ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

A compound that can be useful as emitters in an OLED that includes a ligand LA of Formula I

is disclosed.

FIELD

The present invention relates to compounds for use as emitters, and devices, such as organic light emitting diodes, including the same.

BACKGROUND

SUMMARY

A series of new phosphorescent metal complexes based on ligands containing phenylisoquinoline or phenyl quinazoline that can function as emitters in OLEDs are disclosed. Further functionalization of these moieties allows fine tuning of the properties of the final complexes in OLED application, such as the color of the emission, emission efficiency, lifetime, etc.).

According to an embodiment, a compound comprising a ligand LA of Formula I

is disclosed. In Formula I, RA represents mono to the maximum allowable number of substitutions; X1 to X4 are each independently CR or N; RA, R, R1, and R2 are each independently selected from the group consisting of hydrogen or the general substituents defined above; at least one of R1 and R2 has the formula of - - -L1-G1; L1 is an organic linker or a direct bond, G1 is a substituted cycloalkyl group, or a substituted or unsubstituted multicyclic group; at least one RA is not hydrogen; LA is coordinated to Ir; Ir can be coordinated to other ligands; LA can be linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and any two substituents can be joined or fused together to form a ring, with the proviso that R1 and R2 are not joined to form a ring.

An OLED comprising the compound of the present disclosure in an organic layer therein is also disclosed.

A consumer product comprising the OLED is also disclosed.

DETAILED DESCRIPTION

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.

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 term “ester” refers to a substituted oxycarbonyl (—O—C(O)—Rs or —C(O)—O—Rs) radical.

The term “ether” refers to an —ORs radical.

The term “sulfinyl” refers to a —S(O)—Rs radical.

The term “sulfonyl” refers to a —SO2—Rs radical.

The term “phosphino” refers to a —P(Rs)3 radical, wherein each Rs can be same or different.

The term “silyl” refers to a —Si(Rs)3 radical, wherein each Rs can be same or different.

The term “alkenyl” refers to and includes both straight and branched chain alkene radicals. Alkenyl groups are essentially alkyl groups that include at least one carbon-carbon double bond in the alkyl chain. Cycloalkenyl groups are essentially cycloalkyl groups that include at least one carbon-carbon double bond in the cycloalkyl ring. The term “heteroalkenyl” as used herein refers to an alkenyl radical having at least one carbon atom replaced by a heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl, cycloalkenyl, or heteroalkenyl group is optionally substituted.

The term “alkynyl” refers to and includes both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group is optionally substituted.

The terms “aralkyl” or “arylalkyl” are used interchangeably and refer to an alkyl group that is substituted with an aryl group. Additionally, the aralkyl group is optionally substituted.

The term “heterocyclic group” refers to and includes aromatic and non-aromatic cyclic radicals containing at least one heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si, and Se, preferably, O, S, or N. Hetero-aromatic cyclic radicals may be used interchangeably with heteroaryl. Preferred hetero-non-aromatic cyclic groups are those containing 3 to 7 ring atoms which includes at least one hetero atom, and includes cyclic amines such as morpholino, piperidino, pyrrolidino, and the like, and cyclic ethers/thio-ethers, such as tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, and the like. Additionally, the heterocyclic group may be optionally substituted.

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

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

The terms “substituted” and “substitution” refer to a substituent other than H that is bonded to the relevant position, e.g., a carbon or nitrogen. For example, when R1 represents mono-substitution, then one R1 must be other than H (i.e., a substitution). Similarly, when R1 represents di-substitution, then two of R1 must be other than H. Similarly, when R1 represents no substitution, R1, for example, can be a hydrogen for available valencies of ring atoms, as in carbon atoms for benzene and the nitrogen atom in pyrrole, or simply represents nothing for ring atoms with fully filled valencies, e.g., the nitrogen atom in pyridine. The maximum number of substitutions possible in a ring structure will depend on the total number of available valencies in the ring atoms.

