A new ruthenium sensitizer containing dipyridylamine ligand for effective nanocrystalline dye-sensitized solar cells

Article abstract of DOI:10.1016/j.ica.2012.09.017

Two series of novel ruthenium bipyridyl sensitizers incorporating conjugated dipyridylamine ligands with general formula [Ru (dcbpy) (L) (NCS)₂, where dcbpy is 4,4′-dicarboxylic acid-2,2′- bipyridine and L is N-hexyl-4,4′-di(4-hexylstyryl)-2,2′- dipyridylamine, JJ-95 or N-hexyl-4,4′-di{(5-hexylthiophen-2-yl)vinyl}-2, 2′-dipyridylamine, JJ-99] have been synthesized and demonstrated as efficient sensitizers in dye-sensitized solar cells. A mesoporous titania film stained with JJ-99 exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 84%. Under standard AM 1.5 sunlight, the solar cell using a liquid-based electrolyte exhibits a short-circuit photocurrent density of 18.89 mA/cm², an open-circuit voltage of 0.66 V, and a fill factor of 0.69, corresponding to an overall conversion efficiency of 8.76%.

Full text of DOI:10.1016/j.ica.2012.09.017

Inorganica Chimica Acta 394 (2013) 506–511
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
A new ruthenium sensitizer containing dipyridylamine ligand for effective
nanocrystalline dye-sensitized solar cells
⇑
Jeum-Jong Kim , Jeonghun Yoon
Advanced Solar Technology Research Department, Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 April 2012
Received in revised form 5 September 2012
Accepted 19 September 2012
Available online 27 September 2012
Two series of novel ruthenium bipyridyl sensitizers incorporating conjugated dipyridylamine ligands
with general formula [Ru (dcbpy) (L) (NCS)2, where dcbpy is 4,40-dicarboxylic acid-2,20-bipyridine and
L
is N-hexyl-4,40-di(4-hexylstyryl)-2,20-dipyridylamine, JJ-95 or N-hexyl-4,40-di{(5-hexylthiophen-2-
yl)vinyl}-2,20-dipyridylamine, JJ-99] have been synthesized and demonstrated as efficient sensitizers in
dye-sensitized solar cells. A mesoporous titania film stained with JJ-99 exhibits a remarkable incident
monochromatic photon-to-current conversion efficiency of 84%. Under standard AM 1.5 sunlight, the
solar cell using a liquid-based electrolyte exhibits a short-circuit photocurrent density of 18.89 mA/
cm2, an open-circuit voltage of 0.66 V, and a fill factor of 0.69, corresponding to an overall conversion effi-
ciency of 8.76%.
Keywords:
Ruthenium sensitizer
Dipyridylamine ligand
Dye-sensitized solar cell
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
Recently, we are intrigued by amphiphilic ruthenium sensitizers
with 2,20-dipyridylamine moiety because the HOMO level of its
Dye-sensitized solar cells (DSSCs) have been extensively stud-
ied as a novel sunlight to electricity conversion system [1]. A DSSCs
consist of a dye-sensitized TiO2 electrode, a Pt-sputtered counter
electrode, and a redox couple. In these cells, the sensitizer is one
of the key components for high power conversion efficiencies.
Polypyridyl ruthenium sensitizers such as cis-dithiocyanato-
bis(4,40-dicarboxy-2,20-bipyridine)ruthenium (II) (N719) have
shown to be excellent dyes in DSSCs and their photoconversion
efficiency is more than 10% under air mass 1.5 sunlight [2]. The
main drawback of the sensitizer is the lack of absorption in the
red region of the visible spectrum. An important goal on ruthenium
dyes has been the development of new ruthenium dyes having a
wide and red-shifted MLCT band [3]. Numerous attempts have
been made to molecularly engineer ruthenium sensitizers to
broaden the absorption band and increase the molar absorption
coefficient. One of the successful approaches is to replace one of
the dcbpy anchoring ligands in N3 with a highly conjugated ancil-
lary ligand. Several groups have successfully developed efficient
ruthenium sensitizers by introducing extended conjugation units
on the bipyridyl ligand such as thiophene and alkoxybenzene
derivatives [4,5]. Another approach is to synthesize efficient ruthe-
nium sensitizers through a systematic tuning of the LUMO and
HOMO energy levels of the ruthenium polypyridyl complexes by
introducing a ligand with a low-lying p⁄ molecular orbital or by
destabilizing the metal t2g orbital with a strong donor ligand [6].
ruthenium dyes is lifted due to the more r-donating power of
the amine, resulting in red-shifting the metal-to-ligand charge
transfer (MLCT) band [7]. In addition, enhancing the absorption
coefficient and red-shifting of the MLCT band by increasing the
conjugation length of the ancillary ligand such as a styryl or thio-
phen-2-yl-vinyl-substituted bipyridine are well documented strat-
egy. Accordingly, we envisioned that if alkylamine unit combines
with a highly conjugated system the ruthenium dyes with the
ancillary ligand enhances the molar extinction coefficient as well
as broaden the MLCT band. Here we report the synthesis of amphi-
philic ruthenium (II) sensitizers (JJ-95 and JJ-99) incorporating
highly conjugated amine ligands and their photovoltaic perfor-
mance (Fig. 1).
2. Results and discussion
The synthetic route for the preparation of JJ-95 and JJ-99 is de-
picted in Scheme 1. First, 2-bromo-4-[4-(hexyl)styryl]pyridine was
prepared from the reaction of 4-hexyl-benzaldehyde and
diethyl(2-bromopyridin-4-yl)methylphosphonate using the Horn-
er–Emmons-Wadsworth reaction [8]. Conjugated dipyridylamine
ligand 2 was prepared by the Ullman coupling reaction [9] of 1
and hexylamine. The one-pot synthetic procedure developed for
heteroleptic polypyridyl ruthenium sensitizers was adapted for
the preparation of new JJ-95 [10]. Another ruthenium sensitizer
JJ-99 was prepared using the same procedure of JJ-95. The analyt-
ical and spectroscopic data of both sensitizers are consistent with
the formulated structure.
⇑
Corresponding author. Tel.: +82 42 860 1742; fax: +82 42 860 6495.
E-mail address: bizu4216100@etri.re.kr (J.-J. Kim).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.09.017

J.-J. Kim, J. Yoon / Inorganica Chimica Acta 394 (2013) 506–511
507
HOOC
COOH
HOOC
COOH
N
N
N
N
SCN
SCN
Ru
SCN
SCN
N
Ru
N
N
N
N
S
N
S
JJ-95
JJ-99
Fig. 1. Molecular structures of JJ-95 and JJ-99.
PO(OEt)2
Hexyl
Hexyl
b
a
+
N
OHC
N
Br
Br
HOOC
1
Hexyl
COOH
N
N
S
C
N
Ru
N
c, d, e
N
C
N
S
N
N
N
N
Hexyl
2
Hexyl
JJ-95
Hexyl
Hexyl
PO(OEt)2
S
b
a
CHO
Hexyl
+
S
N
N
Br
Br
3
Hexyl
HOOC
COOH
S
N
N
S
C
N
Ru
c, d, e
N
N
S
C
N
S
Hexyl
N
N
N
N
S
Hexyl
4
S
JJ-99
Hexyl
Scheme 1. Schematic diagram for the synthesis of sensitizers JJ-95 and JJ-99.
Fig. 2a shows the UV–Vis spectra of JJ-95 and JJ-99, together
with the N719 absorption spectrum as a reference. The polypyridyl
complexes of JJ-95 and JJ-99 show very broad and intence absorp-
tion peaks throughout the whole absorption region. The UV–Vis
spectrum of JJ-95 displays two absorption bands at 418 and
531 nm in the visible region, which are characteristic of the

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J.-J. Kim, J. Yoon / Inorganica Chimica Acta 394 (2013) 506–511
2.2
(a)0.7
(b)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.6
0.5
0.4
0.3
0.2
0.1
0.0
400
500
600
700
800
900
400
500
600
700
800
Wavelength (nm)
Wavelength (nm)
Fig. 2. Absorption and emission spectra (a) of JJ-95 (red line), JJ-99 (blue line) and N719 (green line) in EtOH, and absorption spectra (b) of JJ-95(red line), JJ-99 (blue line) and
N719 (green line) adsorbed on TiO2 film. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Table 1
Optical, oxidation and DSSC performance parameters of dyes.
/Mꢁ1 cmꢁ1
)
Eox (V)
E0-0 (V)
ELUMO (V)
Jsc (mA cmꢁ2
)
Voc (V)
FF
ge (%)
a
b
c
d
Dye
kabs (nm) (
e
JJ-95
JJ-99
N719
531 (10,910); 418 (16,920)
531 (15,430); 420 (24,430)
520 (14,400); 380 (14,682)
0.95
0.92
1.95
1.88
ꢁ1.00
ꢁ0.96
17.10
18.89
16.86
0.66
0.66
0.69
0.69
0.69
0.69
7.90
8.76
8.19
a
b
c
Absorption spectra were measured in ethanol solution.
Oxidation potential of dyes on TiO2 were measured in CH3CN with 0.1 M (n-C4H9)4NPF6 with a scan rate of 50 mV sꢁ1 (vs. NHE).
E0ꢁ0 was determined from intersection of absorption and emission spectra in ethanol.
d
e
ELUMO was calculated by Eox – E0ꢁ0
.
Performances of DSSCs were measured with 0.18 cm2 working area. Electrolyte: 0.6 M DMPII, 0.05 M I2, 0.1 M LiI and tert-butylpyridine in acetonitrile.
metal-to-ligand charge transfer bands (MLCT) [11]. The low energy
MLCT band of JJ-95 and JJ-99 at 531 nm is 11 nm red-shifted rela-
tive to that of N719. The red-shift of both sensitizers is attributable
In order to obtain the characteristic features of the electronic
structure, molecular orbital calculations of JJ-95 and JJ-99 have
been carried out by means of the B3LYP/6-31G⁄ as exchange–cor-
relation functional and 3-21G⁄ as a basis set. The orbital profiles
for the HOMO and LUMO of both dyes are presented in Fig. 3.
The HOMO of JJ-95 has amplitudes on the ruthenium metal and
the NCS ligands. Within the NCS ligands, the seizable amplitude
is located on the sulfur atom. The LUMO of JJ-95 is located homo-
geneously on the dcbpy ligand. Examination of the HOMO and
LUMO of both dyes indicates that HOMO–LUMO excitation moves
the electron distribution from the Ru-NCS unit to the dcbpy moi-
ety. Accordingly, the change in electron distribution induced by
photoexcitation results in an efficient charge separation. The dye
JJ-99 showed similar configuration geometry to JJ-95. Fig. 4
shows the incident monochromatic photo-to-current conversion
efficiency (IPCE) using 0.6 M 1,2-dimethyl-3-propylimidazolium
iodide (DMPII), 0.05 M I2, 0.1 M LiI, and 0.5 M tert-butylpyridine
in acetonitrile. The IPCE of JJ-99 showed a plateau of 80% from
465 to 580 nm, reaching a maximum 84% at 510 nm. The decline
of the IPCE above 620 nm toward the red is caused by the decrease
in the extinction coefficient of JJ-99. The band tails of toward
825 nm, contributing to the broad spectral light harvesting that
is characteristic of polypyridyl ruthenium dyes [13].
to the increase of p-conjugation in an ancillary ligand. The low en-
ergy MLCT band at 531 nm of JJ-99 exhibitsa molar extinction coef-
ficient of 15.4 ꢀ 103 Mꢁ1 cmꢁ1, which is higher than that of N719
dye (14.4 ꢀ 103 Mꢁ1 cmꢁ1
)
and JJ-95 (10.9 ꢀ 103 Mꢁ1 cmꢁ1).
Adsorption of JJ-95 and JJ-99 onto a TiO2 electrode was observed
to broaden the absorption band and to red shift the absorption
threshold up to 770 nm, ensuring a good light-harvesting effi-
ciency (Fig. 2b). Such broad-ening and red shift have been observed
in many ruthenium sensitizers on TiO2 electrodes [12].
We also observed that the sensitizers JJ-95 and JJ-99 exhibited
strong luminescence maxima at 740–755 nm when they excited
with their MLCT bands in EtOH at 298 K.
The electrochemical properties of the two sensitizers JJ-95 and
JJ-99 were studied by cyclic voltammetry in CH3CN with 0.1 M
tetrabutylammonium hexafluorophosphate using TiO2 film with
adsorbed dyes as working electrode. The oxidation potential of
JJ-95 and JJ-99 adsorbed on TiO2 film shows a quasi-reversible cou-
ple at 0.95 and 0.92 V versus NHE, respectively (Table 1). The RuIII/II
oxidation potential of JJ-95 is more positive than that of JJ-99. This
reflects the increased electron donating properties of ligand 2 com-
pared to that of 4 due to the 4-hexylstyryl group. The reduction
potentials of two dyes calculated from the oxidation potentials
and the E0ꢁ0 determined from the intersection of absorption and
emission spectra are ꢁ1.00 V for JJ-95 and ꢁ0.96 V for JJ-99 versus
NHE. A positive shift in the reduction potential in JJ-99 compared
The photovoltaic performance of the JJ-95, JJ-99, and N719 sen-
sitized cells are presented in Table 1. Under standard global AM 1.5
solar condition, the JJ-95 and JJ-99 sensitized cell gave a short cir-
cuit Photocurrent density (Jsc) of 17.10 and 18.89 mAcmꢁ2, an open
circuit voltage (Voc) of 0.66 V and a fill factor of 0.69, corresponding
to JJ-95 is attributable to more delocalization of the
system.
p
-conjugate
to an overall conversion efficiencies
respectively.
g of 7.90% and 8.76%,

J.-J. Kim, J. Yoon / Inorganica Chimica Acta 394 (2013) 506–511
509
under open-circuit conditions and under illumination of
100 mW cmꢁ2. The radius of the intermediate-frequency semicir-
cle in the Nyquist plot decreased in the order of JJ-95
(19.43
X) > JJ-99 (13.96 X). This result is in good agreement with
that of short-circuit photocurrent trend shown in Table 1.
In conclusion, two novel ruthenium bipyridyl sensitizers incor-
porating a highly conjugated dipyridylamine units have been syn-
thesized and characterized.
A solar-to-electricity conversion
efficiency of 8.76% for JJ-99 is better than 8.19% for the N719-sen-
sitized solar cell. The efficient performance of JJ-99 is attributed to
its high absorption extinction coefficient of MLCT band and ex-
tended absorption in the visible region. We believe that the devel-
opment of highly efficient ruthenium sensitizers is possible
through meticulously molecular engineering, and work on these
is now in progress.
3. Experimental section
3.1. Electron-transport measurements
The electron diffusion coefficient (De) and lifetimes (se) in TiO2
photoelectrode were measured by the stepped light-induced tran-
sient measurements of photocurrent and voltage (SLIM-PCV) [14–
17]. The transients were induced by a stepwise change in the laser
intensity. A diode laser (k = 635 nm) as a light source was modu-
lated using a function generator. The initial laser intensity was a
constant 90 mW cmꢁ2 and was attenuated up to approximately
10 mW cmꢁ2 using a ND filter which was positioned at the front
Fig. 3. Isodensity surface plots of the HOMO and LUMO of JJ-95 and JJ-99.
20
18
N719
JJ-95
JJ-99
16
100
14
12
10
8
side of the fabricated samples (TiO2 film thickness = ca. 20 lm; ac-
tive area = 0.04 cm2). The photocurrent and photovoltage tran-
sients were monitored using a digital oscilloscope through an
80
60
40
20
0
amplifier. The De value was obtained by a time constant (
mined by fitting a decay of the photocurrent transient with exp(ꢁt/
c) and the TiO2 film thickness (
) using the equation, De = x2
(2.77 c) [14]. The se value was also determined by fitting a decay
sc) deter-
N719
JJ-95
JJ-99
6
s
x
/
4
s
400
500
600
700
800
of photovoltage transient with exp(ꢁt/
se) [14]. All experiments
2
Wavelength (nm)
were carried out at room temperature.
0
-2
-4
3.2. Dye-sensitized solar cells fabrications
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Voltage (V)
Fluorine-doped tin oxide (FTO) glass plates (Pilkington TEC
Glass-TEC 8, Solar 2.3 mm thickness) were cleaned in a detergent
solution using an ultrasonic bath for 30 min and then rinsed with
water and ethanol. Then, the plates were immersed in 40 mM TiCl4
(aqueous) at 70 °C for 30 min and washed with water and ethanol.
A transparent nanocrystalline layer was prepared on the FTO glass
plates by using a doctor blade printing TiO2 paste (Solaronix, Ti-
Nanoxide T/SP), which was then dried for 2 h at 25 °C. The TiO2
electrodes were gradually heated under an air flow at 325 °C for
5 min, at 375 °C for 5 min, at 450 °C for 15 min, and at 500 °C for
15 min. The thickness of the transparent layer was measured by
using an Alpha-step 250 surface profilometer (Tencor Instruments,
San Jose, CA). A Paste containing 400 nm sized anatase particles
(CCIC. PST-400C) was deposited by means of doctor blade printing
to obtain the scattering layer, and then dried for 2 h at 25 °C. The
TiO2 electrodes were gradually heated under an air flow at
325 °C for 5 min, at 375 °C for 5 min, at 450 °C for 15 min, and at
Fig. 4. J–V curve and IPCE of JJ-95 (red line), JJ-99 (blue line) and N719 (green line).
(For interpretation of the references to color in this figure legend, the reader is
referred to the web version of this article.)
Under the same condition, the N719 sensitized cell gave a Jsc of
16.86 mA cmꢁ2, Voc of 0.69 V and a fill factor of 0.69, corresponding
to
g of 8.19%. From this result, of particular note is the 30 mV in-
crease in Voc of the N719 cell. The increase of Voc in N719 can be
interpreted as the suppression of the charge recombination losses
in the device is evident from the dark-current data for the cells
(Fig. 4).
Fig. 5 shows the electron diffusion coefficients and lifetimes of
the DSSCs employing different dyes (i.e. JJ-95, JJ-99 and N719,
respectively) displayed as a function of the Jsc and Voc, respectively.
No significant differences among the De values were seen at the
identical short-circuit current conditions as shown in Fig. 5a. The
order of magnitude of the se values was well consistent with that
of the Voc as shown in Table 1. However, the Ru-complex dyes
showed the Voc and se values somewhat lower than those of
N719 owing to their bulky structures inducing the aggregation
among the dye molecules during the adsorption onto TiO2 surface.
The ac impedances of the cells were measured under the illumi-
nation conditions. Fig. 6 shows the ac impedance spectra measured
500 °C for 15 min. The resulting film was composed of a 20
lm
thick transparent layer and a 4 m thick scattering layer. The
l
TiO2 electrodes were treated again with TiCl4 at 70 °C for 30 min
and sintered at 500 °C for 30 min. Then, they were immersed in
JJ-95 and JJ-99 (0.3 mM in ethanol and 10 mM CDCA) solutions
and kept at room temperature for 24 h. FTO plates for the counter
electrodes were cleaned in an ultrasonic bath in H2O, Acetone, and
0.1 M aqueous HCl, subsequently. The counter electrodes were

510
J.-J. Kim, J. Yoon / Inorganica Chimica Acta 394 (2013) 506–511
(a) 1E-3
1E-4
(b)
JJ-95
JJ-99
N 719
JJ-95
JJ-99
N 719
1E-5
1E-6
10
1
10
0.6
0.7
Short-circuit current mA cm-2
Open-circuit voltage (V)
Fig. 5. Electron diffusion coefficients (a) and lifetimes (b) of the photovoltaic cells employing JJ-95, JJ-99 and N719, respectively.
123.5, 119.9, 35.8, 33.6, 31.8, 29.1, 22.5, 14.1. Anal. calc. for C19H22-
BrN: C, 66.28; H, 6.44. Found: C, 66.32; H, 6.36%.
15
10
5
JJ-95
JJ-99
@ 1sun/ OCV
3.3.2. N-Hexyl-4,40-di(4-hexylstyryl)-2,20-dipyridylamine (2)
2-Bromo-4-[4-(hexylstyryl)] pyridine 1 (340 mg, 1.0 mmol),
hexylamine (50 mg, 0.5 mmol), 1,3-bis(diphenylpho-sphanyl)pro-
pane (15 mg, 0.035 mmol), dipalladiumtris(benzylideneacetone)
(20 mg, 0.022 mmol) and sodium tert-butoxide (120 mg,
1.3 mmol) were combined in a Schlenk vessel under N2. Dry tolu-
ene (35 mL) was then added and the resulting mixture stirred at
80 °C for 13 h. After evaporating the solvent under reduced pres-
sure, H2O (50 ml) and methylene chloride (50 ml) were added.
The organic layer was separated and dried in MgSO4. The solvent
was removed under reduced pressure. The pure product 2 was ob-
tained by column chromatography on silica gel (ethyl acetate:hex-
ane = 1:8, Rf = 0.55).Yield: 55%. 1H NMR (CDCl3): 8.32 (d, 2H,
J = 5.1 Hz), 7.41 (d, 4H, J = 8.1 Hz), 7.19 (d, 2H, J = 16.2 Hz), 7.16
(d, 4H, J = 7.8 Hz), 7.11 (s, 2H), 7.01 (d, 2H, J = 5.4 Hz), 6.90 (d,
2H, J = 16.2 Hz), 4.20 (t, 2H, J = 7.2 Hz), 2.60 (t, 4H, J = 7.8 Hz),
1.73 (m, 2H), 1.60 (m, 4H), 1.30–1.23 (m, 18H), 0.88 (m, 9H). 13C
NMR (CDCl3): 158.5, 148.7, 146.3, 143.9, 133.9, 132.7, 129.0,
127.1, 125.8, 113.9, 112.8, 53.6, 48.8, 35.9, 33.6, 31.8, 31.5, 28.6,
26.9, 22.8, 22.7, 14.2, 14.1. Anal. calc. for C44H57N3: C, 84.16; H,
9.15. Found: C, 84.26; H, 9.06%.
0
0
10
20
Ω
30
Z'
Fig. 6. Electrochemical impedance spectra measured under the illumination (1 sun)
for the cells with different dye adsorption conditions (i.e. JJ-95 (red), JJ-99 (blue).
(For interpretation of the references to color in this figure legend, the reader is
referred to the web version of this article.)
prepared by placing a drop of an H2PtCl6 solution (2 mg Pt in 1 mL
ethanol) on an FTO plate and heating it (at 400 °C) for 15 min. The
dye adsorbed TiO2 electrodes and the Pt counter electrodes were
assembled into a sealed sandwich-type cell by heating at 80 °C
using a hot-melt ionomer film (Surlyn) as a spacer between the
electrodes. A drop of the electrolyte consisting of 0.6 M 1,2-di-
methyl-3-propylimidazolium iodide (DMPII), 0.05 M I2, 0.1 M LiI,
and 0.5 M tert-butylpyridine in acetonitrile was placed in the
drilled hole of the counter electrode and was driven into the cell
via vacumm backfilling. Finally, the hole was sealed using addi-
tional Surlyn and a cover glass (0.1 mm thickness).
3.3.3. JJ-95 complex
A
mixture N-hexyl-4,40-di(4-hexylstyryl)-2,20-dipyridylamine
(105 mg, 0.167 mmol) and a dichloro(p-cymene)ruthenium (II)
dimmer (51 mg, 0.084 mmol) in argon-degassed DMF (15 mL)
was stirred at 70 °C for 4 h under reduced light. Subsequently,
4,40-dicarboxylic-2,20-bipyridine (41 mg, 0.167 mmol) was added
into the flask and the reaction mixture was stirred at 160 °C for
4 h. At last, an excess of NH4NCS (127 mg, 1.67 mmol) was added
to the resulting dark solution and the reaction continued for an-
other 4 h at 140 °C. Then the reaction mixture was cooled down
to room temperature and the solvent was removed under vacuum.
Water was added to get the precipitate. The resulting solid was fil-
tered and washed with water and dried under vaccum. The result-
ing solid was dissolved in methanol containing 2,2 equiv of
tetrabutylammonium hydroxide to confer solubility by deproto-
nating the carboxylic group and purified on a Sephadex LH-20 col-
umn with methanol as eluent. The collected main band was
concentrated and the solution pH was lowered to 5.1 using
0.02 M nitric acid. The precipitate was collected on a sintered glass
crucible by suction filtration and dried in air. Yield: 60%. 1H NMR
(CD3OD): 9.55 (d, 1H, J = 5.1 Hz), 8.94 (d, 1H, J = 6.0 Hz), 8.85 (s,
1H), 8.78 (s, 1H), 8.27 (d, 1H, J = 6.0 Hz), 8.16 (d, 1H, J = 5.4 Hz),
7.75 (d, 1H, J = 4.8 Hz), 7.67–7.14 (m, 15H), 7.01 (d, 2H,
J = 16.2 Hz), 4.21 (m, 2H), 2.61 (m, 4H), 1.64 (m, 6H), 1.36 (m,
3.3. Typical procedures and analytical data
3.3.1. 2-Bromo-4-[4-(hexyl)styryl]pyridine (1)
4-Hexylbenzaldehyde (310 mg, 1.62 mmol), diethyl (2-bromo-
pyridin-4-yl)methylphosphonate (500 mg, 1.62 mmol) and potas-
sium tert-butoxide (289 mg, 2.6 mmol) were dissolved in
Tetrahydrofuran (50 ml) and the mixture was stirred for 1.0 h.
After the solvent was removed under reduced pressure, H2O
(50 ml) and methylene chloride (50 ml) were added. The organic
layer was separated and dried in MgSO4. The solvent was removed
under reduced pressure. The pure product 1 was obtained by col-
umn chromatography on silica gel (methylene chloride:hex-
ane = 1:1, Rf = 0.35).Yield: 90%. 1H NMR (CDCl3): 8.29 (d, 1H,
J = 4.8 Hz), 7.54 (s, 1H), 7.44 (d, 2H, J = 8.1 Hz), 7.30–7.19 (m, 4H),
6.89 (d, 1H, J = 16.2 Hz), 2.63 (t, 2H, J = 8.1 Hz), 1.67–1.59 (m,
2H), 1.42–1.25 (m, 6H), 0.91(t, 3H, J = 7.5 Hz). 13C NMR (CDCl3):
150.4, 148.0, 144.6, 143.0, 134.8, 133.2, 129.1, 127.3, 124.9,

J.-J. Kim, J. Yoon / Inorganica Chimica Acta 394 (2013) 506–511
511
18H), 0.86 (m, 9H). Anal. calc. for C58H65N7O4RuS2: C, 63.95; H,
6.01. Found: C, 63.87; H, 6.04%.
collected on a sintered glass crucible by suction filtration and dried
in air. Yield: 60%. 1H NMR (CD3OD): 9.54 (d, 1H, J = 5.4 Hz), 8.90 (d,
1H, J = 6.0 Hz), 8.84 (s, 1H), 8.77 (s, 1H), 8.24 (d, 1H, J = 5.4 Hz), 8.15
(d, 1H, J = 5.7 Hz), 7.75 (m, 2H), 7.45 (m, 3H), 7.13 (d, 1H,
J = 3.3 Hz), 7.07 (s, 1H), 7.04–6.90 (m, 4H), 6.78 (d, 1H, J = 3.6 Hz),
6.71 (d, 1H, J = 5.1 Hz), 6.64 (d, 1H, J = 16.5 Hz), 4.18 (t, 1H), 3.72
(t, 1H), 2.84 (t, 2H), 2.79 (t, 2H), 1.63 (m, 6H), 1.35 (m, 18H), 0.87
(m, 9H). Anal. calc. for C54H61N7O4RuS4: C, 58.88; H, 5.58. Found:
C, 58.73; H, 5.57%.
3.3.4. 2-Bromo-4-[-2-(5-hexylthiophen-2-yl)vinyl]pyridine (3)
Diethyl (2-bromopyridin-4-yl)-methylphosphonate 2 (310 mg,
1.0 mmol), 5-hexylthiophene-2-carbaldehyde (190 mg, 1.0 mmol),
and potassium tert-butoxide (200 mg, 1.8 mmol) were dissolved
in Tetrahydrofuran (50 ml) and the mixture was stirred for 0.5 h.
After the solvent was removed under reduced pressure, H2O
(50 ml) and methylene chloride (50 ml) were added. The organic
layer was separated and dried in MgSO4. The solvent was removed
under reduced pressure. The pure product 3 was obtained by col-
umn chromatography on silica gel (methylene chloride:hex-
ane = 1:1, Rf = 0.3).Yield: 90%. 1H NMR (CDCl3): 8.26 (d, 1H,
J = 5.1 Hz), 7.47 (d, 1H, J = 1.8 Hz), 7.35 (d, 1H, J = 15.6 Hz), 7.23
(dd, 1H, J = 5.1 Hz), 6.98 (d, 1H, J = 3.6 Hz), 6.71 (d, 1H, J = 3.3 Hz),
6.60(d, 1H, J = 15.6 Hz), 2.81 (t, 2H, J = 7.5, 7.8 Hz), 1.68 (qu, 2H,
J = 6.6, 7.8 Hz), 1.33 (m, 6H), 0.89(t, 3H, J = 6.6, 6.9 Hz). 13C NMR
(CDCl3): 150.3, 148.5, 147.8, 143.0, 138.9, 129.2, 128.1, 125.2,
124.5, 122.4, 119.6, 31.7, 31.6, 30.6 28.9, 22.7, 14.2. Anal. calc. for
Acknowledgment
This work was supported by Electronics and Telecommunica-
tions Research Institute (ETRI).
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3.3.6. JJ-99 complex
A
mixture N-hexyl-4,40-di(5-hexylthiophen-2-yl)vinyl)-2,20-
dipyridyl-amine (112 mg, 0.174 mmol) and
a
dichloro(p-
cymene)ruthenium (II) dimer (54 mg, 0.087 mmol) in argon-de-
gassed DMF (15 mL) was stirred at 70 °C for 4 h under reduced
light. Subsequently, 4,40-dicarboxylic-2,20-bipyridine (43 mg,
0.174 mmol) was added into the flask and the reaction mixture
was stirred at 160 °C for 4 h. At last, an excess of NH4NCS
(132 mg, 1.74 mmol) was added to the resulting dark solution
and the reaction continued for another 4 h at 140 °C. Then the reac-
tion mixture was cooled down to room temperature and the sol-
vent was removed under vacuum. Water was added to get the
precipitate. The resulting solid was filtered and washed with water
and dried under vaccum. The resulting solid was dissolved in
methanol containing 2,2 equiv of tetrabutylammonium hydroxide
to confer solubility by deprotonating the carboxylic group and
purified on a Sephadex LH-20 column with methanol as eluent.
The collected main band was concentrated and the solution pH
was lowered to 5.1 using 0.02 M nitric acid. The precipitate was