A molecular l°Ck and key: Unl°Cked-l°cked conformational switching of a receptor by anions

Article abstract of DOI:10.1002/cplu.201100036

A solution of 4^[16] (1.00 g, 6.8 mmol) in MeOH (10 mL) was added dropwise to a solution of 3 (1.05 g, 6.8 mmol) in MeOH (10 mL). The reaction mixture was heated at reflux for 6 h and then cooled to RT. A yellow residue precipitated from the reaction mixture and was collected by filtration, washed with cold MeOH, and then dried under vacuum. The yellow solid 2 was obtained in 61% yield (1.20 g, 4.2 mmol). Compound 2 was directly used for the next synthetic step. Solid NaBH₄ (0.20 g, 0.005 mmol) was added portionwise to a suspension of 2 (1.00 g, 3.5 mmol) in MeOH (15 mL) at 0 8°C with constant stirring for 1 h. The solvent was evaporated under reduce pressure and the resulting solid was dissolved in cold distilled water. A clear red color solution was obtained and then neutralized (pH=7) with dilute HCl. Compound 1 was precipitated as a light red solid, which was filtered and washed with distilled water. The solid was dried in air and obtained in 85% yield (0.84 g, 3.0 mmol). 1H NMR (300 MHz, CD₃CN): d=4.53 (s, CH₂), 4.85 (s, NH₂), 6.68 (d, J=9 Hz, 1H, H6), 6.84 (t, J=9 Hz, 1H, H3), 7.28 (t, J=9 Hz, 1H, H4), 7.5 (m, 2H, H1, H5), 7.57 (d, J=9 Hz, 1H, H7), 7.7 (s, 1H, H8), 8.28 ppm (d, J=9 Hz, 1H, H2); 13C NMR (75.5 MHz, [D₆]DMSO, 208°C): d=41.89, 104.21, 110.40, 111.14, 111.93, 116.45, 117.79, 124.60, 126.92, 134.09, 137.11, 144.37, 144.44 ppm; IR (KBr): n =3388, 3331, 3131, 1608, 1579, 1524, 1493, 1331, 1317, 1297, 1245, 1142, 1112, 857, 746, 669 cm ^-1; ESI-MS: m/z calcd for C₁₄H₁₃N ₅O₂ ^[M+]: 283.11; found for [M+H⁺]: 283.94.

Full text of DOI:10.1002/cplu.201100036

DOI: 10.1002/cplu.201100036
A Molecular Lock and Key: “Unlocked–Locked” Conformational Switching
of a Receptor by Anions
Sasanka Dalapati,[a] Md. Akhtarul Alam,*[b] Sankar Jana,[a] Rajat Saha,[c] Saptarshi Biswas,[a] and Nikhil Guchhait*[a]
The design of molecular devices with molecular recognition
functionality and signal transduction ability has gained consid-
erable attention in the fields of chemistry,[1] biology,[2] and sen-
sors.[3] The importance and significance in this regard are the
receptors that detect anions,[4] in particular, phosphate ions
that play a crucial role in many physiological processes. In
recent years, several synthetic receptors containing amine,
amide,[5] urea,[6] thiourea,[7] pyrrole,[8] and pyridine moieties as
well as metal-assisted organic frameworks[9] bearing multiple
binding sites have been reported for sensing of phosphate
ions in solution. In such cases, detection was observed through
changes in UV/Vis spectra, 1H NMR chemical shifts, lumines-
cence spectroscopy patterns, and the binding modes which
were determined through experimental result supported by
optimization calculations at different levels of theory.[10] How-
ever, single-crystal X-ray analysis of phosphate-ion-bound re-
ceptors are very rare owing to the tetrahedral structure of the
dihydrogenphosphate ion which creates problems for effective
binding with tailored hydrogen-bonded, donor–acceptor re-
ceptors.[11]
Herein, we demonstrate a conceptually new molecular
À
device (“molecular lock”) that acts as a selective H2PO4 recep-
tor. The dihydrogenphosphate ion (“key”) can lock the molecu-
lar free rotation of the fluorophoric unit of receptor 1 (“molec-
ular lock”), as evidenced by single-crystal X-ray analysis. The re-
striction of free rotation results in the enhancement of fluores-
cent intensity of 1 in CH3CN solution. On the other hand,
À
Scheme 1. Top: “Unlocked–locked” conformational switching; bottom: syn-
thetic approach to give receptor 1.
