Complexation-induced transition of nanorod to network aggregates: Alternate porphyrin and cyclodextrin arrays

Article abstract of DOI:10.1021/ja075981v

Tetrakis(permethyl-β-cyclodextrin)-modified zinc(II) porphyrin (1) and tetra(β-cyclodextrin)-modified zinc(II) porphyrin (2) were synthesized via quot;click chemistry". Intermolecular inclusion complexation of these structurally similar 1 and 2 with tetrasodium tetraphenylporphyrintetrasulfonate (3) led to formation of two distinctly different nanoarchitectures with alternate porphyrin and cyclodextrin arrays, which were proven to be network and nanorod aggregates, respectively, by using transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. From the results of comparative studies in different solutions, we elucidated the mechanisms that result in nanorod to network aggregates transition, concluding that the complexation strength of porphyrin with cyclodextrin is a crucial factor to activate the potential binding sites of a molecular building block.

Full text of DOI:10.1021/ja075981v

Published on Web 12/21/2007
Complexation-Induced Transition of Nanorod to Network
Aggregates: Alternate Porphyrin and Cyclodextrin Arrays
Yu Liu,* Chen-Feng Ke, Heng-Yi Zhang, Jie Cui, and Fei Ding
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry,
Nankai UniVersity, Tianjin, 300071, P. R. China
Received August 8, 2007; E-mail: yuliu@nankai.edu.cn
Abstract: Tetrakis(permethyl-â-cyclodextrin)-modified zinc(II) porphyrin (1) and tetra(â-cyclodextrin)-modified
zinc(II) porphyrin (2) were synthesized via “click chemistry”. Intermolecular inclusion complexation of these
structurally similar 1 and 2 with tetrasodium tetraphenylporphyrintetrasulfonate (3) led to formation of two
distinctly different nanoarchitectures with alternate porphyrin and cyclodextrin arrays, which were proven
to be network and nanorod aggregates, respectively, by using transmission electron microscopy, atomic
force microscopy, and scanning electron microscopy. From the results of comparative studies in different
solutions, we elucidated the mechanisms that result in nanorod to network aggregates transition, concluding
that the complexation strength of porphyrin with cyclodextrin is a crucial factor to activate the potential
binding sites of a molecular building block.
Introduction
(CDs) becomes an important topic for designing functional
6,7
supramolecular assemblies, and the binding behavior, enzyme
mimics, and energy/electron transfer abilities of porphyrin-CD
Self-assembly processes are ubiquitous in chemistry, materials
science, and biology. The morphology of the assembly is usually
determined by the structure of the individual components.
8
conjugates have been investigated. Herein, we report the
1
construction of two supramolecular nanoarchitectures whose
aggregation patterns are controlled by selectively activating the
potential binding sites of the molecular building blocks. Using
transmission electron microscopy (TEM), atomic force micros-
copy (AFM), and scanning electron microscopy (SEM), we will
show that the constructed nanorods or network aggregates are
formed by the noncovalent interactions of meso-tetraphenylpor-
phyrin-4,4′,4′′,4′′′-tetrasulfonic acid tetrasodium salt (3) with
porphyrin-â-CD or porphyrin-permethyl-â-CD conjugates, and
also that the morphology switching is controlled in a predictable
fashion by the complexation strength of porphyrins with CDs.
Therefore, the design of molecular building blocks and binding
motif that organize themselves into desired patterns and
functions is the key to the application of self-assembly. On
2
the other hand, a functional molecular building block employed
in supramolecular chemistry usually possesses an invariable
shape with unambiguous functional binding sites, which lead
them to a supramolecular assembly with a fixed pattern. In
biology, stem cells can differentiate to divergent cell types that
make up the organism when the right signals are provided. That
is, stem cells have the potential to develop into mature cells
that have characteristic shapes and specialized functions. Thus,
the design of functional molecular building blocks which are
similar to stem cells remains challenging.
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molecules 2006, 7, 3527-3533. (b) Kano, K.; Kitagishi, H.; Mabuchi, T.;
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Nishiyabu, R.; Asada, T.; Kuroda, Y. J. Am. Chem. Soc. 2002, 124, 9937-
Porphyrins have been widely used as functional building
blocks in supramolecular chemistry because of their photo-
9944. (d) Deng, W.; Onji, T.; Yamaguchi, H.; Ikedab, N.; Harada, A. Chem.
Commun. 2006, 4212-4214. (e) Lang, K.; Mosinger, J.; Wagnerov a´ , D.
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D. N. Chem.-Eur. J. 2004, 10, 1114-1123.
3
chemical properties, the ability to be used as donor/accepter
4
5
ability in electron or energy transfer process, and so on. In
particular, the combination of porphyrins and cyclodextrins
(
7) (a) Sasaki, K.; Nakagawa, H.; Zhang, X.-Y.; Sakurai, S.; Kano, K.; Kuroda,
Y. Chem. Commun. 2004, 408-409. (b) Kano, K.; Kitagishi, H.; Dagallier,
C.; Kodera, M.; Matsuo, T.; Hayashi, T.; Hisaeda, Y.; Hirota, S. Inorg.
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J. AM. CHEM. SOC. 2008, 130, 600-605
10.1021/ja075981v CCC: $40.75 © 2008 American Chemical Society

Alternate Porphyrin and Cyclodextrin Arrays
A R T I C L E S
Scheme 1. Synthesis of 1 and 2
Results and Discussion
holes, which is consistent with the observations from TEM and
AFM. With the fact that both 1 and 2 contain the same porphyrin
core, and the only difference between the two is the outer CD
moieties (one is a permethylated CD and the other is a native
one), the formation of these two distinct nanoarchitectures led
us to investigate the origin of the difference.
Synthesis. The reactions of 5,10,15,20-tetrakis(4′-propagy-
loxyphenyl)-Zn(II)-porphyrin with 6-deoxy-6-azido-permethyl-
â-CD and 6-deoxy-6-azido-â-CD in THF/H2O afforded tetrakis-
(permethyl-â-CD)-modified Zn(II) porphyrin (1, 90% yield) and
tetra-â-CD-modified Zn(II) porphyrin (2, 70% yield), respec-
tively, via “click chemistry” (Scheme 1), from which the
supramolecular nanoarchitectures were constructed by the
complexation of 3 with 2 and 1 in aqueous solution.
TEM, AFM, and SEM Images. Representative TEM, AFM,
and SEM images of the aggregate of 2 and 3 are shown in Figure
NMR Spectra of 1 and 2. We first investigated the
conformation of 1 and 2 in aqueous solution as well as in organic
solvents by NMR spectroscopy. Compound 1 has high solubility
in both chloroform and aqueous solution, while 2 is soluble in
DMSO and in aqueous solution. For this reason, all NMR
experiments were performed in all three solvents. As shown in
1(a-c), where we can clearly see the nanorods on the substrates.
1
Figure 2, the H NMR spectrum of 1 in CDCl3 is completely
In the TEM image, the length of the nanorods is more than 100
nm, and there are several parallel fiberlike nanowires with
widths of about 2 nm. The AFM image shows two nanorods
with heights of 8 nm and lengths of 500 nm and 3 µm,
respectively. Similarly, a number of nanorods with lengths of
several hundred nanometers are observed in the SEM image.
These observations exclude the possibility that all intermolecular
interactions between four CD cavities in 2 and four sulfonic
acid groups in 3 occur. The self-assembly process should take
place between two opposite CD moieties of 2 and two opposite
phenylsulfonic acid groups.
Surprisingly, the nanoarchitectures formed by the complex-
ation of 1 with 3 in aqueous solutions are distinctly different
from those described above. Both the TEM and the AFM images
show two-dimensional netlike aggregates (Figure 1d,e). The
SEM image in Figure 1f shows the surface morphologies of
the aggregates. The latter are the flakelike structures with many
different from that in D2O. In CDCl3, there are four groups of
signals (δ ) 8.95, 8.14, 7.95, and 7.37 ppm) in the low field
region. They are assigned to the protons of the pyrrole rings,
the ortho-phenyl moieties, the triazole rings, and the meta-phenyl
moieties, respectively (Supporting Information). No protons are
found in the high field region below 2.5 ppm. Interestingly, the
peaks corresponding to the protons of the pyrrole rings and the
phenyl moieties are split into several different subsets in D2O,
with accompanying moderate peak shifts. Many new proton
signals also appear in the range of -0.5 to 2.0 ppm (Figure
2
b). These observations are very similar to those made in the
case of 10,20-bis(3,5-dicarboxylatophenyl)-5,15-diphenylpor-
9
phyrin-permethyl-â-CD conjugate, which allows us to assign
these upfield-shifted protons to the secondary OCH3 groups of
9
the CD moieties. This assignment is validated by the hetero-
(9) Nishiyabu, R.; Kano, K. Eur. J. Org. Chem. 2004, 4985-4988.
J. AM. CHEM. SOC.
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VOL. 130, NO. 2, 2008 601

A R T I C L E S
Liu et al.
Figure 1. TEM (a and d), AFM (b and e), and SEM (c and f) images of the nanoarchitectures formed upon complexation of 3 with 2 (a-c) and 1 (d-f).
that the secondary sides of CDs are located near the pyrrole
and phenyl groups. That means that some CDs in 1 include the
porphyrin part by rotating 360° around the pivot glucopyranose
unit in the methylated CD. Considering the steric hindrance of
6
c
CDs around the porphyrin core, we conclude that only the
two CD moieties of 1 at opposite positions intramolecularly
include the porphyrin part in aqueous solution. The schematic
representations of the partial self-inclusion by a full rotation of
the permethylated glucopyranose units and the conformational
changes of 1 in chloroform and water are illustrated in Figure
3
.
Just as observed for 1 in CDCl3, the aromatic portions in the
1
H NMR spectrum of 2 in DMSO-d6 also exhibit four groups
of signals at δ ) 8.85, 8.36, 8.11, and 7.48 ppm. However, the
triazole protons of 2 shift downfield to a greater extent to 8.36
ppm than those of 1 (7.95 ppm), which suggests that the triazole
groups are included inside the cavity of CD. On the other hand,
1
there are H signals in the high field region below 1.5 ppm and
1
3
C ones below 40 ppm, and the correlation peaks are observed
between these proton signals in the high field region and the
1
3
C signals in the heteronuclear multiple quantum coherence
HMQC) spectrum of 2. Its HMBC spectrum suggests that these
(
high field signals are assigned to the CD’s H-2 and H-3 protons
Supporting Information). Therefore, one can deduce reasonably
(
that the secondary face of some CDs in 2 includes the porphyrin
part. The 2D NMR spectrum of 2 in DMSO-d6 shows strong
NOE cross-peaks between the triazole protons and the CD’s
H3 and H5, and also weak cross-peaks of the pyrrole and phenyl
protons with the CD’s H-3. These observations unambiguously
indicate that the hydrophobic cavity of CD intramolecularly
includes the triazole group from the wide-opening secondary
face. The attempt to obtain a clear-cut spectrum of 2 in D2O
was not successful as the four groups of the peaks as well as
those in CD become broad as the percentage of D2O increases.
This signal broadening may be attributed to the fast equilibrium
Figure 2. 1H NMR spectra of (a) 1 in CDCl3, (b) 1 in D2O, (c) 3 in D2O,
(
d) 1 (0.60 µM) with 3 (2.44 µM) in D2O, and (e) 1 (0.60 µM) with 2-NS
(21.7 µM) in D2O. Filled side triangle, open side triangle, and filled
diamonds represent TMS or residual solvent peaks in CDCl3 and D2O.
nuclear multiple bond coherence (HMBC) spectrum of 1 in D2O
(Supporting Information). Furthermore, the NOESY spectrum
of 1 in D2O (Supporting Information) exhibits the cross-peaks
between the protons of the secondary OCH3 with those of the
porphyrin’s pyrrole and the phenyl moieties, clearly indicating
602 J. AM. CHEM. SOC.
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Alternate Porphyrin and Cyclodextrin Arrays
A R T I C L E S
Figure 3. Schematic representation of (a) the partial self-inclusion caused by a full rotation of the pivotal permethylated glucopyranose units, (b) the
conformational switching of 1 in chloroform and in water, and the corresponding assembly mode with 3, and (c) the conformational switching of 2 in
dimethylsulfoxide and in water, and the corresponding assembly mode with 3.
Table 1. Complex Stoichiometry (n), Stepwise Binding Constants
shift of the CD moiety between the triazole and phenyl moieties,
-
1
-1
(
KS/M ), Enthalpy (∆H/kJ‚mol ), and Entropy Changes (T∆S/
as illustrated in Figure 3c. With the information of 2 in DMSO
and H2O, we can make the reasonable deduction that the CD
moieties in 2 always exist in the intramolecular self-inclusion
mode in both DMSO and H2O. Similar to that of 1, only two
opposite CD moieties of 2 are thought to adopt the self-included
conformation, and the other two remain free, as illustrated in
Figure 3c. We also carried out molecular dynamics simulations,
using the Dreiding force field,10 to compare the stabilities of
the two self-included conformations of 2 (i.e., the oppositely
versus adjacently capped). The calculation results indicate that
the oppositely capped conformer is energetically more stable
than the adjacently capped one, for which the severe steric
hindrance between the two adjacent self-including CDs is
responsible. This contractive conformation of 2 probably comes
from the preferential threading of only two opposite side chains
of the tetrakis(propargyloxyphenyl)porphyrin through the 6-azido-
CD cavity in THF/H2O solution before the click cyclization. In
this way, only the remaining two CDs are active and rod array
can be formed upon interaction with 3.
-1
kJ‚mol ) for 1:n Inclusion Complexation of 2 or 1 with 1-AD/3 in
Aqueous Phosphate Buffer Solutions of pH 7.0 at 298 K
a
host
guest
n
K
S
−∆H
T∆S
4
3
4
7
2
1
2
1
1-AD
1-AD
3
1.9
2.1
1.0
2.0
(8.7 ( 0.3) × 10
(1.4 ( 0.3) × 10
(4.2 ( 0.7) × 10
(2.7 ( 0.4) × 10
29.0 ( 0.2
16.1 ( 0.5
33.1 ( 2.2
70.6 ( 1.3
-0.9
0.4
-6.7
-7.0
3
a
Values corresponding to the one set of binding sites model.13 This model
will work for any number of sites (n), if all sites have the same KS.
the curve fitting of the binding isotherm are very close to 2,
clearly indicating that the majority of the inclusion complexes
of 1 and 2 with 1-AD is 1:2 and there are two free CD cavities
in each porphyrin-CD conjugate.
Although there are four phenylsulfonic groups in 3, only the
opposite two of them can interact with the cavity of CD.6
When 3 was used as a guest in the microcalorimetric experi-
ments, the anticipated 1:1 (n/n) stoichiometry was observed for
the inclusion complexation with 2, while somewhat unexpected
1:2 (n/2n) stoichiometry was obtained upon complexation of 1,
c,7a,c,12
Microcalorimetric Titration. It is well known that adaman-
tane derivatives nicely fit into the cavities of both native and
7
-1
with a binding constant of 2.67 × 10 M (Table 1). One
reasonable explanation for this unusual stoichiometry is that the
very strong affinity of the CD cavity of 1 with the phenylsulfonic
group of 3 induces the turnover of the pivotal permethylglu-
copyranose unit to recover the original position in CD, which
leads 1 to the “expansive mode” in aqueous solution (Figure
3b). As a result, all four CD cavities in 1 become available for
the inclusion complexation with 3 possessing two binding
11
permethylated â-CDs in a 1:1 stoichiometric ratio. Therefore,
we chose 1-adamantaneacetic acid (1-AD) as the reference guest
to measure the number of the “inert” cavities of 1 and 2 in
aqueous solution by titration calorimetry. The microcalorimetric
titration experiments gave typical titration curves for 1:2
stoichiometry for the complexations of both 1 and 2 with 1-AD.
The stoichiometries of complexation (n value) obtained from
6
c,7a,c,12
sites,
resulting in the 1:2 (n/2n) stoichiometry. Both of
(
10) Mayo, S. L.; Olafson, B. D.; Goddard, W. A., III. J. Phys. Chem. 1990,
9
4, 8897-8909.
(
11) (a) Miyauchi, M.; Hoshino, T.; Yamaguchi, H.; Kamitori, S.; Harada, A.
J. Am. Chem. Soc. 2005, 127, 2034-2035. (b) Charlot, A.; Heyraud, A.;
Guenot, P.; Rinaudo, M.; Auzely-Velty, R. Biomacromolecules 2006, 7,
(12) Bonchio, M.; Carofiglio, T.; Carraro, M.; Fornasier, R.; Tonellato, U. Org.
Lett. 2002, 4, 4635-4637.
(13) Tellini, V. H. S.; Jover, A.; Garc ´ı a, J. C.; Galantini, L.; Meijide, F.; Tato,
J. V. J. Am. Chem. Soc. 2006, 128, 5728-5734.
9
07-913.
J. AM. CHEM. SOC.
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A R T I C L E S
Liu et al.
1
the 1:1 binding mode for the inclusion complexation of 2 with
Measurements. H NMR spectra were recorded on a Varian Mercury
Plus 400 MHz spectrometer in D O and DMSO-d using tetramethyl-
3
and the 1:2 binding mode for 1 with 3 were subjected to
2
6
silane as an internal reference. The 1H NMR data are reported as
follows: chemical shift (δ in ppm), multiplicity (bs ) broad singlet,
bt ) broad triplet, bm ) broad multiplet, s ) singlet, d ) doublet, t )
triplet, q ) quartet, m ) multiplet), and peak integrals. H NMR peaks
were assigned from 2D COSY spectra. 2D ROESY spectra were
fluorescence titration studies (Supporting Information), which
further confirmed the results of the above microcalorimetric
experiments.
NMR Spectra of 1 in the Presence of 3. To further validate
the conclusions concerning the conformation change of 1 in
the presence of 3, NMR studies of 1 in the presence of 3 and
sodium 2-naphthalenesulfonate (2-NS)14 were performed in D2O.
As seen from Figure 2b-e, the original single signals in the
range of -0.5 to 2.0 ppm disappear upon the addition of 3,
while they still remain upon the addition of excess 2-NS (Figure
1
13
recorded on a Varian 300 MHz spectrometer. C NMR, HMQC, and
HMBC experiments were carried out on a Bruker 600 MHz NMR
spectrometer. Positive-ion matrix-assisted laser desorption ionization
mass spectrometry was performed on an IonSpec QFT-MALDI MS.
UV-vis spectra were recorded in a conventional quartz cell (10 mm)
at 25 °C on a Shimadzu UV2401 spectrophotometer. Fluorescence
spectra were recorded on a JASCO FP750 or Edinburgh Analytical
Instruments FL900CD (Edinburgh Instruments) spectrometer in a 10-
mm quartz cell at 25 °C.
TEM Measurements. A 50-µL portion of sample solution was
dropped onto a copper grid. The grid was then air-dried. The samples
were examined by a high-resolution TEM (Philips Tecnai G2 20
S-TWIN microscope) operating at an accelerating voltage of 200 keV.
AFM Measurements. A 10-µL portion of sample solution was
dropped onto newly clipped mica and washed with 1 mL of distilled
water and then air-dried. The samples were examined using an AFM
2
e). The 2D NMR spectrum of 1 in the presence of 3
(Supporting Information) shows that 3 is included in the cavities
of the permethyl-CDs, and the NOE cross-peaks between the
CD’s H3 and H5 and the aromatic protons in 1 disappear. These
observations confirm the conformational change of 1 in aqueous
solution from a contractive mode to an expansive mode upon
the inclusion complexation with 3. Consequently, the formation
of the network aggregates of 1-3 is a natural process.
Conclusion
(
Veeco Company, Multimode, Nano IIIa) in tapping mode in the air at
Two distinctly different nanoarchitectures with alternating
porphyrin and CD arrays have been synthesized through the
intermolecular inclusion complexation of guest 3 with structur-
ally resembling tetrad host 1 and dyad host 2, respectively. From
the comparative studies in different solutions, we elucidated the
mechanisms that result in the transition of nanorods to network
aggregates. (a) Host 1 exists in an expansive mode in chloroform
and can be reversed to a contractive mode through a 360°
rotation of the permethylated glucopyranose units while dis-
solved in water. Upon the addition of excess 3, the two rotated
CD moieties are pulled out from the porphyrin core to the
original expansive mode. As a result, all four permethyl CD
moieties can include guest 3 to form a network aggregate. (b)
Host 2 always exists in a contractive mode in both dimethyl-
sulfoxide and water. The addition of excess 3 cannot induce
the two intramolecular self-inclusion CD cavities to become free.
In this case, 3 only can interact with the other two free CD
moieties of 2 and form nanorod-like aggregates. Furthermore,
we concluded that the complexation strength of the porphyrins
toward the CDs is crucial to activating potential building sites
of a molecular building block. This new observation will allow
us to rationally design and construct a wide range of supramo-
lecular nanoarchitectures by carefully choosing the right com-
binations of molecular building blocks.
room temperature.
Microcalorimetric Titration. All the microcalorimetric titration
experiments were performed on a Microcal VP-ITC titration micro-
calorimeter, which permits us to simultaneously determine the enthalpy
S
change (∆H°) and the equilibrium constant (K ) from a single titration
curve. The sample cell volume was 1.4227 mL. Each titration
experiment included 25 successive injections. All solutions were
degassed and thermostated using a ThermoVac accessory before the
titration experiments were performed.
ORIGIN software (Microcal) was used for the calculation of binding
constant (K ) and standard molar reaction enthalpy (∆H°) from each
S
titration curve with a standard derivation on the basis of the scattering
of data points in a single titration experiment. The binding stoichiometry
(n) was also given as a fitting parameter. From the binding constant
(K
S
) and molar reaction enthalpy (∆H°) obtained, one can calculate
the standard Gibbs free energy of binding (∆G°) and the entropy change
(
∆S°).
Preparation of 5,10,15,20-Tetrakis(4′-propargyloxyphenyl)-Zn-
II)-porphyrin. 4-(Prop-2-ynyloxy)benzaldehyde (3.2 g) was dissolved
(
in 500 mL of propionic acid with stirring. The resulting solution was
heated to reflux, and then newly pyrrole (1.3 g) was added. The solution
turned to dark purple rapidly. The solution was cooled down after 3 h,
and propionic acid was removed under reduced pressure. Triethylamine
(5 mL) was then added to the residue, and the mixture was precipitated
by adding methanol (200 mL). The precipitate was collected by filtration
and washed by methanol twice (50 mL). The crude purple product was
purified by silica gel chromatogram using dichloromethane as eluent.
The final 5,10,15,20-tetrakis(4′-propargyloxyphenyl)-porphyrin was
obtained in 13% yield as a purple powder. H NMR (CDCl
Experimental Section
1
Materials. â-Cyclodextrin was purchased from Wako. Propargyl
3
, 300 MHz,
bromide solution (80 wt % in toluene) was purchased from Acros
ppm): δ 8.79 (s, 8H), 8.08 (d, 8H), 7.30 (d, 8H), 4.92 (d, 8H), 2.63 (t,
4H), -2.84 (2H). ESI-MS: m/z 830.8 (M ). After 5,10,15,20-tetrakis-
+
Organics. Sodium ascorbate was purchased from Amresco Company.
15a
6
-Deoxy-6-azido-permethyl-â-CD15 and 6-deoxy-6-azido-â-CD were
(4′-propargyloxyphenyl)-porphyrin was dissolved in chloroform/
methanol (V/V ) 1:1) solution, 10 times zinc acetate in methanol was
added. The solution was refluxed for 3 h and then cooled and dried.
Choloform (20 mL) was added in the residue and then filtrated to
remove the insoluble ones. The filtrate was then dried to get the final
prepared according to the literature procedure. Other chemicals and
solvents were commercially available. DMF and DMSO were distilled
from calcium hydride. Column chromatography was performed on silica
gel (200-300 mesh) or Sephadex G-25.
+
product. ESI-MS: m/z 892.5 (M ).
(
14) There are two reasons for using 2-NS instead of 1-AD: (1) proton signals
Preparation of 1. To a solution of 5,10,15,20-tetrakis(4′-propargy-
loxyphenyl)-Zn(II)-porphyrin (200 mg, 0.223 mmol) in THF (20 mL),
6-deoxyl-6-azido-permethyl-â-CD (2 g, 1.39 mmol) in THF (20 mL)
1
of 1-AD will overlap with the unique six singlet signals of 1 in H NMR
spectrum, and (2) 2-NS has a binding ability with CD similar to that of
1
-AD.
(
15) (a) Hocquelet, C.; Blu, J.; Jankowski, C. K.; Arseneau, S.; Buisson, D.;
Mauclaire, L. Tetrahedron 2006, 62, 11963-11971. (b) Reetz, M. T.;
Waldvogel, S. R. Angew. Chem., Int. Ed. 1997, 36, 865-867.
was added with stirring. To the resulting solution, CuSO
4 2
5H O (360
mg) and then sodium ascorbate (850 mg) dissolved in water (15 mL)
604 J. AM. CHEM. SOC.
9
VOL. 130, NO. 2, 2008

Alternate Porphyrin and Cyclodextrin Arrays
A R T I C L E S
were added. The color of the mixture turned brown immediately and
then dark purple in a few minutes. The solution was heated at about
After being stirred for 1 h, the solutions were freeze-dried to give the
final assemblies as purple powders, which were further characterized
by NMR, AFM, TEM, and SEM.
5
0 °C for 48 h. The mixture was then dried under reduced pressure,
and the residue was dissolved in chloroform. Insoluble precipitates were
removed by filtration, and the filtrates were dried and further purified
Acknowledgment. This work was supported by the 973
Program (2006CB932900), NNSFC (Nos. 90306009, 20421202,
and 20572052), and the Program for New Century Excellent
Talents in University (NCET-05-0222). We thank the reviewers
for their valuable comments and suggestions regarding the
revision. We also thank Prof. Yoshihisa Inoue at Osaka
University (Japan) for his suggestions and discussions, and Prof.
Vernon D. Parker at Utah State University and Dr. Xiaopeng
Bai at Helicos BioSciences Corporation for assistance in the
preparation of this manuscript.
by flash column chromatography using a chloroform-methanol (V/V
1
)
30:1) eluent to give the product as a violet powder in 90% yield. H
NMR (CDCl
3
, 600 MHz, ppm): δ 8.95 (s, 8H), 8.14 (d, 8H), 7.95 (d,
H), 7.37 (d, 8H), 5.47 (s, 8H), 5.23-5.06 (m, 28H), 4.81 (m, 4H),
.22-3.13 (m, 404H). Anal. Calcd for (C304
: C, 49.97%; H, 7.55%; N, 3.38%. Found: C, 49.50%; H,
4
4
472 16 2
H N O140Zn)(H O)36-
(
DMF)
2
+
7
.49%; N, 3.34%. MALDI-MS: m/z 6651 (M ).
Preparation of 2. Almost the same procedures described above were
employed. The crude product obtained was further purified by HPLC
reversed phase) with a water-acetonitrile (V/V ) 72:28) eluent, and
the collected fraction was freeze-dried to obtain violet powder in 70%
(
1
Supporting Information Available: H NMR and MALDI-
MS spectra of 1 and 2; 13C NMR, HMQC NMR, and HMBC
1
yield. H NMR (DMSO-d
6
, 600 MHz, ppm): δ 8.85 (s, 8H), 8.36(s,
H), 8.11(m, 8H), 7.48 (m, 8H), 5.94-5.75 (m, 56H), 5.42 (m, 8H),
.11-4.52 (m, 56H), 4.14-4.12 (m, 8H), 3.66 (m, 76H, overlapped
1
3
4
5
NMR spectra of 1; C NMR, HMQC NMR, HMBC NMR,
and 2D NOESY spectra of 2 and 1 with/without 3; electronic
absorption spectra; schematic representation of 2; fluorescence
titrations of 1 and 2 in the presence of increasing amounts of
with the DOH peak), 3.36 (m, 70H), 1.23 (m, 10H), 0.86 (m, 4H).
Anal. Calcd for (C224 O)23(DMF) : C, 45.37%; H,
.19%; N, 4.31%. Found: C, 45.18%; H, 5.86%; N, 4.49%. MALDI-
H
312
N
16
O
140Zn)(H
2
3
6
3
; and ITC titration curves. This material is available free of
+
MS: m/z 5471 (M + H) .
charge via the Internet at http://pubs.acs.org.
Preparation of Assemblies. Compound 3 solutions in different
molar ratios were added with stirring to aqueous solutions of 1 (or 2).
JA075981V
J. AM. CHEM. SOC.
9
VOL. 130, NO. 2, 2008 605