Efficient Electroluminescence of Two Heteroleptic Platinum Complexes with a 2-(5-Phenyl-1,3,4-oxadiazol-2-yl)phenol Ancillary Ligand

Article abstract of DOI:10.1021/acs.organomet.6b00851

Two new platinum(II) cyclometalated complexes with 2-phenylpyridine (Pt1) and 2-(4-trifluoromethyl)phenylpyridine (Pt2) as the main ligands and 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol (pop) as the electron-transporting ancillary ligand were developed. The photoluminescence quantum efficiency yields of both green Pt1 and Pt2 phosphors (λ_max 490 and 496 nm) are 20.0% and 31.0% in CH₂Cl₂ solutions, respectively. Efficient OLEDs (organic light emitting diodes) of ITO/TAPC (bis[4-(N,N-ditolylamino)phenyl]cyclohexane, 40 nm)/Pt1 or Pt2 (5 wt %):TCTA (4,4′,4″-tri(carbazoyl-9-yl)triphenylamine, 10 nm)/Pt1 or Pt2 (5 wt %):2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tris(m-pyrid-3-ylphenyl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) were fabricated. Particularly, device G1 based on complex Pt1 with 5 wt % doped concentration showed superior performance with a maximum current efficiency (η_max,c) of 55.6 cd A^-1, a maximum power efficiency (η_max,p) of 52.2 lm W^-1, and a maximum external quantum efficiency (EQE_max) of 18.0%. Device G2 with the Pt2 emitter displayed lower efficiency rolloff with η_c values of 48.5 and 43.1 cd A^-1 as the luminance reached 5000 and 10000 cd m^-2, respectively. These research results demonstrate that the Pt(II) complexes with an ancillary ligand attached with the 1,3,4-oxadiazole group have promising applications in efficient OLEDs.

Full text of DOI:10.1021/acs.organomet.6b00851

Article
pubs.acs.org/Organometallics
Efficient Electroluminescence of Two Heteroleptic Platinum
Complexes with a 2‑(5-Phenyl-1,3,4-oxadiazol-2-yl)phenol Ancillary
Ligand
Guang-Zhao Lu, Yi-Ming Jing, Hua-Bo Han, Yu-Liang Fang, and You-Xuan Zheng*
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of
Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People’s Republic of China
S
* Supporting Information
ABSTRACT: Two new platinum(II) cyclometalated complexes with 2-
phenylpyridine (Pt1) and 2-(4-trifluoromethyl)phenylpyridine (Pt2) as the
main ligands and 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol (pop) as the
electron-transporting ancillary ligand were developed. The photolumines-
cence quantum efficiency yields of both green Pt1 and Pt2 phosphors (λmax
490 and 496 nm) are 20.0% and 31.0% in CH2Cl2 solutions, respectively.
Efficient OLEDs (organic light emitting diodes) of ITO/TAPC (bis[4-(N,N-
ditolylamino)phenyl]cyclohexane, 40 nm)/Pt1 or Pt2 (5 wt %):TCTA
(4,4′,4″-tri(carbazoyl-9-yl)triphenylamine, 10 nm)/Pt1 or Pt2 (5 wt
%):2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB
(1,3,5-tris(m-pyrid-3-ylphenyl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm)
were fabricated. Particularly, device G1 based on complex Pt1 with 5 wt %
doped concentration showed superior performance with a maximum current
efficiency (ηmax,c) of 55.6 cd A−1, a maximum power efficiency (ηmax,p) of 52.2 lm W−1, and a maximum external quantum
efficiency (EQEmax) of 18.0%. Device G2 with the Pt2 emitter displayed lower efficiency rolloff with ηc values of 48.5 and 43.1 cd
A−1 as the luminance reached 5000 and 10000 cd m−2, respectively. These research results demonstrate that the Pt(II) complexes
with an ancillary ligand attached with the 1,3,4-oxadiazole group have promising applications in efficient OLEDs.
good electron-injecting and -transporting ability.7 Over the past
few years, in order to enhance the electron-transporting ability
of Ir(III) complexes and improve the device efficiency, several
INTRODUCTION
■
Because of the spin−orbit coupling (SOC),1 transition-metal
complexes have been identified as potential emitters for
research groups have introduced the 1,3,4-oxadiazole deriva-
POLEDs (phosphorescent organic light emitting diodes),
tives into the main ligands.8 As far as we know, Pt(II)
which possess excellent photophysical properties. Especially,
much attention has been attracted by iridium2 and platinum3
complexes using ancillary ligands with 1,3,4-oxadiazole
derivatives have been rarely reported for efficient OLEDs. On
this basis, as is shown in Scheme 1, two new heteroleptic Pt(II)
complexes containing the main ligands 2-phenylpyridine (ppy)
and 2-(4-trifluoromethylphenyl)pyridine (4-tfmppy) and the
ancillary ligand 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol (pop)
were synthesized. The trifluoromethyl moiety at the 4-position
on the phenyl does not change the emission color of the
complexes on the basis of ppy, but the device performances
were improved greatly.6a−d Here, the synthetic process,
structure identification, thermal stability, photophysical proper-
ties, theoretical calculations, and OLED performances of both
Pt(II) complexes are described in detail.
complexes in recent years owing to their outstanding
photophysical properties.4 Extensive studies of the photo-
physical properties of these complexes by modifications of the
phenylpyridine ligands have been carried out by introducing
electron-withdrawing or electron-donating units to the phenyl
or pyridine rings. Furthermore, the good electron-transporting
properties of these emitters are also important for efficient
OLEDs in view of the better hole-transporting ability of the
hole-transporting material in comparison to the electron-
transporting ability of the electron-transporting material. Many
research groups have reported efficient devices based on
complexes containing cyclometalated and ancillary ligands with
nitrogen, oxygen, phosphorus, sulfur, and boron heterocyclic
derivatives for better electron mobility.5 For example, some
high-performance phosphorescent OLEDs were reported by
our group employing Ir(III) emitters with tetraphenylimidodi-
phosphinate derivatives as ancillary ligands, which have PO
units.6
EXPERIMENTAL SECTION
■
The general information on the preparation and measurements of the
materials, procedures and methods of the single-crystal analysis, and
Furthermore, 1,3,4-oxadiazole derivatives also have been
studied extensively in optoelectronic materials because of their
Received: November 10, 2016
© XXXX American Chemical Society
A
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Scheme 1. Synthetic Routes of Ligands and Complexes Pt1 and Pt2
OLED fabrication and measurements are included in the Supporting
Information.
General Syntheses of Complexes Pt1 and Pt2. K2PtCl4 (0.415
g, 1 mmol) and 1.2 equiv of the cyclometalated ligand (1.2 mmol)
were added to a 2-ethoxyethanol and water mixture. Then, the
solution was heated for 16 h at 80 °C. After the addition of water, the
precipitated yellow greenish powder was filtered and reacted with
K(pop) without further purification for another 16 h at 80 °C. After it
was cooled, the solution was concentrated and the resulting residue
was purified by silica gel column chromatography (CH2Cl2/petroleum
ether 1/2 (v/v)); vacuum sublimation gave yellow crystals.
Pt1: yield 40.0%. 1H NMR (500 MHz, CDCl3): δ 9.44 (d, J = 5.58
Hz, 1H), 8.67 (d, J = 7.85 Hz, 1H), 8.22−8.25 (m, 2H), 8.06 (d, J =
6.03 Hz, 2H), 7.96 (d, J = 9.71 Hz, 1H), 7.72 (d, J = 3.93 Hz, 3H),
7.65 (s, 1H), 7.46 (d, J = 6.85 Hz, 2H), 7.20 (d, J = 8.15 Hz, 1H), 7.09
(dd, J = 7.94, 13.63 Hz, 2H), 6.70 (t, J = 7.26 Hz, 1H). HR-MS
(electrospray, m/z): calcd for C25H17N3O2Pt [M + H]+ 587.1047,
found 587.1050. Anal. Calcd for C25H17N3O2Pt: C, 51.20; H, 2.92; N,
7.16. Found: C, 51.12; H, 2.84; N, 7.06%.
Pt2: yield 45.0%. 1H NMR (500 MHz, CDCl3): δ 9.55 (d, J = 6.20
Hz, 1H), 9.22 (s, 1H), 8.20 (dd, J = 2.45, 7.33 Hz, 2H), 7.87−7.83 (m,
2H), 7.72 (d, J = 7.93 Hz, 1H), 7.64−7.57 (m, 4H), 7.38 (ddd, J =
6.95 Hz, 3H), 7.10 (d, J = 8.59 Hz, 1H), 6.68 (t, J = 7.39 Hz, 1H). HR-
MS (electrospray, m/z): calcd for C26H16F3N3O2Pt [M + H]+
655.0921, found 655.0917. Anal. Calcd for C26H16F3N3O2Pt: C,
47.71; H, 2.46; N, 6.42. Found: C, 47.48; H, 2.41; N, 6.33%.
Figure 1. ORTEP diagram of Pt2 (CCDC No. 1495292) with the
atom-numbering schemes. Hydrogen atoms are omitted for clarity.
Ellipsoids are drawn at the 50% probability level.
the complex are in good agreement with the few previously
published structures of this type.9 Additionally, Pt2 exhibits a
different packing in the crystal (Figure S1 in the Supporting
Information), in which the molecules are stacked in a head-to-
tail fashion. Due to the attachment of the bulky trifluoromethyl,
the closest Pt···Pt distance (6.22 Å) is outside the range of 2.7−
3.5 Å for any metallophilic interaction.3d Furthermore, the
presence of the bulky groups effectively inhibits intermolecular
π−π stacking interactions, in which there is a separation of
about 3.36 Å between the only partially overlapping ppy and
pop rings, suggesting only weak π−π interactions between the
Pt2 units.
Thermal Stability. To fabricate stable OLEDs, the thermal
stability of the emitters is also very important. Therefore,
differential scanning calorimetry (DSC) and thermogravimetric
(TG) measurements were applied to characterize the thermal
properties of both platinum complexes under a nitrogen
atmosphere. As observed from Figure 2a, the DSC curves give
the melting points of Pt1 and Pt2 as 295 and 311 °C,
respectively. TG curves suggest that the decomposition
temperatures of Pt1 and Pt2 (5% loss of weight) are as high
as 347 and 358 °C, respectively, indicating that the melting
RESULTS AND DISCUSSION
■
Preparation and Characterization of Compounds. The
platinum complexes were synthesized by the reaction of
[(C∧N)Pt(μ-Cl)]2 chloride-bridged dimers with the pop
potassium salt (K(pop)) (Scheme 1). The crude products
Pt1 and Pt2 were purified by silica chromatography and further
refined by sublimation under 10−7 Torr vacuum. Both Pt(II)
complexes were identified by elemental analyses, 1H NMR, and
HR-MS.
X-ray Crystallographic Analysis. Figure 1 shows the
ORTEP (Oak Ridge thermal ellipsoid plot) diagram of the Pt2
single crystal. The crystallographic data and the selected bond
lengths/angles are summarized in Tables S1 and S2 in the
Supporting Information, respectively. The Pt2−C1 bond length
is 1.997 Å, which is slightly shorter than the Pt2−N1 and Pt2−
N2 bond lengths (2.010 and 2.000 Å, respectively). The Pt2−
O1 bond length is 2.068 Å. The average dihedral angle among
planes [C1−Pt2−N1], [N1−Pt2−O1], and [O1−Pt2−N2] is
179.06°, which suggests that they maintain a good square-
planar coordination geometry. The bond lengths and angles of
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Figure 2. DSC (a) and TG (b) curves of complexes Pt1 and Pt2.
Figure 3. UV−vis absorption (a) and emission (b) spectra of complexes Pt1 and Pt2 in degassed dichloromethane (5 × 10−5 M) at room
temperature.
Table 1. Photophysical Data of Pt1 and Pt2 in CH2Cl2 Solution
a
b
b
b
c
d
compd
Td (°C)
absorption λ (nm)
emission λmax (nm), 298 K
τ298 K (μs)
ΦP (%)
HOMO/LUMO (eV)
Pt1
Pt2
347
358
305/394/452
307/391/460
490/510
1.7
1.8
20.0
31.0
−5.63/−2.84
−5.67/−2.96
496/528
c
a
b
Decomposition temperature. Measured in degassed CH2Cl2;. Φ denotes emission quantum yields, calculated with fac-Ir(ppy)3 standard in
degassed CH2Cl2 solution. HOMO (eV) = −(Eox − E1/2,Fc) − 4.8; LUMO (eV) = HOMO + Eband gap
d
.
point and decomposition temperature will be improved by the
introduction of −CF3 in Pt2.
effect on the emitting properties of Pt(II) complexes because
the molecular packing can be affected by the bulky CF3
substituents on the phenyl rings of ppy and the self-quenching
behavior can be effectively inhibited by the steric protection
around the metal.10 Furthermore, the lifetimes are in the range
of microseconds for the two complexes (1.7 μs for Pt1 and 1.8
μs for Pt2, respectively) (Figure S2 in the Supporting
Information). The short lifetimes would improve the spin-
state mixing and suppress the exciton annihilation.
Theoretical Calculations. To investigate the electronic
states and orbital distributions, density functional theory
(DFT) calculations for both Pt(II) complexes employing
Gaussian09 software with the B3LYP functional were
conducted.11 The 6-31G(d,p) basis set was used for C, H, N,
O, and F atoms, while the LanL2DZ basis set was employed for
Pt atoms.12 The CH2Cl2 effect was taken into consideration by
using the polarizable continuum model (C-PCM) conductor.13
Electronic Spectroscopy. Figure 3 shows the absorption
and photoluminescence (PL) spectra of Pt1 and Pt2 in CH2Cl2
at room temperature, and Table 1 collects the photophysical
data of both complexes. The intense absorption bands below
350 nm in Figure 3a should belong to the π → π* transitions of
the cyclometalated main ligand and ancillary ligand. However,
the lower-energy absorption bands (350−460 nm) can be
1
3
assigned to the mixed MLCT and MLCT (metal-to-ligand
charge-transfer) states or LLCT (ligand-to-ligand charge-
transfer) transition through strong spin−orbit coupling of
platinum atoms.10 In comparison with complex Pt1, which has
a peak emission at 490 nm with a weak band (510 nm) (Figure
3b), complex Pt2 shows a red-shifted emission peak at 496 nm
with a shoulder emission (528 nm). Additionally, the PL
quantum yields for Pt1 and Pt2 are 20.0% and 31.0%,
respectively. The results suggest that the −CF3 moiety has an
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The optimized HOMO/LUMO structures of both complexes
are clearly shown in Figure 4.
negligible contribution from Pt d orbitals (0.99%) and the main
ligand (6.62%). However, for Pt2, the LUMO is distributed
mainly over the π orbitals of the main ligand (88.24%) and
rarely located on Pt d orbitals (4.97%), which illustrates that
the attachment of the −CF3 group with high electron affinity
on the phenyl rings significantly affects the unoccupied frontier
molecular orbitals. In addition, the results fit well with the
calculated LUMO energy levels.
OLED Performances. To study the electroluminescence
performances of complexes Pt1 and Pt2, the OLEDs of ITO/
TAPC (bis[4-(N,N-ditolylamino)phenyl]cyclohexane, 40 nm)/
Pt1 or Pt2 (5 wt %):TCTA (4,4′,4″-tris(carbazol-9-yl)-
triphenylamine, 10 nm)/Pt1 or Pt2 (5 wt %):2,6DCzPPy
(2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine, 10 nm)/
TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 40 nm)/
LiF (1 nm)/Al (100 nm) were fabricated (Scheme 2). The
devices using Pt1 and Pt2 emitters are denoted G1 and G2,
respectively. Due to its high hole mobility (1 × 10−2 cm2 V−1
s−1) and high-lying LUMO level (−1.8 eV), TAPC was used as
both hole-transporting and electron-blocking layer. However,
TmPyPB was applied as both hole-blocking and electron-
transporting layer because of its low-lying HOMO level (−6.7
eV) and high electron mobility (1 × 10−3 cm2 V−1 s−1).14 The
bipolar material 2,6DCzPPy and p-type material TCTA were
used as double-emitting host materials, respectively. Figure 5
displays the EL spectra, luminance (L) versus voltage (V),
current efficiency (ηc) versus luminance, and power efficiency
(ηp) versus luminance characteristics of the optimized devices.
In addition, Table 2 collects most key EL data.
Figure 4. Isodensity surface plots and HOMO/LUMO orbital levels of
Pt1 and Pt2: black line, calculated values; red line, experimental values.
