Synthesis and anion recognition property of acylhydrazone-based tweezer receptors

Article abstract of DOI:10.14233/ajchem.2014.15886

Three acylhydrazone-based receptors have been synthesized. Their anion recognition properties were studied by UV-visible and 1H NMR spectroscopy. The results showed that the receptors 1, 2 and 3 all had a stronger complexity with F-, H2PO4 - and CH3COO-, but no evident binding with Cl-, Br-, I-, NO3 - and HSO₄ -. Moreover,upon addition of such anions as F-, H2PO4 - and CH3COO-, 1 and 2 produced obvious colour changes. The recognition mechanism and binding mode were discussed.

Full text of DOI:10.14233/ajchem.2014.15886

Asian Journal of Chemistry; Vol. 26, No. 1 (2014), 273-276
http://dx.doi.org/10.14233/ajchem.2014.15886
Synthesis and Anion Recognition Property of Acylhydrazone-Based Tweezer Receptors
1,*
2
1
HAI-XIAN REN , AI-HONG ZHANG and YING-JIN WANG
1Department of Chemistry, Xinzhou Teachers Colledge, Xinzhou 034000, Shanxi Province, P.R. China
2Xiaoyi No. 2 Middle School, Xiaoyi 032300, Shanxi Province, P.R. China
*Corresponding author: E-mail: hxren326@163.com
Received: 8 June 2013;
Accepted: 6 November 2013;
Published online: 26 December 2013;
AJC-14522
Three acylhydrazone-based receptors have been synthesized. Their anion recognition properties were studied by UV-visible and 1H NMR
spectroscopy. The results showed that the receptors 1, 2 and 3 all had a stronger complexity with F-, H2PO4- and CH3COO-, but no evident
binding with Cl-, Br-, I-, NO3- and HSO4-. Moreover,upon addition of such anions as F-, H2PO4- and CH3COO-, 1 and 2 produced obvious
colour changes. The recognition mechanism and binding mode were discussed.
Keywords: Anion recognition, Colourimetric, Acylhydrazone, Selectivity, UV-Visible.
respectively, we have synthesized a series of acylhydrazone-
based tweezers receptors for the first time and reported the
synthesis, characterization and anion recognition nature.
(Fig. 1).
INTRODUCTION
The development of colourimetric chemosensors for the
specific anion has been an emerging area of supramolecular
chemistry1. The colourimetric receptors attract the attention
of many workers as they can detect the specific anion quickly
and easily without any instrument2-6. Usually, if auxochrome
or chromophore acts as the signaling units of the receptors7,8,
the colour change occurs when the receptors complex with
the anions. In previous work, we have synthesized a series of
colourimetric chemosensors by introducing auxochrome of
nitro9-11. In order to study the anion recognition difference from
the receptors containing auxochrome and chromophore
EXPERIMENTAL
Dimethyl sulfoxide was dried and distilled before using
according to standard practice. All other commercially avail-
able reagents were used without further purification. The
tetrabutylammonium salts were used as anionic substrates.
Melting points were measured on a X-4 digital melting-point
apparatus (uncorrected). The infrared spectra were performed
N
N
O
NHNCH2CS
CH
O
SCH2CNHN
S
CH
N
N
O
NHNCH2CS
CH
O
SCH2CNHN
CH
OH
HO
N
N
O
NHNCH2CS
CH
O
S
SCH2CNHN
S
CH
OH
HO
N
N
N
N
3
2
1
NO2
NO2
Fig. 1. Anion-binding receptors