In some instance, a pair of adjacent substituents can be optionally joined or fused into a ring. The preferred ring is a five, six, or seven-membered carbocyclic or heterocyclic ring, includes both instances where the portion of the ring formed by the pair of substituents is saturated and where the portion of the ring formed by the pair of substituents is unsaturated. As used herein, “adjacent” means that the two substituents involved can be on the same ring next to each other, or on two neighboring rings having the two closest available substitutable positions, such as 2, 2′ positions in a biphenyl, or 1, 8 position in a naphthalene, as long as they can form a stable fused ring system.

The novelty of the inventive compounds disclosed herein comes from the new side used on the core of the ligand. The use of substituted cycloalkyl side chains on the isoquinoline and quinazoline cores allows to further increase the external quantum efficiencies (EQEs) when used as the emitter in a phosphorescent device. The color of the compound's emission (QMAX) can be fine tuned depending on the position on the isoquinoline or the quinazoline cores the substituted cycloalkyl side chain is added. Furthermore, the substitution on the cycloalkyl side chains enable much better thermal properties for the compound such as better (i.e., lower) sublimation temperature (TsuB) which is beneficial in OLED fabrication process.

This invention describes novel side chains that enables very high EQEs in PhOLEDs application. From a commercial standpoint, the main request is to keep providing phosphorescent emitters that show better efficiency. These new side chains have been added to well-known cores such as isoquinoline but still provided EQE that had not been observed before.

According to an embodiment, a compound comprising a ligand LA of Formula I

is disclosed. In Formula I, RA represents mono to the maximum allowable number of substitutions; X1 to X4 are each independently CR or N; RA, R, R1, and R2 are each independently selected from the group consisting of hydrogen or the general substituents defined above; at least one of R1 and R2 has the formula of - - -L1-G1; L1 is an organic linker or a direct bond, G1 is a substituted cycloalkyl group, or a substituted or unsubstituted multicyclic group; at least one RA is not hydrogen; LA is coordinated to Ir; Ir can be coordinated to other ligands; LA can be linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and any two substituents can be joined or fused together to form a ring, with the proviso that R1 and R2 are not joined to form a ring.

In some embodiments of the compound, RA, R, R1, and R2 are each independently selected from the group consisting of hydrogen or the preferred general substituents defined above.

In some embodiments, G1 is selected from the group consisting of alkyl substituted cycloalkyl, a partially or fully fluorinated cycloalkyl or alkyl substituted cycloalkyl, partially or fully deuterated variants thereof, and combination thereof.

In some embodiments, the compound can be heteroleptic. In some embodiments, the compound can be homoleptic.

In some embodiments, L1 is a direct bond. In some embodiments, L1 is alkyl.

In some embodiments, R1 comprises more C atoms than R2. In some embodiments, R2 comprises more C atoms than R1. In some embodiments, one of R1 and R2 is a substituted cyclohexyl or substituted cyclopentyl group, and the other one is hydrogen.

In some embodiments, R1 is a substituted cyclohexyl group, and R2 is hydrogen.

In some embodiments, the first ligand LA is

In some embodiments, the compound further comprises a substituted or unsubstituted acetylacetonate ligand.

In some embodiments, R1 is a cyclohexyl group that is substituted by at least one alkyl group.

In some embodiments, X1 to X4 are each CH. In some embodiments, one of X1 to X4 is N, and the remainder are CH.

In some embodiments, two RA substituents are joined together to form a ring.

In some embodiments, the first ligand LA is selected from the group consisting of:

and wherein RA1 has the same definition as RA.

In some embodiments of the compound, the first ligand LA is selected from the group consisting of:

LA1 through LA416 based on a structure of Formula II,

in which R3, R4, G, and X are defined as:

Ligand
R3
R4
G
X

LA417 through LA832 based on a structure of Formula III,

in which R3, R4, and G are defined as:

LA833 rough LA1144 based on a structure of Formula III,

in which R3, R4, and G are defined as:

wherein RA1 to RA54 have the following structures:

wherein RB1 to RB22 have the following structures:

wherein RC1 to RC95 have the following structures:

wherein RD1 to RD37 have the following structures:

