Self-assembly of porphyrin-azulene-porphyrin and porphyrin-azulene conjugates

Article abstract of DOI:10.1039/b904009a

In this paper we report the synthesis and self-assembling behavior of new porphyrin-azulene-porphyrin and porphyrin-azulene conjugates. The porphyrin-azulene-porphyrin conjugate gelates a number of organic solvents, while the porphyrin-azulene conjugates form vesicles in a chloroform-methanol binary mixture. The structures of the organogels and vesicles have been characterized by SEM and AFM. Two porphyrin-naphthalene-porphyrin and porphyrin-naphthalene conjugates were also prepared. A comparison of their properties with those of the azulene analogues reveals that the intermolecular dipole-dipole interaction of the azulene units plays an important role in promoting the self-assembly of the porphyrin-azulene-porphyrin and porphyrin-azulene conjugates. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b904009a

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Self-assembly of porphyrin–azulene–porphyrin and porphyrin–azulene
conjugates†
Ze-Yun Xiao, Xin Zhao,* Xi-Kui Jiang and Zhan-Ting Li*
Received 26th February 2009, Accepted 1st April 2009
First published as an Advance Article on the web 28th April 2009
DOI: 10.1039/b904009a
In this paper we report the synthesis and self-assembling behavior of new porphyrin-azulene-porphyrin
and porphyrin-azulene conjugates. The porphyrin-azulene-porphyrin conjugate gelates a number of
organic solvents, while the porphyrin-azulene conjugates form vesicles in a chloroform–methanol
binary mixture. The structures of the organogels and vesicles have been characterized by SEM and
AFM. Two porphyrin-naphthalene-porphyrin and porphyrin-naphthalene conjugates were also
prepared. A comparison of their properties with those of the azulene analogues reveals that the
intermolecular dipole–dipole interaction of the azulene units plays an important role in promoting the
self-assembly of the porphyrin-azulene-porphyrin and porphyrin-azulene conjugates.
few porphyrin-azulene conjugates have been reported,27,28 their
assembling behavior has not been described yet. We herein
Introduction
Supramolecular self-assembly of large p-conjugated systems is
an exciting research area due to their potential applications in
advanced electronics and photonics. In this context, conjugated
porphyrin has attracted special attention because of its unique
photophysical and photochemical properties.1 At present, a large
number of supramolecular systems, such as nano fibers and
tubes,2–6 vesicles,7,8 interlocked topological architectures9–11 and
organogels,12–16 have been constructed based on various por-
phyrin derivatives. An effective strategy of creating porphyrin
supramolecular systems is to introduce new tunable functional
groups. In such a way, a specific assembling property may be
remarkably tuned or improved.
Azulene is a polar structural isomer of naphthalene that
consists of a five-membered ring fused to a seven-membered ring
(Fig. 1). It has a permanent dipole moment of 1.08 D and an
aromatic stabilization energy that is nearly 5 times lower than
that of benzene,17,18 which gives it some unusual characteristics
such as remarkably low HOMO–LUMO separation.19,20 In recent
years, azulene derivatives have been applied in developing
discrete advanced materials including nonlinear chromophores,21
liquid crystals,22 organic semiconductors,23 conducting polymers24
and charge-transfer complexes.25,26 Although the synthesis of a
report the synthesis of three new porphyrin-azulene-porphyrin and
porphyrin-azulene conjugates and their formation of organogels
and vesicles which are enhanced by the dipole–dipole interaction
of the azulene units.
Results and discussion
Synthesis
Compounds T1–T3 were designed and synthesized.