HSO4 (“key”) forms a hydrogen-bonded complex (“unlocked”
conformation of the “molecular lock”) as evidenced by single-
crystal X-ray analysis and the fluorescent intensity of 1 which
did not change remarkably.
Receptor 1 was synthesized by reduction of the Schiff base
2, which was prepared from imidazo[1,2-a]pyridine-2-carboxal-
dehyde 4 and 1,2-diamino-4-nitrobenzene 3 (Scheme 1). Com-
pound 1 was characterized by H NMR spectroscopy, IR analy-
sis, and mass spectrometry (see Figure S1–S4 in the Supporting
Information). The structure of receptor 1 and its complex with
H2PO4 and HSO4 were determined by X-ray crystal structure
analysis. The anion recognition capability and binding affinity
À
À
1
of 1 were studied by absorption and emission spectroscopic
À
changes in the presence of various anions such as FÀ, H2PO4
,
AcOÀ, NO3À, ClO4À, ClÀ, BrÀ, IÀ, and HSO4 in CH3CN medium.
À
¯
Receptor 1 crystallized in the P1 space group and comprised
[a] S. Dalapati, S. Jana, S. Biswas, Dr. N. Guchhait
Department of Chemistry, University of Calcutta
92 A. P. C. Road, Kolkata-700 009 (India)
Fax: (+91)33-23519755
two molecular units and one water molecule (see Figure 1, and
Figure S5 and Table S1 in the Supporting Information).[12] The
E-mail: nguchhait@yahoo.com
[b] Dr. M. A. Alam
Department of Chemistry, Aliah University
DN-41 and 47, Sector-V, Saltlake, Kolkata-700 009 (India)
Fax: (+91)33-27062124
E-mail: alam_iitg@yahoo.com
[c] R. Saha
Department of Physics, Jadavpur University
Jadavpur, Kolkata-700 032 (India)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cplu.201100036.
Figure 1. Crystal structure of 1 “molecular lock” with a water molecule.
Green C, white H, blue N, red O.
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93

À
structure of “molecular lock” 1 is really interesting because the
o-phenylenediamine and imidazo[1,2-a]pyridine moieties are
twisted by an angle of approximately 76.38 8 from one another
and it forms a stable conformer where, the nitrogen atom of
the amino group and nitrogen atom of the imidazo group are
orthogonal to each other and form intermolecular hydrogen
bonds. As shown in Figure 1, two different orientations of each
molecular unit are connected by two different types of inter-
molecular hydrogen bonds, namely; 1) through direct intermo-
lecular hydrogen bonding where N6 and N7 of one molecular
unit act as hydrogen donors and N1 of the other molecular
unit acts as a hydrogen acceptor (bond lengths are: N7···N1
3.043 ꢁ and N6···N1 3.202 ꢁ),[13] and 2) through water-assisted
intermolecular hydrogen bonding where the water molecule
(O1) is located in between N2 and N3 of the o-phenylenedia-
mine moiety and N5 of the imidazo[1,2-a]pyridine moiety and
thus forms strong hydrogen-bonding interactions (bond
lengths are: N3···O1 2.918 ꢁ, N2···O1 3.022 ꢁ, and N5···O1
2.738 ꢁ; Table S2). These intermolecular hydrogen bonds bring
two imidazo[1,2-a]pyridine moieties and two o-phenylenedia-
mine rings in close proximity and form a p–p stacking interac-
tion within distances of 3.69(2) ꢁ and 4.07(3) ꢁ, respectively.
The crystal packing diagram shows that the O1 atom of the
water molecule (Figure 1) is already involved in hydrogen-
bonding interactions with N2, N3, and N5 of dimeric 1 and has
formed a one-dimensional supramolecular polymer network
through hydrogen-bonding interactions with the O4 atom (be-
longing to NO2) of the next dimeric unit (2.971 ꢁ; Figure S6).
This suitable arrangement of “molecular lock” 1 has been ex-
neous hydrogen-bonding between H2PO4 and two amine ni-
trogen atoms (N1, N2) as well as one imidazo[1,2-a]pyridine ni-
trogen atom (N3).
