Synthesis, characterization and electronic properties of trans-[4-(alkoxycarbonyl)phenyl]porphyrin-[RuII(bpy) 3]2 complexes or boron-dipyrrin conjugates as panchromatic sensitizers for DSSCs

Article abstract of DOI:10.1002/ejic.201201248

Two porphyrin-based dyes were synthesized that incorporate two additional chromophores to absorb in a wider UV/Vis region. In the first dye, a porphyrin ring is linked through an amide bond to two [Ru(bpy)₃]²⁺ units, forming a symmetric [Ru(bpy)₃]-porphyrin-[Ru(bpy)₃] {Por(COOH)₂[Ru(bpy)₃]₂} system. The second porphyrin is trans substituted through a triple bond to the meso position with two boron dipyrrin (BDP) molecules {Por(COOH)₂(BDP)₂}. Both porphyrins bear two carboxylic groups capable of binding onto a TiO ₂ surface, with potential applications in dye-sensitized solar cells (DSSCs). The title dyes were characterized by means of ¹H and ¹³C NMR spectroscopy, elemental analysis, MALDI-TOF, UV/Vis absorption and emission studies. Copyright

Full text of DOI:10.1002/ejic.201201248

FULL PAPER
DOI:10.1002/ejic.201201248
Synthesis, Characterization and Electronic Properties of
trans-[4-(Alkoxycarbonyl)phenyl]porphyrin-[RuII(bpy)3]2
Complexes or Boron–Dipyrrin Conjugates as
Panchromatic Sensitizers for DSSCs
Christina Stangel,[a] Kalliopi Ladomenou,[a]
Georgios Charalambidis,[a] Manas K. Panda,[a]
Theodore Lazarides,[a][‡] and Athanassios G. Coutsolelos*[a]
Keywords: Energy transfer / Solar cells / Sensitizers / Dyes/pigments / Porphyrinoids / Ruthenium / Boron
Two porphyrin-based dyes were synthesized that incorporate
two additional chromophores to absorb in a wider UV/Vis
region. In the first dye, a porphyrin ring is linked through an
amide bond to two [Ru(bpy)3]2+ units, forming a symmetric
(BDP) molecules {Por(COOH)2(BDP)2}. Both porphyrins bear
two carboxylic groups capable of binding onto a TiO2 sur-
face, with potential applications in dye-sensitized solar cells
(DSSCs). The title dyes were characterized by means of 1H
and 13C NMR spectroscopy, elemental analysis, MALDI-TOF,
UV/Vis absorption and emission studies.
[Ru(bpy)3]-porphyrin-[Ru(bpy)3]
{Por(COOH)2[Ru(bpy)3]2}
system. The second porphyrin is trans substituted through a
triple bond to the meso position with two boron dipyrrin
loaded onto the semiconductor surface, giving satisfactory
results in several cases.[46–50] In this work, molecules such
as polypyridine-ruthenium(II) complexes and BDP were at-
tached to a porphyrin to build dyes with a wider absorption
range. First, complexes such as [Ru(bpy)3]2+ and its deriva-
tives can be attached to the porphyrin periphery. This suit-
able “auxiliary” ligand displays an absorption maximum
within the 400–500 nm region as well as excellent photo-
physical and redox properties. Therefore, a chromophore
bearing a porphyrin and a ruthenium(II) tris-bipyridine
complex could constitute a good candidate for DSSC appli-
cations because their complementary absorption spectra
can provide an extended absorption range.
A plethora of articles have been published on porphyrins
and [Ru(bpy)3] complexes, allowing the exploitation of their
supramolecular properties particularly for applications in
catalysis, artificial photosynthesis, and molecular de-
vices.[51–65] These types of triads (or larger architectures)
continue to be very interesting due to their ability to act as
efficient sensitizers for energy- and electron-transfer. This
type of ruthenium-porphyrin dyes have been reported as
sensitizers for DSSCs.[13]
Introduction
In recent years dye-sensitized solar cells (DSSCs) have
attracted great attention due to their relatively low pro-
duction cost and high power conversion efficiencies.[1–4] At
present, ruthenium polypyridyl complexes[2,5–20] and several
organic dyes are extensively used as sensitizers for DSSCs,
achieving high efficiencies.[21–38] Among all the organic dyes
used, porphyrins are one of the most widely studied because
of their strong Soret (400–450 nm) and moderate Q bands
(550–600 nm) and their appropriate LUMO and HOMO
energy levels.[39–45] Moreover, porphyrins can be easily
modified by peripheral substitution or inner metal complex-
ation, and this can alter their optical, electrochemical and
photophysical properties. It is well-known that one of the
most important requirements to attain highly efficient solar
energy is broad light absorption capability of the dye. At-
tachment of various chromophores to the porphyrin pe-
riphery will increase the ability of the dye to absorb over a
wide range of the UV/Vis region. A few examples have been
reported in which mixtures of different dyes have been
Secondly, BDP molecules as highly absorbing antenna
chromophores can be attached to the porphyrin ring. More-
over, BDP dyes combine a high fluorescence quantum yield,
a relatively long lifetime, a suitable excited state energy, and
excellent photostability.[66–68] There are examples reported
in the literature in which porphyrin and BDP molecules
(covalently attached or not to the porphyrin) have been
used for DSSC applications.[47,69–71]
[a] University of Crete, Department of Chemistry, Laboratory of
Bioinorganic Chemistry,
P. O. Box 2208, Voutes Campus, 71003 Heraklion, Greece
E-mail: coutsole@chemistry.uoc.gr
Homepage: www.chemistry.uoc.gr/coutsolelos
www.biosolenuti.gr
[‡] Present address: Chemistry Department, University of
Ioannina, 45110, Greece
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201201248.
Eur. J. Inorg. Chem. 2013, 1275–1286
1275
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Herein, we present the synthesis and full characterization according to the literature.[72] The bis-nitro-substituted Por-
of symmetric [Ru(bpy)3]-porphyrin-[Ru(bpy)3] {Por(COOH)2- (COOMe)2(NO2)2 was prepared by condensation of 4-
[Ru(bpy)3]2} and BDP-porphyrin-BDP {Por(COOH)2- (methoxycarbonyl)benzaldehyde with DipNO2 in a ratio of
(BDP)2}, which are A2B2 type systems. In the first case, 1:1, in the presence of trifluoroacetic acid (TFA), followed
two suitably modified [Ru(bpy)3]2+ units are anchored on by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquin-
opposite sides of
a
tetraphenyl-substituted porphyrin one (DDQ), as described in the literature (Scheme 1).[73] Re-
through two amide bonds, whereas each of the remaining duction of the nitro groups was first carried out in concen-
two porphyrinic phenyl substituents carry a carboxylic trated aqueous HCl with SnCl2 by a known procedure.[74]
group capable of immobilizing the system onto TiO2 sub- The amino-substituted Por(COOMe)2(NH2)2 was purified
strate. In the second system, two BDP molecules are at- by column chromatography on silica gel but this gave a low
tached at the meso position of the porphyrin through a tri- yield. Further investigation (column chromatography,
ple bond.
Maldi-Tof mass spectrometry) revealed that another two
byproducts, the mono-hydrolyzed substitute and the di-hy-
drolyzed compounds, had been formed due to the acidic
conditions of the reaction. To avoid the hydrolysis of the
ester groups at the meso position of the porphyrin, a cata-
lytic hydrogenation in tetrahydrofuran (THF) was used,
which afforded the desired Por(COOMe)2(NH2)2 in 95%
yield.[75] Por(COOMe)2(NH2)2 was further treated with an
excess of 4Ј-methyl-2,2Ј-bipyridine-4-carbonyl chloride in
THF in the presence of Et3N to form porphyrin-bipyridine
ligand Por(COOMe)2(bpy)2. This derivative could not be
purified by column chromatography or recrystallization
from the excess of 4Ј-methyl-[2,2Ј-bipyridine]-4-carboxylic
acid (BpyCOOH) and was used without any further purifi-
Results and Discussion
Synthesis
Por(COOH)2[Ru(bpy)3]2
The synthesis of all compounds related to the prepara-
tion of chromophore Por(COOH)2[Ru(bpy)3]2 is shown in
Scheme 1. Bis-amino-substituted Por(COOMe)2(NH2)2 was
prepared in three steps. First, meso-(4-nitrophenyl)dipyrro-
methane (DipNO2) was synthesized in high yield by acid-
catalyzed condensation of 4-nitrobenzaldehyde and pyrrole,
Scheme 1. Synthesis of Por(COOH)2[Ru(bpy)3]2.
Eur. J. Inorg. Chem. 2013, 1275–1286
1276
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Scheme 2. Synthesis of reference compound AnilbpyRu(bpy)2.
cation. By heating the mixture of [Ru(bpy)2Cl2] and Por- Por(COOH)2(BDP)2
(COOMe)2(bpy)2 to reflux in acetic acid, according to a
The synthesis of chromophore Por(COOH)2(BDP)2 is
shown in Scheme 3. Por(COOMe)2Br2 was prepared in ex-
cellent yield following the a literature procedure.[76] Basic
hydrolysis of the latter resulted in formation of Por(COOH)2-
Br2 in high yield. Subsequent Sonogashira coupling with
BDP-ethynyl, which was synthesized according to the litera-
ture,[77] afford the desired Por(COOH)2(BDP)2.
literature method,[55] complex Por(COOMe)2[Ru(bpy)3]2
was obtained in 52% yield. Finally, the latter complex was
hydrolyzed in a mixture of THF/MeOH/aq. KOH at room
temperature and then neutralized with hydrochloric acid
solution to afford the corresponding porphyrin-[RuII-
(bpy)3]2 complex Por(COOH)2[Ru(bpy)3]2 in almost quanti-
tative yield. The aniline-[RuII(bpy)3]2 complex Anilbpy-
Ru(bpy)2 that was used as a reference compound was syn-
thesized in two steps as shown in Scheme 2. Coupling of 4-
methyl-2,2Ј-bipyridinyl-4-carbonyl chloride with aniline af-
forded the aniline-bipyridine ligand Anilbpy and subse-
quent heating to reflux with Ru(bpy)2Cl2 in a mixture of
Photophysical Properties
Por(COOMe)2[Ru(bpy)3]2
The absorption spectrum of the [Ru(bpy)3]-porphyrin
MeOH/acetic acid, afforded the aniline-[RuII(bpy)3] com- conjugate Por(COOMe)2[Ru(bpy)3]2 is essentially the sum
plex AnilbpyRu(bpy)2 in 82% yield.
of those of its constituent chromophores, as can be seen
Scheme 3. Synthesis of Por(COOH)2(BDP)2.
Eur. J. Inorg. Chem. 2013, 1275–1286
1277
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1
in Figure 1. The peak at 288 nm corresponds to the π-π* phores is clearly observed (Figure 2, b). Especially in the
transition of the 2,2Ј-bipyridyl (bpy) ligands of the Ru chro- case of the 77 K emission spectrum, the [Ru(bipy)3]-based
mophores, whereas the intense absorption at 418 nm is due 3MLCT, phosphorescence becomes more apparent due to
to the porphyrin Soret band. The metal-to-ligand charge its matrix and temperature-induced blueshift and enhance-
transfer (MLCT) manifold of the ruthenium units appear ment.
as a shoulder on the low energy side (ca. 460 nm) of the
Soret band, whereas the four Q bands of the free-base por-
phyrin chromophore are found at 513, 549, 590 and
644 nm. Detailed comparison of the absorption spectrum
of Por(COOMe)2[Ru(bpy)3]2 with those of the model com-
pounds Por(COOMe)2(NH2)2 and AnilbpyRu(bpy)2 reveals
only modest shifts in the porphyrin Q bands (ca. 5 nm),
indicating that the two chromophores constituting Por-
(COOMe)2[Ru(bpy)3]2 interact only weakly in the ground
state.
Figure 1. The UV/Vis absorption spectra of Por(COOMe)2-
(NH2)2, Por(COOMe)2[Ru(bpy)3]2, and AnilbpyRu(bpy)2 in
CH3CN at 298Ϯ3 K.
Figure 2. The emission spectra of isoabsorbing (A = 0.1) solutions
(a) Por(COOMe)2[Ru(bpy)3]2 (λex = 461 nm) and AnilbpyRu(bpy)
(λex = 461 nm) in CH3CN at 298Ϯ3 K and (b) Por(COOMe)2-
2
[Ru(bpy)3]2 in CH3CN at 298Ϯ3 K (λex = 288 nm) and in EtOH/
MeOH (4:1) matrix at 77 K (λex = 288 nm).
The room temperature emission spectrum of Por-
(COOMe)2[Ru(bpy)3]2 upon excitation at 461 nm (thus ex-
citing predominantly the [Ru(bpy)3] chromophores) is de-
picted in Figure 2 (a), revealing the characteristic emission
features of the porphyrin chromophore without any appar-
ent Ru-based emission features. The excitation spectra of
Por(COOMe)2[Ru(bpy)3]2 monitored at the two porphyrin
emission peaks at 650 and 730 nm (Figure 3) match well to
the absorption spectrum of the porphyrin chromophore and
1
show a weak bipyridyl π-π* feature at ca. 288 nm and no
apparent 1MLCT Ru(bpy)3-based absorption features, indi-
1
cating that MLCT to porphyrin energy transfer is not op-
erational when the [Ru(bpy)3] chromophore in Por-
(COOMe)2[Ru(bpy)3]2 is excited and that the emission ob-
served upon excitation of Por(COOMe)2[Ru(bpy)3]2 at
461 nm is solely due to excitation of the porphyrin chromo-
phore. The fact that the phosphorescence from the [Ru-
(bpy)3] units is not apparent in the emission spectrum of
Por(COOMe)2[Ru(bpy)3]2 in Figure 2 (a) can potentially be
Figure 3. The excitation spectra of Por(COOMe)2[Ru(bpy)3]2 in
CH3CN at 298Ϯ3 K monitoring at 650 and 730 nm.
Time-resolved fluorescence measurements (Figure 4) in
attributed to the inherently strong fluorescence of the por- MeCN at room temperature and 400 nm pulsed excitation
phyrin unit, which masks the [Ru(bpy)3] emission features, show that Por(COOMe)2[Ru(bpy)3]2 exhibits a dual ex-
as can be witnessed by the emission spectrum of reference ponential decay with lifetimes of ca. 7 and 207 ns. The short
compound AnilbpyRu(bpy)2 in Figure 2 (a). However, lifetime corresponds to the fluorescence of the porphyrin
when Por(COOMe)2[Ru(bpy)3]2 is excited at 288 nm in chromophore in Por(COOMe)2[Ru(bpy)3]2, whereas the
MeCN at room temperature and in a rigid EtOH/MeOH long lifetime is attributed to [Ru(bpy)3] phosphorescence.
(4:1) matrix at 77 K, dual emission due to both chromo- The fact that the [Ru(bpy)3] lifetime of Por(COOMe)2-
Eur. J. Inorg. Chem. 2013, 1275–1286
1278
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[Ru(bpy)3]2 coincides within experimental error with that of the [Ru(bpy)3] donors and the porphyrin acceptor.[80,81]
the reference compound AnilbpyRu(bpy)2 (255 ns), shows This observation was also corroborated by our DFT investi-
that the 3MLCT phosphorescence of Por(COOMe)2- gation, which reveals poor electronic delocalization between
[Ru(bpy)3]2 is not appreciably quenched. Therefore, the the central porphyrin and the terminal [Ru(bpy)3] units.
photophysical data of Por(COOMe)2[Ru(bpy)3]2 show that,
at room temperature, the constituent chromophores do not Por(COOH)2(BDP)2
interact appreciably in the excited state and formation of
The electronic absorption spectra of BDP-ethynyl and
the [Ru(bipy)3]-based 1MLCT is not followed by energy
Por(COOH)2(BDP)2 are presented in Figure 5. All absorp-
tion spectra were measured in tetrahydrofuran. The absorp-
tion spectrum of triad Por(COOH)2(BDP)2 clearly shows a
combination of absorption features from its two constituent
1
transfer to the porphyrin π-π* excited states but instead
rapid intersystem crossing occurs with almost unit effi-
ciency followed by phosphorescence from the MLCT ex-
cited state. This is consistent with the results of other stud-
3
chromophores. The intense peak at 502 nm corresponds to
ies on supramolecular assemblies of Ru complexes and por-
the lowest energy π–π* transitions of the BDP chromo-
phyrins,[62,78] which have shown a lack of energy transfer
phores,[82] whereas the strong Soret band at 451 nm and the
3
from the MLCT excited state of a ruthenium polypyridyl
moderate Q bands at 601 and 654 nm are typical porphyrin
chromophore to a porphyrin 1π-π* excited state at room
absorption features. The porphyrin-based bands of Por-
temperature, likely because of the spin-forbidden nature of
(COOH)2(BDP)2 are red-shifted by ca. 30 nm compared to
such a transition. In addition, the energies of the [Ru-
those of zinc tetraphenylporphyrin,[83] reflecting extended
(bipy)3] 3MLCT and porphyrin 1π-π* excited states are esti-
π-conjugation. This observation is consistent with other re-
mated at 16556 and 15432 cm–1, respectively, from the emis-
ports in the literature on ethylene-substituted por-
sion spectra at 77 K (Figure 2, b). Thus, the gradient for
phyrins.[47,84,85]
3
1
[Ru(bipy)3] MLCT to porphyrin π-π* energy transfer in
Por(COOMe)2[Ru(bpy)3]2 (ERubipy – EPor) is estimated at
ca. 1120 cm–1. This gradient is quite low given the fact that
a gradient higher than 1500 cm–1 is needed to prevent ther-
mal back-energy-transfer in donor–acceptor systems.[79]
Therefore, the spin-forbidden nature of a triplet-to-singlet
transition combined with a poor energy gradient can ac-
count for the observed lack of quenching of the [Ru-
(bipy)3] 3MLCT emission in Por(COOMe)2[Ru(bpy)3]2.
3
However, we would expect the MLCT excited state of the
[Ru(bpy)3] chromophores of Por(COOMe)2[Ru(bpy)3]2 to
be quenched by the porphyrin first triplet excited state, as
has been observed in related bichromophoric systems.[62] In
Por(COOMe)2[Ru(bpy)3]2, phosphorescence from the
[Ru(bpy)3] units is not appreciably quenched, either at room
temperature or at 77 K, which is probably due to the rela-
tively large distance between them and the central por-
phyrin {the average distance between Ru atoms and the cen-
Figure 5. The UV/Vis absorption spectra of BDP-ethynyl and
Por(COOH)2(BDP)2 in THF at 298Ϯ3 K.
The emission spectra of BDP-ethynyl and Por(COOH)2-
ter of the porphyrin is ca. 16 Å as estimated from the DFT (BDP)2 in tetrahydrofuran solutions at room temperature
optimized structure of Por(COOMe)2[Ru(bpy)3]2, see are shown in Figure 6; selected emission data are listed in
below} and the lack of electronic communication between Table 1. BDP-ethynyl shows the typical bright fluorescence
of BDP at 515 nm when excited at 490 nm. In trimer Por-
(COOH)2(BDP)2, irradiation at 490 nm, corresponding to
selective excitation of the two BDP units, results in emission
from the Zn-porphyrin chromophore at 662 nm, as well as
residual fluorescence from the two BDP groups at 517 nm.
BDP emission is strongly quenched, as shown in Figure 6,
in which the fluorescence spectra of isoabsorbing solutions
of BDP-ethynyl and Por(COOH)2(BDP)2 are compared.
The excitation spectrum of Por(COOH)2(BDP)2, monitor-
ing at the fluorescence of the porphyrin moiety at 680 nm,
reveals a pronounced BDP absorption feature at 503 nm
(Figure 7). This is a clear indication of photoinduced en-
ergy transfer from the 1π–π* excited state of the BDP chro-
mophore to the lower lying singlet excited state of the por-
phyrin unit, leading to sensitized fluorescence from the lat-
ter.
Figure 4. Decay of Por(COOMe)2[Ru(bpy)3]2 (black line), fit (red
line), τ1 = 7 ns (due to the porphyrin moiety), τ2 = 207 ns due to
the [Ru(bpy)3] moiety.
Eur. J. Inorg. Chem. 2013, 1275–1286
1279
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Table 1. Summary of spectroscopic data for Por(COOMe)2[Ru(bpy)3]2, AnilbpyRu(bpy)2, BDP-ethynyl, and Por(COOH)2(BDP)2.
Absorption
Emission
λmax [nm]
298 K
λmax [nm] (ε / m–1 cm–1)
Φ
298 K
τ [ns]
298 K
λmax [nm]
77 K
Por(COOMe)2[Ru(bpy)3]2
288 (113.4), 418 (224.2),
457 (30.9), 513 (15.4),
549 (8.6), 589 (3.9), 645 (3.1)
287 (74.4), 456 (16.1)
502 (89.8)
451 (492.6), 502 (176.9),
601 (20.7), 654 (88.2)
653
4.2[a]
7, 207[c]
604, 648, 710
AnilbpyRu(bpy)2
BDP-ethynyl
Por(COOH)2(BDP)2
640
515
517, 662
1.4[a]
7.1[b]
255
600
511
511, 661, 727
2.1
1.4,[d] 2.3[e]
[a] Quantum yields were measured by using [Ru(bpy)3]Cl2 in H2O as standard. [b] Quantum yields were measured by using ZnTPP in
THF as standard. [c] Using a Ϯ40 nm interference filter centered at 600 nm to monitor porphyrin fluorescence. [d] Using a Ϯ40 nm
interference filter centered at 670 nm to monitor porphyrin fluorescence. [e] Using a Ϯ40 nm interference filter centered at 500 nm to
monitor BDP residual fluorescence.
Electrochemistry
Por(COOMe)2[Ru(bpy)3]2
The redox potentials for Por(COOMe)2[Ru(bpy)3]2 and
reference compound AnilbpyRu(bpy)2 are summarized in
Table 2; representative cyclic voltammograms are shown in
Figure S10. The cyclic voltammogram for Por(COOMe)2-
[Ru(bpy)3]2 and AnilbpyRu(bpy)2 was recorded in acetoni-
trile and 0.1 m TBAPF6. The oxidation part of the cyclic
voltammogram exhibited one reversible one-electron pro-
cess peak at E1/2 = 0.91 V vs. Fc/Fc+ assigned to the metal-
based oxidation (Ru2+/Ru3+) couple, compared to reference
compound AnilbpyRu(bpy)2. The irreversible peak at E1/2
Figure 6. Room temperature fluorescence spectra of isoabsorbing
= 0.64 V vs. Fc/Fc+ is assigned to the oxidation of the por-
(A = 0.1) THF solutions of BDP-ethynyl and Por(COOH)2-
(BDP)2 exciting at 480 nm (BDP chromophore).
phyrin unit. Our DFT calculations on Por(COOMe)2[Ru-
(bpy)3]2 shows that the HOMO is dominated by porphyrin-
based orbitals, thus supporting the experimentally observed
first porphyrin-based oxidation. However, contrary to the
DFT results, the second oxidation was found to be [Ru-
(bpy)3]-based. This is probably because of the change of
composition of the frontier orbitals due to solvent effect
under the experimental conditions.[86,87] The reduction side
of Por(COOMe)2[Ru(bpy)3]2 is dominated by irreversible
reduction peaks that could not be assigned.
Por(COOH)2(BDP)2
The redox behavior of Por(COOH)2(BDP)2 and its refer-
ence compound BDP-ethynyl was studied by cyclic and
square wave voltammetry in tetrahydrofuran solutions, with
tetrabutylammonium hexafluorophosphate [(TBA)PF6] as
the supporting electrolyte, using ferrocene as an internal
Figure 7. The excitation spectrum of Por(COOH)2(BDP)2 in THF
at 298Ϯ3 K monitoring at 680 nm.
Table 2. Redox data reported vs. Fc/Fc+ in acetonitrile or tetrahydrofuran using tetrabutylammonium hexafluorophosphate 0.1 m as
supporting electrolyte.
Ox1
Ox2
Red1
Red2
E1/2
[V] (ΔEp [V])[a]
E1/2
1.53[b]
[V]
E1/2
[V]
E1/2
[V]
AnilbpyRu(bpy)2
Por(COOMe)2[Ru(bpy)3]2
0.90 (0.06)
0.64[b]
0.82
–1.77 (0.07)
–1.46[b]
–1.67
–1.98 (0.07)
–2.03[b]
0.91 (0.07)
BDP-ethynyl[c]
Por(COOH)2(BDP)2
[c]
0.50
0.82
–1.56
–1.66
[a] The anodic–cathodic peak separations are given in parenthesis. [b] Irreversible process. [c] Square wave voltammetry was used to
calculate all redox potentials.
Eur. J. Inorg. Chem. 2013, 1275–1286
1280
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
standard. The redox data are summarized in Table 2, and conductor, which is also reflected in the experimentally ob-
representative square wave voltammograms are shown in served low efficiency (0.27%) of the dye Por(COOH)2[Ru-
Figure S11. BDP-ethynyl showed a reversible oxidation at (bpy)3]2.
0.82 V vs. Fc/Fc+ due to formation of the BDP cationic
radical and a reversible reduction at –1.67 V vs. Fc/Fc+,
which is consistent with similar reported BDP deriva-
tives.[82] For Por(COOH)2(BDP)2, it was not possible to es-
timate the redox potentals from cyclic voltammetry because
all the waves were irreversible, so square wave voltammetry
was used to estimate these values. During the anodic scan
an oxidation at 0.50 V vs. Fc/Fc+ attributed to the oxidation
of the porphyrin ring was observed. This value is consistent
with literature reports of porphyrins with ethynyl substitu-
ents at the meso position.[84] A second anodic peak was ob-
served at 0.82 V vs. Fc/Fc+, which is assigned to oxidation
of BDP units. Compound Por(COOH)2(BDP)2 also shows
two irreversible reduction peaks: the first (–1.56 V vs. Fc/
Fc+) corresponds to porphyrin-based reduction and the sec-
ond (–1.66 V vs. Fc/Fc+) to simultaneous reduction of the
BDP molecules.
DFT Results
To obtain further insight into the electron distribution
of the frontier molecular orbitals (FMOs), we carried out
quantum chemical calculations on Por(COOMe)2[Ru-
(bpy)3]2 using density functional theory (DFT). The geome-
try-optimized structure of Por(COOMe)2[Ru(bpy)3]2 re-
vealed two trans oriented terminal [Ru(bpy)3] units on both
sides of the central porphyrin ring (Figure 8). The electron
density map of the selected FMOs and their energy level
diagram (gas- and solution-phase) are shown in Figures 9
and 10 and Figure S15. In the case of Por(COOMe)2[Ru-
(bpy)3]2, the electronic densities of HOMO and HOMO-1
Figure 8. Gas-phase DFT optimized structure of Por(COOMe)2-
[Ru(bpy)3]2 (cyan: Ru; blue: N; red: O; grey: C; off-white: H).
are mainly distributed on the porphyrin ring and could be
characterized as porphyrin π-orbitals. No contribution
from Ruthenium d-orbitals was observed in the frontier side
HOMO orbitals (HOMO to HOMO-3). On the other hand,
LUMO and LUMO+1 exhibit atomic contributions local-
ized over the π*-orbitals of the bpy ligand moiety of the
terminal [Ru(bpy)3] units. A minor contribution from Ru d-
orbitals along with bpy ligand contributions was observed
in LUMO+2. In this regard, it is important to mention that
for a dye in DSSC applications, the LUMO density should
Solar Cell Measurements
The photocurrent J-V curves measured at three different
localize over the anchoring group to allow successful elec- light intensities are shown in Figures S12–S14 (see Support-
tron injection into the TiO2 conduction band.[87,88] How- ing Information). The photovoltaic performance param-
ever, contrary to our expectation, the LUMO electron den- eters are listed in Table S3. The results confirm the activity
sity of Por(COOMe)2[Ru(bpy)3]2 is primarily localized on of the porphyrin complexes in the DSSCs, however, the per-
the terminal bpy ligand moiety, rather than on the caboxy formance of the cells sensitized with Por(COOH)2[Ru-
ester group of the porphyrin. Additionally, very weak delo- (bpy)3]2 was low (less than 0.3%). This finding is in accord-
calization of electronic density was observed between the ance with our DFT results. Moreover, in the case of di-
central porphyrin and the two terminal [Ru(bpy)3] units, bromo dye Por(COOH)2Br2, which was used as a reference
suggesting weak electronic communication between the two. compound, the efficiency was measured to be 1.31% greater
This observation also suggests poor electron injection effi- than that for the bis-BDP dye Por(COOH)2(BDP)2
ciency from the anchoring carboxy group to the TiO2 semi- (0.58%).
Eur. J. Inorg. Chem. 2013, 1275–1286
1281
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Figure 9. Frontier molecular orbitals (gas-phase DFT) of Por(COOMe)2[Ru(bpy)3]2 (cyan: Ru; blue: N; red: O; grey: C; off-white: H).
phyrin and the side [Ru(bpy)3] units in the ground state,
which is consistent with the DFT calculations. The effi-
ciency in DSSC is very poor and the design of the triad is
actually under reinvestigation by a new synthetic approach
in our laboratory. In the case of the BDP-porphyrin-BDP
chromophore Por(COOH)2(BDP)2, photophysical studies
show an interaction between the BDP moieties and the cen-
tral Zn porphyrin in the excited state. The photovoltaic
properties of this dye are, however, very poor, with an effi-
ciency of about 0.6%.
Experimental Section
Figure 10. Energy landscape of frontier MOs of Por(COOMe)2-
1H NMR spectra were recorded with Bruker AMX-500 MHz and
Bruker DPX-300 MHz spectrometers as solutions in deuterated
solvents by using the solvent peak as the internal standard. UV/
Vis absorption spectra were measured with a Shimadzu UV-1700
spectrophotometer using 10 mm path-length cuvettes. The emission
spectra were measured with a JASCO FP-6500 fluorescence spec-
trophotometer equipped with a red-sensitive WRE-343 photomul-
tiplier tube (wavelength range 200–850 nm). Quantum yields were
determined from corrected emission spectra following the standard
methods[89] using tris(bipyridine)ruthenium(II) dichloride [Ru-
(bpy)3Cl2] (Φ = 0.042 in water)[90] or zinc meso-tetraphenylpor-
[Ru(bpy)3]2 (gas-phase DFT). Energy values are given in eV.
Conclusions
Triad chromophores containing porphyrin and tris-bi-
pyridyl-ruthenium derivatives as well as porphyrin and
BDP molecules are reported and fully characterized. The
photophysical data complete this study and describe the
“communication” between the two different entities in both
cases. In the case of Por(COOMe)2[Ru(bpy)3]2, photophysi-
cal studies show weak interactions between the central por- phyrin (ZnTPP) (Φ = 0.03 in toluene)[91] as standards. Emission
Eur. J. Inorg. Chem. 2013, 1275–1286
1282
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
lifetimes were determined by the time-correlated single-photon
counting technique using an Edinburgh Instruments mini-tau life-
time spectrophotometer equipped with an EPL 405 pulsed diode
laser at 406.0 nm with a pulse width of 71.52 ps and pulse periods
of 2 ms and 50 ns and a high-speed red-sensitive photomultiplier
tube (H5773–04) as detector. High-resolution mass spectra were
obtained with a Bruker ultrafleXtreme MALDI-TOF/TOF spec-
trometer using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propen-
ylidene]malononitrile as matrix. Dye-sensitized solar cells were pre-
pared according to Grätzel and co-workers.[92]
concentrated. The porphyrin–bipyridine ligand Por(COOMe)
2(bpy)2 could not purified by column chromatography or
recrystallization from the excess of the 4Ј-methyl-[2,2Ј-bipyridine]-
4-carboxylic acid, and was used without any further purification.
Porphyrin-{NHCO-(bpy)-(CH3)-Ru[(bpy)2]}2[PF6]4 {Por(COOMe)2-
[Ru(bpy)3]2}:
A
mixture of Por(COOMe)2(bpy)2 (150 mg,
0.13 mmol) and [Ru(bpy)2Cl2] (200 mg, 0.39 mmol) in acetic acid
(50 mL) was heated to reflux under N2 for 12 h. After removing
the solvent, the product was purified by column chromatography
on silica gel (CH3CN/H2O/KNO3, 30:2:1). After removing the sol-
vents, the residue dissolved in the minimum amount of water and
NH4PF6 was added until a precipitate was formed. Filtration and
washing with water and diethyl ether gave Por(COOMe)2[Ru-
(bpy)3]2 as a red-brown solid (174 mg, 52% over two steps). 1H
NMR [500 MHz, (CD3)2CO]: δ = 10.50 (s br, 2 H), 9.42 (s, 2 H),
8.99 (s, 2 H), 8.90 (m, 8 H), 8.78 (m, 8 H), 8.43 (d, J = 7.0 Hz, 4
H), 8.37 (d, J = 7.0 Hz, 4 H), 8.29 (m, 6 H), 8.22–7.99 (m, 22 H),
7.91 (d, J = 5.5 Hz, 2 H), 7.58 (m, 8 H), 7.48 (d, J = 5.0 Hz, 2 H),
4.08 (s, 6 H), 2.63 (s, 6 H), –2.73 (s, 2 H) ppm. 13C NMR [75 MHz,
(CD3)2CO]: δ = 167.4, 163.6, 159.2, 158.1, 157.2, 153.4, 152.8,
152.6, 151.9, 151.7, 147.5, 144.4, 139.5, 139.0, 138.8, 135.7, 135.4,
132.1, 130.8, 130.0, 128.9, 126.8, 126.4, 125.3, 123.0, 121.0, 120.1,
119.7, 52.7, 21.3 ppm. UV/Vis (CH3CN): λmax (ε, mm–1 cm–1) = 288
(113.4), 418 (224.2), 457 (30.9), 513 (15.4), 549 (8.6), 589 (3.9), 645
Meso(4-nitrophenyl)dipyrromethane (DipNO2),[72] 5,15-bis(4-
methoxycarbonylphenyl)-10,20-bis(4-nitrophenyl)porphyrin [Por-
(COOMe)2(NO2)2],[73] 4Ј-methyl-[2,2Ј-bipyridine]-4-carboxylic acid
(BpyCOOH),[93]
and
dichlorobis(2,2-bipyridyl)ruthenium(II)
[Ru(bpy)2Cl2],[94] were prepared by using published procedures. All
other chemicals and solvents were purchased from the usual com-
mercial sources and were used as received unless otherwise stated.
Tetrahydrofuran and triethylamine were freshly distilled from
Na/benzophenone and calcium hydride, respectively.
Computational Methods: Theoretical calculations on Por-
(COOMe)2[Ru(bpy)3]2 were performed by using the DFT method
with GAUSSIAN 03[95] program. All the structural optimizations
were carried out in the gas phase by employing Becke three param-
eter exchange functional in conjunction with Lee–Yang–Parr corre-
lation (B3LYP);[96,97] 6-31G(d) basis sets was used for lighter atoms
and LANL2DZ basis set was used for Ru atom. The global mini-
mum of the optimized structures was confirmed by observation of
no negative frequencies in the frequency calculation. Single point
calculations of all the compounds were carried out by employing
the geometry optimized coordinates. All the computed structures
and orbitals were visualized by ChemCraft software (version
1.6).[98]
(3.1) nm. HRMS (MALDI-TOF): m/z calcd. for C112H85F18N18O6-
–
P3Ru2 2416.3928 [M
–
PF6
+H]+; found 2416.3937.
C112H84F24N18O6P4Ru2 (2560.00): calcd. C 52.55, H 3.31, N 9.85;
found C 52.59, H 3.36, N 9.88.
Carboxy-Porphyrin-{NHCO-(bpy)-(CH3)-Ru[(bpy)2]}2[PF6]4 {Por-
(COOH)2[Ru(bpy)3]2}: A solution of Por(COOMe)2[Ru(bpy)3]2
(30 mg, 0.011 mmol) in THF (5 mL), methanol (2 mL) and KOH
(0.3 gr) in H2O (2.5 mL) was stirred at room temperature overnight.
The solution was evaporated to dryness and the precipitate was
dissolved with water and an aqueous solution of HCl was added
dropwise until pH 6. After distillation of the solvent and recrystalli-
zation (MeOH/H2O), the product was obtained as a red-brown so-
lid (27 mg, 95%). UV/Vis (DMSO): λmax (ε, mm–1 cm–1): 292 (60.2),
423 (138.4), 461 (19.6), 516 (10.7), 554 (6.8), 590 (3.8), 647 (3.1)
nm. HRMS (MALDI-TOF): m/z calcd. for C110H81F18N18O6P3Ru2
5,15-Bis(4-methoxycarbonylphenyl)-10,20-bis(4-aminophenyl)-por-
phyrin [Por(COOMe)2(NH2)2]: To a solution of 5,15-bis(4-meth-
oxycarbonylphenyl)-10,20-bis(4-nitrophenyl)porphyrin (300 mg,
0.37 mmol) in anhydrous THF (50 mL) and anhydrous Et3N
(280 μL), was added Pd/C 10% (60 mg). The reaction mixture was
stirred overnight, under a H2 atmosphere, at room temperature.
The solution was passed through Celite and concentrated to dry-
ness under reduced pressure. The residue was purified by column
chromatography on silica gel (CH2Cl2/MeOH, 100:1.5) to obtain
2388.3615 [M – PF6 +H]+; found 2388.3622. C110H80F24N18O6-
–
P4Ru2 (2531.95): calcd. C 52.18, H 3.18, N 9.96; found C 52.15, H
1
3.12, N 9.98. H and 13C NMR spectra could not be obtained due
1
Por(COOMe)2(NH2)2 as a purple solid (260 mg, 95%). H NMR
to solubility problems.
(500 MHz, CDCl3): δ = 8.95 (d, J = 4.5 Hz, 4 H), 8.77 (d, J =
4.5 Hz, 4 H), 8.44 (d, J = 8.0 Hz, 4 H), 8.30 (d, J = 7.5 Hz, 4 H),
7.98 (d, J = 8.0 Hz, 4 H), 7.06 (d, J = 8.0 Hz, 4 H), 4.11 (s, 6
H), 4.05 (s br, 4 H), –2.75 (s, 2 H) ppm. UV/Vis (CH2Cl2): λmax
(ε, mm–1 cm–1) = 422 (291.8), 515 (16.6), 551 (6.0), 590 (5.3),
645 (3.3) nm. HRMS (MALDI-TOF): m/z calcd. for C48H37N6O4
761.2876 [M + H]+; found 761.2871. C48H36N6O4 (760.85): calcd.
C 75.77, H 4.77, N 11.05; found C 75.82, H 4.75, N 11.41.
4Ј-Methyl-N-phenyl-(2,2Ј-bipyridine)-4-carboxamide (Anilbpy):
A
mixture of 4Ј-methyl-[2,2Ј-bipyridine]-4-carboxylic acid (40 mg,
0.19 mmol) and SOCl2 (2.3 mL) was heated to reflux for 2 h. The
excess of SOCl2 was distilled under reduced pressure and the acid
chloride product was dried in vacuo at 70 °C for 1 h. Anhydrous
THF (4.5 mL) and anhydrous Et3N (55 μL) were added and the
mixture was stirred for 5 min. Aniline (25 μL, 0.28 mmol) was
added and the mixture was stirred at 60 °C overnight. After remov-
5,15-Bis(4-methoxycarbonylphenyl)-10,20-bis{4-[4Ј-methyl-(2,2Ј-bi- ing the solvent, CH2Cl2 (15 mL) was added and the mixture was
pyridine)-4-carboxamido]phenyl}porphyrin [Por(COOMe)2(bpy)2]: washed with an aqueous solution of NaCl (2ϫ 15 mL). The or-
A mixture of 4Ј-methyl-[2,2Ј-bipyridine]-4-carboxylic acid (225 mg,
1.05 mmol) and SOCl2 (15 mL) was heated to reflux for 2 h. The
excess of SOCl2 was distilled under reduced pressure and the acyl
chloride product was dried in vacuo at 70 °C for 1 h. Anhydrous
ganic layer was dried with Na2SO4, filtered, and concentrated. The
residue was recrystallized (CH2Cl2 and hexane) to obtain a white
solid (50 mg, 95%). H NMR (500 MHz, CDCl3): δ = 8.84 (m, 2
1
H), 8.55 (d, J = 5.0 Hz, 1 H), 8.45 (s br, 1 H), 8.32 (s, 1 H), 7.88
THF (30 mL) and anhydrous Et3N (400 μL) were added and the (dd, J1 = 5, J2 = 1.5 Hz, 1 H), 7.73 (d, J = 7.5 Hz, 2 H), 7.39 (t, J
mixture was stirred for 5 min. Por(COOMe)2(NH2)2 (200 mg,
0.26 mmol) was added and the mixture was stirred at 60 °C over-
= 7.5 Hz, 2 H), 7.24 (d, J = 4.5 Hz, 1 H), 7.19 (t, J = 7.5 Hz, 1 H),
2.49 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 163.7, 155.6,
night. After removing the solvent, CH2Cl2 (40 mL) was added and 154.4, 150.6, 150.3, 148.0, 143.3, 137.7, 129.3, 125.7, 125.2, 122.9,
the mixture was washed with an aqueous solution of NaCl (2ϫ
30 mL). The organic layer was dried with Na2SO4, filtered, and
122.6, 120.6, 117.9, 21.6 ppm. C18H15N3O (289.34): calcd. C 74.72,
H 5.23, N 14.52; found C 74.78, H 5.19, N 14.61.
Eur. J. Inorg. Chem. 2013, 1275–1286
1283
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Aniline-{NHCO-(bpy)-(CH3)-Ru[(bpy)2]}2[PF6]2 [AnilbpyRu(bpy)2]: ilbpyRu(bpy)2; square wave voltammograms of BDP-ethynyl, Por-
A mixture of Anilbpy (20 mg, 0.07 mmol) and [Ru(bpy)2Cl2]
(30 mg, 0.07 mmol) in a mixture of MeOH/acetic acid (5:1, 12 mL)
was heated to reflux under N2 for 5 h. After removing the solvent,
the product was purified by column chromatography on silica gel
(CH3CN/H2O/KNO3, 30:2:1). After removing the solvents, the resi-
due was dissolved in the minimum amount of water and NH4PF6
was added until a precipitate was formed. Filtration and washing
with water and diethyl ether gave AnilbpyRu(bpy)2 as an orange
(COOH)2(BDP)2; current–voltage characteristics of Por(COOH)2-
[Ru(bpy)3]2, Por(COOH)2Br2, Por(COOH)2(BDP)2; photovoltaic
performances of Por(COOH)2[Ru(bpy)3]2, Por(COOH)2Br2, Por-
(COOH)2(BDP)2.
Acknowledgments
1
solid (57 mg, 82%). H NMR (500 MHz, CD3CN): δ = 9.06 (s br,
The European Commission funded this research FP7-REGPOT-
2008-1, Project BIOSOLENUTI No 229927, Heraklitos grant from
Ministry of Education, and GSRT. Also, Dr. C. Milios is gratefully
acknowledged for our helpful discussions on ruthenium derivatives.
1 H), 8.87 (s, 1 H), 8.51 (dd, J1 = 8.0, J2 = 2.0 Hz, 4 H), 8.07 (m,
4 H), 7.91 (d, J = 6.0 Hz, 1 H), 7.76 (m, 7 H), 7.57 (d, J = 5.5 Hz,
1 H), 7.41 (m, 6 H), 7.29 (d, J = 5.5 Hz, 1 H), 7.22 (t, J = 7.5 Hz),
2.57 (s, 3 H) ppm. 13C NMR (75 MHz, CD3CN): δ = 163.1, 159.0,
158.0, 157.8, 156.9, 153.4, 152.7, 152.5, 151.8, 151.7, 143.9, 138.9,
130.0, 129.7, 128.6, 126.5, 126.1, 125.7, 125.3, 122.8, 121.6,
21.2 ppm. UV/Vis (CH3CN): λmax (ε, mm–1 cm–1) = 287 (74.4),
[1] B. O’ Regan, M. Grätzel, Nature 1991, 353, 737.
[2] M. K. Nazeeruddin, A. Kay, I. Rodicio, R. Humphry-Baker,
E. Mueller, P. Liska, N. Vlachopoulos, M. Graetzel, J. Am.
Chem. Soc. 1993, 115, 6382–6390.
[3] M. Grätzel, Acc. Chem. Res. 2009, 42, 1788–1798.
[4] A. Yella, H.-W. Lee, H. N. Tsao, C. Yi, A. K. Chandiran,
M. K. Nazeeruddin, E. W.-G. Diau, C.-Y. Yeh, S. M.
Zakeeruddin, M. Grätzel, Science 2011, 334, 629–634.
[5] F. Aiga, T. Tada, Sol. Energy Mater. Sol. Cells 2005, 85, 437–
446.
[6] C.-Y. Chen, S.-J. Wu, C.-G. Wu, J.-G. Chen, K.-C. Ho, Angew.
Chem. 2006, 118, 5954; Angew. Chem. Int. Ed. 2006, 45, 5822–
5825.
[7] K. S. Chen, W. H. Liu, Y. H. Wang, C. H. Lai, P. T. Chou,
G. H. Lee, K. Chen, H. Y. Chen, Y. Chi, F. C. Tung, Adv.
Funct. Mater. 2007, 17, 2964–2974.
[8] K. Hara, H. Sugihara, L. P. Singh, A. Islam, R. Katoh, M.
Yanagida, K. Sayama, S. Murata, H. Arakawa, J. Photochem.
Photobiol. A: Chem. 2001, 145, 117–122.
[9] C. Houarner-Rassin, E. Blart, P. Buvat, F. Odobel, J. Pho-
tochem. Photobiol. A: Chem. 2007, 186, 135–142.
[10] C. Houarner-Rassin, F. Chaignon, C. She, D. Stockwell, E.
Blart, P. Buvat, T. Lian, F. Odobel, J. Photochem. Photobiol.
A: Chem. 2007, 192, 56–65.
[11] A. Islam, F. A. Chowdhury, Y. Chiba, R. Komiya, N. Fuke, N.
Ikeda, K. Nozaki, L. Han, Chem. Mater. 2006, 18, 5178–5185.
[12] M. K. Nazeeruddin, P. Pechy, M. Gratzel, Chem. Commun.
1997, 1705–1706.
[13] I. Jung, H. Choi, J. K. Lee, K. H. Song, S. O. Kang, J. Ko,
Inorg. Chim. Acta 2007, 360, 3518–3524.
456 (16.1) nm. HRMS (MALDI-TOF): m/z calcd. for
– +
C38H31F6N7OPRu 848.1275 [M
– PF6 ] ; found 848.1262.
C38H31F12N7OP2Ru (992.70): calcd. C 45.98, H 3.15, N 9.88; found
C 45.92, H 3.17, N 9.91.
[5,15-Dibromo-10,20-bis(4-carboxyphenyl)porphyrinato]zinc [Por-
(COOH)2Br2]: Por(COOMe)2Br2 (60 mg, 0.075 mmol) was dis-
solved in a solution of THF (18 mL), MeOH (8 mL) and H2O
(9 mL) and potassium hydroxide (0.9 g, 16 mmol) was added. The
reaction mixture was stirred at room temperature overnight. After
removing the organic solvents, an aqueous solution of HCl (1 n)
was added dropwise until pH 6. A precipitate was formed, filtered,
and washed with water to give a purple solid (56 mg, 97%). UV/
Vis (THF): λmax (ε, mm–1 cm–1) = 430 (370.4), 565 (17.2), 605 (9.2)
nm. HRMS (MALDI-TOF): m/z calcd. for C34H19Br2N4O4Zn
768.9065 [M + H]+; found 768.9071. C34H18Br2N4O4Zn (771.73):
calcd. C 52.92, H 2.35, N 7.26; found C 52.87, H 2.28, N 7.31.
1H and 13C NMR spectra could not be obtained due to solubility
problems.
BDP-porphyrin-BDP [Por(COOH)2(BDP)2]: Por(COOH)2Br2
(50 mg, 0.06 mmol) was dissolved in anhydrous THF (5 mL) and
anhydrous triethylamine (1.5 mL) was added. The solution was
deoxygenated by bubbling Argon through it for 15 min, then tris-
(dibenzylideneacetone)dipalladium(0)
[Pd2(dba)3]
(15 mg,
0.02 mmol), triphenylphosphane (17 mg, 0.06 mmol), copper(I)
iodide (6 mg, 0.03 mmol) and BDP-ethynyl (70 mg, 0.20 mmol)
were added. The reaction mixture was stirred at 65 °C for 18 h and
then the solvents were removed under reduced pressure. The de-
sired compound was isolated by silica column chromatography
(CH2Cl2/THF/MeOH, 100:10:1) to give Por(COOH)2(BDP)2 as a
brown solid (64 mg, 78%). 1H NMR (500 MHz, d8-THF): δ = 9.83
(d, J = 4.5 Hz, 4 H), 8.87 (d, J = 4.5 Hz, 4 H), 8.48 (d, J = 8.0 Hz,
4 H), 8.32 (d, J = 8.0 Hz, 4 H), 8.29 (d, J = 8.0 Hz, 4 H), 7.63 (d,
J = 8.0 Hz, 4 H), 6.10 (s, 4 H), 2.48 (s, 12 H), 1.62 (s, 12 H) ppm.
13C NMR (75 MHz, [D8]THF): δ = 167.6, 156.3, 152.8, 150.5,
147.8, 143.4, 142.8, 135.1, 132.9, 132.8, 132.0, 131.6, 131.2, 129.6,
128.6, 125.9, 122.7, 121.8, 101.7, 96.7, 95.0, 14.8, 14.4 ppm. UV/
Vis (THF): λmax (ε, mm–1 cm–1) = 451 (492.6), 502 (176.9), 601
(20.7), 654 (88.2) nm. HRMS (MALDI-TOF): m/z calcd. for
[14] D. Kuang, S. Ito, B. Wenger, C. Klein, J.-E. Moser, R.
Humphry-Baker, S. M. Zakeeruddin, M. Grätzel, J. Am. Chem.
Soc. 2006, 128, 4146–4154.
[15] M. K. Lim, S.-R. Jang, R. Vittal, J. Lee, K.-J. Kim, J. Pho-
tochem. Photobiol. A: Chem. 2007, 190, 128–134.
[16]
M. K. Nazeeruddin, F. De Angelis, S. Fantacci, A. Selloni, G.
Viscardi, P. Liska, S. Ito, B. Takeru, M. Grätzel, J. Am. Chem.
Soc. 2005, 127, 16835–16847.
[17] M. K. Nazeeruddin, C. Klein, P. Liska, M. Grätzel, Coord.
Chem. Rev. 2005, 249, 1460–1467.
[18] W.-P. Tai, Sol. Energy Mater. Sol. Cells Sol. Energy Mater. Sol.
C 2003, 76, 65–73.
[19] P. Wang, S. M. Zakeeruddin, J. E. Moser, R. Humphry-Baker,
P. Comte, V. Aranyos, A. Hagfeldt, M. K. Nazeeruddin, M.
Grätzel, Adv. Mater. 2004, 16, 1806–1811.
C76H55B2F4N8O4Zn 1305.3760 [M
+
H]+; found 1305.3452.
[20] H. Yi, J. A. Crayston, J. T. S. Irvine, Dalton Trans. 2003, 685–
C76H54B2F4N8O4Zn (1306.31): calcd. C 69.88, H 4.17, N 8.58;
found C 69.81, H 4.21, N 8.52.
691.
[21] P. G. Bomben, K. C. D. Robson, B. D. Koivisto, C. P. Berling-
uette, Coord. Chem. Rev. 2012, 256, 1438–1450.
[22] Z.-S. Wang, Y. Cui, Y. Dan-oh, C. Kasada, A. Shinpo, K.
Hara, J. Phys. Chem. C 2008, 112, 17011–17017.
[23] T. Horiuchi, H. Miura, K. Sumioka, S. Uchida, J. Am. Chem.
Soc. 2004, 126, 12218–12219.
Supporting Information (see footnote on the first page of this arti-
cle): 1H NMR and 13C NMR of Por(COOMe)2(NH2)2, Por-
(COOMe)2[Ru(bpy)3]2, Anilbpy, AnilbpyRu(bpy)2, Por(COOH)2-
(BDP)2; cyclic voltammograms of Por(COOMe)2[Ru(bpy)3]2, An-
Eur. J. Inorg. Chem. 2013, 1275–1286
1284
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[24] S. Ito, H. Miura, S. Uchida, M. Takata, K. Sumioka, P. Liska,
P. Comte, P. Pechy, M. Gratzel, Chem. Commun. 2008, 5194–
5196.
[25] H. Im, S. Kim, C. Park, S.-H. Jang, C.-J. Kim, K. Kim, N.-G.
Park, C. Kim, Chem. Commun. 2010, 46, 1335–1337.
[26] S. Hwang, J. H. Lee, C. Park, H. Lee, C. Kim, C. Park, M.-H.
Lee, W. Lee, J. Park, K. Kim, N.-G. Park, C. Kim, Chem. Com-
mun. 2007, 4887–4889.
[54] X. Liu, J. Liu, K. Jin, X. Yang, Q. Peng, L. Sun, Tetrahedron
2005, 61, 5655–5662.
[55]
[56]
[57]
X. Liu, J. Liu, J. Pan, S. Andersson, L. Sun, Tetrahedron 2007,
63, 9195–9205.
D. LeGourriérec, M. Andersson, J. Davidsson, E. Mukhtar, L.
Sun, L. Hammarström, J. Phys. Chem. A 1999, 103, 557–559.
H. T. Uyeda, Y. Zhao, K. Wostyn, I. Asselberghs, K. Clays, A.
Persoons, M. J. Therien, J. Am. Chem. Soc. 2002, 124, 13806–
13813.
[27] K. Hara, M. Kurashige, S. Ito, A. Shinpo, S. Suga, K. Sayama,
H. Arakawa, Chem. Commun. 2003, 252–253.
[58]
[59]
[60]
[61]
[62]
A. D. Hamilton, H. D. Rubin, A. B. Bocarsly, J. Am. Chem.
Soc. 1984, 106, 7255–7257.
K. Araki, P. Losco, F. M. Engelmann, H. Winnischofer, H. E.
Toma, J. Photochem. Photobiol. A: Chem. 2001, 142, 25–30.
H. Kitagishi, A. Satake, Y. Kobuke, Inorg. Chem. 2004, 43,
3394–3405.
I. Hamachi, S. Tanaka, S. Tsukiji, S. Shinkai, S. Oishi, Inorg.
Chem. 1998, 37, 4380–4388.
H. E. Toma, K. Araki, Coord. Chem. Rev. 2000, 196, 307–329.
[28] A. Kira, Y. Shibano, S. Kang, H. Hayashi, T. Umeyama, Y.
Matano, H. Imahori, Chem. Lett. 2010, 39, 448–450.
[29] W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang,
C. Pan, P. Wang, Chem. Mater. 2010, 22, 1915–1925.
[30] X. Ma, J. Hua, W. Wu, Y. Jin, F. Meng, W. Zhan, H. Tian,
Tetrahedron 2008, 64, 345–350.
[31] Y.-S. Chen, C. Li, Z.-H. Zeng, W.-B. Wang, X.-S. Wang, B.-W.
Zhang, J. Mater. Chem. 2005, 15, 1654–1661.
[32] J. J. Cid, J. H. Yum, S. R. Jang, M. K. Nazeeruddin, E. Marti-
nez-Ferrero, E. Palomares, J. Ko, M. Gratzel, T. Torres, Angew.
Chem. 2007, 119, 8510; Angew. Chem. Int. Ed. 2007, 46, 8358–
8362.
[33] C. Li, J.-H. Yum, S.-J. Moon, A. Herrmann, F. Eickemeyer,
N. G. Pschirer, P. Erk, J. Schöneboom, K. Müllen, M. Grätzel,
M. K. Nazeeruddin, ChemSusChem 2008, 1, 615–618.
[34] M. V. Martínez-Díaz, M. Ince, T. Torres, Monatsh. Chem.
2011, 142, 699–707.
[63] L. Flamigni, F. Barigelletti, N. Armaroli, J.-P. Collin, I. M. Di-
xon, J.-P. Sauvage, J. A. G. Williams, Coord. Chem. Rev. 1999,
190–192, 671–682.
[64] J. L. Allwood, A. K. Burrell, D. L. Officer, S. M. Scott, K. Y.
Wild, K. C. Gordon, Chem. Commun. 2000, 747–748.
[65] K. Chichak, N. R. Branda, Chem. Commun. 2000, 1211–1212.
[66] E. Maligaspe, T. Kumpulainen, N. K. Subbaiyan, M. E.
Zandler, H. Lemmetyinen, N. V. Tkachenko, F. D’Souza, Phys.
Chem. Chem. Phys. 2010, 12, 7434–7444.
[35] M.-E. Ragoussi, J.-J. Cid, J.-H. Yum, G. de la Torre, D.
Di Censo, M. Grätzel, M. K. Nazeeruddin, T. Torres, Angew.
Chem. Int. Ed. 2012, 51, 4375–4378.
[36] I. López-Duarte, M. Wang, R. Humphry-Baker, M. Ince, M. V.
Martínez-Díaz, M. K. Nazeeruddin, T. Torres, M. Grätzel, An-
gew. Chem. Int. Ed. 2012, 51, 1895–1898.
[37] B. E. Hardin, J.-H. Yum, E. T. Hoke, Y. C. Jun, P. Péchy, T. s.
Torres, M. L. Brongersma, M. K. Nazeeruddin, M. Gratzel,
M. D. McGehee, Nano Lett. 2010, 10, 3077–3083.
[38] J.-H. Yum, B. E. Hardin, E. T. Hoke, E. Baranoff, S. M.
Zakeeruddin, M. K. Nazeeruddin, T. Torres, M. D. McGehee,
M. Grätzel, ChemPhysChem 2011, 12, 657–661.
[39] Y. Ooyama, Y. Harima, Eur. J. Org. Chem. 2009, 2903–2934.
[40] H. Imahori, T. Umeyama, S. Ito, Acc. Chem. Res. 2009, 42,
1809–1818.
[67] Y. Rio, W. Seitz, A. Gouloumis, P. Vázquez, J. L. Sessler, D. M.
Guldi, T. Torres, Chem. Eur. J. 2010, 16, 1929–1940.
[68] T. Lazarides, G. Charalambidis, A. Vuillamy, M. Réglier, E.
Klontzas, G. Froudakis, S. Kuhri, D. M. Guldi, A. G. Coutso-
lelos, Inorg. Chem. 2011, 50, 8926–8936.
[69] M. Shrestha, L. Si, C.-W. Chang, H. He, A. Sykes, C.-Y. Lin,
E. W.-G. Diau, J. Phys. Chem. C 2012, 116, 10451–10460.
[70] M. T. Whited, P. I. Djurovich, S. T. Roberts, A. C. Durrell,
C. W. Schlenker, S. E. Bradforth, M. E. Thompson, J. Am.
Chem. Soc. 2011, 133, 88–96.
[71]
[72]
[73]
J. Warnan, F. Buchet, Y. Pellegrin, E. Blart, F. Odobel, Org.
Lett. 2011, 13, 3944–3947.
C. Brückner, V. Karunaratne, S. J. Rettig, D. Dolphin, Can. J.
Chem. 1996, 74, 2182–2193.
M. E. Milanesio, M. Gervaldo, L. A. Otero, L. Sereno, J. J.
Silber, E. N. Durantini, J. Porphyrins Phthalocyanines 2003, 7,
42–51.
[41] X.-F. Wang, H. Tamiaki, Energy Environ. Sci. 2010, 3, 94–106.
[42] M. V. Martinez-Diaz, G. de la Torre, T. Torres, Chem. Com-
mun. 2010, 46, 7090–7108.
[74]
[75]
[76]
W. J. Kruper, T. A. Chamberlin, M. Kochanny, J. Org. Chem.
1989, 54, 2753–2756.
J.-M. Barbe, G. Canard, S. Brandes, F. Jerome, G. Dubois, R.
Guilard, Dalton Trans. 2004, 1208–1214.
J. A. Mikroyannidis, G. Charalambidis, A. G. Coutsolelos, P.
Balraju, G. D. Sharma, J. Power Sources 2011, 196, 6622–6628.
Z. Li, R. Bittman, J. Org. Chem. 2007, 72, 8376–8382.
F. M. Engelmann, P. Losco, H. Winnischofer, K. Araki, H. E.
Toma, J. Porphyrins Phthalocyanines 2002, 6, 33–42.
L. Armelao, S. Quici, F. Barigelletti, G. Accorsi, G. Bottaro,
M. Cavazzini, E. Tondello, Coord. Chem. Rev. 2010, 254, 487–
505.
[43]
A. Hagfeldt, G. Boschloo, L. Sun, L. Kloo, H. Pettersson,
Chem. Rev. 2010, 110, 6595–6663.
[44]
K. Ladomenou, T. Lazarides, M. K. Panda, G. Charalambidis,
D. Daphnomili, A. G. Coutsolelos, Inorg. Chem. 2012, 51,
10548–10556.
[45]
[46]
M. K. Panda, K. Ladomenou, A. G. Coutsolelos, Coord.
Chem. Rev. 2012, 256, 2601–2627.
C. Siegers, J. Hohl-Ebinger, B. Zimmermann, U. Würfel, R.
Mülhaupt, A. Hinsch, R. Haag, ChemPhysChem 2007, 8,
1548–1556.
[77]
[78]
[79]
[47]
[48]
C. Y. Lee, J. T. Hupp, Langmuir 2010, 26, 3760–3765.
T. Bessho, S. M. Zakeeruddin, C.-Y. Yeh, E. W.-G. Diau, M.
Grätzel, Angew. Chem. 2010, 122, 6796; Angew. Chem. Int. Ed.
2010, 49, 6646–6649.
[80]
[81]
C. Devadoss, P. Bharathi, J. S. Moore, J. Am. Chem. Soc. 1996,
118, 9635–9644.
The Förster critical radius for photoinduced energy transfer
from [Ru(bipy)3] to the first singlet excited state of the central
porphyrin unit is estimated at ca. 19 Å using the spectroscopic
data in Table 1. This critical radius is expected to be signifi-
cantly shorter if the first triplet of the central porphyrin is
taken as the acceptor state due to poorer spectral overlap.
Thus, the observed lack of quenching could be because the ca.
16 Å distance between donor and acceptor is greater than the
Förster critical radius.
[49]
J.-H. Yum, S.-R. Jang, P. Walter, T. Geiger, F. Nuesch, S. Kim,
J. Ko, M. Gratzel, M. K. Nazeeruddin, Chem. Commun. 2007,
4680–4682.
[50]
[51]
[52]
[53]
Y. Chen, Z. Zeng, C. Li, W. Wang, X. Wang, B. Zhang, New
J. Chem. 2005, 29, 773–776.
S. Fukuda, A. Satake, Y. Kobuke, Thin Solid Films 2006, 499,
263–268.
J. M. Lintuluoto, V. V. Borovkov, Y. Inoue, Tetrahedron Lett.
2000, 41, 4781–4786.
X. Liu, J. Liu, J. Pan, R. Chen, Y. Na, W. Gao, L. Sun, Tetrahe-
dron 2006, 62, 3674–3680.
[82]
A. Burghart, H. Kim, M. B. Welch, L. H. Thoresen, J. Reib-
enspies, K. Burgess, F. Bergström, L. B. Å. Johansson, J. Org.
Chem. 1999, 64, 7813–7819.
Eur. J. Inorg. Chem. 2013, 1275–1286
1285
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[83] K. M. Kadish, K. M. Smith, R. Guilard, The Porphyrin Hand-
book, Academic, San Diego, CA, 2000.
[84] C.-F. Lo, S.-J. Hsu, C.-L. Wang, Y.-H. Cheng, H.-P. Lu, E. W.-
G. Diau, C.-Y. Lin, J. Phys. Chem. C 2010, 114, 12018–12023.
[85] S. M. LeCours, S. G. DiMagno, M. J. Therien, J. Am. Chem.
Soc. 1996, 118, 11854–11864.
[86] Y. Xu, W.-K. Chen, M.-J. Cao, S.-H. Liu, J.-Q. Li, A. I. Philip-
popoulos, P. Falaras, Chem. Phys. 2006, 330, 204–211.
[87] S. Fantacci, F. De Angelis, A. Selloni, J. Am. Chem. Soc. 2003,
125, 4381–4387.
[88] J. E. Monat, J. H. Rodriguez, J. K. McCusker, J. Phys. Chem.
A 2002, 106, 7399–7406.
[95]
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, T. Vreven,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Lyengar, J. Tom-
asi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratch-
ian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gom-
perts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C.
Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A.
Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dap-
prich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick,
A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q.
Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayak-
kara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, rev. D.01,
Gaussian, Inc., Wallingford CT, 2004.
[89] G. A. Crosby, J. N. Demas, J. Phys. Chem. 1971, 75, 991–1024.
[90] J. Van Houten, R. J. Watts, J. Am. Chem. Soc. 1976, 98, 4853–
4858.
[91] P. G. Seybold, M. Gouterman, J. Mol. Spectrosc. 1969, 31, 1–
13.
[92] W. M. Campbell, K. W. Jolley, P. Wagner, K. Wagner, P. J.
Walsh, K. C. Gordon, L. Schmidt-Mende, M. K. Nazeeruddin,
Q. Wang, M. Grätzel, D. L. Officer, J. Phys. Chem. C 2007,
111, 11760–11762.
[93] D. G. McCafferty, B. M. Bishop, C. G. Wall, S. G. Hughes,
S. L. Mecklenberg, T. J. Meyer, B. W. Erickson, Tetrahedron
1995, 51, 1093–1106.
[96]
A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100.
[97] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789.
[98] D. A. Zhurko, G. A. Zhurko, CHEMCRAFT.
Received: October 15, 2012
Published Online: January 14, 2013
[94] B. P. Sullivan, D. J. Salmon, T. J. Meyer, Inorg. Chem. 1978, 17,
3334–3341.
Eur. J. Inorg. Chem. 2013, 1275–1286
1286
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim