U.S. patent application number 16/407861 was filed with the patent office on 2019-08-29 for organic electroluminescent materials and devices.
This patent application is currently assigned to UNIVERSAL DISPLAY CORPORATION. The applicant listed for this patent is Universal Display Corporation. Invention is credited to Jason Brooks, Zeinab Elshenawy, Gregg Kottas, Geza Szigethy, JUI-YI TSAI, Chuanjun Xia, Walter Yeager.
Application Number | 20190267555 16/407861 |
Document ID | / |
Family ID | 53495861 |
Filed Date | 2019-08-29 |
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United States Patent
Application |
20190267555 |
Kind Code |
A1 |
TSAI; JUI-YI ; et
al. |
August 29, 2019 |
ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES
Abstract
An organic light emitting device (OLED) that includes an anode,
a first organic layer, a second organic layer, a third organic
layer, an emissive layer, and a cathode is disclosed. The emissive
layer can include a first emissive dopant, and the third organic
layer comprises ##STR00001## A consumer product containing the OLED
is also described.
Inventors: |
TSAI; JUI-YI; (Newto,
PA) ; Kottas; Gregg; (Ewing, NJ) ; Yeager;
Walter; (Yardley, PA) ; Elshenawy; Zeinab;
(Holland, PA) ; Xia; Chuanjun; (Lawrenceville,
NJ) ; Szigethy; Geza; (Ewing, NJ) ; Brooks;
Jason; (Philadelphia, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Universal Display Corporation |
Ewing |
NJ |
US |
|
|
Assignee: |
UNIVERSAL DISPLAY
CORPORATION
Ewing
NJ
|
Family ID: |
53495861 |
Appl. No.: |
16/407861 |
Filed: |
May 9, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15956934 |
Apr 19, 2018 |
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16407861 |
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14310598 |
Jun 20, 2014 |
9978961 |
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15956934 |
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61924752 |
Jan 8, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 2211/1029 20130101;
H01L 51/0085 20130101; H01L 2251/5384 20130101; C07F 15/0033
20130101; C09K 2211/185 20130101; H01L 51/5016 20130101; C09K 11/06
20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; C09K 11/06 20060101 C09K011/06; C07F 15/00 20060101
C07F015/00 |
Claims
1. An organic light emitting device (OLED) comprising,
sequentially: an anode; a first organic layer; a second organic
layer; a third organic layer; an emissive layer; and a cathode;
wherein the emissive layer comprises a first emissive dopant, and
wherein the third organic layer comprises ##STR00240##
2. The OLED of claim 1, wherein the first emissive dopant is a
phosphorescent emitter.
3. The OLED of claim 1, wherein the first emissive dopant is an Ir
complex.
4. The OLED of claim 1, wherein the emissive layer further
comprises a host.
5. The OLED of claim 4, wherein the host comprises an electron
transporting compound and a hole transporting compound.
6. The OLED of claim 4, wherein the host comprises at least one
chemical group selected from the group consisting of carbazole,
dibenzothiphene, dibenzofuran, dibenzoselenophene, azacarbazole,
aza-dibenzothiophene, azadibenzofuran, and
aza-dibenzoselenophene.
7. The OLED of claim 1, wherein the OLED further comprises a fourth
organic layer between the emissive layer and the cathode.
8. The OLED of claim 4, wherein the OLED further comprises a fourth
organic layer between the emissive layer and the cathode.
9. The OLED of claim 8, wherein the fourth organic layer comprises
the host.
10. The OLED of claim 1, wherein at least one of the following is
true: the first organic layer is a hole injection layer, the second
organic layer is a hole transport layer, and the third organic
layer is an electron blocking layer.
11. The OLED of claim 1, wherein the third organic layer is an
electron blocking layer.
12. The OLED of claim 1, wherein the first organic layer is a hole
injection layer, the second organic layer is a hole transport
layer, and the third organic layer is an electron blocking
layer.
13. The OLED of claim 12, further comprising a fourth organic layer
between the emissive layer and the cathode.
14. The OLED of claim 1, wherein the third organic layer contacts
the emissive layer.
15. An organic light emitting device (OLED) comprising: an anode;
an electron blocking layer comprising ##STR00241## an emissive
layer; and a cathode, wherein the emissive layer comprises a first
emissive dopant, and wherein the electron blocking layer is between
the anode and the emissive layer.
16. The OLED of claim 15, further comprising at least one of a hole
injection layer and a hole transport layer between the electron
blocking layer and the anode.
17. The OLED of claim 15, wherein the electron blocking layer
contacts the emissive layer.
18. The OLED of claim 15, further comprising a hole injection
layer, and a hole transport layer, wherein the hole injection layer
and the hole transport layer are between the anode and the electron
blocking layer and the hole injection layer is between the hole
transport layer and the anode.
19. A consumer product comprising an organic light emitting device
(OLED) comprising, sequentially: an anode; a first organic layer; a
second organic layer; a third organic layer; an emissive layer; and
a cathode; wherein the emissive layer comprises a first emissive
dopant, and wherein the third organic layer comprises
##STR00242##
20. The consumer product of claim 19, wherein the consumer product
is one of a flat panel displays, computer monitors, medical
monitors, televisions, billboards, lights for interior or exterior
illumination and/or signaling, heads-up displays, fully or
partially transparent displays, flexible displays, laser printers,
telephones, cell phones, tablets, phablets, personal digital
assistants (PDAs), laptop computers, digital cameras, camcorders,
viewfinders, micro-displays, 3-D displays, vehicles, an area wall,
theater or stadium screens, and signs.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/956,934, filed Apr. 19, 2018, which is a
continuation of U.S. patent application Ser. No. 14/310,598, filed
Jun. 20, 2014, now U.S. Pat. No. 9,978,961, which is a
non-provisional of U.S. Patent Application Ser. No. 61/924,752,
filed Jan. 8, 2014, the entire contents of which are incorporated
herein by reference.
PARTIES TO A JOINT RESEARCH AGREEMENT
[0002] The claimed invention was made by, on behalf of, and/or in
connection with one or more of the following parties to a joint
university corporation research agreement: Regents of the
University of Michigan, Princeton University, University of
Southern California, and the Universal Display Corporation. The
agreement was in effect on and before the date the claimed
invention was made, and the claimed invention was made as a result
of activities undertaken within the scope of the agreement.
FIELD OF THE INVENTION
[0003] The present invention relates to compounds for use as
emitters and devices, such as organic light emitting diodes,
including the same.
BACKGROUND
[0004] Opto-electronic devices that make use of organic materials
are becoming increasingly desirable for a number of reasons. Many
of the materials used to make such devices are relatively
inexpensive, so organic opto-electronic devices have the potential
for cost advantages over inorganic devices. In addition, the
inherent properties of organic materials, such as their
flexibility, may make them well suited for particular applications
such as fabrication on a flexible substrate. Examples of organic
opto-electronic devices include organic light emitting devices
(OLEDs), organic phototransistors, organic photovoltaic cells, and
organic photodetectors. For OLEDs, the organic materials may have
performance advantages over conventional materials. For example,
the wavelength at which an organic emissive layer emits light may
generally be readily tuned with appropriate dopants.
[0005] OLEDs make use of thin organic films that emit light when
voltage is applied across the device. OLEDs are becoming an
increasingly interesting technology for use in applications such as
flat panel displays, illumination, and backlighting. Several OLED
materials and configurations are described in U.S. Pat. Nos.
5,844,363, 6,303,238, and 5,707,745, which are incorporated herein
by reference in their entirety.
[0006] One application for phosphorescent emissive molecules is a
full color display. Industry standards for such a display call for
pixels adapted to emit particular colors, referred to as
"saturated" colors. In particular, these standards call for
saturated red, green, and blue pixels. Color may be measured using
CIE coordinates, which are well known to the art.
[0007] One example of a green emissive molecule is
tris(2-phenylpyridine) iridium, denoted Ir(ppy).sub.3, which has
the following structure:
##STR00002##
[0008] In this, and later figures herein, we depict the dative bond
from nitrogen to metal (here, Ir) as a straight line.
[0009] As used herein, the term "organic" includes polymeric
materials as well as small molecule organic materials that may be
used to fabricate organic opto-electronic devices. "Small molecule"
refers to any organic material that is not a polymer, and "small
molecules" may actually be quite large. Small molecules may include
repeat units in some circumstances. For example, using a long chain
alkyl group as a substituent does not remove a molecule from the
"small molecule" class. Small molecules may also be incorporated
into polymers, for example as a pendent group on a polymer backbone
or as a part of the backbone. Small molecules may also serve as the
core moiety of a dendrimer, which consists of a series of chemical
shells built on the core moiety. The core moiety of a dendrimer may
be a fluorescent or phosphorescent small molecule emitter. A
dendrimer may be a "small molecule," and it is believed that all
dendrimers currently used in the field of OLEDs are small
molecules.
