Selective recognition of acetate ion by perimidinium-based receptors

Article abstract of DOI:10.1016/j.tetlet.2012.09.037

The first perimidinium-based receptors 1 and 2 have been designed and synthesized. The anion binding properties of the receptors were evaluated in DMSO by UV-vis, fluorescence spectroscopy, and 1H NMR methods. The results demonstrate that both receptors 1 and 2 exhibit good selectivity to acetate. The (C- H)+· · ·X- type ionic hydrogen bonding between the perimidinium moieties and acetate is the key interaction for the recognition.

Full text of DOI:10.1016/j.tetlet.2012.09.037

Tetrahedron Letters 53 (2012) 6292–6296
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Selective recognition of acetate ion by perimidinium-based receptors
⇑
Meiyun Feng, Xiaozhi Jiang, Zhiyun Dong, Dawei Zhang, Binshen Wang, Guohua Gao
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, 3663 North Zhongshan Road,
Shanghai 200062, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 June 2012
Revised 1 September 2012
Accepted 11 September 2012
Available online 18 September 2012
The first perimidinium-based receptors 1 and 2 have been designed and synthesized. The anion binding
properties of the receptors were evaluated in DMSO by UV–vis, fluorescence spectroscopy, and 1H NMR
methods. The results demonstrate that both receptors 1 and 2 exhibit good selectivity to acetate. The (C–
+
ꢁ
H) ꢀ ꢀ ꢀX type ionic hydrogen bonding between the perimidinium moieties and acetate is the key inter-
action for the recognition.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Acetate recognition
Perimidinium
Fluorescence enhancement
Hydrogen bonding
The design and synthesis of new receptors that have strong
affinity and selectivity for specific anions have received consider-
able interest in recent years due to the important role that anions
played in a wide range of environmental, industrial, and biological
properties of novel designed perimidinium-based receptors 1 and
2 which show selectivity for acetate over various anions such as
fluoride, chloride, bromide, iodide, hydrogen sulfate, and
dihydrogenphosphate.
1
applications. In this context, searching new hydrogen bonding
The synthetic route of receptors 1 and 2 is illustrated in Scheme
1. Reaction of 1,8-diaminonaphthalene and formic acid in ethanol
motifs to construct novel chemosensors for selective recognition
of anionic species is still a challenge. Hydrogen bonds are particu-
larly useful and effective in binding processes for their relatively
strong and directional adhesive forces. Various receptors based
on hydrogen bonding interactions have been designed in the past
6
gave compound 3 in a 96% yield. Treated 3 with sodium hydride
in DMF, then reacted with 1-bromobutane to afford compound 4
0
in a 87% yield. Compound 4 reacted with
a,a
-dichloro-m-xylene
in toluene under reflux for 72 h followed by the anion exchange
with ammonium hexafluorophosphate to give the desired receptor
1 as a yellow solid in a combined yield of 29%. Receptor 2 was
synthesized by the similar method in a combined yield of 39%.
2
3
decades. Generally, most of these receptors contain urea, thio-
urea, amide, imidazolium5 etc., as the hydrogen bonding syn-
3
b
4
thons appended to different fluorophores.
1
13
As one of the important hydrogen donors, imidazolium groups
Receptors 1 and 2 were fully characterized by H NMR, C NMR,
+
ꢁ
can form strong interaction with anions through (C–H) ꢀ ꢀ ꢀX type
ionic hydrogen bonding in which charge–charge electrostatic inter-
action dominates. In recent years, a great many imidazolium deriv-
atives have been synthesized and investigated as selective anion
and Matrix-assisted laser desorption ionization time-of-flight
7
(MALDI-TOF) mass spectrometry.
