Electrophosphorescent heterobimetallic oligometallaynes and their applications in solution-processed organic light-emitting devices

Article abstract of DOI:10.1002/asia.201000341

By combining the iridium(III) ppy-type complex (Hppy=2-phenylpyridine) with a square-planar platinum(II) unit, some novel phosphorescent oligometallaynes bearing dual metal centers (viz. Ir^III and Pt^II) were developed by combining trans-[Pt(PBu₃)₂Cl₂] with metalloligands of iridium possessing bifunctional pendant acetylene groups. Photophysical and computational studies indicated that the phosphorescent excited states arising from these oligometallaynes can be ascribed to the triplet emissive Ir^III ppy-type chromophore, owing to the obvious trait (such as the longer phosphorescent lifetime at 77 K) also conferred by the Pt^II center. So, the two different metal centers show a synergistic effect in governing the photophysical behavior of these heterometallic oligometallaynes. The inherent nature of these amorphous materials renders the fabrication of simple solution-processed doped phosphorescent organic light-emitting diodes (PHOLEDs) feasible by effectively blocking the close-packing of the host molecules. Saliently, such a synergistic effect is also important in affording decent device performance for the solution-processed PHOLEDs. A maximum brightness of 3356 cdm^-2 (or 2708 cdm ^-2), external quantum efficiency of 0.50% (or 0.67%), luminance efficiency of 1.59 cdA^-1 (or 1.55 cdA^-1), and power efficiency of 0.60 LmW^-1 (or 0.55 LmW^-1) for the yellow (or orange) phosphorescent PHOLEDs can be obtained. These results show the great potential of these bimetallic emitters for organic light-emitting diodes.

Full text of DOI:10.1002/asia.201000341

DOI: 10.1002/asia.201000341
Electrophosphorescent Heterobimetallic Oligometallaynes and Their
Applications in Solution-Processed Organic Light-Emitting Devices
Guijiang Zhou,*[a] Yue He,[a] Bing Yao,[b] Jingshuang Dang,[a] Wai-Yeung Wong,*[c]
Zhiyuan Xie,*[b] Xiang Zhao,*[a] and Lixiang Wang[b]
Abstract: By combining the iridium-
ACHTUNGTRENNUNG(III) ppy-type complex (Hppy=2-phe-
phorescent lifetime at 77 K) also con-
ferred by the PtII center. So, the two
different metal centers show a synergis-
tic effect in governing the photophysi-
cal behavior of these heterometallic
oligometallaynes. The inherent nature
of these amorphous materials renders
the fabrication of simple solution-pro-
cessed doped phosphorescent organic
light-emitting diodes (PHOLEDs) fea-
sible by effectively blocking the close-
packing of the host molecules. Salient-
ly, such a synergistic effect is also im-
portant in affording decent device per-
formance for the solution-processed
PHOLEDs. A maximum brightness of
3356 cdmꢀ2 (or 2708 cdmꢀ2), external
quantum efficiency of 0.50% (or
0.67%), luminance efficiency of
1.59 cdAꢀ1 (or 1.55 cdAꢀ1), and power
nylpyridine) with a square-planar plati-
num(II) unit, some novel phosphores-
cent oligometallaynes bearing dual
metal centers (viz. IrIII and PtII) were
developed by combining trans-[Pt-
ACHTUNGTRENNUNG(PBu3)2Cl2] with metalloligands of iridi-
um possessing bifunctional pendant
acetylene groups. Photophysical and
computational studies indicated that
the phosphorescent excited states aris-
ing from these oligometallaynes can be
ascribed to the triplet emissive IrIII
ppy-type chromophore, owing to the
obvious trait (such as the longer phos-
efficiency
of
0.60 LmWꢀ1
(or
0.55 LmWꢀ1) for the yellow (or
orange) phosphorescent PHOLEDs
can be obtained. These results show
the great potential of these bimetallic
emitters for organic light-emitting
diodes.
Keywords: alkynes
· bimetallic ·
organic light-emitting diodes · phos-
phorescence · polymetallaynes
[a] Prof. G. Zhou, Y. He, J. Dang, Prof. X. Zhao
Introduction
MOE Key Laboratory for Nonequilibrium Synthesis and
Modulation of Condensed Matter and
Department of Chemistry
Since the successful synthesis of Zeiseꢀs salt KACHTNUTGRENNG[U PtCl3ACHTUNGTRENNUNG(C2H4)]
in 1827, organometallic complexes have always been an
active research field in the scientific community for not only
their unique structures and bonding features but also their
intrinsic properties, showing potential applications associat-
ed with new material synthesis,[1] ion sensing,[2] and utiliza-
tion of new energy sources,[3] and so forth. Owing to the in-
herent character of the metal center, transition-metal com-
plexes show a tendency to chelate with certain chemical
groups in molecules which will be activated for further
chemical reaction with other reagents.[4] Furthermore, the
configuration of ligands in transition-metal complexes usual-
ly exert a great effect on the yield of the reaction and the
structure or even the geometry of the final product.[5] So,
transition-metal complexes are very often effective catalysts
for many organic transformations to bring about a diversity
of molecules with special properties for new materials re-
search. The photophysical behavior of some metalated com-
plexes is sensitive to guest ions, such as CNꢀ, Fꢀ, and so
forth, in solution, hence, they can also play the role as ion
Faculty of Science
Xi’an Jiao Tong University
Xi’an 710049 (P.R. China)
Fax : (+86)29-82663914
E-mail: xzhao@mail.xjtu.edu.cn
zhougj@mail.xjtu.edu.cn
[b] B. Yao, Prof. Z. Xie, Prof. L. Wang
State Key Laboratory of Polymer Physics and Chemistry
Changchun Institute of Applied Chemistry
Chinese Academy of Sciences
Changchun 130022 (P.R. China)
Fax : (+86)431-5684937
E-mail: xiezy_n@ciac.jl.cn
[c] Prof. W.-Y. Wong
Institute of Molecular Functional Materials and Department of
Chemistry and Centre for Advanced Luminescence Materials
Hong Kong Baptist University
Waterloo Road, Kowloon Tong, Hong Kong (P.R. China)
Fax : (+852)3411-7348
E-mail: rwywong@hkbu.edu.hk
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201000341.
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FULL PAPERS
sensors, which is an important topic for environment protec-
tion. Besides, the PtII polymetallaynes and RuII bipyridine-
type molecules are able to function as high-performance op-
toelectronic materials for bulk-heterojunction polymer and
dye-sensitized solar cells[3,6] and highly transparent optical
power limiters.[7]
promising light-emitting molecules in realizing phosphores-
cent small-molecule and polymer OLEDs, to our knowl-
edge, linking these IrIII moieties with polyplatinynes in some
bimetallic materials should bring about the best of both
worlds. In view of this, we present here the first examples of
novel phosphorescent heteronuclear oligometallaynes con-
sisting of dual metal centers (namely, IrIII and PtII) in the
main chain, and their photophysical behavior and potential
light-emitting application will be described.
Owing to the large spin-orbit coupling constant of heavy
transition-metal atoms, significant triplet (or phosphores-
cent) state characters are associated with many transition-
metal complexes, especially for the third-row transition-
metal (ReI, OsII, IrIII, and PtII)[8–11] complexes. Successfully
harnessing both of the singlet and triplet excited states in
triplet emitters has brought revolutionary progress to the
field of organic light-emitting diodes (OLEDs). Traditional
singlet/fluorescent emitters will favor a 3:1 ratio of the non-
emissive triplet states over singlet states according to the
quantum spin statistics prediction for the free charge-carri-
ers, which severely limits device efficiency.[12] Among all the
known triplet emitters/phosphors, the unique photophysical
features associated with IrIII and PtII ppy-type (Hppy=2-
phenylpyridine) complexes, such as tunable emission color,
high phosphorescent quantum yield (Fp), relatively short
lifetime (tp), and so forth, would definitely place them in a
favorable position to meet the
Results and Discussion
Synthetic Strategies and Chemical Characterization
Chemical structures and the detailed synthetic protocols of
the new IrACHTUNRGTENN(GU C^N)2ACHTUNGTRENN(UGN acac)-based metalloligands L1 and L2 are
shown in Scheme 1 (Hacac=acetylacetone, C^N=anionic
cyclometalating ligand; also see Supporting Information).
With the selective Stille coupling reaction,[14a] the bromo-
substituted ppy-type chelates were synthesized successfully.
In order to avoid the side reactions under the reaction con-
ditions for the trimethylsilylethynyl group, compounds 1 and
2 were prepared first. They then underwent a Sonogashira-
targets in both full-color flat-
panel displays and low-cost
lighting sources.
While there are numerous
potential uses of transition-
metal complexes nowadays, we
are confident that new applica-
tions or improved performances
would emerge as other new ma-
terials continue to be devel-
oped. Recently, the burgeoning
field of polymetallaynes (espe-
cially polyplatinynes) is gaining
momentum through continued
breakthroughs in materials
design and device engineer-
ing.[6b–f,7] The innovative design
of these functional metal poly-
ynes has been demonstrated to
be useful in energy-producing
(solar cells) and energy-saving
(OLEDs) applications. Though
still in its infancy, the idea of in-
corporating
two
transition
metals in a single metallopo-
lyyne chain also has significant
appeal and there are a few re-
ports on using AuI, FeII, HgII,
ReI, RuII, PdII, PtII, and so
forth, in synthesizing bimetallic
metallayne
While it is well-known that cy-
clometalated IrIII complexes are Scheme 1. Synthesis of the IrIII metalloligands.
materials.[7a,b,13]
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Electrophosphorescent Heterobimetallic Oligometallaynes
type coupling reaction[14b,c] to produce the ligand precursors
3 and 4, respectively. After deprotection with a base under
very mild conditions, L1 and L2 were obtained as orange
solids in high yields of ~85% (see Supporting Information).
For the synthesis of the dual transition-metal-coordinated
polyynes, each of the corresponding metalloligands reacts
tures of P1 and P2 were also characterized by NMR (1H,
13C, and 31P) and GPC. The broad proton signals in their
1H NMR spectra reveal their polyyne character. However,
the GPC results show that the Mn for P1 and P2 is approxi-
mately 1.3ꢂ104 gmolꢀ1 and 1.1ꢂ104 gmolꢀ1, respectively.
The relatively low Mn values with reference to the molecular
with trans-[Pt
G
weight of the metalloACTHNGUTRENlUNG iAHCUTNGTRENgNNUG and comonomer indicate that P1
dehydrohalogenation protocol under a CuI/Et3N catalytic
system (Scheme 2).[15] The oligometallaynes P1 and P2 can
be obtained as orange solids in good yields after precipita-
tion from methanol.
and P2 are better described as oligomers, which can be re-
vealed from the weak FT-IR absorption band at around
390 cmꢀ1 (Figure S1 in the Supporting Information) corre-
ꢀ
sponding to the unreacted terminal Pt Cl bond. The reso-
nance signal at about 4.00 ppm
in the 31P-{1H} NMR of the bi-
metallic polyynes indicates that
the PtACHTNUGTRNEUNG(PBu3)2 moieties adopt a
trans configuration in the oligo-
meric chain.
Thermal and Photophysical
Properties
The thermal properties of the
oligometallaynes with dual
transition-metal centers were
studied by thermogravimetric
analysis (TGA) and differential
scanning calorimetry (DSC)
under a nitrogen atmosphere
(Table 1). The TGA data reveal
that all the metal complexes
have excellent thermal stability
and their 5% weight-reduction
Scheme 2. Synthesis of the bimetallic polymetallaynes of IrIII and PtII.
temperatures (DT5%
)
exceed
3208C. Analysis of the DSC
traces for the polyynes showed no crystallization peaks but
only glass-transition temperatures (Tg), which can be attrib-
uted to the branched and tortuous configuration of the Ir-
The chemical structures of the metalloligands L1 and L2
have been characterized thoroughly by elemental analysis,
NMR (1H and 13C), and mass spectra (see Supporting Infor-
mation). The characteristic signal for the terminal CꢁCH at
A
2ACHTUNGTREN(NUNG acac)-centered moieties in the backbone of the oli-
1
approximately 3.00 ppm in each of the H NMR spectra of
L1 and L2 indicates that the functional group necessary for
A
A
the dehydrohalogenative reaction remains intact. The struc-
Table 1. Photophysical and thermal data for the new oligometallaynes and their corresponding ligand precursors.
Compound
Absorption
labs [nm][a]
293 K
Emission
lem [nm]
293 K/77 K
Fp [%][b]
tp [ms][c]
293 K/77 K
tr [ms][d]
293 K
DT5%/Tg [8C][e]
P1
P2
L1
229, 260, 287, 379, 400, 446, 465, 487
229, 251, 283, 383, 400, 474, 502
227 (31330), 282 (63240), 304 (48055),
350 (8850), 377 (5880), 430 (4390),
464 (3195), 480 (2640)
549, 588/552, 599
577, 625/577, 631
538, 571/538, 581
12.3
4.8
23.5
0.11/10.82
0.51/12.12
0.21/4.99
14.83
6.26
5.43
320/140
334/172
330/110
L2
229 (43225), 294 (39410), 341 (61180),
355 (55690), 400 (17220), 472 (5470),
489 (4760)
567, 608/567, 611
9.2
0.66/7.77
13.47
346/120
[a] Measured in CH2Cl2 at a concentration of 10ꢀ5 m and e values are shown in parentheses. [b] In CH2Cl2 relative to fac-[Ir
ACHTNUGTNREU(NNG ppy)3] (Fp =0.40), lex =
400 nm. [c] Measured in freeze-pump-thaw degassed CH2Cl2 solutions at a sample concentration of ca. 10ꢀ5 m and the excitation wavelength was set at
355 nm. [d] The triplet radiative lifetimes were deduced from tr =tP/FP. [e] DT5% is the 5% weight-reduction temperature and Tg is the glass transition
temperature.
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G. Zhou, W.-Y. Wong, Z. Xie, X. Zhao et al.
FULL PAPERS
mobility and flexibility of the chelating ligands and hence, a
higher Tg was observed for the Ir/Pt-based oligometallaynes
(1408C for P1 and 1708C for P2) which are desirable for
subsequent device study (vide infra).
Both P1 and P2 exhibit two major absorption bands in
their UV/Vis spectra (Figure 1a). The intense UV bands
patterns for the repeat unit of P1 and P2 (Figure 2c and 2d
and Table 2), the dp orbitals of their PtII centers make clear
contributions (12.5% for P1 and 17.6% for P2, respectively)
and the atomic contributions for a p system are distributed
over the two main ligands bonded with the central trans-Pt-
AHCTUNTGRENGUN(N PBu3)2 moiety, which would extend the conjugation length
of IrIII-based chromophore to afford lower-energy spin-al-
1
lowed p–p* transitions.[16] Such a marked difference for the
1p–p* transitions in metalloligands and oligometallaynes is
consistent with the data in Figure 1a. From the distribution
pattern of the frontier orbitals for L1 and L2 and the repeat
units of P1 and P2, the MLCT transitions for both metalloli-
gands and Pt/Ir polyynes involve similar electronic charac-
ters consisting of the dp orbitals of the IrIII center to the p
orbitals of the pyridyl ring in the ligands, despite the fact
that some contribution from the dp orbitals of PtII moieties
cannot be totally excluded. So, the absorption energies for
the MLCT bands are similar for both the polyynes and their
ligand precursors (Figure 1a).
Upon light irradiation at 400 nm, P1 and P2 both produce
intense yellow/orange phosphorescence. Their emission
spectra with obvious vibronic progressions indicate that the
phosphorescent emissions of P1 and P2 mainly originate
from the ligand-centered (LC) 3p–p* states, probably to-
gether with a small contribution from 3MLCT transitions
(Figure 1b and Table 1). The structureless low-energy fea-
tures may be caused by the vibronic coupling interactions
(Figure 1b). In order to account for their photolumines-
cence (PL) behavior, we have examined their electronic
structures which have a close relationship with the photo-
physical behavior. Our TD-DFT calculations show that the
lowest-energy transitions correspond to the HOMO!
LUMO transitions with non-zero oscillator strengths and
only the HOMO–LUMO transition is important for the first
excited state (Table 2). From Table 2, it is shown that the
MO compositions in S1 are similar to those in T1 in our sys-
tems. So, the HOMO–LUMO transition also contains the
character for the T1 states in the bimetallic polyynes and
their metalloligands, which are the origin of the phosphores-
cence. Therefore, we focus our attention on the HOMO–
LUMO analyses in the following discussion for their phos-
phorescent behavior. Similar to their absorption behavior,
Figure 1. a) Absorption and b) PL spectra of P1 and P2 and their
metalloACHTUNGTRENNUNGliACHTUNGTRENNUNGgand precursors in CH2Cl2 at 293 K.
1
near 400 nm are attributed to the spin-allowed p–p* transi-
tions. The weaker, low-energy features result from both
3
1MLCT and MLCT (metal-to-ligand charge transfer) excita-
tions. The strong spin-orbit coupling is confirmed by the
similar oscillator strengths for the two MLCT bands
(Table 1).[11g] Compared with the absorption data of L1 and
L2, the polyynes P1 and P2 show almost similar MLCT
the trans-PtACHTNUTRGNE(UNG PBu3)2 moiety can extend the conjugation
length along the main chain in P1 and P2, as can be re-
vealed from their HOMO/HOMO-1 patterns and also those
found in other reported PtII-arylacetylides.[7a–c] Accordingly,
the conjugation length of the ppy-type ligands chelated with
an IrIII center is increased after copolymerization, which cor-
1
energy states to L1 and L2 while their spin-allowed p–p*
transitions are shifted to a longer wavelength. Since the ab-
sorption behavior for the ground state has a close relation-
ship with the characteristics of the molecular orbitals (espe-
cially for the HOMOs), we carried out time-dependent den-
sity functional theory (TD-DFT) computations for the com-
pounds to elucidate their electronic properties.
Without loss of generality, the theoretical computations
for P1 and P2 were made based on their repeat units to
save the computation times. Such repeating units essentially
serve as model compounds for the photophysical behavior
of the polymeric molecules.[7a,b] From the HOMO/HOMO-1
1
roborates well with the observed red-shift of the p–p* tran-
sitions in the metallopolyynes relative to their metalloli-
gands (Figure 1a). Hence, the enhanced conjugation effect
will lead to bathochromic behavior for the emission maxima
of P1 and P2 (Figure 1b and Table 1). Furthermore, the
photophysical investigation of IrIII ppy-type complexes sug-
gests that the triplet emission would typically exhibit more
LC character with increasing conjugation length of the li-
gands,[11h] which is reflected from the notably more struc-
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Electrophosphorescent Heterobimetallic Oligometallaynes
peating unit of P1 and P2 in
Figure 2, the lowest-energy ex-
cited state is largely dominated
by the LC characteristics.
It is not expected that the
lifetime for P1 and P2 is shorter
at 293 K but longer at 77 K
than that of their corresponding
precursors L1 and L2. It is an-
ticipated that the lifetime of the
polymetallayne might be short-
ened at any temperature com-
pared with that of the free
ligand if they possess similar
emissive triplet excited states,
since copolymerization would
link up the free monomers to-
gether which might cause
a
stronger quenching effect ac-
cordingly. Compared with those
of L1 and L2, the much longer
lifetimes for P1 and P2 at 77 K
certainly need more careful at-
tention here. It appears that the
emissive triplet excited states
probably exhibit different char-
acters for the oligometallaynes
and their metalloligands. From
the HOMO electron distribu-
tion of the repeating units of P1
and P2 (Figure 2 and Table 2),
the contribution from the dp or-
bitals of the PtII center (12.5%
for P1 and 17.6% for P2) indi-
cates that the PtII center can
induce strong spin-orbit cou-
pling.[17] With reference to
many PtII-centered bis(aryle-
neethynylene)s in the literature,
the spin-orbit coupling effect
would facilitate the triplet emis-
sion.[7a–c] So, the emissive triplet
excited states in P1 and P2 nec-
essarily contain some phosphor-
escent character owing to the
PtII-bis(aryleneethynylene)
chromophore which is prone to
be very temperature sensitive
and possess much longer life-
times compared with those in-
duced by the IrIII center in their
Ir ppy-type complexes. The
triplet emissive states for P1
Figure 2. Contour plots of the highest occupied (HOMO-1 and HOMO) and lowest unoccupied (LUMO) mo-
lecular orbitals for a) L1, b) L2, c) repeating unit of P1 and d) repeating unit of P2.
tured line shape of the emission spectra on going from the
metalloligands to the mixed-metal polyynes, indicating that
more LC 3p–p* excited states are involved in P1 and P2
(Figure 1b). By looking at the LUMO pattern of each re-
and P2 at 77 K should consist of a significant contribution
coming from the long-lived triplets of PtII-bis(aryleneethyny-
lene) besides those from the IrIII-centered moiety, which is
not the case for L1 and L2. Hence, P1 and P2 show much
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Table 2. Percentage contribution of the metal d orbitals to HOMO and LUMO together with the TD-DFT calculation results.
compound
contribution
of metal d
orbitals to HOMO
contribution
of metal d
orbitals to LUMO
largest coefficient in the CI
expansion of the T1 state[a]
(S0!T1 excitation energy)
largest coefficient in the CI
expansion of the S1 state[a]
(S0!S1 excitation energy)
oscillator strength (f)
of the S0!S1 transition
P1
P2
12.54% (Pt)
1.23% (Ir1)
13.37% (Ir2)
17.59% (Pt)
1.84% (Ir1)
4.26% (Ir2)
43.20% (Ir)
50.13% (Ir)
0.0021% (Pt)
3.95% (Ir1)
0.00014% (Ir2)
0.0038% (Pt)
2.93% (Ir1)
0.00037% (Ir2)
2.48% (Ir)
H!L: 0.11 (529 nm)
H!L: 0.20 (484 nm)
0.014
H!L: ꢀ0.13 (548 nm)
H!L: ꢀ0.31 (490 nm)
0.029
L1
L2
H!L: 0.61 (521 nm)
H!L: 0.65 (541 nm)
H!L: 0.67 (466 nm)
H!L: 0.68 (482 nm)
0.038
0.050
3.34% (Ir)
[a] H!L represents the HOMO to LUMO transition. CI stands for configuration interaction.
longer lifetimes at 77 K. At
293 K, the long-lived character
for the triplet emissive states of
P1 and P2 would become insig-
nificant. As a result, the life-
time of the oligometallaynes is
very similar to that of their cor-
responding
(Table 1).
metalloligands
Electrophosphorescent
Characterization
The photophysical investigation
described in the previous sec-
tion shows that the new bime-
tallic oligometallaynes P1 and
P2 (P1: HOMO=ꢀ5.44 eV,
LUMO=ꢀ3.00 eV,
2.44 eV; P2:
Eg =
ꢀ5.46 eV,
ꢀ3.07 eV, 2.39 eV) should be
good phosphorescent materials.
Moreover, their oligomeric
nature would simplify electro-
phosphorescent OLED charac-
terization by the solution proc-
essing techniques, so doped
phosphorescent organic light-
Figure 3. The general configuration for the electrophosphorescent OLEDs and the molecular structures of the
relevant compounds used in these devices.
emitting diodes (PHOLEDs) have been prepared. Figure 3
depicts the general structures of the PHOLEDs and the mo-
lecular structures of the compounds employed. 4,4’-N,N’-Di-
carbazolebiphenyl (CBP) was used as the carrier recombina-
tion host for our metallophosphors owing to its ambipolar
charge carrier-transporting properties and suitable triplet
energy level. The composite polymer solution of PE-
DOT:PSS (poly(3,4-ethylene-dioxythiophene)-poly(styrene
sulfonate)) was first spin-coated on the ITO surface to serve
as the hole-injection (HI) layer. Then, the emitting layer of
polymetallayne dopant and CBP host was deposited by
simple spin-coating method. Owing to the highly amorphous
character of the emitter, the inclination for crystallization of
CBP was hindered greatly and a good-quality emission layer
was obtained. 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthro-
line (BCP) was adopted as a hole-blocker, tris(8-hydroxy-
quinolinato)aluminum (Alq3) as an electron-transporter, and
LiF as an electron-injection material. All of the devices con-
sist of the multilayer configuration ITO/PEDOT:PSS
(40 nm)/x% dopant:CBP (50 nm)/BCP (15 nm)/Alq3
(40 nm)/LiF:Al (1:100 nm). To optimize the device efficien-
cy, concentration dependence experiments were carried out
in the range of 5 to 20 wt%. When a proper voltage was ap-
plied to the devices, intense electrophosphorescence har-
nessed by the strong heavy-atom effect of Ir and Pt[11i,j] was
observed (Figure 4 and Figure S2 in the Supporting Informa-
tion). Devices A1–A3 with P1 as the emitter give yellow
electrophosphorescence with an emission maximum at
552 nm while devices B1–B3 made from P2 exhibit orange
electrophosphorescence with an emission maximum at
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Electrophosphorescent Heterobimetallic Oligometallaynes
the emitting sites can be shown to result in a better emission
color purity.
The luminance-voltage-current density (L-V-J) character-
istics for the devices are shown in Figure 5 and Figure S4 in
the Supporting Information. The key performance parame-
Figure 4. The EL spectra for the best devices (devices A2 and B2 at
10 wt% doping level) at 8 V.
580 nm. The close resemblance of the EL spectra with the
corresponding PL spectra in each case indicates that the EL
originates from the triplet states of the phosphorescent poly-
metallayne (Figure 4). No emission from CBP was observed
from the EL spectra of devices A1–A3 and B1–B3, which
indicates the effective energy transfer from CBP host to
phosphorescent dopant (Figure S2 in the Supporting Infor-
mation). However, the EL spectra for the devices with
lower doping levels (1 wt% and 2 wt%) exhibit an obvious
emission band from CBP (ca. 400 nm) and a broad emission
peak (ca. 470 nm) from the exciplex of CBP as indicated by
its structureless spectra, showing that a low amount of
dopant cannot harness all the energy from the host and tend
to block the packing arrangement among the host molecules
(Figure S3 in the Supporting Information). Accordingly, de-
vices with higher doping levels were made. When the
doping level was increased to 5 wt%, the emission bands
arising from CBP and its exci-
Figure 5. The L-V-J curves for devices A2 and B2.
ters for all the devices are summarized in Table 3 and it can
be seen clearly that devices A2 and B2 with a doping level
of 10 wt% give the best performance. They turned on at 5.9
and 5.2 V, respectively. Device B2 produced the maximum
luminance of about 2708 cdmꢀ2 at 15.4 V. The relatively
high driving voltages with respect to the typical vacuum-
evaporated devices may arise from the thicker emissive
layer of CBP:Ir dopant used and the large hole barrier at
the PEDOT:PSS/CBP interface (HOMOs of CBP ~ꢀ6.2 eV
versus PEDOT ~ꢀ5.0 eV). Device A2 can even emit bright-
er light at the luminance of about 3356 cdmꢀ2 at a lower
voltage of 13.4 V. Furthermore, these solution-processed de-
vices show decent efficiency data. Compared with other
polymeric PHOLEDs, device A2 shows respectable peak
plex completely vanished (Fig-
ure S3 in the Supporting Infor-
mation). So, the phosphores-
cent oligometallaynes can con-
sume the energy from the host
properly and provide a highly
amorphous doped emission
layer by virtue of the oligomer-
ic character of the phosphores-
cent emitters, which is necessa-
ry for high-performance devi-
ces. Encouragingly, no obvious
emission bands from the exci-
mer formed by the packing of
the emitting centers were de-
tected even at the doping level
as high as 20 wt% (Figure S2 in
the Supporting Information).
Hence, the advantage of the
novel structures in P1 and P2
Table 3. Performance data of polymetallayne-doped electrophosphorescent OLEDs.
Device
Phosphor dopant
Vturnꢀon
[V]
Luminance L
[cdmꢀ2
hext
hL
[cdAꢀ1
hp
[LmWꢀ1
lmax
[nm][d]
G
]
[%]
U
]
G
]
A1
P1 (5 wt%)
6.4
5.9
5.2
7.2
5.6
5.7
243[a]
0.39
0.35
0.40 (9.8)
0.40
0.40
0.50 (8.8)
0.15
0.16
0.17 (8.8)
0.60
0.43
0.63 (10.0)
0.63
0.47
0.67 (9.4)
0.27
0.26
1.26
1.09
1.26 (9.8)
1.57
1.28
1.59 (8.6)
0.40
0.47
0.48 (8.8)
1.40
0.99
1.45 (10.0)
1.47
0.41
0.31
0.42 (9.2)
0.54
0.36
0.60 (7.8)
0.18
0.17
0.18 (7.8)
0.40
0.24
0.47 (9.4)
0.43
552
(0.46, 0.52)
1117[b]
2262 (13.2)[c]
323[a]
A2
A3
B1
B2
B3
P1 (10 wt%)
P1 (20 wt%)
P2 (5 wt%)
P2 (10 wt%)
P2 (20 wt%)
552
(0.47, 0.52)
1255[b]
3356 (13.4)[c]
81[a]
552
(0.46, 0.52)
476[b]
1650 (12.2)[c]
276[a]
580
(0.56, 0.43)
996[b]
2258 (15.2)[c]
287[a]
580
(0.56, 0.43)
1067[b]
1.08
1.55 (9.4)
0.64
0.23
0.65 (9.6)
0.26
0.55 (8.2)
0.23
0.16
0.24 (8.0)
2708 (15.4)[c]
123[a]
580
(0.56, 0.44)
584[b]
1861 (14.8)[c]
0.28 (9.6)
[a] Values collected at 20 mAcmꢀ2. [b] Values collected at 100 mAcmꢀ2. [c] Maximum values of the devices.
to block close-packing among Values in parentheses are the voltages at which they were obtained. [d] CIE coordinates [x, y] in parentheses.
Chem. Asian J. 2010, 5, 2405 – 2414
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
2411

G. Zhou, W.-Y. Wong, Z. Xie, X. Zhao et al.
FULL PAPERS
current efficiency (hL) of 1.59 cdAꢀ1 at 8.6 V, external quan-
tum efficiency (hext) of 0.50% at 8.8 V, and power efficiency
(hP) of 0.60 LmWꢀ1 at 7.8 V. The best efficiencies for device
B2 are defined by hL =1.55 cdAꢀ1 at 9.4 V, hext =0.67% at
9.4 V, and hP =0.55 LmWꢀ1 at 8.2 V. These results are some-
what unexpected because binding of the iridium-emitting
phorescent characteristics of the bimetallic metallaynes. By
virtue of such advantageous synergistic bimetallic effect,
these new oligometallaynes possess great potential for
simple solution-processed PHOLEDs. These triplet emitters
can be further optimized by structural modifications of the
C^N ligand groups on IrACTHNUTRGNNEG(U C^N)2CAHTUNGTRNE(NUGN acac) unit to fine-tune both
centers with trans-Pt
the phosphorescent Ir
G
the device color and efficiency. We believe that the advan-
tages of electrophosphorescence and solution processing
that our phosphors offer can be seen as a big step forward
in the advance of high-performance solution-processed
PHOLEDs.
E
CHTUNGTRENNUNG
compared with the traditional phosphorescent Ir copoly-
mers, in which the phosphorescent cores are more scattered
along the polymer backbone in the presence of a higher
fraction of the organic components that can avoid the
quenching effect among the emitting sites. Instead, the phos-
phorescent Ir centers tend to get closer to each other in P1
and P2 while the performance data of PHOLEDs prepared
with P1 and P2 are still comparable to or even better than
some reported data from the devices with traditional phos-
phorescent copolymers consisting of Ir in the main chain.[18]
In the previous section, the TD-DFT results show that the
dp orbitals of Pt have a notable contribution to the HOMO
of the oligometallaynes (Table 2). So, the PtII centers would
strengthen the spin-orbit coupling effect to induce their own
organic triplet emission, apart from the original phosphores-
Experimental Section
General Information
All reactions were performed under a nitrogen atmosphere but no special
precautions were required during work-up. Solvents were carefully dried
and distilled from appropriate drying agents prior to use. Commercially
available reagents were used without further purification unless other-
wise stated. All reactions were monitored by thin-layer chromatography
(TLC) with Merck pre-coated aluminum plates. Flash column chromatog-
raphy was carried out using silica gel (200–300 mesh). Fast atom bom-
bardment (FAB) mass spectra were recorded on
a Finnigan MAT
SSQ710 system. The NMR spectra were measured in CDCl3 on a Bruker
AXS 300 or 400 MHz spectrometer with the 1H and 13C chemical shifts
quoted relative to tetramethylsilane and 31P chemical shifts relative to
the 85% H3PO4 external standard.
cence arising from the IrACHTNURTGNEN(UG C^N)2ACHTUNGTNER(NUGN acac) chromophores. Also,
the energy of the triplet state induced by the PtII center is
higher than that of the IrIII center on the basis of the photo-
physical data for the reported PtII-bis(aryleneethyny-
lene)s.[19] Thus, there should be an efficient energy transfer
from the high-energy triplets induced by the PtII centers to
the low-energy ones by IrIII centers, and hence, only peaks
resembling the line shape of the emission of the IrIII phos-
phorescent centers can be observed in both the PL and EL
spectra (Figures 1b and 4 and Figure S2 in the Supporting
Information). Such energy transfer process would not only
maintain good color purity of the emission but also enhance
the phosphorescence intensity of the IrIII center. In other
words, there is a synergistic effect between the two different
metal centers which can offer better phosphorescence prop-
erties. As a result, the performance of PHOLEDs made
from the dual metal-centered oligometallaynes is still satis-
factory. The present work provides a new platform for de-
signing and synthesizing these organometallic compounds
with bimetallic skeletons.
Physical Measurements
FT-IR spectra for the sample in KBr pellet were recorded on Nicolet
Magna-IR 550 Series II spectrometer. UV/Vis spectra were obtained on
a Shimadzu UV-2250 spectrophotometer. The photoluminescent proper-
ties of the compounds were examined using a Hitachi F-4500 fluores-
cence spectrophotometer. The phosphorescence quantum yields were de-
termined in degassed CH2Cl2 solutions at 293 K against fac-[IrACHTUNGTRENNUNG(ppy)3]
standard (FP =0.40).[20] The lifetimes were measured by a single photon
counting spectrometer from Edinburgh Instruments (FLS920) with a hy-
drogen-filled pulse lamp as the excitation source. The data analysis was
conducted by iterative convolution of the luminescence decay profile
with the instrument response function using the software package provid-
ed by Edinburgh Instruments. Differential scanning calorimetry (DSC)
was performed on a NETZSCH DSC 200 PC unit under a nitrogen flow
at a heating rate of 108C minꢀ1. The thermal gravimetric analysis (TGA)
was conducted on a NETZSCH STA 409C instrument under nitrogen
with the heating rate of 208C minꢀ1. Gel permeation chromatography
(GPC) measurements were carried out on a Waters Breeze system
equipped with a Waters 2487 UV/Vis detector and a set of 3 columns
(Styragel HR3, HR4E, and HR4) at 308C. CHCl3 was used as the mobile
phase with a flow rate of 1 mLminꢀ1. Calibration was performed by using
a set of polystyrene standards. Electrochemical measurements were made
using a Princeton Applied Research model 273 A potentiostat. The cyclic
voltammetry experiment of the sample film was performed at a scan rate
of 100 mVsꢀ1 using a eDAQ EA161 potentiostat electrochemical inter-
face equipped with a thin film coated ITO covered glass working elec-
trode, a platinum counter electrode and a Ag/AgCl (in 3m KCl) refer-
ence electrode. The solvent in all measurements was deoxygenated
Conclusions
A prominent class of phosphorescent oligometallaynes of
dual metal centers (IrIII and PtII) were designed and synthe-
sized for the first time. Their thermal and photophysical
properties were also presented. Theoretical TD-DFT investi-
gation together with their detailed photophysics showed that
the emissive species involved in these oligometallaynes
mainly arise from the IrIII-centered building block with
added benefits endowed by the PtII component. Experimen-
tal results indicated that there is a synergistic effect between
the two kinds of metal centers which can improve the phos-
MeCN, and the supporting electrolyte was 0.1m [nBu4N]ACTHNUTRGNENU[G PF6]. Thin
sample films were deposited on the working electrode by dip-coating in
chlorobenzene solution (6 mgmLꢀ1). The onset oxidation potential
(Eonset,ox) and optical bandgap (Eg) were used to determine the HOMO
and LUMO energy levels using the equations EHOMO =[ꢀ(Eonset,ox (vs Ag/Ag-
Cl)ꢀEonset
Ag/AgCl)]ꢀ4.50 eV and ELUMO =(EHOMO+Eg) eV, where the
(N.H.E. vs
potentials for N.H.E. versus vacuum and N.H.E. versus Ag/AgCl are 4.50
and ꢀ0.22 V, respectively.[21]
2412
www.chemasianj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2010, 5, 2405 – 2414

Electrophosphorescent Heterobimetallic Oligometallaynes
General Procedure for the Synthesis of P1 and P2
[1] a) R. Noyori, Angew. Chem. 2002, 114, 2108; Angew. Chem. Int. Ed.
2002, 41, 2008; b) W. S. Knowles, Angew. Chem. 2002, 114, 2096;
Angew. Chem. Int. Ed. 2002, 41, 1998; c) B. Cornils, W. A. Herr-
mann, M. Muhler, C.-H. Wong, Catalysis from A To Z: A Concise
Encyclopedia, Wiley-VCH, Weinheim, 2007; d) R. Sheldon, I.
Arends, U. Hanefeld, Green Chemistry and Catalysis, Wiley-VCH,
Weinheim, 2007; e) Z. Wang, G. Chen, K. Ding, Chem. Rev. 2009,
109, 322; f) G. Ertl, H. Knçzinger, F. Schꢃth, J. Weitkamp, Hand-
book of Heterogeneous Catalysis, Wiley-VCH, Weinheim, 2008.
[2] a) A. Coskun, B. T. Baytckin, E. U. Akkaya, Tetrahedron Lett. 2003,
44, 5649; b) S. Mizukami, T. Nagono, Y. Urano, A. Odani, K. Kiku-
chi, J. Am. Chem. Soc. 2002, 124, 3920; c) M. Melaimi, F. P. Gabbaꢄ,
J. Am. Chem. Soc. 2005, 127, 9680; d) R. Martꢅnez-MꢆÇez, F. Sance-
nꢇn, Chem. Rev. 2003, 103, 4419.
[3] a) A. Hagfeldt, M. Grꢈtzel, Acc. Chem. Res. 2000, 33, 269; b) J.-H.
Yum, P. Chen, M. Grꢈtzel, M. K. Nazeeruddin, ChemSusChem 2008,
1, 699; c) H. Imahori, T. Umeyama, S. Ito, Acc. Chem. Res. 2009, 42,
1809; d) P. Wang, S. M. Zakeeruddin, J. E. Moser, M. K. Nazeerud-
din, T. Sekiguchi, M. Grꢈtzel, Nat. Mater. 2003, 2, 402.
[4] P. W. N. M. van Leeuwen, Homogeneous Catalysis-Understanding
the Art, Kluwer Academic Publishers, Dordrecht 2004.
[5] a) I. Ojima, Catalytic Asymmetric Synthesis, Wiley-VCH, Weinheim,
2000; b) E. N. Jacobsen, A. Pfaltz, H. Yamamoto, Comprehensive
Asymmetric Catalysis, Springer, Berlin, 1999.
Under an inert N2 atmosphere, equimolar amounts of each corresponding
metalloACHTUNGTRENNUNGliACHTUNGTRENNUNGgand and trans-[PtCATHUGNTNER(NGUN PBu3)2Cl2] were added to a mixture of Et3N
and CH2Cl2 (1:1 v/v) with a catalytic amount of CuI. The reaction mix-
ture was stirred at room temperature overnight. Then the reaction mix-
ture was passed through a short silica pad using CH2Cl2 as eluent and the
volatile components were removed under reduced pressure to get a
crude product. A small amount of CH2Cl2 was added to dissolve the
crude polymetallayne. The solution was then poured into methanol. The
orange precipitate formed was collected and dried to get the title oligo-
metallaynes in ~87% yield.
P1: (Yield: 87%). 1H NMR (400 MHz, CDCl3): d=8.40 (d, br, 2H, Ar),
7.68 (d, br, 2H, Ar), 7.60 (t, br, 2H, Ar), 7.31 (d, br, 2H, Ar), 6.97 (t, br,
2H, Ar), 6.70 (d, br, 2H, Ar), 6.15 (s, br, 2H, Ar), 5.16 (s, br, 1H, acac),
1.88 (br, 12H, PBu3), 1.76 (s, br, 6H, acac), 1.40 (br, 12H, PBu3), 1.28
(m, br, 12H, PBu3), 0.81 ppm (t, br, 18H, PBu3); 31P NMR (161.9 MHz,
CDCl3): d=4.15 ppm (1JPꢀPt =2375 Hz); Gel permeation chromatography
(GPC): number-average molecular weight (Mn)=1.3ꢂ104 gmolꢀ1, poly-
dispersity index (PDI)=1.18 (against polystyrene standards).
P2: (Yield: 87%). 1H NMR (270 MHz, CDCl3): d=8.60 (d, br, 2H, Ar),
7.93 (d, br, 2H, Ar), 7.78–7.75 (m, br, 2H, Ar), 7.45 (s, br, 2H, Ar), 7.15–
7.04 (m, 8H, Ar), 6.51 (s, br, 2H, Ar), 5.23 (s, br, 1H, acac), 2.13 (br,
12H, PBu3), 1.90–1.70 (m, 14H, acac and Bu), 1.59 (br, 12H, PBu3), 1.41
(m, br, 12H, PBu3), 1.06 (br, 4H, Bu), 0.88 (m, br, 22H, PBu3 and Bu),
0.69–0.42 ppm (m, 20H, Bu); 31P NMR (161.9 MHz, CDCl3): d=
[6] a) F. Gao, Y. Wang, D. Shi, J. Zhang, M. Wang, X. Jing, R. Humph-
ry-Baker, P. Wang, S. M. Zakeeruddin, M. Grꢈtzel, J. Am. Chem.
Soc. 2008, 130, 10720; b) W.-Y. Wong, X.-Z. Wang, Z. He, A. B.
3.75 ppm (1JPꢀPt =2355 Hz); GPC: Mn =1.1ꢂ104 gmolꢀ1
(against polystyrene standards).
,
PDI=1.56
ˇ ´
Djurisic, C.-T. Yip, K.-Y. Cheung, H. Wang, C. S.-K. Mak, W.-K.
Chan, Nat. Mater. 2007, 6, 521; c) W.-Y. Wong, X.-Z. Wang, Z. He,
OLED Fabrication and Measurements
ˇ ´
K.-K. Chan, A. B. Djurisic, K.-Y. Cheung, C.-T. Yip, A. M.-C. Ng,
Y. Y. Xi, C. S.-K. Mak, W.-K. Chan, J. Am. Chem. Soc. 2007, 129,
14372; d) W.-Y. Wong, Macromol. Chem. Phys. 2008, 209, 14; e) L.
Liu, C.-L. Ho, W.-Y. Wong, K.-Y. Cheung, M.-K. Fung, W.-T. Lam,
The pre-cleaned ITO glass substrates were treated with ozone for 20 min.
Then, the PEDOT:PSS was deposited on the surface of ITO glass by
spin-coating method to form a 40 nm-thick hole-injection layer after
being cured at 1208C for 30 min in air. The emitting layer (50 nm) was
obtained by spin-coating a chloroform solution of each phosphorescent
dopant (x wt%) in CBP at various concentrations. The sample was dried
in a vacuum oven at 508C for 15 min and it was transferred to the deposi-
tion system for organic and metal deposition. BCP (15 nm), Alq3
(40 nm), LiF (1 nm) and Al cathode (100 nm) were successively evapo-
rated at a base pressure less than 10ꢀ6 Torr. The EL spectra and CIE co-
ordinates were measured with a PR650 spectra colorimeter. The L-V-J
curves of the devices were recorded by a Keithley 2400/2000 source
meter and the luminance was measured using a PR650 SpectraScan spec-
trometer. All the experiments and measurements were carried out under
ambient conditions.
ˇ ´
A. B. Djurisic, W.-K. Chan, Adv. Funct. Mater. 2008, 18, 2824; f) X.-
ˇ ´
Z. Wang, W.-Y. Wong, K.-Y. Cheung, M.-K. Fung, A. B. Djurisic,
W.-K. Chan, Dalton Trans. 2008, 5484.
[7] a) G.-J. Zhou, W.-Y. Wong, Z. Lin, C. Ye, Angew. Chem. 2006, 118,
6335; Angew. Chem. Int. Ed. 2006, 45, 6189; b) G.-J. Zhou, W.-Y.
Wong, C. Ye, Z. Lin, Adv. Funct. Mater. 2007, 17, 963; c) G.-J. Zhou,
W.-Y. Wong, D. Cui, C. Ye, Chem. Mater. 2005, 17, 5209; d) G.-J.
Zhou, W.-Y. Wong, S.-Y. Poon, C. Ye, Z. Lin, Adv. Funct. Mater.
2009, 19, 531; e) F. Guo, W. Sun, Y. Liu, K. Schanze, Inorg. Chem.
2005, 44, 4055; f) W. Sun, H. Zhu, P. M. Barron, Chem. Mater. 2006,
18, 2602; g) R. Vestberg, R. Westlund, A. Eriksson, C. Lopes, M.
Carlsson, B. Eliasson, E. Glimsdal, M. Lindgren, E. Malmstrçm,
Macromolecules 2006, 39, 2238; h) R. Westlund, E. Malmstrçm, C.
Lopes, J. ꢉhgren, T. Rodgers, Y. Saito, S. Kawata, E. Glimsdal, M.
Lindgren, Adv. Funct. Mater. 2008, 18, 1939; i) R. Zieba, C. Desroch-
es, F. Chaput, M. Carlsson, B. Eliasson, C. Lopes, M. Lindgren, S.
Parola, Adv. Funct. Mater. 2009, 19, 235.
[8] a) C.-H. Yang, Y.-M. Cheng, Y. Chi, C.-J. Hsu, F.-C. Fang, K.-T.
Wong, P.-T. Chou, C.-H. Chang, M.-H. Tsai, C.-C. Wu, Angew.
Chem. 2007, 119, 2470; Angew. Chem. Int. Ed. 2007, 46, 2418; b) C.-
L. Li, Y.-J. Su, Y.-T. Tao, P.-T. Chou, C.-H. Chien, C.-C. Cheng, R.-S.
Liu, Adv. Funct. Mater. 2005, 15, 387; c) C.-F. Chang, Y.-M. Cheng,
Y. Chi, Y.-C. Chiu, C.-C. Lin, G.-H. Lee, P.-T. Chou, C.-C. Chen, C.-
H. Chang, C.-C. Wu, Angew. Chem. 2008, 120, 4618; Angew. Chem.
Int. Ed. 2008, 47, 4542; d) Y.-H. Song, S.-J. Yeh, C.-T. Chen, Y. Chi,
C.-S. Liu, J.-K. Yu, Y.-H. Hu, P.-T. Chou, S.-M. Peng, G.-H. Lee,
Adv. Funct. Mater. 2004, 14, 1221; e) S. Bettington, M. Tavasli, M. R.
Bryce, A. Beeby, H. Al-Attar, A. P. Monkman, Chem. Eur. J. 2007,
13, 1423; f) J. M. Lupton, I. D. W. Samuel, M. J. Frampton, R. Bea-
vington, P. L. Burn, Adv. Funct. Mater. 2001, 11, 287; g) C.-L. Lee,
R. R. Das, J.-J. Kim, Chem. Mater. 2004, 16, 4642; h) M. K. Nazeer-
uddin, R. Humphry-Baker, D. Berner, S. Rivier, L. Zuppiroli, M.
Grꢈtzel, J. Am. Chem. Soc. 2003, 125, 8790; i) Y. Chi, P.-T. Chou,
Chem. Soc. Rev. 2010, 39, 638; j) P.-T. Chou, Y. Chi, Eur. J. Inorg.
Chem. 2006, 3319; k) P.-T. Chou, Y. Chi, Chem. Eur. J. 2007, 13, 380;
l) Y. You, S. Y. Park, Dalton Trans. 2009, 1267.
Computational Details
Density functional theory (DFT) calculations using the B3LYP functional
were performed. The basis set used for C, H, N, and O atoms was 6-31G
while effective core potentials with a LanL2DZ basis set were employed
for P, Pt, and Ir atoms.[22] Polarization functions were added for P
(zd(P)=0.340). All calculations were carried out using the Gaussian 03
program.[23] Mulliken population analyses were performed using Mull-
Pop.[24] Frontier molecular orbitals obtained from the DFT calculations
were plotted using the Molden 3.7 program written by Schaftenaar.[25]
Acknowledgements
This work was supported by a grant from Xi’an Jiao Tong University
(No. 08140004),
a Research Grant from Shaanxi Province (No.
2009JQ2008), and the National Natural Science Foundation of China
(No. 20902072). W.-Y. Wong thanks the Croucher Foundation for the
Croucher Senior Research Fellowship, Hong Kong Baptist University
(FRG2/08-09/111), the Hong Kong Research Grants Council
(HKBU202508) and a grant from Areas of Excellence Scheme, Universi-
ty Grants Committee, Hong Kong (Project No. [AoE/P-03/08]).
Chem. Asian J. 2010, 5, 2405 – 2414
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
2413

G. Zhou, W.-Y. Wong, Z. Xie, X. Zhao et al.
FULL PAPERS
[9] a) C.-M. Che, S.-C. Chan, H.-F. Xiang, M. C. W. Chan, Y. Liu, Y.
Wang, Chem. Commun. 2004, 1484; b) M. Cocchi, D. Virgili, V. Fat-
tori, D. L. Rochester, J. A. G. Williams, Adv. Funct. Mater. 2007, 17,
285; c) S.-C. Chan, M. C. W. Chan, Y. Wang, C.-M. Che, K.-K.
Cheung, N. Zhu, Chem. Eur. J. 2001, 7, 4180; d) J. Kavitha, S.-Y.
Chang, Y. Chi, J.-K. Yu, Y.-H. Hu, P.-T. Chou, S.-M. Peng, G.-H.
Lee, Y.-T. Tao, C.-H. Chien, A. J. Carty, Adv. Funct. Mater. 2005, 15,
223; e) W.-Y. Wong, Z. He, S.-K. So, K.-L. Tong, Z. Lin, Organome-
tallics 2005, 24, 4079; f) G.-J. Zhou, X.-Z. Wang, W.-Y. Wong, X.-M.
Yu, H.-S. Kwok, Z.-Y. Lin, J. Organomet. Chem. 2007, 692, 3461;
g) C. Yang, X. Zhang, H. You, L. Zhu, L. Chen, L. Zhu, Y. Tao, D.
Ma, Z. Shuai, J. Qin, Adv. Funct. Mater. 2007, 17, 651; h) G. Zhou,
Q. Wang, C.-L. Ho, W.-Y. Wong, D. Ma, L. Wang, Chem. Commun.
2009, 3574; i) C.-L. Ho, W.-Y. Wong, B. Yao, Z. Xie, L. Wang, Z.
Lin, J. Organomet. Chem. 2009, 694, 2735.
[10] a) Y.-H. Niu, Y.-L. Tung, Y. Chi, C.-F. Shu, J. H. Kim, B. Chen, J.
Luo, A. J. Carty, A. K.-Y. Jen, Chem. Mater. 2005, 17, 3532; b) X.
Jiang, A. K.-Y. Jen, B. Carlson, L. R. Dalton, Appl. Phys. Lett. 2002,
81, 3125; c) B. Carlson, G. D. Phelan, W. Kaminsky, L. Dalton, X. Z.
Jiang, S. Liu, A. K.-Y. Jen, J. Am. Chem. Soc. 2002, 124, 14162; d) S.
Bernhard, X. Gao, G. G. Malliaras, H. D. Abruna, Adv. Mater. 2002,
14, 433; e) Y. Ma, H. Zhang, J. Shen, C. Che, Synth. Met. 1998, 94,
245; f) Y.-L. Tung, S.-W. Lee, Y. Chi, Y.-T. Tao, C.-H. Chien, Y.-M.
Cheng, P.-T. Chou, S.-M. Peng, C.-S. Liu, J. Mater. Chem. 2005, 15,
460.
[11] a) M. Ikai, S. Tokito, Y. Sakamoto, T. Suzuki, Y. Taga, Appl. Phys.
Lett. 2001, 79, 156; b) W.-Y. Wong, G.-J. Zhou, X.-M. Yu, H.-S.
Kwok, B.-Z. Tang, Adv. Funct. Mater. 2006, 16, 838; c) W.-Y. Wong,
C.-L. Ho, Z.-Q. Gao, B.-X. Mi, C.-H. Chen, K.-W. Cheah Z. Lin,
Angew. Chem. 2006, 118, 7964; Angew. Chem. Int. Ed. 2006, 45,
7800; d) G.-J. Zhou, C.-L. Ho, W.-Y. Wong, Q. Wang, D.-G. Ma, L.-
X. Wang, Z.-Y. Lin, T. B. Marder, A. Beeby, Adv. Funct. Mater.
2008, 18, 499; e) G.-J. Zhou, W.-Y. Wong, B. Yao, Z.-Y. Xie, L.-X.
Wang, Angew. Chem. 2007, 119, 1167; Angew. Chem. Int. Ed. 2007,
46, 1149; f) G.-J. Zhou, W.-Y. Wong, B. Yao, Z.-Y. Xie, L.-X. Wang,
J. Mater. Chem. 2008, 18, 1799; g) S. Lamansky, P. Djurovich, D.
Murphy, F. Abdel-Razzaq, H.-E. Lee, C. Adachi, P. E. Burrows,
S. R. Forrest, M. E. Thompson, J. Am. Chem. Soc. 2001, 123, 4304;
h) A. Tsuboyama, H. Iwawaki, M. Furugori, T. Mukaide, J. Kamata-
ni, S. Igawa, T. Moriyama, S. Miura, T. Takiguchi, S. Okada, M.
Hoshino, K. Ueno, J. Am. Chem. Soc. 2003, 125, 12971; i) W.-Y.
Wong, C.-L. Ho, J. Mater. Chem. 2009, 19, 4457; j) W.-Y. Wong, C.-
L. Ho, Coord. Chem. Rev. 2009, 253, 1709.
L. Ho, S. Aouba, Y.-Q. Zhao, Z.-H. Lu, S. Petrov, N. Coombs, P.
Dube, H. E. Ruda, W.-Y. Wong, I. Manners, Angew. Chem. 2008,
120, 1275; Angew. Chem. Int. Ed. 2008, 47, 1255.
[14] a) J. K. Stille, Angew. Chem. 1986, 98, 504; Angew. Chem. Int. Ed.
Engl. 1986, 25, 508; b) K. Sonogashira in Comprehensive Organic
Synthesis, Vol. 3 (Eds.: B. M. Trost, I. Fleming), Pergamon, Oxford,
UK, 1991, p. 551; c) F. Diederich, P. J. Stang, R. R. Tykwinski, Acety-
lene Chemistry, Wiley-VCH, Weinheim, 2005.
[15] a) Y. Fujikura, K. Sonogashira, N. Hagihara, Chem. Lett. 1975, 1067;
b) K. Sonogashira, S. Takahashi, N. Hagihara, Macromolecules 1977,
10, 879; c) W.-Y. Wong, G.-L. Lu, K.-H. Choi, J.-X. Shi, Macromole-
cules 2002, 35, 3506.
[16] a) L. A. Emmert, W. Choi, J. A. Marshall, J. Yang, L. A. Meyer,
J. A. Brozik, J. Phys. Chem. A 2003, 107, 11340; b) S. M. Aly, C.-L.
Ho, D. Fortin, W.-Y. Wong, A. S. Abd-El-Aziz, P. D. Harvey, Chem.
Eur. J. 2008, 14, 8341; c) S. M. Aly, C.-L. Ho, W.-Y. Wong, D. Fortin,
P. D. Harvey, Macromolecules 2009, 42, 6902.
[17] a) S. P. McGlynn, F. J. Smith, G. Cilento, Photochem. Photobiol.
1964, 3, 269; b) J. E. Rogers, T. M. Cooper, P. A. Fleitz, D. J. Glass,
D. G. McLean, J. Phys. Chem. A 2002, 106, 10108.
[18] a) Y. Zhang, Y. Xu, Q. Niu, J. Peng, W. Yang, X. Zhu, Y. Cao, J.
Mater. Chem. 2007, 17, 992; b) H. Zhen, C. Jiang, W. Yang, J. Jiang,
F. Huang, Y. Cao, Chem. Eur. J. 2005, 11, 5007; c) Q. Zhao, S.-J. Liu,
W. Huang, Macromol. Rapid Commun. 2010, 31, 794; d) J. Jiang, W.
Yang, Y. Cao, J. Inorg. Organomet. Polym. Mater. 2007, 17, 37.
[19] a) W.-Y. Wong, Coord. Chem. Rev. 2006, 250, 2627; b) W.-Y. Wong,
Dalton Trans. 2007, 4495; c) W.-Y. Wong, P. D. Harvey, Macromol.
Rapid Commun. 2010, 31, 671.
[20] K. A. King, P. J. Spellane, R.-J. Watts, J. Am. Chem. Soc. 1985, 107,
1431.
[21] a) J. Hou, Z. Tan, Y. Yan, Y. He, C. Yang, Y. Li, J. Am. Chem. Soc.
2006, 128, 4911; b) C. G. Van de Walle, J. Neugebauer, Nature 2003,
423, 626.
[22] a) W. R. Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284; b) P. J. Hay,
W. R. Wadt, J. Chem. Phys. 1985, 82, 299.
[23] Gaussian 03, revision B05, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, T.
Vreven Jr., K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K.
Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakr-
zewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K.
Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz,
Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox,
T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challa-
combe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonza-
lez, J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 2003.
[12] a) M. A. Baldo, D. F. OꢀBrien, Y. You, A. Shoustikov, S. Sibley,
M. E. Thompson, S. R. Forrest, Nature 1998, 395, 151; b) M. A.
Baldo, M. E. Thompson, S. R. Forrest, Nature 2000, 403, 750; c) H.
Yersin, Top. Curr. Chem. 2004, 241, 1.
[13] a) M. Shiotsuka, Y. Yamamoto, S. Okuno, M. Kitou, K. Nozaki, S.
Onaka, Chem. Commun. 2002, 590; b) I. E. Pomestchenko, D. E.
Polyansky, F. N. Castellano, Inorg. Chem. 2005, 44, 3412; c) K.-H.
Chang, C.-C. Huang, Y.-H. Liu, Y.-H. Hu, P.-T. Chou, Y.-C. Lin,
Dalton Trans. 2004, 1731; d) J. Vicente, M.-T. Chicote, M. M. Alvar-
ez-Falcꢇn, Organometallics 2005, 24, 2764; e) O. Lavastre, M. Even,
P. H. Dixneuf, A. Pacreau, J.-P. Vairon, Organometallics 1996, 15,
1530; f) N. J. Long, A. J. Martin, R. Vilar, A. J. P. White, D. J. Wil-
liams, M. Younus, Organometallics 1999, 18, 4261; g) K.-L. Cheung,
S.-K. Yip, V. W.-W. Yam, J. Organomet. Chem. 2004, 689, 4451;
h) S. C.-F. Lam, V. W.-W. Yam, K. M.-C. Wong, E. C.-C. Cheng, N.
Zhu, Organometallics 2005, 24, 4298; i) W.-Y. Wong, W.-K. Wong,
P. R. Raithby, J. Chem. Soc. Dalton Trans. 1998, 2761; j) K. Liu, C.-
[24] MullPop, a program written by Reinaldo Pis Diez at the National
University of La Plata, Argentina.
[25] G. Schaftenaar Molden v3.7; CAOS/CAMM Center Nijmegen: Toer-
nooiveld, Nijmegen, Netherlands, 2001.
Received: May 10, 2010
Revised: June 7, 2010
Published online: September 3, 2010
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