Organic electroluminescent materials and devices

Abstract

Novel compounds comprising heteroleptic iridium complexes are provided. The compounds have a particular combination of ligands which includes a single pyridyl dibenzo-substituted ligand. The compounds may be used in organic light emitting devices, particularly as emitting dopants, to provide devices having improved efficiency, lifetime, and manufacturing.

Claims

1. A compound comprising a heteroleptic iridium complex having the ##STR00227## formula: wherein X is selected from the group consisting of NR, O, S, BR, and Se; wherein R is selected from hydrogen and alkyl; wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each represent mono, di, tri, or tetra substitutions; wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is independently selected from the group consisting of hydrogen, alkyl, and aryl; and wherein at least one R.sub.1 is other than hydrogen, at least one R.sub.2 is other than hydrogen, at least one R.sub.3 is other than hydrogen, and at least one R.sub.4 is other than hydrogen.

2. The compound of claim 1, wherein each R.sub.1 and R.sub.4 is independently selected from the group consisting of hydrogen and alkyl having four or fewer carbon atoms; and wherein at least one R.sub.1 is other than hydrogen and at least one R.sub.4 is other than hydrogen.

3. The compound of claim 1, wherein each R.sub.2 and R.sub.3 is independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms and aryl with 6 or fewer ring atoms; and wherein at least one R.sub.2 is other than hydrogen and at least one R.sub.3 is other than hydrogen.

4. The compound of claim 1, wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms and aryl with 6 or fewer ring atoms; and wherein at least one R.sub.1 is other than hydrogen, at least one R.sub.2 is other than hydrogen, at least one R.sub.3 is other than hydrogen, and at least one R.sub.4 is other than hydrogen.

5. The compound of claim 1, wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is are independently selected from the group consisting of hydrogen, methyl and phenyl; and wherein at least one R.sub.1 is other than hydrogen, at least one R.sub.2 is other than hydrogen, at least one R.sub.3 is other than hydrogen, and at least one R.sub.4 is other than hydrogen.

6. The compound of claim 1, wherein R has 4 or fewer carbon atoms.

7. The compound of claim 1, wherein the compound has the formula: ##STR00228##

8. The compound of claim 1, wherein the compound has the formula: ##STR00229##

9. The compound of claim 1, wherein the compound has the formula: ##STR00230##

10. The compound of claim 1, wherein X is O.

11. The compound of claim 1, wherein X is S.

12. A first device comprising an organic light emitting device, further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, the organic layer further comprising a compound comprising a heteroleptic iridium complex having the formula: ##STR00231## wherein X is selected from the group consisting of NR, O, S, BR, and Se; wherein R is selected from hydrogen and alkyl; wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each represent mono, di, tri, or tetra substitutions; wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is independently selected from the group consisting of hydrogen, alkyl, and aryl; and wherein at least one R.sub.1 is other than hydrogen, at least one R.sub.2 is other than hydrogen, at least one R.sub.3 is other than hydrogen, and at least one R.sub.4 is other than hydrogen.

13. The device of claim 12, wherein the organic layer is an emissive layer and the compound having the formula: ##STR00232## is an emitting dopant.

14. The device of claim 12, wherein the organic layer further comprises a host.

15. The device of claim 14, wherein the host comprises a triphenylene moiety and a dibenzothiophene moiety.

16. The device of claim 15, wherein the host has the formula: ##STR00233## wherein R′.sub.1, R′.sub.2, R′.sub.3, R′.sub.4, R′.sub.5, and R′.sub.6 may represent mono, di, tri, or tetra substitutions, or no substitutions; and wherein each of R′.sub.1, R′.sub.2, R′.sub.3, R′.sub.4, R′.sub.5, and R′.sub.6 are independently selected from the group consisting of hydrogen, alkyl, and aryl.

17. The compound of claim 1, wherein at least one of R.sub.1, R.sub.2, R.sub.3, or R.sub.4 comprises aryl.

18. The compound of claim 1, wherein at least one R.sub.4 comprises aryl.

19. The compound of claim 1, wherein at least one of R.sub.1, R.sub.2, R.sub.3, or R.sub.4 is disubstitued.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an organic light emitting device.

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

(3) FIG. 3 shows a heteroleptic iridium complex.

DETAILED DESCRIPTION

(4) 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.

(5) 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.

(6) 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.

(7) 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, and a cathode 160. 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.

(8) 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.sub.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.

(9) 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.

(10) 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.

(11) 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.

(12) 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. 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.

(13) 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, 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.).

(14) 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.

(15) 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.

(16) Novel compounds are provided, the compounds comprising a heteroleptic iridium complex (illustrated in FIG. 3). In particular, the complex has two phenylpyridine ligands and one ligand having the structure

(17) ##STR00008##
The ligand having the structure FORMULA II consists of a pyridine joined to a dibenzofuran, dibenzothiophene, carbazole, dibenzoborole, or dibenzoselenophene (herein also referred to as “pyridyl dibenzo-substituted”). These compounds may be advantageously used in organic light emitting devices as an emitting dopant in an emissive layer.

(18) Iridium complexes containing two or three pyridyl dibenzofuran, dibenzothiophene, carbazole, and fluorene ligands have been reported. By replacing the phenyl group in tris(2-phenylpyridine)iridium with dibenzofuran, dibenzothiophene, carbazole, and fluorene groups, the HOMO-LUMO energy levels, photophysical properties, and electronic properties of the resulting complex can be significantly affected. A variety of emission colors, ranging from green to red, have been achieved by using complexes with different combinations of pyridyl dibenzo-substituted ligands (i.e., bis and tris complexes). However, the existing complexes may have practical limitations. For example, iridium complexes having two or three of these types of ligands (e.g., pyridyl dibenzofuran, dibenzothiophene, or carbazole) have high molecular weights, which often results in a high sublimation temperature. In some instances, these complexes can become non-sublimable due to the increased molecular weight. For example, tris(2-(dibenzo[b,d]furan-4-yl)pyridine)Iridium(III) decomposed during sublimation attempts. Additionally, known compounds comprising a pyridyl fluorene ligand may have reduced stability. Fluorene groups (e.g., C═O and CRR′) disrupt conjugation within the ligand structure resulting in a diminished ability to stabilize electrons. Therefore, compounds with the beneficial properties of pyridyl dibenzo-substituted ligands (e.g., dibenzofuran, dibenzothiophene, carbazole, dibenzoborole, and dibenzoselenophene) and a relatively low sublimation temperature are desirable.

(19) Additionally, iridium complexes having two or three of the ligands having FORMULA II have high molecular weights and stronger intermolecular interactions, which often results in a high sublimation temperature. In some instances, these complexes can become non-sublimable due to the increased molecular weight and strong intermolecular interactions.

(20) Novel heteroleptic iridium complexes are provided herein. The complexes contain pyridyl dibenzo-substituted ligands having the structure FORMULA II. In particular, the novel heteroleptic complexes include a single pyridyl dibenzo-substituted ligand wherein the ligand contains O, S, N, Se, or B (i.e. the ligand is pyridyl dibenzofuran, pyridyl dibenzothiophene, pyridyl carbazole, pyridyl dibenzoselenophene, or pyridyl dibenzoborole) and two phenylpyridine ligands. As a result of the particular combination of ligands in the heteroleptic compounds disclosed herein, these compounds can provide both improved photochemical and electrical properties as well as improved device manufacturing. In particular, by containing only one of the dibenzo-substituted pyridine ligands having FORMULA II, the complexes provided herein will likely have lower sublimation temperatures (correlated with reduced molecular weight and/or weaker intermolecular interactions). Additionally, these compounds maintain all of the benefits associated with the pyridyl dibenzo-substituted ligand, such as improved stability, efficiency, and narrow line width. Therefore, these compounds may be used to provide improved organic light emitting devices and improved commercial products comprising such devices. In particular, these compounds may be particularly useful in red and green phosphorescent organic light emitting devices (PHOLEDs).

(21) As mentioned previously, bis or tris iridium complexes containing ligands having FORMULA II may be limited in practical use due to the high sublimation temperature of the complex. The invention compounds, however, have a lower sublimation temperature which can improve device manufacturing. Table 1 provides the sublimation temperature for several compounds provided herein and the corresponding bis or tris complex. For example, Compound 1 has a sublimation temperature of 243° C. while the corresponding tris complex fails to sublime. Additionally, other tris complexes comprising three pyridyl dibenzo-substituted ligands (i.e., tris complex comprising pyridyl dibenzothiophene) fail to sublime. Therefore, the compounds provided herein may allow for improved device manufacturing as compared to previously reported bis and tris compounds.

(22) TABLE-US-00001 TABLE 1 Sublimation Sublimation temperature temperature Compounds (° C.) Compounds (° C.)   Compound 1 243 0   Compound 4 218 Fail to sublime   Compound 29 230 Fail to sublime 290   Compound 2 232   Compound 10 240   Compound 7 256   Compound 37 224

(23) Generally, the dibenzo-substituted pyridine ligand would be expected to have lower triplet energy than the phenylpyridine ligand, and consequently the dibenzo-substituted pyridine ligand would be expected to control the emission properties of the compound. Therefore, modifications to the dibenzo-substituted pyridine ligand may be used to tune the emission properties of the compound. The compounds disclosed herein contain a dibenzo-substituted pyridine ligand containing a heteroatom (e.g., O, S, or NR) and optionally further substituted by chemical groups at the R.sub.1 and R.sub.4 positions. Thus, the emission properties of the compounds may be tuned by selection of a particular heteroatom and/or varying the substituents present on the dibenzo-substituted pyridine ligand.

(24) The compounds described herein comprise heteroleptic iridium complexes having the formula:

(25) ##STR00019##

(26) Features of the compounds having FORMULA I include comprising one ligand having the structure

(27) ##STR00020##
and two phenylpyridine ligands that may have further substitution, wherein all ligands are coordinated to Ir.

(28) X is selected from the group consisting of NR, O, S, BR, and Se. R is selected from hydrogen and alkyl. R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may represent mono, di, tri, or tetra substitutions; and each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms, and aryl.

(29) In another aspect, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms, and aryl with 6 or fewer atoms in the ring.

(30) The term “aryl” as used herein refers to an aryl, comprising either carbon atoms or heteroatoms, that is not fused to the phenyl ring of the phenylpyridine ligand (i.e., aryl is a non-fused aryl). The term “aryl” as used herein contemplates single-ring groups and polycyclic ring systems. The polycyclic rings may have two or more rings in which two carbons are common by two adjoining rings (the rings are “fused”) wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles and/or heteroaryls. Additionally, the aryl group may be optionally substituted with one or more substituents selected from halo, CN, CO.sub.2R, C(O)R, NR.sub.2, cyclic-amino, NO.sub.2, and OR. “Aryl” also encompasses a heteroaryl, such as single-ring hetero-aromatic groups that may include from one to three heteroatoms, for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. This includes polycyclic hetero-aromatic systems having two or more rings in which two atoms are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is a heteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles and/or heteroaryls. Additionally, the heteroaryl group may be optionally substituted with one or more substituents selected from halo, CN, CO.sub.2R, C(O)R, NR.sub.2, cyclic-amino, NO.sub.2, and OR. For example, R.sub.1, R.sub.2, R.sub.3 and/or R.sub.4 may be an aryl, including an heteroaryl, that is not used to the phenyl ring of the phenylpyridine.

(31) The term “alkyl” as used herein contemplates both straight and branched chain alkyl radicals. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, the alkyl group may be optionally substituted with one or more substituents selected from halo, CN, CO.sub.2R, C(O)R, NR.sub.2, cyclic-amino, NO.sub.2, and OR, wherein each R is independently selected from H, alkyl, alkenyl, alkynyl, aralkyl, aryl and heteroaryl. Preferably, in order to make the compounds sublimable and/or to reduce sublimation temperature, alkyls in the R.sub.1, R.sub.2, R.sub.3 and/or R.sub.4 positions of Formula I have four or fewer carbon atoms (e.g., methyl, ethyl, propyl, butyl, and isobutyl).

(32) In general, the compounds provided herein have relatively low sublimation temperatures compared to previously reported compounds. Thus, these novel compounds provide improved device fabrication among other beneficial properties. Moreover, it is believed that heteroleptic compounds having FORMULA I wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are selected from smaller substituents may be particularly beneficial. A smaller substituents includes, for example, hydrogen or alkyl. In particular, it is believed that compounds wherein the substituents R.sub.1, R.sub.2, R.sub.3 and/or R.sub.4 are selected from smaller substituents may have even lower sublimation temperatures thereby further improving manufacturing while maintaining the desirable properties (e.g., improved stability and lifetimes) provided by the ligand having the structure FORMULA II.

(33) Generally, the compounds provided having FORMULA I have substituents such that R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl, and aryl. Preferably, any alkyl has four or fewer carbon atoms. To minimize molecular weight and thereby lower the sublimation temperature, compounds having smaller substituents on the ligand having the structure FORMULA II are preferred. Preferably, R.sub.1 and R.sub.4 are independently selected from the group consisting of hydrogen and alkyl having four or fewer carbon atoms; more preferably, R.sub.1 and R.sub.4 are independently selected from the group consisting of hydrogen and methyl.

(34) For similar reasons, compounds are preferred having smaller substituents present on the phenylpyridine ligand. Additionally, the phenylpyridine ligand is believed to contribute less to the emission of the complex. Moreover, the complex contains two of the phenylpyridine ligand, thus substituents present on the phenylpyridine ligand contribute more to the overall molecular weight of the complex. For at least these reasons, preferably R.sub.2 and R.sub.3 are independently selected from hydrogen and alkyl having four or fewer carbon atoms; more preferably, R.sub.2 and R.sub.3 are independently selected from hydrogen and methyl; most preferably, R.sub.2 and R.sub.3 are hydrogen.

(35) Compounds having alkyl and aryl substitutions that can decrease intermolecular interactions are also preferred.

(36) In another aspect, preferably R.sub.2 and R.sub.3 are independently selected from hydrogen, alkyl having four or fewer carbon atoms and aryl with 6 or fewer atoms in the ring; more preferably, R.sub.2 and R.sub.3 are independently selected from hydrogen, methyl and phenyl; most preferably, R.sub.2 and R.sub.3 are hydrogen.

(37) Compounds are preferred wherein the overall molecular weight of the complex is low to reduce the sublimation temperature and improve device manufacturing. Toward this end, compounds wherein all substituents are relatively small are preferred. In one aspect, preferably R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen and alkyl having four or fewer carbon atoms; more preferably, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen and methyl; most preferably, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrogen.

(38) In another aspect, preferably R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms and aryl with 6 or fewer atoms in the ring; more preferably, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, methyl and phenyl; most preferably, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrogen.

(39) As discussed above, X can also be BR. Preferably, R has 4 or fewer carbon atoms. For similar reasons as those previously discussed, smaller alkyl groups (i.e., alkyls having 4 or fewer carbon atoms) on the carbazole portion of the substituted ligand will likely lower the sublimation temperature of the complex and thus improve device manufacturing.

(40) Particular heteroleptic iridium complexes are also provided. In one aspect, heteroleptic iridium complexes are provided having the formula:

(41) ##STR00021##

(42) In another aspect, heteroleptic iridium comnlexec are provided having the formula:

(43) ##STR00022##

(44) In yet another aspect, heteroleptic iridium complexes are provided having the formula:

(45) ##STR00023##

(46) Specific examples of heteroleptic iridium complexes are provided, and include compounds selected from the group consisting of:

(47) ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031## ##STR00032##

(48) Additional specific examples of heteroleptic iridium complexes are provided, and include compounds selected from the group consisting of:

(49) ##STR00033## ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041## ##STR00042## ##STR00043## ##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052##

(50) The heteroleptic iridium compound may be selected from the group consisting of Compound 1-Compound 108.

(51) Compounds having FORMULA I in which X is selected from O, S and NR may be particularly advantageous. Without being bound by theory, it is thought that the aromaticity of the ligands comprising a dibenzofuran, dibenzothiophene or carbazole moiety (i.e., X is O, S, or NR) provides electron delocalization which may result in improved compound stability and improved devices. Moreover, it is believed that compounds wherein X is O may be more preferable than compounds wherein X is S or NR. In many cases, dibenzofuran containing compounds and devices comprising such compounds demonstrate especially desirable properties.

(52) In one aspect, compounds are provided wherein X is O. Exemplary compounds where X is O include, but are not limited to, Compounds 1-12. Compounds wherein X is O may be especially preferred at least because these compounds may generate devices having desirable properties. For example, these compounds may provide devices having improved efficiency and a long lifetime. Additionally, the reduced sublimation temperature of these compounds can also result in improved manufacturing of such desirable devices.

(53) Additional exemplary compounds where X is O are provided and include, without limitation, Compounds 37-60. Compounds 1-12 and 37-60 may provide devices having improved efficiency, lifetime, and manufacturing.

(54) In another aspect, compounds are provided wherein X is S. Exemplary compounds where X is S include, but are not limited to, Compounds 13-24. These compounds, containing a pyridyl dibenzofuran ligand, may also be used in devices demonstrating good properties. For example, compounds wherein X is S may provide devices having improved stability and manufacturing.

(55) Additional exemplary compounds where X is S are provided and include, without limitation, Compounds 61-84. Compounds 13-24 and 61-84 may provide devices having improved stability and manufacturing.

(56) In yet another aspect, compounds are provided wherein X is NR. Exemplary compounds wherein X is NR include, but are not limited to, Compounds 25-36. These compounds containing a pyridyl carbazole ligand may also be used to provide devices having good properties, such as improved efficiency.

(57) Additional exemplary compounds where X is NR are provided and include, without limitation, Compounds 85-108. Compounds 26-36 and 85-108 may provide devices having improved efficiency.

(58) Additionally, an organic light emitting device is also provided. The device comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a compound having FORMULA I. X is selected from the group consisting of NR, O, S, BR, and Se. R is selected from hydrogen and alkyl. Preferably, R has 4 or fewer carbon atoms. R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may represent mono, di, tri, or tetra substitutions. Each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms, and aryl. Preferably, R.sub.2 and R.sub.3 are independently selected from the group consisting of hydrogen and alkyl having four or fewer carbon atoms. Selections for the heteroatoms and substituents described as preferred for the compound of FORMULA I are also preferred for use in a device that includes a compound having FORMULA I. These selections include those described for X, R, R.sub.1, R.sub.2 and R.sub.3 and R.sub.4.

(59) In another aspect, each of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms, and aryl with 6 or fewer atoms in the ring. Preferably, R.sub.2 and R.sub.3 are independently selected from the group consisting of hydrogen, alkyl having four or fewer carbon atoms and aryl with 6 or fewer atoms in the ring.

(60) In particular, devices are provided wherein the compound is selected from the group consisting of Compounds 1-36.

(61) In addition, devices are provided which contain a compound selected from the group consisting of Compounds 37-108. Moreover, the devices provided may contain a compound selected from the group consisting of Compounds 1-108.

(62) In one aspect, the organic layer is an emissive layer and the compound having FORMULA I is an emitting dopant. The organic layer may further comprise a host. Preferably, the host comprises a triphenylene moiety and a dibenzothiophene moiety. More preferably, the host has the formula:

(63) ##STR00053##
R′.sub.1, R′.sub.2, R′.sub.3, R′.sub.4, R′.sub.5, and R′.sub.6 may represent mono, di, tri, or tetra substitutions. Each of R′.sub.1, R′.sub.2, R′.sub.3, R′.sub.4, R′.sub.5, and R′.sub.6 are independently selected from the group consisting of hydrogen, alkyl, and aryl.

(64) As discussed above, the heteroleptic compounds provided herein may be advantageously used in organic light emitting devices to provide devices having desirable properties such as improved lifetime, stability and manufacturing.

(65) A consumer product comprising a device is also provided. The device further comprises an anode, a cathode, and an organic layer. The organic layer further comprises a heteroleptic iridium complex having FORMULA I.

