Chiral eighteen-component three-dimensional supramolecular entities stabilized by the hydrogen bonding and coordination interactions

Article abstract of DOI:10.1016/j.tet.2010.04.009

A new class of chiral eighteen-component three-dimensional supramolecular entities has been assembled in toluene and chloroform from twelve zinc porphyrin-appended 2-(ethylamino)- pyrimido[4,5-b][1,8]naphthyridin-4(3H)-one monomers and six chiral bipyridy

Full text of DOI:10.1016/j.tet.2010.04.009

Tetrahedron 66 (2010) 4057–4062
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Chiral eighteen-component three-dimensional supramolecular entities stabilized
by the hydrogen bonding and coordination interactions
,
a
Shi-Gui Chen a, Yong-Chun Fu b, Gui-Tao Wang a, Guang-Yu Li a, Yuguo Ma c , Xi-Kui Jiang ,
*
,
Zhan-Ting Li a
*
a State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
b Shangqiu Technician College, 9 Guilin Lu, Shangqiu 476000, China
c Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry, Peking University,
Beijing 100871, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new class of chiral eighteen-component three-dimensional supramolecular entities has been assem-
bled in toluene and chloroform from twelve zinc porphyrin-appended 2-(ethylamino)- pyrimido[4,5-
b][1,8]naphthyridin-4(3H)-one monomers and six chiral bipyridyl compounds. The heterocyclic
segments form two C6-symmetric cyclic hexamers, which are stabilized by a well-established DDA–AAD
hydrogen bonding motif, while the six chiral bispyridine ligands are coordinated to the corresponding
zinc porphyrin units to give the two-layered architectures. The structures have been characterized by the
1H NMR, UV–vis and circular dichroism experiments, which also reveals that, when the concentration of
the monomers is high enough, the chiral supramolecular entity can be formed exclusively.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 12 February 2010
Received in revised form 30 March 2010
Accepted 2 April 2010
Available online 7 April 2010
Keywords::
Supramolecular chirality
Hydrogen bonding
Coordination interaction
Porphyrin
Bipyridyl
H7
1. Introduction
t-Bu
t-Bu
Over the past decade, the self-assembly of hydrogen bonding-
driven three-dimensional ordered architectures has received con-
siderable interest.1–9 One unique feature of this kind of dynamic
aggregates is that chiral transfer and amplification can be achieved
from simple chiral molecular blocks to the whole supramolecular
entities.6–9 For example, Reinhoudt et al. have used three
calix[4]arene-linked dimelamines and six chiral 5,5-dieth-
ylbarbituric acid derivatives to assemble chiral nine-component
capsular entities via forming two hydrogen bonded rosette motifs
from the complementary heterocyclic units.6,10 However, the self-
assembly of chiral supramolecular systems from even more
molecular components has been a great challenge.11 We previously
reported that an arylamide foldamer, appended with six zinc
H4
N
O
N
t-Bu
t-Bu
H5
H6
H1
N
N
N
N
N
H2
Zn
N
N
N
Et
H3
H8
1
t-Bu
O
t-Bu
Pr-i
O
Pr-i
N
N
N
N
porphyrins from outside the backbone, complexed six chiral C60
-
N
N
N
N
bearing histidine ligands to generate a chiral propeller-like heli-
cate.12 The key for the selective formation of this seven-component
chiral aggregate was that the rigid foldamer backbone enabled the
Pr-i
O
Pr-i
O
2 (R,R and S,S)
3 (R,R and S,S)
appended zinc porphyrins to adopt a roughly uniform arrangement
and thus to maximize the chiral amplifcation.13–15 Considering that
several stable C6-symmetric planar hydrogen bonding motifs have
been established based on the complementary AAD–DDA (A and D:
* Corresponding authors. Tel.: þ86 21 54925122; fax: þ86 21 64166128; e-mail
addresses: ygma@pku.edu.cn (Y. Ma), ztli@mail.sioc.ac.cn (Z.-T. Li).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.04.009

4058
S.-G. Chen et al. / Tetrahedron 66 (2010) 4057–4062
acceptor and donor) motifs,16–19 we became interested in attaching
the zinc porphyrin unit to the monomeric heterocycles to build new
supramolecular synthons for the multi-component chiral assembly.
We herein report that one such molecule (1) interacts with chiral
bispyridines 2 (R,R and S,S) and 3 (R,R and S,S) to produce a new
class of chiral eighteen-component supramolecular entities, that
are stabilized by thirty-six hydrogen bonds and twelve Zn–N(py)
coordination bonds.
d were assigned based on the NOESY and COSY experiments (see
the structure). The H-1–3 signals appeared at 14.33, 11.20, and
10.85 ppm (3 mM), which were very close to the related values of
Zn-free 8 and porphyrin-free analogs,21,22 indicating that the ni-
trogen atoms of the heterocyclic segment of 1 did not interact with
its Zn porphyrin. Thus, this compound should also form a stable
cyclic hexamer (Fig. 1), as reported for the prototype molecules.17,21
2. Results and discussion
Zn
The synthetic route of compound 1 is shown in Scheme 1. Thus,
bromide 420 was first reacted with heterocycle 521,22 in refluxed
actetonitrile and THF to give compound 6 in 63% yield. The latter
was then treated with trifluoroacetic acid to afford compound 7
quantitatively, which was further reacted with ethyl guanidinium
in tert-butanol and THF to produce compound 8 in 50% yield.
Finally, 8 was treated with Zn(OAc)2 to give compound 1. The
synthesis of S,S 2 and 3 are also provided in Scheme 1. The key
intermediate S,S 11 was prepared according to the reported
method.23 The R,R isomers were prepared by using the same
reactions.
N
H
O
N
Zn
N
H
H
N
O
H
N
N
H
N
N
N
N
H
EtN
N
H
N
N
H
O
N
H
N
N
Et
Zn
NEt
N
H
N
N
H
O
O
H
N
N
H
N
NEt
H
EtN
Compound 1 was soluble in chloroform and toluene. Its signals
N
H
in the downfield area of the 1H NMR spectrum in chloroform-
Zn
Et
N
N
N
N
O
N
H
N
N
N
H
H
N
Ar
Zn
CO2Et
Cl
N
N
N
N
Br
Zn
+
Ar
Zn
Ar
BocHN
N
N
= R
4
5
Zn
Zn
CO2Et
Cl
K2CO3, 18-crown-6
TFA, CH2Cl2
Zn
R
N
Boc
N
N
r.t., 1 h, 100%
MeCN-THF
Zn
6
reflux, 5.5 h, 63%
+
NH
Zn
2-
Zn
SO4
EtHN
CO2Et
NH2
2
R
t-BuONa, t-BuOH-THF, sealed
N
H
N
N
Cl
7
tube, 170 °C, 2.5 h, 50%
Zn
O
Zn
Zn(OAc)2, CH2Cl2-MeOH
r.t., 12 h, 100%
NH
Zn
1
R
N
N
N
N
NHEt
H
8
Zn
H
O
N
i-Pr
silica gel, vacuo
220 °C, 6 min, 20%
i-Pr
COOH
NH2
Zn
Zn
i-Pr
N
H
O
9
10
Figure 1. Upper: the structure of the cyclic hexamer of compound 1. Down: the ten-
tative model for the two-layered supramolecular entities formed by two hexamers of 1
and six dipodal ligands, which are represented by the arrows. The chiral ligands induce
the whole architectures to produce the supramolecular chirality.
H
N
i-Pr
LiAlH4, dioxane
relux, 24 h, 100%
i-Pr
N
H
11
O
The binding property of compounds 1–3, and 14 was then in-
vestigated. The apparent association constants of its Zn porphyrin
to the single pyridine unit of the dipodal ligands in toluene were
determined by the UV–vis titration experiments to be 5.6ꢀ105,
4.3ꢀ105, and 2.3ꢀ106 Mꢁ1, respectively,12,24 which were sub-
stantially larger than the related values of the complexes of control
compound 15 with the single pyridine units of the three ligands.
These results showed that the binding of the zinc porphyrin of 1 to
the two pyridines of these dipodal ligands were cooperative, which
11, pyridine
Cl
12
S,S 2
N
50 °C, 4 h, 57%
O
11, pyridine
Cl
S,S 3
40 °C, 8 h, 63%
13
N
Scheme 1. The synthesis of compounds 1–3.

S.-G. Chen et al. / Tetrahedron 66 (2010) 4057–4062
4059
provided the first evidence that two-layered supramolecular enti-
ties were formed from two hexamers of 1 and six dipodal ligands
(Fig. 1), as observed for the linear zinc porphyrin oligomers and
dipodal ligands.25–27
area of the Soret band of the zinc porphyrin. Control experiments
showed that the dipodal ligands or their 1:2 mixtures with com-
pound 15 of the identical concentrations did not exhibit any signal
in the wavelength area. Thus, the above induced CD (ICD) signals
should be attributed to the zinc porphyrin unit of 1 in the chiral
eighteen-component supramolecular entity (Fig. 1). The ICD signal
of the mixtures of ligand 2 was substantially stronger than that of
the mixtures of ligand 3, which might reflect that the chiral su-
pramolecular entity formed by 2 was more compact or ordered
than that of 3. The chloroform solution of the mixtures also gave
rise to similar ICD signals, although the strength was notably
weaker due to the higher polarity of the solvent. As expected,
reducing the temperature caused the signals to strengthen, while
raising the temperature weakened the signals. Thus, compared
with that at 10 ꢃC, the molar absorptivity of the ICD signal of the
mixture of 1 and S,S 2 recorded at 60 ꢃC was decreased by ca. 50% as
a result of the weakening of the two intermolecular interactions at
higher temperatures. Adding polar methanol to the solution caused
the ICD signals to weaken rapidly (Fig. 3b). When about 10% of
methanol was added, the ICD signals vanished completely. These
results again supported the formation of the chiral two-layered
supramolecules in toluene, whose hydrogen bonded propeller-
like hexamers were decomposed in the presence of methanol.
t-Bu
t-Bu
N
t-Bu
t-Bu
N
N
N
N
Zn
Me
N
14
15
t-Bu
t-Bu
Another evidence for the eighteen-component assembled
entities came from 1H NMR titration experiments in chloroform-d.
For example, upon addition of 14, the H-3–8 signals of 1 shifted
upfield or down-field notably, which displayed a turning point
when ca. 0.5 equiv of 14 was added (Fig. 2). The result not only
supported the 2:1 binding stoichiometry and the two-layered
structure, but also implied that the excess ligand did not cause
the formation of other supramolecular species. More solid evidence
for the eighteen-component supramolecular entities came from the
two-dimensional diffusion-ordered NMR (DOSY) experiments in
chloroform-d.28,29 The diffusion coefficients (D) of 1, 1/14 (1:0.5),
and 1/2 (1:0.5) were determined to be 6.1ꢀeꢁ9, 2.6ꢀeꢁ9, and
2.0ꢀeꢁ9 m2/s, respectively ([1]¼4.8 mM). The values of the two
mixtures were remarkably lower than that of 1, supporting that the
two mixtures formed the two-layered supramolecular entities that
had an increased average size. The value of the 1/2 mixture was
notably smaller than that of the 1/14 mixture, which was also
consistent with the fact that 2 is longer than 14 and thus formed
a larger supramolecule.
(a)
20
15
S,S 2
10
R,R 3
5
0
-5
S,S 3
-10
R,R 2
-15
0.3
-20
350
375
400
425
450
475
0.2
Wavelength (nm)
H-6
H-5
0.1
0.0
H-8
H-7
H-4
H-3
(b)
18
12
6
-0.1
-0.2
0
-6
0.0
0.4
0.8
1.2
14/1 (molar/molar)
-12
-18
Figure 2. The change of the chemical shifts of partial signals of compound 1 (10 mM)
in the H NMR spectra in chloroform-d at 25 ꢃC, upon addition of compound 14.
1
Previously, it was reported that the heterocyclic segment
formed the stable cyclic hexamer in toluene even at the low con-
centration of 3.6ꢀ10ꢁ6 M.21 It is thus reasonable to assume that, at
remarkably higher concentrations (ꢂ2.7ꢀ10ꢁ5 M), compound 1
should also exist exclusively in the form of the hexamer in toluene.
The circular dichroism (CD) spectra of the mixtures of compound 1
with chiral 2 and 3 were then recorded in toluene to investigate
their supramolecular chirality. The results are provided in Figure 3a.
It can be found that both pairs of chiral ligands induced the zinc
porphyrin of 1 to form Cotton signals of mirror symmetry in the
350
375
400
425
450
475
Wavelength (nm)
Figure 3. (a) Induced circular dichroism spectra of compound 1 (5.4ꢀ10ꢁ5 M) in the
presence of chiral
2 (R,R and S,S) and 3 C
(R,R and S,S) in toluene at 25 ꢃ
([2]¼[3]¼2.7ꢀ10ꢁ5 M). (b) ICD spectra of 1 (5.4ꢀ10ꢁ5 M) in toluene at 25 ꢃC in the
presence of R,R or S,S 2 (2.7ꢀ10ꢁ5 M), upon addition of 0%, 1%, 2%, 3%, and 10% of
methanol (v%).
As expected, the strength of the ICD signal of the 2:1 mixture of
compounds 1 and S,S 2 was increased with the increase of the

4060
S.-G. Chen et al. / Tetrahedron 66 (2010) 4057–4062
concentration (Fig. 4) at the early stage, implying that, within this
concentration range, the multi-component architectures were
formed in increasing yields. It can be found that, in the range of low
concentrations, the peak shifted pronouncedly, which also
indicated that other simple chiral entities existed. When the con-
centration of 1 was increased to 3ꢀ10ꢁ5 M, the molar absorptivity
of this ICD signal stopped to increase (Inset, Fig. 4). This result
suggested that, above this critical concentration, the two-layered
supramolecular entity was generated exclusively. This low critical
concentration again shows that the three-dimensional supra-
moleuclar entity is highly stable.
obtained on a Voyager-DE STR or IonSpec 4.7 T FTMS spectrometer.
UV–vis spectra were recorded on a CARY 100 spectrometer. Circular
dichroism spectra were recorded on a JASCO 810 circular dichroism
spectrometer.
4.1.1. Compound 6. To a stirred solution of compound 521 (0.37 g,
1.04 mmol), potassium carbonate (1.04 g, 7.2 mmol), and 18-
crown-6 (56 mg, 0.21 mmol) in the mixture of acetonitrile (80 mL)
and THF (60 mL) was added dropwise a solution of compound 420
(1.08 g, 1.04 mmol) in THF (50 mL). The mixture was heated to
reflux for 5.5 h and then cooled to room temperature. The solid
was filtrated off and the filtrate concentrated in vacuo. The
resulting residue was purified by column chromatography (AcOEt/
petroleum ether 1:9) to give compound 6 as a purple solid (0.86 g,
100
18
15
63%). 1H NMR (300 MHz, CDCl3):
d 8.89–8.88 (m, 6H), 8.81
75
12
(d, J¼4.9 Hz, 1H), 8.70 (s, 1H), 8.50 (d, J¼9.1 Hz, 1H), 8.23 (d,
J¼9.1 Hz, 1H), 8.15 (d, J¼7.9 Hz, 2H), 8.08–8.07 (m, 6H), 7.80–7.79
(m, 3H), 7.71 (d, J¼7.9 Hz, 2H), 5.87 (s, 2H), 4.49 (q, J¼7.09 Hz, 2H),
1.62 (s, 9H), 1.52 (s, 54H), 1.46 (t, J¼7.09 Hz, 3H). 13C NMR
9
50
6
3
25
(100 MHz, CDCl3):
d 164.2, 159.3, 155.0, 154.2, 151.3, 150.4, 148.7,
0
2
4
6
[1] (x 10-5 M)
141.5, 141.3, 141.1, 138.5, 137.8, 137.4, 134.4, 131.3, 129.8, 129.7,
125.5, 124.0, 122.1, 121.4, 121.3, 121.0, 120.0, 119.6, 119.5, 117.8,
111.8, 83.16, 62.19, 49.82, 35.04, 31.75, 28.23, 23.86, 14.21. MS
(MALDI-TOF): m/z 1314 [MþH]þ. HRMS (MALDI-FT): calcd for
C85H97N7O4Cl: 1314.7285 [MþH]þ. Found: 1314.7258.