For the investigation of the effect of the azulene unit on the
self-assembling property, naphthalene derivatives T4 and T5, the
isomers of T1 and T3, were also prepared. The synthetic routes
are provided in Scheme 1. Thus, compound 129 was first selectively
hydrolyzed with barium hydroxide to afford 2. The acid was then
coupled with porphyrin 330 to generate T2 in 67% yield. After
treatment with formic acid in dichloromethane, T2 was further
converted to the corresponding acid, which was then coupled with
3 to give T1 in 67% yield. For the preparation of T3, 1 was first
treated with formic acid to form the corresponding acid, which was
then coupled with 3 to afford T3 in 74% yield. For the synthesis
of T4, diacid 4 was first converted to the corresponding diacyl
chloride, which was then treated with 3 to give T4 in 61% yield.
For the preparation of T5, diester 5 was first prepared from 4 and
then hydrolyzed with lithium hydroxide to give acid 6, which was
then coupled with 3 to afford T5 in 49% yield.
Fig. 1 Azulene and its resonance form which characterizes its polar
nature.
Gelation test
The gelation properties of T1–T5 have been tested for twelve
organic solvents and the results are shown in Table 1. It can be
found that T1 has the best gelating ability. Among the twelve
solvents tested, it can gelate eight solvents. In addition, its lowest
gelation concentration is generally lower than the related one of
T4. The gelating ability of the compounds should be controlled
mainly by the intermolecular hydrogen bonding and stacking
State Key Lab of Bioorganic and Natural Products Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling
Lu, Shanghai, 200032, China. E-mail: xzhao@mail.sioc.ac.cn, ztli@mail.
sioc.ac.cn; Fax: 0086-21-64166128; Tel: 0086-21-54925122
† Electronic supplementary information (ESI) available: NMR and IR
spectra of compounds 5, 6 and T1–T5. See DOI: 10.1039/b904009a
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interaction, which induced the formation of three-dimensional
networks of fibrous aggregates (Fig. 2, vide infra). Considering
the similarity of the two compounds, it is reasonable to assume
solvents. This result also supported the importance of the dipole–
dipole interaction of the azulene unit, because this interaction
required that the azulene unit stacked alternately, which would
force the porphyrin units of T2 and T3 to orientate oppositely. T5
did not gelate any solvents, further setting off the promoting effect
of the azulene unit.
=
that the intermolecular N—H ◊ ◊ ◊ O C hydrogen bonding of their
two amides should be comparable in stability. Therefore, the larger
gelating ability of T1 should be attributed to the enhanced stacking
of the azulene unit due to its large dipole–dipole interaction,31
which was particularly important in polar solvents like n-octanol,
ethyl acetate and DMF, where the intermolecular hydrogen
bonding was weakened or destroyed and thus T4 lost the gelating
ability. T2 and T3 only gelated n-docane partially, although T3
also gelated cyclohexane, implying that the stacking interaction of
the porphyrin unit also played an important role in gelating the
Morphology studies
The morphology of the resulting gels was characterized by
SEM. SEM images of the trans-decalin xerogels of T1 and T4
displayed entangled fibrils of micrometres in length and hundreds
of nanometres in width, which is characteristic of a gel state
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Table 1 Gelation properties of compounds T1–T4 a,b
Solvent
T1
T2
T3
T4
n-Hexane
Cyclohexane
n-Decane
Decalin (cis)
Decalin (trans)
Toluene
Dichloromethane
THF
G (15)
G (8)
G (18)
G (7)
G (5)
S
S
S
S
P
S
pG
S
S
S
S
S
P
G (20)
G (15)
G (20)
G (10)
G (20)
pG
S
S
S
S
S
G (8)
S
S
S
S
P
P
P
Acetone
S
S
n-Octanol
Ethyl acetate
DMF
G (20)
G (15)
G (10)
P
P
P
P
P
P
a G, P, pG and S denote gelation, precipitation, part gelation and solution,
respectively. b The critical gelation concentration (mM) is showed in
parenthesis.
Scheme 1 The synthetic routes to compounds T1–T5.
(Fig. 2a and 2b). AFM images of the solution sample of T1 in
cyclohexane (0.1 mM) also gave rise to networks of nanofibrils
(Fig. 2c). If the evaporating process went quickly, only shorter
nanowires were generated (Fig. 2d). These results supported a slow
1D stacking process for the formation of the fibrous structures.32
The formation of nanofibrils by T1 was also supported by the
SEM image (Fig. 2e). T4 at the same low concentration also
self-assembled into wirelike structures, however, they were less
uniform in width (Fig. 2f), possibly indicating a lower assembling
ability.
Fibrous structures were not observed for T2 and T3 at low
concentrations. However, they were found to self-assemble into
vesicular aggregates in the methanol–chloroform binary mixtures
when the content of methanol was 20–43%. The samples were
insoluble when the content of methanol was further increased.
SEM images evidenced the formation of the vesicular structures.
The representative images are shown in Fig. 3a and 3b. The
Fig. 2 SEM images of (a) xerogel of T1 + trans-decalin, (b) xerogel
of T4 + trans-decalin and (e) T1 from a 2.0 mM methanol–chloroform
(1 : 2) solution and AFM images of T1 (c) slow evaporation, (d) quick
evaporation from a 0.1 mM cyclohexane solution, and (f)T4 from a 0.1 mM
cyclohexane solution. The scan size of AFM is 5 mm ¥ 5 mm.
vesicular structures were also observed on the AFM images
(Fig. 3c and 3d). Cross-section analysis of the typical structures
revealed a large diameter–height ratio (ca. 18.1 and 18.2, respec-
tively), which indicated that they were of flattened shape.33 The
results also supported that the spherical structures were hollow
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Fig. 4 SEM images of T3 after incubation at (a) 50 ◦C and (b) 60 ◦C and
SEM images of T5 after incubation at (c) 50 ◦C and (d) 60 ◦C.
X-Ray diffraction (XRD)
Powder XRD measurements were carried out for the cyclohexane
gels of T1 and T4. The profiles are shown in Fig. 5. The gel of T1
˚
gave rise to four peaks at 31.1, 15.2, 10.8 and 9.2 A, respectively.
Since the extended molecular length of T1 was estimated to be ca.
7.3 nm by CPK modeling (4.7 nm for the skeleton of porphyrins
and azulenic unit, and 1.3 nm for each n-dodecyl group) and it
is reasonable to assume that the n-dodecyl groups did not fully
extend, the first peak might be assigned to half of the head-to-tail
distance between the two adjacent molecules at the longitudinal
direction (200 plane), and the second and third peaks should
be those of the secondary (400 plane) and third (600 plane)
˚
diffractions of the first peak, while the 9.2 A peak might belong
Fig. 3 SEM images of (a) T2, (b) T3 and AFM images and cross-section
analysis (bottom ones) of (c) T2 and (d) T3 and TEM images of (e) T2
and (f) T3, all obtained from methanol–chloroform (1 : 2). The scan size
of AFM is 5 mm ¥ 5 mm.
to the edge-to-edge distance of the adjacent molecules. The gel
of T4 displayed a more complicated XRD pattern. Peaks of 24.2,
˚
12.0 and 7.9 A were observed, besides those at 27.3 (200 plane),
˚
13.6 (400 plane) and 9.0 A (600 plane), suggesting that order
arrangement also existed along another direction besides the one-
dimensional growth. The difference shows that T1 grew into
more ordered one-dimensional structures, as revealed by AFM
(Fig. 2).
and contained solvent molecules, which were evaporated after
being transferred from the solution to the surface.34 TEM was
also used to investigate the resulting aggregates, and the clear
contrast between the peripheral and central areas of the spherical
aggregates provided further evidence of their vesicular nature
(Fig. 3e and 3f). Under the same conditions, T5 did not form
similar vesicular structures in the methanol–chloroform binary
mixtures containing 20% and 43% methanol respectively. The
spherical aggregates were observed in the sample of T5 when the
content of methanol was 33%. The result suggested that T5 had a
lower self-assembling ability and proved that the azulene unit in T2
and T3 promoted their ordered aggregation. A thermal stability
test on the spheres formed by T3 and T5 in methanol (33%)–
chloroform showed that the vesicles of T5 collapsed through fusion
UV-Vis and fluorescence spectroscopies
UV-Vis spectra were recorded for T1–T4 to investigate their
stacking properties. The absorption maximum of the Soret band
of T1 in the cyclohexane solution appeared at 421 nm. However,
its UV-Vis spectrum in the cyclohexane gel exhibited two distinct
Soret bands, with one red-shifting by 17 nm and another blue-
shifting by 9 nm (Fig. 6a). Since the red-shifted Soret band
corresponds to a J-type aggregation and the blue-shifting reflects
a H-type aggregation,35 the result suggested that both J- and H-
aggregates contributed to the formation of the organogels.36 The
absorption spectrum of the cyclohexane gel of T4 exhibited a
similar red-shift feature (15 nm), together with a small shoulder
around 412 nm (Fig. 6b), which suggested that the J-aggregation
overwhelmed the H-aggregation. The UV-Vis spectra of T1–T4
were also recorded in the film state. The films were produced
◦
◦
at 50 C and were totally destroyed at 60 C, while the spherical
structures of T3 were still maintained after being heated at 60 ◦C
for 10 minutes (Fig. 4), also suggesting that the dipole–dipole
interaction of azulene really makes a contribution to stabilize the
resulting self-assembling structures.
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Fig. 6 UV-Vis spectra of (a) T1 and (b) T4 in the cyclohexane solution
(solid line, 2 mM) and gel (dotted line), (c) T1 in solution (solid line) and
in film state (dotted line), (d) T2 in solution (solid line) and in film state
(dotted line), (e) T3 in solution (solid line) and in film state (dotted line),
and (f) T4 in solution (solid line) and in film state (dotted line).
Fig. 5 The schematic images of molecular orientation and powder XRD
patterns of the xerogels of (a) T1 and (b) T4 obtained from cyclohexane.
Fig. 7 Fluorescent spectra of T1 (blue), T2 (red), T3 (green) and T4
(black) in cyclohexane (1.0 mM, excitation wavelength = 423 nm).
by drop-casting their chloroform solution (1.0 mM) on quartz
plates. Fig. 6c–6f show their UV-Vis spectra in the film state and
in chloroform (1.0 mM). Compared to that (lmax = 423 nm) in
the monomeric state in solution, their Soret band in the film state
red-shifted by 15 nm, 11 nm, 12 nm, and 14 nm, respectively,
indicating that the J-aggregation mode also dominated in the films.
T1 exhibited the largest red-shifting, implying that it possessed
the largest J-aggregation. Fluorescent experiments in cyclohexane
revealed that, compared to the naphthalene unit in T4, the
azulenic unit in T1 remarkably quenched the emission of their
porphyrin unit (Fig. 7),27,28 which was much more effective than
that observed for T2 and T3. The result supported that T1
possessed an increased aggregating tendency, which facilitated the
quenching process. Such an increase should be ascribed to the
efficient alternate stacking of its azulene unit.
It is well-known that the amide units form intermolecular hydro-
gen bonding in less polar solvents and this interaction can occur in
the presence of polar solvents, such as methanol, when the amide
units are shielded by extensive stacking of adjacent segments from
competitive solvent molecules, as exhibited by DNA or synthetic
systems.37 As expected, IR studies on dry samples of T1–T4
after solvent was removed, exhibited NH stretching vibrations
only around 3315 cm-1 (ESI Fig. S7–10),† indicating that NH units
formed intermolecular H-bonding. Therefore, it is reasonable to
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propose that the self-assembly process for the azulene-porphyrin
conjugates was driven by the cooperation of the hydrogen bonding,
porphyrin-porphyrin p-stacking, and dipole–dipole interactions
of azulenic units. The strong dipole–dipole interaction dictates the
orientation of the array of the molecules to lead to an alternating
head-to-tail stacking of the azulene parts for T1 and T2 (Fig. 8)
and therefore promotes their self-assembling ability.
Compound T2
To a stirred saturated solution of barium hydroxide in ethanol and
water (1 : 1, 6 mL) was added compound 1 (16 mg, 0.053 mmol)
and the solution was stirred at room temperature for 20 h. Diluted
hydrochloric acid (1 N) was added to pH = 5 and the solution
was concentrated with a rotavapor to ca. 3 mL and then extracted
with ethyl acetate (10 mL). The organic phase was washed with
water (10 mL) and brine (10 mL) and dried over magnesium
sulfate. Upon removal of the solvent with a rotavapor, compound
2 was obtained as a green solid, which was then added to a
stirred solution of porphyrin 2 (62 mg, 0.052 mmol) and DMAP
(10 mg) in CH2Cl2 (6 mL). After stirring for 30 min, EDCI (1-ethyl-
3-(3-dimethylaminopropyl)carbodiimide hydrochloride) (100 mg,
0.52 mmol) was added to the solution. Stirring was continued
for 14 h. Then the mixture was successively washed with water
(50 mL), saturated sodium bicarbonate solution (50 mL) and
brine (50 mL) and dried over sodium sulfate. After removal of the
solvent under reduced pressure, the resulting residue was purified
by column chromatography on silica gel (CH2Cl2–CH3OH 100 : 1)
1
Fig. 8 Proposed mode for the formation of nanowire from T1 and vesicles
from T2.
to give compound T2 as a purple solid (50 mg, 67%). H NMR
(300 MHz, CDCl3): 8.86–8.84 (m, 8 H), 8.44 (s, 1 H), 8.33 (d,
J = 10.5 Hz, 2 H), 8.17 (d, J = 8.1 Hz, 2 H), 8.09–7.96 (m,
8 H), 7.70 (s, 2 H), 7.59 (d, J = 10.5 Hz, 2 H), 7.24–7.16 (m,
6 H), 4.18–4.13 (m, 6 H), 1.96–1.91 (m, 6 H), 1.69 (s, 9 H), 1.59–
1.53 (m, 6 H), 1.47–1.25 (m, 48 H), 0.92–0.87 (m, 9 H), -2.73 (s,
2 H). 13C NMR (300 MHz, CDCl3): 168.7, 165.0, 159.0, 158.9,
145.6, 142.4, 140.2, 139.3, 138.9, 137.7, 135.7, 135.6, 135.2, 135.1,
134.4, 134.3, 131.3, 131.2, 130.8, 121.8, 120.2, 120.1, 120.0, 119.0,
118.5, 112.9, 112.8, 112.7, 81.5, 68.3, 32.0, 30.3, 29.8, 29.7, 29.6,
29.5, 29.4, 29.3, 28.4, 26.3, 22.8, 14.2. MS (MALDI-TOF): m/z
1437 [M + H]+. HRMS (MALDI-TOF): Calcd. for C96H118N5O6:
1436.9077. Found: 1436.9089.
Conclusions
In summary, azulene has been designed to connect to porphyrin
to generate a novel type of large p-conjugated structures. The new
compounds can self-assemble into one-dimensional aggregates,
further entangle into three-dimensional network structures in
solution to form organogels, or self-assemble into vesicular
structures, depending on the number of porphyrin units in the
molecules. The intermolecular dipole–dipole interaction between
the azulenic units plays an important role, not only enhancing the
self-assembling abilities, but also dictating the orientation in the
alignment of the conjugates. In the future, we will try to introduce
hydrophilic chains to study their assembling behavior in polar or
aqueous media.
Compound T1
A solution of T2 (55 mg, 0.038 mmol) in formic acid (3 mL)
and CH2Cl2 (4 mL) was stirred at room temperature for 12 h
and concentrated to give the corresponding acid, which was then
added to a stirred solution of 3 (45 mg, 0.038 mmol) and DMAP
(20 mg) in CH2Cl2 (10 mL). After EDCI (100 mg, 0.52 mmol) was
added, the mixture was stirred at room temperature for 12 h and
then worked up as described above for T2. The crude product was
purified by column chromatography (twice) on silica gel (CH2Cl2–
THF 100 : 1) to give T1 as a purple solid (65 mg, 67%). 1H NMR
(300 MHz, THF-d8): 9.06–8.98 (m, 16 H), 8.83 (d, J = 10.5 Hz,
2 H), 8.48 (d, J = 8.4 Hz, 2 H), 8.40–8.34 (m, 6 H), 8.24–8.16
(m, 14 H), 8.01 (d, J = 10.5 Hz, 2 H), 7.45–7.37 (m, 12 H),
4.40–4.34 (m, 12 H), 2.09–2.07 (m, 12 H), 1.78–1.76 (m, 12 H),
1.63–1.45 (m, 96 H), 1.15–1.00 (m, 18 H), -2.51 (s, 4 H). 13C NMR
(300 MHz, CDCl3): 168.7, 159.0, 158.7, 138.7, 135.6, 135.3, 134.3
134.0, 131.4, 130.9, 130.8, 130.7, 119.9, 112.7, 112.4, 68.3, 31.9,
29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 26.2, 22.7, 14.1. MS (MALDI-
TOF): m/z 2544 [M + H]+. HRMS (MALDI-TOF): Calcd. for
C172H211N10O8: 2544.6406. Found: 2544.6423.
Experimental section
General methods
All the reactions were carried out under nitrogen. The 1H NMR
spectra were recorded on 300 or 400 MHz spectrometers (Brucker
AM-300 or 400) in the indicated solvents. Chemical shifts are
expressed in parts per million (d) using residual solvent protons as
internal standards. MALDI-TOF MS were obtained on a Voyager-
DE STR or IonSpec4.7 Tesla FTMS spectrometer (CHCA or
DHB as matrix). UV-Vis spectra were recorded on a CARY 100
spectrometer, and for the absorption of gels measurements, two
quartz plates were used to sandwich a thin layer of the samples.
SEM images were obtained with a JEOL model JSM-6390LV and
the dry samples obtained were shielded with Pt. AFM pictures
were obtained in “tapping” mode on a multimode SPM system
equipped with a Nanoscope IV controller. Powder XRD spectra
were obtained on a X’Pert PROX system using monochromated
Cu Ka (l = 0.1542 nm) radiation. The transmission electron
microscopy (TEM) images were recorded on a JEOL JEM-1230
microscope.
Compound T3
A solution of compound 1 (16 mg, 0.053 mmol) in formic acid
(10 mL) and CH2Cl2 (10 mL) was stirred at room temperature
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for 12 h and then concentrated with a rotavapor to give the
corresponding ethyl ester as a green solid. The ester was added
to a solution of porphyrin 3 (62 mg, 0.052 mmol) and DMAP
(10 mg) in CH2Cl2 (6 mL). After stirring for 20 min, EDCI
(0.10 g, 0.52 mmol) was added. The mixture was stirred at
room temperature for 14 h and then washed with water (5 mL),
saturated sodium bicarbonate solution (5 mL) and brine (5 mL)
and dried over sodium sulfate. After the solvent was removed
under reduced pressure, the resulting residue was purified by
column chromatography on silica gel (CH2Cl2–MeOH 100 : 1)
CDCl3): 8.63 (s, 2 H), 8.13 (d, J = 8.7 Hz, 2 H), 8.00 (d, J =
8.7 Hz, 2 H), 4.46 (q, 4 H), 1.46 (t, J = 7.2 Hz, 6 H). MS (EI): m/z
272 [M]+.