(66) 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.

(67) In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/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 2 below. Table 2 lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

(68) TABLE-US-00002 TABLE 2 MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injection materials Phthalocyanine and porphyrin compounds Appl. Phys. Lett. 69, 2160 (1996) Starburst triarylamines J. Lumin. 72-74, 985 (1997) CF.sub.x Fluorohydrocarbon polymer Appl. Phys. Lett. 78, 673 (2001) Conducting polymers (e.g., PEDOT:PSS, polyaniline, polythiophene) Synth. Met. 87, 171 (1997) WO2007002683 Phosphonic acid and sliane SAMs US20030162053 Triarylamine or polythiophene polymers with conductivity dopants EA01725079A1 0 Arylamines complexed with metal oxides such as molybdenum and tungsten oxides SID Symposium Digest, 37, 923 (2006) WO2009018009 p-type semiconducting organic complexes US20020158242 Metal organometallic complexes US20060240279 Cross-linkable compounds US20080220265 Hole transporting materials Triarylamines (e.g., TPD, α-NPD) Appl. Phys. Lett. 51, 913 (1987) U.S. Pat. No. 5,061,569 EP650955 J. Mater. Chem. 3, 319 (1993) 0 Appl. Phys. Lett. 90, 183503 (2007) Appl. Phys. Lett. 90, 183503 (2007) Triarylamine on spirofluorene core Synth. Met. 91, 209 (1997) Arylamine carbazole compounds Adv. Mater. 6, 677 (1994), US20080124572 Triarylamine with (di)benzothiophene/ (di)benzofuran US20070278938, US20080106190 Indolocarbazoles Synth. Met. 111, 421 (2000) Isoindole compounds Chem. Mater. 15, 3148 (2003) Metal carbene complexes US20080018221 Phosphorescent OLED host materials Red hosts Arylcarbazoles Appl. Phys. Lett. 78, 1622 (2001) Metal 8-hydroxyquinolates (e.g., Alq.sub.3, BAlq) Nature 395, 151 (1998) 0 US20060202194 WO2005014551 WO2006072002 Metal phenoxybenzothiazole compounds Appl. Phys. Lett. 90, 123509 (2007) Conjugated oligomers and polymers (e.g., polyfluorene) Org. Electron. 1, 15 (2000) Aromatic fused rings WO2009066779, WO2009066778, WO2009063833, US20090045731, US20090045730, WO2009008311, US20090008605, US20090009065 Zinc complexes WO2009062578 Green hosts Arylcarbazoles Appl. Phys. Lett. 78, 1622 (2001) US20030175553 WO2001039234 Aryltriphenylene compounds 0 US20060280965 US20060280965 WO2009021126 Donor acceptor type molecules WO2008056746 Aza-carbazole/DBT/DBF JP2008074939 Polymers (e.g., PVK) Appl. Phys. Lett. 77, 2280 (2000) Spirofluorene compounds WO2004093207 Metal phenoxybenzooxazole compounds WO2005089025 WO2006132173 JP200511610 Spirofluorene-carbazole compounds 00 JP2007254297 01 JP2007254297 Indolocarbazoles 02 WO2007063796 03 WO2007063754 5-member ring electron deficient heterocycles (e.g., triazole, oxadiazole) 04 J. Appl. Phys. 90, 5048 (2001) 05 WO2004107822 Tetraphenylene complexes 06 US20050112407 Metal phenoxypyridine compounds 07 WO2005030900 Metal coordination complexes (e.g., Zn, Al with N{circumflex over ( )}N ligands) 08 US20040137268, US20040137267 Blue hosts Arylcarbazoles 09 Appl. Phys. Lett, 82, 2422 (2003) 0 US20070190359 Dibenzothiophene/ Dibenzofuran-carbazole compounds WO2006114966, US20090167162 US20090167162 WO2009086028 US20090030202, US20090017330 Silicon aryl compounds US20050238919 WO2009003898 Silicon/Germanium aryl compounds EP2034538A Aryl benzoyl ester WO2006100298 High triplet metal organometallic complex U.S. Pat. No. 7,154,114 Phosphorescent dopants Red dopants Heavy metal porphyrins (e.g., PtOEP) 0 Nature 395, 151 (1998) Iridium(III) organometallic complexes Appl. Phys. Lett. 78, 1622 (2001) US2006835469 US2006835469 US20060202194 US20060202194 US20070087321 US20070087321 Adv. Mater. 19, 739 (2007) WO2009100991 0 WO2008101842 Platinum(II) organometallic complexes WO2003040257 Osminum(III) complexes Chem. Mater. 17, 3532 (2005) Ruthenium(II) complexes Adv. Mater. 17, 1059 (2005) Rhenium (I), (II), and (III) complexes US20050244673 Green dopants Iridium(III) organometallic complexes   and its derivatives Inorg. Chem. 40, 1704 (2001) US20020034656 U.S. Pat. No. 7,332,232 US20090108737 US20090039776 0 U.S. Pat. No. 6,921,915 U.S. Pat. No. 6,687,266 Chem. Mater. 16, 2480 (2004) US20070190359 US 20060008670 JP2007123392 Adv. Mater. 16, 2003 (2004) Angew. Chem. Int. Ed. 2006, 45, 7800 WO2009050290 US20090165846 US20080015355 Monomer for polymeric metal organometallic compounds 0 U.S. Pat. No. 7,250,226, U.S. Pat. No. 7,396,598 Pt(II) organometallic complexes, including polydentated ligands Appl. Phys. Lett. 86, 153505 (2005) Appl. Phys. Lett. 86, 153505 (2005) Chem. Lett. 34, 592 (2005) WO2002015645 US20060263635 Cu complexes WO2009000673 Gold complexes Chem. Commun. 2906 (2005) Rhenium(III) complexes Inorg. Chem. 42, 1248 (2003) Deuterated organometallic complexes US20030138657 Organometallic complexes with two or more metal centers 0 US20030152802 U.S. Pat. No. 7,090,928 Blue dopants Iridium(III) organometallic complexes WO2002002714 WO2006009024 US20060251923 U.S. Pat. No. 7,393,599, WO2006056418, US20050260441, WO2005019373 U.S. Pat. No. 7,534,505 U.S. Pat. No. 7,445,855 US20070190359, US20080297033 U.S. Pat. No. 7,338,722 0 US20020134984 Angew. Chem. Int. Ed. 47, 1 (2008) Chem. Mater. 18, 5119 (2006) Inorg. Chem. 46, 4308 (2007) WO2005123873 WO2005123873 WO2007004380 WO2006082742 Osmium(II) complexes U.S. Pat. No. 7,279,704 Organometallics 23, 3745 (2004) Gold complexes 0 Appl. Phys. Lett. 74, 1361 (1999) Platinum(II) complexes WO2006098120, WO2006103874 Exciton/hole blocking layer materials Bathocuproine compounds (e.g., BCP, BPhen) Appl. Phys. Lett. 75, 4 (1999) Appl. Phys. Lett. 79, 449 (2001) Metal 8-hydroxyquinolates (e.g., BAlq) Appl. Phys. Lett. 81, 162 (2002) 5-member ring electron deficient heterocycles such as triazole, oxadiazole, imidazole, benzoimidazole Appl. Phys. Lett. 81, 162 (2002) Triphenylene compounds US20050025993 Fluorinated aromatic compounds Appl. Phys. Lett. 79, 156 (2001) Phenothiazine-S-oxide WO2008132085 Electron transporting materials Anthracene- benzoimidazole compounds WO2003060956 0 US20090179554 Aza triphenylene derivatives US20090115316 Anthracene-benzothiazole compounds Appl. Phys. Lett. 89, 063504 (2006) Metal 8-hydroxyquinolates (e.g., Alq.sub.3, Zrq.sub.4) Appl. Phys. Lett. 51, 913 (1987) U.S. Pat. No. 7,230,107 Metal hydroxybenzoquinolates Chem. Lett. 5, 905 (1993) Bathocuprine compounds such as BCP, BPhen, etc Appl. Phys. Lett. 91, 263503 (2007) Appl. Phys. Lett. 79, 449 (2001) 5-member ring electron deficient heterocycles (e.g., triazole, oxadiazole, imidazole, benzoimidazole) Appl. Phys. Lett. 74, 865 (1999) Appl. Phys. Lett. 55, 1489 (1989) Jpn. J. Apply. Phys. 32, L917 (1993) Silole compounds 00 Org. Electron. 4, 113 (2003) Arylborane compounds 01 J. Am. Chem. Soc. 120, 9714 (1998) Fluorinated aromatic compounds 02 J. Am. Chem. Soc. 122, 1832 (2000) Fullerene (e.g., C60) 03 US20090101870 Triazine complexes 04 US20040036077 Zn (N{circumflex over ( )}N) complexes 05 U.S. Pat. No. 6,528,187