The lattice diagram shows that receptor 1 undergoes dimer
formation with the help of a water molecule and H2PO4
À
(Figure 3). Interestingly, the O1 atom of the water molecule is
already involved in hydrogen-bonding interactions with
Figure 3. Dimeric crystal structure of 1·H2PO4À complex. Tetrabutylammoni-
um cations are omitted for clarity. Green C, white H, blue N, red O, orange P,
yellow S.
H2PO4À, which is also involved in dimer formation through a
hydrogen-bonding interaction with the O5 atom of the nearest
À
H2PO4 (bond length is: 2.873 ꢁ). Meanwhile, the O2 atom of
À
À
the H2PO4 ion interacts with the O4 atom of another H2PO4
ion through a hydrogen-bonding interaction (bond length is:
À
2.613 ꢁ) and forms the {(H2O)2·(H2PO4 )2} cluster. Furthermore,
À
ploited by H2PO4 (“key”) as a result it can easily lock the mo-
one dimeric unit containing a water molecule (O1) is hydro-
gen-bonded with the N1 atom of another dimeric unit contain-
ing o-phenylenediamine and vice versa to generate a one-di-
mensional hydrogen-bonded channel consisting of water–dihy-
drogenphosphate (see Figure S8 in the Supporting Informa-
tion). The one-dimensional supramolecular structure is further
stabilized through p–p interactions of the imidazo[1,2-a]pyri-
dine ring (distance is: 3.365 ꢁ; Figure S9) and hydrogen-bond-
ing interactions with another one-dimensional channel to
build up a two-dimensional supramolecular water–dihydrogen-
phosphate architecture (Figure S10).
lecular device through hydrogen-bonding interactions. The X-
À
ray crystal structure of the 1·H2PO4 complex (Figure 2 and Fig-
ure S7) shows that the dihydrogenphosphate ion reinforces
the N3 atom of the imidazo[1,2-a]pyridine moiety pointing uni-
directionally with respect to the N1 and N2 atoms of the
À
amine group. As a result, the O3 and O5 atoms of H2PO4 form
hydrogen-bonding interactions with the N3, N1, and N2 atoms
of 1 (bond lengths are: N3···O5 2.691 ꢁ, N1···O3 2.784 ꢁ, and
N2···O3 2.858 ꢁ; Table S3). Thus, hydrogen-bonding interactions
À
restrict the free rotation of receptor 1; namely, H2PO4 (“key”)
À
locks the bending conformation of receptor 1 due to simulta-
On the other hand, the crystal structure of 1·HSO4 shows
that the O1 atom of HSO4 is hydrogen bonded with only two
À
amine nitrogen atoms (N1, N2) of 1 (bond lengths are: N1···O1
2.945 ꢁ and N2···O1 2.954 ꢁ; Figure 4, Figure S11) and interest-
ingly, the N3 atom of the imidazo[1,2-a]pyridine moiety is hy-
drogen bonded with the O2 atom of the next hydrogensulfate
ion. This structure is completely different from the structure of
À
the 1·H2PO4 complex (bond length is: N3···O2 2.700 ꢁ;
Figure 5). Furthermore, the lattice diagram shows that the N1
atom of one molecular unit is hydrogen bonded with the O4
À
atom of another HSO4 and forms a one-dimensional, hydro-
gen-bonded bisulfate channel (Figure S12). Thus, hydrogen-
À
bonding interactions between HSO4 and receptor 1 lead an
“unlocked” conformation even though the geometries of the
À
À
H2PO4 and HSO4 ions are quite similar.
À
Figure 2. Crystal structure of 1·H2PO4 in a “locked” conformation. Tetrabuty-
The binding nature of 1 with anions was investigated with
the help of UV/Vis titrations in CH3CN solvent. Receptor 1 has
lammonium cations are omitted for clarity. Green C, white H, blue N, red O,
orange P.
