High-Performance Aqueous/Organic Dye-Sensitized Solar Cells Based on Sensitizers Containing Triethylene Oxide Methyl Ether

Article abstract of DOI:10.1002/cssc.201500589

Metal-free dyes (EO1 to EO4) containing the hydrophilic triethylene oxide methyl ether (TEOME) unit in the spacer have been synthesized and used in dye-sensitized solar cells (DSSCs). Efficient lithium-ion trapping by TEOME results in improved open-circuit voltage (V_OC), leading to excellent conversion efficiency of the cells, ranging from 9.02 to 9.98% with I^-/I₃^- electrolyte in acetonitrile under AM1.5 illumination. The TEOME unit also enhances the wettability of the dye molecules for application in aqueous-based DSSCs. Aqueous-based DSSCs with a dual TEMPO/iodide electrolyte exhibit high V_OC values (0.80-0.88V) and very promising cell performances of up to 5.97%.

Full text of DOI:10.1002/cssc.201500589

DOI: 10.1002/cssc.201500589
Full Papers
High-Performance Aqueous/Organic Dye-Sensitized Solar
Cells Based on Sensitizers Containing Triethylene Oxide
Methyl Ether
Ryan Yeh-Yung Lin,[a] Feng-Ling Wu,[a] Chun-Ting Li,[b] Pei-Yu Chen,[b] Kuo-Chuan Ho,*[b, c] and
Jiann T. Lin*[a]
Metal-free dyes (EO1 to EO4) containing the hydrophilic triethy-
lene oxide methyl ether (TEOME) unit in the spacer have been
synthesized and used in dye-sensitized solar cells (DSSCs). Effi-
cient lithium-ion trapping by TEOME results in improved open-
circuit voltage (VOC), leading to excellent conversion efficiency
in acetonitrile under AM 1.5 illumination. The TEOME unit also
enhances the wettability of the dye molecules for application
in aqueous-based DSSCs. Aqueous-based DSSCs with a dual
TEMPO/iodide electrolyte exhibit high VOC values (0.80–0.88 V)
and very promising cell performances of up to 5.97%.
À
of the cells, ranging from 9.02 to 9.98% with IÀ/I3 electrolyte
Introduction
Dye-sensitized solar cells (DSSCs) have been deemed as prom-
ising low-cost, sustainable power sources. An impressively high
efficiency of 13% has been achieved with a DSSC based on
a porphyrin sensitizer and cobalt redox mediator under AM 1.5
solar irradiation.[1a] In comparison, high power conversion effi-
ciencies of 11.50 and 12.5% were reported for DSSCs based on
a polypyridyl ruthenium(II) complex with an IÀ/I3À redox media-
tor[1b] and a metal-free organic sensitizer with a cobalt redox
mediator,[1c] respectively. Metal-free organic dyes have attract-
ed increasing attention due to their high molar extinction coef-
ficients, low cost, and flexibility in the molecular design.
Among them, phenothiazine-based sensitizers are interesting
for the following reasons: 1) the phenothiazine entity is proven
to be an effective electron-donating entity, and 2) the nonpla-
nar nature of the phenothiazine entity is beneficial at imped-
ing molecular aggregation and the formation of intermolecular
excimers.[2a] Several phenothiazine-based sensitizers have also
been successfully used for high-performance DSSCs.[2b–e] In
2013, the group of Wong reported a series of phenothiazine-
based sensitizers for high cell performance DSSCs,[2f] and the
highest power conversion efficiency of 8.18% even surpassed
that of N719 (7.73%) under one sun conditions. In 2015, the
group of Lin also reported phenothiazine-based sensitizers
that possessed double anchors, and the best efficiency exceed-
ed that of the N719-based cell by about 13%.[2g] We therefore
further exploited phenothiazine dyes for high-performance
DSSCs.
Earlier we developed a water-soluble dual-redox couple,
which consisted of imidiazolium iodide and 2,2,6,6-tetramethyl-
piperidin-N-oxyl (TEMPO) units; this could increase the open-
circuit voltage (VOC) of the DSSC due to blocking of the dispro-
portionation of the iodine radical anion.[3] Therefore, aqueous
DSSCs were also tested with the phenothiazine dyes newly de-
veloped by us for DSSCs together with the dual-redox couple,
and an intriguingly high conversion (4.96%) was achieved.[4a]
Compared with organic solvents, water is abundant, inexpen-
sive, and environmentally benign. To date, several aqueous
DSSCs with efficiencies higher than 3% have been reporte-
d,[4a–h] and a record cell efficiency of 5.64% was reported by
Spiccia et al. based on a metal-free dye after surface treatment
with octadecyltrichlorosilane for dark-current suppression.[4e]
Although water is believed to lead to dye leaching,[5a] loss of
iodine,[5b,c] and band edge movement,[5d] there has been one
report on good cell stability with water added to the cells.[5e]
There was also an attempt to improve the dye stability to-
wards leaching in water by replacing the common anchor, a cy-
anoacrylate moiety, with a more robust hydroxamic acid an-
chor.[5f]
[a] Dr. R. Y.-Y. Lin,+ F.-L. Wu,+ Prof. J. T. Lin
Institute of Chemistry, Academia Sinica
Nankang 11529, Taipei (Taiwan)ca.edu.tw
E-mail: jtlin@gate.sini
[b] C.-T. Li, P.-Y. Chen, Prof. K.-C. Ho
Department of Chemical Engineering
National Taiwan University
Taipei 10617 (Taiwan)
Because most organic dyes are hydrophobic, incomplete
wetting of the aqueous electrolyte/dye-coated TiO2 film sur-
face may hamper ion diffusion and slow down dye regenera-
tion. Therefore, nonionic (such as Triton-X100,[4b] Tween-20,[4c]
and polyethylene glycol[5d]) and ionic surfactants[5g] (such as
hexadecyltrimethylammonium bromide and triethylammonium
perfluorooctane sulfonate) were added to water to improve
the interfacial contact between the aqueous electrolyte and
E-mail: kcho@ntu.edu.tw
[c] Prof. K.-C. Ho
Institute of Polymer Science and Engineering
National Taiwan University, Taipei 10617 (Taiwan)
[+] These authors contributed equally to this work.
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201500589.
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dye-coated TiO2 film. Alternatively, a transparent TiO2 layer was
added to the dye-coated photoelectrode by atomic layer dep-
osition to enhance photoelectrode wettability.[5h] Upon observ-
ing that oligo(ethylene oxide) was water compatible, we decid-
ed to develop phenothiazine-based dyes containing triethylene
oxide methyl ether (TEOME) units for application as sensitizers
for aqueous DSSCs. To the best of our knowledge, there have
been few reports on dye molecules with the aim of ameliorat-
ing water compatibility for aqueous-based DSSCs.[4f,g] A sys-
tematic investigation into wettability improvement through
structural modification to dyes is also needed for the advance-
ment of the field. We were also aware that the TEOME entity
incorporated in the bipyridyl ligand of ruthenium complexes
helped with trapping of the lithium ion and resulted in higher
VOC values of the cells.[6] Therefore, TEOME-containing pheno-
thiazine sensitizers also offer an opportunity to boost the cell
performance of DSSCs with organic solvents.
Results and Discussion
Synthesis of the materials
Figure 1 shows the structures of new organic sensitizers and
a known sensitizer (S1)[2f] without TEOME as the reference. The
main synthetic pathways are depicted in Scheme 1 The TEOME
entity can be introduced into the molecule at the nitrogen
atom of the phenothiazine core through a [Pd(dba)2]-catalyzed
CÀN coupling reaction[7a,b] of 10H-phenothiazine with 1-
bromo-4-{[2-(2-methoxyethoxy)ethyl]peroxy}benzene (such as
1). Alternatively, it can be tethered to the molecule through
the C-3 (or C-7) substituent of the phenothiazine by a palladi-
um-catalyzed Suzuki–Miyaura coupling reaction[7c] of TEOME-
substituted phenyl bromide and dioxaborolyl phenothiazine,
or palladium-catalyzed Stille coupling reaction[7d] of TEOME-
substituted phenyl stannane and phenothiazinyl bromide. The
formyl group was introduced through a Vilsmeier–Haack reac-
tion either before or after the catalyzed CÀC coupling reaction.
The last step toward the desired products, EO1–EO5, was
Knoevenagel condensation of the appropriate aldehyde with
cyanoacetic acid. It is worth noting that Suzuki–Miyaura in-
Figure 1. Structure of the dyes described herein.