In some embodiments, the compound has a formula selected from the group consisting of Ir(LA)3, Ir(LA)(LB)2, Ir(LA)2(LB), Ir(LA)2(LC), and Ir(LA)(LB)(LC), where LB and LC are each a bidentate ligand, and LA, LB, and LC are different from each other. In some embodiments, LB and LC are each independently selected from Group A ligands consisting of:

where Y1 to Y13 are each independently selected from the group consisting of carbon and nitrogen; Y1 is selected from the group consisting of B Re, N Re, P Re, O, S, Se, C═O, S═O, SO2, CReRf, SiReRf, and GeReRf; Re and Rf are optionally fused or joined to form a ring; each Ra, Rb, Rc, and Rd can independently represent from mono substitution to the maximum possible number of substitutions, or no substitution; Ra, Rb, Rc, Rd, Re and Rf are each independently selected from the group consisting of hydrogen, or a substituent selected from the group consisting of the general substituents defined above; and any two adjacent substituents of Ra, Rb, Rc, and Rd are optionally fused or joined to form a ring or form a multidentate ligand.

In some embodiments of the compound, where LB and LC are each independently selected from the Group A ligands, LB and LC can each be independently selected from the group consisting of:

In some embodiments where the compound has a formula selected from the group consisting of Ir(LA)3, Ir(LA)(LB)2, Ir(LA)2(LB), Ir(LA)2(LC), and Ir(LA)(LB)(LC), where LB and LC are each a bidentate ligand, and LA, LB, and LC are different from each other, LB can be selected from the group consisting of the following structures:

In some embodiments of the compound having a formula selected from the group consisting of Ir(LA)3, Ir(LA)(LB)2, Ir(LA)2(LB), Ir(LA)2(LC), and Ir(LA)(LB)(LC), where LB and LC are each a bidentate ligand, and LA, LB, and LC are different from each other, LC can be selected from the group consisting of LC1 through LC1260 based on a structure of Formula X,

in which R1, R2, and R3 are defined as:

wherein RD1 to RD81 have the following structures:

In some embodiment of the compound where the first ligand LA is selected from the group consisting of LA1 to LA1144 defined above, the compound is Compound Ax having the formula Ir(LA1)3, Compound By having the formula Ir(LA1)(LBk)2, or Compound Cz having the formula Ir(LA1)2(LC); wherein,

i is an integer from 1 to 1144, and k is an integer from 1 to 468, and j is an integer from 1 to 1260; wherein the corresponding LBk and LCj are as defined above.

According to another aspect, an OLED comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode is disclosed. The organic layer comprises a compound comprising: a ligand LA of Formula I

where, RA represents mono to the maximum allowable substitutions; X1 to X4 are each independently CR or N; RA, R, R1, and R2 are each independently selected from the group consisting of hydrogen or a substituent selected from the general substituents defined above; at least one of R1 and R2 has the formula of - - -L1-G1; L1 is an organic linker or a direct bond, G1 is a substituted cycloalkyl group, or a substituted or unsubstituted multicyclic group; at least one RA is not hydrogen; LA is coordinated to Ir; Ir can be coordinated to other ligands; LA can be linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and any two substituents can be joined or fused together to form a ring, with the proviso that R1 and R2 are not joined to form a ring.

In some embodiments of the OLED, the organic layer is an emissive layer and the compound is an emissive dopant or a non-emissive dopant. In some embodiments of the OLED, the organic layer further comprises a host, wherein host comprises at least one chemical group selected from the group consisting of triphenylene, carbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

In some embodiments of the OLED where the organic layer further comprises a host, the host can be selected from the group consisting of:

and combinations thereof.

In some embodiments of the OLED where the organic layer further comprises a host, the host can comprise a metal complex.

In some embodiments of the OLED, the compound is a sensitizer and the OLED further comprises an acceptor; and wherein the acceptor is selected from the group consisting of fluorescent emitter, delayed fluorescence emitter, and combination thereof.

A consumer product comprising the OLED incorporating the novel compound of the present disclosure as defined above is also disclosed. In some embodiments, such consumer product can be selected from the group of consumer products defined above.