[0010] As used herein, "top" means furthest away from the
substrate, while "bottom" means closest to the substrate. Where a
first layer is described as "disposed over" a second layer, the
first layer is disposed further away from substrate. There may be
other layers between the first and second layer, unless it is
specified that the first layer is "in contact with" the second
layer. For example, a cathode may be described as "disposed over"
an anode, even though there are various organic layers in
between.
[0011] As used herein, "solution processible" means capable of
being dissolved, dispersed, or transported in and/or deposited from
a liquid medium, either in solution or suspension form.
[0012] A ligand may be referred to as "photoactive" when it is
believed that the ligand directly contributes to the photoactive
properties of an emissive material. A ligand may be referred to as
"ancillary" when it is believed that the ligand does not contribute
to the photoactive properties of an emissive material, although an
ancillary ligand may alter the properties of a photoactive
ligand.
[0013] As used herein, and as would be generally understood by one
skilled in the art, a first "Highest Occupied Molecular Orbital"
(HOMO) or "Lowest Unoccupied Molecular Orbital" (LUMO) energy level
is "greater than" or "higher than" a second HOMO or LUMO energy
level if the first energy level is closer to the vacuum energy
level. Since ionization potentials (IP) are measured as a negative
energy relative to a vacuum level, a higher HOMO energy level
corresponds to an IP having a smaller absolute value (an IP that is
less negative). Similarly, a higher LUMO energy level corresponds
to an electron affinity (EA) having a smaller absolute value (an EA
that is less negative). On a conventional energy level diagram,
with the vacuum level at the top, the LUMO energy level of a
material is higher than the HOMO energy level of the same material.
A "higher" HOMO or LUMO energy level appears closer to the top of
such a diagram than a "lower" HOMO or LUMO energy level.
[0014] As used herein, and as would be generally understood by one
skilled in the art, a first work function is "greater than" or
"higher than" a second work function if the first work function has
a higher absolute value. Because work functions are generally
measured as negative numbers relative to vacuum level, this means
that a "higher" work function is more negative. On a conventional
energy level diagram, with the vacuum level at the top, a "higher"
work function is illustrated as further away from the vacuum level
in the downward direction. Thus, the definitions of HOMO and LUMO
energy levels follow a different convention than work
functions.
[0015] More details on OLEDs, and the definitions described above,
can be found in U.S. Pat. No. 7,279,704, which is incorporated
herein by reference in its entirety.
SUMMARY OF THE INVENTION
[0016] According to an embodiment, a compound comprising a ligand
L.sub.A of Formula I:
##STR00003##
[0017] as well as, devices and formulations containing the compound
of Formula 1 are disclosed. In the compounds, having a ligand
L.sub.A of Formula I:
[0018] wherein R.sup.1 represents mono, or di-substitution, or no
substitution;
[0019] wherein R.sup.2 represents mono, di, tri, or
tetra-substitution, or no substitution;
[0020] wherein R is selected from the group consisting of hydrogen,
deuterium, alkyl, cycloalkyl, and combinations thereof;
[0021] wherein R.sup.1 and R.sup.2 are each independently selected
from the group consisting of hydrogen, deuterium, alkyl,
cycloalkyl, aryl, and combinations thereof;
[0022] wherein any adjacent substituents of R.sup.2 are optionally
joined to form a fused ring;
[0023] wherein the ligand L.sub.A is coordinated to a metal M;
and
[0024] wherein the ligand L.sub.A is optionally linked with other
ligands to comprise a tridentate, tetradentate, pentadentate or
hexadentate ligand.
[0025] According to another embodiment, a first device comprising a
first organic light emitting device is also provided. The first
organic light emitting device can include an anode, a cathode, and
an organic layer, disposed between the anode and the cathode. The
organic layer can include a compound having a ligand L.sub.A having
a structure of Formula I. The first device can be a consumer
product, an organic light-emitting device, and/or a lighting
panel.
[0026] Formulations containing a compound having a ligand L.sub.A
having a structure of Formula I are also described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows an organic light emitting device.
[0028] FIG. 2 shows an inverted organic light emitting device that
does not have a separate electron transport layer.
[0029] FIG. 3 shows a ligand L.sub.A of Formula I as disclosed
herein.
[0030] FIG. 4 shows room temperature emission spectra of Compound
1-3 in 2-methyltetrahydrofuran solvent.
[0031] FIG. 5 shows 77K emission spectra of Compound 1-3 in
2-methyltetrahydrofuran solvent.
[0032] FIG. 6 shows thin film emission spectra for Compounds 1-4
doped into Host 1 at 5 wt % on quartz substrate.
[0033] FIG. 7 shows 77K emission spectra of Compound 1, 5 and 11.
Emission spectra were measured in 2-methyltetrahydrofuran
solvent.
[0034] FIG. 8 shows room temperature emission spectra for Compound
1, 5 and 11. Emission spectra were measured in
2-methyltetrahydrofuran solvent.
[0035] FIG. 9 shows emission spectra for Compound 1, 5 and 11 doped
at 5 wt % in Host 1 on quartz substrate.
[0036] FIG. 10 shows spectral data for comparative example 1 at
both room temperature (RT) and 77K in 2-methyltetrahydrofuran
solvent, and polymethacrylate (PMMA) matrix at 5 wt % doping.
DETAILED DESCRIPTION
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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 F4-TCNQ at a molar ratio of 50:1, as
disclosed in U.S. Patent Application Publication No. 2003/0230980,
which is incorporated by reference in its entirety. Examples of
emissive and host materials are disclosed in U.S. 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] Devices fabricated in accordance with embodiments of the
present invention may further optionally comprise a barrier layer.
One purpose of the barrier layer is to protect the electrodes and
organic layers from damaging exposure to harmful species in the
environment including moisture, vapor and/or gases, etc. The
barrier layer may be deposited over, under or next to a substrate,
an electrode, or over any other parts of a device including an
edge. The barrier layer may comprise a single layer, or multiple
layers. The barrier layer may be formed by various known chemical
vapor deposition techniques and may include compositions having a
single phase as well as compositions having multiple phases. Any
suitable material or combination of materials may be used for the
barrier layer. The barrier layer may incorporate an inorganic or an
organic compound or both. The preferred barrier layer comprises a
mixture of a polymeric material and a non-polymeric material as
described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.
PCT/US2007/023098 and PCT/US2009/042829, which are herein
incorporated by reference in their entireties. To be considered a
"mixture", the aforesaid polymeric and non-polymeric materials
comprising the barrier layer should be deposited under the same
reaction conditions and/or at the same time. The weight ratio of
polymeric to non-polymeric material may be in the range of 95:5 to
5:95. The polymeric material and the non-polymeric material may be
created from the same precursor material. In one example, the
mixture of a polymeric material and a non-polymeric material
consists essentially of polymeric silicon and inorganic
silicon.
[0047] Devices fabricated in accordance with embodiments of the
invention may be incorporated into a wide variety of consumer
products, including flat panel displays, computer monitors, medical
monitors, televisions, billboards, lights for interior or exterior
illumination and/or signaling, heads up displays, fully transparent
displays, flexible displays, laser printers, telephones, cell
phones, personal digital assistants (PDAs), laptop computers,
digital cameras, camcorders, viewfinders, micro-displays, 3-D
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.), but could be used outside this
temperature range, for example, from -40 degree C. to +80 degree
C.
[0048] 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.
[0049] The term "halo" or "halogen" as used herein includes
fluorine, chlorine, bromine, and iodine.
[0050] The term "alkyl" as used herein contemplates both straight
and branched chain alkyl radicals. Preferred alkyl groups are those
containing from one to fifteen carbon atoms and includes methyl,
ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the
like. Additionally, the alkyl group may be optionally
substituted.
[0051] The term "cycloalkyl" as used herein contemplates cyclic
alkyl radicals. Preferred cycloalkyl groups are those containing 3
to 7 carbon atoms and includes cyclopropyl, cyclopentyl,
cyclohexyl, and the like. Additionally, the cycloalkyl group may be
optionally substituted.
[0052] The term "alkenyl" as used herein contemplates both straight
and branched chain alkene radicals. Preferred alkenyl groups are
those containing two to fifteen carbon atoms. Additionally, the
alkenyl group may be optionally substituted.
[0053] The term "alkynyl" as used herein contemplates both straight
and branched chain alkyne radicals. Preferred alkyl groups are
those containing two to fifteen carbon atoms. Additionally, the
alkynyl group may be optionally substituted.
[0054] The terms "aralkyl" or "arylalkyl" as used herein are used
interchangeably and contemplate an alkyl group that has as a
substituent an aromatic group. Additionally, the aralkyl group may
be optionally substituted.
[0055] The term "heterocyclic group" as used herein contemplates
aromatic and non-aromatic cyclic radicals. Hetero-aromatic cyclic
radicals also means heteroaryl. Preferred hetero-non-aromatic
cyclic groups are those containing 3 or 7 ring atoms which includes
at least one hetero atom, and includes cyclic amines such as
morpholino, piperdino, pyrrolidino, and the like, and cyclic
ethers, such as tetrahydrofuran, tetrahydropyran, and the like.
Additionally, the heterocyclic group may be optionally
substituted.
[0056] The term "aryl" or "aromatic group" 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 to 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.
