Construction of monomeric and polymeric porphyrin compartments by a Pd(II)-pyridine interaction and their chiral twisting by a BINAP ligand

Article abstract of DOI:10.1021/jo020575+

The construction of chirally twisted porphyrin-based molecular capsule 6 and polymeric capsule 8 was investigated by means of scanning electron microscopy (SEM) and ¹H NMR, UV-visible, and CD spectroscopic observations. Molecular capsule 6 and

Full text of DOI:10.1021/jo020575+

Con str u ction of Mon om er ic a n d P olym er ic P or p h yr in
Com p a r tm en ts by a P d (II)-P yr id in e In ter a ction a n d Th eir Ch ir a l
Tw istin g by a BINAP Liga n d
Masatsugu Ayabe,† Kousei Yamashita,† Kazuki Sada,† Seiji Shinkai,*,† Atsushi Ikeda,‡
Shigeru Sakamoto,§ and Kentaro Yamaguchi§
Department of Chemistry & Biochemistry, Graduate School of Engineering, Kyushu University,
Fukuoka 812-8581, J apan, Graduate School of Materials Science, Nara Institute of Science and
Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, J apan, and Chemical Analysis Center,
Chiba University, Chiba 263-8522, J apan
seijitcm@mbox.nc.kyushu-u.ac.jp.
Received August 29, 2002
The construction of chirally twisted porphyrin-based molecular capsule 6 and polymeric capsule 8
1
was investigated by means of scanning electron microscopy (SEM) and H NMR, UV-visible, and
CD spectroscopic observations. Molecular capsule 6 and polymeric capsule 8 were constructed by
the reaction of chiral cis-Pd(II) complex 4 bearing a (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-
binaphthyl (BINAP) ligand with porphyrin 1 bearing four pyridyl groups and porphyrin 2 bearing
1
eight pyridyl groups, respectively. The peak-splitting pattern of the â-pyrrole protons in the H
NMR spectrum and the specific CD spectral pattern bearing an exciton coupling band indicate
that both molecular capsule 6 and polymeric capsule 8 are chirally twisted. Moreover, it was found
that the CD intensity of the polymeric capsule plotted against [4]/([4] + [3]) shows a sigmoidal
curvature, reflecting a unique cooperativity among the ligand groups; that is, the ligand existing
in excess over the other dominates the twisting direction. These results consistently demonstrate
that “chirality” in these molecular assembly systems is conveniently controlled by the use of chiral
ligands.
In tr od u ction
cially, a great deal of effort has been devoted toward
multiporphyrin arrays3 useful for molecular wires,4 mo-
lecular rulers,5 molecular switches,6 photosynthetic sys-
tems,7 photosensitizers for DNA cleavage,8 and photo-
Metal-mediated self-assembly has been proved to be a
very effective methodology in constructing two- or three-
dimensional supramolecular architectures, such as mac-
rocycles, molecular containers, tubular structures, inter-
locked and intertwined structures, and helicates, which
are useful in molecular or chiral recognition, host-guest
chemistry, catalysis, and memory storage.1 Self-assembly
of large supramolecular cages using pyridyl-Pd linkages,
contributed mainly by Stang and Fujita, is especially
appealing because of their structural variety and func-
tional uniqueness.2 On the other hand, porphyrin deriva-
tives are widely used for designing molecular receptors,
sensors, electron or energy transfer systems, and building
blocks for higher order molecular architectures because
of their specific optical and electrical properties. Espe-
(2) (a) Olenyuk, B.; Whiteford, J . A.; Fechtenkotter, A.; Stang, P. J .
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Soc. 1994, 116, 4981-4982. (c) Stang, P. J .; Cao, D. H.; Saito, S.; Arif,
A. M. J . Am. Chem. Soc. 1995, 117, 6273-6283. (d) Takeda, N.;
Umemoto, K.; Yamaguchi, K.; Fujita, M. Nature 1999, 398, 794-796.
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5645-5647. (f) Fujita, M.; Nagao, S.; Ogura, K. J . Am. Chem. Soc. 1995,
117, 1649-1650. (g) Fox, O. D.; Dalley, N. K.; Harrison, R. G. J . Am.
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† Kyushu University.
‡ Nara Institute of Science and Technology.
§ Chiba University.
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P. J . Chem. Rev. 2000, 100, 853-907. (b) MacGillivray, L. R.; Atwood,
J . L. Angew. Chem., Int. Ed. 1999, 38, 1018-1033. (c) Caulder, D. L.;
Raymond, K. N. Acc. Chem. Res. 1999, 32, 975-982. (d) Piguet, C.;
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10.1021/jo020575+ CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/03/2003
J . Org. Chem. 2003, 68, 1059-1066
1059

Ayabe et al.
CHART 1
current generation.9 A number of multiporphyrin arrays
that are linked by noncovalent bonds in a self-assembly
manner10 or by covalent bonds in a polymeric fashion11
have been reported. Covalently linked multiporphyrin
arrays have attracted a great deal of attention in the
construction of a huge π-conjugation system. Recently,
fully conjugated porphyrin tapes that have electronic
absorption bands in the infrared region have been
reported by Osuka’s group.4f-i However, the molecular
design of such covalently linked multiporphyrin arrays
frequently meets very serious synthetic difficulty. On the
other hand, the molecular design of multiporphyrin
arrays linked by noncovalent bonds in a self-assembly
manner has unlimited future potentials for development
of novel functional materials. In constructing such self-
assembled multiporphyrin arrays, one of the most effec-
tive methodologies is to use coordination bonds such as
pyridine-Pd(II) interaction or axial ligation.12 We previ-
ously found that porphyrin 1 (Chart 1) bearing four
pyridyl groups dimerizes with four cis-Pd(II) complexes
3 into a molecular capsule (5) according to a self-
assembled manner.13 Moreover, the spectroscopic studies
showed that the molecular capsule thus formed can
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J esorka, A.; Balaban, T. S.; Holzwarth, A. R.; Schaffner, K.; Angew.
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Prashar, J . K. J . Chem. Soc., Chem. Commun. 1995, 2379-2380. (d)
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1994, 2313-2315. (b) Stang, P. J .; Fan, J .; Olenyuk B. Chem. Commun.
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D.; Stang, P. J .; Fleischer, E. B. J . Am. Chem. Soc. 1999, 121, 2741-
2752. (d) Fujita, N.; Biradha, K.; Fujita, M.; Sakamoto, S.; Yamaguchi,
K. Angew. Chem., Int. Ed. 2001, 40, 1718-1721. (e) Nagata, N.;
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1060 J . Org. Chem., Vol. 68, No. 3, 2003

Monomeric and Polymeric Porphyrin Compartments
SCHEME 1
specifically include a large bipyridine guest.13 On the
other hand, porphyrin 2 bearing eight pyridyl groups at
the upper and lower sides of each porphyrin forms a
linear compartmentalized aggregate (7) with cis-Pd(II)
complexes 3, which can also include a large bipyridine
guest.14 These novel capsular and polymeric assemblies
are expected to include various guest molecules and can
be further applied to nanowires, redox reactions, photo-
chemical reactions, guest-recognition molecular switches,
etc.
In this paper, we have introduced the concept of
“chirality” into this class of porphyrin-based molecular
assemblies. There are a few precedents in which “chiral”
factors are introduced into molecular capsules formed by
covalent bonds.15 To the best of our knowledge, however,
there are a limited number of studies on the introduction
of “chirality” into molecular capsules or polymeric cap-
sules according to a self-assembled manner.16 The design
of such chiral molecular assembly systems is more
difficult and complicated, but if it is achieved, one can
expect that the systems would show more important and
more interesting inclusion and recognition properties
from the viewpoint of practical applications and combi-
natorial chemistry.16
respectively. These compounds were identified by 1H
NMR and MALDI-TOF mass spectral evidence and
elemental analyses. In an attempt to introduce a concept
of “chirality”, we designed molecular capsule 6, which is
composed of two porphyrin derivatives (1)13 bearing four
4-pyridyl substituents and four chiral cis-Pd(II) com-
plexes (4)17 bearing a (R)-(+)-2,2′-bis(diphenylphosphino)-
1,1′-binaphthyl (BINAP) ligand, and polymeric capsule
8, which is composed of porphyrin derivatives (2)14
bearing eight 4-pyridyl substituents and chiral cis-Pd-
(II) complexes (4) bearing a BINAP ligand.
A Novel Self-Assem bled P or p h yr in Ca p su le Con -
str u cted fr om Ch ir a l cis-P d (II) Com p lexes (4) a n d
P or p h yr in Der iva tives (1). The UV-vis absorption
spectra of 1 (9.5 × 10-6 mol dm-3) were measured in CH2-
Cl2 at 25 °C as a function of 4 concentration (Figure 1).
The Q-band (560 nm for 1) shifted to shorter wavelength
with increasing 4 concentration. Generally, a Soret band
shifts to longer wavelength when a pyridyl group coor-
dinates to Zn(II) as an axial ligand. Therefore, this
experimental result suggests that in the absence of 4,
the pyridyl group intermolecularly coordinates to Zn(II)
as an axial ligand and the product is a mixture of several
species (monomer, Zn(II)-coordinated dimer, trimer, etc.),
whereas in the presence of 4, it is decomplexed from
Zn(II) to interact with Pd(II). Eventually, 1 and 4 form a
capsular structure using 4 as pillar units. As shown in
an inset of Figure 1, a plot of ∆Abs560nm vs [4]/[1] has an
inflection point at [4]/[1] ) 2.0. This value indicates that
the complex is formed with a 1:2 1/4 stoichiometry.18 In
Resu lts a n d Discu ssion
Syn th eses a n d Molecu la r Design . Compounds 1
and 2 were synthesized as shown in Schemes 1 and 2,
(13) Ikeda, A.; Ayabe, M.; Shinkai, S.; Sakamoto S.; Yamaguchi, K.
Org. Lett. 2000, 2, 3707-3710.
1
the H NMR spectrum, the simple splitting pattern was
(14) Ikeda, A.; Ayabe, M.; Shinkai, S. Chem. Lett. 2001, 1138-1139.
