Synthesis and dye-sensitized solar cell application of polyolefinic aromatic molecules with pyrene as surface group

Article abstract of DOI:10.1071/CH10434

Synthesis of polyolefinic aromatic molecules with pyrene as the surface group, and their role as an additive in the redox couple of dye-sensitized solar cells, is described. The studies yield a promising power conversion efficiency of 5.27% with a short circuit current density of 6.50mAcm^-2, an open circuit voltage of 0.60V, and a fill factor of 0.54 under 40mWcm-^-2 simulated air mass (A.M.) 1.5 illumination. Most importantly, the photocurrent responsivity increases with an increase in the number of pyrene units on the surface.

Full text of DOI:10.1071/CH10434

Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2011, 64, 951–956
Synthesis and Dye-sensitized Solar Cell Application
of Polyolefinic Aromatic Molecules with Pyrene
as Surface Group
A
,
C
A
B
Perumal Rajakumar,
Kathiresan Visalakshi, Shanmugam Ganesan,
B
B
Pichai Maruthamuthu, and Samuel Austin Suthanthiraraj
A
Department of Organic Chemistry, University of Madras, Guindy Campus,
Chennai ] 600 025, India.
B
Department of Energy, University of Madras, Guindy Campus,
Chennai ] 600 025, India.
C
Corresponding author. Email: perumalrajakumar@gmail.com
Synthesis of polyolefinic aromatic molecules with pyrene as the surface group, and their role as an additive in the redox
couple of dye-sensitized solar cells, is described. The studies yield a promising power conversion efficiency of 5.27%
ꢀ
2
with a short circuit current density of 6.50 mA cm , an open circuit voltage of 0.60 V, and a fill factor of 0.54 under
ꢀ
2
0 mW cm simulated air mass (A.M.) 1.5 illumination. Most importantly, the photocurrent responsivity increases with
4
an increase in the number of pyrene units on the surface.
Manuscript received: 30 November 2010.
Manuscript accepted: 14 April 2011.
Introduction
We report herein the synthesis of polyolefinic aromatic
molecules 1, 2, 2a, and 3 with pyrene surface group, that show
enhanced energy conversion efficiency of 5.27% (Fig. 1).
Dye-sensitized solar cells (DSSC) have attracted much attention
during recent years because of their low-cost processing, simple
[1–3]
packaging, and compatibility with flexible substrates.
[
4]
Gr a¨ tzel and his co-workers developed a solar cell with energy
conversion efficiency of 7% in 1991. The dye-sensitized solar
cell consists of nanostructured TiO2 film photoelectrodes
covered with a photosensitizing dye such as [cis-dithiocyanato-
N,N-bis(2,2-bipyridyl-4,4-dicarboxylic acid) ruthenium(II)] (N3
Results and Discussion
[
13]
Pyrene-1-carbaldehyde underwent Wittig reaction with
methyl triphenylphosphonium iodide in the presence of potas-
sium tert-butoxide in THF to give 1-vinylpyrene in 59% yield
ꢀ
ꢀ
1
(Scheme 1). The H NMR spectrum of 1-vinylpyrene displayed
dye), a redox electrolyte solution (I /I ), and a Pt counter-
3
electrode on fluorinated tin oxide (FTO)-coated conducting
glass. Under illumination, the dye absorbs light and injects
photo-excited electrons into the conduction band of TiO . The
two doublets at d 5.50 (J ¼ 11.1 Hz) and d 5.87 (J ¼ 17.4 Hz) for
H and H protons, respectively, and a doublet of doublets at
a
b
d 7.63 (J ¼ 11.1, 10.8 Hz) for H proton, in addition to the aro-
2
c
ꢀ
ꢀ
13
matic protons. In the C NMR spectrum of 1-vinylpyrene, the
resulting dye cations are reduced by I , and the generated I
ꢀ
3
diffuses to a platinum counter electrode where the I is reduced
3
vinylic carbons appeared at d 117.2 and 134.3, in addition
to 15 signals for the aromatic carbons, and in the DEPT–135
spectrum the methylene carbon appeared at d 117.2.
ꢀ
back to I . The high efficiency of DSSC is due to the fast
ꢀ
[5–8]
reduction of dye cations by I , and slow recombination kinetics
ꢀ
between the injected electrons and I .
3
Heck coupling of symmetrical tribromobenzene with
1-vinylpyrene using Pd(OAc)2 in the presence of K CO3
Pyrene, a flat aromatic molecule, exhibits excellent fluores-
2
[9]
cent properties, and its derivatives are promising candidates
for applications in material sciences such as components in
and tetrabutylammonium bromide resulted in the formation of
1,3,5-tris((E)-2-(pyren-1-yl)vinyl)benzene (2) in 73% yield.
1
The H NMR spectrum of 1,3,5-tris((E)-2-(pyren-1-yl)vinyl)
[
10,11]
OLEDs.
reported,
Though pyrene-based solar cells have been
polyolefinic aromatic molecules containing
[
12]
benzene (2) displayed two doublets at d 7.16 (J ¼ 16.2 Hz) and
8.45 (J ¼ 9.3 Hz) corresponding to the vinyl and pyrenyl pro-
tons, respectively, and a singlet at d 7.59 for three protons in
pyrene, and with higher orders of extensive conjugation as
additive in solar cells, is not known to the best of our knowledge.
The unique layered architecture of polyolefinic aromatic mole-
cules with pyrene as surface group can be regarded as zeroth
generation dendrimers. Such dendrimers have a globular shape,
radially controlled chemical make-up, multivalent periphery,
variable inner volume, and controlled intramolecular dynamics
leading to a breadth of potential applications.
1
3
C
the benzene unit, in addition to the aromatic protons. In the
NMR spectrum, 19 signals appeared for the aromatic and vinyl
carbons between d 122.7 and 141.3.
Similarly, Heck coupling of 1-vinylpyrene with 1,4-
dibromobenzene, 2,4,6-tribromomesitylene, and hexabromo-
benzene afforded the polyolefinic aromatic molecules 1, 2a,
Ó CSIRO 2011
10.1071/CH10434
0004-9425/11/070951

9
52
P. Rajakumar et al.
R
R
R
1
(2py)
R ꢀ H, 2 (3H ꢁ 3py)
3 (6py)
R ꢀ Me, 2a (Me ꢁ 3py)
Fig. 1. Structures of polyolefinic aromatic molecules with pyrene surface group.
1
(2py)
1
the number of pyrene units. Though, extended conjugation
usually shows a red shift in polar solvents due to the stabilization
of the excited state, benzene being a non-polar solvent, stabilizes
the ground state further and destabilizes the excited state. Hence
a greater widening of the energy gap between p-p* orbitals
of the conjugated system resulted, on going from 1 to 3. The
,4-Dibromobenzene
0.5 equiv.), 12h
(
(
ii)
1
,3,5-Tribromobenzene
0.34 equiv.), 12 h/
,4,6-Tribromomesitylene
0.34 equiv.), 12 h
E
(
insolubility of 2a and 3 in common solvents like CHCl and
3
2
CH Cl necessitated the use of benzene for recording UV and
2
2
(
2
2
(3H ꢁ 3py)/
a (3Me ꢁ 3py)
fluoresence spectra.
All the polyolefinic aromatic molecules exhibit intense
fluorescence emission in the region 393 to 512 nm (excited at
(ii)
E ꢀ CHO
E ꢀ CH CH2
3
50 nm) (Fig. 3). The emission spectra also indicate a shift
(
i)
towards shorter wavelength on going from dendrimer 1 to 3,
again due to destabilization of the excited state of the conjugated
pyrene molecule by use of the non-polar solvent benzene. The
fluorescence quantum yield (F ), fluorescence lifetime (t ),
F
and fluorescence amplitude were also measured for all the
polyolefinic aromatic molecules 1 to 3. The F values of the
Hexabromobenzene
0.17 equiv.), 36h
ii)
(
F
(
F
polyolefinic aromatic molecules were found to be in the range
14]
3
(6py)
[
of 0.14 to 0.54 relative to that of quinine sulfate
(0.54 in
Reagents and conditions: (i) 1.0 equiv. methyltriphenylphosphonium iodide,
t
KO Bu, THF, 12h, 59%. (ii) Pd(OAc) , TBAB, K CO , DMF, 90ꢂC,
benzene). The quantum yield decreases with increasing number
of pyrene units. Fluorescence decays of polyolefinic aromatic
molecules 1 and 2 are biexponential, whereas that of 2a and 3 are
triexponential.
2
2
3
1
(76%), 2 (73%), 2a (75%), 3 (69%).
Scheme 1. Synthesis of polyolefinic aromatic molecules with pyrene
surface group.
Electrochemical Behaviour
and 3 in 76, 75, and 69% yields, respectively (Scheme 1). The
structures of the polyolefinic aromatic molecules 1, 2a, and 3
were confirmed from spectral and analytical data. C NMR of
polyolefinic aromatic molecules 2a and 3 could not be obtained
due to poor solubility.
Cyclic voltammetric studies were carried out to understand
the electrochemical properties of the synthesized polyolefinic
aromatic molecules. Cyclic voltammetric studies were carried
out on a glassy carbon working electrode, Pt wire counter
1
3
electrode, and Ag/AgNO reference electrode from solutions
3
of the substrates (1 mM) in benzene using tetra-
butylammonium hexafluorophosphate (0.1 M) as supporting
electrolyte in the potential range of ꢀ0.2 to 1.4 V. Electro-
chemically, all polyolefinic aromatic molecules exhibit irre-
versible single electron oxidation within the observable
potential window (Fig. 4).
Photophysical Properties
The fluorescence quantum yield (F ), fluorescence lifetime
F
(
tF), and its relative amplitude of the polyolefinic aromatic
molecules 1, 2, 2a, and 3 were recorded in benzene and are
presented in Table 1, along with their absorption and emission
maxima.
The polyolefinic aromatic molecules 1, 2, 2a, and 3 exhibit
absorption maxima between 339 and 414 nm. The lmax observed
for the conjugated pyrene molecules 1, 2, 2a, and 3 could be
ascribed to p-p* transitions of the molecular backbone (Fig. 2).
A hypsochromic shift (blue shift) was observed on increasing
Dye-sensitized Solar Cell Studies
Dye-sensitized solar cells appear to be highly promising alter-
natives to more expensive solar cell technologies. The pyrene-
based polyolefinic aromatic molecules 1, 2, 2a, and 3 were used
ꢀ
ꢀ
redox couple. The
3
as additives for DSSCs, along with an I /I

Polyolefinic Aromatic Molecules with Pyrene Surface
953
Table 1. Photophysical studies of polyolefinic aromatic molecules in benzene
Polyolefinic aromatic molecule
lmax absorption [nm]
lmax emission [nm]
Quantum yield
Life time [ns]
Amplitudes [%]
t
1
t
2
t
3
A
1
A
2
A
3
1
2
350, 370, 414
370, 382
480, 512
0.54
0.47
0.45
0.14
0.63
0.45
0.33
0.24
1.67
2.09
1.46
2.19
–
36.16
4.67
63.84
95.33
77.33
15.59
–
437, 457
–
–
2
3
a
351, 363
393, 427, 441
393, 414, 440
13.91
13.31
14.93
8.89
7.73
75.51
320, 339
1
1
1
1
600000
400000
200000
000000
3Me ꢁ 3py
6py
3H ꢁ 3py
2py
8
6
4
2
00000
00000
00000
00000
0
300
350
400
450
500
Wavelength [nm]
Fig. 2. UV–Visible absorption spectra in benzene.
6
5
4
3
2
1
000000
000000
000000
000000
000000
000000
0
6
py
3
Me ꢁ 3py
H ꢁ 3py
3
2py
300
400
500
600
700
Wavelength [nm]
Fig. 3. Fluorescence spectra in benzene.
polyolefinic aromatic molecule was incorporated into the
electrolyte to coordinate with I and form an interactive bond,
which would prevent the sublimation of I and enhance the
2
lifetime of the electrolyte, as well as increase the efficiency
of the DSSC. Moreover the polyolefinic aromatic molecule
compounds 2a and 3 in the routinely used solvent acetonitrile,
DMF was used for all the compounds.
The comparison of DSSCs using pyrene-based polyolefinic
2
ꢀ
aromatic molecules 1, 2, 2a, and 3 as additives, along with an I /
ꢀ
I
redox couple without additives (Fig. 5), reveals that com-
3
(additive) interacting with the iodine may shift the TiO con-
duction band edge, and result in an increased electron life
pound 3 with six pyrene units has higher efficiency compared
with other three compounds. All three polyolefinic aromatic
molecules 1, 2, and 2a give high efficiency compared to an
undoped redox couple.
Table 2 shows the influence of the polyolefinic aromatic
molecules 1, 2, 2a, and 3 as additives in the electrolyte on the
Voc of the cell. The Voc values for cells containing polyolefinic
aromatic molecules were greater than the cell without an
2
[
15]
time.
