Photo- and electro-luminescence of four cuprous complexes with sterically demanding and hole transmitting diimine ligands

Article abstract of DOI:10.1039/c5dt01108f

Four new cuprous complexes (1-4) containing bisphosphine and triazolylpyridine donors have been prepared in order to examine the effects of the methyl group and the carbazole appendage on photo- and electro-luminescence (PL and EL) properties. Because of

Full text of DOI:10.1039/c5dt01108f

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Photo- and Electro-luminescence of four cuprous complexes with
Sterically Demanding and Hole Transmitting Diimine Ligands
a,b,c
a,b
c
a,b
*,a,b
*,a,b
Qing Zhang, Xu-Lin Chen, Jun Chen, Xiao-Yuan Wu, Rongmin Yu,
and Can-Zhong Lu
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
Four new cuprous complexes (1–4) containing bisphosphine and triazolylpyridine donors have been
prepared in order to examine the effect of methyl group and carbazole appendage on photoꢀ and electroꢀ
luminescent (PL and EL) properties. Because of their additional steric hindrance from methyl substituent
group at 6ꢀpyridine ring, complexes 3 and 4, compared with the methyl group free compounds 1 and 2,
expectedly exhibit largely spectral blue shift and higher intensity both in PL and EL. Meanwhile, the
carbazole appendage of complexes 2 and 4 do not significantly altering their PL performances in
comparison with 1 and 3, respectively, but have a modest increase in their EL efficiency in multilayer
organic lightꢀemitting diodes (OLEDs). Moreover, the OLED with 4 as light emitting material has the
1
0
highest current efficiency (CEmax) of 27.2 cd/A and the maximum external quantum efficiency (EQEmax
)
1
5
of 8.7%.
Introduction
Multilayer OLEDs have attracted considerable attention for
decades due to their huge application potentials in flatꢀpanel
1
ꢀ3
displays and lighting devices . One of the most important
components is the luminescent dopant which dramatically
2
2
3
3
4
4
0
5
0
5
0
5
4ꢀ6
determines the emission colour and the efficiency of the device
.
Therefore, strongly emissive materials which harness both triplet
and singlet excitons in device operation are indispensable in the
7
fabrication of highly efficient OLEDs . There are two types of
8
materials can fully utilize the excitons: phosphorescent materials
9
, 10
and thermallyꢀactivated delayed fluorescent (TADF) materials
The most studied and used phosphors for OLEDs to date are
.
Fig. 1 Molecular structures of 1–4.
1
1ꢀ13
emissive phosphorescent complexes of iridium
and other
. However, the natural resources of
these metals are very limited, and they are usually highly
1
4, 15
heavy transition metals
hindrance can effectively suppress their geometry distortion
which suppress nonꢀradiative deactivation process in the exited
expensive. Under this situation, it is demanding to find alternative 50 state. The other is the higher utilization rate of excitons (caused
materials with reliable resources and affordable cost. The
possible solutions to lower the cost of the dopants are the
application of environment benign and cost advantage TADF
by charge recombination and available to light) which can be
facilitated through optimizing energy levels between charge
transfer layers. It is noticed that introduction of electroꢀ donating
or withdrawing substituent groups at the ligands, because of their
16
17
materials which based on copper and carbon .
With promising electroluminescent properties, the emissive Cu(I) 55 hole injection or electron transmission behaviors, partly improve
32ꢀ34
complexes have caused much attention and have been extensively
the efficiency of the devices
. The incorporation of electron
5
, 18ꢀ21
studied as dopants for use in OLEDs
. Over the last decade,
rich carbazole group into the complexes can boost the hole
injection and transportation properties of OLEDs. This is the
reason why compounds containing carbazole group are the most
many cuprous TADF materials exhibiting excellent
electroluminescence performance comparable to the iridium
2
2ꢀ27
counterparts have been found
. As dopants, there are two 60 studied holeꢀtransfer materials and are widely used as host
35, 36
requirements needed to be satisfied to have highly efficient
OLEDs. One is the highly photoluminescence efficiency, which,
for cuprous complex, is mainly determined by the steric effect of
materials for dopants immobilization
. For the solution
processed OLEDs, the holeꢀtransfer layers were difficult to be
optimized because the requirements for insoluble solvents among
2
8ꢀ31
4
ligands
. For them, the ligands with strong enough steric
the various layers . Recently, the carbazole group had been
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DOI: 10.1039/C5DT01108F
appended to noble metal complexes and the efficiency of the 25 The diimine ligands 2ꢀ(5ꢀphenylꢀ2ꢀphenylꢀ2Hꢀ1,2,4ꢀtriazolꢀ3ꢀ
solution processed OLEDs based on these complexes had been
yl)pyridine (phtz), 2ꢀ(5ꢀ(4ꢀcarbazolyl)phenylꢀ2ꢀphenylꢀ2Hꢀ1,2,4ꢀ
triazolꢀ3ꢀyl)pyridine (phtzcz), 2ꢀ(5ꢀphenylꢀ2ꢀphenylꢀ2Hꢀ1,2,4ꢀ
37, 38
modestly improved
. For the OLEDs using cationic cuprous
complexes as dopants, because these complexes could hardly be
sublimated, almost all of them were prepared by solution process.
Therefore, coupling the carbazole groups to them potentially 30 methylpyridine (mphtzcz) were synthesized with similar
triazolꢀ3ꢀyl)ꢀ6ꢀmethylpyridine
carbazolyl)phenylꢀ2ꢀphenylꢀ2Hꢀ1,2,4ꢀtriazolꢀ3ꢀyl)ꢀ6ꢀ
(mphtz),
2ꢀ(5ꢀ(4ꢀ
5
0
5
0
41
facilitates the efficiency of the OLEDs. However, the reports
about carbazole groups which are coupled to emissive Cu(I)
procedures to the literature . The cationic cuprous complexes
[Cu(phtz)(POP)]BF4 (1), [Cu(phtzcz)(POP)]BF4, (2),
[Cu(mphtz)(POP)]BF (3) and [Cu(mphtzcz)(POP)]BF (4) were
1
8, 39, 40
complexes are very rare
In this work, four novel mononuclear cationic Cu(I)
complexes ( ) featuring functional 2ꢀ(5ꢀphenylꢀ2Hꢀ1,2,4ꢀ 35 and equivalent of corresponding diimine ligand. Spectroscopic
triazolꢀ3ꢀyl)pyridine had been designed and synthesized (Fig. 1)
Their photoꢀ and electroꢀluminescent behaviours have been
carefully studied. For and , methyl group was introduced to
pyridine ring to block the geometry distortion in the excited
.
4
4
1
1
2
obtained from the reaction of the precursors of [Cu(POP)]BF4
1–4
.
pure products of these complexes were obtained by layering
diethyl ether on the top of the CH Cl solution of them and drying
at 200 ºC under nitrogen. These compounds have high stability
in the air no matter in the solid state or in the solutions of
2
2
3
4
state which, expectedly, lead to largely emission spectral blue 40 common organic solvents, such as methylene chloride and
shift and improve their PL and EL efficiency. Moreover,
with carbazole appendage show a modest increase (about 1.3
times) in device efficiency compared to and , respectively.
The device based on show high efficiency with CEmax of 27.2
2
and
chloroform, presumably due to the bulky and ridge coordination
1
4
environment of the cuprous ion. They were characterized by H
31
1
3
NMR, P NMR, thermal analysis and elemental analysis.
4
The single crystals suitable for Xꢀray diffraction were prepared
cd/A and EQEmax of 8.7% while 3 had the CEmax of 21.4 cd/A and 45 by slowly diffusion diethyl ether to the CH Cl solution of these
2
2
EQEmax of 6.7%.
complexes. The ORTEP diagrams of them are displayed in Fig. 2.