In some embodiments, the compound can be an emissive dopant. In some embodiments, the compound can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence; see, e.g., U.S. application Ser. No. 15/700,352, published on Mar. 14, 2019 as U.S. patent application publication No. 2019/0081248, which is hereby incorporated by reference in its entirety), triplet-triplet annihilation, or combinations of these processes. In some embodiments, the emissive dopant can be a racemic mixture, or can be enriched in one enantiomer. In some embodiments, the compound can be homoleptic (each ligand is the same). In some embodiments, the compound can be heteroleptic (at least one ligand is different from others).

When there are more than one ligand coordinated to a metal, the ligands can all be the same in some embodiments. In some other embodiments, at least one ligand is different from the other ligand(s). In som embodiments, every ligand can be different from each other. This is also true in embodiments where a ligand being coordinated to a metal can be linked with other ligands being coordinated to that metal to form a tridentate, tetradentate, pentadentate, or hexadentate ligands. Thus, where the coordinating ligands are being linked together, all of the ligands can be the same in some embodiments, and at least one of the ligands being linked can be different from the other ligand(s) in some other embodiments.

In some embodiments, the compound can be used as a phosphorescent sensitizer in an OLED where one or multiple layers in the OLED contains an acceptor in the form of one or more fluorescent and/or delayed fluorescence emitters. In some embodiments, the compound can be used as one component of an exciplex to be used as a sensitizer. As a phosphorescent sensitizer, the compound must be capable of energy transfer to the acceptor and the acceptor will emit the energy or further transfer energy to a final emitter. The acceptor concentrations can range from 0.001% to 100%. The acceptor could be in either the same layer as the phosphorescent sensitizer or in one or more different layers. In some embodiments, the acceptor is a TADF emitter. In some embodiments, the acceptor is a fluorescent emitter. In some embodiments, the emission can arise from any or all of the sensitizer, acceptor, and final emitter.

According to another aspect, a formulation comprising the compound described herein is also disclosed.

The organic layer can also include a host. In some embodiments, two or more hosts are preferred. In some embodiments, the hosts used maybe a) bipolar, b) electron transporting, c) hole transporting or d) wide band gap materials that play little role in charge transport. In some embodiments, the host can include a metal complex. The host can be a triphenylene containing benzo-fused thiophene or benzo-fused furan. Any substituent in the host can be an unfused substituent independently selected from the group consisting of CnH2n+1, OCH2n+1, OAr1, N(CnH2n+1)2, N(Ar1)(Ar2), CH═CH—CnH2n+1, C≡C—CnH2n+1, Ar1, Ar1-Ar2, and CnH2n—Ar1, or the host has no substitutions. In the preceding substituents n can range from 1 to 10; and Ar1 and Ar2 can be independently selected from the group consisting of benzene, biphenyl, naphthalene, triphenylene, carbazole, and heteroaromatic analogs thereof. The host can be an inorganic compound, for example a Zn containing inorganic material e.g. ZnS.

The host can be a compound comprising at least one chemical group selected from the group consisting of triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. The host can include a metal complex. The host can be, but is not limited to, a specific compound selected from the Host Group consisting of:

and combinations thereof.

Additional information on possible hosts is provided below.

An emissive region in an OLED is also disclosed. The emissive region comprises the compound comprising the ligand LA of Formula I

In some embodiments of the emissive region, the compound is an emissive dopant or a non-emissive dopant. In some embodiments, the emissive region further comprises a host, wherein the host contains at least one group selected from the group consisting of metal complex, triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, aza-triphenylene, aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

In some embodiments, the emissive region further comprises a host, wherein the host is selected from the group consisting of:

and combinations thereof.

In yet another aspect of the present disclosure, a formulation that comprises the novel compound disclosed herein is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, electron blocking material, hole blocking material, and an electron transport material, disclosed herein.

The present disclosure encompasses any chemical structure comprising the novel compound of the present disclosure, or a monovalent or polyvalent variant thereof. In other words, the inventive compound, or a monovalent or polyvalent variant thereof, can be a part of a larger chemical structure. Such chemical structure can be selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule (also known as supermolecule). As used herein, a “monovalent variant of a compound” refers to a moiety that is identical to the compound except that one hydrogen has been removed and replaced with a bond to the rest of the chemical structure. As used herein, a “polyvalent variant of a compound” refers to a moiety that is identical to the compound except that more than one hydrogen has been removed and replaced with a bond or bonds to the rest of the chemical structure. In the instance of a supramolecule, the inventive compound is can also be incorporated into the supramolecule complex without covalent bonds.