(69) EXPERIMENTAL

COMPOUND EXAMPLES

(70) Example 1

(71) Synthesis of Compound 1

(72) ##STR00206##

(73) Synthesis of 2-(dibenzo[b,d]furan-4-yl)pyridine. 4-dibenzofuranboronic acid (5.0 g, 23.6 mmol), 2-chloropyridine (2.2 g, 20 mmol), dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (S-Phos) (0.36 g, 0.8 mmol), and potassium phosphate (11.4 g, 50 mmol) were mixed in 100 mL of toluene and 10 mL of water. Nitrogen is bubbled directly into the mixture for 30 minutes. Next, Pd.sub.2(dba).sub.3 was added (0.18 g, 0.2 mmol) and the mixture was heated to reflux under nitrogen for 8 h. The mixture was cooled and the organic layer was separated. The organic layers are washed with brine, dried over magnesium sulfate, filtered, and evaporated to a residue. The residue was purified by column chromatography eluting with dichloromethane. 4.5 g of desired product was obtained after purification.

(74) ##STR00207##

(75) Synthesis of Compound 1. The iridium triflate precursor (0.97 g, 1.4 mmol) and 2-(dibenzo[b,d]furan-4-yl)pyridine (1.0 g, 4.08 mmol) were mixed in 50 mL of ethanol. The mixture was heated at reflux for 24 h under nitrogen. Precipitate formed during reflux. The reaction mixture was filtered through a celite bed. The product was washed with methanol and hexanes. The solid was dissolved in dichloromethane and purified by column using 1:1 of dichloromethane and hexanes. 0.9 g of pure product was obtained after the column purification. (HPLC purity: 99.9%)

Example 2

(76) Synthesis of Compound 2

(77) ##STR00208##

(78) Synthesis of 3-nitrodibenzofuran. To 80 mL trifluroacetic acid in a250 mL round bottom flask was added dibenzofuran (7.06 g, 42 mmol) and stirred vigorously to dissolve the content at room temperature. The solution was then cooled on ice and 1.2 equivalent 70% HNO.sub.3 (4.54 g, 50.40 mmol) in 20 mL trifluroacetic acid was poured into the stirred solution slowly. After stirring for 30 minutes contents from the flask was poured into 150 mL ice-water and stirred for another 15 minutes. Off white color precipitate was then filtered out and finally washed with 2M NaOH and water. Moist material was then recrystallized from 1.5 L boiling ethanol in the form of light yellow color crystal. 7.2 g of product was isolated.

(79) ##STR00209##

(80) Synthesis of 3-aminodibenzofuran. 3-nitrodibenzofuran (6.2 g, 29.08 mmol) was dissolved in 360 mL ethyl acetate and was degassed 5 minutes by passing nitrogen gas through the solution. 500 mg of Pd/C was added to the solution and the content was hydrogenated at 60 psi pressure. Reaction was let go until pressure in hydrogenation apparatus stabilizes at 60 psi for 15 minutes. Reaction content was then filtered through a small celite pad and off white color product was obtained. (5.3 g, 28.9 mmol)

(81) ##STR00210##

(82) Synthesis of 3-bromodibenzofuran. NaNO.sub.2 (2.21 g, 32.05 mmol) was dissolved in 20 mL conc. H.sub.2SO.sub.4 in conical flask kept at 0° C. Solution of 2-aminodibenzofuran (5.3 g, 28.9 mmol) in minimum volume of glacial acetic acid was then slowly added to the flask so that temperature never raised above 5-8° C. and the mixture was stirred at 0° C. for another 1.5 h. 100 mL ether was added to the stirred mixture and precipitate of corresponding diazo salt immediately settled down. Brown color diazo salt was immediately filtered out and transferred to a flask containing CuBr (6.25 g, 43.5 mmol) in 150 mL 48% HBr. The flask was then placed in a water bath maintained at 64° C. and stirred for 2 h. After cooling down to room temperature, the dark color reaction content was filtered out and the precipitate was washed with water twice. Isolated solid was then flashed over Silica gel column with 5-10% DCM/Hexane to give 4.79 g final compound.

(83) ##STR00211##

(84) Synthesis of 2-(dibenzo[b,d]furan-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. 3-bromodibenzofuran (4.79 g, 19.39 mmol), bispinacolatodiboron (6.4 g, 25.2 mmol), KOAc (7.61 g, 77.54 mmol) was added to 100 mL of dioxane in a r.b. flask. Content was degassed for 30 minutes under bubbling nitrogen gas and Pd(dppf).sub.2Cl.sub.2 (158 mg, 0.019 mmol) was added to the reaction mixture. After degassing for another 10 minutes, the reaction mixture was heated to 80° C. and stirred overnight. Reaction flask was then cooled to room temperature and filtered through a pad of celite. Deep brown color solution was then partitioned in between brine and ethyl acetate. Organic layer was collected, dried over anhydrous Na.sub.2SO.sub.4 and excess solvent was evaporated under vacuum. Brown colored solid was then dry loaded in silica gel column and quickly flashed with 5% ethylacetate/hexane/0.005% triethylamine to give 5.08 g final product.