Highly distorted tetrahedral coordination for these cuprous
complexes were observed with N–Cu–N and P–Cu–P angles in
the range of 79.27º–80.70º and 114.12–118.27º (similar to values
Results and discussion
Synthesis and characterization
50
Fig. 2 ORTEP diagrams of 1–4 with thermal ellipsoids at 30% probability level. Solvent molecules and hydrogen have been omitted for clarity. Selected
bond angles are N3–Cu1–N4 79.27(16), 79.60(11), 80.70(12) and 80.62(15) for 1–4 respectively; P2-Cu1-P3 114.12(6), 114.18(4), 116.29(4) and
1
18.27(5) for 1–4 respectively.
2
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estimate the energy gap (ꢀE ) between HOMO and LUMO of
g
complex. As shown in inset of Fig. 3, complexes 1 and 2 have the
same ꢀE (2.77ev), while 3 and 4 have the same ꢀE (2.85ev),
g
g
suggesting the methyl moiety at pyridine ring increases the
energy gap of the frontier orbitals and the carbazole appendage
have negligible charge contribution to these orbitals (Table S4).
30
Moreover, the larger ꢀE values for 3 and 4, compared to 1 and 2,
g
respectively, potentially suppress the thermal population
2 2
Fig. 3 Absorption spectra in CH Cl of 1 (red), 2 (grey), 3 (green) and 4
(blue). The inset is the onsets of absorption spectra.
3
9, 42, 43
of previous reports
). Obviously, the methyl unit in the
5
pyridine ring act as a steric hindrance group because of their
enlarged N3–Cu–N4 and P2–Cu–P3 angles (> 1º) for 3 and 4
compared to 1 and 2, which probably minimize the distortion that
occurs in the excited state. Meanwhile, the steric influence of the
substituent moiety on N1 seems negligible.
1
0
Photophysical properties
Absorption spectra in dichloromethane for complexes 1–4 are
+
shown in Figure 3. As typical four coordinated Cu(N,N)(P,P)
4
2,
complexes with a diimine and a biphosphine chelating ligands
44
,
the absorption bands for them in the UV region (< 350 nm) are
dominated by the spin allowed intraligand πꢀπ transitions of the
*
1
2
2
5
0
5
diimine ligands and the POP ligands. At longer wavelength, from
3
50 nm to 420 nm, ligandꢀligand charge transfer and metalꢀligand
chargeꢀtransfer (MLCT) states are usually attributed. The broad
1
band centered at about 385 nm for 1 and 3 are typical for MLCT
*
from d orbitals on the copper metal center to empty π orbitals
localized on the diimine ligands. For compounds 2 and 4, the
transitions below 350 nm are more intense in comparison with the
bands of compounds 1 and 3 which are caused by the intraligand
39
charge transitions of carbazole appendage at diimine ligand .
The onset wavelength of absorption spectrum is usually used to
35
Fig. 4 (a) Emission spectra of 1–4 in CH
2 2
Cl . (b) Emission spectra of 1–4 in
PMMA.
Table 1 Photophysical properties of 1–4 in the solvent and PMMA film.
Solvent
PMMA film
−
3
−1
−1
a
b
a
b
-1
-1
λ
abs(nm) (ε×10 M cm )
λ
em(nm)
601
τ
ave (μs)
Φ (%)
λ
em(nm)
532
τ
ave (μs)
Φ (%)
k
r
(s )
k
nr (s )
4
5
1
284(26), 374(3.3)
1.7
3
7.7
16
2.1×10
1.1×10
4
4
5
4
2
3
291(53), 337(21), 374(6.6)
284(31), 374(3.3)
601
567
1.9
1.4
5
537
516
6.3
7.5
14
48
2.2×10
6.4×10
1.4×10
6.9×10
19
4
4
4
291(56), 337(22), 377(5.9)
569
1.6
16
517
6.8
37
5.4×10
9.3×10
a
b
Emission decay time (monoexponential fit, error ±5%). photoluminescence quantum yield (error ± 7%) at 298 K;.
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4
5
radiationless transition more effectively (energy gap law ) and
lead to emission spectral blue shift.
