Preparation and photovoltaic characterization of free-base and metallo carboxyphenylethynyl porphyrins for dye-sensitized solar cells

Article abstract of DOI:10.1002/jccs.201000162

Free-base, manganese, iron, cobalt, nickel, copper and zinc 5-(4-carboxy-phenylethynyl)-10,20-biphenylporphines are synthesized to study the impact of central metal ions to the photovoltaic performance of the solar cells.

Full text of DOI:10.1002/jccs.201000162

1136
Journal of the Chinese Chemical Society, 2010, 57, 1136-1140
Invited Paper
Preparation and Photovoltaic Characterization of Free-Base and Metallo
Carboxyphenylethynyl Porphyrins for Dye-Sensitized Solar Cells
Ching-Yao Lina,* (
Shun-Ju Hsub (
), Chen-Fu Loa (
), Hsueh-Pei Lub (
), Min-Hsu Hsieha (
) and Eric Wei-Guang Diaub,* (
),
)
aDepartment of Applied Chemistry, National Chi Nan University, Puli, Nantou Hsien, Taiwan 54561, R.O.C.
bDepartment of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University,
Hsinchu, Taiwan 30010, R.O.C.
Free-base, manganese, iron, cobalt, nickel, copper and zinc 5-(4-carboxy-phenylethynyl)-10,20-
biphenylporphines are synthesized to study the impact of central metal ions to the photovoltaic perfor-
mance of the solar cells.
Keywords: Porphyrin; Dye-sensitized solar cell; Central metal effect.
INTRODUCTION
porphines (denoted as H2PE1, MnPE1, FePE1, CoPE1,
NiPE1, CuPE1, and ZnPE1, respectively). Fig. 1 depicts the
molecular structures of these new porphyrins. It is known
that the central metals greatly affect the redox and electron
transfer properties of porphyrins.10,11 To the best of our
knowledge, there has been only one report in the literature
that addressed the central metal effects of porphyrin-sensi-
tized solar cells:2b Officer and co-workers found that Zn
porphyrin performs better than the Cu and free-base ana-
logues. Hence, it is curious to know the impact of other cen-
tral metals to the photovoltaic performances of the por-
phyrin-sensitized solar cells as reported herein.
Dye-sensitized solar cells (DSSC) have drawn much
attention in recent decades.1,2 The strategy is to adsorb suit-
able photosensitizers onto high-surface-area nanocry-
stalline TiO2 films for light harvesting. Ru(II) complexes,
such as N3, N719 and C101 dyes, are the most efficient
photosensitizers to-date with overall efficiencies (h)
greater than 11%.3,4 On the other hand, porphyrins have
also been considered for DSSC applications because of
their vital roles in photosynthetic reaction.2b,5-9 Many fac-
tors affect the usefulness of a porphyrin for DSSC and it has
been demonstrated that a fully conjugated system with an
edgewise adsorption mode improves the charge transfer
processes and the surface area coverage, resulting in an en-
hanced overall efficiency.2b By this strategy, the most effi-
cient porphyrin-sensitized solar cell has been reported to
have achieved an overall efficiency of 7.1%.5a
EXPERIMENTAL
Materials
Air-sensitive solids were handled in an MBraun
We have previously reported studies of a series of
zinc porphyrins bearing linear, length-controlled phenyl-
ethynyl anchoring groups (denoted as PE1 to PE4).9a,b In
those reports, we have established that (1) these fully con-
jugated, meso-substituted porphyrins adsorb onto TiO2 sur-
faces in an edgewise fashion and (2) PE1 outperforms other
dyes in the series. In this work, we aim to investigate the
central metal effect of PE1 porphyrin by studying the prop-
erties of free-base, manganese, iron, cobalt, nickel, copper
and zinc 5-(4-carboxy-phenylethynyl)-10,20-biphenyl-
Fig. 1. Molecular structures of porphyrin photo-sen-
sitizers studied in this work.
Special Issue for the 2009 International Symposium of Dye-Sensitized Solar Cells
*Corresponding author. Tel: +886-49-2910960 ext. 4152; Fax: +886-49-2917956; E-mail: cyl@ncnu.edu.tw (CYL);
Tel: +886-3-5131524; Fax: +886-3-5723764; E-mail: diau@mail.nctu.edu.tw (EWGD)

Free-Base and Metallo Carboxyphenylethynyl Porphyrins
J. Chin. Chem. Soc., Vol. 57, No. 5B, 2010 1137
Uni-lab glove box. A vacuum line and standard Schlenk
techniques were employed to process air-sensitive solu-
tions. Solvents used in the synthesis (ACS Grade) were ob-
tained from Mallinckrodt Baker, Inc. (CH2Cl2, CHCl3 and
ethyl acetate; Kentucky, U.S.A.), Haltermann (hexanes;
Hamburg, Germany), and Merck (THF; Darmstadt, Ger-
many). These solvents were used as received unless other-
wise stated. Other chemicals were ordered from Acros
Organics (New Jersey, U.S.A.). Tetrahydrofuran (THF),
DMF and tetrabutylammonium perchlorate (TBAP) were
were purified according to the literature methods.12 For cer-
tain cyclic voltammetry experiments, the THF were puri-
fied and dried by an Asiawong SD-500 Solvent Purifica-
tion System (Taipei, Taiwan). Around 10 ppm of H2O were
found in the THF purified by the system. All NMR solvents
were used as received. Pd(PPh3)4 catalyst was purchased
from Strem Chemical Inc (MA, U.S.A.). Chromatographic
purification was performed with Silica Gel 60 (230-400
mesh, Merck).
spectroscopy. After precipitation from 300 mL of 0.1 M
HCl(aq), chromatographic separation (silica gel, 10%
MeOH in CH2Cl2) and crystallization (THF/hexanes), 30
mg of Cl-Mn(III)PE1 was collected (53% yield).
FePE1:14 40 mg of H2 PE1 and 5 eq. of FeCl2 in 20
mL of DMF under N2 underwent reflux for 1 hour. After
precipitation from 60 mL of 0.5 M KCl(aq), chromato-
graphic separation (silica gel, 7% MeOH in CH2Cl2) and
evaporation under reduced pressure. The solids were
dessolved in 100 mL of THF, followed by drop-wisely add-
ing the THF solution into 300 mL of 0.1 N of HCl(aq) to pre-
vent the formation of m-oxo-dimer. 27 mg (60%) of
Cl-Fe(III)PE1 was obtained after crystallization from
THF/hexanes.
CoPE1:14 50 mg of H2PE1 and 16 eq. of Co(OAc)2 in
30 mL of DMF under N2 were reflux for 40 minutes. After
precipitation from 100 mL of 0.1 M KCl(aq), the precipitates
were put through chromatographic separation (silica gel,
hexanes/THF = 1/4). 24 mg of Co(II)PE1 (44%) was col-
lected after recrystallization from THF/hexanes.
Instrumentation
Absorption spectra were recorded on an Agilent 8453
UV-Visible spectrophotometry system. NMR data were ob-
tained on a Varian Unity Inova 300WB NMR Spectrometer.
Elemental analyses were carried out on an Elementar Vario
EL III (NSC Instrumentation Center at National Chung
Hsing University). Mass Spectroscopy measurements were
performed on either a Liquid Chromatography Tandem
Mass Spectrometer (National Science Council Instrumen-
tation Center at National Chiao Tung University) or a JEOL
JMS MStation (Academia Sinica).
Ni and CuPE1:15 50 mg of H2PE1 and 10-20 eq. of
NiCl2 or Cu(OAC)2 were reflux under N2 in 30 mL of DMF
for 30-40 minutes. After precipitation from 0.1 M
NH4Cl(aq)
, chromatographic separation (silica gel,
CH2Cl2/THF = 1/3 for NiPE1 and hexanes/THF = 1/3 for
CuPE1), and crystallization from THF/hexanes. 71% of
Ni(II)PE1 and 78% of Cu(II)PE1 were afforded.
Characterization data
Charaterization data of ZnPE1 have been published
previously.9a In addition, the fundamental properties of
MnPE1, FePE1 and CoPE1 are consistent with the forms of
Cl-Mn(III)PE1, Cl-Fe(III)PE1 and Co(II)PE1.
Synthesis procedure
ZnPE1: The synthsis of ZnPE1 has been published
previously.9a
1
H2PE1: H-NMR(DMSO-d6 at 2.50 ppm) 10.53(s,
H2PE1: 70 mg of Zn PE1 was demetallated in 100 mL
of CHCl3 with 10 equivalent of HCl at room temperature
for 1 hour. The reaction were monitored by UV-Visible
spectroscopy. Upon completion, the reaction was quenched
by 0.5 M K2CO3(aq) washes, followed by 0.5 M NH4Cl(aq)
washes. The organic layer was collected and dried over
Na2SO4. 92% of H2PE1 was obtained after chromato-
graphic separation (silica gel, 10% MeOH in CH2Cl2) and
crystallization (THF/hexanes).
1H), 9.88(d, J = 4 Hz, 2H), 9.55(d, J 4 Hz, 2H), 8.95(d, J 4
Hz, 2H), 8.89(d, J = 4 Hz, 2H), 8.24(m, 8H), 7.88(m, 6H),
-2.77(s, 2H), Elemental Analysis, C41H26N4O2×1.5 H2O,
calc’d C: 77.71%, H: 4.61%, N: 8.84%; found C: 77.41%, H:
4.88%, N: 8.83%. Mass, MH+: calc’d 607.2, found 607.2.
MnPE1: Elemental Analysis: C41H24ClMnN4O2×1.5
H2O calc’d: C: 68.20%, H: 3.77%, N: 7.76%; found: C:
68.45%, H: 3.98%, N: 7.82%. Mass, M: calc’d 659.1,
found 659.2.
MnPE1:13 50 mg of H2 PE1 was first reacted with 5
eq. of LiN(SiMe3)2 in 30 mL THF under N2. After reflux for
3 hours, a de-gassed THF solution of MnCl2 (5 eq.) was in-
troduced to the reaction mixture. The mixture was allowed
to reflux for another 1 hour and monitored by UV-Visible
FePE1: Elemental Analysis: C41H24ClFeN4O2×H2O
calc’d: C: 68.97%, H: 3.67%, N: 7.85%; found: C: 68.49%,
H: 3.68%, N: 7.32%. Mass, M: calc’d 660.1, found 660.1.
CoPE1: Elemental Analysis: C41H24CoN4O2×1.5 H2O
calc’d: C: 71.30%, H: 3.94%, N: 8.11%; found: C: 71.26%,

1138 J. Chin. Chem. Soc., Vol. 57, No. 5B, 2010
Lin et al.
Table 1. Absorption maxima (in nm) and absorption coefficients (in cm-1M-1) of PE1s and the corresponding TPPs
Porphyrinsa
Soret (log e)
Q (log e)
Porphyrinsb
Soret (log e)
H2PE1
MnPE1
FePE1
CoPE1
NiPE1
CuPE1
ZnPE1
430(5.54)
381(4.69), 426(4.65), 481(4.95)
363(4.56), 434(4.97)
430(5.40)
526(4.12), 566(4.37), 604(3.77), 661(3.96)
544(3.75), 597(3.97), 641(4.22)
519(4.00), 555(3.86), 701(3.62)
541(4.15 ), 577(4.09)
H2TPP
MnTPP
FeTPP
CoTPP
NiTPP
CuTPP
ZnTPP
418(5.55)
478(4.91)
416(5.01)
411(5.23)
415(5.27)
415(5.48)
419(5.62)
427(5.36)
538(4.23 ), 573(4.14)
431(5.50)
552(4.24 ), 594(4.20)
439(5.65)
568(4.23), 616(4.44)
a This work, measured in THF. b Taken from ref. 16, in CHCl3.
H: 4.02%, N: 8.07%. Mass, M: calc’d 663.1, found 663.2.
NiPE1: 1H-NMR (DMSO-d6 at 2.50 ppm) 10.16(s,
1H), 9.80(d, J = 5Hz, 2H), 9.45(d, J = 5Hz, 2H), 8.91(d, J =
5Hz, 2H), 8.85(d, J = 4Hz, 2H), 8.16(two overlapped dou-
blets, J = 9Hz, 4H), 8.04(m, 4H), 7.82(m, 6H), Elemental
Analysis: C41H24NiN4O2×H2O calc’d: C: 72.27%, H:
3.85%, N: 8.22%; found: C: 72.40%, H: 3.82%, N: 7.99%.
Mass, M: calc’d 663.1, found 663.2.
Cu, Zn, (b) Mn and FePE1 in THF. Table 1 lists the absorp-
tion maxima and absorption coefficients of PE1 porphy-
rins, along with the reported B band data of free-base and
metallo tetraphenylporphines (TPPs) for comparison.16
First of all, typical porphyrin absorption spectra are ob-
served for PE1s: strong Soret bands in the higher energy re-
gion and weaker Q bands in the lower energy region. Sec-
ondly, the trend of PE1s’ absorption bands are consistent
with that of the TPP analogues.16 For example, the B band
wavelengths red-shift from H2, Co, Ni, Cu to ZnPE1 and
the absorption coefficients decrease from Zn, H2, Cu, Co to
NiPE1. Similar patterns are observed for the TPP counter-
parts with only slight deviation. Thirdly, Q bands of H2PE1
are divided into four groups due to its lower symmetry.17
Forthly, MnPE1’s split Soret bands are the characteristics
of a Mn(III) porphyrin and are not present in Mn(II) or
Mn(IV) porphyrins.18 Finally, the absorption spectrum of
FePE1 is consistent with that of a monomeric Fe(III)
porphyrin,19 not that of a m-oxo-dimer.20
CuPE1: Elemental Analysis: C41H24CuN4O2×1/2 THF
calc’d: C: 73.33%, H: 4.01%, N: 7.96%; found: C: 73.06%,
H: 3.84%, N: 8.32%. Mass, M: calc’d 667.1 (63Cu) and
669.1 (65Cu), found 667.0 and 669.0.
Device Fabrication and Characterization
Cell Fabrication and photovoltaic performance mea-
surements are the same as those published in our previous
report.9a
RESULTS AND DISCUSSION
Absorption Spectra
Fig. 2 depicts UV-Visible spectra of (a) H2, Co, Ni,
Photovoltaic Measurements
It is known that the central metals greatly affect the
redox and electron transfer properties of porphyrins.10,11
Therefore, the performances of the PE1-sensitized solar
cells may also be affected. Table 2 collects the averaged
photovoltaic parameters of PE1-sensitized solar cells. The
current-voltage (I-V) curves of N3 and PE1 porphyrins are
compared in Fig. 3. For each sensitizer, only the I-V curve
of the best power conversion efficiency is shown in the
figure.
The average overall efficiencies of PE1 porphyrins
vary greatly, and the order is: ZnPE1 (3.6 ± 0.1%) > H2PE1
(2.6 ± 0.0%) > CuPE1 (0.4 ± 0.1%) > NiPE1 (0.1 ± 0.0%) >
CoPE1 (0.0 ± 0.0%), FePE1 (0.0%), and MnPE1 (0.0%). It
is clear that ZnPE1 outperforms other metallo-PE1 porphy-
rins with an open-shell central metal ion. Therefore, it is
Fig. 2. Absorption spectra of (a) H2, Co, Ni, Cu, Zn,
(b) Mn and FePE1 in THF.

Free-Base and Metallo Carboxyphenylethynyl Porphyrins
Table 2. Photovoltaic parameters of PE1-sensitized solar cellsa
J. Chin. Chem. Soc., Vol. 57, No. 5B, 2010 1139
by Officer and co-workers on Zn-, Cu- and H2-1a porphy-
rins.2b In that report, the order of the DSSC performance is
Zn-1a > Cu-1a > H2-1a porphyrins. In our case, however,
H2PE1 performs better than CuPE1, which is consistent
with the reduction model for copper ion to be easily re-
duced while it is not feasible for the free-base porphyrin.
Another reason to account for the discrepancy between the
two porphyrin systems is attributed to the differences in
their structures: porphyrins 1a are pyrrole b-substituted
systems whereas PE1s are meso-substituted porphyrins.
Dye
JSC /mA cm-2
VOC /V
FF
h (%)
N3
12.68 ± 0.27 0.73 ± 0.01 0.64 ± 0.02 5.85 ± 0.16
8.60 ± 0.13 0.65 ± 0.02 0.64 ± 0.02 3.58 ± 0.09
1.27 ± 0.09 0.58 ± 0.01 0.58 ± 0.05 0.43 ± 0.07
0.25 ± 0.00 0.44 ± 0.02 0.43 ± 0.05 0.05 ± 0.01
0.02 ± 0.00 0.08 ± 0.02 0.26 ± 0.03 0.00 ± 0.00
ZnPE1
CuPE1
NiPE1
CoPE1
FePE1
MnPE1
H2PE1
0.01
0.05
0.01
0.01
0.11
0.35
0.00
0.00
5.93 ± 0.01 0.62 ± 0.00 0.71 ± 0.01 2.59 ± 0.04
a under AM1.5 illumination (power 100 mW cm-2) with an active
area of 0.16 cm2. Three independent measurements were performed
for all dyes using the TiO2 films fabricated with an identical pro-
cedure in order to demonstrate the reproducibility of the data.
CONCLUSION
Free-base and several metallo-PE1 porphyrins are
successfully prepared to investigate their spectral and pho-
tovoltaic properties. For the photovoltaic performance,
ZnPE1 outperforms H2PE1, CuPE1, NiPE1, CoPE1, FePE1,
and MnPE1 with an overall efficiency of 3.6%. The poor
performances of CuPE1, NiPE1, CoPE1, FePE1, and
MnPE1 might be due to the d-d transitions of the open-shell
central metal ions, which facilitate reduction of the central
metal ions to impede the electron injection into TiO2.
logical to suggest that the d-d transitions of these open-
shell central metals have a negative impact to the perfor-
mance of the solar cells. The extremely low JSC values in
the devices made of the open-shell species suggest that the
photo-induced reduction of the central metal in those
porphyrin sensitizers might be a more efficient process than
electron injection into TiO2. This phenomenon is also con-
sistent with the trend of the observed VOC values which de-
creased systematically from the central metals of Zn to Cu,
Ni, Co, Fe and Mn. As such, for the open-shell metallo-PE1
sensitizers, we expect that the more efficient central metal
reduction results in the less efficient electron injection into
the conduction band of TiO2. Finally, the trend observed in
this work is relatively consistent with the finding reported
ACKNOWLEDGEMENT
This work was supported by the National Science
Council (CYL: NSC 97-2113-M-260-007-MY2 and NSC
97-2627-M-260-001; EWGD: NSC 98-2113-M-009-014
and NSC 97-3114-M-009-003).
Received November 29, 2009.
REFERENCES
1. (a) O’Regan, B.; Grätzel, M. Nature 1991, 353, 737-740. (b)
Nazeeruddin, M. K.; Kay, A.; Rodicio, I.; Humphry-Baker,
R.; Muller, E.; Liska, P.; Vlachopoulos, N.; Grätzel, M. J.
Am. Chem. Soc. 1993, 115, 6382-6390. (c) Grätzel, M. Inorg.
Chem. 2005, 44, 6841-6851.
2. For recent reviews, see: (a) Grätzel, M. Nature 2001, 414,
338-344. (b) Campbell, W. M.; Burrell, A. K.; Officer, D. L.;
Jolley, K. W. Coord. Chem. Rev. 2004, 248, 1363-1379. (c)
Imahori, H.; Umeyama, T.; Ito, S. Acc. Chem. Res., 2009, 42,
1809-1818.
3. (a) Wang, Q.; Ito, S.; Grätzel, M.; Fabregat-Santiago, F.;
Mora-Seró, I.; Bisquert, J.; Bessho, T.; Imai, H. J. Phys.
Chem. B 2006, 110, 25210-25221. (b) Nazeeruddin, M. K.;
de Angelis, F.; Fantacci, S.; Selloni, A.; Viscardi, G.; Liska,
P. Ito, S.; Takeru, B.; Grätzel, M. J. Am. Chem. Soc. 2005,
127, 16835-16847.
Fig. 3. Current-voltage characteristics of porphyrin-
sensitized solar cells under AM 1.5 one-sun irra-
diation (100 mW cm-2) and an active area of 0.16
cm2.
4. Gao, F.; Wang, Y.; Shi, D.; Zhang, J.; Wang, M.; Jing, X.;
Humphry-Baker, R.; Wang, P.; Zakeeruddin, S. M.; Grätzel,

1140 J. Chin. Chem. Soc., Vol. 57, No. 5B, 2010
Lin et al.
M. J. Am. Chem. Soc. 2008, 130, 10720-10728.
V.; Royal, G. In The Porphyrin Handbook, Kadish, K. M.;
Smith, K. M.; Guilard, G., Eds.; Academic Press: New York,
2000; Vol. 8, pp 1-97. (b) For the database of porphyrins re-
dox potentials in nonaqueous media, see: Kadish, K. M.;
Royal, G.; Caemelbecke, E. V.; Gueletti, L. In The Porphyrin
Handbook, Kadish, K. M.; Smith, K. M.; Guilard, G., Eds.;
Academic Press: New York, 2000; Vol. 9.
5. (a) Campbell, W. M.; Jolley, K. W.; Wagner, P.; Wagner, K.;
Walsh, P. J.; Gordon, K. C.; Schmidt-Mende, L.;
Nazeeruddin, M. K.; Wang, Q.; Grätzel, M.; Officer, D. L. J.
Phys. Chem. C 2007, 111, 11760-11762. (b) Wang, Q.;
Campbell, W. M.; Bonfantani, E. E.; Jolley, K. W.; Officer,
D. L.; Walsh, P. J.; Gordon, K.; Humphry-Baker, R.;
Nazeeruddin, M. K.; Grätzel, M. J. Phys. Chem. B 2005, 109,
15397-15409.
11. Kadish, K. M.; Autret, M.; Ou, Z.; Tagliatesta, P.; Boschi, T.;
Fares, V. Inorg. Chem. 1997, 36, 204-207.
6. (a) Lee, C.-W.; Lu, H.-P.; Lan, C.-M.; Huang, Y.-L.; Liang,
Y.-R.; Yen, W.-N.; Liu, Y.-C.; Lin, Y.-S.; Diau, E. W.-G.;
Yeh, C.-Y. Chem. Eur. J. 2009, 15, 1403-1412. (b) Lu, H.-P.;
Mai, C.-L.; Tsia, C.-Y.; Hsu, S.-J.; Hsieh, C.-P.; Chiu, C.-L.;
Yeh, C.-Y.; Diau, E. W.-G. Phys. Chem. Chem. Phys. 2009,
11, 10270-10274. (c) Lu, H.-P.; Tsai, C.-Y.; Yen, W.-N.;
Hsieh, C.-P.; Lee, C.-W.; Yeh, C.-Y.; Diau, E. W.-G. J. Phys.
Chem. C 2009, 113, 20990-20997.
12. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
13. Arnold, J.; Dawson, D. Y.; Hoffman, C. C. J. Am. Chem. Soc.
1993, 115, 2707-2713.
14. Wang, L; She, Y.; Zhong, R.; Ji, H.; Zhang, Y.; Song, X. Org.
Process Res. Dev. 2006, 10, 757-761.
15. Clement, T. E.; Nurco, D. J.; Smith, K. M. Inorg. Chem.
1998, 37, 1150-1160.
7. (a) Hayashi, S.; Tanaka, M.; Hayashi, H.; Eu, S.; Umeyama,
T.; Matano, Y.; Araki, Y.; Imahori, H. J. Phys. Chem. C 2008,
112, 15576-15585. (b) Tanaka, M.; Hayashi, S.; Eu, S.;
Umeyama, T.; Matano, Y.; Imahori, H. Chem. Commun.
2007, 2069-2071. (c) Eu, S.; Hayashi, S.; Umeyama, T.;
Oguro, A.; Kawasaki, M.; Kadota, N.; Matano, Y.; Imahori,
H. J. Phys. Chem. C 2007, 111, 3528-3537.
16. Rao, S. V.; Srinivas, N. K. M. N.; Rao, D. N.; Giribabu, L.;
Maiya, B. G.; Philip, R.; Kumar, G. R. Opt. Commun. 2000,
182, 255–264.
17. (a).Gouterman, M. J. Mol. Spect. 1961, 6, 138-163. (b)
Gouterman, M.; Wagniere, G. H. J. Mol. Spect. 1963, 11,
108-127.
18. (a) Lin, C.-Y.; Chen, Y.-C.; Yao, C.-W.; Huang, S.-C.;
Cheng, Y.-H. Dalton Trans. 2008, 793-799. (b) Boucher, L.
J. J. Am. Chem. Soc. 1970, 92, 2725-2730. (b) Carnieri, N.;
Harriman, A.; Porter, G. J. Chem. Soc. Dalton Trans. 1982,
1231-1238. (c) Schardt, B. C.; Hollander, F. J.; Hill, C. L. J.
Am. Chem. Soc. 1982, 104, 3964-3972. (d) Lin, C.-Y.; Lin,
Z.-F.; Hseu, T.-M.; Su, Y. O. J. Chin. Chem. Soc. 1990, 37,
335-344.
8. (a) Park, J. K.; Lee, H. R.; Chen, J.; Shinokubo, H.; Osuka,
A.; Kim, D. J. Phys. Chem. C 2008, 112, 16691-16699. (b)
Rochford, J.; Chu, D.; Hagfeldt, A.; Galoppini, E. J. Am.
Chem. Soc. 2007, 129, 4655-4665.
9. (a) Lin, C.-Y.; Lo, C.-F.; Luo, L.; Lu, H.-P.; Hung, C.-S.;
Diau, E. W.-G. J. Phys. Chem. C. 2009, 113, 755-764. (b) Lo,
C.-F.; Luo, L.; Diau, E. W.-G.; Chang, I-J.; Lin, C.-Y. Chem.
Commun. 2006, 1430–1432 (c) Luo, L.; Lo, C.-F.; Lin,
C.-Y.; Chang, I.-J.; Diau, E. W.-G. J. Phys. Chem. B 2006,
110, 410-419. (d) Luo, L.; Lin, C.-J.; Tsai, C.-Y.; Wu, H.-P.;
Lin, L.-L.; Lo, C.-F.; Lin, C.-Y.; Diau, E. W.-G. Phys. Chem.
Chem. Phys. 2010, 11, 10270-10274. (e) Lin, C.-Y.; Wang,
Y.-C.; Hsu, S.-J.; Jiang, K.-R.; Lo, C.-F.; Diau, E. W.-G. J.
Phys. Chem. C 2009, 113, 755-764.
19. (a) Chiniforoshan, H.; Safari, N.; Nezhad, J. M.;
Hadadzadeh, H.; Mahmoudkhani, A. H. Inorg. Chim. Acta
2006, 359, 2101-2106. (b) Hendrickson, D. N.; Kinnaird, M.
G.; Suslick, K. S. J. Am. Chem. Soc. 1987, 109, 1243-1244.
20. (a) Jayaraj, K.; Gold, A.; Toney, G. E.; Helms, J. H.; Hatfield,
W. E. Inorg. Chem. 1986, 25, 3516-3518 (b) Fleischer, E. B.;
Palmer, J. M.; Srivastava, T. S.; Chatterjee, A. J. Am. Chem.
Soc. 1971, 93, 3162-3167.
10. (a) For recent reviews, see: Kadish, K. M.; Caemelbecke, E.