Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube

Article abstract of DOI:10.1021/jo500034f

Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M₂-Ptz- CPD_Py(OC_n); M = H₂ or Ni, OC_n = OC₆ or OC₃) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H₄-Ptz- CPD_Py(OC₆)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10⁶ M ^-1 for C₆₀ and 7.4 ± 0.8 × 10⁷ M^-1 for C₇₀ in toluene. This C₆₀ affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni₂-Ptz-CPD_Py(OC ₆)) also shows high affinities for C₆₀ (1.3 ± 0.2 × 10⁶ M^-1) and C₇₀ (over 10⁷ M^-1). In the crystal structure of the inclusion complex of C ₆₀ within H₄-Ptz-CPD_py(OC₃), the C₆₀ molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 A?) is close to the optimal separation (～12.5 A?) for C₆₀ inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H?N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C₆₀ molecules are linearly arranged in the inner channel of this nanotube.

Full text of DOI:10.1021/jo500034f

Article
pubs.acs.org/joc
Phenothiazine-Bridged Cyclic Porphyrin Dimers as High-Affinity
Hosts for Fullerenes and Linear Array of C60 in Self-Assembled
Porphyrin Nanotube
Ken-ichi Sakaguchi,† Takuya Kamimura,† Hidemitsu Uno,‡ Shigeki Mori,§ Shuwa Ozako,†
Hirofumi Nobukuni,† Masatoshi Ishida,† and Fumito Tani*,†
†Institute for Materials Chemistry and Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
‡Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
§Integrated Center for Sciences, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
S
* Supporting Information
ABSTRACT: Free-bases and a nickel(II) complex of phenothia-
zine-bridged cyclic porphyrin dimers bearing self-assembling 4-
pyridyl groups (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6
or OC3) at opposite meso-positions have been prepared as host
molecules for fullerenes. The free-base dimer (H4-Ptz-
CPDPy(OC6)) includes fullerenes with remarkably high associa-
tion constants such as 3.9 0.7 × 106 M−1 for C60 and 7.4 0.8
× 107 M−1 for C70 in toluene. This C60 affinity is the highest value
ever among reported receptors composed of free-base porphyrins.
The nickel dimer (Ni2-Ptz-CPDPy(OC6)) also shows high
affinities for C60 (1.3 0.2 × 106 M−1) and C70 (over 107 M−1). In the crystal structure of the inclusion complex of C60
within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are
almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60
inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C−H···N hydrogen bonds between
porphyrin β-CH groups and pyridyl nitrogens as well as π−π interactions of the pyridyl groups. The C60 molecules are linearly
arranged in the inner channel of this nanotube.
reported to give stable inclusion complexes with fullerenes so
far.4 In addition, there have been a wealth of chemical
modifications for porphyrin derivatives, and various self-
assembling functional groups have been introduced into
porphyrin frameworks to obtain a variety of assembled
structures.5
INTRODUCTION
■
Fullerenes have been widely used as electron acceptors, owing
to their favorable reduction potentials and small reorganization
energy in electron transfer reactions.1 They are promising
materials for organic photovoltaics (OPV) and molecular
electronics.1 For these applications, it is essential to prepare
well-ordered arrangements of fullerenes. However, the control
of arrangements of fullerenes has not been fully developed,
especially for unmodified fullerenes, because pristine fullerenes
are composed of only sp2-carbon atoms and have neither
polarity nor functional group. Our strategy for solving this
problem is to use a host molecule having the following two
functions: (i) efficient complexation with fullerenes; (ii) ability
to form a self-assembled array of a predictable structure. The
resulting host−guest complex affords a desired arrangement of
fullerene through the self-assembly of the host molecule
(Scheme 1). The molecular design of a host for fullerenes is the
key in this supramolecular approach.2 From this viewpoint,
porphyrin derivatives are especially useful building components
for host molecules fulfilling the above two requirements.3 It has
been known that strong π−π interactions between the curved
π-surfaces of fullerenes and the flat π-planes of porphyrins exist
in both solution and crystalline state. A number of host
molecules composed of multiporphyrinic moieties have been
Meanwhile, porphyrin derivatives have unique light-harvest-
ing properties, for example, strong absorption bands in the
visible region and electron-donating abilities of their photo-
excited states.6 Large numbers of the donor−acceptor
combinations of porphyrins and fullerenes have been studied
as functional mimics of the reaction center for charge
separation in natural photosynthesis.7 Long-lived photoinduced
charge separations with high quantumn yields have been
reported by the optimization of the geometries and energy
levels of these chromophores.8 Porphyrins and fullerenes have
been used as donors and acceptors also for organic photovoltaic
(OPV) devices.9 The mechanism of the conversion from
photons to photocurrent in OPV is composed of three
important processes; light harvesting, charge separation and
charge transport. It has been revealed that a well-ordered
Received: January 8, 2014
Published: March 5, 2014
© 2014 American Chemical Society
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Scheme 1. Formation of Linear Array of Fullerene in Self-Assembled Porphyrin Nanotube
Figure 1. Chemical structures of cyclic porphyrin dimers.
bicontinuous donor−acceptor array in the active layer is an
ideal structure to realize the above processes and is effective for
the improvement of the power conversion efficiency in OPV.10
Therefore, we have focused our attention on the creation of a
linear arrangement of fullerene inside a self-assembled nano-
tube of a porphyrin host, the array of which is expected to
perform photoinduced charge separation and smooth vectorial
charge transport.
state of C60⊂Ni2-C4-CPDPy(H) was not detected in the time-
resolved transient absorption spectra, because the singlet
excited state of the nickel porphyrin transforms very rapidly
to the triplet excited state via the intersystem crossing, then the
low-energy triplet excited state of C60 (3C60*) arises as a
consequence of energy transfer. The estimated energy level of
charge-separated state (1.98 eV) is much higher than that of
3C60* (1.57 eV).13 On the other hand, the inclusion complex of
the free-base dimer and C60 (C60⊂H4-C4-CPDPy(H)) contains
a zigzag array of C60 molecules through van der Waals contact
with each other and also exhibits a high charge mobility (Σμ =
0.13−0.16 cm2 V−1 s−1) along the C60 array in the crystalline
state.12c Further, it affords a photoinduced charge-separated
state via electron transfer from the porphyrin to C60 due to the
lower oxidation potential and the slower intersystem crossing of
the free-base porphyrin than those of the nickel complex.
As mentioned above, C60⊂Ni2-C4-CPDPy(H) gives the self-
assembled nanotube including the linear array of C60, whereas
C60⊂H4-C4-CPDPy(H) is unable to form a nanotube structure.