Compound 6
A mixture of 5 (0.27 g, 1.00 mmol) and lithium hydroxide
monohydrate (42 mg, 1.00 mmol) in THF (15 mL) and water
(5 mL) was stirred at room temperature for 2.5 h and neutralized
with diluted hydrochloric acid (1 N) to pH = 3. The solution was
concentrated under reduced pressure and the resulting slurry was
extracted with ethyl acetate (50 mL). After work up, the crude
product was recrystallized from ethyl acetate and n-hexane to
1
to give T3 as a purple solid (54 mg, 74%). H NMR (300 MHz,
CDCl3): 8.86–8.84 (m, 8 H), 8.42 (s, 1 H), 8.35 (d, J = 10.5 Hz,
2 H), 8.19 (d, J = 8.4 Hz, 2 H), 8.11–7.97 (m, 10 H), 7.70 (s, 2 H),
7.23–7.16 (m, 6 H), 4.45 (q, J = 6.9 Hz, 2 H), 4.19–4.12 (m, 6 H),
2.00–1.90 (m, 6 H), 1.59–1.55 (m, 6 H), 1.48–1.25 (m, 48 H), 0.95–
0.87 (m, 12 H), -2.73 (s, 2 H). 13C NMR (300 MHz, CDCl3): 168.7,
165.0, 159.0, 158.9, 145.6, 142.4, 140.2, 139.4, 138.9, 137.6, 135.6,
135.5, 135.2, 134.4, 134.3, 131.1, 131.0, 121.8, 120.2, 120.1, 120.0,
118.9, 118.4, 112.7, 81.4, 68.3, 32.0, 31.9, 29.8, 29.7, 29.6, 29.5,
29.4, 29.3, 28.4, 26.3, 22.8, 22.7, 14.2. MS (MALDI-TOF): m/z
1409 [M + H]+. HRMS (MALDI-TOF): Calcd. for C94H114N5O6:
1408.8764. Found: 1408.8760.
1
afford 6 as a white solid (0.13 g, 52%). H NMR (300 MHz,
CD3COCD3): 8.72 (d, J = 6.9 Hz, 2 H), 8.23–8.12 (m, 4 H), 4.44
(q, 2 H), 1.43 (t, J = 7.2 Hz, 3 H). MS (EI): m/z 244 [M]+.
Compound T5
To a stirred solution of 6 (13 mg, 0.053 mmol), 3 (62 mg,
0.053 mmol) and DMAP (10 mg) in THF (10 mL) was added
EDCI (0.10 g, 0.52 mmol). The mixture was stirred at room
temperature for 14 h and concentrated. The resulting slurry was
dissolved in CH2Cl2 (30 mL) and the solution washed successively
with water (30 mL), saturated sodium bicarbonate solution
(30 mL), water (30 mL) and brine (30 mL) and dried over sodium
sulfate. Upon removal of the solvent under reduced pressure,
the resulting residue was purified by column chromatography
(CH2Cl2) to give compound T5 as a purple solid (37 mg, 49%).
1H NMR (300 MHz, CDCl3): 8.87 (s, 8 H), 8.68 (s, 1 H), 8.54 (s,
1 H), 8.36 (s, 1 H), 8.24 (d, J = 8.4 Hz, 2 H), 8.12–8.00 (m, 12 H),
7.27–7.22 (m, 6 H), 4.49 (q, 2 H), 4.22–4.19 (m, 6 H), 1.99–1.94
(m, 6 H), 1.63–1.60 (m, 6 H), 1.51–1.25 (m, 48 H), 0.90–0.85 (m,
12 H), -2.74 (s, 2 H). 13C NMR (300 MHz, CDCl3): 167.8, 158.9,
158.3, 138.7, 137.6, 135.6, 135.2, 134.3, 134.0, 133.6, 130.9, 130.3,
129.2, 127.3, 126.4, 124.4, 119.9, 118.4, 112.7, 111.9, 68.3, 31.9,
29.7, 29.6, 29.5, 29.4, 29.3, 26.2, 22.7, 14.4, 14.1. MS (MALDI-
TOF): m/z 1409 [M + H]+. HRMS (MALDI-TOF): Calcd. for
C94H114N5O6: 1408.8764. Found: 1408.8781.
Compound T4
To a mixture of compound 4 (11 mg, 0.05 mmol) in toluene (2 mL)
and oxalyl dichloride (1 mL) was added a drop of DMF. The
mixture was heated under reflux for 4 h and then concentrated
under reduced pressure. The resulting residue was dissolved in
toluene (10 mL) and the solution added to a stirred solution
of porphyrin 3 (120 mg, 0.10 mmol) and pyridine (0.05 mL)
in toluene (5 mL). The solution was stirred for 12 h and
then successively washed with water (10 mL), saturated sodium
bicarbonate solution (10 mL) and brine (50 mL) and dried over
sodium sulfate. Upon removal of the solvent, the crude product
was subjected to column chromatography (CH2Cl2–THF 100 : 1)
1
to give T4 as a purple solid (78 mg, 61%). H NMR (300 MHz,
CDCl3-CD3CN): 8.92–8.88 (m, 16 H), 8.68 (s, 2 H), 8.26–8.25 (m,
6 H), 8.17 (d, J = 7.5 Hz, 2 H), 8.12 (4 H), 8.07 (d, J = 8.7 Hz,
12 H), 7.24 (d, J = 8.7 Hz, 12 H), 4.25–4.21 (m, 12 H), 2.00–1.97
(m, 12 H), 1.63–1.60 (m, 12 H), 1.48–1.26 (m, 96 H), 0.90 (t, J =
6.3 Hz, 18 H), -2.74 (s, 4 H). 13C NMR (300 MHz, CDCl3): 167.8,
158.9, 158.3, 138.7, 137.6, 135.4, 134.9, 134.8, 134.3, 134.0, 133.6,
133.3, 130.9, 129.1, 127.0, 124.4, 120.0, 119.7, 118.9, 112.6, 111.9,
68.2, 67.6, 29.8, 29.7, 29.6, 29.5, 29.4, 29.3, 26.3, 26.2, 22.7, 14.2.
MS (MALDI-TOF): m/z 2546 [M + H]+. HRMS (MALDI-TOF):
Calcd. for C172H211N10O8: 2544.6406. Found: 2544.6423.
Typical process for the gelation test
The tested compound was mixed with 0.1 mL of solvent in a
capped test tube of 0.5 cm in diameter. The mixture was heated
until the solid was dissolved and then allowed to cool down to
25 ◦C. After standing for 1 hour, the sample vial was turned upside
down. When the suppression of the fluidity of the solvent was
observed, it was defined as gelation. For those that formed gel,
more solvent was added and the test was repeated until gel was not
formed. The concentration obtained for the last test was defined
as the lowest gelation concentration.
Compound 5
A solution of compound 4 (216 mg, 1.0 mmol) and sulfuric acid
(98%, 0.5 mL) in ethanol (40 mL) was heated under reflux for 18 h,
cooled to room temperature, neutralized with diluted hydrochloric
acid to pH = 5, and then concentrated under reduced pressure.
The resulting slurry was extracted with ethyl acetate (80 mM).
The organic phase was washed with saturated sodium bicarbonate
solution (40 mL), water (40 mL) and brine (40 mL) and dried over
sodium sulfate. After the solvent was removed, compound 5 was
Acknowledgements
We thank the National Science Foundation of China (Nos.
20732007, 20621062, 20672137, 20872167), the National Basic
Research Program (2007CB80801) and Chinese Academy
of Sciences (KJCX2-YW-H13) for financial support and
Mr Gui-Tao Wang for his assistance.
1
obtained as a white solid (0.26 g, 95%). H NMR (300 MHz,
2546 | Org. Biomol. Chem., 2009, 7, 2540–2547
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