Synthesis and optoelectronic properties of a carbazole-modified platinum(ii) complex in polymer light-emitting devices

Article abstract of DOI:10.1039/c1dt11346a

To improve opto-electronic properties and efficiently suppress excimer emission, a phenylpyridine (ppy)-based platinum(ii) complex (C ₁₆OCz-ppy)Pt(acac) was synthesized and characterized, where C ₁₆OCz-ppy is a 2-phenylpyridine deriv

Full text of DOI:10.1039/c1dt11346a

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PAPER
Synthesis and optoelectronic properties of a carbazole-modified platinum(II)
complex in polymer light-emitting devices†
Jian Luo, Yu Liu, Danyan Shi, Yafei Wang,* Zhiyong Zhang, Junting Yu, Gangtie Lei, Qing Chen, Jianmin Li,
Xianping Deng and Weiguo Zhu*
Received 17th July 2011, Accepted 11th October 2011
DOI: 10.1039/c1dt11346a
To improve opto-electronic properties and efficiently suppress excimer emission, a phenylpyridine
(ppy)-based platinum(II) complex (C16OCz-ppy)Pt(acac) was synthesized and characterized, where
C16OCz-ppy is a 2-phenylpyridine derivative appending a carbazole moiety and three hexadecyloxy
methyl units in the parent phenylpyridine, and acac is acetylacetone. This carbazole-modified
platinum(II) complex exhibited good thermal stability and three times higher photoluminescent
quantum yield than its parent (2-phenylpyridine-C2,N)(2,4-pentanedionato-O,O)platinum(II) complex
[(ppy)Pt(acac)]. Single-emissive-layer polymer light-emitting devices using (C16OCZ-ppy)Pt(acac) as
dopant and a blend of poly(N-vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,
3,4-oxadiazole as host matrix presented a maximum current efficiency of 1.51 cd A-1, which was 1.5
times higher than that from the (ppy)Pt(acac)-doped device with the same device structure. Little
excimer emission and minor aggregation emission were observed in the (C16OCZ-ppy)Pt(acac)-doped
PLEDs at different dopant concentrations and applied voltages. This work indicates that introducing a
carbazole and three hexadecyloxy methyl groups into the planar platinum(II) complex can reduce
molecular aggregation and excimer emissions, thus resulting in high luminance and stable EL spectra in
comparison with the parent (ppy)Pt(acac).
have been developed. For example, Jabbour et al. reported a class
Introduction
of platinum(II) complexes with polyhedral oligomeric silsesquiox-
Phosphorescent cyclometallated complexes have received signif-
ane (POSS) moiety, which presented a reduced interaction and
diminished concentration quenching.5 The groups of Wong and
Lin incorporated multifunctional bulky chromophores into a
platinum complex by conjugation linkage and exhibited good
device performance.6,7
icant attention for their potential applications in organic light
emitting diodes and solar cells.1,2 The strong spin–orbital coupling
effect of the heavy-metal atom core allows for efficient intersystem
crossing from the singlet to the triplet excited state in these
cyclometallated complexes. As a result, these cyclometallated
complexes can utilize both singlet and triplet excitons for the
emission, and to a great extent, theoretically present a 100%
internal quantum efficiency.
Since the pioneering work by Thompson,3 cyclometallated
complexes, such as Ir(III) and Pt(II) complexes based on 2-
phenylpyridine (ppy) ligand, have been extensively studied as
phosphorescent materials.4 Among these cyclometallated com-
plexes, the Pt(II) complexes have square-planar geometry and
often exhibit a tendency to form aggregates or excimers through
axial coordination, resulting in lower emission efficiency and
broad red-shifted emissions. In order to suppress aggregation and
excimer emissions for platinum(II) complexes, various strategies
To our best knowledge, modifying ppy-type ligand by con-
jugation linkage, to some extent, can suppress intermolecular
interaction and reduce the excimer emission. However, extension
of the conjugated p-system readily results in significantly red-
shifted emission for its platinum(II) complex.8 In light of this
consideration, we have designed a modified ppy-based platinum(II)
complex (C16OCz-ppy)Pt(acac), which appends a carbazole moi-
ety and three hexadecyloxy methyl substituted groups in the parent
2-phenylpyridine. As shown in Scheme 1, the carbazole unit,
which is widely used as hole-transporting and emissive materials
for OLEDs,9 is attached into 4-position of the phenyl ring in
2-phenylpyridine via a non-conjugated linkage of a hexyloxy
group. We expect that the introduced carbazole by the non-
conjugated linkage can improve the hole-transporting property
of its platinum(II) complex. Three hexadecyloxy methyl groups
attached in the 3,6-positions of carbazole and 4-position of the
pyridine ring are expected to improve the dispersibility in the host
matrix. The co-effect of carbazole and long-chain hexadecyloxy
methyl groups is able to suppress the formation of aggregation
College of Chemistry, Key Lab of Environment-Friendly Chemistry and Ap-
plication in Ministry of Education, Xiangtan University, Xiangtan, 411105,
China. E-mail: zhuwg18@126.com, qiji830404@hotmail.com; Fax: +86-
731-58292251; Tel: +86-731-58298280
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c1dt11346a
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Scheme 1 Synthetic route of the (C16OCz-ppy)Pt(acac) and (ppy)Pt(acac) complexes.
and excimer in solid state for its platinum(II) complex. Therefore,
this carbazole-modified platinum(II) complex is suggested to
exhibit better photo-physical and electroluminescent properties.
To confirm this speculation, simple single-emissive-layer (SEL)
polymer light-emitting devices (PLEDs) were fabricated by a
solution-process using (C16OCz-ppy)Pt(acac) or (ppy)Pt(acac)
as dopant and a blend of poly(N-vinylcarbazole) (PVK) and
2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as
matrix. Improved EL performance and decreased aggregation and
excimer emissions were obtained in the (C16OCz-ppy)Pt(acac)-
doped devices relative to the (ppy)Pt(acac)-doped devices.
inum(II) complexes were synthesized by two-step procedures with
a moderate yield of about 40% referring to previous reports for
(NŸC)Pt(OŸO) complexes.3b,10 The resulting platinum complexes
were characterized by 1H NMR, 13C NMR and elemental analysis
to confirm their well-defined chemical structures.
Thermal properties
The thermal properties of the platinum(II) complexes was charac-
terized by thermal gravimetric analysis (TGA) under a nitrogen
atmosphere. The recorded TGA graph is shown in Fig. S1 (ESI†)
and the TGA data are listed in Table 1. The decomposition
temperature (Td) values with a 5% weight loss are 283 and 280 ◦C
for (ppy)Pt(acac) and (C16OCz-ppy)Pt(acac), respectively. The
5% weight loss of the platinum(II) complexes is mostly related
to the dissociation of the ancillary acetylacetone ligand.7 This
indicates that the carbazole-modified platinum(II) complex has
almost identical thermal stability to its parent platinum complex.
Incorporating a carbazole unit by non-conjugated linkage and
attaching three hexadecyloxy methyl groups into the ppy ligand
Results and discussion
Synthesis
Scheme 1 outlines the synthetic route of the platinum(II)
complexes. The carbazole-modified phenylpyridine derivative of
C16OCz-ppy was prepared in mild conditions by a Suzuki coupling
reaction with a high yield over 80%. Both cyclometallated plat-
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Table 1 UV-vis absorption, PL and thermal properties of the platinum(II) complexes
Compound
l
abs /nma (emax/dm3 mol-1 cm-1)b
l
em(DCM)c/nm
l
em(film)d/nm
Uem
Tde/◦C
(ppy)Pt(acac)
(C16OCz-ppy)Pt(acac)
278 (20825), 314 (9793), 362 (5554), 399 (2524)
269 (42915), 299 (29583), 351 (9347), 401 (3758)
484, 515
500, 528
500, 528, 570
503, 534, 574
0.15
0.48
283
280
a Measured in DCM at RT at a concentration of 10-5 mol L-1. b Molar extinction coefficient. c Measured in DCM at RT (lex = 400 nm). d Evaluated in the
neat films at RT. e 5% weight-loss temperature.
has only a very minor effect on the thermal stability of its
platinum(II) complex.
under opto-excitation at RT. This inherent structured emission
is attributed to a mixed emission from MLCT and LC state.3b
Compared to (ppy)Pt(acac), the carbazole-modified (C16OCz-
ppy)Pt(acac) exhibits a 16 nm bathochromic-shifted PL spectra
due to the effect of the introduced carbazole and alkyloxy methyl
groups. With increasing concentrations from 10-5 to 10-3 M, two
low-lying emission bands at about 550 and 610 nm are displayed
and gradually enhanced for (ppy)Pt(acac). On the contrary,
(C16OCz-ppy)Pt(acac) exhibits weaker low-lying emission bands
with little change in these conditions. The detailed concentration
dependent emission characteristics for the two complexes are
shown in Fig. S2 and S3 (ESI†). The low-lying emission bands
are considered to arise from aggregation and excimer emissions
based on the literature.4b,11 Therefore, the aggregation and excimer
emissions are effectively suppressed for (C16OCz-ppy)Pt(acac) in
DCM solution. On the other hand, a more intense broad low-
lying emission band at around 540 nm is shown in both platinum
complex-based thin films, besides their inherent structured emis-
sion. This phenomenon was previously also observed by other
groups.5,11a,12 However, (C16OCz-ppy)Pt(acac) provides relatively
weak low-lying emission compared to the parent (ppy)Pt(acac)
in the thin film. This implies that appending carbazole and
hexadecyloxy methyl units into the platinum complex, to some
extent suppresses aggregation induced emission in the neat films
under opto-excitation due to the steric effect of the pendent groups.
In order to further study the influence of carbazole and
UV-vis absorption properties
The UV-vis absorption spectra of the platinum(II) complexes
were measured in dichloromethane (DCM) solution at room
temperature (RT) and are depicted in Fig. 1. The pertinent data
are collected in Table 1. A UV-vis absorption spectrum with four
typical absorption bands is observed in the carbazole-modified
platinum(II) complex (C16OCz-ppy)Pt(acac). The intense high-
lying absorption bands at about 269 and 299 nm are assigned to
the spin-allowed p–p* transitions of the ppy and carbazole units,
respectively. The weak low-lying absorption bands at about 351
and 401 nm are attributed to the spin-allowed singlet metal-to-
ligand charge transfer (1MLCT) and spin-forbidden triplet metal-
to-ligand charge transfer (3MLCT) transitions, to a certain extent,
together with the contribution of the triplet intraligand (3IL) p–p*
transition and ligand-to-ligand charge transfer (LLCT) transition,
respectively. Compared to the parent (ppy)Pt(acac), (C16OCz-
ppy)Pt(acac) exhibits an additional absorption band from the
carbazole unit and enhanced molar absorption coefficient. The
enhanced UV absorption is considered to be available to improve
the energy-transfer efficiency from the host matrix to the platinum
complex in the PLEDs.
hexadecyloxy methyl units on PL, the PL quantum yields (Uem
)
of both platinum(II) complexes were measured. The measured Uem
values were 0.15 and 0.48 for (ppy)Pt(acac) and (C16OCz-ppy)-
Pt(acac) in DCM, respectively. Obviously, (C16OCz-ppy)Pt(acac)
exhibits a triplet Uem level higher than (ppy)Pt(acac). This means
that (C16OCz-ppy)Pt(acac) has inhibited aggregation and excimer
emissions owing to the steric effect of the pendent units under
opto-excitation. Therefore, introducing carbazole and hexadecy-
loxy methyl units into the platinum complex leads to improved PL
efficiency in DCM.
Electrochemical properties
Cyclic voltammetry (CV) was performed using ferrocene as
an internal standard to investigate the redox properties of
the platinum(II) complexes and estimate the highest occupied
molecular orbital (HOMO) and the lowest unoccupied molecular
orbital (LUMO) energy levels. The CV results showed that both
platinum(II) complexes displayed irreversible oxidation waves (Eox)
at 0.48 and 0.52 V vs. Fc/Fc+. (C16OCz-ppy)Pt(acac) had a
decreased Eox level compared to (ppy)Pt(acac). According to
the reported literature, the oxidations originate from the center
metal,3b and the irreversible phenomenon is due to rapid solvolysis
of the resultant platinum complex species. The reduction potential
Fig. 1 UV-vis absorption spectra of platinum(II) complexes in DCM
solution (1¥ 10-5 M) at RT.
Photoluminescent properties
The photoluminescent (PL) spectra of the platinum(II) complexes
in DCM and their neat films are shown in Fig. 2. For comparison,
the corresponding data are summarized in Table 1. Intense dual
vibronically structured emissive peaks at 500 and 528 nm are
observed for (C16OCz-ppy)Pt(acac) in DCM solution (10-5 M)
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Table 2 Electrochemical properties of the platinum(II) complexes
Compound
Ega/eV
Eox/eV
Eredb/eV
EHOMOc/eV
ELUMO d/eV
(ppy)Pt(acac)
(C16OCz-ppy)Pt(acac)
2.93
2.92
0.52
0.48
-2.41
-2.44
-5.32
-5.28
-2.39
-2.36
a Calculated from the optical absorption spectra. b Ered = Eox - Eg. c EHOMO = - (4.80 + Eox) eV. d ELUMO = - (4.80 + Ered) eV.
Fig. 2 PL spectra of platinum(II) complexes (a) in DCM solution (1 ¥ 10-5 and 1¥ 10-3 M) and (b) in neat films at RT (lex = 400 nm).
Fig. 3 EL spectra of (a) (ppy)Pt(acac)- and (b) (C16OCz-ppy)Pt(acac)- doped devices at dopant concentrations from 1 to 8 wt% under the applied voltage
of 10 V.
(Ered) can be estimated by the formula of Eox = Eg + Ered, where Eg
is the optical band gap estimated by the threshold of absorption
spectra. On the basis of Eox and Ered values, we can calculate
the HOMO and LUMO energy levels (EHOMO and ELUMO ) of the
PVK:PBD (45 nm)/Ba (4 nm)/Al (150 nm) were fabricated
by a spin-coating process, whereas ITO acts as the anode,
poly(ethylendioxythiophene)/poly(styrene sulfonic acid) (PE-
DOT:PSS) acts as the hole-injection layer, and Ba/Al is employed
as a cathode. The emitting layer consists of the phosphorescent
Pt(II) complex and a blend of PVK and PBD. The weight ratio of
PBD is 30% in the blend of PVK and PBD. Dopant concentrations
of platinum(II) complexes were varied from 1 to 8 wt%. Fig. 3 dis-
plays EL spectra of the (C16OCz-ppy)Pt(acac)- and (ppy)Pt(acac)-
doped devices at dopant concentrations from 1 to 8 wt%. Four
distinct peaks at about 430, 500, 528 and 563 nm are observed
in the EL spectra of the (ppy)Pt(acac)-doped devices, while the
(C16OCz-ppy)Pt(acac)-doped devices exhibit three distinct EL
peaks at about 430, 502 and 534 at dopant concentrations from
1 to 8 wt%. Among these EL peaks, the high-lying one at about
430 nm is attributed to PVK and significantly decreased with
platinum(II) complexes based on the following formula, EHOMO
=
- (4.80 + Eox) eV, ELUMO = - (4.80 + Ered) eV.13 The obtained
CV data are summarized in Table 2. It is obvious that (C16OCz-
ppy)Pt(acac) exhibits somewhat increased EHOMO and ELUMO values
compared to (ppy)Pt(acac). Therefore, incorporating carbazole
and hexadecyloxy methyl units onto the ppy-based ligand can raise
the HOMO and LUMO energy levels of its platinum(II) complex.
Electroluminescent properties
To illustrate the electrophosphorescent performance of both
platinum(II) complexes, SEL devices with
a configuration
of ITO/PEDOT:PSS (50 nm)/Pt(II) complex (x wt%)
+
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increasing dopant concentrations from 1 to 8 wt%. The medium-
lying peaks at about 501 1 nm and 531 3 nm are assigned
to the emission from the isolated molecular platinum(II) complex.
The low-lying one at 563 nm results from aggregation emission,
together with some contribution from excimer emission of the
platinum(II) complex. In general, differing degree of aggregation
can change the relative intensity between the monomer and
aggregation emissions, the stronger the aggregation, the broader
the EL spectra become.7,9a,14 We note that the (ppy)Pt(acac)-doped
devices exhibit a more intense and broader low-lying emission
band than the (C16OCz-ppy)Pt(acac)-doped devices at different
dopant concentrations and driving voltages. This indicates that
introducing carbazole and hexadecyloxy methyl groups onto the
platinum(II) complex can reduce the intermolecular p-stacking, so
inhibiting aggregation and excimer emissions under an electrical
field.
In order to study EL spectra stability of both platinum(II)
complex-doped devices, the EL spectra of the (ppy)Pt(acac)-
and (C16OCz-ppy)Pt(acac)-doped devices are shown in Fig. 4
and 5, respectively, at different dopant concentrations and ap-
plied voltages. It is obvious that EL spectra are sensitive to
the dopant concentrations and applied voltages for all these
devices. With increasing applied voltages, the intensity of the
low-lying emission significantly increases. On the other hand,
minor emission from PVK is also observed in the devices at 1,
2 and 4 wt% dopant concentrations, but almost disappeared at
8 wt% dopant concentration. The results clearly demonstrate that
the aggregation emission (even excimer emission) of the planar
platinum(II) complexes can be effectively inhibited by modification
of carbazole and hexadecyloxy methyl units.
concentrations, these devices exhibit an increased brightness and
reduced turn-on voltage. The maximum brightness of 733 cd m-2
and current efficiency of 1.5 cd A-1 were obtained in the (C16OCz-
ppy)Pt(acac)-doped PLEDs at 8 wt% doping concentration. This
current efficiency level is 1.5 times higher than that from the
(ppy)Pt(acac)-doped device with the same device configuration.
Therefore, introducing carbazole and three hexadecyloxy methyl
units into the parent (ppy)Pt(acac) can also improve the device
performance.
Conclusion
In summary, we obtained a carbazole-modified green-emitting
platinum(II) complex of (C16OCz-ppy)Pt(acac). Significantly in-
creased PL quantum efficiency in DCM and current efficiency
in the SEL PLEDs were achieved for the (C16OCz-ppy)Pt(acac)
compared with the corresponding levels for (ppy)Pt(acac). Fur-
thermore, the aggregation and excimer emissions were effectively
suppressed in the (C16OCz-ppy)Pt(acac)-doped devices at different
dopant concentrations and applied voltages. This work suggests
that introducing a carbazole moiety by non-conjugated linkage
and further attaching three hexadecyloxy methyl groups into the
cyclometallated ligand are beneficial to reduce the aggregation
and excimer emissions and improve the EL performance for the
corresponding platinum(II) complex.
Experimental
General information
The current density–voltage–luminance (J–V–L) character-
istics of the (ppy)Pt(acac)- and (C16OCz-ppy)Pt(acac)-doped
PLEDs at various dopant concentrations from 1 to 8 wt% are
shown in Fig. S4 (ESI†) and Fig. 6. With increasing dopant
The solvents were carefully dried and distilled by standard
procedures before use. All chemicals, unless otherwise stated,
were obtained from commercial sources and used as received.
The Suzuki coupling and cyclometallated reactions were car-
Fig. 4 EL spectra of the (ppy)Pt(acac)-doped devices at different dopant concentrations and applied voltages.
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Fig. 5 EL spectra of the (C16OCz-ppy)Pt(acac)-doped devices at different dopant concentrations and applied voltages.
a Si photodiode and calibrated by using a PR-705 Spectrascan
spectrophotometer (Photo Research).
Compounds 1, 2 and 3 were synthesized following litera-
ture methods.15 The cyclometallated platinum(II) complexes were
also synthesized according to the literature.3b,10 A mixture of
K2PtCl4, CŸN-chelate ligand C16OCz-ppy (or ppy) (2.5 equiv.),
2-ethoxyethanol and distilled water (3 : 1, v/v) was stirred under
nitrogen atmosphere at 80 ◦C for 24 h. After being cooled to RT,
the resulting precipitate was collected by filtration and washed
successively with water, ethanol and hexane. The dried chloro-
bridged dimer was obtained. This dimer was suspended in 2-
ethoxyethanol and treated with acetylacetone (2.5 equiv.) and
anhydrous Na2CO3 (10 equiv.). The mixture was stirred under
nitrogen atmosphere at 100 ◦C for 16 h. After cooling to RT,
the resulting precipitate was filtered off and washed with water,
ethanol and hexane, respectively. The residue was purified by flash
chromatography on silica gel using dichloromethane/hexane (1 : 1,
v/v) as eluent.
Fig.
6
Current density–voltage–luminance (J–V–L) curves of the
(C16OCz-ppy)Pt- (acac)-doped device at different dopant concentrations.
ried out in inert gas atmosphere and monitored by thin-layer
chromatography (TLC). NMR spectra were recorded on a Bruker
Dex-400 (MHz) NMR instrument using CDCl3 or DMSO-
d6 as a solvent and tetramethylsilane as an internal standard.
Elemental analysis was performed on a Harrios elemental analysis
instrument. UV absorption spectroscopy was measured by a
Shimadzu UV-265 spectrometer. Photoluminescent (PL) spectra
were recorded on Perkin-Elmer LS50B luminescence spectrome-
ter. The emission quantum yields were determined by the optical
dilution method using (ppy)Pt(acac) as a standard in 2-MeTHF
(U = 0.15).3b For electrochemical measurements a conventional
three-electrode configuration, consisting of a platinum working
electrode, a Pt-wire counter electrode, and a calomel electrode
reference electrode, was used. The supporting electrolyte was
0.1 M tetra(n-butyl)ammonium hexafluorophosphate (Bu4NPF6)
in DCM. Electroluminescence (EL) spectra were recorded with an
Instaspec IV CCD system (Oriel). Luminance was measured with
Syntheses
9-(6-(4-Bromophenoxy)hexyl)-9H-carbazole (4). A mixture of
compound 3 (7.5 g, 22.32 mmol), carbazole (6.5 g, 38.90 mmol)
and NaOH (50%, 80 mL) in 80 mL toluene was heated to reflux
under stirring for 20 h. After being cooled to RT, the mixture
was filtered and the solid was washed three times by DCM. The
combined solution was then concentrated under reduced pressure.
The residue was purified by silica gel column chromatography
using dichloromethane–petroleum ether (1 : 2; v/v) as eluent to
provide a white solid (6.5 g, 69.0%). 1H NMR (400 MHz, CDCl3,
TMS), d (ppm): 8.10 (d, J = 7.80 Hz, 2H), 7.47–7.39 (m, 4H), 7.34
(d, J = 8.64 Hz, 2H), 7.25–7.21 (m, 2H), 6.71 (d, J = 8.68 Hz, 2H),
4.32 (t, J = 7.10 Hz, 2H), 3.85 (t, J = 6.36 Hz, 2H), 1.93–1.70 (m,
4H), 1.49–1.44 (m, 4H).
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3,6-Diformoxyl-9-(6-(4-bromophenoxy)hexyl)-9H -carbazole
(5). Compound 5 was synthesized by Vilsmeier formylation
reaction according to the reported literature16 as a yellow solid
in a yield of 43.5%. 1H NMR (400 MHz, CDCl3, TMS), d (ppm):
10.14 (s, 2H), 8.68 (s, 2H), 8.08 (d, J = 8.64 Hz, 2H), 7.55 (d, J =
8.56 Hz, 2H), 7.35 (d, J = 8.76 Hz, 2H), 6.71 (d, J = 8.60 Hz, 2H),
4.42 (t, J = 6.94 Hz, 2H), 3.87 (t, J = 5.90 Hz, 2H), 1.99–1.26 (m,
8H).
2H), 3.51 (t, J = 5.21 Hz, 6H), 1.91–1.60 (m, 15H), 1.59–1.25 (m,
77H), 0.88 (t, J = 6.60 Hz, 9H).
(ppy)Pt(acac). (ppy)Pt(acac) was synthesized by the method
described above for the general synthesis of the platinum complex.
Yellow solid (40.2%). 1H NMR (400 MHz, CDCl3, TMS), d (ppm):
9.00 (d, J = 5.60 Hz, 1H), 7.80 (t, J = 7.61 Hz, 1H), 7.62 (t, J =
6.39 Hz, 2H), 7.45 (d, J = 7.54 Hz, 1H), 7.22 (t, J = 7.23 Hz, 1H),
7.12–7.09 (m, 2H), 5.48 (s, 1H), 2.02 (s, 6H). 13C NMR (100 MHz,
CDCl3, TMS), d (ppm): 185.79, 184.18, 168.47, 147.34, 144.64,
138.98, 138.05, 130.65, 129.26, 123.55, 122.97, 121.11, 118.29,
102.43, 28.22, 27.06. Anal. Calc. for C16H15NO2Pt: C 42.86, H
3.37, N 3.12. Found: C 43.05, H 3.42, N 3.10%.
3,6-Dihydroxymethyl-9-(6-(4-bromophenoxy)hexyl)-9H-carba-
zole (6). Compound 6 was synthesized according to the reported
literature15 as a white solid in a yield of 86.3%. 1H NMR (400 MHz,
DMSO, TMS), d (ppm): 8.10 (s, 2H), 7.50 (d, J = 8.36 Hz, 2H),
7.39–7.36 (m, 4H), 6.80 (d, J = 8.66 Hz, 2H), 5.11 (t, J = 5.54 Hz,
2H), 4.62 (d, J = 5.47 Hz, 4H), 4.35 (t, J = 6.35 Hz, 2H), 3.85 (t,
J = 6.06 Hz, 2H), 1.76–1.22 (m, 8H).
(C16OCz-ppy)Pt(acac). Yellow-orange solid (31.5%). 1H
NMR (400 MHz, CDCl3, TMS), d (ppm): 8.86 (s, 1H), 8.06 (s,
2H), 7.74 (d, J = 8.14 Hz, 1H), 7.46 (d, J = 8.32 Hz, 3H), 7.35 (t,
J = 8.56 Hz, 3H), 7.11 (s, 1H), 6.65–6.63 (m, 1H), 5.47 (s, 1H), 4.68
(s, 4H), 4.53 (s, 2H), 4.32 (t, J = 6.80 Hz, 2H), 4.06 (t, J = 6.06 Hz,
2H), 3.52 (t, J = 6.56 Hz, 6H), 2.02 (s, 3H), 2.00 (s, 3H), 1.93–1.65
(m, 15H), 1.60–0.88 (m, 77H), 0.89 (t, J = 6.49 Hz, 9H). 13C NMR
(100 MHz, CDCl3, TMS), d (ppm): 185.71, 183.98, 167.33, 159.58,
145.83, 141.11, 140.40, 137.27, 137.17, 130.99, 129.12, 126.03,
124.45, 122.79, 120.08, 117.20, 115.08, 110.57, 108.55, 102.40,
73.52, 70.92, 70.22, 69.63, 67.45, 43.10, 31.90, 29.86, 29.73, 29.68,
29.63, 29.57, 29.53, 29.47, 29.33, 29.17, 28.90, 28.21, 27.11, 27.00,
26.26, 26.16, 25.92, 22.65, 14.04. Anal. Calc. for C85H136N2O6Pt:
C 69.12, H 9.28, N 1.90. Found: C 69.20, H 9.31, N 1.94%.
3,6-Dihexadecyloxymethyl-9-(6-(4-bromophenoxy)hexyl)-9H-
carbazole (7). Compound 7 was synthesized according to the
reported literature15 as a white solid in a yield of 46.4%. 1H NMR
(400 MHz, CDCl3, TMS), d (ppm): 8.05 (s, 2H), 7.44 (d, J =
8.40 Hz, 2H), 7.35 (d, J = 8.48 Hz, 4H), 6.72 (d, J = 8.77 Hz, 2H),
4.67 (s, 4H), 4.31 (t, J = 6.85 Hz, 2H), 3.86 (t, J = 6.21 Hz, 2H),
3.52 (t, J = 6.62 Hz, 4H), 1.92–1.63 (m, 8H), 1.58–1.28 (m, 56H),
0.88 (t, J = 6.59 Hz, 6H).
3,6-Dihexadecyloxymethyl-9-(6-(4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)phenoxy)hexyl)-9H-carbazole (8). A nitrogen-
flushed three-neck round bottom flask was charged with
compound
7 (2.8 g, 3.05 mmol), bis(pinacolato)diboron
Acknowledgements
(0.85 g, 3.36 mmol), potassium acetate (0.90 g, 9.16 mmol),
Pd(dppf)Cl2(CH2Cl2) adduct, (74.7 mg, 0.09 mmol), and dimethyl
sulfoxide (DMSO, 60 mL), respectively. The mixture was bubbled
with nitrogen for 15 min, and stirred at 80 ◦C for 24 h. After being
cooled to RT, the mixture was poured into ice-water (200 mL) and
extracted with DCM. The combined organic layer was dried over
anhydrous MgSO4 and then concentrated under reduced pressure.
The residue was purified by silica gel column chromatography
using ethyl acetate–petroleum ether (1 : 15, v/v) as the eluent to
Financial support from the National Natural Science Foundation
of China (50973093, 20872124 and 20772101), the Specialized
Research Fund and the New Teachers Fund for the Doctoral
Program of Higher Education (20094301110004, 200805301013),
the Scientific Research Fund of Hunan Provincial Education
Department (10A119 and 11CY023), the Science Foundation
of Hunan Province (2009FJ2002), the Open Project Program
of Key Laboratory of Environmentally Friendly Chemistry and
Applications of Ministry of Education (09HJYH06), and the Post-
graduate Science Foundation for Innovation in Hunan Province
(CX2009B124).
1
give a white solid (1.27 g, 43.2%). H NMR (400 MHz, CDCl3,
TMS), d (ppm): 8.05 (s, 2H), 7.73 (d, J = 8.37 Hz, 2H), 7.44 (d, J =
8.33 Hz, 2H), 7.36 (d, J = 8.39 Hz, 2H), 6.85 (d, J = 8.41 Hz, 2H),
4.67 (s, 4H), 4.31 (t, J = 6.90 Hz, 2H), 3.94 (t, J = 6.35 Hz, 2H),
3.51 (t, J = 6.66 Hz, 4H), 1.89–1.57 (m, 8H), 1.49–1.37 (t, 56H),
1.33 (s, 12H), 0.88 (t, J = 6.69 Hz, 6H).
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