Conducting polymer networks cross-linked by "isolated" functional dyes: Design, synthesis, and electrochemical polymerization of doubly strapped light-harvesting porphyrin/oligothiophene monomers

Article abstract of DOI:10.1002/chem.200900576

We have synthesized doubly strapped porphyrin derivatives with four bithiophene segments that diverge from the porphyrin core, namely, Por(BT) ₄ and PorZn(BT)₄. These molecules are designed as electrochemically polymerizable monomers

Full text of DOI:10.1002/chem.200900576

DOI: 10.1002/chem.200900576
Conducting Polymer Networks Cross-Linked by “Isolated” Functional Dyes:
Design, Synthesis, and Electrochemical Polymerization of Doubly Strapped
Light-Harvesting Porphyrin/Oligothiophene Monomers
Kazunori Sugiyasu* and Masayuki Takeuchi*[a]
Dedicated to Professor Seiji Shinkai on the occasion of his 65th birthday
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Chem. Eur. J. 2009, 15, 6350 – 6362

FULL PAPER
Abstract: We have synthesized doubly
strapped porphyrin derivatives with
four bithiophene segments that diverge
from the porphyrin core, namely,
Por(BT)4 and PorZn(BT)4. These mol-
ecules are designed as electrochemical-
ly polymerizable monomers that will
yield the highly cross-linked conducting
of the monomers and their model com-
ponents were investigated by UV/Vis
and fluorescence spectroscopic analysis.
An absorption spectral comparison be-
tween the diluted solution and the thin
solid film of Por(BT)4 demonstrated
that the porphyrin molecule is shielded
by the double strap and self-aggrega-
tion is prevented. It is noteworthy that
the fluorescence of the spin-coated film
of the doubly strapped porphyrin mo-
nomer was twice as strong as that of an
unstrapped porphyrin, thus indicating
that the double strap can suppress un-
desired deactivation processes from the
photoexcited state. In addition, fluores-
cence spectral measurements revealed
that quantitative energy transfer from
the oligothiophene segments to the
porphyrin molecule takes place, which
demonstrates an effective electronic in-
teraction between these two chromo-
phores. Electrochemical polymerization
of the monomers Por(BT)4 and
PorZn(BT)4 gave robust films that
showed stable electrochemistry. Ab-
sorption spectral measurements and
electrochemical characterization of the
obtained films showed that the doubly
strapped porphyrins are incorporated
into the conducting polymer networks
without any decomposition and proto-
nation. Given all these observations
above, our new monomer design based
on functional dyes shielded by the
double strap will lead to new organic
optoelectronic materials in which func-
tional molecules are spatially incorpo-
rated and isolated and yet show an ef-
fective electronic interactions with the
conducting polymer backbones.
polymeric networks poly
ACHTUNGTRNEN[UNG Por(BT)4]
and poly[PorZn(BT)4], respectively,
ACHTUNGTRENNUNG
through an oxidative coupling reaction
among the bithiophene moieties. Selec-
tive synthesis of the distal doubly strap-
ped porphyrin derivatives was success-
ful from the bis(formylphenyl) and
bis(dipyrrolylmethylphenyl)
straps
under Lindsey conditions. Slow kinetics
observed for the zinc insertion reaction
toward the doubly strapped porphyrin
derivative revealed that both faces of
the porphyrin plane are overlaid with
alkyl chain straps. To probe this “isola-
tion” effect, photophysical properties
Keywords: conducting materials
·
energy transfer · light-harvesting ·
polythiophenes · porphyrins
Introduction
electronic interactions between them, the integrated materi-
als function as chemosensors.[37,38] Thus, conducting poly-
mers functionalized with photo- and electroactive molecules,
mostly p-conjugated molecules, such as porphyrins,[14–19]
phthalocyanines,[20,21] perylenes,[22–25] fullerenes,[26–28] and so
forth,[29–36] have been reported. A recent example reported
by Wꢁrthner and co-workers showed that oligothiophene-
Conducting polymers are the most promising materials in
the field of future electronics as an alternative to inorganic
counterparts due to their tunable optoelectronic properties
and rich advantages endowed as an organic substance (flexi-
ble, processible, and lightweight).[1–10] The rational design of
conducting polymers has been a challenging subject from
both experimental[11] and theoretical[12] sides; consequently,
desired properties related to the optical band gap and the
redox potential (i.e., electron affinity and ionization poten-
tial) can nowadays be realized at will. In addition to the in-
herent functions of the polymer, the incorporation of photo-
and electroactive molecules either on the side chain or back-
bone of the polymer leads to more advanced materials.[13–36]
For example, a donor/acceptor couple or p–n heterojunction
facilitates the conversions of excitons into electrons and
holes or vice versa in the material, which is applicable to
photovoltaics and electroluminescence devices. In addition,
when these two components are conjugated in such a way
that some chemical stimuli (i.e., analytes) can perturb the
functionalized perylene bisACTHNUTRGENUGN(imide)s yield polymeric net-
works that consist of alternating p- and n-type materials at
the molecular level.[22,23] Swager and co-workers reported
that a porphyrin-incorporated polythiophene network struc-
ture acts as a highly sensitive conductometric fluoride ion
sensor.[17] In these functionalized polymeric materials, not
only the control of the electronic interaction between the
polymer backbone and the incorporated functional molecule
but also the prevention of self-aggregation of these p-conju-
gated systems is of importance. For instance, a charge-trans-
fer interaction between these two components at the ground
state often limits efficient charge transport. In addition, self-
aggregation may cause deactivation processes of the excited
state (i.e., self-quenching), such as the coupling of excitions,
excimer formation, and so forth.[39–45] Therefore, in practice,
there is often a tradeoff in the incorporation of functional
molecules into conducting polymers: spatial isolation of the
functional molecules in the materials and yet a desired elec-
tronic interaction with the polymer backbone are required.
In this context, we herein present a new concept in mono-
mer design toward dye-functionalized polymeric materials.
We have succeeded in the syntheses of bithiophene-func-
tionalized doubly strapped porphyrin derivatives as electro-
[a] Dr. K. Sugiyasu, Dr. M. Takeuchi
Macromolecules Group, Organic Nanomaterials Center
National Institute for Materials Science, 1-2-1 Sengen
Tsukuba, 305-0047 (Japan)
Fax : (+81)29-859-2101
E-mail: Sugiyasu.Kazunori@nims.go.jp
Takeuchi.Masayuki@nims.go.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200900576.
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K. Sugiyasu and M. Takeuchi
chemically polymerizable monomers. The “double strap” is
expected to shield the large p-conjugated system of the por-
phyrin molecule to suppress self-aggregation. Porphyrin
chromophores have been extensively used as photonic and
electronic materials for a long time, originally inspired by
the natural photosynthetic reaction center. A large molar
absorptivity in the visible region and moderate redox poten-
tials are attractive features for optoelectronic devices.[46–48]
Furthermore, porphyrin molecules can be a good probe to
demonstrate the “isolation” effect because the self-aggrega-
tion phenomena of porphyrin derivatives have been studied
in detail by means of spectroscopic methods.[49] In addition,
a metal insertion reaction into the porphyrin core will indi-
rectly show how sterically crowded the porphyrin surface is.
On the other hand, oligothiophenes are known as a p-type
charge carrier and can easily be polymerized by an electro-
chemical oxidative coupling reaction, which is a straightfor-
ward method to obtain modified electrodes. In fact, intrigu-
ing supramolecular combinations of these two building
blocks have been reported so far;[50–52] nevertheless, the
design and application of the corresponding polymeric mate-
rials are still limited. Electrochemical polymerization of the
present monomers based on the doubly strapped porphyrin
will yield conducting polymer networks in which functional
molecules (i.e., porphyrins in this study) are spatially incor-
porated and isolated and yet show an effective electronic in-
teraction with the polymer backbone (see below). Herein, a
basic concept of molecular design, synthesis, and characteri-
zation of porphyrin/bithiophene monomers and their photo-
physical and electrochemical characteristics are described.
Results and Discussion
Synthesis of the monomer and its model compounds: The
structures of electrochemically polymerizable porphyrin/bi-
thiophene monomers (i.e., Por(BT)4 and PorZn(BT)4) and
their model components (i.e., mBT, mQT, PorACHTUNGTRENNUNG(OMe)4,
Por(BT), and Por(QT)) are shown in Schemes 1 and 2
(hereafter, BT and QT denote the bithiophene segments in
Por(BT)4, PorZn(BT)4, or Por(BT) and quaterthiophene
segments in polyACTHNUTRGENN[UG Por(BT)4], polyACHTUNGTREN[NUGN PorZn(BT)4], or
Por(QT), respectively). Por(QT) has a QT segment on a
porphyrin scaffold and was synthesized as a soluble model
compound for the polyACHTNUGTRNEUNG[Por(BT)4] network structure, which
is obtained by an electrochemical coupling reaction among
the BT segments in Por(BT)4.
Scheme 1. Syntheses and chemical structures of doubly strapped porphyrin/bithiophene monomers Por(BT)4 and PorZn(BT)4. Reagents and conditions:
i) pyrrole, TFA; ii) BF3·Et2O, then chloranil; iii) Suzuki–Miyaura coupling reaction using [Pd(PPh3)4] and Na2CO3; iv) zinc acetate; and v) electrochemical
AHCTUNGTRENNUNG
polymerization. A schematic representation of the polymeric network structure is shown. Purple square=porphyrin, red rod=quaterthiophene, and gray
bar=alkyl chain strap. Left) Computer-generated model of Por(BT)4, in which the red and blue enclosures indicate the alkyl chain strap and porphyrin
surface, respectively. Right) Structure of the three-dimensional network. TFA=trifluoroacetic acid.
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Design of Electrochemically Polymerizable Monomers
FULL PAPER
The syntheses of mBT and mQT were carried out by pre-
viously reported well-established thiophene chemistry, and
the resulting molecules were characterized by using the
usual methods. PorACTHNUTRGNEUNG(OMe)4 was synthesized according to a
reported procedure[53] and purified by column chromatogra-
1
phy (silica gel, hexane/chloroform=4:1–0:1). The H NMR
spectrum of PorACTHNUTRGNEUNG(OMe)4 at room temperature showed multi-
ple resonances, however, each integral was identical to a tet-
rakis(2-substituted phenyl)porphyrin: 8H for the b position
of the pyrrole unit, four sets of 4H for the 2-methoxyphenyl
groups, 12H for the methoxy groups, 2H for the inner pro-
tons, and no other ambiguous peaks were observed. With
two-dimensional TLC analysis, the product gave two main
spots and one faint spot along the x axis. After heating the
TLC plate at 808C for 30 min, each spot separated into
three spots on the y axis. These results indicate that the ob-
tained PorACTHNUGRTENUNG(OMe)4 is pure but a mixture of atropisomers, as
reported previously.[53] In fact, these atropisomers are
1
known to isomerize at a slower rate than the H NMR time
scale but not slow enough to be isolable.[53]
The synthesis of the doubly strapped porphyrin intermedi-
ate Por(Br)4 is shown in Scheme 1 (see the Experimental
Section). We have developed a new synthetic approach
toward meso-phenyl doubly strapped porphyrin derivatives
from the bis(formylphenyl) and bis(dipyrrolylmethylphenyl)
straps (1 and 2, respectively) under Lindsey conditions,[54,55]
which selectively yield the distal (5,15:10,20)-strapped de-
Scheme 2. Chemical structures of the model components: mBT, mQT,
PorACHTUNGTRENNUNG(OMe)4, Por(BT), and Por(QT).
Scheme 3. Syntheses and chemical structures of the model components. Reagents and conditions: i) Suzuki–Miyaura coupling using [PdACTHNUTRGNE(UNG PPh3)4], Na2CO3,
and the corresponding boronic acid; ii) NBS; iii) nBuLi, then 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane; iv) pyrrole, propionic acid. NBS=N-
bromosuccinimide.
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K. Sugiyasu and M. Takeuchi
sired porphyrin over the proximal (5,20:10,15)-strapped by-
product in a moderate yield (ca. 25%; for Por(Br)4: Rf =
0.25, chloroform/hexane=1:2). It is convenient that no
other porphyrin derivatives were observed by TLC analysis,
thus indicating that “scrambling” of pyrrole units does not
take place under these reaction conditions.[55] It should be
noted that most synthetic methodologies, that is, porphyrin
synthesis followed by strapping two sets out of four phenyl
groups, can yield a proximal strapped porphyrin that may
have a,a,a,a and a,a,b,b stereoisomers, which causes poor
yield on isolation.[56–58] In addition, another synthetic at-
tempt starting from 1 with two equivalents of pyrrole did
not give Por(Br)4, instead we obtained some porphyrin de-
component followed by tetrakis(4-butoxyphenyl)porphyrin.
These monobrominated porphyrin derivatives were further
subjected to the Suzuki–Miyaura coupling reaction with the
corresponding thiophene boronic acids. Consequently,
model porphyrin compounds (i.e., Por(BT) and Por(QT))
that were pure enough for spectroscopic studies were syn-
thesized.
Characterization of the “double strap”: The 1H NMR
spectrum of Por(Br)4 showed a singlet peak for the b proton
of pyrrole (d=8.77 ppm) in clear contrast to those peaks of
PorACTHUNTRGNENG(U OMe)4, thus indicating a symmetric structure (see the
Supporting Information). In addition, alkyl chain straps ap-
peared in the upfield region (d=À0.13–0.89 ppm) due to
the strong ring-current effect of the porphyrin molecule (see
Figure S2 in the Supporting Information). This result dem-
onstrates that the alkyl chain straps are lying in the porphy-
1
rivatives, of which the H NMR spectrum was complicated
probably due to the aforementioned isomers (see Figure S1
1
in the Supporting Information for the H NMR and absorp-
tion spectra; Rf =0.18, chloroform/hexane=1:2, MALDI-
TOF-MS: observed m/z: 1327.74 [M+H+], the same as that
of Por(Br)4).
The electrochemically polymerizable porphyrin/bithio-
phene monomer Por(BT)4 was synthesized from Por(Br)4 by
using the Suzuki–Miyaura coupling reaction with 2,2’-bithio-
phene-5-boronic acid pinacol ester in a moderate yield
(46%). The Stille coupling reaction from Por(Br)4 with 5-
tributlystannyl-2,2’-bithiophene ([PdACTHUNRTGNEUNG(PPh3)4], DMF) was
also applicable but resulted in a lower yield (approximately
20%). For another monomer PorZn(BT)4, the zinc insertion
reaction was conducted over four days (at 708C), which is
quite a long reaction time relative to that for common por-
phyrins (see below). Four bithiophene segments that diverge
from the porphyrin core yield a polymeric network through
an oxidative coupling reaction (poly
ACHTUNGTRNE[NGNU Por(BT)4] or poly-
ACHTUNGTRENNUNG
phyrin molecule are expected to shield a large p surface; as
can be seen from the computer generated model of
Por(BT)4 (Scheme 1), about 50% of the porphyrin surface is
indeed concealed. Furthermore, rotational fixation of the
meso-phenyl groups by the double straps will define the
polymerization direction, which would result in a three-di-
mensionally cross-linked structure.[36]
A meta-phenylene
linkage of the oligothiophene segments to the porphyrin
core will suppress electronic conjugation between them,[59]
which would allow the consideration that there is a negligi-
ble ground-state interaction between the BT segments and
porphyrin molecule. Por(BT) and Por(QT) were synthesized
from 2-methoxy-5-bromobenzaldehyde or 2-methoxy-5-(5’-
bromo-2,2’-bithien-5-yl)benzaldehyde, respectively, with 4-
butoxybenzaldehyde and pyrrole under the Adler condi-
tions. It is noteworthy that in the synthesis of Por(BT) and
Por(QT) we planned the porphyrin synthesis in the penulti-
mate step because the Adler condition employed two alde-
hyde starting materials, which potentially yields six different
kinds of porphyrins that are difficult to separate. Porphyrin
derivatives with one bromo reaction site (see the Experi-
Figure 1. Absorption spectral changes of a) PorACHTUNRGTNEUNG(OMe)4 and b) Por(Br)4
measured during the zinc insertion reaction: dotted lines are the spectra
measured after the reaction was completed. c) Plots of the absorption in-
tensity change at l=513 nm as a function of the reaction time: Por-
mental Section and Scheme 3 for Por(Br) and PorACTHNUGRTNEUNG(BTBr))
were isolated by column chromatography (silica gel, di-
chloromethane/acetone/hexane=2:1:8, twice) as second
AHCTUNTGREGUN(NN OMe)4 at RT (squares) and Por(Br)4 at 708C (circles). The reaction con-
versions were determined by using the 1H NMR spectroscopic data
shown in Figure 2.
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Design of Electrochemically Polymerizable Monomers
FULL PAPER
rin plane. Another evidence of the shielded porphyrin was
obtained by monitoring a zinc insertion reaction. In general,
this reaction is completed within 30 min at room tempera-
ture; for example, the absorption spectral change of Por-
708C, see the Experimental Section for details), a new set of
peaks assignable to a porphyrin derivative was observed to-
gether with the starting material (conversion=53%). A
sharper peak for a new b-pyrrole proton relative to the spec-
trum of Por(Br)4 arises from the conformational fixation of
the porphyrin plane by the zinc complexation. Plots of the
changes in absorption intensity as a function of the reaction
time is shown with the reaction conversions determined by
the 1H NMR spectroscopic data (Figure 1c). It took three
days at 708C for > 90% of Por(Br)4 to be converted into
the zinc complex (MALDI-TOF-MS: m/z: 1389.7
ACHTUNGTRENNUNG(OMe)4 on the addition of zinc acetate is shown in Fig-
ure 1a. The observed spectral change is consistent with that
observed through zinc complexation. In contrast, in the case
of Por(Br)4, we needed to heat up the reaction mixture to
see the same spectral changes (Figure 1b). Figure 2 shows
1
the H NMR spectral changes of Por(Br)4 measured during
the zinc insertion reaction. After a reaction time of 25 h (at
[PorZn(Br)4+H+];
calcd:
1389.1). It should be noted here
that the 1,12-dodecyl strap is
long enough not to curve the
porphyrin plane,[60] and is thus
ineffective toward the stability
of the metal complex in respect
of the thermodynamic factor.
These results clearly show that
both faces of the porphyrin
molecule are overlaid with the
bulky alkyl chain straps.
Spectroscopic measurements
of solid films: The isolation of
photofunctional molecules, thus
evidenced, should affect the
photophysical properties, par-
ticularly in the solid phase. To
probe this “isolation effect”, we
measured the absorption spec-
tra of PorACHTNUTRGNE(UGN OMe)4, Por(Br)4, and
Por(BT)4 in the film states (pre-
pared on a glass plate by spin-
coating; Figure 3). In the film
states, the absorption maxima
of these porphyrin derivatives
were red-shifted in comparison
with those measured in dilute
solutions of dichloromethane
(1ꢂ10À6 m): Dl=17.5, 12.5, and
10.5 nm
for
PorACHTUNGTRENNUNG(OMe)4,
Por(Br)4, and Por(BT)4, respec-
tively, namely smaller shifts
with the double straps. In addi-
tion, the average full width at
half maximum (FWHM) of the
Soret
(163 meV) was smaller than
that of Por(OMe)4 (228 meV);
band
of
Por(Br)4
AHCTUNGTRENNUNG
however, the FWHM of
Por(BT)4 (203 meV) was slight-
ly larger than expected, which
is due to the absorption overlap
of the bithiophene groups with
the Soret band of the porphyrin
(see Table 1 for the data on
Figure 2. 1H NMR spectra of Por(Br)4 measured during the zinc insertion reaction after the reaction time of
a) 1, b) 25, and c) 73 h.
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K. Sugiyasu and M. Takeuchi
Figure 4. Fluorescence spectra of the spin-coated films of PorACHTUNGTRENNUNG(OMe)4
(solid line) and Por(BT)4 (solid line with filled circle; lex =440 nm). Note
that the fluorescence intensities are normalized by the optical densities
of each film at the excitation wavelength.
by the alkyl chain straps, prevent the porphyrin molecules
from aggregation, thus significant fluorescence can be ach-
ieved even in the solid phase.
Light-harvesting studies: To elucidate an electronic inter-
action between the oligothiophene segments and the por-
phyrin core, the light-harvesting ability of Por(BT)4 was in-
vestigated in a dilute solution of dichloromethane (1ꢂ
10À6 m). We measured the UV/Vis absorption and steady-
state fluorescence spectra of the Por(BT)4 monomer and its
model components (Figures 5 and 6a, respectively). The ab-
sorption band around l=350 nm observed for Por(BT)4 is
attributed to the BT segments: a margin of molar absorptiv-
Figure 3. Absorption spectra of the spin-coated films (solid line) and
dilute solutions (dotted line) of a) Por
c) Por(BT)4.
ACHTUNGTREN(NUNG OMe)4, b) Por(Br)4, and
ities at this wavelength between Por(BT)4 and Por
about fourfold larger than the molar absorptivity of mBT,
thus indicating fourfold bithiophene-functionalization.
ACHTUNGRTEN(NUNG OMe)4 is
a
Table 1. Absorption spectroscopic data of the porphyrin derivatives.[a]
Furthermore, no additional distinctive absorption bands at-
tributable to a charge-transfer complex are observed, which
is indicative of an insignificant ground-state electronic inter-
action between these two chromophores in Por(BT)4. Rela-
tive fluorescence quantum yields FF of these compounds
were determined against rhodamine B (FF =0.97 in etha-
nol) for porphyrin derivatives and quaterthiophene (FF =
0.18 in benzene[62]) for mBT and mQT as standards: FF =
Compound
lmax in solution
[nm]
lmax in film
[nm]
Dlmax
FWHM in film
ACHTUNGTNER[NUNG meV]
[nm]
Por(OMe)4
T
417.0
422.0
422.0
419.5
423.5
425.0
434.5
438.0
437.0
432.0
434.0
438.0
17.5
16.0
15.0
12.5
10.5
13.0
228
228
n.d.[b]
163
203
193
Por(BT)
Por(QT)
Por(Br)4
Por(BT)4
PorZn(BT)4
[a] Determined for the Soret bands of the porphyrin. [b] Not determined
because of the significant overlap between the Soret band of the porphy-
rin and the absorption of the QT segment.
0.023, 0.023, 0.095, and 0.25 for PorACTHNUTRGEN(UNG OMe)4, Por(BT)4, mBT,
and mQT, respectively. When Por(BT)4 was photoexcited at
a wavelength (l=350 nm) at which selective excitation for
the BT segments is possible, the fluorescence from the bi-
thiophene units was completely quenched (>99% decrease
relative to a pure solution of mBT; Figure 6a). In addition,
the fluorescence of the porphyrin was intensified by fivefold
other porphyrin derivatives). These results indicate that in
the solid films, the double strap prevents the porphyrin mol-
ecule from self-aggregation. Consequently, the fluorescence
of the Por(BT)4 films was about twice as strong as that of
in comparison with the fluorescence from PorACHTNUTRGNEG(UN OMe)4 (lex =
Por
(OMe)4 (lex =440 nm; Figure 4). Note that the fluores-
350 nm; Figure 6a inset). These results indicate that efficient
energy transfer from the bithiophene segments to the por-
phyrin molecule takes place in the Por(BT)4 system. The ex-
cence intensities were normalized by the optical densities of
each film at the excitation wavelength. The improvement in
photoluminescent efficiency in the solid phase is comparable
with that confirmed for cyclodextrin-threaded conjugated
polyrotaxanes, “insulated conjugated polymers”, which
shows better electroluminescence efficiency than bare conju-
gated polymers.[61] We expect that not only the shielding
around the p plane of the porphyrin but also the three-di-
mensional persistent structure, both of which are conferred
citation spectra of Por(BT)4 and PorACHTNUGTRNEUNG(OMe)4 monitored at
l=650 nm further demonstrated the contribution of BT to
the fluorescence of porphyrin (Figure 6b). The same light-
harvesting phenomenon was also observed for the
PorZn(BT)4 system (see Figure S3 in the Supporting Infor-
mation). In fact, the fluorescence spectrum of mBT (lex =
400–450 nm) overlaps well with the Soret absorption band
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Design of Electrochemically Polymerizable Monomers
FULL PAPER
of the porphyrin molecules. Furthermore, this light-harvest-
ing effect was confirmed with
a spin-coated film of
Por(BT)4; a quantitative quenching of the fluorescence of
BT segments and an enhanced fluorescence of porphyrin by
about 5.2-fold were observed (lex =350 nm; see Figure S4 in
the Supporting Information). As mentioned earlier
(Figure 4), a photoluminescence improvement of about two-
fold in the solid phase (versus PorACHTNURGTNE(UNG OMe)4, lex =440 nm) is
indebted to the isolation by the double strap, therefore, an
increase of approximately 260% out of 520% would rough-
ly be attributed to the light-harvesting effect in the film
state.
To prospect the light-harvesting ability of the poly-
AHCTUNGTREG[NUNN Por(BT)4] film, the fluorescence and excitation spectra of
Por(QT) and Por(BT) (FF =0.036 and 0.035, respectively)
were also measured. Although the spectral overlaps between
the fluorescence of the donors (i.e., BT or QT) and the ab-
sorption of porphyrin are different, both systems showed
quantitative energy transfer (see Figures S5 and S6 in the
Supporting Information). For example, selective excitation
of the QT segment in Por(QT) resulted in no fluorescence
from QT but yielded an enhanced fluorescence by 27-fold
from the porphyrin core relative to that of PorACHTNUTRGNEG(UN OMe)4 (lex =
440 nm). In fact, the excitation spectrum of Por(QT) re-
vealed a significant contribution of the absorption by QT to
the fluorescence from porphyrin (this finding can obviously
be evidenced by the broad range of excitation at l=440~
490 nm, although the absorption peaks of porphyrin and QT
are partially overlapping; see Figure S6b in the Supporting
Information). Considering that the fluorescence quantum
yield of Por(QT) is almost the same as that of Por(BT), ad-
ditional quenching by the contribution of electron transfer
(i.e., a nonradiative process) between QT and the porphyrin
core is negligible relative to Por(BT), regardless of the dif-
ference in the relative HOMO–LUMO energies of BT and
QT with respect to those of porphyrin molecule.[15,22] These
results indicate that our molecular design of the energy
donor–acceptor conjunction, such as the distance between
these two components and the orientation of their transition
dipole, is appropriate.
Figure 5. Absorption spectra of a) mBT (solid line with open circle) and
mQT (solid line with cross), b) PorACHTNUGTRNEUNG(OMe)4 (solid line) and Por(BT)4
(solid line with filled circle), and c) Por(BT) (slash line with open circle)
and Por(QT) (dotted line with cross) in a dilute solution of dichlorome-
thane (1ꢂ10À6 m).
Electrochemical polymerization and characterization:
Cyclic voltammograms of Por(BT)4 and PorZn(BT)4 were
measured in an argon atmosphere with 100 mm tetrabutyl-
ammonium hexafluorophosphate (TBAPF6) in dichlorome-
thane ([monomer]=0.5 mm). When the oxidation potential
was swept up to 0.56 V (versus the ferrocene/ferrocenium
redox couple (Fc/Fc+)), reversible redox waves of each por-
phyrin molecule were observed at E1/2 =0.46 and 0.39 V for
Por(BT)4 and PorZn(BT)4, respectively (Figure 7a,c). This
result implies that the redox potentials of the incorporated
dyes can easily be controlled by metal complexation, which
will enable fine-tuning of the electronic properties of the
materials. Further repeated potential sweeps between À0.01
and 0.69 V gradually yielded quasi-reversible redox waves
(Figure 7b,d), thus indicating electrochemical polymeri-
zation processes. The growth of the polymer network is re-
flected by a proportional increase in the current to the po-
Figure 6. a) Fluorescence and b) excitation spectra of PorACHTNUTRGNEUNG(OMe)4 (solid
line), Por(BT)4 (solid line with filled circle), and mBT (solid line with
open circle) in a dilute solution of dichloromethane. Inset shows magni-
fied fluorescence spectra: [PorACHTUNGTRNEUNG
(OMe)4]=[Por(BT)4]=1ꢂ10À6 m; [mBT]=
4ꢂ10À6 m; lex =350, lmon =650 nm; RT.
Chem. Eur. J. 2009, 15, 6350 – 6362
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K. Sugiyasu and M. Takeuchi
Figure 7. Cyclic voltammograms of Por(BT)4 and PorZn(BT)4 measured up to a,c) 0.56 and b,d) 0.69 V (15 scans). [monomers]=0.5 mm, [TBAPF6]=
100 mm, dichloromethane, 100 mVsÀ1, RT.
tential cycles. New redox waves at around E1/21 =0.40 V and
E1/22 =0.55 V correspond to the constructed QT/QT+· and
QT+·/QT2+ redox couples, respectively, accompanied with
the superimposed redox processes of the porphyrin; note
that redox potentials of the components (i.e., BT, QT, and
porphyrin) can affect each other in the film as demonstrated
by the cyclic voltammogram of Por(QT) (see Figure S7 in
the Supporting Information), therefore the cyclic voltammo-
grams of these films become somewhat structureless.
(QT/porphyrin=1.6:1). This result indicates that there are
starting material bithiophene defects that can still function
as the energy donor in the network structure. The absorp-
tion spectrum of the polyACTHNUTRGNE[UNG Por(BT)4] film deposited on an
indium tin oxide (ITO)-coated glass electrode indeed evi-
denced the existence of the BT (l=320–380 nm) and con-
structed QT (l=360–480 nm) segments (Figure 9). More-
over, the four characteristic Q bands at l=517, 550, 590,
and 645 nm are identical to those of free base porphyrin (no
peak shift relative to those of the Por(BT)4 spin-coated
film). These results indicate that the porphyrin molecule is
“isolated” as demonstrated with the spin-coated films of the
monomer without any decomposition or protonation (see
Figure S8 in the Supporting Information for the absorption
The obtained polyACTHNUTRGENN[UG Por(BT)4] and polyACHTUNTGNER[NUGN ZnPor(BT)4] films
were electrochemically characterized in an electrolyte solu-
tion free from the monomer. The linear scan-rate dependen-
ces of these films demonstrate that the redox process origi-
nates from electrode-bound redox-active species (Figur-
e 8a,b,d,e). The films were uniform and adhesive to the
working electrode, probably due to the highly cross-linked
network structure. Differential potential voltammetry
(DPV) of the obtained films gave evidence of the incorpora-
tion of the porphyrin molecule. Although the oxidation
peaks of the incorporated porphyrins (Figure 7a,c and Fig-
ure 8c,f; solid line) were concealed beneath those of the
constructed QT segments, the reduction peaks of which
were observable in DPV as also observed for the monomer
solution at around À2 V (Figure 8c,f: dotted line). A molar
ratio of 4:1 between the bithiophene segments and the por-
phyrin core in the monomers can ideally yield polymeric
network films composed of the constructed QT segments
and the porphyrin in a 2:1 ratio. However, the area of the
oxidation peak of the films relative to the reduction peak of
the porphyrin was slightly smaller than this expected ratio
spectrum of the polyACHTNUGRTNE[NUG PorZn(BT)4] film that shows a Q band
at l=556 nm, which is identical to that of the PorZn(BT)4
film). It should be noteworthy that electrochemical polymer-
ization of bithiophene-functionalized metal-free porphyrins
is in most cases unsuccessful due to the interference of the
porphyrin nitrogen atoms with the oligothiophene radical
cations.[18] It seems that the double strap could also play an
important role in protecting the porphyrin molecule against
the electrochemical polymerization conditions. As proved
from the model studies mentioned earlier, the polymeric
films can harvest a wide range of irradiation light (l=320–
650 nm) into the porphyrin core and suppress undesired de-
activation processes. However, the electrochemically poly-
merized films were nevertheless nonfluorescent. One main
reason for this behavior should be that porphyrin molecules
have intrinsically low fluorescence quantum yields. Other
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Chem. Eur. J. 2009, 15, 6350 – 6362

Design of Electrochemically Polymerizable Monomers
FULL PAPER
Figure 8. Cyclic voltammograms of the a) poly
160, and 200 mVsÀ1 from inwards to outwards. Plots of the observed current as a function of the scan rate for the b) poly
[PorZn(BT)4] films. DPVs of the monomers in solution (solid line) and the corresponding polymer films (dotted line) for the c) Por(BT)4 and
ACHUTGTNRENU[NG Por(BT)4] and d) polyACTHUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
f) PorZn(BT)4 systems.
possible reasons for the fluorescence quenching factors, such
as the effect of the band structure of the ITO electrode (see
Figure S9 in the Supporting Information), the electrolyte
used, and the presence of a trace amount of oxidized spe-
cies, would also need to be considered. We will therefore
focus on the development of our strategy by making use of
other functional dyes and the detailed optimization of the
electrochemical polymerization conditions.
meric material by the double strap, which can prevent the
large p-conjugated system from self-aggregation; 2) the con-
junctions composed of functional dyes and conducting poly-
mer backbones are designed in such a way that there is an
effective electronic interaction between them in spite of the
“isolation” of the incorporated dyes. These two distinctive
features were evidenced by using 1H NMR, UV/Vis, and
fluorescence spectroscopic methods. These results demon-
strated that with our strategy, spatial isolation of the func-
tional dyes in the materials and effective electronic interac-
tion between the dye and the polymer backbones can both
be achieved. Hence, the concept described herein may ad-
dress the “tradeoff” that often haunts dye-functionalized
conducting polymers. The photo- and electrochemical char-
acteristics were demonstrated by utilizing two different
monomers, Por(BT)4 and PorZn(BT)4, with different redox
Conclusions
Herein, a new concept in monomer design toward dye-func-
tionalized conducting polymeric materials has been de-
scribed. The main strategies of our monomer design are
1) the functional dyes are spatially isolated within the poly-
Chem. Eur. J. 2009, 15, 6350 – 6362
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6359

K. Sugiyasu and M. Takeuchi
AXIMA-CFR Plus and SHIMADZU LCMS-IT-TOF workstation, re-
spectively. The UV/Vis absorption and fluorescence spectra were ob-
tained on Hitachi U-2900 and Hitachi F-7000 spectrophotometers, re-
spectively. Relative fluorescence quantum yields were determined using
quaterthiophene (FF =0.18 in benzene[62]) for mBT and mQT and rhoda-
mine B (FF =0.97 in ethanol) for PorACHTNUGTRNEUNG(OMe)4, Por(BT)4, PorZn(BT)4,
Por(BT), and Por(QT) as standards. The melting points were determined
on a Yanako NP-500P micro melting-point apparatus. All the electro-
chemical measurements were conducted with an Eco Chemie AUTO-
LAB PGSTAT12 potentiostat with a quasi-internal Ag/Ag+ reference
electrode (Ag wire submersed in a solution of 0.01m AgNO3 and 0.1m
nBu3NPF6 in MeCN). Cyclic voltammograms were recorded with a plati-
num button electrode or ITO-coated glass electrode as the working elec-
trode and a platinum-coil counter electrode. Molecular modeling was
performed using ChemBio3D Ultra software available from Cambridge-
Soft. Model compounds were synthesized according to Scheme 3. Mono-
mer mBT was synthesized through the Suzuki–Miyaura coupling reaction
from 4-ethylhexyloxyiodobenzene and 2,2’-bithiophene-5-boronic acid pi-
nacol ester under the same reaction conditions as for the synthesis of
Por(BT)4 (see below). Selective bromination at the a position of mBT
using NBS[68], thus yielding mBTBr, followed by lithiation and subse-
quent quenching with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lane gave 5-(4-ethylhexyloxyphenyl)-2,2’-bithiophene-5’-boronic acid pi-
nacol ester (mBTB).[69] The obtained intermediates mBTBr and mBTB
were further coupled through the Suzuki–Miyaura coupling reaction,
thus yielding mQT. Compounds BTACHTNUTRGENN(UG CHO) and BTCAHUTNGTREN(NUNG CHO)Br were syn-
thesized by using the same procedure for the synthesis of mBT and
mBTBr, respectively, from 2-methoxy-5-bromobenzaldehyde as a starting
material. For the syntheses of mono-oligothiophene-functionalized por-
phyrins (Scheme 3), Por(Br) and Por
the Adler conditions[53] from 2-methoxy-5-bromobenzaldehyde and 2-me-
thoxy-5-(5’-bromo-2,2’-bithien-5-yl)benzaldehyde (BT(CHO)Br), respec-
ACHTUNGTRNE(NUNG BTBr) were first synthesized under
AHCTUNGTRENNUNG
tively, with 4-butoxybenzaldehyde and pyrrole. Monofunctionalized por-
phyrins were isolated by column chromatography (silica gel, dichlorome-
thane/acetone/hexane=2:1:8) to remove other byproducts, such as tetra-
kis(4-butoxyphenyl)porphyrin.
Figure 9. Absorption spectra of the a) polyACTHNUTRGEN[UNG Por(BT)4] film and
b) Por(BT)4 spin-coated film (the same as Figure 3c), and c) dilute solu-
tion of mBT (solid line with open circle) and mQT (solid line with cross)
in dichloromethane (the same as the parts of Figure 5). In the schematic
representation (inset cartoons), purple square=porphyrin, red rod=QT
segment, green rod=BT segment, and gray bar=alkyl chain strap.
Synthesis of Por(BT): A mixture of Por(Br) (0.4 g, 0.43 mmol), 2,2’-bi-
thiophene-5-boronic acid pinacol ester (0.18 g, 0.62 mmol) and sodium
carbonate (0.16 g, 1.5 mmol) in toluene (30 mL), ethanol (7.5 mL), and
water (7.5 mL) was bubbled with argon for 1 h. Tetrakis(triphenylphos-
phine)palladium(0) (10 mol%/Por(Br)) was added to the solution and
the mixture was heated to reflux for 5 h. After cooling, the reaction mix-
ture was washed with water and the organic layer was dried over sodium
sulfate. The solvent was evaporated and the obtained solid was purified
by column chromatography (silica gel, hexane/chloroform=1:1–0:1) to
potentials. At the beginning in applying these monomers, we
confirmed that electrochemical polymerization of both of
them is effective and gives robust films in which the porphy-
rin molecules are incorporated without any decomposition
and protonation. This molecular design concept based on
the incorporation of “isolated” functional molecules on con-
ducting polymers is closely related to the “insulated molecu-
lar wires” that have already found unique applications in ef-
ficient electroluminescence and ultrasensitive chemosen-
sors,[61,63–67] thus we will progress accordingly by taking ad-
vantage of our materials.
give Por(BT) as
a purple powder (0.38 g, 87%). M.p. 158~1598C;
1H NMR (600 MHz, CDCl3, TMS): d=À2.70 (s, 2H), 1.09–1.12 (m, 9H),
1.63–1.69 (m, 6H), 1.94–1.99 (m, 6H), 3.62 (s, 3H), 4.24–4.27 (m, 6H),
6.98 (dd, J=3.6, 4.2 Hz, 1H), 7.12 (d, J=4.2 Hz, 1H), 7.14 (dd, J=1.2,
4.2 Hz, 1H), 7.17 (dd, J=1.2, 4.2 Hz, 1H), 7.23 (d, J=3.6 Hz, 1H), 7.27–
7.28 (m, 6H), 7.33 (d, J=8.4 Hz 1H), 7.99 (dd, J=2.4, 8.4 Hz, 1H), 8.08–
8.12 (m, 6H), 8.29 (d, J=2.4 Hz, 1H), 8.83 (d, J=6.4 Hz, 2H), 8.86 ppm
(m, 6H); UV/Vis (dichloromethane): lmax (e)=422 (5.0ꢂ105), 517 (2.1ꢂ
104), 554 (1.2ꢂ104), 593 (7.0 ꢂ103), 649 nm (7.0ꢂ103 molÀ1 dm3 cmÀ1);
fluorescence spectrum (dichloromethane) lem (FF)=657 nm (0.035);
MALDI-TOF-MS: m/z: calcd for C65H60N4O4S2: 1024.41; found: 1024.41.
Synthesis of Por(QT): The same procedure for the synthesis of Por(BT)
was applied using mBTB and Por(BT)Br as starting materials. M.p. 227–
2288C; 1H NMR (600 MHz, CDCl3, TMS): d= À2.70 (s, 2H), 0.91–0.94
(m, 6H), 1.09–1.22 (m, 9H), 1.31–1.48 (m, 8H), 1.65–1.69 (m, 6H), 1.73
(m, 1H), 1.94–1.99 (m, 6H), 3.63 (s, 3H), 3.86 (dd, J=2.4, 5.4 Hz, 2H),
4.24–4.27 (m, 6H), 6.90 (d, J=8.4 Hz, 2H), 7.04 (m, 4H), 7.09 (d, J=
1.2 Hz, 2H), 7.12 (d, J=3.6 Hz, 1H), 7.24 (d, J=3.6 Hz, 1H), 7.27–7.29
(m, 6H), 7.34 (d, J=8.4 Hz, 2H), 7.49 (d, J=8.4 Hz, 2H), 7.99 (dd, J=
2.4, 8.4 Hz, 1H), 8.10–8.12 (m, 6H), 8.29 (d, J=2.4 Hz, 1H), 8.83 (d, J=
4.2 Hz, 2H), 8.86 ppm (m, 6H); UV/Vis (dichloromethane): lmax (e)=422
(5.2ꢂ105), 517 (2.3ꢂ104), 554 (1.3ꢂ104), 593 (7.0ꢂ103), 649 nm (7.0ꢂ
103 molÀ1 dm3 cmÀ1); fluorescence (dichloromethane): lem. (FF)=657 nm
Experimental Section
General: Air- and water-sensitive synthetic manipulations were per-
formed in an argon atmosphere using standard Schlenk techniques. All
the chemicals were purchased from Aldrich, Kanto Chemical Co., or
Wako and used as received. The NMR spectra were recorded on a
Bruker Biospin DRX-600 spectrometer, and all the chemical shifts are
referenced to (CH3)4Si (TMS; d=0 ppm for 1H) or residual CHCl3 (d=
77 ppm for 13C). The MALDI-TOF mass spectra and high-resolution
(HR) LCMS-TOF mass spectra were obtained with SHIMADZU
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Design of Electrochemically Polymerizable Monomers
FULL PAPER
(0.036); MALDI-TOF-MS: m/z: calcd for C87H84N4O5S4: 1392.53; found:
1393.72.
1.2, 4.8 Hz, 4H), 7.24 (d, J=4.2, 4H), 7.29 (d, J=9.0, 4H), 7.97 (dd, J=
2.4, 9.0 Hz, 4H), 8.38 (d, J=2.4, 4H), 8.84 ppm (s, 8H); 13C NMR
(150 MHz, CDCl3): d=25.78, 27.16, 27.35, 28.42, 28.89, 68.91, 111.87,
115.10,122.93, 123.28, 124.05, 124.62, 125.26, 127.79, 132.04, 132.59,
135.78, 137.66, 143.29, 159.18 ppm; UV/Vis (dichloromethane): lmax (e)=
423 (5.1ꢂ105), 515 (3.2ꢂ104), 548 (1.2ꢂ104), 590 (1.2ꢂ104), 645 nm (6.0ꢂ
103 molÀ1 dm3 cmÀ1); fluorescence (dichloromethane): lem (FF)=650 nm
(0.023); MALDI-TOF-MS: m/z: calcd for C87H84N4O5S4: 1392.53; found:
1393.72; MALDI-TOF-MS: m/z: calcd for C100H90N4O4S8: 1667.48;
found: 1668.51.
Synthesis of PorZn(BT)4: Zinc acetate dihydrate (264 mg, 1.2ꢂ10À4 mol,
20 equiv/Por(Br)4) in methanol (7.6 mL) was added to a solution of
Por(BT)4 (100 mg, 6.0ꢂ10À5 mol) in CHCl3 (38 mL; CHCl3/methanol=
5:1), and the solution was heated to reflux at 708C for 4 days. The reac-
tion mixture was diluted with CHCl3, washed with water, and dried over
sodium sulfate. The solvent was evaporated and the obtained solid was
purified by column chromatography (silica gel, hexane/chloroform=1:1–
0:1) to give PorZn(BT)4 as a pink powder (102 mg, quant.). M.p. 217–
2198C; 1H NMR (600 MHz, CDCl3, TMS): d= À0.33 (m, 16H), 0.05–
0.88 (m, 16H), 0.95 (m, 8H), 3.96 (t, J=5.4 Hz, 8H), 6.97 (dd, J=3.6,
5.4 Hz, 4H), 7.13 (dd, J=1.2, 3.6 Hz, 4H), 7.14 (d, J=3.6 Hz, 4H), 7.17
(dd, J=1.2, 4.2 Hz, 4H), 7.25 (d, J=4.2 Hz, 4H), 7.29 (d, J=8.4 Hz, 4H),
7.97 (dd, J=2.4, 8.4 Hz, 4H), 8.38 (d, J=2.4, 4H), 8.93 ppm (s, 8H);
13C NMR (150 MHz, CDCl3): d=25.55, 27.07, 27.28, 28.20, 28.77, 68.94,
111.96, 116.08, 122.88, 123.24, 124.03, 124.62, 125.19, 126.67, 127.78,
131.58, 132.44, 132.73, 135.71, 137.68, 143.40, 150.37, 159.20 ppm; UV/Vis
(dichloromethane): lmax (e)=425 (4.8ꢂ105), 549 (2.4ꢂ104), 585 nm (2.0ꢂ
103 molÀ1 dm3 cmÀ1); fluorescence (dichloromethane): lem (FF)=653 nm
(0.023); MALDI-TOF-MS: m/z: calcd for C100H90N4O4S8Zn: 1729.38;
found: 1730.82.
Synthesis of 1: A solution of 5-bromosalicylaldehyde (30.6 g, 152 mmol)
and potassium carbonate (63.0 g, 456 mmol) in DMF (300 mL) was
stirred at 708C for 1 h, and 1,12-dibromododecane (20.0 g, 61 mmol) was
added. The reaction mixture was further stirred at 708C for 10 h. After
cooling to room temperature, the reaction mixture was diluted with di-
chloromethane and the insoluble materials were filtered off. The filtrate
was concentrated, and the precipitate was obtained with the addition of
methanol. A solution of the obtained solid in dichloromethane was
washed with 0.1m sodium hydroxide aqueous solution and dried over
magnesium sulfate. The filtrate was evaporated and the obtained solid
was purified by reprecipitation from dichloromethane with methanol to
give
1 as a
white powder (29.8 g, 86%). M.p. 96–978C; 1H NMR
(600 MHz, CDCl3, TMS): d=1.29–1.37 (m, 12H), 1.47 (m, 4H), 1.84 (m,
4H), 4.06 (t, J=6.3 Hz, 4H), 6.88 (d, J=9.0 Hz, 2H), 7.60 (dd, J=3.0,
9.0 Hz, 2H), 7.91 (d, J=3.0 Hz, 2H), 10.42 ppm (s, 2H); 13C NMR
(150 MHz, CDCl3): d=25.97, 28.95, 29.25, 29.47, 68.95, 113.21, 114.54,
126.12, 130.79, 138.23, 160.41. 188.44 ppm; HRMS: m/z: calcd for
C26H32Br2O4Na: 591.0547 [M+Na]+; found: 591.0444.
Synthesis of 2: Compound 1 (16.97 g, 29.8 mmol) and pyrrole (100 g,
1.49 mol) were dissolved in dichloromethane (200 mL), the solution was
purged with argon for 1 h and trifluoroacetic acid (0.34 mL, 4.47 mmol)
was added. The reaction mixture was stirred at room temperature for 5 h
and washed with 0.1m aqueous solution of sodium hydroxide. The organ-
ic layer was dried over sodium sulfate and the filtrate was evaporated to
remove excess pyrrole. The crude material was purified by column chro-
matography (silica gel, hexane/dichloromethane=1:2~0:1, containing
1% triethylamine). The product was further purified by reprecipitation
from dichloromethane with hexane to give 2 as a white powder (8.0 g,
34%). M.p. 148–1508C; 1H NMR (600 MHz, CDCl3, TMS): d=1.28 (m,
16H), 1.64 (m, 4H), 3.88 (t, J=6.6 Hz, 4H), 5.73 (s, 2H), 5.90 (m, 4H),
6.13 (m, 4H), 6.65 (m, 4H), 6.74 (d, J=8.4 Hz, 2H), 7.20 (d, J=2.4 Hz,
2H), 7.29 (dd, J=2.4, 8.4 Hz, 2H), 8.05 ppm (s, 4H); 13C NMR
(150 MHz, CDCl3): d=25.87, 29.15, 29.31, 29.49, 29.53, 38.03, 68.82,
106.85, 108.39, 113.02, 113.90, 116.89, 130.77, 131.66, 132.07, 133.41,
155.36 ppm; HRMS: m/z: calcd for C42H48Br2N4O2K: 839.1975 [M+K]+;
found: 839.1628.
