New type of ruthenium sensitizers with a triazole moiety as a bridging group

Article abstract of DOI:10.1016/j.jorganchem.2009.12.021

A new type of ruthenium sensitizers JK-91 and JK-92 with a triazole moiety as a bridging group were designed and synthesized in an attempt to increase the π-conjugated system. Two compounds work as highly efficient sensitizers for the dye-sensitized nanocrystalline TiO₂ solar cell. Under standard AM 1.5 sunlight, the sensitizer JK-91 yielded a short-circuit photocurrent density of 12.55 mA/cm², an open-circuit voltage of 0.73 V, and a fill factor of 0.73, corresponding to an overall conversion efficiency of 6.75%.

Full text of DOI:10.1016/j.jorganchem.2009.12.021

Journal of Organometallic Chemistry 695 (2010) 821–826
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
New type of ruthenium sensitizers with a triazole moiety as a bridging group
Sanghyun Paek a, Chul Baik a, Moon-sung Kang b, Hongsuk Kang c, Jaejung Ko a,
*
a Department of New Material Chemistry, Korea University, Jochiwon, Chungnam 339-7000, Republic of Korea
b Energy and Environment Lab, Samsung Advanced Institute of Technology, Yongin 446-712, Republic of Korea
c Department of Nano and Advanced Materials, College of Engineering, Jeonju University, Jeonju, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
A new type of ruthenium sensitizers JK-91 and JK-92 with a triazole moiety as a bridging group were
Received 8 September 2009
Received in revised form 17 December 2009
Accepted 18 December 2009
Available online 4 January 2010
designed and synthesized in an attempt to increase the p-conjugated system. Two compounds work as
highly efficient sensitizers for the dye-sensitized nanocrystalline TiO2 solar cell. Under standard AM
1.5 sunlight, the sensitizer JK-91 yielded a short-circuit photocurrent density of 12.55 mA/cm2, an
open-circuit voltage of 0.73 V, and a fill factor of 0.73, corresponding to an overall conversion efficiency
of 6.75%.
Keywords:
Dye
Ó 2010 Elsevier B.V. All rights reserved.
DSSC
Ru-complex
1. Introduction
In line with the continuation of the efforts in this direction for
improving the power conversion efficiency, we have synthesized
Dye-sensitized solar cells (DSSCs) are attracting widespread
interest as low-cost alternatives to conventional solid-state photo-
voltaic device because of their low-cost and high performance [1–
3]. In these cells, the sensitizer is one of the key elements for high-
power conversion efficiencies. Current high efficiency of DSSCs
achieves with the sensitizer N719 (cis-bis(isothiocyanato)bis(2,20-
bipyridyl-4,40-dicarboxylato)ruthenium-(II)bis(tetrabutyl-
ammonium) [4,5]. However, the main drawback of the N719
sensitizer is the lack of absorption in the red region of the visible
spectrum. One of the approaches to address these issues would
be to substitute one of the 2,20-bipyridyl-4,40-dicarboxylate groups
in the sensitizer into the conjugated bipyridine of the ancillary li-
gand [6–10]. This not only exhibits an intense and red-shifted peak
of the sensitizer but also increases its hydrophobicity, stabilizing
device performance under long-term light soaking. Using this con-
cept, several Ru polypyridyl complexes have achieved power con-
version efficiencies of 10–11% [11–14]. Nevertheless, the quest for
new sensitizers that efficiently harvest solar light still continues to
be an important issue. As small structural variation of sensitizers
results in significant changes in redox energies and photo-physical
properties, affecting dramatically the performance of DSSCs [15–
18], judicious tuning of the LUMO and HOMO energy levels of sen-
sitizer [19], panchromatic sensitization on TiO2, and increasing of
the molar absorption coefficient of sensitizer [20–23] are the strat-
egies to be pursued in the molecular engineering of sensitizer.
a new type of the ruthenium sensitizer, consisting of triazole moi-
ety as a bridging group synthesized using click chemistry. The gen-
eral idea is to use the triazole group for extending the p-conjugated
backbone. In this article, we report the synthesis, characterization,
and photovoltaic properties of a new type of ruthenium(II) com-
plexes JK-91 and JK-92.
