D-π-A dye sensitizers made of polymeric metal complexes containing 1,10-phenanthroline and alkylfluorene or alkoxybenzene: Synthesis, characterization and photovoltaic performance for dye-sensitized solar cells

Article abstract of DOI:10.1002/ejoc.201300192

Four polymeric metal complexes (P1-P4 based on 1,10-phenanthroline metal complexes and alkylfluorene or alkoxybenzene were synthesized by the Heck coupling reaction and were developed for dye-sensitized solar cell applications. The target dyes use alkoxyb

Full text of DOI:10.1002/ejoc.201300192

FULL PAPER
DOI: 10.1002/ejoc.201300192
D–π–A Dye Sensitizers Made of Polymeric Metal Complexes Containing
1
,10-Phenanthroline and Alkylfluorene or Alkoxybenzene: Synthesis,
Characterization and Photovoltaic Performance for Dye-Sensitized Solar Cells
[a]
[a]
[a]
[a]
[a]
[a]
Xiaoguang Yu, Xueliang Jin, Guipeng Tang, Jun Zhou, Wei Zhang, Dahai Peng,
[a]
[a]
Jiaomei Hu, and Chaofan Zhong*
Keywords: Polymeric metal complex / Dye-sensitized solar cells / Energy conversion / Ligand design / Donor–acceptor
systems
Four polymeric metal complexes (P1–P4) based on 1,10-
phenanthroline metal complexes and alkylfluorene or alk-
oxybenzene were synthesized by the Heck coupling reaction
and were developed for dye-sensitized solar cell applica-
tions. The target dyes use alkoxybenzene or alkylfluorene as
the electron donor, a C=C moiety as the π linker, and the
phenanthroline derivative complex was used as the electron
acceptor. Bipyridine derivatives were ancillary ligands as
and I–V curves. Dye-sensitized solar cells with these poly-
meric metal complexes as dye sensitizers exhibited consider-
able power conversion efficiencies (PCE). The dyes contain-
ing alkoxybenzenes (P3, P4) exhibited higher PCE values
than the corresponding target polymers containing alkylfluo-
renes (P1, P2), The dye P3 showed the maximal power con-
2
version efficiency of 2.12% (Jsc = 4.91 mA/cm , Voc = 0.69 V,
FF = 62.5). In addition, the four polymers possessed excellent
well as providing anchoring groups. The thermal, photophys- stabilities, and their thermal decomposition temperatures all
ical, electrochemical and photovoltaic properties of these co-
polymers were investigated by thermogravimetric analysis
exceeded 300 °C, indicating that these polymeric metal com-
plexes are suitable for the fabrication processes of optoelec-
tronic devices.
(
TGA), differential scanning calorimetry (DSC), C–V curves
Introduction
lyte (redoxmediator), and (5) a platinum-coated glass sub-
[
3]
In recent decades, because of the rapid depletion of con- strate. One of the key roles in DSSCs is attributed to the
ventional energy sources and the increasing emission of sensitizers, which are responsible for light absorption and
greenhouse gases, the development of dye-sensitized solar the generation of electric charges. So far, much effort has
cells (DSSCs) has been paid increasing attention, mainly been put forth in the development of various types of or-
due to their potential ease of fabrication, abundant material ganic dye sensitizers for DSSCs. There are two kinds of
sources, and cost effectiveness compared with silicon-based dyes, namely, metal–organic complexes and metal-free or-
photovoltaic devices.[ After two decades of research and ganic dyes. Typical metal–organic dyes are a class of poly-
development, DSSCs based on ruthenium dyes have pyridyl complexes of ruthenium, such as N3, N719,
achieved record light-to-electric power conversion efficien- and “black dye”. These dyes are already commercially
cies of over 11%, and over 10% based on metal-free organic available. Other polymeric dyes including K19, C101,
[
4]
1]
[
5]
[6]
[
7]
[
8]
[9]
[
10]
dyes since the first demonstration in 1991 by O’Regan and and CYC-B11, have also been reported to have high effi-
[
2]
Grätzel.
designing and synthesizing efficient dye sensitizers that are researched in DSSCs. The ruthenium complex dyes have
suitable for practical use.
been distinguished by attaining more than 11% efficiencies
Many recent efforts have been devoted to ciencies of 10–11%. Ru complexes as dyes were extensively
The typical DSSC is composed of a photoanode and a under simulated air mass 1.5 global sunlight. However, Ru-
photoinert counterelectrode (cathode) sandwiching a redox complex dyes have met with some problems, such as limited
mediator. It consists of five materials: (1) a fluorine-doped resources, difficult purification, and environmental pol-
SnO (FTO) glass substrate, (2) a nanocrystalline TiO thin lution. Therefore, dye sensitizers containing common met-
2
2
film as a semiconductor, (3) a dye sensitizer, (4) an electro- als have attracted interest because of their modest cost, con-
venience of customized molecular design, and ease of syn-
[
a] Key Laboratory of Environmentally Friendly Chemistry and thesis. Aswani Yella and coworkers discovered a zinc (Zn)
Applications of Ministry of Education, Xiangtan University,
porphyrin dye with a cobalt (II/III)-based redox electrolyte
College of Chemistry,
Xiangtan, Hunan 411105, P. R. China
leading to record power conversion efficiency approaching
E-mail: zhongcf798@yahoo.com.cn
[11]
13% under simulated air mass 1.5 global sunlight.
This
Homepage: http://hxxy.web.xtu.edu.cn:8081/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201300192.
demonstrates that common-metal dye sensitizers can
achieve the same high efficiency as ruthenium complexes.
Eur. J. Org. Chem. 2013, 5893–5901
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C. Zhong et al.
FULL PAPER
The polymeric metal-complex dyes have their own ad- ing group for adsorption onto the TiO surface. The anchor
2
vantages, such as good thermal stability, processability, and group can bind the molecules to the surface and inject the
easy film-forming ability. Because hybrid polymers contain- electrons from the excited dye molecule to the conducting
ing inorganic and organic segments exhibit properties of band of the semiconductor. 3,3Ј-Dicarboxy-2,2Ј-bipyridine
both inorganic and organic-metal complexes, they are likely is an excellent polydentate ligand, and has been widely used
to meet requirements of highly efficient DSSCs, and many in spectroscopic, electrochemical, and magnetic applica-
[
25]
hybrid polymers have been investigated and used for tions.
[
12]
DSSCs.
structure is the common motif
lecular charge transfer characteristics.[
Among these hybrid polymer dyes, the D–π–A
In this article, four polymeric metal complexes (P1–P4)
because of its intramo- with D–π–A structures
[13–19]
[26]
were synthesized. In these com-
20]
plexes, the phenanthroline derivative part was used as the
The important ligand, 1,10-phenanthroline (phen), is one electron acceptor, a C=C moiety was used as the π linker,
of the most widely used chelating ligands in modern coordi- and an alkoxybenzene or an alkylfluorene group was used
nation chemistry.[21] The unit has a rigid structure, high as the electron donor. Zn or Co was chosen as the metal,
electron transfer capability, and can provide two aromatic each for its interesting charge properties and low cost. Bi-
nitrogens, which allow it to coordinate with many transition pyridine derivatives served as ancillary ligands, as well as
metal ions easily. Considering the distinctive physical and providing anchoring groups. The introduction of alkoxy or
chemical properties of phenanthroline, some researchers alkyl groups to the molecules in question was to improve
have used metal–phenanthroline-derivative complexes in the solubility of the polymers. The photophysical and ther-
DSSCs. For instance, Jen-Fu Yin and co-workers discov- mal properties of the four polymeric metal complexes were
II
II
[22]
ered that [Ru(dcbpy)(otip)(NCS2)]
containing a thio- studied, and the performance of DSSCs based on these four
phene-substituted spacer, has achieved an energy efficiency dyes as photosensitizers was investigated in detail.
of 8.3%. Kohjiro Hara and coworkers discovered that
[23]
[
Ru(dcphen) (NCS) ]
containing cis-dithiocyanatobis-
2
2
Results and Discussion
(
4,7-dicarboxy-1,10-phenanthroline) obtained an energy
[
24]
efficiency of 6.1%, and the similar dye CYC-P1
achieved an energy efficiency of 6.01% in DSSCs. To
achieve high quantum yields for the excited-state electron-
has
Synthesis and Characterization
Scheme 1 shows the synthetic routes to the metal com-
transfer process, the dye needs to have at least one anchor- plexes L1 and L2, as well as to the four main-chain poly-
Scheme 1. Synthesis of the monomers L1, L2 and four polymeric metal complexes (P1–P4).
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D–π–A Dye Sensitizers for Solar Cells
meric metal complexes (P1–P4), which were synthesized by
the Heck coupling.
Gel permeation chromatography (GPC) results of all the
target polymers are shown in Table 1. The average molecu-
[
27]
The IR spectra of the ligand–metal complexes L1 and lar weights of P1–P4 are 12.01, 9.7, 13.0 and 7.9 kg/mol,
L2 and the target polymers (P1–P4) are shown in Figure 1. respectively, with relative polydispersity indexes (PDI) in
In parts a and b of Figure 1 there is a broad absorption the range of 1.26–1.53. These results, combined with ele-
–
1
band at 3500–3280 cm , which is attributable to the exis- mental analysis, indicate that polymerization has taken
tence of lattice and/or coordinated water in the molecule. place between monomers, which also proved that the target
The presence of these water molecules makes it difficult to polymeric dyes have been obtained.
see underlying bands due to the O–H stretching vi-
[
28]
brations.
3
We can see that there are weak peaks around Table 1. Polymerization results, thermal and optical properties of
–
1
polymers P1–P4.
037 cm , which can be attributed to the aromatic CH
stretching vibrations for all the compounds. The peaks at Polymer Mn
Mw
[ϫ10 ]
PDI
n
Td
[°C]
Tg
[°C]
–
1
3
3
[a]
[b]
1
113 and 1107 cm are due to C–O vibrations at the C–O–
[ϫ10 ]
[29]
M sites of the acetate ligands
and L2. Accordingly, the M–N stretching vibration peaks P2
of metal compounds L1
P1
11.8
9.6
13.4
10.3
13.5
13.7
16.3
13.8
1.53
1.41
1.26
1.39
11 311
9 287
13 376
10 357
138
119
147
141
–
1
P3
P4
of metal compounds appear at 559 and 554 cm for ligands
L1 and L2, respectively.[30]
[a] The data were obtained from TGA of the polymeric metal com-
plexes. [b] Glass transition temperatures, measured from DSC
traces of the polymeric metal complexes.
Optical Properties
The UV/Vis and normalized photoluminescent (PL)
spectra of the metal complexes L1 and L2, and the poly-
meric metal complexes P1–P4 (10–5 m in DMF solution)
are shown in Figures 3 and 4. The corresponding data are
summarized in Table 2.
Table 2. The optical properties of metal complexes L1 and L2 and
polymeric metal complexes P1–P4.
UV/Vis absorbance, λa,max [nm][a]
PL, λp,max [nm]
2
352
319, 358
317, 363
411
396
442
L1
L2
P1
P2
P3
P4
474
486
498
491
424
[
a] λa,max: The maxima and onset absorption from the UV/Vis spec-
tra in DMF solution. λp,max: The PL maxima in DMF solution.
Figure 2 shows the UV/Vis spectra of the metal com-
plexes L1 and L2. The light absorption of metal complexes
L1 and L2 is primarily attributable to metal-to-ligand
charge transfer (MLCT). The absorption maxima of the
complexes are concentrated in the ultraviolet and near-
ultraviolet regions. In Figure 3, we can observe that the ab-
sorption maxima of P1–P4 are at 411, 396, 442, and
424 nm, respectively. These strong absorption bands result
from intramolecular charge transfer (ICT) between the elec-
tron-acceptor–metal-phenanthroline unit and the electron-
donating alkoxybenzene or alkylfluorene moiety. In com-
parison with the π-π* transition absorption of the monomer
2
phenanthroline ring, the maximum absorptions of the
Figure 1. Top: FTIR spectra of L1 and polymeric metal complexes
polymeric metal complexes (P1–P4) are obviously red-
shifted due to the introduction of the fluorene or phenylene
(
P1, P3). Bottom: FTIR spectra of L2 and polymeric metal com-
plexes (P2, P4).
Eur. J. Org. Chem. 2013, 5893–5901
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C. Zhong et al.
FULL PAPER
donor unit and coordination of the ligand with metal. The
absorption spectra of the polymers are wider, but maximum
absorption wavelengths are still short, which may be ex-
tremely unfavorable to improving dye-sensitized solar cells’
energy conversion efficiency. Therefore, the proportion of
the donor groups should be improved in order to modify
the structure of polymeric metal complexes containing this
kind phenanthroline derivative.
Figure 4. PL spectra of the four polymeric metal complexes P1–
P4.
Thermal Stability
Stability is an important consideration in the design of
dye-sensitized solar cells. The dye should have good sta-
bility, which can significantly improve the working life of
the photovoltaic devices. Therefore, the thermal stability
study has important implications for DSSCs. The thermal
properties of these four polymeric metal complexes were
studied by TGA and DSC . The TGA traces are shown in
Figure 5, and the corresponding data are listed in Table 1.
Figure 2. Normalized absorption spectra of metal complexes L1
and L2.
The TGA data show the T values (5% weight-loss tem-
d
perature of the product) of the four polymeric metal com-
plexes (P1–P4) at temperatures of 311, 376, 287 and 357 °C,
respectively, under nitrogen, which means all of them are
[
31]
steady.
From the data of Table 1, we can see that the
Figure 3. Normalized absorption spectra of the ligand 2 and poly-
meric metal complexes P1–P4.
The normalized photoluminescent spectra of P1–P4 in
DMF solution are shown in Figure 4. The excitation wave-
lengths were set according to the absorption peak of UV/
Vis spectrum, and the corresponding optical data are also
listed in Table 2. It can be seen that the PL peaks of P1–P4
are at 474, 486, 498and 491 nm, respectively, which can be
attributed to the π-π* transition of each ligand moiety.
Figure 5. TGA curves of P1–P4 with a heating rate of 20 °C/min
under nitrogen atmosphere.
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D–π–A Dye Sensitizers for Solar Cells
glass transition temperatures (T ) of the four polymeric
g
metal complexes (P1–P4) follow the order P3 (147 °C) Ͼ
P4 (141 °C) Ͼ P1 (138 °C) Ͼ P2 (119 °C). The results imply
that alkoxybenzene units hold higher rigidity than do alkyl-
fluorene units. There is no fixed melting point, which means
the polymers are amorphous. The amorphous nature of the
polymers might serve as a drawback for their use in organic
[
32]
solar cells. On the other hand, their high glass-transition
temperature shows that these kinds materials may provide
the solar cell device with greater longevity.[33]
Electrochemical Properties
The highest occupied molecular orbital (HOMO) and
lowest unoccupied molecular orbital (LUMO) energy levels
of the dyes are important parameters in the design of opto-
electronic devices, and they can be estimated by cyclic vol-
tammetry (CV). When a saturated calomel electrode (SCE)
is used as the reference electrode, the HOMO and LUMO
energy levels can be calculated from the onset oxidation po-
Figure 6. CV curves of P1–P4 measured in DMF solution contain-
ing [Bu N]BF as supporting electrolyte at a scan rate of
00 mV/s.
4
6
1
tentials (E ) and the onset reduction potentials (Ered) of
ox
Table 3. Cyclic voltammetry results of polymeric metal complexes
P1–P4.
the polymers according to Equations (1), (2) and (3),
[
34,35]
respectively.
Polymer
E
red
E
[V]
ox
HOMO
[eV]
LUMO
[eV]
E
g
[eV]
[V]
HOMO = –e(Eox + 4.40) (eV)
LUMO = –e(Ered + 4.40) (eV)
(1)
(2)
(3)
P1
P2
P3
P4
–1.02
–1.04
–0.98
–1.05
1.26
1.32
1.15
1.18
–5.66
–5.72
–5.55
–5.58
–3.28
–3.36
–3.42
–3.35
2.28
2.36
2.13
2.23
g
E = HOMO – LUMO
Photovoltaic Properties
The incident photo-to-current conversion efficiency
The cyclic voltammograms of the dyes were measured in
DMF solution containing [Bu N]BF as a supporting elec-
4
6
trolyte, and a SCE as the reference electrode at a scan rate (IPCE) plots for the DSSCs based on L1, L2, and P1–P4
of 100 mV/s. Figure 6 shows cyclic voltammetry curves of are shown in Figures 7 and 8. The two metal complexes
P1–P4, and the corresponding CV data are summarized in responded in the broad range of 350–400 nm, and the maxi-
Table 3. The Eox values were observed to be 1.26, 1.32, 1.15, mum IPCE values were around 5%, which is very low. The
and 1.18 V for P1, P2, P3 and P4, respectively. On the other four polymer dyes all responded in the broad range of 400–
hand, their onset potentials for reduction (Ered) were found 650 nm and showed maximum IPCE values around 420 nm,
to be –1.02, –1.04, –0.98, –1.05 V, respectively. Accordingly, which was in accord with the UV/Vis spectra. The IPCE
the HOMO energy levels of P1, P2, P3 and P4, are values of the dyes P1–P4 reached 35.1% to 38.3%. Among
–5.66 eV, –5.72 eV, –5.55 eV and –5.58 eV, respectively, the four target dyes, P3 had the maximum IPCE, possibly
which are much lower than the standard potential of the because it had the largest adsorption onto the TiO film.
2
–
[36]
I /I redox couple (–4.83 eV vs. vacuum). This difference This indicates that dye P3 would show a relatively high
3
indicates that the dyes will be more effectively regenerated, photocurrent in DSSCs.
and suppress the recapture of the injected electrons by the
The photovoltaic characteristics of DSSCs based on the
[
37]
dye cation radical.
The LUMO energy levels of P1–P4 two metal complexes and four polymer dyes are shown in
are sufficiently higher than the conduction band of Figures 9 and 10. The corresponding open-circuit voltage
[
38]
(
–4.0 eV)
to imply the possibility of an effective charge (V ), short-circuit current density (J ), fill factor (FF) and
oc sc
[39]
transfer from the polymers to TiO2.
The E values of power conversion efficiency (PCE) values are listed in
g
P1–P4 followed the order of P2 (2.36 eV) Ͼ P1 (2.28 eV) Table 4. As can be observed, DSSCs based on metal com-
Ͼ P4 (2.23 eV) Ͼ P3 (2.13 eV). We found that the E values plexes L1 and L2 generated very low power conversion effi-
g
of polymeric metal complexes containing alkoxybenzene ciencies (0.15% and 0.11%), which indicates that due to the
donor units were lower than those of the corresponding limited solubility of the complexes, the monomeric com-
polymeric metal complexes containing alkylfluorene donor plexes can not obtain good photoelectric conversion effi-
units, which indicated that the stronger electron-donating ciencies. Metal complexes L1 and L2 bonded with the do-
ability of alkoxybenzene units decreased the energy gap.
nor moieties by the Heck coupling reaction to form four
Eur. J. Org. Chem. 2013, 5893–5901
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C. Zhong et al.
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Figure 9. J-V curves of DSSCs based on L1, and L2 in DMF solu-
tion.
Figure 7. Incident photon-to-current conversion efficiency of metal
complexes L1 and L2.
Figure 10. J-V curves of DSSCs based on P1–P4 in DMF solution.
Figure 8. Incident photon-to-current conversion efficiency of the
four polymeric metal complexes P1–P4.
target polymer dyes. The formation of polymers extended Table 4. The data of photovoltaic performances of DSSCs based
on L1, L2, P1–P4 under 1.5 G solar illumination.
the conjugated chains, tuned the energy gap between the
donor part and acceptor parts, thus reducing the energy Polymer Solvent
gap, and effectively improving the photovoltage and photo-
Jsc
[mA cm ]
Voc
[V]
FF
[%]
IPCE
η
[%]
–
2
current of the target products. As expected, the
polymer metal complex dyes showed a better photo- P2
voltaic performances than those of metal complexes L1 and
L2.
Further study showed that the Voc values of P1–P4 dyes
are 0.65 V, 0.69 V, 0.60 V, 0.64 V, respectively, and the corre-
P1
DMF
DMF
DMF
DMF
DMF
DMF
4.26
4.37
4.91
4.59
0.63
0.54
0.65
0.60
0.69
0.64
0.52
0.48
63.6 37.1% 1.76
65.0 35.1% 1.71
62.5 38.3% 2.12
61.4 37.5% 1.81
P3
P4
L1
L2
46.3
42.5
5.8%
5.2%
0.15
0.11
sponding FF values are 0.636, 0.625, 0.650 and 0.614. The
2
Jsc values follow the order P3 (4.91 mA/cm ) Ͼ P4 of photocurrent and open circuit voltages than was the oc-
2
2
2
(
4.59 mA/cm ) Ͼ P2 (4.37 mA/cm ) Ͼ P1 (4.26 mA/cm ). tylfluorene unit. The power conversion efficiencies of de-
On the basis of the above data, we can see that the Jsc val- vices based on P3 and P4 reached 1.91%, 1.67%, respec-
ues of the target polymers containing alkoxybenzene (P3, tively, which were higher than those of devices based on P1
1
0
P4) were higher than the corresponding target polymers (1.76%) and P2 (1.71%). The results indicate that the d
II
containing alkylfluorene (P1, P2), which implies that the Zn complexes possessed higher kinetic stability than did
alkoxybenzene unit was more conducive to the generation d Co complexes. Though the power conversion efficien-
7
II
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D–π–A Dye Sensitizers for Solar Cells
cies of the dyes were still low and were not comparable with Titania paste was prepared following a procedure: fluorine-doped
SnO
TiCl
2
conducting glass (FTO) was cleaned and immersed in 40 mm
solution at 70 °C for 30 min, then washed with water and
state-of-the-art ruthenium-based dyes, further work on op-
timizing the device performance is under investigation.
4
2
ethanol. The TiO colloid comprised of 20–30 nm particles was
coated onto the prepared FTO glass by the sliding glass rod
method, and was then sintered at 450 °C for 30 min. This process
Conclusions
was done three times to obtain a TiO
2
film of 15 μm thickness.
After cooling to 100 °C, the TiO film was immersed in a dye solu-
2
In conclusion, four D–π–A polymeric metal complexes tion (0.5 mm in DMF) and then kept at room temperature in the
with phenanthroline–metal complexes as the electron ac- dark for 24 h. After drying, an electrolyte solution containing LiI
(
0
0.5 m), I
.3 m), and 4-tert-butylpyridine (0.5 m) in 3-methoxypropionitrile
was used as the electrolyte. Pt foil was used as the counterelectrode
and was clipped onto the top of the TiO . The dye-coated semicon-
2
(0.02 m), 1-methyl-3-hexylimidazolium iodide (HMII,
ceptor moieties, C=C π-bridges, and alkoxybenzene or alk-
ylfluorene units as electron donors were designed, synthe-
sized and characterized in DSSCs to obtain efficiency val-
ues of up to 2.12%. These results indicate that these poly-
meric metal complexes have unique advantages as new solar
cell materials, and suggest that further structure optimiza-
tion is essential before application in DSSCs.
2
ductor film was illuminated through a conducting glass support
without a mask. Photoelectron chemical performance of the solar
cell was measured using a Keithley 2602 Source meter controlled
by a computer. The cell parameters were obtained under an inci-
For this new type of dye sensitizer there are still many
–2
dent light with intensity 100 mWcm , which was generated by a
challenges to obtaining outstanding energy conversion effi- 500-W Xe lamp passing through an AM 1.5 G filter with an effec-
2
ciencies, for example, the narrow absorption spectra of the tive area of 0.16 cm .
polymers, and the low Jsc values based on the materials’
electron injection efficiency. To improve the conversion effi-
Chemical Reagent Co. Ltd. (Shanghai China) and used without
ciencies, we will further design and synthesize new poly- further purification. All solvents used were analytical grade. 3,8-
Materials: All starting materials were obtained from Shanghai
[
40,41]
meric metal-complex dyes which can broaden the light ab- Dibromo-1,10-phenanthroline,
3,3Ј-dicarboxy-2,2Ј-bipyr-
(3), and 1,4-divinyl-2-
sorption spectrum in the region of visible light, improve idine,[ 2,7-divinyl-9,9-dioctylfluorene
42]
[43]
methoxyl-5-octyloxybenzene[ (4) were synthesized according to
44]
electron transfer efficiency of organic semiconductors and
enhance short-circuit current density. Our work towards
these goals is under way.
the literature methods. Triethylamine was purified by distillation
over KOH. DMF and THF were dried by distillation over CaH .
2
All other reagents and solvents were commercially purchased and
were used as received.
Synthesis of Metal Complex L1: A methanol solution (10 mL) of
Zn(CH COO) ·2H O (0.22 g, 1 mmol) was slowly dropped into a
3 2 2
mixture of 3,8-dibromo-1,10-phenanthroline (0.338 g, 1 mmol),
and 3,3Ј-dicarboxy-2,2Ј-bipyridine(0.244 g, 1 mmol) in THF
Experimental Section
1
Instruments and Measurements: All H NMR spectra were obtained
in CDCl and recorded with a Bruker Avance 400 spectrometer,
3
(
(
20 mL). The reaction system was neutralized carefully with NaOH
1 m) to slightly acidic pH and refluxed for 6 h. The reaction system
using tetramethylsilane (δ = 0.00 ppm) as the internal reference.
Fourier transform infrared (FTIR) spectra were recorded using
KBr pellets (250 mg of dried KBr and 2 mg of lyophilized sample)
with a PerkinElmer Spectrum One FTIR spectrometer over the
was then cooled to room temp., filtered, washed twice with meth-
anol and with water repeatedly, and then dried under vacuum at
room temperature overnight. A white solid product was collected
–1
range 400–4000 cm . UV/Vis spectra were obtained with a
Lambda 25H spectrometer. Samples were dissolved in DMF and
(
0.613 g, yield 80%). FT-IR (KBr): ν˜ = 3402 (OH), 3037, 3009 (Ar-
–
1
–5
–4
–1
CH), 1650 (C=O), 1582.4 (C=N), 1099 (C–O–M), 559 (M–N) cm .
Zn (765.68): calcd. C 43.37, H 2.58, N 7.29; found
diluted to a concentration of 10 –10 molL . Photoluminescent
spectra (PL) were taken with a Perkin–Elmer LS55 luminescence
spectrometer with a xenon lamp as the light source. Gel permeation
chromatography (GPC) analyses were performed with a system
equipped with a set of Waters HT3, HT4 and HT5 Styragel col-
umns, with THF as the eluent, polystyrene as the standard, and
detection using a WATERS 2414 refractive index detector. Ther-
mogravimetric analysis (TGA) was performed with a Shimadzu
TGA-7 instrument under nitrogen atmosphere at a heating rate of
28 2 4 8
C H20Br N O
C 43.92, H 2.63, N 7.32.
Synthesis of Metal Complex L2: The same synthesis method
[Co(CH COO) ·4H O (0.249 g, 1 mmol)] as described for metal
3
2
2
complex L1 yielded a pink–yellow solid (0.629 g 83%). FT-IR
(KBr): ν˜ = 3413 (=C–H), 3017 (aromatic C–H), 1631 (C=O), 1564
–
1
(C=N), 1107 (C=N–M). 554 (M–N) cm . C H Br CoN O
8
2
8
20
2
4
(759.23): calcd. C 44.12, H 2.60, N 7.34; found C 44.30, H 2.66, N
2
(
0 Kmin–1 from 25 to 600 °C. Differential scanning calorimetry 7.38.
DSC) was performed using a PerkinElmer DSC-7 thermal ana-
Synthesis of Polymeric Metal Complex P1: The polymeric metal
complex P1 was synthesized according to the literature.[ A mix-
ture of metal complex L1 (0.3687 g, 0.315 mmol), 2,7-divinyl-9,9-
–
1
lyzer under nitrogen atmosphere at a heating rate of 20 °C min
from 25 to 600 °C. Cyclic voltammetry (CV) was conducted with
a CHI630C Electrochemical Workstation using a three-electrode
31]
dioctylfluorene (0.139 g, 0.315 mmol), Pd(OAc)
0
0
2
(0.0029 g,
.013 mmol), triethylamine (3 mL), tri-o-tolylphosphane (0.022 g,
.072 mmol) and DMF (8 mL) heated at 90 °C in the presence of
system in a [Bu
4 6
N]BF (0.1 m) DMF solution at a scan rate of
100 mV/s. The working electrode was a glassy carbon electrode, the
auxiliary electrode was a platinum wire electrode, and a saturated
calomel electrode (SCE) was used as reference electrode.
nitrogen for 36 h. After the reaction mixture was cooled to room
temperature and filtered, the filtrate was poured into methanol.
The resulting precipitate was filtered and washed with cold meth-
anol. The crude product was purified by dissolving it in THF and
precipitating into methanol to afford a brown solid (0.19 g, 45%).
Fabrication of DSSCs: The DSSC devices with sandwich structure
in this paper are based on TiO semiconductors, and their specific
2
production processes are as follows:
Eur. J. Org. Chem. 2013, 5893–5901
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5899

C. Zhong et al.
FULL PAPER
FT-IR (KBr): ν˜ = 3041 (=C–H), 2927, 2851, 1639 (C=O), 1572
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63 70 4 8
C H N O Zn
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¯
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n
= 10.1 kg/mol, PDI = 1.53.
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[
3
043 (=C–H), 2927, 2852, 1637 (C=N), 1560 (C=N), 1093 (C=N–
–1
M), 536 (N–M) cm . C63
.50, N 5.12; found C 70.70, H 6.59, N 5.24. M
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[
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