A 3-phenoxypropane-1, 2-diol based bichromophore for enhanced nonlinear optical properties

Article abstract of DOI:10.1016/j.dyepig.2010.03.027

The structure of a novel bichromophore that comprised a readily hyperpolarisable chromophore with 3-phenoxypropane-1, 2-diol via esterification, was confirmed by elemental analysis, UV-visible absorption spectra and ¹H NMR. Nonlinear optical polymer films were fabricated by doping the bichromophore and the corresponding monochromophore into poly(4-vinylphenol). In situ second harmonic generation measurements revealed that the bichromophore imparted a 2.2-fold enhancement in the second harmonic generation coefficients of the films, indicating that the novel 3-phenoxypropane-1, 2-diol derivative could be used in the design and synthesis of multi-chromophoric dendrimers with large macroscopic optical nonlinearity.

Full text of DOI:10.1016/j.dyepig.2010.03.027

Dyes and Pigments 87 (2010) 204e208
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
A 3-phenoxypropane-1, 2-diol based bichromophore for enhanced
nonlinear optical properties
*
*
Junkuo Gao, Yuanjing Cui , Jiancan Yu, Wenxin Lin, Zhiyu Wang, Guodong Qian
State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The structure of a novel bichromophore that comprised a readily hyperpolarisable chromophore with
3-phenoxypropane-1, 2-diol via esterification, was confirmed by elemental analysis, UVevisible
absorption spectra and 1H NMR. Nonlinear optical polymer films were fabricated by doping the
bichromophore and the corresponding monochromophore into poly(4-vinylphenol). In situ second
harmonic generation measurements revealed that the bichromophore imparted a 2.2-fold enhancement
in the second harmonic generation coefficients of the films, indicating that the novel 3-phenoxypropane-
1, 2-diol derivative could be used in the design and synthesis of multi-chromophoric dendrimers with
large macroscopic optical nonlinearity.
Received 20 February 2010
Received in revised form
30 March 2010
Accepted 30 March 2010
Available online 7 April 2010
Keywords:
Nonlinear optics
Bichromophore
Tether groups
Ó 2010 Elsevier Ltd. All rights reserved.
Second harmonic generation
Esterification
Poled polymer
1. Introduction
tether cores. Multichromophores using different tether groups have
been widely studied, such as bichromophore and trichromophore
Organic second-order nonlinear optical (NLO) materials have
attracted great interest owing to their potential application in
electro-optic (EO) modulation, optical switching and optical infor-
mation processing [1e5]. Compared with inorganic materials,
organic NLO materials display many advantages such as high EO
coefficient, low dielectric constant, ease of processing and device
integration [6,7]. To generate macroscopic optical nonlinearity,
readily hyperpolarisable chromophores have been incorporated in
a nonlinear optically inactive polymeric host matrix and poled using
an electrical field so as to obtain a noncentrosymmetric arrange-
ment [8,9]. However, a major challenge for this approach is to
bundles, three-armed multi-chromophoric dendrimers, 9,10-dihy-
droanthrancene based azo-type bichromophores, calix[4]arene
linked multichromophores and tris(allyl) silane based trichromo-
phores [19e23]. Multichromophores display larger EO coefficients
than monochromophores [1,24].
This paper describes a simple approach for the design and
synthesis of bichromophores that show enhanced bulk nonlinearity
due to their supramolecular morphology. The bichromophore B1
comprises 1,3-phenoxypropane-1, 2-diol as the tether group;
a typical TCF-type chromophore 1 with large
b was chosen as the
monochromophore [25] (Fig. 1). The bichromophore was synthe-
sized by connecting the carboxylic acid functionalized mono-
chromophore with 3-phenoxypropane-1, 2-diol via esterification.
convert the high hyperpolarisability (b) of the chromophore to large
macroscopic optical nonlinearity in the polymer, because of strong
inter-chromophore dipoleedipole interactions which are detri-
mental to the realisation of large nonlinear susceptibility [10e13].
In recent years, multi-chromophoric dendritic NLO materials
have been introduced as an efficient means of reducing such inter-
chromophore electrostatic interactions and achieving large EO
coefficients [14e18]. Generally, multichromophores are synthe-
sized by incorporating chromophores with tether groups and
2. Experimental
2.1. Materials and measurements
All chemicals were purchased from Aldrich and Alfa Aesar and
used as received. Dichloromethane and DMF were distilled over
drying agents before use; all other solvents were commercially
available and were used without further purification.
UVevisible absorption spectra were obtained using a Per-
kineElmer Lambda 20 spectrophotometer, mass spectrometry
* Corresponding authors. Tel.: þ86 571 87952334; fax: þ86 571 87951234.
E-mail addresses: cuiyj@zju.edu.cn (Y. Cui), gdqian@zju.edu.cn (G. Qian).
0143-7208/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2010.03.027

J. Gao et al. / Dyes and Pigments 87 (2010) 204e208
205
4-dimethylaminopyridine (DMAP; 0.90 g) and pyridine (0.3 mL)
were added. The reaction mixture was stirred at room temperature
overnight and then washed with brine and water. The organic
phase was dried over Na2SO4, and the solvent was removed under
reduced pressure. The residue was purified by silica column chro-
matography using 5% ethanol in CH2Cl2 as the eluent. Yield: 78%. 1H
NMR (500 MHz, DMSO-d6, d ppm): 1.76 (s, 6H, C(CH3)2), 2.34 (d, 2H,
COCH2), 2.41 (m, 2H, CH2COOH), 3.10 (m, 3H, NCH3), 3.77 (d, 2H,
NCH2), 4.23 (d, 2H, CH2O), 6.87e6.91 (d, 3H, ArH, CH]CH), 7.78 (d,
2H, ArH), 7.91 (d, 1H, CH]CH). MS (ESI): exact mass calcd for
C25H24N4O5 [M ꢁ H]ꢁ, 459.1. Found: 459.1.
Fig. 1. Structure of compound 1 and B1.
performed on a Bruker Daltonics esquire3000plus mass spectrom-
eter. High resolution mass analysis was obtained using a Bruker
Apex III (7.0 T) FTICR mass spectrometer. 1H NMR and 13C NMR
spectra were taken on a Bruker Avance DMX500 spectrometer
using tetramethysilane (TMS) as an internal standard. Elemental
analyses were obtained from a Thermo Finnigan Flash EA1112
microelemental analyzer. Differential scanning calorimetry (DSC)
was performed using a Netzsch Instruments 200 F3 with a heating
rate of 10 ꢀC min-1 in nitrogen atmosphere. Thermalgravimetric
analysis (TGA) was performed using a TA Instruments SDT Q600 at
a heating rate of 10 ꢀC minꢁ1 under nitrogen atmosphere. Film
thicknesses were measured using a Tencor alfa-step 200 surface
profilometer. The second harmonic generation (SHG) coefficient
(d33) of the poled film was measured using a Q-switched Nd:YAG
laser at 1064 nm and a Y-cut quartz crystal (d11 ¼ 0.5 pm Vꢁ1) was
used as the reference [26e29].
2.4. Synthesis of compound B1
3-phenoxypropane-1,2-diol (1 mmol, 0.168 g) and compound 2
(2.2 mmol, 1.01 g) were dissolved in CH2Cl2 (80 mL). Dicyclohex-
ylcarbodiimide (DCC; 2.2 mmol, 0.45 g) and DMAP (1 mmol, 0.12 g)
were added and the ensuing mixture was stirred at room temper-
ature for 24 h. The resulting solution was diluted with CH2Cl2
(100 mL) and washed with brine and water. The organic phase was
dried over MgSO4 and the solvent was removed under reduced
pressure. The product was obtained by silica column chromatog-
raphy using 10% ethyl acetate in CH2Cl2 as the eluent. Yield: 71%. 1H
NMR (500 MHz, DMSO-d6,
d ppm): 1.75 (s, 12H, C(CH3)2), 2.59 (m,
8H, COCH2), 3.13 (s, 6H, NCH3), 3.72 (t, 4H, NCH2), 4.10 (d, 2H,
CCH2O), 4.30 (s, 4H, OCH2), 4.33(d, 1H, higher field branch of AB
quartet, ArOCH2), 4.41 (d, 1H, lower field branch of AB quartet,
AreOeCH2), 5.37(s, 1H, CHCH2), 6.76 (d, 4H, ArH; CH]CH,
J ¼ 16 Hz), 6.88 (d, 2H, ArH), 6.97 (s, 1H, ArH), 7.28 (d, 2H, ArH), 7.54
(d, 4H, ArH), 7.60 (d, 2H, CH]CH, J ¼ 16 Hz). 13C NMR (125 MHz,
2.2. Synthesis of compound 1
DMSO-d6,
d ppm):177.855, 176.075, 172.363, 172.276, 172.155,
Chromophore 1 was prepared according to the literature [30]. To
solution of 4-((2-hydroxyethyl)(methyl)amino)benzaldehyde
171.940, 158.491, 153.482, 149.763, 133.293, 130.060, 122.774,
121.616, 115.084, 113.947, 113.117, 112.842, 112.424, 109.279, 98.818,
93.179, 70.179, 66.429, 62.663, 61.998, 51.795, 50.549, 39.200,
29.060, 28.896, 26.134. Elemental analysis calcd (%) for
C59H56N8O11: C, 67.290; H, 5.36; N, 10.64. Found: C, 67.66; H, 5.60;
N, 10.36. MS (ESI): exact mass calcd for C59H56N8O11 [M], 1052.4.
Found: 1051.9. HRMS (ESI): exact mass calcd for C59H56N8O11
[M þ K]þ, 1091.3700. Found: 1091.3645.
a
(1.78 g, 10 mmol) and 2-(3-cyano-4,5,5- trimethylfuran-2(5H)-yli-
dene)malononitrile (2.3 g, 11 mmol) in absolute ethanol (60 mL), 12
drops of piperidine were added. The reaction mixture was refluxed
for 6 h with stirring and then cooled to room temperature. The blue
solid was filtered and recrystallized from ethanol. Yield: 69%. 1H
NMR (500 MHz, DMSO-d6, d ppm): 1.75 (s, 6H, C(CH3)2), 3.12 (s, 3H,
N(CH3)), 3.58e3.59 (d, 4H, NCH2CH2), 4.78 (s, 1H, OH), 6.85e6.87
(d, 3H, ArH, CH]CH), 7.75e7.77 (d, 2H, ArH), 7.90e7.94 (d,1H, CH]
CH). Elemental analysis calcd (%) for C21H20N4O2: C, 69.98; H, 5.59;
N, 15.55. Found: C, 69.76; H, 5.55; N, 15.43.
2.5. Thin film fabrication
Each compound was mixed with solid PVPh. The solid compo-
nents were then dissolved into cyclopentanone (8% of total solid
weight). The solutions were stirred in a vial for 1 h and then filtered
2.3. Synthesis of compound 2
through a 0.22 mm Teflon membrane filter and spin-coated on the
To a solution of 1 (0.29 g, 0.84 mmol) and succinic anhydride
(0.09 g, 0.9 mmol) in anhydrous dichloromethane (30 mL),
indium-tin oxide (ITO) glass substrates. The films were then dried
in a vacuum oven at 85 ꢀC for 10 h to remove the residual solvent.
Scheme 1. Synthesis of bichromophore B1.

206
J. Gao et al. / Dyes and Pigments 87 (2010) 204e208
3. Results and discussion
1.0
0.9
0.8
5 wt.-%
10 wt.-%
15 wt.-%
20 wt.-%
3.1. Synthesis and characterization
The detailed synthetic procedure of bichromophore B1 was pre-
sented in Scheme 1. Chromophore 1 was synthesized via Knoeve-
nagel reaction of 4-((2-hydroxyethyl)(methyl)amino) benzaldehyde
with TCF acceptor 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)
malononitrile. The reaction between succinic anhydride and chro-
mophore 1 produced the carboxylic acid functionalized chromo-
phore 2 to create an attachment point. Compound 2 was then
attached to 3-phenoxypropane-1,2-diol via esterification under DCC
coupling conditions to create bichromophore B1. The reaction was
performed in anhydrous CH2Cl2 with 4-(dimethylamino)-pyridine
(DMAP) as a catalyst and the mixtures were stirred overnight with
the satisfied yield (71%). The structure of B1 was confirmed by
elemental analysis,1H NMR and mass spectrometry. The details of the
synthesis and characterizations are provided in the Experimental
Section.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
450
500
550
600
650
700
Wavelength (nm)
Fig. 3. UVeVisible absorption spectra of thin films of chromophore 1 in PVPh with
different loading densities.
Thermal properties of compound 1 and B1 were explored by
thermalgravimetric analysis (TGA) and differential scanning calo-
rimetry (DSC). The decomposition temperature (Td) of compound
1 and B1 were 283 ꢀC and 300 ꢀC respectively. Bichromophore B1
showed much higher thermal stability than chromophore 1.
Compound 1 displayed a melting point (Tm) of 281 ꢀC. Bichro-
mophore B1 showed a range of glass transition temperature (Tg)
instead of melting point which was about 78 ꢀC. It was attributed
to the long and flexible tether group that connected the mono-
chromophore 1 together.
sub-chromophores in B1 [21,31,32]. Also, the absorption spectra
was slightly broadened from monomer to bichromophore, which is
could be resulted from the larger conformational disorder in the
bichromophore [32,33]. The same trend was also observed in DMF.
NLO polymer films containing bichromophore B1 (Film-B1)
were fabricated by choosing poly(4-vinylphenol) (PVPh) as polymer
matrix. The molecule loading densities were up to 20 wt% without
phase separation. Chromophore 1 doped polymer films (Film-1)
were also prepared and compared with B1 doped films in the same
doping level, since the active chromophore units were almost the
same in the same molecule loading densities. The thickness of the
films was in the range of 500e600 nm. The UVevisible absorption
spectra of Film-1 and Film-B1 in different doping levels are shown
in Figs. 3 and 4. The lmax of Film-1 was about 607 nm, and a red shift
was occurred compared with that of chromophore 1 in solvents.
A slight shoulder (571 nm) was observed with the increasing of
molecule density. It was attributed to the H-type aggregation of
the molecules which lead to the blue shift of the linear absorption
maximum [25,34,35]. The lmax of Film-B1 was about 594 nm, and
a shoulder also appeared around 560 nm with the increase of
doping level which was resulted from H-type aggregation of the
bichromophores. When the molecular loading density was 20 wt%,
the lmax of B1 in PVPh shifted to 560 nm.
3.2. Linear and nonlinear optical properties
The linear optical properties of bichromophore B1 were studied
by UVevisible absorption spectra. Fig. 2 shows the UVevis spectra
of chromophore 1 and bichromophore B1 in tetrahydrofuran (THF)
and DMF. The maximum absorption wavelengths (lmax) of B1 are
546 nm in THF and 573 nm in DMF and show a red shift of 27 nm
with the increase of solvent polarity. This behavior is quite similar
with that of monochromophore 1, while the lmax of 1 shows a red
shift of 24 nm from THF (563 nm) to DMF (587 nm). The red shift
was attributed to the functional monochromophore in B1 since
chromophore 1 shows red shift behaviors with the increase of
solvent polarity. In THF, the lmax of B1 displayed a blue shift of
17 nm compared with that of compound 1. This blue shift may
be attributed to the spatial interactions between the two
5 wt.-%
10 wt.-%
15 wt.-%
1.0
1 in DMF
B1 in DMF
1 in THF
1.2
0.8
0.6
0.4
0.2
0.0
20 wt.-%
1.0
B1 in THF
0.8
0.6
0.4
0.2
0.0
400
450
500
550
600
650
700
400
500
600
700
Wavelength (nm)
Wavelength (nm)
Fig. 4. UVeVisible absorption spectra of thin films of bichromophore B1 in PVPh with
Fig. 2. UVevisible absorption spectra of compound 1 and B1 in THF and DMF.
different loading densities.

J. Gao et al. / Dyes and Pigments 87 (2010) 204e208
207
References
55
50
45
40
35
30
25
20
15
[1] Jang SH, Jen AKY. Electro-Optic (E-O) molecular glasses. Chemistry-An Asian
Journal 2009;4:20e31.
[2] Dalton LR, Sullivan PA, Bale DH. Electric field poled organic electro-optic
materials: state of the art and future prospects. Chemical Reviews
2010;110:25e55.
[3] Marder SR, Kippelen B, Jen AKY, Peyghambarian N. Design and synthesis of
chromophores and polymers for electro-optic and photorefractive applica-
tions. Nature 1997;388:845e51.
[4] Luo JD, Zhou XH, Jen AKY. Rational molecular design and supramolecular
assembly of highly efficient organic electro-optic materials. Journal of Mate-
rials Chemistry 2009;19:7410e24.
[5] Hochberg M, Baehr-Jones T, Wang GX, Shearn M, Harvard K, Luo JD, et al.
Terahertz all-optical modulation in a siliconepolymer hybrid system. Nature
Materials 2006;5:703e9.
[6] Lee M, Katz HE, Erben C, Gill DM, Gopalan P, Heber JD, et al. Broadband
modulation of light by using an electro-optic polymer. Science
2002;298:1401e3.
a
b
4
6
8
10 12 14 16 18 20 22
[7] Facchetti A, Abbotto A, Beverina L, van der Boom ME, Dutta P, Evmenenko G,
et al. Layer-by-layer self-assembled pyrrole-based donor-acceptor chromo-
phores as electro-optic materials. Chemistry of Materials 2003;15:1064e72.
[8] Firestone KA, Reid P, Lawson R, Jang SH, Dalton LR. Advances in organic
electro-optic materials and processing. Inorganica Chimica Acta 2004;
357:3957e66.
Molecule densities (wt.-%)
Fig. 5. d33 values of polymer films as a function of molecule loading densities of
compound 1 and B1: a, Film-B1; b, Film-1.
[9] Dalton LR. Organic electro-optic materials. Pure and Applied Chemistry
2004;76:1421e33.
The second-order NLO properties of the polymer films were
characterized by SHG measurement using the Maker fringe tech-
nique [36,37]. The second harmonic coefficient (d33) of the film can
be calculated by comparison with the SHG intensity of a standard
Y-cut quartz crystal plate. The films were poled by applying a 6 kV
dc voltage. The d33 values of the films were shown in Fig. 5. With
the increase of molecule loading densities, the d33 values of Film-
B1 showed almost linear improvement. The highest d33 values was
51 pm Vꢁ1 when the loading density was 20%. The d33 values of
Film-1 was up to 23 pm Vꢁ1 when the molecule loading density
was 20%. A 2.2-fold enhancement in the second harmonic coeffi-
cient was achieved in bichromophore B1 doped polymer films
compared with monochromophore 1 doped films. The results
indicated that 3-phenoxypropane-1, 2-diol linked bichromophore
could efficiently improve the bulk optical nonlinearities of organic
materials due to its supramolecular morphology. 3-phenox-
ypropane-1, 2-diol derivatives can be easily synthesized by the
reaction between 3-chloropropane-1, 2-diol and phenols
compounds under basic conditions [38]. It provides an efficient
approach to design and synthesize tether cores for the use of
multichromophore dendrimers.
[10] Dalton LR. Nonlinear optical polymeric materials: from chromophore design
to commercial applications. Advances in Polymer Science 2002;158:1e86.
[11] Robinson BH, Dalton LR. Monte carlo statistical mechanical simulations of the
competition of intermolecular electrostatic and poling-field interactions in
defining macroscopic electro-optic activity for organic chromophore/polymer
materials. Journal of Physical Chemistry A 2000;104:4785e95.
[12] Jang HN, No HJ, Lee JY, Rhee BK, Cho KH, Choi HD. The design, synthesis and
nonlinear optical properties of a novel, Y-type polyurethane containing tri-
cyanovinylthiophene of high thermal stability. Dyes and Pigments 2009;
82:209e15.
[13] Li ZA, Wu WB, Hu P, Wu XJ, Yu G, Liu YQ, et al. Click modification of azo-
containing polyurethanes through polymer reaction: convenient, adjustable
structure and enhanced nonlinear optical properties. Dyes and Pigments
2009;81:264e72.
[14] Shi ZW, Luo JD, Huang S, Cheng YJ, Kim TD, Polishak BM, et al. Controlled
Diels-Alder reactions used to incorporate highly efficient polyenic chromo-
phores into maleimide-containing side-chain polymers for electro-optics.
Macromolecules 2009;42:2438e45.
[15] Cho MJ, Lee SK, Jin JI, Choi DH, Dalton LR. Electro-optic property of chromo-
phore-terminated trifunctional dendrimer in a guest-host system. Thin Solid
Films 2006;515:2303e9.
[16] Sullivan PA, Akelaitis AJP, Lee SK, McGrew G, Lee SK, Choi DH, et al. Novel
dendritic chromophores for electro-optics: influence of binding mode and
attachment flexibility on electro-optic behavior. Chemistry of Materials
2006;18:344e51.
[17] Zhou XH, Luo JD, Huang S, Kim TD, Shi ZW, Cheng YJ, et al. Supramolecular
self-assembled dendritic nonlinear optical chromophores: fine-Tuning of
arene-perfluoroarene interactions for ultralarge electro-optic activity and
enhanced thermal stability. Advanced Materials 2009;21:1976e81.
[18] Kim TD, Kang JW, Luo JD, Jang SH, Ka JW, Tucker N, et al. Ultralarge and
thermally stable electro-optic activities from supramolecular self-assembled
molecular glasses. Journal of the American Chemical Society 2007;129:488e9.
[19] Ronchi M, Pizzotti M, Biroli AO, Righetto S, Ugo R, Mussini P, et al. Second-
order nonlinear optical (NLO) properties of a multichromophoric system
based on an ensemble of four organic NLO chromophores nanoorganized on
4. Conclusions
A new type of bichromophore was synthesized by using 3-
phenoxypropane-1,2-diol as the linking group. The esterification
between carboxylic acid functionalized TFC-type chromophore and
3-phenoxypropane-1, 2-diol under DCC coupling conditions
produced bichromophore B1. The d33 value of films containing B1
increased almost linearly with the increase of chromophore doping
levels. The highest d33 value was 51 pm Vꢁ1 (20 wt%), which was
about 2.2 times the value of the films containing chromophore 1.
The easy approach to synthesis and effective improvement in
macroscopic optical nonlinearity made 3-phenoxypropane-1, 2-
diol derivatives have potential applications in the design and
synthesis of multichrmomophore dendrimers with quite large EO
coefficients.
a
cyclotetrasiloxane architecture. Journal of Physical Chemistry
C
2009;113:2745e60.
[20] Zhang CZ, Lu CG, Zhu J, Lu GY, Wang X, Shi ZW, et al. The second-order
nonlinear optical materials with combined nonconjugated D-pi-A units.
Chemistry of Materials 2006;18:6091e3.
[21] Liao Y, Firestone KA, Bhattacharjee S, Luo JD, Haller M, Hau S, et al. Linear and
nonlinear optical properties of a macrocyclic trichromophore bundle with
parallel-aligned dipole moments. Journal of Physical Chemistry
B 2006;
110:5434e8.
[22] Datta A, Terenziani F, Painelli A. Cooperative interactions in supramolecular
aggregates: linear and nonlinear responses in calix[4]arenes. Chemphyschem
2006;7:2168e74.
[23] Rekai E, Baudin JB, Jullien L, Ledoux I, Zyss J, Blanchard-Desce M. A hyperpolar,
multichromophoric cyclodextrin derivative: synthesis, and linear and
nonlinear optical properties. Chemistry-a European Journal 2001;7:4395e402.
[24] Cho MJ, Choi DH, Sullivan PA, Akelaitis AJP, Dalton LR. Recent progress in
second-order nonlinear optical polymers and dendrimers. Progress in Poly-
mer Science 2008;33:1013e58.
[25] Chen LJ, Jin XF, Cui YJ, Qian GD, Wang MQ. Effect of triphenylamine agents as
screening moieties for electrostatic interaction in the nonlinear optical
response of hybrid organic-inorganic films. Thin Solid Films 2008;
516:4153e8.
Acknowledgements
The authors gratefully acknowledge the financial support for
this work from the National Natural Science Foundation of China
(Nos. 50625206, 50802084 and 50972127) and the Natural Science
Foundation of Zhejiang Province (No. Y4090067).

208
J. Gao et al. / Dyes and Pigments 87 (2010) 204e208
[26] Yu JC, Cui YJ, Gao JK, Wang ZY, Qian GD. Enhanced optical nonlinearity and
improved transparency of inorganic-organic hybrid materials containing
multichromophore assemblies: a case study. Chemistry-A European Journal
2006;12:3089e102.
benzimidazole chromophores. Journal of Physical Chemistry
113:14877e83.
[27] Cui YJ, Qian GD, Gao JK, Chen LJ, Wang ZY, Wang MQ. Preparation and
B
2009;
[33] Gao JK, Cui YJ, Yu JC, Wang ZY, Wang MQ, Qiu JR, et al. Molecular design and
synthesis of hetero-trichromophore for enhanced nonlinear optical activity.
Macromolecules 2009;42:2198e203.
nonlinear optical properties of inorganiceorganic hybrid films with various
[34] Priimagi A, Cattaneo S, Ras RHA, Valkama S, Ikkala O, Kauranen M. Polymer-
dye complexes: a facile method for high doping level and aggregation control
of dye molecules. Chemistry of Materials 2005;17:5798e802.
[35] Wurthner F, Yao S, Debaerdemaeker T, Wortmann R. Dimerization of
merocyanine dyes. Structural and energetic characterization of dipolar dye
aggregates and implications for nonlinear optical materials. Journal of the
American Chemical Society 2002;124:9431e47.
[36] Herman WN, Hayden LM. Maker fringes revisited: second-harmonic genera-
tion from birefringent or absorbing materials. Journal of the Optical Society of
America B 1995;12:416e28.
[37] Maker PD, Terhune RW, Nisenoff M, Savage CM. Effects of dispersion and
focusing on the production of optical harmonics. Physical Review Letters
1962;8:21e2.
[38] Bredikhin AA, Bredikhina ZA, Novikova VG, Pashagin AV, Zakharychev DV,
Gubaidullin AT. Three different types of chirality-driven crystallization within
the series of uniformly substituted phenyl glycerol ethers. Chirality
2008;20:1092e103.
substituents on chromophores. Journal of Physical Chemistry
B 2005;
109:23295e9.
[28] Cui YJ, Wang MQ, Chen LJ, Qian GD. Synthesis and characterization of an
alkoxysilane dye for nonlinear optical applications. Dyes and Pigments
2005;65:61e6.
[29] Cui YJ, Wang MQ, Chen LJ, Qian GD. Synthesis and spectroscopic character-
ization of an alkoxysilane dye containing C.I. disperse red 1. Dyes and
Pigments 2004;62:43e7.
[30] Chen LJ, Jin XF, Cui YJ, Gao JK, Qian GD, Wang MQ. Dipolar orientation
stabilities of hybrid films for second-order nonlinear optical applications.
Journal of SoleGel Science and Technology 2007;43:329e35.
[31] Terenziani F, D’Avino G, Painelli A. Multichromophores for nonlinear optics:
designing the material properties by electrostatic interactions. Chem-
PhysChem 2007;8:2433e44.
[32] Terenziani F, Mongin O, Katan C, Bhatthula BKG, Blanchard-Desce M. Effects of
dipolar interactions on linear and nonlinear optical properties of