New "X-type" second-order nonlinear optical (NLO) dendrimers: Fewer chromophore moieties and high NLO effects

Article abstract of DOI:10.1039/c5tc00182j

New types of "X-type" NLO dendrimers, C2 and C3, in which the chromophore moieties were arranged in order, were rationally designed. The special topology of the chromophore moieties contributed a great deal to the good NLO performance of C2 and C3: the d₃₃ value of C2 (containing only five chromophore moieties) was 157.4 pm V^-1, while that of C3 (containing nine chromophore moieties) achieved 195.2 pm V^-1, much larger than that of C1 (74.7 pm V^-1, containing three chromophore moieties) and the fifth generation dendrimer (G5) (193.1 pm V^-1, bearing 62 pieces of chromophore moieties). Through careful experimental and theoretical analysis, their structure-property relationship was explained, and discussed in detail.

Full text of DOI:10.1039/c5tc00182j

Journal of
Materials Chemistry C
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PAPER
New ‘‘X-type’’ second-order nonlinear optical
(NLO) dendrimers: fewer chromophore moieties
and high NLO effects†
Cite this: J. Mater. Chem. C, 2015,
3, 4545
Runli Tang,a Shengmin Zhou,a Wendi Xiang,a Yujun Xie,a Hong Chen,a Qian Peng,b
Gui Yu,b Binwen Liu,c Huiyi Zeng,c Qianqian Lia and Zhen Li*a
New types of ‘‘X-type’’ NLO dendrimers, C2 and C3, in which the chromophore moieties were arranged
in order, were rationally designed. The special topology of the chromophore moieties contributed a
great deal to the good NLO performance of C2 and C3: the d33 value of C2 (containing only five
chromophore moieties) was 157.4 pm VÀ1, while that of C3 (containing nine chromophore moieties)
achieved 195.2 pm VÀ1, much larger than that of C1 (74.7 pm VÀ1, containing three chromophore
moieties) and the fifth generation dendrimer (G5) (193.1 pm VÀ1, bearing 62 pieces of chromophore
moieties). Through careful experimental and theoretical analysis, their structure–property relationship
was explained, and discussed in detail.
Received 19th January 2015,
Accepted 27th March 2015
DOI: 10.1039/c5tc00182j
www.rsc.org/MaterialsC
value of chromophores to large macroscopic NLO activity of
polymers becomes a major obstacle that hinders the rapid
Introduction
Organic second-order nonlinear optical (NLO) material is a development of this field.
kind of advanced material with huge potential applications in
To decrease the strong dipole–dipole interactions, the direct
photonic devices, such as high-speed electro-optic modulators, method is to isolate the chromophore moieties by attaching some
optical switches and frequency converters, which have been isolation groups, according to the ‘‘site isolation principle’’.4
actively pursued with much impressive progress.1 In the view of Based on the excellent work of other scientists, we have synthe-
the molecular structure, chromophores with the donor–p–acceptor sized different types of polymers, and proposed the concept of
(D–p–A) structure are efficient components for NLO-active a ‘‘suitable isolation group’’5 for the rational design of NLO
materials. To exhibit the macroscopic NLO effect, the chromo- polymers (Fig. 1). Accordingly, for the normal azo benzene
phore moieties in organic NLO polymers should have an orderly chromophore with three isolation groups around it, the suitable
noncentrosymmetric arrangement, which could be achieved from isolation group should be the triazole ring, which could be
the natural symmetric alignment state by corona poling technique conveniently constructed from the powerful click chemistry
(Fig. 1).2 However, the inherently strong dipole–dipole interac- reaction.6 For example, with the presence of the triazole rings
tions among the chromophore moieties make their noncentro-
symmetric alignment a daunting task during the poling process.3
For this reason, how to efficiently transform the microscopic b
a Department of Chemistry, Wuhan University, Wuhan 430072, China.
E-mail: lizhen@whu.edu.cn, lichemlab@163.com; Fax: +86 027 68755363
b Institute of Chemistry, the Chinese Academy of Sciences, Beijing 100080, China
c Fujian Institute of Research on the Structure of Matter, the Chinese Academy of
Sciences, Fuzhou 350002, China
† Electronic supplementary information (ESI) available: The structures of den-
drimers Gn (n = 1–5), global-like dendrimers Gn-TPA (n = 1–3), and related
parameters; the synthesis of compounds; NLO measurements including NLO
coefficient theories, preparing thin films, measurement conditions, stability and
error analysis; DFT calculation method for IR spectra; molecular mechanics
simulation including calculation method, results and discussion; NMR spectra,
TOF mass spectra, UV-vis spectra, TGA thermograms; optimized structures of
Fig. 1 The poling process required to demonstrate the macroscopic NLO
Frag1–Frag3 by DFT method; optimized structures of C1–C3, G1–G2 by MM
effect and issues considered to help the design of NLO polymers.
simulation and DFT method. See DOI: 10.1039/c5tc00182j
This journal is ©The Royal Society of Chemistry 2015
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pieces of azo benzene chromophore moieties, was as high as
195.2 pm VÀ1, a little higher than that of G5 bearing 62
chromophore ones. The theoretical calculations confirmed
the advantages of this X-type structure. Herein, we would like
to present the synthesis, characterization, calculations and
NLO properties of C1, C2 and C3 in detail.
Results and discussion
Synthesis
Compounds C1, C2 and C3 shared a similar synthetic method
through the highly-effective, Cu(I)-catalyzed 1,3-dipolar cyclo-
addition reaction between azides and alkynes (the Sharpless
‘‘click’’ reaction).10 C1 was easily obtained from compound 2
and S2, for its simple one-dimension-upward ‘‘Y-type’’ struc-
ture. However, C2 and C3 possessed an ‘‘X-type’’ structure,
thus, a suitable linkage part (compound 4) and a rational
synthetic approach should be carefully chosen. As shown
in Chart 1 and Scheme 1, the converge-then-diverge approach
was utilized to synthesize C2 and C3. Compound 4, which
possessed two alkyne groups (reactive groups for the azido
moieties in compound 2) at the tail and two chlorine
atoms (for further functionalized in the next step) at the head,
served as the linkage part, to yield compound 6 using the
convergent approach. Then, after the conversion of chlorine
atoms of compound 6 into the azido ones of compound 1,
through the divergent approach, compound 1 reacted with
different alkyne-functional compounds to conveniently afford
C2 and C3.
The synthetic route to C1–C3 is demonstrated in Scheme 1,
and the synthesis of some intermediates is presented in the
ESI,† while G1R was prepared according to our previous
work.7 Thus, the whole synthetic procedure to C1, C2 and
C3 was convenient, with satisfactory yields. All the target
molecules were soluble in common organic solvents, such as
dichloromethane, chloroform, THF, and their solutions could
be easily spin-coated into thin solid films. Therefore, it was
convenient to measure their NLO and other properties both in
solutions and thin films.
Fig. 2 The spatial structural diagram and the corresponding two-
dimensional dipole moments of C1, C2, C3 and Gn.
acting as suitable isolation groups, accompanied with the increasing
generation of dendrimers, from G1 to G5 (Fig. 2 and Scheme S1,
ESI†), the measured NLO coefficient increased from 122.7 (G3) to
177.0 (G4), then to 193.1 pm VÀ1 (G5), confirming that the frequently
observed asymptotic dependence of electro-optic activity on
the chromophore number density may be overcome through
rational design, according to the concept of a ‘‘suitable isola-
tion group’’.7
Except for the introduction of a ‘‘suitable isolation group’’,
another parameter, having enough room for the alignment of
chromophores upon poling, is also very important to achieve
large macroscopic NLO effects, which was concerned with the
topological structure of the polymers. Actually, from this point,
Jen, Dalton, and co-workers have put forward the idea that high
macroscopic NLO efficiency could be achieved when treating
chromophore moieties as spheres.8 Previously, we have prepared
many dendrimers, hyperbranched polymers, star-type macromole-
cules, with good NLO performance. Among them, similar to
the reported cases in the literature,1,2 dendrimers possess many
amazing properties and are considered to be the most promising
candidates for the next generation of NLO materials. However,
most of the dendrimers have a conical shape, not an exactly
spherical one. Thus, we have tried to control their shape by using
triphenyl amine as the core, to yield the so called ‘‘global-like
dendrimers’’ (Scheme S1, ESI†).9 Although they demonstrated
better NLO performance, they are still not as effective as a sphere.
With the purpose of designing more sphere-like dendrimers,
and diversifying their topological structure, in this work a new
kind of dendrimer (C1, C2 and C3) was designed, in which C2 and
C3 shared the same framework of ‘‘X-type’’ structure (Fig. 2). As
mentioned above, the triazole rings were utilized as the suitable
isolation groups in C1, C2 and C3, to decrease the strong dipole–
dipole interactions. In addition to the more spherical shape in
particular, the dipole moments of the chromophore moieties in
these molecules were designed to be naturally aligned in
a certain direction, to construct a microscopic noncentro-
symmetric topological structure, which should be beneficial
to the orientation of the chromophore moieties during the
poling process, for the further enhancement of their macro-
scopic NLO effects. Excitingly, the d33 value of C2 was tested
to be 157.4 pm VÀ1, and the d33 value of C3 with only nine
Chart 1 The synthetic route: converge-then-diverge approach.
4546 | J. Mater. Chem. C, 2015, 3, 4545--4552
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Scheme 1 The synthetic route of C1, C2 and C3.
Characterizations
The prepared C1–C3 and other related compounds were well
characterized by using the spectroscopic method, including
Fourier transforming infrared spectrum (FT-IR), nuclear magnetic
resonance (NMR), UV-vis spectroscopy, thermogravimetric ana-
lysis (TGA), differential scanning calorimetry (DSC), elemental
analysis (EA), and MALDI-TOF mass spectrometry. All gave
satisfactory data (see Experimental section and ESI† for
detailed analysis data). Among them, the vibrational spectral
study was basically used for the structure characterization.
For new molecules, especially for macromolecules, it was not
easy to describe the original and intricate vibrational spectral
properties in experiments. Herein, the density functional
theory (DFT) calculation did help, which has been widely used
for the study of NLO active compounds.11 Moreover, the frag-
ment approach provided an effective way to reduce the computa-
tional times with enough accuracy for large systems.12 Based on
DFT, we simulated the FT-IR spectra of C1, C2 and C3, by using
the fragment method. C1, C2 and C3 were broken into three
fragments: Frag1, Frag2, and Frag3, respectively (their optimized
structures are shown in the ESI†).
Fig. 3 shows the chemical structures of these three frag-
ments, and calculated the FT-IR spectra of Frag1, Frag2, Frag3,
and experimental ones of C1, C2, C3. From the spectra, it was
easily seen that the calculation results matched well to the
experimental ones. The absorption region of 3000–2800 cmÀ1
originated from the asymmetrical and symmetrical stretching
bands of the methylene groups. The peak at 1716 cmÀ1 (peak#)
in the spectrum of C3 was found to be at 1680 cmÀ1 in those of
Frag1 and Frag2, which should be attributed to the stretching
mode of CQO from ester groups. As there were no ester groups in
C1, but nine ones in C3, peak# was only found in the spectrum of
C3. The same case occurred for peak*, the out-of-plane ring bend
vibration of benzene (ROCOPh-H), which was found at 714 cmÀ1
in both the experimental and calculation results. Since C3 had
Fig. 3 FT-IR spectra (left) of Frag1, Frag2, Frag3 (calculated results) and
C1, C2, C3 (experimental results); chemical structure of Frags (right).
eight groups of ROCOPh-H, a moderate intensity of peak* was
observed. Labelled as the green region, the peaks at 1595 and
1515 cmÀ1 originated respectively from the asymmetrical and
symmetrical stretching of Ph-Azo-Ph and Ph-Azo-Ph-NO2. How-
ever, the peaks in the yellow region (1400–950 cmÀ1) were mainly
ascribed to the in-plane stretching and rocking vibration of
chromophore moieties (N-Ph-Azo-Ph-NO2) and its linked alkyl
chain. Intuitively, the absorption bands associated with
the carbonyl groups (1716 cmÀ1) and nitro groups (1337 and
1515 cmÀ1) in their FT-IR spectra partially confirmed that the
chromophore moieties were stable during the synthetic process.
Although the calculation-assisted FT-IR spectroscopy provided
detailed structural characteristics, it was far from enough. Thus,
NMR spectroscopic analysis, including 1H-NMR and 13C-NMR
analysis, was conducted, to identify the structure of the target
compounds and intermediates (the Experimental section in the
ESI† for detailed analysis data and spectra). MALDI-TOF mass
spectrometry was used to confirm the exact molecular weight,
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Table 1 Characterization data
demonstrated solvatochromism phenomena, for C1 and C2 the
difference of lmax was about 30 nm from the low polar solvent to
the high polar one, because of the lower number of contained
chromophore moieties (easily affected by solvents), while for C3,
with a small increase in the number of the chromophore
moieties, this difference decreased to 25 nm. In addition, the
m/za
m/z(cal)b
Tg (1C)
Td (1C)
c
d
No.
Yield (%)
C1
C2
C3
81.2
74.4
63.7
1388.0
2395.9
4813.0
1387.7
2395.2
4815.7
—
84
98
285
310
287
a
Measured by MALDI-TOF mass spectroscopy. b Calculated for [M + Na]+.
Glass transition temperature (Tg) detected by DSC analysis under
c
lmax of C3 was blue-shifted in comparison with those of C1 and
argon at a heating rate of 10 1C minÀ1
.
The 5% weight loss tempera- C2, due to their different chemical structures, that is, the main
d
ture of polymers detected by TGA analysis under nitrogen at a heating
electron donor of C1 and C2 was N,N-dihexylaniline, which is
a strong electron donor, while that of C3 was a substituted
aniline group by ethyl benzoate, a slightly weaker donor than
N,N-dihexylaniline. In this case, the difference between C1 and C2
was understandable. The lmax of C2 was slightly red-shifted in
dilute solutions, in comparison with that of C1, while they were
almost the same in the films. Meanwhile, the absorption peak of
C1 was a little wider and more red-shifted than that of C2,
indicating that the inhibition of solid aggregation is better in C2.
rate of 10 1C minÀ1
.
Table 2 The maximum absorption wavelength (lmax, nm) in different
solvents (0.02 mg mLÀ1
)
1,4-Dioxane CH2Cl2 CHCl3 THF DMF DMSO Film
C1 463
C2 465
C3 458
474
477
458
466
471
458
470
476
463
487
492
477
494
498
483
481
480
468
NLO properties
and all the experimental results were in good agreement with
the expected molecular weights for the structures (Table 1).
The dendrimers were thermally stable, as shown in Table 1 and
Fig. S35 (ESI†); the degradation temperatures (Td) for the dendri-
mers were higher than 280 1C. The glass transition temperatures
(Tg) of the dendrimers were also investigated using differential
scanning calorimetry (DSC) (Table 1).
The UV-vis absorption spectra of these compounds were
measured in different solvents. Their maximum absorption
wavelengths for the p - p* transition of the azo moieties are
listed in Table 2, and Fig. 4 shows the UV-vis spectra of the
three molecules in solutions (THF) and thin films; the detailed
UV-vis spectra are presented in the ESI.† All the compounds
To evaluate the NLO activities of C1, C2 and C3, their poled thin
films were prepared by spin-coating. One of the most conve-
nient techniques to study the second-order NLO activity is to
investigate the second harmonic generation (SHG) process,
which was characterized by an SHG coefficient (d33). The
method for the calculation of d33 values of the poled films
has been discussed in the ESI† and reported in our previous
papers.5 The d33 value of each dendrimer was calculated by
averaging the testing values of repeated measurements, includ-
ing that of the same film and different films of a specific
molecule (the testing stability and error analysis were discussed
in the ESI†). The NLO coefficients of these three dendrimers are
listed in Table 3, with other related parameters. Generally, the
d33@1064 value tested under the 1064 nm fundamental beam
was researched as the main parameter in our previous work, as
the 1064 nm laser showed broad applications in research and
technology. From the experimental data, the d33@1064 values
of C2 and C3 were tested to be 157.4 and 195.2 pm VÀ1
,
respectively, while on the same measurement system, it was
only 74.7 pm VÀ1 for C1. Also, the d33@1950 value was tested
under the 1950 nm fundamental beam. The d33@1950 value of
C1 was 17.1 pm VÀ1, while 39.7 pm VÀ1 for C2, and 53.6 pm VÀ1
for C3. The d33@1950 values were smaller than the d33@1064
ones, because of the dispersion of d33 of the poled films.13 Both
d33@1950 and d33@1064 showed the same trend. In order to
subtract out the impact of the fundamental beam, the d33(N)
values were calculated using the approximate two-level model
Fig. 4 The UV-vis spectra of C1, C2, C3 in THF solvent (left) and in thin
films (right).
Table 3 The NLO properties of dendrimers
d33c@1064 (pm VÀ1
)
d33(N)d@1064 (pm VÀ1
)
d3 @1950 (pm VÀ1
c
)
d33(N)d@1950 (pm VÀ1
)
Fe
Nf (%)
a
No.
Te (1C)
lsb (nm)
C1
C2
C3
39
80
100
289 Æ 3.1
227 Æ 3.1
212 Æ 3.1
74.7 Æ 8.2
157.4 Æ 17.2
195.2 Æ 22.3
10.7 Æ 1.1
23.2 Æ 2.6
35.5 Æ 4.0
17.0 Æ 1.8
39.7 Æ 4.5
53.6 Æ 6.1
12.1 Æ 1.3
28.3 Æ 3.2
38.9 Æ 4.4
0.19
0.20
0.19
0.55
0.47
0.55
a
b
c
d
The best poling temperature. Film thickness. Second harmonic generation (SHG) coefficient. The nonresonant d33 values calculated by
e
using the approximate two-level model. Order parameter F = 1 À A1/A0, A1 and A0 are the absorbance of the polymer film after and before corona
f
poling, respectively. The loading density of the effective chromophore moieties.
4548 | J. Mater. Chem. C, 2015, 3, 4545--4552
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(ESI†). The d33(N)@1064 values of C1, C2 and C3, tested under
the 1064 nm laser, were 10.7, 23.2, and 35.5 pm VÀ1 respec-
tively, while the corresponding d33(N)@1950 values were 12.1,
28.3, and 38.9 pm VÀ1, respectively. The small difference in the
d33(N)@1064 and d33(N)@1950 values might be caused by the
extra UV-vis absorption: the UV-vis absorption edges of the
three compounds crossed 532 nm (UV-vis absorption spectra
in solvents and films, ESI†). In other words, the frequency
doubling light might cause little loss to the UV-vis absorption.
From C1 to C2, the number of chromophore moieties went
from just three to five, while the loading density of the effective
chromophores (N) decreased from 0.55 to 0.47. However, the
d33 value increased rapidly, with the d33@1064 value increasing
from 74.7 to 157.4 pm VÀ1, and the d33(N)@1064 value
increased from 10.7 to 23.2 pm VÀ1. This phenomenon raised
a question: why does C2 show such a big improvement in the
d33 value in comparison with C1?
Fig. 5 De-poling curve of C3, C2, C1 and C1/C4 (measured at 1064 nm
fundamental beam).
Analyzing the structure carefully, C2 was equal to one C1
with two additional chromophore moieties on the tail through
covalent bonds. Perhaps these covalent bonds made some linkage should not be the only reason for the high NLO effect
sense in that they could aid the arrangement of the five of C2. To gather more information, additional chromophore
chromophore moieties of C2 in orderly rows, rather than the moieties were further introduced to the head of C2, not only
normal disordered stacking ones. To partially confirm this limited to the tail part, to construct a new dendrimer, C3, in
point, a control experiment was conducted. As shown in which there were nine chromophore moieties in total. Excitingly,
Scheme 2, C2 could be considered to be composed of two parts, the d33@1064 value of C3 was tested to be as high as 195.2 pm VÀ1
,
similar to those of C1 and C4 (the synthesis and characteriza- even higher than that of G5 bearing 62 pieces of chromophore
tion data are presented in the ESI†). Thus, a mixture of moieties (Scheme S1, ESI†). Analyzing the structures of C2 and
compound C1 and C4 was prepared at a molar ratio of 1 : 1.
C3 carefully, it seemed that there was no big difference from
From the SHG measurement, the d33@1064 value of the those of G1–G5, except the presence of one benzene ring as the
C1/C4 mixture was tested to be 71 pm VÀ1, even lower than that additional isolation group. As mentioned in the introduction
of C1 itself, under the best poling temperature of 34 1C. However, part, we have designed so called ‘‘global-like dendrimers’’
once the piece of C4 was bonded onto C1 as a tail, the d33@1064 (Scheme S1, ESI†), which exhibited higher NLO effects than
value of the resultant C2 was as high as 157.4 pm VÀ1, more than those of G1–G5, disclosing the importance of the perfect 3D
double that of C1. The difference could also be observed clearly structure of the dendrimers.
in the de-poling process. Fig. 5 shows the de-poling curves of C2,
However, it was really hard to make it clear how the
C1 and the C1/C4 mixture. The C1/C4 mixture showed the molecular conformation affected the macroscopic coefficient,
poorest performance, once again indicating the importance of as it faced at least three large hurdles: first, the real conforma-
the covalent bonds. Compared to that of G3 (Scheme S1, ESI†), tion of the single molecule, especially for such macromolecular
this value was still very high, no matter that there were 14 dendrimers; secondly, the stacking model of molecules in thin
chromophore moieties in G3 but only 5 in C2. Thus, the covalent films; and third the conformation of the ordered molecules in
the poled films. Actually, even the first one had not been fully
understood; for some NLO effective macromolecules, no direct
data of spatial structure from the crystal has been obtained so
far. In most cases, we reduced the intermediate link but only
observed the original chemical structure and the resultant
efficiency. In this work, we made an attempt to obtain the
single molecular conformation by using molecular mechanics
simulation. We performed a molecular mechanics simulation
for C1, C2, C3, and also for G1 and G2 for comparison (the
calculation method, results and discussion are presented in the
ESI†). The results showed that C1 and G1 had similar con-
formations: approximately planar, and all the chromophore
moieties were exposed to the interface, possibly leading to a
strong interaction of the electrical dipole moments. This was
supposed to be the main reason for their low NLO effects. In
Scheme 2 Structures of C1, C2 and C4.
contrast, other molecules exhibited 3D-extended conformations.
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In particular, the conformation of C3 was almost spherical, provid- water, DMF, THF. Each step was carried out for 20 min. The
ing a good candidate conformation to achieve a large NLO effect. residual solvent of the thin films was removed by heating the
Molecular mechanics simulation was a good way to help obtain films in a vacuum oven at 45 1C.
more microcosmic information, even the single molecular confor-
Measurement condition
mation was only the tip of an iceberg; a better response program to
the second and third hurdles was then expected.
The second-order optical nonlinearity of the materials was
determined by in situ second harmonic generation (SHG)
experiment by using a closed temperature-controlled oven with
optical windows and three needle electrodes. The films were
kept at 451 to the incident beam and poled inside the oven, and
the SHG intensity was monitored simultaneously. Poling con-
ditions were as follows: temperature, different for each polymer
(Table 3); voltage, 7.0 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. The stability and error of the system is
analyzed in the ESI.†
Conclusions
In summary, three dendrimers, C1, C2 and C3, were success-
fully synthesized and carefully investigated. C2 and C3 were
designed as an ‘‘X-type’’ structure, with the chromophore
moieties being arranged partially in order, which was a better
structure for good NLO efficiency. As a result, C2 and C3
exhibited large NLO effects, with d33 values as high as 157.4
and 195.2 pm VÀ1, no matter that there were only five or nine
chromophore moieties in them, respectively. Through the control
experiments and some theoretical calculations, it was found that
C2 and C3 had 3D-extended conformations, and their chromo-
phore moieties were well oriented in nature. For C3, its conforma-
tion was almost spherical, the best conformation to achieve a
large NLO effect. It is believed that by further modifying the
chemical structure more intelligently, even better performance
could be achieved with the utilization of the very simple azo
chromophore moieties.
The NLO efficiencies were also investigated using 1950 nm
laser radiation. The doubled frequency signals (975 nm) were
detected by an Andor’s DU420A-BR-DD CCD after the mixed
signals passed through the monochromator.
Synthesis
C1: compound 3 (121.6 mg, 0.1 mmol) and compound R1
(35.6 mg, 0.15 mmol) were dissolved in DMF (10 mL). After
stirring for 24 h at 0 1C, the mixture was poured into a lot of ice
water, and some sodium bicarbonate was added to adjust the
pH to B7.0. The deep red precipitate was filtered, washed with
water, and purified by column chromatography on silica gel
using chloroform/petroleum ether (3/1) as the eluent to afford a
red solid (110.8 mg, 81.2%). 1H NMR (300 MHz, CDCl3, 298 K),
d (TMS, ppm): 0.90 (br, s, 12H, –CH3), 1.32 (br, s, 24H, –CH2–),
1.62 (br, s, 16H, –CH2–), 2.23 (t, J = 7.2 Hz, –CH2–), 2.96
(t, J = 6.6 Hz, –CH2–), 3.35 (t, J = 7.2 Hz, 8H, –CH2–), 3.71
(t, J = 6.6 Hz, –CH2–), 4.13 (t, J = 6.0 Hz, –CH2–), 4.36 (br, s, 4H,
–CH2), 6.53 (d, J = 8.4 Hz, 2H, –CH2–), 6.67 (br, 4H, ArH), 7.23
(s, 3H, ArH), 7.85–7.62 (m, 11H, ArH), 8.27 (d, J = 7.8 Hz, 2H,
ArH). 13C NMR (100 MHz, CDCl3, 298 K), d (ppm): 154.72,
151.42, 149.31, 147.58, 147.20, 144.50, 143.71, 139.24, 126.32,
125.95, 124.47, 122.74, 122.35, 117.11, 116.52, 113.37, 111.48,
111.06, 109.11, 68.41, 51.20, 47.11, 31.54, 28.27, 28.21, 27.23,
26.63, 22.56, 21.75, 14.80, 13.95, MALDI-TOF MS: calcd for
(C74H96N18O8): m/z [M + Na]+: 1387.7; found: m/z 1388.0. (EA)
(%, found/calcd): C, 65.02/65.08; H, 6.83/7.09; N, 18.34/18.46.
C2: compound 1 (138.7 mg, 0.10 mmol), compound 2 (103.4 mg,
0.21 mmol), CuSO4Á5H2O (10 mol%), NaHCO3 (20 mol%), and
ascorbic acid (20 mol%) were dissolved in DMF (8 mL)/H2O
(1 mL) under nitrogen in a Schlenk flask. The mixture was
stirred at 30 1C overnight, then extracted with chloroform, and
washed with 1 N HCl, 1 N NH4OH and then water. The organic
layer was dried over anhydrous magnesium sulfate. After
Experimental
Instrumentation
1H and 13C NMR spectra were measured on a Varian Mercury300,
Bruker ARX400, or Bruker BioSpin GmbH spectrometer using
tetramethylsilane (TMS; d = 0 ppm) as the internal standard.
UV-visible spectra were obtained using a Schimadzu UV-2550
spectrometer. The Fourier transform infrared (FTIR) spectra
were recorded on a Perkin Elmer-2 spectrometer in the region
3000–400 cmÀ1 on KBr pellets. Elemental analysis was performed
on a CARLOERBA-1106 micro-elemental analyzer. A 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
a NETZSCH STA449C thermal analyzer at a heating rate of
10 1C minÀ1 in nitrogen at a flow rate of 50 cm3 minÀ1 for thermo-
gravimetric analysis (TGA). The thermal transitions of the polymers
were investigated using a METTLER differential scanning calori-
meter DSC822e under nitrogen at a scanning rate of 10 1C minÀ1
The thermometer for measurement of the melting point was
uncorrected. The thickness of the films was measured with an
Ambios Technology XP-2 profilometer.
.
Preparation of thin films
The samples were dissolved in THF (concentration B3 wt%), removal of the solvent, the crude product was purified by
and the solutions were filtered through syringe filters. The thin column chromatography using THF/chloroform (1/8) as the
1
films were spin-coated onto indium-tin-oxide (ITO)-coated glass eluent to afford a deep red solid (176.4 mg, 74.4%). H NMR
substrates, which were subjected to ultrasonication in different (300 MHz, CDCl3, 298 K), d (TMS, ppm): 0.89 (br, s, 12H, –CH3),
solvent systems including 2% soap in water, acetone, deionized 1.08 (t, J = 6.6 Hz, 6H, –CH3), 1.31 (br, s, 24H, –CH2–), 1.79
4550 | J. Mater. Chem. C, 2015, 3, 4545--4552
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(br, s, 4H, –CH2–), 1.94 (br, s, 4H, –CH2–), 2.21 (t, J = 6.6 Hz, 4H, Notes and references
–CH2–), 2.94 (t, J = 6.3 Hz, 4H, –CH2–), 3.21 (m, 4H, –CH2–), 3.34
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(m, 8H, –CH2–), 3.69 (br, s, 4H, –CH2–), 3.92 (br, 4H, –CH2–),
4.11 (br, 4H, –CH2–), 4.20 (br, 2H, –CH2–), 4.27 (br, 2H, –CH2–),
4.36 (br, 4H, –CH2–), 4.59 (br, 4H, –CH2–), 5.12 (s, 4H, –CH2–),
6.58 (d, J = 9.0 Hz, 2H, ArH), 6.66 (m, 8H, ArH), 6.74 (br, s, 2H,
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7.74–7.72 (m, 4H, ArH), 7.89–7.80 (m, 16H, ArH), 8.28 (m, 4H,
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157.57, 156.45, 152.46, 152.01, 149.08, 148.66, 147.99, 147.60,
145.06, 144.37, 133.43, 127.00, 125.41, 125.14, 123.47, 123.09,
117.66, 116.86, 112.44, 112.11, 110.24, 109.49, 107.12, 70.68,
69.62, 68.03, 67.73, 67.44, 67.15, 66.86, 62.89, 51.92, 51.16,
48.23, 47.80, 46.32, 32.71, 29.79, 28.32, 27.63, 26.80, 25.89,
25.62, 25.36, 25.09, 24.83, 23.63, 22.68, 14.44, 12.38. MALDI-TOF
MS: calcd for (C125H150N32O17): m/z [M + Na]+: 2395.2; found: m/z
2395.9. (EA) (%, found/calcd): C, 63.10/63.27; H, 6.20/6.37;
N, 18.74/18.89.
C3: compound 1 (34.6 mg, 0.02 mmol), G1R (93.7 mg,
0.55 mmol), CuSO4Á5H2O (10 mol%), NaHCO3 (20 mol%), and
ascorbic acid (20 mol%) were dissolved in DMF (8 mL)/H2O
(0.8 mL) under nitrogen in a Schlenk flask. The mixture was
stirred at 30 1C overnight, then extracted with chloroform, and
washed with 1 N HCl, 1 N NH4OH and then water. The organic
layer was dried over anhydrous magnesium sulfate. After
removal of the solvent, the crude product was purified by
column chromatography using THF/chloroform (1/3) as the
1
eluent to afford a deep red solid (152.6 mg, 63.7%). H NMR
(300 MHz, CDCl3, 298 K), d (ppm): 1.04 (t, J = 6.9 Hz, 6H, –CH3),
1.25 (br, 2H, –CH2–), 1.90 (br, 2H, –CH2–), 1.92 (br, 2H, –CH2–),
2.19 (br, 12H, –CH2–), 2.91 (br, 12H, –CH2–), 3.19 (m, 4H, –CH2–),
3.69 (m, 12H, –CH2–), 3.90 (br, s, 16H, –CH2–), 4.09 (br, s, 12H,
–CH2–), 4.24 (m, 4H, –CH2–), 4.36 (m, 12H, –CH2–), 4.54 (br, 16H,
–CH2–), 5.11 (s, 4H, –CH2–), 6.48 (m, 4H, ArH), 6.65–6.62 (m, 8H,
ArH), 6.93–6.91 (m, 8H, ArH), 7.15 (s, 2H, ArH), 7.28 (br, s, 4H,
ArH), 7.84–7.37 (m, 24H, ArH), 7.98–9.96 (m, 16H, ArH), 8.23
(m, 4H, ArH). 13C NMR (75 MHz, THF-d8, 298 K), d (ppm): 166.79,
166.46, 160.55, 157.57, 156.79, 156.70, 156.61, 152.37, 152.03,
151.27, 149.59, 149.44, 148.64, 147.73, 147.45, 147.35, 146.12,
145.96, 144.95, 144.41, 133.92, 133.45, 131.09, 130.41, 129.33,
127.03, 126.85, 126.75, 125.43, 125.28, 123.50, 123.25, 117.87,
116.86, 112.98, 112.60, 112.47, 110.32, 109.53, 107.20, 70.71,
69.70, 68.08, 67.78, 67.49, 67.20, 66.91, 65.86, 62.91, 51.97,
51.19, 50.58, 48.30, 47.92, 46.37, 30.03, 29.84, 26.92, 25.94,
25.67, 25.40, 25.14, 24.87, 22.90, 22.73, 12.45. MALDI-TOF MS:
calcd for (C249H242N60O45): m/z [M + Na]+: 4815.7; found: m/z
4813.0. (EA) (%, found/calcd): C, 61.58/62.37; H, 5.29/5.09; N,
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Acknowledgements
We are grateful to the National Science Foundation of China
(no. 21034006 and 21325416), and the National Fundamental
Key Research Program (2011CB932702) for financial support.
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