(15) (a) J udice, J . K.; Cram, D. J . J . Am. Chem. Soc. 1991, 113,
2790-2791. (b) Canceill, J .; Lacombe, L.; Collet, A. J . Am. Chem. Soc.
1985, 107, 6993-6996. (c) Chapman, R. G.; Sherman, J . C. J . Am.
Chem. Soc. 1999, 121, 1962-1963. (d) Paek, K.; Ihm, H.; Yun, S.; Lee,
H. C. Tetrahedron Lett. 1999, 40, 8905-8909.
obtained only when 1 (1.0 × 10-3 mol dm-3) and 4 (2.0 ×
(17) Olenyuk, B.; Whiteford, J . A.; Stang, P. J . J . Am. Chem. Soc.
1996, 118, 8221-8230.
(18) The product is a mixture of several species (monomer, Zn(II)-
coordinated dimer, trimer, etc.) in the 4/1 < 2.0 region, whereas the
spectra are scarcely changed in the 4/1 g 2.0 region. Under these
conditions, one cannot observe tight isosbestic points but may consider
that the stoichiometry is 2:1 in the high 4 concentration region. In
Figure 1, although the isosbestic points are not tight, they do exist at
550, 575, and 600 nm. This lack of tight isobestic points is, as
mentioned above, due to the mixture in the 4/1 < 2.0 region. The
similar spectral situation is also adapted to the polymeric 4/2 system.
(16) (a) Rivera, J . M.; Martin, T.; Rebek, J ., J r. J . Am. Chem. Soc.
2001, 123, 5213-5220. (b) Rivera, J . M.; Rebek, J ., J r. J . Am. Chem.
Soc. 2000, 122, 7811-7812. (c) Rivera, J . M.; Craig, S. L.; Martin, T.;
Rebek, J ., J r. Angew. Chem., Int. Ed. 2000, 39, 2130-2132. (d) Hiraoka,
S.; Fujita, M. J . Am. Chem. Soc. 1999, 121, 10239-10240. (e) Zhong,
Z. L.; Ikeda, A.; Shinkai, S.; Sakamoto, S.; Yamaguchi, K. Org. Lett.
2001, 3, 1085-1087. (f) Ikeda, A.; Udzu, H.; Zhong, Z. L.; Shinkai, S.;
Sakamoto, S. Yamaguchi, K. J . Am. Chem. Soc. 2001, 123, 3872-3877.
J . Org. Chem, Vol. 68, No. 3, 2003 1061

Ayabe et al.
SCHEME 2
1
10-3 mol dm-3) were mixed in a 1:2 molar ratio in CD2-
Cl2 at 25 °C (Figure 2; Figure S1 in Supporting Informa-
tion). When the ratio was higher or lower than this value,
the 1H NMR spectra gave additional peaks and the
splitting pattern became very complicated. The results
support, as already evidenced for a 1/3 complex,13 the
with a 1:2 1/4 stoichiometry. The H NMR spectrum of
the 1:2 1/4 complex is similar to that of the 1:2 1/3
complex with D4h symmetry. The formation of molecular
capsule 6 was further corroborated by cold spray ioniza-
tion mass spectrometery (CSI-MS).19 The CSI-MS spec-
trum of the 1:2 1/4 ([1] ) 4.8 × 10-4 mol dm-3, [4] ) 9.6
× 10-4 mol dm-3) mixture showed strong peaks at m/z
3620.2 and 7388.5, which are assignable to [6 -
formation of molecular capsule 6 (5.0 × 10-4 mol dm-3
)
2CF3SO3 ]
- 2+ and [6 - CF3SO3-]+, respectively (Figure S2
in Supporting Information).
Further details of the molecular structure for 6 were
obtained from the 1H NMR spectra. The R- and â-protons
in the pyridyl groups of 1 gave very broadened peaks,
suggesting that the space between the pyridyl and
diphenylphosphino groups is sterically very crowded.20
It is noteworthy to mention that the â-pyrrole protons
appear as double-doublets (Figure 2, inset); that is,
molecular capsule 6 has two different kinds of â-pyrrole
protons and they couple with each other. This peak-
splitting pattern can be explained by the twisting motion
of four meso-phenyl units around the porphyrin plate
(Figure 3); when the four meso-phenyl units lean to one
side, two different environments are produced in the
porphyrin plate, and consequently, two different kinds
of â-pyrrole protons (grouped into Ha and Hb) appear in
F IGURE 1. Absorption spectral change induced by addition
of [4] in CH2Cl2 at 25 °C: [1] ) 9.5 × 10-6 M, [4] ) 0-2.9 ×
10-5 M. Inset: molar ratio plot.
1
the H NMR spectrum. Since this peak-splitting pattern
is similar to that of a homooxacalix[3]arene-based dimeric
capsule featuring a chiral twisting motion,16f we consider
that the present peak-splitting is also due to the twisting
(19) (a) Sakamoto, S.; Fujita, M.; Kim, K.; Yamaguchi, K. Tetrahe-
dron 2000, 56, 955-964. (b) Sakamoto, S.; Yoshizawa, M.; Kusukawa,
T.; Fujita, M.; Yamaguchi, K. Org. Lett. 2001, 3, 1601-1604. (c)
Addition of a small amount of DMF into the sample greatly enhanced
the peak intensity; see: Blades, A. T.; J ayaweera, P.; Ikonomou, M.
G.; Kebarle, P. J . Chem. Pys. 1990, 92, 5900-5906.
F IGURE 2. Partial 1H NMR spectrum of 6 in CD2Cl2 at 25
°C: [1] ) 1.0 mM, [4] ) 2.0 mM. The full H NMR spectrum
is shown in the Supporting Information (Figure S1).
1
(20) Zhong, Z. L.; Ikeda, A.; Ayabe, M.; Shinkai, S.; Sakamoto, S.;
Yamaguchi, K. J . Org. Chem. 2001, 66, 1002-1008.
1062 J . Org. Chem., Vol. 68, No. 3, 2003

Monomeric and Polymeric Porphyrin Compartments
F IGURE 5. Absorption spectral change induced by addition
of [4] in CH2Cl2 at 25 °C: [2] ) 1.3 × 10-5 M, [4] ) 0-6.8 ×
10-5 M. Inset: molar ratio plot.
F IGURE 3. Possible twisting motion of four meso-phenyl
substituents.
in the porphyrin moieties. This finding clearly reveals
that 6 has a chiral twisting structure under the influence
of chiral BINAP ligands.
A Novel Self-Assem bled P or p h yr in P olym er Con -
str u cted fr om Ch ir a l cis-P d (II) Com p lexes (4) a n d
P or p h yr in Der iva tives (2). It is already established
that porphyrin derivative 2 and cis-Pd(II) complex 3 can
form a one-dimensional polymeric structure (7).14 It thus
occurred to us that when chiral Pd(II) complex 4 is used
as a “comonomer”, polymer 8 might result in a chirally
twisted structure.
First, we determined the stoichiometry of the complex
formed from 2 and 4. The UV-vis absorption spectra of
2 (1.3 × 10-5 M) were measured in CH2Cl2 at 25 °C as a
function of 4 concentration (0-6.8 × 10-5 M) (Figure 5).
The Q-band (620 nm for 2) shifted to longer wavelength,
in contrast to the shorter wavelength shift observed for
a 1 + 4 system (vide supra). Presumably, this longer
wavelength shift is related to the polymeric aggregate,
but the mechanistic origin is not yet clear at present. As
shown in an inset of Figure 5, a plot of ∆Abs620
vs
nm
[4]/[2] has an inflection point at [4]/[2] ) 4.0. This value
supports the view that the complex is formed with a 1:4
2/4 stoichiometry. Since ∆Abs620nm was much less affected
above [4]/[2] ) 4.0, one can conclude that the pyridyl
groups of 2 scarcely interact with Zn(II) in the [4]/[2] )
4.0 complex.18 The absorption spectrum of the 1:4 2/4
complex is similar to that of 1:4 2/3 complex (7),14
supporting the formation of one-dimensional polymeric
structure 8.
Second, to obtain evidence for the formation of a self-
assembled polymeric structure, we measured the molec-
ular weight of polymer 8 in solution by a dynamic light-
scattering method.22 In CH2Cl2, the average particle size
of 8 ([2] ) 1.3 × 10-5 M, [4] ) 5.2 × 10-5 M) was
estimated to be ca. 80 nm. The result indicates that the
self-assembled polymer is formed in solution. On the
other hand, 1H NMR spectroscopy did not give any useful
information, because the solution containing polymer 8
in CD2Cl2 showed a very peak broadened spectrum. To
obtain visual insights into the aggregation mode, we
F IGURE 4. (a) CD spectra of 6 ([1] ) 9.5 × 10-6 M, [4] ) 1.9
× 10-5 M) and 8 ([2] ) 1.3 × 10-5 M, [4] ) 5.2 × 10-5 M) in
CH2Cl2 at 25 °C. (b) Absorption spectra of 6 ([1] ) 6.4 × 10-6
M, [4] ) 1.3 × 10-5 M) and 8 ([2] ) 8.9 × 10-6 M, [4] ) 3.6 ×
10-5 M) in CH2Cl2 at 25 °C: ‚‚‚, 6; -, 8.
motion of four meso-phenyl units around the porphyrin
plate. This means that molecular capsule 6 has “chirality”
arising from its twisting structure.
We confirmed the helicity of 6 by circular dichroism
(CD) spectroscopy (Figure 4a). In CH2Cl2 at 25 °C, a split
CD band of 6 ([1] ) 9.5 × 10-6 M, [4] ) 1.9 × 10-5 M),
which crosses the [θ] ) 0 line at 432 nm (same wave-
length as the λmax ) 430 nm in the Soret band region of
the absorption spectrum of 6 ([1] ) 6.4 × 10-6 M, [4] )
1.3 × 10-5 M)), is ascribed to an exiton coupling. It was
suggested from the most stable conformation of 6 calcu-
lated by computational methods (Discover 3/Insight II
98.0) that 6 has the left-handed helical twisting structure
(Figure S3 in Supporting Information). This conformation
is reasonable for the split CD band with a negative first
Cotton effect and a positive second Cotton effect.21 In
other words, the CD band is not due to induced CD (ICD)
from chiral BINAP ligands but due to molecular chirality
(21) Sugasaki, A.; Ikeda, M.; Takeuchi, M.; Shinkai, S. Angew.
Chem., Int. Ed. 2000, 39, 3839-3842.
(22) Preparation of the sample for dynamic light-scattering:
A
mixture of 2 (1.3 × 10-5 M) and 4 (5.2 × 10-5 M) in CH2Cl2 was stirred
at room temperature for 1 min.
J . Org. Chem, Vol. 68, No. 3, 2003 1063

Ayabe et al.
SCHEME 3
F IGURE 6. SEM image of 8.
prepared dry samples for scanning electron microscope
(SEM) observation.23 In the SEM picture thus obtained
(Figure 6), the well-grown fibrous structures with diam-
eters of ca. 20-40 nm were abundantly observed. The
fibers were very long, suggesting that the 2 + 4 mixture
tends to grow into a one-dimensional direction and the
polymer with porphyrin compartments is stably formed.
Third, we confirmed the presence of the helicity in 8
([2] ) 1.3 × 10-5 M, [4] ) 5.2 × 10-5 M), by CD
spectroscopy (Figure 4a). In CH2Cl2 at 25 °C, a split CD
band, which crosses the [θ] ) 0 line at 439 nm [same as
wavelength λmax ) 439 nm of the absorption spectrum of
8 ([2] ) 8.9 × 10-6 M, [4] ) 3.6 × 10-5 M)], is ascribed to
an exiton coupling. This CD pattern, which consists of a
negative first Cotton effect and a positive second Cotton
effect, is very similar to that of molecular capsule 6. This
result supports the view that polymer 8 is a one-
dimensional polymeric aggregate with a chirally twisting
structure. On the other hand, the CD intensity of 8 is
stronger than that of 6 (Figure 4). This result suggests
that since two pyridyl groups are connected to a meso-
phenyl moiety by rigid acetylene spacers in 2, the helicity
of polymer 8 is transmitted through the meso-phenyl
moieties more efficiently to the polymeric chain (Scheme
3).
We have learned from the molecular modeling of 7 and
8 that these polymeric rods are sterically very rigid. This
suggests that when one 2 unit is twisted by 4, its
neighboring 2 units are enforced to be twisted coopera-
tively. This kind of cooperativity is similar to a “sergeant
and soldiers” relationship rarely observed in molecular
assembly systems and polymeric systems;24,25 that is,
when the CD intensity is plotted against [4]/([4] + [3])
(where the total concentration of [4] + [3] (5.2 × 10-5 M)
is maintained constant), the plot may deviate from the
45° linear relationship, because the influence of achiral
3 predominates that of 4 at [4]/([4] + [3]) < 0.5, whereas
chiral 4 predominates over 3 at [4]/([4] + [3]) > 0.5. The
CD measurements on the 3/4 mixtures were conducted
in CH2Cl2 at 25 °C (Method A). Very interestingly, we
observed a sigmoidal increase in the CD intensity. As
shown in an inset of Figure 7, the CD intensity increases
with the increase in the ratio of 4 and crosses the 45°
line at [4]/([4] + [3]) ) ca. 0.7 ([4] ) 3.6 × 10-5 M, [3] )
1.6 × 10-5 M). Although two plots at [4]/([4] + [3]) > 0.7
only slightly exceed the 45° line, we have repeatedly
confirmed that they are reproducible and higher than the
45° line beyond the error range. The result implies that
at low [4]/([4] + [3]) region 2 tends to form achiral
polymeric rods, whereas only at very high [4]/([4] + [3])
region can 2 form chirally twisted polymeric rods. The
asymmetry in the sigmoidal curvature is explained by
the stability difference between the achiral polymeric rod
and the chirally twisted polymeric rod. In the achiral
structure the meso-phenyl substituents can occupy the
most stable dihedral angle perpendicular to the porphy-
rin plane. In contrast, in the chirally twisted structure
the meso-phenyl substituents must rotate, more or less,
to the energetically unfavorable angle.26 Thus, the region
governed by achiral 3 is larger than that governed by
chiral 4. It is important, however, that the region
governed by chiral 4 does exist. One can propose,
therefore, that one compartment in the polymeric rod
(23) Preparation of the sample for scanning electron microscopy: A
mixture of 2 (1.0 × 10-4 M) and 4 (4.0 × 10-4 M) in CH2Cl2 solvent
was stirred at room temperature for 1 min. One drop of a 2 + 4 mixture
in CH2Cl2 was placed on a carbon-coated grid on a filter paper. The
drop immediately penetrated into the filter paper, and the grids were
allowed to dry in air. This sample was coated with Pt under argon for
30 s.
