Synthesis and photophysical properties of new ruthenium(II) charge-transfer sensitizers containing a 4,7-bis(E-carboxyvinyl)-1,10-phenanthroline ligand

Article abstract of DOI:10.1007/s00706-014-1175-z

A series of ruthenium(II) complexes containing carboxyvinyl-conjugated phenanthroline and another auxiliary ligand have been designed, synthesized, and characterized. Starting from [RuCl₂(p-cymene)]₂, two types of Ru(II) complexes, [Ru(dcvphen)(4,7-R₂-phenanthroline)(NCS) ₂] and [Ru(dcvphen)(4,4′-R₂-bipyridine)(NCS) ₂] (dcvphen = 4,7-bis(E-carboxyvinyl)-1,10-phenanthroline, R = -CH = CHCOOH, -COOH, H), were synthesized by a one-pot reaction in DMF. Final products were obtained as a tetrabutylammonium salt form of Ru(II) complexes with reasonable yields. UV-Vis absorption studies on the newly synthesized Ru(II) complexes were carried out. Furthermore, it was shown that a dye-sensitized solar cell fabricated with representative [Ru(dcvphen)₂(NCS) ₂][TBA]₂ complex dye exhibited a reasonable power conversion efficiency of 1.0 %.

Full text of DOI:10.1007/s00706-014-1175-z

Monatsh Chem (2014) 145:1101–1108
DOI 10.1007/s00706-014-1175-z
ORIGINAL PAPER
Synthesis and photophysical properties of new ruthenium(II)
charge-transfer sensitizers containing a 4,7-bis(E-carboxyvinyl)-
1,10-phenanthroline ligand
•
Jungae Tak Minki Kim Sejoo Park Soo Hong Yun
•
•
•
•
Jihye Kim Byoungchoo Park Byeong Hyo Kim
•
Received: 4 December 2013 / Accepted: 5 February 2014 / Published online: 13 March 2014
Ó Springer-Verlag Wien 2014
Abstract A series of ruthenium(II) complexes containing
carboxyvinyl-conjugated phenanthroline and another aux-
iliary ligand have been designed, synthesized, and
characterized. Starting from [RuCl2(p-cymene)]2, two
types of Ru(II) complexes, [Ru(dcvphen)(4,7-R2-phenan-
throline)(NCS)2] and [Ru(dcvphen)(4,40-R2-bipyridine)
Introduction
The growing global demand for energy and for protecting
our environment can potentially be met by solar cell
technology. If we could harvest merely a tiny fraction of
the solar energy reaching the earth, we would solve many
of our problems regarding not only energy but also the
global environment [1, 2]. Therefore, a great deal of effort
is being directed at the utilization of solar energy.
(NCS)2]
(dcvphen = 4,7-bis(E-carboxyvinyl)-1,10-phe-
nanthroline, R = –CH = CHCOOH, –COOH, H), were
synthesized by a one-pot reaction in DMF. Final products
were obtained as a tetrabutylammonium salt form of Ru(II)
complexes with reasonable yields. UV-Vis absorption
studies on the newly synthesized Ru(II) complexes were
carried out. Furthermore, it was shown that a dye-sensi-
tized solar cell fabricated with representative
[Ru(dcvphen)2(NCS)2][TBA]2 complex dye exhibited a
reasonable power conversion efficiency of 1.0 %.
Dye-sensitized solar cells (DSSCs) based on mesopor-
ous nanocrystalline metal oxide semiconductor films have
attracted significant attention because of their relatively
low production cost and high power conversion efficiency.
In the cell, the photosensitizer is one of the crucial com-
ponents for high power conversion efficiency (PCE) [3–6].
As a photosensitizer, ruthenium(II) polypyridyl complexes
have been the subject of extensive studies because of their
easily tunable redox, photophysical, and photochemical
properties [7–10]. The most efficient sensitizers to date
based on Ru(II) polypyridyl complexes, namely [Ru(dcb-
py)2(NCS)2] (N3), [Ru(dcbpy)2(NCS)2][TBA]2 (N719)
(dcbpy = 4,40-dicarboxy-2,20-bipyridine, TBA = tetrabu-
tylammonium, Fig. 1), and [Ru(tcterpy)(NCS)3][TBA]3
(Black Dye, BD) (tcterpy = 4,40,400-tricarboxy-2,20:60,200-
Keywords Heterocycles ꢀ Metal complexes ꢀ
Organometallic compounds ꢀ Photosensitizers ꢀ
Ru(II) complexes
¨
terpyridine), were sensitizers reported by Gratzel et al. [11–
14]. As the absorption properties of Ru(II) complexes can
be tuned by changing the structure of the main ligand or an
auxiliary ligand, some researchers have attempted to
extend the absorption band to longer wavelengths and
improve the efficiency of the DSSCs [15–20].