Scheme 1. Synthetic pathways for the EO dyes. (i) 1-bromo-4-(hexyloxy)benzene, [Pd(dba)2] (dba=dibenzylideneacetone), Pt(Bu)2, NaOtBu, toluene, 1208C,
20 h; (ii) N-bromosuccinimide (NBS), CH2Cl2, 18 h; (iii) [Pd(PPh3)2Cl2], tributyl[4-(hexyloxy)phenyl]stannane, 908C, 20 h; (iv) POCl3, DMF, 608C, 18 h; (v) cyanoace-
tic acid, NH4OAc, AcOH, 1208C; (vi) bis(pinacolato)diboron, KOAc, [PdCl2(dppf)] (dppf=1,1’-bis(diphenylphosphino)ferrocene), 1,4-dioxane, 1208C, 20 h;
(vii) [Pd(PPh3)4], 2m K2CO3, 1-bromo-2,4-bis{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}benzene, toluene, 1208C, 20 h.
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stead of Stille coupling has to be used for the phenyl bromide
with two TEOME substituents.
Electrochemical properties
Relevant electrochemical data obtained from cyclic voltamme-
try are presented in Table 1 and the spectra are shown in Fig-
ure S1 in the Supporting Information. The first reversible wave
is attributed to the oxidation of phenothiazine and decreases
in the order of EO1ꢀEO2ꢀEO3ꢀEO5>EO4. The presence of
an extra electron-donating TEOME at the ortho position of the
phenyl ring significantly increases the electron density of phe-
nothiazine in EO4. The excited-state potential (E0–0*, À1.17 to
À1.22 V vs. NHE), estimated from the difference of the first oxi-
dation potential at the ground state and the zero–zero excita-
tion energy (E0–0) of the EO sensitizers, is more negative than
the conduction band edge of the TiO2 electrode (À0.5 V vs.
NHE), which ensures enough driving force for electron injec-
tion into the conduction band of TiO2.
Optical properties
The electronic absorption spectra of the EO dyes in THF have
two major bands in the range of l=300–500 nm (Figure 2a).
Photovoltaic devices
The photovoltaic performance statistics of DSSCs with the
iodide electrolyte in CH3CN under AM 1.5G illumination are col-
lected in Table 2. The photocurrent–voltage (J–V) curves and
IPCE spectra of the cells are plotted in Figure 3a and b, respec-
tively. The cell efficiencies of the EO dyes (8.18 to 9.98%) are
higher than that of S1 (8.02%), and EO3 has the best per-
formance of all. For a fair comparison, the dye-loading densi-
ties on the photoanode were also measured (see Table 2). The
slightly lower JSC value of EO1 may be partially attributed to its
lower dye loading. Charge extraction measurements (see
below) indicate a downward shift of the TiO2 conduction band
edge for the DSSCs of EO5 and S1. It is possible that there are
fewer lithium cations adsorbed on the TiO2 surface due to trap-
ping by TEOME, which leads to a lower conduction band edge
of TiO2. All other EO dyes have comparable TiO2 conduction
band edges, which implies that one TEOME chain is sufficient
to trap the lithium cations in solution. The photocurrents esti-
mated from integrating the product of the IPCE value at each
wavelength and the photon flux density data in the AM 1.5
solar spectrum (100 mWcmÀ2) were about 12.9, 13.9, 15.5,
15.4, 12.6, and 13.1 mAcmÀ2 for the EO1–EO5 and S1 cells, re-
spectively. The results are smaller than the experimental value.
Figure 2. (a) Absorption spectra of the dyes in THF. (b) Absorption spectra of
the EO dyes on a thin film of TiO2.
The band at labs <400 nm is attributed to the p–p* transition,
and that in the longer wavelength region (l=380–600 nm) is
ascribed to the intramolecular charge-transfer (ICT) transition
with p–p* transition character. The labs value of EO5 (l=
470 nm) is larger than that of S1 (l=452 nm). Com-
pared with the hexyl group, the better electron-do-
Table 1. Electro-optical parameters of the dyes.
nating 4-hexoxyphenyl group at the nitrogen atom
of the phenothiazine entity clearly more efficiently
enhances the donating power of the phenothiazine
entity.
[a]
[c]
[d]
Dye
labs [nm]
(e”10À4 LmolÀ1 cmÀ1
lem
E1/2(ox)[b]
[mV]
HOMO/LUMO
[eV]
E0–0
E0–0*
[V]
[a]
)
[nm]
[eV]
EO1
EO2
EO3
EO4
EO5
468 (1.48)
467 (1.68)
469 (1.51)
472 (1.30)
470 (1.65)
614
616
614
615
613
378
378
378
352
378
5.48/3.21
5.48/3.23
5.48/3.23
5.45/3.21
5.48/3.18
2.27
2.25
2.25
2.24
2.30
À1.19
À1.17
À1.17
À1.19
À1.22
Although EO4 has two TEOME substituents, there
is only a marginal change in the labs values (<6 nm)
compared with those of other dyes. It is possible that
the TEOME substituent at the ortho position of the
phenyl ring results in a larger twist angle between
the TEOME-containing phenyl ring and the pheno-
thiazine entity. The absorption spectra (Figure 2b) of
the dyes adsorbed on TiO2 extend beyond l=
650 nm, which indicates J aggregation of the dyes.
[a] Recorded in THF at 298 K. [b] Recorded in THF. Eox =1/2(Epa +Epc), DEp =EpaÀEpc, in
which Epa and Epc are the anodic and cathodic peak potentials, respectively. The oxida-
tion potential reported is adjusted to the potential of ferrocene, which was used as
an internal reference. The values in parentheses are the peak separation of the catho-
dic and anodic waves. Scan rate: 100 mVsÀ1. [c] The band gap, E0–0, was derived from
the intersection of the absorption and emission spectra. [d] E0–0*: The excited-state ox-
idation potential versus a normal hydrogen electrode (NHE).
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the C7 carbon (code symbol: C-
PhTEOME) seems to be more ef-
fective in dark-current (Fig-
ure 3a) suppression than that
through nitrogen (code symbol:
N-PhTEOME), as evidenced from
Table 2. DSSC performance parameters of the dyes.[a]
Dye
VOC
[V]
JSC
[mAcmÀ2
FF
h
JSC–IPCE
Dye loading
[molcmÀ2
qc
]
[%]
[mAcmÀ2
]
]
[8]
EO1
EO2
EO3
EO4
EO5
S1
0.77Æ0.004
0.80Æ0.005
0.82Æ0.003
0.81Æ0.004
0.77Æ0.008
0.76Æ0.005
0.72
15.65Æ0.342
16.50Æ0.055
17.81Æ0.101
17.67Æ0.150
15.70Æ0.077
16.12Æ0.062
18.41
0.68Æ0.003
0.68Æ0.007
0.68Æ0.003
0.68Æ0.004
0.68Æ0.004
0.66Æ0.006
0.65
8.22Æ0.190
9.02Æ0.028
9.98Æ0.047
9.79Æ0.031
8.18Æ0.058
8.02Æ0.091
8.61
12.9
13.9
15.5
15.4
12.6
13.1
5.18”10À7
5.56”10À7
5.67”10À7
6.03”10À7
5.48”10À7
5.90”10À7
103.00
95.14
37.39
15.94
117.36
115.63
electrochemical
impedance
spectroscopy (EIS) and intensity-
modulated photovoltage spec-
troscopy (IMVS; see below) data
for EO1 and EO2.
N719
[a] Experiments were conducted by using TiO2 photoelectrodes approximately 12 mm thick with a 0.16 cm2
working area on fluorine-doped tin oxide (FTO; 15 W/sq.) substrates. Each result was obtained from three
DSSCs. JSC is the short-circuit current, FF is the fill factor, IPCE is the incident photon-to-current conversion effi-
ciency, and qc is the contact angle.
Dye S1 on TiO2 has the most
redshifted spectrum compared
with the EO dyes, which is con-
sistent with its dye aggregation
upon adsorption.[2f] Consequent-
ly, the most blueshifted IPCE spectrum and lower short-circuit
current of the S1-based DSSC can be partly attributed to ag-
gregation-induced quenching of the dye excited state. Al-
though less severe than that of S1, dye aggregation of EO5
(Figure 2b) also jeopardizes electron injection and results in
the cutoff of the IPCE spectra (Figure 3b) at a shorter wave-
length, leading to lower short-circuit currents. The EIS data of
DSSCs in the dark are shown in Figure S2 in the Supporting In-
formation. The intermediate frequency semicircle in the Ny-
quist plot provides information on charge transfer between
the TiO2 surface and the electrolyte, that is, the dark current.