[0057] The term "heteroaryl" as used herein contemplates
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. The term heteroaryl also
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.
[0058] The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl,
heterocyclic group, aryl, and heteroaryl may be optionally
substituted with one or more substituents selected from the group
consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl,
heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino,
silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,
heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile,
isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and
combinations thereof.
[0059] As used herein, "substituted" indicates that a substituent
other than H is bonded to the relevant position, such as carbon.
Thus, for example, where R.sup.1 is mono-substituted, then one
R.sup.1 must be other than H. Similarly, where R.sup.1 is
di-substituted, then two of R.sup.1 must be other than H.
Similarly, where R.sup.1 is unsubstituted, R.sup.1 is hydrogen for
all available positions.
[0060] The "aza" designation in the fragments described herein,
i.e. aza-dibenzofuran, aza-dibenzonethiophene, etc. means that one
or more of the C--H groups in the respective fragment can be
replaced by a nitrogen atom, for example, and without any
limitation, azatriphenylene encompasses both
dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. One of ordinary
skill in the art can readily envision other nitrogen analogs of the
aza-derivatives described above, and all such analogs are intended
to be encompassed by the terms as set forth herein.
[0061] It is to be understood that when a molecular fragment is
described as being a substituent or otherwise attached to another
moiety, its name may be written as if it were a fragment (e.g.
naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.
naphthalene, dibenzofuran). As used herein, these different ways of
designating a substituent or attached fragment are considered to be
equivalent.
[0062] According to one embodiment, a compound including a ligand
L.sub.A of Formula I:
##STR00004##
Formula I, is disclosed.
[0063] In the ligand L.sub.A of Formula I:
[0064] R.sup.1 represents mono, or di-substitution, or no
substitution;
[0065] R.sup.2 represents mono, di, tri, or tetra-substitution, or
no substitution;
[0066] R is selected from the group consisting of hydrogen,
deuterium, alkyl, cycloalkyl, and combinations thereof;
[0067] R.sup.1 and R.sup.2 are each independently selected from the
group consisting of hydrogen, deuterium, alkyl, cycloalkyl, aryl,
and combinations thereof;
[0068] where any adjacent substituents of R.sup.2 are optionally
joined to form a fused ring;
[0069] the ligand L.sub.A is coordinated to a metal M; and
[0070] the ligand L.sub.A is optionally linked with other ligands
to comprise a tridentate, tetradentate, pentadentate or hexadentate
ligand.
[0071] In some embodiments, at least one of R.sup.1 and R.sup.2 is
aryl, which can be further substituted by alkyl. In some
embodiments, R.sup.1 includes at least one aryl, which can be
further substituted with alkyl. In some embodiments, R.sup.1
includes exactly one aryl, which can be further substituted with
alkyl. In some embodiments, R.sup.2 includes at least one aryl,
which can be further substituted with alkyl. In some embodiments,
R.sup.2 includes exactly one aryl, which can be further substituted
with alkyl.
[0072] In some embodiments, R is hydrogen. In some embodiments, R
is alkyl.
[0073] In some embodiments, M is selected from the group consisting
of Ir, Rh, Re, Ru, Os, Pt, Au, and Cu. In some embodiments, M is
Ir.
[0074] In some embodiments, L.sub.A is bidentate. In other words,
L.sub.A is exactly bidentate and is not linked to other ligands to
form a tridentate or higher ligand.
[0075] In some embodiments, L.sub.A is selected from the group
consisting of:
##STR00005## ##STR00006## ##STR00007## ##STR00008##
##STR00009##
[0076] In some embodiments, the compound has the formula
M(L.sub.A).sub.m(L.sub.B).sub.n, having the structure:
##STR00010##
In the compound of Formula II:
[0077] L.sub.B is a different ligand from LA;
[0078] m is an integer from 1 to the maximum number of ligands that
may be coordinated to the metal M; and
[0079] m+n is the the maximum number of ligands that may be
coordinated to the metal M.
[0080] In some embodiments having a structure of Formula II, m is 1
or 2; and L.sub.B is selected from the group consisting of:
##STR00011## ##STR00012##
[0081] where R.sub.a, R.sub.b, R.sub.c, and R.sub.d may represent
mono, di, tri, or tetra substitution, or no substitution;
[0082] where R.sub.a, R.sub.b, R.sub.c, and R.sub.d are
independently selected from the group consisting of hydrogen,
deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,
alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,
heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,
carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,
sulfonyl, phosphino, and combinations thereof; and
[0083] where two adjacent substituents of R.sub.a, R.sub.b,
R.sub.c, and R.sub.d are optionally joined to form a fused ring or
form a multidentate ligand.
[0084] In some embodiments, the compound is heteroleptic. In some
embodiments, the compound is homoleptic. In some embodiments, the
compound has a facial configuration. In some embodiments, the
compound has a meridional configuration.
[0085] In some embodiments, the compound has the structure of
Formula III:
##STR00013##
[0086] In some more specific embodiments, the compound is selected
from the group consisting of:
##STR00014## ##STR00015## ##STR00016## ##STR00017##
##STR00018##
[0087] According to another aspect of the present disclosure, a
first device is also provided. The first device includes a first
organic light emitting device, that includes an anode, a cathode,
and an organic layer disposed between the anode and the cathode.
The organic layer may include a host and a phosphorescent dopant.
The emissive layer can include a compound comprising a ligand
L.sub.A affording to Formula I, and variations of the compound as
described herein.
[0088] The first device can be one or more of a consumer product,
an organic light-emitting device and a lighting panel. The organic
layer can be an emissive layer and the compound can be an emissive
dopant in some embodiments, while the compound can be a
non-emissive dopant in other embodiments.
[0089] The organic layer can also include a host. 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
C.sub.nH.sub.2n+1, OC.sub.nH.sub.2n+1, OAr.sub.1,
N(C.sub.nH.sub.2n+1).sub.2, N(Ar.sub.1)(Ar.sub.2),
CH.dbd.CH--C.sub.nH.sub.2n+1, C.ident.C--C.sub.nH.sub.2n+1,
Ar.sub.1, Ar.sub.1-Ar.sub.2, C.sub.nH.sub.2n--Ar.sub.1, or no
substitution. In the preceding substituents n can range from 1 to
10; and Ar.sub.1 and Ar.sub.2 can be independently selected from
the group consisting of benzene, biphenyl, naphthalene,
triphenylene, carbazole, and heteroaromatic analogs thereof.
[0090] The host can be a compound selected from the group
consisting of carbazole, dibenzothiphene, dibenzofuran,
dibenzoselenophene, azacarbazole, aza-dibenzothiophene,
aza-dibenzofuran, and aza-dibenzoselenophene. The host can include
a metal complex. The host can be a specific compound selected from
the group consisting of:
##STR00019## ##STR00020##
and combinations thereof.
[0091] In yet another aspect of the present disclosure, a
formulation that comprises a compound comprising a ligand L.sub.A
affording to Formula I, and variations of the compound as described
herein. 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, and an electron transport layer
material, disclosed herein.
Combination with Other Materials
[0092] 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.
HIL/HTL:
[0093] A hole injecting/transporting material to be used in the
present invention is not particularly limited, and any compound may
be used as long as the compound is typically used as a hole
injecting/transporting material. Examples of the material include,
but not limit to: a phthalocyanine or porphyrin derivative; an
aromatic amine derivative; an indolocarbazole derivative; a polymer
containing fluorohydrocarbon; a polymer with conductivity dopants;
a conducting polymer, such as PEDOT/PSS; a self-assembly monomer
derived from compounds such as phosphonic acid and silane
derivatives; a metal oxide derivative, such as MoO.sub.x; a p-type
semiconducting organic compound, such as
1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex,
and a cross-linkable compounds.
[0094] Examples of aromatic amine derivatives used in HIL or HTL
include, but not limit to the following general structures:
##STR00021##
[0095] Each of Ar.sup.1 to Ar.sup.9 is selected from the group
consisting aromatic hydrocarbon cyclic compounds such as benzene,
biphenyl, triphenyl, triphenylene, naphthalene, anthracene,
phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene,
azulene; group consisting aromatic heterocyclic compounds such as
dibenzothiophene, dibenzofuran, dibenzoselenophene, furan,
thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole,
indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole,
imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole,
dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine,
triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole,
indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole,
quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline,
naphthyridine, phthalazine, pteridine, xanthene, acridine,
phenazine, phenothiazine, phenoxazine, benzofuropyridine,
furodipyridine, benzothienopyridine, thienodipyridine,
benzoselenophenopyridine, and selenophenodipyridine; and group
consisting 2 to 10 cyclic structural units which are groups of the
same type or different types selected from the aromatic hydrocarbon
cyclic group and the aromatic heterocyclic group and are bonded to
each other directly or via at least one of oxygen atom, nitrogen
atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain
structural unit and the aliphatic cyclic group. Wherein each Ar is
further substituted by a substituent selected from the group
consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,
heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,
cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,
carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,
sulfinyl, sulfonyl, phosphino, and combinations thereof.
