Jacketed poly(p-phenyleneethynylene)s: Nonaggregating conjugated polymers as blue-emitting rods

Article abstract of DOI:10.1021/ma048535q

A series of dendronized poly(p-phenyleneethynylene)s were synthesized by the Pd-catalyzed coupling of a tetraphenylbenzene-substituted aromatic diiodide to 2,5-didodecyl-1,4-diethynylbenzene to form PPEs in excellent yield and high degree of polymerizatio

Full text of DOI:10.1021/ma048535q

8212
Macromolecules 2004, 37, 8212-8221
J acketed Poly(p-phenyleneethynylene)s: Nonaggregating Conjugated
Polymers as Blue-Emitting Rods
Br ia n C. En gler t,† Ma r k D. Sm ith ,‡ Ken n eth I. Ha r d ca stle,§ a n d Uw e H. F . Bu n z*,†
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332;
Department of Chemistry and Biochemistry, University of South Carolina,
Columbia, South Carolina 29208; and Department of Chemistry, Emory University,
1515 Pierce Drive, Atlanta, Georgia 30322
Received J uly 16, 2004; Revised Manuscript Received August 10, 2004
ABSTRACT: A series of dendronized poly(p-phenyleneethynylene)s were synthesized by the Pd-catalyzed
coupling of a tetraphenylbenzene-substituted aromatic diiodide to 2,5-didodecyl-1,4-diethynylbenzene to
form PPEs in excellent yield and high degree of polymerization. The tetraphenylbenzene-substituted
monomer was obtained by a Diels-Alder reaction of a diethynylated arene with tetraphenylcyclopenta-
dienone. The influence of the tether length (connecting the tetraphenylbenzene units to the main chain
of the polymer) on the optical properties of the polymers was investigated. The closer the tetraphenyl-
benzene units were placed to the main chain, the larger is their effect upon the PPE’s optical properties.
In the case where the tether is shortest, i.e., two atoms, the optical properties of the PPE in the solid
state and in solution are identical.
In tr od u ction
Dendronization or “jacketing”ofconjugated polymers1-5
is of great current interest as a means of their isolation
from each other in solution and in the solid state. The
isolation of single polymer chains will lead to materials
that do not form excimers and aggregates in the solid
state. Strategies that achieve the isolation of chro-
mophores might lead to colorfast active materials for
light-emitting diodes and potentially for polymer lasers.
Issues that need to be dealt with are stability, electron
transport, and charge carrier injection.
Poly(p-phenyleneethynylene)s (PPEs) are rigid-rod
polymers with attractive optical properties.6,7 Their
chromic behavior and high quantum yield of fluores-
cence makes them useful in sensory and device applica-
tions.8,9 While polyfluorenes grafted by Mu¨llen den-
drimers10 have been reported,1,4 there are no PPEs10
known that are covered by these thermally stable,
robust, and easy-to-make modules. However, Aida3 has
reported PPEs that were appended by Frechet’s11 benzyl
ether dendrons. These polymers display intriguing
photophysical and morphological properties. Densely
dendronized PPEs show unity fluorescence quantum
yields even in relatively concentrated solutions where
interchain interactions play a significant role for the
nondendronized PPE. Dendronization efficiently sup-
presses collisional deactivation of the excited state of
the PPE. While Aida’s experiments are elegant, the
synthesis of Frechet-type dendronized PPEs is lengthy,
and the benzylic groups of the Frechet dendrons are
both thermally and hydrolytically sensitive. Mu¨llen
dendrimers,10 on the other hand, are easily prepared
and robust. We herein report the synthesis and proper-
ties of three different tetraphenylbenzene “miniden-
dron”-substituted PPEs. Their aggregation and photo-
physical properties were investigated.
F igu r e 1. Anisotropic displacement parameter (ADP) repre-
sentations (50%) of the diynes 2 (top), 4 (middle), and 7
(bottom) in the solid state. The diyne 2 shows a perpendicular
trans orientation of the two propargylic units with respect to
the flat arene ring, while in 4 the side chains are coplanar to
the arene ring and show a trans orientation of the methylene
units as found in polyethylene. The monomer 7 shows a
coplanar but helical arrangement of the side chains.
Resu lts a n d Discu ssion
Syn th esis of th e Mon om er s 3, 5, a n d 8. Starting
from the diiodide 1, reaction with 2-(2-chloroethoxy)-
ethanol in the presence of an excess of potassium
carbonate furnished 6 in 78% yield.9c An SN2 reaction
with 3-bromopropyne gave 7, while the reaction of 1
with 3-bromopropyne or 6-chlorohexyne under the same
conditions led to the diynes 2 and 4. The three diynes
(2, 4, 7) were subjected to a double Diels-Alder reaction
† Georgia Institute of Technology.
‡ Universtiy of South Carolina.
§ Emory University.
* To whom correspondence should be addressed: e-mail
uwe.bunz@chemistry.gatech.edu.
10.1021/ma048535q CCC: $27.50 © 2004 American Chemical Society
Published on Web 10/02/2004

Macromolecules, Vol. 37, No. 22, 2004
J acketed Poly(p-phenyleneethynylene)s 8213
F igu r e 2. ADP (50%) (top, left) representations of 3a . The monomer has a step conformation (top right, van der Waals
representation) that leads to an interesting (middle and bottom) solid-state arrangement, in which the phenyl rings of one
tetraphenylbenzene substituent are interlaced with the ones from molecules of 3a above and below.
with tetraphenylcyclopentadieneone to afford 3a , 5, and
8 in yields between 18% and 86%. Because of the
presence of the oligoethylene chains, 8 smeared exces-
sively on the chromatography support. It was difficult
to remove small amounts of impurities, leading to the
low yield for 8. The other two monomers, 3a and 5, are
obtained in excellent yields; 3a was coupled under Pd
catalysis to an excess of 2-methylphenylacetylene to give
the fluorescent model compound 3b in 88% yield after
crystallization from dichloromethane and methanol.
To secure the structures of the diynes 2, 4, and 7,
single crystalline specimens were grown from their
solutions in chloroform or dichloromethane. Figure 1
and Table 1 show the molecular structures and details
of the structure analysis of the diynes in the solid state.
In 2 the propargylic substituents are pointing in two
different hemispheres, trans to each other. In 4 and 7
a more or less flat packing of the side chains is observed.
The alkane chain in 4 takes up a perfect trans confor-
mation, similar to that observed for methylene groups
in polyethylene,12 while in 7 the triethylene glycol
chains adopt a more helical conformation, probably due
to the presence of the oxygen atoms in the linker chain.
The bond lengths and bond angles of 2, 4, and 7 are in
excellent agreement with the expected values for these
unstrained compounds.
Growth of single crystalline specimen was attempted
for 3a , 5, and 8. Alas, we were only successful in
obtaining single-crystalline specimens from 3a and 5.
The molecular structure and the packing of 3a are
shown in Figure 2, and the pertinent crystallographic
data are contained in Table 1. Single molecules of 3a
are Z-shaped. This conformation leads to a solid-state
arrangement in which the molecules are packed in an
interdigitated zigzag motif (Figure 2, middle). If the
view is rotated by 90°, the molecules are stacked on top
of each other, tilted with the tetraphenylbenzene side
chains interlocking (Figure 2, bottom). The central
diiodoarenes are far removed from each other due to the
bulky side chains and do not show any intermolecular
contacts with other diiodoarenes. Bond lengths and bond
angles are in excellent agreement with the expected
values. In Figure 3, the single-crystal structure of 5 is
shown. The three benzene rings are almost coplanar,
and the four phenyl substituents are perpendicularly
oriented around each of the outer phenyl rings. In the

8214 Englert et al.
Macromolecules, Vol. 37, No. 22, 2004
F igu r e 3. ADP (50%) (top) representations of 5. Bottom: Partial packing diagram of 5. Partial interdigitation of the
tetraphenylbenzene substituents of different molecules is visible.
solid state the tetraphenylbenzene substituents are
interdigitated to give a better space filling. The crystal
contains dichloromethane as a disordered solvent.
°C; alas, slow decomposition occurred at that temper-
ature, common for dialkoxy-PPEs. To have a nonjack-
eted PPE for comparison purposes, polymer 12 was
prepared utilizing the same synthetic scheme. The
material was obtained in an 83% yield as a yellow solid
with an Mn of 56 × 103 and a PDI of 4.5. Table 2 shows
the pertinent optical and molecular weight information
of 9-12.
Op tica l P r op er ties of th e P olym er s in Solu tion
a n d in th e Solid Sta te. In Table 2 and Figures 5-7
the optical properties of 9-12 in solution and in the
solid state are shown. Polymer 12 is the PPE standard
to which the other polymers are compared. Its absorp-
tion maximum in solution (Table 2) is 434 nm, typical6a
for this substitution pattern. Its emission maximum in
solution is at 456 nm. Upon going into the solid state,
the absorption and the emission are red-shifted by 14
and 13 nm, respectively. Polymer 10 shows optical
properties that are by and large very similar to those
obtained for 12. The shifts of emission and absorption
when going from the dilute solution into the solid state
are almost identical. The remotely placed tetraphenyl-
benzene unit in 10 therefore does not interfere with the
Syn th esis a n d Ch a r a cter iza tion of th e P oly-
m er s. With the monomers 3a , 5, and 8 available in
gram quantities, the synthesis of conjugated polymers
containing these modules was explored. The homopoly-
mers, synthetically accessible by the reaction of 3a , 5,
or 8 with acetylene gas in the presence of a Pd catalyst,
would be too insoluble. A preliminary experiment with
3a confirmed our concerns, and an insoluble, infusible
yellow material was obtained after removal of the
solvents. However, copolymerization of 3a , 5, and 8 with
a long-chain substituted diyne should give rise to the
formation of soluble copolymers. The polycondensation
of 2,5-didodecyl-1,4-diethynylbenzene with either 3a , 5,
or 8 furnished the jacketed PPE derivatives 9, 10, and
11 in good to excellent yields with molecular weight
ranging between 3 × 104 and 13 × 104 amu; 9-11 were
amorphous according to powder diffraction experiments
but showed a halo at approximately 20°, typical for π-π
stacking interactions. The polymers did not show re-
versible phase transitions upon heating to above 150

Macromolecules, Vol. 37, No. 22, 2004
J acketed Poly(p-phenyleneethynylene)s 8215
Sch em e 1. Syn th esis of 3, 5, a n d 8 Sta r tin g fr om 2,5-Diiod oh yd r oqu in on e (1)
Sch em e 2. Syn th esis of th e P P Es 9-12 by a P d -Ca ta lyzed Cou p lin g
conformational freedom of the polymer chains; i.e., the
a different spectroscopic behavior. Their absorption
maximum in solution is somewhat blue-shifted, from
434 to 418 or 421 nm. A blue-shifted absorption in
solution is unusual because it suggests that the rota-
twist angle between neighboring aryl rings is variable
in solution like in 12, and the polymer chains are
planarized in the solid state. Polymers 9 and 11 show

8216 Englert et al.
Macromolecules, Vol. 37, No. 22, 2004
F igu r e 4. X-ray crystal structure of 3b. Top left: ADP (50%) representation of a single molecule of 3b. Top right: view along the
conjugated diphenylalkynylbenzene axis. Visible is the twist of one external phenylethynyl unit by 34° with respect to the central
benzene ring. Bottom: packing of 3b in the solid state. The phenyl groups of one molecule are in close contact to the tolyl group
of a second one. The distance of the H atom of the phenyl ring to the center of the tolylethynyl ring is 3.12 Å.
F igu r e 5. Absorption and emission of the polymers 9-11 in
chloroform.
F igu r e 6. Absorption and emission of the polymers 9-11 in
spin-cast films. The red-shifted shoulders are Raman-active
tional freedom of the chains might be restricted toward
a greater twist angle between neighboring phenyl
rings.15-17 To investigate this rarely observed behavior,
the model trimer 3b was prepared and suitable single
crystals were obtained from hexafluorobenzene. Figure
4 shows an atomic displacement parameter (ADP) plot
of 3b. The bisphenylethynylbenzene unit is not planar
in this structure, but one benzene ring is twisted by 34°
(Figure 4) perhaps by the steric demand of the two bulky
side groups. All of the hitherto reported bisphenyleth-
ynylbenznenes13 are strictly planar in the solid state,
regardless of their substitution pattern. Figure 4 shows
states that are coupled to the excited state. The observed shifts
are 905 cm-1 for 9, 1227 cm-1 for 10, and 1111 cm-1 for 11.
the packing of 3b in the solid state. The conformation
of the tetraphenylbenzene unit seems to dictate the
packing of 3b in the crystal. The molecules are stacked
parallel in layers but shifted with respect to each other.
In analogous polymers, the side chains therefore could
influence the conformation of the main chain, leading
to a permanently enforced twist. Close contacts between
the central bisphenylethynylbenzene chromophores of
different molecules do not exist. A similar situation was

Macromolecules, Vol. 37, No. 22, 2004
J acketed Poly(p-phenyleneethynylene)s 8217
the bulky tetraphenylbenzene groups. An MM2 simula-
tion (Figure 8) shows a space-filling view of a polymer
chain of 9. Two interesting features are visible. In the
minimized ground state, the polymer backbone is not
planar but twisted (top). The space-filling model (middle)
demonstrates the sterically congested surrounding that
will make a boardlike lamellar packing of the polymer
chains difficult. The bottom of Figure 8 shows an end-
on view, demonstrating that the main chain is buried
deeply beneath the substituents.
A quantum chemical analysis of the rotational energy
potential around the two benzene rings was performed
for the model dimer (Figure 9). Because of the size of
the dimeric unit, it was only possible to perform the
analysis on a semiempirical (AM 1) level. The use of
AM1 can underestimate the barrier of rotation but tends
to give satisfying qualitative results for carbon-based
systems.12 With AM1 a rotational barrier of only 0.2
kcal/mol is obtained for tolane, while Tour and Semi-
nario determined a rotational barrier of 0.8 kcal/mol
utilizing a sophisticated ab initio technique for the same
molecule; AM1 results seem to err toward lower values.12b
Investigation of the model dimer by AM1 shows a
F igu r e 7. Absorption and emission spectra of the model 12
in solution and in the solid state.
observed by Mu¨llen, Setayesh, and Enkelmann for
dendronized fluorenes.4
The absence of diffraction patterns in powders of
9-11 suggests that they all are amorphous. In 9 the
chains of the polymers are probably well separated by
F igu r e 8. MM2 calculations of an octameric model compound of polymer 9.

8218 Englert et al.
Macromolecules, Vol. 37, No. 22, 2004
other polymers a shift of 11-14 nm is observed when
transitioning from solution into the solid state. Like-
wise, 9’s emission is only slightly shifted when going
from solution into the solid state. Polymer 11 shows
unusual optical properties. Its bulky substituent is
farthest away from the PPE backbone, but its optical
properties resemble that of 9. We have attempted to
perform polarizing microscopy and SEM on 11, but both
methods only show the formation of smooth films. In
addition, 11 is amorphous, so we could not obtain any
meaningful powder X-ray diffraction data. As a conse-
quence we are limited in our interpretation of the
spectroscopicproperties of11.Thessomewhat speculatives
explanation in its behavior might be gleaned from the
packing of 7, which shows a helical coiling of the
ethylene glycol side chains in the solid state. A second
possibility is the obvious difference in the hydrophobic-
ity/hydrophilicity of the connector compared to the
tetraphenylbenzene “head”. This might as well lead to
a conformational distortion of the main chain in the
solid state to best accommodate the packing of the whole
object. To test this hypothesis, UV-vis and fluorescence
spectra of 11 were recorded in a series of different
solvents, however, without great effect. As a conse-
quence, the reason for the changed optical properties
in 11 is difficult to explain at the moment, but prepara-
tion of similar polymers with longer oligoethylene chains
is planned in the near future to shed more light on this
behavior.
F igu r e 9. Rotational profile of a dimeric repeat unit of 9
(black squares) and of diphenylacetylene (blue triangles) as a
model compound. The conformational analysis was performed
utilizing SPARTAN with the AM1 basis set implemented on
a windows platform. The X-axis represents the twist angle
between the two arene rings, and the y-axis represents the
relative energy (kcal mol-1).
complex rotational behavior. Contrary to diphenylacety-
lene, the dimer displays several maxima and minima
(Figure 9). This rotational profile is a representative
rotational profile but probably not the global minimum,
despite the routine utilized to minimize all of the
rotamers. Only a costly molecular dynamics calculation
would give a complete picture of all low-energy rota-
tional profiles accessible to this complex system. How-
ever, even with this relatively simple theoretical ap-
proach, the 90° conformation does not seem to be an
energy maximum anymore, contrary to the case of
tolane. The AM1 calculation of the dimer shows a
complex rotational profile around the CC triple bond,
suggesting that polymer 9 also is very “un-PPE-like”
with respect to its conformational behavior.6c,12a The
PPE 9 probably attains nonplanar conformations in both
solution as well as in the solid state. The blue shift in
the absorption of 9 in solution is therefore due to the
preference of nonplanar lowest ground states.
The solution emission spectra of all of the polymers
9-12, on the other hand, are very similar. That can be
understood because Sluch and Berg13 and others14,15
have demonstrated that after excitation of a octameric
phenyleneethynylene model compound planarization of
the backbone occurs to relax the first excited singlet
state into its lowest, planar, state. The driving force for
the planarization is considerably larger in the excited
state than in the ground state due to the allenic
resonance structures involved, leading to almost super-
imposable emission spectra for 9-12. The excited-state
geometries of 9 and of 12 will resemble each other closely,
despite their different rotational preference in the ground
state. The observed shoulders in the fluorescence spectra
of 9-12 in solution and in the solid state are due to the
participation of Raman coupled states.18
Con clu sion s
The novel dialkyl-co-dialkoxy-PPEs 9-12 were pre-
pared. Polymers 9-11 carry tetraphenylbenzene sub-
stituents. If the bulky substituents are close to the main
chain as shown in polymer 9 or attached by a hydro-
philic linker (11) to the conjugated backbone, the optical
properties of the PPE main chain are heavily influenced.
The absorption and emission of 9 are blue-shifted in
comparison to that of the model PPE 12. The reason
for the blue shift is an increased twist of the main chain
in solution and in the solid state and an insulation of
the polymer chains from each other. This observation
was corroborated by crystallographic studies on a tet-
raphenylbenzene-substituted bisphenylethynylbenzene
derivative (3b) that showed a significant twist of a
phenyleneethynylene group. Giving an overall self-
consistent picture, quantum chemical calculations sug-
gest that polymers of the type 9 are not planar but have
multiple conformational minima with respect to the
rotation of two neighboring benzene rings in the con-
jugated main chain. Planarization of the backbone is
therefore difficult to attain for 9.
Exp er im en ta l Section
In str u m en ta tion . The 1H and 13C NMR spectra were taken
on a Varian 300 MHz or a Bruker 400 MHz spectrometer using
a broadband probe. The 1H chemical shifts are referenced to
the residual proton peaks of CDCl3 at δ 7.24 (vs TMS). The
13C resonances are referenced to the central peak of CDCl3 at
δ 77.0 and CDCl2CDCl2 at δ 74.0 (vs TMS). Tetrachloroethane
and chromium(III) acetylacetonate were used when obtaining
13C NMR data for all polymers. UV-vis measurements were
made with a Shimadzu UV-2401PC recording spectrophotom-
eter. Fluorescence data were obtained with a Shimadzu RF-
5301PC spectrofluorophotometer. A Headway Research model
PWM32 instrument was used to spin-coat dilute chloroform
solutions of polymers onto quartz slides for thin film experi-
ments. 1,4-Diiodo-2,5-dihydroquinone,9c 2,5-didodecyl-1,4-di-
Polymer 11 resembles 9, while 10 has similar proper-
ties as the model polymer 12. In the solid state 9 is
attractive as its absorption does only shift by one nm
when going from solution into the solid state. For the

Macromolecules, Vol. 37, No. 22, 2004
J acketed Poly(p-phenyleneethynylene)s 8219
Ta ble 1. Cr ysta l Da ta a n d Un it Cell P a r a m eter s for th e Com p ou n d s 2-5 a n d 7a
compound
formula
(FWT)
space group
unit cell
dimensions
2
C
4
7
3a
5
3b
12H8I2O2
C18H20I2O2
(522.14)
Pbca
C20H24I2O6
(614.19)
P21/c
C68H48I2O2
(1150.9)
P21/n
C74H60I2O2
(1235.1)
P-1
C86H62O2
(1127.4)
P-1
(437.98)
P-1
a ) 4.2569(4) Å
a ) 8.0944(4) Å
a ) 15.8462(9) Å a ) 15.6063(10) Å
a ) 12.560(2) Å
a ) 14.259(2) Å
b ) 8.9180(8) Å
c ) 8.9454(8) Å
R ) 67.777(2)°
â ) 79.244(2)°
γ ) 82.963(2)°
308.34(5) Å3
1
b ) 13.7017(6) Å b ) 7.6297(4) Å
b ) 8.9275(6) Å
c ) 19.2262(13) Å
R ) 90°
b ) 12.952(2) Å
c ) 23.031(3) Å
R ) 84.628(3)°
â ) 81.298(2)°
γ ) 76.837(2)°
3599.2(8) Å3
2
b ) 15.310(2) Å
c ) 17.941(2) Å
R ) 75.054(3)°
â ) 78.969(2)°
γ ) 64.198(2)°
3392.6 (8) Å3
2
c ) 16.9431(8) Å
R ) 90°
c ) 9.3907(6) Å
R ) 90°
â ) 90°
â ) 105.906(1)°
γ ) 90°
â ) 98.979(2)°
γ ) 90°
γ ) 90°
vol
Z
1879.11(15) Å3
4
1091.88(11) Å3
2
2645.9(3) Å3
2
density (calcd) 2.359 mg/m3
1.846 mg/m3
3.351 mm-1
11439
1.868 mg/m3
2.912 mm-1
7165
1.445 mg/m3
1.235 mm-1
16828
1.272 mg/m3
1.041 mm-1
33301
1.104 mg/m3
0.064 mm-1
47536
absorp coeff
reflections
collected
5.081 mm-1
2788
independent
reflections
1253
2073
1924
3485
10700
17018
[R(int) ) 0.0195] [R(int) ) 0.0279] [R(int) ) 0.0292] [R(int) ) 0.0514]
[R(int) ) 0.0693] [R(int) ) 0.0534]
final R indices
[I > 2sigma(I)]
R1 ) 0.0165
R1 ) 0.0201
R1 ) 0.0189
R1 ) 0.0541
R1 ) 0.1695
R1 ) 0.0809
wR2 ) 0.0412
R1 ) 0.0170
wR2 ) 0.0415
0.582 and
wR2 ) 0.0524
R1 ) 0.0209,
wR2 ) 0.0530
0.566 and
wR2 ) 0.0474
R1 ) 0.0196
wR2 ) 0.0479
0.556 and
wR2 ) 0.1256
R1 ) 0.0705
wR2 ) 0.1348
1.645 and
wR2 ) 0.3945
R1 ) 0.1866,
wR2 ) 0.4056
4.512 and
wR2 ) 0.2259
R1 ) 0.1181
wR2 ) 0.2496
1.185 and
R indices
(all data)
largest diff
peak and hole
-0.410 e Å-3
-0.745 e Å-3
-0.546 e Å-3
-0.256 e Å-3
-1.591 e Å-3
-0.338 e Å-3
a
Wavelength/temperature: 0.71073 Å at 150(2) K for 2, 3a , 4, and 7; 173(2) K for 3b and 5.
Ta ble 2. Op tica l P r op er ties a n d Molecu la r Weigh t P r op er ties of P olym er s 9-12
absorption [nm] emission [nm]
a
Mn
Pn
PDI
λmax solution
λmax film
λmax solution
λmax film
9
29 × 103
13 × 104
74 × 103
56 × 103
42
179
98
2.5
4.3
9.9
4.5
418
437
421
434
417; ∆ ) 1 nm
445; ∆ ) 12 nm
432; ∆ ) 11 nm
448; ∆ ) 14 nm
453, 481
456, 483
449, 478
456, 483
460, 480; ∆ ) 7 nm
10
11
12
466, 492; ∆ ) 10 nm
464, 472, 487; ∆ ) 15 nm
469, 493, 516; ∆ ) 13 nm
142
a
Number of phenyleneethynylene units.
ethynylbenzene,19 6,9c 1,4-diiodo-2,5-bisethylhexyloxyben-
zene,20,21 and 2-ethynyltoluene22 were prepared in accordance
to published procedures.
129.64, 129.231, 127.169, 127.017, 126.388, 126.209, 126.121,
125.735, 125.424, 125.103, 86.749, 70.889. IR: v 744.53,
756.53, 831.26, 852.48, 893.94, 1029.43, 1062.22, 1200.61,
1214.59, 1349.11, 1381.42, 1439.76, 1462.19, 1549.70, 2902.19,
3023.69, 3044.91, 3056.48. MS (EI) calcd [C68H48I2O2], 1150.17;
found 1150.4; mp 298 °C.
Syn th esis of 2. 1,4-Diiodo-2,5-dihydroquinone (20.3 g, 5.61
mmol), dimethylformamide (150 mL), potassium carbonate
(9.31 g, 67.4 mmol), and propargyl bromide (18.7 g, 157 mmol)
were placed in a 500 mL round-bottom flask and heated to
reflux for 48 h. The mixture was allowed to cool to room
temperature, and the solvent was removed. The crude product
was dissolved in dichloromethane and washed with 1 N HCl
and water. The organic layer was dried, the solvent was
removed, and the crude solid was purified by chromatography
on silica gel (3:7, ethyl acetate:hexane) to yield 2 as a colorless
solid (23.3 g, 95%). 1H NMR (CDCl3): δ 7.376 (s, 2H), 4.697
(s, 4H), 2.556 (s, 2H). 13C NMR (CDCl3): δ 151.604, 123.584,
85.819, 77.167, 76.120, 57.556. IR: v 616.70, 621.04, 627.79,
648.04, 662.50, 666.36, 678.90, 683.24, 689.02, 730.01, 736.76,
845.73, 851.51, 916.61, 921.43, 994.72, 1004.36, 1009.18,
1062.22, 1180.84, 1193.85, 1200.61, 1219.41, 1233.39, 1238.21,
1244.48, 1248.34, 1254.13, 1272.45, 1276.79, 1308.61, 1311.50,
1318.25, 1326.93, 1333.20, 1343.81, 1377.08, 1429.15, 1435.42,
1442.66, 1445.55, 1469.66, 2118.18, 2926.78, 2968.24, 3270.08,
3286.48, 3289.85. ES+ MS (EI) calcd for [C12H8I2O2], 437.086,
found 437.9; C, 32.91; H, 1.84; found C, 32.96, H, 2.01; mp
155 °C.
Syn th esis of 1,4-Bis(2,3,4,5-tetr a p h en yl)ben zyloxy-2,5-
d iiod oben zen e (3a ). The diiododialkyne compound 2 (6.47
g, 14.8 mmol) o-xylene (20 mL), and tetraphenylcyclopenta-
dienone (17.0 g, 44.2 mmol) were refluxed for 24 h. The solvent
was removed under reduced pressure and the mixture purified
by chromatography on silica gel (1:9, ethyl acetate:hexanes)
to yield 3a as a colorless solid (14.6 g, 86%). 1H NMR (CDCl3):
δ 7.887 (s, 2H), 7.124 (m, 24H), 6.780 (m, 16H), 4.843 (s, 4H).
13C NMR (CDCl3): δ 152.897, 141.378, 140.598, 139.73,
139.679, 139.496, 138.511, 132.925, 131.133, 130.932, 129.982,
Syn th esis of Mod el Com p ou n d 3b. Diiodo monomer 3a
(2.36 g, 2.05 mmol) and 1-ethynyl-2-methylbenzene (0.500 g,
4.30 mmol) were dissolved in dichloromethane (8 mL) and
piperidine (8 mL) in an oven-dried Schlenk flask. The flask
was flushed with nitrogen, frozen, and evacuated three times
after which (Ph3P)2PdCl2 (71 mg, 0.102 mmol) and CuI (20 mg,
0.105 mmol) were added. The mixture was allowed to stir at
room temperature for 48 h. The solvent was removed, and the
mixture was dissolved in dichloromethane and washed with
1 N HCl, 1 N NH4OH, and water. The organic layer was dried
over MgSO4 and the solvent removed. The resulting crude
product was crystallized from a 1:1 mixture of dichloromethane
and methanol to yield pure 3b (2.04 g, 88%). 1H NMR
(CDCl3): δ 7.891 (s, 2H), 7.127 (m, 24H), 6.909 (m, 16H), 4.932
(s, 4H), 2.333 (s, 6H). 13C NMR (TCE): δ 153.644, 141.653,
140.996, 140.308, 140.045, 139.954, 138.964, 133.979, 131.987,
131.856, 131.512, 131.299, 130.349, 129.995, 129.480, 128.357,
128.226, 127.397, 126.790, 126.487, 126.062, 125.496, 125.233,
123.413, 123.201, 118.560, 115.102, 115.091, 94.243, 90.037,
70.159, 20.464. IR: v 698.18, 757.97, 894.91, 975.91, 1195.78,
1217.00, 1272.93, 1371.29, 1504.37, 1598.88, 1801.39, 1947.97,
2206.41, 2318.28, 2335.64, 2858.31, 2920.03, 3022.25, 3055.03.
MS (FAB) calcd for [C86H62O2], 1126.47; found 1126.3; mp 235
°C.
Syn th esis of P olym er 9. Monomer 3 (0.280 g, 0.200 mmol
0.244 mmol) and 2,5-didodecyl-1,4-diethynylbenzene (0.119 g,
0.200 mmol 0.257 mmol) were dissolved in dichloromethane
(0.5 mL) and piperidine (0.5 mL) in an oven-dried Schlenk

8220 Englert et al.
Macromolecules, Vol. 37, No. 22, 2004
flask. The flask was flushed with nitrogen, frozen, and
evacuated three times after which (Ph3P)2PdCl2 (1.4 mg, 2
µmol), and CuI (0.4 mg, 2 µmol) were added. The mixture was
allowed to stir at room temperature for 48 h. The solvent was
removed, and the mixture dissolved in dichloromethane and
washed with 1 N HCl, 1 N NH4OH, and water. The organic
layer was dried over MgSO4 and the solvent removed. The
resulting polymer was dissolved in dichloromethane and
precipitated out of methanol three times to yield 9 (0.284 g,
86%). 1H NMR (CDCl3): δ 7.862 (m 2H), 7.009 (m, 24H), 6.753
(m, 16H), 4.839 (m, 4H), 1.542 (m, 8H), 1.148 (m, 28H), 0.823
(m, 6H). 13C NMR (TCE): δ 152.977, 141.520, 140.827,
139.818, 138.860, 133.794, 132.099, 131.368, 130.225, 129.708,
129.278, 127.291, 126.665, 126.385, 125.962, 125.343, 125.130,
118.654, 115.006, 94.065, 90.965, 71.129, 34.180, 33.838,
31.674, 30.219, 29.073, 26.695, 22.985, 22.413, 13.823. IR: v
693.84, 698.18, 701.56, 742.54, 756.04, 766.17, 890.09, 999.06,
1012.56, 1025.10, 1027.51, 1054.51, 1069.94, 1195.30, 1198.68,
1340.43, 1374.19, 1429.15, 1439.76, 1447.48, 1451.82, 1469.17,
1496.18, 1599.36, 2848.67, 2902.67, 2912.79, 2918.58, 2952.81.
GPC (polystyrene standards): Mn ) 29 350, PDI ) 2.462.
Syn th esis of 4. 1,4-Diydroxy-2,5-diiodobenzene (18.0 g, 49.7
mmol), potassium carbonate (41.8 g, 0.302 mol), and 6-chlo-
rohexyne (24.2 g, 0.208 mol) were dissolved in dimethylform-
amide (200 mL). The mixture was heated to reflux for 48 h
and allowed to cool to room temperature. The mixture was
diluted with dichloromethane and washed with 1 N HCl (2 ×
150 mL). The solvent was removed under vacuum, and the
crude solid was purified by chromatography on silica gel (1:1,
dichloromethane:hexanes) to yield 4 as a colorless crystalline
solid (11.2 g, 43%). 1H NMR (CDCl3): δ 7.151 (s, 2H), 3.922 (t,
4H), 2.254 (m, 4H), 1.890 (m, 6H), 1.724 (m, 4H). 13C NMR
(CDCl3): δ 152.500, 122.506, 86.168, 83.982, 69.502, 68.727,
28.109, 25.043, 18.152. IR: v 731.94, 999.54, 1001.95, 1032.33,
1207.36, 1349.11, 1398.30, 2110.46, 2800.56, 3089.27, 3263.81.
MS (EI) calcd [C18H20I2O2], 521.96; found 522.1; mp 101 °C.
Syn th esis of 5. Diyne 4 (0.826 g, 1.58 mmol) was dissolved
in o-xylene (5 mL), and tetraphenylcyclopentadienone (5.00 g,
13.0 mmol) was added. The mixture was heated to reflux for
24 h and cooled to room temperature, and the solvent was
removed. The crude solid was purified by chromatography on
silica gel (2:8, ethyl acetate:hexanes) to yield 5 (1.45 g, 74%)
1219.41, 1261.84, 2357.33, 2942.21, 3432.09. GPC (polystyrene
standards): Mn ) 13 × 104, PDI ) 4.3.
Syn th esis of 7. Diiodo compound 6 (4.40 g, 8.18 mmol) was
dissolved in dry tetrahydrofuran (25 mL), and under nitrogen
purge NaH (0.665 g, 27.7 mmol) (80% in mineral oil) was
added. 3-Bromopropyne (1.19 g, 10.0 mmol) was added, and
the mixture was allowed to stir at room temperature for 24 h.
The mixture was slowly poured onto water, and the precipi-
tated solid was taken up in dichloromethane. The organic
solution was washed with 0.5 N HCl (150 mL) and then with
water. The organic layer was separated and dried. The solvent
was removed and the crude solid purified by chromatography
over silica gel (4:6, ethyl acetate:hexanes) to yield 7 as a
colorless solid (3.62 g, 72%). 1H NMR (CDCl3): δ 7.212 (s, 2H),
4.211 (m, 4H), 4.072 (t, 4H), 3.850 (t, 4H), 3.774 (m, 4H), 3.697
(m, 4H), 2.406 (t, 2H). 13C NMR (CDCl3): δ 152.998, 123.396,
86.358, 79.588, 74.533, 70.832, 70.212, 69.518, 69.135, 58.398.
IR: v 652.38, 656.72, 661.54, 666.84, 669.74, 678.41, 684.68,
694.81, 697.70, 700.59, 721.81, 725.18, 730.01, 799.92, 833.19,
841.39, 859.23, 877.55, 887.19, 918.54, 1000.50, 1015.93,
1025.58, 1033.77, 1051.13, 1066.08, 1086.33, 1087.78, 1101.28,
1121.05, 1136.96, 1219.41, 1232.91, 1243.04, 1265.70, 1286.43,
1330.31, 1353.45, 1355.86, 1427.71, 1435.42, 1437.83, 1445.55,
1450.37, 1455.67, 1463.87, 1466.28, 1486.05, 1492.80, 2830.34,
2837.09, 2849.63, 2861.68, 2879.04, 2884.35, 2895.44, 2920.99,
2929.19, 2935.94, 2944.62, 237.78, 3272.49. ES+ MS (EI) calcd
[C20H24I2O6], 613.97; C, 39.11; H, 3.94; found 614.1; found C,
39.11; H, 4.02; mp 82 °C.
Syn th esis of 8. Diiododiyne 7 (0.361 g, 0.588 mmol) was
dissolved in o-xylene (10 mL), and tetraphenylcyclopentadi-
enone (8.00 g, 20.8 mmol) was added. The mixture was heated
to reflux for 48 h, cooled to room temperature, and the solvent
was removed. The crude solid was purified by chromatography
over silica gel (4:6, ethyl acetate:hexanes) to yield 8 (0.140 g,
1
18%) as an oil which solidified under high vacuum. H NMR
(CDCl3): δ 7.695 (s, 2H), 7.055 (m, 24H), 6.726 (m, 16H), 4.394
(s, 4H), 4.001 (t, 4H), 3.811 (t, 4H), 3.714 (m, 4H), 3.570 (m,
4H). 13C NMR (CDCl3): δ 153.050, 141.858, 141.474, 140.048,
139.908, 139.372, 139.191, 135.479, 131.456, 131.233, 130.292,
129.929, 129.402, 127.504, 127.314, 126.833, 126.529, 126.294,
126.136, 125.502, 125.268, 123.397, 86.413, 77.327, 77.212,
77.010, 76.693, 71.450, 76.693, 71.450, 71.087, 70.205, 70.084,
69.500. IR: v 696.25, 701.56, 744.95, 763.28, 800.89, 1009.18,
1027.51, 1059.81, 1156.25, 1197.71, 1345.74, 1432.53, 1441.69,
1447.48, 1456.16, 1480.75, 1495.21, 1575.25, 1598.40, 1709.30,
2846.25, 2926.78, 3019.84, 3051.18. ES+ MS (EI) calcd
[C76H64I2O6], 1326.28; C, 68.78; H, 4.86; found fragmentation:
552.2, 408, 262.9; found C, 68.72; H, 5.06; mp 126 °C.
1
as a colorless oil that solidified under high vacuum. H NMR
(CDCl3): δ 7.432 (s, 2H), 7.020 (m, 24H), 6.727 (m, 16H), 3.714
(t, 4H), 2.575 (m, 6H), 1.731 (m, 4H). 13C NMR (CDCl3): δ
152.485, 141.829, 141.343, 140.402, 140.296, 139.962, 139.856,
139.264, 137.518, 131.431, 131.067, 130.278, 129.868, 129.807,
127.379, 127.212, 126.665, 126.316, 125.952, 125.254, 125.011,
122.279, 86.001, 69.608, 33.224, 28.883, 27.714. IR: v 761.35,
1027.51, 1057.40, 1210.73, 1455.19, 1491.35, 1609.97, 1878.54,
1945.56, 2864.58, 2935.94, 3045.87. MS (EI) calcd [C74H60I2O2],
1234.27; found 1234.7; mp 86 °C.
Syn th esis of P olym er 11. Diiodo compound 8 (0.134 g, 101
µmol) and 2,5-didodecyl-1,4-diethynylbenzene (47.0 mg, 0.101
mmol) were dissolved in tetrahydrofuran (0.1 mL) and piper-
idine (0.1 mL) in an oven-dried Schlenk flask. The flask was
flushed with nitrogen, frozen, and evacuated three times, after
which (Ph3P)2PdCl2 (0.7 mg, 1 µmol) and CuI (0.2 mg, 1 µmol)
were added. The mixture was allowed to stir at room temper-
ature for 48 h. The solvent was removed, and the mixture
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried over MgSO4,
and the solvent was removed. The crude polymer was dissolved
in dichloromethane and precipitated out of hexane and then
acetone to yield 11 (93 mg, 60%) as a dark yellow solid. 1H
NMR (CDCl3): δ 7.648 (m, 2H), 7.048 (m, 24H), 6.724 (m 16H),
4.330 (m, 4H), 3.373 (m, 16H), 2.442 (m, 4H), 1.638 (m, 4H),
1.525 (m, 8H), 1.198 (m, 28H), 0.829 (m, 6H). 13C NMR
(TCE): δ 153.867, 142.047, 141.643, 140.703, 140.207, 140.192,
140.146, 139.550, 139.368, 135.465, 132.381, 131.663, 131.350,
130.511, 130.005, 129.419, 127.478, 127.205, 126.729, 126.487,
126.234, 126.052, 125.425, 125.172, 94.809, 90.564, 71.595,
71.524, 70.988, 70.594, 70.058, 69.815, 69.735, 44.771, 34.023,
31.91, 30.555, 29.635, 29.483, 29.251, 22.658, 22.426, 22.274,
14.024. IR: v 617.66, 667.81, 694.81, 697.70, 718.92, 751.70,
897.80, 1053.06, 1061.74, 1094.53, 1117.67, 1125.39, 1142.74,
1258.47, 1439.76, 1460.01, 2363.60, 2943.65, 3402.20, 3537.69.
GPC (polystyrene standards): Mn ) 73 780, PDI ) 9.9.
Syn th esis of P olym er 10. Diiodo compound 5 (0.101 g,
81.8 µmol) and 2,5-didodecyl-1,4-diethynylbenzene (0.0380 g,
82.1 µmol) were dissolved in tetrahydrofuran (0.2 mL) and
piperidine (0.2 mL) in an oven-dried Schlenk flask. The flask
was flushed with nitrogen, frozen, and evacuated three times,
after which (Ph3P)2PdCl2 (6.3 mg, 9.0 µmol) and CuI (1.7 mg,
8.9 µmol) were added. The mixture was allowed to stir at room
temperature for 48 h. The solvent was removed, the mixture
dissolved in dichloromethane and washed with 1 N HCl, 1 N
NH4OH, and water. The organic layer was dried and the
solvent removed. The resulting polymer 10 was dissolved in
dichloromethane and precipitated out of methanol three times
and hexanes three times to yield 10 (74 mg, 63%). 1H NMR
(CDCl3): δ 7.437 (m, 2H), 7.110 (m, 24H), 6.786 (m, 16H), 3.825
(m, 4H), 2.762 (m, 4H), 2.592 (m, 4H), 1.755 (m, 4H), 1.546,
(m, 8H), 1.191 (m, 28H), 0.841 (m, 6H). 13C NMR (TCE): δ
153.77, 143.64, 142.21, 141.61, 140.59, 140.32, 139.16, 137.87,
133.23, 132.28, 131.67, 131.34, 129.54, 127.38, 127.24, 126.65,
126.33, 125.94, 125.20, 124.95, 123.77, 123.05, 120.39, 117.65,
114.90, 94.03, 90.86, 69.70, 44.70, 33.90, 33.49, 31.82, 30.45,
29.57, 29.22, 27.51, 22.55, 13.93. IR: v 667.81, 694.81, 697.70,
794.62, 799.92, 1002.92, 1015.93, 1021.24, 1027.02, 1045.35,
1054.03, 1057.88, 1071.38, 1078.13, 1082.96, 1095.49, 1111.89,

Macromolecules, Vol. 37, No. 22, 2004
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g, 83%) as a dark yellow solid. H NMR (CDCl3): δ 7.362 (m,
2H), 6.979 (m, 2H), 3.887 (m, 4H), 3.176 (m, 4H), 1.907 (m,
4H), 1.500 (m, 2H), 1.222 (m, 52H), 0.849 (m, 18H). 13C NMR
(CDCl3): δ 153.659, 141.901, 132.261, 122.820, 116.623,
114.144, 94.026, 90.751, 71.985, 39.589, 30.549, 29.666, 29.612,
29.529, 29.306, 29.117, 23.917, 23.041, 22.618, 14.001, 11.129.
IR: v 679.86, 717.95, 858.75, 883.82, 989.41, 1050.65, 1210.73,
1277.75, 1464.83, 1516.91, 2163.02, 2854.93, 2940.28, 3841.94.
GPC (polystyrene standards): Mn ) 56 434, PDI ) 4.461.
Differ en tia l Sca n n in g Ca lor im etr y Mea su r em en ts.
DSC measurements were taken on a Mettler Toledo DSC 822.
The samples were weighed into a 40 µL aluminum crucible,
and the lid was punctured. Each sample was heated from 25
to 250 °C at a rate of 10 °C/min under N2.
X-r a y P ow d er Diffr a ction Mea su r em en ts. The X-ray
powder diffraction data were collected on a Rigaku powder
X-ray diffractometer using a Bragg-Brentano geometry with
Cu KR radiation. The step scan covered the angular range
5-50° 2θ in steps of 0.02°.
Ack n ow led gm en t. The NSF (CHE-0138659) and
Georgia Tech funded this work. We thank Dr. Angus
Wilkinson (Georgia Institute of Technology) for the
powder diffraction experiments. U.B. is a Camille Drey-
fus Teacher-Scholar (2000-2004). We thank Prof. Ulli
Scherf (Wuppertal) for helpful discussions.
Su p p or tin g In for m a tion Ava ila ble: CIFs, crystallo-
graphic tables, and experimental details for the single-crystal
X-ray structure determination for 2, 3a , 3b, 4, 5, and 7. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Refer en ces a n d Notes
(1) (a) Lupton, J . M.; Schouwink, P.; Keivanidis, P. E.; Grimsdale,
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