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ChemPlusChem 2012, 77, 93 – 97

However, upon addition of the highly basic FÀ, a new ab-
sorption peak at 450 nm was observed (Figure S13), and this
peak might correspond to deprotonation of NH2 rather than
hydrogen-bonding interaction.[15] Deprotonation of the amino
group increases the electron density on the nitrogen atom
(donor), which undergoes an internal charge transfer (ICT) to
an electron-withdrawing nitro group (acceptor) and therefore
is the cause of the spectral bathochromic shift. Similar types of
spectral change were observed when [Bu4N]OH was added,
and this supports our assumption of deprotonation and ICT
phenomena in the case of FÀ.
À
Figure 4. Crystal structure of 1·HSO4 in an “unlocked” conformation. Tetra-
To investigate the selectivity and excited-state phenomena
of receptor 1 towards the anions, we performed steady-state
fluorescence experiments in CH3CN solvent. Upon excitation at
312 nm, receptor 1 exhibits an emission maximum at 375 nm.
A remarkable fluorescence enhancement of receptor 1 at
375 nm was observed with the addition of an increasing con-
butylammonium cations are omitted for clarity. Green C, white H, blue N,
red O, yellow S, orange P.
À
centration of H2PO4 (Figure 7). This enhancement of fluores-
cence intensity may be attributed to the conformational freez-
Figure 5. Dimeric crystal structure of 1·HSO4À hydrogen-bonded complex.
Tetrabutylammonium cations are omitted for clarity. Green C, white H,
blue N, red O, yellow S, orange P.
absorption bands at 312 nm and 405 nm (Figure 6). Upon addi-
tion of an increasing amount of H2PO4À, the band at 405 nm
was gradually red-shifted to 415 nm. The Benesi–Hildebrand
Figure 7. Emission spectroscopic changes of 1 (0.5 mm) upon addition of
H2PO4À ion (0–2 equiv) in CH3CN solution.
À
(BH) plot[14] of 1/[AÀA0] versus 1/[H2PO4 ] for the titration of 1
À
and H2PO4 exhibits a straight line (inset of Figure 6), thus indi-
ing (“locked”) and hindering of free rotation (“unlocked”) of
cating that a 1:1 complex was formed with an association con-
the fluorophoric unit (imidazo[1,2-a]pyridine moiety) upon
À
stant of K=2.8ꢂ102 mÀ1. A similar kind of spectral change for
complexation with H2PO4
.
The conformation restriction
À
1 was observed in the presence of HSO4 and AcOÀ. Further-
(“locked”) that occurs through hydrogen-bonding interactions
was confirmed by single-crystal X-ray analysis. The fluorescence
more, in the presence of other competitive anions (such as
NO3À, ClO4À, ClÀ, BrÀ, and IÀ) receptor 1 remains almost un-
changed, thus indicating an absence of interaction or complex-
ation between these anions with the receptor (see Figure S13).
À
titration of receptor 1 with H2PO4 also indicates a 1:1 com-
plexation (Figure S14) with an association constant K=0.7ꢂ
102 mÀ1.[14] The association constants determined from absorp-
tion and emission spectra are of similar order, and the small
difference in association constant may be attributed to the
weakening of hydrogen-bonding interactions upon excitation.
Under similar experimental conditions, the fluorescence in-
À
tensity of receptor 1 in the presence of HSO4 is considerably
lower than that of H2PO4À, but higher than that of the other
anions. This outcome might be due to the intermolecular hy-
drogen-bonding interaction between the fluorophoric unit (N3
atom) of 1 and the bisulfate ion (O2 atom; Figure 5) causing a
partial restriction in free rotation as evidenced by single-crystal
X-ray analysis. On the other hand, fluoride and acetate anions
exhibit only a tiny increase in fluorescence intensity—most
probably owing to an absence of such intermolecular hydro-
gen-bonding capability (compared to that of bisulfate and di-
Figure 6. UV/Vis spectroscopic changes of 1 (1 mm) upon addition of
H2PO4À ion (0–2 equiv) in CH3CN solution. Inset: the BH plot for the titration
À
of 1 with H2PO4 anion.