(24) Green, M. M.; Reidy, M. P.; J ohnson, R. J .; Darling, G.; O’Leary,
D. J .; Wilson, G. J . Am. Chem. Soc. 1989, 111, 6452-6454.
(25) (a) Brunsveld, L.; Lohmeijer, B. G. G.; Vekemans, J . A. J . M.;
Meijer, E. W. Chem. Commun. 2000, 2305-2306. (b) Brunsveld, L.;
Lohmeijer, B. G. G.; Vekemans, J . A. J . M.; Meijer, E. W. J . Incl.
Phenom. Macro. 2001, 41, 61-64.
1064 J . Org. Chem., Vol. 68, No. 3, 2003

Monomeric and Polymeric Porphyrin Compartments
filtered and the filtrate was concentrated in vacuo. After
purification by column chromatography (silica gel, chloroform/
hexane ) 1:1 v/v), 2.03 g of colorless oil (Rf ) 0.40, chloroform/
1
hexane ) 1:1 v/v, silica plate) was obtained: yield, 72%; H
NMR (250 MHz, CDCl3) δ 9.82 (s, 1H), 7.85 (d, J ) 1.9 Hz,
1H), 7.40 (d, J ) 1.9 Hz, 1H), 4.09 (t, J ) 6.6 Hz, 2H), 3.90 (s,
3H), 1.92-1.76 (m, 2H), 1.58-1.29 (m, 10H), 0.89 (t, J ) 6.8
Hz, 3H); MALDI-TOF MS m/z 390.8 (M + H+).
3-Met h oxy-4-oct yloxy-5-(4-p yr id yl)et h yn ylb en za ld e-
h yd e (11). A mixture of 10 (1.45 g, 3.70 mmol), bis(tri-
phenylphosphine)palladium(II) dichloride (0.53 g, 0.75 mmol),
and copper(I) iodide (0.14 g, 0.75 mmol) in diisopropylamine
(40 mL) was stirred at room temperature under a nitrogen
atmosphere. After addition of 4-ethynylpyridine27 (0.52 g, 5.00
mmol) into the solution, the mixture was stirred at room
temperature for 24 h. The reaction mixture was filtered and
the filtrate was evaporated to dryness. The residue was
dissolved in chloroform and the solution was washed twice
with water and then dried over anhydrous Na2SO4. After
evaporation to dryness, the residue was purified by column
chromatography (silica gel, ethyl acetate). Thus, 1.15 g of pale
yellow oil (Rf ) 0.70, ethyl acetate, silica plate) was obtained:
yield, 85%;1H NMR (250 MHz, CDCl3) δ 9.85 (s, 1H), 8.63 (d,
J ) 5.8 Hz, 2H), 7.61 (s, 1H), 7.45 (s, 1H), 7.39 (d, J ) 5.8 Hz,
2H), 4.26 (t, J ) 6.6 Hz, 2H), 3.93 (s, 3H), 1.83-1.73 (m, 2H),
1.50-1.25 (m, 10H), 0.85 (t, J ) 6.8 Hz, 3H); MALDI-TOF MS
m/z 366.5 (M + H+).
F IGURE 7. Plot of [θ]obs/[θ]max at 446 nm vs [4]/([4] + [3]) in
CH2Cl2 at 25 °C: [2] ) 1.3 × 10-5 M, [3] + [4] ) 5.2 × 10-5
M
(constant). [θ]max denotes the [θ]446nm value at [4]/([4] + [3]) )
1.0. The 45° line is shown by a dotted line. Inset: CD spectral
change induced by a molar ratio variation.
tends to cooperatively construct the same compartments
in its neighboring units.
5,10,15,20-Tetr a k is[[3-(4-p yr id yl)eth yn yl-4-octyloxy-5-
m eth oxy]p h en yl]p or p h yr in (12). A mixture of 11 (1.00 g,
2.74 mmol) and pyrrole (0.18 g, 2.68 mmol) in propionic acid
(100 mL) was stirred at reflux temperature for 3 h. The solvent
was evaporated, and the residue was dissolved in chloroform.
The solution was washed with aqueous Na2CO3 and water and
then dried over anhydrous Na2SO4. After evaporation to
dryness, the residue was purified by column chromatography
(alumina gel, chloroform/hexane ) 1:1 v/v) and gel permeation
chromatography. Thus, 0.25 g of purple solid (Rf ) 0.50,
chloroform, alumina plate) was obtained: yield, 22%; 1H NMR
(600 MHz, CDCl3) δ 8.96 (s, 8H), 8.60 (d, J ) 5.8 Hz, 8H),
7.97 (d, J ) 5.5 Hz, 4H), 7.82 (d, J ) 5.5 Hz, 4H), 7.39 (d, J )
5.8 Hz, 8H), 4.48 (t, 8H, J ) 6.6 Hz), 3.98 (s, 12H), 2.03-2.01
(m, 8H), 1.80-1.25 (m, 40H), 0.91 (t, J ) 6.8 Hz, 12H), -2.81
(s, 2H); MALDI-TOF MS m/z 1651.9 (M + H+). Anal. Calcd
for C108H114N8O8‚3H2O: C, 76.03; H, 7.09; N, 6.57. Found: C,
75.96; H, 7.10; N, 6.30.