Independent of the matrix, their emission spectra are broad and
unstructured, which is consistent with the charge transfer nature
35
At room temperature, all complexes were found to be strongly 10 of the emission . The photoluminescence quantum yields (ΦPL)
emissive. Their photophysical properties were studied in solid
state, in CH Cl and in PMMA film. Their spectra in the solid
and calculated radiative decay rate (k ) and the nonradiative decay
r
5
rate (k ) from Φ and τave based on the solvent and thin film are
2
2
nr
PL
state are shown in supporting information (Fig. S4 and table S3)
and the spectra in the solvent and thin film are shown in Fig. 4.
listed in table 1. For all of these complexes, blueꢀshifting and
increasing quantum yield of the emissions were observed as the
15
Fig. 5 (a) Device configuration and relate molecular structures of PYD2 and DPEPO. (b) Electroluminescence spectra of devices A–D containing 1–4
respectively. (c), (d) Plots of Current density and luminance vs voltage for devices. (e), (f) Plots of CE and EQE vs luminescence for devices.
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Table 2 Electroluminescence characteristics of OLEDs.
a
a
a
b
Device
Dopant
V
turn-on (V)
7.1
Luminance (cd/A)
CE (cd/A)
EQE (%)
λmax (nm)
A
B
C
D
1
2
3
4
1750
1850
2339
2893
10.7
14.1
21.4
27.1
3.5
537 (0.31, 0.41)
546 (0.32, 0.51)
526 (0.25, 0.45)
516 (0.24, 0.42)
7.8
4.6
7.3
6.7
7.3
8.7
a
Maximum values of the devices. b Data were collected at 10 V; CIE coordinates shown in parentheses.
.
matrix rigidity increases from the solvent to the thin film. This
recombination and confinement in the emitting layer.
observation is common for emissive cuprous complexes because 45 The EL performances of these complexes are in consistent with
5
of the existence of geometric rearrangement from the tetrahedralꢀ
their PL performances which are mainly determined by the
coordination steric effect of the ligands too. As aforementioned,
their geometry distortion were suppressed by the methyl group at
pyrindine ring, thus complexes 3 and 4 show higher device
1
0
9
like ground state (d ) to the flattened excited state (d ) upon
4
6
MLCT excitation . With an increasing of the matrix rigidity, the
freedom for changes of the molecular geometries upon MLCT
excitation is decreased, and the aboveꢀmentioned distortions can 50 efficiency with excellent CEmax of 21.4 cd/A and 27.2 cd/A,
4
7
1
1
2
0
5
0
be suppressed
.
EQEmax of 6.7% and 8.8%, respectively, than 1 (10.7 cd/A, 3.5%)
and 2 (14.1 cd/A, 4.6%). According to this, the EQEmax of the
devices based on complexes 2 and 4 with carbazole appendage
approximate 1.3 times higher than that of 1 and 3 respectively. It
Herein, the discussions focus on their emission properties in the
thin film because these properties are similar to that in devices.
As shown in Table 1, in the PMMA film, complex 3 has the
highest ΦPL and k . The k for 1 is smaller than that for 3 by about 55 is noteworthy mention that 2 and 4 show slightly poorer PL
r
r
two times, while the knr for 1 is larger than that for 3 by about
60%. Similar results were found for complexes 2 and 4. The
larger k for the complexes 3 and 4 which lead to higher Φ of
them ascribe to the methyl group at pyridine ring that act as steric
hindrance group effectively suppressing the geometry distortion 60 which slightly facilitate device efficiency.
efficiency both in the PMMA film and solution than 1 and 3,
respectively. Taken together, these data suggest that the carbazole
group for this series of complexes benefits the utilization of the
excitons that caused by charge recombination in device operation
1
r
PL
in the excited state. Furthermore, the emission spectra of 1 and 2
are very similar, 3 and 4 are similar too. It seems to suggest that
the carbazole groups on N1, unlike at the oꢀposition of
coordination nitrogen , have limited influence on the steric and
electronic character of these complexes.
Conclusions
3
9
In this work, we designed four new emissive cuprous complexes
containing functional 2ꢀ(5ꢀPhenylꢀ2Hꢀ1,2,4ꢀtriazolꢀ3ꢀyl)pyridine
diimine ligands. Complexes 3 and 4 with steric methyl group at
pyridine ring expectedly show largely emission spectral blueꢀshift
and improved efficiency both in PL and EL than 1 and 2 which
further convince the importance of space steric hindrance for
emitting properties. Meanwhile, complexes 2 and 4 with
carbazole appendage show limited spectral variation and slightly
higher device efficiency as compared to 1 and 3, respectively.
The results suggest that the device efficiency based on this kind
of complexes are also mainly determined by the steric effect of
substituent group and can be further elevated by the electron rich
carbazole group while it act as hole carrier.
2
5
Electroluminescence performances
6
5
All of these complexes were chosen to fabricate OLED (A, B, C,
D) with the configuration: ITO/PEDOT:PSS (40 nm)/5 wt% of 1,
2
, 3 or 4:PYD2 (2,6ꢀbis(Nꢀcarbazolyl)pyridine, 30 nm)/DPEPO
bis[2ꢀ(diꢀ(phenyl)phosphino)ꢀphenyl]ether oxide, 50 nm)/LiF
(0.7 nm)/Al (100 nm) (where ITO is indium tinoxide,
PEDOT:PSS is poly (3, 4ꢀethylenedioxythiophene)–
(
70
3
3
4
0
5
0
poly(styrenesulfonic acid). In this configuration, PYD2 and
DPEPO act as hole transmission and electron transmission
materials, respectively. The HOMOs of these complexes were
estimated from onset of their positive potential cyclic
voltammetry curves while the values of LUMOs were calculated
75
Experimental
by adding ꢀE to the values of HOMOs. The holeꢀinjection and
g
General procedures
emitting layers were prepared by spin coating, and the remaining
layers were deposited by thermal evaporation. The configuration
and the EL characteristics of OLED are shown in Fig. 5 and table
Reagents and solvents were purchased from commercial sources
and used without further purification. All reactions were
performed under N2 atmosphere using standard Schlenk
techniques unless specified. The complex [Cu(CH CN) ]BF and
2
. The EL spectra of these devices are in good agreement with
80
3
4
4
their spectra in the PMMA film. Additionally, there are no
additional shoulder of PYD2, indicating effective exciton
the two materials 2,6ꢀbis(Nꢀcarbazolyl)pyridine (PYD2) and
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bis[2ꢀ(diꢀ(phenyl)phosphino)ꢀphenyl]ether oxide (DPEPO) used
in device fabrications were prepared according to literature
CuC H ON P BF : C, 67.17; N, 5.60; H, 4.43. Found: C, 67.21;
56 44 4 2 4
N, 5.38; H, 4.25.
48, 49
1
31
1
procedures
. H NMR and P NMR spectra were recorded on 60 [Cu(mphtzcz)(POP)]BF •0.2(CH Cl )•0.2(diethyl ether) (4). H
4 2 2
a Bruker Avance III 400 MHz NMR spectrometer. Elemental
analyses (C, H, N) were carried out with an Elementar Vario EL
III elemental analyzer.
NMR (400 MHz CDCl ): δ 8.15 (d, 2H), 7.96 (t, 1H), 7.90 (d,
3
5
2H), 7.84 (d, 2H) 7.64–7.58 (dd, 4H), 7.52–7.45 (m, 4H), 7.38–
7.28 (m, 10H) 6.90–7.25 (m, 23H), 5.3 (s, 0.4H), 3.48 (dd, 0.8H),
31
2
.05 (s, 3H), 1.21 (t, 1.2H). P NMR: δ -13.43 (s). Anal. Calcd
Ligands preparation
65
for CuC H53.4O1.2N P BF : C, 69.16; N, 5.84; H, 4.49. Found:
69
5
2
4
The ancillary diimine ligands phtz, phtzcz, mphtz, mphtzcz were
synthesized from the precursors 2ꢀ(5ꢀphenylꢀ2Hꢀ1,2,4ꢀtriazolꢀ3ꢀ
yl)pyridine (HPhtz) and 6ꢀMeꢀ2ꢀ(5ꢀphenylꢀ2Hꢀ1,2,4ꢀtriazolꢀ3ꢀ
yl)pyridine (MePhtz) according to reported procedures (Fig.
S1). The mixture of 1eq. of 6ꢀRꢀpicolinonitrile (R= H, Methyl)
C, 69.05; N, 5.81; H, 4.24.
X-ray Crystallographic Analysis
10
15
20
25
30
41
Diffraction data of complexes 1 and 4 were collected on a
Saturn724 CCD Rigaku Mercury and a diffractometer equipped
and 0.3 eq. of sodium in anhydrous methanol was refluxed for 3 h 70 with graphiteꢀmonochromated Mo Kα radiation (λ = 0.71073 Å),
and then 1 eq. of benzoyl hydrazine was added. The solution was
refluxed till yellow solid precipitated. After filtration and drying,
the solid was added to glycol solution and heated to reflux for 3 h,
then cooled to room temperature and stand overnight. Colourless
crystal (HPhtz or MePhtz) was obtained after the removal of 75 refined by fullꢀmatrix leastꢀsquares methods with SHELXLꢀ97
solvent.
HPhtz or MePhtz (2.07 mmol), 1, 10ꢀphenanthroline (0.827
mmol), copper(I) iodide (0.413 mmol), caesium carbonate (4.13
mmol), 2.07mmol iodobenzene for phtz or mphtz, 9ꢀ(4ꢀ
respectively. Diffraction data of complexes 2 and 3 were
collected on a SuperNova, Dual, Cu at zero, Atlas diffractometer
equipped with graphiteꢀmonochromated Cu Kα radiation (λ
=1.54184 Å). Structures were solved by direct methods and
program package. Hydrogen atoms were added in idealized
positions. All nonhydrogen atoms were refined anisotropically.
Details of crystal and structure refinement are listed in Table S1,
selected bond length and angles are displayed in Table S2. Owing
iodophenyl)ꢀ9Hꢀcarbazole for phtzcz or mphtzcz were dissolved 80 to a serious disorder problem at data collection, there is an alert
in dry DMF (10 mL). The mixture was stirred vigorously for 1 h
at room temperature and then heated to 100 ºC under nitrogen for
another 36 h. At room temperature, the residue was filtrated. The
liquid phase was extracted with CH Cl (3 × 30 mL) and washed
level A for 1 attributed to the serious disorder solvents. The
solvent molecules could not be crystallographically defined
successfully. But the TGA and NMR analysis show that there are
dichloromethane and diethyl ether molecules in the compound 1.
2
2
with water, subsequently dried with anhydrous sodium sulphate. 85 CCDC: 1034650–1034653 contain the supplementary
After the removal of solvent under vacuum, the crude product
was purified by column chromatography on silica gel with ethyl
acetate/petroleum ether.
crystallographic data of complexes 1–4, respectively.
Thermogravimetric analysis (TGA) experiments
TGAs were done on
thermogravimetric analyzer in flowing nitrogen with the sample
a NETZSCH STA 449C Jupiter
Cuprous complexes preparation
–
1
A mixture of [Cu(CH CN) ]BF (1.0 mmol) and POP(1.0 mmol) 90 heated in an Al O crucible at a heating rate of 10 Kmin (Figure
3
4
4
2
3
in CH Cl (10 mL) was stirred at room temperature for 1 h, then
S3). The samples used for experiments have been dried at 90ºC
for 30 min. The weight loss 4%, 1.6% for complexes 1 and 3
under 200ºC belong to the release of residual solvents. The
solvents loss (2.9%) from 220 to 320 ºC for complex 4 attribute
2
2
35
40
45
50
55
the corresponding diimine ligand (1.0 mmol) was added. The
reaction mixture was stirred for another 1 h. The spectroscopic
pure products were obtained through diffuse diethyl ether into the
solution of these complexes and dried 0.5 h at 90 ºC. According 95 to 0.2 eq. of dichloromethane and diethyl ether. The
to the TGA, the samples used for Elemental analyses (C, H, N)
and NMR were dried 5 h at 200 ºC. The 1H NMR diagrams
suggest that there are solvents residual for 4 (about 0.2 eq. of
dichloromethane and 0.2 eq. of diethyl ether) (Appendix). The
content of solvents is in consistent with the weight loss (2.9%)
from 220 to 320 ºC (TGA).
decomposition temperatures for these four complexes are up to
350ºC (Fig. S2).
Electrochemical Measurement
Cyclic voltammetry was performed in
100 compartment threeꢀelectrode cell with
a
a
gastight singleꢀ
BAS Epsilon
1
[Cu(phtz)(POP)]BF (1). H NMR (400 MHz CDCl ): δ 8.29 (d,
Electrochemical Analyzer at room temperature. A glassy carbon
disk and a platinum wire were selected as the working and
4
3
1
7
H), 7.98(d, 2H), 7.81(t, 1H), 7.71(m, 3H), 7.5–7.27(m, 10H),
.25–6.9(m, 25H). P NMR: δ ꢀ11.99(s). Anal. Calcd for
3
1
auxiliary electrodes, respectively. The reference electrode was
+
CuC H ON P BF : C, 66.91; N, 5.68; H, 4.29. Found: C, 66.73;
Ag/Ag (0.1 M of AgNO
3
in acetonitrile). The CV measurements
Cl
2
55
42
4
2
4
N, 5.41; H, 4.18.
[Cu(phtzcz)(POP)]BF (2). H NMR (400 MHz CDCl ): δ 8.35
105 were carried out in anhydrous and nitrogenꢀsaturated CH
2
1
solutions with 0.1 M nꢀtetrabutylammonium perchlorate (TBAP)
and 2.0 mM cuprous complex. The ferrocenium/ferrocene couple
was used as an internal standard. (Fig. S3)
4
3
(
2
1
d, 1H), 8.16 (d, 2H), 7.92–8.02 (m, 5H), 7.71 (d, 2H), 7.61 (d,
H), 7.28–7.53 (m, 12H), 6.9–7.25 (m, 21H). P NMR: δ ꢀ
3
1
1.71(s). Anal. Calcd for CuC H ON P BF : C, 69.83; N, 6.08;
6
7
49
5
2
4
Photophysical Measurements
H, 4.29. Found: C, 69.47; N, 6.03; H, 3.89.
1
1
10 The solution samples for the photophysical studies were carefully
[Cu(mphtz)(POP)]BF (3). H NMR (400 MHz CDCl ): δ 7.80
4
3
2+
degassed ([Ru(bpy)3]
in degassed water was selected as
(
d, 2H), 7.71–7.64 (m, 3H), 7.40–7.28 (m, 10H), 7.25–6.91 (m,
50
3
1
reference for the PL quantum yields of them ). The film samples
2
6H), 2.01 (s, 3H). P NMR: δ -13.45 (s). Anal. Calcd for
6
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†
Electronic Supplementary Information (ESI) available: Supplementary
were prepared by spinꢀcoating a mixture of the cuprous complex
and poly(methyl methacrylate) (PMMA) in distilled CH Cl onto
a quartz glass slide and dried under vacuum at 50 °C for 2 h
before measurements. The powder samples were obtained by
drying the crystals at 90 °C for 0.5 h and measured without
further treatment. UV−vis absorption spectra were recorded with
computational and experimental data. CCDC number 1034650ꢀ1034653.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b000000x/
2
2
6
6
7
7
8
8
9
9
0
5
0
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0
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4
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.
.
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sulfonic acid) (PEDOT:PSS) was purchased from Heraeus and
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1
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−4
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temperature in air. All measurements on the devices were carried
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complexes is listed in table S4.
1
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4
0
This work was supported by the 973 key program of the Chinese
Ministry of Science and Technology (MOST) (2012CB821705),
the Chinese Academy of Sciences (KJCX2ꢀYWꢀ319, KJCX2ꢀ
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Graphical Abstract
Steric methyl group at emissive cuprous complexes largely increases both the PL and
EL efficiency while the carbazole appendage modestly improves the EL efficiency. So
4
show the highest efficiency with CEmax of 27.1 cd/A and EQEmax of 8.7%.