen. The reaction was cooled down and filtered and washed with methanol. The obtained crud product was purified by silica gel column with DCM/heptane as elute to obtain 1.6 g desired product (67%, yield) which was confirmed by LC-MS.

25. Synthesis of Compound III-29

Synthesis of 2-Chloro-4-(p-tolyl)pyridine

A mixture of 2-chloro-4-iodopyridine (10.0 g, 41.8 mmol), p-tolylphenylboronic acid (5.68 g, 41.8 mmol), Pd(Ph 3 P) 4 (1.45 g 1.25 mmol), sodium carbonate (13.3 g, 125 mmol), DME (300 mL) and water (75 mL) was degassed with nitrogen and then refluxed overnight. The reaction mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and vacuum distilled and recrystallized to give 2-chloro-4-(p-tolyl)pyridine (3.75 g, 18.4 mmol, 44% yield).

Synthesis of 2-methyl-8-(4-(p-tolyl)(pyridin-2-yl)benzofuro[2,3-b]pyridine

A mixture of 2-methyl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzofuro[2,3-b]pyridine (2.5 g, 8.03 mmol), 2-chloro-4-(p-tolyl)pyridine (1.80 g, 8.83 mmol), Pd 2 (dba) 3 (0.147 g 0.161 mmol), dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-2-yl)phosphine (0.264 g, 0.642 mmol), potassium phosphate (5.96 g, 28.1 mmol), toluene (100 mL) and water (10 mL) was degassed with nitrogen and then refluxed overnight. The reaction mixture was concentrated and extracted with ethyl acetate. The ethyl acetate layer was dried on Na 2 SO 4 and then further purified by column chromatography using ethyl acetate in hexanes to give 2-methyl-8-(4-(p-tolyl)pyridin-2-yl)benzofuro[2,3-b]pyridine (2.0 g, 5.71 mmol, 71% yield).

A mixture of iridium complex (2.26 g, 3.17 mmol),1 2-methyl-8-(4-(p-tolyl)pyridin-2-yl)benzofuro[2,3-b]pyridine (2.0 g, 5.71 mmol),), 2-ethoxyethanol (45 mL) and DMF (45 mL) was heated at 130° C. overnight. The reaction mixture was concentrated to remove solvents and filtered through a small plug of silica gel with DCM and further chromatographed to give 1.54 g product. After sublimation, it yielded 1.0 g (37% yield) desired product which was confirmed by LC-MS.

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 may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting.