High-generation second-order nonlinear optical (NLO) dendrimers that contain isolation chromophores: Convenient synthesis by using click chemistry and their increased NLO effects

Article abstract of DOI:10.1002/chem.201200441

Herein, high-generation dendrimers G4-NS and G5-NS, which contained 30 and 62 azo-benzene chromophore moieties, respectively, were conveniently prepared in high purity and satisfied yields by a combination of divergent and convergent approaches, coupled w

Full text of DOI:10.1002/chem.201200441

FULL PAPER
DOI: 10.1002/chem.201200441
High-Generation Second-Order Nonlinear Optical (NLO) Dendrimers that
Contain Isolation Chromophores: Convenient Synthesis by Using Click
Chemistry and their Increased NLO Effects
Wenbo Wu,[a] Conggang Li,*[b] Gui Yu,[c] Yunqi Liu,[c] Cheng Ye,[c] Jingui Qin,[a] and
Zhen Li*[a]
Abstract: Herein, high-generation den-
drimers G4-NS and G5-NS, which con-
tained 30 and 62 azo-benzene chromo-
phore moieties, respectively, were con-
veniently prepared in high purity and
satisfied yields by a combination of di-
vergent and convergent approaches,
coupled with the utilization of the pow-
erful Sharpless click reaction. These
dendrimers possessed a regular struc-
ture of alternating layers of nitro-based
and sulfonyl-based azo chromophores
in which the sulfonyl-based azo-chro-
mophore moieties were utilized as co-
isolation groups for the nitro-based
moieties to achieve larger macroscopic
second-order nonlinear optical (NLO)
effects. These high-generation dendrim-
ers (G4-NS and G5-NS) displayed very
large NLO efficiencies (up to
253.0 pmVꢀ1), which is, to the best of
our knowledge, the record highest effi-
ciency for simple azo-chromophore
moieties.
Keywords: azo
compounds
·
chromophores · click chemistry ·
dendrimers · nonlinear optics
Introduction
tions in a variety of fields, including catalysis, biology, and
materials science.[1–5]
Dendrimers are defect-free and perfectly monodisperse
macromolecules with regular and highly branched 3D struc-
tures; their structure can be easily controlled by changing
the core, dendron, or the periphery, thereby conveniently al-
lowing for the design of new multifunctional molecules. For
examples, core- or terminal-modified-,[1] layered-,[2] segment-
ed-,[1a,2a,3] and tailored-type[4] dendrimers have been report-
ed for various applications. Moreover, their special 3D
global highly branched structure can lead to some special
properties, including nanometer size, multivalent character,
the modularity of their assembly, high solubility, and low vis-
cosity, which make them competitive candidates for applica-
In the field of materials science, the development of or-
ganic NLO materials is motivated by their promising perfor-
mance and lower cost for applications in telecommunica-
tions, computing, embedded-network sensing, terahertz-
wave generation and detection, etc.[6] One major obstacle
that hinders the rapid development of this field is the effi-
cient translation of the large mb values of organic chromo-
phores into high macroscopic NLO activities of the poly-
mers because of the strong dipole–dipole interactions be-
tween the chromophore moieties and the donor–p–acceptor
structure in the polymeric system. These interactions make
the poling-induced noncentrosymmetric alignment of chro-
mophore moieties (which are necessary for the materials to
exhibit the NLO effect) a daunting task during the poling
process under an electric field.[7] According to the experi-
mental results and theoretical analysis of Jen, Dalton, and
co-workers, the dendritic structure that is present in den-
drimers, hyperbranched polymers, and dendronized poly-
mers (in which some isolation groups are bonded to the
chromophore moieties to decrease the interactions between
the chromophore moieties and increase the poling efficiency
by applying the site-isolation principle) is considered to be
a very promising molecular topology for the next generation
of highly efficient NLO materials, which are expected to
meet the basic requirements of practical applications: large
macroscopic optical nonlinearity, high physical and chemical
stability, and good optical transparency.[8] In particular,
NLO dendrimers are ideal structures to explore the struc-
ture–property relationships.
[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: lichemlab@163.com
lizhen@whu.edu.cn
[b] Prof. C. Li
China State Key Laboratory of Magnetic Resonance
and Atomic and Molecular Physics
Wuhan Institute of Physics and Mathematics
The Chinese Academy of Sciences, Wuhan, 430071 (P.R. China)
[c] Prof. G. Yu, Prof. Y. Liu, Prof. C. Ye
Organic Solids Laboratories, Institute of Chemistry
The Chinese Academy of Sciences, Beijing 100080 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201200441.
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Based on the pioneering work of scientists in the field of
NLO,[6–8] we have demonstrated that, in the dendronized
polymers, the macroscopic nonlinearity of the NLO poly-
mers could be boosted several times by bonding “suitable
isolation groups” onto the chromophore moieties (see the
Supporting Information, Charts S1–S6).[9] By applying this
concept of “suitable isolation groups” to dendrimers, we re-
cently prepared a new series of NLO dendrimers (G1–G5)
through a convergent approach or the combination of diver-
gent and convergent approaches[9h,i] (a “double-stage”
method) by using click-chemistry reactions (see the Support-
ing Information, Schemes S1–S3).[10] These dendrimers not
only confirmed our theory that the formed triazole rings are
suitable isolation groups for enhancing the macroscopic
NLO effect but also, more excitingly, they also demonstrat-
ed that, on increasing the loading density of the chromo-
phore moieties, the NLO effects increased and the d33 value
of G5 was up to 193.1 pmVꢀ1, which was the highest value
reported at that time for simple azo-chromophore moieties,
thus indicating that the frequently observed asymptotic de-
pendence of EO activity on chromophore density may be
overcome through rational design, in accordance with the
prediction of Sullivan, Robinson, Dalton, and co-workers.[11]
However, additional study
If this postulation was successful, the macroscopic NLO
effect should be further enhanced. To answer this question,
structure P4, which was constructed from two different
chromophore moieties with the regular AB structure
(Scheme 1), was obtained by using Sonogashira coupling re-
actions. For comparison, structures P1–P3 (Scheme 1) were
also prepared (for the synthesis and characterization data,
see the Supporting Information). As shown in Scheme 1,
structure P4 exhibited the highest d33 value (116.8 pmVꢀ1),
whilst the d33 value of its analogue, P3, which had an irregu-
lar structure, was only 45.1 pmVꢀ1 (between the values of
structures P1 and P2). This result indicated that the sulfo-
nyl-based chromophore (C2) could act as an effective isola-
tion group for the nitro-based chromophore (C3), the main
chromophore moiety, but only in the case of compound P4,
which had a regular AB structure.
As mentioned above, one of the advantages of dendrimers
is their controllable, perfect structure. Thus, considering this
interesting result for compound P4 and the abnormal in-
crease in the macroscopic NLO effects of G1–G5, we won-
dered what would happen if these two chromophores were
used to construct dendrimers with a regular structure that
was similar to compound P4 in which the formed triazole
was still needed to check this
abnormal increase in the mac-
roscopic NLO effect on in-
creasing the loading density of
the chromophore moieties in
the dendrimers and to confirm
the reproducibility and relia-
bility of the “double-stage”
method for the formation of
high-generation
dendrimers,
such as G4 and G5 (see the
Supporting
Information,
Scheme S3) by using CuI-cata-
lyzed click chemistry.
One the other hand, in all of
our previous studies, the isola-
tion groups were non-polar
groups to impede the strong
interactions between the chro-
mophore moieties and they
did not directly contribute to
the macroscopic NLO effect
but rather decreased the effec-
tive concentration of the NLO
chromophore moieties. Thus,
we wanted to consider using
one chromophore with a lower
mb value as an isolation group
for
another
chromophore
group with a higher mb value
to achieve a high poling effi-
ciency owing to the decreased
strong electronic interactions.
Scheme 1. Synthesis of polymers P1–P4 and their corresponding d33 values.
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High-Generation NLO Dendrimers with Isolation Chromophores
FULL PAPER
rings acted as “the suitable isolation group”, as in the case
of structures G1–G5. Perhaps, much-better NLO effects
could be achieved.
phore moieties. Herein, we report the synthesis, characteri-
zation, and properties of these new dendrimers.
Thus, we attempted to design a new series of high-genera-
tion dendrimers (Scheme 2) in which two different chromo-
phores (sulfonyl- and nitro-based chromophores) were ar-
ranging orderly. To improve the efficiency of the synthesis,
the “double-stage” method that was used in the preparation
of structures G1–G5 was rational designed; by using this
Results and Discussion
Synthesis: As shown in Scheme 1, Scheme 3, Scheme 4, and
Table 1, the dendrimers were conveniently prepared in good
yields. The success of this synthetic route should be ascribed
to the use of click-chemistry, which afforded the products in
near-quantitative yield, as well as to the well-designed
“double-stage” approach. The end-capped dendrons (G2-
-NS, Scheme 3) were synthesized through a convergent
click-chemistry approach that was similar to the synthetic
route to G2- (see the Supporting Information, Scheme S1):
ꢁ
ꢁ
method, end-capped dendrons G1- -NS and G2- -NS
(Scheme 3) were prepared through a convergent click-
chemistry approach, whilst core structures G1–4N3-S
(Scheme 4) and G2–8N3-NS (Scheme 5) were obtained
through a divergent click-chemistry approach. Excitingly,
the d33 value of G5-NS was 253.0 pmVꢀ1, which is the
record highest value reported so far for simple azo-chromo-
ꢁ
ꢁ
ꢁ
First, G1- -NS was prepared from an efficient azo-coupling
reaction between G1-N and di-
azonium fluoroborate 2 at 08C
and
another
chromophore
group that contained different
acceptors (sulfonyl groups) was
formed. Meanwhile, one reac-
tive alkyne group was intro-
duced for the further growth of
ꢁ
the dendrimers. G1- -NS was
converted into G2-NS by un-
dergoing a click reaction with
N,N-bis(2-azidoethyl)aniline (1)
at room temperature. Simply
repeating the azo-coupling re-
action by using the nitro group
as the electron acceptor readily
ꢁ
afforded G2- -NS from G2-NS.
This convergent synthetic route
took full advantage of the com-
bination of click chemistry and
azo-coupling reactions and all
of the reactions were conducted
under mild conditions; more-
over, there were no need to
protect/deprotect some func-
tional groups or to include con-
version steps from one reactive
group into another. By using
this route, higher-generation
dendrimers might be obtained.
However, owing to steric effects
and difficulties in chromato-
graphic separation, they could
not be easily obtained by using
the convergent method as
lower-generation
dendrimers.
As mentioned in our previous
work,[10b] this difficulty did not
originate from the click reac-
tion, but instead from the intro-
duction of terminal alkyne
Scheme 2. Structures of dendrimers G2-NS–G5-NS.
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C. Li, Z. Li et al.
drimer of G1–4Cl-N was ob-
tained in 75.7% yield and sub-
stitution of the chloride groups
in G1–4Cl-N produced G1–
4N3-N (99.0% yield). Next, the
click reaction between the
azide groups of G1–4N3 and
the terminal alkyne group in
chromophore
4
gave the
second-generation dendrimer of
G2–8Cl-NS, which could fur-
ther undergo a substitution re-
action of the chloride groups to
produce the core of G2–8N3-
NS (88.4% yield).
We were very excited to find
that high-generation dendrim-
ers could be obtained by using
this “double-stage” approach
(Table 1). The preparation of
G3-NS, G4-NS, and G5-NS pro-
ceeded to completion in about
6 h, as monitored by FTIR
spectroscopy (as determined by
the disappearance of the peak
that was centered at 2096 cmꢀ1,
which was associated with the
azido groups). G3-NS could still
be purified by column chroma-
tography on silica gel, whilst
G4-NS and G5-NS were ob-
tained by repeated precipitation
of their solutions in DMF with
ꢁ
acetone, because G2- -NS, G1–
4N3-S and G2–8N3-NS were
highly soluble in acetone.
Thanks to the powerful click-
chemistry reaction, their yields
were satisfactory (84.0, 72.0,
and 77.6%, respectively).
ꢁ
ꢁ
Scheme 3. Synthesis of end-capped dendrons G1- -NS and G2- -NS.
Characterization: The products
were well-characterized by
groups through the azo-coupling reaction. For example, in
spectroscopic analysis and they all gave satisfactory data
(see the Experimental Section and the Supporting Informa-
tion, Table S1) in accordance with their expected molecular
structures (for details, see the Supporting Information, Fig-
ures S5–S35). The Supporting Information, Figures S5–S7
show the IR spectra of the new dendrimers. All of the den-
drimers showed absorption bands that were associated with
nitro groups (about 1520 and 1340 cmꢀ1), sulfonyl groups
(about 1130 cmꢀ1), or the both. From the IR spectra of G1-
ꢁ
the synthesis of G2- -NS, the yield was not higher than
71.5%, although the reaction was performed for 5 days,
ꢁ
whilst the yield of G1- -NS was 89.1%. Thus, the yields of
ꢁ
ꢁ
G3- -NS and G4- -NS in the next steps would be much
lower. Also, with increasing the number of generations, the
purification became much-more difficult. Thus, another
route that involved a divergent approach was designed.
All of the cores (G1–4N3-S and G2–8N3-NS) were pre-
pared from AB2-type monomers 4 or 5, which contained
two chloroethyl groups and one terminal alkyne group
(Scheme 4 and Scheme 5). Herein, we will take the synthesis
of G2–8N3-NS as an example: After the click-chemistry re-
action between compounds 5 and 1, the first-generation den-
ꢁ
ꢁ
-NS and G2- -NS, there was an absorption band that was
ꢁ
derived from the C C-H stretching vibrations at about
3289 cmꢀ1, whereas this band disappeared in the spectra of
G2-NS, G3-NS, G4-NS, and G5-NS. Compared with the
spectra of G1–4Cl-S and G2–8Cl-NS, there was a new peak
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High-Generation NLO Dendrimers with Isolation Chromophores
FULL PAPER
Scheme 4. Synthesis of the G1-4N3-S dendrimer core.
at about 2095 cmꢀ1, which was associated with the azido
groups in the IR spectra of G1–4N3-S and G2–8N3-NS, thus
indicating that the nucleophilic-substitution reaction was
successful. Moreover, the peak that was associated with the
azido groups disappeared in the spectra of G4-NS and G5-
NS, coupled with the appearance of a signal that was due to
the carbonyl group at 1720 cmꢀ1, which showed that G4-NS
and G5-NS were successfully prepared from the end-capping
reactions of G1–4N3-S and G2–8N3-NS.
thus indicating that the reaction of G1–4Cl-S with sodium
azide led to the quantitative formation of the desired azido-
methyl group and that the structures of G2–8Cl-NS and
G2–8N3-NS would be confirmed by the occurrence of a simi-
1
lar phenomenon in their H NMR spectra. The Supporting
1
Information, Figures S24 and S25 show the H NMR spectra
of G4-NS and G5-NS and their chemical shifts were consis-
tent with their structures (Scheme 2), with no unexpected
peaks appearing. To further confirm the structures of G4-NS
and G5-NS, their 1H,1H-COSY and 1H,13C-COSY spectra
(see the Supporting Information, Figures S26 and S27) were
also recorded, which were also consistent with their struc-
tures (Scheme 2).
Analysis of the dendritic growth by MS (MALDI-TOF)
and by gel-permeation chromatography (GPC; see the Sup-
porting Information, Table S1) was performed for the prod-
ucts after each step, as shown in Scheme 1, Scheme 3, and
Scheme 4. MS (MALDI-TOF) was a good method for con-
firming the exact molecular weight of the dendrimers. The
Supporting Information, Figures S28–S35 show the mass
spectra of the prepared dendrimers (Scheme 1, Scheme 3,
and Scheme 4) and all of the experimental results were in
good agreement with their expected molecular weights from
their structures. Compared to the other dendrimers, G1–
4N3-S and G2–8N3-NS did not give neat signals, which
should have been caused by the fragment ions owing to
fragmentation of the unstabilized azide groups during MS
analysis. Unfortunately, we failed to detect any signals
NMR spectroscopy was an especially useful tool for illus-
trating the growth of each new generation of dendrimer; all
1
of the H and 13C NMR spectra are shown in the Supporting
Information, Figures S8–S25. The presence and absence of
the signal for the phenyl proton at the position para to the
amino group in the benzene ring (dꢂ6.7 ppm) before (in
G2-NS and G3-NS and even in G4-NS and G5-NS) and
ꢁ
ꢁ
after the azo-coupling reactions (in G1- -NS and G2- -NS)
in their H NMR spectra, respectively, showed that their cor-
1
responding reactions were successful. The successful forma-
tion of G1–4Cl-S was confirmed by the appearance of
a signal that corresponded the phenyl proton at the position
para to the amino group (dꢂ6.6 ppm), as well as by the ap-
pearance of a signal for the triazole proton (singlet at d
ꢂ7.15 ppm), as shown in the Supporting Information, Fig-
1
ure S9. In the H NMR spectrum of G1–4N3-S (see the Sup-
porting Information, Figure S16), the original peak for the
four chloromethyl groups in G1–4Cl-S (d=3.72 ppm) disap-
peared, whilst the signal at d=3.60 ppm became enhanced,
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C. Li, Z. Li et al.
dendrimers showed narrow
peaks, thus indicating that the
products possessed monodis-
perse molecular weights. How-
ever, in general, the characteri-
zation by GPC was of limited
value because the dendrimers
themselves were less polydis-
perse than the polystyrene
standards that were used for
the calibration; despite this
drawback, the GPC results
could still confirm the success
of the reaction to some degree.
The dendrimers were ther-
mally stable, as shown in the
Supporting Information, Fig-
ure S36, and the 5%-weight-
loss temperatures of the poly-
mers are listed in Table 2. The
degradation temperatures (Td)
for the dendrimers were above
2008C, thus revealing that they
were thermally stable. Upon in-
creasing
the
generation
number, Td decreased, possibly
owing to increasing loading
density of the effective chromo-
phore moieties in the dendrim-
ers. The glass-transition temper-
atures (Tg) of the dendrimers
were also investigated by using
differential scanning calorime-
try (DSC, Table 2).
G2-NS and G3-NS were solu-
ble in common polar organic
solvents, such as CHCl3, THF,
DMF, and DMSO. The solubili-
ty of G4-NS and G5-NS was
a littler poorer than that of G2-
NS and G3-NS, owing to their
high molecular weight; howev-
er, they were still soluble in
DMF and DMSO. As demon-
strated in their UV/Vis spectra,
G4-NS and G5-NS exhibited
good site-isolation effects in
Scheme 5. Synthesis of the G2-4N3-NS dendrimer core.
Table 1. Synthesis of dendrimers G4-NS and G5-NS.
comparison with the free chromophore molecules and low-
generation dendrimers G2-NS and G3-NS, thereby revealing
that the exterior benzene moieties and the interior triazole
rings that surrounded the azo chromophore moieties played
a key role in shielding these moieties from the solvatochro-
mic effect (see the Supporting Information, Figures S37–S42
and Table S2). The enhanced effective-site isolation that was
achieved in G4-NS and G5-NS would directly impede the
strong intermolecular dipole–dipole interactions between
the chromophore moieties and be highly beneficial to the
ꢁ
G1-N
–
G2-NS
G3-NS
ꢁ
ꢁ
G0- -N
G1- -NS
G2- -NS
Compound 1
G1-4N3-N
G1-4N3-S
G2-NS
G3-NS
–
G3-NS[a]
–
–
G4-NS[a]
G5-NS[a]
G2-8N3-NS
[a] These routes were chosen in this work.
within the appropriate mass range for G4-NS and G5-NS,
possibly because their larger molecular weight resulted in
much-lower peak intensity. All of the GPC curves of the
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High-Generation NLO Dendrimers with Isolation Chromophores
Table 2. Physical and NLO data of the dendrimers.
FULL PAPER
onstrated much-higher NLO coefficients (G5-NS: d33 =
253.0 pmVꢀ1, G5: d33 =193.1 pmVꢀ1). This result should be
ascribed to the presence of the isolation (sulfonyl-based)
chromophore, similar to the case of P1–P4. This result could
be explained by the fact that the mb value of the sulfonyl-
based chromophore was lower than that of the nitro-based
one; thus, the sulfonyl-based moieties and the triazole
groups acted as isolation groups to facilitate the noncentro-
symmetric alignment of the nitro-based chromophore moiet-
ies in the dendrimers in the electronic field to contribute to
the macroscopic NLO effect. On the other hand, the sulfo-
nyl-based chromophore groups themselves could be well-
isolated by the triazole moieties, which should be large
enough to shield the electronic interactions between the
chromophore moieties owing to their relatively low mb
value, to contribute to the macroscopic NLO effect. From
G2-NS to G5-NS, the 3D structure of the alternating nitro-
and sulfonyl-based azo-chromophore moieties became more
perfect; also, the loading density of the effective chromo-
phore moieties increased continuously, thus leading to the
increasing trend of the tested macroscopic NLO effects. This
result confirmed that the sulfonyl-based chromophore could
act as an isolation group for the nitro chromophore and lead
to the enhanced NLO effect on one hand, whilst, on the
other hand, the special 3D structure of the dendrimers
really benefit the macroscopic NLO effect.
Because there might be some resonant enhancement
owing to the absorption of the chromophore moieties at
532 nm, the NLO properties of the dendrimers should be
smaller (d33(1), Table 2). Owing to their good wide optical
transparency, as well as their outstanding large d33 values,
the d33(1) values of the dendrimers were still very high (20.1,
29.2, 35.8, and 51.7 pmVꢀ1); as such, these dendrimers have
potential applications in the field of optics. This result
means that the introduction of isolation chromophores into
the dendrimers (or polymers) is a new way to solve the con-
tradictions between nonlinearity and transparency. Howev-
er, to obtain more information on these isolation chromo-
phores, further research is still needed.
To further explore the alignment of the chromophore
moieties in these dendrimers, we measured their order pa-
rameter (F). According to the equation given in the foot-
note in Table 2, the F values of the dendrimers were calcu-
lated and their results are listed in Table 2 (also see the Sup-
porting Information, Figures S43–S46). The trend in the F
values was the same as that in the d33 values of the dendrim-
ers, which further confirmed our theory.
Depoling experiments of the dendrimers were conducted
in which the real-time decays of their SHG signals were
monitored as the poled films were heated from 35 to 1308C
in air at a rate of 48Cminꢀ1. The Supporting Information,
Figure S47, shows the decay of the SHG coefficient of the
dendrimers as a function of temperature. For G2-NS and
G3-NS, the temperatures for decay were only 708C, whilst
those of G4-NS and G5-NS increased to 92 and 828C, re-
spectively, which should be attributed to the 3D macromo-
lecular architecture that might suppress the relaxation of the
[a]
[b]
[d]
[e]
Tg
Td
Te[c]
d33
[pmVꢀ1
d33(1)
[pmVꢀ1
]
F[f]
N[g]
[oC]
[oC]
[oC]
G
]
N
G2-NS
G3-NS
G4-NS
G5-NS
81
93
107
99
282
236
219
206
105
95
135
125
113.8
165.0
175.3
253.0
20.1
29.2
35.8
51.7
0.21
0.28
0.31
0.40
0.517
0.547
0.565
0.571
[a] Temperature that caused 5% weight-loss in the polymers, determined
by TGA analysis under a nitrogen atmosphere at a heating rate of
108Cminꢀ1. [b] Glass-transition temperature (Tg) of the polymers, deter-
mined by DSC analysis under an argon atmosphere at a heating rate of
108Cminꢀ1. [c] The best poling temperature. [d] Second harmonic gener-
ation (SHG) coefficient. [e] Nonresonant d33 values, which were calculat-
ed by using the approximate two-level model. [f] Order parameter F=
1 A1A0ꢀ1, where A1 and A0 are the absorbance of the polymer film after
and before corona poling, respectively. [g] Loading density of the effec-
tive chromophore moieties, which was calculated as the total molecular
weight of all of the chromophores (main chromophore and isolation
chromophore) divided by the molecular weight of the dendrimers.
ordered noncentrosymmetric alignment of the chromophore
moieties during the poling process. In addition, owing to the
presence of sulfonyl chromophores, all of the maximum ab-
sorptions of the dendrimers that contained the isolation
chromophore were blue-shifted compared with that contain-
ing only one type of chromophore; these blue-shifted maxi-
mum absorptions of the dendrimers would result in a wide
optical-transparency window and contribute to practical ap-
plications in the field of photonics.
NLO properties: A convenient technique to study the
second-order NLO activity was to investigate the second-
harmonic-generation (SHG) processes that were character-
ized by their d33 value, which was an SHG coefficient. The
test procedure was similar to that reported previously[12]
and, from the experimental data, their d33 values were calcu-
lated at the 1064 nm fundamental wavelength (Table 2).
In our previous work, the d33 values increased from G1
(100.0 pmVꢀ1) to G5 (193.1 pmVꢀ1), with an accompanying
increase in the loading density of the chromophore moieties
and the more-perfect 3D structure of the dendrimers.[10]
Herein, a similar phenomenon was observed: changing the
loading concentration of the chromophore moieties from
0.517 in G2-NS (because the sulfonyl-based azo chromo-
phores could also directly contribute to the macroscopic
NLO effect, the loading concentration of the chromophore
moieties also contain isolation chromophores in this paper)
to 0.547 in G3-NS, 0.565 in G4-NS, and 0.571 in G5-NS led
to an increase in the NLO coefficients from 113.8 (G2-NS)
to 165.0 (G3-NS), 175.3 pmVꢀ1 (G4-NS), and 253.0 pmVꢀ1
(G5-NS). These encouraging results should be ascribed to
their more-perfect 3D structure and to the isolation effect of
the exterior benzene moieties and the interior triazole rings,
which could impede the interactions and enhance the poling
efficiency, according to the concept of the “suitable isolation
group”.
In comparison with G5, which only contained one kind of
chromophore (the nitro-based chromophore), G5-NS dem-
Chem. Eur. J. 2012, 00, 0 – 0
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C. Li, Z. Li et al.
rate of 108Cminꢀ1. The thermometer for measurement of the melting
point was uncorrected. The thickness of the films was measured on an
Ambios Technology XP-2 profilometer.
ordered dipole alignment to some degree. Thus, coupled
with their large NLO effects and improved optical transpar-
ency, G5-NS might be a promising candidate for practical
NLO applications.
ꢁ
Synthesis of dendrimer G1- -NS: Diazonium salt
2
(224.2 mg,
0.675 mmol) and dendrimer G1 (662.7 mg, 0.450 mmol) were dissolved in
DMF/THF (6 mL/3 mL) at 08C. The mixture was stirred for 40 h at 08C
and was subsequently treated with H2O, extracted with CHCl3, and
washed with brine. The organic layer was dried over anhydrous sodium
sulfate. After removal of the organic solvent, the crude product was puri-
Conclusion
ꢁ
fied by column chromatography on silica gel (EtOAc) to afford G1- -NS
as a red solid (684.4 mg, 89.1%). H NMR (300 MHz, CDCl3, 298 K): d=
In summary, by using a combination of divergent and con-
vergent approaches with the powerful click-chemistry reac-
tion, high-generation dendrimers G3-NS, G4-NS, and G5-
NS were successfully obtained; this synthesis confirmed the
advantage of the “double-stage” method for the preparation
of dendrimers. The high d33 values of these dendrimers, in
particular, the trend of increasing d33 value with increasing
the loading concentration of the chromophore moieties, re-
alized our idea of the chromophore as an isolation group for
another NLO chromophore with a higher mb value and fur-
ther confirmed that the frequently observed asymptotic de-
pendence of electro-optic activity on chromophore density
may be overcome through rational design. Thus, these suc-
cessful examples may open up a new avenue for the synthe-
sis of more NLO dendrimers and this synthetic strategy will
aid other scientists in the preparation of high-generation
dendrimers.
1
ꢁ
1.96 (m, 2H; CH2C), 2.05 (s, 1H; C CH), 2.24 (m, 4H; CH2), 2.62 (m,
2H; CH2), 2.96 (t, J=7.5 Hz, 4H; CH2C), 3.26 (t, J=5.7 Hz, 2H; SCH2),
3.71 (brs, 4H; NCH2), 3.94 (brs, 8H; NCH2), 4.14 (t, J=6.0 Hz, 4H;
NCH2), 4.37 (brs, 4H; OCH2), 4.59 (t, J=6.0 Hz, 8H; COOCH2), 6.56
(d, J=8.4 Hz, 2H; ArH), 6.96 (d, J=9.0 Hz, 4H; ArH), 7.23 (s, 2H; C=
CH), 7.42 (t, J=7.5 Hz, 8H; ArH), 7.53–7.65 (m, 7H; ArH), 7.75–7.91
(m, 12H; ArH), 7.98 ppm (d, J=7.5 Hz, 8H; ArH); 13C NMR (75 MHz,
CDCl3, 298 K): d=17.13, 21.68, 28.27, 47.05, 49.70, 51.2, 54.88, 61.58,
68.31, 70.21, 108.97, 111.76, 116.34, 117.29, 122.26, 122.88, 126.09, 128.38,
128.94, 129.47, 133.22, 144.76, 146.66, 147.02, 148.08, 149.20, 150.68,
ꢁ
154.93, 155.68, 166.33; IR (KBr): n˜ =3289 (C CH), 1716 (C=O), 1514,
1338 (NO2), 1140 ppm (SO2); MS (MALDI-TOF): m/z calcd for
C91H87N17O16S: 1728.6 [M+Na]+; found: 1728.8; elemental analysis calcd
(%) for C91H87N17O16S: C 64.04, H 5.14, N 13.95; found: C 63.64, H 5.31,
N 13.70.
ꢁ
Synthesis of dendrimer G2-NS: Chromophore G1- -NS (510.0 mg,
0.299 mmol), N,N-bis(2-azidoethyl)aniline (2, 31.4 mg, 0.136 mmol),
CuSO4·5H2O (10 mol%), NaHCO3 (20 mol%), and ascorbic acid
(20 mol%) were dissolved in THF/water (5 mL/1 mL) under a nitrogen
atmosphere in a Schlenk flask. The mixture was stirred at RT for 8 h, ex-
tracted with CHCl3, and washed with brine. The organic layer was dried
over anhydrous magnesium sulfate and purified by column chromatogra-
phy on silica gel (THF/CHCl3, 1:1) to afford G2-NS as a red solid
(339 mg, 77.6%). 1H NMR (300 MHz, CDCl3, 298 K): d=1.81 (brs,
CH2), 2.05 (brs, CH2), 2.23 (brs, CH2C), 2.78 (brs, CH2C), 2.94 (brs,
CH2C), 3.13 (brs, SCH2), 3.62 (brs, NCH2), 3.71 (brs, NCH2), 3.93 (brs,
NCH2), 4.13 (brs, NCH2), 4.36 (brs, OCH2), 4.56 (brs, COOCH2), 6.58
(d, J=8.4 Hz; ArH), 6.79 (brs, ArH), 7.05 (m; ArH), 7.15 (brs, ArH),
7.43 (m; ArH), 7.52–7.63 (m; ArH), 7.76–8.00 ppm (m; ArH and C=CH);
13C NMR (75 MHz, CDCl3, 298 K): d=22.18, 23.00, 24.16, 24.30, 28.77,
29.53, 47.62, 47.78, 50.26, 51.50, 51.99, 55.60, 62.10, 68.03, 68.88, 108.31,
109.54, 112.08, 112.30, 113.34, 116.91, 117.85, 119.07, 122.86, 123.36,
126.41, 126.63, 128.91, 129.44, 129.99, 130.31, 133.72, 139.22, 144.93,
145.28, 146.34, 147.20, 147.50, 148.61, 149.68, 151.23, 155.44, 156.11,
166.87 ppm; IR (KBr): n˜ =1716 (C=O), 1514, 1338 (NO2), 1139 (SO2);
MS (MALDI-TOF): m/z calcd for C192H187N41O32S2: 3669.2 [M+Na]+;
found: 3667.9; elemental analysis calcd (%) for C192H187N41O32S2: C 63.27,
H 5.17, N 15.76; found: C 62.39, H 5.23, N 15.75.
Experimental Section
Materials and instrumentation: THF was dried over and distilled from
a K–Na alloy under an atmosphere of dry nitrogen. Triethylamine was
distilled at atmospheric pressure and kept over potassium hydroxide.
CH2Cl2 was dried over and distilled from CaH2 at atmospheric pressure
before use. DMF was dried over and distilled from CaH2 under an atmos-
phere of dry nitrogen. N,N-Di(4-pentynyl)benzenamine (S1), 4-ethylsul-
fonylbenzenediazonium fluoroborate (S2), 4-nitrobenzenediazonium flu-
oroborate (S3), chromophore S4, and compounds 1, 3, 5, G1-N, and G1–
4N3-N were prepared according to our previously reported procedure-
s.[9a,10,13] Compounds 2 and 4 were synthesized according to our previous
work.[9a, 13] N,N,N,N,N-pentamethyldiethylenetriamine (PMDETA) was
purchased from Alfa Aesar. All other reagents were used as received.
1H and 13C NMR spectra were measured on a Varian Mercury300 spec-
trometer by using tetramethylsilane (TMS; d=0 ppm) as an internal
standard; 13C NMR, 1H,1H-COSY, and 1H,13C-COSY spectra of G4-NS
and G5-NS were measured on a Bruker ARX 400 spectrometer. FTIR
spectra were recorded on a PerkinElmer-2 spectrometer in the region
3000–400 cmꢀ1. UV/Vis spectra were obtained on a Shimadzu UV-2550
spectrometer. MS (MALDI-TOF) were measured on a Voyager-DE-STR
MALDI-TOF mass spectrometer (ABI, American) that was equipped
with a 337 nm nitrogen laser and a 1.2 m linear flight path in positive-ion
mode. Elemental analysis was performed on a CARLOERBA-1106 mi-
croelemental analyzer. Gel-permeation chromatography (GPC) was used
to determine the molecular weight of the polymers. GPC analysis was
performed on a Waters HPLC system that was equipped with a 2690D
separation module and a 2410 refractive-index detector. Polystyrene
standards were used as the calibration standards in the GPC analysis.
THF was used as an eluent and the flow rate was 1.0 mLminꢀ1. Thermal
analysis was performed on a NETZSCH STA449C thermal analyzer at
ꢁ
Synthesis of dendrimer G2- -NS: The procedure was similar to that of
dendrimer G1- -NS by using dendrimer G2-NS (250 mg, 0.0686 mmol)
and diazonium salt 3 (65.6 mg, 0.206 mmol). The crude product was puri-
ꢁ
fied by column chromatography on silica gel (THF/CHCl3, 2:1) to afford
G2- -NS as a red solid (190.1 mg, 71.5%). 1H NMR (300 MHz, CDCl3,
ꢁ
ꢁ
298 K): d=1.84 (brs, CH2), 1.95–2.10 (brs, CH2 and C CH), 2.22 (brs,
CH2), 2.48 (brs, CH2C), 2.81 (brs, CH2C), 2.94 (brs, CH2C), 3.13 (brs,
SCH2), 3.71 (brs, NCH2), 3.93 (brs, NCH2), 4.13 (brs, NCH2), 4.20–4.50
(brs, OCH2), 4.56 (brs, COOCH2), 6.54 (d, J=8.4 Hz; ArH), 6.70 (d, J=
8.4 Hz; ArH), 6.95 (d, J=8.4 Hz; ArH), 7.41 (m; ArH), 7.52–7.63 (m;
ArH), 7.76–8.00 ppm (m; ArH and C=CH); 13C NMR (75 MHz, CDCl3,
298 K): d=21.68, 23.82, 28.30, 29.04, 47.10, 49.76, 50.97, 55.02, 61.63,
67.52, 68.39, 107.80, 109.04, 111.78, 116.38, 117.33, 112.36, 122.88, 126.11,
128.39, 128.91, 129.49, 133.22, 144.77, 147.06, 148.10, 150.73, 154.91,
ꢁ
166.38 ppm; IR (KBr): n˜ =3289 (C CH), 1717 (C=O), 1515, 1339 (NO2),
a
heating rate of 108Cminꢀ1 under
a flow of nitrogen (flow rate:
1142 (SO2); MS (MALDI-TOF): m/z calcd for (C203H196N44O35S2): m/z
[M+Na]+: 3899.1; found: m/z 3900.9; elemental analysis calcd (%) for
C203H196N44O35S2: C 62.90, H 5.10, N 15.90; found: C 62.01, H 5.10,
N 15.33.
50 cm3 minꢀ1) for thermogravimetric analysis (TGA). The thermal transi-
tions of the polymers were investigated on a METTLER DSC822e differ-
ential scanning calorimeter under a nitrogen atmosphere at a scanning
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High-Generation NLO Dendrimers with Isolation Chromophores
FULL PAPER
Synthesis of dendrimer G2–4Cl-S: The procedure was similar to that of
dendrimer G2-NS by using compound 4 (497.6 mg, 1.10 mmol) and N,N-
bis(2-azidoethyl)aniline (1, 115.6 mg, 0.50 mmol). The crude product was
purified by column chromatography on silica gel (EtOAc) to afford G1–
4Cl-S as an orange solid (514.1 mg, 90.5%). 1H NMR (300 MHz, CDCl3,
298 K): d=2.08 (m, 4H; CH2), 2.81 (brs, 4H; CH2C), 3.16 (brs, 4H;
SCH2), 3.64 (brs, 4H; NCH2), 3.72 (brs, 8H; CH2Cl), 3.86 (brs, 8H;
NCH2), 4.35 (brs, 4H; NCH2), 6.63 (d, J=7.2 Hz, 2H; ArH), 6.79 (d, J=
7.2 Hz, 5H; ArH), 7.15 (s, 2H; C=CH), 7.80–8.00 ppm (m, 14H; ArH);
13C NMR (75 MHz, CDCl3, 298 K): d=22.52, 23.67, 40.11, 47.24, 51.49,
53.28, 55.13, 111.52, 112.79, 118.49, 122.21, 122.85, 125.97, 128.97, 129.81,
138.59, 144.31, 145.87, 149.45, 155.90 ppm; IR (KBr): n˜ =1131 (SO2); MS
(MALDI-TOF): m/z calcd for (C52H59N13O4S2Cl4): m/z [M+Na]+: 1159.0;
found: m/z 1158.5; elemental analysis calcd (%) for C52H59N13O4S2Cl4:
C 54.98, H 5.23, N 16.03; found: C 54.95, H 5.10, N 15.50.
Synthesis of dendrimer G3-NS: The procedure was similar to that of G1-
ꢁ
NS by using chromophore G1- -NS (150.2 mg, 0.088 mmol) and G1–
4N3-N (23.1 mg, 0.020 mmol). The crude product was purified by column
chromatography on silica gel (THF) to afford G3-NS as a red solid
(134 mg, 84.0%). 1H NMR (300 MHz, CDCl3, 298 K): d=1.85 (brs,
CH2), 2.05 (brs, CH2), 2.21 (brs, CH2C), 2.77 (brs, CH2C), 2.92 (brs,
CH2C), 3.11 (brs, SCH2), 3.69 (brs, NCH2), 3.92 (brs, NCH2), 4.12 (brs,
NCH2), 4.36 (brs, OCH2), 4.54 (brs, COOCH2), 6.53 (d, J=8.4 Hz;
ArH), 6.66 (brs, ArH), 6.95 (m; ArH), 7.15 (brs, ArH), 7.52–7.63 (m;
ArH), 7.76–8.00 ppm (m; ArH and C=CH); 13C NMR (75 MHz, CDCl3,
298 K): d=21.68, 23.61, 28.29, 30.17, 47.01, 49.73, 51.00, 61.60, 68.39,
109.01, 111.75, 116.35, 117.27, 122.36, 122.82, 125.39, 126.08, 128.37,
129.46, 133.19, 138.62, 144.75, 146.65, 147.00, 148.04, 150.70, 154.94,
166.33 ppm; IR (KBr): n˜ =1717 (C=O), 1514, 1338 (NO2), 1141 (SO2);
MS (MALDI-TOF): m/z calcd for
C
416H405N95O70S4: 8007 [M+Na]+;
found: 8010; elemental analysis calcd (%) for C416H405N95O70S4: C 62.58,
H 5.11, N 16.67; found: C 62.91, H 5.47, N 16.16.
Synthesis of dendrimer G1–4N3-S: A Schlenk flask was charged with
compound G1–4Cl-S (284 mg, 0.25 mmol), NaN3 (130 mg, 2.0 mmol), and
DMF (2.5 mL). The mixture was stirred at 808C for 12 h and the solution
was poured into a large volume of water. The precipitate was collected
and washed several times with water and MeOH/water (1:1) and then
dried under vacuum to afford the product as an orange solid (275 mg,
94.6%). 1H NMR (300 MHz, CDCl3, 298 K): d=2.07 (m, 4H; CH2), 2.80
(brs, 4H; CH2C), 3.16 (t, J=7.8 Hz, 4H; SCH2), 3.60 (brs, 8H; CH2N3),
3.69 (brs, 4H; NCH2), 4.35 (brs, 4H; NCH2), 6.62 (d, J=8.1 Hz, 2H;
ArH), 6.81 (d, J=8.1 Hz, 5H; ArH), 7.16 (s, 2H; C=CH), 7.80–8.00 ppm
(m, 14H; ArH); 13C NMR (75 MHz, CDCl3, 298 K): d=22.26, 23.41,
46.91, 48.26, 50.15, 51.00, 54.82, 111.44, 112.30, 117.89, 121.95, 122.50,
125.62, 128.65, 129.39, 138.18, 143.80, 145.30, 145.51, 149.59, 155.60 ppm;
IR (KBr): n˜ =2097 (N3), 1131 (SO2); MS (MALDI-TOF): m/z calcd for
C52H59N25O4S2: 1184.5 [M+Na]+; found: 1184.7; elemental analysis calcd
(%) for C52H59N25O4S2: C 53.73, H 5.12, N 30.13; found: C 53.42, H 5.26,
N 30.02.
General procedure of the synthesis of G4-NS and G5-NS: A mixture of
ꢁ
G1–4N3-N or G2–8N3-NS (1.00 equiv), G2- -NS (4.4 equiv or 8.8 equiv),
and CuBr (1.00 equiv) was dissolved in DMF (0.02m N3) under a nitrogen
atmosphere in
a Schlenk flask. N,N,N,N,N-pentamethyldiethylenetria-
mine (PMDETA, 1.00 equiv) was added and the mixture was stirred at
25–308C for 6 h before being quenched by the addition of water. The
product was purified by repeating precipitation of its solution in DMF
with acetone. The precipitate was filtered, washed with THF, and dried
under vacuum at 408C to a constant weight.
ꢁ
G4-NS: G1–4N3-N (5.8 mg, 0.0050 mmol) and G2- -NS (85.3 mg,
0.022 mmol). G4-NS was obtained as red powder (60.0 mg, 72.0%).
1H NMR (300 MHz, [D6]DMSO, 298 K): d=1.7–2.2 (CH2), 2.7–2.9
(CH2C), 3.6–3.8 (NCH2), 3.8–4.0 (NCH2), 4.1–4.2 (NCH2), 4.2–4.6 (CH2O
and CH2OCO), 6.6–6.9 (ArH), 6.9–7.2 (ArH), 7.3–8.0 ppm (ArH); IR
(KBr): n˜ =1717 (C=O), 1515, 1339 (NO2), 1138 (SO2); elemental analysis
calcd (%) for C864H843N201O144S10
C 62.09, H 4.86, N 15.94.
:
C 62.26, H 5.10, N 16.89; found:
Synthesis of dendrimer G2–8Cl-NS: The procedure was similar to that of
dendrimer G2-NS by using compound 4 (241 mg, 0.533 mmol) and G1–
4N3-N (140 mg, 0.121 mmol). The crude product was purified by column
chromatography on silica gel (THF/CHCl3, 1:1) to afford G2–8Cl-NS as
a red solid (293 mg, 81.5%). 1H NMR (300 MHz, CDCl3, 298 K): d=
1.80–2.30 (CH2), 2.80 (brs, CH2C), 2.91 (brs, CH2C), 3.14 (brs, SCH2),
3.71 (brs, NCH2), 3.85 (brs, CH2Cl), 3.94 (brs, NCH2), 4.14 (brs, NCH2),
4.32 (brs, NCH2), 4.40 (brs, NCH2), 6.56 (brs, ArH), 6.76 (brs, ArH),
7.15–7.33 (ArH and C=CH), 7.60 (brs, ArH), 7.70–8.00 ppm (ArH);
13C NMR (75 MHz, CDCl3, 298 K): d=21.74, 22.47, 23.64, 23.80, 27.67,
28.52, 29.07, 40.15, 47.10, 51.13, 53.22, 55.06, 67.48, 68.44, 107.77, 109.15,
111.55, 111.81, 112.76, 116.25, 117.26, 122.23, 122.49, 122.83, 125.94,
128.91, 129.62, 138.56, 144.26, 145.16, 146.09, 146.33, 146.80, 148.31,
149.13, 149.58, 155.18, 155.83 ppm; IR (KBr): n˜ =1511, 1343 (NO2), 1131
(SO2); MS (MALDI-TOF): m/z calcd for C136H149N39O14S4Cl8: 2988.8
[M+Na]+; found: 2989.5; elemental analysis calcd (%) for
ꢁ
G5-NS: G2–8N3-NS (7.6 mg, 0.0025 mmol) and G2- -NS (85.3 mg,
0.022 mmol). G5-NS was obtained as a red powder (66.0 mg, 77.6%).
1H NMR (300 MHz, [D6]DMSO, 298 K): d=1.7–2.2 (CH2), 2.7–2.9
(CH2C), 3.6–3.8 (NCH2), 3.8–4.0 (NCH2), 4.1–4.2 (NCH2), 4.2–4.6 (CH2O
and CH2OCO), 6.6–6.9 (ArH), 6.9–7.2 (ArH), 7.3–8.0 ppm (ArH); IR
(KBr): n˜ =1716 (C=O), 1514, 1338 (NO2), 1132 (SO2); elemental analysis
calcd (%) for C1760H1717N415O294S20
C 61.83, H 4.92, N 16.14.
: C 62.12, H 5.09, N 17.08; found:
Preparation of polymer thin films: Polymers P1–P4 were dissolved in
THF (about 3 wt.%), dendrimers G2-NS and G3-NS were dissolved in
THF (about 4 wt.%), and G5-NS was dissolved in DMF (about
10 wt.%); the solutions were filtered through syringe filters and the films
were spin-coated onto indium-tin-oxide (ITO)-coated glass substrates,
which were cleaned sequentially with DMF, acetone, distilled water, and
THF in an ultrasound bath before use. Residual solvent was removed by
heating the films in a vacuum oven at 408C. Thin films of dendrimer G4-
NS were prepared by a drop-coating method, owing to its poor solubility
and film-forming ability.
C
136H149N39O14S4Cl8: C 55.08, H 5.06, N 18.42; found: C 55.35, H 5.30,
N 17.47.
Synthesis of dendrimer G2–8N3-NS: The procedure was similar to that of
dendrimer G1–4N3-S by using G2–8Cl-NS (80 mg, 0.027 mmol) and
NaN3 (28.1 mg, 0.43 mmol). The reaction was stirred at 808C for 12 h and
the solution was poured into a large volume of water. The crude product
was purified by repeated precipitation of its solution in THF with MeOH
NLO measurements of poled films: The second-order optical nonlineari-
ty of the dendrimers was determined by in-situ second-harmonic-genera-
tion (SHG) experiments in 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; the SHG intensity was
monitored simultaneously. Poling conditions were as follows: the temper-
ature was different for each polymer (Table 2); voltage: 7.5 kV at the
needle point; gap distance: 0.8 cm. The SHG measurements were carried
out with a Nd:YAG laser operating at a repetition rate of 10 Hz and
a pulse width of 8 ns at 1064 nm. A Y-cut quartz crystal served as the ref-
erence.
to afford G2–8N3-NS as
a
red solid (71.9 mg, 88.4%). 1H NMR
(300 MHz, CDCl3, 298 K): d=1.80–2.30 (CH2), 2.80 (brs, CH2C), 2.91
(brs, CH2C), 3.14 (brs, SCH2), 3.59 (brs, CH2N3), 3.71 (brs, NCH2), 3.95
(brs, NCH2), 4.15 (brs, NCH2), 4.33 (brs, NCH2), 4.43 (brs, NCH2), 6.56
(brs, ArH), 6.76 (brs, ArH), 7.15–7.33 (ArH and C=CH), 7.60 (brs,
ArH), 7.70–8.00 ppm (ArH); 13C NMR (75 MHz, CDCl3, 298 K): d=
21.60, 22.77, 46.26, 47.79, 49.75, 54.20, 110.90, 121.49, 121.93, 125.04,
128.03, 145.24, 148.89, 155.06 ppm; IR (KBr): n˜ =2096 (N3), 1511, 1341
(NO2), 1130 (SO2); MS (MALDI-TOF): m/z calcd for C136H149N63O14S4:
3039 [M+Na]+; found: 3038; elemental analysis calcd (%) for
C
136H149N63O14S4: C 54.12, H 4.95, N 29.24; found: C 54.07, H 5.30,
N 28.85.
Chem. Eur. J. 2012, 00, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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C. Li, Z. Li et al.
Wang, C. Zhang, G. Todorova, M. Lee, R. Aniszfeld, S. Garner, A.
Chen, W. H. Steier, S. Houbrecht, A. Persoons, I. Ledoux, J. Zyss,
A. K.-Y. Jen, Chem. Phys. 1999, 245, 35–50; c) D. R. Kanis, M. A.
Ratern, T. J. Marks, Chem. Rev. 1994, 94, 195.
Acknowledgements
We are grateful to the National Science Foundation of China (21034006
and 21075134) for their financial support.
[8] a) M. J. Cho, D. H. Choia, P. A. Sullivan, A. J.-P. Akelaitis, L. R.
Dalton, Prog. Polym. Sci. 2008, 33, 1013–1058; b) Y. V. Pereverzev,
K. N. Gunnerson, O. V. Prezhdo, P. A. Sullivan, Y. Liao, B. C. Ol-
bricht, A. J. P. Akelaitis, A. K.-Y. Jen, L. R. Dalton, J. Phys. Chem.
C 2008, 112, 4355–4363; c) H. Ma, S. Liu, J. Luo, S. Suresh, L. Liu,
S. H. Kang, M. Haller, T. Sassa, L. R. Dalton, A. K. Y. Jen, Adv.
Funct. Mater. 2002, 12, 565–574; d) W. Shi, J. Luo, S. Huang, X.-H.
Zhou, T.-D. Kim, Y.-J. Cheng, B. M. Polishak, T. R. Younkin, B. A.
Block, A. K.-Y. Jen, Chem. Mater. 2008, 20, 6372–6377.
[9] a) Z. Li, Z. Li, C. Di, Z. Zhu, Q. Li, Q. Zeng, K. Zhang, Y. Liu, C.
Ye, J. Qin, Macromolecules 2006, 39, 6951–6961; b) Q. Zeng, Z. Li,
Z. Li, C. Ye, J. Qin, B. Z. Tang, Macromolecules 2007, 40, 5634–
5637; c) Q. Li, Z. Li, F. Zeng, W. Gong, Z. Li, Z. Zhu, Q. Zeng, S.
Yu, C. Ye, J. Qin, J. Phys. Chem. B 2007, 111, 508–514; d) Z. Li, P,
Li, S. Dong, Z. Zhu, Q. Li, Q. Zeng, Z. Li, C. Ye, J. Qin, Polymer
2007, 48, 3650–3657; e) Z. Li, S. Dong, G. Yu, Z. Li, Y. Liu, C. Ye,
J. Qin, Polymer 2007, 48, 5520–5529; f) Z. Li, S. Dong, P. Li, Z. Li,
C. Ye, J. Qin, J. Polym. Sci. Part A 2008, 46, 2983–2993; g) Z. Li, Q.
Li, J. Qin, Polym. Chem. 2011, 2, 2723–2740; h) Z. Li, G. Yu, W.
Wu, Y. Liu, C. Ye, J. Qin, Z. Li, Macromolecules 2009, 42, 3864–
3868; i) Z. Li, W. Wu, Q. Li, G. Yu, L. Xiao, Y. Liu, C. Ye, J. Qin, Z.
Li, Angew. Chem. 2010, 122, 2823–2827; Angew. Chem. Int. Ed.
2010, 49, 2763–2767.
[10] a) H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew. Chem. 2001, 113,
2056–2075; Angew. Chem. Int. Ed. 2001, 40, 2004–2021; b) V. V.
Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless, Angew. Chem.
2002, 114, 2708–2711; Angew. Chem. Int. Ed. 2002, 41, 2596–2599;
c) M. Meldal, C. W. Tornøe, Chem. Rev. 2008, 108, 2952–3015; d) A.
Qin, J. W. Y. Lam, B. Z. Tang, Chem. Soc. Rev. 2010, 39, 2522–2544;
e) A. Qin, J. W. Y. Lam, B. Z. Tang, Macromolecules 2010, 43, 8693–
8702.
[11] P. A. Sullivan, H. Rommel, Y. Liao, B. C. Olbricht, A. J. P. Akelaitis,
K. A. Firestone, J.-W. Kang, J. Luo, J. A. Davies, D. H. Choi, B. E.
Eichinger, P. J. Reid, A. Chen, A. K. Y. Jen, B. H. Robinson, L. R.
Dalton, J. Am. Chem. Soc. 2007, 129, 7523–7530.
[1] a) P. Furuta, J. Brooks, M. E. Thompson, J. M. J. Frꢁchet, J. Am.
Chem. Soc. 2003, 125, 13165–13172; b) P. Taranekar, T. Fulghum, D.
Patton, R. Ponnapati, G. Clyde, R. Advincula, J. Am. Chem. Soc.
2007, 129, 12537–12548; c) W. Ong, J. Grindstaff, D. Sobransingh,
R. Toba, J. M. Quintela, C. Peinador, A. E. Kaifer, J. Am. Chem.
Soc. 2005, 127, 3353–3361.
[2] a) C. J. Hawker, J. M. J. Frꢁchet, J. Am. Chem. Soc. 1992, 114, 8405–
8413; b) C. Devadoss, P. Bharathi, J. S. Moore, J. Am. Chem. Soc.
1996, 118, 9635–9644; c) K. Sivanandan, S. V. Aathimanikandan,
C. G. Arges, C. J. Bardeen, S. Thayumanavan, J. Am. Chem. Soc.
2005, 127, 2020–2021.
[3] a) S. M. Grayson, J. M. J. Frꢁchet, J. Am. Chem. Soc. 2000, 122,
10335–10344; b) K. L. Wooley, C. J. Hawker, J. M. J. Frꢁchet, J. Am.
Chem. Soc. 1993, 115, 11496–11505.
[4] C. J. Hawker, J. M. J. Frꢁchet, Macromolecules 1990, 23, 4726–4729.
[5] a) J. M. J. Frꢁchet, Science 1994, 263, 1710–1715; b) S. M. Grayson,
J. M. J. Frꢁchet, Chem. Rev. 2001, 101, 3819–3867; c) B. Helms,
E. W. Meijer, Science 2006, 313, 929–930; d) C. Pitois, D. Wiesmann,
M. Lindgren, A. Hult, Adv. Mater. 2001, 13, 1483–1487; e) M. R.
Harpham, ꢂ. Sꢃzer, C.-Q. Ma, P. Bꢄuerle, T. Goodson III, J. Am.
Chem. Soc. 2009, 131, 973–979; f) B. Natarajan, S. Gupta, V. Rama-
murthy, N. Jayaraman, J. Org. Chem. 2011, 76, 4018–4026; g) S. H.
Medina, V. Tekumalla, M. V. Chevliakov, D. S. Shewach, W. D. En-
sminger, M. E. H. El-Sayed, Biomaterials 2011, 32, 4118–4129.
[6] a) D. M. Burland, R. D. Miller, C. A. Walsh, Chem. Rev. 1994, 94,
31–75; b) Y. Bai, N. Song, J. P. Gao, X. Sun, X. Wang, G. Yu, Z. Y.
Wang, J. Am. Chem. Soc. 2005, 127, 2060–2621; c) T. J. Marks,
M. A. Ratner, Angew. Chem. 1995, 107, 167–187; Angew. Chem. Int.
Ed. Engl. 1995, 34, 155–173; d) D. Yu, A. Gharavi, L. P. Yu, J. Am.
Chem. Soc. 1995, 117, 11680–11686; e) S. R. Marder, B. Kippelen,
A. K. Y. Jen, N. Peyghambarian, Nature 1997, 388, 845–851; f) M.
Lee, H. E. Katz, C. Erben, D. M. Gill, P. Gopalan, J. D. Heber, D. J.
McGee, Science 2002, 298, 1401–1403; g) Y. Shi, C. Zhang, H.
Zhang, J. H. Bechtel, L. R. Dalton, B. H. Robinson, W. H. Steier,
L. R. Dalton, Science 2000, 288, 119–122; h) C. V. Mclaughlin, M.
Hayden, B. Polishak, S. Huang, J. D. Luo, T.-D. Kim, A. K. Y. Jen,
Appl. Phys. Lett. 2008, 92, 151107; i) L. R. Dalton, P. A. Sullivan,
D. H. Bale, Chem. Rev. 2010, 110, 25–55; j) J. D. Luo, X. H. Zhou,
A. K. Y. Jen, J. Mater. Chem. 2009, 19, 7410–7424; k) J. D. Luo, S.
Huang, Z. W. Shi, B. M. Polishak, X. H. Zhou, A. K. Y. Jen, Chem.
Mater. 2011, 23, 544–553.
[12] a) Z. Li, J. Qin, S. Li, C. Ye, J. Luo, Y. Cao, Macromolecules 2002,
35, 9232–9235; b) Z. Li, C. Huang, J. Hua, J. Qin, Z. Yang, C. Ye,
Macromolecules 2004, 37, 371–376.
[13] Z. Li, A. Qin, J. W. Y. Lam, Y. Dong, C. Ye, I. D. Williams, B. Z.
Tang, Macromolecules 2006, 39, 1436–1442.
[7] a) B. H. Robinson, L. R. Dalton, J. Phys. Chem. A 2000, 104, 4785–
4795; b) B. H. Robinson, L. R. Dalton, H. W. Harper, A. Ren, F.
Received: February 10, 2012
Published online: && &&, 0000
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www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

High-Generation NLO Dendrimers with Isolation Chromophores
FULL PAPER
Second’s the best: A series of second-
order nonlinear optical dendrimers
that contained isolation chromophores
were conveniently prepared in satisfac-
tory yields through the combination of
divergent and convergent approaches
coupled with the powerful Sharpless
click reaction. Owing to the advan-
tages of the isolation chromophores
and the dendrimers, G5-NS (see struc-
ture) demonstrated large NLO effects
and excellent optical transparency.
Dendrimers
W. Wu, C. Li,* G. Yu, Y. Liu, C. Ye,
J. Qin, Z. Li* ................. &&&& — &&&&
High-Generation Second-Order
Nonlinear Optical (NLO) Dendrimers
that Contain Isolation Chromophores:
Convenient Synthesis by Using Click
Chemistry and their Increased NLO
Effects
Chem. Eur. J. 2012, 00, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!