Combination with Other Materials

In one aspect, Ar1 to Ar9 is independently selected from the group consisting of:

wherein k is an integer from 1 to 20; X101 to X108 is C (including CH) or N; Z101 is NAr1, O, or S; Ar1 has the same group defined above.

wherein Met is a metal, which can have an atomic weight greater than 40; (Y101-Y102) is a bidentate ligand, Y101 and Y102 are independently selected from C, N, O, P, and S; L101 is an ancillary 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.

wherein Met is a metal; (Y103-Y104) is a bidentate ligand, Y103 and Y104 are independently selected from C, N, O, P, and S; L101 is an 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:

wherein k is an integer from 1 to 20; L101 is an another ligand, k′ is an integer from 1 to 3.

Charge Generation Layer (CGL)

Experimental

All reactions were carried out under nitrogen protection unless specified otherwise. All solvents for reactions were anhydrous and used as received from the commercial sources

Synthesis of Comparative Compound 1 (CC1)

Synthesis of 6-Cyclohexyl-1-(3,5-dimethylphenyl)isoquinoline

A solution of 6-chloro-1-(3,5-dimethylphenyl)isoquinoline (20.1 g, 75.0 mmol), palladium(II) acetate (0.505 g, 2.25 mmol) and 2-dicyclohexyl-phosphino-2′,6′-dimethoxybiphenyl (SPhos) (1.85 g, 4.5 mmol) in anhydrous tetrahydrofuran (375 mL) was sparged with nitrogen for 10 minutes then heated at 49° C. for 10 minutes. A 0.52M cyclohexylzinc(II) bromide in tetrahydrofuran (216 mL, 112.5 mmol) was added dropwise over 40 minutes then the reaction mixture heated at 48° C. for 24 hours. Saturated aqueous sodium sulfite and saturated aqueous sodium carbonate were added and the reaction mixture was cooled to room temperature over 30 minutes. The layers were separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with saturated brine, dried over sodium sulfate and passed through a pad of silica gel topped with Celite, washing with ethyl acetate. The crude product was purified with silica gel column, eluting with a gradient of 0-5% ethyl acetate in heptanes, to give 6-cyclohexyl-1-(3,5-dimethylphenyl)-isoquinoline (12.3 g, 52% yield) as a viscous oil.

Synthesis of Comparative Compound 1 (CC1)

(A) A solution of 6-cyclohexyl-1-(3,5-dimethylphenyl)-isoquinoline (4.01 g, 12.71 mmol) in 2-ethoxyethanol (85 mL) and deionized ultra-filtered (DIUF) water (17 mL) was sparged with nitrogen for 5 minutes. Iridium(III) chloride hydrate (1.92 g, 6.05 mmol) was added, sparging continued for 5 minutes then the reaction mixture was heated at 70° C. for 24 hours. The reaction mixture was cooled to ˜50° C., filtered and the solid air-dried for 30 minutes to give crude di-μ-chloro-tetrakis[(6-cyclohexyl-1-(3,5-dimethylphenyl) isoquinoline-2-yl)]diiridium(III) (2.57 g) as a reddish solid which contained some residual solvent.