The reason for the difference of these assembled structures is as
following. In the crystal structure of C60⊂Ni2-C4-CPDPy(H),
the center-to-center distance of the two porphyrins is
12.596(2) Å, being enough to accommodate C60 with the
pseudoparallel conformation of the two porphyrins (Scheme
2). In contrast, in the case of C60⊂H4-C4-CPDPy(H), the
porphyrin dimer takes a clamshell conformation due to the
shorter center-to-center distance (11.126 Å). Only the
pseudoparallel conformation provides the self-assembled nano-
For preparing supramolecular organic nanotubes, one of the
most straightforward methods is to introduce self-assembling
groups into rigid cyclic molecules and align them through
noncovalent interactions (Scheme 1).11 Along this method, we
have prepared the nickel complex and free-base of the
butadiyne-linked cyclic porphyrin dimer bearing self-assembling
4-pyridyl groups at the trans meso-positions (Ni2-C4-CPDPy(H)
and H4-C4-CPDPy(H) in Figure 1).12 Both porphyrin dimers
afford stable inclusion complexes with fullerenes such as
C60,12a−c Li+@C60,12f PCBM ([6,6]-phenyl-C61-butyric acid
methyl ester),12e and C70.12d In the crystal structure of the
inclusion complex of the nickel dimer and C60 (C60⊂Ni2-C4-
CPDPy(H)), C60 molecules are linearly arranged in the inner
channel of the self-assembled porphyrin nanotube.12a The self-
assembly is induced by two kinds of noncovalent interactions:
(i) nonclassical C−H···N hydrogen bonds between porphyrin
β-CH groups and pyridyl nitrogen atoms, (ii) π−π interactions
of the meso-pyridyl groups. This crystal shows anisotropic high
electron mobility (Σμ = 0.72 cm2 V−1 s−1) along with the linear
arrangement of C60.12b However, the expected charge-separated
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On the basis of these results, we have intended to design a
new cyclic porphyrin dimer as a host molecule for fullerenes,
which can satisfy the following two requirements: (i) to form a
self-assembled nanotube structure including a linear array of
C60,14 (ii) to give a photoinduced charge-separated state
between the porphyrin host and fullerenes, that is, the use of a
free-base porphyrin dimer rather than the corresponding nickel
complex. For the self-assembled nanotube structure of a C60
inclusion complex, a new cyclic dimer should have meso-pyridyl
groups as well as rigid longer linkages, which can keep its
center-to-center distance at ∼12.5 Å even for a free-base dimer
to realize a pseudoparallel conformation upon C60 inclusion.
We herein report the synthesis of free bases and a nickel
complex of phenothiazine-bridged cyclic porphyrin dimers and
characterization of their inclusion complexes with fullerene C60
and C70 by spectroscopic and X-ray crystallographic analysis.
Scheme 2. Schematic Illustrations of the Crystal Structures
of the C60 Inclusion Complexes of Butadiyn-Bridged Cyclic
Porphyrin Dimers
tube through the C−H···NPy hydrogen bonds and the π−π
interactions of the pyridyl groups. These noncovalent
interactions are impossible for the clamshell conformation.
Although Ni2-C4-CPDPy(H) and H4-C4-CPDPy(H) have the
same butadiynyl linkages, the nickel porphyrins have ruffled
distortions to achieve the longer center-to-center distance,
while the higher planarity of the free-base porphyrins leads to
the shorter distance.
RESULTS AND DISCUSSION
■
Molecular Design and Synthesis of Phenothiazine-
Bridged Porphyrin Dimers. In order to construct self-
assembled porphyrin nanotubes including a linear array of C60,
Scheme 3
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Figure 2. (a) UV−vis absorption spectral changes of H4-Ptz-CPDPy(OC6) in the course of titration with C60 in toluene at 25 °C. [H4-Ptz-
CPDPy(OC6)] = 5.0 × 10−7 M. The inset shows the magnified Soret band region. (b) Plot of the changes in the UV−vis absorbance (ΔAbs) at 419
nm versus the concentration of C60. The curve was fitted by using eq 1
we have designed new cyclic porphyrin dimers which have 4-
pyridyl groups at the trans-meso-positions and phenothiazine
linkers (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6 or
OC3 in Figure 1). Phenothiazine derivative has a rigid aromatic
framework wherein three six-membered rings are linearly fused.
However, the butterfly structure of phenothiazine has some
extent of flexibility with the change of dihedral angle between
two benzene rings from ∼140° up to ∼160°.15 The cavity size
of the phenothiazine-bridged dimers can thus be adapted for
inclusion of a fullerene molecule through the alteration of the
dihedral angles. Based on the DFT (M06-2X/6-31G(d,p))-
optimized16 model structure of the inclusion complex of a
phenothiazine-bridged free-base dimer (H4-Ptz-CPDPy(H))
and C60, the two porphyrins are in a pseudoparallel
conformation, and the center-to-center distance is estimated
to be 12.2 Å (Figure S1 and Table S1 in Supporting
Information [SI]). In the calculation, the outside alkoxyl
groups are omitted to simplify the structure. The calculated
center-to-center distance is close to the optimal value (∼12.5
Å)4m for C60 inclusion by porphyrin dimers such as our
C60⊂Ni2-C4-CPDPy(H) (12.596(2) Å)12a and the C60 inclusion
complex of the cyclic zinc porphyrin dimer by Aida et al.
(12.352(1) Å).4d
In order to improve the low solubility of the pyridyl-
substituted porphyrins, we have introduced four alkoxyl chains
(e.g., OC6H13 or OC3H7) onto the meso-phenyl groups. H4-Ptz-
CPDPy(OC3) has lower solubility than H4-Ptz-CPDPy(OC6)
but is more suitable for making single crystals for X-ray
crystallographic analysis. The free-base and nickel complex of
the hexyloxy-substituted dimer are mainly employed for the
spectroscopic investigation of the inclusion in solution.
Although the free base of the new cyclic porphyrin dimer is
the main target compound in this study, we additionally
synthesized the nickel complex for the comparative evaluation
of the free base derivative. The reasons for the choice of the
nickel complex are as follows. (a) A nickel(II) complex of
porphyrin is electronically neutral. When a metal complex is
not electronically neutral, the presence of the counterion
sometimes affects the assembled structure of the metal
complex. (b) A nickel(II) complex of porphyrin is air stable.
(c) A nickel(II) complex of porphyrin is diamagnetic and
1
allows usual H- and 13C NMR analysis of the dimer and its
fullerene inclusion complexes. (d) A low-spin nickel(II)
complex of porphyrin favors four-coordinate geometry to
avoid the axial ligation of the meso-pyridyl groups. For example
as another metal complex adopting five- or six-coordinate
geometry, the zinc complex of these dimers is hardly soluble in
organic solvents except pyridine due to the intermolecular axial
coordination of the meso-pyridyl groups. While the zinc
complex of the dimer fulfills the requirements (a−c), it is not
employed in this study because of the last reason, (d).
The new dimers have been prepared by palladium-catalyzed
Suzuki−Miyaura coupling reactions of the dibrominated
porphyrin monomers and the bis-borylated phenothiazine
derivative (Scheme 3). The porphyrin monomers (3) were
obtained by using TFA-catalyzed [2 + 2]-type condensation
reaction of meso-pyridyl-dipyrromethane18 and 3-bromo-5-
alkoxylbenzaldehyde12f (2) and subsequent DDQ (2,3-
dichloro-5,6-dicyano-p-benzoquinone) oxidation in ∼10%
yield.19 The nickel(II) porphyrinato complex (4a) was
synthesized by refluxing (3a) with nickel(II) acetate (10
equiv) in CHCl3/MeOH solution. The bis-pinacolate boronic
ester of phenothiazine (5) was obtained by borylation of the
corresponding dibrominated phenothiazine derivative.20 Fi-
nally, the cyclic porphyrin dimer, H4-Ptz-CPDPy(OC6), was
synthesized by Suzuki−Miyaura coupling reaction of the free-
base porphyrin monomer (3a) and phenothiazine derivative
(5) under refluxing with 40 mol % Pd(PPh3)4 and Cs2CO3 (10
equiv) in THF/H2O (10/1) under N2 atmosphere for 48 h.
The crude product was purified by gel permeation chromatog-
raphy (GPC) to obtain a fraction containing the desired cyclic
dimer. After recrystallization from CHCl3/MeOH, the pure
form of H4-Ptz-CPDPy(OC6) was isolated in 5% yield. It was
found that the use of aqueous THF as a reaction media is
critical to obtain the desired product in this palladium-catalyzed
reaction. Different solvent systems such as toluene/DMF (10/
1) resulted in considerable decrease of the product yields (1−
2%). H4-Ptz-CPDPy(OC3) and Ni2-Ptz-CPDPy(OC6) were also
prepared under the same reaction condition as H4-Ptz-
CPDPy(OC6) in the similar yields. These isolated cyclic
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Figure 3. (a) Fluorescence spectral changes of H4-Ptz-CPDPy(OC6) in the course of titration with C60 in toluene at 25 °C excited at 426 nm. [H4-
Ptz-CPDPy(OC6)] = 5.0 × 10−7 M. (b) Plot of the changes in the fluorescence intensity (ΔInt) at 653 nm versus the concentration of C60. The curve
was fitted by using eq 3
1
porphyrin dimers were fully characterized by H NMR, high
resolution FAB mass, and IR and UV−vis absorption
spectroscopies (see Experimental Section and SI).
absence and presence of fullerenes at the concentrations
corresponding to those of the dimer (Figure S7 in SI). The
negligible decreases of the fluorescence intensities exclude
intermolecular quenching by fullerenes.21 Therefore, the
decreases of the fluorescence intensities of the free-base
dimer by the addition of fullerenes are ascribed to the
intramolecular quenching within the inclusion complexes.
The association constants of the free-base dimers were obtained
also from the fluorescence change by using eq 3, wherein F is
ΔInt at 100% complexation. Kassoc and F were similarly treated
as fitting parameters.
Upon addition of the fullerenes to the toluene solution of the
cyclic dimers, their Soret bands were red-shifted, accompanied
with reduced intensity (Figure 2 and Figures S2−S4 in SI). The
Job plots upon mixing of the dimers and fullerenes confirm the
formation of 1:1 host−guest complexes (Figure S8 in SI). On
the basis of the titrations of the cyclic porphyrin dimers with
C60 and C70 in toluene at 25 °C, the association constants
(Kassoc) were determined by applying a nonlinear curve-fitting
method using eq 1 or 2. Because C70 has non-negligible
absorption near the Soret band region, eq 2 was used in the
cases of C70.
Inclusion of C60 and C70 within CPDPy in Solution. We
have investigated the inclusion behaviors of C60 as well as C70
within the cyclic porphyrin dimers in solution by various
methods such as UV−vis absorption, fluorescence, ESI-MS, and
13C NMR spectroscopies.
Herein, A and X are [CPDPy]0 and [fullerene]0, respectively;
Δε is the difference of absorption coefficient between CPDPy
and its inclusion complex; ε70 is the absorption coefficient of
free C70 at the examined wavelength. Kassoc and Δε were treated
as fitting parameters. The association constants higher than 107
M−1 could not be determined precisely by UV−vis spectros-
copy.
Fullerene inclusion behaviors of the free-base dimers were
also investigated by fluorescence spectroscopy. When the free-
base dimers are photoexcited in toluene, the fluorescence is
observed with λmax = ∼650 and 715 nm as shown in Figure 3,
S5 and S6 in SI. The addition of fullerenes to the free-base
dimers causes a prominent decrease of the fluorescence
intensity. As control experiments, the fluorescence spectra of
the free-base monomer porphyrin 3a were measured in both
[1 + KassocA + KassocX − {(1 + KassocA + KassocX)2 − 4Kassoc2AX}0.5]
ΔAbs = Δε
2Kassoc
(1)
0.5
1 + KassocA + KassocX − {(1 + KassocA + KassocX)2 − 4Kassoc2AX}
ΔAbs = ε70X + (Δε − ε70)
2Kassoc
(2)
0.5
1 + KassocA + KassocX − {(1 + KassocA + KassocX)2 − 4Kassoc2AX}
ΔInt = F
2Kassoc
A
(3)
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Table 1. Association Constants (M−1) of Cyclic Porphyrin Dimers for C60 and C70 in Toluene at 25 °C
Kassoc for C60
Kassoc for C70
host compound
absorption
fluorescence
4.5 0.7 × 106
a
absorption
> 107
> 107
2.2 0.5 × 105
7.3 0.9 × 105
fluorescence
7.4 0.8 × 107
a
b
b
H4-Ptz-CPDPy(OC6)
Ni2-Ptz-CPDPy (OC6)
H4-C4-CPDPy(OC6)
Ni2-C4-CPDPy(OC6)
3.9 0.7 × 106
1.3 0.2 × 106
1.2 0.2 × 105
2.9 0.4 × 105
9.8 1.0 × 104
a
1.4 0.2 × 105
a
a
b
Not determined due to no emission from nickel porphyrins. Not determined due to high association constants over 107 M−1.
Figure 4. 13C NMR spectra of (a) 13C-enriched C70 (0.5 mM), (b) a mixture of H4-Ptz-CPDPy(OC6) (0.5 mM) and 13C-enriched C70 (0.5 mM), (c)
a mixture of Ni2-Ptz-CPDPy(OC6) (0.5 mM) and 13C-enriched C70 (0.5 mM) in CDCl3/CS2 (1:1) at 25 °C. The asterisks indicate signals of
contaminated C60.
This fluorescence titration is valid even for Kassoc higher than
107 M−1. The constants determined by fluorescence spectros-
copy are acceptably close to those obtained by UV−vis
absorption method. The association constants of phenothia-
zine-linked dimers are summarized in Table 1 along with those
of the butadiyn-linked ones12f for comparison.
M−1 in benzene)4d and the dimer by Zhang et al. (1.4 × 105
M−1 in toluene).4t To the best of our knowledge, H4-Ptz-
CPDPy(OC6) exhibited the highest C60 affinity among ever
reported host molecules composed of free-base porphyrins.
Even extending to metalloporphyrin-based hosts, there have
been only four hosts having C60 affinity higher than 106 M−1;
the cobalt, rhodium and iridium dimers by Aida et al. (2.0 ×
106, 2.5 × 107 and >109 M−1 in benzene, respectively)4d,l and
the zinc trimer by Anderson et al. (1.6 × 106 M−1 in
toluene).4m The extraordinary high C60 affinities of the
rhodium and iridium dimers by Aida et al. are due to the
assist of the specific carbophilicity of these metal ions, whose
property is common for group IX metals. Based on these
comparisons, the remarkably high C60 affinity of H4-Ptz-
CPDPy(OC6) implies that its phenothiazine-bridged structure is
highly suitable for C60 inclusion.