J. Tak
Department of Chemistry and Research Institute for Natural
Sciences, Hanyang University, Seoul 133-791, Korea
M. Kim ꢀ S. Park ꢀ J. Kim ꢀ B. H. Kim (&)
Department of Chemistry, Kwangwoon University,
Seoul 139-701, Korea
In this article we describe the synthesis and character-
ization of new ruthenium(II) complexes based on the 4,7-
bis(E-carboxyvinyl)-1,10-phenanthroline ligand in addition
to 1,10-phenanthroline (phen) and 2,20-bipyridine (bpy)
that have been used extensively as ligands to form metal
e-mail: bhkim@kw.ac.kr
S. H. Yun ꢀ B. Park
Department of Electrophysics, Kwangwoon University,
Seoul 139-701, Korea
123

1102
J. Tak et al.
Fig. 1 Structures of N3, N719, and BD
complexes for use in DSSCs as an extension of our fore-
going application of electrochemiluminescent ruthenium
(II) complexes [21–29]. As the introduction of an allyl
conjugated ligand has been barely studied in the field of
metal complexes for DSSCs [30–32], we designed new
ruthenium(II) complexes by introducing methine connected
to a carboxyl group on phen or bpy moieties expecting to
increase the optical extinction coefficient. Such an elon-
gation will contribute to a red shift in the absorption
spectrum as well. Taking into account our previous studies,
we present herein a series of new ruthenium(II) complexes
of the type [Ru(dcvphen)(L)(NCS)2][TBA]x (x = 1 or 2),
where dcvphen = 4,7-bis(E-carboxyvinyl)-1,10-phenan-
throline and L = dcvphen (RS1), dcvbpy (RS2), dcphen
(RS3), dcbpy (RS4), phen (RS5), or bpy (RS6), prepared
via Ru(dcvphen)(L)(NCS)2 acid form of RA1-RA6
(Fig. 2), with the aim of increasing light-harvesting
performance.
treated with a large excess of ammonium thiocyanate to
afford [Ru(dcvphen)(L)(NCS)2] (RA1–RA6, Scheme 1b).
After the treatment of RA1–RA6 with a 1 % tetrabutyl-
ammonium hydroxide solution, a new series of RS1–RS6
was obtained with a reasonable yield (35-51 %). The
complexes RA1–RA6 and RS1–RS6 were characterized
spectroscopically, and all data are consistent with the for-
mulated structures (Fig. 2b).
Figure 3 illustrates the UV-Vis absorption spectra of
RS1–RS6 compared with N719, measured in methanol; the
results are summarized in Table 1. The absorption bands in
the visible region were previously assigned to the MLCT
(metal-to-ligand charge transfer) transition bands for Ru(II)
complexes [3–14]. Table 1 shows the important parameters
for the synthesized Ru(II) complexes in this study. The
spectra of RS1–RS6 ([Ru(dcvphen)(L)(NCS)2][TBA]x)
showed an intense MLCT band in the range of
380–540 nm, and the band at around 300 nm is assigned to
the intraligand p–p* transition of dcvphen and the auxiliary
ligand L (phen/bpy derivatives). As can be observed, in the
case of RS5 and RS6, which have no carboxyl group on the
auxiliary ligand L (phen/bpy), they exhibit a very broad
band and weak peaks in the visible region. The lowest
energy MLCT bands of RS1–RS4 are located at
526–540 nm; their peaks are red shifted 5–19 nm in
comparison with the standard N719, and this induces good
light-harvesting efficiency. This enhancement is produced
because the dcvphen ligand has a rigid structure and
increased conjugation length due to the phenanthroline
[35–39]. Furthermore, the absorption spectrum of RS1,
which contains the same two ligands (dcvphen), is similar
to that of N719 as RS1 showed intense MLCT absorption
peaks at 385 and 527 nm, a slight red shift from the peaks
of 380 and 521 nm shown by N719. The molar extinction
coefficient (e) values (6,500 and 6,700) of RS1 are slightly
greater than those (5,600 and 5,600) of N719 as shown in
Table 1. This outstanding spectral feature makes RS1 a
promising candidate as a highly efficient photosensitizer
for DSSC applications.
Results and discussion
The new ruthenium complexes, [Ru(dcvphen)(L)
(NCS)2][TBA]x (RS1–RS6, Fig. 2b), were synthesized by
the stepwise synthetic protocol illustrated in Scheme 1.
The fixed ligand 4,7-bis(E-carboxyvinyl)-1,10-phenan-
throline (dcvphen) was synthesized in two steps using
formylation and the Wittig coupling reaction to extend the
p-conjugated system of phenanthroline (Scheme 1a).
Ligands 4,40-bis(E-carboxyvinyl)-2,20-bipyridine (dcvbpy),
4,7-dicarboxy-1,10-phenanthroline (dcphen), and 4,40-
dicarboxy-2,20-bipyridine (dcbpy) were synthesized by
applying the reported method [33, 34].