Con clu sion s
In conclusion, this paper demonstrates the molecular
design of novel chiral porphyrin-based molecular capsular
and polymeric structures constructed in a self-assembled
manner. This method has a unique feature that the
helicity is conveniently introduced by the use of an
optically active ligand, BINAP. Reflecting the very rigid
polymeric structure, the plot of the CD intensity vs
[4]/([4] + [3]) shows a sigmoidal curvature arising from
a unique cooperativity occurring along the one-dimen-
sional rod. One may regard this phenomenon as a novel
cooperativity attained in a one-dimensional molecular
assembly. We are now testing how this rule appears
when guest molecules are included in the compartments.
Furthermore, we believe that these chiral capsule 6 and
polymer 8 would be useful not only as conventional hosts
for chiral guest recognition but also as candidates for
switch-functionalized assemblies by redox reactions,
photochemical reactions, guest inclusion, etc.
Zn (II)
5,10,15,20-Tet r a k is[[3-(4-p yr id yl)et h yn yl-4-
octyloxy-5-m eth oxy]p h en yl]p or p h yr in (1). A mixture of
12 (30 mg, 0.018 mmol) and zinc acetate (18 mg, 0.083 mmol)
in a mixed solvent of methanol (3 mL) and dichloromethane
(3 mL) was stirred at room temperature for 20 min. The
solvent was evaporated, and the residue was purified by
column chromatography (silica gel, chloroform/methanol ) 9:1
v/v). Thus, 31 mg of purple solid (Rf ) 0.50, chloroform/
methanol ) 9:1 v/v, silica plate) was obtained: yield, 99%; 1H
NMR (600 MHz, pyridine) δ 9.42 (m, 8H), 8.79 (d, J ) 4.3 Hz,
8H), 7.64 (d, J ) 4.3 Hz, 8H), 4.67 (t, 8H, J ) 6.6 Hz), 4.00
(m, 12H, OMe), 2.17-2.14 (m, 8H), 1.82-1.25 (m, 40H), 0.87
(t, J ) 6.8 Hz, 12H); MALDI-TOF MS m/z 1713.8 (M + H+).
Anal. Calcd for C108H112N8O8Zn‚3H2O: C, 73.31; H, 6.72; N,
6.33. Found: C, 73.52; H, 6.82; N, 6.17.
3,5-Diiod o-4-octyloxyben za ld eh yd e (14). A mixture of
3,5-diiodo-4-hydroxybenzaldehyde28 (1.50 g, 4.00 mmol), 1-iodo-
octane (4.30 g, 18.0 mmol), and K2CO3 (2.50 g, 18.0 mmol) in
a mixed solvent of THF (40 mL) and DMF (10 mL) was stirred
at reflux temperature for 24 h. After cooling, the filtrate was
concentrated in vacuo. After purification by column chroma-
tography (silica gel, chloroform/hexane ) 1:1 v/v), 1.80 g of
colorless solid (Rf ) 0.60, chloroform/ hexane ) 1:1 v/v, silica
Exp er im en ta l Section
Meth od A. The CD measurements on the 2 + 3/4 (mixture)
were conducted in CH2Cl2 at 25 °C. The concentration of [2]
(1.3 × 10-5 M) and the total concentration of [4] + [3] (5.2 ×
10-5 M) are maintained constant. The values of [4]/([4] + [3]),
a ratio of chiral factors, were changed from 0 (i.e., [4] ) 0 M)
to 1.0 (i.e., [4] ) 5.2 × 10-5 M). The CD spectra of mixtures
obtained with various chiral factors were measured.
5-Iod o-3-m eth oxy-4-octyloxyben za ld eh yd e (10). A mix-
ture of 5-iodovanillin (2.00 g, 7.19 mmol), 1-iodooctane (8.63
g, 35.9 mmol), and K2CO3 (5.04 g, 36.5 mmol) in a mixed
solution of THF (40 mL) and DMF (10 mL) was stirred at
reflux temperature for 24 h. After cooling, the mixture was
(26) The most stable conformations of 5 and 6 were estimated by
computational methods (Discover 3/Insight II 98.0). As a result, we
confirmed that the inclination angle of the meso-phenyl groups in 6 is
larger than that in 5. Since the most stable conformation adopts 90°,
one may consider that 5 is more stable than 6. The similar situation
is also adapted to 7 and 8.
(27) Ciana, L. D.; Haim, A. J . Heterocycl. Chem. 1984, 21, 607-
608.
(28) Kajigaeshi, S.; Kakinami, T.; Yamasaki, H.; Fujisaki, S.; Kondo,
M.; Okamoto, T. Chem. Lett. 1987, 2109-2112.
J . Org. Chem, Vol. 68, No. 3, 2003 1065

Ayabe et al.
1
plate) was obtained: yield, 93%; mp 43.3-44.5 °C; H NMR
7.42 (d, J ) 5.9 Hz, 16H), 4.70 (t, 8H, J ) 6.6 Hz), 2.09-2.12
(m, 8H), 1.50-1.20 (m, 40H), 0.84 (t, J ) 6.8 Hz, 12H), -2.83
(s, 2H); MALDI-TOF MS m/z 1936.5 (M + H+). Anal. Calcd
for C132H118N12O4‚CH2Cl2: C, 79.03; H, 5.98; N, 8.32. Found:
C, 79.16; H, 6.21; N, 8.10.
(250 MHz, CDCl3) δ 9.74 (s, 1H), 8.20 (s, 2H), 3.97 (t, J ) 6.6
Hz, 2H), 1.92-1.83 (m, 2H), 1.50-1.20 (m, 10H), 0.84 (t, J )
6.8 Hz, 3H); MALDI-TOF MS m/z 487.3 (M + H+).
3,5-Bis(4-pyr idyl)eth yn yl-4-octyloxyben zaldeh yde (15).
A mixture of 14 (1.80 g, 3.70 mmol), bis(triphenylphosphine)-
palladium(II) dichloride (0.53 g, 0.75 mmol), and copper(I)
iodide (0.14 g, 0.75 mmol) in diisopropylamine (40 mL) was
stirred at room temperature under a nitrogen atmosphere.
After addition of 4-ethynylpyridine27 (0.82 g, 8.00 mmol) into
the solution, the mixture was stirred at room temperature for
24 h. The reaction mixture was filtered and the filtrate was
evaporated to dryness. The residue was dissolved in chloroform
and the solution was washed twice with water and then dried
over anhydrous Na2SO4. After evaporation to dryness, the
residue was purified by column chromatography (silica gel,
ethyl acetate). Thus, 1.20 g of pale yellow solid (Rf ) 0.60, ethyl
Zn (II) 5,10,15,20-Tetr a k is[[3,5-bis(4-p yr id yl)eth yn yl-4-
octyloxy]]p h en ylp or p h yr in (2). A mixture of 16 (60 mg,
0.031 mmol) and zinc acetate (20 mg, 0.093 mmol) in a mixed
solvent of methanol (10 mL) and dichloromethane (3 mL) was
stirred at room temperature for 20 min. The solvent was
evaporated, and the residue was purified by column chroma-
tography (silica gel, chloroform/methanol ) 9:1 v/v). Thus, 60
mg of purple solid (Rf ) 0.50, chloroform/methanol ) 9:1 v/v,
silica plate) was obtained: yield, 96%; 1H NMR (600 MHz,
pyridine) δ 9.04 (s, 8H), 8.50 (s, 8H), 8.46 (d, J ) 5.7 Hz, 16H),
7.28 (d, J ) 5.7 Hz, 16H), 4.53 (t, 8H, J ) 6.6 Hz), 1.98-1.88
(m, 8H), 1.64-0.86 (m, 40H), 0.51 (t, J ) 6.8 Hz, 12H); MALDI-
TOF MS m/z 1998.3 (M + H+). Anal. Calcd for C132H116N12O4-
Zn‚2MeOH: C, 77.98; H, 6.06; N, 8.14. Found: C, 77.76; H,
6.01; N, 7.92.
1
acetate, silica plate) was obtained: yield, 76%; H NMR (250
MHz, CDCl3) δ 9.93 (s, 1H), 8.65 (d, J ) 5.9 Hz, 4H), 8.04 (s,
2H), 7.40 (d, J ) 5.9 Hz, 4H), 4.51 (t, J ) 6.6 Hz, 2H), 1.83-
1.92 (m, 2H), 1.20-1.50 (m, 10H), 0.84 (t, J ) 6.8 Hz, 3H);
MALDI-TOF MS m/z 437.5 (M + H+).
Ack n ow led gm en t. This work was supported by
PRESTO (Precursory Research for Embryonic Science
and Technology) in the J apan Science and Technology
Corporation (J ST) and also by the Grants-in-Aid for
Scientific Research from the Ministry of Education,
Science and Culture of J apan.
5,10,15,20-Tetr a k is[[3,5-bis(4-p yr id yl)eth yn yl-4-octyl-
oxy]]p h en ylp or p h yr in (16). A mixture of 15 (1.00 g, 2.30
mmol) and pyrrole (0.15 g, 2.30 mmol) in propionic acid (150
mL) was stirred at reflux temperature for 3 h. The solvent
was evaporated, and the residue was dissolved in dichlo-
romethane. The solution was washed with aqueous Na2CO3
and water and then dried over anhydrous Na2SO4. After
evaporation to dryness, the residue was purified by column
chromatography (silica gel, chloroform/MeOH ) 9:1 v/v). Thus,
0.11 g of purple solid (Rf ) 0.50, chloroform/methanol ) 9:1
v/v, silica plate) was obtained: yield, 9.9%; 1H NMR (600 MHz,
CDCl3) δ 8.99 (s, 8H), 8.60 (d, J ) 5.9 Hz, 16H), 8.38 (s, 8H),
Su p p or tin g In for m a tion Ava ila ble: 1H NMR (Figure S1)
and CSI-MS (Figure S2) spectra of 6 and molecular modeling
(Figure S3) of 6. This material is available free of charge via
the Internet at http://pubs.acs.org.
J O020575+
1066 J . Org. Chem., Vol. 68, No. 3, 2003