The design, synthesis, and characterization of D-π-A-π-A type organic dyes as sensitizers for dye-sensitized solar cells (DSSCs)

Article abstract of DOI:10.1016/j.tetlet.2014.04.037

New D-π-A-π-A type organic dyes were synthesized and characterized as sensitizers for dye-sensitized solar cells (DSSCs). These dyes showed wide absorption spectra (300-625 nm) and high molar extinction coefficients (ε_{467 nm} = 60,911 M^-1 cm^-1). As dye sensitizers in DSSC, the D-π-A-π-A dye having a cyanoacrylic acid as an acceptor gave the best cell performance with a short-circuit photocurrent density (J_sc) of 7.14 mA/cm², an open-circuit voltage (V_oc) of 0.62 V, and a fill factor (FF) of 0.72, corresponding to an overall conversion efficiency η of 3.19%.

Full text of DOI:10.1016/j.tetlet.2014.04.037

Accepted Manuscript
The design, synthesis and characterization of D-π-A-π-A type organic dyes as
sensitizers for dye-sensitized solar cells (DSSCs)
Tanika Khanasa, Narid Prachumrak, Palita Kochapradist, Supawadee
Namuangruk, Tinnagon Keawin, Siriporn Jungsuttiwong, Taweesak
Sudyoadsuk, Vinich Promarak
PII:
S0040-4039(14)00636-4
DOI:
http://dx.doi.org/10.1016/j.tetlet.2014.04.037
TETL 44499
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
27 January 2014
29 March 2014
10 April 2014
Please cite this article as: Khanasa, T., Prachumrak, N., Kochapradist, P., Namuangruk, S., Keawin, T.,
Jungsuttiwong, S., Sudyoadsuk, T., Promarak, V., The design, synthesis and characterization of D-π-A-π-A type
organic dyes as sensitizers for dye-sensitized solar cells (DSSCs), Tetrahedron Letters (2014), doi: http://dx.doi.org/
10.1016/j.tetlet.2014.04.037
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The design, synthesis and characterization of
D-π-A-π-A type organic dyes as sensitizers
for dye-sensitized solar cells (DSSCs)
Leave this area blank for abstract info.
Tanika Khanasa, Narid Prachumrak, Palita Kochapradist, Supawadee Namuangruk, Tinnagon Keawin, Siriporn
Jungsuttiwong, Taweesak Sudyoadsuk, Vinich Promarak*
NC
CN
A
O
π
π
S
S
C6H13
C6H13
D
X
COOH
N
X = H or CN
t-Bu
A
D-π-A-π-A
t-Bu

1
Tetrahedron Letters
journal homepage: www.els evier.com
The design, synthesis and characterization of D-π-A-π-A type organic dyes as
sensitizers for dye-sensitized solar cells (DSSCs)
Tanika Khanasa,a Narid Prachumrak,b Palita Kochapradist,b Supawadee Namuangruk,c Tinnagon Keawin,a
Siriporn Jungsuttiwong,a Taweesak Sudyoadsuk,a Vinich Promarakb∗
a Center for Organic Electronic and Alternative Energy, Department of Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani, 34190,
Thailand
b School of Chemistry and Center of Excellence for Innovation in Chemistry, Institute of Science, Suranaree University of Technology, Muang District, Nakhon
Ratchasima, 30000, Thailand
c National Nanotechnology Center (NANOTEC), 130 Thailand Science Park, Klong Luang, Pathumthani, 12120, Thailand
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
New D-π-A-π-A type organic dyes were synthesized and characterized as sensitizers for dye-
sensitized solar cells (DSSCs). These dyes showed wide absorption spectra (300-625 nm) and
high molar extinction coefficients (ε467 nm = 60,911 M-1 cm-1). As dye sensitizers in DSSC, the D-
π-A-π-A dye having a cyanoacrylic acid as an acceptor gave the best cell performance with a
short-circuit photocurrent density (Jsc) of 7.14 mA/cm2, an open-circuit voltage (Voc) of 0.62 V,
and a fill factor (FF) of 0.72, corresponding to an overall conversion efficiency η of 3.19%.