Resistance towards the dark current decreases in the order of
EO3>EO4>EO2>EO1>EO5>S1, which is consistent with
the dark current (Figure 3a) and observed VOC values (Table 2).
The VOC value is determined by the position of the conduc-
tion band (ECB) edge and electron density in the TiO2 film.[9]
The relative conduction band shift of TiO2 was estimated by
means of the charge extraction method (CEM), as shown in
Figure 4a. The cell of S1 has the highest dn (electron density)
value of all at the same VOC, which indicates that it has the
most downshifted conduction band edge of TiO2. The cell of
EO5 has the second highest dn, and therefore, also a downshift-
ed conduction band edge of TiO2. All other EO dyes have com-
parable conduction band edges of TiO2. The electron lifetime
(t) was derived as a function of VOC by measuring the IMVS, as
shown in Figure 4b. The trend is also consistent with the VOC
and EIS data in the dark (see above). At the same voltage, the
DSSCs of EO5 and S1 have shorter lifetimes than the other
DSSCs. This further substantiates the importance of TEOME in
dark-current suppression.
Figure 3. (a) J–V curves and (b) IPCE spectra of DSSCs based on the dyes re-
ported herein.
This discrepancy may be attributed to the filtration of IR radia-
tion by a water filter in our light source during measurements,
whereas the real sun spectrum covers the near-IR region.[8] The
dark current (Figure 3a) of the cells decreases in the order of
S1>EO5>EO1>EO2>EO4>EO3. As expected, more effective
dark-current suppression for the cells of EO2, EO3, and EO4
significantly improved the VOC values in these cells. The larger
dark currents in S1 and EO5 clearly indicate that the TEOME
entity helps with dark-current suppression similar to a long
alky chain. TEOME connected to the phenothiazine through
DSSCs with the JC-IL aqueous-based electrolyte
In addition to dye stability, electrolyte diffusion and dye wetta-
bility are also important for aqueous-based DSSCs. In this
study, we deliberately incorporated the TMEOM entity at the
dye molecule to improve the wettability of the dye molecule
to facilitate interfacial electron transfer between the hydrophil-
ic electrolyte and the hydrophobic dye molecule, that is, dye
regeneration. Contact angle analysis was used to investigate
the hydrophilic/-phobic properties of the EO and S1 sensitizers.
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have contact angles of over 1158. As the number of TEOME
unit increases, the contact angle decreases: EO1, 103.008; EO2,
95.148; EO3, 37.398; EO4, 15.948. It appears that EO1–EO4 have
higher wettability than that of EO5 and S1. The J–V curves and
IPCE spectra of the DSSCs with water-based JC-IL (1-butyl-3-{2-
oxo-2-[(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)amino]ethyl}-1H-
imidazol-3-ium iodide) electrolyte[4a] measured under AM 1.5G
illumination are shown in Figure 6a and b, respectively, and
the corresponding photovoltaic parameters are given in
Table 3. The cells of EO1–EO4 exhibited excellent cell perform-
ances compared with those of EO5 and S1, which suggested
that the dye with higher wettability had a better cell per-
formance. Hupp et al. found that enhanced photoelectrode
wettability through post-assembly atomic layer deposition of
additional TiO2 also led to better cell performance.[5h] We spec-
ulate that higher wettability of the dye increases interfacial
electron transfer between the electrolyte and oxidized dye
molecule. However, there is slight discrepancy between EO4
and EO3. In addition to the wettability, the access of the elec-
Table 3. Photovoltaic parameters of the DSSCs with JC-IL water-based
electrolytes.[a]
Dye
VOC
[V]
JSC
[mAcmÀ2
FF
h
]
[%]
EO1
EO2
EO3
EO4
EO5
S1
0.84
0.85
0.88
0.86
0.84
0.81
7.11
8.31
9.87
8.63
5.97
5.76
0.68
0.67
0.68
0.67
0.65
0.66
4.04
4.73
5.97
4.98
3.27
3.11
Figure 4. (a) VOC as a function of electron density for DSSCs sensitized with
EO dyes. (b) Electron lifetime as a function of VOC for DSSCs sensitized with
EO dyes.
[a] Experiments were conducted by using TiO2 photoelectrodes approxi-
mately 10 mm thick with a 0.16 cm2 working area on FTO (15 W/sq.) sub-
strates.
The contact angles of a deionized water drop on the surface of
the EO and S1 sensitizers are shown in Figure 5 and the data
are compiled in Table 2. The dyes without TEOME, EO5 and S1,
Figure 5. Cross-sections of working electrodes with EO sensitizers and a drop of deionized water positioned on the top of the cell; this was used to estimate
qc [8].
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pression, DSSCs based on an organic solvent exhibited excel-
À
lent efficiencies (8.18–9.98%) with the standard IÀ/I3 electro-
lyte under AM 1.5 illumination. The best cell performance was
higher than that of the N719-based standard cell by about
14%. Water-based DSSCs with the JC-IL dual-redox couple had
VOC values exceeding 0.80 V, which was at least 50 mV higher
than that of DSSCs with standard iodide electrolyte. The better
wettability of the dyes (EO1–EO4) with TEOME led to better
cell efficiencies, and the best efficiency surpassed the highest
value reported to date.
Experimental Section
Materials and instrumentation
The solvents used were purified by standard procedures, or
1
purged with nitrogen before use. H and 13C NMR spectra were re-
corded on Bruker AV-400 and AMX-400 spectrometers. Electronic
absorption spectra were measured on a Dynamica DB-20 UV/Vis
spectrophotometer. Mass spectra (FAB) were recorded on a VG70-
250S mass spectrometer. Elemental analyses were carried out on
a PerkinElmer 2400 CHN analyzer. Chromatographic separations
were conducted on silica gel (60M, 230–400 mesh).
Fabrication of DSSCs
The TiO2 films used were comprised of a transparent layer and
a scattering layer with thicknesses of 9 and 3 mm, respectively, as
measured by means of a profilometer (Dektak3, Veeco/Sloan In-
struments Inc., USA). The TiO2 electrodes with a 0.16 cm2 geomet-
ric area were immersed in a solution containing 3”10À4 m organic
sensitizers in THF or in a solution containing 3”10À4 m of N719
(Solaronix S.A., Switzerland) in acetonitrile/tert-butanol (1:1 v/v) for
16 h. Platinized FTO was used as a counter electrode and was con-
trolled to have an active area of 0.16 cm2 by adhered polyester
tape with a thickness of 60 mm. The JC-IL electrolyte contained
0.4m JC-IL and 0.4m NOBF4 in water; and the iodide electrolyte
contained 0.1m LiI, 0.05m I2, 0.6m 1,2-dimethyl-3-propylimidazoli-
um iodide (DMPII), and 0.1m guanidine thiocyanate (GuSCN) dis-
solved in a mixture of CH3CN)/3-methoxypropionitrile (MPN; 1:1 v/
v). A 0.4”0.4 cm2 cardboard mask was clipped onto the device to
constrain the illumination area. Photoelectrochemical characteriza-
tions of the solar cells were carried out by using an Oriel Class A
solar simulator (Oriel 91195 A, Newport Corp.).