(85) ##STR00212##

(86) Synthesis of 2-(dibenzofuran-3-yl)pyridine. Dibenzofuran boronate ester (5.85 g, 20 mmol), 2-bromopyridine (2.93 mL, 30 mmol), 30 mL 2 M Na.sub.2CO.sub.3 (60 mmol) was slurried in 200 mL toluene/ethanol (1:1) in a 500 mL 3-neck round bottom flask and degassed for 30 minutes under bubbling nitrogen gas. Pd(dppf).sub.2Cl.sub.2 (160 mg, 0.2 mmol) was added to the slurry and degassing continued for another 10 minutes. The reaction contents were then refluxed overnight. Reaction content was cooled to room temperature and filtered thru a small celite pad. Brown color biphasic solution was then partitioned between brine and ethylacetate. Organic layer was dried over anhydrous Na.sub.2SO.sub.4and excess solvent was removed under vacuum. Residue from previous step was dry loaded in silica gel column and eluted with 5-8% ethylacetate/hexane to give 4.3 g final product.

(87) ##STR00213##

(88) Synthesis of Compound 2. The iridium triflate precursor (2.8 g, 3.9 mmol), 2-(dibenzofuran-3-yl)pyridine (4 g, 16.3 mmol) were refluxed in 100 mL ethanol overnight. Bright yellow precipitate was filtered out, dried and dry loaded in a silica gel column. 210 mg final compound was isolated after elution with 3:2 DCM/hexane.

Example 3

(89) Synthesis of Compound 4

(90) ##STR00214##

(91) Synthesis of Compound 4. The iridium triflate precursor (1.6 g, 2.2 mmol) and 2-(dibenzo[b,d]furan-4-yl)pyridine (1.6 g, 6.5 mmol) were mixed in 50 mL of ethanol. The mixture was heated at reflux for 24 h under nitrogen. Precipitate formed during reflux. The reaction mixture was filtered through a celite bed. The product was washed with methanol and hexanes. The solid was dissolved in dichloromethane and purified by column using 1:1 of dichloromethane and hexanes. 1.4 g of pure product was obtained after the column purification.

Example 4

(92) Synthesis of Compound 10

(93) ##STR00215##

(94) Synthesis of 4-methyl-2-(dibenzo[b,d]furan-4-yl)pyridine. 4-dibenzofuranboronic acid (5.0 g, 23.6 mmol), 2-chloro-4-methylpyridine (2.6 g, 20 mmol), dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (S-Phos) (0.36 g, 0.8 mmol), and potassium phosphate (11.4 g, 50 mmol) were mixed in 100 mL of toluene and 10 mL of water. Nitrogen is bubbled directly into the mixture for 30 minutes. Next, Pd.sub.2(dba).sub.3 was added (0.18 g, 0.2 mmol) and the mixture was heated to reflux under nitrogen for 8 h. The mixture was cooled and the organic layer was separated. The organic layers are washed with brine, dried over magnesium sulfate, filtered, and evaporated to a residue. The residue was purified by column chromatography eluting with dichloromethane. 4.7 g of desired product was obtained after purification.

(95) ##STR00216##

(96) Synthesis of Compound 10. The iridium triflate precursor (2.0 g, 2.7 mmol) and 4-methyl-2-(dibenzo[b,d]furan-4-yl)pyridine (2.1 g, 8.1 mmol) were mixed in 60 mL of ethanol. The mixture was heated at reflux for 24 h under nitrogen. Precipitate formed during reflux. The reaction mixture was filtered through a celite bed. The product was washed with methanol and hexanes. The solid was dissolved in dichloromethane and purified by column using 1:1 of dichloromethane and hexanes. 1.6 g of pure product was obtained after the column purification.

Example 5

(97) Synthesis of Compound 29

(98) ##STR00217##

(99) Synthesis of 4′-bromo-2-nitrobiphenyl. o-iodonitrobenzene (9.42 g, 37.84 mmol), 4-bromobenzeneboronic acid (7.6 g, 37.84 mmol), potassium carbonate (21 g, 151.36 mmol) was added to 190 mL DME/water (3:2) solution and degassed for 30 minutes. Pd(PPh.sub.3).sub.4 (437 mg, 0.38 mmol) was added to the slurry under nitrogen and the slurry was degassed for another 5 minutes. The reaction was refluxed under nitrogen for 6 h. Content of the flask was filtered through a pad of celite and partitioned in ethyl acetate and brine. Organic phase was dried over anhydrous Na.sub.2SO.sub.4 and evaporated under vacuum. Crude yellow oil was flashed over silica gel using 5% ethylacetate/hexane. Final compound was isolated as colorless oil (9.8 g, 35.4 mmol).

(100) ##STR00218##

(101) Synthesis of 2-bromo-9H-carbazole. 4′-bromo-2-nitrobiphenyl (9.8 g, 35.4 mmol) was refluxed with 30 mL triethylphosphite overnight. After cooling down the solution to room temperature, 40 mL 6(N) HCl was added to it slowly and heated to 80° C. for 3 h. Acidic solution was halfway neutralized with conc. NaOH, rest of the acidic solution was neutralized with solid Na.sub.2CO.sub.3. Cloudy solution was extracted three times with ethylacetate (500 mL). Combined organic layer was evaporated under vacuum and crude was flashed on silica gel (15% to 30% ethylacetate/hexane). 4.1 g final compound was isolated as off white solid.

(102) ##STR00219##

(103) Synthesis of 2-bromo-9-isobutyl-9H-carbazole. 2-bromo-9H-carbazole (4.1 g, 16.74 mmol) was dissolved in DMF. To the stirred solution was slowly added NaH (1.8 g, 75.5 mmol) in 3 portions. Isobutylbromide (4.8 mL, 43.2 mmol) was added to the stirred slurry and after waiting for 20 minute, warmed up to 60° C. for 4 h. Reaction mixture was cooled to room temperature and carefully quenched with drop wise addition of saturated NH.sub.4Cl solution. Content was then partitioned in brine and ethylacetate. Organic layer was dried over anhydrous Na.sub.2SO.sub.4 and evaporated under vacuum. The crude product was flashed over silica gel with 10% ethylacetate/hexane. Final product (4.45 g, 14.8 mmol) was isolated as white solid.

(104) ##STR00220##

(105) Synthesis of 9-isobutyl-2-pinacolboron-9H-carbazole. 2-bromo-9-isobutyl-9H-carbazole (4.45 g, 14.78 mmol), bisboronpinacolate (4.7 g, 18.5 mmol), potassium acetate (5.8 g, 59.1 mmol) were taken in 75 mL anhydrous toluene and degassed for 30 minutes. Pd.sub.2dba.sub.3 (362 mg, 0.443 mmol) was added to the slurry under nitrogen and the slurry was degassed for another 5 minutes. After overnight reflux, content of the reaction was cooled down and filtered through a celite pad. Toluene solution was partitioned in water and ethylacetate. Organic layer was dried over anhydrous Na.sub.2SO.sub.4 and solvent was evaporated under vacuum. Solid crude was flashed in silica gel using 10% ethylacetate/hexane. Isolated solid was subjected to Kugelrohr distillation at 133° C. to remove traces of bisboronpinacolate. Final product (4.77 g, 13.7 mmol) was isolated as off white solid.

(106) ##STR00221##

(107) Synthesis of 9-isobuthyl-2-(pyridine-2-yl)-9H-carbazole. 9-isobutyl-2-pinacolboron-9H-carbazole (1.45 g, 4 mmol), 2-bromopyridine (760 mg, 4.8 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (67 mg, 0.16 mmol), K.sub.3PO.sub.4.H.sub.2O (3.68 g, 16 mmol) were added to 40 mL mixture of 9:1 toluene and water. Contents were degassed for 30 minutes before addition of Pd.sub.2dba.sub.3 (37 mg, 0.04 mmol) and degassed for another 5 minutes. After overnight reflux, reaction content was cooled to room temperature and filtered through a pad of celite. Filtrate was partitioned in water and ethylacetate. Organic layer was isolated, dried over anhydrous Na.sub.2SO.sub.4 and evaporated under vacuum. Crude was then flashed over silica gel using 10%-30% ethylacetate/hexane to remove the protodeborylation product. Final compound (620 mg, 2.1 mmol) was isolated as white solid.

(108) ##STR00222##

(109) Synthesis of Compound 29. Carbazole ligand (620 mg, 2.1 mmol) from previous step was dissolved in ethanol and Intermediate-1 was added to it under nitrogen. Solution was then refluxed overnight. Deep orange color precipitate was filtered out and flashed over silica gel with 50% DCM/hexane. Isolated product was then sublimed to give 310 mg 99.7% pure product.

Example 6

(110) Synthesis of Compound 7

(111) ##STR00223##

(112) Synthesis of Compound 7. The iridium triflate precursor (2.0 g, 2.7 mmol) and 4-methyl-2-(dibenzo[b,d]furan-4-yl)pyridine (2.1 g, 8.1 mmol) were mixed in 60 mL of ethanol. The mixture was heated at reflux for 24 h under nitrogen. Precipitate formed during reflux. The reaction mixture was filtered through a celite bed. The product was washed with methanol and hexanes. The solid was dissolved in dichloromethane and purified by column using 1:1 of dichloromethane and hexanes. 1.0 g of pure product was obtained after the column purification.

Example 7

(113) Synthesis of Compound 37

(114) ##STR00224##

(115) Synthesis of Compound 37. 2-(dibenzo[b,d]furan-4-yl)pyridine (5.0 g, 20.39 mmol) and the iridium triflate (5.0 g, 5.59 mmol) were placed in a 250 mL round bottom flask with 100 mL of a 1:1 solution of ethanol and methanol. The reaction mixture was refluxed for 24 h. A bright yellow precipitate was obtained. The reaction was cooled to room temperature and diluted with ethanol. Celite was added to and the reaction mixture was filtered through a silica gel plug. The plug was washed with ethanol (2×50 mL) followed by hexanes (2×50 mL). The product which remained on the silica gel plug was eluted with dichloromethane into a clean receiving flask. The dichloromethane was removed under vacuum and the product was recrystallized from a combination of dichloromethane and isopropanol. The yellow solid was filtered, washed with methanol followed by hexanes to give bright yellow crystalline product. The product was further purified by recrystallization from toluene followed by recrystallization from acetonotrile to give 1.94 g (37.5% yield) of product with purity 99.5% by HPLC.

DEVICE EXAMPLES

(116) All example devices were fabricated by high vacuum (<10.sup.−7 Torr) thermal evaporation. The anode electrode is 800 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by 1000 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.sub.2O and O.sub.2) immediately after fabrication, and a moisture getter was incorporated inside the package.

(117) Particular devices are provided wherein an invention compound, Compound 1, 2, 4, 7, 10 or 29, is the emitting dopant and H1 is the host. The organic stack of Device Examples 1-11 consisted of, sequentially from the ITO surface, 100 Å of El as the hole injecting layer (HIL), 300 Å of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) as the hole transport layer (HTL), 300 Å of H1 doped with 7% or 10% of the invention compound, an Ir phosphorescent compound, as the emissive layer (EML), 50 Å of H1 as the blocking layer (BL) and 400 Å of Alq.sub.3 (tris-8-hydroxyquinoline aluminum) as the ETL1.

(118) Comparative Examples 1 and 2 were fabricated similarly to the Device Examples, except that E1 and E2. respectively, were used as the emitting dopant.

(119) As used herein, the following compounds have the following structures:

(120) ##STR00225##

(121) The device structures and device data are summarized below in Table 3 and Table 4. Table 3 shows the device structure, and Table 4 shows the corresponding measured results for the devices. Ex. is an abbreviation of Example.

(122) TABLE-US-00003 TABLE 3 Example HIL HTL Host A % BL ETL Example 1 E1 100Å NPD 300Å H1 Compound 1 H1 50Å Alq 400Å 7% Example 2 E1 100Å NPD 300Å H1 Compound 1 H1 50Å Alq 400Å 10% Example 3 E1 100Å NPD 300Å H1 Compound 2 H1 50Å Alq 400Å 7% Example 4 E1 100Å NPD 300Å H1 Compound 2 H1 50Å Alq 400Å 10% Example 5 E1 100Å NPD 300Å H1 Compound 4 H1 50Å Alq 400Å 7% Example 6 E1 100Å NPD 300Å H1 Compound 4 H1 50Å Alq 400Å 10% Example 7 E1 100Å NPD 300Å H1 Compound 7 H1 50Å Alq 400Å 7% Example 8 E1 100Å NPD 300Å H1 Compound 7 H1 50Å Alq 400Å 10% Example 9 E1 100Å NPD 300Å H1 Compound 10 H1 50Å Alq 400Å 7% Example 10 E1 100Å NPD 300Å H1 Compound 10 H1 50Å Alq 400Å 10% Example 11 E1 100Å NPD 300Å H1 Compound 29 H1 50Å Alq 400Å 10% Comparative E1 100Å NPD 300Å H1 Compound E1 H1 50Å Alq 400Å Example 1 7% Comparative E1 100Å NPD 300Å H1 Compound E2 H1 50Å Alq 400Å Example 2 7%