Available online
Keywords:
2009 Elsevier Ltd. All rights reserved.
Pyranylidene malononitrile
Carbazole
Organic dye
D-π-A-π-A
Dye-sensitized solar cell
Dye-sensitized solar cells (DSSCs) have emerged as very
attractive photovoltaic devices because they offer the possibility
of low-cost conversion of photoenergy.1 To date, a variety of dye
sensitizers including transition metal complexes,2 porphyrins3 and
metal-free organic molecules4 have been explored in order to
improve the performance of solar cells and to understand the
structure-property relationships. The advantages of low cost, easy
purification and structural diversity of organic dyes make them
particularly attractive. Although remarkable progress has been
made recently in the development of organic dyes as sensitizers
for DSSCs, with the power conversion efficiency (η) reaching a
new record of η = 9.8% for dye C217,5 this still falls behind the
performance of porphyrin dyes (η = 13%),6 Ru-complex dyes
such as N719 (η = 11.18%)7 and CYC-B11 (η = 11.5%),8 and the
challenging 15% efficiency of the DSSC using an organometal
halide perovskite (CH3NH3PbI3) as a dye sensitizer.9 The
common structure of organic dyes is composed of donor (D), π-
conjugation linkage (π), and acceptor (A) moieties, thereby
forming a D-π-A structure.4,10 To achieve high-performance
organic dyes the following key properties need to be improved
(and are required): (i) high light-harvesting efficiency (LHE), (ii)
low tendency for dye aggregation, and (iii) less chance of charge
recombination of the injected electrons in the TiO2 with the
structure at either the donor or π-spacer moieties.4 It has been
shown that increasing the molar extinction coefficient and red-
shifted absorption spectra of the dye result in greater LHE and
power conversion efficiency (η) of the DSSCs.11 Therefore,
research on new organic dyes with high LHE, i.e., wide
absorption spectra and high molar extinction coefficients, is still
required and could lead to a potent dye for highly efficient
DSSCs.
In this Letter, we present the design, synthesis and
characterization of new D-π-A-π-A type organic dyes (Figure 1)
having a wide and strong absorption, as dye sensitizers for
DSSCs. The molar structures of the dyes consist of carbazole as a
donor, vinyl phenylfluorene and vinyl bithiophene as π-
conjugation spacers and pyran-4-ylidene malononitrile and
cyanoacrylic acid as acceptors. An investigation of their physical
and photophysical properties, and applications as dye sensitizers
in DSSCs are also reported.
The synthesis of the designed D-π-A-π-A type dyes is outlined
in Scheme 1. 2-(3,6-Di-tert-butylcarbazol-N-yl)-7-bromo-9,9-
dioctylfluorene (4), prepared from Ullmann coupling of 2,7-
dibromo-9,9-dioctylfluorene with 3,6-di(tert-butyl)carbazole,
was first cross-coupled with 4-formylphenylboronic acid
catalyzed by Pd(PPh3)4/2 M Na2CO3 (aq) in THF to give the
intermediate araldehyde 5 in a good yield of 89%. Aldol
-
triiodide ions (I3 ) in the electrolyte. In terms of dye development,
these have been mainly achieved by engineering of the molecular
———
condensation of the aldehyde
5
with excess 2-(2,6-
∗ Corresponding author. Tel.: +6-644-224-277; fax: +6-644-224-185; e-mail: pvinich@sut.ac.th

2
Tetrahedron Letters
dimethylpyran-4-ylidene)malononitrile (6)12 in the presence of
NC
CN
a catalytic amount of piperidine in THF/MeCN afforded the
mono-adduct 7 in 57% yield. Further condensation of 7 with 5-
bromo-2-formylthiophene under the same conditions gave the
bromide 8 in 66% yield. Pd-catalyzed cross-coupling of 8 with 5-
formyl-2-thiopheneboronic acid provided the corresponding
aldehyde 9 in a yield of 59%. Finally, Knoevenagel condensation
of 9 with either malonic acid or cyanoacetic acid gave the D-π-A-
π-A dyes 1 and 2 as dark red solids in fairly good yields of 60%
and 74%, respectively. For comparison, a simple D-π-A dye 3
was synthesized by condensation of the aldehyde 5 with
cyanoacetic acid. Product 3 was obtained as a yellow solid in
66% yield. The structures of all the dye molecules were fully
characterized by standard methods.13 These dyes showed good
solubility in most organic solvents allowing dye adsorption on
TiO2 film and fabrication of DSSCs to be performed.