Figure 6. (a) J–V curves with the JC-IL water-based electrolyte. (b) IPCE spec-
tra of DSSCs based on the dyes reported herein with the JC-IL water-based
electrolyte.
trolyte towards the sensitizer for electron transfer is also likely
to be affected by the geometry of the dye molecule. Therefore,
further studies are needed to elucidate the detailed mecha-
nism involved. Sensitizer EO3 has the best cell performance (h:
5.97%; VOC: 0.88 V; JSC: 9.87 mAcmÀ2; FF: 0.68) and slightly out-
paced that in a previous report (h: 5.64%; VOC: 0.821 V; JSC:
10.17 mAcmÀ2; FF: 0.68).[5e] It is noteworthy that, without sur-
face treatment with octadecyltrichlorosilane, the efficiency of
the cell with EO3 drops to 4.09%. Compared with DSSCs with
IÀ/I3À- and CH3CN-based electrolytes, EO-sensitized DSSCs with
JC-IL electrolyte have remarkably higher VOC values, but signifi-
cantly lower JSC values. Similar to our previous observations,
the lower JSC values of the water-based electrolyte may be at-
tributed to the poor diffusion rate in H2O,[4a] and the higher
Characterization of DSSCs
Photocurrent–voltage characteristics of the DSSCs were recorded
with a potentiostat/galvanostat (CHI650B, CH Instruments, Inc.,
USA) at a light intensity of 1.0 sun calibrated by an Oriel reference
solar cell (Oriel 91150, Newport Corp.). The IPCE curves were ob-
tained under short-circuit conditions. The light source was
a class A quality solar simulator (PEC-L11, AM 1.5G, Peccell Technol-
ogies, Inc.); light was focused through a monochromator (Oriel In-
strument, model 74100) onto the photovoltaic cell and measured
with an optical detector (Oriel Instrument, model 71580) and
power meter (Oriel Instrument, model 70310). The IMVS measure-
ments were carried out on an electrochemical workstation (Zahner,
Zennium) with a frequency response analyzer under white light-
emitting diode (LED) illumination. The modulated light intensity
was 10% or less than the base light intensity. The frequency range
was set from 1 kHz to 0.1 Hz.
VOC values stem from the more positive redox potential of
+
C
NÀO /N=O of the redox mediator due to the successful inter-
[10]
ÀC
ception of I2 by the NÀO radical.
Conclusions
Incorporation of the TEOME entity into phenothiazine-based
metal-free organic sensitizers was beneficial at increasing the
wettability of the dyes and stronger trapping of lithium ions in
the electrolytes. They were successfully applied for high-per-
formance organic-solvent- and water-based DSSCs. Because
TEOME helped with lithium-ion trapping and dark-current sup-
ChemSusChem 2015, 8, 2503 – 2513
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Full Papers
tracted with CH2Cl2. The combined organic layers were dried over
MgSO4 and filtered. The filtrate was dried under vacuum, and the
crude product was further purified by column chromatography on
silica gel with hexanes/CH2Cl2 (6:1 v/v) as the eluent. The product
was obtained as a colorless oil (2.2 g, 99%). 1H NMR (CDCl3,
400 MHz): d=7.23 (d, 2H, J=8.4 Hz), 7.09 (d, 2H, J=8.8 Hz), 7.06
(d, 1H, J=2.0 Hz), 6.93 (dd, 1H, J=7.2, 1.6 Hz), 6.87 (dd, 1H, J=
7.2, 1.6 Hz), 6.81–6.76 (m, 2H), 6.14 (dd, 1H, J=7.6, 0.8 Hz), 5.99 (d,
1H, J=8.8 Hz), 4.01 (t, 2H, J=6.0 Hz), 1.84–1.79 (m, 2H), 1.49–1.47
(m, 2H), 1.36 (m, 4H), 0.91 ppm (t, 3H, J=5.0 Hz).
10-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl)-10H-
phenothiazine (1)
10H-Phenothiazine (2.00 g, 10.0 mmol), 1-bromo-4-{2-]2-(2-methox-
yethoxy)ethoxy]ethoxy}benzene (2.00 g, 6.27 mmol), sodium tert-
butoxide (1.45 g, 15.1 mmol), and [Pd(dba)2] (0.12 g) were added
to a 100 mL two-necked round-bottomed flask under nitrogen. Dry
toluene (15 mL) and tri(tert-butyl)phosphine (0.494m in toluene,
1.0 mL) were injected into the flask and the solution was heated at
1208C for 20 h. After the reaction was complete, the solution was
extracted with CH2Cl2 and washed with brine. The organic extracts
collected were dried over MgSO4 and filtered. The filtrate was dried
under vacuum, and the crude product was further purified by
column chromatography by using CH2Cl2/ethyl acetate (EA; 20:1 v/
v) as the eluent. The product was obtained as a brown oil (1.6 g,
10-(4-{2-[2-(2-Methoxyethoxy)ethoxy]ethoxy}phenyl)-10H-
phenothiazine-3-carbaldehyde (5)
1
Compound 1 (1.54 g, 3.52 mmol) was added to a 100 mL round-
bottomed flask and dry DMF (4 mL) was injected under nitrogen at
08C. POCl3 (0.38 mL, 4.06 mmol) was injected slowly into the solu-
tion, which was stirred for 1 h. The mixture was heated at 608C for
20 h. The mixture was extracted with CH2Cl2, and the organic ex-
tracts were collected and dried over MgSO4. After filtration, the fil-
trate was dried under vacuum. The crude product was further puri-
fied by column chromatography with CH2Cl2/EA (10:1 v/v) as the
eluent. The product was obtained as a yellow solid (0.80 g, 52%).
1H NMR ([D6]acetone, 400 MHz): d=9.74 (s, 1H), 7.48 (d, 1H, J=
1.6 Hz), 7.42 (dd, 1H, J=8.4, 2.0 Hz), 7.38 (d, 2H, J=8.8 Hz), 7.28
(d, 2H, J=8.8 Hz), 7.02 (dd, 1H, J=7.2, 2.0 Hz), 6.95–6.87 (m, 2H),
6.29 (d, 1H, J=8.8 Hz), 6.21 (dd, 1H, J=8.0, 1.6 Hz), 4.27 (t, 2H, J=
4.8 Hz), 3.89 (t, 2H, J=4.8 Hz), 3.71–3.68 (m, 2H), 3.64–3.59 (m,
4H), 3.49–3.47 (m, 2H), 3.29 ppm (s, 3H).
65%). H NMR (CDCl3, 400 MHz): d=7.27 (d, 2H, J=8.8 Hz), 7.10 (d,
2H, J=8.8 Hz), 6.96 (dd, 2H, J=7.2, 1.6 Hz), 6.82–6.73 (m, 4H), 6.16
(d, 2H, J=8.8 Hz), 4.19 (t, 2H, J=4.8 Hz), 3.90 (t, 2H, J=4.8 Hz),
3.76 (m, 2H), 3.68 (m, 4H), 3.55 (m, 2H), 3.37 ppm (s, 3H).
10-[4-(Hexyloxy)phenyl]-10H-phenothiazine (2)
10H-Phenothiazine (1.55 g, 7.78 mmol), 1-bromo-4-(hexyloxy)ben-
zene (2.00 g, 7.78 mmol), sodium tert-butoxide (1.12 g, 11.7 mmol),
and [Pd(dba)2] (0.13 g) were added to a 100 mL two-necked round-
bottomed flask under nitrogen. Dry toluene (15 mL) and tri(tert-bu-
tyl)phosphine (0.494m in toluene, 0.6 mL) were injected into the
flask. The mixture was heated at 1208C for 20 h. After the reaction
was complete, the solution was extracted with CH2Cl2 and washed
with brine. The organic extracts collected were dried over MgSO4
and filtered. The filtrate was dried under vacuum and the crude
product was further purified by column chromatography with hex-
anes/CH2Cl2 (6:1 v/v) as the eluent. The product was obtained as
a white solid (2.5 g, 87%). 1H NMR (CDCl3, 500 MHz): d=7.27 (d,
2H, J=8.5 Hz), 7.07 (d, 2H, J=8.5 Hz), 6.96 (d, 2H, J=7.5 Hz),
6.82–6.74 (m, 4H), 6.18 (d, 2H, J=8.0 Hz), 4.01 (t, 2H, J=6.0 Hz),
1.84–1.79 (m, 2H), 1.49–1.47 (m, 2H), 1.36 (m, 4H), 0.91 ppm (t,
3H, J=5.0 Hz).
