Anion-Assisted Complexation of Paraquat by Cryptands Based on Bis(m-phenylene)-[32]crown-10

Article abstract of DOI:10.1002/chem.200903553

The complexation of tightly ion-paired divalent salts such as paraquat dichloride by cryptands based on crown ethers can be improved by the introduction of ion-pair recognition as a means of also binding the counteranions. A series of diamide-based cryptands derived from bis(m-phenylene)-[32]crown-10 and designed to complex the bipyridinium dication with anion assistance was synthesized. The ionpair recognition process was fully characterized by ¹H NMR spectroscopy, UV/Vis spectroscopy, electrospray ionization mass spectrometry and single crystal X-ray analysis. ¹H NMR spectroscopy demonstrated that these new heteroditopic cryptand hosts can complex both the positive and negative components of the paraquat dichloride salt. UV/Vis spectroscopy showed that the addition of chloride anion into equimolar solutions of cryptands 3c or 3g with paraquat bis(hexafluorophosphate) salt (2a) improves the binding of the cryptands to the paraquat guest. Electrospray ionization mass spectrometry and single-crystal X-ray analysis confirmed the 1:1 stoichiometrics and ion-pair recognition of these cryptand/ paraquat complexes. It was found that the cryptand 3g, with 13 atoms and an isophthalamide moiety in the third chain, exhibited the best binding affinity for tightly ion-paired paraquat dichloride (2 b), due to the combination of its spatial compatibility and additional anion-binding site.

Full text of DOI:10.1002/chem.200903553

DOI: 10.1002/chem.200903553
Anion-Assisted Complexation of Paraquat by Cryptands Based on
Bis(m-phenylene)-[32]crown-10
Kelong Zhu, Ling Wu, Xuzhou Yan, Bo Zheng, Mingming Zhang, and Feihe Huang*[a]
Abstract: The complexation of tightly
ion-paired divalent salts such as para-
quat dichloride by cryptands based on
crown ethers can be improved by the
introduction of ion-pair recognition as
a means of also binding the counteran-
ions. A series of diamide-based crypt-
ands derived from bis(m-phenylene)-
[32]crown-10 and designed to complex
the bipyridinium dication with anion
assistance was synthesized. The ion-
pair recognition process was fully char-
acterized by 1H NMR spectroscopy,
UV/Vis spectroscopy, electrospray ioni-
zation mass spectrometry and single
crystal X-ray analysis. 1H NMR spec-
troscopy demonstrated that these new
heteroditopic cryptand hosts can com-
plex both the positive and negative
components of the paraquat dichloride
salt. UV/Vis spectroscopy showed that
the addition of chloride anion into
equimolar solutions of cryptands 3c or
3g with paraquat bis(hexafluorophos-
phate) salt (2a) improves the binding
of the cryptands to the paraquat guest.
Electrospray ionization mass spectrom-
etry and single-crystal X-ray analysis
confirmed the 1:1 stoichiometries and
ion-pair recognition of these cryptand/
paraquat complexes. It was found that
the cryptand 3g, with 13 atoms and an
isophthalamide moiety in the third
chain, exhibited the best binding affini-
ty for tightly ion-paired paraquat di-
chloride (2b), due to the combination
of its spatial compatibility and addi-
tional anion-binding site.
Keywords: anions
·
cryptands
·
host–guest systems · ion-pair recog-
nition · paraquat
Introduction
metal ions, nonmetallic ions and some organic salts.[3] The
strong interactions between cryptands and guests have been
exploited in the efficient preparation of threaded structures
such as rotaxanes and catenanes.[4] The high affinities of the
cryptand hosts are partly attributed to their spatial compati-
bility, which plays a key role in the design of these recep-
tors.
Most cation binding studies have used salts with noncom-
peting counterions, especially hexfluorophosphate anions,
for their good solubility and relatively weak ion-pairing in
organic solvents. However, the luxury of the noncompeting
counterion is not always available and the organic salts usu-
ally exist in many real-life situations or are commercially
available as tight ion-pairs. Actually, the important roles of
anions cannot be neglected either in biological processes or
in some artificial systems. Anions have been used elegantly
in the control of pseudorotaxane formation,[5a] operation of
molecular machines[5b] and morphological evolution of crys-
tals.[5c]
Threaded structures have attracted much attention not only
because of their topological importance but also as a result
of their many potential applications.[1] Bistable [2]rotaxane
molecules, for example, can serve as data storage ele-
ments.[2a] In some bioactive peptides, knotted arrangements
in which the C termini thread through N-terminal macrolac-
tam rings can even be found.[2b] The efficiencies of prepara-
tions of these threaded structures are strongly dependent on
the strength of host–guest complexation between the com-
ponents, based on weak noncovalent forces such as hydro-
gen bonding, p–p stacking and electrostatic interactions. As
a result of the incorporation of additional binding sites and
preorganization of complexation conformations, cryptands
based on crown ethers have proved to be powerful hosts for
[a] Dr. K. Zhu, L. Wu, X. Yan, B. Zheng, M. Zhang, Prof. Dr. F. Huang
Department of Chemistry, Zhejiang University
Hangzhou 310027 (P.R. China)
An alternative paradigm for salt complexation is ion-pair
recognition, in which cations and anions are simultaneously
bound by heteroditopic receptors. This has proved to be an
effective method to promote the binding abilities of recep-
tors for salt guests.[6,7,8] Various ion-pair recognition hosts
Fax : (+86)571-87951895
E-mail: fhuang@zju.edu.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200903553.
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FULL PAPER
have been synthesized to date, and they exhibit excellent af-
finities for inorganic salts.[7] Ion-pair recognition of organic
salts, however, especially those existing as tight ion-pairs,
has been investigated only to a very limited extent.[8]
was believed that ion-pair recognition of paraquat dichloride
(2b), which is commercially available, should be controlled
not only by the cryptand cavity size but also by the anion-
binding moiety (Figure 1). Cryptands 3c and 3g each con-
tains 13 atoms in their third chain backbones, so they are
considered to have the best structural similarity with 1.
Other cryptands were also synthesized to probe the effects
of cryptand cavity size and anion-binding moiety on their
Paraquat (N,N’-dimethyl-4,4’-bipyridinium) dichloride is
an effective but highly toxic herbicide widely used in agri-
culture and horticulture.[9] It and its derivatives have been
widely used in the fabrication of numerous supramolecular
systems, due to their easy availability and interesting physi-
cochemical properties.[10] Improvement of the binding of
paraquat and its derivatives is not only important for envi-
ronmental monitoring and human health[9] but also critical
for the fabrication of large supramolecular systems.[11] The
crown-ether-based cryptand 1 (Figure 1) has proved to be a
powerful host for the paraquat salt 2a.[3a] According to the
1
complexation to paraquat derivatives. H NMR spectrosco-
py, electrospray ionization mass spectrometry, UV/Vis spec-
troscopy and single-crystal X-ray analysis were employed to
characterize the binding of paraquat by these heteroditopic
cryptands.
Results and Discussion
Design and synthesis of crypt-
ands 3, based on bis(m-phenyl-
ene)-[32]crown-10: It has been
reported that the binding affini-
ties of cryptands based on
bis(m-phenylene)-[32]crown-10
for paraquat can be dramatical-
ly enhanced by optimizing the
length of the third chain.[11c]
From the X-ray crystal struc-
ture of the complex of 1·2a
(Figure 1) and the size similari-
ty between the chloride atom
and the oxygen atom, we envi-
sioned that the best number of
atoms in the backbone of the
third chain of the heteroditopic
cryptand host should be 13. In
Figure 1. Compounds used in this study, together with the X-ray crystal structure of the 1·2a·H2O complex.
order to probe the influence of
the length of the third chain,
cryptands
with
different
lengths—containing nine, 11, 13
X-ray structure of the complex 1·2a, the bipyridinium dicat-
ionic part threads into the cavity of the crown-ether-based
cryptand 1 with the assistance from two hydrogen bonds
formed between the two acidic b-pyridinium hydrogen
atoms and the oxygen atom of a water molecule that bridges
to the ether oxygen atoms of the third ethylenoxy chain.
This unique structure inspired us to develop ion-pair recog-
nition for paraquat derivatives. Because the van der Waals
radius (1.75 ꢁ) of the chlorine atom is close to that (1.52 ꢁ)
of the oxygen atom,[12] we envisioned that the replacement
of the water molecule in the crystal structure of complex
1·2a with a chloride anion should result in a similar complex
structure if an additional anion binding moiety—such as iso-
phthalamide or 2,6-pyridinedicarboxamide unit—were intro-
duced in the third chain of the cryptand host. On the basis
of these considerations we designed and synthesized a series
of new cryptands 3 (Scheme 1) possessing third chains of
different lengths and containing anion-binding moieties. It
or 15 atoms in their third chains—were designed and synthe-
sized in order to examine their geometries and intrinsic hy-
drogen bonding abilities.
The key starting material 5[11c] and the diamino intermedi-
ate 4a[10k] were synthesized by literature procedures. As out-
lined in Scheme 1, treatment of 5 with sodium cyanide and
subsequent reduction afforded the diamino intermediate 4b
in good yield.
The intermediate 7 was obtained by treatment of 5 with
diethyl malonate in tetrahydrofuran. Hydrolysis of 7 with
subsequent decarboxylation and methylation afforded 10.
The intermediate 12 was produced by the reduction of 10
and then toluenesulfonylation.
The diamino intermediate 4c was synthesized by
a
method reported for 4a.[10k] Treatment of 12 with excess po-
tassium phthalimide afforded 13, and hydrazinolysis of 13 in
methanol afforded the diamino intermediate 4c in good
yield.