With regard to energy levels and compositions, electronic
structures of HOMOs are wholly different from those of
LUMOs in both complexes. The HOMOs of both Pt1 and Pt2
correspond to an admixture of pop ligand (62.0−68.0%) and Pt
d orbitals (22.4−25.2%) with minor contribution from the ppy
substituents (9.4−12.7%). However, the LUMOs are quite
different from the HOMOs of Pt1 and Pt2 concerning the
composition. For Pt1, the electron cloud density of the LUMO
is mainly distributed over the pop ligand (92.34%) with
In theory, the gradually changed HOMO energy levels of
TAPC (−5.5 eV), TCTA (−5.7 eV), and 2,6DCzPPy (−6.1
eV) are beneficial for the hole injection and transport. Similarly,
these levels are also beneficial for the injection and transport of
electrons owing to the gradually changed LUMO energy levels
a
Scheme 2. Energy Level Diagram of HOMO and LUMO Levels of Materials Investigated and Their Chemical Molecular
Structures
a
The dotted line represents the HOMO/LUMO energy levels of dopants.
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Figure 5. Characteristics of devices with configuration ITO/TAPC (40 nm)/Pt1 or Pt2:TCTA (10 nm, 5 wt %)/Pt1 or Pt2:2,6DCzPPy (10 nm, 5
wt %)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm): (a) EL spectra; (b) L−V curves; (c) ηc−L curves; (d) ηp−L curves for G1 and G2.
Table 2. Key EL Data of Devices G1 and G2
a
b
c
d
Vturn‑on
(V)
Lmax (voltage)
ηp,max (voltage) (lm W−1
ηc,max(voltage)
e
f
device
(cd m−2 (V))
(V))
(cd A−1 (V))
ηc,5000,10000 (cd A−1
)
EQEmax (%)
CIE (x,y)
G1
G2
3.4
3.1
31494 (8.7)
52435 (9.1)
52.2 (3.7)
42.5 (4.4)
55.6 (3.7)
50.5 (4.2)
49.2/36.5
18.0
17.2
(0.24,0.59)
(0.32,0.60)
48.5/43.1
a
b
c
Vturn‑on denotes the turn-on voltage recorded at a luminance of 1 cd/m2. Lmax denotes the maximum luminance. ηp,max denotes the maximum
d
e
power efficiency. ηc,max denotes the maximum current efficiency. ηc,5000 denotes the current efficiency at 5000 cd/m2, and ηc,10000 denotes the
f
current efficiency at 10000 cd/m2. EQEmax denotes the maximum external quantum efficiency.
of TmPyPB (−2.7 eV), 2,6DCzPPy (−2.6 eV), and TCTA
(−2.4 eV). Thus, holes and electrons will be distributed in a
more balanced device and the exciton recombination zone is
expected to be broadened. Furthermore, the HOMO energy
level of 2,6DCzPPy is 0.6 eV higher than that of TmPyPB and
the LUMO energy level of TCTA is 0.6 eV lower than that of
TAPC, which will result in excitons (hole−electron pair) well
conformed within emissive layers and triplet exciton quenching
effectively avoided. In addition, because the Pt1 or Pt2 HOMO
and LUMO levels (−5.63/−5.67 eV and −2.84/−2.96 eV,
respectively) are all within those of 2,6DCzPPy and TCTA, it is
conceivable that carrier (holes and electrons) trapping is the
dominant mechanism of electroluminescence in G1 and G2
devices. Additionally, the reverse energy transferred from
dopant to host materials can be effectively avoided because of
the higher triplet energies of 2,6DCzPPy (2.71 eV) and TCTA
(2.83 eV) in comparison to those of Pt1 or Pt2 (2.53/2.50 eV).
In these devices, the optimized Pt(II) complexes with 5 wt %
doped concentration in TCTA and 2,6DCzPPy, respectively,
were used as the two emitting layers. Usually, the carrier
recombination region can be broadened by the adoption of
double emitting layers, which can improve the hole−electron
utilization ratio, causing the increased EL performance and
impressed efficiency roll-off. The EL emissions of devices G1
and G2 peak at 495/523 and 507/534 nm (Figure 5a) with
Commission Internationale de l’Eclairage (CIE) coordinates of
(0.24, 0.59) and (0.32, 0.60), respectively, are very similar to
the PL spectra of the complexes measured in CH2Cl2, which
indicates that the EL derives from the triplet excited states of
the complexes. Furthermore, the disappearance of the TCTA
and 2,6DCzPPy emission suggests that almost complete energy
transferred from the hosts to the emitter in the device.