O
S
S
C6H13
C6H13
1 X = H
X
COOH
N
2 X = CN
t-Bu
t-Bu
t-Bu
NC
In solution, both dyes 1 and 2 show wide and strong
absorption spectra with the absorption onset reaching 625 nm and
ε values as high as 60911 M-1 cm-1 at 467 nm (Figure 2a). These
spectra consist of three absorption bands appearing at 297, 348-
350, and 455-466 nm. The first two bands correspond to π–π*
electron transitions of the carbazole and vinyl phenylfluorene,
N
COOH
H13C6
C6H13
3
t-Bu
Figure 1. Molecular structures of dyes 1-3.
t-Bu
t-Bu
(HO)2B
CHO
NC
CN
Br
N
N
CHO
Pd(PPh3)4, 2 M Na2CO3
THF, heat; 89%
6
C6H13
H13C6 C6H13
H13C6
O
piperidine, THF/MeCN
57%
4
5
t-Bu
t-Bu
NC
CN
NC
CN
NC
CN
(HO)2B
CHO
OHC
Br
S
S
7
O
O
O
piperidine, THF/MeCN
66%
Pd(PPh3)4, 2 M Na2CO3
THF, heat; 59%
Ar
Ar
Ar
9
8
S
S
Br
S
CHO
t-Bu
CH2(COOH)2
9
1 60%
piperidine, THF/MeCN
N
Ar =
CNCH2COOH
2 74%
3 66%
H13C6
9
5
C6H13
piperidine, THF/MeCN
t-Bu
Scheme 1. Synthesis of dyes 1-3.
respectively, while the bands at longer wavelengths (ca. 455-466
nm) are attributed to intramolecular charge transfer (ICT)
transitions from the donor to the acrylic acid acceptor. This is
confirmed by a hypsochromic shift of the ICT peaks in more
polar solvents, while the positions of the π–π* transition peaks
are almost independent of solvent polarity. The spectrum of 2,
having an electron-withdrawing cyano group (-CN) at the C2-
position of the acrylic acceptor shows significantly higher ε
values, with a slight red-shift compared to that of 1. The
absorption spectra of both dyes adsorbed on TiO2 films (Figure
1b) exhibit broad absorption bands. The spectra are blue shifted
(11-18 nm) compared with the spectra measured in CH2Cl2. Such
an occurrence is usually observed in the spectral response of
other organic dyes, and may be ascribed to the H-aggregation of
the dyes on the TiO2 surface and/or the interaction of the
anchoring groups of the dyes with the surface of TiO2.14 Clearly,
the absorption spectra of dyes 1 and 2, both in solution and
adsorbed on TiO2, are considerably wider and have stronger
absorption (higher ε values) than those of a simple D-π-A dye 3.
It has been known that the power conversion efficiency (η) of a
DSSC is strongly related to the LHE of the sensitizers.
a)
b)
1
60k
50k
40k
30k
20k
10k
0
1
1
1
2
3
2
3
0
0
300
300
400
500
600
700
800
400
500
600
700
Wavelength (nm)
Wavelength (nm)
-8
-6
-4
-2
0
c)
d)
1
2
3
80
60
40
20
0
1
2
3
400
500
600
700
0.0
0.2
0.4
0.6
Wavelength (nm)
Voltage (V)
Figure 2. (a) Absorption and PL spectra of the dyes 1-3 in CH2Cl2. (b)
Absorption spectra of the dyes adsorbed on TiO2 films. (c) IPCE spectra and
(d) I-V characteristics of the fabricated DSSCs.
.

3
Table 1 Physical data of dyes 1-3 and their DSSC device characteristics.
a
c
d
Dye
λ
Abs (ε)a
λEm
(nm) (nm)
Absb
Eox
T5d
(oC) (eV)
Ege HOMO/LUMOf
Jsc
Voc
FF
η
(%)
pa
[nm (M-1cm-1)]
295 (39355), 348
(40345), 455 (47311)
294 (42522), 350
(39454), 467 (60911)
296 (37395), 351
(36524)
(V)
(eV)
-5.48/-3.34
(mA/cm2) (V)
1
628
630
420
-
444 1.19, 1.67, 1.86 286 2.14
3.70
7.14
0.60 0.73 1.64
0.62 0.72 3.19
0.62 0.71 1.23
0.69 0.70 8.07
2
448 1.19, 1.65, 1.91 302 2.16
-5.47/-3.31
-5.50/-2.69
-5.05/-3.25
3
410 1.17, 1.78
250 2.81
1.80
2.78
N719 535 (14400)
-
-
-
16.70
a Measured in CH2Cl2.
b Measured as dye adsorbed on TiO2 films.
c Analyzed by CV with 0.1 M n-Bu4NPF6 as the electrolyte in CH2Cl2 at a scan rate of 50 mV/s (Epa = peak anodic potential).
d Analyzed by TGA at a heat rate of 10 oC/min under N2.
e Calculated by Eg = λabs
.
onset
f Calculated by HOMO = -(4.44 + Eoxonset); LUMO = HOMO + Eg
LUMO
HOMO
NC
CN
NC
CN
NC
CN
2
O
O
O
S
S
S
S
10
11
12
S
S
C6H13
C6H13
S
C6H13
C6H13
N
C6H13
C6H13
t-Bu
N
NC
COOH
NC
COOH
t-Bu
NC
COOH
N
t-Bu
t-Bu
t-Bu
t-Bu
Figure 3. HOMO and LUMO orbitals of dye 2 and predicted dyes 10-12.
The LHE has been estimated from the absorbance [Abs(λ)] of the
dye adsorbed on TiO2 film at wavelength λ according to Eq.
(1):15
promising thermodynamically favorable dye regeneration and
effective charge injection from the excited dyes to TiO2. Besides,
the high LUMO levels of these dyes make them very attractive
for other metal oxide–based DSSCs. Examples are ZnO, Nb2O3,
SrTiO3 and their composites.16 With their conduction bands being
more negative than that of TiO2, the DSSCs will give high open-
circuit voltage (Voc), resulting in much improved cell efficiency.
The thermal analyses of 1 and 2 suggest that both are thermally
stable materials, with temperatures at 5% weight loss (T5d) well
over 286 °C (Table 1). It has been shown that high thermal
stability of the dye is important for the lifetimes of the solar
cells.17
To investigate the photovoltaic properties of dyes 1-3, DSSCs
with effective areas of 0.25 cm2 were fabricated with a 14 µm (9
µm transparent + 5 µm scattering) thick TiO2 working electrode,
a platinum (Pt) counter electrode and an electrolyte solution of
Z960 electrolyte comprising of 1.0 M 1,3-dimethylimidazolium
LHE(λ) = 1-10-Abs(λ)
(1)
From Eq. (1) it is clear that the DSSC performance of dyes 2 and
1 would be significantly higher than that of 3
The electrochemical studies of 1 and 2 revealed multi
irreversible oxidation processes (Table 1). The first oxidation
potentials (Eox ≈ 1.19 V) were assigned to the removal of
pa
electrons from the carbazole donor to give the corresponding
radical cation. The highest occupied molecular orbitals (HOMOs)
and lowest unoccupied molecular orbitals (LUMOs) of the dyes
were calculated to be around -5.4 eV and -2.3 eV, respectively
(Table 1). The HOMOs are lower than the redox potential of the
–
I–/I3 electrolyte (–4.8 eV), while the LUMOs are less negative
than the conduction band of the TiO2 electrode (-4.0 eV),

4
Tetrahedron
S. M.; Humphry-Baker, R.; Comte, P.; Liska, P.; Cevey, L.; Costa, E.;
Shklover, V.; Spiccia, L.; Deacon, G. B.; Bignozzi, C. A.; Grätzel, M. J.
Am. Chem. Soc., 2001, 123, 1613-1624.
iodide, 0.1 M guanidinium thiocyanate, 0.03 M I2, 0.05 M LiI,
and 0.5 M tert-butylpyridine in a mixed solvent of acetonitrile
and valeronitrile (85/15, v/v). The plots of current density-
voltage (J-V) characteristics and the incident monochromatic
photon-to-current conversion efficiency (IPCE) are shown in
Figures 2c and d, and the resulting data are summarized in Table
1. The IPCE spectra of all the cells are well compatible with the
absorption spectra of the dyes. The 2-based cell shows the
broadest IPCE (>60% in the range 365-510 nm with a maximum
of 70% at 445 nm) spectrum. Under standard AM 1.5G 100 mW
3.
4.
(a) Imahori, H.; Umeyama, T.; Ito, S. Acc. Chem. Res., 2009, 42, 1809-
1818. (b) Sirithip, K.; Morada, S.; Namuangruk, S.; Keawin, T.;
Jungsuttiwong, S.; Sudyoadsuk, T.; Promarak, V. Tetrahedron Lett.,
2013, 54, 2435-2439.
(a) Liang, M.; Chen, J. Chem. Soc. Rev., 2013, 42, 3453-3488. (b)
Sudyoadsuk, T.; Pansay, S.; Morada, S.; Rattanawan, R.; Namuangruk,
S.; Kaewin, T.; Jungsuttiwong, S.; Promarak, V. Eur. J. Org. Chem.,
2013, 23, 5051-5053.
5.
6.
Zhang, G.; Bala, H.; Cheng, Y.; Shi, D.; Lv, X.; Yu, Q.; Wang, P.
Chem. Commun., 2009, 2198-2200.
Yella, A.; Lee, H.-W.; Tsao, H. N.; Yi, C.; Chandiran, A. K.;
Nazeeruddin, Md. K.; Diau, E. W.-G.; Yeh, C.-Y.; Zakeeruddin, S. M.;
Grätzel, M. Science, 2011, 334, 629-634.
cm-2 illumination, the 2-based cell gave
a short-circuit
photocurrent density (Jsc) of 7.14 mA/cm2, an open-circuit
voltage (Voc) of 0.62 V, and a fill factor (FF) of 0.72,
corresponding to an overall conversion efficiency (η) of 3.19%,
while the 1-based cell showed a lower Jsc of 3.70 mA cm-2
resulting in a lower η of 1.64%. Both DSSCs exhibit greater cell
performance than that of simple D-π-A dye 3 (Jsc = 2.78
mA/cm2, η = 1.23%). The higher cell performance (wide IPCE,
high Jsc and η) from 2 could be rationalized from its wide
absorption spectrum and high ε value, i.e., greater LHE.
7.
8.
9.
Nazeeruddin, M. K.; Angelis, F. D.; Fantacci, S.; Selloni, A.; Viscardi,
G.; Liska, P.; Ito, S.; Takeru, B.; Grätzel, M. J. Am. Chem. Soc., 2005,
127, 16835-16847.
Chen, C.-Y.; Wang, M.; Li, J.-Y.; Pootrakulchote, N.; Alibabaei, L.;
Ngoc-le, C.-H.; Decoppet, J.-D.; Tsai, J.-H.; Grätzel, C.; Wu, C.-G.;
Zakeeruddin, S. M.; Grätzel, M. ACS Nano, 2009, 3, 3103-3109.
Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J.
Science, 2012, 338, 643-647.
10. Kim, B.-G.; Zhen, C.-G.; Jeong, E. J.; Kieffer, J.; Kim, J. Adv. Funct.
Mater., 2012, 22, 1606-1612.
Despite dye 2 possessing a wide absorption range with high ε,
its DSSC performance is still lower than the fabricated reference
N719 cell (η = 8.07%), and the reported efficient organic dye (η
= 9.8% C217).5 Quantum chemistry calculations were performed
at the TDDFT/B3LYP/6-31G (d,p) level in order to understand
the electronic structures of dye 2.18 As depicted in Figure 3, in the
LUMO, the excited electrons localize on the entire bisthiophene
and cyanoacrylic acid moieties. In the HOMO, electrons are able
to delocalize over the carbazole and fluorene π-linkage through
the lone electron pair of the N-atom of the carbazole. On
overlapping of these energy levels, discontinuation of the
electron density (unfilled space) on the phenyl ring is observed,
leading to an inefficient electron transfer from the donor to
acceptor. This is due to a twist conformation between the
fluorene and phenyl rings. It has been found that in most cases of
efficient organic dyes, an overlap of the electron density of the
HOMO and LUMO are observed and are significant.4,5,11,19 This
might be one of the reasons for the lower conversion efficiency
of dye 2. Additional DFT calculations predict that if the phenyl in
the π-spacer is removed or replaced by either a thiophene ring or
an alkyne bond to form dyes 10-12, a larger overlap of the
electron density of the HOMO and LUMO is observed,
indicating more efficient electron transfer which could lead to
better dyes. To confirm this idea, experimental studies on
compounds 10-12 are under investigation in our laboratory.
In summary, we have successfully designed, synthesized and
characterized new D-π-A-π-A type organic dyes 1 and 2 as
DSSCs. The dyes possess a wide absorption range with high ε
values and can be used as sensitizers in DSSCs with an η value
of 3.19% being achieved. This work suggests that further
structural modification of this type of dye molecule should lead
to a promising candidate for efficient DSSCs.
11. (a) Zhang, M.; Liu, J.; Wang, Y.; Zhou, D.; Wang, P. Chem. Sci., 2011,
2, 1401-1406. (b) Namuangruk, S.; Fukuda, R.; Ehara, M.; Meeprasert,
J.; Khanasa, T.; Morada, S.; Kaewin, T.; Jungsuttiwong, S.;
Sudyoadsuk, T.; Promarak, V. J. Phys. Chem. C, 2012, 116, 25653-
25663.
12. Peng, Q.; Park, K.; Lin, T.; Durstock, M.; Dai, L. J. Phys. Chem. B,
2008, 112, 2801-2808.
13. Characterization data for 1: m.p. >250 oC, FT-IR (KBr, ν, cm-1): 3394
(O-H), 3042, 2926, 2856, 2210 (C≡N), 1637 (C=O), 1600, 1547, 1490,
1473, 1363, 1250, 944, 807; 1H NMR (300 MHz, CDCl3/DMSO-d6, δ,
ppm): 8.31 (2H, s), 7.30-8.16 (24H, m), 7.21 (1H, d, J = 15.7 Hz), 6.95
(1H, d, J = 16.5 Hz), 2.08 (4H, s), 1.41 (18H, s), 1.05-0.72 (22H, m).
