Introduction of an isolation chromophore into an h -shaped NLO polymer: Enhanced NLO effect, optical transparency, and stability

Article abstract of DOI:10.1002/cplu.201300252

In this study, a new polymer P1 embedded with H -type chromophore moieties was designed and synthesized through Suzuki coupling copolymerization, in which the isolation chromophore was introduced to further improve its comprehensive performance. This polymer demonstrated good solubility and film-forming ability. In comparison with normal H -shaped NLO polymers only containing one type of chromophore, nearly all the performance of P1 was improved. Its NLO coefficient was as high as 134 pm V^-1, and its onset temperature for decay was up to 150°C. Coupled with its improved optical transparency, all these properties made it a promising candidate for practical applications in photonic fields. Get in shape: H -shaped NLO polymer P1 was designed and synthesized through Suzuki coupling copolymerization. An isolation chromophore was introduced to improve the comprehensive performance of the designed P1. In comparison with normal H -shaped NLO polymers, which only contain one type of chromophore moiety, performance in almost all areas was improved. Copyright

Full text of DOI:10.1002/cplu.201300252

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DOI: 10.1002/cplu.201300252
Introduction of an Isolation Chromophore into an
“H”-Shaped NLO Polymer: Enhanced NLO Effect, Optical
Transparency, and Stability**
Wenbo Wu,[a] Cheng Ye,[b] Jingui Qin,[a] and Zhen Li*[a]
In this study, a new polymer P1 embedded with “H”-type chro-
mophore moieties was designed and synthesized through
Suzuki coupling copolymerization, in which the isolation chro-
mophore was introduced to further improve its comprehensive
performance. This polymer demonstrated good solubility and
film-forming ability. In comparison with normal ”H”-shaped
NLO polymers only containing one type of chromophore,
nearly all the performance of P1 was improved. Its NLO coeffi-
cient was as high as 134 pmVꢀ1, and its onset temperature for
decay was up to 1508C. Coupled with its improved optical
transparency, all these properties made it a promising candi-
date for practical applications in photonic fields.
Introduction
Over the past two decades, organic/polymeric nonlinear opti-
cal (NLO) materials have been put forth as promising candi-
dates for future applications such as optical information proc-
essing, optical sensing, data storage, and telecommunications
because of their large optical nonlinearity, high bandwidth,
ease of fabrication, and low cost.[1] At present, one of the
major problems encountered in optimizing organic NLO mate-
rials is how to efficiently translate the large hyperpolarizability
(b) values of the organic chromophores into high macroscopic
NLO activities of polymers, since the strong intermolecular
electrostatic dipole–dipole interactions of the highly polar
chromophore moieties make the poling-induced noncentro-
symmetric alignment of chromophore moieties (necessary for
the materials to exhibit the NLO effect), during the poling pro-
cess under an electric field, a daunting task.[2,3] According to
experimental results and some theoretical calculations, Dalton
et al. suggested that to control the shape of the chromophore
some bulky spacers could be introduced to inhibit these
strong dipole–dipole interactions, and further improve the
poling efficiency of NLO materials.[2,4] Based on this site-isola-
tion principle, various structures of chromophores have been
developed, from linear to various other shapes, such as “U”-,
“X”-, “H”-, and star-shaped, to improve their topological struc-
tures.[5] Among the numerous studies on the control of the
shape of the NLO chromophore, “H-type” chromophores are
typically a successful example.[6] Based on the site-isolation
principle, as well as our systematic study on the “concept of
a suitable isolation group”,[6a,7] in 2006, for the first time, we
designed and synthesized this H-type chromophore, in which
the two pieces of D–p–A blocks were linked together through
an isolation group. As shown in Scheme S1 in the Supporting
Information, the order parameter (F, which shows the align-
ment of the chromophore moieties in the polymers) of the
polymer embedded with this H-type chromophore was more
than twice that of its analogues with a normal rodlike chromo-
phore.[6a] Then, from 2009 to 2012, a series of new H-shaped
NLO polymers PS1–PS6 (Scheme S2), in which the linkage posi-
tions of the two H-type chromophores were shoulder-to-
shoulder and the comonomers bonded into the p bridge of
the chromophores act as effective isolation groups, was pre-
pared to further reduce the intermolecular electrostatic interac-
tions between chromophore moieties.[8] Among them, PS5
demonstrated the best performance with a second-harmonic
generation (SHG) coefficient (d33 value) of 94.7 pmVꢀ1.
However, according to the site-isolation principle, nearly all
the isolation groups used before were nonpolar groups, just to
control the shape of the NLO chromophore and decrease the
strong interactions between the chromophore moieties. They
did not contribute directly to the macroscopic NLO effect, but
rather decreased the effective concentration of the NLO chro-
mophore moieties, which was harmful to the macroscopic NLO
activities for the diluted chromophore concentrations. In 2012,
for the first time, our group used one chromophore with
a lower mb value (m=dipole moment), not the normal nonpo-
lar spacer, as the isolation group for another chromophore
with a higher mb value, to achieve high poling efficiency (PS7–
PS10, Scheme S3).[9] The results showed that the isolation chro-
mophore with a lower mb value could act as an isolation group
for the main chromophore with a higher mb value to achieve
[a] W. Wu, Prof. J. Qin, Prof. Z. Li
Department of Chemistry
Hubei Key Laboratory on Organic and Polymeric Opto-Electronic Materials
Wuhan University, Wuhan 430072 (P. R. China)
Fax: (+86)27-68756757
E-mail: lizhen@whu.edu.cn
lichemlab@163.com
[b] Prof. C. Ye
Organic Solids Laboratories, Institute of Chemistry
The Chinese Academy of Sciences
Beijing 100080 (P. R. China)
[**] NLO=nonlinear optical
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cplu.201300252.
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a high poling efficiency owing to the decreased strong elec-
tronic interactions, but would not decrease the effective con-
centration of the NLO chromophore moieties to a large
degree. As a result, the d33 value of PS10 with two different
chromophores (the sulfonyl- and nitro-based ones) arranged
orderly was increased to a large degree, in comparison with
that of PS7, which only contains one type of chromophore.
Thus, it was very reasonable to consider whether the isola-
tion chromophore could work in the H-shaped NLO polymers
to further improve their performance. Therefore, in this paper,
the isolation chromophore was introduced into PS5, the H-
shaped NLO polymer with the highest d33 value, to yield a new
H-shaped NLO polymer P1 (Scheme 1). The result was encour-
aging. The d33 value of P1 was up to 134 pmVꢀ1, nearly
40 pmVꢀ1 higher than that of PS5; its onset temperature for
decay of d33 was up to 1508C, nearly 508C higher than that of
Table 1. The contradistinction of P1 and PS5.
Polymer Tg
lmax
d33
[pmVꢀ1
d33(1)
Tonset
N[f]
[c]
[d]
[8C][a] [nm][b]
]
[pmVꢀ1
]
[8C][e]
P1
PS5[h]
150
122
471
491
134
94.7
23
11
150
101
0.621[g]
0.467
[a] Glass transition temperature of polymers detected by DSC analyses
under nitrogen at a heating rate of 108Cminꢀ1. [b] The maximum absorp-
tion wavelength of polymers in film. [c] SHG coefficient. [d] The nonreso-
nant d33 values calculated by using the approximate two-level model.
[e] Onset temperature for decay of d33. [f] Loading density of the effective
chromophore moieties, which could be calculated from the weight of the
chromophores divided by the weight of all the macromolecular systems.
[g] This value contains both the main chromophore and the isolation
chromophore. [h] Another H-shaped NLO polymer with the best perfor-
mance before; its properties were tested in our previous study.
was very famous for its nearly quantitative yields,
mild reaction conditions, broad tolerance toward
functional groups, low susceptibility to side reac-
tions, and simple product isolation. By use of this
powerful reaction, monomer M1 could be yielded
efficiently (the reaction could be complete in only
3 hours with a yield of 86.2%). And then, under the
typical reaction conditions of the Suzuki coupling
copolymerization, M1 could react with bronic ester
monomer M2 to yield the target H-shaped NLO
polymer P1, embedded with both H-type chromo-
phore and isolation chromophore. Thus, the whole
synthetic route was very simple, making its potential
practical applications much cheaper.
The obtained H-shaped NLO polymer P1 and its
corresponding monomer M1 were characterized by
spectroscopic methods, such as FTIR and NMR, and
all gave satisfactory data. The structure of monomer
M1 was further characterized by MALDI-TOF mass
spectrometry (Figure S1), and the result was consis-
tent with the theoretical value. Figure 1 displays the
1H NMR spectra of P1 and its corresponding mono-
mer M1, which were conducted in the solvent
[D]chloroform. The chemical shifts of M1 are consis-
tent with the proposed structure, with its character-
istic peaks marked in Figure 1. Furthermore, only the
proton peak of 1,4-triazole, which was marked as peak 13,
Scheme 1. The original idea of this study: introducing an isolation chromophore into
a H-shaped NLO polymer.
PS5 (Table 1). Herein, we report the syntheses, characterization,
and properties of this new H-shaped NLO polymer in detail.
1
could be observed in its H NMR spectrum, which confirmed
that M1 was the sole 1,4-isomer. Aside from the resonance
peaks of the monomer M1, there were still some characteristic
peaks assigned to the resonances of protons of the fluorene-
Results and Discussion
1
based monomer in the H NMR spectra of P1, for example, the
Synthesis and structural identification
new peak at d=7.4–7.6 ppm was attributed to ArH of 9,9-di-
hexylfluorene; the new peak at d=0.4–1.0 ppm was attributed
to ꢀCH2ꢀ and ꢀCH3 of 9,9-dihexylfluorene, and so forth. Fur-
Scheme 2 shows the whole synthetic route to the target poly-
mer. The nitro-based chromophore C1 contains one alkyne
group and one bromine atom, the sulfonyl-based chromo-
phore C2 contains two azido groups, and bronic ester mono-
mer M2 was prepared in our previous study. The cycloaddition
between azides and alkynes to yield 1,4-triazoles under a cop-
per(I)-catalyzed, namely, Sharpless “click chemistry” reaction,[10]
1
thermore, in comparison with the H NMR spectrum of M1, the
peaks in that of P1 were broad because of the polymerization.
A similar phenomenon could be observed also in their
13C NMR spectra. As shown in Figure 2, in comparison with mo-
nomer M1, some new peaks appeared in the spectrum of P1
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Scheme 2. The synthesis of H-shaped NLO polymer P1.
Characterization
The weight-average molecular
weight of P1, determined by gel
permeation
chromatography
(GPC) with THF as an eluent and
polystyrene standards as calibra-
tion standards, was tested to be
14850, with
a polydispersity
index (PDI) of 1.10. The low PDI
might be due to the special
topological structure. As shown
in Figure 3, P1 was very stable,
with a 5% weight loss tempera-
ture (Td) as high as 2838C. Also,
its glass transition temperatures
(Tg) were tested by using differ-
ential
scanning
calorimetry
(DSC). To our surprise, as shown
in Figure 3 and Table 1, its
Tg value was found to be 1508C,
which is 288C higher than that
of PS5 (1228C), which should be
ascribed to the presence of iso-
Figure 1. 1H NMR spectra of polymer P1 and its corresponding monomer M1 in [D]chloroform.
after polymerization: d=55.1 ppm, which is the characteristic
peak of C-9’ of 9,9-dihexylfluorene; six new peaks at d=14.1,
22.1, 24.1, 28.7, 31.7, and 40.1 ppm, attributable to the peaks
of the sp3-C atom of the hexyl group in 9,9-dihexylfluorene
and some ArC of 9,9-dihexylfluorene. In addition, the peak at
d=83.4 ppm, a typical signal of the boronic ester group, could
not be observed at all in the 13C NMR spectrum of P1.
lation chromophore moieties. The high Tg value could lead to
the high stability of the ordered dipole alignment of NLO chro-
mophores, and is surely a benefit to their potential practical
applications.
The H-shaped NLO polymer P1 was easily soluble in
common organic solvents, such as CHCl3, THF, DMF, and
DMSO. Thus, its UV-visible absorption spectra in different sol-
vents could be tested easily. As shown in Figure 4, an interest-
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and the different environment
around the NLO chromophore
could lead to different solvato-
chromic effects. In P1, there
were two triazole units and two
nitro-based chromophore moi-
eties surrounding the sulfonyl-
based chromophore, whereas
a fluorine, a triazole, and two
different chromophores sur-
rounded the nitro-based chro-
mophore, which could result in
different solvatochromic effects
in P1. Thus, the peak shapes of
P1 were also a little different in
different solvents, especially in
CH2Cl2 and CHCl3. However, lmax
Figure 2. 13C NMR spectra of polymer P1 and its corresponding monomer M1 in [D]chloroform.
of P1 in films was 471 nm, which was blueshifted 20 nm rela-
tive to that of PS5 (491 nm), thereby resulting in the better
transparency.
The NLO effect should be the most important parameter for
NLO materials, and it could be characterized by the SHG coeffi-
cient, the d33 value. The test procedure was similar to that re-
ported previously,[7–9] and from the experimental data, its
d33 value was found to be 134 pmVꢀ1, at the 1064 nm funda-
mental wavelength. This was an exciting result, since the
d
33 values of all the H-shaped NLO polymers only containing
one type of chromophore were not higher than 94.7 pmVꢀ1
.
This is a large improvement, and indicates that the isolation
chromophore could also work in these H-shaped NLO poly-
mers, thereby confirming our previous idea about isolation
chromophores: when two types of chromophore are arranged
orderly with a regular AB structure, the chromophore with the
lower mb value can act as an isolation group to decrease the
strong electronic interactions between the chromophore moi-
eties with higher mb values, and would not decrease the effec-
tive concentration of the NLO chromophore moieties anymore.
Usually, when the effective concentration of the NLO chromo-
phore moieties was higher than 30%, accompanied by an in-
crease in the concentration of the NLO chromophore moieties
in polymers, the intermolecular dipole–dipole interactions
among chromophore moieties would become stronger and
stronger, which would lead to a much decreased NLO coeffi-
cient (Figure S2).[11] However, from PS5 to P1, owing to the in-
troduction of an isolation chromophore, the concentration of
NLO chromophores improved from 0.467 to 0.621, and the
NLO coefficient also improved from 93.4 to 134 pmVꢀ1, which
indicated that the intermolecular dipole–dipole interactions
could be overcome in P1 to some degree, thanks to the pres-
ence of the isolation chromophore moieties. Also, the special
H-shaped topological structure could contribute greatly to
such high d33 value. As shown in Chart S3, we have synthesized
another normal NLO polymer PS10, also containing two types
of chromophore moieties with a regular AB structure, in our
previous study. Its d33 value was 116.8 pmVꢀ1, which is also
higher than PS7 with only one type of chromophore, but
lower than that of P1, thereby confirming the advantage of
Figure 3. TGA and DSC (insert) thermograms of P1, measured in nitrogen at
a heating rate of 108Cminꢀ1
.
Figure 4. UV/Vis spectra of P1 in different solvents (0.02 mgmLꢀ1).
ing phenomenon was observed. As P1 consisted of two types
of chromophores, and the maximum absorption wavelengths
(lmax) for their p–p* transition was not the same, there was
a broad absorption in its UV-visible spectrum, which actually
possessed two absorptions: one was from the nitro-based
chromophore and the other from the sulfonyl-based one. Gen-
erally, the NLO chromophore displayed different absorption
peaks in different solvents, because of solvatochromic effects,
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the H shape again. As there might be some resonant enhance-
ment due to the absorption of the chromophore moieties at
532 nm, the NLO properties of these polymers should be
smaller, which was calculated by using the approximate two-
level model. Here, owing to the outstanding optical transpar-
ency of P1, which has been already discussed before, the
In the depoling experiment, the real-time decays of their
SHG signals were monitored as the poled film of P1 was
heated from room temperature to 1808C in air at a rate of
48Cminꢀ1. As shown in Figure 6, the NLO stability of P1 was
much better than that of PS5, and its onset temperature for
decay of the d33 value was up to 1508C, which is 508C higher
than that of PS5, as a result of its higher Tg value.
d
33(1) value of P1 was still excellent, up to 23.3 pmVꢀ1, more
than twice that of PS5 (11.0 pmVꢀ1), thereby confirming the
advantages of the isolation chromophore once again. However,
although the d33 value of 134 pmVꢀ1 was not a high value, in
comparison with those of the dendric systems also containing
an isolation chromophore,[7–9] this result still showed that the
concept of an isolation chromophore could be applied also to
this H-type chromophore, and not only limited to the normal
rod one. Thus, if a dendritic NLO system could be constructed
by using this H-type chromophore containing an isolation
chromophore, an even higher NLO coefficient should be ach-
ieved. This research is in progress in our laboratory.
To further study the alignment behavior of the chromophore
moieties in P1, the order parameter (F) of the polymer was
also measured from the change of the UV-visible spectra of
their films before and after poling. As shown in Figure 5, after
Figure 6. Decay curves of the SHG coefficients of polymers as a function of
temperature.
Conclusion
In summary, an H-shaped NLO polymer was prepared success-
fully by means of Suzuki coupling copolymerization. To further
research whether the advantage of an isolation chromophore
could work in this H-shaped topological structure, a sulfonyl-
based chromophore was introduced into P1 to act as the isola-
tion chromophore. In comparison with PS5, which has the
highest d33 value and the best NLO stability in the H-shaped
NLO polymers reported previously, almost all the performance,
including the NLO coefficient, optical transparency, and NLO
stability, of P1 was improved to a large degree. Its d33 value
was up to 134 pmVꢀ1, which is about 40 pmVꢀ1 higher than
that of PS5; its lmax in films was 471 nm, which is 20 nm blue-
shifted relative to that of PS5; its onset temperature for the
decay of its d33 value was up to 1508C, which is 508C higher
than that of PS5. Thus, owing to such good comprehensive
performance and its simple synthetic route, P1 might be
a good candidate for practical applications.
Figure 5. Absorption spectra of the film of P1 before and after poling.
poling, the absorbance of P1 decreased and the F value of P1
was calculated as 0.24, which indicated that the chromophore
moieties in P1 were noncentrosymmetric. In addition, the
shape of the absorption peak after poling was different from
that before poling, owing to the different behavior of the two
types of chromophore moieties. As we know, lmax of the nitro-
based chromophore should be redshifted relative to that of
the sulfonyl-based one. Thus, the blueshifted lmax after poling
indicated that the F value of the nitro-based chromophore of
P1 should be higher than that of the sulfonyl-based one. This
could also confirm our idea: the chromophore moieties with
a higher mb value act as the main chromophore, which contrib-
ute most to the macroscopic NLO effect; while those with
a lower mb value are used as the isolation chromophore, an
isolation group between two main chromophore moieties to
decrease the dipole–dipole interactions among the main chro-
mophore moieties and could be also beneficial to the macro-
scopic NLO effect.
Experimental Section
Materials and instrumentation
THF was dried over and distilled from a K–Na alloy under an at-
mosphere of dry nitrogen. The boronic ester M2[12] and chromo-
phores C1[5h,8a] and C2[9c] have been prepared already in our previ-
ous study. All other reagents were used as received. 1H and
13C NMR spectra were measured on a Varian Mercury300 spectrom-
eter using tetramethylsilane (TMS; d=0 ppm) as internal standard.
The FTIR spectra were recorded on a PerkineElmer-2 spectrometer
in the region of 4000–400 cmꢀ1. UV-visible spectra were obtained
using a Shimadzu UV-2550 spectrometer. GPC was used to deter-
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mine the molecular weights of polymers. GPC analysis was per-
formed on a Waters HPLC system equipped with a 2690D separa-
tion module and a 2410 refractive index detector. Polystyrene
standards were used as calibration standards for GPC. THF was
used as an eluent and the flow rate was 1.0 mLminꢀ1. Matrix-assist-
ed laser desorption ionization time-of-flight mass spectra were
measured on a Voyager-DE-STR MALDI-TOF mass spectrometer
(MALDI-TOF MS; ABI, American) equipped with a 337 nm nitrogen
laser and a 1.2 m linear flight path, in positive-ion mode. Thermal
analysis was performed on NETZSCH STA449C thermal analyzer at
a heating rate of 108Cminꢀ1 in nitrogen at a flow rate of
50 cm3 minꢀ1 for thermogravimetric analysis (TGA). The thickness
of the films was measured with an Ambios Technology XP-2 profil-
ometer.
141.7, 144.9, 147.0, 147.4, 147.8, 150.7, 151.1, 155.3, 156.1 ppm; IR
(KBr): n˜ =1514, 1338 (ꢀNO2), 1139 cmꢀ1 (ꢀSO2ꢀ).
Preparation of polymer thin films
Polymer P1 was dissolved in THF (concentration ꢁ4 wt%), and the
solution was filtered through a syringe filter. Polymer films were
spin-coated onto indium–tin oxide (ITO)-coated glass substrates,
which were cleaned by DMF, acetone, distilled water, and THF se-
quentially in an ultrasonic bath before use. Residual solvent was re-
moved by heating the films in a vacuum oven at 408C.
NLO measurement of poled films
The second-order optical nonlinearity of P1 was determined by an
in situ SHG experiment using a closed temperature-controlled
oven with optical windows and three needle electrodes. The films
were kept at 458 to the incident beam and poled inside the oven,
and the SHG intensity was monitored simultaneously. Poling condi-
tions were as follows: temperature, 1758C; voltage, 7.8 kV at the
needle point; gap distance, 0.8 cm. The SHG measurements were
carried out with a Nd:YAG laser operating at a 10 Hz repetition
rate and an 8 ns pulse width at 1064 nm. A Y-cut quartz crystal
served as the reference.
Synthesis of monomer M1
Chromophore C1 (505.3 mg, 1.10 mmol), chromophore C2
(213.7 mg, 0.50 mmol), CuSO4·5H2O (10 mol%), NaHCO3 (20 mol%),
and ascorbic acid (20 mol%) were dissolved in THF (5 mL)/H2O
(1 mL) under nitrogen in a Schlenk flask. The mixture was stirred at
room temperature for 3 h, then extracted with chloroform, and
washed with brine. The organic layer was dried over anhydrous
magnesium sulfate and purified by column chromatography using
ethyl acetate/chloroform (1:1) as eluent to afford red solid M1
(580.1 mg, 86.2%). 13C NMR (75 MHz, CDCl3, 298 K): d=7.30, 12.48,
21.72, 28.29, 44.80, 47.04, 50.54, 51.00, 68.47, 109.12, 110.76,
111.53, 114.25, 116.43, 117.77, 119.20, 122.21, 122.76, 125.79,
129.03, 131.61, 138.24, 139.90, 144.42, 146.72, 147.01, 147.93,
149.19, 151.39, 155.00 ppm; IR (KBr): n˜ =1514, 1338 (ꢀNO2),
Acknowledgements
We are grateful to the National Science Foundation of China (no.
21034006) for financial support.
1
1139 cmꢀ1 (ꢀSO2ꢀ); H NMR (300 MHz, CDCl3, 298 K): d=1.23 (brs,
6H; ꢀCH3), 1.31 (brs, 2H; ꢀCH3), 2.25 (brs, 4H; ꢀCH2ꢀ), 2.96 (brs,
4H; ꢀCH2Cꢀ), 3.15 (brs, 2H; ꢀSCH2ꢀ), 3.43 (brs, 8H; ꢀNCH2ꢀ), 3.71
(brs, 4H; ꢀNCH2ꢀ), 4.14 (brs, 4H; ꢀNCH2ꢀ), 4.37 (brs, 4H; ꢀOCH2ꢀ
), 6.5–6.7 (m, 4H; ArH), 6.96 (s, 2H; ArH), 7.21 (s, 2H; ꢀC=CH), 7.7–
8.0 ppm (m, 14H; ArH); MALDI-TOF MS: m/z calcd for
C60H67Br2N17O8S: [M+Na]+: 1369.1; found: 1367.9; elemental analy-
sis calcd (%) for C60H67Br2N17O8S: C 53.53, H 5.03, N 17.69; found: C
52.99, H 5.23, N 17.75.
Keywords: chromophores · cross-coupling · nonlinear optics ·
polymers · synthesis design
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Synthesis of H-shaped NLO polymer P1
A mixture of monomer M1 (67.3 mg, 0.05 mmol), monomer M2
(29.3 mg, 0.05 mmol), potassium carbonate (138 mg, 1.0 mmol),
THF (3 mL)/water (1 mL), and a catalytic amount of [Pd(PPh3)4] was
carefully degassed and charged with argon. Then the reaction mix-
ture was stirred at 608C for 4 days. After polymerization, a lot of
methanol was poured into the mixture, and then filtered. The ob-
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due was further purified by several precipitations from THF into
acetone, and the obtained solid was then washed with a lot of ace-
tone and dried under vacuum at 408C to a constant weight. The
resultant polymer P1 was obtained as a red powder (67.2 mg,
88.5%). Mr =14850; Mw/Mn =1.10 (GPC, polystyrene calibration);
1H NMR (300 MHz, CDCl3, 298 K): d=0.4–1.4 (ꢀCH3 and ꢀCH2ꢀ),
1.6–2.0 (ꢀCH2ꢀ), 2.0–2.3 (ꢀCH2ꢀ), 2.8–3.2 (ꢀCH2Cꢀ and ꢀSCH2ꢀ),
3.2–3.9 (ꢀNCH2ꢀ), 4.0–4.4 (ꢀNCH2ꢀ and ꢀOCH2ꢀ), 6.4–6.9 (ArH),
7.0–8.0 ppm (ꢀC=CH and ArH); 13C NMR (75 MHz, CDCl3, 298 K):
d=1.2, 7.6, 13.0, 14.1, 22.1, 22.8, 24.1, 24.4, 28.7, 30.2, 31.8, 40.1,
45.1, 47.4, 50.9, 51.4, 55.1, 68.9, 109.5, 111.5, 111.9, 112.4, 116.9,
117.5, 118.5, 119.2, 122.6, 123.1, 126.2, 129.5, 129.7, 139.1, 140.1,
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Received: July 7, 2013
Published online on September 12, 2013
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ChemPlusChem 2013, 78, 1523 – 1529 1529