Both OLEDs display good EL performances with low turn-
on voltages (Vturn‑on) (G1, 3.4 V; G2, 3.1 V) and high maximum
brightness (G1, 31494 cd m−2; G2, 52435 cd m−2). The ηc,max
(maximum current efficiency), EQEmax (maximum external
quantum efficiency), and ηp,max (maximum power efficiency)
values of G1 and G2 are 55.6/50.5 cd A−1, 18.0/17.2%, and
52.2/42.5 lm W−1, respectively. The performances are close to
those with similar Pt(II) complexes,3 but are still lower than
those of present state of the art OLEDs using green Pt(II)
complexes containing a single, tetradentate, robust chelating
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ligand, which always show high EQE values of above 25%.15
Furthermore, both devices demonstrate low-efficiency rolloff.
For device G1, the current efficiencies (ηc) can still be obtained
as 49.2 and 36.5 cd A−1 when the luminance reaches 5000 and
10000 cd m−2, respectively. The G2 device shows even lower
efficiency rolloff with current efficiencies of 48.5 cd A−1 at the
brightness of 5000 cd m−2 and 43.1 cd A−1 at that of 10000 cd
m−2, respectively.
lifetime curves and cyclic voltammograms of Pt1 and Pt2
(PDF)
Crystallographic data for Pt2 (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail for Y.-X.Z.: yxzheng@nju.edu.cn.
ORCID
■
The good device properties may be ascribed to the following
facts. First, the electron transport ancillary ligand pop is applied
in Pt(II) complexes. Because the hole mobility of TAPC (1 ×
10−2 cm2 V−1 s−1) is much higher than the electron mobility of
the TmPyPB (1 × 10−3 cm2 V−1 s−1) and the high LUMO
energy barrier between TmPyPB and 2,6DczPPy, the excitons
are expected to accumulated near the interface of (Pt
complexes (5 wt %):2,6DCzPPy)/TmPyPB, which is inclined
to lead to the severe triplet−polaron annihilation (TPA),
triplet−triplet annihilation (TTA), high-efficiency rolloff.14,16
Thus, the enhanced electron-transporting ability of the dopants
can increase the excitation lifetime of the OLEDs. In this work,
the −CF3 group and the 1,3,4-oxadiazole unit are introduced
into the framework of the main ligand, which can lower the
LUMO energy levels and benefit the electron transport
properties. Though the maximum efficiency of G2 is lower
than that of G1, the introduction of the CF3 unit in the Pt(II)
complex results in low-efficiency rolloff. Second, the stepwise
changes in HOMO/LUMO energy level of all layers is
beneficial for the injection and transport of both holes and
electrons, which will result in high-performance green OLEDs.
Finally, the broad recombination zone, good balanced
distribution, and improved trapping of carriers caused by
double light-emitting layers are adopted in this device, which
showed higher current efficiency, higher brightness, and slower
efficiency rolloff.17
You-Xuan Zheng: 0000-0002-1795-2492
Notes
The authors declare no competing financial interest.
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CONCLUSION
■
In conclusion, two green cyclometalated Pt(II) complexes Pt1
and Pt2 using 2-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol ancillary
ligand have been successfully prepared with photoluminescence
quantum efficiency yields of 20.0% and 31.0% in CH2Cl2 at
room temperature. EL devices with ITO/TAPC (40 nm)/Pt1
or Pt2 (5 wt %):TCTA (10 nm)/Pt1 or Pt2 (5 wt
%):2,6DCzPPy (10 nm)/TmPyPB(40 nm)/LiF (1 nm)/Al
(100 nm) displayed promising performances with a ηc,max value
of 55.6 cd A−1, a maximum EQE value of 18.0%, and a peak ηp
value of 52.2 lm W−1. This study suggests that Pt(II) complexes
containing the electron-transporting pop ancillary ligand have
potential applications in OLEDs.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00851.
Details of materials and measurements, synthesis details
of 2-[4-(trifluoromethyl)phenyl]pyridine and 2-(5-phe-
nyl-1,3,4-oxadiazol-2-yl)-phenol ligands, details of X-ray
crystallography and electrochemical tests, procedures and
methods of OLED fabrication and measurements,
crystallographic data, selected bond lengths and angles,
and the crystal-packing diagram of Pt2, and selected
F
DOI: 10.1021/acs.organomet.6b00851
Organometallics XXXX, XXX, XXX−XXX

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