(B) A solution of crude di-μ-chloro-tetrakis[6-cyclohexyl-1-(3,5-dimethylphenyl)isoquinoline-2-yl]dairid-ium(III) (2.57 g, 3.0 mmol) and 3,7-diethylnonane-4,6-dione (1.27 g, 6.0 mmol) in 2-ethoxyethanol (60 mL) was sparged with nitrogen for 5 minutes. Powdered potassium carbonate (0.829 g, 6.0 mmol) was added and sparging continued for 3 minutes. The reaction mixture was stirred at room temperature overnight in a flask wrapped in aluminum foil to exclude light. DIUF water was added, the suspension stirred for 30 minutes, the solid filtered and washed with water. The sticky solid was slurried in methanol for 10 minutes, filtered and the solid was washed with methanol. The red solid was dissolved/suspended in dichloromethane (20 mL) and loaded directly onto a column of silica gel topped with basic alumina. The column was eluted with 30% dichloromethane in hexanes. Product fractions were concentrated under reduced pressure and the solid was dried at 50° C. for 4 hours under high vacuum to give bis[(6-cyclohexyl-1-(3,5-dimethylphenyl)-isoquinolin-2-yl)]-(3,7-diethyl-4,6-nonanedionato-k2O,O′)iridium(III) (2.2 g, 35% overall yield) as a red solid.

Synthesis of Compound C25,222

Synthesis of (1,1-Dimethyl)-4-iodocyclohexane

Iodine (218 g, 858 mmol) was added in portions over −30 minutes to an ice cooled solution of triphenylphosphine (225 g, 858 mmol) and imidazole (117 g, 1716 mmol) in dichloromethane (1.32 L) at a rate in which the temperature remained below 5° C. After stirring for −15 minutes, a solution of 4,4-dimethyl-cyclohexanol (100 g, 780 mmol) in dichloromethane (20 mL) was added dropwise, keeping the temperature below 15° C. The solution was warmed gradually to room temperature and stirred overnight. The solvent was removed under reduced pressure and the residue poured in portions into a flask containing heptanes (3.0 L) with vigorous stirring. Stirring was continued over 2 days at which point the gum had partially solidified. The heptanes layer was decanted and passed through a pad of silica gel. The residue in the flask was extracted a second time with heptanes. The heptanes layer was decanted and passed through the silica gel pad, flushing with heptanes. The filtrate was concentrated under reduced pressure (bath temperature ˜30° C.) to give (1,1-dimethyl)-4-iodocyclo-hexane (130 g, 70% yield) as a colorless liquid.

Synthesis of (4,4-Dimethylcyclohexyl)zinc(II) iodide

A mixture of zinc (228 g, 3.49 mol) and anhydrous lithium chloride (74 g, 1.74 mol) in anhydrous tetrahydrofuran (1.6 L) was heated at reflux for 30 minutes under nitrogen. The mixture was cooled to room temperature, 1,2-dibromoethane (10.11 g, 0.058 mol) and chlorotrimethyl-silane (6.32 g, 0.058 mol) were added successively and mixture heated at reflux for 10 minutes. The mixture was cooled to −27° C. and a solution of 4-iodo-1,1-dimethylcyclohexane (277 g, 1.16 mol) in anhydrous tetrahydrofuran (0.52 L) added, keeping the temperature below 30° C. during the addition. The mixture was stirred at room temperature overnight. The solids were allowed to settle and the solution decanted into nitrogen flushed bottles and stored until needed.

Synthesis of 6-(4,4-dimethylcyclohexyl)-1-(3,5-dimethylphenyl)isoquinoline

An ice cooled mixture of 6-chloro-1-(3,5-dimethylphenyl)isoquinoline (50 g, 187 mmol), palladium(II) acetate (1.26 g, 5.60 mmol) and 2-dicyclohexylphosphino-2′,6′-dimethoxy-biphenyl (SPhos) (4.60 g, 11.20 mmol) in anhydrous tetrahydrofuran (346 mL) was sparged with nitrogen for 20 minutes. 0.5M 4,4-Dimethylcyclohexylzinc(II) iodide solution (549 mL, 187 mmol) was added dropwise to the mixture over −30 minutes, keeping the temperature below 5° C. The mixture was stirred at room temperature overnight then diluted with ethyl acetate (100 mL) and saturated aqueous sodium carbonate. The layers were separated and the organic layer was washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified with silica gel column, eluting with 100% heptanes for 10 minutes followed by a gradient of 0-20% ethyl acetate in heptanes for 40 minutes, 20-50% ethyl acetate in heptanes for 5 minutes, then 100% ethyl acetate for 5 minutes, to afford 1-(3,5-dimethylphenyl)-6-(4,4-dimethylcyclohexyl)-isoquinoline (36 g, 72% yield) as a pale yellow oil.