0
-25
4.1.2. Compound 7. Compound
dissolved in the mixture of dichloromethane (16 mL) and tri-
fluoroacetic acid (8 mL). After stirring at room temperature for
6
(0.34 g, 0.26 mmol) was
375
400
425
Wavelength (nm)
450
475
Figure 4. Induced circular dichroism spectra of the 2:1 mixture of compound 1 and S,S
2 in toluene at 25 ꢃC at different concentrations ([1]¼0.13–6.3ꢀ10ꢁ5 M). Inset: the plot
of the CD molar absorptivity of 1 at 432 nm versus its concentration.
1 h, the solution was concentrated with
a rotavapor. The
resulting residue was dissolved in ethyl acetate (50 mL) and the
solution was washed with saturated sodium bicarbonate
solution (20 mL), water (20 mL), and brine (20 mL), and dried
over sodium sulfate. Upon removal of the solvent under reduced
pressure, compound 7 was obtained as a purple solid (0.31 g,
100%). The compound was further purified by recrystallization
3. Conclusion
In summary, we have successfully assembled a new class of
chiral eighteen-component three-dimensional supramolecular
entities by making use of the cooperative interactions of the
hydrogen bonding and coordination interaction as the driving
forces. When the concentrations of the components are high
enough, the chiral entities can be formed exclusively. This strat-
egy may act as a new design rationale for the formation of chiral
layer-styled supramolecular polymers. For this goal, we are
synthesizing new chiral hexadentate ligands with their six
binding sites alternately pointing to the opposite sides of the
backbones. By appending two heterocyclic segments to the zinc
porphyrin unit, new two-layered molecular containers may also
be assembled from six monomers, which may also exhibit unique
binding property.
from methanol for analysis. 1H NMR (300 MHz, CDCl3):
d 8.90–
8.89 (m, 6H), 8.84–8.83 (m, 2H), 8.53 (s, 1H), 8.22 (d, J¼8.0 Hz,
2H), 8.08–8.05 (m, 6H), 7.91 (d, J¼8.5 Hz, 1H), 7.80–7.79 (m, 3H),
7.74 (d, J¼8.0 Hz, 2H), 6.86 (d, J¼8.5 Hz, 1H), 5.73 (br, 1H), 5.21
(d, J¼6.97 Hz, 2H), 4.46 (q, J¼7.1 Hz, 2H), 1.56 (t, J¼7.1 Hz, 3H),
1.52 (s, 54H), ꢁ2.72 (s, 2H). 13C NMR (100 MHz, CDCl3):
d 164.6,
160.7, 157.4, 151.3, 148.8, 141.8, 141.4, 141.3, 137.5, 134.8, 131.5,
129.9, 129.7, 126.0, 121.6, 121.5, 121.0, 120.3, 119.1, 115.5, 61.76,
45.51, 35.06, 31.76, 14.28. MS (MALDI-TOF): m/z 1214.5 [MþH]þ.
HRMS (MALDI-FT): calcd for C80H89ClN7O2: 1214.6761 [MþH].
Found: 1214.6803.
4.1.3. Compound 8. Bis(N-ethyl guanidinium) sulfate (62 mg,
0.23 mmol) and sodium tert-butoxide (39 mg, 0.41 mmol) were
suspended in the mixture of tetrahydrofuran (3 mL) and tert-bu-
tanol (3 mL), and then the mixture was heated to reflux for half an
hour. The resulting turbid solution was separated from the
insoluble salts by pipette and then added to compound 7 (50 mg,
0.041 mmol). The mixture was then sealed into a glass tube,
heated at 170 ꢃC for 2.5 h and cooled to room temperature. The
solvent was removed with a rotavapor, and the resulting residue
was purified by column chromatography (CH2Cl2/CH3OH 25:1) to
give compound 8 as a purple solid (26 mg, 50%). 1H NMR
4. Experimental section
4.1. General methods
All reactions were carried out under a dry nitrogen atmosphere.
All solvents were dried before use following the standard pro-
cedures. Unless otherwise indicated, all starting materials were
obtained from commercial suppliers and were used without further
purification. Analytical thin-layer chromatography (TLC) was
performed on 0.2 mm silica 60 coated on glass plates with F254
indicator. The 1H and 13C NMR spectra were recorded on 300, 400
or 500 MHz spectrometers in the indicated solvents. Chemical
(300 MHz, CDCl3):
d 14.36 (s, 1H), 11.26 (s, 1H), 10.88 (s, 1H), 8.88–
8.87 (m, 8H), 8.63 (s, 1H), 8.28 (d, J¼6.3 Hz, 2H), 8.01–8.00
(m, 6H), 7.92 (d, J¼6.3 Hz, 2H), 7.78 (d, J¼8.7 Hz, 1H), 7.57 (s, 3H),
6.86 (d, J¼8.7 Hz, 1H), 5.41 (s, 1H), 5.11 (s, 1H), 4.52 (d, J¼38.4 Hz,
2H), 1.70 (s, 3H), 1.34 (s, 54H), ꢁ2.72 (s, 2H). 13C NMR (100 MHz,
shifts are expressed in parts per million (
protons as internal standards (1H: chloroform:
2.49 ppm; 13C: CDCl3: 77.2 ppm). Elemental analysis was con-
ducted at the SIOC analytical center. MALDI-FT spectra were
d
) using residual solvent
d
7.26 ppm; DMSO:
d
CDCl3) d 166.0, 163.2, 162.8, 160.4, 154.6, 148.7, 141.6, 141.4, 141.3,
139.6, 138.4, 138.1, 135.1, 132.2, 131.4, 131.1, 130.5, 130.3, 129.8,

S.-G. Chen et al. / Tetrahedron 66 (2010) 4057–4062
4061
125.4, 121.4, 120.9, 119.4, 113.9, 110.1, 107.5, 46.66, 35.77, 35.08,
34.93, 31.80, 31.65, 16.96. MS (MALDI-TOF): m/z 1220.0 [MþH]þ.
HRMS (MALDI-FT): calcd for C81H91N10O 1219.7372 [M]þ. Found:
1219.7374.
d 170.1, 150.9, 147.3, 134.5, 132.0, 123.7, 57.06, 44.57, 30.31, 19.41. MS
(ESI): m/z 381 [MþH]þ. Anal. Calcd for C22H28N4O2: C, 69.45; H, 7.42;
N, 14.73. Found: C, 69.02; H, 7.70; N, 14.64.
4.1.8. Compound S,S 3. Compound S,S 3 was prepared by using the
4.1.4. Compound 1. Compound 8 (30 mg, 0.027 mmol) was dis-
solved in the solution of zinc acetate in dichloromethane and
methanol (4:1) (0.05 M, 5 mL) and stirred at room temperature for
12 h. After removing the solvents with a rotavapor, the resulting
residue was dissolved in dichloromethane (20 mL). The solution
was washed with water (10 mL) and brine (20 mL), and dried over
sodium sulfate. Upon removal of the solvent under reduced
pressure, compound 1 was obtained as a purple solid (33 mg,
same procedure and characterized by the 1H NMR and MS methods.
25
[a
]
ꢁ183 (c 0.54, CH2Cl2).
D
4.2. Typical procedures for the UV–vis titration and method
for determining the apparent association constants12,24
Aliquots of a fixed solution of 2, 3, and 14 in toluene were
added to a toluene solution of 1, and the mixture was subjected to
UV–vis spectroscopy at 25 ꢃC. The spectrum was corrected with
a dilution factor and background subtraction. The difference in
100%). 1H NMR (300 MHz, CDCl3):
d 14.35 (s, 1H), 11.23 (s, 1H),
10.85 (s, 1H), 8.93–8.92 (m, 8H), 8.64 (s, 1H), 8.24 (d, J¼7.0 Hz, 2H),
7.98–7.97 (m, 6H), 7.89 (d, J¼7.0 Hz, 2H), 7.74 (d, J¼7.3 Hz, 1H),
7.58–7.57 (m, 3H), 6.87 (d, J¼7.3 Hz, 1H), 5.36 (s, 1H), 5.12 (s, 1H),
4.42–4.40 (m, 2H), 1.68–1.64 (m, 3H), 1.27 (s, 54H). 13C NMR
absorbance (DA) of the receptor in the presence of the guest and
absence of the guest was recorded and the data were plotted
against [guest]. The UV–vis spectral change of the receptor upon
titration with the guest clearly showed isobestic points, suggest-
ing that each zinc porphyrin moiety in the receptor binds with
a nitrogen ligand unit. The apparent association constants were
derived by using the non-linear curve fitting based on the
equation:
(100 MHz, CDCl3)
d 165.9, 163.2, 160.4, 154.5, 150.4, 150.1, 148.4,
142.0, 141.8, 139.5, 138.1, 134.9, 132.3, 132.1, 131.7, 129.6, 125.1,
122.4, 120.7, 120.4, 113.8, 110.1, 107.6, 46.59, 37.41, 35.03, 34.88,
31.96, 31.76, 16.90. MS (MALDI-FT): m/z 1281.7 [MþH]þ. HRMS
(MALDI-FT): calcd for C81H89N10OZn 1281.6507 [M]þ. Found:
1281.6529.