(123) TABLE-US-00004 TABLE 4 At 1000 nits At 40 mA/cm.sup.2 λ max, CIE V LE EQE PE Lo, RT.sub.80%, Example nm X Y (V) (cd/A) (%) (lm/W) nits h Ex. 1 532 0.354 0.616 6.1 60.1 15.9 31 17,382 180 Ex. 2 530 0.367 0.607 6.5 43.2 11.5 21 13,559 170 Ex. 3 527 0.355 0.612 6.2 51.7 13.9 26.1 14,565 210 Ex. 4 528 0.361 0.609 6 44.4 11.9 23.3 13,618 360 Ex. 5 528 0.348 0.620 5.7 68.7 18.1 37.7 19,338 98 Ex. 6 528 0.356 0.616 5.2 70.1 18.5 42.4 21,199 96 Ex. 7 522 0.326 0.630 5.6 68.2 18.4 38.6 18,431 120 Ex. 8 524 0.336 0.623 5.2 58.2 15.7 35.0 17,606 200 Ex. 9 522 0.320 0.634 5.4 70.7 19 41.4 19,996 75 Ex. 10 522 0.327 0.631 5 71.1 19.1 44.9 21,703 58 Ex. 11 576 0.538 0.459 5.6 50.6 19 28.1 14,228 800 Comparative 527 0.344 0.614 6.4 56.7 15.6 27.6 15,436 155 Ex. 1 Comparative 519 0.321 0.621 6 45.1 12.6 23.6 13,835 196 Ex.2

(124) From Device Examples 1-11, it can be seen that the invention compounds as emitting dopants in green phosphorescent devices provide high device efficiency and longer lifetime. In particular, the lifetime, RT.sub.80% (defined as the time for the initial luminance, Lo, to decay to 80% of its value, at a constant current density of 40 mA/cm.sup.2 at room temperature) of devices containing Compounds 1, 2, 7 and 29 are notably higher than that measured for Comparative Example 2 which used the industry standard emitting dopant Ir(ppy).sub.3. Additionally, Compound 1 in Device Example 1 achieved high device efficiency (i.e., LE of 60 cd/A at 1000 cd/m.sup.2), indicating that the inventive compounds comprising a single substituted pyridyl ligand (e.g., pyridyl dibenzofuran) have a high enough triplet energy for efficient green electrophosphorescence.

(125) Additional device structures and device data are summarized below. The device structures and device data are summarized below in Table 5 and Table 6. Table 5 shows the device structure, and Table 6 shows the corresponding measured results for the devices. Ex. is an abbreviation of Example.

(126) As used herein, the following compounds have the following structures:

(127) ##STR00226##

(128) H2 is a compound available as NS60 from Nippon Steel Company (NSCC) of Tokyo, Japan.

(129) TABLE-US-00005 TABLE 5 Example HIL HTL Host A % BL ETL Example 12 E1 100Å NPD 300Å H2 Compound 1 H2 100Å Alq 400Å 10% Example 13 E1 100Å NPD 300Å H2 Compound 2 H2 100Å Alq 400Å 7% Example 14 E1 100Å NPD 300Å H2 Compound 2 H2 100Å Alq 400Å 10% Example 15 E1 100Å NPD 300Å H2 Compound 4 H2 100Å Alq 400Å 10% Example 16 E1 100Å NPD 300Å H2 Compound 7 H2 100Å Alq 400Å 10% Example 17 E1 100Å NPD 300Å H2 Compound 10 H2 100Å Alq 400Å 10% Example 18 E1 100Å NPD 300Å H2 Compound 29 H2 100Å Alq 400Å 10% Example 19 E3 100Å NPD 300Å H1 Compound 37 H1 100Å Alq 400Å 7% Example 20 E3 100Å NPD 300Å H1 Compound 37 H1 100Å Alq 400Å 10% Example 21 E3 100Å NPD 300Å H2 Compound 37 H2 100Å Alq 400Å 10%

(130) TABLE-US-00006 TABLE 6 At 1000 nits At 40 mA/cm.sup.2 λ max, CIE V LE EQE PE Lo, RT.sub.80%, Example nm X Y (V) (cd/A) (%) (lm/W) nits h Ex. 12 530 0.361 0.612 4.1 78.6 20.9 60.0 24,069 220 Ex. 13 526 0.354 0.615 4.7 48.9 13.1 33.0 14,002 210 Ex. 14 527 0.349 0.620 4.9 49.8 13.3 31.6 14,510 190 Ex. 15 528 0.363 0.612 5.1 67.8 18 42.1 21,146 116 Ex. 16 522 0.334 0.626 4.8 65.9 17.8 43.1 20,136 170 Ex. 17 522 0.333 0.627 5.7 62.1 16.7 34.0 18,581 98 Ex. 18 576 0.542 0.455 6.4 36.2 13.9 17.9 10,835 740 Ex. 19 532 0.386 0.593 5.6 67.8 18.5 37.9 21,426 98 Ex. 20 532 0.386 0.593 5.7 67.7 18.5 37.5 21,050 103 Ex. 21 532 0.380 0.598 6.5 54.8 14.8 26.7 16,798 315

(131) From Device Examples 12-21, it can be seen that the invention compounds as emitting dopants in green phosphorescent devices provide devices with high efficiency and long lifetimes. In particular, the lifetime, RT.sub.80% (defined as the time for the initial luminance, L.sub.0, to decay to 80% of its value, at a constant current density of 40 mA/cm.sup.2 at room temperature) of devices containing Compounds 29 and 37 are notably higher than those measured for the Comparative Examples. In particular, Compound 29 in Device Example 18 and Compound 37 in Device Example 21 measured 740 h and 315 h, respectively. Devices with Compound 1 in H2, as shown in Example 12, had exceptionally high efficiency, 78.6 cd/A and long lifetime. It is unexpected that Compound 1 worked extremely well in H2. Additionally, Compounds 1, 4, 7, 29, and 37 in Device Examples 12, 15, 17, 19, and 20, respectively, achieved high device efficiency (i.e., LE of greater than 60 cd/A at 1000 cd/m.sup.2), indicating that the inventive compounds comprising a single substituted pyridyl ligand (e.g., pyridyl dibenzofuran) have a high enough triplet energy for efficient green electrophosphorescence.

(132) The above data suggests that the heteroleptic iridium complexes provided herein can be excellent emitting dopants for phosphorescent OLEDs, providing devices having improved efficiency and longer lifetime that may also have improved manufacturing.

(133) 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 includes 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.