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F. Huang et al.
Scheme 1. Synthesis of cryptand hosts 3, based on bis(m-phenylene)-[32]crown-10: a) NaCN, THF/H2O, reflux, 85%; b) borane methylsulfide, THF,
reflux, 84%; c) CH2ACHTUNGTRENNUNG(COOEt)2, NaH, THF, 98%; d) i) NaOH (2m), EtOH, reflux; ii) HCl, H2O, 99% (two steps); e) 1408C, N2, 75%; f) H2SO4, CH3OH,
89%; g) LiAlH4, THF, 92%; h) TsCl, Et3N, CH2Cl2, 73%; i) potassium phthalimide, DMF, 908C, 93%; j) i) hydrazine monohydrate, CH3OH, reflux;
ii) HCl, H2O, iii) NaOH, H2O, 90% (three steps); k) NaCN, DMF, 808C, 92%; l) borane methylsulfide, THF, reflux, 88%; m) isophthaloyl dichloride or
2,6-dipyridinecarbonyl dichloride, Et3N, CH2Cl2, 6–54%.
The diamino intermediate 4d was obtained by the same
method as used for 4b. Treatment of 12 with sodium cyanide
followed by reduction afforded the diamino intermediate 4d
in good yield.
The cryptands 3 were finally obtained in reasonable yields
by cyclization of the precursors 4 with isophthaloyl dichlor-
ide or 2,6-dipyridinecarbonyl dichloride, as appropriate, in
CH2Cl2. Even cryptands with larger cavities can be obtained
by these carbon-chain-extending reactions and ring-closure
methods.
(Figure 2) based on UV/Vis spectroscopy absorbance data
in CHCl3/CH3OH (1:1) demonstrated that the complexes of
3 with 2b were of 1:1 stoichiometry in solution. Most of the
positive electrospray ionization mass spectra (see the Sup-
porting Information) of equimolar mixtures of 3 and 2b
gave mass fragments corresponding to [3·2bÀ2Cl]2+ and
[3·2bÀCl]+, confirming the 1:1 stoichiometries of these
cryptand/paraquat complexes.
The association constant (Ka) values (Table 1) for com-
plexes 3·2b were determined by probing the charge-transfer
bands of the complexes by UV/Vis spectroscopy with em-
ployment of a titration method (Figures S69–S80 in the Sup-
porting Information). In the pyridine series, complex 3c·2b
complex gives the highest Ka value, corresponding to a com-
plexation free energy of 5.0 kcalmolÀ1, when compard to
3a·2b, 3b·2b and 3d·2b. Also in the benzene series, com-
plex 3g·2b (n=3) gives the highest Ka value, corresponding
to a complexation free energy of 5.8 kcalmolÀ1, when com-
pared to 3e·2b, 3 f·2b and 3h·2b. These differences in Ka
values indicated that the cryptands 3c and 3g offered the
Complexation of the new cryptands 3 with paraquat: Equi-
molar (0.500 mm) acetonitrile solutions of 2a and each of
the eight new cryptands 3 are yellow, due to charge transfer
between the electron-rich aromatic rings of the cryptand
host and the electron-poor pyridinium rings of the guest 2a.
The same yellow colour in equimolar (0.500 mm) CHCl3/
CH3OH (1:1) solutions of 3 with 2b provided evidence that
the charge transfer interaction also occurred when the PF6
anions were replaced by the chloride anions. Job plots[13]
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Anion-Assisted Complexation of Paraquat
FULL PAPER
Table 2. Ka values for complexes 3c·2c, 3g·2c, 3c·2d and 3g·2d in
CHCl3/CH3OH (1:1) at 258C.
3c·2c
3c·2d
3g·2c
3g·2d
10À3 ꢂKa
[mÀ1
0.78 (Æ0.05)
2.4 (Æ0.1)
0.63 (Æ0.04)
3.4 (Æ0.2)
N
]
ÀDG298 K
3.9
4.6
3.8
4.8
[kcalmolÀ1
]
The Ka values for the 3c·2d and 3g·2d complexes were
about 2.1 and 4.4 times greater, respectively, than the Ka
values for the 3c·2c and 3g·2c complexes. These increases
in the Ka value indicated that the addition of ClÀ could en-
hance the binding affinities of cryptands 3 for 4,4’-bipyridi-
nium dication. The higher Ka value for complex 3g·2d than
for 3c·2d confirmed that the isophthalamides were better
anion receptors than 2,6-pyridinecarcarboxamides.[14] It is
worth noting that the Ka value for the 3c·2c complex is
slightly higher than that for 3g·2c. This can be attributed to
the preference for the syn-syn conformation of the two
amide NH groups on the 2,6-pyridinecarboxamide fragment
of 3c when no ClÀ is present.[14c] Without the anion assis-
tance, 3c can exhibit better binding affinity for the 4,4’-bi-
pyridinium dication than 3g.
Here the cryptands 3 gave lower binding affinities than 1
for the incorporation of anions.[3a] However, this incorpora-
tion makes it possible to recognize paraquat dichloride as a
tight ion pair and to fabricate anion-driven molecular ma-
chines or other self-assembly systems based on the new mo-
lecular recognition motif of 3 for paraquat.
Figure 2. Job plots showing the 1:1 stoichiometries of the complexes
formed between hosts 3 and 2b in CHCl3/CH3OH (1:1). The absorbance
intensities at l=388 nm (the host–guest charge-transfer band) were plot-
ted against the mole fractions of the hosts. [3]0 and [2b]0 are initial con-
Anion-assisted complexation of paraquat by cryptand 3c:
The pale yellow colour of an equimolar (0.500 mm) acetoni-
trile solution of cryptand 3 with paraquat 2a indicated weak
interaction between the host and guest. Upon gradual addi-
tion of tetrabutylammonium chloride (TBACl), however,
the intensity of the charge-
centrations of 3 and 2b, respectively. a) [3a]0+
[2b]0 =2.00 mm; [2b]0 =1.00 mm;
c) [3c]0+
e) [3e]0+ f) [3 f]0+
[2b]0 =1.00 mm; [2b]0 =1.00 mm;
1.00 mm; h) [3h]0+
[2b]0 =1.00 mm.
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
transfer band (388 nm) in-
creased without any new band
Table 1. Ka values for complexes 3·2b in CHCl3/CH3OH (1:1) at 258C.
3a·2b
3b·2b
3c·2b
3d·2b
3e·2b
3 f·2b
3g·2b
3h·2b
being observed (Figure 3). This
intensity reached its maximum
after addition of 2.0 equiv of
ClÀ. These results indicated that
the addition of ClÀ enhanced
the complexation between the
cryptand host 3c and the para-
10À3 ꢂKa
[mÀ1
0.90
0.32
4.8
2.7
3.3
2.2
17
5.6
G
]
(Æ0.10)
(Æ0.01)
(Æ0.2)
(Æ0.5)
(Æ0.4)
(Æ0.5)
(Æ2)
(Æ0.2)
ÀDG298 K
4.0
3.4
5.0
4.7
4.8
4.6
5.8
5.1
[kcalmolÀ1
]
best spatial fit for the 4,4’-bipyridinium dication with chlo-
ride anions. The Ka value for the 3g·2b complex is about 2.5
times higher than that for the 3c·2b complex. This can be
attributed to the additional anion-binding site supplied by
the acidic third-chain phenyl hydrogen atom in 3g.[14]
The determination of the Ka values of the complexes of
cryptands 3 with 2a in CHCl3/CH3OH (1:1) failed because
of the poor solubility of 2a in this solvent system. In order
to estimate the anion effect in the promotion of the binding
affinity, the Ka values (Table 2) for complexes 3c·2c, 3g·2c,
3c·2d and 3g·2d were determined in this solvent system.
quat guest. The positive electrospray ionization mass spec-
trum (Figure S61 in the Supporting Information) of an equi-
molar mixture of 3c and 2b in CH3CN/CH3OH (9:1, v/v)
gave mass fragments corresponding to [3c·2bÀ2Cl]2+ at m/z
483.7 (100%) and [3c·2bÀCl]+ at m/z 1002.4 (31%), con-
firming the 1:1 stoichiometry and ion-pair complexation.
The anion-assisted complexation was also detected by a
proton NMR titration study (Figure 4). Relatively small up-
field shifts after complexation were observed for the aro-
matic protons (He and Hf) of host 3c and the pyridinium
protons (Ha and Hb) of 2a (spectra a, b and g in Figure 4),
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F. Huang et al.
propyl ether into a 1:1:1 solution of 3c, 2a and TBACl in
acetonitrile/methanol (20:1, v/v) at room temperature. The
X-ray crystal structure of the 3c2·2a2·2b complex (Figure 5)
confirmed the ion-pair recognition process. A chloride atom
was found to fill into the “pocket” in the inclusion complex
structure formed on threading of the bipyridinium dication
guest into the cavity of the cryptand host, in accordance
with our design. The chloride atom forms three hydrogen
bonds with the two amide hydrogens Hd and one pyridinium
hydrogen Hb (Figure 5a and 5b).[15] These three hydrogen
bonds adopt a “cone” conformation, indicating that the
chloride anion is somewhat too large to fit completely into
the cryptand host cavity to form the “tetrahedral” confor-
mation we expected. As in the X-ray crystal structure of the
1·2a complex (Figure 1), water bridges can also be found in
this structure (Figure 5b). Here, however, the two water
bridges are between two chloride anions to connect two
cryptand/paraquat complexes (Figure 5b) whereas in the X-
ray crystal structure of 1·2a a water bridge exists between
the cryptand host and paraquat guest, providing additional
noncovalent interactions between the cryptand host and par-
aquat guest (Figure 1). The two chloride anions form four
hydrogen bonds (d and e in Figure 5b) with the four hydro-
gen atoms of two water molecules. Two cryptand/paraquat
complexes are linked in the packing structure by the combi-
nation of the resulting “rhombus” and “cone” conforma-
Figure 3. Absorbance spectral changes of an equimolar solution
(2.00 mL) of 3c (0.500 mm) and 2a (0.500 mm) upon addition of TBACl
(from 0 to 2.00 mm).
indicating relatively weak host–
guest binding relative to report-
ed complexation between crypt-
ands and paraquat 2a.[11c] The
significant downfield shift of
the amide protons (Hd) of
cryptand 3c indicated the dra-
matic change in the chemical
environment in the cryptand
cavity after the complexation.
Upon the addition of ClÀ, the
chemical shift of the amide pro-
tons Hd moved even further
downfield, due to the hydrogen
bond formation between the
chloride anion and amide pro-
tons. The signals of protons He,
Hf and Hg moved even further
Figure 4. Partial 1H NMR spectra (500 MHz, CD3CN, 208C) of: a) 3c (0.500 mm), b) an equimolar mixture of
3c (0.500 mm) and 2a (0.500 mm), c) (b)+TBACl (0.180 mm), d) (b)+TBACl (0.220 mm), e) (b)+TBACl
(0.500 mm), f) (b)+TBACl (1.00 mm), and g) 2a (1.00 mm).
upfield, indicating enhanced
host–guest binding, consistently
with the above UV/Vis titration
study. The pyridinium protons
Hb moved downfield upon addi-
tion of ClÀ whereas no clear change was observed for the
pyridinium protons Ha. This difference can be attributed to
the hydrogen bonding between protons Hb and the chloride
anion, as would be expected.
Crystals of the 3c2·2a2·2b complex suitable for single-crys-
tal X-ray analysis were obtained by vapour diffusion of iso-
tions. What is more interesting is that two cryptand/paraquat
complexes are also noncovalently connected together by a
paraquat molecule through face-to-face p-stackings between
the pyridine ring of the 3c molecule in one cryptand/para-
quat complex and a pyridinium ring of a paraquat molecule
and between the other pyridinium ring of the paraquat mol-
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Anion-Assisted Complexation of Paraquat
FULL PAPER
ecule and the pyridine ring of the 3c molecule in another
cryptand/paraquat complex (Figure 5c). This unique connec-
tion may provide extra stability for the crystal structure.
These results, combined with the above NMR study, con-
firmed the improved complexation of paraquat assisted by
anion binding.
band (388 nm) again increased without any new band being
observed (Figure 6). After addition of 2.0 equiv of ClÀ, the
solution reached its maximum absorption. The resulting
light yellow colour of the solution, which resulted from en-
hanced charge transfer, indicated that the addition of ClÀ
also enhanced the complexation between the cryptand 3g
and the bipyridinium dication. The positive electrospray ion-
ization mass spectrum (Figure S63 in the Supporting Materi-
al) of an equimolar mixture of 3g and 2b in CH3CN/
CH3OH (9:1, v/v) gave mass fragments corresponding to
[3g·2bÀ2Cl]2+ at m/z 483.6 (100%) and [3g·2bÀCl]+ at m/z
1001.1 (26%), confirming the 1:1 stoichiometry and ion-pair
complexation.
Anion-assisted complexation of paraquat by cryptand 3g:
An equimolar (0.500 mm) acetonitrile solution of cryptand
3g with paraquat 2a also gives a weak yellow colour due to
charge transfer between the host and guest. Upon gradual
addition of ClÀ, however, the intensity of the charge transfer
Figure 6. Absorbance spectral changes of an equimolar solution
(2.00 mL) of 3g (0.500 mm) and 2a (0.500 mm) upon addition of TBACl
(from 0 to 2.00 mm).
Figure 5. Views of the X-ray crystal structure of the 3c2·2a2·2b complex.
a) 3c is shown as a ball and stick model and chloride and bipyridinium
dication are shown as space-filling models. b) and c) Ball and stick repre-
sentation of the packing of two adjacent cryptand/paraquat complexes in
the unit cell in different directions. Noninteracting hydrogen atoms have
The anion-assisted complexation of 3g with bipyridinium
dication was also detected by a proton NMR titration study
(Figure 7). Relatively small upfield shifts after complexation
were observed for the aromatic protons (He and Hf), the
ethylenoxy protons Hg of host 3g and the pyridinium pro-
tons (Ha and Hb) of 2a (spectra a, b and f in Figure 7), indi-
cating relatively weak host–guest binding relative to previ-
ously reported complexation between cryptands and para-
quat 2a.[11c] Upon addition of ClÀ, the chemical shifts of pro-
been omitted for clarity. Hydrogen bond parameters: H···O
ACHTUNGTRENUN(NG F, Cl) dis-
tance [ꢁ], C(N)-H···O(F, Cl) angle [8], C(N)···O(F, Cl) distance [ꢁ].
A
ACHTUNGTRENNUNG
a) 2.75, 143, 3.57, b) 2.56, 154, 3.35, c) 2.50, 151, 3.27, d) 2.38, 178, 3.23,
e) 2.33, 178, 3.18, f) 2.69, 142, 3.47, g) 2.91, 132, 3.63, h) 2.54, 129, 3.23,
i) 2.49, 136, 3.35, j) 2.70, 151, 3.91, and k) 2.49, 149, 3.91. Face-to-face p-
stacking parameters: centroid–centroid distances [ꢁ]: 4.60, 3.8, 4.49, 3.69;
ring plane/ring plane inclinations [8]: 5.0, 6.0, 1.82, 1.19.
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6093

F. Huang et al.
phenyl proton Hc (Figure 8b). The cryptand 3g was there-
fore demonstrated to be an effective host for 2b through
ion-pair recognition.
Figure 7. Partial 1H NMR spectra (500 MHz, CD3CN, 208C) of: a) 3g
(0.500 mm), b) an equimolar mixture of 3g (0.500 mm) and 2a
(0.500 mm), c) (b)+TBACl (0.200 mm), d) (b)+TBACl (0.500 mm),
e) (b)+TBACl (1.00 mm), and f) 2a (0.500 mm).
Figure 8. Views of the X-ray crystal structure of the 3g·2b complex. a) 3g
is shown as a ball and stick model and chloride and bipyridinium dication
are shown as space-filling models. b) Ball and stick representation of the
3g·2b complex. c) Ball and stick representation of the packing structure
of the 3g·2b complex. Noninteracting hydrogen atoms have been omitted
for clarity. Hydrogen bond parameters: H···OACTHNUTRGENUG(N F, Cl) distance [ꢁ], C(N)-
H···O(Cl) angle [8], C(N)···O(Cl) distance [ꢁ]. a) 2.58, 166, 3.42, b) 2.57,
169, 3.49, c) 2.51, 161, 3.34, d) 2.80, 141, 3.58, e) 2.83, 160, 3.74, f) 2.34,
156, 3.21, g) 2.56, 103, 2.92, and h) 2.40, 129, 3.07. Face-to-face p-stacking
parameters: centroid-centroid distances [ꢁ]: 3.68, 4.80, 4.65, 3.84; ring
plane/ring plane inclinations [8]: 7.7, 22.3, 9.07, 13.9.
tons Hd and Hc were shifted even further downfield due to
the hydrogen bond formation between these protons and
ClÀ. The two peaks corresponding to protons He and Hf
became a single broadened peak and moved even further
upfield. These chemical shift changes indicate enhanced
charge transfer, which is consistent with the above UV/Vis
titration study. The pyridinium protons Hb were shifted
downfield upon addition of ClÀ, whereas no clear chemical
shift change was observed for protons Ha. This can be attrib-
uted to the hydrogen bonding between hydrogens Hb and
the chloride anion, as would be expected.
Crystals of the 3g·2b complex suitable for single crystal
X-ray analysis were obtained by vapour diffusion of isopro-
pyl ether into a 1:1 solution of 3g and 2b in acetonitrile/
methanol (30:1, v/v) at room temperature. The X-ray crystal
structure (Figure 8) of the 3g·2b complex confirmed the
ion-pair recognition. A chloride anion fills the “pocket” in
the inclusion complex structure formed on threading of the
pyridinium dication into the cavity of the cryptand 3g, as we
designed. Unlike in the crystal structure of the 3c2·2a2·2b
complex, the ClÀ forms four hydrogen bonds with the two
amide protons, one pyridinium proton (Hb) and one phenyl
proton (Hc). The four hydrogen bonds also adopt a “cone”
conformation, again indicating that the chloride is somewhat
too large to form the “tetrahedral” conformation, similarly
to what we had observed in the crystal structure of the
3c2·2a2·2b complex. One of the pyridinium protons Hb
forms a hydrogen bond with the oxygen atom of a carba-
mide of the adjacent 3g. This results in a polymer-like pack-
ing structure (Figure 8c). The higher Ka value for complex
3g·2b than for complex 3c·2b can be explained by the addi-
tional H-bonding between the chloride anion and the
Solid-state structure of the 3a·2a complex: The relatively
low Ka values of the complexes 3a·2b and 3e·2b are consid-
ered to result from the smaller cavities of these two crypt-
ands, which cannot bind cations and anions simultaneously.