ꢀ
ꢁ
À
Á
À
D
A ¼
D
AN 1 þ Kassoc½Gꢄ þ Kassoc½Hꢄ0
ꢁ
1 þ Kassoc½Gꢄ
4.1.5. Compound R,R 2. Isonicotinic acid (0.22 mg, 1.8 mmol) was
suspended in thionyl chloride (4.0 mL) and DMF (0.1 mL), heated
under reflux for 1 h and then concentrated in vacuo. The
resulting residue 12 was dissolved in pyridine (2.0 mL) and then
the solution was added to a solution of 1123 (0.1 g, 0.59 mmol) in
pyridine (2.0 mL). The mixture was stirred at 50 ꢃC for 4 h and
then concentrated under reduced pressure. The crude product
was dissolved in dichloromethane (10 mL) and the solution
washed with saturated sodium bicarbonate solution (5 mL),
water (5 mL) and brine (5 mL), and dried over sodium sulfate.
After removing the solvent, the resulting residue was purified by
ꢃꢄ
ꢂ
0:5
Á
À
Á
2
þ Kassoc½Hꢄ0 ꢁ4Ka2ssoc½Hꢄ0½Gꢄ
2Kassoc½Hꢄ0
where
D
A ¼ A ꢁ
D
A0;
D
AN ꢁ A0
[G] is the pyridine concentration of ligands (2ꢀ[2], 2ꢀ[3]
or 2ꢀ[14]).
½Hꢄ ¼ ½1ꢄ
Acknowledgements
column chromatography (CH2Cl2/CH3OH 50:1) to give com-
We thank NSFC (No. 20732007), Ministry of Science and Tech-
nology of China (2007CB-808001), Chinese Academy of Sciences
(KJCX2-YW-H13) and Science and Technology Commission of
Shanghai Municipality (09XD1405300) for financial support.
25
pound R,R 2 as a white solid (0.13 g, 57%). [
CH2Cl2). 1H NMR (300 MHz, CDCl3):
4.38 (s, 2H), 3.59 (s, 2H), 3.13–3.10 (m, 2H), 1.94–1.91 (m, 2H),
0.92–0.87 (m, 12H). 13C NMR (100 MHz, CDCl3):
170.1, 150.3,
a
]
þ148 (c 0.25,
D
d
8.70 (s, 4H), 7.34 (s, 4H),
d
143.7, 120.6, 56.84, 44.31, 30.10, 19.30. MS (ESI): m/z 381
[MþH]þ. HRMS (ESI): calcd for C22H29N4O2 [MþH]þ: 380.2291.
Found: 381.2285.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2010.04.009.
4.1.6. Compound S,S 2. Compound S,S 2 was prepared by using the
same procedure and characterized by the 1H NMR and MS methods.
25
[
a]
ꢁ149 (c 0.24, CH2Cl2).
D
References and notes
4.1.7. Compound R,R 3. Isonicotinic acid (0.22 g, 1.8 mmol) was
suspended in thionyl chloride (4.0 mL) and DMF (0.1 mL). The
mixture was heated to reflux for 1 h to give a light yellow solution,
which was concentrated under reduced pressure to give compound
13, which was then dissolved in pyridine (2.0 mL). To this solution
was added dropwise a solution of compound 11 (96 mg, 0.59 mmol)
in pyridine (2.0 mL). The mixture was stirred at 50 ꢃC for 4 h and
then concentrated in vacuo. The resulting residue was dissolved in
dichloromethane (10 mL). The solution was washed with saturated
sodium bicarbonate solution (5 mL), water (5 mL) and brine (5 mL),
and dried over sodium sulfate. After removing the solvent with
a rotavapor, the resulting residue was purified by column chroma-
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