A high photocurrent is obtained with the increase in
the number of pyrene units, since the pyrene is a potent photo-
reductant and the pyrene radical cation is a strong oxidant that
[
16]
is expected to oxidize iodide rapidly.
photovoltaic performance of DSSCs based on the incorpo-
Table 2 shows the
ration of pyrene-based polyolefinic aromatic molecules 1, 2,
2
a, and 3 in the redox couple. Due to the poor solubility of the
additive. Among the tested additives, the highest V , 600 mV,
oc

9
54
P. Rajakumar et al.
(
a) 2.0
0
(b)
2.0
1.0
0
ꢁ
ꢁ
1.0
2.0
ꢁ
ꢁ
ꢁ
ꢁ
2.0
4.0
6.0
8.0
ꢁ3.0
ꢁ
ꢁ
4.0
5.0
ꢁ6.0
ꢁ
ꢁ
ꢁ
7.0
8.0
9.0
ꢁ
ꢁ
ꢁ
10.0
12.0
14.0
ꢁ
10.0
ꢁ11.0
1.2
1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
1.0
0.8
0.6
0.4
0.2
0
ꢁ0.2
Potential [V]
Potential [V]
(
c)
2.0
0
(d)
6.0
3.0
ꢁ
2.0
4.0
6.0
8.0
0
ꢁ
ꢁ
ꢁ
ꢁ3.0
ꢁ6.0
ꢁ9.0
ꢁ12.0
ꢁ15.0
ꢁ18.0
ꢁ21.0
ꢁ
ꢁ
ꢁ
ꢁ
10.0
12.0
14.0
16.0
1
.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10
1.2
1.0
0.8
0.6
0.4
0.2
0
ꢁ0.2
Potential [V]
Potential [V]
ꢀ1
4 6
Fig. 4. Typical cyclic voltammograms of (a) 1, (b) 2, (c) 2a, and (d) 3 in benzene on a glassy carbon electrode containing 0.1 M Bu NPF ; scan rate 0.05 V s .
Conclusions
7
In conclusion, we have successfully synthesized polyolefinic
aromatic molecules with pyrene surface groups, which dem-
onstrate the effect of the pyrene group and conjugation on
controlling optical and photovoltaic properties. It should be
noted that the power conversion efficiency reaches 5.27%,
which is the highest value among pyrene-based additives in the
redox couple. Further, synthesis of higher generations of con-
jugated dendrimers, and their application as additives in the
redox couple in DSSCs are under way.
6py
6
5
4
3
2
1
0
3
mepy
Hpy
py
3
2
Experimental
0
100
200
300
400
500
600
General Procedure for Dye-sensitized Solar Cell Studies
Voltage [mV]
The TiO photoelectrode was prepared as reported in the liter-
2
[
17]
ature.
The N3 dye was adsorbed on the TiO surface by
2
Fig. 5. I–V curve for polyolefinic aromatic molecules 1, 2, 2a, and 3 as
soaking the TiO photoelectrode in an ethanol solution of the N3
2
additives.
dye (5 ꢁ 10ꢀ M concentration) for 24 h at room temperature.
The photoelectrode was washed, dried, and immediately used
for the measurement of solar cell performance. A sandwich-type
photoelectrochemical cell was composed of a dye-coated TiO2
photoanode. Platinum coated flourinated tin oxide (FTO) con-
ducting glass was the counter electrode. The electrolyte solution
was injected into the space between the two electrodes. The
5
was observed when compound 3 with six pyrene units was added
to the electrolyte.
The values are derived from the equation Z ¼ (V ꢁ J ꢁ
oc
sc
s
FF)/P , where V is the open circuit potential [mV], J is the
oc
sc
ꢀ2
short circuit current density [mA cm ], FF is the fill factor, and
s
P is the power of the incident (solar) light (Table 2). From the
ꢀ3
electrolyte solution was composed of 3.2 ꢁ 10 M of KI,
ꢀ
6
4
results it is clear as the number of pyrene units increases, Z value,
open circuit voltage (V ), and short circuit current density (J )
of the DSSCs increase.
4.1 ꢁ 10 M of I , and the polyolefinic aromatic molecules of
ꢀ
2
6.4 ꢁ 10 M as additives in DMF (10 mL). The solar to electric
oc
sc
energy conversion efficiency was measured under simulated

Polyolefinic Aromatic Molecules with Pyrene Surface
955
Table 2. Performance of cells fabricated with and without additives
ꢀ
2
]
Electrolyte systems
Jsc [mA cm
Voc [mV]
FF
Z [%]
ꢀ
ꢀ
3
1
2
2
3
þ I /I
redox couple
redox couple
3.17
4.00
4.90
6.50
2.00
490
540
550
600
480
0.46
0.47
0.50
0.54
0.56
1.78
2.54
3.38
5.27
1.34
ꢀ
ꢀ
þ I /I
3
ꢀ
ꢀ
a þ I /I
3
redox couple
ꢀ
ꢀ
þ I /I
3
redox couple
ꢀ
ꢀ
3
redox couple
Without additive þ I /I
ꢀ
2
solar light at 40 mW cm . The photocurrent-photovoltage
was purified by column chromatography, using hexane as
eluant, to give 1-vinylpyrene (59%) as a yellow solid, mp 888C
was measured using a BAS 100A electrochemical analyzer. The
2
[19]
apparent cell area of TiO photoelectrode was 1 cm (1 cm ꢁ
(lit.
87–898C). dH (300 MHz, CDCl ) 8.19–7.82 (m, 9H),
3
2
1
cm).
7.63 (dd, J 11.1, 10.8, 1H, H ), 5.87 (d, J 17.4, 1H, H ), 5.50 (d,
c b
J 11.1, 1H, H ). d (75 MHz, CDCl ) 134.3, 132.4, 131.5, 131.2,
3
a
C
General Procedure for Cyclic Voltammetric Measurements
131.0, 130.9, 128.1, 127.6, 127.5, 127.3, 126.0, 125.3, 125.0,
þ
124.9, 123.7, 123.0, 117.2. m/z (EI) 228 (M ). Anal. Calc. for
C H : C 94.70, H 5.30. Found: C 94.63, H 5.38%.
Cyclic voltammetric measurements of all the polyolefinic
aromatic molecules were performed on a CHI model 1100A
series electrochemical analyzer (CH Instrument, USA). A three
compartmental cell, containing glassy carbon as a working
electrode, silver/silver nitrate as the reference electrode, and
Pt wire as a counter electrode was used. Cyclic voltammetric
studies were carried out from solutions of the substrates (1 mM)
in benzene using tetrabutylammonium hexafluorophosphate
18 12
Synthesis of Polyolefinic Aromatic Molecules 1, 2, 2a, and 3
Compounds 1, 2, 2a, and 3 were prepared by Heck coupling of 1,4-
dibromobenzene, 1,3,5-tribromobenzene, 1,3,5-tribromo-2,4,6-
trimethylbenzene, or hexabromobenzene with 1-vinylpyrene.
(
0.1 M) as supporting electrolyte in the potential range of ꢀ0.2
General Procedure for Heck Coupling
ꢀ1
to 1.4 V at 50 mV s . All electrochemical experiments were
performed at room temperature (25 ꢂ 18C).
A stirredmixture of 1,4-dibromobenzene/1,3,5-tribromobenzene/
1
0
,3,5-tribromo-2,4,6-trimethylbenzene/hexabromobenzene (0.6/
.4/0.4/0.3mmol), Pd(OAc) (0.18/0.12/0.12/0.09 mmol) in dry
2
Synthesis and Spectroscopy
DMF (25mL) under nitrogen was successively treated with
K CO (3.5/2/2/1.5mmol) and tetrabutylammonium bromide
Reactions were carried out under nitrogen. Melting points are
uncorrected and solvents were purified by standard proce-
2
3
(
1
0.18/0.12/0.12/0.09 mmol), and then heated at reflux for 30 min.
-vinylpyrene (1.2/1.4/1.4/1.8mmol) was added to the reaction
[
18]
dures. Thin-layer chromatography (TLC) was carried out on
glass plates coated with functionalized silica gel-G (Acme) of
mixture and heated at reflux for 12/12/12/36h, cooled, and then
filtered. The filtrate was evaporated to dryness under vacuum.
,0.25 mM thickness, and were visualized with iodine. Column
chromatography was carried out with silica gel (Acme, 100–200
The residue was extracted with CHCl (3 ꢁ 100 mL), washed
3
1
mesh). H and C NMR spectra were recorded on a Bruker
13
with water (3 ꢁ 100 mL) and dried over anhydrous Na SO .
2
4
1
300 MHz for H and 75 MHz for C) spectrometer in CDCl3
13
Evaporation of the organic layer gave a residue, which was
purified by column chromatography using hexane as eluant to
give the corresponding conjugated pyrene derivatives.
(
and [d6]benzene, chemical shifts were noted in d [ppm], and
coupling constants (J) are expressed in hertz. Electron impact
mass spectrometry (EI-MS) spectra were recorded on a JEOL
DX-303 mass spectrometer at 70 eV. The Fast Atom Bom-
bardment (FAB)-MS spectra were recorded on a JEOL SX 102/
DA-6000 mass spectrometer using p-nitrobenzyl alcohol as
matrix. Elemental analyses were performed on a Perkin–Elmer
1,4-Bis[(E)-2-(pyren-1-yl)vinyl]benzene (1)
Following the general procedure for Heck coupling, 1,4-bis[(E)-
2-(pyren-1-yl)vinyl]benzene (1, 76%) was obtained as a yellow
solid from 1,4-dibromobenzene (0.14 g, 0.6 mmol) and 1-vinyl
pyrene (0.27 g, 1.2 mmol), mp 1828C. dH (300 MHz, CDCl3)
8.26 (d, J 9.3, 2H), 8.12–8.06 (m, 10H), 8.01 (d, J 15.3, 2H),
7.97–7.87 (m, 12H). d (75 MHz, CDCl ) 138.2, 134.7, 131.5,
2
40B elemental analyzer. The UV-Vis spectra were recorded on
a Shimadzu 260 spectrophotometer. The emission spectra were
recorded on a Perkin–Elmer LS-5B spectrophotometer.
C
3
1
126.1, 125.6, 125.4, 125.1, 125.0, 124.8, 123.7, 122.7. m/z (EI)
31.1, 130.8, 130.5, 128.8, 128.5, 128.1, 127.8, 127.4, 126.2,
Synthesis of 1-Vinylpyrene
þ
5
C 95.11, H 5.01%.
30 (M ). Anal. Calc. for C H : C 95.06, H 4.94. Found:
4
2 26
To a suspension of methyl triphenylphosphoniumiodide (2.0 g,
4
.9 mmol) in dry THF (100 mL), under nitrogen atmosphere
at room temperature, was added potassium tert-butoxide (3.3 g,
9.4 mmol). The solution was stirred for 1 h and then a solution
of pyrene-1-carbaldehyde (1.13 g, 4.9 mmol) in dry THF
25 mL) was added slowly. The mixture was stirred at room
1,3,5-Tris[(E)-2-(pyren-1-yl)vinyl]benzene (2)
2
Following the general procedure for Heck coupling, 1,3,5-tris
[(E)-2-(pyren-1-yl)vinyl]benzene (2, 73%) was obtained as a
yellow solid from 1,3,5-tribromobenzene (0.13 g, 0.4 mmol) and
1-vinyl pyrene (0.31 g, 1.4 mmol), mp 2348C. dH (300 MHz,
CDCl ) 8.45 (d, J 9.3, 3H), 8.27–7.72 (m, 27H) 7.59 (s, 3H),
(
temperature for 12 h, and then evaporated to dryness. Unreacted
potassium tert-butoxide was quenched with saturated aqueous
NH Cl solution (10 mL) and then extracted with CHCl3
4
3
,
(
2 ꢁ 100 mL). The combined organic layers were washed with
7.16 (d, J 16.2, 3H). d (75 MHz, CDCl ) 141.3, 132.7, 131.4,
C 3
130.8, 130.6, 128.7, 128.6, 128.2, 128.0, 127.7, 127.4, 126.1,
125.6, 125.3, 125.1, 124.8, 123.7, 123.3, 122.7. m/z (FAB-MS)
water (2 ꢁ 200 mL), brine (100 mL), and dried over anhydrous
Na SO . Evaporation of the organic layer gave a residue which
2
4

9
56
P. Rajakumar et al.
þ
7
C 95.15, H 4.72%.
56 (M ). Anal. Calc. for C H : C 95.21, H 4.79. Found:
6
[3] C. J. Brabec, N. S. Sariciftci, J. C. Hummelen, Adv. Funct. Mater.
2001, 11, 374. doi:10.1002/1616-3028(200110)11:5,374::AID-
ADFM374.3.0.CO;2-W
0 36
[
4] B. O’Regan, M. Gr a¨ tzel, Nature 1991, 353, 737. doi:10.1038/
53737A0
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1
-(2,4,6-Trimethyl-3,5-bis[(E)-2-(pyren-1-yl)vinyl]styryl)
3
pyrene (2a)
[
Following the general procedure for Heck coupling, 1-(2,4,6-
[
trimethyl-3,5-bis[(E)-2-(pyren-1-yl)vinyl]styryl)pyrene
(2a,
5%) was obtained as a colourless solid from 1,3,5-tribromo-
,4,6-trimethylbenzene (0.16 g, 0.4 mmol) and 1-vinyl pyrene
7
2
[
(
8
0.31 g, 1.4 mmol), mp .2808C. dH (300 MHz, [d6]benzene)
.47 (d, J 9.3, 3H), 8.24–7.85 (m, 24H), 7.34 (d, J 16.2, 3H), 6.63
8
7. doi:10.1039/A803991G
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þ
(d, J 16.2, 3H), 2.85 (s, 9H). m/z (FAB-MS) 798 (M ). Anal.
Calc. for C H : C 94.70, H 5.30. Found: C 94.77, H 5.23%.
1
6
3 42
[
(
1
,2,3,4,5,6-Hexakis[(E)-2-(pyren-1-yl)vinyl]benzene (3)
[
10] C. Tang, F. Liu, Y. J. Xia, J. Lin, L. H. Xie, G. Y. Zhong, Q. L. Fan,
Following the general procedure for Heck coupling, 1,2,3,4,5,6-
hexakis[(E)-2-(pyren-1-yl)vinyl]benzene (3, 69%) was
obtained as a yellow solid from hexabromobenzene (0.17 g,
W. Huang, Org. Electron. 2006, 7, 155. doi:10.1016/J.ORGEL.2006.
0
1.001
[
11] H. Shimizu, K. Fujimoto, M. Furusyo, H. Maeda, Y. Nanai, K. Mizuno,
M. Inouye, J. Org. Chem. 2007, 72, 1530. doi:10.1021/JO061959T
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G. J. Meyer, J. Phys. Chem. B 2006, 110, 15734. doi:10.1021/
JP0623847
0
1
.3 mmol) and 1-vinyl pyrene (0.40 g, 1.8 mmol), mp 195–
978C. d (300 MHz, [d6]benzene) 8.24 (d, J 9.3, 6H), 8.20 (d,
[
H
J 8.1, 6H), 8.10–7.88 (m, 42H), 7.37 (d, J 16.5, 6H), 7.02 (d,
þ
J 16.2, 6H). m/z (FAB-MS) 1434 (M ). Anal. Calc. for C1 H :
14
66
[13] H. Ji, T. Mizugaki, K. Ebitani, K. Kaneda, Tetrahedron Lett. 2002, 43,
C 95.37, H 4.63. Found: C 95.45, H 4.55%.
7
179. doi:10.1016/S0040-4039(02)01678-7
[
[
[
14] A. N. Fletcher, Photochem. Photobiol. 1969, 9, 439. doi:10.1111/
J.1751-1097.1969.TB07311.X
15] G. Schlithrol, S. Y. Huang, J. Sprague, A. J. Frank, J. Phys. Chem. B
Acknowledgement
The authors thank DST – FIST, New Delhi for their NMR spectral facility.
K.T.V. thanks CSIR for the award of Senior Research Fellowship (SRF),
Prof. P. Ramamurthy, National Center for Ultra Fast Processes, University of
Madras for fluorescence studies and Prof. S. Sriman Narayanan, Department
of Analytical Chemistry, University of Madras for cyclic voltammetry
studies.
1
997, 101, 8139.
16] (a) O. Enea, J. Moser, M. Gratzel, J. Electroanal. Chem. 1989, 259, 59.
doi:10.1016/0022-0728(89)80038-5
(
b) S. Ferrere, B. Gregg, New J. Chem. 2002, 26, 1155. doi:10.1039/
B203260K
[
17] S. Ganesan, B. Muthuraaman, J. Madhavan, P. Maruthamuthu, S. A.
Suthanthiraraj, Sol. Energy Mater. Sol. Cells 2008, 92, 1718.
doi:10.1016/J.SOLMAT.2008.08.004
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