The failure to observe any mass fragments corresponding to
ion-pair-binding complexes in the MS analysis may also be a
consequence of this spatial problem. Although attempts to
prepare single crystals from solutions either of 3a and 2b or
of 3e and 2b with different host/guest molar ratios and or-
ganic solvents failed, crystals of the 3a·2a complex suitable
for single-crystal X-ray analysis were obtained by vapour
diffusion of pentane into an equimolar solution of 3a and
2a in acetone. The X-ray crystal structure of the 3a·2a com-
plex is shown in Figure 9. The phenylene rings of the
[32]crown-10 part are face-to-face p-stacked with only one
pyridinium ring of the guest, whereas in most of the previ-
ously reported 1:1 cryptand/paraquat complexes the phenyl-
ene rings are face-to-face p-stacked with both pyridinium
rings of the paraquat guest.[3a,4,11b,c,16] This big difference in
the solid-state structure means that the cavity of the crypt-
and 3a is too small to bind ClÀ and bipyridinum dication si-
multaneously. One fluorine atom of the PF6 anion is hydro-
gen-bonded (a, b and c in Figure 9a) to the two amide hy-
drogen atoms of the cryptand 3a host and one b-pyridinium
hydrogen (Hb) of the paraquat guest and another fluorine
atom is hydrogen-bonded (d in Figure 9a) to an a-pyridini-
um hydrogen (Ha) of the paraquat guest. This structural fea-
6094
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ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 6088 – 6098

Anion-Assisted Complexation of Paraquat
FULL PAPER
Experimental Section
All commercial-grade chemicals were used without further purification.
Solvents were either employed as purchased or dried as described in the
literature. 1H NMR spectra were collected with
a Bruker Avance
DMX 500 spectrometer or a Varian Unity INOVA-400 spectrometer with
TMS as internal standard. 13C NMR spectra were recorded with a Bruker
Avance DMX 500 spectrometer at 125 MHz or a Varian Unity INOVA-
400 spectrometer at 100 MHz. Mass spectra were obtained with a Bruker
Esquire 3000 plus mass spectrometer (Bruker–Franzen Analytik GmbH
Bremen, Germany) with an ESI interface and ion trap analyzer. HRMS
were obtained with a Bruker 7-Tesla FT-ICRMS equipped with an elec-
trospray source (Billelica, MA, USA). C, H and N were analyzed with a
Carlo Erba 1110 elemental analyzer. The starting materials 4a[10k] and
5[11c] were synthesized by literature procedures. The paraquat salt 2b was
purchased from Aldrich. The other salts 2a,[3a] 2c[17] and 2d[18] were syn-
thesized by literature procedures.
Figure 9. Views of the X-ray crystal structure of the 3a·2a complex.
a) Ball and stick representation of the 3a·2a complex. b) 3a is shown as
a ball and stick model, and the bipyridinium cation is shown as a space-
filling model. Noninteracting hydrogen atoms have been omitted for
clarity. Hydrogen bond parameters: H···OACTHNUTRGNE(NUG F, Cl) distance [ꢁ], C(N)–
General method for the syntheses of the cryptands 3a–3h: A solution of
H···O(Cl) angle [8], C(N)···O(Cl) distance [ꢁ]. a) 2.30, 156, 3.11, b) 2.29,
146, 3.05, c) 2.57, 123, 3.18, d) 2.39, 163, 3.30, e) 2.43, 159, 3.35, f) 2.48,
141, 3.28, g) 2.31, 162, 3.21, and h) 2.34, 166, 3.25. Face-to-face p-stacking
parameters: centroid–centroid distances [ꢁ] 3.60, 5.25, 3.65, 5.57; ring-
plane/ring-plane inclinations [8]: 4.5, 29.5, 0.64, 27.4.
isophthaloyl dichloride or 2,6-pyridinedicarboxyl dichloride (0.400 mmol)
in CH2Cl2 (15.0 mL) was added by syringe pump at
a speed of
1.00 mLhÀ1 under N2 to a stirred solution of 4 (0.400 mmol) and Et3N
(4.00 mmol) in CH2Cl2 (300 mL). After addition, the mixture was stirred
at room temperature for 12 h. The reaction mixture was concentrated to
about 100 mL and washed with HCl solution (0.1m). The organic layer
was dried over anhydrous Na2SO4 and concentrated. The desired product
3 was obtained by flash column chromatography (SiO2, dichloromethane/
acetone 3:1).
ture indicates that the complexation of paraquat with crypt-
and 3a can also be assisted by anion-binding.
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-[2’’,6’’-di(methyle-
necarboxamido)pyridine] (3a): Yield: 11%; m.p. 160–1628C; 1H NMR
(400 MHz, CDCl3, RT): d=8.46 (d, J=8.0 Hz, 2H), 8.12 (t, J=8.0 Hz,
1H), 7.93 (br, 2H), 6.44 (d, J=2.0 Hz, 4H), 6.38 (s, 2H), 4.61 (d, J=
6.0 Hz, 2H), 3.99 (t, J=4.0 Hz, 8H), 3.78 (t, J=4.0 Hz, 8H), 3.66–
3.62 ppm (m, 16H); MS (ESI+): m/z (%): 748.5 (100) [M+Na]+; HRMS
(ESI): m/z: calcd for C37H47N3O12Na: 748.3057 [M+Na]+; found:
748.3009 (error 6.5 ppm).
Conclusion
The complexation of divalent salts such as paraquat by
cryptands can be improved through the introduction of ion-
pair recognition as a means of also binding the counterions.
We have designed and synthesized a series of diamide-based
cryptands based on bis(m-phenylene)-[32]crown-10. The
anion-assisted complexation of bipyridinium dications with
these new cryptands was confirmed by a combination of
1H NMR characterization, UV/Vis spectroscopy, electro-
spray ionization mass spectrometry and single-crystal X-ray
analysis. It was found that the cryptand 3g, with its third
chain incorporating 13 backbone atoms and an isophthala-
mide moiety, exhibited the best binding affinity for the tight-
ly ion-paired paraquat dichloride salt (2a) through ion-pair
recognition. The relatively smaller cavities in the cryptands
3a and 3e may make it possible for them to bind bipyridini-
um dication more efficiently through employment of anions
smaller than chloride, such as fluoride. These studies dem-
onstrated that the efficient complexation of tight ion-pairs,
such as paraquat dichloride (2b), in organic solvents can be
achieved through the introduction of heteroditopic cryptand
hosts, such as 3. This anion-assisted recognition motif can be
used not only in the efficient preparation of threaded struc-
tures, but can also be applied to the development of anion-
driven switchable molecular devices. Currently we are focus-
ing on these projects.
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-[2’’,6’’-di(ethylene-
carboxamido)pyridine] (3b): Yield: 30%; m.p. 144–1458C; 1H NMR
(400 MHz, CDCl3, RT): d=8.33 (d, J=8.0 Hz, 2H), 8.04 (t, J=8.0 Hz,
1H), 7.53 (t, J=6.0 Hz, 2H), 6.49 (d, J=1.6 Hz, 4H), 6.36 (s, 2H), 4.05
(t, J=4.4 Hz, 8H), 3.85 (t, J=4.4 Hz, 8H), 3.70–3.76 (m, 20H), 2.77 ppm
(t, J=7.2 Hz, 4H); 13C NMR (125 MHz, CDCl3, 228C): d=162.9, 160.2,
148.5, 140.9, 139.1, 124.7, 107.9, 99.3, 70.9, 70.9, 69.6, 67.6, 39.6, 35.9 ppm;
MS (ESI+): m/z (%): 776.5 (100) [M+Na]+, 771.6 (19) [M+NH4]+;
HRMS (ESI): m/z: calcd for C39H52O12N3 754.3546 [M+H]+; found:
754.3542 (error 0.5 ppm).
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-[2’’,6’’-di(propyl-
enecarboxamido)pyridine] (3c): Yield: 20%; m.p. 152–1548C; 1H NMR
(400 MHz, CDCl3, RT): d=8.34 (d, J=7.6 Hz, 2H), 8.02 (t, J=7.6 Hz,
1H), 7.66 (br, 2H), 6.29 (m, 6H), 3.98 (m, 8H), 3.80 (m, 8H), 3.68 (m,
16H), 3.46 (m, 4H), 2.62 (t, J=7.2 Hz, 4H), 1.94 ppm (4H, m); 13C NMR
(125 MHz, CDCl3, 228C): d=163.6, 159.9, 148.8, 143.6, 138.9, 124.9,
107.3, 98.8, 70.8, 70.8, 69.7, 67.4, 39.0, 33.5, 30.8 ppm; MS (ESI+): m/z
(%): 782.9 (100) [M+H]+; HRMS (ESI): m/z: calcd for C41H56N3O12
782.3859 [M+H]+; found: 782.3830 (error 3.7 ppm).
:
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-[2’’,6’’-di(butane-
carboxamido)pyridine] (3d): Yield: 24%; m.p. 147–1488C; 1H NMR
(400 MHz, CDCl3, RT): d=8.27 (d, J=7.6 Hz, 2H), 7.98 (t, J=7.6 Hz,
1H), 7.47 (br, 2H), 6.34 (m, 4H), 6.22 (s, 2H), 4.01 (t, J=3.6 Hz, 8H),
3.80 (t, J=3.6 Hz, 8H), 3.66–3.69 (m, 16H), 3.43 (m, 4H), 2.56 (t, J=
5.6 Hz, 4H), 1.65–1.68 (4H, m), 1.53–1.56 ppm (4H, m); MS (ESI+): m/z
(%): 810.5 (100) [M+H]+; HRMS (ESI): m/z: calcd for C43H60N3O12
810.4177 [M+H]+; found: 810.4148 (error 3.6 ppm).
:
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-(N’’,N’’-dimethyl-
eneisophthalamide) (3e): Yield: 6%; m.p. 157–1588C; 1H NMR
(400 MHz, CDCl3, RT): d=8.17 (d, J=8.0 Hz, 2H), 7.79 (s, 1H), 7.61 (t,
J=8.0 Hz, 1H), 6.44 (m, 8H), 4.47 (s, 4H), 4.01 (m, 8H), 3.79 (m, 8H),
3.57–3.67 ppm (m, 16H); 13C NMR (100 MHz, CDCl3, 228C): d=166.3,
Chem. Eur. J. 2010, 16, 6088 – 6098
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6095

F. Huang et al.
160.1, 139.8, 134.2, 131.6, 129.5, 122.9, 107.6, 100.6, 70.7, 69.6, 67.5,
44.9 ppm; MS (ESI+): m/z (%): 747.4 (100) [M+Na]+, 742.4 (91)
[M+NH4]+, 725.4 (23) [M+H]+. MS (ESIÀ): m/z (%): 759.4 (100)
[M+Cl]À; HRMS (ESI): m/z: calcd for C38H48O12N2Na: 747.3099
[M+Na]+; found: 747.3065 (error 4.5 ppm).
Bis[5-(4’-aminobutyl)-m-phenylene]-[32]crown-10 (4d): A solution of 14
(200.0 mg, 0.300 mmol) in THF (20.0 mL) was cooled to 08C and borane
methylsulfide (0.400 mL, 3.92 mmol) was added by syringe. After addi-
tion, the reaction mixture was heated at reflux for 12 h and then allowed
to cool to room temperature. The excess borane methylsulfide was de-
stroyed by addition of methanol, the mixture was stirred for an hour, and
concentrated HCl (5.00 mL) was then added. The resulting mixture was
heated at reflux for an hour and then neutralized to pH >12. The solvent
was evaporated under reduced pressure and the residue was partitioned
between CH2Cl2 (50.0 mL) and water (20.0 mL). The organic layer was
dried over Na2SO4 and concentrated to afford a colourless oil. Yield:
180 mg (88%); 1H NMR (400 MHz, CDCl3, RT): d=6.31 (m, 6H), 4.05
(m, J=4.8 Hz, 8H), 3.82 (m, J=4.8 Hz, 8H), 3.67–3.71 (m, 16H), 2.67 (t,
J=7.2 Hz, 4H), 2.51 (t, J=7.2 Hz, 4H), 1.42–1.61 ppm (m, 8H);
13C NMR (125 MHz, CDCl3, 228C): d=160.0, 145.0, 119.8, 107.7, 98.9,
71.0, 69.9, 67.6, 42.3, 36.2, 33.7, 28.7 ppm; MS (ESI): m/z (%): 679.7 (100)
[M+H]+; HRMS (ESI): m/z: calcd for C36H59O10N2: 679.4170 [M+H]+;
found: 679.4146 (error 3.5 ppm).
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-(N’’,N’’-diethyl-
eneisophthalamide) (3 f): Yield: 13%; m.p. 136–1388C; 1H NMR
(500 MHz, CDCl3, RT): d=7.94 (d, J=7.5 Hz, 2H), 7.50 (m, 4H), 6.38
(d, J=2.0 Hz, 4H), 6.32 (t, J=2.0 Hz, 2H), 6.19 (br, 2H), 4.02 (t, J=
4.5 Hz, 8H), 3.79 (t, J=4.5 Hz, 8H), 3.66–3.73 (m, 20H), 2.88 ppm (t, J=
6.0 Hz, 4H); 13C NMR (100 MHz, CDCl3, 228C): d=167.4, 160.0, 141.2,
134.8, 130.7, 129.3, 124.1, 107.9, 99.7, 70.7, 70.6, 69.6, 67.5, 40.7, 35.2 ppm.
MS (ESI): m/z (%): 791.4 (13) [M+K]+, 775.5 (100) [M+Na]+, 753.5
(31) [M+H]+; HRMS (ESI): m/z: calcd for C40H52N2O12Na: 775.3412
[M+Na]+; found: 775.3444 (error 4.1 ppm).
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-(N’’,N’’-dipropyl-
eneisophthalamide) (3g): Yield: 33%; m.p. 140–1428C; 1H NMR
(400 MHz, CDCl3, RT): d=7.76 (d, J=7.6 Hz, 2H), 7.43 (t, J=7.6 Hz,
1H), 7.32 (s, 1H), 6.40 (d, J=2.0 Hz, 4H), 6.23 (t, J=2.0 Hz, 2H), 6.09
(br, 2H), 3.98 (m, 8H), 3.78 (m, 8H), 3.65–3.69 (m, 16H), 3.50 (q, J=
6.4 Hz, 4H), 2.68 (t, J=6.8 Hz, 4H), 2.00 ppm (m, 4H); MS (ESI+): m/z
(%): 798.6 (100) [M+NH4]+, 819.4 (23) [M+K]+, 803.5 (93) [M+Na]+,
781.5 (11) [M+H]+. MS (ESIÀ): m/z (%): 815.7 (67) [M+Cl]À, 779.6
(100) [MÀH]À; HRMS (ESI): m/z: calcd for C42H56N2O12Na: 803.3731
[M+Na]+; found: 803.3646 (error 9 ppm).
Bis[5-(cyanomethyl)-m-phenylene]-[32]crown-10 (6):
A mixture of 5
(100 mg, 0.140 mmol), NaCN (30.0 mg, 0.610 mmol) and THF/H2O (10:1,
20.0 mL) was heated at reflux for 25 h. The mixture was cooled and the
solvent was removed on a rotary evaporator. The residue was dissolved
in CHCl3 (10.0 mL) and washed with water (10.0 mL ꢂ 3). The combined
organic phase was dried over anhydrous Na2SO4, filtered and concentrat-
ed. The residue was separated by flash column chromatography with
CHCl3/CH3OH (30:1) as the eluent to afford 6 as a white solid (73.6 mg,
85%). M.p. 192–1938C; 1H NMR (400 MHz, CDCl3, RT): d=6.47 (s,
4H), 6.23 (s, 2H), 4.07 (t, J=4.8 Hz, 8H), 3.85 (t, J=4.8 Hz, 8H), 3.69–
3.73 (m, 16H), 3.65 ppm (s, 4H); 13C NMR (125 MHz, CDCl3, 228C): d=
160.6, 132.1, 118.0, 107.1, 101.2, 71.1, 69.8, 67.9, 23.9. MS (ESI): m/z (%):
654.6 (19) [M+K]+, 637.5 (100) [M+Na]+, 632.6 (51) [M+NH4]+; ele-
mental analysis (%) calcd for C32H42O10N2: C 62.53, H 6.89, N 4.56;
found: C 62.93, H 6.80, N 4.38.
Bis(1,3,5-phenylene)di(1’,4’,7’,10’,13’-pentaoxatridecyl)-(N’’,N’’-dibutane-
isophthalamide) (3h): Yield: 54%; m.p. 135–1378C; 1H NMR (400 MHz,
CDCl3, RT): d=7.94 (m, 2H), 7.87 (s, 1H), 7.49 (t, J=6.0 Hz, 1H), 6.29
(m, 8H), 4.01 (t, J=4.0 Hz, 8H), 3.81 (t, J=4.0 Hz, 8H), 3.42–3.46 (m,
16H), 3.44 (q, J=5.6 Hz, 4H), 2.56 (t, J=5.6 Hz, 4H), 1.54–1.70 ppm (m,
8H); 13C NMR (100 MHz, CDCl3, 228C): d=166.8, 159.7, 144.0, 134.6,
130.4, 129.1, 124.3, 107.4, 98.8, 70.7, 69.7, 67.4, 39.9, 35.3, 28.5, 27.8 ppm;
MS (ESI+): m/z (%): 831.5 (100) [M+Na]+; HRMS (ESI): m/z: calcd for
C44H60N2O12Na: 831.4038 [M+Na]+; found: 831.4041 (error 1.0 ppm).
Bis[5-(2’,2’-dicarbethoxyethyl)-m-phenylene]-[32]crown-10 (7): NaH
(60% in mineral oil, 100 mg, 2.50 mmol) and 5 (300 mg, 0.415 mmol)
were added sequentially to a mixture of diethyl malonate (400 mg,
2.50 mmol) and THF (10.0 mL). The resulting mixture was stirred at
room temperature for 24 h, and the solvent was removed in vacuum, fol-
lowed by addition of CH2Cl2 (10.0 mL). The mixture was isolated by
flash column chromatography with ethyl acetate/petroleum ether (2:1) as
the first eluent and CH2Cl2/MeOH (50:1) as the second eluent. The de-
sired product was obtained from the second fraction as a colourless oil
(360 mg, 98%). 1H NMR (400 MHz, CDCl3, RT): d=6.30 (s, 6H), 4.00–
4.13 (m, 8H), 3.99 (t, J=4.8 Hz, 8H), 3.76 (t, J=4.8 Hz, 8H), 3.63–3.67
(m, 16H), 3.55 (t, J=8.0 Hz, 2H), 3.06 (d, J=8.0 Hz, 4H), 1.16 ppm (t,
J=6.4 Hz, 12H); 13C NMR (100 MHz, CDCl3, 228C): d=169.8, 160.1,
140.2, 106.2, 101.3, 71.5, 69.9, 68.1, 53.7, 51.9, 35.2 ppm; MS (ESI): m/z
(%): 903.6 (100%) [M+Na]+, 881.6 (34%) [M+H]+; HRMS (ESI): m/z:
calcd for C44H65O18: 881.4171 [M+H]+; found: 881.4150 (error 2.4 ppm).
Bis[5-(2’-aminoethylene)-m-phenylene]-[32]crown-10 (4b): A solution of
6 (85.0 mg, 0.138 mmol) in THF (20.00 mL) was cooled to 08C and
borane methylsulfide (0.400 mL, 3.92 mmol) was added by syringe. After
addition, the reaction mixture was heated at reflux for 5 h and then al-
lowed to cool to room temperature. Methanol (2.00 mL) was added, the
mixture was stirred for an hour, and concentrated HCl (5.00 mL) was
then added. The resulting mixture was heated at reflux for two hours and
then neutralized to pH >12. The solvent was evaporated under reduced
pressure and the residue was partitioned between CH2Cl2 (50.0 mL) and
water (20.0 mL). The organic layer was dried over Na2SO4 and concen-
trated to afford a light yellow oil. Yield: 75.0 mg (84%); 1H NMR
(400 MHz, CDCl3, RT): d=6.35 (s, 6H), 4.06 (m, 8H), 3.83 (m, 8H), 3.69
(m, 16H), 3.63 (t, J=6.8 Hz, 4H), 2.91 (t, J=6.0 Hz, 4H), 2.64 ppm (t,
J=6.4 Hz, 4H); 13C NMR (125 MHz, CDCl3, 228C): d=160.2, 108.1,
107.8, 99.4, 77.1, 70.0, 69.1, 45.2, 29.6 ppm. MS (ESI): m/z (%): 623.5
(100) [M+H]+; HRMS (ESI): m/z: calcd for C32H51N2O10: 623.3538
[M+H]+; found: 623.3543 (error 0.9 ppm).
Bis[5-(2’,2’-dicarboxyethyl)-m-phenylene]-[32]crown-10
(8):
NaOH
(2.0m, 3.0 mL) was added to a solution of 7 (360 mg, 0.409 mmol) in
EtOH (5.0 mL). The mixture was heated at reflux for 10 h. The starting
material disappeared as monitored by TLC. The ethanol was removed by
evaporation, and the remaining aqueous portion was washed with chloro-
form. The washed aqueous portion was acidified to pH 2 with cold HCl.
The precipitated olivine solid was washed twice with water and dried at
608C for 10 h (310 mg, 99%). M.p. 240–2438C; 1H NMR (400 MHz,
[D6]DMSO, RT): d=6.35 (s, 6H), 4.00 (t, J=4.4 Hz, 8H), 3.69 (t, J=
4.4 Hz, 8H), 3.53–3.57 (m, 16H), 3.33 (br, 2H,), 2.92 ppm (d, J=7.6 Hz,
4H); 13C NMR (100 MHz, CDCl3, 228C): d=170.8, 160.0, 141.2, 107.9,
99.3, 70.6, 69.4, 67.6, 53.7, 34.9 ppm; MS (ESI): m/z (%): 767.5 (100)
[MÀH]À; elemental analysis (%) calcd for C36H48O18: C 56.24, H 6.29;
found: C 55.92, H 6.30.
Bis[5-(3’-aminopropyl)-m-phenylene]-[32]crown-10 (4c): A solution of
13 (91.1 mg, 0.100 mmol), hydrazine monohydrate (2.00 mL, 34.0 mmol)
and methanol (15.0 mL) was heated at reflux for 17 h. The mixture was
allowed to cool to room temperature and concentrated by rotary evapo-
ration. Concentrated HCl (5.00 mL) was added. The resulting mixture
was heated at reflux for 2 h. After it had cooled to room temperature, a
solid precipitated and was filtered off. The filtrate was neutralized to
pH >12 with NaOH (2n) and extracted with CHCl3 (50.0 mL). The or-
ganic layer was dried over anhydrous Na2SO4 and concentrated to afford
a light yellow oil. Yield: 58.8 mg (90%); 1H NMR (400 MHz, CDCl3,
RT): d=6.32–6.34 (m, 6H), 4.05 (t, J=4.8 Hz, 8H), 3.83 (t, J=4.8 Hz,
8H), 3.70 (m, 16H), 2.69 (t, J=7.2 Hz, 4H), 2.55 (t, J=8.0 Hz, 4H),
1.72 ppm (m, 4H); 13C NMR (100 MHz, CDCl3, 228C): d=159.8, 144.3,
107.3, 99.7, 70.8, 69.6, 67.3, 41.7, 35.0, 33.4 ppm; MS (ESI): m/z (%):
651.6 (100%) [M+H]+; HRMS (ESI): m/z: calcd for C34H55O10N2:
651.3857 [M+H]+; found: 651.3873 (error 2.5 ppm).
Bis[5-(3’-carboxyethyl)-m-phenylene]-[32]crown-10 (9): Compound
8
(110 mg, 0.143 mmol) was heated at 1408C under N2 for 2 h and the re-
sulting oil was dissolved with CHCl3 (10.0 mL) and isolated by flash
column chromatography with CHCl3/CH3COOH (100:1) as the eluent to
afford the pure product as a white solid (73.0 mg, 75%). M.p. 190–
6096
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ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 6088 – 6098

Anion-Assisted Complexation of Paraquat
FULL PAPER
1918C; 13C NMR (100 MHz, CDCl3, 228C): d=148.7, 147.6, 121.3, 119.8,
113.9, 113.1, 71.0, 69.8, 69.3, 69.1 ppm. MS (ESI): m/z (%): 679.4 (100%)
[MÀH]À; HRMS (ESI): m/z: calcd for C34H48O14Na: 703.2942 [M+Na]+;
found: 703.2904 (error 5.4 ppm).
(2.00 mL) was heated at 808C for 12 h. The product had the same Rf
value as the starting material 12 when monitored by TLC (SiO2, ethyl
acetate). After the reaction mixture had cooled to room temperature,
CH2Cl2 (30.0 mL) and water (100 mL) were added. The organic phase
was washed with water (50.0 mL ꢂ 2), dried over anhydrous Na2SO4 and
concentrated. The residue was isolated by flash column chromatography
(SiO2, petroleum ether/ethyl acetate 1:2, v/v) as a white solid (86.0 mg,
92%). M.p. 150–1528C; 1H NMR (500 MHz, CDCl3, RT): d=6.34 (m,
6H), 6.32 (t, J=2.0 Hz, 2H), 4.06 (t, J=4.5 Hz, 8H), 3.84 (t, J=4.5 Hz,
8H), 3.68–3.72 (m, 16H), 2.67 (t, J=7.0 Hz, 4H), 2.29 (t, J=7.0 Hz, 4H),
1.93 ppm (m, 4H); 13C NMR (125 MHz, CDCl3, 228C): d=160.3, 142.1,
119.8, 107.7, 99.6, 71.1, 69.9, 67.7, 34.7, 26.8, 16.5 ppm; MS (ESI): m/z
(%): 693.4 (100) [M+Na]+, 671.5 (21) [M+H]+; HRMS (ESI): m/z: calcd
for C36H50N2O10Na: 693.3363 [M+Na]+; found: 693.3359 (error 0.6 ppm).
Bis[5-(3’-carbomethoxyethyl)-m-phenylene]-[32]crown-10 (10):
A mix-
ture of 9 (100 mg, 0.147 mmol), sulfuric acid (1.00 mL) and methanol
(20.0 mL) was heated at reflux for 12 h. The solution was cooled and di-
luted with water (20.0 mL). The methanol in the solution was removed
with
a rotary evaporator. The residue was extracted with CHCl3
(20.0 mL ꢂ 2). The combined organic phase was dried over anhydrous
Na2SO4, filtered and concentrated. The residue was separated by flash
column chromatography with ethyl acetate as the eluent to afford 10 as a
1
white solid (92.0 mg, 89%). M.p. 145–1468C; H NMR (400 MHz, CDCl3,
RT): d=6.28–6.37 (m 6H), 4.04 (t, J=4.4 Hz, 8H), 3.82 (t, J=4.4 Hz,
8H), 3.66–3.70 (m, 22H), 2.84 (t, J=6.8 Hz, 4H), 2.58 ppm (t, J=6.8 Hz,
4H); 13C NMR (100 MHz, CDCl3, 228C): d=173.3, 160.0, 142.7, 107.3,
99.3, 70.9, 69.7, 67.5, 51.7 35.5, 31.1 ppm; MS (ESI): m/z (%): 731.6
(100%) [M+Na]+; elemental analysis (%) calcd for C36H52O14: C 61.00,
H 7.39; found: C 61.20, H 7.43.
Acknowledgements
This work was supported by the National Natural Science Foundation of
China (20774086 and 20834004), the National Basic Research Program
Bis[5-(3’-hydroxypropyl)-m-phenylene]-[32]crown-10 (11): A mixture of
10 (92.0 mg, 0.131 mmol), LiAlH4 (100 mg, 2.63 mmol) and THF
(20.0 mL) was stirred at room temperature for 4 h. The reaction was
quenched with water and the reaction mixture was filtered. The solvent
in the solution was removed with a rotary evaporator. The residue was
extracted with CHCl3 (20.0 mL ꢂ 2). The combined organic phase was
dried over anhydrous Na2SO4, filtered and concentrated. The residue was
separated by flash column chromatography with CHCl3/CH3OH (10:1) as
the eluent to afford 11 as a white solid (79.0 mg, 92%). M.p. 122–1248C;
1H NMR (400 MHz, CDCl3, RT): d=6.32–6.36 (m, 6H), 4.06 (t, J=
4.8 Hz, 8H), 3.84 (t, J=4.8 Hz, 8H), 3.69–3.73 (m, 16H), 3.64 (t, J=
6.4 Hz, 4H), 2.61 (t, J=7.4 Hz, 4H), 1.85 (t, J=7.0 Hz, 4H), 1.68 ppm
(br, 2H); 13C NMR (100 MHz, CDCl3, 228C): d=160.1, 144.3, 107.7, 99.1,
71.0, 69.9, 67.7, 62.3, 34.1, 32.5 ppm; MS (ESI): m/z (%): 653.5 (25)
[M+H]+, 675.5 (100) [M+Na]+; HRMS (ESI): m/z: calcd for
C34H52O12Na: 675.3351 [M+Na]+; found: 675.3327 (error 3.6 ppm).
(2009CB930104),
the
Chinese
Universities
Scientific
Fund
(2009QNA3008), and the Project-sponsored by SRF for ROCS, SEM
(J20080410). We thank Prof. Wanzhi Chen, Dr. Jie Han, and Mr. Jiyong
Liu for their kind assistance with X-ray crystallography.
[1] a) J. C. Chambron, A. Harriman, V. Heitz, J.-P. Sauvage, J. Am.
Chem. Soc. 1993, 115, 6109–6114; b) F. M. Raymo, J. F. Stoddart,
Chem. Rev. 1999, 99, 1643–1663; c) M. V. Martꢃnez-Dꢃaz, M. S. Ro-
drꢃguez-Morgade, M. C. Feiters, P. J. M. van Kan, R. J. M. Nolte, J. F.
Stoddart, T. Torres, Org. Lett. 2000, 2, 1057–1060; d) L. Wang,
M. O. Vysotsky, A. Bogdan, M. Bolte, V. Boehmer, Science 2004,
304, 1312–1314; e) D.-H. Qu, Q.-C. Wang, H. Tian, Angew. Chem.
2005, 117, 5430–5433; Angew. Chem. Int. Ed. 2005, 44, 5296–5299;
f) F. Huang, H. W. Gibson, Prog. Polym. Sci. 2005, 30, 982–1018;
g) V. Sindelar, S. Silvi, A. E. Kaifer, Chem. Commun. 2006, 2185–
2187; h) S. J. Loeb, Chem. Soc. Rev. 2007, 36, 226–235; i) V. Serreli,
C. F. Lee, E. R. Kay, D. A. Leigh, Nature 2007, 445, 523–527; j) T.
Han, Q.-S. Zong, C.-F. Chen, J. Org. Chem. 2007, 72, 3108–3111;
k) P. Hidalgo Ramos, R. G. E. Coumans, A. B. C. Deutman, J. M. M.
Smits, R. de Gelder, J. A. A. W. Elemans, R. J. M. Nolte, A. E.
Rowan, J. Am. Chem. Soc. 2007, 129, 5699–5702; l) S. Nygaard,
S. W. Hansen, J. C. Huffman, F. Jensen, A. H. Flood, J. O. Jeppesen,
J. Am. Chem. Soc. 2007, 129, 7354–7363; m) C. Ke, C. Yang, T.
Mori, T. Wada, Y. Liu, Y. Inoue, Angew. Chem. 2009, 121, 6803–
6805; Angew. Chem. Int. Ed. 2009, 48, 6675–6677; n) W. Jiang, M.
Han, H.-Y. Zhang, Z.-J. Zhang, Y. Liu, Chem. Eur. J. 2009, 15,
9938–9945; o) A. I. Prikhod’ko, J. P. Sauvage, J. Am. Chem. Soc.
2009, 131, 6794–6807.
[2] a) J. E. Green, J. W. Choi, A. Boukai, Y. Bunimovich, E. Johnston-
Halperin, E. Delonno, Y. Luo, B. A. Sheriff, K. Xu, Y. S. Shin, H.
Tseng, J. F. Stoddart, J. R. Heath, Nature 2007, 445, 414–417;
b) T. A. Knappe, U. Linne, S. Zirah, S. Rebuffat, X. Xie, M. A. Mar-
ahiel, J. Am. Chem. Soc. 2008, 130, 11446–11454.
[3] a) W. S. Bryant, J. W. Jones, P. E. Mason, I. Guzei, A. L. Rheingold,
D. S. Nagvekar, H. W. Gibson, Org. Lett. 1999, 1, 1001–1004;
b) J. M. Mahoney, A. M. Beatty, B. D. Smith, J. Am. Chem. Soc.
2001, 123, 5847–5848; c) P. A. Rupar, V. N. Staroverov, K. M.
Baines, Science 2008, 322, 1360–1363.
Bis[5-ACHTUNGTRENNUNG(3’-(tosyloxyl)propyl)-m-phenylene]-[32]crown-10 (12): A mixture
of 11 (65.2 mg, 0.100 mmol), TsCl (100 mg, 0.530 mmol) and Et3N
(0.100 mL) in THF (10.0 mL) was stirred at room temperature for 12 h.
The solvent was evaporated and the residue was washed first with HCl
(0.100m, 50.0 mL) and then with brine (50.0 mL). The organic layer was
dried over Na2SO4 and concentrated to afford a yellow oil. The crude
product was passed through a short pad of SiO2 eluted with CH2Cl2/
MeOH (60:1) to give the title compound as a colourless oil (70.0 mg,
73.0%). 1H NMR (400 MHz, CDCl3, RT): d=7.78 (d, J=8.0 Hz, 4H),
7.35 (d, J=8.0 Hz, 4H), 6.32 (s, 2H), 6.27 (m, 4H), 4.00–4.05 (H, 12 m),
3.82–3.84 (m, 8H), 3.70–3.84 (m, 16H), 2.56 (t, J=7.2 Hz, 4H), 2.46 (s,
6H), 1.88–1.95 ppm (m, 4H); 13C NMR (100 MHz, CDCl3, 228C): d=
160.2, 145.0, 142.9, 133.2, 130.1, 128.1, 107.6, 99.4, 71.1, 69.9, 67.6, 31.9,
30.5, 21.9 ppm; MS (ESIÀ): m/z (%): 995.4 (100) [M+Cl]À; HRMS
(ESI): m/z: calcd for C48H65O16S2: 961.3709 [M+H]+; found: 961.3692
(error 1.8 ppm).
Bis[5-(3’-phthalimidopropyl)-m-phenylene]-[32]crown-10 (13): A solution
of 12 (0.960 g, 1.00 mmol), potassium phthalimide (1.00 g, 5.40 mmol)
and DMF (25.0 mL) was heated at 908C for 16 h. After the mixture had
cooled to room temperature, water (100 mL) was added and the mixture
was then extracted with CHCl3. The extract was washed with NaOH
(0.100m) and concentrated to give a crude oil. Recrystallization from
CH3CN/iPr2O afforded pure 13 as a white solid (847 mg, 93.0%). M.p.
203–2058C; 1H NMR (400 MHz, CDCl3, RT): d=7.82–7.79 (m, 4H),
7.68–7.71 (m, 4H), 6.31 (s, 4H), 6.15 (s, 2H), 4.02 (t, J=4.4 Hz, 8H), 3.82
(t, J=4.4 Hz, 8H), 3.70–3.74 (m, 20H), 2.59 (t, J=7.6 Hz, 4H), 2.00 ppm
(m, 4H); 13C NMR (100 MHz, CDCl3, 228C): d=168.6, 167.1, 160.0,
143.3, 134.6, 134.0, 132.2, 131.9, 124.0, 123.4, 107.3, 99.2, 71.1, 69.9, 67.6,
40.6, 38.0, 33.7, 29.4 ppm; MS (ESI): m/z (%): 933.6 (100) [M+Na]+; ele-
mental analysis (%) calcd for C50H58N2O14: C 65.92, H 6.42, N 3.08;
found: C 65.78, H 6.40, N 3.08.
[4] a) S. Li, M. Liu, J. Zhang, B. Zheng, C. Zhang, X. Wen, N. Li, F.
Huang, Org. Biomol. Chem. 2008, 6, 2103–2107; b) S. Li, M. Liu, J.
Zhang, B. Zheng, X. Wen, N. Li, F. Huang, Eur. J. Org. Chem. 2008,
6128–6133; c) M. Liu, S. Li, M. Zhang, Q. Zhou, F. Wang, M. Hu,
F. R. Fronczek, N. Li, F. Huang, Org. Biomol. Chem. 2009, 7, 1288–
1291; d) F. Wang, Q. Zhou, K. Zhu, S. Li, C. Wang, M. Liu, N. Li,
F. R. Fronczek, F. Huang, Tetrahedron 2009, 65, 1488–1494; e) S. Li,
M. Liu, B. Zheng, K. Zhu, F. Wang, N. Li, X. Zhao, F. Huang, Org.
Lett. 2009, 11, 3350–3353.
Bis[5-(3’-cyanopropyl)-m-phenylene]-[32]crown-10 (14): A mixture of 12
(135 mg, 0.140 mmol) and NaCN (30.0 mg, 0.610 mmol) in DMF
Chem. Eur. J. 2010, 16, 6088 – 6098
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6097

F. Huang et al.
[5] a) J. A. Wisner, P. D. Beer, N. G. Berry, B. Tomapatanaget, Proc.
Natl. Acad. Sci. USA 2002, 99, 4983–4986; b) C.-F. Lin, C.-C. Lai,
Y.-H. Liu, S.-M. Peng, S.-H. Chiu, Chem. Eur. J. 2007, 13, 4350–
4355; c) H. Fang, L. Li, Y. Yang, G. Yan, G. Li, Chem. Commun.