Synthesis of Compound C25,222

(A) To a solution of 1-(3,5-dimethylphenyl)-6-(4,4-dimethylcyclohexyl)isoquinoline (70 g, 204 mmol) in 2-ethoxyethanol (773 mL) and DIUF water (258 mL), iridium(III) chloride tetrahydrate (34 g, 92 mmol) was added and the reaction mixture was heated at 85° C. for 52 hours. The reaction mixture was cooled, filtered and the solid washed with hot methanol. The red solid was air-dried for 30 minutes to give di-μ-chloro-tetrakis[((1-(3,5-dimethylphenyl-2′-yl)-6-(4,4-(di-methyl)cyclohexyl)isoquinolin-2-yl)]diiridium(III) (48 g, 57.3% yield) as a red solid.

(B) To a suspension of di-μ-chloro-tetrakis[((1-(3,5-dimethylphenyl-2′-yl)-6-(4,4-(di-methyl)cyclohexyl)isoquinolin-2-yl)]diiridium(III) (48 g, 26.3 mmol) and 3,7-diethylnonane-4,6-dione (22.33 g, 105 mmol) in 2-ethoxyethanol (730 mL), powdered potassium carbonate (14.54 g, 105 mmol) was added. The reaction mixture was stirred at room temperature in the dark for 72 hours. DIUF water (730 mL) was added and the slurry was stirred for 1 hour. The suspension was filtered, the solid was washed with water then returned to the reaction flask. Methanol was added and the mixture was stirred for 45 minutes. The suspension was filtered, the solid washed with methanol and air-dried. The red solid (52 g) was dissolved in 1:1 heptanes:di-chloromethane (500 mL) and basic alumina was added. The suspension was loaded directly unto a silica gel column, eluting with 50% dichloro-methane in heptanes. Product fractions were concentrated and air-dried overnight to give bis[((1-(3,5-dimethylphenyl-2′-yl)-6-(4,4-(dimethyl)cyclohexyl)-isoquinolin-2-yl)]-(3,7-diethyl-4,6-nonanedionato k2O,O′)iridium(III) (24 g, 42% yield) as a red solid.

Device Examples

All example devices were fabricated by high vacuum (<107 Torr) thermal evaporation. The anode electrode was 1150 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of Liq (8-hydroxyquinoline lithium) followed by 1,000 Å of Al. All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H2O and O2) 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 LG101 (from LG chem) as the hole injection layer (HIL); 400 Å of a hole transporting material (HTM) as a hole transporting layer (HTL); 300 Å of an emissive layer (EML) containing Compound H as a host, a stability dopant (SD) (18%), and Comparative Compound 1 or Compound C25,222 as the emitter (3%); 100 Å of Compound H as a blocking layer; and 350 Å of Liq (8-hydroxyquinoline lithium) doped with 40% of ETM as the ETL. The emitter was selected to provide the desired color, efficiency and lifetime. The stability dopant (SD) was added to the electron-transporting host to help transport positive charge in the emissive layer. The Comparative Example devices were fabricated similarly to the device examples except that Comparative Compounds were used as the emitters in the EML. Table 1 below provides the materials used for the device layers and the layer thicknesses.

Device layer materials and thicknesses

Layer
Material
Thickness [Å]

The device performance data are normalized to comparative compound and summarized in Table 2 below. The maximum wavelength of emission (Qmax) is similar for Comparative Compound 1 and Compound C25,222 at 625 nm the emission line shape is also the same (FWHM). The inventive compound (Compound C25,222) shows improved external quantum efficiency (EQE) compared to Comparative Compound 1 (1.03 vs. 1.00). The luminous efficacy (LE) is also better for Compound C25,222 (1.08 vs. 1.00). This data shows that the current invention of adding substitution on cycloalkyl side chains is beneficial to the overall performance of the metal complexes.

Performance of the devices made with Comparative

Compounds and Inventive Compounds.

Device

1931 CIE
max
FWHM
Voltage
EQE
LE

Compound

The chemical structures for the materials used in the experimental OLED devices are shown below: