Synthesis, structure-properties of planar, end-substituted, light-emitting oligophenylenevinylenes

Article abstract of DOI:10.1039/b000827n

A novel homologous series of highly soluble, multiple alkoxy end-substituted oligophenylenevinylenes (OPV) containing up to six phenyl rings were synthesized. In contrast to the lateral substituted OPVs, our theoretical and experimental evidences have shown that the electron donating groups incorporated at the cnds of an oligomer do not affect co-planarity of the π-conjugated system. They can also promote a faster convergence of the HOMO-LUMO energy gap relative to those of unsubstituted OPVs suggesting a shorter effective conjugation length in this series. These end-substituted OPVs containing more than three phenyl-rings exhibit very high fluorescence quantum yields (more than 74%). Multi-layer LEDs using these end-substituted OPVs as emissive layers were fabricated and investigated. We have found that there is a bathochromic shift of the PL and EL maxima with an increase of chain length in this series. All these oligomer-based multi-layer LEDs show very low turn-on-voltage. In addition, the higher homologues of these oligomers suffered from severe interchain interaction leading to a dramatic decrease in the external quantum efficiency; however, this can be alleviated by doping the oligomer into the host matrix.

Full text of DOI:10.1039/b000827n

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J O U R N A L O F
Synthesis, structure±properties of planar, end-substituted, light-
emitting oligophenylenevinylenes
Man Shing Wong,*a Zhong Hui Li,a Man Fai Shek,a Kei Hau Chow,a Ye Taob and
Marie D'Ioriob
Communication
C H E M I S T R Y
aDepartment of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
E-mail: mswong@hkbu.edu.hk
bInstitute for Microstructural Sciences, National Research Council of Canada, M-50
Montreal Road, Ottawa, Ontario, Canada K1A 0R6
Received 31st January 2000, Accepted 23rd May 2000
Published on the Web 6th July 2000
A novel homologous series of highly soluble, multiple alkoxy end-substituted oligophenylenevinylenes (OPV)
containing up to six phenyl rings were synthesized. In contrast to the lateral substituted OPVs, our theoretical
and experimental evidences have shown that the electron donating groups incorporated at the ends of an
oligomer do not affect co-planarity of the p-conjugated system. They can also promote a faster convergence of
the HOMO±LUMO energy gap relative to those of unsubstituted OPVs suggesting a shorter effective
conjugation length in this series. These end-substituted OPVs containing more than three phenyl-rings exhibit
very high ¯uorescence quantum yields (more than 74%). Multi-layer LEDs using these end-substituted OPVs as
emissive layers were fabricated and investigated. We have found that there is a bathochromic shift of the PL
and EL maxima with an increase of chain length in this series. All these oligomer-based multi-layer LEDs show
very low turn-on-voltage. In addition, the higher homologues of these oligomers suffered from severe interchain
interaction leading to a dramatic decrease in the external quantum ef®ciency; however, this can be alleviated by
doping the oligomer into the host matrix.
Investigation of well-de®ned p-conjugated oligomers is of
considerable interest since it can provide an insight into the
structural and electronic properties of the related polymeric
materials.1,2 In addition, the ease of obtaining oligomers of
high purity and fabricating oligomers into a thin-®lm offers
advantages for using functionalized oligomer as an active
component for device applications such as light emitting
diodes,3,4 light modulators5 and ®eld-effect transistors.6,7 It is
well known that an effective (optimal) conjugation length in p-
conjugated polymers exists that is responsible for the ultimate
optical and electronic properties of a polymer.8 However, the
subtle modi®cation of the monomeric unit can often lead to a
dramatic change in the physical properties of a polymer such as
an energy gap or a ¯uorescent ef®ciency. As a result, knowledge
of the structure±property relationship will certainly be
important and useful for the exploration and development of
``better'' molecular based materials. The promise of ef®cient
light emitting properties of polyphenylenevinylene (PPV) and
its derivatives9 has increasingly drawn attention on its
oligomer, oligo-phenylenevinylenes (OPV) which has become
one of the widely investigated p-conjugated oligomers over the
last few years.1,10 Because of the planarity and rigidity of the
phenylenevinylene unit which are responsible for its unique
functional properties, the higher homologues of OPVs are
highly insoluble.11 This often limits further investigations and
potential applications. One of the common approaches to
enhance the solubility and processability of p-conjugated
oligomers and polymers is to introduce substituents (i.e.
alkyl or alkoxy groups) on the lateral sides of the p-conjugated
main chain. However, this often leads to a distortion of the co-
planarity of the p-conjugated backbone12 due to the steric
hindrance as well as a change in inter-chain packing mode (or
interaction) and hence affecting favourable physical properties
such as spectral shift, quantum ef®ciency of ¯uorescence13 and
turn-on voltage in light emitting diodes (LED).14 As a result, it
may be of interest to conserve the integrity of the co-planarity
of the phenylenevinylene p-conjugated backbone but only a
few OPV derivatives have been developed towards this
direction.
Wong et al.15 have recently shown that solublizing
substituents such as polyalkyleneoxy and alkylsulfonyl
groups incorporated at the ends of the p-conjugated skeleton
of distyrylstilbene can improve solubility without disrupting
the co-planarity of the p-conjugation backbone. Our attempt
to prepare longer 4,4'-disubstituted OPVs was again hampered
by their insolubility. Although side-substituted OPVs contain-
ing up to 11 phenyl-rings were recently synthesized, their p-
conjugation backbones are again twisted out of co-planarity.10
On the other hand, substituents incorporated at the end of the
conjugated position of the main chain i.e. 4,4'-positions can
shift the HOMO and/or LUMO level by electronic effects and
thus alter the HOMO±LUMO energy gap of an oligomer.
This provides a means to tune the energy gap leading to a
change in optical and electronic properties of an oligomer.16
To further enhance the solubilities of higher homologous
OPVs, a multiple end-substitution approach could be used.
We herein report the synthesis and optical properties of a
novel homologous series of highly soluble, symmetrically
multi-alkoxy substituted OPVs containing up to six phenyl
rings which were shown to have co-planar p-conjugation
backbones. The ground and excited state molecular properties
DOI: 10.1039/b000827n
J. Mater. Chem., 2000, 10, 1805±1810
This journal is # The Royal Society of Chemistry 2000
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Scheme 1 Reagents and conditions: i, Na2CO, KI, DMF, 60±70 ³C; ii, LAH, THF, 0 ³C, then HCl; iii, SOCl2, Py, 0 ³C; iv, P(OEt)3, 150 ³C; v, NaH,
DME, room temp.; vi, HCl, acetone.
of the end-substituted OPVs were investigated by PM3 semi-
empirical quantum mechanical
calculations to understand and correlate the structure±optical
properties of the oligomers. In addition, multi-layer LEDs
using these end-substituted OPVs as emissive layers were
fabricated by vacuum deposition technique and their photo-
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J. Mater. Chem., 2000, 10, 1805±1810

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luminescent and electroluminescent properties were investi-
gated.
Results and discussion
The stereoselective Wadsworth±Emmons reaction was used as
a key step to synthesize the all trans carbon±carbon double
bonds of an OPV. The general synthetic sequences are outlined
in Scheme 1. In general, the odd-phenyl-ring oligomers (e.g.
®ve-phenyl-ring oligomer, 3) were prepared by the double
Wadsworth±Emmons reactions of bis-phosphonate 12 and the
corresponding aldehyde (i.e. 11). The even-phenyl-ring oligo-
mers were synthesized by a convergent nzn approach (i.e. 3z3
for six-phenyl-ring oligomer, 4). The starting precursors were
prepared as follows. The tri-alkoxy substituted benzaldehyde 8
was synthesized by the Williamson ether reaction of 3,5-
dimethoxy-4-hydroxybenzaldehyde 6 and 2-(2-butoxyethoxy)-
ethyl tosylate 7 in the presence of Na2CO3. Phosphonate 9 was
prepared according to the following reaction sequence: ®rstly
reduction of 8 by LiAlH4, subsequent transformation of the
alcohol into the corresponding benzyl chloride by means of
SOCl2 and ®nally reaction with neat P(OEt)3. The Wadsworth-
Emmons reaction of phosphonate 9 and terephthalaldehyde
mono(diethyl acetal) 10, followed by an acid work up, afforded
the corresponding styrylbenzaldehyde 11. Dropwise addition
of tri-alkoxy substituted benzaldehyde 8 over excess of bis-
phosphonate 12 and NaH in high dilution afforded mono-
phosphonate 13 in good yields (62%) relative to three-phenyl-
ring oligomer 1 (20%) which is signi®cantly improved over the
previous procedure.15 In a similar fashion, the higher homo-
logous precursors, such as three-phenyl-ring aldehyde 14 was
prepared by the Wadsworth±Emmons reaction of mono-
phosphonate 13 and aldehyde 10 while three-phenyl-ring
phosphonate 15 was prepared from the reaction of 11 and
12. The seven-phenyl-ring oligomer, 5, was also synthesized
accordingly; however, its solubility is rather poor.
Fig. 1 a Plots of PM3 calculated HOMO±LUMO energy gap of un-
substituted OPVs (OPV) and 4,4'-dimethoxy substituted OPVs
(OPV(n)-OMe) with correction of solvent interaction against number
of phenylenevinylene units (n). b Plots of absorption and emission
maxima of tri-alkoxy substituted OPVs, n~0±5, and absorption
maxima of tert-butyl substituted OPVs (tB-OPV) (from ref 11) against
number of phenylenevinylene units (n).
The ground state molecular geometries of 4,4'-dimethoxy-
and 3,3',4,4',5,5'-hexamethoxy-substituted OPVs were opti-
mized by PM3 semi-empirical methods. The results indicate
that the (multiple) end substitution does not disrupt the co-
planarity of the p-conjugated backbone of oligomers in the
PM3-optimized geometry. It was also found from the
calculations that the frontier molecular orbitals of 4,4'-
dimethoxy-substituted OPVs are destabilized by the methoxy
donating groups as compared to those of the unsubstituted
counterparts. However, the unsymmetric destabilization results
in the overall decrease in the HOMO±LUMO energy gap
(Fig. 1a) in which the HOMO level destabilizes more than the
The solvatochromic effect for this series is rather small
(dlmax~9 nm from hexane to DMSO for 1). Consistent with
the theoretical ®ndings shown above, the alkoxy donating
groups incorporated at the ends of the main chain promote a
faster convergence of the absorption maxima (or energy gap).
In contrast, the propoxy groups incorporated on the lateral
sides of the p-conjugated main chain slow down the
convergence of the absorption maxima.10 The faster conver-
gence of absorption maxima induced by end-substituted
donating groups has also recently been observed in oligothie-
nylenevinylenes.19
As found from the ¯uorescence spectra of the end-
substituted OPVs the emission bands are apparently composed
of two major emissions. (Fig. 2b) Similar to the absorption
behaviour, the emission bands sequentially shift to longer
wavelengths with an extension of the conjugation length
(Table 1); however, the emission cut-offs remain relatively
constant throughout the series. Although the two emission
LUMO level.
A similar destabilization trend has been
theoretically shown in the PPV pentamer side-substituted
with methoxy groups.17 In addition, the destabilization effect
diminishes with an increase in the conjugation length. It is
important to note that the methoxy donating groups reduce the
energy gaps of 4,4'-dimethoxy-substituted OPVs approaching a
limit of convergence faster than those of unsubstituted OPVs
(Fig. 1a) which suggests a shorter effective conjugation length
for the energy gap in this series.
In the electronic absorption spectra, the homologous series
of end-substituted oligomers consistently shows vibronic ®ne
structure indicating planarity and restricted rotation of the p-
conjugated backbone of OPVs (Fig. 2a). There is a sequential
increase in the absorption maxima of the end-substituted OPVs
with a concomitant increase in extinction coef®cient (e) as the
conjugation length increases (Table 1). The red shifts are
towards longer wavelengths relative to those of the corre-
sponding unsubstituted18 and non-conjugated meta-tert-butyl-
substituted OPVs11 before levelling off (Fig. 1a). However,
when compared with those of the corresponding OPVs side-
substituted with propoxy groups, the red shifts are smaller.10
peaks undergo
a red shift to a different extent, the
corresponding peak maxima also exhibit a tendency of
saturation as the conjugation length increases (Fig. 1b).
Importantly, there is a dramatic increase in the ¯uorescence
quantum yield moving from two-phenyl-ring oligomer to three-
phenyl-ring oligomer 1 (Table 1); however, further addition of
the phenylenevinylene unit does not lead to further substantial
improvements. On the whole, these end-substituted OPVs
J. Mater. Chem., 2000, 10, 1805±1810
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Fig. 2 a Absorption spectra of tri-alkoxy substituted OPVs, n~0±4,
measured in CHCl3. b Emission spectra of tri-alkoxy substituted OPVs,
n~0±5, measured in CHCl3.
Fig. 3 a Photoluminescence spectra of tri-alkoxy substituted OPVs,
n~1±3. b Electroluminescence spectra of tri-alkoxy substituted OPVs,
n~1±3.
containing more than three phenyl-rings exhibit very high
¯uorescence quantum yields (more than 74%) suggesting that
they may be potential candidates for light emitting applica-
tions. Such a high ¯uorescence quantum yield in this series is
likely due to the co-planarity of the p-conjugated system.
The thermal gravimetric analysis indicated that this series of
oligomers shows good thermal stability with decomposition
temperature in the range of 250±370 ³C (Table 1). This suggests
that thin-®lms of these oligomers can be prepared by vacuum
evaporation. To avoid the uncertainties involved in wet processes, a
vacuum deposition technique which can provide an ultra clean and
well controlled environment was employed for the preparation of
multi-layer LEDs. Multi-layer LEDs using this series of oligomers
as an emissive layer with a structure of (ITO/TPD (40 nm)/OPV
(40 nm)/PBD (15 nm)/LiF (1 nm)/Al (150 nm)) were fabricated.
The photoluminescence (PL) and electroluminescence (EL) spectra
were shown in Fig. 3. In general, the spectral features of the EL are
very similar to those of the solid-state PL of the corresponding
oligomer suggesting that both emissions arise from the same
oligomers. In addition, the EL spectral characteristics of all these
devicesarevoltageindependentwhichexcludestheformationofthe
exciplex at the interfaces. However, EL spectra exhibit various
extents of peak broadening and shift relative to those of PL spectra
as the chain length increases. The peak broadening may be due to a
broad range of energy sites (emissive states) acting as traps and
Table 1 Summaries of physical measurements of tri-alkoxy-substituted OPVs, n~0±5 and results of PM3 semi-empirical calculations of 4,4'-
dimethoxy substituted OPVs, OPV(n)-OMe
External
lmaxa/nm
(emax/1024
M21 cm21
Emission
band
Fluorescence Decomposition
quantum
quantum
ef®ciency
d/cd A21
temperature
c/³C
Calcd
Calcd
Calcd
Corrected calcd
n
)
maximaa/nm yieldb
HOMOe/eV LUMOe/eV energy gap/eV energy gapf/eV
0
1
2
3
4
5
331 (1.8)
371 (6.2)
392 (9.2)
406 (10.7)
413 (11.7)
417
369, 390
420, 434
438, 463
451, 478
458, 488
463, 493
0.11
0.78
0.81
0.78
0.74
335
317
369
250
259
28.25
23.109
23.246
23.279
23.384
23.398
23.4
5.141
4.889
4.737
4.683
4.663
4.651
3.241
2.989
2.837
2.783
2.763
2.751
0.31
0.52
0.15
28.135
28.092
28.067
28.061
28.051
c
aMeasured in CHCl3. bDetermined by dilution method. Determined by TGA. dCalculated from the measured luminance divided by the current
e
density passing through the device. Calculated by PM3 semi-empirical quantum mechanical calculations. Corrected for solvent interaction by
f
21.9 eV (from ref. 22).
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J. Mater. Chem., 2000, 10, 1805±1810

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recombination centres for injected carriers20 but the cause of the
spectral shift is not known yet.
The methoxy substituents attached onto the non-conjugated
Experimental
TPD represents N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-
biphenyl-4,4'-diamine. PBD represents 2-(biphenyl-4-yl)-5-(4-
tert-butylphenyl)-1,3,4-oxadiazole. All the new compounds
were fully characterized with standard spectroscopic techni-
ques. All the physical measurements were performed in CHCl3.
1H NMR spectra were recorded using a JEOL JHM-EX270 FT
NMR spectrometer and are referenced to the residual CHCl3
7.24 ppm. Electronic absorption (UV±vis) and ¯uorescence
spectra were recorded using a Varian Cary 100 Scan Spectro-
photometer and a PTI Luminescence Spectrophotometer
respectively. The corrected energy gaps reported in the
Table 1 were calculated by an addition of 21.9 eV for solvent
interaction.22 The ¯uorescence quantum yields in chloroform
using 9,10-diphenylanthracene as a standard were determined
by dilution method as described by Parker et al.23 The quantum
yields reported here are the average of two independent
measurements. Thermal stabilities were determined by using
Thermal Gravimetric Analyzer (DTA), Shimadzu TGA-40
with a heating rate of 10 ³C min21. The semi-empirical
calculations using the PM3 parameterization were carried
out by MOPAC 6 in the Alchemy 2000 software package. The
experimental details of the LEDs fabrication can be found in
ref. 16 and 21. The general synthetic procedure for the
Wadsworth±Emmons reaction can be found in ref. 15.
ortho-positions of the end-capped phenyl rings have
a
pronounced effect on the solid-state luminescence properties.
In addition to the difference in spectral features, the emission
maxima of both EL and PL are signi®cantly blue-shifted
(y20 nm) in the three-phenyl-ring oligomer, 1, when compared
to that of the corresponding unsubstituted counterparts.21 Our
initial measurement showed that this LED emits blue light at
456 nm with 120 cd m212 at a bias voltage of 7 V which shows
potential for further development of blue LEDs.
There is a bathochromic shift of both PL and EL maxima
with an extension of the chain length as the energy gap is
lowered which is also consistent with the ¯uorescence
behaviour in solution. In addition, all the devices showed
clear rectifying behaviour in their current-voltage character-
istics. The turn-on voltages of these oligomer-based multi-layer
LEDs are all around 4±5 volts.
Based on the initial multilayer device structure mentioned
above, the external quantum ef®ciencies derived from the
measured luminance divided by the current density passing
through the device were calculated and tabulated in Table 1.
The external quantum ef®ciencies are expected to be enhanced
with an increase of chain length; however, there is a dramatic
decrease in the external quantum ef®ciency with a device based
on 3 which is likely due to the severe interchain interaction in
this longer homologue which is known to be detrimental to the
device ef®ciency. One of the remedies to avoid aggregation is by
means of doping an emissive dye into the host material. The
external quantum ef®ciency of an OLED using co-evaporated
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-
diamine and 1 (TPD?1) as an emissive layer improved to
0.82 cd A21 as compared to 0.31 cd A21 using a single 1
emissive layer. The external ef®ciency could be increased to
Improved procedure for the preparation of diethyl 4-[2-(2-
butoxyethoxy)ethoxy]-3,5-dimethoxystyrylbenzylphosphonate
13
To a stirred solution of bisphosphonate 12 (6.92 g, 18.3 mmol)
and 1.2 equivalent of NaH (0.88 g, 22 mmol) in 500 mL
anhydrous DME at 0 ³C was added dropwise a solution of
trialkoxy-substituted benzaldehyde 8 (2 g, 6.1 mmol) over 1 h.
After stirring for 0.5 h at 0 ³C, the reaction mixture was slowly
warmed up to rt. After stirring for 2 h at rt, the solution
mixture was quenched with water. The crude product was
either collected by suction ®ltration or extracted twice with
CH2Cl2, dried over anhydrous MgSO4 and evaporated to
dryness. The crude product was then puri®ed by silica gel
chromatography using the gradient elution technique with
CH2Cl2±ethyl acetate as eluents affording 2.1 g (62%) of 13 and
0.88 g (20%) of 1.
1.3 cd A21 using
a composite emissive layer of 1 and
LiF. Besides the aggregation improvement, this enhancement
may be also due to the improvement of the charge transport
properties in the composite layer. We have also observed
fragmentation of higher homologues i.e. 4 during thermal
evaporation and the LED obtained exhibit signi®cant blue shift
in the EL and PL and higher turn±on voltage which is likely
due to the contribution of its fragments.
In summary, a novel homologous series of highly soluble,
multiple alkoxy end-substituted oligophenylenevinylenes con-
taining up to six phenyl rings were synthesized. We have shown
that the multiple solubilizing groups substituted at the end of
oligophenylenevinylenes can enhance solubility of higher
homologues of oligomers but do not disrupt the co-planarity
of the p-conjugation backbone. In addition, we have
theoretically and experimentally shown that the electron
donating groups substituted at the end of OPVs can lead to
a faster approach to a limit of convergence and hence promote
a shorter effective conjugation length relative to those of the
unsubstituted and lateral substituted OPVs. The emission
spectra also exhibit a similar tendency of saturation as the
conjugation length increases. End-substituted OPVs containing
more than three phenyl rings exhibit very high ¯uorescence
quantum yields. Multi-layer LEDs using these end-substituted
OPVs as emissive layers were fabricated by vacuum evapora-
tion technique and were investigated. We have found that there
is a bathochromic shift of the PL and EL maxima with an
increase of chain length in the series. All these oligomer-based
multi-layer LEDs show very low turn-on-voltage. Further-
more, there is an increase in the external quantum ef®ciency
with an increase in chain length; however, the higher
homologues of these oligomers suffered from severe interchain
interaction leading to a dramatic decrease in the external
quantum ef®ciency. Nevertheless, the interchain interaction
can be alleviated by doping the oligomer into the host matrix.
1H NMR (270 MHz, CDCl3) d 7.43 (d, J~7.56 Hz, 2H),
7.26 (dd, J~8.19 Hz, J~2.16 Hz, 2H), 6.98 (s, 2H), 6.70 (s,
2H), 4.12 (t, J~5.22 Hz, 2H), 3.99 (m, 4H), 3.82 (s, 12H), 3.84
(t, J ~ 4.98 Hz, 2H), 3.70 (m, 2H), 3.58 (m, 4H), 3.49 (t,
J~6.72 Hz, 2H), 3.14 (d, J~21.87 Hz, 1H), 1.55 (m, 2H), 1.32
(m, 2H), 1.23 (t, J~6.89 Hz, 6H), 0.89 (t, J~7.29 Hz, 3H).
1,4-Bis-4-{[2-(2-butoxyethoxy)ethoxy]-3,5,-dimethoxy}styryl-
benzene 1:. 1H NMR (270 MHz, CDCl3) d 7.42 (s, 4H), 6.99 (d,
J~16.2 Hz, 2H), 6.91 (d, J~16.2 Hz, 2H), 6.66 (s, 4H), 4.10 (t,
J ~ 4.86 Hz, 4H), 3.82 (s, 12H), 3.77 (t, J~5.00 Hz, 4H), 3.64
(m, 4H), 3.54 (m, 4H), 3.40 (t, J~6.75 Hz, 4H), 1.50 (m, 4H),
1.28 (m, 4H), 0.84 (t, J~7.16 Hz, 6H). MS (FAB) m/z 722.6
(Mz). HRMS(FAB) C42H58O10Na: calc. 745.3928 found
745.3918. Found: C, 69.78; H, 8.09. C42H58O10 requires C,
69.72; H, 8.17%. Mp~66 ³C.
1,2-Bis(4-{4-[2-(2-butoxyethoxy)ethoxy]-3,5-dimethoxystyr-
yl}phenyl)ethene 2. 1H NMR (270 MHz, CDCl3) d 7.43 (s, 8H),
7.05 (s, 2H), 6.99 (d, J~16.2 Hz, 2H), 6.91 (d, J~16.2 Hz, 2H),
6.66 (s, 4H), 4.10 (t, J~5.25 Hz, 4H), 3.83 (s, 12H), 3.75 (t,
J~5.13 Hz, 4H), 3.64 (m, 4H), 3.53 (m, 4H), 3.40 (t,
J~6.675 Hz, 4H), 1.51 (m, 4H), 1.29 (m, 4H), 0.84 (t,
J~7.43 Hz, 6H). MS (FAB) m/z 824.6 (Mz). HRMS(FAB)
C50H64O10: calc. 824.4499 found 824.4513. Mp~110 ³C.
J. Mater. Chem., 2000, 10, 1805±1810
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3
4
5
N. N. Barashkov, D. J. Guerrero, H. J. Olivos and J. P. Ferrais,
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1,4-Bis(4-{4-[2-(2-butoxyethoxy)ethoxy]-3,5-dimethoxystyr-
yl}styryl)benzene 3. 1H NMR (270 MHz, CDCl3) d 7.44 (s,
12H), 7.06 (s, 4H), 7.00 (d, J~16.2 Hz, 2H), 6.92 (d,
J~16.47 Hz, 2H), 6.67 (s, 4H), 4.10 (t, J~5.13 Hz, 4H), 3.83
(s, 12H), 3.75 (t, J~5.13 Hz, 4H), 3.65 (m, 4H), 3.53 (m, 4H),
3.40 (t, J~6.62 Hz, 4H), 1.51 (m, 4H), 1.28 (m, 4H), 0.84 (t,
J~7.29 Hz, 6H). MS (FAB) m/z 926.7 (Mz). HRMS(FAB)
C58H70O10: calc. 926.4969 found 926.4989. Found: C, 74.86; H,
7.58. C58H70O10 requires C, 75.13; H, 7.61%. Mp~210 ³C.
6
7
8
9
A. Kraft, A. C. Grimsadle and A. B. Holmes, Angew. Chem., Int.
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1,2-Bis[4-(4-{4-[2-(2-butoxyethoxy)ethoxy]-3,5-dimethoxy-
styryl}styryl)phenyl]ethene 4. 1H NMR (270 MHz, CDCl3) d
7.51 (s, 8H), 7.45 (s, 8H), 7.10 (s, 6H), 7.05 (d, J~16.2 Hz, 2H),
6.98 (d, J~16.47 Hz, 2H), 6.72 (s, 4H), 4.16 (t, J~5.27 Hz,
4H), 3.89 (s, 12H), 3.83 (t, J~5.40 Hz, 4H), 3.72 (m, 4H), 3.61
(m, 4H), 3.46 (t, J~6.62 Hz, 4H), 1.53 (m, 4H), 1.34 (m, 4H),
0.90 (t, J~7.16 Hz, 6H). MS (FAB) m/z 1028.9 (Mz). Found:
C, 76.68; H, 7.56. C66H76O10 requires C, 77.01; H, 7.44%.
Mp~269 ³C.
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Acknowledgements
This work was supported by Faculty Research Grants (FRG/
98-99/II-09) and (FRG/99-00/I-04) from Hong Kong Baptist
University. We gratefully acknowledge N. T. Lucas for the
HRMS analysis at ANU.
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