The reaction of Ru-dimer [RuCl2(p-cymene)]2 with
dcvphen according to a 1:2 stoichiometry in DMF at 80 °C
under nitrogen resulted in a mononuclear Ru(II) complex.
Then the auxiliary ligand L (Fig. 2a) was added, and the
resulting mixture was refluxed for 4 h in DMF at 160 °C in
the dark. The [Ru(dcvphen)(L)Cl2] complexes were then
123

Synthesis and photophysical properties of new ruthenium(II) charge-transfer sensitizers
1103
(a)
HO2C
CO2H
HO2C
CO2H
N
N
N
N
N
N
dcvphen
dcphen
phen
HO2C
CO2H
HO2C
CO2H
N
N
N
N
N
N
dcvbpy
dcbpy
bpy
(b)
CO2H
CO2H
CO2H
CO2H
RO2C
RO2C
N
N
N
N
N
N
N
Ru
Ru
N
N
N
N
C
S
N
C
S
C
C
S
S
CO2R
CO2R
Ru(dcvphen)2(NCS)2 (R = H, RA1)
[Ru(dcvphen)2(NCS)2[TBA]2 (R = TBA, RS1)
Ru(dcvphen)(dcvbpy)(NCS)2 (R = H, RA2)
[Ru(dcvphen)(dcvbpy)(NCS)2[TBA]2 (R = TBA, RS2)
CO2H
CO2H
CO2H
CO2H
RO2C
RO2C
N
N
N
N
N
N
Ru
Ru
N
N
N
N
N
C
N
C
CO2R
CO2R
S
S
C
C
S
S
Ru(dcvphen)(dcphen)(NCS)2 (R = H, RA3)
[Ru(dcvphen)(dcphen)(NCS)2[TBA]2 (R = TBA, RS3)
Ru(dcvphen)(dcbpy)(NCS)2 (R = H, RA4)
[Ru(dcvphen)(dcbpy)(NCS)2][TBA]2 (R = TBA, RS4)
CO2H
CO2H
RO2C
RO2C
N
N
N
N
N
N
Ru
Ru
N
N
N
N
N
C
N
C
S
C
S
C
S
S
Ru(dcvphen)(phen)(NCS)2 (R = H, RA5)
[Ru(dcvpehn)(phen)(NCS)2][TBA] (R = TBA, RS5)
Ru(dcvphen)(bpy)(NCS)2 (R = H, RA6)
[Ru(dcvphen)(bpy)(NCS)2][TBA] (R = TBA, RS6)
Fig. 2 Molecular structures of a ligands (L) and b acid and salt form of Ru(II) complexes Ru(dcvphen)(L)(NCS)2 for photosensitizers utilized in
the present study
To examine the utilization of our synthesized complexes
as a photosensitizer in DSSCs, a representative device
loaded with RS1 was fabricated. The J–V characteristics
were obtained under one sun illumination, and the corre-
sponding derived electric parameters of RS1 and N719 are
summarized in Table 2. At the current stage, a maximum
123

1104
J. Tak et al.
Scheme 1
(a)
(b)
1.6
1.4
1.2
1
Table 1 UV–Vis absorption parameters for Ru(II) complexes in
methanol
RS1
RS2
RS3
RS4
RS5
RS6
N719
Complexes
Absorption kmax/nm (e/mol-1 dm3 cm-1
)
RS1
RS2
RS3
RS4
RS5
RS6
N719
527 (6,700), 385 (6,500), 306 (13,600)
540 (3,100), 439 (2,200)
531 (3,300)
0.8
0.6
0.4
0.2
0
526 (5,000), 302 (12,500)
504 (4,300)
500 (2,100)
300
400
500
600
700
800
521 (5,600), 380 (5,600), 308 (15,800)
Wavelength/nm
Fig. 3 UV-Vis absorption spectra of RS1–RS6 and N719 measured
at 298 K under aerobic conditions in methanol
123

Synthesis and photophysical properties of new ruthenium(II) charge-transfer sensitizers
1105
ppm relative to the residual solvent as an internal standard.
HRMS spectra were recorded on a JEOL JMS-DX 303
mass spectrometer (Jeol, Tokyo, Japan), and GC/MS was
recorded on an HP 5973 mass spectrometer connected with
a HP 6890 GC (Hewlett-Packard Co., Palo Alto, CA,
USA). Infrared spectra (IR) were recorded on a MB104
FT-IR (ABB Bomen Inc., Zurich, Switzerland), and UV-
Vis spectra were recorded on a S-3100 (Scinco, Seoul,
Korea). Emission spectra were obtained with the use of a
luminescence spectrometer LS 50B (excitation source at
400 nm; Perkin-Elmer, Waltham, MA, USA). Melting
points were determined on an electrothermal apparatus
(Kru¨ss Optronic, Hamburg, Germany).
Table 2 Photovoltaic performance of DSSCs using TiO2 electrodes
sensitized with RS1 and N719
Complexes
Voc/V
Jsc/mA cm-2
ff
g/%
RS1
0.65
0.71
5.00
9.60
28.43
47.31
1.00
3.24
N719
power conversion efficiency of 1 % was achieved under
AM1.5 with a DSSC based on RS1. This result indicates
that the prospects for using RS1 complex photosensitizers
in DSSCs are promising. This solar cell has the potential to
produce 8–9 % efficiencies because its spectral response is
almost equal to that of a reference DSSC based on the N719
dye; however, we must overcome several problems in order
to attain high conversion efficiencies. For example, lower
3,30-(1,10-Phenanthroline-4,7-diyl)bis(2-propenoic
acid) (C18H12N2O4)
V
OC and FF prevent the achievement of efficiencies higher
than 6 %. To improve VOC and FF, we have to reduce the
recombination process in the cells by modification of the
RS1 complex through controlling both LUMO and HOMO
at more negative levels than those of N719 dye.
4,7-Diformyl-1,10-phenanthroline (2.00 mmol) and 2.00 g
[(methoxycarbonyl)methylene]triphenylphosphorane (6.00
mmol) were dissolved in 40 cm3 toluene. The mixture was
heated to reflux for 1.5 h, and then the solvent was evap-
orated. The synthesized crude conjugated ester product was
purified using column chromatography (1 % MeOH/ethyl
acetate). After drying, it was dissolved in 10 cm3 of 1 N
aq. NaOH solution/MeOH (1:1 ratio) and stirred at room
temperature for 4 h. The pH of the solution was lowered to
3.5 by adding 1 M HCl aqueous solution. The solution was
kept overnight in a refrigerator, and the precipitate was
filtered off from the solution. The precipitate was further
washed with distilled water and dried using a vacuum oven.
Light yellow solid; m.p.: [355 °C (dec.); 1H NMR
(400 MHz, DMSO-d6): d = 13.0 (s, 2H), 9.04 (d, 2H,
J = 4.4 Hz), 8.27 (d, 2H, J = 15.9 Hz), 8.17 (s, 2H), 8.01
(d, 2H, J = 4.4 Hz), 6.80 (d, 2H, J = 15.9 Hz) ppm; 13C
NMR (100 MHz, DMSO-d6): d = 166.8, 149.6, 144.9,
140.0, 137.4, 126.8, 125.6, 122.7, 120.8 ppm; IR (KBr):
m = 3,400–2,450 (broad), 3,118, 1,732, 1,645, 1,558,
1,514, 1,426, 1,373, 1,317, 1,174, 974 cm-1; HR-ESI–MS:
m/z calc. for C18H12N2O4 320.0797, found 320.0779.
Conclusions
In this article, we report the design, synthesis, and char-
acterization of new Ru(II) complexes, RS1–RS6
[Ru(dcvphen)(L)(NCS)2][TBA]x (x = 1 or 2), based on the
4,7-bis(E-carboxyvinyl)-1,10-phenanthroline
(dcvphen)
ligand. The new compounds were especially designed for
their suitability as potential photosensitizers for DSSCs.
The absorption spectra of the new Ru(II) complexes
exhibited an intense band at around 380–540 nm, which
was assigned to the MLCT. The complexes display high
molar extinction coefficients that are comparable to those
of N719. Furthermore, it was shown that a DSSC fabricated
with representative [Ru(dcvphen)2(NCS)2][TBA]2 (RS1)
complex dye exhibited a reasonable PCE of 1.0 %.
Experimental
General procedure for synthesis of ruthenium
complexes containing acid form ligand
Most chemical reagents were purchased from Aldrich
Chemical Co. (St. Louis, MO, USA) and used as received
without further purification. All the reactions were carried
out under a dry nitrogen atmosphere, unless stated other-
wise. Solvents were dried using the standard method. 4,40-
Dicarboxy-2,20-bipyridine (dcbpy) [34], 4,7-dicarboxy-
1,10-phenanthroline (dcphen) [34], and 4,40-bis(E-carb-
oxyvinyl)-2,20-bipyridine (dcvbpy) [33] were prepared by
methods known in the literature.
Dichloro(p-cymene)ruthenium(II)
dimer
(154 mg,
0.25 mmol) and 160 mg 4,7-bis(E-carboxyvinyl)-1,10-
phenanthroline (0.5 mmol) were dissolved in 40 cm3 of
DMF under nitrogen gas. The solution was heated at
80 °C with vigorous stirring for 4 h in the dark under a
nitrogen atmosphere. To the solution was added another
ligand (0.5 mmol, L = 4,7-bis(E-carboxyvinyl)-1,10-phe-
nanthroline, 4,40-bis(E-carboxyvinyl)-2,20-bipyridine, 4,7-
dicarboxy-1,10-phenanthroline, 4,40-dicarboxy-2,20-bipyri-
dine, 1,10-phenanthroline, or 2,20-bipyridine) and heated
1H NMR spectra were recorded on a 400-MHz NMR
(Jeol, Tokyo, Japan), and chemical shifts were reported in
123

1106
J. Tak et al.
cis-(1,10-Phenanthroline-4,7-carboxyvinyl)-cis-(2,20-
bipyridine-4,40-carboxy)dithiocyanatoruthenium(II)
at 160 °C for 4 h. To the resulting solution was added
1.24 g NH4NCS (16.2 mmol), and the resulting mixture
was heated at 160 °C for an additional 4 h. After evap-
oration of the DMF, the resulting residue was suspended
in water and filtered by suction filtration and dried.
(RA4, C32H20N6O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 9.47 (s, 1H), 9.28 (d,
1H, J = 5.7 Hz), 8.68 (m, 2H), 8.49 (m, 2H), 8.02 (m, 1H),
7.95 (d, 1H, J = 5.6 Hz), 7.76 (m, 1H), 7.74 (s, 1H), 7.55
(d, 1H, J = 5.7 Hz), 7.39 (m, 1H), 7.25 (d, 1H,
J = 5.9 Hz), 7.06 (m, 1H), 6.75 (d, 1H, J = 15.5 Hz), 6.44
(d, 1H, J = 15.5 Hz) ppm; IR (KBr): m = 3,684–2,447
(broad), 3,064, 2,922, 2,851, 2,106, 1,980, 1,714,
1,626 cm-1; UV-Vis (DMSO, c = 1.10-4 mol dm-3): kmax
(e) = 583 (2,690), 302 (11,600) nm (mol-1 dm3 cm-1).
cis-Bis(1,10-phenanthroline-4,7-
carboxyvinyl)dithiocyanatoruthenium(II)
(RA1, C38H24N6O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 13.0 (s, 2H), 9.64 (d,
1H, J = 5.2 Hz), 8.67 (m, 2H), 8.47 (d, 2H, J = 15.5 Hz),
8.17 (d, 2H, J = 15.4 Hz), 7.82 (m, 1H), 7.68 (m, 1H),
7.17 (d, 1H, J = 15.4 Hz), 6.73 (d, 1H, J = 15.6 Hz) ppm;
IR (KBr): m = 3,688–2,608 (broad), 3,054, 2,921, 2,854,
cis-(1,10-Phenanthroline-4,7-carboxyvinyl)-
cis-(1,10-phenanthroline)dithiocyanatoruthenium(II)
(RA5, C32H20N6O4RuS2)
2,108, 1,975, 1,707, 1,637 cm-1
; UV-Vis (DMSO,
c = 1.10-4 mol dm-3): kmax (e) = 549 (5,260), 307
(16,900) nm (mol-1 dm3 cm-1).
1H NMR (400 MHz, DMSO-d6): d = 12.9 (s, 2H) 9.67 (m,
2H), 8.91 (m, 1H), 8.73 (m, 1H), 8.66 (d, 1H, J = 9.3 Hz),
8.52 (m, 1H), 8.46 (d, 1H, J = 8.3 Hz), 8.37 (m, 2H), 8.22
(d, 1H, J = 8.5 Hz), 7.94 (s, 1H), 7.82 (m, 2H), 7.74 (m,
1H), 7.45 (m, 1H), 7.18 (d, 1H, J = 15.8 Hz), 6.71 (d, 1H,
J = 15.6 Hz) ppm; IR (KBr): m = 3,697–2,381 (broad),
3,070, 2,920, 2,106, 1,973, 1,706, 1,634 cm-1; UV-Vis
(DMSO, c = 1.10-4 mol dm-3): kmax (e) = 518 (7,760),
298 (14,900) nm (mol-1 dm3 cm-1).
cis-(1,10-Phenanthroline-4,7-carboxyvinyl)-
cis-(2,20-bipyridine-4,40-carboxyvinyl)-
dithiocyanatoruthenium(II)
(RA2, C36H24N6O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 12.8 (s, 2H), 9.57 (d,
1H, J = 5.1 Hz), 9.31 (d, 1H, J = 5.4 H), 9.19 (m, 1H),
8.99 (s, 1H), 8.67 (m, 2H), 8.53 (m, 2H), 8.30 (m, 2H), 8.01
(m, 1H), 7.89 (d, 1H, J = 5.6 Hz), 7.83 (d, 1H,
J = 15.6 Hz), 7.50 (m, 2H), 7.30 (d, 1H, J = 5.6 Hz), 7.20
(m, 2H), 6.95 (d, 1H, J = 15.6 Hz), 6.79 (d, 1H,
J = 15.6 Hz) ppm; IR (KBr): m = 3,688–2,584 (broad),
3,058, 2,913, 2,109, 1,976, 1,703, 1,633 cm-1; UV-Vis
(DMSO, c = 1.10-4 mol dm-3): kmax (e) = 559 (15,100),
312 (18,500) nm (mol-1 dm3 cm-1).
cis-(1,10-Phenanthroline-4,7-carboxyvinyl)cis-
(2,20-bipyridine)dithiocyanatoruthenium(II)
(RA6, C30H20N6O4RuS2)
1H NMR (400 MHz, DMSO-d6): d = 13.0 (s, 2H), 9.60 (d,
1H, J = 5.6 Hz), 9.33 (d, 1H, J = 5.4 Hz), 8.81 (m, 1H),
8.69 (m, 1H), 8.63 (m, 2H), 8.54 (m, 2H), 8.32 (m, 2H),
7.99 (m, 2H), 7.90 (d, 1H, J = 5.7 Hz), 7.86 (m, 1H), 7.42
(d, 1H, J = 5.4 Hz), 7.14 (m, 2H), 6.79 (d, 1H,
J = 15.6 Hz) ppm; IR (KBr): m = 3,688–2,338 (broad),
3,066, 2,916, 2,107, 1,977, 1,731, 1,631 cm-1; UV-Vis
(DMSO, c = 1.10-4 mol dm-3): kmax (e) = 559 (13,700),
311 (16,500) nm (mol-1 dm3 cm-1).
cis-(1,10-Phenanthroline-4,7-carboxyvinyl)-
cis-(1,10-phenanthroline-4,7-carboxy)-
dithiocyanatoruthenium(II)
(RA3, C34H20N6O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 13.1 (s, 2H), 9.82 (d,
1H, J = 5.4 Hz), 9.66 (d, 1H, J = 5.4 Hz), 9.13 (m, 1H),
9.01 (m, 1H), 8.76 (m, 1H), 8.70 (m, 2H), 8.58 (m, 2H),
8.30 (m, 1H), 8.03 (m, 2H), 7.88 (d, 1H, J = 5.4 Hz), 7.74
(m, 2H), 7.20 (d, 1H, J = 15.6 Hz), 6.72 (d, 1H,
J = 15.6 Hz) ppm; IR (KBr): m = 3,696–2,639 (broad),
3,081, 2,920, 2,850, 2,111, 1,987, 1,709, 1,623 cm-1; UV-
Vis (DMSO, c = 1.10-4 mol dm-3): kmax (e) = 505
(4,960), 299 (13,300) nm (mol-1 dm3 cm-1).
General procedure for synthesis of salt form
of ruthenium complexes
The substrate prepared in accordance with previous general
procedure was dissolved into 20 cm3 of a 10 % tetrabutl-
yammonium hydroxide solution. The solution was stirred
for a while and the residue filtered off through a sintered
glass filter, and the solution was charged onto an LH-20
Sephadex column, which was dissolved in methanol. The
123

Synthesis and photophysical properties of new ruthenium(II) charge-transfer sensitizers
1107
adsorbed complex was eluted using methanol. The major
band was collected, and the pH of the solution was lowered
to 3.8 using 0.5 M aq. HNO3 solution. At this pH, most of
the complex precipitated out, and the flask was kept in a
refrigerator over 12 h. The precipitate was collected on a
sintered glass filter. The isolated solid was washed once
with 5 cm3 of pH 3.8 water and dried using a vacuum oven.
8.31 (d, 1H, J = 15.5 Hz), 8.02 (d, 1H, J = 4.7 Hz), 7.89
(d, 1H, J = 4.7 Hz), 7.74 (s, 2H), 7.21 (d, 1H,
J = 15.7 Hz), 6.73 (d, 1H, J = 15.7 Hz), 3.15 (m, 16H),
1.62–1.50 (m, 8H), 1.29 (m, 8H), 1.23 (m, 16H), 0.95–0.74
(m, 24H) ppm; IR (KBr): m = 3,711–2,596 (broad), 3,064,
2,960, 2,977, 2,875, 2,107, 1,972, 1,716, 1,635 cm-1; UV-
Vis (MeOH, c = 1.10-4 mol dm-3): kmax (e) = 531
(3,300) nm (mol-1 dm3 cm-1).
Bis(tetrabutylammonium) cis-bis(1,10-phenanthroline-
4-carboxyvinyl-7-carboxylatovinyl)dithio-
cyanatoruthenium(II)
Bis(tetrabutylammonium) cis-(1,10-phenanthroline-4-
carboxyvinyl-7-carboxylatovinyl)-cis-(2,20-bipyridine-
4-carboxy-40-carboxylato)dithiocyanatoruthenium(II)
(RS4, C64H90N8O8RuS2)
(RS1, C70H94N8O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 9.64 (d, 1H,
J = 5.4 Hz), 8.72–8.66 (m, 2H), 8.52 (d, 2H,
J = 15.0 Hz), 8.21 (d, 1H, J = 15.0 Hz), 7.84 (d, 1H,
J = 5.6 Hz), 7.69 (d, 1H, J = 5.6 Hz), 7.19 (d, 1H,
J = 15.8 Hz), 6.75 (d, 1H, J = 15.8 Hz), 3.14 (t, 16H,
J = 8.3 Hz), 1.61–1.48 (m, 16H), 1.29 (q, 16H,
J = 7.3 Hz), 0.91 (t, 24H, J = 7.3 Hz) ppm; IR (KBr):
m = 3,700–2,404 (broad), 3,058, 2,962, 2,931, 2,871,
1H NMR (400 MHz, DMSO-d6): d = 9.61 (d, 1H,
J = 5.7 Hz), 9.34 (d, 1H, J = 5.7 Hz), 9.02 (s, 1H), 8.82
(s, 1H), 8.71–8.64 (m, 2H), 8.54 (m, 2H), 8.24 (m, 2H),
7.92 (s, 1H), 7.86 (s, 1H), 7.47 (d, 1H, J = 5.5 Hz), 7.38
(m, 1H), 7.2–7.12 (m, 1H), 6.88 (m, 1H), 3.15 (m, 16H),
1.62–1.50 (m, 8H), 1.29 (m, 8H), 1.23 (m, 16H), 0.95–0.74
(m, 24H) ppm; IR (KBr): m = 3,704–2,651 (broad), 3,062,
2,960, 2,921, 2,870, 2,104, 1,966, 1,715, 1,614 cm-1; UV-
Vis (MeOH, c = 1.10-4 mol dm-3): kmax (e) = 526
(5,000), 302 (12,500) nm (mol-1 dm3 cm-1).
2,104, 1,968 1,706, 1,630 cm-1
;
UV-Vis (MeOH,
c = 1.10-4 mol dm-3): kmax (e) = 527 (6,700), 385
(6,500), 306 (13,600) nm (mol-1 dm3 cm-1).
Bis(tetrabutylammonium) cis-(1,10-
phenanthroline-4-carboxyvinyl-7-carboxylatovinyl)-
cis-(2,20-bipyridine-4-carboxyvinyl-40-
carboxylatovinyl)dithiocyanatoruthenium(II)
(RS2, C68H94N8O8RuS2)
Bis(tetrabutylammonium) cis-(1,10-phenanthroline-4-
carboxyvinyl-7-carboxylatovinyl)-cis-(1,10-
phenanthroline)dithiocyanatoruthenium(II)
(RS5, C64H90N8O4RuS2)
1H NMR (400 MHz, DMSO-d6): d = 9.66 (m, 2H), 8.91
(m, 2H), 8.67 (m, 2H), 8.45 (m, 2H), 8.36 (m, 2H), 8.21 (m,
2H), 7.87–7.76 (m, 2H), 7.72 (s, 1H), 7.44 (s, 1H), 7.18 (d,
1H, J = 15.6 Hz), 6.71 (d, 1H, J = 15.7 Hz), 3.15 (m,
8H), 1.55 (m, 8H) 1.32–1.21 (m, 8H), 0.92 (m, 12H) ppm;
IR (KBr): m = 2,692–2,471 (broad), 3,070, 2,959, 2,928,
2,873, 2,103, 1,970, 1,704, 1,626 cm-1; UV-Vis (MeOH,
c = 1.10-4 mol dm-3): kmax (e) = 654 (500), 504 (4,300)
nm (mol-1 dm3 cm-1).
1H NMR (400 MHz, DMSO-d6): d = 9.53 (d, 1H,
J = 5.7 Hz), 9.28 (d, 1H, J = 5.7 Hz), 9.17 (s, 1H), 8.97
(s, 1H), 8.65 (s, 1H), 8.51 (d, 1H, J = 9.4 Hz), 8.44 (d, 1H,
J = 15.4 Hz), 8.19 (m, 2H), 7.97 (d, 1H, J = 5.7 Hz), 7.82
(d, 1H, J = 4.8 Hz), 7.77–7.71 (m, 1H), 7.43–7.22 (m,
5H), 7.16 (d, 1H, J = 15.5 Hz), 7.02 (d, 1H, J = 15.5 Hz),
6.85 (d, 1H, J = 15.5 Hz), 3.14 (m, 16H), 1.55 (m, 16H),
1.29 (q, 16H, J = 7.1 Hz), 0.92 (t, 24H, J = 7.1 Hz) ppm;
IR (KBr): m = 3,704–2,600 (broad), 3,062, 2,960, 2,929,
2,871, 2,104, 1,976, 1,703, 1,639 cm-1; UV-Vis (MeOH,
c = 1.10-4 mol dm-3): kmax (e) = 540 (3,100), 439
(2,200) nm (mol-1 dm3 cm-1).