3-[4-(Hexyloxy)phenyl]-10-(4-{2-[2-(2-methoxyethoxy)ethoxy]e-
thoxy}phenyl)-10H-phenothiazine (6)
Compound 3 (1.50 g, 2.90 mmol), tributyl[4-(hexyloxy)phenyl]stan-
nane (2.00 g, 4.28 mmol), and [PdCl2(PPh3)2] (0.10 g, 5 mol%) as the
catalyst were added under nitrogen to a 50 mL round-bottomed
flask. Dry DMF (3 mL) was injected into the mixture, which was
heated at 1008C for 18 h. After cooling, the mixture was quenched
with an aqueous solution of KF and the aqueous layer was extract-
ed with CH2Cl2. The combined organic layers were dried over
MgSO4 and evaporated to dryness. The crude product was further
purified by column chromatography on silica gel with CH2Cl2/EA
(50:1 v/v) as the eluent. The product was obtained as a colorless
3-Bromo-10-(4-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}phen-
yl)-10H-phenothiazine (3)
1
oil (0.4 g, 22%). H NMR ([D6]acetone, 400 MHz): d=7.48 (d, 2H, J=
8.4 Hz), 7.36 (d, 2H, J=8.8 Hz), 7.26 (d, 2H, J=8.8 Hz), 7.24 (s, 1H),
7.13 (dd, 1H, J=8.8, 2.0 Hz), 7.02 (dd, 1H, J=7.6, 2.0 Hz), 6.95 (d,
2H, J=8.4 Hz), 6.92–6.88 (m, 1H), 6.84–6.80 (m, 1H), 6.25 (d, 1H,
J=8.4 Hz), 6.22 (d, 1H, J=8.0 Hz), 4.26 (t, 2H, J=4.8 Hz), 4.01 (t,
2H, J=6.4 Hz), 3.89 (d, 2H, J=4.8 Hz), 3.71–3.68 (m 2H), 3.64–3.59
(m, 4H), 3.50–3.47 (m, 2H), 3.30 (s, 3H), 1.80–1.73 (m, 2H), 1.50–
1.44 (m, 2H), 1.36–1.31 (m, 4H), 0.90 ppm (t, 3H, J=5.6 Hz).
Compound 1 was dissolved in CH2Cl2 (1.5 mL) in a round-bottomed
flask and a solution of NBS (0.63 g, 3.54 mmol) in CH2Cl2 (1.5 mL)
was added to the reaction mixture. The mixture was stirred for
18 h at room temperature and then poured into ice water, and ex-
tracted with CH2Cl2. The combined organic layers were dried over
MgSO4 and evaporated to dryness. The crude product was further
purified by column chromatography on silica gel with CH2Cl2/EA
(20:1 v/v) as the eluent. The product was obtained as a brown oil
(1 g, 56%). 1H NMR (CDCl3, 400 MHz): d=7.23 (d, 2H, J=8.4 Hz),
7.09 (d, 2H, J=8.8 Hz), 7.06 (d, 1H, J=2.0 Hz), 6.93 (dd, 1H, J=7.2,
1.6 Hz), 6.87 (dd, 1H, J=7.2, 1.6 Hz), 6.81–6.76 (m, 2H), 6.14 (dd,
1H, J=7.6, 0.8 Hz), 5.99 (d, 1H, J=8.8 Hz), 4.18 (t, 2H, J=4.8 Hz),
3.89 (t, 2H, J=4.8 Hz), 3.76–3.74 (m, 2H), 3.70–3.64 (m, 4H), 3.56–
3.53 (m, 2H), 3.37 ppm (s, 3H).
10-[4-(Hexyloxy)phenyl]-3-(4-{2-[2-(2-methoxyethoxy)ethox-
y]ethoxy}phenyl)-10H-phenothiazine (7)
Compound 4 (0.80 g, 1.76 mmol), tributyl(4-{2-[2-(2-methoxyethox-
y)ethoxy]ethoxy}phenyl)stannane
(1.2 g,
2.27 mmol),
and
[PdCl2(PPh3)2] (0.040 g, 5 mol%) as the catalyst were added to
a 50 mL round-bottomed flask under nitrogen. Dry DMF (3.0 mL)
was injected into the mixture, which was heated at 1008C for 18 h.
After cooling, the mixture was quenched with an aqueous solution
of KF and the aqueous layer was extracted with CH2Cl2. The com-
bined organic layers were dried over MgSO4 and filtered. The fil-
trate was evaporated to dryness, and the crude product was fur-
ther purified by column chromatography on silica gel with CH2Cl2/
3-Bromo-10-[4-(hexyloxy)phenyl]-10H-phenothiazine (4)
Compound 2 was dissolved in CH2Cl2 (4.0 mL) in a round-bottomed
flask and a solution of NBS (0.90 g, 5.31 mmol) in CH2Cl2 (4 mL)
was added to the reaction mixture. The mixture was stirred for
18 h at room temperature and then poured into ice water, and ex-
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EA (50:1 v/v) as the eluent. The product was obtained as a colorless
oil (0.50 g, 65%). 1H NMR ([D6]acetone, 400 MHz): d=7.49 (d, 2H,
J=8.4 Hz), 7.35 (d, 2H, J=8.8 Hz), 7.25 (d, 2H, J=8.8 Hz), 7.24 (s,
1H), 7.14 (dd, 1H, J=8.8, 2.0 Hz), 7.02 (dd, 1H, J=7.6, 2.0 Hz), 6.99
(d, 2H, J=8.4 Hz), 6.95–6.91 (m, 1H), 6.88–6.80 (m, 1H), 6.25 (d,
1H, J=8.4 Hz), 6.22 (d, 1H, J=8.0 Hz), 4.26 (t, 2H, J=4.8 Hz), 4.01
(t, 2H, J=6.4 Hz), 3.89 (d, 2H, J=4.8 Hz), 3.71–3.68 (m, 2H), 3.64–
3.59 (m, 4H), 3.50–3.47 (m, 2H), 3.30 (s, 3H), 1.80–1.73 (m, 2H),
1.50–1.44 (m, 2H), 1.36–1.31 (m, 4H), 0.90 ppm (t, 3H, J=5.6 Hz).
8.8 Hz), 7.49 (s, 1H), 7.42 (d, 1H, J=8.4 Hz), 7.39 (d, 2H, J=8.8 Hz),
7.28 (d, 2H, J=8.8 Hz), 7.26 (dd, 1H, J=7.2, 2.0 Hz), 7.15 (dd, 1H,
J=8.8, 2.0 Hz), 6.96 (d, 2H, J=8.4 Hz), 6.28 (d, 1H, J=8.4 Hz), 6.23
(d, 1H, J=8.4 Hz), 4.27 (t, 1H, J=4.0 Hz), 4.01 (t, 2H, J=6.4 Hz),
3.89 (t, 2H, J=4.4 Hz), 3.70 (t, 2H, J=4.0 Hz), 3.64–3.59 (m, 4H),
3.48 (t, 2H, J=4.4 Hz), 3.30 (s, 3H), 1.77 (m, 2H), 1.47 (m, 2H), 1.35
(m, 4H), 0.90 ppm (t, 3H, J=6.8 Hz); HRMS (FAB): m/z calcd for
C38H43NO6S [M]+: 641.2811; found: 641.2806.
3,10-Bis[4-(hexyloxy)phenyl]-10H-phenothiazine (8)
(E)-2-Cyano-3-[7-(4-(hexyloxy)phenyl]-10-(4-{2-[2-(2-methox-
yethoxy)ethoxy]ethoxy}phenyl)-10H-phenothiazin-3-yl)acryl-
ic acid (EO1)
Compound 4 (0.48 g, 1.06 mmol), tributyl[4-(hexyloxy)phenyl]stan-
nane (0.6 g, 1.28 mmol), and [PdCl2(PPh3)2] (0.040 g, 5 mol%) as the
catalyst were added to a 50 mL round-bottomed flask under nitro-
gen. Dry DMF (3 mL) was injected into the mixture, which was
heated at 1008C for 18 h. After cooling, the mixture was quenched
with an aqueous solution of KF and the aqueous layer was extract-
ed with CH2Cl2. The combined organic layers were dried over
MgSO4 and filtered. The filtrate was evaporated to dryness, and the
crude product was further purified by column chromatography on
silica gel with hexanes/CH2Cl2 (6:1 v/v) as the eluent. The product
Sensitizer EO1a (0.10 g, 0.16 mmol), cyanoacetic acid (0.05 g,
0.32 mmol), and NH4OAc (2.97 mg) were added to a 100 mL round-
bottomed flask. AcOH (2 mL) was added to the mixture, which was
heated at 110 8C for 20 h. After the solution was cooled to room
temperature, the volatile compounds were removed in vacuo, and
the residue was extracted with EA. The organic extracts were col-
lected and dried over MgSO4. After filtration, the filtrate was dried
under vacuum. The crude product was further purified by column
chromatography on silica gel with CH2Cl2/EA (1:1 v/v) as the
eluent. The product was obtained as an red solid (80 mg, 73%).
1H NMR ([D6]acetone, 400 MHz): d=8.06 (s, 1H), 7.81 (s, 1H), 7.62
(d, 1H, J=8.8 Hz), 7.51 (d, 2H, J=8.4 Hz), 7.42 (d, 2H, J=8.8 Hz),
7.30 (d, 2H, J=8.8 Hz), 7.28 (d, 1H, J=2.0 Hz), 7.17 (dd, 1H, J=8.8,
1.6 Hz), 6.97 (d, 1H, J=8.8 Hz), 6.27 (d, 1H, J=8.8 Hz), 6.24 (d, 1H,
J=8.8 Hz), 4.28 (t, 2H, J=4.8 Hz), 4.02 (t, 2H, J=6.4 Hz), 3.90 (t,
2H, J=4.8 Hz), 3.70 (dd, 2H, J=5.2, 4.0 Hz), 3.64–3.59 (m, 4H), 3.49
(dd, 2H, J=5.2, 4.4 Hz), 3.30 (s, 3H), 1.81–1.74 (m, 2H), 1.50–1.44
(m, 2H), 1.39–1.34 (m, 4H), 0.90 ppm (t, 3H, J=6.8 Hz); 13C NMR
([D6]acetone, 500 MHz): d=164.3, 160.5, 160.0, 153.3, 149.1, 142.3,
137.4, 133.2, 132.6, 132.4, 129.3, 128.2, 127.0, 126.1, 125.1, 120.6,
120.2, 118.1, 118.0, 117.3, 116.4, 115.9, 72.8, 71.6, 71.5, 71.3, 70.5,
69.1, 68.8, 32.4, 26.6, 23.4, 14.4 ppm; HRMS (FAB): m/z calcd for
C41H44N2O7S [M]+: 708.2863; found: 708.2856; elemental analysis
calcd (%) for C41H44N2O7S: C 69.47, H 6.26, N 3.95; found: C 69.23,
H 6.15, N 4.20.
1
was obtained as a colorless oil (0.2 g, 34%). H NMR ([D6]acetone,
400 MHz): d=7.48 (d, 2H, J=8.4 Hz), 7.35 (d, 2H, J=8.8 Hz), 7.24
(d, 2H, J=8.8 Hz), 7.22 (s, 1H), 7.13 (dd, 1H, J=8.4, 2.0 Hz), 7.02
(dd, 1H, J=7.6, 2.0 Hz), 6.95 (d, 2H, J=8.4 Hz), 6.90–6.88 (m, 1H),
6.84–6.80 (m, 1H), 6.24 (d, 1H, J=8.4 Hz), 6.22 (dd, 1H, J=8.4,
1.2 Hz), 4.11 (t, 2H, J=6.4 Hz), 4.01 (t, 2H, J=6.4 Hz), 1.88–1.81 (m,
2H), 1.80–1.73 (m, 2H), 1.54–1.44 (m, 4H), 1.40–1.33 (m, 8H),
0.94 ppm (t, 6H, J=5.2 Hz).
7-Bromo-10-[4-(hexyloxy)phenyl]-10H-phenothiazine-3-carb-
aldehyde (9)
Compound 5 was dissolved in CH2Cl2 (2 mL) in a round-bottomed
flask and a solution of NBS (0.53 g, 2.98 mmol) in CH2Cl2 (2 mL)
was added to the reaction mixture. The mixture was stirred for
18 h at room temperature and then poured into ice water, and ex-
tracted with CH2Cl2. The combined organic layers were dried over
MgSO4 and filtered. The filtrate was evaporated to dryness, and the
crude product was further purified by column chromatography on
silica gel with hexanes/CH2Cl2 (6:1 v/v) as the eluent. The product
was obtained as a yellow oil (1.3 g, 99%). 1H NMR ([D6]acetone,
400 MHz): d=9.75 (s, 1H), 7.69 (d, 1H, J=1.6 Hz), 7.45 (dd, 1H, J=
8.4, 1.6 Hz), 7.38 (d, 2H, J=8.8 Hz), 7.28 (d, 2H, J=8.8 Hz), 7.19 (d,
1H, J=2.0 Hz), 7.07 (dd, 1H, J=8.8, 2.0 Hz), 6.30 (d, 1H, J=8.8 Hz),
6.12 (d, 1H, J=8.8 Hz), 4.01 (t, 2H, J=6.0 Hz), 1.84–1.79 (m, 2H),
1.49–1.47 (m, 2H), 1.36 (m, 4H), 0.91 ppm (t, 3H, J=5.0 Hz).
10-[4-(Hexyloxy)phenyl]-7-(4-{2-[2-(2-methoxyethoxy)ethox-
y]ethoxy}phenyl)-10H-phenothiazine-3-carbaldehyde (EO2a)
Compound 7 (0.53 g, 0.96 mmol) was added to a 100 mL round-
bottomed flask and dry DMF (3.0 mL) was injected under nitrogen
at 08C. POCl3 (0.16 mL, 1.92 mmol) was injected slowly into the so-
lution, which was stirred for 1 h and then heated at 658C for 20 h.
The mixture was extracted with CH2Cl2, and the organic extracts
were collected and dried over MgSO4. After filtration, the filtrate
was dried under vacuum. The crude product was further purified
by column chromatography with CH2Cl2/EA (6:1 v/v) as the eluent.
7-[4-(Hexyloxy)phenyl]-10-(4-{2-[2-(2-methoxyethoxy)ethox-
y]ethoxy}phenyl)-10H-phenothiazine-3-carbaldehyde (EO1a)
1
Compound 6 (0.40 g, 0.65 mmol) was added to a 100 mL round-
bottomed flask and dry DMF (2 mL) was injected under nitrogen at
08C. POCl3 (0.3 mL, 3.25 mmol) was injected slowly into the solu-
tion, which was stirred for 1 h. The mixture was heated at 658C for
20 h. The mixture was extracted with CH2Cl2, and the organic ex-
tracts were collected and dried over MgSO4. After filtration, the fil-
trate was dried under vacuum. The crude product was further puri-
fied by column chromatography with CH2Cl2/EA (6:1 v/v) as the
eluent. The product was obtained as a yellow oil (0.3 g, 75%).
1H NMR ([D6]acetone, 400 MHz): d=9.74 (s, 1H), 7.50 (d, 2H, J=
The product was obtained as a yellow solid (0.14 g, 25%). H NMR
([D6]acetone, 400 MHz): d=9.74 (s, 1H), 7.51 (d, 2H, J=8.8 Hz),
7.50 (s, 1H), 7.42 (d, 1H, J=8.4 Hz), 7.41 (d, 2H, J=8.8 Hz), 7.27 (d,
2H, J=8.8 Hz), 7.26 (dd, 1H, J=7.2, 2.0 Hz), 7.15 (dd, 1H, J=8.8,
2.0 Hz), 6.99 (d, 2H, J=8.4 Hz), 6.28 (d, 1H, J=8.4 Hz), 6.24 (d, 1H,
J=8.4 Hz), 4.27 (t, 1H, J=4.0 Hz), 4.01 (t, 2H, J=6.4 Hz), 3.89 (t,
2H, J=4.4 Hz), 3.70 (t, 2H, J=4.0 Hz), 3.64–3.59 (m, 4H), 3.48 (t,
2H, J=4.4 Hz), 3.30 (s, 3H), 1.77 (m, 2H), 1.47 (m, 2H), 1.35 (m,
4H), 0.90 ppm (t, 3H, J=6.8 Hz); HRMS (FAB): m/z calcd for
C38H43NO6S [M]+: 641.2811; found: 641.2820.
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lution was heated at 110 8C for 20 h. After the solution was cooled
to room temperature, the volatile compounds were removed in
vacuo, and the residue was extracted with EA. The organic extracts
were collected and dried over MgSO4. After filtration, the filtrate
was dried under vacuum. The crude product was further purified
by column chromatography on silica gel with EA as the eluent. The
product was obtained as a red solid (0.17 g, 47%). 1H NMR
([D6]acetone, 400 MHz): d=8.07 (s, 1H), 7.81 (d, 1H, J=2.0 Hz),
7.63 (dd, 1H, J=8.8, 2.0 Hz), 7.52 (d, 2H, J=8.8 Hz), 7.42 (d, 2H,
J=8.8 Hz), 7.30 (d, 2H, J=8.8 Hz), 7.29 (d, 1H, J=2.0 Hz), 7.17 (dd,
1H, J=8.8, 2.0 Hz), 6.99 (d, 2H, J=8.8 Hz), 6.27 (d, 1H, J=8.4 Hz),
6.24 (d, 1H, J=8.4 Hz), 4.28 (t, 2H, J=4.4 Hz), 4.15 (t, 2H, J=
4.4 Hz), 3.90 (t, 2H, J=4.8 Hz), 3.82 (t, 2H, J=4.8 Hz), 3.70–3.58 (m,
12H), 3.50–3.45 (m, 4H), 3.29 (s, 3H), 3.27 ppm (s, 3H); 13C NMR
([D6]acetone, 500 MHz): d=164.7, 160.6, 160.0, 153.6, 149.3, 142.5,
137.4, 133.3, 132.9, 132.8, 129.7, 128.5, 127.2, 126.4, 125.4, 120.8,
120.4, 118.27, 118.2, 117.7, 116.6, 116.2, 110.6, 73.08, 73.05, 71.9,
71.8, 71.70, 71.66, 71.52, 71.50, 70.74, 70.69, 69.2, 68.8, 59.23,
59.21 ppm; HRMS (FAB): m/z calcd for C42H46N2O10S [M]+: 770.2868;
found: 770.2861; elemental analysis calcd (%) for C42H46N2O10S: C
65.44, H 6.01, N 3.63; found: C 65.31, H 5.92, N 3.69.
(E)-3-{7-[4-(2,5,7,9-Tetraoxaundecan-11-yl)phenyl]-10-[4-(hex-
yloxy)phenyl]-10H-phenothiazin-3-yl}-2-cyanoacrylic acid
(EO2)
Sensitizer EO2a (0.14 g, 0.16 mmol), cyanoacetic acid (0.05 g,
0.32 mmol), and NH4OAc (2.97 mg) were added to a 100 mL round-
bottomed flask. AcOH (2 mL) was added as the solvent, and the so-
lution was heated at 110 8C for 20 h. After the solution was cooled
to room temperature, the volatile compounds were removed in
vacuo, and the residue was extracted with EA. The organic extracts
were collected and dried over MgSO4. After filtration, the filtrate
was dried under vacuum. The crude product was further purified
by column chromatography on silica gel with CH2Cl2/EA (1:1 v/v) as
the eluent. The product was obtained as a red solid (80 mg, 73%).
1H NMR ([D6]acetone, 400 MHz): d=8.06 (s, 1H), 7.81 (d, 1H, J=
1.6 Hz), 7.62 (dd, 1H, J=8.8, 2.0 Hz), 7.52 (d, 2H, J=8.8 Hz), 7.40
(d, 2H, J=8.8 Hz), 7.27 (d, 2H, J=8.8 Hz), 7.26 (d, 1H, J=2.4 Hz),
7.17 (dd, 1H, J=8.8, 2.4 Hz), 6.99 (d, 1H, J=8.8 Hz), 6.27 (d. 1H,
J=8.8 Hz), 6.24 (d, 1H, J=8.8 Hz), 4.28 (t, 2H, J=4.8 Hz), 4.02 (t,
2H, J=6.4 Hz), 3.90 (t, 2H, J=4.8 Hz), 3.70 (dd, 2H, J=5.2, 4.0 Hz),
3.64–3.59 (m, 4H), 3.49 (dd, 2H, J=5.2, 4.4 Hz), 3.30 (s, 3H), 1.81–
1.74 (m, 2H), 1.50–1.44 (m, 2H), 1.39–1.34 (m, 4H), 0.90 ppm (t,
3H, J=6.8 Hz); 13C NMR ([D6]acetone, 500 MHz): d=164.7, 161.0,
160.2, 153.7, 149.6, 142.7, 137.7, 133.3, 133.1, 133.0, 129.8, 128.7,
127.4, 126.5, 125.5, 121.0, 120.5, 118.4, 117.7, 116.8, 116.4, 110.7,
73.2, 72.0, 71.8, 71.7, 70.9, 69.6, 69.0, 59.3, 32.9, 29.9, 27.0, 23.9,
14.9 ppm; HRMS (FAB): m/z calcd for C41H44N2O7S [M]+: 708.2864;
found: 708.2853; elemental analysis calcd (%) for C41H44N2O7S: C
69.47, H 6.26, N 3.95; found: C 69.52, H 6.57, N 3.71.
7-(2,4-Bis{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}phenyl)-10-
{4-[2-(2-methoxyethoxy)ethylperoxy]phenyl}-10H--
phenothiazine-3-carbaldehyde (EO4a)
10-{4-[2-(2-methoxyethoxy)ethylperoxy]phenyl}-7-(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)-10H-phenothiazine-3-carbaldehyde
(0.57 g, 0.96 mmol), 1-bromo-2,4-bis{2-[2-(2-methoxyethoxy)ethox-
y]ethoxy}benzene (0.55 g, 1.14 mmol), potassium carbonate (0.90 g,
6.51 mmol), and [Pd(PPh3)4] (0.060 g) were added to a 100 mL two-
necked round-bottomed flask under nitrogen. Dry toluene (2.0 mL)
and water (2.0 mL) were injected into the flask, and the solution
was heated at 1208C for 20 h. The mixture was extracted with
CH2Cl2 and washed with brine. The collected organic extracts were
dried over MgSO4 and filtered. The filtrate was dried under
vacuum, and the crude product was further purified by column
chromatography with EA/MeOH (20:1 by v/v) as the eluent. The
product was obtained as a yellow oil (0.12 g, 15%). 1H NMR
([D6]acetone, 400 MHz): d=9.74 (s, 1H), 7.49 (d, 1H, J=2.0 Hz),
7.43 (dd, 1H, J=8.8, 2.0 Hz), 7.41 (d, 2H, J=8.8 Hz), 7.31 (d, 2H,
J=8.8 Hz), 7.30 (d, 1H, J=2.0 Hz), 7.21 (d, 1H, J=8.4 Hz), 7.12 (dd,
1H, J=8.8, 2.0 Hz), 6.67 (d, 1H, J=2.0 Hz), 6.59 (dd, 1H, J=8.4,
2.0 Hz), 6.29 (d, 1H, J=8.8 Hz), 6.21 (d, 1H, J=8.8 Hz), 4.28 (t, 2H,
J=4.8 Hz), 4.16 (t, 4H, J=4.8 Hz), 3.90 (t, 2H, J=4.8 Hz), 3.83–3.78
(m, 4H), 3.70 (t, 2H, J=4.8 Hz), 3.65–3.57 (m, 14H), 3.54–3.41 (m,
8H), 3.29 (s, 3H), 3.28 (s, 3H), 3.25 ppm (s, 3H); HRMS (FAB): m/z
calcd for C46H59NO13S [M]+: 865.3702; found: 865.3707.
7-[4-(2,5,7,9-Tetraoxaundecan-11-yl)phenyl]-10-{4-[2-(2-me-
thoxyethoxy)ethylperoxy]phenyl}-10H-phenothiazine-3-
carbaldehyde (EO3a)
10-[4-(hexyloxy)phenyl]-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)-10H-phenothiazine-3-carbaldehyde (1.09 g, 1.86 mmol), 1-
bromo-4-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}benzene
(0.89 g,
1.86 mmol), potassium carbonate (1.54 g, 11.16 mmol), and
[Pd(PPh3)4] (0.11 g) were added to a 100 mL two-necked round-bot-
tomed flask under nitrogen. Dry toluene (3 mL) and water (3 mL)
were injected into the flask. The mixture was heated at 1208C for
20 h. The mixture was extracted with CH2Cl2 and washed with
brine. The organic extracts collected were dried over MgSO4. The
crude product was further purified by column chromatography
with CH2Cl2/EA (4:1 v/v) as the eluent. The product was obtained
1
as a yellow solid (0.57 g, 44%). H NMR (CDCl3, 400 MHz): d=9.68
(s, 1H), 7.44 (d, 1H, J=2.0 Hz), 7.36 (d, 2H, J=8.8 Hz), 7.27 (d, 2H,
J=8.8 Hz), 7.26 (dd, 1H, J=8.8, 2.0 Hz), 7.15 (d, 2H, J=8.8 Hz),
7.12 (d, 1H, J=2.0 Hz), 6.97 (dd, 1H, J=8.8, 2.0 Hz), 6.92 (d, 2H,
J=8.8 Hz), 6.17 (d, 1H, J=8. 0 Hz), 6.15 (d, 1H, J=8.0 Hz), 4.28 (t,
2H, J=4.4 Hz), 4.15 (t, 2H, J=4.4 Hz), 3.90 (t, 2H, J=4.8 Hz), 3.82
(t, 2H, J=4.8 Hz), 3.70–3.58 (m, 12H), 3.50–3.45 (m, 4H), 3.29 (s,
3H), 3.27 ppm (s, 3H); HRMS (FAB): m/z calcd for C39H45NO9S [M]+:
703.2810; found: 703.2807.
(E)-3-[7-(2,4-Bis{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}phen-
yl)-10-{4-[2-(2-methoxyethoxy)ethylperoxy]phenyl}-10H-phe-
nothiazin-3-yl]-2-cyanoacrylic acid (EO4)
Sensitizer EO4a (0.12 g, 0.14 mmol), cyanoacetic acid (0.060 g,
0.71 mmol), and NH4OAc (2.97 mg) were added to a 100 mL round-
bottomed flask. AcOH (2.0 mL) was added as the solvent, and the
solution was heated at 110 8C for 20 h. After the solution was
cooled to room temperature, the volatile compounds were re-
moved in vacuo, and the residue was extracted with EA. The or-
ganic extracts were collected and dried over MgSO4. After filtration,
the filtrate was dried under vacuum. The crude product was fur-
ther purified by column chromatography on silica gel with EA as
(E)-3-(7-[4-(2,5,7,9-Tetraoxaundecan-11-yl)phenyl]-10-{4-[2-
(2-methoxyethoxy)ethylperoxy]phenyl}-10H-phenothiazin-3-
yl)-2-cyanoacrylic acid (EO3)
Sensitizer EO3a (0.30 g, 0.43 mmol), cyanoacetic acid (0.08 g,
0.94 mmol), and NH4OAc (2.97 mg) were added to a 100 mL round-
bottomed flask. AcOH (2 mL) was added as the solvent, and the so-
ChemSusChem 2015, 8, 2503 – 2513
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Full Papers
the eluent. The product was obtained as a red solid (0.12 g, 28%).
1H NMR (CDCl3, 400 MHz): d=7.89 (s,1H), 7.51 (s, 1H), 7.44 (d, 1H,
J=8.8 Hz), 7.23 (d, 2H, J=8.8 Hz), 7.14 (d, 2H, J=8.8 Hz), 7.13 (s,
1H), 7.10 (d, 1H, J=8.0 Hz), 6.94 (d, 1H, J=8.8 Hz), 6.51 (s, 1H),
6.49 (d, 1H, J=8.8 Hz), 6.10 (d, 1H, J=8.8 Hz), 6.08 (d, 1H, J=
8.8 Hz), 4.19 (t, 2H, J=4. Hz), 4.11 (t, 2H, J=4.8 Hz), 4.06 (t, 2H, J=
4.8 Hz), 3.90 (t, 2H, J=4.8 Hz), 3.83 (t, 2H, J=4.8 Hz), 3.77–3.63 (m,
20H), 3.60–3.43 (m, 6H), 3.37 (s, 3H), 3.35 (s, 3H), 3.32 ppm (s, 3H);
13C NMR (CDCl3, 500 MHz): d=166.1, 159.4, 159.0, 156.5, 153.6,
148.7, 140.5, 134.8, 132.1, 131.6, 131.5, 130.4, 129.2, 127.9, 127.5,
125.3, 122.0, 120.1, 118.0, 117.0, 116.3, 116.1, 115.2, 106.0, 100.8,
97.4, 71.93, 71.90, 71.9, 70.9, 70.8, 70.71, 70.68, 70.63, 70.56, 70.53,
70.47, 69.7, 69.6, 69.5, 68.0, 67.8, 67.5, 59.0, 59.02, 58.98 ppm;
HRMS (FAB): m/z calcd for C49H60N2O14S [M]+: 932.3760; found:
932.3754; elemental analysis calcd (%) for C49H60N2O14S: C 63.07, H
6.48, N 3.00; found: C 63.12, H 6.51, N 2.78.
elemental analysis calcd (%) for C40H42N2O4S: C 74.27, H 6.54, N
4.33; found: C 74.28, H 6.57, N 4.25.
Acknowledgements
We acknowledge support from the National Taiwan University,
the Academia Sinica (AC), the Ministry of Science and Technology
(MST) (Taiwan), and the Instrumental Center of Institute of
Chemistry (AC).
Keywords: dyes/pigments · electrochemistry · sensitizers ·
solar cells · synthesis design
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7,10-Bis[4-(hexyloxy)phenyl]-10H-phenothiazine-3-carbalde-
hyde (EO5a)
Compound 8 (0.20 g, 0.36 mmol) was added to a 100 mL round-
bottomed flask and dry DMF (2.0 mL) was injected as the solvent
under nitrogen at 08C. POCl3 (0.10 mL, 1.08 mmol) was injected
slowly into the solution, which was stirred for 1 h, and the mixture
was heated at 658C for 20 h. The mixture was extracted with
CH2Cl2, and the organic extracts were collected and dried over
MgSO4. After filtration, the filtrate was dried under vacuum. The
crude product was further purified by column chromatography
with hexanes/CH2Cl2 (1:1 v/v) as the eluent. The product was ob-
tained as
a
yellow oil (70 mg, 33%). 1H NMR ([D6]acetone,
400 MHz): d=9.67 (s, 1H), 7.44 (d, 1H, J=2.0 Hz), 7.35 (d, 2H, J=
8.8 Hz), 7.27 (dd, 1H, J=8.4, 2.0 Hz), 7.23 (d, 2H, J=8.8 Hz), 7.12 (s,
1H), 7.11 (d, 2H, J=8.8 Hz), 6.97 (dd, 1H, J=8.8, 2.0 Hz), 6.89 (d,
2H, J=8.8 Hz), 6.18 (d, 1H, J=8.4 Hz), 6.16 (d, 1H, J=8.8 Hz), 4.03
(t, 2H, J=6.4 Hz), 4.95 (t, 2H, J=6.4 Hz), 1.86–1.73 (m, 4H), 1.50–
1.40 (m, 4H), 1.38–1.30 (m, 8H), 0.92 (t, 3H, J=6.8 Hz), 0.90 ppm (t,
3H, J=7.2 Hz); HRMS (FAB): m/z calcd for C37H41NO3S [M]+:
579.2801; found: 579.2807.
(E)-3-{7,10-Bis[4-(hexyloxy)phenyl]-10H-phenothiazin-3-yl}-2-
cyanoacrylic acid (EO5)
Sensitizer EO5a (0.070 g, 0.12 mmol), cyanoacetic acid (0.030 g,
0.46 mmol), and NH4OAc (2.97 mg) were added to a 100 mL
round-bottomed flask. AcOH (2.0 mL) was added as the solvent,
and the solution was heated at 110 8C for 20 h. After the solution
was cooled to room temperature, the volatile compounds were re-
moved in vacuo, and the residue was extracted with EA. The or-
ganic extracts were collected and dried over MgSO4. After filtration,
the filtrate was dried under vacuum. The crude product was fur-
ther purified by column chromatography on silica gel with EA as
the eluent. The product was obtained as a red solid (50 mg, 58%).
1H NMR ([D6]acetone, 400 MHz): d=7.96 (s, 1H), 7.56 (d, 1H, J=
1.6 Hz), 7.51 (dd, 1H, J=8.8, 1.6 Hz), 7.35 (d, 2H, J=8.4 Hz), 7.24
(d, 2H, J=8.4 Hz), 7.11 (d, 2H, J=8.8 Hz), 7.10 (s, 1H), 6.97 (dd, 1H,
J=8.8, 2.0 Hz), 6.89 (d, 2H, J=8.8 Hz), 6.16 (d, 1H, J=8.4 Hz), 6.15
(d, 1H, J=8.8 Hz), 4.03 (t, 2H, J=6.4 Hz), 4.95 (t, 2H, J=6.4 Hz),
1.86–1.74 (m, 4H), 1.50–1.42 (m, 4H), 1.37–1.32 (m, 8H), 0.91 (t,
3H, J=6.8 Hz), 0.88 ppm (t, 3H, J=7.2 Hz); 13C NMR (CDCl3,
400 MHz): d=159.5, 158.8, 154.2, 148.9, 140.9, 136.8, 131.8, 131.7,
131.4, 129.5, 127.4, 125.3, 125.2, 124.6, 120.0, 119.3, 116.9, 116.0,
115.3, 114.9, 68.5, 68.2, 31.6, 29.7, 29.2, 25.7, 22.6, 14.0 ppm; HRMS
(FAB): m/z calcd for C40H42N2O4S [M]+: 646.2859; found: 646.2858;
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Revised: May 19, 2015
Published online on June 22, 2015
ChemSusChem 2015, 8, 2503 – 2513
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