The Kassoc value of Ni2-Ptz-CPDPy(OC6) for C60 (1.3 0.2 ×
106 M−1) is lower than that of the free-base counterpart (3.9
0.7× 106 M−1). The less efficient inclusion of C60 would be
derived from that its cavity size is slightly too large for C60
inclusion due to the distortion of the nickel porphyrins,22 as
suggested by the previous result that C60⊂Ni2-C4-CPDPy(H)
has the longer center-to-center distance than the C60 complex
of the corresponding free-base dimer.12a,c
The Kassoc value of H4-Ptz-CPDPy(OC6) for C60 (3.9 0.7 ×
106 M−1) is much larger (over 30 times) than that of H4-C4-
CPDPy(OC6) (1.2 0.2 × 104 M−1). In order to interpret this
high affinity, the structure of H4-Ptz-CPDPy(H) was also
optimized by DFT (M06-2X/6-31G(d,p) calculation.16 H4-Ptz-
CPDPy(H) has a slipped form of the two porphyrins (Figure S1
in SI), which conformation is similar to that of the crystal
structure of H4-C4-CPDPy(H).12c The dihedral angles between
the meso-phenyl groups and the mean planes of the porphyrins
are ca. 64° (Table S1 in SI). Upon C60 inclusion, these dihedral
angles increase to ca. 88° to give a fully overlapped form of the
two porphyrins, indicating that the inclusion occurs in an
induced-fit fashion. However, there are only small changes in
the center-to-center distance and the butterfly angles of the
phenothiazine groups (Table S1 in SI). Hence, the high affinity
of H4-Ptz-CPDPy(OC6) to C60 would be derived mainly from
the following two factors: i) the flexibility of the dihedral angles
between the phenyl groups and the porphyrin planes, and ii)
the suitable length of the phenothiazine bridges.
Notably, the Kassoc value of H4-Ptz-CPDPy(OC6) for C70 (7.4
0.8 × 107 M−1), which is significantly higher (ca. 500 times)
than that of H4-C4-CPDPy(OC6) (1.4 0.2 × 105 M−1), reveals
There have been free-base porphyrin hosts having relatively
high C60 affinities such as the dimer by Aida et al. (7.9 × 105
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that its molecular design is also effective for C70 inclusion. This
result would be owing to the fact that the length of the shorter
axis of C70 (7.1 Å) is almost the same as the diameter of C60.23
The Kassoc value of H4-Ptz-CPDPy(OC6) for C70 is one of the
highest constants of porphyrin-based hosts, while there have
been few better examples; the rhodium dimer by Aida et al. (1.0
× 108 M−1 in benzene),4d the zinc trimer by Anderson et al.
(1.6 × 108 M−1 in toluene)4m and the free-base dimer by Zhang
et al. (1.5 × 108 M−1 in toluene).4t Although the Kassoc value of
Ni2-Ptz-CPDPy(OC6) for C70 could not be determined
precisely, it is worth of noting that its C70 affinity is fairly
high (over 107 M−1) and appreciably improved by at least 15
times in comparison with that of Ni2-C4-CPDPy(OC6) (7.3
0.9 × 105 M−1).
The electrospray inonization mass (ESI-MS) spectra of 1:1
mixtures of fullerenes and the cyclic porphyrin dimers in
CHCl3/MeOH/CH3COOH (25/25/1) showed prominent ion
peak clusters of the inclusion complexes (Figure S9 in SI), for
example, at m/z = 1387.7 for [H4-Ptz-CPDPy(OC6) + C60]2+
and m/z = 1444.5 for [Ni2-Ptz-CPDPy(OC6) + C60]2+. These
observations by ESI-MS spectroscopy also confirm the 1:1
inclusions of C60 and C70 within the present cyclic porphyrin
dimers in solution, respectively.
crystals of C60⊂H4-Ptz-CPDPy(OC3) suitable for X-ray
crystallographic analysis from CHCl3/chlorobenzene solution
by slow evaporation. The crystal structure clearly reveals 1:1
inclusion of C60 within the cavity of H4-Ptz-CPDPy(OC3)
(Figure 5). This inclusion complex has a plane of symmetry
between the two porphyrin moieties, which are equivalent to
each other due to this plane. Therefore, the included C60
molecule can be regarded as the union of two equivalent
hemispheres divided by this plane.
The two benzene rings of each phenothiazine moiety are
equivalent to each other and the nitrogen, sulfur, and methyl
carbon atoms are on the symmetry plane. Two pairs of the
pyridyl groups are treated as disordered structures. Addition-
ally, two pairs of the propyl groups outside the cavity were
modeled as two disordered structures.
Though the porphyrin planes are almost planar, the meso-
carbons are slightly displaced from the mean plane of the four
pyrrole nitrogens. The pyridyl-substituted meso-carbons show
larger inward displacements (0.107 and 0.214 Å) than the
phenyl-substituted ones shifting outward (0.007 and 0.026 Å).
The two phenothiazine groups have butterfly structures; the
dihedral angles between the two phenyl rings are 150.83° and
151.26°. The C60 molecule is located just above the centers of
the porphyrins, exhibiting a large difference from the off-center
location of C60 in the crystal structure of C60⊂Ni2-C4-
CPDPy(H) which has a shorter separation between the two
opposite phenyl rings connected to linker groups.25 The 6:6
ring-juncture C−C bond at each pole of C60 is closest to the
porphyrin as in most examples of C60-porphyrin cocrystals.3a
This C−C bond has near alignment with a trans N···N vector
with a short separation (2.830 Å) between the closest C60
carbon and the porphyrin center (Figure 6), suggesting a strong
π−π interaction of the two π-systems. The two porphyrins are
almost parallel to each other, and the center-to-center distance
is 12.454 Å. This value is in the quite favorable range for C60
inclusion as predicted in the molecular design. Hence, it is
rational to assign the remarkably high C60 affinity of H4-Ptz-
CPDPy(OC6) in solution to these structural features of
C60⊂H4-Ptz-CPDPy(OC3).
The 13C NMR spectra of 1:1 mixtures of 13C-enriched
fullerenes and the cyclic dimers in CDCl3/CS2 (1/1) exhibited
high-field-shifted signals of the included fullerenes due to the
ring current effects of the porphyrins (Figure 4 and Figure S10
in SI). Included C60 molecule shows one singlet signal due to
its Ih symmetry and its very rapid rotation, while C70 gives five
different signals (alphabetical labels are indicated in Figure 4).
The chemical shifts (δ) and high-field shift values (Δδ) in ppm
are shown in Table 2 and 3. In general, high-field shifts of C70
Table 2. 13C-NMR Data of Free and Included C60 in CDCl3/
CS2 (1:1) at 25 °C
cmpd
δ
Δδ
free C60
143.1
139.6
141.3
C60⊂H4-Ptz-CPDPy(OC6)
C60⊂Ni2-Ptz-CPDPy (OC6)
−3.5
−1.8
Most interestingly, a desired self-assembled porphyrin
nanotube is observed in the crystal packing of C60⊂H4-Ptz-
Table 3. 13C-NMR Data of Free and Included C70 in CDCl3/
CS2 (1:1) at 25 °C
12a
CPDPy(OC3) as seen in the case of C60⊂Ni2-C4-CPDPy
(Figure 7). The tubular structure is formed by multiple
cooperative noncovalent interactions between each dimer; a
pair of complementary C−H···N hydrogen-bonding interac-
tions between the pyrrole β-CH and nitrogen atoms of the
pyridyl groups with C···N distances of 3.38(1) and 3.40(1) Å
for the major ones of the disordered pyridyl groups (Figure 8;
for the minor pyridyl groups, see Figure S11 in SI). The second
interaction is a weak π−π interaction between the meso-pyridyl
groups; the shortest C−C distances of 3.75(1) Å and the
dihedral angle of 5.00° are confirmed. The C60 molecules are
linearly arranged inside the channel of the nanotube with the
distance between the C60 centers of 14.794 Å, which is slightly
longer than that of C60⊂Ni2-C4-CPDPy(H) (14.498 Å). It is
noteworthy that this self-assembly for the porphyrin nanotube
including the C60 linear array is induced by the meso-pyridyl
groups irrespective of central metal ions (nickel and free-base)
and linkage groups (butadiynyl and phenothiazine).
cmpd
free C70
δa (Δδ) δb (Δδ) δc (Δδ) δd (Δδ) δe (Δδ)
150.5
148.8
147.2
144.8
148.0
145.1
145.3
141.6
130.8
126.8
C70⊂H4-Ptz-
CPDPy(OC6)
(−1.7)
149.2
(−2.4)
145.5
(−2.9)
145.9
(−3.7)
142.7
(−4.0)
128.1
C70⊂Ni2-Ptz-CPDPy
(OC6)
(−1.3)
(−1.7)
(−2.1)
(−2.6)
(−2.7)
signals are good indicators to clarify the C70 orientation with
respect to a porphyrin plane.4b,e,d,l,24 In the case of an end-on
orientation, carbon atoms near the poles show larger high-field
shifts (in absolute values). When C70 takes a side-on
orientation, carbon atoms near the equator have larger high-
field shifts. In the 13C NMR spectra of all the present C70
inclusion complexes, carbon atoms near the equator exhibit
larger high-field shifts than ones near the poles, implying that
the side-on orientation of the C70 molecule is dominant in these
inclusion complexes in solution.
CONCLUSION
In order to construct efficient and nanotube-forming hosts for
fullerenes, we have designed and prepared free-bases and a
■
Crystal Structure of the Inclusion Complex of C60 with
H4-Ptz-CPDPy(OC3). We have successfully obtained single
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Figure 5. ORTEP drawing of C60⊂H4-Ptz-CPDPy(OC6) with 50% probability thermal ellipsoids. Hydrogen atoms, disordered structures, and solvent
molecules are omitted for clarity. (a) Front view; (b) side view; (c) top view.
Figure 6. Orientation of the 6:6 ring-juncture of C60 over the
porphyrin center.
nickel complex of cyclic porphyrin dimers having self-
assembling 4-pyridyl groups and phenothiazine linkers at the
opposite meso-positions. The porphyrin dimers have been
obtained by Suzuki−Miyaura cross-coupling of dihalogenated
porphyrins and bisborylated phenothiazine derivative. The
phenothiazine-bridged free-base dimer, H4-Ptz-CPDPy(OC6),
showed very high affinities for fullerenes such as Kassoc = 3.9
0.7 × 106 M−1 for C60 and Kassoc = 7.4 0.8 × 107 M−1 for C70.
This C60 affinity is the highest value ever reported among host
molecules composed of free-base porphyrins, indicating that
Figure 7. Tubular assembly and linear array of C60 in the crystal
packing of C60⊂H4-Ptz-CPDPy(OC3). (a) Front view; (b) side view;
(c) top view.
H4-Ptz-CPDPy(OC6) has an optimum molecular cavity for C60
inclusion. On the other hand, the C60 affinity of Ni2-Ptz-
CPDPy(OC6) (1.3 0.2 × 106 M−1) is lower than that of H4-
Ptz-CPDPy(OC6) probably due to the slightly larger size of its
stackings of the meso-pyridyl groups in the crystal packing of
this inclusion complex. The C60 molecules are linearly aligned
in the inner channel of this nanotube to produce a
supramolecular peapod. Further electrochemical and photo-
physical studies of these supramolecular architectures are now
in progress.
cavity. The association constant of Ni2-Ptz-CPDPy(OC6) for
C70 is, however, found to be over 107 M−1. The 13C NMR
spectra of the C70 inclusion complexes suggest that the included
C70 molecule adopts mainly a side-on orientation within the
cavity of these cyclic dimers. X-ray crystallographic analysis of
C60⊂H4-Ptz-CPDpy(OC3) revealed that the included C60
molecule is localized just above the centers of the porphyrin
moieties due to the strong π−π interaction. The two porphyrin
planes are almost parallel to each other, and the center-to-
center distance (12.454 Å) was found to be quite suitable for
C60 inclusion. The very high C60 affinity of H4-Ptz-
CPDpy(OC6) is rationally assigned to these structural features
revealed by X-ray crystallography. Along with our expectation,
C60⊂H4-Ptz-CPDpy(OC3) forms a self-assembled nanotube
through porphyrin β-C−H···NPy hydrogen bonds and π−π
EXPERIMENTAL SECTION
■
General Information. Reagents and solvents of best grade
available were purchased from commercial suppliers and were
used without further purification unless otherwise noted. N,N-
Dimethylformamide (DMF) was purified by distillation from
CaH2 under reduced pressure. Dry tetrahydrofuran (THF) was
obtained by distillation from Na and benzophenone under N2
atmosphere. Analytical thin-layer chromatography (TLC) was
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Deposition number CCDC-973900. Copies of the date can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Date
Centre, 12, Union Road, Cambridge, CB2 1EZ, U.K.; fax: +44
1223 336033; e-mail: deposit@ccdc.cam.ac.uk)
1,3-Dibromo-5-(propyloxy)benzene (1b). A mixture of 3,5-
dibromophenol30 (17.0 g, 67.5 mmol), 1-bromopropane (9.83
g, 80.0 mmol) and K2CO3 (13.8 g, 100 mmol) in 2-butanone
(150 mL) was heated to reflux under N2 atmosphere overnight.
After cooling, water (300 mL) and CHCl3 (300 mL) were
added. The organic phase was separated, and the aqueous phase
was extracted with CHCl3 (100 mL × 2). The combined
organic phase was dried with Na2SO4 and evaporated in vacuo.
The crude product was purified by column chromatography
(silica gel, hexane) to give colorless oil (18.4 g, 89%). 1H NMR
(400 MHz, CDCl3): δ 7.23 (s, 1H, Ar−H), 6.99 (s, 2H, Ar−
H), 3.88 (t, J = 6.6 Hz, 2H, OCH2), 1.79 (sext, J = 7.2 Hz, 2H,
OCH2CH2CH3), 1.02 (t, J = 7.2 Hz, 3H, CH3); 13C NMR
(CDCl3, 150 MHz): δ 160.5 (aromatic C), 126.3 (aromatic C),
123.2 (aromatic C), 117.1 (aromatic C), 70.3 (OCH2), 22.5
(CH2), 10.6 (CH3); IR (oil): v = 3080, 2966, 2937, 2877, 1583,
1568, 1439, 1419, 1339, 1298, 1255, 1230, 1107, 1088, 1066,
1046, 1022, 987, 889, 853, 829, 744, 669 cm−1; HR-FAB-MS
(NBA): m/z calcd for C9H11Br2O: 292.9177; found: 292.9149.
3-Bromo-5-(propyloxy)benzaldehyde (2b). 1,3-Dibromo-5-
(propyloxy)benzene 1b (2.94 g, 10.0 mmol) was added into a
three-neck flask, and the flask was filled with N2. Then, dry
THF (100 mL) was added into the flask under N2 atmosphere,
and the solution was cooled to −78 °C. Then, n-butyllithium
(2.69 M solution in n-hexane, 3.7 mL, 10 mmol) was added
dropwise to the solution. After 1 h, excess DMF was added to
the mixture. After warming to room temperature, the reaction
mixture was quenched with water. The separated organic phase
was washed with water (100 mL, 2 times), and dried over
Na2SO4 and evaporated in vacuo. The crude product was
purified by column chromatography (silica gel, n-hexane/
CHCl3, 3:1) to furnish the product as a light-yellow oil (1.87 g,
Figure 8. Details of the noncovalent interactions linking the cyclic
porphyrin dimers in the crystal of C60⊂H4-Ptz-CPDpy(OC3). The
major parts of the disordered pyridyl groups are shown. Hydrogen
atoms are omitted except in the C−H···N moieties. N = purple; C =
gray; H = pink; S = yellow.
performed on silica gel 60 F254 precoated aluminum sheets.
Colunm chromatography was carried out using silica gel (63-
210 mesh) or florisil (60−120 mesh). Chemical shifts of
nuclear magnetic resonance (NMR) spectra were reported as δ
values in ppm relative to tetramethylsilane. High-resolution fast
atom bombardment mass spectra (HR-FAB-MS) were
measured with 3-nitrobenzyl alcohol (NBA) or a mixture of
dithiothreitol and dithioerythritol (Magic Bullet) as a matrix
and recorded on a double-focusing magnetic sector mass
spectrometer. Recycling preparative GPC-HPLC was carried
out with CHCl3/NEt3 (100:1) as an eluent at a flow rate of 3.5
mL/min. The computation was carried out using the computer
facilities at Research Institute for Information Technology,
Kyushu University.
X-ray Structure Determination. The free-base dimer (H4-
Ptz-CPDPy(OC3)) in CHCl3 (0.01 mM, 1 mL) and C60 in
chlorobenzene (0.01 mM, 1 mL) were mixed in a loosely
closed vial and stored in the dark at room temperature. The
slow and preferential evaporation of chloroform afforded single
crystals due to the lower solubility of the inclusion complex in
chlorobenzene. X-ray crystallography was carried out on a
single crystal of C60⊂H4-Ptz-CPDPy(OC3) with a monochro-
mated synchrotoron radiation (λ = 0.7104 Å) at SPring-8
BL02B1. Reflection data were corrected for Lorentz and
polarization effects. The structure was solved by a direct
method (SIR-2004)26 with the Crystal Structure27 crystallo-
graphic software package, and refined by full-matrix least-
squares procedures on F2 for all reflections (SHELXL-97).28
Non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were refined by using the rigid model. Some solvent
molecules, such as chloroform and chlorobenzene were not
properly modeled due to their disorder. Therefore, the
structure was refined without these solvents by PLATON
Squeeze technique.29 The final structure was validated by using
PLATON cif check. Crystallographic data for C60⊂H4-Ptz-
CPDPy(OC3): C122H94N14O4S2·C60, brown prismatic crystal,
crystal dimensions 0.08 × 0.05 × 0.06 mm3, monoclinic, P21/m,
a = 14.794(19) Å, b = 32.47(5) Å, c = 17.79(3) Å, β =
100.281(16)°, V = 8410(22) Å3, Z = 2, ρcalc = 1.029 g cm−3,
2θmax = 54.10°, T = 123 K, 79175 reflections collected; 19368
reflections used and 1091 parameters. R1 = 0.0832 [I >
2.0σ(I)], Rw = 0.2384 (all data). Crystallographic data have
been deposited with Cambridge Crystallographic Date Centre:
1
77%). H NMR (600 MHz, CDCl3): δ 9.89 (s, 1H, CHO),
7.55 (t, J = 1.6 Hz, 1H, Ar−H), 7.30 (m, 2H, Ar−H), 3.96 (t, J
= 6.6 Hz, 2H, OCH2), 1.81 (sext, J = 7.2 Hz, 2H,
OCH2CH2CH3), 1.04 (t, J = 7.2 Hz, 3H, CH3); 13C NMR
(CDCl3, 150 MHz): δ 190.8 (CHO), 160.7 (aromatic C),
139.1 (aromatic C), 125.6 (aromatic C), 124.5 (aromatic C),
123.8 (aromatic C), 113.2 (aromatic C), 70.6 (OCH2), 22.8
(CH2), 10.8 (CH3); IR (oil): v = 3385, 3078, 2966, 2937, 2879,
2725, 2409, 2289, 1705, 1591, 1590, 1452, 1383, 1317, 1273,
1246, 1151, 1099, 1065, 953, 939, 849, 690, 671 cm−1; HR-
FAB-MS (NBA): m/z calcd for C10H12BrO2: 243.0021; found:
243.0021.
5,15-Bis[3-bromo-5-(hexyloxy)phenyl]-10,20-di[4-pyridyl]-
porphine (3a). A solution of 3-Bromo-5-(hexyloxy)-
benzaldehyde12f 2a (570 mg, 2.00 mmol) and meso-(4-
pyridyl)dipyrromethane18 (446 mg, 2.00 mmol) in 200 mL
CH2Cl2 was purged with N2 for 15 min and shielded from light.
To the solution, trifluoroacetic acid (1.86 mL, 25.0 mmol) was
added, and the solution was stirred for 30 min at room
temperature. Then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
(680 mg, 3.00 mmol) dissolved in THF was added to the
solution; the resulting solution was stirred for an additional 1 h.
The reaction mixture was neutralized with triethylamine (3.36
mL, 24.1 mmol). After evaporation, the mixture was purified by
column chromatography (silica gel, CHCl3/EtOH, 100:1 to
CHCl3/EtOH, 50:1). The crude product was washed with
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MeOH and dried in vacuo to give the porphyrin as a purple
powder (98 mg, 10%). Mp: >300 °C; H NMR (600 MHz,
H), 8.84 (d, J = 4.8 Hz, 4H, pyrrole β-H), 8.71 (d, J = 4.8 Hz,
4H, pyrrole β-H), 7.96 (d, J = 4.8 Hz, 4H, Ar−H), 7.75 (s, 2H,
Ar−H), 7.48 (s, 2H, Ar−H), 7.43 (s, 2H, Ar−H), 4.08 (t, J =
6.6 Hz, 4H, OCH2), 1.84 (quin, J = 7.2 Hz, 4H,
OCH2 CH2 (CH2 )3 CH3 ), 1.51−1.44 (m, 4H, O-
(CH2)2CH2(CH2)2CH3), 1.38−1.30 (m, 8H, O-
(CH2)3(CH2)2CH3), 0.89 (t, J = 6.6 Hz, 6H, CH3); 13C
NMR (150 MHz, CDCl3): δ 158.4 (aromatic C), 149.0
(aromatic C), 148.7 (aromatic C), 143.2 (aromatic C), 142.9
(aromatic C), 142.1 (aromatic C), 133.0 (aromatic C), 132.1
(aromatic C), 129.2 (aromatic C), 128.7 (aromatic C), 121.6
(aromatic C), 119.7 (aromatic C), 118.2 (aromatic C), 117.7
(aromatic C), 116.5 (aromatic C), 68.8 (OCH2), 31.7 (CH2),
29.3 (CH2), 25.8 (CH2) 22.7 (CH2), 14.2 (CH3); IR (KBr): v
= 2928, 2858, 1593, 1427, 1352, 1273, 1182, 1077, 1007, 867,
769, 713, 672 cm−1; UV−vis (CHCl3): λmax (ε, cm−1 M−1) =
415 (268250), 527 (18400) nm; HR-FAB-MS (NBA): m/z
calcd for C54H48Br2N6NiO2: 1028.1559; found: 1028.1533.
10-Methyl-3,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)-10H-phenothiazine (5). 10-Methyl-3,7-dibromo-10H-
phenothiazine20 (834 mg, 2.25 mmol) was added into a
three-neck flask, and the air inside of the flask was replaced with
N2. Then, dry THF (10 mL) was added into the flask, and the
solution was cooled to −78 °C. Then, n-butyllithium (2.69 M
solution in n-hexane, 2.1 mL, 5.6 mmol) was added dropwise to
the solution. After stirring for 1 h, 2-isopropoxy-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane (1.82 mL, 8.92 mmol) was
added to the reaction mixture. After warming to room
temperature, the reaction mixture was quenched with water.
The reaction mixture was extracted with CH2Cl2, dried over
Na2SO4, and evaporated. The crude product was purified by
column chromatography (silica gel, n-hexane/CH2Cl2, 1:1 then
CH2Cl2) to furnish the product as a colorless powder (633 mg,
60%). Mp: 259−260 °C; 1H NMR (500 MHz, CDCl3): δ 7.57
(d, J = 8.6 Hz, 2H, Ar−H), 7.53 (s, 2H, Ar−H), 6.77 (d, J = 8.6
1
CDCl3): δ 9.05 (d, J = 4.8 Hz, 4H, Ar−H), 8.95 (d, J = 4.2 Hz,
4H, pyrrole β-H), 8.82 (d, J = 4.2 Hz, 4H, pyrrole β-H), 8.16
(d, J = 5.4 Hz, 4H, Ar−H), 7.94 (s, 2H, Ar−H), 7.69 (s, 2H,
Ar−H), 7.51 (s, 2H, Ar−H), 4.14 (t, J = 6.6 Hz, 4H, OCH2),
1.87 (quin, J = 6.6 Hz, 4H, OCH2CH2(CH2)3CH3), 1.53−1.46
(m, 4H, O(CH2)2CH2(CH2)2CH3), 1.38−1.32 (m, 8H,
O(CH2)3(CH2)2CH3), 0.90 (t, J = 6.6 Hz, 6H, CH3), −2.92
(br s, 2H, NH); 13C NMR (150 MHz, CDCl3): δ 158.3
(aromatic C), 150.2 (aromatic C), 148.5 (aromatic C), 144.4
(aromatic C), 130.1 (aromatic C), 129.5 (aromatic C), 121.4
(aromatic C), 120.6 (aromatic C), 120.6 (aromatic C), 119.3
(aromatic C), 117.7 (aromatic C), 117.5 (aromatic C), 68.9
(OCH2), 31.7 (CH2), 29.3 (CH2), 25.9 (CH2) 22.7 (CH2),
14.2 (CH3); IR (KBr): v = 3317, 2929, 2869, 1591, 1474, 1426,
1350, 1269, 1171, 1050, 975, 921, 859, 800, 730, 659 cm−1;
UV−vis (CHCl3): λmax (ε, cm−1 M−1) = 419 (467500), 514
(21250), 547 (6150), 588 (6300), 646 (3400) nm; HR-FAB-
MS (NBA): m/z calcd for C54H50Br2N6O2: 972.2362; found
972.2369.
5,15-Bis[3-bromo-5-(propyloxy)phenyl]-10,20-di[4-
pyridyl]porphine (3b). A solution of 3-bromo-5-(propyloxy)-
benzaldehyde 2b (486 mg, 2.00 mmol) and meso-(4-pyridyl)-
dipyrromethane18 (446 mg, 2.00 mmol) in 200 mL of CH2Cl2
was purged with N2 for 15 min and shielded from light. To the
solution was added trifluoroacetic acid (1.86 mL, 25.0 mmol),
and the solution was stirred for 30 min at room temperature.
Then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (680 mg,
3.00 mmol) dissolved in THF was added to the solution; the
resulting solution was stirred for an additional 1 h. The reaction
mixture was neutralized with triethylamine (3.36 mL, 24.1
mmol). After evaporation, the mixture was purified by column
chromatography (silica gel, CHCl3/EtOH, 100:1 to CHCl3/
EtOH, 50:1). The crude product was washed with MeOH and
dried in vacuo to give the porphyrin as a purple powder (80 mg,
9%). Mp: >300 °C; 1H NMR (600 MHz, CDCl3): δ 9.05 (d, J
= 4.8 Hz, 4H, Ar−H), 8.95 (d, J = 4.2 Hz, 4H, pyrrole β-H),
8.82 (d, J = 4.2 Hz, 4H, pyrrole β-H), 8.16 (d, J = 5.4 Hz, 4H,
Ar−H), 7.94 (s, 2H, Ar−H), 7.70 (s, 2H, Ar−H), 7.51 (s, 2H,
Ar−H), 4.12 (t, J = 6.6 Hz, 4H, OCH2), 1.90 (sext, J = 7.2 Hz,
4H, OCH2CH2CH3), 1.09 (t, J = 7.2 Hz, 6H, CH3), −2.92 (br
s, 2H, NH); 13C NMR (150 MHz, CDCl3): δ 158.7 (aromatic
C), 150.6 (aromatic C), 149.0 (aromatic C), 144.8 (aromatic
C), 130.6 (aromatic C), 130.0 (aromatic C), 121.9 (aromatic
C), 121.0 (aromatic C), 119.7 (aromatic C), 118.1 (aromatic
C), 118.0 (aromatic C), 70.8 (OCH2), 23.2 (CH2), 11.1
(CH3); IR (KBr): v = 3317, 2934, 2876, 1592, 1475, 1426,
1350, 1269, 1172, 1051, 973, 927, 859, 800, 730, 659 cm−1;
UV−vis (CHCl3): λmax (ε, cm−1 M−1) = 419 (444000), 514
(21250), 547 (6450), 589 (6380), 647 (3150) nm; HR-FAB-
MS (NBA): m/z calcd for C48H39N6Br2O2: 889.1501; found:
889.1504.
Hz, 2H, Ar−H), 3.38 (s, 3H, NCH3), 1.32 (s, 24H, CH3); 13
C
NMR (150 MHz, CDCl3): δ 147.9 (aromatic C), 134.5
(aromatic C), 133.6 (aromatic C), 122.8 (aromatic C), 113.7
(aromatic C), 83.8 (B−O−C), 35.6 (NCH3), 25.0 (CH3); IR
(KBr): ν = 2983, 2933, 1605, 1583, 1408, 1389, 1375, 1354,
1298, 1261, 1211, 1169, 1146, 1130, 1115, 1105, 966, 858, 739,
692, 669 cm−1; UV−vis (THF): λmax (ε, cm−1 M−1) = 270
(57000), 326 (5200) nm; HR-FAB-MS (NBA): m/z calcd for
C25H33O4NB2S: 465.2316; found: 465.2308; Elemental analysis
(%) calcd for C25H33B2NO4S: C 64.54 H 7.15 N 3.01; found: C
64.57 H 7.14 N 2.99.
H4-Ptz-CPDPy(OC6). A THF/H2O (40 mL, THF/H2O, 10/1)
solution of 3a (97 mg, 0.10 mmol), 5 (47 mg, 0.10 mmol),
Pd(PPh3)4 (46 mg, 0.040 mmol), and Cs2CO3 (325 mg, 1.00
mmol) was purged with N2 for 30 min. The mixture was
refluxed for 2 days under N2 in the dark. After cooling to room
temperature and evaporation, the reaction mixture was diluted
with CHCl3/NEt3 (CHCl3/NEt3, 100:1) and washed with
water (50 mL) twice. The organic layer was dried over Na2SO4
and evaporated. The residue was passed through short column
chromatography (florisil, CHCl3/NEt3, 100:1). After evapo-
ration of the solvent, the crude product was passed through gel
permeation chromatography (CHCl3/NEt3, 100/1 as an
eluent) and recrystallized from CHCl3/MeOH to give the
{5,15-Bis[3-bromo-5-(hexyloxy)phenyl]-10,20-di[4-
pyridyl]porphinato}Ni(II) (4a). A solution of Ni(OAc)2·4H2O
(496 mg, 2.00 mmol) in MeOH (20 mL) was added to a
solution of 3a (195 mg, 0.200 mmol) in CHCl3 (100 mL) and
refluxed under N2 for 1 day. The reaction mixture was diluted
with CHCl3 and washed with water (200 mL) twice. The
organic layer was dried over Na2SO4, and the solvent was
evaporated. The crude product was recrystallized from CHCl3/
MeOH to give 4a as an orange powder (142 mg, 69%). Mp:
>300 °C; 1H NMR (400 MHz, CDCl3): δ 8.97 (br s, 4H, Ar−
1
dimer as a purple powder (4.8 mg, 5%). Mp: >300 °C; H
NMR (600 MHz, CDCl3): δ 8.96 (br s, 4H, Ar−H), 8.90 (br s,
4H, Ar−H), 8.87 (d, J = 4.2 Hz, 8H, pyrrole β-H), 8.66 (d, J =
4.2 Hz, 8H, pyrrole β-H), 8.04 (br s, 4H, Ar−H), 7.94 (br-s,
2989
dx.doi.org/10.1021/jo500034f | J. Org. Chem. 2014, 79, 2980−2992

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Article
4H, Ar−H), 7.80 (s, 4H, Ar−H), 7.69 (d, J = 8.4 Hz, 4H, Ar−
H), 7.65 (s, 4H, Ar−H), 7.46 (s, 4H, Ar−H), 7.29 (s, 4H, Ar−
H), 6.98 (d, J = 8.4 Hz, 4H, Ar−H), 4.14 (t, J = 8.0 Hz, 8H,
OCH2), 3.52 (s, 6H, NCH3), 1.86 (quin, J = 7.2 Hz, 8H,
O C H 2 C H 2 ( C H 2 ) 3 C H 3 ) , 1 . 5 1 ( m , 8 H , O -
( C H 2 ) 2 C H 2 ( C H 2 ) 2 C H 3 ) , 1 . 3 1 ( m , 1 6 H , O -
(CH2)3(CH2)2CH3), 0.90 (t, J = 6.6 Hz, 12H, CH3), −3.08
(br s, 4H, NH); IR (KBr): v = 3317, 2927, 2868, 1590, 1480,
1430, 1262, 1055, 975, 921, 800, 725, 661 cm−1; UV−vis
(CHCl3): λmax (ε, cm−1 M−1) = 418 (601900), 515 (32566),
549 (10100), 590 (9300), 647 (6200) nm; HR-FAB-MS
(NBA): m/z calcd for C134H118N14O4S2: 2050.8902; found
2050.8921; 13C NMR spectrum could not be obtained due to
the low solubility.
H4-Ptz-CPDPy(OC3). A THF/H2O (40 mL, THF/H2O, 10/1)
solution of 3b (89 mg, 0.10 mmol), 5 (47 mg, 0.10 mmol),
Pd(PPh3)4 (46 mg, 0.040 mmol), and Cs2CO3 (325 mg, 1.00
mmol) was purged with N2 for 30 min. The mixture was
refluxed for 2 days under N2 in the dark. After cooling to room
temperature and evaporation, the reaction mixture was diluted
with CHCl3/NEt3 (CHCl3/NEt3, 100:1) and washed with
water (50 mL) twice. The organic layer was dried over Na2SO4
and evaporated. The residue was passed through short column
chromatography (florisil, CHCl3/NEt3, 100:1). After evapo-
ration of the solvent, the crude product was passed through gel
permeation chromatography (CHCl3/NEt3, 100/1 as an
eluent) and recrystallized from CHCl3/MeOH to give the
dimer as a purple powder (2 mg, 2%). Mp: >300 °C; 1H NMR
(600 MHz, CDCl3): δ 8.95 (br s, 4H, Ar−H), 8.90 (br s, 4H,
Ar−H), 8.87 (d, J = 4.2 Hz, 8H, pyrrole β-H), 8.66 (d, J = 4.2
Hz, 8H, pyrrole β-H), 8.04 (br s, 4H, Ar−H), 7.93 (br s, 4H,
Ar−H), 7.80 (s, 4H, Ar−H), 7.69 (d, J = 7.2 Hz, 4H, Ar−H),
7.65 (s, 4H, Ar−H), 7.46 (s, 4H, Ar−H), 7.29 (s, 4H, Ar−H),
6.98 (d, J = 8.4 Hz, 4H, Ar−H), 4.11 (t, J = 6.6 Hz, 8H,
OCH2), 3.52 (s, 6H, NCH3), 1.89 (sext, J = 7.2 Hz, 8H,
OCH2CH2CH3), 1.07 (t, J = 7.2 Hz, 12H, CH3), −3.08 (br s,
4H, NH); IR (KBr): v = 3317, 2963, 2876, 1589, 1480, 1430,
1262, 1068, 974, 930, 800, 731, 689 cm−1; UV−vis (CHCl3):
λmax (ε, cm−1 M−1) = 418 (666700), 515 (38200), 549 (13000),
588 (11700), 647 (7100) nm.; HR-FAB-MS (Magic Bullet):
m/z calcd for C122H95N14O4S2: 1883.7102; found: 1883.7078;
13C NMR spectrum could not be obtained due to the low
solubility.
Hz, 8H, OCH2CH2(CH2)3CH3), 1.51 (m, 8H, O-
( C H 2 ) 2 C H 2 ( C H 2 ) 2 C H 3 ) , 1 . 3 5 ( m , 1 6 H , O -
(CH2)3(CH2)2CH3), 0.89 (t, J = 6.6 Hz, 12H, CH3); IR
(KBr): v = 2928, 2868, 1592, 1480, 1430, 1355, 1262, 1180,
1077, 1006, 867, 799, 713 cm−1; UV−vis (CHCl3): λmax (ε,
cm−1 M−1) = 415 (360132), 527 (28597) nm; HR-FAB-MS
(NBA): m/z calcd for C134H114N14O4S2Ni2: 2162.7296; found
2162.7346; 13C NMR spectrum could not be obtained due to
the low solubility.
ASSOCIATED CONTENT
* Supporting Information
■
S
DFT-optimized structure, UV−vis absorption spectra, fluo-
rescence spectra, titration data, ESI-MS spectra, NMR spectra
and X-ray crystallographic data. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: tanif@ms.ifoc.kyushu-u.ac.jp
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by Grants-in-Aid (Scientific Research
on Innovative Areas No. 20108009 to F.T., “pi-Space,” and the
Global COE Program “Science for Future Molecular Systems”)
from Ministry of Education, Culture, Sports, Science and
Technology of Japan, by the Cooperative Research Program of
Network Joint Research Center for Materials and Devices
(Institute for Materials Chemistry and Engineering, Kyushu
University),” and by a Research Grant to F.T. from Tokuyama
Science and Technology Foundation and Iketani Science and
Technology Foundation. We acknowledge Prof. T. Shinmyozu
of Kyushu University for his kind cooperation on the use of
GPC and microbalance instruments, Prof. H. Nakano of
Kyushu University and Dr. I. Hisaki of Osaka University for
their advices on DFT calculation and X-ray crystallography,
respectively.
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