13C NMR (75 MHz, CDCl3/DMSO-d6, δ, ppm): 159.8, 157.0, 152.0,
151.8, 142.8, 139.1, 129.4, 129.1, 123.8, 123.2, 121.3, 116.6, 109.3,
107.6, 55.6, 34.8, 32.2, 31.7, 31.4, 29.4, 23.9, 22.5, 22.4 14.2. HRMS
calcd for C74H74N3O3S2: m/z 1116.5172; found: m/z 1116.5824 [MH+].
-1
2: m.p. >250 oC, FT-IR (KBr, ν, cm ): 3421 (O-H), 3052, 2926, 2856,
2201 (C≡N), 1637 (C=O), 1600, 1537, 1490, 1473, 1418, 1363, 1250,
1203, 994, 807; 1H NMR (300 MHz, CDCl3/DMSO-d6, δ, ppm): 8.23
(2H, s), 7.26-8.06 (24H, m), 7.07 (1H, d, J = 15.6 Hz), 6.85 (1H, d, J =
14.4 Hz), 2.09 (4H, s), 1.39 (18H, s), 1.02-0.70 (22H, m); 13C NMR (75
MHz, CDCl3/DMSO-d6, δ, ppm): 164.4, 159.0, 158.5, 156.0, 152.8,
151.8, 142.8, 142.7, 142.3, 140.2, 139.5, 139.1, 138.8, 137.6, 137.0,
136.7, 134.4, 133.1, 131.5, 130.3, 129.1, 127.7, 127.5, 126.3, 126.5,
125.8, 125.4, 123.9, 123.2, 121.7, 121.4, 121.3, 120.9, 119.3, 116.8,
115.7, 115.7, 109.3, 107.6, 57.9, 55.6, 34.8, 32.2, 31.3, 29.3, 23.9, 22.4,
14.2; HRMS calcd for C75H73N4O3S2: m/z 1141.5124; found: m/z
1141.2758 [MH+].
3: m.p. 220-221 oC; FT-IR (KBr, ν, cm-1): 3520 (O-H), 3037, 2955,
2926, 2854, 2217 (C≡N), 1654 (C=O), 1637, 1617, 1490, 1474, 1364,
1034, 877, 810; 1H NMR (300 MHz, CDCl3/DMSO-d6, δ, ppm): 8.41
(1H, s), 8.14 (2H, s), 8.02 (1H, m), 7.79 (1H, d, J = 7.8 Hz), 7.65-7.50
(7H, m), 7.40-7.33 (5H, m), 2.03 (4H, s), 1.42 (18H, s), 1.27-0.73 (22H,
m); 13C NMR (75 MHz, CDCl3/DMSO-d6, δ, ppm): 168.6, 152.9, 151.9,
145.2, 140.8, 139.2, 139.1, 138.5, 137.3, 131.5, 131.0, 127.7, 127.5,
126.5, 125.4, 123.5, 123.4, 121.4, 121.3, 120.9, 120.4, 116.3, 109.1,
55.6, 40.3, 34.7, 32.0, 31.8, 29.9, 24.06, 22.2, 14.0; HRMS calcd for
C55H63N2O2: m/z 783.4890: found: m/z 783.4377 [MH+].
Acknowledgements
14. Lu, M.; Liang, M.; Han, H.-Y.; Sun, Z.; Xue, S. J. Phys. Chem. C,
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This work was financially supported from SUT (Grant No. 1-
102-56-12-02). We also thank the support from the post-doctoral
scholarship from SUT and the Higher Education Research
Promotion and National Research University Project of Thailand,
OHEC, and PERCH-CIC.
16. Lee, J.-J.; Rahman, M. M.; Sarker, S.; Nath, D. Advances in Composite
Materials for Medicine and Nanotechnology, InTech 2011, 181-210.
17. Tsai, M.-S.; Hsu, Y.-C.; Lin, J. T.; Chen, H.-C.; Hsu, C.-P. J. Phys.
Chem. C, 2007, 111, 18785-18793.
18. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M.
A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.;
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