5
receptors. However, to the best of our knowledge, perimidinium
as binding site has never been explored so far. As the same with
imidazolium groups, perimidinium groups may also form
N
N
N
N
N
N
N
N
Hb
Ha
Hc
+
ꢁ
(
C–H) ꢀ ꢀ ꢀX type ionic hydrogen bonds with anions. Meanwhile,
perimidinium possessing large conjugate system may be perfect
chromophore groups, without attaching any extra fluorophores to
the receptors. Therefore, we introduce perimidinium groups as
2
PF6
1
2PF6
+
new anion binding hydrogen bond moieties to exploit the (C–H)
2
functionalities of perimidinium for supramolecular interaction
with anions. In this Letter, we report the synthesis and binding
The anion binding properties of receptors 1 and 2 were investi-
gated by H NMR, UV–vis, and fluorescence spectroscopic methods
⇑
Corresponding author. Tel./fax: +86 (21)62233323.
E-mail address: ghgao@chem.ecnu.edu.cn (G. Gao).
1
0
040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.09.037

M. Feng et al. / Tetrahedron Letters 53 (2012) 6292–6296
6293
H
NH
2
NH
2
N
N
N
N
HCOOH
1-Bromobutane
DMF
CH CH OH
3
2
4
3
1.
Cl
. NH
Cl
1
2
4 6
PF
N
N
1
.
Cl
Cl
4
2
2
. NH PF6
4
Scheme 1. The synthetic route of the anion receptors 1 and 2.
using tetrabutylammonium salts of particular anions. The receptors
ꢁ
5
1
and 2 (c = 3.0 ꢂ 10 M) displayed strong absorption bands at 316
0
0
0
0
0
.8
.6
.4
.2
.0
and 330 nm and a weak band at about 400 nm in DMSO. The
absorption band at 400 nm illustrates the faint yellow of the solu-
tion. Upon the complexation with anions such as acetate, fluoride,
and dihydrogenphosphate, the absorption of the receptors changed
to different extents. Figures 1 and 2, in this regard, represent the
changes in the absorption of receptors 1 and 2 in the presence of
-
CH COO
3
-
F
2
equiv amounts of these different anions, respectively. As shown
receptor 2
- - -
in Figure 1, the absorption spectrum of receptor 1 changed signifi-
cantly when acetate and fluoride were added, which suggested that
receptor 1 could selectively recognize acetate and fluoride over
other anions. Receptor 2 gave the similar results as illustrated in
Figure 2. Figures 3 and 4 showed the absorption spectra changes ob-
served over the course of the titration of receptors 1 and 2
Cl , Br , I
-
HSO4
3
00
350
400
450
ꢁ5
(
c = 3.0 ꢂ 10 M) with acetate in DMSO, respectively. The absor-
Wavelength (nm)
bance peaks at 316 and 330 nm of receptors 1 and 2 were gradually
decreased with increasing addition of acetate ion and new absorp-
tion bands centered at 356 nm were observed. In addition, there
were well-defined isosbestic points at 332 nm, which indicated that
new species were formed by the interaction of receptors 1 and 2
ꢁ
5
Figure 2. Changes in absorption of receptor 2 (c = 3.0 ꢂ 10 M) in the presence of
2
equiv amounts of various anions in DMSO.
8
1.2
1.0
with acetate. Meanwhile, the acetate also induced the band at
00 nm decreased during titration, which was in accordance with
the color change when acetate was added to the solution of recep-
0.6
0
0
0
0
.5
.4
.3
.2
4
0
0
0
0
0
.8
.6
.4
.2
.0
0.1
.0
0
0
.0 0.5 1.0 1.5 2.0 2.5 3.0
C /C
G
H
0
0
0
0
0
.8
.6
.4
.2
.0
-
F
-
CH COO
3
receptor1
-
3
00
350
400
450
-
-
Cl , Br , I
Wavelength (nm)
-
HSO
4
-
4
ꢁ5
H PO
Figure 3. Changes in absorption of receptor 1 (c = 3.0 ꢂ 10 M) upon addition of
acetate in DMSO; inset: the non-linear fitting curve of absorption at 356 nm with
respect to amounts of acetate added.
2
3
00
350
400
450
Wavelength (nm)
tors (see Supplementary data,Figs. S5–S6). Similar changes were ob-
served in UV–vis spectra of receptors 1 and 2 upon addition of
fluoride and dihydrogenphosphate (see Supplementary data, Figs.
ꢁ
5
Figure 1. Changes in absorption of receptor 1 (c = 3.0 ꢂ 10 M) in the presence of
equiv amounts of various anions in DMSO.
2

6
294
M. Feng et al. / Tetrahedron Letters 53 (2012) 6292–6296
1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
8000
0
0
0.4
0
0
.6
.5
COO-
CH
3
7
6
5
000
000
000
F-
.3
.2
0.1
.0
0
receptor 2
0
.0 0.5 1.0 1.5 2.0 2.5 3.0
-
-
-
C /C
4000
Cl , Br , I ,
G
H
-
HSO
4
3
2
000
000
-
H
2
PO
4
1000
0
3
90
420
450
480
510
540
570
300
350
400
450
Wavelength (nm)
Wavelength (nm)
Figure 6. Changes in fluorescent emission of receptor 2 in the presence of 5 equiv
amounts of anions (excitation at 358 nm; excitation and emission slit: 5 nm).
Figure 4. Changes in absorption of receptor 2 (c = 3.0 ꢂ 10ꢁ M) upon addition of
acetate in DMSO; inset: the non-linear fitting curve of absorption at 356 nm with
respect to amounts of acetate added.
5
3
,000
2
2
700
400
S7–S10). The only difference is that a higher concentration of fluo-
ride and dihydrogenphosphate was needed for the receptors to
reach the balance than that of acetate. Nevertheless, receptors 1
and 2 were insensitive to the addition of excess chloride, bromide,
iodide, and hydrogen sulfate.
2,500
2,000
1,500
1,000
2100
800
1500
200
00
600
1
5
00
0
ꢁ
6
In fluorometric studies, both receptor 1 (c = 6.0 ꢂ 10 M) and
ꢁ
6
receptor 2 (c = 6.0 ꢂ 10 M) displayed weak emission bands at
02 nm in DMSO. It is not surprising for the weak emission since
1
0
1
2
3
4
5
4
C /CH
G
9
the fluorescence spectra of receptors 1 and 2 overlap with their
absorption bands centered at 400 nm. The inner filter effect (IFE)
9
of themselves leads to the less efficient fluorescence. Figure 5 rep-
resents the change in emission of receptor 1 in the presence of
3
00
0
5
equiv amounts of different anions. It can be seen that a sharp in-
3
60 390 420 450 480 510 540 570 600 630 660
crease in emission at 402 nm was observed only upon addition of
acetate. Meanwhile, it is evident from Figure 6 that a marked
enhancement in the emission of receptor 2 was noticed on addition
of 5 equiv. amounts of acetate and fluoride. However, other anions
such as chloride, bromide, iodide, and hydrogen sulfate weakly
perturbed the emission of receptors 1 and 2. Figures 7 and 8 show
fluorescent titration for receptors 1 and 2 with acetate, respec-
tively. With gradual addition of acetate, the fluorescence emission
of receptors 1 and 2 increased steadily up to 50 and 104 fold,
respectively. Meanwhile, the fluorescent intensity of receptors 1
and 2 also enhanced upon gradual addition of fluoride (see Supple-
Wavelength (nm)
ꢁ
6
Figure 7. Changes in fluorescent emission of receptor 1 (c = 6.0 ꢂ 10 M) upon
addition of acetate in DMSO (excitation at 347 nm; excitation and emission slit:
5
nm); inset: the non-linear fitting curve of emission at 402 nm with respect to
amounts of acetate added.
8
000
7000
000
5000
7
6
5
4
3
000
000
000
000
000
6
4
3
2
1
000
000
000
000
0
3
2
2
1
1
000
500
000
500
000
CH
3
COO-
0
1
2
3
4
5
C
G
/C
H
2000
1
000
0
receptor1
-
-
-
Cl , Br , I ,
-
-
HSO
4
, H
2
PO
4
390 420 450 480 510 540 570 600 630
F-
Wavelength (nm)
ꢁ
6
Figure 8. Changes in fluorescent emission of receptor 2(c = 6.0 ꢂ 10 M) upon
500
addition of acetate in DMSO (excitation at 358 nm; excitation and emission slit:
5
nm); inset: the non-linear fitting curve of emission at 402 nm with respect to
amounts of acetate added.