[0096] In one aspect, Ar.sup.1 to Ar.sup.9 is independently
selected from the group consisting of:
##STR00022##
wherein k is an integer from 1 to 20; X.sup.101 to X.sup.108 is C
(including CH) or N; Z.sup.101 is NAr.sup.1, O, or S; Ar.sup.1 has
the same group defined above.
[0097] Examples of metal complexes used in HIL or HTL include, but
not limit to the following general formula:
##STR00023##
wherein Met is a metal, which can have an atomic weight greater
than 40; (Y.sup.101-Y.sup.102) is a bidentate ligand, Y.sup.101 and
Y.sup.102 are independently selected from C, N, O, P, and S;
L.sup.101 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.
[0098] In one aspect, (Y.sup.101-Y.sup.102) is a 2-phenylpyridine
derivative. In another aspect, (Y.sup.101-Y.sup.102) is a carbene
ligand. In another aspect, Met is selected from Ir, Pt, Os, and Zn.
In a further aspect, the metal complex has a smallest oxidation
potential in solution vs. Fc.sup.+/Fc couple less than about 0.6
V.
Host:
[0099] The light emitting layer of the organic EL device of the
present invention preferably contains at least a metal complex as
light emitting material, and may contain a host material using the
metal complex as a dopant material. Examples of the host material
are not particularly limited, and any metal complexes or organic
compounds may be used as long as the triplet energy of the host is
larger than that of the dopant. While the Table below categorizes
host materials as preferred for devices that emit various colors,
any host material may be used with any dopant so long as the
triplet criteria is satisfied.
[0100] Examples of metal complexes used as host are preferred to
have the following general formula:
##STR00024##
wherein Met is a metal; (Y.sup.103-Y.sup.104) is a bidentate
ligand, Y.sup.103 and Y.sup.104 are independently selected from C,
N, O, P, and S; L.sup.101 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.
[0101] In one aspect, the metal complexes are:
##STR00025##
wherein (O--N) is a bidentate ligand, having metal coordinated to
atoms O and N.
[0102] In another aspect, Met is selected from Ir and Pt. In a
further aspect, (Y.sup.103-Y.sup.104) is a carbene ligand.
[0103] Examples of organic compounds used as host are selected from
the group consisting aromatic hydrocarbon cyclic compounds such as
benzene, biphenyl, triphenyl, triphenylene, naphthalene,
anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene,
perylene, azulene; group consisting aromatic heterocyclic compounds
such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan,
thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole,
indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole,
imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole,
dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine,
triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole,
indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole,
quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline,
naphthyridine, phthalazine, pteridine, xanthene, acridine,
phenazine, phenothiazine, phenoxazine, benzofuropyridine,
furodipyridine, benzothienopyridine, thienodipyridine,
benzoselenophenopyridine, and selenophenodipyridine; and group
consisting 2 to 10 cyclic structural units which are groups of the
same type or different types selected from the aromatic hydrocarbon
cyclic group and the aromatic heterocyclic group and are bonded to
each other directly or via at least one of oxygen atom, nitrogen
atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain
structural unit and the aliphatic cyclic group. Wherein each group
is further substituted by a substituent selected from the group
consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,
heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,
cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,
carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,
sulfinyl, sulfonyl, phosphino, and combinations thereof.
[0104] In one aspect, host compound contains at least one of the
following groups in the molecule:
##STR00026## ##STR00027##
wherein R.sup.101 to R.sup.107 is independently selected from the
group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,
heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,
cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,
carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,
sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is
aryl or heteroaryl, it has the similar definition as Ar's mentioned
above. k is an integer from 0 to 20 or 1 to 20; k''' is an integer
from 0 to 20. X.sup.101 to X.sup.108 is selected from C (including
CH) or N.
[0105] Z.sup.101 and Z.sup.102 is selected from NR.sup.101, O, or
S.
HBL:
[0106] A hole blocking layer (HBL) may be used to reduce the number
of holes and/or excitons that leave the emissive layer. The
presence of such a blocking layer in a device may result in
substantially higher efficiencies as compared to a similar device
lacking a blocking layer. Also, a blocking layer may be used to
confine emission to a desired region of an OLED.
[0107] In one aspect, compound used in HBL contains the same
molecule or the same functional groups used as host described
above.
[0108] In another aspect, compound used in HBL contains at least
one of the following groups in the molecule:
##STR00028##
wherein k is an integer from 1 to 20; L.sup.101 is an another
ligand, k' is an integer from 1 to 3.
ETL:
[0109] Electron transport layer (ETL) may include a material
capable of transporting electrons. Electron transport layer may be
intrinsic (undoped), or doped. Doping may be used to enhance
conductivity. Examples of the ETL material are not particularly
limited, and any metal complexes or organic compounds may be used
as long as they are typically used to transport electrons.
[0110] In one aspect, compound used in ETL contains at least one of
the following groups in the molecule:
##STR00029##
wherein R.sup.101 is selected from the group consisting of
hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,
arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,
heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,
carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,
sulfonyl, phosphino, and combinations thereof, when it is aryl or
heteroaryl, it has the similar definition as Ar's mentioned above.
Ar.sup.1 to Ar.sup.3 has the similar definition as Ar's mentioned
above. k is an integer from 1 to 20. X.sup.101 to X.sup.108 is
selected from C (including CH) or N.
[0111] In another aspect, the metal complexes used in ETL contains,
but not limit to the following general formula:
##STR00030##
wherein (O--N) or (N--N) is a bidentate ligand, having metal
coordinated to atoms O, N or N, N; L.sup.101 is another ligand; k'
is an integer value from 1 to the maximum number of ligands that
may be attached to the metal.
[0112] In any above-mentioned compounds used in each layer of the
OLED device, the hydrogen atoms can be partially or fully
deuterated. Thus, any specifically listed substituent, such as,
without limitation, methyl, phenyl, pyridyl, etc. encompasses
undeuterated, partially deuterated, and fully deuterated versions
thereof. Similarly, classes of substituents such as, without
limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also
encompass undeuterated, partially deuterated, and fully deuterated
versions thereof.
[0113] 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 A below. Table A lists
non-limiting classes of materials, non-limiting examples of
compounds for each class, and references that disclose the
materials.
TABLE-US-00001 TABLE A MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS
Hole injection materials Phthalocyanine and porphryin compounds
##STR00031## Appl. Phys. Lett. 69, 2160 (1996) Starburst
triarylamines ##STR00032## J. Lumin. 72-74, 985 (1997) CF.sub.x
Fluorohydrocarbon polymer ##STR00033## Appl. Phys. Lett. 78, 673
(2001) Conducting polymers (e.g., PEDOT: PSS, polyaniline,
polythiophene) ##STR00034## Synth. Met. 87, 171 (1997) WO2007002683
Phosphonic acid and silane SAMs ##STR00035## US20030162053
Triarylamine or polythiophene polymers with conductivity dopants
##STR00036## EP1725079A1 ##STR00037## ##STR00038## Organic
compounds with conductive inorganic compounds, such as molybdenum
and tungsten oxides ##STR00039## US20050123751 SID Symposium
Digest, 37, 923 (2006) WO2009018009 n-type semiconducting organic
complexes ##STR00040## US20020158242 Metal organometallic complexes
##STR00041## US20060240279 Cross-linkable compounds ##STR00042##
US20080220265 Polythiophene based polymers and copolymers
##STR00043## WO 2011075644 EP2350216 Hole transporting materials
Triarylamines (e.g., TPD, .alpha.-NPD) ##STR00044## Appl. Phys.
Lett. 51, 913 (1987) ##STR00045## US5061569 ##STR00046## EP650955
##STR00047## J. Mater. Chem. 3, 319 (1993) ##STR00048## Appl. Phys.
Lett. 90, 183503 (2007) ##STR00049## Appl. Phys. Lett. 90, 183503
(2007) Triarylamine on spirofluorene core ##STR00050## Synth. Met.
91, 209 (1997) Arylamine carbazole compounds ##STR00051## Adv.
Mater. 6, 677 (1994), US20080124572 Triarylamine with
(di)benzothiophene/ (di)ben zofuran ##STR00052## US20070278938,
US20080106190 US20110163302 Indolocarbazoles ##STR00053## Synth.
Met. 111, 421 (2000) Isoindole compounds ##STR00054## Chem. Mater.
