Synthesis and properties of new chiral donor-embedded polybinaphthalenes for nonlinear optical applications

Article abstract of DOI:10.1021/ma0491816

Eight new chiral, chromophore-functionalized donor-embedded polybinaphthalenes were prepared and characterized for their (nonlinear) optical properties. The polymers were prepared by direct polymerization using a Stille coupling reaction between a chiral bis(trimethyltin) binaphthalene derivative and diiodo-functionalized chromophores. The use of diiodo-functionalized instead of dibromo-functionalized chromophores resulted in a significant increase of molecular weight, as demonstrated by end group analysis, GPC, and MALDI-TOF experiments. The reaction conditions allowed the use of a great variety of chromophores with different DπA structures. The typical treelike macromolecular architecture of the polymers is reflected in the behavior of the glass transition temperature and, more clearly, in the nonlinear optical properties. The nonlinear optical response shows a continuous, linear increase in function of chromophore concentration, indicating that the dipolar interactions between the chromophores are eliminated. Moreover, chiral contributions to the nonlinear optical response were observed and mounted 14% of the highest achiral contribution.

Full text of DOI:10.1021/ma0491816

8530
Macromolecules 2004, 37, 8530-8537
Synthesis and Properties of New Chiral Donor-Embedded
Polybinaphthalenes for Nonlinear Optical Applications
Guy Koeckelberghs,†,‡ Marnix Vangheluwe,† Isabel Picard,‡ Leen De Groof,†
Thierry Verbiest,‡ Andre´ Persoons,‡ and Celest Samyn*,†
Laboratory of Macromolecular and Physical Organic Chemistry, Katholieke Universiteit Leuven,
Celestijnenlaan 200 F, B-3001, Belgium, and Laboratory of Chemical and Biological Dynamics,
Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001, Belgium
Received April 27, 2004; Revised Manuscript Received August 17, 2004
ABSTRACT: Eight new chiral, chromophore-functionalized donor-embedded polybinaphthalenes were
prepared and characterized for their (nonlinear) optical properties. The polymers were prepared by direct
polymerization using a Stille coupling reaction between a chiral bis(trimethyltin) binaphthalene derivative
and diiodo-functionalized chromophores. The use of diiodo-functionalized instead of dibromo-functionalized
chromophores resulted in a significant increase of molecular weight, as demonstrated by end group
analysis, GPC, and MALDI-TOF experiments. The reaction conditions allowed the use of a great variety
of chromophores with different DπA structures. The typical treelike macromolecular architecture of the
polymers is reflected in the behavior of the glass transition temperature and, more clearly, in the nonlinear
optical properties. The nonlinear optical response shows a continuous, linear increase in function of
chromophore concentration, indicating that the dipolar interactions between the chromophores are
eliminated. Moreover, chiral contributions to the nonlinear optical response were observed and mounted
14% of the highest achiral contribution.
Introduction
to a rigid backbone (trunk)) is optimal in these materi-
als: the chromophores can still easily be poled in an
electric field (in contrast to systems in which the
chromophores are part of the main chain), but the
chromophores are attached to the backbone as close as
possible. This allows a very tight relation between the
nonlinearity, originating from the chromophores, and
the chirality, situated in the backbone, and chiral
contributions to the nonlinear optical response are
present.5 Therefore, the importance of chirality is
2-fold: first, rigid, helical conformations can only be
formed if chiral monomers are polymerized, and second,
chiral contributions to the nonlinear optical response
can only be present in chiral samples. Furthermore,
polybinaphthalenes show excellent thermal and (photo)-
chemical stability.5
We already reported6 the synthesis of two chiral
donor-embedded polybinaphthalenes, functionalized with
chromophores. Those polymers were prepared by a Stille
coupling between a bis(trimethyltin)binaphthalene mono-
mer and dibromo-functionalized chromophores with
rather weak to moderate NLO properties. Here, we
report the synthesis and properties of eight new, chiral
donor-embedded polybinaphthalenes, functionalized with
chromophores with negligible to superb NLO properties.
These polymers were prepared in an analogues way, but
diiodo-functionalized instead of dibromo-functionalized
chromophores were used. One of the polymers (pol-2-
1) was prepared from a diiodo-functionalized chro-
mophore with the same DπA structure as described
earlier (where dibromo-functionalized chromophores
were used). As a consequence, this allows the investiga-
tion of the influence of the synthetic procedure on the
polymer’s properties.
Design and synthesis of polymeric materials for
second-order nonlinear optical (NLO) applications have
received considerable interest. These materials usually
consist of dipolar chromophores, embedded in a polymer
matrix. A large variety of polymers have been used, but
seldom were rigid, helical, chromophore-functionalized
polymers studied, although they show some additional
advantages compared to their random coil analogues.
First, the rigidity of the backbone can greatly diminish
unwanted dipolar interactions between the chromo-
phores, allowing a very high chromophore density.1
Second, when chiral polymers are used, the system can
benefit from its chirality,2 giving rise to the relaxation
of the need of polar order and the presence of contribu-
tions, inherent to chirality, which can increase the
nonlinear optical response.
Polymers containing binaphthalene units can also
adopt a helical configuration.3 Due to the twisted
configuration of the binaphthalene moiety, polymers in
which these units are connected through rigid groups
(in the case of triphenylamine derivatives) are helices.
The rigidity of the system gives rise to a rigid, rodlike,
helical structure. A helix is a highly regular structure
in which all bonds that form the helix have the same
configuration (either S or R). As a consequence, if both
R and S monomers are incorporated in the same
backbone, no helical configuration can be formed.4
Chromophores were introduced to trigger a nonlinear
optical response. Here, we have chosen to prepare donor-
embedded polybinaphthalenes. The treelike macromo-
lecular design (chromophores (branches) are attached
* Corresponding author. Telephone: + 32 (0) 16 32 74 38. Fax:
+ 32 (0) 16 32 79 90. E-mail: Celest.samyn@chem.kuleuven.ac.be.
† Laboratory of Macromolecular and Physical Organic Chem-
istry, Katholieke Universiteit Leuven.
Results and Discussion
‡ Laboratory of Chemical and Biological Dynamics, Katholieke
Universiteit Leuven.
Synthesis of the Polymers. The synthesis of the
chromophores is presented in Schemes 1 and 2. All
10.1021/ma0491816 CCC: $27.50 © 2004 American Chemical Society
Published on Web 10/19/2004

Macromolecules, Vol. 37, No. 23, 2004
Chiral Donor-Embedded Polybinaphthalenes 8531
Scheme 1. Synthesis of Chr 1
Scheme 2. Synthesis of Chr 2-5
chromophores were prepared starting from the aldehyde
1. Reaction of 1 with tert-butylmagnesium chloride
resulted in 2. Chr 1 was then prepared by oxidation of
the secondary alcohol 2 using K2Cr2O7/H2SO4, followed
by iodation of 3 (Scheme 1). It is worthwhile to note that,
if the iodation is performed as the first step, side
reactions dominate when the resulting aldehyde (i.e.,
4, Scheme 2) is treated with tert-butylmagnesium
chloride.
condensation of 4 with 2-(3,5,5)-trimethyl-2-cyclohexene-
1-ylidenepropanedinitrile 57 resulted in chr 2. A Wit-
tig-Horner reaction of the aldehyde 4 and phosphonium
salt 68 yielded 7 as a cis/trans mixture. Reaction with
lithium diisopropyl amide (LDA), quenching of the
lithium derivative with dimethylformamide (DMF) and
subsequent hydrolysis resulted in the formation of the
target aldehyde 8, still in a cis/trans mixture. However,
it was possible to separate both isomers by careful
column chromatography. Finally, chr 3-5 were pre-
pared by a Knoevenagel condensation under appropriate
The first step in the synthesis of chr 2-5 was the
iodation of the starting aldehyde 1. A Knoevenagel

8532 Koeckelberghs et al.
Macromolecules, Vol. 37, No. 23, 2004
Scheme 3. Polymer Synthesis
reaction conditions with 3-phenyl-5-isoxazolone (9),
diethylthiobarbituric acid (10) and 2-dicyanomethylene-
3-cyano-4,5,5-trimethyl-(2H,5H)-furan (11),8 respec-
tively. In the cases of chr 3 and chr 5, only the trans
isomer of the chromophore was obtained, starting from
a mixture of cis/trans 8. This is consistent with an
increase in bond length alternation in the chromophore,
which is observed when stronger withdrawing groups
are attached to an aromatic π-conjugated system. In the
chromophore, the double bond character of the central
vinyl is thus reduced, allowing isomerization to the more
stable trans-chromophore. Surprisingly,1,9 this was not
the case with 10: chr 4 was isolated as a mixture of
both isomers, even after heating in an ethanol solution.
Pure trans-chr 4 could only be obtained starting from
trans-8.
The polymers were prepared by a Stille coupling
between (S)-(-)-6,6′-di(trimethyltin)-2,2′-dihexyloxy-
[1,1′-binaphthalene] (S)-126 and the diiodo-substituted
chromophores chr 1-5 (Scheme 3). Attempts were done
to improve the polymerization conditions. In several
batches, THF appeared to be a better choice as solvent
than DMF (Mh w ) 8.0 and 6.9 kg/mol respectively, GPC,
pol-2-1). Moreover, sometimes, some degradation of the
chromophore seemed to be present, as indicated by UV-
vis spectroscopy. As expected,10 the system Pd2dba3/
AsPh3 was the catalyst/ligand of choice: with Pd[PPh3]4,
for instance, only oligomers could be isolated (Mh w ) 0.43
kg/mol).
Homopolymers with all 5 chromophores as well as
copolymers with chr 1 and chr 4 in different ratios were
prepared. All chromophores have an analogous build-
up: they consist of a triphenylamine moiety, which is
substituted in the 4-position with an electron-withdraw-
ing group. Therefore, we can assume that they are all
more or less equally reactive in the Stille coupling
reaction. As a consequence, the ratio of chr 1 and chr
4 in the copolymers can easily be adjusted, simply by
varying the feed ratios (Table 1).
Characterization of the Polymers. Composition.
In this way, eight new polymers were prepared. Their
composition, yields, molecular weights, and polydisper-
sities are presented in Table 1.
In the way described above, all polymers could be
prepared in very high yields (except for pol-1-1), without
any decomposition of the chromophore, as judged by 1H

Macromolecules, Vol. 37, No. 23, 2004
Chiral Donor-Embedded Polybinaphthalenes 8533
Table 1. Composition, Yield, Molecular Weight, and Polydispersity of the Polymers
y′chr 4, copolymerc
1H NMR (UV-vis)
polymera
chr 1 (x)/chr i (y), feedb
Fd/%
Mh we/(kg/mol)
Df
pol-1-1
chr 1 (1)
32
98
90
91
91
90
95
97
4.5
8.0
5.9
4.7
3.3
3.6
3.8
6.6
2.1
2.1
2.4
2.2
2.4
2.7
2.7
2.3
pol-2-1
chr 1 (0)/chr 2 (1)
chr 1 (0)/chr 3 (1)
chr 1 (0.75)/chr 4 (0.25)
chr 1 (0.50)/chr 4 (0.50)
chr 1 (0.25)/chr 4 (0.75)
chr 1 (0)/chr 4 (1)
chr 1 (0)/chr 5 (1)
pol-3-1
pol-4-0.25
pol-4-0.50
pol-4-0.75
pol-4-1
0.30 (0.27)
0.50 (0.54)
0.75 (0.73)
pol-5-1
a The code number of the polymers is constituted as follows: the first number denotes for the chromophore used in the homopolymers
(in the copolymers, chr 4, which shows much better nonlinear optical properties than chr 1, is taken); the second number indicates the
mole ratio of the chr i in the feed of the copolymers. b Nature and mole ratio of chromophores in the feed. c Mole ratio of chr 4 in the
copolymers, determined by 1H NMR and UV-vis spectroscopy. d Yield of the isolated polymers. e Weight-average molecular weight,
measured GPC. f Polydispersity, Mh w/Mh n,determined by GPC.
NMR and UV-vis spectroscopy. The Stille reaction has
already been used for the polymerization of chro-
mophore-functionalized monomers for nonlinear optics,
even for chromophores related to chr 4.1,11 Here, we
show that the Stille coupling can be expended to a large
number of chromophores with several, distinctly differ-
ent DπA systems and even to chromophores with superb
NLO properties (chr 5).
The ratio chr 4/chr 1 in the copolymers is measured
1
by H NMR and UV-vis spectroscopy and resembles
the ratio in the feed. If the high yields are taken into
account, this is no proof that the different chromophores
are randomly distributed in the chain. However, since
they are electronically equal (the 1H and 13C NMR
signals, for instance, are the same), we can expect that
Figure 1. CD spectrum of pol-2-1.
they are equally reactive and therefore randomly dis-
which constitute the main-chain of the polymers, this
tributed in the polymer chain.
means that the chromophore does not influence the
GPC Analysis. The molecular weights were deter-
supramolecular architecture of the polymers.
mined by gel permeation chromatography (GPC) toward
A surprising feature of these polymers is the signifi-
polystyrene standards in THF. It has been demon-
cant red shift of λmax when the chromophores are
strated that the molecular weights determined in this
polymerized. λmax of the chromophores in THF are 318
way are underestimated.12 In a previous publication, in
(chr 1), 471 (chr 2), 519 (chr 3), 538 (chr 4), and 568
nm (chr 5). As displayed in Table 2, λmax of the
chromophores in the polymers is 21-32 nm higher than
λmax of the chromophore-monomers. Clearly, polymeri-
zation leads to planarization of the triphenylamine unit
and, consequently, a better conjugation in the chro-
mophore.
which the chromophores were functionalized with two
bromine atoms instead of iodine, we have determined
this parameter by end group analysis with 1H NMR. In
the polymers obtained by polymerization of diiodo-
substituted chromophores, no peaks or very small peaks
of end groups were presented, indicating that these
polymers have a significantly higher molecular weight.
To get a better estimation of the molecular weights,
pol-2-1 was fractionated by GPC and the fractions (D
≈ 1.1) were analyzed by MALDI-TOF. This revealed
that the unfractionated sample has an overall polydis-
persity of 1.5, Mh w ) 7.4 kg/mol and Mh n ) 5.0 kg/mol,
which is about 20% higher than that determined by
GPC toward polystyrene standards. These results are
in line with those Pu et al. found for analogous polybi-
naphthalenes by LLS.12 The same polymer, but pre-
pared from the dibromo-substituted chromophore, showed
a much lower molecular weight (Mh w ) 3.0 kg/mol, Mh n
) 1.7 kg/mol and D ) 1.8). Therefore, we can conclude
that the Stille coupling of diiodo-substituted chro-
mophores produces polymers of significantly higher
molecular weights. This is consistent with the fact that
Stille couplings proceed better with aryl iodides instead
of aryl bromides.10b
The specific optical rotations of the polymers are
summarized in Table 2. The values greatly depend on
λmax of the polymers and are therefore resonantly
enhanced. Since the CD spectra of all polymers are the
same, we can conclude that the macromolecular archi-
tecture of the polymers is independent of the chro-
mophore used. The difference in optical rotations can
then be ascribed to resonant enhancement and possible
differences in end groups.
Molecular Modeling. To visualize the supramolecu-
lar (helical) rodlike structure, some molecular modeling
was performed. We performed a molecular mechanics
simulation modeling of pol-2-1 (Hyperchem 7.1). Eight
repeating units were used. As can be seen in Figure 2,
parts a and b, the polymer adopts a helical, rodlike
conformation.
DSC Analysis. The glass transition temperatures
(Tg) of the polymers were measured by differential
scanning calorimetry (DSC) and are listed in Table 2.
The observed Tg of rigid, chromophore-functionalized
polybinaphthalenes is the Tg of the chromophores in the
material and not of the whole polymer material.1,8
Therefore, the Tg of the polymers depends on the Tg of
CD and UV)Vis Spectroscopy and Polarimetry.
A representative CD spectrum of pol-2-1 in THF is
shown in Figure 1.
All polymers have essentially the same CD spectrum,
both in solution as in thin film. Since the observed
Cotton effects are due to the binaphthalene moieties,

8534 Koeckelberghs et al.
Macromolecules, Vol. 37, No. 23, 2004
Table 2. λmax, Specific Optical Rotations, Glass Transition Temperatures, and NLO Properties of the Polymers
[R]D20°C b/deg.dm-1.g-1.mL
Tg /°C
ø(z2z)z(ω)/(pm/V)
ø(z2z)z(0)d/(pm/V)
c
polymer
λmaxa/nm
pol-1-1
349
518
562
582
582
577
577
625
0.49
1.3
71
157
186
184
162
162
165
183
193
0
99
115
22
81
107
129
98
0
3.9
9.7
3
11
13
16
25
pol-2-1
pol-3-1
pol-4-0.25
pol-4-0.50
pol-4-0.75
pol-4-1
4.3
66
64
71
pol-5-1
15
a In THF. b c ) 0.002 in THF. c Determined by DSC (50 °C/min). d Calculated using the two-level model.13
samples. Therefore, a polar ordering of the chro-
mophores remains, in practice, necessary and was
achieved by corona poling. We have optimized the poling
conditions and found that for this class of polymers, the
highest polar order was achieved by poling at 7 °C above
Tg during 20 min. The applied voltage was 8.2 kV.
The nonlinear optical properties were analyzed using
SHG measurements.14 Polarized UV-vis showed that
the poled films have a C∞ symmetry. For such samples,
there are four nonvanishing susceptibility components,
that is, øz(2z)z, øx(2x)z, ø(z2x)x, and ø(x2y)z. The first three compo-
nents originate from the polar ordering, while the latter
can only be present in chiral media. The ratio ø(z2z)z/ø(2)
xxz
) 3 confirms the symmetry mentioned above.15
The macroscopic second-order nonlinear optical re-
sponse (ø(2)) of chromophore-functionalized polymer
materials arises from the hyperpolarizability (â) of the
incorporated chromophores. As a consequencesin the
absence of intermolecular interactionssø(2) is directly
proportional to the hyperpolarizability and the number
density of the chromophores, N. Furthermore, if the
polar ordering is achieved by orienting the dipolar
chromophores in an external electrical field E, ø(2)
depends also on the dipole moment and the orienting
Figure 2. Molecular mechanics simulations: (a) front view
and (b) top view of pol-2-1.
the incorporated chromophore built in and on the
flexibility of the chromophores in the polymer material.
The Tg’s of the respective chromophores were measured
at 49 (chr 1), 77 (chr 2), 87 (chr 3), and 111 °C (chr 4)
by DSC (30 °C/min). chr 5 degrades around 275 °C and
could not be vitrified. From Table 2, it is clear that the
Tg of the homopolymers depends on the Tg of the
incorporated chromophores. Moreover, the observed Tg
of the copolymers is intermediate to the Tg’s of the
respective homopolymers. The results confirm the above-
mentioned phenomenom.
The Tg of the polymer, similar to pol-2-1, but pre-
pared from the dibromo-substituted chromophore, was
measured under identical conditions and found to be 152
°C.6 This is 34 °C lower than the Tg of the polymer,
prepared from the diiodo-chromophore (Table 2). Since
the only difference in both materials is the molecular
weight, this means that the molecular weight has a
profound influence on the Tg of the polymers, and, as a
consequence, on the flexibility of the chromophores in
the polymer material. This also explains why the
relationship between the Tg of the chromophores and
the Tg of the polymers is not very clear. The molecular
weight of pol-2-1, for instance, is much higher than
those of the others, which might explain the fact that
pol-2-1 shows a high Tg, while the Tg of the chro-
mophore is rather low.
field: ø(2)
NµâE (µ is the dipole moment of the
chromophore).16 Since all polymers are poled at the
same voltage and N is always more or less the same in
the homopolymers, this implies that ø(2) should increase
with increasing “chromophore strength”, i.e. with in-
creasing µâ. This is perfectly reflected in the ø(z2z)z(0)
values of the homopolymers: chr 1 has negligible
nonlinear optical properties, while chr 5 is an excellent
chromophore. The nonlinear optical response is very
stable at room temperature. After 6 months at room
temperature, only 95% of the response of pol-5-1 is lost,
which can be explained by the high Tg.
ø(z2z)z(0) of pol-2-1, prepared from the dibromo-substi-
tuted chromophore, was measured at 13.5 pm/V,5 which
is significantly higher than ø(z2z)z(0) of pol-2-1, prepared
from the diiodo-substituted chromophore. Since the
molecular structure of both samples is identical, this
difference cannot be due the chromophore itself, but it
must reflect the difference in poling order in both
samples. DSC measurements already indicated that the
flexibility of the chromophores in the lower molecular
weight sample is much higher than in the higher
molecular weight samples. Higher mobility allows a
better alignment of the chromophore in the poling field,
which leads to higher susceptibilities.
Nonlinear Optical Properties. The polymers were
spin-coated onto ITO glass slides from chloroform solu-
tions, which resulted in high quality films. Poly(acrylic
acid) was spin-coated on top of the polymer film, to
prevent bleaching during the poling process. Although
a chiral sample is inherently noncentrosymmetric and
should therefore, in principle, not be poled, the ordering
of the chromophores was insufficient to allow a NLO
response. Moreover, electric-dipole second-harmonic
generation (SHG) is symmetry-forbidden in isotropic
As mentioned above, the linear relationship ø(2)
NµâE only counts when no electrostatic interactions
between the chromophores are present. However, good
chromophores tend to have high dipole moments and
above a critical loading density, electrostatic interac-
tions occur, which favor centrosymmetrical ordering of

Macromolecules, Vol. 37, No. 23, 2004
Chiral Donor-Embedded Polybinaphthalenes 8535
bromo-substituted chromophores. Furthermore, the po-
lymerization conditions allowed the use of a great
variety of chromophores.
The properties, the Tg, and the NLO response of these
polymers were compared to those of the lower molecular
weights samples, which revealed a reduced flexibility
of the chromophores in the higher molecular weight
material. The typical treelike macromolecular architec-
ture of the polymers eliminates the dipolar interactions
between the chromophores, resulting in a linear in-
crease of the nonlinear optical response as a function
of chromophore concentration. Finally, chiral contribu-
tions to the nonlinear optical response were observed,
which can be ascribed to the donor-embedded structure.
We can therefore conclude that these polymers show a
unique combination of three assets: first, the possibility
to use excellent chromophores, second, the (almost)
complete elimination of dipolar interaction between the
chromophores, allowing very high chromophore concen-
tration, and third, the presence of chiral contributions,
which increase the nonlinear optical response.
Figure 3. Evolution of ø(2) of the copolymers with increasing
chromophore concentrations.
the chromophores in the polymer matrix. As a result,
severe attenuation of ø(2) as a function of N is expected
to occur for chromophores with dipole moments of 7 D
and higher. The dipole moment of chr 4 was determined
by capacity measurements and found to be 9 ( 1 D.
We have already shown that the macromolecular
architecture of chiral, rigid polybinaphthalenes with
chromophores as pendant groups diminishes the elec-
trostatic interactions between the chromophores.1 Here,
we investigate whether the same tendency is present
in donor-embedded polybinaphthalenes.
Experimental Section
Reagents. All reagents were purchased from Aldrich
Chemical Co., Acros Organics, Merck, Fluka, and Avocado.
Reagent grade solvents were dried when necessary and
purified by distillation.
The glass transition temperatures were measured with a
DSC-7 apparatus from Perkin-Elmer at a heating rate of 50
°C/min (polymers) or 30 °C/min (chromophores). Gel perme-
ation chromatography (GPC) measurements were performed
with a Waters apparatus with a tunable absorbance detector
and a differential refractometer in tetrahydrofuran (THF) as
eluent toward polystyrene standards. 1H nuclear magnetic
resonance (NMR) measurements were carried out with a
Bruker Avance 300 MHz. UV-vis spectra were recorded with
a Varian Cary 400. The optical rotations were measured with
an Analis Optical Activity Polaar 20.
Since pol-1-1 shows no nonlinear optical response, the
nonlinear optical properties of the copolymers pol-4-
0.25 to pol-4-1 arise from the presence of chr 4. As a
consequence, the evolution of ø(2) in function of the
chromophore density (N∼wt %) can be investigated by
plotting the ratio of chr 4 in the copolymers in function
of ø(2). Figure 3 states a continuous, linear increase of
the nonlinear optical response of the copolymers with
increasing chromophore concentration, indicating that
the electrostatic interactions between the chromophores
are more or less eliminated in these materials. In
classical systems, the nonlinear optical response reaches
a maximum at chromophore concentrations of ∼15 wt
% (µ ) 10 D). Clearly, the electrostatic interactions are
in these polymers eliminated by the typical treelike
macromolecular structure, which is a unique feature of
these polymers. This phenomenon is much more pro-
nounced in donor-embedded polybinaphthalenes than
in polybinaphthalenes with chromophores as pendant
groups. Finally, we investigated whether the chirality
of the system is reflected in its nonlinear optical
response. Preliminary results6 already indicated that
chiral contributions are present in chromophore-func-
Synthesis of the Chromophores. Synthesis of 1-[4-
(N,N-Diphenylamino)]phenyl-2,2-dimethylpropanol, 2.
Under argon atmosphere, 100 mL (160 mmol) of tert-butyl-
magnesium chloride (1.6 M in THF) was added to a solution
of 41.0 g (150 mmol) of 1 in 100 mL of dry THF at 0 °C. The
mixture was refluxed for 2 h, after which it was cooled in an
ice bath and 100 mL of a HCl solution (0.1 M) was carefully
added. The product was extracted with dichloromethane, and
the combined organic layers were washed with a saturated
NaHCO3 solution and with brine and dried over MgSO4. After
removal of the solvents, the crude reaction product was
purified by column chromatography (silica gel; eluent: hexane/
ethyl acetate 80/20 (v/v)) and isolated as an oil.
Yield: 18.0 g (36%).
1H NMR (CDCl3, ppm): δ ) 7.26 (t; 4H), 7.19 (d; 2H), 7.08
(d; 4H), 7.06 (d; 2H), 7.02 (t; 2H), 4.38 (d; J ) 2.7 Hz; 1H),
1.83 (d; J ) 2.7 Hz; 1H), 0.96 (s; 9H).
tionalized polybinaphthalenes, if the donor is embedded
(2)
xyz
13C NMR (CDCl3, ppm): δ ) 147.8, 146.9, 136.4, 129.2,
128.4, 124.1, 123.0, 122.7, 82.1, 35.7, 26.0.
in the polymer backbone. ø (ω) of pol-2-1 was mea-
sured at 14 pm/V, which is 14% of the highest achiral
MS: m/z ) 331 (M+), 274 (M+ - C4H9).
contribution (ø(z2z)z). Therefore, the chirality of the sys-
tem significantly enhances the nonlinear optical re-
sponse in two ways: first, by eliminating the dipolar
interactions between the chromophores, which allows
very high chromophore concentrations, and second, by
the presence of chiral contributions.
Anal. Calcd for C23H25NO: C, 83.34; H, 7.60; N, 4.23.
Found: C, 83.06; H, 7.48; N, 4.12.
Synthesis of 1-[4-(N,N-Diphenylamino)]phenyl-2,2-
dimethylpropanone, 3. A solution of 3.55 g (11.4 mmol) of
K2Cr2O7 in 3 mL of concentrated sulfuric acid and 100 mL of
water was dropwise added to a solution of 18.0 g of 2 in 100
mL of diethyl ether at 0 °C. The reaction mixture was stirred
for 2 h at room temperature and then extracted with diethyl
ether. The combined organic layers were washed with a
saturated NaHSO3 solution, a saturated NaHCO3 solution, and
with brine and dried over MgSO4. The crude reaction product
was purified by column chromatography (silica gel; eluent:
hexane/dichloromethane 70/30 (v/v)) and isolated as a yellow
solid.
Conclusion
In this work, we have prepared and studied eight new,
chiral, chromophore-functionalized donor-embedded po-
lybinaphthalenes. The use of diiodo-functionalized chro-
mophores resulted in significantly higher molecular
weights, compared with materials, prepared from di-

8536 Koeckelberghs et al.
Macromolecules, Vol. 37, No. 23, 2004
Yield: 3.20 g (18%).
Mp: 124 °C.
1H NMR (CDCl3, ppm): δ ) 7.59 (d; 4H), 7.39 (d; 2H), 7.03
(d; 2H), 7.01 (d; J ) 16.1 Hz; 1H), 6.88 (d; J ) 16.1 Hz; 1H),
6.87 (d; 4H), 6.83 (s; 1H), 2.61 (s; 2H), 2.47 (s; 2H), 1.09 (s;
6H).
1H NMR (CDCl3, ppm): δ ) 7.75 (d; 2H), 7.29 (t; 4H), 7.12
(d; 4H), 7.10 (t; 2H), 6.96 (d; 2H), 1.37 (s; 9H).
13C NMR (CDCl3, ppm): δ ) 205.8, 150.7, 146.7, 130.4,
129.6, 129.5, 125.7, 124.3, 119.7, 43.8, 28.5.
13C NMR (CDCl3, ppm): δ ) 169.1, 154.0, 148.1, 146.3,
138.6, 130.2, 129.0, 128.9, 128.2, 126.7, 125.3, 123.0, 113.7,
112.9, 87.4, 43.0, 39.2, 32.0, 28.0.
MS: m/z ) 329 (M+), 272 (M+ - C4H9).
MS: m/z ) 693 (M+).
Anal. Calcd for C23H23NO: C, 83.85; H, 7.04; N, 4.25.
Found: C, 83.48; H, 6.98; N, 4.12.
λmax (ꢀ): 471.5 nm (2.1 × 104 L‚mol-1‚cm-1).
Anal. Calcd for C31H25I2N3: C, 53.70; H, 3.63; N, 6.06.
Found: C, 53.49; H, 3.47; N, 5.98.
Synthesis of 1-[4-[N,N-Di(4-iodophenyl)amino]phenyl-
2,2-dimethylpropanone, chr 1. A 3.23 g (19.5 mmol) sample
of KI and 6.24 g (29.2 mmol) of KIO3 were added to a solution
of 3.20 g (9.72 g) of 3 in 100 mL of glacial acetic acid. The
flask was equipped with a CaCl2 tube and the mixture was
stirred at 70 °C until completion of the reaction (TLC analysis,
takes about 3 h). The reaction mixture was cooled and the salts
were filtered off and washed copiously with water and dichlo-
romethane. The aqueous phase was extracted with dichlo-
romethane. The combined organic layers were washed with a
diluted ammonia solution until pH ≈ 8, with a NaHSO3
solution and with brine, and dried over MgSO4. After removal
of the solvents, the crude compound was recrystallized from
2-propanol.
Synthesis of 2-[2-[4-[N,N-Di(4-iodophenyl)amino]phe-
nyl]ethenyl]thiophene, 7. To a solution of 66.5 g (127 mmol)
of 4 and 55.5 g (127 mmol) of 6 in 200 mL of dry THF was
added 190 mL (190 mmol, 1 M in ethanol) of a NaOEt solution.
The reaction mixture was refluxed for 4 h under argon
atmosphere. Then, 150 mL of ethanol was added, and THF
was evaporated off under reduced pressure. After cooling, the
solids were filtered off and redissolved in THF, and the organic
layer was washed with water (to remove inorganic salts) and
dried over MgSO4. Evaporation of the solvent yielded pure 7
as a mixture of cis and trans isomers (50/50).
Yield: 65.6 g (86%).
Mp: 116 °C (mixture of isomers).
1H NMR (CDCl3, ppm): cis δ ) 7.52 (d; 4H), 7.26 (d; 2H),
7.10 (m; 1H), 7.00 (m; 3H), 6.80 (m; 5H), 6.64 (d; J ) 11,9 Hz;
1H), 6.48 (d; J ) 11,9 Hz; 1H); trans δ ) 7.52 (d; 4H), 7.34 (d;
2H), 7.10 (m; 2H), 7.00 (m; 4H), 6.80 (m; 5H).
Yield: 2.70 g (48%).
Mp: 105 °C.
1H NMR (CDCl3, ppm): δ ) 7.75 (d; 2H), 7.60 (d; 4H), 7.00
(d; 2H), 6.88 (d; 4H), 1.38 (s; 9H).
13C NMR (CDCl3, ppm): δ ) 146.9, 146.8, 145.9, 142.9,
139.7, 138.3, 132.5, 130.1, 128.3, 128.1, 127.6, 127.4, 127.3,
126.5, 126.0, 125.4, 124.4, 124.2, 123.0, 120.1, 86.2, 86.0.
MS: m/z ) 605 (M+), 478 (M+ - I), 351 (M+ - I2).
Anal. Calcd for C24H17I2NS: C, 47.63; H, 2.83; N, 2.31.
Found: C, 47.38; H, 2.76; N, 2.26.
13C NMR (CDCl3, ppm): δ ) 206.1, 149.4, 146.2, 138.6,
131.3, 130.4, 127.0, 121.1, 87.7, 43.9, 28.3.
MS: m/z ) 581 (M+), 524 (M+ - C4H9), 397 (M+ - C4H9I),
270 (M+ - C4H9I2).
λmax (ꢀ): 318.5 nm (2.8 × 104 L‚mol-1‚cm-1).
Anal. Calcd for C23H21I2NO: C, 47.53; H, 3.64; N, 2.41.
Found: C, 47.12; H, 3.51; N, 2.35.
Synthesis of 2-[2-[4-[N,N-Di(4-iodophenyl)amino]phe-
nyl]ethenyl]thien-5-al, 8. Under argon atmosphere, 50 mL
(100 mmol, 2 M in THF) of a LDA solution was added dropwise
to a solution of 45.4 g (75.0 mmol) of 7 in 150 mL of dry THF
at -78 °C. The reaction mixture was warmed to 0 °C and
stirred for 30 min. Then, 17 mL of dry DMF was added at -40
°C, and the mixture was stirred for 1 h at room temperature,
after which 400 mL of a HCl solution (0.1 M) was carefully
added. After 2 h of vigorously stirring, the product was
extracted with dichloromethane and the combined organic
layers were washed with a saturated NaHCO3 solution and
with brine and dried over MgSO4. The crude reaction product
was purified by column chromatography (silica gel; eluent:
hexane/dichloromethane 40/60 (v/v)) and isolated as a mixture
of cis and trans isomers (cis/trans 40/60). Separation of the
isomers could be accomplished by column chromatography
(silica gel; eluent: hexane/dichloromethane 40/60 (v/v)), if
relative small qualities are used (approximately 10 g of 8 for
300 g of silica gel)
Synthesis of 4-[N,N-Di(4-iodophenyl)amino]benzalde-
hyde, 4. Under heavy stirring and slightly warming, 95.0 g
(347 mmol) of 1 was dissolved in 1 L of glacial acetic acid.
Then, 115 g (693 mmol) of KI and 223 g (1.04 mol) of KIO3
were added, and the reaction mixture was stirred for 3 h at
70 °C. After cooling, the salts were filtered off and washed
thoroughly with water (500 mL) and dichloromethane (700
mL). The aqueous phase was extracted several times with
dichloromethane. The combined organic phases were washed
with a diluted ammonia solution until pH ≈ 8, with a NaHSO3
solution, and with brine and dried over MgSO4. After removal
of the solvents, the crude compound was stirred for 15 min in
500 mL of boiling ethanol; the solution was cooled, and the
pure product was isolated by filtration.
Yield: 133 g (73%).
Mp: 142 °C.
1H NMR (CDCl3, ppm): δ ) 9.82 (s; 1H), 7.69 (d; 2H), 7.35
(d; 4H), 7.18 (d; 4H), 7.03 (d; 2H).
Yield: 37.2 g (78%).
Mp: 143.5 °C (trans), 128.2 °C (cis).
13C NMR (CDCl3, ppm): δ ) 190.4, 152.2, 145.7, 138.9,
131.4, 130.3, 127.6, 120.7, 88.8.
1H NMR (CDCl3, ppm): cis δ ) 9.82 (s; 1H), 7.58 (d; 4H),
7.56 (d; J ) 4.0 Hz; 1H), 7.22 (d; 2H), 7.08 (d; J ) 4.0 Hz; 1H),
7.02 (d; 2H), 6.86 (d; 4H), 6.75 (d; J ) 11,7 Hz; 1H), 6.65 (d; J
) 11,7 Hz; 1H); trans δ ) 9.85 (s; 1H), 7.65 (d; J ) 4.0 Hz;
1H), 7.56 (d; 4H), 7.38 (d; 2H), 7.12 (d; J ) 4.0 Hz; 1H), 7.10
(s; 2H), 7.02 (d; 2H), 6.84 (d; 4H).
MS: m/z ) 525 (M+), 398 (M+ - I), 271 (M+ - I2).
Anal. Calcd for C19H13I2NO: C, 43.46; H, 2.50; N, 2.67.
Found: C, 43.21; H, 2.39; N, 2.44.
Synthesis of 2-[3-[2-[4-[N,N-Di(4-iodophenyl)amino]-
phenyl]ethenyl]-5,5-dimethyl-2-cyclohexenylidene]-1,3-
propanedinitrile, chr 2. To a solution of 13.1 g (25.0 mmol)
of 4 and 5.19 (27.8 mmol) of 5 in dry DMF were added 2.5 mL
of glacial acetic acid, 2.5 mL of acetic acid anhydride, and 4.5
mL of piperidine. The flask was equipped with a CaCl2 tube,
and the mixture was stirred overnight at 60 °C. After cooling,
the reaction mixture was poured into iced water. The precipi-
tate was filtered off, thoroughly washed with a NaHCO3
solution and with brine, and dried. The crude reaction product
was purified by column chromatography (silica gel; eluent:
hexane/dichloromethane 20/80 (v/v)) and recrystallized from
toluene/hexane and isolated as a dark red solid.
Yield: 13.5 g (78%).
13C NMR (CDCl3, ppm): cis δ ) 182.8, 149.4, 146.9, 146.6,
142.6, 138.5, 136.0, 133.2, 131.1, 129.9, 129.0, 126.4, 124.1,
122.5, 86.5; trans δ ) 182.5, 152.7, 147.2, 146.6, 141.3, 138.5,
137.3, 132.1, 130.8, 128.1, 126.4, 126.3, 123.7, 119.6, 86.8.
MS: m/z ) 633 (M+), 506 (M+ - I).
Anal. Calcd for C25H17I2NOS: C, 47.42; H, 2.71; N, 2.21.
Found: C, 47.14; H, 2.58; N, 2.09.
Synthesis of 4-[5-[2-[4-[N,N-Di(4-iodophenyl)amino]-
phenyl]ethenyl]2-thienylmethylidene]-3-phenylisoxazol-
5-one, chr 3. To a solution of 9.50 g (15.0 mmol) of 8 (mixture
of cis and trans) and 3.90 g (24.2 mmol) of 9 in 150 mL of
chloroform was added 0.5 mL of piperidine. The flask was
equipped with a Soxhlet extraction apparatus, containing a
thimble, filled with molecular sieves. The reaction mixture was
Mp: 137-139 °C.

Macromolecules, Vol. 37, No. 23, 2004
Chiral Donor-Embedded Polybinaphthalenes 8537
refluxed overnight. After removal of the solvent, the crude
reaction product was recrystallized from ethanol. Pure trans-
10 was obtained as a red solid.
Synthesis of the Polymers. A typical procedure is as
follows: A solution of 156 mg (200 µmol) (S)-12, 200 µmol of
diiodo-substituted chromophore (chr 1-5 or a combination
thereof), 4.58 mg (5.0 µmol) of Pd2dba3, and 12.3 mg (40.0 µmol)
of AsPh3 in 10 mL of dry THF was purged with argon and
then refluxed for 64 h. After cooling, the polymer was
precipitated in methanol and filtered. For purification, the
polymer was redissolved in THF, precipitated in methanol and
filtered. This procedure was repeated twice.
Yield: 9.37 g (79%).
Mp: 146.3 °C.
1H NMR (CDCl3, ppm): δ ) 7.83 (d; J ) 4.2 Hz; 1H), 7.68
(s; 1H), 7.60 (m; 5H), 7.57 (d; 4H), 7.42 (d; 2H), 7.29 (d; J )
16.3 Hz; 1H), 7.20 (d; J ) 4.2 Hz; 1H), 7.16 (d; J ) 16.3 Hz;
1H), 7.05 (d; 2H), 6.88 (d; 4H).
13C NMR (CDCl3, ppm): δ ) 169.5, 163.4, 158.4, 147.6,
146.4, 143.8, 140.6, 138.5, 135.1, 133.9, 130.8, 130.6, 129.3,
128.5, 128.4, 127.9, 127.0, 126.6, 123.4, 119.4, 111.5, 87.1.
MS: m/z ) 776 (M+).
Acknowledgment. We are very grateful to R. Bovee
and dr. X. Lou (TUEindhoven) for the MALDI-TOF
measurements. This work was supported by the Fund
for Scientific Research-Flanders (FWO-Vlaanderen;
G.026102), by the Katholieke Universiteit Leuven (GOA/
2000/03), and by the Belgian Government (IUAP P5/
03). G.K. is a postdoctoral fellow of the Fund for
Scientific Research-Flanders (FWO-Vlaanderen).
λmax (ꢀ): 519.0 nm (4.2 × 104 L‚mol-1‚cm-1).
Anal. Calcd for C34H22I2N2O2S: C, 52.60; H, 2.86; N, 3.61.
Found: C, 52.31; H, 2.74; N, 3.48.
Synthesis of N,N′-Diethyl-1-[5-[2-[4-[N,N-di(4-iodo-
phenyl)amino]phenyl]ethenyl]2-thienylmethylidene]-
(1H,3H,5H)-pyrimidine-2,4-dion-6-thione, chr 4.. A solu-
tion of 3.50 g (5.53 mmol) of trans-8 and 1.16 g (5.81 mmol) of
10 was stirred for 2 h at room temperature. The reaction
mixture was poured into water and the precipitate was filtered
off and washed with water. Finally, the crude reaction product
was recrystallized from ethanol to yield a dark purple solid.
Yield: 4.16 g (92%).
References and Notes
(1) Koeckelberghs, G.; Sioncke, S.; Verbiest, T.; Van Severen, I.;
Picard, I.; Persoons, A.; Samyn, C. Macromolecules 2003, 36,
9736.
(2) (a) Verbiest, T.; Kauranen, M.; Persoons, A. J. Mater. Chem.
1999, 9, 2005. (b) Kauranen, M.; Verbiest, T.; Persoons, A.
J. Nonlinear Opt. Phys. 1999, 8, 171. (c) Beljonne, D.; Shuai,
Z.; Bre´das, J. L.; Kauranen, M.; Verbiest, T.; Persoons, A. J.
Chem. Phys. 1998, 108, 1301.
(3) Kondo, F.; Takahashi, D. Kimura, H.; Takeishi, M. Polym.
J. 1998, 30, 161.
(4) Koeckelberghs, G.; Verbiest, T.; Vangheluwe, M.; De Groof,
L.; Asselberghs, I.; Picard, I.; Clays, K.; Persoons, A.; Samyn,
C. J. Am. Chem. Soc., submitted for publication.
(5) Hu, Q. S.; Vitharana, D.; Liu, G.; Jain, V.; Pu, L. Macromol-
ecules 1996, 29, 5075.
(6) Koeckelberghs, G.; Sioncke, S.; Verbiest, T.; Persoons, A.;
Samyn, C. Chem. Mater. 2003, 15, 2870.
(7) Van den Broeck, K.; Verbiest, T.; Van Beylen, M.; Persoons,
A.; Samyn, C. Macromol. Chem. Phys. 1999, 200, 2629.
(8) Koeckelberghs, G.; Sioncke, S.; Verbiest, T.; Persoons, A.;
Samyn, C. Polymer 2003, 44, 3785.
Mp: 226-232 °C.
1H NMR (CDCl3, ppm): δ ) 8.63 (s; 1H), 7.81 (d; J ) 4.2
Hz; 1H), 7.59 (d; 4H), 7.43 (d; 2H), 7.37 (d; J ) 16.3 Hz; 1H),
7.27 (d; J ) 4.2 Hz; 1H), 7.17 (d; J ) 16.3 Hz; 1H), 7.05 (d;
2H), 6.88 (d; 4H), 4.61 (m; 4H), 1.35 (m; 6H).
13C NMR (CDCl3, ppm): δ ) 178.6, 161.1, 160.4, 160.0,
149.2, 147.7, 147.4, 146.4, 138.6, 136.1, 130.6, 128.4, 127.0,
126.6, 123.3, 119.6, 109.6, 87.1, 44.0, 43.2, 12.5, 12.4.
MS: m/z ) 815 (M+), 688 (M+ - I), 605 (M+ - C9H10N2O2S).
λmax (ꢀ): 538.5 nm (5.2 × 104 L‚mol-1‚cm-1).
Anal. Calcd for C33H27I2N3O2S2: C, 48.60; H, 3.34; N, 5.15.
Found: C, 48.37; H, 3.18; N, 5.04.
Synthesis of 2-Dicyanomethylene-3-cyano-4-[2-[5-[2-[4-
[N,N-di(4-iodophenyl)amino]phenyl]ethenyl]2-thienyl]-
ethenyl]-5,5-dimethyl-(2H,5H)-furan, chr 5. To a solution
of 12.7 g (20.0 mmol) of 8 (mixture of cis and trans) and 4.78
g (24.0 mmol) of 11 in 150 mL of chloroform was added 1.0
mL of triethylamine. The flask was equipped with a Soxhlet
extraction apparatus, containing a thimble filled with molec-
ular sieves, and the reaction mixture was refluxed overnight.
After removal of the solvent, the crude reaction product was
purified by column chromatography (silica gel; eluent: dichlo-
romethane), yielding pure trans-14 as a dark blue solid.
Yield: 8.80 g (54%).
(9) Thayumanavan, S.; Mendez, J.; Marder, S. R. J. Org. Chem.
1999, 64, 4289.
(10) (a) Farina, V.; Krihnan, B. J. Am. Chem. Soc. 1991, 113, 9585.
(b) Bao, Z.; Chan, K.; Yu, L. J. Am. Chem. Soc. 1995, 117,
12426.
(11) Saadeh, H.; Wang, L.; Yu, L. Macromoleules 2000, 33, 1570.
(12) Ma, L.; Hu, Q. S.; Musick, K. Y.; Vitharana, D.; Wu, C.; Kwan,
C. M. S.; Pu, L. Macromolecules 1996, 29, 5083.
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(14) Kauranen, M.; Van Elshocht, S.; Verbiest, T.; Persoons, A.
J. Chem. Phys. 2000, 112, 1497.
Mp: >275 °C dec.
1H NMR (CDCl3, ppm): δ ) 7.78 (d; J ) 15.7 Hz; 1H), 7.59
(d; 4H), 7.40 (m; 3H), 7.11 (d; J ) 5.1 Hz; 1H), 7.05 (m; 4H),
6.87 (d; 4H), 6.65 (d; J ) 15.7 Hz; 1H), 1.78 (s; 6H).
13C NMR (CDCl3, ppm): δ ) 175.5, 172.9, 152.2, 147.6,
146.4, 138.6, 138.4, 133.0, 130.5, 128.3, 128.0, 126.6, 123.4,
112.0, 111.2, 110.8, 97.3, 97.1, 87.1, 56.8, 26.5.
MS: m/z ) 814 (M+), 688 (M+ - I), 562 (M+ - I2).
λmax (ꢀ): 568.5 nm (4.8 × 104 L‚mol-1‚cm-1).
(15) Burland, D. M.; Miller, R. D.; Walsh, C. A. Chem. Rev. 1994,
94, 31.
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R.; Robinson, B. H.; Steier, W. H. Science 2000, 288, 119. (b)
Dalton, L. R. Opt. Eng. 2000, 39, 589. (c) Dalton, L. R.; Steier,
W. H.; Robinson, B. H.; Zhang, C.; Ren, A.; Garner, S.; Chen,
A.; Londergan, T.; Irwin, L.; Carlson, B.; Fifield, L.; Phelan,
G.; Kincaid, C.; Amend, J.; Jen, A. J. Mater. Chem. 1999, 9,
1905.
Anal. Calcd for C36H24I2N4OS: C, 53.09; H, 2.97; N, 6.88.
Found: C, 52.87; H, 2.86; N, 6.59.
MA0491816