2008, 9, 1118–1120.
F. Huang, N. Li, H. Wang, H. W. Gibson, P. Gantzel, A. L. Rhein-
gold, J. Org. Chem. 2007, 72, 8935–8938; e) E. R. Kay, D. A. Leigh,
F. Zerbetto, Angew. Chem. 2007, 119, 72–196; Angew. Chem. Int.
ˇ
´
Ed. 2007, 46, 72–191; f) W. R. Dichtel, O. S. Miljanic, W. Zhang,
J. M. Spruell, K. Patel, I. Aprahamian, J. R. Heath, J. F. Stoddart,
Acc. Chem. Res. 2008, 41, 1750–1761; g) Y.-L. Zhao, I. Aprahamian,
A. Trabolsi, N. Erina, J. F. Stoddart, J. Am. Chem. Soc. 2008, 130,
6348–6350; h) T. B. Gasa, J. M. Spruell, W. R. Dichtel, T. J. Søren-
[6] Reviews on ion-pair recognition: a) P. D. Beer, P. A. Gale, Angew.
Chem. 2001, 113, 502–532; Angew. Chem. Int. Ed. 2001, 40, 486–
516; b) P. A. Gale, Coord. Chem. Rev. 2003, 240, 191–221. Selected
publications on ion-pair recognition: c) M. T. Reetz, C. M. Niemey-
er, K. Harms, Angew. Chem. 1991, 103, 1517–1519; Angew. Chem.
Int. Ed. Engl. 1991, 30, 1474–1476; d) P. D. Beer, P. K. Hopkins,
J. D. McKinney, Chem. Commun. 1999, 1253–1254; e) D. J. White,
N. Laing, H. Miller, S. Parsons, S. Coles, P. A. Tasker, Chem.
Commun. 1999, 2077–2078; f) R. Shukla, T. Kida, B. D. Smith, Org.
Lett. 2000, 2, 3099–3102; g) X. Shi, J. C. Fettinger, J. T. Davis,
Angew. Chem. 2001, 113, 2909–2913; Angew. Chem. Int. Ed. 2001,
40, 2827–2831; h) K. Niikura, E. V. Anslyn, J. Org. Chem. 2003, 68,
10156–10157; i) S. L. Tobey, E. V. Anslyn, J. Am. Chem. Soc. 2003,
125, 10963–10970; j) S. L. Tobey, E. V. Anslyn, J. Am. Chem. Soc.
2003, 125, 14807–14815; k) A. T. Wright, E. V. Anslyn, Org. Lett.
2004, 6, 1341–1344; l) D. R. Turner, E. C. Spencer, J. A. K. Howard,
D. A. Tocherb, J. W. Steed, Chem. Commun. 2004, 1352–1353;
m) D. Garozzo, G. Gattuso, A. Notti, A. Pappalardo, S. Pappalardo,
M. F. Parisi, M. Perez, I. Pisagatti, Angew. Chem. 2005, 117, 4970–
4974; Angew. Chem. Int. Ed. 2005, 44, 4892–4896; n) M. D. Lank-
shear, I. M. Dudley, K-M. Chan, P. D. Beer, New J. Chem. 2007, 31,
684–690; o) M. Cametti, M. Nissinen, A. Dalla Cort, L. Mandolini,
K. Rissanen, J. Am. Chem. Soc. 2007, 129, 3641–3648; p) M. P. Win-
tergerst, T. G. Levitskaia, B. A. Moyer, J. L. Sessler, L. H. Delmau,
J. Am. Chem. Soc. 2008, 130, 4129–4139.
ˇ
sen, D. Philp, J. F. Stoddart, P. Kuzmic, Chem. Eur. J. 2008, 14, 106–
116; i) Y. Liu, A. Bruneau, J. He, Z. Abliz, Org. Lett. 2008, 10, 765–
ˇ
´
768; j) I. Yoon, D. Benꢃtez, Y.-L. Zhao, O. S. Miljanic, S.-Y. Kim, E.
Tkatchouk, K. C.-F. Leung, S. I. Khan, W. A. Goddard III, J. F. Stod-
dart, Chem. Eur. J. 2009, 15, 1115–1122; k) K. Zhu, S. Li, F. Wang,
F. Huang, J. Org. Chem. 2009, 74, 1322–1328; l) L. M. Klivansky, G.
Koshkakaryan, D. Cao, Y. Liu, Angew. Chem. 2009, 121, 4249–4253;
Angew. Chem. Int. Ed. 2009, 48, 4185–4189.
[11] a) F. Huang, F. R. Fronczek, H. W. Gibson, J. Am. Chem. Soc. 2003,
125, 9272–9273; b) F. Huang, H. W. Gibson, W. S. Bryant, D. S. Nag-
vekar, F. R. Fronczek, J. Am. Chem. Soc. 2003, 125, 9367–9371; c) F.
Huang, K. A. Switek, L. N. Zakharov, F. R. Fronczek, C. Slebodnick,
M. Lam, J. A. Golen, W. S. Bryant, P. E. Mason, A. L. Rheingold,
M. Ashraf-Khorassani, H. W. Gibson, J. Org. Chem. 2005, 70, 3231–
3241; d) H. W. Gibson, H. Wang, C. Slebodnick, J. Merola, W. S.
Kassel, A. L. Rheingold, J. Org. Chem. 2007, 72, 3381–3393; e) F.
Wang, B. Zheng, K. Zhu, Q. Zhou, C. Zhai, S. Li, N. Li, F. Huang,
Chem. Commun. 2009, 4375–4377.
[12] A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
[13] P. Job, Ann. Chim. 1928, 9, 113–203.
[14] a) S.-K. Chang, D. Van Engen, E. Fan, A. D. Hamilton, J. Am.
Chem. Soc. 1991, 113, 7640–7645; b) K. Kavallieratos, C. M. Bertao,
R. H. Crabtree, J. Org. Chem. 1999, 64, 1675–1683; c) M. J. Chmie-
lewski, J. Jurczak, Chem. Eur. J. 2005, 11, 6080–6094; d) V. S.
Bryantsev, B. P. Hay, J. Am. Chem. Soc. 2005, 127, 8282–8283;
e) M. J. Chmielewski, J. Jurczak, Chem. Eur. J. 2006, 12, 7652–7667;
[7] M. J. Deetz, M. Shang, B. D. Smith, J. Am. Chem. Soc. 2000, 122,
6201–6207; M. D. Lankshear, I. M. Dudley, K. Chan, A. R. Cowley,
S. M. Santos, V. Felix, P. D. Beer, Chem. Eur. J. 2008, 14, 2248–
2263; J. L. Sessler, S. K. Kim, D. E. Gross, C. Lee, J. S. Kim, V. M.
Lynch, J. Am. Chem. Soc. 2008, 130, 13162–13166.
´
f) T. Zielinski, M. Ke˛dziorek, J. Jurczak, Chem. Eur. J. 2008, 14,
[8] M. R. Sambrook, P. D. Beer, J. A. Wisner, R. L. Paul, A. R. Cowley,
F. Szemes, M. G. B. Drew, J. Am. Chem. Soc. 2005, 127, 2292–2302;
S. Le Gac, I. Jabin, Chem. Eur. J. 2008, 14, 548–557.
838–846.
[15] Here a hydrogen bond is believed to exist when the H···O (F, Cl)
distance is less than the sum—2.72 (2.67, 2.95) ꢁ—of the van der
Waals radii (see Ref. [12]) of the hydrogen atom and the acceptor O
[9] a) R. K. Russell, J. Agric. Food Chem. 1978, 26, 1460–1463; b) C.
Mastichiadis, S. E. Kakabakos, I. Christofidis, M. A. Koupparis, C.
Willetts, K. Misiakos, Anal. Chem. 2002, 74, 6064–6072; c) F.
Merino, S. Rubio, D. Perez-Bendito, Anal. Chem. 2004, 76, 3878–
3886; d) M. A. Bacigalupo, G. Meroni, M. Mirasoli, D. Parisi, R.
Longhi, J. Agric. Food Chem. 2005, 53, 216–219; e) M. A. Bacigalu-
po, G. Meroni, J. Agric. Food Chem. 2007, 55, 3823–3828; f) J.
Zhang, C. Zhai, F. Wang, C. Zhang, S. Li, M. Zhang, N. Li, F.
Huang, Tetrahedron Lett. 2008, 49, 5009–5012.
À
(F, Cl) atom and the C H···O (F, Cl) angle is greater than 908 (see
ref. [10d]).
[16] F. Huang, F. R. Fronczek, H. W. Gibson, Chem. Commun. 2003,
1480–1481; F. Huang, C. Slebodnick, K. A. Switek, H. W. Gibson,
Chem. Commun. 2006, 1929–1931.
[17] M. Kamieth, F. Klꢄrner, J. Prakt. Chem. 1999, 341, 245–251.
[18] P. Brochette, T. Zemb, P. Mathis, M.-P. Pileni, J. Phys. Chem. 1987,
91, 1444–1450.
[10] a) D. B. Amabilino, J. F. Stoddart, Chem. Rev. 1995, 95, 2725–2828;
b) F. Huang, P. Gantzel, D. S. Nagvekar, A. L. Rheingold, H. W.
Gibson, Tetrahedron Lett. 2006, 47, 7841–7844; c) Y. Yang, H.-Y.
Hu, C.-F. Chen, Tetrahedron Lett. 2007, 48, 3505–3509; d) J. Zhang,
Received: December 27, 2009
Revised: February 12, 2010
Published online: April 13, 2010
6098
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 6088 – 6098