15, 3148 (2003) Metal carbene complexes ##STR00055## US20080018221
Phosphorescent OLED host materials Red hosts Arylcarbazoles
##STR00056## Appl. Phys. Lett. 78, 1622 (2001) Metal
8-hydroxyquinolates (e.g., Alq.sub.3, BAlq) ##STR00057## Nature
395, 151 (1998) ##STR00058## US20060202194 ##STR00059##
WO2005014551 ##STR00060## WO2006072002 Metal phenoxybenzothiazole
compounds ##STR00061## Appl Phys. Lett. 90, 123509 (2007)
Conjugated oligomers and polymers (e.g., polyfluorene) ##STR00062##
Org. Electron. 1, 15 (2000) Aromatic fused rings ##STR00063##
WO2009066779, WO2009066778, WO2009063833, US20090045731,
US20090045730, WO2009008311, US20090008605, US20090009065 Zinc
complexes ##STR00064## WO2010056066 Chrysene based compounds
##STR00065## WO2011086863 Green hosts Arylcarbazoles ##STR00066##
Appl. Phys. Lett. 78, 1622 (2001) ##STR00067## US20030175553
##STR00068## WO2001039234 Aryltriphenylene compounds ##STR00069##
US20060280965 ##STR00070## US20060280965 ##STR00071## WO2009021126
Poly-fused heteroaryl compounds ##STR00072## US20090309488
US20090302743 US20100012931 Donor acceptor type molecules
##STR00073## WO2008056746 ##STR00074## WO2010107244 Aza-carbazole/
DBT/DBF ##STR00075## JP2008074939 ##STR00076## US20100187984
Polymers (e.g., PVK) ##STR00077## Appl. Phys. Lett. 77, 2280 (2000)
Spirofluorene compounds ##STR00078## WO2004093207 Metal
phenoxybenzooxazole compounds ##STR00079## WO2005089025
##STR00080## WO2006I32173 ##STR00081## JP200511610 Spirofluorene-
carbazole compounds ##STR00082## JP2007254297 ##STR00083##
JP2007254297 Indolocarbazoles ##STR00084## WO2007063796
##STR00085## WO2007063754 5-member ring electron deficient
heterocycles (e.g., triazole, oxadiazole) ##STR00086## J. Appl.
Phys. 90, 5048 (2001) ##STR00087## WO2004107822 Tetraphenylene
complexes ##STR00088## US20050112407 Metal phenoxypyridine
compounds ##STR00089## WO2005030900 Metal coordination complexes
(e.g., Zn, Al with N{circumflex over ( )}N ligands) ##STR00090##
US20040137268, US20040137267 Blue hosts Arylcarbazoles ##STR00091##
Appl. Phys. Lett, 82, 2422 (2003) ##STR00092## US20070190359
Dibenzothiophene/ Dibenzofuran- carbazole compounds ##STR00093##
WO2006114966, US20090167162 ##STR00094## US20090167162 ##STR00095##
WO2009086028 ##STR00096## US20090030202, US20090017330 ##STR00097##
US20100084966 Silicon aryl compounds ##STR00098## US20050238919
##STR00099## WO2009003898 Silicon/Germanium aryl compounds
##STR00100## EP2034538A Aryl benzoyl ester ##STR00101##
WO2006100298 Carbazole linked by non-conjugated groups ##STR00102##
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EXPERIMENTAL
[0114] Blue phosphorescent compounds with fluorine substituents,
like
bis[2-(4,6-difluorophenyl)pyridinato-C.sup.2,N](picolinato)iridium(III)
(FIrpic) or
tris[2-(4,6-difluorophenyl)pyridinato-C.sup.2,N]iridium(III), are
known to be unstable in electroluminescent devices. Therefore,
fluorine substitution is an undesirable feature on a blue emitter.
Furthermore, the research leading to the compounds described herein
show that non-blocked tris(pyridylpyridine) iridium compounds are
desirably blue-shifted in room temperature solution and solid state
thin film when compared to alkyl blocked analogues. Thus, it is
believed the blue shift may be due to less steric twisting of the
pyridyl-pyridine ligand resulting in less distortion in the excited
state.
[0115] It has been learned that the iridium tris facial isomer with
the cyclometalated pyridyl-pyridine (pypy) ligand, where the
uncoordinated nitrogen is substituted para to the metal has highly
desirable blue phosphorescent emission with high photoluminescent
quantum yield and short excited state lifetime. The synthesis of
this isomer is complicated by two factors, coordination of the free
pyridine in synthesis and non-selectivity of the metallation site.
Because three metallation events have to occur in the correct
configuration to get the desired blue emitting isomer, finding a
way to improve the synthetic yield is important.
##STR00205##
[0116] Calculations used to develop the compounds described herein
show the triplet of the undesired isomer, where the uncoordinated
nitrogen is ortho to the metal, is significantly redshifted from
the desired isomer. This effect is shown in Table 1 with
Comparative Example 2.
[0117] The compounds described herein include blue phosphorescent
emitting tris facial complexes that can employ an alkyl
substitution to block metallation at the undesired site on the
pyridyl pyridine ligand. Density functional calculations (DF)
calculations performed using the B3LYP/cep-31g functional and basis
set using a Gaussian software package show that methyl substitution
has minimal effect on the triplet energy, as shown in Table 1.
TABLE-US-00002 TABLE 1 DFT calculations comparing the desired and
undesired facial isomers to inventive compound 1. HOMO LUMO Gap
Dipole S1.sub.gas Structure (eV) (ev) (ev) (Debye) (nm)
T1.sub.gas(nm) Compound 13 ##STR00206## -5.81 -1.89 -3.91 16.22 395
462 Comparative Example 2 ##STR00207## -5.42 -1.75 -3.66 12.78 423
495 Compound 1 ##STR00208## -5.61 -1.73 -3.88 13.48 399 464
Comparative Example 3 ##STR00209## -5.63 -1.67 -3.96 7.81 389 464
Comparative Example 4 ##STR00210## -5.63 -1.59 -4.04 7.90 377 464
Comparative Example 5 ##STR00211## -5.64 -1.67 -3.96 13.68 387 466
Comparative Example 6 ##STR00212## -5.54 -1.76 -3.78 12.57 407 492
Comparative Example 7 ##STR00213## -5.12 -1.44 -3.68 5.14 401 503
Comparative Example 8 ##STR00214## -4.88 -1.33 -3.55 2.27 410
511
[0118] The compounds described herein are also compared to
comparative example 1, difluoro pyridyl pyridine analogue:
##STR00215##
[0119] The spectra for comparative example 1 is shown in FIG. 10.
Spectral data is measured in 2-methyltetrahydrofuran solvent at
both room temperature (RT) and 77K, as well as in
polymethylmethacrylate (PMMA), an optically inert polymer host
matrix, at 5 weight %. At 77K, the highest energy peak is at 430
nm, and at RT and in PMMA matrix, the highest energy peak is at 437
nm. The photoluminescent quantum yield (PLQY) of the
PMMA:Comparative Example 1 (5 wt %) sample was compared to
PMMA:Host 3:Comparative Example 1 (5 wt %), where PMMA and Host 3
are in an approximate 50:50 ratio and Comparative Example 1
comprises 5 weight % of the total. PLQY measurements were carried
out on a Hamamatsu C9920 system equipped with a xenon lamp,
integrating sphere, and a model C10027 photonic multi-channel
analyzer. Host 3 is a representative high triplet host comprised of
standard OLED building blocks, such as, carbazole and dibenzofuran.
The 77K solution triplet of Host 3 is approximately 420 nm. It is
found that the PLQY for PMMA:Comparative Example 1 is very high at
95%. However, in the matrix that includes Host 3, the efficiency
drops to only 9%. Therefore, the triplet of Comparative Example 1
is readily quenched by a carbazole containing OLED host material,
and therefore cannot be tested and studied in standard OLED devices
used with the compounds having a ligand L.sub.A of Formula I
described herein.
[0120] Table 1 also compares calculated values of Compounds 1 and
13 with Comparative Examples 3 to 5. It is known in the art that
compounds with an OMe group, such as those in Comparative Examples
3 to 5, can have a high triplet energy. In this case, OMe has a
positive Hammett constant ((.sigma..sub.m=0.12, C. Hansch, et al.
Chem. Rev. 1991, 91, 165-195), which actually provides an electron
withdrawing effect to Ir atom. Meanwhile, with a substituent having
a negative Hammett constant, i.e., an electron donating group, such
as NMe.sub.2 (.sigma..sub.m=-0.16) in Comparative Examples 6-8, the
compounds should show a red shift in the triplet energy. As shown
in Table 1, this is true of Comparative Examples 6 to 8. However,
Compound 1 and Compound 13 unexpectly show that with a substituent
having a small negative value or zero value of the Hammet constant,
such as hydrogen (.sigma..sub.m=0), or methyl
(.sigma..sub.m=-0.07), as well as, other alkyl analogs, the
compounds can still have the same or even higher triplet energy
than those having substituents with more positive or negative
Hammett constants.
Synthesis of Compound 1
Step 1
##STR00216##
[0121] Synthesis of 2',6'-dimethyl-2,3'-bipyridine
[0122] 2,6-dimethyl-3-bromopyridine (44.54 g, 240 mmol),
2-tributyltin-pyridine (82.83 g, 225 mmol) and
tetrakis(triphenylphosphine)palladium(0) (6.516 g, 5.62 mmol) were
charged into a reaction flask with 720 mL of m-xylene. This mixture
was degassed, then heated to 130.degree. C. for 35 hrs. The
reaction mixture was cooled to room temperature. The reaction
mixture was extracted with 15% aqueous HCl. The aqueous phase was
first washed with ether, then neutralized by 50% NaOH aqueous
solution. The aqueous phase was then extracted by chloroform. The
organic layer was separated and dried over magnesium sulfate. The
organics were then filtered and concentrated under vacuum. The
residue was them subjected to kugelrohr distillation and yielded
2',6'-dimethyl-2,3'-bipyridine (34.52 g, 187 mmol, 83% yield).
Step 2
##STR00217##
[0123] Synthesis of Iridium chloro bridge dimer
[0124] A 100 ml round bottom flask was charged with
2',6'-trimethyl-2,3'-bipyridine (5 g, 27.1 mmol), IrCl.sub.3
hydrate (5.032 g, 13.5 mmol), and 2-ethoxyethanol (60 ml). The
reaction mixture was heated to 70.degree. C. for 64 hrs. The
desired product was isolated by filtration and washed with
isopropanol. (6.94 g, 86% yield)
Step 3
##STR00218##
[0125] Synthesis of Iridium ACAC complex
[0126] A 500 ml round bottom flask was charged with Iridium chloro
bridge dimer from the previous step (2 g, 1.684 mmol),
2,2,6,6-tetramethylheptane-3,5-dione (1.86 g, 10.1 mmol), sodium
carbonate (2.14 g, 20.2 mmol), and 2-ethoxyethanol (10 ml). The
reaction mixture was stirred at room temperature for 64 hrs. The
reaction mixture was diluted with water and extracted with
methylene chloride. The organic layer was separated and dried over
magnesium sulfate. The organics were then filtered and concentrated
under vacuum and yield desired compound. (1.88 g, 2.53 mmol, 75%
yield)
Step 4
##STR00219##
[0127] Synthesis of Compound 1
[0128] A 100 ml round bottom flask was charged with Iridium ACAC
complex from the previous step (11.74 g, 15.8 mmol),
2',6'-trimethyl-2,3'-bipyridine (8.74 g, 47.5 mmol), and glycerol
(10 ml). The reaction was heated to 115.degree. C. for 89 hrs. The
reaction mixture was poured into a 10% LiCl aqueous solution and
extracted with dichloromethane. The organic portion was
chromatographed on an Et.sub.3N-pretreated silica column with 99/1
DCM/MeOH to 80/20 DCM/MeOH to give 1.0 g of a gold solid. (8.5%
yield)
Synthesis of Compound 2
##STR00220##
[0129] Synthesis of 2',4-Dimethyl-2,3'-Bipyridine
[0130] Isopropylmagnesium chloride (61.5 ml, 123 mmol) was charged
into the reaction flask. 2-bromo-4-methylpyridine (16.8 g, 98 mmol)
was added dropwise to this reaction mixture over a 30 minute period
while maintaining the internal temperature below 30.degree. C. This
mixture was stirred at room temperature for 2 hours. Zinc chloride
in tetrahydrofuran (THF) (240 ml, 120 mmol) was added dropwise to
this reaction mixture over a 30 minute period while maintaining the
internal temperature below 30.degree. C. Stirring was continued
overnight at room temperature.
Tris(dibenzylideneacetone)palladium(0) (1.2 g, 1.311 mmol) and
2-Dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (2.4 g, 5.03
mmol) were charged into a reaction vessel with 75 mL of THF. This
mixture was refluxed for 45 minutes, then was cooled to room
temperature. 3-bromo-2-methylpyridine (11.4 g, 66.3 mmol) was added
to the reaction mixture. The organozinc solution formed was
transferred to an addition funnel and was added dropwise over 15
minutes to the reaction mixture. The mixture was degassed using
nitrogen, then was heated at reflux for 18 hours. The resulting
reaction mixture was cooled to room temperature, then was quenched
with aqueous ammonium chloride. This mixture was extracted 2 times
using 300 mL ethyl acetate. These extracts were dried over
magnesium sulfate, then were filtered and concentrated under
vacuum. The crude residue was passed through a neutral alumina
column using 10-20% ethyl acetate/dichloromethane (DCM).
2',4-dimethyl-2,3'-bipyridine (2.2 g, 11.94 mmol, 12% yield) was
isolated as an off-white solid.
##STR00221##
Synthesis of Compound 2
[0131] 2',4-dimethyl-2,3'-bipyridine (2.7 g, 14.66 mmol) and
Ir(acac).sub.3 (1.4 g, 2.9 mmol) were added to tridecane (0.5 mL)
in a Schlenk flask and the contents were evacuated and backfilled
with nitrogen five (5) times. The reaction was heated to
235.degree. C. for 60 hours. The reaction was cooled to room
temperature and chromatographed on an Et.sub.3N-pretreated silica
column with 99/1 DCM/MeOH to 80/20 DCM/MeOH to give 1.0 g of a gold
solid. The solid was lixiviated with toluene followed by ether to
give 0.93 g of Compound 2 as a yellow solid. The product was
confirmed by NMR and LC/MS.
Synthesis of Compound 3
##STR00222##
[0132] Synthesis of
2,6-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine
[0133] 3-bromo-2,6-dimethylpyridine (11 g, 59.1 mmol),
4,4,4',4',5,5,5',5'-octamethyl-2,2'-bi(1,3,2-dioxaborolane) (19.52
g, 77 mmol), Potassium acetate (6.95 g, 70.9 mmol),
Tris(dibenzylideneacetone)palladium(0) (1.082 g, 1.182 mmol) and
2-dicyclohexylphosphino-2',6'dimethoxybiphenyl (1.939 g, 4.73 mmol)
were charged into a reaction flask with 200 mL of dioxane. The
mixture was degasssed with nitrogen, then was heated at reflux
overnight. The reaction mixture was cooled to room temperature,
then was diluted with 300 mL of water. This mixture was extracted
two times with 300 mL ethyl acetate. The organics were combined and
then washed with brine. The organics were combined, were dried over
magnesium sulfate, then were filtered and concentrated under
vacuum. This crude residue was passed through a silica gel column
using 1-20% methanol/DCM as the eluant yielding
2,6-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyri-
dine (1.2 g, 5.15 mmol, 9% yield).
##STR00223##
Synthesis of 2',4,6'-trimethyl-2,3'-bipyridine
[0134]
2,6-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridin-
e (1.2 g, 5.15 mmol), 2-bromo-4-methylpyridine (0.974 g, 5.66 mmol)
and tetrakis(triphenylphosphine)palladium(0) (0.238 g, 0.206 mmol)
were charged into the reaction flask with 50 mL of dimethoxyethane
(DME). Potassium carbonate (2.131 g, 15.44 mmol) was dissolved in
10 mL of water and then charged into the reaction flask. This
mixture was degassed, then was heated at reflux overnight. The
reaction mixture was cooled to room temperature. The reaction
mixture was diluted with 100 mL water and 200 mL ethyl acetate. The
organic layer was separated and dried over magnesium sulfate. The
organics were then filtered and concentrated under vacuum. The
crude residue was purified via silica gel chromatography using 1-5%
Methanol/DCM yielding 2',4,6'-trimethyl-2,3'-bipyridine (0.55 g,
2.77 mmol, 54% yield).
##STR00224##
Synthesis of Compound 3
[0135] 2',4,6'-trimethyl-2,3'-bipyridine (2.8 g, 13.8 mmol) and
Ir(acac).sub.3 (1.4 g, 2.8 mmol) were added to tridecane (1 mL) in
a Schlenk flask and the contents were evacuated and backfilled with
nitrogen five (5) times. The reaction mixture was heated to
235.degree. C. for 16 hours. The reaction mixture was cooled to
room temperature and DCM was added. The insoluble material was
filtered and washed with DCM to give 0.70 g (32%) of Compound 3 as
a golden solid. The product was confirmed by NMR.
Synthesis of Compound 4
##STR00225##
[0136] Synthesis of 2',4,5-Trimethyl-2,3'-Bipyridine
[0137]
2-Methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine
(1.178 g, 5.37 mmol), 2-bromo-4,5-dimethylpyridine (1 g, 5.37 mmol)
and tetrakis(triphenylphosphine)palladium(0) (0.249 g, 0.215 mmol)
were charged into a reaction vessel with 75 mL of toluene.
Potassium carbonate (2.225 g, 16.12 mmol) was dissolved in 15 mL of
water and was charged into the reaction vessel. The reaction
mixture was degassed with nitrogen then was heated at reflux. The
reaction mixture was heated at reflux for 3 days. The reaction
mixture was hen diluted with 100 mL ethyl acetate and 50 mL of
water. The organic layer was separated and dried over magesium
sulftate. The organics were then filtered and concentrated under
vacuum. The crude product was purified using silica gel
chromatography using 1-5% methanol/DCM as the eluant.
2',4,5-trimethyl-2,3'-bipyridine (0.35 g, 1.765 mmol, 32.8% yield)
was isolated as a tan solid.
##STR00226##
Synthesis of Compound 4
[0138] 2',4,5-Trimethyl-2,3'-bipyridine (4.0 g, 20.2 mmol) and
Ir(acac).sub.3 (2.0 g, 4.0 mmol) were added to tridecane (1 mL) in
a Schlenk flask and the contents were evacuated and backfilled with
nitrogen five (5) times. The reaction was heated to 255.degree. C.
for 96 hours. The reaction was cooled to room temperature and
chromatographed on an Et.sub.3N-pretreated silica column with 99/1
DCM/MeOH to 70/30 DCM/MeOH to give 1.7 g of a golden brown solid.
The solid was lixiviated with toluene followed by ether to give 1.5
g of Compound 4 as a light golden solid. The product was confirmed
by NMR and LC/MS.
Synthesis of Compound 5
##STR00227##
[0139] Synthesis of 2'-methyl-2,3'-bipyridine
[0140] Tris(dibenzylideneacetone)palladium(0) (0.798 g, 0.872 mmol)
and 2-Dicyclohexylphosphino-2',4',6-triisopropylbiphenyl (1.664 g,
3.49 mmol) were charged into the reaction mixture with 50 mL of
THF. This reaction mixture was refluxed for 45 minutes. The
reaction mixture was cooled to room temperature.
3-bromo-2-methylpyridine (7.5 g, 43.6 mmol) was charged into the
reaction mixture followed by the dropwise addition of
pyridin-2-ylzinc(II) bromide (100 ml, 50.0 mmol). After the
addition was completed, the reaction mixture was heated to reflux
overnight. The reaction mixture was poured into aqueous ammonium
chloride then was extracted twice using 300 mL ethyl acetate. The
extracts were dried over magnesium sulfate then were filtered and
concentrated under vacuum. This crude residue was passed through a
neutral alumina column using 10-25% ethyl acetate/DCM. The cleaned
product fractions were combined and concentrated under vacuum
yielding 2'-methyl-2,3'-bipyridine (1.800 g, 10.58 mmol, 14%
yield).
##STR00228##
Synthesis of Compound 5
[0141] 2'-methyl-2,3'-bipyridine (1.5 g, 8.8 mmol) and
Ir(acac).sub.3 (0.86 g, 1.8 mmol) were added to tridecane (0.5 mL)
in a Schlenk flask and the contents were evacuated and backfilled
with nitrogen five (5) times. The reaction was heated to
235.degree. C. for 60 hours. The reaction was cooled to room
temperature and chromatographed on an Et.sub.3N-pretreated silica
column with 99/1 DCM/MeOH to 80/20 DCM/MeOH to give 0.71 g of a
gold solid. The solid was lixiviated with ether to give 0.70 g of
Compound 5 as a yellow solid. The product was confirmed by NMR and
LC/MS.
Synthesis of Compound 11
##STR00229##
[0143] Synthesis of 5-chloro-2-isopropylpyridine.
2,5-dichloropyridine (15.0 g, 101 mmol) and (dppe)NiCl.sub.2 (0.268
g, 0.507 mmol) were dissolved in dry THF (338 ml) under nitrogen,
cooled by ice bath, and isopropylmagnesium chloride solution in THF
(2M, 62 ml, 124 mmol) was added dropwise over half an hour, causing
the mixture to turn dark brown. The mixture was stirred cold for 1
hour, then overnight at room temperature. The mixture was quenched
with aqueous NH.sub.4Cl, then brine and water were added. The
mixture was extracted twice with ether, then the organics were
washed with brine, dried, vacuumed down and coated on celite. The
mixture was purified by column chromatography to yield a slightly
yellow liquid, 12.61 g (80%).
##STR00230##
Synthesis of 6'-isopropyl-2,3'-bipyridine
[0144] Pd.sub.2(dba).sub.3 (0.944 g, 1.031 mmol) and X-Phos (1.965
g, 4.12 mmol) were dissolved in THF (150 ml) under nitrogen, heated
to reflux until orange, then added via cannula to a solution of
5-chloro-2-isopropylpyridine (8.02 g, 51.5 mmol) in THF (50 ml).
The mixture was warmed to 65.degree. C. for about 5 minutes, then
pyridin-2-ylzinc(II) bromide solution in THF (0.5 M, 113 ml, 56.7
mmol) was slowly added via syringe. The brown mixture was heated at
very gently refluxed for 4 hours, resulting in the formation of
solids. The reaction solution was diluted with 250 mL EtOAc and
filtered through celite. The solvent was removed under vacuum. The
residue was partitioned between EtOAc and water, and the pH was
brought to .about.9 using K.sub.2CO.sub.3. The thick emulsion was
filtered through celite, separated, and the aqueous layer was
extracted several times more with EtOAc. The organics were washed
with brine, dried, vacuumed down and coated on celite. The product
was purified by column chromatography, yielding a yellow/brown oil
which was distilled via kugelrohr), yielding a colorless oil, 8.06
g (79%).
##STR00231##
Synthesis of Compound 11
[0145] 6'-isopropyl-2,3'-bipyridine (8.00 g, 40.3 mmol),
Ir(acac).sub.3 (3.95 g, 8.07 mmol), and tridecane (1 ml) were
combined in a schlenk tube, and the mixture was degassed by cycling
vacuum/nitrogen several times. The mixture was heated at
.about.260.degree. C. under nitrogen for 4 days, then a gentle
vacuum was applied while the solution was still hot to remove
tridecane. The residual mixture was heated at 270.degree. C.
overnight, resulting in blue luminescence. After cooling to room
temperature, the reaction mixture was dissolved in DCM, transferred
to a kugelrohr flask and excess ligand was distilled off. The
residue was purified by column chromatography and the residue from
the cleanest fraction was triturated in .about.100 mL hot EtOAc,
cooled to RT and filtered, and washed with lots of EtOAc. The
product was dried to give 0.936 g of dark yellow powder. This
material was boiled in .about.100 mL EtOAc, cooled to RT, and
insoluble, beige solids were filtered out. The yellow filtrate was
condensed, dissolved again in 100 mL hot EtOAc, cooled to RT, then
.about.100 mL of heptanes were added and the resulting solution was
stirred at RT. The resulting material collected was 0.550 g of
yellow solid.
Synthesis of Compound 12
##STR00232##
[0146] Synthesis of 5-chloro-2-(2,6-dimethylphenyl)pyridine
[0147] 2,5-dichloropyridine (10 g, 67.6 mmol),
(2,6-dimethylphenyl)boronic acid (11.15 g, 74.3 mmol), and
potassium carbonate (14.01 g, 101 mmol) were combined in dioxane
(113 ml) and water (113 ml), degassed for 30 minutes, then
Pd(PPh.sub.3).sub.4 (3.90 g, 3.38 mmol) was added. Degassing was
continued another 10 minutes, then the mixture was heated to reflux
under nitrogen with stirring to produce a homogeneous reaction
mixture. The reaction was heated overnight, then partitioned
between water and EtOAc. The organics were washed with brine,
dried, and coated on celite. Column chromatography yielded a nearly
colorless oil, 10.99 g (75%).
##STR00233##
Synthesis of 6'-(2,6-dimethylphenyl)-2,3'-bipyridine
[0148] Pd.sub.2(dba).sub.3 (0.925 g, 1.010 mmol) and X-Phos (1.925
g, 4.04 mmol) were stirred in THF (150 ml) under nitrogen, heated
to reflux until orange (10 min), cooled to room temperature, then
added via cannula to a solution of
5-chloro-2-(2,6-dimethylphenyl)pyridine (10.99 g, 50.5 mmol) in THF
(50 ml). Pyridin-2-ylzinc(II) bromide solution in THF (0.5 M, 111
ml, 55.5 mmol) was added via syringe, and the resulting brown
mixture was heated at gentle reflux for 4 hours then cooled to room
temperature. Most of the THF was removed under vacuum and the
residue was diluted with EtOAc and filtered through celite. Water
was then added, the pH was borught to .about.9 with
Na.sub.2CO.sub.3. The suspension was filtered through celite,
partitioned and the aqueous layer was extracted with 2.times.EtOAc.
The organics were washed with brine, dried, vacuumed down and
coated on celite. Column chromatography yielded a yellow/brown oil
that was distilled using a kugelrohr to yield a colorless, tacky
oil. Acidification using HCl in dioxane, followed by trituration
three times of the HCl salt in hot acetone yielded a more pure
solid that was basified using NaOH and extracted into ether,
yielding a colorless oil of approximately 99% purity, 6.09 g
(46%).
##STR00234##
Synthesis of Compound 12
[0149] 6'-(2,6-dimethylphenyl)-2,3'-bipyridine (6.07 g, 23.32
mmol), Ir(acac).sub.3 (2.24 g, 4.58 mmol), and 10 drops of
tridecane were combined in a schlenk tube, which was cycled several
times through vacuum/nitrogen backfill, then heated the 270.degree.
C. under nitrogen. The reaction solution turned dark brown
overnight. In the morning, the mixture was cooled to 160.degree. C.
and held under vacuum until most bubbling had subsided. The mixture
was heated at 270.degree. C. for five days more, then cooled and
coated on celite. Column chromatography followed by trituration in
boiling EtOAc yielded a shiny yellow solid, 0.865 g.
Synthesis of Compound 13
##STR00235##
[0150] Synthesis of 2,3'-bipyridine
[0151] Pd.sub.2(dba).sub.3 (1.129 g, 1.233 mmol), S-Phos (2.025 g,
4.93 mmol), pyridin-3-ylboronic acid (8.34 g, 67.8 mmol), and
potassium phosphate (26.2 g, 123 mmol) were combined in a flask,
degassed by vacuum/backfill, then a degassed mixture of dioxane
(205 ml) and water (103 ml) was added via cannula, and
2-chloropyridine (5.79 ml, 61.6 mmol) was added via syringe. The
mixture was heated at 100.degree. C. for 3 hours and cooled to room
temperature. Brine and EtOAc were added and, after separation, the
aqueous layer was extracted three times with EtOAc. The combined
organic layers were washed with brine, dried, the solvent was
removed, and residue was coated on celite. Column chromatography
yielded a yellow oil that was distilled under vacuum (bath:
200.degree. C.; vapor: 162.degree. C.), yielding 8.50 g (88%) of
colorless oil.
##STR00236##
Synthesis of Compound 13
[0152] 2,3'-bipyridine (6.99 g, 44.7 mmol), Ir(acac).sub.3 (4.38 g,
8.95 mmol), and 10 drops of tridecane were combined in a schlenk
tube, cycled with vacuum/nitrogen several times, then heated to
.about.275.degree. C. (active reflux) under nitrogen. The reaction
solution turned homogeneous and brown quickly once at temperature.
In the morning, the mixture was heated at 160.degree. C. under
active vacuum for several hours, then heating was continued at
275.degree. C. over the weekend under nitrogen. After cooling to
room temperature, the reaction mixture was dissolved in .about.50
mL DCM, diluted with heptanes, and filtered through a celite pad
and washed with lots of heptanes. The filtrates were vacuumed down,
then dissolved again in a couple mL of DCM, diluted with heptanes
and washed again through the same celite pad, washing with
heptanes. The celite cake was loaded onto a silica column and
subsequent chromatography yielded 0.87 g of material which was
triturated in 250 mL hot EtOAc to yield 0.84 g of yellow
powder.
Synthesis of Compound 14
##STR00237##
[0153] Synthesis of 4-methyl-2,3'-bipyridine
[0154] Pd.sub.2(dba).sub.3 (1.279 g, 1.396 mmol), S-Phos (2.293 g,
5.59 mmol), pyridin-3-ylboronic acid (9.44 g, 77 mmol), and
potassium phosphate (29.6 g, 140 mmol) were combined in a flask,
degassed by vacuum/backfill, then a degassed mixture of dioxane
(233 ml) and water (116 ml) was added via cannula, and
2-chloro-4-methylpyridine (7.8 ml, 69.8 mmol) was added via
syringe. The mixture was heated at 100.degree. C. overnight. After
cooling to room temperature, brine and EtOAc were added. After
separation, the aqueous layer was extracted three times with EtOAc,
the combined organic layers were washed with brine, dried, vacuumed
down, and coated on celite. Column chromatography yielded a yellow
oil that was distilled under vacuum (sand bath: 270.degree. C.;
vapor: .about.190.degree. C.), yielding 10.98 g (92%) of a
colorless oil.
##STR00238##
Synthesis of Compound 14
[0155] 4-methyl-2,3'-bipyridine (8.28 g, 48.6 mmol), Ir(acac).sub.3
(4.76 g, 9.72 mmol), and 10 drops of tridecane were combined in a
schlenk tube, degassed with several long vacuum/nitrogen backfill
cycles. The mixture was heated to 100.degree. C. while stirring
under vacuum for a last degassing, then backfilled with nitrogen,
and heated at 270.degree. C. overnight. After one day, the mixture
was heated at 160.degree. C. under vacuum for several hours, then
heated again at 275.degree. C. for an additional 5 days. The
mixture was cooled to room temperature and coated on celite using
DCM/MeOH. Column chromatography followed by trituration in EtOAc
yielded 0.71 g of yellow solid.
Photoluminescent (PL) Spectra
[0156] The emission spectra of Compounds 1-3 are shown in FIGS. 4
and 5. It can be seen in FIG. 4 that the compounds emit at room
temperature with blue-green color with a highest energy emission
peak around 475 nm. FIG. 5 shows the emission at 77K. Here the
intrinsic deep blue triplet energy is demonstrated for this family
of compounds with emission maxima between 452-456 nm.
[0157] The compounds also emit at 77K with a very short excited
state lifetime. For example Compound 1 and 3 have excited state
lifetimes of 2.95 and 2.52 microseconds, respectively. For
comparison, the tris facial iridium phenylpyridine green emitting
compound fac-Ir(ppy).sub.3 was measured to have a lifetime of 4.03
microseconds in 77K 2-methyltetrahydrofuran. The short excited
state lifetime may be a desirable feature for improved stability as
the compound spends less time in the highly energetic excited
state.
[0158] The compounds are also measured to have a very high
photoluminescent quantum yield when doped in a host matrix. Thin
film samples of Compounds 1-4 were prepared where Compounds 1-4
were doped into Host 1 at 5 weight % on a quartz substrate. Thin
film photoluminescent quantum yields for compounds 1-5 were 92%,
87%, 69%, 90%, and 94% respectively, demonstrating that these
compounds are very efficient emitters. Emission spectra for the
doped films are shown in FIG. 6. It can be seen that the blue
emission properties improve in the doped film compared to room
temperature solution spectra shown in FIG. 4. Here the highest
energy peak is now the highest intensity peak resulting in a more
blue emission color.
Device Examples
##STR00239##
[0160] Devices were fabricated by high vacuum (<10.sup.-7 Torr)
thermal evaporation. The anode electrode is 800 .ANG. of indium tin
oxide (ITO). The cathode was formed of 10 .ANG. of LiF followed by
1000 .ANG. of Al. All devices were 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. LG101 was purchased
from LG Chemical.
TABLE-US-00003 TABLE 2 VTE device architecture. LG101 (.ANG.) NPD
(.ANG.) Host 2 (.ANG.) EML Host 1 (.ANG.) AlQ.sub.3 (.ANG.) Device
1 100 300 50 Host1:Host2:Compound 4 (70, 25, 5%), 300 .ANG. 50 400
Device 2 100 300 50 Host1:Host2:Compound 4 (70, 25, 5%), 300 .ANG.
50 450 Device 3 100 1400 50 Host1:Host2:Compound 4 (70, 25, 5%),
300 .ANG. 50 400 Device 4 100 1400 50 Host1:Host2:Compound 4 (70,
25, 5%), 300 .ANG. 50 450 Device 5 100 300 50 Host1:Host2:Compound
12 (70, 25, 5%), 300 .ANG. 50 400 Device 6 100 300 50
Host1:Host2:Compound 13 (80, 15, 5%), 300 .ANG. 50 400 Device 7 100
300 50 Host1:Host2:Compound 14 (80, 15, 5%), 300 .ANG. 50 400
TABLE-US-00004 TABLE 3 VTE Device Data 1931 CIE At 1000 nits 20
mA/cm.sup.2 Device# X Y .lamda. max (nm) FWHM (nm) Voltage (V) LE
(Cd/A) EQE (%) PE lm/W Lo (nits) 1 0.182 0.419 502 72 4.3 38.0 16.2
27.8 6910 2 0.190 0.437 502 74 5.0 38.1 15.6 24.1 6831 3 0.180
0.373 474 58 4.7 30.3 14.2 20.4 5576 4 0.181 0.383 474 58 5.3 30.4
13.9 18.0 5563 5 0.169 0.378 474 62 5.6 17.6 8.1 9.9 3536 6 0.163
0.367 496 68 4.9 24.5 11.3 15.7 4581 7 0.160 0.334 468 66 4.9 23.8
11.7 15.3 4350
[0161] Devices 1-7 were fabricated in order to demonstrate
saturated blue emission from pyridyl-pyridine dopants in an OLED
device. All devices employ a two host emissive layer comprised of
an electron transporting Host 1 and a hole transporting Host 2.
Devices 1-4 are doped with Compound 4, which has a methyl blocking
substituent on the covalently attached pyridine ring. Device 1 was
found to have the highest efficiency, with an external quantum
efficiency of 16.2% at 1000 nits and brightness of 6910 cd/m.sup.2
at 20 mA/cm.sup.2. Compounds 12-14, used in Devices 5-7, do not
have a methyl blocking substituent, and are found to have blue
shifted emission color in the device. Of these examples, Device 7
(Compound 14) is found to have the bluest electroluminescent
spectrum with CIE coordinates of (0.160, 0.334) and a lambda max of
468 nm.
[0162] It is understood that the various embodiments described
herein are by way of example only, and are not intended to limit
the scope of the invention. For example, many of the materials and
structures described herein may be substituted with other materials
and structures without deviating from the spirit of the invention.
The present invention as claimed may therefore include variations
from the particular examples and preferred embodiments described
herein, as will be apparent to one of skill in the art. It is
understood that various theories as to why the invention works are
not intended to be limiting.
* * * * *