Organoselenium-substituted poly(p-phenylenevinylene)

Article abstract of DOI:10.1002/hc.20167

A new type of conjugated polymer, organoselenium substituted poly(p-phenylenevinylene) (PPV), was synthesized from the corresponding alkylselenenyl p-xylylene dibromide via a Gilch route using potassium tert-butoxide in THF. The p-xylylene dibromide precu

Full text of DOI:10.1002/hc.20167

Heteroatom Chemistry
Volume 16, Number 7, 2005
Organoselenium-Substituted
Poly(p-phenylenevinylene)
Nicolai Stuhr-Hansen,1 Edwin H. A. Beckers,2 Lars Engman,3
and Rene´ A. J. Janssen2
1Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Denmark
2Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology,
PO Box 513, 5600 MB Eindhoven, The Netherlands
3Uppsala University, Department of Chemistry, Organic Chemistry, Box 599, BMC, S-751 24
Uppsala, Sweden
Received 2 February 2005; revised 9 August 2005
INTRODUCTION
ABSTRACT: A new type of conjugated polymer,
organoselenium substituted poly(p-phenyleneviny-
lene) (PPV), was synthesized from the correspond-
ing alkylselenenyl p-xylylene dibromide via a Gilch
route using potassium tert-butoxide in THF. The
p-xylylene dibromide precursors were synthesized
by reacting lithiated bis(methoxymethyl)benzenes
with elemental selenium, followed by alkylation of
the generated selenolates. As a final demasking step,
the bromomethyl functions were liberated by ether
cleavage using boron tribromide. Bis-alkylselenenyl
PPV was obtained with an average molecular
weight Mw of approximately 300,000 g/mol and
with polydispersity Mw/Mn = 2. Due to low solubil-
ity, monoalkylselenenyl PPV was obtained with a
considerably lower average molecular weight in the
proximity of 16,000 g/mol and with a polydispersity
slightly larger than 3. Absorption and fluorescence
spectroscopy revealed that the bis-alkylselenenyl
In 1966, Gilch reported [1] the polymerization of p-
xylylene dibromides into poly(p-phenylenevinylene)
(PPV) using hindered alkoxides. Since the dis-
covery [2] of electroluminescence in light-emitting
diodes (LEDs) based on PPV in 1990, derivatives
of PPV have aroused extreme attention [3]. Alkoxy-
substituted PPVs have been the most extensively
studied primarily due to easy access to these deriva-
tives. However, apart from germyl-substituted PPV
[4] and silicon-substituted derivatives [5] applied
in the synthesis of trialkylsilyl PPV-derivatives [6],
only a few examples of PPV substituted with het-
eroatoms, e.g. sulfur on the benzene ring [7], have
been reported. Studies on the influence of sulfur-
containing substituents [8] on the phenylene moi-
ety indicated that alkylthio groups hardly affects
the electronic properties of the PPV backbone as an
electron-donating group.
In order to see how the properties of the material
would be affected, we wished to extend the series
of heteroatom-substituted PPVs to include sele-
nium. Selenium-containing polymers based on se-
lenophenes have been described [9]. The proper-
ties of these materials are directly related to the
Se-atom in the heterocycle, and the lower (as com-
pared with the corresponding thiophene derivative)
PL quantum efficiency [10] was ascribed to the
ꢀ
C
PPV is extensively conjugated.
2005 Wiley
Periodicals, Inc. Heteroatom Chem 16:656–662, 2005;
Published online in Wiley InterScience (www.interscience.
wiley.com). DOI 10.1002/hc.20167
Correspondence to: Nicolai Stuhr-Hansen; e-mail: nsh@kiku.dk.
2005 Wiley Periodicals, Inc.
c
ꢀ
656

Organoselenium-Substituted Poly(p-phenylenevinylene) 657
ety during the synthetic sequences, followed by con-
version to the benzyl bromide in a final step, proved
to be a valuable way of obtaining PPV monomers of
types A and B.
A successful route to monoalkylselenenyl-subs-
tituted PPV monomers (type A) was found by
metallation of 2-bromo-1,4-bis(methoxymethyl)ben-
zene 1 with two equivalents of tert-butyllithium in
THF at −78◦C followed by addition of elemental
selenium (Scheme 2). The aryllithium reagent gen-
erated in situ smoothly consumed selenium by
warming the suspension to room temperature, upon
which alkylation of the lithium arylselenolate with
2-ethylhexyl bromide afforded 1,4-bis(methoxyme-
thyl)-2-(2-ethylhexylseleno)benzene 2.
The key step in the synthesis of type B monomers
was generation of benzene bis-selenolates from
dilithiobenzenes prepared by using the proce-
dures [11,12] for double transmetallation of di-
bromobenzenes. Two equivalents of selenium and
two equivalents 2-ethylhexyl bromide were con-
secutively added to the slurry of the dilithio salt
of 1,4-dibromo-2,5-bis(methoxymethyl)benzene 3
in THF, affording 1,4-bis(2-ethylhexylseleno)-2,5-
bis(methoxymethyl)benzene 4 in analogy with the
synthesis of 2 (Scheme 2).
SCHEME 1
lower aromaticity of the selenophene moiety and
the heavy atom effect. We thought it would be inter-
esting to prepare PPV carrying alkylselenenyl sub-
stituents on the aromatic backbone of the polymer.
Here we report, for the first time, the synthesis and
characterization of such materials. Two new classes
of alkylselenenyl p-xylylene dibromides (types A and
B, Scheme 1) were synthesized by few-step proce-
dures utilizing 1,4-bis(methoxymethyl)benzenes as
masked p-xylylene dibromides. After conversion into
the corresponding dibromides, the alkylselenenyl-
substituted monomers were polymerized in a Gilch
reaction using potassium tert-butoxide to pro-
vide π-conjugated, high molecular weight polymers
(Scheme 1).
Demasking of the benzylic ether functions into
the corresponding p-xylylene dibromides was at-
tempted with 48% aqueous hydrobromic acid on
the model compound 1,4-bis(methoxymethyl)-2-
(butylseleno)benzene 7. Interestingly, after heating
at 80◦C for 2 h, exclusive monocleavage of the methyl
ether function ortho to the alkylselenenyl group
was observed. 1-(Bromomethyl)-2-(butylseleno)-5-
(methoxymethyl)benzene 8 was isolated in high yield
as the only cleavage product (Scheme 3). The reason
for the selective formation of compound 8 could be
neighboring group participation by selenium. The
RESULTS AND DISCUSSION
An obvious route to alkylselenenyl p-xylylene dibro-
mides (type A or B, Scheme 1) would involve side-
chain bromination of the corresponding alkylsele-
nenyl p-xylylenes. Unfortunately, the C Se bond was
attacked under radical bromination conditions and
bond cleavage occurred even in the case of arylse-
lenenyl p-xylylenes. In this case, arylselenenyl bro-
mides and aryl bromides were formed. A different
strategy was therefore considered. Masking the ben-
zyl bromide functionality as a methoxymethyl moi-
SCHEME 2

658 Stuhr-Hansen et al.
SCHEME 3
intermediate selenonium compound formed by ex-
pulsion of methanol was then attacked by bromide at
the benzylic position. The corresponding p-xylylene
dibromide formed only after several hours at re-
flux. The structure of 8 was established by selective
INEPT experiments [13].
SCHEME 5
molecular weight, and lower polydispersity than
MASe-PPV.
BASe-PPV was isolated in high purity. Molecu-
lar weight determination by SEC revealed an aver-
age molecular weight Mw = 300,000 g/mol and poly-
dispersity Mw/Mn = 2, corresponding to an average
of approximately 310 monomer units. The polymer
was only slightly contaminated with oligomeric ma-
terial (less than 5%). BASe-PPV was found soluble
in chlorinated solvents, but the solubility dropped
dramatically upon evaporation and drying. Solubil-
ity was too low to get well-defined 1H-NMR data.
Only low molecular weight polymers were
obtained upon the Gilch polymerization of alkoxy-
substituted p-xylylene dibromides. For making com-
parative studies, we decided to synthesize a dialkyl-
PPV and subjected the readily available monomer
1,4-bis(bromomethyl)-2,5-didodecylbenzene 9 [12]
to the same conditions as used for the prepara-
tion of BASe-PPV. Under these Gilch conditions, 9
smoothly polymerized into poly(2,5-didodecyl-1,4-
phenylenevinylene) DIAL-PPV, which in the SEC
analysis displayed an average molecular weight
Mw = 200, 000 g/mol, and a polydispersity Mw/Mn =
2, which corresponds to an average of approximately
225 monomer units.
The UV/Vis absorption spectrum of a BASe-
PPV solution in CHCl3 was compared with the
spectrum of its monomer to investigate the ex-
tent of π-conjugation after polymerization (Fig. 1).
The monomer showed a featureless spectrum with
an onset at 400 nm (3.1 eV), while the polymer
has a clearly observable π-π* transition with a
maximum at 439 nm (2.82 eV) and an onset at
525 nm (2.36 eV). These changes indicate that
the polymer is conjugated over several monomer
units. The absorption spectrum in the solid state
was recorded by drop casting a BASe-PPV solu-
tion in CHCl3 on a quartz plate. After drying,
the UV/Vis spectrum showed a π-π* transition with
a maximum at 466 nm (2.66 eV) and an onset at
600 nm (2.07 eV), similar to previously reported
PPV derivatives [14]. The fluorescence spectra of
BASe-PPV exhibited maxima at 518 nm (2.39 eV)
and 567 nm (2.19 eV) for a solution in CHCl3 and a
solid-state film, respectively (Fig. 1).
Due to poor solubility, demasking the ether func-
tionality with hydrobromic acid proved quite ineffi-
cient when longer than butyl alkylselenenyl groups
were present. Among other reagents tried for trans-
formation of compounds 2 and 4 to the corre-
sponding p-xylylene dibromides, boron tribromide
turned out to be generally useful. Reaction with this
reagent in dichloromethane at room temperature
smoothly afforded 1,4-bis(bromomethyl)-2-(2-ethyl-
hexylseleno)benzene 5 and 1,4-bis(bromomethyl)-
2,5-bis(2-ethylhexylseleno)benzene 6 (Scheme 4).
Organoselenium containing PPV was syn-
thesized by the Gilch polymerization of the
alkylselenenylated p-xylylene dibromides 5 and
6. The optimal conditions in terms of the least
oligomeric contamination and lowest polydisper-
sity were found by rapid addition of the p-
xylylene dibromide into a solution of potassium tert-
butoxide in THF at room temperature. Polymer-
ization of 5 gave poly(2-{2-ethylhexylseleno}-1,4-
phenylenevinylene) MASe-PPV. Molecular weight
determination by SEC revealed an average molecular
weight Mw = 16,000 g/mol (versus polystyrene stan-
dard) with a polydispersity Mw/Mn of approximately
3 (λmax = 430 nm). The MASe-PPV was found to be
only sparsely soluble in organic solvents, and precip-
itation during polymerization was presumably the
reason for the formation of short-chained almost
nonprocessable polymer.
The Gilch polymerization of the bis(alkylsel-
enenyl) p-xylylene dibromide 6 gave poly(2,5-bis{2-
ethylhexylseleno}-1,4-phenylenevinylene) BASe-PPV
(Scheme 5), which possesses higher solubility, higher
SCHEME 4

Organoselenium-Substituted Poly(p-phenylenevinylene) 659
pared to alkyl-PPV derivatives (viz. DIAL-PPV). This
red-shift is similar to that observed for dialkoxy-PPV,
and we infer that the most important contribution to
the shift is due to electron-donating alkylselenenyl
substituents [15].
EXPERIMENTAL SECTION
Characterization
UV/Vis absorption and fluorescence spectra were
recorded on a Perkin Elmer Lambda 900 spectrom-
eter and an Edinburgh Instruments FS920 double-
monochromator luminescence spectrometer using a
Peltier-cooled red-sensitive photomultiplier, respec-
tively. All photoluminescence spectra were recorded
by excitation of the sample at 400 nm. NMR-spectra
were recorded on 250, 300, or 400 MHz NMR spec-
trometers. Gas chromatography mass spectrome-
try (GC-MS) was recorded on a HP 5972 with
mass selective detector, and direct inlet spectra
were recorded on a JMS-HX/HX100A (JEOL) tan-
dem mass spectrometer by Katrine M. Petersen and
Solveig K. Hansen. Size-exclusion chromatography
(SEC) was performed on a Shimadzu LC10-AT ver-
sus a polystyrene standard, using a Polymer Labo-
ratories PL Gel 5 micrometer mixed-D column and
identically reproduced on a Macherey-Nagel Nucle-
osil 50-7 column, a Shimadzu SPD-10AV UV-Vis de-
tector at 254 nm and chloroform as eluent. All chem-
icals were purchased from Aldrich Chemical Co.
FIGURE 1 Normalized UV/Vis absorption (solid symbols)
and fluorescence (open symbols) spectra of BASe-PPV in
CHCl3 (squares) and the solid state (circles) together with
absorption spectrum of the monomer species 6 in CHCl3
(triangles).
The absorption spectrum of MASe-PPV in CHCl3
(Fig. 2) shows an absorption maximum at 420 nm
(2.95 eV) with an onset around 530 nm (2.34 eV),
whereas the maximum of the photoluminescence is
observed at 497 nm (2.49 eV). The monomer 5 shows
a featureless absorption spectrum with an onset at
370 nm (3.35 eV).
For a DIAL-PPV solution in CHCl3, an π-π*-
absorption was observed (Fig. 1) with a maximum at
391 nm (3.17 eV) indicating that polymerization of
9 also results in a conjugated polymer, since the ab-
sorption of 9 only shows a featureless spectrum with
an onset at 330 nm (3.76 eV). The fluorescence max-
imum in CHCl3 was observed at 492 nm (2.52 eV).
These results indicate that the optical spectra
for BASe-PPV and MASe-PPV are red-shifted com-
Synthesis of 1,4-Bis(2-ethylhexylseleno)-2,5-
bis(methoxymethyl)benzene 4
tert-Butyllithium was titrated with N-pivaloyl-
o-toluidine [16] prior to use. 1,4-Dibromo-2,5-
bis(methoxymethyl)benzene 3 [17] (4.86 g, 15 mmol)
was added in one portion to a solution of t-
BuLi (1.5 M in hexane, 40 mL, 60 mmol) and
TMEDA (10 mL) in THF (100 mL) efficiently cooled
in a dry ice/acetone bath under Ar. The reaction
mixture was then allowed to warm to room tem-
perature. Already after a few minutes at room tem-
perature, the dilithio salt began to form as a white
precipitate [18]. The reaction mixture was stirred at
room temperature for 1 h and then cooled again in
a dry ice/acetone bath, after which selenium (2.37 g,
30 mmol) was added in one portion. Subsequently,
the reaction mixture was stirred at room tempera-
ture for 1 h under argon. Then 2-ethylhexyl bromide
(6.37 g, 33 mmol) was added in one portion, and
stirring under nitrogen was continued at room tem-
perature for another 1 h. The reaction mixture was
poured into water (200 mL) and after separation of
FIGURE 2 Normalized UV/Vis absorption and fluorescence
spectra for MASe-PPV (solid/open squares) and DIAL-PPV
(solid/open triangles) in CHCl3 together with absorption spec-
trum of the monomeric species 5 (solid circles) and 9 (open
circles) in CHCl3.

660 Stuhr-Hansen et al.
the phases the water phase was further extracted
with diethyl ether (3 × 25 mL). The combined etheral
phases were evaporated on silica gel 60 (2 g), and a
foul-smelling fraction was washed through silica gel
60 (10 g) by means of pentane. Subsequent elution
with dichloromethane gave the masked p-xylylene
dibromide 4 (4.01 g, 49%) as a colorless oil. Anal.
calcd for C26H46O2Se2: C 56.93, H 8.45; found: C
57.07, H 8.44. Mass spectrum (EI; m/z, relative inten-
(2.42 g, 80%) as a colorless oil (purity >99% (GC-
MS)). Anal. calcd for C14H22O2Se: C 55.81, H 7.36;
found C 56.10, H 7.44. Mass spectrum (EI; m/z, rel-
ative intensity): 302 (M+, 35), 270 (3), 245 (100). 1H-
NMR (250 MHz,CDCl3) δ: 0.91 (3H, t, J = 7.3 Hz),
1.35–1.50 (2H, m), 1.61–1.73 (2H, m), 2.90 (2H, t,
J = 7.4 Hz), 3.36 (3H, s), 3.39 (3H, s), 4.42 (2H, s),
4.54 (2H, s), 7.17 (1H, dd, J = 7.8, 1.4 Hz), 7.35 (1H,
d, J = 7.8 Hz), 7.46 (1H, d, J = 1.4 Hz) ppm. 77Se-
NMR (57.3 MHz, CDCl3): δ = 249 ppm.
1
sity): 550 (M+, 100), 406 (22), 294 (9), 262 (23). H
NMR (250 MHz, DMSO-d6): δ = 0.79–0.87 (m, 12H),
1.19–1.21 (m, 8H), 1.30–1.48 (m, 10H), 2.90 (d, 4H,
J = 5.8 Hz), 3.29 (s, 6H), 4.44 (s, 4H), 7.49 (s, 2H).77Se
NMR [19] (57.3 MHz, DMSO-d6): δ = 200 ppm.
Synthesis of p-Xylylene Dibromides 5 and 6
General Procedure. To a mixture of bis(metho-
xymethyl)benzene 2 or 4 (10 mmol) in dichlorome-
thane (40 mL) was added boron tribromide (1 M in
dichloromethane, 22 mL, 22 mmol) in one portion
and stirring was maintained at room temperature
for 2 h. The clear dark reaction mixture was poured
into water, and the phases were separated. The aque-
ous phase was further extracted with pentane (2 ×
30 mL). The combined organic phases were pooled,
washed with water (15 mL), and filtered through sil-
ica gel 60 (10 g) by means of pentane. Evaporation of
the solvent and drying (vacuum oven, 50◦C) afforded
the products.
Synthesis of 1,4-Bis(methoxymethyl)-2-(2-
ethylhexylseleno)benzene 2
2-Bromo-1,4-bis(methoxymethyl)benzene 1 [20]
(2.45 g, 10 mmol) in THF (50 mL) was cooled in a
dry ice/acetone bath while tert-butyllithium (1.5 M
in hexane, 13.3 mL, 20 mmol) was added dropwise
under nitrogen during a 10-min period. The reac-
tion mixture was stirred under nitrogen for 1 h at
–78◦C. Selenium (0.79 g, 10 mmol) was added in
one portion, and the reaction mixture was stirred
at room temperature for 45 min. 2-Ethylhexyl bro-
mide (1.93 g, 10 mmol) was added in one portion,
and the reaction mixture was further stirred at room
temperature for 30 min. The clear reaction mixture
was diluted with water (200 mL), and the phases
were separated. The aqueous phase was further ex-
tracted with diethyl ether (2 × 25 mL). The combined
etheral phases were washed with water (15 mL).
After evaporation of the solvent and removal of a
bad-smelling nonpolar material on a silica gel 60
(10 g) column by means of pentane, the product
was eluted with dichloromethane. Evaporation of
the solvent gave selenide 2 (2.33 g, 65%) as a light
yellow oil (purity >99% (GC-MS)). Anal. calcd for
C18H30O2Se: C 60.49, H 8.46; found: C 60.54, H 8.34.
Mass spectrum (EI; m/z, relative intensity): 358 (M+,
42), 245 (87), 214 (100), 183 (47). 1H NMR (300
MHz, CDCl3): δ = 0.85–0.90 (m, 6H), 1.21–1.31 (m,
6H), 1.36–1.52 (m, 2H), 1.54–1.62 (m, 1H), 2.91–
2.93 (m, 2H), 3.36 (s, 3H), 3.40 (s, 3H), 4.42 (s, 2H),
4.55 (s, 2H), 7.17 (d, 1H, J = 8.9 Hz), 7.34 (d, 1H,
J = 8.9 Hz), 7.48 (s, 1H).77Se NMR (57.3 MHz,
CDCl3): δ = 251 ppm.
Synthesis of 1,4-Bis(bromomethyl)-2-(2-ethylhe-
xylseleno)benzene 5. Following the general proce-
dure, a colorless oil (3.36 g, 74%) was obtained.
Anal. calcd for C16H24Br2Se: C 42.22, H 5.31; found:
C 42.56, H 5.34. Mass spectrum (EI; m/z, relative
intensity): 456 (M+, 7), 375 (9), 345 (5), 252 (22),
183 (60), 91 (62), 57 (100). 1H NMR (400 MHz,
CDCl3): δ = 0.85–0.90 (m, 6H), 1.23–1.28 (m, 4H),
1.31–1.49 (m, 4H), 1.55–1.61 (m, 1H), 2.98 (d, 2H,
J = 6.0 Hz), 4.40 (s, 2H), 4.68 (s, 2H), 7.19 (dd, 1H,
J = 7.8, 1.6 Hz), 7.33 (d, 1H, J = 7.8 Hz), 7.53 (d,
1H, J = 1.6 Hz). 77Se NMR (57.3 MHz; DMSO-d6):
δ = 210 ppm.
Synthesis of 1,4-Bis(bromomethyl)-2,5-bis(2-eth-
ylhexylseleno)benzene 6. Following the general pro-
cedure, light-yellow crystals (3.99 g, 62%, after pre-
cipitation from ethanol) were obtained; mp 51–52◦C.
Anal. calcd for C24H40Br2Se2: C 44.60, H 6.24; found:
C 44.88, H 6.14. Mass spectrum (EI; m/z, relative in-
1
tensity): 646 (M+, 100), 534 (8), 455 (32). H NMR
Synthesis of 1,4-Bis(methoxymethyl)-2-
(butylseleno) benzene 7
(400 MHz, CDCl3): ꢀ = 0.81–0.85 (m, 12H), 1.20–1.21
(m, 8H), 1.33–1.40 (m, 8H), 1.48–1.50 (m, 2H), 3.01
(d, 4H, J = 5.5 Hz), 4.77 (s, 4H), 7.71 (s, 2H). 77Se
NMR (57.3 MHz; DMSO-d6): δ = 189 ppm.
Procedure is identical to the synthesis of 2. Kugel-
rohr distillation (air-bath 230◦C, 10 mmHg) gave 7

Organoselenium-Substituted Poly(p-phenylenevinylene) 661
Synthesis of 1-(Bromomethyl)-2-(butylseleno)-5-
(methoxymethyl)benzene 8
Synthesis of Poly(2,5- didodecyl-1,4-
phenylenevinylene) (DIAL-PPV)
1,4-Bis(methoxymethyl)-2-(butylseleno)benzene
7
DIAL-PPV was prepared following the procedure
used for preparing BASe-PPV using 9 [12] instead of
6 in 87% yield (yellow flakes). Anal. calcd for C32H54:
C 87.60, H 12.40; found: C 87.01, H 11.98.
(0.90 g, 3 mmol) was vigorously stirred in hy-
drobromic acid (48 aq., 25 mL) at 80◦C for 2 h.
The cooled reaction mixture was then diluted
with water (100 mL) and extracted with pentane
(3 × 25 mL). The combined organic phases were
filtered through silica gel 60 (6 g) by means of
pentane-dichloromethane (1:1). Evaporation of the
solvent and drying (vacuum oven, 50◦C) gave se-
lenide 8 (0.83 g, 79%) as a colorless oil. Anal. calcd
for C13H19BrOSe: C 44.59, H 5.47; found: C 44.68,
H 5.32. Mass spectrum (EI; m/z, relative intensity):
350 (M+, 18), 293 (8), 271 (9), 239 (13), 183 (35), 135
CONCLUSIONS
In summary, we have presented a route to novel
PPVs incorporating alkylselenenyl substituents. The
alkylselenenyl-p-xylylene dibromide precursors used
for preparing PPV via the Gilch route were prepared
by implementing organometallic procedures [11,12]
during which benzylic bromide moieties were
masked as ether functions. The bis-alkylselenenyl
PPV was obtained with a high molecular weight. The
optical properties are similar to those of dialkoxy
PPVs and characterized by strong absorption and
fluorescence bands of a π-π* transition. Going from
solution to a thin solid-state film, there is a distinct
red shift of the optical transitions that is ascribed to
interchain interactions occurring in the film.
1
(28), 91 (60), 45 (100). H NMR (250 MHz, CDCl3):
δ = 0.89–0.94 (m, 3H), 1.38–1.48 (m, 2H), 1.60–1.75
(m, 2H), 2.95–3.00 (m, 2H), 3.39 (s, 3H), 4.44 (s,
2H), 4.72 (s, 2H), 7.19 (d, 1H, J = 8.0 Hz), 7.39 (1H,
d, J = 8.0 Hz), 7.51 (s, 1H). 77Se NMR (57.3 MHz,
CDCl3): δ = 250 ppm.
Synthesis of Poly(2,5-bis{2-ethylhexylseleno}-
1,4-phenylenevinylene) (BASe-PPV)
ACKNOWLEDGMENTS
1,4-Bis(bromomethyl)-2,5-bis(2-ethylhexylseleno)-
benzene 6 (0.19 g, 0.3 mmol) was added in one
portion to a vigorously stirred solution of potas-
sium tert-butoxide in THF (1 M, 3 mL, 3 mmol) at
room temperature. After the addition, the reaction
mixture became yellow. The reaction mixture was
stirred at room temperature under Ar for 3 h, during
which it became dark orange, and then poured into
water (50 mL). The polymer was filtered off and
washed by Soxhlet extraction with methanol for
12 h. The filter was dried in a vacuum oven (110◦C,
10 mmHg) overnight. The polymer was then Soxhlet
extracted with chloroform for 12 h and analyzed
with GPC and UV/Vis at this stage. Evaporation and
drying in a vacuum oven (110◦C, 10 mmHg) gave
the bis-alkylselenenyl PPV, BASe-PPV (0.10 g, 69%)
as a yellow gum. Anal. calcd for C24H38Se2: C 59.50,
H 7.91; found: C 58.97, H 7.65.
We thank Dr. Magnus Besev for carrying out the se-
lective INEPT experiments. We are grateful to Dr.
Tommi Remonen, Dr. Jonas S. E. Hellberg, Dr. Jonas
Malmstro¨m, and Dr. Lars Henriksen for supporting
fundamental ideas.
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MASe-PPV was prepared following the procedure
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6 in 74% yield (yellow gum; contains approximately
15% unreacted monomer according to SEC).

662 Stuhr-Hansen et al.
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