* Corresponding author. Tel.: +82 41 860 1337; fax: +82 41 867 5396.
E-mail address: jko@korea.ac.kr (J. Ko).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.12.021

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S. Paek et al. / Journal of Organometallic Chemistry 695 (2010) 821–826
4,40-dicarboxyl-2,20-bipyridine. The chloro intermediates reacted
with a large excess of ammonium thiocyanate to afford the ruthe-
nium sensitizers JK-91 and JK-92 (Scheme 1). The sensitizers JK-91
and JK-92 were spectroscopically characterized, and all data are
consistent with the formulated structures.
The UV–Vis and emission spectra of JK-91 and JK-92 in DMF are
shown in Fig. 1, together with the UV–Vis spectra of the corre-
sponding dyes adsorbed on TiO2 film. The absorption spectrum of
JK-91 exhibits two visible absorption bands at 388 and 529 nm,
which are assigned as the metal-to-ligand charge transfer (MLCT)
bands. Under the same conditions the sensitizer JK-92 that con-
tains the hexyloxy group instead of hexyl group causes a blue shift
to 521 nm and a slightly narrow peak relative to the JK-91. The
molar extinction coefficients of the low energy MLCT bands in
JK-91
15,500 dm3 molꢀ1 cmꢀ1
= 14,700 dm3 molꢀ1 cmꢀ1) [25].
The enhanced molar extinction coefficients of both sensitizers
are attributable to the extension of the -conjugation in the ancil-
(e
= 16,100 dm3 molꢀ1 cmꢀ1
are higher than that of N719
)
and
JK-92
(e =
)
(e
p
lary ligand. Anchoring of JK-91 and JK-92 on TiO2 film was ob-
served to broaden the absorption spectrum and to red shift the
absorption threshold up to 730 nm. Similar broadening and red
shift have been observed in other ruthenium sensitizers on TiO2
films [26]. We observed that the sensitizers JK-91 and JK-92 exhib-
ited strong luminescence maxima at 753 and 763 nm, respectively,
when they are excited within their MLCT bands in an air-equili-
brated solution at 298 K.
The cyclic voltammograms of JK-91 and JK-92 on TiO2 films in
CH3CN with 0.1 M tetrabutylammonium hexafluorophosphate
show quasi-reversible couples at 0.87 and 0.93 V vs. NHE, respec-
tively (Fig. 2). The ground state redox potential of both sensitizers
is higher than that of the iodide electron donor, providing a thermo-
dynamic driving force for efficient dye regeneration. The reduction
potential of two sensitizers calculated from the oxidation potential
and the E0–0 determined from the intersection of normalized absorp-
tion and emission spectra is listed in Table 1. The excited-state redox
2. Results and discussion
The synthetic procedures of ruthenium sensitizers JK-91 and
JK-92 are outlined in Scheme 1. The ligands 3 and 4 were synthe-
sized by the copper(I)-catalyzed click chemistry between a bis-al-
kyne and azides [24]. The reaction of [Ru(p-cymene)Cl2]2 complex
with 3 or 4 in DMF under nitrogen resulted in the formation of a
mononuclear complex. The hetero-leptic dichloro complexes were
synthesized by reaction of the mononuclear intermediate with
Scheme 1. Schematic diagram for the synthesis of ruthenium sensitizers 5 and 6.

S. Paek et al. / Journal of Organometallic Chemistry 695 (2010) 821–826
823
We carried out the molecular orbital calculation of JK-91 and
JK-92 to gain insight into the photo-physical properties using the
*
*
B3LYP/6-31G as exchange correlation function and 3-21G as a
basis set (Fig. 3). The calculation illustrates that the filled frontier
orbital (HOMO) of both sensitizers is mainly composed of Ru 4d
orbital with a sizable contribution from the NCS ligand orbital.
*
The LUMO of both sensitizers is
p orbital delocalized on the dcbpy
ligand. Examination of the HOMO and LUMO of both sensitizers
indicates that photoexcitation was directly charged from the
ruthenium–NCS unit to the carboxy pyridine ligand bound to the
TiO2 surface.
Fig. 4 shows action spectra of monochromatic incident photo-
to-current conversion efficiencies (IPCEs) for DSSCs based on JK-
91 and JK-92 using an acetonitrile-based electrolyte (electrolyte:
0.6 M 3-hexyl-1,2-dimethyl imidazolium iodide, 0.05 M I2, 0.1 M
LiI, and 0.5 M 4-tert-butylpyridine). The IPCE of JK-91 shows a pla-
teau of over 60% from 430 to 620 nm, reaching the maximum of
76% at 528 nm. The photo-response of the cell extends up to
780 nm. The decline of the IPCE above 630 nm toward the red is
caused by the decrease in the extinction coefficient of JK-91 in that
region. The JK-91 sensitizer shows a relatively large photocurrent
and broad IPCE relative to those of JK-92, which is consistent with
the absorption spectra of JK-91 and JK-92. Under a standard global
AM 1.5 solar condition, JK-91 and JK-92 sensitized cell gave a short
circuit photocurrent density (Jsc) of 12.55 and 11.41 mA cmꢀ2, an
open circuit voltage (Voc) of 0.73 and 0.73 V and a fill factor of
0.73 and 0.74, corresponding to an overall conversion efficiencies
Fig. 1. Absorption spectra of JK-91 (red solid line), JK-92 (blue solid line) and N719
(block solid line) in DMF, together with the absorption spectra of JK-91 (red dash
line) and JK-92 (blue dash line) adsorbed on TiO2 film and their emission spectra of
JK-91 (red dot line) and JK-92 (blue dot line). (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
g
of 6.75 and 6.22%, respectively (Fig. 5). Under the same condition,
the N719 sensitized cell gave a Jsc of 14.68 mA cmꢀ2, a Voc of 0.75 V
and a fill factor of 0.73, corresponding to of 8.06% (Table 1). Of
g
particular importance is the 1.14 mA cmꢀ2 increase in JK-91 rela-
tive to JK-92. To clarify the high photocurrent of JK-91 sensitized
cell compared to the JK-92 sensitizer, we have measured the
amount of dyes adsorbed on TiO2 film. The adsorbed amounts of
2.6 ꢁ 10ꢀ7 mmol cmꢀ2 for JK-91 and 2.7 ꢁ 10ꢀ7 mmol cmꢀ2 for
JK-92 are observed. Therefore, it is assumed that the enhanced
photocurrent in JK-91 is originated from a broad and intense
absorption spectrum rather than their adsorbed amounts.
Fig. 5 shows the electron diffusion coefficients and lifetimes of
the DSSCs employing different dyes (i.e. JK-91, JK-92 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, meaning that the struc-
tural changes in the dye molecules are not the important factor
dominating the electron diffusivity through nanocrystalline TiO2
film [34]. In the case of the se values, however, the significant dif-
ference was observed among the cells employing different dyes.
The order of magnitude of the se values was well consistent with
that of the Voc as shown in Table 1. The results demonstrate that
Fig. 2. CV of JK-91 (solid line) and JK-92 (dash line) on TiO2 film with 0.1 M (n-
C4H9)4NPF6 acetonitrile solution (scan rate of 50 mV sꢀ1).
potentials, U0(S+/S*), of the dyes (JK-91: ꢀ0.92 V; JK-92: ꢀ0.90 V vs.
NHE) are much negative than the conduction band of TiO2 at approx-
imately ꢀ0.5 V versus NHE, providing enough driving force for elec-
tron injection [27–29]. A slightly positive shift in the reduction
potential in JK-91 compared to JK-92 is due to more delocalization
of the p-conjugated system on the ancillary ligand.
Table 1
Optical, redox and DSSC performance parameters of dyes.
/Mꢀ1 cmꢀ1
)
kemb/nm (
e
/Mꢀ1 cmꢀ1
)
Eoxc/V
E0–0d/V
ELUe/V
ꢀ0.92
Jsc (mA/cm2)
Voc (V)
F.Fh
gi (%)
f
g
Dye
kabsa/nm (
e
JK-91
388(22,000)
529(16,100)
384(21,500)
521(15,500)
753
0.87
1.79
12.55
11.41
14.68
0.73
0.73
0.75
0.73
6.75
JK-92
763
0.93
1.83
ꢀ0.90
0.74
0.73
6.22
8.06
N719
a
b
c
d
e
f
Absorption spectra were measured in ethanol.
Emission spectra were measured in ethanol.
Eox is oxidation potential. Red-ox potential of dyes on TiO2 were measured in CH3CN with 0.1 M (n-C4H9)4NPF6 with a scan rate of 50 mV sꢀ1 (vs. Fc/Fc+).
E0–0 is voltage of intersection point between absorption and emission spectra. E0–0 was determined from intersection of absorption and emission spectra in ethanol.
ELUMO was calculated by Eox ꢀ E0–0
Jsc: short photocurrent density.
Voc: open-circuit photovoltage.
FF: fill factor.
.
g
h
i
g
: total power conversion efficiency.

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S. Paek et al. / Journal of Organometallic Chemistry 695 (2010) 821–826
Fig. 3. Isodensity surface plots of the HOMO and LUMO of JK-91 and JK-92.
4. Experimental section
4.1. General methods
All reactions were carried out under an argon atmosphere. Sol-
vents were distilled from appropriate reagents. All reagents were
purchased from Sigma–Aldrich, TCI and Acros Organics. 1H NMR
Fig. 4. I–V curves and IPCE spectra for JK-91 (red solid line) and JK-92 (blue dash
line). (For interpretation of the references to colour in this figure legend, the reader
is referred to the web version of this article.)
the introduction of hydrophobic alkyl chains could effectively re-
tard the electron recombination originated from the direct contact
between the electrons on TiO2 surface and Iꢀ3 ions in electrolyte.
However, the Ru-complex dyes showed the Voc and se values lower
than those of N719 owing to their bulky structures inducing the
aggregation among the dye molecules during the adsorption onto
TiO2 surface.
3. Conclusion
In summary, we have synthesized new efficient ruthenium dyes
JK-91 and JK-92 containing the triazol-4-yl unit by click chemistry
that not only enhances the molar extinction coefficient but also
shifts to the red region. The power conversion efficiency of the
DSSCs based on the JK-91 and JK-92 reaches 6.22 and 6.75%. The
power conversion efficiency was sensitive to the substituent unit.
Alkyl introduction of dye in both sensitizers the Voc due to the
blocking effect of the charge recombination. The low photocurrent
of JK-91 and JK-92 relative to that of N719 is due to the low ad-
sorbed quantity of two sensitizers. We believe that the develop-
ment of efficient ruthenium sensitizers will be possible through
the structural modifications of ancillary group.
Fig. 5. Electron diffusion coefficients (A) and lifetimes (B) in the photoelectrodes
adsorbing different dyes (i.e., JK-91, JK-92 and N719).

S. Paek et al. / Journal of Organometallic Chemistry 695 (2010) 821–826
825
and 13C NMR spectra were recorded on a Varian Mercury 300 spec-
trometer. Elemental analyses were performed with a Carlo Erba
Instruments CHNS-O EA 1108 analyzer. Mass spectra were re-
corded on a JEOL JMS-SX102A instrument. The absorption and pho-
toluminescence spectra were recorded on a Perkin–Elmer Lambda
2S UV–vis spectrometer and a Perkin LS fluorescence spectrometer,
respectively.
Cyclic voltammogram was carried out with a BAS 100B (Bioan-
alytical System, Inc.). A three electrode system was used and con-
sisted of a gold disk, working electrode, and a platinum wire
electrode. Redox potential of dyes on TiO2 was measured in CH3CN
with a scan rate at 50 mV sꢀ1(vs. Fc/Fc+).
bromo-4-hexylbenzene (1 g, 4.1 mmol) dissolved in THF (10 ml)
and stirred for 15 min at ꢀ78 °C. Then tosylazide (0.8 g, 4.1 mmol)
dissolved in THF (10 ml) was added dropwise. During tosylazide
addition the colour of the solution turned red. The reaction mixture
was stirred for 14 h at ꢀ78 °C under argon atmosphere. A saturated
solution of aqueous ammonium chloride (10 ml) was added drop-
wise at ꢀ78 °C and finally the reaction mixture was allowed to
warm to room temperature. THF was removed by rotary evapora-
tion and residue was extracted with Et2O and washed with brine.
The organic layer was dried over MgSO4 and concentrated in vacuo.
Column chromatography and recrystallisation (MeOH) afforded 4
as
a d 7.15 (d, 2H,
light yellow solid. 1H NMR (CDCl3):
3J = 8.1 Hz), 6.94 (d, 2H, 3J = 8.1 Hz), 2.57 (t, 2H, 3J = 6.6 Hz), 1.59
(m, 2H), 1.32 (m, 6H), 0.88 (t, 3H, 3J = 6.6 Hz). 13C NMR (CDCl3): d
158.3, 132.3, 116.4, 112.6, 35.5, 31.6, 29.2, 25.8, 22.7, 14.1. MS:
m/z 202.27 [M+]. Anal. Calc. for C12H17N3: C, 70.90; H, 8.43. Found:
C, 70.68; H, 8.33.
4.2. Fabrication of DSSC
For the preparation of DSSC,
s qꢀ1) glass plate was immerged in 40 mM TiCl4 aqueous solu-
tion as reported by the Grätzel group. The first TiO2 layer of 7
a washed FTO (Pilkington,
8
X
lm
thickness was prepared by screen printing with transparent meso-
porous TiO2 paste (13 nm anatase, solaronix), and the second opa-
4.5.2. Synthesis of 1-azido-4-(hexyloxy)benzene 2
que layer of 4
l
m thickness (400 nm, CCIC) was coated for the
The product was synthesized according to the procedure as de-
scribed above for synthesis of 1. 1H NMR(CDCl3): d 6.94 (d, 2H,
3J = 9 Hz), 6.87 (d, 2H, 3J = 9 Hz), 3.92 (t, 2H, 3J = 6.6 Hz), 1.76 (m,
2H), 1.34 (m, 6H), 0.91 (t, 3H, 3J = 6.6 Hz). 13C NMR (CDCl3): d
156.7, 132.2, 120.0, 115.8, 68.5, 31.7, 29.3, 25.8, 22.7, 14.1. MS:
m/z 218.28 [M+]. Anal. Calc. for C12H17N3O: C, 65.73; H, 7.81.
Found: C, 65.93; H, 7.88.
purpose of light scattering. The TiO2 electrodes were immersed
into the dyes (JK-91, and JK-92) solutions (0.3 mM in DMF contain-
ing 10 mM 3a,7a-dihydroxy-5b-cholic acid) and kept at room tem-
perature for 18 h. Counter electrodes were prepared by coating
with a drop of H2PtCl6 solution (2 mg Pt in 1 mL ethanol) on a
FTO plate. The electrolyte was then introduced into the cell, which
was composed of 0.6 M 3-hexyl-1,2-dimethyl imidazolium iodide,
0.05 M iodine, 0.1 M LiI and 0.5 M 4-tert-butylpyridine in
acetonitrile.
4.5.3. Synthesis of 4,40-bis(1-(4-hexylphenyl)-1H-1,2,3-triazol-4-yl)-
2,20-bipyridine 3
4.3. Characterization of DSSC
A three necked flask was charged with 4,40-bis(ethynyl)-2,20-
bipyridyl (1 equiv.), the aryl azides 1 (2.2 equiv. per acetylene func-
tionality), sodium ascorbate (0.1–0.2 equiv.), CuSO4 (0.2 equiv.),
NaOH (0.2 equiv.) and a solvent mixture of H2O/tert-BuOH/CH2Cl2
(1/2/1). The flask was evacuated and flushed with argon twice.
CuSO4 was added (stock solution, 10 mg CuSO4 per 0.3 ml of
water) and the mixture was stirred for 3 days at room temperature
in the dark. After the acetylene starting material was consumed
(TLC monitoring), the mixture was transferred into a separation
funnel and CH2Cl2 was added. The aqueous phase was extracted
with CH2Cl2. The organic phases were combined and washed with
brine. After drying over MgSO4, followed by filtration and removal
of the solvent in vacuo, a colored solid was obtained that was puri-
fied by column chromatography to yield the respective products in
high analytical purities. 1H NMR(CDCl3): d 8.81 (d, 2H, 3J = 6 Hz),
8.80 (s, 2H), 8.51 (s, 2H), 8.09 (d, 2H, 3J = 6 Hz), 7.72 (d, 4H,
3J = 8.7 Hz), 7.37 (d, 4H, 3J = 8.7 Hz), 2.70 (t, 4H, 3J = 6.6 Hz), 1.66
(m, 4H), 1.33 (m, 12H), 0.90 (t, 6H, 3J = 6.6 Hz). 13C NMR (CDCl3):
d 156.5, 150.1, 146.1, 144.5, 139.0, 134.7, 129.9, 120.6, 120.4,
119.7, 117.6, 35.5, 31.6, 29.2, 25.8, 22.7, 14.1. MS: m/z 609.78
[M+]. Anal. Calc. for C38H42N8: C, 74.72; H, 6.93. Found: C, 74.52;
H, 6.83.
The cells were measured using 1000W xenon light source,
whose power of an AM 1.5 Oriel solar simulator was calibrated
by using KG5 filtered Si reference solar cell. The incident photon-
to-current conversion efficiency (IPCE) spectra for the cells were
measured on an IPCE measuring system (PV measurements).
4.4. Electron transport measurements
Electron diffusion coefficients and lifetimes were measured by
the stepped light-induced transient measurements of photocurrent
and voltages (SLIM-PCV). The transients were induced by a step-
wise change in the laser intensity [30–33].
A diode laser
(k = 635 nm) as a light source was modulated using a function gen-
erator (UDP-303, PNCYS Co., Ltd., Korea). The initial laser intensity
was 90 mW cmꢀ2 constantly and less than 10% of the light inten-
sity was turned down using a ND filter. The laser beam was posi-
tioned at the front side of the fabricated samples (0.04 cm2). The
laser was operated at the voltage of 3.0 V and stepped down to
2.9 V for 5 s. Then the single shot of the time-profiles of the photo-
current and photovoltage was obtained from an oscilloscope (TDS
3052B, Tektronix) through a current amplifier (SR570, Stanford Re-
search Systems) and a voltage amplifier (5307, NF electronic
Instruments), respectively. A total of 5 points were measured to
determine the electron diffusion coefficients and lifetimes. For
the measurement of SLIM-PCV, the TiO2 thickness of the photoelec-
4.5.4. Synthesis of 4,40-bis(1-(4-(hexyloxy)phenyl)-1H-1,2,3-triazol-4-
yl)-2,20-bipyridine 4
The product was synthesized according to the procedure as de-
scribed above for synthesis of 3. 1H NMR(CDCl3): d 8.81 (d, 2H,
3J = 6 Hz), 8.80 (s, 2H), 8.45 (s, 2H), 8.09 (d, 2H, 3J = 6 Hz), 7.68 (d,
4H, 3J = 8.7 Hz), 7.06 (d, 4H, 3J = 8.7 Hz), 3.92 (t, 4H, 3J = 6.6 Hz),
1.76 (m, 4H), 1.34 (m, 12H), 0.90 (t, 6H, 3J = 6.6 Hz). 13C NMR
(CDCl3): d 156.7, 150.1, 146.1, 144.5, 139.0, 132.2, 129.9, 120.6,
120.4, 119.7, 117.6, 68.3, 31.7, 29.3, 25.8, 22.7, 14.1, MS: m/z
641.79 [M+]. Anal. Calc. for C38H42N8O2: C, 71.00; H, 6.59. Found:
C, 70.80; H, 6.49.
trode was controlled as approximately 10
lm.
4.5. Synthesis of sensitizers
4.5.1. Synthesis of 1-azido-4-hexylbenzene 1
To a three-necked flask tert-butyllithium (1.6 ml of 2.5 M solu-
tion in pentane, 4.1 mmol) and THF (30 ml) were charged under ar-
gon atmosphere at ꢀ78 °C. To this solution was dropwise added 1-

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4.5.5. Synthesis of cis-[Ru(R3)(H2dcbpy)(NCS)2] JK-91
[{RuCl(p-cymene)}2] (0.188 mmol) was dissolved in DMF
(30 mL) and 3 (2 equiv.) was added. The reaction mixture was
heated at 80 °C under nitrogen for 4 h and then, 2,20-bipyridine-
4,40-dicarboxylic acid (2 equiv.) was added. The reaction mixture
was refluxed at 160 °C for another 4 h. Then an excess of NH4NCS
was added to the reaction mixture and heated at 130 °C for a fur-
ther 5 h. The solvent was removed using a rotary-evaporator under
vacuum. Water was added to the resulting semisolid to remove ex-
cess NH4NCS. The water-insoluble product was collected on a sin-
tered glass crucible by suction filtration and washed with distilled
water, and diethylether. The crude complex was dissolved in a
solution of tetra(n-butyl) ammonium hydroxide in methanol. The
concentrated solution was charged onto a Sephadex LH-20 column
and eluted with methanol. 1H NMR(CDCl3): d 9.76 (s, 1H), 9.58 (s,
1H), 9.45 (d, 1H, 3J = 5.8 Hz), 9.32 (d, 1H, 3J = 6 Hz), 9.25 (s, 1H),
9.15 (s, 1H), 9.07 (s, 1H), 8.98 (s, 1H), 8.41 (d, 1H, 3J = 5.8 Hz),
8.28 (d, 1H, 3J = 6 Hz), 7.91–7.44 (br, 12H), 2.65 (t, 4H,
3J = 6.6 Hz), 1.57 (m, 4H), 1.28 (m, 12H), 0.91 (t, 6H, 3J = 6.6 Hz).
MS: m/z 1072.26 [M+]. Anal. Calc. for C52H50N12O4RuS2: C, 58.25;
H, 4.70. Found: C, 58.50; H, 4.60.
4.5.6. Synthesis of cis-[Ru(R4)(H2dcbpy)(NCS)2] JK-92
The product was synthesized according to the procedure as de-
scribed above for synthesis of 5. 1H NMR(CDCl3): d 9.73 (s, 1H),
9.55 (s, 1H), 9.47 (d, 1H, 3J = 5.8 Hz), 9.32 (d, 1H, 3J = 6 Hz), 9.28
(s, 1H), 9.15 (s, 1H), 9.10 (s, 1H), 8.98 (s, 1H), 8.38 (d, 1H,
3J = 5.8 Hz), 8.31 (d, 1H, 3J = 6 Hz), 7.97 (d, 1H, 3J = 6 Hz), 7.91 (d,
2H, 3J = 9 Hz), 7.80 (d, 2H, 3J = 9 Hz), 7.68–7.65 (br, 3H), 7.20 (d,
2H, 3J = 8.1 Hz), 7.15 (d, 2H, 3J = 8.1 Hz), 3.92 (t, 4H, 3J = 6.6 Hz),
1.76 (m, 4H), 1.34 (m, 12H), 0.90 (t, 6H, 3J = 6.6 Hz). MS: m/z
1104.25 [M+]. Anal. Calc. for C52H50N12O6RuS2: C, 56.56; H, 4.56.
Found: C, 56.50; H, 4.60.
Acknowledgments
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We are grateful to the KOSEF through National Research Labo-
ratory (No. R0A-2005-000-10034-0) program, WCU program (No.
R31-2008-000-10035-0) and the Ministry of Information and Com-
munication, Korea under ITRC (No. ITRC 2008 C 1090 0904 0013)
and BK21.
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