Synthesis and nonlinear optical properties of branched pyrroline chromophores

Article abstract of DOI:10.1002/poc.1772

New tricyanopyrroline (TCP) chromophores with rigid-flexible dendron were prepared for second-order nonlinear optical (NLO) application. The chromophores were fully characterized using ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry. Thermal gravimetric analysis (TGA) revealed that the chromophores had excellent thermal stability. Large λ_max and high solvate chromic effects revealed that the chromophores had large second-order optical nonlinearity. The electro-optic coefficients (r₃₃) were measured in the chromophores-doped poly(bisphenol A carbonate) films at the fundamental wavelength of 1310 nm, and the highest γ₃₃ achieved was 217 pmV^-1. Copyright

Full text of DOI:10.1002/poc.1772

Research Article
Received: 15 April 2010,
Revised: 3 June 2010,
Accepted: 8 June 2010,
Published online in Wiley Online Library: 24 August 2010
(wileyonlinelibrary.com) DOI 10.1002/poc.1772
Synthesis and nonlinear optical properties of
branched pyrroline chromophores
Jialei Liua, Wenjun Houa, Shuwen Fenga, Ling Qiua, Xinhou Liua
and Zhen Zhena
*
New tricyanopyrroline (TCP) chromophores with rigid–flexible dendron were prepared for second-order nonlinear
optical (NLO) application. The chromophores were fully characterized using ultraviolet-visible spectroscopy, nuclear
magnetic resonance spectroscopy and mass spectrometry. Thermal gravimetric analysis (TGA) revealed that the
chromophores had excellent thermal stability. Large lmax and high solvate chromic effects revealed that the
chromophores had large second-order optical nonlinearity. The electro-optic coefficients (r33) were measured in
the chromophores-doped poly(bisphenol A carbonate) films at the fundamental wavelength of 1310 nm, and the
highest g33 achieved was 217 pmVS1. Copyright ß 2010 John Wiley & Sons, Ltd.
Keywords: chromophore; electro-optic effect; NLO; rigid–flexible dendron; TCP; thiophene
containing both rigid group and flexible group). Both of the
1
chromophores are characterized with H NMR, MS, and UV–Vis
INTRODUCTION
Organic second-order nonlinear optical (NLO) materials have
many excellences, for example, large NLO coefficients, ultra-fast
response time, large bandwidth, low dielectric constant, small
dispersion in the refractive index, structural flexibility, ease of
integration, and so on,[1,2] so they have been extensively
investigated for potential applications in telecommunications
and electro-optic devices in the last decades. But there are still
some disadvantages in their practical applications, such as: the
strong intermolecular electrostatic interaction, the incompat-
ibility of the chromophores in polymers, and poor solubility in
most common organic solvents. Fortunately, controlling the
shape, size and conformation of the chromophores has been
proved to be an effective approach for minimizing intermolecular
electrostatic interaction and enhancing the poling efficiency of
electro-optic (EO) materials.[3–5,6–8]
Recently Jen and coworkers have firstly reported the
strong potential of tricyanopyrroline (TCP) chromophore and
their detailed microscopic analysis data.[9,10,11] The electro-
n-withdrawing properties of TCP unit are considerably stronger
than those of tricyanofuran (TCF) and other electron acceptors.
In their research, the largest molecular first hyperpolarizability
was 8700 ꢀ 10ꢁ30 esu, which was six times higher than the
chromophore with TCF acceptor, but the macroscopic electro-
optic coefficients could not increase so obviously.[12,13,14] It is
inferred that the chromophores packing is easily formed due to
the strong electrostatic interaction.[15,16] From both theoretical
and experimental analyses, the Dalton group has shown that
the maximum achievable EO activity of a chromophore can
be greatly enhanced by modification of its shape. In fact, the
derivatization of chromophores with bulky substituents will make
them more spherical and hence limit intermolecular electrostatic
interactions.[3,17–21] Therefore the rigid–flexible dendron is
introduced into the TCP acceptor to prevent parallel chromo-
phores’ packing and improve the solubility of the materials in
this paper. We report the syntheses and properties of these novel
TCP chromophores with rigid–flexible dendron (the dendron
spectra. The thermal stabilities are studied by thermal gravimetric
analysis (TGA). The NLO properties are measured in the polymer
films by ATR method[22] at the wavelength of 1310 nm.
RESULTS AND DISCUSSION
Synthesis of chromophores
The 3,5-bis(20-ethylhexyloxy)benzylalcohol (1) was prepared
from 2-ethylhexyl bromide and 3,5-dihydroxybenzyl alcohol
using K2CO3 as base, in the solvent of DMF. Then the 3,
5-bis(20-ethylhexyloxy)benzylalcohol was brominated by carbon
tetrabromide using triphenyl phosphorous as the catalyzer.
The synthetic routes to chromophores are sketched in
Scheme 1. The chromophores were prepared according to a
synthetic methodology as follows: p-N,N-bis(2-hydroxyethyl)-
aminobenzaldehyde was synthesized according to a well known
method. The thiophene bridge compound was prepared in eight
steps to yield the Wittig salt. After the final Wittig condensation
of the thiophene ylide with the aldehyde, the desired donor
bridges were prepared. Donor bridge was subjected to Vilsmeier
reactions in the presence of POCl3 and DMF, affording the
desired aldehyde function on the thiophene ring. The donor
bridge was then reacted with the acceptor to yield the
chromophore.
*
Correspondence to: Z. Zhen, Key Laboratory of Photochemical Conversion and
Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese
Academy of Sciences, Beijing, 100190, P. R. China.
E-mail: zhenzhen@mail.ipc.ac.cn
a
J. Liu, W. Hou, S. Feng, L. Qiu, X. Liu, Z. Zhen
Key Laboratory of Photochemical Conversion and Optoelectronic Materials,
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences,
Beijing, P. R. China
J. Phys. Org. Chem. 2011, 24 439–444
Copyright ß 2010 John Wiley & Sons, Ltd.

J. LIU ET AL.
Scheme 1. Syntheses of 3,5-bis(20-ethylhexyloxy)benzyl bromide.
Physical properties of chromophores
The NLO properties of the chromophores
It was found that TCP chromophores have poor solubility in
common organic solvents such as ethyl acetate, dichloro-
methane, tetrahydrofuran, probably due to the existence of
strong intermolecular electrostatic interaction. As expected,
chromophores reported here exhibit good solubility in the
above-mentioned solvents, which is a necessary condition for
subsequent preparation of device-quality polymer films. The
enhanced solubility may be attributed to the introduction of
bulky flexible chain in the bridge and acceptor.
The absorption spectra have been obtained in both THF and
DCM, the absorption maxima (lmax) are summarized in Table 1.
Absorption peaks in THF were observed in visible region at 782
and 805 nm, respectively for chromophore FTC-z-1 and FTC-z-2. It
has been experimentally and theoretically illustrated that a large
In order to investigate the NLO properties of the chromophores,
guest-host systems were explored. The chromophores were
doped into APC [poly (bisphenol A carbonate)] at the same
molecular densities (10 wt%). Solutions of 20% total solids
were prepared in dibromomethane and 2–3 mm thick films were
spun cast onto the substrate coated by indium tin oxide (ITO). The
films were vacuum dried at 50 8C overnight, and corona poled
at 145 8C (the glass transition temperature is about 138 8C)
for 10 min under the electric field of 9 kV. After the films were
cooled to room temperature, the electric field was removed.
In the process of poling, we also researched the stability of
the chromophore in electric field. The highest electric field the
chromophore can bear is summarized in Table 1. It is seen that
TCP chromophore with dendron shows better stability than the
chromophore without dendron.
lmax, meaning low charge transition energy, is often directly
associated with an enhanced second-order NLO response.[23]
And the absorption peaks in DCM were observed at 869 and
873 nm, respectively, the shifts of the absorption maxima in
different solvents show the effect of solvent on the energy gap
between the ground state and excited state molecules,[24,25]
which reflects different electronic distribution in the molecules.
Demartino et al. have suggested that the high solvatechromic
effects were related with a large second-order optical non-
linearity.[26] Chromophore FTC-z-1 shows larger shift of absorp-
tion (87 nm) than chromophore FTC-z-2 (68 nm). Maybe the
first-order hyperpolarizability is reduced, due to the introduction
of bulky flexible chain in TCP acceptor.
The UV–Vis absorption spectrum changes of EO films were
employed to describe the chromophore alignment, as shown
in Fig. 2. After the corona poling, the dipole moments of
the chromophore moieties in the polymer were aligned, and
the absorption curve decreased due to birefringence. From the
absorption change, the order parameter (F) for polymer can be
calculated according to the following equation:
A1
F ¼ 1 ꢁ
(1)
A0
where A1 and A0 are the absorbances of the polymer film after
and before cornona poling, respectively. The F value of the poled
film contained chromophore FTC-z-2 is about 24%, but the order
parameter of the film contained FTC-z-1 is only 18%. It indicates
that the dendritic moieties make the chromophore molecular
radius increase largely, the interaction among the dendritic
chromophore molecules is less and the material is easier to be
polarized.
The thermal stabilities of the chromophores were investigated
by TGA under nitrogen, with a heating rate of 10 8Cminꢁ1
.
The results are listed in Table 1 and the weight loss diagrams
are attached (Fig. 1). This result indicates that both the
chromophores are thermally stable with decomposition tem-
peratures higher than 260 8C. From Table 1, we can see that
decomposition temperature of the chromophore with dendron
in the TCP acceptor is a little higher than the chromophores
without dendron.
A reflective EO polymer light modulator was fabricated using
the EO material. The EO characterization of the EO film in this
modulator was conducted by an improved ATR technique. The
Table 1. Properties of chromophores
l
max(THF)
(nm)
e(THF)
l
max(DCM)
nm
e(DCM)
Dlmax
(nm)
g33
(pmVꢁ1
Chromophore
(L molꢁ1 cmꢁ1
)
(L molꢁ1 cmꢁ1
)
pV (V)
)
Td (8C)
FTC-z-1
FTC-z-2
782
805
50702
57425
869
873
71250
74851
87
68
11000
12000
147
217
261
279
pV is the polarization voltage the chromophore can bear.
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Copyright ß 2010 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 439–444

SYNTHESIS AND PROPERTIES OF PYRROLINE CHROMOPHORES
Scheme 2. Syntheses of the chromophores.
ATR spectrum of this multilayer waveguide system for
TM-polarized light of l ¼ 1310 nm was obtained through angular
scanning, which was carried out by a computer-controlled u/2u
goniometer. Several resonance dips correspond to different
guide modes. Since the width of the dip is a function of the loss
and determines the driving voltage, TM1 mode, which has the
narrowest resonance width and means the largest k value in
Eqn (2), is used as the working probe. The working angle is
chosen at the midst of the fall-off of the reflection dip, where
the linearity is fairly good. When applying an electrical field of
V ¼ 40 V (peak-to-peak) at a frequency of 50 kHz to the electrode
across the poled polymer, the polymer refractive index will
change due to Pockels effect and the propagation constant of the
guided wave will change. So the energy coupling efficiency and
Figure 1. TGA curves of the chromophores.
Figure 2. UV–Vis spectra of EO films before and after poling.
J. Phys. Org. Chem. 2011, 24 439–444
Copyright ß 2010 John Wiley & Sons, Ltd.
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J. LIU ET AL.
light reflectivity can be electrically modulated. The stable traces
of the modulation drive voltage and the reflected light intensity
were observed through an oscilloscope.
Syntheses
1 3,5-Bis(2’-ethylhexyloxy)benzyl bromide (2)
The EO coefficients (r33) of the films are also summarized in
Table 1. The poled film shows very high EO coefficient up to
217 pmVꢁ1 for chromophore FTC-z-2/APC, this value is excep-
tionally large compared to the poled film forFTC-z-1/APC
(147 pmVꢁ1). Such a great increase in EO activity is attributed
to structural features of the chromophore. The rigid–flexible
dendron in the end of the chromophore provides effective site
isolation to decrease the strong electrostatic interactions among
chromophore molecules. The chromophores with similar struc-
ture with chromophore FTC-z-1 in literature[6] showed an r33
of 51 pmVꢁ1, the difference between the chromophore in
literature[6] and chromophore FTC-z-1 was that we instead of
the simple thiophene electron bridge with 3,4-dihexyloxy
thiophene electron bridge. There were three reasons for such
a great increase in EO activity. The first one is that the oxygen
atom in the thiophene increased the electron density of the
conjugated system, which made the first-order hyperpolariz-
ability larger than the chromophore without oxygen atom in
the thiophene electron bridge. The second reason is that the
large flexible chain in the thiophene electron bridge decreased
the electrostatic interactions among chromophore molecules.
The third one is that the wavelength used to measure r33 in
literature[6] is 1550 nm, we measured it in 1310 nm, the
wavelength has a great impact on r33.[27]
2-Ethylhexyl bromide (9.6 g, 0.050 mol), 3,5-dihydroxybenzyl
alcohol (2.9 g, 0.021 mol), anhydrous potassium carbonate (5 g),
and dibenzo-18-crown-6 in catalytic amount were dissolved in
50 ml anhydrous DMF, and kept at 70 8C under stirring in N2
atmosphere for 24 h. The mixture was poured into 100 ml water.
The organic phase was then extracted twice with ether
*
(2 100 ml), washed with water, and dried over Na2SO4. The
solvent was then removed, obtaining a yellow oil, which is
3,5-bis(20-ethylhexyloxy)benzylalcohol (1). Yield: 71%. The crude
product was used in the next step directly.
3,5-bis(20-ethylhexyloxy)benzyl alcohol (1 g, 2.7 mmol) and
tetrabromomethane (1.1 g, 3.4 mmol) were dissolved in 20 ml
THF, under stirring in N2 atmosphere at room temperature.
After the entire solid dissolved, Triphenyl phosphorous (0.88 g,
3.4 mmol) was added. After half an hour, the mixture was poured
into 50 ml water. The organic phase was then extracted twice
*
with dichloromethane (2 50 ml), washed with water and dried
over Na2SO4. The crude product was purified with short column
chromatography. Yield: 75%. IR(KBr), ymax/cmꢁ1: 2929, 2873,
1460, 947, 841, 695; MS, m/z: 426(Mþ); 1H NMR(300 MHz,
CD3COCD3), d: 6.60(s, 2H), 6.44(s,1H), 4.53(s,2H), 3.86(t, 4H),
2.04(m, 2H), 1.45(m, 8H), 1.33(m, 8H), 0.91(t, 6H), 0.86(t, 6H).
3, 4-Bis (hexyloxy) thiophenmethanol (4)
The solution of 3, 4-bis (hexyloxy)-2-thiophene (2.84 g, 10 mmol)
in 5.5 ml DMF and 35 ml 1,2-dichloroethane was stirred and
cooled to 0 8C, then 5.4 ml phosphorus oxychloride was added
dropwise to the solution. The mixture was refluxed for 2 h,
cooled to room temperature and poured to 150 ml solution of
sodium carbonate (20%). The water phase was then extracted
CONCLUSIONS
New NLO chromophores with TCP acceptors and rigid–flexible
dendron as spacers have been synthesized and characterized.
The Uv–Vis data indicate that the chromophores have large
solvatachromic effects. Thermal tests by TGA indicate that the
TCP chromophores possess the high decomposition tempera-
ture. The NLO measurements of chromophores doped polymer
films indicated the relatively large macroscopic EO activities.
Typically, the EO coefficient of 217 pmVꢁ1 for chromophore
FTC-z-2 doped polymer system was obtained at 1310 nm. In
summary, these outstanding properties associated with the
chromophores are indicative of very promising candidates
for practical applications in the field of electro-optics and
photonics.
*
twice with ether (2 150 ml). The organic phase was dried over
magnesium sulfate, and then the ether was removed by
evaporation under reduced pressure. The yield of 3,4-bis
(hexyloxy)thiophenecarboxaldehyde (3) was 2.96 g (95%).
The solution of 3, 4-bis (hexyloxy)thiophenecarboxaldehyde (3)
(3 g, 9.6 mmol) in 30 ml methanol was cooled to 0 8C, 0.2 g sodium
hydride was added. The mixture was stirred for 24 h, and then
the methanol was removed. The solution was acidificated by
hydrochloric acid and extracted twice with ether, and dried over
magnesium sulfate. The yield of compound was 3 g (99%). MS
(MALDI-TOF), m/z: 314 (Mþ), 1H NMR (300 MHz, CD3COCD3), d:
6.1(s, 1H), 4.7(s, 2H), 4.0(m, 2H), 3.9(m, 2H), 1.7(m, 4H), 1.45(m, 4H),
1.3(m, 8H), 0.9 (t, 6H).
EXPERIMENTAL
3, 4-Bis (hexyloxy){4-[N,N-di [2-(acetyloxy) ethyl] amino] styryl}
thiophene (6)
Materials and characterization
All the reagents were used as received unless stated. DMF
and POCl3 were freshly distilled prior to use; TCP acceptor was
prepared according to the literature.[6] 1H NMR spectra were
determined by Varian Gemini 300 (300 MHz) NMR spectrometer
(tetramethylsilane as internal reference). FT-IR spectra were
recorded on BIO-RAD FTS-165 spectrometer; MS spectra were
obtained on MALDI-TOF (Matrix Assisted Laser Desorption/
Ionization of Flight) on BIFLEX III (Bruker Inc.) spectrometer.
UV–Vis spectra were performed on Hitachi U2001 photo spectro-
meter. TGA was determined by TA5000-2950TGA (TA co) with a
heating rate of 10 8Cminꢁ1 under the protection of nitrogen.
The mixture of 3,4-bis(hexyloxy)thiophenmethanol (4) (3 g,
9.6 mmol), PPh3HBr (3 g, 8.7 mmol), and 50 ml chloroform was
refluxed for 3 h, and then the chloroform was removed. 50 ml
ether was added and filtrated. After the ether was removed, the
compound 6 precipitated. The yield was 5 g (82%).
The solution of compound 6 (4 g, 6.4 mmol), NaH (5.5 g) and
4-[N,N-bis[2-(acetyloxy)ethyl]amino]benzaldehyde (1.9 g, 6.4 mmol)
in 100 ml ether was stirred at room temperature for 24 h under
N2 atmosphere, then poured into 200 ml water. The mixture was
*
then extracted twice with ether (2 200 ml), dried over magnes-
ium sulfate, 3,4-bis (hexyloxy){4-[N,N-di [2-(acetyloxy) ethyl]
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Copyright ß 2010 John Wiley & Sons, Ltd. J. Phys. Org. Chem. 2011, 24 439–444

SYNTHESIS AND PROPERTIES OF PYRROLINE CHROMOPHORES
amino] styryl} thiophene (6) was purified with short column
chromatography. The yield was 1 g (27%). MS (MALDI-TOF), m/z:
141.4, 136.4, 134.6, 130.7, 123.1, 122.8, 112.6, 112.3, 76.0, 74.8,
62.7, 61.9, 54.4, 48.8, 32.6, 31.4, 26.7, 23.5, 18.8, 14.5, ꢁ5.0.
1
573(Mþ); H NMR(300 MHz, CD3COCD3), d: 7.3(d, 2H), 7.15(s, 1H),
7.0(d, 1H), 6.7(d, 2H), 6.0(d, 1H), 4.2(t, 4H), 4.1(t, 2H), 3.9(t, 2H), 3.6(t,
4H), 2.1(s, 6H), 1.7(m, 4H), 1.45(m, 4H), 1.3(m, 8H), 0.9 (t, 6H).
Chromophore FTC-z-2
Potassium carbonate (2.0 mmol) was added by steps to
the solution of chromophore FTC-z-1 in 2 ml acetonitrile,
the solution was heated to 65 8C for 10 min. Then the
3,5-bis(20-ethylhexyloxy)benzyl bromide (1.0 mmol) was added
slowly. The mixture was refluxed for 2 h. After the solvent was
removed, the product was purified with short column chroma-
tography. Yield: 63%, UV–Vis(CH3COCH3): lmax ¼ 826.5 nm, MS
(MALDI-TOF), m/z: 1260(Mþ); 1H NMR(300 MHz, CD3COCD3), d:
7.26(d, 2H), 6.52(m, 6H), 6.40(s, 3H), 4.41(m, 6H), 3.81(m, 12H),
1.71(m, 6H), 1.45(m, 8H), 1.32(m, 20H), 0.90(m, 36H), 0.15(s, 12H);
13C NMR (100 MHz, CD3COCD3): d (ppm) 166.7, 163.5, 161.9, 150.8,
147.9, 145.2, 142.4, 138.5, 136.6, 135.4, 130.4, 124.5, 120.3, 114.0,
113.1, 11.2.7, 105.9, 100.9, 75.8, 75.0, 71.1, 61.4, 54.3, 45.2, 40.3,
32.5, 32.4, 31.3, 30.9, 26.3, 24.6, 23.7, 23.4, 18.8, 14.5, 11.7, ꢁ5.0.
3,4-Bis(hexyloxy)-2-{4-[N,N-bis
[2-(acetyloxy)ethyl]amino]styryl}thiophenecarboxaldehyde (7)
The solution of 3,4-bis (hexyloxy){4-[N,N-di [2-(acetyloxy) ethyl]
amino] styryl} thiophene (6) (1 g, 13.4 mmol) in 40 ml DMF was
stirred and cooled to 0 8C. Then phosphorus oxychloride (1.7 ml)
was added dropwise to the solution. After the phosphorus
oxychloride being added, the temperature was raised to 90 8C
slowly, and kept for 3 h, then cooled to room temperature. The
mixture was poured into 150 ml solution of sodium carbonate
*
(10%), extracted twice with chloroform (2 100 ml), washed
with water, and dried over magnesium sulfate. 3,4-bis(hexyloxy)-
2-{4-[N,N-bis [2-(acetyloxy)ethyl]amino]styryl} thiophenecarbox-
aldehyde (7) was purified with short column chromatography.
The yield was 0.6 g (29%). MS (MALDI-TOF), m/z: 601(Mþ); 1H
NMR(300 MHz, CD3COCD3), d: 10.0(s, 1H), 7.3(d, 2H), 7.2 (d, 1H),
7.0(d, 1H), 6.7(d, 2H), 4.2(t, 4H), 4.1(t, 2H), 3.9(t, 2H), 3.6(t, 4H), 2.1(s,
6H), 1.7(m, 4H), 1.45(m, 4H), 1.3(m, 8H), 0.9(t, 6H).
EO modulator fabrication and NLO properties measurement
An EO ATR modulator, whose cross-section view is shown in Fig. 3,
was fabricated using the chromophores doped APC as EO
material. The modulator consists of five parts: (1) a high index
prism, (2) a thin silver film as the coupling layer and the top
electrode, (3) a poled EO film as the guiding layer, (4) a ITO glass
as the bottom electrode.[18,20] The silver film was sputtered onto
the hypotenuse face of a high index prism served as the top
electrode. The EO film was spin-coated onto ITO glass substrate
with a thickness of 1.5–3 mm depending on the polymer solution
concentration and the spin rate. The corona poling was
performed to make the chromophore dipoles aligned along
the direction of the electric field. Finally, the ITO glass with EO film
was press on the prism with silver film.
3,4-Bis(hexyloxy)-2-{4-[N,N-di[2-hydroxyethyl]
amino]styryl}thiophenecarboxaldehyde (8)
The solution of 3,4-bis(hexyloxy)-2-{4-[N,N-bis [2-(acetyloxy)-
ethyl]amino]styryl}thiophenecarboxaldehyde (7) (0.6 g, 1 mmol)
in 25 ml methanol was kept for 40 8C, and then 10 ml solution
of potassium carbonate (10%) was added. And the temperature
was raised to 80 8C, and kept for 6 h. After the methanol
and water removed, the solid was dissolved in alcohol,
and filtrated. Remove the alcohol of the solution, and
3,4-bis(hexyloxy)-2-{4-[N,N-di[2-hydroxyethyl]amino]styryl}thiop-
henecarboxaldehyde (8) precipitated. The yield was 0.42 g (94%).
The EO coefficient of active polymer layer in the EO modulator
can be determined according to the following equation:
1
Mþ: 517; H NMR(300 MHz, CD3COCD3), d: 10.0(s, 1H), 7.3(d, 2H),
2l IAC @n
n3 IDC @u
r33
¼
ꢀ
ꢀ
(2)
7.2 (d, 1H), 7.0(d, 1H), 6.7(s, 2H), 6.0(s, 1H), 4.2(t, 4H), 4.1(t, 2H),
3.9(t, 2H), 3.6(t, 4H), 1.7(m, 4H), 1.45(m, 4H), 1.3(m, 8H), 0.9(t, 6H).
where r33 is the EO coefficient of the poled polymer layer; n is the
refractive indices of the polymer film; IAC is the modulated light
Chromophore FTC-z-1
The solution of 3,4-bis(hexyloxy)-2-{4-[N,N-di[2-hydroxyethyl]-
amino]styryl}thiophenecarboxaldehyde (8) (0.52 g, 1 mmol), imi-
dazole (0.8 g, 10 mmol) and tert-butyldimethylsilyl chloride
(0.75 g, 5 mmol) in 25 ml DMF, was kept in room temperature
for 8 h, then poured into 200 ml water, extracted twice with ethyl
*
acetate (2 50 ml). After removed the ethyl acetate, the crude
product was purified with short column chromatography. The
yield of compound 9 was 0.46 g (62%).
The solution of compound 9 (0.46 g) and TCP acceptor (0.6 g) in
5 ml alcohol was kept at 70 8C for 2 h. After removed the alcohol,
the crude product was purified with short column chromatog-
raphy using petroleum ether as eluent to afford chromophore
FTC-z-1 as a green solid (0.25 g), 79%. UV–Vis(CH3COCH3):
lmax ¼ 796.5 nm; MS (MALDI-TOF), m/z: 911(Mþ); 1H NMR-
(300 MHz, CD3COCD3), d: 8.81(d, 1H), 8.05(d, 1H), 7.41(d, 2H),
7.13(d, 1H), 7.09(d, 1H), 6.81(s, 1H), 6.73(d, 2H), 4.35(t, 2H), 4.02(t,
2H), 3.79(t, 4H), 3.59(t, 4H), 1.78(m, 4H), 1.50(m, 4H), 1.35(m, 4H),
1.25(m, 4H), 0.92(t, 6H), 0.85 (s, 18H), 0.15(s, 12H); 13C NMR
(100 MHz, CD3COCD3): d (ppm) 167.0, 157.2, 150.6, 147.3, 145.0,
Figure 3. Schematic diagram of the ART modulator.
J. Phys. Org. Chem. 2011, 24 439–444
Copyright ß 2010 John Wiley & Sons, Ltd.
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J. LIU ET AL.
intensity; IDC is the reflected light intensity; u is the light incident
angle which is defined as the modulator’s working interior angle.
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We are grateful to the Chinese Academy of Science Knowledge
Innovation Project Key Direction Project foundation (KJCX2.HO2)
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