ChemPlusChem 2012, 77, 93 – 97
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www.chempluschem.org
95

08C with constant stirring for 1 h. The solvent was evaporated
under reduce pressure and the resulting solid was dissolved in
cold distilled water. A clear red color solution was obtained and
then neutralized (pHꢀ7) with dilute HCl. Compound 1 was precipi-
tated as a light red solid, which was filtered and washed with dis-
tilled water. The solid was dried in air and obtained in 85% yield
hydrogenphosphate ions)—and as a result the fluorophoric
unit of 1 remains completely “unlocked”. Other anions tested
did not show any significant change in fluorescence intensity
(see Figure 8 as well as Figure S15 in the Supporting Informa-
tion). This result indicates that the fluorophoric unit (imidazo-
[1,2-a]pyridine moiety) can rotate freely (“unlocked” conforma-
1
(0.84 g, 3.0 mmol). H NMR (300 MHz, CD3CN): d=4.53 (s, CH2), 4.85
(s, NH2), 6.68 (d, J=9 Hz, 1H, H6), 6.84 (t, J=9 Hz, 1H, H3), 7.28 (t,
J=9 Hz, 1H, H4), 7.5 (m, 2H, H1, H5), 7.57 (d, J=9 Hz, 1H, H7), 7.7 (s,
1H, H8), 8.28 ppm (d, J=9 Hz, 1H, H2); 13C NMR (75.5 MHz,
[D6]DMSO, 208C): d=41.89, 104.21, 110.40, 111.14, 111.93, 116.45,
117.79, 124.60, 126.92, 134.09, 137.11, 144.37, 144.44 ppm; IR (KBr):
n˜ =3388, 3331, 3131, 1608, 1579, 1524, 1493, 1331, 1317, 1297,
1245, 1142, 1112, 857, 746, 669 cmÀ1
; ESI-MS: m/z calcd for
C14H13N5O2 [M+]: 283.11; found for [M+H+]: 283.94.
Preparation of crystals suitable for X-ray diffraction
Single crystals of 1 were grown from a solution in water by slow
diffusion of methanol to give deep red crystals. Single crystals of
À
Figure 8. Relative change in fluorescence of 1 (0.5 mm) upon addition of dif-
ferent anions in CH3CN solution.
1·H2PO4 were grown from a solution of 1/tetrabutylammonium di-
hydrogenphosphate (1:1) in CH3CN by slow diffusion of diethyl
ether. Single crystals of 1·HSO4 were grown from a solution of 1/
À
tetrabutylammonium hydrogensulfate (1:1) in CH3CN by slow diffu-
sion of diethyl ether.
tion, as evidenced by the X-ray crystal structure) about the CÀ
C bond and that the energy in the excited state can be dissi-
pated by nonradiative decay channels. As shown in Figure 8,
Acknowledgements
À
receptor 1 can selectively detect H2PO4 over the other anions
tested (FÀ, AcOÀ, NO3À, ClO4À, ClÀ, BrÀ, IÀ, and HSO4À). It is ob-
vious that the hydrogen-bonding interaction of receptor 1
with the anion imparts rigidity (“locked”) to the entire molecu-
lar framework, thereby decreasing the rotation/vibrational de-
grees of freedom and hence contributing to fluorescence en-
hancement.
This work is supported by grants from DST, India (Project No. SR/
S1/PC/26/2008) to N.G. and S.D. S.J. acknowledges UGC for a fel-
lowship. M.A.A. thanks the VC of Aliah University for giving him
permission to work at the University of Calcutta.
Keywords: conformational switching · conformation analysis ·
dihydrogenphosphate ions · hydrogensulfate ions · molecular
locks · UV/Vis spectroscopy
In summary, we have designed a simple molecular device
(receptor 1) having complementary hydrogen-bonding, donor–
acceptor groups for efficient and selective binding of tetrahe-
dral H2PO4À. The dihydrogenphosphate anion (“key”) efficiently
freezes (“locked”) the conformational free rotation of receptor
1 (“molecular lock”) by hydrogen-bonding interactions as evi-
denced by single-crystal X-ray analysis. The structural changes
[1] A. P. Silver, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, C. P.
McCoy, J. T. Rademacher, T. E. Rice, Chem. Rev. 1997, 97, 1515–1566.
[2] M. S. T. GonÅalves, Chem. Rev. 2009, 109, 190–212.
[3] a) L. Fabbrizzi, M. Licchelli, L. Parodi, A. Poggi, A. Taglietti, J. Fluoresc.
1998, 8, 263–271; b) S. M. Borisov, O. S. Wolfbeis, Chem. Rev. 2008, 108,
423–461.
À
of 1 in the presence of H2PO4 effectively enhanced the fluo-
rescence intensity in acetonitrile; however, structurally similar
[4] a) P. D. Beer, P. A. Gale, Angew. Chem. 2001, 113, 502–532; Angew.
Chem. Int. Ed. 2001, 40, 486–516; b) T. Wang, X.-P. Yan, Chem. Eur. J.
2010, 16, 4639–4649.
[5] a) P. D. Beer, Acc. Chem. Res. 1998, 31, 71–80; b) M. A. Hossain, J. M. Lli-
nares, D. Powell, K. Bowman-James, Inorg. Chem. 2001, 40, 2936–2937;
c) J. B. Cooper, M. G. B. Drew, P. D. Beer, J. Chem. Soc. Dalton Trans.
2000, 2721–2728; d) P. D. Beer, V. Timoshenko, M. Maestri, P. Passaniti,
V. Balzani, Chem. Commun. 1999, 1755–1756.
[6] a) T. Gunnlaugsson, M. Glynn, G. M. Tocci, P. E. Kruger, F. M. Pfeffer,
Coord. Chem. Rev. 2006, 250, 3094–3117; b) B. H. M. Snellink-Ruꢃl,
M. M. G. Antonisse, J. F. J. Engbersen, P. Timmerman, D. N. Reinhoudt,
Eur. J. Org. Chem. 2000, 165–170; c) M. Li, B. Wu, C. Jia, X. Huang, Q.
Zhao, S. Shao, X.-J. Yang, Chem. Eur. J. 2011, 17, 2272–2280; d) H. Xie,
S. Yi, X. Yang, S. Wu, New J. Chem. 1999, 23, 1105–1110.
[7] a) S. Sasaki, M. Mizuno, K. Naemura, Y. Tobe, J. Org. Chem. 2000, 65,
275–283; b) P. Bꢄhlmann, S. Nishizawa, K. P. Xiao, Y. Umezawa, Tetrahe-
dron 1997, 53, 1647–1654.
À
HSO4 did not act in a similar way. In the presence of other
competitive anions (FÀ, AcOÀ, NO3À, ClO4À, ClÀ, BrÀ, and IÀ) re-
ceptor 1 remained unchanged.
Experimental Section
Synthesis of Receptor 1
A solution of 4[16] (1.00 g, 6.8 mmol) in MeOH (10 mL) was added
dropwise to a solution of 3 (1.05 g, 6.8 mmol) in MeOH (10 mL).
The reaction mixture was heated at reflux for 6 h and then cooled
to RT. A yellow residue precipitated from the reaction mixture and
was collected by filtration, washed with cold MeOH, and then
dried under vacuum. The yellow solid 2 was obtained in 61% yield
(1.20 g, 4.2 mmol). Compound 2 was directly used for the next syn-
thetic step. Solid NaBH4 (0.20 g, 0.005 mmol) was added portion-
wise to a suspension of 2 (1.00 g, 3.5 mmol) in MeOH (15 mL) at
[8] a) J. Yoo, M. S. Kim, S. J. Hong, J. L. Sessler, C. H. Lee, J. Org. Chem. 2009,
74, 1065–1069; b) P. Anzenbacher, K. Jursikova, J. L. Sessler, J. Am.
Chem. Soc. 2000, 122, 9350–9351; c) C. B. Black, B. Andrioletti, A. C. Try,
C. Ruiperez, J. L. Sessler, J. Am. Chem. Soc. 1999, 121, 10438–10439.
96
www.chempluschem.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2012, 77, 93 – 97

[9] a) H. Z. Lin, J. S. Ou, Y. C. Duan, G. B. Zhang, P. Z. Bai, Chem. Commun.
2006, 624–626; b) P. Plitt, D. E. Gross, V. M. Lynch, J. L. Sessler, Chem.
Eur. J. 2007, 13, 1374–1381; c) H. Z. Lin, G. Y. Zhao, Y. C. Duan, G. B.
Zhang, P. Z. Bai, Dalton Trans. 2006, 3678–3684; d) R. Custelcean, J.
Bosano, P. V. Bonnesen, V. Kertesz, B. P. Hay, Angew. Chem. 2009, 121,
4085–4089; Angew. Chem. Int. Ed. 2009, 48, 4025–4029; e) C. R. Bondy,
P. A. Gale, S. J. Loeb, J. Am. Chem. Soc. 2004, 126, 5030–5031.
[10] a) S. K. Kim, N. J. Singh, J. Kwon, I. C. Hwang, S. J. Park, K. S. Kim, J. Yoon,
Tetrahedron 2006, 62, 6065–6072; b) D. H. Lee, S. Y. Kim, J. I. Hong,
Angew. Chem. 2004, 116, 4881–4884; Angew. Chem. Int. Ed. 2004, 43,
4777–4780; c) L. Fabbrizzi, N. Marcotte, F. Stomeo, A. Taglietti, Angew.
Chem. 2002, 114, 3965–3968; Angew. Chem. Int. Ed. 2002, 41, 3811–
3814; d) P. Anzenbacher, Jr., K. Jursı- kova, J. L. Sessler, J. Am. Chem. Soc.
2000, 122, 9350–9351; e) H. Sun, A. M. S. Poulsen, H. Gu, I. Jakobsen,
J. M. Kossmann, W. B. Frommer, K. Almdal, ACS Nano 2008, 2, 19–24;
f) N. Marcotte, A. Taglietti, Supramol. Chem. 2003, 15, 617–625.
Fava, M. Lanfranchi, C. Pelizzi, P. Tarasconi, J. Chem. Soc. Dalton Trans.
1991, 1951–1957; d) R. Anulewicz, I. Wawer, T. M. Krygowski, F. Msnnle,
H. Limbach, J. Am. Chem. Soc. 1997, 119, 12223–12230.
[14] a) H. A. Benesi, J. H. Hildebrand, J. Am. Chem. Soc. 1949, 71, 2703–2707;
b) B. K. Indirapriyadharshini, P. Karunanithi, P. Ramamurthy, Langmuir
2001, 17, 4056–4060; c) R. A. Agbaria, M. T. Butterfield, I. M. Warner, J.
Phys. Chem. 1996, 100, 17133–17137; d) S. In, J. Kang, Bull. Korean
Chem. Soc. 2005, 26, 1121–1124; e) S. K. Lee, J. Kang, Bull. Korean Chem.
Soc. 2011, 32, 3215–3218; f) N. A. Bayri, O. Kocak, Tr. J. Chem. 1997, 21,
173–181; g) R. R. Avirah, K. Jyothish, D. Ramaiah, J. Org. Chem. 2008,
73, 274–279.
[15] a) M. V. Lꢆpez, M. R. Bermejo, M. E. Vꢇzquez, A. Taglietti, G. Zaragoza, R.
Pedrido, M. Martꢈnez-Calvo, Org. Biomol. Chem. 2010, 8, 357–362; b) J.
Kang, J. H. Lee, Y. H. Kim, S. K. Lee, E. Y. Kim, H. G. Lee, C. Kim, J. Inclusion
Phenom. Macrocyclic Chem. 2011, 70, 29–35.
[16] a) O. Chavignon, C. J. Teulade, M. Madesclaire, A. Gueiffier, Y. Blache, H.
Viols, J. P. Chapat, G. Dauphin, Heterocyclic Chem. 1992, 29, 691; b) S.
Dalapati, B. K. Paul, S. Jana, N. Guchhait, Sens. Actuators B 2011, 157,
615–620.
[11] C. Jia, B. Wu, S. Li, Z. Yang, Q. Zhao, J. Liang, S. Q. Li, X. J. Yang, Chem.
Commun. 2010, 46, 5376–5378.
[12] CCDC-815879 (1), CCDC-835846 (1·H2PO4À), and CCDC-835843 (1·HSO4
À
)
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Received: October 15, 2011
[13] a) A. Dorazco-Gonzꢅlez, H. Hopfl, F. Medrano, A. K. Yatsimirsky, J. Org.
Chem. 2010, 75, 2259–2273; b) Y. G. Zhao, B. G. Zhang, C. Y. Duan, Z. H.
Lin, Q. Meng, New J. Chem. 2006, 30, 1207–1213; c) M. B. Feerrari, G. G.
Revised: December 1, 2011
Published online on January 4, 2012
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