Bis(tetrabutylammonium) cis-(1,10-phenanthroline-4-
carboxyvinyl-7-carboxylatovinyl)-cis-(2,20-
bipyridine)dithiocyanatoruthenium(II)
(RS6, C62H90N8O4RuS2)
Bis(tetrabutylammonium) cis-(1,10-phenanthroline-4-
carboxyvinyl-7-carboxylatovinyl)-cis-(1,10-
phenanthroline-4-carboxy-7-carboxylato)-
dithiocyanatoruthenium(II)
1H NMR (400 MHz, DMSO-d6): d = 9.57 (d, 1H,
J = 5.7 Hz), 9.34 (d, 1H, J = 5.2 Hz), 8.77 (m, 2H), 8.66
(m, 1H), 8.61 (d, 1H, J = 8.3 Hz), 8.49 (m, 2H), 8.28 (d,
1H, J = 8.7 Hz), 8.22 (m, 1H), 8.01–7.92 (m, 2H), 7.84
(m, 1H), 7.41 (d, 1H, J = 5.2 Hz), 7.16 (d, 1H,
J = 15.7 Hz), 7.09 (m, 1H), 6.80 (d, 1H, J = 15.7 Hz),
3.14 (m, 8H), 1.55 (m, 8H) 1.32–1.22 (m, 8H), 0.93 (m,
12H) ppm; IR (KBr): m = 3,688–2,620 (broad), 3,070,
(RS3, C66H90N8O8RuS2)
1H NMR (400 MHz, DMSO-d6): d = 9.81 (d, 1H,
J = 4.2 Hz), 9.67 (d, 1H, J = 4.2 Hz), 9.15 (d, 1H,
J = 9.1 Hz), 9.01 (d, 1H, J = 9.1 Hz), 8.80–8.52 (m, 5H),
123

1108
J. Tak et al.
2,961, 2,929, 2,871, 2,104, 1,969, 1,709, 1,633 cm-1; UV-
Vis (MeOH, c = 1.10-4 mol dm-3): kmax (e) = 654 (400),
500 (2,100) nm (mol-1 dm3 cm-1).
10. Vougioukalakis GC, Philippopoulos AI, Stergiopoulos T, Falaras
P (2011) Coord Chem Rev 255:2602
¨
11. O’Regan B, Gratzel M (1991) Nature 353:737
12. Nazeeruddin MK, Kay A, Rodicio I, Humphry-Baker R, Mu¨ller
¨
E, Liska P, Vlachopoulos N, Gratzel M (1993) J Am Chem Soc
115:6382
13. Nazeeruddin MK, Zakeeruddin SM, Humphry-Baker R, Jirousek
Fabrication of DSSCs
¨
M, Liska P, Vlachopoulos N, Shklover V, Fischer CH, Gratzel M
(1999) Inorg Chem 38:6298
TiO2 colloid was prepared according to the following
procedure. TiO2 (3 g, Degussa P25) and 0.27 cm3 acetyl-
acetone were added to 17 cm3 distilled water. After
ultrasonication for 10 min, 0.13 cm3 surfactant TritonX-
100, 0.75 g polyethylene glycol (PEG-20,000), and 0.15 g
poly(ethylene oxide) (PEO-2,000,000) were added to the
solution. On a well-cleaned ITO conducting glass, porous
TiO2 film was then deposited by the doctor-blade method,
followed by sintering at 450 °C for 30 min. RS1 complex
dye sensitization was carried out by soaking the porous
film for 12 h in 0.20 wt% isopropyl alcohol (20 mg of
RS1/1 g IPA). As a reference, the dye N719 was also used
(Solaronix SA, Aubonne, Switzerland). An electrolyte was
then spread on the sensitized semiconductor layer by spin
coating, and then the Pt counter electrode was added. The
structure of the DSSC was glass substrate/ITO/porous
TiO2/RS1 complex dye/electrolyte/Pt. The performance of
the DSSC was measured under an illumination intensity of
100 mW cm-2 generated by an AM1.5 light source (96,000
Solar Simulator, Newport Corp., Irvine, CA, USA). The
photocurrent characteristics were measured with a source
meter (2400 Keithley, Cleveland, OH, USA) and calibrated
by using a reference solar cell (BS-520, Bunkoh-koiki,
Tokyo, Japan). The characterization of the device was
carried out at room temperature under ambient conditions,
without encapsulation.
14. Nazeeruddin MK, Pechy P, Renouard T, Zakeeruddin SM,
Humphry-Baker R, Comte P, Liska P, Cevey L, Costa E, Shk-
¨
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Am Chem Soc 123:1613
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´ ˇ
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Chem 51:2097
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117:2059
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(2004) Talanta 62:595
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(2006) Bull Korean Chem Soc 27:99
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SH, Lee WY, Kim BH (2006) Synth Met 156:885
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Acknowledgments This work is supported by research funds of
Hanyang University (HY-2012-G, J. Tak).
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