274 Ren et al.
Asian J. Chem.
on a Digilab FTS- 3000 FT-IR spectrophotometer. Elemental
analyses were determined by a PE-2400 CHN elemental
autoanalyzer. 1H NMR spectras were recorded on a Varian
Mercury plus-400 MHz spectrometer. UV-visible spectra were
taken on a Lab Tech UV- 2100 spectrometer.
CH3COO– and H2PO4– to the solutions of the receptors but no
detectable changes upon addition of such anions as Cl–, Br–, I–.
Especially, the UV-visible absorption bands of 1, 2 undergo a
red shift respectively when such anions as F-, CH3COO- and
H2PO4- are bounded, as a result of auxochrome or chromophore
introduced.At the same time, colour changes could be observed
from the receptors of 1, 2 immediately. The same phenomenon
was not observed in the receptor 3.
Synthesis of receptors: The syntheses of 1, 2 and 3 are
outlined in Scheme-I. 4 and 5 were obtained by the procedures
of the literatures12,13
.
N
N
N
N
NaOH, ClCH2COOCH3
NH2NH2
O
O
0.8
a
HS
SH
H2NHNCH2CS
SCH2CNHNH2
S
S
F–,
OH
1
AcO–,
0.6
2
N
C2H5OH/reflux, 6 h
C2H5OH/reflux, 6 h
4 +
H2PO4
1
2
N
COH
5
0.4
COH
OH
2
2
4 +
O2N
other anions
C2H5OH/reflux, 6 h
0.2
0.0
3
4 +
COH
Scheme-I:Syntheses of 1, 2 and 3. (Chemical structural formula of the
receptors 1, 2 and 3 are in Fig. 1)
300
400
500
600
Wavelength (nm)
Compound 1: Yield: 67 %; m.p.: 239-241 °C; IR (KBr,
νmax, cm-1): 3742 (-OH), 3185.24 (N-H), 2974.24 (N=C-H),
1
1498 (-N=N-), 1685.78 (C=O), 1527.55 (C=N); H NMR
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-
-
Cl
Br
(DMSO-d6): 11.40 (2H,C=O-NH-N), 11.16 (2H, OH), 4.24
(4H, -SCH2-), 3.358 (2H, N=C-H), 6.2-8.4 (16H,Ar); 13C NMR
(DMSO-d6): 128.51, 127.49 (-N=C-S); 164.84 (CONH),
115.63 (-N=C-) 65.3,66.7 (CH2),127.37-135.23 (Ar) Anal.
calcd. for C32H26 N10O4S3: C, 54.08; H, 3.66; N, 19.72. Found:
C, 54.13; H, 3.58; N, 19.67.
b
2
Compound 2:Yield: 72 %; m.p.: 218 - 220 °C; IR (KBr,
νmax, cm-1): 3738 (-OH), 3183.76 (N-H), 2965.67 (N=C-H),
1683.64 (C=O), 1524.17 (C=N); 1H NMR (DMSO-d6): 11.28
(2H, C=O-NH-N), 11.13 (2H, OH), 4.13 (4H, -SCH2-), 3.17
(2H, N=C-H), 7.4-8.45 (6H, Ar); 13C NMR (DMSO-d6):
128.13, 127.19 (-N=C-S); 164.73 (CONH), 115.52 (-N=C-)
65.1,66.9 (CH2), 129.57-138. 87 (Ar). Anal. calcd. for C20H16
N8O8S3: C, 40.54; H, 2.70; N, 18.92. Found: C, 40.24; H, 2.55;
N, 18.71.
-
H2PO4
-
F
-
CH3COO
-
+F
300
400
500
Wavelength (nm)
0.5
0.4
0.3
0.2
0.1
0.0
-
F
Compound 3: Yield: 85 %; m.p.: 205-207 °C; IR (KBr,
νmax, cm-1): 3180.13 (N-H), 2980.14 (N=C-H), 1683.56 (C=O),
1529.34 (C=N); 1H NMR (DMSO-d6): 11.43 (2H, C=O-NH-
N), 4.18 (4H, -SCH2-), 3.27 (2H, N=C-H), 7.31-8.24(10H,
Ar); 13C NMR (DMSO-d6): 128.15, 127.87 (-N=C-S); 164.33
(CONH), 115.58 (-N=C-) 64.9,65.7 (CH2),130.87-135.23 (Ar).
Anal. calcd. for C20H18 N6O2S3: C, 51.06; H, 3.83; N, 17.87.
Found: C, 51.13; H, 3.91; N, 17.78.
-
c
CH3COO
-
4
H PO
2
-
Br
-
Cl
3
RESULTS AND DISCUSSION
UV-visible spectral titrations: The sensing abilities of
the receptors 1, 2 and 3 with anions in dimethyl sulfoxide
were monitored by using UV-visible absorptions, which were
recorded from the solutions of these compounds in the
absence or presence of anions such as F-, Cl-, Br-, I-, CH3COO–,
H2PO4–. Fig. 2 showed that the obvious change in the absor-
ption spectra of receptors (1, 2 and 3) upon addition of F–,
300
350
Wavelength (nm)
400
450
Fig. 2. UV-visible absorption spectras of receptors (1, 2, 3) in the presence
of various anions; a, b and c are corresponding to receptor 1, 2, 3,
respectively

Vol. 26, No. 1 (2014)
Synthesis and Anion Recognition Property of Acylhydrazone-Based Tweezer Receptors 275
Upon the addition of F-, CH3COO- or H2PO4- ions to the
solution of 2, the colour of the solution produced almost the
same change from pale yellow to orange. In addition, for the
receptor 1, the colour of its solution changes similarly from
pale yellow to dark red when the addition of F–, CH3COO– or
H2PO4– to its solution.
stotichiometry (2:F-) and 1:1 binding stoichiometry (2:CH3COO-
or H2PO4-). The same fact happened to the receptor 1, which
could be interpreted as that F- is too small in volume to
reorganize the hydrogen donor sites of the receptors (1, 2) in
comparison with CH3COO- and H2PO4-.
0.8
0.6
obs
calc
1.2
0.05
0.4
F
0.2
1.0
0.04
0.03
0.02
0.01
0.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0
[H2PO4] (mmol L–1
)
0.8
0.6
0.4
0.2
0.0
300
400
500
Wavelength (nm)
-
0.0
0.2
0.4
0.6
0.8
1.0
Fig. 4. UV-Visible titration spectra of receptor 2 with H2PO4 in DMSO
(298 K). [2] = 2 × 10-5 mol L-1. The inset represents the change in
absorbance of 2 at 375 nm with varying molar equivalents of anions
[G]/[G] + [H])
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
-0.005
Fig. 4 shows the significant UV-visible spectral changes
of sensor 2 on addition of H2PO4-. As we gradually added the
H2PO4- into the solution of the receptor 2, the absorbance bands
centered at 375 nm and 391 nm diminished little by little,
accompanied with a new band generated at 452 nm, suggesting
the formation of the complex between receptor 2 and H2PO4-
ion. Meanwhile, two clear isosbestic points were observed at
348 nm and 402 nm. In the same time, we examined the comp-
-
CH3COO
-
lexity with H2PO4 of receptors 1 and 3. The association
constants and correlation coefficient can be obtained by the
nonlinear least-squares method according to the curve fitting
equation14. The association constants (Ks) and correlation
coefficients (R) are listed in Table-1.
0.0
0.2
0.4
0.6
0.8
1.0
The data indicated that the binding ability of the three
-
receptors with H2PO4 and CH3COO- followed the trend:
[G]/[G]+[H]
receptor 2 > 1 > 3 (for H2PO4-); receptor 1 > 2 > 3 ( for CH3COO-);
Receptors 1 and 2 contain two acylhydrozone NH groups and
two phenolic OH groups, which can provide hydrogen donor
sites. In comparison, receptor 3 contains no phenolic OH
groups. So receptor 3 exhibited the weakest complexity for
H2PO4- and CH3COO-. In addition, the selectivity of the diffe-
rent receptors for the same anion depends on the geometrical
conformation of the receptors. Nitro-group has a smaller volume
than azobenzene group, so 2 would have a smaller repulsive
interaction than 1 and form a larger cavity to bind the anions;
also, H2PO4- with four oxygens makes the strongest complex
via multitopic hydrogen-bonding interactions with 2, which
thanks to the conformational complementarity between 2 and
H2PO4-. The possible binding model of the complex of receptor
2 with H2PO4- is presented in Fig. 5.
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
-
H2PO4
0.0
0.2
0.4
0.6
0.8
1.0
[G]/[G]+[H]
Fig. 3. Job plots for the receptor 2 with F-, CH3COO- and H2PO4- anions at
Contrary to H2PO4-, a larger steric of azobenzene group
didnot weaken the complexity between 1 and the planar trian-
gular acetate, also, its stronger conjugation effect leads to that
1 exbits the stronger hydrogen bonding complexity with
CH3COO– than 2.
a total concentration of 3 × 10-5 mol L-1 in DMSO
The Job plots of the receptor 2 with F-, CH3COO- and
-
H2PO4 were reported in Fig. 3. It conformed 1:2 binding

276 Ren et al.
Asian J. Chem.
TABLE-1
ASSOCIATION CONSTANTS Ks (mol-1 L) AND CORRELATION COEFFICIENTS (R) OF
RECEPTORS 1, 2 AND 3 WITH THE ANIONS IN DMSO AT 298 K
Anion
H2PO4–
CH3COO–
F–
Receptor 1(Ks/R)
Receptor 2 (Ks/R)
Receptor 3 (Ks/R)
481410
0.9921
0.9930
–
526420
0.9971
0.9967
–
278023
122280
–
0.9957
0.9941
–
559707
–
471082
–
Conclusion
In summary, we have synthesized three receptors by
N
N
simple method and studied their properties of anion recogni-
tion by UV-visible spectroscopy. The results showed that
receptors 1, 2 and 3 formed 1:1 complex with anions such as
H2PO4-, CH3COO- by multiple hydrogen bonding interactions
and formed 1:2 complex with F- ions. Concerning the anion
recognition difference from the receptors containing auxo-
chrome and chromophore, respectively. This study is helpful
in designing a new colourimetric receptor for certain anion in
polar solvent. Extensive efforts are being directed toward this
end.
S
S
S
CH
H C
2
2
O
C
O
C
N
N
H
O
N
H
N
C
P
HO
OH
C
O
O
O
H
H
ACKNOWLEDGEMENTS
This work was supported by Scientific and Technological
Innovation Programs of higher Education Institutions in Shanxi
in China (No. 2013149).
O N
2
NO
2
Fig. 5. Proposed recognition mechanism of receptor 2 with H2PO4–
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Fig. 6. 1H NMR spectra of receptor 2 in DMSO-d6; a) receptor 2 in the
presence of H2PO4-, b) receptor 2