0
360
390
420
450
480
510
540
570
Wavelength (nm)
mentary data, Figs. S11–S12). The fluorescence enhancement could
be attributed to decrease of the IFE efficiency. As evidenced by the
absorption spectra (Figs. 3 and 4), the absorption bands centered at
Figure 5. Changes in fluorescent emission of receptor 1 in the presence of 5 equiv
amounts of anions (excitation at 347 nm; excitation and emission slit: 5 nm).

M. Feng et al. / Tetrahedron Letters 53 (2012) 6292–6296
6295
Table 1
receptors and acetate, fluoride, and dihydrogenphosphate (see
Supplementary data, Figs. S17–S18).
In order to understand the binding potencies and selectivity of
receptors 1 and 2 for anions, UV–vis and fluorescence titration data
were used to calculate the binding constant values (Table 1).11 The
sensing capability of receptors 1 and 2 for anions in DMSO is in the
The association constants of receptors 1 and 2 with anions
Anionsa
K
(M ) of receptor 1
ꢁ1
K
(M ) of receptor 2
ꢁ1
a
a
UV
Fluorescence
method
UV
Fluorescence
method
method
method
ꢁ
4
4
3
6
5
4
4
4
5
5
4
CH
F
3
COO
4.25 ꢂ 10
1.01 ꢂ 10
1.37 ꢂ 10
4.28 ꢂ 10
1.86 ꢂ 10
4.09 ꢂ 10
1.21 ꢂ 10
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
4
ꢁ
order of CH
COO > F > H
PO
4
> Cl ꢃ Br ꢃ I ꢃ HSO
. This
1.43 ꢂ 10
3
2
2
PO
4ꢁ
6.10 ꢂ 10
b
1.14 ꢂ 10
1.13 ꢂ 10
may be attributed to the structure and the basicity of various an-
ions. The higher selectivity of receptor 1 than receptor 2 for acetate
may account for the structure complementarity between receptor
1 and the acetate. In receptor 1, two perimidinium groups are lo-
cated in the meta-position of the benzene ring, and the configura-
H
Cl
ꢁ
b
b
b
b
b
b
b
ꢁ
b
b
b
b
b
b
b
b
b
Br
ꢁ
I
4ꢁ
HSO
a
Tetrabutylammonium salts were used.
The association constants were not determined due to minor changes.
1
tion may be more suitable for binding acetate. In fact, H NMR gave
b
the direct evidence of the interaction between acetate and the pro-
ton of 2-position of benzene ring in receptor 1 (more detail discus-
1
4
00 nm of receptors 1 and 2 decreased gradually with the addition
sion see H NMR studies in below).
of acetate, and finally disappeared when enough acetate was pres-
ent. The decrease of the absorption centered at 400 nm gave rise to
more detectable emission light, and consequently, the fluorescence
of receptors 1 and 2 enhanced. A blue light of receptors 1 and 2 in
the presence of acetate and fluoride was also observed by the
naked eye upon exposure to UV irradiation at 365 nm (see Supple-
mentary data, Figs. S13–S14). Furthermore, the sensing properities
of 1 and 2 were also examined in aqueous solution (DMSO:-
To understand the nature and strength of complexation of
receptors 1 and 2 with acetate, H NMR titrations were carried
out in DMSO-d . As shown in Figure 9, proton Ha in perimidinium
6
1
ring and proton Hb in benzene ring of receptor 1 underwent down-
field chemical shifts upon addition of acetate. When 7 equiv
amounts of acetate were added, Ha and Hb moved 0.49 ppm and
0.11 ppm, respectively. The results suggest that receptor 1 inter-
+
ꢁ
acted with acetate through (C–H) ꢀ ꢀ ꢀX type ionic hydrogen bonds.
In addition, new peaks were observed at range from 5.5 to 7.5 ppm
and Ha in perimidinium ring splits into two peaks in the course of
titration. Although these new peaks cannot be accurately assigned,
they are probably resulted from the asymmetric structure of the
perimidinium groups while acetate interacted with one of perimid-
inium protons. When more acetate (50 equiv) was added, a broad
peak around 10.6 ppm was observed, which assigned to the proton
2
H O = 9:1 v/v). The emission of 1 and 2 was still ‘turn on’ after
introducing the acetate to the solutions (see Supplementary data,
Figs. S15–S16). More details of the anion recognition in aqueous
solution are under investigation.
The stoichiometric ratios of the receptors and anions were con-
10
firmed by Job’s plot using UV–vis spectroscopy. The results
showed that 1:1 stoichiometry complex was formed between the
Figure 9. Family of 1H NMR spectra of receptor 1 (c = 0.01 M) on addition of acetate in DMSO-d
.
6

6
296
M. Feng et al. / Tetrahedron Letters 53 (2012) 6292–6296
Figure 10. Family of 1H NMR spectra of receptor 2 (c = 0.01 M)on addition of acetate in DMSO-d
6
.
of acetate acid,12 this result indicates that the deprotonation of
perimidinium groups undergoes in a high concentration of acetate.
The H NMR titration of receptor 2 gave the similar results as
shown in Figure 10. The only difference was the chemical shift of
protons in the benzene ring of receptor 2 did not shift upon the
addition of acetate, indicating that acetate did not bind with the
proton in benzene ring. The different binding modes between
receptors 1 and 2 account for the higher selectivity of receptor 1
for acetate than that of receptor 2.
References and notes
1
1. (a) Zhou, Y.; Xu, Z.; Yoon, J. Chem. Soc. Rev. 2011, 40, 2222; (b) Steed, J. W. Chem.
Soc. Rev. 2009, 38, 506; (c) Kim, S. K.; Lee, D. H.; Hong, J.-I.; Yoon, J. Acc. Chem.
Res. 2009, 42, 23; (e) Gale, P. A.; Garcia-Garrido, S. E.; Garric, J. Chem. Soc. Rev.
2008, 37, 151; (f) Cametti, M.; Rissanen, K. Chem. Commun. 2009, 2809.
2.
(a) Sukai, C.; Tuntulani, T. Chem. Soc. Rev. 2003, 32, 192; (b) Choi, K.; Hamilton,
A. D. Coord. Chem. Rev. 2003, 240, 101; (c) Beer, P. D.; Gale, P. A. Angew. Chem.,
Int. Ed. 2001, 40, 486; (d) Sessler, J. L.; Camiolo, S.; Gale, P. A. Coord. Chem. Rev.
2003, 240, 17.
3. (a) Amendola, V.; Fabbrizzi, L.; Mosca, L. Chem. Soc. Rev. 2010, 39, 3889; (b) Li,
A.-F.; Wang, J.-H.; Wang, F.; Jiang, Y.-B. Chem. Soc. Rev. 2010, 39, 3729.
In conclusion, we have successfully developed a novel series of
perimidium-based receptors 1 and 2. The 1H NMR, UV–vis, and
fluorescence studies show that the receptors are particularly effi-
4.
(a) Bondy, C. R.; Loeb, S. J. Coord. Chem. Rev. 2003, 240, 77; (b) Caltagirone, C.;
Gale, P. A. Chem. Soc. Rev. 2009, 38, 520; (c) Kubik, S. Chem. Soc. Rev. 2009, 38,
585.
5. (a) Xu, Z.; Kim, S. K.; Yoon, J. Chem. Soc. Rev. 2010, 39, 1457; (b) Yoon, J.; Kim, S.
K.; Singh, N. J.; Kim, K. S. Chem. Soc. Rev. 2006, 35, 355.
+
ꢁ
cient for recognizing acetate in DMSO. The (C–H) ꢀ ꢀ ꢀX type ionic
hydrogen bonding between the perimidinium moieties and acetate
is the key interaction for the recognition.
6.
Herbert, J. M.; Woodgate, P. D.; Denny, W. A. J. Med. Chem. 1987, 30, 2081.
7. Receptor 1: 1H NMR (400 MHz, DMSO-d
): d 0.99 (t, 6H, J = 7.0 Hz), 1.49–1.52
m, 4H), 1.81–1.83 (m, 4H), 4.01–4.03 (m, 4H), 5.26 (s, 4H), 6.69 (d, 2H,
6
(
1
3
J = 7.2 Hz), 7.20–7.22 (m, 4H), 7.47–7.64 (m, 9H), 7.79 (s, 1H), 9.21 (s, 2H).
NMR (100 MHz, DMSO-d ): d 13.96, 19.47, 28.26, 51.98, 54.74, 108.75, 108.94,
21.68, 124.07, 124.31, 126.51, 127.56, 128.21, 128.84, 130.03, 131.89, 133.97,
C
Acknowledgments
6
1
1
2+
34.74, 154.09. MALDI–TOF mass: calcd for C38
H
6
] :
40
N
4
P
6
F
12 [Mꢁ2PF
m/z = 697.2884,
6
97.2275.Receptor 2: H NMR (500 MHz, DMSO-d ) d 0.98 (t, 6H, J = 7.3 Hz),
6
ꢁH] : m/
The financial support from the National Natural Science Foun-
dation of China (21072061) and Shanghai Leading Academic Disci-
pline Project (B409).
+
z = 551.3242,
6
found1
551.2540;
[MꢁPF
found
1.47–1.52 (m, 4H), 1.82–1.86 (m, 4H), 4.03 (t, 4H, J = 7.4 Hz), 5.27 (s, 4H), 6.83
d, 2H, J = 7.7 Hz), 7.19 (d, 2H, J = 7.7 Hz), 7.35 (t, 2H, J = 8.0 Hz), 7.52–7.56 (m,
H), 7.62 (d, 2H, J = 8.3 Hz), 7.66 (s, 4H), 9.15 (s, 2H). 13C NMR (125 MHz,
DMSO-d ): d 13.25, 18.85, 27.73, 51.46, 54.01, 108.16, 108.38, 121.17, 123.57,
23.70, 127.69, 127.79, 128.21, 131.39, 132.89, 134.23, 153.45. MALDI–TOF
(
4
Supplementary data
6
1
2
+
mass: calcd for
C
38
H
40
N
4
P
6
F
12 [Mꢁ2PF
6
ꢁH]
:
m/z = 551.3242, found
Supplementary data (synthesis procedures of receptors 1 and 2,
+
551.2389; [MꢁPF
6
] : m/z = 697.2884, found 697.2266.
1
H NMR spectrum, 13C NMR spectrum of receptors 1 and 2, UV and
8
.
.
(a) Lin, Y.-D.; Peng, Y.-S.; Su, W.-T.; Tu, C.-H.; Sun, C.-H.; Chowa, T. J.
Tetrahedron Lett. 2012, 68, 2523; (b) Sumiya, S.; Doi, T.; Shiraishi, Y.; Hirai, T.
Tetrahedron Lett. 2012, 68, 690.
fluorescence titration of receptors 1 and 2 upon the addition of a
particular anion and the Job plots of receptors 1 and 2 with acetate,
fluoride and dihydrogenphosphate are available) associated with
this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.tetlet.2012.09.037.
9
Yuan, P.; Walt, D. R. Anal. Chem. 1987, 59, 2391.
1
0. Job, P. Ann. Chim. 1928, 9, 113.
11. Ghosh, K.; Masanta, G.; Chattopadhyay, A. P. Eur. J. Org. Chem. 2009, 4515.
2. Upadhyay, K. K.; Kumar, A.; Zhao, J. Z.; Mishra, R. K. Talanta 2010, 81, 714.
1