Zinc insertion for Por(Br)4 and PorACHTNUTRGNENUG(OMe)4: Because of the simplicity of
the 1H NMR spectrum in the aromatic region, Por(Br)4 was used instead
of Por(BT)4 to evaluate a zinc insertion reaction of a doubly strapped
porphyrin. Zinc acetate dihydrate (83 mg, 3.8ꢂ10À4 mol, 10 equiv/
Por(Br)4) in methanol (7.6 mL) was added to a solution of Por(Br)4
(50 mg, 3.8ꢂ10À5 mol) in CHCl3 (38 mL; CHCl3/methanol=5/1), and the
solution was heated to reflux at 708C. After a period of time (see
Figure 2), a small amount of the reaction mixture was sampled and the
solvent was evaporated. The solid materials were subjected to 1H NMR
and absorption spectroscopic analysis without purification. In the case of
Synthesis of Por(Br)4: Compound 1 (0.82 g, 1.43 mmol) and 2 (1.15 g,
1.43 mmol) were dissolved in CHCl3 (1500 mL) and ethanol (11 mL) and
the solution was purged with argon for 2 h. Boron trifluoride diethyl
etherate (0.25 mL, 2.03 mmol) was added to the solution under light
shielding, the mixture was stirred for 3 h at room temperature, and chlor-
anil (1.2 g, 4.88 mmol) was added. The solution was further stirred at
room temperature for 2 h. The obtained black solution was passed
through silica gel and the filtrate was evaporated. The solid material was
further purified by column chromatography (silica gel, hexane/chloro-
form=2:1~1:1) to yield Por(Br)4 as a purple powder (0.46 g, 25%). M.p.
176–1788C; 1H NMR (600 MHz, CDCl3, TMS): d=À2.86 (s, 2H), À0.13
(m, 8H), 0.09 (m, 16H), 0.15 (m, 8H), 0.89 (m, 8H), 3.90 (t, J=5.1 Hz,
8H), 7.15 (d, J=9.0 Hz, 4H), 7.84 (dd, J=2.4, 9.0 Hz, 4H), 8.19 (d, J=
2.4, 4H), 8.77 ppm (s, 8H); 13C NMR (150 MHz, CDCl3): d=26.31, 27.19,
27.58, 28.68, 29.03, 69.04, 111.41, 112.95, 114.41, 132.40, 133.20, 137.62,
140.82, 158.52 ppm; MALDI-TOF-MS: m/z: calcd for C68H70Br4N4O4:
1326.21; found: 1326.60.
PorACHTNUTRGNENG(U OMe)4, the zinc insertion reaction was complete within 30 min at
room temperature, as confirmed by absorption spectral change.
Film preparation and solid-state absorption and fluorescence spectral
measurements: Solutions of the compounds in dichloromethane (2 mm)
were spin-coated onto glass plates (1000 rpm for 20 s). Ten films were
prepared for each compound and the absorption spectra were measured.
The obtained FWHMs and peak shifts of the absorption spectra are
given as average values and were reproducible within Æ1 nm. The fluo-
rescence spectra of the spin-coated films were measured with the solid-
sample holder for the Hitachi F7000 spectrophotometer and all the fluo-
rescence intensities (see Figures S3 and S8 in the Supporting Information
and Figure 4) were normalized by the optical densities of each film at the
excitation wavelengths.
Synthesis of Por(BT)4: A mixture of Por(Br)4 (0.3 g, 0.23 mmol), 2,2’-bi-
thiophene-5-boronic acid pinacol ester (0.39 g, 1.34 mmol), and sodium
carbonate (0.51 g) in toluene (30 mL), ethanol (7.5 mL), and water
(7.5 mL) was bubbled with argon for 1 h. Tetrakis(triphenylphosphine)-
palladium(0) (10 mol%/Por(Br)4) was added to the solution and the mix-
ture was refluxed for 5 h. After cooling, the reaction mixture was washed
with water and the organic layer was dried over sodium sulfate. The sol-
vent was evaporated and the obtained solid was purified by column chro-
matography (silica gel, hexane/chloroform=1:1–0:1) to give Por(BT)4 as
a purple powder (0.17 g, 46%). M.p. 220~2218C; 1H NMR (600 MHz,
CDCl3, TMS): d=À2.59 (s, 2H), À0.20 (m, 8H), À0.13 (m, 8H), 0.13 (m,
16H), 0.95 (m, 8H), 3.95 (t, J=5.1 Hz, 8H), 6.98 (dd, J=3.6, 4.8 Hz,
4H), 7.14 (dd, J=1.2, 3.6 Hz, 4H), 7.14 (d, J=4.2 Hz, 4H), 7.17 (dd, J=
Acknowledgements
This work was partially supported by KAKENHI (No. 20750097) for K.S.
and the “Nanotechnology Network Project” of the Ministry of Educa-
tion, Culture, Sports, Science, and Technology Japan (MEXT). The au-
thors thank Dr. K. Isozaki (NIMS) and R. Shomura (NIMS) for the mass
spectral measurements. The authors are grateful to Prof. T. Konishi (Shi-
baura Institute of Technology), Dr. T. Nakanishi (MPI-NIMS Interna-
tional Joint Laboratory), and Dr. T. Ikeda (Kyushu University) for valua-
ble comments.
Chem. Eur. J. 2009, 15, 6350 – 6362
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6361

K. Sugiyasu and M. Takeuchi
[34] L. Huchet, S. Akoudad, J. Roncali, Adv. Mater. 1998, 10, 541.
[35] H. C. Ko, S. Kim, H. Lee, B. Moon, Adv. Func. Mater. 2005, 15, 905.
[36] P.-L. Vidal, B. Divisia-Blohorn, G. Bidan, J. L. Hazemann, J.-M.
Kern, J.-P. Sauvage, Chem. Eur. J. 2000, 6, 1663.
[37] K. Sugiyasu, T. M. Swager, Bull. Chem. Soc. Jpn. 2007, 80, 2074.
[38] T. M. Swager, Acc. Chem. Res. 1998, 31, 201.
[39] R. Jakubiak, C. J. Collison, W. C. Wan, L. J. Rothberg, J. Phys.
Chem. A 1999, 103, 2394.
[40] M. Fujitsuka, A. Masuhara, H. Kasai, H. Oikawa, H. Nakanishi, O.
Ito, T. Yamashiro, Y. Aso, T. Otsubo, J. Phys. Chem. B 2001, 105,
9930.
[1] Handbook of Conducting Polymers, (Eds.: T. A. Skotheim, J. R.
Reynolds), Taylor & Francis, Milton Park, 2006.
[2] J. H. Burroughes, C. A. Jones, R. H. Friend, Nature 1988, 335, 137.
[3] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.
Mackay, R. H. Friend, P. L. Burns, A. B. Holmes, Nature 1990, 347,
539.
[4] N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, A. B.
Holmes, Nature 1993, 365, 628.
[5] N. S. Sariciftci, L. Smilowitz, A. J. Heeger, F. Wudl, Science 1992,
258, 1474.
[6] G. Yu, J. Gao, J. C. Hemmelen, F. Wudl, A. J. Heeger, Science 1995,
270, 1789.
[7] S. Gꢁnes, H. Neugebauer, N. S. Sariciftci, Chem. Rev. 2007, 107,
1324.
[8] X. Yang, J. Loos, Macromolecules 2007, 40, 1353.
[9] A. P. Kulkarni, C. J. Tonzola, A. Babel, S. A. Jenekhe, Chem. Mater.
2004, 16, 4556.
[10] F. Hide, A. M. Dꢃaz-Garcꢃa, B. J. Schwartz, A. J. Heeger, Acc. Chem.
Res. 1997, 30, 430.
[41] L. M. Herz, C. Silva, R. H. Friend, R. T. Phillips, S. Setayesh, S.
Becker, D. Marsitsky, K. Mꢁllen, Phys. Rev. B 2001, 64, 195203.
[42] H.-H. Sung, H.-C. Lin, Macromolecules 2004, 37, 7945.
[43] A. P. Kulkarni, S. A. Jenekhe, Macromolecules 2003, 36, 5285.
[44] T. Konishi, A. Ikeda, M. Asai, T. Hatano, S. Shinkai, M. Fujitsuka,
O. Ito, Y. Tsuchiya, J.-i. Kikuchi, J. Phys. Chem. B 2003, 107, 11261.
[45] F. Montilla, R. Esquembre, R. Gꢅmez, R. Blanco, J. L. Segura, J.
Phys. Chem. C 2008, 112, 16668.
[46] H. Imahori, J. Mater. Chem. 2007, 17, 31.
[11] J. Roncali, Chem. Rev. 1997, 97, 173.
[47] H. Imahori, Y. Sakata, Adv. Mater. 1997, 9, 537.
[48] T. Konishi, M. Horie, T. Wada, S. Ogasawara, J.-i. Kikuchi, A.
Ikeda, J. Porphyrins Phthalocyanines 2007, 11, 342.
[49] J. A. A. Elemans, N. R. van Hameren, R. J. M. Nolte, A. E. Rowan,
Adv. Mater. 2006, 18, 1251.
[50] F. Wuerthner, M. S. Vollmer, F. Effenberger, P. Emele, D. U. Meyer,
H. Port, H. C. Wolf, J. Am. Chem. Soc. 1995, 117, 8090.
[51] M. S. Vollmer, F. Wꢁrthner, F. Effenberger, P. Emele, D. U. Meyer,
T. Stꢁmpfig, H. Port, H. C. Wolf, Chem. Eur. J. 1998, 4, 260.
[52] T. Otsubo, Y. Aso, K. Takimiya, J. Mater. Chem. 2002, 12, 2565.
[53] J. W. Dirks, G. Underwood, J. C. Matheson, D. Gust, J. Org. Chem.
1979, 44, 2551.
[54] J. S. Lindsey, R. W. Wanger, J. Org. Chem. 1989, 54, 828.
[55] B. J. Littler, Y. Ciringh, J. S. Lindsey, J. Org. Chem. 1999, 64, 2864.
[56] B. Stꢄubli, H. Fretz, U. Piantini, W.-D. Woggon, Helv. Chim. Acta
1987, 70, 1173.
[12] M. Kertesz, C. H. Choi, S. Yang, Chem. Rev. 2005, 105, 3448.
[13] Only the functionalized conducting polymer systems based on elec-
trochemical polymerization are cited in ref. [14–36].
[14] F. Bedioui, J. Devynck, C. Bied-Charreton, Acc. Chem. Res. 1995,
28, 30.
[15] T. Shimidzu, Synth. Met. 1996, 81, 235.
[16] B. Ballarin, S. Masiero, R. Seeber, D. Tonelli, J. Electroanal. Chem.
1998, 449, 173.
[17] M. Takeuchi, T. Shioya, T. M. Swager, Angew. Chem. 2001, 113,
3476; Angew. Chem. Int. Ed. 2001, 40, 3372.
[18] M. Schꢄferling, P. Bꢄuerle, J. Mater. Chem. 2004, 14, 1132.
[19] K. Yamashita, M. Ikeda, M. Takeuchi, S. Shinkai, Chem. Lett. 2003,
32, 264.
[20] R. P. Kingsborough, T. M. Swager, Angew. Chem. 2000, 112, 3019;
Angew. Chem. Int. Ed. 2000, 39, 2897.
[21] T. Muto, T. Temma, M. Kimura, K. Hanabusa, H. Shirai, Chem.
Commun. 2000, 1649.
[57] S. Shanmugathasan, C. Edwards, R. W. Boyle, Tetrahedron 2000, 56,
1025.
[22] C.-C. You, P. Espindola, C. Hippius, J. Heinze, F Wꢁrthner, Adv.
Func. Mater. 2007, 17, 3764.
[23] C.-C. You, C. R. Saha-Mçller, F. Wꢁrthner, Chem. Commun. 2004,
2030.
[58] M. Momenteau, C. A. Reed, Chem. Rev. 1994, 94, 659.
[59] C. Song, T. M. Swager, Macromolecules 2005, 38, 4569.
[60] A. Osuka, F. Kobayashi, K. Maruyama, Bull. Chem. Soc. Jpn. 1991,
64, 1213.
[24] J. L. Segura, R. Gomez, E. Reinold, P. Bꢄuerle, Org. Lett. 2005, 7,
2345.
[25] S. Chen, Y. Liu, W. Qiu, X. Sun, Y. Ma, D. Zhu, Chem. Mater. 2005,
17, 2208.
[26] T. Benincori, E. Brenna, F. Sannicolꢅ, L. Trimarco, G. Zotti, P. Soz-
zani, Angew. Chem. 1996, 108, 718; Angew. Chem. Int. Ed. Engl.
1996, 35, 648.
[27] B. Jousselme, P. Blanchard, E. Levillain, R. de Bettignies, J. Roncali,
Macromolecules 2003, 36, 3020.
[28] G. Sonmez, C. K. F. Shen, Y. Rubin, F. Wudl, Adv. Mater. 2005, 17,
897.
[29] J. L. Reddinger, G. A. Sotzing, J. R. Reynolds, Chem. Commun.
1996, 1777.
[30] H. Brisset, A.-E. Navarro, C. Moustrou, I. F. Perepichka, J. Roncali,
Electrochem. Commun. 2004, 6, 249.
[31] M. Catellani, S. Luzzati, N.-O. Lupsac, R. Mendichi, R. Consonni,
A. Famulari, S. V. Meille, F. Giacalone, J. L. Segura, N. Martin, J.
Mater. Chem. 2004, 14, 67.
[61] F. Cacialli, J. S. Wilson, J. J. Michels, C. Daniel, C. Silva, R. H.
Friend, N. Severin, P. Samorꢃ, J. P. Rabe, M. J. OꢆConnell, P. N.
Taylor, H. L. Anderson, Nat. Mater. 2002, 1, 160.
[62] R. S. Becker, J. S. de Melo, A. L. Macanita, F. Elisei, J. Phys. Chem.
1996, 100, 18683.
[63] M. J. Frampton, H. L. Anderson, Angew. Chem. 2007, 119, 1046;
Angew. Chem. Int. Ed. 2007, 46, 1028.
[64] D. J. Cardin, Adv. Mater. 2002, 14, 553.
[65] D. Lee, T. M. Swager, Synlett 2004, 149.
[66] Q. Zhou, T. M. Swager, J. Am. Chem. Soc. 1995, 117, 7017.
[67] Q. Zhou, T. M. Swager, J. Am. Chem. Soc. 1995, 117, 12593.
[68] J.-H. Wan, J.-C. Feng, G.-A. Wen, W. Wei, Q.-L. Fan, C.-M. Wang,
H.-Y. Wang, R. Zhu, X.-D. Yuan, C.-H. Huang, W. Huang, J. Org.
Chem. 2006, 71, 2565.
[69] C.-Q. Ma, E. Mena-Osteritz, T. Debaerdemaeker, M. M. Wienk,
R. A. Jannsen, P. Bꢄuerle, Angew. Chem. 2007, 119, 1709; Angew.
Chem. Int. Ed. 2007, 46, 1679.
[32] R. P. Kingsborough, T. M. Swager, Adv. Mater. 1998, 10, 1100.
[33] S. S. Zhu, R. P. Kingsborough, T. M. Swager, J. Mater. Chem. 1999,
9, 2123.
Received: March 3, 2009
Revised: March 13, 2009
6362
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Chem. Eur. J. 2009, 15, 6350 – 6362